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BACKGROUND OF THE INVENTION This invention relates to an improved process for converting petroleum residuals. More particularly, this invention relates to an improved process for hydrocracking petroleum residuals. Heretofore, several processes have been proposed for converting or demetalizing petroleum residuals. Such conversions and demetalizations may be accomplished over a relatively broad range of pressures and, generally, such conversions or demetalizations are accomplished at temperatures known to be effective in hydrocracking operations. It is known to effect such conversions or demetalizations in the presence of a solvent capable of donating hydrogen at the conditions employed to effect the conversion or demetalization and molecular hydrogen may or may not be present. The processes which have been proposed, heretofore, are used primarily for the purpose of upgrading the petroleum residuals such that the converted and demetalized product can satisfactorily be used as a feedstock to various petroleum processes such as catalytic cracking, hydrocracking and the like. As a result, however, the processes proposed heretofore have not resulted in significant conversion of the petroleum residual or in significant production of lighter boiling materials, particularly those in the naptha boiling range. The need, then, for an improved process for converting petroleum residuals to lighter products which may be used directly as a fuel is believed readily apparent. SUMMARY OF THE INVENTION It has now been discovered that the foregoing and other disadvantages of the prior art processes can be avoided with the method of the present invention and an improved process for converting petroleum residuals provided thereby. It is, therefore, an object of this invention to provide an improved process for the conversion of petroleum residuals. It is another object of this invention to provide such a conversion process wherein the total conversion of residuals is increased. It is still a further object of this invention to provide such an improved process wherein the relative yield of lighter boiling materials is increased. The foregoing and other objects and advantages will become apparent from the description set forth hereinafter and from the drawings appended thereto. In accordance with the present invention, the foregoing and other objects and advantages are accomplished by converting a petroleum residual in the presence of molecular hydrogen and a hydrogen donor solvent at an elevated pressure and temperature. As pointed out more fully hereinafter, the total conversion of petroleum residual to lower boiling materials is increased by controlling the pressure within a relatively narrow critical range and by effecting the conversion in the presence of a hydrogen donor solvent containing at least 0.8 weight percent donatable hydrogen. As also pointed out more fully hereinafter, continuous operation of the process can be maintained by controlling the concentration of aromatic and hydroaromatic materials in the solvent relative to the amount of paraffinic materials therein. BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a plot comparing total conversion as a function of holding time for two different solvents; FIG. 2 is a schematic flow diagram of a process within the scope of the present invention; FIG. 3 is a plot showing total conversion as a function of pressure for a given solvent; FIG. 4 is a plot showing the amount of coke produced during operation of the process of this invention as a function of the ratio of paraffinic content to the aromatic and hydroaromatic content of the solvent. DETAILED DESCRIPTION OF THE INVENTION As indicated, supra, the present invention relates to an improved process for converting petroleum residuals to lower boiling materials wherein total conversion of the petroleum residual and the yield of lighter boiling materials is increased. As indicated more fully hereinafter, it is critical to the present invention that the liquefaction be accomplished in the presence of a solvent containing at least about 0.8 weight percent donatable hydrogen at the time the solvent is fed to the conversion step; that the ratio of paraffinic materials to aromatic and hydroaromatic materials in the solvent be controlled such that the ratio is within the range from about 0:1 to about 0.5:1; and that the conversion be accomplished in the presence of molecular hydrogen at a partial pressure within the range from about 1500 to about 2500 psia. In general, the method of the present invention can be used to convert any petroleum residual material. For purposes of this invention, petroleum residual material shall mean the material remaining after a crude oil has been processed to separate lower boiling constitutents. In general, the petroleum residuals will have an initial boiling point within the range from about 650 to about 1050° F. and will be normally solid at atmospheric conditions. The petroleum residuals will, however, be liquid at the conditions used to effect the conversion. The petroleum residuals may be derived or separated from essentially any crude including those generally classed as aromatic, napthenic and paraffinic. In general, the petroleum residuals useful in the method of this invention will be bottoms from a vacuum distillation column but the same could be any residual from a carbonaceous material having an initial boiling point within the range hereinbefore noted that is also liquid at the conditions used to effect the conversion. In the method of the present invention, the petroleum residual will be combined with a solvent or diluent capable of donating hydrogen at the conditions employed to effect the conversion and containing at least 0.8 weight percent donatable hydrogen. The solvent may be a pure component but is preferably a mixture of components, some of which are capable of donating hydrogen and some of which are not. In a most preferred embodiment, at least a portion of the solvent will be a distillate fraction separated from the conversion liquid product and, depending on the particular petroleum residual subjected to conversion, this distillate fraction may be separately hydrotreated to produce components therein which are capable of donating hydrogen during conversion. In this regard, it should be noted that when the petroleum residual is highly aromatic, the distillate fraction will, generally, contain sufficient aromatic materials, that can be converted via hydrotreating to corresponding hydroaromatic materials to provide all of the donatable hydrogen required in the solvent. When the petroleum residuals are primarily napthenic or paraffinic, however, it will, generally, be necessary to add aromatic and/or hydroaromatic materials to the distillate fraction which has been separated from the conversion product for use as a solvent. Also, it may be necessary, particularly with paraffinic crudes, to remove at least a portion of the paraffinic material in the solvent fraction. When aromatics are added, separate hydrotreating will be necessary to convert at least a portion of the aromatics to corresponding hydroaromatics. When hydroaromatics are added directly, however, such separate hydrotreating will not be necessary. In this regard, it should be noted that an important feature of the present invention is the discovery that paraffins are the principal contributor to coke formation during conversion and that the presence of aromatics and hydroaromatics during such conversions either inhibit the formation of coke or solubilize the same to avoid plugging during conversion operations. Also, in a most preferred embodiment, use of a solvent having characteristics similar to the characteristics of the conversion product increases total conversion of the petroleum residuals. The use of a solvent which is a distillate fraction containing a relatively broad range of compounds is, therefore, particularly advantageous and when the petroleum residual is an aromatic, the solvent should contain aromatic materials, when the petroleum residual is napthenic, the solvent should contain napthenic materials and when the residual is paraffinic, the solvent should contain paraffins. Compounds which will donate hydrogen during liquefaction are believed well-known in the prior art and many are described in U.S. Pat. No. 3,867,275. These include the indanes, the dihydronapthalenes, the C 10 -C 12 tetrahydronapthalenes, the hexahydroflourines, the dihydro-, tetrahydro-, hexahydro- and octahydrophenanthrenes, the C 12 -C 13 acid napthenes, the tetrohydro-, hexahydro-, and decahydropyrenes, the di-, tetra-, and octahydroanthracenes, and other derivatives of partially saturated aromatic compounds. Particularly effective mixed solvents for use in the present invention include mixtures comprising a distillate fraction separated from the conversion product which is separately hydrotreated to convert at least a portion of the aromatic materials contained therein to the corresponding hydroaromatic components, hydrogenated creosote oils and hydrogenated catalytic cracking cycle stock and mixtures of such mixtures. Particularly effective solvents include distillate fractions of such mixtures having an initial boiling point within the range from about 400° to about 650° F. and a final boiling point within the range from about 850° to about 1050° F. which have been hydrogenated so as to contain at least 25 weight percent of hydrogen donor species and preferably at least 50 weight percent of such species. In general, the petroleum residual and the solvent will be combined in a solvent-to-residual weight ratio within the range from about 0.5:1 to about 2:1. The combination may be effected in accordance with any procedure obvious to one of ordinary skill in the art which will be effective in uniformly distributing the petroleum residual throughout the solvent. Best results are generally, however, obtained at elevated temperatures within the range from about 100° to about 350° F. in suitable mixing equipment. After the mixture of petroleum residual and solvent is prepared, the same is then subjected to conversion at a temperature within the range from about 800° to about 850° F. in the presence of molecular hydrogen. Generally, molecular hydrogen will be present at a concentration within the range from about 4 to about 8 weight percent based on petroleum residual and the partial pressure of molecular hydrogen will be within the range from about 1500 to about 2500. The mixture will be held at these conditions for nominal holding time within the range from about 30 to about 120 minutes. Another important feature of the present invention is the discovery that when a properly selected solvent is used the nominal holding time in either a batch or continuous operation can be extended when the hydrogen partial pressure is maintained within the critical range heretofore noted without a reduction in total conversion of the petroleum residual which has been experienced in processes heretofore proposed. In this regard, it should be noted that total conversion as used herein means the percentage of the petroleum residual which is converted to materials having boiling points less than the initial boiling point of the petroleum residual subjected to conversion. This discovery is illustrated in FIG. 1. Referring then to FIG. 1, curve 1 is a plot of conversion vs. contacting time when a heavy Arab resid was treated in the presence of a non-donor solvent at 840° F. at a solvent-to-residual ratio of 1.5:1 and at a hydrogen partial pressure of 2000 psia. Curve 2 is a plot of conversion vs. holding time at the same conditions except that a solvent capable of donating hydrogen during conversion was employed. In the runs used to generate curve 2, hydrogenated creosote oil was used as a solvent at a solvent-to-residual ratio of 1.5:1. As will be apparent from FIG. 1, significantly increased conversions can be achieved when operating in accordance with the method of the present invention. While the inventors do not wish to be bound by any particular theory, it is believed that when the hydrogen partial pressure is increased during conversion of a petroleum residual to a value within the critical range heretofore specified in the presence of a solvent capable of donating hydrogen at the conditions of the conversion, free radicals which have formed at the more severe conditions associated with increased holding time in processes proposed heretofore are scavenged by reaction with hydrogen contributed either by the donor solvent or from the molecular hydrogen. Surprisingly, however, a reduction in total conversion has been experienced when the hydrogen partial pressure is increased above about 2500 psia. While also not wishing to be bound by any particular theory, it is believed that the solvent must contain a sufficient amount of donatable hydrogen to provide at least 0.4 weight percent of such hydrogen based on petroleum resid in the initial mixture of petroleum resid and solvent. It is also believed necessary that the solvent contain at least 50 weight percent aromatic plus hydroaromatic components to prevent plugging as the result of coke formation during conversion. During the conversion, at least a portion of the petroleum residual will be converted to a normally gaseous product and at least a portion will be converted to a normally liquid product. Generally, the liquid product will have an initial boiling point at or near the atmospheric temperature and a final boiling point equal to the initial boiling point of the petroleum residual and within the range from about 650° to about 1050° F. The liquid product may then be fractionated into any desired fractions for further upgrading or direct use as an end product. Unconverted material; i.e., material having a boiling point equal to or greater than the initial boiling point of the petroleum residual subjected to conversion may either be recycled to the conversion step, burned directly as a fuel or discarded. In general, at least a portion of the liquid product will be separated and recycled to provide at least a portion of the solvent required to effect the conversion. When the separated fraction contains sufficient aromatics and/or hydroaromatics, it will not be necessary to combine this fraction with any extraneous solvent fractions. To the extent that the separated fraction contains primarily aromatics, this fraction may be subjected to hydrotreating to convert at least a portion of the aromatics to a corresponding hydroaromatic material. When this fraction does not, however, contain sufficient aromatic or hydroaromatic materials, it will be necessary to combine the same with an extraneous solvent fraction to produce a solvent having an aromatic/hydroaromatic concentration within the ranges heretofore specified. A catalytic cracking recycle oil is a particularly preferred extraneous fraction to employ since this oil is particularly high in aromatic materials. Creosote oils may also be used as an extraneous solvent fraction since these oils, too, generally, contain significant concentrations of aromatic materials. PREFERRED EMBODIMENT In a preferred embodiment of the present invention, the petroleum residual will be converted at a temperature within the range from about 820° to about 845° F. in the presence of a solvent capable of donating at least about 1.0 weight percent hydrogen, based on petroleum resid in the initial mixture of petroleum resid and solvent, and in the presence of molecular hydrogen at a hydrogen partial pressure within the range from about 1700 to about 2200 psia. In the preferred embodiment, the petroleum residual will be maintained at these conditions for a nominal holding time within the range from about 60 to about 90 minutes. Also in the preferred embodiment, the solvent will contain at least 60 weight percent aromatic and hydroaromatic components and the ratio of paraffinic materials to aromatic and hydroaromatic materials will be within the range from about 0:1 to about 0.25. In a preferred embodiment, the aromatic and hydroaromatic materials may be contained in a distillate fraction of the conversion liquid product or obtained by hydrotreating such a fraction containing aromatic materials or the same may be obtained from alternate sources such as a catalytic cracking cycle oil or a creosote oil. In a most preferred embodiment, however, a petroleum residual containing sufficient aromatic materials will be subjected to liquefaction and a sufficient concentration of aromatic materials will be present in a distillate fraction separated from the conversion liquid product and the required hydroaromatic concentration will be provided by hydrotreating this fraction to convert at least a portion of the aromatic materials to corresponding hydroaromatic materials. Any suitable catalyst may be used during the hydrotreating. It is believed that the invention will be even better understood by reference to attached FIG. 2 which illustrates a particularly preferred embodiment. Referring then to FIG. 2, a petroleum resid, a suitable solvent and molecular hydrogen are fed into mixing manifold 201 through lines 202, 203 and 204, respectively. The petroleum resid will be introduced at a temperature above the temperature at which the same is liquid and pumpable, generally at a temperature within the range from about 100° to about 350° F. In general, any suitable solvent may be introduced through line 203 to effect "start up" of a commercial operation but at steady state recycle solvent will be introduced through line 205 and only makeup or extraneous solvent will be introduced through line 203. Extraneous solvent will, of course, be introduced when the recycle solvent introduced through line 205 is deficient in aromatic and/or hydroaromatic content. To the extent that hydroaromatic materials are introduced through line 203, the solvent will, preferably, be a hydrogenated creosote oil or a hydrogenated catalytic cracking cycle stock. In general, the solvent and molecular hydrogen will be preheated to a temperature within the range from about 800° to about 850° F. In general, the solvent will contain sufficient donatable hydrogen to provide at least 0.4 weight percent donatable hydrogen based on petroleum resid in the initial mixture and the combined aromatic/hydroaromatic concentration in the solvent will be at least 50 weight percent. The solvent will be combined with a petroleum resid in a ratio within the range from about 0.5:1 to about 2:1, preferably from about 1:1 to about 1.5:1 and hydrogen will be added at a rate within the range from about 4 to about 8 weight percent based on petroleum residual in the initial mixture. After mixing in mixing manifold 201, the petroleum resid, solvent and molecular hydrogen mixture is fed to conversion reactor 206. In the conversion reactor, the mixture is heated to a temperature within the range from about 800° to about 850° F. at a hydrogen partial pressure within the range from about 1500 to about 2500 psia and at a total pressure within the range from about 1800 to about 2800 psia. The nominal holding time in conversion reactor 206 will range from about 30 to about 120 minutes. In the conversion reactor, at least a portion of the petroleum resid will be converted to a normally gaseous product and at least a portion will be converted to a normally liquid product. Generally, at least a portion of the petroleum resid will remain unconverted. In the embodiment illustrated, the entire conversion product is withdrawn through line 207 and passed to a first separator 208. In the first separator, a product containing the normally gaseous product and all of the liquid product which is to be recycled as solvent is separated overhead through line 209 and a bottoms product is separated through line 210. In those embodiments where the recycle solvent will contain aromatics, the fraction withdrawn overhead through line 209 is passed to hydrotreater 211. In the hydrotreater, at least a portion of the aromatic materials are converted to corresponding hydroaromatic materials. Such conversion is believed to be well known in the prior art. Normally, such hydrotreatment will be accomplished at a temperature within the range from about 600° F. to about 950° F., preferably at a temperature within the range from about 650° F. to about 800° F. and at a pressure within the range from about 650 to about 2000 psia, preferably 1000 to about 1500 psia. The hydrogen treat rate during such hydrotreating generally will be within the range from about 1000 to about 10,000 scf/bbl. Any of the known hydrogenation catalyst may be employed, but a "nickel moly" catalyst is most preferred. In the embodiment illustrated, then, the hydrotreated fraction is withdrawn through line 212 and recombined with the bottoms fraction from separator 208 in line 213. The recombined fractions are then passed to a second separator 214. In the second separator 214, products boiling below the initial boiling point of the solvent fraction, including normally gaseous materials, are separated overhead through line 215, a fraction, at least a portion of which is intended for use as recycle solvent, is withdrawn through line 216, a fraction having an initial boiling point equal to the higher boiling point of the solvent fraction is withdrawn through line 217 and a bottoms product generally having an initial boiling point equal to the initial boiling point of the petroleum resid subjected to conversion is withdrawn through line 218. In general, the fraction intended to be recycled as solvent will have an initial boiling point within the range from about 400° to about 650° F. and preferably an initial boiling point within the range from about 500° to about 650° F. and, generally, a final boiling point within the range from about 850° to about 1050° F. and preferably a final boiling point within the range from about 950° to about 1050° F. To the extent that this fraction exceeds the amount of solvent required, a portion thereof may be withdrawn as product through line 219 and the remainder recycled as solvent through line 205. It will be appreciated that while hydrotreating has been illustrated on a relatively broad boiling range product and between a first and second separator, the hydrotreating could be accomplished after the solvent fraction has been separated from the second separator through line 216. As is well known in the prior art, however, hydrogenation does alter the boiling range of the solvent and further separation after hydrogenation affords better control over the boiling range of the solvent fraction. As a result, operation in the manner illustrated in the Figure is preferred. The overhead product withdrawn through line 215 may be further separated into a normally gaseous product and a liquid product boiling, generally, in the naptha range. The gas may be scrubbed to remove impurities and used as a pipeline gas or as a process fuel. The naptha fraction may be further upgraded in accordance with well-known procedures to yield a high quality gasoline. The material withdrawn through line 219 boils, generally, within the known fuel oil ranges and may be used as such or further upgraded and used either as a diesel fuel or as a fuel oil. The material withdrawn through line 217 boils, generally, within the vacuum gas oil range and may be used as such or further upgraded or converted to different boiling range materials. The bottoms product withdrawn through line 218 may be at least partially recycled to the conversion reactor, burned for fuel value or discarded. Having thus broadly described the present invention and a preferred embodiment thereof, it is believed that the same will become more apparent by reference to the following examples. It will be appreciated, however, that the examples are presented solely for purposes of illustration and should not be construed as limiting the invention. EXAMPLE 1 In this example, four runs were completed in an autoclave using a vacuum resid from a heavy Arab crude oil having an initial boiling point of 1000° F. to determine the effect of hydrogen partial pressure on conversion. In each run, a raw creosote oil was used. The solvent was used at a ratio of 1.5:1 based on petroleum residual in the initial blend. The solvent was, then, capable of donating 2.4 weight percent hydrogen based on petroleum resid in the initial mixture. The solvent contained essentially no paraffinic materials and, therefore, the ratio of paraffins to total aromatics plus hydroaromatics was 0. The hydrogen partial pressure was varied between about 1300 and about 2500 psig. After 90 minutes at 820° F. the total conversion, based on petroleum resid was determined. For convenience, the pressures employed and the total conversions obtained are tabulated below and for purposes of easy comparison, the total conversion as a function of pressure is plotted in FIG. 3 for RCO solvent. ______________________________________ Approximate Total ConversionRun Number Pressure, psig Wt. % on Resid______________________________________1 1300 542 1500 583 2000 684 2500 64______________________________________ EXAMPLE 2 In this example, a series of runs were completed using the same vacuum resid used in Example 1 at a hydrogen partial pressure of 2000 psig at a temperature of 840° F. and at a nominal holding time of 60 minutes. The composition of the solvent was, however, varied in each run to determine the effect of solvent composition on the amount of coke make. At completion of experiment, the amount of coke actually prepared or generated was determined. The critical parameters relating to the composition of each solvent and the amount of coke generated is summarized and plotted in FIG. 4. EXAMPLE 3 In this example, a heavy Arab vacuum resid was converted in a continuous unit using a hydrogenated creosote oil. The hydrogenated creosote oil contained 1.6 weight percent donatable hydrogen and was used in a solvent to resid ratio of 1.5:1. At this ratio, the solvent was capable of donating 2.4 weight percent hydrogen based on resid. The run was completed at 2000 psig at a space velocity of 0.75 v/hour/v and at a hydrogen treat rate of 4500 scf/bbl. The runs were completed at two different temperatures; viz., 840° and 845° F. The total conversion and product yields are tabulated in the table below. ______________________________________Reactor Temperature °F. 840 845______________________________________Yields, Wt %C.sub.1 -C.sub.3 10 12C.sub.4 -350° F. 23 25350-650° F. 25 29650-1000° F. 19 12CONVERSION OF 77 781000° F..sup.+, WT %______________________________________ As will be apparent from the foregoing, particularly when viewed in light of FIG. 1, relatively high total conversions of a petroleum residual can be achieved when operating in accordance with the method of the present invention. As will also be apparent, the yield of lighter boiling range materials is significantly higher than has been achieved with processes heretofore proposed. The method of the present invention, then, offers an improved process for converting petroleum residuals to in-use products.

An improved process for hydrocracking petroleum residuals wherein total conversion and the yield of lower boiling range products are increased. The hydrocracking is accomplished in the presence of a hydrogen donor solvent and molecular hydrogen. The conversion is accomplished at a pressure within the range from about 1500 to about 2500 psig and at a temperature within the range from about 800°to about 850° F. Operation at these conditions is essential to achieving the increased conversion and the increased yield of lower boiling liquid products. While the present invention has been described and illustrated by reference to particular embodiments thereof, it will be appreciated by those of ordinary skill in the art that the same lends itself to variations not necessarily illustrated herein. For this reason, then, references should be made solely to the appended claims for purposes of determining the true scope of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-ply paper as well as to a method and an apparatus for the manufacture of such multi-ply paper. 2. Description of the Related Art In the manufacture of paper with specific application profiles, notably packing papers, attempts are presently being made at producing papers which in their Z-axis (perpendicular to the surface of the vertical axis) depend heavily on depth as regards their fiber and solids concentration. For ones attempts are directed at embedding, with the aid of multilayer headboxes, low-cost materials (wastepaper basis) in the middle ply of the paper and applying the high-quality, or expensive materials only on the outer plies or one outer ply where they substantially determine the quality of the paper, e.g., to make them suited for printing. Reference is made to European Patent Document No. EP 0 651 092 A1. This document teaches a multilayer headbox and a method for the manufacture of a multi-ply paper with which it is possible to specifically enrich the stock suspension of the outer layers with the desired materials. Thereby, the desired profile of the concentration across the Z-axis is maximally approached, so as to obtain a maximally white surface of good printability on the paper top side. The desired profile has a low concentration in the center and a high concentration at the edges, also known as a “smiley profile.” In another method, several headboxes (secondary headboxes) successively apply individual paper layers with different properties on one or several fourdrinier wires, thus creating a multi-ply paper. The multi-ply paper includes a high-quality, mostly bleached and printable chemical wood pulp layer (e.g., “white top liner”) on at least one side. Problems associated with all of the above methods are that very much dewatering energy is necessary in forming the plies and that the machinery expense for the manufacture is considerable. The biggest problem, however, is that all of the above methods are based on the use of expensive bleached chemical wood pulp or deinked fiber stock as raw material. A further problem is that there are many paper machines in operation which no longer satisfy today's needs with respect to the quality of the papers they produce. SUMMARY OF THE INVENTION The present invention creates a paper product which is easier and less expensive to produce and which offers a better surface with respect to its printability. The present invention also provides a method and apparatus which enable a reduction of the dewatering energy and require only low machinery expense. According to the invention, a paper is proposed which as a top layer (cover layer) contains no paper layer of expensive raw materials, but rather contains only a top coating. The inventors have recognized that existing paper machines for single-ply papers can easily be retrofitted to a two-ply product (single paper layer and top coating) with the inventional solution, and that, surprisingly, the above desired properties are obtained. The invention proposes a method for the manufacture of paper or cardboard with at least one top layer, notably white, containing no paper fibers, wherein a fiber material layer is produced with a headbox and a following former or fourdrinier wire. The fiber material layer is dried with at least one press section and a following dryer section. The wet section and/or dryer section may be equipped with a sizing or film press or other coater. At least one coating is applied with the aid of a coater or film press, the coating giving the paper a top layer with particular properties, e.g., sound printability, or a special appearance (e.g., mottled). BRIEF DESCRIPTION OF THE DRAWINGS The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: FIG. 1 is a schematic, side, sectional view of an embodiment of a paper-making machine of the present invention; FIG. 2 is a fragmentary, cross-sectional view of an embodiment of a multi-ply paper of the present invention; FIG. 3 is a fragmentary, perspective view of the doctor element of FIG. 1; and FIG. 4 is a fragmentary, front view of the doctor element of FIG. 3 . Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate one preferred embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, and more particularly to FIG. 1, there is shown at least one coater or applicator 10 which provides a traveling paper or cardboard web 12 (FIG. 2) with a top coating 14 instead of the previous, more expensive “white” fiber material layer (paper layer). Coater 10 may be installed substantially anywhere between a headbox 16 and a winder (not shown) of an existing paper machine for the manufacture of paper or cardboard webs without modification of the machine concept, i.e., of the existing paper machine. For example, applicator 10 can be arranged within a paper machine in a wet section 18 , in a dryer section 20 , and/or other sections of the paper machine. In the method of the present invention, fiber material layer 12 is produced with headbox 16 and a following former 22 or fourdrinier wire. Web 12 is dried with at least one press section 24 and the following dryer section 20 . Top coating 14 may be applied as a single or multiple coating with or without intermediate drying. Additionally, the method may be carried out on-line or off-line. An overall coating weight of 1 to 25 g/m 2 is possible. The fiber material layer, which inventionally contains no expensive bleached raw materials, allows superb top coating. The top coating (single or multiple coating) may include color only, with the color, in turn, including additives, pigments and binders suspended in liquid (such as water). The top coating may also contain fiber material in addition to color. If desired, the properties (solids content, amount of coating, composition, viscosity, pigment size, etc.) of the top coating may be adjusted in keeping with the selected applicator such that, e.g., a homogenous, inhomogeneous, striated, flamelike or mottled impression is created. Such appearance, of course, may also be created with a doctor element such as a doctor rod 26 (FIG. 3) as a coating organ which features a specifically defined surface pattern 28 (FIG. 4 ). The top-coated paper may then be additionally smoothed in a customary manner in smoothing apparatuses with a hard nip, hard hot nip, soft nip, hot soft nip, so-called deep nip, or any combination thereof. A single-nip smoothing device 30 (FIG. 1) is shown positioned after coater 10 . Particular advantages of the inventional method and apparatus are: Reduced energy demand in dewatering and drying, due to not having to dewater the top layer. Material cost reduction, since the applied coating medium is less expensive than fiber material. Lower machinery expense for the manufacture of the paper, since a simple headbox with a following coater (e.g., blade coater, speed coater, speed sizer, short dwell time coater, open-jet nozzle applicator) are sufficient for direct or indirect coating. The manufactured product is characterized by increased ply strength (ply bond strength), since the couching necessary with a multi-ply paper is dispensable here. Very good optical properties and printability can be imparted very easily to the product with the aid of the coating medium. The optical density of the top layer is greater than that of a white fiber material layer and allows a more homogeneous application. While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

A multi-ply paper includes a fiber material base layer, which is unbleached or made of wastepaper, and a top layer. Instead of a conventional “white” fiber material top layer, the top layer is in the form of a white or colored top coating.

BACKGROUND Present embodiments relate to a roll-up door. More specifically, present embodiments relate to a guard for a roll-up door which inhibits damage to the door or door shroud from objects passing through the doorway, such as fork lifts for example. Roll-up doors are utilized for a variety of functions. One usage is to allow passage through firewall openings within a building or warehouse. The roll-up door is opened during most usage but is lowered during fire conditions to inhibit spread of or contain a fire. However, during operation of a warehouse, for example, forklifts and hand trucks are used on a regular basis and pass through these openings in the firewall. Often the forks of the forklifts for example are in a raised condition when the vehicle is moving. During passage through openings, the forks, the load or otherwise elevated structure can impact the door or door shroud of the roll-up door assembly. This has two results. First, the shroud may be damaged, which may result in the roll-up door being inoperable. Second, if the impact is severe enough, the door may be damaged as well as the shroud. This will also adversely impact door operation. In either instance, the damage to the shroud or the door and shroud may preclude use of the door which presents an undesirable fire hazard. Specifically, the door cannot be closed in a fire condition which, as a result, allows the spread of fire through the building housing the roll-up door. As may be seen by the foregoing, there is a need to provide a structure for inhibiting damage to the door shroud and the roll-up door from equipment passing through the doorway. SUMMARY According to some embodiment, a roll-up door guard assembly comprises a first guard mount for positioning adjacent a first end of a roll-up door assembly and a second guard mount for positioning along a second end of said roll-up door assembly, a sleeve mounted to each of the first guard mount and the second guard mount, a bar extending between the first sleeve and the second sleeve, the bar capable of being positioned forward of the roll-up door assembly. The roll-up door guard assembly wherein the sleeves are formed to receive the bar. The roll-up door guard assembly wherein the sleeves are formed to be received by the bar. The roll-up door guard assembly wherein the sleeves are removably connected to the first and second guard mounts. The roll-up door guard assembly wherein the sleeves are integrally connected to the first and second guard mounts. The roll-up door guard assembly wherein the roll-up door guard is configured for connection to said roll-up door assembly. The roll-up door guard assembly wherein the roll-up door guard is configured for connection to a wall adjacent the door cover assembly. The roll-up door guard assembly wherein the bar is of a length equal to a distance between the first guard mount and the second guard mount. The roll up door guard assembly wherein the bar is welded to the first guard mount and said second guard mount. The roll-up door guard assembly wherein said bar is welded to the first sleeve and the second sleeve. The roll-up door guard assembly wherein the bar is of a length greater than a distance between the first sleeve and the second sleeve. The roll-up door guard assembly wherein the bar is captured between the first sleeve and the second sleeve. The roll-up door guard assembly further comprising a set screw connecting the bar to the first and second sleeves. The roll-up door guard assembly wherein the sleeves and the bar are square-shaped in cross-section. According to some other embodiments, a roll-up door guard assembly comprises a bar extending between a first sleeve and a second sleeve, a first guard mount at a first end of the bar and a second guard mount at a second end of the bar, the first sleeve extends from the first guard mount and the second sleeve extends from the second guard mount, the first and second guard mounts being connectable to a roll-up door assembly. The roll-up door guard assembly wherein the bar is hollow. The roll-up door guard assembly wherein the bar is disposed adjacent a storage area for a roll up door. The roll-up door guard assembly wherein the first sleeve and the second sleeve are L-shaped. The roll-up door guard assembly may be U-shaped. According to still other embodiments, a roll-up door guard assembly, comprises a first guard mount and a second guard mount capable of being mounted at ends of a roll-up door, a bar extending between the first guard mount and the second guard mount, the roll up door disposed between the bar and a wall to which the roll-up door is connected, the guard mounts connected to one of a wall and said roll-up door. The roll-up door guard assembly wherein the guard mount further comprises a sleeve. The roll-up door guard assembly wherein the bar is one of removably or fixedly connected to the sleeve. All of the above outlined features are to be understood as exemplary only and many more features and objectives of the roll-up door guard assembly may be gleaned from the disclosure herein. Therefore, no limiting interpretation of this summary is to be understood without further reading of the entire specification, claims, and drawings included herewith. BRIEF DESCRIPTION OF THE ILLUSTRATIONS The above-mentioned and other features and advantages of this disclosure, and the manner of attaining them, will become more apparent and the roll-up door guard will be better understood by reference to the following description of embodiments taken in conjunction with the accompanying drawings, wherein: FIG. 1 is an isometric view of the roll-up door at the doorway and a roll up door guard assembly. FIG. 2 is an isometric view of the roll-up door with the guard assembly exploded away. FIG. 3 is an isometric view of an exemplary roll-up door guard assembly. FIG. 4 is a top view of an exemplary door guard assembly. FIG. 5 is an alternate embodiment of a door guard assembly. DETAILED DESCRIPTION Reference now will be made in detail to embodiments provided, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation, not limitation of the disclosed embodiments. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present embodiments without departing from the scope or spirit of the disclosure. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to still yield further embodiments. Thus it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. Referring now to FIGS. 1-5 , a roll-up door guard assembly is depicted in various embodiments. The roll-up door guard assembly allows for positioning adjacent to a rollup door assembly such that when the roll-up door is in the up position allowing passage through the doorway, vehicles loading equipment or loads having a substantial height cannot directly contact the roll-up door assembly and cause damage to the door or shroud. Instead the guard receives the contact and precludes damage to the roll-up door which would otherwise occur without the door assembly. Referring now to FIG. 1 , a doorway 10 is depicted defined by a wall 12 having an opening 13 and a header 14 extending above the opening 13 . The doorway 10 has a first track 20 in a second track 22 adjacent the wall 12 along the opening 13 and extending vertically to guide roll up or down of a door 24 . A floor 16 is depicted below the header 14 and a threshold 18 is defined between the walls 12 and across the opening 13 wherein the door 24 may be seated when in the closed position. The door 24 is shown partly open, merely for illustration. One skilled in the art will understand that the door 24 will likely be in the fully open position when traffic, such as moving machinery is passing therethrough. In case of a fire, the door is closed to inhibit spread of fire through the building. Above the doorway 10 is a roll-up door assembly 30 . The door assembly 30 comprises a first door bracket 32 and a second door bracket 34 which provide two functions. First the brackets 32 , 34 allow connection of the roll-up assembly 30 to the wall 12 . Second, the brackets allow for rotation of the assembly allowing the door 24 to move up and down for opening and closing. The roll-up door assembly 30 further includes a door shroud cover 36 wherein the door 24 is housed when in the up or open position. The roll up door assembly 30 includes a pivot assembly 40 at each end of the assembly 30 which allows rotation of the door 24 during the roll up or roll down function to open or close the doorway 10 . The pivot assembly 40 may include a biasing structure which is not shown for clarity purpose but may include, for example, a coil or torsion spring to aid in lifting or lowering the door and controlling the weight thereof. Positioned in front of the door assembly 30 is a door guard assembly 50 . The guard assembly 50 is positioned in front of the roll up door assembly 30 in order to inhibit machines from damaging the door assembly 30 when passing through the doorway 10 . In use within a warehouse, or manufacturing facility, forklifts or other load movers tend to utilize structure which is moveable through a range of heights. As such mover or loading equipment raises the load or equipment, the may exceed the maximum height allowed for clearance by the roll-up door assembly 30 . When this occurs and the driver does not correct the situation, the equipment will strike the roll-up door assembly 30 . The result is that at a minimum that the cover 36 is dented. More typically though, the cover is damaged inhibiting operation of the door 24 or the strike is so severe as to damage the door 24 in addition to the cover 36 . The guard assembly 50 is positioned forward of the roll up door assembly 30 in order to protect from such damage. The guard assembly 50 receives the impact from the moving equipment passing through the doorway 10 rather than the roll-up door assembly 30 . This guard assembly 50 therefore will reduce repair and replacement costs for door assemblies 30 and related components. Referring now to FIG. 2 , an exploded view of the rollup door assembly 30 and the guard assembly 50 is depicted in isometric view. The guard assembly 50 includes a first mounting member 52 and a second mounting member 54 position for mounting at axial ends of the roll-up door assembly 30 . Each of the mounting members 52 , 54 have a first end which is mounted toward the wall 12 wherein the doorway 10 is positioned and a second end spaced away from the first end. The mounting members 52 , 54 may be of various shapes and may be formed of steel or other fire rated high strength materials which allow for mounting in a variety of ways. The mounting members 52 , 54 are shown as generally rectangular in shape, however the members 52 , 54 may vary in shape and may alternatively be formed of various materials. Connected to the first and second mounting members 52 , 54 are sleeves 56 , 58 . Each sleeve 56 , 58 has a first end spaced toward the corresponding mounting member 52 , 54 and a second end spaced away from the mounting member. The exemplary sleeves 56 , 58 in combination with the mounting member 52 , 54 form an L-shaped structure. However, such description should not be considered limiting, but instead merely exemplary. The sleeve 56 is shown with a square cross-section of may be any of various shapes which may or may not correspond to a bar structure 60 which, discussed further here in. According to some exemplary embodiments, the sleeve 56 , 58 is shown as receiving the bar 60 and therefore is at least partially hollow in shape. Alternatively, the sleeves 56 , 58 may be sized and configured so that the bar 60 receives the sleeves 56 , 58 opposite to the depicted embodiment. The combination of the mounting number 52 , 54 and each sleeve 56 , 58 forms an L-shaped according to the instant embodiment. However various configurations may be formed with this configuration. Additionally, the sleeves 56 and 58 may be permanently connected to mounting members such as by welding or integrally forming such as by molding or cast forms. In a further embodiment, the sleeves 56 , 58 may be removably attached to the mounting number 52 , 54 effectively. For example, a set screw 59 may be used retain bar 60 within sleeves 56 , 58 . Referring now to FIG. 3 , an exploded view of the sleeves 56 , 58 and bar 60 . The sleeves 56 , 58 receive the bar 60 at hollow ends of the sleeve 56 , 58 . As described previously, various shapes may be sued to form the sleeves 56 , 58 and the corresponding shape of the bar 60 . For example, circular bar stock may be used instead of the square bar. Additionally, the bar 60 may be hollow or may be solid. Weight requirements related to mounting as well as the width or span of the doorway 10 may dictate the type of bar 60 used and the size of sleeves 56 , 58 . According to some embodiments the bar 60 may be formed hollow and large enough to receive the sleeves 56 , 58 . Referring now to FIG. 4 , a top view of the guard assembly 50 is shown in the assembled configuration. According to one embodiment, the sleeves 56 , 58 are spaced apart a distance d 1 . The bar 60 is accordingly cut to a length d 2 which is either equal to or greater than the distance d 1 . The receiving ends of the sleeves 56 , 58 may be spaced apart a distance d 1 . The bar 60 is cut to a length equal to d 1 wherein the bar is welded to the sleeves 56 , 58 . In an alternative, the bar 60 is a length d 2 that is greater than the distance d 1 . In this embodiment, the bar 60 may be slidably positioned within the sleeves 56 , 58 or may be positioned exteriorly thereof. As shown in the depicted embodiment, the broken lines within the sleeves 56 , 58 show the oversized bar length. In this embodiment, the oversized length of the bar 60 results in capture of the bar 60 so that it cannot be removed when the mounting members 52 , 54 are fixedly mounted. In addition, for example, the bar 60 may or may not additionally be welded to the sleeves 56 , 58 . Alternatively, the bar may be locked by a set screw passing through sleeves 56 , 58 . Additionally shown in FIG. 4 , along the mounting members 52 , 54 are flanges 53 which may be used to connected the mounting members 52 , 54 to the roll-up door assembly 30 . The flange 53 may be positioned at any location along the members 52 , 54 . In the alternative, a fastener aperture 55 ( FIG. 2 ) may be disposed in the members 52 , 54 . This will allow for multiple mounting options to accommodate for various roll-up door assemblies. As shown in FIG. 5 , alternative mounting members 152 , 154 are shown. In this embodiment, flanges 53 are disposed at ends of the members in order to allow mounting of the members to a wall. This embodiment is used to connected the guard to a wall as opposed to or in addition to the roll-up door assembly. While multiple inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the invent of embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure. Examples are used to disclose the embodiments, including the best mode, and also to enable any person skilled in the art to practice the apparatus and/or method, including making and using any devices or systems and performing any incorporated methods. These examples are not intended to be exhaustive or to limit the disclosure to the precise steps and/or forms disclosed, and many modifications and variations are possible in light of the above teaching. Features described herein may be combined in any combination. Steps of a method described herein may be performed in any sequence that is physically possible. All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms. The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.” The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. It should also be understood that, unless clearly indicated to the contrary, in any methods claimed herein that include more than one step or act, the order of the steps or acts of the method is not necessarily limited to the order in which the steps or acts of the method are recited. In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of” and “consisting essentially of” shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.

A roll-up door guard assembly includes a first guard mount and a second guard mount capable of being mounted at ends of a roll-up door, a bar extending between the first guard mount and the second guard mount, the roll up door disposed between the bar and a wall to which said roll-up door is connected, the guard mounts connected to one of a wall and the roll-up door.

FIELD OF THE INVENTION This invention relates to sheltering structures particularly for protection against hurricanes, tornadoes, squalls and the like. BACKGROUND OF THE INVENTION Storms, hurricanes, typhoons, tornadoes and the like are devastating to building structures. In the United States, wind damage to building structures result in numerous injuries and deaths each year. Moreover, these storms also cause millions of dollars in property losses each year. Hurricane Andrew, which struck Florida in 1992, caused numerous injuries and deaths as well as an estimated $100 million in damages to residential homes alone. Even in the heaviest hit areas in Florida, however, where wind speeds exceeded 150 Knots, reinforced structures withstood the wind far better than non-reinforced structures. Much of the wind damage to the structures occurred at “weak links” of the building structure, namely the junction between the roof and vertical support structures, i.e., walls. Another “weak link” of the building structures most affected by the storm, was the nailedsecured joints, i.e., where the aluminum siding attached to the outside of the structure or a joint securing one piece of material to another. When wind is able to get under these “weak links,” as one is weakened, additional pieces that are attached are also weakened, causing the integrity of the structure to be compromised and sometimes totally destroyed. In addition to winds causing damage to the outside of a structure, high velocity winds can also destroy a structure from the inside out. For example, if any of the openings in a structure are breached, the high velocity force of the winds entering the structure create positive pressure against the roof weakening the structure. At the same time the high velocity of the winds streaming over the roof on the outside creates a suction. This combination of internal positive pressure and external suction will inevitably tare the roof off of the house. In an effort to prevent the breach of openings in the structure as well as, to protect windows and doors against shattering from debris colliding at high velocity, homeowners and businesses usually board-up openings with various types of panels when there is a threat that the weather pattern will bring high velocity winds. In the case of certain types of wind driven storms, i.e. squalls and tornadoes, however, the landowner may not have sufficient time to secure windows and doors from eminent destruction. Thus, in this situation the structure is left unprotected and is vulnerable to the force of the high velocity winds generated by the fast approaching weather pattern. In cases where landowners have enough warning and are able to protect the openings in the structure, in many instances, corrugated metal panels are fastened over the openings by top and bottom rails which remain in place at all times even in non-hurricane seasons. Of course, the rails are very unsightly and distract from the clean lines of a structure. Other panels are fastened to the openings by screws screwed into permanent anchors which are placed into the flush walls surrounding the openings. These again are permanent installations that are very unsightly, are subject to corrosion, and potentially represent another “weak link” that may be affected by high velocity winds. In addition, hurricane force winds of one hundred miles/hr and higher are known to set up harmonic vibrations that will result in rattling loose the above described installation because of the metal to metal contact between the fasteners and the corrugated metal panels. Further, anchors of various types are also prone to failure because of progressive corrosion in coastal areas. In addition, anchors driven into blocks which are hollow and only ½ inch thick are inadequate to hold a large force form shaking loose during a major storm. In a residential setting where the resident decides to nail protective covers, i.e., plywood sheets, to the side of the house, most homeowner have no experience in nailing into concrete and any nailing close to the edge of an opening will simply break the block away behind the panel and any anticipated holding power is greatly diminished from this common mistake. Even assuming that the homeowner is able to nail the protective covers to the side of the house, there will always be at least one opening unprotected so as to provide for egress. This one opening when breached is enough to cause the internal positive pressure discussed above. Moreover, the nailed protective covers add additional “weak links” to the structure which are vulnerable to high velocity winds. In addition, although the techniques discussed above may provide some protection to a structure against high wind velocity, these techniques do not protect the walls and roofs of the structure. These sections of the structure remain vulnerable to the high velocity winds. In view of the problems associated with the foregoing, there is a need for a protection system for building structures that is easy to implement, can withstand high winds, reduce the number of “weak links” in a structure, and protect a structure against destruction during high wind situations. SUMMARY OF THE INVENTION The present invention provides an interlocking roof and wall system for protecting a building structure. The interlocking roof and protective wall system comprises a plurality of supports that form downward facing open channels which are either already attached o an overhang or for existing roofs are attachable to the overhang. For the purpose of this application the term “interlocking” means any system where one piece fits into another. The plurality of protective walls that interlock into the overhang surround the building structure, a portion of the walls fit into the channel formed by the supports. The interlocking roof and protective walls can be secured in place by additional mechanisms or can simply lie within one another. Surrounding at least a portion of the plurality of protective walls is a plurality of retainer walls. The retainer walls form a cavity which is at least partially below grade wherein the protective walls are positioned within. At the base of the protective walls is a hydraulic lifting system that is in contact with a portion of the protective walls. The hydraulic lifting system is actuable to extend a member which pushes against the protective walls, thereby lifting the protective walls out of the cavity formed by the retainer walls. The protective walls are lifted to a height whereby at least a portion of the protective walls interlock in the downward facing open channel attached to the overhang of the roof. After the storm is over, the protective walls can be lowered back into the cavity formed by the retainer walls by releasing the hydraulic fluid from the pressurized cylinders, causing the protective walls to slowly disengage from the interlocking supports and rest in the cavity. This system can be installed at the time of construction or can be retrofitted to most existing building structures. It is understood that some building structures may need additional construction, i.e., building an overhang, for the system to work. BRIEF DESCRIPTION OF THE FIGURES FIG. 1 illustrates a cross-section of a structure incorporating the protectable building system of one embodiment of the invention. FIG. 2 illustrates a cross-section of a structure incorporating the protectable building system showing the hydraulic system of one embodiment of the invention. FIG. 3 illustrates a cross-section of a structure incorporating the protectable building system showing the roof overhang support of one embodiment of the invention. FIG. 4 illustrates cross-section of a structure incorporating the protectable building system of an alternative embodiment of the invention. FIG. 5A is a cutaway view of a roller and ratchet mechanism of one embodiment of the invention. FIG. 5B is a cutaway view of a roller and ratchet mechanism of an alternative embodiment of the invention incorporating a cross-sectional view of the roller and ratchet mechanism. DETAILED DESCRIPTION OF THE INVENTION According to one embodiment of the present invention, a protectable building system 10 that has the appearance of a conventional house is depicted in FIG. 1 . The protectable building system 10 may have a slab 15 foundation which is not required for the operation of the protectable building system, but is an easy construction method for building the structure. In addition to making construction easier, the slab 15 provides additional support for the protectable building 30 as well as protective walls 20 and 25 (described below). The protectable building system 10 may be constructed on site, or may be a prefabricated modular design which is assembled on site. The protectable building system 10 is used as an illustrative example of the present invention which includes protectable building structures other than residential houses, such as commercial buildings. Surrounding the protectable building structure 30 are protective walls 20 and 25 . Protective walls 20 and 25 are spaced far enough away from the protectable building 30 so that when the protective walls 20 and 25 are extended (described below) there is ample clearance of any projections extending from the protectable house i.e. window frames, extended bay windows, or air conditioners. The preferable space between the protectable building 30 and protective walls 20 and 25 is between about 1 to about 4 feet, most preferably between about 1 to about 2 feet. The protective walls 20 and 25 are constructed from material that is strong enough to withstand forces placed on the walls by high velocity winds. The width of the protective walls 20 and 25 vary according to the material used for its construction. In other words, the stronger the material, the thinner the wall; the weaker the material, the thicker the wall. The combination of material and thickness used, however, must be able to withstand forces associated with a wind velocity up to about 85 mph, preferably up to about 100 mph, more preferably up to about 150 mph. The height of the protective walls 20 and 25 vary with the height of the structure being protected. Preferably the protective walls are at least about 1 to about 3 feet higher than the height of the structure being protected. The portion of the wall in excess of the height of the structure remains below grade even when the protective walls 20 and 25 are fully extended (described below). The portion of the protective wall that remains below grade provides additional support to the protective walls. In other words, if the protectable building structure 30 is about 15 feet above grade, the protective walls 20 and 25 are about 16 to 18 feet height. When these walls are extended to reach the roof (as described below) at least about 1 to about 3 feet remains below grade as support. In one embodiment, surrounding the protective walls 20 and 25 are first and second retainer walls 35 and 40 , respectively. The first retainer wall 35 is located closest to the protectable building structure 30 and second retainer wall 40 is furthest from the building structure 30 . The width of the cavity formed by the space between the first and second retainer walls is greater than the width of protective walls 20 and 25 so that the protective walls fit within the first and second retainer walls 35 and 40 . The first and second retainer walls 35 and 40 can be constructed from treated plywood, PVC, plastics, corrugated steel or the like. The number of retainer walls needed is directly proportional to the nuinber of protective walls needed to protect the building structure. In other words, if the size or shape of the structure requires additional protective walls, the number of retainer walls is also increased. The protective walls 20 and 25 are in contact with a hydraulic system 45 which is used to raise the protective walls 20 and 25 towards the roof. The hydraulic system 45 exerts an upward force against a lifting plate 50 which is embedded at the base of protective walls 20 and 25 . The lifting plates 50 can be made of steel or any other material capable of enduring an upward force equal to or greater than the force exerted back on the plate by the weight of the wall. The hydraulic system 45 also includes at least two pressurizes cylinders shown in FIG. 2 . The pressurized cylinders may be located inside the protective walls or outside the protective walls. FIG. 2 illustrates hydraulic cylinders that are located inside the protective walls. In FIG. 2 a pressurized cylinder 55 is shown in the unextended and extended view. The pressurized cylinder 55 shows the base 60 , a boom 65 , and a top 70 . The pressurized cylinders located within protective walls 20 and 25 do not require a lifting plate. The pressurized cylinder 55 , can be activated by either air or fluid. The boom 65 , whether located inside the protective walls or outside the protective walls, desirably has three stages and is capable of extending a height at least equal to the height of the protectable building structure 30 . In one embodiment illustrated in FIG. 2, the pressurized cylinders are located outside the protective walls and the top 70 of boom 65 is anchored to the lifting plate 50 located at the bottom of the protective walls. The lifting plate located on the top portion of the pressurized cylinder is attached flush against the underside portion of the lifting plate 50 . Desirably, lifting plate 50 includes a depression into which the top portion of the pressurized cylinder 55 is attached. The depressed portion of the lifting plate 50 provides additional lateral strength to the connection between the pressurized cylinder 55 and lifting plate 50 . This connection prevents slippage of the pressurized cylinder 55 when the hydraulic system 45 is applying lifting forces to the lifting plate. The hydraulic system also includes a pressurized hydraulic line 75 which extends from a pump 80 to an inlet valve 85 (FIG. 3) located at the base 60 of the pressurized cylinder 55 . At least four pressurized cylinders positioned beneath the protective walls 20 and 25 are required to lift the protective walls from the cavity to protect a four sided building structure. Additional protective walls and pressurized cylinders may be required to accommodate uniquely shaped structures, i.e., structures having a shape different than a square or a rectangle. When the pump 80 is activated, fluid or air is pumped into the inlet valve 85 in the base 60 of the pressurized cylinder 55 and the boom 65 begins to rise. The boom 65 provides an upward vertical force on the lifting plate 50 , thereby lifting the protective wall above grade. In one embodiment, the hydraulic cylinders are equipped with the control valves that maintain the hydraulic cylinders at a predetermined height until the locking control valves are deactivated and the hydraulic cylinders lowered to a resting position. The pump 80 can be powered by electric and can be connected to a back-up 12-volt battery in case of power failure. In the alternative the pump can be powered by a gas generator. FIG. 3 illustrates one embodiment where the roof 90 of the protectable building structure 30 has a overhang 95 . Attached to the underside of the overhang 95 is a support 100 forming a downward facing channel 105 . The downward facing channel 105 has a width that is greater than the width of the protective walls 20 and 25 so that the top portion of the protective walls fit within the channel 105 of the support 100 . In one embodiment, the top portion of the protective wall has a cut-away portion (not shown) that interlocks into the channel 105 of the support 100 whereby the outside portion of the support is flush with the outside portion of the protective walls 20 and 25 . This arrangement reduces the production of “weak links” discussed above, which in turn reduces the chance of high velocity winds can weakening the building structure. The supports 100 can be made of a reinforced material such as corrugated galvanized metals, reinforced wood, or the like. In any case, the supports 100 must be strong enough to both support the protective walls 20 and 25 and to prevent the roof from disconnecting from the building structure, when subjected to high velocity winds. In one embodiment of the present invention, the supports 100 are located at the outermost portion of the overhang 95 . Positioning the supports 100 at the outermost portion of the overhang 95 reduces the amount of the overhang that is exposed to the high velocity winds once the protective walls 20 and 25 are in place. In other words, the outside surface of the protective walls 20 and 25 , once positioned into the supports 100 , sit flush against the rim of the overhang 90 thereby exposing little if any of the overhang 95 to the high velocity winds. Since winds can easily get under the rim of the overhang 95 and pry the roof from the building structure, reducing the exposure of the overhang 95 to the winds reduces yet another “weak link” in the building structure. The supports may be equipped with a locking mechanism that interlocks the top portion of the protective walls into the supports. The locking mechanism (not shown) can be manually or automatically engaged once the top portion of the protective walls comes in contacts with the support. When fluid is drained from the hydraulic cylinders the locking mechanism can be manually or automatically disengaged so as to permit the protective walls to be lowered back into the cavity formed by the reinforced walls. Since the protective walls 20 and 25 are usually heavy, one embodiment is equipped with one or more guide posts that are position in close proximately to the protective walls. These guide posts 110 shown in FIG. 4 provide strength and rigidity to the protective walls and are used to maintain the path of the walls as they are lifted and lowered. The guide posts 110 as well as the protective walls 20 and 25 are anchored in caissons 115 . Illustratively, the caissons 115 are concrete caissons made by pouring cement into cylindrical sona tubes made of waterproof cardboard which act as a mold and disintegrate over time. The caissons 115 begin at the existing grade level and extend below ground a distance dictated by the soil density and size/height of the protective walls 20 and 25 . Preferably, the distance is at least about 2 to about 5 feet below the existing grade level. The soil and protective wall size also dictate the size of the caissons 105 as well as the guide posts 110 . Preferably, the diameter of the caissons 115 is about twice the diameter of the guide posts 110 . Illustratively the guide posts 110 are 4″×8″ steel H-beams which may be galvanized to prevent corrosion, and the diameter of the caissons 115 is about 16″, being twice the 8″ dimension of the guideposts 110 . FIG. 5A illustrates one embodiment wherein the guide posts 110 work in conjunction with roller guides 120 and a ratchet mechanism 115 . The protective walls 20 and 25 have rollers 125 which roll along the guide posts 110 during vertical movement of the protective walls, i.e., when the hydraulic cylinders are activated. Below the rollers 125 , the ratchet mechanism 115 is located between the protective walls 20 and 25 and the guide post 110 . The ratchet mechanism 115 permits the protective walls 20 and 25 to rise along the guide posts 110 as the boom of the hydraulic cylinder is extended and prevents a accidental lowering of the protective walls. The roller 125 is attached to the outer surface of the protective walls 20 and 25 . The ratchet mechanism 115 has two parts. The first part is attached to the guide posts 110 and the outer surface of the protective walls and the second part is attached to the outer portion of the protective walls. Each guide post 110 has its own ratchet 115 and roller 125 mechanism. The rollers 125 roll along the larger section of the guide post 110 . The rollers 125 may be bolted or anchored into the protective walls 20 and 25 using bolts, two J-hooks or a single U-shaped J-hook (not shown). The rollers 125 maybe rubber, Teflon™, hard plastic or rubberized metal. Illustratively in FIG. 5B, the rollers 125 are located above the ratchet mechanism 115 . Alternatively, the rollers 125 may be located adjacent to the ratchet mechanism 115 . This allows the first part of the ratchet mechanism 115 to extend further up the guide post 110 , thus permitting the protective walls 20 and 25 to remain locked in place at a higher height. The ratchet mechanism 115 keeps the protective walls 20 and 25 in an elevated position after the protective walls have been raised by pressurized cylinders. The first part of the ratchet mechanism 115 is attached to the guide post 110 via bolts, welding or the like. The first part of the ratchet mechanism 115 has fixed teeth 140 separated by segments. The second part of the ratchet mechanism 115 has a body which is attached, e.g., bolted, to the outer surface of the protective walls 20 and 25 with bolts. In addition, the second part of the ratchet mechanism 115 has a locking lever 130 which is attached to the body via a hinge 135 located at the top of the movable tooth 145 . The fixed teeth 140 of the first part mate with the movable teeth 145 of the second part to prevent a premature lowering of the protective walls 20 and 25 . In other words, the surfaces 155 of the movable teeth and the surfaces 145 of the fixed teeth 150 complement each other so as to temporarily lock together. This ratchet system allows the protective walls 20 and 25 to rise but prevent them from descending. Preferably, the surface 155 of the movable teeth 145 has a downward slant and the surface 150 of the fixed teeth 140 have an upward slant. This provides a better locking of the first and second parts of the ratchet when the surfaces 155 of the movable teeth 145 mate with the surfaces 150 of a fixed teeth 140 . In one embodiment, the movable teeth 145 of the second part are pushed forward by a spring loaded rod (not shown) which is attached to the back of the movable teeth 145 . The ratchet mechanism 115 can also be equipped with a locking lever 130 that locks the ratchet mechanism 115 in place when the walls are stationary in the raised position. The locking lever 130 can be attached to an emergency locking lever release cord that releases the ratchet mechanism 115 when it is pulled away from the protective walls. In other words, the locking lever 130 disengages from the fixed teeth 140 and the protective walls 20 and 25 are free to move in the vertical position. Upon releasing the locking lever, fluid, i.e., gas or oil, can be released from the pressurized fluid resulting lowering of the protective walls into the cavity formed by the first and second retainer walls 35 and 40 . The operation of the protective wall system is as follows. In the event of an approaching weather front with sustained winds greater than 50 mph, the hydraulic lifting system 45 can be activated to lift the protective walls 20 and 25 into position. When the hydraulic system is activated a pump, which is attached to the pressurized cylinders 55 via a pressurized hydraulic line 75 , begins to pump fluid into the pressurized cylinders 55 . The pump 80 is attached to a flow divider (not shown) by connecting lines. The flow divider evenly distributes the fluid pumped by the pump to the pressurized cylinders 55 . As the pressured cylinders begin to fill with fluid, the booms begin to extend out of the pressurized cylinders and exert an upward force on the protective walls. As shown in the figures, the boom 65 may be located within the protective walls 20 and 25 or positioned so that a portion of the boom 65 is in contact with a portion of the protective walls 20 and 25 . When the boom is outside the protective walls, the portion of the protective walls that experience the bulk of the stress due to the upward force is further supported by a lifting plate 50 . If the boom 65 is inside the protective wall, no lifting plate is necessary. As a result of this upward force, the protective walls 20 and 25 rise out of the cavity formed by the first and second retainer walls 30 and 40 . In one embodiment, the walls are guided by several guide posts 110 that provide support as well as guidance for the vertical movement of the rising walls. In another embodiment no guide posts are utilized. When the protective walls 20 and 25 rise, the movable teeth 145 of the ratchet system attached to the guide posts 110 are pushed back toward the walls as it slides up the fixed teeth 140 . When the movable teeth 145 reaches over one of the fixed teeth 140 , the spring loaded rod pushes the movable teeth 145 forward toward the guide post 110 . This extends the movable teeth 145 over the fixed teeth 140 and prevents the protective walls 20 and 25 from accidentally lowering. The protective walls 20 and 25 are lifted until the upper portion of the protective walls fit into a downward facing channel formed by the supports 100 attached to the overhang 95 of the roof. Once at least a portion of the protective walls fit into the downward channel 105 of the supports 100 , the protective walls 20 and 25 enclose the building structure 30 and protect it from high velocity winds. Once the walls are in this position, the pressurized cylinders 55 are locked in place by the ratchet mechanism 15 . After the winds diminish, in order to allow a lowering of the protective walls 20 and 25 of the embodiment containing guide posts 100 , the movable tooth 145 that is in the locked position is manually pulled back and locked in a recessed position. Illustratively, a release cord 165 (FIG. 5 A), which may be constructed of braided rope or metal mesh, has one end attached to the spring loaded rod and the other to a handle. Alternatively, the spring loaded rod can be dispensed and the release cord 165 directly attached to the movable teeth 145 . In this embodiment, instead of the spring being coiled around the rod, it is coiled around a portion of the release cord 165 which is between the outer surface of the protective wall 20 and 25 and the movable teeth 145 . The spring, whether it is coiled around the braided rope or the rod has a diameter larger than the diameter of the hole that the braided rope and the rod pass through. This keeps the spring between the outer surface of the wall 20 and 25 and the movable teeth 145 . Alternatively, or in addition to the spring, the hinge 135 of the movable teeth 145 may be spring loaded to bias the movable teeth 145 in the forward direction toward the guide post 110 . The movable teeth 145 is recessed back by pulling on the handle. To lock the movable teeth 145 in a recessed position, the handle is hooked on the protrusions attached to the inner surface of the protective walls 20 and 25 . In an alternative, a safety pin 160 (FIG. 5A) may be inserted in a hole of a fixed plate positioned on the side of the movable teeth 145 . The fixed plate (not shown) is located at the other side of the movable teeth 145 . When the safety pin 160 enters the hole in the fixed plate, the movable teeth 145 is locked in a recessed position. When the movable teeth 145 are locked in this position, the protective walls 20 and 25 can freely slide down the guide posts 110 . The movable teeth 145 may be pulled back easily when it is located along the segments between two of the fixed teeth 140 . However, pulling back the movable teeth 145 is nearly impossible when it is resting on the fixed teeth 140 , supporting the weight of the protective walls 20 and 25 and preventing it from lowering. Therefore, to be able to pull back the movable teeth 145 while it is supporting the weight of the protective walls 20 and 25 , it is necessary to lift the protective walls 20 and 25 . This removes the weight of the protective walls from the movable teeth 145 so that it may be pulled back to the recessed position. The protective walls may be lifted using the pressurized cylinders 55 . The protective walls 20 and 25 need only be lifted approximately ¼ inch in order to release the engagement of the movable teeth 145 into the fixed teeth 140 and allow the protective walls to lower back into the cavity formed by the reinforced walls. In the embodiments that are not equipped with guide posts, the protective walls are lowered by simply releasing the fluid from the hydraulic cylinders so that the boom begins to lower. When substantially all the fluid is released from the hydraulic cylinders, the boom is in the resting position. To lift the boom, fluid is again pumped into the hydraulic cylinders. While the invention has been described by the references to specific embodiments, this was for the purposes of illustration only and should not be construed to limit the spirit or the scope of the invention. Numerous alternative embodiments may be devised by those skilled in the art without departing from the spirit and scope of the following claims.

An interlocking wall and roof system for the protection of a building structure is disclosed. The interlocking roof and wall system is equipped with a plurality of supports that form downward facing open channels that are either already attached to the overhang of the roof or are easily attachable to the overhang. The system also includes a plurality of protective walls that surround the building structure. The protective walls can be lifted from a resting position to a position where at least a portion of the walls fit into the downward facing open channels of the overhang. These walls are lifted by a hydraulic lifting system. The invention also provides a complete building structure already fitted with the supports, hydraulic lifting system and protective walls.

The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2008-037648 filed on Feb. 19, 2008. The content of the application is incorporated herein by reference in its entirety. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration actuator, and a lens barrel and a camera provided with the same. 2. Description of the Related Art In the prior art, a vibration actuator is known wherein progressive vibration waves (below referred to as progressive waves) are generated at a driving face of an elastic body utilizing the expansion and contraction of an electromechanical conversion element, which generates elliptical motion at the driving face by these progressive waves, whereby a relative moving member making pressure contact with the wave crests of the elliptical motion is driven (for example, refer to Japanese Examined Patent Publication No. H1-17354. SUMMARY OF THE INVENTION In recent years, there has been demand to miniaturize such vibration actuators. However, as the vibration actuators are miniaturized, the surface area of the joining face of the electromechanical converter and the elastic body becomes smaller, and if the conditions of the electromechanical converter other than the thickness and dielectric constant and the like are fixed, the capacitance of the electromechanical converter will decrease. As the capacitance of the electromechanical converter is reduced, the driving performance such as the startup torque of the vibration actuator and the like will accordingly be reduced. An objective of the present invention is to provide a vibration actuator which has good driving performance even when miniaturized, and a lens barrel and camera provided with the same. A first aspect of the present invention is to provide a vibration actuator comprising, an electromechanical conversion element having a first joining face and which is subject to excitation, an elastic body having a second joining face which is joined to the first joining face and a driving face which gives rise to vibration waves as a result of said excitation, and a relative moving member having a contact face which is in pressure contact with the driving face which is driven by the vibration waves and which moves relative to the elastic body, wherein an outer shape of said first joining face has a shape which differs from an outer shape of said contact face. The contact face may be round, and in the first joining face, a width in a direction orthogonal to a progressive direction of the relative moving member may differ depending on the position in the progressive direction of the relative moving member. The contact face may be round, and in the first joining face, a width in a radial direction of the contact face may be nonuniform. The outer shape of the contact face may be smaller than an outer shape of the second joining face. An outer shape of the driving face may be smaller than an outer shape of the second joining face. The outer shape of the first joining face and the outer shape of the second joining face may be elliptical shapes. A short radius of the second joining face may be approximately the same as a length in a direction parallel to the short radius of the driving face. The second joining face may have a shape which is approximately the same as the first joining face. The driving face may have a similar shape to the contact face. The outer shape of the contact face may be round. A second aspect of the present invention is to provide an electromechanical conversion element comprising, a joining face having an outer shape other than round and which is joined to an elastic body, and a round through-hole formed in a central portion of the joining face. A third aspect of the present invention is to provide an elastic body comprising, a joining face having an outer shape other than round, and which is joined to an electromechanical conversion element, and a driving face which gives rise to vibration waves due to excitation of the electromechanical conversion element. The driving face may be round. The outer shape of the joining face may be an elliptical shape. An outer shape of the driving face may be smaller than the outer shape of the joining face. A fourth aspect of the present invention is to provide a lens barrel comprising the vibration actuator according to the above aspects. The lens barrel may, further comprise, a lens unit driven by the vibration actuator, a lens retaining mount which retains the lens unit, and a housing which encloses the lens retaining mount wherein, the vibration actuator is positioned between the lens retaining mount and the housing. A fifth aspect of the present invention is to provide a camera comprising the vibration actuator according to above aspects. According to the present invention, it is possible to provide a vibration actuator which has good driving performance even when miniaturized, and a lens barrel and camera provided with the same. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a drawing explaining the camera of the first embodiment; FIG. 2 is a drawing of the lens barrel in the camera of FIG. 1 , viewed from the photographic object side; FIG. 3 is a cross sectional drawing of the ultrasonic wave motor of the first embodiment; FIGS. 4A to 4C are drawings showing the vibrating element of the first embodiment; and FIGS. 5A to 5C are drawings showing the vibrating element of the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Below, embodiments of the present invention are explained with reference to the figures. Further, the following embodiments explain the vibration actuator giving an ultrasonic wave motor as an example. (First Embodiment) FIG. 1 is a drawing explaining the camera 1 of the first embodiment. FIG. 2 is a drawing showing the lens barred 3 in the camera 1 viewed form the photographic object side. The camera 1 of the first embodiment is provided with a camera body 2 having an imaging element, and a lens barrel 3 having a lens 7 . The lens barrel 3 is an interchangeable lens which is removable from the camera body 2 . Further, in the present embodiment, the lens barrel 3 is shown by an example of an interchangeable lens, but this is not a limitation, and it may for example also be a lens barrel which is integrated with the camera body. The lens barrel 3 is provided with a lens 7 , a cam tube 6 , gears 4 , 5 , an ultrasonic wave motor 10 , enclosed in a housing 9 , and the like. In the present embodiment, the ultrasonic wave motor 10 , as shown in FIG. 2 , is located in the gap between the cam tube 6 and the housing 9 . The ultrasonic wave motor 10 is used as an actuator for driving the lens 7 during the focus operation of the camera 1 , and the driving power obtained from the ultrasonic wave motor 10 is transmitted to the cam tube 6 via the gears 4 , 5 . The lens 7 is a focusing lens retained by the cam tube 6 , and is moved approximately parallel to the optical axis direction (the direction of the arrow L in FIG. 1 ) by the driving power of the ultrasonic wave motor 10 , to carry out focusing. In FIG. 1 , an image is formed of the photographic object at the imaging surface of the imaging element 8 by a lens group (including the lens 7 ) not shown in the drawing, provided in the lens barrel 3 . The formed image of the photographic object is converted to an electric signal by the imaging element 8 , and image data is obtained by A/D conversion of this signal. FIG. 3 is a cross sectional drawing of the ultrasonic wave motor 10 of the first embodiment. The ultrasonic wave motor 10 of the first embodiment is provided with a vibrating element 11 , a moving element 15 , an output shaft 18 , a pressurizing member 19 , and the like, and is configured so that the vibrating element 11 side is fixed, and the moving element 15 is rotationally driven. The vibrating element 11 is a member with a hollow form, and having an elastic body 12 , and a piezoelectric body 13 which is joined to the elastic body 12 . The vibrating element 11 of the present embodiment, as shown in FIG. 4A described later, has an outer shape which is an approximately elliptical shape when viewed from the moving element 15 side, and in its central portion, a through-hole 11 c having an approximately round shape is formed. In this specification the word “round” means a shape in which every part of the circumference is equidistant from the center. The elastic body 12 is a member formed of a metal material having a high resonance sharpness. The elastic body 12 has a hollow form, and its shape is an approximately elliptical shape when viewed from the moving element 15 side (refer to FIG. 4A ), and this elastic body 12 has a comb tooth portion 12 a , a base portion 12 b , a flange portion 12 c , and the like. The comb tooth portion 12 a is formed with a plurality of grooves cut at the surface on the opposite side of the surface joining the piezoelectric body 13 (the elastic body-side joining surface 12 e ), and the tip surface of this comb tooth portion 12 a is in pressure contact with the moving element 15 , and becomes the driving face 12 d which drives the moving element 15 . A lubricant surface treatment such as Ni—P (nickel-phosphorous) plating or the like is applied to this driving surface. The reason for providing the comb tooth portion 12 a is to make the neutral plane of the progressive waves arising at the driving face 12 d by the expansion and contraction of the piezoelectric body 13 get as close as possible to the side of the piezoelectric body 13 , thereby increasing the amplitude of the progressive waves of the driving face 12 d. The base portion 12 b is a portion which is continuous in the peripheral direction of the elastic body 12 , and the piezoelectric body 13 is joined at the elastic body-side contact face 12 e , which is the opposite side to the comb tooth portion 12 a of the base portion 12 b. The flange portion 12 c is a brim-shaped portion which projects in the inner radial direction of the elastic body 12 , and is arranged in the center of the thickness direction of the base portion 12 b . The vibrating element 11 is fixed to the fixed member 16 by this flange portion 12 c. Further, the details concerning the form of the elastic body-side joining face 12 e and the driving face 12 d , as well as the later described piezoelectric body-side joining face 13 a will be explained later. The piezoelectric body 13 is an electromechanical conversion element which converts electrical energy into mechanical energy. In the present embodiment, a piezoelectric element is used as the piezoelectric body, but it is also possible to use an electrostrictive element or the like. The piezoelectric body 13 has an approximately planar shape, and has a piezoelectric body-side joining face 13 a which is joined with the elastic body 12 , and is a member with a hollow form where a through-hole 13 c with a round shape is formed in the central portion of the piezoelectric body-side joining face 13 a (refer to FIG. 4 ). In the piezoelectric body 13 , the piezoelectric body-side joining face 13 a is joined to the elastic body-side joining face 12 e using an adhesive. This piezoelectric body 13 has electrode portions formed thereon, not shown in the drawings, in order to input a driving signal. The wiring of flexible printed circuit board 14 is connected to the electrode portions of the piezoelectric body 13 . The flexible printed circuit board has the function of providing the driving signal to the piezoelectric body 13 . The elastic body 12 is excited by the expansion and contraction of the piezoelectric body 13 caused by the driving signal provided from this flexible printed circuit board 14 , and progressive waves are generated on the driving face of the elastic body 12 . In the present embodiment, four progressive waves are generated. The moving element 15 is a member which is rotationally driven by the progressive waves arising on the driving face of the elastic body 12 . The moving element 15 is a member having an approximately disk-like shape, formed of a light metal such as aluminum or the like, and has a contact face 15 a which contacts the vibrating element 11 (the driving face 12 d of the elastic body 12 ). The contact face 15 a has an approximately round shape, and a surface treatment of alumite or the like is applied to the surface of the contact face 15 a in order to improve the abrasion resistance. The output shaft 18 is a member having an approximately cylindrical shape. One end of the output shaft 18 contacts the moving element 15 via a rubber member 23 , and it is arranged so as to rotate as one piece with the moving element 15 . The rubber member 23 is a member of an approximately round shape, formed of rubber. This rubber member 23 has the function of allowing the moving element 15 and the output shaft 18 to rotate as one piece due to the viscoelasticity of the rubber, and the function of absorbing vibrations so that vibrations from the moving element 15 are not transmitted to the output shaft 18 , and butyl rubber, silicon rubber, propylene rubber and the like can be used. The pressurizing member 19 is a member which generates pressure to make pressure contact between the vibrating element 11 and the moving element 15 . This pressurizing member 19 is arranged between a gear 4 and a bearing receiving member 21 . As the pressurizing member 19 in the present embodiment, a compression coil spring is used, but it is not limited to this. The gear 4 is inserted so as to fit with a D-cut of the output shaft 18 , and is fixed with a stopper 22 such as an E-ring or the like, and is arranged so as to be integral in the rotational direction and the axial direction with the output shaft 18 . The gear 4 , by rotating with the rotation of the output shaft 18 , transmits driving power to the gear 5 (refer to FIG. 1 ). Further, the bearing receiving member 21 is arranged at the inner radial side of the bearing 17 , and the bearing 17 is constituted to be arranged at the inner radial side of the fixed member 16 . The pressurizing member 19 pressurizes the vibrating element 11 towards the moving element 15 side, in the axial direction of the shaft 18 , and as a result of this pressure, the moving element 15 is in pressure contact with the driving face of the vibrating element 11 , and is rotationally driven. Further, between the pressurizing member 19 and the bearing receiving member 21 , a pressure adjusting washer may be arranged, so that an appropriate pressure can be obtained for the driving of the ultrasonic wave motor 10 . Next, the shape of the driving face 12 d , the elastic body-side joining face 12 e and the piezoelectric body-side joining face 13 a will be explained. FIG. 4 is a drawing showing the vibrating element 11 of the first embodiment. Further, in order to facilitate understanding, in FIG. 4 and the below shown FIG. 5 , the orthogonal coordinate system XYZ is provided. The direction parallel to the axial direction of the output shaft 18 is set as the Z axis direction, and the direction facing the moving element 15 side in the Z axis direction is set as the Z axis positive direction. Then, the direction parallel to the long radius (long axis) of the elliptical shape of the outer shape of the vibrating element 11 viewed from the Z axis positive direction (the moving element 15 side) is set as the X axis direction, and the direction parallel to the short radius (short axis) is set as the Y axis direction. FIG. 4A is a drawing showing the vibrating element 11 as seen from the moving element 15 side, FIG. 4B is a cross sectional drawing of the vibrating element 11 along the cross section of the S 1 -S 2 arrows, parallel to the XZ plane, and FIG. 4C is a cross sectional drawing of the vibrating element 11 along the cross section of the S 3 -S 4 arrows, parallel to the YZ plane. Further, in FIG. 4A , the shape shown by the dotted lines is the shape of the contact face 15 a of the moving element 15 contacting the driving face 12 d , and the contact face 15 a contacts the driving face 12 d in the region shown by this dotted line. The piezoelectric body 13 is member having an approximately planar shape, having a piezoelectric body-side joining face 13 a joined to the elastic body 12 , and a through-hole 13 c with a round shape is formed in the center portion of the piezoelectric body-side joining face 13 a . This piezoelectric body-side joining face 13 a has an outer shape which is an elliptical shape when viewed from the elastic body 12 side (the Z axis positive side). As shown in FIG. 4 , the end face in the Z axis direction positive side of the elastic body 12 is the driving face 12 d , and the end face in the Z axis direction negative side is the elastic body-side joining face 12 e. The outer shape of the elastic body-side joining face 12 e is an elliptical shape. The shape of this elastic body-side joining face 12 e approximately coincides with the shape of the piezoelectric body-side joining face 13 a . Further, in the present embodiment, the outer shape of the driving face 12 d approximately coincides with the outer shape of the elastic body-side joining face 12 e , and when viewed from the moving element 15 side along the Z axis direction, as shown in FIG. 4A , the outer shapes of the piezoelectric body-side joining face 13 a , the elastic body-side joining face 12 e , and driving face 12 d approximately coincide. In the present embodiment, when a is the long radius of the elliptical shape which is the outer shape of the piezoelectric body-side joining face 13 a , the elastic body-side joining face 12 e , and the driving face 12 d , and b is the short radius, the length ratio of the long radius and short radius is, a:b=1.5:1 Table 1 compares the ultrasonic wave motor of the present embodiment and ultrasonic wave motors of the Comparative Examples concerning the capacitance of the piezoelectric body and the like. TABLE 1 Comparative Present Comparative Example 1 Embodiment Example 2 Ratio a:b of long radius to 1:1 1.5:1 3:1 short radius Ratio of capacitance of 1 1.5 3 piezoelectric body (for inner radius of 0) Difference in vibration ∘ Δ x amplitude in radial direction of driving face Irregularity in rotational ∘ Δ x speed in peripheral direction of moving element ∘ = good; Δ = usable; x = unusable The ultrasonic wave motors of Comparative Example 1 and Comparative Example 2, not shown in the drawings, have approximately the same shape as the ultrasonic wave motor 10 of the present embodiment, except for the point that the outer shapes of the piezoelectric body-side joining face 13 a and the like differ. The vibrating element of the ultrasonic wave motor of Comparative Example 1 has an approximately round shape. Accordingly, the outer shapes of the piezoelectric body-side joining face, the elastic body-side joining face and the driving face of Comparative Example 1 are round shapes, and a:b=1:1. The outer diameters of the piezoelectric body-side joining face, the elastic body-side joining face, and the driving face of this Comparative Example 1 have the same length as the short radius b of the outer shape of the piezoelectric body-side joining face 13 a of the present embodiment. The outer shapes of the piezoelectric body-side joining face, the elastic body-side joining face and the driving face of the ultrasonic wave motor of Comparative Example 2 are elliptical-shapes, and the ratio of the long radius of the elliptical shape and the short radius is a:b=3:1. The short radius of the piezoelectric body-side joining face of this Comparative Example 2 has similar lengths to the short radius of the piezoelectric body-side joining face 13 a of the present embodiment, and the long radius is twice as long as the length of the long radius of the piezoelectric body-side joining face 13 a of the present embodiment. The ratios of the capacitances of the piezoelectric bodies shown in Table 1 are the ratios of the capacitances of the piezoelectric body of the other Comparative Example and the present embodiment for the case that the capacitance of the piezoelectric body of Comparative Example 1 is set to 1. Further, this capacitance is for the case that the inner diameter c of the through-hole formed in the center of each of the piezoelectric bodies is c=0, namely, it is a comparison for the state in which the through-hole is not formed. The difference in vibration amplitude in the radial direction of the driving face is a result of comparing the inner peripheral side and the outer peripheral side of the driving face of the driving face concerning the size of the vibration amplitudes of the progressive waves arising at the driving face. A small difference in the size of the vibration amplitude in the radial direction of the driving face is evaluated as “good” and indicated as “o” in Table 1; some difference in the radial direction, which is nonetheless suitable for use, is evaluated as “usable”, and indicated as “Δ” in Table 1; and a large difference in the radial direction, which is not suitable for use, is evaluated as “unusable” and indicated as “x” in Table 1. Further, the irregularity in the rotational speed in the peripheral direction of the moving element is an irregularity in the rotational speed in the peripheral direction of the contact face 15 a when the moving element 15 is rotationally driven by the progressive waves of the driving face. In the peripheral direction of the contact face 15 a , a small irregularity of the rotational speed is evaluated as “good” and indicated as “o” in Table 1; some irregularity in the rotational speed, which is nonetheless suitable for use, is evaluated as “usable” and indicated as “Δ” in Table 1; and a large irregularity in the rotational speed, which is not suitable for use, is evaluated as “unusable” and indicated as “x” in Table 1. As shown in Table 1, it can be understood that the capacitance increases as the long radius a becomes larger. This is because, when the conditions of the thickness and dielectric property and the like are fixed, the capacitance of the piezoelectric body is proportional to the surface area of the polarized region of the piezoelectric body; therefore, by increasing the surface are of the piezoelectric body, the area of the polarized region can be increased. Namely, if the surface area of the joining face of the piezoelectric body and the elastic body increases, it is possible to increase the region of polarization of the piezoelectric body, and it is possible to increase the capacitance of the piezoelectric body. In this way, it is possible to obtain a larger driving force. However, as shown in Table 1, as the ratio of the long radius a and the short radius b becomes large, the difference between the vibration amplitude in the radial direction of the driving face become large. The vibration amplitude of the progressive waves has a tendency to become large towards the outer peripheral side in the radial direction of the driving face. Accordingly, usually, compared to the inner peripheral side of the driving face, the outer peripheral side has a larger vibration amplitude of the progressive waves. When the outer shape of the driving face is an elliptical shape, for example in the present embodiment, for the point t 1 in the vicinity of the outer peripheral edge of the short radial direction of the driving face 12 d , and the point t 2 in the vicinity of the outer peripheral edge of the long radial direction, the size of the vibration amplitude differs, and the vibration amplitude of the point t 2 is larger than the vibration amplitude of the point t 1 . This change in the size of the vibration amplitudes is not simply proportional to the position in the radial direction, thus in the region contacting the contact face 15 a of the moving element 15 (the region enclosed by the dotted lines in FIG. 4A ), for example, for the point t 3 positioned in the short radial direction of the driving face 12 d of the present embodiment, and the point t 4 positioned in the vicinity of the outer peripheral edge of the long radial direction, the vibration amplitude of the point t 3 is large compared to the vibration amplitude of the point t 4 . As is the case with the difference in the vibration amplitude of the progressive waves at the point t 3 and the point t 4 , the difference in vibration amplitude in the region which the contact face 15 a contacts becomes larger as the ratio of the long radius a of the elliptical shape of the driving face to the short radius b becomes larger (refer to Table 1). As stated above, because differences in the vibration amplitude arise in the region where the contact face 15 a contacts the driving face, irregularities arise in the rotational speed of the moving element 15 in its peripheral direction. If these irregularities in the rotational speed become large, it becomes impossible to carry out stable driving of the moving element 15 , and reductions or the like in the driving performance and driving efficiency of the ultrasonic wave motor will arise. However, in the present embodiment, the ratio of the long radius a to the short radius b, of the elliptical shape which form the outer shape of the driving face 12 d and the like, is set to a:b=1.5:1, thus the desired driving power and stable driving can be made compatible. Therefore, according to the present embodiment, it is possible to obtain an ultrasonic wave motor with good driving performance, even if miniaturized. For example, if an ultrasonic wave motor of the prior art, where the vibrating element has an round shape, is miniaturized, when a comparison is made for the case that the outer radius of the vibrating element has the same length as the short radius b of the present embodiment, the ultrasonic wave motor 10 of the present embodiment can provide greater torque. Further, according to the present embodiment, the outer shape when viewed from the Z axis direction is elliptical. Accordingly, it can be located in a space where one length is long and the other length is short in the X axis and Y axis directions, when viewed from the Z axis direction, for example, as shown in FIG. 3 , in the gap between the cam tube 6 in the inner portion of the lens barrel 3 and the outer tube of the lens barrel 3 , thus the efficiency in terms of space is increased. (Second Embodiment) The ultrasonic wave motor of the second embodiment has approximately the same shape as the first embodiment, except for the point that the outer shape of the driving face 32 d of the vibrating element 31 is different. Accordingly, the parts performing the same function as for the first embodiment described above have the same reference numbers, and overlapping explanations are omitted where appropriate. FIG. 5 is a drawing showing the vibrating element 31 of the ultrasonic wave motor of the second embodiment. FIG. 5A is a drawing of the vibrating element 31 viewed from the moving element 15 side; FIG. 5B is a cross-sectional drawing of the vibrating element 31 along the cross section of the S 5 -S 6 arrows parallel to the XZ plane, and FIG. 5C is a cross sectional drawing of the vibrating element 31 along the cross section of the S 7 -S 8 arrows parallel to the YZ axis. Further, the region shown by the dotted lines in FIG. 5A is the shape of the contact face 15 a of the moving element 15 which contacts the driving face 32 d , and is approximately the same as the region where the contact face 15 a contacts the driving face 32 d. The vibrating element 31 of the second embodiment has an elastic body 32 , a piezoelectric body 13 , and a through-hole 31 c . The through-hole 31 c has a shape approximately the same as the through-hole 11 c of the first embodiment. The elastic body 32 of the second embodiment has a comb tooth portion 32 a , a base portion 32 b , a flange portion 32 c , a driving face 32 d , and an elastic body-side joining face 32 e . The comb tooth portion 32 a , the base portion 32 b , the flange portion 32 c , and the elastic body-side joining face 32 e are parts which perform approximately the same function as the functions shown for the first embodiment, but the outer shape of the driving face 32 d differs from the first embodiment, thus the shapes of the outer peripheral sides of the comb tooth portion 32 a and the base portion 32 b are different from those of the first embodiment (refer to FIG. 5B ). These differences in shape will be described below. The driving face 32 d , as shown in FIG. 5A and the like, has a shape which when viewed from the moving element 15 side (the Z axis positive side) is an round shape with an outer radius r, and is a similar shape to the contact face 15 a of the moving element 15 . The center of the driving face 32 d and the center of the elliptical shape of the elastic body-side joining face 32 e are located on the same straight line parallel to the Z axis direction, and the length of the outer radius r of the driving face 32 d is the same as the length of the short radius b of the elastic body-side joining face 32 e , r=b=(⅔)×a. As shown in FIGS. 5B and 5C , in the short radius direction (Y axis direction) of the elastic body-side joining face 32 e , the dimension of the elastic body-side joining face 32 e (2×b), and the dimension of the driving face 32 d (2×r) are the same, but in the long radius direction (X axis direction) of the elastic body-side joining face 32 e , the dimension of the driving face 32 d (2×r) is smaller than the dimension of the elastic body-side joining face 32 e (2×a). Accordingly, the outer shape of the driving face 32 d is small compared to the outer shape of the elastic body-side joining face 32 e , and as shown in FIG. 5B , a portion of the outer peripheral side of the comb tooth portion 32 a and the base portion 32 b have a shape which is inclined towards the inner peripheral side. The driving face 32 d of the present embodiment has an outer shape which is a round shape, thus the progressive waves arising on the driving face 32 d have a small difference in the size of the vibration amplitude in the peripheral direction. For example, the difference in the size of the vibration amplitude of the progressive waves of the point t 5 located in the vicinity of the outer peripheral edge in the Y axis direction on the driving face 32 d , and the point t 6 located in the vicinity of the outer peripheral edge in the X axis direction, is small compared to the difference of the vibration amplitude of the progressive waves at the points t 1 ad t 2 (refer to FIG. 5A ) shown for the above described first embodiment. Further, by making the outer shape of the driving face 32 d a round shape, for the region where the contact face 15 a contacts the driving face 32 d , the position in the radial direction of the outer radius of the driving face 32 d is approximately constant regardless of the position in the peripheral direction. Accordingly, in the region of the driving face 32 d which contacts the contact face 15 a (the region shown by the dotted lines in FIG. 5A ), the difference in the size of the vibration amplitude of point t 7 located in the Y axis direction and the point t 8 located in the X axis direction is small. From the above, according to the present embodiment, the difference in the size of the vibration amplitude in the peripheral direction of the region of the driving face 32 d which contacts the contact face 15 a is small, and the irregularity of the rotational speed in the peripheral direction of the moving element 15 can be made small. Accordingly, the moving element 15 can be stably driven, and the driving performance of the ultrasonic wave motor can be improved. Further, according to the present embodiment, in the same way as for the first embodiment, the ultrasonic wave motor can be miniaturized without reducing the driving force. Furthermore, the radius r of the driving face 32 d has the same length as the short radius b of the elastic body-side joining face 32 e , thus the region which contacts the contact face 15 a can be made the outer peripheral side in the radial direction of the driving face 32 d , regardless of the position in the peripheral direction. Accordingly, it is possible to drive the moving element 15 by a greater vibration amplitude, and the torque of the ultrasonic wave motor can be improved. (Modifications) The present invention is not limited to the above-described embodiments, and many modifications or alterations are possible. (1) In each of the embodiments, an example was shown where the outer shapes of the piezoelectric body-side joining face 13 a and the elastic body-side joining face 12 e , 32 e have an elliptical shape, but this is not a limitation, and for example, they may be polygonal, to further increase the efficiency in the use of space. (2) In each of the embodiments, a rotationally driven ultrasonic wave motor was given as an example to explain the moving element 15 , but this is not a limitation, and the moving element can be applied to a vibration actuator of a linear type which is driven in a straight line. (3) In each of the embodiments, an ultrasonic wave motor using vibrations in the ultrasonic wave region was used as an example for the explanation, but this is not a limitation, and for example, it can be applied to a vibration actuator using vibrations outside of the ultrasonic wave region. (4) In each of the embodiments, an example of an ultrasonic wave motor used to drive a lens at the time of the focusing operation is shown, but this is not a limitation, and for example, the ultrasonic wave motor can be used for driving at the time of the zooming operation of a lens. (5) In each of the embodiments, an example of an ultrasonic wave motor used for a camera is shown, but this is not a limitation, and for example, it can be used as a driving portion of a copying machine, or a driving portion of a steering wheel tilt device or headrest of an automobile. Further, the above embodiments and modifications can also be used in appropriate combinations, but detailed explanations thereof are omitted. Further, the present invention is not limited by the above-explained embodiments.

To provide a vibration actuator having good driving performance even when miniaturized, and a lens barrel and camera provided with the same. A first aspect of the present invention is to provide a vibration actuator comprising, an electromechanical conversion element, having a first joining face, and which is subject to excitation, an elastic body having a second joining face which is joined to the first joining face, and a driving face which gives rise to vibration waves as a result of said excitation, and a relative moving member, having a contact face which is in pressure contact with the driving face, which is driven by the vibration waves, and which moves relative to the elastic body, wherein an outer shape of said first joining face has a shape which differs from an outer shape of said contact face.

COPYRIGHT AND LEGAL NOTICES A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyrights whatsoever. BACKGROUND INFORMATION The present invention relates in general to electronic signal processing, and more specifically, to digital to analog signal conversion. A current steering digital-to-analog converter (DAC) converts a digital data stream input into a corresponding analog signal output. FIG. 1 shows a portion of a typical current steering DAC 100 in which a digital data stream is applied to a synchronous digital output latch 101 . “Synchronous” means that the data on the latch input is transferred to the output in response to triggering of the latch by a clocking signal. In some applications, considerable digital processing is involved in producing such a digital data stream, but in the context of a DAC, such preceding digital circuitry need not be described. When the latch 101 is clocked, the data present on the D-input is transferred to the Q output, and its complement is transferred to the Q-bar output. The outputs of latch 101 asynchronously control switch drivers 102 , which in turn control differential switching elements 103 . “Asynchronously” means that the logic state of the outputs of the switch drivers 102 and the differential switching elements 103 change state in response to their inputs changing state rather than in response to a clocking signal. For a given logic state present on the output of the latch 101 , one switch of the differential switching elements 103 will be “ON,” and the other will be “OFF”. When the logic state on the output latch 101 changes, the ON-OFF states of the differential switching element 103 provide an analog signal at output terminals 106 . In theory, such a current steering DAC 100 can operate at any frequency to provide an analog output corresponding to the digital data input. In practice, errors and noise occur throughout the system, the effects of which increase with operating frequency. These effects may be code dependent and may result in harmonic distortion and harmonic spurs in the analog output signal. A current switching DAC may employ multiple current switching elements. If each individual switching element is clocked from the same clock buffer, which may be desirable to minimize switching instant mismatch, the clock buffer may see a load dependent upon the number of elements switching. As the number of elements switching is related to the signal being processed, the clock may see a signal dependent load. Consequently, there may be a signal dependent clocking instant, resulting in third order distortion. For example, FIG. 2 illustrates a clock driver 210 connected to switching element 240 which may be a PFET or an NFET. When clock input 205 changes state, for example from high to low, the output of the driver 210 will change from low to high, thereby turning “ON” switching element 240 . Switching element 240 has inherent coupling capacitance 220 between the gate to drain and coupling capacitance 230 between gate to source. Thus, due to coupling, the clock driver 210 is dependent on the data that is on nodes 250 and 255 . For example there is a difference in the current flowing into and out of the clock driver 210 when the data between node 250 and node 255 is changing and when the data is not changing. This difference in load, seen by clock driver 210 , based on the data on nodes 250 and 255 introduces third order harmonic distortion, which is not desirable. One approach to reducing code dependent noise is presented in FIG. 8 of U.S. Pat. No. 6,344,816, which describes adding an additional clocked circuit called a “dummy latch” in parallel with the output latch 101 . The output of the dummy latch is not itself used in any way, rather the dummy latch and the output latch 101 are connected and operated such that with every cycle of the clocking signal, one of the latches will change state and the other will not. Thus, if the output latch 101 changes state with the data signal, the dummy latch maintains its logic state, and if the output latch 101 maintains its logic state constant with an unchanging data signal, then the dummy latch will change logic states. However, the attempt to equalize the loading to the clock by the addition of dummy latches and the corresponding support circuitry, may add to the overall complexity, overhead, mismatch, power consumption, and size of the implementation. Thus, there is a need for an efficient system and method for a low distortion current switch, which ensures that the load seen by the clock buffer is the same in every clocking cycle, while achieving low third harmonic distortion. BRIEF DESCRIPTION OF THE DRAWINGS The invention is illustrated in the figures of the accompanying drawings, which are meant to be exemplary and not limiting, and in which like references are intended to refer to like or corresponding parts. FIG. 1 shows a portion of a typical current steering DAC. FIG. 2 shows an example of the data dependent load that a clocking driver may see. FIG. 3 a shows a digital control circuitry with a NAND implementation of the SR latch in accordance with an embodiment of the invention. FIG. 3 b shows a digital control circuitry with a NOR implementation of the SR latch in accordance with an embodiment of the invention. FIG. 4 a shows a truth table for a NAND implementation of an SR latch. FIG. 4 b shows a truth table for a NOR implementation of an SR latch. FIG. 5 shows exemplary waveforms related to the digital control circuitry with a NAND implementation of the SR latch in accordance with an embodiment of the invention. FIG. 6 a shows a complementary current switch configuration as may be used with an embodiment of the invention. FIG. 6 b shows input waveforms which may prevent cross-over distortion in accordance with an embodiment of the invention. DETAILED DESCRIPTION A system and method are provided for making the load of the clock driver independent of data, thereby reducing third order harmonic distortion. FIG. 3 a shows a digital control circuitry with a NAND implementation of an SR latch in accordance with an embodiment of the invention. Such architecture may comprise a data input 310 and a complementary input 315 , clock input 320 , pre-charging switches 340 and 345 , an SR Latch 390 , comprising NAND gates 350 and 355 , and complementary current outputs 370 and 375 , controlled by switches 360 and 365 which may be supplied by current source 380 . Switching elements 330 and 335 are coupled to data inputs 310 and 315 accordingly. When turned “ON,” switching elements 330 and 335 provide a path to the SR Latch 390 comprising NAND gates 350 and 355 . In one embodiment, switching elements 330 and 335 may be NFETS. The gates of the switching elements 330 and 335 are controlled by clocking signal 320 . When the clock is “high,” data from input 310 and complementary input 315 is passed through switching devices 330 and 335 to NAND 350 and 355 respectively. When the clock is “low,” data input 310 and complementary input 315 is prevented to pass through switching devices 330 and 335 . Further, when the clock is “low,” switching devices 340 and 345 pre-charge node Id and Idb to “high” respectively. In one embodiment, switching devices 340 and 345 are PFETs. Thus, when the clock is “low,” both input nodes Id and Idb to the SR Latch 390 are at “high.” When the clock is “high,” data input 310 and complementary input 315 is passed to the input nodes Id and Idb, respectively, becoming the inputs to the SR Latch 390 . The latch 390 is a basic SR latch comprising two cross-coupled NAND gates 350 and 355 . The input to NAND 350 is signal Id and the output of NAND 355 (signal swb). Similarly, the input of NAND 355 is Idb and the output of NAND 350 (signal sw). Outputs sw and swb are complements of each other. The NAND embodiment of the SR latch 390 “holds” the data stored in the SR latch 390 when inputs Id and its complement Idb are forced to “high” during the pre-charge state. The SR latch 390 is “reset” when Id input is “high” and the complementary input Idb is “low.” The “reset” forces output of NAND 350 (signal sw) to go to “low” while the complementary output at the output of NAND 355 (signal swb) goes to “high.” This situation may arise when the clock input 320 is “high,” and, thus, not in the pre-charge state, and the data from input 310 is “high” while complementary input 315 is “low.” Alternatively, the SR latch 390 is “set” when Id input is “low” and the complementary input Idb is “high.” The “set” forces output of NAND 350 (signal sw) to go to “high” while the complementary output at the output of NAND 355 (signal swb) goes to “low.” This situation may arise when the clock input 320 is “high,” and, thus, not in the pre-charge state, and the data from input 310 is “low” while complementary input 315 is “high.” FIG. 4 offers a truth table that summarizes the operation of a NAND configured SR latch 390 . The “set” column S, corresponds to input Id while the “reset” input R, corresponds to the complementary input Idb. Outputs Q and Q′ of the table correspond to signals sw and the complementary signal swb respectively. Thus, during the pre-chare state, S=1 (high) and R=1 (high), the outputs Q and Q′ “hold” the previous information stored in the SR latch 390 . State S=0 (low), R=0 (low) is a forbidden state. Since the inputs to the SR latch 390 are either S=1 and R=1 during pre-charge or, when not in pre-charge, are complementary, state S=0, R=0 does not occur in the embodiment shown in configuration 300 of FIG. 3 a. In one embodiment, the output of the SR latch 390 may be coupled to differential switching elements 360 and 365 , as illustrated in FIG. 3 a . Current source 380 may be coupled to ground and provide the current for switching elements 360 and 365 . When sw is “high,” the complementary signal swb is “low,” turning “ON” switch 360 while turning “OFF” switch 365 . Thus, the current from current source 380 flows substantially through switch 360 and output Iout, 370 . Alternatively, if sw is “low,” the complementary signal swb is “high,” turning “OFF” switch 360 while turning “ON” switch 365 . Now, the current from current source 380 flows substantially through switch 365 and output Ioutb, 375 . Switches 360 and 365 may be FETs or bipolar devices. In the preferred embodiment of FIG. 3 a , switches 360 and 380 are NFETs. Those skilled in the art will readily understand that the concepts described above can be applied with different devices and configurations. For example, FIG. 3 b illustrates digital control circuitry with a NOR implementation of the SR latch in accordance with an embodiment of the invention. Such architecture may comprise a data input 310 and a complementary input 315 , clock input 320 , pre-charging switches 440 and 445 , an SR Latch 490 , comprising NOR gates 450 and 455 , and complementary current outputs 370 and 375 , controlled by switches 460 and 465 which may be supplied by current source 480 . Switching elements 430 and 435 are coupled to data inputs 310 and 315 respectively. When turned “ON,” switching elements 430 and 435 provide a path to the SR Latch 490 comprising NOR gates 450 and 455 . In one embodiment, switching elements 430 and 435 may be PFETS. The gates of the switching elements 430 and 435 are controlled by clocking signal 320 . When the clock is “low,” data from input 310 and complementary input 315 is passed through switching devices 430 and 435 to NOR 450 and 455 respectively. When the clock is “high,” data input 310 and complementary input 315 is prevented to pass through switching devices 430 and 435 . Further, when the clock is “high,” switching devices 440 and 445 pre-charge node Id and Idb to “low” respectively. In one embodiment, switching devices 440 and 445 are NFETs. Thus, when the clock is “low,” both input nodes Id and Idb to the SR Latch 490 are at “low.” When the clock is “low,” data input 310 and complementary input 315 is passed to the input nodes Id and Idb, respectively, to the SR Latch 490 . The latch 490 is a basic SR latch comprising two cross-coupled NOR gates 450 and 455 . The input to NOR 450 is signal Id and the output of NOR 455 (signal swb). Similarly, the input of NOR 455 is signal Idb and the output of NOR 450 (signal sw). As in the NAND configuration, the outputs sw and swb are complements of each other. The NOR embodiment of the SR latch 490 “holds” the data stored in the SR latch 490 when inputs Id and its complement Idb are forced to “low” during the pre-charge state. The SR latch 490 is “reset” when Id input is “high” and the complementary input Idb is “low.” The “reset” forces output of NOR 450 (signal sw) to go to “low” while the complementary output at the output of NOR 455 (signal swb) goes to “high.” This situation may arise when the clock input 320 is “low,” and, thus, not in the pre-charge state, and the data from input 310 is “high” while complementary input 315 is “low.” Alternatively, the SR latch 490 is “set” when Id input is “low” and the complementary input Idb is “high.” The “set” forces output of NOR 450 (signal sw) to go to “high” while the complementary output at the output of NOR 455 (signal swb) goes to “low.” This situation may arise when the clock input 320 is “low,” and, thus, not in the pre-charge state, and the data from input 310 is “low” while complementary input 315 is “high.” FIG. 4 b offers a truth table that summarizes the operation of a NOR configured SR latch 490 . The “set” column S, corresponds to input Idb while the “reset” input R, corresponds to the complementary input Id. Outputs Q and Q′ of the table correspond to signals sw and the complementary signal swb accordingly. Thus, during the pre-chare state, S=0 (low) and R=0 (low), the outputs Q and Q′ “hold” the previous information stored in the SR latch 390 . State S=1 (high), R=1 (high) is a forbidden state. Since the inputs to the SR latch 490 are S=0 and R=0 during pre-charge, or, when not in pre-charge, are complementary, state S=0, R=0 does not occur in configuration 400 of FIG. 3 b. In one embodiment, the output of the SR latch 490 may be coupled to differential switching elements 460 and 465 , as illustrated in FIG. 3 b . Current source 480 may be coupled to vdd and provides the current for switching elements 460 and 480 . When sw is “high,” the complementary signal swb is “low,” turning “ON” switch 465 while turning “OFF” switch 460 . Thus, the current from current source 480 flows substantially through switch 465 and output Ioutb, 375 in such a situation. Alternatively, if sw is “low,” the complementary signal swb is “high,” turning “OFF” switch 465 while turning “ON” switch 460 . Now, the current from current source 480 flows substantially through switch 460 and output Iout, 470 . Switches 460 and 465 may be FETs or bipolar devices. In the preferred embodiment of FIG. 3 b , switches 460 and 480 are PFETs. As provided for in the above description of the RS latch, which may be, for example, NAND configuration 390 or NOR configuration 490 , there is a condition where if both inputs Id and Idb are at the same logic state, the outputs of the RS latch ( 390 or 490 ) will “hold” state. This may be achieved, for example, through pre-charging input nodes Id and Idb to the same logic state, which may be “high” for a NAND configured RS latch 390 or “low” for a NOR configured RS latch 490 . The RS latch changes state when either of the inputs Id or Idb is taken to the opposite level. Data input d ( 310 ) and its complement db ( 315 ) to the SR latch is each in series with a switch, controlled by the clock signal 320 . When the switches are “OFF” the inputs Id and Idb to the SR latch ( 390 or 490 ) are pre-charged to a level that would induce the RS latch ( 390 or 490 ) to a “hold” state. When the clock signal 320 turns “ON” the series switches, there will only be a single data transition, regardless of the previous data held by the RS latch ( 390 or 490 ). This ensures that the clock driver only sees a single data transition every clock cycle. Therefore, the clock driver is independent of the data signals 310 and 315 , thereby reducing third order harmonic distortion. FIG. 5 shows exemplary waveforms associated with the digital control circuitry of FIG. 3 a in accordance with an embodiment of the invention. Signal 510 represents the clock signal that controls the series switches 330 and 335 , as well as pre-charge switches 340 and 345 of FIG. 3 a . Signals 520 and 530 are the complementary data inputs d and db, each in series with switches 340 and 345 respectively. Signals Id ( 540 ) and Idb ( 550 ), are “high” when clock signal 510 is “low,” and thus in a pre-charge state. When the clock is “high,” the signal d ( 520 ) is forced onto Id ( 540 ) while the signal db ( 530 ) is forced onto Idb ( 550 ). Signals sw ( 560 ) and swb ( 570 ) are the complementary outputs of the NAND SR latch 390 . When the signals Id ( 540 ) and Idb ( 550 ) are “high,” the data in the latch is held. When signal Id ( 540 ) is “high” while signal Idb ( 550 ) is “low,” the data is reset, forcing sw ( 560 ) to “low” and its complementary signal swb ( 570 ) to “high.” On the other hand, when signal Id ( 540 ) is “low” while signal Idb ( 550 ) is “high,” the data is set, forcing sw ( 560 ) to “high” and its complementary signal swb ( 570 ) to “low.” One inherent benefit in using an SR latch configuration is that it reduces cross-over distortion. For example, FIG. 6 a shows closer view of the complementary current switch configuration of FIG. 3 a , as may be used in an embodiment of the invention. A linear sweep from “high” to “low” of signal sw at the gate of switch 360 and a proportional sweep of “low” to “high” of signal swb at the gate of switch 365 , where both sw and swb signals are equal in magnitude at the cross-over point, may create a dead-band region, where both switches 360 and 365 are “OFF,” which is undesirable. However, as illustrated in FIG. 6 b , the output of an SR latch inherently has a crossover which is about a threshold voltage above the common mode, CS, of the sw and swb signals. This high cross-over prevents dead-band, which assures smooth current transition from one switch to the other, for example switch 360 to 365 , thereby preventing crossover distortion. Although the present invention has been described with reference to particular examples and embodiments, it is understood that the present invention is not limited to those examples and embodiments. The present invention as claimed, therefore, includes variations from the specific examples and embodiments described herein, as will be apparent to one of skill in the art. Accordingly, it is intended that the invention be limited only in terms of the appended claims.

A system and method is provided for code independent switching in a digital-to-analog converter (DAC). A synchronous digital circuit is triggered by a synchronizing clocking signal and develops a digital data signal. A circuit arrangement provides the synchronizing clock a constant load at every clocking cycle, thereby assuring a data independent load. By providing a data independent load to the synchronizing clock at every clocking cycle, third harmonic distortion is advantageously reduced.

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority to U.S. Provisional Patent Application No. 60/591,761, “A Control Layer Algorithm for Ad hoc Networks in Support of Urban Search and Rescue (USAR) Applications”, filed Jul. 28, 2004. BACKGROUND OF INVENTION [0002] The world has witnessed a tremendous growth in the deployment of wireless network technology driven by the need for ubiquitous service and rapid developments in telecommunications infrastructure. Mobile hosts such as notebook computers, featuring powerful CPUs and gigabytes of disk space are now easily affordable and becoming quite common in everyday life. At the same time, huge improvements have been made in wireless network hardware, and efforts are being made to integrate the two into a meaningful resource such as the Internet. We are witness to large scale proliferation of mobile computing and wireless technology in our day-to-day lives in the form of various hardware interfaces and technology devices, running numerous applications catering specifically to wireless technology. The use of cell phones and PDA's for mobile video conferencing, GPS based tracking systems and remote wireless sensor surveillance gives us an indication of the growth and proliferation of wireless technology in today's world. [0003] The increased demand and usage of mobile devices, directly correlates to the inflated demand for mobile data and Internet services. The number of subscribers to wireless data services is predicted to reach 1.3 billion by end of 2004, and the number of wireless messages is sent per month is predicted to reach 244 billion by December 2004. But these devices and technology use the standard wireless network model of a base station, repeaters, access points, and wireless nodes. Oftentimes however mobile users will want to communicate in situations in which no fixed wired infrastructure is available, because it may not be possible to provide the necessary infrastructure or because the expediency of the situation does not permit this installation. The term, “ad hoc network” refers to such a collection of wireless mobile hosts forming a temporary network without the aid of any established infrastructure or centralized administration. [0004] The history of ad hoc networks dates back to the DARPA radio packet network in 1972, which was primarily inspired by the efficiency of the packet switching technology, such as bandwidth sharing and store and forward routing, and its possible application in mobile wireless environment. But, it was not until the early 90's when research in the area of ad hoc networks gained significant momentum and widespread attention. This could be attributed to the surge in cheap availability of network hardware, the micro computer revolution, and the increasing number of applications that required an ad hoc network kind of setup. Some of the common applications for ad hoc networks include: conference halls, classrooms, search and rescue operations, vehicular communication, wireless surveillance and military operations. In an ad hoc network, every node acts as a router, and forwards packets towards the destination. It is a self-organized network where every node cooperates to provide connectivity and services. [0005] MANET's or Mobile Ad hoc Networks have gained significant momentum as they are the solution for providing network services to mobile users at places where there is no infrastructure or an existing infrastructure needs wireless extensions. Wireless Mobile Ad Hoc Networks (MANETs) are very well suited to substitute current 802.11 Wireless Local Area Networks in practical implementations of semi-autonomous ground robots in Urban Search and Rescue (USAR) operations. MANETs are infrastructureless, self-configurable and self-forming networks with multi-hop capabilities, all very important features for USAR applications. However, node mobility may still cause partitions in the network topology, isolating robots from the network or even losing them, hindering the mission's success. [0006] Urban Search and Rescue (USAR) focuses on locating life and resources in collapsed buildings or disaster sites affected by artificial or natural calamities. These disaster sites pose several situational hazards that drastically affect the efficiency of human rescue teams. Disaster sites are inherently unsafe, and movement inside these sites is extremely restricted due to the availability of only small or no entry voids to explore the rubble. Vibrations might further affect the foundation of the collapsed construction and could trigger a secondary collapse. Disaster sites are usually contaminated by water/sewage distribution systems, toxic gas spills, body fluids and other hazardous materials and gases. All of the above mentioned factors make it imperative to look for other effective means to carry out rescue operations. The use of mobile robots provides an effective alternative for improved efficiency in USAR operations. Due to smaller sizes and robust design, robots can explore disaster sites that pose numerous hazard threats and are not conducive for exploration by relief workers. [0007] In USAR operations, and in general, in Safety, Security and Rescue (SSR) operations, a group of semi-autonomous ground vehicles is sent out to perform a determined mission under the guidance of the main controller, such as surveying a disaster site for life and resources. The success of the mission highly depends on the quality of the communication among the robots and the robots and the main controller. If communication is lost, the robots will lose contact with the main controller and the mission will likely fail. On the other hand, effective communication could actually enhance and increase the mission's success if it provided for a wider range of coverage, supported coordinated rescue operations and tele-operation, and guaranteed permanent connectivity despite network conditions and signal propagation effects. Communication among mobile robots and the main controller is currently known in the prior art to be achieved by using wireless local area networks (WLANs) based on the IEEE 802.11 standard. [0008] The idea of using a WLAN of mobile robots in USAR operations has several drawbacks. First, WLANs require networking (access point) and energy (power outlet for access point) infrastructures, which are not readily available at disaster sites. Second, WLANs must be set up and configured, taking away precious search and rescue time. Third, communication performance is heavily affected by interferences, signal propagation effects, and the distance of the mobile nodes from the access point. 802.11 WLANs have an automatic fallback mechanism that reduces the transmission rate according to the quality of the transmission media. This feature makes the exploration of distant areas from the access point really difficult and risky. Finally, WLANs can't guarantee permanent connectivity. In USAR operations, mobile robots maneuvering the disaster site would need to maintain constant communication with a stationary controller, transmitting search findings and location information. The main controller is usually stationary and provides scope for tele-operation and analyzes findings of the robots to provide meaningful information to the relief workers. To ensure this constant communication with the main controller, the mobile robots and the main controller need to stay within the transmission range of the access point. Nodes moving beyond the transmission range of the access point are considered lost unless they use inherent position awareness protocols to trace route back to the main controller or work on an autonomous manner. Loss of robots not only produces financial loss but also jeopardize the mission's final success. [0009] Most of the above mentioned issues could be resolved by forming a wireless mobile ad hoc network (MANET) of robots, where every node cooperates to provide connectivity and services. MANETs are self-organized and self-configured networks with multi-hop routing capabilities that operate without the need of any fixed infrastructure. Therefore, MANETs can be deployed and used rapidly, can drastically increase the area of coverage compared to WLANs, and can maintain communication with the main controller at all times in an easier manner, either by direct links or through intermediate nodes. MANETs may also reduce network congestion as routing remains distributed and the use of multi-hop routing may provide alternate routes for communication with the main controller. [0010] Associated with these advantages and application possibilities are some inherent drawbacks that hold MANETs from being used as the communication platform of choice for semi-autonomous robots in USAR applications. For example, the nodes in an ad hoc network can move arbitrarily in a random direction and speed, which results in a very dynamic topology with frequent link breakages, disrupting communication among nodes and the main controller. Signal propagation effects in those harsh environments also cause communication problems. Nodes operating in ad hoc networks usually rely on batteries for energy, thus for these nodes energy-efficient protocols become a critical design criterion. Also, bandwidth utilization is another significant factor of concern, thus necessitating reduced routing overhead and good congestion control mechanisms. [0011] By providing a constant communication link between the mobile robots and the main controller, it is ensured that the robots do not get lost. The term “node connectivity” is introduced here to denote the same. Node connectivity is defined as the ability of a node to continue or stop its mobility without breaking away from the network of nodes, while remaining in constant communication with the main controller. Forming an ad hoc network of the mobile robots and the main controller effectively addresses the issue of maximized area of coverage. By forming an ad hoc network, intermediate nodes act as a router forwarding packets towards the destination. By this method, robots continue their mobility beyond the transmission range of the main controller if an intermediate node exists through which it can establish a connection with the main controller. However, forming an ad hoc network of mobile robots does not address the issue of node connectivity. It is essential to ensure node connectivity in applications where loss of a node mobile robot in the case of urban and search and rescue operations could be detrimental to the performance of the system. [0012] The vast majority of the research work done in the area of ad hoc networks has been focused on designing and developing routing protocols to address the issues of node mobility, overhead and energy efficiency. There has been an increased attention in developing routing protocols that consider the issue of link stability and the design of link stability based routing protocols, where routes to the destination are selected based on the strength of signals received from neighboring nodes or the duration for which the link has been active. It is well-known that there is no unique routing protocol that satisfies the requirements of all types of applications and rather, routing protocols are designed to optimize the performance of the application under consideration. For example, while an ad hoc network of laptops in a classroom presents low or no mobility and infrequent topology changes, the topology of an ad hoc network of nodes with random mobility in a military environment is highly dynamic. Similarly, the requirements for an ad hoc network of robots operating in urban search and rescue environments is different as robots have low but random mobility and work in unfriendly environments for signal propagation. The idea of applying ad hoc networking to a team of mobile robots is known in the art. The protocols known in the art include, Topology Broadcast based on Reverse-Path Forwarding (TBRPF), Ad hoc On-Demand Distance Vector (AODV), Associativity Based Routing (ABR), Temporally Ordered Routing Algorithm (TORA) and Zone Routing Protocol (ZRP). However, none of the prior art solutions are capable of guarantying node connectivity considering the energy available in the robots and the signal strength, a quite important characteristic for USAR applications where the final goal is to extend the area of coverage, avoid network partitions and loss of robots, and also extend the length of the mission under harsh signal propagation environments. [0013] As illustrated in FIG. 1 , a stationary main controller, and 6 mobile nodes (robots) are connected to form an ad hoc network. Robots 1 , 2 , 3 and 4 are within the transmission range of the main controller (denoted by a circle), while robots 5 and 6 are outside its transmission range. This doesn't necessarily mean that robots 5 and 6 have lost their communication with main controller. For example, robot 6 can still communicate with the main controller through robot 2 . Here robot 2 acts as a router, transmitting packets to and from robot 6 . Similarly robot 5 can transmit its packets to the main controller through robot 3 or 4 . But as it can be seen, robot 2 is moving outside the transmission range of the main controller. This not only breaks the communication link between robot 2 and the main controller, but also the link between robot 6 and the main controller, as robot 2 was serving as the link between these two nodes. None of the existing routing protocols current known in the art address this issue as illustrated and described with reference to FIG. 1 . None of the prior art routing protocols is able to ensure that in addition to the existing demands of ad hoc networks such as node mobility, link stability, energy efficiency and reduced routing overhead, that the requirement for node connectivity is satisfied. [0014] Accordingly, what is needed in the art is a system and method that is effective in assuring node connectivity in an ad hoc network. [0015] However, in view of the prior art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in the pertinent art how the identified need could be fulfilled. SUMMARY OF INVENTION [0016] In accordance with the present invention is provided a system and method effective in establishing a control layer algorithm that finds and maintains stable links among the mobile nodes and the main controller of an ad hoc network considering the energy of the nodes and the quality of the signal, thereby assuring node connectivity within the ad hoc network. In accordance with the present invention, the term “node connectivity” is defined as the ability of a node to continue or stop its mobility without breaking away from the network of nodes, while remaining in constant communication with the main controller. [0017] The system and method in accordance with the present invention are implemented in a control layer that operates between the network and data link layers to provide for node connectivity. This modularity provides the flexibility of selecting the routing and link layer protocols that best suit the current application. In a particular embodiment, the control layer in accordance with the present invention is implemented on top of a MAC layer of the IEEE 802.11 type and below the Ad Hoc On-Demand Distance Vector (AODV) routing protocol. [0018] In a particular embodiment in the field of mobile search and rescue, the present invention provides for synergy between communications and control by implementing a control layer algorithm that considers the energy level in mobile nodes and the quality of the received signals to control the mobility of the robots and guarantee continuous node connectivity, avoiding loss of robots and network partitions. Accordingly, the present invention guarantees node connectivity, increases the area of coverage and the throughput in the network with minimum extra overhead under different mobility patterns. [0019] In accordance with the present invention is provided, a method to assure node connectivity in an ad hoc wireless network comprising a wireless main controller, a plurality of wireless nodes having a plurality of neighboring nodes and a plurality of wireless links connecting the wireless main controller, the plurality of wireless nodes and the plurality of neighboring nodes. The proposed method includes, computing a composite threshold for each of a plurality of neighboring nodes of a plurality of nodes, assigning a mobility to each of the plurality of nodes based on the composite threshold for each of the plurality of neighboring node and using the mobility assigned to each of the plurality of nodes to assure node connectivity in the ad hoc network. [0020] The composite threshold in accordance with the present invention is computed for each of the plurality of neighboring nodes for a particular node by transmitting a hello signal from each of the plurality of nodes, the hello signal comprising an energy level and a signal power level, receiving a plurality of transmitted hello signals at each of the plurality of nodes, the plurality of transmitted hello signals received from each of the plurality of neighboring nodes, identifying the signal power level and the energy level for each of the plurality of transmitted hello signals received from each of the plurality of neighboring nodes, accessing an information table stored at each of the plurality of nodes and computing a composite threshold for each of the neighboring nodes based on the information table. As such, the composite threshold is a measure of the quality and stability of a wireless connection between a node and each of the neighboring nodes. [0021] The information table in accordance with the present invention includes an entry for each of the plurality of neighboring nodes, a corresponding entry for the normalized energy level for each of the plurality of neighboring nodes and a corresponding entry for the normalized signal power level at which the hello packet was received from each of the neighboring nodes. [0022] In computing a composite threshold for each of the neighboring nodes a weighting factor, ALPHA is used. ALPHA is determined by identifying the normalized energy level for each of the plurality of neighboring nodes, identifying the normalized signal power level for the hello signal received from each of the neighboring nodes and calculating the composite threshold for each of the neighboring nodes based on the following relationship: composite threshold=(weighting factor*normalized energy level)+(1−weighting factor)*normalized signal power level) [0023] The normalized energy level is equal to a ratio of the energy level of each of the plurality of neighboring nodes to a predetermined maximum possible energy level for the node and the normalized signal power level is equal to a ratio of the signal power level of each of the plurality of neighboring nodes to a predetermined maximum possible signal power level for the node. In particular, the predetermined maximum possible energy level for the node is equal to the energy value of a node battery when fully charged and the predetermined maximum possible signal power level for the node is equal to the signal power level between two nodes in close proximity and assuming ideal transmission conditions. [0024] The weighting factor may be a dynamic weighting factor based on current network behavior or a static weighting factor. [0025] Once the composite threshold values for each of the neighboring nodes have been determined, they are stored in update table at each of the plurality of nodes and the update table is transmitted to the main controller. As such, the update table contains an entry for each of the plurality of neighboring nodes and a corresponding entry for the composite threshold for each of the plurality of neighboring nodes. [0026] In a particular embodiment, the method and system to assure node connectivity in accordance with the present invention are adapted to be implemented at a control layer, thereby operating between a routing layer and a data link layer. The routing layer may be selected from any number of routing protocols known in the art. In a particular embodiment, the routing layer selected is AODV protocol. Additionally, the data link layer may be selected from any number of data link layers known in the art and in a particular embodiment, the IEEE 802.11b MAC protocol is selected. [0027] Assigning a mobility to each of the plurality of nodes is based on the composite threshold for each of the plurality of neighboring nodes and further includes the steps of, evaluating the composite threshold for each of the plurality of neighboring nodes received from each of the plurality of nodes to determine if each of the plurality of nodes has a link connection to the main control and assigning a mobility to stop the movement of the node if the node if is determined to not have a link connection to the main controller. The link connection between the node and the main controller may be a direct connection or a connection through a safe neighbor, such that the link connection is above the composite threshold for the node. [0028] After the mobility of the node has been stopped, the mobility may be assigned to restart the movement of the node if the node is determined to have reestablished a link connection to the main controller or the a request may be made to move the node closer to the main controller. [0029] In a particular embodiment of the present invention, a computer readable medium for providing instructions for directing a processor to carry out a method to assure node connectivity in an ad hoc wireless network comprising a wireless main controller, a plurality of wireless nodes having a plurality of neighboring nodes and a plurality of wireless links connecting the wireless main controller, the plurality of wireless nodes and the plurality of neighboring nodes is provided. The instructions including steps for computing a composite threshold for each of a plurality of neighboring nodes and transmitting the composite threshold for each of a plurality of neighboring nodes and means for assigning a mobility to each of the plurality of nodes based on the composite threshold for each of the plurality of neighboring nodes and transmitting the assigned mobility to each of the plurality of nodes to assure node connectivity in the ad hoc network. [0030] As such, the present invention provides for the maintenance of a constant link between the mobile nodes and the main controller. The prevent invention provides additional benefits over the systems and methods currently known in the art. [0031] The present invention provides for a minimal increase in routing overhead thereby reducing congestion in the network conserving the battery power of the nodes. [0032] The present invention does not confine and restrict the area of coverage for providing node connectivity. [0033] The present invention considers the energy of each of the mobile nodes; as a node might be well within the transmission range of the main controller, yet have very little or no battery life. Such nodes should not be used to relay packets and should return to the main controller. [0034] The present invention provides for nodes at the threshold of a connection to stop their mobility if breaking away from this connection would disrupt the node's communication with the main controller. For example, robot 2 in FIG. 1 is at threshold, as its direction of movement is away from the main controller. Its mobility would break its connection with the main controller as well as the connection of robot 6 with the main controller, since robot 2 connects robot 6 . [0035] The present invention provides a means for nodes to constantly monitor the signal strength of the packets received from the neighboring nodes. [0036] Accordingly, the present invention guarantees node connectivity, increases the area of coverage and the throughput in the network with minimum extra overhead under different mobility patterns. BRIEF DESCRIPTION OF THE DRAWINGS [0037] For a fuller understanding of the invention, reference should be made to the following detailed description, taken in connection with the accompanying drawings, in which: [0038] FIG. 1 is an illustrative embodiment of an exemplary ad hoc network topology in accordance with the present invention. [0039] FIG. 2 is an illustration of the layered approach to implement the control layer method and system in accordance with the present invention. [0040] FIG. 3 is a flow diagram illustrating the logic flow at each of the nodes in accordance with the present invention. [0041] FIG. 4 is an exemplary information table in accordance with an embodiment of the present invention. [0042] FIG. 5 is a diagrammatic view of an exemplary network topology for an illustrative example in accordance with the present invention at time t=1 s. [0043] FIG. 6 is a table showing the illustrative data for the example at time t=1 s. [0044] FIG. 7 is a table illustrating the update table generated at each of the individual nodes in the illustrative example at time t=1.2 s. [0045] FIG. 8 is a table illustrating the data structure at the main controller in the illustrative example at time t=1.2 s. [0046] FIG. 9 is a diagrammatic view illustrating the network topology of the illustrative example at time t=50 s. [0047] FIG. 10 is a table illustrating the information table at time t=50 s for the illustrative example. [0048] FIG. 11 is a table illustrating the update table at time t=50.4 s for the illustrative example. [0049] FIG. 12 is a table illustrating the data structure at the main controller at time t=50.4 s for the illustrative example. [0050] FIG. 13 is a diagrammatic view illustrating the network topology of the illustrative example at time t=100 s. [0051] FIG. 14 is a table illustrating the information table at time t=100 s for the illustrative example. [0052] FIG. 15 is a table illustrating the update table at time t=100.8 s for the illustrative example. [0053] FIG. 16 is a table illustrating the data structure at the main controller at time t=100.8 s for the illustrative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT [0054] The present invention provides a system and method for the exchange of control message among mobile nodes and a main controller and the ability to stop the mobility of the robots when their connections with the main controller, either directly or through another mobile node, are in danger of being lost. The decision to stop the mobility of a node is based on the signal strength and the energy level of the surrounding nodes. [0055] With reference to FIG. 2 , the present invention is implemented in a control layer 10 that operates between the network routing layer 15 and data link layers 20 to provide for node connectivity. [0056] In a particular embodiment, the robots and the main controller are deployed at the same location at the start of a search and rescue operation. The main controller remains stationary throughout the entire operation and the robots begin to explore the disaster zone. [0057] Referring to FIG. 3 , which illustrates the flow diagram illustrating the logic at the local nodes in accordance with the present invention, after the main controller and the mobile nodes are stationed at the disaster site 25 , every mobile node broadcasts a periodic hello message with its energy information in a standard packet format 30 . The hello messages are exchanged based on a predetermined interval. The node receiving a broadcast message does not forward the packet, thus the packet is delivered only to the nodes that are within the transmission radius of the sender node. Each node that receives the hello messages 35 from its neighbors, calculates the signal strength at which the packet was received and inserts the energy value and power at which the packet was received in an information table 40 . An information table is maintained at every node, where, for each node in the network an entry is maintained. This table has fields corresponding to the neighboring node id, its normalized energy level, and the normalized power level at which the hello packet was received from that node. At periodic intervals every node in the network, computes the composite threshold for each of its neighboring nodes, based on the values in the information table 45 . The composite threshold refers to a combined value of energy and signal strength calculated using the following relationship: ((alpha*normalized_energylevel)+(I-alpha)*normalized_powerlevel) where ALPHA is a weighting factor determined by the system. [0058] In determining the values for the normalized_energylevel and the normalized_powerlevel, the battery power and signal power values stored in the information table of the nodes need to be normalized to the same scale before being used in the above given equation. The battery power is measured in joules and is usually a positive number in the range of zero to the maximum power of the battery. The signal strength is measured in decibels and is of the order of 10 −x , where the range of x depends on the wireless interface and other channel parameters. The battery power and the signal strength are converted to ratios, denoted as a fraction of the maximum energy and maximum signal strength possible according to the following relationship: normalized_energylevel=energy of neighboring node÷maximum energy possible for this node normalized_powerlevel=signal strength for this link÷maximum signal strength possible for any link from this node [0059] The maximum possible values for node energy and signal strength of any link are pre-determined and remain constant for the entire duration of the application. The maximum possible value for the energy level would be the energy value of the batteries when fully charged. And the maximum possible value for signal strength for any link would be the signal power level calculated between two nodes that are very close to each other assuming ideal transmission conditions. [0060] The value of ALPHA may be static or dynamic. A static value of ALPHA provides a constant weight factor for the energy and power levels of nodes and links, irrespective of the current nodes and network conditions. A more appropriate strategy is to dynamically change the value of ALPHA to adapt the calculation to reflect current network behavior. For example, at the start of the simulation, all nodes have energy values close to the maximum. In this case, it would be better to have a small ALPHA value, e.g. 0.1, thus giving more weight to the neighboring link power level. Similarly, when all the nodes are in close proximity to the main controller, the signal strength of the received packets would be close to maximum. An ALPHA value of 0.8 would be better, as the calculated composite threshold will be more biased toward energy values. To illustrate this aspect further, let us consider a more numerical example. Let us assume a network of 5 nodes and a main controller, with static a value of 0.5 at each node. With reference to the table in FIG. 4 , the values in the information table at node 1 along with their composite threshold values are given. As it can be seen from the table, node 4 has the best link with this node (normalized signal power of 0.63), while neighbor node 2 has the most energy (normalized energy value of 0.92). The table also shows the composite threshold for the neighbors of node 1 , calculated with a=0.5. This results in node 2 having the maximum value for composite threshold, and being chosen as the immediate parent for this node. The parent node is just the node having the maximum value for composite threshold among all the neighbors of a node and indicates the presence of a neighbor node through which a node can communicate with the main controller. In this case, it would have been better to choose node 4 as the parent node since it had better signal strength. An ALPHA value of 0.1 would have biased the calculation of composite threshold to the node with better power level, while an ALPHA value of 0.9 would have biased the calculation to the neighbor node with better energy level. Thus, in order to balance the biasing factor, ALPHA values are dynamically estimated. Each node has its own ALPHA value and is estimated based on the previous ALPHA value and the current data in the information table. The procedure is listed as an algorithm below and is run once every time the update table is updated by the nodes and sent to the main controller. [0061] It is to be noted that the energy and power level values of the node with maximum composite threshold need not necessarily be the maximum energy and power level values. Thus, if the maximum energy value in the information table is greater than the energy value of the node with the maximum composite threshold. ALPHA value is increased by the fraction of the difference between these two values. An increase in ALPHA value would result in higher weighting for the energy values in the computation of composite threshold. Similarly, if the maximum value for power level in the information table is greater than the power level of the node with maximum composite threshold, ALPHA value is decreased by the fraction of difference between these two values. [0062] Referring again to FIG. 3 , once determined, the value of the composite threshold is stored along with the corresponding neighbor id in the update table. Each node then forwards its update table to the main controller 50 . The main controller receives update tables from all nodes at periodic intervals and performs a local computation on each of the received tables to see if every node in the network has a connection to the main controller 50 . The main controller loops through every node in the network to check if it has a direct connection with the main controller or through any other intermediate node, or if it has such a connection, but is at the link threshold. The link threshold is the minimum composite threshold for the network below which the link is considered a weak link. The main controller sends a message to these nodes 55 , with its mobility flag set to false, thereby stopping the mobility of the node. Nodes that receive messages from the main controller with its mobility flag set to false, stop their mobility 60 (if not stopped already), and wait for a certain period of time to see if it receives a message from the main controller with mobility flag set to true, in which case it continues its mobility 65 . If this wait time expires, and the nodes do not receive a message from the main controller with mobility flag set to true, they begin to move towards the main controller as a preemptive measure. [0063] In a specific embodiment, the main controller receives update tables from every node in the network once every predetermined update interval, wherein the predetermined interval is the time interval between successive update packets sent by the individual nodes. The information in these tables is copied into a data structure maintained at the main controller. For each node in the network the main controller maintains a data structure comprising the number of neighbors of that node, mobility flag that specifies if that node is mobile or not, an array of neighbor id's, composite threshold values and the sequence number of the update packet expected from that node. Use of sequence numbers for update packets is similar to the implementation of sequence numbers for TCP packets. Entries in this data structure are modified as and when update packets are received. [0064] The main controller runs an algorithm once every predetermined interval to check for mobility status of every node in the network, wherein the predetermined interval is the time interval between successive loops through the algorithm at them main controller to check for mobility status of the nodes in the network. The algorithm loops through the information table of every node in the network, and checks for a connection to the main controller that is above the composite threshold. If no such link exists, then it finds the neighbor of this node that has the maximum value of composite threshold and looks in the information table of the neighbor node for a connection (The node that has the maximum value of composite threshold among all neighbors, should have its composite threshold greater than the link threshold). The algorithm stops the mobility of the mobile node, if after recursively iterating through the information table of all neighbors, it does not find a direct or multi-hop connection to the main controller. [0065] If there is no direct link between any of the nodes and the main controller, the algorithm recursively loops through every safe neighbor to find a link to the main controller. Safe neighbors are neighbor nodes that have a composite threshold value greater than link threshold. This ensures maximum safe area of coverage without loosing contact with the main controller. By making sure that all nodes have a direct or routed link to the main controller, the algorithm also ensures that there is a communication link between individual nodes, i.e. a tree structure of the network is always maintained. [0066] Accordingly, in a particular embodiment, the present invention uses a centralized mechanism to monitor the mobility of the nodes, and all nodes use the underlying distributed ad hoc routing protocol to exchange hello packets and send the computed information table to the main controller. However, it is the main controller that decides on the mobility of all the nodes based on the data in the information table, and hence this approach is classified as centralized. [0067] In a particular embodiment, the present invention utilizes AODV as the routing layer protocol to provide for routing information between nodes. The forwarding of update tables to the main controller once every predetermined interval relies on the underlying routing protocol for the transmission. The functionalities at the MAC layer required by an ad hoc network control layer are very similar to that required by a wireless network. In a specific embodiment, the IEEE 802.11 standard for wireless LAN's is chosen as the Medium Access Control (MAC) layer protocol, while the routing layer protocol is chosen from one of the several protocol designed specifically for ad hoc networks. This specific embodiment is not meant to be limiting and other routing layer protocols and wireless network protocols are within the scope of the present invention. [0068] Several variations are possible regarding the responsibilities of the main controller and the mobile nodes. In an additional embodiment of the invention, the proposed control layer is modified to work in a completely distributed manner. For instance, instead of computing the composite threshold at every node and sending this information to the main controller in an update table, each node could send its information table (consisting of neighbor id, energy level of the neighbor, and received signal power level), and the ALPHA value, and leave the computation to the main controller. This could help in reducing the computation time at the individual nodes at the expense of an increase in the routing overhead. [0069] In yet another embodiment, the control layer algorithm can also be modified so that the mobile nodes can have complete mobility control. Instead of having the main controller validate the mobility of nodes by iterating through the update tables received from each node, the network could be flooded with update tables from each node, so that every node in the network has a copy of the update table of the other nodes. By doing this, the control of deciding on mobility is left entirely to the individual nodes rather than to the main controller. [0070] In accordance with an exemplary embodiment of the present invention, consider the example of a 700 m×500 m disaster site being explored with a main controller 70 and 2 mobile robots, Node 1 75 and Node 2 77 , as shown with referenced to FIG. 5 . The main controller remains stationary during the entire course of the search and rescue operations. All three nodes exchange hello packets containing the node energy value, once every predetermined interval. The information table is maintained at each node and stores this energy information for its neighbors, along with the power level at which the packet was received. The power level of the received packets is used as an estimator of signal strength. Assuming the transmission range for a node to be 250 m, and a link threshold of 0.32, wherein the link threshold is the minimum value for the composite threshold, below which a link is considered to be a weak link. Let the interval between successive hello signals be 1 second, the interval between update tables sent to the main controller to be 1.2 seconds, and interval between the main controller monitoring the update table sent from the nodes to be 1.5 seconds. Also, ALPHA is set to 0.5 at all nodes, implying a constant weight factor between energy and power. The table as shown in FIG. 5 illustrates the values in the information table at node 1 , along with their composite threshold values. Assume all nodes move at a speed of 4 meters per second in a specific direction. Thus assuming that the nodes travel in a straight direction, they would be out of the transmission range of the main controller in 50 seconds. Nodes 1 and 2 are close to the main controller and their direction of movement is indicated. Hello messages are exchanged between the nodes, and data in the information table gets updated for each received hello message. The table of FIG. 6 shows the data stored in information table at time t=1. It is to be noted that energy and signal power values are normalized as previously explained, while updating the contents of the information table. At time t=1.2 s the function call to send the update table is evoked, that calculates composite threshold, estimates ALPHA value, and sends the update table to the main controller 70 . Using the equation for composite threshold previous given, the update tables are generated at the individual nodes as shown with reference to the table of FIG. 7 . [0071] To further illustrate the calculation of composite threshold, let us take the example of node 1. Node 2 is a neighbor of node 1 with energy level of 0.95 and signal power of 0.9. Hence the composite threshold for this neighbor of node 1 would be: (0.5*0.95)+(0.5*0.9) which is 0.925 [0073] After calculation of the composite threshold, each node estimates its ALPHA value. At node 1 , the neighbor that has the maximum value for composite threshold is the main controller (from update table). Thus the best_energylevel and best_powerlevel correspond to the energy and signal power values of this node, i.e, 0.96 and 0.92 respectively. Also, from the information table, it can be seen that the local_maxenergy and local_maxpower correspond to the values of the main controller. This implies that the current value of ALPHA is properly biased between energy and signal strength, and thus the ALPHA value for this node remains the same. Again among the neighbors of node 2 , the main controller has the maximum value for composite threshold. Variables best_energylevel and best_powerlevel correspond to values 0.93 and 0.9 respectively. But the values for local_maxenergy and local_maxpower correspond to 0.95 and 0.9 respectively. Despite having a greater energy value, node 1 doesn't have the maximum composite threshold value. Thus the alpha value is biased to give more weight to the energy value in the calculation of composite threshold. Since max(normalized energy)>normalized energy of node with max(composite threshold), [0074] ALPHA=ALPHA+(1−best_energylevel/local_maxenergy)=0.5+(1−0.93/0.95)=0.521 The ALPHA value for node 1 remains at 0.5, while node 2 now has an ALPHA value of 0.521, increased weight for energy value of neighbors. After ALPHA estimation, each node sends its update table to the main controller. On receiving these tables from the individual nodes, the main controller updates its data structure to reflect the current network topology. Thus at t=1.2 s, the main controller has a data structure similar to that of the table shown in FIG. 8 . At every predetermined interval (=1.5 in this case) the main controller runs its local algorithm to check for links from all nodes to itself. From the table in FIG. 8 , it can be seen that nodes 1 and 2 , both have a direct connection with the main controller, and is above the link threshold (=0.32). So both nodes can remain mobile, and the mobility flag for these nodes is set to true. [0075] FIG. 9 represents the network topology at time t=50.0 s. The table shown in FIG. 10 illustrates the information table at nodes 1 and 2 , updated based on the hello messages received from their neighbors at time t=50.0 seconds. Again at t=50.4 s, the function call to update table is evoked. Since ALPHA values are dynamically estimated every UPDATE INTERVAL, using the value of 0.5 and 0.521 for nodes 1 and 2 , estimated at t=1.2 s would not be appropriate. Thus ALPHA is assumed to be 0.2 at t=50.0 s. The generated update table is shown in the table of FIG. 11 . ALPHA values are estimated in the same way as in the previous case and is not shown here. At t=50.4 s, the nodes forward their update tables to the main controller, where the local data structure is updated based on the data received from the nodes in the network. The updated data structure at the main controller is shown in the table of FIG. 12 . [0076] The main controller executes its local algorithm at again at t=51 s. As can be seen from the table of FIG. 12 , node 1 has a direction with the main controller, but the composite threshold value is at the link threshold. So the algorithm loops through the update tables of other neighbors of this node, which have a composite threshold value greater than link threshold, for a connection to the main controller. The only other neighbor for node 1 is node 2 , and its composite threshold value is greater than link threshold. Hence the algorithm checks the neighbors list of node 2 for a strong link to the main controller. But node 2 has an even weaker connection to main controller (composite threshold=0.24), and hence the algorithm stops the mobility of node 1 since its only connection to the main controller is at threshold. The mobility flag of node 1 is set to false, and a message is sent to the node with the mobility flag. [0077] Similarly, the algorithm looks for a connection from node 2 to the main controller. The direct link from node 2 to the main controller is below the link threshold (=0.24), and the algorithm checks for a connection to main controller through other neighbors of this node which have threshold values greater than link threshold. Neighbor node 1 has a connection with the main controller, which is at link threshold. But since its mobility has already been stopped, and is not in danger of breaking away from the main controller, the algorithm sets node 1 as the parent node of 2 , and node 2 continues to have its mobility flag set to true. [0078] FIG. 13 presents the network topology at t=100 s. It is to be remembered that node 1 has its mobility flag set to false, and node 2 has its mobility based on node 1 , i.e. node 2 has a link to the main controller through node 1 . ALPHA value is assumed to be 0.3 at t=100 s. [0079] Based on the hello messages exchanged between the nodes at t=100 s, the information table of each node gets updated and is shown in the table of FIG. 14 . It is to be noted that there is no entry for the main controller in the table of node 2 , and this is due to the fact that node 2 has moved well beyond the transmission range of main controller and the hello messages broadcasted by the main controller are not received at node 2 . At t=100.4 s, the update table function is evoked by every node, which generates the update table shown in FIG. 15 for that node, estimates ALPHA value and sends out the update table to main controller. The contents of the data structure at the main controller get updated on receiving these tables form the mobile nodes and are shown in the table of FIG. 16 . Node 1 has its mobility flag set to false and the algorithm at the main controller is not able to find any better link to the main controller (this occurs if a node with a strong link to the main controller moves within the transmission range of node 1 ). But, node 2 now has only one neighbor, node 1 and this link has a composite threshold value equal to link threshold. Node 2 can still communicate with the main controller through node 1 , but both the links are at threshold limits. [0080] The algorithm at the main controller iterates through the data collected from update tables and checks for mobility of the nodes. A timer is attached to every node to keep track of the duration for which it has been stopped. Based on this time value, the main controller can issue callback functions to the nodes requesting them to move towards the base. [0081] This detailed exemplary embodiment is illustrative in nature and is not intended to limit the scope of the present invention. [0082] It will be seen that the advantages set forth above, and those made apparent from the foregoing description, are efficiently attained and since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matters contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. [0083] It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween. Now that the invention has been described,

In accordance with the present invention is provided, a method to assure node connectivity in an ad hoc wireless network comprising a wireless main controller, a plurality of wireless nodes having a plurality of neighboring nodes and a plurality of wireless links connecting the wireless main controller, the plurality of wireless nodes and the plurality of neighboring nodes. The proposed method includes, computing a composite threshold for each of a plurality of neighboring nodes of a plurality of nodes, assigning a mobility to each of the plurality of nodes based on the composite threshold for each of the plurality of neighboring node and using the mobility assigned to each of the plurality of nodes to assure node connectivity in the ad hoc network.

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a Divisional of U.S. application Ser. No. 14/104,914, filed Dec. 12, 2013, now U.S. Pat. No. 9,221,880, issued Dec. 29, 2015, which claims the benefit of U.S. Provisional Application Ser. No. 61/736,476, filed on Dec. 12, 2012. The entire content of the applications referenced above are hereby incorporated by reference herein. GOVERNMENT FUNDING This invention was made with government support under grants AI072766, AI104660 and GM041376 awarded by the National Institutes of Health. The government has certain rights in this invention. BACKGROUND Bacterial infectious diseases kill 100,000 persons each year in the US and 11 million persons each year worldwide, representing nearly a fifth of deaths each year worldwide (Heron et al., Final Data for 2006. National Vital Statistics Reports, Vol. 57 (Centers for Disease Control and Prevention, Atlanta Ga.) and World Health Organization (2008) The Global Burden of Disease: 2004 Update (World Health Organization, Geneva)). In the US, hospital-acquired bacterial infections strike 2 million persons each year, resulting in 90,000 deaths and an estimated $30 billion in medical costs (Klevins et al., (2007) Estimating health care-associated infections and deaths in U.S. hospitals. Public Health Reports, 122, 160-166; Scott, R. (2009) The direct medical costs of healthcare - associated infections in U.S. hospitals and benefits of prevention (Centers for Disease Control and Prevention, Atlanta Ga.)). Worldwide, the bacterial infectious disease tuberculosis kills nearly 2 million persons each year. One third of the world's population currently is infected with tuberculosis, and the World Health Organization projects that there will be nearly 1 billion new infections by 2020, 200 million of which will result in serious illness, and 35 million of which will result in death. For six decades, antibiotics have been a bulwark against bacterial infectious diseases. This bulwark is failing due to the appearance of resistant bacterial strains. For all major bacterial pathogens, strains resistant to at least one current antibiotic have arisen. For several bacterial pathogens, including tuberculosis, strains resistant to all current antibiotics have arisen. Bacterial RNA polymerase (RNAP) is a target for antibacterial therapy (Darst, S. (2004) Trends Biochem. Sci. 29, 159-162; Chopra, I. (2007) Curr. Opin. Investig. Drugs 8, 600-607; Villain-Guillot, P., Bastide, L., Gualtieri, M. & Leonetti, J. (2007) Drug Discov. Today 12, 200-208; Ho, M., Hudson, B., Das, K., Arnold, E., Ebright, R. (2009) Curr. Opin. Struct. Biol. 19, 715-723; and Srivastava et al. (2011) Curr. Opin. Microbiol. 14, 532-543). The suitability of bacterial RNAP as a target for antibacterial therapy follows from the fact that bacterial RNAP is an essential enzyme (permitting efficacy), the fact that bacterial RNAP subunit sequences are highly conserved (permitting broad-spectrum activity), and the fact that bacterial RNAP-subunit sequences are not highly conserved in human RNAP I, RNAP II, and RNAP III (permitting therapeutic selectivity). Accordingly, new antibacterial agents are needed. SUMMARY OF CERTAIN EMBODIMENTS OF THE INVENTION The invention provides new compositions of matter that inhibit bacterial RNA polymerase and inhibit bacterial growth. The compounds described herein are anticipated to have applications in analysis of RNA polymerase structure and function, control of bacterial gene expression, control of bacterial growth, antibacterial chemistry, antibacterial therapy, and drug discovery. Accordingly, the invention provides a compound according to general structural formula (I): wherein: X is one of —Br, —I, —OR, —SR, and —NHR; Y is one of —Br, —I, —OR, —SR, and —NHR; and at least one of X and Y is OH; each R is independently H or a branched or unbranched, saturated or unsaturated, hydrocarbon chain, having from 3 to 15 carbon atoms, wherein one or more of the carbon atoms is optionally replaced by (—O—) or (—NR a —), and wherein the chain is optionally substituted on carbon with one or more substituents independently selected from the group consisting of (C 1 -C 6 )alkoxy, (C 3 -C 6 )cycloalkyl, (C 1 -C 6 )alkanoyl, (C 1 -C 6 )alkanoyloxy, (C 1 -C 6 )alkoxycarbonyl, (C 1 -C 6 )alkylthio, azido, cyano, nitro, halo, hydroxy, oxo, carboxy, aryl, aryloxy, heteroaryl, heteroaryloxy, a hydrogen-bonding group, and a negatively charged functional group; and each R a is independently H or (C 1 -C 6 )alkyl; or a salt thereof. The invention provides methods of structure-based design, synthesis, and assay of a compound according to general structural formula (I). The invention provides use of a compound according to general structural formula (I), e.g., to promote an anti-bacterial effect. The invention also encompasses a crystal structure of a bacterial RNA polymerase in complex with salinamide A and a crystal structure of a bacterial RNA polymerase in complex with a compound according to general structural formula (I). The compounds of this invention have utility as RNAP inhibitors. The compounds of this invention have utility as antibacterial agents. The invention provides novel derivatives of salinamide A that contain replacements of the salinamide A epoxide that, it is believed, provide one or more of the following advantages as compared to the salinamide A epoxide: (1) improvement of interactions with the salinamide binding site and an adjacent pocket on a bacterial RNA polymerase (e.g., improving interactions with a residue corresponding to, and alignable with, one of residues beta678, beta1105, beta1106, beta′731, and beta′736 of Escherichia coli RNA polymerase), (2) increased potency of inhibition of a bacterial RNA polymerase, (3) increased potency of antibacterial activity, (4) increased stability, and (5) decreased genotoxicity. BRIEF DESCRIPTION OF THE FIGURES FIG. 1 . Structures of SalA (compound 1) and SalB (compound 2). FIGS. 2A-C . Crystal structure of RNAP in complex with Sal: overview. ( FIG. 2A ) Crystallization and refinement statistics for crystal structure of Escherichia coli RNAP holoenzyme in complex with SalA at 3.9 Å resolution. ( FIG. 2B ) Overall structure (two orthogonal views; gray surface labelled “*,” SalA; dark sphere, RNAP active-center Mg 2+ ion). ( FIG. 2C ) Electron density and model for SalA [two orthogonal views; mesh, F 0 -F C omit map for SalA (NCS averaged and contoured at 3.2σ); BH, bridge helix; FL, fork loop; LR, link region. FIGS. 3A-B . Crystal structure of RNAP in complex with Sal: details. ( FIG. 3A ) Stereoview showing RNAP-Sal interactions as observed in the crystal structure of Escherichia coli RNAP holoenzyme in complex with SalA at 3.9 Å resolution. Gray, RNAP backbone (ribbon representation) and RNAP side-chain atoms (stick representation). Dashed lines, H-bonds. ( FIG. 3B ) Schematic summary of contacts between RNAP and SalA. Black circle, part of SalA that has unobstructed access to RNAP secondary channel and RNAP active-center i+1 site. Dashed lines, H-bonds. Arcs, van der Waals interactions. FIGS. 4A-B . Crystal structure of RNAP in complex with Sal derivative. ( FIG. 4A ) Electron density, bromine anomalous difference density, and model for Escherichia coli RNAP holoenzyme in complex with Sal-Br (two orthogonal views). Dark mesh, F 0 -F C omit map for SalA (NCS averaged and contoured at 3.2σ); light mesh labelled “Br”, bromine anomalous difference density (contoured at 7σ); BH, bridge helix; FL, fork loop; LR, link region. ( FIG. 4B ) Schematic summary of contacts between RNAP and Sal-Br. Black circle, part of SalA that has unobstructed access to RNAP secondary channel and RNAP active-center i+1 site. Dashed lines, H-bonds. Arcs, van der Waals interactions. DETAILED DESCRIPTION OF THE INVENTION The following definitions are used, unless otherwise described: halo is fluoro, chloro, bromo, or iodo. Alkyl, alkoxy, alkenyl, alkynyl, etc. denote both straight and branched groups; but reference to an individual radical such as propyl embraces only the straight chain radical, a branched chain isomer such as isopropyl being specifically referred to. Aryl denotes a phenyl radical or an ortho-fused bicyclic carbocyclic radical having about nine to ten ring atoms in which at least one ring is aromatic. Heteroaryl encompasses a radical of a monocyclic aromatic ring containing five or six ring atoms consisting of carbon and one to four heteroatoms each selected from the group consisting of non-peroxide oxygen, sulfur, and N(X) wherein X is absent or is H, O, (C 1 -C 4 )alkyl, phenyl or benzyl, as well as a radical of an ortho-fused bicyclic heterocycle of about eight to ten ring atoms comprising one to four heteroatoms each selected from the group consisting of non-peroxide oxygen, sulfur, and N(X). The following definitions are used, unless otherwise indicated. The term “hydrogen-bonding group” includes moieties that contain an O, N, or S atom able to donate or accept a hydrogen bond in aqueous solution, such as, for example, amine, hydroxyl, thiol, ether, thioether, carbonyl, thionyl, carboxyl, thiocarboxyl, amide, thioamide, ester, thioester, sulfonic acid, sulfonic acid ester, sulfonamide, phosphoric acid, phosphoric acid ester, phosphonamide, boronic acid, boronic acid ester, pyrrole, pyrrolidine, carbazole, pyrroline, indole, isoindole, indoline, indolizine, furan, pyran, benzofuran, thiophene, benzothiophene, pyridine, quinoline, isoquinoline, quinazoline, napthyridine, oxazole, isoxazole, benzoxazole, thiazole, isothiazole, benthiazole, oxadiazole, thiadiazole, imidazole, triazole, tetrazole, benzimidazole, pyrazole, pyrazine, pyridazine, pyrimidine, triazine, indazole, purine, pteridine, phthalazine, quinoxaline, quinazoline, cinnoline, acridine, phenazine, phenothiazine, phenoxazine, and ionized forms and salts thereof, as known to those skilled in the art. The term “negatively charged functional group” includes moieties that contain an O, N, or S atom that predominantly carries a −1 negative charge in aqueous solution at a physiologically relevant pH, between about pH 4 and about pH 10, such as, for example, carboxyl, thiocarboxyl, sulfonic acid, phosphoric acid, phosphoric acid ester, boronic acid, triazole, tetrazole, purine, thiol, and ionized forms and salts thereof, as known to those skilled in the art. A combination of substituents or variables is permissible only if such a combination results in a stable or chemically feasible compound. The term “stable compounds,” as used herein, refers to compounds which possess stability sufficient to allow for their manufacture and which maintain the integrity of the compound for a sufficient period of time to be useful for the purposes detailed herein (e.g., formulation into therapeutic products, intermediates for use in production of therapeutic compounds, isolatable or storable intermediate compounds, treating a disease or condition responsive to therapeutic agents). Unless otherwise stated, structures depicted herein are also meant to include all stereochemical forms of the structure (i.e., the R and S configurations for each asymmetric center). Therefore, single stereochemical isomers, as well as enantiomeric and diastereomeric mixtures, of the present compounds are within the scope of the invention. Similarly, E- and Z-isomers, or mixtures thereof, of olefins within the structures also are within the scope of the invention. When a bond in a compound formula herein is drawn in a non-stereochemical manner (e.g. flat), the atom to which the bond is attached includes all stereochemical possibilities. When a bond in a compound formula herein is drawn in a defined stereochemical manner (e.g. bold, bold-wedge, dashed or dashed-wedge), it is to be understood that the atom to which the stereochemical bond is attached is enriched in the absolute stereoisomer depicted unless otherwise noted. In one embodiment, the compound may be at least 51% the absolute stereoisomer depicted. In another embodiment, the compound may be at least 60% the absolute stereoisomer depicted. In another embodiment, the compound may be at least 80% the absolute stereoisomer depicted. In another embodiment, the compound may be at least 90% the absolute stereoisomer depicted. In another embodiment, the compound may be at least 95 the absolute stereoisomer depicted. In another embodiment, the compound may be at least 99% the absolute stereoisomer depicted. Unless otherwise stated, structures depicted herein also are meant to include compounds that differ only by the presence of one or more isotopically enriched atoms. For example, compounds having the present structures except for the replacement of a hydrogen atom by a deuterium or tritium, or the replacement of a carbon by a 13 C- or 14 C-enriched carbon, are within the scope of this invention. Compounds of this invention may exist in tautomeric forms, such as keto-enol tautomers. The depiction of a single tautomer is understood to represent the compound in all of its tautomeric forms. The term “pharmaceutically acceptable,” as used herein, refers to a component that is, within the scope of sound medical judgment, suitable for use in contact with the tissues of humans and other mammals without undue toxicity, irritation, allergic response and the like, and are commensurate with a reasonable benefit/risk ratio. A “pharmaceutically acceptable salt” means any non-toxic salt that, upon administration to a recipient, is capable of providing, either directly or indirectly, a compound of this invention. Accordingly, certain embodiments of the invention are directed to salts of the compounds described herein, e.g., pharmaceutically acceptable salts. Acids commonly employed to form pharmaceutically acceptable salts include inorganic acids such as hydrogen bisulfide, hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid and phosphoric acid, as well as organic acids such as para-toluenesulfonic acid, salicylic acid, tartaric acid, bitartaric acid, ascorbic acid, maleic acid, besylic acid, fumaric acid, gluconic acid, glucuronic acid, formic acid, glutamic acid, methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, lactic acid, oxalic acid, para-bromophenylsulfonic acid, carbonic acid, succinic acid, citric acid, benzoic acid and acetic acid, as well as related inorganic and organic acids. Such pharmaceutically acceptable salts thus include sulfate, pyrosulfate, bisulfate, sulfite, bisulfate, phosphate, monohydrogenphosphate, dihydrogenphosphate, metaphosphate, pyrophosphate, chloride, bromide, iodide, acetate, propionate, decanoate, caprylate, acrylate, formate, isobutyrate, caprate, heptanoate, propiolate, oxalate, malonate, succinate, suberate, sebacate, fumarate, maleate, butyne-1,4-dioate, hexyne-1,6-dioate, benzoate, chlorobenzoate, methylbenzoate, dinitrobenzoate, hydroxybenzoate, methoxybenzoate, phthalate, terephthalate, sulfonate, xylene sulfonate, phenylacetate, phenylpropionate, phenylbutyrate, citrate, lactate, β-hydroxybutyrate, glycolate, maleate, tartrate, methanesulfonate, propanesulfonate, naphthalene-1-sulfonate, naphthalene-2-sulfonate, mandelate and other salts. In one embodiment, pharmaceutically acceptable acid addition salts include those formed with mineral acids such as hydrochloric acid and hydrobromic acid, and especially those formed with organic acids such as maleic acid. The pharmaceutically acceptable salt may also be a salt of a compound of the present invention having an acidic functional group, such as a carboxylic acid functional group, and a base. Exemplary bases include, but are not limited to, hydroxide of alkali metals including sodium, potassium, and lithium; hydroxides of alkaline earth metals such as calcium and magnesium; hydroxides of other metals, such as aluminum and zinc; ammonia, organic amines such as unsubstituted or hydroxyl-substituted mono-, di-, or tri-alkylamines, dicyclohexylamine; tributyl amine; pyridine; N-methyl, N-ethylamine; diethylamine; triethylamine; mono-, bis-, or tris-(2-OH—(C 1 -C 6 )-alkylamine), such as N,N-dimethyl-N-(2-hydroxyethyl)amine or tri-(2-hydroxyethyl)amine; N-methyl-D-glucamine; morpholine; thiomorpholine; piperidine; pyrrolidine; and amino acids such as arginine, lysine, and the like. Antibacterial Agents Specific values listed below for radicals, substituents, and ranges, are for illustration only; they do not exclude other defined values or other values within defined ranges for the radicals and substituents Specifically, (C 1 -C 6 )alkyl can be methyl, ethyl, propyl, isopropyl, butyl, iso-butyl, sec-butyl, pentyl, 3-pentyl, or hexyl; (C 3 -C 6 )cycloalkyl can be cyclopropyl, cyclobutyl, cyclopentyl, or cyclohexyl; (C 3 -C 6 )cycloalkyl can be cyclopropyl, cyclobutyl, cyclopentyl, or cyclohexyl; (C 1 -C 6 )alkoxy can be methoxy, ethoxy, propoxy, isopropoxy, butoxy, iso-butoxy, sec-butoxy, pentoxy, 3-pentoxy, or hexyloxy; (C 1 -C 6 )alkanoyl can be acetyl, propanoyl or butanoyl; (C 1 -C 6 )alkoxycarbonyl can be methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, isopropoxycarbonyl, butoxycarbonyl, pentoxycarbonyl, or hexyloxycarbonyl; (C 2 -C 6 )alkanoyloxy can be acetoxy, propanoyloxy, butanoyloxy, isobutanoyloxy, pentanoyloxy, or hexanoyloxy; aryl can be phenyl, indenyl, or naphthyl; and heteroaryl can be furyl, imidazolyl, triazolyl, triazinyl, oxazoyl, isoxazoyl, thiazolyl, isothiazoyl, pyrazolyl, pyrrolyl, pyrazinyl, tetrazolyl, pyridyl, (or its N-oxide), thienyl, pyrimidinyl (or its N-oxide), indolyl, isoquinolyl (or its N-oxide) or quinolyl (or its N-oxide). Certain embodiments of the present invention provide a compound of general structural formula (I): wherein: X is one of —Br, —I, —OR, —SR, and —NHR; Y is one of —Br, —I, —OR, —SR, and —NHR; and at least one of X and Y is OH; R is H or a branched or unbranched, saturated or unsaturated, hydrocarbon chain, having from 3 to 15 carbon atoms, wherein one or more of the carbon atoms is optionally replaced by (—O—) or (—NR a —), and wherein the chain is optionally substituted on carbon with one or more substituents independently selected from the group consisting of (C 1 -C 6 )alkoxy, (C 3 -C 6 )cycloalkyl, (C 1 -C 6 )alkanoyl, (C 1 -C 6 )alkanoyloxy, (C 1 -C 6 )alkoxycarbonyl, (C 1 -C 6 )alkylthio, azido, cyano, nitro, halo, hydroxy, oxo, carboxy, aryl, aryloxy, heteroaryl, heteroaryloxy, a hydrogen-bonding group, and a negatively charged functional group; and each R a is independently H or (C 1 -C 6 )alkyl; or a salt thereof. In certain embodiments the compound of formula (I) is a compound of formula (Ia): In certain embodiments R is a branched or unbranched, saturated or unsaturated, hydrocarbon chain, having from 3 to 8 carbon atoms, wherein one or more of the carbon atoms is optionally replaced by (—O—) or (—NR a —), and wherein the chain is optionally substituted on carbon with one or more substituents independently selected from the group consisting of (C 1 -C 6 )alkoxy, (C 1 -C 6 )alkanoyl, (C 1 -C 6 )alkanoyloxy, (C 1 -C 6 )alkoxycarbonyl, halo, hydroxy, oxo, carboxy, aryl, aryloxy, a hydrogen-bonding group, and a negatively charged functional group. In certain embodiments, R consists of a chain of about 3 to about 6 consecutively bonded non-hydrogen atoms and preferably contains a hydrogen-bonding or negatively charged functional group. In certain embodiments, X is one of —Br and —I. In certain embodiments, X is one of —OR, —SR, and —NHR, and R is H or consists of a chain of about 3 to about 8 consecutively bonded non-hydrogen atoms and optionally contains one or more (e.g., 1, 2, or 3) hydrogen-bonding or negatively charged functional groups. In certain embodiments, X is one of —OR, —SR, and —NHR, and R is H or consists of a chain of about 3 to about 8 consecutively bonded non-hydrogen atoms and contains one or more (e.g., 1, 2, or 3) hydrogen-bonding or negatively charged functional groups. In certain embodiments, X is one of —OR, —SR, and —NHR, and R is H or consists of a chain of about 3 to about 6 consecutively bonded non-hydrogen atoms and optionally contains one or more (e.g., 1, 2, or 3) hydrogen-bonding or negatively charged functional groups. In certain embodiments, X is one of —OR, —SR, and —NHR, and R is H or consists of a chain of about 3 to about 6 consecutively bonded non-hydrogen atoms and contains one or more (e.g., 1, 2, or 3) hydrogen-bonding or negatively charged functional groups. In certain embodiments, X is one of —O(CH 2 ) n C(OH)(R′)R″, —O(CH 2 ) n C(O)R′, —O(CH 2 ) n C(O)OR′, —O(CH 2 ) n C(O)NR′R″, —O(CH 2 ) n OC(H)(R′)R″, —S(CH 2 ) n C(OH)(R′)R″, —S(CH 2 ) n C(O)R′, —S(CH 2 ) n C(O)OR′, —S(CH 2 ) n C(O)NR′R″, —S(CH 2 ) n OC(H)(R′)R″, —NH(CH 2 ) n C(OH)(R′)R″, —NH(CH 2 ) n C(O)R′, —NH(CH 2 ) n C(O)OR′, —NH(CH 2 ) n C(O)NR′R″, and —NH(CH 2 ) n OC(H)(R′)R″; wherein n is 1, 2, 3, 4, 5, 6, or 7; and wherein R′ and R″ each independently is one of H, C 1 -C 3 alkyl, and C 1 -C 3 alkyl substituted by one or more (e.g. 1, 2, or 3) halogen. In certain embodiments, Y is OH. In certain embodiments, Y is one of —Br and —I. In certain embodiments, Y is one of —OR, —SR, and —NHR, and R is H or consists of a chain of about 3 to about 8 consecutively bonded non-hydrogen atoms and optionally contains one or more (e.g., 1, 2, or 3) hydrogen-bonding or negatively charged functional groups. In certain embodiments, Y is one of —OR, —SR, and —NHR, and R is H or consists of a chain of about 3 to about 8 consecutively bonded non-hydrogen atoms and contains one or more (e.g., 1, 2, or 3) hydrogen-bonding or negatively charged functional groups. In certain embodiments, Y is one of —OR, —SR, and —NHR, and R is H or consists of a chain of about 3 to about 6 consecutively bonded non-hydrogen atoms and optionally contains one or more (e.g., 1, 2, or 3) hydrogen-bonding or negatively charged functional groups. In certain embodiments, Y is one of —OR, —SR, and —NHR, and R is H or consists of a chain of about 3 to about 6 consecutively bonded non-hydrogen atoms and contains one or more (e.g., 1, 2, or 3) hydrogen-bonding or negatively charged functional groups. In certain embodiments, Y is one of —O(CH 2 ) n C(OH)(R′)R″, —O(CH 2 ) n C(O)R′, —O(CH 2 ) n C(O)OR′, —O(CH 2 ) n C(O)NR′R″, —O(CH 2 ) n OC(H)(R′)R″, —S(CH 2 ) n C(OH)(R′)R″, —S(CH 2 ) n C(O)R′, —S(CH 2 ) n C(O)OR′, —S(CH 2 ) n C(O)NR′R″, —S(CH 2 ) n OC(H)(R′)R″, —NH(CH 2 ) n C(OH)(R′)R″, —NH(CH 2 ) n C(O)R′, —NH(CH 2 ) n C(O)OR′, —NH(CH 2 ) n C(O)NR′R″, and —NH(CH 2 ) n OC(H)(R′)R″; wherein n is 1, 2, 3, 4, 5, 6, or 7; and wherein R′ and R″ each independently is one of H, C 1 -C 3 alkyl, and C 1 -C 3 alkyl substituted by one or more (e.g. 1, 2, or 3) halogen. In certain embodiments, n is 1, 2, 3, 4, or 5. Certain embodiments of the present invention provide a method of structure-based design of a compound described here that includes inspection of a crystal structure of a bacterial RNA polymerase in complex with one of salinamide A and a compound described herein. Certain embodiments of the present invention provide a method of synthesis of a compound described herein, comprising reaction of salinamide A with HX in the presence of an acid. Certain embodiments of the present invention provide a method of synthesis of a compound described herein, comprising reaction of salinamide A with HX in the presence of a base. Certain embodiments of the present invention provide a method of synthesis of a compound described herein, comprising reaction of salinamide A with YX, wherein Y is a cation. Certain embodiments of the present invention provide a method of synthesis of a compound described herein, comprising reaction of salinamide B with HX in the presence of a base. Certain embodiments of the present invention provide a method of synthesis of a compound described herein, comprising reaction of salinamide B with YX, wherein Y is a cation. Certain embodiments of the present invention provide an assay for inhibition of a RNA polymerase comprising contacting a bacterial RNA polymerase with a compound described herein. Certain embodiments of the present invention provide an assay for potential antibacterial activity comprising contacting a bacterium with a compound described herein. Certain embodiments of the present invention provide a use of a compound described herein as an inhibitor of a bacterial RNA polymerase. Certain embodiments of the present invention provide a use of a compound described herein as an antibacterial agent. Certain embodiments of the present invention provide a use of a compound described herein as one of a disinfectant, a sterilant, an antispoilant, an antiseptic, and an antiinfective. Certain embodiments of the present invention provide a pharmaceutical composition comprising a compound of formula (I), or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier. Certain embodiments of the present invention provide a compound of formula (I), or a pharmaceutically acceptable salt thereof, for use in therapy. Certain embodiments of the present invention provide a method to treat a bacterial infection in an animal (e.g. a mammal, such as a human) comprising administering a compound of formula (I), or a pharmaceutically acceptable salt thereof, to the animal. The invention also provides a synthetic intermediate of formula 7 or 9: or a salt thereof. The synthetic intermediates are useful for preparing other compounds of formula (I). Applicant has synthesized the compound according to general structural formula (I) wherein X is bromine. Applicant has shown that the compound according to general structural formula (I) wherein X is bromine potently inhibits bacterial RNA polymerase (RNAP) in vitro ( Escherichia coli RNAP; IC50=0.78±0.05 μM [radiochemical assay]; Staphylococcus aureus RNAP; IC50=0.54±0.04 μM [radiochemical assay]), and does not detectably inhibit human RNAP I, H, and III (IC50>100 μM [radiochemical assay]) Applicant has shown that the compound according to general structural formula (I) wherein X is bromine exhibits potent antibacterial activity against Gram-negative bacteria in culture ( Escherichia coli D21f2tolC, MIC50=0.049 μg/ml; Enterobacter cloacae , MIC50=1.56 μg/ml; Neisseria gonorrhoeae , MIC50=1.56 μg/ml; Haemophilus influenzae , MIC50=6.25 μg/ml; Pseudomonas aeruginosa , MIC50=50 μg/ml), and does not detectably inhibit growth of mammalian cells in culture (Vero E6 cells, MIC>50 μg/ml). Applicant has synthesized the compounds according to general structural formula (I) wherein X is —OH, —OBu, —NH(CH 2 ) 3 NHBoc, and —NH(CH 2 ) 3 NHBoc). Applicant has shown that the compounds according to general structural formula (I) wherein wherein X is —OH, —OBu, —NH(CH 2 ) 3 NHBoc, or —NH(CH 2 ) 3 NHBoc potently inhibit bacterial RNAP in vitro ( Escherichia coli RNAP; IC50s=0.3-6 μM [fluorescence-detected assays]; Table 1). Applicant has shown that the compounds according to general structural formula (I) wherein X is —OH, —OBu, —NH(CH 2 ) 3 NHBoc, or —NH(CH 2 ) 3 NHBoc exhibit potent antibacterial activity against Gram-negative bacteria in culture ( Escherichia coli D21f2tolC, MIC50s=0.78-1.56 μg/ml; Enterobacter cloacae , MIC50s=12.5-100 μg/ml; Table 2). Applicant has determined crystal structures of (1) Escherichia coli RNAP in complex with salinamide A and (2) Escherichia coli RNAP in complex with the compound according to general structural formula (I) wherein X is bromine. The crystal structures enable structure-based design of compounds according to general structural formula (I). Salinamides Compounds according to general structural formula (I) are analogs of salinamide A (Sal; SalA; compound 1) and salinamide B (SalB; compound 2). SalA and SalB are bicyclic depsipeptides, each consisting of seven amino-acid residues and two non-amino-acid residues (Trischman et al., J. Am. Chem. Soc., 116:757-758, 1994; Moore et al., J. Org. Chem., 64:1145-1150, 1999; FIG. 1 ). Residue 9 of SalA contains an epoxide moiety. Residue 9 of SalB contains a chlorohydrin moiety. SalA and SalB are produced by Streptomyces sp. CNB-091, a marine bacterium isolated from the surface of the jellyfish Cassiopeia xamachana (Trischman et al., J. Am. Chem. Soc., 116:757-758, 1994; Moore et al., J. Org. Chem., 64:1145-1150, 1999; Moore & Seng, Tetrahedron Lett. 39:3915-3918, 1998). SalA also is produced by Streptomyces sp. NRRL 21611, a soil bacterium (Miao et al., J. Nat. Prod. 60, 858-861, 1997). A total synthesis of SalA has been reported (Tan & Ma, Angew. Chem. Int. Ed. 47:3614-3617, 2008). Salinamides: RNAP-Inhibitory Activity and Antibacterial Activity It has been reported previously that SalA inhibits Gram-positive and Gram-negative bacterial RNAP in vitro (Miao et al., J. Nat. Prod. 60, 858-861, 1997). It is disclosed herein that SalB also inhibits Gram-positive and Gram-negative bacterial RNAP in vitro. It further is disclosed herein that SalA and SalB do not detectably inhibit human RNAP I, II, and III. It has been reported previously that SalA and SalB exhibit antibacterial activity against Gram-positive bacterial pathogens (Trischman et al., J. Am. Chem. Soc., 116:757-758, 1994; Moore et al., J. Org. Chem., 64:1145-1150, 1999). It is disclosed herein that SalA and SalB exhibit antibacterial activity against Gram-negative bacterial pathogens, including Enterobacter cloacae, Haemophilus influenzae, Neisseria gonorrhoeae , and Pseudomonas aeruginosa . It further is disclosed herein that SalA and SalB do not detectably inhibit growth of mammalian cells in culture. The inhibition of bacterial RNAP by Sal accounts, in part or in whole, for the antibacterial activity of Sal (Ebright et al., WO/2012/129173, 2012). Sal inhibits RNA synthesis not only in vitro but also in bacterial cells in culture (Ebright et al., WO/2012/129173, 2012). Mutations in genes encoding RNAP beta and beta′ subunits confer resistance to the antibacterial activity of Sal (Ebright et al., WO/2012/129173, 2012). Salinamides: Binding Site on RNAP The binding site on bacterial RNAP for Sal—the“Sal target” (also referred to as the “bridge-helix-cap target”)—was identified by mapping sites of substitutions that confer Sal-resistance onto the three-dimensional structure of RNAP (Ebright et al., WO/2012/129173, 2012). The binding site on bacterial RNAP for Sal was confirmed by determining crystal structures of Escherichia coli RNAP holoenzyme in the absence of Sal (resolution=4.0 Å) and Escherichia coli RNAP holoenzyme in the presence of Sal (resolution=4.2 Å) (Ebright et al., WO/2012/129173, 2012). Comparison of electron density maps revealed difference density attributable to Sal. The difference density was located in the Sal target and was in contact with or close to sites of substitutions conferring Sal resistance are obtained. The resolution was sufficient to conclude that the Sal target is the binding site on RNAP for Sal, and that sites of substitutions that confer Sal-resistance correspond to RNAP residues of RNAP that contact or are close to Sal. However, the resolution was insufficient to define the orientation of Sal relative to the Sal target and to define interatomic contacts between Sal and the Sal target. Disclosed herein are crystal structures of Escherichia coli RNAP holoenzyme in the absence of Sal and Escherichia coli RNAP holoenzyme in the presence of Sal at a resolution sufficient to define the orientation of Sal relative to the Sal target and to define interatomic contacts between Sal and the Sal target (resolution, =3.9 Å; FIGS. 2A-C and 3 A-B). Further disclosed herein are electron density and bromine anomalous difference density for Escherichia coli RNAP holoenzyme in complex with Sal-Br, the compound according to general structural formula (I) wherein X is bromine ( FIGS. 4A-B ). The location of the Sal-Br bromine anomalous difference density peak relative to the Sal target unequivocally confirms the orientation of Sal relative to the Sal target ( FIGS. 4A-B ). The Sal target is located adjacent to, and partly overlaps, the RNAP polymerase active center (Ebright et al., WO/2012/129173, 2012). It is inferred that Sal most likely inhibits RNAP by inhibiting RNAP active-center function. The Sal target does not overlap the RNAP active-center Mg 2+ ion and does not overlap RNAP residues that interact with the DNA template, the RNA product, or the nucleoside triphosphate substrate (Ebright et al., WO/2012/129173, 2012). It is inferred Sal inhibits RNAP active-center function allosterically, through effects on RNAP conformation, rather than through direct interactions with RNAP residues that mediate bond formation, product binding, and substrate binding. The Sal target overlaps an RNAP active-center module referred to as the “bridge-helix cap,” which, in turn, comprises three active-center subregions: the “bridge-helix N-terminal hinge” (BH—H N ), the “F-loop,” and the “link region” (Ebright et al., WO/2012/129173, 2012). It has been proposed that the BH—H N undergoes hinge-opening/hinge-closing conformational changes coupled to, and essential for, the nucleotide-addition cycle in RNA synthesis, and that the F-loop and link region, coordinate these conformational changes (Weinzierl, BMC Biol. 8:134, 2010; Hein & Landick, BMC Biol. 8:141, 2010; Kireeva et al., BMC Biophys. 5:11-18, 2012; Nedialkov et al., Biochim. Biophys. Acta 1829:187-198, 2013). It is inferred that Sal may inhibit RNAP active-center function by inhibiting BH—H N hinge-opening and/or hinge-closing (Ebright et al., WO/2012/129173, 2012). The Sal target is located close to, but does not overlap, the target of the rifamycin antibacterial agents (e.g., rifampin, rifapentine, rifabutin, and rifalazil), which are RNAP inhibitors in current clinical use in antibacterial therapy (Ebright et al., WO/2012/129173, 2012; see Darst. Trends Biochem. Sci. 29:159-162, 2004; Chopra, Curr. Opin. Investig. Drugs 8:600-607, 2007; Villain-Guillot et al., Drug Discov. Today 12:200-208, 2007; Ho et al., Curr. Opin. Struct. Biol. 19:715-723, 2009). Consistent with the lack of overlap between the Sal target and the rifamycin target, Sal-resistant mutants are not cross-resistant to rifamycins, and rifamycin-resistant mutants are not cross-resistant to Sal (Ebright et al., WO/2012/129173, 2012). The Sal target also is located close to, but does not overlap, the target of CBR703, an RNAP inhibitor under investigation for clinical use in antibacterial therapy (Ebright et al., WO/2012/129173, 2012; see Darst. Trends Biochem. Sci. 29:159-162, 2004; Chopra, Curr. Opin. Investig. Drugs 8:600-607, 2007; Villain-Guillot et al., Drug Discov. Today 12:200-208, 2007). Consistent with the lack of overlap between the Sal target and the CBR703 target, Sal-resistant mutants are not cross-resistant to CBR703, and CBR703-resistant mutants are not cross-resistant to Sal (Ebright et al., WO/2012/129173, 2012). It is disclosed herein that the Sal target does not overlap the targets of the RNAP inhibitors streptolydigin, myxopyronin, and lipiarmycin (see Chopra, Curr. Opin. Investig. Drugs 8:600-607, 2007; Villain-Guillot et al., Drug Discov. Today 12:200-208, 2007; Ho et al., Curr. Opin. Struct. Biol. 19:715-723, 2009; Srivastava et al., Curr. Opin. Microbiol. 14:532-543, 2011). The Sal target is located adjacent to, but does not overlap, the streptolydigin target. The Sal target is distant from the myxopyronin and lipiarmycin targets. It further is disclosed herein that, consistent with the absence of overlap between the Sal target and the streptolydigin, myxopyronin, and lipiarmycin targets, Sal-resistant mutants do not exhibit cross-resistance with streptolydigin, myxopyronin, and lipiarmycin, and, conversely, streptolydigin-resistant, myxopyronin-resistant, and lipiarmycin-resistant mutants do not exhibit cross-resistance with Sal. Salinamides: Mechanism of Inhibition of RNAP It is disclosed herein that Sal inhibits RNAP through a mechanism that is different from the mechanisms of rifamycins, streptolydigin, myxopyronin, and lipiarmycin. It is disclosed herein that Sal does not inhibit formation of the RNAP-promoter open complex in transcription initiation. This result indicates that Sal inhibits RNAP through a mechanism different from the mechanisms of myxopyronin and lipiarmycin (which inhibit formation of RNAP-promoter open complex). It is disclosed herein that Sal inhibits nucleotide addition in both transcription initiation and transcription elongation. Sal inhibits both primer-dependent transcription initiation and de novo transcription initiation. In primer-dependent transcription initiation, Sal inhibits all nucleotide-addition steps, including the first nucleotide-addition step yielding a 3-nucleotide RNA product from a 2-nucleotide RNA primer and an NTP. In de novo transcription initiation, Sal inhibits all nucleotide-addition steps, including the first nucleotide-addition step yielding a 2-nucleotide RNA product from two NTPs. These results confirm that Sal inhibits RNAP through a mechanism different from the mechanisms of myxopyronin and lipiarmycin (which do not inhibit transcription elongation) and indicate that Sal inhibits RNAP through a mechanism different from the mechanism of rifamycins (which do not inhibit the first nucleotide addition step in transcription initiation and which do not inhibit transcription elongation). It is disclosed herein that transcription inhibition by Sal does not require the RNAP active-center subregion referred to as the trigger loop. Sal inhibits wild-type RNAP and an RNAP-derivative having a deletion of the trigger loop to equal extents and with nearly equal concentration-dependences. This result indicates that Sal inhibits RNAP through a mechanism different from the mechanisms of streptolydigin (for which transcription inhibition requires the trigger loop). It is disclosed herein that transcription inhibition by Sal is noncompetitive with respect to NTP substrate. It is inferred that Sal does not inhibit the NTP binding sub-reaction of the nucleotide-addition cycle, but, instead, inhibits one or more of the bond-formation, pyrophosphate-release, and translocation sub-reactions of the nucleotide-addition cycle. Salinamides: Novel Sal Analogs The syntheses disclosed herein of Sal-Br, Sal-OH, Sal-OR, Sal-SR, and Sal-NHR show that the SalA epoxide moiety and SalB chlorohydrin moieties provide chemical reactivity that can be exploited for semi-synthesis of novel Sal analogs (Examples 3-7). The observation that certain synthesized Sal analogs retain RNAP-inhibitory activity and antibacterial activity shows that certain substitutions of the SalA epoxide moiety and SalB chlorohydrin moiety can be tolerated without loss of activity (Tables 1-2). The crystal structure of RNAP-Sal indicates that the SalA epoxide moiety and SalB chlorohydrin moiety make few or no interactions with RNAP and are located at the entrance to the Sal binding pocket, directed towards the RNAP secondary channel and the RNAP active-center i+1 site ( FIGS. 3A-B and 4 A-B). These findings set the stage for structure-based design of semi-synthetic, novel Sal analogs with increased potency. By way of example, appending a sidechain that carries hydrogen-bonding functionality at the SalA epoxide moiety or SalB chlorohydrin moiety, could provide favorable hydrogen-bonded interactions with polar residues on the floor of the RNAP secondary channel (e.g., residues β678, β31105, β1106, β′731, and β′736 in RNAP from Escherichia coli , and residues corresponding to, and alignable with, these residues in RNAP from other bacterial species). By further way of example, appending a sidechain carrying negatively charged functionality at the SalA epoxide moiety or SalB chlorohydrin moiety could provide favorable electrostatic interactions with positively charged residues on the floor of the RNAP secondary channel (e.g., residues β678, β31106, and β′731 in RNAP from Escherichia coli , and residues corresponding to, and alignable with, these residues in RNAP from other bacterial species). Administration of Pharmaceutical Compositions The compounds described herein may be formulated as pharmaceutical compositions and administered to a mammalian host, such as a human male or female patient in a variety of forms adapted to the chosen route of administration (e.g., orally or parenterally, by intravenous, intramuscular, topical or subcutaneous routes). Thus, the present compounds may be systemically administered, e.g., orally, in combination with a pharmaceutically acceptable vehicle such as an inert diluent or an assimilable edible carrier. They may be enclosed in hard or soft shell gelatin capsules, may be compressed into tablets, or may be incorporated directly with the food of the patient's diet. For oral therapeutic administration, the active compound may be combined with one or more excipients and used in the form of ingestible tablets, buccal tablets, troches, capsules, elixirs, suspensions, syrups, wafers, and the like. Such compositions and preparations should contain at least 0.1% of active compound. The percentage of the compositions and preparations may, of course, be varied and may conveniently be between about 2 to about 60% of the weight of a given unit dosage form. The amount of active compound in such therapeutically useful compositions is such that an effective dosage level will be obtained. The tablets, troches, pills, capsules, and the like may also contain the following: binders such as gum tragacanth, acacia, corn starch or gelatin; excipients such as dicalcium phosphate; a disintegrating agent such as corn starch, potato starch, alginic acid and the like; a lubricant such as magnesium stearate; and a sweetening agent such as sucrose, fructose, lactose or aspartame or a flavoring agent such as peppermint, oil of wintergreen, or cherry flavoring may be added. When the unit dosage form is a capsule, it may contain, in addition to materials of the above type, a liquid carrier, such as a vegetable oil or a polyethylene glycol. Various other materials may be present as coatings or to otherwise modify the physical form of the solid unit dosage form. For instance, tablets, pills, or capsules may be coated with gelatin, wax, shellac or sugar and the like. A syrup or elixir may contain the active compound, sucrose or fructose as a sweetening agent, methyl and propylparabens as preservatives, a dye and flavoring such as cherry or orange flavor. Of course, any material used in preparing any unit dosage form should be pharmaceutically acceptable and substantially non-toxic in the amounts employed. In addition, the active compound may be incorporated into sustained-release preparations and devices. The active compound may also be administered intravenously or intraperitoneally by infusion or injection. Solutions of the active compound or its salts can be prepared in water, optionally mixed with a nontoxic surfactant. Dispersions can also be prepared in glycerol, liquid polyethylene glycols, triacetin, and mixtures thereof and in oils. Under ordinary conditions of storage and use, these preparations contain a preservative to prevent the growth of microorganisms. The pharmaceutical dosage forms suitable for injection or infusion can include sterile aqueous solutions or dispersions or sterile powders comprising the active ingredient which are adapted for the extemporaneous preparation of sterile injectable or infusible solutions or dispersions, optionally encapsulated in liposomes. In all cases, the ultimate dosage form should be sterile, fluid and stable under the conditions of manufacture and storage. The liquid carrier or vehicle can be a solvent or liquid dispersion medium comprising, for example, water, ethanol, a polyol (for example, glycerol, propylene glycol, liquid polyethylene glycols, and the like), vegetable oils, nontoxic glyceryl esters, and suitable mixtures thereof. The proper fluidity can be maintained, for example, by the formation of liposomes, by the maintenance of the required particle size in the case of dispersions or by the use of surfactants. The prevention of the action of microorganisms can be brought about by various antibacterial and antifungal agents, for example, parabens, chlorobutanol, phenol, sorbic acid, thimerosal, and the like. In many cases, it will be preferable to include isotonic agents, for example, sugars, buffers or sodium chloride. Prolonged absorption of the injectable compositions can be brought about by the use in the compositions of agents delaying absorption, for example, aluminum monostearate and gelatin. Sterile injectable solutions are prepared by incorporating the active compound in the required amount in the appropriate solvent with various of the other ingredients enumerated above, as required, followed by filter sterilization. In the case of sterile powders for the preparation of sterile injectable solutions, the preferred methods of preparation are vacuum drying and the freeze drying techniques, which yield a powder of the active ingredient plus any additional desired ingredient present in the previously sterile-filtered solutions. For topical administration, the present compounds may be applied in pure form, e.g., when they are liquids. However, it will generally be desirable to administer them to the skin as compositions or formulations, in combination with a dermatologically acceptable carrier, which may be a solid or a liquid. Useful solid carriers include finely divided solids such as talc, clay, microcrystalline cellulose, silica, alumina and the like. Useful liquid carriers include water, alcohols or glycols or water-alcohol/glycol blends, in which the present compounds can be dissolved or dispersed at effective levels, optionally with the aid of non-toxic surfactants. Adjuvants such as fragrances and additional antimicrobial agents can be added to optimize the properties for a given use. The resultant liquid compositions can be applied from absorbent pads, used to impregnate bandages and other dressings, or sprayed onto the affected area using pump-type or aerosol sprayers. Thickeners such as synthetic polymers, fatty acids, fatty acid salts and esters, fatty alcohols, modified celluloses or modified mineral materials can also be employed with liquid carriers to form spreadable pastes, gels, ointments, soaps, and the like, for application directly to the skin of the user. Examples of useful dermatological compositions which can be used to deliver the compounds of formula I to the skin are known to the art; for example, see Jacquet et al. (U.S. Pat. No. 4,608,392), Geria (U.S. Pat. No. 4,992,478), Smith et al. (U.S. Pat. No. 4,559,157) and Wortzman (U.S. Pat. No. 4,820,508). Useful dosages of the compounds of formula I can be determined by comparing their in vitro activity, and in vivo activity in animal models. Methods for the extrapolation of effective dosages in mice, and other animals, to humans are known to the art; for example, see U.S. Pat. No. 4,938,949. The amount of the compound, or an active salt or derivative thereof, required for use in treatment will vary not only with the particular salt selected but also with the route of administration, the nature of the condition being treated and the age and condition of the patient and will be ultimately at the discretion of the attendant physician or clinician. In general, however, a suitable dose will be in the range of from about 0.5 to about 150 mg/kg, e.g., from about 10 to about 125 mg/kg of body weight per day, such as 3 to about 75 mg per kilogram body weight of the recipient per day, preferably in the range of 6 to 120 mg/kg/day, most preferably in the range of 15 to 90 mg/kg/day. The compound may be conveniently formulated in unit dosage form; for example, containing 5 to 1000 mg, conveniently 10 to 750 mg, most conveniently, 50 to 500 mg of active ingredient per unit dosage form. In one embodiment, the invention provides a composition comprising a compound of the invention formulated in such a unit dosage form. The desired dose may conveniently be presented in a single dose or as divided doses administered at appropriate intervals, for example, as two, three, four or more sub-doses per day. The sub-dose itself may be further divided, e.g., into a number of discrete loosely spaced administrations; such as multiple inhalations from an insufflator or by application of a plurality of drops into the eye. The invention will now be illustrated by the following non-limiting Examples. EXAMPLES Example 1 Crystal Structure of RNAP in Complex with Sal Crystal structures of Escherichia coli RNAP holoenzyme at 3.9 Å resolution and Escherichia coli RNAP holoenzyme in complex with SalA at 3.9 Å resolution were determined as follows: Crystallization trials were performed using Crystal Former microfluidic chips (Microlytic, Inc.) and SmartScreen solutions (Microlytic, Inc.) (precipitant inlet: 1.5 μl screening solution; sample inlet: 1.5 μl 10 mg/ml Escherichia coli RNAP holoenzyme in 10 mM Tris-HCl, pH 7.9, 100 mM NaCl, 1% glycerol; 22° C.). Under one condition, small crystals appeared within two days. Conditions were optimized using the hanging-drop vapor-diffusion technique at 22° C. The optimized conditions (reservoir: 500 μl 0.1 M HEPES, pH 7.0, 0.2 M CaCl 2 , and 18% PEG400; drop: 1 μl 10 mg/ml Escherichia coli RNAP holoenzyme in 10 mM Tris-HCl, pH 7.9, 100 mM NaCl, 1% glycerol plus 1 μl reservoir solution; 22° C.) yielded large crystals with dimensions of 0.2 mm×0.2 mm×0.2 mm in one week. SalA was soaked into RNAP crystals, yielding RNAP-Sal crystals, by addition of 0.2 μl 20 mM SalA or Sal-Br in (±)-2-methyl-2,4-pentanediol (Hampton Research, Inc.) to the crystallization drop and incubation 30 min at 22° C. RNAP and RNAP-SalA crystals were transferred to reservoir solutions containing 15% (v/v) (2R, 3R)-(−)-2, 3-butanediol (Aldrich, Inc.) and then flash-cooled with liquid nitrogen. Diffraction data were collected from cryo-cooled crystals at Cornell High Energy Synchrotron Source beamline F1 and at Brookhaven National Laboratory beamline X25. Data were processed using HKL2000. The structure of Escherichia coli RNAP holoenzyme was solved by molecular replacement using AutoMR. The search model was generated by starting with the crystal structure of Thermus thermophilus RNAP-promoter open complex (PDB 4G7H), deleting DNA and non-conserved protein domains, modelling Escherichia coli RNAP holoenzyme α I and α II subunit N-terminal domains by superimposing the crystal structure of Escherichia coli RNAP holoenzyme α N-terminal domain dimer (PRB 1BDF), and modelling Escherichia coli RNAP holoenzyme β, β′, ω, and σ 70 subunits using Sculptor (backbone and sidechain atoms for identical residues; backbone and Cβ atoms for non-identical residues). Two RNAP molecules were present in the asymmetric unit. Crystal structures of Escherichia coli RNAP holoenzyme α subunit C-terminal domain (PDB 3K4G), the Escherichia coli RNAP holoenzyme β subunit β2-βi4 and βflap-βi9 domains (PDB 3LTI and PDB 3LU0), and Escherichia coli RNAP holoenzyme σ 70 region 2 (PDB 1 SIG) were fitted manually to the (Fo-Fc) difference electron density map. Early-stage refinement of the structure was performed using Phenix and included rigid-body refinement of each RNAP molecule in the asymmetric unit, followed by rigid-body refinement of each subunit of each RNAP molecule, followed by rigid-body refinement of 216 segments of each RNAP molecule, followed by group B-factor refinement with one B-factor group per residue, using Phenix. Density modification, including non-crystallographic-symmetry averaging and solvent flattening, were performed to remove model bias and to improve phases. The resulting maps allowed segments that were not present in the search model to be built manually using Coot. Cycles of iterative model building with Coot and refinement with Phenix improved the model. The final E. coli RNAP holoenzyme model, refined to Rwork and Rfree of 0.276 and 0.325, respectively, was deposited in the PDB with accession code 4MEY. The structure of Escherichia coli RNAP holoenzyme coli in complex with SalA was solved by molecular replacement in AutoMR, using the above crystal structure of Escherichia coli RNAP holoenzyme as the search model. After rigid-body refinement with 216 domains, an electron density feature corresponding to one molecule of SalA per holoenzyme was clearly visible in the (Fo-Fc) difference map. A structural model of SalA derived from the crystal structure of SalB (CSD 50962; enantiomorph corrected based on Moore et al., et al., J. Org. Chem., 64:1145-1150, 1999) was fitted to the (Fo-Fc) difference map with minor adjustments of SalA conformation. The final Escherichia coli RNAP holoenzyme-SalA complex model, refined to Rwork and Rfree of 0.286 and 0.325, respectively, was deposited in the PDB with accession code 4MEX. The structure of E. coli RNAP holoenzyme in complex with Sal at 3.9 Å resolution shows unambiguous experimental electron density for Sal in the genetically-defined Sal target, confirming the hypothesis that the Sal target represents the Sal binding site on RNAP ( FIGS. 2A-C ). The structure shows that Sal binds within the RNAP bridge-helix cap, making direct interactions with the BH—H N , the fork loop, and the link region ( FIGS. 2A-C and 3 A-B). Sal makes direct interactions with all residues at which substitutions conferring highest-level (≧128-fold) Sal-resistance are obtained (β′ residues R738, A779, and G782, and β residues D675 and N677; FIGS. 3A-B ). Six residues that make direct contact with SalA are conserved across Gram-positive bacterial RNAP, Gram-negative bacterial RNAP, and human RNAP. Eight residues that contact Sal are conserved in Gram-positive bacterial RNAP and Gram-negative bacterial RNAP, but are not conserved, and indeed are radically different, in human RNAP. The observed interactions account for and explain the observation that Sal inhibits Gram-positive and Gram-negative bacterial RNAP, but does not inhibit human RNAP. Sal binds within a ˜600 Å 3 pocket formed by the BH—H N , the fork loop, and the link region. Backbone atoms of residues that form the pocket have the same conformations in RNAP holoenzyme in the absence of Sal and in RNAP holoenzyme in complex with Sal, indicating that the pocket pre-exists in RNAP holoenzyme in the absence of Sal. The pocket opens at one end onto the RNAP secondary channel and the RNAP active-center “i+1” NTP-insertion site. It seems likely that Sal enters the pocket from the RNAP secondary channel or the active-center “i+1” site. Within the binding pocket, Sal residues 4, 5, 7, and 8 interact with the RNAP BH—H N , Sal residues 1-3 and 6-7 interact with the RNAP fork loop, and Sal residues 8 and 9 interact with the RNAP link region ( FIGS. 3A-B ). Sal residue 9 is at the end of the pocket that opens onto the RNAP secondary channel and the active-center “i+1” site ( FIGS. 3A-B ). The Sal residue-9 epoxide moiety and methyl moiety extend into this opening and make only limited interactions with residues of RNAP ( FIGS. 3A-B ). The crystal structure of the RNAP-Sal complex also defines effects of Sal on RNAP conformation. The crystal structure of RNAP-Sal shows that Sal interacts with the BH—H N in an “open” (unbent) state. This conformation is different from the “closed” (bent) BH—H N conformation that has been observed in molecular-dynamics simulations of nucleotide-addition reactions in transcription elongation complexes, and that has been postulated to serve as an intermediate in the pyrophosphate-release and/or translocation reactions of the nucleotide-addition cycle (Weinzierl, BMC Biol. 8:134, 2010; Hein & Landick, BMC Biol. 8:141, 2010; Kireeva et al., BMC Biophys. 5:11-18, 2012; Nedialkov et al., Biochim. Biophys. Acta 1829:187-198, 2013). It is inferred that Sal interacts with an “open” (unbent) BH—H N conformational state, and it is hypothesized that, through its interactions with that state, Sal stabilizes that state and inhibits BH—H N conformational dynamics required for nucleotide addition. In the crystal structure of RNAP-Sal, the RNAP active-center trigger loop is disordered. Modeling indicates that the structure of RNAP-Sal could accommodate the “open” (unfolded) trigger loop conformations observed in crystal structures of some transcription initiation and elongation complexes, but could not accommodate the “closed” (folded) trigger loop conformations observed in other crystal structure of transcription initiation and elongation complexes. It is inferred that Sal favors “open” (unfolded) trigger loop conformational states, and may disfavor the “closed” (folded) trigger loop conformational states. However, experiments with an RNAP derivative lacking the trigger loop indicate that the trigger loop is not essential for transcription inhibition by Sal. Therefore, although effects of Sal on trigger loop conformation could contribute to transcription inhibition by Sal, they are neither necessary nor sufficient for transcription inhibition by Sal. The interactions observed in the structure, or predicted based on the structure, suggest opportunities for preparation of novel Sal analogs with improved potencies by use of semi-synthesis or by total synthesis. The structure shows that the SalA residue-9 epoxide moiety is directed toward the RNAP secondary channel and RNAP active-center “i+1” site ( FIGS. 3A-B ) but makes limited interactions with RNAP ( FIGS. 3A-B ). The SalA epoxide can be altered with little or no loss of activity (Tables 1-2), and has unique chemical reactivity (Examples 3-5). Accordingly, it is inferrd herein that it should be possible—by semi-synthesis or by total synthesis—to append at the SalA residue-9 epoxide moiety by chemical functionality that makes favorable interactions with the RNAP secondary channel or active-center “i+1” site, thereby increasing the potency of RNAP inhibitory activity and potentially increasing the potency of antibacterial activity. The structure predicts that the SalB residue-9 chlorohydrin moiety likewise makes limited interactions with RNAP and is directed toward the RNAP secondary channel and RNAP active-center “i+1” site and. The SalB chlorohydrin can be altered with little loss of activity (Tables 1-2), and has unique chemical reactivity (Examples 6-7). Accordingly, it is inferred herein that it should be possible—by semi-synthesis or by total synthesis—to append at the SalB residue-9 chlorohydrin moiety chemical functionality that makes favorable interactions with the RNAP secondary channel or active-center “i+1” site, thereby increasing the potency of RNAP inhibitory activity and potentially increasing the potency of antibacterial activity. By way of example, appending a sidechain that carries hydrogen-bonding functionality at the SalA residue-9 epoxide moiety or SalB residue-9 chlorohydrin moiety, could allow for favorable hydrogen-bonded interactions with polar residues on the floor of the RNAP secondary channel (e.g., residues β678, β1105, β1106, β′731, and β′736 in RNAP from Escherichia coli , and residues corresponding to, and alignable with, these residues in RNAP from other bacterial species). By further way of example, appending a sidechain carrying negatively charged functionality at the SalA residue-9 epoxide moiety or SalB residue-9 chlorohydrin moiety could allow for favorable electrostatic interactions with positively charged residues on the floor of the RNAP secondary channel (e.g., residues β678, β1106, and β′731 in RNAP from Escherichia coli , and residues corresponding to, and alignable with, these residues in RNAP from other bacterial species). Example 2 Crystal Structure of RNAP in Complex with Sal Derivative To confirm the binding position and binding orientation of Sal inferred from the crystal structure of RNAP-SalA, x-ray diffraction data and bromine anomalous scattering data were collected for crystals of Escherichia coli RNAP holoenzyme soaked with the bromine-containing Sal derivative Sal-Br (compound 3; crystal soaks, structure determination, and structure refinement performed essentially as described for SalA in Example 1). Sal-Br contained a residue-9 bromohydrin moiety analogous to the residue-9 chlorohydrin moiety of SalB, and was prepared by semi-synthesis from SalA, exploiting the chemical reactivity of the SalA residue-9 epoxide (Example 3). Sal-Br exhibited essentially full RNAP-inhibitory activity and antibacterial activity (Tables 1-2). Electron density for Sal-Br from crystals of RNAP-Sal-Br complex matched electron density for SalA in the RNAP-SalA complex. Bromine anomalous difference density showed a single peak ( FIGS. 3A-B ). The peak was located adjacent to the electron density for Sal-Br, in the position predicted for the bromine atom of the Sal-Br residue-9 bromohydrin carbon atom ( FIGS. 3A-B ). The results unequivocally define the SalA and Sal-Br binding positions and binding orientations. Example 3 Synthesis of Sal Derivatives Exploiting Reactivity of SalA Epoxide: Sal-Br (Compound 3) SalA (1; 5 mg; 4.9 μmol; prepared as in Trischman et al., J. Am. Chem. Soc., 116:757, 1994; provided by William Fenical, Scripps Institution of Oceanography) was dissolved in 0.25 ml chloroform at 25° C. To the solution was added 48% HBr (10 μl, 89 μmol; Aldrich). The reaction mixture was stirred 15 min at 25° C., and then quenched with 200 μl 50% sodium bicarbonate. The organic layer was separated, re-washed with 100 μl water, and dried to a white solid. Products were purified using silica flash chromatography (0-10% methanol in chloroform as eluent). Yield: 5 mg, 93%. MS (MALDI): calculated: m/z 1099.41, 1101.41. found: 1122.48, 1124.48 (M+Na + ). Example 4 Synthesis of Sal Derivatives Exploiting Reactivity of SalA Epoxide: Sal-OH (Compound 4) SalA (1; 1 mg; 0.98 μmol; prepared as in Trischman et al., J. Am. Chem. Soc., 116:757, 1994; provided by William Fenical, Scripps Institution of Oceanography) was dissolved in 0.5 ml n-butanol, and 1 μl 98% sulfuric acid was added. The reaction mixture was heated 10 min at 100° C. in a microwave reactor (Initiator, Biotage, Inc.), cooled to 25° C., and then neutralized with 400 μl 50% sodium bicarbonate. The organic layer was retrieved and evaporated to dryness. Products were purified by reversed-phase HPLC [Luna C18, 5μ, 100 A, 250 mm×4.6 mm (Phenomenex, Inc.); A, 60% methanol; B, 75% methanol; 0-15 min, 0% B; 15-30 min, 0-100% B; flow rate 1 ml/min)]. Compound 4 eluted at 38 min. Yield: 80 μg, 7.7%. MS (MALDI): calculated: m/z 1037.50. found: 1060.50 (M+Na + ). Example 5 Synthesis of Sal Derivatives Exploiting Reactivity of SalA Epoxide: Sal-OR 5.1. Sal-OBu A (Compound 5A) and Sal-OBu B (Compound 5B) SalA (1; 1 mg; 0.98 μmol; prepared as in Trischman et al., J. Am. Chem. Soc., 116:757, 1994; provided by William Fenical, Scripps Institution of Oceanography) was dissolved in 0.5 ml n-butanol, and 1 μl 98% sulfuric acid was added. The reaction mixture was heated 10 min at 100° C. in a microwave reactor (Initiator, Biotage, Inc.), cooled to 25° C., and then neutralized with 400 μl 50% sodium bicarbonate. The organic layer was retrieved and evaporated to dryness. Products were purified by reversed-phase HPLC [Luna C18, 5μ, 100 A, 250 mm×4.6 mm (Phenomenex, Inc.); A, 60% methanol; B, 75% methanol; 0-15 min, 0% B; 15-30 min, 0-100% B; flow rate 1 ml/min)]. Compound 5A eluted at 56 min. Compound 5B eluted at 53 min. Compound 5A: Yield: 140 μg, 9%. MS (MALDI): calculated: m/z 1093.62. found: 1094.63, 1116.59 (M+Na + ). Compound 5B: Yield: 69 μg, 4.4%. MS (MALDI): calculated: m/z 1093.62. found: 1094.63, 1116.59 (M+Na + ). Example 6 Synthesis of Sal Derivatives Exploiting Reactivity of SaIA Epoxide: Sal-SR 6.1. Sal-SBu (Compound 6) Compound 6 is prepared as described for compound 5A, except that 0.5 ml benzene, 5 μmol lithium perchlorate, and 10 μmol butanethiol are used in place of 0.5 ml n-butanol, and 1 μl 98% sulfuric acid. Example 7 Synthesis of Sal Derivatives Exploiting Reactivity of SalB Chlorohydrin: Sal—NHR 7.1. Sal-NH(CH 2 ) 3 NHBoc (Compound 7) SalB (2; 5 mg; 4.7 μmol; prepared as in Trischman et al., J. Am. Chem. Soc., 116:757, 1994; provided by William Fenical, Scripps Institution of Oceanography) was dissolved in 1 ml ethanol, and N-Boc-1,3-diaminopropane (3.4 mg, 19.5 μmol; Aldrich, Inc.) was added. The reaction mixture was heated 5 min at 150° C. in a microwave reactor (Initiator; Biotage, Inc.), cooled to 25° C., and then evaporated to dryness. Products were purified by reversed-phase HPLC [Luna C18, 5μ, 100 A, 250 mm×4.6 mm (Phenomenex, Inc.); A, 60% methanol; B, 75% methanol; 0-15 min, 0% B; 15-30 min, 0-100% B; flow rate 1 ml/min)]. Compound 7 eluted at 35 min. Yield: 0.261 mg, 4.5%. MS (MALDI): calculated: m/z 1193.39. found: 1216.71 (M+Na + ). 7.2. Sal-NH(CH 2 ) 3 NHBoc (Compound 8) Compound 8 is prepared from compound 7 by reaction with 50 μl trifluoroacetic acid in 200 μl chloroform for 30 min at 25° C., and is purified by reversed-phase HPLC. 7.3. Sal-NH(CH 2 ) 6 NHBoc (Compound 9) SalB (2; 10 mg; 9.5 μmol; prepared as in Trischman et al., J. Am. Chem. Soc., 116:757, 1994; provided by William Fenical, Scripps Institution of Oceanography) was dissolved in 1 ml ethanol, and N-Boc-1,6-diaminohexane (4.1 mg, 18.95 μmol; Acros, Inc.) was added. The reaction mixture was heated 6 min at 160° C. in a microwave reactor (Initiator; Biotage, Inc.), cooled to 25° C., and then evaporated to dryness. Products were purified by reversed-phase HPLC [Luna C18, 5μ, 100 A, 250 mm×4.6 mm (Phenomenex, Inc.); A, 60% methanol; B, 75% methanol; 0-15 min, 0% B; 15-30 min, 0-100% B; flow rate 1 ml/min)]. Compound 8 eluted at 39 min. Yield: 1.46 mg, 14%. MS (MALDI): calculated: m/z 1235.67. found: 1236.56 (M+H + ), 1258.58 (M+Na + ). 7.4. Sal-NH(CH 2 ) 6 NHBoc (Compound 10) Compound 10 is prepared from compound 9 by reaction with 50 μl trifluoroacetic acid in 200 μl chloroform for 30 min at 25° C. and is purified by reversed-phase HPLC. Example 8 RNAP-Inhibitory Activity Radiochemical RNAP assays with Escherichia coli RNAP and Staphylococcus aureus RNAP were performed as follows: Reaction mixtures contained (10 μl): 0-100 μM test compound, bacterial RNAP holoenzyme [75 nM Escherichia coli RNAP holoenzyme (prepared as in Mukhopadhyay et al., Meths. Enzymol. 371:144-159, 2003) or 75 nM Staphylococcus aureus RNAP core enzyme and 300 nM Staphylococcus aureus σ A (prepared as in Srivastava et al., Curr. Opin. Microbiol. 14:532-543, 2011)], 20 nM DNA fragment N25-lacUV5-14 [positions −100 to −1 of the bacteriophage T5 N25 promoter followed by positions +1 to +29 of the lacUV5(+10 A;+15C) promoter; prepared by PCR amplification of a synthetic nontemplate-strand oligodeoxyribonucleotide], 0.5 mM ApA, 100 μM □[α 32 P]UTP (0.2 Bq/fmol), 100 μM ATP, and 100 μM GTP in TB (50 mM Tris-HCl, pH 7.9, 100 mM KCl, 10 mM MgCl 2 , 1 mM DTT, 100 μg/ml bovine serum albumin, and 5% glycerol). Reaction components except DNA, ApA, and NTPs were pre-incubated 10 min at 24° C.; DNA was added and reaction mixtures were incubated 10 min at 37° C.; ApA, 0.15 μl 7 μM [α 32 P]UTP (200 Bq/fmol), ATP, and GTP were added and reaction mixtures were incubated 5 min at 37° C.; and 0.5 μl 2 mM UTP was added and reaction mixtures were incubated 5 min at 37° C. Reactions were terminated by adding 10 μl A loading buffer (80% formamide, 10 mM EDTA, 0.02% bromophenol blue, and 0.02% xylene cyanol) and heating 2 min at 95° C. Products were applied to 7 M urea 15% polyacrylamide (19:1 acrylamide:bisacrylamide) slab gels (Bio-Rad), electrophoresed in TBE (90 mM Tris-borate, pH 8.0, and 2 mM EDTA), and analyzed by storage-phosphor scanning (Typhoon; GE Healthcare, Inc.). Radiochemical assays with human RNAP I, II, and III were performed essentially as described [Sawadogo and Roeder, Cell 43:165-75, 1985]. Reaction mixtures contained (20 μl): 0-100 μM test compound, 8 U HeLaScribe Nuclear Extract (Promega, Inc.), 1 μg human placental DNA (Sigma-Aldrich), 400 μM ATP, 400 μM [α 32 P]UTP (0.11 Bq/fmol), 400 μM CTP, 400 μM GTP, 50 mM Tris-HCl, pH 8.0, 7 mM HEPES-NaOH, 70 mM (NH 4 ) 2 SO 4 , 50 mM KCl, 12 mM MgCl 2 , 5 mM DTT, 0.1 mM EDTA, 0.08 mM phenylmethylsulfonyl fluoride, and 16% glycerol. Reaction components other than DNA and NTPs were pre-incubated 10 min at 30° C., DNA was added and reaction mixtures were incubated 15 min at 30° C., NTPs were added and reaction mixtures were incubated 60 min at 30° C. Reaction mixtures were spotted on DE81 filter discs (Whatman, Inc.; pre-wetted with water) and incubated 1 min at room temperature. Filters were washed with 3×3 ml Na 2 HPO 4 , 2×3 ml water, and 3 ml ethanol, using a filter manifold (Hoefer, Inc.). Filters were placed in scintillation vials containing 10 ml Scintiverse BD Cocktail (Thermo Fisher, Inc.), and radioactivity was quantified by scintillation counting (LS6500; Beckman-Coulter, Inc.). Fluorescence-detected RNAP assays with Escherichia coli RNAP were performed by a modification of the procedure of Kuhlman et al., Anal. Biochem. 324:183-190, 2004]. Reaction mixtures contained (20 μl): 0-100 nM test compound, 75 nM Escherichia coli RNAP σ 70 holoenzyme, 20 nM 384 bp DNA fragment containing the bacteriophage T4 N25 promoter, 100 μM ATP, 100 μM GTP, 100 μM UTP, 100 μM CTP, 50 mM Tris-HCl, pH 8.0, 100 mM KCl, 10 mM MgCl 2 , 1 mM DTT, 10 μg/ml bovine serum albumin, and 5.5% glycerol. Reaction components other than DNA and NTPs were pre-incubated for 10 min at 37° C. Reactions were carried out by addition of DNA and incubation for 5 min at 37° C., followed by addition of NTPs and incubation for 60 min at 37° C. DNA was removed by addition of 1 μl 5 mM CaCl 2 and 2 U DNaseI (Ambion, Inc.), followed by incubation for 90 min at 37° C. RNA was quantified by addition of 100 μl RiboGreen RNA Quantitation Reagent (Invitrogen, Inc.; 1:500 dilution in Tris-HCl, pH 8.0, 1 mM EDTA), followed by incubation for 10 min at 25° C., followed by measurement of fluorescence intensity [excitation wavelength=485 nm and emission wavelength=535 nm; QuantaMaster QM1 spectrofluorometer (PTI, Inc.)]. Half-maximal inhibitory concentrations (IC50s) were calculated by non-linear regression in SigmaPlot (SPSS, Inc.). Example 9 Antibacterial Activity Antibacterial activity was quantified using broth microdilution [Clinical and Laboratory Standards Institute (CLSI/NCCLS), Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria That Grow Aerobically; Approved Standard, Eighth Edition. CLIS Document M 07- A 8 (CLIS, Wayne Pa.), 2009]. Assays with Enterobacter cloacae ATCC13047, Pseudomonas aeruginosa ATCC 10145, and Escherichia coli D21f2toIC, employed a starting cell density of 2-5×10 5 cfu/ml, Mueller Hinton II cation adjusted broth (BD Biosciences, Inc.), and an air atmosphere. Assays with Haemophilus influenzae ATCC49247 and Neisseria gonorrhoeae ATCC19424 employed a starting cell density of 2-5×10 5 cfu/ml, Haemophilus Test Medium broth (Barry et al., 1993) and a 5% CO2/95% air atmosphere. MIC50 was defined as the minimal concentration resulting in ≧50% inhibition of bacterial growth. Example 10 Cytotoxicity MICs for mammalian cells (Vero E6) in culture were quantified using CellTiter96 assay (Promega. Inc.; procedures as specified by the manufacturer). Screening data for SalA and SalB (compounds 1 and 2) and representative compounds of this invention (compounds 3-9) are presented in Tables 1-2: TABLE 1 RNAP-inhibitory activity (fluorescent-detected RNAP assays) IC50 IC50 Escherichia coli human RNAP RNAP I/II/III compound (μM) (μM) SalA (1) 1 >100 SalB (2) 1 >100 Sal-Br (3) 3 >100 Sal-OH (4) 2 Sal-OBu A (5A) 6 Sal-OBu B (5B) >25 Sal-NH(CH 2 ) 3 NHBoc (7) 0.6 Sal-NH(CH 2 ) 6 NHBoc (9) 1 TABLE 2 Antibacterial activity MIC50 MIC50 Escherichia coli Enterobacter cloacae D21f2toIC ATCC 13047 compound (μg/ml) (μg/ml) SalA (1) 0.024 1.56 SalB (2) 0.098 6.25 Sal-Br (3) 0.049 1.56 Sal-OH (4) 0.78 25 Sal-OBu A (5A) 1.56 12.5 Sal-NH(CH 2 ) 3 NHBoc (7) 1.56 100 Sal-NH(CH 2 ) 6 NHBoc (9) 0.78 25 TABLE 3 Absence of cytotoxicity to mammalian cells in culture MIC50 Vero E6 ATCC CRL1586 compound (μg/ml) SalA (1) >100 SalB (2) >100 Sal-Br (3) >100 All documents cited herein are incorporated by reference. While certain embodiments of invention are described, and many details have been set forth for purposes of illustration, certain of the details can be varied without departing from the basic principles of the invention. The use of the terms “a” and “an” and “the” and similar terms in the context of describing embodiments of invention are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. In addition to the order detailed herein, the methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate embodiments of invention and does not necessarily impose a limitation on the scope of the invention unless otherwise specifically recited in the claims. No language in the specification should be construed as indicating that any non-claimed element is essential to the practice of the invention.

The invention provides compounds of formula (I): and salts thereof, wherein X and Y have any of the values defined herein. The compounds inhibit bacterial RNA polymerase, inhibit bacterial growth, and have applications in, analysis of RNA polymerase structure and function, control of bacterial gene expression, control of bacterial growth, antibacterial chemistry, antibacterial therapy, and drug discovery.

The present application is a continuation of U.S. application Ser. No. 09/066,964, filed Apr. 27, 1998, now U.S. Pat. No. 6,079,506 which is incorporated in its entirety by reference. BACKGROUND OF THE INVENTION The present invention relates generally to underground boring tool guidance and, more particularly, to a remote walk over locator/controller configured for determining the underground location of a boring tool and for remotely issuing control commands to a drill rig which is operating the boring tool. Installing underground utility cable using a steerable boring tool is well known in the art. Various examples are described in U.S. Pat. Nos. 5,155,442, 5,337,002, 5,444,382 and 5,633,589 as issued to Mercer et al (collectively referred to herein as the Mercer Patents), all of which are incorporated herein by reference. An example of the prior art Mercer technique is best illustrated in FIG. 1 herein which corresponds to FIG. 2 in the Mercer Patents. For purposes of clarity, the reference numerals used in the Mercer Patents have been retained herein for like components. As seen in FIG. 1, an overall boring machine 24 is positioned within a starting pit 22 and includes a length of drill pipe 10 , the front end of which is connected to the back end of a steerable boring head or tool 28 . As described in the Mercer Patents, the boring tool includes a transmitter for emitting a dipole magnetic field 12 which radiates in front of, behind and around the boring tool, as illustrated in part in FIG. 1. A first operator 20 positioned at the starting pit 22 is responsible for operating the boring machine 24 ; that is, he or she causes the machine to let out the drill pipe, causing it to push the boring tool forward. At the same time, operator 20 is responsible for steering the boring tool through the ground. A second locator/monitor operator 26 is responsible for locating boring tool 28 using a locator or receiver 36 . The boring tool is shown in FIG. 1 being guided beneath an obstacle 30 . The locator/monitor operator 26 holds locator 36 and uses it to locate a surface position above tool head 28 . Once operator 26 finds this position, the locator 36 is used to determine the depth of tool head 28 . Using the particular locator of the present invention, operator 26 can also determine roll orientation and other information such as yaw and pitch. This information is passed on to operator 20 who then may use it to steer the boring tool to its target. Unfortunately, this arrangement requires at least two operators in order to manage the drilling operation, as will be discussed further. Still referring to FIG. 1, current operation of horizontal directional drilling (HDD) with a walkover locating system requires a minimum of two skilled operators to perform the drilling operation. As described, one operator runs the drill rig and the other operator tracks the progress of the boring tool and determines the commands necessary to keep the drill on a planned course. In the past, communication between the two operators has been accomplished using walkie-talkies. Sometimes hand signals are used on the shorter drill runs. However, in either instance, there is often confusion. Because an operating drill rig is typically quite noisy, the rig noise can make it difficult, if not impossible, to hear the voice communications provided via walkie-talkie. Moreover, both the walkie-talkie and the hand signals are awkward since the operator of the drill rig at many times has both of his hands engaged in operation of the drill rig. Confused steering direction can result in the drill being misdirected, sometimes with disastrous results. The present invention provides a highly advantageous boring tool control arrangement in which an operator uses a walk-over locator unit that is configured for remotely issuing control commands to a drill rig. In this way, problems associated with reliable communications between two operators are eliminated. In addition, other advantages are provided, as will be described hereinafter. SUMMARY OF THE INVENTION As will be described in more detail hereinafter, there is disclosed herein a locator/control arrangement for locating and controlling underground movement of a boring tool which is operated from a drill rig. An associated method is also disclosed. The boring tool includes means for emitting a locating signal. In accordance with the present invention, the locator/control arrangement includes a portable device for generating certain information about the position of the boring tool in response to and using the locating signal. In addition to this means for generating certain information about the position of the boring tool, the portable device also includes means for generating command signals in view of this certain information and for transmitting the command signals to the drill rig. Means located at the drill rig then receives the command signals whereby the command signals can be used to control the boring tool. In accordance with one aspect of the present invention, the means located at the drill rig for receiving the command signals may include means for indicating the command signals to a drill rig operator. In accordance with another aspect of the present invention, the means located at the drill rig for receiving the command signals may include means for automatically executing the command signals at the drill rig in a way which eliminates the need for a drill rig operator. In accordance with still another aspect of the present invention, drill rig monitoring means may be provided for monitoring particular operational parameters of the drill rig. In response to the particular operational parameters, certain data may be generated which may include a warning that one of the parameters has violated an acceptable operating value for that parameter. In one feature, the certain data regarding the operational parameters may be displayed at the drill rig. In another feature, the certain data regarding the operational parameters may be displayed on the portable device. The latter feature is highly advantageous in embodiments of the invention which contemplate elimination of the need for a drill rig operator. BRIEF DESCRIPTION OF THE DRAWINGS The present invention may be understood by reference to the following detailed description taken in conjunction with the drawings, in which: FIG. 1 is a partially broken away elevational and perspective view of a boring operation described in the previously recited Mercer Patents. FIG. 2 is an elevational view of a boring operation being performed in accordance with the present invention in which a portable locator/controller is used. FIG. 3 is a diagrammatic perspective view of the portable locator/controller which is used in the boring operation of FIG. 2, shown here to illustrate details of its construction. FIG. 4 is a partial block diagram illustrating details relating to the configuration and operation of the portable locator/controller of FIG. 3 . FIG. 5 is a partial block diagram illustrating details relating to the configuration and operation of one arrangement of components located at the drill rig for receiving command signals transmitted from the portable locator/controller of the present invention. FIG. 6 is a partial block diagram illustrating details relating to the configuration and operation of another arrangement of components located at the drill rig for receiving command signals transmitted from the portable locator/controller and for, thereafter, executing the commands signals so as to eliminate the need for a drill rig operator. DETAILED DESCRIPTION OF THE INVENTION Turning again to the drawings, attention is immediately directed to FIG. 2 which illustrates a horizontal boring operation being performed using a boring/drilling system generally indicated by the reference numeral 70 . The drilling operation is performed in a region of ground 72 including a boulder 74 . The surface of the ground is indicated by reference numeral 76 . System 70 includes a drill rig 78 having a carriage 80 received for movement along the length of an opposing pair of rails 82 which are, in turn, mounted on a frame 84 . A conventional arrangement (not shown) is provided for moving carriage 80 along rails 82 . During drilling, carriage 80 pushes a drill string 86 into the ground and, further, is configured for rotating the drill string while pushing, as will be described. The drill string is made up of a series of individual drill string sections or pipes 88 , each of which includes a suitable length such as, for example, ten feet. Therefore, during drilling, sections 88 must be added to the drill string as it is extended or removed from the drill string as it is retracted. In this regard, drill rig 78 may be configured for automatically adding or removing the drill string sections as needed during the drilling operation. Underground bending of the drill string sections enables steering, but has been exaggerated for illustrative purposes. Still referring to FIG. 2, a boring tool 90 includes an asymmetric face 92 and is attached to the end of drill string 86 . Steering of the boring tool is accomplished by orienting face 92 of the boring tool (using the drill string) such that the boring tool is deflected in the desired direction. Boring tool 90 includes a mono-axial antenna such as a dipole antenna 94 which is driven by a transmitter 96 so that a magnetic locating signal 98 is emanated from antenna 94 . Power may be supplied to transmitter 96 from a set of batteries 100 via a power supply 102 . A control console 104 is provided for use in controlling and/or monitoring the drill rig. The control console includes a drill rig telemetry transceiver 106 connected with a telemetry receiving antenna 108 , a display screen 110 , an input device such as a keyboard 112 , a processor 114 , and a plurality of control levers 116 which, for example, hydraulically control movement of carriage 80 along with other relevant functions of drill rig operation. Still referring to FIG. 2, in accordance with the present invention, drilling system 70 includes a portable locator/controller 140 held by an operator 141 . With exceptions to be noted, locator 140 may be essentially identical to locator 36 , as described in the Mercer Patents. Turning to FIG. 3 in conjunction with FIG. 2, the same reference numerals used to describe locator 36 in the Mercer Patents have been used to designate corresponding components in locator/controller 140 . In order to understand and appreciate the present invention, the only particular components of locator 36 that form part of locator 140 and that are important to note here are the antenna receiver arrangement comprised of orthogonal antennas 122 and 124 and associated processing circuitry for measuring and suitably processing the field intensity at each antenna and roll/pitch antenna 126 and associated processing circuitry 128 for measuring the pitch and roll of the boring tool. Inasmuch as the Mercer patents fully describe the process by which locator 140 is used to find the position of boring tool 90 , the reader is referred to the patents for a detailed description of the locating method. Referring to FIGS. 2-4, in accordance with the present invention, locator/controller 140 includes a CPU 144 , interfaced with a remote telemetry transceiver 146 , a joystick 148 and a display 150 . Remote transceiver 146 is configured for two-way communication with drill rig transceiver 106 via an antenna 152 . Joystick 148 is positioned in a convenient location for actuation by operator 141 . In accordance with one highly advantageous feature of the present invention, operator 141 is able to remotely issue control commands to drill rig 78 by actuating joystick 148 . Commands which may be issued to the drill rig by the operator include, but are not limited to (1) roll orientation for steering direction purposes, (2) “advance” and (3) “retract.” It should be appreciated that the ability to issue these commands from locator/controller 140 , in essence, provides for complete boring tool locating and control capability from locator/controller 140 . A locator/controller command is implemented using CPU 144 to read operator actuations of the joystick, interpret these actuations to establish the operator's intended command, and then transfer the command to remote transceiver 146 for transmission to the command drill rig telemetry transceiver 106 at the drill rig, as will be described immediately hereinafter. Still referring FIGS. 2-4, control commands are entered by using display 150 in conjunction with joystick 148 . Display 150 includes an enhanced roll orientation/steering display 154 having a clock face 156 which shows clock positions 1 through 12. These clock positions represent the possible steering directions in which boring tool 90 may be set to travel. That is, the axis of the boring tool is assumed to extend through a center position 158 of the clock display and perpendicular to the plane of the figure. The desired roll orientation is established by moving joystick 148 either to the left or right. As the joystick is moved, a desired roll orientation pointer 160 incrementally and sequentially moves between the clock positions. For instance, if the desired roll pointer was initially located at the 12 o'clock position (not shown), the locator/controller operator may begin moving it to the 3 o'clock position by moving and holding the joystick to the right. CPU 144 detects the position of the joystick and incrementally moves the desired roll pointer to the 1 o'clock, then 2 o'clock, and finally the 3 o'clock position. At this point, the operator releases the joystick. Of course, at the 3 o'clock position, the command established is to steer the boring tool to the right. Similarly, the 6 o'clock position corresponds to steering downward, the 9 o'clock position corresponds to steering to the left and the 12 o'clock position corresponds to steering upward. As mentioned previously, steering is accomplished by setting face 92 of the boring tool in an appropriate position in accordance with the desired roll of the boring tool. With regard to boring tool steering, it is to be understood that boring tool steering has been implemented using concepts other than that of roll orientation and that the present invention is readily adaptable to any steering method either used in the prior art or to be developed. Having established a desired steering direction, operator 141 monitors an actual roll orientation indicator 162 . As described in the Mercer patents, roll orientation may be measured within the boring tool by a roll sensor (not shown). The measured roll orientation may then be encoded or impressed upon locating signal 90 and received by locator/controller 140 using antenna 126 . This information is input to CPU 144 as part of the “Locator Signal Data” indicated in FIG. 4 . CPU 144 then causes the measured/actual roll orientation to be displayed by actual roll orientation indicator 162 . In the present example, operator 141 can see that the actual roll orientation is at the 2 o'clock position. Once the desired roll orientation matches the actual roll orientation, the operator will issue an advance command by moving joystick 148 forward. Advancement or retraction commands for the boring tool can only be maintained by continuously holding the joystick in the fore or aft positions. That is, a stop command is issued when joystick 148 is returned to its center position. If the locating receiver were accidentally dropped, the joystick would be released and drilling would be halted. This auto-stop feature will be further described in conjunction with a description of components which are located at the drill rig. Still referring to FIGS. 2-4, a drill string status display 164 indicates whether the drill rig is pushing on the drill string, retracting it or applying no force at all. Information for presentation of drill string status display 164 along with other information to be described is transmitted from transceiver 106 at the drill rig and to transceiver 146 in the locator/controller. Once the boring tool is headed in a direction which is along a desired path, operator 141 can command the boring tool to proceed straight. As previously described, for straight drilling, the drill string rotates. In the present example, after having turned the boring tool sufficiently to the right, the operator may issue a drill straight command by moving joystick 148 to the left and, thereafter, immediately back to the right. These actuations are monitored by CPU 144 . In this regard, it should be appreciated that CPU 144 may respond to any suitable and recognizable gesture for purposes of issuance of the drill straight command or, for that matter, CPU 144 may respond to other gestures to be associated with other desired commands. In response to recognition of the drill straight gesture, CPU 144 issues a command to be transmitted to the drill rig which causes the drill string to rotate during advancement. At the same time, CPU 144 extinguishes desired roll orientation indicator 160 and actual roll orientation indicator 162 . In place of the roll orientation indicators, a straight ahead indication 170 is presented at the center of the clock display which rotates in a direction indicated by an arrow 172 . It is noted that the straight ahead indication is not displayed in the presence of steering operations which utilize the desired or actual roll orientation indicators. Alternatively, in order to initiate straight drilling, the locator/controller operator may move the joystick to the left. In response, CPU 144 will sequentially move desired roll indicator 160 from the 3 o'clock position, to the 2 o'clock position and back to the 1 o'clock position. Thereafter, the desired roll indicator is extinguished and straight ahead indication 170 is provided. Should the operator continue to hold the joystick to the left, the 12 o'clock desired roll orientation (i.e., steer upward) would next be presented. In addition to the features already described, display 150 on the locator/controller of the present invention may include a drill rig status display 174 which presents certain information transmitted via telemetry from the drill rig to the locator/controller. The drill rig status display and its purpose will be described at an appropriate point below. For the moment, it should be appreciated that commands transmitted to drill rig 78 from locator/controller 140 may be utilized in several different ways at the drill rig, as will be described immediately hereinafter. Attention is now directed to FIGS. 2 and 5. FIG. 5 illustrates a first arrangement of components which are located at the drill rig in accordance with the present invention. As described, two-way communications are established by the telemetry link formed between transceiver 106 at the drill rig and transceiver 146 at locator/controller 140 . In this first component arrangement, display 110 at the drill rig displays the aforedescribed commands issued from locator/controller 140 such that a drill rig stationed operator (not shown) may perform the commands. Display 110 , therefore, is essentially identical to display 150 on the locator/controller except that additional indications are shown. Specifically, a push or forward indication 180 , a stop indication 182 and a reverse or retract indication 184 are provided. It is now appropriate to note that implementation of the aforedescribed auto-stop feature should be accomplished in a fail-safe manner. In addition to issuing a stop indication when joystick 148 is returned to its center position, the drill rig may require periodic updates and if the updates were not timely, stop indication 182 may be displayed automatically. Such updates would account for loss of the telemetry link between the locator/controller and the drill rig. Still referring to FIGS. 2 and 5, the forward, stop and retract command indications eliminate the need for other forms of communication between the drill rig operator and the locator/controller operator such as the walkie-talkies which were typically used in the prior art. At the same time, it should be appreciated that each time a new command is issued from the locator/controller, an audible signal may be provided to the drill rig operator such that the new command does not go unnoticed. Of course, the drill rig operator must also respond to roll commands according to roll orientation display 154 by setting the roll of the boring tool to the desired setting. In this regard, it should be mentioned that a second arrangement (not shown) of components at the drill rig may be implemented with a transmitter at the locator/controller in place of transceiver 152 and a receiver at the drill rig in place of transceiver 106 so as to establish a one-way telemetry link from the boring tool to the drill rig. However, in this instance, features such as operations status display 174 and drill string status display 164 cannot be provided at the locator/controller. It should be appreciated that the first and second component arrangements described with regard to FIG. 5 contemplate that the drill rig operator may perform tasks including adding or removing drill pipe sections 88 from the drill string and monitoring certain operational aspects of the operation of the drill rig. For example, the drill rig operator should insure that drilling mud (not shown) is continuously supplied to the boring tool so that the boring tool does not overheat whereby the electronics packaged housed therein would be damaged. Drilling mud may be monitored by the drill rig operator using a pressure gauge or a flow gauge. As another example, the drill rig operator may monitor the push force being applied to the drill string by the drill rig. In the past, push force was monitored by “feel” (i.e., reaction of the drill rig upon pushing). However, push force may be directly measured, for instance, using a pressure or force gauge. If push force becomes excessive as a result of encountering an underground obstacle, the boring tool or drill string may be damaged. As a final example, the drill rig operator may monitor any parameters impressed upon locating signal 98 such as, for instance, boring tool temperature, battery status, roll, pitch and proximity to an underground utility. In this latter regard, the reader is referred to U.S. Pat. No. 5,757,190 entitled A SYSTEM INCLUDING AN ARRANGEMENT FOR TRACKING THE POSITIONAL RELATIONSHIP BETWEEN A BORING TOOL AND ONE OR MORE BURIED LINES AND METHOD which is incorporated herein by reference. Referring to FIG. 5, another feature may be incorporated in the first and second component arrangements which is not requirement, but which nonetheless is highly advantageous with regard to drill rig status monitoring performed by the drill rig operator. Specifically, a rig monitor section 190 may be included for monitoring the aforementioned operational parameters such as drilling mud, push force and any other parameters of interest. As previously described, proper monitoring of these parameters is critical since catastrophic equipment failures or damage to underground utilities can occur when these parameters are out of range. In accordance with this feature, processor 114 receives the status of the various parameters being monitored by the rig monitor section and may provide for visual and/or aural indications of each parameter. Visual display occurs on operations status display 174 . The display may provide real time indications of the status of each parameter such as “OK”, as shown for drilling mud and push force, or an actual reading may be shown as indicated for the “Boring Tool Temperature”. Of course, visual warnings in place of “OK” may be provided such as, for example, when excessive push force is detected. Audio warning may be provided by an alarm 192 in the event that threshold limits of any of the monitored parameters are violated. In fact, the audio alarm may vary in character depending upon the particular warning being provided. It should be mentioned that with the two-way telemetry link between the drill rig and locator/controller according to the aforedescribed first component arrangement, displays 164 and 174 may advantageously form part of overall display 150 on locator/controller 140 , as shown in FIG. 4 . However, such operational status displays on the locator/controller are considered as optional in this instance since the relevant parameters may be monitored by the drill rig operator. The full advantages of rig monitor section 190 and associated operations status display 174 will come to light in conjunction with a description of a fully automated arrangement to be described immediately hereinafter. Referring to FIGS. 2 and 6, in accordance with a third, fully automated arrangement of the present invention, a drill rig control module 200 is provided at drill rig 78 . Drill rig control module 200 is interfaced with processor 114 . In response to commands received from locator/controller 140 , processor 114 provides command signals to the drill rig control module. The latter is, in turn, interfaced with drill rig controls 116 such that all required functions may be actuated by the drill rig control module. Any suitable type of actuator (not shown) may be utilized for actuation of the drill rig controls. In fact, manual levers may be eliminated altogether in favor of actuators. Moreover, the actuators may be distributed on the drill rig to the positions at which they interface with the drill rig mechanism. For reasons which will become apparent, this third arrangement requires two-way telemetry between the drill rig and locator/controller such that drill string status display 164 and operations status display 174 are provided as part of display 150 on the locator/controller. At the same time, these status displays are optional on display 110 at the drill rig. Still referring to FIGS. 2 and 6, in accordance with the present invention, using locator/controller 140 , operator 141 is able to issue control commands which are executed by the arrangement of FIG. 6 at the drill rig. Concurrent with locating and controlling the boring tool, operator 141 is able to monitor the status of the drill rig using display 150 on the locator/controller. In this regard, display 174 on the locator/controller also apprises the operator of automated drill rod loading or unloading with indications such as, for example, “Adding Drill Pipe.” In this manner, the operator is informed of reasons for normal delays associated with drill string operations. Since push force applied by the drill rig to the drill string is a quite critical parameter, the present invention contemplates a feature (not shown) in which push force is measured at the drill rig and, thereafter, used to provide push force feedback to the operator via joystick 148 for ease in monitoring this critical parameter. The present invention contemplates that this force feedback feature may be implemented by one of ordinary skill in the art in view of the teaching provided herein. Still other parameters may be monitored at the drill rig and transmitted to locator/controller 140 . In fact, virtually anything computed or measured at the drill rig may be transmitted to the locator/controller. For example, locator/controller 140 may display (not shown) deviation from a desired path. Path deviation data may be obtained, for example, as set forth in U.S. Pat. No. 5,698,981 entitled BORING TECHNIQUE which is incorporated herein by reference. Alternatively, path deviation data may be obtained by using a magnetometer (not shown) positioned in the boring tool in combination with measuring extension of the drill string. With data concerning the actual path taken by the boring tool, the actual path can be examined for conformance with minimum bend radius requirements including those of the drill string or those of the utility line which, ultimately, is to be pulled through the completed bore. That is, the drill string or utility line can be bent too sharply and may, consequently, suffer damage. If minimum bend radius requirements for either the drill string or utility are about to be violated, an appropriate warning may be transmitted to locator/controller 140 . It should be appreciated that with the addition of the drill rig control module, complete remote operation capability has been provided. In and by itself, it is submitted that integrated locating capability and remote control of a boring tool has not been seen heretofore and is highly advantageous. When coupled with remote drill rig status monitoring capability, the present invention provides remarkable advantages over prior art horizontal directional drilling systems. The advantages of the fully automated embodiment of the present invention essentially eliminate the need for a skilled drill rig operator. In this regard, it should be appreciated that the operator of a walkover locator is, in most cases, knowledgeable with respect to all aspects of drill rig operations. That is, most walkover locator operators have been trained as drill rig operators and then advance to the position of operating walkover locating devices. Therefore, such walkover locator operators are well versed in drill rig operation and welcome the capabilities provided by the present invention. It should be understood that an arrangement for remotely controlling and tracking an underground boring tool may be embodied in many other specific forms and produced by other methods without departing from the spirit or scope of the present invention. Therefore, the present examples are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope of the appended claims.

A locating and control arrangement forms part of a drilling apparatus which also includes a boring tool that emits a locating signal. The locating and control arrangement is used for locating and controlling underground movement of a boring tool which is operated from a drill rig. The locating and control arrangement includes a portable device for generating certain information about the position of the boring tool in response to the locating signal. The portable device includes a command arrangement forming one portion of the locating and control arrangement for generating at least one movement command such that maintaining the movement command requires a continuous interaction between the portable device and a user, and for transmitting the movement command to the drill rig. A receiving arrangement forms another portion of the locating and control arrangement, located at the drill rig, for receiving the movement command for use in controlling the boring tool responsive to the movement command.

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of U.S. application Ser. No. 14/297,849 filed Jun. 6, 2014, which claims foreign priority benefits under 35 U.S.C. §119(a)-(d) to European patent application number EP 13 002 981.2, filed Jun. 11, 2013, each of which is incorporated herein by reference in its entirety. TECHNICAL FIELD The present disclosure relates to a paving screed to be employed on a road finisher. BACKGROUND Such paving screeds are known in practice. They are used in road construction to smooth and compact layers of pavement, for example made of asphalt. Paving screeds of various designs are used, for example, fixed-width screeds whose width is invariable, fixed-width screeds whose width may be modified by means of separate add-on components, as well as extendable screeds whose width may be variably modified with the aid of extending units. Here too, separate bolt-on extensions may also be attached. So-called side plates are attached to each of the outer ends of the screed, which prevent material in front of and under the screed from escaping to the sides. The width of the entire screed, also referred to as operating width, is an important parameter, since it affects important regulating variables of the road finisher, for example, the material needed in front of the screed and, therefore, the output or the speed of the material delivery systems of the road finisher. Due to the increasing automation of the operation of road finishers, it is advantageous to in some way provide the various control systems with the width of the paving screed. In conventional screeds this still occurs frequently by manual input. In extendable screeds, measuring systems are used which identify the sliding path of the screed extensions. In the simplest case, this involves scales with pointers. Once read, the value must be added to the width of the base screed and input into the control system. Other measuring systems identify the sliding path and provide this directly to the machine control system. The addition of the respective sliding path and the width of the base screed is then handled by the control system. However, such systems do not take into account potentially separately mounted bolt-on extensions such that when the latter are used, another input by the operator must be made. Applicant's European patent application EP 2 239 374 A1 discloses a road finisher which may be upgraded with multiple auxiliary components. Said auxiliary components are equipped with wirelessly readable identification devices which can be read out by a reading device on the road finisher. Auxiliary components mentioned are, among others, extending units of extendable paving screeds as well as fixed bolt-on extensions. Also provided is a measurement of the distance between the reading device on the road finisher and the identification means mounted on the extending units or bolt-on extensions. It has turned out that this system has optimization potential. For one, both the extending units of extending screeds as well as all separate bolt-on extensions must be provided with identification means. For another, the plurality of identification means gives rise to a significant fault potential. For example, it is necessary in very long screeds which have multiple add-on components to process a large number of signals, which increases the susceptibility to failures. Moreover, it may happen that the signal of the outermost add-on component cannot be received by the reading unit due to limited range or to distortions. If the latter then receives a signal of an add-on component situated further inward, the system, unbeknownst to the operator, is then provided with a false operating screed width. In addition, problems may also arise in conjunction with asymmetrically widened screeds, since it then becomes difficult to determine which signal from an add-on component indicates the correct screed width. SUMMARY An object of the present disclosure is to provide a paving screed for a road finisher of which the design is improved in the simplest possible way, in order to enable an operation that is user-friendly and least susceptible to failure. The disclosure provides for at least one reference element for determining the operating width to be mounted on at least one of a plurality of side plates. In this configuration the at least one reference element is detectable by means of sensor units when the side plates are mounted on the respective outer ends of the base screed or of the extending units or of the bolt-on extensions. As a result, only one reference element per screed section is required. By attaching the reference element to the respective side plate, it is ensured that the latter is always attached to the outermost point of the paving screed. In the event the reference element is located out of range of the sensor units or the signal path is disrupted in some other way, the sensor unit will receive no signal. In this way a disruption of the operation would be noticed immediately. Preferably, in the event that no signal is received, the operator may be shown an error signal, for example, a visual, an acoustic or a tactile signal. Conceivable in such case are, for example, warning sounds from existing signal generators or signal generators provided for specifically this purpose, as well as special warning lights for just this purpose or else messages on a display, such as for example, an alphanumeric display, a dot-matrix display or else a liquid crystal or LED display. The sensor unit and the reference element may be based on various measuring methods, for example, ultrasound, radar, microwave, radio signals or optical measuring methods such as, for example, laser. Accordingly, a suitable or several suitable sensors may be provided in the sensor unit as well as suitable reference elements. Thus, at least one sensor for detecting the aforementioned signals can be provided in the sensor unit. Various types of reflectors or transceiver units on the reference element are conceivable. Additionally, the sensor unit or the sensor units may contain at least one transmitting device which is configured to send a measuring signal of the aforementioned kind. The measuring signals may simply be reflected or else received by suitable transceiver units and, sent back, optionally supplemented with auxiliary information such as, for example, time stamp, position or identification information. It is conceivable to provide at least one sensor on the base screed which is configured to measure the distances to the at least one reference element. In this arrangement, a sensor unit may be provided, for example, which detects all reference elements on all side plates and measures the distance to them. In a further example, a sensor unit may be provided for each screed section which is configured to measure the distance to an associated reference element on an associated side plate. In paving screeds that have a left and right screed section, two sensor units would be provided in such case. A first, right sensor unit would measure the distance to a reference element on a right side plate, a second left sensor unit would in such case measure the distance to a reference element on the left side plate. For cases in which the respective sensor units are attached to the left and right side of the base screed, it would be possible to upgrade a control system of a road finisher in which heretofore only the extending units were taken into account, without having to modify the control. In a further advantageous variant, a sensor unit is provided on at least one of the side plates which is configured to measure the distance to the at least one reference element on another of the side plates. This makes it possible to minimize the number of both the sensor units as well as the reference elements. In embodiments having a left and a right side plate, only one sensor unit and one reference element are necessary. In addition, the entire screed width is immediately detected without having to add various lengths. It is conceivable that the reference elements are attached directly to the side plates. These may be, for example, adhesive or screw-on elements that are attached on a side of the side plate which faces the respective sensor unit. Structures integrated into the respective side plates are also conceivable. In a further variant, the reference elements are attached indirectly to the side plates by adapters. In this way, the alignment with the respective sensor unit may potentially be improved, or adjusted during operation. In systems which react sensitively to objects that are placed in the signal path, the signal path may also be shaped in such a way that as few objects as possible are situated therein. It is advantageous if the respective reference element is aligned with an associated sensor unit if the respective side plate is mounted on the respective outer ends of the base screed or the extending unit or the bolt-on extensions. This may facilitate the mounting of the side plate and the reference elements. In addition, it is conceivable that the side plates and/or the adapters may only be affixed in one correctly aligned configuration. This avoids errors during assembly. It is conceivable that the sensor units may be configured for determining the operating width by triangulation. This permits a flexible arrangement of the sensor units. Moreover, disruptive objects may be circumvented in this way. Preferably, the paving screed according to the disclosure is employed on a road finisher. It is particularly advantageous if the road finisher having the paving screed according to the disclosure includes a control system which is configured to utilize the ascertained operating width as an input variable. Using the operating width, it is possible to set various regulating variables of the road finisher, for example, the speed of various conveying systems. It is also conceivable that at least one of the sensor units for determining the operating width is provided on the road finisher. This may be very useful in the case of very large paving widths, since potentially more exposed mounting positions exist on the road finisher than on the paving screed itself. In addition, the expenditure involved in connecting a sensor unit to the control system of the road finisher would be reduced, since for the sensor unit at least there is no coupling necessary between road finisher and screed. The present disclosure also relates to a method for determining the operating width of a paving screed which may be employed on a road finisher. The paving screed comprises a base screed, the operating width of which may be modified by extending units and/or separate bolt-on extensions, multiple side plates which are mounted respectively on the outer ends of the base screed or of the extending units or of the bolt-on extensions and which delimit the operating width. The method is characterized in that reference elements are used in the area of the side plates for determining the operating width. It is conceivable that the distance to at least one reference element attached to one of the side plates, respectively, is measured by at least one sensor unit associated with the respective side plate. If, for example, a base screed is provided with a right and a left extending unit, in which a side plate is attached at the outer end of each of the left and the right extending units, a right and a left sensor unit would then be used to measure the respective distances to the at least one reference element which is attached to each of the right and left side plates. In this case, the left and right sensor unit may each be attached to the left and the right end respectively of the base screed. However, it is equally conceivable for both sensor units to be mounted centrally between the side plates, on the screed or also on a road finisher which pulls the screed. It is likewise conceivable to combine the two aforementioned sensor units into one sensor unit. In this variant, one sensor unit would be positioned between the side plates or reference elements and would measure the distances to the reference elements in two directions. In such case, the two measured values would merely have to be added together in order to obtain the operating width of the screed. The width of the base screed would not need to be known by the system. Such a sensor unit would merely have to be positioned between the reference elements, i.e., a central arrangement is necessarily required. Instead, in this arrangement it must only be ensured that the sensor unit lies along a straight line connecting two reference elements, and that the ranges of the sensor unit in both directions is not exceeded. It is equally conceivable that the distance to a reference element attached to a first side plate is measured by a sensor unit attached to a second of the side plates. In such case, a paving screed having two side plates mounted opposite one another would require merely one sensor unit and one reference element. Moreover, the measured value, optionally taking into account the dimensions of each sensor unit and of each reference element, would correspond directly to the operating width of the screed. Accordingly, this configuration would allow for a particular simple design and a simple further processing of the measured value. In a further advantageous variant the distance between the reference elements may be measured by means of triangulation. Several sensor units are necessary in this case. However, there are advantages such as, for example, greater latitude in the arrangement of the sensor units. The latter may be distributed at various locations on the screed and the road finisher. A skillful arrangement of the sensor units can also prevent disruption caused by objects in the signal path. Several advantageous embodiments of the disclosure are described in greater detail below with reference to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 a shows a perspective view of a paving screed according to the disclosure with extending units protracted; FIG. 1 b shows the screed from FIG. 1 a with extending units retracted; FIG. 2 shows as side plate of the paving screed from FIGS. 1 a and 1 b; FIG. 3 shows a schematic top view of a paving screed with extending units protracted and mounted bolt-on extensions according to a first embodiment of the disclosure; FIG. 4 shows a schematic top view of a paving screed according to a second embodiment of the disclosure; FIG. 5 shows the paving screed from FIG. 3 with two protracted extending units but with only one mounted bolt-on extension, resulting in an asymmetrical configuration of the paving screed; FIG. 6 shows a schematic top view of a paving screed according to a third embodiment of the disclosure, in which the reference elements are mounted on the side plates with the aid of adapters; FIG. 7 shows a schematic top view of a paving screed according to a fourth embodiment of the disclosure; FIG. 8 shows a schematic rear view of a paving screed according to a fifth embodiment of the disclosure; FIG. 9 shows a schematic rear view of a paving screed according to a sixth embodiment of the disclosure; and FIG. 10 shows a road finisher on which a paving screed according to the disclosure may be mounted. DETAILED DESCRIPTION As required, detailed embodiments of the present disclosure are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the disclosure that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present disclosure. FIG. 1 a shows a paving screed 1 . It comprises a base screed 2 which may be widened by first and second extending units 3 , 4 . Mounted on the outer ends of the first and second extending units 3 , 4 are a first and a second side plate 5 , 6 . They prevent the road construction material from being distributed beyond a desired width. Provided on the base screed 2 are mounting devices 7 with which the paving screed 1 may be mounted on a road finisher 8 (see FIG. 10 ). According to a first embodiment, the paving screed 1 includes a first sensor unit 9 as well as a second sensor unit 10 (see FIG. 3 ). In this embodiment they are mounted on the base screed 2 . The first sensor unit 9 measures a distance a to a first reference element 11 , which is affixed to the first side plate 5 . The second sensor unit 10 measures a distance b to a second reference element 12 , which is affixed to the second side plate 6 . The measured distances a and b are then added to the width of the base screed 2 , taking into account the overhang of the sensor units 9 , 10 , by means of which an operating width 26 of the paving screed 1 is obtained. The mounting positions of the sensor units 910 and the reference elements 11 , 12 are by way of example merely schematically indicated. The mounting positions of sensor units 9 , 10 may be varied arbitrarily. The reference elements 11 , 12 may be affixed at any arbitrary position on the respective side plates 5 , 6 . When positioning the sensor units 9 , 10 and when positioning the reference elements, however, it must be ensured that the signal flow between sensor unit 9 , 10 and the associated reference element 11 , 12 is not adversely affected. In addition, the screed 1 may include, in addition to the extending units 3 , 4 an arbitrary number of rigid bolt-on extensions 13 , 14 which are mounted on the extending units. It is equally conceivable that the paving screed 1 includes a fixed base screed 2 with no extending units 3 , 4 and may be widened with the aid of rigid bolt-on extensions 13 , 14 . In any case, both symmetrical as well as asymmetrical screed configurations are conceivable. FIG. 1 b shows a perspective view of the screed from FIG. 1 a , but in this case the extending units 3 , 4 are retracted and therefore not visible. FIG. 2 shows by way of example the first side plate 5 . Just like the second side plate 6 or else all side plates of the paving screed 1 according to the present disclosure, it is designed to be mountable at each outer end of the paving screed 1 . FIG. 3 is a schematic top view of the paving screed 1 , but widened in this case by first and second bolt-on extensions 13 , 14 . In this arrangement, the bolt-on extensions 13 , 14 are exemplary of all screed configurations which may be implemented with the aid of an arbitrary number of bolt-on extensions 13 , 14 , which may be arbitrarily dimensioned. As previously mentioned above, the sensor units 9 , 10 measure the two distances a and b to the reference elements 11 and 12 . In the embodiment shown, the dimensions of the sensor units 9 , 10 must also be taken into consideration when summing up the width of the base screed 2 . This can be avoided not by mounting the sensor units 9 , 10 , as shown, on the lateral surfaces of the base screed 2 , but rather by attaching them flush with these same lateral surfaces. For example, mounting on an upper surface of the base screed 2 is conceivable. It is equally feasible to integrate the sensor units 9 , 10 in the base screed 2 in such a way that they close flush with the lateral surfaces. FIG. 4 shows the paving screed 1 according to a second embodiment of the disclosure. In this embodiment the first sensor unit 9 is mounted on the second side plate 6 . The first reference element 11 is still mounted on the first side plate 5 . The first sensor unit 9 measures the distance to the first reference element 11 . As a result, only the measurements of the first sensor unit 9 and the first reference element 11 need be considered in order to obtain the operating width 26 of the paving screed 1 . To avoid this intermediate step, it is conceivable to mount both the first sensor unit 9 as well as the first reference element 11 on the respective side plates 5 , 6 in such a way that they lie in the same plane as the side plates 5 , 6 . This may be achieved, for example, with the aid of adapters 15 , 16 (see FIGS. 6 and 7 ). FIG. 5 shows a variant of the first embodiment of the disclosure. Here only the first bolt-on extension 13 is mounted. This gives rise to an asymmetrical screed configuration. This changes nothing in terms of determining the operating width 26 of the screed 1 . FIG. 6 shows a schematic top view of a third embodiment of the paving screed 1 . In this configuration the reference elements 11 and 12 were mounted on the first and second side plate 5 , 6 with the aid of a first and a second adapter 15 , 16 . On the one hand, this may offer the advantage that, as previously mentioned above, the reference elements 11 , 12 may be arranged in the same plane as the side plates 5 , 6 , thereby enabling a corrective step to be eliminated when ascertaining the operating width of the paving screed 1 . As a further advantage, the reference elements 11 , 12 may possibly be better aligned with the respective sensor units 9 , 10 . The same applies to the mounting of the sensor units 9 , 10 with the aid of fastening units 17 , 18 . Here too, it is possible to select a configuration which improves the alignment of the sensor units 9 , 10 with the reference elements 11 , 12 . Moreover, it is also possible here to arrange the sensors 9 , 10 in such a way that their dimensions need not be taken into consideration when determining the operating width 26 of the paving screed 1 . FIG. 7 shows schematically a top view of the paving screed 1 according to a fourth embodiment. The configuration is essentially the same as that of the preceding embodiment. However, instead of the two sensor units 9 , 10 , only one single sensor unit 19 is provided. It is located along a straight line between the reference elements 11 , 12 and measures both the distance to the first reference element 11 as well as the distance to the second reference element 12 . Thus, these two measured distances need only be added together in order to obtain the operating width of the paving screed 1 . The only correction is the addition of the width of the sensor unit 19 . In processing the measured values, this corresponds to the addition of the measured widths a and b to the width of the base screed 2 from the first embodiment. Hence, existing systems could be retrofitted in a simple manner. FIG. 8 shows schematically a rear view of the paving screed 1 according to a fifth embodiment of the disclosure. This embodiment also provides a single sensor unit 19 . The, latter, however is not positioned along a straight line between the reference elements 11 , 12 as in the previous embodiment, but rather is mounted on the base screed 2 with the aid of a holding unit 20 . The holding unit 20 allows the sensor unit 19 to be positioned at an exposed location and thus to prevent a disruption of the signal path (represented by a dotted line) by objects positioned in the latter. This may be advantageous, particularly in systems that rely on direct visual contact such as, for example, optical methods or else acoustic methods. In this arrangement, the holding unit 20 and the sensor unit 19 mounted thereon may be provided on the paving screed 1 as well as on a road finisher 8 pulling the paving screed 1 . Only one sensor unit 19 is provided in the embodiment shown in FIG. 8 . Since this sensor unit is not located along a straight line between the reference elements 11 , 12 , the vertical distance between the sensor unit 19 and the reference elements 11 , 12 and, if necessary, the horizontal distance in the direction perpendicular to the straight line between the reference elements 11 , 12 must be known or set in order to calculate the operating width of the paving screed 1 . FIG. 9 shows schematically a rear view of the paving screed 1 according to a sixth embodiment. Here a second two-sided sensor unit 21 is provided. The vertical distance of these sensors 19 , 21 to the reference elements 11 , 12 need no longer be known in this embodiment. Instead, the operating width of the paving screed 1 may be determined by means of triangulation. In this arrangement, the sensor units 19 , 21 may be implemented in a structural unit. They may also be mounted on the base screed 2 as well as at any arbitrary location on the road finisher 8 with the aid of the holding unit 20 . The number of sensor units used for triangulation may also be greater than two. This makes it possible to determine more precisely the position of the reference elements 11 , 12 and to also increase the robustness of the system to disruptive objects in the signal path. FIG. 10 shows a perspective view of the road finisher 8 . The road finisher includes mounting devices 22 which may be connected to the mounting devices 7 of the screed 1 . The road finisher includes a control system 23 . It can be used to control the operation of the road finisher, for example, the conveying speed of various conveyor systems. Shown in FIG. 10 are transverse augers 27 exemplary of all the conveyor devices of the road finisher. The control system 23 may use the operating width 26 determined with the aid of one of the above mentioned methods and devices as an input variable. It is also conceivable to affix one or several of the previously described sensor units 9 , 10 , 19 , 21 or additionally provided sensor units on the road finisher 8 , for example, on the roof structure thereof, or else to a mast 25 mounted on the road finisher 8 . As distance measuring methods it is possible in all embodiments to use laser, ultrasound or radar measurement methods, for example. Accordingly, various types of reference elements 11 , 12 are conceivable, for example, different reflectors or transceiver units which receive a distance measurement signal and send it back, optionally supplemented with auxiliary information such as, for example, time stamp, position or identification information. The embodiments described may represent merely a selection of possible combinations of the described features. The features described may be combined in any arbitrary manner, while also omitting individual features, in order to obtain additional advantageous embodiments of the disclosure. While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.

A paving screed to be employed on a road finisher comprises a base screed, the operating width of which may be modified by protractable extending units and/or separate removable bolt-on extensions. The paving screed also includes a plurality of side plates, each being mountable on an outer end of the base screed or an extending unit or a bolt-on extension and which delimit the operating width. At least one reference element for determining the operating width is provided on one of the side plates, and that the at least one reference element is detectable by one or more sensor units when the side plates are each mounted on the outer ends of the base screed, an extending unit or a bolt-on extension.

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] This invention relates to a plasma film-forming apparatus and a cleaning method for cleaning the plasma film-forming apparatus. [0003] 2. Description of the Prior Art [0004] [0004]FIG. 1 shows a plasma film-forming apparatus 1 of the prior art. It is an apparatus to form a film on a substrate 9 by a plasma CVD (Chemical Vapor Deposition) method. A cathode electrode 4 is arranged on the upper wall of a vacuum tank 2 . An anode electrode 3 is arranged opposite to the cathode electrode 4 , in a film-forming chamber 10 of the vacuum tank 2 . The cathode electrode 4 is connected to a high frequency electric power source 8 . The anode electrode 3 is connected to the earth. It functions also as a supporter for substrate. The substrate 9 is mounted on the anode electrode 3 . [0005] The cathode electrode 4 is dish-shaped. A gas-introducing pipe 13 is connected to a central hole of the upper wall of the cathode electrode 4 . A shower plate 5 is fixed to a lower end of the cathode electrode 4 . Numerous small holes are made in the shower plate 5 which is facing to the substrate 9 . [0006] One end of a film-forming gas introducing pipe 6 is connected to the gas-introducing pipe 13 . Another end of the film-forming gas-introducing pipe 16 is connected to a not-shown film-forming gas supply source. A radicals producing source 11 is connected to one end of a gas-introducing pipe 12 . Another end of the gas-introducing pipe 12 is connected to a not-shown cleaning gas sipply source. The radicals producing source 11 is further connected to the pipe 13 . [0007] Next, operations of the above described plasma film-forming apparatus 1 will be described. [0008] For example, there will be described a case of forming a film of SiNx on the substrate 9 . First, the film-forming chamber 10 is evacuated through an exhaust port 7 and so is put under the lower pressure. For example, SiH 4 gas and NH 3 gas are introduced onto the shower plate 5 through the film-forming gas introducing pipe 6 and the gas introducing pipe 13 . They are ejected through the numerous holes of the shower plate 5 uniformly into the film-forming chamber 10 and toward the substrate 9 . [0009] Next, a high frequency electric power is supplied to the cathode electrode 4 form the high frequency power source 8 , to decompose and make the introduced gases to react on each other gases in the film-forming chamber 10 . Thus, a film of SiNx is formed on the substrate 9 . [0010] The above film-forming operations are repeated, and so SiNx films are adhered and piled onto the shower plate 5 , anode electrode 3 , cathode electrode 4 and inner walls of the vacuum tank 2 besides the substrate 9 . The SiNx films on the above portions besides the substrate 9 should be removed (cleaned). [0011] Next, there will be described cleaning operations of the interior of the film-forming chamber 10 . [0012] As on the film-forming operation, the film-forming chamber 10 is evacuated through the exhaust port 7 and so put under the lower pressure. For example, NF 3 gas is supplied into the radicals producing source 11 . Microwave is applied to the NF 3 gas there, so that fluorine free radicals are produced there. NF 3 gas including fluorine free radicals are introduced into the film-forming chamber 10 through the gas-introducing pipe 13 and the shower plate 5 . [0013] Then, fluorine radicals react chemically on the materials (SiNx film) to be cleaned. The SiNx films piled on the inner wall of the vacuum tank 2 are removed. The removed SiNx materials are discharged through the exhaust port 7 together with the cleaning gas. [0014] The method that the radicals for cleaning are thus previously produced and then introduced into the film-forming chamber 10 , has the advantage that the plasma damage of the shower plate 5 is decreased, in comparison with the method that free radicals for cleaning are produced in the film-forming chamber 10 by the high frequency electric power applied to the cathode electrode 4 from the high frequency power source 8 , as on the film-forming operation. introduced into the film-forming chamber 5 , most of the radicals are dissipated, since the passing rate of the shower plate 5 having numerous small holes is low. Thus there is the problem that the cleaning rate is lowered. [0015] Further, in consideration of the problem that most of the radicals are dissipated through in the shower plate 5 , a very high frequency microwave such as 2.45 GHz is applied to the radicals-producing source 11 to produce more radicals, in some cases. However, such method requires high cost. SUMMARY OF THE INVENTION [0016] Accordingly, it is an object of this invention to provide a plasma film-forming apparatus and the cleaning method that the dissipation of the radicals to be introduced into the film-forming chamber can be prevented. [0017] Another object of this invention is to provide a plasma film-forming apparatus and the cleaning method that the radicals as the cleaning gas produced outside the film-forming chamber, can be effectively used for cleaning the film-forming chamber. [0018] In accordance with one aspect of the invention, in a plasma film-forming apparatus which includes a film-forming chamber in which a substrate is arranged, a film-forming gas introducing pipe connected to a supply source of a film-forming gas at its first end, a shower plate through numerous holes of which a second end of said film-forming gas introducing pipe communicate with said film-forming chamber, film-gas exciting means for exciting film-forming gas introduced through said shower plate into said film-forming chamber, to form a film on the surface of said substrate with the chemical reaction, radicals-producing means which excites said cleaning gas and produces radicals, and cleaning-gas introducing means which introduces said cleaning gas containing said radicals into said film-forming chamber, the improvement in which said cleaning-gas introducing means communicate directly with said film-forming chamber. film-forming chamber. [0019] In accordance with another aspect of the invention, in a cleaning method of a plasma film-forming apparatus which, in the film-forming operation, introduces a film-forming gas through a shower plate having numerous holes into a film-forming chamber, excites the introduced gas and forms a film, with the chemical reaction, on a surface of substrate arranged in said film-forming chamber, and in the cleaning operation, introduces a cleaning-gas containing radicals produced by exciting of said cleaning-gas, into said film-forming chamber and cleans said film-forming chamber by chemical reaction of said radicals and removes materials to be cleaned, the improvement in which said cleaning gas containing said radicals is introduced directly into said film-forming chamber. BRIFE DESCRIPTION OF THE DRAWINGS [0020] [0020]FIG. 1 is a vertical cross-sectional view of a plasma film-forming apparatus of the prior art; [0021] [0021]FIG. 2 is a vertical cross-sectional view of a plasma film-forming apparatus according to first and second embodiment of this invention; [0022] [0022]FIG. 3 is vertical cross-sectional view of a plasma film-forming apparatus according to a third embodiment of this invention; [0023] [0023]FIG. 4 is a cross-sectional view taken along the line iv-iv in FIG. 3; [0024] [0024]FIG. 5 is a graph for showing the comparisons of the cleaning rates of SiNx films between the prior art and the first embodiment of this invention; and [0025] [0025]FIG. 6 is a graph for showing the cleaning rates of SiOx film by the second embodiment of the invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS [0026] Next, embodiments of this invention will be described with reference to the drawings. The parts corresponding to the parts of the above prior art are denoted by the same reference numerals, the detailed description of which will be omitted. [0027] [0027]FIG. 2 shows a plasma (CVD) film-forming apparatus 20 according to a first embodiment of this invention. A cathode electrode 4 connected to a high frequency electric power source 8 is arranged in the upper wall of a vacuum tank 2 . An anode electrode 3 supporting a substrate 9 and connected to the earth is arranged opposite to the cathode electrode 4 in the film-forming chamber 10 . [0028] A film-forming gas introducing pipe 15 is connected to a central hole of the upper wall of the cathode electrode 4 . A shower plate 5 having numerous small holes is fixed to the lower end of the cathode electrode 4 , opposite to the substrate 9 . [0029] A radicals-producing means 21 is arranged outside the vacuum tank 2 . An input side of the radicals-producing means 21 is connected through a conduit 22 to a not-shown cleaning gas supply source. The radicals-producing means 21 consists of a chamber for a cleaning gas introduced from the conduit 22 and a high frequency electric power source applying a high frequency electric power to the contained cleaning gas in the chamber for producing radicals. [0030] An output side of the radicals-producing means 21 is connected through a valve 24 to one end of a pipe 23 for introducing a cleaning gas. Another end of the pipe 23 is connected to a hole made in the side wall of the vacuum tank 2 , positioning between the shower plate 5 and the anode electrode 3 . Thus, the pipe 23 for introducing the cleaning gas directly communicates with the inside of the film-forming chamber 10 . [0031] In the film-forming operation, the film-forming chamber 10 is evacuated through the exhaust port 7 and is put under the lower pressure, as in that the prior art. A film-forming gas (SiH 4 gas, NH 3 gas) is supplied through the film-forming gas introducing pipe 15 onto the shower plate 5 . It is ejected into the film-forming chamber 10 from the numerous small holes of the shower plate 5 . A high frequency electric power is supplied to the cathode electrode 4 by the high frequency electric power source 8 to decompose and make the introduced film-forming gas reacting. Thus, a film of SiNx is formed on the substrate 9 . [0032] In the cleaning operation of the film-forming chamber 10 , the film-forming chamber 10 is evacuated through the exhaust port 7 and put under the lower pressure. Then, the cleaning gas such as NF 3 gas is supplied to the radicals producing source 21 to which a high frequency electric power (400 kHz) is supplied. Fluorine radicals are produced in the radicals-producing source 21 . The valve 24 is opened to introduce directly the NF 3 gas containing the fluorine radicals into the film-forming chamber 10 through the gas-introducing pipe 23 as the means for introducing the cleaning gas. The fluorine radicals react on the SiNx film to be cleaned. Thus, the interior of the film-forming chamber 10 is cleaned. Thus, in this embodiment, the radicals pass not through the shower plate 5 , but directly introduced into the film-forming chamber 10 to be cleaned. Thus, most of the radicals can be prevented from dissipating before introduced into the film-forming chamber 10 . The film-forming chamber 10 can be effectively cleaned. As shown in FIG. 5, the cleaning rate of the SiNx according to this embodiment is higher about twenty times than the prior art method in which the radicals pass through the shower plate 5 . [0033] Further, the micro-wave generator of a high frequency such as 2.45 GHz was used for producing radicals in the radicals-producing means of the prior art. It is very expensive. In the embodiment of this invention, it is not necessary to use such as an expensive high-frequency electric power source. A high frequency electric power source of 400HKz, which takes lower cost, can be used to produce radicals. The experimental results as shown in FIG. 3 were obtained with the electric power source of 400 KHz. The frequency is not limited to 400 KHz. Similar effects can be obtained within the range of 100 to 1000 KHz. A high frequency electric power source of lower frequency than 1000KHz takes low cost. Accordingly, a plasma film-forming apparatus using such a high frequency electric power source takes lower cost, in comparison with the prior art plasma film-forming apparatus. [0034] Further, in the embodiment of this invention, polyfluoro ethylene (trade name-Tefron) is coated on the inner surface of the cleaning gas introducing pipe 23 . Accordingly, the radicals can be transported through the cleaning gas introducing pipe 23 without the dissipation. Thus, the life of the produced radicals can be longer. [0035] Sufficient cleaning rate can be obtained for SiNx film, even only by radicals. However, radicals are very directional. Accordingly, there is the possibility that the films are not removed around the shower plate 5 and anode electrode 3 , when only the radicals are used for cleaning. Accordingly, in the cleaning operation, Argon gas as inert gas for sputter cleaning is introduced into the film-forming chamber 10 besides NF 3 gas including fluorine radicals. A high frequency electric power of 27.12 MHz frequency and 0.15 W/cm 2 electric power density is applied to the introduced gases from the high frequency electric power source 8 which is used also for film-forming. [0036] Thus, the argon gas is electrically devided into Ar ions (Ar + ) and electrons. The film-forming chamber 10 is cleaned both with the chemical reaction by radicals and with Ar ions sputtering. It can be more uniformly cleaned, and the cleaning efficiency can be improved. The Ar gas is introduced into the film-forming chamber 10 through the cleaning gas introducing pipe 23 or through the film-forming gas introducing gas 15 . Insteads, it may be introduced through a special pipe for spluttering gas. [0037] Next, there will be described a second embodiment of this invention. SiO 2 film is formed in the same plasma film-forming apparatus 20 as in the first embodiment. For example, SiH 4 gas and N 2 O gas are used as a film-forming gas. The SiO 2 film is formed on the substrate 9 in the same manner as the first embodiment. [0038] In the cleaning operation of the film-forming chamber 10 , NF 3 gas containing fluorine radicals is directly introduced into the film-forming chamber 10 from the gas introducing pipe 23 . The fluorine radicals reacts chemically with the SiO 2 film to be cleaned. Thus, the film-forming chamber 10 is cleaned. [0039] Although the radicals are effectively introduced into the film-forming chamber 10 , a sufficient cleaning rate cannot be obtained for SiO 2 film. Accordingly, Ar gas is introduced into the film-forming chamber 10 . The high frequency electric power is applied to the Ar gas from the cathode electrode 4 by the high frequency electric power source 8 . Ar ions are produced. The film-forming chamber 10 is cleaned also by the Ar ion sputtering. [0040] [0040]FIG. 6 shows the comparison results of the cleaning of the SiO 2 films among the cleaning only by the radicals (fluorine radicals), the cleaning only by the ions (Ar + ) and the cleaning by the ions (Ar + ) and radicals. When the film-forming chamber 10 was cleaned only by the ions, the high frequency electric power was applied to the cathode electrode 4 at the frequency of 27.12 MHz and the power density of 0.67W/cm 2 . When the film-forming chamber 10 was cleaned by the radicals and ions, the high frequency electric power was applied to the cathode electrode 4 at the same frequency as that of the cleaning only by the ions, and at the half power density of that of the cleaning only by the ions. [0041] The cleaning rate of the cleaning operation only by the radicals are low. However, that of the cleaning operation by combination of the radicals and ions is substantially equal to that of the cleaning operation only by the ions. The required power of high frequency in the cleaning operation by combination of the radicals and ions is about half of that in the cleaning operation only by the ions. Accordingly, the plasma damage to the shower plate 5 can be reduced, and so the shower plate 5 can be prevented from being deteriorated. [0042] Next, there will be described a third embodiment of this invention. Parts in this embodiment which correspond to those in the first and the second embodiments, are denoted by the same reference numerals, the detailed description of which will be omitted. [0043] [0043]FIG. 3 shows a vertical cross-sectional view of a plasma film-forming apparatus 30 according to this embodiment. FIG. 4 shows a cross-sectional view taken along the lines IV-IV in FIG. 3. It is used for a large-sized substrate. [0044] In the first and the second embodiments as shown in FIG. 2, the radicals are introduced laterally into the film-forming chamber 10 . Accordingly, portions nearer to the outlet of the gas-introducing pipe 23 are sooner cleaned. When the size of the substrate 9 is about 400 mm×500 mm, there is no problem. However, when the size of the substrate is large as 730 mm×920 mm, the cleaning rate is generally lowered. The film-forming chamber 10 is large-sized for a large substrate. The cleaning rates are considerably different between portions near to the outlet of the gas-introducing pipe 23 and portions farther from that. Totally, the cleaning rate is lowered. [0045] In this embodiment, a first cleaning-gas introducing pipe 33 a is connected to one side wall 2 a of the film-forming chamber 10 , and another cleaning-gas introducing pipe 33 b is connected to another side wall 33 b of the film-forming chamber 10 , which is facing to the one side wall 2 b. [0046] The cleaning-gas is introduced into the film-forming chamber 10 from the two outlets. As shown in FIG. 3, the first and second cleaning-gas introducing pipes 33 a and 33 b are shifted from the centers of the walls in opposite directions. The cleaning-gas is more uniformly introduced into the film-forming chamber 10 than in the case that the cleaning-gas introducing pipes 33 a and 33 b are connected to the walls, facing to each other. Of course, they may be connected to the walls, facing to each other. [0047] The cleaning rate of the large film-forming chamber 10 with the arrangement of FIG. 4 is about three times as high as that in the case that only one cleaning-gas introducing pipe 22 is connected to the one side wall as in FIG. 2. The high frequency electric power source of about 100to 1000 KHz for producing radicals, is simple in constructions and small-sized in comparison with the micro-wave generator. [0048] The price of the former is one third as low as that of the latter. Accordingly, plural radical-producing sources can be easily arranged, and the manufacturing cost is not so high. [0049] While the preferred embodiments have been described, variations thereto will occur to those skilled in the art within the scope of the present inventive concepts which are delineated by the following claims. [0050] For example, in the above embodiments, NF 3 is used as the cleaning-gas. However, it is not limited to NF 3 , but CF 4 , C 2 F 6 , C 3 F 3 , CHF 3 , SF 6 etc. may be used as the cleaning-gas. Inert gas for sputtering cleaning is not limited to Ar. Further, the film to be formed in the substrate or to be cleaned, is not limited to SiNx and SiO 2 . Further, the high frequency power to be applied to the cathode electrode 4 , is not limited to the above frequency and to the above electric power density. Frequency between 10 to 100 MHZ may be adjusted. [0051] Electric power density between 0.03 to 0.7 W/cm 2 may be adjusted. [0052] In the third embodiment, two cleaning-gas introducing pipes are connected to the film-forming chamber 10 . The number of the connected pipes is not limited to two, and more than two. The wall connecting the cleaning-gas introducing pipe, is not limited to the side wall, and may be upper wall or bottom wall, of the vacuum tank 2 .

In a plasma film-forming apparatus which includes a film-forming chamber in which a substrate is arranged, a film-forming gas introducing pipe connected to a supply source of a film-forming gas at its first end, a shower plate through numerous holes of which a second end of said film-forming gas introducing pipe communicate with said film-forming chamber, film-gas exciting means for exciting film-forming gas introduced through said shower plate into said film-forming chamber, to form a film on the surface of said substrate with the chemical reaction, radicals-producing means which excites said cleaning gas and produces radicals, and cleaning-gas introducing means which introduces said cleaning gas containing said radicals into said film-forming chamber, the improvement in which said cleaning-gas introducing means communicate directly with said film-forming chamber.

CROSS REFERENCE TO RELATED APPLICATION [0001] This application claims priority from U.S. Provisional Patent Application Ser. No. 60/596311, filed Sep. 14, 2005 and entitled “Method and Apparatus For Forming A melt Spun Nonwoven Web”. The disclosure of this provisional patent application is incorporated herein by reference in its entirety. FIELD OF THE INVENTION [0002] The present invention pertains to methods and apparatus for spinning thermoplastic polymer filaments and, more particularly, to improvements therein using non-eductive drawing. BACKGROUND [0003] In general, spun bond nonwoven production machines can be classified as eductive “open” spinning systems and non-eductive “closed” spinning systems. Conventional broad loom eductive systems can generally trace their roots to the subject matter disclosed in U.S. Pat. No. 3,802,817 (Matsuki et al.) which describes a system that extrudes a curtain of filaments, extending the full width of the machine into, atmosphere (and/or impinged with cooled air). The curtain is then subjected to the action of a pair of air jet streams in a sucker, or filament drawing unit, the jet velocity of said jet streams being selected in the turbulent range. The jets act to entrain air from atmosphere along with the fibers which are then projected from the drawing unit onto a gas pervious conveyor belt collector to form a web. The quenching air system is separate from the filament drawing unit system. The fibers being spun are typically exposed to atmosphere at least once and usually twice: once just after being extruded and then again between the drawing device and the collector belt. This basic design has evolved into modern systems, for example, see U.S. Pat. Nos. 6,183,684 (Lu), 6,783,722 (Taylor) and 6,692,601 (Najour), all of which describe improved non-eductive “open” spinning nonwoven production systems. [0004] Conventional broad loom non-eductive spinning systems can generally trace their roots to the disclosure in U.S. Pat. No. 4,405,297 (Appel et al.) which describes a system for forming spun bond nonwoven webs by spinning a plurality of filaments into a quench chamber where they are contacted with a quenching fluid, then utilizing the quench fluid to draw the filaments through a nozzle spanning the full machine width, and collecting the filaments as a web on a gas pervious conveyor belt collector. The fibers being spun are usually enclosed or shielded from atmosphere until they are formed into a web on a conveyor. This basic design has evolved into modern systems, for example U.S. Pat. No. 5,032,329 (Reifenhauser). [0005] There are also hybrids of the two arts in which closed systems are aided by high pressure eductive jets to increase filament speeds, as shown in U.S. Pat. Nos. 5,503,784 (Balk) and 5,814,349 (Geus et al.). [0006] The systems and methods discussed above have various disadvantages and limitations. Specifically, eductive (open) type systems inherently create high levels of turbulence and vorticity that are hard to control from day to day, and which tend to entangle and group the filaments into bundles, thereby limiting the uniformity of the final products. Furthermore, prior art eductive systems involve small fixed eductor throat openings which suffer drawbacks such as frequent plugging and cannot be opened to clear drips and plugs. In addition to plugging the throat of an eductor, small deposits of polymer drippings, monomer build up and scratches from constant cleaning all affect the patterns of turbulence on a day to day, and even on an hour to hour basis. The high speed jet nozzles themselves tend to become clogged by debris that enter from the process air supply and monomer, thereby drastically upsetting flow in the highest speed areas and creating vortices in the drawing unit. These systems also require two sources of air and two sets of associated equipment; one, a low pressure cooled air source that is used to quench the molten filaments by removing heat energy; and the other, a high pressure air source required to produce high velocity air to draw the filaments. The high velocity air generates high noise levels as it draws the filaments. While higher spin speeds required for spinning polyester and Nylon can be achieved with specialized eductive systems, the problems of turbulence and system hygiene are amplified by higher air jet pressures and velocities. Thus, forming a uniform web is very difficult with these systems because the fiber/air stream is moving very fast relative to the vertically stationary (but horizontally moving) collector belt. The amount of energy in the stream is so high at the belt that the fibers tend to bounce off the belt. The fibers can also be blown off the belt by the excess of air that cannot be passed through the below-the-belt vacuum system that generally is not able to evacuate all of the process air. [0007] Conventional non-eductive (closed) systems typically permit somewhat more web formation control than do eductive systems; however, the non-eductive systems have fiber spin speed limitations. The long nozzle or throat sections where the fibers are attenuated are subjected to large structural loads from pressurized quench fluid. Even at pressures slightly above atmosphere, these walls must sustain loads of thousands of kilograms. These pressure loads cause deflection of the walls which, in turn, have to be pushed back into place uniformly across the machine width. The geometry of the nozzle controls quench fluid speed, which in turn controls fiber speed and formation of the web. Structural support of the wall geometry severely limits the pressure of the quench fluid, ergo the permissible velocity of the fluid in the nozzle and fiber speed. Also, the large surface areas of the nozzle have the same system hygiene problems as are present in eductive systems, but there is more surface area for deposits to collect, and it is not easy to get inside these nozzles to effect cleaning. [0008] Hybrid systems were conceived primarily to increase the spin speeds of non-eductive systems. Hybrids typically incorporate eductive air jets somewhere along the nozzle area, which act to boost nozzle velocity without increasing quench fluid pressure. These systems have worked for some but not all higher speed spinning applications, and tend to be very complicated and capital intensive, and require substantial operation and maintenance attention. SUMMARY OF THE INVENTION [0009] In contrast to the prior art systems described above, the system and method of the present invention involve an initial quench chamber and the use of a continuous two-dimensional slot across the entire machine width which produces a linear plane of filaments in the slot impingement point section. The linear plane of filaments has substantially constant filament distribution across the machine width, and provides for good control of cross-machine uniformity. As used throughout this description, “machine widths” refers to a dimension corresponding to the width generally of the spinning plate and is perpendicular to the collector belt travel. It is preferred that the width correspond to the desired end web width. The width of the machine is only limited by the ability to machine and maintain close geometric tolerance of the impingement slot dimensions. The process equipment is very simple compared to both eductive and non-eductive systems. [0010] No air is educted into this system as the quench fluid, usually air, undergoes uniform acceleration into the impingement slot where the drawing force is developed. The same air is used for two purposes: first to quench the filaments and then to draw them as the air exits through the drawing impingement slot at high velocity. The drawing chamber is relatively small and there is substantially no nozzle length parallel to the fiber/air stream; therefore higher quench pressures can be obtained without leading to structural deflection problems that affect spinning area geometric tolerances which in turn would cause variations in spin velocities and turbulence. Higher pressures and the mixing effect of the exiting fiber/quench stream produce very high air and fiber velocities. The small amount of close tolerance machined surface area that is exposed to the fiber stream (i.e., only the tips of the air knives) collect far less dirt, polymer drippings and monomer build up than other systems. Cleaning is much simpler and only takes a few seconds while the machine is running by opening the slot for a few seconds and wiping clean the knife edges. An automatic wiper could be employed. This can be done several times a day, if needed, whereas most other conventional systems require hours and even days to clean educator and nozzle surfaces. [0011] By selecting a suitable slot gap opening, the necessary drawing tension can be obtained. Filament cooling is controlled by regulating the temperature of the quench fluid and controlling the rate of flow of air past the filaments to exhaust ports near the top of the quench chamber, as is known in the prior art. The amount of quench air exiting the duct is important to the operation of the process, so this flow rate is preferably closely monitored and controlled. If there is too high an exhaust flow, the velocity of the air through the filament bundle will cause the filaments to waver and stick to each other, thereby causing filament breakage. The filaments will also be cooled too rapidly and large denier, brittle filaments will be produced. With too little exhaust, the filaments may not be totally quenched when they enter the drawing impingement slot, increasing the incidence of sticking to the slot's air knives. [0012] To achieve the benefits of the present invention, it is desirable that the apparatus be constructed and the method carried out within certain ranges of parameters. For example, the quench air should be maintained at a temperature in the range of from about 40° F. to 200° F. The air flow rate should be maintained within the range of from 850 cubic meters per hour to 3,400 cubic meters per hour per meter of machine width, and the slot opening should have a length from about 0.5 mm to 10 mm. As indicated above, the exhaust flow rate is important in achieving the desired filament properties and, generally, will be within the range of from nearly 0 to about 400 cubic meters per hour per meter of machine width. [0013] The length of the quench chamber for a particular application will depend, of course, upon the material being spun and the particular web properties desired. Accordingly, these parameters may vary widely, but, in general, will be at least 250 mm and, preferably within the range of from about 250 mm to 1500 mm for the length of the quench zone from the spinneret to the impingement slot. Similarly, the spinneret capillaries may be in many configurations but will, generally, be employed in the range of from about 500 to 8000 holes per meter of machine width in a uniform capillary array. As will be apparent from the foregoing description, the method and apparatus of the present invention are extremely flexible and can be varied to accommodate a wide variety of materials and operating conditions. That constitutes a particular advantage and feature of the present invention. [0014] The above and still further features and advantages of the present invention will become apparent upon consideration of the following definitions, descriptions and descriptive figures of specific embodiments thereof wherein like reference numerals in the various figures are utilized to designate like components. While these descriptions entail specific details of the invention, it should be understood that variations may and do exist and would be apparent to those skilled in the art based on the descriptions herein. BRIEF DESCRIPTION OF THE DRAWINGS [0015] FIG. 1 is a schematic flow diagram of a preferred embodiment of the present invention shown operating in a “run” mode. [0016] FIG. 2 is a schematic flow diagram of the preferred embodiment of FIG. 1 shown operating in a “run” mode. DESCRIPTION OF THE PREFERRED EMBODIMENTS [0017] The following detailed explanations of FIGS. 1 and 2 of the preferred embodiments reveal the methods and apparatus of the present invention. The architecture depicted in the drawings is a conceptual diagram illustrating major functional units, and does not necessarily illustrate physical relationships. [0018] The present invention harnesses the positive aspects of both eductive and non-eductive (and hybrid) systems into a more efficient and simpler design. More importantly, the invention solves many of the problems associated with conventional nonwoven spun bond systems including: spinning speed limitations, energy consumption, machine element cleanliness (i.e., hygiene), web uniformity, capital costs and process control. The invention also incorporates aspects of another, different type of nonwoven web forming technology, the meltblown process, as shown in U.S. Pat. No. 3,825,380 (Harding et al.) to help improve web formation control. [0019] While the invention is described in connection with preferred embodiments, it will be understood that it is not intended to limit the invention to those embodiments. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. [0020] Referring to FIG. 1 , the first step in the method of the invention is to provide a thermoplastic polymer in fluid condition for spinning. The flexibility of the system and method of the present invention allows a wide variety of polymers to be processed. For example, any of the following may be employed: polyamides, polyesters, polyolefins, polyvinyl acetate, polyvinyl chloride, polyvinyl alcohol, and the like. It is, of course, contemplated to also utilize other spinable materials which may not be ordinarily considered polymers such as, for example, molten glass and carbon fiber pre-cursors. It is important that the material be capable of being made sufficiently fluid for spinning and otherwise have the properties necessary to undergo drawing in the filament drawing zone. Other examples will become apparent to those skilled in the polymer art. [0021] The molten polymer or other raw material is fed from supply 2 to hopper 4 , then through screw extruder 6 , filter 8 , and polymer transfer pipe 10 to spin box 12 , which contains one or more metering pumps 14 . Filaments 16 are spun through spinneret 18 with appropriate openings arranged in one or more rows forming a curtain of filaments 16 directed into the quench chamber 20 . In the quench chamber 20 the filaments 16 are contacted with air or other cooling fluid 22 received through fluid inlet 24 and diffused through perforated apertured plates 26 . The quench fluid, usually air, is maintained cooler than the filaments, preferably near ambient temperature, but anywhere, for example, in the range of from about 40° F. to 200° F. The quenching fluid is supplied under pressure of less than 4 bar, preferably less than 2 bar, and a portion is preferably directed through the filament curtain 16 and removed as exhaust through ports 28 . [0022] As described above, the proportion of the air supplied that is discharged as exhaust will depend on the polymer being used and the rapidity of quenching needed to give desired filament characteristics such as denier, tenacity and the like, and to exhaust by-products of extrusion i.e.: smoke and monomer. [0023] As quenching is completed, the filament curtain is directed through a narrowing lower end 30 of the quenching chamber into the impingement point slot opening 32 where the quench air attains a velocity that can be anywhere in the approximate range of 3,000 to 21,000 meters per minute. The drawing slot extends across the full machine width and is preferably formed by two identical air knives 34 having an angle in the range from about 15° degrees to 80°, with a preferred angle of 45°, spanning the width of the machine. In the preferred embodiment the bottom surfaces of the knives 34 are co-planar and substantially horizontal; however, it is to be understood that these surfaces can be angled to converge toward one another for certain applications. The convergence, if provided, would typically be such as to provide a protruding or convex bottom surface for the chamber, although in some instances a recessed or concave bottom surface may be provided. The movable air knives can be retracted from one another under the chamber assembly using a manually actuable and lockable slide arrangement, or a hydraulically or otherwise actuable arrangement. FIGS. 1 and 2 depict knives forming a 90° entry angle between them. The blades may either slide laterally or instead pivot about a point near the upper corner of the blade, whereby the tip of each blade would swing down in an arc until the upper blade surfaces came into a parallel relationship for cleaning. To pass slubs, the tips would only need to move ½″ or so apart. [0024] Referring to FIG. 2 , during start-up, the knives are fully retracted or spaced from one another so that the filaments can fall by gravity through the wide open slot. The low velocity of the incoming quench air is maintained through the wide open slot so that little aerodynamic drawing actually occurs. When polymer flow is fully established, the air knives are slowly moved toward one another to decrease the slot opening, increase the air velocity, and draw the filaments. If a major process upset occurs and the drawing slot becomes partially plugged or clogged with polymer during operation, one or both air knives can be momentarily drawn back until the polymer plug falls through the enlarged nozzle opening. The air knives 34 can then be moved back to their normal operating position. [0025] The position of the air knives relative to each other determines the size of the drawing nozzle opening and thus the velocity of the air going through the nozzle for a given quench air flow rate, pressure and exhaust setting. The filament drawing force increases as the air velocity increases so that the filament denier can be easily changed by simply increasing or decreasing the size of the nozzle opening. Filament denier can also be increased several other ways i.e.: enlarging the slot gap; reducing the air flow rate through the slot by decreasing the pressure in the chamber; increasing the exhaust air flow rate; lowering the quench air temperature; decreasing the polymer temperature; increasing the polymer viscosity; or increasing the polymer throughput per capillary. [0026] Thus, the filament deniers can be changed relatively easily and rapidly in several different ways which do not affect the distribution of filaments exiting the slot to atmosphere. In all cases, the slot desirably spans the entire width of the machine. Therefore, a distribution of filaments corresponding substantially identically to the distribution of the orifices in the spin plate across the machine width is maintained all the way to the outlet of the slot. When the fibers and quench fluid exit the impingement slot 32 , they are exiting to atmosphere. Exposing the filaments to the interior of a high speed air stream, similar in speed to an eductive fiber draw unit jet stream, produces very good energy transfer from quench fluid velocity to fiber speed, for several reasons: The air jet formed at the impingement point is transferring energy only to fibers (like a non eductive system) and not wasting energy entraining air from atmosphere to create the low pressure suction at the top of an eductive drawing device. The fibers are exposed to the air jet formed inside the impingement point, which means that the fibers see the peak velocity of the stream. In eductive systems, the fibers enter the stream (in the fiber draw unit) after the jet achieves peak velocity, after it mixes with atmosphere and entrained air, so that that the resultant energy transfer, directly to the fibers, is lower. When a stream of fluid is directed through an air knife slot to atmosphere, it immediately loses its pressure as it expands to atmosphere. Energy of the quench fluid mass is transformed from pressure to velocity. The stream begins to “opens up” or widen from the original slot width as the pressurized compressible gas expands, which, in turn, begins to slow the stream velocity. If one adds fibers at this point, the mix of expanding fluid and independent flexible fibers creates a highly turbulent mixing zone just below the exit which tremendously aids the transferring of quench fluid energy (mass×velocity) to fiber velocity. This also acts to slow down the stream. More specifically, within the first few inches after leaving the slot opening of the pressurized quench chamber, the stream of fibers and quench fluid is rapidly slowed as velocity energy of the quench fluid is transferred to the fibers and the fiber air stream entrains air from atmosphere, resulting in velocities of quench fluid and fibers that are much closer matched than conventional eduction open spinning systems. The fibers have a chance to slow down to a speed lower than their peak spinning speed which causes them to collapse on themselves and interweave and entangle before they reach the conveyor belt, resulting in improved web formation uniformity and isotropicity. [0030] The distance from the spinneret to the impingement point is comparatively short; thus, the effects of friction between the spinning fibers' velocity and the quench fluid do not create much friction resistance on the fiber bundle compared to conventional systems with long quench and spin line distances. The higher density (compared to atmosphere) acts to remove heat energy faster, but can also lead to higher friction losses. Hence the spin line can be shorter than conventional systems [0031] The dynamic nature of this fiber and quench fluid “stream” after it exits the slot impingement point is similar in nature to the fiber and air stream in meltblown processes. Therefore, those skilled in the art of forming meltblown nonwoven webs can control the laydown process in a similar manner. An additional advantage of this system is that the velocity energy of the system expands and dissipates very quickly, which means that the lay down speed of the fibers when they land on the conveyor collector are significantly slower than in conventional systems, which is much easier to control and leads to better web uniformity. As the fiber bundle slows down before hitting the belt, the fibers bunch up and fold over on each other, leading to better fiber distribution, which makes a more isotropic web in terms of strength and elongation and visual uniformity of basis weight distribution. [0032] Referring again to FIG. 1 , a very important element of the invention involves the web forming table 40 positioned below the slot 32 of the quench chamber 20 to receive filaments 16 and form the filaments into a non-woven web. The web forming table 40 comprises a vacuum suction box 42 for pulling down filaments onto a moving mesh wire belt conveyor 44 which transports the as-formed web to the next stage of the process for strengthening the web by conventional techniques to produce the final non-woven fabric web. For example, one possible bonding method could be calendering, 50 . After bonding, the nonwoven fabric can be wound into rolls 60 for ease of shipping to final end user. [0033] The specific test results listed in the Table below are illustrative of the operation of the present invention. The tests were carried out on apparatus of the type illustrated in FIGS. 1 and 2 having parameters indicated in the Table, a quench zone length of 24 inches from spinneret face to slot opening, slot gap openings as indicated in the Table, and a capillary throughput as indicated in the Table. The polymer spun was 35 MFI polypropylene with a melt temperature of about 235° C. The incoming angle of the combined air knives forming the slot opening was 90°, with an outgoing angle of 180°. TABLE Quench Air slot Fume pack spin air Press. gap, Exh Low High Avg. Spin press, speed Run # temp F. psig gm/hole/min in. Diam. Denier Denier Denier Well? psi m/min 23 44 7.5 1 0.067 3/16″ 2.2 3.8 3.00 stable 1580 3,000 24 45 10 1 0.067 3/16″ 2.5 4.2 3.35 stable 1600 2,687 25 48 12 1 0.067 3/16″ 2.2 2.8 2.50 stable 1620 3,600 26 50 12 1.21 0.067 none 2.5 3.4 2.95 stable 1810 3,692 27 52 12.5 1.5 0.067 none 2.8 4.2 3.50 stable 2040 3,857 28 51 12.5 0.83 0.067 none 1.7 2.5 2.10 stable 1580 3,557 29 54 12.5 0.55 0.067 none 0.5 2.2 1.35 stable 1320 3,667 30 43 15 0.55 0.05 none 1.2 2.5 1.85 stable 1360 2,676 31 43 15 1 0.05 none 2.8 4.2 3.50 stable 1800 2,571 Conditions common to all runs: 35 MFI polypropylene polymer temperature 230° to 240° C. spinneret with 27 round spinning orifices in a 2″ diameter pattern spinning distance from spinneret face to slot knife edges = 24″ slot entrance vee = 90 degrees and exit flat [0034] In summary, the foregoing specific examples illustrate the present invention and its operation highlighting spinning advantages. Preferred embodiments include the formation of low basis weight webs from fine polypropylene filaments of under 5 denier and production rates over 200 kg per hour per meter of beam width; point bonding these webs to produce a nonwoven material useful for many applications including (1) liners for sanitary products, (2) limited use garments, (3) surgical drapes and even (4) durable goods. [0035] Another embodiment would include the formation of webs from fine or coarse filaments of polyester under 15 denier and production rates over 200 kg per hour per meter of beam width; point bonding or area bonding these webs to produce a nonwoven material useful for (1) industrial filtration, (2) automotive carpet, (3) roofing applications, (4) commercial dryer sheets (5) hygiene products. [0036] The method and apparatus of the present invention are useful to make fine continuous filaments even if they are not formed into a spunbond web. For example, the spun fibers can be collected and used as pillow and cushion stuffing. For this purpose the fibers can be feed directly into the pillow or cushion casing from the slot opening of the quench chamber. Alternatively, the fibers can be baled and sold. [0037] Thus it is apparent that there has been provided, in accordance with the invention, an improved method and apparatus for forming fine continuous filaments having particular utility in forming nonwoven webs in a manner that that fully satisfies the objects, aims, and advantages set forth above. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. [0038] Having described preferred embodiments of a new and improved method and apparatus for forming fine continuous filaments in general and melt spun nonwoven webs in particular, it is believed that other modifications, variations and changes will be suggested to those skilled in the art in view of the teachings set forth herein. It is therefore to be understood that all such variations, modifications and changes are believed to fall within the scope of the present invention as defined by the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

A method and apparatus for forming nonwoven melt spun webs by spinning a curtain of filaments into a pressurized chamber where they are contacted with pressurized quenching fluid, then using the fluid to draw the filaments through a slot at the bottom of the chamber. The slot is a narrow two dimensional impingement point running the length of the filament curtain where the pressurized quench fluid passes through, escaping to atmosphere. The fluid pressure (potential) energy in the chamber is exchanged for velocity (kinetic) energy at the slot impingement point. The fast moving stream of fluid inside and exiting the slot acts to pull, or draw the filaments through the slot. The fluid and fiber stream is deposited onto a porous collection conveyor belt, forming a fleece web. The invention is more efficient, less complicated, easier to maintain and easier to control than prior systems for melt spinning nonwoven webs.

FIELD OF THE INVENTION This invention relates to chiral scaffolds, to their preparation and also to novel chemical intermediates useful in the synthesis of such scaffolds; the scaffolds can be used for the preparation of information-rich single enantiomer compound libraries. BACKGROUND OF THE INVENTION Drug discovery may utilise, for screening, a library in which individual compounds are single isomers. This generates 3-dimensional information that can be enhanced by applying computational methods for lead optimisation. In order to prepare single isomer libraries, the appropriate chiral scaffold precursors should be in isomerically pure form, in which relative and absolute configuration is defined across all stereogenic centres. It is equally important that, for a scaffold having a particular bond connectivity, all possible stereoisomers can be prepared. Thus a series of scaffolds of this type can be elaborated chemically into different but defined directions of 3-D space, to give isomeric compounds which may have very different properties in a chiral biological environment. An important consideration in the development of synthetic routes towards scaffolds is that the chemistry should have the potential for scale-up. Then, in the event that the library screens generate useful lead compounds, the appropriate scaffold can be produced in sufficient quantity to support any subsequent drug discovery and development. Pipecolic acid and 4-hydroxypipecolic acid are natural non-proteinogenic amino acids found in plants. In addition to the free amino acid, pipecolic acid is also found in complex biologically active molecules (for an example, see Nicolaou et al.; J. Am. Chem. Soc. 1993, 115, 4419–4420). Derivatives of pipecolic acid are known to display anaesthetic (GB-A-1166802), NMDA agonist and antagonist (Ornstein et al.; J. Med. Chem. 1989, 32, 827–833), anticoagulant (Okamoto et al.; Biochem. Biophys. Res. Commun. 1981, 101, 440446) and glycosidase activity (Bruce et al.; Tetrahedron 1992, 46, 10191–10200). Pipecolic acids have also been used in peptide chemistry as analogues of proline (Copeland et al.; Biochem. Biophys. Res. Commun. 1990, 169, 310–314). In the light of the diverse activities displayed by such pipecolic acid derivatives, single enantiomer libraries using such compounds as the scaffold would be a highly desirable tool for screening. For a recent review of the synthesis of pipecolic acids, see Couty, Amino Acids 1999, 16, 297–320. A common synthetic route to racemic 4-hydroxypipecolic acid derivatives, has been to use an acyliminium ion cyclisation on a suitably protected homoallylic amine (Hays et al.; J. Org. Chem. 1990, 56, 4084–4086). This approach has been adapted to furnish enantiomerically pure cis 4-hydroxypipecolic acid derivatives provided a chiral protecting group is used in the synthesis (Beaulieu et al.; J. Org Chem. 1997, 62, 3440–3448). However, the protecting group does not offer any asymmetric induction, and the enantiomers have to be separated by a laborious co-crystallisation with (−)-camphorsulphonic acid. A similar approach to the synthesis reports a separation by recrystallisation of a diastereoisomeric intermediate (Skiles et al.; Bioorg. Med. Chem. Lett. 1996, 6, 963–966). Another common theme in the synthesis of enantiomerically pure cis 4-hydroxypipecolic acid derivatives has been to fix the stereochemistry of the carboxylate group using a (L)-aspartic acid, and use this stereocentre to direct reduction of a ketone at the 4-position (Golubev et al.; Tetrahedron Lett. 1995, 36, 2037–2440; Bousquet et al.; Tetrahedron 1997, 46, 15671–15680). Two routes derived from carbohydrate starting materials have been reported, an atom inefficient synthesis starting from D-glucoheptono-1,4-lactone (Di Nardo and Varela; J. Org. Chem. 1999, 64, 6119–6125) and from D-glucosamine (Nin et al.; Tetrahedron 1993, 42, 9459–9464). All of these approaches yield only the cis-diastereoisomer. In particular, it remains a challenge to synthesise the two stereoisomers of trans-4-hydroxypipecolic acid in conveniently protected form, especially the N-Boc derivatives (i) and (ii) The most common approach has been to synthesise the cis-diastereoisomer, followed by a tedious inversion of the 4-hydroxy group. An alternative approach has utilised a ring expansion of 4-hydroxy-L-proline (Pellicciari et al.; Med. Chem. Res. 1992, 2, 491–496) and provides access to both diastereoisomers of 4-hydroxy-L-pipecolates. However, this route is unattractive on a large scale, owing to the two chromatographic steps needed for the separation of regio- and diastereomeric mixtures, and also the requirement for the hazardous reagent ethyl diazoacetate to effect ring expansion. Both enantiomers of 2-acetamidopent-4-enoic acid are readily available in large quantities via bioresolution of a racemic mixture, and as such are valuable chiral building blocks. Using standard literature chemical methods, it is possible to convert both enantiomers of suitably protected 2-acetamidopent-4-enoic acid into mixtures of diastereoisomers (A) and (B) These diastereoisomeric ester mixtures (A) and (B) may be convenient intermediates for the preparation of scaffolds if their separation could be readily achieved. Although selective crystallisation can often provide a simple means to achieve scaleable separation of diastereoisomers, this technique is not applicable to mixtures (A) and (B), which are obtained as oils. There are isolated reports in the literature that biocatalysis can be used as a means to effect separation of diastereoisomeric mixtures. For example, see Wang et al.; J. Org. Chem., 1998, 63, 4850–3; Hiroya et al.; Synthesis, 1995, 379–81; Mulzer et al.; Liebigs Ann. Chem., 1992, 1131–5. SUMMARY OF THE INVENTION One aspect of the present invention is based on a combination of realising the utility of a combination of complementary chiral scaffolds and of finding process chemistry that allows the preparation of such compounds on a commercial scale. For example, the present invention is based around novel process chemistry for the generation of a series of scaffolds comprising four trifunctionalised piperidines, the pipecolic acid derivatives (a)–(d) wherein R 1 is H, alkyl, alkoxy or aryl, and R 2 is H or alkyl. Such groups typically have up to 20 C atoms. In a preferred embodiment of the present invention, R 1 is benzyloxy and R 2 is methyl. For the purpose of this invention, R 2 =H is understood to include salt forms. The presence of N-Boc and methyl ester (or similar) protecting groups in these compounds allows selective elaboration of each of the functionalities present. Elaboration methods are well known to those skilled in the art. For such further use, e.g. for the generation of libraries in combinatorial chemistry, the four chiral scaffolds (a–d) should be provided in a format where they can each be treated in the same manner, usually by the parallel, selective introduction of a group at one functionality on the ring, followed by deprotection of another functionality and the introduction of another group, etc. For this purpose, the scaffolds may be provided, in separate containers, in a single unit, e.g. a multi-well plate. From this arrangement, it is possible to generate a library of compounds comprising single enantiomers of respective compounds where structural distinction derives from the stereochemistry of ring substituents as shown by formulae (a)–(d). In a particular aspect, the present invention is based on the discovery of biocatalytic separations of both of the diastereoisomeric mixtures (A) and (B), thus providing access to all four diastereoisomers of the piperidines without resorting to a chemical inversion step. The process described uses chemistry that is amenable to scale-up at each step. Another aspect of the present invention is based on the discovery that novel salts of N-tert-butoxycarbamoyl-2S-carboxy-4S-hydroxypiperidine (i) and (ii), and the opposite enantiomers thereof, allow for the enhancement of diastereoisomeric excess (de) by recrystallisation/crystallisation of partially enriched material from a suitable solvent. Thus, while the corresponding free acid is an oil, the present invention provides, via simple cracking of enriched salts, a practical and scaleable method to access N-tert-butoxycarbamoyl-2S-carboxy-4S-hydroxypiperidine (i) or the opposite enantiomer thereof. This process offers a very high degree of purity control (chemical, diastereoisomeric and enantiomeric) over the products. The novel salts may be represented by formula (1) or the opposite enantiomer thereof, wherein X + is a cation. DESCRIPTION OF PREFERRED EMBODIMENTS By means of the invention, a piperidine of formula (4) in which the relative stereochemistry of C-2 and C-4 substituents is trans, may be conveniently prepared via the enzymic separation of the mixture of diastereoisomers represented by formula (5) wherein Z is any suitable group. The same approach is applicable to the opposite enantiomeric series. The resolution alone may not yield the piperidine (4) in sufficiently high diastereomeric purity. Thus, the corresponding N-Boc derivative (i), a conveniently protected form for further chemical elaboration, may be contaminated with the cis-diastereoisomer; the present invention provides means to separate these compounds. An essential characteristic of novel salts (1) of the present invention is crystallinity. Suitable salts were identified by screening a range of amine bases, both achiral and chiral. Thus, in formula (1), X + represents a protonated amine, and X is typically a primary amine. Preferred primary amines are selected from the group comprising ethylamine, benzylamine and (S)-α-methylbenzylamine [(R)-α-methylbenzylamine for the opposite enantiomer]. Benzylamine is especially preferred. The process of the present invention requires the salt (1) to be partially diastereomerically enriched prior to crystallisation/recrystallisation. Preferably, a salt of at least 60% de is used, more preferably of at least 80% de. Recrystallisation of such material leads to a significant enhancement of diastereomeric purity, typically to at least 90% de, and frequently to at least 95% de, or higher. The identification of a solvent or a mixture of solvents suitable for recrystallisation of the salt (1) is carried out by conventional means, as would be practised routinely by a skilled practitioner. Such solvents are usually selected from C 1-4 alkanols, dialkyl ethers, and simple carboxylic esters such as ethyl acetate. In a preferred embodiment of the present invention, recrystallisation of the benzylamine salt of (1) from a 2:1 mixture of tert-butyl methyl ether and methanol effects an increase in diastereomeric purity from 80% de to >98% de. The two pairs of diastereoisomers A and B can be resolved using an enzyme in a volume efficient manner; the substrate concentration is typically 100 g/L or higher. Suitable enzymes for the biocatalytic separation may be identified by conventional screening techniques. Although such screening may identify non-functional or less preferred enzymes, the general procedure is known and, as is routinely done, can be used to identify further functional enzymes. For the mixture of diastereoisomers A, the preferred enzyme is Lipase AY30. For the mixture of diastereoisomers B, the preferred enzyme is Chirazyme L9. Although both enzymes hydrolyse the trans-diastereoisomer preferentially, their modes of differentiating between cis and trans are clearly different. If each of the enzymes is used to hydrolyse the alternative diastereoisomeric pair, differences are clearly seen. Lipase AY30 preferentially hydrolyses the trans-diastereoisomer of Pair (B) whereas Chirazyme L9 does not hydrolyse either of Pair (A). Hence it can clearly be seen that in this case the selectivity of Lipase AY is governed by the relative stereochemistry at C-2 and C-4. This is a very unusual observation in enzymic resolutions, which normally differentiate stereocentres based on the absolute configuration of the site at which reaction occurs. In Scheme 1, R 3 is H, alkyl or aryl, e.g. of up to 20 C atoms. The products of the resolution are (A1) and (A2) from Pair (A), as shown in Scheme 1. (A1) and (A2) are inseparable, but reaction of the mixture with phthalic anhydride forms the hemiphthalate derivative (A3) from (A2), which can be separated from (A1) by partitioning between saturated aqueous ammonium carbonate and toluene (step (i)). (A3) is recovered from the aqueous phase by acidification to pH 1 and extraction into toluene and refluxing in 2M HCl (step (ii)) leaves the free amino acid (A4). The N-Boc derivative A4 can be subjected to the diastereoisomeric enrichment described above. In step (iii), (A1) is deformylated using standard conditions, typically potassium carbonate in methanol, to (A5), which, if R 1 is benzyloxy and R 2 is methyl, is a crystalline solid. Recrystallisation of this allows a control over the purity as well as a method to enhance the diastereomeric excess of this compound such that a single diastereoisomer compound can be obtained. Compounds (A5) and (A4) are easily converted to chiral scaffolds (a) and (b) respectively by conventional protecting group manipulations. In a similar manner, products from the resolution of Pair (B) are the corresponding enantiomeric compounds (B1) and (B2) which can be elaborated using the same chemistry to scaffolds (c) and (d). Overall, the process of the present invention provides a scaleable and operationally simple means of obtaining any one of the four chiral scaffolds (a)–(d) and congeners thereof. The following Examples illustrate the invention. With regard to Example 4, see also Esch, et al; Tetrahedron 1991, 47, 4063–4076. EXAMPLE 1 Synthesis of N-tert-butoxycarbamoyl-2R-carboxy-4R-hydroxypiperidine To a solution of 2R-carboxy-4R-hydroxypiperidine (80% de, 140 g, 0.97 mol) in H 2 O (1 L) and THF (500 mL), Et 3 N (135 mL, 0.97 mol) was added dropwise. Di-tert-butyl dicarbonate (317 g, 1.46 mol) in THF (500 mL) was added in a steady stream. As the pH started to drop, a further portion of Et 3 N (135 mL, 0.97 mol) was added and the solution stirred at room temperature for 16 h. The THF was removed in vacuo and the resultant cloudy solution acidifed to pH 4 with 6M HCl and then to pH 3 with 1 M HCl. EtOAc was added and the mixture stirred for 2 min. The layers were separated, and the aqueous extracted with EtOAc (3×1 L). The combined organic extracts were washed with brine (1 L), dried (MgSO 4 ) and concentrated in vacuo to give N-tert-butoxycarbamoyl-2R-carboxy-4R-hydroxypiperidine as a viscous yellow oil (182 g, 76%). This material was used directly in the crystallisation described in Example 3. Preparation of N-tert-butoxycarbamoyl-2S-carboxy-4S-hydroxypiperidine from 2S-carboxy-4S-hydroxypiperidine was carried out using the same method. EXAMPLE 2 Crystallisation Screen: Amine Salts of N-tert-butoxycarbamoyl-2S-carboxy-4S-hydroxypiperidine Eight amines salts of N-tert-butoxycarbamoyl-2S-carboxy-4S-hydroxypiperidine were made using the following method: to a solution of 500 mg of 19% de N-tert-butoxycarbamoyl-2S-carboxy-4S-hydroxypiperidine in EtOAc (5 ml) at room temperature, a 1.1 molar equivalent of the amine was added. The solution was stirred at room temperature for 1 hr, then cooled in the fridge. Any crystals were harvested by filtration. The amines screened were ethylamine, octylamine, diisopropylamine, cyclohexylamine, dicyclohexylamine, benzylamine, R-α-methylbenzylamine and S-α-methylbenzylamine. The following amines gave crystalline salts: ethylamine, benzylamine and R-α-methylbenzylamine. The salts were recrystallised, and de values were determined by GC. Ethylammonium salt: recrystallised from MeOH/EtOAc, de 70% Benzylamine salt: recrystallised from MTBE, de 94% R-α-methylbenzylammonium salt: recrystallised from MeOH/MTBE, de 98% EXAMPLE 3 Preparation and Recrystallisation of N-tert-butoxycarbamoyl-2R-carboxy-4R-hydroxypiperidine, Benzylamine Salt N-tert-butoxycarbamoyl-2R-carboxy-4R-hydroxypiperidine (80% de, 182 g, 0.74 mol) was dissolved in EtOAc and the solution cooled on ice. Benzylamine (81.2 mL, 0.74 mol) was added dropwise and stirring maintained for 2 h. After overnight refrigeration, the solid was collected by filtration and dried. This solid (154 g) was recrystallised from MeOH (150 mL) and MTBE (300 mL). Filtration yielded N-tert-butoxycarbamoyl-2R-carboxy-4R-hydroxypiperidine, benzylamine salt of de >98% as a white solid (104 g, 40%). 1 H NMR (400 MHz, CD 3 OD) 7.40 (5H, m) 4.67 (0.4 H, minor rotamer, m) 4.59 (0.6H, d, J 5.5, major rotamer) 4.10 (2H, s) 3.94 (1H, br d, J 13.0) 3.59 (1H, m) 3.17 (1H, m) 2.48 (1H, m) 1.80 (1H, m) 1.43 (10H, m) 1.25 (1H, m). Preparation and recrystallisation of N-tert-butoxycarbamoyl-2S-carboxy-4S-hydroxypiperidine, benzylamine salt was carried out using the same method. EXAMPLE 4 Preparation of N-benzyloxycarbamoyl-2S-carbomethoxy-4R,S-formyloxypiperidine(methyl(N-benzyloxycarbamoyl)-4-formyloxypipecolate) Paraformaldehyde (144.0 g, 4.8 mol) was dissolved in hot formic acid (6.5L) and the resultant solution cooled to 25° C. Methyl (2S-benzyloxycarbamoyl)-pent-4-enoate (904.3 g, 3.4 mol) was added and the solution stirred for 72 hrs, at which time GC analysis showed no starting material remained. Excess solvent was removed in vacuo, and the residual oil dried by azeotroping with toluene (4×750 mL) and passed through a silica plug, eluting with EtOAc. Evaporation of the solvent in vacuo left N-benzyloxycarbamoyl-2S-carbomethoxy-4R,S-formyloxypiperidine as a yellow oil (1056.3 g, 96%), of diastereomeric ratio 1:1. GC gave: retention time 26.9 min (trans diastereoisomer) 27.6 min (cis diastereoisomer) Synthesis of N-benzyloxycarbamoyl-2R-carbomethoxy-4R,S-formyloxypiperidine was carried out from methyl (2R-benzyloxycarbamoyl)-pent-4-enoate using the same method and resulted in an equivalent set of products. EXAMPLE 5 Enzymic Hydrolysis Screen of N-benzyloxycarbamoyl-2S-carbomethoxy-4R,S-formyloxypiperidine (Mixture A) Eight enzymes were screened to evaluate their potential for hydrolysing either the R- or S-formate ester. The enzymes used were Chirazyme L1, Chirazyme L2, Chirazyme L9, Lipase PS, Lipase AY30, Lipase A6, Porcine Pancreatic Lipase and Rhizopus javanicus Lipase. In each case, 150 mg of substrate was placed in a scintillation vial with 1.5 mL of 50 mM potassium phosphate buffer pH 7.0, 1.5 mL MTBE and 10 mg of enzyme. The reactions were continuously agitated at 25° C. in a water bath/shaker. After 24 hr, tlc analysis showed Chirazyme L1 and Lipase AY30 selectively hydrolysed the substrate. GC analysis of these two reactions indicated that Lipase AY30 was the more selective enzyme, preferentially hydrolysing the trans-diastereoisomer, and that Chirazyme L1 showed an opposite selectivity, towards cis-diastereoisomer. A similar screen was carried out on the substrate N-benzyloxycarbamoyl-2R-carbomethoxy-4R,S-formyloxypiperidine (mixture B) using the same eight enzymes. In this case, Lipase AY30 and Chirazyme L9 were the only enzymes to selectively hydrolyse the substrate. Both demonstrated the same selectivity, preferentially hydrolysing the trans-diastereoisomer, with Chirazyme L9 the more selective. EXAMPLE 6 Enzymic Resolution of N-benzyloxycarbamoyl-2S-carbomethoxy-4R,S-formyloxypiperidine A 10 L jacketed reaction vessel equipped with an overhead stirrer was charged with N-benzyloxycarbamoyl-2S-carbomethoxy-4R,S-formyloxypiperidine (1056.3 g), MTBE (3.6 L) and 50 mM potassium phosphate buffer pH 7.0 (4.5 L). Stirring was started to achieve an emulsion, the pH adjusted back to 7.0 with 5M NaOH and the temperature set to 20° C. Lipase AY30 (300 g) was added and stirring continued at 20° C. At all times in the reaction, the pH was kept constant at pH 7.0 by the addition of 5M NaOH. After 4 days at 20° C., the reaction was stopped by filtration through Celite 521. The two layers in the filtrate were separated, and the organic layer reserved. The Celite was slurried with acetone (500 mL) and filtered. This filtrate was concentrated in vacuo until only aqueous material remained, when it was extracted with MTBE (2×500 mL). The organic layers were combined, dried (MgSO 4 ) and concentrated in vacuo to yield a viscous, cloudy yellow oil (903 g) that was a mixture of the residual starting material, N-benzyloxycarbamoyl-2S-carbomethoxy-4R-formyloxypiperidine, of 83% de, and product, N-benzyloxycarbamoyl-2S-carbomethoxy-4S-hydroxypiperidine, of 90% de in an approximate 1:1 ratio. This oil was used immediately in the next step. EXAMPLE 7 Separation of the Mixture of Compounds Obtained from the Enzymic Resolution The mixture obtained in Example 6 (900 g) and DMAP (17.9 g, 0.14 mol) was dissolved in CH 2 Cl 2 (6 L) at 20° C. Et 3 N (450 mL, 3.22 mol) was added using a pressure equalising dropping funnel over a 10 minute period. Solid phthalic anhydride (239 g, 1.61 mol) was added batch-wise and stirring continued for 18 hr. The reaction mixture was washed with 1 M HCl (3.5 L), and the organic layer concentrated in vacuo. The residue was redissolved in toluene (4 L) and extracted with saturated (NH 4 ) 2 CO 3 (3 L). This aqueous layer was washed with toluene (1 L), and the combined organic extracts dried (MgSO 4 ) and concentrated in vacuo to yield N-benzyloxycarbamoyl-2S-carbomethoxy-4R-formyloxypiperidine (545 g, 81% d.e., 52% yield overall from Example 3). The aqueous layer was acidified to pH 1 with conc. HCl and extracted with toluene (2 L). The layers were separated, and the aqueous extracted once more with toluene (1 L). These two organic layers were combined, dried (MgSO 4 ) and concentrated in vacuo to yield N-benzyloxycarbamoyl-2S-carbomethoxy-4S-hydroxypiperidine, 4-hemiphthalate derivative (553 g, 38% yield overall from Example 6). Both products were used directly in the next steps. Using the same methods as outlined in Examples 6 and 7, N-benzyloxycarbamoyl-2R-carbomethoxy-4R,S-formyloxypiperidine was separated into N-benzyloxycarbamoyl-2R-carbomethoxy-4S-formyloxypiperidine and N-benzyloxycarbamoyl-2R-carbomethoxy-4R-hydroxypiperidine, 4-hemiphthalate derivative, the only difference being the use of Chirazyme L9 in place of Lipase AY30 in the enzymic resolution. EXAMPLE 8 Preparation of N-benzyloxycarbamoyl-2S-carbomethoxy-4R-hydroxypiperidine 81% de N-Benzyloxycarbamoyl-2S-carbomethoxy-4R-formyloxypiperidine (545 g, 1.70 mol) was dissolved in MeOH (1.5 L) and K 2 CO 3 (23.5 g, 0.17 mol) added. The mixture was stirred for 2 hr at room temperature, by which time the reaction was complete. MTBE (5 L) was added and the solution washed with H 2 O (3 L). The organic phase was dried and concentrated in vacuo. The residue was dissolved in hot EtOAc (600 mL), cooled and crystallisation induced by the addition of heptane (75 mL). The crystals obtained were filtered and recrystallised from EtOAc (850 mL) to yield N-benzyloxycarbamoyl-2S-carbomethoxy-4R-hydroxypiperidine (145.4 g, >99% d.e.). A further crop of identical quality crystals (58.2 g, >99% d.e.) were obtained from the liquors (overall yield 41%). 1 H NMR (400 MHz, d 6 -DMSO) 7.37 (5H, m) 5.08, 2H, m) 4.64 (2H, m) 3.90 (1H, br s) 3.70 (1H, dt, J 8.5, 3.5) 3.59 (3H, br s) 3.47–3.27 (1H, br m) 2.19 (1H, m) 1.82 (1H, dd, J 13.5, 6.5) 1.54 (2H, m). GC (material derived to acetate) gave retention times 28.2 (minor diastereoisomer), 29.0 (major diastereoisomer) in a ratio 1:220. Synthesis of N-benzyloxycarbamoyl-2R-carbomethoxy-4S-hydroxypiperidine was carried using the same method and resulted in an equivalent product. An X-ray structure was used to confirm the stereochemistry of this compound. EXAMPLE 9 Preparation of 2S-carboxy-4S-hydroxypiperidine N-benzyloxycarbamoyl-2S-carbomethoxy-4S-hydroxypiperidine 4-hemiphthalate (365 g, 0.82 mol) was mixed with 2M HCl (1.5 L) and heated to reflux for 5 days. The mixture was cooled and extracted with EtOAc (3×1 L). The aqueous layer was concentrated in vacuo to leave a cloudy paste (170 g). This was redissolved in H 2 O (500 mL) and the solution neutralised using Amberlite IRA-93. The resin was filtered and washed with H 2 O (1.5 L). The filtrate was concentrated in vacuo and dried by azeotroping with toluene (2×500 mL) to leave a cream solid (94.5 g, 79%, 88% de). 1 H NMR (400 MHz, D 2 O) major diastereoisomer 4.21 (1H, m) 3.90 (1H, dd, J 11.5, 3.5) 3.28 (2H, m) 2.20 (1H, m) 1.97–1.84 (3H, m). Minor diastereoisomer 3.95 (1H, m) 3.63.(1H, dd, J 13.0, 3.0) 3.47 (1H, ddd, J 13.0, 4.5, 2.5)3.02 (1H, dt, J 13.5, 3.5)2.47 (1H, m) 2.10 (1H, m), 1.58 (2H, m). Synthesis of 2R-carboxy-4R-hydroxypiperidine was carried using the same method and resulted in an equivalent product.

A crystalline salt according to formula (1): or the opposite enantiomer thereof, wherein X + is a cation. Such salts are useful in preparing chiral scaffolds, in particular of formulae (a)–(d)

[0001] This application is a continuation of U.S. patent application Ser. No. 11/217,688, filed Sep. 2, 2005, which is a continuation in part of U.S. patent application Ser. No. 10/430,298, filed on May 7, 2003 (now U.S. Pat. No. 6,973,756), both of which are incorporated herein by reference in their entirety. FIELD OF THE INVENTION [0002] This invention relates to a connector for securing veneer to back-up walls. BACKGROUND OF THE INVENTION [0003] Many construction techniques have been developed for commercial buildings utilizing a back-up wall and a set of thin walled veneer panels that are supported on the back-up wall. Typically, there is a cavity between the veneer panels and the back-up wall to allow for the insertion of insulation and other materials. The veneer panels are connected to the back up wall using any of several different styles of connectors that are currently available. In addition to supporting the veneer panels, these connectors typically withstand various other loads, such as shear and wind loads. [0004] Typically prior art connectors are relatively expensive to manufacture, and offer relatively poor load-bearing capacity for their weight and cost. One such prior art connector consists of an L-shaped member, and a veneer connector plate. The vertical portion of the L-shaped member is mounted to the back-up wall, and the horizontal portion extends outwardly therefrom. The horizontal portion typically includes slotted holes therethrough, for the mounting of the veneer connector plate thereon. The veneer connector plate extends outwards and supports at its outwardmost edge, a portion of a veneer panel. [0005] For several reasons, these connectors are typically relatively expensive, and can add to the overall cost of erecting a building. One reason for their cost is that, to support the required loads during use, such connectors are typically required to be made from relatively thick materials. For example, for some applications, the L-shaped member is made from angle having a ⅜″ wall thickness. Furthermore, many building codes require such connectors to be made from stainless steel, to resist corrosion and subsequent weakening or failure. Because of this materials requirement, the cost of the L-shaped member is increased substantially. [0006] Furthermore, in order to cut ⅜″ thick angle when making the L-shaped member, a sophisticated cutting device may be required, such as, for example, a plasma cutter. Plasma cutters are typically more expensive to operate than other cutting devices, and also, plasma cutter operators are more expensive than other cutting machine operators due to their relatively uncommon expertise. [0007] A further issue driving the cost of prior art connectors is that, typically, they include at least two stainless steel bolts in their assembly, for example, to attach the veneer connector to the L-shaped piece. Stainless steel bolts are relatively expensive and can add significantly to the overall cost of the connector. [0008] Accordingly, there is a need for a connector that is relatively inexpensive to manufacture, for use in supporting veneer panels. SUMMARY OF THE INVENTION [0009] According to one aspect, a connector for retaining at least one veneer panel on a back up wall is provided. The veneer panel may have a top edge and a bottom edge. The connector comprises a veneer connector and a support member. The support member comprises a mounting flange adapted for securing the support member to the back-up wall, and first and second support member side walls extending outwardly from the mounting flange. The first and second support member side walls define at least one generally horizontal surface when the support member is secured to the back-up wall. The veneer connector is securable to the horizontal surface by a mechanical fastener and is adapted to support a generally horizontal edge of the at least one veneer panel when the support member is secured to the back-up wall and when the veneer connected is supported by the generally horizontal surface. The connector is mountable on the back up wall such that the veneer connector supports one of the top and bottom edges of the at least one veneer panel. [0010] The mounting flange may have an adjustment aperture therethrough. The adjustment aperture may be elongate and may be adapted to adjustably receive a fastener therethrough for mounting the support member to the back-up wall. The adjustment aperture may be generally vertical. [0011] The generally horizontal surface may be provided by an upper surface of the first and second support member side walls. [0012] The connector may further comprise a separate fastener for securing the veneer connector to the generally horizontally extending surface. [0013] The veneer connector may comprise a section that abuts the veneer panel and is adapted to receive fasteners that engage the veneer panel. [0014] According to another aspect, a connector for coupling a veneer panel to a back-up wall is provided. The connector comprises a support member comprising a mounting flange adapted for securing the support member to said back-up wall, and first and second support member side walls extending outwardly from the mounting flange. The first and second support member side walls define at least one generally horizontal slot when the support member is secured to the back-up wall. The connector further comprises a veneer connector configured for non-rotational sliding receipt in the generally horizontal slot and adapted to support a generally horizontal edge of said veneer panel when the veneer connector is received in the generally horizontal slot and when the support member is secured to the back-up wall. [0015] The veneer connector may have a load transfer region for supporting the veneer panel, and the first and second support member side walls may extend outward from the mounting flange sufficiently to support the veneer connector proximate the load transfer region. [0016] The veneer connector may have at least one veneer connector side wall. The veneer connector side wall may be generally vertical and may extend at least along a portion of the veneer connector that is unsupported by the support member. [0017] The veneer connector may have a generally horizontal load transfer region for mounting to a horizontal edge of the veneer panel. [0018] The generally horizontal slot may comprise a generally horizontal lower surface. [0019] The mounting flange may comprise a first mounting flange portion and a second mounting flange portion. Each may have an aperture therethrough for mounting the support member to the back-up wall. At least one of the apertures may be positioned above the slot. [0020] An elongate veneer connector adjustment aperture may be defined in the veneer connector. An elongate support member adjustment aperture may be defined in the support member. The support member adjustment aperture and the veneer connector adjustment aperture may extend generally perpendicularly to each other. [0021] A veneer connector aperture may be defined in the veneer connector. A support member aperture may be defined in the support member. The support member aperture and the veneer connector aperture may be alignable with respect to each other for the pass through of a single mechanical fastener for securing the veneer connector to the support member. [0022] The first and second side walls may be connected to each other by a side wall connecting portion. The first and second side walls may be joined together by a horizontal load support wall. The horizontal load support wall may be positioned at the top of the side walls. [0023] The veneer connector may comprise a section that abuts the veneer panel and is adapted to receive fasteners that engage the veneer panel. BRIEF DESCRIPTION OF THE DRAWINGS [0024] For a better understanding of the present invention and to show clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: [0025] FIG. 1 is a perspective view of a system of connectors in accordance with a first embodiment of the present invention, supporting panels of veneer on a back up wall; [0026] FIG. 2 is a magnified plan view of a veneer connector shown in FIG. 1 ; [0027] FIG. 2 a is a plan view of a variant of the veneer connector shown in FIG. 2 ; [0028] FIG. 3 is a perspective view of a portion of the veneer connector shown in FIG. 2 , supporting a panel of veneer; [0029] FIG. 4 is a magnified perspective view of a support member shown in FIG. 1 ; [0030] FIG. 5 is a magnified perspective view of the connector shown in FIG. 1 ; [0031] FIG. 5 a is an end view of the connector shown in FIG. 5 , partially sectioned for greater clarity, with a variant to the fastener shown in FIG. 5 ; [0032] FIG. 6 a is a magnified plan view of the support member shown in FIG. 1 , in a partial state of manufacture; [0033] FIG. 6 b is a perspective view of the support member shown in FIG. 6 a in a further state of manufacture; [0034] FIG. 7 is a magnified perspective view of an alternative veneer connector to that which is shown in FIG. 1 ; [0035] FIG. 8 is a perspective view of a variant of the support member shown in FIG. 4 ; [0036] FIG. 8 a is an end view the support member variant shown in FIG. 8 , supporting a veneer panel; [0037] FIG. 9 is an end view of another variant of the support member shown in FIG. 4 ; [0038] FIG. 10 is an end view of yet another variant of the support member shown in FIG. 4 ; [0039] FIG. 11 is a plan view of a work piece that is in a partial state of manufacture, which can be made into either of the support members shown in FIGS. 9 and 10 ; [0040] FIGS. 12 a and 12 b are perspective views of the work piece shown in FIG. 11 , in a further state of manufacture; [0041] FIG. 13 is a plan view of a system, made up of the connectors shown in FIGS. 9 and 10 , supporting veneer panels to a back-up wall; [0042] FIG. 14 is a top view of a variant of the support member shown in [0043] FIG. 4 ; [0044] FIG. 15 is an front view of another variant of the support member shown in FIG. 4 ; [0045] FIG. 16 is a perspective view of a connector in accordance with another embodiment of the present invention; [0046] FIG. 17 is a front view of the connector shown is FIG. 16 ; [0047] FIG. 18 is a perspective view of another variant of the support member shown in FIG. 4 ; and [0048] FIG. 19 is a perspective view of another variant of the support member shown in FIG. 4 . DETAILED DESCRIPTION OF THE INVENTION [0049] Reference is made to FIG. 1 , which shows a system of connectors 10 in accordance with a preferred embodiment of the present invention. Each connector 10 includes a veneer connector 12 for connecting with a veneer panel 14 , and a support member 16 adapted for receiving the veneer connector 12 and for securement to a back-up wall 18 . The connectors 10 may be made of any suitable material, such as 10 or 11 gauge stainless steel. The connectors 10 are preferably free of welds and formed from a single sheet of metal manufactured into the desired shape. The veneer panel 14 is may be a natural stone material, such as marble or granite. The veneer panel 14 may be a thin-walled panel, which is typically known as a thin masonry veneer panel, which many building codes require to be individually supported (i.e., each panel must be supported individually). It will be noted that the mortar that would typically exist between adjacent veneer panels 14 has been removed from the Figures for greater clarity. [0050] The back-up wall 18 may be of form-poured concrete construction. Alternatively, the back-up wall 18 may be constructed of any suitable material, such as, for example, metallic studs, or block masonry. The veneer panels 14 may be spaced from the back-up wall 18 to provide a cavity 20 therebetween. Optionally, an insulation material 24 and a vapor barrier 26 may be installed in the cavity 20 . [0051] Reference is made to FIG. 2 , which shows the veneer connector 12 in plan view. The veneer connector 12 may have a generally rectangular shape and has a first edge 28 and a second edge 30 . An adjustment aperture 32 may be positioned adjacent the first edge 28 . Referring to FIG. 5 , the adjustment aperture 32 is used to receive a fastener 65 to join the veneer connector 12 to the support member 16 . Referring to FIG. 2 , the adjustment aperture 32 may be generally elongate to permit adjustment of the position of the veneer connector 12 within the support member 16 , as will be discussed further below. [0052] The veneer connector 12 includes a plurality of veneer connection apertures 34 , which may be positioned proximate the second edge 30 . The veneer connector 12 may include any suitable number of veneer connection apertures 34 , such as, for example, three apertures 34 , as shown in FIG. 2 . Referring to FIG. 3 , the veneer connection apertures 34 permit the pass-through of fastening ties 36 that extend from the edge of the veneer panel 14 . The veneer connection apertures 34 may be generally circular, and may be sized to permit easy pass-through of the fastening ties 36 , but are not required to be so large as to facilitate substantial adjustment of the veneer 14 relative to the veneer connector 12 . [0053] The veneer connection apertures 34 are positioned proximate the second edge 30 of the veneer connector 12 to prevent the unwanted protrusion of the second edge 30 past the outer face of the veneer 14 . Thus, the second edge 30 can be buried in the mortar between vertically adjacent panels of veneer 14 . [0054] Referring to FIG. 2 a , an alternative veneer connector 12 ′ is shown, which has a plurality of veneer connection apertures 34 ′ which are elongate to provide further adjustability of the veneer connector 12 with respect to the fastening ties 36 . [0055] Referring to FIG. 3 , a securing means 40 prevents veneer 14 from disengaging from veneer connector 12 . Securing means 40 may be any suitable means, such as, for example, a mechanical fastener or a weld. [0056] The veneer connector 12 supports the veneer panel 14 ( FIG. 1 ) during use generally in the region of the veneer connection apertures 34 . The load imparted to the veneer connector 12 from the weight of the veneer panel 14 is shown at F. [0057] Reference is made to FIG. 4 , which shows the support member 16 in more detail. The support member 16 includes a mounting flange 42 and a support portion 44 . The mounting flange 42 is adapted for mounting the support member 16 to the back-up wall 18 ( FIG. 1 ). As shown, the mounting flange 42 is formed by a first mounting flange and a second mounting flange 48 (shown in FIG. 4 ) [0058] The mounting flange 42 has an adjustment aperture 50 therethrough, which is adapted to receive a fastener 52 , for fastening the support member 16 to the back-up wall 18 ( FIG. 1 ). The adjustment aperture 50 may be generally elongate, as shown in FIG. 4 , to permit adjustment of the support member 16 in the vertical direction. Such vertical adjustment capability facilitates aligning the support members 16 in a row on the back-up wall 18 ( FIG. 1 ). [0059] The mounting flange 42 also includes a securing aperture 54 therethrough, may be positioned on the second mounting flange 48 , generally opposite the adjustment aperture 50 . The securing aperture 54 is adapted for receiving a fastener 56 therethrough to further retain the support member 16 on the back-up wall 18 ( FIG. 1 ), and to fix the position of the support member 16 therewith. Once the desired adjustment to the position of the support member 16 has been made using the fastener 52 and the adjustment aperture 50 , the fastener 56 may be passed through the aperture 54 and into the back up wall 18 ( FIG. 1 ), to fix the position of the support member 16 . [0060] Reference is made to FIG. 5 , which shows the support portion 44 of the support member 16 more clearly. The support portion 44 extends from the mounting flange 42 , and specifically, extends from the first mounting flange 46 and the second mounting flange 48 , in a generally vertical plane denoted by the axes (y) and (z), and joins the first mounting flange 46 and second mounting flange 48 along two generally vertical lines which extend generally in the vertical (y) direction. By extending in a generally vertical plane, the support portion 44 is provided with a generally greater resistance to vertical bending forces, which result from the load F, that arise when the connector 10 supports a veneer panel 14 ( FIG. 1 ). In other words, the configuration of the support portion 44 provides the support member 16 with a relatively high moment of inertia in the vertical (y) direction, compared to a typical L-shaped member used in connectors of the prior art. [0061] The support portion 44 is made up of two spaced apart side walls 58 , which are connected at their respective upper ends by a top portion 59 . The top portion 59 and the spaced configuration of the side walls 58 provide resistance to bending loads that can occur in the lateral (x) direction during use. It is expected that any lateral loads will be smaller than the vertical loads incurred from the weight of the veneer 14 ( FIG. 1 ). As a result, the moment of inertia in the lateral (x) direction may be smaller than that in the vertical (y) direction. [0062] The top portion 59 can thus be referred to as a horizontal load support wall 59 . As such it is not necessary for the horizontal load support wall 59 to be positioned at the top of the support member 16 . For example, referring to FIG. 18 , a support member 16 ″″″ is shown, having a horizontal load support wall 132 positioned at the bottom of the two side walls 58 . The support member 16 ″″″ may otherwise be similar to the support member 16 ( FIG. 5 ). [0063] In the embodiments in FIG. 5 , the horizontal load support wall 59 may be made contiguous such that the adjustment aperture 62 is not provided thereon. Instead the opposing end (ie. the bottom end) of the side walls 58 , which is not covered, may act as the adjustment aperture in the Z direction. Thus, the fastener 65 could mount between the open bottom end of the side walls 58 and the veneer connector 14 . Similarly, in the embodiment in FIG. 18 , horizontal support wall 132 may be made contiguous such that the adjustment aperture 62 is not provided thereon. Instead the opposing end (ie. the top end) of the side walls 58 , which is not covered, may act as the adjustment aperture in the Z direction. Thus, the fastener 65 (not shown in FIG. 18 ) 65 could mount between the open top end of the side walls 58 and the veneer connector 14 . [0064] Referring to FIG. 5 , the side walls 58 are advantageously joined together by the horizontal load support wall 59 . However, the horizontal load support wall 59 could be omitted, as shown in the embodiment shown FIG. 19 . FIG. 19 shows a support member 16 ″″″ that has a contiguous flange portion 136 . The side walls 138 extend outwards from the flange portion 136 and are joined to the flange portion along generally vertical, spaced apart lines. The side walls 138 could be joined to the flange portion by any suitable means, such as, for example, welding. [0065] Referring to FIG. 5 , the side walls 58 together define a slot portion 60 , which may extend in a generally horizontal (x-z) plane, for receiving and supporting the veneer connector 12 . The slot 60 permits the lateral adjustment of the veneer connector 12 in both the (x) direction and in the z direction. The slot 60 is made sufficiently deep so that the veneer connector 12 is supported along a substantial portion of its length. More particularly, the support portion 44 extends outwards to support the veneer connector 12 proximate its load supporting region, ie. the region about the apertures 34 where the load F is imparted to the veneer connector 12 by the veneer panel 14 ( FIG. 1 ). This reduces bending stresses on the veneer connector 12 in use when supporting a veneer panel 14 ( FIG. 1 ). [0066] The slot 60 is preferably positioned proximate the upper ends of the side walls 58 , to reduce its impact on the overall moment of inertia of the support portion 44 in the vertical (y) direction. It will be noted that the slot 60 may extend in a plane that is other than horizontal. For example the slot 60 may be angled generally downwards towards its blind end, so that the veneer connector 12 may be retained in place temporarily without the use of a fastener. [0067] An adjustment aperture 62 may be defined in the upper portion 59 , for receiving the fastener 65 therethrough. The fastener 65 may pass through the adjustment aperture 62 and the adjustment aperture 32 in the veneer connector 12 for fixedly retaining the veneer connector 12 in place in the support member 16 . The adjustment aperture 62 may be generally elongate, and may extend in a direction that is generally perpendicular the aperture 32 in the veneer connector 12 . In this way, the apertures 62 and 32 cooperate to provide adjustment for the veneer connector 12 within the slot 60 in both the (x) and (z) directions. [0068] The fastener 65 may be any suitable type of fastener. For example, the fastener 65 may be made up of a stainless steel hex-head bolt 65 a , a washer 65 b , and a nut 65 c . The hex head bolt 65 a extends upwards from under the veneer connector 12 , and is sized so that the side walls 58 capture the head of the bolt 65 a and prevent it from rotating. The threaded end of the bolt 65 a passes up and through the adjustment aperture 62 on the support member 16 . The washer 65 b and nut 65 c are positioned on the exposed end of the bolt 65 a and are tightened to provide a secure connection between the support member 16 and the veneer connector 12 . By having captured the bolt 65 a between the side walls 58 , the task of installing the fastener 65 is facilitated. It will be noted that other types of bolts and other types of fasteners altogether could alternatively be used to connect the support member 16 and the veneer connector 12 . [0069] Reference is made to FIG. 5 a , which shows an alternative washer 65 b ′ that can be used as part of the connector 65 . The washer 65 b ′ may have a generally arcuate shape in side view and extends downwards to capture the side walls 58 of the support member 16 . When the nut 65 c is tightened, the washer 65 b ′ captures and pushes together the side walls 58 , further strengthening their capture of the head of the bolt 65 a . Thus, as the tightening force on the nut 65 c is increased, the capturing force of the side walls 58 on the bolt 65 a is increased, inhibiting the bolt 65 a from rotating as a result of the increased tightening force. [0070] It will be noted that the washer 65 b ′ may have any suitable shape for pushing the side walls 58 together. For example, the washer 65 b ′ may alternatively have an inverted V-shape in side view instead of an arcuate shape. Furthermore, the washer 65 b ′ may have any shape in plan view. For example, the washer 65 b ′ may have a generally circular shape or may alternatively have a rectangular shape so that it better captures the side walls 58 . [0071] Reference is made to FIG. 6 a , which shows a plate 70 which may be used to manufacture the support member 16 ( FIG. 1 ). The plate 70 may be machined with a plurality of apertures and slots which will ultimately form the slot 60 , the aperture 62 and the mounting apertures 50 and 54 . Furthermore, a slot 72 may be machined into the plates 70 , to remove unnecessary material. Once the plate 70 is machined with the appropriate slots and apertures, it may be bent into the shape of the support member 16 by two primary bending operations. The first bending operation bends the two tabs shown at 74 and 76 along a bend line 78 , resulting in the structure 79 shown in FIG. 6 b . The tabs 74 and 76 will ultimately form the mounting flange 42 ( FIG. 4 ). The second bending operation involves folding the plate 70 generally about a fold line. The folding of the plate 70 may be performed on a radiused surface thereby forming the upper portion 59 and the spaced apart side walls 58 . Manufacturing the support member 16 in this way saves cost and manufacturing time while providing a relatively strong resulting structure. It will be noted that the order of operations described is preferable, but may alternatively be rearranged in any suitable way. [0072] By making the support member 16 by appropriately machining and by applying two simple bends to the single, integral plate 70 , the cost of manufacture for the support member 16 are reduced, relative to complex structures of the prior art which are made from multiple pieces which are welded together. [0073] Reference is made to FIG. 1 , which shows the connector 10 in use. In use, a plurality of connectors 10 are used to support a plurality of panels of veneer 14 in a spaced relationship from the back up wall 18 of a structure such as an office tower. The support members 16 are mounted to the back-up wall, and may be spaced from each other in a generally horizontally and vertically extending array. The veneer connectors 12 are positioned in the slots 60 ( FIG. 5 ), and extend therefrom to support the veneer panels 14 . The fastening ties 36 ( FIG. 3 ) extend between vertically adjacent veneer panels 14 and pass through the veneer connection apertures 34 , which retain the panels 14 in place. Furthermore, mortar may be used to close any air gap adjacent veneer panels 14 , and to assist in retaining the panels 14 in place. The vertical load F that results from the weight of the veneer panels 14 is supported by the veneer connectors 12 , and in turn, by the support members 16 . Because the support members 16 have generally high moments of inertia in the vertical direction, they are able to be made with relatively thin gauge material for supporting the load imposed thereon by the veneer panels 14 . It will be noted that while two connectors 10 are shown along the top edge of each veneer panel 14 , any suitable number of connectors 10 may be used to support each veneer panel 14 , depending on the nature of the specific application. [0074] Reference is made to FIG. 7 , which shows a veneer connector 12 ′″, which may be used alternatively to the veneer connector 12 . The veneer connector 12 ′″ may be similar to the veneer connector 12 ( FIG. 2 ), or the veneer connector 12 ′ ( FIG. 2 a ), except that the veneer connector 12 ′″ has a pair of side webs 84 that extend vertically from the side edges of the veneer connector 12 ′″. The side webs 84 may extend generally along substantially the entire length of the veneer connector 12 ′″, except for the portion 86 of the veneer connector 12 ′″ that will be embedded within the gap between adjacent veneer panels 14 ( FIG. 1 ). The side webs 84 provide increased bending resistance to the veneer connector 12 ′″, relative to the veneer connector 12 ( FIG. 2 ), because the side webs 84 generally increase the moment of inertia of the veneer connector 12 ′″. [0075] Reference is made to FIG. 8 , which shows a support member 16 ′ that maybe used as an alternative to the support member 16 ( FIG. 4 ). The support member 16 ′ may be similar to the support member 16 , except that the support member 16 ′ has a slot 90 that positioned closer to the bottom of the support member 16 ′, relative to the slot 60 on the support member 16 ( FIG. 4 ). The slot 90 may otherwise be similar to the slot 60 , and is for receiving and retaining the veneer connector 12 or 12 ′″ ( FIGS. 2 and 2 a ). Referring to FIG. 8 a , the slot 90 is positioned sufficiently low, so that, when the support member 16 ′ is being mounted to the back-up wall 18 proximate the top edge of a veneer panel 14 , the veneer panel 14 does not completely obstruct access to the adjustment aperture and the securing aperture, which are shown at 92 and 94 respectively. Thus, the relatively lower position of the slot 90 facilitates the mounting of the support member 16 ′. [0076] Reference is made to FIG. 9 , which shows a support member 16 ″, which is another alternative to the support member 16 . The support member 16 ″ may be similar to the support member 16 , except that the support member 16 ″ has an adjustment aperture 98 that is elongate along an angle A from the vertical. The adjustment aperture 98 in the embodiment shown in FIG. 9 provides vertical adjustability for the support member 16 ″, in a similar way to the adjustment aperture 50 on the support member 16 ( FIG. 4 ). During vertical adjustment of the support member 16 ″, however, the support member 16 ″ will be shifted by a certain amount horizontally. Preferably, the angle A from the vertical is small, to reduce the horizontal shift that occurs during vertical adjustment of the support member 16 ″. Referring to FIG. 10 , a support member 16 ′″ may also be made which has an adjustment aperture 98 ′ that is a mirror image of the adjustment aperture 98 ( FIG. 9 ). [0077] The support member 16 , as shown in FIG. 5 , has a support portion 44 that extends generally orthogonally outwards from the plane of the mounting flange 42 . It is, however, possible for the support portion 44 to extend outwards from the mounting flange 42 , at an angle such that it is not orthogonal to the mounting flange 42 , as shown in FIG. 14 . In the support member 16 ″ of the variant shown in FIG. 14 , the side walls 58 of the support portion 44 are supported along generally vertical lines by the mounting flange 42 and thus have a greater resistance to bending under a vertical load imposed thereupon, relative to a typical L-shaped member used in connectors of the prior art. This is true even though the side walls 58 extend outward from the mounting flange 42 at an angle such that they are not orthogonal to the mounting flange 42 . [0078] The side walls 58 of the support portion 44 are shown in FIG. 5 as being supported along vertical lines by the mounting flange 42 . It is not necessary that the support be provide along strictly vertical lines however. Referring to FIG. 15 , the support member 16 ″″ is advantageous relative to L-shaped members of the prior art, even though the side walls 58 are not strictly vertical, and are supported by the mounting flange 42 along lines that are off of vertical by some small amount. Throughout this disclosure and the accompanying claims, the term “generally vertical” is meant to include lines or planes that are strictly vertical and those that are off of vertical within a selected range. While the selected range is preferably small so that the side walls 58 are relatively close to vertical, the range could alternatively be relatively large while still providing a structure that is advantageous relative to L-shaped connectors of the prior art. For example, the range could be as large as 45 degrees off of vertical in each direction. [0079] Reference is made to FIG. 16 , which shows a connector 110 , in accordance with another embodiment of the present invention. The connector 110 includes a support member 16 ′″″ and a veneer connector 12 ″. The support member 16 ′″″ may be similar to the support member 16 ( FIG. 4 ), except that the support member 16 ″″″ supports the veneer connector on its upper surface, shown at 116 , instead of supporting the veneer connector 12 ″ in a slot. [0080] The upper support wall 116 may be made generally planer to assist in supporting and stabilizing the veneer connector 12 ″. The adjustment aperture 62 is provided in the upper support wall 116 . The upper support wall 116 extends between the two spaced apart side walls 118 . The side walls 118 may be similar to the side walls 58 , shown in the support member 16 , shown in FIG. 5 . The upper support wall 116 , thus acts as the horizontal support for the side walls 118 . [0081] The veneer connector 12 ″ rests on top of the upper support wall 116 . The veneer connector 12 ″ has the adjustment aperture 32 which is alignable with the adjustment aperture 62 on the support member 16 ′″″ when the veneer connector is positioned on the upper support wall 116 . The adjustment aperture 32 is generally perpendicular to the adjustment aperture 62 in order to provide adjustability for the veneer connector 12 ″ on the support member 16 ′″″ in two orthogonal directions in a horizontal plane. [0082] Referring to FIG. 17 , the fastener 65 may be provided for joining the veneer connector 12 ″ to the support member 16 ″′″. The fastener 65 may include the hex head bolt 65 a , the washer 65 b , the nut 65 c , and a washer 65 d. [0083] The washers 65 b and 65 d are provided to inhibit the pulling through of the bolt 65 a or nut 65 c through the adjustment apertures 62 and 32 during assembly and use of the connector 110 . [0084] Referring to FIG. 16 , the veneer connector 12 ″ includes the veneer connection apertures 34 , positioned proximate its second, or outside, edge 30 . The veneer connection apertures 34 may include a centre aperture 34 a and two outer apertures 34 b . The centre aperture 34 a may be generally circular while the outer apertures 34 b may be slotted to provide flexibility in receiving imperfectly positioned fastening ties 36 ( FIG. 3 ) on the veneer panels 14 ( FIG. 3 ). [0085] The veneer connector 12 ″ may include a pair of side webs 120 , which may be similar to the side webs 84 on the veneer connector 12 ′″, as shown in FIG. 7 . [0086] The veneer connector 12 ″ may include one or more strengthening ribs 121 on its upper surface 122 . The strengthening ribs 121 provide additional vertical bending resistance for the central region of the veneer connector 12 ″ which is spaced relatively far away from the side webs 120 . By positioning the strengthening ribs 121 on the upper surface 122 , they do not create an interference hazard when mounting the veneer connector 12 ″ on the support member 16 ″′″. Like the side webs 120 , the strengthening ribs 121 must be positioned so as not to obstruct the connection of the veneer connector 12 ″ with the veneer panel 14 that will ultimately sit above it (see FIG. 3 ). [0087] Referring to FIG. 11 , the support members 16 ″ and 16 ′″ may be manufactured from a common plate 100 . The common plate 100 may be similar to the plate 70 ( FIG. 6 a ), except that the common plate 100 has an aperture therein, that will ultimately become the adjustment aperture 98 ( FIG. 9 ), or the adjustment aperture 98 ′ ( FIG. 10 ), depending on which way the plate 100 is folded during manufacture. For example, referring to FIG. 12 a , the tabs on the plate 100 , which are shown at 104 may be folded in a first direction, so that the plate 100 will ultimately form the support member 16 ″. However, referring to FIG. 12 b , the tabs 104 may be folded in a second direction that is opposite the first direction, so that the plate 100 ultimately forms the support member 16 ′″. [0088] Reference is made to FIG. 13 , which shows a system of connectors 106 and 108 , which cooperate in pairs to support veneer panels 14 . The connectors 106 and 108 may be similar to the connector 10 ( FIG. 1 ), and include a suitable veneer connector, such as the veneer connector 12 . However, the connectors 106 and 108 include the support members 16 ″ and 16 ′″ respectively, instead of the support member 16 ( FIG. 1 ). [0089] The top and bottom edges of the panel 14 are supported by at least one of each connector 106 and 108 . As a result, the weight of the panel 14 is prevented from dragging the connectors 106 and 108 down the wall 18 , because the adjustment apertures extend in different directions. Thus, because the adjustment apertures 98 and 98 ′ are not parallel to each other when the connectors 106 and 108 are installed on the back-up wall and are in use, the adjustment apertures 98 and 98 ′ cooperate with their respective fasteners and with each other to prevent the connectors 106 and 108 from being dragged down from their supported load. [0090] It will be noted that more than one of each connector 106 and 108 may be used to support an edge of the veneer panel 14 . For example, several of one type of connector, eg. connector 106 and one or two of the other type of connector, eg. connector 108 , may be used to support an edge of the veneer panel 14 . At least one of each connector 106 and 108 is used, however. [0091] It will be noted that the features shown in the support members disclosed herein may all be combined into a support member in accordance with the present invention in any desired way. For example, a support member may be provided that includes the basic structure of support member 16 , but that has a low-positioned slot, similar to the slot 90 of support member 16 ′ ( FIG. 8 ), and that also has a slanted adjustment aperture, similar to the adjustment aperture 98 or 98 ′ of support members 16 ″ and 16 ′″ ( FIGS. 9 and 10 ). Similarly, the features shown in the veneer connectors disclosed herein may all be combined into a veneer connector in accordance with the present invention in any desired way. [0092] In the embodiments described above, the side walls of the support members have been described and shown as extending outwardly from the mounting flanges along vertical planes. It will be noted that the vertical planes need not be strictly vertical, but are at least generally vertical. In another alternative, the side walls of the support members need not be strictly planar, and may instead be curved or may have further folds, which are preferably generally vertical. [0093] In the embodiments described above, the veneer connector mounts to the support member using a single fastener, such as a bolt. Using a single fastener instead of a plurality of fasteners can provide a significant cost savings in the overall cost of the connector, particularly in jurisdictions which require the use of stainless steel for connectors supporting veneer panels in a cavity wall. [0094] The connectors of the present invention are able to support the same loads as the L-shaped connectors of the prior art, but can be manufactured from thinner material, with fewer fasteners. As a result the connectors of the present invention can be less expensive than the L-shaped connectors of the prior art. [0095] While what has been shown and described herein constitutes the preferred embodiments of the subject invention, it will be understood that various modifications and adaptations of such embodiments can be made without departing from the present invention, the scope of which is defined in the appended claims.

A connector for coupling a veneer panel to a back-up comprises a support member comprising a mounting flange adapted for securing the support member to said back-up wall, and first and second support member side walls extending outwardly from the mounting flange. The first and second support member side walls define at least one generally horizontal slot when the support member is secured to the back-up wall. The connector further comprises a veneer connector configured for non-rotational sliding receipt in the generally horizontal slot and adapted to support a generally horizontal edge of said veneer panel when the veneer connector is received in the generally horizontal slot and when the support member is secured to the back-up wall.

FIELD OF THE INVENTION The present invention relates generally to safety restraints, and, more particularly, to a safety railing for temporary installation around the edge of a building roof during construction work. BACKGROUND OF THE INVENTION A recurring safety problem has been workers falling from the roofs of buildings which are under construction, or on which other work is being performed. Oftentimes, these accidents occur when the workers are moving about and carrying materials back and forth, and it sometimes happens that a worker will simply back over the edge of the roof while not looking. The magnitude of this hazard has drawn the attention of several regulatory bodies, including the Occupational Safety and Health Administration in the United States, and the Department of Occupational Safety and Health in Canada. As a result, some form of barrier is now required around roof edges where people will be working, and various attempts have been made to comply with this, with very modest success to date. For example, one approach has been to plant a series of posts on the roof and string a cord and warning flags between these; obviously, the actual restraint which is provided by the cord is minimal, and so this must be placed a considerable distance (about 6 feet) inboard from the edge of the roof, which tends to greatly reduce the available working space, and also presents a problem when it becomes necessary to work in the area outside the cord. A somewhat similar approach has involved the use of rails mounted to posts supported by base plates which rest on top of the roof; while this provides a somewhat more positive restraint, the base plates must still be set in a significant distance from the edge of the roof, which restricts the ability of the workers to work near the edge, and this also necessitates a laborious and time consuming effort to move the railings as the work progresses over the surface of the roof. Attempts have also been made to mount a railing at the very edge of the roof, usually by mounting a plain bracket (such as a conventional leg-and-shield type arrangement) to the outer wall of the building and then mounting the bottom of a stanchion to this so that the stanchion extends up above the edge of the roof and supports railings which are mounted to this. Several problems have been encountered with this approach, and these stem primarily from the inability of this arrangement to withstand any significant loading or impact on the upper railing. Current requirements call for the upper rail to be positioned about 42 inches above the edge of the roof, and OSHA standards require this to be able to withstand the impact of a 200 pound worker, while Canadian standards call for this rail to be able to support a 200 pound static load in either outward or inward directions. When a conventional bracket arrangement is used, these loads translate to a pull-out force on the order of 1000 pounds or more at the wall bracket; for example, if an outwardly directed impact is received by the rail at the upper end of the stanchion, this will tend to force the lower edge of the bracket plate into the wall of the building so that this acts as a pivot point, and this provides a lever arm for pulling out the fasteners which hold the plate to the wall, much in the same manner that a claw hammer provides leverage for removing a nail. Of course, if there is the force at the rail is directed inwardly, the upper edge of the bracket serves as the pivot point, with the same result. Also, because of this pivoting action, essentially the entire pull-out force must be born by whichever fastener is located near the outwardly moving edge of the plate, while the fasteners near the pivot edge bears relatively little of this. The net result of this situation is that conventional railings of this type are either wholly inadequate in terms of their ability to restrain workers against potential accidents, or they must be constructed so massively as to be very difficult to install and remove, which renders them impractical for many applications. For example, those fasteners which are favored for quick installation and removal from concrete (e.g., those sold under the trade names "Tap-Con" and "Scru-It") simply do not have the load-bearing capacity necessary to withstand the pull-out loads to which they would be subjected in an conventional bracket-mounting arrangement, and so fasteners of a heavier and usually more permanent nature (e.g., lag bolts) must be employed, which simply renders this approach impractical for temporary installations. Accordingly, there exists a need for a railing system which can be mounted right at the edge of a roof so as to make the maximum space available for work, and also eliminate the need to move this as the work progresses. Furthermore, there exists a need for a railing system of this type which is easily installed and removed, so that this can be efficiently used on a temporary basis during building construction. Still further, there is a need for a railing system of this type which is economical to fabricate, and which takes advantage of readily available railing members, such as standard length 2×4s. SUMMARY OF THE INVENTION The present invention has solved the problems cited above, and this is a safety railing for installation about the roof edge of a building, the safety railing comprising vertically elongate stanchion members each having a lower end and an upper end which is configured to extend above the roof edge, the upper end being configured for mounting to a railing member. A bracket member is provided for mounting to an outer wall of the building, and a pivoting link member is provided for interconnecting the bracket member and a middle portion of the stanchion member so that in response to application of an outwardly directed force to the railing member on the upper end of the stanchion, the lower end of the stanchion is pivoted inwardly against the wall of a building, and the pivoting link member is pivoted outwardly at an angle to the bracket member such that the force is transmitted to the bracket member in a combined pull-out and shear direction. The assembly may include a plurality of fasteners for mounting the bracket member to the wall, and for transmitting the force in the combined direction thereto. Preferably, the safety railing further comprises hinge means for connecting the pivoting link member to the base member so that the link member is pivotable about an axis which extends in a horizontal direction. An attachment member may be mounted to the middle portion of the stanchion member for detachably mounting the stanchion to an outer end of the pivoting link, and this may be a laterally-extending pivot pin. To receive this, the pivoting link member may comprise at least one hook portion which is configured to receive and support the pivot pin so that this pivots about an axis which extends in a horizontal direction, this being parallel to the axis of the hinge on the bracket member. Preferably, there are first and second stopper assemblies mounted to the stanchion member and extending inwardly from this so as to abut the wall of the building, the first being mounted below the pivot pin and the second being mounted above this. The stopper assemblies are each configured for selective adjustment of the distance which they extend inwardly from a stanchion member, so as to permit adjustment of the stanchion member to a vertical alignment, and also to an outwardly displaced position such that the possibility of accidental dislodgement of the pivot pin from the hook portion of the swinging link as a result of movement of the stanchion member is eliminated. At the upper end of the stanchion member, there may be a loop member which is configured to receive the overlapped ends of first and second railing members. These railing members may be wooden boards, and the loop member may be provided with an opening for extending a nail through the loop member and into the overlapped ends of the wooden rail member so as to lock these together within the loop member. Objects and advantages of the invention not clear from the above will be understood by a reading of the detailed description and a review of the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of the railing system of the present invention, this showing the system mounted at the roof edge of a building, with 2×4 railing members extending between the stanchions; FIG. 2 is a perspective view of the stanchion and mounting bracket assemblies of the railing system of FIG. 1; FIG. 3 is a side elevational view of a portion of the railing system of FIG. 1, showing this being installed on the roof edge of the building, the building being shown partly in cross section; FIG. 4 is a side elevational view similar to that of FIG. 3, showing the railing system having been installed and properly adjusted; FIG. 5 is a side elevational view similar to that of FIGS. 3-4, showing an outwardly directed force being applied to the upper railing of the system, and how the system responds by the swinging link pivoting outwardly from the wall bracket so that a combined loading is applied to the fasteners which hold this to the building; and FIG. 6 is a side elevational view of the upper end portion of the stanchion assembly shown above, this showing the ends of 2×4 railing members positioned in this in side-by-side relationship, as opposed to being overlapped on top of one another as shown in FIGS. 4-5. DETAILED DESCRIPTION FIG. 1 provides an overview of the railing system 10, this being mounted to the roof edge of a building 12. The railing system comprises a series of spaced-apart support assemblies 14, each of these being made up of a swinging link bracket assembly 16 which is mounted to the vertical outer wall 18, and a stanchion assembly 20 which is mounted to the bracket assembly and extends upwardly from this above the edge of the roof 22. At the upper end of each stanchion assembly there is a square loop portion 24, and there is a second square loop portion 26 positioned a short distance down the stanchion below this. These square loop portions provide receptacles through which the ends of rail members 28 extend; as can be seen in FIG. 1, the end of a first rail member is received in each loop portion, and then the end of the next rail member in the series is also received in this loop so as to overlap against the end of the first member. Thus, those rail members which are received and supported in the upper loop portions 24 form a continuous upper rail 30, while those which are received in the lower loop portions 26 form a continuous lower rail 32. It has been found that standard 10-foot long wooden 2×4s provide eminently suitable rail members for this system, and are well up to bearing the necessary impact loads. Having provided an overview of the railing system of the present invention, its components and their operation will now be described in greater detail. FIG. 2 illustrates the two primary support components of the system, the stanchion assembly 20 and the swinging link bracket assembly 16. The primary structural component of the stanchion assembly 20 is an elongate bar member 34, this preferably being a tubular steel member; a 6-foot length of 11/4 inch square steel tubing has been found eminently suitable for this purpose. As was noted above, an upper loop portion 24 is mounted at the upper end of the stanchion, and a lower loop portion 26 is mounted a short way below this. Each of these loop portions is preferably formed of a piece of flat bar stock bent to form a square receiving area 36, 38, and welded to the bar member 34 at the desired locations; it has been found desirable to position the lower loop portion (and hence the lower rail) about 19 inches below the upper. Each of the square receiving areas 36, 38 is sized so that the ends of two rail members can be received in this, either in side-by-side relationship or overlapped on top of one another: for conventional 2×4s, 3 3/4 inch square receiving areas have been found appropriate. The upper and side legs of each of these square loop portions are pierced by upper and side nail openings 40, 42, the use of which will be discussed below. Then, generally toward the lower end of the stanchion, there is a pivot pin 44 which is mounted to the bar member 34 so as to extend transversely across this. In order to obtain the desired height of the upper rail above the roof edge (i.e., about 42 inches), it has been found desirable for many applications to mount the pivot pin 44 about 501/2 inches below the upper end of a 72-inch stanchion. The pivot pin may be provided by a 1/2-inch steel pin approximately 4 inches long, and this is preferably mounted to the same, inboard face of the square bar member 34 as the loop portions, so that the rail members are supported against the inboard side of the bar member (i.e., toward the working area) when the assembly is in place. A first adjustable stopper assembly 46 is mounted a relatively short distance (e.g., about 6 inches) above the horizontally extending pivot pin, and this is made up of a base nut 50 which is welded to the inboard face of the bar member, and a foot portion 52 having a threaded shaft which is engaged by the base nut so that the distance by which the foot portion extends inwardly from the bar member 34 is selectively adjustable. A hole (not shown) is formed in the inboard wall of bar member 34 for the shaft of the foot portion to extend through in order to permit a greater range of adjustment, and an elastomeric friction pad 54 is mounted on the outer end of the foot portion so as to enhance the frictional engagement of the stopper assembly with the outer wall of the building. The lower stopper assembly 48, in turn, is mounted at or near the very lower end of bar member 34 (about 21-22 inches below pivot pin 44 on a 6-foot long stanchion assembly), and this similarly comprises a base nut 56, adjustable foot portion 58, and friction pad 60. As will become apparent from the description provided below, these stopper assemblies serve to provide the correct vertical alignment of the stanchion assembly, and also make it impossible for this to be accidentally dislodged from the bracket assembly once the system has been properly installed and adjusted. Turning now to the bracket assembly 16, it will be seen in FIG. 2 that this comprises generally a base plate portion 62 and a swinging link portion 64. The swinging link portion is made up of first and second parallel hook portions 66, 68, these having U-shaped enclosed ends which together define an area for receiving the pivot pin 44 of the stanchion assembly, and supporting this in pivoting relationship; hook portions providing a receiving channel about 2 inches long and about 3/8 inch wide have been found suitable for use with a stanchion assembly having the exemplary dimensions described above. The two hook portions 66, 68 are interconnected by the pin of a hinge 70 so that these move together in unison. The central loop 72 of the hinge, in turn, is mounted to the base plate portion of the assembly. This base plate portion is a flat, preferably rectangular member which is configured to abut the outer wall of the building. This is pierced by bores 74 above and below the hinge loop for the fasteners to extend through. A suitable spacing for these fastener bores has been found to be about 3 inches, centered on the horizontal hinge of the assembly, with a lower portion of the base plate extending about 31/2 inches below the lower bore to give an overall plate length of about 7 inches. First and second upstanding, parallel ears 78 are mounted at the lower end of the base plate, and these define a gap for receiving the bar member 34 of the stanchion assembly and fitting closely adjacent the sidewalls of this; these ears 78 serve to steady the stanchion assemblies against side-to-side "tipping" motion before the rail members have been installed therein. The installation of these assemblies and their adjustment will now be described with reference to FIGS. 3-4. The building structure 12 shown in FIG. 3 represents a typical wooden construction, in which there are wooden wall studs 80, 82 covered by an exterior facia 84, and these provide anchors for the fasteners of the railing system 10. However, it will be understood that the mounting shown here is equally applicable to concrete block structures, in which there is a concrete bond beam at the upper edge of the wall, as well as to those buildings which are constructed with a poured wall which extends all the way to the roof edge. To install the railing system, the bracket assembly 16 is positioned a sufficient distance below the upper edge 86 of the exterior facia that the upper stopper assembly 46 will be positioned to abut the facia when the stanchion is received in the bracket assembly. The fastener bores are placed in proper vertical alignment, and then fasteners 88 are driven through these into the underlying wall structure. Since the configuration of the railing system of the present invention is such that the fasteners do not have to resist the tremendous pull-out forces which are experienced when using the conventional railing systems discussed above, these can be fasteners of the type which are easily and quickly installed and then removed to provide a temporary installation, such as the Tap-Con™ or Scru-It™ fasteners noted above. The bracket assembly having been installed, the next step is to set the stanchion assembly in this. This is done by pivoting the swinging link portion 64 of the bracket assembly outwardly so that the gap between the tips of the hook portions 66, 68 and the hinge 70 extends laterally to receive the pivot pin on the stanchion assembly. As may be seen in FIG. 3, the hook portions of the bracket assembly are preferably sized so that this gap is only just large enough to let the pivot pin 44 pass through, so as to further reduce the chances of accidental dislodgment of the stanchion from the bracket assembly. As the pivot pin is set in the hook portion of the bracket assembly, the lower portion of the bar member 34 is simultaneously received in the gap between the upstanding ear portions 78 these steady the stanchion assembly against side-to-side rocking. The stanchion assembly is then lowered until the pivot pin rests in the closed ends of the hooks 66, 68 and the stanchion is suspended therein, and the foot portions of the stopper assemblies 46, 48 are extended outwardly from bar member 34 until the stanchion is aligned in a vertical direction. Further outward adjustment of the stopper assemblies is made, if necessary, until the pivot pin 44 has pulled the swinging link portion of the bracket assembly outwardly a short distance to the point where the receiving areas in the hook portions no longer extend in a vertical direction, as this is shown in FIG. 4. It will be understood that in this position it is no longer possible for the pivot pin 44 to become accidentally dislodged from the hook portions of the bracket assembly, whether by lifting or pivoting of the stanchion assembly, being that it is not possible to move the pin in a vertical direction within the receiving areas of the hooks. Having completed the installation and alignment of the bracket and stanchion assemblies, the next step is to install the rail members 28, and this is done by inserting their ends in the receiving areas of the loop portions 24, 26 (24 only shown in FIGS. 3-4). These are overlapped in the manner previously described, and a suitable nail 90 is then inserted through the appropriate nail opening (top opening 40, in the arrangement shown in FIG. 4) and hammered into the overlapped ends of the rail members so as to lock these together and prevent them from sliding out of the loop portion. This is done at each of the spaced-apart support assemblies until the continuous rail is completed, and the same is done for the lower rail as well. The installation is then complete and ready for work to commence. FIG. 5 illustrates the operation of the railing system 10, as this would prevent a person from moving outwardly over the edge of the roof. As can be seen, the force of the outwardly directed load or impact is represented in FIG. 5 by arrow 96. As this is applied to the upper railing, this force is transmitted through the railing to the upper end of the bar member 34. This outward movement of the upper end of the bar member causes the stanchion assembly to pivot about pivot pin 44, forcing the lower stopper assembly 48 against the exterior facia 84, and lifting the upper stopper assembly 46 away from this. Simultaneously, as the bar member 34 pivots outwardly about the pivot point which is provided by the lower stopper assembly 48, pivot pin 44 pulls outwardly on the swinging link portion of the bracket assembly, causing the hook portions thereof to pivot outwardly. In this position, with the hook portions of the bracket assembly extending at an angle from the base plate, and the outward force being transmitted from the stanchion assembly to the bracket assembly in this direction, the fasteners 88 are subjected to a "combined" loading. That is, they are not subjected to a pure pull-out force, nor to a pure shear force, but instead they are subjected to a force which combines elements of both pull-out and shear. As a result, because the fasteners' capacity with respect to both of these forces is being employled, the effective load-bearing ability of each fastener is greatly increased (relative to that for pure pull-out or shear), to the point of being nearly doubled. Also, because the pivot point is now provided by the lower stopper assembly 48, instead of the lower edge of the bracket plate, the ratio of the two lever arms is greatly reduced, and the magnitude of the pull-out force is therefore much smaller. Furthermore, because the force is transmitted to the base plate of the bracket assembly at the midpoint between the two fasteners 88, the load is equally shared by these, rather than one or the other of the fasteners having to bear most of this alone. As was noted above, these factors render the mounting of the railing system of the present invention much safer and more secure than conventional railing systems, and also make it possible to use easily installed temporary fasteners which would not be able to withstand the severe loading which would be encountered when using a conventional bracket arrangement. As was also noted above, the loop portions 24, 26 of the stanchion assemblies are configured so that their receiving areas are able to accommodate the ends of railing members (such as 2×4s) which are laid on top of one another, so that the railing members themselves rest horizontally, or these ends may be positioned in side-by-side relationship so that the railing members stand on edge. FIG. 6 shows this latter arrangement, with the two railing members 28a set on edge in the loop portion 24, and then a nail 98 is inserted through the side nail opening and driven into the boards to hold these in place. Having described the invention in its preferred embodiments, it will be clear that changes and modifications may be made without departing from the spirit of the invention. It is therefore not intended that the words used to describe the invention or the drawings illustrating the same be limiting on the invention. Rather, it is intended that the invention only be limited by the scope of the appended claims.

A safety railing for installation about a roof edge of a building. Vertically extending stanchion members are mounted to wall brackets by pivoting links. These swing outwardly in response to an impact on the railing at the upper ends of the stanchions, so that a combined pull-out and shear loading is applied to the wall bracket. This effectively increases the load-bearing capacity of the fasteners which attach the bracket to the wall. The swinging link member may be a pivoting hook, and this detachably engages a horizontally-extending pivot pin which is mounted to a middle portion of the stanchion.

RELATED APPLICATIONS [0001] This application claims rights under 35 USC § 119(e) from U.S. Application Ser. No. 60/560,004 filed Apr. 6, 2004, the contents of which are incorporated herein by reference. FIELD OF THE INVENTION [0002] This invention relates to the detection and localization of incoming missiles or other ordinances and more particularly to a system for rapid identification of and ranging to close-in targets. BACKGROUND OF THE INVENTION [0003] In combat situations, or in situations in which troops and vehicles are deployed for policing purposes, combat vehicles and personnel are subject to attack at very close range through the use of rocket-propelled grenades (RPGs) or other ordinances which are launched from sites which are very close to the personnel or vehicles. Thus, troops and vehicles are subject to weapons launched in their immediate vicinity. There is therefore a need to be able to detect an incoming missile and to countermeasure it all within the space of, for instance, less than a second. [0004] This presents challenges not only to the countermeasure system in which one might, for instance, have to aim and fire a so-called shotgun in the direction of the incoming missile with a sufficiently dense pellet pattern but also to be able to detect and track where the incoming missile is in the first place. [0005] For instance, personnel and vehicles are oftentimes attacked from very close range in tens of feet, where enemy personnel launch a missile, for instance, from the side of a road or from a nearby building. [0006] While one could attempt to detect the launching of such a missile using radar, the use of radar to provide situational awareness in the immediate proximity of a vehicle suffers from a number of problems. [0007] Since the reaction time is a fraction of a second to a second, not only would the response time need to include being aware of some kind of munition, one would also have to include the amount of time necessary to countermeasure the threat. [0008] In order to countermeasure such close-in threats, one would have to localize the projectile to its own size. Thus, if the missile is, for instance, a foot long and six inches in diameter, one would have to know where the missile was to the same accuracy so that one effectuates a direct hit. [0009] As will be appreciated, microwave radars might not have sufficient resolution to be able to pinpoint the incoming missile. Moreover, such radars generally have rotating heads that move an antenna around to cover a specific area. There is thus an associated scan time that may be much too long to permit effective countermeasuring of an incoming missile. [0010] There is also an associated processing time when using a radar involving calculating the trajectory of the missile and what is necessary to countermeasure it. Thus, there is a calculational lag that may put the response time outside of the fraction of a second response time required. [0011] By way of further background, optical rangefinders are well known in gunnery to determine the distance to a target. In a basic form, such devices may be constructed to give the solution of a triangle having the target at its apex and the rangefinder at the lower base. [0012] The prior art discusses improvements on optical rangefinder designs. U.S. Pat. No. 4,062,267 to Vinches et al., for example, discloses apparatus for conducting firing adapted to the aiming of a cannon movable bearing and in elevation around a turning axis as a function of aim values given by a firing table. The apparatus comprises a telescopic sight with an optical deviator element for displacement of the line of sight, the optical deviator element being mounted on a support coupled in bearing and in elevation with the cannon and being subjected to the action of a cam whose profile is determined by the aim values from the firing table and which is coupled to a motor controlled by a rangefinder device whose transmission and reception beams are connected in bearing and in elevation to the axis of the observation scope of the telescope. The optical deviator element is articulated through the intermediary of a spherical articulation on the support connected to the cannon and the optical deviator element is subjected to the signal of a detector of the vertical operating so that the observation axis must be maintained in a substantially vertical plane passing through the direction of the target. [0013] While such devices have tended to work well for the purpose of controlling fire directed against stationary or slow moving targets at a substantial range, these devices have limitations with respect to fast moving targets in close proximity to the sensing vehicle or structure. [0014] U.S. Pat. No. 4,556,313 to Miller et al. discloses a rangefinder that is adapted for use as a proximity fuse. This patent discloses an optical rangefinder having a transmitter and receiver located closely adjacent for short-range operation, as when a projectile or bomb is sent on a trajectory to intercept a large object. An optical window region is established where the transmitter look axis intersects the receiver look axis and is adjustable for providing an output signal when the rangefinder and target are less than approximately ten feet apart. The transmitter may emit either noncoherent or coherent infrared energy. The receiver includes zero crossing detection when a received maximum signal intensity is reached and adequate signal detection means that activates when the signal level exceeds a desired minimum. An output signal is generated when the outputs of these two detection circuits are coincident. [0015] This system, however, does not address the problem of detecting incoming projectiles or missiles that can be coming in from all directions. Also it does not address the issue of computation time that is exceedingly short when it is necessary to detect and localize close-in missiles or projectiles. [0016] A need therefore exists for a close-in system that does not involve location calculations or slewing of optics. In particular, a need exists for a for a system that may be used to accurately determine the existence and range of an approaching rocket-propelled grenade, RPG, or other rapidly-moving ordnance. [0017] While the prior devices have tended to work well for the purpose of controlling fire directed against stationary or slow moving targets at a substantial range, these devices may have limitations with respect to fast moving targets in close proximity to protected vehicles or personnel. SUMMARY OF INVENTION [0018] In the subject invention, rather than using conventional monochrome radar or LIDAR techniques, and rather than using other optical ranging systems, a polyspectral rangefinder is provided that projects narrow vertical fans of light of different colors outwardly from two or more positions such that each of the narrow fan beams has a color different from that of the next adjacent fan beam. The fan beams cross each other at various positions away from the position at which the beams are projected so as to map the surrounding space by bathing the surveilled area with crossing fan beams. The crossing point of two or more colors constitutes a color-coded cell. This map of color-coded cells is stored as color bins in a lookup table such that, by detecting light reflected from an incoming missile or target, one can detect its location by simply determining the colors returned at any given instant of time. [0019] Thus an incoming missile might be illuminated by a green beam from one position and a red beam from the other position when the particular missile enters into a cell or region where these two beams cross. Where these two beams cross defines a cell in space in which returns of red and green light indicate the exact point in space that the missile is passing through. [0020] The fan beams are arranged so that each color is projected outwardly at a different angle. This establishes a map of unique color combinations for each cell at the crossovers of the fan beams from the two sources. [0021] For instance, if one were to use two so-called showerhead projectors in which fanned light beams are projected out at 200 different angles from each of the two showerhead projectors, then for instance at 30 meters one would have a unique 5-cm-by-5-cm cell, the returns from which would uniquely specify the location of the reflecting object. [0022] The detection of what colors are returned instantly determines, by virtue of the lookup table without computationally intensive algorithms, where the missile is. One then can direct countermeasures along the line from the place where the returns are sensed to the cell, thus to be able to countermeasure the incoming threat before it impacts the vehicle. [0023] Since no computations are involved in locating the missile other than accessing a lookup table, detection of an incoming missile can be obtained in only a fraction of a second, virtually instantaneously. This permits rapid repositioning and firing, for instance, of a shotgun-type countermeasuring device. [0024] It will also be appreciated that to minimize the size of the colored cells, one could increase the number of different colored fan beams projected, so that one could pre-map the area around the vehicle with greater resolution. [0025] It will be appreciated that as the incoming missile or projectile proceeds into the area at which crossed differently colored beams exist, light from one colored beam is reflected simultaneously with the light of the other colored beam. [0026] If the beams were of the same color, then one could not tell along which beam the threat existed. [0027] In one embodiment, the showerhead projectors are mounted at two sides of a vehicle that would spew out or project rainbows of light. One way of obtaining the fans or wedges of the differently colored light is to use conventional analog wavelength division multiplexing units common in communications systems. In these systems, laser-generated light from a broadband laser is divided up into a number of colors through the use of a multiplexer. The multiplexer basically takes the broadband light and taps off different colors through specially designed gratings that couple light of a predetermined color into a particular optical fiber. [0028] The light from the end of an optical fiber is then focused to project out the required fan beam of light at a given angular orientation with respect to the optical centerline of the projection head and thus the optical centerline of the system. Each fan beam of colored light thus goes out at a predetermined angle with respect to the centerline of the vehicle. [0029] Note that wideband lasers are available to produce a spectrum of light that can be coupled into a self-contained array of filters utilizing the aforementioned tapped optical fibers, with each filter picking off a predetermined color and then feeding it to its own little optical nozzle. Each of these nozzles is located in a slightly different direction so that, when light from each of the nozzles goes out through space around the protected area, the associated color goes in a different direction from that associated with the adjacent beam. [0030] By detecting the colors that are returned, one uses a lookup table that maps the particular colored cells in color bins so that one can at minimum tell the direction to the incoming threat, that direction being the line from the sensor that detects the reflected light to the particular cell in question. [0031] As to protecting vehicles, in deploying the subject system, one would architect the projectors for each vehicle. If one wanted to surround the entire vehicle in 360° with intersecting fans of differently colored light, as a practical matter one might wish to segment the surveilled area into sectors having a 60° included angle. It is also possible to re-use colors from one side of the vehicle to the other because one could use detectors, for instance, that would only pick up light coming in from one particular direction. [0032] It will be noted that in the subject system, each color is sent out in a beamlet of a predetermined width that cuts a little narrow pie-shaped sector in space. When that sector in space is crossed by another beamlet of a different color, it defines a little cell of space or a volume in space that is uniquely identified by the colors existing at the cell. The result is that one color-codes the space. [0033] In summary, what one is doing is to break up the space around the vehicle into cells, with each cell having its own description in terms of a limited number of colors that could only have come from that particular point in space. [0034] As to the wavelength division multiplexing technology mentioned above, filters have been developed that either multiplex or demultiplex various colors of light. From the detection array point of view, one would channel all of the incoming light into one fiber having pickoffs provided by different gratings such that light carried by a particular fiber would be identified as having a particular color. These types of detectors are inexpensive, with the light exiting a particular fiber being detected by a particular pin diode or similar detector. One would therefore have one pin diode per channel or color. Additionally, thresholding circuits may be used to threshold out the ambient or ground clutter so that the signal received from a reflecting object entering into a particular cell is distinguished from the background. [0035] As to the generation of the multiple colored beams, one could typically use a wavelength multiplexer to generate wavelengths π 1 , λ 2 , λ 3 . . . λn. In this case the broadband laser output is divided up and outputted from various of the associated fibers. The light in the fibers is then projected out through a small lens or projection system at the so-called showerhead. [0036] As to detecting the color-coded reflections, it will be appreciated that the output of a pin diode or pixel would be one-to-one correlatable with a particular wavelength. The identification of the particular wavelength makes possible the use of the aforementioned lookup table, such that the output of any series of particular pin diodes specifies a particular color-coded cell. [0037] As far as the transmitted beams and wavelength division multiplexing filters, one has an input fiber on which one grafts a number of branch fibers. A diffraction grating is located at each graft that determines the particular wavelength of light that can be picked off of the fiber. Thus, the fiber is an assemblage of wavelength-selective taps connected to a main fiber such that a number of different wavelengths are projected out by different fibers at slightly different angles. [0038] As to the number of colors required for a given mapping or area, one can go from 100 to 1,000 different colors depending on how finely one can divide the light going into and out of the multiplexers. [0039] Thus, in terms of resolution, one must decide how many volume cells one wants in a particular space, with each volume cell requiring either two, three or four colors to uniquely specify it. [0040] Note that the number of different colors that is required for a given resolution varies with the distance out from the vehicle. It is noted that one has to have a finer angular resolution when a threat is relatively far out, for instance at 30 meters, than when an incoming threat is in close, for instance at ten meters. For this purpose one could arrange the showerhead of light projectors to be non-uniformly distributed so that, in the far field segments, the beams are more narrowly spaced and angled than those associated with the close-in positions. [0041] In one embodiment, beam width is 1/10 of a degree or 1/600 of a radian for a five-centimeter accuracy at 30 meters. [0042] As will be appreciated, the subject invention minimizes the computing time for curing the countermeasure weapon because all that is necessary is to read out a lookup table. Note that by identifying the unique color cell, one instantly has the direction to the incoming ordnance from the lookup table. One therefore has provided a system for detecting incoming missiles that involves minimal computing so that one can respond more quickly to an incoming threat. [0043] While the subject system is described in terms of protecting a vehicle, the subject system also includes protecting any area that has special protection requirements. As such, the subject system can protect buildings or other structures, aircraft or even personnel. [0044] In summary, what is provided is a computationless method for determining the direction of and distance to a target, involving bathing an area surrounding a vehicle, article or individual to be protected with a polyspectral series of narrow fan beams of different colors from at least two spaced-apart projectors. The differently colored beams go out at different angles, thus to color-code map the area surrounding the protected space where beams of different colors cross to form color-coded cells. Light reflected back to the protected space from a threat has a color code corresponding to the colors associated with beams that cross at the threat, thus to identify by the reflected colors where in space the threat is located. [0045] This method includes the first step of directing a first beam of light comprising a first plurality of colors from a first position on a sensor platform. A second beam of light including a second plurality of colors is directed from a second position on a second sensor platform so that the second beam of light intersects the first beam of light in an intersection area. This intersection area includes a plurality of color cells formed by the intersection of the first plurality of colors and second plurality of colors. Each of these color cells has a unique two-color signature. Reflected light from the target is received, and the position of the target is ascertained based on the unique two color signature of the color cell in which the target is located. The present invention also includes a polyspectral range finder for carrying out this method. BRIEF DESCRIPTION OF THE DRAWINGS [0046] These and other features of the subject invention will be better understood in connection with a Detailed Description, in conjunction with the Drawings, of which: [0047] FIG. 1 is a diagrammatic illustration of an incoming threat in terms of a rocket-propelled grenade, showing a 60° elevation field of regard and a 75° azimuth field of regard to form a surveillance area for the detecting of an incoming missile to a 5 cm range resolution for ranges between 1 and 30 meters; [0048] FIG. 2 is a diagrammatic illustration of a vehicle, such as a tank, provided with the subject polyspectral rangefinder in which, for one location on the vehicle, narrow fan beams of color are projected out from the side of the vehicle into the surveillance area so that an incoming missile or ordnance will reflect one of the beams impinging on it; [0049] FIG. 3 is a diagrammatic illustration of the tactical situation in FIG. 2 in which multiple differently colored fan beams are projected out from two spaced-apart projectors such that the fan beams intersect each other to provide a color-coded range map of individual cells at which two or more colored beams intersect; [0050] FIG. 4 is a block diagram illustrating the detection of light reflected from an object that passes through the surveillance area of FIG. 3 in which the receipt of two or more colors is mapped to a predetermined location through the use of a lookup table for determining the direction and range of the incoming object, from which a countermeasure such as a shotgun can be deployed; [0051] FIG. 5 is a schematic diagrammatic of the production of variously colored adjacent fan beams using a broadband laser and a multiplexer in which various optical fibers are tapped off a main fiber, with the tap including optical gratings to facilitate tapping off various colors, also indicating the projection of different colors at different angles from the optical axis of the system; [0052] FIG. 6 is a schematic diagram illustrating the receipt and detection of returns from an object in the mapped space of FIG. 3 , illustrating that incoming returns are focused onto a main fiber in a demultiplexer, and in which a multiplicity of other fibers are grafted to the main fiber at gratings such that an output of a detector at the end of one of these fibers indicates receipt of a reflection of a predetermined wavelength; [0053] FIG. 7 is a diagrammatic illustration of the resolution of the subject system, with a projected stripe at a range of 30 meters from a projector, assuming a 30-watt, 600-channel system, with 50 milliwatts per channel, a 3,000 cm 2 illustration/interrogation area (3×10 −4 sr), assuming a staring system with no gimbals and assuming transmit/receive optics shared or matched; [0054] FIG. 8 is a diagrammatic illustration of uniform target length resolution that requires non-uniform angular distribution of channels in which the distance between projectors is 6.5 meters and the range to a threat is 30 meters; [0055] FIG. 9 is a graph of color beam separation in milliradians versus target distance, illustrating that the color probe beam separation is greater close in; and, [0056] FIG. 10 is a diagrammatic illustration of the color beam separation calculation of FIG. 9 , showing that for a resolution element of length=5 cm at a range from one to 30 meters, the color probe beam separation is proportional to 1 L/2R 2 . DETAILED DESCRIPTION [0057] Referring now to FIG. 1 , in order to be able to protect a vehicle 10 such as a tank from an incoming missile or ordnance 12 such as an rocket-propelled grenade or TOW missile, from a practical standpoint one needs, in one embodiment, 60° in elevation for a field of regard as well as 75° in azimuth for a field of regard. Thus, the surveilled area is divided up into 60° sections. [0058] It is possible using standard techniques to cue a countermeasure module or system from conventional warning or tracking radar for crude or rough aiming, assuming a minimal time is spent in the rough positions of the countermeasure device. However, such conventional fire control systems may be too slow; and the subject system may be used in place of prior fire control systems. The subject system may thus be integrated into an active protection system, with the purpose to provide aim point refinement for close-in defensive rounds and to provide a target identification, i.e., an RPG, TOW missile or a ballistic round. [0059] Referring now to FIG. 2 , in one embodiment, vehicle 10 projects out differently colored fan beams 14 , 16 , 18 and 20 into a surveilled and protected area when they are able to impinge on a threat 22 as it approaches vehicle 10 . What can be seen in this figure is that the beams projected from a point or projector 24 on vehicle 10 are narrow in lateral extent, are displaced angularly in the horizontal direction and cut a relatively thin swath or wedge upwardly. [0060] Referring to FIG. 3 , if vehicle 10 were provided with two projectors, here shown at 30 and 32 , these projectors project differently colored fan beams illustrated by λ 1 , λ 2 , λ 3 , λ 4 , λ 5 , λ 99 and λ 100 , λ 101 , λ 102 , λ 103 , λ 104 , λ 105 , λ 106 , and λ 107 , respectively with each beam having a different color. [0061] The intersection of the beams from projectors 30 and 32 effectively maps the area around vehicle 10 such that intersections of, for instance beam at λ 3 with beam at λ 107 define a cell 40 where the beam having color λ 3 intersects the beam having color λ 107 . [0062] As will be seen, the size of cell 40 is determined by the number of adjacent differently colored beams that can be generated, with the desired cell size being no longer than the projected size of the incoming threat. In one embodiment the desired resolution size corresponds to a cell size of 5 cm on a side. [0063] It will be noted that missile 22 has a forward end 42 that reflects a portion of beam λ 5 and a portion of beam λ 104 back towards vehicle 10 as illustrated by arrow 46 . This is the specular return from target 22 that directly indicates target direction, position and extent. [0064] It will be appreciated that what is depicted is that the adjacent space to the vehicle is color coded using intersecting fans of distinct colored beams, with the range to a threat being defined by range bins that are one-to-one correlatable with color bins. The color code of returned radiation thus uniquely specifies the location of the threat reflecting the projected beams. [0065] In one embodiment, the two projectors are 600-beam showerhead projectors using, for instance, microlens arrays. A detector or sensor 50 detects reflected radiation from the surveilled scene and, as illustrated in FIG. 4 , couples the result of having received colors λ 5 and λ 104 to a lookup table 52 . The lookup table maps the detected colors with the map of the color-coded space around the vehicle. A read-out of the lookup table thus specifies location and direction of the threat. The size of the threat can be determined by what color-coded cells are detected at one time. [0066] In order to be able to provide such a lookup table, one has to map the colored space relative to the vehicle as illustrated at 54 and to provide this map in terms of the aforementioned color bins. [0067] Without complicated algorithms, by simply noting from the lookup table the range bin that is associated with a color bin, then as illustrated at 56 the direction and range to the threat can be quickly ascertained. Once having ascertained the direction and range, or simply the direction in the case of a shotgun type of countermeasure, shotgun 58 is swiveled in the general direction indicated and fired, with the pellet pattern being sufficient to intercept the detected incoming ordnance, missile or round. Note that knowing the location of the threat is used to decide when to fire the shotgun for optimum pellet cloud size. [0068] It will be appreciated that the amount of time necessary to detect the presence of an incoming threat is de minimus due to the fact that calculations are not required to determine the direction and range of the threat. The remainder of the time spent in countermeasuring the threat is centered about the response of the countermeasure itself, once knowing the direction and range of the threat. [0069] It has been shown that present shotgun-type countermeasuring devices can project a lethal pellet pattern in the direction of the incoming threat in less than half a second, once knowing where to aim the shotgun. The time necessary to aim and shoot the shotgun determines the response time of the system, since direction and range detection is virtually instantaneous upon receipt of reflections or returns from the threat. [0070] Referring now to FIG. 5 , in one embodiment, in order to project the differently colored and differently angled fan beams, a broadband laser 60 is provided that may be a 600-watt solid state laser having a broadband output of between 1540 nm and 1570 nm. The output of the broadband laser is coupled to a conventional dense wavelength division multiplexer 62 available from Nippon Telephone & Telegraph of Tokyo, Japan. Multiplexer 62 includes a main fiber 64 and a number of tapped fibers 66 , 68 , 70 and 72 grafted to main fiber 64 . At the point of the graft is a spectral grating that selects what frequency light is permitted to enter the fiber such that, with multi-microlens projection optics 74 , one can project differently colored fan beams as illustrated by λ 1 , λ 2 , λ 3 , and λ 4 , at different angles to the optical axis 76 of the projector. [0071] Referring to FIG. 6 , in one embodiment detector 50 of FIGS. 3 and 4 includes an optical focusing system 80 that focuses returned light 82 onto focal plane 84 . Focused light enters the end 86 of a main optical fiber 88 , with fibers 90 , 92 , 94 and 96 grafted to one main fiber 88 . This assemblage constitutes a demultiplexer 100 in which differently colored light is injected into different fibers due to spectral gratings at the tap points. The result is that detectors 102 , 104 , 106 and 108 have outputs indicating the receipt of light at λ 1 , λ 2 , λ 3 and λ 4 . The outputs of detectors 102 - 108 contain signals indicating a spectral return imaged onto fiber end 86 having the indicated color-coded components. Here the return is color coded with λ 1 and λ 4 light. The result is that detector 102 and 108 each generate an output signal. [0072] Referring now to FIG. 7 , what is depicted is that from a vehicle 10 with a 60° elevation field of regard 110 , at a 30-meter cross-section as illustrated at 112 and at a range of 30 meters, the cross-sectional width or thickness of a fan beam is quite small, on the order of 1 cm. For instance, for a 30-watt laser at 600 channels with 50 milliwatts per laser and a 3,000 cm 2 illumination/integration area (3×10 4 sr), and assuming a staring system with no gimbals and with transmit/receive optics that are shared or matched, then for a first color there is a resolution width of 5 cm as illustrated at 114 , with a projected stripe width of 1 cm as illustrated at 116 . [0073] The next color would occupy a different portion of space as illustrated by dotted line 120 . [0074] Thus, with a projected stripe having a narrow stripe width of 1 cm and a resolution width of 5 cm, one can achieve a 5 cm-by-5 cm range cell. Note, the height of the projected fan beam at 30 meters is 30 meters, whereas the thinness of the projected fan beam is a stripe that is a narrow 1 cm stripe, leading to the above-mentioned resolution width of 5 cm. [0075] Referring now to FIG. 8 , assuming a uniform target length, the resolution required is as illustrated, assuming vehicle 10 has projectors 30 and 32 that are spaced apart by 6.5 meters. Assuming a threat 22 at a range of 30 meters from each of the projectors, then as illustrated in FIG. 9 , which is a graph of color beam separation in milliradians versus target distance in meters, for 600 channels for a 5-cm target length resolution is a non-uniform angular distribution of channels is required. This means, for instance, that at 30 meters the color probe beam separation in the horizontal direction is about 0.4 milliradians, whereas close in at 10 meters the color probe beam separation is approximately 1.2 milliradians. [0076] Referring to FIG. 10 , how graph 9 is calculated is shown. Here projector 30 is shown projecting a fan beam towards a resolution element 130 of 51=5 cm. The calculation Θ(R)˜1L/2R 2 , where 1 is the resolution element length and L is the separation between the projectors, yields a color probe beam separation for 200 channels that produces a 15 cm target length resolution. For 1,000 channels one would have a 3 cm resolution. [0077] Note that the distance indicated by double-ended arrow 132 is L/2=3.25 meters. [0078] What will be seen is that one has provided a polyspectral rangefinder based on wavelength division multiplexing technology with a realizable resolution in a few centimeters that uses a lookup table readout of target position and extent without calculation-intensive algorithms that would delay threat detection and position indication. [0079] The subject polyspectral rangefinder is inexpensive when based on commercial communication multiplexing and demultiplexing hardware and importantly provides sufficient resolution to be able to countermeasure an incoming RPG, TOW missile or even a projectile due to the rapid response time achievable. [0080] While the present invention has been described in connection with the preferred embodiments of the various figures, it is to be understood that other similar embodiments may be used or modifications or additions may be made to the described embodiment for performing the same function of the present invention without deviating therefrom. Therefore, the present invention should not be limited to any single embodiment, but rather construed in breadth and scope in accordance with the recitation of the appended claims.

A computationless system 10 is provided for determining the direction of and distance to a target 42 , involving bathing an area surrounding an area to be protected with a polyspectral series of narrow fan beams (xi,)ioo) of different colors from at least two spaced-apart projectors 30, 32 . The differently colored beams go out at different angles, thus to color-code map the area surrounding the protected space where beams of different colors cross to form color-coded cells. Light 46 reflected back to the area to be protected from a threat 42 has a color code corresponding to the colors associated with beams that cross at the threat, thus to identify by the reflected colors where in space the threat is located.

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a division of application Ser. No. 09/705,484 filed Nov. 3, 2000 entitled, “Thin Film Transistors on Plastic Substrates with Reflective Coatings for Radiation Protection.” [0002] The United States Government has rights in this invention pursuant to Contract No. W-7405-ENG-48 between the United States Department of Energy and the University of California for the operation of Lawrence Livermore National Laboratory. BACKGROUND OF THE INVENTION [0003] The present invention relates to thin film transistors, and more particularly to the formation of silicon based thin film transistors on inexpensive, low-temperature plastic substrates. The present invention relates to a method of fabricating thin film transistors wherein heat sensitive substrates, such as inexpensive and flexible plastic substrates, may be used in place of standard glass, quartz, and silicon wafer-based substrates. A reflective coating for radiation protection of the plastic substrates is utilized during processing. The reflective coating layer is deposited above the plastic substrate to protect it from high intensity irradiation during processing by a laser or other high intensity radiation source. [0004] Traditional techniques used in manufacturing high-performance polycrystalline silicon (poly-si) thin film transistors require processing temperatures of at least 600° C. This minimum temperature requirement is imposed by silicon crystallization and dopant activation anneals. Processes have recently been developed for crystallizing and doping amorphous silicon on a low cost, so-called low-temperature plastic substrates using a short pulsed high energy source in a selected environment, without heat propagation and build-up in the substrate so as to enable use of plastic substrates incapable of withstanding sustained processing temperatures higher than about 120° C. Such processes are described and claimed in U.S. Pat. No. 5,346,850 issued Sep. 13, 1994, to J. L. Kaschmitter et al. and U.S. Pat. No. 5,817,550 issued Oct. 6, 1998, to P. G. Carey et al., both assigned to the Assignee of the instant application. [0005] As exemplified by the above-referenced U.S. Pat. No. 5,346,850, high performance polycrystalline silicon devices have been produced at low temperatures (<250° C.). This is accomplished by crystallizing the amorphous silicon layer (and activating dopants) with a short-pulse ultra-violet laser, such as an ArF excimer laser having a wavelength of 308 nm. The extremely short pulse duration (20-50 ns) allows the silicon thin film to melt and recrystallize without damaging the substrate or other layers in the device. Polycrystalline layers produced in this manner provide high carrier mobilities and enhanced dopant concentrations, resulting in better performance. [0006] The present invention extends the capability of the above-mentioned method and processes for fabricating amorphous and polycrystalline channel silicon thin film transistors at temperatures sufficiently low to prevent damage to low cost, so-called low-temperature plastic substrates. The present invention utilizes a reflective coating for radiation protection of the plastic substrates during processing. A reflective coating layer is deposited above the plastic substrate to protect it from high intensity irradiation during processing by a laser or other high intensity radiation source. The process for fabrication of silicon thin film transistors on low-temperature plastic substrates, the thin film transistor, and the set of thin film transistor substrates for use in manufacturing thin film transistors of the present have different characteristics than existing thin film transistors. They have many and varied uses. For example, plastic displays and microelectronic circuits on flexible, rugged plastic substrates constructed in accordance with the present invention may be used for portable consumer electronics (video cameras, personal digital assistants, cell phones, etc.) or on large-area flat panel displays. Large area plastic displays are in need for high resolution large area flight simulators. Flexible detector arrays have use in radiation (X-ray, gamma-ray) detection. Silicon-on-insulator films may be used in radiation-hardened IC circuits. Many other uses exist and the development of the invention will produce additional uses. SUMMARY OF THE INVENTION [0007] The present invention relates to the fabrication of silicon-based thin film transistors (TFT), and more particularly, to a method of fabricating TFT wherein inexpensive and flexible plastic substrates are used in place of standard glass, quartz, and silicon wafer-based substrates. The present invention also relates to the fabrication of silicon-based TFT with plastic substrates utilizing a reflective coating for radiation protection of the plastic substrates during processing. A reflective coating layer is deposited above the plastic substrate to protect it from high intensity irradiation during processing by a laser or other high intensity radiation source. [0008] The invention provides a method for the formation of TFT on inexpensive plastic substrates. The method of this invention utilizes sufficiently lower processing temperatures so that inexpensive flexible plastic substrates may be used. The so-called low-temperature plastic substrates have several advantages over conventionally used substrates such as glass, quartz, and silicon. Processing temperatures of the method of this invention are such that sustained temperatures are below a temperature of 120° C. although short duration high temperatures are used during the processing. This is accomplished using pulsed laser processing which produces the needed temperatures for short time periods while maintaining the sustained temperature of the substrate below a damage threshold (i.e. below about 120° C.). A reflective coating for radiation protection of the plastic substrates is utilized in the processing. A reflective coating layer is deposited above the plastic substrate to protect it from high intensity irradiation during processing by the laser or other high intensity radiation source. Thus, by the use of fabrication techniques of the present invention, the sustained temperature of the substrate is sufficiently low to prevent damage to the inexpensive and flexible low-temperature plastic substrates. The present invention provides a method which relies on techniques for depositing semiconductors, dielectrics, and metal at low temperatures, crystallizing and doping semiconductor layers in the TFT with a pulsed energy source. [0009] The present invention significantly increases the type of plastic substrates that can be utilized in the fabrication of thin film transistors. In addition, plastic substrates have several advantages over conventional substrates, such as glass or silicon in that plastic can be much less expensive, lighter, more durable, rugged, and flexible. The process for fabrication of silicon thin film transistors on low-temperature plastic substrates, the thin film transistor, and the set of thin film transistor substrates for use in manufacturing thin film transistors of the present have different characteristics than existing thin film transistors. They have many and varied uses. For example, plastic displays and microelectronic circuits on flexible, rugged plastic substrates constructed in accordance with the present invention have multiple uses such as in field-deployable portable electronics, battlefield operations facilities, and the interior of ships, tanks and aircraft. Large area plastic displays are in need for high resolution large area flight simulators. Flexible detector arrays have use in radiation (X-ray, gamma-ray) detection. Silicon-on-insulator films may be used in radiation-hardened IC circuits. Many other uses exist and the development of the invention will produce additional uses. [0010] It is an object of the present invention to enable fabrication of silicon-based thin film transistors on plastic substrates. [0011] A further object of the invention is to provide a method for manufacturing thin film transistors wherein low cost, low-temperature substrates can be utilized. [0012] Another object of the invention is to provide a method of fabricating thin film transistors wherein inexpensive plastic substrates may be used in place of standard glass, quartz, and silicon wafer-based substrates. [0013] Another object of the invention is to provide a method for fabricating thin film transistors involving replacement of standard fabrication procedures with procedures utilizing sufficiently lower processing temperatures so that inexpensive plastic substrates may be used. [0014] Another object of the invention is to enable the manufacture of thin film transistors using plastic substrates which enable use for large area low cost electronics, such as flat panel displays and portable electronics. [0015] Another object of the invention is to protect transparent plastic substrates from damage due to exposure by radiation during processing through the use of a narrow-band reflective layer. [0016] Other objects and advantages of the present invention will become apparent from the following description, accompanying drawings, and through practice of the invention. BRIEF DESCRIPTION OF THE DRAWINGS [0017] The accompanying drawings, which are incorporated into and form a part of the disclosure, illustrate embodiments of the invention, and, together with the description, serve to explain the principles of the invention. [0018] [0018]FIGS. 1A, 1B, and 1 C illustrate pulsed laser melting of silicon on a plastic substrate to form poly-si. [0019] [0019]FIGS. 2A, 2B, and 2 C provide an illustration of damage which can occur to a plastic substrate during pulsed laser melting of a patterned silicon film. [0020] [0020]FIG. 3 shows the results of measuring reflectance of the coating. [0021] [0021]FIGS. 4A, 4B, 4 C, 4 D, and 4 E show configurations in which a reflective layer can be used to protect an underlying substrate or layer from high intensity radiation during the processing of another layer. [0022] [0022]FIGS. 5A, 5B and 5 C show a TFT structure that is produced using laser processing. [0023] [0023]FIG. 6 shows shallow junction formation in a MOSFET by laser doping. [0024] [0024]FIG. 7 shows the results of measuring reflectance of another coating used in the preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION [0025] The present invention involves ( 1 ) a method or process for fabrication of silicon thin film transistors on low-temperature plastic substrates, ( 2 ) a thin film transistor, ( 3 ) a set of thin film transistor substrates for use in manufacturing thin film transistors, and ( 4 ) the preparation of a reflective coating to protect the substrate and device from process radiation. The present invention utilizes techniques for depositing semiconductors, dielectrics, reflective coatings, and metals at low temperatures and crystallizing and doping semiconductor layers in the thin film transistors with a pulsed energy source, such as an excimer laser. The present invention enables the fabrication of amorphous and polycrystalline channel silicon thin film transistors at temperatures sufficiently low to prevent damage to plastic substrates. Low-temperature substrates are defined as those materials incapable of withstanding sustained processing temperatures higher than about 150°-250° C., compared to the so-called high-temperature materials such as silicon, glass, quartz, etc., which can withstand sustained processing temperatures of 400° C. and higher. While the low-temperature substrate may be heated higher than about 150°-250° C. for short time durations, such may be damaged if that time duration is longer than about 10 −4 seconds ( 100 μs). [0026] High intensity radiation is used to process materials in the manufacture of the thin film transistors (TFT). In many cases it is desirable to expose only specific materials or regions of the TFT to the radiation. This is often the case because other materials that are present, including the substrate, may be vulnerable to damage by the radiation. The TFT of the present invention is constructed by depositing a reflective coating in a layer above these vulnerable materials so that the radiation is reflected away and prevents such damage. High intensity radiation sources can be used on TFT that would otherwise be damaged by direct exposure to such radiation. It also enables greater flexibility in designing processes using materials that are vulnerable to damage by high intensity radiation. [0027] Processes in which this procedure may be applied include using high intensity radiation for annealing, melting, crystallization, doping, ablation, photolithography, direct laser writing/patterning, etc. High intensity radiation sources include those with a short wavelength that will be readily absorbed by the substrate material (e.g. pulsed UV excimer lasers, frequency doubled NdYAG lasers, UV flashlamps, X-ray sources, etc.). Reflective coatings include single layer and multiple layers for narrowband or broadband reflection. [0028] Methods or processes for fabrication of silicon TFT on low-temperature plastic substrates including techniques for depositing semiconductors, dielectrics, and metals at low temperatures and crystallizing and doping semiconductor layers in the thin film transistors with a pulsed energy source, such as an excimer laser. processes are described and claimed in U.S. Pat. No. 5,817,550 issued Oct. 6, 1998, to P. G. Carey et al., assigned to the Assignee of the instant application. The description, specification, and drawings of U.S. Pat. No. 5,817,550 are incorporated herein by reference. [0029] A better understanding of the present invention can be obtained from the descriptions of the following specific (1) methods or processes for fabrication of silicon thin film transistors on low-temperature plastic substrates, (2) thin film transistors, and (3) sets of thin film transistor substrates for use in manufacturing thin film transistors. The descriptions provide a preferred embodiment of the invention. [0030] The first embodiment provides pulsed laser crystallization or doping of a patterned silicon film on a transparent plastic substrate which has a multilayer narrowband reflective coating. The second embodiment provides pulsed laser doping of CMOS junctions whereby a reflective layer is deposited on top of the MOSFET gates, isolation oxides, and other regions to protect them from the laser pulse. This procedure will make possible the manufacture of: 1) Shallow junction formation for CMOS integrated circuits using silicon substrates or silicon-on-insulator; 2) Shallow junction formation for silicon (or germanium) microelectronics on plastic substrates; 3) Active matrix flat panel displays on plastic substrates; 4) High performance silicon (or germanium)-based electronic circuits on plastic substrates. [0031] Two technical hurdles that have been overcome are (1) to manufacture and (2) to dope a poly-si film while preventing any thermal damage to the plastic substrate. Conventional processes to produce or dope poly-si require sustained temperatures at or above 600° C., a temperature range that will damage plastics. The present invention overcomes these hurdles by utilizing pulsed laser annealing to produce poly-si and using a reflective coating to prevent damage to the plastics. [0032] Information that is helpful in an understanding of the present invention is provided with reference to FIGS. 1A, 1B, and 1 C. These figures show a process of pulsed laser melting on a plastic substrate, generally designated by the reference numeral 10 , to form poly-si. This illustrates manufacturing polycrystalline silicon (poly-si) based thin film transistors at low temperatures on plastic substrates. [0033] The technique, illustrated in FIGS. 1A, 1B, and 1 C involves using a high intensity ultraviolet excimer laser pulse that is absorbed at the surface of the silicon film 11 . The pulse energy is sufficient to melt the silicon film 11 . However, due to the short time scales involved, and the thermal barrier layer 12 below the silicon, the plastic substrate 13 experiences a small thermal load for only a brief time (tens of microseconds) which prevents any damage to the plastic substrate 13 . In FIG. 1A the initial amorphous silicon film and thermal barrier on plastic substrate is shown. In FIG. 1B the melting of silicon layer by laser pulse 15 is shown. In FIG. 1C the resulting p-si 16 after solidification is shown. [0034] One limitation of this process is that if the plastic substrate is directly exposed to the laser pulse it would be severely damaged. In the current implementation of this process the entire area of the substrate is covered by the silicon film, preventing any exposure to the laser. [0035] However, it is sometimes desirable to pattern the silicon film prior to laser exposure, which would lead to the situation illustrated in FIGS. 2A, 2B, and 2 C. A high intensity ultraviolet excimer laser pulse 25 is absorbed at the surface of the silicon film 21 . The pulse energy is sufficient to melt the silicon film 21 . The thermal barrier layer 22 below the silicon 24 protects the plastic substrate 23 and prevents any damage to the plastic substrate 23 in that region. [0036] As shown in FIGS. 2A, 2B, and 2 C, when a pattern is used, the silicon 21 / 24 does not cover the entire area of the thermal barrier 22 . The region of the thermal barrier/plastic substrate that is not covered by Si 21 / 24 is exposed to the laser pulse 25 . As shown in FIG. 2B, the laser energy 25 is transmitted through the thermal barrier 22 layer and absorbed by the plastic substrate 23 . Those regions of the plastic substrate 23 that are exposed to the laser energy 25 are readily damaged, and any films covering those regions may also be damaged or delaminated. The damaged area 24 is shown in FIG. 2C. [0037] In the present invention, a highly reflective coating is deposited in a layer above the substrate to protect the plastic from the laser pulse. In a specific application where an optically transparent substrate is desirable, a narrow-band reflective coating which is designed to transmit in the visible, while being highly reflective at the wavelength of the laser, is deposited. Incorporating an appropriately engineered high reflectance layer allows for more flexibility in the procedures of laser processing. [0038] A narrow band reflectance coating is deposited by sputtering on a polyester (PET) substrate. This is an actual multi-layer design. It was manufactured using the materials SiNx and SiO 2 . The results of measuring reflectance of this coating are shown in FIG. 3. As displayed, the coating had a high reflectance in the UV, greater than 70% for wavelengths between 300 nm and 335 nm, while still being visibly transparent. This coated plastic was then exposed to Excimer laser pulses with a 308 nm wavelength. The plastic survived laser pulses with energy densities up to 350 millijoules cm −2 . An uncoated PET wafer was tested and could only survive energy densities up to 50 millijoules cm −2 . This clearly illustrates that a plastic wafer coated with such a reflective layer could be used in a process sequence where the substrate would be exposed to an intense laser pulse. [0039] The results of measuring reflectance of another coating used in the preferred embodiment of the present invention are shown in FIG. 7. It can be produced using the materials HfOx and SiO 2 . HfOx, has less absorption at the design wavelength (308 nm) than SiNx, and is also much easier to fabricate. This reflectance coating is deposited by sputtering on a polyester (PET) substrate. The graph, FIG. 7, shows the theoretical reflection and transmission curves of this layer design. The design will give greater than 99% reflection at 308 nm and >94% transmission of visible wavelengths, (400 nm-700 nm). [0040] The present invention consists of the procedure and the physical product of depositing a reflective layer above a substrate and/or other material layers to protect them from high intensity irradiation during processing by a laser or other high intensity radiation source. [0041] Referring again to the drawings and in particular to FIGS. 4A, 4B, 4 C, 4 D, and 4 E configurations in which a reflective layer 32 can be used to protect an underlying substrate or layer 31 from high intensity radiation 35 during the processing of another layer are shown. The reflective layer 32 is configured such that the radiation used during processing would be reflected away from the substrate and/or any material layer 31 that is vulnerable to undesired damage by the radiation. This is illustrated in FIGS. 4A, 4B, 4 C, 4 D, and 4 E for several layer configurations. [0042] In FIG. 4A a reflective layer 32 is deposited directly on the substrate 31 and the material to be processed 33 is deposited directly on the reflective layer 32 . FIG. 4B is similar to 4 A except for the possibility of a transparent layer(s) located directly above the reflective layer 32 . FIG. 4C illustrates the scenario in which the reflective layer 32 protects not only the substrate 31 but also any layer(s) above the substrate that could absorb the radiation and be damaged. [0043] The reflective layer 32 could also be configured to protect materials that are located above the material to be processed 33 . This is illustrated in FIG. 4D in which the layer(s) 36 that need to be protected are located above the layer to be processed 33 , and the reflective layer 32 is patterned to allow irradiation of specific areas. FIG. 4E provides an example where the radiation is used to process exposed regions of the substrate 37 , while the reflective layer 32 is patterned to protect layer(s) 36 that are above the substrate. [0044] As illustrated, the reflective layer reflects the radiation that would otherwise cause undesired damage to the substrate or any other layer(s) on the substrate. This invention will enable processing using high intensity radiation sources on substrates that would otherwise be damaged by direct exposure to such radiation. Furthermore, the configurations in FIGS. 4D and 4E can be useful in laser processing of silicon substrate during IC fabrication. [0045] Processes in which the present invention may be applied include using high intensity radiation for annealing, melting, crystallization, doping, ablation, photolithography and direct laser writing/patterning of either the substrate or any materials above it. High intensity radiation sources include those with a short wavelength that will be readily absorbed by the substrate material (e.g. pulsed UV excimer lasers, frequency doubled NdYAG lasers, UV flashlamps, X-ray sources, etc.). Reflective coatings include single layer and multiple layers for narrowband or broadband reflection. A narrowband reflective coating has the advantage that the coating can be transparent to visible wavelengths of light in situations where it is desirable to have a transparent substrate. The narrow band reflectance coating can be deposited by sputtering on a polyester (PET) substrate. This can be a multi-layer design using the materials SiNx and SiO 2 . The coating has a high reflectance in the UV, greater than 70% for wavelengths between 300 nm and 335 nm, while still being visibly transparent. Another coating used in the preferred embodiment of the present invention can be produced using the materials HfOx and SiO 2 . HfOx has less absorption at the design wavelength (308 nm) than SiNx and is also much easier to fabricate. This reflectance coating is deposited by sputtering on a polyester (PET) substrate. The design will give greater than 99% reflection at 308 nm and >94% transmission of visible wavelengths, (400 nm-700 nm). [0046] The present invention is further illustrated by the example of processing a silicon thin film transistor (TFT) on a plastic substrate. Background can be obtained from a review of U.S. Pat. No. 5,817,550 issued Oct. 6, 1998, to P. G. Carey et al. and assigned to the Assignee of the instant application. The disclosure of U.S. Pat. No. 5,817,550 is incorporated herein by reference. [0047] [0047]FIG. 5A shows one embodiment of the completed structure produced using the present invention. The device is made on plastic substrate 41 . A transparent PET (polyethyleneterephthalate) substrate was used. This PET is readily damaged when exposed to an excimer laser pulse with energy densities used in laser processing of semiconductors. A reflective coating 42 is deposited directly on the substrate 41 . For the process this layer could be a narrow-band reflective coating consisting of a multilayer that reflects ultraviolet radiation but is transparent in the visible. An optional thermal barrier may be deposited above or below the reflective layer 42 . This barrier is currently either SiO x or SiN x and protects the plastic from the high intensity radiation used during laser processing of the silicon layer. [0048] The TFT consists of a metal gate 46 , a gate insulator 45 , and a semiconductor layer which contains a source 44 , drain 47 and channel 48 region. We currently use Aluminum as the metal and SiO 2 as the insulator. The semiconductor can be either silicon or germanium, and the source and drain regions are doped to achieve high conductivity and ohmic contact. This is a conventional top-gate TFT structure. [0049] The present invention is best understood by considering the laser melting and laser doping steps used in producing the TFT. These two steps are illustrated in FIGS. 5B and 5C. During laser melting, excimer laser pulses (308 nm wavelength) are used to melt the semiconductor layer. As illustrated in FIG. 5B, in regions where there is no semiconductor, the laser pulse is reflected by the reflective layer. Without this reflection, the laser energy would be absorbed by the plastic substrate, resulting in damage. Without this reflective layer it has been necessary to leave the entire substrate area covered with the semiconductor film to protect the substrate. This reflective layer enables patterning the semiconductor before the laser processing, increasing the flexibility of arranging processing steps. [0050] The plastic substrate is also protected by the reflective layer during laser doping (FIG. 5C). In this step, the laser pulse melts the source and drain regions of the semiconductor, while being reflected away from the channel region by the gate metal. While the semiconductor is molten, dopant molecules diffuse into the semiconductor. These dopant species are introduced either in the gas phase (traditional GILD processing) or in a thin film deposited on the surface just prior to the laser melt. Background information can be obtained from a review of U.S. Pat. No. 5,918,140 incorporated herein by reference. U.S. Patent No. 5,918,140 was issued Jun. 16, 1997, to P. Wickboldt, P. G Carey, P. M. Smith, A. Ellingboe and T. W. Sigmon for deposition of dopant impurities and pulsed energy drive-in. A semiconductor doping process which enhances the dopant incorporation achievable using the Gas Immersion Laser Doping (GILD) technique. The enhanced doping is achieved by first depositing a thin layer of dopant atoms on a semiconductor surface followed by exposure to one or more pulses from either a laser or an ion-beam which melt a portion of the semiconductor to a desired depth, thus causing the dopant atoms to be incorporated into the molten region. After the molten region recrystallizes the dopant atoms are electrically active. The dopant atoms are deposited by plasma enhanced chemical vapor deposition (PECVD) or other known deposition techniques. [0051] Again, in regions where there is no semiconductor, the reflective layer reflects the laser pulse and protects the plastic substrate. The thermal barrier included in FIGS. 5 A-C need not be located above the reflective layer but could also be located below it. This could be beneficial in situations where this layer is not transparent to ultraviolet. In addition, if other materials are used that are vulnerable to damage by the laser pulse, they could be located below the reflective layer. [0052] This current process is tailored for making TFTs for use on transparent PET for use in flat panel displays where a transparent plastic substrate is desired. This invention, however, could be used in the laser processing of devices for use in flexible circuitry and other applications where semiconductor devices are needed on substrates that can be damaged if exposed to the laser. [0053] This invention can also be used in laser processing of CMOS devices. FIG. 6 illustrates the particular example of shallow junction doping of a MOSFET. The semiconductor junctions 51 are doped by laser melting using an excimer laser pulse 56 . While the semiconductor is molten, dopant molecules diffuse into the semiconductor. These dopant species are introduced either in the gas phase (traditional GILD processing) or in a thin film deposited on the surface just prior to the laser melt (see U.S. Pat. No. 5,918,140 issued Jun. 16, 1997, to P. Wickboldt, P. G Carey, P. M. Smith, A. Ellingboe, and T. W. Sigmon for deposition of dopant impurities and pulsed energy drive-in). Prior to the laser exposure, reflective layer 55 is deposited over the device structure and patterned. The reflective layer is patterned to cover and protect the gate region 52 and 54 , the isolation oxide region 53 , and any other regions across the substrate which may contain materials vulnerable to laser damage 57 . Correspondingly, the reflective layer is patterned to expose those regions the silicon substrate 50 that are doped to make the junctions 51 . [0054] This application can be used to protect poly-silicon or silicide gates 54 which will absorb the laser radiation, resulting in undesired damage. In addition, the “field regions” 53 are conventionally made with thermally grown oxide on a silicon substrate and could be damaged by laser melting. [0055] This example illustrates use of the invention in MOSFET fabrication. However, a similar approach can be adopted to make use of this invention in laser processing of a variety of IC devices. [0056] The process for fabrication of silicon thin film transistors on low-temperature plastic substrates, the thin film transistor, and the set of thin film transistor substrates for use in manufacturing thin film transistors of the present invention have many and varied uses. The process for fabrication of silicon thin film transistors on low-temperature plastic substrates, the thin film transistor, and the set of thin film transistor substrates for use in manufacturing thin film transistors of the present have different characteristics than existing thin film transistors. There will be many and varied uses of the new thin film transistors. For example, plastic displays and microelectronic circuits on flexible, rugged plastic substrates constructed in accordance with the present invention have multiple uses such as in field-deployable portable electronics, battlefield operations facilities, and the interior of ships, tanks and aircraft. Large area plastic displays are in need for high resolution large area flight simulators. Flexible detector arrays have use in radiation (X-ray, gamma-ray) detection. Silicon-on-insulator films may be used in radiation-hardened IC circuits. Other uses, too numerous to describe here, also exist. While particular embodiments, operational sequences for fabrication, materials, parameters, etc., have been set forth to exemplify and explain the principles of the invention, such are not intended to be limiting. Modifications and changes may become apparent to those skilled in the art, and it is intended that the invention be limited only by the scope of the appended claims.

Fabrication of silicon thin film transistors (TFT) on low-temperature plastic substrates using a reflective coating so that inexpensive plastic substrates may be used in place of standard glass, quartz, and silicon wafer-based substrates. The TFT can be used in large area low cost electronics, such as flat panel displays and portable electronics such as video cameras, personal digital assistants, and cell phones.

RELATED APPLICATION This application is a continuation in part of application Ser. No. 09/330,207 filed Jun. 11, 1999 now U.S. Pat. No. 6,180,668, which is in turn a continuation in part 2000, Ser. No. 09/128,271 filed Aug. 3, 1998 now U.S. Pat. No. 6,013,818. FIELD OF THE INVENTION The present invention relates to a series of oils that have been “reconstituted”. The present invention covers the reaction product of meadowfoam oil and an ester selected from the group consisting of beeswax, jojoba oil, carnauba wax, and candellia wax. The term reconstituted as used hereon refers to a process in which two or more waxes or oils of natural origin are transesterified under conditions of high temperature and catalyst to make a “reconstituted product” having an altered alkyl distribution and consequently altered chemical and physical properties. BACKGROUND Natural waxes and oils fall into two distinct classes, based upon their chemistry. The first class is made up on the triglycerides and are generally referred to as oils. They are tri-esters of glycerin, hence the name triglycerides. The structure of the triglyceride is: Naturally occurring triglycerides are natural products derived from plant species and have a species specific carbon distribution in the “R” portion. For example Soybean oil has a naturally occurring “R” 29% oleic C 17 H 33 (oleic), and 54% linoleic C 17 H 31 (linoleic). Soybean oil is a low viscosity oil that is not good for dispersing pigments. The use of meadowfoam oil, in the preparation of reconstituted oils results in unique, unexpected oxidative stability rendered to the reconstituted oil. Specifically, the reconstituted oils containing minor amounts of meadowfoam oil have unexpected improvements in their oxidative stability. The unique structure of the meadowfoam results in this oxidative stability heretofore unattainable. The fatty distribution of the oil ranges from 20 to 22 carbons and has unsaturation in specific locations. The oil contains 97% by weight higher unsaturated alkyl groups. Typically, meadowfoam oil contains 60-65% of a twenty carbon mono-carboxy acid having one unsaturation between carbon 5 and 6. Additionally, it contains 12-20% of a twenty two carbon mono-carboxy acid having one unsaturation between either carbon 5 and 6, or carbon 13 and 14 and 15-28% of a twenty two carbon mono-carboxy acid having one unsaturation between both carbon 5 and 6, or carbon 13 and 14. The combination of the fact that there are 20 to 22 carbon atoms in the group leads to lack of volatility, the presence of unsaturation leads to liquidity and the fact that the di-unsaturated moieties are not conjugated leads to outstanding oxidative stability. Meadowfoam oil is a triglyceride that conforms to the following structure: Wherein R is: 60-65% by weight —(CH 2 ) 3 —CH═CH—(CH 2 ) 13 —CH 3 12-20% by weight a mixture of —(CH 2 ) 3 —CH═CH—(CH 2 ) 15 —CH 3 and —(CH 2 ) 11 —CH═CH—(CH 2 ) 7 —CH 3 and and 15-28% by weight —(CH 2 ) 3 —CH═CH—(CH 2 ) 6 —CH═CH—(CH 2 ) 6 —CH 3 . The process of the current invention will allow for the synthesis of a reconstituted oil having a “mixed” carbon distribution and very desirable properties that can be customized for particular applications. Another example of where reconstitution improves properties is mitigation of drying properties in so called drying oils. These oils have a high iodine value, generally over 175. These oils homo-polymerize to make films and generate heat. The heat is not properly dissipated can cause spontaneous combustion. By reacting a high iodine value oil with a lower iodine value oil we can lower the heat generated and the hardness of the film that forms. It must be understood that these are not blends of oils. For example, if one blends meadowfoam oil and jojoba oil, the resultant mixture is s cloudy mass, that rapidly separates on standing. The process of the present invention makes the compounds react and remain clear and homogeneous. Not only that, the range of meadowfoam to Jojoba can be altered widely to change functional properties. Beeswax separates from soybean oil, but when reacted according to the process of our invention, remains clear and results in an altered melting point and hardness of the resulting wax. The process allows for very wide variation and preparation of materials heretofore unattainable. The term “wax” refers to a series of esters. Unlike triglycerides that are trimesters of glycerin, these products are monoesters having alkyl distributions on both sides of the ester. A typical ester is beeswax. Beeswax conforms to the following structure: R′—O—C(O)—R″ Botanists attempt to alter the distribution of the “R” group using genetic engineering and plant selection processes for both waxes and esters. This is a difficult, expensive and time-consuming process that allows for only marginal modification of the “R” group in natural oils. We have discovered that by using a process called “Reconstitution of the waxes or oils” we are able to prepare compounds that can be made to vary far more radically in “R′ composition and consequently have new unique and controllable properties, heretofore unattainable using genetic manipulation and plant selection. The present invention to provides a series of products that are produced by this process for use in applications where the altered properties can be used. For example the modification of the melting point of beeswax by reconstituting it with soybean oil results in an ability to custom tailor melting points of the resulting wax for use in lipsticks, where the ability to have a melting point near body temperature is important. Another example of an application is pigment processing. Meadowfoam oil is commonly used as a solvent for milling pigment. The high viscosity of meadowfoam oil can be a problem however. By reconstituting meadowfoam oil and coconut oil the viscosity can be made to a desired value and the pigment dispersing ability and viscosity specifically controlled. Attempts to control these properties by genetic engineering have not been successful. We can simply make more and different variations of reconstituted products than can be bio-engineered. THE INVENTION Objective of the Invention It is the objective of the present invention to provide unique and heretofore unknown reconstituted oils and waxes having unique oxidative stability, especially when heated. It is another objective of the present invention to provide a series of products that are produced by this process for use in applications where the altered properties can be used. Other objectives will become clear reading the disclosure. SUMMARY OF THE INVENTION Detailed Description of the Invention There are three different combination of raw materials that can be used to practice the current invention. They are: 1. Two or more different triglycerides—U.S. Pat. No. 6,013,818 incorporated herein by reference, covers this class of products. The present invention covers class 3 (below). A process for reconstituting triglycerides which comprises reacting two or more triglycerides having different “R” functionalities with each other to produce a reconstituted triglyceride. Typical of this reaction is the reconstitution of 0.33 moles of soybean oil and 0.67 moles of meadowfoam oil to produce a new reconstituted oil. The reaction is as follows: 2. Two or more different waxes—A process for reconstituting waxes which comprises reacting two or more waxes having different “R” functionalities with each other to produce a reconstituted wax. Typical of this reaction is the reconstitution of 1.0 moles of beeswax and 1.0 moles of Jojoba to produce a new reconstituted wax. The reaction is as follows: 3. One or more waxes and one or more triglyceride—The present invention relates to this class of compounds. A process for reconstituting triglycerides and waxes, which comprises: reacting one or more triglyceride and one or more waxes with each other to produce a reconstituted wax and reconstituted triglyceride. Typical of this reaction is the reconstitution of 0.33 moles of soybean oil and 0.67 moles of beeswax to produce a new reconstituted oil and a new reconstituted wax. As will become evident from the current disclosure, the reconstituted products prepared using the process of the current invention have altered properties, like melting point, viscosity, pigment dispersion properties and others that make these compounds very useful in a variety of applications, including personal care and preparations of inks, polishes and waxes for industrial applications. DETAILED DESCRIPTION OF THE INVENTION The present invention discloses a process for reconstituting triglyceride and waxes which comprises, reacting meadowfoam oil with one or more reactants selected from the group of waxes in the presence of an esterification catalyst at a temperature of between 150 and 250 C. In a preferred embodiment, meadowfoam oil is one of the triglycerides reacted. Meadowfoam oil is a unique triglyceride. Meadowfoam Oil has the CAS number 153065-40-8. These compounds are prepared by reconstituting meadowfoam oil and a triglyceride group consisting of soybean oil, corn oil, sunflower oil, safflower oil, olive oil and cottonseed oil . The process comprises, reacting meadowfoam oil with two or more reactants selected from the group consisting of soybean oil, corn oil, sunflower oil, safflower oil, olive oil and cottonseed oil in the presence of an esterification catalyst at a temperature of between 150 and 250 C. PREFERRED EMBODIMENT The reconstituted triglyceride made by the transesterification reaction of meadowfoam oil and an ester selected from the group consisting of beeswax, jojoba oil, carnauba wax, and candellia wax. In a preferred embodiment the reconstituted triglyceride of the present invention, said transesterification reaction is conducted by mixing said meadowfoam and an ester selected from the group consisting of beeswax, jojoba oil, carnauba wax, and candellia wax, then heating said mixture in the presence of an esterification catalyst to a temperature of between 150 and 250° C. In a preferred embodiment said ester is beeswax. In a preferred embodiment said ester is jojoba. In a preferred embodiment said ester is carnauba wax. In a preferred embodiment said ester is candellia wax. EXAMPLES Raw Materials The raw materials useful in the preparation of the products of the current invention are natural products derived from both plant and animal sources. We have described them giving their common name, source CAS numbers and carbon distribution. All these materials are items of commerce, available from many sources including The Fanning Corporation (Chicago Ill.), Angelia Oils (Kramer Chemical) Glen Rock N.J. Triglycerides Example 1 Milk Fat Milk fat is the triglyceride from cow's milk, it is also known as butter. It is made up of the following carbon distribution (R value): 4% C3H5 (butyric), 2% C5H15 (caproic), 2% C7H15 (caprylic), 3% C9H19 (capric), 4% C11H23 (lauric) , 10% C13H27 (myristic), 32% C15H31 (palmitic), 14% C17H35 (stearic), 30% C17H33 (oleic) and 2% C17H31 (linoleic). Milk fat has a CAS Number of 144635-07-4, and an EINCS Number: of 415-310-5. Example 2 Tallow Tallow is the triglyceride also known as animal fat. It is made up of the following carbon 3% C13H27 (myristic), 30% C15H31 (palmitic), 20% C17H35 (stearic), 40% C17H33 (oleic) and 6% C17H31 (linoleic) . It has a CAS Number of 61789-13-7 and a EINECS Number: 263-035-2. Example 3 Japan Wax Japan Wax is a triglyceride secreted by the insect Coccus cerriferus. The wax is deposited over the tree branches in which the insect lives. The wax is scrapped and refined much like beeswax is refined. It is 79% C15H31 (palmitic) and has a CAS Number of 8001-139-6. Example 4 Coconut Oil Coconut oil is the most abundant oil processed. It is the most common oil raw material used in the cosmetic industry. It comes principally from Southeast Asia and the Philippines and is the major source of lauric acid. Coconut oil is 48% C11H23 (lauric), and 20% C13H27 (myristic). The CAS Number is 8001-31-8. Example 5 Babassu Oil Babassu oil is derived from the tallest palm in Brazil ( Attelea martiana Martius). Chemically, it is very similar to coconut oil, having a carbon distribution shifted slightly toward the higher molecular weights. It is 45% C11H23 (lauric), 17% C13H27 (myristic), 8% C15H31 (palmitic), and 15% C17H33 (oleic). It has a CAS Number of 91078-92-1 and an EINECS Number of 293-376-2. Example 6 Palm Kernel Oil Palm kernel oil is a triglyceride derived from the dried fruit of the coconut palm ( Cocos nucifera L.). It comes from Southeast Asia. It is 50% C11H23 (lauric), 15% C13H27 (myristic), and 15% C17H33 (oleic) It has a CAS Number of 8023-79-8 and EINECS Number is 232-282-8. Example 7 Soybean oil Soybean oil is a triglyceride derived from the soybean ( Glycerin max L). The soybean originated in China, as far back as 2,300 BC. It is 30% C17H33 (oleic), and 54% C17H31 (linoleic). The CAS Number is 8001-22-7 and the EINECS Number is 232-274-4. Example 8 Peanut Oil Peanut oil is a triglyceride derived from peanuts ( Arachis hypogea L.). It is cultivated in many areas of the world, since it is easy to grow. It is 60% C17H33 (oleic), and 23% C17H31 (linoleic). It has a CAS Number of 8002-03-07 and a EINECS Number of 232-296-4.h Example 9 Corn Oil Corn oil is a triglyceride derived from corn ( Zea mais, Graminae). It is cultivated in all the temperate areas of the world. It is 46% C17H33 (oleic) and 43% C17H31 (linoleic). The CAS Number is 8001-30-7. Example 10 Sunflower Seed Oil Sunflower seed oil is a triglyceride derived from the seeds of the sunflower ( Helianthus annus L.). It was originally cultivated in North America by native Indians. It is now cultivated in North America, Russia, Europe South America, India and China. It is a rather common plant. It is 20% C17H33 (oleic ) and 70% C17H31 (linoleic). The EINECS Number is 232-273-9 and the CAS Number is 8001-21-6. Example 11 Grapeseed Oil Grapeseed oil is a triglyceride derived from grape ( Vitis vinifera ). It is cultivated in many areas of the world, but originated in the Mediterranean coast (Italy, France, Turkey, Greece and Yugoslavia). It is 70% C17H29 (linoleic). EINECS number is 287-896-9 and the CAS Number is 8024-22-4. Example 12 Safflower Oil Safflower oil is a triglyceride derived from the species Carthamus tinctorius. This is the high oleic species. It originates in the Orient, but the U.S. production has been selected to maximize oil content. The oil is 77% C17H33 (oleic), and 17% C17H31 (linoleic). The CAS Number is 8001-23-9, and the EINECS Number is 232-276-6. Example 13 Poppy Seed Oil Poppy seed oil is a triglyceride derived from the poppy ( Papaver orientiale ). It was originally cultivated in Asia Minor, but is now produced in Europe. It is 10% C15H31 (palmitic), 15% C17H33 (oleic), and 73%, C17H31 (linoleic). The CAS Number is 8002-11-7. Example 14 Sweet Almond Oil Sweet almond oil is a triglyceride derived from the almond ( Prunus amygdalus ). It is cultivated in all the temperate areas of the world. The oil is 73% C17H33 (oleic), and 20% C17H31 (linoleic). The CAS Number is 8007-69-0. Example 15 Hazelnut Oil Hazelnut oil is a triglyceride derived from the nut of the hazelnut tree ( Corylus avellana ). It is cultivated in Europe, principally Italy, Spain and Turkey. Hazelnut oil contains natural preservatives and antioxidants, which render the oil very stable. It is 80% C17H33 (oleic) and 15% C17H31 (linoleic). Example 16 Walnut Oil Walnut oil is a triglyceride derived from the walnut ( Juglans regia ). It originated in Persia, and is now cultivated in Europe. Southern France is the major area in which Walnuts are grown. It is 26% C17H33 (OLEIC), 48% C17H31 (linoleic), and 16% C17H29 (linolenic). The CAS Number is 8024-09-7, and the EFNECS Number is 84604-00-2. Example 17 Olive Oil Olive oil is a triglyceride, which has occupied a unique position in civilization. It is the oldest oil known to man. It is produced throughout the area that was once the Roman Empire. Olive oil is 84% C17H33 (oleic). The CAS Number is 8001-25-0, and the EINECS Number is 232-277-0. Example 18 Avocado Oil Avocado oil is a triglyceride coming from the avocado ( Persea grantissima ). The pulp of the fruit has a great deal of oil present (70% by weight). It is 22% C15H31 (palmitic), 62% C17H33 (oleic), and 13% C17H31 (linoleic). The CAS Number is 8024-32-6, and the EINECS Number is 232-274-4. Example 19 Sesame Oil Sesame oil is a triglyceride, which is derived from Sesamun indicum. It is cultivated in Africa, Europe, China, Central and South America and the southern U.S. It is one of the world's oldest crops. It is 47% C17H33 (oleic), and 40% C17H31 (linoleic). The CAS Number is 8008-74-0, and the EINECS Number is 232-370-6. Example 20 Cottonseed Oil Cottonseed oil is a triglyceride derived from cotton ( Gossypium hirsutum ). Cotton, like soybean, is a very important crop, in that the crop has a protein, and fatty component, but unlike soybean, the fiber is very useful in textile applications. It is 21% C15H31 (palmitic), 32% C17H33 (oleic), and 44% C17H31 (linoleic). The CAS Number is 8001-29-4 and the EINECS Number is 232-280-7. Example 21 Palm Oil Palm oil is a triglyceride extracted from the fruit of Elaeis guineensis Jacq, which is among the most efficient oil producing plants per acre in the world. It is 42% C15H31 (palmitic), and 44% C17H33 (oleic). The CAS Number is 8002-75-3, and the EINECS Number is 232-316-1. Example 22 Rice Bran Oil Rice Bran oil is a triglyceride extracted from rice. It comes from Japan. It is 18% C15H31 (palmitic), 41% C17H33 (oleic), and 37% C17H31 (linoleic). The CAS Number is 68553-81-1 and the EINECS Number is 271-397-8. Example 23 Canola Canola oil is a triglyceride produced from genetically modified rapeseed. It is 77% C17H33 (oleic), 11% C17H31 (linoleic). The CAS Number is 8002-13-9. Example 24 Cocoa Butter Coca butter is a triglyceride obtained from the cocoa bean ( Theobroma cacoa L.). The species was originally found along the Amazon. It is now grown commonly along the equator where there is abundant rainfall. Cocoa Butter is the ingredient that gives chocolate its characteristic melting properties and unique texture. “Pure prime pressed” denotes the highest possible quality of cocoa butter used in the food industry. It is 27% C15H31 (palmitic), 35% C17H35 (stearic), and 35% C17H33 (oleic). The CAS Number is 8002-31-1. Example 25 Borneo Illipe (Shea Butter) Borneo Illipe is a triglyceride derived from the tree ( Shorea stenoptera L.), which is native to India. It is also called Shea Butter. It is 20% C15H31 (palmitic), 45% C17H35 (stearic), and 33% C17H33 (oleic). The CAS Number is 977026-99-5, and the EFNECS Number is 293-515-7. Example 26 Linseed Oil Linseed oil is a triglyceride derived from flax ( Linum usitatissium ). It is cultivated in all the temperate areas of the world. Linseed oil is a drying oil, meaning it dries into a solid. This is due to the high number of double bonded and the triple bonded species present in the material. Linseed oil is a drying oil. Linseed oil is 17%, C17H33 (oleic), 15% C17H31 (linoleic), and 61% C18H29 (linolenic). The CAS Number is 8001-26-1, and the EINECS Number is 232-278-6. Example 27 Veronia Oil Veronia oil is a triglyceride, which is obtained from the seed of Veronia galamensis. It contains a very high concentration of epoxy functionality, making it unique. It is 79% C17H31O (Cis 12-13 epoxy oleic). The CAS Number is 169360-96. Example 28 Tung Oil Tung oil is a triglyceride obtained from the seed of the Tung tree ( Aleurites fordii ). The tree is native to China and Indochina. Tung is described as a drying oil. This is because the abundance of double and triple bonds in it, particularly the high concentration of the conjugated double bonds, make this oil homo polymerize into a film. Tung oil is 80% C17H29 (conj. double bonds). The CAS Number is 8001-20-5. Example 29 Ongokea Oil Ongokea oil is a triglyceride derived from the species Ongokea gore. It originates in Africa. This material is somewhat unique because of it's high concentration of an acetylenic bond. Ongokea oil is a drying oil. It is 80% C17H29 having a unique triple bond. Waxes Example 30 Beeswax Beeswax is a complex ester, produced by worker bees, Apis mellifica. Beeswax, which is also known as white wax, is an insect wax cultured worldwide; it is found on all continents of the globe. The chemical composition of the wax depends on the species of the bee producing the wax. To extract the beeswax for use, the honeycomb is melted or boiled with water and the crude wax is skimmed off the top. The color of the crude material is dependent upon the type of flower producing the pollen and the age of the hive. Beeswax is a complex structure and as such, possesses unique properties that renders it an invaluable raw material for many of today's industries. Beeswax was the first wax. It consists of about 15% free fatty acids, 15% hydrocarbon resins, and the balance the esters. Carbon Distribution Principal Ester Composition Alcohol/Acid % C-30/C-16 23 C-30/C-26 12 C-30/C-30 12 C-26/C-16* 10 *Hydroxy-palmitate The CAS Number is 8006-40-4, the EINECS Number is 232-383-7. Example 31 Carnauba Wax At present, the only place in the world where the Carnauba Palm tree can be found is in northeastern Brazil. This Palm tree ( Capernicea cerifera ), often called the “tree of life,” produces a wax on its leaves, protecting them from the severe weather conditions of the area. Harvesting occurs around September following traditional procedures, the leaves are cut and are laid on the ground to dry in the sun. Modern technology takes over to scrape this valued product from its leaf. Carnauba wax is composed of mono and di hydroxy containing fatty alcohols, having 28 to 34 carbon atoms, and hydroxy acids, their esters and polyesters. This polymeric nature of the wax results in its hardness and high melting point. The CAS Number is 8015-86-9. Example 32 Jojoba Oil Jojoba is an ester derived from the woody evergreen shrub Simmondsia chinensis (link). Jojoba is a desert shrub that grows in coarse well-drained desert soil. It is found in southern Arizona and northwest Mexico. Jojoba oil is a liquid ester having C20 to C22 acids and alcohols. It has a CAS Number of 61789-91-1. Example 33 Candellia Wax Candellia Wax is extracted from the outer surface of Candellia plants, which are native to the arid regions of Northern Mexico. The plants grow wild in the plains and in the foothills of Mexico's North-Central plateau. With a Melting point ranging from 66 to 71 C, Candellia is well suited to the preparation of many wax products where resistance to heat is an important consideration. Candellia wax is used in polish dressings, coatings, and finishes, where a reasonably high melting point is desirable. In addition, this wax blends easily with fatty acids, paraffin, and other waxes used in the manufacture of candles and tapers. Candellia can be used for dyes in the printing of various materials providing excellent lubricant properties and resistance to high pressure. Candellia Wax is composed of hydrocarbon (50%) and the remainder is fatty acids, aliphatic triterpenic alcohols and their esters as well as some resin. Component % Weight Chemical Nature Acids 8 C30-C34 Alcohols 10 C20-C32 Esters 30 C42-C64 Hydrocarbons 50 C31 Resin 2 — CAS Number: 8006-44-8 Raw Material Examples Example Example (Number) Description (Number) Description (1) milk fat, (2) tallow, (3) Japan wax, (4) coconut oil, (5) babassu oil, (6) palm kernel oil, (7) soybean oil, (8) peanut oil, (9) corn oil, (10) sunflower oil, (11) grapeseed oil, (12) safflower oil, (13) poppy seed oil, (14) sweet almond oil, (15) hazelnut oil, (16) walnut oil, (17) olive oil, (18) avacado oil, (19) sesame oil (20) cottonseed oil, (21) palm oil (22) rice bran oil, (23) canola oil, (24) coco butter oil, (25) shea butter, (26) linseed (27) veronia oil, (28) Tung (29) ongokea oil, (30) beeswax, (31) carnauba wax, (32) jojoba oil, (33) candelillia wax. General Procedure 1. Reconstitution Reacting Two or More Different Triglycerides The compounds of the present invention are prepared according to the following procedure: Into a suitable vessel with agitation and nitrogen sparge is placed the specified number of grams of the first specified triglyceride. Next add the specified number of grams of the specified second triglyceride. A suitable esterification catalyst is then added. Esterification catalysts are selected from the group consisting of methane sulfonic acid, sulfuric acid, oragno-tin compounds, titinates. Of particular interest is the use of stannous oxylate. Stannous oxylate is used at a concentration of 0.1 percent based upon the total number of grams of all materials charged. The contents of the vessel are heated to between 150-250 C. A preferred range is 180-190 C. The contents are held at this temperature for at least four hours. During that time the batch clears and becomes homogenous and the reaction progress is followed by thin layer chromatography. The concentration of the original triglycerides drop down to low levels and the new reconstituted triglycerides are formed. The materials are cooled and used without additional purification. Clay treatment to improve color or filtration may be used if desired. Example 34 Into a suitable vessel with agitation and nitrogen sparge is placed 100.0 grams of the first specified triglyceride (Example 1). Next add 500.0 grams of the second triglyceride (Example 2). Next add 0.1% stannous oxylate. Stannous oxylate is used at a concentration of 0.1 percent based upon the total number of grams of all materials charged. The contents of the vessel are heated to between 180-190 C. for at least six hours. During that time the batch clears and becomes homogenous and the reaction progress is followed by thin layer chromatography. The concentration of the original concentration of the triglycerides drop down to low levels and the new reconstituted triglycerides are formed. Example 35-69 Example 34 is repeated, only this time the specified number of grams of the specified first triglyceride are substituted for the original first triglyceride and the specified number of grams of the specified second triglyceride is substituted for the original second triglyceride. First Triglyceride Second Triglyceride Example Example Grams Example Grams 35 1 500.0 30 500.0 36 2 500.0 29 500.0 37 3 500.0 30 400.0 38 4 500.0 29 400.0 39 5 500.0 28 300.0 40 6 500.0 27 300.0 41 7 500.0 26 600.0 42 8 500.0 25 100.0 43 9 500.0 24 50.0 44 10 500.0 23 50.0 45 11 500.0 22 150.0 46 12 500.0 21 250.0 47 13 500.0 20 500.0 48 14 500.0 19 5.0 49 15 500.0 18 150.0 50 16 500.0 17 500.0 51 17 500.0 16 325.0 52 18 500.0 15 450.9 53 19 500.0 14 500.0 54 20 500.0 13 5.0 55 21 500.0 12 900.0 56 22 500.0 11 500.0 57 23 500.0 10 500.0 58 24 500.0 9 50.0 59 25 500.0 8 400.0 60 26 500.0 7 400.0 61 27 500.0 6 300.0 62 28 500.0 5 35.0 63 29 500.0 4 500.0 64 30 500.0 3 500.0 65 26 500.0 2 150.0 66 28 500.0 1 50.0 67 21 500.0 1 100.0 68 21 500.0 2 500.0 69 23 500.0 3 250.0 Example 70 Into a suitable vessel with agitation and nitrogen sparge is placed 100.0 grams of the first specified triglyceride (Example 1), and 100 grams of specified second triglyceride (Example 2). Next add 500.0 grams of the third triglyceride (Example 3). Next add 0.1% stannous oxylate. Stannous oxylate is used at a concentration of 0.1 percent based upon the total number of grams of all materials charged. The contents of the vessel are heated to between 180-190 C. for at least six hours. During that time the batch clears and becomes homogenous and the reaction progress is followed by thin layer chromatography. The concentration of the original triglycerides drop down to low levels and the new reconstituted triglycerides are formed. Example 71-79 Example 70 is repeated, only this time the specified number of grams of the specified first triglyceride are substituted for the original first triglyceride, the specified number of grams of the specified second triglyceride is substituted for the original second triglyceride and the specified number of grams of the specified third triglyceride is substituted for the original third triglyceride. Exam- First Triglyceride Second Triglyceride Third Triglyceride ple Example Grams Example Grams Example Grams 72 1 500.0 29 100.0 16 100.0 73 2 500.0 28 200.0 17 200.0 74 3 500.0 27 500.0 18 50.0 75 4 500.0 26 400.0 20 5.0 76 5 500.0 25 200.0 21 150.0 77 6 500.0 28 50.0 23 200.0 78 7 500.0 26 5.0 25 100.0 79 8 500.0 29 5.0 28 50.0 2. Reconstitution Reacting Two or More Different Waxes The compounds of the present invention are prepared according to the following procedure: Into a suitable vessel with agitation and nitrogen sparge is placed the specified number of grams of the first specified wax. Next add the specified number of grams of the specified second wax. A suitable esterification catalyst is then added. Esterification catalysts are selected from the group consisting of methane sulfonic acid, sulfuric acid, oragno-tin compounds, titinates. Of particular interest is the use of stannous oxylate. Stannous oxylate is used at a concentration of 0.1 percent based upon the total number of grams of all materials charged. The contents of the vessel are heated to between 150-250 C. A preferred range is 180-190 C. The contents are held at this temperature for at least four hours. During that time the batch clears and becomes homogenous and the reaction progress is followed by thin layer chromatography. The concentration of the original wax drop down to low levels and the new reconstituted waxes are formed. The materials are cooled and used without additional purification. Clay treatment to improve color or filtration may be used if desired. Example 80 Into a suitable vessel with agitation and nitrogen sparge is placed 500.0 grams of the first specified wax (Example 30). Next add 500.0 grams of the second wax (Example 31). Next add 0.1% stannous oxylate. Stannous oxylate is used at a concentration of 0.1 percent based upon the total number of grams of all materials charged. The contents of the vessel are heated to between 180-190 C. for at least six hours. During that time the batch clears and becomes homogenous and the reaction progress is followed by thin layer chromotography. The concentration of the original wax drop down to low levels and the new reconstituted waxes are formed. Example 81-91 Example 80 is repeated, only this time the specified number of grams of the specified first wax are substituted for the original first wax and the specified number of grams of the specified second wax is substituted for the original second wax. First Wax Second Wax Example Example Grams Example Grams 81 31 500.0 30 500.0 83 32 500.0 31 500.0 84 33 500.0 32 500.0 85 30 500.0 33 500.0 86 31 500.0 33 500.0 87 32 500.0 30 100.0 88 33 500.0 31 300.0 Example 89 Into a suitable vessel with agitation and nitrogen sparge is placed 100.0 grams of the first specified wax (Example 30), and 100 grams of second specified wax (Example 31). Next add 500.0 grams of the third wax (Example 32). Next add 0.1% stannous oxylate. Stannous oxylate is used at a concentration of 0.1 percent based upon the total number of grams of all materials charged. The contents of the vessel are heated to between 180-190 C. for at least six hours. During that time the batch clears and becomes homogenous and the reaction progress is followed by thin layer chromatography. The concentration of the original triglycerides drop down to low levels and the new reconstituted triglycerides are formed. Example 90-102 Example 89 is repeated, only this time the specified number of grams of the specified first wax is substituted for the original first triglyceride, the specified number of grams of the specified second wax is substituted for the original second wax and the specified number of grams of the specified third wax is substituted for the original third wax. Exam- First Wax Second Wax Third Wax ple Example Grams Example Grams Example Grams 90 30 500.0 33 250.0 32 55.0 91 31 500.0 32 250.0 30 127.0 92 32 500.0 31 250.0 33 485.0 93 33 500.0 30 250.0 31 560.0 94 30 500.0 31 250.0 31 100.5 95 31 500.0 32 250.0 32 158.0 96 32 500.0 33 250.0 33 135.0 97 33 500.0 32 250.0 31 159.0 98 30 500.0 31 250.0 33 600.0 99 31 500.0 30 250.0 33 152.0 100 32 500.0 31 25.0 33 50.0 101 33 500.0 31 10.0 33 5.0 102 30 500.0 31 5.0 33 5.0 3. Reconstitution Reacting One or More Waxes and One or More Triglycerides The compounds of the present invention are prepared according to the following procedure: Into a suitable vessel with agitation and nitrogen sparge is placed the specified number of grams of the specified triglyceride. Next add the specified number of grams of the specified wax. A suitable esterification catalyst is then added. Esterification catalysts are selected from the group consisting of methane sulfonic acid, sulfuric acid, oragno-tin compounds, titinates. Of particular interest is the use of stannous oxylate. Stannous oxylate is used at a concentration of 0. percent based upon the total number of grams of all materials charged. The contents of the vessel are heated to between 150-250 C. A preferred range is 180-190 C. The contents are held at this temperature for at least four hours. During that time the batch clears and becomes homogenous and the reaction progress is followed by thin layer chromatography. The concentration of the original reactants drop down to low levels and the new reconstituted products are formed. The materials are cooled and used without additional purification. Clay treatment to improve color or filtration may be used if desired. Example 103 Into a suitable vessel with agitation and nitrogen sparge is placed 500.0 grams of the specified triglyceride (Example 1). Next add 500.0 grams of the wax (Example 30). Next add 0.1% stannous oxylate. Stannous oxylate is used at a concentration of 0.1 percent based upon the total number of grams of all materials charged. The contents of the vessel are heated to between 180-190 C. for at least six hours. During that time the batch clears and becomes homogenous and the reaction progress is followed by thin layer chromatography. The concentration of the original reactants drop down to low levels and the new reconstituted products are formed. Example 104-130 Into a suitable vessel with agitation and nitrogen sparge is placed 500.0 grams of the triglyceride (Example 1). Next add 500.0 grams of the wax (Example 30). Next add 0.1% stannous oxylate. Stannous oxylate is used at a concentration of 0.1 percent based upon the total number of grams of all materials charged. The contents of the vessel are heated to between 180-190 C. for at least six hours. During that time the batch clears and becomes homogenous and the reaction progress is followed by thin layer chromotography. The concentration of the original reactants drop down to low levels and the new reconstituted products are formed. Triglyceride Wax Example Example Grams Example Grams 104 7 95.0 30 5.0 105 7 90.0 30 10.0 106 7 30.0 30 70.0 107 7 20.0 30 80.0 108 29 95.0 30 5.0 109 29 90.0 30 10.0 110 29 80.0 30 20.0 111 29 30.0 30 70.0 112 29 20.0 30 80.0 113 1 500.0 31 500.0 114 2 500.0 31 500.0 115 3 500.0 31 500.0 116 4 500.0 31 50.0 117 5 500.0 31 10.0 118 6 500.0 31 500.0 119 7 500.0 31 500.0 120 8 500.0 31 500.0 121 9 500.0 31 500.0 122 10 500.0 31 500.0 123 11 500.0 31 50.0 124 12 500.0 31 500.0 125 13 500.0 31 500.0 126 14 500.0 32 500.0 127 15 500.0 32 500.0 128 16 500.0 32 500.0 129 17 500.0 32 500.0 130 18 500.0 33 500.0 Example 131 Into a suitable vessel with agitation and nitrogen sparge is placed 500.0 grams of the specified triglyceride (Example). Next add 500.Ograms of the wax (Example 34). Next, add 500.0 grams of the second triglyceride (Example 2). Next add 0.1% stannous oxylate. Stannous oxylate is used at a concentration of 0.1 percent based upon the total number of grams of all materials charged. The contents of the vessel are heated to between 180-190 C. for at least six hours. During that time the batch clears and becomes homogenous and the reaction progress is followed by thin layer chromatography. The concentration of the original reactants drop down to low levels and the new reconstituted products are formed. Example 132-150 Repeat example 131 only this time replace the specified amount of the first triglyceride with the specified amount of the new specified triglyceride. Replace the specified amount of wax with the specified amount of the specified wax, and the specified amount of the specified second triglyceride with the specified amount of the newly specified second triglyceride. Exam- First Wax Second Wax Third Wax ple Example Grams Example Grams Example Grams 138 19 500.0 30 500.0 1 50.0 139 20 500.0 31 500.0 2 500.0 140 21 500.0 32 50.0 3 5.0 141 22 600.0 33 400.0 4 500.0 142 23 600.0 30 10.0 5 500.0 143 24 600.0 31 5.0 6 500.0 144 25 600.0 32 500.0 7 500.0 145 26 600.0 33 500.0 8 500.0 146 27 600.0 30 500.0 9 50.0 147 28 500.0 31 500.0 10 5.0 148 29 500.0 32 500.0 11 500.0 149 1 500.0 33 500.0 12 500.0 150 2 400.0 33 45.0 7 500.0

The present invention relates to a series of “reconstituted meadowfoam oils”. The term reconstituted as used heron refers to a process in which meadowfoam oil and one or more oils of natural origin are transesterfied under conditions of high temperature and catalyst to make a “reconstituted product” having an altered alkyl distribution and consequently altered chemical and physical properties. The present invention deals with the reaction of meadowfoam oil and beeswax, carnauba wax, candellia wax, and jojoba oil.

[0001] This is a continuation-in-part application of application Ser. No. 10/785174 filed Feb. 24, 2004, now pending. BACKGROUND OF THE INVENTION [0002] (1) Field of the Invention [0003] This invention relates to a heat pipe, in particular, a microchannel flat-plate heat pipe used for heat dissipation for a central processing unit (CPU) or other electronic integrated circuit (IC) chips. [0004] (2) Brief Description of Related Art [0005] The latest generation of Pentium IV CPU generates power more than 100 watts (Joule/sec). In order to maintain its normal performance and avoid overheating of the unit, more effective heat dissipating mechanism is needed. U.S. Pat. No. 5,880,524 discloses a heat pipe for spreading the heat generated by a semiconductor device as shown in FIG. 1 . A cavity 105 is enclosed by a base metal 100 for a working liquid (not shown in the figure) to recycle. Heat sink fins 101 are arranged on the top of the base metal 100 for heat dissipation. Heat transfer medium 102 is under the base metal 100 to contact with a CPU. [0006] A two-phase vaporizable liquid resides within the cavity 105 and serves as the working fluid (the coolant) for the heat pipe. A metal wick 103 is disposed on the inner walls to form a recycling loop within cavity 105 to facilitate the flow of the working fluid within the cavity. The working liquid in the cavity 105 flows in a direction as shown in arrows in FIG. 1 . Firstly the working liquid is absorbed in the bottom portion of the wick 103 . It evaporates when heat is transferred from the CPU and then condenses on the top portion of the wick 103 . Heat is further transferred upward to the heat sink fins 101 . The condensed liquid absorbed in the top portion of the wick 103 is then moved to the lower portion of the wick 103 due to capillary action of the wick 103 . SUMMARY OF THE INVENTION [0007] An objective of this invention is to devise a coolant recycle mechanism with space passages as part of the recycling passage to decrease the friction for the coolant flow in a heat pipe. Another objective of this invention is to devise a coolant recycle mechanism with parallel grooves as a part of the passage to decrease the friction for the flow of the working fluid. A further objective of this invention is to devise a more effective heat dissipation mechanism for a heat pipe. By using space passages, parallel grooves or a combination of both as part of the passage, the friction for the liquid flow is reduced and the capillary action effectively enhances the recycling of the coolant. BRIEF DESCRIPTION OF THE DRAWINGS [0008] FIG. 1 Prior art. [0009] FIG. 2 First embodiment of this invention. [0010] FIG. 3 Enlarged plane view of the recycle mechanism of FIG. 2 . [0011] FIG. 4 Explosive perspective view of the recycle mechanism of FIG. 2 . [0012] FIG. 5 Second embodiment of this invention. [0013] FIG. 6 Third embodiment of this invention. [0014] FIG. 7 Fourth embodiment of this invention. [0015] FIG. 8 Fifth embodiment of this invention. [0016] FIG. 9 Sixth embodiment of this invention. [0017] FIG. 10 Seventh embodiment of this invention. [0018] FIG. 11 Eighth embodiment of this invention. [0019] FIG. 12 Vertical use of the invention. [0020] FIG. 13 Ninth embodiment of this invention. [0021] FIG. 14 Tenth embodiment of this invention. [0022] FIG. 15 Eleventh embodiment of this invention. [0023] FIG. 16 Twelfth embodiment of this invention. [0024] FIG. 17 Thirteenth embodiment of this invention. [0025] FIG. 18 Fourteenth embodiment of this invention. [0026] FIG. 19 Fifteenth embodiment of this invention. [0027] FIG. 20 Sixteenth embodiment of this invention. [0028] FIG. 21 Seventeenth embodiment of this invention. [0029] FIG. 22 Eighteenth embodiment of this invention [0030] FIG. 23 Explosive perspective view of the embodiment FIG. 22 . [0031] FIG. 24 Nineteenth embodiment of this invention. [0032] FIG. 25 Twentieth embodiment of this invention. [0033] FIG. 26 Twenty-first embodiment of this invention. [0034] FIG. 27 Twenty-second embodiment of this invention. [0035] FIG. 28 Twenty-third embodiment of this invention. DETAILED DESCRIPTION OF THE INVENTION [0036] The principle of this invention is to use space passages, parallel grooves or a combination of both as part of the passage for the flow of the working liquid within a flat-plate heat pipe. FIG. 2 shows the first embodiment of this invention. Cavity 105 is enclosed by a base metal 100 . Multiple sections are divided in the cavity 105 for the recycling of the working liquid. The working liquid moves in a direction following the arrows shown in the figure. [0037] FIG. 3 shows an enlarged plane view of the recycle mechanism in the cavity 105 of FIG. 2 . There are four sets of parallel grooves shown in this design. A first set of left parallel grooves 201 and a second set of left parallel grooves 202 are arranged on the left of the wick 203 . A third set of right parallel grooves 201 and a fourth set of right parallel grooves 202 are arranged on the right side of the wick 203 . The two sets of grooves 201 and 202 are separated with an isolation plate 205 . The recycling principle for the left two sets of grooves 201 and 202 is exactly the same as that for the right-side two sets of grooves 201 and 202 , and therefore only two left-side grooves are described below. [0038] Working liquid (not shown) is absorbed in the wick 203 . The wick 203 can be made of sintered copper (Cu) powder, sintered nickel (Ni) powder, or sintered stainless-steel powder. Alternatively, the wick 203 can be made of single-layer or multi-layer of metal wire mesh (not shown) or metal wire cloth (not shown). When the heat pipe is attached to a heat generating unit such as a central process unit (CPU), a certain amount of the working liquid in the wick 203 is heated and vaporized as shown by the arrows. Part of the vapor condenses on the inner top surface within the cavity 105 , which is enclosed by the base metal 100 . Part of the vapor enters a first set of parallel grooves 201 to condense. The condensed liquid is collected in the corners of the parallel grooves. The liquid is then driven by the vapor flow and the capillary action to a second set of parallel grooves 202 under the first set of parallel grooves 201 through a slot 204 . The conveying slot 204 is located at a common end of the two sets of grooves to connect the two sets of grooves 201 and 202 . The wick 203 is located on the other end of the grooves 202 and has a height no less than the height of the grooves 202 . The evaporation of the liquid in the wick 203 leads to a liquid-vapor interface within the wick 203 . This liquid-vapor interface results in a capillary pulling force on the working liquid in grooves 202 toward the wick 203 to make a full cycle: liquid→vapor→cooling→liquid, following the arrows as shown in FIG. 3 . [0039] FIG. 4 shows the explosive perspective view of the recycle mechanism of FIG. 2 . The parallel grooves 201 and 202 can be made separately before being connected together. Alternatively, the parallel grooves 201 and 202 can also be made integrally as a single body by molding or extrusion, or by etching, cutting, or machining on a metal plate. The cross-sectional shape of the grooves is triangular as illustrated, or of other shapes, such as rectangular or trapezoidal, etc. The base material for grooves 201 and 202 can be metal or nonmetal such as silicon or plastics, etc. may also be used. [0040] In this embodiment, the grooves 201 and 202 are essentially independent of each other except being communicated by the slot 204 so that the liquid flowing in grooves 202 is not dragged by the vapor flow in grooves 201 in the opposite direction. [0041] In order for effective condensation of the vapor molecules in the first set of parallel grooves 201 , single-sided grooves in contact with the inner top surface of the cavity is desired for the first set of parallel grooves 201 . However, for the second set of parallel grooves 202 where condensed liquid flows, either a set of single-sided grooves or a set of double-sided grooves works equally well. Double-sided grooves can be made using a corrugated sheet (not shown). Single-sided grooves 202 are shown in FIG. 4 . They can be made by the way of molding, extrusion, or by etching, cutting, or machining on a metal plate. [0042] FIG. 5 shows a second embodiment of this invention. This embodiment includes a vertical guiding plate 207 above the wick 203 to bridge the wick 203 and the inner top surface of the base metal 100 . The guiding plate 207 allows part of the condensed liquid on the inner top surface to flow downward back to the wick 203 directly. The guiding plate 207 also serves as a strengthener against the inward pressure when the cavity 105 is evacuated. [0043] FIG. 6 shows a third embodiment of this invention. This embodiment uses an elongated grooves 201 B over the top of the wick 203 . [0044] FIG. 7 shows a fourth embodiment of this invention. Shown herein is a half-cut piece, with the front surface representing the mid-plane cross-section of the whole unit. This embodiment shows that the first set of parallel grooves and the conveying slot 204 can be integrated with the top part of the base metal 100 to form a top metal base 201 C. The parallel grooves 2011 and the conveying slot 204 can be fabricated by molding, or by cutting, scribing, or etching the base metal 100 . [0045] FIG. 8 shows a fifth embodiment of this invention. Shown herein is also a half-cut piece, with the front surface representing the mid-plane cross-section of the whole unit. Similar to the fourth embodiment of FIG. 7 , the second set of parallel grooves 202 and the conveying slot 204 can be integrated with the bottom part of the base metal 100 to form the bottom metal base 202 B. Parallel grooves 2021 and the conveying slot 204 can be fabricated by molding, or by cutting, scribing, or etching the base metal 100 . [0046] FIG. 9 shows a sixth embodiment of this invention. This embodiment shows that the wick 203 in the previous embodiments can be replaced with a pin-array block 203 B. The space between the pins is used to absorb the working liquid by capillary attraction. The vertically open space allows for easy escape of bubbles once they are formed under high heat power conditions. This design is aimed at extending the dry-out limits of the working liquid in the wick 203 . [0047] FIG. 10 shows a seventh embodiment of this invention. This embodiment uses a different shape of corrugated metal 207 B. The square corrugated metal 207 B used herein differs from the V-shaped corrugated metal 207 in FIG. 5 . Other forms of corrugation are also usable, such as spiral corrugation, S-shaped corrugation, etc., and are not exhaustive in this specification. [0048] FIG. 11 shows an eighth embodiment of this invention. This embodiment uses a meshed metal 207 C as the guiding plate, rather than the non-meshed guiding plate 207 B in FIG. 10 . [0049] FIG. 12 shows that the invention as shown in FIG. 3 can be used in a vertical direction. Part of the vapor from the wick 203 condenses directly on the inner wall opposite to the wick 203 or enters the first set of bottom parallel grooves 201 and condenses herein. The condensed liquid flows downward, driven by the vapor flow as well as the gravity, into the liquid pool at the bottom end (not shown). With the combined capillary action of the wick 203 and of the parallel grooves 202 , the working liquid is pulled up back to the wick 203 . [0050] Part of the vapor from the wick 203 goes up to the first set of top parallel groves 201 and condensed herein. Some of the condensed liquid may drop into the first set of bottom parallel grooves 201 . Some of the condensed liquid is driven upward by the vapor flow to enter the top conveying slot 204 and then the second set of parallel grooves 202 , before it finally flows back to the wick 203 . [0051] In order to enhance the capillary pulling force on the recycled liquid for those embodiments where two sets of parallel grooves are used, the hydraulic diameters (or the cross-sectional areas of the flow path) of the second set of parallel grooves 202 are made smaller than those of the first set of parallel grooves 201 . [0052] FIG. 13 shows a ninth embodiment of this invention. This embodiment is a modified version of FIG. 12 . The first set of top parallel grooves 201 in FIG. 12 is replaced with a space A. As the vapor from the wick 203 enters space A, part of it condenses on the inner wall of the metal base 100 . The condensed liquid either drops to the first set of bottom parallel grooves 201 or is driven upward by the vapor flow across the conveying slot 204 into the second set of top parallel grooves 202 . The second set of parallel grooves 202 functions as a passage for the condensed liquid to flow back to the wick 203 by the capillary force provided by the micro grooves 202 and the wick 203 . [0053] FIG. 14 shows a tenth embodiment of this invention. This embodiment is a modified version of FIG. 12 . The second set of top parallel grooves 202 in FIG. 12 is replaced with a space B. The space B functions as a passage for the condensed liquid to flow back to the wick 203 by gravity and the capillary force provided by the thin space B and the wick 203 . [0054] FIG. 15 shows an eleventh embodiment of this invention. This embodiment is a modified version of FIG. 12 . The first set of top parallel grooves 201 in FIG. 12 is replaced with a space A; while the second set of top parallel grooves 202 is replaced with a space B. The space B functions as a passage for the condensed liquid to flow back to the wick 203 by gravity and the capillary force provided by the thin space B and the wick 203 . [0055] FIG. 16 shows a twelfth embodiment of this invention. This embodiment is a simplified version of FIG. 3 or FIG. 4 . A single first set of parallel grooves 201 and a single second set of parallel grooves 202 are used. The recycle mechanism is exactly the same as described in FIG. 3 or FIG. 4 . [0056] FIG. 17 shows a thirteenth embodiment of this invention. This embodiment is a modified version of FIG. 16 . The first set of parallel grooves 201 in FIG. 16 is replaced with a space A. As the vapor form the wick 203 enters space A, part of it condenses on the inner wall of the metal base 100 . The condensed liquid is driven by the vapor flow across the conveying slot 204 into the second set of parallel grooves 202 . The liquid in the grooves 202 then flows back to the wick 203 by gravity and the capillary force provided by the micro grooves 202 and the wick 203 . [0057] FIG. 18 shows a fourteenth embodiment of this invention. This embodiment is a modified version of FIG. 16 . The second set of parallel grooves 202 in FIG. 16 is replaced with a space B. The space B functions as a passage for the condensed liquid to flow back to the wick 203 by the capillary force provided by the thin space B and the wick 203 . [0058] FIG. 19 shows a fifteenth embodiment of this invention. This embodiment is a modified version of FIG. 16 . The first set of parallel grooves 201 in FIG. 16 is replaced with a space A; while the second set of parallel grooves 202 is replaced with a space B. As the vapor form the wick 203 enters space A, part of it condenses on the inner wall of the metal base 100 . The condensed liquid is driven by the vapor flow across the conveying slot 204 into the space B. The space B functions as a passage for the condensed liquid to flow back to the wick 203 by the capillary force provided by the thin space B and the wick 203 . [0059] FIG. 20 shows a sixteenth embodiment of this invention. This embodiment is a modification to all the previous embodiments. FIG. 20 shows a second wick 204 B inserted into the slot 204 to smooth the liquid flow. The capillary action within 204 B grabs the condensed liquid stronger than a slot 204 as shown in the previous embodiments. This design prevents the vapor from entering the second set of parallel grooves 202 and, therefore, leads to a smoother liquid flow. [0060] FIG. 21 shows a seventeenth embodiment of this invention. This embodiment is a modification to FIG. 3 by replacing the grooves 202 in the lower section with a space B. The space B functions as a passage for the condensed liquid to flow back to the wick 203 by the capillary force provided by the thin space B and the wick 203 . [0061] FIG. 22 shows an eighteenth embodiment of this invention. This embodiment uses an elongated wick 203 C as wide as that of the lower section. The middle part of the elongated wick 203 C is used as an evaporator to absorb the heat from a heat-generating device attached below it (not shown). The other parts under the grooves 201 are used as a passage for the liquid to flow back to the middle part of the wick 203 C The wick 203 C can be sintered metal powder, metal wire mesh or metal wire cloth. [0062] FIG. 23 is the explosive perspective view of the embodiment in FIG. 22 . Two sets of parallel grooves 201 are placed in the two sides of the upper section of the cavity 105 to help collect the condensed liquid. [0063] FIG. 24 shows a nineteenth embodiment of this invention. A V-shaped corrugated metal 207 is placed on top of the wick 203 C and between the two sets of parallel grooves 201 . FIG. 25 shows a twentieth embodiment of this invention. This embodiment uses a set of elongated grooves 201 B over the top of the long wick 203 C. An isolation plate 205 made of a metal or nonmetal sheet is placed in between the elongated grooves 201 B and the long wick 203 C except for a space 300 arranged for the vapor to enter the grooves 201 B. In this embodiment, the isolation plate 205 can alternatively be made of wire mesh or wire cloth so that a part of the condensed liquid collected in the grooves 201 C can enter the wick 203 C directly without flowing through the conveying slot 204 [0064] FIG. 26 shows a twenty-first embodiment of this invention. This embodiment shows that a V-shaped corrugated wire mesh 302 is used to replace the elongated grooves 201 B in the previous embodiment. The isolation plate 205 can alternatively be made pf wire mesh or wire cloth in this embodiment. [0065] FIG. 27 shows a twenty-second embodiment of this invention. This embodiment shows that the elongated wick 203 C as in FIG. 25 can be replaced with a corrugated metal wire mesh 302 . [0066] FIG. 28 shows a twenty-third embodiment of this invention. This embodiment shows that a sheet of wire mesh 304 can be added above the corrugated metal mesh 302 to enhance capillary force, especially for the evaporator. [0067] While the preferred embodiment of the invention have been described, it will be apparent to those skilled in the art that various modifications may be made without departing from the spirit of the present invention. Such modifications are all within the scope of this invention.

Heat from a heat generating device such as a CPU is dissipated by a heat sink device containing a recycled two-phase vaporizable coolant. The coolant recycles inside a closed metal chamber, which has an upper section and a lower section connected by a conveying conduit, and a wick evaporator placed in the lower section. The liquid coolant in the evaporator is vaporized by the heat from the heat generating device. The coolant vapor enters the upper section and condenses therein, with the liberated latent heat dissipated out through the inner top chamber wall. The condensed coolant is then collected and flows into the lower section, and further flows back to the wick evaporator by capillary action of the evaporator, thereby recycling the coolant. Space or a piece of element with parallel grooves is used to form at least one of the sections to reduce friction in the liquid flow path.

The invention described herein was made in the course of work under a grant or award from the Department of Health, Education and Welfare. CROSS REFERENCE TO RELATED APPLICATION This is a continuation-in-part of Ser. No. 113,414 filed Jan. 18, 1980 (now abandoned). BACKGROUND This invention relates to a diagnostic test device for fecal occult blood utilizing guaiac as the test indicator. More particularly, this invention relates to a test matrix such as paper impregnated with guaiac together with a combination of substances which according to the invention prevent false-positive results in the presence of peroxidases. A sensitive, specific and simple laboratory test for colorectal cancer is helpful in screening patients for early neoplastic lesions. A test already available is the Hemoccult slide test for occult blood in stool (see U.S. Pat. No. 3,996,006). This simple, inexpensive laboratory test is capable of detecting blood in stool that may be related to an early cancerous lesion of the gastrointestinal tract. The test rationale which uses guaiacimpregnated paper as a test matrix is based on the phenolic oxidation of guaiac by hemoglobin in the presence of hydrogen peroxide. The production of a blue color on the test paper usually indicates the presence of blood. However, there is a 4 to 6% false positive reaction (i.e., positive test reaction without disease) as a result of non-hemoglobin interfering compounds present in the stool. It has been found that these interfering compounds are peroxidases ubiquitous to bacterial flora in the gut and in certain food sources. Each false-positive test may result in an exhaustive clinical investigation that is costly to the patient and time consuming for the physician. Aside the waste of money and manpower, the patient may be subjected to tremendous anxiety as the presence of blood in the feces may be an indication of cancer or other serious maladies. In order to reduce the incident of interference by peroxidase in the guaiac test procedure for hemoglobin, it is a usual practice to prohibit a patient from eating vegetable products that contain peroxidase, e.g., potato, cabbage, onions, horseradish, etc. for several days. This gives time for possible interfering substances to be cleared from the body. However, indigenously present perioxidase (bacterial peroxidase) may still interfere with the test. Also patients may inadvertantly or otherwise ingest interfering substance containing vegetables notwithstanding instructions to avoid them. The reaction of hemoglobin in fetal occult blood with guaiac in the presence of hydrogen peroxide, to give a blue color, is a known method for detection of the presence of blood as discussed above. This reaction takes advantage of the peroxidase activity of hemoglobin, which is similar to the reaction of peroxidase enzymes except that the peroxidase enzyme reaction is due to biochemical enzymatic activity while hemoglobin is not an enzyme. It is the recognition that peroxidase reacts with guaiac through enzymatic action while hemoglobin does not, that forms the basis of the present invention. By at least partially denaturing the protein that forms the peroxidase enzyme and removing the calcium and magnesium ions necessary for efficient peroxidase enzyme activity from the reaction mixture, one can eliminate the interfering effect of the peroxidase without practically affecting the hemoglobin. It is therefor an object to avoid the problems inherent in prior art techniques by deactivating interfering peroxidase that may be present. SUMMARY The present invention provides an improvement in the diagnostic test technique for fecal occult blood which employs the reaction of guaiac with hemoglobin in the presence of peroxide to indicate the presence of hemoglobin by preventing false positive results. The improvement for preventing false-positive results in the presence of peroxidases comprises deactivating the peroxidase enzyme and removing the calcium and magnesium ions necessary for its efficient biochemical activity. This is preferably accomplished by cleaving the hydrogen bonds in the protein that forms the peroxidase enzyme thereby denaturing the peroxidase enzyme; and binding the calcium and/or magnesium ions with a chelating agent thereby reducing the efficiency of biochemical activity of the enzyme. BRIEF DESCRIPTION OF THE DRAWING The present invention will be more fully understood from the following description taken in conjunction with the accompanying drawing wherein: FIG. 1 is a graph charting intensity against time in connection with 3:1 mixtures of turnip peroxidase in whole blood; FIG. 2 is a graph charting intensity against time in connection with 1:1 mixtures of turnip peroxidase in whole blood; and FIG. 3 is a graph charting intensity against time in connection with 1:3 mixtures of turnip peroxidase in whole blood. DESCRIPTION The thrust of the present invention is the neutralization of the effect of peroxidase enzymes on the fecal occult blood test based on a color reaction of hemoglobin with guaiac in the presence of peroxide. This is in contradistinction to the usual procedure whereby mainly through dietary restrictions, it is attempted to eliminate the peroxidases from the sample. In the presently preferred embodiments of the invention, the effect of peroxidase enzymes is neutralized by a combination of at least partially denaturing the enzyme proteins; and effectively removing the metal ions (calcium and magnesium) from the reaction mixture which the enzyme requires for efficient biochemical activity. The effective removal of the metal ions, which can be accomplished without physical removal by use of complexing agents, avoids the need for complete denaturization of the enzyme. Thus milder methods, unlikely to greatly effect any hemoglobin that may be present, can be used. Normal color development with hydrogen peroxide is thereafter accomplished. Heating to about 100° C. and the use of strong acids are examples of two possible denaturing methods for the enzyme protein. These are not preferred, however, as heating feces results in obnoxious smells and both heating and the use of strong acids can cause damage to any hemoglobin present. The most preferred denaturing method is the use of an effective amount of a compound that will cleave hydrogen bonds in the protein that forms the peroxidase enzyme. This will at least partially attenuate biochemical activity of the enzyme. The effective removal of calcium and magnesium ions from the reaction by complexing with a chelating agent further attenuates the biochemical activity of the enzyme to a point where, for practical purposes, the interfering effect of the peroxidase is eliminated. This combination of steps allows the use of moderate amounts of reagents and mild conditions to avoid effect on the hemoglobin to be tested. Guaiac containing test matrices suitable for the practice of the fecal occult blood determination tests of the type over which the present invention is an improvement are known. One such device, a guaiac impregnated paper, is sold under the trademark Hemoccult and described in U.S. Pat. No. 3,996,006 referred to hereinabove. It is contemplated in the preferred embodiments hereof that the materials for neutralizing the effect of the peroxidase can be used in conjunction with known test matrices and may be applied to the test matrix either before or after the test sample is applied. For ease of application, the compunds are dissolved in a suitable solvent, most usually water, and aliquoted amounts applied to the test matrix. Suitable compounds for at least partially denaturing the enzyme protein by cleaving hydrogen bonds include the soluble (water) salts of guanidine, urea and salicylic acid. The preferred compound is guanidine hydrochloride. As noted above, heating or the use of strong acids has possible undesirable side effects that are difficult or impossible to control. Chelating agents that have been found suitable to sufficiently remove the metal ions necessary for effective enzyme action include ethylenediamine tetraacetic acid (EDTA) and ethyleneglycol tetraacetic acid (EGTA). Effective amounts of the compound and chelating agent are utilized in the guaiac containing test matrix. For example, a 3 to 6 molar solution of guanidine hydrochloride in water can be used with a 10-100 millimolar solution of EDTA in water. These two solutions are combined in equal volume to form a test reagent solution and then added in an aliquot portion to the guaiac test matrix. If the test reagent solution is added before the test sample, the water can be removed so that the test matrix can be stored for receipt of a test sample at a subsequent time and location (e.g. for a doctor's office or hospital use). Alternatively, a test matrix to which a sample has already been applied can subsequently have the test reagent solution added. In either case, after a suitable reaction period, the test can proceed in a usual manner with the development of possible color using hydrogen peroxide. At concentrations lower than about 3 moles/l, guanidine hydrochloride shows no effect while in concentrations at about 6 moles, guanidine hydrochloride undesirably crystallizes out on paper when the test matrix used is guanidine impregnated paper. In concentrations below 10 millimolar for EDTA, the desirable results in the invention are not shown and at concentrations at above 100 millimoles/l for EDTA, there is no demonstrated increase in effect. A preferred embodiment of the invention involves the use of guaiac impregnated paper such as the Hemoccult slide to which is added EDTA and guanidine hydrochloride such that the guaiac impregnated paper contains 0.25 millimoles of EDTA and 0.15 millimoles of guanidine hydrochloride. This can be accomplished by combining equal solutions of 3 molar guanidine hydrochloride and a 100 millimolar solution of EDTA and depositing the 25 microliters of the combined solution on the Hemoccult slide. Where the test solution is to be added to the paper before the sample, the solution containing guanidine hydrochloride and EDTA can be simply combined with the guaiac test matrix in the case where guaiac is in a liquid test matrix, or it can be sprayed or rolled on to a guaiac impregnated paper in the instance where the test matrix is paper. If added after the test sample, the test solution will necessarily be sprayed or dropped onto the matrix. The following examples are intended to illustrate the invention without limiting the same in any manner. These examples report results of the embodiment wherein the test reagent solution is added to the test matrix before the sample. In all the examples that follow, color intensity is scored as follows: Negative--no color response Trace--color response barely visible to naked eye +1--slight color response +2--moderate color response +3--strong color response +4--very strong color response EXAMPLE 1 ______________________________________Effects of EDTA and Guanidine hydrochloride on vegetable andhemoglobin peroxidase activity on Hemoccult slides. Control Slides: 0.36 mg/ml 0.36 mg/ml no Horseradish Powdered peroxidase Peroxidase Hemoglobin added______________________________________Control I +3 +4 neg.non-treated slidesControl II +3 +3 neg.slides treatedwith H.sub.2 O6M Guanidine +4 +4hydrochloride10mM EDTA +3 +4 neg.10mM EDTA in Trace +4 neg.6M Guanidinehydrochloride100mM EDTA +2 +3 neg.100mM EDTA in Trace +3 neg.6M Guanidinehydrochloride______________________________________ Applications of 25 μl of the treatment solutions were dried on slides, followed by the applications of 25 μl of vegetable peroxidase and hemoglobin (Hb). The slides were developed 17-21 hours after applications. EXAMPLE 2 ______________________________________Effects of EDTA plus Guanidine Hydrochloride on vegetableperoxidases and hemoglobin peroxidase activity onHemoccult slides. 0.36 Turnip Per- 0.36 mg/ml 0.36 oxidase Crude mg/ml Pow- mg/ml Extract Horse- dered Whole (1 mg/ml) radish Hemo- Blood Un- Per- globin Lysate diluted Diluted oxidase______________________________________Control I +4 +4 +4 +3 +3non-treated slidesControl II +3 +4 +4 +3 +3slides treated withH.sub.2 O10mM EDTA in +4 +4 +1 neg. Trace6M Guanidine HCl100mM EDTA in +3 +4 Trace neg. Trace6M Guanidine HCl______________________________________ Applications of EDTA and water treatments (25 μl/slide window) were dried on slides prior to the 25 μl applications of peroxidases and hemoglobin. The slides were developed 17-21 hours after applications. EXAMPLE 3 ______________________________________Whole Blood and Turnip Peroxidase Volume: Volume Mixtures:Effects of EDTA plus Guanidine Hydrochloride.______________________________________Water (Control) Not Treated TreatedWater WaterVolume Turnip Peroxidase Volume Turnip Peroxidaseratio 1 2 3 ratio 1 2 3______________________________________1 +2 +3 +3 1 Neg. Neg. Trace2 +2 2 Neg.3 +1 3 Neg.______________________________________Whole Blood Lysate (Control) Not Treated TreatedWhole Blood Lysate Whole Blood LysateVolume Water Volume Waterratio 1 2 3 ratio 1 2 3______________________________________1 +1 Trace Trace 1 +2 +1 Trace2 +1 2 +23 +1 3 +2______________________________________Whole Blood Lysate With Turnip Peroxidase Not Treated TreatedWhole Blood Lysate Whole Blood LysateVolume Turnip Peroxidase Volume Turnip Peroxidaseratio 1 2 3 ratio 1 2 3______________________________________1 +1 +2 +2 1 +1 +1 Trace2 +2 2 +13 +3 3 +2______________________________________ Undiluted turnip peroxidase extract and 0.06 mg Hb/ml whole blood lysated were combined in the volume: volume ratios indicated of which 25 μl were applied on untreated and treated Hemoccult II slides lot 7087 (10/81). Hemoccult slides were treated with 25 μl 0.01 M EDTA in 6 M Guanidine hydrochloride. EXAMPLE 4 ______________________________________Whole blood and powdered hemoglobin in stool specimens: Timestudy with EDTA plus Guanidine Hydrochloride on Hemoccultslides.Powdered Hemoglobin Whole Blood Lysate0.075 gm Hb/ 0.100 gm Hb/Time 100 gm Specimen 100 gm SpecimenDays Untreated Treated Untreated Treated______________________________________1 +2 +2 +3 +34 +2 +2 +3 +35 +2 +2 +3 +37 +2 +2 +3 +38 +2 +2 +3 +311 +2 +2 +3 +312 +2 +2 +3 +314 +2 +1 +3 +315 +2 +1 +3 +3______________________________________ Stool specimens, negative for occult blood, were "spiked" with powdered hemoglobin and whole blood. Hemoccult slides were treated with 25 μl 0.01 M EDTA in 6 M Guanidine hydrochloride per slide window, dried and spotted with 25 μl hemoglobin and whole blood. The slides were stored in the dark for times indicated. EXAMPLE 5 __________________________________________________________________________Inhibition of vegetable peroxidases by EDTA plus Guanidine Hydrochlorideon Hemoccult slides. Turnip Turnip Peroxidase Horseradish Peroxidase Diluted Powdered Whole Blood Peroxidase Undiluted 3:1 with Hemoglobin lysate(Hb) 0.36 mg/ml (1 mg/ml) water 0.36 mg/ml 0.36 mg/ml Treated* Untreated Treated* Untreated Treated* Untreated Treated* Untreated Treated* Untreated__________________________________________________________________________Color Trace +4 Trace +3 neg. +2 +3 +3 +3 +3Intensity__________________________________________________________________________ *Treated with 10 mM EDTA in 6M Guanidine hydrochloride. Hemoccult slides were treated with 10 mM EDTA in 6 M Guanidine hydrochloride, dried and stored in the dark for one month. After one month, 25 μl of hemoglobin and vegetable peroxidase were applied to the slides. The slides were developed 17-21 hours after application of hemoglobin or peroxidase. EXAMPLE 6 Whole Blood and Turnip Peroxidase Volume: Volume mixtures: Effectiveness of EDTA plus Guanidine hydrochloride with storage time on Hemoccult slides. FIG. 1. Turnip Peroxidase: Whole Blood=3:1 (vol:vol). FIG. 2. Turnip Peroxidase: Whole Blood=1:1 (vol:vol). FIG. 3. Turnip Peroxidase: Whole Blood-1:3 (vol:vol). Hemoccult slides were treated with 25 μl 10 mM EDTA in 6 M Guanidine hydrochloride per window and dried. Mixtures of 0.06 mg Hb/ml whole blood and undiluted turnip peroxidase extract were prepared volume:volume and 25 μl per window were applied to treated and untreated slides. The slides were stored in the dark at room temperature and developed on days indicated. EXAMPLE 7 __________________________________________________________________________Hemoglobin and vegetable peroxidases: Effectiveness of EDTA plusGuanidine hydrochloride with storage time on Hemoccult slides. 10 mM EDTA in 6 M Guanidine 1 2 3 4 5 6 7 hydrochloride month months months months months months months__________________________________________________________________________0.36 mg/ml not treated +4 +4 +4 +4 +4 +4 +4HorseradishPeroxidase treated Trace Trace Trace neg. neg. neg. +1Undiluted extract not treated +3 +3 +4 +3 +3 +3 +2TurnipPeroxidase treated Trace neg. Trace Trace Trace Trace TraceDiluted extract not treated +2 +3 +3 -- -- -- --3:1 water:Turnip treated Trace neg. Trace -- -- -- --Peroxidase0.36 mg/ml not treated +3 +3 +3 +3 +3 +3 +3PowderedHemoglobin treated +3 +3 +3 +3 +3 +3 +30.36 mg/ml not treated +3 + 3 +4 +3 +3 +3 +3Whole BloodLysate treated +3 +3 +4 +3 +3 +3 +3__________________________________________________________________________ Hemoccult slides were treated with 25 μl 10 mM EDTA in 6 M Guanidine hydrochloride, dried and stored in the dark at room temperature. At one month intervals, 25 μl hemoglobin or vegetable peroxidase were applied to the slides. The slides were developed at 17-21 hours after application of the hemoglobin or peroxidase. The following examples illustrate the second preferred embodiment wherein the test reagent solution is added to the test matrix at a time subsequent to the application of the sample. This is presently more preferred because it avoids storage-life problems and permits use of readily commercially available test materials. Basically, guanidine hydrochloride and EDTA are applied to the fecal occult blood test matrix prior to the normal color development procedure by addition of hydrogen peroxide. This simple modification in technique effectively inhibits peroxidase activity present in the stool specimen and is applicable to any test matrix, regardless of previous chemical impregnation, size or shape of the test matrix. TEST PROCEDURE One hundred micro-liters (100 μl) or approximately 2 drops of a solution of guanidine hydrochloride-EDTA (0.01 M EDTA in 3 M guanidine hydrochloride) are applied to the test window of the fecal occult blood test matrix. After approximately 21/2 hours of pretreatment at room temperature, the color developing process is completed by the usual procedure involving the addition of 2 drops of hydrogen peroxide to the slide. A pretreatment period before addition of the peroxide of 2 to 3 hours is required to effectively inhibit peroxidase activity. The following examples illustrate the effectiveness of peroxidase inhibition by a solution of guanidine hydrochloride (3 M) and EDTA (0.01 M): EXAMPLE 8 ______________________________________Application of Guanidine Hydrochloride-EDTAPrior to Color Development ProcessTime (hours)(pretreatmentprior to addition Horseradish Whole Bloodof peroxide Peroxidase Lysate Powdered Hbreagent) (0.36 mg/ml) (0.36 mgHb/ml) (0.36 mg/ml)______________________________________ 1/2 +4 +4 +411/2 +3 +4 +42 +2 +4 +421/2 +1 +4 +43 Trace +4 +431/2 Trace +4 +44 Neg. +4 +441/2 Neg. +4 +4______________________________________ EXAMPLE 9 ______________________________________Effect of Peroxidase Activity on ColorDevelopment Without Prior Treatmentwith Guanidine Hydrochloride and EDTA Horseradish Whole Blood Peroxidase Lysate Powdered HbTime (0.36 mg/ml) (0.36 mg/ml) (0.36 mg/ml)______________________________________ 1/2 +4 +4 +411/2 +4 +4 +42 +4 +4 +421/2 +4 +4 +43 +4 +4 +431/2 +4 +4 +44 +4 +4 +441/2 +4 +4 +4______________________________________ Similar results are obtained using EGTA as a chelating agent and urea or salicylic acid to cleave protein hydrogen bonds. The above is intended to be illustrative of presently preferred embodiments, and not in any way restrictive on the scope of the invention.

Diagnostic test device for fecal occult blood utilizing a test matrix such as paper impregnated with guaiac. False-positive results in the presence of peroxidases are prevented by adding to the matrix a compound that cleaves protein hydrogen bonds such as guanidine hydrochloride and a chelating agent that binds calcium and/or magnesium such as EDTA.

BACKGROUND OF THE INVENTION [0001] This application is a continuation of U.S. patent application Ser. No. 10/478,043, filed Jun. 7, 2004, which claims priority of PCT Patent Application No. PCT/AU02/00602, filed May 17, 2002. [0002] The present invention relates to a spiral separator and to a method of spiral separation, and in particular, to a deflector to use in a spiral separator and method of spiral separation. In particular, the present invention relates to the use of such a deflector for the improved separation of particles of different densities. DESCRIPTION OF THE PRIOR ART [0003] The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that that prior art forms part of the common general knowledge in Australia. [0004] Spiral separators are extensively used for the wet gravity separation of solids 15 according to their specific gravity, for example, for separating various kinds of mineral sands from silica sands. [0005] Separators of the kind under discussion are shown, for example, in the Applicant's Australian Patent No. 552425 (82717/82). Such separators commonly include a vertical column about which there are supported one or more helical troughs. ill operation, a “pulp” or slurry of the materials to be separated and water is introduced to the upper end of a trough and, as the pulp descends the helix, centrifugal forces act on the dense particles in a radially outwards direction while the more dense particles segregate to the bottom of the flow, and after slowing, through close approach to the working surface of the trough, gravitate towards the vertical column. [0006] During operation of a spiral separator there is a general migration of water from the inner portion or smaller radius of the flow to the outer portion of the flow. However, particularly when there are high proportions of high specific gravity particles present in the pulp, the total water supply at the inner portion can be used up before segregation is completed. As this takes place there is an accumulation of particles at the inner portion which, while it does not prevent the stream from continuing to move, changes the effective shape of the volute cross section and separation proceeds no further. [0007] To improve on the operation of such spiral separators, a deflector has been previously developed by the Applicants of the present invention, as described in Australian Patent Serial No. 575046 (27077/84). In that specification, there is described a spiral separator characterized by the inclusion of at least one deflector located adjacent an outer edge of the spiral separator, the deflector having a contoured upper surface to receive and deflect a portion of the low solids, high velocity, stream component in a fan like spray from the outer edge of the pulp stream back across the stream towards the inner edge. In particular, that device interrupts a portion of low density, high water content, stream from the ‘tailing zone’ and sprays or redeposits it into the high density, low water content, ‘middling zone’. [0008] Whilst the deflector of Australian Patent Serial No. 575046 improved the recovery of minerals, due to the inability for the device to be readily adjusted, and due to its somewhat inflexible design, the deflector device has been found to be somewhat limited, identifying a need for an improved product thereto. SUMMARY OF THE INVENTION [0009] The present invention seeks to provide a deflector device which seeks to overcome at least some of the disadvantages of the prior art deflector devices, including that described in Australian Patent Serial No. 575046 (27077/84). [0010] The present invention seeks to provide a deflector device which has a more refined action and has much greater scope for influencing the stream in a spiral separation, to enhance separation. [0011] In one broad form, the present invention provides a deflector adapted to be attached to a spiral separator for capturing and redirecting a controlled portion of a flowing stream 25 of material flowing through said spiral separator, said deflector including: [0012] attachment means, for attachment of said deflector to said spiral separator; [0013] a capturing portion, shaped to substantially ride atop and capture a portion of said flowing stream of material; and, [0014] a redirecting portion, integrally formed with said capturing portion, shaped to emit 30 said portion of said stream of material captured by said capturing portion. [0015] Preferably, said attachment means includes an arm member, to permit substantially resilient and/or pivotal movement of said deflector connected to said spiral separator. [0016] Also preferably, said arm member includes anyone or combination of a pivoting arm, a flexible arm, a string, line, flap, magnetic field or any other mechanical means. [0017] Most preferably, said capturing portion captures the ‘tailing’ portion of said flowing stream of material from an outer region of the trough of the spiral separator. [0018] Also most preferably; said redirecting portion redirects said captured material into the ‘middlings’ portion of the flowing stream. [0019] Also preferably, said redirecting portion redirects said captured material into said flow stream in a patterned spray. [0020] In a preferred form, said patterned spray is in a ‘fan-like’ shape, a substantially hemispherical shape, or other thin broad canopy of spray that re-enters the main stream substantially in an arc about the head of the reflector. [0021] Alternatively, but also preferably, said redirecting portion redirects said captured material to another device such as, but not limited to, a gallery or distributor to administer the water in a controlled manner. [0022] Preferably, said deflector is formed to function in a substantially buoyant manner. Also preferably, said deflector is at least partly formed from substantially buoyant material. [0023] Also preferably, said device substantially rides on or aquaplanes on the surface of said stream. [0024] Also preferably, said device is weighted or tensioned for heavier action (heavier fan) or unweighted for lighter action by adjusting the flexibility, weight, tension and/or tightness of the arm member or the like. [0025] Preferably also, said device may be twisted or pivotally adjusted to enable adjustment of the rate and/or other characteristics of the emission of the captured material. [0026] Also preferably, said arm member is lengthened or shortened to change the angle and/or weighting with which the capturing portion penetrates the stream. [0027] In a further broad form, the present invention provides a spiral separator adapted to receive a flowing stream of water and particulate material at an upper end thereof, to separate particles of different densities as the stream moves downwardly therethrough, said separator including at least one deflector therein to capture and redirect a portion of said material flowing adjacent to an outer edge of said separator, said deflector including: [0028] attachment means, for attachment of said deflector to said spiral separator; [0029] a capturing portion, shaped to substantially ride atop and capture a portion of said flowing stream of material; and, a redirecting portion, integrally formed with said capturing portion, shaped to emit said portion of said stream of material captured by said capturing portion. [0030] In yet a further broad form, the present invention provides a method of separating particles of different densities using a spiral separator including a deflector, substantially as herein described. BRIEF DESCRIPTION OF THE DRAWINGS [0031] The present invention will become more fully understood from the following detailed description of preferred but non-limiting embodiments thereof, described in connection with the accompanying drawings, wherein: [0032] FIG. 1 illustrates sketches of a deflector device in accordance with the present invention, showing front, plan and side views in FIGS. 1 ( a ), 1 ( b ) and 1 ( c ), respectively; [0033] FIG. 2 illustrates the deflector device attached to a spiral separator in accordance with the present invention; and, [0034] FIG. 3 illustrates top, sectional and end views of the deflector shown attached to the spiral separator, in FIGS. 3 ( a ), 3 ( b ) and 3 ( c ), respectively. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS [0035] Throughout the drawings, like numerals will be used to identify similar features, except where expressly otherwise indicated. [0036] As shown in the drawings, the deflector, generally designated by the numeral I, is adapted to be attached to a spiral separator, generally designated by the numeral 2 . The deflector 1 is designed to capture and redirect a controlled portion of the flowing stream of material flowing through the spiral separator. The deflector 1 , generally includes an attachment means 3 , for attachment of the deflector 1 to the spiral separator 2 , a capturing portion 4 shaped to substantially ride atop and capture a portion of the flowing stream of material 5 , and a redirecting portion 6 , which is integrally formed with the capturing portion 4 , and which is shaped to spray or otherwise emit the captured material, as illustrated by reference numeral 7 . The spray 7 may be patterned to be of any desired shape, depending upon the desired pattern of the spray as it re-enters the main stream. For example, the spray may be fan-shaped, substantially hemispherical in shape, or any other thin broad canopy of spray such that it re-enters the main stream-substantially in an arc about the head of the reflector. [0037] Other than the attachment means 3 being used to affix the deflector 1 to the side of the spiral separator 2 , the attachment means 3 may incorporate an arm member 12 , to permit substantially resilient and/or pivotal movement of the deflector 1 when connected to the spiral separator 2 . The arm member 12 may include anyone or combination of a pivoting arm, a flexible arm, a string, line, flap, magnetic field, or any other mechanical means. Other forms of arm member may alternatively become apparent to persons skilled in the art and should be considered to be encompassed within the scope of this invention. [0038] The capturing portion 4 of the deflector 1 , is shown in the drawings as capturing the “tailings” portion of the flowing stream of material 5 from an outer region ill of the trough 11 of the spiral separator 2 . [0039] As will be understood by persons skilled in the art, and as shown in FIG. 3 ( b ), spiral separators are generally used to recover minerals, and function by separating materials in to three generally known streams, including the ‘concentrate’ 8 found at the inner edge of the trough 11 of a spiral separator 2 and which is formed of particles of higher specific gravity, a ‘tailing’ stream 10 which is found towards the outer part of the trough 11 being the particles of lower specific gravity, and the ‘middlings’ stream 9 which is found intermediate the concentrate and tailings in the central transition zone. [0040] As such, it will be appreciated that the deflector 1 shown in the drawings, redirects the portion of the material from the ‘tailings’ stream 10 in to the ‘middlings’ 9 portion of the flowing stream 5 . It is also shown in the drawings that this is redirected in a fan like spray manner. [0041] By redirecting the material in this manner, the ‘middlings’ 9 stream is exposed to two gentle influences, firstly as it enters the fan upstream, and again when it emerges downstream. Such an effect provides a significant performance enhancement of the spiral separator. [0042] In an alternative arrangement, the redirecting portion, could redirect the captured material to another device (not shown), such as, but not limited to, a gallery or distributor to administer the water in a controlled manner. [0043] The deflector device 2 of the present invention may either be at least partly formed from substantially buoyant material and/or, can be shaped to function in a substantially buoyant manner, then being formed of any desirable material. The device may be weighted or tensioned for heavier action (heavier fan), or unweighted for lighter action by adjusting the flexibility, weight, tension or tightness of the arm member portion of the device, or by other means. Depending on the particular amount of capture desired, these attributes can be selectively varied such that it either substantially ‘rides’ or ‘aquaplanes’ the surface of the stream due to the pressure, velocity of the liquid, or, it can be submerged to a greater or lesser extent. [0044] The device may also be twisted or pivotally adjusted to enable adjustment of the rate and/or format of the emission of the captured material. [0045] The arm member may also be lengthened or shortened to change the angle and/or the weighting in which the capturing portion penetrates the stream. [0046] It will be appreciated that the present invention therefore provides a deflector device which is novel and inventive over the known prior art, including the Applicant's prior Australian Patent No. 575046 (27077/84). The differences and advantages of the device of the present invention is at least partially due to the freedom of movement of the device, whereby the head of the device floats or “rides” on top of the ‘tailing’ stream where it captures and redirects a controlled quantity of the flow in to another region of the trough. As described, usually, the redirected flow would typically take the form of a gentle fan or other patterned spray, and the fan or spray is usually directed in to the ‘middlings’ stream. [0047] The head of the device is buoyant, created either by the material and/or by hydraulic pressure, to remain skimming the surface of the stream regardless of the flow rate of the spiral feed. The deflector therefore always remains in position for optimal performance. When the flow rate on a spiral increased, the stream at the outer wall rises. This causes conventional deflectors with fixed position, such as described in the [0048] Applicant's earlier Australian Patent No. 575046 (27077/84) to become more violent in its action, causing excessive disruption of the flow. When the flow rate on a spiral decreased, the level of the stream falls. This reduces the influence of prior art deflectors, and in some cases, the stream may fall completely below the point where the deflector is attached. [0049] It will be appreciated that numerous variations and modifications may be envisaged by persons skilled in the art to the device hereinbefore described. All such variations and modifications should be considered to fall within the scope of the invention as broadly herein described and as hereinafter claimed.

A deflector ( 1 ) for attachment to a spiral separator ( 2 ), for capturing and redirecting a portion of a flowing stream of material ( 5 ). The deflector ( 1 ) includes an attachment means ( 3 ), to attach the deflector ( 1 ) to the spiral separator ( 2 ), a capturing portion ( 4 ) to capture a portion of the flowing stream ( 5 ), and, a redirecting portion ( 6 ) to emit a portion ( 7 ) of the stream. A method of separating particles of different densities using the deflector device ( 1 ) in conjunction with a spiral separator ( 2 ) is also disclosed.

The U.S. Government has rights in this invention pursuant to NIH Grant No. DE08144. BACKGROUND OF THE INVENTION A. Field of the Invention The present invention relates generally to the field of cell culture. In particular, the invention relates to devices and methods that allow for the growth maintenance of cell cultures at high cell density. Some aspects of the invention involve a perfusable culture device designed so that a constant culture media level is maintained. Other aspects of the invention involve the use of the devices of the invention for time-lapse cinemicrography. B. Background of the Related Arts Traditional tissue culture procedures involve growing or maintaining cells in liquid or on solid media in culture flasks. One of the limitations of this type of system has been the fact that it is difficult to grow high-density tissue cultures in such a system. Cells maintained in culture systems frequently have defined and stringent nutrition needs. In order to meet these needs, it has been necessary to maintain a relatively high media-to-cell ratio. Otherwise, the cells rapidly deplete the media of nutritive components and fill the media with metabolic waste. Further, CO 2 gas bubbles build up and obscure the growing cells when one attempts to grow the cells to high density. This leads to difficulty in recording the growth of cells in culture via time lapse photography. In order to forestall these problems, traditional cell culture has involved growing cells until they are just confluent, then trypsinizing the cells to remove them from the culture vessel and placing a portion of the cells in a new vessel with fresh media. Allowing cells to grow into a higher density is difficult with flasks because once the media becomes low in nutritive value, the cells either die or grow in aberrant manners. There is a current need in the field of cell growth research, e.g. in clinical organogenesis, for a system which allows for the growth of dense tissue cells which are multiple cell-layers thick. One favorable characteristic of such a system could be that it would maintain a constant level of culture media within the device. Unfortunately, there has been no system which readily permits such a constant culture media level. Another form of culture used by researchers is organ culture, where whole or sliced animal organs are grown in culture media. Organ culture confronts the same problems as cell culture in that the need for nutrients requires a high media-to-cell ratio. Further, organ culture also confronts problems because it is difficult to diffuse nutrients into the center of thicker masses of organ tissue. One of the current frontiers in the field of cell growth is the study of how cells live and grow in vivo. In vivo, cells are in contact with each other, many of the cells are quiescent, and cells undergo morphogenesis into various tissue types. Each of these states of cell growth and development has been difficult to observe in traditional tissue culture systems. The known culturing systems have not allowed cells to be grown until they reach a quiescent state where morphogenesis can occur. This is because of the constant need to cycle cell media and reduce the number of cells. Further, it has been difficult to study and perform organogenesis, a subset of morphogenesis. In organogenesis, a population of cells morphologically differentiates such that an organ is formed. While there has been some limited success at growing very thin, often single cell thick, layers of skin for medical use. The growth of thicker tissues and organs for clinical use has proven difficult. A large part of this difficulty has been the inability to constantly supply nutrients to the growing cells in a system where the media-to-cell ratio is low. Time lapse cinemicrography devices provide a valuable tool for the study of cell growth and differentiation. While systems for such studies have been known, the data obtained have been limited since only low density cell cultures have been grown for long periods of time. The prior art tissue culture chambers are not suited for growing high density tissue cultures for periods long enough to allow for tissue morphogenesis to occur. Prior time lapse cinemicrography studies have usually involved observation of individual cells at high magnification. In such studies, cells have been maintained at very low density since many microscopic features of cells are obscured under confluent conditions. For such studies, the Rose (Rose 1954) and Sykes-Moore chambers (Sykes, et al., 1959) have proven to be quite satisfactory. The present inventors attempted to use the Sykes-Moore chamber for time-lapse studies of cells maintained at very high cell density and found that several problems occurred even when the Sykes-Moore chamber was perfused several times a day with medium delivery by a peristaltic pump. The chief problems encountered were the production of CO 2 gas bubbles which interrupted the optical path and resulted in constant defocusing of the system due to the deformation of the coverslip walls of the chamber. Time-lapse cinemicrography studies of cells maintained at very high cell density in Sykes-Moore chambers even with a medium perfusion system, gave unsatisfactory results for several reasons. First, CO 2 produced by cells led to the formation of gas bubbles which often obstructed the optical path. Second, the specimen regularly went out of focus due to gas pressure build up which caused the glass coverslips to warp, and, in some cases, break. Third, after several days cells underwent degenerative changes apparently due to lack of oxygen. To observe morphological changes in cells maintained at high cell density studies were initiated with Sykes-Moore chambers. In such studies, MDCK cells were planted in Sykes-Moore chambers that had been completely filled with medium and connected to a peristaltic pump which perfused the culture. Gas bubbles formed once cells had become confluent and that the microscope appeared to continually go out of focus in spite of several attempts to bolster the stage lock mechanism. By sealing all orifices with silicone rubber glue, it was determined that the formation of gas bubbles was not due to a leak in the peristaltic pump tubing or chamber itself. The present inventors concluded that the gas bubbles were due to CO 2 produced by the cells. The constant problem of the microscope going out of focus was determined to be due to CO 2 pressure deforming the glass coverslips that make up the top and bottom of the Sykes-Moore chamber. Indeed, on several occasions, the glass coverslips of the Sykes-Moore chamber split due to gas pressure build-up. These problems caused the Sykes-Moore chamber to be of use for only about one day when observing cells at moderately high density. This is too short to allow for dense cultures to grow and for meaningful time-lapse micrography. The failure of existing technology forced the present inventors to develop a new culture apparatus that would allow cells to grow to high cell density and allow long-term time-lapse cinemicrography. Initially, Applicants attempted to maintain a constant media level in profusion chambers by having a single culture media inlet and a single culture media outlet, both positioned below the desired fluid level. The idea was that if culture media could be pumped into the device at exactly the same rate it was being pumped out of the device, a constant fluid level would be maintained. While theoretically workable, this configuration proved to be very difficult to place in practice. It was found to be almost impossible to obtain exactly equal inflow and outflow of the media. Therefore, over a period of time, the culture chamber would either fill with media or be drained below the desired level. This can cause at least two problems: (1) cells die in an empty chamber, and (2) even if the chamber were not to become completely empty or full, a constantly shifting media level will obscure the focus necessary for time lapse micrography. Confronted with these problems, the present inventors created a simple, dependable, and inexpensive system for maintaining high density tissue cultures for a long period of time. SUMMARY OF THE INVENTION A simple culture chamber is described which permits cells to be maintained at very high cell density for a week or more. This simple culture vessel allows for long term observation of cells at extremely high cell density and permits an unobscured view of cells for over a week. In general, the invention relates to a perfusable culture device capable of maintaining a substantially constant culture media level. This device allows for either continuous or intermittent cycling of the media through the culture device. Therefore, fresh media containing nutrients is available to cells growing in the culture device, while aged media collected waste is gradually removed from the culture device. During use, the culture device is typically connected to a pump, which allows the use of a culture media inlet system for injection of new media and a culture media outlet system for the withdrawal of old media on a continuous or intermittent basis. With some applications, it may be desirable to continually pump media into and out of the system. With other applications, it might be desirable to change the medium in the system every few hours or days. Regardless of the timing of the media circulation, the present culture device allows for circulation of the medium in the chamber without disrupting the cells or opening the chamber while maintaining a constant media level. Generally, the perfusable culture device has a chamber, at least one culture media inlet which flows into the chamber, and at least one culture media outlet which flows out of the chamber. The chamber can be of almost any liquid-containing material, and can be of almost any shape. For example, the chamber can be made of plastic, glass, metal, or the like. Usually, it will be advantageous to make the chamber out of a transparent material, so that the growing cells can be observed. Further, it is anticipated that plastic or other inexpensive material will be most often employed in the manufacture of the chamber. These materials lend themselves to easy manufacture and are relatively inexpensive such that the culture devices can be disposable. Of course, should certain desirable property qualities be desired, for example, improved optical qualities which could only be obtained with optical quality glass, the chambers may be made of material with these qualities. The chambers may be cylindrical, round, square, rectangular or irregularly shaped. Typically, they will be somewhat flattened so that there is a large service area between the gas space above the media and the media. A large surface area at the bottom of the chamber aids in providing a large space for the growing cells to rest upon. The chamber should be sealable so that microorganisms do not contaminate the culture. The chamber may be fitted with a gas inlet and/or outlet that serves to flow gas to and/or from the chamber and maintain the proper atmosphere. A small gas pressure relief fitting may be included to permit venting of CO 2 produced by the cells and to allow air into the system. In a preferred embodiment of the invention, the chamber will be shaped much as a typical cell culture flask is shaped, e.g., a flattened bottle which is designed to lie on its side and has a neck with a cap on it at one end. Such flasks are well known in the art. Perfusable culture devices according to the invention shaped like culture flasks have the advantage of fitting in and on existing laboratory culture equipment. There are many different innovations and designs of tissue culture flasks which may be employed as the basis for the present culture device. For example, Lyman, et al., U.S. Pat. No. 4,927,764 details a flask which has improved optical qualities and a top wall which has a large opening covered by a flexible transparent film which can be peeled off to provide access to the flask interior. Carver, U.S. Pat. No. 4,334,028, discusses a flask with a frangible zone formed into the top wall, which allows for easy access to the contents of the flask. Lyman et al., U.S. Pat. No. 4,770,854, describes a laboratory flask with a ramp that allows accessibility to the four corners of the rear wall and the four corners of the growing surface for a scraper. Honda et al., U.S. Pat. No. 5,139,952, describes a flask shaped such that a scraper can reach the entire bottom of the surface area through the neck. These U.S. patents are incorporated by reference herein, for their teachings related to culture flasks. Each of the flasks described above has features which should be of benefit when used in conjunction with Applicants' perfusable culture device. Since the culture device is essentially a culture vessel modified so that culture media can be circulated through it, the advantages of the prior art flasks, when incorporated into the invention, are clear. The culture media outlet is typically a tube that passes through the wall of the chamber into the interior of the chamber. The outlet allows media to be pumped out of the chamber. The outlet has an exterior portion which is adapted to receive a hose or tube which runs to a pump. The outlet has an interior portion that has a port at the desired media level. The culture media outlet may be formed of metal, glass, plastic, etc. In preferred embodiments of the invention, the culture media inlet enters the chamber in the gas space above the desired liquid level and extends downward to the desired liquid level. This positioning of the culture media outlet prevents liquid leakage at the juncture of the outlet and the chamber wall, and does not interfere with the positioning of the flask on a supporting surface. More than one culture media outlet may be employed in the device, and not all culture media outlets in a device must have a chamber interior port which is positioned at the desired culture media level. Rather, so long as one port is positioned at the culture media level, other ports may be positioned below the desired media level. The perfusable culture device must have at least one culture media inlet leading from the exterior of the chamber to the interior of the chamber. This inlet is designed so that media can be pumped into the chamber. The inlet may be constructed of any of the materials from which the outlet can be constructed, and is, like the outlet, typically a tubular passage. The culture media inlet has a chamber interior port through which media passes into the chamber. Typically this port is positioned below the desired fluid level, so that the flow of media into the chamber does not disrupt the surface of the fluid. However, in certain applications it may be desirable to position the port above the desired fluid level so that the incoming media drops down into the supply of media in the chamber. The culture media inlet is typically hooked up to a pump which pumps media into the chamber on either a continuous or intermittent basis. The inlet typically enters the chamber in the gas space above the desired liquid level and descends into the media. In this manner, leaks from the junction of the inlet and the chamber are minimized. Of course, more than one culture media inlet may be present in a single device. One of the inventive aspects of the present invention is its ability to maintain a constant culture media level. A constant level is maintained due to the difference between the media inlet and media outlet capacities of the device. The device is designed so that at least one culture media outlet port is positioned at the desired culture media level and quickly removes any media which would raise the media level above the desired level. This requires that the media outlet capacity is greater than the media inlet capacity. The culture media outlet capacity is determined by summing the total rate of media removal from all of the outlets of a single device. The culture media inlet capacity is the sum of all of the rates of media input from all inlets. In order for the device to maintain a constant level, the culture media outlet with the media level port positioned at the desired level syphons away any excess media before the fluid level can be raised. The culture media outlet with the media level port draws fluid only when there is sufficient fluid in the chamber to contact the port. During use, the culture media inlets function to add media to the chamber until the level of the culture media outlet's port at the desired fluid level is reached. At that point, because the culture media outlet capacity is greater than the culture media inlet capacity, any additional fluid that flows into the chamber from the inlets, it is immediately removed and constant fluid level is maintained. Additional culture media outlets can be used to syphon media from below the desired culture media level, so long as the capacity of any sublevel culture media outlets is less than the capacity of all of the culture media inlets. If the sublevel outlets had a greater capacity than the media inlets, then the fluid level would be reduced to the level of the sublevel outlets. An outlet that has a port at the bottom of the chamber can remove small debris which form during the prolonged cultivation of cells. The fluid level outlet, being positioned at the air-liquid interface, will not remove such small debris. The presence of the bottom level port removes debris which would settle down to the cell layer, and this is of particular use during time-lapse studies where debris could obscure the image of the cells. In some preferred embodiments of the claim device, there are two culture media inlets. The advantage of this system is that, should one inlet become clogged, the other inlet will permit the continued flow of media into the chamber, albeit at a slower rate. In certain preferred embodiments, the perfusable device will have two culture media outlets and two culture media inlets, such that the advantages of both of these configurations systems are realized. The perfusable culture device is typically hooked up to a pump, such that media is pumped into the chamber through each culture media inlet and media is pumped out of the chamber through each culture media outlet. As previously stated, the outlet pump capacity must be greater than the inlet pump capacity in order for the culture device to function properly and maintain a constant media level. Further, the outlet capacity of any below media surface outlets must be less than the total inlet capacity. A variety of pumps may be used in conjunction with the perfusable culture device. However, it is anticipated that peristaltic pumps will be one of the most convenient forms of pumps to use. Peristaltic pumps are available from many companies, including Masterflex® and Ismatec®. One advantage of peristaltic pumps is that the flow rate from a single culture media outlet or culture media inlet can be controlled by the diameter of tubing attached to that outlet or inlet. Therefore, in order to get an outlet capacity which is greater than the inlet capacity, it is merely necessary to use a larger bore tube attached to the culture media outlet than is attached to the culture media inlet. In one embodiment of the invention, the inventors attach tubes of equal bore to two culture media inlets and a submedia outlet. A larger bore tube is attached to the culture media outlet whose port is at the desired media level. When the tubes are hooked to individual heads on a multihead peristaltic pump, this result is that the culture media outlet capacity is greater than the culture media inlet capacity and the system maintains a constant fluid level. Of course, the invention is in no way limited solely to the use of peristaltic pumps or this manner of controlling the rate of flow, and those of skill in the art will appreciate that there are numerous equivalent arrangements. Other embodiments of the present invention involve methods of culturing cells at high density. These methods involve obtaining a culture device and adding culture media and cells to be cultured, attaching the culture media outlet(s) and culture media inlet(s) to a pump, and perfusing the chamber by either constantly or intermittently pumping culture media into the chamber through the inlets and pumping culture media out of the chamber through the outlets, thereby maintaining the desired media level in the chamber while replenishing the nutrients in the media and removing waste on a regular basis. The culture device is then placed in a situation facilitating or allowing for cell growth and the cells are allowed to grow. Other embodiments of the present invention involve methods for performing time-lapse cinemicrography of cell cultures. Using the device of the present claims, it is possible to maintain focus of cells growing at high density for long periods of time. This device avoids CO 2 gas bubbles from obscuring the focus and also avoids lack of nutrients and waste accumulation from causing cell growth problems. This cinemicrography is performed by growing cells according to the methods defined above, with the culture device being placed upon the stage of a microscope. Typically, an inverted phase microscope is used. The optical quality of culture devices made of standard culture flask materials is sufficient to allow for observation at 10 to 400 times magnification. 100 times magnification is typically employed by the inventors in their studies. It is possible to obtain higher magnification microscopy, however, with magnifications of 1000 times or more, one might wish to employ a flask or culture device which has improved optical qualities. Such a flask is detailed by Lyman, et al. in U.S. Pat. No. 4,927,764 which is incorporated by reference herein. A camera may be set up to record the course of cell growth through the microscope. Either a film camera or a videotape camera may be employed in this manner. By using a motion picture camera and a timer or a time lapse VCR, it is possible to obtain time-lapse photography of the cells. BRIEF DESCRIPTION OF THE DRAWINGS Certain aspects of the invention will become more clear upon the viewing of the accompanied drawings. FIG. 1 A perspective view of an embodiment of the perfusable culture device. FIG. 2 A top view of embodiment of the perfusable culture device. FIG. 3 A side view of embodiment of the perfusable culture device. FIG. 4 A view of one embodiment of the culture device hooked up to a peristaltic pump in an operating configuration. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The following examples detail specific embodiments of the claimed invention. Those with skill in the art will understand that many non-inventive variations of these devices and methods are possible. These variations are within the scope of Applicants' invention and the claims are in no way limited to those embodiments detailed in this section of the application. The device eliminates problems inherent in existing time-lapse cinemicrography chambers that prevent the use of existing devices for cell cultured at high cell density. Production of CO 2 gas by cells grown to high density is sufficient to warp a glass coverslip, resulting in the specimen going out of focus. Warping can become so extreme that the glass coverslips of past systems crack. The device has the addition advantage of allowing one to grow tissue cultures to high density while maintaining a constant volume of medium in the device during frequent automatic medium changes. EXAMPLE I Flask-Shaped Culture Profusion Device One embodiment of the present invention is a flask-shaped, perfusable cultural device. Such a device is illustrated in FIGS. 1, 2 and 3. As can be seen, the device has the general form of a culture flask. The device is typically made of clear plastic material, although it may be made of glass, metal or another non-permeable material. For use in cinemicrography, transparent materials are preferred. Plastic flasks are typically manufactured by injection molding, a technique which is well-suited to the manufacture of the device of the embodiment since it is possible to injection-mold the flask, along with its inlets and outlets. The specifics of the flask-shaped perfusable culture device are as follows. Perfusable culture device 10, has chamber portion 30, outlets 40 and 50, inlets 60, and neck region 20. Chamber portion 30 has bottom 32, top 34, side walls 35, rear wall 36, and neck proximal walls 38. Neck 22 projects at an upward angle from neck walls 38. The chamber typically has a 25 cm 2 surface area. Neck region 20 comprises neck 22 and cap 24. Neck 22 is designed such that cap 24 screws or snaps securely onto neck Cap 24 may form a gas-tight seal between itself and neck 22, because tissue culture often requires a specific gas environment above the tissue media. For example, a 5 to 10% CO 2 concentration is often required for cell culture. In order to help maintain the desired gas environment by allowing excess CO 2 to escape, vent 48 Top outlet 40 is a tubular outlet having external port 42 and internal port 44. In the Figures, top outlet 40 is formed of a hypodermic needle with the Leur-lock fitting still in place. In FIGS. 1 and 2, top outlet 40 enters chamber 30 through top 34. Top outlet 40 is positioned such that internal port 44 is at the desired media liquid level. While top outlet 40 can enter chamber 30 from any angle through any wall or side, it is preferable that top outlet 40 enter the chamber in gas space 70, so that any media leaks between the juncture of top outlet 40 and chamber 30 are minimized. Top outlet 40, as with other outlets and inlets in the invention, can be made of varying materials. The inventors have used metal outlets which have been cemented or glued in place in some prototypes of the invention. These outlets have worked well, however, it is somewhat difficult to obtain a solid seal between the metal outlets and the plastic chamber wall. The inventors have helped remedy this problem by bending outlets and inlets at the portion that passes through the wall of the chamber. When these bent outlets and inlets are glued in place, they are difficult to pull out, and a solid seal is achieved. Applicants anticipate that outlets can be injection molded at the same time as the chamber, thereby forming a continuous piece of plastic-type material forming both outlets 40 and 50, inlets 60, and chamber 30. Outlet 50 has external port 52 and internal port 54. Internal port 54 is positioned such that it is below the desired liquid level 74. Outlet 50 can enter chamber 30 through any wall or side. In the illustration, outlet 50 enters the chamber through side wall 35. Although the illustration shows outlet 50 entering the chamber below the desired fluid level 74, if outlet 50 enters the chamber in gas space 70 and then extends below liquid level 74, the risk of leakage between the junction of outlet 50 and chamber 30 is reduced. Outlet 50 is not a required part of all embodiments of the invention. Outlet 50, when employed, may serve to remove debris from the bottom of the flask. Inlets 60 allow for culture media to be fed into chamber 30. This embodiment of the device has two inlets 60, thereby having a back-up should one inlet become clogged. Inlet 60 has external port 62, and internal port 64. Inlet 60 can enter chamber 30 through any wall or side, however, in the illustrated embodiments inlets 60 enter the chamber through side wall 35. As with outlets 40 and 50, certain advantages are realized if inlets 60 enter chamber 30 in gas space 70 and then pass into the media reservoir. The combined capacity of outlets 40 and 50 must be greater than the combined capacity of inlets 60 in order for a constant media level to be maintained. Further, in order for the constant media level to be maintained at the level of internal port 44, the capacity of outlet 50 must be less than the combined capacity of inlets 60. The inventors have obtained these differences in capacity by hooking a peristaltic pump with the outlets and inlets of the same diameter to tubing of appropriate diameters. During use, outlets 40 and 50 are hooked up to a pump such that media can be moved from the flask through them. As shown in FIG. 4, fluid level outlet 40 is hooked up to fluid level outlet tube 41, and outlet 50 is hooked up to outlet tube 51. Inlets 60 are hooked up to a pump and media reservoir via inlet tubes 61, such that media can be introduced into the chamber through them. When the pump(s) is operating, outlet 40 functions to maintain a constant media level. As additional media is added through inlets 60, outlet 40 syphons away any media rising to the level of outlet port 44. Since the total outlet capacity is greater than the total inlet capacity, but the capacity of outlet is less than the capacity of inlets 60, the media level will constantly be maintained at the level of port 44. During use, for the device may be placed in the configuration shown in FIG. 4. The device 10 is placed upon the stage of a microscope 90. Inlet tubes 61 are attached to the media inlets 60. Outlet tube 41 is attached to fluid level outlet 40, while outlet tube 51 is attached to outlet 50. Inlet tubes 61 are connected to pump 80, in such a way that they can draw fresh media from media reservoir 65. Outlet tubes 41 and 51 are connected to pump 80 and then to waste media container 45. A camera can be positioned so as to allow for still pictures or cinemicrography. EXAMPLE II Manufacture and Use of a Prototype Culture Chamber Materials A. Equipment-although brands of equipment and some model numbers are given, Applicants in no way limit their claims to these specific pieces of equipment. Peristaltic pump, Model G-07521-50, Cole Parmer Four Easy-Load pump heads, Model G-07518-00, Cole Parmer Timer, 6 events/day, 1 minute resolution, Inverted phase microscope, Television camera, Time lapse tape recorder, Panasonic CO 2 -incubator, National Appliance 37° C. warm room (or similar devise for maintaining cultures at 37° during time lapse observations). B. Supplies PharMed® peristaltic pump tubing, size 13, Cole Parmer 1 PharMed® peristaltic pump tubing, size 14, Cole Parmer 1 Tissue culture flasks, Corning® 25 cm 2 , Model 251107?? 16 gauge hypodermic needles, Glue Procedure Preparation of Liquid Level Control for Culture Flask 1. Cut the Leur-lock plastic fitting off of the 16 gauge needle. The inventors hold the needle in a small vice and cut the plastic fitting off with a hack saw. The needle is bent at the point it enters the flask to reduce the chance of the needle being accidentally pulled out of the chamber. 2. Mark the side of the flask at the intended liquid level with a marking pen. 3. Using a drill bit or a red hot gauge needle, make four holes in the sides of a Corning 25 (well above the intended liquid level) and one hole was placed in the top of the flask. 4. Three 16 gauge needles prepared as described in (1.) above were inserted into the three side holes in the flask such that the beveled needle opening faced the bottom of the flask. The needle should be inserted such that the needle opening will be constantly submerged at the intended liquid level. Glue the needles in place with glue. 5. Insert the cut end of a 16 gauge into the top hole of the flask such that the end of the needle is at the intended liquid level and the glue the needle in place with glue. Planting Prototype Chamber with Cells 1. After the glue has dried, sterilize the flask by, for example, rinsing with Chlorox®, 95% ethanol, and sterile water. 2. Plant cells at the desired cell density. 3. Connect the needle together with two sterile pieces of PharMed® tubing to prevent entry of undesired organisms into the flask during the remaining steps. 4. Add 10 ml culture medium, for example Dulbecco's MEM, and the desired number and types of cells. 4. Place the flask in the CO 2 -incubator to establish the desired CO 2 -percentage. For example, 10% CO 2 may be used. C. Connection of Prototype chamber to the Peristaltic Pump. 1. Connect the needle in the top of the flask to PharMed® size 14 tubing such that medium will be withdrawn from the flask through the needle. 2. Connect one needle in the side of the flask to PharMed® size 13 tubing such that medium will be withdrawn from the flask through the needle. 3. Connect the other two needles in the side of the flask with PharMed® size 13 tubing such that medium will be pumped into the flask through these needles. Use of Chamber for Time Lapse Cinemicrography. 1. Focus the microscope on a region of the flask near an inlet needle to avoid the possible interference of the observations by cell debris. The fluid flowing through the inlet needle will push away debris for an area around the inlet. 2. Turn on the video camera and television monitor. 3. Focus the microscope and adjust lighting conditions. 4. Start the videotape recorder at the desired time lapse setting. 5. Program the timer to deliver a desired volume of medium at desired intervals. Discussion of Use and Operation of Prototype Chamber In making an exemplary model of their perfusable culture chamber, the inventors modified a standard 25 cm 2 culture flask so that medium could be perfused into the flask without altering the liquid level. Maintenance of a constant liquid level is essential in order to keep a cinemicrography chamber containing a specimen in focus. The prototype device operates as follows. Medium is pumped into the chamber through two narrow bore (size 13) pieces of PharMed tubing. Medium is withdrawn from the chamber by one narrow bore size 13 tubing and one piece of larger bore size 14 tubing which is connected to the needle in the top of the flask. At the selected peristaltic pump speed (setting 4.0), each size 13 tubing has a flow rate of 2.6 ml/min while the size 14 tubing has a flow rate of 10.1 ml/min. Hence, the two size 13 inlet tubings have a net flow rate of 5.2 ml/min while the size 13 plus size 14 outlet tubing have a maximum flow rate of 12.7 ml/min. Liquid level is maintained at the level of the opening of the top needle for two reasons. First, medium can never be entirely depleted from the chamber since the two size 13 tubings are used to pump into the chamber and only one size tubing is used to pump from the bottom of the chamber, (once the liquid level falls below the level of the needle positioned in the top of the flask, no liquid can be withdrawn by the size 14 tubing. Second, medium can never go above the level of the top outflow needle since the maximum inflow rate is 5.2 ml/min while the maximum outflow rate is 12.7 ml/min. Note that the size 14 tubing port only withdraws medium from the chamber on an intermittent basis. Hence, this system maintains a constant liquid level. There are several designs for a peristaltic pump heads currently on the market. Where two different sizes of tubing are used by one pump, it is advantageous that the pump use the independent pump heads rather than a single pump head that can accept several pieces of tubing. In the case of pump heads that accept several pieces of tubing, a screw or similar devise is used to apply pressure to tubing, and it is difficult to accurately set the flow rates of two different sized tubings. The times at which the pump turns on and off and the interval during which it is active can easily be set by a household timer which supplies current to the pump during desired time intervals. The inventors have used an inexpensive timer allowing them to turn the pump on and off for intervals as short as 1 min. Using such a system, it is possible to automatically feed cultures with desired volume of medium at multiple times/day or continuously during the day. The inventors have used the device described above to observe cells maintained at confluence for over a week without the specimen going out focus even when 200× magnification was used, thereby demonstrating the usefulness of the invention in time-lapse micrography studies. The foregoing examples are provided to illustrate some of the preferred embodiments of the claimed invention. Of course, those of skill in the field will understand that many variations of the described invention are possible without departing from the spirit of the invention. All such variations are also considered to be within the scope of the invention. References The following articles and patents are incorporated by reference in pertinent part herein. Carver, "Flask," U.S. Pat. No. 4,334,028, 1982. Honda et al., "Tissue Culture Flask, " U.S Pat. No. 5,139,952, 1992. Lyman, "Tissue Culture Flask," U.S. Pat. No. 4,927,764, 1990. Lyman, "Laboratory Flask," U.S. Pat No. 4,770,854, 1988. Rose, "A Separable and Multipurpose Tissue Culture Chamber," Tissue Culture Laboratory, 1075-1083, 1954. Sykes et al., "A New Chamber for Tissue Culture," P.S.E.B.M., 125-127, 1958.

The present application relates generally to methods and devices allowing for high density tissue culture techniques to be practiced. Specifically, the application relates to a perfusable culture device which allows for the maintenance of high-density tissue cultures. The application also details methods of using the device to grow cells of varying densities, and methods of observing cell growth at high densities with time-lapse micrography.

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation-in-part of International Patent Application No. PCT/CN2012/087604 with an international filing date of Dec. 27, 2012, designating the United States, now pending, and further claims priority benefits to Chinese Patent Application No. 201210002005.9 filed Jan. 5, 2012. The contents of all of the aforementioned applications, including any intervening amendments thereto, are incorporated herein by reference. Inquiries from the public to applicants or assignees concerning this document or the related applications should be directed to: Matthias Scholl P.C., Attn.: Dr. Matthias Scholl Esq., 245 First Street, 18 th Floor, Cambridge, Mass. 02142. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The invention relates to the application of biomass, and more particularly to a method for preparation of amorphous silica (silicon dioxide) from biomass. [0004] 2. Description of the Related Art [0005] Although silica is abundant in natural resources, the high purity of amorphous silica is hardly found. Conventional methods for preparation of amorphous silica from inorganic materials involve high production costs, large energy consumption, and serious environmental pollution. And methods for preparation of amorphous silica from biomass have low coefficient of utilization of organic matters and energy. SUMMARY OF THE INVENTION [0006] It is one objective of the invention to provide a method for preparation of amorphous silica from biomass. [0007] To achieve the above objective, in accordance with one embodiment of the invention, there is provided a method for preparation of amorphous silica from biomass. The method comprises pyrolyzing the biomass under anaerobic conditions to yield pyrolysis gas and solid residues, collecting the pyrolysis gas, and calcining the solid residues under aerobic conditions to yield amorphous silica. [0008] In a class of this embodiment, the biomass containing amorphous silica is rice hull. [0009] In a class of this embodiment, the method further comprises step A: acid-washing and drying the biomass before the pyrolysis of the biomass, or step B: acid-washing and drying the biomass after the pyrolysis of the biomass. The acid-washing and drying of the biomass before the pyrolysis of the biomass can transform metallic elements therein into soluble metal salts, which facilitates the removal of the metallic elements by water washing. Meanwhile, the long chain organic matters of the biomass are reduced, which facilitates the subsequent pyrolysis. [0010] In a class of this embodiment, the acid-washing and drying of the biomass comprises soaking the biomass in an acid solution at normal temperature for between 8 and 24 hours, or at between 80 and 100° C. for between 2 and 6 hours, washing the biomass to be neutral, and drying the biomass. [0011] In a class of this embodiment, the acid solution is hydrochloric acid, sulfuric acid, or nitric acid, and a weight concentration thereof is between 3 and 10 wt. %. [0012] In a class of this embodiment, the biomass is pyrolyzed at a temperature of between 500 and 1000° C. [0013] In a class of this embodiment, the pyrolysis gas comprises CO, CO 2 , H 2 , CH 4 , C 2 H 2 , C 2 H 4 , C 2 H 6 , C 3 H 8 , C 3 H 10 , or a mixture thereof. [0014] In a class of this embodiment, the calcination is carried out in the presence of air, and a calcination temperature of the solid residues is between 500 and 800° C. [0015] In a class of this embodiment, a thermal flue gas resulting from the calcination of the solid residues is conveyed back to a pyrolysis furnace for the heat cycle of the pyrolysis. [0016] In a class of this embodiment, before the pyrolysis of the biomass or before the acid-washing and drying of the biomass, the method further comprises washing with water the biomass for removal of impurities. [0017] Advantages according to embodiments of the invention are summarized as follows. The biomass containing amorphous silica is pyrolyzed under anaerobic conditions, that is to say, the cellulose, hemicellulose, and lignin of the biomass are pyrolyzed to yield pyrolysis gas which is recycled for power generation or for preparation of syngas. However, the structure of amorphous silica is not destroyed. The resulting solid residues are calcined under aerobic conditions for removal of carbon residue. Thus, high added value of amorphous nano silica is obtained. The method has a simple process, high energy transformation and usage ratio, thereby being environment-friendly and energy-saving. BRIEF DESCRIPTION OF THE DRAWINGS [0018] FIG. 1 is a process flow chart of a method for preparation of amorphous silica from biomass containing amorphous silica in accordance with one embodiment of the invention; [0019] FIG. 2 is a scanning electron microscope (SEM) image of amorphous silica prepared in accordance with Example 1 of the invention; and [0020] FIG. 3 is an X-Ray Diffraction (XRD) spectrum of amorphous silica prepared in accordance with Example 1 of the invention. DETAILED DESCRIPTION OF THE EMBODIMENTS [0021] Further description of the invention will be given below in conjunction with specific embodiments and accompanying drawings. EXAMPLE 1 [0022] As shown in FIG. 1 , rice hull was washed with water for removal of impurities such as mud, soaked in 10 wt. % of hydrochloric acid solution for 24 hours, and washed with water repeatedly until the pH value of the washing solution grew neutral. The washed rice hull was dried in a dry oven at 100° C. to achieve constant weight. [0023] The dried rice hull was conveyed to a pyrolysis furnace via a screw conveyer, where the rice hull was pyrolyzed at 600° C. under anaerobic conditions to yield pyrolysis gas and solid residues. The pyrolysis gas was conveyed to a purifying device, purified and stored, or directly conveyed to a gasifier for the production of syngas, or conveyed to a boiler and combusted for power generation. [0024] The solid residues were conveyed to a calcinator and calcined at 650° C. in the presence of air to yield thermal flue gas and calcined product. The thermal flue gas was conveyed back to the pyrolysis furnace for the heat cycle. The calcined product was ground to yield amorphous silica. [0025] Measurement results from a gas analyzer showed that, the pyrolysis gas comprised CO, CO 2 , H 2 , CH 4 , C 2 H 2 , C 2 H 4 , C 2 H 6 , C 3 H 8 , C 3 H 10 , or a mixture thereof. FIG. 2 shows a scanning electron microscope (SEM) image of the amorphous silica prepared in the example, and FIG. 3 shows an X-Ray Diffraction (XRD) spectrum of the amorphous silica. The amorphous silica is unconsolidated spherical particles having a particle size of about 80 nm. XRD spectrum showed that there was no specific crystal diffraction peak, which implied that the silica has an amorphous structure. EXAMPLE 2 [0026] Rice hull was washed with water for removal of impurities such as mud, soaked in 5 wt. % of nitric acid solution for 24 hours, and washed with water repeatedly until the pH value of the washing solution grew neutral. The washed rice hull was dried at 110° C. to have a moisture content of less than 20%. [0027] The dried rice hull was conveyed to a pyrolysis furnace via a screw conveyer, where the rice hull was pyrolyzed at 800° C. under anaerobic conditions to yield pyrolysis gas and solid residues. The pyrolysis gas was conveyed to a purifying device, purified and stored, or directly conveyed to a gasifier for the production of syngas, or conveyed to a boiler and combusted for power generation. [0028] The solid residues were conveyed to a calcinator and calcined at 800° C. in the presence of air to yield thermal flue gas and calcined product. The thermal flue gas was conveyed back to the pyrolysis furnace for the heat cycle. The calcined product was amorphous silica. [0029] Measurement results from a gas analyzer showed that, the pyrolysis gas comprised CO, CO 2 , H 2 , CH 4 , C 2 H 2 , C 2 H 4 , C 2 H 6 , C 3 H 8 , C 3 H 10 , or a mixture thereof. The amorphous silica was analyzed using a scanning electron microscope (SEM) and an X-Ray Diffraction (XRD), which showed the amorphous silica was unconsolidated spherical particles having a particle size of about 80 nm. XRD spectrum showed that there was no specific crystal diffraction peak, which implied that the silica had an amorphous structure. EXAMPLE 3 [0030] Rice hull was washed with water for removal of impurities such as mud, and dried at 120° C. to have a moisture content of less than 20%. The dried rice hull was conveyed to a pyrolysis furnace via a screw conveyer, where the rice hull was pyrolyzed at 1000° C. under anaerobic conditions to yield pyrolysis gas and solid residues. The pyrolysis gas was conveyed to a purifying device, purified and stored, or directly conveyed to a gasifier for the production of syngas, or conveyed to a boiler and combusted for power generation. [0031] The solid residues were boiled in 5 wt. % of sulfuric acid solution for 4 hours, and washed with water thrice until the pH value of the washing solution grew neutral. The washed rice hull was dried in a dry oven at 102° C. to have a moisture content of less than 30%. [0032] Thereafter, the solid residues were conveyed to a calcinator and calcined at 500° C. in the presence of air to yield thermal flue gas and calcined product. The thermal flue gas was conveyed back to the pyrolysis furnace for the heat cycle. The calcined product was amorphous silica. [0033] Measurement results from a gas analyzer showed that, the pyrolysis gas comprised CO, CO 2 , H 2 , CH 4 , C 2 H 2 , C 2 H 4 , C 2 H 6 , C 3 H 8 , C 3 H 10 , or a mixture thereof. The amorphous silica was analyzed using a scanning electron microscope (SEM) and an X-Ray Diffraction (XRD), which showed the amorphous silica was unconsolidated spherical particles having a particle size of about 80 nm. XRD spectrum showed that there was no specific crystal diffraction peak, which implied that the silica had an amorphous structure.

A method for preparation of amorphous silica from biomass. The method includes pyrolyzing the biomass under anaerobic conditions to yield a pyrolysis gas and solid residues, collecting the pyrolysis gas, and calcining the solid residues under aerobic conditions to yield amorphous silica.

CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of a prior application Ser. No. 11/223,557, filed Sep. 9, 2005, and claims the priority benefit of Taiwan application serial no. 95141897, filed on Nov. 13, 2006. The prior application Ser. No. 11/223,557 claims the priority benefit of Taiwan application serial no. 94125065, filed on Jul. 25, 2005. The entirety of each of the above-mentioned patent applications is hereby incorporated by reference herein and made a part of this specification. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection display technology, and more particularly, to a high efficiency liquid crystal display projection system. 2. Description of Related Art The projection liquid crystal display technology has been a usual technology. The traditional liquid crystal display projection system mainly uses the reflective liquid crystal on silicon (LCOS) panel to process the colors and the gray levels of the image pixels. One of the main characteristics of the so-called reflective LCOS panel is that most of the driving devices are formed on the lower substrate while the liquid crystal layer is formed between the upper and the lower substrates. The light source enters the lower substrate from the upper substrate and the light is then reflected from the reflective layer of the lower substrate. Therefore, the reflected light will not be blocked by the driving devices and the utility efficiency of lights can be improved. FIG. 1 shows a traditional liquid crystal display system. In FIG. 11 , a light source 100 emits a white beam 102 . The white beam 102 enters a dichroic mirror 104 to be split into a blue beam 108 and a red/green (R/G) mixing beam 106 . The R/G mixing beam 106 is then incident to another dichroic mirror to be split into a red beam 116 and a green beam 118 . The light path and the mechanism of the blue beam 108 is first described. The non-polarized blue beam 108 comprises P-polarization and S-polarization. Then, the blue beam 108 enters a polarized beam splitter (PBS) device 110 a . The functions of the PBS device include reflecting S-polarized light but allowing P-polarized light to penetrate through. Accordingly, the PBS device 110 a will reflect the S-polarized light of the blue beam 108 , which then enters the reflective LCOS panel 112 a . The reflective LCOS panel 112 a contains a pixel region. Through controlling the liquid crystal molecule rotation of the corresponding pixels, the S-polarized blue light will tilt to produce a new polarization state, comprising partial S-polarization and partial P-polarization. The amount of P-polarization varies according to the desired gray level, generating a gray level of colors in cooperation with the PBS device 110 a. The blue light that is reflected back to the PBS device 110 a by the reflective LCOS panel 112 a contains P-polarization based on the requirement of the image pixel. This P-polarized blue light can penetrate through the PBS device 110 a to be incident to a color-combination prism 120 . The amount of P-polarization is determined by the blue light gray level required by the image. If blue light is not required, the value of the P-polarization will be zero. Hence, no blue light will penetrate through the PBS device 110 a . As a result, the value of the P-polarization increases when the blue light gray level increases. Based on the same mechanism, the red beam 116 is reflected by a reflective mirror and enters the PBS device 110 b and then gets reflected to the PBS device 110 b by the LCOS panel 112 b , wherein the P-polarized red light will enter the color-combination prism 120 . Similarly, the green beam 118 is reflected by a reflective mirror and enters a PBS device 110 c and then gets reflected to the PBS device 110 c by the LCOS panel 112 c , wherein the P-polarized green light will enter the color-combination prism 120 . The color-combination prism 120 receives the image lights of three colors to form an image 122 . This image 122 can be projected to a screen. This type of liquid crystal display projection system processes the three primary colors, (red/green/blue, R/G/B), respectively, hence, it is bigger in volume with a higher manufacturing cost and a poorer utility efficiency of lights. FIG. 2 shows a traditional dual-panel liquid crystal display projection system. In FIG. 2 , the light source 200 of R/G/B lights emits light through a PBS device 202 in succession. Since human eyes experience a phenomenon known as visual retention, therefore, when the light emitted by the light source 200 of R/G/B lights enters the human eyes within the range of visual retention, the overlap of R/G/B lights results in what is perceived as colors by the human eyes. As a result, the projection system shown in FIG. 2 requires only one PBS device 202 , but two LCOS panels, namely 204 a and 204 b . For instance, after the light source 200 of R/G/B emits lights through the PBS device 202 , the P-polarized red light 206 will penetrate through the PBS device 202 to be reflected by the LCOS panel 204 b and the polarization varies according to the requirement of the gray level, which might be converted to S-polarization. Subsequently, the reflected PBS device 202 will reflect out a red beam 210 . The generation mechanisms for green light and blue light are the same as the aforementioned, which will not be described again. In addition, the PBS device 202 also reflects a S-polarized red light 208 , which enters the LCOS panel 204 a to be converted to a P-polarized red light 220 . This P-polarized red light 220 and the S-polarized red light 210 form one red light image. Since there are two LCOS panels, namely 204 , the utility efficiency of lights is increased. Moreover, only one PBS device, namely 202 , is needed because the light source of R/G/B lights emits light in succession. Furthermore, the light-emitting surface of the traditionally used light source gives off uneven brightness. Thus, the choice of the light source affects the illumination of display. Although different designs of liquid crystal projection system have been developed based on the traditional technology, there is still room for further research and development. SUMMARY OF THE INVENTION The present invention provides a liquid crystal projection system comprising a more uniform planar light source. The present invention provides a liquid crystal projection system that uses a transmitting-type LCOS panel to produce three primary color lights either through the direct employment of the three primary color filter or following a time sequence. The present invention provides a liquid crystal projection system, including a planar light source. This planar light source includes a plurality of light-emitting units arranged in an array. Each light-emitting unit comprises a conoid-like reflective surface, wherein an edge of a light outputting surface of a conoid-like reflective surface and that of the adjacent conoid-like reflective surface are conformal. A plurality of light emitting devices controls the light emission of a planar light source. Wherein, the planar light source emits either a white beam or cyclically R/G/B beams in succession. A first polarization filter receives the planar light source and polarizes the planar light to a first polarization light beam in a first polarization state. A transmitting-type liquid crystal light valve receives the first polarization light beam for converting the first polarization state based on a gray level to produce a second polarization state having the corresponding gray level. A second polarization filter receives a light output from the liquid crystal light valve to produce a second polarization light beam in a second polarization state. A projection unit projects the second polarization light beam onto a display plane. The present invention provides a liquid crystal display projection system, including a planar light source and a plurality of light-emitting units arranged in an array. Each light-emitting unit comprises a conoid-like reflective surface, wherein an edge of a light outputting surface of a conoid-like reflective surface and that of the adjacent conoid-like reflective surface are conformal. A plurality of light emitting devices controls the light emission of a planar light source. The planar light source emits either a white beam or cyclically RIG/B beams in succession. A PBS device receives the planar light source, allowing a first light beam in a first polarization state to penetrate through and reflecting a second light beam in a second polarization state. A reflective first liquid crystal light valve receives either the first light beam or the second light beam to serve as a third light beam, and reflects a first reflection light back to the PBS device. The first liquid crystal light valve converts the third light beam in a polarization state into the first reflection light in a first reflective polarization state according to the requirement of gray level. Then, the PBS device splits a first image light from the first reflective polarization state. A projection unit projects the first image light onto a display plane. In order to the make the aforementioned and other objects, features and advantages of the present invention comprehensible, a preferred embodiment accompanied with figures are described in detail below. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a schematic view that illustrates a traditional liquid crystal display projection system. FIG. 2 shows a schematic view that illustrates a traditional dual-panel liquid crystal display projection system. FIG. 3 is a cross-sectional view, schematically illustrating a structure of an illuminating light source, according to an embodiment of the present invention. FIG. 4 is a top view, schematically illustrating a top view of the structure of the light source corresponding to FIG. 3 . FIG. 5 shows a schematic view that illustrates the structure of a transmitting-type liquid crystal display projection system, according to an embodiment of the present invention. FIG. 6 shows a schematic view that illustrates a distribution of the pixels on the liquid crystal light valve 154 . FIG. 7 shows a schematic view that illustrates another distribution of pixels on the liquid crystal light valve 154 . FIG. 8 shows a schematic view that illustrates the structure of a reflective-type liquid crystal display projection system, according to an embodiment of the present invention. DESCRIPTION OF EMBODIMENTS First, the present invention provides an improved and innovative design of the light source used in the liquid crystal display projection system, which comprises a more uniform planar light source that allows better utility efficiency of lights and provides a more uniform image brightness. It will be illustrated through the following embodiments, and the present invention is not limited to the recited embodiments. FIG. 3 is a cross-sectional view, schematically illustrating a structure of an illuminating light source, according to an embodiment of the present invention. FIG. 4 is a top view, schematically illustrating a top view of the structure of the light source corresponding to FIG. 3 . In FIG. 3 and FIG. 4 , the array of the illuminating light source can include, for example, four illuminating units on one side. An illuminating unit includes a point-like light emitting device, such as an LED having a substrate electrode part 130 and a packaged light emitting part 132 . The point-like light emitting device radially emits light within a range of a solid angle from a center point. This point-like light emitting device is structured based on a light emitting diode (LED) that gives off white beam. However, the point-like light emitting device can also be structured according to three LED's that respectively give off R/G/B beams to provide a variety of the desired effects. Wherein, the point-like light emitting device based on the LED that gives off R/G/B beams demonstrates a more desirable performance (See FIG. 5 ). It is because each individual color light in the R/G/B emitting LED has a different frequency. As a result, interferences are minimized to achieve a better gamut. The primary projection direction of the light emitted from the point-like light emitting device is defined as an optical axis. At the periphery of the point-like light-emitting device, according to the embodiment in the present invention such as shown in FIG. 3 and FIG. 4 , two-stage reflective surfaces 134 a and 136 a are installed. Due to the arrangement of the angles for the two-stage reflective surfaces 134 a and 136 a , a large portion of the light emitted from the point-like light-emitting device travels along the optical path 138 to be reflected by the reflective surfaces 134 a and 136 a once or multiple times, forming a collimating beam along the optical axis. Further, the light is well-mixed as a result of the single or multiple reflections. Additionally, the conoid-like reflective surface can be arranged in three or more stages according to the description of design above when needed. For the two-stage conoid-like reflective surfaces 134 a and 136 a , each stage can form, for example, a four-plane pyramid having a convergent opening end and a divergent opening end. Wherein, the point-like light emitting device is located at the convergent opening end and the optical axis is directed towards the divergent opening end to allow light emission. Generally, the conoid planes can be formed by multiple pyramid planes. A desirable form would be in a case where the shape of the cross-section is a square or a rectangle. To have a good fit, the cross-sectional shape of the conoid planes can also be triangular or polygonal. Nonetheless, when a good fit is not required, the conoid planes can be circles, ovals or smooth curves. Some modified examples are to be described later. The present invention is designed in conformity with square LED crystalline grains, forming a plurality of four-face pyramid-like reflective surfaces. For instance, the reflective mirror collimates lateral lights through multiple reflections and ensures uniform mixing of lights. As a result, the reflective mirror reduces the space between the two adjacent light-emitting openings to zero, ensuring continuous array of light source and providing a collimating and uniform light source with a high density. This kind of application is suitable for highly directional light source such as the light source for projectors, scanners, professional lightings used on stage and searchlights because it is compact, portable and will not cause overheating. The reflective surface 134 a and the reflective surface 136 a can be arranged in many different ways. Nevertheless, to effectively and firmly put together the planar light source using a plurality of point-like light emitting devices, it would be desirable if the reflective surface 134 a and the reflective surface 136 a are each supplied with the two material layers, 134 and 136 . Openings that are predetermined for the conoid-like reflective surface 134 a and the conoid-like reflective surface 136 a are located on the material layer 134 . The light emitting device can be firmly installed on the material layer 134 and it emits light through the opening. Furthermore, the second-stage material layer 136 is placed on top of the first-stage material layer 134 and the openings of the two layers are coupled to each other. In such design, the light emitting devices of different light emitting units are not arranged tightly together. However, a light emitting unit can have as many point-like light emitting devices as necessary. It should be noted that if the design is based on conoid-like reflective surfaces, the openings of the second-stage conoid-like reflective surfaces 136 a must be closely connected to one another since conoids are regular shapes that can fit together perfectly with one another. Hence, non-illuminating regions can be further minimized. This is another effect achieved by the present invention. The present invention provides an improved planar light source that can be utilized in liquid crystal display projection system. FIG. 5 illustrates the structure of a transmitting-type liquid crystal display projection system, according to an embodiment of the present invention. In FIG. 5 , the transmitting-type liquid crystal display projection system uses the planar light source 150 that is described previously. However, the light source consists of a plurality of point-like light emitting devices comprising R/G/B light emitting diodes (LED) 162 ( r,g,b ). For instance, a more uniform planar light source is achieved through conversion by the second-stage conoid-like reflective surfaces 160 a and 160 b . RIG/B light emitting diodes (LED) 162 ( r,g,b ) can simultaneously emit lights to produce a white beam or individually emit lights to produce colored beams in succession. There will be no further description about the light source. The mechanism of display is described as follows. The transmitting-type liquid crystal display projection system includes a first polarization filter 152 , a transmitting-type liquid crystal light valve 154 , a second polarization filter 156 and a projection unit 158 . Moreover, the light source can be used together with a lens 164 , which is not necessary. First, if the light source is based on the design of R/G/B beams that emit colored lights in succession, the resulting image is accomplished by visual retention. Red, green and blue lights all share the same displaying mechanism. To facilitate the illustration, red light is used in the following explanation. First, red light penetrates through the first polarization filter 152 such as a P-polarization filter. The red light that penetrating through the P-polarization filter will become P-polarized. The P-polarized red light then enters the liquid crystal light valve 154 . An example of the liquid crystal light valve is a transmitting-type LCOS panel. Each pixel corresponds accordingly to the requirement of the gray level in order to control the rotation angle of the liquid crystal. Due to the rotation angel of the liquid crystal, the passing P-polarized incident light will tilt. When the value of the gray level is not zero, a portion of the red light will be S-polarized. According to the design of the present invention, the amount of S-polarization will correspond to the requirement of the gray level. Also, the amount of P-polarization can be used to correspond to the requirement of the gray level. The following example uses S-polarization corresponding to the requirement of the gray level to illustrate the embodiment of the present invention. A portion of the red light will be S-polarized after penetrating through the liquid crystal light valve 154 . As a result, only S-polarized red light will be able to enter the second polarization filter 156 since it is a S-polarized filter. Different pixels will result in different amount of light penetrated through, depending on the corresponding requirement of the gray level needed by each pixel. Therefore, a red light image is achieved. This red light image is projected onto a display plane by the projection unit 158 . In this case, it is a display screen. Similarly, both green light and blue light follow the same mechanism to produce green light image and blue light image respectively. Visual retention allows the images produced by the three colored lights to overlap, resulting in a colored image. FIG. 6 shows a schematic view that illustrates the pixel distribution on the liquid crystal light valve 154 . In FIG. 6 , the liquid crystal light valve 154 contains a plurality of pixels 170 that are shared by R/G/B lights. Therefore, a R/G/B color filter is not needed by the liquid crystal light valve 154 . According to another mechanism of the embodiment, if the planar light source 150 gives off white beam, the liquid crystal light valve 154 needs a corresponding R/G/B color filter. FIG. 7 shows a schematic view that illustrates another pixel distribution on the liquid crystal light valve 154 . In FIG. 7 , a pixel 172 includes three sub-pixels 174 ( r,g,b ). Each sub-pixel 174 has a corresponding color filter. Hence, each pixel will produce the desired color directly. Here is a schematic view that illustrates the arrangement of the sub-pixels 174 . In fact, there can be different combinations of the sub-pixels. Next, in FIG. 5 , the white beam emitted by the planar light source 150 contains both P-polarization and S-polarization. When the white beam penetrates the first polarization filter 152 , it will, for instance, become P-polarized. The P-polarized white beam then enters the liquid crystal light valve 154 . As illustrated in FIG. 7 , each sub-pixel eliminates other color light but its own. Similarly, the gray level required by each sub-pixel controls the rotation angle of the liquid crystal. Due to the rotation angel of the liquid crystal, the passing P-polarized incident light will tilt, resulting in S-polarization. This S-polarized light will then be filtered by the second polarization filter 156 , resulting in a colored image light. Also, the present invention is not limited to the design of the liquid crystal projection system shown in FIG. 5 . FIG. 8 shows a schematic view that illustrates the structure of a reflective-type liquid crystal display projection system, according to an embodiment of the present invention. In FIG. 8 , the planar light source 150 as described by the previous embodiment is used as the light source for this liquid crystal projection system. When needed, the lens 164 can be used to obtain the desired light source. The present embodiment only uses one PBS device 180 . In this embodiment, the planar light source 150 produces the three primary color lights, red, green and blue in succession. To facilitate the illustration, red light is used in the following explanation. For instance, the P-polarized red light will penetrate through the PBS device 180 to reach the reflective liquid crystal light valve 184 . If the light reaches a reflective LCOS panel, it will be converted to an equivalent amount of S-polarization according to the requirement of gray level. This S-polarization will be reflected to a projection unit 158 by the PBS device 180 . Another way to display is to use the S-polarization generated by the planar light source 150 as the light source for display. The S-polarized red light will be reflected by the PBS device 180 to the reflective liquid crystal light valve 182 . Subsequently, according to the requirement of the gray level, an equivalent amount of the S-polarized red light will be converted to P-polarized red light. This P-polarized red light that is reflected to the PBS device 180 can penetrate through the PBS device 180 , producing a red image. This is obtained through another light path. Nonetheless, the aforementioned two methods drastically cause greater losses in the utility efficiency of light. This is because only either S-polarized light or P-polarized light produced by the planar light source 150 is used to generate the image. In other words, generally only 50% of the light produced by the planar light source 150 is used. Although the efficiency of the planar light source 150 in the present invention has been enhanced, it still can be further improved. Therefore, to further improve the efficiency of the planar light source is to optically combine the lights obtained through the two aforesaid light paths to form an image together. In other words, the PBS device 180 will split the incoming light to the first light beam and the second light beam. In terms of employing the single light path of the single-panel design, such employment facilitates the present invention to use either the reflective liquid crystal light valve 182 or the reflective liquid crystal light valve 184 as the first reflective liquid crystal light valve for receiving S-polarization light beam or P-polarization light beam. Wherein, for easy identification and brief description, the light beam received by the first liquid crystal light valve is denoted as the third light beam. On the other hand, when the employment of dual light path of the dual-panel design is necessary, another one of the reflective liquid crystal light valve 182 and the reflective liquid crystal light valve 184 is used as the second liquid crystal light valve to receive the incoming light, which is known as the fourth light beam. According to the embodiment shown in FIG. 8 , a single light path design can employ the corresponding light path provided by either the liquid crystal light valve 182 or the liquid crystal light valve 184 alone. When necessary, the liquid crystal light valve 182 and the liquid crystal light valve 184 are used simultaneously. Similarly, the same mechanism can be applied to obtain the green light image and the blue light image. Making use of visual retention, red light, green light and blue light are generated using the appropriate frequency to form a true color image. In this embodiment, the liquid crystal light valve 182 and the liquid crystal light valve 184 can be arranged according to FIG. 6 without the installation of a filter. Additionally, when the planar light source 150 needs to generate a white beam, the polarization mechanism will be similar to the description above and the liquid crystal light valve 182 and the liquid crystal light valve 184 can be arranged according to FIG. 7 to control the value of the gray level of the three primary color sub-pixels and simultaneously form the pixels of the desired color. Certainly, the arrangement shown in FIG. 7 is merely an embodiment of the present invention. The display mechanism thereof is the same as the aforementioned, which will not be further elaborated. The present invention provides an efficient and highly uniform light source that can be applied in various designs of liquid crystal display projection system to enhance the brightness and the uniformity of images. The designs shown in FIG. 5 and FIG. 8 are based on the similar principles but each has distinct features of its own. While being less expensive, the transmissive single-panel design shown in FIG. 5 is comparatively more compact than the reflective dual-panel design shown in FIG. 8 , thus it has a lower utility efficiency of lights. In the case where R/G/B lights are emitted successively in an alternating fashion, such design reduces power dissipation and allows easy heat dissipation. Although the present invention has been disclosed above by the preferred embodiments, they are not intended to limit the present invention. Anybody skilled in the art can make some modifications and alteration without departing from the spirit and the scope of the present invention. Therefore, the protecting range of the present invention falls in the appended claims.

A transmitting-type liquid crystal display projection system including a planar light source which emits planar white beam or planar R/G/B beams in succession is provided. A first polarization filter receives the planar light source and polarizes the same to be in a first polarization state. A liquid-crystal light valve receives the polarized planar light source, and converts the first polarization state to a second polarization state having a corresponding gray level. A second polarization filter receives a light output from the liquid crystal light valve to produce a second polarization light beam. A projection unit projects the second polarization light beam onto a display plane. Using the same planar light source, a polarization beam splitting (PBS) device with a refection-type liquid crystal light valve can be used to achieve the reflection-type projection system.

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates generally to papermaking, and relates more specifically to multilayer fabrics employed in papermaking. The invention also relates to the binding of multilayered forming fabric with warp yarns. The present invention also relates to. multilayer papermaker's fabrics that utilizes warp yarns to bind top and bottom layers such without disrupting the top fabric surface. The invention also provides for a fabric which utilizes a condensed sequence of warp knuckles in a weft float dominate structure in order to provide space in the weave for the binding warps to smoothly transition from the top layer to the bottom layer. The invention also provides for a fabric wherein the warp knuckles of several repeats of a weft float dominate pattern are condensed into a plain weave sequence that allows space for warps to float under the wefts for a distance. [0003] 2. Discussion of Background Information [0004] In the conventional fourdrinier papermaking process, a water slurry, or suspension, of cellulosic fibers (known as the paper “stock”) is fed onto the top of the upper run of an endless belt of woven wire and/or synthetic material that travels between two or more rolls. The belt, often referred to as a “forming fabric,” provides a papermaking surface on the upper surface of its upper run which operates as a filter to separate the cellulosic fibers of the paper stock from the aqueous medium, thereby forming a wet paper web. The aqueous medium drains through mesh openings of the forming fabric, known as drainage holes, by gravity or vacuum located on the lower surface of the upper run (i.e., the “machine side”) of the fabric. [0005] After leaving the forming section, the paper web is transferred to a press section of the paper machine, where it is passed through the nips of one or more pairs of pressure rollers covered with another fabric, typically referred to as a “press felt.” Pressure from the rollers removes additional moisture from the web; the moisture removal is often enhanced by the presence of a “balt” layer of the press felt. The paper is then transferred to a dryer section for further moisture removal. After drying, the paper is ready for secondary processing and packaging. [0006] Typically, papermaker's fabrics are manufactured as endless belts by one of two basic weaving techniques. In the first of these techniques, fabrics are flat woven by a flat weaving process, with their ends being joined to form an endless belt by any one of a number of well-known joining methods, such as dismantling and reweaving the ends together (commonly known as splicing), or sewing on a pin-seamable flap or a special foldback on each end, then reweaving these into pin-seamable loops. A number of auto-joining machines are available, which for certain fabrics may be used to automate at least part of the joining process. In a flat woven papermaker's fabric, the warp yarns extend in the machine direction and the filling yarns or weft yarns extend in the cross machine direction. [0007] In the second basic weaving technique, fabrics are woven directly in the form of a continuous belt with an endless weaving process. In the endless weaving process, the warp yarns extend in the cross machine direction and the filling yarns or weft yarns extend in the machine direction. Both weaving methods described hereinabove are well known in the art, and the term “endless belt” as used herein refers to belts made by either method. [0008] Effective sheet and fiber support are important considerations in papermaking, especially for the forming section of the papermaking machine, where the wet web is initially formed. Additionally, the forming fabrics should exhibit good stability when they are run at high speeds on the papermaking machines, and preferably are highly permeable to reduce the amount of water retained in the web when it is transferred to the press section of the paper machine. In both tissue and fine paper applications (i.e., paper for use in quality printing, carbonizing, cigarettes, electrical condensers, and like) the papermaking surface comprises a very finely woven or fine wire mesh structure. [0009] In prior art fabrics, there is typically not enough space within the weave pattern for top warps to bind to the bottom wefts without disrupting the top fabric surface. Such fabrics also do not typically provide space in the weave for the top warps to smoothly transition from the top layer to the bottom layer. Such fabrics also do not typically provide space for warps to float under the wefts for a distance. SUMMARY OF THE INVENTION [0010] The fabric of the present invention may be made using the prior art methods described above. The invention also provides for a multilayer fabric employed in papermaking. The invention further also provides for the binding of multilayered forming fabric using warp yarns such as warp yarns that weave in the top layer. The present invention also relates to multilayer papermaker's fabrics that utilizes warp yarns to bind top and bottom layers such without disrupting the top fabric surface. [0011] The present invention also recognizes that it is better for a warp yarn weaving in the top layer to pass between a top and bottom weft yarn before weaving or binding with one or more bottom weft yarns than for the warp yarn to pass from over a top weft yarn to directly over a bottom weft yarn without first passing between top and bottom weft yarns. [0012] By way of non-limiting example, the present invention provides for a forming fabric having a 5 shed/5 shed warp bound 3:2 weft ratio. [0013] The invention also provides for a fabric which utilizes a condensed sequence of warp knuckles in a weft float dominate structure in order to provide space in the weave for the warps which weave in the top layer to smoothly transition from the top layer to the bottom layer. The invention also provides for a fabric wherein the warp knuckles of several repeats of a weft float dominate pattern are condensed into a plain weave sequence that allows space for warps to float under the wefts for a distance. [0014] The present invention relates to a forming fabric comprising a top layer comprising top weft yarns, a bottom layer comprising bottom weft yarns, binding warp yarns weaving with the top weft yarns and binding to the bottom layer, and at least one of the binding warp yarns passing between at least one top and bottom weft yarns before passing over at least one bottom weft yarn. [0015] The fabric may further comprise at least one of bottom warp yarns weaving with non-adjacent bottom weft yarns and bottom warp yarns weaving only in the bottom layer. [0016] At least one of the at least one binding warp yarn may pass under at least two adjacent top weft yarns before passing over at least one bottom weft yarn and each binding warp yarn may bind to bottom layer by binding to non-adjacent bottom weft yarns. The binding warp yarns may weave with the top weft yarns and bind to different non-adjacent bottom weft yarns per pattern repeat. Each binding warp yarn may bind to at least three non-adjacent bottom weft yarns per pattern repeat. After weaving with the top weft yarns, each binding warp yarn may bind to at least two non-adjacent bottom weft yarns per pattern repeat before again weaving with the top weft yarns. The binding warp yarns may bind to at least four non-adjacent bottom weft yarns per pattern repeat. After weaving with the top weft yarns, the at least one binding warp yarn may pass under at least two adjacent top weft yarns before binding with the bottom weft yarns. After weaving with the top weft yarns, the at least one binding warp yarn may pass under at least two adjacent top weft yarns before binding to two non-adjacent bottom weft yarns. After weaving with the top weft yarns, the at least one binding warp yarn may pass under at least three adjacent top weft yarns before binding with the bottom weft yarns. After weaving with the top weft yarns, the at least one binding warp yarn may pass under at least three adjacent top weft yarns before binding to-two non-adjacent bottom weft yarns. [0017] The top layer and bottom layer may be bound together only by the binding warp yarns and the binding warp yarns are intrinsic warp yarns. Each binding warp yarn in a pattern repeat may weave with a plain weave with top weft yarns before binding with non-adjacent bottom weft yarns. Each binding warp yarn in a pattern repeat may weave with a plain weave with top weft yarns before binding with two non-adjacent bottom weft yarns. [0018] In a pattern repeat, each binding warp yarn may weave with a plain weave with top weft yarns, then binds with two non-adjacent bottom weft yarns, and then weaves with a plain weave with top weft yarns. In a pattern repeat, the at least one binging warp yarn may bind with first and second non-adjacent bottom weft yarns and a bottom warp yarn weaves with the first and second bottom weft yarns. In a pattern repeat, the at least one binding warp yarn may bind with first, second and third non-adjacent bottom weft yarns and a bottom warp yarn weaves with the first, second and third bottom weft yarns. In a pattern repeat, the at least one binding warp yarn may bind with only first, second and third non-adjacent bottom weft yarns and a bottom warp yarn weaves with the first, second and third bottom weft yarns. In a pattern repeat, each binding warp yarn may bind with only first, second and third non-adjacent bottom weft yarns and corresponding bottom warp yarns weave only with a same first, second and third bottom weft yarns. In a pattern repeat, the at least one binding warp yarn may bind with first, second, third and fourth non-adjacent bottom weft yarns and a bottom warp yarn weaves with the first, second, third and fourth bottom weft yarns. In a pattern repeat, the at least one binding warp yarn may bind with only first, second, third and fourth non-adjacent bottom weft yarns and a bottom warp yarns weave with the first, second, third and fourth bottom weft yarns. In a pattern repeat, each binding warp yarn may bind with only first, second, third and fourth non-adjacent bottom weft yarns and corresponding bottom warp yarns weave only with the first, second, third and fourth bottom weft yarns. In a pattern repeat, all bottom warp yarns may weave only in the bottom layer to non-adjacent bottom weft yarns. [0019] All of the binding warp yarns may weave only with a plain weave when in the top layer. All of the binding warp yarns may bind to non-adjacent bottom weft yarns in a pattern repeat. The binding warp yarns may bind to different non-adjacent bottom weft yarns in a pattern repeat. The top layer may have a papermaking surface and the bottom has a machine side surface. [0020] In a pattern repeat, each of the binding warp yarns may be vertically stacked with respect to bottom warp yarns. In a pattern repeat, more top weft yarns may be utilized that bottom weft yarns. In a pattern repeat, 30 top weft yarns may be utilized and 20 bottom weft yarns are utilized. In a pattern repeat, 30 top weft yarns may be utilized and 15 bottom weft yarns are utilized. In a pattern repeat, 20 top or binding warp yarns are utilized and 20 bottom warp yarns may be utilized. [0021] At least one of the binding warp yarns per pattern repeat may differ from bottom warp yarns in at least one of the following characteristics size, modulus, and material. At least one of the top weft yarns per pattern repeat may differ from the bottom weft yarns in at least one of the following characteristics size, modulus, and material. At least one of the binding warp yarns may be smaller in size than at least one bottom warp yarn. At least one of the top layer may have a different weave pattern than the bottom layer and the top layer may utilize a plain weave and the bottom layer does not utilize a plain weave. [0022] The invention also provides for a forming fabric comprising a top layer comprising top weft yarns, a bottom layer comprising bottom weft yarns, at least one binding warp yarn weaving with the top weft yarns and binding to at least two non-adjacent bottom weft yarns, and at least one bottom warp yarn weaving only with bottom weft yarns. [0023] The invention also provides for a forming fabric comprising a top layer comprising top weft yarns, a bottom layer comprising bottom weft yarns, at least one binding warp yarn weaving with top weft yarns and binding to at least two non-adjacent bottom weft yarns in a pattern repeat, and at least one bottom warp yarn weaving with the at least two non-adjacent bottom weft yarns. [0024] The invention also provides for a method of making the fabric of any of the types described above, wherein the method comprises binding together the top and bottom layers using only the binding warp yarns. [0025] The invention also provides for a method of making the fabric of any of the types described above, wherein the method comprises binding the top and bottom layers together using the binding warp yarns, wherein each binding warp yarn binds to at least three non-adjacent bottom weft yarns per pattern repeat. [0026] Additional aspects of the present invention include methods of manufacturing warp-stitched triple layer fabrics and methods of using the triple layer papermaker's fabric described herein for making paper. BRIEF DESCRIPTION OF THE FIGURES [0027] The present invention is further described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of exemplary embodiments of the present invention, in which like reference numerals, represent similar parts throughout the several views of the drawings, and wherein: [0028] FIG. 1 shows a weave pattern repeat of a first embodiment of the present invention; [0029] FIG. 2 a shows a cross-section view of the repeat shown in FIG. 1 and illustrates binding yarns 2 , 4 , 6 , 8 and 10 (listed from the bottom up on the left-hand side) and bottom warp yarns 1 , 3 , 5 , 7 and 9 (listed from the bottom up on the left-hand side). The top and bottom weft yarns 1 - 50 are listed right to left; [0030] FIG. 2 b shows a cross-section view of the repeat shown in FIG. 1 and illustrates binding warp yarns 12 , 14 , 16 , 18 and 20 (listed from the bottom up on the left-hand side) and bottom warp yarns 11 , 13 , 15 , 17 and 19 (listed from the bottom up on the left-hand side). The top and bottom weft yarns 1 - 50 are again listed right to left; [0031] FIG. 3 shows a photograph of a top side or paper facing side of an actual forming fabric utilizing the weave pattern shown in FIGS. 1-2 b; [0032] FIG. 4 shows a photograph of a bottom side or machine side of the forming fabric shown in FIG. 3 ; [0033] FIG. 5 shows a weave pattern repeat of a second embodiment of the present invention; [0034] FIG. 6 a shows a cross-section view of the repeat shown in FIG. 6 and illustrates binding warp yarns 1 , 3 , 5 , 7 and 9 (listed from the top down on the left-hand side) and bottom warp yarns 2 , 4 , 6 , 8 and 10 (listed from the top down on the left-hand side). The top and bottom weft yarns 1 - 45 are listed right to left; [0035] FIG. 6 b shows a cross-section view of the repeat shown in FIG. 6 and illustrates binding warp yarns 11 , 13 , 15 , 17 and 19 (listed from the top down on the left-hand side) and bottom warp yarns 12 , 14 , 16 , 18 and 20 (listed from the top down on the left-hand side). The top and bottom weft yarns 145 are again listed right to left; [0036] FIG. 7 shows a photograph of a top side or paper facing side of an actual forming fabric utilizing the weave pattern shown in FIGS. 5-6 b ; and [0037] FIG. 8 shows a photograph of a bottom side or machine side of the forming fabric shown in FIG. 7 . DETAILED DESCRIPTION OF THE INVENTION [0038] The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the present invention may be embodied in practice. [0039] FIG. 1 shows a first non-limiting embodiment of the invention and depicts a top pattern view of the top fabric layer of the multilayer fabric (i.e., a view of the papermaking surface). The numbers 1 - 20 shown on the bottom of the pattern identify the upper and lower warp yarns while the right side numbers 1 - 50 show the upper or top and lower or bottom weft yarns. The bottom warp yarns shown on the bottom of the pattern are 1 , 3 , 5 , 7 , 9 , 11 , 13 , 15 , 17 and 19 . The upper warp yarns shown on the bottom of the pattern are 2 , 4 , 6 , 8 , 10 , 12 , 14 , 16 , 18 and 20 . The upper weft yarns shown on the right side of the pattern are 1 , 3 , 5 , 6 , 8 , 10 , 11 , 13 ,: 15 , 16 , 18 , 20 , 21 , 23 , 25 , 26 , 28 , 30 , 31 , 33 , 35 , 36 , 38 , 40 , 41 , 43 , 45 , 46 , 48 and 50 . The lower weft yarns shown on the right side of the pattern are 2 , 4 , 7 , 9 , 12 , 14 , 17 , 19 , 22 , 24 , 27 , 29 , 32 , 34 , 37 , 39 , 42 , 44 , 47 and 49 . [0040] Also in FIG. 1 , a blank cell is shown in locations where a binding warp yarn passes under a top weft yarn while a bottom warp yarn passes under a bottom weft yarn. Symbol X is shown in locations where a binding warp yarn passes over a top weft yarn while a bottom warp yarn passes under a bottom weft yarn. A shaded cell is shown in locations where a binding warp yarn passes over a bottom weft yarn while a bottom warp yarn passes over the same bottom weft yarn. As used herein, the term “over” in reference to a weave pattern of a warp yarn in the top layer means that the yarn passes vertically above a paper-side surface of the fabric and then over a top weft yarn. The term “over” in reference to a weave pattern of a warp yarn in the bottom layer means that the yarn passes vertically below a machine-side surface and then over a top weft yarn as opposed to passing between the top and bottom weft yarns. [0041] FIGS. 2 a and 2 b depict the paths of the upper and lower warp yarns 1 - 20 as they weave through the upper and lower weft yarns 1 - 50 . The fabric of FIG. 1 thus shows a single repeat of the fabric that encompasses 50 weft yarns (yarns 1 - 50 represented horizontally in the figures) and 20 warp yarns (yarns 1 - 20 represented vertically in the figures). While FIGS. 1-2 b only show a single repeat unit of the fabric, those of skill in the art will appreciate that in commercial applications, the repeat unit shown in FIGS. 1-2 b would be repeated many times, in both the warp and weft directions, to form a large fabric suitable for use on a papermaking machine. [0042] As seen in FIG. 2 a , bottom warp yarn 1 passes under bottom weft yarns 2 , 4 , 7 , 9 , 12 and 14 , then passes over bottom weft yarn 17 , then passes under bottom weft yarns 19 and 22 , then passes over bottom weft yarn 24 , then passes under bottom weft yarns 27 , 29 , 32 , 34 , 37 and 39 , then passes over bottom weft yarn 42 , then passes under bottom weft yarns 44 and 47 , and then passes over bottom weft yarn 49 . The bottom warp yarn 1 weaves only in the bottom layer and only with non-adjacent bottom weft yarns, e.g., four non-adjacent bottom weft yarns 17 , 24 , 42 and 49 . [0043] Also seen in FIG. 2 a , binding warp yarn 2 passes from the bottom layer to the top layer by passing under top weft yarns 1 and 3 , then weaves with the top layer weft yarns 5 , 6 , 8 , 10 and 11 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 13 and 15 , then passes over bottom weft yarn 17 , then passes under bottom weft yarns 19 and 22 , then passes over bottom weft yarn 24 , then passes from the bottom layer to the top layer by passing under top weft yarns 25 , 26 , and 28 , then weaves with the top weft yarns 30 , 31 , 33 , 35 and 36 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 38 and 40 , then passes over bottom weft yarn 42 , then passes under bottom weft yarns 44 and 47 , then passes over bottom weft yarn 49 , and then begins to pass back to the top layer. The binding warp yarn 2 binds to the bottom layer by weaving with the same non-adjacent bottom weft yarns that the bottom warp yarn 1 was woven with, e.g., by passing over the four non-adjacent bottom weft yarns 17 , 24 , 42 and 49 . [0044] FIG. 2 a also illustrates bottom warp yarn 3 passing over bottom weft yarn 2 , then passes under bottom weft yarns 4 and 7 , then passes over bottom weft yarn 9 , then passes under bottom weft yarns 12 , 14 , 17 , 19 , 22 and 24 , then passes over bottom weft yarn 27 , then passes under bottom weft yarns 29 and 32 , then passes over bottom weft yarn 34 , and then passes under bottom weft yarns 37 , 39 , 42 , 44 , 47 and 49 . The bottom warp yarn 3 weaves only in the bottom layer and only with non-adjacent bottom weft yarns, e.g., four non-adjacent bottom weft yarns 2 , 9 , 27 and 34 . The pattern formed by bottom warp yarn 3 is the same as that of bottom warp yarn 1 except that it is shifted sideways by six bottom weft yarns. [0045] Also seen in FIG. 2 a , binding warp yarn 4 passes over bottom weft yarn 2 , then passes under bottom weft yarns 4 and 7 , then passes over bottom weft yarn 9 , then passes from the bottom layer to the top layer by passing under top weft yarns 10 , 11 and 13 , then weaves with the top layer weft yarns 15 , 16 , 18 , 20 and 21 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 23 and 25 , then passes over bottom weft yarn 27 , then passes under bottom weft yarns 29 and 32 , then passes over bottom weft yarn 34 , then passes from the bottom layer to the top layer by passing under top weft yarns 35 , 36 , and 38 , then weaves with the top weft yarns 40 , 41 , 43 , 45 and 46 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 48 and 50 . The binding warp yarn 4 binds to the bottom layer by weaving with the same non-adjacent bottom weft yarns that the bottom warp yarn 3 was woven with, e.g., by passing over the four non-adjacent bottom weft yarns 2 , 9 , 27 and 34 . The pattern formed by binding warp yarn 4 is the same as that of binding warp yarn 2 except that it is shifted sideways by six top weft yarns. [0046] FIG. 2 a additionally shows bottom warp yarn 5 passing under bottom weft yarns 2 , 4 , 7 and 9 , then passes over bottom weft yarn 12 , then passes under bottom weft yarns 14 and 17 , then passes over bottom weft yarn 19 , then passes under bottom weft yarns 22 , 24 , 27 , 29 , 32 and 34 , then passes over bottom weft yarn 37 , then passes under bottom weft yarns 39 and 42 , and then passes over bottom weft yarn 44 , then passes under bottom weft yarns 47 and 49 . The bottom warp yarn 5 weaves only in the bottom layer and only with non-adjacent bottom weft yarns, e.g., four non-adjacent bottom weft yarns 12 , 19 , 37 and 44 . The pattern formed by bottom warp yarn 5 is the same as that of bottom warp yarn 3 except that it is shifted sideways by four bottom weft yarns. [0047] Also seen in FIG. 2 a , binding warp yarn 6 weaves with the top weft yarns 1 , 3 , 5 and 6 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 8 and 10 , then passes over bottom weft yarn 12 , then passes under bottom weft yarns 14 and 17 , then passes over bottom weft yarn 19 , then passes from the bottom layer to the top layer by passing under top weft yarns 20 , 21 and 23 , then weaves with the top weft yarns 25 , 26 , 28 , 30 and 31 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 33 and 35 , then passes over bottom weft yarn 37 , then passes under bottom weft yarns 39 and 42 , then passes over bottom weft yarn 44 , then passes from the bottom layer to the top layer by passing under top weft yarns 45 , 46 and 48 , then passes over top weft yarn 50 . The binding warp yarn 6 binds to the bottom layer by weaving with the same non-adjacent bottom weft yarns that the bottom warp yarn 5 was woven with, e.g., by passing over the four non-adjacent bottom weft yarns 12 , 19 , 37 and 44 . The pattern formed by binding warp yarn 6 is the same as that of binding warp yarn 4 except that it is shifted sideways by six top weft yarns. [0048] FIG. 2 a further shows bottom warp yarn 7 passing under bottom weft yarn 2 , then passes over bottom weft yarn 4 , then passes under bottom weft yarns 7 , 9 , 12 , 14 , 17 and 19 , then passes over bottom weft yarn 22 , then passes under bottom weft yarns 24 and 27 , then passes over bottom weft yarn 29 , then passes under bottom weft yarns 32 , 34 , 37 , 39 , 42 and 44 , and then passes over bottom weft yarn 44 , then passes under bottom weft yarn 49 . The bottom warp yarn 7 weaves only in the bottom layer and only with non-adjacent bottom weft yarns, e.g., four non-adjacent bottom weft yarns 4 , 22 , 29 and 47 . The pattern formed by bottom warp yarn 7 is the same as that of bottom warp yarn 5 except that it is shifted sideways by four bottom weft yarns. [0049] Also seen in FIG. 2 a , binding warp yarn 8 passes under bottom weft yarn 2 , then passes over bottom weft yarn 4 , then passes from the bottom layer to the top layer by passing under top weft yarns 5 , 6 and 8 , then weaves with the top weft yarns 10 , 11 , 13 , 15 and 16 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 18 and 20 , then passes over bottom weft yarn 22 , then passes under bottom weft yarns 24 and 27 , then passes over bottom weft yarn 29 , then passes from the bottom layer to the top layer by passing under top weft yarns 30 , 31 and 33 , then weaves with the top weft yarns 35 , 36 , 38 , 40 and 41 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 43 and 45 , then passes over bottom weft yarn 47 , then passes under bottom weft yarn 49 . The binding warp yarn 8 binds to the bottom layer by weaving with the same non-adjacent bottom weft yarns that the bottom warp yarn 7 was woven with, e.g., by passing over the four non-adjacent bottom weft yarns 4 , 22 , 29 and 47 . The pattern formed by binding warp yarn 8 is the same as that of binding warp yarn 6 except that it is shifted sideways by six top weft yarns. [0050] Additionally, FIG. 2 a shows bottom warp yarn 9 passing under bottom weft yarns 2 and 4 , then passes over bottom weft yarn 7 , then passes under bottom weft yarns 9 and 12 , then passes over bottom weft yarn 14 , then passes under bottom weft yarns 17 , 19 , 22 , 24 , 27 and 29 , then passes over bottom weft yarn 32 , then passes under bottom weft yarns 34 and 37 , and then passes over bottom weft yarn 39 , then passes under bottom weft yarns 42 , 44 , 47 and 49 . The bottom warp yarn 9 weaves only in the bottom layer and only with non-adjacent bottom weft yarns, e.g., four non-adjacent bottom weft yarns 7 , 14 , 32 and 39 . The pattern formed by bottom warp yarn 9 is the same as that of bottom warp yarn 7 except that it is shifted sideways by four bottom weft yarns. [0051] Finally, FIG. 2 a shows binding warp yarn 10 passing over the top weft yarn 1 , then passes from the top layer to the bottom layer by passing under top weft yarns 3 and 5 , then passes over bottom weft yarn 7 , then passes under bottom weft yarns 9 and 12 , then passes over bottom weft yarn 14 , then passes from the bottom layer to the top layer by passing under top weft yarns 15 , 16 and 18 , then weaves with the top weft yarns 20 , 21 , 23 , 25 and 26 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 28 and 30 , then passes over bottom weft yarn 32 , then passes under bottom weft yarns 34 and 37 , then passes over bottom weft yarn 39 , then passes from the bottom layer to the top layer by passing under top weft yarns 40 , 41 and 43 , then weaves with binding warp yarns 45 , 46 , 48 and 50 to form a plain weave. The binding warp yarn 10 binds to the bottom layer by weaving with the same non-adjacent bottom weft yarns that the bottom warp yarn 9 was woven with, e.g., by passing over the four non-adjacent bottom weft yarns 7 , 14 , 32 and 39 . The pattern formed by binding warp yarn 10 is the same as that of binding warp yarn 8 except that it is shifted sideways by six top weft yarns. [0052] With reference to FIG. 2 b , bottom warp yarn 11 passes under bottom weft yarns 2 , 4 , 7 , 9 , 12 and 14 , then passes over bottom weft yarn 17 , then passes under bottom weft yarns 19 and 22 , then passes over bottom weft yarn 24 , then passes under bottom weft yarns 27 , 29 , 32 , 34 , 37 and 39 , then passes over bottom weft yarn 42 , then passes under bottom weft yarns 44 and 47 , and then passes over bottom weft yarn 49 . The bottom warp yarn 11 weaves only in the bottom layer and only with non-adjacent bottom weft yarns, e.g., four non-adjacent bottom weft yarns 17 , 24 , 42 and 49 . [0053] Also seen in FIG. 2 b , binding warp yarn 12 passes from the bottom layer to the top layer by passing under top weft yarns 1 and 3 , then weaves with the top layer weft yarns 5 , 6 , 8 , 10 and 11 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 13 and 15 , then passes over bottom weft yarn 17 , then passes under bottom weft yarns 19 and 22 , then passes over bottom weft yarn 24 , then passes from the bottom layer to the top layer after passing under top weft yarns 25 , 26 , and 28 , then weaves with the top weft yarns 30 , 31 , 33 , 35 and 36 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 38 and 40 , then passes over bottom weft yarn 42 , then passes under bottom weft yarns 44 and 47 , then passes over bottom weft yarn 49 , and then begins to pass back to the top layer. The binding warp yarn 12 binds to the bottom layer by weaving with the same non-adjacent bottom weft yarns that the bottom warp yarn 11 was woven with, e.g., by passing over the four non-adjacent bottom weft yarns 17 , 24 , 42 and 49 . [0054] FIG. 2 b also illustrates bottom warp yarn 13 passing over bottom weft yarn 2 , then passes under bottom weft yarns 4 and 7 , then passes over bottom weft yarn 9 , then passes under bottom weft yarns 12 , 14 , 17 , 19 , 22 and 24 , then passes over bottom weft yarn 27 , then passes under bottom weft yarns 29 and 32 , then passes over bottom weft yarn 34 , and then passes under bottom weft yarns 37 , 39 , 42 , 44 , 47 and 49 . The bottom warp yarn 13 weaves only in the bottom layer and only with non-adjacent bottom weft yarns, e.g., four non-adjacent bottom weft yarns 2 , 9 , 27 and 34 . The pattern formed by bottom warp yarn 13 is the same as that of bottom warp yarn 11 except that it is shifted sideways by six bottom weft yarns. [0055] Also seen in FIG. 2 b , binding warp yarn 14 passes over bottom weft yarn 2 , then passes under bottom weft yarns 4 and 7 , then passes over bottom weft yarn 9 , then passes from the bottom layer to the top layer by passing under top weft yarns 10 , 11 and 13 , then weaves with the top layer weft yarns 15 , 16 , 18 , 20 and 21 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 23 and 25 , then passes over bottom weft yarn 27 , then passes under bottom weft yarns 29 and 32 , then passes over bottom weft yarn 34 , then passes from the bottom layer to the top layer by passing under top weft yarns 35 , 36 , and 38 , then weaves with the top weft yarns 40 , 41 , 43 , 45 and 46 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 48 and 50 . The binding warp yarn 14 binds to the bottom layer by weaving with the same non-adjacent bottom weft yarns that the bottom warp yarn 13 was woven with, e.g., by passing over the four non-adjacent bottom weft yarns 2 , 9 , 27 and 34 . The pattern formed by binding warp yarn 14 is the same as that of binding warp yarn 12 except that it is shifted sideways by six top weft yarns. [0056] FIG. 2 b also illustrates bottom warp yarn 15 passing under bottom weft yarns 2 , 4 , 7 and 9 , then passes over bottom weft yarn 12 , then passes under bottom weft yarns 14 and 17 , then passes over bottom weft yarn 19 , then passes under bottom weft yarns 22 , 24 , 27 , 29 , 32 and 34 , then passes over bottom weft yarn 37 , then passes under bottom weft yarns 39 and 42 , and then passes over bottom weft yarn 44 , then passes under bottom weft yarns 47 and 49 . The bottom warp yarn 15 weaves only in the bottom layer and only with non-adjacent bottom weft yarns, e.g., four non-adjacent bottom weft yarns 12 , 19 , 37 and 44 . The pattern formed by bottom warp yarn 15 is the same as that of bottom warp yarn 13 except that it is shifted sideways by four bottom weft yarns. [0057] Also seen in FIG. 2 b , binding warp yarn 16 weaves with the top weft yarns 1 , 3 , 5 and 6 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 8 and 10 , then passes over bottom weft yarn 12 , then passes under bottom weft yarns 14 and 17 , then passes over bottom weft yarn 19 , then passes from the bottom layer to the top layer by passing under top weft yarns 20 , 21 and 23 , then weaves with the top weft yarns 25 , 26 , 28 , 30 and 31 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 33 and 35 , then passes over bottom weft yarn 37 , then passes under bottom weft yarns 39 and 42 , then passes over bottom weft yarn 44 , then passes from the bottom layer to the top layer by passing under top weft yarns 45 , 46 and 48 , then passes over top weft yarn 50 . The binding warp yarn 16 binds to the bottom layer by weaving with the same non-adjacent bottom weft yarns that the bottom warp yarn 15 was woven with, e.g., by passing over the four non-adjacent bottom weft yarns 12 , 19 , 37 and 44 . The pattern formed by binding warp yarn 16 is the same as that of binding warp yarn 14 except that it is shifted sideways by six top weft yarns. [0058] FIG. 2 b further illustrates bottom warp yarn 17 passing under bottom weft yarn 2 , then passes over bottom weft yarn 4 , then passes under bottom weft yarns 7 , 9 , 12 , 14 , 17 and 19 , then passes over bottom weft yarn 22 , then passes under bottom weft yarns 24 and 27 , then passes over bottom weft yarn 29 , then passes under bottom weft yarns 32 , 34 , 37 , 39 , 42 and 44 , and then passes over bottom weft yarn 44 , then passes under bottom weft yarn 49 . The bottom warp yarn 17 weaves only in the bottom layer and only with non-adjacent bottom weft yarns, e.g., four non-adjacent bottom weft yarns 4 , 22 , 29 and 47 . The pattern formed by bottom warp yarn 17 is the same as that of bottom warp yarn 15 except that it is shifted sideways by four bottom weft yarns. [0059] FIG. 2 b further shows binding warp yarn 18 passing under bottom weft yarn 2 , then passes over bottom weft yarn 4 , then passes from the bottom layer to the top layer by passing under top weft yarns 5 , 6 and 8 , then weaves with the top weft yarns 10 , 11 , 13 , 15 and 16 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 18 and 20 , then passes over bottom weft yarn 22 , then passes under bottom weft yarns 24 and 27 , then passes over bottom weft yarn 29 , then passes from the bottom layer to the top layer by passing under top weft yarns 30 , 31 and 33 , then weaves with the top weft yarns 35 , 36 , 38 , 40 and 41 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 43 and 45 , then passes over bottom weft yarn 47 , then passes under bottom weft yarn 49 . The binding warp yarn 18 binds to the bottom layer by weaving with the same non-adjacent bottom weft yarns that the bottom warp yarn 17 was woven with, e.g., by passing over the four non-adjacent bottom weft yarns 4 , 22 , 29 and 47 . The pattern formed by binding warp yarn 18 is the same as that of binding warp yarn 16 except that it is shifted sideways by six top weft yarns. [0060] FIG. 2 b also shows bottom warp yarn 19 passing under bottom weft yarns 2 and 4 , then passes over bottom weft yarn 7 , then passes under bottom weft yarns 9 and 12 , then passes over bottom weft yarn 14 , then passes under bottom weft yarns 17 , 19 , 22 , 24 , 27 and 29 , then passes over bottom weft yarn 32 , then passes under bottom weft yarns 34 and 37 , and then passes over bottom weft yarn 39 , then passes under bottom weft yarns 42 , 44 , 47 and 49 . The bottom warp yarn 19 weaves only in the bottom layer and only with non-adjacent bottom weft yarns, e.g., four non-adjacent bottom weft yarns 7 , 14 , 32 and 39 . The pattern formed by bottom warp yarn 19 is the same as that of bottom warp yarn 17 except that it is shifted sideways by four bottom weft yarns. [0061] Finally, as seen in FIG. 2 b , binding warp yarn 20 passes over the top weft yarn 1 , then passes from the top layer to the bottom layer by passing under top weft yarns 3 and 5 , then passes over bottom weft yarn 7 , then passes under bottom weft yarns 9 and 12 , then passes over bottom weft yarn 14 , then passes from the bottom layer to the top layer by passing under top weft yarns 15 , 16 and 18 , then weaves with the top weft yarns 20 , 21 , 23 , 25 and 26 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 28 and 30 , then passes over bottom weft yarn 32 , then passes under bottom weft yarns 34 and 37 , then passes over bottom weft yarn 39 , then passes from the bottom layer to the top layer by passing under top weft yarns 40 , 41 and 43 , then weaves with binding warp yarns 45 , 46 , 48 and 50 to form a plain weave. The binding warp yarn 20 binds to the bottom layer by weaving with the same non-adjacent bottom weft yarns that the bottom warp yarn 19 was woven with, e.g., by passing over the four non-adjacent bottom weft yarns 7 , 14 , 32 and 39 . The pattern formed by binding warp yarn 20 is the same as that of binding warp yarn 18 except that it is shifted sideways by six top weft yarns. [0062] As is apparent from a comparison of FIG. 2 a and 2 b , the paths taken by the warp yarns 1 - 10 through the weft yarns 1 - 50 are respectively the same as paths taken by the warp yarns 11 - 20 through the weft yarns 1 - 50 , i.e., warp yarn 1 has the same path through the weft yarns 1 - 50 as warp yarn 11 , warp yarn 2 has the same path through the weft yarns 1 - 50 as warp yarn 12 , etc,. [0063] FIG. 3 shows a photograph of a top side or paper facing side of an actual forming fabric utilizing the weave pattern shown in FIG. 1 and FIG. 4 shows a photograph of a bottom side or machine side of the forming fabric shown in FIG. 3 . [0064] By way of non-limiting example, the binding warp yarns 2 , 4 , 6 , 8 , 10 , 12 , 14 , 16 , 18 and 20 of the embodiment shown in FIGS. 1-2 b can have the following characteristics: acceptable size range of between approximately 0.10 mm and approximately 0.50 mm, preferable size ranges of between approximately 0.20 mm and approximately 0.80 mm, and most preferred size range of between approximately 0.12 mm and approximately 0.20 mm. The material for these yarns can be any natural or synthetic material, preferably a synthetic monofilament, and most preferably a polyester monofilament. [0065] By way of non-limiting example, the bottom warp yarns 1 , 3 , 5 , 7 , 9 , 11 , 13 , 15 , 17 and 19 of the embodiment shown in FIGS. 1-2 b can have the following characteristics: acceptable size range of between approximately 0.15 mm and approximately 0.60 mm, preferable size ranges of between approximately 0.20 mm and approximately 0.40 mm, and most preferred size range of between approximately 0.25 mm and approximately 0.35 mm. The material for these yarns can be any natural or synthetic material, preferably a synthetic monofilament, and most preferably a polyester monofilament. The bottom warp yarns can preferably be constructed using relatively large diameter yarns that are well suited to sustain the wear caused by the friction between the machine side surface of the fabric and the papermaking machine during use of the fabric. [0066] By way of non-limiting example, the top weft yarns 1 , 3 , 5 , 6 , 8 , 10 , 11 , 13 , 15 , 16 , 18 , 20 , 21 , 23 , 25 , 26 , 28 , 30 , 31 , 33 , 35 , 36 , 38 , 40 , 41 , 43 , 45 , 46 , 48 and 50 of the embodiment shown in FIGS. 1-2 b can have the following characteristics: acceptable size range of between approximately 0.10 mm and approximately 0.50 mm, preferable size ranges of between approximately 0.20 mm and approximately 0.80 mm, and most preferred size range of between approximately 0.12 mm and approximately 0.80 mm. The material for these yarns can be any natural or synthetic material, preferably a synthetic monofilament, and most preferably a polyester monofilament. [0067] By way of non-limiting example, the bottom weft yarns 2 , 4 , 7 , 9 , 12 , 14 , 17 , 19 , 22 , 24 , 27 , 29 , 32 , 34 , 37 , 39 , 42 , 44 , 47 and 49 of the embodiment shown in FIGS. 1-2 b can have the following characteristics: acceptable size range of between approximately 0.15 mm and approximately 0.60 mm, preferable size ranges of between approximately 0.20 mm and approximately 0.40 mm, and most preferred size range of between approximately 0.25 mm and approximately 0.35 mm. The material for these yarns can be any natural or synthetic material, preferably a synthetic monofilament, and most preferably a polyester monofilament. These bottom weft yarns may also be constructed using larger diameter yarns than the upper warp yarns. [0068] In the embodiment shown in FIGS. 1-2 b all of the binding warp yarns form a plain weave in the top layer by weaving with five top weft yarns and bind to the bottom layer by weaving with four bottom weft yarns with a non-plain weave in two spaced apart locations, i.e., spaced apart by ten top weft yarns and/or sic bottom weft yarns in each repeat of the fabric. Furthermore, all of the bottom warp yarns weave only in the bottom layer. Additionally, when a binding warp yarn passes from the bottom layer to the top layer, it passes under three adjacent top weft yarns before weaving with a plain weave in the top layer. When a binding warp yarn passes from the top layer to the bottom layer, it passes under two adjacent top weft yarns before weaving with a non-plain weave in the bottom layer. Thus, the area of the plain weave (between a binding warp yarn and top weft yarns) is off-center with respect to an area or spacing between the two areas where the same binding warp yarn weaves to the bottom layer. Also, in the area or spacing between two the plain weave areas (between a binding warp yarn and top weft yarns), the area where the binding warp weaves with the bottom layer is off-center. These features are also desirable in numerous papermaking applications. [0069] FIG. 5 shows a second non-limiting embodiment of the invention and depicts a top pattern view of the top fabric layer of the multilayer fabric (i.e., a view of the papermaking surface). The numbers 1 - 20 shown on the bottom of the pattern identify the upper and lower warp yarns while the right side numbers 1 - 45 show the upper and lower weft yarns. The upper warp yarns shown on the bottom of the pattern are 1 , 3 , 5 , 7 , 9 , 11 , 13 , 15 , 17 and 19 . The lower warp yarns shown on the bottom of the pattern are 2 , 4 , 6 , 8 , 10 , 12 , 14 , 16 , 18 and 20 . The top weft yarns shown on the right side of the pattern are 1 , 3 , 4 , 6 , 7 , 9 , 10 , 12 , 13 , 15 , 16 , 18 , 19 , 21 , 22 , 24 , 25 , 27 , 28 , 30 , 31 , 33 , 34 , 36 , 37 , 39 , 40 , 42 , 43 and 45 . The bottom weft yarns shown on the right side of the pattern are 2 , 5 , 8 , 11 , 14 , 17 , 20 , 23 , 26 , 29 , 32 , 35 , 38 , 41 and 44 . [0070] Also in FIG. 5 , a blank cell is shown in locations where a binding warp yarn passes under a top weft yarn while a bottom warp yarn passes under a bottom weft yarn. Symbol X is shown in locations where a binding warp yarn passes over a top weft yarn while a bottom warp yarn passes under a bottom weft yarn. A shaded cell is shown in locations where a binding warp yarn passes over a bottom weft yarn while a bottom warp yarn passes over the same bottom weft yarn. As used herein, the term “over” in reference to a weave pattern of a warp yarn in the top layer means that the yarn passes vertically above a paper-side surface of the fabric and then over a top weft yarn. The term “over” in reference to a weave pattern of a warp yarn in the bottom layer means that the yarn passes vertically below a machine-side surface and then over a top weft yarn as opposed to passing between the top and bottom weft yarns. [0071] FIGS. 6 a and 6 b depict the paths of the upper and lower warp yarns 1 - 20 as they weave through the upper and lower weft yarns 1 - 45 . The fabric of FIG. 5 thus shows a single repeat of the fabric that encompasses 45 weft yarns (yarns 1 - 45 represented horizontally in the figures) and 20 warp yarns (yarns 1 - 20 represented vertically in the figures). While FIGS. 5-6 b only show a single repeat unit of the fabric, those of skill in the art will appreciate that in commercial applications, the repeat unit shown in FIGS. 5-6 b would be repeated many times, in both the warp and weft directions, to form a large fabric suitable for use on a papermaking machine. [0072] As seen in FIG. 6 a , binding warp yarn 1 passes from the bottom layer to the top layer by passing under top weft yarns 1 and 3 , then weaves with the top layer weft yarns 4 , 6 , 7 , 9 and 10 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 12 , 13 and 15 , then passes over bottom weft yarn 17 , then passes under bottom weft yarn 20 , then passes over bottom weft yarn 23 , then passes from the bottom layer to the top layer by passing under top weft yarns 24 and 25 , then weaves with the top weft yarns 27 , 28 , 30 , 31 and 33 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 34 and 36 , then passes over bottom weft yarn 38 , then passes back to the top layer by passing under top weft yarns 39 , 40 , 42 , 43 and 45 . The binding warp yarn 1 binds to the bottom layer by weaving with the same adjacent bottom weft yarns that the bottom warp yarn 2 was woven with, e.g., by passing over the three non-adjacent bottom weft yarns 17 , 23 and 38 . [0073] Also seen in FIG. 6 a , bottom warp yarn 2 passes under bottom weft yarns 2 , 5 , 8 , 11 and 14 , then passes over bottom weft yarn 17 , then passes under bottom weft yarn 20 , then passes over bottom weft yarn 23 , then passes under bottom weft yarns 26 , 29 , 32 and 35 , then passes over bottom weft yarn 38 , then passes under bottom weft yarns 41 and 44 . The bottom warp yarn 2 weaves only in the bottom layer, weaves first with three adjacent bottom weft yarns, e.g., bottom weft yarns 17 , 20 and 23 , and then binds with only one bottom weft yarn, e.g., bottom weft yarn 38 . [0074] FIG. 6 a also illustrates binding warp yarn 3 passing over bottom weft yarn 2 , then passes under bottom weft yarns 3 , 4 , 6 , 7 , 9 , 10 and 12 , then weaves with the top layer weft yarns 13 , 15 , 16 , 18 and 19 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 21 , 22 and 24 , then passes over bottom weft yarn 26 , then passes under bottom weft yarn 29 , then passes over bottom weft yarn 32 , then passes from the bottom layer to the top layer by passing under top weft yarns 33 and 34 , then weaves with the top weft yarns 36 , 37 , 39 , 40 and 42 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 43 and 45 . The binding warp yarn 3 binds to the bottom layer by weaving with the same bottom weft yarns that the bottom warp yarn 4 was woven with, e.g., by passing over the three non-adjacent bottom weft yarns 2 , 26 and 32 . The pattern formed by binding warp yarn 3 is different from that of binding warp yarn 1 in both position and weaving path. [0075] Also seen in FIG. 6 a , bottom warp yarn 4 passes over bottom weft yarn 2 , then passes under bottom weft yarns 5 , 8 , 11 , 14 , 17 , 20 and 23 , then passes over bottom weft yarn 26 , then passes under bottom weft yarn 29 , then passes over bottom weft yarn 32 , then passes under bottom weft yarns 35 , 38 , 41 and 44 . The bottom warp yarn 4 weaves only in the bottom layer, weaves first with one bottom weft yarn, e.g., bottom weft yarn 2 , and then weaves with three bottom weft yarns, e.g., bottom, weft yarns 26 , 29 and 32 . The pattern formed by bottom warp yarn 4 is the same as that of bottom warp yarn 2 except that it is shifted sideways by three bottom weft yarns. [0076] FIG. 6 a also shows binding warp yarn 5 weaving with the top weft yarns 1 , 3 , 4 and 6 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 7 and 9 , then passes over bottom weft yarn 11 , then passes from the bottom layer to the top layer by passing under top weft yarns 12 , 13 , 15 , 16 , 18 , 19 and 21 , then weaves with the top weft yarns 22 , 24 , 25 , 27 and 28 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 30 , 31 and 33 , then passes over bottom weft yarn 35 , then passes under bottom weft yarn 38 , then passes over bottom weft yarn 41 , then passes from the bottom layer to the top layer by passing under top weft yarns 42 and 43 , then passes over top weft yarn 45 . The binding warp yarn 5 binds to the bottom layer by weaving with the same bottom weft yarns that the bottom warp yarn 6 weaves with, e.g., by passing over the three non-adjacent bottom weft yarns 11 , 35 and 41 . The pattern formed by binding warp yarn 5 is the same as that of binding warp yarn 3 except that it is shifted sideways by nine top weft yarns. [0077] As seen in FIG. 6 a , bottom warp yarn 6 passes under bottom weft yarns 2 , 5 and 8 , then passes over bottom weft yarn 11 , then passes under bottom weft yarns 14 , 17 , 20 , 23 , 26 , 29 and 32 , then passes over bottom weft yarn 35 , then passes under bottom weft yarn 38 , then passes over bottom weft yarn 41 , then passes under bottom weft yarn 44 . The bottom warp yarn 6 weaves only in the bottom layer, weaves first with one bottom weft yarn, e.g., bottom weft yarn 11 , and then weaves with three bottom weft yarns, e.g., bottom weft yarns 35 , 38 and 41 . The pattern formed by bottom warp yarn 6 is the same as that of bottom warp yarn 4 except that it is shifted sideways by three bottom weft yarns. [0078] Additionally, FIG. 6 a shows binding warp yarn 7 passing from the top layer to the bottom layer by passing under top weft yarns 1 and 3 , then under bottom weft yarn 5 , then passes from the bottom layer to the top layer by passing under top weft yarns 6 and 7 , then weaves with the top weft yarns 9 , 10 , 12 , 13 and 15 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 16 and 18 , then passes over bottom weft yarn 20 , then passes from the bottom layer to the top layer by passing under top weft yarns 21 , 22 , 24 , 25 , 27 , 28 and 30 , then weaves with the top weft yarns 31 , 33 , 34 , 36 and 37 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 39 , 40 and 42 , then passes over bottom weft yarn 44 , then begins to pass back to the top layer from the bottom layer by passing under top weft yarn 45 . The binding warp yarn 7 binds to the bottom layer by weaving with the same non-adjacent bottom weft yarns that the bottom warp yarn 8 weaves with, e.g., by passing over the three non-adjacent bottom weft yarns 5 , 20 and 44 . The pattern formed by binding warp yarn 7 is different from that of the binding warp yarns 1 , 3 , 5 and 9 . [0079] As seen in FIG. 6 a , bottom warp yarn 8 passes under bottom weft yarn 2 , then passes over bottom weft yarn 5 , then passes under bottom weft yarns 8 , 11 , 14 and 17 , then passes over bottom weft yarn 20 , then passes under bottom weft yarns 23 , 26 , 29 , 32 , 35 , 38 and 41 , then passes over bottom weft yarn 44 . The bottom warp yarn 8 weaves only in the bottom layer and only with non-adjacent bottom weft yarns, e.g., three non-adjacent bottom weft yarns 5 , 20 and 44 . The pattern formed by bottom warp yarn 8 is different from that of the bottom warp yarns 2 , 4 , 6 and 10 . [0080] Furthermore, FIG. 6 a shows binding warp yarn 9 passing over the top weft yarn 1 , then passes from the top layer to the bottom layer by passing under top weft yarns 3 , 4 and 6 , then passes over bottom weft yarn 8 , then passes under bottom weft yarn 11 , then passes over bottom weft yarn 14 , then passes from the bottom layer to the top layer by passing under top weft yarns 15 and 16 , then weaves with the top weft yarns 18 , 19 , 21 , 22 and 24 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 25 and 27 , then passes over bottom weft yarn 29 , then passes from the bottom layer to the top layer by passing under top weft yarns 30 , 31 , 33 , 34 , 36 , 37 and 39 , then weaves with top weft yarns 40 , 42 , 43 and 45 to form a plain weave. The binding warp yarn 9 binds to the bottom layer by weaving with the same bottom weft yarns that the bottom warp yarn 10 weaves with, e.g., by passing over the three non-adjacent bottom weft yarns 8 , 14 and 29 . The pattern formed by binding warp yarn 9 is the same as that of binding warp yarn 1 except that it is shifted sideways by six top weft yarns. [0081] Finally, as seen in FIG. 6 a , bottom warp yarn 10 passes under bottom weft yarns 2 and 5 , then passes over bottom weft yarn 8 , then passes under bottom weft yarn 11 , then passes over bottom weft yarn 14 , then passes under bottom weft yarns 17 , 20 , 23 and 26 , then passes over bottom weft yarn 29 , then passes under bottom weft yarns 32 , 35 , 38 , 41 and 44 . The bottom warp yarn 10 weaves only in the bottom layer and only with non-adjacent bottom weft yarns, e.g., three bottom weft yarns 8 , 14 and 29 . The pattern formed by bottom warp yarn 10 is the same as that of bottom warp yarn 2 except that it is shifted sideways by three bottom weft yarns. [0082] With reference to FIG. 6 b , binding warp yarn 11 passes from the bottom layer to the top layer by passing under top weft yarns 1 and 3 , then weaves with the top layer weft yarns 4 , 6 , 7 , 9 and 10 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 12 , 13 and 15 , then passes over bottom weft yarn 17 , then passes under bottom weft yarn 20 , then passes over bottom weft yarn 23 , then passes from the bottom layer to the top layer by passing under top weft yarns 24 and 25 , then weaves with the top weft yarns 27 , 28 , 30 , 31 and 33 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 34 and 36 , then passes over bottom weft yarn 38 , then passes back to the top layer by passing under top weft yarns 39 , 40 , 42 , 43 and 45 . The binding warp yarn 11 binds to the bottom layer by weaving with the same adjacent bottom weft yarns that the bottom warp yarn 12 was woven with, e.g., by passing over the three non-adjacent bottom weft yarns 17 , 23 and 38 . [0083] Also seen in FIG. 6 b , bottom warp yarn 12 passes under bottom weft yarns 2 , 5 , 8 , 11 and 14 , then passes over bottom weft yarn 17 , then passes under bottom weft yarn 20 , then passes over bottom weft yarn 23 , then passes under bottom weft yarns 26 , 29 , 32 and 35 , then passes over bottom weft yarn 38 , then passes under bottom weft yarns 41 and 44 . The bottom warp yarn 12 weaves only in the bottom layer, weaves first with three adjacent bottom weft yarns, e.g., bottom weft yarns 17 , 20 and 23 , and then binds with only one bottom weft yarn, e.g., bottom weft yarn 38 . [0084] FIG. 6 b also illustrates binding warp yarn 13 passing over bottom weft yarn 2 , then passes under bottom weft yarns 3 , 4 , 6 , 7 , 9 , 10 and 12 , then weaves with the top layer weft yarns 13 , 15 , 16 , 18 and 19 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 21 , 22 and 24 , then passes over bottom weft yarn 26 , then passes under bottom weft yarn 29 , then passes over bottom weft yarn 32 , then passes from the bottom layer to the top layer by passing under top weft yarns 33 and 34 , then weaves with the top weft yarns 36 , 37 , 39 , 40 and 42 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 43 and 45 . The binding warp yarn 13 binds to the bottom layer by weaving with the same bottom weft yarns that the bottom warp yarn 14 was woven with, e.g., by passing over the three non-adjacent bottom weft yarns 2 , 26 and 32 . The pattern formed by binding warp yarn 13 is different from that of binding warp yarn 11 in both position and weaving path. [0085] Also seen in FIG. 6 b , bottom warp yarn 14 passes over bottom weft yarn 2 , then passes under bottom weft yarns 5 , 8 , 11 , 14 , 17 , 20 and 23 , then passes over bottom weft yarn 26 , then passes under bottom weft yarn 29 , then passes over bottom weft yarn 32 , then passes under bottom weft yarns 35 , 38 , 41 and 44 . The bottom warp yarn 14 weaves only in the bottom layer, weaves first with one bottom weft yarn, e.g., bottom weft yarn 2 , and then weaves with three bottom weft yarns, e.g., bottom weft yarns 26 , 29 and 32 . The pattern formed by bottom warp yarn 14 is the same as that of bottom warp yarn 12 except that it is shifted sideways by three bottom weft yarns. [0086] FIG. 6 b also illustrates binding warp yarn 15 weaving with the top weft yarns 1 , 3 , 4 and 6 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 7 and 9 , then passes over bottom weft yarn 11 , then passes from the bottom layer to the top layer by passing under top weft yarns 12 , 13 , 15 , 16 , 18 , 19 and 21 , then weaves with the top weft yarns 22 , 24 , 25 , 27 and 28 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 30 , 31 and 33 , then passes over bottom weft yarn 35 , then passes under bottom weft yarn 38 , then passes over bottom weft yarn 41 , then passes from the bottom layer to the top layer by passing under top weft yarns 42 and 43 , then passes over top weft yarn 45 . The binding warp yarn 15 binds to the bottom layer by weaving with the same bottom weft yarns that the bottom warp yarn 16 weaves with, e.g., by passing over the three non-adjacent bottom weft yarns 11 , 35 and 41 . The pattern formed by binding warp yarn 15 is the same as that of binding warp yarn 13 except that it is shifted sideways by nine top weft yarns. [0087] Additionally, FIG. 6 b shows bottom warp yarn 16 passing under bottom weft yarns 2 , 5 and 8 , then passes over bottom weft yarn 11 , then passes under bottom weft yarns 14 , 17 , 20 , 23 , 26 , 29 and 32 , then passes over bottom weft yarn 35 , then passes under bottom weft yarn 38 , then passes over bottom weft yarn 41 , then passes under bottom weft yarn 44 . The bottom warp yarn 16 weaves only in the bottom layer, weaves first with one bottom weft yarn, e.g., bottom weft yarn 11 , and then weaves with three bottom weft yarns, e.g., bottom weft yarns 35 , 38 and 41 . The pattern formed by bottom warp yarn 16 is the same as that of bottom warp yarn 14 except that it is shifted sideways by three bottom weft yarns. [0088] Also seen in FIG. 6 b , binding warp yarn 17 passes from the top layer to the bottom layer by passing under top weft yarns 1 and 3 , then under bottom weft yarn 5 , then passes from the bottom layer to the top layer by passing under top weft yarns 6 and 7 , then weaves with the top weft yarns 9 , 10 , 12 , 13 and 15 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 16 and 18 , then passes over bottom weft yarn 20 , then passes from the bottom layer to the top layer by passing under top weft yarns 21 , 22 , 24 , 25 , 27 , 28 and 30 , then weaves with the top weft yarns 31 , 33 , 34 , 36 and 37 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 39 , 40 and 42 , then passes over bottom weft yarn 44 , then begins to pass back to the top layer from the bottom layer by passing under top weft yarn 45 . The binding warp yarn 17 binds to the bottom layer by weaving with the same non-adjacent bottom weft yarns that the bottom warp yarn 18 weaves with, e.g., by passing over the three non-adjacent bottom weft yarns 5 , 20 and 44 . The pattern formed by binding warp yarn 17 is different from that of the binding warp yarns 11 , 13 , 15 and 19 . [0089] FIG. 6 b also illustrates bottom warp yarn 18 passing under bottom weft yarn 2 , then passes over bottom weft yarn 5 , then passes under bottom weft yarns 8 , 11 , 14 and 17 , then passes over bottom weft yarn 20 , then passes under bottom weft yarns 23 , 26 , 29 , 32 , 35 , 38 and 41 , then passes over bottom weft yarn 44 . The bottom warp yarn 18 weaves only in the bottom layer and only with non-adjacent bottom weft yarns, e.g., three non-adjacent bottom weft yarns 5 , 20 and 44 . The pattern formed by bottom warp yarn 18 is different from that of the bottom warp yarns 12 , 14 , 16 and 20 . [0090] Also shown in FIG. 6 b , binding warp yarn 19 passes over the top weft yarn 1 , then passes from the top layer to the bottom layer by passing under top weft yarns 3 , 4 and 6 , then passes over bottom weft yarn 8 , then passes under bottom weft yarn 11 , then passes over bottom weft yarn 14 , then passes from the bottom layer to the top layer by passing under top weft yarns 15 and 16 , then weaves with the top weft yarns 18 , 19 , 21 , 22 and 24 to form a plain weave, then passes from the top layer to the bottom layer by passing under top weft yarns 25 and 27 , then passes over bottom weft yarn 29 , then passes from the bottom layer to the top layer by passing under top weft yarns 30 , 31 , 33 , 34 , 36 , 37 and 39 , then weaves with top weft yarns 40 , 42 , 43 and 45 to form a plain weave. The binding warp yarn 19 binds to the bottom layer by weaving with the same bottom weft yarns that the bottom warp yarn 20 weaves with, e.g., by passing over the three non-adjacent bottom weft yarns 8 , 14 and 29 . The pattern formed by binding warp yarn 19 is the same as that of binding warp yarn 11 except that it is shifted sideways by six top weft yarns. [0091] Finally, as seen in FIG. 6 b , bottom warp yarn 20 passes under bottom weft yarns 2 and 5 , then passes over bottom weft yarn 8 , then passes under bottom weft yarn 11 , then passes over bottom weft yarn 14 , then passes under bottom weft yarns 17 , 20 , 23 and 26 , then passes over bottom weft yarn 29 , then passes under bottom weft yarns 32 , 35 , 38 , 41 and 44 . The bottom warp yarn 20 weaves only in the bottom layer and only with non-adjacent bottom weft yarns, e.g., three bottom weft yarns 8 , 14 and 29 . The pattern formed by bottom warp yarn 20 is the same as that of bottom warp yarn 12 except that it is shifted sideways by three bottom weft yarns. [0092] As is apparent from a comparison of FIG. 6 a and 6 b , the paths taken by the warp yarns 1 - 10 through the weft yarns 1 - 45 are respectively the same as paths taken by the warp yarns 11 - 20 through the weft yarns 1 - 45 , i.e., warp yarn 1 has the same path through the weft yarns 1 - 45 as warp yarn 11 , warp yarn 2 has the same path through the weft yarns 1 - 45 as warp yarn 12 , etc,. [0093] FIG. 7 shows a photograph of a top side or paper facing side of an actual forming fabric utilizing the weave pattern shown in FIG. 5 and FIG. 8 shows a photograph of a bottom side or machine side of the forming fabric shown in FIG. 7 . [0094] By way of non-limiting example, the binding warp yarns 1 , 3 , 5 , 7 , 9 , 11 , 13 , 15 , 17 and 19 of the embodiment shown in FIGS. 5-6 b can have the following characteristics: acceptable size range of between approximately 0.10 mm and approximately 0.50 mm, preferable size ranges of between approximately 0.20 mm and approximately 0.80 mm, and most preferred size range of between approximately 0.12 mm and approximately 0.20 mm. The material for these yarns can be any natural or synthetic material, preferably a synthetic monofilament, and most preferably a polyester monofilament. [0095] By way of non-limiting example, the bottom warp yarns 2 , 4 , 6 , 8 , 10 , 12 , 14 , 16 , 18 and 20 of the embodiment shown in FIGS. 5-6 b can have the following characteristics:,acceptable size range of between approximately 0.15 mm and approximately 0.60 mm, preferable size ranges of between approximately 0.20 mm and approximately 0.40 mm, and most preferred size range of between approximately 0.25 mm and approximately 0.35 mm. The material for these yarns can be any natural or synthetic material, preferably a synthetic monofilament, and most preferably a polyester monofilament. The bottom warp yarns can preferably be constructed using relatively large diameter yarns that are well suited to sustain the wear caused by the friction between the machine side surface of the fabric and the papermaking machine during use of the fabric. [0096] By way of non-limiting example, the top weft yarns 1 , 3 , 4 , 6 , 7 , 9 , 10 , 12 , 13 , 15 , 16 , 18 , 19 , 21 , 22 , 24 , 25 , 27 , 28 , 30 , 31 , 33 , 34 , 36 , 37 , 39 , 40 , 42 , 43 and 45 of the embodiment shown in FIGS. 5-6 b can have the following characteristics: acceptable size range of between approximately 0.10 mm and approximately 0.50 mm, preferable size ranges of between approximately 0.20 mm and approximately 0.80 mm, and most preferred size range of between approximately 0.12 mm and approximately 0.80 mm. The material for these yarns can be any natural or synthetic material, preferably a synthetic monofilament, and most preferably a polyester monofilament. [0097] By way of non-limiting example, the bottom weft yarns 2 , 5 , 8 , 11 , 14 , 17 , 20 , 23 , 26 , 29 , 32 , 35 , 38 , 41 and 44 of the embodiment shown in FIGS. 5-6 b can have the following characteristics: acceptable size range of between approximately 0.15 mm and approximately 0.60 mm, preferable size ranges of between approximately 0.20 mm and approximately 0.40 mm, and most preferred size range of between approximately 0.25 mm and approximately 0.35 mm. The material for these yarns can be any natural or synthetic material, preferably a synthetic monofilament, and most preferably a polyester monofilament. These bottom weft yarns may also be constructed using larger diameter yarns than the upper warp yarns. [0098] In the embodiment shown in FIGS. 5-6 b all of the binding warp yarns form a plain weave in the top layer by weaving with five top weft yarns and bind to the bottom layer by weaving With at least one bottom weft yarns in two or more spaced apart locations. Furthermore, all of the bottom warp yarns weave only in the bottom layer. Additionally, when a binding warp yarn passes from the bottom layer to the top layer, it passes under at least two adjacent top weft yarns before weaving with a plain weave in the top layer. When a binding warp yarn passes from the top layer to the bottom layer, it passes under at least two adjacent top weft yarns before weaving with the bottom layer. The area of the plain weave (between a binding warp yarn and top weft yarns) is off-center with respect to an area or spacing between the two areas where the same binding warp yarn weaves to the bottom layer. Also, in the area or spacing between two the plain weave areas (between a binding warp yarn and top weft yarns), the area where the binding warp weaves with the bottom layer is off-center. These features are also desirable in numerous papermaking applications. [0099] The invention encompasses a variety of different types of fabrics. For instance, the invention noted herein encompasses fabrics woven with different repeat than that pictured and described above. The fabric can have various top to bottom warp yarn ratios. The invention further contemplates other multilayer fabrics and not just the multilayer fabrics depicted in the figures. [0100] The fabrics pictured and otherwise described and claimed herein may be employed in a variety, of applications, including board and packaging grades. [0101] The configurations of the individual yarns utilized in the fabrics of the present invention can vary, depending upon the desired properties of the final papermakers' fabric. For example, the yarns may be multifilament yarns, monofilament yarns, twisted multifilament or monofilament yarns, spun yarns, or any combination thereof. Also, the materials comprising yarns employed in the fabric of the present invention may be those commonly used in papermakers' fabric. For example, the yarns may be formed of polypropylene, polyester, nylon, or the like. The skilled artisan should select a yarn material according to the particular application of the final fabric. Those of skill in the art will appreciate that yarns having diameters outside the herein disclosed ranges may be used in certain applications. In one embodiment of the present invention, one or more of the weft and warp yarns can have a diameter of about 0.13 mm, or about 0.17 mm, or about 0.33, or about 0.36 mm. Fabrics employing these yarn sizes may be implemented with polyester yarns or with a combination of polyester and nylon yarns. [0102] The fabrics of the present invention have been described herein are flat woven fabrics and hence the warp yarns for these fabrics run in the machine direction (a direction aligned with the direction of travel of the papermakers' fabric on the papermaking machine) when the fabric is used on a papermaking machine and the weft yarns for these fabrics run in the cross machine direction (a direction parallel to the fabric surface and traverse to the direction of travel) when the fabric is used on a papermaking machine. However, those of skill in the art will appreciate that the fabrics of the present invention could also be woven using an endless weaving process. If such endless weaving were used, the warp yarns would run in the cross machine direction and the weft yarns would run in the machine direction when the fabric was used on a papermaking machine. [0103] Pursuant to another aspect of the present invention, methods of making the papermaker's fabrics are provided. Pursuant to these methods, the fabrics can be woven using separate warp and weft beams. [0104] Pursuant to another aspect of the present invention, methods of making paper are provided. Pursuant to these methods, one of the exemplary papermaker's forming fabrics described herein is provided, and paper is then made by applying paper stock to the forming fabric and by then removing moisture from the paper stock. As the details of how the paper stock is applied to the forming fabric and how moisture is removed from the paperstock is well understood by those of skill in the art, additional details regarding this aspect of the present invention will not be provided herein. [0105] To the extent that the pattern repeat symbols shown in FIGS. 1 and 5 are inconsistent with the respective weave patterns shown in FIGS. 2 a - 2 b and 6 a - 6 b , the paths shown in FIGS. 2 a - 2 b and 6 a - 6 b shall serve as a basis for correcting the symbols shown in FIGS. 1 and 5 . Applicant also reserves the right to submit any additional drawings showing weave patterns of the type shown in FIGS. 2 a - 2 b and 6 a - 6 b for any pattern repeat shown in FIGS. 1 and 5 which are not deemed to be consistent with the weave patterns shown in FIGS. 2 a - 2 b and 6 a - 6 b. [0106] It is noted that the: foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While,the present invention has been described with reference to exemplary embodiments, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular means, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.

Forming fabric that includes a top layer including top weft yarns and a bottom layer including bottom weft yarns. Binding warp yarns weave with the top weft yarns and bind to the bottom layer. This Abstract is not intended to define the invention disclosed in the specification, nor intended to limit the scope of the invention in any way.

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application is a divisional of U.S. patent application Ser. No. 11/743,201, filed on May 2, 2007, which claims the benefit of U.S. Provisional Application Ser. No. 60/798,806 filed on May 4, 2006. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to tissue holding devices, and more particularly to tissue holding devices and methods for making the same that are particularly suited for tissue reinforcement, approximation and/or repositioning, or for securing tissue to implantable prostheses. [0004] 2. Background Discussion [0005] Sutures have been used for many decades for wound closure and/or tissue approximation in a variety of medical applications. More recently, barbed sutures have been gaining attention for various medical applications as well. Barbed sutures typically have a series of “barbs” that extend outwardly from the suture, with the objective being that such barbs increase the holding strength of the suture and/or eliminate the need for knot tying. In most barbed sutures that exist in the marketplace, the barbs are formed by cutting into the suture shaft with a blade of some sort. An exemplary barbed suture 10 of this type is illustrated in FIG. 1 . For each barb 11 that is cut into the suture shaft 12 , the end of the cut area, or base 13 of the barb acts as a weak lever that allows the barb to bend backwards under stress. In addition, the diameter of the suture D 1 is reduced along the area into which a barb has been cut (as illustrated at D 2 ), which greatly reduces the tensile strength of the suture. Cutting into the suture shaft to form the barbs also has another disadvantage in that the number, size and geometry of the barbs is limited. This is so because the spacing between the barbs, the barb length etc. are greatly constrained by the size of the original suture because the cuts begin to interfere with one another and/or adversely affects the mechanical strength of the suture. There are also size limitations on what can be achieved with such a barbed suture. For example, as the barb size decreases, the size of the tooling necessary to cut the barbs becomes very small and precise, and thus very difficult to manufacture. Further, as the suture diameter decreases, cutting a barb into a very small cross-section decimates the strength of the suture due to the resultant thin core. Other means for creating suture-like products have been suggested. [0006] For example, U.S. Patent Publication No. 2004/0060410 and WO 2006/005144 make reference to other processes such as injection molding, stamping and laser cutting. U.S. Patent Publication No. 2003/0149447 also suggests stamping, progressive die cutting, injection molding, and chemical etching as methods to produce barbed sutures out of a flat material. Each of these suggested methods has its drawbacks. For example, injection molding is a process by which liquid material is injected into a die until the material fills the die, and is then allowed to cool. The sample is subsequently ejected from the die. With this method, however, because the material is first melted to allow for injection into the die, any mechanical strength due to molecular orientation (i.e., such as that seen in a polymer that has been extruded) is mainly lost. Significant thermal treatment such as that experienced in injection molding, decreases the amount of molecular orientation as the chains are able to rearrange into a more random structure. The loss of molecular orientation can adversely affect mechanical properties such as yield strength and bending modulus, which adversely affects the holding strength of the suture. In addition, there is a limitation on the size and shape of the devices that can be made by injection molding. Capillary forces will limit the ability to fill a mold in small areas, long run areas, and intricate geometries. Also, injection molded parts suffer from issues such as warpage and shrinkage. [0007] The publications mentioned above also suggest stamping and die cutting as alternative methods for forming such products. Die cutting is simply the process of cutting shapes from sheets by pressing a shaped knife-edge into one or more layers of sheeting. Stamping is a more general term to denote sheet material press-working. It typically involves impressing a material with some mark or figure. Because these processes only make imprints in, or “cookie cut” shapes in a given material, they cannot be used to create intricate 3-dimensional geometries. Further, die cutting or stamping processes do not promote material flow to fill in a double-female die cavity. [0008] The present invention described herein provides new processes for forming tissue holding devices that overcome the disadvantages of the processes described above. Further, the present invention provides various tissue holding devices having unique geometries achievable using the methods described herein. SUMMARY OF THE INVENTION [0009] A method is provided for forming a tissue holding device having a predetermined shape suitable for use in surgical applications. The method includes providing a first set of dies each having a top surface having a recess therein sized and shaped such that, when the recesses face and are aligned with one another, a first mold cavity is formed therebetween, providing a polymeric feedstock material, placing the feedstock material between opposing top surfaces of the first set of dies, and with the feedstock material therebetween, pressing the top surfaces of the first set of dies together until substantially in contact with one another so that the feedstock material deforms to fill the first mold cavity formed therebetween to thereby form a pre-form having a shape of the first mold cavity. The method further includes providing a second set of dies each having a top surface having a recess therein sized and shaped such that, when the recesses face and are aligned with one another, a second mold cavity is formed therebetween. The second mold cavity defines the predetermined shape of the tissue holding device. The pre-form is placed between opposing top surfaces of the second set of dies, and with the pre-form therebetween, the method further includes pressing the top surfaces of the second set of dies together until substantially in contact with one another so that the pre-form deforms to fill the second mold cavity formed therebetween to thereby form the tissue holding device having the predetermined shape. The predetermined shape includes a core extending along a length thereof, and a plurality of tissue holding elements extending outwardly therefrom along at least a portion of the length. [0010] In various embodiments the core may have an outermost dimension of less than or equal to 0.02 inches, the plurality of tissue holding elements may have a length less than or equal to 0.2 inches, and/or at least first and second tissue holding elements positioned opposite one another at substantially the same location along the length of the core. [0011] In yet another embodiment, the plurality of tissue holding elements may extend outwardly from the core at an angle, and the tissue holding device may further include a web-like portion extending between an inner side of the tissue holding elements and the core, where the web-like portion is thinner than the tissue holding element. [0012] Also provided is a method for forming a tissue holding device having a predetermined shape suitable for surgical applications, including the steps of providing first and second female dies each having respective first and second top surfaces with first and second recesses formed therein, wherein the first and second recesses are sized and shaped such that, when aligned with one another, they together form a mold cavity defining the predetermined shape. The predetermined shape includes a core extending along a length thereof, and a plurality of tissue holding elements extending outwardly from the core. The method further includes providing a polymeric feedstock material, placing the feedstock material between the top surfaces of the first and second dies, and with the feedstock material therebetween, pressing the top surfaces of the first and second dies together until the top surfaces of the first and second dies are substantially in contact with one another and the recesses of the first and second dies substantially aligned to form the mold cavity, so that the feedstock material deforms and fills the cavity therebetween to thereby form the tissue holding device having the predetermined shape. [0013] Various embodiments may further include a core having an outermost dimension less than or equal to 0.02 inches, a plurality of tissue holding elements having a length less than or equal to 0.2 inches, and/or a plurality of sets of first and second tissue holding elements, wherein for each set the first and second tissue holding elements are positioned substantially opposite one another at substantially the same location along the length of the core. [0014] Also provided are tissue holding devices produced in accordance with the method described above, wherein the core of the tissue holding device has a cross-sectional shape including opposing upper and lower outwardly curved sides and opposing first and second substantially flat lateral sides. The device may further have the plurality of tissue holding elements extending outwardly from the first and/or second lateral sides. In other embodiments of the device, the tissue holding elements may have a length less than or equal to 0.2 inches, and/or the core may have an outmost cross-sectional dimension of less than or equal to 0.02 inches. [0015] In another device produced in accordance with the method described above, at least one of the plurality of tissue holding elements has a web-like portion extending between an inner side of the tissue holding element and the core. In various other devices produced in accordance with the methods described above, the device may include at least one tissue holding element having an inner side having a recess therein, and/or a core having a cross-section that increases in size along at least a portion of the length of the device. [0016] Finally, yet another method is provided for forming a tissue holding device having a predetermined shape suitable for use in surgical applications. The method includes providing a polymeric feedstock material, using a first set of dies, press forming the polymeric feedstock material into a pre-form, and providing a receiver plate and a stripper plate each having a top surface with a recess formed therein having a three-dimensional shaped such that, when the recesses are aligned and facing one another, a cavity is formed therebetween capable of receiving therein the pre-form and having a substantially complementary shape as that of the pre-form. The stripper plate further has a opening therethrough for receiving a punch. The method further includes aligning the receiver and stripper plates and placing the pre-form in the cavity formed therebetween, providing a punch having a punch element having an outer periphery substantially identical to an outer periphery of the predetermined shape of the tissue holding device, and having a three dimensional surface contour substantially complementary to a top surface of a portion of the pre-form to be punched, and pressing the punch element through the top die and into the pre-form to thereby create the tissue holding device of the predetermined shape. The predetermined shape of the tissue holding device includes a core extending along a length thereof, and a plurality of tissue holding elements extending outwardly therefrom along at least a portion of the length. [0017] The pre-form may further have a central portion and first and second enlarged distal ends, with the punch element pressing into only the central portion of the pre-form. [0018] Various tissue holding devices produced in accordance with this method are also provided. Embodiments of such tissue holding devices may further include a core having an outermost cross-sectional dimension of less than or equal to 0.02 inches, the tissue holding elements having a length less than or equal to 0.02 inches, and/or a core having a cross-sectional shape including upper and lower outwardly curved sides and opposing first and second substantially flat lateral sides. In the latter embodiment, the plurality of tissue holding elements may further extend outwardly from the first and/or second lateral sides. [0019] In yet another embodiment, the device further includes a plurality of sets of first and second tissue holding elements, wherein for each set the first and second holding elements are positioned substantially opposite one another at substantially the same location along the length of the core. [0020] In other alternative embodiments, the core may have a substantially uniform cross-section along its length, or may increase in cross-section along at least a portion of its length. [0021] In yet another embodiment, at least one of the plurality of tissue holding elements has an inner side having a recess therein. [0022] Finally, in yet another embodiment, the length of the tissue grasping elements may increases along at least a portion of the length of the tissue holding device. BRIEF DESCRIPTION OF THE DRAWINGS [0023] FIG. 1 is a side view of an exemplary prior art suture having barbs cut therein; [0024] FIGS. 2 a - 2 c illustrate an exemplary die assembly that can be used in connection with the present invention; [0025] FIGS. 3 a - 3 g illustrate feedstock material at various stages during the formation of a tissue holding device according to exemplary methods of the present invention, and various cross-sectional shapes at such stages; [0026] FIGS. 4 a - 4 b illustrate an exemplary compound profile forming/cutting punch and receiver assembly; [0027] FIGS. 5 a and 5 b illustrate an exemplary rotary die assembly; [0028] FIG. 6 illustrates an exemplary barbed suture formed by cutting as previously known; [0029] FIGS. 7-9 b illustrate various configurations of tissue holding devices according to the present invention; and [0030] FIG. 10 is an exemplary illustration of molecular orientation and optimization thereof. DETAILED DESCRIPTION OF THE INVENTION [0031] Before explaining the present invention in detail, it should be noted that the invention is not limited in its application or use to the details of construction and arrangement of parts illustrated in the accompanying drawings and description. The invention as illustrated may be implemented or incorporated in other embodiments, variations and modifications, and may be practiced or carried out in various ways. [0032] Referring first to FIGS. 2 a -c and 3 , methods for press forming tissue holding devices according to the present invention will now be described in detail. FIGS. 2 a - 2 c illustrate first 20 and second 21 female dies that together form a die assembly 22 used to form a material into the desired shape using some type of press, such as a hydraulic or pneumatic press or the like. As illustrated in FIGS. 2 a and 2 b , the top surfaces 20 a, 21 a of the first and second dies each have a recess 20 b, 21 b therein having a configuration resembling a portion of the desired tissue holding device to be produced. When the top surfaces are aligned and brought in contact with one another, the recesses together form a cavity or mold in the shape of the desired tissue holding device. The feedstock material, or material to be formed into the tissue holding device, is typically a solid polymeric material having any suitable cross-section, such as circular, elliptical, rectangular, square etc., and having a length necessary for the given application. The material is placed between the first and second dies as shown in FIG. 2 c , and the dies closed and forcibly pressed together by a suitable press as described above. Guide pins 23 or the like are typically used to ensure that the proper orientation is maintained between the first and second dies. During the pressing process, the pressure causes material to move into and fill all portions of the die cavities, even any intricate geometries that may exist. [0033] The dies 20 , 21 may be compound dies that perform more than one operation in a single stroke of a press. For example, a given set of dies may simultaneously form the tissue holding device and trim excess flash material away by means of pinching, cutting, shearing or the like. The dies and/or the material can be heated to a temperature that aids in material flow, but does not significantly compromise the mechanical properties as occurs with injection molding. In other words, the temperature used will be such that the material softens, but molecular orientation is not completely lost and therefore, the strength and stiffness of the material are not significantly compromised. Softening the material may allow the use of lower pressures during processing and reduce the amount of flash on the finished samples. In fact, some thermal treatments may even improve the “functional” properties of the material. For example, an annealing treatment may be used to relieve stresses and toughen the material. [0034] FIGS. 3 a - 3 f illustrate a similar method using multiple dies. A suitable feedstock material 25 , such as a polymeric material having a generally rectangular cross section, is shown in FIGS. 3 a and 3 b . First and second female dies 26 , 27 having cavities shaped as shown in FIG. 3 d , are press fit together as described above to cause the polymeric material 25 to take the new shape 25 a shown in FIGS. 3 c and 3 d , which has a rhombohedral-like cross-section, with a curved top 24 a and bottom 24 b portions. A second set of dies 28 , 29 is then used to form the material into the final shape 25 b as shown in FIGS. 3 e and 3 f , and to trim off excess material if desired. The use of multiple sets of dies allows for shaping a given feedstock into a more desirable shape from which to form the final device shape. As indicated above, the dies can be compound dies and the dies and/or material may be heated to aid in material flow into the die cavities. The use of multiple sets of dies can serve to limit the amount of heat and/or pressure needed relative to forming with only one set of dies. [0035] In yet another method, a first set of dies is used to form the pre-form in a similar manner as described above, then, instead of using a second set of dies, a compound profile forming/cutting punch and receiver assembly 100 (as shown in FIGS. 4 a and 4 b ) is subsequently used to profile cut or shear the final shape out of the pre-form. The cross-sectional shape of the pre-form may differ from the cross-sectional shape of the final product. In a preferred embodiment illustrated in FIGS. 3 g and 4 b , the cross-sectional shape of the pre-form 600 may have more of an “I-beam” shape with a central portion 62 and first and second enlarged distal ends 61 a , 61 b . By “enlarged distal ends” what is meant is that the distal ends are enlarged as compared to the adjacent section of the central portion, but are not necessarily larger than the entire central portion. For example, as shown in FIG. 3 g , the thickness t 1 of the enlarged distal ends is greater than the thickness t 2 of the adjacent portion of the central portion 62 , but is substantially similar to (and may be larger than) the thickness t 3 at the center of the central portion. These enlarged ends assist in aligning and holding the pre-form in place within the stripper plate 101 and profile receiver 103 during the subsequent punching step as described below. Providing an angled transition zone 64 (i.e., at a 45 degree angle) can also improve holding and alignment of the pre-form. [0036] The stripper plate 101 and receiver plate 103 similarly have recesses 70 a, 70 b therein that together, when aligned, form a cavity therebetween. [0037] This cavity is capable of receiving the pre-form without exerting any significant forces on the pre-form. Thus, the recesses include portions 610 a , 610 b ( FIG. 4 b ) that are complementary to the first and second enlarged distal ends 61 a, 61 b of the pre-form, which aid in aligning the pre-form, and minimizing movement of the pre-form during punching. The stripper plate 101 further includes an opening 72 therethrough designed to receive the punch as will be described further and having a complementary shape. [0038] The profile punch 102 has an outer periphery 74 that is designed to define the outer periphery of the final product, as can best be seen in FIG. 4 a . This outer periphery defines both the shape of the central core 77 and tissue grasping elements 78 in the final product. Further, the distal end 615 ( FIG. 4 b ) of the punch has a unique three-dimensional recess 616 therein that is substantially complementary to the top surface 617 of the central portion of the pre-form that is to be punched. This three-dimensional aspect minimizes deformation of the pre-form during the final step as the profile punch 102 punches out the material. Finally, a width w 1 of the punch 102 is preferably less than or equal to a width w 2 of the central portion of the pre-form so that pre-form can be aligned and held firmly in place at the enlarged distal ends during the final punching step. As is well known in the art, the final punching step is performed by passing the punch element 618 through the complementary opening 72 in the stripper plate, into the pre-form, and preferably further through a complementary shaped opening 72 a in the receiver plate, thereby punching out the final product. The advantages of this method are that it may be easier to use a compound profile forming/cutting punch as the final step instead of a forming die, to thereby limit the amount of heat and pressure that is needed. This method may also reduce the amount of flash produced. [0039] Finally, press-forming or compound profile punching according to the present invention may also be accomplished using a rotary forming or rotary through punch and receiver process, similar to a radial forging-type process, for example, whereby the first 42 and second 44 female dies are circular in shape and have mold recesses or cavities 46 , 48 formed in the outer circumference, and rotate in compression against one another to form the material into the desired shape as is illustrated in FIGS. 5 a and 5 b . This process has the advantage of permitting production of a continuous device, or one having discrete portions with and without tissue holding elements. [0040] As indicated previously, the above-described methods have distinct advantages over other known methods in that they enable production of tissue holding devices having superior mechanical properties, and also enable production of a tissue holding devices having tissue holding elements of virtually any geometry. With cut barbed sutures, every barb is carved into the suture shaft thereby adversely affecting the holding and tensile strength of the suture at the location of the barb, and providing extensive limitations on the barb geometry and configuration. For example, it is undesirable to place cut barbs 650 opposite one another along the suture shaft, as shown in FIG. 6 , since such a configuration doubles the reduction in the suture shaft at that location, as can be seen in comparing the suture shaft diameter s 1 to the suture shaft diameter 52 at the location of the barbs. Further, intricate geometries are not possible with cutting, and are limited with injection molding due to the limitations on flowability and the reduction in mechanical properties brought about by this method. With the above-described methods, there are no barbs cut into the core diameter, but rather there are tissue holding means or elements, such as protrusions, extensions or the like, extending outwardly from an intact core, which may be of any circular or non-circular cross-sectional shape The tissue holding elements can readily be place opposite one another, for example as shown in FIG. 3 e , as there is no reduction in the cross-sectional area of the core. Not only is reduction in tensile strength of less concern with press-forming, but it also allows for greater flexibility in suture size selection, since the original suture diameter or cross-section need not be greater than desired to accommodate for any reduction associated with cutting into the suture core or shaft. [0041] Another tissue holding device according to the present invention is illustrated in FIGS. 7-8 . Multiple tissue holding elements 30 extend outwardly from suture shaft 31 , with each element further including a web-like portion 32 extending between the inner side 36 of the tissue holding element and the suture shaft. Preferably, this web-like portion is thinner than the main tissue holding element 30 . The web-like portion 32 allows the tissue holding elements to fold against the suture shaft during insertion into tissue or other material, but also serves to reinforce the strength of the tissue holding element and provide resistance against peeling back of the tissue holding element. This can greatly increase the holding strength for a given suture diameter and configuration of the tissue holding element 30 . Each tissue holding element may also be configured with a radiused tip 34 to reduce tissue irritation and the like while still maintaining holding ability. Further, the web-like portion 32 may be continuous or non-continuous. For example, a section 32 a nearest the base may be eliminated leaving only a strip 32 b of the web-like portion between the tissue holding element and the shaft or core 31 . [0042] In the configuration described above, with or without the web-like portions, the suture may have a core diameter 35 of approximately 0.005-0.035 inches, and preferably 0.014 inches. The central core of the device may also be of any other suitable cross-section, such as the exemplary embodiment illustrated in FIG. 3 f . In this embodiment, opposing upper and lower sides 45 a, 45 b are curved, whereas opposing lateral sides 43 a, 43 b are substantially flat or straight. The width w and length l are each preferably in the range of 0.006-0.020 inches, and more preferably approximately 0.012 inches. For purposes of this disclosure, the term “outermost dimension” refers to the largest dimension that can be measured across the cross-section of the core. The length L (see FIG. 7 ) of the tissue holding elements may be 0.010-0.20 inches, and preferably approximately 0.030-0.065 inches. Although the tissue holding elements 30 illustrated in FIG. 7 are substantially conical in shape, any other suitable configuration may also be used, such as pyramidal, cylindrical etc. In a preferred embodiment, the base 37 or proximal end of the main tissue holding element 30 has a diameter of approximately 0.006-0.05 inches, and a tip 38 or distal end has a diameter of approximately 0.001-0.006 inches. Further, although the illustrated embodiment shows tissue holding elements at approximately 180 degrees spacing about the circumference of the suture shaft (opposite sides), any other suitable spacing (i.e., 120 degree spacing) may also be achieved with the methods described herein . Tissue holding element angle a may be any suitable angle between 1 and 90 degrees, with a currently preferred embodiment being approximately 52 degrees. Finally, the spacing between successive barbs on a given side of the suture may be approximately 0.01-0.1 inches, and preferably approximately 0.030 inches. [0043] The tissue holding devices described herein may be formed of any material suitable for press-forming and suitable for implantation into the body. A preferred material is polypropylene or polyvinylidene fluoride [0044] (PVDF). Other suitable polymeric materials include absorbable materials such as polydioxanone, polyglactin, polyglycolic acid, copolymers of glycolide and lactide, polyoxaesters, poliglecaprone etc., or non-absorbable materials such as polypropylene, polyethylene, polyvinylidene fluoride (PVDF), polyesters, polyethylene terephthalate, glycol-modified polyethylene terephthalate, polytetrafluoroethylene, fluoropolymers, nylons etc. and the like, or copolymers of combinations thereof, including combinations of absorbable and non-absorbable materials. In addition, metals or ceramics may be suitable for certain applications, such as instances where specific strength or corrosion resistance is necessary. Yet another embodiment allows for the addition of fibers, such as glass fibers, to a polymeric material to provide reinforcement and subsequent increased mechanical properties. Finally, shape memory metals or polymers could be used that, for example, maintain the tissue holding elements in a collapsed position during normal room temperatures, but that return to an uncollapsed position when exposed to body temperature. [0045] Referring now to FIGS. 9 a and 9 b , the tissue holding elements 900 may be configured to better facilitate folding against the suture shaft 901 during insertion by providing a notch, recess or the like 902 on the inner side 903 thereof, preferably in proximity to the proximal end 904 of the tissue holding element as shown. The recessed area may decrease tissue trauma by allowing the tissue holding elements to “fold” during insertion. Further, the tissue holding elements 900 may be formed with a reinforced or wider proximal end as shown to provide added strength and to help prevent peeling back of the tissue holding element. [0046] The devices of the present invention may also incorporate a variety of additional features such as a tapered leading end 1100 having a smaller cross-section at the distal end 1101 to lessen resistance and tissue trauma during insertion. The device of FIG. 9 b further has a gradually increasing outer dimension x (distance between distal tips of opposing or nearly opposing tissue holding elements) along the length or a portion of the length from the leading end 1101 toward the distal end 1105 . This feature similarly serves to facilitate insertion of the device into tissue. In addition, the device of FIG. 9 b may include one or more recesses 1106 behind the tissue holding elements designed and positioned such that the tissue holding element fold backward at least partially into the recess when the device is drawn through tissue, which serves to reduce the outer cross-sectional profile and therefore facilitate insertion, minimize tissue trauma, and minimize the channel formed in the tissue. [0047] Another advantage of devices formed according to the methods described above is that such devices can readily take advantage of molecular orientation and the properties that such orientation imparts to the final product. For example, the feedstock material can be provided in a sheet 1000 such as that shown in FIG. 10 . With a polymeric material, the sheet may be constructed so as to have a particular molecular orientation, such as one that is primarily in the direction of arrow A. If a high tensile strength is desired in the end product, the feedstock may be cut out of the sheet in that same direction, such as is shown by reference numeral 1002 . If the holding strength of the tissue grasping devices is the most important, the feedstock could be cut as shown by reference numeral 1004 . [0048] As is apparent from the description above, the use of press-forming or compound profile punching to form tissue holding devices is highly advantageous in that it can be used to achieve virtually any three-dimensional configuration without regard to intricate geometries of the tissue holding elements, without regard to positioning of the tissue holding elements, without concern as to reducing the tensile strength of the suture, and without adversely affecting the structural integrity of the original feedstock material. [0049] It will be apparent from the foregoing that, while particular forms of the invention have been illustrated and described, various modifications can be made without departing from the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited, except as by the appended claims.

Various methods are provided for forming tissue holding devices having predetermined shapes suitable for use in surgical applications, and devices formed in accordance with such methods are also provided. These methods include press forming methods, and press forming methods in combination with profile punching. Tissue holding devices formed in accordance with such methods include various configurations for a core and a plurality of tissue holding elements extending outwardly from the core.

CROSS REFERENCE TO RELATED APPLICATIONS [0001] The present application claims benefit of U.S. provisional application No. 60/118,564, filed Feb. 4, 1999, entitled “Improved Synthesis of Oligonucleotides”, the content of which is hereby incorporated by reference in its entirety. FIELD OF THE INVENTION [0002] This invention relates to improved methods for the preparation of oligomeric compounds having phosphodiester, phosphorothioate, phosphorodithioate or other linkages. In preferred embodiments, the methods of the invention provide oligomers that have reduced amounts of unwanted side-products. BACKGROUND OF THE INVENTION [0003] Antisense and other oligonucleotide therapies have gone beyond academic publications to the level of approved drug as shown by the recent FDA approval of an antisense oligonucleotide therapeutic for ocular cytomegalovirus infections. More and more oligonucleotides are entering the clinic for the treatment of a variety of diseases such as inflammation, cancer, viral disease and others. There is an urgent need for improved methods for the synthesis of oligonucleotides in high quantity and with high quality. Solid phase chemistry is the present method of choice. Typical synthons now used are O-cyanoethyl protected nucleoside phosphoamidite monomers. At the end of the synthesis, the oligonucleotide product is treated typically with 30% aqueous ammonium hydroxide to deprotect the cyanoethyl groups on the phosphorothioate backbone as well as exocyclic amino groups. During this deprotection step, one molecule of acrylonitrile is produced for every cyanoethyl group present. [0004] It is now known that acrylonitrile is a rodent carcinogen and that, at pH 7, it can react with T, dC, dG, dA and dI, resulting in the formation of a variety of adducts. See, Solomon et al., Chem. - Biol. Interactions, 51, 167-190 (1984). It is greatly desired to eliminate these impurities in synthesis of oligonucleotides, especially phosphorothioate oligonucleotides. [0005] Eritja et al. ( Tetrahedron, 48, 4171-4182 (1992)) report the prevention of acrylonitrile adduct formation of nucleobase moieties during deprotection of β-cyanoethyl protected oligomers by 40% triethylamine in pyridine for 3 hours followed by treatment with 0.5 M DBU/pyridine. However, as will be seen infra, their conditions failed to eliminate adduct formation to a suitable extent. [0006] Given the demand for oligonucleotides and analogs thereof for clinical use, and the known toxicity of acrylonitrile nucleobase adducts, methods of preparing phosphate linked oligomers having reduced amount of such adducts are greatly desired. The present invention is directed to this, as well a other, important ends. SUMMARY OF THE INVENTION [0007] The present invention provides an improved method for the preparation of phosphate-linked oligomers that have significantly reduced amounts of exocyclic nucleobase adduct resulting from the products of removal of phosphorus protecting groups. In one aspect of the invention, methods are provided comprising: [0008] a) providing a sample containing a plurality of oligomers of the Formula I: [0009] wherein: [0010] R 1 is H or a hydroxyl protecting group; [0011] B is a naturally occurring or non-naturally occurring nucleobase that is optionally protected at one or more exocyclic hydroxyl or amino groups; [0012] R 2 has the Formula III or IV: [0013] wherein [0014] E is C 1 -C 10 alkyl, N(Q 1 ) (Q 2 ) or N═C(Q 1 ) (Q 2 ) [0015] each Q 1 and Q 2 is, independently, H, C 1 -C 10 alkyl, dialkylaminoalkyl, a nitrogen protecting group, a tethered or untethered conjugate group, a linker to a solid support, or Q 1 and Q 2 , together, are joined in a nitrogen protecting group or a ring structure that can include at least one additional heteroatom selected from N and O; [0016] R 3 is OX 1 , SX 1 , or N(X 1 ) 2 ; [0017] each X 1 is, independently, H, C 1 -C 9 alkyl, C 1 -C 8 haloalkyl, C(═NH)N(H)Z 8 , C(═O)N(H)Z 9 or OC(═O)N(H) Z 8 ; [0018] Z 8 is H or C 1 -C 8 alkyl; [0019] L 1 , L 2 and L 3 comprise a ring system having from about 4 to about 7 carbon atoms or having from about 3 to about 6 carbon atoms and 1 or 2 hetero atoms wherein said hetero atoms are selected from oxygen, nitrogen and sulfur and wherein said ring system is aliphatic, unsaturated aliphatic, aromatic, or saturated or unsaturated heterocyclic; [0020] Y is alkyl or haloalkyl having 1 to about 10 carbon atoms, alkenyl having 2 to about 10 carbon atoms, alkynyl having 2 to about 10 carbon atoms, aryl having 6 to about 14 carbon atoms, N(Q 1 ) (Q 2 ), 0(Q 1 ), halo, S(Q 1 ), or CN; [0021] each q 1 is, independently, from 2 to 10; [0022] each q 2 is, independently, 0 or 1; [0023] m is 0, 1 or 2; [0024] pp is from 1 to 10; and [0025] q 3 is from 1 to 10 with the proviso that when [0026] pp is 0, q 3 is greater than 1; [0027] R t is a phosphorus protecting group of formula: (R 10 ) 2 —C(R 10 ) 2 —W or —C(R 10 ) 2 —(CH═CH) p —C(R 10 ) 2 —W [0028] each R 10 is independently H or lower alkyl; [0029] W is an electron withdrawing group; [0030] p is 0 to 3; [0031] each Y 2 is independently, O, CH 2 or NH; [0032] each Z is independently O or S; [0033] each X is independently O or S; [0034] Q is a linker connected to a solid support, —OH or [0035] O—Pr where Pr is a hydroxyl protecting group; and [0036] n is 1 to about 100; [0037] b) contacting said sample with a deprotecting reagent for a time and under conditions sufficient to remove substantially said R t groups from said oligomers; and [0038] c) reacting said oligomers with a cleaving reagent; [0039] wherein said deprotecting reagent comprises at least one amine, the conjugate acid of said amine having a pKa of from about 8 to about 11; said deprotecting reagent optionally further comprising one or more solvents selected from the group consisting of alkyl solvents, haloalkyl solvents, cyanoalkyl solvents, aryl solvents and aralkyl solvents. [0040] Preferably, the methods further comprises a washing step before step (c). [0041] In some preferred embodiments, Q is a linker connected to a solid support. In further preferred embodiments, said deprotecting reagent does not cleave said oligomers from said solid support. [0042] In some preferred embodiments, the deprotecting reagent comprises an aliphatic amine, which is preferably triethylamine or piperidine. [0043] In further preferred embodiments, the deprotecting agent comprises a haloalkyl solvent or a cyanoalkyl solvent, which is preferably acetonitrile or methylene chloride. [0044] In particularly preferred embodiments, the phosphorus protecting group is —CH 2 —CH 2 —C≡N or —CH 2 —(CH═CH) p —CH 2 —C≡N, where p is an integer from 1 to 3, with —CH 2 —CH 2 —C≡N or —CH 2 —CH═CH—CH 2 —C≡N being preferred, and —CH 2 —CH 2 —C≡N being particularly preferred. [0045] In some preferred embodiments, the deprotecting reagent or cleaving reagent further comprises a scavenger, which is preferably a purine, a pyrimidine, inosine, a pyrrole, an imidazole, a triazole, a mercaptan, a beta amino thiol, a phosphine, a phosphite, a diene, a urea, a thiourea, an amide, an imide, a cyclic imide, a ketone, an alkylmercaptan, a thiol, ethylene glycol, a substituted ethylene glycol, 1-butanethiol, S-(2-amino-4-thiazolylmethyl)isothiourea hydrochloride, 2-mercaptoethanol, 3,4-dichlorobenzylamine, benzylamine, benzylamine in the presence of carbon disulfide, hydroxylamine, 2-phenylindole, n-butylamine, diethyl ester of acetaminomalonic acid, ethyl ester of N-acetyl-2-cyanoglycine, 3-phenyl-4-(o-fluorophenyl)-2-butanone, 3,4-diphenyl-2-butanone, desoxybenzoin, N-methoxyphthalimide, p-sulfobenzenediazonium chloride, or p-sulfamidobenzenediazonium chloride. [0046] In some preferred embodiments, the scavenger is a resin containing a suitable scavenging molecule bound thereto. Exemplary scavenger resins include polymers having free thiol groups and polymers having free amino groups, for example a polymer-bound amine resin wherein the amine is selected from benzylamine, ethylenediamine, diethylamine triamine, tris(2-aminoethyl)amine, methylamine, methylguanidine, polylysine, oligolysine, Agropore™ NH 2 HL, Agropore™ NH 2 LL (available from Aldrich Chem. Co. St. Louis. Mo.), 4-methoxytrityl resin, and thiol 2-chlorotrityl resin. [0047] In some preferred embodiments, Q is —OH or O—Pr. [0048] In some preferred embodiments, the cleaving reagent comprises an aqueous methanolic solution of a Group I or Group II metal carbonate, preferably aqueous methanolic CaCO 3 . In further preferred embodiments, the cleaving reagent comprises an aqueous metal hydroxide. In yet further preferred embodiments, the cleaving reagent comprises a phase transfer catalyst. Preferred phase transfer catalysts include quaternary ammonium salts, quaternary phosphonium salts, crown ethers and cryptands (i.e., crown ethers which are bicyclic or cycles of higher order). It is more preferred that the phase transfer catalyst be t-Bu 4 N −1 OH, or t-Bu 4 N + F − . [0049] In further preferred embodiments, the cleaving reagent comprises NaNH 2 . [0050] In preferred embodiments, the oligomers produced by the methods of the invention have from 0.001% to about 1% acrylonitrile adduct, with from about 0.1% to about 1% acrylonitrile adduct being more preferred, from about 0.1% to about 0.75% acrylonitrile adduct being even more preferred, and from about 0.1% to about 0.5% acrylonitrile adduct being even more preferred. In even more preferred embodiments, the oligomers are substantially free of detectable acrylonitrile adduct. [0051] In some preferred embodiments, steps b) and c) are performed simultaneously. [0052] In some particularly preferred embodiments, Q is a linker connected to a solid support; said aliphatic amine is triethylamine or piperidine; said solvent is acetonitrile or methylene chloride; and said phosphorus protecting group is —CH 2 —CH 2 —C≡N or —CH 2 —CH═CH—CH 2 —C≡N, and wherein the deprotecting reagent, said cleaving reagent, or both preferably further comprises a scavenger. [0053] In further preferred embodiments, the deprotecting reagent comprises a secondary alkyl amine which is preferably piperidine, and said cleaving reagent comprises an alkali metal carbonate, which is preferably potassium carbonate. [0054] Also provided by the present invention are methods for deprotecting a phosphate-linked oligomer, said oligomer having a plurality of protected phosphorus linkages of Formula II: [0055] wherein: [0056] Each X is O or S; [0057] R t is a phosphorus protecting group of the formula: —C(R 10 ) 2 —C(R 10 ) 2 —W or —C(R 10 ) 2 —(CH═CH) p —C(R 10 ) 2 —W [0058] each R 10 is independently H or lower alkyl; [0059] W is an electron withdrawing group; [0060] p is 1 to 3; [0061] comprising: [0062] (a) providing a sample containing a plurality of said phosphate linked oligomers; [0063] (b) contacting said oligomers with a deprotecting reagent for a time and under conditions sufficient to remove substantially all of said R t groups from said oligomers, said deprotecting reagent containing at least one amine, the conjugate acid of said amine having a pKa of from about 8 to about 11; said deprotecting reagent optionally further comprising one or more solvents selected from the group consisting of alkyl solvents, haloalkyl solvents, cyanoalkyl solvents, aryl solvents and aralkyl solvents; and [0064] (c) reacting said oligomers with a cleaving reagent. [0065] Preferably, the methods further comprises a washing step before step (c). [0066] In some preferred emboidiments, the oligomers are in solution. In other preferred embodiments, the oligomers are linked to a solid support. [0067] In some preferred embodiments, said deprotecting reagent does not cleave said oligomers from said solid support. [0068] In some preferred embodiments, the deprotecting reagent comprises an aliphatic amine, which is preferably triethylamine or piperidine. [0069] In further preferred embodiments, the deprotecting agent comprises a haloalkyl solvent or a cyanoalkyl solvent, which is preferably acetonitrile or methylene chloride. [0070] In particularly preferred embodiments, the phosphorus protecting group is —CH 2 —CH 2 —C≡N or —CH 2 —(CH═CH) p —CH 2 —C≡N, where p is an integer from 1 to 3, with —CH 2 —CH 2 —C≡N or —CH 2 —CH═CH—CH 2 —C≡N being preferred, and with —CH 2 —CH 2 —C≡N being particularly preferred. [0071] In some preferred embodiments, the deprotecting reagent or cleaving reagent further comprises a scavenger, which is preferably a purine, a pyrimidine, inosine, a pyrrole, an imidazole, a triazole, a mercaptan, a beta amino thiol, a phosphine, a phosphite, a diene, a urea, a thiourea, an amide, an imide, a cyclic imide, a ketone, an alkylmercaptan, a thiol, ethylene glycol, a substituted ethylene glycol, 1-butanethiol, S-(2-amino-4-thiazolylmethyl)isothiourea hydrochloride, 2-mercaptoethanol, 3,4-dichlorobenzylamine, benzylamine, benzylamine in the presence of carbon disulfide, hydroxylamine, 2-phenylindole, n-butylamine, diethyl ester of acetaminomalonic acid, ethyl ester of N-acetyl-2-cyanoglycine, 3-phenyl-4-(o-fluorophenyl)-2-butanone, 3,4-diphenyl-2-butanone, desoxybenzoin, N-methoxyphthalimide, p-sulfobenzenediazonium chloride, or p-sulfamidobenzenediazonium chloride. [0072] In some preferred embodiments, the scavenger is a resin containing a suitable scavenging molecule bound thereto. Exemplary scavenger resins include polymers having free thiol groups and polymers having free amino groups, for example a polymer-bound amine resin wherein the amine is selected from benzylamine, ethylenediamine, diethylamine triamine, tris(2-aminoethyl)amine, methylamine, methylguanidine, polylysine, oligolysine, Agropore™ NH 2 HL, Agropore™ NH 2 LL, 4-methoxytrityl resin, and thiol 2-chlorotrityl resin. [0073] In some preferred embodiments, the cleaving reagent comprises an aqueous methanolic solution of a Group I or Group II metal carbonate, preferably aqueous methanolic potassium carbonate. In further preferred embodiments, the cleaving reagent comprises an aqueous metal hydroxide. In yet further preferred embodiments, the cleaving reagent comprises a phase transfer catalyst. Preferred phase transfer catalysts include quaternary ammonium salts, quaternary phosphonium salts, crown ethers and cryptands (i.e., crown ethers which are bicyclic or cycles of higher order). It is more preferred that the phase transfer catalyst be t-Bu 4 N + OH, or t-Bu 4 N + F − . [0074] In further preferred embodiments, the cleaving reagent comprises NaNH 2 . [0075] In preferred embodiments, the produced by the methods of the invention oligomers have from about 0.001% to about 1% acrylonitrile adduct, with from about 0.001% to about 0.5% acrylonitrile adduct being more preferred, from about 0.001% to about 0.1% acrylonitrile adduct being even more preferred, and from about 0.001% to about 0.05% acrylonitrile adduct being even more preferred. In even more preferred embodiments, the oligomers are substantially free of acrylonitrile adduct. [0076] In some preferred embodiments, steps b) and c) are performed simultaneously. [0077] In some particularly preferred embodiments, said aliphatic amine is triethylamine or piperidine; said solvent is acetonitrile or methylene chloride; and said phosphorus protecting group is —CH 2 —CH 2 —C≡N or —CH 2 —CH═CH—CH 2 —C≡N, and wherein the deprotecting reagent, said cleaving reagent, or both preferably further comprises a scavenger. [0078] In further preferred embodiments, the deprotecting reagent comprises a secondary alkyl amine which is preferably piperidine, and said cleaving reagent comprises an alkali metal carbonate, which is preferably potassium carbonate. [0079] Also provided by the present invention are methods for deprotecting a phosphate-linked oligomer, said oligomer having a plurality of protected phosphorus linkages of Formula II: [0080] wherein: [0081] Each X is O or S; [0082] R t is a phosphorus protecting group of formula: —C(R 10 ) 2 —C(R 10 ) 2 —W or —C(R 10 ) 2 —(CH═CH) p —C(R 10 ) 2 —W [0083] each R 10 is independently H or lower alkyl; [0084] W is an electron withdrawing group; [0085] p is 1 to 3; [0086] comprising: [0087] (a) providing a sample containing a plurality of said-phosphate linked oligomers; [0088] (b) contacting said oligomers with a deprotecting reagent for a time and under conditions sufficient to remove substantially all of said R t groups from said oligomers; [0089] (c) washing said deprotected oligomers with a washing reagent comprising at least one amine, the conjugate acid of said amine having a pKa of from about 8 to about 11; said deprotecting reagent optionally further comprising one or more solvents selected from the group consisting of alkyl solvents, haloalkyl solvents, cyanoalkyl solvents, aryl solvents and aralkyl solvents; and [0090] (d) reacting said oligomers with a cleaving reagent. [0091] In some preferred embodiments, the oligomers are in solution. In other preferred embodiments, the oligomers are linked to a solid support. [0092] In some preferred embodiments, the deprotecting reagent does not cleave said oligomers from said solid support. [0093] In further preferred embodiments, the deprotecting reagent comprises an aliphatic amine, which is preferably triethylamine or piperidine. In still further preferred embodiments, the deprotecting agent comprises a haloalkyl solvent or a cyanoalkyl solvent which is preferably acetonitrile or methylene chloride. [0094] In particularly preferred embodiments, the phosphorus protecting group is —CH 2 —CH 2 —C≡N or —CH 2 —(CH═CH) p —CH 2 —C≡N, where p is an integer from 1 to 3, with —CH, —CH —C≡N or —CH 2 —CH═CH—CH 2 —C≡N being preferred, and with —CH 2 —CH 2 —C≡N being particularly preferred. [0095] In some preferred embodiments, the deprotecting reagent, the cleaving reagent or the washing reagent further comprises a scavenger, which is preferably a purine, a pyrimidine, inosine, a pyrrole, an imidazole, a triazole, a mercaptan, a beta amino thiol, a phosphine, a phosphite, a diene, a urea, a thiourea, an amide, an imide, a cyclic imide a ketone, an alkylmercaptan, a thiol, ethylene glycol, a substituted ethylene glycol, 1-butanethiol, S-(2-amino-4-thiazolylmethyl)isothiourea hydrochloride, 2-mercaptoethanol, 3,4-dichlorobenzylamine, benzylamine, benzylamine in the presence of carbon disulfide, hydroxylamine, 2-phenylindole, n-butylamine, diethyl ester of acetaminomalonic acid, ethyl ester of N-acetyl-2-cyanoglycine, 3-phenyl-4-(o-fluorophenyl)-2-butanone, 3,4-diphenyl-2-butanone, desoxybenzoin, N-methoxyphthalimide, p-sulfobenzenediazonium chloride, or p-sulfamidobenzenediazonium chloride. [0096] In some preferred embodiments, the scavenger is a resin containing a suitable scavenging molecule bound thereto. Exemplary scavenger resins include polymers having free thiol groups and polymers having free amino groups, for example a polymer-bound amine resin wherein the amine is selected from benzylamine, ethylenediamine, diethylamine triamine, tris(2-aminoethyl)amine, methylamine, methylguanidine, polylysine, oligolysine, Agropore™ NH 2 HL, Agropore™ NH 2 LL, 4-methoxytrityl resin, and thiol 2-chlorotrityl resin. [0097] In some preferred embodiments, the cleaving reagent comprises an aqueous methanolic solution of a Group I or Group II metal carbonate, preferably aqueous methanolic potassium carbonate. In further preferred embodiments, the cleaving reagent comprises an aqueous metal hydroxide. In yet further preferred embodiments, the cleaving reagent comprises a phase transfer catalyst. Preferred phase transfer catalysts include quaternary ammonium salts, quaternary phosphonium salts, crown ethers and cryptands (i.e., crown ethers which are bicyclic or cycles of higher order). It is more preferred that the phase transfer catalyst be t-Bu 4 N + OH, or t-Bu 4 N + F −. [0098] In further preferred embodiments, the cleaving reagent comprises NaNH 2 . [0099] In preferred embodiments, the oligomers produced by the methods of the invention have from 0.001% to about 1% acrylonitrile adduct, with from about 0.1% to about 1% acrylonitrile adduct being more preferred, from about 0.1% to about 0.75% acrylonitrile adduct being even more preferred, and from about 0.1% to about 0.5% acrylonitrile adduct being even more preferred. In even more preferred embodiments, the oligomers are substantially free of detectable acrylonitrile adduct. [0100] In some particularly preferred embodiments, said aliphatic amine is triethylamine or piperidine; said solvent is acetonitrile or methylene chloride; and said phosphorus protecting group is —CH 2 —CH 2 —C≡N or —CH 2 —CH═CH—CH 2 —C≡N, and wherein the deprotecting reagent, the washing reagent, the cleaving reagent, or each preferably further comprise a scavenger. [0101] In further preferred embodiments, the deprotecting reagent comprises a secondary alkyl amine which is preferably piperidine, and said cleaving reagent comprises an alkali metal carbonate, which is preferably potassium carbonate. [0102] The present invention also provides methods for deprotecting a phosphate-linked oligomer, said oligomer having a plurality of phosphorus linkages of Formula II: [0103] wherein: [0104] Each X is O or S; [0105] R t is a phosphorus protecting group of the formula: (R 10 ) 2 —C(R 10 ) 2 —W or —C(R 10 )—(CH═CH) p —C(R 10 ) 2 —W [0106] each R 10 is independently H or lower alkyl; [0107] W is an electron withdrawing group; [0108] p is 1 to 3; [0109] comprising: [0110] (a) providing a sample containing a plurality of said phosphate linked oligomers; and [0111] (b) contacting said oligomers with a deprotecting reagent for a time and under conditions sufficient to remove substantially all of said R t groups from said oligomers, said deprotecting reagent comprising gaseous ammonia. [0112] Also provided in accordance with the present invention are compositions comprising phosphodiester, phosphorothioate, or phosphorodithioate oligonucleotides produced by the methods of the invention. [0113] The present invention also provides compositions comprising phosphodiester, phosphorothioate, or phosphorodithioate oligonucleotides, said oligonucleotides having from about 0.001% to about 1% acrylonitrile adduct, with from about 0.1% to about 1% acrylonitrile adduct being more preferred, from about 0.1% to about 0.75% acrylonitrile adduct being even more preferred, and from about 0.1% to about 0.5% acrylonitrile adduct being even more preferred. In particularly preferred embodiments, compositions comprising phosphodiester, phosphorothioate, or phosphorodithioate oligonucleotides, said oligonucleotides are provided that are substantially free of detectable acrylonitrile adduct. [0114] The present invention also provides composition comprising oligonucleotides that are substantially free of acrylonitrile adduct prepared by the methods of the invention. [0115] Further provided in accordance with the present invention are methods of preparing a sample of a phosphate linked oligonucleotide having a substantially reduced content of acrylonitrile adduct comprising: [0116] (a) providing a sample containing a plurality of oligomers, said oligomers having a plurality of phosphorus protecting groups; [0117] (b) contacting said oligomers with a deprotecting agent to remove substantially all of said phosphorus protecting groups from said oligomers; [0118] said deprotecting reagent comprising at least one amine, the conjugate acid of said amine having a pKa of from about 8 to about 11; said deprotecting reagent optionally further comprising one or more solvents selected from the group consisting of alkyl solvents, haloalkyl solvents, cyanoalkyl solvents, aryl solvents and aralkyl solvents; [0119] (c) optionally washing said oligomers; and [0120] (d) reacting said oligomers with a cleaving reagent. Further provided in accordance with the present invention are methods of preparing a sample of a phosphate linked oligonucleotide having a substantially reduced content of acrylonitrile adduct comprising: [0121] (a) providing a sample containing a plurality of oligomers, said oligomers having a plurality of phosphorus protecting groups; [0122] (b) contacting said oligomers with a deprotecting agent to remove substantially all of said phosphorus protecting groups from said oligomers; [0123] (c) washing said oligomers with a washing reagent, said washing reagent comprising at least one amine, the conjugate acid of said amine having a pKa of from about 8 to about 11; said deprotecting reagent optionally further comprising one or more solvents selected from the group consisting of alkyl solvents, haloalkyl solvents, cyanoalkyl solvents, aryl solvents and aralkyl solvents; and [0124] (d) reacting said oligomers with a cleaving reagent. DESCRIPTION OF PREFERRED EMBODIMENTS [0125] The present invention provides methods for the preparation of oligomeric compounds having phosphodiester, phosphorothioate, phosphorodithioate, or other internucleoside linkages, and to composition produced by the methods. [0126] The methods of the invention are applicable to both solution phase and solid phase chemistries. Representative solution phase techniques are described in U.S. Pat. No. 5,210,264, which is assigned to the assignee of the present invention. In some preferred embodiments, the methods of the present invention are employed for use in iterative solid phase oligonucleotide synthetic regimes. Representative solid phase techniques are those typically employed for DNA and RNA synthesis utilizing standard phosphoramidite chemistry, (see, e.g., Protocols For Oligonucleotides And Analogs, Agrawal, S., ed., Humana Press, Totowa, N.J., 1993, hereby incorporated by reference in its entirety). A preferred synthetic solid phase synthesis utilizes phosphoramidites as activated phosphate compounds. In this technique, a 5′-protected phosphoramidite monomer is reacted with a free hydroxyl on the growing oligomer chain to produce an intermediate phosphite compound, which is subsequently oxidized to the P v state using standard methods. This technique is commonly used for the synthesis of several types of linkages including phosphodiester, phosphorothioate, and phosphorodithioate linkages. [0127] Typically, the first step in such a process 's attachment of a first monomer or higher order subunit containing a protected 5′-hydroxyl to a solid support, usually through a linker, using standard methods and procedures known in the art. See for example, Oligonucleotides And Analogues A Practical Approach , Eckstein, F. Ed., IRL Press, N.Y, 1991, hereby incorporated by reference in its entirety. The support-bound monomer or higher order first synthon is then treated to remove the 5′-protecting group. The solid support bound monomer is then reacted with an activated phosphorous monomer or higher order synthon which is typically a nucleoside phosphoramidite, which is suitably protected at the phosphorus atom, and at any vulnerable exocyclic amino or hydroxyl groups. Typically, the coupling of the phosphoramidite to the support bound chain is accomplished under anhydrous conditions in the presence of an activating agent such as, for example, 1H-tetrazole, 5-(4-nitrophenyl)-1H-tetrazole, or diisopropylamino tetrazolide. [0128] The resulting linkage is a phosphite or thiophosphite, which is subsequently oxidized prior to the next iterative cycle. Choice of oxidizing or sulfurizing agent will determine whether the linkage will be oxidized or sulfurized to a phosphodiester, thiophosphodiester, or a dithiophosphodiester linkage. [0129] At the end of the synthetic regime, the support-bound oligomeric chain is typically treated with strong base (e.g., 30% aqueous ammonium hydroxide) to cleave the completed oligonucleotide form the solid support, and to concomitantly remove phosphorus protecting groups (which are typically β-cyanoethyl protecting groups) and exocyclic nucleobase protecting groups. Without intending that the invention be bound by any particular theory, it is believed that the loss of the cyanoethyl phosphorus protecting group occurs via a β-elimination mechanism, which produces acrylonitrile as a product. The acrylonitrile is believed to react in a Michael addition with nucleobase exocyclic amine and/or hydroxyl moieties, and in particular the N 3 position of thymidine residues, to form deleterious adducts. The methods of the present invention significantly reduce the content of such adducts formed during the removal of phosphorus protecting groups that are capable of participating in such adduct-forming addition reactions. [0130] Thus, in one aspect, the present invention provides synthetic methods comprising: [0131] a) providing a sample containing a plurality of oligomers of the Formula I: [0132] wherein: [0133] R 1 is H or a hydroxyl protecting group; [0134] B is a naturally occurring or non-naturally occurring nucleobase that is optionally protected at one or more exocyclic hydroxyl or amino groups; [0135] R 2 has the Formula III or IV: [0136] wherein [0137] E is C 1 -C 10 alkyl, N(Q 1 ) (Q 2 ) or N═C(Q 1 ) (Q 2 ) [0138] each Q 1 and Q 2 is, independently, H, C 1 -C 10 alkyl, dialkylaminoalkyl, a nitrogen protecting group, a tethered or untethered conjugate group, a linker to a solid support, or Q 1 and Q 2 ′ together, are joined in a nitrogen protecting group or a ring structure that can include at least one additional heteroatom selected from N and C; [0139] R 3 is OX 1 , SX 1 , or N(X 1 ) 2 ; [0140] each X 1 is, independently, H, C 1 -C 9 alkyl, C 1 -C 8 haloalkyl, C(═NH)N(H)Z 8 , C(═O)N(H)Z 8 or OC (═O)N(H) Z 9 ; [0141] Z 8 is H or C 1 -C 8 alkyl; [0142] L 1 , L 2 and L 3 comprise a ring system having from about 4 to about 7 carbon atoms or having from about 3 to about 6 carbon atoms and 1 or 2 hetero atoms wherein said hetero atoms are selected from oxygen, nitrogen and sulfur and [0143] wherein said ring system is aliphatic, unsaturated aliphatic, aromatic, or saturated or unsaturated heterocyclic; [0144] Y is alkyl or haloalkyl having 1 to about 10 carbon atoms, alkenyl having 2 to about 10 carbon atoms, alkynyl having 2 to about 10 carbon atoms, aryl having 6 to about 14 carbon atoms, N(Q 1 ) (Q 2 ), C(Q 1 ), halo, S(Q 1 ), or CN; [0145] each q 1 is, independently, from 2 to 10; [0146] each q 2 is, independently, 0 or 1; [0147] m is 0, 1 or 2; [0148] pp is from 1 to 10; and [0149] q 3 is from 1 to 10 with the proviso that when pp is 0, q 3 is greater than 1; [0150] R t is a phosphorus protecting group of formula: —C(R 10 ) 2 —C(R 10 ) 2 —W or —C 10 (R 10 ) 2 —(CH═CH) p —C(R 10 ) 2 —W [0151] each R 10 is independently H or lower alkyl; [0152] W is an electron withdrawing group; [0153] p is 0 to 3; [0154] each Y 2 is independently, O, CH 2 or NH; [0155] each Z is independently O or S; [0156] Each X is independently O or S; [0157] Q is a linker connected to a solid support, —OH or O—Pr where Pr is a hydroxyl protecting group; and [0158] n is 1 to about 100; [0159] b) contacting said sample with a deprotecting reagent for a time and under conditions sufficient to remove substantially said R t groups from said oligomers; and [0160] c) reacting said oligomers with a cleaving reagent; [0161] wherein said deprotecting reagent comprises at least one amine, the conjugate acid of said amine having a pKa of from about 8 to about 11; said deprotecting reagent optionally further comprising one or more solvents selected from the group consisting of alkyl solvents, haloalkyl solvents, cyanoalkyl solvents, aryl solvents and aralkyl solvents. [0162] Also provided by the present invention are methods for deprotecting a phosphate-linked oligomer, said oligomer having a plurality of protected phosphorus linkages of Formula II: [0163] wherein X and R t are as defined above, comprising: [0164] (a) providing a sample containing a plurality of said phosphate linked oligomers; [0165] (b) contacting said oligomers with a deprotecting reagent for a time and under conditions sufficient to remove substantially all of said R t groups from said oligomers, said deprotecting reagent containing at least one amine, the conjugate acid of said amine having a pKa of from about 8 to about 11; said deprotecting reagent optionally further comprising one or more solvents selected from the group consisting of alkyl solvents, haloalkyl solvents, cyanoalkyl solvents, aryl solvents and aralkyl solvents; and [0166] (c) reacting said oligomers with a cleaving reagent. [0167] In further embodiments, the present invention provides methods for deprotecting a phosphate-linked oligomer, said oligomer having a plurality of protected phosphorus linkages of formula II comprising: [0168] (a) providing a sample containing a plurality of said phosphate linked oligomers; [0169] (b) contacting said oligomers with a deprotecting reagent for a time and under conditions sufficient to remove substantially all of said R t groups from said oligomers; [0170] (c) washing said deprotected oligomers with a washing reagent comprising at least one amine, the conjugate acid of said amine having a pKa of from about 8 to about 11; said deprotecting reagent optionally further comprising one or more solvents selected from the group consisting of alkyl solvents, haloalkyl solvents, cyanoalkyl solvents, aryl solvents and aralkyl solvents; and [0171] (d) reacting said oligomers with a cleaving reagent. [0172] The present invention also provides methods for deprotecting a phosphate-linked oligomer, said oligomer having a plurality of phosphorus linkages of formula II comprising: [0173] (a) providing a sample containing a plurality of said phosphate linked oligomers; and [0174] (b) contacting said oligomers with a deprotecting reagent for a time and under conditions sufficient to remove substantially all of said R t groups from said oligomers, said deprotecting reagent comprising gaseous ammonia. [0175] Further provided in accordance with the present invention are methods of preparing a sample of a phosphate linked oligonucleotide having a substantially reduced content of acrylonitrile adduct comprising: [0176] (a) providing a sample containing a plurality of oligomers, said oligomers having a plurality of phosphorus protecting groups; [0177] (b) contacting said oligomers with a deprotecting agent to remove substantially all of said phosphorus protecting groups from said oligomers; [0178] said deprotecting reagent comprising at least one amine, the conjugate acid of said amine having a pKa of from about 8 to about 11; said deprotecting reagent optionally further comprising one or more solvents selected from the group consisting of alkyl solvents, haloalkyl solvents, cyanoalkyl solvents, aryl solvents and aralkyl solvents; [0179] (c) optionally washing said oligomers; and [0180] (d) reacting said oligomers with a cleaving reagent. [0181] Further provided in accordance with the present invention are methods of preparing a sample of a phosphate linked oligonucleotide having a substantially reduced content of acrylonitrile adduct comprising: [0182] (a) providing a sample containing a plurality of oligomers, said oligomers having a plurality of phosphorus protecting groups; [0183] (b) contacting said oligomers with a deprotecting agent to remove substantially all of said phosphorus protecting groups from said oligomers; [0184] (c) washing said oligomers with a washing reagent, said washing reagent comprising at least one amine, the conjugate acid of said amine having a pKa of from about 8 to about 11; said deprotecting reagent optionally further comprising one or more solvents selected from the group consisting of alkyl solvents, haloalkyl solvents, cyanoalkyl solvents, aryl solvents and aralkyl solvents; and [0185] (d) reacting said oligomers with a cleaving reagent. [0186] Thus, in some preferred methods of the invention, a support-bound or solution phase oligomer having a plurality of phosphorus protecting groups that are capable of producing acrylonitrile, or a structurally similar product that can form an adduct with nucleobase amino groups, is contacted with a deprotecting reagent that includes at least one amine. The amine is selected such that it is a sufficiently strong base to effect the removal of a substantial majority of the phosphorus protecting groups, but insufficiently strong to cause deprotonation the thymidine N 3 position, and hence activation of that position to adduct formation. It has been found that suitable amines include those whose conjugate acids have a pKa of from about 8 to about 11, more preferably from about 9 to about 11, even more preferably from about 10 to about 11. In general, it is preferred that the amine be an aliphatic amine of the formula (R) 3 N, (R) 2 NH, or RNH 2 where R is alkyl Two particularly suitable amines are triethylamine and piperidine. [0187] As used herein, the term “deprotect” or deprotection” is intended to mean the removal of the vast majority, and more preferably substantially all phosphorus protecting groups from the oligomers of interest. [0188] In preferred embodiments, the deprotecting reagent can be either an aliphatic amine, or a solution of one or more amines aliphatic as described above. In more preferred embodiments, the deprotecting reagent further comprises one or more solvents selected from the group consisting of alkyl solvents, haloalkyl solvents, cyanoalkyl solvents, aryl solvents and aralkyl solvents. Preferably, the solvent is a haloalkyl solvent or a cyanoalkyl solvent. Examples of particularly suitable solvents are acetonitrile and methylene chloride. [0189] In the practice of the present invention, it is greatly preferred that the vast majority of the cyanoethyl groups be removed before the oligomer is treated with the relatively strong conditions of the cleavage reagent (e.g., 30% aqueous ammonium hydroxide). The rate of deprotection of β-cyanoethyl groups from oligonucleotides has been shown to exhibit a marked solvent effect. For example, the half-life of a dimer containing a single cyanoethyl group in a 1:1 v/v solution of triethylamine in acetonitrile or methylene chloride is, very approximately, 10 min. at 25° C., whereas the half-life of the same compound in triethylamine-pyridine (1:1, v/v) is about ten times longer. Eritja et al. ( Tetrahedron, 48, 4171-4182 (1992)) recommend a three hour treatment with a 40% solution of triethylamine in pyridine as sufficient to avoid formation of acrylonitrile adduct to thymidine residues in oligonucleotides subsequently treated with DBU. However, it has been discovered that under the conditions described by Eritja, many of the cyanoethyl protecting groups would remain intact. While not wishing to be bound by a specific theory, it is believed that subsequent treatment with ammonium hydroxide (or any other strong base such as DBU) would lead to the formation of unacceptable levels of residues having acrylonitrile adducts. Thus, in the present invention it is preferred that the solvent which is contained in the deprotection reagent not include pyridine, or similar heterocyclic base solvents that could extend the time for removal of oligomer-bound β-cyanoethyl or other electronically similar protecting groups. [0190] At present, the detectable limit of acrylonitrile adduct by HPLC methodologies is believed to be about 0.1%. However, it is believed that the present methods provide oligomers having as little as 0.001% of such adduct. Thus, in preferred embodiments, the oligomers produced by the methods of the invention have from 0.001% to about 1% acrylonitrile adduct, with from about 0.1% to about 1% acrylonitrile adduct being more preferred, from about 0.1% to about 0.75% acrylonitrile adduct being even more preferred, and from about 0.1% to about 0.5% acrylonitrile adduct being even more preferred. In even more preferred embodiments, the oligomers are substantially free of detectable acrylonitrile adduct. [0191] As used herein, the term “acrylonitrile adduct” refers to adducts to exocyclic nucleobase adducts that result from the acrylonitrile formed during removal of β-cyanoethyl phosphorus protecting groups, or similar adducts formed by removal of protecting groups that form electronically similar products upon removal. [0192] Representative examples of such protecting groups are those having the formula: (R 10 ) 2 —C(R 10 ) 2 —W or —C(R 10 ) 2 —(CH═CH) p —C(R 10 )—W [0193] wherein each R 10 is independently H or lower alkyl, W is an electron withdrawing group, and p is 1 to 3. The term “electron withdrawing group” is intended to have its recognized meaning in the art as a chemical moiety that attracts electron density, whether through resonance or inductive effects. Examples of electron withdrawing groups are cyano, nitro, halogen, phenyl substituted in the ortho or para position with one or more halogen, nitro or cyano groups, and trihalomethyl groups. Those of skill in the art will readily recognize other electron withdrawing groups, as well as other phosphorus protecting groups that have similar potential to form adducts with exocyclic amino or hydroxyl functions. [0194] After contact with the deprotecting reagent, the oligomers can be further washed prior to reaction with a cleavage reagent, or reacted with the cleaving reagent directly. The cleaving reagent is a solution that includes a single reagent or combination of reagents that effect the cleavage of the deprotected oligomer from a solid support, and/or, where the oligomer is in solution, effects cleavage of exocyclic protecting groups, for example 30% aqueous ammonium hydroxide. [0195] In the methods of the invention, it is generally advantageous to effect removal of substantially all phosphorus protecting groups from the oligomers, and separating the acrylonitrile or acrylonitrile-like products from the oligomers prior to exposing oligomers to the more severe basic conditions that effect cleavage from the solid support, or removal of exocyclic and/or hydroxyl protecting groups. Thus, in some preferred embodiments, a washing step is utilized in between contact with deprotecting reagent and cleaving reagent. In some preferred embodiments the washing step is performed using one or more suitable solvents, for example acetonitrile or methylene chloride. In other preferred embodiments, washing is performed with a washing reagent that contains one or more amines as is employed in the deprotecting reagent. [0196] In some particularly preferred embodiments, a scavenger can be included in the deprotection reagent, cleaving reagent, washing reagent, or combinations thereof. In general, the scavenger is a molecule that reacts with the acrylonitrile or acrylonitrile-like products of deprotection, lowering the possibility of nucleobase adduct formation. Suitable scavengers include purines, pyrimidines, inosine, pyrroles, imidazoles, triazoles, mercaptans, beta amino thiols, phosphines, phosphites, dienes, ureas, thioureas, amides, imides, cyclic imides and ketones. Further useful scavengers include alkylmercaptans, thiols, ethylene glycol, substituted ethylene glycols, 1-butanethiol, S-(2-amino-4-thiazolylmethyl)isothiourea hydrochloride, 2-mercaptoethanol, 3,4-dichlorobenzylamine, benzylamine, benzylamine in the presence of carbon disulfide, hydroxylamine, 2-phenylindole, n-butylamine, diethyl ester of acetaminomalonic acid, ethyl ester of N-acetyl-2-cyanoglycine, 3-phenyl-4-(o-fluorophenyl)-2-butanone, 3,4-diphenyl-2-butanone, desoxybenzoin, -methoxyphthalimide, p-sulfobenzenediazonium chloride, p-sulfamidobenzenediazonium chloride. [0197] In some preferred embodiments, the scavenger is a resin containing a suitable scavenging molecule bound thereto. Exemplary scavenger resins include polymers having free thiol groups and polymers having free amino groups, for example a polymer-bound amine resin wherein the amine is selected from benzylamine, ethylenediamine, diethylamine triamine, tris(2-aminoethyl)amine, methylamine, methylguanidine, polylysine, oligolysine, Agropore™ NH 2 HL, Agropore™ NH 2 LL, 4-methoxytrityl resin, and thiol 2-chlorotrityl resin. [0198] The methods of the present invention are useful for the preparation of oligomeric compounds containing monomeric subunits that are joined by a variety of linkages, including phosphite, phosphodiester, phosphorothioate, and/or phosphorodithioate linkages. [0199] As used herein, the terms “oligomer” or “oligomeric compound” are used to refer to compounds containing a plurality of nucleoside monomer subunits that are joined by internucleoside linkages, preferably phosphorus-containing linkages, such as phosphite, phospho-diester, phosphorothioate, and/or phosphorodithioate linkages. The term “oligomeric compound” therefore includes naturally occurring oligonucleotides, their analogs, and synthetic oligonucleotides. [0200] In some preferred embodiments of the compounds of the invention, substituent W can be an electron withdrawing group selected such that it facilitates attack by a nucleophile. Accordingly, W can be any of a variety of electron withdrawing substituents, provided that it does not is otherwise interfere with the methods of the invention. Preferred non-silyl electron withdrawing W groups include cyano, NO 2 , alkaryl groups, sulfoxyl groups, sulfonyl groups, thio groups, substituted sulfoxyl groups, substituted sulfonyl groups, or substituted thio groups, wherein the substituents are selected from the group consisting of alkyl, aryl, or alkaryl. Particularly preferred are alkanoyl groups having the formula R—C(═O)— where R is an alkyl group of from 1 to six carbons, with acetyl groups being especially preferred. W can also be a trisubstituted silyl moiety, wherein the substituents are alkyl, aryl or both. [0201] In some preferred embodiments, the scavenger is a resin containing a suitable scavenging molecule bound thereto. Exemplary scavenger resins include polymers having free thiol groups and polymers having free amino groups, for example a polymer-bound amine resin wherein the amine is selected from benzylamine, ethylenediamine, diethylamine triamine, tris(2-aminoethyl)amine, methylamine, methylguanidine, polylysine, oligolysine, Agropore™ NH 2 HL, Agropore™ NH 2 LL (available from Aldrich Chem. Co. St. Louis. Mo.), 4-methoxytrityl resin, and thiol 2-chlorotrityl resin. [0202] When used as part of the cleaving reagent, contact with fluoride ion preferably is effected in a solvent such as tetrahydrofuran, acetonitrile, dimethoxyethane, or water. Fluoride ion preferably is provided in the form of one or more salts selected from tetraalkylammonium fluorides (e.g., tetrabutylammonium fluoride (TBAF)), potassium fluoride, cesium fluoride, or triethylammonium hydrogen fluoride. [0203] The present invention is applicable to the preparation of phosphate linked oligomers having a variety of internucleoside linkages including phosphite, phosphodiester, phosphorothioate, and phosphorodithioate linkages, and other linkages known in the art [0204] In preferred embodiments, the methods of the invention are used for the preparation of oligomeric compounds including oligonucleotides and their analogs. As used herein, the term “oligonucleotide analog” means compounds that can contain both naturally occurring (i.e. “natural”) and non-naturally occurring (“synthetic”) moieties, for example, nucleosidic subunits containing modified sugar and/or nucleobase portions. Such oligonucleotide analogs are typically structurally distinguishable from, yet functionally interchangeable with, naturally occurring or synthetic wild type oligonucleotides. Thus, oligonucleotide analogs include all such structures which function effectively to mimic the structure and/or function of a desired RNA or DNA strand, for example, by hybridizing to a target. The term synthetic nucleoside, for the purpose of the present invention, refers to a modified nucleoside. Representative modifications include modification of a heterocyclic base portion of a nucleoside to give a non-naturally occurring nucleobase, a sugar portion of a nucleoside, or both simultaneously. [0205] Representative nucleobases useful in the compounds and methods described herein include adenine, guanine, cytosine, uracil, and thymine, as well as other non-naturally occurring and natural nucleobases such as xanthine, hypoxanthine, 2-aminoadenine, 6-methyl and other alkyl derivatives of adenine and guanine, 2-propyl and other alkyl derivatives of adenine and guanine, 5-halo uracil and cytosine, 6-azo uracil, cytosine and thymine, 5-uracil (pseudo uracil), 4-thiouracil, 8-halo, oxa, amino, thiol, thioalkyl, hydroxyl and other 8-substituted adenines and guanines, 5-trifluoromethyl and other 5-substituted uracils and cytosines, 7-methylguanine. Further naturally and non naturally occurring nucleobases include those disclosed in U.S. Pat. No. 3,687,808 (Merigan, et al.), in chapter 15 by Sanghvi, in Antisense Research and Application , Ed. S. T. Crooke and B. Lebleu, CRC Press, 1993, in Englisch et al., Angewandte Chemie , International Edition, 1991, 30, 613-722 (see especially pages 622 and 623, and in the Concise Encyclopedia of Polymer Science and Engineering , J. I. Kroschwitz Ed., John Wiley & Sons, 1990, pages 858-859, Cook, P. D., Anti - Cancer Drug Design, 1991, 6, 585-607, each of which are hereby incorporated by reference in their entirety. The term ‘nucleosidic base’ is further intended to include heterocyclic compounds that can serve as like nucleosidic bases including certain ‘universal bases’ that are not nucleosidic bases in the most classical sense but serve as nucleosidic bases. Especially mentioned as a universal base is 3-nitropyrrole. [0206] As used herein, the term “alkyl” includes but is not limited to straight chain, branch chain, and alicyclic hydrocarbon groups. Alkyl groups of the present invention may be substituted. Representative alkyl substituents are disclosed in U.S. Pat. No. 5,212,295, at column 12, lines 41-50, hereby incorporated by reference in its entirety. [0207] As used herein, the term “aralkyl” denotes alkyl groups which bear aryl groups, for example, benzyl groups. The term “alkaryl” denotes aryl groups which bear alkyl groups, for example, methylphenyl groups. “Aryl” groups are aromatic cyclic compounds including but not limited to phenyl, naphthyl, anthracyl, phenanthryl, pyrenyl, and xylyl. [0208] As used herein, the term “alkanoyl” has its accustomed meaning as a group of formula —C(═O)-alkyl. A preferred alkanoyl group is the acetoyl group. [0209] In general, the term “hetero” denotes an atom other than carbon, preferably but not exclusively N, O, or S. Accordingly, the term “heterocycloalkyl” denotes an alkyl ring system having one or more heteroatoms (i.e., non-carbon atoms). Preferred heterocycloalkyl groups include, for example, morpholino groups. As used herein, the term “heterocycloalkenyl” denotes a ring system having one or more double bonds, and one or more heteroatoms. Preferred heterocycloalkenyl groups include, for example, pyrrolidino groups. [0210] In some preferred embodiments of the invention oligomers can be linked connected to a solid support. Solid supports are substrates which are capable of serving as the solid phase in solid phase synthetic methodologies, such as those described in Caruthers U.S. Pat. Nos. 4,415,732; 4,458,066; 4,500,707; 4,668,777; 4,973,679; and 5,132,418; and Koster U.S. Pat. Nos. 4,725,677 and Re. 34,069. Linkers are known in the art as short molecules which serve to connect a solid support to functional groups (e.g., hydroxyl groups) of initial synthon molecules in solid phase synthetic techniques. Suitable linkers are disclosed in, for example, Oligonucleotides And Analogues A Practical Approach , Eckstein, F. Ed., IRL Press, N.Y, 1991, Chapter 1, pages 1-23. Other linkers include the “TAMRA” linker described by Mullah et. al., Tetrahedron Letters, 1997, 38, 5751-5754, and the “Q-linker” described by Pon et. al., Nucleic Acid Reserach, 1997, 25, 3629-3635. [0211] Solid supports according to the invention include those generally known in the art to be suitable for use in solid phase methodologies, including, for example, controlled pore glass (CPG), oxalyl-controlled pore glass (see, e.g., Alul, etal., Nucleic Acids Research 1991, 19, 1527, hereby incorporated by reference in its entirety), TentaGel Support—an aminopolyethyleneglycol derivatized support (see, e.g., Wright, et al., Tetrahedron Letters 1993, 34, 3373, hereby incorporated by reference in its entirety) and Poros—a copolymer of polystyrene/divinylbenzene. [0212] In some preferred embodiments of the invention hydroxyl groups can be protected with a hydroxyl protecting group. A wide variety of hydroxyl protecting groups can be employed in the methods of the invention. Preferably, the protecting group is stable under basic conditions but can be removed under acidic conditions. In general, protecting groups render chemical functionalities inert to specific reaction conditions, and can be appended to and removed from such functionalities in a molecule without substantially damaging the remainder of the molecule. Representative hydroxyl protecting groups are disclosed by Beaucage, et al., Tetrahedron 1992, 48, 2223-2311, and also in Greene and Wuts, Protective Groups in Organic Synthesis , Chapter 2, 2 d ed, John Wiley & Sons, New York, 1991, each of which are hereby incorporated by reference in their entirety. Preferred protecting groups used for R 2 , R 3 and R 3a include dimethoxytrityl (DMT), monomethoxytrityl, 9-phenylxanthen-9-yl (Pixyl) and 9-(p-methoxyphenyl)xanthen-9-yl (Mox). The hydroxyl protecting group can be removed from oligomeric compounds of the invention by techniques well known in the art to form the free hydroxyl. For example, dimethoxytrityl protecting groups can be removed by protic acids such as formic acid, dichloroacetic acid, trichloroacetic acid, p-toluene sulphonic acid or with Lewis acids such as for example zinc bromide. See for example, Greene and Wuts, supra. [0213] In some preferred embodiments of the invention amino groups are appended to alkyl or to other groups such as, for example, to 2′-alkoxy groups. Such amino groups are also commonly present in naturally occurring and non-naturally occurring nucleobases. It is generally preferred that these amino groups be in protected form during the synthesis of oligomeric compounds of the invention. Representative amino protecting groups suitable for these purposes are discussed in Greene and Wuts, Protective Groups in Organic Synthesis , Chapter 7, 2 d ed, John Wiley & Sons, New York, 1991. Generally, as used herein, the term “protected” when used in connection with a molecular moiety such as “nucleobase” indicates that the molecular moiety contains one or more functionalities protected by protecting groups. [0214] Sulfurizing agents used during oxidation to form phosphorothioate and phosphorodithioate linkages include Beaucage reagent (see e.g. Iyer, R. P., et.al., J. Chem. Soc., 1990, 112, 1253-1254, and Iyer, R. P., et.al., J. Org. Chem., 1990, 55, 4693-4699); 3-methyl-1,2,4-thiazolin-5-one (MEDITH; Zong, et al., Tetrahedron Lett. 1999, 40, 2095); tetraethylthiuram disulfide (see e.g., Vu, H., Hirschbein, B. L., Tetrahedron Lett., 1991, 32, 3005-3008); dibenzoyl tetrasulfide (see e.g., Rao, M. V., et.al., Tetrahedron Lett., 1992, 33, 4839-4842); di(phenylacetyl)disulfide (see e.g., Kamer, P. C. J., Tetrahedron Lett., 1989, 30, 6757-6760); Bis(O,O-diisopropoxy phosphinothioyl)disulfides (see Stec et al., Tetrahedron Lett., 1993, 34, 5317-5320); 3-ethoxy-1,2,4-dithiazoline-5-one (see Nucleic Acids Research, 1996 24, 1602-1607, and Nucleic Acids Research, 1996 24, 3643-3644); Bis(p-chlorobenzenesulfonyl)disulfide (see Nucleic Acids Research, 1995 23, 4029-4033); sulfur, sulfur in combination with ligands like triaryl, trialkyl, triaralkyl, or trialkaryl phosphines. The foregoing references are hereby incorporated by reference in their entirety. [0215] Useful oxidizing agents used to form the phosphodiester or phosphorothioate linkages include iodine/tetrahydrofuran/water/pyridine or hydrogen peroxide/water or tert-butyl hydroperoxide or any peracid like m-chloroperbenzoic acid. In the case of sulfurization the reaction is performed under anhydrous conditions with the exclusion of air, in particular oxygen whereas in the case of oxidation the reaction can be performed under aqueous conditions. [0216] Oligonucleotides or oligonucleotide analogs according to the present invention hybridizable to a specific target preferably comprise from about 5 to about 100 monomer subunits. It is more preferred that such compounds comprise from about 5 to about 50 monomer subunits, more preferably 10 to about 30 monomer subunits, with 15 to 25 monomer subunits being particularly preferred. When used as “building blocks” in assembling larger oligomeric compounds, smaller oligomeric compounds are preferred. Libraries of dimeric, trimeric, or higher order compounds can be prepared by the methods of the invention. The use of small sequences synthesized via solution phase chemistries in automated synthesis of larger oligonucleotides enhances the coupling efficiency and the purity of the final oligonucleotides. See for example: Miura, K., et al., Chem. Pharm. Bull., 1987, 35, 833-836; Kumar, G., and Poonian, M. S., J. Org. Chem., 1984, 49, 4905-4912; Bannwarth, W., Helvetica Chimica Acta, 1985, 68, 1907-1913; Wolter, A., et al., nucleosides and nucleotides, 1986, 5, 65-77, each of which are hereby incorporated by reference in their entirety. [0217] The present invention is amenable to the preparation of oligomers that can have a wide variety of 2′-substituent groups. As used herein the term “2′-substituent group” includes groups attached to the 2′ position of the suagr moiety with or without an oxygen atom. 2′-Sugar modifications amenable to the present invention include fluoro, O-alkyl, O-alkylamino, O-alkylalkoxy, protected O-alkylamino, O-alkylaminoalkyl, O-alkyl imidazole, and polyethers of the formula (O-alkyl) m , where m is 1 to about 10. Preferred among these polyethers are linear and cyclic polyethylene glycols (PEGs), and (PEG)-containing groups, such as crown ethers and those which are disclosed by Ouchi, et al., Drug Design and Discovery 1992, 9, 93, Ravasio, et al., J. Org. Chem. 1991, 56, 4329, and Delgardo et. al., Critical Reviews in Therapeutic Drug Carrier Systems 1992, 9, 249, each of which are hereby incorporated by reference in their entirety. Further sugar modifications are disclosed in Cook, P. D., Anti - Cancer Drug Design, 1991, 6, 585-607. Fluoro, O-alkyl, O-alkylamino, O-alkyl imidazole, O-alkylaminoalkyl, and alkyl amino substitution is described in U.S. patent application Ser. No. 08/398,901, filed Mar. 6, 1995, entitled Oligomeric Compounds having Pyrimidine Nucleotide(s) with 2′ and 5′ Substitutions, hereby incorporated by reference in its entirety. [0218] Representative 2′-O— sugar substituents of formula XII are disclosed in U.S. patent application Ser. No. 09/130,973, filed Aug. 7, 1998, entitled Capped 2′-Oxyethoxy Oligonucleotides, hereby incorporated by reference in its entirety. [0219] Sugars having O-substitutions on the ribosyl ring are also amenable to the present invention. Representative substitutions for ring 0 include S, CH 2 , CHF, and CF 1 , see, e.g., Secrist, et al., Abstract 21 , Program & Abstracts, Tenth International Roundtable, Nucleosides, Nucleotides and their Biological Applications , Park City, Utah, Sep. 16-20, 1992, hereby incorporated by reference in its entirety. [0220] Representative cyclic 2′-O— sugar substituents of formula XIII are disclosed in U.S. patent application Ser. No. 09/123,108, filed Jul. 27, 1998, entitled RNA Targeted 2′-Modified Oligonucleotides that are Conformationally Preorganized, hereby incorporated by reference in its entirety. [0221] In one aspect of the invention, the compounds of the invention are used to modulate RNA or DNA, which code for a protein whose formation or activity it is desired to modulate. The targeting portion of the composition to be employed is, thus, selected to be complementary to the preselected portion of DNA or RNA, that is to be hybridizable to that portion. [0222] The oligomeric compounds and compositions of the invention can be used in diagnostics, therapeutics and as research reagents and kits. They can be used in pharmaceutical compositions by including a suitable pharmaceutically acceptable diluent or carrier. They further can be used for treating organisms having a disease characterized by the undesired production of a protein. The organism should be contacted with an oligonucleotide having a sequence that is capable of specifically hybridizing with a strand of nucleic acid coding for the undesirable protein. Treatments of this type can be practiced on a variety of organisms ranging from unicellular prokaryotic and eukaryotic organisms to multicellular eukaryotic organisms. Any organism that utilizes DNA-RNA transcription or RNA-protein translation as a fundamental part of its hereditary, metabolic or cellular control is susceptible to therapeutic and/or prophylactic treatment in accordance with the invention. Seemingly diverse organisms such as bacteria, yeast, protozoa, algae, all plants and all higher animal forms, including warm-blooded animals, can be treated. Further, each cell of multicellular eukaryotes can be treated, as they include both DNA-RNA transcription and RNA-protein translation as integral parts of their cellular activity. Furthermore, many of the organelles (e.g., mitochondria and chloroplasts) of eukaryotic cells also include transcription and translation mechanisms. Thus, single cells, cellular populations or organelles can also be included within the definition of organisms that can be treated with therapeutic or diagnostic oligonucleotides. [0223] As will be recognized, the steps of the methods of the present invention need not be performed any particular number of times or in any particular sequence. Additional objects, advantages, and novel features of this invention will become apparent to those skilled in the art upon examination of the following examples thereof, which are intended to be illustrative and not intended to be limiting. EXAMPLES Example 1 [0224] Comparative Example: Present Invention Versus Prior Art Method of Erjita et al. [0225] Treatment of cyanoethyl protected oligonucleotide phosphorothioates with ammonium hydroxide results in the generation of one equivalent of acrylonitrile (AN) per phosphorothioate linkage. In the presence of ammonium hydroxide a small percentage of thymidine residues react with the liberated AN to form N 3 -cyanoethylthymidine (CN-T) residues. [0226] Nonadecathymidinyloctadecaphosphorothioate (T-19 P═S) was synthesized and deprotected under three sets of conditions: [0227] (a) Ammonium hydroxide, 60° C., 16 h; [0228] (b) Triethylamine-pyridine (2:3 v/v), 25° C., 3 h then ammonium hydroxide, 60° C., 16 h; [0229] (c) Triethylamine-acetonitrile (1:1, v/v), 25° C., 12 h, then ammonium hydroxide, 60° C., 16 h. [0230] The second set of conditions are those recommended by Erijta. The crude oligonucleotides obtained by evaporation of the ammonium hydroxide lysates were detritylated and inspected by liquid chromatography-mass spectroscopy (LC-MS) in order to quantify the amount of CN-T present. It was shown that the levels of CN-T in T-19 P—S samples subjected to conditions a), b) and c) were ca. 15%, 2% and less than 0.1%, respectively. [0231] The results demonstrate that the conditions proposed by Erijta lead to the formation of oligonucleotides that still contain high levels of CN-T residues, where as the methods of the present invention suppress CN-T formation to a level below the detection limit of the assay. Example 2 [0232] Synthesis of Fully-Modified 5′-D(TTT-TTT-TTT-TTT-TTT-TTT-T)-3′ Phosphorothioate 20-mor [0233] The synthesis of the above sequence was performed on a Pharmacia OligoPilot I Synthesizer on a 30 micromole scale using the cyanoethyl phosphoramidites obtained from Pharmacia and Pharmacia's HL 30 primary support. Detritylation was performed using 3% dichloroacetic acid in toluene (volume/volume). Activation of phosphoramidites was done with a 0.45 M solution of 1H-tetrazole in acetonitrile. Sulfurization was performed using a 0.2 M solution of phenylacetyl disulfide in acetonitrile:3-picoline (1:1 v/v) for 1 minute. At the end of synthesis, the support was washed with a solution of triethylamine in acetonitrile (1:1, v/v) for 12 h, cleaved, deprotected and purified in the usual manner. Example 3 [0234] Synthesis of Fully-Modified 5′-d(GCC-CAA-GCT-GGC-ATC-CGT-CA)-3′ phosphoro-thioat 20-mer [0235] The synthesis of the above sequence was performed on a Pharmacia OligoPilot I Synthesizer on a 160 micromole scale using the cyanoethyl phosphoramidites obtained from Pharmacia and Pharmacia's HL 30 primary support. Detritylation was performed using 3% dichloroacetic acid in toluene (volume/volume). Activation of phosphoramidites was done with a 0.45 M solution of 1H-tetrazole in acetonitrile. Sulfurization was performed using a 0.2 M solution of phenylacetyl disulfide in acetonitrile:3-picoline (1:1 v/v) for 2 minutes. At the end of synthesis, the support was washed with a solution of triethylamine in acetonitrile (1:1, v/v) for 12 h, cleaved, deprotected and purified in the usual manner. Example 4 [0236] Synthesis of Fully-Modified 5′-d(TTT-TTT-TTT-TTT-TTT-TTT-T)-3′ phosphorothioate 20-mer [0237] The synthesis of the above sequence was performed on a Pharmacia OligoPilot I Synthesizer on a 30 micromole scale using the cyanoethyl phosphoramidites obtained from Pharmacia and Pharmacia's HL 30 primary support. Detritylation was performed using 3% dichloroacetic acid in toluene (volume/volume). Activation of phosphoramidites was done with a 0.45 M solution of 1H-tetrazole in acetonitrile. Sulfurization was performed using a 0.2 M solution of phenylacetyl disulfide in acetonitrile:3-picoline (1:1 v/v) for 1 minute. At the end of synthesis, the support was transferred to a container, stirred with a solution of triethylamine in acetonitrile (1:1, v/v) for 12 h, filtered, then treated with 30% aqueous ammonium hydroxide, cleaved, deprotected and purified in the usual manner. Example 5 [0238] Synthesis of Fully-Modified 5′-d(GCC-CAA-GCT-GGC-ATC-CGT-CA)-3′ phosphorothioate 20-mer [0239] The synthesis of the above sequence was performed on a Pharmacia OligoPilot I Synthesizer on a 160 micromole scale using the cyanoethyl phosphoramidites obtained from Pharmacia and Pharmacia's HL 30 primary support. Detritylation was performed using 3% dichloroacetic acid in toluene (volume/volume). Activation of phosphoramidites was done with a 0.45 M solution of 1H-tetrazole in acetonitrile. Sulfurization was performed using a 0.2 M solution of phenylacetyl disulfide in acetonitrile:3-picoline (1:1 v/v) for 2 minutes. At the end of synthesis, the support was transferred to a container, stirred with a solution of triethylamine in acetonitrile (1:1, v/v) for 12 h, filtered, then treated with 30% aqueous ammonium hydroxide, cleaved, deprotected and purified in the usual manner. Example 6 [0240] Synthesis of Fully-Modified 5′-d(TTT-TTT-TTT-TTT-TTT-TTT-T)-3′ phosphorothioate 20-mer [0241] The synthesis of the above sequence was performed on a Pharmacia OligoPilot I Synthesizer on a 30 micromole scale using the cyanoethyl phosphoramidites obtained from Pharmacia and Pharmacia's HL 30 primary support. Detritylation was performed using 3% dichloroacetic acid in toluene (volume/volume). Activation of phosphoramidites was done with a 0.45 M solution of 1H-tetrazole in acetonitrile. Sulfurization was performed using a 0.2 M solution of phenylacetyl disulfide in acetonitrile:3-picoline (1:1 v/v) for 1 minutes. At the end of synthesis, the support was taken in 30% aqueous ammonium hydroxide along with thymidine, cleaved, deprotected and purified in the usual manner. Example 7 [0242] Synthesis of Fully-Modified 5′-d(GCC-CAA-GCT-GGC-ATC-CGT-CA)-3′ phosphorothioate 20-mer [0243] The synthesis of the above sequence was performed on a Pharmacia OligoPilot I Synthesizer on a 160 micromole scale using the cyanoethyl phosphoramidites obtained from Pharmacia and Pharmacia's HL 30 primary support. Detritylation was performed using 3% dichloroacetic acid in toluene (volume/volume). Activation of phosphoramidites was done with a 0.45 M solution of 1H-tetrazole in acetonitrile. Sulfurization was performed using a 0.2 M solution of phenylacetyl disulfide in acetonitrile:3-picoline (1:1 v/v) for 2 minutes. At the end of synthesis, the support was taken in 30% aqueous ammonium hydroxide along with thymidine, cleaved, deprotected and purified in the usual manner. Example 8 [0244] Synthesis of Fully-Modified 5′-d(TTT-TTT-TTT-TTT-TTT-TTT-T)-3′ phosphorothioate 20-mer [0245] The synthesis of the above sequence was performed on a Pharmacia OligoPilot I Synthesizer on a 30 micromole scale using the cyanoethyl phosphoramidites obtained from Pharmacia and Pharmacia's HL 30 primary support. Detritylation was performed using 3% dichloroacetic acid in toluene (volume/volume). Activation of phosphoramidites was done with a 0.4 M solution of 1H-tetrazole in acetonitrile. Sulfurization was performed using a 0.2 M solution of phenylacetyl disulfide in acetonitrile:3-picoline (1:1 v/v) for 1 minute. At the end of synthesis, the support was taken in 30% aqueous ammonium hydroxide along with uridine, cleaved, deprotected and purified in the usual manner. Example 9 [0246] Synthesis of Fully-Modified 5′-d(GCC-CAA-GCT-GGC-ATC-CGT-CA)-3′ phosphorothioate 20-mer [0247] The synthesis of the above sequence was performed on a Pharmacia OligoPilot I Synthesizer on a 160 micromole scale using the cyanoethyl phosphoramidites obtained from Pharmacia and Pharmacia's HL 30 primary support. Detritylation was performed using 3% dichloroacetic acid in toluene (volume/volume). Activation of phosphoramidites was done with a 0.45 M solution of 1H-tetrazole in acetonitrile. Sulfurization was performed using a 0.2 M solution of phenylacetyl disulfide in acetonitrile:3-picoline (1:1 v/v) for 2 minutes. At the end of synthesis, the support was taken in 30% aqueous ammonium hydroxide along with uridine, cleaved, deprotected and purified in the usual manner. Example 10 [0248] Synthesis of Fully-Modified 5′-d(TTT-TTT-TTT-TTT-TTT-TTT-T)-3′ phosphorothioate 20-mer [0249] The synthesis of the above sequence was performed on a Pharmacia OligoPilot I Synthesizer on a 30 micromole scale using the cyanoethyl phosphoramidites obtained from Pharmacia and Pharmacia's HL 30 primary support. Detritylation was performed using 3% dichloroacetic acid in toluene (volume/volume). Activation of phosphoramidites was done with a 0.45 M solution of 1H-tetrazole in acetonitrile. Sulfurization was performed using a 0.2 M solution of phenylacetyl disulfide in acetonitrile:3-picoline (1:1 v/v) for 1 minutes. At the end of synthesis, the support was taken in 30% aqueous ammonium hydroxide along with imidazole, cleaved, deprotected and purified in the usual manner. Example 11 [0250] Synthesis of Fully-Modified 5′-d(GCC-CAA-GCT-GGC-ATC-CGT-CA)-3′ phospharothioate 20-mer [0251] The synthesis of the above sequence was performed on a Pharmacia OligoPilot I Synthesizer on a 160 micromole scale using the cyanoethyl phosphoramidites obtained from Pharmacia and Pharmacia's HL 30 primary support. Detritylation was performed using 3% dichloroacetic acid in toluene (volume/volume). Activation of phosphoramidites was done with a 0.45 M solution of 1H-tetrazole in acetonitrile. Sulfurization was performed using a 0.2 M solution of phenylacetyl disulfide in acetonitrile:3-picoline (1:1 v/v) for 2 minutes. At the end of synthesis, the support was taken in 30% aqueous ammonium hydroxide along with imidazole, cleaved, deprotected and purified in the usual manner. Example 12 [0252] GN Manufacture of Fully-Modified 5′-d(GCC-CAA-GCT-GGC-ATC-CGT-CA)-3′ phosphorothioate 20-mer (ISIS 2302) on OligoProcess [0253] ISIS 2302 [5′-d(GCC-CAA-GCT-GGC-ATC-CGT-CA)-3′] was manufactured under Good Manufacturing Practice (GMP) conditions on a Pharmacia OligoProcess Synthesizer on a 150 mmole scale using the cyanoethyl phosphoramidites obtained from Pharmacia and Pharmacia's HL 30 primary support. Detritylation was performed using 3% dichloroacetic acid in toluene (volume/volume). Activation of phosphoramidites was done with a 0.4 M solution of 1H-tetrazole in acetonitrile. Sulfurization was performed using a 0.2 M solution of phenylacetyl disulfide in acetonitrile:3-picoline (1:1 v/v) for 2 minutes. At the end of synthesis, the support was washed with a solution of triethylamine in acetonitrile (1:1, v/v) for 30 minutes and then let stand at room temperature overnight, filtered, washed with acetonitrile solvent and then treated with 30% aqueous ammonium hydroxide, cleaved, deprotected and purified in the usual manner. The oligonucleotide was analyzed by mass spectroscopy to confirm the elimination of acrylonitrile adduct. Example 13 [0254] Synthesis of fully-modified 5′-d(TTT-TTT-TTT-TTT-TTT-TTT-T)-3′ phosphorothioate 20-mer [0255] The synthesis of the above sequence was performed on a Pharmacia OligoPilot I Synthesizer on a 30 micromole scale using the cyanoethyl phosphoramidites obtained from Pharmacia and Pharmacia's HL 30 primary support. Detritylation was performed using 3% dichloroacetic acid in toluene (volume/volume). Activation of phosphoramidites was done with a 0.4 M solution of 1H-tetrazole in acetonitrile. Sulfurization was performed using a 0.2 M solution of phenylacetyl disulfide in acetonitrile:3-picoline (1:1 v/v) for 2 minutes. At the end of synthesis, the support was incubated with thymidine nucleoside (20 equivalents), deprotected and purified in the usual manner. Example 14 [0256] Synthesis of Fully-Modified 5′-d(TTT-TTT-TTT-TTT-TTT-TTT-T)-3′ phosphorothioate 20-mer [0257] The synthesis of the above sequence was performed on a Pharmacia OligoPilot I Synthesizer on a 30 micromole scale using the cyanoethyl phosphoramidites obtained from Pharmacia and Pharmacia's HL 30 primary support. Detritylation was performed using 3% dichloroacetic acid in toluene (volume/volume). Activation of phosphoramidites was done with a 0.4 M solution of 1H-tetrazole in acetonitrile. Sulfurization was performed using a 0.2 M solution of phenylacetyl disulfide in acetonitrile:3-picoline (1:1 v/v) for 2 minutes. At the end of synthesis, the support was incubated with uridine nucleoside (20 equivalents), deprotected and purified in the usual manner. Example 15 [0258] Synthesis of Fully-Modified 5′-d(TTT-TTT-TTT-TTT-TTT-TTT-T)-3′ phosphorothioate 20-mer [0259] The synthesis of the above sequence was performed on a Pharmacia OligoPilot I Synthesizer on a 30 micromole scale using the cyanoethyl phosphoramidites obtained from Pharmacia and Pharmacia's HL 30 primary support. Detritylation was performed using 3% dichloroacetic acid in toluene (volume/volume). Activation of phosphoramidites was done with a 0.4 M solution of 1H-tetrazole in acetonitrile. Sulfurization was performed using a 0.2 M solution of phenylacetyl disulfide in acetonitrile:3-picoline (1:1 v/v) for 2 minutes. At the end of synthesis, the support was incubated with inosine nucleoside (20 equivalents), deprotected and purified in the usual manner. Example 16 [0260] Synthesis of Fully-Modified 5′-d(TTT-TTT-TTT-TTT-TTT-TTT-T)-3′ phosphorothicate 20-mer [0261] The synthesis of the above sequence was performed on a Pharmacia OligoPilot I Synthesizer on a 30 micromole scale using the cyanoethyl phosphoramidites obtained from Pharmacia and Pharmacia's HL 30 primary support. Detritylation was performed using 3% dichloroacetic acid in toluene (volume/volume). Activation of phosphoramidites was done with a 0.4 M solution of 1H-tetrazole in acetonitrile. Sulfurization was performed using a 0.2 M solution of phenylacetyl disulfide in acetonitrile:3-picoline (1:1 v/v) for 2 minutes. At the end of synthesis, the support was incubated with thymine (25 equivalents), deprotected and purified in the usual manner. Example 17 [0262] Synthesis of Fully-Modified 5′-d(TTT-TTT-TTT-TTT-TTT-TTT-T)-3′ phosphorothioate 20-mer [0263] The synthesis of the above sequence was performed on a Pharmacia OligoPilot I Synthesizer on a 30 micromole scale using the cyanoethyl phosphoramidites obtained from Pharmacia and Pharmacia's HL 30 primary support. Detritylation was performed using 3% dichloroacetic acid in toluene (volume/volume). Activation of phosphoramidites was done with a 0.4 M solution of 1H-tetrazole in acetonitrile. Sulfurization was performed using a 0.2 M solution of phenylacetyl disulfide in acetonitrile:3-picoline (1:1 v/v) for 2 minutes. At the end of synthesis, the support was incubated with uracil (25 equivalents), deprotected and purified in the usual manner. Example 18 [0264] Synthesis of Fully-Modified 5′-d(TTT-TTT-TTT-TTT-TTT-TTT-T)-3′ phosphorothioate 20-mer [0265] The synthesis of the above sequence was performed on a Pharmacia OligoPilot I Synthesizer on a 30 micromole scale using the cyanoethyl phosphoramidites obtained from Pharmacia and Pharmacia's HL 30 primary support. Detritylation was performed using 3% dichloroacetic acid in toluene (volume/volume). Activation of phosphoramidites was done with a 0.4 M solution of 1H-tetrazole in acetonitrile. Sulfurization was performed using a 0.2 M solution of phenylacetyl disulfide in acetonitrile:3-picoline (1:1 v/v) for 2 minutes. At the end of synthesis, the support was incubated with imidazole (50 equivalents), deprotected and purified in the usual manner. Example 19 [0266] Synthesis of Fully-Modified 5′-d(TTT-TTT-TTT-TTT-TTT-TTT-T)-3′ phosphorothioate 20-mer [0267] The synthesis of the above sequence was performed on a Pharmacia OligoPilot I Synthesizer on a 30 micromole scale using the cyanoethyl phosphoramidites obtained from Pharmacia and Pharmacia's HL 30 primary support. Detritylation was performed using 3% dichloroacetic acid in toluene (volume/volume). Activation of phosphoramidites was done with a 0.4 M solution of 1H-tetrazole in acetonitrile. Sulfurization was performed using a 0.2 M solution of phenylacetyl disulfide in acetonitrile:3-picoline (1:1 v/v) for 2 minutes. At the end of synthesis, the support was incubated with benzyl mercaptan (50 equivalents), deprotected and purified in the usual manner. Examples 20-27 [0268] Oligonucleotide Synthesis. [0269] Oligodeoxynucleotides were assembled on an ABI 380B DNA Synthesizer using 5′-O-(4,4′-dimethoxytrityl)nucleoside 3′-O-(carboxymethyloxy)acetate derivatized CPG 1 (shown in Scheme 1 below) phosphoramidite chemistry, and either commercial oxidizer or 3H-1,2-benzodithiol-3-one 1,1-dioxide (0.05 M in MeCN) as the sulfur-transfer reagent. [0270] Deoxynucleoside CE phosphoramidites protected in a standard manner (A bz , C bz , G ib ) were used to synthesize oligonucleotides presented in Examples 21, 23-27. Those used for the preparation of oligonucleotides presented in Examples 20 and 22 were uniformly protected with either phenoxyacetyl (PAC) or 4-(t-butyl)phenoxyacetyl (tBPA) groups. Example 20 [0271] Two Step Deprotection of Oligonucleotides with Secondary Amines in an Organic Solvent Followed by Mothanolic K 2 CO 3 [0272] Deprotection procedure is exemplified on Scheme 2 for dodecathymidylate 5. After completeness of oligonucleotide synthesis a solid support-bound 2 was decyanoethylated with either 2M diethylamine or 1M piperidine in MeCN, dioxane, THF, or DMF (3 mL) for 2 to 12 h. The column was washed with dioxane (10 mL) to give 3. Other amines, for instance, morpholine, pyrrolidine, or dimethylamine can also be used on this step. [0273] The oligonucleotide 4 was released from the solid support 3 by treatment with 0.01 to 0.05 M K 2 CO 3 in MeOH (25 mL and 2′20 mL for 1 and 15 mmol syntheses, respectively). Each portion was passed forth and back through the column for 45 min, neutralized by passing through short column with Dowex 50 W′B (PyH + ; ca. 1 mL). The combined eluates were evaporated to dryness, co-evaporated with MeCN (10 mL), and dissolved in water. Target oligonucleotide 4 was isolated by RP HPLC on a Delta Pak 15 mm C18 300 Å column (3.9×300 mm and 7.8×300 mm for 1 and 15 mmol syntheses, respectively), using 0.1 M NH 4 OAc as buffer A, 80% aq MeCN as buffer B, and a linear gradient from 0 to 60% B in 40 min at a flow rate 1.5 and 5 mL min −1 , respectively. Collected fractions were evaporated and detritylated with 80% aq AcOH for 30 min at room temperature. The solvent was evaporated, the product was re-dissolved in water and desalted by injecting on to the same column, then washing with water (10 min) and eluting an oligonucleotide 5 as an ammonium salt with 50% aq MeCN (20 min). Homogeneity of 5 was characterized by R? HPLC and capillary electrophoresis. ESMS: 3764.2 (found); 3765.1 (calculated) [0274] The efficiency of the deprotection method was verified in preparation of oligonucleotide phosphorothioates 6 and 7 (Isis 1939) and phosphodiester oligonucleotide 8 in 1 to 15 mmol scale. [0275] 6: C 5 A 2 T 11 thioate. ESMS: 5628.3 (found); 5629.6 (calculated). [0276] 7: C 5 AC 2 ACT 2 C 4 TCTC thioate. ESMS: 6438.6 (found); 6440.2 (calculated). [0277] 8: C 5 A 2 T 11 . ESMS: 5355.8 (found); 5356.4 (calculated). Example 21 [0278] Two Step Deprotection of Oligonucleotide TGCATC 5 AG 2 C 2 AC 2 AT (9) With Secondary Amines in an Organic Solvent Followed by Ammonolysis [0279] A solid support-bound oligonucleotide was decyanoethylated with either 2M diethylamine or 1M piperidine, morpholine, or diethylamine in MeCN, dioxane, THF, or DMF as described in Example 20. Other amines, for instance, morpholine, pyrrolidine, or dimethylamine can also be used on this step. [0280] The solid support was treated with conc. aq ammonia for 2 h at room temperature, the solution was collected and kept at 55° C. for 8 h. On removal of solvent, the residue was re-dissolved in water and purified as described in Example 20. [0281] 9: ESMS: 5980.9 (found); 5982.8 (calculated). [0282] 10: TGCATC 5 AG 2 C 2 AC 2 AT thioate. ESMS: 6287.8 (found); 6288.0 (calculated). Example 22 [0283] Deprotection of Synthetic Oligonucleotides with Aqueous Amines. [0284] Deprotection procedure is exemplified for oligonucleotide 10. A solid support-bound material (20 μmol) was treated with 1 M aq piperidine for 2 h at room temperature. Other amines, for instance, morpholine, pyrrolidine, diethylamine, dimethylamine, ethylamine, or methylamine can also be used on this step. The solid support was washed with another portion of the deprotecting reagent, and combined solutions were evaporated under reduced pressure. Crude 5′-DMTr protected oligonucleotide was dissolved in water (5 mL) and purified by semipreparative HPLC on a DeltaPak C18 column (Waters, 15 mm; 300 Å; 25 100 mm) using 0.1 M NH 4 OAc as buffer A, 80% aq MeCN as buffer B, and a linear gradient from 0 to 40% B in 50 min at a flow rate 15 mL min −1 . Collected fractions were evaporated, the residue was treated with 80% aq AcOH for 30 min and evaporated to dryness. The obtained material was dissolved in 50% aq DMSO and loaded onto the same column. The column was washed with 0.05 M aq NaOAc (15 min) and water (15 min) at a flow rate 15 mL min −1 . Elution with 60% aq MeCN and evaporation to dryness gave 23.0 mg (20%) of desalted oligonucleotide 10 (Na + salt), ESMS: 6286.4 (found); 6288.0 (calculated). Example 23 [0285] Deprotection of Synthetic Oligonucleotides with Aqueous Secondary Amines. [0286] On completeness of oligonucleotide synthesis, a solid support-bound material (20 mmol) was treated with an aq amine as described in Example 22. On evaporation of the solution of the deprotecting reagent, the residue was treated with ammonium hydroxide for 8 h at 55° C., and the solvent was evaporated. The product, 6, was isolated and characterized as described in Example 22. Example 24 [0287] Deprotection of Synthetic Oligonucleotides with Ammonia in the Presence of Aminoalkyl Resins as Acrylonitrile Scavengers. Method A. [0288] On completeness of oligonucleotide synthesis, a solid support-bound material (20 mmol) is mixed with an aminoalkyl resin [for instance, aminoalkyl CPG or polymer-bound tris(2-aminoethyl)amine] and treated with conc. aq ammonia for 2 h at room temperature. The solid phase is filtered off, and the deprotection is completed by keeping the solution at 55° C for 8 h. The solvent was evaporated, and the product is isolated and characterized as described in Example 22. Example 25 [0289] Deprotection of Synthetic Oligonucleotides with Ammonia in the Presence of Aminoalkyl Resins as Acrylonitrile Scavengers. Method B. [0290] A solid support-bound material (20 mmol) is treated with a flow of conc. aq ammonia for 2 h at room temperature. On leaving the reaction vessel, the solution is passed through a second column that contained an aminoalkyl resin as in Example 24, and collected. Optionally, the collected solution may be recycled by passing again through both columns. When the releasing of oligonucleotide from CPG is complete, the oligonucleotide solution is collected and treated as in Example 24. Example 26 [0291] Deprotection of Synthetic Oligonucleotides with Ammonia in the Presence of Mercaptanes as Acrylonitrile Scavengers. [0292] A solid support-bound oligonucleotide was treated with conc. aq ammonia and thiocresol (0.1 M) for 2 h at room temperature, the solution was collected and kept at 55° C. for 8 h. On removal of solvent, the residue was re-dissolved in water and extracted twice with methylene chloride. The aqueous layer was collected, and the product, 5, was isolated and characterized as described in Example 20. Other thiols, for instance, thiophenol, mercaptoethanol, 1,3-ethanedithiol, or ethanethiol can also be used as acrylonitrile scavengers. Example 27 [0293] Deprotection of Synthetic Oligonucleotides with Amonia in the Presence of Mercaptoalkylated Resins as Acrylonitrile Scavengers. [0294] A solid support-bound oligonucleotide is treated as in Example 25, but the second column contains a mercaptoalkylated resin (for instance, reported previously mercaptoalkylated resins 1 or NovaSyn o TG thiol resin). The product is isolated and characterized as described in Example 20. [0295] It is intended that each of the patents, applications, printed publications, and other published documents mentioned or referred to in this specification be herein incorporated by reference in their entirety. [0296] Those skilled in the art will appreciate that numerous changes and modifications may be made to the preferred embodiments of the invention and that such changes and modifications may be made without departing from the spirit of the invention. It is therefore intended that the appended claims cover all such equivalent variations as fall within the true spirit and scope of the invention. 1 5 1 19 DNA Artificial Sequence Synthetic Construct 1 tttttttttt ttttttttt 19 2 20 DNA Artificial Sequence Synthetic Construct 2 gcccaagctg gcatccgtca 20 3 18 DNA Artificial Sequence Phosphorothioate backbone 3 cccccaattt tttttttt 18 4 20 DNA Artificial Sequence Phosphorothioate backbone 4 cccccaccac ttcccctctc 20 5 20 DNA Artificial Sequence Phosphorothioate backbone 5 tgcatccccc aggccaccat 20

Synthetic processes are provided wherein oligomeric compounds are prepared having phosphodiester, phosphorothioate, phosphorodithioate, or other covalent linkages. The oligomers have substantially reduced exocyclic adducts deriving from acrylonitrile or related contaminants.

FIELD OF THE INVENTION [0001] The present invention relates to apparatus for preheating substrates prior to inserting them into a processing chamber for conducting a semiconductor manufacturing process step. BACKGROUND OF THE INVENTION [0002] Semiconductor processing chambers are used to provide process environments for the fabrication of integrated circuits and other semiconductor devices on wafers. Wafers are sequentially processed through a series of many different processing steps which include depositions of various layers (metal, insulator and dielectric) on the wafer, each of which may be followed by masking and etching process steps with or without planarization steps also being involved. By selective repetition of the deposition and processing of these layers, integrated circuits may be fabricated on the wafer or substrate. [0003] Deposition and etching processes may be accomplished by various techniques, including various chemical vapor deposition (CVD) processes, physical vapor deposition (PVD) processes, such as sputtering, and plasma processes, to name a few. Most processing chambers used in conducting these processes include a vacuum chamber containing a wafer support member upon which the wafer is placed to be processed. A gas inlet having a mass flow controller, and a throttled exhaust coupled to a vacuum pump through a gate valve communicate with the vacuum chamber to provide the process gas flow and the vacuum conditions required for processing the wafer. A slit valve is provided in the vacuum chamber which allows access by a robot blade used to load the wafer on the wafer support for processing, as well as to remove the wafer from the wafer support and chamber after the process step has been completed. [0004] Many such processes require elevated temperatures for best results. Although it is possible that the wafer support may start out at room temperature initially for processing of a first wafer, this is certainly not the usual case, since there is very little cooling of the wafer support, and certainly not cooling to room temperature during the time that a first wafer is removed and another wafer is loaded to be processed. When a wafer at room temperature is loaded onto a wafer support that is at operating temperature, a phenomenon has been observed where the wafer tends to “chatter” or “dance” on the wafer support initially after placement there. This phenomenon is believed to be caused when the pins, which support the wafer to allow the robot arm to slide out from between the wafer and wafer support, withdraw to allow the wafer to contact the wafer support. It is believed that cold (i.e., relative to the operating temperature) air is trapped between the wafer and wafer support, and as that air is heated it expands and causes the wafer to chatter as it escapes from between the wafer support and the wafer. This phenomenon, although observed with 200 mm wafer processing, was not as severe a problem as it has become with 300 mm wafer processing, where the chattering is much more pronounced, due to the larger surface area of the wafer, and this is likely to cause misalignment of and/or damage to the wafer. [0005] One way of eliminating the chattering is to leave the wafer on the lift pins for a significant period of time (e.g., about 45 seconds) after placing it in the processing chamber to allow it to heat up prior to contacting it with the chuck. However, this additional time requirement seriously impacts the throughput of the processing. The chattering phenomenon can also be eliminated by preheating the wafers to a temperature significantly above room temperature, although they do not need to be heated all the way up to operating temperature. Such preheating also increases throughput in the processing chamber, since it then takes less time to get the wafer up to processing temperatures. A conventional heater may be used to preheat a wafer substrate. Conventional heaters are generally thick plates, having a thickness of at least 0.5″ up to about 1″, and are often made of cast aluminum or aluminum alloy and having a tube heater filament or embedded metal electrode running through the plate to heat the overall plate. A general idea of such construction can be gained from a reading of the description of the susceptor plate described in U.S. Pat. No. 5,633,073. Although the susceptor plate in the patent is described for use within a processing chamber, a similar construction can be used for preheating. [0006] Conventional heaters have certain drawbacks including the fact that they are relatively thick and bulky, which limits their effectiveness if they are to be used in a stack arrangement for heating of multiple wafers simultaneously. This thickness also translates to a relatively large mass to be heated, and therefor the response time for initial heating up of the heater or changing the steady state temperature of a heater is relatively large (i.e., slow response time). Still further, conventional heaters are relatively heavy and expensive, costing on the order of $4,000 to $5,000 per heater plate. [0007] In view of the foregoing, there remains a need for a heater system that has better response time, is more adaptable to stacked usage, and is less expensive. SUMMARY OF THE INVENTION [0008] A heating chamber assembly is provided with a stack of at least two thick film heater plates forming at least one slot configured to receive a wafer therein. A chamber surrounds the stack and has a door therethrough which opens to allow insertion of wafers and withdrawal of wafers from the assembly. Each slot is alignable with the door for receiving a wafer, or allowing a robot arm to access a wafer already in the slot and withdraw it. [0009] Multiple slots can be provided by stacking enough thick film heater plates to form the desired number of slots. A slot is formed between two thick film heater plates, so that for “n” slots, “n+1” heater plates are required. [0010] A drive shaft may be mounted to the stack, and the drive shaft extends through the chamber and engages a driver or motor which drives the drive shaft and stack for the purpose of aligning each of the slots with said door as desired. When the door is closed, it forms a pressure seal with the chamber. A sealing mechanism forms a pressure seal around the drive shaft and with the chamber, such that the chamber is capable of maintaining positive pressure. A gas inlet may be provided in the chamber, to enable the passing of a purge gas into the chamber to positively pressurize said chamber. [0011] Each of the thick film heater plates comprises a pair of electrodes through which power is inputted to a resistive circuit to generate heat. A pair of supports underlies and supports each thick film heater plate in the stack, with one of each pair of supports aligning with the pair of electrodes on the respective thick film heater plate. The supports not only support the stack, but separate each adjacent pair of thick film heater plates to form the slots therebetween. The supports which align with the electrodes of the heater plates electrically interconnect the plates. Each of the electrically connecting supports includes a pair of electrodes for extending therethrough which align with and contact the electrodes in thick film heater plates on opposite sides thereof. An electrical power supply can than be connected at any location along the interconnected circuit of supports and heater plates, to supply power to the entire stack. Although the heater plates could be individually connected to separately controlled power supplies, such an arrangement is more expensive and cumbersome given the greater number of electrical line and power supplies that would be required, and as such is not considered as practical commercially. [0012] The supports comprise a nonconducting material to prevent electrical conduction from the power source to any wafer in a slot. A nonconductive sleeve may surround a portion of each of the electrodes passing through the supports to further insulate the power from the wafers. [0013] A controller may be provided to automatically and remotely control the chamber door led to open and close. The controller may also be connected with the driver or motor and the electric power supply to control their functions. [0014] At least one thermocouple may be provided within the chamber and electrically connected to the controller to provide feedback regarding a temperature inside of the chamber. A more preferred arrangement is to provide three thermocouples 78 , 80 , 82 , one probing the top heater plate, one probing the bottom heater plate, and one probing the middle heater plate or one of a pair of heater plates nearest the middle of the stack if an even number of heater plates is employed. The middle thermocouple is used to provide feedback for temperature control purposes. The top and bottom thermocouples are used for comparison with the reading generated by the middle thermocouple. If a difference between the reading from the middle thermocouple and either one or both of the top and bottom thermocouples becomes more than a predetermined amount, this is an indicator of an operational problem, at which time the operation would be shut down. [0015] Further, a sensor may be mounted on the chamber to detect when a wafer has been placed out of position in the chamber, and the sensor may be electrically connected to the controller to input a message to the controller when a misaligned wafer has been detected. [0016] A heater subassembly for a wafer heating chamber is provided which includes a stack of thick film heater plates electrically interconnected with one another and defining slots therebetween. The slots are dimensioned for receiving wafers. At least a pair of supports are positioned between each pair of interfacing surfaces of the plates. [0017] A support base may be provided to underlie the bottom thick film heater plate of the stack, to further support the stack. A drive shaft extending from the bottom of the stack or support base and is adapted to be driven to traverse the stack. [0018] The supports comprise nonconductive blocks, at least a portion of which have a thickness that defines a height of the slots. Another portion of each nonconductive block is thinner than the thickness defining the height of the slots and forms a portion of a pedestal adapted to support a wafer. [0019] The supports may include spring loaded connectors in combination with a rigid shaft passing therethrough. [0020] These and other objects, advantages, and features of the invention will become apparent to those persons skilled in the art upon reading the details of the heat chamber assemblies and subassemblies as more fully described below. BRIEF DESCRIPTION OF THE DRAWINGS [0021] [0021]FIG. 1 is a diagrammatic sectional view of a heater according to the present invention. [0022] [0022]FIG. 2 is top view of an example of a thick film heater plate used in a heater according to the present invention. [0023] [0023]FIG. 3 is an isolated, perspective view of a bake chamber assembly isolated from the chamber of the heater. [0024] [0024]FIG. 4 is a partially exploded view of a bake chamber assembly, absent the drive shaft. [0025] [0025]FIG. 5 is an exploded partial view of a bake chamber assembly showing electrical connections between the thick film heater plates. [0026] [0026]FIG. 6 is an exploded partial view of a bake chamber assembly detailing electrical connection components between the thick film heater plates. [0027] [0027]FIG. 7 is a partial assembly view of a dual chamber heater assembly, absent the chambers. [0028] [0028]FIG. 8 is a perspective view of a dual chamber heater assembly, absent a top plate. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS [0029] Before the present invention is described, it is to be understood that this invention is not limited to particular examples or embodiments described, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present invention will be limited only by the appended claims. [0030] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are now described. All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited. [0031] It must be noted that as used herein and in the appended claims, the singular forms “a”, “and”, and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a capacitor” includes a plurality of such capacitors reference to “the layer” includes reference to one or more layers and equivalents thereof known to those skilled in the art, and so forth. [0032] The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present invention is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided may be different from the actual publication dates which may need to be independently confirmed. [0033] Referring now to the figures, wherein like reference characters denote like or corresponding parts throughout the views, examples of the present invention are explained. The major components of a heater 1 according to the present invention are diagrammatically illustrated in the sectional view of FIG. 1. Heater 1 includes a bake chamber assembly 10 that is movably mounted within a heater chamber 30 . Bake chamber 30 is pressure sealed and may be formed of cast aluminum (preferably A1 6061 T6). Preferably a block of cast aluminum is machined to form a twin heater chamber, as shown in FIG. 8, for receiving a pair of side by side stacked heater plates, although a single chamber, such as chamber 30 in FIG. 1 can be machined similarly. Aluminum is a preferred material, since it has good heat transfer properties, is easy to machine, and contains no nickel which could be attacked and corroded by O 3 . Aluminum is also chemically compatible with other processing gases used in the related processes that the present invention is to be used for. The chamber is preferably a single piece, as noted above. A top plate 30 a seals against the chamber 30 . [0034] A bake chamber according to the present invention may be formed to assume a position where one of a plurality of processing chambers would otherwise reside, for use in a multichamber system such as The Producer, available from Applied Materials, Santa Clara, Calif. As noted above, a bake chamber may be similarly arranged for use in conjunction with a single processing chamber. In yet another arrangement, a heating or bake chamber assembly may be incorporated into a load lock of one or more processing chambers, for direct preheating in the load lock. [0035] The bake chamber assembly 10 includes a plurality of thick film heater plates 12 mounted in a stack on support plate 14 . Support plate 14 is mounted on drive shaft 16 . Support plate 14 and drive shaft 16 may be formed of aluminum (A1 6061 T6), for example. The support plate 14 and heater plates 12 are dimensioned to be freely slidable within chamber 13 . The bake chamber assembly 10 is assembled within the chamber 30 with drive shaft 16 passing through opening 32 in the bottom 30 b of chamber 30 . A flexible sealing member 34 , e.g., a bellows or other sealing member, is secured to the bottom 30 b to surround the entire perimeter of the hole 32 and to form a pressure seal with the bottom 30 b . The flexible sealing member also encapsulates the drive shaft 16 , or at least forms a pressure seal with the bottom of the drive shaft 16 , so that the drive shaft can traverse in and out of the chamber 30 with no loss of pressure within the chamber 30 . [0036] The top lid 30 a of the chamber includes a gas inflow valve 36 through which nitrogen or other purging gas (such as helium or oxygen, for example) is inputted to pressurize the chamber, which is generally pressurized to about 700±50 Torr at the bake pressure. Pressurization of the chamber insures a positive pressure always exists during heating processes, so that when a wafer is placed into or removed from the chamber, there is an outflow of the purge gas which prevents possible inflows of contaminants. Also, the pressurized purge gas increases the efficiency of heat transfer within the chamber. A sensor 38 , which may be an infrared transmitter or other optical type of sensor, is also provided in the top lid 30 a and is aligned with holes in the supports interconnecting the heater plates 12 . In the case of an infrared transmitter 38 , an infrared receiver 40 is aligned therewith on the bottom 30 b of the chamber. This sensor system is used to detect when a wafer is out of alignment with its intended position in the heater, and is discussed in more detail below. [0037] A motor 50 having an extendable and retractable motor drive shaft 52 is provided for traversing the bake chamber assembly. The motor is actuated and controlled by a computer controller 60 so that motor drive shaft 52 engages the drive shaft 16 and extends to raise the position of the bake chamber assembly 10 with respect to the chamber 30 , while retracting to lower the position of the bake chamber assembly 10 relative to the chamber 30 . In the configuration of FIG. 8, the motor 50 is mounted in the lift bracket 51 , to simultaneously actuate both bake chamber assemblies. The motor 50 may be a stepper motor, such as a five phase stepper motor available from Oriental Motors, 291 Beach Road, Singapore, where precise positioning of the bake chamber assembly can be controlled by the stepper motor without the need for any additional position sensor. Alternatively, other motors or drivers may be employed along with a position sensor that may be placed on the motor drive shaft 52 or drive shaft 16 , or anywhere else on the movable bake chamber assembly, with feedback to the controller 60 , which would then control inputs to the motor 50 for precise positioning of the bake chamber assembly 10 . [0038] The chamber 30 includes a robot door 42 , which may be a remotely controlled slit valve or the like as is generally known in the art. The robot door 42 is controlled by controller 60 to open to allow an insertion or removal of a wafer, and then to close after that operation is complete, to reseal the chamber 30 and allow the purge gas to repressurize the interior of the chamber 30 . [0039] Turning to FIG. 2, a top view of a thick film heater plate 12 is shown. Heater plate 12 includes a substrate or plate 12 a that forms the base of the plate. A thick film heater 12 b is printed on the plate 12 a to form the thick film heater plate. (Thick film heaters are available from Watlow Industries, Hannibal Mo.). The thick film heater 12 b includes an electrically resistive circuit which covers a substantial portion of the surface of the plate 12 a , and a pair of electrodes 12 d connected to the circuit 12 c , which are adapted to connect with a power source. Since no embedding or additional layer to house a tube type of electrode is required with this arrangement, the thick film heater plates can be manufactured about one order thinner than conventional heater plates. For example, conventional aluminum or ceramic heater plates are generally on the order of greater than 0.50″ and usually at least around 0.7″ thick. In contrast, thick film heater plates for purposes of this invention can be produced having a thickness of less than 0.5″ and typically about 0.125″ and thinner. For heating applications at about 400° C., the thickness may be as little as about 0.08″, and for heating at about 200° C., the thick film heater plates 12 may be even thinner, as thin as about 0.05″. [0040] The fact that the thick film heater plates 12 are substantially thinner than conventional heater plates results in several advantages of the present invention over conventional bake chambers. Being one order thinner also translates into a one order smaller heat mass. Thus, the response time for temperature control and temperature changes is much faster than that of ordinary heater plates. Also, the heat loss and power consumption of thick film heater plates 12 is substantially lower than conventional heater plates. This leads to a reduction in the cost of production, increased throughput, and less energy consumption. Thick film heaters can be printed on many different substrates, including, but not limited to, stainless steel, aluminum, alumina, ceramics, quartz, etc. This increases design flexibility in the ability to meet different temperature and chemical compliance requirements. [0041] Since the thick film heater plates 12 are substantially thinner than conventional heater plates, more of them can be stacked in the same chamber than could conventional plates, thereby providing an increased number of slots 18 to receive wafers 22 and increasing throughput. For example, a chamber that can contain enough conventional heater plates to form only three slots can contain enough thick film heater plates to form six slots. On a slot to slot comparison (a slot is a compartment for receiving a wafer, formed by stacking one heater plate on top of another) a stack of thick film heater plates has a much lower height and the distance between slots is much smaller, compared to the conventional arrangement. This reduces the travel requirements for the drive mechanism required to align each slot with the robot door. The result is increased accuracy, for any time the drive is out of alignment in the least, the degree of misalignment is amplified as the travel distance increases. Additionally, a shorter travel drive unit is less space consuming and less expensive to produce than what is needed for the conventional arrangement. Also, the elongation requirements of the bellows 34 are less stringent, reducing the number of folds in the bellows needed, thereby reducing the opportunity for failure of this component. The lower mass of the thick film heater plates lowers the amount of power required for the motor/driver 50 , which also lowers costs. The cost of producing a thick film heater plate itself is significantly lower than the cost of a conventional heater plate, costing around $1,000 or less compared to $4,000-$5,000 for a conventional heater plate. [0042] [0042]FIG. 3 is an isolated, perspective view of a bake chamber assembly 10 isolated from the chamber of the heater. The thick film heater plates 12 are stacked one on top of another and interconnected by supports 70 , which may be ceramic iso blocks, or other substantially non-conductive and structurally supporting material. The thickness of the supports 70 establishes a slot 18 in between each adjacent pair of thick film heater plates for receiving a wafer therebetween. A heater base 16 ′ is provided at the free end of drive shaft 16 for engaging the drive shaft 52 of the drive motor 50 . Although an arrangement of seven thick film heater plates 12 is shown (thereby forming six slots 18 ), it is noted that the present invention is not limited to such number, as fewer or greater numbers of thick film heater plates can be stacked in a bake chamber assembly 10 to form the desired number of slots. A cutout 26 is provided in each thick film heater plate 12 to facilitate the circulation of the purge gas through the chamber. The cutouts 26 are preferably arranged in an alternating manner, such that a cutout 26 of any plate 12 appears on an opposite side (e.g., is diametrically opposed) to the cutouts 26 of the plates 12 immediately adjacent it. This type of arrangement acts to direct the flow of the purge gas across the surfaces of the plates 12 (and thus also any wafers 22 in slots 18 ), forming a much more effective purge. [0043] [0043]FIG. 4 is a partially exploded view of a bake chamber assembly 10 , absent the drive shaft 16 . Supports 70 are formed in a stepped, or “L-shaped” design, where the thicker portion 70 a of the support contacts thick film heater plates 12 on both sides and establishes the spacing between the plates 12 to form the slots 18 . The thinner portion 70 b of each support 70 forms a support or pedestal 70 b upon which the wafer 22 is supported when it is inserted into the slot 18 . This maintains the wafer 22 out of direct contact with the underlying heater plate 12 and at a desired distance between both heater plates 12 above and below the wafer so that heating and temperature control operations are much more consistent and are applied through convection and radiant heat, rather than a direct heat transfer. Another benefit is that a pin lift system is not needed to raise the wafer to allow access by the robot blade, as the pedestal supports 70 b leave enough space underlying the wafer to allow the robot blade to access the slot and then pick the wafer 22 off the pedestal supports 70 b , and remove the wafer through the robot door 42 , without the need for any mechanism to lift the wafer for access clearance. Conversely, the robot arm can also insert a wafer 22 into a slot 18 (after having gained access through robot door 42 ), lower the wafer 22 onto the pedestal supports, thereby separating contact between the robot arm and wafer 22 , and withdraw from the chamber through the robot door, again without any need for a mechanism to receive the wafer 22 and lower it onto a support. [0044] [0044]FIG. 5 is a blown up partial view of the bake chamber assembly in FIG. 4, showing the area outlined in FIG. 4, V. An assembly which provides the electrical connections between the thick film heater plates 12 is shown. Bores 72 are provided in the insulating supports 70 and are dimensioned to receive terminals 74 with a close fit. Terminals 74 may be formed of copper or other relatively good conducting metal or material which is also nonreactive in the environment for which it is designed. The large diameter end 74 a lies substantially flush with the surface of the support 70 , or extends minimally therefrom, to contact a terminal 12 d of a thick film heater plate when is assembled on top of the supports 70 . An insulator sleeve 76 fits over a portion of the reduced diameter part 74 b of terminal 74 to continue the insulation provided by supports 70 . The end portion of the reduced diameter part 74 b extends beyond the insulator sleeve and is dimensioned for a close, contacting fit with bore 74 c provided in the large diameter end 74 a (of another terminal 74 ). Thus, the terminals form a continuous, electrically conducting column when assembled upon one another, by the contact provided between a reduced diameter end 74 b of an overlying terminal 74 , with a large diameter end 74 a of an underlying terminal 74 via bore 74 c . This “peg in hole” interfit at the same time provides lateral structural support to the stack. Upon assembly of the entire stack, the plates are further secured together using a conventional clamping mechanism. For example, a rod can be passed through each side of the stack and a wave washer can be applied against the plates at both (or only one of) the top and bottom of the stack, with a nut or other compression fixture applying a clamping pressure against the wave washer(s) to maintain a compressive force against the plates and supports to maintain them as a unit. [0045] Alternatively, the thick film heater plates may be provided with Luvatech™ connectors (available from AMP, Cupertino, Calif.) fixed to terminals 12 d . This type of an arrangement allows easy assembly of the stack, as the Luvatech connectors are spring loaded and clamp to an electrically conductive rod that can be passed through the connectors to form the stack. This way, one or more heater plates may be added, removed or exchanged without dismantling the entire stack. [0046] [0046]FIG. 6 is a further exploded partial view of a bake chamber assembly which shows that the supports 70 are provided with pegs 70 c , extending from the bottom surface of the support, that are dimensioned to pass through holes 12 e in plates 12 and interfit with holes 70 d in an underlying support 70 (or, in the case of the supports 70 which sit directly on the support plate 14 , in holes provided in the support plate 14 (not shown) to provide further structural stability as well as to insure proper placement of the plates 12 with respect to the supports 70 . [0047] [0047]FIG. 7 is a partial assembly view of a dual chamber heater assembly 100 , absent the chambers. The construction of the bake chamber assemblies 10 is essentially the same as that described above, however, two assemblies are ganged together in this arrangement, so that a single robot having a pair of arms can service twice as many process chambers in tandem, for increased production. A single drive motor 50 is mounted in lift bracket 51 for raising a lowering the pair of stack assemblies in tandem. Each chamber is provided with a robot door 42 for access thereto to input and extract substrates. Although not shown, a single controller may be connected to both bake chamber assemblies for the tandem operation thereof. Of course, separate and independent controllers, motors and robots could be provided, if one so desired, although it would be commercially less cost effective. [0048] [0048]FIG. 8 is a perspective view of a dual chamber heater assembly 100 ′, absent a top plate. The assembly 100 ′ varies slightly from assembly 100 in design, in that the robot doors 42 are oriented at a slight angle to one another. Both bake or heater chambers 30 are pressure controlled by a single pump input which normalizes the pressure in both chambers. The two chamber are preferably machined from a single block of aluminum to form the two assembly, “ganged” unit. Only one bellows 34 is shown in FIG. 8, for contrast with the drive shaft 16 , shown without the bellows. Of course, each drive shaft, during operation, would be surrounded by a bellows 34 or other flexible sealing mechanism. [0049] The following example is put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how to make and use the present invention, and is not intended to limit the scope of what the inventors regard as their invention nor is it intended to represent that the arrangement below is the only arrangement experimented with. Efforts have been made to ensure accuracy with respect to numbers used (e.g. amounts, temperature, etc.) but some experimental errors and deviations should be accounted for. Unless indicated otherwise, parts are parts by weight, molecular weight is weight average molecular weight, temperature is in degrees Centigrade, and pressure is at or near atmospheric. EXAMPLE [0050] A multi-slot bake chamber is assembled with a stack of seven thick film heater plates, separated by six sets of supports to form six slots. Another set of supports separates the bottom thick film heater plate from a support base which is mounted to a drive shaft that extends through the chamber. A remotely controlled robot arm is provided to access each of the slots as the slots are aligned, via a motor and the drive shaft, with a robot door in the chamber. The controller opens the door to allow such access. Three processing chambers (in this example, CVD chambers) are also accessible by the robot arm. Therefor the robot arm can move wafers between any of the three processing chambers and the bake chamber. [0051] Six wafers, originally at room temperature (e.g., about 25° C.) are loaded into the bake chamber, which has been set to heat to about 300° C. After a period of less than or equal to about 30 seconds, the wafers will have achieved a steady state temperature of about 300° C. and can be further processed. The robot door is opened and the robot arm is activated to remove a wafer from the bake chamber and transfer it to one of the CVD chambers. The same process is carried out for the other two CVD chambers which may be programmed to perform the same process step, or a different process step from the first CVD chamber. The chambers use a process temperature of about 480° C. in this example. When the wafers are placed on the chucks of the CVD chambers, they come to rest stably in their intended positions, and do not “dance” because the wafers are already in a preheated state. [0052] Upon completion of a process step in one of the CVD chambers, the robot arm is activated to remove the wafer from the CVD chamber and return it to an empty slot in the bake chamber, where it will await further processing, or from where it can be removed after it has returned to about 300° C. Because the bake chamber has six slots, it will always have another wafer ready for processing in the CVD chamber from which it receives a wafer, thereby greatly enhancing throughput of the CVD chambers. [0053] While the present invention has been described with reference to the specific embodiments thereof, it should be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, process, process step or steps, to the objective, spirit and scope of the present invention. All such modifications are intended to be within the scope of the claims appended hereto.

A heating chamber assembly for heating or maintaining the temperature of at least one wafer, employs thick film heater plates stacked at an appropriate distance to form a slot between each pair of adjacent heater plate surfaces. The heating chamber assembly may be employed adjacent one or more processing chambers to form a preheat station separate from the processing chambers, or may be incorporated in the load lock of one or more such processing chambers. The thick film heater plates are more efficient and have a better response time than conventional heat plates. A chamber surrounding the stack of heater plates is pressure sealable and may include a purge gas inlet for supply purge gas thereto under pressure. A door to the chamber opens to allow wafers to be inserted or removed and forms a pressure seal upon closing. The slots in the stack are alignable with the door for loading and unloading of wafers. The stack is mounted on a drive shaft that extends through the chamber where it interfaces with a drive that traverses the drive shaft in and out of the chamber to align various slots as desired.

[0001] This application claim priority to U.S. Provisional Patent Application Serial No. 60/438,571, filed Jan. 7, 2003, titled: “Formation Of Gas Hydrates By Fluidized Bed Granulation,” incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to gas hydrates, and more specifically, it relates to a process for the production of gas hydrate granules in a fluidized bed whereby water is contacted with gas hydrate particles and a gas or mixture of gases known to produce gas hydrates under proper thermodynamic conditions. [0004] 1. Description of Related Art [0005] Potential benefits have been associated with the exploitation of gas hydrates. Gas hydrates are non-stoichiometric crystalline compounds that belong to the inclusion group known as Clathrates. Hydrates occur when water molecules attach themselves through hydrogen bonding and form cages that can be occupied by a single gas or volatile liquid molecule. The presence of a gas or volatile liquid inside the water network thermodynamically stabilizes the structure through physical bonding via weak van der Waals forces. Naturally occurring hydrates, containing mostly methane, exist in vast quantities within and below the permafrost zone and in sub-sea sediments and are being looked upon as a future energy source. At present, the amount of organic carbon entrapped in hydrate exceeds all other reserves (fossil fuels, soil, peat, and living organisms) (Seuss et al., 1999). [0006] An important benefit of gas hydrates deals with the transportation and storage of natural gas. Khokhar et al. (1998) reported a study demonstrating that transport of natural gas from the northern North Sea to Central Europe in hydrated form compared to liquefied natural gas can reduce overall costs by 24%. FIG. 1 shows a comparison of three different methods to store and transport natural gas. Each method demonstrates the thermodynamic conditions and phases required for a 1 m 3 container to store an equivalent amount of natural gas (160 m 3 at STP) when expanded to standard temperature and pressure. Gas hydrates require the more cost effective storage conditions, but necessitate a safe and efficient method for their production. [0007] Natural gas hydrates will also be important for the development of hydrogen, methanol and solid-oxide fuel cells since all three can directly use or convert methane to produce the desired fuel. Carbon dioxide hydrate is also an important hydrate. Carbon dioxide is a major contributor to global warming and, following the Kyoto protocol, several countries have set a carbon dioxide emissions target of 6% below the year 1990 levels by year 2008-2012. Work is being conducted on capturing carbon dioxide by transforming it into hydrates (Brewer, P G., Peltzer, E T., Friederich, G., Aya, I. and Yamane, K., Experiments on the Ocean Sequestration of Fossil Fuel CO 2 : pH Measurements and Hydrate Formation, Marine Chemistry, 72 (2-4), 83-93, 2000). [0008] Gudmundsson describes various systems for making gas hydrates (see U.S. Pat. No. 5,536,893 and WO Patent Publication No. 93/01153). In a typical system of Gudmundsson, natural gas is compressed, cooled and fed to a continuously stirred tank reactor vessel. Water from a suitable source is pumped through a cooler to form water/ice slurry that is introduced into the stirred tank. The tank is maintained under conditions appropriate to produce a gas hydrate (e.g., 50° F., 720 psig). The gas hydrate slurry produced in the tank is transported to a separator where water is removed. The separator includes a series of cyclones and a rotary drum filter. Finally, the purified hydrates are frozen to 5° F. in a freezer, from where the hydrates are transferred to a storage or transport device. It is important to note that this process utilizes water as the continuous phase. Other examples of patents that produce hydrate in reactors where water is the continuous phase are Hutchinson et al. (1945) in U.S. Pat. No. 2,375,559, U.S. Pat. No. 2,904,511 to Donath (1959), U.S. Pat. No. 3,514,274 to Cahn et al. (1970) and U.S. Pat. No. 6,350,928 to Waycuilis et al. (2002). [0009] U.S. Pat. No. 6,180,843 of Heinemann et al. (2001) resembles a fluidized spray drying process employed in the drying industry for handling slurries. In their process, water is finely dispersed above a fluidized bed. Some of the injected water forms seed hydrate particles, while the rest coats already-formed particles surrounding the atomizing nozzle. These particles receive successive coats of water and may agglomerate with neighboring particles until they reach a sufficient size and fall by gravity to the bottom of the vessel. The lower section of the vessel has a smaller cross-section and the particles will remain in suspension, absorbing more gas before finally exiting by the bottom of the fluidized bed. [0010] The process of Heinemann et al. does not require recycling of particles to the fluidized bed. They leave this as an option for start-up. Thus, in order to maintain a constant inventory of particles in the bed and ensure continuous steady operation, fresh nuclei particles must be created in the fluidized bed by either the water atomization process (i.e., injected water droplets produce gas hydrates particles, not only coat surrounding particles) or by particles continuously fragmenting due to intense mixing in the bed. [0011] The Heinemann et al. (2001) process presents favorable hydrate formation kinetics and is easier to operate than reactors where water is the continuous phase. However, it will still be less efficient than a process where there is an attempt to contact all the feed liquid with particles in the fluidized bed. The reasons are as follows: [0012] 1. The rate of conversion of water to hydrate (i.e., kinetics) is much greater if there is a precursor such as a seed particle that is already a hydrate than for an isolated water droplet in a gas stream. [0013] 2. The overall particle surface area available for the liquid to spread may be greater or, at least, not lower. In the Heinemann et al. process, the volumetric concentration of particles surrounding the nozzle may not be as high as the bottom of the chamber in the fluidized bed. [0014] 3. The heat transfer rate will be greater since all the liquid will transfer heat by both convection with the gas and conduction with the particles. Furthermore, by forming a thin film around the particles, the resistance to heat transfer is smaller than for a liquid droplet of the same volume. [0015] 4. If hydrates nucleate on water droplets they will create a thin film of hydrates, on the interface, enveloping a volume of unconverted water. This thin film will act as a barrier to further conversion of enclosed water into hydrate. Hence, another benefit of coating a hydrate seed with water is that the thin water layer can more effectively interact with the surrounding gas to form hydrate. Increasing the water-gas interaction will result in a more efficient and faster hydrate growth. SUMMARY OF THE INVENTION [0016] This invention relates to a process for the production of gas hydrate granules in a fluidized bed whereby water is contacted with gas hydrate particles and a gas or mixture of gases known to produce gas hydrates under proper thermodynamic conditions. This process will have superior heat, mass and kinetic rates than others presently available, thus resulting in a greater volumetric product yield. [0017] In steady-state operation, water is atomized onto hydrate particles in a fluidized bed. Particles grow by successive coating of hydrates similar to a “granulation” process. In this case, particle growth is dictated not only by heat and mass transfer, but also by hydrate formation kinetics. Particles are continuously removed from the bottom of the chamber and then fragmented. If desired, the fragmented hydrate particles can be fluidized in a subsequent chamber by a hydrate forming gas in order to increase the gas content in the hydrate cages (i.e., similar to an “absorption” process). A portion of these fragmented hydrate particles is recycled to the granulation chamber as seed particles and the remainder is kept as a product Potential fine particles present in the hydrate forming gases exiting the fluidized beds can be removed by cyclones or other gas-solid separation devices and returned to the granulation chamber as seed particles. The un-reacted hydrate forming gas is compressed, cooled and recycled to the reactor. Under steady-state operation, the entire process may operate at temperatures between 255-320 K and pressures ranging from 100-50,000 kPa. Examples of hydrate-forming gases include methane, propane, ethane, carbon dioxide, and other natural gas components. BRIEF DESCRIPTION OF THE DRAWINGS [0018] [0018]FIG. 1 compares natural gas storage conditions (adapted from Khokhar et al., 1998). [0019] [0019]FIG. 2 is a schematic of the main components of the hydrate fluidized bed granulation process. [0020] [0020]FIG. 3 is a schematic of the lower section of the hydrate fluidized bed granulation chamber DETAILED DESCRIPTION OF THE INVENTION [0021] The invention utilizes a fluidized bed granulation process that allows the continuous production of gas hydrates. The principal advantages of this process are that it is simple, uses a minimal amount of equipment and is efficient, i.e., provides a large surface area for the hydrate reaction, has favorable heat and mass transfer rates and employs hydrates as seed particles. Hydrates are not likely to form quickly from water being atomized into a gas stream as with the Heinemann et al. (2001) and Gudmundsson (1996) processes due to the stochastic nature of hydrate crystal nucleation. On the other hand, water transforms into hydrates at a faster and predictable rate when contacted with hydrate seeds. [0022] 1. A start-up procedure is employed to create a bed of seed hydrate particles. It should be noted that the following procedure allows for the generation of hydrate seeds in situ. If the operator chooses to do so he may bypass the following by inserting hydrate crystals or any other suitable crystal seeds into the reactor. These seeds only serve as an aid to startup and at steady state hydrates generated within the process will be used as seeds. [0023] Referring to FIG. 2, at first, the temperature in the granulation chamber ( 1 ) is kept below the freezing point of water. Water (W 1 ) is introduced from the top of the chamber ( 1 ) and contacted with a hydrate-forming gas (G 3 ) in a countercurrent fashion in order to produce ice particles. Water is introduced by one or more atomizing devices ( 6 ) that provide the smallest possible droplet size and the highest possible surface to volume ratio, thus facilitating the nucleation of ice. The desired droplet size would be under 1000 micrometers. This step is similar to a spray drying process. A review of fluid atomizing devices is given by Masters, K, in “ Spray Drying Handbook,” Longman Scientific and Technical, 1991. [0024] These ice particles remain in suspension by keeping the gas flow rate (G 3 ) above the point of minimum fluidization. [0025] After sufficient ice granules have been formed, the water flow rate (W 1 ) is reduced or even stopped and the temperature and pressure in the chamber ( 1 ) are increased to negate the possibility of ice crystals forming but sufficient to sustain hydrate growth, at least at the particle surface. The transition from ice to hydrate particles can be evaluated by monitoring pressure fluctuations (i.e., drop) in the chamber ( 1 ). [0026] 2. What follows is the description of the important constraints and features of the process operated at steady-state. [0027] The number, geometry, locations (above and/or in the bed), positions (angle of fluid jets) and operating conditions (fluid flow rates and pressures) of the atomizing devices ( 6 ) are adjusted to provide optimal contact between the water droplets, gas and hydrate particles in the fluidized bed at the highest possible water throughput Optimal contact is achieved when all water droplets reach particles and these particles grow primarily by successive coating of hydrates (i.e., layering) rather than agglomeration of multiple hydrate particles. U.S. Pat. No. 6,159,252 of Schutte et al. (2000) presents several options for the locations and positions of fluid nozzles to achieve a high throughput of liquid during fluidized bed granulation operations. [0028] The fluidized bed will primarily remain in the tapered section (angle (γ) between 0 and 90°) of the granulation chamber ( 1 ) in order to provide good mixing conditions. A circulatory and cyclic motion can further be imparted to the particles by designing the gas distributor ( 8 ) with a greater open area at its center. It has been shown that “overlap gill” or “nostril-like” gas outlets in the distributor plate promote particle movement, thus reducing dead zones and the risk of particles clogging the gas distributor (U.S. Pat. No. 6,159,252). Through these outlets, particles are obliquely fluidized at angles less than 90° relative to horizontal. One can also not use the gas distributor plate ( 8 ), thus avoiding potential clogging, and introduce the gas horizontally above the base of the granulation chamber through several nozzles (G 3 ′). [0029] Since the formation of hydrates is an exothermic process, the temperature in the granulation chamber ( 1 ) is continuously monitored and controlled between 255 and 320 K by adjusting the inlet temperature of the hydrate-forming gas (G 3 ) and water (W 1 ) streams with refrigeration units. [0030] The pressure in the granulation chamber ( 1 ) is monitored and controlled between 100 and 50,000 kPa by adjusting the inlet pressures of the gas (G 3 ), liquid (W 1 ) and solid (H 4 ) streams. [0031] Since gas is consumed by the hydrate reaction and the average particle size, shape and density in the bed may fluctuate throughout the granulation operation, the gas volumetric flow rate (G 3 ) is controlled to maintain smooth fluidization conditions and the bed height at an operating level. [0032] The bed inventory is regulated by removing granulated hydrate particles (H 1 ) and adding seed hydrate particles (H 4 ), which are smaller in size. It is important to mention that the locations and operating conditions of the atomizing devices ( 6 ) and feed gas nozzles (G 3 ′) may also contribute to generating seed particles in-situ by fragmenting the larger particles present in the bed, as described in U.S. Pat. No. 6,159,252 of Schutte et al. (2000), incorporated herein by reference. If it is possible to easily control the quantity and resulting size of the fragmented particles, this would be the preferred method of continuous hydrate seed generation over the use of an external embodiment such as the particle crusher ( 3 ). [0033] Hydrate particles are discharged through one or several standpipes ( 7 ) placed near the bottom of the chamber ( 1 ) where there is a greater probability of removing particles larger is size than the bed average. These standpipes ( 7 ) can be located on the chamber side walls (side outlet) or on the gas distributor plate (bottom outlet). Furthermore, gas can be introduced in the particle discharge standpipe ( 7 ) in a countercurrent fashion to the particles for pneumatic classification. This will further increase the probability of removing the larger particles in the bed. There are several other classification devices (see Perry, R. H. and Green, D. W., Perry's Chemical Engineer's Handbook, McGraw-Hill, 1999) that can be implemented to the present process where the oversize discharged particles are fragmented, combined with undersized particles and then recycled back to the granulation unit, while the desired size particles are kept as final product or further processed in the fluidized bed absorber ( 2 ). [0034] The removed hydrate particles (H 1 ) from the granulation chamber ( 1 ) are then fragmented in a particle size reduction device ( 3 ). such as a crusher or roll mill as described by Rhodes, M. J., Principles of Powder Technology, Wiley, 1990 and Perry and Green (1999), incorporated herein by reference. [0035] A portion (H 4 ) of these fragmented hydrate particles is recycled to the granulation chamber ( 1 ) as seed particles. Optimally, these seeds should be introduced in the vicinity of the atomizing devices ( 6 ) situated above the fluidized bed. [0036] The non-recycled portion (H 3 ) of fragmented hydrates is kept as a product. In a final stage, the hydrates are compressed and stored in containers suitable for transport by truck, rail and/or sea. [0037] If necessary, the fragmented hydrate particles (H 1 ′) can be fluidized in a subsequent unit ( 2 ) by a hydrate-forming gas (G 4 ) in order to fill or partially fill the remaining cages in the hydrate and to convert the free-water that may be present This is similar to an “absorption” process. The fluidized bed ( 2 ) can be a single chamber where the particle flow pattern is considered perfectly mixed. However, in order to obtain a tighter particle residence time distribution and thus a better product uniformity, the fluidized bed ( 2 ) may be staged (i.e., multiple chambers) where the particles flow in a crosscurrent or countercurrent manner to the hydrate forming gas. Although a countercurrent design may be more gas efficient for a single pass, the crosscurrent flow design is simpler to operate. Details of the design of multistage fluidized bed absorbers can be found in Kunii, D. and Levenspiel, O., Fluidization engineering, Butterworths, 1991, incorporated herein by reference. [0038] The unconsumed gas streams (G 5 and G 6 ) exiting both fluidized beds are combined (G 7 ) and then compressed, cooled and recycled. If necessary, a cyclone or other methods to remove particulates will be employed to remove potential fine particles generated in the fluidized beds. These fine hydrate particles would then be recycled to the granulation chamber ( 1 ) as seeds. Alternatively, the fines can be captured in-situ and returned to the respective fluidized beds by having the cyclones in the fluidized bed chambers. [0039] As shown in FIG. 2, the main components of this process are a fluidized bed granulation unit ( 1 ), a particle size reduction unit ( 3 ) and possibly a fluidized bed absorption unit ( 2 ). The words granulation and absorption are used throughout the text with the understanding that these physical phenomena also include hydrate reactions. [0040] The particle size reduction unit (e.g., crusher or roll mill) can be of standard design as described by Rhodes (1990) and Perry and Green (1999). [0041] One embodiment for the fluidized bed granulator is a vessel that stands vertical. The top piece has a constant cross-section, while the bottom piece is tapered with an angle (γ) between 0 and 90°. Particles rest in the tapered section in order to give increased mixing conditions. Hydrate forming gas enters from the bottom of the bed, while the liquid may be injected from above and/or in the bed. Seed particles should preferably be introduced near the liquid injectors situated above the bed. [0042] Another fluidized bed can be employed to further introduce gas into the fragmented hydrated particles. This fluidized bed can be a single chamber where the particle flow pattern is considered perfectly mixed or multiple chambers where the particle flow pattern can approach plug flow, see Kunii and Levenspiel (1991). One embodiment is a multi-stage fluidized bed with the particles flowing crosscurrent to the gas. [0043] The fluidized beds can be constructed from metal (e.g., stainless steel 316, Platinum, Titanium, etc.) and have viewing ports made of transparent material such as Al 2 O 3 , PMMA, Polycarbonate, etc. [0044] Finally, the process according to the invention may be performed in several known devices for fluidized bed granulation. One embodiment of the granulation chamber is tapered, but may be of other geometry, allowing the efficient contacting of a gas, solid and liquid in order to obtain optimal conditions for successive coating of the hydrate particles by a thin film of liquid at maximum liquid throughput There are several multiphase contacting modes that can be employed for this granulation process (see Geldart, 1986; Rhodes, 1990; Kunii and Levenspiel, 1991; Mujumdar, 1995; Fayed and Otten, 1997; Perry and Green, 1999; Yang, 2003). The variables affecting multiphase contacting may include the vessel geometry, the gas distributor design, the presence or absence of internals (e.g., draft-tube, heat exchangers), the physical properties of the phases, injection locations and operating conditions. The granulation process may operate as a fluidized, spouted or spout-fluid bed under various flow regimes to achieve the desired phase contact. Those skilled in the art of fluidized bed granulation will recognize that various changes and modifications can be made without departing from the spirit and scope of the invention, as defined in the appended claims. [0045] The foregoing description of the invention has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. The embodiments disclosed were meant only to explain the principles of the invention and its practical application to thereby enable others skilled in the art to best use the invention in various embodiments and with various modifications suited to the particular use contemplated. The scope of the invention is to be defined by the following claims.

A steady-state method for producing gas hydrates provides seed gas hydrate particles in a reaction chamber, flows a hydrate-forming gas into the reaction chamber and flows water into the reaction chamber to produce several possible reactions. One reaction occurs from the combination of the seed gas hydrate particles, the hydrate-forming gas and the water to provide gas hydrate growth onto the seed gas hydrate particles. Another reaction occurs from the interaction of the hydrate-forming gas and the water to form new gas hydrate particles. Material is removed from the reaction chamber and fragmented and some of fragmented gas hydrate particles are recycled back into the reaction chamber.

RELATED APPLICATIONS This application is a continuation-in-part of application Ser. No. 08/195,186 filed Feb. 14, 1994 now U.S. Pat. No. 5,558,995, which is a continuation-in-part of U.S. application Ser. No. 08/008,446, filed Jan. 22, 1993 now abandoned. It is also a continuation-in-part of Ser. No. 08/196,630 filed Feb. 15, 1994 now U.S. Pat. No. 5,683,386. FIELD OF THE INVENTION This invention relates to various therapeutic methodologies derived from the recognition that certain abnormal cells present complexes of HLA-Cw*1601 (previously referred to as HLA-C-clone 10) (Bodmer et al., Tissue Antigens 44: 1 (1994)) and peptides derived from a molecule referred to as MAGE-1 on their surfaces. In addition, it relates to the ability to identify those individuals diagnosed with conditions characterized by cellular abnormalities whose abnormal cells present this complex. BACKGROUND AND PRIOR ART The process by which the mammalian immune system recognizes and reacts to foreign or alien materials is a complex one. An important facet of the system is the T cell response. This response requires that T cells recognize and interact with complexes of cell surface molecules, referred to as human leukocyte antigens (“HLA”), or major histocompatibility complexes (“MHCs”), and peptides. The peptides are derived from larger molecules which are processed by the cells which also present the HLA/MHC molecule. See in this regard Male et al., Advanced Immunology (J.P. Lipincott Company, 1987), especially chapters 6-10. The interaction of T cell and complexes of HLA/peptide is restricted, requiring a T cell specific for a particular combination of an HLA molecule and a peptide. If a specific T cell is not present, there is no T cell response even if its partner complex is present. Similarly, there is no response if the specific complex is absent, but the T cell is present. This mechanism is involved in the immune system's response to foreign materials, in autoimmune pathologies, and in responses to cellular abnormalities. Recently, much work has focused on the mechanisms by which proteins are processed into the HLA binding peptides. See, in this regard, Barinaga, Science 257: 880 (1992); Fremont et al., Science 257: 919 (1992); Matsumura et al., Science 257: 927 (1992); Latron et al., Science 257: 964 (1992). The mechanism by which T cells recognize cellular abnormalities has also been implicated in cancer. For example, in PCT application PCT/US92/04354, filed May 22, 1992, published on Nov. 26, 1992, as WO92/20356 and incorporated by reference, a family of genes is disclosed which are processed into peptides which, in turn, are expressed on cell surfaces, and can lead to lysis of the tumor cells by specific CTLs. These genes are referred to as the “MAGE” family, and are said to code for “tumor rejection antigen precursors” or “TRAP” molecules, and the peptides derived therefrom are referred to as “tumor rejection antigens” or “TRAs”. See Traversari et al., Immunogenetics 35: 145 (1992); van der Bruggen et al., Science 254: 1643 (1991), for further information on this family of genes. In U.S. patent application Ser. No. 938,334, the disclosure of which is incorporated by reference, nonapeptides are taught which bind to the HLA-A1 molecule. The reference teaches that given the known specificity of particular peptides for particular HLA molecules, one should expect a particular peptide to bind one HLA molecule, but not others. This is important, because different individuals possess different HLA phenotypes. As a result, while identification of a particular peptide as being a partner for a specific HLA molecule has diagnostic and therapeutic ramifications, these are only relevant for individuals with that particular HLA phenotype. There is a need for further work in the area, because cellular abnormalities are not restricted to one particular HLA phenotype, and targeted therapy requires some knowledge of the phenotype of the abnormal cells at issue. In a patent application filed on Dec. 22, 1992 in the name of Boon-Falleur et al., entitled “Method For Identifying Individuals Suffering From a Cellular Abnormality, Some of Whose Abnormal Cells Present Complexes of HLA-A2/Tyrosinase Derived Peptides and Methods for Treating said Individuals”, the complex of the title was identified as being implicated in certain cellular abnormalities. The application does not suggest, however, that any other HLA molecules might be involved in cellular abnormalities. The prior presentation of MAGE-1 by an HLA-A molecule, as disclosed supra, also does not suggest that the protein can be presented by another HLA molecule. Thus, it is surprising that the very MAGE molecule presented by HLA-A1 has now been shown to be presented by HLA-Cw*1601. While the prior research is of value in understanding the phenomenon, it in no way prepares the skilled artisan for the disclosure which follows. BRIEF DESCRIPTION OF THE FIGURE FIG. 1 depicts experiments involving transfection of COS-7 with coding sequences for MAGE-1 and HLA-Cw*1601. FIG. 2A sets forth results of a 51 Cr release assay using MZ2 cells infected with Epstein Barr Virus, which had been incubated with the peptide of SEQ ID NO: 4, for 30 minutes. The effector cells were from CTL 81/12. FIG. 2B parallels FIG. 2A, the only difference being that the effector was CTL 82/35. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS EXAMPLE 1 In the experiments which follow, various melanoma cell lines were used. These were obtained from melanoma patients identified as MZ2 and LB73. Cell lines MZ2-MEL.43, MZ2-MEL-3.0, and MZ2-MEL3.1 are cloned sublines of MZ2-MEL, and are described in Van den Eynde et al., Int. J. Canc. 44: 634 (1989), as well as PCT patent application WO92/20356 (Nov. 26, 1992), both disclosures being incorporated by reference and in their entirety herewith. Cell line LB73-MEL was derived from patient LB73 in the same manner as the other cell lines described herein. Samples containing mononuclear blood cells were taken from patient MZ2. A sample of the melanoma cell line MZ2-MEL.43 was irradiated, and then contacted to the mononuclear blood cell containing samples. The mixtures were observed for lysis of the melanoma cell lines, this lysis indicating that cytolytic T cells (“CTLs”) specific for a complex of peptide and HLA molecule presented by the melanoma cells were present in the sample. The lysis assay employed was a chromium release assay following Herin et al., Int. J. Cancer 39:390-396 (1987), the disclosure of which is incorporated by reference. The assay, however, is described herein. The target melanoma cells were grown in vitro, and then resuspended at 10 7 cells/ml in DMEM, supplemented with 10 mM HEPES and 30% FCS, and incubated for 45 minutes at 37° C. with 200 μCi/ml of Na( 51 Cr)O 4 . Labelled cells were washed three times with DMEM, supplemented with 10 mM Hepes. These were then resuspended in DMEM supplemented with 10 mM Hepes and 10% FCS, after which 100 ul aliquots containing 10 3 cells, were distributed into 96 well microplates. Samples of PBLs were added in 100 ul of the same medium, and assays were carried out in duplicate. Plates were centrifuged for 4 minutes at 100 g, and incubated for four hours at 37° C. in a 5.5% of CO 2 atmosphere. Plates were centrifuged again, and 100 ul aliquots of supernatant were collected and counted. Percentage of 51 Cr release was calculated as follows: %       51  Cr     release = ( ER - SR ) ( MR - SR ) × 100 where ER is observed, experimental 51 Cr release, SR is spontaneous release measured by incubating 10 3 labeled cells in 200 ul of medium alone, and MR is maximum release, obtained by adding 100 ul 0.3% Triton X-100 to target cells. Those mononuclear blood samples which showed high CTL activity were expanded and cloned via limiting dilution, and were screened again, using the same methodology. These experiments led to the isolation of several CTL clones from patient MZ2 including CTL clone “81/12”. The experiment was repeated as described, using both cell line MZ2-MEL 3.0 and MZ2-MEL 3.1. The results indicated that clone 81/12 recognized both MZ2-MEL.43 and MZ2-MEL 3.0, but not MZ2-MEL 3.1. The antigen being recognized by 81/12 is referred to hereafter as “antigen Bb”. EXAMPLE 2 In view of prior work, as summarized supra, it was of interest to determine the HLA class 1 profile for patient MZ2. This was determined following standard methodologies, which are now set forth. To obtain cDNA clones coding for the genes of the HLA class 1 molecules of the patients, a cDNA library was prepared, starting with total mRNA extracted from cell line MZ2-MEL.43, using well known techniques not repeated here. The library was inserted into plasmid pcD-SRα, and then screened, using an oligonucleotide probe containing a sequence common to all HLA class 1 genes, i.e.: 5′-ACTCCATGAGGTATTTC-3′ (SEQ ID NO: 1) One clone so identified was clone IC4A7 which, upon sequencing, was found to be functionally equivalent, if not identical to, HLA-Cw*1601, a well known human leukocyte antigen molecule. The sequence of the DNA coding for HLA-Cw*1601 is given at, e.g. Cianetti et al., Immunogenetics 29: 80-91 (1989), where it was named HLA-C clone 10 and the sequence is available under GENBANK accession number HUMMHCACA. An updated sequence is reported by Zemmour et al., Immunogenetics 37: 239-250 (1993), the disclosure of which is incorporated by reference in its entirety, as is Cianetti et al., supra. The Zemmour sequence is also available in the EMBL sequence bank. EXAMPLE 3 It was of interest to determine if the HLA molecule identified supra presented a mage derived tumor rejection antigen, and if the resulting complex of antigen and HLA molecule was recognized by a CTL clone of patient MZ2. To determine this, recipient cells were transfected with cDNA coding HLA-Cw*1601, and with one of MAGE-1, MAGE-2, or MAGE-3 cDNA. The MAGE-1 cDNA was inserted into plasmid pcDNA I/Amp, while MAGE-2 and MAGE-3 cDNA were inserted into plasmid pcD-SRα. Samples of recipient COS-7 cells were seeded, at 15,000 cells/well into tissue culture flat bottom microwells, in Dulbecco's modified Eagles Medium (“DMEM”) supplemented with 10% fetal calf serum. The cells were incubated overnight at 37° C., medium was removed and then replaced by 30 μl/well of DMEM medium containing 10% Nu serum, 400 μg/ml DEAE-dextran, 100 μM chloroquine, and 100 ng of the subject plasmids (i.e., 100 ng of the IC4A7 clone, and 100 ng of the MAGE-cDNA plasmid). Following four hours of incubation at 37° C., the medium was removed, and replaced by 50 μl of PBS containing 10% DMSO. This medium was removed after two minutes and replaced by 200 μl of DMEM supplemented with 10% FCS. Following this change in medium, COS cells were incubated for 48 hours at 37° C. Medium was then discarded, and 2000 cells of CTL clone 81/12 were added, in 100 μl of Iscove medium containing 10% pooled human serum. Supernatant was removed after 24 hours, and TNF content was determined in an assay on WEHI cells, as described by Traversari et al., Immunogenetics 35: 145-152 (1992), the disclosure of which is incorporated by reference. The results, set forth in FIG. 1 demonstrate that a tumor rejection antigen, derived from MAGE-1 is presented by HLA-Cw*1601, and is recognized by CTL clone 81/12, whereas expression of MAGE-2 and MAGE-3 does not lead to presentation of the appropriate antigen. EXAMPLE 4 Following the experiments discussed supra, additional work was carried out to determine the peptide which HLA-Cw*1601 presented. MAGE-1 cDNA in expression vector pcDNA I/Amp was digested with restriction endonucleases NotI and SphI following the supplier's instructions, and then with exonuclease III. This treatment generated a series of progressive deletions of the MAGE-1 cDNA, starting at the 3′ end. The deletion products were ligated back into pcDNAI/Amp, and then electroporated into E. coli strain DH5αF′IQ, using well known techniques. The transformants were selected with ampicillin (50 ug/ml), and six hundred clones were obtained. The plasmid DNA was removed from each clone, and was then transfected into COS-7 cells, together with a vector which coded for HLA-Cw*1601. The protocol used follows the protocols described above. The transfectants were then tested in the TNF release assay described in example 3. This permitted separation of positive and negative clones. The comparison showed that one of the positive clones contained nucleotides 1-730 from the MAGE-1 gene, while a negative clone contained nucleotides 1-706. The sequence of positive and negative clones was compared, and a region of 16 amino acids was identified as putatively containing the antigenic peptide. This sequence is: Glu His Ser Ala Tyr Gly Glu Pro Arg Lys Leu Leu Thr Gln Asp Leu (SEQ ID NO: 2) Based upon this sequence, a first set of experiments was carried out where synthetic peptides were made, and tested for their ability to render COS-7 cells transfected with HLA-Cw*1601 capable of stimulating lysis. A positive 12 mer was identified, i.e.: Glu His Ser Ala Tyr Gly Glu Pro Arg Lys Leu Leu (SEQ ID NO: 3) Truncation of this 12 mer led to the identification of nonapeptide Ser Ala Tyr Gly Glu Pro Arg Lys Leu (SEQ ID NO: 4) as the best stimulator of lysis. Half maximal lysis was observed at a peptide concentrations of 10 nM. In experiments not presented herein, but set forth in Ser. No. 08/196,630, filed Feb. 15, 1994 and incorporated by reference herein, the peptide Ala Ala Arg Ala Val Phe Leu Ala Leu (SEQ ID NO: 5) was also found to be presented by HLA-Cw*1601, and lysed by various cytolytic T cell clones, such as CTL 82/82. EXAMPLE 5 The identification of two separate peptides being presented by HLA-Cw*1601 suggested the desirability of an assay to determine expression of HLA-Cw*1601 in patients. Serological testing is not a viable option because antibodies to HLA-Cw*1601 are not available. Polymerase chain reaction (“PCR”), however, provided an alternative. Development of a viable, useful PCR assay for expression of HLA-Cw*1601 based upon a nested primer system follows. The model described generally by Browning et al., Proc. Natl. Acad. Sci. USA 90: 2842 (1993), was used. This reference discusses the use of oligonucleotide primers, the 3′ ends of which are specific for the coding sequence for the HLA molecule. Using this approach, primers: 5′-CAAGCGCCAGGCACAGA-3′ (SEQ ID NO: 6) and 5′-GCCTCATGGTCAGAGACGA-3′(SEQ ID NO: 7) were synthesized. To test the method, various cell samples from patients were used. Total RNA was extracted, using the well known guanidine isothiocyanate method of Davis et al., Basic Methods in Molecular Biology (Elsevier, N.Y., 1986), pp. 130. For cDNA synthesis, 2 ug of RNA was diluted with water, and 4 ul of 5× reverse transcriptase buffer. Added were 1 ul each of 10 mM dNTP, 2 ul of a 20 uM solution of oligo (dT), 20 U of RNasin, 2 ul of 0.1M dithiothreitol, and 200 U of MoMLV reverse transcriptase, in a 20 ul reaction volume. The mixture was incubated for 60 minutes at 42° C. To amplify the cDNA, 1% of the cDNA reaction was supplemented with 5 ul of 10× thermostable DNA polymerase buffer, 1 ul each of 10 mM dNTP, 0.5 ul each of 80 uM solution of primers (SEQ ID NO: 6 and 7), 1U of DynaZyme, and water to a final volume of 50 ul. The PCR was carried out for 30 cycles (one minute at 95° C., one minute at 62° C., two minutes at 72° C.). The products were diluted to 1/500. Then, a second PCR was carried out, using 1 ul of diluted PCR product, supplemented with 5 ul of 10× thermostable DNA polymerase buffer, 1 ul each of 10 mM dNTP, 0.5 uM each of a 80 uM solution of primers: 5′-GAGTGAGCCTGCGGAAC-3′ (SEQ ID NO: 8) and 5′-CCTCCAGGTAGGCTCTCT-3′ (SEQ ID NO: 9), and 1U of DynaZyme. SEQ ID NO: 8 and SEQ ID NO: 9 represent nucleotide sequences located internally to the first set of primers, i.e., SEQ ID NOS: 6 and 7. Water was added to 50 ul, and 20 cycles of PCR were carried out (one minute 95° C.; one minute at 65° C.; two minutes at 72° C.). The PCR products were then size fractionated on a 1.5% agarose gel in TAE buffer. This methodology was utilized in two separate sets of experiments. In the first of these, transfectants, prepared as described supra and lysed by cytolytic T cell clones against either SEQ ID NO: 4 or SEQ ID NO: 5 complexed to an HLA molecule were tested. All positive transfectants were found to present the HLA-Cw*1601 molecule on their surfaces. Any sample which generated no PCR products was considered negative. In further experiments using the negative samples, the PCR protocol utilized above was employed a second time but the primers were based upon sequences common to all HLA-C sequences. See Zemmour et al., J. Exp. Med. 176: 937 (1992), incorporated by reference herein. The negative samples proved to be cells expressing different, i.e., non HLA-Cw*1601 HLA-C subtypes. EXAMPLE 6 In the second set of experiments, the ability of cells, either PBL or tumor, to present peptides via HLA-Cw*1601, was tested. To do this, cells taken from patients were washed in Hank's solution, and resuspended at 5×10 6 cells/ml. They were then fixed by treating them for 10 minutes, at room temperature, with 1% paraformaldehyde. Following fixation, they were washed, twice, in Hank's solution, and resuspended in Iscove's medium with 10% human serum added. The cells were then distributed in 96V-bottom wells, at either 3×10 4 PBLs or 1×10 4 tumor cells, and pulsed with varying concentrations of peptides. After two hours of incubation at 37° C., the cells were washed, twice, before CTLs (1500, 100 ul Iscove medium, 10% human serum, 20 U/ml recombinant human IL-2) were added, and TNF release from WEHI-164 cells measured. See, e.g., Traversari et al., Immunogenetics 35: 145 (1992), incorporated by reference for particulars of the assay. The effector cells in the assay were from CTL 82/35. The results are summarized in the following table. TNF was only produced in the presence of target cells, derived from patients who had tested positive for HLA-Cw*1601, based upon the PCR assay, set forth supra, which had been pulsed with peptide. The experiments, summarized in Table 1, used cells which had been fixed with glutaraldehyde, pulsed with the peptide, and then tested for recognition by cytolytic T cell line CTL 82/35. As the table shows, TNF was produced only in the presence of peptide pulsed target cells, which had tested positive for HLA-Cw*1601 in the PCR assay discussed supra. TABLE 1 Peptide HLA-Cw*1601 Presentation Patient PCR To CTL 82/35 MZ2 + + LB17 + + LB678 + + LB708 + + MI4024/1 + + LB73 − − LY-2 − − SK19 − − SK37 − − EXAMPLE 7 Approximately 8% of samples (7 of 99) were positive for this HLA type, and five of the positives were tested for CTL lysis; as described supra. All provoked lysis, as indicated in Table 1. In contrast, samples from four patients who were not positive for HLA-Cw*1601, did not provoke lysis by CTLs. EXAMPLE 8 In another experiment, MZ2 lymphoblastoid cells, infected with Epstein Barr Virus, were used in a 51 Cr release assay. The infected cells, referred to as “MZ2-EBV”, were 51 Cr labelled, and then incubated for 30 minutes in the presence of MAGE-1 peptide, at concentrations ranging from 1 to 5000 nM. CTLs (either CTL 81/12 or CTL 82/35) were added at an effector/target ratio of 3:1. Chromium release was measured after four hours. The results are shown in FIGS. 2A and 2B, showing lysis by CTL 81/12 (FIG. 2A) and CTL 82/35 (FIG. 2 B). Arrows indicate the level of lysis of MZ2-MEL 43(B + ) and MZ2 lymphoblastoid cells (B − ), incubated without peptides. The experiments set forth supra suggest that a peptide with a particular binding motif is required for binding to HLA-Cw*1601. Peptides of this formula, i.e.: Xaa Ala (Xaa) 6 Leu (SEQ ID NO: 10), are one feature of the invention. In SEQ ID NO: 10, Xaa refers to any amino acid, with the following preferences: Ala or Ser at position 1 Tyr or Arg at position 3 Gly or Ala at position 4 Glu or Val at position 5 Pro or Phe at position 6 Arg or Leu at position 7 Lys or Ala at position 8 Isolated peptides of this formula are useful, e.g., in diagnosing cancer, as will be explained. It is known, as per the references cited herein, that patients do develop cytolytic T cells against their own tumors. For HLA-Cw*1601 positive patients, these cytolytic T cells recognize and react with any cell which presents complexes of HLA-Cw*1601 and a peptide of the formula in SEQ ID NO: 10, most preferably SEQ ID NO: 4 or SEQ ID NO: 5. The recognition may be monitored via TNF release by the CTLs, proliferation of the CTLs, and/or release of some agent contained by the target cells, e.g., radioactive chromium ( 5 Cr). Thus, in one aspect of the invention, a sample of a subject's blood, containing PBLS, is contacted to HLA-Cw*1601 presenting cells. These cells are contacted, such as by pulsing, with a peptide in accordance with SEQ ID NO: 10. These peptides complex with the HLA-Cw*1601 molecules, and any CTLs in the PBL containing sample react therewith. Thus, one aspect of the invention is a diagnostic assay for the determination of tumor specific CTLs, it having been established that only tumor cells present MAGE derived TRAs. The one exception to this appears to be testicular cells, but it is a simple matter to simply exclude the possibility that CTLs in the subject's blood are reacting with testes cells. One may also transfect an HLA-Cw*1601 positive cell with a MAGE gene, e.g., MAGE-1, to produce the desired complexes. In another aspect of the invention, the peptides disclosed herein may be used alone or complexed to carrier proteins, and then be used as immunogens. Such immunogens can be used alone, or preferably with a pharmaceutically acceptable adjuvant. The antibodies are useful, also in diagnostic assays, to determine if and when the particular peptides are presented on cells. Again, such presentation is indicative of cancer. The isolated nucleic acid molecules of the invention are also useful, as indicated, as probes for the determination of expression of HLA-Cw*1601. It hardly needs to be said that HLA typing is important in, e.g., tissue typing for transplantation, and other areas. Thus, it is useful to have available materials which can be used in this context. The primers used in the PCR work can be used, alone or in combination, in amplification assays such as polymerase chain reaction. They can also be used, when labelled, e.g., radioactively or non-radioactively, as probes for determining whether or not HLA-Cw*1601 is expressed, in other diagnostic assays. Thus, combinations of two or more of SEQ ID NOS: 6, 7, 8 and 9 may be used, in “one-pot” or kit forms, as diagnostic reagents. A kit form is expressly preferred, where separate portions of SEQ ID NOS: 6 and 7 and SEQ ID NOS: 8 and 9 are provided, in a packaging means, for use in an amplification or other formats. The kits may also include polymerases, such as Tag polymerase, in specific embodiments. The foregoing experiments demonstrate that HLA-Cw*1601 presents a MAGE-1 derived peptide as a tumor rejection antigen, leading to lysis of the presenting cells. There are ramifications of this finding, discussed infra. For example, CTL clone 81/12 is representative of CTLs specific for the complex in question. Administration of such CTLs to a subject is expected to be therapeutically useful when the patient presents HLA-Cw*1601 phenotype on abnormal cells. It is within the skill of the artisan to develop the necessary CTLs in vitro. Specifically, a sample of cells, such as blood cells, are contacted to a cell presenting the complex and capable of provoking a specific CTL to proliferate. The target cell can be a transfectant, such as a COS cell of the type described supra. These transfectants present the desired complex on their surface and, when combined with a CTL of interest, stimulate its proliferation. It has been pointed out that the sequence for HLA-Cw*1601 is known to the art through GENBANK and EMBL, and the sequence for MAGE-1, together with a detailed protocol for its isolation, is provided by the PCT application and Van den Bruggen et al., both of which are incorporated by reference in their entirety, supra. COS cells, such as those used herein are widely available, as are other suitable host cells. To detail the therapeutic methodology, referred to as adoptive transfer (Greenberg, J. Immunol. 136(5): 1917 (1986); Riddel et al., Science 257: 238 (Jul. 10, 1992); Lynch et al., Eur. J. Immunol. 21: 1403-1410 (1991); Kast et al., Cell 59: 603-614 (Nov. 17, 1989)), cells presenting the desired complex are combined with CTLs leading to proliferation of the CTLs specific thereto. The proliferated CTLs are then administered to a subject with a cellular abnormality which is characterized by abnormal cells presenting the particular complex. The CTLs then lyse the abnormal cells, thereby achieving the desired therapeutic goal. The foregoing therapy assumes that the subject's abnormal cells present the HLA-Cw*1601/MAGE-1 derived peptide complex. This can be determined very easily. For example CTLs are identified using the transfectants discussed supra, and once isolated, can be used with a sample of a subject's abnormal cells to determine lysis in vitro. If lysis is observed, then the use of specific CTLs in such a therapy may alleviate the condition associated with the abnormal cells. A less involved methodology examines the abnormal cells for HLA phenotyping, using standard assays, and determines expression of MAGE-1 via amplification using, e.g., PCR. Adoptive transfer is not the only form of therapy that is available in accordance with the invention. CTLs can also be provoked in vivo, using a number of approaches. One approach, i.e., the use of non-proliferative cells expressing the complex, has been elaborated upon supra. The cells used in this approach may be those that normally express the complex, such as irradiated melanoma cells or cells transfected with one or both of the genes necessary for presentation of the complex. Chen et al., Proc. Natl. Acad. Sci. USA 88: 110-114 (January, 1991) exemplify this approach, showing the use of transfected cells expressing HPVE7 peptides in a therapeutic regime. Various cell types may be used. Similarly, vectors carrying one or both of the genes of interest may be used. Viral or bacterial vectors are especially preferred. In these systems, the gene of interest is carried by, e.g., a Vaccinia virus or the bacteria BCG, and the materials de facto “infect” host cells. The cells which result present the complex of interest, and are recognized by autologous CTLs, which then proliferate. A similar effect can be achieved by combining MAGE-1 itself with an adjuvant to facilitate incorporation into HLA-Cw*1601 presenting cells. The enzyme is then processed to yield the peptide partner of the HLA molecule. The foregoing discussion refers to “abnormal cells” and “cellular abnormalities”. These terms are employed in their broadest interpretation, and refer to any situation where the cells in question exhibit at least one property which indicates that they differ from normal cells of their specific type. Examples of abnormal properties include morphological and biochemical changes, e.g. Cellular abnormalities include tumors, such as melanoma, autoimmune disorders, and so forth. Other aspects of the invention will be clear to the skilled artisan and need not be repeated here. The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, it being recognized that various modifications are possible within the scope of the invention.

This invention relates to MAGE-1 derived nonapeptides. The therapeutic and diagnostic ramifications of this observation are the subject of the invention.

FIELD OF INVENTION This invention relates to a method and apparatus for delivering cotton modules and cotton therefrom to a cotton gin and more particularly concerned with a cotton module handling system having flat bed carts with rubber tires and a stationery cotton gin feeder which progressively fluffs and blends cotton from successive cotton modules being fed thereto. BACKGROUND OF THE INVENTION The season of cotton harvesting is a rather short one, occurring in the early Fall of each year. It is every farmer's goal to harvest as much cotton as possible before inclement weather prevents the harvesting and transportation of the cotton to a gin where it can be processed. Presently, harvested cotton is compacted in the field into 32'×9' foot modules by special equipment known as module builders. The modules are then loaded onto a truck or tractor trailer having a movable bed to effectuate the loading and unloading of a module. The truck then transports the module to a gin where it is commonly stored in an open field usually situated about a high point and commonly called a module yard. The modules are unloaded from the truck and placed directly on the ground until the gin is ready for that particular module. While being stored in the module yard, the modules are exposed to the elements of nature causing portions of the modules to rot. Additionally, the bottom portion of the module is contaminated by the dirt and rocks upon which it rests. When the gin is ready for the next module of cotton, a movable bed truck is sent to receive the module and transport it to the gin where it can be fed into the gin. This double-handling of cotton results in several undesirable effects. First, the modules tend to deform and lose their shape, the more they are handled, increasing the risk of the module breaking apart. Secondly, a portion of each module is left behind each time the module is loaded onto a truck having a movable bed. This results in a sizeable cumulative loss as easily discernable by the common sight of white patches on the ground in a module yard. Lastly, multiple loading and unloading of a module contributes to the knotting of cotton fibers by the chain beds of the truck which are believed to cause rib fires and gin stand problems. As a practical matter, these inadequacies of the prior art cannot be solved by merely loading the movable bed trucks with modules when the cotton is harvested and leaving the modules on the trucks until the gin is ready for that module. This is because the cost of each truck would make it impractical to purchase the number of trucks necessary for the operation of the gin, not to mention the down time associated with breakdowns of the truck. Compelled by these shortcomings in the industry, I invented and patented a system for handling cotton modules, disclosed in U.S. Pat. No. 5,017,076, issued May 21, 1991. The system is known in the market place as "MOD-TRACK", wherein the modules are stored on trailers which utilize a network of railway tracks. Associated with the railway track is a transfer station for receiving modules from movable bed trucks and delivering them successively onto carts for either storing or transporting to the gin. Because the cotton is stored on carts and does not touch the ground, and the module is not double handled, a high quality yield results with minimal amounts of cotton lost. The system disclosed in my '076 patent does require the dedication of land on which railway tracks may be laid, and therefore, lacks flexibility. Moreover, a railway system potentially limits the storage capacity of a gin to that portion of the track covered by a roofing apparatus. Even with the railway track system and carts described in the '076 patent for preserving the quality and yield of the harvested cotton up to the point where it is fed into the gin, the gin is not fed cotton at its maximum rate, and the desirable efficiency is lost. To date, feeders are not capable of feeding the gin fast enough to maximize the capacity of most gins. Currently in use are movable feeder heads in conjunction with suck pipes. Essentially, the movable feeder head consist of a dome-like structure containing rotating cylinders each having a plurality of radial fingers which, when the feeder head is passed over a module, disperses the cotton which is then sucked by the suck pipe into the incoming separator of the gin. Typically a module is placed on a flat concrete surface and the movable feeder head progressively moves over the module sitting on the surface as the fingers of the rotating cylinders disperse the cotton from the modules by downwardly striking on the module with the fingers extending from each cylinder. The inherent deficiencies of such suck pipe feeders are substantially the same as described above in regard to the movable feeder head. However, a movable feeder head only moves in one direction, thus requiring an interval of time so that the feeder head may be reloaded with another module and the contaminated cotton not fed into the gin is swept away. Thus, a marked amount of cotton harvested by the farmer is lost due to the inefficiency of the feeder and the double handling of the module. The movable feeder head will also leave wet spots in the cotton clumped together as it is sent to the incoming separator. Along with the wet spots of cotton, there will be rocks, mud and debris gathered by the module while being stored in the module yard. To operate a movable feeder head requires approximately two to three workers. Alternatively, some gins utilize hydraulically controlled suck pipes which pass over an unloaded module, sucking off portions of the module as they pass over the module. BRIEF DESCRIPTION OF THE INVENTION Briefly described, the present invention includes a transportation station for unloading cotton modules from transport trucks onto flat bed carts supported by and riding on a plurality of rubber tires for delivery to a cotton feeder system having a stationery feeder head. In more detail, a transport truck with a movable bed, loaded with a cotton module, transports this module from the module builder, which is usually located in or near the field being harvested, to the cotton gin. Adjacent to the site of the gin, a transfer station is provided with a housing with a flat unloading deck or platform. The transport truck is driven up a ramp and positioned on the deck at the transfer station so that its unloading end is substantially on the same vertical plane as the end of the deck. The deck is above a concrete driveway, allowing a cart to be positioned substantially underneath the deck in the opening below the deck. The cart is steered into position by placing the tongue of the cart in a trench running longitudinally in a linear path along the concrete driveway. A tractor attached to the cart pushes the cart into position, thus removing the opportunity for human error in positioning the cart. The truck opens its hatch and extends its movable floor, expelling the module down the inclined movable floor onto the cart. The module contacts an upright bulkhead attached to the tractor as it is discharged over the flat bed of the cart. The force of the module against the bulkhead moves the tractor and the module in a direction away from the ramp, the weight of the module becoming a ballast on the cart so that the force of the moving module moves the cart. At such time when the entire module has been off-loaded onto the cart, the tractor will move the cart and module to either a storage area or to the conveyor assembly where the module is progressively fed toward a feeder head for processing. Consequently, the module stays off the ground so that it will not be contaminated by dirt, rocks or debris. Moreover, the cotton is not double handled which generates waste by leaving behind cotton each time the module is moved. At the conveyor assembly, the carts are successively moved by a tractor into a position where the cart tongue is placed in a trench running in a linear path longitudinally along a second concrete driveway. The tongue will then steer the care into alignment with other carts as the cart is pushed by the tractor. At this stage, progressively narrowing guide rollers, positioned on one side of the pathway, receive the bottom of one side flange of the cart for guiding the cart. As the rollers guide the cart into alignment, along the pathway, troughs beneath the wheels of the cart also guide the wheels. The cart then progresses into a second segment of the conveyor where the feed-in rollers are on both sides of the cart and a chain belt with outwardly extending lugs, engages a similar lug located on the underneath side of the cart for propelling the cart. The tractor then disengages automatically from the cart and is available to proceed for engaging and pushing the next cart at the transfer station. The in-feed conveyor is motor driven and propels the cart to the next segment of the conveyor known as the "feeder conveyor" where like lugs on the conveyor chain engage the lugs on the cart for propelling it. The feeder conveyor is motor driven by a second motor, capable of variable speeds. The speed of the cart is critical in that it is set at a rate so that the feeder head, which separates the cotton from the module, is being fed cotton at its maximum rate and without interruption. The conveyed cart, propelled by the feeder conveyor, actually pushes the cart in front of it, through the feeder head. Without the presence of the propulsion or a conveyed cart, the conveyor and the feeder head are shut off. Idler rollers upon which the other side flange of the cart rests, positions the horizontal surface of the cart bed to a prescribed height for movement beneath the feeder head. Troughs are provided in the driveway so that a substantial portion of the weight of the cart is carried by the idler rollers while the tires remain in contact with the driveway. The feeder head comprises a dome or housing encompassing a plurality of vertically spaced, transversely rotatable disposed shafts having parallel horizonal axes and radially protruding fingers extending therefrom. Behind the lowermost rotatable shaft is positioned a transverse auger, substantially horizontally parallel with the lowest rotatable shaft. The auger pushes the cotton into an air box separator where the debris in the cotton are separated and the cotton is them removed by air to the gin. As the cart is being pushed into the feeder housing, the top rotating shaft is the first to contact the module, rotating upwardly against the module, so that the disbursed cotton is thrown upwardly and is sucked into a plenum chamber at the back of the feeder housing. The fingers on the shafts are divided into segments along the length of each shaft, the rows of fingers in each segment being 45° offset from the fingers in the adjacent segments. This distributes the load on the fingers while they are in contact with the module. Angle iron braces are utilized to form depth gauges to regulate the penetration of the fingers into the compressed cotton and act as holders for reinforcement of the fingers. Additionally, the fingers, adjacent the ends of each shaft, are bent outwardly to prevent the wrapping of cotton around the shafts, thus reducing the chances of fire in the feeder head. The disbursed cotton is delivered to turbulent air in the plenum at the rear of the feeder housing and is thus fluffed and blended. This allows wet spots and contaminated cotton in the module to blend with the other cotton. The cotton is accumulated on the portion of the cart which temporarily forms a part of the bottom of the plenum chamber and is pushed to one side by an auger which progressively conveys the cotton into an air box separator located at the side of the feeder housing. In the air box separator, the cotton is separated from the contaminants, such as debris, rocks, steel or wood particles. A suck pipe, connected to the conventional incoming separator of the gin, is attached to the air box separator. The vacuum created by the suck pipe in the air box separator is controlled by a plurality of slideably-mounted or hinged doors. By partially opening and closings these doors, the ginner can create the proper vacuum in the air box separator, such that the contaminants in the cotton stay in the air box separator and only the cotton is sucked into the suck pipe. The contaminants merely remain in the bottom of the air box separator until they are manually removed. Thus, the progressively separated and conditioned cotton from the module is sent to the incoming separator of the gin, while the empty carts are progressively passed beneath the air box separator. When the cart is empty, a tractor will be attach to the tongue for taking it to the transfer station for loading with another module, so that the process can be repeated. A feature of the system of the present invention is its ability to stop feeding modules to the feeder head upon the occurrence of specific events. Such events may be the malfunction of the gin, stopping the gin in process, a loss of vacuum in the suck pipe, a change in the owner's of the modules to be fed in or the absence of the propulsion cart for pushing the forwardmost cart through and beneath the feeder. Accordingly, it is an object of the present invention to provide a system for handling cotton modules and feeding the cotton therefrom into a cotton gin which system is inexpensive to manufacture, durable in structure and efficient and reliable in operation. Another object of the present invention to provide an apparatus and process for removing cotton from a module which will overcome the deficiencies and inadequacies of the prior art module handlers and feeders. Another object of the present invention is to provide an apparatus and process for removing cotton from a module which provides substantially continuous flow of cotton to the gin. Another object of the present invention to provide a process and apparatus which will remove the need for double handling of modules, reducing gin strand problems while maximizing the capacity of the gin. Another object of the present invention is to provide an apparatus and process of delivering cotton to a gin so as to provide a continuous flow of cotton to the gin. Another object of the present invention is provide an apparatus and process for supplying cotton to a gin so as to reduce the labor force necessary to handle the cotton modules and feeder. Another object of the present invention is to provide an apparatus and process for delivering cotton to a gin which will blend the wet or contaminated portions of the module with other cotton. Another object of the present invention is to provide an apparatus and process of delivering cotton to a gin so as to reduce the repair or maintenance cost associated with the module handlers and feeders. Another object of the present invention is to provide an apparatus and process of delivering cotton to a gin so as to provide a feeder that can be cleaned without shutting it down. Another object of the present invention is to provide an apparatus and process of delivering cotton to a gin so as to reduce the risk of fire associated with cotton being wrapped around the drive shafts. Another object of the present invention is to provide an apparatus and process of delivering cotton to a gin so that an operator can readily detect a change in the modules fed to the feeder and permit a separation of cotton from one farmer before feeding cotton from another farmer. Another object of the present invention is to provide a process for delivering cotton modules and cotton therefrom into a cotton gin efficiently and in a substantially continuous manner. Another object of the present invention is to provide an apparatus for successively unloading and disposing modules of cotton from successive carts carrying the modules. Another object of the present invention is to provide a feeder head for a cotton gin which is capable of successively unloading compressed modules carried by moveable carts and deliver the cotton therefrom in a fluffed and separated condition to the gin. Another object of the present invention is to provide a system of handling successive modules of cotton and deliver the cotton of these modules successively to a cotton gin in an efficient and inexpensive way. Another object of the present invention is to provide a process of delivering the cotton to a cotton gin in a manner which will reduce to a minimum the manual labor required. Another object of the present invention is to provide a cotton gin feeder head assembly which is capable of automatically removing successive compressed cotton modules from carts and delivering the cotton in a separated condition in an efficient and facial manner. Another object of the present invention is to provide a cotton gin feeder head assembly which will automatically shut down whenever there is an overload of cotton being fed to the cotton gin. Another object of the present invention is to provide a system of handling cotton modules supplied to a cotton gin so that an uninterrupted supply of compacted cotton modules will be supplied to the feeder head and a substantially uninterrupted supply of fluffed cotton to the gin. Other objects, features and advantages of the present invention will become apparent from the following description when considered in conjunction with the accompanying drawings wherein like characters of reference designate corresponding parts throughout the several views. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic perspective view of a system for delivering cotton modules to a cotton gin and removing cotton therefrom, constructed in accordance with the preferred embodiment of the present invention; FIG. 2 is a fragmentary side elevational view of a portion of the transfer station of the system shown in FIG. 1 and showing a module being unloaded onto a cart thereof; FIG. 3 is a perspective view of a bulkhead stop attachment for the tractor shown in FIGS. 1 and 2; FIG. 4 is a perspective view of the automatic latching hitch attached to for the tractor shown in FIGS. 1 and 2; FIG. 5 is a top plan view of the conveyor feeder head assembly and driveway showing only the portions of the conveyor system for the feeder head assembly for the system shown in FIG. 1; FIG. 6 is a fragmentary side elevational view of a portion of the conveyor system shown in FIG. 5, and showing the chain lugs and cart lug for propelling the cart; FIG. 7 is an enlarged front elevational view of a portion of the feeder head assembly of FIG. 1, and having portions removed so as to reveal the auger; FIG. 8A is an enlarged fragmentary front elevational view a portion of the feeder head depicted in FIG. 7; FIG. 8B is a vertical sectional view taken substantially along line 8B-8B in FIG. 8A; FIG. 9 is a fragmentary side elevational view of a portion of the feeder head assembly of the apparatus shown in FIG. 1; FIG. 10A is a fragmentary rear elevational view of a portion of the feeder head assembly of the system shown in FIG. 1, and showing the air box separator; and FIG. 10B is a fragmentary perspective view of a portion of the apparatus shown in FIG. 1, and showing the air box separator depicted in FIG. 10A, and the baffle plate, and auger in broken lines. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now in detail to the embodiment chosen for purposes of illustrating the present invention, numeral 10 denotes, generally, a housing or transfer station at which the cotton module 15 is transferred to a cart 23. Housing 10 includes upstanding side walls, such as wall 11, and a flat horizontal deck 12 on which a truck or tractor trailer T which contains a cotton module 15, in FIG. 2, can be off-loaded. A movable floor conveyor, such as conveyor 16, either in the truck or mounted on the deck 12 provides an upper flight which is capable of moving the module 15 from left to right in FIG. 2. Therefore, when a truck is positioned on the deck 12, the module 15 which it contains can be progressively off-loaded from left to right in FIG. 2. A pair of stops 17 prevent the truck from being backed up sufficiently that its rear wheels fall off of the deck 12. The housing 10 has a hollow interior open at one end and there is a straight flat concrete roadway or driveway 20 which leads into the housing 10. This roadway 20 has a straight or linear central trench or trough 21 extending the full length of the roadway 20 and into the hollow interior of housing 10. This trench 21 forms a guide for the tongue guide 22a of a cart, denoted, generally, by the numeral 23. This cart 23 has a flat rectangular bed or platform 26 which is supported in a horizontal position by a plurality of rear wheels 24 and a plurality of front wheels 25. The front wheels 25 are steerable by the tongue 22, the tongue 22 protruding forwardly beyond the front end of the cart 23. As best seen in FIG. 6, the tongue guide 22a is a downwardly protruding V-shaped member, the lower end portion of which is adapted to be received in the trough or trench 21. The flat rectangular bed 26 is supported by a plurality of equally spaced transversely extending ribs 26a which are, in turn, supported on longitudinal beams 26b, carried by the wheels 24 and 25. Depending from the side edges of the deck or bed 26 are a pair of opposed, complimentary, downwardly protruding longitudinal side flanges 26c and 26d. Their lower edge portions 26e and 26f are straight parallel lower surfaces, the front end portions of which are inclined upwardly and forwardly as at numeral 26g. The cart 23 is adapted to be pulled or pushed, selectively, by the tractor 27. When an empty cart 23 is delivered to the driveway 20, the tractor 27 pulls the cart 23 by its tongue 22 so that it is positioned in about the position shown in FIG. 1 and then releases the tongue 22 so that the tongue guide 22a is received in the trough 21. Thereafter, the tractor 27 moves around to the backside of the cart 23 and pushes the cart 23 forwardly until only a rearmost portion of the cart 23 protrudes from beneath the deck 12. The tongue guide 22a riding within the trough 21 guides the cart 23 as it moves into position in the housing 10. As best seen in FIGS. 2 and 3, the front end portion of the tractor 27 is provided with a stop frame, denoted generally by numeral 30. This stop frame 30 includes a pair of opposed, essentially parallel, beams 31 which are mounted to opposite sides of the tractor 27 and protrude forwardly beyond the front end of the tractor 27. The front end portions of the beams 31 respectively support a pair of opposed upright channel members 32, the end portions of which are connected by cross bars, such as cross bar 33. Braces 34, extending between the central portion of the beams 31 and the central portion of the channel members 32, support the channel members 32 in their upright positions. A pair of pivot arms 35 are mounted by pivot pins 36 to the upper end portions of channel members 32. These pivot arms 35 protrude forwardly and their distal ends are respectively connected to the central portions of a pair of upstanding struts 37 which form a part of an abutment frame 40. In more detail, the abutment frame 40 is an open rectangular frame having side bars 38 which are respectively outwardly adjacent to and parallel to the struts 37. The upper and lower ends of the rectangular or square frame 40 are formed by end bars 39 which join the upper and lower ends, respectively, of the side bars 38. Thus, the frame 40 is adapted to be pivoted from a vertical position as shown in FIG. 3 to an inclined position as shown in FIG. 2, so as to form a stop to receive the end of the module 15. A bumper 41 at the lower end of the frame 40 arrests the movement of the frame 40 when it is returned to its upright position. Below the frame 40 and mounted on the lower end portions of the channel members 32, are a pair of cross bars 42 and 43 connected together by a central strap 44. A vertically movable latching lug 45 protrudes through a downwardly opening slot in the cross bar 43, the latching lug 45 having an upwardly and rearwardly inclined forward camming surface 46 which forms a part of the upstanding hook or bill 47 of lug 45. The latching lug 45 is spring loaded to the position shown in FIG. 3 but will yieldably move downwardly to pass under the rear end portion of the cart 23 and latch in place as shown in FIG. 2. A camming rod 50, seen in FIG. 3 supports the latching lug 45 in its normal position as shown in FIGS. 2 and 3 and this camming rod 50 is provided with a lever 51 which is spring loaded by spring 49 to its position supporting the latching lug 45 in its latching position. Connected to the lever 51 is a cable or line 52 which passes over a pulley 53 and thence, rearwardly to the operator of the tractor 27. When the operator of the tractor 27 pulls the cable or line 52, it, in turn, rotates the lever 51 so as to cause the latch lug 45 to be pushed downwardly so as to disengage the end portion 23a of the cart 23. As best seen in FIG. 4, the rear portion of the tractor 27 is provided with a tongue engaging assembly 60 which is adapted to engage the coupling 22b at the end of tongue 22 so as to tow it. In more detail, the tongue engaging assembly 60 includes a transversely disposed tow bar 61 having forwardly extending lower hitch engaging lugs 62 and upper hitch engaging lugs 63, the upper hitch engaging lugs 63 being mounted on support blocks 64 which protrude upwardly from the tow bar 61. It will be understood by those skilled in the art that by passing latch pins 65 through the lugs 63, the assembly 60 can be mounted on the side hitches of the tractor 27. There are also a top pair of lugs 67 on central upstanding bar 70, with their pin 68 for engaging the top hitch (not shown) of the tractor 27. Thus, this assembly 60 can be moved upwardly or downwardly in an arcuate path. The lower lugs, such as lugs 62 are for the larger tractors. The upstanding bar 70 has a rearwardly extending upper plate 71. This upper plate 71 journals the upper end portion of a vertically disposed shaft 73, the lower portion of which is journaled by a stationery rearwardly protruding bifurcated latch element 74 which also functions as a thrust bearing for the lower end portion of the shaft 73. A guard plate 72 supported by brackets 75 prevent the shaft 73 from being inadvertently bent. The latch element 74 is a flat plate, the forward end of which has a pair of rearwardly protruding fingers which taper rearwardly, thus defining a pair of opposed guide surfaces, such as guide surface 76. These guide surfaces 76 converge forwardly forming a throat which receives a vertical bale 22c on coupling 22b of tongue 22. Above the latch element 74 is an L-shaped spring loaded latch 77. The shaft 73 passes through the apex of the L-shaped latch 77 and rotates the latch 77 when the shaft 73 is rotated. The latch 77 has a rearwardly extending arm 77a which tapers to a point so as to provide an inner camming surface 77b against which the bale 22c of the tongue 22 rides when the tractor is moved rearwardly to engage the cart 23. Inwardly of the camming surface 77b, the latch is provided with a bale 22c engaging surface 77c which is adapted to pass behind and hold the bale when the cart 23 is to be towed. A spring 78 mounted on a brace 79 of a lever arm 80 of latch 77, urges latch 77 to a closed position in which the bale 22c is latched. This latching is accomplished as the tractor moves rearwardly for engaging the bale 22c, the bale 22c passing between the surfaces 77b and 76 causing the latch 77 to be rotated in a clockwise direction as viewed in FIG. 4 and then spring back into its normal position as shown in FIG. 4. A disengaging lever 81 is mounted on the upper end portion of the shaft 73 and is provided with a lanyard or line 82 by which the lever 81 may be rotated in a clockwise direction so as to release the bale 22c whenever the lanyard 82 is pulled by the operator of the tractor. When a bale 15 is to be off-loaded from a truck or van, the truck or van T, seen in FIG. 2, is backed into position and its ramp or moving floor 16 lowered so as to incline toward the cart 23 and guide the module 15 downwardly and toward the tractor and against the stop or abutment frame 40. The truck T can then back up slowly so as to push the module 15, the tractor 27 and the cart 23 away from the housing 10. When a portion of the module 15 is received on the deck 26, the tractor 27 may move away from housing 10, thereby carrying the module 15 so that it progressively is off-loaded onto the cart 23. In such a procedure, the abutment frame 40 is initially disposed in an angular position as shown in FIG. 2, and as the module 15 is received on the deck 26, the end of the module 15 will pivot the abutment frame 40 to a vertical position. The tractor 27 can then be placed in reverse so that it pulls the cart 23 away from the housing 10, the latch 45 remaining in its up position, as shown in FIG. 2, so as to remain engaged with the cart 23. When the tractor 27 has removed the cart 23, the operator pulls the line 52 so as to release the latch 45 and then backs away from the cart 23 and returns to the front end of the cart 23 where the tongue is manually lifted out of the trough and attached no the latch 77. The tractor 27 can then transport the cart 23 to a waiting zone or directly to the in-feed conveyor section 80. In the in-feed conveyor section 80 of the system is a straight flat rectangular elongated driveway 100 which is provided with a central longitudinally extending linear trench or trough 101 for guiding the tongue 22 of the cart 23 toward and through the feeder head assembly of the system. There is also an inner wheel trough 102 which is parallel to the central trough 101, throughout substantially the length of the driveway 100. This second trough 102 is to receive the wheels 24 and 25 of the cart 23 so as to lower one side of the cart 23 after the cart 23 is on the driveway 100. Extending from a mid-portion or intermediate portion of the driveway 100 and terminating inwardly of the exit end 100b of the driveway 100 is a third trough 103, the wheel trough 103 being parallel to trough 101 and 102 for receiving the wheels 24 and 25 on the other side of the cart 23. Outwardly adjacent to the left hand side of the driveway 100 are a plurality of longitudinally aligned, spaced uprights 105, which support a longitudinally extending channel member 106, seen best in FIG. 5. This channel member 106, in turn, supports a plurality of longitudinally spaced rollers 107 which are progressively more narrow and are adapted to receive the left-hand flange 26c of the cart 23 so that as the cart 23 is moved inwardly along driveway 100, with its guide 22a received in trough 101, the cart 23 will be aligned properly for its further travel inwardly along driveway 100. Thus, the first section of the in-feed conveyors section 80 functions for aligning each cart 23 appropriately for being fed toward the feeder head assembly. For providing power to feed the carts 23 along the driveway 100, a motor M1, seen in FIG. 6 is provided. Motor M1 drives a continuous belt 108 which drives a sheave 109 for rotating shaft 110. Shaft 110, in turn, drives a sprocket (not shown) around which passes a continuous chain 111 which, in turn, passes around an idler sprocket 112 on shaft 113 supported between adjacent uprights 105. The chain 111 has spaced outwardly extending lugs 114 which are for the purpose of propelling the cart 23 when its flange 26c is riding on the rollers 107. The outwardly protruding lugs 114 of the upper flight of chain 111 are adapted to engage downwardly protruding lugs, such as lug 115, carried by beam 26b of each cart 23. Thus, when motor M1 is rotated, and a cart 23 is delivered to the conveyor section 80, and moved inwardly along the driveway 100, a lug 114 will engage lug 115 and thereby urge the cart 23 in an inwardly direction. As the cart 23 is moved inwardly by the conveyor chain 111, its wheels 24 and 25 will be received in the trough 102 and hence, assure that the flange 26c remains in the rollers 107 and that the cart 23 is in appropriate alignment. From the first conveyor section, the carts 23 move to a second conveyor section where a conveyor chain 120 driven by a variable speed motor M2 conveys the successive carts 23 at a critical speed so as to feed a module 15 into the feeder head 225 as will be explained. As a cart 23 enters this second conveyor section, being pushed by cart a 23 from the first conveyor section, the lugs 214, which are identical to lugs 114, engage the lug 115 (seen in FIG. 6) of the cart 23 and conveys it along its path of travel toward the exit end 100b. At this stage, the left wheels 24 and 25 ride in the trough 102 and the left rollers 207, supported on a horizontal rail 206, carries a substantial part of the load of the cart 23. As the cart 23 is fed inwardly by the chain 220, the right hand flange 26d of the cart 23 rides upon a plurality of idler rollers 209 supported by a horizontal rail 210. When the cart 23 is supported by the rollers 209, the wheels 24 and 25 on the right hand side of the cart 23 are received in the trough 103 and hence, the deck 26 is supported in a prescribed horizontal plane as it continues its travel toward the exit end 100b. The cart 23 then enters the feeder head assembly or section 90 of the system. At this stage, the foremost cart 23 is no longer propelled by the lug 240 of the conveyor chain 220 and if it is the only cart 23 in place on the driveway 100, then the cart 23 will not be propelled further into the feeder head section 90. There will usually, however, be several carts 23 arranged in tandem so that the second cart 23, which is then being propelled by the conveyor chain 220, will push the forwardmost cart 23 into and through a major portion of the feeder head section or assembly 90. Referring now specifically to the feeder head section or assembly 90, seen best in FIGS. 7 and 9, the channel menders 206 which support the rollers 207 are supported in their horizontal positions, extending longitudinally on opposite sides of tile driveway 100, by upstanding stanchions 215. Upstanding brackets 216 which, in turn, support opposed parallel beams 217. Opposed upstanding walls 218 are mounted on these beams 217 and the upstanding walls 218, in turn, support a transversely extending roof 219. The walls 218 and the roof 219 form a feeder dome or housing, denoted generally by numeral 221, which is open on its upstream end for receiving the carts 23 and their modules 15, the cart 23 passing beneath the inwardly turned flanges of the beams 217, as illustrated in FIG. 7. Thus, each cart 23 delivers its module 15 into the housing 221, being pushed by its preceding cart 23. At the rear portion of the housing 221, is the feeder head, denoted generally by numeral 225. The function of the feeder head 225 is to progressively engage the modules 15 as they are carried by their respective carts 23, in the travel of the cart 23, in its downstream path beneath the housing 221. Referring specifically to the feeder head 225, this feeder head includes a plurality of transversely extending equally, vertically, spaced shafts 222 which are journaled by their end portions in the opposed walls 218. As best seen in FIGS. 8a and 8b, each shaft 222 is preferably a hollow tubular cylindrical member which is provided at both of its end portions with sprockets, such as sprocket 223, outwardly of the walls 218. Adjacent pairs of sprockets 223 are connected together by timing belts, such as belts 224, tensions by idler pulleys 226. Thus, all shafts 222 are rotated in the same direction and at the same speed in synchronization with each other. Axially spaced along each shaft 222 are a plurality of annular spacer plates 227. These spacer plates 227 are concentrically mounted on each shaft 222. Extending radially between adjacent pairs of spacer plates 227 are a plurality of circumferentially 90° spaced angle irons braces 228, each angle iron brace 228 having a flange 228a which extends generally radially away from the shaft 222 and a flange 228b which is spaced from the shaft 222 and is provided with a plurality of holes (not shown). The edge 229 of flange 228a is welded to the shaft 222. A plurality of outwardly protruding rigid metal rods or fingers 230 protrude radially outwardly from the periphery of each shaft 222. These fingers 230 extend through the holes in flanges 228b and outwardly beyond the flange 228b so that the fingers 230 exteriorly of flange 228b engage and dig into the side of the module 15 as the module 15 is fed toward the feeder head 225. The flange 228b serves a double function of reinforcing the fingers 230 and acting as depth gauges to limit the penetration of the fingers 230 into the cotton of module 15. The fingers 230 are arranged in axially aligned rows spaced 90° circumferentially from each other, there being even and odd fingers so that the fingers of each segment between adjacent partitions 227, are staggered with respect to each other. Furthermore, the fingers 230 of adjacent rows which are separated by a partition 227 are circumferentially staggered with respect to the adjacent fingers by about 45°. Thus, a group or row of fingers 230 of one segment will strike the cotton 45° out of phase with the fingers 230 of an adjacent row. The outer fingers 230a are angled outwardly and are mounted on the periphery of the outermost partitions 227 as seen in FIG. 8a. Motor M3 drives through a geared train 231, the lowermost shaft 222 and hence, all of the shafts 222 are rotated in a counter-clockwise direction as viewed in FIG. 9, so that the fingers tend to toss the cotton upwardly and inwardly into to a plenum chamber 234, defined by a back wall 235 of housing 221 and portions of the side walls 218. A bottom portion of bed 26 of cart 23 forms the temporary bottom of the plenum chamber 234. The accumulation of the cotton in the plenum chamber 234 can be viewed through a window 236 in wall 218. As seen in FIG. 9, the shafts 222 are arranged at an incline, so that the uppermost shaft 222 is forwardly of the lowermost shaft 222 so that all shafts 222 are in a common inclined plane with respect to the path of travel of the module 15. Thus, the fingers 230 of the uppermost shaft 222 first engages the end of the module 15 as the module 15 is initially fed inwardly into housing 221. Disposed at the bottom portion of the plenum chamber 234 is a transversely disposed conveyor auger 250 seen in FIG. 7. This auger 250 has a central shaft 251 and a helical blade 252. Shaft 251 is driven by a separate variable speed motor (not shown). Outwardly of the plenum chamber 234 on one side thereof, is an air box separator 260 own in FIGS. 7, 10a and 10b. This air box separator 260 is a generally a cubical shaped member having side walls 261 and 262, a top 263 and a removable end plate 265. A bracket 266 on the end plate 265 supports a pillar block 267 which, in turn, journals the end of the shaft 251. At the top 263 in an access plate 268. Along the bottom portion of wall 261 is a slidable or hinged front door 270a and a rear door 270b. Similarly, side wall 262 has a front door 270c and a back door 270d. The air box separator 260 has an open rectangular inner end which communicates with the plenum chamber 234 through the wall 218 so that a portion of the auger blade 252 protrudes into the air box separator 260. The air box separator 260 is also provided with an inclined panel 272 which forms a chute of the housing 221 leading from the plenum chamber 234 to the edge of the horizontal bottom 271. Thus, when the cotton is removed from the bale 15 by the fingers 230, the cotton is accumulated in the plenum chamber on top of the bed 26 and is swept sidewise by the auger 250 into the air box separator 260. A window 280, seen in FIG. 10b, is provided so that the accumulation of the cotton in the air box separator 260 can be observed. The side 262 of the air box separator 260 is provided with an discharge port 275 which communicates with the suck pipe 276 leading to the gin. Disposed with the central interior of the air box separator 260 is a swingable curtain or rubber movable baffle 290 denoted in broken lines in FIGS. 10a and 10b. This baffle 290 is hingedly suspended by a piano hinge 291 from the top 263 and, therefore, is free to swing back and forth. The shaft 251 of the auger 250 protrudes through an appropriate slot 298 in the central portion of the baffle 291. The function of this baffle is to detect a drop in the vacuum drawn on the air box separator 260, detecting an equalization of the air pressure and thereby indicating that the suck pipe 276 has been clogged up by cotton. A microswitch 292 mounted on the side 262, detects the position of the baffle 290 and will signal the shut down of motors M1, M2, M3 and the motor for auger 250. An air tube 295 also functions to detect a lack of a vacuum in the suck pipe 276. It too will provide a signal for the shut down of motors M1, M2, M3 and the motor for auger 250. The air doors 270a, 270b, 270c and 270d are preferably slidable doors which can be progressively opened and shut for admitting air to the bottom portion of the air separator 260. As a result of the suction drawn on the suck pipe 276, a vacuum is drawn on the air box separator 260 so that a flow of air is drawn from the plenum chamber 234 and across the fingers 230 so that the cotton picked from the module 15 and delivered to the plenum chamber 234 will be tossed about and fluffed in the plenum chamber 234. This cotton eventually falls downwardly and is drawn by the vacuum and also fed positively by the auger 250 transversely across bed 26 and into the air box separator 260. In the air box separator 260, the heavy materials, such as rocks, will fall down the inclined chute of panel 272 and accumulate in the bottom portion of the air box separator 260. By opening the front doors 270a and 270c, ambient air will be drawn into the air box separator 260 and pass beneath the baffle 291, thereby assuring that so long as a vacuum is drawn on the air box separator 260, the baffle 291 will swing inwardly to a position so that the switch 292 will permit the motors to operate. When, however, the vacuum is no longer drawn, thereby indicating that the suck pipe 276 has been stopped up, or the gin stopped, the baffle will return to its initial position, thereby shutting down the motors M1, M2, and M3 and the auger motor (not shown). Furthermore, since the baffle 291, by manipulation of the doors 270a, 270b, 270c and 270d, an appropriate air differential between the air passing through the front doors 270a and 270c and the air passing through the rear doors 270b and 270d, will regulate the amount of vacuum which is to be drawn on the plenum chamber 234. After the cart 23 has been propelled sufficiently for the entire module 15 carried thereby to be consumed by the feeder head 225, and this cotton has been propelled sidewise by the auger 250 into the air box separator 260 and thence through the suck pipe 276, the tube 295 will detect the lack of a vacuum and thereby indicate that the module IS has been completely consumed and that a subsequent module 15 carried by a subsequent cart 23 is about to be processed. This will provide a signal for a counter for the modules 15 and also enable the operator to be signaled that perhaps another owner's cotton is to be processed. When the empty cart 23 has passed through the feeder head section 90, its tongue 22 is available to be picked up by the tractor 27 and returned to the transfer station 10 for receiving another module 15. By the system of the present invention, modules 15 can be fed successively into the feeder head section 90 and thence the cotton, in a fluffed and cleaned condition, can be delivered to the gin. Since this procedure is automated to a very large extent, very few workman are necessary in order to maintain a proper supply of modules 15 for the feeder head section 90. It will be obvious to those skilled in the art that many variations may be made in the embodiments here chosen for the purposes of illustrating the present invention, without departing from the scope thereof as defined by the appended claims.

Carts successively installed in a transfer station, receives a cotton module from above and are successively transported by a tractor into a conveyor assembly which feeds the carts successively toward a stationary feeder head where the cotton of each module is removed progressively as the cart is passed under the feeder head fluffing the cotton and delivering it to a plenum chamber. An auger, which sweeps laterally over the empty portion of the cart forming a temporary bottom for the chamber delivers the fluffed cotton to an air box separator in which rocks and stones are removed by gravity and a suck pipe removes the fluffed cotton to convey it to the gin.

FIELD OF THE INVENTION The present invention relates to a tumbler type washing/drying machine and a method of controlling the same, and more specifically, it relates to a washing/drying machine which performs various process steps of keeping the washing in wash water, washing, rinsing, dehydrating (extracting water), and drying, and to a method of controlling the washing/drying machine. DESCRIPTION OF THE RELATED ART There is a conventionally well-known tumbler type washing/drying machine which performs a series of functions from washing to drying by horizontally rotating a drum containing the washing therein in a tub (e.g., see Japanese Unexamined Patent Publication Nos. 78996/1980 and 12686/1983). However, such a conventional washing/drying machine has disadvantages as follows: (1) In the step of washing, washing for the washing is processed through the so-called tumbling operation in which the washing is drawn up by an inner wall of the drum and then tumbled down into the wash water. This performance brings about a poor washability, and it needs a washing time double as long as that of a pulsator type full automatic washing machine. (2) In the step of dehydrating, the tub greatly vibrates due to precession or mutation with high-speed retation of the drum. Therefore, a concrete or iron balancer of about 20 kg must be attached to the tub to restrain the undesired vibration, with a result that the total weight of the machine is made large. (3) In the step of drying, it is difficult to expose dry air uniformly to the washing all over, and therefore, the washing may partially remain undried, or excessive drying causes the cloth to be damaged easily. SUMMARY OF THE INVENTION The present invention provides a washing/drying machine which includes a tub, means for feeding water to the tub, means for draining water from the tub, a tumbling drum rotatably along a lateral axis in the tub, having a plurality of holes through which air and water pass and an opening for introducing the washing, and a lid for closing the opening, means for rotating the drum at various speeds, a disc for agitating the washing, disposed in the drum adjacent to a flat end wall of the drum in parallel with the wall, means for rotatably bearing the disc, means for selectively fixing the disc, means for supplying hot air to the drum and means for controlling the fixing means to intermittently fix the disc against the rotation of the drum. Preferably, the disc bearing means includes a bearing for rotatably supporting an axis of the disc, and the fixing means includes a clutch for mechanically engaging/disengaging the axis of the disc with/from the tub. The agitating disc may include a plurality of projections and a plurality of air holes. Preferably, the drum has an annular rib in the periphery of its circular side wall. Preferably, the hot air supplying means includes a duct located outside the tub, for communicating both flat end walls of the tub, a blower located in the duct for circulating the air in the tub through the duct, and a heater located at the outlet end of the duct. Further, preferably, the heater is arched in shape and located on one of the end walls of the tub and above the axis of the drum. The heater may be accommodated in an arched concavity provided on the side wall of the tub and covered with a cover. The heater may also be accommodated in a heater case attached to the side wall of the tub. Preferably, the hot air supplying means further includes cooling means for cooling the circulating air in the duct to dehumidify it. The cooling means may include a U-shaped air duct. The drum rotating means may be a DC brushless motor composed of a stator provided with a winding and a rotor including a permanent magnet. Preferably, an ON-OFF duty ratio of the line voltage applied to the winding of the stator in the washing condition, such as water-extracting and the like, where the motor works at high speed, is made larger than an ON-OFF duty ratio of the line voltage applied to the winding of the stator in the washing condition, such as washing, rinsing and the like, where the motor works at low speed, for controlling the revolution of the motor in accordance with the washing conditions. The line voltage applied to the winding of the stator of the motor may be subjected to pulse width modulation in order to control the motor speed in a range of the washing conditions. The present invention provides a method of controlling a washing/drying machine, which includes a tub and a tumbling drum for containing the washing horizontally disposed rotatable in the tub, for performing the steps of washing, water-extracting, and drying, the water-extracting step comprising the steps of storing in advance in storing means a plurality of programs for increasing the rotating speed of the drum by stages with time, loosening the washing by rotating the drum forward and backward alternately, reading the programs corresponding to an amount of the washing contained in the drum from the storing means, rotating the drum in one direction in accordance with the program read out, for gradually pushing the washing against the inner walls of the drum by centrifugal force, detecting a degree of vibration of the tub while the drum is rotating and comparing it with a given or reference value, and rotating the drum at higher speed than a maximum limit rotating speed according to the program to extract water from the washing when the vibration of the tub is smaller than the reference value. Preferably, when the vibration of the tub attains the reference value in the step of rotating the drum according to the program read out, the drum is rotated forward and backward alternately to loosen the washing after temporarily stopped, and then further rotated according to the same program. The water-extracting step may further include the steps of feeding the drum with water and then rotating it forward and backward alternately and draining the water from the drum when the vibration of the tub attains the reference value even with a predetermined times of repetitive performance of rotating the drum according to the program after the loosening of the washing. The present invention also provides a method of controlling a washing/drying machine, which includes a tub and a tumbling drum for containing the washing horizontally disposed rotatable in the tub, for performing the steps of washing, rinsing, water-extracting, and drying, the water-extracting step comprising the steps of storing in advance in storing means a plurality of programs for increasing the rotating speed of the drum by stages with time, loosening the washing by rotating the drum forward and backward alternately, reading the programs corresponding to an amount of the washing contained in the drum from the storing means, rotating the drum in one direction in accordance with the program read out, for gradually pushing the washing against the inner walls of the drum by centrifugal force in a well-balanced condition, rotating the drum at higher speed than the maximum limit rotating speed according to the program to extracting water from the washing, rotating the drum again forward and backward alternately to loosen the washing, rotating the drum in one direction according to the program, and rotating the drum at higher speed than the speed in the previous step to further extract water from the washing. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a tumbler type washing/drying machine according to the present invention; FIG. 2 is a vertical cross-sectional view showing the tumbler type washing/drying machine according to the present invention; FIG. 3 is a side view showing the left side of the tumbler type washing/drying machine according to the present invention; FIG. 4 is a frontal elevational view showing the tumbler type washing/drying machine according to the present invention; FIG. 5 is rear elevational view showing the tumbler type washing/drying machine according to the present invention; FIG. 6 is a sectional view showing a clutch; FIGS. 7 to 9 are partial sectional view showing the operation of a major portion of the clutch; FIG. 10 is a partial cutaway view showing a major portion of the tumbler type washing/drying machine according to the present invention; FIG. 11 is a sectional view showing a configuration of the fixing of a heater of the tumbler type washing/drying machine according to the present invention; FIG. 12 is a frontal elevational view showing a heater cover; FIG. 13 is a frontal elevational view showing a configuration of the heater; FIG. 14 is a diagram showing a circulating path of hot air; FIG. 15 is a sectional view showing a dehumidifying heat exchanger; FIG. 16 is a sectional view showing a major portion of an annular rim; FIG. 17 is a block diagram showing a control device of the tumbler type washing/drying machine according to the present invention; FIG. 18 is a sectional view showing a motor for rotating a tumbling drum; FIG. 19 is a wave form chart showing rotor position signals and driving voltage of the motor; FIG. 20 is a diagram showing characteristic curves of the torque-revolution speed of the motor; FIGS. 21(a) and 21(b) are wave form charts of PWM voltage applied to the motor; FIG. 22 is a diagram showing characteristic curves of the torque-revolution speed related to the duty ratio of PWM; FIG. 23 is a diagram for explaining a state of the washing in the tumbling drum related to an increase of the rotation speed; FIG. 24 is a diagram for explaining the relations between the rotation speed of the drum and time for a well-balanced condition; FIG. 25 is a graph showing curves of the time and temperature in the step of drying; FIGS. 26 to 28 are flow charts showing the operation of the tumbler type washing/drying machine in the step of drying; FIGS. 29 and 30 are graphs showing a curve of the heater current related to the temperature variation with time in the step of drying; FIGS. 31(a)-31(f) are flow charts successively showing the steps of washing, rinsing, dehydrating (extracting water) and drying in the tumbler type washing/drying machine according to the present invention; and FIGS. 32(a)-32(e) are time charts in correspondence with FIGS. 31(a)-31(f). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Now, the present invention will be described in detail in conjunction with the preferred embodiments shown in the accompanying drawings. 1. Overall Structure of Washing/Drying Machine FIG. 1 is a perspective view showing a washing/drying machine according to the present invention. Referring to FIG. 1, the washing/drying machine has a cabinet 1, a front panel 2, an upper plate 3, a lid 4, a bottom plate 5, a control panel 6 having various control keys, a program display 7 having a start button, and a power switch 8. FIG. 2 is a vertical cross sectional view showing the washing/drying machine in FIG. 1. FIG. 3 is a side view of the left side of the washing/drying machine, where an inner structure except a part of the cabinet is shown. FIG. 4 is a frontal elevational view showing an inner structure with the front panel removed. FIG. 5 is a rear elevational view showing an inner structure with the cabinet removed. As shown in FIGS. 2 to 5, in the cabinet 1, there are provided a washtub 9, a drain valve 11, a washing drum 12 horizontally and rotatably supported in the washtub 9, a DC brushless motor 13 rotating the drum 12 forward and backward and capable of varying its rotating speed, a agitator disc 15 inside and in parallel with a flat end wall 14a of the drum 12, an electromagnetic clutch 16 selectively bearing the agitator disc 15 in either a freely rotatable state or a fixed state, a duct 17 formed outside the washtub 9 for communicating between two different side walls of the washtub 9, a blower 18 provided in a passage between opposite ends of the duct 17 for circulating air in the washtub 9 through the duct 17, a dehumidifying heat exchanger 19 provided between the opposites ends of the duct 17 for dehumidifying the circulating air in the duct 17 by cooling, a spring hanger 20 for hanging the washtub 9 from the cabinet 1, and a shock absorber 21 for fixing the washtub 9 to the cabinet 1. The drum 12 has apertures 22 over its circular wall and side walls 14a, 14b, through which air and water pass, an opening 23 at the circular wall, through which the washing is introduced and drawn out, and a door 24 for the opening 23. An elastic tube 25 is provided in an upper portion of the cabinet 1, communicating an opening 26 closed by the lid 4 and an opening 27 at the top of the washtub 9 and serving as a guide for the washing introduced into the drum 12. A plurality of baffles 28 are attached at regular intervals in the circular inner wall of the drum 12 to catch the washing while the drum 12 is rotating. The agitator disc 15 has a plurality of projections 29 at regular intervals on its surface and has throughholes 30 all over to which air and water pass. A heater 31 is placed in a juncture of the duct 17 to the washtub 9 for heating air to be fed through the duct 17 to the washtub 9. A heater 32 is placed inside a bottom of the washtub 9 for heating wash water in the washtub 9. The drum 12 has one of rotation axes 33 held by a bearing 34 at the side wall of the washtub 9 with a pulley 35 fixed on its end. The pulley 35 is connected to a pulley 36 on an output shaft of the motor 13 by a belt 37, and is driven by the motor 13. The other rotation axis 40 of the drum 12 and a rotation axis of the agitator disc 15 are coaxially held inside the clutch 16. A closing valve 38 drains cooling water from the dehumidifying heat exchanger 19, while an overflow pipe 39 drains water overflowing from the dehumidifying heat exchanger 19. A water level sensor S1 is connected to the bottom of the washtub 9 through a air tube for detecting a water level in the washtub (see FIG. 2). A water temperature sensor S2 (FIG. 2) is provided at the bottom of the washtub 9 for detecting the temperature of wash water reserved in the washtub 9. A vibration sensor S3 (FIG. 4) is a sensor having a limit switch which works when the vibration of the washtub 9 becomes a given limit value or over. A flow rate sensor S4 is provided close to a feed valve 10 for detecting an amount of water fed to the washtub 9. 2. Agitator Disc and Electromagnetic Clutch The agitator disc 15 and electromagnetic clutch 16 will be explained in detail below. As shown in FIG. 6, the rotation axis 40 of the drum 12 is a sleeve shaft, where an axis 41 of the disc 15 is borne by metal pieces 42, 43 so as to be able to rotate relative to the drum 12. The axis 40 has its flange 44 screwed on the end wall 14a of the drum 12. The axis 41 of the disc 15 has a seal 45 for sealing against wash water, and a clutch boss 46. A bearing holder 47 of a bearing 47a carrying the axis 40 is screwed on a bracked 49 together with a housing 48 extending up to the periphery of the clutch boss 46. As shown in FIG. 7, the housing 48 has a plurality of concavities 48a positioned at regular intervals in its inner surface, and a retainer 50 is attached between the housing 48 and the clutch boss 46, while cylindrical rollers 51 are rotatably held between the concavities 48a and the clutch boss 46. The cylindrical rollers 51 are always pressed against the clutch boss 46 by a pressing element which is formed integral with or separate from the retainer 50. The retainer 50 has a groove 50a formed on its outer surface, in which a plunger 52a of a solenoid 52 is received so as to prevent the retainer 50 from moving. When the solenoid 52 is energized and the plunger 52a reaches the bottom of the groove 50a, the cylindrical rollers 51 are rotatably retained in the center of the concavities 48a by the retainer 50, and consequently, the agitator disc 15 is rotatably supported by the clutch boss 46 and the metal pieces 42, 43. When the energizing of the solenoid 52 is broken and the plunger 52 is pulled out of the groove 50a, that is, the clutch boss 46 tends to rotate, then the cylindrical rollers 51 are moved by contact of the rotating clutch boss 46 until they are stopped by a wedge action between the housing 48 and clutch boss 46; that is, as shown in FIG. 8 or 9, the cylindrical rollers 51 chock the clutch boss 46 up in the housing 48, and therefore, the disc 15 does not rotate even with the rotation of the drum 12. Thus, the following effects are attained in the washing step where the drum 12 is rotated: (1) When the solenoid 52 is turned off so that the disc 15 may be stationary in opposition to the drum 12 on rotating, the projections 29 on the agitator disc 15 act beating and rubbing to the washing, and additionally, the washing tumbles in the three-dimensional way in the drum 12 and jumbles with high efficiency, so that substantially the washing can be washed by friction and pressure caused by the rubbing and crumpling. (2) When the solenoid 52 is turned on so that the disc 15 may freely move independently of the rotation of the drum 12, the disc 15 moves in accordance with the movement of the washing, so a simple movement of the washing is repeated in the drum 12, that is the washing hangs on the baffles 28, are lifted up and tumbles down. Thus, substantially the washing can be washed by the beating as in the conventional tumbler type washing machines. The method mentioned in the above paragraph (1) significantly excels the method in (2) in washability. A combination of (1) and (2) attains a uniform washing of every part of the washing, and enables a wide range of regulation in washability. 3. Heater for Drying The heater 31 is arched in shape, of which center corresponds to the axis of the drum, and located on one of the end walls of the washtub and above the axis of the drum, and its configuration will be explained in detail below. As shown in FIG. 11, an arched groove 53 is formed facing outside on the upper half of one the end walls of the washtub 9 by means of drawing and others. The arched groove 53 on the washtub 9 may alternatively be formed with a separate heater case fixed to the side wall of the washtub 9 by means of welding or the like. The heater 31 is attached inside the arched groove 53 of the washtub 9. The arched groove 53 having the heater 31 therein has its opening facing to the drum 12 covered with an arched heater cover 54. Air for the drying is heated by the heater 31 in an arched space defined by the arched groove 53 and heater cover 54. The arched groove 53 has an inlet 53a (FIG. 10) of the air for the drying in its center, and the outlet 53a is connected to an exhaust outlet of the duct 17. The heater cover 54 has outlets 55, 55a of the air for the drying at its arched opposite ends (see FIG. 12). The air outlets 55a at the arched opposite ends may be formed one at each end, or more than one at each end (two at each end in FIG. 12). The size of the air outlets 55, 55a at the arched opposite ends is determined so that an amount of air for the drying blown out of them may be the same. When two of the air outlets 55, 55a are provided at each of the arched opposite ends, the outlets 55 having a longer air path from the air inlet 53a in the arched groove 53 are larger than the outlets 55a; that is, all of the outlets exhaust the same amount of air as they can. The heater cover 54 is reinforced by forming a diaphragm, folds, ribs or the like and is adapted not so as to be warped because of an attachment to the washtub 9. The washtub 9 also has an exhaust outlet of hot air in its lower half opposite the position where the arched groove 53 is formed, from which hot humid air after touching the wet washing should be extracted. The duct 17 connect the exhaust outlet to the dehumidifying heat exchanger 19. FIG. 13 is a diagram showing the heater 31, which is composed of arched heaters 31a, 31b, and 31c having their respective opposite ends fixed to heater flanges 56, and each of the heaters 31a to 31c is solely energized. The heater 31 is fixed to the arched groove 53 on the washtub 9 with packing 57 attached to the heater flanges 56. A plurality of heater supporting angles 58 are fixed to the arched groove 53 by spot welding, and the heater cover 54 is screwed on the heater supporting angles 58. Air for the drying is fed through an arched path defined by the arched groove 53 on the washtub 9 and heater cover 54 into the drum 12 and traverses the drum 12 as an air flow passing through all over the washing. Therefore, the heated air for the drying dehumidifies the washing without causing a local increase in temperature and without remaining undried part, and thus, the washing can be dried with high drying efficiency. The temperature in the washtub 9 never rise near 100° C. unlike an ordinary tumbler type washing/drying machine, but reaches about 60° C. like a general cloth dryer. Since the heater 31 is composed of a plurality of arched heaters each of which can be solely energized, a drying temperature for cloth of chemical fiber which must be dried at low temperature can be easily controlled in a considerably wide temperature range by changing a combination of the number of the heaters to be energized. For example, if the heater having the total electric power of 1200 W is composed of three arched heaters having 350 W, 400 W and 450 W, respectively, the heater can be regulated in seven levels in accordance with the combination of energizing the heaters. 4. Dehumidifying Heat Exchanger Means for feeding hot air to the drum 12 in the drying step is provided outside the washtub 9, as shown in FIG. 14, and it is composed of the duct 17 for connecting one of the side walls of the washtub 9 to the other side wall, the blower 18 for circulating air in the washtub 9 through the duct 17, the heater 31 for heating air to be fed to the washtub 9, and the dehumidifying heat exchanger 19 for dehumidifying air to be exhausted from the washtub 9 by cooling. The heat exchanger 19 is composed of a U-shaped air duct 60 connecting between a hot air exhaust outlet of the washtub 9 and an inlet of the blower 18, a cooling water spray nozzle 61 placed on the side of air inflow in the air duct 60, a drain outlet 62 formed at the bottom of the air duct 60, and the closing valve 38 (see FIG. 4) for opening and closing the drain outlet 62. To keep a fixed amount of water in the sharp bend 63 of the U-shaped air duct 60, an overflow outlet 64 is formed above the drain outlet 62 and below an wall above the bend 63. The air duct 60 is positioned on the side of the washtub 9, placing the sharp bend 63 down, and it has a first end on the inlet side connected through the duct 17 to the hot air exhaust outlet of the washtub 9 while having a second end on the outlet side connected to the inlet of the blower 18 in a position higher than the first end. The hot air exhaust outlet of the washtub 9 is positioned at higher level than the level of wash water, serving also as an overflow outlet 64 of the washtub 9. The cooling water spray nozzle 61 is attached to an upper surface of the first end on the inlet side of the air duct 60 and sprays water from a water supply device downward to have a large area as possible where the cooling water directly touches hot humid circulating air and consequently to take a good cooling effect. Thus, the dehumidifying capability can be enhanced, and additionally, the circulating air is reduced in temperature to prevent cloth from being damaged. A drain pipe 65 is fitted on the drain outlet 62 and is connected through the closing valve 38 to the drain valve 11. A drain hose 66 (FIG. 4) is connected to the drain valve 11 to lead to the outside. A drain pipe 9 (FIG. 4) provided at the bottom of the washtub 9 is connected between the closing valve 27 and the drain valve 9 to prevent wash water from flowing into the heat exchanger 19 in washing. The overflow outlet 64 is settled in the position where an area of the water surface in the air duct 60 can be defined large and the air path for the circulating air does not narrow (i.e., there is no large difference between sectional areas taken along segments A and B in FIG. 15). The overflow pipe 39 has one end connected to the overflow outlet 64 and the other end connected to the drain hose 66 on the downstream side from the drain valve 11. The cooling water which has been heated at the end of the heat exchange is always drained out of the overflow outlet 64 no matter whether the machine is energized and further drained through the overflow pipe 39 out of the machine. A sensor 67 is placed on the inlet side of the air duct 60 while a sensor 68 is placed on the outlet side; both the sensors 67, 68 are temperature sensors for detecting temperature of the circulating air. The heat exchanger 19 can be provided with a humidity sensor for detecting a dehumidifying state and other devices beside the above-mentioned devices. Now, a flow of the air for the drying and the cooling water in the drying step in the tumbler type washing/drying machine will be described. When the drying operation is started, the closing valve 38 is closed, while the heater 31, blower 18 and motor 13 are energized. The circulating air which becomes hot and humid after drying the washing in the drum 12 pass through the duct 17 into the air duct 60, where it touches the cooling water sprayed by the cooling water spray nozzle 61 and further touches the surface of the cooling water kept in the lower part of the air duct 60. Then, the circulating air is condensed and releases humidity, and thereafter, it turns upward into the inlet of the blower 18. Then, the air is fed through the duct 17 to the washtub 9 and further to the heater 31, and is heated again. The humidity cooled and condensed is drained together with the cooling water through the overflow outlet 64 and overflow pipe 39 out of the machine. In the drying operation, minute floating matter, lint, originated from the washing is also drained out of the washtub 9, and drops down in the water kept in the lower part of the air duct 60 along with the cooling water from the spray nozzle 61. The closing valve 38 is intermittently opened and closed, and accordingly, the water with the lint is drained. The closing valve 38 keeps closed for the most time except the time when the lint is drained with water, and therefore, the cooling water reaches the level of the overflow outlet 64, and the water over the water level is to be drained. In the drying step, the sensors 67, 68 detect the temperature of the circulating air, and the drying operation is stopped when a difference between the temperatures detected by the temperature sensor 67, 68 is more than the given value. Positioning the junction between the duct 17 at the inlet of the air duct 60 and the hot air exhaust outlet of the washtub 9 at a higher level than the surface of the rinsing water and at a lower level of the opening 27 for introducing the washing, the water can be drained through the heat exchanger 19 and overflow outlet 64 out of the machine when an abnormal rising of the water level is caused by water level sensor trouble or the like. During the drying operation, the closing valve 38 keeps closed except the time when it is intermittently opened for a short time. The closing valve 38 may be closed after the operation is ended, but it can be manually opened if it is not used for a long time or if the water in it may possibly be frozen in winter. The heat exchanger 19 can have the hot air circulating path taking a large sectional area according to the abovementioned configuration. As a result, it can ensures a flow rate of the circulating air by making a pressure loss small, and can take a large contact area of the cooling water with the hot humid air. In this way, the circulating air sufficiently touches the cloths in the drum 12 and the cooling water. Thus, the drying capability can be improved, and the temperature of the circulating air can remain low. Making a water pool in the air duct 60, the water surface of the pool can be useful for heat exchange. Thus, a small amount of cooling water is effectively utilized to enhance the dehumidifying capability and to further improve the drying capability. Additionally, in this case, the hot air is directed almost orthogonal to the water surface, and therefore, minute lint in the hot air can be eliminated. In this way, since almost all lint can be eliminated in the heat exchanger, there is no need of using a special filter and the like and no need of the frequent inspection. The hot air feeding means composed of the heater 31, dehumidifying heat exchanger 19, blower 18 and duct 17, as previously mentioned, supplies hot air to the washtub 9, and especially, the hot air feeding means is designed so that the hot air can be effectively supplied to the washing in the drum 12 in the washtub 9. As shown in FIG. 16, the drum 12 has an annular rim 69 horizontally projecting on the whole periphery of its wall opposite to the heater 31. The rim 69 is integrally formed with the peripheral wall of the drum 12. A projecting length of the rim 69 is about 80% of an interval between the circular side wall of the drum 12 and the side wall of the washtub 9. An annular guide 70 projecting toward the drum 12 is attached to the inner surface of the side wall of the washtub 9. The guide 70 is of rubber, and it is composed of a part in contact with the inner surface of the side wall of the washtub 9 and a part projecting contiguous to the previous part, as shown in FIG. 2. The guide 70 has a shape of bellows having the whole inner circular surface of the projecting part wound by reinforcing wire 71 in spiral. The guide 70 has a smaller diameter than the rim 69. The projecting part of the guide 70 has a length of about 95% of an interval between the side wall of the washtub 9 and the circular side wall of the drum 12. When the hot air heated by the heater 31 is supplied to the washtub 9, the guide 70 on the washtub 9 and the rim 69 of the drum 12 prevent almost all the hot air from flowing toward the circular side wall of the drum 12, but guide the hot air to the throughholes on the side walls of the drum 12 so that the hot air may effectively blow into the drum 12. 5. Control Device of the Washing/Drying Machine A major portion of a control device of the washing/drying machine is accommodated in an operating unit 6 and a display unit 7 shown in FIG. 2, and its structure is shown in a block diagram of FIG. 17. Referring to FIG. 17, voltage from an A.C. power source is applied through the power switch 8 to a driving circuit 73, a rectifying circuit 74 and a motor control circuit 75 for controlling the brushless motor 13. A microcomputer 76 starts when receiving D.C. voltage from the rectifying circuit 74. The microcomputer 76 receives output from the control unit 6, water level sensor S1, water temperature sensor S2, temperature sensors 67, 68, vibration sensor S3, flow rate sensor S4 and motor control circuit 75 to output a signal for controlling the program display 7, feed valve 10, drain valve 11, closing valve 38, heater 31, hot water heater, solenoid 52 and blower 18 to the driving circuit 73 and output a signal for controlling the brushless motor 13 to the motor control circuit 75. 6. Motor Control for Controlling Revolving Speed of Drum As previously mentioned, the drum 12 is driven by the revolving force transmitted from the DC brushless motor 13 through the pulley 36 and belt 37 to the pulley 35. The motor 13 requires a large torque to lift up the washing soaked with wash water in washing and requires high speed revolutions in water-extracting. More specifically, the motor 13 must implement a large torque (about 38 kg.cm) and a low speed (about 400 rpm), and a low torque (about 2.5 kg.cm) and a high speed (about 8000 rpm). The structure of the motor 13 will be described with reference to FIG. 18. A permanent magnet 77 of a rotor 78 is made of ferrite and has a ring-like shape, having eight magnetic poles. The rotor 78 is borne by the bearing 79 and fixed to the motor case 80 in freely revolving condition, while a stator 81 is wound by winding so as to make three phases and fixed to the motor case 80. The D.C. voltage produced from supply voltage of the power supply 72 by the rectifying circuit 83 is distributed in a transistor module 84 to drive the motor 13 in three-phase. The revolution angle position of a rotor of the motor 13 is detected by three hole sensors 82 and applied to the microcomputer 76, which performs arithmetic operations therein to output base control signals of the transistor module 84 of the three phases. The signals are subjected to pulse width modulation in a PWM circuit 85 for controlling the number of revolutions and amplified in a base drive circuit 86, and thereafter, turn the transistor module 84 on. Now, with reference to FIG. 19, a timing chart for producing the base signal of each phase of the transistor module 84 in accordance with a rotor position signal by the arithmetic operations performed in the microcomputer 76 will be described. In this embodiment, the ON-OFF duty ratio of a line voltage pattern applied to the winding of the stator of the motor is one third in the low speed operation but one half in the high speed operation. The rotor position signal is detected at each pole of the permanent magnet 77 (for example, there are eight poles in this embodiment, so one cycle corresponds to 90°) by the three hole sensors 82 settled in predetermined positions of the motor 13. Three rotor position signals from the three hole sensors 82 are designated by (1), (2) and (3), respectively. The base control signal varying with the revolution of the rotor in the counter clockwise direction (CCW) in the low speed operation (indicated by solid line), if it is a U-phase signal, is turned ON when the rotor position signal (1) falls, and is turned OFF as the rotor is retained at an angle 30°. In this way, the total ON-OFF duty ratio becomes 1/3. Similarly, V- and W-phase outputs are controlled with reference to the falling of the rotor position signals (2) and (3). X-, Y- and Z-phase outputs are controlled with reference to the rising of the rotor position signals (1), (2) and (3). For a ON- time with the rotor angle of 30, if the U-phase signal is employed as an example, the rising of the rotor position signal (2) is detected and some processing is performed to turn it off. In the high speed operation (indicated by broken lines), the signal output is controlled to turn on a rotor angle 15° earlier than the case in the low speed operation, and thus the total ON-OFF duty ratio becomes 1/2. Practically, employing the U-phase signal as an example, the rising of the rotor position signal 2 is the reference. While the base signal varying with the revolution of the rotor the clockwise direction (CW) is being turned on, the reference of the falling of the signal varying with the revolution of the rotor in the CCW direction becomes the reference of the rising. The order of the turning-off time of the U-, V- and W-phases and the X-, Y- and Z-phases is reversed; if the references of the rising and falling are reversed, the result is shown in FIG. 19, where a motor characteristic similar to the signal varying in the CCW direction can be observed. Then, the motor measured characteristic when the motor works in accordance with the timing chart in FIG. 19 will be explained with reference to FIG. 20. In FIG. 29, points A and B are operating points for the tumbler type washing/drying machine according to the present invention. Solid line expresses a control characteristic in the low speed operation, while broken line expresses it in the high speed operation. Referring to FIG. 20, it is apparent that the method of controlling in the high speed operation satisfies the requirement for both the operating points. However, the operating point A of the washing is an operating point for the case where the drum just starts or the clothes are entangled with each other, and it attains 400 rpm, one third or below of the maximum torque in practical operation. This method has the disadvantage that the motor must be large-sized because if the control method is applied not to the low speed operation which needs small consumed current but to the high speed operation which needs large consumed current, heat generated by the motor is too large. Although the generation of heat can be inhibited with a permanent magnet of rare earth elements or the like because magnetic force becomes stronger, such a magnet of rare earth elements about twenty times as much in price as a ferrite magnet, and it is difficult to employing the magnet of rare earth elements for electric appliances. Unlike the washing operation, a load torque does not vary once the drum starts revolutions at the point B in accordance with the method of controlling the high speed operation. A torque the motor requires corresponds to an amount of friction of a revolving mechanism when the accelerating period for revolutions ends, so consumed current is small even with the ON-OFF duty ratio of 1/2, and there is no possibility that the motor generates heat. This is why a cheap magnet having low magnetic force allows the motor to attain from a great torque at low speed to high speed revolutions without speed changing means. Now, a method of controlling the number of revolutions of the motor will be explained with reference to FIGS. 21 and 22. It has been described that the operating points A and B in FIG. 20 is in a range of the power of the motor and that the drum can be rotated. In practical operation with the revolution speed predetermined, the power of the motor must pass the operating points. FIG. 21 shows a waveform in which the output base signal shown in FIG. 19 is subjected to pulse width modulation, where a duty ratio is about 2/3 in a waveform (a) while it is about 1/3 in a waveform 8b). As shown in FIG. 22, as the duty ratio of PWM becomes smaller, the power decreases to have a curve drawn in lower position. While the motor 13 is working, the microcomputer 76 always inspects a state of the rotor position signal shown in FIG. 19. In this embodiment, if the revolution speed is set a single turn per second, the duty ratio of PWM is controlled to be increased or decreased so that the cycle of the rotor position signal becomes 1/4 second (this is because the motor make a turn in four cycles). If a rotor position signal pulse is not inputted after 1/4 second obtained by calculation elapses, the microcomputer 76 decides that a too large load delays the revolution of the rotor, and it applies a higher duty ratio of the output base signal next time. On the contrary, if the pulse is inputted before the 1/4 second elapses, the microcomputer 76 decides that the rotor rotates too fast, and it applies a lower duty ratio of the output base signal next time. In this way, the power of the motor always passes the operating point of a load, and hence, the motor keep a predetermined speed of revolutions in spite of the variation in a load torque. Thus, the drum 12 can perform a non-stage transmission in a wide range of speed. 7. Revolutions of Drum and Balance Control The drum 12 is cylindrical in shape, and is rotated forward or backward at the specified number of revolutions by the motor 13, as previously mentioned. In the washing step, the washing operation is performed under control of the program (for the tumbling washing) according to which the drum 12 is rotated with the rotation speed ωs smaller than the critical rotation speed ωo at which the washing is tumbled, under control of the program (for the light cleaning washing where the washing laying against the wall of the drum is soaked in wash water) according to which the drum 12 is rotated with the rotation speed ωh larger than the critical rotation speed ωo, or under control of the program (for the high washability washing) according to which the drum 12 causes the washing to be tumbled with the agitator disc 15 fixed and with outer force (physical force) being applied to the washing to enhance the washability. The gravitational acceleration is well-balanced with centrifugal force, and this leads to an equation mg=mrωo 2 . In accordance with the equation, the critical rotation speed (angular velocity) ωo is calculated as follows: ##EQU1## where m denotes a quantity of the washing, r denotes a radius of the drum and g denotes a gravitational acceleration. The rotation of the drum 12 with the rotation speed higher than the critical rotation speed (angular velocity) ωo causes the washing to be pushed against the inner circular wall of the drum 12 in some distribution state. Uneven distribution of the washing in the drum, uneven distribution of the washing results in the center of gravity of the composite quantity of the washing deviating from a horizontal axis of the drum, and this causes the drum to vibrate, and this also causes the washtub 9 having the motor 13 and the like to vibrate. An amplitude X of the vibration of the washtub 9 is obtained in accordance with the following equation: ##EQU2## where m A is an unbalance quantity, ω is a rotation speed of the drum, ω is a proper frequency, ξ is an attenuation ratio, and M is a total mass of a vibrator. In accordance with the above formula, it is apparent that as the total mass M increases, the vibration (amplitude) becomes small. In practical use, it is possible that a concrete block or an iron block is attached to the washtub 9 as a vibration proofing weight and the total mass M is made larger so that the vibration may be reduced. However, this method is not preferable because of the disadvantage that the resultant product has an undesirable large weight. In the present invention, the revolution speed of the motor 13 can be set arbitrarily, and so it is possible to make the vibration caused by the rotation of the drum 12 (ω>>ω 0) close to the vibration when the drum contains no load by gradually increasing the rotation speed of the drum 12 and unifying the distribution of the quantity of the washing in the drum 12 (the center of gravity of the composite quantity of the washing distributed in the drum is positioned corresponding to the horizontal axis of the drum). The washing in the drum 12 is gradually push against the inner circular wall of the drum 12 as the drum 12 revolves faster, and soon the washing makes a distribution in the shape of a ring. FIGS. 23(a) to 23(e) show the stages of making the distribution. In the dehydrating step, as shown in FIG. 23, since the washing tumbled in the drum 12 is gradually push against the inner circular wall of the drum as the drum revolves faster, the diameter of the drum (inner diameter of the ring of the washing) becomes apparently smaller, and eventually, all the washing lie against the inner surface of the circular wall of the drum 12. When the distribution of the quantity of the washing is good, the center of gravity of the washing distributed along the inner circular wall of the drum 12 corresponds to the axis of the drum 12; this means a balanced state in which only considerably slight vibration occurs even in the centrifugal water-extracting (the rotation speed of the drum is 800 to 1000 rpm.). Thus, the rotation of the drum 12 when the dehydrating operation is started varies from the low speed rotation (about 50 rpm) to the rotation speed (about 130 rpm) lower than both the resonance rotation speed of the washtub 9 and the high speed rotation in correspondence with the capacity for the washing in accordance with a balance chart shown in FIG. 24 in which the rotation speed of the drum 12 and the rotation time at the rotation speed are preset. In this case, when the vibration of the washtub 9 which is detected by the vibration sensor S3 is an allowable value or under, the drum 12 continuously proceeds to the high speed rotation (e.g., 800 to 1000 rpm); contrarily, when it is more than the allowable value, the drum 12 is temporarily stopped, or it switch to the low speed rotation (cloth of the washing is loosened) and thereafter works in accordance with the balance chart in FIG. 24 again. If the vibration of the washtub 9 does not reach the allowable value or under even when this operation is thoroughly repeated a specified number of times (e.g., three times), the drum 12 is controlled to start with the rinsing operation again. On the other hand, when the dehydrating operation just before the drying step is started, the drum 12 does not proceed to the maximum speed rotation (800 to 1000 rpm) even if the high speed rotation of the drum 12 causes the washtub 9 to vibrate at a level of the allowable value or under, but the drum 12 is rotated with the intermediate rotation speed (500 rpm) between the resonance rotation speed of the elastically supported washtub 9 and the high speed rotation speed of the drum 12 for a relatively long time (10 seconds or over, for example) so that the water-extracting efficiency may be 45% or so. After that, the rotation of the drum 12 is temporarily stopped, and then the drum 12 proceeds to the maximum speed rotation in accordance with the previously mentioned process. When the dehydrating operation just before the drying step is performed in accordance with the above-mentioned process, there are advantages over the case in which water is rapidly extracted from the wet washing by utilizing centrifugal force as in the ordinary dehydrating step; that is, the washing can be prevented from tightly lying against the inner circular wall surface of the drum 12, the washing can be easily tumbled when the process proceeds t the drying step to enhance the drying efficiency, and the washing finished in the drying operation is wrinkled at a lower rate. The capacity for the washing is detected by the water level sensor S1 and flow rate sensor S4. For example, water is supplied to a predetermined water level after the washing is introduced in the washtub, and thereafter, the washtub is rotated at low speed for a predetermined period. After that, water is further supplied to the predetermined water level to detect the capacity in accordance with an amount of the water supplied at that time. The capacity shown in FIG. 24 is classified into "small" for 1 to 2 kg, "medium" for 3 to 4 kg and "large" for 5 to 6 kg when the maximum capacity is 6 kg, for example. 8. Control of the Drying Operation In the control device shown in FIG. 17, when the heater 31, blower 18 and motor 13 are energized, the drum 12 revolves while it is fed with hot water, and thus the drying operation starts. In the drying process of the washing in the drum 12, temperature "ta" detected by the temperature sensor 67 and temperature "t" detected by the temperature sensor 68 vary as shown in FIG. 25. Specifically, the temperatures "ta," and "t" gradually rise at the beginning, and soon the temperatures assume an increment Δt≈0 (constant rate period). When the constant rate period ends, the temperature "ta,", "t" begin to rise again, and if it is left as it is, the washing is excessively dried. Therefore, when a difference ΔT between "ta" and "t" attains a predetermined value, the energizing the heater 31 may be stopped to complete the drying. Conventionally, the excessive drying condition is intentionally maintained to prevent the washing from partially remaining undried. In the present invention, however, the agitator disc 15 is fixed in opposition to the rotating drum 12 to stir the washing, or an arithmetic operation is performed about a signal of the temperature sensor 67 to control a current value of the heater 31 for preventing temperature from rising. Consequently, the washing can be dried well, and there is no possibility of excessive drying and excessively high temperature. The drying operation will be further explained in detail with reference to the flow chart shown in FIGS. 26 and 27. First, when the heater 31 is energized (Step 301) and the temperature "t" begins to rise, the temperature variation rate Δt is detected, which is stored as Δtu in the microcomputer 76 (Step 302). When the constant rate period set in, the temperature t does not vary (Δt≈0), the constant rate temperature is stored as CT (Step 303). When the variation rate of temperature Δt (>0) is detected after the constant rate period changes at a constant temperature for a while (Step 304), the microcomputer 76 control (reduce) the current to the heater 31 (Step 305). Then, a condition of the temperature t is checked at Steps 306, 307 and 308, and the process proceeds to the drying completing step (Step 309) immediately or after the drying operation is continually completed for a predetermined time (Step 310), depending upon the condition of the temperature variation in the previous checking steps. When a disturbance (a state in which the washing in the drum 12 is temporarily put to one side and tumbled) causes the temperature to temporarily rise for the constant rate period, the temperature t quickly drops due to the reduction of thermal power of the heater 31 to a lower value than CT stored in the microcomputer 76. Then, the thermal power of the heater 31 is increased (recovered) (Step 311), and it is checked whether the detected temperature t recovers to CT stored in the microcomputer 76 (Step 312). After that, Step 304 is implemented while the drying is advanced under control. In this way, eventually imperfect drying and excessive drying can be avoided. In the ironing course, sometimes the drying must be completed attaining a drying efficiency the user desires, as shown in FIG. 27 (Steps 313a, 313b, 313c and 313d). At this time, the operation is controlled so that the thermal power of the heater 31 may be intentionally changed (Step 314), and after the variation rate Δt in temperature is stored as Δtd in the microcomputer 76 (Step 315), the current supplied to the heater 31 is recovered (Step 316). When the temperature is recovered, the drying efficiency is controlled in accordance with fuzzy inference and fuzzy control, comparing the variation rate Δt with Δtu stored in the microcomputer 76, and the operation is completed. (Steps 313a, 313b, 313c and 313d). F1, F2, F3, and F4 are measured values which are experimentally obtained using devices in this embodiment. In this embodiment, when the non-tumbling drying course (the drying by rotating the drum with the critical rotation speed or over) is selected, uneven drying is easily caused especially when less load is charged, and moreover, the constant rate period is short; the temperature t varies in a short period. In this case, when Δt>0 is detected, the rotation speed of the drum 12 is reduced to ω<ωo (critical rotation speed), the drum 12 tumbles the washing therein to vary the distribution of the clothes, and then the drum 12 is rotated with the non-tumbling rotation speed (ω>ωo) again for advancing the drying stage). The variation in the rotation speed is automatically repeated until the drying is completed. The power of the heater 31 can be selected among HIGH, MEDIUM, LOW depending upon a kind and quantity of the load in advancing the above-mentioned drying operation. The non-tumbling (ω>ωo) drying will be described in detain in conjunction with a flow chart in FIG. 28 below. First, the heater 31 is turned ON (Step 440), the drum 12 is rotated in non-tumbling (ω>ωo) (Step 441), and thus, the non-tumbling drying process starts. The microcomputer 76 performs arithmetic operations based upon load data in the washing process (capacity for the load, quality of the cloth, quantity of rinsing water, water-extracting efficiency, etc.) and manually input data to infer an approximate drying time, and the power of the heater 31 is selected among HIGH, MEDIUM and LOW (Step 442). An increase in temperature of the washing is detected (Step 443), the temperature rising rate Δtu is stored in the microcomputer (Step 444). A temperature variation at the ensuing time is detected (Step 445); if it becomes almost constant, the constant rate temperature CT is stored in the microcomputer 76 (Step 446). A temperature variation at the ensuing time is observed (Step 447); if a temperature rising is recognized, the drum 12 repeats the programmed operation several times, under control with the tumbling rotation speed (Step 448), and thereafter, it revolves with non-tumbling rotation speed again (Step 449). In the ensuing time, the Steps 447 to 449 may be repeated. The ensuing steps are performed under control in accordance with Steps 304 to 312 shown in FIG. 26, and thus the drying is completed. FIG. 29 shows a temperature variation in the washing and related current value in the ordinary drying operation. When a temperature variation at the end of the drying operation is detected and a current value to the heater 31 is decreased, the drying is completed in accordance with Steps 306, 307, 308, 309 and 310 in FIG. 26. FIG. 30 shows a current variation and temperature variation when the current value of the heater 31 is intentionally reduced to check the drying efficiency (Step 314 to 316 in FIG. 27) and also shows a state in which the temperature automatically reaches a temperature at the end of the drying operation after the first current variation. Sometimes, intentionally the current is automatically varied several times to pre-estimate the desired drying efficiency. 9. Continuous Operation from Washing to Drying Continuous operation steps of washing, dehydrating and drying in the washing/drying machine according to the present invention will be explained in conjunction with flow charts in FIGS. 31(a)-31(f) and timing charts in FIGS. 32(a)-32(e). When the power switch 8 and start key of the operating unit 6 are turned on, the feed valve 10 is energized and water supply is started (Steps 101 to 103). When a water temperature is set in the operating unit 6, the hot water heater 32 is energized until the water temperature reaches the preset temperature (Steps 104 to 107). Next, when "keeping the washing in wash water before washing" is preset in the operating unit 6, "keeping in wash water before washing" is carried out for a predetermined period (60 minutes) (Steps 108 to 110). At this time, as shown in FIG. 29, the agitator disc 15 is in free rotation condition to revolve forward at 50 rpm. Then, the "washing" is carried out for a predetermined period (12 minutes), and as shown in FIG. 32(a), the drum 12 repetitively revolves forward and backward alternately, and the agitator disc 15 is intermittently fixed (Steps 111, 112). Next, the rinsing operation is performed. In the rinsing operation, first water is drained, and then, the drum 12 is rotated forward and backward alternately at 50 rpm several times to loosen the clothes (Steps 113, 113a). Then, the drum 12 is rotated in one way, and the rotation speed of the drum 12 is increased in stages from 50 rpm to 130 rpm to regulate the balance (Step 113b). If the vibration of the washtub 9 is a given value or under (Step 113c), the drum 12 is rotated at 400 rpm for 20 seconds to perform "intermediate water-extracting" (Step 114). Then, water is supplied (Step 115), and the drum 12 is rotated forward and backward alternately at 50 rpm several times to rinse the washing (Step 116). As the operation including the Steps 113 to 116 are repeated three times, water is drained (Step 118), and thus, the operation proceeds to the draining step. At Step 113c, unless the vibration of the washtub 9 is the given value or under, the operation including the Steps 113a to 113b is repeated four times at most, and after the fourth performance is completed, the rinsing operation in accordance with Steps 146 to 148 is performed. If the rinsing operation in accordance with the steps 146 to 148 is repeated twice (Step 149), it is recognized that it is difficult to control the vibration of the washtub 9 to the given value or under, and the operation is interrupted and the display unit 7 indicates "ABNORMAL" (Steps 150, 150a). In the dehydrating operation, the drum 12 is rotated forward and backward alternately several times at 50 rpm for 35 seconds to loosen the clothes (Step 119). The rotation speed of the drum is increased in stages from 50 rpm to 130 rpm to regulate the balance. If the vibration of the washtub 9 is a given value or under, the drum 12 is rotated at 500 rpm for two minutes to perform "low speed water-extracting" (Steps 120 to 122). "Loosening the clothes" and "regulating the balance" are carried out again, and if the vibration of the washtub 9 is a given value or under, the drum 12is rotated at 800 to 1000 rpm for 300 seconds to perform "high speed water-extracting" (Steps 113 to 126). At Step 121, unless the vibration of the washtub 9 is the given value or under, the operation including the Steps 119 to 120 is repeated four times at most, and the fourth performance includes the rinsing steps, Steps 140 to 142. If the rinsing operation in accordance with the Steps 140 to 142 is repeated twice, it is recognized that it is difficult to control the vibration of the washtub 9 to the given value or under, and the operation is interrupted and the display unit 7 indicates "ABNORMAL" (Steps 144, 144a). As the "high speed water-extracting" at Step 126 is completed, the drying operation is carried out. In the drying operation, the heater 31 and blower 18 are energized, hot air is supplied to the drum 12, a temperature control of the hot air is carried out, and the drum 12 is rotated forward and backward alternately while the agitator disc 15 is fixed or released as shown in FIG. 32(e) (Steps 127, 128). When the drying operation is completed (Step 129), the energizing of the heater 31 is stopped (Step 130), cooling air is supplied to the drum 12 until the temperature detected by the temperature sensor 68 falls to a given value or under to perform "cooling down" (Steps 131, 132), and thus, the process is thoroughly completed. 10. Comparison Test of This Embodiment with Prior Art Embodiment With regard to the basic performance from the washing to the drying, the results of a comparison test of this embodiment with a prior art embodiment is shown in the following Table I. TABLE I______________________________________ THIS PRIORITEMS EMBODIMENT ART______________________________________WASHING PERFORMANCEWASHABILITY RATIO 1.1 0.86WASHING CAPACITY 6.0 4.5WASHING TIME 12 26RINSING PERFORMANCE 16 16REMAINING ABS CON-CONCENTRATION (ppm)DEHYDRATINGPERFORMANCEWATER-EXTRACTING 60 57-59EFFICIENCY (%)TUB VIBRATION 7.0 12-20AMPLITUDE (mm)CABINET VIBRATION 2.1 2.5AMPLITUDE (mm)DRYING PERFORMANCEDRYING EFFICIENCY (%) 60 46-51DRYING TIME (min/kg) 41 44-52______________________________________ A method of the test is in accordance with Japanese Industrial Standard, JIS C 9606 and JIS C 9608. With regard to the temperature of the outer wall of the washtub, the inside of the drum and the cabinet, it was recognized that about 30° deg lower in this embodiment than in the prior art embodiment.

A washing/drying machine including a washtub, a feeding device for feeding water to the washtub, a draining device for draining water from the washtub, a tumbling drum, rotatably supported by a lateral axis in the washtub, having a plurality of holes through which air and water pass and an opening for introducing the washing, and a lid for closing the opening, a motor for rotating the drum at various speeds, a disc for agitating the washing, disposed in the drum adjacent to a flat end wall of the drum in parallel with the wall, a bearing device for rotatably bearing the disc, a fixing device for selectively fixing the disc, a device for supplying hot air to the drum, and a controller for controlling the fixing device to intermittently fix the disc against the rotation of the drum, and a controlling method thereof.

This application claims the benefit of Danish Application No. PA 1999 01408 filed Oct. 1, 1999 and PCT/DK00/00542 filed Sep. 29, 2000. BACKGROUND OF THE INVENTION The present invention concerns a method for operating a printing unit in which the printing unit comprises a doctor blade used for coating and as moistening unit for applying water, and where the coating means and the water application means are constituted by a unit comprising a doctor blade and at least one roller for transferring coating or water from the doctor blade. Offset machines are well-known within the art and are therefore only described briefly. A web or a sheet on which printing is to be performed is led around back-pressure rollers or transfer rollers. The web or the sheets are brought into contact with a blanket cylinder for being applied the print to the applied in each single printing unit in the offset machine. The blanket cylinder is in contact with a plate cylinder transferring the colour print to be placed on the web. The plate cylinder is in contact with a moistening unit and a inking unit applying water and ink, respectively. Thus, an offset plate on the plate cylinder is rotated whereby water susceptible parts are moistened by the rollers of the moistening unit. Then the ink susceptible parts of the offset plate are supplied with ink from the ink rollers in the inking unit. The print image formed is then deposited on the blanket cylinder which further prints the ink on the web or the sheet. Preferentially, it will be a paper web but other materials may also be printed. A printing unit according to the present invention may be used in a traditional offset machine, for example of the kind described in European patent application no 767,058. The content of this patent application is hereby incorporated by reference as the printing unit may be a part of an offset machine which is built up according to the same principle and with the same paper delivering and paper receiving means at the beginning and the finish of the printing unit as well as corresponding means for transferring paper web or single sheets between different printing units disposed in succession can be used for imparting the web the finished print. Also, the same kinds of printing ink may be used. Offset machines may be equipped with a coating unit. The coating unit will typically be constructed with a cylinder on which the coating is applied from a roller arrangement which is supplied from a vessel with clear coating. In International patent application PCT/DK98/00303 there is described a system of the type mentioned in the introduction which is improved and thereby enables a broader application and more efficient operation of printing units in offset machines, where the printing unit may be used for coating and water application. In this system, the coating is established indirectly via the plate cylinder. However, it is desirable to apply coating directly on the blanket cylinder due to quality and finish in the formed print. Furthermore, GB-A-2,119,711 discloses a stationary fountain comprising a doctor blade co-operating with a ductor. A lacquer roller is displaceable between a first position for transferring water via a plate cylinder and a second position for transferring coating directly to the blanket cylinder. There is no disclosure that the doctor blade could be displaced together with the interactive roller as a unit. SUMMARY OF THE INVENTION It is the object of the present invention to indicate a method for operating a printing unit and a printing unit for an offset machine which enables a wider use and a more efficient operation of printing units in existing and new offset machines. Furthermore, it is an object to indicate a moistening unit which simultaneously may be used for coating and which also enables flexoprinting in an offset machine. According to the present invention this is achieved by a method which is peculiar in that the doctor blade and an interacting roller are displaced between a first position for transferring water via a plate cylinder to a blanket cylinder and a second position for transferring coating directly to the blanket cylinder. The printing unit for use by the method is peculiar in that the coating and water application unit is arranged slidable between a first position for bringing said at least one roller in contact with a roller engaging the plate cylinder, and a second position for bringing said at least one roller in direct contact with the blanket cylinder of the printing unit. The method and the apparatus make it possible that the doctor blade together with the roller form a unit which is slidable between the two positions. By using such a method and such a unit it becomes possible to make offset machines so that they obtain wider application, and simultaneously the process may run more efficiently as the coat is not applied indirectly via the plate cylinder to the blanket cylinder. The slidable unit may be designed so that it may be retrofitted on existing offset machines. Coating or water from the chamber is transferred to the blanket cylinder or the plate cylinder via a roller which preferably is a screen roller in the form of an Anilox roller, and the liquid lying in the cups of the screen roller is transferred to the blanket or plate cylinder. Transfer of water to the plate cylinder occurs as a rubber roller is inserted between the screen roller and the printing plate of the plate cylinder. Transfer of coating occurs directly to the blanket cylinder from the screen roller. When the transfer unit is displaced to its second position for contact with the blanket roller, it is also possible to run flexographic printing. The blanket cylinder is provided with a printing plate, and the plate cylinder is displaced out of contact with the blanket cylinder. Then flexo inks may be transferred from the chamber and the transfer roller in the shape of an Anilox roller to the printing plate. If a completely covering print is desired, a blanket may be used on the blanket cylinder as in the case of coating. It will be possible to use separate doctor blades for inking/coating and water application. However, it will also be possible to use one and the same doctor blade for coating and water application. In a coating unit, which typically is the last printing unit in an offset machine, it is advantageous that the coating means only comprise one screen roller in the form of an Anilox roller for transferring the coating which is applied directly form the doctor blade to the blanket cylinder. Most machines will be provided with a frame with coupling means for supporting a cleaning system consisting of a liquid spray nozzle and cleaning paper. In some cases the printing unit according to the invention may be mounted in coupling means of this fame. Hereby, the need for special adaptation of the machine frame is avoided. Hereby it becomes particularly simple to modify an existing machine as the coupling means located in the frame of the offset machine are re-used as coupling means for the unit according to the invention. The motor used for driving the screen roller is independent in order to adjust the rotational speed to different offset machines. Thus the unit does not need a special adaptation of the drive of the screen roller for different offset machines. In the machine, there will only be need for a suspension which in its most simple form consists of four pegs or screws on a rack. By using a unit according to the invention, which is based on a doctor blade, it will be possible to apply highly pigmented inks, as for example metal enamels. This will not be possible with common offset printing units as pigments/inks will clog here and make impossible the formation of a quality print. The unit according to the invention may also be use as a moistening unit. In the known moistening units, an environmental problem arises. In order to transfer the moistening water with the present roller arrangement, it is necessary to add solvents. At the moment, this has been prohibited at several places. Alternatively, it has been attempted to solve the problem by teflon coating for forming a kind of mask with the purpose of avoiding ink depositing in certain areas. This is known as dry offset and is a different process in principle. Thus teflon has been used for substituting the water application from the moistening rollers. This system has an advantage as the paper is not moistened and thereby the risk that coating adheres badly do not arise. Instead of using the traditional moistening units, there may be used a system which comprises a doctor blade and a screen roller and a rubber roller between the doctor blade and the plate cylinder as described in the above International patent application. This is advantageous as faster operation than previously is feasible. The amount of water or water sausage formed in a wedge-shaped interspace between the rubber roller and the plate cylinder may be varied by running with varied speed between the rubber roller and the plate cylinder. By running the rubber roller with greater speed it is thus possible to provide a greater amount of water in the wedge. The amount of water may also be adjusted by varying the slot width occurring between the rubber roller and the plate cylinder. The printing unit according to the invention is thus advantageous in that the amount of water situated in the slot may be varied according to need. As printing unit may be intended for coating and as moistening unit, it will be possible to use the same unit consisting of a doctor blade and transfer roller for both water and coating. By using a common moistening unit it will not be possible to apply coating. Due to the surface speeds, a great and unallowable contamination of the surroundings will occur as coating will be sprayed from the periphery of the roller and from the ends of the rollers. By using the unit according to the invention for coating, it will be possible to avoid contamination. It is also possible that, together with a plate cylinder and a blanket cylinder, there may be provided two units according to the invention of which one unit is used for coating and the other for water application. Hereby it becomes possible to provide stripes of coating and stripes of ink side by side on the plate cylinder. This is made possible as the doctor blade may be divided up for giving off liquid/ink over a part of their length. Hereby is thus achieved the possibility of making print with quite new effects. BRIEF DESCRIPTION OF THE DRAWINGS In the following, the invention will now be explained with reference to the accompanying schematic drawing, where: FIG. 1 shows a side view of a typical offset machine comprising four printing units, FIG. 2 shows a partial view for illustrating a known printing unit comprising a moistening unit and an inking unit, FIG. 3 shows a view corresponding to FIG. 2 for illustrating an embodiment of a printing unit according to the above International patent application, FIG. 4 shows a view corresponding to FIG. 3 for illustrating a first embodiment of a printing unit according to the invention, and FIG. 5 shows a view for illustrating a further embodiment of a printing unit according to the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a traditional offset printing machine 1 comprising four printing units 2 . The machine has a transport direction 3 for sheets that are printed. The sheets comes from a delivery station 4 and are conveyed to a receiving station 5 by means of a delivery arrangement 6 comprising a conveyor belt 7 . The conveyor belt 7 runs about two chain wheels 8 , 9 . The single sheets are conveyed from the unit 4 via a path 10 around an impression cylinder or back-pressure cylinder 12 . The single sheets are placed at a position indicated by 13 . The sheets are thus placed in an area between a blanket cylinder 14 and the impression cylinder 12 . The blanket cylinder 14 is in contact with a plate cylinder 15 . Besides the impression cylinder 12 , the offset machine also comprises transfer cylinders 16 for the sheets. The offset machine furthermore comprises gripping means for holding sheets and a long row of rollers for moistening units and inking units which are in connection with the plate cylinder. Since these are well-known, they are not shown in FIG. 1 which serves as illustration of the structure of the offset unit. These rollers, however, appear in FIG. 2 . FIG. 2 shows a printing unit 1 comprising an impression cylinder 12 , a blanket cylinder 14 and a plate cylinder 15 . These cylinders are rotating according to the arrows 17 , 18 , 19 . A moistening unit comprises a container 21 for water. From the water container 21 the water is led via a system of rollers 22 to the last contact roller 23 which is in contact with the plate cylinder 15 . The printing unit 1 furthermore comprises an inking unit 24 comprising a number of rollers 25 transferring ink from an ink container 26 to contact rollers 27 which apply the ink on a soft printing plate (not shown) situated on the plate cylinder 15 . The printing plate located on the plate cylinder will thus be imparted ink in the areas where water has not been applied from the moistening unit 20 . The printing plate is usually an etched metal plate. As a coating unit is built up in principle as the moistening unit 20 , FIG. 2 may also be said to illustrate a coating unit. The coating will thus be conveyed up from the container 21 containing coating and transferred via rollers 22 to the last contact roller 23 which is also called the forming roller. However, a coating unit will preferably be mounted on the blanket cylinder 14 for avoiding undesired dirtying. The embodiment shown have some environmental and printing disadvantages. Instead of using the existing moistening unit, the printing unit in FIG. 2 may be modified as illustrated in FIG. 3 . In FIG. 3 the contact roller 23 is substituted by a unit 28 comprising a doctor blade system 30 and a screen roller 29 , preferably an Anilox roller of the kind also used for flexographic printing. The screen roller 29 may be mounted directly in the existing suspension. Between the screen roller 29 and the plate cylinder 15 there is mounted a soft roller 32 , preferably a rubber roller. The unit 28 may, even by great peripheral speeds, ensure a constant and uniform amount of water and/or coating transferred to the plate cylinder 15 . If the unit 28 is desired to be used for coating, the rollers 27 of the inking unit are brought out of contact with the plate cylinder 15 . If the unit 28 is used for water application, the inking unit 24 is kept in engagement with the plate cylinder 15 . The embodiment shown in FIG. 3 may be changed when it is only used for coating. Thus the hard screen roller 29 may be used directly without a soft roller for coating. This will, however, necessitate the use of a rubber blanket on the plate cylinder 15 . The printing unit shown will be very simple and easy to maintain. At the same time, the system is easy to replace depending on whether the printing unit is desired to be used for one or the other purpose. Thus it will be possible, according to wish, to use the existing moistening unit concurrently with the unit 28 according to the invention. When the unit 28 is used for water application, it will be easy to adjust the water amount in a simple way. Such an adjustment is difficult in traditional moistening units where the rollers are running synchronously with the plate cylinder 15 . The rubber roller 32 may be provided with its own motor which is driven independently of the plate cylinder. This creates possibility of a differentiated periphery speed and thereby possibility of stemming up of greater or lesser amount of water in the wedge-shaped interspace 31 formed between the rubber roller 32 and the plate cylinder 15 . In FIG. 4 is shown a first embodiment of a printing unit 1 according to the invention. FIG. 4 differs from the printing unit shown in FIG. 3 by the unit 28 being suspended pivotably about an axis 33 of pivot running in parallel with axes of rotation 34 and 35 for the blanket cylinder 14 and the plate cylinder 15 . The unit 28 is shown in a first position 36 , where the screen roller 29 is in contact with a soft roller 32 engaging the plate cylinder 15 , and a second position 37 where the screen roller 29 is directly engaging the blanket cylinder 14 . These two positions are used for water application (position 36 ) and coating (position 37 ), respectively. FIG. 5 shows a further embodiment of a printing unit according to the invention. In this printing unit there is simultaneous use of two units 28 . The unit 28 illustrated to the right in the Figure is used for applying moistening water. The unit 28 shown to the left is used for applying coating. Since it is possible to divide up the doctor blade over its length, it will be possible to apply coating in stripes where the moistening unit does not apply any moisture. Such an effect will not be possible in traditional printing units. The coating unit and the moistening unit as illustrated in FIG. 5 will function according to the same principle as explained above with reference to the preceding Figures. Alternatively, the unit 28 in the left side may be used for transferring coating and flexographic ink. If there is a blanket on the blanket cylinder 14 , a completely covering ink will be printed, and if a printing plate is placed on the blanket cylinder 14 , a desired flexographically printed image may be established.

There is described a printing unit ( 1 ) for use in an offset machine. The printing unit enables wider application of offset machines ( 1 ). This is achieved by the coating means and the water application means comprising a unit ( 28 ) consisting of a doctor blade ( 30 ) and at least one roller ( 29, 32 ) for transferring coating or water from the doctor blade ( 30 ) to the plate cylinder ( 15 )/blanket cylinder ( 14 ) of the printing unit. The unit ( 28 ) is arranged for pivoting so that water is transferred to plate cylinder, and coating is transferred directly to the blanket cylinder.

BACKGROUND [0001] Many sheet-like products, such as paper products, are spirally wound into bobbins for sale to wholesalers, retailers, consumers and other manufacturing entities. In order to protect the bobbins during shipment and storage, an overwrap material is typically wound around the bobbin to protect its contents. [0002] For example, cigarette papers, such as outer wrappers, inner wrappers, filter papers, porous plug wrap papers, and the like, are typically supplied to cigarette makers in the form of a spirally wound bobbins. A heavier overwrap material, such as a heavier paper, is typically attached to the leading edge of the cigarette paper and wound around the circumference of the bobbin. The end of the overwrap material is then adhesively secured so that the paper product does not unwind until the product is needed. [0003] Cigarette manufacturers are known to provide vary detailed specifications as to not only the construction of the overwrap material but how the overwrap material is applied to the bobbin. The overwrap material, for instance, is typically used as a leader for threading the cigarette paper through a cigarette making machine. Thus, cigarette manufacturers typically have requirements for the overwrap material that make the overwrap material compatible with the cigarette making machines. [0004] In the past, the process for applying the overwrap material to the bobbin has been tedious and labor intensive. For instance, the overwrap material is typically applied to cigarette paper by an operator after parent bobbins have been produced. For example, an operator may need to attach the overwrap material to the cigarette paper and apply adhesive where necessary. After the overwrap material is placed on the parent bobbin, the bobbin is then typically run through a slitter so as to produce multiple bobbins having a desired width. [0005] After the overwrap material is applied, the individual bobbins are then typically subject to inspection prior to shipment to a customer. In fact, not only is the process for applying the overwrap material labor intensive, but, since it is typically carried out by an operator, the resulting bobbin products may not always be uniform. In view of the above, a need currently exists for a system and method for applying an overwrap material to a bobbin of sheet-like material, such as a bobbin of paper. In particular, a need exists for a system and method that is capable of automatically applying the overwrap material to a bobbin while staying within customer required specifications. SUMMARY [0006] In general, the present disclosure is directed to an automated system for applying an overwrap material to a bobbin and to a corresponding method. The present disclosure is also directed to a method of opening a sealed spirally wound bobbin of material. [0007] In one embodiment, for instance, a method for overwrapping a paper bobbin includes the steps of loading a bobbin of spirally wound paper on a mandrel. Although depending upon the particular circumstances, an outer layer of paper of the bobbin may be adhesively secured to the outer circumference of the bobbin prior to attaching an overwrap material. In order to initially break the outer layer open, a breakfoot is placed against an outer circumference of the bobbin. The breakfoot, for instance, may comprise a hydraulic or pneumatic actuator. Once the breakfoot is placed against the outer circumference, the outer layer of paper is then pulled causing the outer layer to break at a location adjacent to the breakfoot. The paper may be pulled, for instance, by applying a suction force against the outer layer. [0008] Once the bobbin of paper is broken open, the bobbin can be partially unwound in order to remove at least a portion of the outer layer of paper. The outer layer can then be cut in order to form a leading edge. [0009] The leading edge of the bobbin can then be attached to a leading edge of an overwrap material by applying an adhesive material in between the leading edge of the paper and the leading edge of the overwrap material. [0010] Once the overwrap material is adhesively secured to the leading edge of the bobbin, the bobbin can be wound in order to wrap the overwrap material around the bobbin. A second adhesive material may then be applied to the overwrap material and the overwrap material may be cut upstream from the location where the second adhesive material has been placed. The trailing edge of the overwrap material can then be adhered to the outer circumference of the bobbin using the second adhesive material. In one embodiment, the adhesive material may be placed upstream from the trailing edge in order to form a pullable tab that allows the overwrap material to be broken open when the bobbin of paper is ready to be used. [0011] In one embodiment, once the leading edge of the bobbin is formed, the leading edge may be drawn against a vacuum roll positioned adjacent to the bobbin. The leading edge of the overwrap material, on the other hand, may be held on a vacuum plate that is suspended over the vacuum roll. An adhesive applicator may apply an adhesive material to the leading edge of the overwrap material in order to secure the overwrap material to the leading edge of the bobbin. [0012] The second adhesive material that is used to secure the trailing edge of the overwrap material to the circumference of the bobbin may comprise, for instance, a two sided cleavable tape. The second adhesive material may be applied to the overwrap material at a distance upstream from the bobbin that is equal to or greater than about 75% of the circumference of the bobbin. [0013] The present disclosure is also directed to a system for applying an overwrap material onto a bobbin of paper. The system includes a mandrel for receiving a bobbin of paper. A vacuum roller is positioned adjacent to the mandrel. The vacuum roller is configured to hold a leading edge of a bobbin of paper loaded on the mandrel. A moveable gripping device, such as a vacuum plate, is configured to hold a leading edge of an overwrap material proximate to the vacuum roller. The gripping device can be moveable towards the vacuum roller for contacting the leading edge of the overwrap material with the leading edge of the bobbin of paper. [0014] An adhesive applicator may be provided that applies adhesive to the overwrap material for attaching the leading edge of the overwrap material to the leading edge of the bobbin of paper when the leading edges are contacted with one another. [0015] The system may further include a tape applicator that applies a double-sided adhesive tape to the overwrap material downstream from the leading edge of the overwrap material. A first cutting device can be used to cut the overwrap material after the bobbin of paper has been wound. The cutting device can also be configured to cut the overwrap material downstream from the adhesive tape so that the adhesive tape can secure the overwrap material to the outside circumference of the bobbin of paper. [0016] In one embodiment, when it is necessary to initially break open the bobbin of paper, the system can further include at least one breakfoot that is moveable onto and away from the circumference of the bobbin positioned on the mandrel. The system can also include a moveable suction device positioned proximate to the breakfoot. The suction device can be configured to pull against an outer layer of the paper causing the paper to break open adjacent to the breakfoot. BRIEF DESCRIPTION OF THE DRAWINGS [0017] A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, which makes reference to the appended figures in which: [0018] FIG. 1 is a side view of one embodiment of a system for applying an overwrap material onto a bobbin of material in accordance with the present disclosure; [0019] FIGS. 2A and 2B are perspective views of a bobbin of material that is to be loaded in the system as illustrated in FIG. 1 ; [0020] FIG. 2C is a perspective view and FIG. 2D is a plan view of a bobbin of material that has been wrapped by an overwrap material in accordance with the present disclosure; and [0021] FIGS. 3A through 3J are perspective views illustrating the manner in which the system illustrated in FIG. 1 is used to apply an overwrap material to a bobbin of material. [0022] Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the present disclosure. DETAILED DESCRIPTION [0023] It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only, and is not intended as limiting the broader aspects of the present invention. [0024] In general, the present disclosure is directed to a system and method for applying an overwrap material onto a bobbin of material. In one embodiment, for instance, the bobbin comprises of a roll of paper, such as cigarette paper. It should be understood, however, that virtually any spirally wound roll of material may be overwrapped with the system and process of the present disclosure. [0025] As will be explained in more detail below, the system of the present disclosure provides various benefits and advantages. For instance, the system is capable of automatically applying an overwrap material around the circumference of a bobbin of material. By being fully automated, the process of applying the overwrap material is not labor intensive and is much faster than a manual process. Also, the system is capable of placing the overwrap material on a bobbin within carefully controlled limits. In addition, the system is capable of producing wrapped bobbins that are uniform and consistent with little to no variation in the overwrap properties. [0026] Referring to FIG. 1 , for example, one embodiment in a system for applying an overwrap material to a bobbin is illustrated. As shown, the system includes a mandrel 10 for holding a bobbin of material 12 . For instance, in one embodiment, the bobbin 12 can be a bobbin of paper, such as cigarette paper. It should be understood, however, that any suitable bobbin of material may be loaded on the mandrel 10 . [0027] In some embodiments, the bobbin 12 may be supplied in a sealed condition. For instance, the leading edge of the paper or other material may be adhesively adhered to the circumference of the bobbin. In these embodiments, a breaking device 14 may be included in the system for initially breaking opening the bobbin. The breaking device 14 can include at least one breakfoot 16 located proximate to a suction device 18 . As will be described in greater detail below, the breaking device 14 is capable of breaking open the bobbin 12 in order to form a leading edge for attachment to an overwrap material. [0028] As shown in FIG. 1 , the system includes an overwrap supply 20 containing a roll of overwrap material 22 . As shown, the overwrap material is threaded through the apparatus. A leading edge of the overwrap material is held by a gripping device 24 . The gripping device 24 can be any suitable device capable of holding and releasing the free end of the overwrap material. In one embodiment, for instance, the gripping device 24 may comprise a vacuum plate that has a top surface and a bottom surface. The bottom surface of the vacuum plate may be configured to hold the leading edge of the overwrap material by applying a suction force to the overwrap material. [0029] In order to apply a first adhesive material to the overwrap material 22 in order to attach the overwrap material to a leading edge of the bobbin of paper 12 , the system includes an adhesive applicator 26 . In addition, the system includes a tape applicator 28 located downstream on the overwrap material from the adhesive applicator 26 . The tape applicator 28 is configured to apply a second adhesive material, such as a double-sided tape to the overwrap material for adhering the trailing edge of the overwrap material to the bobbin of paper 12 after the overwrap material has been wrapped around the bobbin and cut. [0030] Generally, when applying an overwrap material to a bobbin, the bobbin 12 is first loaded on the mandrel 10 . For instance, in one embodiment, a robot can be configured to lift the bobbin from a bobbin supply and properly position the bobbin on the mandrel 10 . [0031] One example of a bobbin 12 is shown in FIGS. 2A and 2B . As described above, in some applications, bobbins to be fed into the system are supplied in a sealed state. More particularly, as shown in FIG. 2B , the leading edge of the bobbin may be adhered to the outer circumference of the bobbin using an adhesive 30 . In these applications, the bobbin must first be broken open prior to applying the overwrap material to the bobbin especially in applications such as cigarette papers where the overwrap material may later be used to feed the bobbin of paper into a process. [0032] Referring to FIGS. 3A through 3J , one embodiment of a process by which the bobbin 12 is broken open and wrapped with an overwrap material is shown. As shown in FIG. 3A , the bobbin 12 is loaded on the mandrel 10 . In this first step, the adhesive applicator 26 applies an adhesive to the overwrap material at a location proximate to a leading edge 32 of the overwrap material 22 . As shown, the leading edge 32 of the overwrap material is held against the vacuum plate 24 . The adhesive applicator 26 moves toward the leading edge 32 and applies an adhesive. In particular, in this embodiment, the adhesive applied to the overwrap material is supplied on a release tape 34 . As shown, a pressing device 36 moves upwards causing the release tape 34 to contact the leading edge 32 of the overwrap material 22 . When contact is made, an adhesive on the release tape is transferred to the leading edge 32 . [0033] As also shown in FIG. 3A , a second adhesive material is also applied to the overwrap material downstream from the leading edge 32 . In particular, the tape applicator 28 applies a double-sided adhesive tape 38 to the overwrap material 22 . The double-sided adhesive tape will later be used to seal the trailing edge of the overwrap material to the circumference of the bobbin 12 . In one embodiment, the double-sided adhesive tape 38 that is applied to the overwrap material 22 includes a first side and a second side. The first side is the side that is applied to the overwrap material. The second side, on the other hand, may be protected with a backing material that protects the second side of adhesive until the trailing edge of the overwrap material is adhered to the bobbin. As will be described later, the process can be configured to automatically remove the backing material as the overwrap material advances. [0034] Referring to FIG. 3B , once the adhesive material is applied to the leading edge 32 of the overwrap material 22 , the adhesive applicator 26 moves downward and disengages. Similarly, the tape applicator 28 also disengages from the overwrap material 22 once the double-sided tape 38 is applied to the overwrap material. [0035] As also shown in FIG. 3B , the bobbin of paper 12 is broken open using the breaking device 14 . In particular, in order to break open the outer layer of paper, at least one breakfoot 16 is applied against the outer circumference of the bobbin 12 . In FIG. 3B , for instance, a pair of breakfeet 16 are shown. Each breakfoot can be any suitable device that is capable of applying pressure against the outer circumference. For instance, in one embodiment, each breakfoot may comprise a hydraulic or pneumatic cylinder. [0036] After the breakfeet 16 are applied against the outer circumference of the bobbin 12 , the suction device 18 applies a suction force to the outer layer of paper and then pivots away from the outer circumference as shown in FIG. 3B . The suction device, for instance, may include at least one suction nozzle 40 such as a pair of suction nozzles. The suction nozzles apply a suction force to the outer layer of paper. As the suction device pivots away from the outer circumference, the outer layer of paper rips and breaks at a location adjacent to the breakfeet 16 . A vacuum hose 42 is then activated which captures the free end of the outer layer of paper where the break has occurred. [0037] Referring to FIG. 3C , after the outer layer of paper is broken open, the mandrel 10 rotates (clockwise in this embodiment) so as to remove the entire outer layer of paper. For instance, in one embodiment, the mandrel can be rotated from one to three revolutions. As the mandrel 10 is rotated, the outer layer of paper is captured by the vacuum hose 42 . [0038] After the mandrel 10 has rotated, a clamping device 44 is pressed against the outer circumference of the bobbin 12 . The clamping device 44 as shown in FIG. 3C can be a movable roller that moves toward and away from the bobbin. The clamping device holds the outer layer of paper against the bobbin as the paper is cut by a cutting device 46 . The cutting device 46 can comprise any suitable cutting device and may vary depending upon the type of material present on the bobbin 12 . For instance, the cutting device 46 may have a blade that strikes against a backing plate causing the paper to cut. Cutting the paper creates a leading edge 48 as shown in FIG. 3D . [0039] Referring to FIG. 3D , once the leading edge 48 is formed, the clamping device 44 is moved out of engagement with the bobbin 12 . A vacuum roller 50 is then activated as the mandrel 10 is rotated. The vacuum roller 50 moves towards the bobbin 12 . Due to the suction force created by the vacuum roller 50 , the leading edge is drawn to and positioned on the vacuum roller. [0040] As shown in FIG. 3E , once the leading edge 48 of the bobbin of material 12 is positioned on the vacuum roller 50 , the vacuum plate 24 holding the leading edge of the overwrap material is advanced towards the vacuum roller. More particularly, the vacuum plate 24 moves above the vacuum roller 50 and, as shown in FIG. 3F , then moves downward so as to contact the leading edge of the overwrap material with the leading edge of the bobbin. Due to the adhesive that has already been placed on the overwrap material, the overwrap material becomes connected to the bobbin of paper. [0041] As shown in FIGS. 3E and 3F , as the vacuum plate 24 moves forward, the vacuum plate pulls on the overwrap material causing the overwrap material to unwind and advance. [0042] Referring to FIG. 3G , once the leading edge 48 of the bobbin is attached to the leading edge 32 of the overwrap material, the mandrel 10 is rotated causing the overwrap material to wind around the circumference of the bobbin. Rotation of the mandrel 10 also causes the overwrap material 22 to unwind and advance. [0043] As shown in FIG. 3G , in this embodiment, the leading edge 32 of the overwrap material is positioned under the leading edge 48 of the paper. It should be understood, however, that in other embodiments the leading edge of the overwrap material may be over the leading edge of the paper. [0044] Referring to FIG. 3H , as the mandrel 10 continues to rotate and wrap the overwrap material around the circumference of the bobbin, the double-sided adhesive tape 38 contacts a backing removal device 52 . The backing removal device 52 removes the backing member from the adhesive tape 38 thereby exposing the adhesive. In one embodiment, as shown, a vacuum hose 54 may be provided in order to capture the backing material that is removed. [0045] In general, the backing removal device 52 can comprise any suitable device capable of removing the backing material without adversely affecting the adhesive. In one embodiment, for instance, the backing removal device 52 comprises a blade that engages the backing material as the overwrap material is advanced. If desired, the backing removal device 52 can be positioned adjacent to a guide roller having a relatively small diameter. In this manner, the backing material becomes more readily available for being removed from the adhesive layer. [0046] Referring to FIGS. 3I and 3J , as shown, the overwrap material 22 continues to advance and encircle the bobbin after the vacuum material is moved from the double-sided adhesive tape 38 . As shown in FIG. 3I , the mandrel 10 is rotated until the adhesive tape is at a position for securing the overwrap material to the circumference of the bobbin 12 . As shown particularly in FIG. 3I , the overwrap material 22 is cut upstream from the adhesive tape 38 as the overwrap material is advanced. In order to cut the overwrap material, a cutting device 56 is used. [0047] The cutting device 56 can be any suitable cutting device capable of cutting, tearing or ripping the overwrap material. The cutting device 56 , for instance, may be the same as the cutting device 46 as shown in FIG. 3C or may be different. In FIGS. 3I and 3J , the cutting device 56 is illustrated as a shearing device. Any suitable device, however, may be used. [0048] Referring to FIG. 3J , after the overwrap material 22 is cut by the cutting device 56 , the trailing edge of the overwrap material is formed that can be adhered to the outer circumference of the bobbin 12 by the adhesive tape 38 . As shown, in one embodiment, the overwrap material can be cut upstream from the adhesive tape 38 in order to form a tab 58 . The tab 58 can be used later to open the bobbin for use. For instance, a user can pull on the tab 58 in order to break the attachment between the adhesive tape and the outer circumference. [0049] The amount of overwrap material that is placed on the bobbin 12 can vary depending upon the particular application. For example, in one embodiment, sufficient overwrap material may be placed on the bobbin so as to completely encircle the circumference. Alternatively, the overwrap material may encircle the bobbin more than once. In this manner, the adhesive tape 38 is adhered to another layer of overwrap material instead of directly to the paper or other material used to make the bobbin 12 . [0050] Referring back to FIG. 31 , in one embodiment, as the overwrap material is cut by the cutting device 56 , the adhesive applicator 26 may be activated so as to apply an adhesive material to the overwrap material when a new leading edge of the overwrap material is formed by the cutting device 56 . The adhesive applicator 26 may be activated in order to repeat the process when a new bobbin is placed on the mandrel 10 . [0051] Referring to FIGS. 2C and 2D , a finished bobbin 12 is illustrated that has been wrapped with an overwrap material. As shown, the overwrap material 22 is adhered to the outer circumference of the bobbin by an adhesive tape 38 . The adhesive tape is also spaced a distance from the edge of the overwrap material in order to form the tab 58 . [0052] The overwrap material 22 can be made from any suitable material. In one embodiment, for instance, the overwrap material may comprise a paper material. The overwrap material can have the same width as the bobbin of material, can have a width less than the bobbin of material or can have a width greater than the bobbin of material. In one particular embodiment, for instance, the overwrap material has a width that is approximately 0.5 mm less than the width of the bobbin. [0053] The adhesive tape 38 and the tab 58 can also have various dimensions. In one embodiment, for instance, the adhesive tape 38 has a length of from about 15 mm to about 25 mm. The tab 58 , on the other hand, can have a length from about 0.5 inches to about 4 inches, such as from about 0.5 inches to about 1 inch. [0054] As shown in FIGS. 2C and 2D , if desired, a label 60 may be applied to the bobbin 12 . The label 60 , for instance, may supply information about the product, when it was made, and any other desired information. The label 60 can be automatically placed on the bobbin using a label dispenser or can be manually placed on the bobbin. [0055] These and other modifications and variations to the present invention may be practiced by those of ordinary skill in the art, without departing from the spirit and scope of the present invention, which is more particularly set forth in the appended claims. In addition, it should be understood that aspects of the various embodiments may be interchanged either in whole or in part. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention so further described in such appended claims.

A system and method for placing an overwrap material on a bobbin of material is disclosed. The bobbin of material may be, for instance, a bobbin of paper, such as cigarette paper. The system automatically attaches the overwrap material to a leading edge of the bobbin, wraps the bobbin in the overwrap material, cuts the overwrap material, and secures the overwrap material to the bobbin. The overwrap material is used to protect the bobbin during shipping and storage. The overwrap material can also be used to assist in feeding of the bobbin of material into a process.

FIELD [0001] This invention relates to the field of irons. BACKGROUND [0002] Clothing irons, also known as flatirons or merely irons, are devices used to press clothing to remove wrinkles and creases. Such irons were originally heated using hot coals, but are now more commonly heated using electricity. [0003] But the process of using a household iron is time-consuming, requiring one to remove clothing from its hanger, locate an ironing-board, position the clothing with the portion to be ironed on a flat portion of the board, and finally iron the clothing. This is time-consuming at home, only made worse when traveling. Furthermore, a typical iron requires a large heated plate because a small plate does not provide a stable base for the iron. [0004] The result is that ironing specific sections of an article of clothing is difficult, often requiring the use of different parts of the ironing board to iron different sections of an article of clothing. [0005] What is needed is a low-weight iron that can be used on clothing while it remains hanging, allowing a user to iron specific parts of the clothing without creating creases in unwanted parts. SUMMARY [0006] The hand-held clothing iron solves the problems of the prior art by providing a clamping iron that is used on an article of clothing while it remains hanging. [0007] Furthermore, the hand-held iron is not limited to applying a single level of heat across its entire surface, but is rather divided into zones. [0008] The first zone is the gather-gap, where clothing is gathered/folded to allow the hand-held iron to reach sections of the article of clothing that are further away than its throat is long. [0009] Past the gather-gap, the pairs of plates are divided into two or more zones, allowing for two or more levels of heating to be applied to the article of clothing. The plates are separated from one another by an insulating material, such as a ceramic. Or the plates are separated merely by an air-gap, the air-gap being of sufficient width to minimize heat transfer. The result of the insulator is to minimize heat transfer between the neighboring plates. [0010] While the use of two pairs of plates is discussed herein, the use of three or more pairs of plates is anticipated. [0011] The benefits of the gather-gap and the multi-zone heating are numerous. [0012] First, the hand-held iron can reach sections of the article of clothing that are further away than the hand-held iron is long, without applying heat to the near portions. The result is fewer creases, without requiring a very long hand-held iron. [0013] Second, the hand-held iron can iron disparate adjacent materials, applying the appropriate level of heat for each material. For example, a high-temperature setting for cotton and a low-temperature setting for synthetic material. Example heat settings include: Linen: 445° F. Cotton: 400° F. Wool: 300° F. Polyester: 300° F. Silk: 300° F. Lycra/Spandex: 275° F. [0020] Third, if the gather-gap is full of material, and the material to be ironed is still outside of the reach of the near pair of plates, the hand-held iron can still iron distant material without creating creases by leaving the plates adjacent to the gather-gap at ambient temperature, only heating a further set of plates. Such a set-up creates additional reach for the hand-held iron. [0021] The plates are made of a material with a high coefficient of heat transfer, e.g., steel, copper, aluminum, and optionally coated with an anti-static material and/or anti-friction coating, such as Teflon. [0022] The dials used to choose from the multiplicity of heat settings include indications of which heat settings are appropriate for which materials. For example, indications of a heat setting of 1 for synthetics, 2 for silk/wool, and 3 for linen/cotton. [0023] The housing is constructed of a material with a low coefficient of heat transfer to prevent the hot plates from warming the housing and burning the user. [0024] The hand-held iron is anticipated to be powered by household current, although it is anticipated that battery power is possible. If powered by household current, the electrical cord is mounted to the hand-held iron by a swivel, resulting in a cord that is unlikely to tangle. BRIEF DESCRIPTION OF THE DRAWINGS [0025] The invention can be best understood by those having ordinary skill in the art by reference to the following detailed description when considered in conjunction with the accompanying drawings in which: [0026] FIG. 1 illustrates a top view of a first embodiment. [0027] FIG. 2 illustrates a side view of the first embodiment. [0028] FIG. 3 illustrates a view illustrating the first embodiment ironing an exemplary hanging garment. DETAILED DESCRIPTION [0029] Reference will now be made in detail to the presently preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Throughout the following detailed description, the same reference numerals refer to the same elements in all figures. [0030] Referring to FIG. 1 , a top view of the first embodiment of the hand-held iron 1 is shown. The hand-held iron 1 includes a first housing member 2 and a second housing member 4 , each made of a material with a low coefficient of heat transfer to maintain a cool housing. [0031] First plate pair 10 is shown separated from second plate pair 16 by first insulator 20 . First indicator light 30 is lit when first plate pair 10 is energized, and second indicator light 32 is lit when second plate pair 16 is energized. [0032] Alternatively, the indicator lights 30 / 32 may be lit depending not on whether the plates are energized, but whether the plates are above a specified temperature. For example, if the plates 10 / 16 are hot enough to burn the user. [0033] First temperature control 34 sets the temperature for first plate pair 10 , and second temperature control 36 sets the temperature for second plate pair 16 . [0034] First power switch 38 energizes first plate pair 10 , and second power switch 40 energizes second plate pair 16 . [0035] Referring to FIG. 2 , a side view of the first embodiment of the hand-held iron is shown. Here, it is shown that first plate pair 10 is made of two separate plates, Plate- 1 a 11 and Plate- 1 b 12 . Furthermore, second plate pair 16 is shown as made of two separate plates, Plate- 2 a 17 and Plate- 2 b 18 . Plate- 1 a 11 is separated from Plate- 2 a by first insulator 20 . Plate- 1 b 11 is separated from Plate- 2 b by second insulator 20 . [0036] There is no requirement of limiting the plates to only two pairs. Additional pairs may be added, either increasing the length of the hand-held iron, changing the relative length of one pair of plates as compared to another, or increasing the quantity of divisions. [0037] Gathering gap 24 is shown, and as indicated is between the plates 11 / 12 / 17 / 18 and the hinge 26 . The hinge 26 allows the plates to be separated for the introduction of material, and subsequently closed upon the material. [0038] While ironing a garment, it is helpful to identify to the user the location of the respective plates. Thus, a plate separation indicator 50 is provided on the first housing member 2 , and optionally on the second housing member 4 . The plate separation indicator may be raised portion of the housing member 2 / 4 , an applied label, a disparate color of material, a light, or other type of indicator. The intention is to allow the user to visually identify the location of insulators 20 / 22 without requiring rotation of the hand-held iron 1 to view it from the side. [0039] Similarly, it may be helpful to the user to identify which plates 10 / 16 are heated. This is accomplished through the optional first auxiliary indicator light 52 and second auxiliary indicator light 54 . First auxiliary indicator light 50 is lit when first plate pair 10 is energized, and second auxiliary indicator light 52 is lit when second plate pair 16 is energized. [0040] All indicator lights 30 / 32 / 52 / 54 may be of multiple types: simple on/off; color-switching (e.g., red for off and green for on); or color changing (e.g., blue for cool, yellow for warm, orange for warmer, red for hot). [0041] Referring to FIG. 3 , an exemplary view of the first embodiment of the hand-held iron pressing an exemplary hanging garment is shown. [0042] A discussion of specific uses for the hand-held iron 1 illuminates its versatility. An exemplary blouse 60 is shown. The hand-held iron 1 is small enough to be used on the collar 62 of the blouse 60 without needing to remove the blouse 60 from its hanger. Ruffles 64 can be ironed without having to unbutton the blouse 60 , or to lay it on a flat surface, as can cuffs 66 . A user may even reach through the separates created by buttons 72 and iron two disparate materials, such as first material 68 and second material 70 . In the process the hand-held iron allows for the application of the ideal amount of heat for each material, all without requiring an ironing board, or an iron to heat up/cool down when moving from one material to another. [0043] Equivalent elements can be substituted for the ones set forth above such that they perform in substantially the same manner in substantially the same way for achieving substantially the same result. [0044] It is believed that the system and method as described and many of its attendant advantages will be understood by the foregoing description. It is also believed that it will be apparent that various changes may be made in the form, construction and arrangement of the components thereof without departing from the scope and spirit of the invention or without sacrificing all of its material advantages. The form herein before described being merely exemplary and explanatory embodiment thereof. It is the intention of the following claims to encompass and include such changes.

A hand-held clothing iron that solves the problems of the prior art by providing a clamping iron that is used on an article of clothing while it remains hanging, including the ability to apply disparate levels of heat to different sections of the clothing to provide the ideal temperature for each section.

BACKGROUND OF THE INVENTION The invention generally relates to improvements in personal medication regimen compliance. More particularly, the invention relates to a medication storage and dispenser unit suitable to be associated with a holder for the units and a medication regimen monitor, either singly, in partial combination or in full combination. Personal management of daily medication use has witnessed many developments directed to improving storage and dispensing or providing means for reminding a user when to take medication to remain in compliance with the regimen prescribed by the medical professional or which is to be otherwise complied with in connection with the ingestion of medication. Medication is understood to encompass synthetic or natural medications, including pharmaceuticals, prescription drugs, over-the-counter drugs, vitamins, minerals, phytochemicals, pills, caplets, tablets, capsules, gels, and the like. An example of a portable dispenser for dispensing small articles such as pills is found in Madden U.S. Pat. No. 5,620,109, incorporated hereinto by reference. Dispensers of this type are designed to be easily operable by a person experiencing difficulty in grasping and manipulating small objects. Its sliding mode of operation assists those who are hindered in finger strength and/or dexterity. Access to the interior of the container is gained by pushing on the exterior of a tray wall so as to push a tray and slide the container open. Also generally know are medication alarm devices to provide daily reminders of times to take medication. Often these types of units provide a reminder function only, leaving it up to the user or caregiver to keep track of issues such as whether or not the medication was actually taken at the proper time and whether or not a scheduled medication dose or combination of medications was missed, and if so which dose or combination was missed. Developments such as these provide independent functions. That is, one provides a storage and perhaps an organizational function, whereas the other provides a reminder function, at least in the short term. It would be desirable to provide improved units which organize, store and dispense medication. It would be desirable to provide units which enhance and supplement the basic medication reminder system. It also has been determined that a useful combined effect could be achieved by providing a system that performs some or all of these functions, and particularly a system which is designed to be capable of performing all of these functions, the selection of which can be at the discretion of the user. SUMMARY OF THE INVENTION In accordance with the present invention, a personal medication storage and dispensing unit is provided which is of a type having a tray within a sleeve. The unit includes one or more dividers transversely positioned to segment the tray into a plurality of compartments. In a preferred arrangement of the unit, cooperating engagement members provide a plurality of registry locations which are operative when the tray is extended to open one or more of the compartments. Also included as being suitable for use with the storage and dispensing units is a multiple-day medication storage and dispensing holder having a plurality of the storage and dispensing units nestable within saddles of the holder. Preferably each saddle corresponds to a day during which medication is to be taken. In another aspect of the invention, a system is provided which includes a medication regimen monitor preferably in a form by which the monitor is securely attachable and readily detachable from the medication storage and dispensing unit. The medication regimen monitor has operational logic which provides settable multiple alarm times, a compliance indicator arrangement, and a non-compliance indicator arrangement. It is a general object of the present invention to provide an improved medication storage and dispensing unit, system and method. Another object of this invention is to provide an improved apparatus and method for managing daily medication use. Another object of the present invention is to provide an improved apparatus and method for providing reminder information and compliance information for facilitating the maintenance of a regimen of medication as noted herein, which encompasses vitamins, minerals, phytochemicals, prescription and non-prescription drugs, and other pharmaceuticals, whether in the form of pills, capsules, caplets, gels, tablets or in some other form, and the like. Another object of this invention is to provide an improved apparatus and method which incorporate a system for electronically monitoring a regimen of medication contained within a slidable storage tray which is readily attachable to the monitor, which can be in further combination with a holder for a plurality of the dispensing units. Another object of the present invention is to provide an improved system for storing, monitoring and conveniently dispensing medication in accordance with a prescribed regimen or other need. Another object of this invention is to provide an improved apparatus and method for electronically monitoring a medication regimen, which preferably includes displaying a non-compliance message and maintaining a non-compliance message for a substantial time period. These and other objects, features and advantages of the invention will be apparent from and clearly understood through a consideration of the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS In the course of this description, reference will be made to the attached drawings, wherein: FIG. 1 is a perspective view illustrating an entire system incorporating all aspects of the invention; FIG. 2 is a perspective view of a preferred embodiment of a holder component of the invention; FIG. 3 is a perspective view of the combination of a medication storage and dispensing unit with a medication regimen monitor; FIG. 4 is a perspective view of the combination shown in FIG. 3, with the sliding aspects of this embodiment being illustrated; FIG. 5 is a perspective view of a preferred medication regimen monitor, showing its protective cover in an open mode; FIG. 6 is a front elevational view of the monitor as shown in FIG. 5; FIG. 7 is a left elevational view of the preferred medication regimen monitor; FIG. 8 is a right elevational view of the preferred medication regimen monitor; FIG. 9 is a cross-sectional view along the line 9 — 9 of FIG. 1; FIG. 10 is a sectional view similar to FIG. 9, with the storage and dispensing unit removed from the holder, and with the tray shown in an open condition; FIG. 11 is a data or logic flow chart incorporating a preferred example of operational logic suitable for the medication regimen monitor; FIG. 12 is a detail view of the display panel of the illustrated medication regimen monitor; and FIG. 13 is an electronic schematic detail of electronic circuitry suitable for use in the medication regimen monitor. DESCRIPTION OF THE PREFERRED EMBODIMENTS The entire system incorporating each of the basic aspects of the invention is generally illustrated at 21 in FIG. 1 . Included in this full system is a holder 22 , shown receiving a plurality of storage and dispenser units, generally shown at 23 . A medication regulator monitor, generally shown at 24 , is illustrated positioned onto one of the storage and dispenser units. When the holder 22 is included within the system, it can have an overall structure as shown in FIG. 2. A holder is provided when there is a desire to provide an organized array of a number of the storage and dispenser units 23 . Including a holder provides a neatening and unifying effect, as well as a set location for each unit 23 . A plurality of saddles 25 accommodates a like number of storage and dispenser units 23 . In the illustrated embodiment, seven such saddles are provided, and each is marked with indicia to signify a different day of the week. In this arrangement, the storage and dispenser unit 23 within the saddle 25 denoted with the Sunday indicia contains the medication and the like scheduled to be taken on that day. It will be appreciated that certain medication regimens can vary medications or dosages from day-to-day, making it important to have a means for designating the medication needed for a given day. The illustrated holder 22 is a generally planar tray which conveniently rests on a flat surface. Other configurations can be suitable for the holder. It can have a stacked configuration. It can be curved rather than planar in its overall appearance. It can be generally vertically oriented. Means can be provided to assist in holding each unit within each saddle, and such is especially suitable when the holder supports the storage and dispenser units in an orientation which is not horizontal. Typical means for assuring the maintenance of the units within the saddles until removal is desired include opposing surfaces with interference tapers, indents, detents, tabs, snaps, hook-and-loop members, or any other suitable approaches by which components can be releaseabley attached. Such arrangements are illustrated in FIG. 2 and FIG. 4 and FIG. 9 . At least one detent 26 is associated with each saddle 25 . When a storage and dispenser unit 23 is fitted within the saddle, an indent or depression 30 (FIG. 4) is provided in the tray and/or sleeve, or a projecting edge portion 27 (FIG. 9) of the tray snaps under detent 26 . While only one detent is shown, more than one can be provided as desired or needed, depending upon the orientation and configuration of the holder and the storage and dispenser units. Indents or depressions 30 can be provided on the storage and dispenser unit which are complementary in size and shape so as to accommodate detent 26 and provide an especially secure and positive snap-fit of the unit onto the holder. With further reference to the aspect of the invention concerning the storage and dispenser units 23 , each includes a tray component 28 and a sleeve component 29 . Particular reference in this regard is made to FIG. 3, FIG. 4, FIG. 9 and FIG. 10 . Tray 28 and sleeve 29 are longitudinally slidable with respect to each other. In the illustrated embodiment, this is facilitated by having the internal surface of the sleeve have a shape and size so as to closely and slidingly accommodate the outside surface of the tray. A sidewall 31 of the sleeve overlies a body wall 32 of the tray. In the drawings, sidewall 31 and body wall 32 are generally curved elongated surfaces. In addition, in the illustrated embodiment of the holder 22 , the saddles 25 each also have an elongated curved surface. This combination of curved surfaces provides an attractive, compact interfitting relationship among the holder, the sleeve and the tray. Tray component 28 also includes end walls 33 , 34 . Preferably, a permanent divider is provided within the tray component 28 . Illustrated in this regard is a permanent, transverse divider wall 35 . This divider wall splits the tray volume into two volumes. Either or both of these volumes can be further split by a removable divider 36 , one being shown in FIG. 4, FIG. 9 and FIG. 10 . Removable divider 36 rests in a slot 37 . Preferably, removable divider 36 is held in place by a suitable interference fit, such as between a notch 38 , shown in the divider 36 in FIG. 4, and a rib 39 , shown in empty slot 41 in FIG. 9 and FIG. 10 . It will be appreciated that another removable divider can be positioned within the empty slot 41 . With both removable dividers in place in the embodiment which is illustrated, a total of four volumes are provided within which medicaments, such as different medicaments, are positioned. In a desirable use, the medicaments to be taken at the first dosage time in a given day will be within an outside one of these compartments, with the next medicament(s) being within the next compartment, and so-forth. Solely for purposes of illustration, the depicted four compartments are designated as A, B, C and D in FIG. 10 . This illustrates a sequence of emptying the compartments for dosage intake. In this example, compartment A would be opened first and depleted first. That tray would then be closed until the next medicament dosage time arrives. Then, the tray would be slid (to the right in FIG. 9) until compartment B is opened by sliding the tray to the right until compartment B is no longer covered by elongated wall 42 . After that medicament regimen is removed, the tray is slid to the left, and the unit is again fully closed. At the next dosage time, the tray is again slid to the right as shown in the drawings, until compartment C is exposed. After the medicaments have been removed, the unit is again closed. Then, at the last dosage time in the day in this example, tray is slid to left until reaching the relationship shown in FIG. 10 . At that time, medicament can be removed from compartment D. Accessing compartments one at a time as achieved in the preceding example is facilitated by stop members. With particular reference to FIG. 9, the stop arrangements which are provided in the illustrated embodiment are as follows. Interference members are provided both on the inside surface of the sleeve and on the outside surface of the tray. The location of these interfering members can be selected as desired. For example, they may be differently placed depending upon the cross-sectional configuration of the tray and the cross-sectional configuration of the sleeve. Interference members could also be provided in association with the permanent divider, such as by sizing the permanent divider to interfere with a lip on the sleeve. The specific interference members which are shown it FIG. 9 and FIG. 10 include a raised pip 43 in the longitudinal and lateral center of the sleeve, along with an indented channel 44 positioned longitudinally on the outside bottom surface of the tray component 28 . Channel 44 includes a plurality of raised stops, including end stops 45 and 52 , central stop pair 48 , 49 , and intermediate stop pairs 46 , 47 and 50 , 51 . The preferred cross-sectional configuration of the tray component 28 , as well as of the sleeve component 29 , is generally semi-circular. The preferred shape includes a generally flatted bottom surface 53 of the sleeve component and a corresponding generally flattened bottom surface 54 of the tray component. Preferably, the saddles 25 of the holder 22 are similarly shaped so that each of these three components are complementarily shaped with respect to each other. This shape provides a broader lateral dimension to the compartments within the tray, which has been found to advantageously accommodate multiple medications, including differently shaped pills, capsules, disks, caplets, gel capsules, and the like. Turning now to the sleeve component 29 and particularly its upper portion as viewed in the drawings, the sleeve component will have an attachment portion when designed to be used in conjunction with the medication regulator monitor 24 within the complete system and method which can be provided and carried out as desired. Whatever attachment structures are used, they should provide secure attachment between the sleeve component and the medication regulator monitor. This secure attachment also should be easily made and released so as to be manageable by the medication taker or caregiver. It has been found that these objectives are conveniently attained by the illustrated approach, which continues with the sliding engagement arrangement which is present in the illustrated sleeve and tray attachment. With more particular reference to the illustrated sliding engagement, reference is made particularly to FIG. 3, FIG. 4, FIG. 9 and FIG. 10 . Rails 55 are provided in the illustrated embodiment. In order to maintain a narrow overall width profile, a clearance slot 56 adjoins each rail 55 . An attachment side of the illustrated medication regulator monitor is provided with structure which is slidingly complementary to the attachment system of the sleeve. In the illustrated housing, interlock slots 57 are sized and shaped to slidingly receive the rails 55 of the storage and dispenser unit, and interlocking rails 58 correspondingly slide within the clearance slot 56 of the storage and dispenser unit. The medication regulator monitor 24 which is illustrated has a housing which includes the attachment structure as discussed. Its housing further includes a control interface area 61 and a display panel 62 . A protective cover 63 is shown to pivot open and pivot closed so as to prevent unintentional changes to the settings which the user had made by way of interface members, such as buttons or pads of the control interface area 61 . The illustrated unit is battery powered, and door 64 is provided to allow battery access and contact to provide power to the unit in a customary manner. A suitable control element is accessible by the user. The illustrated element in this regard is a slide switch 65 , which performs as a function selector. Control interface area 61 which is illustrated has the following user interface locations. In the illustrated embodiment, these are in the form of push buttons. It will be understood other interface devices besides buttons can be used, including touch pads. Interface areas 66 and 67 allow for changing the hour (HR) setting and the minute (MIN) setting which is shown on the display panel 62 . Interface area 68 allows change between a 12-hour clock and a 24-hour clock. The interface area labeled ALARM and SELECT allows the user to choose one of the alarm choices provided by the unit. The illustrated alarm choices are an alarm sound (such as Bi-Bi-Bi), this selection being indicated by a bell icon or any other selected logo 71 (FIG. 12 ). Another selection is a short message as: “time to take your pill,” designated by the lips icon 72 or any other suitable display. The third choice is a visual signal. When this is chosen, the light icon 73 , or other suitable display, is shown. When the alarm mode is activated at this setting, a light 74 or the like illuminates and/or flashes. When one of the audible alarms is selected, a speaker 75 or the like is provided. Control interface area 61 also includes an ALARM ON/OFF interface area 76 . An illustrative display panel is shown in FIG. 12 . The specific mechanism by which the display is generated will be appreciated by those in the art. In addition to the time and alarm displays which are illuminated or otherwise made visible at times consistent with the operation of the unit, non-compliance displays also are provided. Illustrated displayed panel includes a MISSED PILL message which is illuminated or otherwise made visible, preferably in a flashing type of mode. This provides a message that a medication or the like was not timely taken, more particularly that the compliance interface location was not engaged. In the illustrated embodiment, this compliance interface location is the ALARM STOP button or area 77 . If compliance is not thereby indicated, the non-compliance message can persist, such as by stopping and then repeating for a number of appropriate times. Another non-compliance signal is given by a designation associated with each of the medication time or number indicia. In the illustrated embodiment, the numbers 1, 2, 3 and 4 correspond to the first, second, third and fourth, respectively, times within a 24-hour day, at which the medication regimen is to be complied with. In the event of non-compliance, the appropriate number is flagged. A suitable flag is the illustrated “X” out symbol which is shown in FIG. 12 in association with each of the dosage time numbers. Specifics of the circuitry of the preferred embodiment which is shown in the drawings are provided in FIG. 13 . This is in the context of a chip and its communications with the components that are exemplified, particularly in the drawings. Variations on this specific chip and its components are possible in order to achieve the logic of the monitor, whether using hardware, software or other alternative technology which achieves the desired functions and result. A preferred logic sequence is shown in FIG. 11 . In its basic form, this logic prompts compliance at multiple times within a 24-hour period and also records non-compliance so that corrective measures can be taken by the patient, caregiver or medical professional, as appropriate. These functions are carried out by operational data circuitry which can be provided in any suitable form. The illustrated form incorporates a chip, but the invention is not so limited. A window 78 can be provided for displaying the particular function being carried out by the switch or selector 65 . One is the LOCK function at which all settings made during programing the unit are set in place until re-programming is desired. The next function selection of the selector or switch 65 is the CLOCK function, by which the hour and the minute, preferably that of the time of programming, is entered into the unit. Four other selector settings are provided in the illustrated example, each setting corresponding to one of the administration times programed into the device by the user. When at one of these settings, identified as A 1 , A 2 , A 3 and A 4 in the working example, the user sets the hour and minute at which the compliance time signal is to be given. In use, the clock typically first will be set to the current local time. Each intended compliance time then will be set, as needed, up to four designated compliance times being possible in the illustrated embodiment. Activating the alarm can be accomplished, if necessary, by engaging an activating area 76 . In order to properly function as a system unit, typically the desired compliance times will be set in ascending time order and corresponding ascending setting number order. When each setting is selected, the function selector or switch is moved to the LOCK position. The illustrated embodiment allows for selection among a beeping alarm sound, a voiced phrase sound, or a visual indicator. The voice indicator can be any suitable phrase, preferably one which will be readily understood by the user. The visual indicator can take the form of a flashing light or other convenient approach. During operation, when each programmed compliance time is reached by the clock function, the selected message that compliance is due is given. This prompts the patient to take the medication, at which time the appropriate party is to activate the alarm stop 77 , thereby indicating compliance. Another round or more of compliance prompts can be provided, such as at one minute intervals, until compliance is indicated by activating the alarm stop function. In the illustrated embodiment, a total of three compliance prompts are provided at each set alarm time. If the total number of compliance prompts provided are not responded to, that is after the total compliance time has passed, a non-compliance indication will be given. In the illustrated embodiment, this takes the form of the appearance of a properly informing message, such as “MISSED PILL” or other appropriate indicator. In addition, in the preferred arrangement which is illustrated, a flag will be provided at the indicator for the desired compliance time or number which was not heeded. The flag shown in FIG. 12 includes a square around an appropriate number, combined with an indication of non-compliance with that desired dosage time, in this case a crossed-out symbol. These displays will continue for almost 24 hours, at which time they will automatically disappear. Until then, a persisting message of non-compliance is provided, which message also indicates which of the desired compliance times have not been adhered to. In the illustrated embodiment, activation of the alarm stop function after the compliance prompts have been completed will remove the “MISSED PILL” display; however, the indicator such as the cross-out flags will remain evident until the programed time is reached for removal of the non-compliance message(s), or until the unit is re-programmed. In the event of multiple non-compliance events, the indicator for each instance of non-compliance will remain until cycled out as discussed. It will be appreciated that the medication regulator monitor 24 can be used alone, with only a single storage and dispenser unit 23 securely and removably attached to it, or with the entire system including multiple storage and dispenser units positioned within a holder. In this instance, the user will fill the units 23 with appropriate medication or the like within an appropriate compartment(s). Then, at a designated date, such as the day of the week noted on the holder, the user has the monitor positioned in place on that so-designated storage and dispenser unit. As each compliance time is reached and signaled, the appropriate compartment within that storage and dispenser unit is accessed, the medication is taken, and the compliance interface area is contacted in order to stop the reminder function and avoid appearance of the non-compliance flag for that dosage time. This process continues from day to day. At an appropriate time, the medication will be replenished. The combination of the monitor and the dispenser unit provides a convenient assembly which can be carried by or with the patient. Both the indicator and the medication are in the same unit, and there is no need for the patient or the caregiver to locate both in order to proceed with the process according to the invention. It will be understood that the embodiments of the present invention which have been described are illustrative of some of the applications of the principles of the present invention. Numerous modifications may be made by those skilled in the art without departing from the true spirit and scope of the invention.

A personal medication in storage dispensing unit is provided for receiving and storing medication, vitamins, minerals, phytochemicals, pills capsules, gel tablets and the like in a manner which is easily accessible and which is conducive to inclusion within a medication regimen system. A medication regimen monitor can be included in this system in order to be programmed to signal proper medication dosage times. The monitor preferably provides non-compliance information, preferably information which persists and which designates which portion of the medication regimen was not complied with. The system also can include a holder for multiple storing and dispensing units in an ordered fashion consistent with daily requirements of the medication regimen.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT [0001] The United States Government has rights in this invention pursuant to contract No. DE-AC05-96OR22464 between the United States Department of Energy and Lockheed Martin Energy Research Corporation. BACKGROUND OF THE INVENTION [0002] The present invention relates to carbon foam, and more particularly to a process and apparatus for extruding a thermally conductive carbon foam. [0003] The extraordinary mechanical properties of commercial carbon fibers are due to the unique graphitic morphology of the extruded filaments. See Edie, D. D., “Pitch and Mesophase Fibers,” in Carbon Fibers, Filaments and Composites, Figueiredo (editor), Kluwer Academic Publishers, Boston, pp. 43-72 (1990). Contemporary advanced structural composites exploit these properties by creating a disconnected network of graphitic filaments held together by an appropriate matrix. Carbon foam derived from a pitch precursor can be considered to be an interconnected network of ligaments or struts. As such interconnected networks, they would represent a potential alternative as a reinforcement in structural composite materials. [0004] Recent developments of fiber-reinforced composites has been driven by requirements for improved strength, stiffness, creep resistance, and toughness in structural engineering materials. Carbon fibers have led to significant advancements in these properties in composites of various polymeric, metal, and ceramic matrices. [0005] However, current applications of carbon fibers has evolved from structural reinforcement to thermal management in application ranging from high density electronic modules to communication satellites. This has stimulated research into novel reinforcements and composite processing methods. High thermal conductivity, low weight, and low coefficient of thermal expansion are the primary concerns in thermal management applications. See Shih, Wei, “Development of Carbon-Carbon Composites for Electronic Thermal Management Applications,” IDA Workshop, May 3-5, 1994, supported by AF Wright Laboratory under Contract Number F33615-93-C-2363 and AR Phillips Laboratory Contract Number F29601-93-C-0165 and Engle, G. B., “High Thermal Conductivity C/C Composites for Thermal Management,” IDA Workshop, May 3-5, 1994, supported by A F Wright Laboratory under Contract F33615-93-C-2363 and A R Phillips Laboratory Contract Number F29601-93-C-0165. Such applications are striving towards a sandwich type approach in which a low density structural material (i.e. honeycomb or foam) is sandwiched between a high thermal conductivity facesheet. [0006] Structural cores are limited to low density materials to ensure that the weight limits are not exceeded. Unfortunately, carbon foams and carbon honeycomb materials are the only available materials for use in high temperature applications (>1600° C.). High thermal conductivity carbon honeycomb materials are extremely expensive to manufacture compared to low conductivity honeycombs, therefore, a performance penalty is paid for low cost materials [0007] Typical foaming processes utilize a “blowing” technique to produce a foam of the pitch precursor. The pitch is melted and pressurized, and then the pressure is reduced. Thermodynamically, this produces a “Flash,” thereby causing the low molecular weight compounds in the pitch to vaporize (the pitch boils), resulting in a pitch foam. See Hagar, Joseph W. and Max L. Lake, “Novel Hybrid Composites Based on Carbon Foams,” Mat. Res. Soc. Symp., Materials Research Society, 270:29-34 (1992), Hagar, Joseph W. and Max L. Lake, “Formulation of a Mathematical Process Model Process Model for the Foaming of a Mesophase Carbon Precursor,” Mat. Res. Soc. Symp., Materials Research Society, 270:35-40 (1992), Gibson, L. J. and M. F. Ashby, Cellular Solids: Structures & Properties, Pergamon Press, New York (1988), Gibson, L. J., Mat. Sci. and Eng A110, 1 Knippenberg and B. Lersmacher, Phillips Tech. Rev., 36( 4 ), (1976), and Bonzom, A., P. Crepaux and E. J. Moutard, U.S. Pat. No. 4,276,246, (1981). Additives can be added to promote, or catalyze, the foaming, such as dissolved gases (like carbon dioxide, or nitrogen), talc powder, freons, or other standard blowing agents used in making polymer foams. [0008] Then, unlike polymer foams, the pitch foam must be oxidatively stabilized by heating in air (or oxygen) for many hours, thereby, cross-linking the structure and “setting” the pitch so it does not melt, and deform the structure, during carbonization. See Hagar, Joseph W. and Max L. Lake, “Formulation of a Mathematical Process Model Process Model for the Foaming of a Mesophase Carbon Precursor, Mat. Res. Soc. Symp., Materials Research Society, 270:35-40 (1992) and White, J. L., and P. M. Shaeffer, Carbon, 27:697 (1989). This is a time consuming step and can be an expensive step depending on the part size and equipment required. [0009] Next, the “set” or oxidized pitch foam is then carbonized in an inert atmosphere to temperatures as high as 1100° C. Then, a final heat treatment can be performed at temperatures as high as 3000° C. to fully convert the structure to carbon and produce a carbon foam suitable for structural reinforcement. However, these foams as just described exhibit low thermal conductivities. [0010] Other techniques may utilize a polymeric precursor, such as phenolic, urethane, or blends of these with pitch. See Hagar, Joseph W. and Max L. Lake, “Idealized Strut Geometries for Open-Celled Foams,” Mat. Res. Soc. Symp., Materials Research Society, 270:41-46 (1992), Aubert, J. W., (MRS Symposium Proceedings, 207:117-127 (1990), Cowlard, F. C. and J. C. Lewis, J. of Mat Scid., 2:507-512 (1967) and Noda, T., Inagaki and S. Yamada, J. of Non - Crystalline Solids, 1:285-302, (1969). However, these precursors produce a “glassy” or vitreous carbon which does not exhibit graphitic structure and, thus, has a very low thermal conductivity and low stiffness as well. See Hagar, Joseph W. and Max L. Lake, “Idealized Strut Geometries for Open-Celled Foams,” Mat. Res. Soc. Symp., Materials Research Society, 270:41-46 (1992). [0011] One technique developed by the inventor of the present invention, and is fully disclosed in commonly assigned U.S. patent application Ser. No. 08/921,875. It overcomes these limitations, by not requiring a “blowing” or “pressure release” technique to produce the foam. Furthermore, an oxidation stabilization step is not required, as in other methods used to produce pitch-based carbon. This process is less time consuming, and therefore, will be lower in cost and easier to fabricate than the prior art above. More importantly, this process is unique in that it produces carbon foams with high thermal conductivities, greater than greater greater 58 W/m·K. However, the method described in U.S. patent application Ser. No. 08/921,875 is a batch process. This prevents large scale production at reasonable costs. Therefore, it is desirable to provide a continuous process that will produce carbon foam, so as to reduce costs and increase throughput. SUMMARY OF THE INVENTION [0012] The present invention provides a method of extruding a pitch or mesophase (herein after called pitch) based foam. The method includes the steps of: forming a viscous pitch foam; passing the viscous pitch foam through an extrusion tube; and subjecting the viscous pitch foam in the extrusion tube to a temperature gradient which varies along the length of the extrusion tube to form an extruded pitch derived foam, carbon foam, or graphitic foam, depending on the maximum temperature during the extrusion cycle. [0013] A general objective of the present invention is to provide an extrusion method which can be continuous. This objective is accomplished by passing a viscous pitch foam through an extrusion tube and coking (solidifying) the viscous pitch foam as it passes through the tube. [0014] Another objective of the present invention is to extrude carbon foam having specific properties. This objective is accomplished by heat treating the pitch derived foam in the extrusion tube to form carbon foam having specific properties, such as a carbonized or graphitized carbon foam. [0015] Another aspect of the present invention provides an apparatus for extruding carbon foam. The apparatus includes a melting chamber for melting pitch, a foaming chamber communicatively connected to the melting chamber for foaming the melted pitch to form a viscous pitch foam, and a heated extrusion tube having a passageway communicatively connected to the foaming chamber, wherein the viscous pitch foam formed in the foaming chamber passes through said extrusion tube passageway to form an extruded pitch based foam of virtually any extrudable shape. [0016] These and other objectives are accomplished by a method of extruding a pitch based foam which includes the steps of: forming a viscous pitch foam in a container; transferring the precursor from the container into an extrusion tube; and hardening the extruded pitch based foam. BRIEF DESCRIPTION OF THE DRAWINGS [0017] [0017]FIG. 1 is a batch apparatus for extruding carbon foam which incorporates the present invention; [0018] [0018]FIG. 2 is a graph showing an optimum foaming temperature range for ARA24 mesophase pitch; [0019] [0019]FIG. 3 is a temperature gradient suitable for use with the apparatus of FIG. 1; and [0020] [0020]FIG. 4 is a continuous carbon foam extruding apparatus incorporating the present invention; and [0021] [0021]FIG. 5, is another embodiment of a continuous carbon foam extruding apparatus incorporating the present invention DETAILED DESCRIPTION OF THE INVENTION [0022] A pitch based foam, such as fully disclosed in U.S. patent application Ser. Nos. 08/921,875, and 08/923,877 which are commonly owned by the assignee of the present application, and which teachings are fully incorporated herein by reference, is formed by first extruding a viscous pitch foam, such as derived from a mesophase or isotropic pitch, through an extrusion tube. The viscous pitch foam can be heat treated in the tube to form an extruded carbon foam having desirable properties. The extrusion process can be continuous to provide continuous production of the carbon foam or a batch process. If the extrusion is only a pitch derived foam, then it can be heat treated in a separate furnace to produce a carbon or graphitic foam. [0023] Whether the foam is pitch derived, carbon, or graphitic depends upon the heat treatment of the foam. If the maximum temperature of the extrusion is less than 800° C. then the molecular structure of the material still contains non-carbon atoms, and therefore is considered a pitch derived foam. If the maximum temperature of the extrusion is between 800° C. and about 2000° C., then the molecular structure of the material contains only carbon atoms, and therefore is considered a pitch derived carbon foam. If the maximum temperature is greater than 2000° C., then the material is beginning to show signs of graphitic structure (depending on original pitch precursor) and therefore is considered a pitch derived graphitic foam. The foam, whether viscous, pitch derived, carbon, or graphitic is generically referred to in this application as pitch based. [0024] As shown in FIG. 1, an apparatus 10 for extruding carbon foam in a batch process includes a melting/foaming chamber 12 for melting pitch materials 14 , and foaming the melted pitch materials 14 to form a viscous pitch foam 16 . The melting/foaming chamber 12 is a heatable container, such as a crucible, which can withstand internal pressures exerted on container walls by the expanding viscous pitch foam 16 . The viscous pitch foam 16 expands in the chamber 12 and forces its way into an extrusion tube 18 communicatively connected to the chamber 12 . The extrusion tube 18 heats the extruded foamed pitch precursor 16 in accordance with a predetermined temperature gradient along the tube length to coke the viscous pitch foam 16 , and heat treat the hardened foam 20 . As discussed above, the properties of the extruded foam will depend on the maximum temperature of the heat treatment in the extrusion tube 18 . [0025] The melting/foaming chamber 12 is a crucible 22 with a lid 24 . Pitch 14 is placed in the crucible 22 , and the lid 24 is secured to the crucible top 26 . Grafoil gasket material 28 is clamped between the lid 24 and crucible 22 using graphite clamps 30 to provide a tight seal. [0026] The heated extrusion tube 18 extends from the lid 24 , and has a shaped inner passageway 32 through which the extruded materials pass. The passageway 32 is shaped to form a desired extruded material cross section shape. Alternatively, the viscous pitch foam can pass through an orifice disposed in the passageway 32 to form the desired extruded material cross section. [0027] The extrusion tube 18 is heated to provide a predetermined temperature gradient along the tube length. The temperature gradient along the length of the tube determines the characteristics of the extruded carbon foam 20 . The tube 18 is heated using conventional heating methods known in the art, such as by using radiant energy, in the form of IR lamps, microwave energy, induction heating, band heaters, and the like. [0028] When the viscous pitch foam 16 expands, it forces its way out of the chamber 12 through the extrusion tube 22 . A throttle valve 31 disposed in the extrusion tube throttles the flow of extruded material to maintain the desired pressure in the foaming chamber 12 , and control the flow of extruded material. [0029] Once the extruded carbon foam 20 passes through the extrusion tube 18 , a sectioning device 33 disposed downstream of the tube 18 cuts the extruded foam 20 to desired section lengths. The sectioning device 33 can be any suitable cutting devices, such a saw, shear, and the like. [0030] In use, the pitch 14 , in the form of pitch powder, granules, pellets, or the like, are placed in the chamber 12 . The pitch 14 can be solvated if desired. The pitch 14 is heated in a substantially oxygen-free environment to avoid oxidation of the pitch materials 14 during heating. Preferably, the pitch 14 is heated by placing band heaters around the chamber 12 to a temperature approximately 50 to 100° C. above its softening point. For example, where Mitsubishi ARA24 mesophase pitch is used, a temperature of 300° C. is sufficient. The chamber is pressurized initially with a nitrogen purge (or other inert gas) to the desired pressure of foaming and the throttle valve is used to regulate the pressure during foaming [0031] Preferably, the pressure inside the chamber 12 is then increased up to 1000 psi. The temperature of the pitch 14 is then raised to cause the evolution of pyrolysis gases in the pitch 14 . The pyrolysis gases foams the melted pitch 14 to form the viscous pitch foam 16 which expands into the extrusion tube 18 . Preferably, the temperature of the pitch 14 is increased to an optimum foaming temperature range for the particular molten pitch in the melting/foaming chamber 12 . An optimum foaming temperature is a temperature in which the foam yield is maximized. For example, as shown in FIG. 2, a preferred foaming temperature range for ARA24 mesophase pitch is between 420 C and 520 C. Most preferably, the foaming temperature range is between 420 C and 450 C. [0032] The expanding viscous pitch foam 16 passes through the throttle valve and into the extrusion tube 18 which shapes and heat treats the extruded material to form the carbon foam. The extrusion tube 18 is heated in order to subject the extruded material to a temperature gradient, such as disclosed in FIG. 3, which forms carbonized and graphitized carbon foam 20 . [0033] As shown in FIG. 3, the extruded viscous pitch foam 16 is heated in a first zone to coke (harden) the extruded viscous pitch and form the pitch derived foam 20 . For example, the temperature of a viscous pitch foam derived from ARA mesophase pitch is preferably increased along the length of the tube to about 500 C-1000 C [0034] The pitch derived foam 20 can be exposed to additional temperature gradients in the extrusion tube 18 to produce carbon foam or graphitized foam. For example, prior to cooling the pitch derived foam 20 , the temperature of the foam 20 can be further increased to carbonize or graphitize the foam. As shown in FIG. 3, the pitch derived foam 20 is further heated in a second zone to further increase the foam temperature to carbonize the foam 20 . Following carbonizing, the extruded material is heated in a third zone to approximately 2800 C to further increase the carbon foam temperature causing it to graphitize, depending on the pitch precursor. Preferably, the graphitizing zone includes a period of constant peak temperature to ensure the carbon foam is substantially isothermal. [0035] Finally, the graphitized carbon foam 20 is cooled in a fourth zone below includes 200 C in order to allow-handling of the extruded material, such as conveying or sectioning the extruded carbon foam 20 . Preferably, the temperature along the length of the tube 18 in the fourth zone is gradually decreased to a temperature at which the carbon foam does not oxidize. [0036] It will thus be seen that the present invention provides for the production of an extruded pitch-based foam. The process involves the fabrication of a foam from a mesophase or isotropic pitch which can be synthetic, petroleum, or coal-tar based. A blend of these pitches can also be employed. The foam is formed by melting the pitch in a melting chamber, and then foaming the melted pitch in a foaming chamber (which may be the same as the melting chamber) to form a viscous pitch foam The viscous pitch foam is extruded through an extrusion tube which heat treats the precursor to provide a pitch derived foam or pitch derived carbon foam, depending on maximum temperature. [0037] Preferably, the foam can have a relatively uniform distribution of pore sizes (average between 50 and 500 microns), very little closed porosity, and a density ranging from approximately 0.20 g/cm 3 to 0.7 g/cm 3 . However, deviations from this preferable properties are possible by changing the operating conditions and the pitch precursor. When a mesophase pitch is used, the domains are stretched along the struts (or cell walls) of the foam structure and thereby produces a highly aligned graphitic structure parallel to the cell walls (or struts). When graphitized, these struts will exhibit thermal conductivities similar to the very expensive high performance carbon fibers (such as P-120 and K1100). Thus, the foam will exhibit high thermal conductivity at a very low density (≈0.5 g/cc). By utilizing an isotropic pitch, the resulting foam can be easily activated to produce a high surface area activated carbon. Also, isotropic pitches will typically results in stronger materials, especially if derived from coals. [0038] The carbon foam can also be continuously extruded using an apparatus incorporating the present invention. This is very similar to the previously described apparatus with the addition of a separate melting chamber and device to continuously add molten pitch to the foaming chamber. As shown in FIG. 4, an apparatus 40 for continuously extruding carbon foam 42 includes a melting chamber 44 for melting pitch materials 46 , and a foaming chamber 48 . The foaming chamber 48 is communicatively connected to the melting chamber 44 by a passageway 50 for foaming the melted pitch materials 47 to form a viscous pitch foam 52 . A pump, not shown, between the melting chamber and the foaming chamber will regulate the flow of molten pitch into the pressurized foaming chamber. The viscous pitch foam 52 produced in the foaming chamber expands into an extrusion tube 54 communicatively connected to the foaming chamber 48 . The extrusion tube 54 heats viscous pitch foam 52 in accordance with a predetermined temperature gradient along the tube length to coke the viscous pitch foam 52 , and shape the foam 42 . Preferably, the extrusion tube 54 also heat treats the carbon foam 42 to provide a carbon or graphitic foam with specific properties. [0039] The melting chamber 44 is a heatable container having a feed tube 58 which feeds solid pitch 46 into the chamber 44 . The feed tube 58 continuously feeds pitch powder, granules, pellets, or the like into the melting chamber 44 which is heated to transform the solid pitch 46 into molten pitch 47 . The pitch 46 is heated in the melting chamber 44 in an oxygen free environment, such as nitrogen, and exits the chamber 44 through an outlet 60 formed in a melting chamber wall into the passageway 50 . Preferably, the pitch is heated to about 100 C above the pitch softening point to provide a flowable molten pitch 47 . For example, an ARA24 mesophase pitch is preferably heated to about 350 C. [0040] Preferably, an agitating mechanism 64 agitates the molten pitch 47 in the melting chamber 44 to ensure uniform pitch temperature and homogeneity. The agitating mechanism 64 includes a rotatable mixing shaft 66 having a mixing end 68 disposed in the molten pitch 47 . The mixing end 68 rotates to agitate the molten pitch 47 . Although a rotating mixing shaft 46 is disclosed, other methods known in the art can be used to agitate the molten pitch 47 , such as rotating the melting chamber, vibrating paddles in the molten pitch, and the like. [0041] The molten pitch 47 passes through the passageway 50 to the foaming chamber 48 . The passageway 50 has an inlet 70 which receives the molten pitch 47 from the melting chamber 44 , and an outlet 72 through which the molten pitch 47 enters the bottom 74 of the foaming chamber 48 . In one embodiment, the melting chamber 44 is disposed above the foaming chamber 48 to gravity feed the molten pitch 47 into the foaming chamber 48 . A valve 76 or meter pump disposed in the passageway 50 can regulate the flow of molten pitch into the foaming chamber 48 to maintain a pressure therein. [0042] The foaming chamber 48 is a pressurized heatable container which heats the molten pitch 47 under pressure to cause the evolution of pyrolysis gases to form the foam precursor 52 . As in the melting chamber 44 , the molten pitch is heated in an oxygen free environment to avoid oxidation of the molten pitch 47 . [0043] The molten pitch 47 enters the foaming chamber 48 through the passageway outlet 72 , and is heated in the foaming chamber to a temperature sufficient to cause the molten pitch 47 to foam at the foaming chamber pressure to form the foam precursor 52 . For example, at a pressure of approximately 68 atm (1000 psi), ARA24 mesophase pitch will foam at a temperature between approximately 420 C and 480 C. Preferably, the temperature in the foaming chamber is maintained at approximately 450 C. under a pressure between approximately 27 atm and 68 atm (400 psi and 1000 psi) when foaming molten ARA24 mesophase pitch. [0044] The viscous pitch foam 52 expands in the foaming chamber 48 , forcing its way through the extrusion tube 54 . As in the first embodiment, a throttle valve (not shown) disposed in the extrusion tube 54 throttles the flow of extruded materials to maintain the desired pressure in the foaming chamber 48 , and control the flow of extruded materials. [0045] The expanding viscous pitch foam 52 passes through the extrusion tube 54 which shapes and heat treats the extruded material to form the pitch derived foam 42 . The extrusion tube 54 subjects the extruded material to a temperature gradient, such as disclosed in FIG. 3, which forms carbonized and graphitized carbon foam 42 . [0046] As in the first embodiment, the extrusion tube 54 is heated to provide a predetermined temperature gradient along the tube length such as disclosed above in FIG. 3. The temperature gradient along the length of the tube 54 determines the characteristics of the extruded foam 42 . The tube 54 is heated using conventional heating methods known in the art, such as by using radiant energy, in the form of IR lamps, microwave energy, induction heating, and the like. [0047] In another embodiment of the present invention, shown in FIG. 5, molten pitch is continuously fed into a foaming chamber 80 by a metering pump 82 interposed between the foaming chamber 80 and a melting chamber B 4 . Pitch is continuously supplied to the melting chamber 84 by a hopper 86 mounted proximal to a feed end 88 of the cylindrical melting chamber 84 . The heated melting chamber 84 melts the pitch and, and a feed screw 90 disposed in the melting chamber urges the melted pitch toward the metering pump 82 disposed at the melting chamber pump end 92 . Advantageously, the feed screw 90 mixes the pitch to ensure uniform temperature and homogeneity of the melted pitch. Exposure of the pitch to oxygen is minimized to avoid oxidation by methods known in the art, such as by evacuating the melting chamber 84 , maintaining an inert gas blanket in the melting chamber 84 , and the like. [0048] The metering pump 82 disposed at the melting chamber pump end 92 pumps the molten pitch into the pressurized foaming chamber 80 . The foaming chamber 80 foams the molten pitch to form a viscous pitch foam by heating the molten pitch under pressure to cause the formation of pyrolysis gases. The pitch is foamed in an oxygen free environment, such as in the presence of an inert gas, to avoid oxidation. The expanding viscous pitch foam forces its way through an opening 94 in the foaming chamber 80 , and into an extrusion tube 96 . A modified standard screw feed melt extruder would be suitable for this task. [0049] As disclosed in the first embodiment, the extrusion 96 tube subjects the extruded viscous pitch foam, and resulting carbon foam to a predetermined temperature gradient. The predetermined temperature gradient cokes and heat treats the extruded material to form carbon foam having particular qualities, such as disclosed in the first embodiment. Although not shown, valves controlling the extrusion process, and a cutting mechanism can be provided as in the first embodiment. [0050] While there has been shown and described a preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention defined by the appended claims.

A method and apparatus for extruding pitch based foam is disclosed. The method includes the steps of: forming a viscous pitch foam; passing the precursor through an extrusion tube; and subjecting the precursor in said extrusion tube to a temperature gradient which varies along the length of the extrusion tube to form an extruded carbon foam. The apparatus includes an extrusion tube having a passageway communicatively connected to a chamber in which a viscous pitch foam formed in the chamber passes through the extrusion tube, and a heating mechanism in thermal communication with the tube for heating the viscous pitch foam along the length of the tube in accordance with a predetermined temperature gradient.

CROSS-REFERENCE TO RELATED APPLICATION This is a divisional application of Ser. No. 710,960 filed Aug. 2, 1976, now U.S. Pat. No. 4,125,593. BACKGROUND OF THE INVENTION It is ecologically unacceptable to release halogenated hydrocarbons into the atmosphere or into public waters. Among the methods used in attempts to abate such pollution has been combustion (thermal oxidation) of the halogenated hydrocarbons in bricklined furnaces or other refractory furnaces. There have been some attempts to extract some of the heat values and chemical values by heat exchange and aqueous scrubbing of the combustion gases which are emitted from the refractory furnace. It is the field of thermal oxidation of halogenated hydrocarbons to which the present invention most closely pertains. More precisely, the invention pertains to thermally oxidizing halogenated hydrocarbons in such a manner that the heat of combustion and the halogen values in the combustion product are recovered, thus salvaging valuable energy and chemical values. It is an object of the present invention to provide for improved disposal of halogenated hydrocarbons by employing thermal oxidation. It is a further object to provide for combusting of halogenated hydrocarbons in such a manner that pollution of public waters and the atmosphere is abated. It is also an object to provide for combusting of halogenated hydrocarbons in such a manner that valuable energy and chemical values are recovered. Another object is to provide a horizontal fire-tube boiler which has been modified so as to withstand the highly corrosive gases from the thermal oxidation of halogenated hydrocarbons for extended periods of time. These, and other objects, are attained by performing the combustion (thermal oxidation) of halogenated hydrocarbons in accordance with the present invention. SUMMARY OF THE INVENTION It has now been found, surprisingly and unexpectedly, that halogenated hydrocarbons can be burned, generally along with a supplemental fuel, directly in the water-cooled combustion chamber of a horizontal fire-tube boiler and that the intense corrosion of the water-cooled metal surfaces in contact with the hot combustion gases which one would expect to get are substantially avoided by carefully controlling the pressure of the saturated steam which is produced in the boiler. Corrosion of other boiler surfaces which are contacted by the hot corrosive gases, and which are not water-cooled, are either constructed of corrosion-resistant material, e.g. nickel or nickel alloy, or else are protected by insulation which keeps the metal surfaces in the desired temperature range at which corrosion is substantially minimized. In its broadest sense the present invention comprises the combustion (thermal oxidation) of halogenated hydrocarbon fuels directly in a modified horizontal fire-tube boiler wherein the heat of combustion is transferred through the metal walls directly into water to make saturated steam and to substantially cool the combustion gases. Preferably, the combustion gases are then passed into contact with liquid-absorbents, e.g., water-scrubbers, to recover halogen values. As used herein, the terms "halogenated hydrocarbon" and "halogenated hydrocarbons" refers to single chemical entities or to mixtures of various halogenated hydrocarbons. The halogenated hydrocarbons may be either liquid or gaseous or both. DETAILED DESCRIPTION OF THE INVENTION Halogenated hydrocarbons are thermally oxidized to gaseous products CO 2 , H 2 O, HX (X=halogen), and some free halogen by being burned in an excess of air in a horizontal fire-tube boiler in which water is directly heated to form useable saturated steam and, preferably, the halogen values are collected from the exit gases by an aqueous scrubber. The fire-tube boiler is substantially of a conventional design, but since such conventional fire-tube boilers are not normally intended for use with highly corrosive fuels, it has been found to be advantageous to employ corrosion resistant surfaces at certain places in the boiler. The fire-tube boiler comprises, basically, a boiler section, a front-end section, and a rear section. The boiler section is essentially a horizontally-positioned shell and tube heat-exchanger. This heat-exchanger comprises a shell having its ends closed with tube-sheets. Extending between and communicating through the tube-sheets are a plurality of tubes. One of the tubes is a relatively large-diameter tube, herein called combustion chamber or furnace, and a plurality of smaller tubes, herein called return-tubes. The front-end section, sometimes referred to in the industry as a front-end door or front door, can, conveniently, be swung open or removed, even partly, to expose the front tube-sheet of the boiler section and allow inspection or maintenance to be performed. The front-end section contains the feed means for transmitting air, supplemental fuel, and halogenated hydrocarbon fuel into the burner which is positioned at about the front-end of the combustion tube. The front-end section may contain baffles, as needed, to cause flow of hot gases entering it to flow back through the fire-tube boiler through a different set of return-tubes. The rear section which, conveniently, can be swung open, may also contain baffles, as needed, to cause the flow of hot gases to flow back through the fire-tube boiler through a different set of return-tubes. The rear section may, conveniently, contain one or more ports or sight glasses for inspection or observation purposes. The inner surfaces of the rear section may be lined with a refractory material or other such insulation which will help prevent heat losses and help protect the metal from the hot, corrosive gases. Optionally, the rear section may be water-cooled by having water circulate between an inner wall and the outer wall or by having water flow through tubes which are juxta-positioned with the inside of the rear section wall. Operation of the process is performed by mixing air, supplemental fuel (as needed), and halogenated hydrocarbon to provide a combustible mixture to the combustion chamber. The mixture is then burned in the combustion chamber. The ratio of supplemental fuel/halogenated hydrocarbon is adjusted to maintain flame stability and high halogen conversion to HX. The amount of supplemental fuel can vary from 0 to about 95% of the total heat input, depending on the heating value and the uniformity of the halogenated hydrocarbon which is being burned. The higher the heating value of the halogenated hydrocarbon, the less supplemental fuel is needed. The water flow through the fire-tube boiler is adjusted to maintain a water level covering all the tubes; it is critical to keep all the tubes submerged to prevent their overheating. It has been found that corrosion is held to a surprisingly low minimum by operating in a manner to produce saturated steam at a pressure in the range of about 150 to about 275 psig., even when the fire-tube boiler is constructed of relatively inexpensive metals, such as carbon steel which is commonly and conventionally used to construct ordinary boilers. In this steam pressure range, the water in the boiler is maintained at a temperature in the range of about 186° to about 210° C. and this, along with maintaining scale-free metal surfaces on the water side of the boiler, keeps the walls of the furnace, return-tubes and tube-sheets which are exposed to the hot corrosive gases, at about 200° C. to about 250° C. If the steam pressure is allowed to drop below about 150 psig the walls of the furnace, return-tubes, and tube sheets can cool down to the point (downwards from 200° C.) at which accelerated corrosion is encountered. On the other hand, if the pressure is allowed to climb upwards much above 275 psig, the walls of the furnace, return-tubes, and tube-sheets can approach 300° C. or more (especially if any scale has formed) and severe corrosion may be encountered. It is essential that care be taken to assure that the water in the boiler be non-scale-forming so as to substantially avoid formation of scale on the water side of the return-tubes, tube-sheets and combustion chamber. If significant amounts of scale accumulate on these surfaces, heat transfer through these metal walls is adversely affected and the resulting higher wall temperature on the combustion gas side of the walls will cause severe corrosion rates. Persons skilled in the art of boiler water control are aware of the various water treatments which are customarily used for prevention of scale. The exact nature of any scale-inhibitors or other means used for avoiding scale formation is not especially critical. Obviously, ingredients in the water which are corrosive or will cause substantial oxidation of the metal surfaces should be avoided or inhibited. The expression "fire-tube boiler" as used herein refers to commonly used and well-known boilers which have water-cooled combustion chambers and which are called "stationary, horizontal, internally-fired, fire-tube boilers." These boilers are available commercially and can be built, or modified, to be multi-pass, e.g., two-pass, three-pass, four-pass, or more passes. The expression "pass" refers to the travel of the combustion gases through one or more tubes in one direction; a second "pass" occurs when the hot gases travel in the reverse direction through one or more other tubes. In multiple-pass boilers, the flow of gases in each "pass" is through one or more tubes not used in another "pass". FIG. 1 depicts a cross-section view, not to scale, showing the principal features of a horizontal fire-tube boiler. FIG. 2 depicts an end-view, not to scale, of a fire-tube boiler tube-sheet with end views of the combustion chamber and return tubes depicted. FIG. 3 is a flow-sheet diagram, not to scale, showing a generalized view of a fire-tube boiler and two scrubbing units, with appropriate piping, for halogen recovery. A common embodiment of a fire-tube boiler, modified according to the present invention, is defined, generally, by reference to FIG. 1 which is a cross-sectional view depicting the essential main parts of the boiler, as a boiler having a boiler section (1), a front-end section (2), and a rear section (3). The boiler section comprises a horizontal combustion chamber (4) in parallel alignment with a plurality of return-tubes (5), said combustion chamber and return-tubes being positioned within said boiler section, terminating at the tube-sheets (6) and (8) at the ends of the boiler section and communicating with the space contained within (3), said space within (3) being designated as (7). The other ends of the return-tubes and combustion chamber terminate at tube-sheet (8) and communicate with the space contained within (2) said space within (2) being designated, generally, as (9). A supplemental fuel, air, and halogenated hydrocarbon feeder device (denoted generally as 10) communicates from the supplemental fuel, air, halogenated hydrocarbon supply lines through front end section (2) and through space (9) into combustion chamber (or furnace) (4). Conveniently, there is a sight glass (11) through rear section (3) which allows one to observe the burning in the combustion chamber. Also, conveniently, there is a thermocouple (12) protruding through rear section (3). The interior wall surface (14) of rear section (3) is conveniently lined with refractory material or high-temperature insulation (13). The external wall surface (14a) may be water-cooled by, e.g., water conduits (not shown) or may be protected against the vagaries of weather and against loss of heat by refractory or insulation material (13a). The wall defining section (3) should be protected against contact with corrosive agents, e.g., HCl. Preferably the amount of insulation used at (13) and (13a) is selected on the basis of keeping the wall in the range of about 200° C. to about 250° C. during the combustion of halogenated hydrocarbon. The space within rear section (3), which is designated as (7) may be divided into two or more separate spaces, if desired, by using one or more corrosion-resistant baffles (15) which direct flow of hot gases back through return-tubes not yet traveled. In space (7), at the area at which hot combustion gases from the combustion chamber impinge on the inner surface of the insulation or refractory (13), there is preferably installed a corrosion-resistant material (15a) which is selected for its ability to withstand hot, corrosive material over a substantial length of time and also to help in avoiding heat losses. Many refractories are known which will withstand the hot, corrosive gases encountered in the present invention. Within section (2) there may be, if desired, one or more baffles (32) to direct the flow of hot gases through the appropriate return-tubes. The space within section (2) may be divided into two major spaces (9) and (9a) by the use of a barrier wall (17) having a corrosion-resistant or insulated surface (31) and an insulated surface (16) which serve to keep the wall (17) in the desired temperature range during operation. The inner major space (9), which may contain one or more baffles (32) carries the hot gases which flow from space (7) until the gases eventually flow from the exit (18) provided and on to further processing. Depending on the number of passes, exit (18) may communicate with space (7) instead of space (9). The feeder device (10) communicates through spaces (9a) and (9) into the combustion chamber (4). The space within the feeder device does not communicate directly with space (9). Passages (not shown) in the walls of the feeder device receive air from space (9a). Air may be supplied to space (9a) by means of forced air (19) or by being drawn in with induced draft attained by drawing exit gases out through exit (18). Damper means (not shown) may be employed on the feeder device (10) to regulate the amount of air reaching the burner. In one embodiment of an actual operation atomizing air (21) and halogenated hydrocarbon (22) are mixed in a feed line approximately centrally located within feeder device (10) and are thereby supplied to the atomizing nozzle (23) of the feeder device. Supplemental fuel gas (26) is fed to the pilot (25) and/or through the vapor inlet pipe (24) and through openings (30) where it mixes with air (19) in the region of the nozzle (23). Chlorinated hydrocarbon vapors may also be conveniently fed to the burner through pipe (26). The mixture of air, fuel and halogenated hydrocarbon is mixed and burned in combustion chamber (4), the hot gases passing into one portion of space (7), then through a plurality of return-tubes (5) to one portion of space (9), then through a plurality of return-tubes (5) into another portion of space (7), then back to another portion of space (9) where it then exits (18) the boiler into other processing equipment (not shown in FIG. 1). During operation non-scaling water is supplied to the boiler so as to completely surround the return-tubes and the combustion chamber. The combustion is regulated by adjusting the flow of fuel and/or air so as to maintain excess oxygen in the exit gases and to keep the temperature of the gases leaving the combustion chamber space near thermocouple (12) at not more than about 1100° C. and to maintain a saturated steam pressure in the range of about 150 to about 275 psig which gives a boiler water temperature in the range of about 186° to about 210° C. The desired water level is maintained by regulating the flow of make-up water. The desired pressure is maintained by regulating the flow of saturated steam from the boiler at steam vent (27) and/or by regulating the fuel mixture being fed to the combustion chamber. FIG. 2 depicts an end-view of a fire-tube boiler section (1) and shows a plurality of return-tubes (5) communicating through tube-sheet (6) or (8). Combustion chamber (4) is considerably larger in diameter than the return-tubes. Even though combustion chamber (4) is depicted as a straight-wall tube, practitioners of the art of fire-tube boilers will realize that the combustion chamber walls may be convoluted. It will also be readily apparent that the positioning of baffles (15) and (32) should be done commensurately with the contracting volume of the gases as they cool during flow through the return-tubes. That is, the total cross-sectional area of the first "set" of return-tubes should be less than the cross-sectional area of the combustion chamber; the second "set" of return-tubes should have a total cross-sectional area less than the first "set" and so on. Thus, the gas velocity from one "pass" to another is kept high so as to keep heat transfer rates efficient. In a typical operation in the depicted apparatus, the temperature profile in a boiler such as depicted in FIG. 1 will be: about 2100°-1600° C. (average) in the combustion chamber (4); about 500°-1100° C. in the area of thermocouple (12); about 280°-400° C. in first space (9), measured by thermocouple (12a); about 250°-320° in space (7), measured by thermocouple (12b); and about 215°-260° C. in second space (9), mesured by thermocouple (12c) as the gases leave through exit (18). FIG. 3 is a flow-sheet diagram depicting an embodiment of the overall process wherein supplemental fuel (24), air (21) and halogenated hydrocarbon (22) are burned in a fire-tube boiler (1), combustion gases which exit are carried by conduit (18) to a liquid-contactor, e.g., an aqueous scrubber (30), through a separator (31) from which aqueous solution is drawn (43), then through conduit (18a) to a second aqueous scrubber (30a), on through a second separator (31a) from which aqueous solution is drawn (32a), then through a conduit (18b) to a vent or other suitable processing. Water (40) and/or other appropriate aqueous scrubbing liquid, e.g., dilute caustic (40a) is supplied to scrubbers (30) and (30a) and aqueous solution is drawn from the separators at a rate commensurate with the flow of aqueous solution from the scrubbers. A blower or other appropriate gas-moving device (50) may be conveniently employed to enhance the flow of the combustion gases through the system and to safeguard against leaks of corrosive materials from the system in the event a leak occurs. By pulling the combustion gases through the system, a positive pressure is avoided, and in fact, a slightly reduced pressure within the system may be attained. Steam exits the boiler through vent (27) and is used elsewhere. The supplemental fuel used in the burning process may be any of the lower hydrocarbons ordinarily employed as fuels, such as, methane, ethane, propane, butane, isopropane, isobutane, pentane, hexane, heptane, octane, isoctane or mixtures of these or may be L.P.G. (liquified petroleum gas). Any aliphatic hydrocarbon having 1-12 carbons, especially 1-4 carbons, are suitable. The most ordinary fuel and most preferred as supplemental fuel, is natural gas. Virtually any vaporizable or atomizable hydrocarbon may be employed, such as gasoline, kerosene, petroleum ether, fuel oil, No. 2 fuel oil, No. 4 fuel oil, Bunker C oil, etc. Clean-burning fuels or clean-burning mixtures of fuels are preferred. The "halogenated hydrocarbon" as used herein includes hydrocarbons which have chlorine, bromine, or iodine values. Usually the halogenated hydrocarbon desired to be burned according to the present invention is a waste stream of chlorinated hydrocarbon or mixture of chlorinated hydrocarbons. It is within the purview of the present invention to combine various streams containing chlorinated, brominated, or iodinated organics for burning. Fluorinated organics may also be mixed in for burning, but since fluorine values are normally so highly corrosive as to substantially limit the life of the equipment, it is best to hold the maximum amount of organic fluorides to a small percent. The present invention also contemplates that the air supplied to the burner may contain vapors of halogenated hydrocarbons, such as vinyl chloride and others, which may be swept from an area for protection of personnel in the area. The following examples are meant to illustrate operation of some embodiments of the present invention. The scope of the invention is restricted only by the attached claims. EXAMPLES Various halogentaed hydrocarbons were burned in a 4-pass fire-tube boiler substantially in accordance with the above teachings. The data are shown in Table I. The supplemental fuel was natural gas. The calculated average temperature in the furnace was the arithmetic average of measured outlet temp. and theoretical flame temperature, based on the measured temperature at the thermocouple (12) positioned at the end of the first pass. The steam pressure was maintained in the range of about 150 to about 275 psig and the water in the boiler was in the range of about 186° C. to about 210° C. The water level was maintained so as to completely cover the uppermost return-tubes. During operation a blower at the vent stack operated to pull excess air through the burner, through two aqueous caustic scrubbers in series and out through the vent stack. The RCl's (halogenated hydrocarbons) in the vent gas were determined by entrapment in heptane followed by electron capture gas chromatography analysis except for Run Nos. 9, 11, and 12. Run Nos. 9 and 11 were determined by total organic chloride analysis of RCl's trapped in heptane and Run No. 12 was determined by trapping RCl's on activated charcoal, extracting with carbon disulfide and analyzing by hydrogen flame gas chromatography. The RCl feed streams in Table I are identified as follows (percents are by weight): A. Commercial grade propylene dichloride. B. Waste mixture of about thirty different RCl's with elemental analysis of 32.8% C, 63.2% Cl, 4.0% H. C. Waste mixture of 6 RCl's containing mostly dichloroisopropyl ether with elemental analysis 40.2% C, 43.6% Cl, 6.7% H, 9.5% O. D. Waste mixture of about 23 RCl's containing mainly trichloroethane, trichlorobromopropane, and pentachloroethane; also contained hexachloroethane, hexachlorobutane, hexachlorobutadiene and had elemental analysis 17.2% C, 77.1% Cl, 4.6% H, 1.1% Br. E. Waste mixture of about 13 RCl's containing mainly hexachlorobutadiene and symmetrical tetrachloroethane; also contained hexachloroethane and hexachlorobenzene and had elemental analysis of 17.5% C, 81.6% Cl, 0.9% H. F. Waste mixture of about 14 RCl's containing mainly propylene dichloride, hexachloroethane, sym-tetrachloroethane; also contained hexachlorobenzene and had elemental analysis 24.5% C, 72.3% Cl, 3.2% H. G. Waste mixture of about 5 RCl's containing mainly sym-tetrachloroethane, hexachloroethane, hexachlorobutadiene; 1.9 wt. % iron as Fe, 2.7 wt. % ash at 950° C.; elemental analysis 15.61% C, 82.96% Cl, 1.46% H. It will be readily apparent to persons skilled in the art that other embodiments and modifications in the process and in the apparatus may be made without departing from the present invention. TABLE I__________________________________________________________________________Furnace Parameters Feed to Boiler Calc. T.C.* Residence RCL in RCL ChlorineRun RCL Feed Lb./Hr. Ave. Temp. Temp. Time Outlet Gas Conversion ConversionNo. Stream RCL CH.sub.4 (° C.) (° C.) (Sec.) (wt. ppm) (%) To HCl (%)__________________________________________________________________________1 A 66.5 9.6 1361 870 0.36 0.083 99.99++ 97.92 B 74.0 17.0 1327 888 0.27 0.076 99.99++ 98.93 B 64.8 17.3 1312 870 0.28 0.128 99.99++ 98.94 C 88.0 8.5 1423 1050 0.24 0.234 99.99++ 98.45 C 101.5 6.0 1374 990 0.22 0.203 99.99++ 98.36 D 159.4 14.7 1291 790 0.33 8.06 99.99++ 93.47 D 100.0 31.7 1339 875 0.24 1.57 99.99++ 97.78 E 67.3 34.0 1293 837 0.25 1.13 99.99++ NA**9 E 67.3 34.0 1293 837 0.25 0.53 99.99++ NA10 F 96.6 19.1 1333 923 0.26 8.8 99.99++ NA11 F 96.6 19.1 1333 923 0.26 1.98 99.99++ NA12 G 75.1 26.4 1362 945 0.29 14.7 99.98++ 99.3__________________________________________________________________________ *T.C. Temp. is measured by the thermocouple at end of first pass. **NA: Not Analyzed

Halogenated hydrocarbon materials are burned in an internally-fired horizontal fire-tube boiler and the heat of combustion directly produces saturated steam. Halogen values may be recovered from the combustion gases, e.g., by being absorbed in water. Thus halogenated hydrocarbon material which may need to be disposed of, is beneficially converted to energy and useful product.

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a division of application Ser. No. 10/815,829 filed Apr. 2, 2004, now U.S. Pat. No. 7,216,853, which claims the benefit of U.S. Provisional Patent Application Ser. No. 60/459,965, filed Apr. 4, 2003. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to solid barriers, sound partitions, privacy fences and, more particularly, to barrier systems that may be attached to cement anchored posts from a preexisting cyclone fence. 2. Description of Related Art Many homeowners have standard cyclone fences around their yards. A standard cyclone fence can keep unwanted visitors off of the property. A cyclone fence, however, does not provide much privacy for the user. The structure of a cyclone fence allows outsiders to look through the fence and see what is located in the yard. There are several common types of privacy fences that prevent outsiders from looking into the area surrounded by the fence, thus providing the user with a heightened degree of privacy. Examples of common fences are described in the following patent documents. U.S. Pat. No. 4,266,757 issued to Kirkwood discloses a corner fence post clip. The invention is a device for attaching horizontal fence rails or a fence panel to tubular fence post. The device is an attachment member equipped with a top section in the shape of a hook that engages the open top of a tubular fence post. The attachment member is further equipped with a plurality of U-shaped clips that are adapted to receive the fence rails or panels. U.S. Pat. No. 5,402,988 issued to Eisele discloses a portable fence. The portable frame comprises a frame supporting a fencing net. A base element engages the bottom of the fence and holds it in a vertical position. A collapsible mechanism attaches the base element to the frame and permits the base to disengage from the frame on application of a predetermined force to the frame. U.S. Pat. No. 5,529,289 issued to Lancer, Sr. discloses a plastic multi-functional privacy fence. The fence is comprised of vertical slats that interlock along each adjacent edge to create an effective barrier against intrusions. The vertical slats are interlocked at mating seams and are attached to a frame that provides rigidity to the fence. The frame is comprised of horizontal rails that are attached by fasteners to vertical posts that are anchored to the ground. U.S. Pat. No. 5,556,080 issued to Vise discloses a fence system that includes a frame and a plurality of panels attached to the frame. The frame includes vertical posts and non-vertical rails. Adjacent panels are positioned on the frame to provide an overlapping area. A reinforcing member is positioned on the overlapping area. A fastener extends through the overlapping area of two panels to attach the panels to the frame. U.S. Pat. No. 5,649,689 issued to Wilson discloses a flexible and detachable fence apparatus. The fence comprises fence panels for providing a barrier, posts for vertically supporting the fence panels and posthole inserts for securing the fence to the ground. The fence panel is equipped with a connector means for securing the fence panel to the posts. The posts have receptacle means for receiving and interlocking with the connector means of the fence panel. Preferably, the connector means and receptacle means provide a mechanism for detachably securing the fence panel to the posts. U.S. Pat. No. 6,152,428 issued to Simioni discloses a fence system including a plurality of wooden posts encased in sections of vinyl eaves, a frame constructed of galvanized track and stud elements, J-strips located on each end of the frame abutting the posts, and vertical panels formed of vinyl siding connected to each other and to the frame between the posts. U.S. Pat. No. 6,260,828 to English comprises a prefabricated interlocking fence post. The interlocking fence post includes slots that slidably receive adjoining fence panels. A cap may be secured to the top of the post after the panel is slid into position. An L-shaped bracket on the outside of the post slot may be rigidly clamped to provide a variable-height attachment site for horizontal support rails. The problem with existing privacy fences is that they are usually difficult to assemble. Another problem with the privacy fences occurs when a homeowner already has a preexisting cyclone fence in place and wants to replace it with a privacy fence. Normally the preexisting fence must be completely disassembled and removed before the new fence can be assembled. Then the homeowner must erect the new fence. This is both time-consuming and expensive. It would be much more efficient to adapt the existing fence into a privacy fence. Therefore what is needed is a privacy fence system that can reuse the existing fence posts from the previous fence. What is further needed is a privacy fence system that can easily be assembled by a single person with common hand tools. What is still further needed is a privacy fence system that can adapt to existing irregularities in placement of existing poles. Finally, what is still further needed is a privacy fence system that can be non-destructably disassembled and moved. None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed. SUMMARY OF THE INVENTION The present invention is a privacy fence system that is attached to the cement anchored posts of a preexisting cyclone fence. When a homeowner has a cyclone fence installed in his yard the chain mesh body portion may be removed while leaving the fence posts in their original position. The present privacy fence system provides a way to install a new privacy fence without having to remove the preexisting posts and replace them with new posts. The present privacy fence system is made up of a plurality of interconnected fence panels where a first end of each of the fence panels is adapted to fit the fence panels to an existing fence post. The first end of each of the fence panels further comprises an attachment releasably securing adjacent fence panels to one another around an existing fence post. The first end of each of the fence panels comprises a post-receiving cavity. The post-receiving cavity allows adjacent fence panels to fit around a preexisting fence post. The attachment then releasably secures the adjacent fence panels to one another while fit to the fence post. The second end of each fence panel is adapted to releasably secure each fence panel to another adjacent fence panel, without fitting the adjacent fence panels around a fence post. The second end of each of the fence panels is attached to another adjacent fence panel by a plurality of molded pop rivets. The pop rivet securing allows the adjacent fence panels to overlap one another when they are attached. It is usually necessary to provide a structure for overlapping the adjacent panels to compensate for irregularities of previously misplaced fence posts. The privacy fence system provides both linear fence panel segments and corner fence panel segments. The fence panels are made from a lightweight, one piece, molded construction. The fence panels may be non-destructably disassembled so that the privacy fence system may be removed and installed in another location. In one embodiment of the present invention the attachment means comprises an interlocking mechanism. The interlocking mechanism on a first fence panel comprises a plurality of connector slots. The interlocking mechanism on an adjacent fence panel comprises a plurality of connector projections. The connector slots are adapted to receive the connector projections of an adjacent fence panel. When the connector projections are received into the connector slots of an adjacent fence panel, the fence panels are releasably secured to one another around the existing fence post. In a particular embodiment of the interlocking design, the interlocking mechanism on each fence panel provides both connector slots and connector projections. The top half of each fence panel interlocking mechanism comprises either connector slots or connector projections. The bottom half of each fence panel interlocking mechanism comprises either connector slots or connector projections. For example, a first fence portion has connector projections on the top half of the interlocking mechanism and connector slots on the bottom half. The adjacent fence portion has connector slots on the top half of the interlocking mechanism and connector projections on the bottom half. The first fence panel is lifted to the mid point of the adjacent fence portion and then it is slid into place, connecting the two adjacent fence portions. The alternating configuration of the interlocking mechanism in this embodiment provides a more secure connection and easier assembly. In the preferred embodiment of the present invention the attachment means comprises a threaded fastener. The fence post receiving slots fit the ends of adjacent fence panels around a fence post. The threaded fastener extends through adjacent ends of the adjacent fence panels, releasably securing said adjacent fence panels to one another around the existing fence post. The privacy fence system optionally includes a fence post cap. The fence post cap is a rain cap that has a circular base and a plurality of sidepieces forming a pyramidal top portion. The circular base is equipped with a snap-in retainer lip and a compression relief slit that allows the fence post cap to be releasably secured to the top of the fence posts. Accordingly, the instant invention provides a privacy fence system that can be attached to and reuse the existing fence posts from a previously installed cyclone fence. The system can easily be assembled by a single person with common hand tools and is adaptable to existing irregularities in the placement of the preexisting poles. The system can be non-destructably disassembled and moved. The present invention presents improved elements and arrangements thereof in an apparatus for the purposes described which are inexpensive, dependable and fully effective in accomplishing their intended purposes. A clear understanding of the invention will become readily apparent upon further review of the following specification and drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an environmental, perspective view of a privacy fence system according to the present invention. FIG. 2 is an enlarged-scale perspective view of a linear segment of a first embodiment of the privacy fence system depicting adjacent fence panels connected to an existing fence pole. FIG. 3 is an exploded perspective view of a linear segment of the first embodiment of the privacy fence system depicting adjacent fence panels and the existing fence post. FIG. 4 is a perspective view of a corner segment of the first embodiment of the privacy fence system depicting adjacent corner fence panels attached to the existing fence post. FIG. 5 is a perspective view of a linear segment of the preferred embodiment of the privacy fence system depicting adjacent fence panels connected to an existing fence post. FIG. 6 is a perspective view of a corner segment of the preferred embodiment of the privacy fence system depicting adjacent corner fence panels attached to the existing fence post. FIG. 7 is a top view of the connection point between adjacent corner fence panels according to the preferred embodiment of the privacy fence system depicting the location of the threaded screw through the fence panels. FIG. 8 is a side view of a horizontal corrugated fence panel according to the present privacy fence system. FIG. 8A is a side view of a vertical fence panel design according to the present privacy fence system. FIG. 9 is a perspective view of a post cap according to the present privacy fence system. FIG. 10 is a side view of the post cap depicted in FIG. 9 . FIG. 11 is a top view of the post cap depicted in FIG. 9 . FIG. 12 is a perspective view of a fence panel according to an alternate embodiment depicting the alternating interlock mechanism. FIG. 13 is a perspective view displaying the overlapping connection of two adjacent fence panels of a horizontal corrugated design. FIG. 13A is a perspective view displaying the overlapping connection of two adjacent fence panels of a vertical panel design. FIG. 14 is a perspective view of a molded linear segment of a horizontal corrugated panel of the preferred embodiment of the privacy fence system. FIG. 15 is a perspective view of a molded linear segment of a vertical panel the privacy fence system. FIG. 16 is a perspective view displaying the fence panel of FIG. 13A and FIG. 15 . Similar reference characters denote corresponding features consistently throughout the attached drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is a solid barrier system, for use as a privacy fence, which fence replaces an existing cyclone fence while reusing the preexisting fence posts of the cyclone fence. The present privacy fence system allows the user to remove the wire mesh fencing from an installed cyclone fence but leave the cement anchored fence posts in their original places. The privacy fence is adapted to fit onto the preexisting fence posts. The solid barrier system is not limited to the embodiments discussed below but may also be used for any solid barrier or sound partition. FIG. 1 depicts an environmental, perspective view of a privacy fence system 10 according to the present invention. The privacy fence system 10 comprises a plurality of fence panels with at least one end of the fence panels being adapted to fit around the preexisting fence posts. FIG. 2 depicts a perspective view of a linear segment of a first embodiment of the privacy fence system 10 depicting adjacent fence panels connected to an existing fence post. Adjacent fence panels 30 and 40 are fit around a fence post 20 . The seam 22 between the fence panels 30 , 40 defines the connection point of the adjacent fence panels 30 , 40 around the fence post 20 . A first end of each fence panel 30 , 40 is adapted to securely fit around the fence post 20 . The distal end 42 of the fence panel 40 is not adapted to fit around a fence post 20 . The distal end 42 is adapted to releasably attach to the distal end of another adjacent fence panel. FIG. 3 is an exploded, perspective view of the linear segment of the privacy fence system 10 depicting the fence panel attachment means according to one embodiment of the present invention. A first end 34 , 44 of each fence panel provides respective post receiving slots 36 , 46 , which slots are adapted to fit the fence panels 30 , 40 around the fence post 20 . The first ends 34 , 44 of each fence panel further comprise an attachment means for releasably securing adjacent fence panels 30 , 40 together around the existing fence post 20 . As shown in FIG. 3 , the attachment means comprises an interlocking attachment mechanism. The interlocking attachment mechanism on panel 30 is a plurality of connector projections 35 , 37 . The interlocking mechanism on an adjacent fence panel 40 is a plurality of connector slots 45 , 47 , which slots are adapted to receive the connector projections 35 , 37 of panel 30 . To connect the fence panels, the first fence panel 30 is raised above the top of the adjacent fence panel 40 so that the connector projections 35 , 37 are aligned with and can slide into the connector slots 45 , 47 . Only the first ends 34 , 44 of each fence panel are equipped with the attachment means. The distal ends 32 , 42 of each fence panel are adapted to be secured to the distal ends of other adjacent fence panels. FIG. 4 is a perspective view of a corner segment of the first embodiment of the privacy fence system 10 depicting adjacent corner fence panels 30 , 40 attached to the existing fence post 20 . The attachment means for the corner fence panels 30 , 40 is identical to that of the linear segments discussed above. The only difference between the corner and linear segments is the position of the attachment means. At a corner fence post, the attachment means are positioned at a different angle so that the adjacent fence panels 30 , 40 provide a corner for the fence system 10 . FIG. 5 is a perspective view of a linear segment of the preferred embodiment of the privacy fence system 10 depicting adjacent fence panels 30 , 40 connected to an existing fence post 40 . In the preferred embodiment each fence panel 30 , 40 is equipped with an attachment means for releasably securing the adjacent fence panels 30 , 40 around a fence post 20 . The attachment means in the present embodiment comprises a plurality of threaded fasteners 50 . FIG. 6 is a perspective view of a corner segment of the preferred embodiment of the privacy fence system 10 depicting adjacent corner fence panels 30 , 40 attached to the existing fence post 20 by the threaded fasteners 50 . The threaded fasteners 50 are positioned along the entire height of each fence panel 30 , 40 . The threaded fasteners 50 are preferably conventional 2 inch wood screws. The fasteners, however, are not limited to conventional wood screws but may take the form of any appropriate fastener. FIG. 7 is a top view of the connection point 22 between adjacent corner fence panels 30 , 40 according to the second embodiment of the privacy fence system 10 depicting the location of the threaded screws 52 , 53 through the fence panels 30 , 40 . The adjacent fence panels 30 , 40 are fitted to a fence post 20 in the same manner as was described in the earlier embodiments. Once the adjacent panels 30 , 40 are positioned around the fence post 20 they are releasably secured by the plurality of threaded fasteners 50 . Each of the holes created by threaded fasteners 50 is filled with a respective decorative plug 54 , 55 . FIG. 8 is a side view of a fence panel 40 according to the present privacy fence system 10 . The panel surface is configured to define horizontal corrugations therealong. The corrugated surface provides additional support for the fence panel 40 making it sturdier than if the panel 40 were flat. FIG. 8A is illustrative of an embodiment wherein the fence panel 40 a has a flat, vertical configuration and is provided with a vertical reinforcing strut 40 b. The privacy fence system 10 optionally comprises a plurality of fence post caps located on the top of the fence posts. FIG. 9 is a perspective view of a post cap 60 according to the present privacy fence system. FIG. 10 is a side view of the post cap depicted in FIG. 9 . FIG. 11 is a top view of the post cap depicted in FIG. 9 . The fence post cap 60 is a rain cap that has a circular base 64 and a plurality of sidepieces 67 that come to a point 69 forming a pyramidal top portion. The circular base is equipped with a snap-in retainer lip 66 and a compression relief slit 68 that allows the fence post cap 60 to be releasably secured to the top of the fence posts 20 . Side members 62 , 63 fit around the top portion of each fence panel 30 , 40 and hold the fence post cap 60 in place. FIG. 12 depicts an alternate embodiment of the interlocking mechanism. In this embodiment the first end 94 of a fence panel 90 is equipped with connector slots 97 and connector projections 98 . The connector slots 97 are located on the top half portion 95 of the first end 94 of the panel 90 . The connector projections 98 are located on the bottom half portion 96 . An adjacent fence panel (not depicted) would be equipped with connector projections on the top half portion of the panel and connector slots on the bottom half portion of the panel. The interlocking mechanism depicted in FIG. 12 provides a more secure attachment of the adjacent fence panels around the fence post 20 . The present embodiment also allows for easier assembly of the privacy fence system 10 . In the present embodiment the fence panel 90 only has to be raised to half of the height of the adjacent fence panel. The projections 96 on each fence panel then slide into the slots 97 of the adjacent panel. FIG. 13 is a perspective view displaying the overlapping connection of two adjacent fence panels 40 , 80 of the horizontal corrugated design. The distal end 42 of fence panel 40 is not adapted to fit around a fence post 20 . The distal end 42 of the fence panel 40 is adapted to be releasably secured to the distal end 82 of another adjacent fence panel 80 . The fence panel 40 overlaps the adjacent fence panel 80 and is releasably secured to the adjacent panel 80 by an overlapping securing means. The overlapping securing means is preferably a plurality of typical pop rivets, which rivets are located along the entire height of each fence panel. The pop rivets are located on the fence panels at position 70 . The overlapping securing means allows the length of the linear segments to be adapted to irregularities in the placement of the original fence posts. The adjacent fence panels 40 , 80 can be altered in the distance that they overlap to compensate for fence post misplacements. If two of the original fence posts were positioned too close to one another, the adjacent fence panels 40 , 80 will overlap a greater distance to effectively shrink the privacy fence system to accommodate the misplacement of the posts. In FIG. 13 a, the overlapping feature is illustrated in fence panels 40 a and 80 a having a vertical design. FIG. 14 is a perspective view of a molded linear segment 100 of the privacy fence system. The segment 100 is formed by pouring material into a mold to form the shape of the segment. The front portion 102 of each segment 100 includes a plurality of mold receiving slots 106 . The mold receiving slots 106 receive projections inside of the mold that form the shape of the segment 100 . FIG. 15 is a perspective view similar to FIG. 14 but illustrating the flat panel design as discussed above. FIG. 16 is a perspective view depicting the fence panel as discussed separately in FIGS. 13A and 15 . The fence panels are preferably made from a light-weight, one piece, molded construction. The fence panels are preferably six feet high and have a length of 67 inches. The height of six feet allows for ten pop rivets to be positioned along the distal end of the fence panel. These dimensions, however, are only illustrative and are not meant to limit the present privacy fence system. It is to be understood that the present invention is not limited to the sole embodiments described above, but encompasses any and all embodiments within the scope of the following claims.

A solid barrier, sound partition and privacy fence system including a plurality of interconnected fence panels whose ends are adapted to fit to pre-existing fence posts. The ends of the fence panels include attachment structure for releasably securing adjacent fence panels to one another around an existing fence post. The privacy fence system provides for installing a privacy fence that reuses existing cement anchored fence posts. The attachment structure may comprise either an interlocking fastening device or a threaded fastening device. The privacy fence may also include an optional fence post cap that is attached to the top portion of the existing poles. Each fence panel is constructed of a lightweight, one piece, molded material.

FIELD OF THE INVENTION This invention relates to a motorized operator for opening and closing an upwardly acting door and, in particular, to an operator having an improved switch mechanism associated therewith to permit optimum control over the door movement. BACKGROUND OF THE INVENTION Persons acquainted with the operation of upwardly acting doors having an electrical operator for effecting door movement are aware that some door operators have a safety switch whereby the direction of door movement is automatically reversed if the door engages an obstruction during movement in its downward or closing direction. This safety feature, as disclosed in U.S. Pat. No. 3,474,317 owned by the assignee of this application, has been provided to prevent damage to equipment and injury to personnel which might result from continued operation of the door. While operators of this type have been commercially acceptable, nevertheless they do possess structural and operational features which have been undesirable either from a cost, maintenance or operational viewpoint. To improve upon operators of this type, U.S. Pat. No. 3,764,875 discloses an operator having a mechanical override system for deactivating the safety switch when the door is within a preselected distance from either its fully opened or fully closed position to prevent reversal of the door movement. While the operator of this patent does possess the ability to deactivate the safety switch, nevertheless this operator is structurally complex and does not possess the degree of flexibility necessary to provide for optimum control over all of the door movements. Accordingly, the objects and purposes of the invention have been met by providing a motorized door operator having improved switch mechanism and circuitry capable of overcoming the problems and achieving the results set forth above. A further object of the invention is the provision of a door operator, as aforesaid, which represents a substantial improvement, both structurally and operationally, over the operators disclosed in the patents mentioned above. A still further object of the invention is the provision of a door operator, as aforesaid, which is fool proof in operation, simple in construction, can be adapted to existing door operating mechanisms, and does not interfere with the normal manual or remote control conventionally utilized for energizing the electrical system. Still a further object of the invention is the provision of a door operator, as aforesaid, which possesses (1) a reversing safety switch for automatically causing upward movement of the door when the door strikes an obstruction during the downward movement thereof, (2) up and down limit switches for deactivating the operator when the door respectively reaches its fully opened and fully closed positions, and (3) up and down cut-off switches for overriding the safety switch when the door is within a preselected distance from its respective fully opened and fully closed position. Another object of the invention is the provision of a door operator, as aforesaid, which incorporates a slide assembly within the switch mechanism for controlling the limit and cut-off switches in a simple yet reliable manner. Other objects and purposes of this invention will be apparent to persons familiar with this type of equipment upon reading the following specification and inspecting the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a broken, elevational view of an upwardly acting door in combination with a motorized door operator embodying the switch mechanism and circuitry of the present invention. FIG. 2 is a bottom view of the structure as appearing in FIG. 1, same being taken substantially along line II--II in FIG. 1. FIG. 3 is a fragmentary view of the switch mechanism according to the present invention. FIG. 4 is an enlargement of the switch mechanism of FIG. 2. FIG. 5 is a fragmentary sectional view taken along line V--V in FIG. 4. FIG. 6 is a sectional view taken along line VI--VI in FIG. 4. FIG. 7 illustrates a portion of the switch mechanism except that the screw and traveling nuts have been eliminated for purposes of illustration. FIG. 8 is a perspective view of the slide assembly. FIG. 9 is a fragmentary sectional view taken along line IX--IX in FIG. 4. FIG. 10 is a diagrammatic sketch of the circuitry associated with the switch mechanism of the invention. FIG. 11 illustrates the manner in which the sliders coact with the limit and cut-out switches. For convenience in description, the terms "upper", "lower", "leftward" and "rightward" will have reference to directions as appearing in the drawings. The word "front" and "rear" will be used to designate the structure appearing on the left and right sides, respectively, of FIG. 1. The words "inwardly" and "outwardly" will refer to directions toward and away from, respectively, the geometric center of the apparatus and designated parts thereof. Said terminology will include the words above specifically mentioned, derivatives thereof, and words of similar import. SUMMARY OF THE INVENTION The objects and purposes of the present invention have been met by providing an operator which includes a reversible electrical motor drivingly connected to the door by an intermediate power transmitting device. A safety switch coacts with the power transmitting device for causing reversal in the rotational direction of the motor during downward movement of the door when the driving force exceeds a preselected maximum. A switch mechanism is associated with the operator and includes a control member in the form of a rotatable screw having first and second nuts mounted thereon. The first nut which controls the door when adjacent its closed position, coacts with a first slide which is adjacent the screw and is slidable relative thereto, whereupon the nut contacts the first slide and causes movement thereof only when the door approaches its closed position. The second nut coacts with a second slide which is slidably disposed adjacent the screw and is also slidable with respect to the first slide. The second nut and second slide have a limited amount of lost motion therebetween. The first and second slides are connected by a slide rod which permits the two slides to move with respect to one another but limits the maximum separation therebetween. The first slide coacts with a first pair of microswitches, one of which functions as the down limit switch for shutting off the motor when the door reaches its fully closed position and the other of which functions as a down cut-off switch for deactivating the safety switch when the door is a preselected distance from its fully closed position. The second slide coacts with a second pair of microswitches which includes an uplimit switch for shutting off the motor when the door is in its fully open position and an up cut-off switch which deactivates the safety switch when the door is within a preselected distance from its fully opened position. DETAILED DESCRIPTION FIGS. 1 and 2 illustrate therein a motor driven door operator 11 which may be manually or remotely controlled for opening and closing an upwardly acting door 12. One such door, which is designed for covering an opening 13 defined above a floor 14, is comprised of several horizontally hinged sections having rollers 16 mounted thereon for engagement with side rails 17 for guiding the movement of the door between a substantially vertical closed position and a substantially horizontal open position. However, the invention can be readily adapted to other types of doors and other patterns of door movement. The operator 11 includes an elongated horizontal beam 18 defined by a pair of guide rails 19 and 21 between which a carriage 22 is supported for movement lengthwise thereof. The carriage 22 is pivotally connected to the upper end of an arm 23, which arm at its lower end is connected to the door 12 by means of an intermediate spring box 24. To permit movement of the carriage 22, the operator 11 includes a reversible electric motor 26 which is drivingly connected by an intermediate belt 27 to an intermediate shaft 28, which in turn is drivingly connected by a chain drive 29 to a main drive shaft 31. The shaft 31 is rotatably supported by bearings 32 and 33 on a housing 34 which is fixed with respect to the stationary beam 18. A driving sprocket 36 is fixed to the shaft 31 and is engaged with an elongated chain 37 which is connected at its opposite ends to the opposite ends of a cable 38, which cable extends around a pulley 39 rotatably supported upon the front end of the beam. Two corresponding ends of the chain 37 and cable 38 are interconnected by mutual engagement with the shuttle 22, as shown in FIG. 2. Accordingly, as the chain and cable are moved around the sprocket 36 and pulley 39, respectively, the carriage 22 is moved lengthwise of the guide rails 19 and 21, whereby the door 12 is moved in either an opening or closing direction. The lengths of the chain 37 and cable 38 are selected so that the chain is always in engagement with the sprocket 36 and the cable is always in engagement with the pulley 39 throughout the full extent of linear movement of carriage 22. To control energization of reversible motor 26, the operator 11 includes a switch mechanism 41 associated therewith, which switch mechanism includes a threaded control shaft 42 which comprises an extension of the main drive shaft 31. Shaft 42 threadably supports a pair of traveling nuts 43 and 44 which have a plurality of closely spaced slots 46 in the peripheral portions thereof. A U-shaped timing bar 47 is pivotally supported on and extends between the sidewalls 48 and 49 of the housing, and is resiliently urged by spring 51 into a pair of aligned slots 46 as formed in the nuts 43 and 44 for preventing rotation of the nuts. Rotation of shafts 31 and 42 thus causes the nuts 43 and 44 to move lengthwise of the shaft. As shown in FIG. 9, the chain 37 engages an idler sprocket 52 supported by a bracket 53 having a safety switch actuating plate 54. Bracket 53 is pivotally mounted on the beam 18 adjacent the switch mechanism 41 for movement around an axis parallel with the drive shaft 31. The bracket 53 is normally urged against a portion of the beam by means of a spring 57. The bracket 53, when urged in opposition to the spring 57 due to an increase in the drive force being transmitted through the chain, causes the plate 54 to engage a switch actuator 58 associated with a normally open safety switch 59 for closing same. Thus, when the door is being moved in a downward direction and strikes an obstruction which interferes with further downward movement, the chain cannot continue to move around the drive sprocket 36, whereby the tension applied by drive sprocket 36 to chain 37 tends to straighten out the bend in the chain where it passes around the idler sprocket 52, so that bracket 53 is swung outwardly against the urging of spring 57. The plate 54 thus engages the switch actuator 58 and causes the safety switch 59 to be closed, thus causing reversal in the rotational direction of motor 26. The above described structure substantially corresponds to the operator disclosed in U.S. Pat. No. 3,474,317, whereby further description of same is not believed necessary. In the present invention, the switch mechanism 41 additionally includes a first pair of normally closed microswitches 61 and 62 having actuators 63 and 64, respectively, associated therewith. Switch 61 functions as an "up" limit switch, whereas switch 62 functions as a "down" limit switch. The limit switches 61 and 62 are controlled by a floating slide assembly 66 which includes first and second sliders 67 and 68 positioned for engagement with the up and down limit switches 61 and 62, respectively. The slide assembly 66 also coacts with a second pair of normally closed microswitches 71 and 72 which are positioned directly beneath the limit switches 61 and 62, respectively. The limit switch 71, which will be referred to as the up cut-out switch, has a switch actuator 73 positioned for engagement with the slider 67. In a similar manner, the switch 72, which will be referred to as the down cut-out switch, has an actuator 74 positioned for engagement with the slider 68. The sliders 67 and 68 are each slidably supported on an elongated rail 76 which is of a substantially channel-shaped cross-section and extends between and is fixedly mounted on the sidewalls 48 and 49. The rail 76, as illustrated in FIG. 6, has opposed inwardly directed flanges which are slidably accommodated within narrow slots formed in the opposite sides of the sliders 67 and 68 so as to confine the sliders for slidable movement longitudinally of the rail 76. The rail 76 also has a flange 77 fixed thereto and projecting sidewardly therefrom, which flange has the pairs of switches 61-62 and 71-72 stationarily mounted thereon. The sliders 67 and 68 are also connected together by an elongated rod 78, such as a bolt, which rod slidably extends through each of the sliders 67 and 68 and has an enlarged head 79 on one end thereof and a nut 81 on the other end thereof. Rod 78 permits each slider 67 or 68 to be individually slidably displaced therealong, while at the same time the rod 78 limits the maximum spacing between the sliders. As illustrated in FIG. 8, each of the sliders 67 and 68 has a leaf spring 82 associated therewith, which spring coacts between the respective slider and the bottom wall of the rail 76 to create a frictional holding force which prevents undesired displacement of the individual sliders along the rail. While the springs 82 may comprise individual leaf springs if desired, they are each preferably formed integrally with the respective sliders, as by being molded from nylon or other suitable plastic materials. To permit actuation of the microswitches, slider 67 is provided with a pair of cams 83 and 84 positioned to respectively engage the actuators 63 and 73 as associated with the switches 61 and 72, respectively. Slider 68 similarly has cams 86 and 87 positioned to respectively engage the switch actuators 64 and 74 associated with the switches 62 and 72. The cams 83 and 84 associated with the slider 67, and the cams 86 and 87 associated with the slider 68, are offset from one another in the direction of slider movement so that cams 83 and 86 are positioned inwardly and spaced a smaller distance apart than the cams 84 and 87. The sliders 67 and 68 also have suitable support walls 67A and 68A, respectively, formed thereon and projecting outwardly beyond the cams as illustrated in FIG. 8. The liner displacement of sliders 67 and 68 along the rail 76 is controlled by the traveling nuts 43 and 44, respectively. For this purpose, the slider 68 has a wall 88 formed thereon and projecting outwardly in a direction substantially transverse to the direction of movement. The wall 88 projects upwardly a sufficient extent so as to lie within the path of movement of the traveling nut 44, whereupon the traveling nut 44 will abut the wall 88 when the nut 44 approaches an endmost position which corresponds to the door being in a closed position. The other slider 67 has a pair of walls 91 and 92 formed thereon and projecting outwardly therefrom in a direction substantially transverse to the direction of slider movement. The walls 91 and 92 project outwardly a sufficient extent so as to be positioned for abutting engagement with the traveling nut 43, and define therebetween a slot 93 into which projects a portion of the nut 43. However, as illustrated in FIG. 5, the slot 93 has a width which is substantially greater than the thickness of the nut 43 for a purpose to be explained hereinafter. Referring now to FIG. 10, same diagrammatically illustrates therein an electrical circuit 94 for the operator of the present invention. The circuit 94 includes the reversible electric motor 26 which is adapted to be energized from a conventional 110-volt source. Motor 26 is connected to two parallel paths which contain the up and down limit switches 61 and 62, respectively. Motor 26 is also connected in series with a heater coil 98 which, when energized, causes closure of the normally-open delay contact 97 so that lights 96 will be energized during the opening and closing movement of the door. The contact 97 also remains closed for a preselected time after the motor 26 is deenergized. To permit selection in the direction of motor rotation and to permit activation of the overall circuit, same includes a start circuit 99 which is connected to the potential source by means of an intermediate transformer 101. The start circuit contains therein a conventional relay coil 102 which in turn controls a double throw relay switch 103 in a conventional manner, whereby sequential energization of coil 102 results in relay switch 103 being alternately connected to the up and down limit switches 61 and 62. A manually controlled start button 104, which in a conventional manner is normally maintained in an open position, is also connected in series with the coil 102 so that the coil can be energized whenever the start button 104 is manually depressed. Coil 102 is also connected in series with a further circuit branch which contains therein the normally closed cutout switches 71 and 72 and the normally open safety switch 59. These latter switches, which are all connected in series, are disposed in a circuit branch which is in parallel with the manual push button 104. Coil 102 can also be energized in a conventional manner from a remote control, such as a conventional radio frequency control panel, and for this purpose start circuit 99 includes a radio frequency receiver 106 which includes contacts 107 and 108 therein, which contacts are electrically connected upon receipt of an appropriate signal so as to permit energization of coil 102. OPERATION Before considering the operation of operator 11, it will be assumed that the door is initially in its upper opened position substantially as illustrated in FIGS. 3-7 and 11. When in this uppermost or open position, the sliders 67 and 68 are maintained at their maximum spacing adjacent the opposite ends of the rod 78, and the nuts 43 and 44 are both positioned adjacent the free end of the threaded control shaft 42 with the nut 43 abutting the slider wall 92, as shown in FIG. 5. The slider 67 when so positioned results in the switch actuators 63 and 73 being engaged with the cams 83 and 84, respectively, as illustrated in FIGS. 7 and 11, whereby switches 61 and 71 are maintained in open positions. At the same time, the slider 68 is positioned slightly inwardly from its endmost position so that, as illustrated in FIG. 11, the switch actuators 64 and 74 are engaged with the bearing surface 68A whereby the switches 62 and 72 are in their normally closed positions. The safety switch 59 is also in its normal open position and the relay switch 103 is connected in series with the up limit switch 61 (which is now open), as illustrated in FIG. 10. When closing of the door is desired, then button 104 is manually depressed or a suitable radio signal is supplied to receiver 106 so that coil 102 is momentarily energized, thereby causing relay switch 103 to shift into series connection with the closed down limit switch 62, whereby motor 26 is energized in a direction suitable to cause movement in the door closing direction. The energization of motor 26 causes rotation of threaded control shaft 42 whereby the traveling nuts 43 and 44 are moved upwardly along the shaft as illustrated in FIG. 5. Due to the lost motion connection provided between the nut 43 and the slider walls 91 and 92, the nut 43 moves upwardly through a small distance until coming into contact with the slider wall 91, which lost motion permits a limited amount of door movement away from its fully open position, which amount may be in the order of approximately 6 inches of door travel depending upon the magnitude of lost motion between nut 43 and slider 67. This lost motion connection and the permissible door travel permitted thereby is desirable since it prevents the door from receiving another signal after it has been opened, should the door coast back down due to wear or slight misadjustment of the springs, which would otherwise cause the door to undergo a "yo-yo" or oscillating motion. After this lost motion is taken up, whereby nut 43 contacts slider wall 91, slider 67 is then slidably displaced along the rod 78 due to continued upwardly movement of nut 43 as caused by rotation of shaft 42. When slider 67 is displaced upwardly a small distance by nut 43, then actuator 63 drops off of the cam 83 onto the surface 67A, whereby up limit switch 61 returns to its normally closed position. After closing of switch 61, the slider 67 is still further moved upwardly by the nut 43 whereby after a further preselected displacement of the slider 67, the switch actuator 73 falls off of the cam 84 and engages the surface 67A, whereby cut-out switch 71 is accordingly returned to its normally closed position. This additional displacement required to close switch 71 after closure of switch 61 will normally amount to an additional door travel of approximately six inches. However, during this initial travel of the door away from its fully open position, the holding open of the up cut-out switch 71 allows the operator to overcome the force required to start the door moving in its closing direction, which force would normally be sufficient to cause closure of the safety switch 59 but, in this situation, the closure of the safety switch 59 is immaterial since it is connected in series with the cut-out switch 71 which is maintained open during at least approximately the first 12 inches of door closing travel. After the door has moved in its closing direction a sufficient extent to result in closing of the up cut-out switch 71, the door will continuously move towards its closed position and, during this time, the slider 67 will be moved upwardly in FIG. 5) by the nut 43, whereas the slider 68 will remain stationary with respect to the rail 76 due to the frictional holding force developed by its spring 82. If the door should encounter an obstruction which prevents further closing movement of the door, then this results in the force transmitted through the chain being substantially increased and causes displacement of bracket 53 in opposition to the urging of spring 57, whereby safety switch 59 is momentarily closed. Since the cut-out switches 71 and 72 are already closed, this results in momentary energization of the coil 102 so that relay switch 102 flips over into engagement with the already closed down limit switch 62. Motor 26 is thus energized to rotate in the reverse direction, thereby moving the door upwardly in an opening direction. On the other hand, if the door does not encounter an obstruction during its closing movement, then as the door approaches its fully closed position, the traveling nut 44 engages the wall 88 of slider 68. After a small displacement of slider 68 in the upwardly direction in FIG. 5, the cam 87 causes switch actuator 74 to be cammed outwardly whereby down cut-out switch 72 is moved into an open position when the lower edge of the door is spaced a small distance above the threshold 14, which distance may be in the order of approximately 2 inches. This opening of the cut-out switch 72 thus overrides the safety switch 59 due to the series connection therebetween, so that the motor cannot be reversed when the door is adjacent its fully closed position. The motor continues to move the door downwardly and continues upward movement of slider 68 until switch actuator 64 engages cam 86 and activates down limit switch 62 into an opened position, which results in immediate deenergization of motor 26 and stoppage of the door in its fully closed position wherein the lower edge of the door is substantially in engagement with the threshold 44. When the door, during its closing movement, reaches the position wherein the down cut-out switch 72 is deactivated (which position may occur when the lower edge of the door is about two inches above the threshold), the top section of the door is almost vertical at this point and the carriage 22 is moving the arm 23 through an overcenter position. Accordingly, if the door should encounter an obstruction during the last two inches of travel (after opening of the cut-out switch 72), which obstruction may constitute mud, ice or the like, then the motor 26 will continue to drive the carriage 22 and likewise the slider 68 until it engages and opens the down limit switch 62. However, since the door is prevented from moving downwardly during this latter phase, the movement of the carriage 22 and specifically the arm 23 will be absorbed by the spring box 24 inasmuch as the actual downward movement during this phase is relatively small. Thus, the operator will still operate until it reaches and activates the down limit switch so as to shut off the operator. This thus allows the door to remain closed and also allows the motor to shut off, and an undesired reversing or opening of the door is thus avoided. When the door is in its down or closed position as described above, the down limit switch 62 and the down cut-out switch 72 are both open, whereas the up limit switch 61 and the up cut-out switch 71 are both closed. If it is desired to open the door, the relay coil 102 is again energized either due to depression of push button 104 or receipt of a radio signal from a remote operator. Relay switch 103 is thus shifted so as to be again connected in series with the closed up limit switch 61, and motor 26 is thus energized in a direction causing an opening movement of the door. This energization of motor 26 causes the control shaft 42 to rotate in a reverse direction so that nuts 43 and 44 now travel downwardly in FIG. 5. During the initial downwardly movement of the door, the nut 44 moves away from the slider wall 88, and the slider 68 remains stationary due to the frictional holding force created by its respective spring 82. The other nut 43 also moves across the slot 93 and engages the wall 92, whereby slider 67 is thus moved downwardly along the rail 76. If, during this upward or opening movement of the door, the push button 104 or the remote radio is again activated so as to cause energization of the coil 102, which in turn causes a shifting of relay switch 103 so that same is connected in series with the down limit switch 62, then the motor 26 will be energized and the door stopped (and not reversed) since the down limit switch 62 is still being held in its open position by the slider 68. Thus, an accidental or deliberate activation of coil 102 during the opening movement of the door will merely result in a stoppage of the door at a location disposed between the fully open and fully closed positions. A still further energization of the coil 102 will again cause switch 103 to shift into a series connection with the closed up limit switch 61 so that the upward opening movement of the door will then continue. As the door approaches its fully open position, the slider 67 first contacts the actuator 73 whereby up cut-out switch 71 is opened and then contacts actuator 63 whereby up limit switch 61 is opened, thereby deenergizing motor 26 so that the door is stopped in a fully opened position. However, just before slider 67 engages the actuator 63, the slider 67 will be spaced from the slider 68 by the maximum spacing permitted between the bolt head 79 and the nut 81. Thus, during the last portion of downward travel of the slider 67, the slider 68 will also be pulled downwardly due to the connection provided by the intermediate rod 78. Slider 68 is thus moved downwardly a sufficient distance to cause both of the followers 64 and 74 to move into engagement with surface 68A so that down limit switch 62 and down cut-out switch 72 both return to their normal closed positions. Thus, the complete system is accordingly returned to its original position and is ready for initiation of the next closing cycle. Although a particular preferred embodiment of the invention has been disclosed in detail for illustrative purposes, it will be recognized that variations or modifications of the disclosed apparatus, including the rearrangement of parts, lie within the scope of the present invention.

An operator for an upwardly acting door. A reversible electric motor is drivingly connected to the door by an intermediate drive linkage. A switch assembly is associated with the operator for controlling the upward and downward movement of the door, which switch assembly includes first and second limit switches for deactivating the motor when the door reaches its lowermost and uppermost positions, respectively. A third switch functions as a safety switch for causing reversal in the motor rotation when the driving force exceeds a preselected maximum. Fourth and fifth cut-off switches are respectively positioned adjacent the first and second switches for overriding the third switch when the door is within a preselected distance from its closed or open position. The limit and cut-off switches are controlled by a rotatable screw member having a pair of traveling nuts thereon which coact with a pair of individually movable control slides. One of the control slides activates the first and fourth switches, and the other control slide activates the second and fifth switches.

BACKGROUND OF THE INVENTION The invention set forth in this specification pertains to new and improved electrically controlled valves. The valves of this invention are presently intended for use with pneumatic fluids. It is considered, however, that these valves can either directly be employed with hydraulic fluids or can be easily modified so as to be suitable for use with hydraulic fluids in various different applications. A wide variety of different electrically controlled valves are, of course, known. They are used in many different environments for many different purposes. Fortunately an understanding of the present invention does not require an understanding of the vast majority of such prior structures. It is considered, however, that an understanding of this invention is best predicated upon an understanding of two different types of prior electrically controlled valves. Valves of the first of these types are constructed so as to utilize a torque motor in order to control the position of am armature so as to in turn either directly or indirectly control the flow from a source of fluid under pressure to a load so as to accomplish useful work. In general, these prior valves employing a torque motor are constructed so that the torque motor is in effect a separate and distinct element from the actual valve structure with which it is used. In effect, the torque motor in a valve of this type is coupled to the valve structure through the armature. Such an armature is normally a comparatively rigid structure which is movably mounted on the valve structure at the location or locations where it passes more or less from the torque motor into the interior of the valve structure by an appropriate flexible or deformable member such as a bellows-like diaphragm or a comparative thin walled deflection tube. This type of deformable member is used to isolate the torque motor for the interior of the valve structure. Within the valve structure in this type of valve the armature can be utilized in different ways. It is conventional to use the armature so that an end of it is disposed between two opposed nozzles in such a manner that the position of the armature relative to the nozzles determines the amount of flow from the nozzles. It is also known to form the armature in this type of valve so it has ends or bifurcations extending into two different separate chambers which are connected to one another by what may be referred to as load passages. Each of the load passages used in this type of structure is connected to an opening or nozzle in each of the separate chambers. With this type of structure when the armature is moved so as to control the flow between it and the two nozzles in one of the chambers it is concurrently moved so as to control the flow in the other of the chambers. The so-called "load" on a valve of this type is connected generally between or across the two load passages as, for example, by connecting one end of a cylinder serving as a load to one of the passages and the other end of such a cylinder to the other of the passages. While this particular type of torque motor actuated valve employing such a bifurcated armature is considered to be effective and utilitarian it is also considered to be comparatively undesirable because of the close tolerances necessary to make a desirable valve of this type because of the relative slowness of the response time of the valve to an electric signal resulting from the inherent characteristics of the torque motor--armature type structure involved. This latter particularly involves the inertia of the armature used. Further, this type of valve is comparatively undesirable from an economic standpoint because of the costs involved in manufacturing a valve of this type. In this connection it is noted that while a torque motor is not prohibitively expensive to manufacture that such a motor is still a separate element which, on a comparative basis, is somewhat undesirably expensive to construct. Valves of the second type which are important to an understanding of this invention are those valves which are constructed so as to utilize a piezoelectric strip as an actuator so as to control flow from opposed orifices. Known valves of this type utilize a piezoelectric strip cantilevered so that it's unsupported end is located in a chamber between two opposed orifices corresponding to the opposed nozzles commonly utilized in connection with the armature on the torque motor. With structures of this type the relative position of the strip with respect to the two different orifices can be used so as to control flow from both of these nozzles so as to in turn change the pressures in passages connected to different parts of a load used to perform different useful work. Valves of this type are different from those torque motor valves described in the preceding discussion in which the bifurcations or spaced ends of an armature extend into two different chambers in several ways. They employ only a single chamber. The position of the piezoelectric strip in such a valve alone is responsible for any variable pressure change in this type of valve. In addition, of course, there are other obvious differences. Piezoelectric valves as described in the preceding are considered to be disadvantageous for different reasons than the torque motor operated valves previously discussed. It is considered that these known piezoelectric valves can not provide an adequate pressure differential between the two different orifices to perform many different types of tasks normally associated with different types of loads such as cylinders as indicated in the preceding discussion. This is considered to be extremely significant. Further, these prior valves have apparently been constructed so as to utilize relatively small orifices. This is considered rather surprising since other related valves utilizing piezoelectric strips have been constructed so that such a strip is used in controlling the flow from a single comparatively large opening or port to the interior of a chamber from which the emitted fluid passes through one or more openings or ports which are spaced significantly from the piezoelectric strip. In any event, the utilization of such small orifices obtaining a significant pressure drop is disadvantageous in that such an orifice can only pass or convey a limited amount of fluid and inasmuch as such an orifice can become clogged rather easily. This particular matter of an orifice or nozzle becoming clogged is of comparative importance in connection with any pneumatic or hydraulic servo valve. When an orifice or similar opening in any such a valve becomes clogged with one or more contaminant particles there is a significant danger of the valve either not performing in an intended manner and/or one or more parts of the valve breaking. This can be particularly significant in valves such as the torque motor type valves indicated in the preceding discussion where, the spacing between nozzles and an end of an armature is comparatively restricted in nature even at the comparatively extreme position of the armature. This is because of the possibility of a particle becoming lodged generally between the nozzle and the armature. This is a different type of blocking or clogging action than is caused by a particle merely plugging up a comparatively restricted orifice. Clogging of this type has the potential of interfering with the operation of the torque motor used. As a result of this clogging problem it has normally been considered necessary to utilize both of the types of valves indicated in the preceding discussion with comparatively expensive filters capable of removing comparatively small particles of contaminants and concurrently causing a significant pressure drop between the ends of the filter. The latter is, of course, undesirable in these instances where it is desirable to maintain as much of a pressure differential as possible across a load so as to accomplish a significant amount of useful work. BRIEF SUMMARY OF THE INVENTION As a result of various considerations such as are indicated in the preceding discussion it is considered that there is a distinct need for new and improved electrically controlled valves. The present invention is to fulfill this comparatively broad, generic-type need. More specifically it is intended to provide electrically controlled valves which are capable of being utilized instead of prior torque motor valves as in various applications where such torque motor valves were not satisfactory or desirable. The invention is further intended to provide valves of a type hereinafter described which are particularly desirable in that they provide what may be referred to as an adequate pressure gain or pressure differential which is material enough so that a load controlled by such a valve can perform a significant amount of useful work. The invention is also intended to provide valves as described in which there is an adequate volume of fluid flow which, in general, is normally greater than that in prior related valves of a comparable size as indicated in the prior discussion so that these valves are, by reason of the volume of flow, capable of doing significant useful work per volume of fluid passing through the valve. In addition, the invention is intended to provide electrically controlled valves which are desirable because of their comparatively short or "good" response time. From a consideration of valves in this invention as subsequently discussed it will also be realized that the invention is intended to provide valves which may be easily and neatly constructed at a comparatively nominal cost, which are of such a character that they are capable of rendering prolonged, reliable service even with fluids containing quantities of contaminants which would be significant in effecting the performance of other related valves over prolonged periods. In accordance with this invention these various objectives are achieved by providing a valve, said valve having a body formed so as to include separate pressure and return chambers, separate first and second load passages, each of said passages extending between and terminating in an opening in each of said chambers, a pressure port leading into said pressure chamber, a return port leading from said return chamber, first and second load ports connected to said first and second load passages, respectively, actuator means extending into said chambers for controlling the flow of fluid from said pressure port through said openings in said pressure chamber into each of said load passages for controlling the flow of fluid from said openings in said return chamber from said load passages to said return port in which the improvement comprises: said actuator means comprising a member mounted on said body so as to extend into each of said chambers in such a manner that said chambers are isolated from one another, said member being capable of being electrically actuated so that the portion of it within said pressure chamber and the portion of it within said return chamber are concurrently moved relative to said openings in said chambers upon the application of an electric signal so as to permit increased flow to either one of said passages from said pressure chamber and concurrently to restrict the flow from such passage into said return chamber while concurrently restricting the flow into the other of said flow passages from said pressure chamber and increasing the flow from such other passages into said return chamber. BRIEF DESCRIPTION OF THE DRAWINGS Because of the nature of this invention it is best more fully explained with reference to the accompanying drawings in which: FIG. 1 is an isometric view of a presently preferred embodiment or form of an electrically controlled valve in accordance with this invention; FIG. 2 is a cross-sectional view at an enlarged scale taken at line 2--2 of FIG. 1; FIG. 3 is a cross-sectional view taken at line 3--3 of FIG. 2; FIG. 4 is a cross-sectional view taken at line 4--4 of FIG. 2; FIG. 5 is a cross-sectional view taken at line 5--5 of FIG. 3; FIG. 6 is a partial cross-sectional view taken at line 6--6 of FIG. 3; FIGS. 7, 8 and 9 are diagrammatic views intended to explain the operation of the valve shown in the preceding Figs. in controlling the operation of a cylinder serving as a load; and FIG. 10 is an isometric view in which various passages and nozzles shown in FIGS. 1-6 are shown as tangible elements and in which the parts of the valve containing these various elements are shown in phantom. The precise valve shown in the drawings is constructed so as to utilize the operative principles or concepts of the present invention defined and set forth in the appended claims forming a part of this specification. These concepts or principles can be utilized in a number of somewhat differently appearing, somewhat differently constructed valves through the use or exercise or routine engineering skill in the field of electrically operated valves by a person possessing such skill who has had an opportunity of understanding the principles or concepts of this invention. Because of this the accompanying drawings are not to be taken as limiting the scope of this invention in any respect. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The electrically controlled valve shown in the drawing is designated by the numeral 10. It includes a valve body 12 which consists of a base plate 14, first and second end members 16 and 18 and two holding blocks 20. The holding blocks 20 will normally be formed of a rigid, electrically nonconducting material such as an appropriate grade of nylon, teflon or the like. The plate 14 and the members 16 and 18 are conveniently formed of a metal such as aluminum or steel, but they can also be formed out of a rigid polymer material if, for any reason, this is desired. The various parts of the body 12 are preferably secured to one another in the manner illustrated in the drawings through the use of conventional fasteners 22. Inasmuch as the manner in which the fasteners 22 serve their intended function is essentially self-obvious it is not described in detail in this specification. The holding blocks 20 are clamped together by four of the fasteners 22 so that these blocks 20 are held with surfaces 24 on them in direct contact to a sufficient extent so that there is no reasonable possibility of any fluid flowing generally between these two blocks. Flat grooves 26 are formed in the surfaces 24 for the purpose of holding an elongated piezoelectric strip or actuator 28 in the manner shown in FIGS. 2, 3 and 5 of the drawings. This actuator 28 is, in effect, clamped between the blocks 20 so that equally sized ends 30 of it extend from the blocks 20 as shown in FIGS. 2 and 3. It is held in such a manner that there is no possibility of fluid passing within the grooves 26 generally along or around the actuator 28. The surfaces 24 are provided with opposed grooves 32 which extend generally along the actuator 28 within the surfaces 24. These grooves 32 are in communication with a passage 34 in the base plate 14 which leads to a small conventional connector socket 36. This socket is adapted to be used in connection with a conventional electrical plug 38 for the purpose of connecting the plug 38 with wires 40 extending through the passage 34 and through the grooves 32 to adjacent to the actuator 28. There these wires 42 are connected to opposed surfaces 44. The nature of this actuator 28 is quite important in connection with this invention. The preferred actuator 28 for use with this invention is a piezoceramic bender element including a centrally located, elongated metal strip 46 secured to two layers 48 of a piezoelectric ceramic material. A very thin electrode 50 is applied to each of the layers 48. With the structure shown the actuator 28 is in the nature of a sandwich consisting of the metal strip 46 bonded between the two layers 48. If desired an appropriate conventional adhesive (not shown) may be used in securing the layer 48 to the strip 46. The electrodes 50 used are normally quite thin and do not interfere with any bending of the complete actuator 28. One of the wires 40 in the structure shown is preferably connected to the strip 46 in a conventional manner while the other of the wires 40 is connected to each of the electrodes 50. The metal strip 46 is preferably of a type conventionally used in reinforcing a piezoelectric bender element which either is of a material conventionally used as a spring or which has spring like characteristics. It is presently considered that it will be best to form this actuator 48 so that the strip is of a beryllium copper alloy. It is considered obvious that other reasonably related materials may be used. The two end members 16 and 18 are of nearly an identical construction. The end member 16 may be referred to as a pressure end member 16 because it contains a pressure port 52 leading into an enlarged internal pressure chamber 54. Holes 56 lead to opposed sides 58 of this chamber 54. The end member 18 may be referred to as a return end member 18 inasmuch as it contains a return port 60 leading from a return chamber 62 corresponding to the pressure chamber 54. Holes 64 corresponding to the holes 56 extend between the sides 66 of this return chamber 62. One of the holes 56 is connected to one of the holes 64 through the use of what may be referred to as a first load passage 68. The other of the holes 56 is connected to the other of the holes 64 through the use of what may be referred to as a second load passage 70. These two load passages 68 and 70 extend not only through the end members 16 and 18, but in addition, extend through the holding blocks 20. In effect, they could be regarded as a series of separate passages joined to one another in the manner in which piping is assembled. The manner in which these individual passages 68 and 70 extend is shown in FIG. 10. In this figure they are shown in solid lines, whereas the blocks 20 and the members 16 and 18 are shown in this figure by phantom lines. In order to achieve the preferred manner of operation each of the holes 56 and 64 is provided with a nozzle 72. All of the nozzles 72 are of identical construction. Each of them includes an internal passage 74 leading to an elongated vertically extending somewhat slot-like nozzle opening 76. These passages 74 are connected to peripheral grooves 78 in the nozzles 72 through the use of small openings 80. When the nozzles 72 are in place these grooves 78 are in direct communication with either the passage 68 or the passage 70. The nature of the nozzle openings 76 employed in connection with the nozzles 72 is considered important in obtaining a preferred valve in accordance with this invention. In each nozzle 72 the opening 76 should be of an elongated rectilinear or oval shape which maximizes the perimeter length around the nozzle per unit of cross sectional area of the nozzle opening. This type of known structure maximizes the flow between the nozzle 72 and the ends 30 of the actuator 28. This is advantageous in maximizing the useful work obtainable from the fluid used with the valve 10. These nozzles 72 may, of course, be positioned in place in a number of different ways. Preferably they are press fitted within the holes 56 and 64 so that the nozzle opening 76 are equally spaced from the ends 30 when the actuator 28 extends linearly as shown in the initial six figures of the drawing and as shown in FIG. 7. The openings 76 are oriented relative to these ends 30 so as to extend substantially parallel to the holding blocks 20 while the actuator 28 is oriented so as to extend substantially perpendicularly to these blocks 20. This is considered important with respect to the present invention. Threaded holes 77 may be provided in the nozzles 72 for use in removing them for servicing. The physical structure of the valve 10 is completed by the addition of first and second load ports 82 and 84 respectively in the base plate 14 which lead to the first and second load passages 68 and 70 respectively. If desired conventional seals 86 may be placed around these ports 82 and 84 between the base plate 14 and the holding blocks 20. When the valve 10 is to be used the pressure port 52 is, of course, connected to a source of fluid (not shown)--preferably, but not necessarily a pneumatic fluid--under pressure while the load ports 82 and 84 are connected to a load 88 such as a hydraulic cylinder diagramatically illustrated in FIGS. 7, 8 and 9. These ports 82 and 84 are, of course, connected to opposed ends 90 of the cylinder 88 so as to be separated by a piston 92 within the cylinder 88. In addition the return port 60 is either connected to a conventional return line (not shown) or is vented to the ambient. At this time the valve 10 is in a ready to use position or configuration. When it is in this "configuration" because of the ends 30 of the actuator 28 being located midway between the nozzles 72 and because of the nozzle openings 76 being oriented in a corresponding manner, the flow from the pressure port 52 through the pressure chamber 54 will result in equal pressures being conveyed to the passages 68 and 70. Concurrently because the end 30 of the actuator 28 within the return chamber 62 is located relative to the nozzle 72 leading into this chamber in a similar manner the pressures within the two passages 68 and 70 will be held so as to be the same. As a result no useful work will be performed by the load 88. When, however, an electronic signal is applied to the actuator 28 through the wires 40 in a conventional or different manner the actuator 28 will be caused to be bent or bowed in either the manner shown in FIG. 8 or the manner shown in FIG. 9 of the drawings. Only the ends 30 of this actuator 28 will bow in the manner shown because of the holding action of the holding blocks 20. The manner in which the ends 30 are bowed can, of course, be changed at will by changing the direction of the current applied to this actuator 28. When the actuator 28 is bowed as indicated in FIG. 8 flow from the pressure port 52 to the first load passage 68 will be blocked while concurrently flow from this first load passage 68 to the return port 60 will be expedited as a result of the configuration of the actuator 28. Concurrently, flow from the pressure port 52 into the second passage 70 will be expedited as a result of the movement of the actuator 28 while flow from this second passage 70 to the return port 60 will be blocked as a result of the movement of the actuator 28. These various "actions", of course, create a pressure differential which will create pressure differentials which will be transmitted to the load 88 through the ports 82 and 84. This will cause the piston 92 to move from a position as shown in FIG. 7 to a position as shown in FIG. 8. At this point the actuator 28 may be caused to assume its initial position by an appropriate signal being passed to it. The spring-like character of the strip 46 is considered important in causing the actuator 28 to resume such an initial position as shown in FIG. 7. When the actuator 28 has been moved in this manner the forces within the passages 68 and 70 will become rapidly equalized and as a consequence no fluid will be supplied to be used in performing work by the load 88. At this point of time or immediately after the actuator 28 has been caused to assume a position as indicated in FIG. 8, the signal supplied by the wires 40 may be changed in accordance with conventional practice or otherwise so as to bow the actuator 28 as shown in FIG. 9. This will result in a pressure build up within the first load passage 68 and a lessening of the pressure within the second load passage 70 which will cause the piston 92 to move in the opposite direction from the direction it moved previously. It is considered that it will be obvious that it will be possible to modify the valve 10 in quite a number of manners within the scope of routine skill or ability. It is considered possible to provide a useful valve corresponding to the valve 10 in which the individual nozzles 72 are omitted and in which the holes 56 and 64 are used as these nozzles 72. The use of nozzles 72 as discussed, is however, considered to be highly advantageous in increasing the volume of flow within a valve to do useful work to as great an extent as reasonably possible. This is important from a practical standpoint. It is also important that the pressure port 52 be located relative to the actuator 28 as shown or in such other manner that the flow from this port 52 will not affect the position or movement of the actuator 28 by impinging on it. It is also important from a practical standpoint that the pressure gain achievable with a valve such as the valve 10 will normally be large enough for the normal needs of a pneumatic or hydraulic system. In effect a comparatively large pressure gain to do useful work is achieved with a valve such as the valve 10. It is also considered quite important that the response time of a valve such as a valve 10 is quite low. This is considered to be related to the inherent characteristics of the actuator 28 used. Such an actuator is not a comparatively large or bulky member such as an armature used in a conventional valve employing or incorporating a torque motor. As a result of this the inertia of the actuator 28 is, on a comparative basis, quite low when compared to a conventional torque motor armature. The inherent resiliency of the complete actuator 28 resulting from the use of the metal strip 46 is considered to be quite important from a practical standpoint. Valves such as this valve 10 are capable of "accomodating" comparatively large contaminants such as would normally be expected to interfere with the operation of other prior valves of a similar, related character. It is considered that this is in part related to the fact that the actuator 28 can temporarily deform to at least a degree so as to minimize the chances of a nozzle such as the nozzle 72 becoming clogged. As a consequence of the valve 10 being able to handle somewhat contaminated--albeit not horribly contaminated--fluids, it is not considered necessary to filter a fluid passed to the valve 10 to the degree that a fluid is normally filtered in connected with similar valves.

An electrically controlled valve using a piezoelectric strip as an actuator can be constructed so as to include a valve body having separate pressure and return chambers connected by two different load passages. These load passages are connected to service ports used to connect a load to the valve. These passages are open at their ends into the two chambers. A pressure port is used to supply a fluid under pressure to the pressure chamber while a return port is used to convey fluid from the return chamber. The actuator is mounted in such a manner that it can be actuated by an electric signal to move with respect to the openings in the chambers so as to cause an increase in the pressure in one of the load passages and a decrease in the pressure in the other. The position of the actuator can be reversed. When the valve is not in use the actuator is located so that the pressures in both of the load passages are the same.

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit of U.S. Provisional Application No. 60/237,803, filed Oct. 4, 2000. Application Ser. No. 60/237,803 is incorporated herein by reference in its entirety. FIELD OF THE INVENTION [0002] This description generally relates to the field of electrical circuit inspection. More particularly, the field of interest involves systems and methods for fabricating and inspecting electrical circuit conductors in electrical circuits. BACKGROUND OF THE INVENTION [0003] The production of printed circuit boards is an expensive undertaking, and many extraordinary measures are routinely taken to ensure the highest possible production quality. Automated optical inspection (AOI) harnesses the power, speed, and reliability of computer technology to assist with the task of inspection of printed circuit boards for defects. Existing automated optical inspection (AOI) systems, such as the PC-14 Micro™ and Blaser™ AOI systems, are available from Orbotech of Yavne, Israel. [0004] Existing AOI systems that just inspect conductor width, however, do not provide information for evaluating the cross-section of the conductors. [0005] As used herein, the term “printed circuit board” will be understood to refer in general to any electrical circuit on any substrate, including printed circuit boards, multi-chip modules, ball grid array substrates, integrated circuits and other suitable electrical circuits. SUMMARY OF THE INVENTION [0006] A general aspect of the present invention relates to employing a combination of inspection inputs or attributes for the width of a conductor along a top surface and for the width of a conductor along a bottom surface thereof to determine an inspection attribute that may indicate the presence of a defect in a conductor or in a manufacturing process used to fabricate an electrical circuit. [0007] A more particular aspect of the present invention relates to an automated optical inspection system operative to inspect electrical circuits to determine the width of a top surface of conductors forming the circuit at a multiplicity of locations, the width of a bottom surface of conductors forming the circuit at a multiplicity of locations, and the slope of the side walls of conductors, or other defects in the shape of conductor side walls, forming the circuit at a multiplicity of locations. [0008] Another more particular aspect of the present invention relates to a system and method for optically inspecting electrical circuits and calculating therefrom impedance values for conductors forming the electrical circuit. [0009] Another more particular aspect of the present invention relates to a method of producing printed circuit boards, whereby production and/or fabrication process control decisions (such as whether a defect exists in a conductor or in a manufacturing process) are based on inspection outputs indicative of the conductor dimension along the top surface and bottom surface respectively, or the slope of the sides of conductors. [0010] The above and other aspects of the invention are achieved by a system, described in detail below, in which a laser scanner is provided to scan a laser beam across an electrical circuit being inspected. The laser produces a beam which has sufficient energy to cause fluorescence (also referred to herein as luminescence) of the substrate on which conductors are formed. In addition, the beam is reflected by copper conductors which typically have a higher work function than the substrate and do not fluoresce under illumination of the laser beam. The reflected and fluorescent light is collected and the respective intensities of the reflective and fluorescent light are analyzed. Fluorescent light provides an indication of the width of a conductor along its bottom surface, while the reflected light (another attribute) provides an indication of the width of the conductor along its top surface. Comparison of the respective widths of the bottom surfaces and top surfaces of the conductors provides an indication of the slope of the side-walls of a conductor. [0011] The top and bottom dimensions can be used in combination to provide an inspection attribute for a single point or at various sampling points along the length of conductors, and can be used for various analyses of characteristics of the electrical circuit. For example, information about the slope of the side walls of conductors may be used to calculate a cross sectional dimension of an electrical circuit at various sampling points which can be used to derive an impedance value for a conductor. Additionally, statistical information about uniformity in the respect widths of conductors along their top and bottom surfaces may be used to indicate various flaws in etching processes. [0012] The above and other aspects of the invention will be more fully understood and appreciated when read in the light of the detailed description provided below, and the enclosed drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0013] [0013]FIG. 1 is a functional block diagram of an automated optical inspection system operative to inspect electrical circuits for defects in accordance with a preferred embodiment of the present invention. [0014] [0014]FIG. 2 is a simplified representation of a conductor on a substrate, shown in cross-section. [0015] [0015]FIG. 3 shows a signal generated in correspondence to an amount of detected luminescent light generated when the conductor and substrate of FIG. 2 are scanned with a laser. [0016] [0016]FIG. 4 shows a signal generated in correspondence to an amount of detected reflective light generated as in FIG. 3. [0017] [0017]FIG. 5 is a report of distribution of top surface and bottom surface dimension of conductors in an electrical circuit in accordance with a preferred embodiment of the present invention. [0018] [0018]FIG. 6 shows, in highly simplified schematic form, a system for manufacturing electrical circuits according to an embodiment of the invention. [0019] [0019]FIG. 7 is a flow diagram for explaining the processing of the system shown in FIG. 6. [0020] [0020]FIG. 8 shows, in highly simplified schematic form, another system for manufacturing electrical circuits according to an embodiment of the invention. [0021] [0021]FIG. 9 is a flow diagram for explaining the processing of the system shown in FIG. 8. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS [0022] Using the above-identified figures, the invention will now be described with respect to various embodiments of the invention. Although many specificities will be mentioned, it must be emphasized that the scope of the invention is not be taken to be that of only the embodiments described herein, but should be construed in accordance with the claims appended below. [0023] In FIG. 1, automated optical inspection system 10 is operative to inspect electrical circuits for defects in accordance with an embodiment of the present invention. [0024] AOI system 10 suitably is a V- 300 automated optical inspection system available from Orbotech Ltd., of Yavne Israel. In FIG. 1, reference numeral 12 indicates a source of radiant energy; reference numeral 14 indicates a beam of radiant energy; reference numeral 16 indicates a portion of a printed circuit board substrate under inspection; reference numeral 18 indicates a conductor; reference numeral 20 indicates a substrate on which the conductor 18 is disposed; reference numeral 22 indicates a device such as a rotating polygonal mirror that scans the beam 14 across the printed circuit board 16 ; reference numeral 24 indicates a luminescence (also referred to herein as fluorescence) collector; and reference numeral 34 indicates a reflectance collector. [0025] Operation of certain aspects of system 10 are described in U.S. Pat. No. 5,216,479, and are readily grasped by those familiar with this field. Thus, a highly detailed description of the operation of AOI system 10 is omitted here in favor of a brief overview. [0026] The source of radiant energy 12 may be a laser, such as any suitable CW or solid state laser, and preferably is a He:Cd laser, available from Kimmon Electric Company of Japan, producing coherent light in the blue spectrum, at about 442 nm. Substrate 20 may, e.g., be a fiberglass or organic substrate. [0027] The beam 14 is scanned across the circuit portion 16 , and the collectors 24 and 34 are kept operationally positioned to collect their respective types of light at the point at which the beam 14 impinges on the circuit portion 16 . To this end, it is convenient if the collectors 24 and 34 are linear in a main scanning direction of the beam 14 , although this is not essential. The collectors 24 and 34 are shown in FIG. 1, in highly simplified form, as point collectors instead of linear collectors for the sake of ease of illustration. [0028] It will be appreciated that the collectors, sensors, and processors mentioned above may together be thought of as an inspection functionality. [0029] [0029]FIG. 2 shows a cross section of a conductor 18 on a substrate 20 . Reference numeral 35 indicates an upper, substantially flat surface of conductor 18 . The upper surface 35 of conductor 18 has shoulders 19 on either side of it, sloping down in some shape to the substrate 20 . Reference numeral 17 indicates a lower, bottom surface of conductor 18 . [0030] The width of conductor 18 at its top surface 35 may be referred to hereinafter as a top surface width, or top width, or also a surface dimension. [0031] The width of conductor 18 at its bottom surface 17 may be referred to hereinafter as a bottom surface width, or bottom width, or also as a footprint dimension. [0032] When the spot of beam 14 impinges on the substrate 20 at a location free of conductor 18 , a localized part of the substrate fluoresces, giving off luminescent light collected by luminescence collector 24 and sensed by luminescence sensor 26 . At such a location, the reflected light given off by substrate 20 is very low because substrate 20 tends to diffuse the light, and a substantially zero value is output by reflectance sensor 36 . [0033] When the spot of beam 14 impinges on the substrate 20 at a location where a conductor 18 is present, the conductor does not fluoresce because the work function of the conductor 18 is greater than required to release a photon, due to the quantum effect of illumination by beam 14 . Thus, luminescence sensor 26 outputs a substantially zero value. Conductor 18 , however, is relatively reflective. Reflectance collector 34 therefore collects reflectance and reflectance sensor 36 outputs a value above zero at such a point. [0034] [0034]FIG. 3 shows a luminescence signal 30 produced by luminescence sensor 26 , indicative of an amount of luminescence emitted by the surface as a beam spot scans over the cross-section of conductor 18 shown. When the beam spot is over the substrate only, the luminescence has a non-zero value. As the spot begins to cross from the exposed substrate to the shoulder portion 19 of the conductor 18 , the detected luminescence decreases rapidly. It will be appreciated that, in the example shown, the beam spot has a finite width, and so as it moves to the shoulder portion 19 from the exposed substrate, the amount of exposed substrate being impinged upon by the beam spot decreases to zero, as does the amount of detectable luminescence. It will also be appreciated that the inspection is not strictly limited to only the conductor itself, but includes also the exposed substrate in the area. The conductor and the exposed substrate in the area may be referred to, for linguistic convenience, as a “conductor location, ” and a conductor location may comprise several pixels in the digital map 31 . [0035] [0035]FIG. 4 shows a reflectance signal 40 output by reflectance sensor 36 , indicative of an amount of reflectance emitted by the surface as a beam spot scans over the cross-section of conductor 18 shown. When the beam spot is over the substrate only, the reflectance has a substantially zero value. As the spot begins to cross from the exposed substrate to the shoulder portion 19 of the conductor 18 , the detected reflectance increases. Depending on the angle of incidence, the reflectance may reach a maximum value when the spot is impinging on only the top surface 35 , as shown in FIG. 4. When the spot begins to move from the top surface 35 to the shoulder portion 19 , the amount of reflectance that is collected by the reflectance collector 34 decreases quickly, but is greater than zero. This is because the angle of the shoulder portion 19 tends to reflect some of the light in a direction away from the reflectance collector 34 . [0036] In operation, the sensor 26 may include analogue to digital circuitry processing luminance signal 30 to produce a digital image or map 31 (FIG. 1) of luminance values at selected locations on the surface of substrate 20 . Digital image 31 is supplied to bottom width processor 28 . Likewise, the reflectance sensor 36 may include analogue to digital circuitry processing reflectance signal 40 , to produce a digital image or map 41 (FIG. 1) of reflectance values at selected locations on the surface of substrate 20 . [0037] The bottom width processor 28 calculates a footprint dimension of one or more conductors 18 at selected conductor locations therealong. This footprint dimension, as can be seen from FIG. 1, is based on the luminance signal 30 . The top width processor 38 calculates a top surface dimension of one or more conductors 18 at selected conductor locations therealong. This top surface dimension, as can be seen from FIG. 1, is based on the reflectance signal 30 . [0038] The respective outputs of bottom width processor 28 and top width processor 38 may be thought of as different attributes of the conductor, and are provided to an analyzer 42 , which may be operative on several modes. In one mode of operation, analyzer 42 calculates a cross section configuration of conductors based on the respective width dimensions measured for the top surface 35 and bottom surface 32 respectively of conductors 18 . Analyzer 42 may also be thought of as an attribute analyzer [0039] In another mode of operation, analyzer 42 derives the slope of side walls of conductors 18 , at one or more locations along a conductor, from the respective top surface width and bottom surface widths of conductors 18 at those locations. [0040] In another mode of operation, analyzer 42 analyzes a distribution of top surface widths and of bottom surface widths of conductors disposed along all or part of the surface of substrate 20 . Analysis of the distribution of top widths and bottom widths provides information which can be used to control etching processes. In a system configuration enabling this mode of operation, a histogram generator 44 may be included in cross section configuration analyzer 42 . Reference is made to FIG. 5 which is a pictorial illustration of a report of the distribution of top surface and bottom surface dimensions of conductors in an electrical circuit in accordance with an embodiment of the present invention. [0041] As seen in FIG. 5, histogram generator 44 produces a statistical report of the respective width distribution of top surfaces and bottom surfaces for predetermined sampling points along selected conductors. From the histogram, an average top surface width and an average bottom surface width may be determined, along with other useful statistical calculations. These calculations, and the difference between the top and bottom dimensions, are indicative of a shape of conductors, including a slope of conductor side walls. It will be appreciated that information relating to the shape of conductors is useful for understanding and improving photo-lithography and/or etching processes that are employed in manufacturing printed circuit boards. [0042] Moreover, information relating to the shape of conductors may be employed, for example, to calculate a nominal impedance of conductors. The nominal impedance may be calculated in a manner that will be readily grasped, since impedance is a function of the cross sectional dimension of a conductor. [0043] The cross sectional shape of the conductor can be approximated in various ways, once the surface and footprint dimensions have been determined. For example, it could be assumed that the shoulders were constituted by straight lines, and that the cross sectional shape was a trapezoid. Thus, the cross sectional area of the conductor (and hence, impedance) could be computed in a simplified manner. [0044] Another use of information relating to the cross sectional shape of conductors is to control photolithography and/or etching processes in order to obtain conductors having an optimized shape. Ideally, the top surface dimension 35 of conductors 18 should be slightly smaller than the bottom surface dimension 17 in order to maximize the usage of space along the surface of a printed circuit board substrate 20 . Thus if the distribution of top surface width dimensions is too small relative to the distribution of bottom surface width dimensions, then impedance problems are likely to occur since statistically some portions of conductors are likely to have an insufficient volume for efficiently carrying charge. Conversely, if the distribution of top surface width dimensions of conductors is too close relative to the distribution of bottom surface width dimensions, then shoulders 19 (FIG. 2) will typically be bowed inwardly in an exaggerated manner and there will be a high likelihood of cuts along conductors. [0045] It is thus appreciated that analysis of a width distribution report of top width dimensions and bottom width dimensions, as seen in FIG. 5, is useful in adjusting photolithography and/or etching processes in order to optimize the relative dimensions of top and bottom surfaces of conductors 18 . [0046] It will be appreciated that the report shown in FIG. 5 is just one possible example of a report 46 that may be generated by the cross section configuration analyzer 42 . For example, a report 46 may include an indication of top and bottom width dimensions of conductors at various locations along a conductor. [0047] [0047]FIG. 6 shows a fabrication and inspection system, in which a controller 1 controls fabrication activities 9 that produce a printed circuit board 16 from input materials 6 . The printed circuit board 16 is input to the inspection system 10 . The report 46 is provided in a feedback loop to the controller 1 . The report 46 may include surface dimension information, and footprint dimension information. The surface dimension information and footprint dimension information may be thought of as a kind of cross-section information. Based on the cross-section information provided to the controller, the controller may, through an automatic or manual process, adjust the assembly activities 9 in response thereto. That is to say, the controller may cause equipment used during fabrication activities 9 to be adjusted, so that the assembly activities are performed in a manner that is projected to produce another printed circuit board 16 with more desirable inspection results. [0048] [0048]FIG. 7 shows a flow diagram that illustrates the steps just described. In particular, in step 100 , a conductor is formed on a substrate. At least one conductor is formed, but as many as necessary are formed during assembly activities 9 to produce the desired printed circuit board 16 . The printed circuit board 16 is provided to the inspection system 10 . In step 110 , the printed circuit board 16 is inspected to determine the cross-section information (i.e., the surface dimension and the footprint dimension, and any other cross-section information that may be desired). [0049] The report 46 is produced, containing cross-section information, and provided to the controller 1 in step 120 . In step 130 , the controller determines whether the cross-section information is acceptable. That is to say, the controller determines whether the cross-section information indicates a problem that needs correction, or does not indicate such a problem. If there is a problem that needs correction, processing continues from step 130 to step 140 , in which the controller adjusts the assembly activities based on the cross-section information prior to resuming production at step 100 . If there is not a problem that needs correction, processing may continue from step 130 to step 100 , and production may continue as before. [0050] [0050]FIG. 8 shows another method of manufacturing electrical circuits, and is similar in many ways to the method illustrated in FIG. 6 except that the report 46 provided by the inspection system 10 is used to determine whether to undertake repair activities, to discard the printed circuit board, or to approve the printed circuit board. It will be appreciated that in this mode of operation, inspection system 10 typically provides an inspection report 47 containing inspection data correlated to specific locations on an inspected printed circuit board substrate 20 . This enables a decision making process that facilitates further automatic or manual inspection of defective locations, and ultimately the repair of those defective portions of the printed circuit board substrate 20 which are deemed repairable. [0051] [0051]FIG. 9 is a flow diagram that illustrates the steps just mentioned. In particular, steps 100 - 120 are the same as mentioned above with respect to FIG. 7. In step 130 , however, if the cross-section information is acceptable, the printed circuit board 16 is approved. On the other hand, if the cross-section information is not deemed to be acceptable in step 130 , processing continues to step 230 in which it is determined whether repair can or cannot be performed. If it is determined that repair can be performed, then processing continues with the printed circuit board 16 being repaired in the step indicated as “repair conductor”. If it is determined that repair cannot be performed, then the printed circuit board 16 is discarded. [0052] Another way of saying this, is that the circuit is discarded or repaired in response to a determination based on the cross sectional information. [0053] It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the present invention includes both combinations and subcombinations of the features described hereinabove as well as modifications and variations thereof which would occur to a person of skill in the art upon reading the foregoing description and which are not in the prior art.

Surface dimension and footprint dimension values are determined by scanning a printed circuit board with a laser. Exposed substrate parts of the printed circuit board fluoresce significantly, emitting detectable luminance, while conductors do not. Conductors reflect the laser light much more strongly than the exposed substrate, especially at the substantially flat part of the top surface. Luminescence and reflectivity collectors provide signals indicative of the footprint and surface dimensions. This cross-sectional information is used in making adjustment determinations in the manufacturing process, and also decisions relating to repair or discard operations.

DESCRIPTION 1. Technical Field This invention pertains to flooring units or panels, either in the form of elongated planks or in smaller rectangular or square parquet, and more particularly, to interconnecting adjacent such units together by a simple snap-together locking system. 2. Background of the Invention Flooring in the form of elongated planks or strips and rectangular or square parquet panels are well known. Generally it is desirable to be able to inter-fit the flooring so that it has a tight inter-fit and an outer appearance devoid of large gaps or cracks. In general, it is also desirable that the flooring be easily and quickly assembled, to reduce installation costs. Various techniques in the past have been proposed for providing such flooring and flooring systems. U.S. Pat. No. 3,310,919 shows a flooring system in which interlocking flooring units are engaged by tongue and grooves with interlocking screws locking a groove to a tongue. U.S. Pat. No. 3,657,852 shows interlocking tongue and grooves with the panels or units having to be overlaid and tilted to allow the tongue to fit within the groove. While the known prior art systems have been adequate in many cases, they are not adequate in locations where speed of installation is of the essence, and the interlock must be tight. SUMMARY OF THE INVENTION It is an object of this invention to provide a flooring that can be interconnected one to another to make up a flooring system in which each of the individual flooring or flooring units is interlocked by a mechanical interlock system that can be quickly snapped together at the installation site without the need for tools. Furthermore, it is another object of this invention to provide a versatile flooring system in which individual flooring units such as planks or parquet squares or other shapes can be inter-fitted together in various different patterns simply by snapping together the flooring to make the total system. In one embodiment, the flooring has base members, each with four outer peripheral edges. A tongue connector is attached to one outer edge and a groove connector is attached to another of the outer edges. The groove connector has an outer opening of a reduced width, and an inner opening with a width greater than the width of the outer opening. The tongue has a forward end with forwardly converging opposed elastically flexible sidewalls. The sidewalls can be compressed toward one another to form a transverse width smaller than the outer opening of the groove. The expanded width of the sidewalls of the tongue, however, is greater than the outer opening of the groove, so that once the tongue is inserted into a groove the tongue can expand in the inner opening of the groove and provide positive interlocking abutting surface between the tongue and the groove to hold the two base members together. Preferably, the connectors are attached to the base members in recesses in the outer edges by additional tongues and grooves. The connectors are preferably attached to the base members at the factory during manufacture. As is readily apparent, the flooring can be interconnected together quickly and positively locks in a variety of patterns to enable rapid construction of the flooring system in the dwelling or other structure. The base member generally will have a top side covered by a wood veneer or other attractive wear surface, and an underside which may be covered by a rubber cushion layer. The flooring units when assembled can have various different arrangements of their outer peripheral edges connected to one another, and in the case of the elongated planks the planks may be laid side-by-side, end-for-end, or with an end abutting a side. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a flooring unit of the invention locked together with another flooring unit to form the flooring system. FIG. 2 is a fragmentary vertical cross section through two interconnected flooring units. FIG. 3 is a plan view of an elongated plank of one embodiment of the invention. FIG. 4 is a plan view of a second embodiment of an elongated plank with grooves and tongues running the full length of the side edges of the plank. FIG. 5 is a fragmentary isometric exploded view of the invention. DETAILED DESCRIPTION OF THE INVENTION As best shown in FIG. 1, a typical flooring unit 10 can be rectangular or square of the parquet type or an elongated plank. A second flooring unit 11, identical to flooring unit 10, can be interconnected to flooring unit 10. The arrangement of units connected can be different lengths and widths to fit the size of the room in which the flooring is to be laid. As best shown in FIG. 2, a flooring unit includes a base member 12. The base member of each flooring unit except for its dimensions is identical, so only one will be described. Preferably, the base member is plywood or other solid, durable material. The base member for flooring unit 10 has a tongue connector 14 attached to it. A groove connector 16 is attached to flooring unit 11. All connectors are preferably made from plastic having some flexibility. The tongue connector has a forwardly protruding tongue 18. The groove connector has a forwardly protruding groove 20. The tongue is provided with a pair of forwardly diverging sidewalls 22 and 24 separated by an elongated groove 26. The sidewalls terminate rearwardly at transverse rear locking surfaces 28. The sidewalls can be compressed together to a narrower width, and are made of elastic or resilient plastic to naturally expand outwardly into an enlarged width as shown in FIG. 2. The groove 20 has an outer opening 30 with inwardly converging sidewalls 32 which terminate at substantially transverse intermediate locking surfaces 36. The intermediate locking surfaces 36 partly form an enlarged inner opening 38 of a size slightly larger than the periphery of the sides of the sidewalls of the tongue when in its expanded position. The outer opening 30, however, is smaller in cross-section than the width of the inner sidewalls of the tongue, so that the transverse rear locking surfaces 28 of the tongue overlay and abut against the intermediate locking surfaces 36 of the groove. As is readily apparent, by forcing the tongue into the groove the sidewalls of the tongue compress into the center groove or slot 26, allowing the sidewalls to pass beyond the outer opening of the groove 30. Once past the outer opening, the sidewalls of the tongue expand into the position in FIG. 2 to positively interlock the two connectors together. Each connector is provided with additional tongues or ribs in the shape of barbs 40 having enlarged heads 42 that fit into elongated grooves 44 in the base member. Two such tongues 40 and grooves 44 are provided for each connector. The grooves 44 and the tongues 40 run the entire length of an outer edge of the base member. Preferably the base member is cut away or recessed with a flat surface 50, a sloping surface 52, and a bottom flat surface 54 substantially parallel to the surface 50. Preferably each base member has its underside covered by a cushioning layer 60 and its top surface covered by a wood veneer or other hard finish decorative surface 62. Normally the peripheral outer edges of the planking or of a square or rectangular parquet unit will be as in FIG. 4 and in a circumferential direction around the unit will have one edge with a groove connector 16, the next edge with a tongue connector 14, the next edge with another tongue connector 14 and the final edge around the periphery being another groove connector 16. Also, the arrangement of alternating tongue and groove connectors around the circumference of the flooring unit is also feasible. In the embodiment shown in FIG. 3, a planking 82 will have a tongue connector 14 at one end, a groove connector 16 at the opposite end, but will have a groove connector 16 for one half of an elongated side and a tongue connector 14 for the remaining half. Likewise on the opposite elongated side, a tongue connector 14 will be for one half and a groove connector 16 will extend for the other half. In this arrangement, the end 86 of one plank can be inserted against a sidewall 87 with the tongue connector 14 fitting in the groove connector 16. A second plank can then be fitted against the remainder of the sidewall 88 with a groove connector 16 of that plank fitted into the tongue connector 14 of the side 88. Alternatively, the planks 82 can be interconnected side-by-side. As is readily apparent, installation of the planking or parquet units is quite quick and simple. A supply of the units is delivered to the job site. The workman needs only begin snapping the units together quickly, until the entire room is made up. No special tools of any kind are needed. While the preferred embodiments of the invention have been illustrated and described, it should be apparent that variations will be apparent to one of ordinary skill in the art without departing from the principles herein. Accordingly, the invention is not to be limited to the specific embodiments shown in the drawing.

A flooring system having a base member having a top side, an underside, and four circumferentially spaced outer edges, a tongue connector secured to one outer edge by an interlocking rib and groove, a groove connector secured to another outer edge by an interlocking rib and groove, the tongue connector having forwardly converging compressible sidewalls terminating in rear transverse locking surfaces, the groove connector having an enlarged inner opening and a smaller outer opening, the tongue sidewalls in a compressed position being smaller than said groove outer opening to pass through the outer opening but elastically expandable to be larger than said outer opening to lock a tongue in a groove.

BACKGROUND OF THE INVENTION This invention relates to the use of chelating molecules to deactivate iron species to prevent fouling in hydrocarbon fluids. In a hydrocarbonn stream, saturated and unsaturated organic molecules, oxygen, peroxides, and metal compounds are found, albeit the latter three in trace quantities. Of these materials, peroxides can be the most unstable, decomposing at temperatures from below room temperature and above depending on the molecular structure of the peroxide (G. Scott, "Atmospheric Oxidation and Antioxidants", published by Elsevier Publishing Co., NY, 1965). Decomposition of peroxides will lead to free radicals, which then can start a chain reaction resulting in polymerization of unsaturated organic molecules. Antioxidants can terminate free radicals that are already formed. Metal compounds and, in particular, transition metal compounds such as copper and iron can initiate free radical formation in three ways. First, they can lower the energy of activation required to decompose peroxides, thus leading to a more favorable path for free radical formation. Second, metal species can complex oxygen and catalyze the formation of peroxides. Last, metal compounds can react directly with organic molecules to yield free radicals. The first row transition metal species manganese, iron, cobalt, nickel, and copper are already found in trace quantities (0.01 to 100 ppm) in crude oils, in hydrocarbon streams that are being refined, and in refined products. C. J. Pedersen (Ind. Eng. Chem., 41, 924-928, 1949) showed that these transition metalspecies reduce the induction time for gasoline, an indication of free radical initiation. Copper compounds are more likely to initiate free radicals than the other first row transition elements under these conditions. To counteract the free radical initiating tendencies of the transition metal species so called metal deactivators are added to hydrocarbons with transition metal species already in the hydrocarbon. These materials are organic chelators that tie up the orbitals on the metal rendering the metal inactive. When metal species are deactivated, fewer free radicals are initiated and smaller amounts of antioxidants would be needed to inhibit polymerization. Not all chelators will function as metal deactivators. In fact, some chelators will act as metal activators. Pedersen showed that while copper is deactivated by many chelators, other transition metals are only deactivated by selected chelators. Prior Art Schiff Bases such as N,N'-salicylidene-1,2-diaminopropane are the most commonly used metal deactivators. In U.S. Pat. Nos. 3,034,876 and 3,068,083, the use of this Schiff Base with esters were claimed as synergistic blends for the thermal stabilization of jet fuels. Gonzalez, in U.S. Pat. No. 3,437,583 and 3,442,791, claimed the use of N,N'-disalicylidene-1,2-diaminopropane in combination with the product from the reaction of a phenol, an amine, and an aldehyde as a synergistic antifoulant. Alone the product of reaction of the phenol, amine, and aldehyde had little, if any, antifoulant activity. Products from the reaction of a phenol, an amine, and an aldehyde (known as Mannich-type products) have been prepared in many ways with differing results due to the method of preparation and due to the exact ratio of reactants and the structure of the reactants. Metal chelators were prepared by a Mannich reaction in U.S. Pat. No. 3,355,270. Such chelators were reacted with copper to form a metal chelate complex. The metallic complex was then added to the furnace oil as a catalyst to enhance combustion. Mannich-type products were used as dispersants in U.S. Pat. No. 3,235,484 and U.S. Pat. No. Re. 26,330 and 4,032,304 and 4,200,545. A Mannich-type product in combination with a polyalkylene amine was used to provide stability in preventing thermal degradation of fuels in U.S. Pat. No. 4,166,726. Copper, but not iron, is effectively deactivated by metal chelators such as N,N'-disalicylidene-1,2-diaminopropane. Mannichtype products, while acting as chelators for the preparation of catalysts or as dispersants, have not been shown to be transition metal ion deactivators. DESCRIPTION OF THE INVENTION Accordingly, it is an object of the inventors to provide an effective iron deactivator for use in hydrocarbon mediums so as to inhibit free radical formation during the high temperature (e.g., 100°-1000° F., commonly 600°-1000° F.) processing of the hydrocarbon fluid. It is an even more specific object to provide an effective iron deactivator that is capable of performing efficiently even when used at low dosages. We have found that iron is effectively deactivated by the use of certain Mannich-type products formed via reaction of the reactants (A), (B), and (C); wherein (A) is an alkyl substituted phenol of the structure ##STR1## wherein R is selected from alkyl, aryl, alkaryl, or arylalkyl of from about 1 to 20 carbon atoms; wherein (B) is a polyoxyalkylenediamine selected from the group consisting of ##STR2## where the sum of x and z is from 1 to 6 and ##STR3## where y is from 1 to 6; and wherein (C) is an aldehyde of the structure ##STR4## wherein R 1 is selected from hydrogen and an alkyl having from 1 to 6 carbon atoms. As to exemplary compounds falling within the scope of Formula I supra, p-cresol, 4-ethylphenol, 4-t-butylphenol, 4-t-amylphenol, 4-t-octylphenol, 4-dodecylphenol, and 4-nonylphenol may be mentioned. At present, it is preferred to use 4-nonylphenol as the formula I component. Exemplary polyoxyalkylenediamines which can be used in accordance with Formula II include dipropylene glycol diamine, tripropylene glycol diamine, tetrapropylene glycol diamine, diethylene glycol diamine, triethylene glycol diamine, tetraethylene glycol diamine and mixtures thereof. The aldehyde component can comprise, for example, formaldehyde, acetaldehyde, propanaldehyde, butrylaldehyde, hexaldehyde, heptaldehyde, etc. with the most preferred being formaldehyde which may be used in its monomeric form, or, more conveniently, in its polymeric form (i.e., paraformaldehyde). As is conventional in the art, the condensation reaction may proceed at temperatures from about 50° to 200° C. with a preferred temperature range being about 75°-175° C. As is stated in U.S. Pat. No. 4,166,726, the time required for completion of the reaction usually varies from about 1-8 hours, varying of course with the specific reactants chosen and the reaction temperature. As to the molar range of components (A):(B):(C) which may be used, this may fall within 0.5-5:1:0.5-5. The iron deactivator of the invention may be dispersed within the hydrocarbon medium within the range of about 0.05 to 50,000 ppm based upon one million parts of the hydrocarbon medium. Preferably, the iron deactivator is added in an amount from about 1 to 10,000 ppm. A Mannich product-metal complex is formed in situ upon Mannich product addition to the hydrocarbon medium. The complex deactivates the metal so as to inhibit free radical formation. EXAMPLES The invention will now be further described with reference to a number of specific examples which are to be regarded solely as illustrative and not as restricting the scope of the invention. Testing Method The peroxide test was employed to determine the deactivating ability of the chelators. The peroxide test involves the reaction of a metal compound, hydrogen peroxide, a base, and a metal chelator. In the presence of a base, the metal species will react with the hydrogen peroxide yielding oxygen. When a metal chelator is added, the metal can be tied up resulting in the inhibition of the peroxide decomposition or the metal can be activated resulting in the acceleration of the rate of decomposition. The less oxygen generated in a given amount of time, the better the metal deactivator. A typical peroxide test is carried out as follows: In a 250 mL two-necked, round-bottomed flask equipped with an equilibrating dropping funnel, a gas outlet tube, and a magnetic stirrer, was placed 10 mL of 3% (0.001 mol) hydrogen peroxide in water, 10 mL of a 0.01 M (0.0001 mol) metal naphthenate in xylene solution, and metal deactivator. To the gas outlet tube was attached a water-filled filled trap. The stirrer was started and stirring kept at a constant rate to give good mixing of the water and organic phases. Ammonium hydroxide (25 mL of a 6% aqueous solution) was placed in the dropping funnel, the system was closed, and the ammonium hydroxide added to the flask. As oxygen was evolved, water was displaced, with the amount being recorded as a factor of time. A maximum oxygen evolution was 105 mL. With metal species absent, oxygen was evolved over 10 minutes. Example 1 A 2:1:2 mole ratio of 4-nonylphenol:triethylene glycol diamine:paraformaldehyde was prepared as follows. In a three-necked, round-bottomed flask equipped with a mechanical stirrer, a reflux condenser, and a thermometer was placed 55 g (0.25 mole) of nonylphenol, 7.88 g (0.25 mole) of paraformaldehyde, and 76.9 g of xylene. On addition of the 18.5 g (0.125 mole) of triethylene glycol diamine, the temperature rose to 63° C. The mixture was held at about 70° C. for 1 hour. A Dean Stark trap was inserted between the condenser and the flask and the temperature was increased to 150° C., by which the time water of formation was azeotroped off --4.5 mL was collected (approximately the theoretical amount). The mixture was cooled to room temperature, the xylene returned to the mixture, and the mixture used as is at 50% actives. When 100 mg of the solution in the above mixture was used in the peroxide test, only 37 mL of oxygen was evolved in 5 minutes. In contrast, when the product was not used in the peroxide test, 72 mL of oxygen was evolved. The example shows that the product reduced the iron activity by 49%. Example 2 A 2:1:2 mole ratio of p-cresol:triethylene glycol diamine: paraformaldehyde was prepared as follows. In a three-necked, roundbottomed flask equipped with a mechanical stirrer, a reflux condenser, and a thermometer was placed 43.26 g (0.4 mole) of p-cresol, 12.61 (0.4 mole) of paraformaldehyde, and 78.4 g of xylene. On addition of the 29.6 g (0.2 mole) of triethylene glycol diamine, the temperature rose to 66° C. The mixture was held at 70° C. for 1 hour. A Dean Stark trap was inserted between the condenser and the flask and the temperature was increased to 150° C., by which time water of formation was azeotroped off --7.4 mL was collected (approximately the theoretical amount). The mixture was cooled to room temperature, the xylene returned to the mixture, and the mixture used as is at 50% actives. When 100 mg of the actives in the mixture was used in the peroxide test, 39 mL of oxygen was evolved in 5 minutes. In contrast, when the product was not used in the peroxide test, 72 mL of oxygen was evolved. This example shows that the product reduced the iron activity by 46%. Example 3 A 2:1:2 mole ratio of 4-nonylphenol:mixture of tripropylene glycol diamine and tetrapropylene glycol diamine:paraformaldehyde was prepared as follows. In a three-necked, round-bottomed flask equipped with a mechanical stirrer, a reflux condenser, and a thermometer was placed 44 g (0.2 mole) of 4-nonylphenol, 6.30 g (0.2 mole) of paraformaldehyde, and 23.5 g of xylene. On addition of the 23 g (0.1 mole) of the mixture of tripropylene glycol diamine and tetrapropylene glycol diamine, the temperature rose to 63° C. The mixture was held at 70° C. for 1 hour. A Dean Stark trap was inserted between the condenser and the flask and the temperature was increased in 151° C., by which time water of formation was azeotroped off --3.6 mL (approximately the theoretical amount). The mixture was cooled to room temperature, the xylene returned to the mixture, and the mixture used as is at 75% actives. When 100 mg of the actives in the above mixture was used in the peroxide test, 24 mL of oxygen was evolved in 5 minutes. In contrast, when the product was not used in the peroxide test, 52 mL of oxygen was evolved. This example shows that the product reduced the iron activity by 54%. While this invention has been described with respect to particular embodiments thereof, it is apparent that numerous other forms and modifications of this invention will be obvious to those skilled in the art. The appended claims and this invention generally should be construed to cover all such obvious forms and modifications which are within the true spirit and scope of the present invention.

Certain Mannich reaction products (i.e., alkylated phenol, polyoxyalkylenediamine, and an aldehyde) are used to deactivate iron species already present in hydrocarbon fluids. Left untreated, such iron species lead to decomposition resulting in the formation of gummy, polymer masses in the hydrocarbon liquid.

BACKGROUND OF THE INVENTION 1. Field of the Invention: This invention relates to the conversion of a standard gasoline carburetor to an alcohol and/or nitro-methane fueled carburetor. More specifically, the invention relates to a metering block that accepts a pair of alcohol containing fuel bowls. 2. Description of the Prior Art: The basic concept of operating an internal combustion engine using alcohol as the fuel is a well established practice, particularly in certain high performance areas such as racing. Thus, the alcohol burning race car, hydroplane, motorcycle or the like, is generally known but is also considered to be for a specialty type event. In fact, alcohol has sometimes been categorized as an exotic fuel. To a great extent, this label is a consequence of the contemporary mass production of internal combustion engines being almost exclusively directed to either gasoline or diesel fuel systems, wherein the carburetor must be essentially reengineered to be made compatible with alcohol fuel. More specifically, it is known that for maximum power output, an alcohol burning engine needs a fuel to air ratio in the region of 5.5 or 6.5 whereas the maximum power output for the gasoline engine occurs at about 13. Yet, it is also generally accepted that alcohol has an inherent resistance to detonation (resists preignition and spark knock) and low combustion temperatures, making it highly suitable for high compression racing engine applications. Furthermore, with the advent of contemporary emission laws and the consequential redirection of selected gasoline feed stocks into unleaded gasoline production, the price of ultra-high octane racing fuel has increased to such an extent that the use of alcohol fuel is becoming cost effective. Although, as indicated above, the conversion of the standard gasoline engine to an alcohol fueled racing engine is in principle attractive, up to this point in time the conversion has been expensive. Either the carburetor is replaced by an alcohol carburetor specifically manufactured for such purpose or the stock gasoline carburetor has to be completely reengineered (frequently leading to unsatisfactory results). Thus, the need for an inexpensive yet reliable method of adapting a conventional gasoline carburetor to alcohol fuel is still present. SUMMARY OF THE INVENTION In view of the problems and expense of converting a conventional gasoline carburetor to operate an alcohol fuel, I have discovered an improved carburetor metering block that is adapted to replace the conventional carburetor metering block and accept, simultaneously, a pair of separate conventional fuel bowls each supplying alcohol or other exotic fuel to the engine. In this manner, the present invention provides sufficient fuel flow and adequate control of fuel level, while using predominantly conventional carburetor components. Thus, the present invention provides in a carburetor having at least one removable fuel bowl and metering block the specific improvement comprising: a carburetor metering block means adapted to attach to the carburetor and replace the removable fuel bowl and metering block, and the carburetor metering block means is further characterized in that it is adapted to accept, simultaneously, a plurality of individual and separate fuel bowls. In one embodiment of the present invention, the carburetor metering block means has a pair of fuel bowls feeding a two barrel carburetor, while in another embodiment, two carburetor metering block means, each with a pair of fuel bowls, are feeding a four barrel carburetor. It is a primary object of the present invention to provide an inexpensive, yet reliable way of converting a conventional gasoline carburetor to alcohol and/or nitromethane fuel. It is an associated object to accomplish the conversion such that a plurality of alcohol fuel bowls will simultaneously feed fuel through the carburetor such that both sufficient fuel flow and adequate fuel level control are accomplished. Fulfillment of these objects and the presence and fulfillment of other objects will be apparent upon reading of the specification and claims taken in conjunction with the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top view of a conventional two-barrel carburetor equipped with a pair of fuel bowls mounted to the improved metering block according to the present invention. FIG. 2 is a front view of the carburetor illustrated in FIG. 1 as seen through line A--A. FIG. 3 is a front view of the metering block illustrated in FIG. 1 removed from the carburetor. FIG. 4 is a top view of the metering block illustrated in FIG. 3. FIG. 5 is a back view of the metering block illustrated in FIG. 3. FIG. 6 is a bottom view of the mtering block illustrated in FIG. 3. DESCRIPTION OF THE PREFERRED EMBODIMENTS The improved carburetor metering block of the present invention, how it is used to convert a standard carburetor to alcohol-type fuels and how its use overcomes certain problems implicit in such conversions can perhaps be best explained and understood by reference to the drawings. FIGS. 1 and 2 are a top and front view, respectively, of a standard two-barrel Holly carburetor 10 equipped with a dual fuel bowl metering block 12 according to the present invention. This metering block 12 is designed to replace the original metering block by attaching to the carburetor at the same relative position as the original. Attached to the front face of the metering block 12 are a pair of standard or conventional fuel bowls 14 and 16 with separate fuel inlet needle-valves with seat and internal fuel float. The overall use of the multiple fuel bowl metering block is readily applicable to any gasoline carburetor that has a removable metering block and fuel bowl, but, in principle, it can also be utilized with any carburetor that can be converted to the detachable metering block concept. Furthermore, more than one multiple fuel bowl metering block can readily be used on a single carburetor such as when replacing both the primary and secondary metering blocks of a four-barrel carburetor. FIG. 3 illustrates the front face of the metering block 12 with the fuel bowls removed. The metering block attaches to the carburetor through a set of bolt holes 18 which are aligned with the points of attachment on the original metering block. A series of eight threaded holes 20 are provided to accept and retain attachment bolts at the four corners of the pair of fuel bowls mounted to the front face of the metering block 12 (see FIGS. 1 and 2). At the lower central corner of each fuel bowl are the fuel inlets to the main fuel circuit. Each inlet involves a replaceable main jet 22 and 24 and an auxiliary main jet 26 and 28 of fixed or constant size that diagonally intersect within the metering block forming part of the main fuel circuit. Each fuel circuit supplies a separate venturi within the carburetor throat; i.e., each barrel of the carburetor is supplied by its own fuel bowl. In this manner, the two-fold or greater increase in the rate of fuel delivered to the engine (approximately corresponding to the required relative change in fuel to air ratio when converting from gasoline to alcohol) can be readily achieved. In essence, each venturi of the two-barrel carburetor will now be supplied with liquid fuel at a rate in excess of the previous sum of fuel flow rates to both venturis; yet, the absolute liquid flow rate within the individual fuel bowls and through the respective needle and seat will be approximately the same as before the conversion. As further illustrated in FIG. 3, the auxiliary main jets 26 and 28 are fixed, while the main jets 22 and 24 are replaceable. In this manner, a total fuel flow rate in excess of twice the previous flow rate can be achieved while the fine tuning or final jetting of each system can be performed with the use of already available replaceable jet sizes. Also, from the front side view of FIG. 3 the metering block fuel inlet ports 30 and 32 for the accelerator pump circuit can be seen at the right corner of each fuel bowl. These fuel inlets 30 and 32 ultimately deliver fuel through external tube 34 and fitting 36 to the metering block accelerator injection circuit as explained later. The elongated openings 38 and 40 which encompass the upper inner pair of attachment bolt holes 18 also serve as part of the air vent or bowl vent circuit by virtue of the diagonal ports (dashed lines) that extend upward to the pair of peened ball bearings 42 and 44 (see also FIG. 4). It should be apparent from FIG. 3 that the metering block 12 differs from a conventional metering block by the absence of the intermediate power circuit. The elimination of the power circuit is viewed as a matter of convenience and choice in that the illustrated embodiment is intended for an all out racing version of the invention. As such, the power circuit is optional, but is considered compatible with the present invention and may be present in alternate embodiments. As seen in the metering block top view of FIG. 4, the pair of peened ball bearings 42 and 44 cap the air bowl vent circuit. To each side of these ball bearings are the sealed main fuel wells 46 and 48 followed by the sealed idle wells 50 and 52. The the far right side is the plugged accelerator pump well 54. FIG. 5 illustrates the reverse or back side of the metering block 12. The external portion of the accelerator pump circuit including tube 34 and lower fitting 36 can be seen to connect to metering block 12 at fitting 56, such that the fuel can be ultimately delivered to the accelerator pump discharge passage 58. Directly above the accelerator pump discharge passage 58 is a pair of bowl vent passages 60 and 62. Symmetrically located to each side of the discharge passage 58 and bowl vent passages 60 and 62 are separate main fuel circuit discharge nozzles 64 and 66, main air wells 68 and 70 with air bleed holes 72 into main well and idle fuel ports 74 from main well and idle fuel restrictions to idle well 76. Each of these separate circuits is associated with the individual and separate fuel bowls to be attached on the other side. Also, two separate idle circuits can be seen in FIG. 4, including separate needle valves 78, curb idle discharge ports 80, idle down wells 82, idle air bleed openings 84 and idle-transfer fuel openings 86. The underside or bottom view of FIG. 6 again shows the external accelerator pump circuit with external fittings 36 and 56 and tube 34. Thus, as described above, the multi or dual float metering block of the present invention and the associated method of converting a conventional gasoline fuel carburetor to alcohol fuel, can be accomplished by employing predominantly standard or conventional components once the metering block of the present invention is available. Some modification to the throat of the carburetor may be appropriate such as enlarging the main fuel circuits to each venturi; however, this is viewed as a conventional consideration in auto racing and the like. Also, the use of a dual or multiple accelerator pump linkage system is viewed as advantageous and the appropriate fuel pump/pressure regulator as known in the art should be employed. Thus, the general concept of using a dual float metering block of the present invention is viewed as a replacement type modification not necessarily requiring total reengineering of the carburetor. The number of additional fuel bowls added is a matter of choice. Preferably a two for one conversion should be sufficient, however, for extremely large fuel requirements, the three for one conversion can be, in principle, accomplished. Also, the concept of replacing both the primary and secondary metering block on a four-barrel carburetor with a so-called four corner accelerator pump circuit is viewed as compatible with the basic concept of the present invention. The metering block can be manufactured out of essentially any of the materials well known in the art. The particular physical appearance and respective circuits can be made compatible with various specific carburetor requirements and should not be limited to the details of the illustrated embodiment. Various circuits can be made external to the block, if necessary, or incorporated within the metering block. Thus, for example, the external accelerator pump circuit of the illustrated embodiment can be readily incorporated within the metering block. Having thus described and exemplified the preferred embodiment with a certain degree of particularity, it is manifest that many changes can be made within the details of construction, arrangement and fabrication of the components and their uses without departing from the spirit and scope of this invention. Therefore, it is to be understood that the invention is not limited to the embodiments set forth herein for purposes of exemplification, but is to be limited only by the scope of the attached claims, including the full range of equivalents to which each element thereof is entitled.

An improved carburetor metering block for converting a conventional gasoline carburetor to alcohol fuel involving a carburetor metering block means adapted to attach to a conventional carburetor and replace the removable fuel bowl and standard metering block wherein the improved carburetor metering block means is adapted to accept, simultaneously, a plurality of individual and separate fuel bowls. Such a device can inexpensively convert a conventional carburetor to the use of alcohol fuel consistent with sufficient fuel flow and adequate fuel level control.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to improving the performance of matrix evaluations. The invention is also related to an improvement in performance in evaluating sparse matrices having at least one model containing information for at least one node in the matrix being evaluated. The invention is still further related to an improvement in the performance of matrix evaluations where the sparse matrix represents Kirchoff's voltage and current laws for an electronic circuit being evaluated, and where the models represent specific structures and contain at least one conductance contribution value of an electronic circuit component of the electronic circuit. 2. Discussion of the Background The use of matrix based solvers (matrix solutions) to simulate transient behavior of electronic circuits dates back to 1 975, and is in wide use in the electronic design community. Nagel, L., SPICE 2: A Computer Program to Simulate Semiconductor Circuits, ERL Memo UCB/ERL M75/520, University of California, Berkeley, May 1975, hereinafter, SPICE; see also Cohen, E., Program Reference for SPICE 2, ERL, University of California, Berkeley, June 1976, hereinafter Cohen, and Quarles, T., Analysis of Performance and Convergence Issues for Circuit Simulation, EECS, University of California, Berkeley, April 1989, hereinafter, Quarles. This method of solution relies on the fact that differential circuit equations that describe transient behavior of circuits can be written as conductance coefficients (G) into a matrix, and the matrix can be solved to obtain new voltage values at each node of the circuit. The use of matrix solutions has relied on a number of techniques to improve solution performance. Starting with SPICE, sparse matrix techniques have been utilized to reduce the amount of memory required to store the entire matrix. While sparse matrix systems reduce the amount of memory needed, they require a trade-off in performance due to the fact that the location of an individual matrix entry must be stored and because the matrix solution cannot be calculated through simple matrix index mathematics as in non-sparse systems. FIG. 1A is a circuit diagram of a two resistor circuit (R 1 and R 2 ) having three circuit nodes (N 1 , N 2 , and N 3 ). FIG. 1B is a matrix representing conductance values (G) of the two resistor circuit. The matrix element labeled G 1 +G 2 represents the circuit equation coefficients for the node N 2 between the resistors. In a single processor computer, matrix evaluation cycles proceed according to the flow diagram in FIG. 2. For each time point in the simulation, all of the device models are evaluated and the result is added to the matrix entry in a serial fashion. At Step 20, a model is evaluated. Such model can be, for example, a model representing resistor R 1 in FIG. 1A. The model evaluation determines the conductance values (G) of the circuit element, resistor R 1 . At Step 22, the matrix is loaded with the conductance values determined in the model evaluation Step 20. In this example, the conductance values of the circuit element resistor R, is collectively referred to as a matrix stamp R, is inserted into the matrix (see Matrix stamp of R 1 , FIG. 1B). Steps 20 and 22 are repeated for each model to be evaluated. At Step 24, the matrix is solved to determine voltage values at each node of the circuit. At Step 26, a convergence test is utilized to determine whether or not the circuit has reached a steady state solution. An example convergence test compares values at a vector of new nodal voltages (X i ) to values from a last convergent time point (X i-1 ), and is defined as: X.sub.i -X.sub.i-1 ≦Abstol+Reltol*Max(X.sub.i, X.sub.i-1), where Astol and Reltol are user defined convergence control variables of the simulator (having default values of 1e-6 and 1e-3 respectively), and the function Max() returns the largest of two values. If the convergence test does not reach steady state, the entire process is repeated for another simulated time point. In the above process, because the model evaluation can occupy as much as 50 percent of the processor's time, this leads to extremely long runs in large circuit simulation can be experienced. The conventional implementation of matrix solvers has relied on device model structures similar to Resistor Model Structure 30 shown in FIG. 3. Resistor Model Structure 30 stores identifying information 32, including an instance and model identifier, and the conductance value G 36, as evaluated during model evaluation (Step 20 in FIG. 2, for example). In addition, Resistor Model Structure 30 stores the memory locations of the matrix entries (Pointers 38, for example). This mechanism requires that after each device model is evaluated, the new values of G (36, for example) must be `stamped` into the matrix during the matrix load phase. In a multiple processor system, each evaluation of a device model can be handed to a separate processor. As shown in FIG. 4, model evaluations 40a, 40b, and 40c are processed in parallel. While this can lead to some improvement in simulation time, the overall performance of the system will not be improved dramatically due to the nature of shared memory systems. Shared memory is utilized because some circuit equations cause overlapping entries at matrix positions where two or more circuit elements meet to form a circuit node, therefore the effect of adding additional processors is reduced because of a time consuming, serial process of matrix load (Step 42). If each device model is evaluated by a separate processor, then the simulation can enter a situation known as a blocking memory write in which two (or more) processors attempt to write to the same memory location. This can be seen by referring to the matrix entry labeled G1+G2 in FIG. 1B and corresponding to node N 2 in FIG. 1A, which shows that the value of this element has conductance contributions G 1 and G 2 from resistors R 1 and R 2 , respectively. Some mechanism must be provided to prevent two processors from writing to a given memory location simultaneously. A blocking memory write prevents simultaneous writes by locking a memory location (matrix entry), reading it's value, adding the evaluation of the other models (conductances) that contribute to this nodal voltage, and then unlocking the memory location. However, blocking memory writes are expensive due to the fact that all other processes that are contributing to the value at the memory location being written are blocked until the lock/unlock cycle completes. Furthermore, in order to avoid an enormous number of memory location lock operations and associated bookkeeping and memory consumption involved in managing those locks, multi-processing systems have historically locked and unlocked the entire matrix before and after each stamping step. Bischoff and Greenburg's original method Bischoff, G., and Greenburg, S., Cayenne--A Parallel Implementation of the Circuit Simulator SPICE, Digital Equipment Corporation, Hudson Mass., CH2353-1/86/0000/0182© 1986 IEEE, hereinafter Bischoff and Greenburg, overcomes this blocking problem by changing the matrix entry from a single scalar value to a sum value and a vector of individual conductances. As shown in FIG. 5, each matrix position (50, for example) includes a vector 52 where each vector entry (G2, for example) is a collection point for a single model evaluation. Thus, if two device models are connected to a circuit node, that node is represented in the matrix as a matrix position having three values, two of which provide locations for non-blocking writes by separate model evaluation processes (vector 52), and one of which is a sum value 54. The effect of Bischoff and Greenburg's method on the matrix evaluation loop is shown in FIG. 6. Model evaluations 40a, 40b, and 40c are performed as before, however, matrix loads shown as matrix load 62a, 62b and 62c are now performed in parallel. Each matrix load performs stamping, via nonblocking writes, of individual conductance values from individual circuit elements into a single matrix position (vector entry). Steps 64a, 64b and 64c represent the summing of the sum values at each matrix position (sum value 54, FIG. 5, for example). Bischoff and Greenburg's method provides an improvement in evaluation time of circuit simulations. However, because of the complexity of most circuits being evaluated, significant computational time is still required. SUMMARY OF THE INVENTION Accordingly, it is an object of this invention to provide an improvement in time required to evaluate a matrix by providing an arrangement of device models having values stored therein and providing pointers in the matrix being evaluated to the device model stored values. It is another object of the present invention to provide an improvement in evaluation of electrical circuits via a matrix having pointers to device models containing conductance values of electronic components in the electrical circuit. It is yet another object of the present invention to provide a method of evaluating a matrix representing an electrical circuit by eliminating the need for matrix locking and a matrix load phase by reading conductance values for electronic components in the circuit from a device model. It is yet another object of the present invention to reduce the amount of memory required to maintain a matrix being evaluated. These and other objects are accomplished by an apparatus for storing and accessing matrix coefficients for a circuit simulation, which apparatus includes an input device configured to input conductance elements corresponding to matrix coefficients, a storage device configured to store each conductance element in at least one component model structure, a data structure comprising plural nodes, each node corresponding to a matrix coefficient and having at least one pointer, a pointer reference mechanism configured to reference pointers in each respective node of the data structure to conductance elements which are stored in the component model structure and which correspond to the matrix coefficient of the respective node, and an access device configured to access one or more of said matrix coefficients utilizing a corresponding node of the data structure. Alternatively, the above objects may be accomplished via a method of storing and accessing matrix coefficients, comprising the steps of retrieving data elements corresponding to at least one matrix coefficient, storing each data element in at least one model, building a data structure having plural nodes, each node corresponding to a matrix coefficient and having at least one pointer, referencing pointers in each respective node of said data structure to reference model stored data elements corresponding to at least part of the matrix coefficient of the respective node, and accessing a matrix coefficient utilizing a corresponding node of said data structure. The above described apparatus and method eliminate the matrix load phase in favor of directly reading the conductance values from the model data structures. This leads to performance enhancement by eliminating the need to lock the matrix for writes. It also reduces the amount of memory required by reducing the number of double floating point values held in the matrix (total of 32 bytes for a resistor) to four single precision pointers (16 bytes total). Other aspects and advantages of the present invention can be seen upon review of the figures, the detailed description, and the claims which follow. BRIEF DESCRIPTION OF THE DRAWINGS A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: FIG. 1A is a circuit diagram of a two-resistor circuit; FIG. 1B is an illustration of a matrix representing the two-resistor circuit of FIG. 1A; FIG. 2 is a flowchart illustrating matrix evaluation, matrix load, and matrix solve that occur at each time point in a matrix solution loop in a single processor system; FIG. 3 illustrates a conventional data structure utilized in matrix solvers; FIG. 4 is a flowchart illustrating a matrix solution loop with multiple processors and memory write blocking; FIG. 5 illustrates a matrix incorporating the original Bischoff and Greenburg method of utilizing a sum value and a vector of individual conductances to overcome write blocking; FIG. 6 is a flowchart illustrating a matrix solution loop with multiple processors and no memory write blocking; FIG. 7 illustrates a matrix solution loop with multiple processors and inverted data structures according to the present invention; FIG. 8 illustrates an inverted model and matrix data structure according to the present invention; FIG. 9 illustrates a complex matrix element structure according to the present invention; FIG. 10A illustrates a matrix data structure for R 1 at rows N 1 and N 2 of column N 2 for the two-resistor circuit of FIG. 1A according to the present invention; and FIG. 10B illustrates a matrix data structure for node N 2 of the two-resistor circuit of FIG. 1A, according to the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present inventors have realized that although Bischoff and Greenburg improves the performance of the simulation loop significantly, it still is expensive in the matrix load phase due to the fact that many copies of the same number must be `stamped` into the matrix. The present inventors have also realized that one of the most time consuming phases of a simulation as implemented in SPICE, Cohen, and Quarles is the matrix load phase. This phase consists of `stamping` the matrix with new values of conductance whenever the model is reevaluated. Since this phase takes place on every simulated time point it is responsible for as much as 50 percent of the overall run time. The present invention involves the nature of the values that are written at each point in a device element's matrix stamp (Matrix stamp of R 1 , 12, FIG. 1B, for example). In FIG. 1, the entries for G 1 represent the conductance of the device R 1 at any point in the simulation. If the device model that is used to evaluate the resistor R 1 . is a basic resistor model, then the value of G 1 will always equal 1/R 1 . Thus the value of G 1 can be calculated once and stored in the model. This is true for many of the device models that can be simulated by SPICE, Cohen, and Quarles. However, by reversing the model data structures with respect to SPICE, Cohen, and Quarles, and by extending Bischoff and Greenburg, this invention can reduce the evaluation time of the matrix. The Matrix Solution Loop according to the present invention is shown In FIG. 7. FIG. 7 includes a model evaluation phase having Model Evaluations 40a, 40b, and 40c in parallel without a matrix load. After the model evaluation phase, the available processors can be handed a set of rows or columns and be allowed to calculate the final sum (placing it in the sum location, i.e., summation phase) independent of each other via entry sum 70a, 70b, and 70c, for example. The horizontal arrows represent that all model evaluations are completed prior to any Entry Sum Calculations. This summation phase can operate in parallel and taken together, the entire process can achieve very high matrix evaluation performance without complex, time consuming memory locking schemes. In achieving the above, the present invention inverts the model and matrix data structures as show in FIG. 8. During the matrix evaluation phase, the values of the matrix entries can be found by reference (matrix entries G n and -G n reference G=1/R, 86, for example) instead of being replaced ("stamped") during matrix load. Thus, the present invention improves the overall simulation time due to the fact that the locations in memory of the matrix entries can simply be dereferenced to obtain the required values instead of actively updating each location (i.e., matrix entries G n and -G n are not actively updated). Since the model contains the knowledge of when a conductance value is updated, and the matrix refers to that value (updated or not), there is no need to actively stamp each matrix entry during a matrix load phase. FIG. 9 illustrates an example of a complex matrix element structure (structure of a matrix entry) according to the present invention. In FIG. 9, the matrix element structure 90 includes a sum of conductances 92, a number of positive conductances 93, a number of negative conductances 94, and two groups of pointers 96 and 98, containing pointers to positive and negative conductance values respectively. A portion of the matrix data structure for the two resistor example (FIG. 1A) using the present invention is shown in FIGS. 10A and 10B. As shown in FIG. 10A, matrix entries at rows N 1 and N 2 for column N 1 of the matrix data structure (FIG. 1B) for R 1 is illustrated. At row N 1 , a G Sum value 102, a number of positives 103, a number of negatives 104, and a pointer to G 1 105 is shown. At row N 2 , a G Sum 106, a number of positives 107, and a number of negatives 108, and a pointer to G 1 109 is shown. In FIG. 10B, the matrix entry (at row N 2 , column N 2 , FIG. 1B) corresponding to node N 2 (FIG. 1A) of the two resistor circuit is shown, including G Sum 112, number of positives 113, number of negatives 114, pointer to G 1 115, and pointer to G 2 116. The evaluation of the final conductances for any given node is achieved by equation (1): ##EQU1## where each conductance contribution to G Sum (G i and G j , for example) is not locked, thus allowing G sum for each node to be calculated without memory blocking by a separate processor. Therefore, applying equation 1 to the matrix entries defined in FIG. 10A, conductance values of G 1 and -G 1 are derived for rows N 1 and N 2 , respectively, for column N 1 . Similarly, a conductance value of G 1 +G 2 is derived for the matrix entry corresponding to node N 2 (row N 2 , column N 2 ). One of the primary time savings of this invention derives from the elimination of many addition operations during the model evaluation phase when compared to the original SPICE method. In the flow diagram of FIG. 2, the matrix load phase for a multiple connection matrix entry requires the processor operations shown in Table 1 (SPICE column) in order to calculate the final conductance contribution for the two resistor example. Pseudo code for a Zero Matrix and the Matrix Load phases of the original SPICE algorithm is: ______________________________________ Operations______________________________________<Zero Maxtrix>For each Matrix EntryWrite A Zero 1 Write Double<Load Matrix>For Each Model InstanceFor Each G PointerGet G Pointer 1 Read SingleGet G Value 1 Read DoubleContribute 1 Add/SubtractWrite G Value 1 Write Double______________________________________ Since Bischoff and Greenburg's method eliminates the Zero Matrix phase and moves part of the Matrix Load phase into the Model Evaluation phase, it provides a significant performance enhancement. However, the increased performance also requires the expense of more memory to hold the data structures. The pseudo code for the Model Evaluation and Entry Sum phases of Bischoff and Greenburg's method and this invention is: ______________________________________ Operations______________________________________<Model Evaluation>For Each Model InstanceFor Each G PointerGet G Pointer 1 Read SingleWrite G Value 1 Write Double<Sum Entries>For Each Matrix EntryGet 1.sup.st G Value 1 Read DoubleFor G Values 2-NGet G Value 1 Read DoubleContribute 1 Add/SubtractWrite G.sub.Sum Value 1 Write Double______________________________________ Therefore, in addition to enabling non-write blocked multi-processing, Bischoff and Greenburg's method significantly reduces the number of time-expensive double precision math operations at the expense of increasing the amount of memory required to hold the data structures. Table 1 compares the number of operations for the three methods when applied to the two resistor example in FIG. 1. TABLE 1______________________________________Comparison of OperationsOperation SPICE B&G New______________________________________Read 16 16 16Add/Subtract 8 1 1Write 15 15 15______________________________________ Therefore, the present invention takes full advantage of the performance improvements of Bischoff and Greenburg's method. In addition, the present invention significantly reduces the amount of memory required to perform these operations. Table 2 summarizes the memory requirements for the three methods when applied to the two resistor example in FIG. 1. ______________________________________MemoryRequirements SPICE B&G New______________________________________Double Precision 9 17 9(64 bit, 8 bytes)Pointer (32 bit, 4 8 15 22bytes)Total Bytes 104 196 160______________________________________ An additional benefit of the inverted data structure mechanism in this invention is the ability to enhance the performance of the Matrix Solution phase due to the inversion of the conductance pointers. In SPICE and it's derivatives, the node `0` is, by definition, the ground node and is always defined to be a value of zero volts. The definition of the ground node at zero volts causes the set of linear equations of N nodes to be over-constrained due to the addition of the extra equation: V.sub.Ground =0 (2) Because an over constrained system presents additional solution difficulties, no SPICE simulator (or any matrix-based solver for simultaneous linear equations) attempts to place the row or column for the ground node in the matrix. This leads to a problem in the Model Evaluation phase because the target locations for conductances of models that have nodes connected to the ground node do not exist in instances of the matrix, but do exist in the Model structures. In SPICE and Cohen, the Model Evaluation phase has a different implementation from Quarles in that they attempt to avoid the problems caused by the missing ground node row and column. In SPICE and COHEN, the Model Evaluation phase must consider whether the matrix element for the conductance that is about to be stamped is actually in the ground node row or column. This requires three conditional tests according to the following algorithm: ______________________________________// In the Model Instance/Matrix Construct PhaseIf((Row == 0) or (Column == 0)) Ptr = -1. . .// In the Model Evaluation Phaseif( Ptr != -1 ) Matrix[Ptr] = Matrix[Ptr] + <G>______________________________________ That is, if the row or the column is the ground node row or column, the value of the variable Ptr is set to -1. This requires two conditional tests (or at least one in optimized compilers). The value of Ptr is then tested during the Model Evaluation phase to see if it is a -1 (an additional test). If it is not equal to -1, then the existing value in the matrix is retrieved and the addition operator is used to add the conductance G. In Quarles, the model instance data structure contains a pointer Ptr that is set to a dummy location (Junk) if the node is connected to the ground node (giving the model instance somewhere to point). This implementation eliminates the conditional tests during the Model Evaluation phase, but still makes a reference to the value stored in the variable Junk (hence, an additional operation performed in the model evaluation phase). The expense here is that the addition operation takes place whether or not the matrix element is in the ground node row or column. This addition operation always adds G to the Junk location. To prevent arithmetical over/underflow, the value of Junk is occasionally set to zero. ______________________________________// In the Model Instance/Matrix Construct PhaseIf(( Row == 0 ) or ( Column == 0 )) Ptr = &Junk// Just someplace to write. . .// In the Model Evaluation Phase*Ptr += <G>______________________________________ Implementations according to SPICE, Cohen, and Quarles construct each model structure instance independent of whether a node is the ground. This is required due to the fact that Model structures are required to point into the matrix and must have valid pointers during Matrix Load in order to prevent a segmentation violation during the write phase. That is, there must be some place to write the data or the simulator will fail. The present invention eliminates the need to consider the ground node as part of the Matrix Solution due to the fact that the Device Model structures have no knowledge of where in the matrix the model is used. During the Matrix Construction Phase, this invention never constructs the ground node row and column in the matrix. Since the row or column are never constructed and the Matrix Load no longer exists, the Matrix Solution phase never attempts to dereference them, thereby leading to reduced memory use and enhanced performance. The entire effect of the present invention in terms of memory savings and performance enhancements depends on circuit configuration. In many integrated circuits, particularly CMOS circuits, there are many transistors (and other devices) that are tied by one or more terminals to the ground node. In SPICE and Cohen, this leads to much longer solution times due to the fact that the Model Evaluation code must continually either consider whether the connections are to the ground node in SPICE or continually perform an operation with no effect on the system of equations (adding a zero in Quarles). In general, any circuit that has many connections to ground will have increased performance and reduced memory use when evaluated in accordance with the present invention. Portions of this invention may be conveniently implemented using a conventional general purpose digital computer or microprocessor programmed according to the teachings of the present specification, as will be apparent to those skilled in the computer art. Appropriate software coding can readily be prepared by skilled programmers based on the teachings of the present disclosure, as will be apparent to those skilled in the software art. The invention may also be implemented by the preparation of application specific integrated circuits or by interconnecting an appropriate network of conventional component circuits, as will be readily apparent to those skilled in the art. Any portion of the present invention may be implemented on a general purpose digital computer or microprocessor and includes a computer program product which is a storage medium including instructions which can be used to program a computer to perform any of the above described processes of the invention. The storage medium can include, but is not limited to, any type of disk including floppy disks, optical discs, CD-ROMs, and magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, magnetic or optical cards, or any type of media suitable for storing electronic instructions. The foregoing description of the preferred embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.

A device for reducing evaluation time of a matrix representing an electrical circuit. Conductance values of each circuit component in the circuit are written to corresponding models utilizing non-blocking writing techniques. The matrix is represented by a reduced memory structure where each matrix node is represented by a matrix element structure having at least one pointer to a conductance value contained in a model structure corresponding to a circuit component that contributes to a value of the matrix node. A set of rows or columns of the matrix are then processed to calculate final matrix node values independently.

FIELD OF THE INVENTION The invention concerns a method for manufacture of a calender roll provided with an elastic coating, in which method the roll frame is composed of a continuous axle and of a filler material fitted onto the axle. The invention also concerns a calender roll manufactured in accordance with the method, comprising a continuous roll axle, a filler material fitted onto the axle, which filler material, together with the axle, forms the roll frame, and an elastic polymer coating fitted onto the roll frame. BACKGROUND OF THE INVENTION A supercalender normally comprises a stack of rolls consisting of a number of rolls fitted one above the other, in which stack, between the upper roll and the lower roll in the calender, there are a number of intermediate rolls, which are alternatingly chilled rolls and soft-faced rolls. Earlier, as soft-faced rolls, almost exclusively so-called fibre rolls were used, which consisted of disks or rings of fibrous material fitted on the roll axle and pressed together axially by means of end pieces and end nuts so that the soft face of the roll consisted of said fibre disks. It was one drawback of such fibre rolls that the deflections and rigidities of said fibre rolls differed quite substantially from corresponding properties of the chilled rolls, because the frame of the fibre rolls is quite slender as compared with the chilled rolls. As second significant drawback was relatively rapid wear of the fibre rolls. Development of rolls and roll coatings made it possible, in supercalenders, in stead of fibre rolls, to employ rolls provided with elastic coating, in particular with a polymer coating, as soft rolls. In such rolls, the thickness of the coating in relation to the roll diameter is quite little, in which case the roll frame can be made quite rigid. Thus, in particular when rolls with polymer faces are employed, the rolls can be constructed so that the rigidities and deflections of all of the intermediate rolls in the calender are substantially equal, or at least the differences in these properties from roll to roll are quite little. It is a second improvement in polymer-coated rolls, as compared with fibre rolls, that their service life is considerably longer, i.e. the intervals of replacement of rolls can be made considerably longer. In conventional rolls with polymer coatings, a significant problem, however, consists of the relatively high weight of the rolls as compared with fibre rolls. Thus, these polymer-coated rolls of novel type cannot be used as such in renewals and modernizations of existing calenders in which fibre rolls were used as soft-faced rolls earlier. This comes simply from the fact that, in a calender which was originally designed so that fibre rolls are employed as intermediate rolls, the mechanical strength of the spindles and spindle nuts on whose support the rolls are suspended does not endure the increased weight resulting from the polymer-faced rolls. Thus, in modernizations of supercalenders, if it is desirable to employ polymer-coated rolls of new type, considerable changes and renewals must be carried out in the frame constructions of the calender and in the means of suspension of the rolls. Thus, it is an aim to be able to reduce the weight of the polymer-faced rolls employed in supercalenders substantially in order that such rolls, whose other properties are better than those of fibre rolls, could be used simply also in modernizations of supercalenders. With respect to the prior art, reference is made to the U.S. Pat. No. 3,711,913, to the DE Patent 195 11 595 (corresponding to U.S. Pat. No. 5,766,120), to the published DE Patent Application 195 33 823 (corresponding to U.S. Pat. No. 5,759,141), and to the published EP Patent Application 735,287 (also corresponding to U.S. Pat. No. 5,766,120). In said U.S. Patent, a method is described for conditioning of a fibre roll, in which method a worn or damaged fibre roll is machined to a measure smaller than its original diameter, after which a coating of a synthetic plastic material is fitted onto the roll, i.e. directly onto the fibre disks. With this procedure, the roll can be made suitable for a certain purpose of use, but the properties of a roll manufactured or conditioned in compliance with said method do not correspond to what is required from a modern polymer-faced calender roll. First, the rigidity of the roll is considerably lower than the rigidity of a tubular polymer roll, and further, since the coating has been fitted directly onto the fibre disks, the properties of resilience of the roll differ considerably from what is expected, for example, from a modern tubular polymer roll. In the DE and EP publications referred to above, polymer-faced calender rolls are described which have been formed so that, in the roll, the axle of an existing fibre roll is used so that, onto the axle, in place of the filler material of the fibre roll, for example, disks made of aluminum cell material are fitted, in which disks at least a part of the walls of the cells are perpendicular to the roll axle. Then, onto these disks, an elastic polymer coating has been fitted. The roll formed in this way has quite good properties, in particular because the weight of the roll has become so low that it can be utilized easily in renewals of supercalenders, because the difference in weight of the roll as compared with a fibre roll is very little. It is a significant drawback of these rolls that, according to a first embodiment, the roll is manufactured by pressing loose disks between locking flanges, as is the case in traditional paper rolls, in which case it is very difficult to provide the desired rigidity. The rigidity is determined in accordance with the pre-stress of the axle and with the compression strength of the disks, as is the case in traditional paper rolls. In a second embodiment desribed in the cited prior-art publications, the support construction is composed of a plate of cellular construction which is wound as layers onto the axle. In the embodiment described in the publications, this procedure requires formation of joints in the longitudinal direction of the roll and bending of large plate-like pieces into correct shape, which requires high precision and care of manufacture. A further drawback is the high cost, which comes, besides from the above reasons, also from the technique of manufacture that has been used, which requires casting and machining of the disks. Also, depending on the purpose of use and on the diameter of the roll, the disks must always be designed anew, and a number of different cast models must be prepared for different rolls. In said publications, as a further alternative embodiment, forming of disks has been suggested out of a material that contains reinforcement fibres, such as epoxy reinforced with fibreglass, carbon fibres, aramide fibres, or equivalent. Such solutions are, of course, usable in themselves, and they provide a roll of quite low-weight construction, but the problem is an even higher cost. The object of the present invention is to provide a novel method for manufacture of a calender roll provided with an elastic coating as well as a calender roll manufactured in accordance with the method, which method and roll do not involve the drawbacks involved in the prior art and by means of which method and roll, further, a significant improvement is achieved over the prior art. In view of achieving the objectives of the invention, the method in accordance with the invention is mainly characterized in that the filler material is made of a continuous profile band, which is wound onto the axle as the desired number of windings in order to produce the desired roll diameter, in which connection an elastic coating is formed onto the cylindrical outer face of the filler material. OBJECTS AND SUMMARY OF THE INVENTION On the other hand, the calender roll in accordance with the invention is mainly characterized in that the filler material has been made of a uniform and continuous profile band, which has been wound onto the axle as the desired number of windings in order to produce the desired roll diameter. The invention provides significant advantages over the prior art, and of the advantages obtained by means of the invention, for example, the following can be stated. First, the manufacture of the roll in accordance with the invention is very easy. Owing to this easy mode of manufacture and, also, of the materials employed, the cost of manufacture of the roll is essentially low, as compared with the prior art described above. The roll produced in accordance with the present invention is of low-weight construction, owing to which it can be employed readily in modernizations of supercalenders as substitution for earlier fibre rolls. The properties of operation of the roll, however, meet the requirements imposed on a modern polymer-coated tubular roll. Owing to the winding technique that is employed, the rigidity of the roll can be made fully as desired, and in particular if the layers that are wound are glued or welded together, the construction of the roll becomes highly rigid. Further, since the roll has been formed by means of the winding technique and since the intermediate layers have been locked from their ends directly on the roll axle or on a lower intermediate layer, no locking flanges are needed, but the roll frame itself forms a struture that remains in its position on the axle, and the end flanges, if any, operate just as a piece for the supply of a cooling/heating medium to the roll frame. This is why the end pieces of the roll are just covering flanges and fixed to the profile bands only, and not at all fixed to the axle. The firrer advantages and characteristic features of the invention will come out from the following detailed description of the invention. BRIEF DESCRIPTION OF THE DRAWINGS In the following, the method in accordance with the invention and the calender roll manufactured in compliance with the method will be described in more detail with reference to the figures in the accompanying drawing. FIG. 1 is a schematic illustration partly in section of a roll in accordance with the invention. FIG. 2 is a schematic illustration of an embodiment of a roll in accordance with the invention. FIG. 2A is a detail from FIG. 2 . FIG. 3 shows a further embodiment in a roll as shown in FIG. 2 . DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, the roll is denoted generally with the reference numeral 10 . The roll 10 has preferably been formed so that, in the manufacture of the roll 10 , an existing fibre roll has been used, from which the fibre disks have been removed. Thus, as the starting point of the novel method, the axle of such a fibre roll has been adopted, which axle is denoted with the reference numeral 11 in the figure. This axle 11 has been mounted in a winding machine, and in the winding machine the desired number of layers of a profile band 13 have been wound onto the axle 11 , one layer onto the other, so that said layers of profile band 13 form a filler material onto the axle 11 , which filler material, together with the axle 11 , forms the roll frame. Then, onto this roll frame, a resilient polymer coating 14 has been applied fully similarly to the way in which it is currently applied onto tubular polymer rolls. The reference numeral 12 denotes the end pieces of the rolls 10 , taken as such from the old fibre roll. The profile band 13 is favourably made of aluminum material, because this material is already in itself of low weight and because, out of said material, a band of the desired profile can be prepared by extruding. The band can also be made, for example, by rolling, but an extrusion process is preferable exactly because by its means, for example, a hollow profile of the sort illustrated in the figure in the drawing can be obtained, in which case the filler material of the roll becomes of even lower weight. By varying the shape of the profile, it is possible to optimize the amount of material and the amount of air in the filler material, by which means it is, in a simple way, possible to affect the weight of the filler material and of the whole roll. The filler material or, in fact, the weight of the filler material must be optimized so that it endures all the loads applied to the roll 10 but does not have any extra weight. The mass of the filler material and the additional rigidity of the roll frame obtained by means of the filler material are preferably optimized so that the natural deflection of the roll arising from its own weight is substantially equal to the corresponding deflections of the other rolls in the calender. By means of this system, it is very easy, by slightly altering the extrusion tool, to change the material-to-air ratio of the filler material without any machining operations. The filler material made of the profile band 13 is particularly advantageous also because the diameter of the roll frame can be regulated by varying the number of winding layers of the profile band 13 or by varying the height of the profile to be wound. Thus, all different dimensions of rolls can be accomplished by means of one and the same profile, in which case manufacture of the rolls is highly advantageous. A roll manufactured in the way in accordance with the invention already becomes very robust in itself and endures loading very well. The load holding capacity and the robustness can be increased substantially, for example, so that, in connection with the winding, the profile band is immersed in an adhesive agent, in particular epoxy, whereby the wound profile band is glued into a solid “package” and forms a robust roll frame. It is also possible to think that the layers of profile band, or at least the topmost layer, are/is welded, in which case the layer forms a good foundation for the roll coating 14 . It is a significant additional property of the roll in accordance with the invention that, as the profile is hollow and tubular in the way illustrated in the figure, some medium can be passed to flow inside the profile, such as air or water, which medium transfers heat and equalizes differences in temperature in the roll. In particular in cases in which there is an even number of winding layers, the heat transfer medium runs back and forth from end to end in the roll, in which case the temperature profile of the roll becomes highly uniform. In FIGS. 2 . . . 3 in the drawing, an additional embodiment of a roll is shown, which is denoted generally with the reference numeral 20 . FIGS. 2 and 3 illustrate the roll without a roll coating, which coating is, however, also supposed to be used in the solution in accordance with these figures. FIG. 2A shows a detail from FIG. 2 . The embodiment shown in FIGS. 2 and 3 differs from FIG. 1 in particular in the respect that, in the embodiment that is now being discussed, the profile bands 23 have been wound as filler material onto the roll or at least as the outer layer of the filler material, substantially less steeply than in the embodiment shown in FIG. 1 . As a matter of fact, in the embodiment shown in FIGS. 2 and 3, the direction of the threading of winding differs from the axial direction of the roll to a substantially lower extent than it differs from the direction transverse to said axial direction. By means of this solution, attempts have been made to improve and to facilitate the introduction of the heat transfer medium into the ducts 23 a in the profile band 23 and the circulation of said heat transfer medium in the ducts. Circulation of such a heat transfer medium in the ducts 23 a in the profile band is advantageous, for example, when it is desirable to use a heat transfer medium for cooling of the roll and in particular of the roll coating, because an excessive heating of the coating makes the wear quicker and may result in damage to the coating in a very short time. As was already stated earlier, it is preferable to make the profile band 23 out of aluminum material by extrusion, because in such a case the profile band can be provided with the desired shape very easily. As a preferred solution of the shape of the profile band, in FIG. 2A a shape of the profile band is illustrated owing to which the profile band is “self-locking” so that adjacent profile bands are attached to one another because of their shape. In the attaching, gluing can also be employed as an aid, and, as an additional alternative, it is further possible to employ friction welding of the profile band at least in the outermost layer of the filler material. In such a case, the manufacture of the roll could be made automatic so that friction welding is carried out at the joints 25 between adjacent profile bands 23 in connection with the winding. As was already stated above, in the solution of FIGS. 2 and 3, the profile band 23 has been wound as very gently inclined at least in the outermost layer of the filler material. It is not advantageous the arrange the profile bands 23 fully axially, because such an axial alignment might cause vibration in the roll during operation and also a barring pattern in the paper. Such drawbacks can be avoided even with a slight spiral form of the profile band. FIG. 3 is a schematic illustration of a solution of how a heat transfer medium can be passed into the ducts 23 a in the profile bands 23 . This has been accomplished simply so that, into the roll 20 axle 21 , or at least into the end of the axle, a duct or bore has been formed for the heat transfer medium, and similarly, into the end piece 22 of the roll, a necessary system of ducts 26 has been formed, which communicates with the bore that has been formed into the axle 21 , on one hand, and with the ducts 23 a in the profile bands 23 , on the other hand. Further, to the end of the axle 21 , a water couping 27 or equivalent has been connected, by whose means the heat transfer medium is passed into the roll. The shape of the profile band 13 does not necessarily have to be a hollow profile similar to that shown in the figures, but, as the profile, it is also possible to employ an open profile, for example an I-section profile. Such a profile is very easy to produce, besides by means of extrusion, also by rolling. When such an open profile is wound onto the axle side by side, between the profiles, ducts remain which are closed ducts. In particular in cases in which the medium that is circulated in the ducts is air, such an open profile operates very well, in particular in cases in which, in connection with winding, gluing is also employed, as was already explained earlier. As the preferred materal alternative for a profile band, aluminum material can probably be considered, even if other materials can also be considered to be employed in the roll. The material must, however, be such that, out of the material, such a profile band can be formed readily in which, at least in connection with winding, ducts can be formed in the filler material, as was described above. Of materials that can be thought of, it is possible to mention, for example, different polymer materials, even though a limiting factor in their case is a cost substantially higher than the cost of aluminum. It is a further feature of the roll in accordance with the invention that, in cases in which a heat transfer medium is made to flow in the ducts in the filler material, the heat transfer medidn can be utilized for heating of the roll at least during the starting stage of the calender, in which case said start-up stage can be made shorter. Further, it is evident that the heat transfer medium can also be used for cooling the roll. Above, the invention has been described by way of example with reference to the figure in tihe accompanying drawing. The invention is, however, not confined to the exemplifying embodiment illustrated in the figure alone, but different alternative embodiments of the invention may show variation within the scope of the inventive idea defined in the accompanying patent claims.

A method for manufacturing a calendar roll in which a continuous band of filler material is wound onto an axle until a desired diameter for the roll is obtained, and then an elastic coating is applied to an outermost surface of the band, i.e., the outermost layer of windings. An adhesive agent may be applied onto the band such that adjacent windings of the band adhere to one another during winding of the band onto the axle. Adjacent windings of the band in an uppermost layer of windings may be welded together to provide a foundation for the elastic coating. The calender roll includes an axle, a uniform and continuous band of filler material wound onto the axle to provide the roll with a desired diameter, and an elastic polymer coating arranged on an outermost layer of windings of the band on the axle.

The present invention refers to new cysteine derivatives of the general formula (I) ##STR2## in which R represents a radical of a fatty saturated or unsaturated acid, or a radical of an aromatic acid, such as benzoic, salicylic, cynnamic, 2-acetoxy-benzoic acid or of a heterocyclic acid, as well as their salts, particularly Ca and Mg salts. The new derivatives are excellent bronchial liquefiers and expectorants, INVENTION FIELD The invention refers to new cysteine derivatives having a bronchial liquefying and expectorant activity, to a process for their preparation and to pharmaceutical compositions containing them as active ingredients. DESCRIPTION Operating according to the above mentioned reaction series, the starting compound for the preparation of derivatives of formula (I) according to the invention is the chloride of 3-chloro-L-alanine(II) which may be obtained from 3-chloro-1-alanine by any of the conventional methods employed for transforming an acid into its chloride, for instance by reaction with phosphorus pentachloride in a suitable solvent, such as chloroform or diethyl ether. The chloride is obtained as a precipitate from the reaction mixture by addition of e.g. ligroin (in the ether solutions) or of diethyl ether (in the chloroform solutions). The filtered product is reacted with an excess of potassium hydrosulfide (III) to obtain the L-2-ammino thiopropionic acid (IV). Compound (IV) is acetylated to obtain (VI) by any of the conventional methods employed for acylating an amino group, e.g. by reaction with acetyl chloride in a suitable solvent, such as chloroform, in the presence of an acid acceptor. Derivative (VI) by reaction in an alkaline medium with a thio-acid (VII) provides compound (VIII), which by reaction in an alkaline medium with derivative (IX) provides derivative (I). The reaction between compound (VIII) and compound (IX) is carried out at a pH between 5 and 7 and at a temperature between 15° and 25° C. Derivative (I) is obtained in a state of high purity by purification on a silica gel column, using as eluent chloroform-methanol (7:3). Operating according to (b) above, an alkali salt of acetyl-3-chloroalanine (X) is reacted with ethyl chloroformate (XI) and the mixed anhydride obtained (XII) as reacted with L-acetyl-cysteine (XIII) to give derivative (XIV); finally (XIV) by reaction in alkaline medium with the thioacid (VII), gives (I) which is purified on a silica gel column, employing as a eluent a chloroform-methanol 7:3 mixture. The reaction between compound (XII) and compound (XIII) is carried out at a pH between 6 and 8 and at a temperature of between -23° and -17° C., while the reaction between compound (XIV) and (VII) is carried out at a pH between 5 and 7 and at a temperature of between 15° and 25° C. The present invention also comprises pharmaceutical compositions containing as active ingredients one or more of the compounds of the invention, together with parmaceutically acceptable vehicles and diluents. The pharmaceutical compositions may be in the following forms: solid, such as capsules, tablets or bonbons with instantaneous or retarded action, monodosis sachets; liquid, such as solutions or emulsions instantaneous or retarded; as suppositories; solutions for injection or for instantaneous or delayed inhalation. In the treatment of bronchial affections, the compounds according to the invention may be administered orally in posologic doses containing, e.g., between 100 and 5000 mg of active substance two, three or four times a day; by injection and inhalation in posologic units of between 50 and 500 mg of active substance, two, three or four times a day; rectally in posologic units of 100 to 1000 mg of active substance two, three or four times a day. The derivatives of the invention are good bronchial liquefiers and expectorants, superior to cysteine at equal doses, while showing low toxicity. The DL 50 value determined on mice and rats, both intraperitoneally and orally, is higher than 3000 mg/Kg for all the examined compounds. The expectorant activity (DE 50 ), determined on rabbits according to (Boyd and Sheppard, Arch. Int. Pharm, 1966, 163, 284, is 100 mg/Kg. The same DE 50 determined on mice according to a modified Mavatari method shown in (Graziani, Cazzulani, I1 Farmaco Ed. Prat. 1981 XXXVI, 3, 167, is respectively of 37 mg/Kg. The following examples will illustrate the process of the invention without limiting it. EXAMPLE 1 Preparation of N-acetyl-S-{N-acetyl[(benzoyl)thio]alanyl}cysteine 1. Preparation of L-3-chloro-2-acetamido-thiopropanoic acid: In a 200 ml flask a solution is prepared by stirring 20 g (0.3 mol) of potassium hydroxide in 80 ml 90% ethanol. Into the flask a 50 ml separatory funnel is inserted and provided with a tube through which hydrogen sulphide is introduced until the solution is saturated and no longer alkaline to phenotphthalein. The mixture is cooled on ice to 10°-15° C. and 0.3 mol (49.3 g) of 3 chloro-L-alanine chloride-hydrochloride are added in 90 minutes while stirring at a temperature of 15° C.; the reaction mixture is then stirred for an additional hour. The potassium chloride which is formed is filtered off, washed with 20 ml 95% ethanol, the solutions are put together and ethanol is evaporated under reduced pressure. The solid residue is dissolved in 70 ml of cold water and the solution is filtered. 0.3 mol acetyl chloride are then added slowly, under strong stirring and under control of the pH, which should be about 8. The solution is stirred for an additional hour and acidified to pH 2.0 with hydrochloric acid. The formed precipitate is filtered off, washed with water and dried in a oven. The dry product is crystallized from water. 15 g of product are obtained. The structure is confirmed by spectral analysis. ______________________________________Elemental Analysis: C H Cl N S______________________________________Calculated Amount: 33.06% 4.43% 19.50% 7.71% 17.65%Amount Found: 33.5% 4.5% 19.3% 7.7% 17.5%______________________________________ 2. Preparation of L-3-benzoyl mercapto-2-acetamido thiopropanoic acid: 54.3 g (0.3 mol) of L-3-chloro-2-acetamido-thiopropanoic acid are suspended in 150 ml of water brought to pH 5.0 by addition of sodium hydroxyde. The temperature is brought to 20° C. and 46 g thiobenzoic acid, 24 g anydrous potassium carbonate and 300 ml water are added rapidly. A yellow, almost clear solution is obtained at pH 6.06 which is left standing overnight (in the darkness) at about 18° C. Thereafter 21 mol 35% hydrochloric acid are added slowly under pH control until a stable pH of 4.0 is reached. The formed precipitate is filtered on a Buchner funnel and washed with 4×100 ml water. The product is then oven dried. Approximately 80 g of product are obtained. The structure is confirmed by spectral analyses. ______________________________________51.14% 5.07% 5.42% 24.85%51.2% 5.04% 5.44% 24.7%______________________________________ 3. Preparation of N-acetyl-S-{N-acetyl[(benzoyl)thio]alanyl}cysteine: 49.69 g (0.3 mol) 3-chloro-N-acetyl-alanine are suspended in 150 ml of water, which is then brought of pH 5.0 by adding sodium hydroxide. The temperature is brought to 20° C. and 78.5 g of L-3-benzoyl mercapto-2-acetamido-thiopropanoic acid, 24 g anhydrus potassium carbonate and 300 ml water are rapidly added. A yellow almost clear solution is obtained at a pH of 6.06 which is left standing for one night at 18° C., in the darkness. Thereafter 35% hydrochloric acid is added slowly, under pH control, to a stable pH to 4.0. The precipitate is filtered off, washed with 4×100 ml water and oven dried. 120 g of product are obtained which can be purified by dissolving it in ethyl acetate and reprecipitating it by addition of ligroin or ethyl ether. The structure is confirmed by spectral analysis. ______________________________________51.36% 5.277% 7.046% 16.13%51.4% 5.28% 7.1% 16.2%______________________________________ EXAMPLE 2 Preparation of N-acetyl-s-(N-acetyl alanyl)cysteine: 1. Preparation of N-acetyl-s-(N-acetyl-3-chloro-alanyl) cysteine Suspension A In a 4 neck, 2 liter flask provided with stirrer, thermometer, calcium chloride protection tube, 67.20 g (0.330 mol) of finely powdered potassium salt of N-acetyl-3-chloro-L-alanine and 600 ml acetone are introduced. After cooling to 20° C., 33.6 g ethyl chloroformate and 26 mol N-methyl morpholine are added. The suspension is left standing for two hours at a temperature of 10° C. or lower, and then brought to 30° C. Solution B 50 g (0,276 mol) of N-acetyl-cysteine, 70 ml acetone and 25 g triethylamine are placed into a 400 ml beaker while stirring and under pH control in such a way that the pH does not rise above 7.5. The solution is then cooled to 0° to -3° C. Reaction Solution B is added to suspension A under stirring within a few minutes keeping the temperature at -15° to -20° C. The turbid solution is kept at -15° to -20° C. for three hours under stirring, then the temperature is raised to 0° C. and the stirring is continued for an additional 4 hours. 170 ml of water are then added and the solution is placed into a 2 liter beaker. It has a pH of aproximately 6.25. Keeping the temperature at between 0° and 5° C., hydrochloric acid is added to a constant pH of 4.0. The solution is extracted with 1000 ml methylene chloride. The precipitate which is formed is filtered off and washed with 4×100 ml of water. It is then dried in an oven obtaining 70 g of product. The structure is confirmed by spectral analysis. ______________________________________38.09% 5.656% 9.871% 11.299% 12.495%38.2% 5.66% 9.88% 11.25% 12.4%______________________________________ 2. (Preparation of N-acetyl-s-(N-acetyl-alanyl)cysteine In a 200 ml flask a solution of 20 g (0.3 mol) of potassium hydroxide in 80 ml 90% ethanol is prepared. Into the flask a 50 ml separatory funnel is inserted and provided with a tube through which hydrogen sulphide is introduced until the solution is saturated and no longer alkaline to phenophthalein. The mixture is cooled on ice to 10°-15° C. and 0.3 mol (85.12 g) of N-acetyl-s-(N-acetyl-3-chloro alanyl) cysteine are added. The mixture is heated on reflux for two hours. After cooling and filtration, the filtrate is diluted with 100 ml water. The pH is brought to 4.0. The obtained precipitate is filtered off, washed with water and oven dried. Aproximately 75 g of product are obtained. The structure is confirmed by instrumental analysis ______________________________________38.95% 5.198% 9.083% 20.79%38.9% 5.2% 9.1% 20.2%______________________________________ EXAMPLE 3 Preparation of N-acetyl-s-{N-acetyl[(benzoyl)thio]alanyl}cysteine Thiobenzoic acid is reacted with N-acetyl-s-(N-acetyl-3-chloroalanyl)cysteine EXAMPLE 4 The derivatives obtained in the preceding examples are treated with Ca(OH) 2 to obtain the respective salts.

The present invention covers D or L or DL-cysteine derivatives of the general formula (I) ##STR1## wherein R represents H or a fatty saturated or unsaturated acid radical, or a radical of an aromatic acid such as benzoic, cynnamic, salycilic, 2-acetoxybenzoic acid or a heterocyclic acid, as well as their salts, in particular the Ca and Mg salts. The invention refers also to a process for preparing said derivatives and to the pharmaceutical preparations containing them as active principle, having a bronchial liquefying and expectorating activity.

FIELD OF THE INVENTION [0001] The invention relates to radio navigation in general, and, more particularly, to generating an accurate estimate of the location of a wireless terminal despite apparently reasonable but misleading or erroneous data. BACKGROUND [0002] FIG. 1 depicts a diagram of the salient components of wireless telecommunications system 100 in accordance with the prior art. Wireless telecommunications system 100 comprises: wireless terminal 101 , cellular base stations 102 - 1 , 102 - 2 , and 102 - 3 , Wi-Fi base stations 103 - 1 and 103 - 2 , wireless switching center 111 , assistance server 112 , location client 113 , and Global Positioning System (“GPS”) constellation 121 . Wireless telecommunications system 100 provides wireless telecommunications service to all of geographic region 120 , in well-known fashion. [0003] The salient advantage of wireless telecommunications over wireline telecommunications is the mobility that is afforded to the user of the wireless terminal. On the other hand, the salient disadvantage of wireless telecommunications lies in that fact that because the wireless terminal is mobile, an interested party might not be able to readily ascertain the location of the wireless terminal. [0004] Such interested parties might include both the user of the wireless terminal and remote parties. There are a variety of reasons why the user of a wireless terminal might be interested in knowing his or her location. For example, the user might be interested in telling a remote party where he or she is or the user might seek advice in navigation. [0005] In addition, there are a variety of reasons why a remote party might be interested in knowing the location of the user. For example, the recipient of an 9-1-1 emergency call from a user might be interested in knowing the location of the wireless terminal so that emergency services vehicles can be dispatched to the user. [0006] There are many techniques in the prior art for estimating the location of a wireless terminal. The common theme to these techniques is that location of the wireless terminal is estimated based on the electromagnetic (e.g., radio, etc.) signals—in one form or another—that are processed (i.e., transmitted or received) by the wireless terminal. [0007] In accordance with one family of techniques, the location of a wireless terminal is estimated based on the transmission range of the base stations with which it is communicating. Because the range of a base station is known to be N meters, this family of techniques provides an estimate for the location that is generally accurate to within N meters. A common name for this family of techniques is “cell identification” or “cell ID.” [0008] There are numerous tricks that can be made to the basic cell ID technique to improve the accuracy of the estimate for the location, and numerous companies like Ericsson, Qualcomm, and Google each tout their own flavor. The principal disadvantage of the family of cell ID techniques is that there are many applications for which the accuracy of the estimate for the location it generates is insufficient. [0009] In accordance with a second family of techniques, the location of a wireless terminal is estimated by analyzing the angle of arrival or time of arrival of the signals transmitted by the wireless terminal. A common, if somewhat inaccurate, name for this family of techniques is called “triangulation.” [0010] There are numerous tricks that can be made to the basic triangulation technique to improve the accuracy of the estimate for the location, and numerous companies like TruePosition each tout their own flavor. The principal disadvantage of the triangulation techniques is that there are many applications for which the accuracy of the estimate for the location it generates is insufficient. [0011] In accordance with a third family of techniques, the location of a wireless terminal is estimated by a receiver in the wireless terminal that receives signals from satellites in orbit. A common name for this family of techniques is “GPS.” [0012] There are numerous tricks that can be made to the basic GPS technique to improve the accuracy of the estimate for the location, and numerous companies like Qualcomm each tout their own flavor. The principal advantage of the GPS techniques is that when it works, the estimate for the location can be accurate to within meters. The GPS techniques are disadvantageous in that they do not work consistently well indoors, in heavily-wooded forests, or in urban canyons. [0013] In accordance with a fourth family of techniques, the location of a wireless terminal is estimated by pattern matching one or more location-dependent traits of one or more electromagnetic signals that are processed (i.e., transmitted and/or received) by the wireless terminal. Common names for this family of techniques include “Wireless Location Signatures,” “RF Pattern Matching,” and “RF Fingerprinting.” [0014] The basic idea is that some traits of an electromagnetic signal remain (more or less) constant as a signal travels from a transmitter to a receiver (e.g., frequency, etc.) and some traits change (e.g., signal strength, relative multi-path component magnitude, propagation delay, etc.). A trait that changes is considered a “location-dependent” trait. Each location can be described or associated with a profile of one or more location-dependent traits of one or more electromagnetic signals. A wireless terminal at an unknown location can observe the traits and then attempt to ascertain its location by comparing the observed traits with a database that correlates locations with expected or predicted traits. [0015] There are numerous tricks that can be made to the basic Wireless Location Signatures technique to improve the accuracy of the estimate for the location, and numerous companies like Polaris Wireless each tout their own flavor. The principal advantage of the Wireless Location Signatures technique is that it is highly accurate and works well indoors, in heavily-wooded forests, and in urban canyons. [0016] All of these techniques rely on empirical data as their basis, and the accuracy of these techniques suffer when some or all of the data is misleading or erroneous. Typically, it is easy to identify and disregard data that is clearly unreasonable. For example, if one datum indicates that a wireless terminal is inside of the Sun, that datum is clearly erroneous and can be disregarded. In some cases a reasonable estimate for the location of the wireless terminal can be generated with the remaining data, and sometimes it cannot. [0017] In contrast, it is difficult to identify data that is apparently reasonable, but misleading or erroneous. For example, if one datum in a set of data suggests a wireless terminal is on a lake near a highway, the datum appears reasonable, but it might or might not be erroneous. For example, the datum might be entirely correct because the wireless terminal is on a boat on the lake. Alternatively, the datum might be erroneous because the wireless terminal is in a car on the highway next to the lake. In either case, it is not easy to know whether using that datum is improving or degrading the overall accuracy of the estimate. [0018] Unfortunately, apparently reasonable, but erroneous or misleading empirical data is commonly used as the basis for estimating the location of a wireless terminal, and, therefore, a technique is needed that ameliorates or eliminates the effect of such data. SUMMARY OF THE INVENTION [0019] The present invention enables an estimate of the location of a wireless terminal to be generated without some of the costs and disadvantages of techniques for doing so in the prior art. For example, some embodiments of the present invention are adept at discounting the contribution of apparently reasonable but erroneous or misleading data. [0020] For example, the illustrative embodiment of the present invention receives data that is evidence of the location of a wireless terminal at each of a plurality of different times. The illustrative embodiment then generates an initial hypothesis for the location of the wireless terminal at each time assuming that all of the data is correct and equally probative. Next, the illustrative embodiment generates an alternative hypotheses for each initial hypothesis on the assumption that each proper subset of datum is erroneous. This is accomplished by underweighting or discarding each datum in the proper subset. [0021] For example, if the set of data for time t(1) is {A, B, C}, then the initial hypothesis for time t(1) is based on an equal weighting of A, B, and C. Because the set comprises three datum, there are six non-empty subsets of datum: {A}, {B}, {C}, {A, B}, {A, C}, and {B, C}. Each alternative hypothesis for time t(1) can be generated by using the data in each of the non-empty subsets and by underweighting or discarding the data not included in the subset. [0022] These alternative hypothesis can be “snapped” or moved to a nearby road or transportation path, or they can be left alone. [0023] Finally, the illustrative embodiment generates the estimate for the location of the wireless terminal at each time in a time frame by determining which combination of initial hypotheses and alternative hypothesis is the most self-consistent during the entire time frame. [0024] The illustrative embodiment comprises: receiving, at a location engine, a first signal value whose value is evidence of the location of the wireless terminal at time t(1); receiving, at the location engine, a second signal value whose value is evidence of the location of the wireless terminal at time t(1); receiving, at the location engine, a third signal value whose value is evidence of the location of the wireless terminal at time t(2); generating, at the location engine, a first hypothesis for the location for the wireless terminal at time t(1) based on the first signal value having first weight and the second signal value having second weight, wherein the first weight is greater than the second weight; generating, at the location engine, a second hypothesis for the location for the wireless terminal at time t(1) based on the first signal value having third weight and the second signal value having fourth weight, wherein the third weight is less than the fourth weight; generating, at the location engine, a first hypothesis for the location for the wireless terminal at time t(2) based on the third signal value; and generating, at the location engine, an estimate for the location of the wireless terminal at time t(2) based on: the first hypothesis for the location for the wireless terminal at time t(1), the second hypothesis for the location for the wireless terminal at time t(1), and the first hypothesis for the location for the wireless terminal at time t(2); and transmitting, from the location engine, the estimate for the location of the wireless terminal at time t(2) for use by a location-based application; wherein the first weight, the second weight, the third weight, and the fourth weight are all real non-negative numbers. BRIEF DESCRIPTION OF THE DRAWINGS [0037] FIG. 1 depicts a diagram of the salient components of wireless telecommunications system 100 in accordance with the prior art. [0038] FIG. 2 depicts a diagram of the salient components of wireless telecommunications system 200 in accordance with the illustrative embodiment of the present invention. [0039] FIG. 3 depicts a block diagram of the salient components of location engine 214 in accordance with the illustrative embodiment. [0040] FIG. 4 depicts a flowchart of the salient processes performed in accordance with the illustrative embodiment of the present invention. [0041] FIG. 5 depicts a road map of geographic region 220 that indicates the four initial hypotheses from Table 2. [0042] FIG. 6 depicts a road map of geographic region 220 that indicates the nine alternative hypotheses generated in task 403 . [0043] FIG. 7 depicts a road map of geographic region 220 that indicates the nine snapped alternative hypotheses generated in task 403 . [0044] FIG. 8 depicts the weighted directed graph that corresponds the initial hypotheses and snapped alternative hypotheses generated in task 406 . [0045] FIG. 9 depicts the minimum weight path through the weighted directed graph depicted in FIG. 8 . [0046] FIG. 10 depicts the road map of geographic region 220 that indicates the final refined hypotheses of the location of wireless terminal at time t, for all t. DETAILED DESCRIPTION [0047] Overview [0048] FIG. 2 depicts a diagram of the salient components of wireless telecommunications system 200 in accordance with the illustrative embodiment of the present invention. Wireless telecommunications system 200 comprises: wireless terminal 201 , cellular base stations 202 - 1 , 202 - 2 , and 202 - 3 , Wi-Fi base stations 203 - 1 and 203 - 2 , wireless switching center 211 , assistance server 212 , location client 213 , location engine 214 , and GPS constellation 221 , which are interrelated as shown. The illustrative embodiment provides wireless telecommunications service to all of geographic region 220 , in well-known fashion, hypothesizes the location of wireless terminal 201 within geographic region 220 at different times, and uses those hypotheses in a location-based application. [0049] In accordance with the illustrative embodiment, wireless telecommunications service is provided to wireless terminal 201 in accordance with the air-interface standard of the 3 rd Generation Partnership Project (“3GPP”). After reading this disclosure, however, it will be clear to those skilled in the art how to make and use alternative embodiments of the present invention that operate in accordance with one or more other air-interface standards (e.g., Global System Mobile “GSM,” UMTS, CDMA-2000, IS-136 TDMA, IS-95 CDMA, 3G Wideband CDMA, IEEE 802.11 Wi-Fi, 802.16 WiMax, Bluetooth, etc.) in one or more frequency bands. As will be clear to those skilled in the art, a wireless terminal is also known as a “cell phone,” “mobile station,” “car phone,” “PDA,” and the like. [0050] Wireless terminal 201 comprises the hardware and software necessary to be 3GPP-compliant and to perform the processes described below and in the accompanying figures. For example and without limitation, wireless terminal 201 is capable of: a. measuring one or more location-dependent traits of each of one of more electromagnetic signals (transmitted by cellular base stations 202 - 1 , 202 - 2 , and 202 - 3 and Wi-Fi base stations 203 - 1 and 203 - 2 ) and of reporting the measurements to location engine 214 , and b. transmitting one or more signals and of reporting the transmission parameters of those signals to location engine 214 , and c. receiving GPS assistance data from assistance server 212 to assist wireless terminal 201 in acquiring and processing GPS ranging signals. [0054] Wireless terminal 201 is mobile and can be at any location within geographic region 220 at any time. Although wireless telecommunications system 200 comprises only one wireless terminal, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention that comprise any number of wireless terminals. [0055] Cellular base stations 202 - 1 , 202 - 2 , and 202 - 3 communicate with wireless switching center 211 via wireline and with wireless terminal 201 via radio in well-known fashion. As is well known to those skilled in the art, base stations are also commonly referred to by a variety of alternative names such as access points, nodes, network interfaces, etc. Although the illustrative embodiment comprises three base stations, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention that comprise any number of base stations. [0056] In accordance with the illustrative embodiment of the present invention, cellular base stations 202 - 1 , 202 - 2 , and 202 - 3 are terrestrial, immobile, and within geographic region 220 . It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which some or all of the base stations are airborne, marine-based, or space-based, regardless of whether or not they are moving relative to the Earth's surface, and regardless of whether or not they are within geographic region 220 . [0057] Cellular base stations 202 - 1 , 202 - 2 , and 202 - 3 comprise the hardware and software necessary to be 3GPP-compliant and to perform the processes described below and in the accompanying figures. For example and without limitation, cellular base stations 202 - 1 , 202 - 2 , and 202 - 3 are capable of: a. measuring one or more location-dependent traits of each of one of more electromagnetic signals (transmitted by wireless terminal 201 ) and of reporting the measurements to location engine 214 , and b. transmitting one or more signals and of reporting the transmission parameters of those signals to location engine 214 . [0060] Wi-Fi base stations 203 - 1 and 203 - 2 communicate with wireless terminal 201 via radio in well-known fashion. Wi-Fi base stations 203 - 1 and 203 - 2 have a shorter range than cellular base stations 202 - 1 , 202 - 2 , and 202 - 3 , but have a higher bandwidth. The location of Wi-Fi base stations 203 - 1 and 203 - 2 is only known to within approximately 30 meters by detecting their signals through drive testing. Wi-Fi base stations 203 - 1 and 203 - 2 are terrestrial, immobile, and within geographic region 220 . [0061] Wi-Fi base stations 203 - 1 and 203 - 2 are capable of: c. measuring one or more location-dependent traits of each of one of more electromagnetic signals (transmitted by wireless terminal 201 ) and of reporting the measurements to location engine 214 , and d. transmitting one or more signals and of reporting the transmission parameters of those signals to location engine 214 . [0064] Wireless switching center 211 comprises a switch that orchestrates the provisioning of telecommunications service to wireless terminal 201 and the flow of information to and from location engine 214 , as described below and in the accompanying figures. As is well known to those skilled in the art, wireless switching centers are also commonly referred to by other names such as mobile switching centers, mobile telephone switching offices, routers, etc. [0065] Although the illustrative embodiment comprises one wireless switching center, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention that comprise any number of wireless switching centers. For example, when a wireless terminal can interact with two or more wireless switching centers, the wireless switching centers can exchange and share information that is useful in estimating the location of the wireless terminal. For example, the wireless switching centers can use the IS-41 protocol messages HandoffMeasurementRequest and HandoffMeasurementRequest2 to elicit signal-strength measurements from one another. The use of two or more wireless switching centers is particularly common when the geographic area serviced by the wireless switching center is small (e.g., local area networks, etc.) or when multiple wireless switching centers serve a common area. [0066] In accordance with the illustrative embodiment, all of the base stations servicing wireless terminal 201 are associated with wireless switching center 211 . It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which any number of base stations are associated with any number of wireless switching centers. [0067] Assistance server 212 comprises hardware and software that is capable of performing the processes described below and in the accompanying figures. In general, assistance server 212 generates GPS assistance data for wireless terminal 201 to aid wireless terminal 201 in acquiring and processing GPS ranging signals from GPS constellation 221 . In accordance with the illustrative embodiment, assistance server 212 is a separate physical entity from location engine 214 ; however, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which assistance server 212 and location engine 214 share hardware, software, or both. [0068] Location client 213 comprises hardware and software that uses the hypothesis for the location of wireless terminal 201 —provided by location engine 214 —in a location-based application, as described below and in the accompanying figures. [0069] Location engine 214 comprises hardware and software that generates one or more hypotheses of the location of wireless terminal 201 as described below and in the accompanying figures. It will be clear to those skilled in the art, after reading this disclosure, how to make and use location engine 214 . Furthermore, although location engine 214 is depicted in FIG. 2 as physically distinct from wireless switching center 211 , it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which location engine 214 is wholly or partially integrated with wireless switching center 211 . [0070] In accordance with the illustrative embodiment, location engine 214 communicates with wireless switching center 211 , assistance server 212 , and location client 213 via a local area network; however it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which location engine 214 communicates with one or more of these entities via a different network such as, for example, the Internet, the Public Switched Telephone Network (PSTN), a wide area network, etc. [0071] In accordance with the illustrative embodiment, wireless switching center 211 , assistance server 212 , location client 213 , and location engine 214 are physically located within geographic region 220 . It will be clear to those skilled in the art, however, after reading this disclosure, how to make and use alternative embodiments of the present invention in which some or all of wireless switching center 211 , assistance server 212 , location client 213 , and location engine 214 are physically located outside of geographic region 220 . [0072] Location Engine 214 [0073] FIG. 3 depicts a block diagram of the salient components of location engine 214 in accordance with the illustrative embodiment. Location engine 214 comprises: processor 301 , memory 302 , and local-area network transmitter/receiver 303 , which are interconnected as shown. [0074] Processor 301 is a general-purpose processor that is capable of executing operating system 311 and application software 312 , and of populating, amending, using, and managing Location-Trait Database 313 , as described in detail below and in the accompanying figures. For the purposes of this specification, a “processor” is defined as one or more computational elements, whether co-located or not and whether networked together or not. [0075] For the purposes of this specification, the “Location-Trait Database” is defined as a database that associates one or more location-dependent traits of electromagnetic signals processed (i.e., transmitted and/or received) by wireless terminal 201 with each of a plurality of locations. In general, the Location-Trait Database is what enables location engine 214 to convert observed location-dependent traits into an estimate for the location of wireless terminal 201 . It will be clear to those skilled in the art how to make and use processor 301 . [0076] Memory 302 is a non-volatile memory that stores: [0077] a. operating system 311 , and [0078] b. application software 312 , and [0079] c. Location-Trait Database 313 . [0000] It will be clear to those skilled in the art how to make and use memory 302 . [0080] Transmitter/receiver 303 enables location engine 214 to transmit and receive information to and from wireless switching center 211 , assistance server 212 , and location client 213 . In addition, transmitter/receiver 303 enables location engine 214 to transmit information to and receive information from wireless terminal 201 and cellular base stations 202 - 1 through 202 - 3 via wireless switching center 211 . It will be clear to those skilled in the art how to make and use transmitter/receiver 303 . [0081] Operation of the Illustrative Embodiment [0082] FIG. 4 depicts a flowchart of the salient processes performed in accordance with the illustrative embodiment of the present invention. [0083] At task 401 , location engine 214 receives signals from wireless switching center 211 whose values are evidence of the location of wireless terminal 201 at different times. Each signal radiates from a different source (e.g., cellular base stations 202 - 1 , 202 - 2 , and 202 - 3 , Wi-Fi base stations 203 - 1 and 203 - 2 , wireless terminal 201 , etc.). Table 1 depicts three signals, S(1), S(2), and S(3), and the values of those signals at times t(1), t(2), t(3), and t(4). [0000] TABLE 1 Nine signals whose values are evidence of the location of wireless terminal 201 in geographic region 220 at four different times. time Signal S(1) Signal S(2) Signal S(3) t(1) SV(1, 1) SV(1, 2) Not Available t(2) SV(2, 1) SV(2, 2) SV(2, 3) t(3) SV(3, 1) Not Available SV(3, 3) t(4) Not Available SV(4, 2) SV(4, 3) In the signal value SV(t, j), t represents the time for which the signal is evidence, and j represents the source of the signal. [0084] In accordance with the illustrative embodiment, the value of each signal is a signal-strength measurement made by wireless terminal 201 of a radio signal transmitted by one of cellular base stations 202 - 1 and 202 - 2 and Wi-Fi base station 203 - 1 . It will be clear to those skilled in the art, however, after reading this disclosure, how to make and use alternative embodiments of the present invention in which the value of each received signal is a measurement of any location-dependent trait of an electromagnetic signal that is evidence of the location of wireless terminal 201 . For example and without limitation, each signal can be: i. evidence of the propagation delay—in either one-direction or round-trip—between wireless terminal 120 and another entity (e.g., a cellular base station, a GPS satellite, a Wi-Fi base station, etc.), or ii evidence of the time difference of arrival of a signal transmitted by wireless terminal 201 and two other entities (e.g., a cellular base station, a GPS satellite, a Wi-Fi base station, etc.), or iii. evidence of the angle of arrival of a signal transiting between wireless terminal 201 and another entity (e.g., a cellular base station, a GPS satellite, a Wi-Fi base station, etc.), or iv. evidence that wireless terminal 201 can receive and decode a signal from another entity (e.g., a cellular base station, a GPS satellite, a Wi-Fi base station, etc.), or v. evidence that an entity (e.g., a cellular base station, a GPS satellite, a Wi-Fi base station, etc.) can receive and decode a signal from wireless terminal 201 , or vi. evidence of any location-dependent trait (e.g., signal strength, rake receiver coefficients, phase delay, etc.) of an electromagnetic signal that is processed by wireless terminal 201 , or vii. any combination of i, ii, iii, iv, v, or vi. [0092] In accordance with the illustrative embodiment, three signals are received for time t(2) but only two signals are received for times t(1), t(3), and t(4) because signal value SV(1, 3), SV(3, 2) and SV(4, 1) were not measured or reported. It will be clear to those skilled in the art, however, after reading this disclosure, how to make and use alternative embodiments of the present invention in which any number of signals are received and used for each moment of time. [0093] In accordance with the illustrative embodiment, all of the signals are evidence of the same type of physical quantity (i.e., received signal strength), but it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which the type of physical quantity represented varies (e.g., three signal-strength measurements are received for one moment, one signal-strength measurement and two time-difference of arrival measurements are received for the next moment, etc.). In accordance with the illustrative embodiment, there is signal data available for four moments of time, but it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which data is available for any number of moments. [0094] At task 402 , location engine 214 generates an “initial” hypothesis for the location of wireless terminal 201 at each of times t(1), t(2), t(3), and t(4). Each hypothesis and each estimate of the location of wireless terminal 201 is a latitude-longitude pair. [0095] Each initial hypothesis for the location of wireless terminal 201 is a hypothesis that does not discount the probative value of any signal value. In other words, all of the signals that are evidence of the location of wireless terminal 201 at one time are accorded equal probity for the purposes of creating the initial hypotheses. In practice, this is achieved by weighting each signal value SV(t, j) with weight W(t, j, 0), wherein W(t, j, 0) are equal and non-negative real values for all t and all j. [0096] In accordance with the illustrative embodiment, location engine 215 generates the initial hypotheses using the signals received at task 401 and the technique of wireless location signatures. The wireless location signatures technique is well-known to those skilled in the art and is taught, for example, in U.S. Pat. No. 7,257,414 B2, which is incorporated by reference. It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which the initial hypotheses are generated using: [0097] i. wireless location signatures, or [0098] ii. triangulation, or [0099] iii. trilateration, or [0100] iv. cellular-base-station cell identification, or [0101] v. Wi-Fi-base-station cell identification, or [0102] vi. any combination of i, ii, iii, iv, and v. [0103] At time t(2), the initial hypothesis is based on three signals, but at times t(1), t(3), and t(4) the initial hypotheses are based on only two signals. Table 2 depicts the values of each of the four initial hypotheses. [0000] TABLE 2 The initial locations of wireless terminal 201 in geographic region 220 at four different times. time Initial Hypothesis t(1) IH(1) t(2) IH(2) t(3) IH(3) t(4) IH(4) [0104] FIG. 5 depicts a road map of geographic region 220 that indicates the four initial hypotheses from Table 2. In the map the initial hypothesis for the location of wireless terminal 201 at time t(i) is depicted by a bull's-eye with the identifier IH(i). [0105] Therefore, the initial hypothesis IH(1) for wireless terminal 201 at time t(1) is on West Street, just south of Left Street. The initial hypothesis IH(2) at time t(2) is between Top Street and North Street, just east of West Street. The ambiguity of whether wireless terminal 201 was on Top Street or North Street at time t(2) is undesirable because a known drug-dealer operates on Top Street and it would be advantageous to know whether the operator of wireless terminal 201 might be involved with the drug dealer or not. The illustrative embodiment of the present invention resolves that ambiguity beginning in task 403 below. The initial hypothesis IH(3) for wireless terminal 201 at time t(3) is between Lakeside Road, North Street, and East Street. The initial hypothesis IH(4) at time t(4) is unambiguously on Lakeside Road. [0106] In accordance with the illustrative embodiment, the initial hypotheses are used as is, but it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which one or more of the initial hypotheses are “snapped” or repositioned to one or more roadways or other transportation paths in the vicinity of the initial hypothesis. [0107] Referring again to FIG. 4 , at task 403 location engine 214 generates additional “alternative” hypotheses for the location of wireless terminal 201 at each time for which two or more signal values are available. Each alternative hypothesis is also a hypothesis for the location of wireless terminal 201 . [0108] In accordance with the illustrative embodiment, location engine 214 uses the same location technique to generate the alternative hypotheses as it did to generate the initial hypotheses in task 402 . It will be clear to those skilled in the art, however, after reading this disclosure, how to make and use alternative embodiments of the present invention in which the candidates hypotheses are generated using an alternative method, such as: [0109] i. wireless location signatures, or [0110] ii. triangulation, or [0111] iii. trilateration, or [0112] iv. cellular-base-station cell identification, or [0113] v. Wi-Fi-base-station cell identification, or [0114] vi. any combination of i, ii, iii, iv, and v. [0115] In accordance with the illustrative embodiment, each alternative hypothesis for a given time is generated by discounting as unreliable exactly one signal value. For example, when there are N>1 signal values available for a given time, there are N alternative hypotheses generated for that time. When there is only one signal available for a given time, no alternative hypotheses are generated because the one signal value cannot be discounted with respect to itself. [0116] It will be clear to those skilled in the art, however, how to make and use alternative embodiments of the present invention in which there are a different number of alternative hypotheses generated for a given time (e.g., 1, 2, 3, N−1, 2 N −2, N!, etc.). For example, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which each alternative hypothesis for a given time is generated by discounting as unreliable every combination of signal values. This would generate 2 N −2 alternative hypotheses. Furthermore, some alternative embodiments of the present invention could discount each signal value by a continuous value, which would generate up to N! alternative hypotheses. [0117] In practice, the illustrative embodiment generates each alternative hypothesis AH(t, k) for the location of wireless terminal 201 at time t by weighting each signal value SV(t, j) with weight W(t, j, k), wherein W(t, j, k) is a non-negative real value for all times i, all signals j, and all hypotheses k. It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which some or all of the discounted signal's values have a weight of zero (0). [0118] Table 3 depicts signals SV(1, 1) and SV(1, 2) and their associated weights for the purposes of generating alternative hypotheses AH(1, 1) and AH(1, 2). [0000] TABLE 3 The weights and their relationships for generating the alternative hypotheses at time t(1). Alternative Signal Signal Signal Weight Hypothesis SV(1, 1) SV(1, 2) SV(1, 3) Relationship AH(1, 1) W(1, 1, 1) W(1, 2, 1) Not W(1, 1, 1) < Available W(1, 2, 1) AH(1, 2) W(1, 1, 2) W(1, 2, 2) Not W(1, 1, 2) > Available W(1, 2, 2) Not Applicable Not Applicable Not Not Not Applicable Applicable Available [0119] Table 4 depicts signals SV(2, 1), SV(2, 2), and SV(2, 3) and their associated weights for the purposes of generating alternative hypotheses AH(2, 1), AH(2, 2), and AH(2, 3). [0000] TABLE 4 The weights and their relationships for generating the alternative hypotheses at time t(2). Alter- native Hy- Signal Signal Signal Weight pothesis SV(2, 1) SV(2, 2) SV(2, 3) Relationship AH(2, 1) W(2, 1, 1) W(2, 2, 1) W(2, 3, 1) W(2, 1, 1) < W(2, 2, 1) W(2, 1, 1) < W(2, 3, 1) W(2, 2, 1) = W(2, 3, 1) AH(2, 2) W(2, 1, 2) W(2, 2, 2) W(2, 3, 2) W(2, 2, 2) < W(2, 1, 2) W(2, 2, 2) < W(2, 3, 2) W(2, 1, 2) = W(2, 3, 2) AH(2, 3) W(2, 1, 3) W(2, 2, 3) W(2, 3, 3) W(2, 3, 3) < W(2, 1, 3) W(2, 3, 3) < W(2, 2, 3) W(2, 1, 3) = W(2, 2, 3) [0120] In Table 4, W(2, 2, 1)=W(2, 3, 1), W(2, 1, 2)=W(2, 3, 2), and W(2, 1, 3)=W(2, 2, 3), but it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which some or all of these relationships are not true in order to partially discount some signal values. For example, W(2, 2, 1)<W(2, 3, 1), W(2, 1, 2)<W(2, 3, 2), W(2, 1, 3)<W(2, 2, 3), W(2, 2, 1)>W(2, 3, 1), W(2, 1, 2)>W(2, 3, 2), and W(2, 1, 3)>W(2, 2, 3). [0121] Table 5 depicts signals SV(3, 1) and SV(3, 3) and their associated weights for the purposes of generating alternative hypotheses AH(3, 1) and AH(3, 3). [0000] TABLE 5 The weights and their relationships for generating the alternative hypotheses at time t(3). Alternative Signal Signal Signal Weight Hypothesis SV(3, 1) SV(3, 2) SV(3, 3) Relationship AH(3, 1) W(3, 1, 1) Not W(3, 3, 1) W(3, 1, 1) < Available) W(3, 3, 1) Not Applicable Not Applicable Not Not Not Applicable Available Applicable AH(3, 3) W(3, 1, 3) Not W(3, 3, 3) W(3, 1, 3) > Available W(3, 3, 3) [0122] Table 6 depicts signal values SV(4, 2), and SV(4, 3) and their associated weights for the purposes of generating alternative hypotheses AH(4, 2), and AH(4, 3). [0000] TABLE 6 The weights and their relationships for generating the alternative hypotheses at time t(4). Alternative Signal Signal Signal Weight Hypothesis SV(4, 1) SV(4, 2) SV(4, 3) Relationship Not Applicable Not Not Applicable Not Not Applicable Available Applicable AH(4, 2) Not W(4, 2, 2) W(4, 3, 2) W(4, 2, 2) < Available W(4, 3, 2) AH(4, 3) Not W(4, 2, 3) W(4, 3, 3) W(4, 2, 3) > Available W(4, 3, 3) [0123] FIG. 6 depicts a road map of geographic region 220 that indicates the four initial hypotheses generated in task 402 plus the nine alternative hypotheses generated in task 403 . In the map the alternative hypotheses of the location of wireless terminal 201 are represented by a bull's-eye with the identifier AH(t, k). [0124] In general, the alternative hypotheses for time t(t) are in the general vicinity of the initial hypotheses for the same time, as generally would be expected. But the generation and mapping of the alternative hypotheses does not, per se, resolve the ambiguities presented by the initial hypotheses. For example, the alternative hypothesis AH(1,2) on Left Street and the alternative hypothesis AH(1, 1) on West Street do not unambiguously resolve the question presented by the initial hypothesis IH(1) of whether wireless terminal 201 was on West Street or Left Street at time t(1). Ambiguities like these are resolved beginning in task 404 below. [0125] At task 404 , location engine 214 generates a snapped alternative hypothesis SAH(t, k) for each alternative hypothesis AH(t, k). The snapped alternative hypothesis SAH(t, k) is also a hypothesis for the location of wireless terminal 201 . [0126] In accordance with the illustrative embodiment, the snapped alternative hypothesis SAH(t, k) is a location on a road that is the shortest Euclidean distance between the alternative hypothesis AH(t, k) and any point on any road. The snapped alternative hypothesis SAH(t, k) corresponding to each alternative hypothesis AH(t, k) is depicted in Table 7 and FIG. 7 . [0000] TABLE 7 The alternative hypotheses and their corresponding snapped alternative hypotheses. Snapped Alternative Alternative Hypothesis Hypothesis AH(1, 1) SAH(1, 1) AH(1, 2) SAH(1, 2) AH(2, 1) SAH(2, 1) AH(2, 2) SAH(2, 2) AH(2, 3) SAH(2, 3) AH(3, 1) SAH(3, 1) AH(3, 3) SAH(3, 3) AH(4, 2) SAH(4, 2) AH(4, 3) SAH(4, 3) [0127] In accordance with the illustrative embodiment, there is one snapped alternative hypothesis for each alternative hypothesis, but it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which some or all of the alternative hypothesis have a plurality of snapped alternative hypotheses. [0128] Referring again to FIG. 4 , at task 405 , location engine 214 generates a measure of distance between each snapped alternative hypothesis SAH(t, k) and the corresponding initial hypothesis B(t) to generate a measure of discrepancy MOD(t, k). In accordance with the illustrative embodiment, the measure of distance is the Euclidean distance. The measures of discrepancy are depicted in Table 8. [0000] TABLE 8 The alternative hypotheses and their associated measures of discrepancy. Snapped Corresponding Alternative Initial Measure of Hypothesis Hypothesis Discrepancy SAH(1, 1) B(1) MOD(1, 1) SAH(1, 2) B(1) MOD(1, 2) SAH(2, 1) B(2) MOD(2, 1) SAH(2, 2) B(2) MOD(2, 2) SAH(2, 3) B(2) MOD(2, 3) SAH(3, 1) B(3) MOD(3, 1) SAH(3, 3) B(3) MOD(3, 3) SAH(4, 2) B(4) MOD(4, 2) SAH(4, 3) B(4) MOD(4, 3) [0129] At task 406 , location server 214 generates a weighted directed graph that comprises: (i) a node that corresponds to each initial hypothesis B(t), for all t, and (ii) a node that corresponds to each snapped alternative hypothesis SAH(t, k), for all t and all k, and (iii) a directed link from each initial hypothesis B(t) to initial hypothesis B(t+1), for all t, and (iv) a directed link from each initial hypothesis B(t) to each snapped alternative hypothesis SAH(t+1, k), for all t and all k, and (v) a directed link from each snapped alternative hypothesis SAH(t, k) to each initial hypothesis B(t+1), for all t and all k, and (vi) a directed link from each snapped alternative hypothesis SAH(t, k) to each snapped alternative hypothesis SAH(t+1, k), for all t and all k. The result is a directed graph, as shown in FIG. 8 , that represents every possible combination of paths from time t(1) to time t(4). All of the nodes that correspond to the same time t are depicted in a single column, and the nodes corresponding to time t are depicted in a column to the left of the nodes corresponding to time t+1. [0136] In accordance with the illustrative embodiment, (i) each node that corresponds to a initial hypothesis B(t) has an associated cost of zero (0), and (ii) each node that corresponds to a snapped alternative hypothesis SAH(t, k) has an associated cost equal to its associated measure of discrepancy MOD(t, k), and (iii) each directed link from node X to node Y has a cost equal to a measure of the distance between the location associated with node X and the location associated with node Y. [0140] In accordance with the illustrative embodiment, the measure of distance from node X to node Y is the road travel time, but it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which the measure of distance is another metric, such as for example and without limitation, the Euclidean distance from node X to node Y, the road travel time, etc. [0141] At task 407 , location server 214 generates an estimate E(t) for the location of wireless terminal 201 for all t. To accomplish this, location server 214 determines the minimum-cost path through the graph constructed in task 406 using well-known dynamic programming techniques. [0142] Once the minimum-cost path has been determined, the nodes in the minimum-cost path constitute the final, best estimates of the location of wireless terminal 201 at each time. [0143] The minimum-cost path through the directed graph is depicted in FIG. 9 as beginning at snapped alternative hypothesis SAH(1, 1), proceeding to snapped alternative hypothesis SAH(2, 3), proceeding to snapped alternative hypothesis SAH(3, 3), and terminating at initial hypothesis IH(4). Therefore, E(1) is the location corresponding to snapped alternative hypothesis SAH(1, 1), E(2) is the location corresponding to base hypothesis SAH(2, 3), E(3) is the location corresponding to snapped alternative hypothesis SAH(3, 3), and E(4) is the location corresponding to snapped alternative hypothesis IH(4). This is summarized in Table 9. [0000] TABLE 9 The alternative hypotheses and their corresponding hypotheses. Estimate Hypothesis E(1) SAH(1, 1) E(2) SAH(2, 2) E(3) SAH(3, 3) E(4) IH(4) [0144] FIG. 10 depicts the road map of geographic region 220 that indicates the final refined hypotheses of the location of wireless terminal at time t, for all t. As part of task 407 , each of the refined hypotheses is transmitted from location engine 214 to location client 213 for use in a location-based application.

A location engine is disclosed that estimates the location of a wireless terminal using (i) cell ID, (ii) triangulation, (iii) GPS, (iv) RF pattern-matching, or (v) any combination of them. The location engine is adept at discounting the contribution of apparently reasonable but erroneous data. The location engine receives data that are evidence of the location of a wireless terminal at each of a plurality of different times. The location engine then generates an initial hypothesis for the location of the wireless terminal at each time assuming that all of the data is correct and equally probative. Next, the location engine generates one alternative hypothesis for each initial hypothesis and each datum assuming that the datum is erroneous. Finally, the location engine generates the estimate for the location of the wireless terminal at each time by determining which combination of initial hypotheses and alternative hypothesis is the most self-consistent.

FIELD OF THE INVENTION [0001] The present invention relates to incorporation of a carboxylation system into the bleach plant of a wood pulp mill to provide carboxylated cellulosic fibers. BACKGROUND OF THE INVENTION [0002] Cellulose is a carbohydrate consisting of a long chain of glucose units, all β-linked through the 1′-4 positions. Native plant cellulose molecules may have upwards of 2200 anhydroglucose units. The number of units is normally referred to as degree of polymerization (D.P.). Some loss of D.P. inevitably occurs during purification. A D.P. approaching 2000 is usually found only in purified cotton linters. Wood derived celluloses rarely exceed a D.P. of about 1700. The structure of cellulose can be represented as follows: [0003] Chemical derivatives of cellulose have been commercially important for almost a century and a half. Nitrocellulose plasticized with camphor was the first synthetic plastic and has been in use since 1868. A number of cellulose ether and ester derivatives are presently commercially available and find wide use in many fields of commerce. Virtually all cellulose derivatives take advantage of the reactivity of the three available hydroxyl groups (i.e., C2, C3, and C6). Substitution at these groups can vary from very low, about 0.01, to a maximum of 3. Among important cellulose derivatives are cellulose acetate, used in fibers and transparent films; nitrocellulose, widely used in lacquers and gunpowder; ethyl cellulose, widely used in impact resistant tool handles; methyl cellulose, hydroxyethyl, hydroxypropyl, and sodium carboxymethyl cellulose, water soluble ethers widely used in detergents, as thickeners in foodstuffs, and in papermaking. Cellulose itself has been modified for various purposes. Cellulose fibers are naturally anionic in nature, as are many papermaking additives. A cationic cellulose is described in U.S. Pat. No. 4,505,775, issued to Harding et al. This cellulose has greater affinity for anionic papermaking additives such as fillers and pigments and is particularly receptive to acid and anionic dyes. U.S. Pat. No. 5,667,637, issued to Jewell et al., describes a low degree of substitution (D.S.) carboxyethyl cellulose which, along with a cationic resin, improves the wet to dry tensile and burst ratios when used as a papermaking additive. U.S. Pat. No. 5,755,828, issued to Westland, describes a method for increasing the strength of articles made from crosslinked cellulose fibers having free carboxylic acid groups obtained by covalently coupling a polycarboxylic acid to the fibers. [0004] For some purposes, cellulose has been oxidized to make it more anionic to improve compatibility with cationic papermaking additives and dyes. Various oxidation treatments have been used. Among these are nitrogen dioxide and periodate oxidation coupled with resin treatment of cotton fabrics for improvement in crease recovery as suggested by Shet, R. T. and A. M. Nabani, Textile Research Journal, November 1981: 740-744. Earlier work by Datye, K. V. and G. M. Nabar, Textile Research Journal, July 1963: 500-510, describes oxidation by metaperiodates and dichromic acid followed by treatment with chlorous acid for 72 hours or 0.05 M sodium borohydride for 24 hours. Copper number was greatly reduced by borohydride treatment and less so by chlorous acid. Carboxyl content was slightly reduced by borohydride and significantly increased by chlorous acid. The products were subsequently reacted with formaldehyde. Southern pine kraft springwood and summer wood fibers were oxidized with potassium dichromate in oxalic acid. Luner, P., et al., Tappi 50(3):117-120 (1967). Handsheets made with the fibers showed improved wet strength believed to be due to aldehyde groups. Pulps have also been oxidized with chlorite or reduced with sodium borohydride. Luner, P., et al., Tappi 50(5):227-230, 1967. Handsheets made from pulps treated with the reducing agent showed improved sheet properties over those not so treated. Young, R. A., Wood and Fiber 10(2):112-119, 1978 describes oxidation primarily by dichromate in oxalic acid to introduce aldehyde groups in sulfite pulps for wet strength improvement in papers. Shenai, V. A. and A. S. Narkhede, Textile Dyer and Primer, May 20, 1987: 17-22 describes the accelerated reaction of hypochlorite oxidation of cotton yarns in the presence of physically deposited cobalt sulfide. The authors note that partial oxidation has been studied for the past hundred years in conjunction with efforts to prevent degradation during bleaching. They also discuss in some detail the use of 0.1 M sodium borohydride as a reducing agent following oxidation. The treatment was described as a useful method of characterizing the types of reducing groups as well as acidic groups formed during oxidation. The borohydride treatment noticeably reduced copper number of the oxidized cellulose. Copper number gives an estimate of the reducing groups such as aldehydes present on the cellulose. Borohydride treatment also reduced alkali solubility of the oxidized product, but this may have been related to an approximate 40% reduction in carboxyl content of the samples. Andersson, R., et al. in Carbohydrate Research 206: 340-346 (1990) describes oxidation of cellulose with sodium nitrite in orthophosphoric acid and describe nuclear magnetic resonance elucidation of the reaction products. [0005] Davis, N. J., and S. L. Flitsch, Tetrahedron Letters 34(7): 1181-1184 (1993) describe the use and reaction mechanism of 2,2,6,6-tetramethylpiperidinyloxy free radical (TEMPO) with sodium hypochlorite to achieve selective oxidation of primary hydroxyl groups of monosaccharides. Following the Davis et al. paper this route to carboxylation then began to be more widely explored. de Nooy, A. E. J., et al., Receuil des Travaux Chimiques des Pays-Bas 113: 165-166 (1994) reports similar results using TEMPO and hypobromite for oxidation of primary alcohol groups in potato starch and inulin. The following year, these same authors in Carbohydrate Research 269:89-98 (1995) report highly selective oxidation of primary alcohol groups in water soluble glucans using TEMPO and a hypochlorite/bromide oxidant. [0006] WO 95/07303 (Besemer et al.) describes a method of oxidizing water soluble carbohydrates having a primary alcohol group, using TEMPO with sodium hypochlorite and sodium bromide. Cellulose is mentioned in passing in the background although the examples are principally limited to starches. The method is said to selectively oxidize the primary alcohol at C-6 to carboxylic acid group. None of the products studied were fibrous in nature. [0007] WO 99/23117 (Viikari et al.) describes oxidation using TEMPO in combination with the enzyme laccase or other enzymes along with air or oxygen as the effective oxidizing agents of cellulose fibers, including kraft pine pulps. [0008] A year following the above noted Besemer publication, the same authors, in Cellulose Derivatives, Heinze, T. J. and W. G. Glasser, eds., Ch. 5, pp. 73-82 (1996), describe methods for selective oxidation of cellulose to 2,3-dicarboxy cellulose and 6-carboxy cellulose using various oxidants. Among the oxidants used were a periodate/chlorite/hydrogen peroxide system, oxidation in phosphoric acid with sodium nitrate/nitrite, and with TEMPO and a hypochlorite/bromide primary oxidant. Results with the TEMPO system were poorly reproduced and equivocal. In the case of TEMPO oxidation of cellulose, little or none would have been expected to go into solution. The homogeneous solution of cellulose in phosphoric acid used for the sodium nitrate/sodium nitrite oxidation was later treated with sodium borohydride to remove any carbonyl function present. [0009] Chang, P. S. and J. F. Robyt, Journal of Carbohydrate Chemistry 15(7):819-830 (1996), describe oxidation of ten polysaccharides including α-cellulose at 0 and 25° C. using TEMPO with sodium hypochlorite and sodium bromide. Ethanol addition was used to quench the oxidation reaction. The resulting oxidized α-cellulose had a water solubility of 9.4%. The authors did not further describe the nature of the α-cellulose. It is presumed to have been a so-called dissolving pulp or cotton linter cellulose. Barzyk, D., et al., in Transactions of the 11 th Fundamental Research Symposium, Vol. 2, 893-907 (1997), note that carboxyl groups on cellulose fibers increase swelling and impact flexibility, bonded area and strength. They designed experiments to increase surface carboxylation of fibers. However, they ruled out oxidation to avoid fiber degradation and chose to form carboxymethyl cellulose in an isopropanol/methanol system. [0010] Isogai, A. and Y. Kato, in Cellulose 5:153-164, 1998 describe treatment of several native, mercerized, and regenerated celluloses with TEMPO to obtain water soluble and insoluble polyglucuronic acids. They note that the water soluble products had almost 100% carboxyl substitution at the C-6 site. They further note that oxidation proceeds heterogeneously at the more accessible regions on solid cellulose. [0011] Kitaoka, T., A. Isogai, and F. Onabe, in Nordic Pulp and Paper Research Journal 14(4):279-284, 1999, describe the treatment of bleached hardwood kraft pulp using TEMPO oxidation. Increasing amounts of carboxyl content gave some improvement in dry tensile index, Young's modulus, and brightness, with decreases in elongation at breaking point and opacity. Other strength properties were unaffected. Retention of PAE-type wet strength resins was somewhat increased. The products described did not have any stabilization treatment after the TEMPO oxidation. [0012] U.S. Pat. No. 6,379,494 describes a method for making stable carboxylated cellulose fibers using a nitroxide-catalyzed process. In the method, cellulose is first oxidized by nitroxide catalyst to provide carboxylated as well as aldehyde and ketone substituted cellulose. The oxidized cellulose is then stabilized by reduction of the aldehyde and ketone substituents to provide the carboxylated fiber product. Nitroxide-catalyzed cellulose oxidation occurs predominately at the primary hydroxyl group on C-6 of the anhydroglucose moiety. In contrast to some of the other routes to oxidized cellulose, only very minor oxidation occurs at the secondary hydroxyl groups at C-2 and C-3. [0013] In nitroxide oxidation of cellulose, primary alcohol oxidation at C-6 proceeds through an intermediate aldehyde stage. In the process, the nitroxide is not irreversibly consumed in the reaction, but is continuously regenerated by a secondary oxidant (e.g., hypohalite) into the nitrosonium (or oxyammonium or oxammonium) ion, which is the actual oxidant. In the oxidation, the nitrosonium ion is reduced to the hydroxylamine, which can be re-oxidized to the nitroxide. Thus, in the method, it is the secondary oxidant (e.g., hypohalite) that is consumed. The nitroxide may be reclaimed or recycled from the aqueous system. [0014] The resulting oxidized cellulose product is an equilibrium mixture including carboxyl and aldehyde substitution. Aldehyde substituents on cellulose are known to cause degeneration over time and under certain environmental conditions. In addition, minor quantities of ketone may be formed at C-2 and C-3 of the anhydroglucose units and these will also lead to degradation. Marked degree of polymerization loss, fiber strength loss, crosslinking, and yellowing are among the consequent problems. Thus, to prepare a stabilized carboxylated product, aldehyde and ketone substituents formed in the oxidation step are reduced to hydroxyl groups, or aldehyde substituents are oxidized to a carboxyl group in a stabilization step. [0015] In addition to TEMPO, other nitroxide derivatives for making carboxylated cellulose fibers have been described. See, for example, U.S. Pat. No. 6,379,494 and WO 01/29309, Methods for Making Carboxylated Cellulose Fibers and Products of the Method. [0016] A method of preparation of carboxylic acids or their salts by oxidation of primary alcohols using hindered N-chloro hindered cyclic amines and hypochlorite, in aqueous solutions or in mixed solvent systems containing ethyleneglycol dimethyl ether, diethyleneglycol dimethyl ether, triethyleneglycol dimethyl ether, toluene, acetonitrile, ethylacetate, t-butanol and other solvents is described in JP10130195, “Manufacturing Method of Carboxylic Acid and Its Salts”. Other oxidants described include chlorine, hypobromite, bromite, trichloro isocyanuric acid, tribromo isocyanuric acid, or combinations. [0017] Despite the advances made in the development of methods for making carboxylated cellulose pulps including catalytic oxidation systems, there remains a need for improved methods and catalysts for making carboxylated cellulose pulp. The present invention seeks to fulfill these needs and provides further related advantages. SUMMARY OF THE INVENTION [0018] A carboxylation system and process for wood pulp which may be placed in an existing pulp mill bleach plant, or incorporated into a new bleach plant with little additional equipment. A carboxylation system and process for wood pulp which will allow the mill to transition from regular pulp to carboxylated pulp and back with ease. [0019] What is needed is a process and equipment that allows pulp to be carboxylated in an existing pulp mill without large capital costs. [0020] Long reaction times require large tanks, land on which to put the tanks and a great deal of capital. One of the aspects of the present carboxylation reaction is the ability to place the needed equipment into the confines of an existing pulp mill bleach plant. This required reducing the time of reaction so that it could take place within the confines of the equipment in the plant. [0021] A wood pulp carboxylation system has a first stage in which the pulp is oxidized to provide a pulp containing both carboxyl and aldehyde functional groups and second stage in which the aldehyde groups are converted to carboxyl groups. The first stage is a carboxylation stage and the second stage is a stabilization stage. [0022] It was initially thought that the first stage of carboxylation would require at least 15 minutes so that carboxylating wood pulp would require two additional units after the bleach plant. The first unit would be a tank for the carboxylation process and the second unit would be another tank for the stabilization reaction. These would be expensive to install. [0023] After much work the time for the first stage was reduced to 2 minutes. This still required a separate tank for the first stage carboxylation. [0024] Additional work reduced the time for the first stage to 1 minute. The carboxylation unit could be placed between the extraction stage and the chlorine dioxide stage of the bleach plant, but additional piping was required to provide the necessary reaction time. The chlorine dioxide tower could be used for the stabilization reaction. Again the carboxylation unit would be expensive to install, though not as expensive as with longer reaction times. [0025] Additional work reduced the first stage reaction time to 30 seconds or less. Now it was possible to use the existing pulp mill equipment with only the addition of mixers and supply lines and supply storage. [0026] By using advantageous chemical loadings and chemicals it was found that the time for the first stage of carboxylation could be shortened into a range of less than a minute. Times of 1 second to 60 seconds are preferred and times of 5 to 30 seconds most preferred. [0027] The first stage of the carboxylation unit can now be a short length of pipe between the extraction stage washer and the chlorine dioxide tower. The length and diameter of pipe will depend on the time required for the first stage of carboxylation process. The chlorine dioxide tower can be the stabilization unit. In mills which have two chlorine dioxide towers with a washer between them, the unit for the first stage of carboxylation can be placed between the first chlorine dioxide washer and the second chlorine dioxide tower. [0028] Another aspect was to use chemicals normally found at the pulp mill and keep new chemicals to a minimum. BRIEF DESCRIPTION OF THE DRAWINGS [0029] FIG. 1 is diagram of an extraction stage and a chlorine dioxide stage of a standard pulp mill. [0030] FIGS. 2 and 3 are diagrams of an extraction stage and a chlorine dioxide stage showing the changes to provide a carboxylation reaction. DETAILED DESCRIPTION OF THE INVENTION [0031] In Applicant's copending U.S. patent application Ser. No. 09/875,177 filed Jun. 6, 2001, which is incorporated herein by reference in its entirety, the use of chlorine dioxide is disclosed as a secondary oxidant for use with a hindered cyclic oxammonium salt as the primary oxidant. [0032] This application discusses the nitroxide, oxammonium salt, amine or hydroxylamine of a corresponding hindered heterocyclic amine compound. The oxammonium salt is the catalytically active form but this is an intermediate compound that is formed from a nitroxide, continuously used to become a hydroxylamine, and then regenerated, presumably back to the nitroxide. The secondary oxidant will convert the amine form to the free radical nitroxide compound. The term “nitroxide” is normally used for the compound in the literature. The secondary oxidant will also regenerate the oxammonium salt from the hydroxylamine. [0033] The method described in the application is suitable for carboxylation of chemical fibrous cellulose pulp. This may be bleached sulfite, kraft, or pre-hydrolyzed kraft hardwood or softwood pulps or mixtures of hardwood or softwood pulps. [0034] The cellulose fiber in an aqueous slurry or suspension is first oxidized by addition of a primary oxidizer comprising a cyclic oxammonium salt. This may conveniently be formed in situ from a corresponding amine, hydroxylamine or nitroxyl compound which lacks any α-hydrogen substitution on either of the carbon atoms adjacent the nitroxyl nitrogen atom. Substitution on these carbon atoms is preferably a one or two carbon alkyl group. For sake of convenience in description it will be assumed, unless otherwise noted, that a nitroxide is used as the primary oxidant and that term should be understood to include all of the precursors of the corresponding nitroxide or its oxammonium salt. [0035] Nitroxides having both five and six membered rings have been found to be satisfactory. Both five and six membered rings may have either a methylene group or a heterocyclic atom selected from nitrogen, sulfur or oxygen at the four position in the ring, and both rings may have one or two substituent groups at this location. [0036] A large group of nitroxide compounds have been found to be suitable. 2,2,6,6-tetramethylpiperidinyl-1-oxy free radical (TEMPO) is among the exemplary nitroxides found useful. Another suitable product linked in a mirror image relationship to TEMPO is 2,2,2′,2′,6,6,6′,6′-octamethyl-4,4′-bipiperidinyl-1,1′-dioxy di-free radical (BITEMPO). Similarly, 2,2,6,6-tetramethyl-4-hydroxypipereidinyl-1-oxy free radical; 2,2,6,6-tetramethyl-4-methoxypiperidinyl-1-oxy free radical; and 2,2,6,6-tetramethyl-4-benzyloxypiperidinyl-1-oxy free radical; 2,2,6,6-tetramethyl-4-aminopiperidinyl-1-oxy free radical; 2,2,6,6-tetramethyl-4-acetylaminopiperidinyl-1-oxy free radical; 2,2,6,6-tetramethyl-4-piperidone-1-oxy free radical and ketals of this compound are examples of compounds with substitution at the 4 position of TEMPO that have been found to be very satisfactory oxidants. Among the nitroxides with a second hetero atom in the ring at the four position (relative to the nitrogen atom), 3,3,5,5-tetramethylmorpholine-1-oxy free radical (TEMMO) is useful. [0037] The nitroxides are not limited to those with saturated rings. One compound anticipated to be a very effective oxidant is 3,4-dehydro-2,2,6,6-tetramethyl-piperidinyl-1-oxy free radical. [0038] Six membered ring compounds with double substitution at the four position have been especially useful because of their relative ease of synthesis and lower cost. Exemplary among these are the 1,2-ethanediol, 1,2-propanediol, 2,2-dimethyl-1-3-propanediol (1,3-neopentyldiol) and glyceryl cyclic ketals of 2,2,6,6-tetramethyl-4-piperidone-1-oxy free radical. [0039] Among the five membered ring products, 2,2,5,5-tetramethyl-pyrrolidinyl-1-oxy free radical is anticipated to be very effective. [0040] The following groups of nitroxyl compounds and their corresponding amines or hydroxylamines are known to be effective primary oxidants: in which R 1 -R 4 are one to four carbon alkyl groups but R 1 with R 2 and R 3 with R 4 may together be included in a five or six carbon alicyclic ring structure; X is sulfur or oxygen; and R 5 is hydrogen, C 1 -C 12 alkyl, benzyl, 2-dioxanyl, a dialkyl ether, an alkyl polyether, or a hydroxyalkyl, and X with R 5 being absent may be hydrogen or a mirror image moiety to form a bipiperidinyl nitroxide. Specific compounds in this group known to be very effective are 2,2,6,6-tetramethylpiperidinyl-1-oxy free radical (TEMPO); 2,2,2′,2′,6,6,6′,6′-octamethyl-4,4′-bipiperidinyl-1,1′-dioxy di-free radical (BI-TEMPO); 2,2,6,6-tetramethyl-4-hydroxypiperidinyl-1-oxy free radical (4-hydroxy TEMPO); 2,2,6,6-tetramethyl-4-methoxypiperidinyl-1-oxy free radical (4-methoxy-TEMPO); and 2,2,6,6-tetramethyl-4-benzyloxypiperidinyl-1-oxy free radical (4-benzyloxy-TEMPO). in which R 1 -R 4 are one to four carbon alkyl groups but R 1 with R 2 and R 3 with R 4 may together be included in a five or six carbon alicyclic ring structure; R 6 is hydrogen, C 1 -C 5 alkyl, R 7 is hydrogen, C 1 -C 8 alkyl, phenyl, carbamoyl, alkyl carbamoyl, phenyl carbamoyl, or C 1 -C 8 acyl. Exemplary of this group is 2,2,6,6-tetramethyl-4-aminopiperidinyl-1-oxy free radical (4-amino TEMPO); and 2,2,6,6-tetramethyl-4-acetylaminopipdereidinyl-1-oxy free radical (4-acetylamino-TEMPO). in which R 1 -R 4 are one to four carbon alkyl groups but R 1 with R 2 and R 3 with R 4 may together be included in a five or six carbon alicyclic ring structure; and X is oxygen, sulfur, NH, N-alkyl, NOH, or NO R 8 where R 8 is lower alkyl. An example might be 2,2,6,6-tetramethyl-4-oxopiperidinyl-1-oxy free radical (2,2,6,6-tetramethyl-4-piperidone-1-oxy free radical). wherein R 1 -R 4 are one to four carbon alkyl groups but R 1 with R 2 and R 3 with R 4 may be linked into a five or six carbon alicyclic ring structure; and X is oxygen, sulfur, -alkyl amino, or acyl amino. An example is 3,3,5,5-tetramethylmorpholine-4-oxy free radical. In this case the oxygen atom takes precedence for numbering but the dimethyl substituted carbons remain adjacent the nitroxide moiety. wherein R 1 -R 4 are one to four carbon alkyl groups but R 1 with R 2 and R 3 with R 4 may be linked into a five or six carbon alicyclic ring structure. An example of a suitable compound is 3,4-dehydro-2,2,6,6-tetramethylpiperidinyl-1-oxy free radical. wherein R 1 -R 4 are one to four carbon alkyl groups but R 1 with R 2 and R 3 with R 4 may together be included in a five or six carbon alicyclic ring structure; X is methylene, oxygen, sulfur, or alkylamino; and R 9 and R 10 are one to five carbon alkyl groups and may together be included in a five or six member ring structure, which in turn may have one to four lower alkyl or hydroxy alkyl substitutients. Examples include the 1,2-ethanediol; 1,3-propanediol,2,2-dimethyl-1,3-propanediol, and glyceryl cyclic ketals of 2,2,6,6-tetramethyl-4-piperidone-1-oxy free radical. These compounds are especially preferred primary oxidants because of their effectiveness, lower cost, ease of synthesis, and suitable water solubility. in which R 1 -R 4 are one to four carbon alkyl groups but R 1 with R 2 and R 3 with R 4 may together be included in a five or six carbon alicyclic ring structure; X may be methylene, sulfur, oxygen, —NH, or NR 11 , in which R 11 is a lower alkyl. An example of these five member ring compounds is 2,2,5,5-tetramethylpyrrolidinyl-1-oxy free radical. [0048] Where the term “lower alkyl” is used it should be understood to mean an aliphatic straight or branched chain alky moiety having from one to four carbon atoms. [0049] The above named compounds should only be considered as exemplary among the many representatives of the nitroxides suitable for use with the invention and those named are not intended to be limited in any way. [0050] During the oxidation reaction the nitroxide is consumed and converted to an oxammonium salt then to a hydroxylamine. Evidence indicates that the nitroxide is continuously regenerated by the presence of a secondary oxidant. Chlorine dioxide, or a latent source, is a preferred secondary oxidant. Since the nitroxide is not irreversibly consumed in the oxidation reaction only a catalytic amount of it is required. During the course of the reaction it is the secondary oxidant which will be depleted. [0051] The amount of nitroxide required is in the range of about 0.0005% to 1.0% by weight based on carbohydrate present, preferably about 0.005-0.25%. The nitroxide is known to preferentially oxidize the primary hydroxyl which is located on C-6 of the anhydroglucose moiety in the case of cellulose or starches. It can be assumed that a similar oxidation will occur at primary alcohol groups on hemicellulose or other carbohydrates having primary alcohol groups. [0052] The chlorine dioxide secondary oxidant is present in an amount of 0.2-35% by weight of the carbohydrate being oxidized, preferably about 0.5-10% by weight. [0053] Abundant laboratory data indicates that a nitroxide catalyzed cellulose oxidation predominantly occurs at the primary hydroxyl group on C-6 of the anhydroglucose moiety. In contrast to some of the other routes to oxidized cellulose, only very minor reaction has been observed to occur at the secondary hydroxyl groups at the C-2 and C-3 locations. Using TEMPO as an example, the mechanism to formation of a carboxyl group at the C-6 location proceeds through an intermediate aldehyde stage. [0054] The TEMPO is not irreversibly consumed in the reaction but is continuously regenerated. It is converted by the secondary oxidant into the oxammonium (or nitrosonium) ion which is the actual oxidant. During oxidation the oxammonium ion is reduced to the hydroxylamine from which TEMPO is again formed. Thus, it is the secondary oxidant which is actually consumed. TEMPO may be reclaimed or recycled from the aqueous system. The reaction is postulated to be as follows: nitrosonium) ion which is the actual oxidant. During oxidation the oxammonium ion is reduced to the hydroxylamine from which TEMPO is again formed. Thus, it is the secondary oxidant which is actually consumed. TEMPO may be reclaimed or recycled from the aqueous system. The reaction is postulated to be as follows: [0055] The resulting oxidized cellulose product will have a mixture of carboxyl and aldehyde substitution. Aldehyde substituents on cellulose are known to cause degeneration over time and under certain environmental conditions. In addition, minor quantities of ketone carbonyls may be formed at the C-2 and C-3 positions of the anhydroglucose units and these will also lead to degradation. Marked D.P., fiber strength loss, crosslinking, and yellowing are among the problems encountered. For these reasons it is desirable to oxidize aldehyde substituents to carboxyl groups, or to reduce aldehyde and ketone groups to hydroxyl groups, to ensure stability of the product. [0056] To achieve maximum stability and D.P. retention the oxidized product may be treated with a stabilizing agent to convert any substituent groups, such as aldehydes or ketones, to hydroxyl or carboxyl groups. The stabilizing agent may either be another oxidizing agent or a reducing agent. Unstabilized oxidized cellulose pulps have objectionable color reversion and may self crosslink upon drying, thereby reducing their ability to redisperse and form strong bonds when used in sheeted products. It has been found that acidifying the initial reaction mixture to the pH range given for chlorites without without draining or washing the product is often sufficient to convert the aldehyde moieties to carboxyl functions. Peroxide and acid is also a desirable stabilizing mixture under the conditions shown for chlorite. Otherwise one of the following oxidation treatments may be used. Alkali methyl chlorites are one class of oxidizing agents used as stabilizers, sodium chlorite being preferred because of the cost factor. Other compounds that may serve equally well as oxidizers are permanganates, chromic acid, bromine, silver oxide, and peracids. A combination of chlorine dioxide and hydrogen peroxide is also a suitable oxidizer when used at the pH range designated for sodium chlorite. Oxidation using sodium chlorite may be carried out at a pH in the range of about 0-5, preferably 2-4, at temperatures between about 10°-110° C., preferably about 20°-95° C., for times from about 0.5 minutes to 50 hours, preferably about 10 minutes to 2 hours. One factor that favors oxidants as opposed to reducing agents is that aldehyde groups on the oxidized carbohydrate are converted to additional carboxyl groups, thus resulting in a more highly carboxylated product. These oxidants are referred to as “tertiary oxidizers” to distinguish them from the nitroxide/chlorine dioxide primary/secondary oxidizers. The tertiary oxidizer is used in a molar ratio of about 1.0-15 times the presumed aldehyde content of the oxidized carbohydrate, preferably about 5-10 times. In a more convenient way of measuring the needed tertiary oxidizer, the preferred sodium chlorite usage should fall within about 0.01-20% based on carbohydrate, preferably about 1-9% by weight based on carbohydrate, the chlorite being calculated on a 100% active material basis. [0057] When stabilizing with a chlorine dioxide and hydrogen peroxide mixture, the concentration of chlorine dioxide present should be in a range of about 0.01-20% by weight of carbohydrate, preferably about 0.3-1.0%, and concentration of hydrogen peroxide should fall within the range of about 0.01-10% by weight of carbohydrate, preferably 0.05-1.0%. Time will generally fall within the range of 0.5 minutes to 50 hours, preferably about 10 minutes to 2 hours and temperature within the range of about 10°-110° C., preferably about 30°-95° C. The pH of the system is preferably about 3 but may be in the range of 0-5. [0058] In Applicant's copending U.S. patent application (attorney's docket 25065) filed contemporaneously herewith, which also is incorporated herein by reference in its entirety, the use of chlorine dioxide is a secondary oxidant for use with N-halo hindered cyclic amine compounds as the primary oxidant. The N-halo hindered cyclic amine compounds are as effective as TEMPO and other related nitroxides in methods for making carboxylated cellulose fibers. [0059] The N-halo hindered cyclic amine compounds are fully alkylated at the carbon atoms adjacent to the amino nitrogen atom (i.e., the N—Cl or N—Br) and have from 4 to 8 atoms in the ring. In one embodiment, the N-halo hindered cyclic amine compounds are six-membered ring compounds. In another embodiment, the N-halo hindered cyclic amine compounds are five-membered ring compounds. [0060] Representative N-halo hindered cyclic amine compounds useful in the method of the invention for making carboxylated cellulose pulp fibers include Structures (I)-(VII). Structure (I): [0062] For Structure (I), R 1 -R 4 can be C1-C6 straight-chain or branched alkyl groups, for example, methyl, ethyl, propyl, butyl, pentyl, or hexyl groups. Alternatively, R 1 and R 2 taken together can form a five- or six-carbon cycloalkyl group, and R 3 and R 4 taken together can form a five- or six-carbon cycloalkyl group. The cycloalkyl group can be further substituted with, for example, one or more C1-C6 alkyl groups or other substituents. X can be sulfur or oxygen. R 5 can be hydrogen, C1-C12 straight-chain or branched alkyl or alkoxy, aryl, aryloxy, benzyl, 2-dioxanyl, dialkyl ether, alkyl polyether, or hydroxyalkyl group. Alternatively, R 5 can be absent and X can be hydrogen or a mirror image moiety to form a bipiperidinyl compound. A is a halogen, for example, chloro or bromo. Representative compounds of Structure (I) include N-halo-2,2,6,6-tetramethylpiperidine; N,N′-dihalo-2,2,2′,2′,6,6,6′,6-octamethyl-4,4′-bipiperidine; N-halo-2,2,6,6-tetramethyl-4-hydroxypiperidine; N-halo-2,2,6,6-tetramethyl-4-methoxypiperidine; and N-halo-2,2,6,6-tetramethyl-4-benzyloxypiperidine. Structure (II): [0064] For Structure (II), R 1 -R 4 can be C1-C6 straight-chain or branched alkyl groups, for example, methyl, ethyl, propyl, butyl, pentyl, or hexyl groups. Alternatively, R 1 and R 2 taken together can form a five- or six-carbon cycloalkyl group, and R 3 and R 4 taken together can form a five- or six-carbon cycloalkyl group. The cycloalkyl group can be further substituted with, for example, one or more C1-C6 alkyl groups or other substituents. X can be oxygen or sulfur. R 6 can be hydrogen, C1-C6 straight-chain or branched alkyl groups. R 7 can be hydrogen, C1-C8 straight-chain or branched alkyl groups, phenyl, carbamoyl, alkyl carbamoyl, phenyl carbamoyl, or C1-C8 acyl. A is a halogen, for example, chloro or bromo. Representative compounds of Structure (II) include N-halo-2,2,6,6-tetramethyl-4-aminopiperidine and N-halo-2,2,6,6-tetramethyl-4-acetylaminopiperidine. Structure (III): [0066] For Structure (III), R 1 -R 4 can be C1-C6 straight-chain or branched alkyl groups, for example, methyl, ethyl, propyl, butyl, pentyl, or hexyl groups. Alternatively, R 1 and R 2 taken together can form a five- or six-carbon cycloalkyl group, and R 3 and R 4 taken together can form a five- or six-carbon cycloalkyl group. The cycloalkyl group can be further substituted with, for example, one or more C1-C6 alkyl groups or other substituents. X can be oxygen, sulfur, NH, alkylamino (i.e., NH-alkyl), dialkylamino, NOH, or NOR 10 , where R 10 is a C1-C6 straight-chain or branched alkyl group. A is a halogen, for example, chloro or bromo. A representative compound of Structure (III) is N-halo-2,2,6,6-tetramethylpiperidin-4-one. Structure (IV): [0068] For Structure (IV), R 1 -R 4 can be C1-C6 straight-chain or branched alkyl groups, for example, methyl, ethyl, propyl, butyl, pentyl, or hexyl groups. Alternatively, R 1 and R 2 taken together can form a five- or six-carbon cycloalkyl group, and R 3 and R 4 taken together can form a five- or six-carbon cycloalkyl group. The cycloalkyl group can be further substituted with, for example, one or more C1-C6 alkyl groups or other substituents. X can be oxygen, sulfur, alkylamino (i.e., N—R 10 ), or acylamino (i.e., N—C(═O)-R 10 ), where R 10 is a C1-C6 straight-chain or branched alkyl group. A is a halogen, for example, chloro or bromo. A representative compound of Structure (IV) is N-halo-3,3,5,5-tetramethylmorpholine. Structure (V): [0070] For Structure (V), R 1 -R 4 can be C1-C6 straight-chain or branched alkyl groups, for example, methyl, ethyl, propyl, butyl, pentyl, or hexyl groups. Alternatively, R 1 and R 2 taken together can form a five- or six-carbon cycloalkyl group, and R 3 and R 4 taken together can form a five- or six-carbon cycloalkyl group. The cycloalkyl group can be further substituted with, for example, one or more C1-C6 alkyl groups or other substituents. A is a halogen, for example, chloro or bromo. A representative compound of Structure (V) is N-halo-3,4-dehydro-2,2,6,6,-tetramethylpiperidine. Structure (VI): [0072] For Structure (VI), R 1 -R 4 can be C1-C6 straight-chain or branched alkyl groups, for example, methyl, ethyl, propyl, butyl, pentyl, or hexyl groups. Alternatively, R 1 and R 2 taken together can form a five- or six-carbon cycloalkyl group, and R 3 and R 4 taken together can form a five- or six-carbon cycloalkyl group. The cycloalkyl group can be further substituted with, for example, one or more C1-C6 alkyl groups or other substituents. X can be methylene (i.e., CH 2 ), oxygen, sulfur, or alkylamino. R 8 and R 9 can be independently selected from C1-C6 straight-chain or branched alkyl groups, for example, methyl, ethyl, propyl, butyl, pentyl, or hexyl groups. Alternatively, R 8 and R 9 taken together can form a five- or six-membered ring, which can be further substituted with, for example, one or more C1-C6 alkyl groups or other substituents. A is a halogen, for example, chloro or bromo. Representative compounds of Structure (VI) include N-halo-4-piperidone ketals, such as ethylene, propylene, glyceryl, and neopentyl ketals. Representative compounds of Structure (VI) include N-halo-2,2,6,6-tetramethyl-4-piperidone ethylene ketal, N-halo-2,2,6,6-tetramethyl-4-piperidone propylene ketal, N-halo-2,2,6,6-tetramethyl-4-piperidone glyceryl ketal, and N-halo-2,2,6,6-tetramethyl-4-piperidone neopentyl ketal. Structure (VII): [0074] For Structure (VII), R 1 -R 4 can be C1-C6 straight-chain or branched alkyl groups, for example, methyl, ethyl, propyl, butyl, pentyl, or hexyl groups. Alternatively, R 1 and R 2 taken together can form a five- or six-carbon cycloalkyl group, and R 3 and R 4 taken together can form a five- or six-carbon cycloalkyl group. The cycloalkyl group can be further substituted with, for example, one or more C1-C6 alkyl groups or other substituents. X can be methylene, oxygen, sulfur, NH, (i.e., N—R 10 ), or acylamino (i.e., N—C(═O)—R 10 ), where R 10 is a C1-C6 straight-chain or branched alkyl group. A is a halogen, for example, chloro or bromo. A representative compound of Structure (VII) is N-halo-2,2,5,5-tetramethylpyrrolidine. [0075] In general, the N-halo hindered cyclic amine compounds noted above can be prepared by chlorination or bromination of the corresponding amine compounds. [0076] Carboxylated cellulose pulp fibers can be made using hindered cyclic amine compounds or N-halo hindered cyclic amine compound in aqueous media under heterogeneous conditions. In the method, the hindered cyclic amine compound or the N-halo hindered cyclic amine compound reacts with a secondary oxidizing agent (e.g., chlorine dioxide, peracids, hypochlorites, chlorites, ozone, hydrogen peroxide, potassium superoxide) to provide a primary oxidizing agent that reacts with cellulose pulp fibers to provide cellulose pulp fibers containing both carboxyl and aldehyde functional groups. In one embodiment, the cellulosic fibers containing carboxyl and aldehyde functional groups are further treated to provide stable carboxylated cellulosic fibers. In the method, under basic pH conditions and in the presence of a secondary oxidizing agent, the primary oxidizing agent is generated from the hindered cyclic amine compound or the N-halo hindered cyclic amine compound. In one embodiment, the cellulosic fibers containing both carboxyl and aldehyde functional groups obtained at the end of the first stage of the carboxylation process are further treated to provide stable carboxylated cellulosic fibers. [0077] As noted above, in one embodiment, the method for making carboxylated cellulose pulp fibers includes two steps: (1) a first stage of carboxylation; and (2) a stabilization step in which any remaining aldehyde groups are converted to carboxyl groups providing a stable pulp. [0078] In the first stage of carboxylation, cellulose pulp fibers are oxidized (i.e.,oxidized to aldehyde and carboxyl functional groups) under basic pH conditions and in the presence of a secondary oxidizing agent, such as chlorine dioxide, hypochlorite, peracids, or certain metal ions, with a catalytically active species (e.g., an oxammonium ion) generated from a N-halo hindered cyclic amine compound described above. [0079] The first stage of the carboxylation process generally takes place at a temperature from about 20° C. to about 90° C. The hindered cyclic amine compound or the N-halo hindered cyclic amine compound is present in an amount from about 0.002% to about 0.25% by weight based on the total weight of the pulp. The secondary oxidizing agent is present in an amount from about 0.1 to about 10% by weight based on the total weight of the pulp. Reaction times for the first stage of carboxylating the pulp range from about 5 seconds to about 10 hours, depending upon reaction temperature and the amount of hindered cyclic amine compound or N-halo hindered cyclic amine compound and secondary oxidizing agent. [0080] Chlorine dioxide is a suitable secondary oxidizing agent. The pH during oxidation should generally be maintained within the range of about 6.0 to 11, preferably about 6.0 to10, and most preferably about 6.25 to 9.0. The oxidation reaction will proceed at higher and lower pH values, but at lower efficiencies. [0081] A study was conducted to determine effects of time and chemical loadings on the carboxyl content and viscosity of the pulp. The study was conducted at 50° C. and 70° C. [0082] In each set of studies, water sufficient to achieve a final pulp consistency of 7.5% was placed in a Quantum mixer. The water was heated to the desired temperature (50° C. or 70° C.). Sodium hydroxide was added to the water in the amounts shown in Tables 2 and 3. 32.1% never-dried partially bleached softwood pulp from the Weyerhaeuser Prince Albert SK mill was added to the water. The pulp was taken from the E2 bleach stage. It weighed 150 g. on an oven-dry basis. The sample was quickly mixed at 100% power. [0083] 2.25 grams of 2% EGK-TAA (ethylene glycol ketal of triacetonamine) was added to a chlorine dioxide solution. The amount of EGK-TAA was 0.03 weight % of the dry oven dry weight of the pulp. The amount of chlorine dioxide was varied as shown in the Tables 2 through 5. [0084] The EGK-TAA/chlorine dioxide mixture was injected into the mixer while it was being stirred. Time 0 is the time that the injection of the mixture started. [0085] At the end of the reaction time the stabilizing mixture was pressure injected into the pulp to quench the stage 1 oxidation and start the stage 2 stabilization. The pulp was stabilized with 0.5% HOOH and 3.9% sulfuric acid (pH<4) for 1 hours. The pH was not measured, but based on earlier experience the pH would have been below 4 and was probably between 2 and 3. There was a yellow color indicating the regeneration of chlorine dioxide by the reaction of chlorite with aldehyde groups which also indicated that the pH was below 4. Each sample was stabilized for about 1 hour. The stabilization temperature was targeted to be either 50° C. or 70° C. All samples were washed with DI water, treated with NaOH to convert the carboxylic acid groups on the pulp to the sodium salt form and washed. The samples were analyzed for carboxyl, viscosity, brightness and brightness reversion. [0086] The control was the uncarboxylated pulp. The carboxyl content, viscosity, brightness and brightness reversion are shown in table 1. TABLE 1 Carboxyl Visc Brightness Brightness Example meq/100 g mPa * s ISO Reversion 1 4.61 33.0 85.37 84.17 [0087] The results of the 70° C. tests are shown in Table 2 and the results of the 50° C. tests are shown in Table 3. The results of the 70° C. and 50° C. tests are listed by carboxyl content in Tables 4 and 5, respectively. TABLE 2 Time ClO 2 NaOH Ratio Carboxyl Visc Brightness Brightness Ex. sec wt. % wt % ClO 2 :NaOH meq/100 g mPa * s ISO Reversion  2 5 1.0 0.70 0.70 7.14 28.0 91.07 89.61  3 5 1.0 1.00 1.00 7.56 24.5 91.74 90.37  4 15 1.0 0.85 0.85 7.85 25.4 91.90 90.45  5 25 1.0 0.70 0.70 8.02 25.8 91.23 89.32  6 25 1.0 1.00 1.00 6.88 19.4 91.39 89.80  7 5 1.2 1.02 0.85 8.35 24.1 91.48 89.99  8 15 1.2 0.84 0.70 8.53 24.8 91.56 90.26  9 15 1.2 1.02 0.85 7.74 20.3 91.55 90.20 10 15 1.2 1.02 0.85 8.11 20.0 92.14 90.56 11 15 1.2 1.02 0.85 8.21 20.2 91.93 90.61 12 15 1.2 1.20 1.00 7.59 19.4 91.64 90.19 13 25 1.2 1.02 0.85 7.32 18.9 91.19 89.73 14 5 1.4 1.40 1.00 7.81 21.6 91.73 90.38 15 5 1.4 0.98 0.70 8.71 24.1 92.00 90.79 16 15 1.4 1.19 0.85 8.77 19.4 92.07 90.65 17 25 1.4 0.98 0.70 9.23 24.8 91.61 90.06 18 25 1.4 1.40 1.00 8.23 17.5 92.22 90.69 [0088] TABLE 3 Time ClO 2 NaOH Ratio Carboxyl Visc Brightness Brightness Ex. sec wt. % wt % ClO 2 :NaOH meq/100 g mPa * s ISO Reversion 20 5 1.0 0.70 0.70 7.58 29.0 91.66 90.18 19 5 1.0 1.00 1.00 7.12 26.0 91.81 90.34 21 15 1.0 0.85 0.85 6.82 24.8 92.08 90.49 23 25 1.0 0.70 0.70 7.71 27.3 90.87 89.00 22 25 1.0 1.00 1.00 6.74 21.7 92.14 90.71 24 5 1.2 1.02 0.85 7.90 26.0 92.18 90.45 28 15 1.2 0.84 0.70 8.60 27.9 90.91 89.50 26 15 1.2 1.02 0.85 7.58 22.8 91.88 90.35 27 15 1.2 1.02 0.85 8.14 24.9 91.81 90.32 29 15 1.2 1.02 0.85 8.54 25.1 92.13 90.76 30 25 1.2 1.02 0.85 8.21 24.4 92.16 90.69 25 15 1.2 1.20 1.00 6.96 24.2 92.52 91.00 32 5 1.4 0.98 0.70 8.83 26.0 92.19 90.63 31 5 1.4 1.40 1.00 7.85 23.4 92.90 91.42 33 15 1.4 1.19 0.85 8.63 23.6 91.87 90.13 34 25 1.4 0.98 0.70 9.34 27.9 91.77 90.29 35 25 1.4 1.40 1.00 8.03 19.8 92.41 90.79 [0089] TABLE 4 Time ClO 2 NaOH Ratio Carboxyl Visc Brightness Brightness Ex. sec wt. % wt % ClO 2 :NaOH meq/100 g mPa * s ISO Reversion  6 25 1.0 1.00 1.00 6.88 19.4 91.39 89.80  2 5 1.0 0.70 0.70 7.14 28.0 91.07 89.61 13 25 1.2 1.02 0.85 7.32 18.9 91.19 89.73  3 5 1.0 1.00 1.00 7.56 24.5 91.74 90.37 12 15 1.2 1.20 1.00 7.59 19.4 91.64 90.19  9 15 1.2 1.02 0.85 7.74 20.3 91.55 90.20 14 5 1.4 1.40 1.00 7.81 21.6 91.73 90.38  4 15 1.0 0.85 0.85 7.85 25.4 91.90 90.45  5 25 1.0 0.70 0.70 8.02 25.8 91.23 89.32  7 5 1.2 1.02 0.85 8.35 24.1 91.48 89.99 10 15 1.2 1.02 0.85 8.11 20.0 92.14 90.56 11 15 1.2 1.02 0.85 8.21 20.2 91.93 90.61 18 25 1.4 1.40 1.00 8.23 17.5 92.22 90.69  8 15 1.2 0.84 0.70 8.53 24.8 91.56 90.26 15 5 1.4 0.98 0.70 8.71 24.1 92.00 90.79 16 15 1.4 1.19 0.85 8.77 19.4 92.07 90.65 17 25 1.4 0.98 0.70 9.23 24.8 91.61 90.06 [0090] TABLE 5 Time ClO 2 NaOH Ratio Carboxyl Visc Brightness Brightness Ex. sec wt. % wt % ClO 2 :NaOH meq/100 g mPa * s ISO Reversion 22 25 1.0 1.00 1.00 6.74 21.7 92.14 90.71 21 15 1.0 0.85 0.85 6.82 24.8 92.08 90.49 25 15 1.2 1.20 1.00 6.96 24.2 92.52 91.00 19 5 1.0 1.00 1.00 7.12 26.0 91.81 90.34 20 5 1.0 0.70 0.70 7.58 29.0 91.66 90.18 26 15 1.2 1.02 0.85 7.58 22.8 91.88 90.35 23 25 1.0 0.70 0.70 7.71 27.3 90.87 89.00 31 5 1.4 1.40 1.00 7.85 23.4 92.90 91.42 24 5 1.2 1.02 0.85 7.90 26.0 92.18 90.45 35 25 1.4 1.40 1.00 8.03 19.8 92.41 90.79 27 15 1.2 1.02 0.85 8.14 24.9 91.81 90.32 30 25 1.2 1.02 0.85 8.21 24.4 92.16 90.69 29 15 1.2 1.02 0.85 8.54 25.1 92.13 90.76 28 15 1.2 0.84 0.70 8.60 27.9 90.91 89.50 33 15 1.4 1.19 0.85 8.63 23.6 91.87 90.13 32 5 1.4 0.98 0.70 8.83 26.0 92.19 90.63 34 25 1.4 0.98 0.70 9.34 27.9 91.77 90.29 [0091] Another set of studies was conducted to determine carboxylation at times of 15 seconds, 30 seconds, 60 seconds, 120 seconds, 180 seconds and 240 seconds. Example 35 [0092] Never-dried partially bleached softwood pulp collected after the E2 bleach stage of the Weyerhaeuser Prince Albert SK mill pulp having an oven dry weight of 60 g, and 9.2 g sodium carbonate was added to 310 g of DI water and the mixture was heated to 70° C. 98 mL of chlorine dioxide, 6.7 g/L, and 1.2 g of ethylene glycol ketal of triacetoneamine (EGK-TAA) were mixed and added to the pulp. The pulp was mixed rapidly by hand. Samples were taken at 15, 30, 60, 120, 180 and 240 seconds after the ClO 2 /EGK-TAA solution first contacted the pulp. Each of the samples were placed in a solution of 0.5 g NaBH 4 in 100 mL of water and left overnight at room temperature with periodic stirring. The pulps were then tested for carboxyl content. The carboxyl content in meq/100 g were as follows: 15 seconds—6.7, 30 seconds—6.8, 60 seconds—7.2, 120 seconds—7.5, 180 seconds—7.55, 240 seconds—7.6. Example 36 [0093] Northern softwood partially bleached kraft pulp collected after the E2 stage of the Weyerhaeuser Prince Albert, SK pulp mill was dewatered to 25-30% solids with a screw press. [0094] All percentages are weight percentages based on the oven dry weight of the pulp. [0095] The pulp was slurried in water and fed to a twin roll press which delivered pulp at a predetermined constant rate of 3.0 kg/minute pulp solids at 8-9% consistency (weight of pulp/weight of water) to a pilot process. Just after the twin roll press, sodium hydroxide was sprayed on the pulp stream at a rate of 0.65%. The pulp slurry was then mixed and heated in a steam mixer and fed to a Seepex progressive cavity pump which provided pulp slurry flow through two high intensity mixers and an upflow tower. The upflow tower fed a downflow tower by gravity. Pulp product was mined from the bottom of the downflow tower, adjusted to pH 7-9 with sodium hydroxide and dewatered on a belt washer. [0096] EGK-TAA was dissolved in water and metered into a chlorine dioxide line. The mixture was 0.03% EGK-TAA and 0.88% chlorine dioxide. This line was connected to the pulp slurry process pipe just before it entered the first high intensity mixer. The Chlorine dioxide/EGK-TAA mixture was injected into the flowing pulp slurry and immediately mixed in the first high intensity mixer. Just before the second high intensity mixer, a mixture of sulfuric acid (0.17%) and hydrogen peroxide (0.5%) was injected into the pulp slurry. The distance between the 1 st high intensity mixers and the injection of the sulfuric acid/hydrogen peroxide, and the speed of the pulp slurry will determine the reaction time for the first stage of the carboxylation of the pulp. This setup allowed times as short as 6 seconds, but was preferred to be 15-30 seconds. In this example the time was 6 seconds. The pulp immediately enters the 2 nd high intensity mixer and mixed again. The pulp slurry flowed into the upflow tower and spent approximately 30 minutes there before entering the downflow tower where it spent approximately an hour. It was then mined from the bottom of the downflow tower. [0097] The temperature at the bottom of the upflow tower was maintained at 50° C. by adjustments to the steam flow to the steam mixer. The pH was monitored near the end of the retention pipe prior to the sulfuric acid/hydrogen peroxide injection and was maintained at 6.25-6.75 by minor adjustments to the sodium hydroxide addition level to the pulp after the twin wire press. The pH was monitored at the bottom of the upflow tower and was maintained at 3.5-4.0 by minor adjustments to the sulfuric acid flow. [0098] The dewatered pulp product had a carboxyl level of 8.5 meq/100 g, an ISO brightness of 90.38% and a viscosity of 25.6 mPa-s. [0099] It can be seen that short reaction times are possible and that it is possible to use existing equipment with little modification to carboxylate wood pulp. [0100] FIG. 1 shows a standard extract stage and a chlorine dioxide stage of a pulp mill. Pulp, in slurry form, which has been bleached with a bleaching chemical such as chlorine, chlorine dioxide or hydrogen peroxide is treated with sodium hydroxide is extraction tower 10 . Sodium hydroxide solubilizes the chemicals in the pulp that have reacted with the bleaching chemical. The pulp is carried to washer 12 in which the solubilized material is washed from the pulp. [0101] The pulp slurry is moved from the washer 12 to the next stage by pump 18 (shown in FIGS. 2 and 3 ) and then mixed with chlorine dioxide in mixer 24 (shown in FIGS. 2 and 3 ) and flows into the upflow section 13 of chlorine dioxide tower 14 . The pulp slurry then passes through the downflow section 15 of the tower 14 where it continues to react with the chlorine dioxide. The slurry then leaves the tower 14 and is washed in a washer 16 (shown in FIGS. 2 and 3 ). [0102] The short reaction time of the first stage of the carboxylation process allows a simple modification to the standard extraction and chlorine dioxide stage to allow carboxylation and stabilization in these units. [0103] This is shown in FIGS. 2 and 3 . These are different representations of the process. [0104] There is an additional mixer and a reaction chamber between the washer 12 and the chlorine dioxide tower 14 . [0105] The pump 18 mixes a base chemical with the pulp slurry. The base chemical is any chemical which will provide an appropriate pH for the slurry. Sodium hydroxide or sodium carbonate are preferred. Sodium hydroxide is the most preferred because it is the chemical used in the extraction reaction and no new chemical is required. The base chemical is supplied from unit 17 through line 19 . The base chemical may be supplied to the slurry either before or at the pump 18 . The base chemical should be mixed thoroughly with the slurry before the addition of the carboxylation chemicals. [0106] The mixer 20 mixes the carboxylation chemicals with the pulp slurry. The carboxylation chemicals are supplied from units 21 or 21 ′ through lines 22 and 22 ′. The carboxylation chemicals may be supplied to the slurry either before or at mixer 20 . The carboxylation chemicals may be any of those mentioned. The preferred secondary oxidant is chlorine dioxide. The preferred primary oxidant is triacetoneamine ethylene glycol ketal (TAA-EGK). [0107] The pulp slurry then enters the reaction chamber 23 in which the first stage of the carboxylation process occurs. The size of the reaction chamber 23 will depend on the length of time of the catalytic oxidation reaction. The reaction chamber will be a tank if the reaction is over 1 minute. It will be a good-sized tank if the reaction is over 2 minutes and a large tank if the reaction is over 15 minutes. The reaction chamber 23 can be a pipe if the reaction is under a minute. It will be a large and probably curved pipe, as shown, if the reaction is over 30 seconds. It can be a straight pipe, and possibly the existing pipe, if the reaction is 30 seconds or less. The reaction can be around 15 seconds and can, in certain instances, be as short as 1 second. The diameter and length will be of a size that will accommodate the flow of pulp slurry for the time required for the oxidation reaction. [0108] Mixer 24 mixes the stabilization chemicals with the pulp slurry. The stabilization chemicals are supplied from units 25 and 25 ′ through lines 26 and 26 ′. The chemicals may be supplied to the slurry either before or at mixer 24 . The stabilization chemicals can be any of those mentioned. Alkali metal chlorites, hydrogen peroxide, acid, chlorine dioxide and peracids are among the chemicals that may be used. It is preferred that an acid, such as sulfuric acid, and a peroxide, such as hydrogen peroxide, be used. It is most preferred that an acid be used. [0109] The pulp slurry then enters the upflow section 13 of the chlorine dioxide tower 14 and then transfers to the downflow section 15 of tower 14 . The stabilization reaction occurs in tower sections 13 and 15 . [0110] While the system has been described in terms of an extraction stage 10 , it can also be used in systems in which there are two chlorine dioxide towers separated by a washing stage. The system would be identical to that described herein except that extraction tower 10 would be a chlorine dioxide tower. It may be necessary to use more chlorine dioxide in this system. [0111] It can be seen that the system can be changed from a regular pulp bleach stage to a carboxylation stage may simply adding or removing chemicals from the system. The addition of the base chemicals, the catalyst, the acid and the peroxide turns it into a carboxylation unit, the absence of these chemicals returns it to a standard pulp bleach stage. [0112] Those skilled in the art will recognize that the present invention is capable of many modifications and variations without departing from the scope thereof. Accordingly, the detailed description set forth above is meant to be illustrative only and is not intended to limit, in any manner, the scope of the invention as set forth in the appended claims. It will be noted that other catalytic oxidation and stabilization chemicals may be used, but the chemicals noted are the preferred chemicals.

An apparatus for carboxylating wood pulp which utilizes the wood pulp bleach plant and the method of carboxylating the pulp which takes place in the bleach plant.

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a national stage entry of International Application No. PCT/GB2015/051230, filed Apr. 28, 2016, which claims priority to GB Application No. 1408655.7, filed on May 15, 2014, the disclosures of which are incorporated by reference in their entirety. TECHNICAL FIELD [0002] The present invention relates to a method and apparatus for electrochemical etching and relates particularly, but not exclusively, to a method and apparatus for electrochemical etching for the purpose of sharpening probes or blades. BACKGROUND [0003] Microscopy methods, such as scanning tunnelling microscopy, require the use of probes having extremely sharp tips with well-defined shapes in order to provide a desired level of resolution for high quality images. A sharper probe, that is a probe with a narrower tip, provides higher resolution information about a sample while a well-defined probe shape lowers noise levels on resulting images. [0004] Probes with sharp tips are known to be made using a process known as the “drop-off method”. In this process, an object to be etched, such as a piece of tungsten wire, has a lower portion immersed in an electrolyte such as sodium hydroxide or potassium hydroxide, while an upper portion of the piece of wire remains in air. The depth of immersion of the lower portion is chosen depending on a desired drop-off time, which governs the ultimate shape of the tips formed by the process. A ring-shaped electrode is placed around the immersed portion of the piece of wire and a voltage is applied between the piece of wire and the electrode. [0005] An electrochemical reaction takes place between the piece of wire and hydroxide ions in the electrolyte, creating water molecules and molecules of, in the case of the object being made of tungsten, an oxidised compound of tungsten and oxygen called tungstate. As the portion of the tungsten piece surrounded by the electrode decomposes in this way, a neck of decreasing radius is formed. The rate of decomposition of this portion is inhomogeneous due to two effects: the formation of a meniscus of electrolyte around the piece at the surface of the electrolyte, and the accumulation of tungstate as it descends as a viscous flow near the immersed surface of the piece. The process culminates in the lower part of the piece falling away as the neck breaks, resulting in the formation of two sharp tips, the shapes of which are dependent on the rate of etching. A high rate of etching results in irregularly-shaped tips, and a low rate of etching results in very long and fragile tips. The applied voltage must be immediately terminated upon breakaway of the lower part to prevent further undesired etching taking place. Only one pair of tips can be made at a time in this manner, and in practice it is often the case that only one of the tips of the pair is usable. [0006] The shape of the tips can be further affected by the behaviour of the meniscus. As the neck radius decreases and the surface area of the neck increases during the reaction, the meniscus position can change, which leads to the formation of a second neck. This causes undesired variations in the shapes of the final tips, rendering them unsuitable for use in very sensitive applications. Control of the apparatus is required to prevent this from happening. [0007] Preferred embodiments of the present invention seek to overcome one or more of the above disadvantages associated with the prior art. SUMMARY [0008] According to a first aspect of the present invention, there is a provided an electrochemical etching method comprising: immersing at least part of one first part of at least one object to be etched and at least part of at least one electrode in an electrolyte; and applying a voltage between at least one said object and at least one said electrode to cause an electrochemical reaction between at least one said first part and said electrolyte to cause at least one reaction product; wherein at least one said first part and at least one said electrode are positioned relative to each other such that at least part of at least one said reaction product accumulates by means of gravity on at least one said first part to reduce a reaction rate of said electrochemical reaction. [0009] By positioning at least one said first part and at least one said electrode relative to each other such that at least part of at least one said reaction product accumulates by means of gravity on at least one said first part to reduce a reaction rate of said electrochemical reaction, the rate of the electrochemical reaction at each point on the surface of said first part is made dependent on its orientation, providing a scalable etching procedure with a simpler apparatus. [0010] The method may further comprise providing a magnetic field in the vicinity of at least one said first part to cause flow of said electrolyte to adjust said reaction rate. [0011] This provides the advantage that the rate of electrochemical etching of the object can be adjusted by the magnetic field. [0012] The magnetic field may be adjustable. [0013] This provides the advantage of providing further control of the rate of electrochemical etching of the object. [0014] The method may further comprise surrounding at least one second part of at least one said object by at least one electrically insulating material. [0015] This provides the advantage of protecting the second part of the object from the etching process. [0016] At least one said electrically insulating material may be immiscible with the electrolyte and more dense than the electrolyte. [0017] At least one said electrically insulating material may comprise perfluorinated carbon fluid. [0018] The method may further comprise controlling said voltage. [0019] Said voltage may be controlled in dependence on an electrical current drawn by said electrochemical reaction. [0020] This provides the advantage of allowing the etching process to be dynamic. [0021] Said voltage may be controlled in dependence on a profile of at least part of at least one said first part. [0022] This provides the advantage that the final lengths and sharpnesses of a plurality of objects being etched simultaneously can be made substantially equal. [0023] At least one said first part may be elongate. [0024] At least one said first part may be a sheet of material. [0025] According to a second aspect of the present invention, there is provided an electrochemical etching apparatus comprising: at least one electrode; container means for accommodating at least one first part of at least one object to be etched such that at least one said first part and at least part of at least one said electrode are immersed in an electrolyte; and voltage application means for applying a voltage between at least one said object and at least one said electrode to cause an electrochemical reaction between at least one said first part and said electrolyte to cause at least one reaction product; wherein at least one said first part and at least one said electrode are positioned relative to each other such that at least part of at least one said reaction product accumulates by means of gravity on at least one said first part to reduce a reaction rate of said electrochemical reaction. [0026] The apparatus may further comprise magnetic field generating means for providing a magnetic field in the vicinity of at least one said first part to cause flow of said electrolyte to adjust said reaction rate. [0027] The magnetic field generating means may be adapted to provide an adjustable magnetic field. [0028] This provides the advantage of controlling the flow of the electrolyte, and therefore the rate of the electrochemical reaction. [0029] The container means may be adapted to accommodate at least one second part of at least one said object such that at least one said second part is surrounded by at least one electrically insulating material. [0030] The apparatus may further comprise voltage control means for controlling said voltage. [0031] The voltage control means may be adapted to control said voltage in dependence on an electrical current drawn by at least part of said apparatus. [0032] The voltage control means may be adapted to control said voltage in dependence on a profile of at least part of at least one said first part. BRIEF DESCRIPTION OF DRAWINGS [0033] A preferred embodiment of the present invention will now be described, by way of example only and not in any limitative sense, with reference to the accompanying drawings, in which: [0034] FIG. 1 is a front view of an electrochemical etching apparatus embodying the present invention; [0035] FIG. 2 is a side view of the apparatus of FIG. 1 ; [0036] FIG. 3 is a perspective view of the apparatus of FIG. 1 ; [0037] FIG. 4 is a graph showing a profile of a current drawn from the power supplying means during a process embodying the present invention; [0038] FIG. 5 is an image, generated by a scanning electron microscope, of a probe etched according to an embodiment of the present invention; and [0039] FIG. 6 is an image, generated by a scanning electron microscope, of an edge of a razor blade etched according to an embodiment of the present invention. DETAILED DESCRIPTION [0040] Referring to FIGS. 1 to 3 , five cylindrically-shaped pieces of tungsten wire ( 2 ) of diameter 10 mm are secured to a stainless steel block ( 12 ) using stainless steel screws ( 14 ). One end of an insulated wire ( 16 ) is also secured to the block ( 12 ) by means of a screw ( 14 ), while another end of the wire ( 16 ) is connected to a power supply (not shown). The block ( 12 ), screws ( 14 ) and lower parts of each of the pieces of tungsten wire ( 2 ) are immersed in an electrically insulating layer of C-15 perfluorinated carbon fluid ( 10 ), while the upper parts of the pieces of tungsten wire ( 2 ) protrude upwards from the fluid ( 10 ) into a layer of potassium hydroxide electrolyte ( 4 ) above. Positioned above the pieces of tungsten wire ( 2 ) are two U-shaped stainless steel electrodes ( 6 ) connected to the power supply and a substantially rectangular permanent magnet ( 8 ), the magnet ( 8 ) secured between the electrodes ( 6 ) by means of two plastic struts ( 18 ) adhered to both the magnet ( 8 ) and each electrode ( 6 ). The magnet ( 8 ) is oriented such that one of its poles points towards the pieces ( 2 ). In FIGS. 1-3 , the face of the magnet ( 8 ) nearest the pieces ( 2 ) is a pole of the magnet. The magnet ( 8 ), struts ( 18 ) and a part of each electrode ( 6 ) are immersed in the electrolyte ( 4 ). The electrodes ( 8 ) are placed at a distance of 20 mm above the ends of the pieces of tungsten wire ( 2 ). The fluid ( 10 ) and electrolyte ( 4 ) are contained within a glass container ( 20 ). [0041] The pieces of tungsten wire ( 2 ) and electrodes ( 4 ) are energised by a voltage supplied by the power supply. The voltage supplied by the power supply to the pieces of tungsten wire ( 2 ) and the electrodes ( 4 ) is controlled by a microcontroller and a computer program. The microcontroller measures a current drawn from the power supply during the etching process and the computer program adjusts a duty cycle and polarity of the voltage supplied depending on the current drawn. An example of a profile of the current drawn from the power supply during an etching process embodying the present invention is shown in FIG. 4 . [0042] While the pieces of tungsten wire ( 2 ) and the electrodes ( 4 ) are energised, a voltage is applied between the pieces ( 2 ) and the electrodes ( 4 ) causing an electrochemical reaction to take place at the interface between the surface of each piece of tungsten wire ( 2 ) that is exposed to the electrolyte ( 4 ) and the electrolyte. The product of the reaction is denser than the electrolyte. The product forms a layer around each piece of tungsten wire ( 2 ) from which it originated and flows downwards, in a viscous manner, due to the force of gravity. Each layer of the product surrounding each piece of tungsten wire ( 2 ) partially insulates the surface of the respective piece of tungsten wire ( 2 ) from the electrolyte ( 4 ), consequently reducing a rate at which the surface of that piece of tungsten wire ( 2 ) decomposes. As the reaction continues, the product near to each piece of tungsten wire ( 2 ) accumulates, creating a layer of product near to each piece of tungsten wire ( 2 ) which is thinner at the ends of the pieces of tungsten wire ( 2 ) closest to the electrodes ( 6 ) than at the opposite ends of the pieces of tungsten wire ( 2 ), consequently causing the rate at which each point on the surface of each piece of tungsten wire ( 2 ) decomposes to be dependent on a distance of those points from the electrodes ( 6 ). As a result, each piece ( 2 ) decomposes into a substantially conically-shaped piece of tungsten with a sharp point at the end of each piece of tungsten nearest the electrodes ( 6 ). [0043] During the electrochemical reaction, the magnet ( 8 ) radiates a magnetic field (not shown) which interacts with ions in the electrolyte. Given the position and orientation of the magnet ( 8 ) as shown in FIGS. 1-3 and described above, the magnetic field accelerates the ions moving toward each piece of tungsten wire ( 2 ), by means of a Lorentz force, along a substantially circular path around each piece ( 2 ), creating a flow. Since the magnetic field strength decreases with distance from the magnet ( 8 ), a rate of the flow around each piece of tungsten wire ( 2 ) also decreases with that distance, the flow rate being proportional to the Lorentz force and therefore to the magnetic field strength. As a result, the greater flow rate at the ends of each piece of tungsten wire ( 2 ) nearest the magnet ( 8 ) causes faster circulation of the electrolyte around each piece of tungsten wire ( 2 ). The rate of decomposition of the surface of each piece of tungsten wire ( 2 ) is proportional to a rate of this circulation, therefore the generation of a circulation profile around each piece ( 2 ), via the presence of the magnetic field in the electrolyte, causes the decomposition of the surface of each piece of tungsten wire ( 2 ) to be well-defined and controllable in terms of the magnetic field. [0044] If two or more pieces of tungsten wire ( 2 ) are to be etched simultaneously, the etching process may be allowed to continue for a period of time after one or more sharp points have been formed, for the purpose of equalising the lengths and sharpnesses of the pieces of tungsten wire ( 2 ). The combination of the divergent magnetic field and the accumulation of the product during the reaction ensures that each piece of tungsten wire ( 2 ) experiences a rate of etching dependent on its proximity to the magnet ( 8 ), and therefore that a piece of tungsten wire ( 2 ) to be etched that is longer than another when the reaction begins, and therefore is closer to the magnet ( 8 ), is etched at a greater rate than a shorter piece of tungsten wire ( 2 ). [0045] The embodiment described above may be adapted for the etching of conductive sheets such as stainless steel razor blades rather than the aforementioned pieces of tungsten wire ( 2 ) by replacing the piece or pieces of tungsten wire ( 2 ) with the sheet or sheets, substituting the potassium hydroxide for 2M hydrochloric acid as the electrolyte ( 4 ) and appropriately adjusting the computer program. [0046] The object or objects to be etched may be made from a material other than tungsten or stainless steel. Any conductive material that can be electrochemically etched and that has a chemical by-product that flows downwards and partially insulates the object from further etching in the manner described above is suitable. Examples of such materials are nickel, copper, and silicon. [0047] It will be appreciated by persons skilled in the art that the above embodiment has been described by way of example only and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the invention as defined by the appended claims.

A method and apparatus for electrochemical etching are disclosed. The method comprises immersing parts of objects ( 2 ) to be etched in an electrolyte ( 4 ), applying a voltage between the objects ( 2 ) and at least one electrode ( 6 ) to cause an electrochemical reaction between the objects ( 2 ) and the electrolyte ( 4 ), and positioning the objects ( 2 ) and electrodes ( 6 ) relative to each other such that a reaction product accumulates on the objects ( 2 ) during the reaction to reduce the rate of the reaction.

FIELD OF INVENTION This invention relates to compounds of organic acids and to methods of making and using the same. BACKGROUND OF THE INVENTION U.S. Pat. No. 3,722,504 describes a screen for testing pharmaceutical compounds based at least partly on their ability to increase the negative surface charge of the vascular system. U.S. Pat. No. 3,722,504, by way of example, discloses a pharmaceutical compound which prevents thombosis by modifying the intimal surface charge of the vascular system. Para amino benzoic acid increases the net negative surface charge of blood vessels and blood cells. It produces a marked increases in the current-induced occlusion time in rat mesentery vessels (see U.S. Pat. No. 3,956,504). It produces no measurable effect on blood coagulation studies. It has a limited effect on blood vessel wall pores as shown by electro-osmotic studies. Para amino benzoic acid, further, has good anti-thrombotic characteristics but tends to have relative little anti-coagulant activity as shown by its lack of effect on the coagulation studies including partial thromboplastin time, thrombin time and recalcification time. It is therefore a very useful antithrombotic drug. Para amino benzoic acid has various very significant properties as a drug: 1. It is inexpensive; 2. It is known to be non-toxic in humans; 3. It can be used for long periods of time without significant incidence of pathological manifestations: 4. The material can be taken orally in large dosage without significant toxicity. In man, dosages have been administered, for example, as high as 12 to 24 grams a day without significant side effects. It has furthermore been used for a large number of diseases in man including the therapy of Ricketsial diseases before the development of anti-biotics, for tuberculosis in very large dosage and in the treatment of certain protozoan diseases and other infestation. It has long been thought to be a mild anti-inflammatory agent. In humans with arteriosclerotic peripheral vascular disease, para amino benzoic acid has been shown to increase blood flow in ischemic limbs as measured by Barcroft plethysmographic studies and Doppler blood flow measurements. Studies which were carried out in approximately fifty patients resulted in an approximate doubling of blood flows in patients in which para amino benzoic acid salt was effective. U.S. Pat. No. 3,956,504 has been issued on the effect of para amino benzoic acid on blood flow in man. The long term effects of vitamin C on scurvy in man is a primary event of historical interest in medicine. The effects of vitamin C to prevent scurvy are extraordinarily well documented throughout the world. Man, deprived of vitamin C for periods longer than approximately sixty days, starts to display evidence of capillary fragility and bleeding into all tissues and organs. Vitamin C has the following characteristics: 1. It is a co-enzyme in the Kreb's cycle. 2. It is a reducing agent and electron donor in all known biological systems. L-ascorbic acid or vitamin C has a variety of biological functions some of which are not completely understood (Ziten et al 1964). Large doses of L-ascorbic acid appear to have value in prevention and symptom reduction in the common cold and other viral diseases (Linus Pauling 1974). Recent experimental evidence indicates that L-ascorbic acid is effective in reducing serum chloresterol levels. C. Spittle (The Lancet, July 28, 1973; pp. 199-201 and Dec. 11, 1971; pp. 1280-1281) suggested that dosages of 1 to 2 grams of vitamin C per day can be beneficial in the prevention of deep vein thrombosis as well as in reducing the incidence of atherosclerotic complications in man. Recent research indicates that ascorbic acid may reduce the incidence of myocardial infarction (Knox, E. G., The Lancet, pp. 1465, June 30, 1973). L-ascorbic acid, further, appears to offset the thrombogenic effects of oral contraceptives as demonstrated by prolongation of occlusion times in the mesenteric vessels. Good results were obtained in a pilot study using seven volunteer subjects to determine the effects of ascorbic acid on (1) plasma coagulation characteristics (2) serum cholesterol levels (3) platelet aggregability and (4) surface charge characteristics of red cells and platelets. Vitamin C in these subjects was shown to decrease platelet aggregability and increase the electrophoretic mobility of all the tested cells. There has been little evidence to indicate that vitamin C effects measured blood coagulability as demonstrated by partial thromboplastin time, thrombin times and thrombin recalcification times. Spittle et al have tested vitamin C in a randomized group of patients with thrombophlebitis. The protective effect of vitamin C against thrombosis has been shown by a randomized double-blind trial using patients who were shown to be prone to deep venous thrombosis. In a total of fifty-three patients, it was observed that the incidence of deep venous thrombosis was 33% in patients dosed with L-ascorbic acid compared to 60% in the placebo groups (Spittle, C. R., The Lancet pp. 199, July 28, 1973). The dose given was 1 gram per day. This correlation between the intake of vitamin C and reduction in the number of thrombotic episodes has been confirmed by other sources. In burn patients, where it is customary to use large doses of vitamin C to speed healing, there has been an apparent demand for treatment of deep-vein thrombosis. This information is based on the experience of one hospital over a five and one-half year period during which time 159 patients over forty years of age were treated with large doses of vitamin C (Spittle, C. R., The Action of Vitamin C on Blood Vessels, Amer. Heart J. 88:387, 1974). SUMMARY OF THE INVENTION It is an object of the invention to provide a synergistic combination of para amino benzoic acid and L-ascorbic acid. It is another object of the invention to provide an improved pharmaceutical compound having improved utility for extended periods following administration. Yet another object of the invention is to provide improved methods for the treatment of hosts and the prevention of vascular conditions. Still another object is to promote the development of useful compounds based on organic acids and the like. A further object of the invention is to provide new methods for the development of pharmaceutical compounds. To achieve the above and other objects of the invention, there is provided a method comprising reducing thrombotic tendencies in a host by administering to the host a compound derived from two organic acids. According to one embodiment of the invention, one of the acids is L-ascorbic acid and the other is para amino benzoic acid. The compound which is derived may be a salt and this compound may be administered in a dosage of 1-100 mg./kg. of body weight. The dosage is preferably administered orally, although it can be administered parenterally. The compound may be formed by mixing solutions of L-ascorbic acid and para amino benzoic acid and evaporating the thusly resulting mixture and recovering the thusly resulting solid. The acids are preferably used in a ratio of 1:1 on a molar basis. The solid may be recovered in crystal form or may be recovered as a cake. The invention includes, as one aspect thereof, compounds prepared according to the above method or specifically salts of L-ascorbic acid and para amino benzoic acid. BRIEF DESCRIPTION OF DRAWING The sole FIGURE of the drawing is a chart demonstrating the prolonged activity of dosages of the compound of the invention. DETAILED DESCRIPTION Hereinabove, reference had been made to para amino benzoic acid. The formula for this organic acid is as follows: ##STR1## Reference has also been made to L-ascorbic acid or vitamin C, the formula for which is: ##STR2## The present invention relates to compounds derived from these organic acids, namely, salts, esters and amides thereof, the synthesization of the same and the applicability thereof to the treatment of the vascular system, notably in rats, dogs and human hosts requiring such treatment. The formula for the salt is as follows: ##STR3## The original approach was to prepare a salt of ascorbic acid with para amino benzoic acid. Such a salt can be shown in two forms -- one using the open form of ascorbic acid, the other using the enol form. Two manufacturing procedures used are described below. Because of the ease of oxidation of ascorbic acid, it is essential to perform all operations under nitrogen and free of water and air. In one case, substantial darkening of the product resulted. It was believed this was due to the presence of moisture. EXAMPLE I 1. A solution of para amino benzoic acid in a mixture of 50% acetone and 50% methanol was prepared with gentle heating. The concentration was approximately 100 grams per liter. 2. A similar solution was prepared with L-ascorbic acid. 3. The two solutions were mixed. Water was excluded to the extent possible. 4. The mixture was evaporated under vacuum, with nitrogen being utilized to flush the system. As the material concentrated, crystals began to appear. 5. When the solution was evaporated, until it was a thick slurry, the material was filtered through a coarse filter paper and allowed to drain as dry as possible. The surface was blanketed with nitrogen, with great care to exclude all filtered water. 6. The resultant solid was dried under high vacuum at room temperature. The ratio of L-ascorbic acid to para amino benzoic acid used was one to one on a molar basis. EXAMPLE II 1. An alternative method of preparation used was to evaporate the solvent with careful exclusion of water and air to the point where a solid semi-dry cake was obtained in the container in which the evaporation was conducted. 2. This moist cake was then transfered to an appropriate container and dried under high vacuum. All operations are protected against exposure to air and moisture. Other solvent systems will undoubtedly work. The above were used largely as a matter of convenience. An odor develops in the process which is removed with high vacuum drying, but must represent a by-product which is formed during the process. It must also be volatile, since it can be removed. The first salt shown above, theoretically, only requires the removal of a molecule of water to form the amide. In general, this does not happen too readily. The distillation of the solvents may help pull off water. Initial studies were directed toward determining the toxicity of the above indicated compound in mammalia. A very high dosage per kilogram of body weight in rats and dogs has been shown essentially non-toxic. The new compound was next tested to determine its effect on rat-mesentery occlusion studies. Half lives of para amino benzoic acid have been shown to approximate one day. Half lives of vitamin C approximate 12 hours to a maximum of 1 day. The half lives of the new compound have been shown to approximate 4 to 5 days with a tail. A single dose lasts approximately 14 days. Mechanical mixing of para amino benzoic acid and L-ascorbic acid have been shown to have a maximal tail of approximately 5 to 6 days indicating by direct logic that the new compound is biologically different from the two components mixing together mechanically. Specifically, the compound derived appears to be more potent than the starting materials mixed together in a 50/50 ratio. If the agents are mixed together in the same ratio as used when making the new compound, the mechanical mixture is still not as potent as the compound derived. The new compound has been evaluated in rat-mesentery studies. In the rat-mesentery, the new compound has been shown to prolong coagulation 3 to 4 times the normal rat-mesentery thrombosis time. The result is dramatic and prolonged since the effect of a single dose appears to extend out to 14 days before rat-mesentery occlusion times return to a normal level. This result is based on 26 rats. Blood cells of male dogs fed with the new compound, display an increase in negative surface charge which increases sequentially from the third day to approximately the 14th day, so that at 14 days there is a doubling of electrophoretic mobility over the effects seen on the fifth, sixth and seventh day. The available evidence suggests that, as with most normal pharmacologic agents, the new compound will not produce super normality. It will, however, return toward normal any grossly abnormal measurements concerning the electrokinetic characteristics of blood cells and blood vessels in dogs. The available evidence indicates that the new compound derived from L-ascorbic acid and para amino benzoic acid is a rather potent anti-thrombotic agent. Its effect is cumulatively greater than the effect of either of its components even when they are mechanically mixed together and given orally to rats and/or dogs. The compound is an elegant example of an electron donor compound which is useful in treating the vascular system. The following are some results of tests comparing the new compound with a mixture of the starting materials and with the starting materials individually: TABLE I__________________________________________________________________________Dosages - Oral Route DURATIONMATERIAL RANGE MGS/KG/DAY ADMINSTRATION TOXICITY EFFECT__________________________________________________________________________ Minimum MaximumPABA (X) 1 10 Indefinite Low cutaneous Relatively manifestation. limitedL-Ascorbic 0.25 10 Indefinite Low cutaneous Critical inAcid (Y) mgs. manifestation. maintenance Gastritis. Some of tissue evidence dis- integrity turbence gene particularly pool in massive vascular tree dosage. Catalytic oxidizer Krebs cycle essential vitamins.X + Y 1 100mg/kg Unknown Very low gas- Prolonged rat(mixture) rats long term tritis in one mesentery rat, in high occlusion dosage 1mg/gm time. Single body weight dose run dosage. (day 1): 170±20 min. Tail - 7 days.X - Y 2 100mg/kg May be Very low Prolonged.(compound) given long gastritis. Longer tail term than X + Y Tail - 14 days Occlusion time: 206 = 24 min.__________________________________________________________________________ X - Y tail - minimum 14 days in experimental animals X + Y tail - minimum 7 days in experimental animals The following additional data was obtained relative to the utility of the new compound: ______________________________________EFFECT OF NEW COMPOUND ON ELECTRICALLY IN- -DUCED THROMBOSIS IN RATMESENTERIC VESSELS______________________________________SINGLE LOADING DOSE20mg/100g B.W. MALEMELTING POINT - 147° C.1 DAY AFTER SINGLE LOADING DOSE1 Rat The occlusion time was 240 minutes3 DAYS AFTER SINGLE LOADING DOSE1 Rat The occlusion time was 150 minutes2 Rat The occlusion time was 195 minutes______________________________________ The following data relates to rat-mensentery occlusion time: ______________________________________RAT-MESENTERY OCCLUSION TIME OCCLUSION TIME CONTROL______________________________________PABA35 mg p.o./d × 3 d (F) 95 min (1F) 45+5 min (3F)35 mg p.o./d × 3 d (M) 53±13 min (7M)L-ASCORBIC ACID10mg/100g body weight/per day × 3 days (F) 112±18 min (5F) 45±5 min (2F)10mg/100g body weight/per day × 3 days (M) 135±14 min (2M) 38±10 min (3M)PABA +L-ASCORBIC ACID35 mg + 10mg/100g bodyweight 108±23.0 min (6F) 45±5 min (2F) 128±18.0 min (2M) 38±10 min (3M)10 mg + 10 mg 160 min (2F) 50 minutes (1F)(3M + 3F) 175 min (3M) 55 minutes (1M) AF + 3MPABA -L-ASCORBIC ACIDSALT(NEW COMPOUND)20 mgs/100 grams 1 day after Single Loading Dose 240 min (1F) 3 days after Single Loading Dose 150 min (1M) 195 min (2F)______________________________________ The following data relates to the occlusion time tail in female rats: ______________________________________(X - Y) - NEW COMPOUND - SINGLE DOSE/ P.O.100mg/100g body weight Average Occluding Time______________________________________1 day 206 ± 24.0 min (5F) 5 days 143 ± 9.5 min (5F) 9 days 137 ± 12.0 min (5F)11 days 127 ± 34.0 min (4F)14 days 67 ± 4.5 min (4F) Control - 48 ± 1.1 min (5F)______________________________________ Below are tabulated some physical characteristics of batches of the compound which were made: ______________________________________ MELTING POINT SOLUBILITY______________________________________Batch 1 157° C. Sparingly Soluble; 1gm/100cc. H.sub.2 OBatch 2 157° C. SameBatch 3 147° C. Same______________________________________ Referring next to the sole FIGURE of the drawing, it is seen that there is illustrated the effects of a single loading dose on a number of rats. A control is provided in the form of five animals and it is noted from the chart in the drawing that the control provides a rat-mesentery occlusion time relative to electrically-induced thrombosis which is at the outset, less than a single loading dose of the new compound after 14 days. More particularly, it will be noted that five animals were sacrificed after one day following administration of the new compound, five animals were sacrificed after five days, five more animals were sacrificed after nine days, four additional animals were sacrificed after 11 days and finally, four animals were sacrificed after 14 days. The occlusion time (in minutes) after the first day is markedly greater than that of the controls. After five days, the occlusion time is reduced but is still more than double that of the controls. Similarly, after nine days, the occlusion time is substantially greater than the controls and has reduced only very slightly from the fifth day measurements. Similarly, after 11 days, there is very little reduction in occlusion time which is still at least twice as great as that of the controls. After 14 days, measurement of four sacrificed animals still reveals an occlusion time which is greater than that of the controls. The measurements in the drawing are based upon an administration of the compound in a dosage of 100 mg/100 g of body weight and single loading doses are employed for both the controls and the animals to which the new compound has been administered. This shows a substantial tail inures to the benefit of administration of the new compound and this is important with respect to the treatment of humans wherein oral administration of the new compound is expected to lead to a scheduled administration which provides for spaced-oral dosages over a period of days, such as, for example, one oral administration per week. There will now be obvious to those skilled in the art, many modifications and variations of the above methods and compounds. These modifications and variations will not depart from the scope of the invention if defined by the following claims or if generally equivalent thereto.

A solution of L-ascorbic acid and a solution of para amino benzoic acid are mixed and the mixture evaporated to permit recovery of a solid compound. The compound is adminstered to a host to reduce thrombotic tendencies.

BACKGROUND OF THE INVENTION The present invention relates to a novel rope or cable construction and the method of making same. Although the making of rope or cable is an ancient art, modern materials and methods have improved the art substantially. The following U.S. patents and what they describe are illustrative of the background for the present invention and represent the closest prior art of which applicant is aware: Buhler U.S. Pat. No. 2,107,567 dated Nov. 23, 1934, for Finishing Welt. A decorative rope formed of a central core, twisted or straight, and a cover, woven or braided. Thompson U.S. Pat. No. 2,146,275, dated Feb. 7, 1939, for Impregnated Woven Sheath. A core of parallel yarns is bonded at intervals, and a nonporous layer around the core and an outer coating of neoprene are formed to prevent the instrusion of moisture. Buhler U.S. Pat. No. 2,360,106, dated Oct. 10, 1944, for Joint Packing. A rope with a resilient core is bound in a woven or braided cover and used for packing. Poirier et al. U.S. Pat. No. 2,737,075, dated Mar. 6, 1956, for Cord Structure. A plurality of casings are successively braided over the core and applied loosely to permit slipping and thus allow flexing of the cord. Creve U.S. Pat. No. 2,985,056, dated May 23, 1961, for Line and Method of Manufacture Thereof. A core of animal fibers and synthetic fibers are twisted together, moistened to bind them and provide high tensile strength, and then covered with strands of braided synthetic fibers to form a string for a tennis racquet or the like. The strands and core are bonded by a synthetic material which dries hard. The braided cover is for the purpose of good wear. Morieras U.S. Pat. No. 3,265,809, dated Aug. 9, 1966, for Cables with Bonded Organic Filamentary Insulation. A central conductor is surrounded by bonded, parallel twisted yarns of insulating fibers impregnated with latex. Then a sheath is braided about the core. The assembly is sized through a die and oven-cured. The rope is intended to afford good insulating qualities and tensile strength. Durkee et al. U.S. Pat. No. 3,457,717, dated July 29, 1969, for Plastic Coated Cable and Method of Making Same. Strands of wire are aligned in several cables, bundled into a larger cable, and spaces in the outside of the bundle receive smaller cables to tend to fill in and smooth the outer periphery. Molded plastic strips with butt or lap joints fill the outer interstices. Caulking of a soft plastic material is then applied. A thin binder of glass adhesive tape holds the strips in position, and then a spiral wrap of nylon or other plastic is followed by a layer of acrylic resin which is then cured. This cable is intended for suspension-bridge cabling, the outer cover providing a moisture barrier. Hood U.S. Pat. No. 3,911,785, dated Oct. 14, 1975, for Parallel Yarn Rope, and Hood divisional U.S. Pat. No. 4,019,940, date Apr. 26, 1977, for Method of Manufacturing Parallel Yarn Rope. A plurality of slightly twisted filaments are paralleled together and bonded by a binder disposed predominantly on the surface of the yarns to form a core. A nonporous layer of flexible, water-impervious insulating material surrounds the core. A jacket is braided over the insulating material, and a final costing of neoprene completes the rope. Applying the binder only on the surface of the yarns is intended to aid flexibility; the rope is intended to have good insulation qualities. Phillips U.S. Pat. No. 3,936,336, dated Feb. 3, 1976, for Method of Forming Reinforced Plastic Articles Utilizing Openwork Tubes. A glass fiber tube, such as a braided covering, is charged with a core of resin-impregnated fibers. The tube is tensed to reduce the tube diameter, impregnate the core, and cover with excess resin. Then the resin is cured to produce a strong rod of reinforced plastic and may be tensed when bent to provide a curved-shaped article. Morieras U.S. Pat. No. 4,312,260, dated Jan. 26, 1982, for Flexible Cable. A core is formed of a bundle of parallel threads. The threads are impregnated at spaced intervals at a nonperpendicular angle to the axis of the parallel fibers, thus systematically mixing the overlaps, that is, mixing systematically the impregnated, inflexible portions and the nonimpregnated, flexible portions of the core. The core is surrounded by a bonded outer layer over which a cover is braided. The spacing between the impregnated portions is to afford some flexibility to the final product, whereas the impregnated portions are intended to give tensile strength. Also of interest are Kippen U.S. Pat. No. 3,415,919 dated Dec. 10, 1968; 3,446,002 dated May 27, 1969; and 3,551,280 dated Dec. 29, 1970; which show twines having a core comprising a bundle of untwisted monofilaments with a wrap or casing applied to the core to complete the twine. SUMMARY OF THE INVENTION A plurality of parallel filaments are aligned and compacted to form a core. The core is then wrapped to form a uniform jacket that is torsionally stable. Urethane or other plastic material is applied to the jacket to penetrate the wrapping without penetrating the core. Then the urethane or other material is cured. The rope or cable thus has a core of parallel filaments free to move within the urethane jacket. In some cases, an outer sheath, such as a braided sheath, may be used, with or without the urethane impregnation. DESCRIPTION OF THE DRAWING The various objects, advantages, and novel features of the invention will be more fully apparent from the following detailed description when read in connection with the accompanying drawing in which like reference numerals refer to like parts and in which: FIG. 1 is a highly schematic representation illustrating a method embodying the invention to make a rope of the invention; FIG. 2 is an enlarged schematic sectional view along lines 2--2 of FIG. 1 showing bundles of fibers being positioned by a registration plate in preparation for a core of the rope or cable being manufactured; FIG. 3 is a sectional view along lines 3--3, not to scale, of FIG. 1 showing one method of wrapping the core; FIG. 4 is an enlarged sectional view along lines 4--4 of FIG. 1 illustrating the inner appearance of a wrapped core before curing; FIG. 5 is an enlarged fragmentary side view of the rope or cable of FIG. 4 with a braided sheath being applied thereover; FIG. 6 is a fragmentary enlarged sectional view along lines 6--6 of FIG. 1 illustrating the appearance of the finished urethane impregnated rope or cable made by the method of the instant invention; and FIG. 7 is an enlarged fragmentary side view of the rope or cable of FIG. 6 with a braided sheath being applied thereover. DESCRIPTION OF THE INVENTION Referring to FIG. 1, a plurality of filaments 8 are organized into a group of parallel, preferably untwisted, filaments in a zone 10, dried in a zone 11, compacted into a core 7 in a zone 12, wrapped with ribbon to form a jacket 9 in a zone 13, and further compressed or compacted in a zone 14. Then a plastic material 19, such as urethane, is applied in a zone 15 and the material 19 compressed into the wraps of jacket 9 in a zone 16 to penetrate the wraps only and not the filaments 8, which are left free to move relative to each other. Finally the urethane or other material 19 which penetrated the jacket 9 is cured in a zone 17 to provide a completed rope or cable 18. In the organizing zone 10, filaments 8 are drawn from supply source 21 and thence through apertures 22a of a registration plate 22 (FIG. 2, not to scale). The registration plate 22 is only schematically indicated. The number of apertures 22a may be much greater than the number shown and symmetrically arranged about an axis to align the filaments 8 into substantial parallelism. Each supply source 21 may feed a non-twisted yarn with many filaments 8, and each aperture may pass a like plurality of filaments 8 from the source 21. After leaving the plate 22, the filaments 8 advance into a drying zone 11 where they pass through a drying chamber 23 heated by any suitable heat source 24. After drying, the filaments 8 are compacted by a die 26. Means, such as a pair of rollers 25, the drive means for which is not shown, serve to draw the core 7 of the filaments 8, now compacted into compressed core 27, through the die 26, and also serve to draw the filaments 8 from the supply source 21 over the tensioning devices 20 and through the plate 22. The compacted core 27 of filaments 8 is now wrapped in a zone 13 to provide the jacket 9. In this exemplification, the jacket 9 is applied by winding or twisting around the compacted core 27 from respective spools 28a and 28b narrow ribbons or tapes 29a and 29b in opposite directions (see arrows, FIG. 3) so the parallel filaments 8 are not inadvertently or undesirably twisted. The tension for each spool may be controlled by means of a friction release (not shown) applied to the respective spools 28a and 28b. The higher the friction, the more force is required to draw the ribbon from the spools 28a, 28b; and the greater the tension as the ribbons 29a and 29b are wound upon the core, the more tightly the core is compressed at this stage. Mechanisms for such wraps are known, and that of FIGS. 1 and 3 is only schematically illustrated. Preferably the ribbons 29a, and 29b are ribbons of absorbent material so that the later-applied urethane 19 may readily impregnate the ribbon, but not penetrate into the core. Also, more than the two layers of ribbons 29a and 29b may be applied if desired, i.e., there may be more than two spools used at a time, but preferably an even number to avoid accumulating a twist in the filaments being wrapped. Although a knitted fabric is preferred for the ribbon, other ribbons, such as those of woven or nonwoven fabrics or synthetics films, may also be used. For simplicity, speed of application, and low cost, I prefer to use ribbons of narrow polyester knit fabric, and helically wrapped in opposite hand about the core. The degree of overlap of the ribbons may also be controlled to provide a desired number of layers at a point along the axis. Although it has been found preferable to wrap the core with a like number of ribbons in each direction, it is possible to provide an effective wrap comprising one or more ribbons spirally wound around the core in the same direction, so long as the core is completely covered by the wrap. The rope or cable 30 comprising the compacted core 27 of filaments 8 and the wrap 29a, 29b now passes into zone 14 for further compacting to a specified size by passage through a die 32. The rope 30 is drawn from the rollers 25 and past the wrapping zone 13, and thence through the die 32 by means such as rollers 33 and 34, the drive means for which is not shown. From compacting zone 14 the rope or cable 30 enters at zone 15 a urethane or other material bath 35 in a tank 36 which may be replenished as needed from a pipe 40. The material may also be extruded directly onto the rope or cable. The rope, coated with such urethane or other material, is fed through a die 38 in a zone 16. The die forces the urethane or other material to impregnate jacket 9 of the rope. At the same time, the excess coating is wiped off and returns to the bath 35. The die 38 aperture is selected to force impregnation of only the jacket 9 with urethane or other material, and not to have urethane or other material penetrate the core or inner bundle of monofilaments 8, which are left free. Preferably the filaments 8 are not penetrated at all, or, at the very least, only the very outermost ones of the bundle. On the other hand, it is not essential to completely impregnate all the layers of the ribbon to its complete depth. I prefer to have the urethane penetrate substantially completely the layers of ribbon, and not at all the filaments 8. The impregnated rope is pulled through the die 38 by means such as rollers 39, the drive means for which is not shown. A layer of urethane 19 may be left on the outer surface of the rope or cable for abrasion-resistance and moisture-barrier purposes. Then the rope or cable is advanced into a curing or heating zone 17 where it is cure--for example, in an oven 42 heated by a suitable heat source 43. Means such as a pair of rollers 44 draw the rope through the oven 42 from the rollers 39 and discharges the completed rope 18, which now may be wound onto a suitable spool 46. As it is being wound on the spool 46 or at any convenient time after leaving the curing oven 42, indicia 47 may be marked on the rope so that the length of the rope withdrawn or used may be readily ascertained. In FIG. 6 the finished rope or cable is indicated in cross section, and outer ribbon 29b and inner ribbon 29a are indicated as penetrated with the cured urethane or other material by stippling. The number of filaments may be in the thousands and are illustrated as in FIG. 4. The filaments are left free; that is, they are non-adhered to each other or to the jacket 9 impregnated with the cured urethane. It will be understood that while the use of urethane or the like coating is preferred, in some applications it may be desirable to substitute an outer sheath 48 that could be braided, extruded or otherwise applied directly to the jacket 9 as shown in FIG. 5. On the other hand, in some cases it may be desirable to apply such an outer sheath over the jacket 9 after the latter has been impregnated with urethane or the like, as shown in FIG. 7. Furthermore, after the braided sheath 48 has been applied to the rope of either FIG. 5 or FIG. 7, it may in some cases be desirable to impregnate the sheath with urethane or the like, which can be accomplished by any suitable means, such as by passing through another tank similar to that shown at 36 in FIG. 1. As an example in one successful and preferred embodiment, I provide filaments 8 of polyester, six denier per filament, and there may be about 33,000 filaments 8 in the core. The die 26 opening or aperture is about 0.185 inch diameter. When the ribbons 29a, 29b are drawn from the spools 28a, 28b, their tension is about twelve pounds. The angle of wrap is about 35°, and the overlap about 40 percent. Thus, there are about four total number of layers or ribbons at any point along the rope 30. The heat of drying chamber should be gentle, preferably about 200° F., although this is not critical. The opening for the die 32 is about 0.250 inch diameter. The ribbons 29a and 29b are polyester and are about one inch wide. The temperature of the curing oven is about 200° F. The resultant rope or cable is about 0.250 inch outer diameter, and the wall of the jacket 9 after impregnation and curing is about 0.080 inch in thickness. Rope or cable of other outer dimensions may be made by the process. The urethane-impregnated jacket provides improved abrasion and moisture resistance. A rope or cable of the invention has many advantages. No heat seal or end taping is required when the rope is cut, because it does not unravel. It may be manufactured to close tolerances; and the rope lends itself to various standard end terminations. For example, an eye may be easily formed at either end of the rope and secured by any desirable means, such as a metal sleeve, or the rope may be spliced. The rope or cable is excellent for use in construction and placement of concrete revetment mats. It is highly resistant to ultraviolet rays, to most chemicals, and to biological conditions encountered at most deployment sites for that purpose. The rope or cable is also highly useful in conditions where a high dielectric constant is desirable. Also, the rope has high tensile strength. For example, a one-quarter-inch size outer diameter has a tensile strength of 3500 pounds; a 5/16 inch outer diameter size has a tensile strength of 7000 pounds; and a half-inch outer diameter size has a tensile strength of 15,000 pounds. Lengths are easily provided of up to 25,000 feet without a core splice. Because of the parallel filaments of the core being free, that is, not adhered or bound to each other, the rope or cable has a high flexibility compared to other ropes of like strength. The tightly wound jacket holds the core firmly together under compression, eliminating need for any adhesive bond of the fibers, and eliminates the necessity of braiding a cover over the core, although such a cover may be applied over the wound jacket. The cured urethane or other material cover holds the jacket and core together and allows the rope or cable to be cut without unraveling. No binding, heating or melting is required to prevent unraveling. The cured coating, as noted above, is abrasion resistant and creates a moisture barrier. Unlike ropes not resistant to moisture, the invention may be used with minimal risk of creating a conductive path near high-voltage lines and towers. Double-braided rope is relatively flexible and strong, but it tends to hold moisture, which tends to make it conductive when wet. There is also an undesirable elongation of double-braided rope under tension. These faults are absent in the rope or cable of the present invention, which is resistant to moisture, is still flexible and strong, and exhibits minimum elongation under tension, primarily because of its non-twisted core. The method of the present invention can produce rope or cable more rapidly than the prior methods. The rope or cable of the invention can be produced at a rate, for example, of about 40 feet per minute, and if desired at greater speeds, up to about 80 feet per minute, with no spooling or twisting, with only one machine, and with a waste factor about equal to, or even less than, one percent, far better than current speeds and production losses. By varying the tension of the cover wrap, the size of the compacting die, and the hardness of the urethane or other material, various degrees of flexibility, size and tensile strength can be obtained for the rope or cable of the present invention without the necessity of changing production speeds, machinery, or feed set-ups. These factors contribute to a low production cost and make possible a low price for the rope or cable of the present invention. While there is shown and described herein certain specific structure embodying the invention, it will be manifest to those skilled in the art that various modifications and rearrangements of the parts may be made without departing from the spirit and scope of the underlying inventive concept and that the same is not limited to the particular forms herein shown and described except insofar as indicated by the scope of the appended claims.

In making synthetic rope or cable, a plurality of filaments are brought in parallelism into a core and compacted by a plurality of ribbons or tapes wound about the core under tension in opposite directions to form a uniform jacket that is torsionally stable. An outer sheath which may be urethane or other plastic material is applied to the jacket under sufficient pressure to penetrate the jacket but not the core, and then the urethane is cured. The rope or cable of the invention has a core of substantially parallel filaments free to move within the jacket of ribbons wound about the core and penetrated with the urethane or other plastic material. The method affords many advantages in speed of manufacture and cost, and provides a rope or cable of greater tensile strength and flexibility than other rope or cable constructions.

This application is a division of application Ser. No. 945654, filed 12/23/86 now U.S. Pat. No. 4,242,331. FIELD OF THE INVENTION This invention relates to reset circuitry for resistance capacitance voltage ramp generators. BACKGROUND OF THE INVENTION In modern computer control systems, it is frequently necessary to reset convert a digital signal (which is used internally in the computer) to a variety of analog signals which are used to directly control or measure the environment. Two conversion devices which are ofter used in manufacturing systems are digital-to-analog converters (DACs) and analog-to-digital converters (ADCs). These units convert between analog signals generated by the environment and the digital signals used by the computer. Another, perhaps less widely used, conversion device is a digital-to-time converter. This unit accepts a digital signal and produces a proportional time delay. The delay usually appears as a time difference between two pulses appearing at the output of the device or between a trigger pulse and a pulse appearing at the output of the device. Such programmable time delay circuits are often used in automated test equipment and are used to delay digital signals. Digital-to-time converters have conventionally been fabricated from discrete semiconductor devices. In such devices, the conversion is often performed by comparing a linearly-increasing voltage or current ramp signal to a threshold voltage or current. In one conventional form of a digital-to-time converter, a fixed threshold voltage is set by a precision voltage reference source and the time delay is generated by comparing the threshold voltage to a ramp with a variable slope. The slope of the ramp is set by the value of the digital word to program the device. In another conventional form of the converter, a ramp with a fixed slope is generated and the time delay is obtained by comparing the ramp voltage to a variable threshold whose level is set in accordance with input digital word. In either of the above variations, when the value of the ramp voltage equals the value of the threshold voltage a pulse signal is generated. If a pulse signal is generated at the start the ramp signal, the time elapsing between the two pulse signals represents a delay which depends on the value of the digital input word. The starting pulse may also be the trigger pulse which is used to start the ramp signal generation. In a conventional digital-to-time converter designed with discrete devices, the internal ramp signal is created by charging a capacitor with a stable current generated by placing a precision voltage reference source across a precision resistor. Once a stable charging current has been established, the voltage across the capacitor provides a stable ramp output. Such a ramp generator is usually reset by means of a shorting transistor connected in shunt across the capacitor. When the shorting transistor is turned "on", the voltage across the capacitor is returned to zero, resetting the circuit. The shorting capacitor is normally controlled by the output of a flip-flop or other memory circuit which determines whether the circuit is operational or rest in response to the application of set or reset signals. The problem with the conventional arrangement is that the reset signal which operates the flip-flop must propagate through the flip-flop to turn on the shorting transistor and reset the circuit. Since the flip-flop contains many transistors and other elements, the time consumed between the receipt of a reset signal at the flip-flop input and the actuation of the shorting transistor is usually significant and thus the reset time of the entire circuit is increased by the propagation delay of the flip-flop. Since the reset time of the circuit is a substantial portion of the operating cycle of the circuit, the entire operational frequency is reduced. Accordingly, it is an object of the present invention to provide a reset circuit for a ramp generator which can operate at high speed. It is another object of the present invention to provide a reset circuit for a ramp generator in which the reset function operates at a higher speed than conventional circuits. It is yet a further object of the present invention to provide a reset circuit for a ramp generator which can be easily fabricated in a monolithic integrated circuits. It is yet a further object of the present invention to provide a reset circuit for a ramp generator which can be easily intergated with existing control circuitry. SUMMARY OF THE INVENTION The foregoing objects are achieved and the foregoing problems are solved in one illustrative embodiment of the invention in which a current switch is connected to the shorting transistor. The current switch is directly actuated by a reset signal and immediately diverts current to the shorting transistor causing the circuit to reset. The current switch holds the circuit in the reset condition until the flip-flop changes state in order to maintain the circuit reset. More particularly, the shorting transistor is connected to a bias circuit which normally provides base current to turn the transistor "on". During circuit operation, in order to hold the shorting transistor "off", the shorting transistor base current is drawn away from the shorting transistor by means of a control transistor which is located in the output circuitry of the flip-flop. The control transistor acts as a current switch to divert the shorting transistor base current to ground. In accordance with the invention, a second current switch is connected in series with the control transistor. This second current switch is directly responsive to a reset signal applied to the circuit. When a reset signal is applied, the second current switch opens and allows the bias circuit to immediately apply base current to the shorting transistor. The shorting transistor thereupon turns "on" and resets the circuit. Subsequently, the flip-flop changes state to maintain the circuit in the reset state. In order to allow the reset circuitry to be fabricated as a monlithic integrated circuit, both the control transistor and the second current switch are fabricated as pair of emitter-coupled transistors connected to a current source. This conventional arrangement allows current to be switched between circuit elements without changing the overall current flow through the system. BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a block schematic diagram of the inventive digital-to-time converter circuit. FIG. 2 is a detailed electrical schematic diagram of the trigger/reset flip-flop circuitry. FIG. 3 is a electrical schematic diagram of the ramp generator. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An illustrative digital-to-time converter has a TRIGGER input, a RESET input, a minimum delay output and a programmed delay output. The TRIGGER input accepts a positive-going-edge signal to trigger the circuit. Internal circuitry prevents an erroneous re-triggering until the circuit function has been completed. After the circuit has been triggered, and after a propagation delay, a pulse appears at the minimum delay output. This pulse is used in the same fashion as analog ground in a digital-to-analog converter to reference the zero state (zero time delay in the present circuit). Subsequently, after a programmed time delay depending on the values of the digital input word (on leads B1-B8), a second pulse appears at the programmed delay output. The time elapsing between the two pulses represents the time delay generated by the device. The RESET input is dominant over the TRIGGER input. In the presence of a RESET input the device cannot be triggered and, if already triggered, it resets. More particularly, as shown in FIG. 1, the device accepts a differential, or single-ended, emitter-coupled-logic (ECL) signal applied to its TRIGGER input 100. The TRIGGER signal on lead 100 is applied to input and ramp start circuitry 106. Upon a rising edge being detected, the ramp start circuitry controls the charging of capacitor 120 which, as will hereinafter be described, generates the ramp voltage used to generate the programmed time interval. Circuitry 106 also responds to signals on the RESET leads 108, but contrary to the operation of the TRIGGER portion of the circuit, circuit 106 is designed to be sensitive to the level of the RESET signal rather than the signal edges. When a "high" RESET signal is applied to the RESET leads 108, the charging of capacitor 120 is terminated and the circuit is reset regardless of the state of the TRIGGER inputs or the state of the circuit. When the ramp start circuitry is activated, it removes the base drive signal on lead 114 which is normally applied to transistor 116 (transistor 116, in the quiescent state, is normally "on" and short circuits timing capacitor 120). However, when the ramp start circuitry is activated, it applies a "low" signal to the base of transistor 116 which turns "off" the transistor. Capacitor 120 then begins charging from VCC, 118, through voltage coupling circuit 122 and resistor 124. As will be hereinafter described in detail, circuit 106 is designed to accelerate the turn-on of transistor 116 when a reset signal is sensed so that the reset time of the circuit is minimized. Since the reset time is an appreciable part of the overall cycle time, high-speed operation is facilitated. The voltage across capacitor 120 is compared, by comparator 138, to a minimum delay voltage to generate the minimum delay output. The minimum delay voltage is generated across resistor 117. The voltage appearing across resistor 117 is determined by the voltage coupling circuit 122 which will be described in detail below. In the quiescent state of the circuit, a current source, 127, create an "offset" that maintains the output comparator 138 in an "off" state to avoid an indeterminate state at the output. However, as capacitor 120 charges, the voltage across it quickly exceeds the offset voltage and comparator 138 shifts to a "high" MDO signal indicating a minimum propagation delay through the device. As previously mentioned, the "high" MDO signal can be used as a zero-time reference in a manner similar to the use of analog ground as a zero-voltage reference for a conventional digital-to-analog converter. The voltage across capacitor 120 increases as the capacitor charges and, eventually, generates a programmed delay output (PDO) signal. The PDO signal on leads 134 is generated by comparator 132 which has inputs 135 which are, in turn, connected to timing capacitor 120 and to a threshold circuit which comprises DAC 128 resistor 119 and current source 127. DAC 128 accepts TTL signals representing a digital word on its inputs 130. This digital word is latched into converter 128 by means of a level-sensitive latch signal appearing on lead 131. The DAC effectively appears as a plurality of parallel-connected, binary-weighted current sources 129. In response to the digital word, converter 128 connects these current sources either to supply voltage 118 or resistor 119. The current running through each of the parallel sources is determined by components in the DAC and in voltage coupling circuit 122 so that the total DAC current is independent of the digital word. The portion of the current running through the resistor 119 is determined by the value of the digital word and is also proportional to the total DAC current since it is comprised of the current running through selected ones of the parallel-connected sources. The current running through resistor 119 causes a threshold voltage to develop at point 125, the value of which is dependent on the combination of current sources connected to resistor 119, which combination is, in turn, dependent on the value of the digital word and on the total DAC current. The total current running through the DAC is determined by internal DAC components, components in voltage coupling circuit 122 and resistor 126. In particular, the DAC current runs through reference resistor 126 to create a reference voltage VA, and, accordingly, the voltage VA is representative of the changes in the DAC current caused by thermal and supply variations. Since the current running through the resistor 119 is proportional to the total DAC current, the threshold voltage appearing across resistor 119 is proportional to the reference voltage VA and variations in the threshold voltage caused by thermal and supply variations are represented by variations in the reference voltage VA. Voltage coupling circuit 122 is arranged to force the voltage, VB, appearing across ramp resistor 124 to be equal to the reference voltage VA. Thus, the charging current to the ramp generating capacitor 120 and the resulting ramp voltage is dependent on the voltage VB, which is equivalent to reference voltage VA. Thus, variations in the internal threshold voltage appearing across resistor 119 appear as corresponding variations in the ramp voltage. Since both the threshold voltage appearing at point 125 and the ramp voltage appearing at point 123 are applied to differential comparator 132, any variations in the voltages due to temperature changes, power supply variations or component variations appears as a common mode signal to differential comparator 132 and are rejected. Comparator 132 develops an output when the ramp voltage at point 123 reaches the threshold voltage at point 125. At that point, a "high" signal appears on leads 134 which "high" signal indicates the programmed time delay from the occurrence of the MDO signal (or the trigger signal). As with the circuit that generates the MDO signal, an offset current source 136 is connected to point 125. Current source 136 maintains comparator 132 in its "off" state in the absence of signals from capacitor 120 and converter 128. FIG. 2 shows a detailed electrical schematic of the TRIGGER/RESET flip-flop and input signal comparator circuitry. As previously mentioned, the TRIGGER/RESET flip-flop is designed so that the TRIGGER input is rising-edge sensitive and the RESET input is level sensitive and dominates over the TRIGGER input. The circuitry is arranged so that either single-ended or differential inputs can be used. In the case of a single-ended input, the unused input is pulled by internal resistors to the emitter-coupled logic (ECL) midpoint voltage (VBB). For example, for single-ended operation of the SET input, resistor R148 pulls the SET* input to the midpoint voltage VBB. Midpoint voltage VBB is established by transistor Q249. More particularly, the base of transistor Q249 is held at a potential between gorund and the negative supply (VEE) by means of a voltage divider consisting of resistor R138, diodes Q250 and Q251 and resistor R139. The emitter of transistor Q249 thus establishes the ECL midpoint voltage by means of current running through resistor R140. It should be noted that some transistors have a notation "A" next to the transistor symbol. This notation refers to the relative emitter area. Thus, a transistor with a notation of 2A has twice the emitter area of a transistor with the notation "A". An absence of a notation denotes a transistor with an area equivalent to a transistor with a notation of "A". A "high" signal applied to the SET input triggers the device. This "high" signals is applied to the base of transistor Q409. Transistors Q409 and Q410 are connected in a well-known emitter-coupled differential circuit. In this circuit, the emitters of both transistors are tied to a current source which conducts a predetermined amount of current. More specifically, the current source consists of transistor Q424. The base of transistor Q424 is connected to a voltage source whose output is driven by transistor Q203 (shown in FIG. 4). Consequently, the emitter of transistor Q424 is fixed at a predetermined potential and a predetermined, constant current is drawn through resistor R420 to the negative supply voltage, VEE. Returning to the emitter-coupled differential pair, Q409 and Q410, in accordance with conventional operation, when transistor Q409 turns "on", it conducts the entire current drawn by the current source. Thus, transistor Q410 is turned "off". With transistor Q410 turned "off", resistor R407 pulls the base of transistor Q411 "high", turning "on" transistor Q411. Turned-on transistor Q411 applies a "high" signal to the base of transistor Q416, in turn, turning it "on". Transistors Q412, Q413, Q415 and Q416 are connected in a flip-flop configuration and, when transistor Q416 turns "on" it pulls the base of transistor Q413 "low", which, in turn, pulls the base of transistor Q415 "low", turning it "off". When transistor Q415 turns "off", it allows resistor R408 to pull the base of transistor Q412 "high" and turn "on" transistor Q412, which transistor maintains transistor Q416 in an "on" state. The base of transistor Q157 is also tied to the base of transistor Q416 so that, when the Q412-Q416 flip-flop is set, transistor Q157 is also turned "on". As will hereinafter be described, the collector of transistor Q157 is connected to the ramp generator circuitry so that ramp generation begins when transistor Q157 is turned "on". At the time when the Q412-Q416 flip-flop is "set", both transistors Q415 and Q156 (connected in parallel to transistor Q415) are turned "off". When transistor Q156 turns "off", it allows resistor R401 to pull the base of transistor Q401 "high". This latter action sets a flip-flop consisting of transistors Q402, Q403, Q406 and Q407. When the Q402-Q407 flip-flop is "set", it turns Q408 "on" which pulls the base of transistor Q411 "low". Transistor Q411 is thus inhibited, to prevent improper re-triggering of TRIGGER input. As previously mentioned, a RESET signal applied to the RESET input overrides the signals applied to the TRIGGER inputs. Thus, if a "high" RESET signal is applied to the RESET inputs, the converter circuit cannot be triggered and, if the converter circuit had already been triggered, the circuit is reset. In accordance with the invention, the reset circuitry is designed to rapidly turn off transistor Q157, thus resetting the circuit. This rapid turn off is accomplished by immediately depriving transistor Q157 of collector current upon the occurrence of a RESET signal. Subsequently, the triggering flip-flops are reset to maintain the circuit in a reset condition. More particularly, a "high" signal applied to the RESET input is applied to the base of transistor Q429 turning it "on". Transistors Q428 and Q429 are connected in an emitter-coupled differential pair and, thus, transistor Q428 turns "off" when transistor Q429 turns "on". When transistor Q428 turns "off", it deprives transistor Q157 of collector current (since the current for transistors Q156 and Q157 passes through transistor Q428) and transistor Q157 immediately turns "off" resetting the ramp generation circuitry. In addition, the "high" RESET signal is applied to the base of transistor Q419 turning it "on". Transistors Q418 and Q419 are also connected in an emitter-coupled differential pair and, thus, transistor Q418 turns "off". This latter action allows resistor R412 to pull the base of transistor Q430 "high", resetting the Q412-Q416 flip-flop and maintaining the circuit in the reset condition. When the Q412-Q416 fil-flop is reset Q408 is also turned "on", which action pulls the base of Q411 "low", in turn, inhibiting trigger pulses from retriggering the system. The ramp generator and inventive voltage coupling circuit is shown in detail in FIG. 3. The Ramp generator circuit consists of timing capacitor C s and timing resistor R s . The voltage coupling circuit consists of transistors Q174-Q180. Ramp generation begins when the TRIGGER/RESET flip-flop is "set" as previously described. More particularly, when transistor Q157 (FIG. 2) turns "on", the base of transistor Q158 is pulled "low" turning the latter transistor "off". Transistor Q158 normally shorts timing capacitor C s . Therefore, when transistor Q158 turns "off", it allows capacitor C s to begin charging from VCC, through transistors Q164, Q168, resistor R141, Q174, Q178 and timing resistor R s to the supply voltage VEE. Transistors Q164 and Q168 act as part of a current divider, however, transistors Q174 and Q178 act, as will hereinafter be described, to insure that the timing capacitor charging current tracks variations in the DAC current caused by thermal and supply variations and, accordingly, that the ramp voltage tracks the threshold voltage. A capacitor, C1, is connected to the base of transistor Q158 to delay the rise of the base voltage of transistor Q158 during reset of the ramp generator when control transistor Q157 (FIG. 2) turns "off". The small delay produced by capacitor C1 is necessary to prevent transistor Q158 from going into saturation as it charges capacitor C s during reset operation. Capacitor C1 thus speeds the ramp reset cycle. The ramp voltage developed across capacitor C s is applied to the base of transistor Q159 which acts as an emitter follower. From the emitter of transistor Q159 the ramp signal is applied through diode Q265 to point A. The signal at point A is one of the signals which is provided to the output comparator. In order to convert the ramp voltage into a time delay, the ramp voltage is compared to a threshold voltage which is generated by a DAC. The DAC threshold voltage appears at the base of transistor Q161 and is applied through transistor Q161 (which acts as emitter follower) and diodes Q160 and Q266 to point B. The signal at point B acts is compared to the signal at point A by the output comparator. Since the ramp slope, the initial ramp starting voltage and the threshold voltage are known, a predictable delay can be generated. More particularly, the threshold voltage is generated by a current drawn through resistor R76 by the DAC. The DAC converts the value of a digital word into a predetermined current flow through resistance R76 by selectively connecting internal current sources either to resistor R76 or to the power supply. The internal DAC current sources are weighted as binary submultiples of the total DAC current which is independent of the value of the digital word. Accordingly, although the value of the threshold voltage depends on the exact combination of current sources connected to resistor R76, it will always be proportional to the total DAC current. The total DAC current flows from the DAC through the voltage coupling circuit path consisting of transistors Q175 and Q179 and the reference resistor R84 to the supply voltage VEE. Accordingly, the voltage across the reference resistor R84 is proportional to the threshold voltage. In the illustrative embodiment shown in FIGS. 2-3, resistor values are noted next to each resistor. The values are given in ohms with the notation "K" equivalent to a multiplier of 1000. Capacitor values are given in picofarads. The transistors are of standard NPN configuration.

A ramp voltage generator which utilizes a simple resistance/capacitance charging circuit to generate a linear ramp voltage is reset by means of a shorting transistor connected across the capacitor. The shorting transistor is, in turn, controlled by the output of a flip-flop that responds to set and reset signals applied to the circuit. In order to decrease the overall reset time of the circuit and thereby increase the operational frequency, a current switch is provided which bypasses the flip-flop and immediately diverts current to the shorting transistor upon the application of a reset signal to the circuit.

BACKGROUND OF THE INVENTION The government may own certain rights in the present invention pursuant to EPA Cooperative Agreement CR 81-1531. This application is a continuation of U.S. Ser. No. 163,864, filed March 3, 1988, now abandoned, which was a continuation-in-part of Ser. No. 928,337, filed Nov. 7, 1986, now U.S. Pat. No. 4,804,521, and a continuation-in-part of Ser. No. 930,171, filed Nov. 10, 1986, now abandoned. Both are hereby incorporated by reference. Reference is made under 35 U.S.C. & 120 to copending applications, U.S. Ser. No. 930,171 filed Nov. 10, 1986, and U.S. Ser. No. 928,337, filed Nov. 7, 1986. These disclosures are incorporated herein by reference. 1. Field of the Invention The present invention relates to processes for reducing the level of sulfur in a sulfur-containing gas. In particular, the invention relates to the use of improved sulfur dioxide-absorbing calcium alkali sorbents, which include a calcium-reactive alumina or silica source, in the desulfurization of sulfur-containing flue gases, and methods for improving the sulfur dioxide absorbing capabilities of such sorbents. 2. Description of the Related Art Coal represents one of the most bountiful sources of energy in the world today. For example, it has been estimated that the known coal reserves in the U.S. alone could supply sufficient energy for domestic consumption for several hundred years. Unfortunately much of this coal contains high levels of sulfur which, when the coal is burned, is released into the atmosphere, generally in the form of sulfur dioxide. One of the most serious environmental problems associated with such sulfur emissions is the generation of atmospheric sulfuric acid, resulting in so-called "acid rain." Attempts at controlling sulfur dioxide emissions from coal burning plants have led to the development of a number of advanced systems and processes for flue gas desulfurization. Fluidized-bed combustion, lime injection, and flue gas desulfurization are some of the examples. In these processes, limestone has been used as a sorbent which forms primarily calcium sulfate at a temperature above 700° C. Regeneration of the sorbent has been a difficult problem because of the high chemical stability of the sulfate. Yet, regeneration is desirable from the points of view of conservation, cost, and ecology. As a result, a considerable amount of research effort has been expended in developing alternate sorbents which are regenerative as well as reactive to sulfur dioxide. Fluidized bed combustion (FBC) and scrubbers for flue gas desulurization (FGD) represent two of the more promising advanced processes for power generation. FBC relates to the combustion of coal with limestone particles as the bed material, and has received increasing attention as a promising and versatile technology for clean power generation. Equally promising has been FGD, wherein sulfurreactive sorbents are employed to remove sulfur from flue gases prior to their venting into the atmosphere. In developing the technologies for FBC and FGD, a search for sorbents more effective than limestone, especially ones which are economically regenerative, has been a challenging task. Flue gas desulfurization by the means of spray dryer absorber and bag filter or electrostatic precipitator has recently received much attention. In the spray dryer/bag filter system, flue gas is contacted with a fine spray of an aqueous solution or slurry of a reactive alkali (typically lime), with SO 2 removal and drying occurring simultaneously. The sulfur dioxide is absorbed into the water droplet during the constant rate period of drying until it shrinks to the extent that the particles touch each other. During the following falling rate period, the remaining water diffuses through the pores of agglomerated particles until the solids establish pseudo-equilibrium with the humid environment of spray dryer. The third stage of drying may be called the second-falling rate period. Any drying/mass transfer during this period is limited by the diffusion of moisture from within tightly packed particles. The first two stages take place exclusively in the spray dryer. The majority of pseudo-equilibrium period occurs in the duct joining spray dryer and bag filter and in the bag filter itself. Since not all moisture is removed from the solids in the spray dryer, the remaining moisture promotes further removal of SO 2 in the bag filter. Therefore the total SO 2 removal in the system is a sum of removal in the spray dryer and bag filter. The recycle of product solids is among the options that have been tested to increase the utilization of reagent. Reports indicate that recycle of product solids and fly ash results in substantial improvement of reagent utilization and SO 2 removal. This option provides a higher Ca(OH) 2 concentration in the slurry feed at the same Ca(OH) 2 stoichiometry (moles of Ca(OH) 2 fed to the system/moles of SO 2 in the feed gas). In one pilot plant, increasing the recycle ratio (g solids recycled/g fresh Ca(OH) 2 ) from 6:1 to 12:1 increased SO 2 removal in the spray dryer from 70% to 80% at stoichiometry 1.0 (Blythe et al., 1983, Proceedings: Symposium or Flue Gas Desulfurization, Vol. 2, NTIS PB84-110576). In another installation, compared to once-thru tests, recycle tests gave 10 to 15% more SO 2 removal at stoichiometry 1.5 (Jankura et al., presented at the Eighth EPA/EPRI Symposium on Flue Gas Desulfurization, New Orleans, La., 1983). Another option enhancing lime utilization uses the recycle of both solids captured downstream in the spray dryer and solids from the baghouse. However, removal does not appear to be significantly different when either spray dryer solids or fabric filter solids are employed as the recycled material. At stoichiometry 1.0 the removal increased from 53% when no recycle was employed to 62% increased from 5% to 20%, SO 2 removal in the spray dryer increased from 80% to 92% for stoichiometry 1.6 (Jankura et al., 1983). U.S. Pat. No. 4,279,873, to Felsvang et al., relates several experiments investigating the effects of fly ash recycle and proved it to be beneficial for SO 2 removal in a spray dryer. It was found that substantially higher removal of SO 2 may be achieved when recycling the fly ash and Ca(OH) 2 than when recycling Ca(OH) 2 alone. Corresponding efficiencies for stoichiometry 1.4, 500 ppm inlet SO 2 , and comparable solids concentration were 84% and 76%, respectively. For the same stoichiometry and SO 2 concentration, removal was only 67% for the simple once-thru process. At low SO 2 concentration and high recycle ratios, over 90% removal was achieved even at extremely low stoichiometries. At 548 ppm SO 2 , 25:1 recycle, 0.76 stoichiometry and at 170 ppm SO 2 , 110:1 recycle, 0.39 stoichiometry, SO 2 removal was 93.8% and 97.8%, respectively. Removal efficiencies up to 65% were reported with a slurry of highly alkaline (20% CaO) fly ash only (Hurst and Bielawski, Proceedings: Symposium on FGD, EPA-600/9-81-019b, 853-860, 1980). In another experiment, 25% SO 2 removal was achieved when spraying slurried fly ash collected from a boiler burning 3.1% sulfur coal (Yeh et al., Proceedings: Symposium on Flue Gas Desulfurization, EPRI CS-2897, 821-840, 1983). A weak trend was found in a study of 22 samples of fly ashes that a slurry with a higher total slurry alkalinity tended to have a higher SO 2 capture (Reed et al., Environ. Sci. Technol., 18, 548-552, 1984). Therefore, while it is clear that desulfurization processes employing flue gas scrubbers represents an important advance, it is equally clear that such techniques presently have economic and technical drawbacks, not the least of which is the low degree of reagent utilization. While recycle of product solids with fly ash has resulted in some improvement, such processes are still not economically feasible for certain applications, and much room remains for the improvement of reagent utilization in such systems. SUMMARY OF THE INVENTION Accordingly, the present invention is directed to improved processes for reducing the level of sulfur in a sulfur-containing gas which in their most general and overall scope include four basic steps. One step involves the preparation of an aqueous slurry comprising a calcium alkali together with a calcium-reactive silica or alumina which are present in amounts sufficient to allow for the formation of a sulfur dioxide-absorbing component which includes a calcium silicate or calcium aluminate. Virtually any composition which includes a calcium alkali (CaO or Ca(OH) 2 ) may be employed in the practice of the present invention. For example, calcium alkali in the form of lime, slaked lime, hydrated lime, calcidic lime, dolomitic lime, calcium hydroxide or calcium oxide may be employed. For economic reasons, due to its lower cost, a preferred embodiment of the present invention employs lime or slaked lime. Similarly, virtually any composition which includes a calcium reactive silica or alumina may be employed, wherein a calcium-reactive silica or alumina is defined as a source of silica or alumina which is readily soluble in alkaline solutions. Such compositions include, but are not limited to, fly ash, diatomaceous earth, clay, bentonite, montmorillonite, activated alumina, or silicic acid. Again, for economic reasons, one would generally employ fly ash in that fly ash is a natural by-product of coal combustion and is therefore readily available at coal burning power plants. Thus, fly ash may be included in the slurry in the form of spent solids. Although some degree of sulfur absorption may be obtained with slurries which contain virtually any mass ratio of calcium reactive silica or alumina to calcium alkali, in one embodiment, mass ratios ranging from about 1:1 to about 16:1, respectively, are preferred. In a more preferred embodiment, the slurry comprises a mass ratio of calcium reactive silica or alumina to calcium alkali from about 1:1 to about 5:1, respectively. As with mass ratio, the total amount of solids which are slurried is not of critical importance. However, the total solids amount will generally be determinative of the amount of sulfur which is removed from the gas by the slurry. Typically, about one to three moles of calcium alkali is added for every mole of sulfur to be removed from the gas. However, in a more preferred embodiment, the slurry comprises about one to two moles of calcium alkali for every mole of sulfur to be removed from the gas. In a further embodiment, the slurry also includes sodium hydroxide in a concentration ranging from about 0.03 molar to about 1 molar. More preferably, the slurry comprises about 0.05 to about 0.5 molar sodium hydroxide. Even more preferably, the slurry comprises sodium hydroxide in a concentration ranging from about 0.1 molar to about 0.25 molar. Therefore, typically, the slurry will comprise about 0.02 to 0.3 moles of sodium hydroxide for every mole of calcium alkali. Or more preferably, 0.05 to 0.2 moles of sodium hydroxide for every mole of calcium alkali. Another step of the most general process of the present invention involves heating the slurry to a temperature above ambient in a manner to facilitate the formation of the sulfur dioxide-absorbing component. Virtually any increase in temperature of the slurry over ambient, as well as increases in slurrying time, will result in an improved sulfur dioxide absorbing slurry. The upper temperature limit is bounded only by temperatures at which the calcium reactive silicates or aluminates will become dehydrated. Generally, such dehydration will occur at temperatures above 200° centrigrade. It is believed that dehydrated calcium silicates or aluminates will not prove as advantageous in sulfur absorption as hydrated calcium silicates or aluminates. Moreover, extremely high slurrying temperatures (for example, above 200° C.) will generally prove to be uneconomic in commercial practice. Accordingly, in the practice of the invention, the slurry is heated to between about 40° and about 200° C. for between about 0.5 and about 48 hours. In one embodiment, the slurry is heated to between about 40° and about 60° C. for between about 2 and about 36 hours. More preferably, the slurry is heated for between about 4 to about 12 hours. In another embodiment, the slurry is heated to between 60° and about 80° C. for between about 1 and about 24 hours. More preferably, the slurry is heated at such temperatures for between about 2 and about 12 hours. In still another embodiment, the slurry is heated to between about 80° and about 100° C. for between about 0.5 and 12 hours. More preferably, the slurry is heated to such temperatures for between about 1 and about 8 hours. In more preferred embodiments of the invention, the slurry is activated at temperatures between about 100 and about 200° C. It has been surprisingly discovered by the present inventors that heat treatment of mixtures of calcium alkali and calcium-reactive silica at temperatures above 100° and below 200° C. provides a sorbent having a reactivity almost four-fold higher than that provided by treatments at elevated temperatures below 100° C. Even more importantly, maximal activation of the sorbent mixture may be obtained in the range of 100°-200° C. in a much shorter time than at lower temperatures. For example, the reactivity of a lime/fly ash sorbent can be doubled in less than an hour when activated at between about 140°-160° C., whereas treatment at 50°-80° C. requires generally 9-12 hours to achieve a doubling. Moreover, the surprisingly short activation time realized at temperatures in the 100°-200° C. range actually makes such high temperature treatment more economical than treatments at lower temperatures. Thus, in general it has been noted, that the temperature to which the slurry is heated and maintained is inversely proportional to the amount of time necessary to obtain highly sulfur-reactive calcium silicates and aluminates. Another step of the most general process requires contacting gas with the heat-treated slurry in a manner sufficient to allow for absorption of sulfur-dioxide by the absorbing component. Numerous embodiments are known in the art for performing such a contacting step. In one embodiment, the contacting step includes atomizing the slurry into a stream of the sulfur-containing gas, drying the resulting atomized droplets so as to form a gas/solid suspension having a gaseous component and a solid component which solid component includes the sulfur-dioxide-absorbing component, and retaining the gaseous and solid components in contact in a manner sufficient to allow for the absorption of the sulfur dioxide by the absorbing component. In another embodiment, the contacting steps further includes directing the gas/solid suspension onto a reaction surface to allow for deposition of the solid component onto the surface, and passing the suspension over the deposited solid component in order to: 1) further effect absorption of the sulfur-dioxide by the absorbing component, 2) effect a separation of the gas from the solid component and, 3) further effect a drying of the solid component. Typically, the reaction surface will include a bag filter. However, in certain embodiments which do not employ a bag filter, the process includes carrying the gas/solid suspension in a stream to allow for substantial contact between the gaseous and solid component and separating the solid component from the gas by means of an electrostatic precipitator or cyclones. Therefore, the bag filter, electrostatic precipitator and cyclone offer alternative means for separating sulfur-absorbed solids from the gas. However, as will be appreciated, the bag filter alternative offers the additional benefit of providing a reaction surface particularly well adapted to the practice of the present invention. Due to economic and other considerations, one should typically employ a recycling of a portion of the sulfur-absorbed solids back to the aqueous slurry. This will achieve not only a partial regeneration of the sulfur absorbed solids but will also improve the performance, and economics, of the process. Therefore, the process can be seen as a cyclical process wherein a portion of sulfur absorbed solids are recycled to form a slurry which includes an admixture of sulfur absorbed solids and the calcium alkali. Since flue gas itself will typically contain sufficient fly ash content, there is generally no need to add fly ash directly to the slurry, it being added in the form of spent solids. In a preferred process embodiment directed primarily to dry injection technology, the steps of preparing an aqueous slurry, and heating the slurry, are the same as in the general overall embodiment. However, following heating of the slurry, for dry injection purposes, the slurry is dried to provide a solid component which includes the sulfur dioxide-absorbing component, prior to contacting the gas with the sulfur dioxide-absorbing material. In this embodiment, it has been found that the gas must be conditioned to a relative humidity of between about 5 and 95%. Additionally, the temperature of the hot flue gas must be conditioned to between about 120° and 140° C. Preferably, the relative humidity of the humidified gas is brought to between about 20% and 80% and its temperature to between about 60° and 100° C. More preferably, the relative humidity of the humidified gas is brought to between about 30% and 70% and its temperature is reduced to between about 65° and 85° C. It will be appreciated that the most convenient means of achieving a humidification of a gas, and temperature reduction of gas, will be through the utilization of water, for example, mixed with the gas in a humidifier, prior to contacting the gas with the solid component. However, other methods of conditioning could be employed as exemplified by cooling of the flue gas or by steam injection into the flue gas. Another step in the dry injection process involves contacting the humidified gas with the dried or partially dried solid component to form a gas/solid suspension, for a period of time sufficient to allow some absorption of gaseous sulfur dioxide by the solid component, and separating the solid component from the gas in the form of spent solids. This step can be achieved by the previously mentioned contactors and/or separators including bagfilter, electrostatic precipitators (ESP), and cyclones. More particular aspects of the present disclosure relate to the preparation of improved sorbents produced at elevated temperature ranges. It has been discovered that sorbents produced at selected elevated temperatures under pressure possess particularly high surface area and a surface structure which renders them significantly more reactive than sorbents produced at lower temperatures. In particular, it has been found that calcium silicate sorbents prepared through the admixture of a calcium alkali together with a calcium reactive silica or alumina source posses surprisingly good sorbent properties when heat treated at temperatures between about 100° C. and about 200° C., and at pressures above atmospheric pressure. This temperature range is critical to the preparation of the most highly reactive sorbent in that calcium silicate hydrates prepared outside of this range are not nearly as reactive. When the temperature and pressure of calcium silicate hydrates formation process are carefully controlled to meet the "thermal window" requirements, an amorphous material with high surface area is produced which is very reactive toward SO 2 . If the temperature is lower, for example, below 100° C., the surface of this gel-like, amorphous material is less than fully developed and results in lower reactivity to SO 2 . Conversely, if the temperature is too high, for example, above 200° C., the product morphology changes into a framework of distinct needle-shaped crystals. The well crystallized needle-shaped calcium silicate hydrates are similarly found not as reactive toward SO 2 . Typically, the calcium silicate hydrates are prepared as an aqueous mixture of a calcium alkali containing material such as lime and a calcium-reactive silica containing material such as fly ash, diatomaceous earth, clay or recycled solids. Preferably,, this aqueous mixture exists as a slurry, containing moisture greater than about 60 wt %. If fly ash and lime are used as the raw materials, the typical weight ratio is preferably in the range of 1:1 to 3:1. The slurry should be maintained well mixed at a controlled temperature and pressure on the order of about 100° to 200° C., and between about 15 to about 220 psia, for at least about 10 to 15 minutes. For the case of fly ash/lime mixture, the preferred thermal window employs a temperature controlled in the range of about 140° to 160° C. for a minimum of 20 minutes with pressure in the range of about 20 to 100 psia. After heating and mixing, the slurry can be dried by conventional dewatering/drying procedures such as filtration/centrifuge, oven drying, spray drying, or spin flash drying to produce a welldispersed, fine powder well suited for dry flue gas desulfurization purposes. The present invention is also directed to an apparatus for reducing the level of sulfur in a sulfur-containing gas which apparatus includes a means for slurrying an aqueous suspension, which suspension includes a sulfur dioxide-absorbing component, the slurry means further including a means for elevating the temperature of the suspension to above ambient; a means for admixing the gas with the aqueous suspension to provide a gas/liquid suspension; a means for drying the gas/liquid suspension to provide a gas/solid suspension; a means for separating the gas/solid suspension to provide a gaseous component and a solid component; and means for venting the treated gas; wherein the temperature elevating means is positioned in a manner to elevate the temperature of the suspension prior to admixture of the suspension with the gas by the admixing means. As noted, slurry tanks in accordance with the present apparatus should also include a means for heating the slurry in a manner to conform with the processes of the present invention. For example, heating means in the form of an electrical heating element, steam driven heat exchanger, an aqueous preheating step or a steam injector are believed to work well in this regard. However, any method of heating the slurry to the desired temperatures for the desired time periods will suffice in the practice of the present invention. In one embodiment, the admixing means comprises a rotary atomizer for atomization of the slurry into the gas. While a rotary atomizer is a preferred means for admixing the gas, other means may also be employed including, but not limited to, a fluid atomizer. In the present apparatus, drying may be achieved in either one or two steps. In an apparatus adapted for practicing this two-step drying process, a drying function in the form of a spray dryer is provided in a housing which houses the rotary atomizer. In such housing, generally an almost total drying of the gas/liquid suspension is achieved. The dried gas/solid suspension is carried in a stream to a second absorption stage, which includes, for example, a pulse-jet baghouse for further reaction between the sulfur dioxide absorbing component and the sulfur-containing gas, to further achieve drying of the gas/solid suspension, and to separate dried spent solids, containing sulfur-absorbed solids, from the gas. In a one-step drying procedure, a bagfilter alone will generally prove satisfactory. However, in certain embodiments, for example, retrofit application to existing embodiments, an electrostatic precipitator or cyclone may be employed in place of a bagfilter. Lastly, the apparatus includes a means for venting the treated gas into the atmosphere, for example a venting stack. The present invention is also directed to an apparatus which is particularly suited to the dry injection of solids to humidified gas. In this apparatus, a drying means is provided to dry the slurry after it has been heated in accordance with the present invention, but prior to admixture of the slurry with the gas. In this embodiment, the drying means can be employed in the form of a fluidized bed, flash dryer, spray dryer, or other such means known in the art. The drying means may also employ a dewatering device, for example a vacuum device, before the primary drying means. The dry injection apparatus will further include a means for humidifying the gas and means for admixing the humidified gas with the solid component to provide a gas/solid suspension. The humidifying means will typically be in the form of a humidifying chamber wherein, for example, an atomizer is employed to atomize water into the gas and thereby achieve both humidification and reduction in the temperature of the hot flue gas. The admixing means will generally be in the form of a dry sorbent injector system as is commonly known in the art. The separating means (for example, a baghouse or electrostatic precipitator) can be employed as in the general embodiment. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1. Schematic Diagram of a Spray Dryer System. FIG. 2. Experimental apparatus. FIG. 3. The effect of fly ash I, II, III, and IV and relative humidity on Ca(OH) 2 utilization. 0.4 g of Ca(OH) 2 slurried with 1.6 g of fly ash I for 4 hours at 65° C. Atmospheric drying used for the preparation of samples. L=Ca(OH) 2 alone. FIG. 4. The effect of fly ash I loading (g fly ash/g Ca(OH) 2 ) on lime utilization. Samples slurried for 4 hours at 65° C. Atmospheric drying. FIG. 5. A fly ash simulation experiment carried out at 54% RH. Samples of simulated fly ash (Av.Fa), H 2 SiO 3 , Al 2 O 3 , and Fe 2 O 3 slurred with Ca(OH) 2 for 4 hours at 65° C. Atmospheric drying. FIG. 6. The effect of silica (H Zeothix 265, or Zeofree 80) loading (g silica/g Ca(OH) 2 ) on time utilization. Atmospheric drying. FIG. 7. The effect of alumina loading (g alumina/g Ca(OH) 2 ) on lime utilization. Atmospheric drying. FIG. 8. The effect of fly ash IV on Ca(OH) 2 reactivity. Fly ash IV loading 16. Vacuum drying. FIG. 9. Effect of NaOH concentration on SO2 removal. 1 Ca(OH) 2 :4 Fly Ash:4 CaSO 3 -10 mol % NaOH; Removal after 1 hour; 500 ppm SO 2 ; 500 ppm NO x ; 14 mol % H 2 O; gas flow: 4.6 l/min--7% O 2 , 10% CO 2 ; 83% N 2 . FIG. 10. Generalized process schematic for high temperature sorbent preparation and use. FIG. 11. Effects of pressure hydration on the reactivity of calcium silicate hydrates prepared at the weight ratio of fly ash to lime of 3:1. FIG. 12. The effect of temperature of pressure hydration on the reactivity of calcium silicate hydrates prepared at the weight ratio fly ash to lime of 3:1. FIG. 13. Correlation between measured B.E.T. surface area and the reactivity of various calcium silicate hydrates prepared from fly ash and lime. FIG. 14. Correlation between temperature of sorbent preparation and incubation time required to obtain a doubling of sorbent reactivity. DETAILED DESCRIPTION OF THE INVENTION The CaO--SiO--Al 2 O 3 --H 2 O Sulfur Absorption System The nature of calcium silicate hydrate and calcium aluminate hydrate as well as calcium aluminate silicate hydrate formation in CaO--SiO 2 --H 2 O systems is very complicated. It is usually impossible to assign a simple chemical formula to it, especially at ordinary temperatures of interest in flue gas desulfurization. At temperatures from 20° C. to about 100° C., two main calcium silicate hydrates are formed, mono- and dicalcium silicate hydrates. Their ratio appears to depend on the initial ratio of calcium to silica in the slurry. Both mono-calcium silicate hydrate--CaOxSiO 2 xH 2 O--and dicalcium silicate hydrate--(CaO) 2 xSiO 2 xH 2 O--are fibrous gels of specific surface areas in the range of 100-300 m 2 /g. At 20°-100° C. after 8 hours of hydration, tobermorites (calcium silicate hydrates) may crystallize, also of high surface area. The reaction of fly ash and Ca(OH) 2 in the presence of water is called a pozzolanic reaction. A pozzolan is a siliceous or siliceous and aluminous material which in itself possesses little or no cementitous value but will, in finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ordinary temperatures to form compounds possessing cementitous properties. Due to small particle size and generally noncry stalline character, fly ash usually shows pozzolanic properties, or pozzolanic and cementitous properties in case of high-calcium ashes. High-calcium fly ash contains tricalcium aluminate hydrate, which is the most reactive mineral present within portland cement. Pozzolanic reactions give products with cementitous properties and with high surface area that can enhance SO 2 removal. Pozzolan originated as a mortar of lime and ash (from Pozzouli, Italy) which the Romans used for stone constructions. The definition of pozzolanic reaction implies that spray dryer off-products, fly ashes, clays, and sands should be able to provide components to form calcium silicate hydrates, calcium aluminate hydrates, calcium alumino-ferrite hydrates, calcium sulfo-aluminate hydrates (ettringites), and calcium sulfo-aluminate-ferrite hydrates. However, not all siliceous and aluminous minerals are pozzolans. Crystalline minerals (mullite, silica as quartz) do not react with lime, especially at ordinary temperatures. Siliceous and/or aluminous materials must be non-crystalline and in small particles, in order to provide silica and alumina, after hydration in alkaline solutions, to form cementitous products. These reactions are the ones which constituents of portland cement undergo in the presence of water. The hydration reaction of aluminates in the presence of gypsum and lime and reaction of calcium silicates are as follows: ##STR1## Typical portland cement consists of 50% tricalcium silicate, 25% dicalcium silicate, 10% tricalcium aluminate, 9% calcium alumino-ferrite, and 6% calcium sulfate. Tricalcium silicate appears to be the most reactive mineral present within the portland cement. The main product of hydration of portland cement's silicate materials is calcium silicate hydrate of colloidal dimensions. All calcium silicate hydrates are fibrous gels in early stage of formation and their surface area is in the range of 100-300 m 2 /g. Moreover, Tobermorite gel plays a vital role in establishing the strength of concrete. When considering the spray dryer/bag filter system, typically one is dealing with fly ash as a source of silica instead of amorphous silica. The solubility of quartz particles of 3-15 um diameter in water is 11 ppm at 25° C. and 60 ppm at 100° C. The corresponding values for amorphous silica are 130 ppm and 420 ppm, respectively. Temperature and pH have strong effects on the solubility of amorphous silica. When pH was adjusted with NaOH up to 10.5 from 7 at 25° C., solubility was found to increase to 1000 ppm. Above a pH of 10.7, all the solid phase of amorphous silica dissolves to form soluble silicate. Therefore it would be reasonable to expect the dissolution of fly ash to be the limiting step in the formation of calcium silicate hydrates. Because of the lower solubility of fly ash, the specific surface area of the Ca(OH) 2 /silica reaction product is smaller than values reported for laboratory studies with amorphous silica. Also, it is not clear whether the development of the specific surface area of the product of hydration (for a given ratio of Ca(OH) 2 /fly ash) increases proportionally to the amount of conditioned lime. Because of low fly ash reactivity it is often desirable to know the exact characteristics of fly ash to be used. Usually fly ashes are divided into two categories: low-calcium (containing less than 5% of analytical CaO) from burning bituminous or anthracite coals and highcalcium (up to 35% Ca) from burning lignite or subbituminous coals. However, from the point of perspective reactivity and formation of calcium silicate hydrates, it is generally more important how much more amorphous material there is within the fly ash as compared with crystalline substances. Higher contents of crystalline phases (alpha-quartz, mullite, sillimanite, hematite, magnetite) lowers the reactivity of fly ash. Low-calcium fly ashes consist mainly of aluminosilicate glass due to the high proportions of silica and alumina. However, some crystallization takes place in the boiler when fly ash is cooling and, as a result, crystalline phases are detected under glass. For high-calcium fly ash it appears that the glass structure is different. It has been postulated that it is composed of significant amounts of CaO & Al 2 O 3 , which is known to be highly reactive. Since the non-crystalline component comprises sometimes as much as 80% of highcalcium fly ash it seems that the reason for high reactivity of high-calcium fly ash may be in the composition of glass. On the other hand, higher contents of unburnt carbon in the low-calcium fly ash may add to its reactivity. These carbon particles are usually of high internal surface area and may bind water and admixtures when the fly ash is slurried. In a study of surface area and porosity of fractionated fly ash from burning low-sulfur, high-ash coal, the largest fraction (>125um) had a surface area of 9.44m 2 /g whereas the finest fraction (>7um) had a surface area of 1.27 2 /g. Since large particles constitute a small fraction of fly ash only, the above effect is relatively insignificant. Industrial experiments should outperform laboratory tests, since it has been found that high-calcium fly ash passed the lime pozzolanic activity test when commercial source of lime was used, but failed to do so in the presence of a reagent grade Ca(OH) 2 . This effect is possibly the result of impurities in lime which have formed poorly-crystallized hydrates. The prospect of having calcium silicate hydrates in the spray dryer/bag filter therefore appears to be very attractive since they have high surface area and are highly hydrated and therefore should offer high SO 2 removal potential. The formation would take place in the recycle system, specifically in the reactant tank. During fly ash recycle in dry flue gas desulfurization systems, reaction of fly ash with makeup Ca(OH) 2 probably takes place in several steps. First lime would be dissolved, then silica and alumina--originally contained within the fly ash--would be digested and, by the means of providing favorable slurrying conditions, calcium silicate/aluminate hydrates would be formed. System Overview Referring to FIG. 1 is seen a diagram of a typical spray dryer system which is particularly well suited to the practice of the processes of the present invention. Depicted therein is a spray dryer 1, a baghouse 3, and a slurry tank 5. The slurry tank 5 is adapted to receive calcium alkali, in the form of, for example, lime from storage by means of conduit 7, and water by means of conduit 9. The slurry tank further includes a heating element 11 adapted to heat the slurry for times and to temperatures in accordance with processes of the present invention. The system may be adapted to provide calcium reactive alumina or silica directly to the slurry from storage by means of conduit 13 or, alternatively, calcium reactive silica or alumina is supplied to the slurry tank 5 by means of a recycle conduit 15 containing a sulfur-absorbed solids recycle, which includes, for example, fly ash from the boiler. To obtain best results, the slurry tank 5 is designed to mix a mass ratio of water to solids ranging from 1:1 to 20:1. Moreover, the slurry tank 5--and heating element 11, are adapted so as to enable a heating of the slurry to a temperature ranging from about 40° C. to about 140° C. for between about 0.5 to about 48 hours. The heat-treated slurry is conveyed to the spray dryer 1 by means of conduit 17. In the spray dryer 1, the slurry is admixed with flue gas from the boiler by mean of a rotary atomizer 19. The gas/slurry mixture is partially dried in the spray dryer 1 which is typically designed to achieve a gas/slurry contact time of between about 2 and about 10 seconds. In addition, a partial absorption of sulfur by the slurry is achieved in the spray dryer 1. From the spray dryer 1, the partially dried particles sulfur-absorbed gas/slurry admixture is conveyed to the baghouse 3 by means of conduit 21, wherein further drying and further absorption of sulfur by the sulfur-adsorbing component of the slurry takes place. Within the baghouse 3, the gas/slurry mixture is directed onto a bagfilter 23 wherein sulfur-absorbed solids are deposited and further absorption and drying takes place. The bagfilter 23 thus serves a dual purpose of separating gas from dried solids and collecting the solids for disposal by means of conduits 25, or recycle of solids by means of conduit 15. Separated gases are vented by means of conduit 29. Solids collected in the spray dryer are mixed with baghouse solids by means of conduit 27. Typically, the baghouse 3 and bagfilter 23 are designed to achieve a residence time of between about 5 and 300 minutes. In system embodiments for use in conjunction with dry injection of solids, the system will typically include a humidifier 29 in place of the spray dryer 1, wherein hot flue gas is admixed with water to provide humidified, cooled gas. Moreover, the system would also further include a drying tank 31 wherein the slurry is dried prior to admixture of the dried slurry with the humidified gas. Additionally, the dry injection system may include a recycle conduit 33 for admixture of recycled solids with the slurry mixture in the drying tank 31, to further assist in drying the slurry mixture. Alternatively, the spray dryer 1 itself can serve as a combination humidifier and injector wherein the dried slurry is injected into the spray dryer 1 along with water to provide admixture of the dried slurry together with the water and the gas. EXAMPLE I LAB SCALE EXPERIMENTS Apparatus Experiments were conducted in the apparatus shown in FIG. 2. The glass reactor (40 mm in diameter, 120 mm in height) was packed with a powdered reagent mixed with 40 g of 100 mesh silica sand to prevent channelling of Ca(OH) 2 . The reactor was immersed in a water bath thermostated to within approximately 0.1° C. Simulated flue gas was obtained by mixing nitrogen and sulfur dioxide from gas cylinders. The flow of gas was monitored using rotameters. Water was metered by a syringe pump, evaporated, and injected into dry gas. Reactor upstream tubing was heated to prevent the condensation of the moisture. Before entering the analyzer, the gas was cooled and water condensed in an ice bath. The SO 2 concentration was measured with a pulsed fluorescent SO 2 analyzer (ThermoElectron Model 40). A bypass of the reactor was provided to allow preconditioning of the bed and stabilization of gas flow at the desired SO 2 concentration. Prior to each run the bed was humidified by passing pure nitrogen at a relative humidity of about 98% for 6 minutes and then pure nitrogen at a relative humidity at which the experiment was to be performed for 10 minutes. Most of the experiments were performed at a relative humidity of 54% with some experiments at 17% and 74%. At typical flue gas conditions, 17, 54, and 74% relative humidity corresponds to 38°, 9.5°, and 4.7° C. approach to saturation, respectively. Reactor temperature was 95°, 66°, and 64.4° C. for 17, 54, 74% relative humidity, respectively. Common purity (99.5%) nitrogen at 4.6 l/min (0° C., 1 atm) was used as a carrier gas. The nominal concentration of SO 2 was 500 ppm and exposure time of the sample to the sulfurized gas was 1 hour. Preparation of the Samples The sample preparation consisted of two essential steps: stirring and drying. In every experiment 0.4 of reagent grade Ca(OH) 2 was used. This amount of lime was slurried with fly ash or other additive at the desired weight ratio. The water to solids ratio was between 10:1 and 20:1--most often 15:1. A propeller stirrer at 350 rpm was used to agitate the slurry. Slurrying time varied from 2 to 24 hours and the temperature of the slurry was set at 25° to 92° C. Two different methods of sample preparation was used during this study. In atmospheric drying, samples were not filtered after slurrying and were dried overnight in an atmospheric over at 85°-90° C. It took several hours to evaporate the water. The new drying procedure--vacuum drying--was introduced to minimize the additional reaction time of a wet sample in high oven temperature (85°-90° C). In this method the samples were vacuum filtered (about 5 min) and subsequently vacuum dried (about 10 min) at 95° C. The time of vacuum filtering and drying depended on the fineness of the sample and was monitored by the thermocouple placed in the dried sample and connected to the temperature recorder. In this way the moment when all the free moisture was evaporated could be easily seen and vacuum drying stopped, therefore minimizing the residence time of the sample in the oven. Characterization of the Samples Four different fly ashes were slurried with Ca(OH) 2 . The characterization of fly ashes is given in Table I. During the experiments on slurrying conditions, a new batch of fly ash IV was used. It was obtained from the same vendor and was produced by burning coal from, reportedly, the same source. These samples were characterized by scanning electron microscopy (SEM). The composition of the particles has been found using Kevex Micro-X 7000 X-ray Energy Spectrometer (XES). Mean particle size was determined using the Hiac-Royco particle counter. TABLE I__________________________________________________________________________Fly Ash Characterization Fly Ash I II III IV__________________________________________________________________________Power Plant Bull Run Plant Gibson Plant Seminole San Miguel TVA Public Service Electric Coop. Electric Coop. of Indiana Palatka, FL San Miguel, TXCoal Type bituminous bituminous bituminous ligniteXES Analysis[weight %]Ca 34 5 4 .sup. 11.sup.1 .sup. 15.sup.2Si 42 41 59 66 68Fe 6 31 15 4 2Al 16 20 20 18 14Mass Median 19 9 14 10 10Particle Size [um]__________________________________________________________________________ .sup.1 Old Batch .sup.2 New Batch The Effect of Fly Ash Type and Ratio Four samples of fly ash were slurried with 0.4 g of lime at a fly ash loading of 4 (4 g fly ash/g Ca(OH) 2 ) for 4 hours at 65° C. and reacted at a relative humidity of 54% (RH 54%). Atmospheric drying was used for the preparation of samples. The samples having the best and the worst performance at RH 54% were also tested at the extreme humidities of 17% and 74%. The results of these experiments are presented in FIG. 3. Also shown in FIG. 3 are the conversions when lime only was exposed to the sulfurized gas. As can be seen, all fly ashes improved the utilization at every RH investigated. Samples with fly ash loading of 16 (slurried at the same conditions as above) enhanced utilization of RH 54% to a greater extent than was the case for fly ash loading of 4. The utilization of lime was 67, 79, 65, 71% when fly ash I, II, III, IV was used, respectively. These values were much higher than the ones presented in FIG. 3. Based on these two series of experiments no correlation was found between SO removed and calcium content of fly ash sample. SEM photographs of the mixtures of Ca(OH) 2 with fly ash II, III, and IV at fly ash loading of 4 demonstrated a highly irregular deposit covering the spherules of fly ash in every picture. Fly ash I was selected to test the effect of fly ash loading on the utilization of lime. The results of experiments at RH 54% are presented in FIG. 4. The conversion of Ca(OH) 2 increased with increasing loading of fly ash. The increase of fly ash loading from 0.5 to 20 increased the Ca(OH) 2 utilization from 17 to 78%. An SEM photograph of fly ash I slurried with Ca(OH) 2 at the low loading of 0.5 demonstrated that the deposit is very slight and unreacted chunks of Ca(OH) 2 were seen next to fly ash particles. The Effect of Reagent Grade Additives The other main components of fly ash were also investigated. Reagent grade Al 2 O 3 , Fe 2 O 3 , and H 2 SiO 3 (silicic acid) were used as a source of alumina, iron, and silica, respectively. Fly ash was simulated as a mixture of three substances: 49% H 2 SiO 3 , 29% Al 2 O 3 , and 22% Fe 2 O 3 (weight %). Atmospheric drying was used for the preparation of samples. The results are presented in FIG. 5, giving the conversion of Ca(OH) 2 at RH 54%. During these experiments Ca(OH) 2 was slurried with additives for 4 hours at 65° C. As can be seen from FIG. 5, 1.6 g of mixture slurried with 0.4 g of Ca(OH) 2 modelled closely the utilization when fly ash I was used (30 and 27%, respectively). This again implies that calcium content of fly ash is not of primary importance, since the utilization of added Ca(OH) 2 was even higher when no fly ash-bound calcium was present. Next 0.4 g of Ca(OH) 2 was slurried separately with each component used to simulate the fly ash. Component loading was kept the same as it was when 1.6 g of mixture was used (i.e., 0.78 g, 0.47 g, and 0.35 g of H 2 SiO 3 , Al 2 O 3 , Fe 2 O 3 were used, respectively). The addition of silicic acid had the most significant effect, increasing Ca(OH) 2 utilization from 12 to 40%. No SO 2 removal was observed when silicic acid alone was exposed to simulated flue gas. FIG. 6 gives the effect of silica loading on conversion at RH 17 and 54%. Silicic acid was used for most of these experiments. SEM photographs were taken of samples of silicic acid/Ca(OH) 2 slurried at 65° C. for 4 hours at silicic acid loading of 4 and 10, respectively. In both, highly developed surface of irregularly shaped particles were seen. Some experiments were performed with artificial precipitated silicas of extremely high surface areas. They were Zeothix 265 and Zeofree 80 of surface area 250 and 140 m 2 /g, respectively (samples and surface area data obtained courtesy of Huber Corp.). However, these substances did not enhance Ca(OH) 2 utilization significantly better than silicic acid (FIG. 6). As can be seen from FIG. 6, both values of RH tested, Ca(OH) 2 utilization increased with the increasing loading of silicic acid. The comparison of the results presented in FIGS. 4 and 6 shows that silicic acid promotes Ca(OH) 2 utilization better than fly ash. For example, at RH 54% and fly ash loading of 8 (total fly ash) the conversion of Ca(OH) 2 was 78% when silicic acid was used and 61% when fly ash I was used. Reactivities of fly ash and silicic acid should be compared on the basis of silica content. Assuming that fly ash I is 50% silica, a silicic acid loading of 8 should be compared to fly ash I loading of 16 (conversions of 78 and 68%). The difference between silicic acid and fly ash is more apparent at lower loadings. For silicic acid loading of 1, conversion was 53% and for the fly ash I loading of 2 it was 32%. This comparison shows that Ca(OH) 2 conversion depends on the reactivity of siliceous material used. Experiments were performed at RH of 54% with precipitated calcium silicate XP-974 (also from Huber Corp., surface area of 215 m 2 /g, average particle size 6.1 um). The sample was taken "as received" and was not slurried. As SEM photograph of this sample showed the particle of calcium silicate as having an irregular surface area similar to that produced when silicic acid and Ca(OH) 2 were slurried. The effect of alumina loading was tested using two sources of alumina. The results of experiments at 54% RH are shown in FIG. 7. As can be seen, when reagent grade Al 2 O 3 was used, increasing the loading did not change SO 2 removal. No SO 2 removal was observed for Al 2 O 3 alone. The removal increased with increasing loading of alumina when activated alumina of chromatographic grade (80-200 mesh) was used. However, activated alumina alone removed SO 2 . The adsorptive capacity of activated alumina was calculated as 0.023 g of SO 2 per gram. Based on this value, the corrected SO 2 removal has been determined due to the possible formation of calcium aluminates. The empty points in FIG. 7 (o) represent the overall removal of SO 2 while the filled points (o) show the corrected values. These corrected values are lower than the ones observed for the same loading when silicic acid was used instead of alumina. Therefore, the silica content of fly ash is mainly responsible for the enhancement of Ca(OH) 2 utilization. The Effect of Slurrying Conditions Slurrying tests were performed at 25°, 45°, 55°, 64°, and 92° C. and time was varied from 2 to 24 hours. The samples for these tests were prepared by vacuum filtration and vacuum drying. Both old and new batches of fly ash IV were used as a source of silica at 16 g fly ash/g Ca(OH) 2 . Relative humidity during exposure was 54%. The results are presented in FIG. 8. As can be seen, the temperature was the decisive parameter affecting the process. The results show that there is a critical slurrying time for every temperature tested after which Ca(OH) 2 conversion reaches a maximum value. Ca(OH) 2 conversion converged on 40% after 16 hours of slurrying at 25° C. and 80% after 5 hours at 92° C. It took 15 hours to converge on 80% conversion of Ca(OH) 2 when slurrying at 65° C. Compared with 12% utilization of Ca(OH) 2 alone at 54% RH, the 80% utilization of fly ash/Ca(OH) 2 slurried at 65° C. was dramatically improved. The maximum utilization of Ca(OH) 2 is not a uniform function of slurry temperature (40, 50, 55, 80, and 80%, for 25°, 45°, 55°, 65°, and 92° C., respectively). There appeared to be a discontinuity between 55° and 65° C. slurrying temperature that may indicate a change in the hydration state of the calcium aluminum silicate. The resulting solid had better reactivity for SO 2 removal than that formed below 65° C. When tested by Differential Scanning Calorimeter (DSC) the solids formed at 65° C. and 92° C. have an additional endothermic peak between 416 and 465K. No peak was observed for samples slurried at 25°, 45° and 55° C. The effect of a step change in reactivity also took place when fly ash III was slurried with Ca(OH) 2 at the fly ash loading of 16:1 at 65° and 45° C. The conversion of Ca(OH) 2 was 63 and 43%, respectively. SEM photographs were taken to document the development of the surface area of the samples. In samples slurried for "0" time, separate fly ash spheres with smooth surfaces (as in an unslurried fly ash) and irregular particles of lime were seen. After 24 hours of slurrying at 25° C., the particles were covered with tiny deposits. The product on the surface of the fly ash became more densely precipitated after 24 hours of slurrying at 65° C. Increasing the temperature of slurrying to 92° C. resulted in a very well developed surface area of the deposit. The Effect of Calcium Sulfite/Sulfate Calcium sulfite or calcium sulfate were slurried with Ca(OH) 2 to simulate the recycle of spent lime. Laboratory produced calcium sulfite hemihydrate (90% CaSO 3 12H 2 O+10% CaSO 4 ) and reagent grade calcium sulfate dihydrate were used in these experiments. Vacuum drying was used for the preparation of the samples. Samples of fly ash IV/Ca(OH) 2 /CaSO 3 at a weight ratio of 16:1:4 were slurried for 6 hours at 25°, 45°, and 65° C. The resulting conversions of Ca(OH) 2 were 41, 61, and 74%, respectively. Conversion of the fly ash/Ca(OH) 2/ CaSO 3 sample at a weight ratio of 16:1:4 slurried for 6 hours at 65° C. was higher than conversion of the corresponding fly ash/Ca(OH) 2 sample at a weight ratio of 20:1, which was 70%. Samples at a weight ratio of 16:1:1 were slurried for 6 hours at 25° and 65° C. and yielded Ca(OH).sub. 2 conversions of 21 and 61%, respectively. SEM photographs of the fly ash IV/Ca(OH) 2 /CaSO 3 samples at weight ratios of 16:1:4 and 16:1:1 demonstrated long crystals that may be calcium aluminate sulfate hydrates (ettringite) of general formula 3CaO Al 2 O 3 3CaSO 4 xH 2 O (x is most often within the range 30-32). These long crystals were not formed when only calcium sulfite was slurried with Ca(OH) 2 for 6 hours at 65° C. and at the weight ratio of 4:1 (Ca(OH) 2 conversion was 16%). Separate clusters of calcium sulfite and Ca(OH) 2 were visible by SEM. It may be that the formation of ettringite provides additional potential for SO 2 removal. Two ratios of fly ash/Ca(OH) 2 /calcium sulfate were tried. At a ratio of 16:1:4, Ca(OH) 2 conversion was 60% for samples slurried for 6 hours at both 25° and 65° C. At a lower ratio of 16:1:1, the conversion was 51 and 31% for samples slurried for 6 hours at 65° and 25° C., respectively. SEM photographs of the sample at a weight ratio of 16:1:4 slurried for 6 hours at 65° C. revealed fly ash speres with the precipitate on the surface, as well as calcium sulfate and long crystals (ettringite). Both calcium sulfite and calcium sulfate improved the utilization of Ca(OH) 2 after slurrying the samples for 6 hours at 25° C. and a weight ratio of 16:1:4. However, at a fly ash/Ca(OH) 2 /CaSO 3 ratio of 16:1:1, the conversion for samples slurried for 6 hours at 25° and 65° C. was lower than when fly ash was slurried at the same conditions with Ca(OH) 2 alone (21, 61, and 67%, respectively). The Effect of Fly Ash Particle Size Fly ash IV was wet-sieved into five fractions which are characterized in Table II. The fractionated fly ash was slurried with 0.4 g of Ca(OH) 2 at a loading of 16 for 6 hours at 65° C. Vacuum drying was used for the preparation of samples. The results of these experiments are shown in Table II. Also shown in Table II is the base case conversion of Ca(OH) 2 when it was slurried with fly ash IV ("natural"-whole spectrum of particle size). Calculated weighted average from obtained fractional conversions was 52%. The reason why the weighted average is lower than the base case (52 and 67%, respectively) may be that imperfect wet-sieving left fine particles agglomerated with coarse fractions. The general trend was that for the same fly ash loading, the conversion increased with the decreasing particle size of fly ash. An increase of the fly ash loading from 156 to 30 when the finest fraction of fly ash was used (d≦20 um) resulted in an increase of Ca(OH) 2 conversion from 76 to 92%. An increase of fly ash loading from 16 to 25 when coarser fraction was used (45 um<d≦75 um) resulted in an increase of Ca(OH) 2 conversion from 42 to 52%. TABLE II______________________________________Fractional Characterization of Fly Ash IV Composition.sup.1Fraction Particle Diameter Weight Fraction Con-Ca(OH).sub.2 [um] [%] Ca Si version______________________________________1 d ≦ 1251 15 12 63 242 75 < d ≦ 125 13 8 55 283 45 < d ≦ 75 20 9 60 434 20 < d ≦ 45 12 14 67 505 d ≦ 20 .sup. 40.sup.2 14 63 776 0 < d ≦ 125+ 100 15 68 67______________________________________ .sup.1 Weight percent, normalized Energy Dispersion Spectrometry results. .sup.2 All losses during wetsieving assumed for the finest fraction. Alternate Sources of Silica Several alternative sources of silica were tested. These included siliceous clays (kaolinite and bentonite) and talc (MgO 4SiOSO 2 H 2 O). Kaolinite of the molecular composition Al 2 O 3 2SiO 2 2H 2 O is the principal constituent of kaolin and the most frequently occurring component of clays. Bentonite (montmorillonite clay) of general formula Al 2 O 3 4SiO 2 H 2 H 2 O exists as very fine particles (up to 60% below 0.1 um), which form colloidal solutions with water. Montmorillonite No. 24 (Ward's Classification) was tested. All samples were slurried for 6 hours at 65° C. at clay loading of 2. Montmorillonite was also tested at loading of 16. The conversions of Ca(OH) 2 were 39, 25, and 23% for montmorillonite, kaolinite, and talc, respectively (at loading of 2). At similar slurrying conditions and loading of 2, fly ash I promoted Ca(OH) 2 utilization to 28% (fly ash I slurried at 65° C. for 4 hours only). At montmorillonite loading of 16, it increased the conversion to 61%, which was slightly less than fly ash I and fly ash IV. An SEM photograph was taken of the sample of montmorillonite clay No. 24 slurried with reagent grade Ca(OH) 2 at loading of 16 for 6 hours at 65° C. The highly irregular particle surface which was observed was reminiscent of the appearance of silicic acid/Ca(OH) 2 samples and of the deposit on the surface of the fly ash spheres. In conclusion, enhanced performance of spray dryer/bag filter systems with recycle of fly ash an calcium solids is probably due to the reaction of Ca(OH) 2 with fly ash to produce calcium silicates. The calcium silicate solids were found to have greater surface area than the unreacted Ca(OH) 2 and are more effective for gas/solid reactions. Moreover, calcium silicates were found to be more reactive than aluminates or ferrites. The available silica content of the fly ash is more important. Increased time and temperature gave more reactive solids from the reaction of lime and fly ash and solids formed above 65 were substantially more reactive than solids formed at lower temperatures. Experiments with silicic acid and fly ash support the hypothesis that the reaction of added Ca(OH) 2 and silica from fly ash is responsible for the enhancement of Ca(OH) 2 utilization when slurried with fly ash, as compared with the utilization of lime alone. The newly formed solids are of high surface area and are highly hydrated. Prior to the formation of highly reactive solids of calcium silicate hydrates two steps apparently need to take place: Ca(OH) 2 dissolution and digestion of silica from the fly ash. Since Ca(OH) 2 dissolution is very fast compared with fly ash dissolution, digestion of silica from fly ash seems to be the rate controlling step. This was confirmed by experiments with silicic acid, precipitated silica, and precipitated calcium silicate. However, the high price of precipitated silica ($750-1750/ton) make it noneconomic. Therefore enhanced calcium silicate hydrate formation should be sought by carefully selecting slurrying conditions rather than using costly additives. Experiments showed that increasing slurrying time and temperature can dramatically enhance the utilization of Ca(OH) 2 . At each temperature the Ca(OH) 2 utilization asymptoted to a specific maximum value with increasing time. The time needed to achieve the maximum utilization varied and was generally higher for lower slurrying temperatures. A step increase of reactivity was observed between solids slurried at 55° and 65° C. It took 15 hours to converge on 80% conversion of Ca(OH) 2 at 65° C. When lime was slurried with fly ash and calcium sulfite or calcium sulfate the formation of ettringite was observed. The addition of calcium sulfite/sulfate enhanced utilization when slurried at 25° C. at the fly ash/lime/calcium salt weight ratio of 16:1:14. The effect was dramatic when calcium sulfate was used. Experiments with clays as an alternate source of silica proved that they also may be effective in the formation of calcium silicate hydrates. Montmorillonite performed as well as fly ash at a loading of 2. At high loading it was only slightly less effective. The use of clays in the place of fly ash offers the advantage of uncontaminated by-product fly ash. Also from the above presented results it becomes clear that fly ash TAMO (total alkaline metal oxide content) has no decisive effect on the removal of SO 2 in the spray dryer when slurried alone, the recycle of spray dryer/bag filter off-product provides the opportunity for unspent Ca(OH) 2 to be reacted with fly ash in addition to providing the unspent Ca(OH) 2 with another chance to see and react with SO 2 , enhancing the reaction of Ca(OH) 2 with fly ash in the recycle system should improve the overall performance of the spray dryer/bag system. The advantage of highly reactive solids may be fully utilized in a commercial unit after optimization of the recycle conditions. Presently it is commercial practice to design the recycle tank for about 2 hours residence time. At ambient temperature or adiabatic conditions the effect of heat evolving when warm spray dryer solids are added is negligible. As shown by the results of this study, it would be preferred to increase the size of recycle tank up to 6 hours, preferably even 8 hours. The temperature of the slurry should preferably not be lower than 65° C. to take advantage of a steep change in a reactivity of solids. One option to provide the necessary amount of heat would be to add fly ash directly to the CaO slaker. The recycle tank should be designed carefully to avoid problems with plugging from reaction products and excessive deposit built-up on the walls. It is possible that the spray dryer could be operated with wider approach to the saturation temperature because more reactive solids would be sprayed. Additional increase of Ca(OH) 2 reactivity in the fly ash-Ca(OH) 2 system might be possible with deliquescent salt additives. Sand bed studies showed the increase of Ca(OH) 2 reactivity when calcium and sodium salts were used. Sodium and calcium salts are widely used as cement retarders and by analogy they should work well also in the fly ash system. The lab scale experiments also indicate that dry injection of solids into the duct should be accompanied by humidification of the gas. High humidification could be used in installations with ElectroStatic Precipitators (ESP). One option is that the dry solids would be produced outside the system and then injected into the duct and later humidified. Second is that the reacted slurry of fly ash and lime would be introduced into spray dryer operating at wide approach to the saturation. This spray dryer would operate as dryer and absorption of SO 2 would be of secondary concern. Spray dryer-dry solids would be then passed into the duct where they would contact humidified gas. Dry injection in the system with ESP requires additional laboratory studies of the rates of reaction at short times. The idea of producing the reactive solids could be also retrofitted into existing desulfurization installations. It should be feasible for example to collect the product solids from Limestone Injection Multistage Boiler (LIMB), slurry them at favorable conditions and redistribute. The typical product of LIMB is CaO, CaSO 4 , and fly ash at the ratio of 3:1:2, which could be simulated in sand bed reactor. Still another possibility would be Slurry Atomization into Multistage Burner (SAMB) which would consist of spray drying of lime/fly ash slurry at burner temperatures and collecting the dry solids in either ESP or bag filter after additional humidification in the duct. EXAMPLE II THE EFFECT OF NaOH ADDITION TO THE SLURRY It has also been observed that the addition of sodium hydroxide to the slurry serves to potentiate the slurry's sulfur-adsorbing capability, possibly due to the increased formation of calcium silicates and aluminates at more alkaline pH's. In FIG. 9, about 1 part Ca(OH) 2 was slurried at 65° C. for 6 hours with 4 parts fly ash and 4 parts CaSO 3 , but without the addition of NaOH. SO 2 removal (moles SO 2 /100 moles Ca(OH) 2 ) ranged from about 20, when solids were reacted with gas at about 65° C., to about 10, when reacted with gas at about 92° C. When 0.03M NaOH was added to a level of 10 mole %, the SO 2 removal ranged from about 22, when reacted with gas at 65° C., to about 10°, when reacted with gas at about 105°. When 0.08M NaOH was added after the slurry was slurried for 6 hours, and then dried an additional 30 hours in the presence of the added NaOH, the SO 2 removal increased to a range of about 58, when reacted with gas at 65° C., to about 30, when reacted with gas at about 92° C., and to about 22, when reacted with gas at about 125° C. When this concentration of NaOH was slurried for only 4 hours, the SO 2 removal observed ranged from about 64, at 65° C., to about 20, at 92° C. A longer slurrying time prior to NaOH addition gave similar results. The addition of 0.25M NaOH demonstrated only slight improvement over control. However, in all cases, it was observed that the addition of NaOH to the slurry improved SO 2 removal efficiency. SORBENTS PREPARED AT TEMPERATURES BETWEEN 100° and 200° C. A generalized flowsheet including the major embodiments of processes according to this aspect of the invention is shown in FIG. 10. The sorbent is prepared by mixing water, calcium source, and the silica source in a pressurized hydrator/mixer at elevated temperature. A sufficient quantity of water (greater than 60 wt. %) is added to maintain the mixture in a slurry form, the water acting as a medium for reactions between lime and silica source to form calcium silicate hydrates. As with temperatures below 100°, at pressure hydration temperatures above 100° and below 200° C., virtually any composition which includes a source of calcium alkali [CaO or Ca(OH) 2 ] may be employed in the practice of the present invention For example, calcium alkali in the form of lime, slaked lime, hydrated lime, calcitic lime, dolomitic lime, carbide lime, calcium hydroxide or calcium oxide may be employed. For economic reasons, due to its lower cost, a preferred embodiment of the present invention employs lime or slaked lime. Similarly, virtually any composition which includes a calcium reactive silica may be employed, wherein a calcium-reactive silica is defined as a source of silica which is readily soluble in alkaline solutions. Such compositions include, but are not limited to, fly ash, diatomaceous earth, clay, bentonite, montmorillonite, or silicic acid. Again, for economic reasons, one would generally prefer to employ fly ash in that fly ash is a natural by-product of coal combustion and is therefore readily available at coal burning power plants Moreover, fly ash may be included in the slurry in the form of spent solids recycled. When fly ash and lime are the raw materials, the weight ratio is preferably in the range of 1:1 to 3:1. When clay, diatomaceous earth or recycle solids is used as the silica source and lime is the calcium source, the silica to calcium ratio is preferably less than 2:1. The current invention enables the use of relatively low fly ash/lime or silica/calcium ratio to reduce the raw material consumption rate, the size of the hydrator and the energy requirement. Another step of the most general process of the present invention involves heating the slurry to an optimum temperature range or thermal window and maintain the slurry temperature within the thermal window for a period of time. Since the optimum temperature range is higher than 100° C., the pressure inside the hydrator/mixer is necessarily kept above atmospheric pressure. The preferred temperature range of this thermal window varies with the type of silica used, the ratio of calcium/silica mixed and the mixing time employed. In the case of a typical coal-fired power plant using lime and fly ash (including fly ash in recycled solids from the particulate collector), the temperature range of the preferred thermal window will typically be on the order of about 110° to 180° C. and a corresponding pressure range of about 20 to 100 psia. An even more preferred temperature window ranges from between about 140° and 160° (3 to 7 psia), wherein a particularly active sorbent is produced. The fly ash to lime weight ratio charged to the hydrator is preferably controlled in the range of 1:1 to 3:1. However, broadly speaking, advantages may be realized with virtually any of the aforementioned calcium and silica sources, wherein the sorbent activation is conducted at between about 100° and 200° C. (1 to 15 psia). Controlling the temperature and pressure to within this thermal window is believed to result in the production of a highly sulfur-reactive species of calcium silicate hydrate. Another advantage of the above described thermal window is the reduced reaction time required to achieve optimal reactivity. For example, at slurrying temperatures below 100° C., optimal reactivity is achieved in 6 to 12 hours or more. However, at temperatures above 100° C., optimal reaction times are reduced to below 4 hours and, at the most preferred range of 140° to 160° C., the optimal reaction time is reduced to less than about 1 hours. The significant reduction in fly ash to lime ratio and reaction time results in considerable savings in capital cost (smaller hydrator, conveyor, and storage tanks) and operating cost (lower energy and raw material consumption) makes the current invention an economical and technically desirable process for application to large coal-fired power plants. After the slurry has been adequately mixed and heated, a drying means is preferable included to dewater and dry the slurry into discrete, fine powders. In this embodiment, the drying means can be employed in the form of a fluidized bed, flash dryer, spray dryer or other means known in the art. Oven drying followed by crushing and screening can also accomplish the purpose. The drying means may also employ a dewatering device, for example a vacuum or centrifuge device, before the primary drying means. The dry silicate hydrates are used as the sorbent for dry flue gas desulfurization process. The dry flue gas desulfurization process includes a means for humidifying the flue gas, means for admixing the flue gas with the solid component to provide a gas/solid suspension, and means for separating the solid product from the gas/solid suspension before the flue gas is directed to a stack as shown in FIG. 10. The most convenient means of achieving a humidification of gas will be through the utilization of water, for example, mixed with the gas with a spray of fine water droplets. The gas is preferably conditioned to a relative humidity of between about 20 to 90%. Additionally, the temperature of the hot flue gas (generally between about 150° and 300° C.) is preferably conditioned to between about 50° and 100° C. The dry calcium silicate hydrates can be transported into the flue gas stream by conventional dry solids injection means such as pneumatic or mechanical conveyor. The means for admixing the flue gas and the injected sorbent can be a section of ductwork, a gas/solid contractor such as a moving bed or a circulating fluidized bed, or the like. It is commonly known in the art that low flue gas temperature and high humidity increase sulfur dioxide solubility and reactivity with sorbent. The gas/solid admixing means provides intimate sulfur dioxide/sorbent contact and lengthens the contact time which would enhance mass transfer and overall sulfur dioxide removal efficiency. Following the gas/solid admixing, the sorbent used and sulfur dioxide absorbed should be separated from the gas stream. The separating means including baghouse, electrostatic precipitator, mechanical impactor or cyclone. Additional sulfur dioxide removal is obtained if a long solids residence time device such as a baghouse is used as the particulate collector. The solids collected can be recycled to the hydrator as the silica source to produce more reactive calcium silicate hydrates for further sulfur dioxide removal. EXAMPLE III SORBENTS PREPARED AT ELEVATED TEMPERATURES Various experiments have been performed in support of this aspect of the invention Calcium silicate hydrates were prepared in a pressure reactor (300 ml) by mixing lime and siliceous material at elevated temperature. The pressure reactor was equipped with a stirrer and an electrical heater controlled by a thermocouple inside the reactor. After reactants (lime and siliceous material) were placed in the reactor, the vessel was sealed and heated electrically. Pressurized water was injected into the reactor when the temperature reached the experimental value. The reactants and water were vigorously stirred for a designated time period. After completion of each run, the reactor vessel was opened and the product was removed and dried. The reactivity of the calcium silicate hydrates produced was evaluated in an apparatus similar to that shown in FIG. 2 and discussed above. Briefly, a glass reactor (40 mm in diameter, 120 mm in height) was packed with the dried calcium silicate hydrates mixed with 40 g of 100 mesh, silica sand to prevent channelling. The reactor was immersed in a water bath thermostated to within approximately 0.1° C. Simulated flue gas was obtained by mixing nitrogen and sulfur dioxide (500 ppm) from gas cylinders. The flow of gas was monitored using rotameters. Water was metered by a syring pump, evaporated, and injected into dry gas to control the humidity at 60%. The SO 2 concentration coming in and going out of the glass reactor was measured with a pulsed fluorescent SO 2 analyzer (Thermo-Electron Model 40). Exposure time of the packed bed to the gas was 1 hour. The reactivity of the calcium silicate hydrates tested was described by conversion of lime [Ca(OH) 2 ] added to the reactor. Conversion of Ca(OH) 2 is the number of moles of SO 2 reacted per mole of Ca(OH) 2 used, multiplied by 100 percent. The results of the first set of experiments are presented in FIG. 11 as a plot of product reactivity vs. preparation time (employed for heating the lime and fly ash slurry). The upper curve represents the reactivity of calcium silicate hydrates prepared under pressure at 150° C. The lower curve represents reactivity of product prepared in an open beaker at atmospheric pressure and heated to 90° C. It is apparent that the pressure hydration resulted in a much more reactive product than atmospheric hydration. Since the upper curve leveled off after about 4 hours, it means that only 4 hours or less preparation time is required to achieve the maximum effect of pressure hydration. The effect of temperature of pressure hydration was investigated during the second set of experiments. As shown in FIG. 12, the reactivity of the calcium silicate hydrates produced under pressure demonstrated surprisingly good reactivities when prepared at temperatures between 100° and 200° C., and peaked at temperature about 140° and about 160° C., evidencing the thermal window effect. The data shown in FIG. 12 indicated that when preparation temperature exceeded 160° C. the reactivity dropped precipitously, with temperatures above 200° C. being much less reactive. Surface area of the calcium silicate hydrates was measured during a third set of experiments. FIG. 13 represents the correlation of reactivity with B.E.T. surface area. This figure shows that, in general, the reactivity correlated quite well with the B.E.T. surface area and that it increased with the increasing surface area of the product. The three data points expressed as open circles represent reactivity of calcium silicate hydrates produced at temperatures below the thermal window of 140° to 160° C. It is apparent that the surface area of those products had not been fully developed, probably resulting in a shortage of reaction sites and, hence, low reactivities. On the other hand, the two open squares on FIG. 13 represent reactivities of calcium silicate hydrates produced at temperatures higher than the thermal window of 140° to 160° C. The reactivities of those two data points do not fit the correlation curve with B.E.T. surface area as shown in FIG. 13, although moderate to high surface area was obtained, the reactivity was extremely low. To further investigate the temperature effects on product reactivity, the crystal morphology was examined by scanning electron microscope. It was found that the calcium silicate hydrates produced within the thermal window are gel-like, amorphous particles. However, needle-like, well-defined crystals were formed when the temperature is above the optimal temperature. Apparently, the high temperature caused solid phase transition and a different crystal was formed. This new crystal, although still possessed moderately large surface area, was not nearly as reactive toward sulfur dioxide. It is possible that this new crystal has a composition, e.g., containing very little hydrated water molecule, that is unfavorable toward sulfur dioxide absorption. It is also possible that the high temperature caused structural property changes and resulted in low reactivity. Therefore, the combination of degree of crystallization-transition of the final product's composition and the clay-like structure's temperature sensitivity could account for thermal window effect. Further experimentation was conducted in order to demonstrate the surprising reduction in treatment time provided by the use of elevated temperatures. In particular, experiments were conducted wherein the incubation times required to approximately double the reactivity of the sorbent were determined. From the results shown in FIG. 14, it is apparent that sorbents produced the reactivity of temperatures above about 100° C. and below about 200° C. are at least doubled in less than 6 hours. Moreover, in the more preferred range of about 120° to about 180° C., reactivities are doubled in less than about 2 hours. Surprisingly, at the most preferred temperature range of about 140° to about 160° C., sorbent reactivities were doubled in less than 1 hour.

The present disclosure relates to improved processes for treating hot sulfur-containing flue gas to remove sulfur therefrom. Processes in accordance with the present invention include preparing an aqueous slurry composed of a calcium alkali source and a source of reactive silica and/or alumina, heating the slurry to above-ambient temperature for a period of time in order to facilitate the formation of sulfur-absorbing calcium silicates or aluminates, and treating the gas with the heat-treated slurry compounds. Examples disclosed herein demonstrate the utility of these processes in achieving improved sulfur-absorbing capabilities. Additionally, disclosure is provided which illustrates preferred configurations for employing the present processes both as a dry sorbent injection and for use in conjunction with a spray dryer and/or bagfilter. Retrofit application to existing systems is also addressed.

PRIORITY [0001] This application claims priority to U.S. Provisional Patent Application Ser. No. 61/588,932, filed Jan. 20, 2012, entitled “Thin Airfoil Ceiling Fan Blade,” the disclosure of which is incorporated by reference herein. BACKGROUND [0002] A variety of fan systems have been made and used over the years in a variety of contexts. For instance, various ceiling fans are disclosed in U.S. Pat. No. 7,284,960, entitled “Fan Blades,” issued Oct. 23, 2007; U.S. Pat. No. 6,244,821, entitled “Low Speed Cooling Fan,” issued Jun. 12, 2001; U.S. Pat. No. 6,939,108, entitled “Cooling Fan with Reinforced Blade,” issued Sep. 6, 2005; and U.S. Pat. No. D607,988, entitled “Ceiling Fan,” issued Jan. 12, 2010. The disclosures of each of those U.S. patents are incorporated by reference herein. Additional exemplary fans are disclosed in U.S. Pat. No. 8,079,823, entitled “Fan Blades,” issued Dec. 20, 2011; U.S. Pat. Pub. No. 2009/0208333, entitled “Ceiling Fan System with Brushless Motor,” published Aug. 20, 2009; and U.S. Pat. Pub. No. 2010/0278637, entitled “Ceiling Fan with Variable Blade Pitch and Variable Speed Control,” published Nov. 4, 2010, the disclosures of which are also incorporated by reference herein. It should be understood that teachings herein may be incorporated into any of the fans described in any of the above-referenced patents, publications, or patent applications [0003] A fan blade or airfoil may include one or more upper air fences and/or one or more lower air fences at any suitable position(s) along the length of the fan blade or airfoil. Merely exemplary air fences are described in U.S. Pat. Pub. No. 2011/0081246, entitled “Air Fence for Fan Blade,” published Apr. 7, 2011, the disclosure of which is incorporated by reference herein. Alternatively, any other suitable type of component or feature may be positioned along the length of a fan blade or airfoil; or such components or features may simply be omitted. [0004] The outer tip of a fan blade or airfoil may be finished by the addition of an aerodynamic tip or winglet. Merely exemplary winglets are described in U.S. Pat. No. 7,252,478, entitled “Fan Blade Modifications,” issued Aug. 7, 2007, the disclosure of which is incorporated by reference herein. Additional winglets are described in U.S. Pat. No. 7,934,907, entitled “Cuffed Fan Blade Modifications,” issued May 3, 2011, the disclosure of which is incorporated by reference herein. Still other exemplary winglets are described in U.S. Pat. No. D587,799, entitled “Winglet for a Fan Blade,” issued Mar. 3, 2009, the disclosure of which is incorporated by reference herein. In some settings, such winglets may interrupt the outward flow of air at the tip of a fan blade, redirecting the flow to cause the air to pass over the fan blade in a perpendicular direction, and also ensuring that the entire air stream exits over the trailing edge of the fan blade and reducing tip vortex formation. In some settings, this may result in increased efficiency in operation in the region of the tip of the fan blade. In other variations, an angled extension may be added to a fan blade or airfoil, such as the angled airfoil extensions described in U.S. Pat. No. 8,162,613, entitled “Angled Airfoil Extension for Fan Blade,” issued Apr. 24, 2012, the disclosure of which is incorporated by reference herein. Other suitable structures that may be associated with an outer tip of an airfoil or fan blade will be apparent to those of ordinary skill in the art. Alternatively, the outer tip of an airfoil or fan blade may be simply closed (e.g., with a cap or otherwise, etc.), or may lack any similar structure at all. [0005] The interface of a fan blade and a fan hub may also be provided in a variety of ways. For instance, an interface component is described in U.S. Pat. No. 8,147,204, entitled “Aerodynamic Interface Component for Fan Blade,” issued Apr. 3, 2012, the disclosure of which is incorporated by reference herein. In addition, or in the alternative, the fan blade may include a retention system that couples the tip of a fan blade to an attachment point on the fan hub via a cable running through the fan blade, such as that disclosed in U.S. Pat. Pub. No. 2011/0262278, published Oct. 27, 2011. Alternatively, the interface of a fan blade and a fan hub may include any other component or components, or may lack any similar structure at all. [0006] Fans may also include a variety of mounting structures. For instance, a fan mounting structure is disclosed in U.S. Pat. No. 8,152,453, entitled “Ceiling Fan with Angled Mounting,” issued Apr. 10, 2012, the disclosure of which is incorporated herein. Of course, a fan need not be mounted to a ceiling or other overhead structure, and instead may be mounted to a wall or to the ground. For instance, a fan may be supported on the top of a post that extends upwardly from the ground. Examples of such mounting structures are shown in U.S. Design Pat. No. D635,237, entitled “Fan with Ground Support,” issued Mar. 29, 2011, the disclosure of which is incorporated by reference herein; U.S. Design Pat. No. D641,075, entitled “Fan with Ground Support and Winglets,” issued Jul. 5, 2011, the disclosure of which is incorporated by reference herein; and U.S. Pat. App. No. 61/720,077, entitled “Fan Mounting System,” filed Oct. 30, 2012, the disclosure of which is incorporated by reference herein. Alternatively, any other suitable mounting structures and/or mounting techniques may be used in conjunction with embodiments described herein. [0007] It should also be understood that a fan may include sensors or other features that are used to control, at least in part, operation of a fan system. For instance, such fan systems are disclosed in U.S. Pat. No. 8,147,182, entitled “Ceiling Fan with Concentric Stationary Tube and Power-Down Features,” issued Apr. 3, 2012, the disclosure of which is incorporated by reference herein; U.S. Pat. No. 8,123,479, entitled “Automatic Control System and Method to Minimize Oscillation in Ceiling Fans,” issued Feb. 28, 2012, the disclosure of which is incorporated by reference herein; U.S. Pat. Pub. No. 2010/0291858, entitled “Automatic Control System for Ceiling Fan Based on Temperature Differentials,” published Nov. 18, 2010, the disclosure of which is incorporated by reference herein; U.S. Provisional Patent App. No. 61/165,582, entitled “Fan with Impact Avoidance System Using Infrared,” filed Apr. 1, 2009, the disclosure of which is incorporated by reference herein; and U.S. Pat. App. No. 61/720,679, entitled “Integrated Thermal Comfort Control System Utilizing Circulating Fans,” filed Oct. 31, 2012, the disclosure of which is incorporated by reference herein. Alternatively, any other suitable control systems/features may be used in conjunction with embodiments described herein. [0008] In some settings, it may be desirable to replicate or approximate the function of a winglet in a component that may be located at a position on a fan blade other than at the free end of the fan blade. For instance, such components are disclosed in U.S. Pat. Pub. No. 2011/0081246, entitled “Air Fence For Fan Blade,” published Apr. 7, 2011, the disclosure of which is incorporated by reference herein. Such a component may provide an effect on fan efficiency similar to the effect provide by a winglet, albeit at one or more additional regions of the fan blade. In particular, such a component or accessory may serve as an aerodynamic guide or air fence, interrupting slippage of air along the length or longitudinal axis of the fan blade; and redirecting the air flow to a direction perpendicular to the longitudinal axis of the fan blade, above and/or below the fan blade. [0009] In some ceiling fans, flat planar blades are used by inclining the blades at an angle of approximately ten to twenty degrees from the horizontal to displace airflow in a downward direction. These flat blades might not be aerodynamically efficient in some settings. Accordingly, to move a given volume of air, the fan must operate at a higher speed, thereby consuming more electricity. In addition, these flat blades might be manufactured from wood or fiberboard, harvested from trees, such as Monterey Pine, which typically take 25-30 years to reach maturity. Since the regrowth time of the raw materials may exceed the lifespan of the ceiling fan, continued production in this manner is not an environmentally sustainable practice. [0010] While flat planar blades have been used, attempts have been made to improve upon ceiling fan blade designs. For example, Parker, et al, U.S. Pat. No. 6,039,541, issued Mar. 21, 2000, describes a ceiling fan blade that includes the SD7032, GM15, MA409, and Hibbs 504 airfoils. Airfoils of this type may operate with higher coefficients of lift versus angle of attack at Reynolds numbers greater than 100,000. In the instance of a fan blade with a chord length of 10.16 centimeters (4 inches) and blade span with the root located 22.5 centimeters (9 inches) from the center of rotation and a tip located 76.2 centimeters (30 inches) from the center of rotation, operating at 50 rotations per minute may experience Reynolds numbers ranging from 8,000 at the root to 28,000 at the tip. While at 200 rotations per minute, the fan blade may experience Reynolds numbers ranging from 33,000 at the root to 110,000 at the tip. At speeds below 180 rotations per minute, the entire blade may experience Reynolds numbers less than 100,000. Accordingly, the airfoils described by Parker, et al. may operate below their optimal performance under the majority of operating conditions for the ceiling fan. Furthermore, airfoil blades of the types disclosed in Parker, et al. may increase manufacturing complexity since the airfoil thickness has a teardrop profile and varies substantially from leading edge to trailing edge. In some instances, to create this teardrop profile the blade must be manufactured by plastic injection molding or, alternatively, machined from a flat sheet material, which may result in significant wastage. Thus, a need exists for an improved blade design that offers optimal airflow performance at the low Reynolds numbers experienced by a ceiling fan and is capable of being manufactured by simple techniques using sustainable materials. [0011] While several systems and methods have been made and used for ceiling fan blades, it is believed that no one prior to the inventors has made or used the invention described in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS [0012] While the specification concludes with claims which particularly point out and distinctly claim this technology, it is believed this technology will be better understood from the following description of certain examples taken in conjunction with the accompanying drawings, in which like reference numerals identify the same elements and in which: [0013] FIG. 1 depicts a front perspective view of an exemplary fan having a plurality of exemplary ceiling fan blades attached thereto; [0014] FIG. 2 depicts an exploded perspective view of the fan of FIG. 1 ; [0015] FIG. 3 depicts an side elevation view of the fan of FIG. 1 ; [0016] FIG. 4 depicts a plan view of the exemplary ceiling fan blade of FIGS. 1-3 ; [0017] FIG. 4A depicts a cross-sectional view of the ceiling fan blade of FIG. 4 taken along section line A-A of FIG. 4 ; [0018] FIG. 4B depicts a cross-sectional view of the ceiling fan blade of FIG. 4 taken along section line B-B of FIG. 4 ; [0019] FIG. 4C depicts a cross-sectional view of the ceiling fan blade of FIG. 4 taken along section line C-C of FIG. 4 ; [0020] FIG. 5 depicts a combination cross-sectional view of the blade sections shown in FIGS. 4A-4C , showing the relative curvature of each section; [0021] FIG. 6 depicts a front elevation view of the fan blade of FIGS. 1-5 ; [0022] FIG. 7 depicts a perspective view of an alternative fan having a plurality of exemplary ceiling fan blades attached thereto; [0023] FIG. 8 depicts an exploded perspective view of the fan of FIG. 7 ; [0024] FIG. 9 depicts a plan view of the exemplary fan blade of FIG. 7 ; and [0025] FIG. 10 depicts an elevation view taken from a root end of the fan blade of FIG. 9 . [0026] The drawings are not intended to be limiting in any way, and it is contemplated that various embodiments of the technology may be carried out in a variety of other ways, including those not necessarily depicted in the drawings. The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present technology, and together with the description serve to explain the principles of the technology; it being understood, however, that this technology is not limited to the precise arrangements shown. DETAILED DESCRIPTION [0027] The following description of certain examples of the technology should not be used to limit its scope. Other examples, features, aspects, embodiments, and advantages of the technology will become apparent to those skilled in the art from the following description, which is by way of illustration, one of the best modes contemplated for carrying out the technology. As will be realized, the technology described herein is capable of other different and obvious aspects, all without departing from the technology. Accordingly, the drawings and descriptions should be regarded as illustrative in nature and not restrictive. [0028] I. Exemplary Fan Overview [0029] Referring to FIG. 1 , a fan ( 10 ) of the present example comprises a support ( 20 ), a motor ( 30 ) (shown in FIG. 2 ), and a plurality of fan blades ( 50 ). While three fan blades ( 50 ) are shown, it should be understood that any other suitable number of fan blades ( 50 ) may be used. Fan blades ( 50 ) of the present example may define a fan diameter ranging from approximately 0.5 meters (1.64 feet), inclusive, to approximately 5 meters (16.4 feet), inclusive. In the present example, fan blades ( 50 ) define a fan diameter of approximately 1.5 meters (4.92 feet). Alternatively, fan ( 10 ) and/or fan blades ( 50 ) may have any other suitable dimensions. [0030] Support ( 20 ) is configured to be coupled to a surface or other structure at a first end such that fan ( 10 ) is substantially attached to the surface or other structure. Support ( 20 ) of the present example comprises an elongate metal tube-like structure that couples fan ( 10 ) to a ceiling, though it should be understood that support ( 20 ) may be constructed and/or configured in a variety of other suitable ways as will be apparent to one of ordinary skill in the art in view of the teachings herein. In one merely exemplary version, support ( 20 ) is configured to couple to an electrical junction box (not shown) located within or on a ceiling. With support ( 20 ) comprising an elongate metal tube, wires or other power supply or control members are extended through support ( 20 ) to motor ( 30 ). By way of example only, support ( 20 ) need not be coupled to a ceiling or other overhead structure, and instead may be coupled to a wall or to the ground. For instance, support ( 20 ) may be positioned on the top of a post that extends upwardly from the ground. Alternatively, support ( 20 ) may be mounted in any other suitable fashion at any other suitable location. This includes, but is not limited to, the teachings of the patents, patent publications, or patent applications cited herein. By way of example only, support ( 20 ) may be configured in accordance with the teachings of U.S. Pat. Pub. No. 2009/0072108, entitled “Ceiling Fan with Angled Mounting,” published Mar. 19, 2009, the disclosure of which is incorporated by reference herein. As yet another alternative, support ( 20 ) may have any other suitable configuration. [0031] As shown in FIG. 2 , fan ( 10 ) of the present example includes a motor ( 30 ) that is coupled to fan blades ( 50 ). Motor ( 30 ) of the present example is coupled to fan blades ( 50 ) via fasteners ( 32 ). Fasteners ( 32 ) may include screws, bolts, clips, clamps, and/or any other suitable fastener ( 32 ) for coupling fan blades ( 50 ) to motor ( 30 ). Alternatively, fasteners ( 32 ) may be omitted and fan blades ( 50 ) may be adhesively attached or integrally formed with a portion of motor ( 30 ) such that fan blades ( 50 ) rotate when motor ( 30 ) is operated. In the present example, a blade shoe ( 40 ) is interposed between motor ( 30 ) and each fan blade ( 50 ). In some versions, blade shoe ( 40 ) may comprise a rubber, synthetic rubber, or other vibratory buffering material such that fan blades ( 50 ) are substantially isolated from vibrations of motor ( 30 ) and/or other portions of fan ( 10 ). Alternatively, blade shoe ( 40 ) may comprise a plastic, metal, wood, composite, and/or any other material. Of course it should be understood that blade shoe ( 40 ) is merely optional and may be omitted. [0032] In some versions, motor ( 30 ) comprises an AC induction motor having a drive shaft, though it should be understood that motor ( 30 ) may alternatively comprise any other suitable type of motor (e.g., a permanent magnet brushless DC motor, a brushed motor, an inside-out motor, etc.). In the present example, motor ( 30 ) is fixedly coupled to support ( 20 ) and is configured to rotate fan blades ( 50 ) relative to support ( 20 ) such that air is propelled by fan ( 10 ) away from the structure to which support ( 20 ) is coupled. In an alternative version, shown in FIGS. 7-10 , a hub ( 430 ) may be included in addition to, or instead of, blade shoes ( 40 ). In the version shown in FIGS. 7-10 , hub ( 430 ) comprises an annular member having a plurality of holes ( 432 ) disposed about the circumference to which fan blades ( 50 ) may be coupled. Hub ( 430 ) is coupled to motor ( 30 ) such that rotation of hub ( 430 ) by motor ( 30 ) rotates fan blades ( 50 ). Of course motor ( 30 ) may be constructed in accordance with at least some of the teachings of U.S. Pat. Pub. No. 2009/0208333, entitled “Ceiling Fan System with Brushless Motor,” published Aug. 20, 2009, the disclosure of which is incorporated by reference herein. Furthermore, fan ( 10 ) may include control electronics that are configured in accordance with at least some of the teachings of U.S. Pat. Pub. No. 2010/0278637, entitled “Ceiling Fan with Variable Blade Pitch and Variable Speed Control,” published Nov. 4, 2010, the disclosure of which is incorporated by reference herein. Of course, motor ( 30 ), blade shoe ( 40 ), and/or hub ( 430 ) may have any other suitable components, configurations, functionalities, and operability, as will be apparent to those of ordinary skill in the art in view of the teachings herein. [0033] In the present example, fan ( 10 ) further includes a top cover ( 34 ). Top cover ( 34 ) comprises a dome-shaped component configured to enclose the top of motor ( 30 ). Top cover ( 34 ) of the present example is attached to support ( 20 ) to form a dome over the top of motor ( 30 ) when motor ( 30 ) is coupled to support ( 20 ). In some versions, top cover ( 34 ) is threadably coupled to support ( 20 ). In other versions, top cover ( 34 ) may be integrally formed with support ( 20 ), coupled via fasteners (not shown), or otherwise attached to support ( 20 ) and/or motor ( 30 ). When fan blades ( 50 ) of the example shown in FIGS. 1-3 are coupled to motor ( 30 ), fan blades ( 50 ) and top cover ( 34 ) substantially enclose motor ( 30 ), as seen best in FIG. 1 . [0034] Fan blades ( 50 ) of the example shown in FIGS. 1-6 each include an arcuate cutout ( 54 ) at a root end ( 52 ) of each fan blade ( 50 ). When fan blades ( 50 ) are coupled to motor ( 30 ), arcuate cutouts ( 54 ) form a cylindrical aperture ( 56 ). A semi-transparent lens ( 48 ) is inserted into aperture ( 56 ). A sensor (not shown) is mounted within aperture ( 56 ) and is configured to receive infrared signals from a remote control (not shown) or other source. The sensor is coupled to a motor control module that is operable to control fan ( 10 ). Fan ( 10 ) may be further configured in accordance with at least some of the teachings of the fan systems disclosed in U.S. Pat. Pub. No. 2009/0097975, entitled “Ceiling Fan with Concentric Stationary Tube and Power-Down Features,” published Apr. 16, 2009, the disclosure of which is incorporated by reference herein; U.S. Pat. Pub. No. 2009/0162197, entitled “Automatic Control System and Method to Minimize Oscillation in Ceiling Fans,” published Jun. 25, 2009, the disclosure of which is incorporated by reference herein; U.S. Pat. Pub. No. 2010/0291858, entitled “Automatic Control System for Ceiling Fan Based on Temperature Differentials,” published Nov. 18, 2010, the disclosure of which is incorporated by reference herein; and U.S. Provisional Patent App. No. 61/165,582, entitled “Fan with Impact Avoidance System Using Infrared,” filed Apr. 1, 2009, the disclosure of which is incorporated by reference herein Still further configurations for lens ( 48 ), arcuate cutouts ( 54 ), aperture ( 56 ), and the sensor will be apparent to one of ordinary skill in the art in view of the teachings herein. Of course, it should be understood that lens ( 48 ), arcuate cutouts ( 54 ) and aperture ( 56 ) are merely optional and may be omitted. [0035] While some merely exemplary features of fan ( 10 ) have been described herein, it should be understood that fan ( 10 ) may have other features, components, and/or configurations as will be apparent to one of ordinary skill in the art in view of the teachings herein. [0036] II. Exemplary Fan Blades [0037] A single fan blade ( 50 ) is shown plan form in FIG. 4 having a root end ( 52 ), a tip ( 70 ), a leading edge ( 80 ) and a trailing edge ( 90 ). Sections A-A, B-B, and C-C are shown in FIG. 4 and correspond to cross-sectional FIGS. 4A , 4 B, and 4 C, respectively. Sections A-A, B-B, and C-C will be discussed in greater detail below. As noted above, root end ( 52 ) of the present example comprises an arcuate cutout ( 54 ) configured to permit lens ( 48 ) be inserted in a central aperture ( 56 ) formed when fan blades ( 50 ) are mounted. Root end ( 52 ) further includes a pair of openings ( 58 ) that permit fasteners ( 32 ) to extend therethrough to couple fan blade ( 50 ) to motor ( 30 ) and/or hub ( 42 ). As shown in FIGS. 1-3 , root end ( 52 ) of the present exemplary fan blade ( 50 ) comprises a domed sector that corresponds to an approximately 120 degree sector of a dome for the present fan ( 10 ) having three fan blades ( 50 ). The domed sector of root end ( 52 ) is substantially flat, or parallel, relative to the plane of rotation for fan blades ( 50 ) at or near arcuate cutout ( 54 ). The domed sector curves upwardly toward motor ( 30 ) and/or support ( 20 ). Root end ( 52 ) may of course include an approximately 180 degree, 90 degree, 60 degree, 45 degree and/or any other sector portion of a dome or may omit a domed sector end. Of course other root ends ( 52 ) will be apparent to one of ordinary skill in the art in view of the teachings herein. [0038] Fan blade ( 50 ) also includes a transition region ( 60 ) extending from root end ( 52 ), shown best in FIGS. 4 and 6 . In the present example, transition region ( 60 ) comprises a first portion ( 62 ), an inflection portion ( 64 ), and a second portion ( 66 ). First portion ( 62 ) comprises an extension of the domed sector of root end ( 52 ) that terminates at inflection portion ( 64 ). Inflection portion ( 64 ) of the present example comprises a quasi-parabolic shaped portion that extends from leading edge ( 80 ) to trailing edge ( 90 ) and transitions fan blade ( 50 ) from the upwardly extending domed shape of first portion to a planar portion. Second portion ( 66 ) extends from inflection portion ( 64 ) and transitions fan blade ( 50 ) from the planar inflection portion ( 64 ) to the downwardly curved root airfoil profile ( 100 ), shown in FIG. 4A . By way of example only, a non-dimensional matrix of coordinates in Table 1 below generally describes the surface formed by transition region ( 60 ) and airfoil profile ( 100 ). It should be understood that the domed sector of root end ( 52 ) is omitted from the coordinates in Table 1. In addition, the Z coordinate corresponds to the vertical height of the point at the transition point from root end ( 52 ) (e.g., a height of 0 corresponds to where root end ( 52 ) ends and transition region ( 60 ) beings), the X coordinate corresponds to the longitudinal distance from a central point about which blade ( 50 ) rotates, and the Y coordinate corresponds to the chord-wise position, where negative coordinates approach trailing edge ( 90 ) and positive coordinates approach leading edge ( 80 ). [0000] TABLE 1 Z X Y 0 0.0892 −0.01 0 0.0991 −0.009 0 0.1072 −0.008 0 0.1145 −0.007 0 0.1209 −0.006 0 0.1263 −0.005 0 0.1305 −0.004 0 0.1337 −0.003 0 0.1358 −0.002 0 0.137 −0.001 0 0.1373 0 0 0.1366 0.001 0 0.1351 0.002 0 0.1327 0.003 0 0.1294 0.004 0 0.1252 0.005 0 0.1201 0.006 0 0.1141 0.007 0 0.1071 0.008 0 0.0989 0.009 0 0.0888 0.01 0.005 0.0986 −0.01 0.005 0.1273 −0.009 0.005 0.1897 −0.008 0.005 0.1452 −0.007 0.005 0.1471 −0.006 0.005 0.1521 −0.005 0.005 0.1564 −0.004 0.005 0.1595 −0.003 0.005 0.1614 −0.002 0.005 0.1621 −0.001 0.005 0.1617 0 0.005 0.1602 0.001 0.005 0.1578 0.002 0.005 0.1544 0.003 0.005 0.1501 0.004 0.005 0.145 0.005 0.005 0.139 0.006 0.005 0.1322 0.007 0.005 0.1248 0.008 0.005 0.1166 0.009 0.01 0.4002 −0.007 0.01 0.3408 −0.006 0.01 0.286 −0.005 0.01 0.1931 −0.004 0.01 0.1902 −0.003 0.01 0.1913 −0.002 0.01 0.1909 −0.001 0.01 0.1892 0 0.01 0.1863 0.001 0.01 0.1824 0.002 0.01 0.1776 0.003 0.01 0.1718 0.004 0.01 0.1653 0.005 0.01 0.1581 0.006 0.01 0.1503 0.007 0.01 0.1421 0.008 0.015 0.4724 −0.007 0.015 0.4133 −0.006 0.015 0.3586 −0.005 0.015 0.3085 −0.004 0.015 0.2616 −0.003 0.015 0.2246 −0.002 0.015 0.2212 −0.001 0.015 0.2175 0 0.015 0.2126 0.001 0.015 0.2067 0.002 0.015 0.2 0.003 0.015 0.1926 0.004 0.015 0.1846 0.005 0.015 0.1762 0.006 0.015 0.1675 0.007 0.015 0.1585 0.008 0.02 0.5299 −0.007 0.02 0.4852 −0.006 0.02 0.4308 −0.005 0.02 0.3807 −0.004 0.02 0.3352 −0.003 0.02 0.2942 −0.002 0.02 0.2551 −0.001 0.02 0.2442 0 0.02 0.2369 0.001 0.02 0.2289 0.002 0.02 0.2204 0.003 0.02 0.2115 0.004 0.02 0.2023 0.005 0.02 0.1929 0.006 0.02 0.1834 0.007 0.02 0.1745 0.008 0.025 0.5627 −0.006 0.025 0.5024 −0.005 0.025 0.4526 −0.004 0.025 0.4072 −0.003 0.025 0.3662 −0.002 0.025 0.3296 −0.001 0.025 0.2975 0 0.025 0.2696 0.001 0.025 0.2502 0.002 0.025 0.2395 0.003 0.025 0.2297 0.004 0.025 0.2203 0.005 0.025 0.2117 0.006 0.025 0.2042 0.007 0.025 0.1988 0.008 0.03 0.5734 −0.005 0.03 0.5241 −0.004 0.03 0.4789 −0.003 0.03 0.438 −0.002 0.03 0.4014 −0.001 0.03 0.3692 0 0.03 0.3412 0.001 0.03 0.3175 0.002 0.03 0.2977 0.003 0.03 0.2818 0.004 0.03 0.2696 0.005 0.03 0.2614 0.006 0.03 0.2566 0.007 0.03 0.2548 0.008 0.035 0.595 −0.004 0.035 0.5502 −0.003 0.035 0.5095 −0.002 0.035 0.473 −0.001 0.035 0.4408 0 0.035 0.4128 0.001 0.035 0.3891 0.002 0.035 0.3693 0.003 0.035 0.3535 0.004 0.035 0.3414 0.005 0.035 0.333 0.006 0.035 0.328 0.007 0.035 0.3264 0.008 0.04 0.6211 −0.003 0.04 0.5808 −0.002 0.04 0.5445 −0.001 0.04 0.5124 0 0.04 0.4844 0.001 0.04 0.4606 0.002 0.04 0.4409 0.003 0.04 0.4252 0.004 0.04 0.4133 0.005 0.04 0.4051 0.006 0.04 0.4005 0.007 0.04 0.3994 0.008 [0039] Of course, it should be understood that other configurations for transition region ( 60 ) and/or other regions of fan blade ( 50 ) may be used. For instance, if root end ( 52 ) omits a domed sector, then fan blade ( 50 ) may omit first portion ( 62 ) and, in some versions, inflection portion ( 64 ), having only second portion ( 66 ) transition to root airfoil profile ( 100 ) directly. Still further constructions for transition region ( 60 ), etc., will be apparent to one of ordinary skill in the art in view of the teachings herein. [0040] Referring now to FIG. 4A , a cross-sectional root airfoil profile ( 100 ) is shown taken along section A-A of FIG. 4 . Root airfoil profile ( 100 ) comprises a top surface ( 102 ), a bottom surface ( 104 ), a leading edge ( 106 ), and a trailing edge ( 108 ). Root airfoil profile ( 100 ) of the present example comprises a curved airfoil having a substantially constant thickness ( 110 ) and a substantially constant radius of curvature ( 120 ). By way of example only, thickness ( 110 ) may range from approximately 1 millimeter (0.03937 inches), inclusive, to approximately 5 millimeters (0.19685 inches), inclusive. In the example shown, thickness ( 110 ) is approximately 4 millimeters (0.15748 inches) though this is merely one embodiment. Still further values for thickness ( 110 ) will be apparent to one of ordinary skill in the art in view of the teachings herein. Also by way of example only, radius of curvature ( 120 ) is measured from a center point ( 118 ) and may range from approximately 2 meters (6.56167 feet), inclusive, to approximately 5 meters (16.4042 feet), inclusive. In the example shown, radius of curvature ( 120 ) is approximately 3.7 meters (12.1391 feet). Still further values for radius of curvature ( 120 ) will be apparent to one of ordinary skill in the art in view of the teachings herein. In the example shown in FIG. 4A , root airfoil profile ( 100 ) is defined when radius of curvature ( 120 ) is swept through a root angle ( 122 ). Root angle ( 122 ) of the present example is approximately 14 degrees, though it should be understood that this is merely exemplary and other smaller and/or larger root angles ( 122 ) will be apparent to one of ordinary skill in the art in view of the teachings herein. Furthermore, leading edge ( 106 ) and trailing edge ( 108 ) comprise rounded surfaces connecting top surface ( 102 ) to bottom surface ( 104 ), though this is merely optional. Leading edge ( 102 ) and trailing edge ( 104 ) of the present example form rounded surfaces having a radius of curvature substantially equal to thickness ( 110 ). Thus, as shown in FIG. 4A , a substantially constant thickness root airfoil profile ( 100 ) is formed. [0041] FIG. 4B depicts a cross-sectional intermediate airfoil profile ( 200 ) taken along section B-B of FIG. 4 at an approximate midpoint between root airfoil profile ( 100 ) and tip airfoil profile ( 300 ), discussed in greater detail below. It should be understood that while the term intermediate is used, it does not necessarily connote that the shape, size, or values defining intermediate airfoil profile ( 200 ) are in between those of root airfoil profile ( 100 ) and tip airfoil profile ( 300 ). Intermediate airfoil profile ( 200 ) of the present example comprises a top surface ( 202 ), a bottom surface ( 204 ), a leading edge ( 206 ), and a trailing edge ( 208 ). Intermediate airfoil profile ( 200 ) of the present example is substantially identical to root airfoil profile ( 100 ) and has a substantially identical thickness ( 110 ) and is defined by a substantially identical radius of curvature ( 120 ) with the exception that radius of curvature ( 120 ) is swept through an intermediate angle ( 222 ). By way of example only, intermediate angle ( 222 ) is approximately 12.5 degrees, though of course other smaller and/or larger intermediate angles ( 222 ) will be apparent to one of ordinary skill in the art in view of the teachings herein. [0042] FIG. 4C shows a cross-sectional tip airfoil profile ( 300 ) taken along section C-C of FIG. 4 at an approximate tip ( 70 ) of fan blade ( 50 ). Tip airfoil profile ( 300 ) of the present example comprises a top surface ( 302 ), a bottom surface ( 304 ), a leading edge ( 306 ), and a trailing edge ( 308 ). Tip airfoil profile ( 300 ) of the present example is substantially identical to root airfoil profile ( 100 ) and has a substantially identical thickness ( 110 ) and is defined by a substantially identical radius of curvature ( 120 ) with the exception that radius of curvature ( 120 ) is swept through a tip angle ( 322 ). By way of example only, tip angle ( 322 ) is approximately 7 degrees, though of course other smaller and/or larger tip angles ( 322 ) will be apparent to one of ordinary skill in the art in view of the teachings herein. [0043] FIG. 5 depicts a composite overlay of the cross-sections of FIGS. 4A-4C . As noted above, root airfoil profile ( 100 ), intermediate airfoil profile ( 200 ), and tip airfoil profile ( 300 ) are substantially identical in shape and thickness with the exception of each being formed by sweeping radius of curvature ( 120 ) to various angle ( 122 , 222 , 322 ). In some versions, the tip angle ( 322 ) is a minimum value for the angles through which radius of curvature ( 120 ) is swept while root angle ( 122 ) is a maximum value for fan blade ( 50 ). Though, it should be understood that tip angle ( 322 ) need not necessarily be the minimum value for the angles through which radius of curvature ( 120 ) is swept and/or root angle ( 122 ) need not necessarily be the maximum value for the angles through which radius of curvature ( 120 ) is swept. In addition, or in the alternative, angles ( 122 , 222 , 322 ) may linearly increase in value from tip angle ( 322 ) to root angle ( 122 ). In other versions, angles ( 122 , 222 , 322 ) may increase in value logarithmically, parabolically, cubically, and/or in any other manner from tip angle ( 322 ) to root angle ( 122 ). Referring briefly to FIG. 6 , fan blade ( 50 ) is also configured to have a blade rise angle ( 98 ). In the example shown, blade rise angle ( 98 ) corresponds to the angle formed between the plane in which the fan rotates and the top surface of fan blade ( 50 ). Thus, the absolute height of each fan blade ( 50 ) increases from root end ( 52 ) to tip ( 70 ). By way of example only, blade rise angle ( 98 ) may be an angle of approximately 0 degrees, inclusive, to approximately 20 degrees, inclusive. More specifically, blade rise angle ( 98 ) may be from 2.5 degrees, inclusive, to 5 degrees, inclusive. In the example shown, blade rise angle ( 98 ) is approximately 3.8 degrees. Still further configurations for airfoil profiles ( 100 , 200 , 300 ) and/or fan blade ( 50 ) will be apparent to one of ordinary skill in the art in view of the teachings herein. By way of example only, flaps, slats, extensions, electrical or mechanical actuators, and/or other features may be added to fan blades ( 50 ). [0044] Fan blade ( 50 ) of the present example is manufactured from thin sheets of material laminated together. For instance, fan blade ( 50 ) may be constructed by combining individual sheets with adhesive between each layer and forcing the sheets together under pressure in a shaped mold to form fan blade ( 50 ) shown in FIGS. 1-6 . By way of example only, fan blade ( 50 ) may be manufactured using 7 layers of 0.5 millimeter (0.019685 inches) thick bamboo veneer that are compressed together as described above. Of course other thicknesses and/or number of layers may be used. Alternatively, other types of wooden veneer may be used or may be combined with other woods to form composite fan blades ( 50 ). In yet a further alternative, fan blade ( 50 ) may be formed from of a thermoplastic resin that is injected into a mold for fan blade ( 50 ) to achieve the desired profile. Further still, fan blade ( 50 ) may be formed from a single layer of plastic that is heated and bent or inserted into a mold to form the profile of fan blade ( 50 ). In still a further alternative, fan blade ( 50 ) may be formed from layers of fiberglass matting or carbon fiber composite materials combined with epoxy resins. In yet another alternative, layers of wood veneer or other materials (e.g., carbon fiber, fiberglass, etc.) may initially be layered within a mold and plastic or another resin may be injected or otherwise added to form fan blade ( 50 ). Of course still further constructions for fan blade ( 50 ) will be apparent to one of ordinary skill in the art in view of the teachings herein. [0045] III. Exemplary Alternative Fan [0046] FIGS. 7-10 depict an alternative fan ( 400 ) having a support ( 410 ), a motor ( 420 ), a hub ( 430 ), and a plurality of fan blades ( 450 ). Support ( 410 ) and motor ( 420 ) of the present example may be constructed in substantial accordance with support ( 20 ) and motor ( 30 ) described above. Hub ( 430 ), shown best in FIG. 8 , comprises an annular member disposed about and coupled to motor ( 420 ) such that rotation of motor ( 420 ) rotates hub ( 430 ). Hub ( 430 ) further includes a plurality of holes ( 432 ) to which fasteners ( 434 ) may be coupled to substantially fixedly coupled fan blades ( 450 ) with hub ( 430 ). Accordingly, when motor ( 420 ) rotates, fan blades ( 450 ) and hub ( 430 ) also rotate. It should be understood that additional components, such as grommets or other vibratory-reducing members may be included between fan blades ( 450 ) and hub ( 430 ) and/or between hub ( 430 ) and motor ( 420 ). In the present example, fan ( 400 ) further includes a top cover ( 412 ) having a circular center (not shown) and a plurality of rectangular fan extensions ( 414 ). In the present example, rectangular fan extensions ( 414 ) curve downwardly relative to support ( 410 ) and are configured to nest within top recesses ( 454 ) formed in fan blades ( 450 ), described below, to form a substantially smooth transition between top cover ( 414 ) and fan blades ( 450 ). [0047] A circular bottom cover ( 416 ) includes a plurality of upwardly projecting L-shaped tabs ( 418 ) disposed about the circumference of bottom cover ( 416 ) and a central lens ( 419 ). Lens ( 419 ) may be constructed in accordance with lens ( 48 ) described above. Bottom cover ( 416 ) is configured to couple to a bottom portion of fan blades ( 450 ) via tabs ( 418 ) inserting into recesses (not shown) formed in fan blades ( 450 ) and then being rotated such that an axial projection from each tab locks into the recesses. Accordingly, when bottom cover ( 416 ) is coupled to fan blades ( 450 ), a substantially smooth lower surface for fan ( 400 ) is formed. Of course it should be understood that bottom cover ( 416 ) may couple to fan blades ( 450 ) through other attachment members, such as screws, bolts, clips, clamps, straps, resilient tabs, etc. In addition, or in the alternative, bottom cover ( 416 ) may be directly coupled to motor ( 420 ). Fan ( 400 ) may be further configured in accordance with the teachings of fan ( 10 ) described above or in any other manner as will be apparent to one of ordinary skill in the art in view of the teachings herein. [0048] Referring now to FIGS. 9-10 , fan blade ( 450 ) of the present example comprises a root end ( 452 ), a tip ( 470 ), a leading edge ( 480 ), and a trailing edge ( 490 ). Fan blade ( 450 ) of the present example comprises airfoil profiles that substantially correspond to airfoil profiles ( 100 , 200 , 300 ) described above. In the present example, however, fan blade ( 450 ) comprises an alternative root end ( 452 ) and transition region ( 466 ). Transition region ( 466 ) of the present example comprises a tapered portion of fan blade ( 450 ) that transitions from root end ( 452 ) to airfoil profiles ( 100 , 200 , 300 ) for fan blade ( 450 ). Root end ( 452 ) of the present example includes a top recess ( 454 ) configured to receive a respective extension ( 414 ) therein. Thus, when extensions ( 414 ) are nested within respective top recesses ( 454 ) a substantially smooth transition is formed from top cover ( 414 ) to fan blades ( 450 ) for fan ( 400 ). In addition, one or more openings ( 456 ) are formed through a lower portion of root end ( 452 ) to permit fasteners ( 434 ) therethrough to substantially fixedly coupled fan blade ( 450 ) to hub ( 430 ) described above. [0049] Root end ( 452 ) is further includes a recessed ledge ( 458 ) and an outer lip ( 460 ) disposed on opposing ends of root end ( 452 ). As shown in FIGS. 8-9 , recessed ledge ( 458 ) corresponds to the side of fan blade ( 450 ) with leading edge ( 480 ) while outer lip ( 460 ) corresponds to the side of fan blade ( 450 ) with trailing edge ( 490 ). Accordingly, when fan blades ( 450 ) are assembled for fan ( 400 ), recessed ledge ( 458 ) nests with and below outer lip ( 460 ) of the fan blade ( 450 ) to form a substantially smooth and continuous surface from one fan blade ( 450 ) to the next. In the present example, fan blades ( 450 ) have root ends ( 452 ) with recessed ledges ( 458 ) and outer lips ( 460 ) disposed approximately 120 degrees from each other such that three fan blades ( 450 ) may be combined to form a substantially continuous fan blade structure (as shown in FIG. 7 ). Of course it should be understood that other angular relationships may be used as well (e.g., 180 degrees for a dual fan blade ( 450 ) assembly, 90 degrees for a four fan blade ( 450 ) assembly, 60 degrees for a five fan blade ( 450 ) assembly, etc.). In addition, or in the alternative, fasteners (not shown) may be used to couple corresponding recessed ledges ( 458 ) and outer lips ( 460 ) together for fan blades ( 450 ). Further still, rubber grommets (not shown) or other vibratory-reducing members may be interposed between corresponding recessed ledges ( 458 ) and outer lips ( 460 ) to vibrationally isolate fan blades ( 450 ) from one another. In the present example, a pair of rib members ( 462 ) are provided within root end ( 452 ) to reinforce or otherwise provide additional rigidity to root end ( 452 ), though these are merely optional. Still further constructions for root end ( 452 ) and/or fan blade ( 450 ) will be apparent to one of ordinary skill in the art in view of the teachings herein. [0050] Fan blade ( 450 ) of the present example is manufactured by a thermoplastic resin that is injected into a mold for fan blade ( 450 ) to achieve the desired profile. Alternatively, fan blade ( 450 ) may be formed from thin sheets of material laminated together and anchored to a thermoplastic or other material root end ( 452 ). For instance, fan blade ( 450 ) may be constructed by combining individual sheets with adhesive between each layer and forcing the sheets together under pressure in a shaped mold to form fan blade ( 450 ) shown in FIGS. 9-10 and anchored to root end ( 452 ). In one version, fan blade ( 450 ) may be manufactured using 7 layers of 0.5 millimeter (0.019685 inches) thick bamboo veneer that are compressed together as described above. Of course other thicknesses and/or number of layers may be used. Alternatively, other types of wooden veneer may be used or may be combined with other woods to form composite fan blades ( 450 ). Further still, fan blade ( 450 ) may be formed from a single layer of plastic that is heated and bent or inserted into a mold to form the profile of fan blade ( 450 ) which is subsequently joined to root end ( 452 ). In still a further alternative, fan blade ( 450 ) may be formed from layers of fiberglass matting or carbon fiber composite materials combined with epoxy resins. In yet another alternative, layers of wood veneer or other materials (e.g., carbon fiber, fiberglass, etc.) may initially be layered within a mold and plastic or another resin may be injected or otherwise added to form fan blade ( 450 ). Of course still further constructions for fan blade ( 450 ) will be apparent to one of ordinary skill in the art in view of the teachings herein. [0051] It should be appreciated that any patent, publication, or other disclosure material, in whole or in part, that is said to be incorporated by reference herein is incorporated herein only to the extent that the incorporated material does not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. As such, and to the extent necessary, the disclosure as explicitly set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material set forth herein will only be incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material. [0052] Having shown and described various embodiments of the present invention, further adaptations of the methods and systems described herein may be accomplished by appropriate modifications by one of ordinary skill in the art without departing from the scope of the present invention. Several of such potential modifications have been mentioned, and others will be apparent to those skilled in the art. For instance, the examples, embodiments, geometrics, materials, dimensions, ratios, steps, and the like discussed above are illustrative and are not necessarily required. Accordingly, the scope of the present invention should be considered in terms of the following claims and is understood not to be limited to the details of structure and operation shown and described in the specification and drawings.

A fan blade comprising a root end, a blade region, and a transition region. Wherein each of the root end and blade region comprise a unique profile, and wherein the transition region comprises a profile which transitions the root end profile to the blade region profile. The root end profile comprises a substantially convex top surface, a substantially concave domed sector, and reliefs to allow for the root end to be coupled with a similarly shaped fan hub extrusion. The blade region profile comprises a substantially convex top surface and bottom surface which terminate at a leading edge and trailing edge. The blade region slopes upward along a length of the blade region and terminates at a curved tip.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to zoom lenses and, more particularly, to zoom lenses of increased relative aperture with good optical performance over the entire zooming range, while still permitting the physical size to me minimized with the total length shortened to be suited to photographic cameras, video cameras, etc. 2. Description of the Related Art To photographic cameras and video cameras there has been a demand for a zoom lens having a good compromise between the requirement of increasing the relative aperture with a high range and the requirement of reducing the bulk and size in such a manner that high grade optical performance is preserved. Of these, for the video camera, because of its image pickup element being relatively low in sensitivity, the zoom lens has to get as high a relative aperture as possible. At present, the 2/3 in. image pickup tube is widely used in the video camera from the two points of view of compactness and image quality. Also, from the standpoint of good manageability and high facility for further minimization of the size, 8 m/m video cameras are coming to be used in gradually increasing numbers. The image pickup tube to be used in this camera is required to be furthermore reduced in size while preserving high grade imagery. Recently the 1/2 in. image pickup tube or plate has found its use in 8 m/m video cameras. If the zoom lens is of the so-called 4-unit type in principle, it is in general case that an increase of the relative aperture to as high as 1.4-1.6 or thereabout in F-number can be achieved when proper rules of lens design are set forth particularly for the fourth lens unit that is arranged on the image side of the zoom section to be stationary during zooming, and the image forming section or the fifth lens unit to well correct the residual aberrations of the zoom section. Also, in order to shorten the total length of the entire lens system, the effective method is to reduce the bulk and size of the front or first lens unit. To allow for this to be achieved, the F-number may be increased. But, to avoid the F-number from being so much increased, it becomes important to set forth proper rules of design for the image forming section. In addition thereto, if the reduction of the physical size of the entire lens system and the increase of the relative aperture are attempted by relying merely on strengthening of the refractive power of each lens unit, then the spherical aberration in the paraxial region, the coma from the zonal to the marginal region, and higher order aberrations such as sagittal halo are increased largely. So, it becomes difficult to get high optical performance. Suppose, for example, the front or first lens unit is selected for shortening the total length by the method of increasing the refractive power, then the overall magnifying power of the zoom section up to the image forming section has to be increased. As a result, the first lens unit produces many aberrations, and the tolerances for the lens design parameters becomes severer. Thus, it becomes difficult to assure the prescribed optical performance. Also, in the case of using the 2/3 in. image pickup element, according to the prior art, the total length L of the entire lens system in terms of the diagonal φ A of the effective picture frame falls in a range of 10φ A to 12φ A , as disclosed in Japanese Laid-Open Patent Application No. Sho 60-260912. This implies that the total length of the entire lens system is caused to become comparatively long. Like this, it has been very difficult to achieve a reduction of the total length L to shorter than 10φ A in such a manner that good optical performance is preserved throughout the zooming range. As other concomitant techniques mention may be made of U.S. Pat. Nos. 4,518,228, 4,525,036, 4,618,219, 4,621,905, 4,653,874, and 4,659,187. SUMMARY OF THE INVENTION An object of the present invention is to provide a zoom lens having a small F-number, a high zoom ratio and the standard image angle at the wide angle end with the size of the entire lens system being reduced while still permitting high grade optical performance to be preserved throughout the entire zooming range. The zoom lens of the invention comprises, from front to rear, a first lens unit of positive power for focusing, a second lens unit of negative power having the magnification varying function, a third lens unit of negative power for compensating for the shift of an image plane resulting from the variation of the magnification, a fourth lens unit having a positive lens for making the diverging light beam from the third lens unit an almost parallel light beam, and a fifth lens unit having an image forming function and having lenses of positive, negative, positive, negative, positive and positive powers in this order, wherein letting the focal length of the j-th lens in the i-th lens unit be denoted by f i ,j, the radius of curvatyre of the j-th lens surface in the i-th lens unit by R i ,j, the Abbe number of the glass of the j-th lens in the i-th lens unit by ν i ,j, and the focal length of the i-th lens unit by Fi, the following conditions are satisfied: 0.7<|R.sub.4,2 /F.sub.4 |<0.85 (1) 1.05<|f.sub.5,2 /F.sub.5 |<1.5 (2) 0.6<|f.sub.5,4 /f.sub.5,5 |<1.5 (3) 50<(ν.sub.5,1 +ν.sub.5,6)/2<59 (4) BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal section view of a typical one of examples of specific zoom lenses of the invention. FIGS. 2(A) and 2(B) to FIGS. 5(A) and 5(B) are graphic representations of the aberrations of numerical examples 1 to 4 of the invention respectively, with FIGS. 2(A), 3(A), 4(A) and 5(A) in the wide angle end, and FIGS. 2(B), 3(B), 4(B) and 5(B) ij tge telephoto end. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the form of a zoom lens of the invention in correspondence to numerical examples thereof. In the figure, I is a first lens unit of positive refractive power axially movable for focusing. II is a second lens unit of negative refractive power axially movable for varying the image magnification. III is a third lens unit of negative refractive power for compensating for the shift of an image plane as it occurs when the image magnification varies. IV is a fourth lens unit of positive refractive power for making the diverging light beam incident thereon from the third lens unit III almost afocal in emerging therefrom. V is a fixed fifth lens unit having the image forming function and comprising six lens elements of positive, negative, positive, negative, positive and positive powers in this order. SP is a fixed, aperture size-variable diaphragm. In the embodiments of the invention, in such a zoom type, by satisfying the above-mentioned inequalities of conditions (1)-(4) for the construction and arrangement of the elements of the fourth and fifth lens units, despite a great increase in each of the relative aperture and the range of variation of the magnification, good correction of aberrations is achieved for high grade optical performance throughout the entire zooming range. The technical signifcances of the above-defined conditions each are explained below. The inequalities of condition (1) represent the range of refracting power for the rear surface of the first lens in the fourth lens unit. The use of a lens form of strong rearward curvature in the first lens of the fourth lens unit leads to production of various aberrations, particularly spherical aberration and coma, when the light beam diverging in passing through the first to the third lens units travels across that lens. In order that the light beam leaves as an almost afocal one for the fifth lens unit without causing such aberrations to be increased as far as possible, the condition (1) must be satisfied. Also, the requirement of making up the almost afocal beam from the diverging light beam of the third lens unit, when fulfilled, unequivocally determines the refractive power for the fourth lens. For this reason, when the refracting power of the rear lens surface becomes too weak as exceeding beyond the upper limit of the inequalities of condition (1), the refracting power of the front lens surface must be so much increased. As a result, the tendency toward under-correction of spherical aberration is intensified. When the refracting power of the rear lens surface becomes too strong beyond the lower limit, on the other hand, the coma is increased largely. The inequalities of condition (2) give a range of refractive power ratio for the second lens in the fifth lens unit to the whole of the fifth lens unit to well correct particularly spherical aberration. When the upper limit is exceeded, it is over-corrected. When the lower limit is exceeded, under-correction comes to result. The inequalities of condition (3) give a range of refractive power ratio for the fourth and fifth lenses in the fifth lens unit to well correct astigmatism without causing other aberrations, mainly coma, to be produced as far as possible. When the upper limit is exceeded, the coma is increased largely. When the lower limit is exceeded, the astigmatism becomes difficult to well correct. The inequalities of condition (4) give a range of the Abbe numbers of the media of the first and sixth lenses in the fifth lens unit to correct longitudinal and lateral chromatic aberrations in good balance. When the upper limit is exceeded, over-correction of longitudinal chromatic aberration results. When the lower limit is exceeded, the lateral chromatic aberration is under-corrected objectionably. In order to achieve a reduction of the physical length of the entire lens system while minimizing the variation with zooming of the aberrations, it is preferred to satisfy the following condition: 0.75<|F.sub.2 /Fw|<0.85 (5) where Fw is the shortest focal length of the entire system. The factor in the inequalities of condition (5) represents the refractive power of the second lens unit. When the lower limit is exceeded, the refractive power of the second lens unit becomes too strong, causing the range of variation of aberrations with zooming to increase. When the refractive power of the second lens unit becomes weak beyond the upper limit, the physical length is increased objectionably, because it must be compensated for by increasing the total zooming movement of the second lens unit to obtain the equivalent zoom ratio. The objects of the invention are accomplished when all the conditions set forth above are satisfied. Yet, to achieve a further improvement of the aberration correction, it is preferred that the fourth and fifth lens units are constructed in such forms as described below. The fourth lens unit is a bi-convex lens with the rear surface of strong curvature toward the rear. The fifth lens unit comprises, from front to rear, a bi-convex first lens with the front surface having a stronger curvature than the rear surface, a negative meniscus-shaped second lens of forward convexity, a positive third lens with the front surface of strong curvature toward the front, a negative meniscus-shaped fourth lens of forward convexity, a bi-convex fifth lens with the rear surface of strong curvature, and a positive sixth lens with the front surface of strong curvature toward the front. The air separation between the third and fourth lenses is longest in this lens unit. It should be noted that the term "rear surface of strong curvature" means that it is compared with the curvature of the other or front surface. This applies to the term "front surface of strong curvature" as well. By designing the fourth and fifth lens units in such a way, the residual aberrations, for example, spherical aberration and inward coma from the zonal to the marginal region of the picture frame, of the zoom section are corrected entirely in good balance. Four examples of specific zoom lenses of the invention can be constructed in accordance with the numerical data given in the following tables for the radii of curvature, R, the axial thicknesses or air separations, D, and the refractive indices, N, and Abbe numbers, ν, of the glasses of the various lenses with the subscriptions numbered consecutively from front to rear. A block defined between flat surfaces R28 and R29 represents a face plate, or a filter. The values of the factors in the above-cited conditions for the numerical examples are given in Table 1. ______________________________________Numerical Example 1 (FIGS. 2(A) and 2(B))F = 1-5.56 FNo = 1:1.6-2.4 2ω = 47.6°-9.0°______________________________________R1 = 4.9342 D1 = 0.0945 N1 = 1.80518 ν1 = 25.4R2 = 2.3937 D2 = 0.4961 N2 = 1.51633 ν2 = 64.1R3 = -10.2228 D3 = 0.0118R4 = 2.1189 D4 = 0.3622 N3 = 1.60311 ν3 = 60.7R5 = 11.8103 D5 = VariableR6 = 5.1504 D6 = 0.0630 N4 = 1.69680 ν4 = 55.5R7 = 0.9067 D7 = 0.2717R8 = -1.1671 D8 = 0.0630 N5 = 1.69680 ν5 = 55.5R9 = 1.1671 D9 = 0.2441 N6 = 1.84666 ν6 = 23.9R10 = 11.5367 D10 = VariableR11 = -2.2007 D11 = 0.0630 N7 = 1.71300 ν7 = 53.8R12 = -50.7152 D12 = VariableR13 = 9.2253 D13 = 0.3465 N8 = 1.69680 ν8 = 55.5R14 = -1.7144 D14 = 0.0787R15 = Stop D15 = 0.1575R16 = 2.7254 D16 = 0.2913 N9 = 1.65844 ν9 = 50.9R17 = -11.0099 D17 = 0.1417R18 = -1.8215 D18 = 0.0866 N10 = 1.84666 ν10 = 23.9R19 = -7.3111 D19 = 0.0118R20 = 1.6340 D20 = 0.2520 N11 = 1.56384 ν11 = 60.7R21 = 6.1695 D21 = 0.8189R22 = 2.5700 D22 = 0.0630 N12 = 1.83400 ν12 = 37.2R23 = 1.2021 D23 = 0.1024R24 = 1.8982 D24 = 0.2362 N13 = 1.51633 ν13 = 64.1R25 = -2.9332 D25 = 0.0118R26 = 3.6846 D26 = 0.2283 N14 = 1.51742 ν14 = 52.4R27 = -15.6427 D27 = 0.3150R28 = ∞ D28 = 0.4331 N15 = 1.51633 ν15 = 64.1R29 = ∞______________________________________f 1 5.56______________________________________D5 0.0910 1.5119D10 1.5019 0.2231D12 0.2359 0.0938Total Length = 8.109 (= 9.19 · φ.sub.EA)______________________________________ ______________________________________Numerical Example 2 (FIGS. 3(A) and 3(B))F = 1-5.56 FNo = 1:1.6-2.4 2ω = 47.6°-9.0°______________________________________R1 = 4.9314 D1 = 0.0945 N1 = 1.80518 ν1 = 25.4R2 = 2.3926 D2 = 0.5042 N2 = 1.51633 ν2 = 64.1R3 = -10.2219 D3 = 0.0118R4 = 2.1255 D4 = 0.3624 N3 = 1.60311 ν3 = 60.7R5 = 11.9694 D5 = VariableR6 = 5.5784 D6 = 0.0630 N4 = 1.69680 ν4 = 55.5R7 = 0.9197 D7 = 0.2721R8 = -1.1850 D8 = 0.0630 N5 = 1.69680 ν5 = 55.5R9 = 1.1855 D9 = 0.2285 N6 = 1.84666 ν6 = 23.9R10 = 10.6989 D10 = VariableR11 = -2.1763 D11 = 0.0788 N7 = 1.71300 ν7 = 53.8R12 = -40.3230 D12 = VariableR13 = 9.2309 D13 = 0.3545 N8 = 1.69680 ν8 = 55.5R14 = -1.7155 D14 = 0.0788R15 = Stop D15 = 0.1800R16 = 3.0328 D16 = 0.2758 N9 = 1.65844 ν9 = 50.9R17 = -7.4073 D17 = 0.1534R18 = -1.7877 D18 = 0.0867 N10 = 1.84666 ν10 = 23.9R19 = -6.5984 D19 = 0.0118R20 = 1.5956 D20 = 0.2994 N11 = 1.56384 ν11 = 60.7R21 = 7.4734 D21 = 0.8036R22 = 4.0283 D22 = 0.0630 N12 = 1.83400 ν12 = 37.2R23 = 1.1962 D23 = 0.0561R24 = 1.6708 D24 = 0.3230 N13 = 1.51823 ν13 = 59.0R25 = -2.3852 D25 = 0.0118R26 = 2.9824 D26 = 0.1418 N14 = 1.51742 ν14 = 52.4R27 = ∞ D27 = 0.3151R28 = ∞ D28 = 0.3151 N15 = 1.51633 ν15 = 64.1R29 = ∞______________________________________f 1 5.56______________________________________D5 0.0907 1.5128D10 1.5412 0.2586D12 0.2329 0.0934Total Length = 8.0734 (= 9.15 · φ.sub.EA)______________________________________ ______________________________________Numerical Example 3 (FIGS. 4(A) and 4(B))F = 1-5.56 FNo = 1:1.6-2.4 2ω = 47.3°-9.18°______________________________________R1 = 4.9866 D1 = 0.0956 N1 = 1.80518 ν1 = 25.4R2 = 2.4194 D2 = 0.5099 N2 = 1.51633 ν2 = 64.1R3 = -10.3364 D3 = 0.0120R4 = 2.1493 D4 = 0.3665 N3 = 1.60311 ν3 = 60.7R5 = 12.1034 D5 = VariableR6 = 5.6408 D6 = 0.0637 N4 = 1.69680 ν4 = 55.5R7 = 0.9300 D7 = 0.2752R8 = -1.1983 D8 = 0.0637 N5 = 1.69680 ν5 = 55.5R9 = 1.1988 D9 = 0.2310 N6 = 1.84666 ν6 = 23.9R10 = 10.8187 D10 = VariableR11 = -2.2007 D11 = 0.797 N7 = 1.71300 ν7 = 53.8R12 = -40.7745 D12 = VariableR13 = 9.4928 D13 = 0.3585 N8 = 1.69680 ν8 = 55.5R14 = -1.7292 D14 = 0.0797R15 = Stop D15 = 0.1593R16 = 3.1390 D16 = 0.2788 N9 = 1.65844 ν9 = 50.9R17 = -7.0677 D17 = 0.1502R18 = -1.8030 D18 = 0.0876 N10 = 1.84666 ν10 = 23.9R19 = -6.3846 D19 = 0.0120R20 = 1.5990 D20 = 0.3027 N11 = 1.56384 ν11 = 60.7R21 = 7.3765 D21 = 0.8126R22 = 4.2344 D22 = 0.0637 N12 = 1.83400 ν12 = 37.2R23 = 1.2054 D23 = 0.0700R24 = 1.7071 D24 = 0.3266 N13 = 1.51823 ν13 = 59.0R25 = -2.3530 D25 = 0.0120R26 = 3.0106 D26 = 0.1434 N14 = 1.51742 ν14 = 52.4R27 = -95.6033 D27 = 0.3187R28 = ∞ D28 = 0.3187 N15 = 1.51633 ν15 = 64.1R29 = ∞______________________________________f 1 5.56______________________________________D5 0.0918 1.5297D10 1.5584 0.2615D12 0.2350 0.0939Total Length = 8.1461 (= 9.13 · φ.sub.EA)______________________________________ ______________________________________Numerical Example 4 (FIGS. 5(A) and 5(B))F = 1-5.56 FNo = 1:1.6-2.4 2ω = 47.6°-9.0°______________________________________R1 = 4.9254 D1 = 0.1102 N1 = 1.80518 ν1 = 25.4R2 = 2.3897 D2 = 0.4934 N2 = 1.51633 ν2 = 64.1R3 = -10.2094 D3 = 0.0118R4 = 2.1229 D4 = 0.3620 N3 = 1.60311 ν3 = 60.7R5 = 11.9548 D5 = VariableR6 = 5.5715 D6 = 0.0630 N4 = 1.69680 ν4 = 5.5R7 = 0.9186 D7 = 0.2718R8 = -1.1836 D8 = 0.0630 N5 = 1.69680 ν5 = 55.5R9 = 1.1841 D9 = 0.2282 N6 = 1.84666 ν6 = 23.9R10 = 10.6858 D10 = VariableR11 = -2.1737 D11 = 0.0787 N7 = 1.71300 ν7 = 53.8R12 = -40.2737 D12 = VariableR13 = 9.2196 D13 = 0.3541 N8 = 1.69680 ν8 = 55.5R14 = -1.7134 D14 = 0.0787R15 = Stop D15 = 0.1479R16 = 3.4482 D16 = 0.2675 N9 = 1.51633 ν9 = 64.1R17 = -5.6826 D17 = 0.1841R18 = -1.5079 D18 = 0.0866 N10 = 1.84666 ν10 = 23.9R19 = -2.8542 D19 = 0.0118R20 = 1.5567 D20 = 0.3620 N11 = 1.60311 ν11 = 60.7R21 = -43.2099 D21 = 0.6372R22 = -5.5552 D22 = 0.0630 N12 = 1.83400 ν12 = 37.2R23 = 1.3759 D23 = 0.1036R24 = 4.4717 D24 = 0.3305 N13 = 1.51633 ν13 = 64.1R25 = -1.3545 D25 = 0.0118R26 = 2.0246 D26 = 0.2203 N14 = 1.51742 ν14 = 52.4R27 = ∞ D27 = 0.3148R28 = ∞ D28 = 0.3148 N15 = 1.51633 ν15 = 64.1R29 = ∞______________________________________f 1 5.56______________________________________D5 0.0885 1.5088D10 1.5393 0.2583D12 0.2326 0.0933Total Length = 8.0698 (= 9.16 · φ.sub.EA)______________________________________ TABLE 1______________________________________ Numeri- Numeri- Numerical Numerical cal Ex- cal Ex-Conditions Example 1 Example 2 ample 3 ample 4______________________________________(1) |R.sub.4,2 /F.sub.4 | 0.8156 0.8153 0.8129 0.8153(2) |f.sub.5,2 /F.sub.5 | 1.1123 1.1068 1.1329 1.4736(3) |f.sub.5,4 /f.sub.5,5 | 1.2187 1.0575 1.0392 0.6413(4) (ν.sub.5,1 + ν.sub.5,6)/2 51.65 51.65 51.65 58.25(5) |F.sub.2 /Fw| 0.7874 0.7880 0.7968 0.7870 Total Length 9.19φ.sub.EA 9.15φ.sub.EA 9.13φ.sub.EA 9.16φ.sub.EA of Lens______________________________________ It will be appreciated from the foregoing that according to the present invention, it is made possible to realize a large relative aperture, high range zoom lens of reduced size, while still preserving high grade optical performance, suited to photographic camera or video camera. In particular, the present invention has achieved a great advance in reduction of the size of the zoom lens in terms of the total length to as short as L=9.13φ A to 9.19φ A .

A zoom lens comprising a positive first lens unit for focusing, a negative second lens unit as the variator, a negative third lens unit as the compensator, a positive fourth lens unit for making afocal the diverging light beam from the third unit in travelling thereacross, and an image forming or fifth lens unit having six lenses, satisfying the following conditions: 0.7<|R.sub.4,2 /F.sub.4 |<0.85 1.05<|f.sub.5,2 /F.sub.5 |<1.5 0.6<|f.sub.5,4 /f.sub.5,5 |<1.5 50<(ν.sub.5,1 +ν.sub.5,6)/2 59 where R 4 ,2 is the radius of curvature of the second surface counting from front of the fourth lens unit, F 4 and F 5 are the focal lengths of the fourth and fifth lens units respectively; f 5 ,2, f 5 ,4, and f 5 ,5 are the focal lengths of the second, fourth and fifth lenses in the fifth lens unit, and ν 5 ,1 and ν 5 ,6 are the Abbe numbers of the glasses of the first and sixth lenses in the fifth lens unit, respectively.

CROSS-REFERENCE TO RELATED APPLICATION This is a divisional of U.S. application Ser. No. 297,354 filed Jan. 17, 1989, now abandoned which is a divisional of U.S. application Ser. No. 920,536 filed Oct. 20, 1986, now U.S. Pat. No. 4,822,801, which is a continuation-in-part of U.S. application Ser. No. 770,897 filed Aug. 30, 1985, now abandoned, which is a continuation-in-part of U.S. application Ser. No. 633,153 filed Jul. 20, 1984, now abandoned, and which claims priority to Irish Application 1666/85 filed Feb. 7, 1985. BACKGROUND OF THE INVENTION U.S. Pat. No. 4,341,784 discloses certain substituted 7-(3-amino-1-pyrrolidinyl)-1-ethyl-6-fluoro-1,4-dihydro-4-oxo-1,8-naphthyridine-3-carboxylic acids having the general formula: ##STR1## The compounds are disclosed to have antibacterial activity. The Journal of Medicinal Chemistry, 23, 1358 (1980) discloses certain substituted quinoline-3-carboxylic acids having the structural formula ##STR2## wherein ##STR3## may be pyrrolidinyl. See also U.S. Pat. No. 4,146,719. The compounds are disclosed to have antibacterial activity. European Patent Application 81 10 6747, Publication Number 047,005, published Mar. 10, 1982, discloses certain benzoxazine derivatives having the structural formula ##STR4## wherein A is halogen and B may be a cyclic amine substituent such as pyrrolidine, or piperidine. Certain 7-heterocyclic substituted 1,8-naphthyridines are disclosed in Eur. J. Med. Chem.-Chimica Therapeutica, 29, 27 (1977). U.S. Pat. Nos. 3,753,993 and 3,907,808 disclose certain 7-pyridylquinolones. The references teach that these compounds possess antibacterial activity. SUMMARY OF THE INVENTION The invention in a first generic chemical compound aspect are compounds having the structural formula I and II ##STR5## wherein Z is ##STR6## Y is NH 2 , NHR, NRR', OR, or OH wherein R and R' are each independently an alkyl of from one to six carbon atoms or a cycloalkyl of from three to six carbon atoms; X is CH, CF, CCl, CBr, COR, COH, CCF 3 , or N; n is 1, 2, 3, or 4; n' is 1, 2, 3, or 4 wherein n+n' is a total of 2, 3, 4, or 5, and n" is 0, 1, or 2; R 1 is hydrogen, alkyl having from one to six carbon atoms or a cation; R 2 is alkyl having from one to four carbon atoms, vinyl, haloalkyl, or hydroxyalkyl having from two to four carbon atoms, or cycloalkyl having three to six carbon atoms; R 3 is hydrogen, alkyl having from one to four carbon atoms or cycloalkyl having three to six carbon atoms; R 4 is hydrogen, alkyl from one to four carbon atoms, hydroxyalkyl having two to four carbon atoms, trifluoroethyl or R 7 CO-- wherein R 7 is alkyl having from one to four carbon atoms, or alkoxy having from one to four carbon atoms; R 5 is hydrogen, or alkyl having from one to three carbon atoms; R 6 is hydrogen or alkyl having from one to three carbon atoms; and the pharmaceutically acceptable acid addition or base salts thereof. The preferred compounds of this invention are those wherein Z is ##STR7## Also preferred compounds of this invention are those wherein Z is ##STR8## Other preferred compounds of this invention are those wherein R 1 is hydrogen or a pharmaceutically acceptable base salt such as a metal or amine salt. Other preferred compounds of this invention are those wherein R 2 is ethyl, vinyl, 2-fluoroethyl, or cyclopropyl. The most preferred compounds are those wherein X is N, CF, or CCl, Z is ##STR9## R 1 is hydrogen, R 2 is ethyl, vinyl, 2-fluoroethyl or cyclopropyl; n" is 0 or 1 and R 3 is hydrogen, methyl, ethyl, 1- or 2-propyl, Y is NH 2 or a pharmaceutically acceptable acid addition or base salt thereof. Particularly preferred species of the invention are the compounds having the names: 8-amino-9-fluoro-3-methyl-10[(3-cyclopropylaminomethyl)-1-pyrrolidinyl]-7-oxo-2,3-dihydro-7H-pyrido[1,2,3-de][1,4]benzoxazine-6-carboxylic acid; 8-amino-9-fluoro-3-methyl-10-(3-amino-1-pyrrolidinyl)-7-oxo-2,3-dihydro-7H-pyrido[1,2,3-de][1,4]benzoxazine-6-carboxylic acid hydrochloride; 8-amino-9-fluoro-3-methyl-10-[3-(aminomethyl)-1-pyrrolidinyl]-7-oxo-2,3-dihydro-7H-pyrido[1,2,3-de][1,4]benzoxazine-6-carboxylic acid; 8-amino-9-fluoro-3-methyl-10-[3-[(propylamino)methyl]-1-pyrrolidinyl]-7-oxo-2,3-dihydro-7H-pyrido [1,2,3-de][1,4]benzoxazine-6-carboxylic acid; 8-amino-9-fluoro-3-methyl-10-[3-[(2-hydroxyethyl)amino)methyl]-1-pyrrolidinyl]-7-oxo-2,3-dihydro-7H-pyrido[1,2,3-de][1,4]benzoxazine-6-carboxylic acid; 8-amino-9-fluoro-3-methyl-10-[3-[(2-propylamino)methyl]-1-pyrrolidinyl]-7-oxo-2,3-dihydro-7H-pyrido [1,2,3-de][1,4]benzoxazine-6-carboxylic acid; 8-amino-9-fluoro-3-methyl-10-[3-[(2,2,2-trifluoroethyl)amino]methyl]-1-pyrrolidinyl]-7-oxo-2,3-dihydro-7H-pyrido[1,2,3-de][1,4]benzoxazine-6-carboxylic acid; 8-amino-9-fluoro-3-methyl-10-[3-[(ethylamino)methyl]- 1-pyrrolidinyl]7oxo-2,3-dihydro-7H-pyrido[1,2,3-de][1,4]benzoxazine-6-carboxylic acid; 8-amino-9-fluoro-3-methyl-10-[2,7-diazaspiro[4.4]non-2-yl]-7-oxo-2,3-dihydro-7H-pyrido[1,2,3-de][1,4]benzoxazine-6-carboxylic acid; 8-amino-9-fluoro-3-methyl-10-[7-(7-methyl-2,7-diazaspiro[4.4]non-2-yl]-7-oxo-2,3-dihydro-7H-pyrido [1,2,3-de][1,4]benzoxazine-6-carboxylic acid; 8-amino-9-fluoro-3-methyl-10-[7-(7-ethyl-2,7-diazaspiro[4.4]non-2-yl]-7-oxo-2,3-dihydro-7H-pyrido [1,2,3-de][1,4]benzoxazine-6-carboxylic acid; 1-ethyl-5-amino-6,8-difluoro-7-(3-amino-1-pyrrolidinyl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid hydrochloride; 1-ethyl-5-amino-6,8-difluoro-7-[3-(ethylamino)methyl-1-pyrrolidinyl)]-4-oxo-1,4-dihydroquinoline-3-carboxylic acid; 1-ethyl-5-amino-6,8-difluoro-7-[3-(aminomethyl)-1-pyrrolidinyl]-4-oxo-1,4-dihydroquinoline-3-carboxylic acid; 1-ethyl-5-amino-6,8-difluoro-7-[3-(propylaminomethyl)-1-pyrrolidinyl]-4-oxo-1,4-dihydroquinoline-3-carboxylic acid; 1-ethyl-5-amino-6,8-difluoro-7-[3-(2-propylaminomethyl)-1-pyrrolidinyl]-4-oxo-1,4-dihydroquinoline-3-carboxylic acid; 1-ethyl-5-amino-6,8-difluoro-7-[3-(cyclopropylaminomethyl)-1-pyrrolidinyl]-4-oxo-1,4-dihydroquinoline-3-carboxylic acid; 1-ethyl-5-amino-6,8-difluoro-7-[2,7-diazaspiro[4.4]non-2-yl]-4-oxo-1,4-dihydroquinoline-3-carboxylic acid; 1-ethyl-5-amino-6,8-difluoro-7-[7-(7-methyl-2,7-diazaspiro[4.4]non-2-yl]-4-oxo-1,4-dihydroquinoline-3-carboxylic acid; 1-ethyl-5-amino-6,8-difluoro-7-[7-(7-ethyl-2,7-diazaspiro[4.4]non-2-yl]-4-oxo-1,4-dihydroquinoline-3-carboxylic acid; 1-ethyl-5-amino-6,8-difluoro-7-[3-[[(2-hydroxyethyl)amino]methyl]-1-pyrrolidinyl]-4-oxo-1,4-dihydroquinoline-3-carboxylic acid; 1-ethyl-5-amino-6,8-difluoro-7-[3-[[(2,2,2-trifluoroethyl)amino]methyl]-1-pyrrolidinyl]-4-oxo-1,4-dihydroquinoline-3-carboxylic acid; 5-amino-7-(3-amino-1-pyrrolidinyl)-1-ethyl-6-fluoro-1,4-dihydro-4-oxo-1,8-naphthyridine-3-carboxylic acid; 5-amino-7-(3-amino-1-pyrrolidinyl)-8-chloro-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid; 5-amino-8-chloro-1-cyclopropyl-6-fluoro-1,4-dihydro-7-[3-[(methylamino)methyl]-1-pyrollidinyl]-4-oxo-3-quinolinecarboxylic acid; 5-amino-7-(3-amino-1-pyrrolidinyl)-8-bromo-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid; and 5-amino-7-(3-amino-1-pyrrolidinyl)-1-cyclopropyl-6,8-difluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid. The following process for preparing compounds of the formula ##STR10## wherein R 1 , R 2 , X, and Z are as defined for formula I which comprises reacting a compound having the following structural formula ##STR11## with an amine corresponding to the group Z wherein Z is the compound having the structural formula ##STR12## wherein all of the above terms are as defined in formulae I and II and L is a leaving group which is preferably fluorine or chlorine. This invention also includes novel intermediates. In a second generic chemical aspect are compounds having the structural formula VII ##STR13## wherein X is CH, N, CF, CCl, CBr, CCF 3 , COH, or COR; Y is NH 2 , NHR, NRR', OR or OH wherein R and R" are each independently an alkyl of from one to six carbon atoms or a cycloalkyl of from three to six carbon atoms; R 1 is as defined above and the pharmaceutically acceptable acid addition or base salts thereof. The preferred compounds are those wherein X is CCl, CBr, or CF and Y is NH 2 , NHR, or NRR'. Particularly preferred species of the invention are compounds having the names: 5-amino-8-chloro-1-cyclopropyl-6,7-difluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid; 5-amino-8-bromo-1-cyclopropyl-6,7-difluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid; and 5-amino-1-cyclopropyl-6,7,8-trifluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid. The invention also includes a pharmaceutical composition which comprises an antibacterially effective amount of a compound having structural formula I and the pharmaceutically acceptable salts thereof in combination with a pharmaceutically acceptable carrier. The invention further includes a method for treating bacterial infections in a mammal which comprises administering an antibacterially effective amount of the above defined pharmaceutical composition to a mammal in need thereof. DESCRIPTION OF THE PREFERRED EMBODIMENTS The compounds of the invention having the structural formula III or IIIa may be readily prepared by treating a corresponding compound having the structural formula IV or V with the desired cyclic amine VIa or VIb. For purposes of this reaction, the alkylamine substituent of compound VIa or VIb may, if desired, be protected by a group which renders it substantially inert to the reaction conditions. Thus, for example, protecting groups such as the following may be utilized: carboxylic acyl groups such as formyl, acetyl, trifluoroacetyl; alkoxycarbonyl groups such as ethoxycarbonyl, t-butoxycarbonyl, β,β,β-trichloroethoxycarbonyl, β-iodoethoxycarbonyl; aryloxycarbonyl groups such as benzyloxycarbonyl, p-methoxybenzyloxycarbonyl, phenoxycarbonyl; silyl groups such as trimethylsilyl; and groups such as trityl, tetrahydropyranyl, vinyloxycarbonyl, o-nitrophenylsulfenyl, diphenylphosphinyl, p-toluenesulfonyl, and benzyl, may all be utilized. The protecting group may be removed, after the reaction between compound IV or V and compound VIa or VIb if desired, by procedures known to those skilled in the art. For example, the ethoxycarbonyl group may be removed by acid or base hydrolysis and the trityl group may be removed by hydrogenolysis. The reaction between the compound of structural formula IV or V and a suitably protected compound of formula VIa or VIb, may be performed with or without a solvent, preferably at elevated temperature for a sufficient time so that the reaction is substantially complete. The reaction is preferably carried out in the presence of an acid acceptor such as an alkali metal or alkaline earth metal carbonate or bicarbonate, a tertiary amine such as triethylamine, pyridine, or picoline. Alternatively an excess of the compound of formula VI may be utilized as the acid acceptor. Convenient solvents for this reaction are nonreactive solvents such as acetonitrile, tetrahydrofuran, ethanol, chloroform, dimethylsulfoxide, dimethylformamide, pyridine, picoline, water, and the like. Solvent mixtures may also be utilized. Convenient reaction temperatures are in the range of from about 20° to about 150° C.; higher temperatures usually require shorter reaction times. The removal of the protecting group R 4 may be accomplished either before or after isolating the product, III. Alternatively, the protecting group R 4 need not be removed. Some of the starting compounds having structural formulae IV and V are known in the art or, if new, may be prepared from known starting materials by standard procedures or by variations thereof. Thus the following compounds are disclosed in the noted references: ##STR14## Other starting compounds having structural formula IV wherein Y is NRR' and R and/or R' are not hydrogen may be prepared from the known 5-amino quinolines or naphthyridines by an alkylation sequence shown below wherein L is a leaving group as previously defined. ##STR15## The 5-amino group is preferably acylated by trifluoroacetic acid anhydride although other acyl moieties may be employed. The alkylation of R proceeds with the presence of sodium hydride or other nonnucleophilic bases. Removal of the acyl activating group is accomplished with acid or base hydrolysis such as 2N hydrochloric acid in acetic acid. A second alkylation, if desired, with R'L, again in the presence of base such as, for example, potassium carbonate provides compounds of formula IV where both R and R' are not hydrogen. Alternatively, the 5-alkylamino compounds of formula II may be prepared from the nitro or amino acids IV through reductive amination procedures as illustrated in the following scheme. ##STR16## Using appropriate control of the aldehyde (RCHO) equivalents mono and disubstituted amines may be obtained. The substituted amino acids may be converted to the desired compounds of formula II by methods described in the references cited in the Background of the Invention. The compounds of formula IV wherein Y is OR may be prepared from the polysubstituted acids or esters by displacement of an ortho leaving group with OR as shown: ##STR17## Other compounds of formula IV wherein X is CH, CCl, CBr, COR, COH, CCF 3 or N are made by the sequence shown below according to the general methods in the references cited in the background of the invention. ##STR18## The general pathway to the compounds of formula IV is illustrated with 2-nitro-3,4,5,6-tetrafluorobenzoyl chloride. This starting material is treated with n-butyl lithium and malonic half acid ester to form 2-nitro-3,4,5,6-tetrafluoro-β-oxo-benzene propanoic acid ethyl ester. This product can be converted to 5-nitro-1-cyclopropyl-6,7,8-trifluoro-1,4-dihydro-4-oxo-quinoline-3-carboxylic acid ethyl ester by a three step reaction. The starting material is first treated with triethylorthoformate and subsequently with cyclopropyl amine in t-butyl alcohol. The product is ring closed with potassium t-butoxide to form 5-nitro-1-cyclopropyl-6,7,8-trifluoro-1,4-dihydro-4-oxoquinoline-3-carboxylic acid ethyl ester. This product is hydrogenated to form the corresponding 5-amino compound. This is then hydrolyzed to form 1-cyclopropyl-5-amino-6,7,8-trifluoro-1,4-dihydro-4-oxo-3-quinoline carboxylic acid. Alternatively compounds of the formula IV may be prepared by a series of reactions illustrated with 3,4,5,6-tetrafluoroanthranilic acid. The acid is reacted with acetic anhydride and acetic acid to form 2-acetylamino-3,4,5,6-tetrafluorobenzoic acid. This compound is reacted with oxalyl chloride and dichloromethane in the presence of N,N-dimethylformamide catalyst to form 2-acetylamino-3,4,5,6-tetrafluorobenzoyl chloride. This product is treated with n-butyl lithium and malonic half acid ester to form 2-acetylamino-3,4,5,6-tetrafluoro-β-oxobenzenepropanoic acid ethyl ester. This product can be converted to 5-acetylamino-1-cyclopropyl-6,7,8-trifluoro-1,4-dihydro-4-oxoquinoline-3-carboxylic acid ethyl ester by a three step reaction. The 2-acetylamino-3,4,5,6-tetrafluoro-β-oxobenzene-propanoic acid ethylester is first treated with triethylorthoformate and acetic anhydride. After removal of the solvent the residue is treated with a solution of cyclopropylamine in t-butanol. After the reaction is complete a solution of potassium t-butoxide in t-butanol is added. The resulting product is 5-acetylamino-1-cyclopropyl-6,7,8-trifluoro-1,4-dihydro-4-oxo-quinoline-3-carboxylic acid ethyl ester. The ester is hydrolyzed to form 1-cyclopropyl-5-amino-6,7,8-trifluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid. The compounds of the invention having structural formula VIa or VIb are either known compounds or they may be prepared from known starting materials by standard procedures or by variations thereof. For example, 3-pyrrolidinemethanamines having the structural formula D ##STR19## may be readily prepared from the known starting material methyl 5-oxo-1-(phenylmethyl)-3-pyrrolidinecarboxylate, A, [J. Org. Chem., 26, 1519 (1961)] by the following reaction sequence. ##STR20## The compound wherein R 3 is hydrogen, namely 3-pyrrolidinemethanamine, has been reported in J. Org. Chem., 26, 4955 (1961). Thus compound A may be converted to the corresponding amide B by treatment with R 3 NH 2 ; for example, a saturated solution of ethylamine in an alkanol such as methyl alcohol may be utilized. The diamide B may next be reduced to produce the corresponding diamine C. This reduction may be carried out using lithium aluminum hydride, for example, in a convenient solvent such as tetrahydrofuran. Compound C may next be debenzylated, for example using hydrogen and 20% palladium on carbon catalyst to produce the diamine D. Alternatively, when R=H in C, the primary amine function may be protected with a group R 4 as defined, hereinabove. For example, the primary amine function may be acylated with an acyl halide such as acetyl chloride by well known procedures. The primary amine function of C may also be converted to a carbamate ester such as the ethyl ester by treatment with ethyl chloroformate in the presence of a strong base such as 1,8-diazabicyclo[5.4.0]undec-7-ene in a convenient solvent such as methylene chloride. The benzyl group may next be removed, for example as described above for compound C, thereby producing compound D where R is --CO 2 Et, which after conversion to a compound of the type VIa or VIb may be reacted with a compound having the structural formula IV or V to thereby produce a corresponding compound having the structural formula I or Ia. The --CO 2 Et group may be removed by standard procedures. Likewise spiroamino compounds represented by structural formula VIb may be readily prepared from the known starting material 3-ethoxycarbonyl-5-oxo-3-pyrrolidineacetic acid ethyl ester [J. Org. Chem. 46, 2757 (1981)] by the following reaction sequence. ##STR21## The compound 2,7-diazaspiro[4.4]nonane where R 3 is H is described in the above reference. Thus compound E may be converted to the corresponding amide F by treatment with R 3 NH 2 , for example, methyl amine in water followed by benzylation which may be carried out with sodium hydride and benzyl chloride to give G. Reduction to the diamine H may be accomplished with lithium aluminum hydride. Subsequent debenzylation, for example, with hydrogen and 20% palladium on carbon catalyst produces the diamine J. The compounds of the invention display antibacterial activity when tested by the microtitration dilution method as described in Heifetz, et al, Antimicr. Agents & Chemoth., 6, 124 (1974), which is incorporated herein by reference. The compounds of the invention are capable of forming both pharmaceutically acceptable acid addition and/or base salts. Base salts are formed with metals or amines, such as alkali and alkaline earth metals or organic amines. Examples of metals used as cations are sodium, potassium, magnesium, calcium, and the like. Examples of suitable amines are N,N'-dibenzylethylenediamine, chloroprocaine, choline, diethanolamine, ethylenediamine, N-methylglucamine, and procaine. Pharmaceutically acceptable acid addition salts are formed with organic and inorganic acids. Examples of suitable acids for salt formation are hydrochloric, sulfuric, phosphoric, acetic, citric, oxalic, malonic, salicyclic, malic, gluconic, fumaric, succinic, ascorbic, maleic, methanesulfonic, and the like. The salts are prepared by contacting the free base form with a sufficient amount of the desired acid to produce either a mono or di, etc salt in the conventional manner. The free base forms may be regenerated by treating the salt form with a base. For example, dilute solutions of aqueous base may be utilized. Dilute aqueous soldium hydroxide, potassium carbonate, ammonia, and sodium bicarbonate solutions are suitable for this purpose. The free base forms differ from their respective salt forms somewhat in certain physical properties such as solubility in polar solvents, but the salts are otherwise equivalent to their respective free base forms for purposes of the invention. Use of excess base where R' is hydrogen gives the corresponding basic salt. The compounds of the invention can exist in unsolvated as well as solvated forms, including hydrated forms. In general, the solvated forms, including hydrated forms and the like are equivalent to the unsolvated forms for purposes of the invention. The alkyl groups contemplated by the invention comprise both straight and branched carbon chains of from one to about six carbon atoms. Representative of such groups are methyl, ethyl, propyl, isopropyl, and the like. The cycloalkyl groups contemplated by the invention comprise those having three to six carbon atoms such as cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl. The alkoxy groups contemplated by the invention comprise both straight and branched carbon chains of from one to about six carbon atoms unless otherwise specified. Representative of such groups are methoxy, ethoxy, propoxy, i-propoxy, t-butoxy, hexoxy, and the like. The term, haloalkyl, is intended to include halogen substituted straight and branched carbon chains of from two to four carbon atoms. Those skilled in the art will recognize that the halogen substitutent may not be present on the α-carbon atom of the chain. Representative of such groups are β-fluoroethyl, β-chloroethyl, β,β-dichloroethyl, β-chloropropyl, β-chloro-2-propyl, -iodobutyl, and the like. The term halogen is intended to include fluorine, chlorine, bromine, and iodine unless otherwise specified. Certain compounds of the invention may exist in optically active forms. The pure D isomer, pure L isomer as well as mixtures thereof; including the racemic mixtures, are contemplated by the invention. Additional asymmetric carbon atoms may be present in a substitutent such as an alkyl group. All such isomers as well as mixtures thereof are intended to be included in the invention. The compounds of the invention can be prepared and administered in a wide variety of oral and parenteral dosage forms. It will be obvious to those skilled in the art that the following dosage forms may comprise as the active component, either a compound of formula I or a corresponding pharmaceutically acceptable salt of a compound of formula I. For preparing pharmaceutical compositions from the compounds described by this invention, inert, pharmaceutically acceptable carriers can be either solid or liquid. Solid form preparations include powders, tablets, dispersible granules, capsules, cachets, and suppositories. A solid carrier can be one or more substances which may also act as diluents, flavoring agents, solubilizers, lubricants, suspending agents, binders, or tablet disintegrating agents; it can also be an encapsulating material. In powders, the carrier is a finely divided solid which is in admixture with the finely divided active compound. In the tablet the active compound is mixed with carrier having the necessary binding properties in suitable proportions and compacted in the shape and size desired. The powders and tablets preferably contain from 5 or 10 to about 70 percent of the active ingredient. Suitable solid carriers are magnesium carbonate, magnesium sterate, talc, sugar, lactose, pectin, dextrin, starch, gelatin, tragacanth, methyl cellulose, sodium carboxymethyl cellulose, a low melting wax, cocoa butter, and the like. The term "preparation" is intended to include the formulation of the active compound with encapsulating material as carrier providing a capsule in which the active component (with or without other carriers) is surrounded by carrier, which is thus in association with it. Similarly, cachets are included. Tablets, powders, cachets, and capsules can be used as solid dosage forms suitable for oral administration. Liquid form preparations include solutions, suspensions and emulsions. As an example may be mentioned water or water-propylene glycol solutions for parenteral injection. Such solutions are prepared so as to be acceptable to biological systems (isotonicity, pH, etc). Liquid preparations can also be formulated in solution in aqueous polyethylene glycol solution. Aqueous solutions suitable for oral use can be prepared by dissolving the active component in water and adding suitable colorants, flavors, stabilizing, and thickening agents as desired. Aqueous suspension suitable for oral use can be made by dispersing the finely divided active component in water with viscous material, i.e., natural or synthetic gums, resins, methyl cellulose, sodium carboxymethyl cellulose, and other well-known suspending agents. Preferably, the pharmaceutical preparation is in unit dosage form. In such form, the preparation is subdivided into unit doses containing appropriate quantities of the active component. The unit dosage form can be a packaged preparation, the package containing discrete quantities of preparation, for example, packeted tablets, capsules, and powders in vials or ampules. The unit dosage form can also be a capsule, cachet, or tablet itself or it can be the appropriate number of any of these packaged forms. The quantity of active compound in a unit dose of preparation may be varied or adjusted from 1 mg to 100 mg according to the particular application and the potency of the active ingredient. In therapeutic use as agents for treating bacterial infections the compounds utilized in the pharmaceutical method of this invention are administered at the initial dosage of about 3 mg to about 40 mg per kilogram daily. A daily dose range of about 6 mg to about 14 mg per kilogram is preferred. The dosages, however, may be varied depending upon the requirements of the patient, the severity of the condition being treated, and the compound being employed. Determination of the proper dosage for a particular situation is within the skill of the art. Generally, treatment is initiated with smaller dosages which are less than the optimum dose of the compound. Thereafter, the dosage is increased by small increments until the optimum effect under the circumstances is reached. For convenience, the total daily dosage may be divided and administered in portions during the day if desired. The following nonlimiting examples illustrate the inventors' preferred methods for preparing the compounds of the invention. PREPARATION OF STARTING MATERIALS Example A 1-Ethenyl-6,7,8-trifluoro-1,8-dihydro-4-oxo-3-quinolinecarboxylic acid 6,7,8-Trifluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid ethyl ester was treated with dibromo ethane to afford the 1-ethenyl-6,7,8-trifluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid ester, mp 134-135° C. Subsequent hydrolysis with hydrochloric acid gave 1-ethenyl-6,7,8-trifluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid, mp 186-187° C. Example B 6,7,8-Trifluoro-1-(2-fluoroethyl)-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid In identical fashion, 6,7,8-trifluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid ethyl ester was converted to 6,7,8-trifluoro-1-(2-fluoroethyl)-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid, mp 207-211° C. Example C N-Methyl-3-pyrrolidinemethanamine N-Methyl-5-oxo-1-(phenylmethyl)-3-pyrrolidinecarboxamide A mixture of 100 g (0.43 mole) of methyl 5-oxo-1-(phenylmethyl)-3-pyrrolidinecarboxylate [J. Org. Chem., 26, 1519 (1961)], 500 ml methanol and 100 g (3.2 mole) of methylamine was heated at 100° C. in a pressure reactor for 16 hours. The reaction mixture was cooled and the ammonia and methanol were removed under pressure. The residue was taken up in dichloromethane and washed 3×100 ml 1N sodium hydroxide. The organic layer was dried over magnesium sulfate and the solvent removed at reduced pressure to give 88.3 g of N-methyl-5-oxo-1-(phenylmethyl)-3-pyrrolidinecarboxamide as a white solid, mp 82.5-83.0° C. ______________________________________Analysis calculated for C.sub.13 H.sub.16 N.sub.2 O.sub.2 :______________________________________ C, 67.22; H, 6.94; N, 12.06Found C, 66.98; H, 6.69; N, 12.02.______________________________________ This material was used in the next step. N-Methyl-1-(phenylmethyl)-3-pyrrolidinemethanamine To a suspension of 37.4 g (1.00 mole) lithium aluminum hydride in 1000 ml tetrahydrofuran, was added a solution of 88.3 g (0.380 mole) of N-methyl-5-oxo-1-(phenylmethyl)-3-pyrrolidinecarboxamide in tetrafuran dropwise under nitrogen. The reaction was then refluxed overnight. The reaction flask was cooled in an ice bath and 37.4 ml of water 37.4 ml of 15% sodium hydroxide and 112.2 ml of water were added. The precipitated solids were filtered and washed with hot ethanol. The combined filtrates were concentrated, then dissolved in dichloromethane, filtered, dried over magnesium sulfate, and the solvent evaporated under reduced pressure to give 68.7 g of N-methyl-1-(phenylmethyl)-3-pyrrolidinemethanamine as an oil. This material was used without further purification in the step. N-Methyl-3-pyrrolidinemethanamine A mixture of 67.3 g (0.32 mole) of N-methyl-1-(phenylmethyl)-3-pyrrolidinemethanamine, 3 g of 20% palladium on carbon, and 600 ml of methanol was shaken in an atmosphere of hydrogen at about 4.5×10 5 Pa and at room temperature for 18 hours. Another 3 g of 20% palladium on carbon was added and the hydrogenation continued for 6.5 hours. Another 3.0 g of 20% palladium on charcoal was added and the hydrogenation continued for another 4.5 hours. The catalyst was filtered and the filtrate evaporated under reduced pressure. The residue was distilled under vacuum (72-76° C, 10.5 mm Hg) to give 8.32 g N-methyl-3-pyrrolidinemethanamine. Example D N-Ethyl-3-pyrrolidinemethanamine N-Ethyl-5-oxo-1-(phenylmethyl)-3-pyrrolidinecarboxamide A mixture of 200 g (0.86 mole) of methyl-5-oxo-1-(phenylmethyl)pyrrolidinecarboxylate (J. Org. Chem., 26, 1519 (1961)], 1000 ml methanol and 200 g (4.4 mole) of ethylamine was heated at 100° C. in a pressure reactor for 17.2 hours. The reaction mixture was cooled and the excess ethylamine and methanol were removed under reduced pressure. The residue was taken up in dichloromethane and washed 3×150 ml 1N sodium hydroxide. The organic layer was dried over magnesium sulfate and the solvent removed at reduced pressure to give 104.6 g of N-ethyl-5-oxo-1-(phenylmethyl)-3-pyrrolidinecarboxamide as a white solid, mp 97-99° C. This materials was used in the next step. N-Ethyl-1-(phenylmethyl)-3-pyrrolidinemethanamine To a suspension of 108.8 g (2.86 mole) lithium aluminum hydride in 800 ml tetrahydrofuran, was added a solution of 194.5 g (0.79 mole) of N-ethyl-5-oxo-1-(phenylmethyl)-3-pyrrolidinecarboxamide in 600 ml tetrahydrofuran dropwise under nitrogen. The reaction was then refluxed four hours. The reaction flask was cooled in an ice bath and 108 ml of water, 108 ml of 15% sodium hydroxide, and 324 ml of water were added. The precipitated solids were filtered and washed with hot ethanol. The combined filtrates were concentrated, then dissolved in dichloromethane, filtered, dried over magnesium sulfate, and the solvent evaporated under reduced pressure to give 151.9 g of N-ethyl-1-(phenylmethyl)-3-pyrrolidinemethanamine as an oil. This material was used without further purification in the next step. N-Ethyl-3-pyrrolidinemethanamine A mixture of 151.6 g (0.69 mole) of N-ethyl-1-(phenylmethyl)-3-pyrrolidinemethanamine, 5 g of 20% palladium on carbon, and 1100 ml of ethanol was shaken in an atmosphere of hydrogen at about 4.5×10 5 Pa and at room temperature for 21.6 hours. Another 5 g of 20% palladium on carbon was added and the hydrogenation continued for 24 hours. The catalyst was filtered and the filtrate evaporated under reduced pressure. The residue was distilled under vacuum (88-91° C., 11.5 mm Hg) to give 66.0 g N-ethyl-3-pyrrolidinemethanamine. Example E N-(2,2,2-Trifluoroethyl)-3-pyrrolidinemethanamine 5-Oxo-1-(phenylmethyl)-N-(2,2,2-trifluoroethyl)-3-pyrrolidine carboxamide A mixture of 21.9 g (0.10 mole) methyl 5-oxo-1-(phenylmethyl)-3-pyrrolidinecarboxylate in 150 ml tetrahydrofuran, was cooled to 0° C. in an ice bath under nitrogen and 24.3 g (0.15 mole) carbonyl diimidazole was added. The reaction was stirred at 0° C. for 30 minutes, then at room temperature for 30 minutes. A solution of 13.6 g (0.10 mole) of 2,2,2-trifluoroethylamine hydrochloride, 15.2 g (0.10 mole) 1,8-diazabicyclo[5.4.0]undec-7-ene and 100 ml tetrahydrofuran was added. The reaction was stirred at room temperature overnight. The solvent was removed at reduced pressure. The residue was taken up in dichloromethane and washed 3×150 ml saturated sodium bicarbonate. The organic layer was dried over magnesium sulfate and the solvent removed under reduced pressure. The product was purified by column chromatography on silica with ethyl acetate to give 8.50 g of 5-oxo-1-(phenylmethyl)-N-(2,2,2-trifluoroethyl)-3-pyrrolidinecarboxamide, mp 110-112° C. This material was used in the next step. 1-(Phenylmethyl)-N-(2,2,2-trifluoroethyl)-3-pyrrolidinemethanamine A mixture of 8.50 g (28.3 mole) of 5-oxo-1-(phenylmethyl)-N-(2,2,2-trifluoroethyl)-3-pyrrolidinecarboxamide in 100 ml tetrahydrofuran was added dropwise to 3.22 g (84.9 mmole) of lithium aluminum hydride in 50 ml tetrahydrofuran. The reaction was refluxed two hours, then stirred at room temperature overnight. The reaction was cooled in an ice bath and 3.2 ml of water, 3.2 ml of 15% sodium hydroxide, and 9.6 ml of water were added. The precipitated salts were filtered and washed with hot ethanol. The combined filtrates were concentrated under reduced pressure. The residue was taken up in dichloromethane, filtered, and dried over magnesium sulfate. The solvent was removed at reduced pressure to give 7.15 g of 1-(phenylmethyl)-N-(2,2,2-trifluoroethyl)-3-pyrrolidinemethanamine. This material was used without further purification in the next step. N-(2,2,2-Trifluoroethyl)-3-pyrrolidinemethanamine A mixture of 7.15 g (26.3 mmole) 1-(phenylmethyl)-N-(2,2,2-trifluoroethyl)-3-pyrrolidinemethanamine 100 ml of methanol and 0.7 g of 20% palladium on carbon was shaken in an atmosphere of hydrogen at about 4.5×10 5 Pa and at room temperature for 24 hours. The catalyst was filtered and the filtrate evaporated under reduced pressure. The residue was distilled under vacuum (63-65° C., 2.8 mm Hg) to give 2.55 g of N-(2,2,2-trifluoroethyl)-3-pyrrolidinemethanamine. Example F N-Propyl-3-pyrrolidinemethanamine 5-Oxo-1-(phenylmethyl)-N-propyl-3-pyrrolidinecarboxamide To a solution of 10.9 g (50 mmole) of 5-oxo-1-phenylmethyl)-3-pyrrolidinecarboxylic acid in 150 ml of acetonitrile was added 9.73 g (60 mmole) of 1,1'-carbonyldiimidazole. The reaction was heated to 60° C. for one hour, cooled to room temperature and treated with 4.13 g (70 mmole) of n-propylamine. After stirring for two hours, the solvent was removed in vacuo and the residue partitioned between ether and water. The organic layer was washed with water, 1N hydrochloric acid, dried over magnesium sulfate, filtered, and evaporated in vacuo to give 12.0 g of 5-oxo-1-(phenylmethyl)-N-propyl-3-pyrrolidinecarboxamide, mp 86-87° C. 1-(Phenylmethyl)-N-propyl-3-pyrrolidinemethanamine To a suspension of 8.2 g (0.2 mole) of lithium aluminum hydride in 150 ml of dry tetrahydrofuran was added portionwise, 12.0 g (45.6 mmole) of solid 5-oxo-1-(phenylmethyl)-N-propyl-3-pyrrolidinecarboxamide. When the addition was complete, the reaction mixture was stirred at room temperature for 18 hours and then at reflux for two hours. After cooling to room temperature, the mixture was treated dropwise, successively, with 8 ml of water, 8 ml of 15% aqueous sodium hydroxide and 24 ml of water, titrating the final addition to produce a granular precipitate. The solid was removed by filtration, washed with tetrahydrofuran and the filtrate evaporated in vacuo to give 9.6 g of 1-(phenylmethyl)-N-propyl-3-pyrrolidinemethanamine, as a heavy syrup. This material was used for the next step without further purification. N-Propyl-3-pyrrolidinemethanamine A mixture of 14.0 g (60.0 mmole) of 1-(phenylmethyl)-N-propyl-3-pyrrolidinemethanamine, 1.0 g of 20% palladium on carbon and 140 ml of methanol was shaken in an atmosphere of hydrogen at about 4.5×10 5 Pa and room temperature for 24 hours. The catalyst was removed by filtering through Celite, the filtrate concentrated and distilled in vacuo to give 7.1 g of N-propyl-3-pyrrolidinemethanamine, bp 49-50° C./0.25 mm. Example G N-Cyclopropyl-3-pyrrolidinemethanamine 5-Oxo-1-(phenylmethyl)-N-cyclopropyl-3-pyrrolidinecarboxamide To a solution of 16.4 g (75 mmole) of 5-oxo-1-(phenylmethyl)-3-pyrrolidinecarboxylic acid in 150 ml of acetonitrile was added 13.8 g (85 mmole) of 1,1'-carbonyldiimidazole. The reaction was heated to 60° C. for one hour, cooled to room temperature and treated with 4.85 g (85 mmole) of cyclopropylamine. The reaction was stirred at room temperature for 18 hours, the solvent removed in vacuo and the residue partitioned between chloroform and water. The organic layer was washed with water, 1N hydrochloric acid, dried over magnesium sulfate, filtered, and evaporated in vacuo to give 18.3 g of 5-oxo-1-(phenylmethyl)-N-cyclopropyl-3-pyrrolidinecarboxamide, mp 94-96° C. 1-(Phenylmethyl)-N-cyclopropyl-3-pyrrolidine methanamine To a suspension of 8.2 g (0.20 mole) of lithium aluminum hydride in 150 ml of dry tetrahydrofuran was added portionwise 18.0 g (70.0 mmole) of solid 5-oxo-1-(phenylmethyl)-N-cyclopropyl-3-pyrrolidinecarboxamide. When the addition was complete, the reaction mixture was stirred at room temperature for 18 hours and then at reflux for two hours. After cooling to room temperature, the mixture was treated dropwise, successively, with 8 ml of water, 8 ml of 15% aqueous sodium hydroxide and 24 ml of water, titrating the final addition to produce a granular precipitate. The solid was removed by filtration, washed with tetrahydrofuran and the filtrate evaporated in vacuo to give 16.0 g of 1-(phenylmethyl)-N-cyclopropyl-3-pyrrolidinemethanamine, as a heavy oil. This was used for the next step without further purification. N-Cyclopropyl-3-pyrrolidinemethanamine A mixture of 13.6 g (59.0 mmol) of 1-(phenylmethyl)-N-cyclopropyl-3-pyrrolidinemethanamine, 0.5 g of 20% palladium on carbon and 140 ml of methanol was shaken in an atmosphere of hydrogen at about 4.5×10 5 Pa and room temperature for 24 hours. The catalyst was removed by filtering through Celite, the filtrate concentrated and distilled in vacuo to give 6.3 g of N-cyclopropyl-3-pyrrolidinemethanamine, bp 88-90°/13 mm. Example H N-(2-Propyl)-3-pyrrolidinemethanamine 5-Oxo-1-(phenylmethyl)-N-(2-propyl)-3-pyrrolidinecarboxamide To a solution of 16.4 g (75.0 mmole) of 5-oxo-1-(phenylmethyl)-3-pyrrolidinecarboxylic acid in 150 ml of acetonitrile was added 13.8 g (85.0 mmole) of 1,1-'carbonyldiimidazole. The reaction was heated to 60° C. for one hour, cooled to room temperature and treated with 5.0 g (85 mmole) of isopropylamine. The reaction was stirred at room temperature for 18 hours, the solvent removed in vacuo and the residue partitioned between chloroform and water. The organic layer was washed with water, 1N hydrochloric acid, dried over magnesium sulfate, and evaporated in vacuo to give 18.6 g of 5-oxo-1-(phenylmethyl)-N-(2-propyl)-3-pyrrolidinecarboxamide, mp 122-124° C. 1-(Phenylmethyl)-N-(2-propyl)-3-pyrrolidinemethanamine To a suspension of 8.2 g (0.2 mole) of lithium aluminum hydride in 150 ml of dry tetrahydrofuran was added portionwise, 18.3 g (70.0 mmole) of solid 5-oxo-1-phenylmethyl)-N-(2-propyl)-3-pyrrolidinecarboxamide. When the addition was complete, the reaction mixture was stirred at room temperature for 18 hours and then refluxed for two hours. After cooling to room temperature, the mixture was treated dropwise, successively, with 8 ml of water, 8 ml of 15% aqueous sodium hydroxide and 24 ml of water, titrating the final addition to produce a granular precipitate. The solid was removed by filtration, washed with tetrahydrofuran and the filtrate evaporated in vacuo to give 15.6 g of 1-(phenylmethyl)-N-(2-propyl)-3-pyrrolidinemethanamine as a heavy syrup. This materials was used for the next step without further purification. N-(2-Propyl)-3-pyrrolidinemethanamine A mixture of 13.4 g (58.0 mmol) of 1-phenylmethyl-N-(2-propyl)-3-pyrrolidinemethanamine, 1.0 g of 20% palladium on carbon and 130 ml of methanol was shaken in an atmosphere of hydrogen at about 4.5×10 5 Pa and room temperature for 24 hours. The catalyst was removed by filtration through Celite; the filtrate concentrated and distilled in vacuo to give 6.3 g of N-(2-propyl)-3-pyrrolidinemethanamine, bp 58-60° C./3.5 mm. Example I 1,1-Dimethylethyl(3-pyrrolidinyl)carbamate 1,1-Dimethylethyl[1-(phenylmethyl)-3-pyrrolidinyl]carbamate A solution of 77.0 g (0.44 mole) of 3-amino-1-(phenylmethyl)pyrrolidine [J. Med. Chem., 24, 1229 (1981)], 440 ml (0.44 mole) 1.0N sodium hydroxide and 600 ml of tertiarybutyl alcohol was treated dropwise with 98.2 g (0.45 mole) of di-tertiarybutyl dicarbomate. The reaction was stirred at room temperature for 18 hours and the solvent removed in vacuo. The residue was partitioned between ether and water. The aqueous layers were reextracted with ether, the combined ether layers were washed with water, dried (MgSO 4 ), filtered, and evaporated on a steam bath replacing the ether with petroleum ether. The crystals which formed were removed by filtration, washed with ether/petroleum ether (1:1), and dried in vacuo to give 84.8 g of 1,1-dimethylethyl[1-(phenylmethyl)-3-pyrrolidinyl]carbamate, mp 114-115° C. A second crop (16.7 g) was obtained by concentrating the filtrate. 1,1-Dimethylethyl(3-pyrrolidinyl)carbamate A mixture of 101.5 g (0.37 mole) of 1,1-dimethylethyl[1-(phenylmethyl)-3-pyrrolidinyl]carbamate, 5.0 g of 20% palladium on carbon and 1 liter of tetrahydrofuran was shaken in an atmosphere of hydrogen at about 50 psi and room temperature for 24 hours. The catalyst was removed by filtering through Celite, and the filtrate was concentrated in vacuo to give 6.8 g of 1,1-dimethylethyl (3-pyrrolidinyl)carbamate which solidified upon standing and was of sufficient purity to be used as is for the ensuing steps. Example J 2-[(3-Pyrrolidinylmethyl)amino]ethanol N-(2-Hydroxyethyl)-5-oxo-1-(phenylmethyl)-3-pyrrolidinecarboxamide A mixture of 46.7 g (0.2 mole) of methyl 5-oxo-1-(phenylmethyl)-3-pyrrolidinecarboxylate [J. Org. Chem., 26, 1519 (1961)], 36.7 g (0.6 mole) of 2-aminoethanol and 500 ml methanol was refluxed overnight. The reaction was cooled to room temperature and the solvent removed at reduced pressure. The residue was taken up in dichloromethane and extracted 3×100 ml 1N sodium hydroxide. The aqueous layer was taken to pH 5, extracted 3×150 ml dichloromethane, then taken to pH 8 and again extracted 3×150 ml dichloromethane. The aqueous layer was concentrated at reduced pressure and the resulting slurry stirred in dichloromethane. The salts were filtered off. The combined organic layers were dried over magnesium sulfate, the solvent removed at reduced pressure to yield 47.9 g of N-(2-hydroxyethyl)-5-oxo-1-(phenylmethyl)-3-pyrrolidinecarboxamide as an oil. This was used in the next step without further purification. 2-[[[1-(Phenylmethyl)-3-pyrrolidinyl]methyl]amino]ethanol A mixture of 46.6 g (0.18 mole) of N-(2-hydroxyethyl)-5-oxo-1-(phenylmethyl)-3-pyrrolidinecarboxamide in 200 ml of tetrahydrofuran was added dropwise to a slurry of 20.25 g (0.534 mole) of lithium aluminum hydride in 150 ml tetrahydrofuran. The reaction was refluxed three hours, then cooled in an ice bath. The work up consisted of sequential addition of 20 ml water, 20 ml 15% sodium hydroxide then 60 ml water. The reaction was filtered and the precipitate washed with ethanol. The filtrate was concentrated at reduced pressure, the residue taken up in dichloromethane, dried over magnesium sulfate, and the solvent removed at reduced pressure to give 32.31 g of 2-[[[1-(phenylmethyl)-3-pyrrolidinyl]methyl]amino]ethanol as an oil. This material was used in the next step without further purification. 2-[(3-Pyrrolidinylmethyl)amino]ethanol A mixture of 32.3 g of 2-[[[1-(phenylmethyl)-3-pyrrolidinyl]methyl]amino]ethanol, 330 ml of methanol and 3 g of 20% palladium on charcoal was shaken in an atmosphere of hydrogen at about 4.5×10 5 Pa and at room temperature for 18 hours. The solvents were then removed at reduced pressure. The residue was distilled under vacuum (bp 129-131° C., 1.5 mm Hg) to give 11.43 g of 2-[(3-pyrrolidinylmethyl)amino]ethanol. Example K 2-Methyl-2,7-diazaspiro[4.4]nonane Dihydrochloride 2-Methyl-2,7-diazaspiro[4.4]nonane-1,3,8-trione A solution of 20.3 g (0.084 mole) 3-ethoxycarbonyl-5-oxo-3-pyrrolidineacetic acid, ethyl ester [J. Org. Chem., 46, 2757 (1981)] in 40 ml of 40% aqueous methylamine was stirred at room temperature overnight, then placed in an oil bath and gradually heated to 220° C. over 30 minutes allowing volatiles to distill from the open flask. The crude product was crystallized from ethanol to afford 12.6 g of 2-methyl-2,7-diazaspiro[4.4]nonane-1,3,8-trione, mp 201-204° C. ______________________________________Analysis calculated for C.sub.8 H.sub.10 N.sub.2 O.sub.3 :______________________________________ C, 52.74; H, 5.53; N, 15.38Found C, 52.87; H, 5.60; N, 15.25.______________________________________ 7-Benzyl-2-methyl-2,7-diazaspiro[4.4)nonane-1,3,8-trione A solution of 1.82 g (10 mmol) of 2-methyl-2,7-diazaspiro[4.4]nonane-1,3,8-trione in 20 ml N,N-dimethylformamide was added gradually under a nitrogen atmosphere to 0.05 g (10.4 mmol) of 50% oil suspension of sodium hydride which had been previously washed twice with toluene and covered with 10 ml N,N-dimethylformamide. After stirring one hour there was added 1.40 g (11 mmol) of benzyl chloride and stirring was continued overnight at room temperature. After concentrating to a small volume in vacuo, the residue was diluted with 40 ml water and extracted twice with dichloromethane. The combined organic phase was washed with water, dried over magnesium sulfate, and evaporated to give a solid. Crystallization from toluene:hexane to afford 1.74 g of 7-benzyl-2-methyl-2,7-diazaspiro[4.4]nonane-1,3,8-trione, mp 157-158° C. ______________________________________Analysis calculated for C.sub.15 H.sub.16 N.sub.2 O.sub.3 :______________________________________ C, 66.16; H, 5.92; N, 10.27Found C, 66.45; H, 5.79; N, 10.09.______________________________________ 7-Phenylmethyl-2-methyl-2,7-diazaspiro[4.4]nonane Dihydrochloride A solution of 1.36 g (5.0 mmol) 7-phenylmethyl-2-methyl-2,7-diazaspiro[4.4]nonane-1,3,8-trione in 50 ml tetrahydrofuran was added dropwise to a suspension of 0.95 g (25 mmol) lithium aluminum hydride in 30 ml tetrahydrofuran. The mixture was stirred overnight at room temperature, refluxed one hour, cooled, and treated dropwise with 0.95 ml water, 0.95 ml 15% sodium hydroxide solution, and 2.8 ml water. After removal of the inorganic solids by filtration, the filtrate was concentrated in vacuo to give a syrup which was dissolved in isopropanol and treated with excess 6N hydrogen chloride in isopropanol. Crystallization afforded 0.97 g of the title compound, mp 233-234° C. ______________________________________Analysis calculated for C.sub.15 H.sub.24 N.sub.2 Cl.sub.2 :______________________________________ C, 59.40; H, 7.98; N, 9.24; Cl, 23.38Found C, 59.37; H, 7.98; N, 9.03; Cl, 23.09.______________________________________ 2-Methyl-2,7-diazaspiro[4.4]nonane Dihydrochloride A solution of 7-benzyl-2-methyl-2,7-diazaspiro ]4.4]nonane dihydrochloride in 150 ml of methanol with 1.0 g 20% palladium on carbon catalyst was hydrogenated at 4.5×10 5 Pa for two days. After filtration, the filtrate was concentrated to a thick syrup which crystallized on addition of acetonitrile to give 11.5 g of 2-methyl-2,7-diazaspiro[4.4]nonane dihydrochloride, softened at 164° C. and melted at 168-170 ° C. ______________________________________Analysis calculated for C.sub.8 H.sub.18 N.sub.2 Cl.sub.2 :______________________________________ C, 45.08; H, 8.51; N, 13.15; Cl, 33.27Found C, 45.24; H, 8.77; N, 13.18; Cl, 33.26.______________________________________ Example L 2-Ethyl-2,7-diazaspiro[4.4]nonane Dihydrochloride 2-Ethyl-2,7-diazaspiro[4.4]nonane-1,3,8-trione A suspension of 24.3 g (0.10 mmole) 3-ethoxycarbonyl-5-oxo-3-pyrrolidineacetic acid, ethyl ester in an excess of 2N sodium hydroxide, was stirred three hours at room temperature, acidified with dilute hydrochloric acid, and evaporated to dryness in vacuo. The product, 3-carboxy-5-oxo-3-pyrrolidineacetic acid, was taken up in isopropyl alcohol, separated from insoluble sodium chloride by filtration, concentrated to a syrup and dissolved in 100 ml 70% ethylamine. The solution was gradually heated in an oil bath up to 230° C. allowing volatiles to distill and then maintained at 230-240° C. for ten minutes. After cooling, the product was crystallized from isopropyl alcohol to afford 10.1 g of 2-ethyl-2,7-diazaspiro[4.4]nonane-1,3,8-trione, mp 168-169° C. ______________________________________Analysis calculated for C.sub.9 H.sub.12 N.sub.2 O.sub.3 :______________________________________ C, 55.09; H, 6.17; N, 14.28Found C, 55.03; H, 5.84; N, 14.01.______________________________________ 2-Ethyl-7-benzyl-2,7-diazaspiro[4.4]nonane-1,3,8-trione A suspension of sodium hydride (2.20 g of 60% oil suspension (0.055 mole) washed with toluene) in 50 ml N,N-dimethylformamide was treated gradually with a solution of 10.0 g (0.051 mole) 2-ethyl-2,7-diazaspiro[4.4]nonane-1,3,8-trione in 100 ml N,N-dimethylformamide. After stirring 15 minutes, there was added dropwise 6.4 ml (0.055 mole) benzyl chloride and the mixture was stirred overnight, concentrated in vacuo and shaken with water-methylene chloride. The organic layers were dried, evaporated, and the product crystallized from toluene-hexane to afford 11.1 g of the title compound, mp 125-126.5° C. ______________________________________Analysis calculated for C.sub.16 H.sub.18 N.sub.2 O.sub.3 :______________________________________ C, 67.11; H, 6.34; N, 9.79Found C, 67.41; H, 6.33; N, 9.79.______________________________________ 2-Benzyl-7-ethyl-2,7-diazaspiro[4.4]nonane Dihydrochloride A solution of 11.0 g (0.038 mole) 2-ethyl-7-benzyl-2,7-diazaspiro[4.4]nonane-1,3,8-trione in 100 ml tetrahydrofuran was added dropwise to a suspension of 6.00 g (0.158 mole) lithium aluminum hydride in 250 ml tetrahydrofuran. After stirring overnight, the mixture was refluxed one hour, cooled, and treated dropwise with 6 ml water, 6 ml 15% sodium hydroxide, and 18 ml water. Inorganic solids were separated by filtration and the filtrate was concentrated, taken up in ether, dried with magnesium sulfate, and reevaporated. The resulting syrup was dissolved in isopropyl alcohol and treated with excess hydrogen chloride in isopropyl alcohol to afford 9.63 g of the title compound, mp 196-198° C. (dec). ______________________________________Analysis calculated for C.sub.16 H.sub.26 N.sub.2 Cl.sub.2 :______________________________________ C, 60.56; H, 8.26; N, 8.83; Cl, 22.35Found C, 60.51; H, 8.08; N, 8.69; Cl, 22.26.______________________________________ 2-Ethyl-2,7-diazaspiro[4.4]nonane Dihydrochloride A solution of 9.5 g (0.03 mole) 2-benzyl-7-ethyl-2,7-diazaspiro[4.4]nonane dihydrochloride in 100 ml methanol was hydrogenated with 1.0 g 20% palladium on carbon catalyst at 4.5×10 5 Pa for 22 hours. After filtration, the solution was concentrated to a syrup and crystallized from acetonitrile to afford 6.7 g of the title compound, mp 168-172° C. ______________________________________Analysis calculated for C.sub.9 H.sub.20 N.sub.2 Cl.sub.2 :______________________________________ C, 47.58; H, 8.86; N, 12.33; Cl, 31.21Found C, 47.70; H, 8.58; N, 12.39; Cl, 30.92.______________________________________ Example M 1-Cyclopropyl-6,7,8-trifluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic Acid 2,3,4,5-Tetrafluorobenzoylacetic Acid, Ethyl Ester To 25.2 g (0.117 mol) of sodium 2,3,4,5-tetrafluorobenzoate, prepared as a dry powder from 2,3,4,5-tetrafluorobenzoic acid [J. Org. Chem., 29, 2381 (1961)] and aqueous sodium hydroxide with concentration to dryness, was added 400 ml of dry ether and the suspension was cooled to 0° C. Slowly, 25 ml (≈2.5 equivalents) of oxalyl chloride in 50 ml of ether was added and the mixture brought to room temperature where it was maintained for 2.0 hours. It was filtered and concentrated to remove low boiling impurities. The residue was dissolved in 100 ml of ether and placed in an addition funnel. Meanwhile, 2.9 g (0.119 mol) of magnesium turnings were treated with 100 ml of absolute ethanol and 0.3 ml of carbon tetrachloride. To this mixture was added 18.6 ml (0.12 mol) of diethyl malonate in 75 ml of ether at a rate to keep the temperature just below reflux. When addition was complete, the reaction was refluxed for two hours. At -20° C., the etheral acid chloride was slowly added. When addition was complete, the reaction was brought to 0° C. over 18 hours. The mixture was poured into dilute hydrochloric acid and was extracted into dichloromethane which was dried (MgSO 4 ) and concentrated. The residue was then treated with 340 mg of p-toluenesulfonic acid in 600 ml of water at 100° C. for two hours with rapid stirring. The oil was extracted into dichloromethane, dried (MgSO 4 ) and concentrated. The residue was purified by column chromatography (silica gel, using toluene:hexane:ether, 4:5:1), to give 18.5 g of a reddish oil. This material was triturated with pentane to give 10.2 g of 2,3,4,5-tetrafluorobenzoylacetic acid, ethyl ester, mp 49-51° C. (2,3,4,5-Tetrafluorobenzoyl)-3-cyclopropylaminoacrylic Acid, Ethyl Ester To 10.2 g (38.5 mmol) of the 2-(2,3,4,5-tetrafluorobenzoylacetic acid, ethyl ester was added 8.4 g (57.0 mmol) of triethylorthoformate and 9.3 g (91.5 mmol) of acetic anhydride. The mixture was heated to 150° C. for two hours and was then placed under high vacuum at 75-85° C. for one hour. The residue dissolved, without purification, in 100 ml of isopropyl alcohol and treated with 2.4 ml of cyclopropylamine. The reaction was allowed to stand overnight. It was concentrated and purified by column chromatography (silica gel 70-200, using hexane:chloroform:isopropyl alcohol, 80:15:5). The product off the column was recrystallized from pentane to give 6.16 g of 2-(2,3,4,5-tetrafluorobenzoyl)-3-cyclopropylaminoacrylic acid, ethyl ester, mp 63-64° C. 1-Cyclopropyl-6,7,8-trifluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic Acid To 2.0 g (6.0 mmol) of the 2-(2,3,4,5-tetrafluorobenzoyl)-3-cyclopropylaminoacrylic acid, ethyl ester in 60 ml of dry dioxane was added 0.29 g of sodium hydride 50% dispersion) that was prewashed with pentane. The sodium hydride was delivered in 10 ml of dry tetrahydrofuran at 0° C. When evolution of hydrogen began to slow, the mixture was refluxed for two hours. It was concentrated, and the residue taken up in dichloromethane, which was water extracted, dried (MgSO 4 ), and concentrated. The residue was purified by column chromatography (silica gel 70-200 mesh, using chloroform:hexane:isopropanol, 4:5:1) to give 0.95 g of the 1-cyclopropyl-6,7,8-trifluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid, ethyl ester, mp 168-169° C. This material was dissolved in acetic acid at 100° C. and was treated with 10 ml of 0.5N hydrochloric acid for 2.5 hours. The mixture was cooled and water added. The solids were then collected to give 0.7 g of 1-cyclopropyl-1,4-dihydro-4-oxo-6,7,8-trifluoro-3-quinolinecarboxylic acid, mp 226-228° C. Example N 7-Chloro-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-naphthyridine-3-carboxylic Acid 4-[6-(Cyclopropylamino)-3-nitro-2-pyridinyl]-1-piperazinecarboxylic Acid, Ethyl Ester A solution of 126.0 g (0.4 mole) of 4-(6-chloro-3-nitro-2-pyridinyl)-1-piperazinecarboxylic acid, ethyl ester (prepared as described in European Patent Publication No. 9425), 76.1 g (0.5 mole) of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 28.6 g (0.5 mole) of cyclopropylamine and 500 ml of absolute ethanol was stirred at room temperature for 48 hours. The solution was then heated at reflux for four hours and concentrated in vacuo. The residue was partitioned between chloroform and water. The chloroform layer was dried over magnesium sulfate and concentrated in vacuo. The residue was triturated with ether to give 64.0 g of the title compound, mp 100-103° C. 4-[6-(Acetylcyclopropylamino)-3-nitro-2-pyridinyl]-1-piperazinecarboxylic Acid, Ethyl Ester A solution of 64.0 g (0.19 mole) of 4-[6-(cyclopropylamino)-3-nitro-2-pyridinyl]-1-piperazinecarboxylic acid, ethyl ester, 115 ml of acetic anhydride and 115 ml of acetic acid was heated on a steam bath for 36 hours. The solvents were removed in vacuo, the residue was triturated with a mixture of ethanol and toluene which was also evaporated in vacuo to give 68.3 g of the title compound, mp 90-93° C. 4-[6-(Acetylcyclopropylamino)-3-amino-2-pyridinyl]-1-piperazinecarboxylic Acid, Ethyl Ester A mixture of 17.0 g (45 mmole) of 4-[6-(acetylcyclopropylamino)-3-nitro-2-pyridinyl-1-piperazine carboxylic acid, ethyl ester, 1.5 g of Raney nickel and 180 ml of absolute ethanol was shaken in an atmosphere of hydrogen at about 50 psi and room temperature for approximately 24 hours. The catalyst was removed by filtering through Celite and the solvent removed in vacuo to give 15.2 g of the title compound, mp 149-150° C. 2-[4-(Ethoxycarbonyl)-1-piperazinyl]-6-(acetylcyclopropylamino)-3-pyridinediazonium Tetrafluoroborate A solution of 20.8 g (60 mmole) of 4-(6-acetylcyclopropylamino)-3-amino-2-pyridinyl]-1-piperazine carboxylic acid, ethyl ester, 44 ml of ethanol and 27 ml of 48% tetrafluoroboric acid was cooled to 0° C. and treated dropwise with a solution of 4.56 g (66 mmol) of sodium nitrite in 8 ml of water under a nitrogen atmosphere keeping the temperature 0-5° C. After the addition was complete, the reaction was stirred at 0-5° C. for one hour and treated with 150 ml of anhydrous ether keeping the temperature below 10° C. The solid was removed by filtration, the precipitate was washed with ethanol/ether (1:1), ether and dried in vacuo to give 24.5 g of the title compound, mp 100-105° C. (dec). 4-[6-(Acetylcyclopropylamino)-3-fluoro-2-pyridinyl]-1-piperazinecarboxylic Acid, Ethyl Ester To 800 ml of refluxing toluene was added in portions, as a solid, 46.2 g (0.1 mole) of 2-[4-(ethoxycarbonyl)-1-piperazinyl]-6-acetylcyclopropylamino)-3-pyridinediazonium tetrafluoroborate. After the addition was complete, the reaction was refluxed for ten minutes and the toluene was decanted from the insoluble precipitate. The toluene was evaporated in vacuo and the residue was partitioned between chloroform and water. The chloroform layer was washed with 5% aqueous sodium bicarbonate, water, dried over magnesium sulfate, and evaporated in vacuo to give 13.7 g of the title compound, as a viscous oil. An additional 10.2 g could be obtained by partitioning the original toluene insoluble material in chloroform and water. The organic layer was washed with 5% aqueous sodium bicarbonate, dried over magnesium sulfate, evaporated in vacuo and the residue was chromatographed on silica gel eluting with chloroform/ethyl acetate (6:4). This fraction was also a viscous oil which did not crystallize upon standing. Both fractions were of sufficient purity to be used as is in the ensuing steps. 4-[6-(Cyclopropylamino)-3-fluoro-2-pyridinyl]-1-piperazinecarboxylic Acid, Ethyl Ester A solution of 21.9 g (63 mmole) of 4-[6-(acetylcyclopropylamino)-3-fluoro-2-pyridinyl]-1-piperazinecarboxylic acid, ethyl ester, 170 ml of 15% hydrochloric acid and 235 ml of methanol was refluxed for one hour and allowed to stir at room temperature for 18 hours. The methanol was removed in vacuo and the aqueous acid was made basic with 1.0N sodium hydroxide to pH 10.5. The mixture was extracted with chloroform, the chloroform layer washed with water, dried over magnesium sulfate, and evaporated in vacuo to give 17.6 g of the title compound, mp 68-70° C. 1-Cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-1,8-naphthyridine-3-carboxylic Acid Route A [[Cyclopropyl[6-[4-(ethoxycarbonyl)-1-piperazinyl]-5-fluoro-2-pyridinyl]amino]methylene]propanedioic Acid, Diethyl Ester A solution of 3.8 g (12.3 mmole) of 4-[6-(cyclopropylamino)-3-fluoro-2-pyridinyl]-1-piperazine carboxylic acid, ethyl ester, 2.7 g (12.3 mmole) of diethyl(ethoxymethylene)malonate and 50 ml of xylene was refluxed for 24 hours. The solvent was removed in vacuo and the residue was chromatographed over silica gel eluting with chloroform/ethyl acetate (80/20) to give 2.3 g of the title compound as a viscous oil which was used without further purification. Ethyl 1-Cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-4-(ethoxycarbonyl)-1-piperazinyl]-1,8-naphthyridine-3-carboxylate A solution of 2.3 g (4.8 mmole) of [[cyclopropyl[6-[4-(ethoxycarbonyl)-1-piperazinyl]-5-fluoro-2-pyridinyl]amino]methylene]propanedioic acid, diethyl ester, in 15 ml of acetic anhydride was treated dropwise with 5 ml of 98% sulfuric acid keeping the temperature 55-60° C. When the addition was complete, the reaction was stirred for one hour and poured onto 50 g of ice. The aqueous suspension was extracted with chloroform, the chloroform layer washed with water, dried over magnesium sulfate, filtered, and evaporated in vacuo. The residue was triturated with several portions of ethanol/toluene which were also removed in vacuo to give 0.4 g of the title compound, mp 184-186° C. An additional 0.5 g of product could be obtained by concentrating the original aqueous fraction, mp 184-186° C. 1-Cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-1,8-naphthyridine-3-carboxylic Acid A suspension of 0.7 g (1.6 mmole) of ethyl 1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-[4-(ethoxycarbonyl)-1-piperazinyl]-1,8-naphthyridine-3-carboxylate, 6 ml of 10% aqueous sodium hydroxide and 2 ml of ethanol was refluxed for three hours. The reaction was filtered through a fiber glass pad to clarify and acidified to pH 1.5 with 6.0M hydrochloric acid and lyophilized. The residue was dissolved in 10 ml of ammonium hydroxide and the solution concentrated in vacuo. The precipitate which formed was removed by filtration, washed with aqueous ethanol, ether, and dried in vacuo to give 0.04 g, mp 274-276° C. Route B 4-[6-[Cyclopropyl(2,2-dimethyl-4,6-dioxo-1,3-dioxan 5-ylidine)amino]-3-fluoro-2-pyridinyl]-1-piperazinecarboxylic Acid, Ethyl Ester A solution of 17.6 g (57 mmole) of 4-[6-(cyclopropylamino)-3-fluoro-2-pyridinyl]-1-piperazine carboxylic acid, ethyl ester, 11.6 g (63 mmole) of 5-(methoxymethylene)-2,2-dimethyl-1,3-dioxane-4,6-dione and 250 ml of methanol was stirred at room temperature for four hours. The solid was removed by filtration, washed with methanol, ether and dried in vacuo to give 17.6 g of the title compound, mp 177-178° C. 1-Cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-[4-(ethoxycarbonyl)-1-piperazinyl]-1,8-naphthyridine-3-carboxylic Acid A solution of 17.0 g (37.0 mmole) of 4-[6-(cyclopropyl-(2,2-dimethyl-4,6-dioxo-1,3-dioxan-5-ylidene)amino]-3-fluoro-2-pyridinyl]-1-piperazinecarboxylic acid, ethyl ester in 125 ml of acetic anhydride was treated dropwise with 35 ml of 98% sulfuric acid keeping the temperature 50-60° C. When the addition was complete, the reaction was stirred for two hours and poured onto 600 g of ice. The mixture was stirred for one hour and the resulting precipitate was removed by filtration, washed with water, and dried in vacuo to give 10.2 g of the title compound, mp 277-279° C. 1-Cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl-1,8-naphthyridine-3-carboxylic Acid A solution of 10.2 g (25 mmole) of 1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-[4-(ethoxy carbonyl)-1-piperazinyl]-1,8-naphthyridine-3-carboxylic acid, 100 ml of 10% aqueous sodium hydroxide and 40 ml of ethanol was refluxed for three hours. The solution was concentrated to 125 ml and acidified to pH 7.3 with glacial acetic acid. The resulting precipitate was removed by filtration, washed with 50% aqueous ethanol, ether and dried in vacuo to give 7.2 g of the title compound, mp 274-276° C. 1-Cyclopropyl-6-fluoro-1,4-dihydro-7-hydroxy-4-oxo-1,8-naphthyridine-3-carboxylic Acid To a solution of 2 ml of 70% nitric acid in 10 ml of 98% sulfuric acid was added in portions 1.0 g (3.0 mmole) of 1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-1,8-naphthyridine-3carboxylic acid, keeping the temperature between 25-30° C. The resulting solution was stirred at room temperature for 18 hours and poured onto 40 g of ice. The mixture was stirred at room temperature for 24 hours, concentrated in vacuo, the pH adjusted to 12 with aqueous sodium hydroxide, and filtered through a fiber glass pad. The filtrate was acidified to pH 3.5 with 6.0M hydrochloric acid, the resulting precipitate removed by filtration, washed with water then ether and dried in vacuo to give 0.23 g of the title compound, mp 325-327° C. 7-Chloro-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-naphthyridine-3-carboxylic Acid A suspension of 0.19 g (0.72 mmole) of 1-cyclopropyl-6-fluoro-1,4-dihydro-7-hydroxy-4-oxo-1,8-naphthyridine-3-carboxylic acid in 2 ml of phosphorus oxychloride was heated at reflux for one-half hour. The resulting solution was cooled to room temperature and the solvent was removed in vacuo. The residue was triturated with ice water and the resulting solid was removed by filtration, washed with water, then ether, and dried in vacuo to give 0.11 g of the title compound, mp 209-212° C. Example O 2-Nitro-3,4,5,6-tetrafluorobenzoyl Chloride A solution of 6.7 g (28 mmoles) of 2-nitro-3,4,5,6-tetrafluorobenzoic acid [Tetrahedron, 23, 4719, (1967)], 3.8 g (30 mmoles) of oxalyl chloride and 50 ml of dichloromethane was treated with four drops of N,N-dimethylformamide and stirred at room temperature overnight. The solvent was removed and the residue was used as is without further purification. Example P 2-Nitro-3,4,5,6-tetrafluoro-β-oxobenzenepropanoic Acid, Ethyl Ester To a solution of 7.5 g (56.8 mmoles) of malonic half acid ester in 125 ml of dry tetrahydrofuran was added 20 mg of 2,2'-bipyridyl. The reaction mixture was cooled to -30° C. and treated dropwise with 24 ml (57.6 mmoles) of 2.4N n-butyl lithium. The reaction was then allowed to warm to -5° C. where a second equivalent, 24 ml (57.6 mmoles), of 2.4N n-butyl lithium was added until a light pink color persisted for 15 minutes. The reaction mixture was then cooled to -75° C. and treated dropwise with a solution of 7.2 g (28 mmoles) of 2-nitro-3,4,5,6-tetrafluorobenzoyl chloride in 15 ml of tetrahydrofuran. The reaction was stirred at -75° C. for one hour, warmed to -35° C., and quenched by pouring onto a solution of 28 ml of concentrated hydrochloric acid in 50 ml of ice water. The reaction was extracted with dichloromethane (3×200 ml), the organic layer was washed with 5% aqueous sodium bicarbonate (2×100 ml), and with 1.0M hydrochloric acid (1×100 ml), dried (MgSO 4 ), and evaporated in vacuo to give 7.3 g of the title compound which was used for the ensuing step without further purification. Example Q Ethyl 1-Cyclopropyl-5-nitro-6,7,8-trifluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylate A solution of 6.8 g (22 mmoles) of 2-nitro-3,4,5,6-tetrafluoro-β-oxobenzenepropanoic acid, ethyl ester, 4.9 g (33 mmoles) of triethylorthoformate and 50 ml of acetic anhydride was heated at reflux for two hours. The solvent was removed in vacuo and then in high vacuo at 80° C. for 1.5 hours. The residue was dissolved in 25 ml of t-butanol and treated with 1.43 g (25 mmoles) of cyclopropylamine. The mixture was heated at 45° C. for four hours, cooled to room temperature and treated dropwise with a solution of 2.47 g (25 mmoles) of potassium t-butoxide in 25 ml of t-butanol. The reaction was heated at 60° C. for six hours and the solvent was removed in vacuo. The residue was dissolved in chloroform, washed with water, dried (MgSO 4 ), and evaporated in vacuo. The residue was chromatographed over silica gel eluting with chloroform/ethyl acetate (80/20) to give 1.9 g of the title compound as an oil which was used without further purification. Example R Ethyl 5-Amino-1-cyclopropyl-6,7,8-trifluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylate A suspension of 1.9 g (5.3 mmoles) of ethyl 1-cyclopropyl-5-nitro-6,7,8-trifluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylate, 0.5 g of Raney nickel and 100 ml of ethanol was shaken in a hydrogen atmosphere at pressures of 42.5-50 psi and temperatures of 24-26.5° C. for ten hours. The mixture was filtered through Celite and some insoluble product was dissolved in tetrahydrofuran with filtration. The combined filtrates were evaporated in vacuo and the residue was chromatographed on silica gel to give 600 mg of the title compound, mp 223-225° C. Example S 5-Amino-1-cyclopropyl-6,7,8-trifluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic Acid A solution of 0.5 g (1.5 mmoles) of ethyl 5-amino-1-cyclopropyl-6,7,8-trifluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylate, 5 ml of 6.0M hydrochloric acid and 5 ml of ethanol was heated at reflux for two hours. The solvent was removed in vacuo to give 430 mg of the title compound, mp 269-271° C. Example T 3-Chloro-2,4,5-trifluoro-6-nitrobenzoic Acid To a solution of 42.1 g (200 mmol) of 3-chloro-2,4,5-trifluorobenzoic acid (E.P.O. 0 183 129) in 100 ml of sulfuric acid was added concentrated nitric acid (50 ml) dropwise such that the reaction temperature stayed below 40° C. The reaction mixture was heated at 60° C. for 18 hours, then poured cautiously onto 500 g of ice water. The aqueous solution was extracted with ether, and the ether extracts were washed with water, dried over magnesium sulfate, and concentrated to give 26.5 g of 3-chloro-2,4,5-trilfuoro-6-nitrobenzoic acid. Example U 3-Chloro-2,4,5-trifluoro-6-nitrobenzoyl Chloride To a suspension of 25.6 g (100 mmol) of 3-chloro-2,4,5-trifluoro-6-nitrobenzoic acid in 75 ml of dichloromethane was added 14.0 g (110 mmol) of oxalyl chloride. This mixture was treated with four drops of dry N,N-dimethylformamide, and the rapidly bubbling solution was stirred overnight at room temperature. The mixture was concentrated to give 27.0 g of the title compound which was used without purification in the next step. Example V Ethyl (3-Chloro-2,4,5-trifluoro-6-nitro)-β-oxophenylpropanoate To 26.4 g (200 mmol) of malonic half ethyl ester in 500 ml of dry tetrahydrofuran at -35° C. was added 91 ml of n-butyllithium (2.2M, 200 mmol) dropwise. A catalytic amount of bipyridyl (10 mg) was added, and the suspension was warmed to -5° C. Another equivalent of n-butyllithium (91 ml, 200 mmol) was added until the indicator turned pink. The mixture was cooled to -78° C., and a solution of 27 g of 3-chloro-2,4,5-trifluoro-6-nitrobenzoyl chloride in 50 ml of tetrahydrofuran was added dropwise. The reaction mixture was kept at -78° C. for one hour, then warmed to -35° C. and poured into a mixture of ice water (400 ml) and concentrated hydrochloric acid (17 ml). The solution was extracted with dichloromethane; the extracts were combined and washed with 5% sodium bicarbonate, 2M hydrochloric acid, and water. The dichloromethane was dried over magnesium sulfate and concentrated to give 27.4 g of the title compound. Example W Ethyl 2-(3-Chloro-2,4,5-trifluoro-6-nitrobenzoyl)-3-ethoxyacrylate To 27.4 g (84.1 mmol) of the ethyl (3-chloro-2,4,5-trifluoro-6-nitro)-β-oxophenyl propanoate was added 18.7 g (126 mmol) of triethyl orthoformate and 100 ml of acetic anhydride. The mixture was refluxed for two hours, then cooled to 80° C., and concentrated to give 31.5 g of the title compound. Example Y Ethyl 8-Chloro-1-cyclopropyl-6,7-difluoro-1,4-dihydro-5-nitro-4-oxo-3-quinolinecarboxylate The ethyl 2-(3-chloro-2,4,5-trifluoro-6-nitrobenzoyl)-3-ethoxyacrylate prepared in the previous step was dissolved in 200 ml of t-butanol and treated with 5.0 g (88 mmol) of cyclopropylamine. The reaction mixture was warmed to 45° C. and stirred for three hours at that temperature. The solution was then cooled to room temperature and treated with a slurry of 9.4 g (84 mmol) of potassium t-butoxide in 50 ml of t-butanol. The mixture was stirred at 60° C. for five hours; the suspension was filtered, and the solid was washed with water and ether to give 21.7 g of the title compound. Example Z Ethyl 5-Amino-8-chloro-1-cyclopropyl-6,7-difluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylate A suspension of 21.7 g (58.2 mmol) of ethyl 8-chloro-1-cyclopropyl-6,7-difluoro-1,4-dihydro-5-nitro-4-oxo-3-quinolinecarboxylate in 300 ml of ethanol and 300 ml of tetrahydrofuran was catalytically reduced using 3 g of Raney nickel in a hydrogen atmosphere of 50 psi. After twelve hours the mixture was diluted with dichloromethane and the catalyst was removed by filtration. The filtrate was concentrated to give 17.2 g of the title compound. Example AA 5-Amino-8-chloro-1-cyclopropyl-6,7-difluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic Acid A suspension of 17.2 g (50.2 mmol) of ethyl 5-amino-8-chloro-1-cyclopropyl-6,7-difluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylate in 100 ml of 6M hydrochloric acid was refluxed for three hours. The mixture was cooled to room temperature, and the solids were filtered, washed with water and ether, and dried to give 14.2 g of the title compound. Using the same sequence of reactions the following compounds could be prepared: 5-amino-8-bromo-1-cyclopropyl-6,7-difluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid; 5-amino-1-cyclopropyl-6,7-difluoro-8-trifluoro-methyl-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid; 5-amino-1-cyclopropyl-6,7-difluoro-1,4-dihydro-8-methoxy-4-oxo-3-quinolinecarboxylic acid; 5-amino-1-cyclopropyl-6,7-difluoro-1,4-dihydro-8-hydroxy-4-oxo-3-quinolinecarboxylic acid; 5,8-diamino-1-cyclopropyl-6,7-difluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid; 5-amino-1-cyclopropyl-6,7-difluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid; and 5-amino-7-chloro-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-naphthyridine-3-carboxylic acid. Example BB 1-Cyclopropyl-6,7,8-trifluoro-1,4-dihydro-5-(methylamino)-4-oxo-3-quinolinecarboxylic Acid A solution of 5.9 g (20 mmol) of 5-amino-1-cyclopropyl-6,7,8-trifluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid, 20 ml of trifluoroacetic anhydride, and 100 ml of trifluoro acetic acid was stirred at room temperature overnight. The solution was evaporated to dryness and the residue was triturated with water and filtered to give 7.55 g of 1-cyclopropyl-6,7,8-trifluoro-1,4-dihydro-4-oxo-5-[(trifluoroacetyl)amino]-3-quinolinecarboxylic acid, mp 188° C. A solution of 5.53 g (14.0 mmol) of the trifluoroacetyl intermediate above, 55 ml of DMF and 1.42 g (30.9 mmol) of 50% sodium hydride was stirred at 50-55° C. for 35 minutes. To this mixture was added 2.8 ml (45 mmol) of iodomethane with continued stirring at 50-55° C. for two hours and for three hours at room temperature. The reaction mixture was evaporated and the residue was triturated with water and filtered. The solid was dissolved with 60 ml of acetic acid and 30 ml of 6N HCl was added and the solution was heated under reflux for two hours. The solution was concentrated and the residual oil was treated with isopropanol to give 3.0 g of the title compound, mp 205-207° C. In a similar manner, the following compounds were prepared: 8-chloro-1-cyclopropyl-6,7-difluoro-1,4-dihydro-5-(methylamino)-4-oxo-3-quinolinecarboxylic acid; 8-bromo-1-cyclopropyl-6,7-difluoro-1,4-dihydro-5-(methylamino)-4-oxo-3-quinolinecarboxylic acid; and 1-cyclopropyl-6,7-difluoro-8-trifluoromethyl-1,4-dihydro-5-(methylamino)-4-oxo-3-quinolinecarboxylic acid. Example CC 1-Cyclopropyl-6,7,8-trifluoro-1,4-dihydro-5-dimethylamino-4-oxo-3-quinolinecarboxylic Acid 2-(Dimethylamino)-3,4,5,6-tetrafluorobenzoic Acid A solution of 10.0 g (41.8 mmol) of 2-nitro-3,4,5,6-tetrafluorobenzoic acid, 10 ml of 37% formaldehyde solution, 1.5 g of Raney nickel and 100 ml of ethanol was hydrogenated until TLC indicated absence of starting material. The reaction mixture was filtered and evaporated to an oil which was recrystallized with ethyl acetate-hexane to give 2.15 g of the title compound, mp 110-112° C. An additional 2.28 g, mp 90-100° C. was isolated from the filtrate. 2-(Dimethylamino)-3,4,5,6-tetrafluorobenzoyl Chloride To a suspension of 4.22 g (17.8 mmol) of 2-(dimethylamino)-3,4,5,6-tetrafluorobenzoic acid and 85 ml of dichloromethane, added 1.7 ml (19.5 mmol) of oxalyl chloride. After the bubbling subsided, five drops of DMF were added and the solution was stirred at room temperature for 21 hours. The solution was evaporated to 4.8 g of an oil which was used in the next step without purification. 2-(Dimethylamino)-3,4,5,6-tetrafluoro-β-oxobenzenepropanoic Acid, Ethyl Ester To a solution of 4.76 g (36 mmol) of malonic acid monoethyl ester and 75 ml of THF at -35° C. was added 25 ml (40 mmol) of 1.5N n-butyl lithium solution. The remaining 25 ml (40 mmol) of 1.5N butyllithium solution was added at 0° . After cooling to -78° C., a solution of the 4.8 g of 2-(dimethylamino)-3,4,5,6-tetrafluorobenzoyl chloride in 50 ml of THF was added to the dilithio malonate over a 15 minute period. The reaction mixture was stirred for 1.75 hours while the temperature came up to -30° C. The reaction mixture was poured into ice, water, and 50 ml of 1N HCl. The mixture was extracted with ether and the ether extract was washed with H 2 O, 5% NaHCO 3 , and HCl. After drying over MgSO 4 the ether solution was concentrated to 4.4 g of oil product. NMR spectra indicated the desired product. 2-(Dimethylamino)-α-(ethoxymethylene)-3,4,5,6-tetrafluoro-β-oxobenzenepropanoic Acid, Ethyl Ester A solution of 4.4 g (14.3 mmol) of the crude ketoester, 3.57 ml (21.5 mmol) of triethylortho formate, and 25 ml of acetic anhydride was heated under reflux for two hours. The solution was evaporated to 5.2 g of oil which was used in the next step without purification. α-[(Cyclopropylamino)methylene]-2-(dimethylamino)-3,4,5,6-tetrafluoro-β-oxobenzenepropanoic Acid, Ethyl Ester To a solution of 5.2 g (14.3 mmol) of the above crude product in 50 ml of t-butanol was added 1.2 ml (17 mmol) of cyclopropylamine. The reaction solution was stirred for 18 hours at room temperature. The reaction mixture was filtered to give 0.12 g of the title compound, mp 122-124° C. TLC of the filtrate showed it to be the same as the solid. 5-(Dimethylamino)-1-cyclopropyl-6,7,8-trifluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic Acid To the above filtrate was added 1.7 g (15 mmol) of potassium t-butoxide and the mixture was stirred at room temperature for 1.5 hours. TLC showed no change in reactants. An additional 1.7 g (15 mmol) of potassium t-butoxide was added and the reaction mixture was heated at 50-55° C. for two hours. After TLC indicated the reaction was complete, the solution was evaporated to 4 g of an oil. This oil was heated with 100 l 6N HCl for three hours on the steam bath. The solution was evaporated and the residue was recrystallized from isopropanol to give 0.3 g of the title compound, mp 160-163° C. An additional 1.0 g of solid was added from the filtrate. Following the same sequence, the following compounds were prepared: 8-chloro-1-cyclopropyl-6,7difluoro-1,4-dihydro-5-dimethylamino-4-oxo-3-quinolinecarboxylic acid, and 8-bromo-1-cyclopropyl-6,7-difluoro-1,4-dihydro-5-dimethylamino-4-oxo-3-quinolinecarboxylic acid. Example DD 1-Cyclopropyl-6,7,8-trifluoro-1,4-dihydro-5-methoxy-4-oxo-3-quinolinecarboxylic Acid To 22.4 g (100 mmol) of the 2-methoxy-3,4,5,6-tetrafluorobenzoic acid prepared as in [J. Fluorine Chem., 28, 361 (1985)] was added 400 ml of tetrahydrofuran, 1 ml of dimethylformamide, and 13 ml of oxalylchloride. The acid chloride mixture was concentrated, diluted with 100 ml of tetrahydrofuran, and added to a solution of the dilithio anion of malonic acid monoethylester (200 mmol) in 800 ml of tetrahydrofuran at -70° C. The reaction was stirred for one hour at -30° C., poured over ice and dilute hydrochloric acid and taken into dichloromethane. The product was isolated by an extraction at pH 7, followed by drying the dichloromethane (MgSO 4 ) and concentration. The crude product was then treated neat with 2.5 equivalents of triethylorthoformate and 2.8 equivalents of acetic anhydride at 150° C. for two hours. The mixture was concentrated and at room temperature a slight excess of cyclopropylamine (6.0 g) was added in 150 ml of t-butanol. The mixture was stirred overnight. To this mixture was added 11.3 g of potassium t-butoxide and the temperature brought to 50° C. The mixture was concentrated after 18 hours and the residue treated with 100 ml of acetic acid and 100 ml of 4N hydrochloric acid. From this mixture after four hours at 100° C., 12.7 g of the title compound precipitated. In a similar manner, the following compounds were prepared: 8-chloro-1-cyclopropyl-6,7-difluoro-1,4-dihydro-5-methoxy-4-oxo-3-quinolinecarboxylic acid; 8-bromo-1-cyclopropyl-6,7-difluoro-1,4-dihydro-5-methoxy-4-oxo-3-quinolinecarboxylic acid; 1-cyclopropyl-6,7-difluoro-8-trifluoromethyl-5-methoxy-4-oxo-3-quinolinecarboxylic acid; and 1-cyclopropyl-6,7-difluoro-1,4-dihydro-5-methoxy-4-oxo-3-quinolinecarboxylic acid. Example EE 1-Cyclopropyl-6,7,8-trifluoro-1,4-dihydro-5-hydroxy-4-oxo-3-quinolinecarboxylic Acid To 1.5 g of 1-cyclopropyl-6,7,8-trifluoro-1,4-dihydro-5-methoxy-4-oxo-3-quinolinecarboxylic acid was added 25 ml of hydrogen bromide in acetic acid (32%). The mixture was stirred at room temperature for 16 hours and concentrated to dryness. The residue was triturated with water:ethanol and filtered to give 1.15 g of the title compound. In a similar manner the following compounds were prepared: 8-chloro-1-cyclopropyl-6,7-difluoro-1,4-dihydro-5-hydroxy-4-oxo-3-quinolinecarboxylic acid; 8-bromo-1-cyclopropyl-6,7-difluoro-1,4-dihydro-5-hydroxy-4-oxo-3-quinolinecarboxylic acid; 1-cyclopropyl-6,7-difluoro-8-trifluoromethyl-5-hydroxy-4-oxo-3-quinolinecarboxylic acid and 1-cyclopropyl-6,7-difluoro-1,4-dihydro-5-hydroxy-4-oxo-3-quinolinecarboxylic acid. Example 1 1-Ethyl-5-amino-6,8-difluoro-7-[3-(t-butoxycarbonylamino)-1-pyrrolidinyl]-4-oxo-1,4-dihydroquinoline-3-carboxylic Acid A suspension of 3.02 g (10 mmole) of 1-ethyl-5-amino-6,7,8-trifluoro-4-oxo-1,4-dihydro quinoline-3-carboxylic acid, 2.79 g (15 mmole) of 3-(t-butoxycarbonylamino)pyrrolidine, 3.0 g (30 mmole) of triethylamine and 100 ml of acetonitrile is refluxed for 18 hours. The reaction mixture is cooled to room temperature and the precipitate is removed by filtration, washed with acetonitrile, ether, and dried in vacuo to give 1-ethyl-5-amino-6,8-difluoro-7-[3-(t-butoxycarbonylamino)-1-pyrrolidinyl]-4-oxo-1,4-dihydroquinoline-3-carboxylic acid. Example 2 1-Ethyl-5-amino-6,8-difluoro-7-(3-amino-1-pyrrolidinyl)-4-oxo-1,4-dihydroquinoline-3-carboxylic Acid Hydrochloride A near solution of 4.5 g (10 mmole) of 1-ethyl-5-amino-6,8-difluoro-7-[3-(t-butoxycarbonylamino)-1-pyrrolidinyl]-4-oxo-1,4-dihydroquinoline-3-carboxylic acid, 10 ml of 6.0M hydrochloric acid and 100 ml of glacial acetic acid is heated at 60° C. for four hours and then stirred at room temperature for 18 hours. The solvent is removed in vacuo, the residue triturated with ethanol/ether (1:1), filtered, washed with ether, and dried in vacuo to give the title compound. Example 3 1-Ethyl-5-amino-6,8-difluoro-7-[3-(ethylamino)methyl-1-pyrrolidinyl)]-4-oxo-1,4-dihydroquinoline-3-carboxylic Acid A suspension of 3.02 g (10 mmole) of 1-ethyl-5-amino-6,7,8-trifluoro-4-oxo-1,4-dihydro quinoline-3-carboxylic acid, 1.93 g (15 mmole) of N-ethyl-3-pyrrolidinemethanamine, 3.0 g (30 mmole) of triethylamine and 100 ml of acetonitrile is refluxed for 18 hours. The reaction mixture is cooled to room temperature and the precipitate is removed by filtration, washed with acetonitrile, ether, and dried in vacuo to give 1-ethyl-5-amino-6,8-difluoro-7-[3-(ethylamino)methyl-1-pyrrolidinyl)]-4-oxo-1,4-dihydroquinoline-3-carboxylic acid. The following compounds may be prepared from 1-ethyl-5-amino-6,7,8-trifluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid and the desired amine or protected amine using the method above: 1-ethyl-5-amino-6,8-difluoro-7-[3-(aminomethyl)-1-pyrrolidinyl]-4-oxo-1,4-dihydroquinoline-3-carboxylic acid; 1-ethyl-5-amino-6,8-difluoro-7-[3-(propylaminomethyl)-1-pyrrolidinyl]-4-oxo-1,4-dihydroquinoline-3-carboxylic acid; 1-ethyl-5-amino-6,8-difluoro-7-[3-(2-propylaminomethyl)-1-pyrrolidinyl]-4-oxo-1,4-dihydroquinoline-3-carboxylic acid; 1-ethyl-5-amino-6,8-difluoro-7-[3-(cyclopropylaminomethyl)-1pyrrolidinyl]-4-oxo-1,4-dihydroquinoline-3-carboxylic acid; 1-ethyl-5-amino-6,8-difluoro-7-[2,7-diazaspiro [4.4]non-2-yl]-4-oxo-1,4-dihydroquinoline-3-carboxylic acid; 1-ethyl-5-amino-6,8-difluoro-7-[7-methyl-2,7-diazaspiro[4.4]non-2-yl]-4-oxo-1,4-dihydroquinoline-3-carboxylic acid; 1-ethyl-5-amino-6,8-difluoro-7-[7-ethyl-2,7-diazaspiro[4.4]non-2-yl]-4 -oxo-1,4-dihydroquinoline-3-carboxylic acid; 1-ethyl-5-amino-6,8-difluoro-7-[3-[[(2-hydroxyethyl)amino]methyl]-1-pyrrolidinyl]-4-oxo-1,4-dihydroquinoline-3-carboxylic acid; and 1-ethyl-5-amino-6,8-difluoro-7-[3-[[(2,2,2-trifluoroethyl)amino]methyl]-1-pyrrolidinyl]-4-oxo-1,4-dihydroquinoline-3-carboxylic acid. Example 4 8-Amino-9-fluoro-3-methyl-10-[(3-t-butoxycarbonylamino)-1-pyrrolidinyl]-7-oxo-2,3-dihydro-7H-pyrido [1,2,3-de][1,4]benzoxazine-6-carboxylic Acid A solution of 2.9 g (10 mmole) of 8-amino-9,10-difluoro-3-methyl-7-oxo-2,3-dihydro-7H-pyrido [1,2,3-de][1,4]benzoxazine-6-carboxylic acid, 2.8 g (15 mmole) of 3-(t-butoxycarbonylamino)pyrrolidine, 3.03 g (30 mmole) of triethylamine and 100 ml of N,N-dimethylformamide is heated at 100° C. for four hours. The solvent is removed in vacuo and the residue is triturated with water. The aqueous slurry is adjusted to pH 7.2 with 1.0M hydrochloric acid and the precipitate is removed by filtration, washed with water, and dried in vacuo to give the 8-amino-9-fluoro-3-methyl-10-[(3-t-butoxycarbonylamino)-1-pyrrolidinyl]-7-oxo-2,3-dihydro-7H-pyrido[1,2,3-de][1,4]benzoxazine-6-carboxylic acid. Example 5 8-Amino-9-fluoro-3-methyl-10-(3-amino-1-pyrrolidinyl)-7-oxo-2,3-dihydro-7H-pyrido[1,2,3-de][1,4]benzoxazine-6-carboxylic Acid, Hydrochloride A suspension of 4.63 g (10.0 mmole) of 8-amino-9-fluoro-3-methyl-10-[(3-t-butoxycarbonyl amino)-1-pyrrolidinyl]-7-oxo-2,3-dihydro-7H-pyrido [1,2,3-de][1,4]benzoxazine-6-carboxylic acid 5 ml of 6.0M hydrochloric acid and 50 ml of glacial acetic acid is heated at 60° C. for four hours. The solvent is removed in vacuo and the residue is triturated with ethanol/ether (1:1). The precipitate is removed by filtration, washed with ether, and dried in vacuo to give 8-amino-9-fluoro-3-methyl-10-(3-amino-1-pyrrolidinyl)-7-oxo-2,3-dihydro-7H-pyrido[1,2,3-de][1,4]benzoxazine-6-carboxylic acid, hydrochloride. Example 6 8-Amino-9-fluoro-3-methyl-10-[(3-cyclopropylaminomethyl)-1-pyrrolidinyl]-7-oxo-2,3-dihydro-7H-pyrido [1,2,3-de][1,4]benzoxazine-6-carboxylic Acid A mixture of 2.96 g (10 mmole) of 8-amino-9,10-difluoro-3-methyl-7-oxo-2,3-dihydro-7H-pyrido [1,2,3-de][1,4]benzoxazine-6-carboxylic acid, 2.1 g (15 mmole) of N-cyclopropyl-3-pyrrolidinemethanamine, 3.03 g (30 mmole) of triethylamine and 100 ml of N,N-dimethylformamide is heated at 100° C. for four hours. The solvent is removed in vacuo and the residue triturated with water. The aqueous suspension is adjusted to pH 7.2 with 1.0M hydrochloric acid. The solid is removed by filtration, washed with water, and dried in vacuo to give 8-amino-9-fluoro-3-methyl-10-[(3-cyclopropylaminomethyl)-1-pyrrolidinyl]-7-oxo-2,3-dihydro-7H-pyrido[1,2,3-de][1,4]benzoxazine-6-carboxylic acid. The following compounds may be prepared from 8-amino-9,10-difluoro-3-methyl-7-oxo-2,3-dihydro-7H-pyrido[1,2,3-de][1,4]benzoxazine-6-carboxylic acid and the desired amine or protected amine using the above method: 8-amino-9-fluoro-3-methyl-10-[3-(aminomethyl)-1-pyrrolidinyl]-7-oxo-2,3-dihydro-7H-pyrido[1,2,3-de][1,4]benzoxazine-6-carboxylic acid; 8-amino-9-fluoro-3-methyl-10-[3-[(propylamino)methyl)-1-pyrrolidinyl]-7-oxo-2,3-dihydro-7H-pyrido [1,2,3-de][1,4]benzoxazine-6-carboxylic acid; 8-amino-9-fluoro-3-methyl-10-[3-[(2-hydroxyethyl)amino)methyl]-1-pyrrolidinyl]-7-oxo-2,3-dihydro-7H-pyrido[1,2,3-de][1,4]benzoxazine-6-carboxylic acid; 8-amino-9-fluoro-3-methyl-10-[3-[(2-propylamino)methyl]-1-pyrrolidinyl]-7-oxo-2,3-dihydro-7H-pyrido[1,2,3-de][1,4]benzoxazine-6-carboxylic acid; 8-amino-9-fluoro-3-methyl-10-[3-[(2,2,2-trifluoroethyl)amino]methyl]-1-pyrrolidinyl] -7-oxo-2,3-dihydro-7H-pyrido[1,2,3-de][1,4]benzoxazine-6-carboxylic acid; 8-amino-9-fluoro-3-methyl-10-[3-[(ethylamino)methyl]-1-pyrrolidinyl]-7-oxo-2,3-dihydro-7H-pyrido[1,2,3-de][1,4]benzoxazine-6-carboxylic acid; 8-amino-9-fluoro-3-methyl-10-[2,7-diazaspiro[4.4]non-2-yl]-7-oxo-2,3-dihydro-7H-pyrido [1,2,3-de][1,4]benzoxazine-6-carboxylic acid; 8-amino-9-fluoro-3-methyl-10-[7-(7-methyl)-2,7-diazaspiro[4.4]non-2-yl]-7-oxo-2,3-dihydro-7H-pyrido [1,2,3-de][1,4]benzoxazine-6-carboxylic acid; and 8-amino-9-fluoro-3-methyl-10-[7-(7-ethyl)-2,7-diazaspiro[4.4]non-2-yl]-7-oxo-2,3-dihydro-7H-pyrido [1,2,3-de][1,4]benzoxazine-6-carboxylic acid. Example 7 5-Amino-1-cyclopropyl-6,8-difluoro-7-[(3-ethylaminomethyl)-1-pyrrolidinyl]-1,4-dihydro-4-oxo-3-quinolinecarboxylic Acid A solution of 0.43 g (1.5 mmoles) of 5-amino-1-cyclopropyl-6,7,8-trifluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid, 0.61 g (6.0 mmoles) of triethylamine, 0.77 g (6.0 mmoles) 3-(ethylaminomethyl)pyrrolidine and 25 ml of acetonitrile was heated at reflux for two hours. The solvent was removed in vacuo and the residue was dissolved in water and filtered through a fiber glass pad to remove a trace of insoluble material. The filtrate was adjusted to pH 7.0 and the resulting precipitate removed by filtration, washed with water, and dried in vacuo to give 200 mg of the title compound, mp 250-252° C. Example 8 5-Amino-7-(3-amino-1-pyrrolidinyl)-8-chloro-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic Acid To 1.57 g (5 mmol) of 5-amino-8-chloro-1-cyclopropyl-6,7-difluoro-1,4-dihydro-4-oxo-3-quinoline carboxylic acid in 20 ml of acetonitrile was added 0.93 g (5 mmol) of 3-[(t-butoxycarbonyl)amino]pyrrolidine and 1.0 g (10 mmol) of triethylamine. The mixture was refluxed for three hours, cooled, and filtered. The solids were washed with acetonitrile and ether, then dissolved in 10 ml of acetic acid and 2 ml of 3N hydrochloric acid. The mixture was heated at 100° C. for four hours, concentrated, and triturated with 2-propanol. The solid that formed was filtered and washed with ether to give 1.2 g of the title compound. The following compounds were also prepared by a similar procedure: 5-amino-8-chloro-1-cyclopropyl-7-[3-[(ethylamino)methyl]-1-pyrrolidinyl]-6-fluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid; 5-amino-8-chloro-1-cyclopropyl-6-fluoro-1,4-dihydro-7-[3-[(methylamino)methyl]-1-pyrrolidinyl]-4-oxo-3quinolinecarboxylic acid; 5-amino-8-chloro-1-cyclopropyl-6-fluoro-1,4-dihydro-7-[3-[(dimethylamino) methyl]-1-pyrrolidinyl]-4-oxo-3-quinolinecarboxylic acid; 5-amino-7-[3-(aminomethyl)-3-methyl-1-pyrrolidinyl]-8-chloro-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid; 5-amino-8-bromo-1-cyclopropyl-7-[3-[(ethylamino)methyl]-1-pyrrolidinyl]-6-fluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid; 5-amino-8-bromo-1-cyclopropyl-6-fluoro-1,4-dihydro-7-[3-[(methylamino)methyl]-1-pyrrolidinyl]-4-oxo-3-quinolinecarboxylic acid; 5-amino-8-bromo-1-cyclopropyl-6-fluoro-1,4-dihydro-7-[3-[(dimethylamino)methyl]-1-pyrrolidinyl]-4-oxo-3-quinolinecarboxylic acid; 5-amino-7-(3 -amino-1-pyrrolidinyl)-8-bromo-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid; 5-amino-7-(3-amino-1-pyrrolidinyl)-1-cyclopropyl-6-fluoro-8-trifluoromethyl-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid; 5-amino-1-cyclopropyl-6-fluoro-8-trifluoromethyl-1,4-dihydro-7-[3-[(methylamino) methyl]-1-pyrrolidinyl]-4-oxo-3-quinolinecarboxylic acid; 5-amino-1-cyclopropyl-7-[3-[(ethylamino) methyl]-1-pyrrolidinyl]-6-fluoro-8-trifluoromethyl-4-oxo-3-quinolinecarboxylic acid; 5-amino-1-cyclopropyl-6-fluoro-8-trifluoromethyl-1,4-dihydro-7-[3-[(dimethylamino)methyl]-1-pyrrolidinyl]-4-oxo-3-quinolinecarboxylic acid; 5-amino-1-cyclopropyl-7-[3-[(ethylamino)methyl]-1-pyrrolidinyl]-6-fluoro-1,4-dihydro-8-methoxy-4-oxo-3-quinolinecarboxylic acid; 5-amino-1-cyclopropyl-6-fluoro-1,4-dihydro-7-[3-[(methylamino)methyl]-1-pyrrolidinyl]-8-methoxy-4-oxo-3-quinolinecarboxylic acid; 5-amino-1-cyclopropyl-6-fluoro-1,4-dihydro-7-[3-[(dimethylamino)methyl]-1-pyrrolidinyl]-8-methoxy-4-oxo-3quinolinecarboxylic acid; 5-amino-7-(3-amino-1-pyrrolidinyl)-1-cyclopropyl-6-fluoro-1,4-dihydro-8-methoxy-4-oxo-3-quinolinecarboxylic acid; 5-amino-1-cyclopropyl-7-[3-[(ethylamino)methyl]-1-pyrrolidinyl]-6-fluoro-1,4-dihydro-8-hydroxy-4-oxo-3-quinolinecarboxylic acid; 5-amino-1-cyclopropyl-6-fluoro-1,4-dihydro-8-hydroxy-7-[3-[(methylamino) methyl]-1-pyrrolidinyl]-4-oxo-3-quinolinecarboxylic acid; 5-amino-1-cyclopropyl-6-fluoro-1,4-dihydro-8-hydroxy-7-[3-[(dimethylamino)methyl]-1-pyrrolidinyl]-4-oxo-3-quinolinecarboxylic acid; 5-amino-7-(3-amino-1-pyrrolidinyl)-1-cyclopropyl-6-fluoro-1,4-dihydro-8-hydroxy-4-oxo- 3-quinolinecarboxylic acid; 7-(3-amino-1-pyrrolidinyl)-8-chloro-1-cyclopropyl-6-fluoro-1,4-dihydro-5-methoxy-4-oxo-3-quinolinecarboxylic acid; 7-(3-amino-1-pyrrolidinyl)-8-chloro-1-cyclopropyl-6-fluoro-1,4-dihydro-5-hydroxy-4-oxo-3quinolinecarboxylic acid; 7-(3-amino-1-pyrrolidinyl)-8-chloro-1-cyclopropyl-6-fluoro-1,4-dihydro-5-methylamino-4-oxo-3-quinolinecarboxylic acid; 7-(3-amino-1-pyrrolidinyl)-8-chloro-1-cyclopropyl-6-fluoro-1,4-dihydro-5-dimethylamino-4-oxo-3-quinolinecarboxylic acid; 8-chloro-1-cyclopropyl-7-[3-[(dimethylamino) methyl]-1-pyrrolidinyl]-6-fluoro-1,4-dihydro-5-methoxy-4-oxo-3-quinolinecarboxylic acid; 8-chloro-1-cyclopropyl-7-[3-[(dimethylamino)methyl]-1-pyrrolidinyl]-6-fluoro-1,4-dihydro-5-hydroxy-4-oxo-3-quinolinecarboxylic acid.

Novel naphthyridine-, quinoline- and benzoxazinecarboxylic acids as antibacterial agents are described as well as methods for their manufacture, formulation, and use in treating bacterial infections including the description of certain novel intermediates used in the manufacture of the antibacterial agents.

This application is a continuation of application Ser. No. 08/079,632, filed Jun. 18, 1993, abandoned. BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to storm shutters for temporarily or permanently covering exterior windows and doors to prevent damage from high winds, rains, and severe storms such as hurricanes and typhoons, and in particular, to an improved, highly durable storm shutter for windows or doors that can withstand great wind forces, while at the same time allow for the transmission of light through the storm shutters so that an occupant can see outdoors from within when the storm shutter is in place. 2. Description of the Prior Art Storm shutters have become an essential component of a residential home or commercial building in certain areas of the United States due to the occurrence regularly of tropical and severe storms that generate extremely high winds and heavy rains. Such areas as South Florida and the Gulf of Mexico are prone to hurricanes, which can generate winds up to 200 mph. Stringent building codes in some of these areas have given rise to a variety of storm shutters that can be either permanently installed or removably moved from the window or door area through the use of manual or electrical devices so that during periods when there is no storm, the shutters can be moved out and away from the window area. Typically, these storm shutters are made of very rigid material, such as extruded aluminum, and are hinged together for movable storage in a rolled up form. Other types of storm shutters include extruded aluminum sheets that are pinned or screwed in place, or hinged, louvered shutters that can be moved up and back to allow some light in. Typical of most of these shutters, except for perhaps louvered shutters, is that once in place, they do not allow the transmission of light into the building. Therefore, during a severe storm, the occupants of the building are literally without an outside view and without light to see out to experience what is happening during the storm, or to even have light in the building because often, electric power fails and the building is without electricity and elementary lighting. Storm shutters have also become important for security reasons to prevent unauthorized access into residential and commercial buildings. However, again, with the storm shutter in place to provide maximum security, the occupant of the building is again without light to see out and cannot conveniently or practically keep the shutters in place at all times while occupying the building. U.S. Pat. No. 5,099,904, issued to Susnar Mar. 31, 1992 for a "FOLDING SHUTTER PROVIDING SECURITY" shows the use of elongated, transparent, unprotected panels that slide in tracks and are folded. U.S. Pat. No. 5,155,936, issued to Johnson Oct. 20, 1992 shows a "SLIDING PANEL SHUTTER ASSEMBLY" that includes a transparent panel surrounded by a plurality of wooden rails. U.S. Pat. No. 5,097,883, issued to Robinson et al. Mar. 24, 1992 for a "FOLDING SHUTTER SYSTEM" shows the use of a small vent panel having a transparent shield. None of these devices show the use of complete storm shutters that provide strength and rigidity for high velocity winds at low cost, while allowing for light transmission. The purpose of the present invention is to overcome the problems shown in the prior art by providing an extremely rigid storm shutter that is economical to install and will allow for wind protection over 200 mph, while at the same time allowing the occupant to have light transmission sufficient for providing light into the building while the shutters are in place, while at the same time allowing the occupants to look outward from the building. SUMMARY OF THE INVENTION This invention relates to an improved exterior storm shutter for use in protecting windows, sliding glass doors, and doors from severe wind and rain damage or flying object damage during storms such as hurricanes, that also allows for the transmission of light through the storm shutter to allow the inhabitants to view outward from the building. The storm shutters can be manufactured at reasonable cost, making them cost effective. The storm shutter for a particular window, door, or sliding glass door is comprised of a rectangular, aluminum extruded channel frame, each of the frame members on each side being U-shaped in cross section, and having a predetermined dimension, such as one-half inch between the U-shaped channel members, a transparent, polycarbonate sheet, sized in thickness to receive each of the U-shaped frame members around its outside edge, and an expanded aluminum element that includes a plurality of openings typically in an assorted design, the expanded aluminum being of a predetermined thickness and being mounted flush against the polycarbonate sheet on one side, with an exterior perimeter shape and size as the polycarbonate sheet so that the exterior frame members receive both the peripheral edges of the polycarbonate sheet and the expanded aluminum element, fitting snugly in each U-shaped channel along each side. The four frame members with U-shaped channels, forming the exterior frame, may be riveted or bolted together by threaded fasteners to form a rigid shutter, having a sturdy aluminum frame, a one-quarter inch polycarbonate sheet, and a one-quarter inch aluminum member, which fit snugly within the one-half inch inside U-shaped frame channel dimension. This basic storm shutter unit can be mounted over a window, door, or sliding glass door, in a multitude of different ways. Each storm shutter may be mounted in two U-shaped tracks, firmly attached to the building exterior at the window top and bottom, including stopping means at each end of the tracks so that the windows can be permanently mounted in place or can be removed by sliding them along and outside the frame members horizontally. In a second embodiment, each storm shutter can be constructed of a corrugated, transparent polycarbonate sheet that has a predetermined thickness and substantially trapezoidally-shaped, cross sectional portions, which have flat, parallel sections spaced three-quarters of an inch apart or more for larger applications, that is used in conjunction with the expanded aluminum element to fit snugly within an extruded aluminum frame that is rigidly attached around the periphery of the polycarbonate corrugated sheet and the expanded aluminum element, firmly holding them in place. The various sizes in lengths and widths and thicknesses may be altered, depending on the size of the windows. The shutter may include two sections with an H-shaped center frame member to provide a storm shutter that includes two polycarbonate sheets of predetermined, substantially rectangular or square sizes, and two expanded aluminum elements mounted in a large, rectangular aluminum frame that is U-shaped, the frame including a center, rigid member that is H-shaped to receive both polycarbonate sheets on each side and both edges of the expanded aluminum. This could be used for large window mountings if necessary. One advantage of the invention, and the primary advantage, is that there is sufficient spacing and openings between the expanded aluminum structural members that provide more than 50% lighting through the shutter when the shutter is mounted in place over a window or sliding glass door. This allows an occupant inside the building, when the storm shutters are installed, to easily peer outward, while at the same time allowing light into the building during daylight. The second advantage is that the expanded aluminum pattern can be greatly varied for aesthetic purposes, providing round or diamond or square-type patterns across each of the openings. Each shutter also provides for ultraviolet ray protection of sunlight coming into the building because of the nature of the polycarbonate sheet, which in one example would be manufactured under the trademark Lexan, a registered trademark of the General Electric Company. These transparent Lexan polycarbonate sheets come in tinted or clear sheets, each of which has ultraviolet protection. Thus, if the storm shutter is permanently mounted over a window that receives intense sunlight, draperies or other objects inside the building can be likewise protected from ultraviolet rays. If the improved shutters are installed, they can also reduce air conditioning bills by cutting down ultraviolet rays and providing additional insulation over windows and sliding glass door areas. It is an object of this invention to provide an improved storm shutter for use in protecting residential and commercial buildings, and in particular, windows, doors, and sliding glass doors from destructive effects resulting from hurricanes or other severe windstorms, while allowing the transmission of light into the building when the shutters are in place. It is another object of this invention to provide an improved storm shutter that allows the occupant to see out of a building through a window or sliding glass door when the storm shutter is in place, while at the same time protecting the building from unauthorized entrance for increased security. It is another object of this invention to provide an improved storm shutter that allows for light transmission, while at the same time, protecting against extremely high winds and allowing for various decorative embellishments of the improved shutter for aesthetic purposes for use with residential and commercial buildings. And yet still another object of this invention is to provide an improved storm shutter that allows for light transmission through a window or sliding glass door while reducing ultraviolet radiation received inside the building from sunlight, thereby protecting object inside the building. But yet still another object of this invention is to provide an improved storm shutter that is economical in manufacture and installation, while at the same time providing extremely sturdy protection against wind velocities exceeding 200 mph. In accordance with these and other objects which will be apparent hereinafter, the instant invention will now become described with particular reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a perspective exploded view of an improved storm shutter in accordance with the present invention. FIG. 2 shows a top plan view in cross section through a mid-portion of a storm shutter made in accordance with the present invention. FIG. 3 shows a top plan view in cross section of an alternate embodiment of the present invention, employing a polycarbonate, transparent sheet of a different cross sectional profile that is corrugated. FIG. 4 shows a front elevational view of a house with storm shutters as would be typically installed on the exterior wall of a building. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, and in particular, FIG. 1, the present invention is shown generally at 10, representing a single shutter that would cover a single window in accordance with the present invention. The shutter itself can be changed in dimensional sizes for larger windows, for covering a sliding glass door, or for covering doors. Typically, the improved shutter 10 is installed on the exterior wall surface of a building, such as a residential home or commercial building, over the window or door section. A typical installation can be done, wherein top and bottom U-shaped tracks are provided that are made of a rigid material, such as aluminum, that are permanently anchored above the top ledge and below the bottom ledge of the window opening on the exterior portion of the building. An improved shutter, as shown in FIG. 1, would then be positioned over the window by sliding from one direction or another horizontally along the tracks. Additional end fasteners would then be provided at each end to prevent lateral movement of the shutter while it is mounted on the tracks. Looking at FIG. 1, the basic improved shutter 10 includes substantially a rectangular frame made up of four single frame elements 12 and 12a that are U-shaped, extruded aluminum for rigidity, having parallel members 12 and 12a on opposite sides that can overlap and be joined together by fasteners 15 that are disposed through a plurality of apertures 14 in each corner area. The particular length of the frame members 12 and 12a can be varied, and in fact, a double-type storm shutter can be produced with a center H-shaped frame member to form two separate, independent sections in one large frame housing for larger applications. The shutter 10 includes a single rectangular one-quarter inch thick polycarbonate sheet 16 that is transparent to allow light therethrough that may be typically sized one-quarter inch in thickness and be rectangularly shaped to fit snugly within the plurality of frame members 12 and 12a on each edge. The polycarbonate sheet composition is basically a linear polymer of carbonic acid, which is a thermoplastic, synthetic resin made from bisphenol and phosgene, typically is used. In one example, the polycarbonate can be a group of polyesters formed from carbonic acid, generally called polycarbonate and currently sold under various trade names, including the trademark Lexan, which is owned by the General Electric Company. In addition to the polycarbonate, transparent sheet 16 shown in FIG. 1, the shutter 10 includes a rigid, expanded metal (preferably aluminum) element 18, which has a pattern of openings or spaces integrally formed by rigid expanded aluminum one-quarter inch thick strips that are formed in a sheet that have at least 50% open space or more between the strips to insure adequate light transmission. The expanded aluminum can be done in distinctive spatial patterns, i.e. diamond-shaped, elliptical-shaped, or other desired patterns for aesthetic purposes. One expanded aluminum element 18 is sized around its perimeter and thickness to correspond to the perimeter of the polycarbonate sheet and to fit snugly within the frame members 12 and 12a as shown in FIG. 1 along all sides. The thickness of the expanded aluminum element is approximately one-quarter inch in the preferred embodiment, such that when placed against one side of the one-quarter inch polycarbonate sheet, and encompassed by the U-shaped aluminum frame members, which are one-half inch across each U-shaped inside channel of each frame member 12 and 12a, both the polycarbonate sheet and the expanded aluminum are snugly fit tight into the frame members 12 and 12a to eliminate any type of vibration and to form a completely rigid, independent storm shutter. Once the frame members and the polycarbonate sheet 16 and the expanded aluminum element 18 are firmly housed within the frame, and the frame member is secured by fasteners or rivets, the shutter 10 is ready for a plurality of different types of mountings on the exterior surface, covering the window, glass sliding doors or regular door. Such a mounting could be in sliding tracks, side-to-side, with a top and bottom U-shaped track permanently affixed to the building above and below the window opening. Each improved shutter could also be hinged on either side of a window or door and swing away. The shutter 10 could also be permanently or semi-permanently mounted in place by bolts at each corner in frames to hold the device firmly in place. Finally, each improved shutter could be hinged at the top for mobility away from the building at the bottom and held in place by support arms at the bottom that are adjustable in length. The polycarbonate sheet utilized in the present invention as shown in FIG. 1 can be clear or can be tinted, depending on the manufacturer. It is very desirable that the polycarbonate sheet 16 filters out undesirable ultraviolet rays that may come through from the sun to protect objects inside the building from damage from ultraviolet rays. This is typically provided in polycarbonate sheets, such as are made under the Lexan trademark. FIG. 2 shows a top plan view of the shutter including the frame members 12a and the snug fit of the polycarbonate sheet 16 at each end and against the inside channel of the frame members 12a, in conjunction with the snug fit of the expanded aluminum element 18 at each end and against the inside channel of frame members 12a so that there is no room for vibration between either the polycarbonate sheet 16 or the expanded aluminum element 18 and the frame members 12 and 12a themselves. FIG. 3 shows an alternate embodiment of the invention, wherein the polycarbonate sheet 20 may be corrugated while still retaining its strength and snug fit so that the corrugated surface still has a tightness that is provided between the ends of the frame members 12a and between the expanded aluminum element 18 for a tight fit in the frame. The corrugated polycarbonate sheet 20 is a variation of the flat polycarbonate sheet for aesthetic or sizing considerations. FIG. 4 shows the improved shutters 10 as they would be installed on a typical dwelling, covering windows. Each shutter 10, as shown in FIG. 1, constitutes an independent shutter that will cover a particular window. The size of each shutter can be varied to fit the need of the particular window. In the preferred embodiment, the polycarbonate sheet is one-quarter inch in thickness and the expanded aluminum is one-quarter inch in thickness, which has been found to withstand winds in excess of 200 mph. In order to cover a large area with sufficient strength, a center bar that is H-shaped in cross section could be employed within a rectangular aluminum frame as a center member, dividing an improved shutter into two separate sections, each containing its own polycarbonate sheet, and each containing its own expanded aluminum, with sufficient spacing in it to provide translucent light. With the use of the present invention, the storm shutter can provide protection for winds above 200 mph for windows and doors. It also protects from pounding rains and flying projectiles. The device can be installed as a security device and does not have to be removed when there are occupants in the house because of the ability to allow light to pass through the shutter without sacrificing security. The device can be made cost-effective and competitive with other types of shutters by virtue of the small quantity of polycarbonate sheet required, which still has strength when used in conjunction with the expanded aluminum, which provides strength and also openness. Another important aspect is that overall, each improved shutter can be lightweight, can be easy to install, and does not require electrical devices for raising or lowering. Finally, the shutters will protect the objects inside the building from ultraviolet rays. The instant invention has been shown and described herein in what is considered to be the most practical and preferred embodiment. It is recognized, however, that departures may be made therefrom within the scope of the invention and that obvious modifications will occur to a person skilled in the art.

A storm shutter for use in high wind severe storms, such as hurricanes and cyclones, that will protect windows, doors, and sliding glass doors on the outside of a building, which can be permanently or temporarily mounted, and which allow for protection in extremely high winds while permitting the transmission of light into the building, while allowing occupants in the building to look out through the storm shutters at all times. The storm shutters can also provide protection from intruders and ultraviolet rays from the sun when in place. Each shutter includes a rigid peripheral frame with a U-shaped channel, a polycarbonate transparent sheet, and an expanded aluminum element mounted snugly in the peripheral frame.

TECHNICAL FIELD [0001] The present invention relates in general to board level transmission line drivers and receivers, and in particular, to methods for compensating for timing skew between differential data channels. BACKGROUND INFORMATION [0002] Digital computer systems have a history of continually increasing the speed of the processors used in the system. As computer systems have migrated towards multiprocessor systems, sharing information between processors and memory systems has also generated a requirement for increased speed for the off-chip communication networks. Designers usually have more control over on-chip communication paths than for off-chip communication paths. Off-chip communication paths are longer, have higher noise, impedance mismatches, and have more discontinuities than on-chip communication paths. Since off-chip communication paths are of lower impedance, they require more current and thus more power to drive. [0003] When using inter-chip high-speed signaling, noise and coupling between signal lines (cross talk) affects signal quality. One way to alleviate the detrimental effects of noise and coupling is through the use of differential signaling. Differential signaling comprises sending a signal and its compliment to a differential receiver. In this manner, noise and coupling affect both the signal and the compliment equally. The differential receiver only senses the difference between the signal and its compliment as the noise and coupling represent common mode signals. Therefore, differential signaling is resistant to the effects that noise and cross talk have on signal quality. On the negative side, differential signaling increases pin count by a factor of two for each data line. Additionally, an empty wiring channel is usually added between each differential channel which further adds to the wiring inefficiency. [0004] The structure of a printed circuit board (PCB) is sometimes not homogeneous. It is common to find a weave structure on many laminates as shown in FIG. 1 . Given the space between the components of a differential pair and the weave structure of PCBs, it is possible to find differential pairs with an orientation as shown in FIG. 1 where the exemplary signal traces Data 103 and Data_b 105 do not have the same substrate configuration. In one case, the signal trace Data 103 has a dielectric substrate comprising the continuous fiberglass strand material 102 . In the other case, the signal trace Data_b has a dielectric substrate comprising fiberglass strands 101 in one direction and an epoxy fiberglass mix 104 in between the channels of fiberglass strands 101 . This results in the transmission lines formed by the signal traces having differing relative permittivities which results in the transmission lines having differing propagation delays. [0005] A differential pair having a signal and complement signal transmitted over matched transmission lines would have a received signal waveform substantially represented by the waveforms of FIG. 2A where the transition cross over points 203 and 204 are symmetrical. However, if the two transmission lines had different propagation delays, the resulting waveforms may look like the waveforms of FIG. 2B where the transition cross over points 203 and 204 are no longer symmetrical and occur at differing voltage levels resulting in timing skew between the two signals when detected in a differential receiver. [0006] With net lengths of tens of centimeters, differential skew delays due to PCB laminate weaves may approach tens of picoseconds. Presently transmission data rates of 10 gigabits per second means a bit width of only 100 picoseconds. Clearly, tens of picoseconds of in-pair timing skew for differential pairs is not negligible for these high data rates. In-pair differential skew may cause asymmetric crossover and aggravate common mode sensitivities. One solution that is been proposed is to use a diagonal trace pattern as shown in FIG. 3 where signal traces Data 301 and Data_b 302 are run at a diagonal with respect to the orthogonal strands 101 and 102 . See U.S. Pat. No. 6,304,700 and U.S. Patent Application 2004/0181764. This solution allows both signal traces Data 301 and Data_b 302 to have an equal mix of substrate composition. While this may be an improvement of FIG. 1 , adhering to this configuration may make wiring rules difficult. [0007] There is, therefore, a need for a signaling scheme that enables the skew between differential data channels to be compensated without complicating layout rules. The scheme must be programmable and easy to implement and modify. SUMMARY OF THE INVENTION [0008] The present invention uses two single ended off-chip drivers (OCD) to implement differential signal by having each data path transmit a data signal and its complement. Each of the OCDs is preceded by a programmable delay element. The input to the delay elements are coupled to the output of a two-input multiplexer (MUX) that receives the data signal for the path and a common clock signal. Under control of a select signal, either a data signal or a common clock signal is coupled to the data path comprising a transmission lines over the non-homogeneous PCB substrate. Each of the transmission lines is terminated in a suitable terminator and received in one input of a differential receiver. The two inputs to the differential receiver are also coupled to a phase detector whose output is coupled to the input of a Nx1 MUX. Skew control logic generates the select signals for the driver side MUXes as well as the select signal for the receiver side Nx1 MUX. The output of the Nx1 MUX is coupled as a feedback error signal to the skew control logic in a single feedback channel which is used to align each differential data channel. [0009] To align the differential data channels, each differential data channel is selected in sequence by coupling the common clock signal to the drivers of the two transmission lines and selecting the phase detector for that channel as the output of the Nx1 MUX. The skew control logic then adjusts the delays in series with each driver until the phase detector output measures a predetermined amount of phase shift or delay error. Then a next differential data channel is selected and the process is repeated until all the delays for the differential data channels are set to minimize the inter-channel timing skew. [0010] The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. BRIEF DESCRIPTION OF THE DRAWINGS [0011] For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: [0012] FIG. 1 illustrates signal traces on a PCB with orthogonal strands of fiberglass; [0013] FIG. 2A illustrates waveforms of ideal matched differential signals; and [0014] FIG. 2B illustrates waveforms of differential signals with unequal delay causing timing skew; [0015] FIG. 3 illustrates a prior art diagonal signal trace pattern to reduce delay differences; [0016] FIG. 4 is a circuit diagram illustrating a current steering circuit for differential signaling; [0017] FIG. 5 is a circuit diagram illustrates a true-complement differential signaling; [0018] FIG. 6 is a circuit diagram illustrates a true-complement differential signaling with programmable delay according to embodiments of the present invention; [0019] FIG. 7 is a circuit diagram illustrates a true-complement differential signaling with programmable delay and selectable input data according to embodiments of the present invention; [0020] FIG. 8 is a circuit block diagram illustrating a system for aligning a N channel bus according to embodiments of the present invention; [0021] FIG. 9 is a circuit block diagram illustrating a phase detector output states according to embodiments of the present invention; [0022] FIG. 10 is a flow diagram of method steps employed to align N differential data channels according to embodiments of the present invention; and [0023] FIG. 11 is a block diagram a data processing system suitable for practicing embodiments of the present invention. DETAILED DESCRIPTION [0024] In the following description, numerous specific details are set forth to provide a thorough understanding of the present invention. However, it will be obvious to those skilled in the art that the present invention may be practiced without such specific details. In other instances, well-known circuits may be shown in block diagram form in order not to obscure the present invention in unnecessary detail. For the most part, details concerning timing considerations and the like have been omitted inasmuch as such details are not necessary to obtain a complete understanding of the present invention and are within the skills of persons of ordinary skill in the relevant art. [0025] Refer now to the drawings wherein depicted elements are not necessarily shown to scale and wherein like or similar elements are designated by the same reference numeral through the several views. In the following, data channel refers to a single transmission path and differential data channel refers to a pair of transmission paths. Each differential data channel comprises transmission paths for a logic signal and the complement of the logic signal coupled to a single differential receiver. [0026] FIG. 4 is a circuit diagram of a current steering circuit for realizing differential signaling. Current source 409 supplies a constant current to field effect transistors (FETs) 407 and 408 . When Data 103 is a logic one and Data_b 105 is a logic zero, FET 407 is turned ON and FET 408 is turned OFF. The current 409 flows through transmission line 404 and resistor 403 and pulls node 413 to a logic zero. Since FET 408 is OFF, resistor 402 and power supply voltage 411 pulls node 414 to a logic one. Therefore, the output of differential receiver 401 is a logic one corresponding to the value of Data 103 . When Data_b 105 is a logic one and Data 103 is a logic zero, the input logic states of nodes 413 and 414 reverse. The current 409 now flows through transmission line 405 and resistor 402 and pulls node 414 to a logic zero. FET 407 is OFF, thus resistor 403 and power supply voltage 411 pulls node 413 to a logic one. In this case, the output of differential receiver 401 is a logic zero corresponding to the value of Data_b 105 . [0027] FIG. 5 is a circuit diagram of true-complement data transmission using single ended drivers to realize differential signaling. Data 103 is coupled to off-chip driver (OCD) 501 and Data_b 105 is coupled to OCD 502 . The output of OCD 501 drives transmission line 404 and output of OCD 502 drives transmission line 405 . The transmission lines 404 and 405 are terminated in a compatible termination network 503 coupled to nodes 413 and 414 and the inputs of receiver 401 . Data 103 transmits the true state of a logic signal and Data_b 105 transmits the complement of the logic signal. The circuit configuration 500 is used for differential signaling because single ended OCDs are generally easier to implement than true differential drivers. [0028] FIG. 6 is a circuit diagram of true-complement data transmission using single ended drivers where programmable delay elements 601 and 602 are inserted between the input signals Data 103 and Data_b 105 , respectively. Programming signals 603 and 604 are used to set the insertion delay in each data channel. In this manner, the skew between the data channel transmitting Data 103 and the data channel transmitting Data_b 105 is adjusted so the signals arriving at nodes 413 and 414 may be phase or transition aligned. [0029] FIG. 7 is a circuit diagram of the circuit in FIG. 6 with the addition of a multiplexer (MUX) in each differential data channel to allow either a clock signal 704 or the data signals Data 103 and Data_b 105 to be transmitted to differential receiver 401 . If the data channels are to be aligned, then data select 701 selects clock 704 as the input to both data channels. Since the same signal is transmitted over both data channels, then the inherent delay differences may be compensated by adjusting programmable delay elements 601 and 602 . Initially, program signal 603 and delay select 604 may be programmed to set programmable delay elements 601 and 602 to one-half their maximum delays. This allows delay to be added or subtracted to compensate for either leading or lagging phase shifts between the data channels. The common clock signals are transmitted by OCDs 501 and 502 through transmission lines 404 and 405 respectively. Termination network 503 is configured to be compatible with the transmission lines and the drivers and receivers. The phase shift between the signals arriving at nodes 413 and 414 represents the time delay difference between the two data channels. Unless compensated for by adjusting the relative delays of programmable delay elements 601 and 602 , the data channel timing skew will effect the signal quality of the signal generated on the output of differential receiver 401 . [0030] FIG. 8 is a block diagram of a system for aligning N differential channels according to embodiments of the present invention. Skew controller 801 controls the channel skew alignment process. When align channels command 807 transitions to a logic one, skew controller 801 starts the alignment process by selecting differential data channel 1 for the alignment process. Control signal 701 selects clock 704 as the input to programmable delay elements 601 and 602 using MUXes 702 and 703 . Likewise, control programming signals 603 and 604 set programmable delay elements 601 and 602 to a portion of their maximum delay (e.g., one-half). OCDs 501 and 502 drive the common clock signal 704 over transmission lines 404 and 405 where they are terminated by termination network 503 at nodes 413 and 414 . Phase detector 803 generates logic states corresponding to the phase differences between the signals arriving at nodes 413 and 414 . Skew controller 801 selects the output of phase detector 803 as the phase error feedback signal 805 using MUX 802 . Depending on the number of outputs (P) necessary to determine the phase between the signals at nodes 413 and 414 , MUX 802 is a PxN by P MUX. In one embodiment, phase detector 803 has two logic outputs with four logic states, thus MUX 802 would be a 2Nx2 MUX. [0031] Depending on the “value” of the phase error feedback signal 805 , skew controller adjusts the delays of programmable delay elements 601 and 602 until the phase error feedback 805 indicates that the timing skew between the data channels in differential data channel 1 is within a predetermined minimum value. When this value is reached, the program values of program signals 603 and 604 are latched or held while the next channel is selected for alignment. Alignment continues until differential data channel N is aligned using phase detector 804 . When the alignments are completed, then skew controller 801 signals to the system (e.g., system 1300 ) that bus alignment is complete and the system can switch to operation mode wherein actual data signals (e.g., Data 103 and Data_b 105 ) are transmitted between the driver side and the receiver. [0032] FIG. 9 is a block diagram of an exemplary phase detector 803 illustrating the logic states of the two outputs PD_out 904 and PD_out 905 . Phase detectors are known in the art and may be tailored to meet the requirements of skew controller 801 . In one embodiment, phase detector 803 has two digital outputs representing four logic states as follows: [0033] State 1: first delay signal 901 lags second delay signal 902 and PD_out 904 is a logic 1 and PD_out 905 is a logic 0. [0034] State 2: first delay signal 901 leads second delay signal 902 and PD_out 904 is a logic 0 and PD_out 905 is a logic 1. [0035] State 3: first delay signal 901 is in phase with second delay signal 902 and PD_out 904 is a logic 1 and PD_out 905 is a logic 1. [0036] State 4: the phase difference between first delay signal 901 and second delay signal 902 is indeterminate and PD_out 904 is a logic 0 and PD_out 905 is a logic 0. [0000] It is understood that other phase detector states may be used that are compatible with a skew controller 801 and still be within the scope of the present invention. [0037] FIG. 10 is a flow diagram of method steps used in embodiments of the present invention. In step 1001 , skew controller 801 receives a align channels command 807 from the system employing embodiments of the present invention. In step 1002 , controller 801 selects the differential data channel 1 to align. In step 1003 , the clock 704 is selected as the input to both of the data channels and phase detector 803 is selected to provide the phase error feedback signal 805 . In step 1004 , the delays of programmable delay elements 601 and 602 are set to one-half their maximum delay. The phase error is measured in step 1005 and in step 1006 , the delays in programmable delay elements 601 and 602 are adjusted until phase error feedback indicates the phase error is within a predetermined minimum value. The program inputs setting the delays in the preceding data channels are latched. In step 1007 , the next differential data channel is selected. In step 1008 , a test is done to determine if all channels have been aligned. If all channels have been aligned, then in step 1009 a functional mode is resumed by selecting Data 103 and Data_b 105 as the transmitted data signals. If all the differential data channels have not been aligned, then a branch is taken back to step 1003 . [0038] FIG. 11 is a high level functional block diagram of a representative data processing system 1100 suitable for practicing the principles of the present invention. Data processing system 1100 includes a central processing system (CPU) 1110 operating in conjunction with a system bus 1112 . System bus 1112 operates in accordance with a standard bus protocol, such as the ISA protocol, compatible with CPU 1110 . CPU 1110 operates in conjunction with electronically erasable programmable read-only memory (EEPROM) 1116 and random access memory (RAM) 1114 . Among other things, EEPROM 1116 supports storage of the Basic Input Output System (BIOS) data and recovery code. RAM 1114 includes, DRAM (Dynamic Random Access Memory) system memory and SRAM (Static Random Access Memory) external cache. I/O Adapter 1118 allows for an interconnection between the devices on system bus 1112 and external peripherals, such as mass storage devices (e.g., a hard drive, floppy drive or CD/ROM drive), or a printer 1140 . A peripheral device 1120 is, for example, coupled to a peripheral control interface (PCI) bus, and I/O adapter 1118 therefore may be a PCI bus bridge. User interface adapter 1122 couples various user input devices, such as a keyboard 1124 or mouse 1126 to the processing devices on bus 1112 . Display 1138 which may be, for example, a cathode ray tube (CRT), liquid crystal display (LCD) or similar conventional display units. Display adapter 1136 may include, among other things, a conventional display controller and frame buffer memory. Data processing system 1100 may be selectively coupled to a computer or telecommunications network 1141 through communications adapter 1134 . Communications adapter 1134 may include, for example, a modem for connection to a telecom network and/or hardware and software for connecting to a computer network such as a local area network (LAN) or a wide area network (WAN). CPU 1110 and other components of data processing system 1100 may contain logic circuitry in two or more integrated circuit chips that are coupled with off-chip differential signaling. The timing skew between data channels of the differential data channels may be aligned using the system and method according to embodiments of the present invention. [0039] Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Data busses are configured as N differential channels driven by a data signal and its complement through two off-chip drivers (OCDs). Each OCD is preceded by a programmable delay element and a two way MUX. The two data channels either transmit the data signals or a common clock signal as determined by a select signal from a skew controller. The differential signals are received in a differential receiver and a phase detector. The output of the phase detector in each differential channel is routed through an Nx1 MUX. The Nx1 MUX is controlled by the skew controller. The output of the Nx1 MUX is fed back as a phase error feedback signal to the skew controller. Each differential data channel is sequentially selected and the programmable delays are adjusted until the phase error feedback signal from the selected phase detector reaches a predetermined minimum allowable value. Periodic adjustment may be implemented for calibration.

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of and priority to U.S. Provisional Patent Application No. 60/987,444, filed Nov. 13, 2007, the entire disclosure of which is incorporated by reference herein. BACKGROUND 1. Technical Field The present disclosure relates to a dual lumen catheter having an operative passageway for use in minimally invasive endoluminal surgery. More particularly, the present disclosure relates to a duel lumen catheter and method of performing minimally invasive endoluminal surgery through the stomach of a patient. 2. Background of Related Art Surgeons are constantly searching for ways of performing surgical procedures within the body of a patient in a minimally invasive manner. This is desirable in order to reduce scarring, as well as, to shorten the healing or recuperation time of a patient from the surgery. As an example, one way to accomplish this is through the use of trans-luminal or trans-gastric surgery. In these methods, the surgeon inserts various instruments through the esophagus of the patient to gain access to the stomach. Once the stomach has been reached, and opening in the gastric wall is accomplished to gain access to the peritoneal cavity and perform various surgeries, such as, for example, hernia repair, etc. In these surgical procedures the peritoneal cavity is typically insufflated to provide a visualization area and\or working room for the surgical instruments. However, a potential problem exists when the peritoneal cavity is pressurized in that the pressure created within the peritoneal cavity pushes down on the stomach thereby flattening the stomach and making it difficult to manipulate surgical and/or visualization instruments through the interior of the stomach. Thus, it would be desirable to provide a catheter and method of performing a trans-gastric surgery without the attendant problem of stomach collapse due to pressurization of the adjacent peritoneal cavity. SUMMARY There is disclosed a dual lumen catheter for use in minimally invasive surgery. The catheter generally includes a hub, a first tube extending through the hub and defining an operative lumen from the hub to a distal end of the first tube. A second tube extends parallel to the first tube and sealed at its distal end. The distal end of the second tube is positioned proximally of the distal end of the first tube, wherein the second tube defines an inflation lumen. In one embodiment the second tube is positioned concentrically about the first tube. The second tube includes inflation ports positioned adjacent the distal end of the second tube. A seal is positioned between the first and second tubes to seal the distal end of the second tube. A valve system is in fluid communication with the inflation lumen such that the valve system applies a source of fluid through the inflation lumen. The first tube includes ports positioned adjacent the distal end of the first tube and includes a cutting edge at the distal end thereof. In an alternative embodiment, the first and second tubes extend through and distally of a support tube associated with the hub. A seal is positioned within the support tube and about the first and second tubes to seal interior of the support tube. The second tube includes inflation ports positioned adjacent the distal end of the second tube. There is also disclosed a method of performing a minimally invasive procedure utilizing a dual lumen catheter. A catheter is provided having a first tube defining an operative lumen and a second tube, parallel to the first tube, defining an inflation lumen and terminating proximally of the distal end of the first tube. The catheter is inserted through the esophagus of a patient so as to position a distal end of the second tube within the stomach of a patient. The catheter is further advanced through the esophagus of a patient so as to position the distal end of the first tube outside of the stomach of the patient and a surgical operation is performed through the first tube and outside the stomach of the patient. The method further includes pressurizing the interior of the stomach by forcing a fluid through the inflation lumen and pressurizing an area outside of the stomach by forcing a fluid through the operative lumen. In one use of the disclosed method the wall of the stomach is punctured with the distal end of the first tube. DESCRIPTION OF THE DRAWINGS Various embodiments of the presently disclosed dual lumen surgical catheter are disclosed herein with reference to the drawings, wherein: FIG. 1 is a perspective view of one embodiment of a duel lumen catheter for use in minimally invasive endoluminal surgery; FIG. 2 is a cross-sectional view taken along the line 2 - 2 of FIG. 1 ; FIG. 3 is a cross-sectional view taken at the junction of the outer tubular member and the inner tubular member; FIG. 4 is a perspective view, partially shown in section, illustrating the embodiment of FIG. 1 initially inserted into a patient; FIG. 5 is a perspective view, similar to FIG. 4 , illustrating the operating end of the catheter positioned within the peritoneal cavity of the patient; FIG. 6 is a perspective view of an alternative embodiment of a duel lumen catheter for use in minimally invasive endoluminal surgery; FIG. 7 is a cross-sectional view taken along lines 7 - 7 of FIG. 6 ; FIG. 8 is a cross-sectional view taken at the junction of an outer sheath with the inner lumens; FIG. 9 is a perspective view, partially shown in section, illustrating the embodiment of FIG. 6 initially inserted into a patient; and FIG. 10 is a perspective view, similar to FIG. 9 , illustrating the operating end of the catheter positioned within the peritoneal cavity of a patient. DETAILED DESCRIPTION OF EMBODIMENTS Embodiments of the presently disclosed dual lumen catheter and methods of endoluminal surgery will now be described in detail with reference to the drawings wherein like numerals designate identical or corresponding elements in each of the several views. As is common in the art, the term ‘proximal” refers to that part or component closer to the user or operator, i.e. surgeon or physician, while the term “distal” refers to that part or component further away from the user. Referring to FIG. 1 , there is disclosed a dual lumen catheter 10 particularly suitable for use in endoluminal surgery to support the stomach against collapse during surgical procedures. Catheter 10 generally includes a hub 12 having an outer sheath 14 extending distally from hub 12 . An operative or inner tube 16 extends through hub 12 and sheath 14 and defines an operative lumen 18 extending from a proximal end 20 of inner tube 16 to a distal end 22 of inner tube 16 . Operative lumen 18 in inner tube 16 provides an access passageway for surgical instruments as well as a fluid flow path for insufflation fluids to insufflate the peritoneal cavity. A plurality of insufflation ports 24 are provided adjacent distal end 22 of inner tube 16 . Insufflations ports 24 are provided in case the instruments inserted through inner tube 16 block or seal the distal end of operative lumen 18 and thus prevent the flow of insufflation fluid out of the open end of operative lumen 18 . Distal end 22 of inner tube 16 may additionally be provided with a cutting edge 26 to facilitate advancement of distal end 22 through a stomach wall and a peritoneal lining. In order to steer or direct catheter 10 through the body of a patient, hub 12 may be provided with a pair of wings 28 . It should be noted that, however, other methods of steering catheter 10 to the body of a patient are contemplated here in such as, for example, various steerable guide wires etc. Additionally, other means or instruments known in the art may be provided to penetrate the stomach wall and peritoneal lining to provide access to the peritoneal cavity. Catheter 10 is additionally provided with an outer tube 30 which extends partially over inner tube 16 to define a common longitudinal axis A-A. Outer tube 30 is sealed at a distal end 32 to inner tube 16 . A plurality of inflation ports 34 are provided adjacent distal end 32 of outer tube 30 and are spaced proximally from insufflation ports 24 at a distal end 22 of inner tube 16 . A T-collar 36 surrounds sheath 14 and is in fluid communication with inflation ports 34 at distal end 32 of outer tube 30 . A valve system 38 is in fluid communication with T-collar 36 through a fluid tube 40 . The inner tube 16 extends to a position 50 distal from the distal end 32 of the outer or insufflation tube 30 to define the common longitudinal axis A-A, the common longitudinal axis A-A extending at least to the position 50 . The distal end 22 of the inner tube 16 defines a portion 16 ′ of the inner tube 16 that extends at least from the position 50 to define an offset axis B-B with respect to the common longitudinal axis A-A. The offset axis B-B defines an offset angle θ with respect to the common longitudinal axis A-A of the inner tube 16 . Consequently, the radially oriented insufflation ports 24 in proximity to the distal end 22 of the operative or inner tube 16 are positioned at a position that is offset from the radially oriented insufflation ports 34 at the distal end 32 of the outer or insufflation tube 30 . Referring for the moment to FIG. 2 , an inflation lumen 42 is defined between outer tube 30 and inner tube 16 . As shown, inner tube 16 and outer tube 30 , and thus operative lumen 18 and inflation lumen 42 , are concentric. Inflation lumen 42 carries inflation fluid from valve system 38 to inflation ports 34 at a distal end of outer tube 30 . Referring to FIG. 3 , and as noted hereinabove, distal end 32 of outer tube 30 terminates proximally of distal end 22 of inner tube 16 and is sealed to inner tube 16 . Specifically, distal end 32 of outer tubes 30 is sealed to inner tube 16 by a circumferential seal 44 . Seal 44 may be formed by gluing distal end 32 to inner tube 16 or may be provided as a separate member which is glued, welded, or otherwise affixed to distal end 32 and inner tube 16 . Thus, fluid flowing from valve system 38 through inflation lumen 42 can only exit inflation ports 34 formed in distal end 32 of outer tube 30 . Referring to FIGS. 4 and 5 , and initially with regard to FIG. 4 , the use of catheter 10 in endoluminal surgery to access the peritoneal cavity through the stomach will now be described. Initially, catheter 10 is inserted through the mouth M of a patient P and advanced through the esophagus E so as to position distal end 22 of inner tube 16 , as well as distal end 32 of outer tube 30 , within the stomach S of the patient. Once catheter 10 has been so positioned, a first source of insufflation fluid (not shown) may be attached to a valve system 38 and actuated to force a first inflation fluid F 1 through inflation lumen 42 and out inflation ports 34 in outer tube 30 in order to insufflate stomach S. The first source of inflation fluid may provide various auxiliary functions such as, for example, providing for pressure measurement so as to maintain constant pressure within the stomach, etc. While the present procedure is being described as insufflating stomach S prior to penetration of the stomach and the peritoneal cavity and insufflation of the peritoneal cavity, insufflation of stomach S may be delayed until after one or more of these steps have been accomplished. With continued reference to FIG. 4 , catheter 10 is then further advanced through the esophagus E to cause cutting edge 26 at distal end 22 of inner tube 16 to engage and puncture stomach S. Referring now to FIG. 5 , continued advancement of catheter 10 through esophagus E causes cutting edge 26 to form a hole 46 through stomach S and a hole 48 in peritoneal cavity PC to position distal end 22 of inner tube 16 within peritoneal cavity PC. Thereafter, a second source of inflation fluid (not shown) is connected to hub 12 and actuated to force a second inflation fluid F 2 through operative lumen 18 so as to insufflate peritoneal cavity PC. Once peritoneal cavity PC has been insufflated, operative lumen 18 is used as the access passageway for the insertion of instruments into peritoneal cavity PC to perform any of various surgical procedures. It should be noted that, during the performance of the surgical procedures, the fluid pressure within stomach S due to inflation fluid F 1 prevents the flattening or collapse of stomach S due to the inflation pressure in the peritoneal cavity PC and the activities of the surgical procedures being conducted therein. As with the first source of inflation fluid described hereinabove, the second source of inflation fluid might also be provided with auxiliary functions such as, for example, pressure measurement, pressure monitors and control devices, etc. in order to manage and adjust any losses in inflation pressure within peritoneal cavity PC during the surgical procedure. It should be further noted that the disclosed catheter 10 and disclosed surgical method allows the surgeon to precisely control the pressures within peritoneal cavity PC and stomach S concurrently. While not specifically shown, it is also contemplated that catheter 10 may be provided with the various anchoring and or sealing structures, such as, for example anchoring or sealing balloons adjacent distal ends 22 and 32 of inner tube 16 and outer tubes 30 , respectively. This will assist in preventing movement of catheter 10 during the surgical procedures as well as preventing leakage and/or transfer of inflation fluids between stomach S and peritoneal cavity PC. Referring now to FIG. 6 , there is disclosed in alternative embodiment of a dual lumen catheter 50 . In contrast to dual lumen catheter 10 described hereinabove, the operative and inflation lumens of catheter 50 are parallel but not concentric as was the case with dual lumen catheter 10 . Catheter 50 generally includes a hub 52 having an outer sheath 54 extending distally therefrom. A support tube 56 extends through hub 52 and outer sheath 54 and encases the operative and inflation lumens of catheter 50 as described in more detail hereinbelow. Hub 52 is provided with a pair of wings 58 to facilitate manipulation of catheter 50 through the body of a patient. A distal tube 60 extends through hub 52 , outer sheath 54 and support tube 56 to define a longitudinal axis N-A′. A proximal end 62 of distal tube 60 is positioned adjacent hub 52 while a distal end 64 of distal tube 60 is provided with a plurality of ports 66 . A cutting edge 68 may be provided on distal end 64 to facilitate puncturing of the stomach and the peritoneal cavity. A proximal tube 70 extends partially through sheath 54 and through support tube 56 . Proximal tube 70 has a sealed distal end 72 and a plurality of ports 74 adjacent sealed distal end 72 . A T-collar 76 surrounds sheath 54 and is in fluid communication with ports 74 in proximal tube 70 . A valve system 78 is provided to receive of source of fluid and is connected to T-collar 76 by a fluid tube 80 . Distal tube 60 defines an operative lumen 82 extending from proximal end 62 to distal end 64 . As best shown in FIG. 7 , inner tube 70 defines an inflation lumen 84 . Distal tube 60 and proximal tube 70 , and thus operative lumen 82 and inflation lumen 84 , extend through support tube 56 in parallel, but not concentric, fashion. The distal tube 60 extends at least to a position 92 that is distal from the sealed end 72 of the proximal tube 70 to define the longitudinal axis A′-A′. The distal end 64 of the distal tube 60 defines a portion 60 ′ of the distal tube 60 that extends at least from position 92 to define an offset axis B′-B′ with respect to the longitudinal axis A′-A′. Additionally, the sealed distal end 72 of proximal tube 70 extends through hub 52 , outer sheath 54 and support tube 56 to define a longitudinal axis A″-A″ along the proximal tube 70 . Since the distal tube 60 and proximal tube 70 , and thus operative lumen 82 and inflation lumen 84 , extend through support tube 56 in parallel fashion, the longitudinal axes A′-A′ and A″-A″ are also parallel to each other. The offset axis B′-B′ of the portion 60 ′ of the distal tube 60 defines an offset angle θ 1 with respect to the longitudinal axis A′-A′ of the distal tube 60 . The offset axis B′-B′ also defines an offset angle θ 2 with respect to the longitudinal axis A″-A″ of the proximal tube 70 . When the two longitudinal axes A′-A′ and A″-A″ are precisely parallel, the offset angles θ 1 and θ 2 are equal. Consequently, the radially oriented insufflation ports 66 in proximity to the distal end 64 of the distal tube 60 are positioned at a position that is offset from the radially oriented insufflation ports 74 at the sealed distal end 72 of the proximal tube 70 . Referring for the moment to FIG. 8 , both distal tube 60 and proximal tube 70 extend beyond support tube 56 . A seal 86 is provided within support tube 56 and about distal tube 60 and proximal tube 70 to prevent the influx of any fluids or other matter within support tube 56 during a surgical procedure. Referring to FIGS. 9 and 10 , and initially with regard to FIG. 9 , the use of catheter 50 in endoluminal surgery to access the peritoneal cavity through the stomach will now be described. The following procedure is substantially identical to that described hereinabove with respect to catheter 10 . Initially, catheter 50 is inserted through the mouth M of a patient P and advanced through the esophagus E so as to position in distal end 64 of distal tube 60 as well as distal end 72 of proximal tube 70 within stomach S of the patient. Once catheter 50 has been so positioned, a first source of insufflation fluid (not shown) may be attached to a valve system 78 and actuated to force a first inflation fluid F 1 through inflation lumen 84 and out inflation ports 74 in proximal tube 70 in order to insufflated stomach S. As above, the first source of inflation fluid may provide various auxiliary functions such as, for example, providing for pressure measurement so as to maintain constant pressure within the stomach, etc. While the present procedure is being described as insufflated stomach S prior to penetration of the stomach and the peritoneal cavity and insufflation of the peritoneal cavity, insufflation of stomach S may be delayed until after one or more of these steps have been accomplished. With continued reference to FIG. 9 , catheter 50 is then further advanced through the esophagus E to cause cutting edge 68 at distal end 64 of distal tube 60 to engage and puncture stomach S. Referring now to FIG. 10 , continued advancement of catheter 50 through esophagus E causes cutting edge 68 to form a hole 88 through stomach S and a hole 90 in peritoneal cavity PC to position distal end 64 of distal tube 60 within peritoneal cavity PC. Thereafter, a second source of inflation fluid (not shown) may be connected to hub 12 and actuated to force a second inflation fluid F 2 through operative lumen 82 so as to insufflate peritoneal cavity PC. Once peritoneal cavity PC has been insufflated, operative lumen 82 is used as the access passageway for the insertion of instruments into peritoneal cavity PC to perform any of various surgical procedures. As noted hereinabove, the fluid pressure within stomach S due to inflation fluid F 1 prevents the flattening or collapse of stomach S due to the inflation the peritoneal cavity PC and the activities of the surgical procedures being conducted therein. As with the first source of inflation fluid described hereinabove the second source of inflation fluid might also be provided with auxiliary functions such as, for example, pressure measurement, pressure monitors and control devices, etc. in order to manage and adjust any losses in inflation pressure within peritoneal cavity PC during the surgical procedure. It should be further noted that the disclosed catheter 50 and the disclosed surgical method allow the surgeon to precisely control the pressures within peritoneal cavity PC and stomach S concurrently. While not specifically shown, it is also contemplated that catheter 50 , similar to catheter 10 described hereinabove, may be provided with the various anchoring and or ceiling structures, such as, for example anchoring or sealing balloons adjacent distal ends 64 and 72 of distal tube 60 and proximal tube 70 , respectively. This will assist in preventing movement of catheter 50 during the surgical procedures as well as preventing leakage and/or transfer of inflation fluids between stomach S and peritoneal cavity PC. It will be understood that various modifications may be made to the embodiments disclosed herein. For example, additional lumens may be provided through the disclosed catheters to provide for auxiliary instruments such as, for example, endoscopes, etc. Further, as noted hereinabove, various anchoring and/or sealing structures may be provided on the disclosed tubes to prevent leakage as well as movement of the catheter within the body of the patient. Additionally, various known types of fluid sources and auxiliary devices for maintaining and monitoring pressure through the various lumens and within the various cavities in the body of the patient may be provided. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.

A duel lumen catheter is provided for use in minimally invasive surgery. The catheter generally includes a first tube defining an operative lumen and a second tube terminating proximally of the first tube and defining an inflation lumen. In one embodiment, the first and second tubes are concentric. In an alternative embodiment, the first and second tubes are separate and extend parallel to each other. The first and second tubes are provided with inflation ports adjacent their respective distal ends. There is also provided a method for performing minimally invasive surgery by inserting the catheter through the esophagus of a patient, insufflating the stomach and performing a surgical operation through the catheter and external to the stomach.

REFERENCE TO RELATED APPLICATION [0001] This application claims priority to and is a continuation-in-part of U.S. patent application Ser. No. 15/142,934, filed Apr. 29, 2016, with title ROTATIONAL POSITIONAL MONITORING OF VEHICLE LIFTS, which is hereby incorporated by reference herein. BACKGROUND [0002] Vehicle lift systems may be used to lift various kinds of vehicles relative to the ground. Some vehicle lifts operate by positioning two runways at, or near, a shop floor level. The vehicle may be then driven or rolled onto the runways, allowing the runways to support the vehicle. The underside of each runway may be attached to a plurality of hydraulically driven lifting assemblies. The lifting assemblies may be actuated to raise the runways and the vehicle to a desired height. Afterward, the vehicle may then be lowered once the user has completed his or her task requiring the vehicle lift. In some cases, the lifting assemblies may comprise a single elongated member which may rotate relative to the floor to pivot the runways upwardly. In other cases, the lifting assemblies may comprise a plurality of linkages which pivot relative to one another to cause the runways to rise upwardly, similar to a pair of scissors. [0003] Other vehicle lift systems are formed by a set of mobile, above-ground lift columns. An example of a mobile column lift system is the MACH 4 Mobile Column Lift System by Rotary Lift of Madison, Indiana. Each mobile column may include a hydraulically driven lifting assembly. The mobile columns may be readily positioned in relation to the vehicle. The mobile columns may then be activated such that lifting assemblies actuate to raise the vehicle from the ground in a coordinated/synchronized fashion. The mobile columns may be controlled through wireless communication with a wireless control center. The wireless control center may associate with each mobile column in order to form a synchronized lift. [0004] While a variety of systems and configurations have been made and used to control lift systems, it is believed that no one prior to the inventors has made or used the invention described herein. BRIEF DESCRIPTION OF THE DRAWINGS [0005] While the specification concludes with claims which particularly point out and distinctly claim the invention, it is believed the present invention will be better understood from the following description of certain examples taken in conjunction with the accompanying drawings, in which like reference numerals identify the same elements and in which: [0006] FIG. 1A shows a perspective view of an exemplary hydraulic cylinder assembly in a withdrawn position; [0007] FIG. 1B shows a perspective view of the hydraulic cylinder assembly of FIG. 1A in an expanded position; [0008] FIG. 2 shows a partial cross-sectional exploded view of the hydraulic cylinder assembly of FIG. 1A ; [0009] FIG. 3 shows a cross-sectional perspective view of the hydraulic cylinder assembly of FIG. 1A ; [0010] FIG. 4A shows a cross-sectional elevation view of the hydraulic cylinder assembly of FIG. 1A ; [0011] FIG. 4B shows a cross-sectional elevation view of the hydraulic cylinder assembly of FIG. 1A and 1B in a partially expanded position; [0012] FIG. 4C shows a cross-sectional elevation view of the hydraulic cylinder assembly of FIG. 1B ; [0013] FIG. 5 shows a perspective view of an exemplary vehicle lift with the hydraulic cylinder assembly of FIG. 1A ; [0014] FIG. 6A shows a side elevational view of the vehicle lift of FIG. 5 in a retracted position; [0015] FIG. 6B shows a side elevational view of the vehicle lift of FIG. 5 is an extended position; [0016] FIG. 7 shows an exploded perspective view of a lift assembly of the vehicle lift of FIG. 5 ; [0017] FIG. 8A shows a perspective view of the lift assembly of FIG. 7 , with the lift assembly in a retracted position; [0018] FIG. 8B shows a perspective view of the lift assembly of FIG. 7 , with the lift assembly in an extended position; [0019] FIG. 9A shows a cross-sectional elevation view of an alternative hydraulic cylinder assembly in a retracted position, where the alternative hydraulic cylinder assembly may be used in place of the hydraulic cylinder assembly of FIG. 1A ; [0020] FIG. 9B shows a cross-sectional elevation view of the hydraulic cylinder assembly of FIG. 9A in a partially expanded position; [0021] FIG. 9C shows a cross-sectional elevation view of the hydraulic cylinder assembly of FIG. 9A in an expanded position; [0022] FIG. 10A shows a cross-sectional elevation view of another alterative hydraulic cylinder assembly in a retracted position, where the alternative hydraulic cylinder assembly may be used in place of the hydraulic cylinder assembly of FIG. 1A ; [0023] FIG. 10B shows a cross-sectional elevation view of the hydraulic cylinder assembly of FIG. 10A in a partially expanded position; [0024] FIG. 10C shows a cross-sectional elevation view of the hydraulic cylinder assembly of FIG. 10A in an expanded position. DESCRIPTION [0025] The following description of certain examples should not be used to limit the scope of the present invention. Other examples, features, aspects, embodiments, and advantages of the invention will become apparent to those skilled in the art from the following description, which is by way of illustration, one of the best modes contemplated for carrying out the invention. As will be realized, the invention is capable of other different and obvious aspects, all without departing from the invention. Accordingly, the drawings and descriptions should be regarded as illustrative in nature and not restrictive. A. Exemplary Hydraulic Actuator Assembly [0026] FIGS. 1-4C show an exemplary hydraulic actuator assembly ( 100 ) that may be readily incorporated into a variety of vehicle lift assemblies. As best shown in FIG. 2 , hydraulic actuator assembly ( 100 ) includes a cylinder assembly ( 110 ), a linear actuating assembly ( 120 ), and a linear displacement measuring assembly ( 130 ). As will be described in greater detail below, linear actuating assembly ( 120 ) may move relative to cylinder assembly ( 110 ) from a fully withdrawn position, as shown in FIG. 1A , to a fully extended position, as shown in FIG. 1B . Additionally, linear actuating assembly ( 120 ) may move to any number of positions between the fully withdrawn and the fully extended position. Therefore, movement of linear actuating assembly ( 120 ) may be utilized in order to actuate a vehicle lift assembly in order to raise or lower a vehicle to a desired height. Such vehicle lift assemblies may include a scissor lift assembly, a carriage style lift assembly, an in-ground lift assembly, an above-ground lift assembly, or any other suitable lift assembly that would be apparent to one having ordinary skill in the art. [0027] Cylinder assembly ( 110 ) includes a hydraulic cylinder ( 102 ) and an attachment feature ( 112 ). While in the current example, hydraulic cylinder ( 102 ) and attachment feature ( 112 ) are unitarily connected, it should be understood that hydraulic cylinder ( 102 ) and attachment feature ( 112 ) may be fixedly coupled with any other suitable means known to a person having ordinary skill in the art in view of the teachings herein. For example, hydraulic cylinder ( 102 ) and attachment feature ( 112 ) may be fixedly coupled with a plurality of nuts and bolts. [0028] Attachment feature ( 112 ) is located at the bottom of hydraulic cylinder ( 102 ) in order to couple cylinder assembly ( 110 ) to a portion of a vehicle lift assembly, as will be described in greater detail below. In the current example, attachment feature ( 112 ) is configured to receive a pin ( 298 ) (see FIG. 7 ) in order to attach hydraulic cylinder ( 102 ) to a portion of a vehicle lift assembly. Therefore, attachment feature ( 112 ) may allow hydraulic actuator assembly ( 100 ) to rotate about an axis defined by pin ( 298 ). In other words, hydraulic cylinder ( 102 ) may be rotatably coupled to a portion of a vehicle lift assembly (e.g., a lift assembly ( 250 ) as shown in FIG. 5 ) via attachment feature ( 112 ). [0029] However, it should be understood that rotational capabilities of attachment feature ( 112 ) are merely optional. Some vehicle lift assemblies do not require rotation of hydraulic cylinder ( 102 ) in order to raise or lower a vehicle. For example, hydraulic cylinder ( 102 ) may alternatively be slidably coupled to a portion of vehicle lift assembly. Hydraulic cylinder ( 102 ) may alternatively be fixedly coupled to a portion of a vehicle lift assembly (e.g., a lift assembly ( 250 ) as shown in FIG. 5 ). Any suitable attachment feature known by a person having ordinary skill in the art in view of the teachings herein may be employed. [0030] Turning to FIG. 2 , hydraulic cylinder ( 102 ) includes an interior base end ( 116 ), an interior annular wall ( 114 ), and an interior head end ( 118 ); all of which collectively define a cavity ( 106 ). Head end ( 118 ) further defines a tunnel ( 104 ) extending from cavity ( 106 ) to an exterior of hydraulic cylinder ( 102 ). Tunnel ( 104 ) is dimensioned to slidably house a rod ( 122 ) of linear actuating assembly ( 120 ) while cavity ( 106 ) is dimensioned to slidably house a plunger ( 124 ) of linear actuating assembly ( 120 ). Plunger ( 124 ) and rod ( 122 ) are coupled with each other such that plunger ( 124 ) and rod ( 122 ) slide relative to tunnel ( 104 ) and cavity ( 106 ) together. [0031] Hydraulic cylinder ( 102 ) also has a fluid channel ( 107 ) associated with the base end ( 116 ) and a fluid channel ( 105 ) associated with the head end ( 118 ). Each fluid channel ( 105 , 107 ) is in fluid communication with a chamber ( 106 A, 106 B) of cavity ( 106 ), respectively. Chamber ( 106 A) is defined by interior base end ( 116 ), interior annular wall ( 114 ), and a radial face ( 136 ) of plunger ( 124 ). Chamber ( 106 B) is defined by interior head end ( 118 ), interior annular wall ( 114 ), and a radial face ( 134 ) of plunger ( 124 ). It should be understood that because plunger ( 124 ) is slidable within cavity ( 106 ), chambers ( 106 A, 106 B) are capable of changing volume as plunger ( 124 ) actuates within cavity ( 106 ). [0032] Each fluid channel ( 105 , 107 ) may fill respective chamber ( 106 A, 106 B) with hydraulic fluid. Tunnel ( 104 ) and rod ( 122 ) may fluidly isolate chamber ( 106 B) from the exterior of hydraulic cylinder ( 102 ) by using a seal gland or in any other suitable manner known to the art in view of the teachings herein. As will be described in greater detail below, fluid channels ( 105 , 107 ) may help actuate plunger ( 124 ) within cavity ( 106 ). [0033] Base end ( 116 ) further defines a rotary sensor mount ( 108 ) dimensioned to house a rotary sensor ( 140 ). Rotary sensor mount ( 108 ) is capable of fixing a portion of rotary sensor to hydraulic cylinder ( 102 ). While in the current example, rotary sensor mount ( 108 ) is a recess defined by base end ( 116 ), bolts, nuts, threaded rods, or any other suitable structures may be utilized to fix a portion of rotary sensor ( 114 ) to hydraulic cylinder ( 102 ). [0034] Linear actuating assembly ( 120 ) includes rod ( 122 ) having one end fixed to plunger ( 124 ) and another end fixed to an attachment feature ( 126 ). Rod ( 122 ) defines channel ( 128 ). Channel ( 128 ) extends from the portion of rod ( 122 ) that is fixed to plunger ( 124 ) toward the portion of rod ( 122 ) fixed to attachment feature ( 126 ). Rod ( 122 ) also has a pin ( 125 ) located at the portion of rod ( 122 ) fixed to plunger ( 124 ). As will be described in more detail below, channel ( 128 ) and pin ( 125 ) are dimensioned to interact with linear displacement measuring assembly ( 130 ) to measure the distance linear actuating assembly ( 120 ) actuates relative to cylinder assembly ( 110 ). This information may be utilized to determine the individual height of each hydraulic actuator assembly ( 100 ) in a vehicle lift system. A vehicle lift system may utilize this data in order to level a vehicle lift system, to limit or manage movement of linear actuating assembly ( 120 ), and for other purposes as will occur to those skilled in the art. [0035] While in the current example, rod ( 122 ) and attachment feature ( 126 ) are unitarily connected, it should be understood that rod ( 122 ) and attachment feature ( 126 ) may be fixedly coupled with any other suitable means known to a person having ordinary skill in the art in view of the teachings herein. For example, rod ( 122 ) and attachment feature ( 126 ) may be fixedly coupled with a plurality of nuts and bolts. [0036] Attachment feature ( 126 ) is located at the top of rod ( 122 ) in order to couple rod ( 122 ) to a portion of a vehicle lift assembly, as will be described in greater detail below. In the current example, attachment feature ( 126 ) is configured to receive a pin ( 300 ) in order to attach rod ( 122 ) to a portion of a vehicle lift assembly. Therefore, attachment feature ( 126 ) may allow hydraulic actuator assembly ( 100 ) to rotate about an axis defined by pin ( 300 ). In other words, rod ( 122 ) may be rotatably coupled to a portion of vehicle lift assembly via attachment feature ( 126 ). [0037] However, it should be understood that rotational capabilities of attachment feature ( 126 ) are merely optional. Some vehicle lift assemblies do not require rotation of rod ( 122 ) in order to raise or lower a vehicle. For example, rod ( 122 ) may be fixedly coupled to a portion of a vehicle lift assembly, or any other suitable attachment feature known by a person having ordinary skill in the art in view of the teachings herein may be employed. [0038] As mentioned above, rod ( 122 ) is slidably housed within tunnel ( 104 ) of hydraulic cylinder ( 102 ). Plunger ( 124 ) may be fixed to rod ( 122 ) by threads, bolts, or nuts, or any other structures known to one having ordinary skill in the art in view of the teachings herein. As mentioned above, plunger ( 124 ) is slidably housed within cavity ( 106 ). Plunger ( 124 ) is also positioned and dimensioned such that a circumferential face ( 132 ) of plunger ( 124 ) makes contact with interior annular wall ( 114 ). Circumferential face ( 132 ) of plunger ( 124 ) may be machined with grooves configured to fit elastomeric or metal seals and bearing elements. Plunger ( 124 ) is configured to separate cavity ( 106 ) into two fluidly isolated chambers ( 106 A, 106 B). Therefore, first chamber ( 106 A) and second chamber ( 106 B) defined by cavity ( 106 ) and plunger ( 124 ) may fill or empty with fluid via fluid channels ( 105 , 107 ) in order to actuate plunger ( 124 ). [0039] As mentioned above, hydraulic cylinder ( 102 ) has two fluid channels ( 105 , 107 ) on opposite ends of hydraulic cylinder ( 102 ). Additionally, as mentioned above, first fluid chamber ( 106 A) and second fluid chamber ( 106 B) are in fluid isolation from one another. First fluid channel ( 107 ) may be in fluid communication with first chamber ( 106 A) while second fluid channel ( 105 ) may be in fluid communication with second chamber ( 106 B). One fluid channel ( 105 , 107 ) may be in communication with a fluid source such as a pump while the other fluid channel ( 105 , 107 ) may be in fluid communication with another fluid source such as a reservoir. Fluid sources in fluid communication with channels ( 105 , 107 ) may fill first chamber ( 106 A) with hydraulic fluid while emptying second chamber ( 106 B) with hydraulic fluid. Because first chamber ( 106 A) and second chamber ( 106 B) are in fluid isolation, plunger ( 124 ) and the rest of linear actuating assembly ( 120 ) may actuate, similar to that shown in FIGS. 1A-1B and FIGS. 4A-4C , due to the change in volume of chambers ( 106 A, 106 B). [0040] It should be understood that there may be additional, external forces acting on hydraulic actuator assembly ( 100 ) which the pressure in first fluid chamber ( 106 A) or second fluid chamber ( 106 B) may need to overcome in order to actuate linear actuating assembly ( 120 ). For instance, if attachment feature ( 126 ) is connected to a portion of a vehicle lift assembly that is supporting a portion of a vehicle, the force provided by the pressure in first fluid chamber ( 106 A) acting on radial face ( 136 ) may need to overcome the load provided from supporting a portion of the vehicle. [0041] For example, as shown in FIGS. 1A-1B and FIGS. 4A-4C , if hydraulic fluid is filled within first chamber ( 106 A) while hydraulic fluid is emptied from second chamber ( 106 B), an upward force is generated on plunger ( 124 ), which actuates linear actuating assembly ( 120 ) in an upward direction with respect to hydraulic cylinder ( 102 ). In the opposite way, if hydraulic fluid is emptied from first chamber ( 106 A) while hydraulic fluid is being filled within the second chamber ( 106 B), a downward force may be generated on plunger ( 124 ), which actuates linear actuating assembly ( 120 ) in a downward direction with respect to hydraulic cylinder ( 102 ). [0042] Linear displacement measuring assembly ( 130 ) includes a rotation sensor ( 140 ) and a rotational actuating assembly ( 150 ). Rotation sensor ( 140 ) includes a rotating element ( 142 ) rotatably housed within a static element ( 148 ). Static element ( 148 ) is fixedly housed within rotary sensor mount ( 108 ) of hydraulic cylinder ( 102 ). Static element ( 148 ) may not rotate or actuate relative to hydraulic cylinder ( 102 ). Rotating element ( 142 ) defines an aperture ( 144 ) and a keyed hole ( 146 ). Static element ( 148 ) is configured to measure the rotational displacement of rotating element ( 142 ). As will be described in greater detail below, rotation sensor ( 140 ) is in electrical communication with a circuit board of a vehicle lift assembly or related sensing and/or control circuitry. The vehicle lift assembly may utilize the rotational displacement of rotating element ( 142 ) relative to static element ( 148 ) in order to monitor the positions of each of any number of hydraulic actuator assemblies ( 100 ) utilized in the vehicle lift assembly, using the rotational displacement to calculate the linear displacement of each hydraulic actuator assembly ( 100 ), and using that calculated linear displacement in a feedback control loop to manage the operation of the collection of hydraulic actuator assemblies ( 100 ). [0043] Rotational actuating assembly ( 150 ) includes a rotating shaft ( 152 ) and a keyed member ( 156 ). Rotating shaft ( 152 ) extends from a free end ( 154 ) to a coupling end ( 158 ). Coupling end ( 158 ) is housed within aperture ( 144 ) of rotation sensor ( 140 ), while keyed member ( 156 ) is housed with keyed hole ( 146 ). Coupling end ( 158 ) may be dimensioned for an interference fit with aperture ( 144 ) such that rotating shaft ( 152 ) may not actuate in the vertical direction relative to rotating element ( 142 ). For example, free end ( 154 ) may be dimensioned small enough to fit within aperture ( 144 ) while coupling end ( 158 ) may be dimensioned for an interference fit. Rotating shaft ( 152 ) may be inserted through aperture ( 144 ) via free end ( 154 ) until coupling end ( 158 ) develops an interference fit with aperture ( 144 ). Of course, rotating shaft ( 152 ) may be fixed in a vertical direction relative to rotating element ( 142 ) in any other suitable manner as would be apparent to one having ordinary skill in the art in view of the teachings herein. For example, coupling end ( 158 ) may be fixed to a bearing attached to base end ( 116 ) of cylinder assembly ( 110 ). [0044] Rotating shaft ( 152 ) also defines a helical slot ( 155 ) extending from coupling end ( 158 ) towards free end ( 154 ). Helical slot ( 155 ) is dimensioned to receive pin ( 125 ). As seen in FIGS. 4A-4C , as hydraulic fluid enters chamber ( 106 A) and exits chamber ( 106 B), linear actuating assembly ( 120 ) moves from a withdrawn position to an extended position. Additionally, pin ( 125 ) travels along helical slot ( 155 ), providing a camming effect to rotate rotating shaft ( 152 ) about the axis defined by movement of linear actuating assembly ( 120 ). As described above, keyed member ( 156 ) and coupling end ( 158 ) are rotationally fixed to rotating element ( 142 ) of rotation sensor ( 140 ) via keyed hole ( 146 ) and aperture ( 144 ). Therefore, as pin ( 125 ) rotates rotating shaft ( 152 ) via movement of linear actuating assembly ( 120 ), coupling end ( 158 ) and keyed member ( 156 ) rotate rotating element ( 142 ) relative to static element ( 148 ) of rotation sensor ( 140 ). Static element ( 148 ) may measure the rotational displacement of rotating element ( 142 ). Helical slot ( 155 ) may be shaped and dimensioned such that rotation of rotating shaft ( 152 ) directly correlates to linear displacement of linear actuating assembly ( 120 ) along rotating shaft ( 152 ). In other words, linear displacement measuring assembly ( 130 ) may measure the linear displacement of linear actuating assembly ( 120 ) relative to cylinder assembly ( 110 ) by measuring the rotation of rotating shaft ( 152 ) caused by camming action of pin ( 125 ). [0045] It should be understood that since rotation of rotating shaft ( 152 ) relative to linear actuating assembly ( 120 ) is used to measure linear displacement of linear actuating assembly ( 120 ), there should be no accidental rotation about the axis defined by movement of linear actuating assembly ( 120 ) of rotating shaft ( 152 ) relative to linear actuating assembly ( 120 ). Accidental rotation of rotating shaft ( 152 ) relative to linear actuating assembly ( 120 ) could give a false reading of linear displacement along the axis defined by movement of linear actuating assembly ( 120 ). Therefore, attachment features ( 112 , 126 ) need to rotationally fix cylinder assembly ( 110 ) and linear actuating assembly ( 120 ) relative to one another, along the axis defined by movement of linear actuating assembly ( 120 ), to prevent false readings. While in the current example, attachment features ( 112 , 126 ) include pin eyes, any other suitable attachment features may be used as would be apparent to one having ordinary skill in the art. [0046] Having linear displacement measuring assembly ( 130 ), or at least a portion of linear displacement measuring assembly ( 130 ) stored within cylinder assembly ( 110 ) and linear actuating assembly ( 120 ), may provide benefits of protecting linear displacement measuring assembly ( 130 ) from external moving parts, dust, and debris. Additionally, linear displacement measuring assembly ( 130 ) may be rigid for durability, as compared to known string potentiometers currently used. B. First Alternative Hydraulic Actuator Assembly [0047] FIGS. 9A-9C show an alternative exemplary hydraulic actuator assembly ( 600 ) that may be readily incorporated into a variety of vehicle lift assemblies in place of hydraulic actuator assembly ( 100 ) described above. Hydraulic actuator assembly ( 600 ) includes a cylinder assembly ( 610 ), a linear actuating assembly ( 620 ), and a linear transducer assembly ( 630 ). [0048] Cylinder assembly ( 610 ) and linear actuating assembly ( 620 ) may be substantially similar to cylinder assembly ( 110 ) and linear actuating assembly ( 120 ) described above, respectively, with differences described below. Therefore, linear actuating assembly ( 620 ) may move relative to cylinder assembly ( 610 ) from a fully withdrawn position, as shown in FIG. 9A , to a fully extended position, as shown in FIG. 9C . Additionally, linear actuating assembly ( 620 ) may move to any number of positions between the fully withdrawn and fully extended position. Therefore, movement of linear actuating assembly ( 620 ) may actuate a vehicle lift assembly to raise or lower a vehicle to a desired height, similar to the process described above for hydraulic actuator assembly ( 100 ). Such vehicle lift assembly may include a scissor lift assembly, a carriage-style lift assembly, an in-ground lift assembly, an above-ground lift assembly, or any other suitable lift assembly that would be apparent to those having ordinary skill in the art in view of the teachings herein. [0049] Cylinder assembly ( 610 ) includes a hydraulic cylinder ( 602 ) and an attachment feature ( 612 ), which are substantially similar to hydraulic cylinder ( 102 ) and attachment feature ( 112 ) described above, respectively. Hydraulic cylinder ( 602 ) includes an interior base end ( 616 ), an interior annular wall ( 614 ), and an interior head end ( 618 ), which are substantially similar to interior base end ( 116 ), interior annular wall ( 114 ), and interior head end ( 118 ) described above, respectively. Interior base end ( 616 ), interior annular wall ( 614 ), and interior head end ( 618 ) collectively define cavity ( 606 ). [0050] Head end ( 618 ) defines tunnel ( 604 ) extending from cavity ( 606 ) to an exterior of hydraulic cylinder ( 602 ). Tunnel ( 604 ) is dimensioned to slidably house a rod ( 622 ) of linear actuating assembly ( 620 ) while cavity ( 606 ) is dimensioned to slidably house a plunger ( 624 ) of linear actuating assembly ( 620 ). Plunger ( 624 ) and rod ( 622 ) are substantially similar to plunger ( 124 ) and rod ( 122 ) described above, respectively, with differences described below. Therefore, plunger ( 624 ) and rod ( 622 ) are coupled with each other such that plunger ( 624 ) and rod ( 622 ) slide together relative to tunnel ( 604 ) and cavity ( 606 ). [0051] Hydraulic cylinder ( 602 ) also has fluid channels ( 605 , 607 ), which are substantially similar to fluid channels ( 105 , 107 ) described above, respectively. Therefore, each fluid channel ( 605 , 607 ) is in fluid communication with a chamber ( 606 A, 606 B). Chambers ( 606 A, 606 B) are substantially similar to chambers ( 106 A, 106 B) described above. Chamber ( 606 A) is defined by interior base end ( 616 ), interior annular wall ( 614 ), and a radial face ( 636 ) of plunger ( 624 ). Chamber ( 606 B) is defined by interior head end ( 618 ), interior annular wall ( 615 ), and a radial face ( 634 ) of plunger ( 624 ). It should be understood that because plunger ( 624 ) is slidable within cavity ( 606 ), chambers ( 606 A, 606 B) are capable of changing in volume as plunger ( 624 ) actuates within cavity ( 606 ). [0052] Each fluid channel ( 605 , 607 ) may fill respective chamber ( 606 A, 606 B) with hydraulic fluid. Tunnel ( 604 ) and rod ( 622 ) may fluidly isolate chamber ( 606 B) from the exterior of hydraulic cylinder ( 602 ) by using a seal gland or in any other suitable manner known to the art in view of the teachings herein. As will be described in greater detail herein, fluid channels ( 605 , 607 ) may help actuate plunger ( 624 ) within cavity ( 606 ). [0053] Base end ( 616 ) defines a sensor mount ( 608 ) dimensioned to house a portion of linear transducer assembly ( 630 ). Sensor mount ( 608 ) is capable of fixing a portion of linear transducer assembly ( 630 ). While in the current example, sensor mount ( 608 ) is a recess defined by base end ( 616 ), bolts, nuts, threaded rods, or any other suitable structures may be utilized to fix a portion of linear transducer assembly ( 630 ) to hydraulic cylinder ( 602 ). [0054] Linear actuating assembly ( 620 ) includes rod ( 622 ) having one end fixed to plunger ( 624 ) and another end fixed to an attachment feature ( 626 ). Rod ( 622 ) defines a channel ( 628 ). Channel ( 628 ) extends from a portion of rod ( 622 ) that is fixed to plunger ( 624 ) toward the portion of rod ( 622 ) fixed to attachment feature ( 626 ). A seal ( 625 ) may be located at the open end of channel ( 628 ) or any other suitable location within channel ( 628 ) as would be apparent to one having ordinary skill in the art in view of the teachings herein. As will be described in greater detail below, seal ( 625 ) may prevent hydraulic fluid from entering certain portions of channel ( 628 ). However, it should be understood that seal ( 625 ) is merely optional. [0055] Attachment feature ( 626 ) may be substantially similar to attachment feature ( 126 ) described above, with differences described below. Attachment feature ( 626 ) may rotatably couple rod ( 622 ) to a portion of vehicle lift assembly. However, it should be understood that rotatably coupling rod ( 622 ) to a vehicle lift assembly is merely optional. For instance, rod ( 622 ) may couple with vehicle lift assembly in any suitable manner that would be apparent to one having ordinary skill in the art in view of the teachings herein. [0056] As mentioned above, plunger ( 624 ) is slidably housed within cavity ( 606 ). Plunger ( 624 ) makes contact with interior annular wall ( 614 ). Circumferential face ( 632 ) of plunger ( 624 ) may be machined with grooves configured to fit elastomeric or metal seals and bearing elements. Therefore, plunger ( 624 ) is configured to separate cavity ( 606 ) into two fluidly isolated chambers ( 606 A, 606 B). [0057] Linear transducer assembly ( 630 ) includes a coil assembly ( 640 ) fixed within hydraulic cylinder ( 602 ) via a base ( 642 ), and an actuating transducer member ( 644 ) fixed to rod ( 622 ) at the closed end of channel ( 628 ) via actuating coupling portion ( 646 ). Actuating coupling portion ( 646 ) may include any suitable coupling means known to one having ordinary skill in the art in view of the teachings herein. For example, actuating coupling portion ( 646 ) may include welding, an interference fit, bolts, and the like as will occur to those having ordinary skill in the art in view of this disclosure. [0058] Additionally, actuating transducer member ( 644 ) is slidably housed within coil assembly ( 640 ) via an opening ( 641 ) defined at the open end of coil assembly ( 640 ). Actuating transducer member ( 644 ) also includes a core member ( 648 ) located at the end of actuating transducer member ( 644 ) opposite actuating coupling portion ( 646 ). Of course, coil member ( 648 ) may be located at any other suitable location along actuating transducer member ( 644 ) as would occur to one having ordinary skill in the art in view of the teaching here. [0059] Coil assembly ( 640 ), actuating transducer member ( 644 ), and coil member ( 648 ) may function like a linear variable differential transformer. Coil assembly ( 640 ) is able to determine the location of core member ( 648 ) within opening ( 641 ) of coil assembly ( 640 ). Because core member ( 648 ) is fixedly attached to actuating transducer member ( 644 ), which is also fixedly attached to linear actuating assembly ( 620 ); and coil assembly ( 640 ) is fixedly attached within cylinder assembly ( 610 ); coil member ( 640 ) is capable of measuring the displacement of linear actuating assembly ( 620 ) relative to cylinder assembly ( 610 ) based on the location of core member ( 648 ). In other words, coil assembly ( 640 ) may determine the location of linear actuating assembly ( 620 ) relative to cylinder assembly ( 610 ) by locating core member ( 648 ). [0060] As mentioned above, seal ( 625 ) may prevent hydraulic fluid from entering certain portions of channel ( 628 ). In particular, seal ( 625 ) may be placed within channel ( 628 ) to prevent hydraulic fluid from entering within opening ( 641 ) of coil assembly ( 640 ). [0061] Unlike linear displacement measuring assembly ( 130 ) descried above, linear transducer assembly ( 630 ) may correctly measure the distance between linear actuating assembly ( 620 ) and cylinder assembly ( 610 ) even if there is accidental rotation of linear actuating assembly ( 620 ) relative to cylinder assembly ( 610 ). [0062] Having at least a portion of linear transducer assembly ( 630 ) stored within cylinder assembly ( 610 ) and linear actuating assembly ( 620 ) may provide benefits of protecting linear displacement measuring assembly ( 630 ) from external moving parts, dust, and debris. Additionally, linear displacement measuring assembly ( 630 ) may be rigid for durability, as compared to known string potentiometers currently used. [0063] As will be described in greater detail below, coil assembly ( 640 ) is in electrical communication with a circuit board of a vehicle lift assembly or related sensing and/or control circuitry. The vehicle lift assembly may utilize the displacement of core member ( 648 ) within coil assembly ( 640 ) in order to monitor the positions of each of any number of hydraulic actuator assemblies ( 600 ) utilized in the vehicle lift assembly, using the displacement to calculate the linear displacement of each hydraulic actuator assembly ( 600 ), and using that calculated linear displacement in a feedback control loop to manage the operation of the collection of hydraulic actuator assemblies ( 600 ). C. Second Alternative Hydraulic Actuator Assembly [0064] FIGS. 10A-10C show an alternative exemplary hydraulic actuator assembly ( 700 ) that may be readily incorporated into a variety of vehicle lift assemblies. Therefore, hydraulic actuator assembly ( 700 ) may be used in substitution for hydraulic actuator assembly ( 100 , 600 ) described above. Hydraulic actuator assembly ( 700 ) includes a cylinder assembly ( 710 ), a linear actuating assembly ( 720 ), and a linear transducer assembly ( 730 ). [0065] Cylinder assembly ( 710 ) and linear actuating assembly ( 720 ) may be substantially similar to cylinder assembly ( 110 ) and linear actuating assembly ( 120 ) described above, respectively, with differences described below. Therefore, linear actuating assembly ( 720 ) may move relative to cylinder assembly ( 710 ) from a fully withdrawn position, as shown in FIG. 10A , through a partially extended position, as shown in FIG. 10B , to a fully extended position, as shown in FIG. 10C . Additionally, linear actuating assembly ( 720 ) may move to any number of positions between the fully withdrawn and fully extended position. Therefore, movement of linear actuating assembly ( 720 ) may be used to actuate a vehicle lift assembly to raise or lower a vehicle to a desired height, similar to the process described above for hydraulic actuator assembly ( 100 ). Such vehicle lift assembly may include a scissor lift assembly, a carriage-style lift assembly, an in-ground lift assembly, an above-ground lift assembly, or any other suitable lift assembly that would be apparent to one having ordinary skill in the art in view of the teachings herein. [0066] Cylinder assembly ( 710 ) includes a hydraulic cylinder ( 702 ) and an attachment feature ( 712 ), which are substantially similar to hydraulic cylinder ( 102 ) and attachment feature ( 112 ) described above, respectively. Therefore, hydraulic cylinder ( 702 ) includes an interior base end ( 716 ), an interior annular wall ( 714 ), and an interior head end ( 718 ), which are substantially similar to interior base end ( 116 ), interior annular wall ( 114 ), and interior head end ( 118 ) described above, respectively. Interior base end ( 716 ), interior annular wall ( 714 ), and interior head end ( 718 ) collectively define cavity ( 706 ). [0067] Head end ( 718 ) defines tunnel ( 704 ) extending from cavity ( 706 ) to an exterior of hydraulic cylinder ( 702 ). Tunnel ( 704 ) is dimensioned to slidably house a rod ( 722 ) of linear actuating assembly ( 720 ), while cavity ( 706 ) is dimensioned to slidably house a plunger ( 724 ) of linear actuating assembly ( 720 ). Plunger ( 724 ) and rod ( 722 ) are substantially similar to plunger ( 124 ) and rod ( 122 ) described above, respectively, with differences described below. Therefore, plunger ( 724 ) and rod ( 722 ) are coupled with each other such that plunger ( 724 ) and rod ( 722 ) slide relative to tunnel ( 704 ) and cavity ( 706 ) together. [0068] Hydraulic cylinder ( 702 ) also has fluid channels ( 705 , 707 ), which are substantially similar to fluid channels ( 105 , 107 ) described above, respectively such that each fluid channel ( 705 , 707 ) is in fluid communication with a chamber ( 706 A, 706 B). Chambers ( 706 A, 706 B) are substantially similar to chambers ( 106 A, 106 B) described above. Therefore, chamber ( 706 A) is defined by interior base end ( 716 ), interior annular wall ( 714 ), and a radial face ( 736 ) of plunger ( 724 ). Chamber ( 706 B) is defined by interior head end ( 718 ), interior annular wall ( 715 ), and a radial face ( 734 ) of plunger ( 724 ). It should be understood that because plunger ( 724 ) is slidable within cavity ( 706 ), chambers ( 706 A, 706 B) are capable of changing volume as plunger ( 724 ) actuates within cavity ( 706 ). [0069] Each fluid channel ( 705 , 707 ) may fill respective chamber ( 706 A, 706 B) with hydraulic fluid. Tunnel ( 704 ) and rod ( 722 ) may fluidly isolate chamber ( 706 B) from the exterior of hydraulic cylinder ( 702 ) by using a seal gland or in any other suitable manner known to the art in view of the teachings herein. As will be described in greater detail below, fluid channels ( 705 , 707 ) may help actuate plunger ( 724 ) within cavity ( 706 ). [0070] Base end ( 716 ) defines a sensor mount ( 708 ) dimensioned to house a portion of linear string potentiometer assembly ( 730 ). Sensor mount ( 708 ) is capable of fixing a portion of linear string potentiometer assembly ( 730 ), and in the current example, sensor mount ( 708 ) is a recess defined by base end ( 716 ). Bolts, nuts, threaded rods, or any other suitable structures may be utilized to fix a portion of linear string potentiometer assembly ( 730 ) to hydraulic cylinder ( 702 ). [0071] Linear actuating assembly ( 720 ) includes rod ( 722 ) having one end fixed to plunger ( 724 ) and another end fixed to an attachment feature ( 726 ). Attachment feature ( 726 ) may be substantially similar to attachment feature ( 126 ) described above, with differences described below. Therefore, attachment feature ( 726 ) may allow rod ( 722 ) to rotatably couple to a portion of vehicle lift assembly. However, it should be understood that rotatably coupling rod ( 722 ) to a vehicle lift assembly is merely optional. [0072] As mentioned above, plunger ( 724 ) is slidably housed within cavity ( 706 ). Plunger ( 724 ) makes contact with interior annular wall ( 714 ). Circumferential face ( 732 ) of plunger ( 724 ) may be machined with grooves configured to fit elastomeric or metal seals and bearing elements. Therefore, plunger ( 724 ) is configured to separate cavity ( 706 ) into two fluidly isolated chambers ( 706 A, 706 B). [0073] Linear string potentiometer assembly ( 730 ) includes a sensor assembly ( 740 ) fixed to cylinder assembly ( 710 ) via sensor mount ( 708 ), a measuring cable ( 742 ), and a coupling feature ( 744 ). A portion of measuring cable ( 742 ) is housed within sensor assembly ( 740 ). Measuring cable ( 742 ) is capable of extending and retracting relative to sensor assembly ( 740 ). Coupling feature ( 744 ) fixes an end of measuring cable ( 742 ) to radial face ( 736 ) of plunger ( 724 ). Therefore, measuring cable ( 742 ) extends and retracts relative to sensor assembly ( 740 ) in accordance with linear actuating assembly ( 720 ) actuating within hydraulic cylinder ( 702 ). [0074] Sensor assembly ( 740 ) and measuring cable ( 742 ) are configured to act as standard string potentiometer. Therefore, as measuring cable ( 742 ) extends and retracts relative to sensor assembly ( 740 ), sensor assembly ( 740 ) may measure the distance defined by the portion of measuring cable ( 742 ) extending from sensor assembly ( 740 ). Because measuring cable ( 742 ) is fixed to plunger ( 724 ) at one end, and sensor assembly ( 740 ) is fixed to cylinder assembly ( 710 ), measuring cable ( 742 ) and sensor assembly ( 740 ) are configured to measure the displacement of linear actuating assembly ( 720 ) relative to cylinder assembly ( 710 ). [0075] Having at least a portion of linear string potentiometer assembly ( 730 ) stored within cylinder assembly ( 710 ) and linear actuating assembly ( 720 ) may provide benefits of protecting linear string potentiometer assembly ( 730 ) from external moving parts, dust, and debris. D. Exemplary Vehicle Lift Assembly [0076] FIG. 5 shows a perspective view of vehicle lift system ( 200 ) in a raised position. Vehicle lift system ( 200 ) comprises two runways ( 220 ), four lift assemblies ( 250 ), a control circuit ( 500 ), and a pump ( 400 ). Runways ( 220 ) are generally rectangular in shape, extending from one lift assembly ( 250 ) to another. Each runway ( 220 ) comprises two longitudinally extending side rails ( 222 ) and a relatively flat top plate ( 224 ). Side rails ( 222 ) are comprised of any suitable rigid material, such as steel, iron, aluminum, composites, etc. Although side rails ( 222 ) are shown as having a generally rectangular construction, it should be understood that side rails ( 222 ) may have any suitable cross-sectional geometry such as square, round, I-shaped, L- shaped, Z-shaped, or the like. [0077] Top plate ( 224 ) is secured to the top of side rails ( 222 ) by any suitable means such as welding, mechanical fastening, adhesive boding, etc. In the present example, top plate ( 224 ) is comprised of a thin sheet of a rigid material such as steel, iron, aluminum, composite, or the like. Top plate ( 224 ) is configured to support the load of a vehicle resting on runways ( 220 ). The load of a vehicle is also distributed by top plate ( 224 ) to runways ( 220 ), which provide additional structural rigidity. [0078] Each runway ( 220 ) is positioned relative to the other a transverse distance that is approximately equivalent to the wheel track of a vehicle that is desired to be lifted. The transverse distance thus permits a vehicle's wheels to rest on top of runways ( 220 ). In some embodiments, runways ( 220 ) may include angled sloped ramps (not shown) or other features to facilitate rolling or driving a vehicle onto and off of runways ( 220 ). Of course, such a feature is entirely optional and may be omitted in other comments. Runways ( 220 ) may also include other features suitable to support a vehicle as will be apparent to one of ordinary skill in the art in view of the teachings herein. Some examples of additional and/or alternative features that may be incorporated into runways ( 220 ) and/or other features of lift system ( 200 ) are disclosed in U.S. Pat. No. 6,763,916, entitled “Method and Apparatus for Synchronizing a Vehicle Lift,” issued Jul. 20, 2004, the disclosure of which is incorporated by reference herein; U.S. Pat. No. 6,059,263, entitled “Automotive Alignment Lift,” issued May 9, 2000, the disclosure of which is incorporated by reference herein; U.S. Pat. No. 5,199,686, entitled “Non-Continuous Base Ground Level Automotive Lift System,” issued Apr. 6, 1993, the disclosure of which is incorporated by reference herein; U.S. Pat. No. 5,190,122, entitled “Safety Interlock System,” issued Mar. 2, 1993, the disclosure of which is incorporated by reference herein; U.S. Pat. No. 5,096,159, entitled “Automotive Lift System,” issued Mar. 17, 1992, the disclosure of which is incorporated by reference herein; and U.S. Pub. No. 2012/0048653, entitled “Multi-Link Automotive Alignment Lift,” published Mar. 1, 2012, the disclosure of which is incorporated by reference herein. It should be understood that that the teachings herein may be readily combined with the teachings of the various references cited herein. [0079] As can be seen in FIGS. 6A-6B , and as will be discussed in greater detail below, vehicle lift ( 200 ), by using runways ( 220 ) and lift assemblies ( 250 ), is operable to lift a vehicle vertically from a height approximately even with a shop floor to a desired working height. As will be understood, lift assemblies ( 250 ) are operable to lift runways ( 220 ) with substantially vertical movement of runways ( 220 ). [0080] FIG. 7 shows an exploded view of lift assembly ( 250 ). Lift assembly ( 250 ) comprises a base ( 252 ), a linkage assembly ( 260 ), and an actuation assembly ( 350 ). Base ( 252 ) comprises a generally rectangular base plate ( 254 ) and two mounting brackets ( 257 ). Base plate ( 254 ) may be comprised of a rigid material such as steel, iron, aluminum, composite, or the like. Base plate ( 254 ) is shown as having a plurality of mounting holes ( 256 ). In the present example, mounting holes ( 256 ) may be used to receive bolts and/or other anchors to mount base plate ( 254 ) to a shop floor, thus providing a fixed platform for lifting assembly ( 250 ). In other examples, mounting holes ( 256 ) may be omitted entirely and base plate ( 254 ) may be secured to a shop floor by some other means such as welding, adhesive bonding, mechanical fastening, etc. Yet in other examples, mounting holes ( 256 ) may be used to secure lift assembly ( 250 ) to another surface such as a portable rack for vehicle lift systems ( 200 ) designed for smaller vehicles. [0081] Mounting brackets ( 257 ) extend vertically from base plate ( 254 ). Mounting brackets ( 257 ) may be fixedly secured to base plate ( 254 ) by any suitable means such as welding, adhesive bonding, mechanical fastening, and/or the like. Alternatively, mounting brackets ( 257 ) may be integral to base plate ( 254 ). As can best be seen in FIG. 7 , each mounting bracket ( 257 ) comprises a pair of mounting holes ( 258 , 259 ). As will be described in greater detail below, components of linkage assembly ( 260 ) and actuation assembly ( 350 ) are rotatably coupled to mounting brackets ( 257 ). [0082] Mounting holes ( 258 , 259 ) are positioned at each end of mounting bracket ( 257 ). In particular, a rear mounting hole ( 258 ) is positioned near the rear of mounting bracket ( 257 ), and a front mounting hole ( 259 ) is positioned near the front of mounting bracket ( 257 ). Rear mounting hole ( 258 ) is positioned vertically higher than front mounting hole ( 259 ). As will be understood in view of the description below, mounting holes ( 258 , 259 ) are oriented such that linkage assembly ( 260 ) and actuation assembly ( 350 ) are operable to fold up, thus minimizing the height of vehicle lift system ( 200 ) when vehicle lift system ( 200 ) is in the retracted position as shown in FIG. 6A . Accordingly, the shape of mounting brackets ( 257 ) is configured to arrange mounting holes ( 258 , 259 ) in the positions described above. Thus, although mounting brackets ( 257 ) are shown as having a particular shape, mounting brackets ( 257 ) may be of any suitable shape as will be apparent to those of ordinary skill in the art in view of the teachings herein. [0083] Turning to FIGS. 8A-8B , linkage assembly ( 260 ) comprises a set of four lower links ( 262 ) and a third pair of armatures ( 282 ). Lower links ( 262 ) comprise a first pair of armatures ( 264 ) and a second pair of armatures ( 272 ). First armatures ( 264 ) are generally similar, having the same size and shape, and comprising an elongated portion ( 266 ) positioned between two rounded end portions ( 268 ). Likewise, second armatures ( 272 ) are generally similar, having the same size and shape, and comprising an elongated portion ( 274 ) positioned between two rounded end portions ( 276 ). Although they differ in shape, the rounded end portions ( 268 , 276 ) of lower links ( 262 ) each comprise bores ( 270 , 278 ) that permit the first and second pairs of armatures ( 264 , 272 ) to be respectively attached to pins ( 296 , 298 ) associated with mounting brackets ( 257 ) at one end, and pins ( 300 , 302 ) associated with third armatures ( 282 ) at another end. It should be noted that each pair of rounded end portions ( 268 , 276 ) do not necessarily have equal dimensions. [0084] As can be seen in FIGS. 8A-8B , first armatures ( 264 ) are generally longer in length relative to second armatures ( 272 ). As will be described in greater detail below, the greater length of first armatures ( 264 ) relative to second armatures ( 272 ) is generally necessitated by the configuration of linkage assembly ( 260 ). Although lower links ( 262 ) are shown as having a certain length, it should be understood that their lengths may be varied depending on the design specifications of vehicle lift system ( 200 ). For instance, some vehicle lift systems ( 200 ) may be designed to have a higher or lower working height. Thus, longer or shorter lower links ( 262 ) may be used to increase or decrease the range of motion of lift assembly ( 250 ), respectively. [0085] Elongated portions ( 266 , 274 ) of lower links ( 262 ) are generally rectangular in shape. Alternatively, any suitable shape may be used, such as an elongated rod, elongated hexagon, hollow tubing, or the like. Rounded end portions ( 268 , 276 ) are generally circular to accommodate bores ( 270 , 278 ) and generally reduce the area occupied by rounded end portions ( 268 , 276 ). In other examples, rounded end portions ( 268 , 276 ) may have any suitable shape. Lower links ( 262 ) are relatively rigid and may be comprised of any suitable material such as steel, iron, aluminum, composite, or the like. Of course, lower links ( 262 ) may have any other suitable configuration and composition as will be apparent to those of ordinary skill in the art in view of the teachings herein. [0086] Third armatures ( 282 ) are generally the same size and shape. In particular, each third armature ( 282 ) is approximately rectangular and includes a taper from one end to another. The front end of third armature ( 282 ) is wider relative to the rear end to accommodate two connecting bores ( 284 , 285 ). As will be described in greater detail below, upper connecting bore ( 284 ) and lower connecting bore ( 285 ) are used to rotatably couple lower links ( 262 ) to third armatures ( 282 ) via pins ( 300 , 302 ) respectively. As will also be described in greater detail below, connecting bores ( 284 , 285 ) are positioned on third armature ( 282 ) to provide pivot points about which lower links ( 262 ) may pivot relative to third armature ( 282 ). The rear end of third armature ( 282 ) is rounded and includes an attachment bore ( 286 ). Attachment bore ( 286 ) is positioned to permit rotatable coupling between third armature ( 282 ) and runway ( 220 ) via pin ( 304 ) and pin blocks (not shown). [0087] As can best be seen in FIG. 7 , lift assembly ( 250 ) includes a plurality of pins ( 296 , 298 , 300 , 302 ) that rotatably couple various components of lift assembly ( 250 ). In particular, bore ( 270 ) of the lower portion of first armatures ( 264 ) is rotatably coupled to rear mounting holes ( 258 ) of mounting brackets ( 257 ) via pin ( 296 ). Pin ( 296 ) may be welded or fixed to mounting bracket ( 257 ) of base ( 252 ) by any suitable methods as will be apparent to one of ordinary skill in the art in view of the teachings herein. Bore ( 278 ) of the lower portion of second armatures ( 272 ) is rotatably coupled to front mounting holes ( 259 ) of mounting brackets ( 257 ) via pin ( 298 ). Pin ( 298 ) may be welded or fixed to mounting bracket ( 257 ) of base ( 252 ) by any suitable methods as will occur to one of ordinary skill in the art in view of the teachings herein. Alternatively, pin ( 298 ) may rotate freely relative to mounting bracket ( 257 ). As described above, pin ( 298 ) at this joint also rotatably couples to attachment feature ( 112 ) of hydraulic actuator assembly ( 100 ). Similarly, another pin ( 300 ) provides rotatable coupling between upper connecting bore ( 284 ) of third armatures ( 282 ), bores ( 270 ) of the upper portions of first armatures ( 264 ), and sleeve ( 362 ). As described above, pin ( 300 ) at this joint also rotatably coupled attachment feature ( 126 ) of hydraulic actuator assembly ( 100 ). Finally, bores ( 278 ) of the upper portions of second armatures ( 272 ) are rotatably coupled to lower connecting bore ( 285 ) of third armatures ( 282 ) via pin ( 302 ). Pin ( 302 ) may be welded or fixed to third armatures ( 282 ) by any suitable methods as will occur to one of ordinary skill in the art in view of the teachings herein. Pins ( 296 , 298 , 300 , 302 ) are shown as being fastened to their respective mating parts using bolts ( 292 ) and washers ( 294 ). Of course, pins ( 296 , 298 , 300 , 302 ) may be fastened to their respective mating parts by any other suitable means. Although not shown, it should be understood that the various joints described above may also include bushings, bearings, or other devices suitable to reduce friction between the various parts. [0088] FIGS. 8A-8B show linkage assembly ( 260 ) and base ( 252 ) in an exemplary mode of operation as the linkage assembly ( 260 ) transitions from the retracted position to an extended position. It should be understood that the combination of mounting brackets ( 257 ), lower links ( 262 ), and third armatures ( 282 ) forms a four-bar linkage such that rotation of lower links ( 262 ) is operable to produce substantially vertical motion of attachment bore ( 286 ) of third armatures ( 282 ). [0089] FIG. 8A shows linkage assembly ( 260 ) in the retracted position. As can be seen, lower links ( 262 ) and third armatures ( 282 ) are configured to fold relative to each other so that the lower links ( 262 ) and third armatures ( 282 ) have limited vertical extension. Additionally, hydraulic actuator assembly ( 100 ) is in the withdrawn position. Accordingly, when linkage assembly ( 260 ) is in the retracted position, runway ( 220 ) is relatively close to ground level. Additionally, in the retracted position, lower links ( 262 ) and third armatures ( 282 ) are nearly parallel with each other. [0090] FIG. 8B shows linkage assembly ( 260 ) in the extended position. As described above, the extended position of linkage assembly ( 260 ) corresponds to runway ( 220 ) being raised to a desired working height. In the operation of transitioning between the retracted position and the extended position, pin ( 300 ) is forced away from pin ( 298 ) via extension of linear activating assembly ( 120 ). Because linkage assembly ( 260 ) is a four-bar linkage, forcing pin ( 298 ) away from pin ( 300 ) causes lower links ( 262 ) to simultaneously rotate about pins ( 296 , 298 ) and pivot third armatures ( 282 ) about a point between the center of pins ( 300 , 302 ). The pivoting action of third armatures ( 282 ) causes attachment bores ( 286 ) of third armatures ( 282 ) to move upwardly. It should be understood that the motion of attachment bores ( 286 ) is substantially vertical as lift assembly ( 250 ) transitions from the retracted position to the extended position. Of course, the precise path of lift assembly ( 250 ) may vary depending on a number of factors such as the length of each armature ( 264 , 272 , 282 ), the relative lengths of armatures ( 264 , 272 , 282 ), and other similar factors. [0091] As mentioned above and shown in FIGS. 5-8B , each lift assembly ( 250 ) includes a hydraulic actuator assembly ( 100 ). Each hydraulic actuator assembly ( 100 ) is in fluid communication with pump ( 400 ) via a pair of hydraulic hoses ( 402 ). Hydraulic hoses ( 402 ) and pump ( 400 ) may provide fluid communication to fluid channels ( 105 , 107 ) in the same or similar fashion as described above in order to move linear actuating assembly ( 120 ). [0092] Each hydraulic actuator assembly ( 100 ) is in electrical communication with control circuit ( 500 ) via communication wires ( 502 ). In the current example, communication wires ( 502 ) are connected to rotation sensor ( 140 ) of each hydraulic actuator assembly ( 100 ). Communication wires ( 502 ) may also be in electrical communication with other aspects of each lift assembly ( 250 ). [0093] Communication wires ( 502 ) may be configured to provide electrical power from circuit board ( 500 ) to rotation sensor ( 140 ). Additionally, rotation sensor ( 140 ) may be able to communicate the rotational displacement of rotating element ( 142 ) relative to static element ( 148 ). As mentioned above, the rotational displacement of rotation element ( 142 ) relative to static element ( 148 ) corresponds to the linear displacement of linear actuating assembly ( 120 ) relative to cylinder assembly ( 110 ). Therefore, circuit board ( 500 ) may be configured to determine the linear displacement of linear actuating assembly ( 120 ) relative to cylinder assembly ( 110 ) through a predetermined formula based on dimensions of hydraulic actuator assembly ( 100 ). Additionally, the linear displacement of linear actuating assembly ( 120 ) relative to cylinder assembly ( 110 ) may correspond with a predetermined height of the portion of lift assembly ( 250 ) directly connected to runways ( 220 ) based on the dimensions of lift assembly ( 250 ). Therefore, circuit board ( 500 ) may be configured to determine the vertical height of the portion of lift assembly ( 250 ) connected to runways ( 220 ), or any other suitable portion of lift assembly ( 250 ) as will be apparent to one having ordinary skill in the art in view of the teachings herein. [0094] Circuit board ( 500 ) is also in electrical communication with pump ( 400 ). Circuit board ( 500 ) may control the amount of hydraulic fluid that pump ( 400 ) distributes to individual hydraulic actuator assemblies ( 100 ). Therefore, circuit board ( 500 ) may control the individual heights of each hydraulic actuator assembly ( 100 ). For example, circuit board ( 500 ) may determine individual heights of each lift assembly ( 250 ) in order to determine the lowest lift assembly ( 250 ). Circuit board ( 500 ) may then calculate the difference of the heights of each of the other three lift assemblies ( 250 ) in order to equal the lowers lift assembly ( 250 ). Circuit board ( 500 ) may then communicate instructions to pump ( 400 ) in order to adjust the three, higher, lift assemblies ( 250 ) to lower accordingly to equalize the height of each lift assembly ( 250 ). Therefore, communication between linear displacement measuring assembly ( 130 ), circuit board ( 500 ), and pump ( 400 ) may help keep vehicle lift system ( 200 ) level. [0095] Of course, utilizing the lowest lift assembly ( 250 ) as the datum point is just one option. Circuit board ( 500 ) could determine the highest lift assembly ( 250 ). Circuit board ( 500 ) may then calculate the difference of the heights of each of the other three lower lift assemblies ( 250 ) in order to equal the highest lift assembly ( 250 ). Circuit board ( 500 ) may the communicate instructions to pump ( 400 ) in order to adjust the three, lower, lift assemblies ( 250 ) to raise accordingly to equalize the height of each lift assembly ( 250 ). Any other suitable means of equalizing the height of each lift assembly ( 250 ) may be utilized as would be apparent to one having ordinary skill in the art in view of the teachings herein. [0096] It should be understood that while in the current example, hydraulic actuator assembly ( 100 ) is used in vehicle lift system ( 200 ), hydraulic actuator assembly ( 600 , 700 ) may be readily incorporated into vehicle lift system ( 200 ) in place of hydraulic actuator ( 100 ). [0097] While in the current example, vehicle lift system ( 200 ) includes linkage assemblies, armatures, and pins, any other suitable vehicle lift system having a linear displacement measuring assembly ( 130 ) in communication with a circuit board ( 500 ) lift assembly ( 250 ). [0098] Although actuation assembly ( 350 ) is shown as being hydraulically actuated, it should be understood that any suitable device may be used to actuate lift assembly ( 250 ). For instance, actuation assembly ( 350 ) may comprise a linear actuator having a lead screw and a motor, a pneumatic actuator, spring loaded actuator, or any other suitable actuator as will be apparent to those of ordinary skill in the art in view of the teachings herein. [0099] The illustrated embodiment is double-acting; that is, it uses pressure fluid on both sides of plunger ( 124 ) in cylinder ( 102 ), and the pressure differential between the two sides moves plunger ( 124 ) axially through the cylinder ( 102 ). In alternative embodiments, cylinder ( 102 ) is single-acting, where there is fluid on only one side of the plunger ( 124 ) (e.g., between plunger ( 124 ) and head end ( 118 )), and the other side of the plunger ( 124 ) (e.g., between plunger ( 124 ) and base end ( 116 )) is air- or gas-filled or even vented. In such embodiments, fluid channel ( 105 ) is a breather that leads air in and out, and fluid channel ( 107 ) is a pressure line/return line.

A vehicle lift includes a vehicle support member, a cylinder, and a controller. A linear transducer—such as a string potentiometer—is (preferably removably) positioned inside the cylinder. The transducer detects the position of the cylinder and sends a corresponding signal to a controller that controls the height of the support member in response to the signal. The cylinder acts on the vehicle support member through a scissor mechanism, parallelogram linkage, or straight vertical hydraulic lifting.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for the liquid treatment of cloth in which cloth can be impregnated advantageously with a treating liquid in an untensioned state. In subjecting a cloth to the liquid treatment such as dyeing, scouring, bleaching and washing continuously, it is necessary to impregnate the cloth with a prescribed amount of a treating liquid in an efficient manner. There have been many proposals for the liquid treatment apparatus of a cloth to perform the impregnation treatment uniformly with high efficiency. For instance, as for the liquid treatment of an easily expandable cloth such as a knitted one, a liquid treatment apparatus has been proposed to perform the treatment with no tension. 2. Description of Prior Art However, in a conventional liquid treatment apparatus, particularly in a liquid treatment apparatus with no tension, it is the present status that a sufficient impregnation with a liquid cannot be done due to the reason that a cloth can hardly be held in a liquid tank for a sufficient period. To prolong the dwell period in the liquid medium, it has been considered to enlarge the liquid treating tank, but there are problems in the space required for and cost of the apparatus. An apparatus has also been proposed to use a deep liquid tank having a U-shaped cloth passage, but such an apparatus has not as yet any distinguished merit in prolonging the dwell period of the cloth in the liquid medium. SUMMARY OF THE INVENTION The present invention affords an adequate dwell time. The principal object of the present invention is, in a liquid tank having a U-shaped cloth passage, to U-turn the cloth by folding it zigzag at the lower portion of the passage to increase the amount of the cloth held in the tank and thus to prolong its dwell period in liquid medium. Another object of the invention is to offer an apparatus in which a cloth can be transferred through a U-shaped passage smoothly with no tension by U-turning the cloth at the lower portion of the U-shaped passage without destroying the zigzag arrangement of the cloth passing through the U-shaped passage in a folded state. While such an arrangement of a cloth, as in the first object, is apt to be destroyed frequently to tangle the cloth owing to the buoyancy of the cloth and others, the second object is to avoid such a problem. BRIEF EXPLANATION OF THE DRAWINGS The figures show sectional side views of different embodiments of the present inventive apparatus for the liquid treatment of a cloth. FIG. 1 displaying Example 1, FIG. 2 displaying Example 2 and, FIG. 3 displaying Example 3. DETAILED DESCRIPTION OF THE INVENTION The present invention will be explained in detail according to the accompanied figures in the following. In FIG. 1, (1) is a nearly U-shaped liquid tank. In about an upper half portion of the tank (1), there are provided a freely rotatable central endless net conveyor (2) extending vertically and a pair of outer endless net conveyors (3) and (3') which are equipped rotatably along the central net conveyor (2) in parallel on both sides thereof to form narrow cloth inlet- and outlet-passages (a) and (a') therebetween. In about a lower half portion of the liquid tank (1), there are provided a freely rotatable rotary drum (4) at the center and a freely rotatable endless net conveyor (5) along the wall to form a cloth passage in liquid medium (b) broader than the cloth inlet- and outlet-passages. (6) is a liquid receiving tank to receive a treating liquid flowing over the liquid tank (1), and the liquid receiving tank (6) is connected through a pump (7) to a plurality of liquid jet nozzles (9) so as to jet the liquid received in the liquid receiving tank (6) against a cloth to be treated passing through the cloth passages (a) and (a') and to return the jetted liquid to the liquid tank (1). Four comb-like cloth holding frames (10) are attached to the rotary drum (4) and extend radially outwardly from it at equal intervals so as to be rotatable with the rotation of the rotary drum (4), thereby avoiding contact with comb-like guide frames (11) provided vertically along the broader cloth passages between the central conveyor (2) and the rotary drum (4). Namely, the teeth of the cloth holding frames (10) are arranged so as to pass the gaps of the guide frames (11). (12) are a plurality of steam jet pipes provided at the bottom of the liquid tank (1). While the construction of the apparatus in Example 1 is as above mentioned, the operation process by using said apparatus will be described in the following. At first, the endless net conveyors (2), (3) and (3') are rotated respectively in the direction of the arrow with a prescribed speed, and the drum (4) and the endless net conveyor (5) are rotated at the lower portion of the liquid tank also respectively in the direction of the arrow but with a speed slower than the conveyors (2), (3) and (3'). The treating liquid is sprayed through the liquid jet nozzles (9) by driving the pump (7). Two sheets of cloth (8), (8') piled one on the other en bloc are then transferred into the cloth inlet passage (a), sent down therethrough by rotating the conveyors (2) and (3), and the liquid is sprayed from the liquid jet nozzles (9). The cloths collide alternately with the conveyors (2) and (3) on both sides of the cloth passage (a) due to the jetting liquid pressure from the nozzles (9), releasing the weight of the cloths of their own, so that the cloths descend zigzag through the cloth passage (a) in a relaxed state with no tension. The cloths thus sent down are immersed in a treating liquid in the liquid tank (1) and are transferred in a folded state zigzag through the broader cloth passage in liquid medium (b) because the revolution speeds of the drum (4) and the conveyor (5) are slow and the buoyancy of the cloth is superposed. Furthermore, since the drum is equipped with the cloth holding frames (10) rotating together with the drum (4), the folded cloths are transferred orderly without missing their arrangement and with no tension, and can be U-turned smoothly in the liquid medium. In consequence of the effect that the cloths are folded zigzag in the liquid medium, there is such merit in that the cloths are immersed in the treating liquid for a long time prolonging the reaction time and affording an efficient liquid treatment. Example 2 in FIG. 2 differs from Example 1 in its construction for transferring the cloth in the liquid tank. The cloth transferring construction in this example comprises a central endless net conveyer (13) extending vertically down to the lower portion of the liquid tank and an endless net conveyer (15) passing around the central conveyer (13) in a way as shown in the figure with the aid of a plurality of guide rolls (14) provided on both sides of said central conveyer (13). The means to flow the treating liquid and other operation processes are the same as in Example 1. In this example, a pair of endless net conveyers (13) and (15) forms the cloth inlet- and outlet-passages (a) and (a') as well as a cloth passage in liquid medium (b) to transfer the cloth in a folded state simultaneously. Therefore, Example 2 has the merit in that the conveyers are spared as compared with Example 1 and the construction of the apparatus is simplified. FIG. 3 shows the construction of the apparatus in Example 3. (1) is a nearly U-shaped liquid tank. In the central portion of this liquid tank, a central endless net conveyer (2) is provided vertically down to the lower portion of the liquid tank so as to rotate freely guided by a pair of guide rolls (4) and (4') situated at a certain distance. (3) is an inlet endless net conveyer provided vertically along one side of the central endless net conveyer (2) extending over the whole length thereof forming a narrow space therebetween, and (5') is an outlet endless net conveyer provided vertically along the other side of the central endless net conveyer (2) within the upper portion thereof forming a narrow space therebetween. Thus, narrow cloth inlet- and outlet-passages (a) and (a') are formed respectively between the central endless net conveyer (2) and the inlet endless net conveyer (3) and between the central endless net conveyer (2) and the outlet endless net conveyer (5'). In this example, the cloth inlet- and outlet-passages (a) and (a') are filled with the treating liquid. At the lower side of both of the cloth inlet- and outlet-passages (a) and (a') a vertically extending, nearly J-shaped cloth passage (b) broader than the cloth inlet- and outlet-passages is formed between the central endless net conveyer (2) and the inner wall of the liquid tank (1) as shown in the figure. (6) is a liquid receiving tank for receiving the treating liquid flowing over the liquid tank (1), and the liquid receiving tank (6) is connected to a plurality of liquid jet nozzles (9) so as to jet the liquid received in the liquid receiving tank (6) by means of the driving force of a pump (7) against the cloth passing through the cloth passages (a) and (a') and to return the jetted liquid to the liquid tank (1). (12) are a plurality of steam jet pipes at the bottom of the liquid tank (1). In the process using the apparatus in this example, the endless net conveyers (2), (3) and (3') are rotated respectively in the direction of the arrow, and the treating liquid is sprayed through the liquid jet nozzles (9) by driving the pump (7). Then, two sheets of a cloth (8) and (8') piled en bloc are transferred into the cloth passage (a) in the treating liquid in the liquid tank (1). The cloths adopt a wave-like configuration by receiving the liquid pressure due to the jetting of liquid from the liquid jet nozzles (9), they are pressed alternately to collide with both of the endless net conveyers (2) and (3), so that the cloths are sent down in a zigzag manner by rotating the conveyers (2) and (3) through the liquid medium in a relaxed state with no tension. The cloths thus transferred successively to the bottom portion of the liquid tank are folded zigzag with no tension in the broader cloth passage (b), are transferred smoothly toward the outlet due to their own buoyancy, and are supplied to the cloth outlet passage (a') situated between the two endless net conveyers (2) and (5'). The cloths in this cloth passage (a') are pressed alternately to collide with the both endless net conveyers (2) and (5') due to the jetting liquid pressure of the liquid jetted from the liquid jet nozzles (9), so that the cloths are transferred upward with no tension by the driving force of the endless net conveyers (2) and (5'). As above explained, the present inventive apparatus enables a cloth to be transferred with a single sheet or two more sheets piled en bloc, in a liquid tank in a relaxed state with no tension, so that the apparatus is quite effective to treat an easily expandable cloth such as a knitted one in a liquid medium. Since the cloth is immersed in the liquid medium in a folded zigzag state the impregnation duration of the cloth is prolonged, and therefore, the impregnation can be done uniformly and sufficiently. Moreover, since the present inventive apparatus is arranged so that the cloth existing at the bottom of the liquid tank can float up in a folded state by its own buoyancy, the cloth can be transferred orderly with no entanglement in the liquid tank. The present invention is particularly effective in the liquid treatment of two or more sheets of an easily expandable cloth en bloc at the same time.

An apparatus for the liquid treatment of cloth consists of a U-shaped liquid tank for a treating liquid, a cloth inlet passage and a cloth outlet passage located in the tank and each having a relatively narrow spacing between vertical endless net conveyers which define the opposed sides of the passages. A plurality of liquid jet nozzles are provided along the cloth passages to spray a treating liquid against a cloth so that the cloth collides alternately with the conveyers on the opposite sides of each passage. Another cloth passage is located in the treating liquid below and forms a connecting passage between the cloth inlet-and outlet-passages. The cloth passes in a folded zigzag state through the another cloth passage. This apparatus is particularly suitable for the liquid treatment of an easily expandable cloth such as a knitted cloth by piling a plurality of the sheets thereof en bloc.

TECHNICAL FIELD The present invention relates to a device which is connectable to the rear cover of a connector for facilitating entry and exit of the cable leads of the connector. The device includes a hood-shaped portion with a casing which is provided with one or more socket-shaped transition members for the cable leads. The present invention is applicable for use with multi-way connectors. BACKGROUND ART Connectors of the type contemplated here are previously known in this art and, by way of example, mention may be made of the connector manufactured by "Raychem" and marketed under number CHA-0081. Such a connector is provided with a transition member which forms a separate part in relation to the rest of the connector. The transition member is, in a known manner, adapted to be secured to and removed from the rear cover of the connector. The prior art transition member essentially comprises a socket-shaped portion for the transition function and the transition member as such consists of a molded part. SUMMARY OF THE INVENTION In connectors of the above type, there is a need for greater utilization of the space available in each respective connector. This is due to steadily increasing demands on packing density in the equipment which is to be electrically connected using the connector(s). The interior space in such a connector is extremely cramped, with numerous connection stubs (to terminal blocks), and soldering and marking sockets. There are also demands for improved serviceability of such connectors. Fault-tracing functions in ancillary equipment and connectors could also be facilitated. The above requirements may not be fulfilled by greater complexity in the design and construction of the connector, more rational production, and the like. The electrical tightness of the connector must also be maintainable where necessary. SUMMARY OF THE INVENTION The object of the present invention is to propose a device which solves the above and other problems. The novel device according to the present invention includes the casing made of two or more combinable modular elements, which consist of one or more plate-like apertured parts each provided with its own transition member, and of one or more non-apertured plate-like parts functioning as blind washers. In one preferred embodiment, the modular elements are provided, with corresponding tongues and grooves for allowing simple assembly of the casing. At its region supporting the casing, the hood-shaped portion is also provided with tongues and grooves which fit into corresponding tongues and grooves on the modular elements. In one preferred embodiment, the hood is divided into a main portion and a lid removably disposed in relation thereto and preferably forming one longitudinal side of the hood when it is attached. The modular element parts are provided with transition means which include socket-shaped transition members of different diameters. Each respective socket-shaped transition member may extend perpendicularly or at an angle to the plane of the casing. The same connector may be provided with a plurality of parts fitted with transition members, each respective transition member being allocated to cable leads whose destinations differ from those of the other cable leads. The modular elements are applied to the body portion and to each other when the lid is removed or moved aside. Thus applied modular elements are thereafter mutually lockable to one another and to the main portion and lid when the lid is in attached or secured position in relation to the main portion. In the event that the transition member on a part provided therewith is of a diameter which exceeds the width of the hood-shaped portion, this part provided with transition member assumes a size which corresponds to the size of two assembled parts functioning as washers. The connectors may be disposed beside one another. In connectors with parts whose diameters exceed the width of the hood-shaped portion, the parts in an adjacent connector must be mutually displaced in the longitudinal direction of each respective hood-shaped part. The present invention makes it possible to provide a more destination-geared service and fault tracing within each respective connector and its associated equipment. It is now no longer necessary to desolder a common cable transition in all service and fault-tracing cases. Only that cable/destination which is subject to remedial action needs to be removed, while the remaining cable transitions can remain unaffected. As a result of the novel module system according to the invention, the construction and use of the product/connector will be optimized and may be well adapted to each particular physical application. The degree of utilization in each respective connector will be substantially increased. It is also possible to individualize cable routing within and in association with the connector. Hence, for example, it is possible to arrange the connection with small bends on the connecting cable, for example by selecting transition members which are angled in relation to the plane of the casing. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS One preferred embodiment of a device according to the present invention will be described hereinafter with particular reference to the accompanying Drawings, in which: FIG. 1 is a horizontal view of a number of adjacently disposed connectors, FIG. 2 shows, in longitudinal section, the construction of a connector, FIG. 3 is a cross-section of a connector, FIG. 4 is a side elevation of one modular element in a first embodiment, FIG. 5 is a side elevation of a modular element of a second embodiment, FIG. 6 schematically illustrates connection to different destinations of cables to connectors with a plurality of transition members, FIGS. 7-7a are different views of a first embodiment of a connector, and FIGS. 8-8a are different views of a second embodiment of a connector. DESCRIPTION OF PREFERRED EMBODIMENT Referring to the Drawings, FIG. 1 shows, in horizontal view from above, connectors numbered 1-6 which are disposed adjacent to and parallel to one another. The connectors are of different construction as regards the part illustrated in FIG. 1. Each respective connector displays a casing composed of different modular elements 7-10. The first modular element 7 includes a washer-shaped (apertured plate-like) portion 7a and a protruding transition member 7b for a cable. The transition member displays a diameter D1. The second modular element 8 includes a plate-like portion 8a and a protruding transition member 8b for a cable. The transition member displays a diameter D2 which exceeds the width b of each respective connector. In this embodiment, the connectors are of the same width b. The washer-shaped (plate-like) element 8a is of a length which is twice the length of the washer-shaped part 7a. The third modular element 9 consists of a non-apertured plate-like member 9a. The fourth modular element includes a washer portion 10a and a transition member 10b with a diameter D3. The washer portion 10a displays a length which corresponds to the length of the washer 8a. The diameter D3 corresponds to the width of each respective connector. In this embodiment, each respective connector may be considered as including a casing which consists of four (in respect of connector 1) or two (in respect of connectors 2, 3, 4 and 5) modular elements which together make up a length of L. Connector 6 has a covering plane/casing of a length l=L/2 and only one modular element. The modular elements may be assembled mutually with one another and with a hood-shaped connector portion in accordance with the following disclosure. Such assembling is effectuated with the aid of tongues and grooves in the modular elements and the hood-shaped portion. Several types of modular elements may occur. In connectors located adjacent one another and provided with transition members which are larger than the width of each respective connector, the modular element portions 8a are mutually offset in relation to one another in order to ensure efficient utilization of the space occupied by the connectors. According to FIGS. 2 and 3, each respective connector includes a hood-shaped portion 11 which, in turn, consists of a main body portion 11a and a lid 11b. The main body portion carries the covering plane/casing 11c composed of the modular elements in accordance with the foregoing. Essentially, the lid 11b forms one longitudinal side of the hood-shaped portion 11 and is lockable to the body portion 11a by means of retainers, for instance in the form of two screws of which one is shown by broken lines in FIG. 3. Assembly of the part 11a and the lid 11b is effected by means of mutual guides disposed in a known manner in the part and the lid, respectively. A cable 13 is anchored to the socket-shaped transition member 8b and the sheath of the cable is secured in a known manner, for instance by means of a clamping ring 14. The leads 13' of the cable are passed through the socket-shaped transition member 8b to the interior/inner space 11d of the hood-shaped portion 11. The hood-shaped portion 11 illustrated in FIGS. 2 and 3 consists of a separate transition member which is connectable to a rear cover on a known connector. In the prior-art connector, the transition portion of the connector is thus replaced by the transition member according to the present invention. Connection and securing are accomplished by means of screws, for instance two screws whose holes in the body portion have been indicated by reference numerals 11a' and 11a". In FIG. 2, screw holes for the screws 2 of the lid are indicated by reference numerals 11b' and 11b". The main body portion and the lid are provided with longitudinal flanges 11d which are included in the fixing function to the prior-art rear cover. The rear cover in the prior-art connector is symbolized in FIG. 2 by reference numeral 15. The prior-art rear cover includes connection terminals/blocks 16, 17 to which the cable leads are led down and connected. Insertion of the cable leads is done with the lid removed. The modular elements are assembled together with the aid of tongues 18, 19 and 20 in the modular elements and tongues 21 in the lid/main body portion. The tongues are insertable in corresponding grooves in adjacent modular elements/body portions/lids. The modular elements may be connected to the body portion and to one another when the lid is removed and locking of the entire package with modular elements, body portion and lid is achieved when the lid is secured/screwed to the body portion. FIG. 4 shows how each respective modular element is designed with the tongue 22 and the groove 23 which thus fit into a corresponding groove and corresponding tongue in an adjacent modular element/body portion/lid. The modular element is insertable in only one direction, namely that direction which coincides with the direction at right angles to the plane of the figure of FIG. 4. In FIG. 4, the longitudinal axis 24 of the transition member is at right angle to the plane of the casing which, in FIG. 4, is symbolized by reference numeral 25. FIG. 5 illustrates an example of a fifth modular element 8a', 8b', whose longitudinal axis 24' forms an angle α with the plane 25' of the casing. This angle may be different for different modular elements and, in the illustrated embodiment, is approximately 45°. This angular setting facilitates cable routing in associated equipment, since the cable does not need to be bent heavily on connection in those cases when the cable is passed at an angle in towards the connector. FIG. 6 shows how the transition portion may be built up from a number of transition members, for example four transition members 26-29. Each respective transition member is allocated its cable 30-33 which may be given different destinations. The leads 34-37 are, for instance, allocated each to its terminal block 38-41. Each respective cable and terminal block in the connector may, by such means, be treated separately without intervening in or interferring with other cables/terminal blocks, which is to be compared with prior-art cases when a remedial measure or inspection at any point in the equipment necessitated dismantling the entire connector. Marking and soldering sockets are represented by reference numeral 42. According to FIGS. 7-8a, transition portions 43 and 44 of two different lengths L1 and l1 may be employed. the width b is the same. In each respective embodiment, the screws of the lid are designated 12' and 12". The present invention should not be restricted to the embodiment described above and shown on the drawings, many modifications being conceivable without departing from the spirit and scope of the appended claims and the inventive concept as herein disclosed.

A connector incorporates an apparatus for facilitating entry and exit of the cable leads of the connector. The apparatus includes a hood-shaped member with a top portion which is provided with one or more socket-shaped transition members for the cable leads. The top portion consists of at least two combinable modular elements. These include one or more plate-like parts, each provided with its transition member, and one or more plate-like parts without transition members. The modular elements are connectable with the aid of tongues and grooves provided in the modular elements and the side portion of the hood-shaped member.

FIELD OF THE INVENTION [0001] The present invention relates to a shield for a breast pump having a breast receiving member to receive the breast of a user. The invention also relates to a breast pump comprising the shield of the invention. BACKGROUND OF THE INVENTION [0002] Breast pumps are well known devices for extracting milk from a breast of a user. A breast pump may be used if the baby or infant is not itself able to extract milk from the breast, or if the mother is separated from the baby or infant and is to be fed with breast milk by someone else. Breast pumps typically comprise a rigid, funnel-shaped shield connected to a vacuum pump having a container for collecting the milk. [0003] The shield of a breast pump is the interface between the user's breast and nipple with the pump and so its sizing is critical to maintaining the user's comfort whilst using the device. It is also important to ensure that the vacuum seal between the breast and the shield is maintained for optimal pumping. A problem with a conventional breast pump is that it has a shield of fixed size, so it can only cater for a limited range of breast and nipple sizes. However, if the shield is too small relative to the nipple, the nipple tends to fill the available space inside the shield and is likely to touch on the sides of the shield, resulting in chafing, friction and discomfort as negative pressure generated during use of the pump draws the nipple into the shield. On the contrary, if the shield is too large relative to the nipple, then there will be more dead space inside the shield which will reduce the efficiency of the pump system and limit the negative pressure achievable. It also introduces the possibility that the nipple will be pulled deeper into the pump and that the skin on areola or breast area surrounding the nipple will be subjected to chafing. [0004] If the breast shield is not of the optimum size in relation to the size of the breast, there is a tendency for the user to apply greater pressure to the breast pump to urge the breast shield into closer contact with their breast. However, undue pressure on the breast can have a negative effect on the milk production and comfort for the mother. Excessive pressure may also cause the breast shield to block a milk duct resulting in further discomfort and inflammation of the breast tissue. Furthermore, as breast feeding is a delicate matter and is largely influenced by hormones, undue pressure on the breasts can have a negative impact on milk generation and lactation. [0005] An ill-fitting breast shield can cause further problems for the user. Hormones, created by the body, trigger breast milk production and the creation of these hormones depends greatly on the comfort and confidence of the user. If the user perceives the breast shield to be uncomfortable, either visually or by feel, they may loose confidence and milk production may be impaired. [0006] Research has shown that nipple diameter and length varies throughout the population and across different geographic regions and also that the size of the nipple can be different before, during and after expressing. Therefore, as fit is an important consideration when attempting to achieve maximum comfort for a user, a breast pump shield for a breast pump that is capable of accommodating a wide range of breast and nipple sizes is desirable. Furthermore, a breast will change shape and size during lactation. It would therefore be desirable to have the ability to adjust the breast shield during use, and without having to remove the shield from the breast, to ensure that the comfort and effectiveness does not deteriorate. [0007] It is known to provide a breast pump body with a removable shield that may be replaced with another shield of a different size. However, removable shields are generally made from a hard plastic material and do not generally offer the user an enhanced level of comfort whilst using such a device. It is also necessary to store, and have readily accessible, the alternate breast shield, which is not always desirable or convenient. Changing a breast shield is also time consuming and means that the user has to remove their breast from the shield currently in use. As the shields are of finite sizes, they do not allow precise adjustment and it is necessary for a user to be satisfied with a breast shield which is closest in size or shape to that which is actually desired. [0008] It is also known to provide a soft elastomer liner that may be disposed within a rigid shield of a breast pump and which is designed to adapt to the contour of the breast so as to provide comfort and a vacuum seal necessary for operating the pump. The resilience and compliance of such a liner helps to provide a vacuum and milk seal around the user's breast and also reduces friction on the breast and/or nipple when the negative pressure draws the breast and nipple in a direction into the pump. A cushion or insert may be formed from silicon or thermoplastic elastomer (TPE) which, in addition to providing an enhanced level of comfort, can also provide a warmer feeling to the breast. [0009] Although a liner may improve the comfort for a user, a breast pump shield equipped with a liner still suffers from the problem that the liner will only accommodate a relatively small range of breast and/or nipple sizes resulting in a poor fit between the breast and/or the nipple with the insert for a relatively large number of breastfeeding women, causing discomfort and poor vacuum pressure generation. [0010] The present invention seeks to overcome or substantially alleviate the aforementioned problems. SUMMARY OF THE INVENTION [0011] It is known, for example from EP 2,172,236 A1, to provide a shield for a breast pump comprising a body attachable to a breast pump, a resilient, flexible insert received in the body and configured to receive a user's breast, the insert being mountable to a body and an adjuster operable by a user to alter the shape of the insert, wherein the body has a narrow, inner end for attachment to a breast pump body and a wider, outer end through which a breast is inserted into the shield, a first end of the flexible insert being immovably mounted to the wider, outer end of the body with a second end of the insert extending through the body towards its inner end. [0012] According to the present invention, there is provided a breast shield for a breast pump characterised in that the adjuster is configured to move the second end of the insert towards said wider, outer end of the body to axially compress, and thereby change the shape of, the insert. As the shape of the insert is adjustable, the user may adapt the insert to suit the shape of their breast and so have a more comfortable pumping experience. [0013] Adjustment of the breast shield prevents the need for interchanging breast shields for different shapes and sizes of breast. This reduces the number of components that need to be sold with a breast pump making it easier to use and cheaper to produce. [0014] The adjuster may comprise a collar received on the inner end of the body, said second end of the insert being in contact with said collar which is configured such that rotation relative to the body in one direction moves it axially towards said wider, outer end of the body to axially compress, and thereby change the shape of, the insert. This configuration provides an easy way for a user to simply and quickly adjust the shape of the insert to suit their requirements and provides a wide range of adjustment. Preferably, the collar is configured such that rotation relative to the body in the opposite direction moves it axially away from said wider, outer end of the body, the resilience of the insert causing it to expand in an axial direction and thereby change the shape of the insert. This enables the user to simply adjust the shape of the insert back to its original form, i.e. the user is quickly able to appreciate that the shape can be adjusted simply by turning the collar in opposite directions. [0015] The collar may be threadingly received on the inner end of the body. This enables rotation of the collar by the user to be translated into axial movement of the second end of the insert towards, and away from, the first end of the insert. [0016] Preferably, a thread is formed on an inner surface of the collar and at least one radially extending thread follower on the outside of the body, the follower cooperates with the thread to enable the collar to rotate relative to the body. The thread follower may simply be a post extending outwardly from the body which locates in a helically shaped groove in the collar. [0017] In a preferred embodiment, the collar extends beyond the inner end of the body and comprises a radially inwardly extending shoulder, said second end of the insert being in contact with said shoulder. The second end of the insert is in contact with the collar, but is not attached to the body. This means that the second end of the insert will move axially within the body in response to rotation of the collar in either direction, thereby moving it towards, or away from, the fixed first end of the insert. This movement has the result of deforming or changing the shape of the insert. [0018] Preferably, the body has a generally conical portion that narrows from its wider outer end in a direction towards its inner end and a substantially cylindrical portion that extends from said conical portion to said inner end, said insert also narrowing in the same direction and having a substantially cylindrical tubular section extending through the substantially cylindrical portion of the retaining element. The generally conical portion of the body supports the conical portion of the insert. Similarly, the cylindrical portion receives the collar and guides movement of the second end of the insert within the body. [0019] The substantially cylindrical portion of the body may have openings therein. In which case, the tubular section of the insert may also have radially outwardly extending protrusions. The protrusions locate in said openings when the insert is received in the body. This prevents rotation of the insert relative to the body when adjustment is being carried out as a result of rotation of the collar. [0020] Preferably, the generally conical portion of the body comprises a circular frame to which the first end of the insert is attached and a plurality of arms extending radially inwardly towards each other at an angle away from said frame, the substantially cylindrical portion comprising generally axially extending tips to the end of each arm, said openings being formed by spaces between said tips. As the body is formed from a frame, the amount of material used in its construction is reduced. It is also lighter and easier to clean. [0021] The section of the insert that narrows from the wider, outer end of the body towards its tubular section may comprise a series of ribs in the wall of the insert, each rib being parallel to each other and to a plane extending across the wider outer end of the retaining element. This increases the flexibility of the insert, which can fold more easily between the ribs when its shape is being adjusted. [0022] A flexible liner may be removably receivable in the insert. As the liner will form the material that makes direct contact with the breast tissue, it may further provide the user with an enhanced level of comfort and as it can be removed easily will also make the breast pump easier to clean. [0023] According to the invention, there is also provided a pump body having a milk receiving inlet, including a shield according to the invention for attachment to said milk receiving inlet. BRIEF DESCRIPTION OF THE DRAWINGS [0024] Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [0025] FIG. 1 shows an exploded view of a first embodiment of the breast shield according to the invention. [0026] FIG. 2 a shows a side view of the embodiment described in FIG. 1 , the breast shield is adjusted to a first maximum position. [0027] FIG. 2 b shows a side view of the embodiment described in FIG. 1 and FIG. 2 a , the breast shield is adjusted to a second maximum position. [0028] FIG. 3 shows an example of a breast shield for background information only. [0029] FIG. 4 shows a cross-sectional view of an example of a breast shield, for background information only showing two different states of adjustment. DETAILED DESCRIPTION [0030] Referring to the drawings, FIG. 1 shows a first embodiment of the adjustable breast shield 1 , comprising a rigid body 2 , a flexible insert 3 , an adjuster including an adjusting collar 4 and a removable liner 5 . [0031] The rigid body 2 comprises a wider, outer end defined by a frame having a ring 6 and three arms 7 extending downwardly from the upper ring 6 at an angle towards the axis of the upper ring 6 to form a generally conical or funnel-like shape. The distal ends 8 of the arms 7 each have tips 9 that extend substantially axially to form a tubular-shaped portion with a smaller internal diameter than the upper ring 6 . The tips 9 terminate at a second, inner end of the body 2 which can be rigidly, and releasably, connected to a milk inlet of a breast pump body (not shown). [0032] The adjustment collar 4 comprises an annular body 10 with an internal thread 11 and a radially inwardly extending internal lip or shoulder 12 at its lower end. The opposite end of the collar couples to the body 2 over the tips 9 and extends beyond the second, inner, end of the body 2 with the lip 12 extending radially inwardly across the second end of the body 2 and beyond an inner surface of each of the tips 9 . [0033] The tips 9 of the body 2 comprise thread engagement protrusions or members 13 extending radially outwardly from their outer surface that engage with an internal thread 11 formed on an inner surface of the adjusting collar 4 so that, when the adjusting collar 4 is turned, the thread 11 and the thread engagement members 13 cooperate so that the collar 4 moves in an axial direction along the tips 9 of the body 2 , the direction of axial movement depending on the direction of rotation of the collar 4 relative to the body 2 . [0034] Rotation of the collar 4 is limited, in one direction, as a result of the tips 9 coming into contact with the lip 12 on the adjusting collar 4 and, in the other direction, by an end of the threaded part 11 formed on the adjusting collar 4 . [0035] The flexible insert 3 comprises a deformable cone 14 having a first end immovably and releasably coupled to the wider, outer end of the body 2 . The insert 3 extends through the body 2 towards its second end and narrows into a tubular section 15 . The deformable cone 14 may comprise a plurality of folds 24 that open and close to provide increased flexibility in the cone 14 . These folds may be formed between a series of circular ribs parallel to each other and to a plane extending across the wider, outer end of the body 2 . [0036] When assembled, the first end of the insert 3 is attached to the outer end of the body 2 and the second end extends into the body 2 with the tubular section 15 of the flexible insert 3 being slideably received through, and guided by, the tubular portion 9 of the rigid body 2 , formed by the tips 9 . The second end of the insert 3 contacts the internal lip 12 of the adjusting collar 4 that protrudes radially inwardly beyond the inner surface of the tips 9 . [0037] The tubular section 15 comprises a plurality of radially extending ribs 18 on its external face that each extend longitudinal to the axis of the tubular section 15 and are positioned so that they locate in the gaps between the tips 9 . The ribs 18 engage side edges 19 of the tips 9 and prevent rotation of the flexible insert 3 with respect to the rigid body 2 . [0038] The arrangement is such that, as the adjustment collar 4 is turned in a first direction, the collar 4 moves axially towards the outer end of the body 2 . As the second end of the insert 3 is in contact with the collar 4 , via the lip 12 , the insert 3 is resiliently deformed under axial compression, i.e. the distance between its fixed first end, and its movable second end is reduced. This changes the shape of the deformable cone 14 of the insert 3 from a position, as shown in FIG. 2 a , in which it generally lies against and conforms to the shape of the body 2 , into the shape shown in FIG. 2 b , in which the conically shaped portion 14 has been substantially flattened. [0039] Similarly, when the adjustment collar 4 is turned in the opposite direction, it moves axially towards the inner end of the body 2 . This increases the distance between the first and second ends of the insert 3 , releasing the insert 3 and allowing it to regain its original shape, as shown in FIG. 2 a. [0040] The collar 4 may be a friction fit on the tips 9 of the body 2 , so that the insert 3 may be positioned at any location between the two extremes shown by FIGS. 2 a and 2 b , thereby enabling a user to select the most appropriate shape for the insert 3 to accommodate their breast size. [0041] As the ribs 18 cooperate with the side edges of the tips 9 , rotation of the flexible insert 3 is prevented. [0042] The removable liner 5 is made of a flexible material and is inserted into the insert 3 so as to cover the inner face of the flexible insert 3 . The liner 5 provides the direct interface to the breast and provides a removable part for cleaning purposes, although the entire shield may be also be disassembled for replacement of parts or for cleaning The liner 5 comprises a conical portion 20 and a cylindrical portion 21 and closely matches the interior form of the flexible insert 3 . The peripheral edge 22 of the liner 5 has a folded over lip 23 that is hooked over the edge 16 of the flexible insert 3 to fix the liner 5 and the outer edge 16 of the cone 14 of the flexible insert 3 to the upper ring 16 . [0043] FIG. 3 shows an example of an adjustable breast shield which is described for background information only. The adjustable breast shield 30 comprising a flexible conical body portion 31 , a tubular portion 32 extending from the smaller end of the conical body 31 and an adjustable diameter collar 33 around the larger end of the conical body 31 . [0044] The adjustable diameter collar 33 comprises an incomplete loop with ends 34 , 35 and a mechanism 36 to either pull together or push apart the ends 34 , 35 of the incomplete loop, so changing the diameter of the loop. As the diameter of the outer collar 33 is adjusted the shape of the conical body 31 will change in a radial direction. If the diameter is made larger then the cone becomes flatter, and vice versa. The limits of the screw mechanism 36 limit the amount of adjustment possible. The conical body 31 is made of an elastically deformable material and is at the smallest adjustment size when in its natural state, i.e. not under any force. The mechanism 36 can be adjusted to increase the diameter of the outer ring 33 and elastically stretch the conical body 31 until the required breast shield shape is achieved. The mechanism is finger operated and an adjustment knob can be turned by a user to change the size of the insert. [0045] The breast shield 30 is attachable to a supporting body (not shown in FIG. 3 ). [0046] FIG. 4 shows another example of an adjustable breast shield 40 which is described for background information. More specifically, it shows a sectional view of two halves at different stages of adjustment. [0047] The adjustable breast shield of FIG. 4 comprises a flexible conical body 41 , a tubular portion 42 extending from the smaller end of the conical body 41 and an adjustable diameter ring 43 on the larger, outer edge of the conical body 41 . In this example the adjustable diameter ring comprises an inflatable tube 44 that is attached to, or integrally formed with, the larger edge of the conical body 41 . Means for inflating the tube 44 may be a hand, or small electric, air pump or the tube 44 may be inflated by a one-way mouth air valve. It is envisaged that a release valve is included to allow the tube 44 to be deflated when required. [0048] The conical body 41 is made of an elastically deformable material. The right hand side of FIG. 4 shows the third example of the adjustable breast shield 40 with little or no inflation of the adjustable diameter ring 43 . In this state the conical body 41 is in its natural state with no elastic deformation. This is the smallest size of adjustment that can be achieved. The left hand side of the example of FIG. 4 shows the adjustable breast shield when the adjustable diameter ring 43 has been inflated, showing the increase in the size of the breast shield. The conical body 41 has been elastically enlarged. [0049] Although FIG. 4 has been described with reference to an inflatable ring 43 that is integral with the conical body 41 , it will be appreciated that the inflatable element may be entirely separate from both the body and the insert and form a separate component that is received between the body and the insert and is inflated in order to change the shape of the insert. [0050] The breast shield 40 is attachable to a supporting body (not shown in FIG. 4 ). [0051] It will be appreciated that the term “comprising” does not exclude other elements or steps and that the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to an advantage. Any reference signs in the claims should not be construed as limiting the scope of the claims. [0052] Although claims have been formulated in this application to particular combinations of features, it should be understood that the scope of the disclosure of the present invention also includes any novel features or any novel combinations of features disclosed herein either explicitly or implicitly or any generalisation thereof, whether or not it relates to the same invention as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as does the parent invention. The applicants hereby give notice that new claims may be formulated to such features and/or combinations of features during the prosecution of the present application or of any further application derived therefrom. [0053] Other modifications and variations falling within the scope of the claims hereinafter will be evident to those skilled in the art.

A shield for a breast pump is disclosed. It comprises a resilient, flexible insert configured to receive a user's breast, and an adjuster operable by a user to alter the shape of the insert.

CROSS REFERENCE [0001] This application is a continuation-in-part of U.S. Non-provisional application Ser. No. 13/211,817 filed on Aug. 17, 2011. The parent application is incorporated by reference herein in its entirety. BACKGROUND [0002] Isolation of downhole environments depends on the deployment of a downhole tool that effectively seals the entirety of the borehole or a portion thereof, for example, an annulus between a casing wall and production tube. Swellable packers, for example, are particularly useful in that they automatically expand to fill the cross-sectional area of a borehole in response to one or more downhole fluids. Consequently, swellable packers can be placed in borehole locations that have a smaller inner diameter than the cross-sectional area of the fully expanded swellable packer. However, certain downhole conditions, such as the presence of monovalent and polyvalent cations (e.g., Ca 2+ , Zn 2+ , etc.) in the aqueous downhole fluids contacting the swellable packer, tend to decrease both the amount of swelling and the rate at which the packer swells, and may also accelerate degradation of the packer. In order to overcome these issues and to continually improve upon swelling efficiency under a variety of conditions, the industry is always desirous of new and alternate swelling systems. SUMMARY [0003] A swellable system reactive to a flow of fluid, including an article including a swellable material operatively arranged to swell upon exposure to a flow of fluid, the flow of fluid containing ions therein; and a filter material disposed with the swellable material and operatively arranged to remove the ions from the flow of fluid before exposure to the swellable material. [0004] A method of operating a swellable system including filtering ions from a flow of fluid with a filter material; and swelling a swellable material responsive to the flow of fluid upon exposure to the fluid. BRIEF DESCRIPTION OF THE DRAWINGS [0005] The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: [0006] FIG. 1 is a cross-sectional view of a swellable article in an initial configuration; [0007] FIG. 2 is a cross-sectional view of the swellable article of FIG. 1 in a swelled configuration; [0008] FIG. 3 is a swellable system according to an embodiment disclosed herein where a swellable article is disposed with a filter material in a shell covering a swellable core; and [0009] FIG. 4 is a swellable system according to another embodiment disclosed herein where a filter material is separately disposed from a swellable article. DETAILED DESCRIPTION [0010] A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. [0011] Referring now to FIG. 1 , a system 10 including a tubular or string 12 and a downhole article 14 , e.g., a packer or sealing element, disposed thereon is illustrated. The downhole article 14 includes, for example, a base composition and a filter component, discussed in more detail below. The base composition comprises an elastomeric material and/or an absorbent material. Due to fluid absorption by the absorbent material, e.g. absorption of water, brine, hydrocarbons, etc., the article 14 expands or swells to a second configuration shown in FIG. 2 . Various absorbent materials are known and used in the art. For example, with respect to water swellable embodiments any so-called Super Absorbent Polymer could be used, or those marketed by Nippon Shokubai Co., Ltd. under the name AQUALIC® CS-6S. The elastomeric material is included, for example, to provide a seal against a downhole structure 16 , e.g., a borehole in a subterranean formation 18 , shown in FIG. 2 . Of course, the structure 16 could be any other tubing, casing, liner, etc. located downhole and engagable by the article 14 . The elastomeric material could be any swellable or non-swellable material. In some embodiments, the elastomeric material is absorbent with respect to one or more downhole fluids thus also encompassing the absorbent material. In this way, for example, the article 14 can be run-in having an initially radially compressed configuration, exposed to fluids once located downhole, and expanded to engage between the tubular 12 and the structure 16 . In one embodiment, the structure 16 is isolated by expansion of the article 14 such that fluids (e.g., from the formation 18 ) are substantially prevented from flowing past the article 14 once the article 14 is expanded. [0012] Downhole fluids typically comprise an aqueous component, which more accurately is a brine containing various ions, e.g., metal cations from dissolved salts. As noted above, monovalent and polyvalent cations can interact with the absorbent material, and decrease the overall rate and ratio of expansion of the absorbent material, thereby hindering the sealing efficacy of the article. It has been generally found that polyvalent cations such as Ca 2+ , Zn 2+ , etc. have a more profound effect on the performance of swellable materials, particularly in water swellable articles, than monovalent cations and are thus usually more desirable to be removed. It is to be appreciated that while water-swellable materials are discussed as an exemplary embodiment that is adversely affected by the presence of cations, other materials may be swellable in response to different fluids and/or adversely affected by anions. For example, in one embodiment the swellable material is adversely affected (e.g., reduced swelling, shorter life span, slower swelling rate, etc.) by the presence of anions. For this reason, the term “ions” as used herein will refer to any cation or anion that has a negative effect on the performance of a corresponding swellable material. [0013] To mitigate the deleterious effect of such ions on the absorbent material, the filter material acts to remove or filter ions from the downhole fluids before they interact with the swellable material. By remove or filter, it is meant that the filter material captures or holds the ions in, at, or proximate a capture site or location proximate to the filter material, or otherwise neutralizes the ions such that the flow of fluid is at least partially relatively devoid of ions downstream of the filter material. Thus, while the ions are still technically in the fluid, they are prevented from adversely affecting the swelling of the swellable material and therefore considered to be removed or filtered. The removal, filtering, or capture may be done by chemical or physical bonding between the filter material and the ions, physisorption or chemisorption at or by the filter material or a surface thereof, electrostatic and/or van der Waals attraction between the filter material or an atomic structure thereof (e.g., functionalized group) and the ions, etc., examples of which are discussed in more detail below. [0014] In the embodiment of FIGS. 1 and 2 , the filter material, the elastomeric material, and/or the absorbent material can all be mixed together, e.g., homogeneously, then formed into the article 14 . An alternate embodiment for a system 22 is shown in FIG. 3 , the system 22 including an article 24 on a tubular or string 26 . The article 24 is formed from a core 28 and a shell 30 . In this embodiment, the core 28 includes the aforementioned swellable material, while the shell 30 includes the filter material. The core 28 and the shell 30 may both, for example, include suitable elastomeric and/or filler materials to provide sealing for the article 24 and to impart chemical and physical properties to the article 24 . In this way, the flow of fluid to which the swellable material in the core 28 is reactive will first be filtered of ions by the filter material in the shell 30 . [0015] A system 32 according to another embodiment is shown in FIG. 4 in which a swellable article 34 is disposed with a tubular or string 36 . In this embodiment, a formation 38 is separated from the article 34 by a radially disposed tubular or string 40 , e.g., a casing, liner, tubing, etc. The tubular/string 40 includes at least one port or opening 42 for enabling a flow of fluid, generally designated by an arrow 44 , to encounter the article 34 . The filter material can be arranged in a plug 46 positioned in the opening 42 , in a membrane or film 48 positioned over the opening 42 , etc. The plug 46 can be formed as any suitable fluid permeable member for creating a passageway for communicating fluid to the swellable material. In this way, the flow of fluid is filtered by the filter material before it reaches the article 34 . The plug 46 and/or the membrane 48 could be formed from any suitable permeable material, e.g., a porous foam, fibers, with the filter material disposed in or with the permeable material, e.g., in pores of the permeable material. [0016] In another embodiment, essentially a combination of the above, the shell 30 could be a protective or elastomeric shell impermeable to downhole fluids and resistant to corrosion and degradation. A permeable plug, such as discussed with respect to the plug 46 could be included in the shell 30 as opposed the an outer tubular 40 . In this way, the swellable article will benefit from an outer shell made of an elastomeric or other material that can be selected to provide beneficial properties such as corrosion resistance, fluid impermeability, etc., while also maintaining the advantageous ion filtering properties provided by the current invention as discussed herein. [0017] In one embodiment, the filter material comprises one or more graphene-based compounds. By graphene-based it is meant a compound that includes or is derived from graphene, such as graphene itself, graphite, graphite oxide, graphene oxide, etc. The compounds could take any form used with such graphene-based compounds, such as sheets or nanosheets, particles, flakes, nanotubes, etc. Advantageously, the unique properties of graphene enable effective donor—acceptor interactions between both the anions and the cations and the graphene flakes or particles. The graphene-based materials, associated oxides, or other derivatives or functionalized compounds thereof may contain a corresponding relatively large number of capture sites for attracting and binding ions via van der Waals and/or Coulombic interactions. Of course, other materials with electron-rich surfaces can be used for similarly filtering cations, while highly electron deficient materials may be utilized with respect to anions. [0018] To further increase the ability of graphene-based filter materials to capture the aforementioned polyvalent cations, the filter materials can be functionalized to include one or more functional groups. The process of forming graphite or graphene oxide, for example, results in the inclusion of various functional groups that are relatively negatively charged (e.g., carboxylic acid groups) or polar (e.g., carbonyl groups). Polyvalent cations will be attracted to and captured by these groups. In one embodiment the filter material is covalently modified with thiol groups according to known diazonium chemistry procedures. Thiol groups are naturally excellent at capturing positively charged ions, notably doubly charged mercury cations, although other metallic cations ions such as the aforementioned Ca 2+ , Zn 2+ , etc., contained in downhole brines will also be readily captured by thiol groups. Other functional groups such as disulfide groups, carboxylic acid, sulfonic acid groups may also be used for their ability to capture polyvalent cations, particularly doubly charged cations. Other functional groups include chelating ligand groups, such as iminodiacetic acid, iminodiacetic acid group, N-[5-amino-1-carboxy-(t-butyl)pentyl]iminodi-t-butylacetate) group, N-(5-amino-1-carboxypentyl)iminodiacetic acid group, N-(5-amino-1-carboxypentyl)iminodiacetic acid tri-t-butyl ester group, aminocaproic nitrilotriacetic acid group, aminocaproic nitrilotriacetic acid tri-tert-butylester group, 2-aminooxyethyliminodiacetic acid group, and others that would be recognized by those of ordinary skill in the art in view of the disclosure herein. [0019] The graphene-based materials could also be functionalized to filter anions, e.g., with quaternary ammonium, quaternary phosphonium, ternary sulfonium, cyclopropenylium cations, or primary, secondary, ternary amino, or other groups. These groups are either positively charged or become protonated in acidic environments and thus require anions to compensate for the charge. In some situations, the anion can be exchanged with another anion while preserving charge. For example, in one embodiment, the graphene-based material is functionalized with a quaternary ammonium group, the positive charge of which is balanced by hydroxide anions. In this example, in brine containing SO 4 2− anions, one SO 4 2− anion will be captured and two hydroxide anions (OH − ) will be released. In an embodiment, a mixture of graphene-based material functionalized with sulfonic acid groups and graphene-based material functionalized with quarternary ammonium groups balanced by hydroxide anions is used to neutralize a CaCl 2 brine. In the cation-exchange process, Ca 2+ cations are captured with a simultaneous release of two H + ions for each Ca 2+ cation. In the anion-exchange process, Cl − ions are captured by the quaternary ammonium group with a simultaneous release of OH − anion for each Cl − ion. Recombination of released H + and OH − ions results in the formation of water molecules, which may contribute to the swelling process of water-swellable materials. [0020] While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.

A swellable system reactive to a flow of fluid including an article having a swellable material operatively arranged to swell upon exposure to a flow of fluid containing ions therein. A filter material is disposed with the swellable material and operatively arranged to remove the ions from the flow of fluid before exposure to the swellable material.

[0001] The present application claims priority to U.S. Provisional Patent Application Ser. No. 60/752,459, filed Dec. 20, 2005 and entitled “EXTENDED MAINFRAME DESIGNS FOR SEMICONDUCTOR DEVICE MANUFACTURING EQUIPMENT,” (Attorney Docket No. 10799/L) which is hereby incorporated herein by reference in its entirety for all purposes. FIELD OF THE INVENTION [0002] The present invention relates to semiconductor device manufacturing, and more particularly to extended mainframe designs for semiconductor device manufacturing equipment. BACKGROUND OF THE INVENTION [0003] Semiconductor device manufacturing processes often are performed with tools having mainframes in which multiple processing chambers and/or load lock chambers are coupled around a central transfer chamber. The processing chambers may each perform unique processes, or in many instances, may perform redundant and/or related processes. [0004] To ensure proper operation of a semiconductor device manufacturing tool, processing, load lock and other chambers of the tool must be maintained. Sufficient access to maintain the chambers is required. However, in some cases, providing such access may limit system throughput. SUMMARY OF THE INVENTION [0005] In a first aspect of the invention, a first mainframe is provided for use during semiconductor device manufacturing. The first mainframe includes (1) a sidewall that defines a central transfer region adapted to house a robot; (2) a plurality of facets formed on the sidewall, each adapted to couple to a process chamber; and (3) an extended facet formed on the sidewall that allows the mainframe to be coupled to at least four full-sized process chambers while providing service access to the mainframe. [0006] In a second aspect of the invention, a system is provided for use during semiconductor device manufacturing. The system includes a mainframe having (1) a sidewall that defines a central transfer region adapted to house a robot; (2) a plurality of facets formed on the sidewall, each adapted to couple to a process chamber; and (3) an extended facet formed on the sidewall that allows the mainframe to be coupled to at least four full-sized process chambers while providing service access to the mainframe. The system also includes (a) a robot positioned within the central transfer region of the mainframe; (b) a load lock chamber coupled to a first of the plurality of facets; and (c) a process chamber coupled to the extended facet. The extended facet is adapted to increase a distance between the load lock chamber coupled to the mainframe and the process chamber coupled to the extended facet. [0007] In a third aspect of the invention, a second mainframe is provided for use during semiconductor device manufacturing. The second mainframe includes a first transfer section having (1) a first sidewall that defines a first central transfer region adapted to house a first robot; (2) a plurality of facets formed on the first sidewall, each adapted to couple to a process chamber; and (3) an extended facet formed on the first sidewall that allows the mainframe to be coupled to at least four full-sized process chambers while providing service access to the mainframe. The second mainframe also includes a second transfer section coupled to the first transfer section and having (1) a second sidewall that defines a second central transfer region adapted to house a second robot; (2) a plurality of facets formed on the second sidewall, each adapted to couple to a process chamber; and (3) an extended facet formed on the second sidewall that allows the mainframe to be coupled to at least four full-sized process chambers while providing service access to the mainframe. [0008] In a fourth aspect of the invention, a third mainframe is provided for use during semiconductor device manufacturing. The third mainframe includes (1) a sidewall that defines a central transfer region adapted to house a robot; (2) a plurality of facets formed on the sidewall, each adapted to couple to a process chamber; and (3) a spacer coupled to at least one of the facets, the spacer adapted to allow the mainframe to be coupled to at least four full-sized process chambers while providing service access to the mainframe. Numerous other aspects are provided in accordance with these and other aspects. [0009] Other features and aspects of the present invention will become more fully apparent from the following detailed description, the appended claims and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0010] FIG. 1 is a top plan view of a conventional vacuum mainframe that may be employed during semiconductor device manufacturing. [0011] FIG. 2 is a top plan view of the mainframe of FIG. 1 showing four large chambers coupled to the mainframe. [0012] FIG. 3A is a top plan view of a first exemplary mainframe provided in accordance with the present invention. [0013] FIG. 3B is a top plan view of a first alternative embodiment of the mainframe of FIG. 3A provided in accordance with the present invention. [0014] FIG. 3C is a top plan view of a second alternative embodiment of the mainframe of FIG. 3A provided in accordance with the present invention. [0015] FIG. 4 is a top plan view of the first exemplary mainframe of FIG. 3A having four large process chambers coupled to the mainframe. [0016] FIG. 5A is a top plan view of a second exemplary mainframe provided in accordance with the present invention. [0017] FIG. 5B is a top plan view of a first alternative embodiment of the mainframe of FIG. 5A provided in accordance with the present invention. [0018] FIG. 5C is a top plan view of a second alternative embodiment of the mainframe of FIG. 5A provided in accordance with the present invention. [0019] FIG. 6 is a top plan view of the second exemplary mainframe of FIG. 5A having five large process chambers coupled to the mainframe. [0020] FIG. 7A is a top plan view of a third exemplary mainframe provided in accordance with the present invention. [0021] FIG. 7B is a top plan view of a first alternative embodiment of the mainframe of FIG. 7A provided in accordance with the present invention. [0022] FIG. 7C is a top plan view of a second alternative embodiment of the mainframe of FIG. 7A provided in accordance with the present invention. [0023] FIG. 8A is a top plan view of an exemplary pass through chamber employing one or more spacers in accordance with the present invention. [0024] FIG. 8B is a top plan view of an exemplary extended pass through chamber provided in accordance with the present invention. [0025] FIG. 9 is a top plan view of an exemplary load lock chamber provided in accordance with the present invention. DETAILED DESCRIPTION [0026] The present invention relates to extended mainframe designs that allow additional and/or larger chambers to be placed around a mainframe while maintaining service access to the mainframe, as well as to the process chambers and/or load lock chambers coupled to the mainframe. [0027] FIG. 1 is a top plan view of a conventional vacuum mainframe 100 that may be employed during semiconductor device manufacturing. The vacuum mainframe 100 includes a central transfer chamber region 101 and a plurality of facets 102 a - f each adapted to couple to a process chamber, load lock chamber, or other chamber (e.g., a preclean, bake-out, cool down, or metrology or defect detection chamber, or the like). While the mainframe 100 of FIG. 1 is shown as having six facets, it will be understood that fewer or more facets may be provided. [0028] During a typical application, a plurality of load lock chambers 104 a - b are coupled to the mainframe 100 , such as at facets 102 e, 102 f as shown. A factory interface 106 may be coupled to the load lock chambers 104 a - b and may receive substrate carriers 108 a - c at load ports (not separately shown) of the factory interface 106 . A factory interface robot (not separately shown) within the factory interface 106 thereafter may obtain substrates from the substrate carriers 108 a - c and transfer the substrates to the load lock chambers 104 a - b (or transfer substrates from the load lock chambers 104 a - b to the substrate carriers 108 a - c ). A mainframe robot 110 may transfer substrates between the load lock chambers 104 a - b and any process or other chambers coupled to the mainframe 100 (e.g., at facets 102 a - d ) during semiconductor device manufacturing. [0029] FIG. 2 is a top plan view of the mainframe 100 of FIG. 1 showing four large chambers 200 a - d coupled to the mainframe 100 . With reference to FIGS. 1 and 2 , in the conventional mainframe 100 , a shorter reach is employed by the mainframe robot 110 for transferring substrates to and from the load lock chambers 104 a, 104 b than is used for transferring substrates to and from the process chambers 200 a - d coupled to the mainframe 100 (as shown). [0030] To increase clearance between the load lock chambers 104 a - b and the process chambers 200 a - d (e.g., for serviceability), the load lock chambers typically are rotated together (as shown). Nonetheless, serviceability issues may arise when large process chambers, such as etch chambers, chemical vapor deposition (CVD) chambers, atomic layer deposition (ALD) chambers, physical vapor deposition (PVD) chambers or the like, are employed with the mainframe 100 . For example, when four large process chambers are coupled to the mainframe 100 as shown in FIG. 2 , the mainframe 100 and/or the load lock chambers 104 a - b may become unserviceable, or service access may be limited and/or unsafe (e.g., less than the 24 ″ SEMI standard). Accordingly, only up to three large process chambers typically are employed with the mainframe 100 . [0031] FIG. 3A is a top plan view of a first exemplary mainframe 300 provided in accordance with the present invention. Compared to the conventional mainframe 100 of FIGS. 1 and 2 , the mainframe 300 is “stretched” toward the factory interface 106 (as shown). The mainframe 300 may be stretched, for example, to the maximum reach of the mainframe robot 110 (or to any other suitable distance). In at least one embodiment, the mainframe 300 is stretched so that the extension of the mainframe robot 110 is increased by about 10 inches when transferring substrates to and from the load lock chambers 104 a - b (compared to the extension of the mainframe robot 110 within the conventional mainframe 100 ). (As shown in FIG. 3A , the mainframe 300 is stretched by increasing the length of facets 102 c, 102 d formed in a sidewall of the mainframe 300 , which may lead to a slight increase in the size of a central transfer region 301 ). [0032] By stretching the mainframe 300 , four large chambers may be installed around the mainframe 300 and still serviced safely. For example, FIG. 4 is a top plan view of the first exemplary mainframe 300 having four large process chambers 400 a - d coupled to the mainframe 300 . Service access is improved and safe, even when full-sized chambers are employed. Servicing may be performed, for example, between the process chambers coupled to facet 102 c or 102 d and the factory interface 106 . In some embodiments, SEMI standard access requirements, such as 24 ″ or greater of access, may be provided. [0033] By stretching the mainframe 300 by an amount that does not exceed the reach constraints of the mainframe robot 110 , no significant cost is incurred by modifying the mainframe 300 . For example, the same mainframe robot 110 , slit valves, load lock chambers, etc., used within the conventional mainframe 100 may be employed within the stretched mainframe 300 . [0034] With reference to FIG. 3B , in addition or as an alternative, greater service access may be achieved by placing a spacer 303 a between the facet 102 e and the load lock chamber 104 a and/or a spacer 303 b between the facet 102 f and the load lock chamber 104 b so as to create additional space between the process chambers 400 a and/or 400 d and the factory interface 106 ( FIG. 4 ). The spacers 303 a - b may include, for example, tunnels or similar structures that extend between the mainframe 300 and the load lock chambers 104 a and/or 104 b. Similar spacers 303 a - b may be used between the load lock chambers 104 a and/or 104 b and the factory interface 106 as shown in FIG. 3C (e.g., about a 6 ″ to 8 ″ length sheet metal or similar tunnel). [0035] The length of the body of the load lock chamber 104 a and/or 104 b additionally or alternatively may be increased so as to create additional space between the process chambers 400 a and/or 400 d and the factory interface 106 . The use of spacers and/or an extended load lock chamber body length may increase the distance between the mainframe 300 and the factory interface 106 and provide great service access. [0036] FIG. 5A is a top plan view of a second exemplary mainframe 500 provided in accordance with the present invention. Compared to the conventional mainframe 100 of FIGS. 1 and 2 , a single facet 102 d of the mainframe 500 (formed in a sidewall of the mainframe) is “stretched” toward the factory interface 106 (as shown). The facet 102 d of the mainframe 500 may be stretched, for example, to the maximum reach of the mainframe robot 110 (or to any other suitable distance). In at least one embodiment, the facet 102 d of the mainframe 500 is stretched so that the extension of the mainframe robot 110 is increased by about 10 inches when transferring substrates to and from a single load lock chamber 502 employed with the mainframe 500 (compared to the extension of the mainframe robot 110 within the conventional mainframe 100 ). Note that a central transfer region 504 of the mainframe 500 is not significantly increased in size over that of the conventional mainframe 100 . [0037] By stretching only the facet 102 d of the mainframe 500 , five large chambers may be installed around the mainframe 500 and still serviced safely. For example, FIG. 6 is a top plan view of the second exemplary mainframe 500 having five large process chambers 600 a - e coupled to the mainframe 500 . Service access is improved and safe, even when full-sized chambers are employed. Servicing may be performed, for example, between the process chamber coupled to facet 102 d and the factory interface 106 . In some embodiments, SEMI standard access requirements, such as 24 ″ or greater of access, may be provided. [0038] Note that the facet 102 c alternatively may be stretched while the facet 102 d remains unstretched. In such an embodiment, the load lock chamber 502 is coupled to the facet 102 e and servicing may be performed, for example, between the process chamber coupled to facet 102 c and the factory interface 106 . [0039] By stretching a single facet of the mainframe 500 by an amount that does not exceed the reach constraints of the mainframe robot 110 , no significant cost is incurred by modifying the mainframe 500 . For example, the same mainframe robot 110 , slit valves, load lock chambers, etc., used within the conventional mainframe 100 may be employed within the stretched mainframe 500 . [0040] As shown in FIG. 5A , the load lock chamber 502 is rotated in a manner similar to the load lock chambers 104 a - b of FIG. 3A (e.g., by about 5 to 10 degrees, although other degrees of rotation may be used). The mainframe 500 of FIG. 5A may be serviced even when five large (full-size) chambers are coupled to the mainframe 500 . The combination of a stretched mainframe and load lock chamber rotation increases serviceability. [0041] As a further example, when all chambers are operated in parallel (e.g., perform the same process), the use of five chamber facets is 25% more productive than the use of four chamber facets. For a sequential process sequence, additional throughput improvement may be realized. For example, a typical metal etch process employs two etch chambers and two strip chambers. Each etch chamber generally has about two-thirds (⅔) of the throughput of a strip chamber (e.g., 20 wafers/hour for etch versus 30 wafers/hour for strip). By employing all five facets, an additional etch chamber may be coupled to the mainframe 500 so that three etch chambers and two strip chambers are present. The use of three etch chambers and two strip chambers leads to a 50% throughput improvement when compared to the use of two etch chambers and two strip chambers in other mainframe configurations. [0042] In addition or as an alternative, greater service access may be achieved by placing a spacer 506 between the facet 102 f and the load lock chamber 502 so as to create additional space between the process chamber 600 d and the factory interface 106 ( FIG. 6 ). The spacer 506 may include, for example, a tunnel or similar structure that extends between the mainframe 500 and the load lock chamber 502 . A similar spacer may be used between the load lock chamber 502 and the factory interface 106 as shown in FIG. 5C (e.g., about a 6 ″ to 8 ″ length sheet metal or similar tunnel). [0043] The length of the body of the load lock chamber 502 additionally or alternatively may be increased so as to create additional space between the process chamber 600 d and the factory interface 106 . The use of spacers and/or an extended load lock chamber body length may increase the distance between the mainframe 500 and the factory interface 106 and provide great service access. [0044] FIG. 7A is a top plan view of a third exemplary mainframe 700 provided in accordance with the present invention. The third mainframe 700 includes a first mainframe section 702 (e.g., a high vacuum section) coupled to a second mainframe section 704 (e.g., a lower vacuum, input section). The first and second mainframe sections 702 , 704 are coupled via pass through chambers 706 a - 706 b. The first mainframe section 702 includes facets 708 a - f (formed in a first sidewall of the mainframe) and the second mainframe section 704 includes facets 710 a - f (formed in a second sidewall of the mainframe). Each mainframe section 702 , 704 includes a mainframe robot 712 a, 712 b. [0045] As shown in FIG. 7A , the first mainframe section 702 is similar to the mainframe 300 of FIGS. 3 A-C and 4 . That is, the facets 708 c and 708 d of the first mainframe section 702 are “stretched” toward the factory interface 106 (as shown). The facets 708 c, 708 d of the first mainframe section 702 may be stretched, for example, to the maximum reach of the first mainframe robot 712 a (or to any other suitable distance). In at least one embodiment, the facets 708 c, 708 d of the first mainframe section 702 are stretched so that the reach of the first mainframe robot 712 a is increased by about 10 inches when transferring substrates to and from the pass through chambers 706 a, 706 b (compared to the reach of a mainframe robot within a conventional mainframe). By stretching the first mainframe section 702 as described, four large chambers may be installed around the first mainframe section 702 and still serviced safely. [0046] In the second mainframe section 704 , a single facet 710 d of the mainframe section 704 is “stretched” toward the factory interface 106 (as shown). The facet 710 d of the second mainframe section 704 may be stretched, for example, to the maximum reach of the second mainframe robot 712 b (or to any other suitable distance). In at least one embodiment, the facet 710 d of the second mainframe section 704 is stretched so that the extension of the mainframe robot 712 b is increased by about 10 inches when transferring substrates to and from a single load lock chamber 502 employed with the mainframe 700 (compared to the extension of a mainframe robot within a conventional mainframe). By stretching only the facet 710 d of the second mainframe section 704 , five large chambers may be installed around the second mainframe section 704 and still serviced safely. [0047] Through use of the stretched mainframe sections 702 , 704 , the mainframe 700 may provide a total of seven facets for large, full-sized chambers. A central transfer region 714 of the first mainframe section 702 is slightly larger than a central transfer region 716 of the second mainframe section 704 . [0048] In addition or as an alternative, greater service access may be achieved by placing a spacer 720 ( FIG. 7B ) between the facet 710 f and the load lock chamber 502 so as to create additional space between any process chamber coupled to facet 710 d and the factory interface 106 . The spacer 720 may include, for example, a tunnel or similar structure that extends between the second mainframe section 704 and the load lock chamber 502 . A similar spacer 720 may be used between the load lock chamber 502 and the factory interface 106 as shown in FIG. 7C (e.g., about a 6 ″ to 8 ″ length sheet metal or similar tunnel). [0049] In addition or as an alternative, greater service access may be achieved by placing a spacer between the facet 708 e and the pass through chamber 706 a and/or a spacer between the facet 708 f and the pass through chamber 706 b so as to create additional space between the pass through chambers 706 a, 706 b and process chambers coupled to facets 708 c, 708 d ( FIG. 7A ). The spacers may include, for example, tunnels or similar structures that extend between the first mainframe section 702 and the pass through chambers 706 a, 706 b. Spacers also may be used between the pass through chambers 706 a, 706 b and the second mainframe section 704 . [0050] FIG. 8A is a top plan view of an exemplary embodiment of the first pass through chamber 706 a having a first spacer 802 a and a second spacer 802 b coupled thereto in accordance with the present invention. The second pass through chamber 706 b may be similarly configured. [0051] The length of the body of the pass through chambers 706 a and/or 706 b additionally or alternatively may be increased. For example, FIG. 8B is an exemplary embodiment of the second pass through chamber 706 b having a body region 804 extended in accordance with the present invention. Other body portions may be extended. The first pass through chamber 706 a may be similarly configured. [0052] The length of the body of the load lock chamber 502 additionally or alternatively may be increased so as to create additional space between any process chamber coupled to facet 710 d and the factory interface 106 . For example, FIG. 9 illustrates an exemplary embodiment of the load lock chamber 502 having a body region 902 extended in accordance with the present invention. Other body portions may be extended. The load lock chambers 104 a - b may be similarly extended. The use of spacers and/or an extended load lock chamber body length may increase the distance between the mainframe 700 (or 500 ) and the factory interface 106 and provide great service access. [0053] The foregoing description discloses only exemplary embodiments of the invention. Modifications of the above disclosed apparatus and methods which fall within the scope of the invention will be readily apparent to those of ordinary skill in the art. For instance, the mainframes 300 , 500 and/or the mainframe sections 702 , 704 may include more or fewer than six facets. Accordingly, while the present invention has been disclosed in connection with exemplary embodiments thereof, it should be understood that other embodiments may fall within the spirit and scope of the invention, as defined by the following claims.

In a first aspect, a first mainframe is provided for use during semiconductor device manufacturing. The first mainframe includes (1) a sidewall that defines a central transfer region adapted to house a robot; (2) a plurality of facets formed on the sidewall, each adapted to couple to a process chamber; and (3) an extended facet formed on the sidewall that allows the mainframe to be coupled to at least four full-sized process chambers while providing service access to the mainframe. Numerous other aspects are provided.

This application is a continuation of my applications Ser. Nos. 103,432 and 310,831 filed Jan. 4, 1971, and Nov. 30, 1972, both now abandoned respectively. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to apparatus for protecting a partially or fully submerged metallic structural element against corrosion from air, water or a combination of both. 2. Description of the Prior Art It is common to protect the submerged portion of a metallic structural element from corrosion by cathodic methods. Such cathodic protection is expensive and only protects the submerged portion of the metallic element and not the portion thereof in the splash zone. Corrosion protection has also been provided for both the submerged and air-exposed portions of such metallic elements by means of noncorrosive coatings. When such coatings fail, however, they cannot readily be replaced on the submerged portion of the metallic element, and it is expensive to replace such coatings on the splash zone portion of such element. It has also been proposed to add concrete sleeves around such metallic elements. This process is quite expensive, and additionally, such concrete sleeves are difficult to install. For section of metallic elements above water and exposed to air and mixture, the usual practice has been to apply noncorrosive coatings, such as paints, metallic coatings, epoxies and the like to protect against corrosion. These methods have been expensive and the service life is limited. SUMMARY OF THE INVENTION The present invention is characterized by a pliable watertight and airtight encasement which is wrapped about the length of a metallic structural element to be protected from water and air corrosion in a sealing relationship with respect to both water and air. This arrangement prevents corrosion of the covered portion of the metallic element. Filler blocks are provided where the metallic element is not of cylindrical transverse cross-section. Such filler blocks have a circular outer edge so as to permit the encasement to be snugly wrapped around and then secured to such blocks. For the installation of this pliable waterproof and airtight sealed encasement, any existing surface corrosion deposits will not be removed as this corrosion coating provides an initial surface protection of the base metal surface. This corrosion deposit will only be made sufficiently smooth to provide a reasonably snug contact of the encasement with the metallic element surface. The advantages of this invention are the use of proven, long life materials of proven corrosion resistance, no surface cleaning required, the installation can be made in-place on any metallic element, whether above water, at the splash zone or completely below water without any interferences with operations of the structure, in installation is very simple and easy to apply, the cost is far below other present corrosion protective methods and the service life will greatly exceed that now being realized with other methods. It is estimated that this design of pliable sheet encasement will provide a service life of over 30 years. DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view showing apparatus embodying the present invention being applied to a metallic structural element; FIG. 2 is a broken perspective view of such apparatus; FIG. 3 is a side view of said apparatus being secured to the structural element; FIG. 4 is a side view showing the appearance of said apparatus after it has been applied to a structural element; FIG. 5 is a broken side elevational view taken in enlarged scale and particularly showing the end seals of such apparatus; FIG. 6 is a horizontally exploded fragmentary view taken in further enlarged scale showing an end sealing arrangement which may be utilized with said apparatus; FIG. 7 and 8 are views similar to FIG. 6 showing how the sealing rings are applied; FIG. 9 is a horizontal sectional view taken on line 9--9 of FIG. 1; FIG. 10 is a horizontal sectional view taken in enlarged scale along line 10--10 of FIG. 3; FIG. 11 is a side elevational view showing how the apparatus of the present invention is applied to an H-shaped metallic structural element; FIG. 12 is a view similar to FIG. 1, but showing a V-shaped element; FIG. 13 is a view similar to FIG. 11, but showing the use of spacers with an H-shaped element where circular wrapping is not used; FIG. 14 is a view similar to FIG. 13 but showing another form of spacer arrangement; FIG. 15 is a horizontal sectional view taken in enlarged scale along line 15--15 of FIG. 11; FIG. 16 is a vertical sectional view taken in cross-section along line 16--16 of FIG. 15; FIG. 17 is a horizontal sectional view taken in enlarged scale along line 17--17 of FIG. 12; FIG. 18 is a vertical sectional view taken along line 18--18 of FIG. 17; FIG. 19 is a horizontal sectional view taken in enlarged scale along line 19--19 of FIG. 13; FIG. 20 is a horizontal sectional view taken in enlarged scale along line 20--20 of FIG. 14; FIG. 21 is a horizontal sectional view similar to FIG. 17, but showing a different configuration of the spacers; FIG. 22 is a side elevational view showing how concrete, mastic, epoxies, or other sealing materials can be utilized to seal the lower end of an encasement of the present invention; and FIG. 23 is a side view showing a seal between two modular units of the present invention. DESCRIPTION OF PREFERRED EMBODIMENTS Referring to the drawings and particularly FIG. 1 thereof, there is shown a metallic structural element M which is shown partially submerged in seawater to a level indicated at 40. A pliable water and airtight encasement E is shown being applied to a submerged portion of element M and the splash zone portion of such element above the submerged portion. The encasement E includes a substantially rectangular sheet of synthetic plastic material 41. A suitable synthetic plastic is polyvinyl chloride. Other similar materials, however, will prove satisfactory. The sheet 41 has a width throughout its length exceeding the corresponding circumference of the element M. The vertical edges of the encasement sheet E are stiffened or rigidly reenforced against bending by a pair of vertically extending pole pieces 46 and 48. Referring now additionally to FIG. 2, both of the pole pieces 46 and 48 are semicylindrical and are formed of wood, metal, synthetic plastic or the like. The flat side of each pole piece is rigidly affixed as by the stapling or cement to its respective edge of the encasement sheet 41. The pole pieces 46 and 48 permit the sheet to be readily manipulated for placement around the structural element M. Along the flat sides of pole pieces 46 and 48 are attached strips 49 of polyurethane foam, polyether foam, neoprene foam, mastic or any other suitable material that, when compressed, will form a waterproof and air proof longitudinal seal. With the encasement sheet E partially wrapped around the columnar element M in the manner shown in FIG. 1., the lower ends of the pole pieces 46 and 48 are releasably joined by means of a lower socket 50 secured to the lower end of one of the pole pieces 46. Thereafter, the lower end of the other pole piece 48 is inserted in the socket 50 in a nonrotational manner. Next, the two pole pieces are brought together to define a substantially cylindrical unit. Referring now to FIG. 3, the joined-together pole pieces may then be tightened by means of wrenches 52, such wrenches rotating the pole pieces about their vertical axes. During this tightening operation, the strips 49 will be compressed to form a longitudinal waterproof and air proof seal against the entry of corrosive media. Referring now to FIG. 4, thereafter a plurality of wrapping bands 53 are applied to vertically-shaped points along the encasement E to retain it upon the element M. Upper and lower sealing bands are provided for the upper and lower edges of the encasement sheet E, such bands being designated 54 and 56 in FIGS. 1 and 3, and showing as bulges 54 and 56 in FIG. 3. These sealing bands 54 and 56 are wrapped about the structural element M at points corresponding to the upper and lower edge portion of the encasement sheet 41 when the latter has been installed upon element M. Such seal bands 54 and 56 are preferably formed of a material having physical characteristics such that it will have a memory and may be compressed to a fraction of its unconfined volume and thereafter it will exert a pressure in its attempt to regain its original uncompressed shape. Suitable materials are polyurethane foam, polyether foam, neoprene foam or other readily compressible materials with high resilience and with a memory such that they will continually exert a sealing pressure while compressed. It should be understood that the material of the upper and lower sealing bands are compressed by the encasement sheet 41 when the latter is installed. Referring again to FIG. 4 and additionally to FIG. 5, the wrapping bands 53 are of like construction. Conveniently, these bands will take the form of a noncorrosive plastic, synthetic or metallic strap which is tightened about the element M by means of a suitable hand tool, and the ends of such band thereafter rigidly secured together by means of a clamp or clip 58. It will be apparent that other sealing arrangements may be utilized. With the wrapping bands 53 in position, the encasement E will be firmly retained upon the element M. The upper and lower wrapping will serve to compress the upper and lower edge of encasement sheet 41 and the foam seal bands against the element E and in this manner effect a water and airtight seal at the upper and lower edges of the encasement E. Accordingly, the portion of the element M covered by the encasement E will be effectively sealed against contact with both seawater and air. Corrosion from these elements will thereby be effectively prevented. Referring now to FIGS. 6, 7 and 8, the arrangement for sealing the end portions of the encasement E to the exterior surface of the element M is disclosed in detail. It will be noted from these drawings that the interior of the element M may be filled with concrete 60. Referring particularly to FIG. 8, after the wrapping bands 53 have been tightened and wedged together by means of the clip 58, a tapered pin 62 may be driven through a bore 64 formed centrally through the clip 58 and an aligned bore 66 formed in the element M to be thereafter embedded in the concrete 60. This will provide effective securement for the wrapping band 53 to the element. The pin 62 may be formed of fiberglass or some other suitable noncorrosive material. Alternate commercial banding methods can also be used. Referring now to FIGS. 11 and 15, there is shown a metallic structural element M-1 having a noncontinuous transverse cross-sectional configuration, i.e., said element is of generally H-shaped configuration. In order to provide a smooth, continuous exterior cross-sectional profile to receive the encasement E, a pair of filler blocks 68 and 70 are inserted between the opposed cavities 72 and 74 defined by the legs of the element M-1. The filler blocks 68 and 70 extend approximately the length of encasement E and may be formed of wood or any other suitable corrosion resistant material. If wood is used, it should be chemically treated to resist marine borers, dry rot and fungus decay in a conventional manner. Additionally, it should be noted that if wood is used, such wood may be covered with a suitable synthetic plastic such as polyvinyl chloride. The filler blocks could also be formed of molded, noncorrosive synthetic plastic. The encasement E is generally similar to that shown and described hereinbefore, including pole pieces 46 and 48. As indicated in FIG. 15, however, the pole pieces are maintained against rotation by means of a noncorrosive nail or pin 76 which is driven through the pole and into one of the filler blocks 70. Wrapping bands 53 similar to those shown and described hereinbefore are employed to retain the encasement E in place on element M-1, with the upper and lower edges thereof sealed relative to such element by sealing bands such as those designated 54 and 56 hereinbefore. Alternatively, a sealant such as a conventional mastic may be employed. Referring now to FIGS. 12, 17 and 18, there is shown a metallic structural element M-2 of generally V-shaped transverse cross-section. A longitudinally extending filler block 80 is provided for the space between the legs of the element M-2. This filler block 80 extends for approximately the length of the encasement E, such encasement E being similar to that shown and described hereinbefore. As with the form of the invention shown in FIGS. 11 and 15, the pole pieces are affixed to the filler block 80 by means of a nail or pin 76. Referring now to FIGS. 13 and 19, there is shown a generally H-shaped metallic structural element M-1 similar to that shown in FIGS. 15 and 14. In this form of the invention, however, the filler blocks do not extend longitudinally a length approximating the length of the encasement E. Instead, filler blocks 84 are provided only at the upper and lower portion of the encasement E. These filler blocks 84 are of arcuate configuration and serve to define a cylindrical transverse cross-section for receiving seals and wrapping bands 53 at the upper and lower portions of the encasement E. A suitable sealant (not shown) is interposed between the outer curved edges 86 of the filler blocks 84. A suitable nail or pin 76 is driven through the pole pieces 46 and 48 into one of the filler blocks 84, as indicated in FIG. 19. Referring now to FIGS. 14 and 20, a generally H-shaped structural element M-1 is again shown. In this form of the invention, however, filler blocks 90 having a profile similar to the filler blocks 84 are provided. However, the filler blocks 90 extend longitudinally the approximate length of the encasement E to form a cylindrical edge surface 91. A nail or pin 76 is again driven through the pole pieces 46 and 48 to secure such pole pieces to the element M-1. Suitable sealing means (not shown) are provided underneath the wrapping bands 53. Referring now to FIG. 21, there is shown a metallic structural element M-2 of generally V-shaped transverse cross-section similar to that shown in FIGS. 12, 17 and 18. In FIG. 12, however, the element M-2 is shown provided with a pair of filler blocks 92 and 94 secured to the exterior surfaces of the legs of such element and a third filler block 96 of semicylindrical profile. The filler blocks 92, 94 and 96 cooperate to define a cylindrical edge surface 98 for receiving the encasement E. A nail or pin 76 is extended through the pole pieces 46 and 48 into the filler block 96. Referring now to FIG. 22, there is shown a cylindrical metallic columnar element M which is driven into the earth 100 and extends upwardly through a body of water. The lower portion of an encasement E of the type described hereinabove the foam 54 and seal band 53, is covered with a hand-packed quantity of concrete or mortar 102 to assist in the sealing of the lower portion of the encasement E. Referring now to FIG. 23, there is shown a sidewall of a metallic structural element M, provided with a pair of like upper and lower encasements E-1 and E-2, respectively. These upper and lower encasements define modular encasement units. The pole pieces 46 and 48 of the upper and lower encasement units E-1 and E-2 are sealed by means of a single foam seal band 104 and a pair of wrapping bands 53. Various modifications and changes may be made with respect to the foregoing detailed description without departing from the spirit of the present invention.

Apparatus for protecting a partially or fully submerged metallic structural element against corrosion from water, air or a combination of both. A pliable watertight and airtight encasement is wrapped around the portion of the element to be protected. Seal means are utilized to seal the edges of the encasement against water and air. If the encasement is of an irregular shape, fillers are secured to the structural element, such fillers having a circular configuration, and the encasement is wrapped around the fillers.

FIELD OF THE INVENTION [0001] The invention relates to a method of making a dental restoration, and in particular to a method in which a color structure of a tooth and an overall tooth color are independently determined. Based on such determination a dental restoration is machined from a multicolored block. BACKGROUND ART [0002] Dental restorations are often manufactured by an automated process, which typically includes: capturing the shape of a patient's teeth, for example by scanning a plaster model of the patient's teeth or alternatively by scanning the actual teeth in the patient's mouth; designing the shape of a dental restoration precursor based on the captured shape using a computer-aided design (CAD) software; and machining the dental restoration precursor to correspond to the designed shape, for example, by an automated Computer Numerical Controlled (CNC) machine. [0006] It is desirable that the dental restoration has an appearance that matches or approximates the appearance of adjacent teeth. The appearance of natural teeth is on the one hand provided by color shades, and further by a certain translucency. A dental technician or a dental practitioner, for example, typically selects the color of the ceramic material to be used for the dental restoration according to the teeth in a patient's mouth that are located next to the tooth or teeth to be restored. For example, the appearance of relevant teeth in a patient's mouth may be determined using shade guides and an appropriate color shade for the framework and the veneer may be selected accordingly. Exemplary shade guide types are available under the designations “VITA Classical Shade Guide” or “VITA Toothguide 3D-Master®” from the company VITA Zahnfabrik H. Rauter GmbH & Co. KG, Germany. General types of materials for dental restorations are typically selected to meet certain mechanical and aesthetic requirements, which are for example the desired color and/or translucency. [0007] Manufacturers of dental materials often offer dental restorative materials in a variety of different color shades, and a dental technician or a dental practitioner usually selects the shade of the material that is closest to the desired shade. Many approaches have been tried to provide dental restorative materials in color shades that match the desired color as closely as possible. There are also dental restorative materials in the form of milling or grinding blocks, which exhibit a certain pre-determined color gradation to approximate the appearance of the finished dental toward the appearance of a natural tooth. [0008] Although the current approaches for manufacturing of dental restorations may provide a variety of advantages, there is still a desire for a method of manufacturing dental restorations in a reproducible, cost efficient manner and at a good aesthetic quality. SUMMARY OF THE INVENTION [0009] The invention in one aspect relates generally to a two-phase approach of determining a shade structure of a dental restoration. In one phase the overall color of a tooth, for example in a patient's mouth, is determined. In an independent or separate further phase the color structure, in particular the structure or proportioning of different color areas, of that tooth is determined. [0010] In a particular aspect the invention relates to a method of making a dental restoration, which method comprises the steps of: capturing an image of a tooth at a color depth that is based on a multiplicity of color values; posterizing the image by: detecting in the tooth image a contiguous first tooth color area having color values within a predetermined first range of different color values and assigning the first tooth color area one common first false color value; detecting in the tooth image a contiguous second tooth color area having color values within a predetermined second range of different color values and assigning the second tooth color area one common second false color value; determining a tooth color structure based on the first and second false color value of the first and second color area, respectively, within the tooth image; providing information about a multicolored block that has a predetermined color shading formed by at least a first block color zone and a second block color zone, wherein the information comprises data about a block color structure with respect to dimensions and/or positions of the first and second block color zone; matching the tooth color structure and the block color structure; and based on the matching; determining a position within the block in which the tooth color structure and the block color structure match within predetermined limits; and machining the dental restoration from the block at the determined position. [0020] The invention is advantageous in that it allows for the determination of a tooth color structure independent from the determination of the overall tooth color itself, and thus allows for maximizing the aesthetic appearance of a dental restoration. Further the selection of a block based simply on a tooth color code helps minimizing efforts and maximizing the accuracy of the color of the dental restoration. Nevertheless due to the multicolor structure of the block the inventions allows for providing the dental restoration with a color shading resembling that of a natural tooth. [0021] The image is preferably captured digitally, for example using a digital camera or an intra-oral scanner. For the purpose of the present invention the term “image” as used herein refers to the optical image as well as the digital data representing the optical image. The step of capturing the tooth image may for example comprise taking a two-dimensional photograph from the tooth. Accordingly the image is preferably a two-dimensional representation of the tooth and for example provided in the form of a bitmap. Desirably the image is taken as a color image, for example at a color depth of about 16 million colors or more which is sometimes referred to as True Color Image in the art of computer graphics. [0022] In an embodiment the step of capturing the tooth image may further comprise determining an outline of the tooth based on the two-dimensional photograph and thereby creating the tooth image. The outline may be determined manually or automatically. A computer may for example display the image taken and a user may define the tooth outline manually, for example by drawing a virtual line into the image. The computer may, based on this, assume the area of the image inside the outline as the tooth image. An automatic approach may be based for example on computer algorithms for edge finding. [0023] For posterization of the image, in particular the data representing the image, the image may be converted into a grayscale image. The conversion from a color image into a grayscale image is well known in the art of computer graphics and implemented in many standard software packages for image processing. The conversion may be part of the detection of the contiguous first and second tooth color area. This is because the conversion of the color image of a great color depth into a grayscale image of fewer levels of gray also results in a partial posterization, because similar but different colors are assigned one common gray value. For the purpose of the present invention preferably the grayscale image is based on 256 levels (0-255) of gray. In a so formed grayscale image the first range of different color values may be defined between two threshold values within the grayscale, and that first range may be assigned a single color while the remainder of the grayscale forms the second range of different colors and is assigned a different single color. In one example the first false color value corresponds to white and the second false color value corresponds to black. It is noted that for the purpose of the present invention “black”, “white” and “gray” are designated as “colors” although in other fields achromatic tones, like black, white and gray, may not be regarded as colors. This procedure which is based on the definition of thresholds is also referred to as “thresholding” in the art of computer graphics. [0024] Accordingly in one embodiment the step of posterization is based on thresholding. The first false color value and the second false color value may particularly each correspond to a value in a grey scale or correspond to black and white, respectively. The skilled person will recognize that any color may be the basis for the first and second false color value as long as the first and second false color value are different. Further the skilled person will recognize other posterization procedures, for example procedures that are based on multiple different false color values. [0025] In an embodiment the steps of capturing the image and posterizing may be performed in one common step, for example using appropriate hardware like a CCD camera operating based on more than the conventional three color filters. [0026] The tooth color structure is preferably determined based on the first false color value and the second false color value in that the dimensions and positions of the first and second false colors are analyzed. This can be performed by a computer algorithm which analyzes the dimensions of any contiguous areas of the image being assigned a certain false color value, and the position of transitions between areas being assigned different false color values. [0027] In a further embodiment the method further comprises the steps of: providing a database holding information about a plurality of blocks with each of the blocks having a shade structure in accordance with the first and second block color zone, wherein each block being assigned an overall block color code which is based on the colors of the first and second block color zone in combination; determining a tooth color code; and selecting a block having a block color code corresponding to the tooth color code. [0031] The data about the block color structure may comprise (preferably three-dimensional) dimensions of the first and second block color zone. Further the data about the block color structure may comprise positions of the first and second block color zone relative to each other and relative to the outer boundaries of the block. The positions may be defined by coordinates in a three-dimensional coordinate system and optionally by orientations in that coordinate system. Further the position within the block in which the tooth color structure and the block color structure match may be defined by coordinates in a three-dimensional coordinate system and optionally by orientations in that coordinate system. [0032] The method may further comprise the step of determining an average color value from the tooth image and calculating the tooth color code. In this embodiment the image taken for determining the tooth color structure may be used also for determining the tooth color and corresponding color code. In this regard the tooth color code preferably is a numerical or alphanumerical designation for a certain actual color. A common code system is for example defined in the VITA Shade System of the company VITA Zahnfabrik H. Rauter GmbH & Co. KG, Germany. [0033] The method may further comprise the step of determining the tooth color code by matching a physical shade guide and the tooth. In this case the color and thus the color code are determined manually, for example by use of a shade guide or a color measuring device, both available from the company VITA Zahnfabrik H. Rauter GmbH & Co. KG, Germany. Automatic tooth color determination based on the image as described above and manual tooth color determination may be combined to maximize the accuracy in color determination. [0034] In a further embodiment the method further comprises the steps of: displaying at least part of the tooth image and the tooth color structure; and modifying boundaries of the tooth color structure based on user input. [0037] This allows, for example, a manual modification of any automatically (by posterization or thresholding) determined color structure. [0038] In an embodiment the method further comprises the steps of: providing a three-dimensional virtual model of the dental restoration; and creating a positional relationship between the tooth color structure and the dental restoration model; and wherein the step of machining the dental restoration is controlled based on the dental restoration model. [0042] For creating the positional relationship between the tooth color structure and the dental restoration model a two-dimensional view on the three-dimensional dental restoration model and the tooth color structure may be overlaid in the appropriate scale. The two-dimensional view may for example correspond to a view approximately perpendicular on the labial side of the tooth represented by the model, which essentially corresponds to the view from which the image is taken. [0043] In a further embodiment, the method further comprises the steps of: scanning a patient's teeth; designing the dental restoration based on the scan and thereby providing the dental restoration model; and transferring the dental restoration model by data transfer to a machine for machining the dental restoration. [0047] The block may be made of a ceramic or glass ceramic material. Further the step of machining the dental restoration preferably involves milling and/or grinding. The dental restoration is preferably machined at a position in which the tooth color structure and the block color structure match. Such position may be determined based on the tooth color code, for example obtained by calculation or provided on a physical shade guide. The tooth color code may be input into a machine for machining the dental restoration manually or by electric data transfer. The machine may further be provided with the block color code of a block to be machined and may be configured (for example by software) for determining the position within the block at which the dental restoration is to be machined. BRIEF DESCRIPTION OF THE FIGURES [0048] FIG. 1 is a view of a patient's teeth taken as image for use in the method according to an embodiment of the invention; [0049] FIGS. 2, 3 illustrate the step of posterization according to an embodiment of the invention; [0050] FIG. 4 visualizes boundaries of a tooth color structure as determined in a step of the method according to an embodiment of the invention; [0051] FIG. 5 illustrates a step of determining a tooth color according to an embodiment of the invention; [0052] FIG. 6 illustrates a step of determining a tooth color according to a further embodiment of the invention; [0053] FIG. 7 is a schematic view of a shade guide as it may be used with the present invention; [0054] FIG. 8 is a perspective view of blocks as they may be used in the method of the invention; and [0055] FIG. 9 illustrates steps of determining a position of the tooth color structure in the blank according to an embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION [0056] FIG. 1 illustrates an exemplary clinical situation 100 of some of a patient's teeth. The Figure shows a number of incisal teeth including a tooth 10 which for the sake of explanation of the invention is assumed to be a tooth to be restored. In the example the tooth to be restored 10 is present and in a condition to be used as reference for determining the desired shade structure and the desired color of a dental restoration intended to replace the tooth to be restored 10 or part of it. However, in other examples the tooth to be restored may not be present entirely or partly or may be present in a bad condition (for example stained or discolored) so that the determination of the desired shade structure and color of a dental restoration cannot be appropriately performed using the tooth to be restored as reference. In such a case a neighboring tooth 10 ′ may be used as reference instead. In the following it is not consistently differentiated whether the tooth to be restored or any neighboring tooth is used as reference. The skilled person will understand that a suitable tooth can be selected as reference depending on the specific clinical situation of an individual patient. Further for the purpose of the present invention a “neighboring tooth” is not limited to mean any directly neighboring tooth but encompasses for example an opposite or another tooth adjacent the directly neighboring or opposite tooth. [0057] According to one step of the method of the invention an image is captured of the clinical situation 100 . The image taken from the clinical situation 100 comprises also partial images of individual teeth, such as the tooth to be restored 10 and the neighboring tooth 10 ′. In the example the image is taken in the form of a digital photograph using a camera. Typically the captured image is provided in the form of image data, for example a bitmap, having a certain color depth that is based on a multiplicity of color values. There are certain standard color depths available to the skilled person, like for example 256, 65536 or more different colors per image. At present photographs are typically taken at “True Color” which currently corresponds to a color depth of about 16 million different colors. [0058] FIG. 2 illustrates a further step of the method of the invention. The image data provided by the camera are stored in a computer and are posterized. In the example the posterized image 200 is displayed, for example on a computer screen, to make it visible to a user. However in another example the posterization may be performed partly or entirely virtually without displaying. For posterization typically a color gradation based on a first color depth is converted to several single-colored regions based on a lower color depth, with abrupt changes between the different color regions to another. In the example contiguous color areas are determined in which the color values are within a predetermined range of different color values. Such areas are then assigned one common false color value. In particular in this example the color data of the image are virtually converted in grayscale data, using commonly known techniques. Based on this, areas of the image which correspond to a grayscale value within a range defined between a lower and upper threshold (in the example between 151 and 172 as shown in dialog box 201 ) are assigned a white color value and areas which correspond to a grayscale value outside that range are assigned a black color value. This allows for identifying one or more areas of a similar color or grayscale in the image and masking or fading out the remainder of the image. This step of the invention may be repeated based on a different range as shown in FIG. 3 . [0059] FIG. 3 shows a repetition of the step as described in FIG. 2 , but with the threshold range selected differently. In this example the lower threshold is 174 and the upper threshold is 193 as shown as shown in dialog box 201 . The posterized image 200 ′ is different from the posterized image 200 in FIG. 2 in that it displays different contiguous areas of similar color. [0060] In summary FIGS. 2 and 3 illustrate the detection of a contiguous first tooth color area ( 21 a , 21 b ), which has color values within a predetermined first range of different color values. This first tooth color area ( 21 a , 21 b ) is then assigned one common first false color value which in the example corresponds to white. Further FIGS. 2 and 3 illustrate the detection of a contiguous second tooth color area ( 22 a , 22 b ) that has color values within a predetermined second range of different color values. The second tooth color area ( 22 a , 22 b ) is assigned one common second false color value which in the example corresponds to black. The predetermined second range of different color values in the example corresponds to a composition of partial ranges outside the predetermined first range of different color values. For example in FIG. 2 the second range of different color values includes partial ranges 0-150 and 173-255, and in FIG. 3 the second range of different color values includes partial ranges 0-173 and 194-255. [0061] The posterized image is then used to determine a tooth color structure of the first and second false color area 21 a / 21 b , 22 a / 22 b as described in FIG. 4 . [0062] FIG. 4 illustrates a further step of the invention in which a tooth color structure of the first false color area 21 a , 21 b and second false color area 22 a , 22 b are determined. The first false color area 21 a and the second false color area 22 a correspond to the areas determined in the method step illustrated in FIG. 2 , and first false color area 21 b and the second false color area 22 b correspond to the areas determined in the method step illustrated in FIG. 3 . The tooth color structure may be provided in the form of data comprising data about the size and position of the areas 21 a , 21 b , 22 a , 22 b in the image. Further the tooth color structure maybe provided in the form of a tooth structure code representative of that tooth color structure. [0063] The relevant tooth 10 may be identified, and the image may be restricted to a portion representing only the tooth 10 . In other words the outline of the tooth 10 may be determined and the image may be cropped to the area within the outline. The shape of the tooth and thus the outline may be determined manually by a user, for example by drawing a spline in the image. The skilled person will recognize the possibility of automatic cropping eventually in combination with manual correction. The restriction of the image to a particular tooth may be performed prior to posterization or after. [0064] FIG. 5 illustrates a further step of the invention in which the overall color of the tooth to be restored (or a neighboring tooth) is determined. It is noted that the determination of the tooth color structure as described above and the determination of the overall color as described in the following do not need to be performed in the order described. In contrast, the determination of the overall color may be performed prior to or during the determination of the tooth color structure. [0065] In the example shown the overall color of the tooth 10 is determined from the image data of the image captured from the tooth. Thereby the different colors in the overall area of the tooth 10 are averaged and provided in the form of a tooth color code. The skilled person is however aware of other methods for color measuring, for example by measuring the color using a color measuring device as for example available under the designation Easyshade from the company VITA Zahnfabrik H. Rauter GmbH & Co. KG, Germany. [0066] FIG. 6 illustrates a further step in which the overall color of the tooth to be restored (or a neighboring tooth) is determined using a shade guide, for example as available from the company VITA Zahnfabrik H. Rauter GmbH & Co. KG, Germany. [0067] FIG. 7 shows a shade guide 30 comprising a plurality of shade specimens 31 , 32 , 33 , 34 . The shade guide 30 comprises a plurality of specimens defining two or more color areas. The specimens 31 - 34 differ in the proportioning in which individual color areas are arranged. The color areas in the example are identified by borderlines. Thus different color structures are provided on the different specimens 31 - 34 , which can be matched with a tooth color structure of a patient's tooth. The actual color of the specimens 31 - 34 is independent from the color structure and may be different from the color of natural teeth. In the example the specimens 31 - 34 are colorless (for example transparent or pure white) with black borderlines. Accordingly the actual color of the specimens 31 - 34 preferably does not influence the matching of the color structure. The skilled person will recognize that other colors for the specimens and the borderlines may be used as appropriate. [0068] In the example the shade guide 30 exhibits a coding providing the tooth structure code. Such a shade guide may be used, for example, to determine the tooth color structure of that tooth. [0069] FIG. 8 illustrates a kit of differently colored blocks 40 , 50 . Each of the blocks 40 , 50 is multicolored. In particular each of the blocks has a predetermined color shading which is preferably non-uniform in at least one dimension of the respective block 40 , 50 . For example each block 40 , 50 may in one dimension be made of two or more zones, with the zones having different colors. Each zone further exhibits a certain translucency so that different zones may have different translucencies. It is noted that a block may be made of a precursor of the final material. For example the block may be made of a pre-sintered ceramic or glass-ceramic material. In such a case the different colors and/or different translucencies as disclosed herein refer to the colors and/or translucencies at the material's final stage, for example after sintering. [0070] In the example the blocks 40 , 50 are made of a dental material. Suitable dental materials comprise ceramic, glass-ceramic and dental composite materials. [0071] According to the invention information about the multicolored milling block are provided, for example in the form of a block color code which is representative of an overall color of the block. Further such information may comprise data about the block color structure, in particular about dimensions and positions of the different block color zones relative to each other and relative to outer boundaries of the block. [0072] In one step a block 40 / 50 is selected based on the block color code and the tooth color code. In a further step the tooth color structure is matched with the block color structure as illustrated in FIG. 9 . [0073] FIG. 9 shows a virtual representation of a block 40 as an image. The block 40 has four block color zones 41 , 42 , 43 and 44 . In the example the four color zones 41 , 42 , 43 , 44 are formed by curved layers which extend through the block 40 at relatively uniform cross-section. Thus the layers are arranged in only one dimension of the block but provide variations in color in two dimensions due to the curved configuration of the layer cross-sections. The skilled person will recognize that the zones may be provided at any desired shape. However for minimizing the complexity, for example during matching, a relatively simple and geometrically defined shape of the individual zones is advantageous. Further it has been found that a structure as illustrated is sufficient for a multiplicity of different situations. [0074] Further an image of the tooth 10 is overlaid with the image of a block 40 . The images in the example are displayed as two- or preferably three-dimensional renderings to a user, so that the user can move and/or rotate the image of the tooth 10 relative to the image of the block 40 . As illustrated the image of the tooth 10 has a tooth color structure comprising color areas 11 , 12 , 13 . In the example the tooth color areas 11 , 12 , 13 have a color which resembles the color of the block color zones 42 , 43 , 44 respectively. Although the dimensions and positions of the tooth color areas 11 , 12 , 13 do not exactly match with the dimensions and positions of the block color zones 42 , 43 , 44 , the user can move and/or rotate the image of the tooth 10 and the image of the block 40 relative to each other to provide a relatively good match. Although the skilled person is aware of automatic matching algorithms (with or without any display to a user) it may be advantageous to perform the matching manually, in cases in which a user desires personal influence on the optical appearance of the dental restoration. [0075] Once the position and orientation of the image of the tooth 10 and the image of the block 40 relative to each other is determined through matching, the dental restoration can be machined from the block 40 at the determined position and orientation. Each of the image of the tooth 10 and the image of the block 40 preferably are represented in a coordinate system, for example a Cartesian three-dimensional coordinate system. By determining the difference of the origins and the difference of the angulations between these coordinate systems in all dimensions, the position and orientation of the image of the tooth 10 and the image of the block 40 relative to each other can be determined.

A method of making a dental restoration has the steps of capturing an image of a tooth, posterizing the image, determining a tooth color structure, providing information about a multicolored block having a block color structure, matching the tooth color structure and the block color structure, based on the matching, determining a position within the block in which the tooth color structure and the block color structure match, and machining the dental restoration from the block at the determined position. The invention helps facilitating the making of dental restorations at maximized aesthetics.

BACKGROUND OF THE INVENTION The conventional gate valve is made up of carefully machined castings that require patterns, and molds for making them. The result is a long delay between ordering of the valves and the completion and delivery. Many times this delay is not acceptable as it may excessively delay completion of the project utilizing these valves. In many instances the cost of and the time required in making precisely machined valve parts including the main housing would be prohibitive and prevent use of such a valve. If such a valve were made to order, the time required would mean that the valve would not be available when needed. It may be desirable to make such valves from available structural shapes such as pipes or tubes, and plates which may be welded into the desired valve construction. SUMMARY OF THE INVENTION The principal feature of this invention is a gate valve construction in which most of the parts of the valve are made up of conventional metal shapes such as plates, sheets, rods, etc., thereby permitting construction of a valve at a minimum cost and within a short time. Another feature is the adaptability of this construction to various sizes of gate valves limited only to the structural shapes available. According to the invention, the valve housing is made up of a cylinder, larger in diameter than the dimension of the conduit for which the valve is needed. The cylinder has short sections of pipe of the dimension of the conduit welded crosswise of the cylinder, with the inner ends of the sections spaced apart to accept the gate valve elements. Guide plates made of flat sheet stock are supported within the cylinder in alignment with the pipe ends to guide the valve elements into and out of closed position, and the ends of the cylinder are closed by flat discs, one of which is modified so as to be removable. The foregoing and other objects, features, and advantages of the present invention will become more apparent in the light of the following detailed description of preferred embodiments thereof as illustrated in the accompanying drawing. BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a sectional view longitudinally through the valve. FIG. 2 is a sectional view along line 2--2 of FIG. 1. FIG. 3 is a sectional view along line 3--3 of FIG. 1. DESCRIPTION OF THE PREFERRED EMBODIMENT As shown, the valve housing is a cylinder 2 of larger diameter than the conduit for which the valve is adapted that is to say the valve diameter. This housing has aligned, diametrically arranged holes 4 and 6 in which short sections of pipe 8 and 10 corresponding to the conduit dimension are welded. The inner ends 12 and 14 of the pipe sections are precisely spaced apart and aligned to receive therebetween the valve elements or discs 16 and 18 by which the valve is opened or closed. Each disc is so dimensioned as to engage and close the inner ends 12 and 14, respectively, of the pipe sections. These valve discs are interconnected by a support structure which engages with an actuating rod 22 extending through a bonnet 24 on the upper end of the housing 2. This bonnet has a seal 25 to permit axial motion of the rod and the latter is actuated by a means, not shown, to open or close the valve. The bonnet 24 may be secured as desired to the housing. For ease of removal of the bonnet, the latter may have a frusto-conical-shaped rib 26 on an integral flange 28 on the bonnet and the adjacent end of the housing has a cooperating frusto-conical rib 30. A suitable ring seal 32 is positioned at this point and the conical ribs are engaged by a surrounding clamping ring 34 to hold the bonnet and housing together. The bottom end of the housing is closed by a flat disc 36 welded therein. As a guide for the valve discs, two flat plates 38 and 40 are positioned with their adjacent surfaces aligned with the end surfaces 12 and 14 of the pipe sections. These plates extend between and engage with the pipe sections and the bonnet 24 and are thus held securely in position within the housing. For precise spacing of these plates they may be held by threaded rods 41 and 42 extending between and through the plates with suitable nuts 44 engaging on both sides of both plates as shown. As above stated most of the valve is made of conventional structural shapes. The housing 2, bonnet 24, the end cap 36, the pipe sections 8 and 10, the plates 38 and 40, the rod 22 (of two diameters of rod), and the valve discs 16 and 18 may all be machined out of standard structural shapes. To make the frusto-conical rib 30, a strip of sheet stock may be welded to the end of the pipe 2 and then machined to dimension. The bonnet 24 may be plate stock drilled to receive the actuating rod and with a ring formed of sheet welded to the underside and then machined to form the conical surface 26. The result is a valve that can readily be made with a minimum of cost from material readily available and requiring a minimum of machining. Even the valve discs may be machined from plate stock and welded up to form the movable valve element. The support structure 29 for the valve discs includes a wedge element 46 on the actuating rod 22 having a recess 48 on the back side to receive a boss 50 on the disc 16 and a cooperating wedge element 52 has a recess 54 to receive a boss 56 on the disc 18. Thus as the actuating rod is moved toward closing position, there is no lateral closing pressure on the discs until a projection 60 on wedge element 52 engages the end closure 36 at which time the valve disc 18 is in alignment with the pipe section 10. With continued closing movement of the rod, the wedge section 46 continues to move and the wedge action moves the discs laterally into tight valve closing position. As the valve is opened, opening movement of the rod first moves the element 46 to relieve the lateral pressure, and continued movement carries both wedge elements and the attached valve discs into open position. Cooperating detents 62 and 64 on wedge elements 46 and 52, respectively, assure opening movement of both valve discs in unison. Although the invention has been shown and described with respect to a preferred embodiment thereof, it should be understood by those skilled in the art that other various changes and omissions in the form and detail thereof may be made therein without departing from the spirit and the scope of the invention.

A gate valve for a large diameter conduit that is fabricated to a great extent from standard structural shapes to avoid the need for expensive patterns and castings and associated machining requirements.

GOVERNMENT INTEREST This invention was made with United States support under Grant No. 9975806 awarded, by the National Science Foundation. The United States has certain rights in the invention. FIELD OF THE INVENTION This invention is in the field of pine tree breeding and selection. In particular, this invention relates to methods and compositions for identifying pine trees that harbor the null cinnamyl alcohol dehydrogenase (CAD) allele (cad-n1). BACKGROUND OF THE INVENTION Global consumption of wood products is projected to increase 25% over current levels by 2015 (McLaren 1999). Full citations for the references cited herein are provided before the claims. Forest plantations are increasingly important to meet these global demands because their faster growth rates result in much more harvestable volume per unit area than natural forests (Hagler 1996, Sedjo 1999). Thus, reliance on plantations reduces the need to harvest natural forests, allowing them to be used for other societal purposes. In fact, as little as 5 to 10% of the total area of world's forests would be required to meet global demands for wood products if this area were devoted to fast-growing plantations (Hagler 1996, Sedjo and Botkin 1997). Further, the faster growth rates mean high rates of carbon sequestration that may mitigate the effects of global warming. These facts, coupled with the declining area available for commercial forest harvests due to deforestation and government restrictions, have led to a global effort to increase plantation growth rates per unit area above current values through both classical and new technologies (Fox 2000). Viewed as an agricultural crop, timber is the single highest-valued crop in the USA and loblolly pine ( Pinus taeda L) is the most important commercial tree species in the USA. Each year more than 900 million seedlings are used to establish loblolly pine plantations on more than half a million hectares (Pye et al. 1997). The total acreage of the loblolly pine plantation estate is estimated at more than 12 million hectacres (Byram et al. 1999). Loblolly pine is also important for its ecological and biological importance in native forests. Its native range spans 14 states from southern New Jersey south to central Florida and west to Texas. In these natural forests it is the dominant tree species on 11.7 million ha (Baker and Langdon 1990). Thus, loblolly pine is nearly equal in its distribution between native and planted forests totaling 23.7 million hectares. By comparison, the total expanse of plantations of hybrid poplar in the Pacific Northwest is approximately 25,000 ha (Nuss 1999), which is only 0.2% of the area planted in loblolly pine. Due to its overwhelming commercial importance, tree breeding programs for loblolly pine began in the 1950's, and virtually all forest products companies and state agencies are involved in genetic improvement programs (more than 30 organizations) (Byram et al. 1999, Li et al. 1999). These programs have used classical methods of selection, genetic testing and breeding to make demonstrable genetic progress. Unfortunately the progress is hindered, compared to that in agricultural crops, by the large size and long-lived nature of pines (eight years in field tests to make selections followed by another five or more years to complete breeding). For these reasons, most loblolly pine programs are only in their second or third cycle of breeding after nearly 50 years, when in some crops more than one cycle is completed in a single year. Loblolly pine ( Pinus taeda L.) is the most intensively grown tree species in the USA for pulp and solid wood products with plantations exceeding 12 million hectares. The extraction of lignin from wood during the production of pulp and paper requires the use of costly chemicals that are toxic to the environment. Significant progress towards increasing pulping efficiency has been achieved in poplar through the genetic manipulation of genes involved in lignin biosynthesis (Baucher et al., 1996, Hu et al., 1999; Pilate et al., 2002). One of the key enzymes successfully targeted, cinnamyl alcohol dehydrogenase (CAD), catalyzes the final step in the synthesis of monolignols by converting cinnamaldehydes to cinnamyl alcohols. Field-grown transgenic poplar with reduced-CAD allowed easier delignification, using smaller amounts of chemicals and yielded more high quality pulp without an adverse effect on growth (Pilate et al., 2002). A null CAD allele (cad-n1) has been discovered in the loblolly pine clone 7-56 which is heterozygous for the null allele (MacKay et al., 1997). Homozygous seedlings (cad-n1/cad-n1) obtained by selfing, contain between 0-1% of wild type CAD activity (MacKay et al., 1997) and display a brown-red wood phenotype. The expression level of cad transcript in shoot, megagametophyte and xylem tissues was 20 times less in cad-n1 homozygous plants compared to wild type (MacKay et al., 1997). Deficiency of CAD in cad-n1 homozygotes only slightly reduces lignin content but drastically alters lignin composition (MacKay et al., 1997; Ralph et al., 1997; Lapierre et al., 2000; MacKay et al., 2001). The major lignin composition change was attributed to the incorporation of dihydroconiferyl alcohol (DHCA), a minor component of most lignins, but elevated to levels 10-fold higher in cad-n1 homozygous trees. Coniferaldehyde, the substrate of CAD, and vanillin are also present in increased levels while the coniferyl alcohol component of normal lignin decreased. The mutation has a variable effect on pulping efficiency, depending on the age of the trees and whether the mutation is present in a homozygous or heterozygous state. In totally CAD-deficient trees (cad-n1/cad-n1), delignification was significantly easier but the pulp yields were relatively low (˜33%) compared to normal trees (48%) (Dimmel et al., 2001). In 4-6 year old partially CAD-deficient trees (heterozygous) delignification increased in efficiency by ˜20% and yields were similar to wild type (Dimmel et al., 2002). In contrast to these younger trees, a small sample of 14 year old partially CAD-deficient trees displayed no major differences in ease of delignification and pulp yield (Dimmel et al., 2002). In addition to lignin composition changes, the cad-n1 allele appears to be associated with increased stem-growth traits in heterozygous trees (Wu et al., 1999). This growth promotion correlates to an increase in debarked volume of 4-year old trees (14%) (Wu et al., 1999) that is also observed in 14-year old trees (Dimmel et al., 2002). A likely explanation could be that trees harboring the cad-n1 allele may invest fewer resources into the production of monolignols, allowing reallocation of resources towards growth. Promotion of growth was also observed in transgenic poplar with the lignin biosynthetic enzyme 4-coumarate:coenzyme A ligase (4CL) down-regulated (Hu, et al., 1999). For the above reasons, it is desirable to be able to select pine trees that harbor the null CAD allele (cad-n1). Traditionally, the mutation has been diagnosed using CAD isozyme analysis on haploid megagametophytes obtained from seed or by using genetic markers closely linked to the mutation (MacKay et al., 1997). These prior art methods are slow and tedious. It takes numerous years for pine tree seedlings to produce suitable seed for CAD isozyme marker analysis. In addition, linked genetic marker analysis is slow and often yields inaccurate results. There is thus a tremendous need to develop methods that allow rapid and accurate identification of pine trees that harbor the null CAD allele (cad-n1). SUMMARY OF THE INVENTION In order to meet these needs, the present invention relates to the identification of a sequence mutation responsible for the loss of function associated with the cad-n1 allele. This mutation was identified during single nucleotide polymorphism (SNP) discovery within the cad gene of loblolly pine. Identification of this mutation allows breeders to accurately determine the presence, absence and/or copy number of the cad-n1 allele in their germplasm before it reaches sexual maturity. The present invention is directed to a method of identifying a loblolly pine tree harboring a null CAD allele (cad-n1) wherein the pine tree contains a cad gene and the cad gene has a fifth exon. A pine tree is said to “harbor” or contain the null CAD allele if it is homozygous for the null CAD allele (cad-n1/cad-n1) or is heterozygous for the null CAD allele (cad-n1/cad). Pine trees that are homozygous for the wild type CAD allele (cac/cad) do not harbor the null CAD allele. This sequence differs from the wild type sequence of the fifth exon of the cad gene depicted in SEQ ID NO:1. It is expected that there will be some genetic variation in the wild type cad gene sequence resulting in slight differences in the wild type sequence compared to SEQ ID NO:1. In one format, the method includes identifying a pine tree containing a two base pair adenosine insertion in the fifth exon of the cad gene wherein the DNA sequence of the two base pair adenosine insertion includes the nucleotide sequence depicted in SEQ ID NO:3 or the complement thereof. The present invention is further directed to a method of selecting a loblolly pine tree harboring a null CAD allele (cad-n1) wherein the pine tree contains a cad gene and the cad gene has a fifth exon. The method includes a) providing a sample including DNA from the pine tree wherein the DNA includes the cad gene; b) determining whether the fifth exon contains a two base pair adenosine insertion wherein the nucleotide sequence of the fifth exon containing the two base pair adenosine insertion includes the nucleotide sequence depicted in SEQ ID NO:3 or the complement thereof wherein the identification of the two base pair adenosine insertion is indicative of a pine tree harboring a null CAD allele (cad-n1) and c) identifying a sample containing the two base pair adenosine insertion to thereby select a loblolly pine tree harboring a null CAD allele (cad-n1). The present invention is further directed to a method of identifying a loblolly pine tree harboring a null CAD allele (cad-n1) wherein the method includes a) providing a sample including DNA from the pine tree wherein the DNA contains a cad gene and the cad gene has a fifth exon; b) performing template-directed dye-terminator incorporation and fluorescence polarization detection (FP-TDI) on the DNA to determine whether the fifth exon in the sample contains a two base pair adenosine insertion wherein the nucleotide sequence of the fifth exon containing the two base pair adenosine insertion includes the nucleotide sequence depicted in SEQ ID NO:3 wherein the two base pair adenosine insertion is indicative of a pine tree harboring a null CAD allele (cad-n1) and c) selecting a sample containing the two base pair adenosine insertion in the cad gene to thereby identify a loblolly pine tree harboring a null CAD allele (cad-n1). The present invention is further directed to a method of identifying a loblolly pine tree harboring a null CAD allele (cad-n1) by first providing a sample including DNA from the pine tree wherein the DNA contains a cad gene and the cad gene has a fifth exon wherein the DNA in the sample is amplified by PCR using PCR primers wherein the sequences of the primers is SEQ ID NO:11 and SEQ ID NO:12. Next, template-directed dye-terminator incorporation and fluorescence polarization detection (FP-TDI) is performed on the DNA using oligonucleotides having nucleotide sequences SEQ ID NO:1 3 and SEQ ID NO:14 to determine whether the fifth exon of the cad gene in the sample contains a two base pair adenosine insertion wherein the nucleotide sequence of the fifth exon containing the two base pair adenosine insertion includes the nucleotide sequence depicted in SEQ ID NO:3 wherein the two base pair adenosine insertion is indicative of a pine tree harboring the null CAD allele (cad-n1). Finally, samples are selected containing the two base pair adenosine insertion in the cad gene to thereby identify a loblolly pine tree harboring a null CAD allele (cad-n1). The present invention is further directed to a method of identifying a loblolly pine tree homozygous for the null CAD allele (cad-n1/cad-n1) wherein the pine tree contains a cad gene and the cad gene has a fifth exon, by identifying a pine tree, wherein the pine tree contains DNA with a two base pair adenosine insertion in the fifth exon of the cad gene wherein the DNA sequence of the two base pair adenosine insertion includes the nucleotide sequence depicted in SEQ ID NO:3 or the complement thereof. In this format, the selected pine tree does not contain DNA with wild type sequence for the fifth exon of the cad gene wherein the wild type sequence is depicted in SEQ ID NO:1. The present invention is further directed to a method of identifying a loblolly pine tree heterozygous for the null CAD allele (cad/cad-n1) wherein the pine tree contains a cad gene and the cad gene has a fifth exon, by identifying a pine tree, wherein the pine tree contains DNA with a two base pair adenosine insertion in the fifth exon of the cad gene wherein the DNA sequence of the two base pair adenosine insertion includes the nucleotide sequence depicted in SEQ ID NO:3 or the complement thereof. In this format, the pine tree also contains wild type sequence for the fifth exon of the cad gene wherein the wild type sequence is depicted in SEQ ID NO:1 or the complement thereof. The present invention is further directed to a method of identifying a loblolly pine tree homozygous for the wild type CAD allele (cad/cad) wherein the pine tree contains a cad gene and the cad gene has a fifth exon by identifying a pine tree, wherein the pine tree lacks DNA with a two base pair adenosine insertion in the fifth exon of the cad gene wherein the DNA sequence of the two base pair adenosine insertion includes the nucleotide sequence depicted in SEQ ID NO:3 or the complement thereof to thereby identify a pine tree homozygous for the wild type CAD allele (cad/cad). In the methods of the invention, the identifying step may be performed on a sample isolated from a pine tree, a pine tree seedling, a pine tree tissue culture, a pine tree cell culture or a pine tree megagametophte. The sample may also be from pine bark, pine needle, pine tissue or pine seed. In the methods of the invention, the two base pair adenosine insertion may be identified by any genotyping assay that relies on the detection of the presence or absence of the double adenosine insertion mutation. Such methods include DNA sequencing, PCR assays and single base pair extension assays. The single base pair extension assay may be template-directed dye-terminator incorporation and fluorescence polarization detection (FP-TDI). In one format of the invention, the FP-TDI assay may include the use of oligonucleotides wherein the sequences of the oligonucleotides are SEQ ID NO:13 or SEQ ID NO:14. The FP-TDI assay may also include the use of PCR to amplify DNA prior to the FP-TDI assay. In the PCR assay, oligonucleotides such as those depicted in SEQ ID NO:11 and SEQ ID NO:12 may be utilized. The present invention is further directed to an isolated oligonucleotide having a nucleotide sequence selected from SEQ ID NO:9, SEQ ID NO:10, SEQ ID NO:11, SEQ ID NO:12, SEQ ID NO:13, SEQ ID NO:14. In another format, the present invention is directed to a kit for the detection of the null CAD allele (cad-n1) in loblolly pine. The kit may include an oligonucleotide such as SEQ ID NO:13 or SEQ ID NO:14. The kit may further include materials to perform PCR reactions. Such materials to perform PCR reactions may include PCR primers such as those depicted in SEQ ID NO:11 and SEQ ID NO:12. The kit may further include one or more buffers. The kit may also include directions for using the kit. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows the position of the cad-n1 sequence mutation within the cad gene and the effect of the frame-shift on amino acid sequence. A portion of the wild type cad DNA sequence is depicted as SEQ ID NO:1 with the corresponding amino acid sequence depicted as SEQ ID NO:2. A portion of the cad-n1 DNA sequence is depicted as SEQ ID NO:3 with the corresponding amino acid sequence depicted as SEQ ID NO:4. FIG. 2 shows a single base extension assay design for both the forward and reverse reactions. Forward (1528F) and reverse (1528R) assay primer positions and the corresponding fluorescent dideoxynucleotide terminator incorporated for the wild type and cad-n1 allele are also depicted. The sequences depicted in the figure are SEQ ID NO:5, SEQ ID NO:6, SEQ ID NO:7 and SEQ ID NO:8. FIG. 3 shows the detection of the cad-n1 sequence mutation in 96 samples analyzed by the forward and reverse Template-directed Dye-terminator Incorporation and Fluorescence Polarization detection (FP-TDI) assay. Plants are grouped as control (heterozygous), control (homozygous wild type), control (homzygous null), negative controls and unknown plants. DETAILED DESCRIPTION OF THE INVENTION Loblolly pine clone 7-56 is heterozygous for the null cad allele (cad/cad-n1) (MacKay et al., 1997). Selfing of these heterozygous 7-56 clones produce 25% homozygous mutant seedlings: (cad-n1/cad-n1), 50% heterozygous seedlings (cad/cad-n1) and 25% homozygous wild type seedlings: (cad/cad). The homozygous cad-n1 seedlings contain between 0-1% of wild type CAD activity. Field-grown transgenic poplar with reduced-CAD allows for easier delignification, using smaller amounts of chemicals and yields more high quality pulp without an adverse effect on growth. As such, loblolly pine tree breeders have a stong interest in being able to rapidly identify such cad-n1 homozygous plants. It would be particularly useful if a mutation in the cad gene could be identified that was associated with the reduced CAD activity in homozygous plants. Identification of such a mutation would enable the use of various rapid molecular genetic assays for the identification of (cad-n1/cad-n1), (cad/cad-n1) and (cad/cad) trees and seedlings. The present invention is directed to methods and compositions useful for indentifying and distinguishing (cad-n1/cad-n1), (cad/cad-n1) and (cad/cad) trees and seedlings. As discussed in the Example, SNP discovery within the cad gene was performed on haploid megagametophyte DNA from clone 7-56 and 31 other unrelated individuals. A two-base pair adenosine insertion was identified unique to clone 7-56, known to be deficient in CAD activity. The insertion was located in the second codon of exon five and creates a frame-shift that generates a premature stop codon (FIG. 1 ). Seventeen haploid megagametophytes from the heterozygous 7-56 clone were assayed by isozyme gel electrophoresis and DNA sequence analysis to confirm the sequence mutation discovered was associated with CAD-deficiency. In every case, the two-base pair adenosine insertion corresponded with the absence of CAD activity and therefore provides a means for rapidly identifying and distinguishing (cad-n1/cad-n1), (cad/cad-n1) and (cad/cad) trees and seedlings. Plants homozygous for the null cad allele (cad-n1/cad-n1) will contain DNA having the two base adenosine insertion in the fifth exon of the cad gene (at positions 4 and 5 of SEQ ID NO:3) but will not contain wild type DNA for the fifth exon of the cad gene as depicted in SEQ ID NO:1. As such, these plants harbor or contain the null CAD allele but do not harbor or contain the wild type CAD allele. Plants homozygous for the wild type cad allele (cad/cad) will not contain DNA having the two base adenosine insertion in the fifth exon of the cad gene (at positions 4 and 5 of SEQ ID NO:3) but will instead only contain wild type DNA for the fifth exon of the cad gene as depicted in SEQ ID NO:1. Such plants do not harbor or contain the null CAD allele but do harbor the the wild type CAD allele. Plants heterozygous for the null cad allele (cad-n1/cad) will contain DNA having the two base adenosine insertion in the fifth exon of the cad gene (at positions 4 and 5 of SEQ ID NO:3) and will also contain wild type DNA for the fifth exon of the cad gene as depicted in SEQ ID NO:1. As such, these plants harbor both the null CAD allele and the wild type CAD allele. The two-base pair adenosine insertion (at positions 4 and 5 of SEQ ID NO:3) or lack thereof (the wild type sequence, SEQ ID NO:1) can be rapidly identified by numerous methods well known to those of skill in the art. Such methods include any genotyping assay that relies on the detection of the presence or absence of the double adenosine insertion mutation. Such methods include but are not limited to PCR amplification reactions, single base extension assays, primer extension assays, DNA sequencing assays and assays utilizing molecular probes [i.e. Taqman & Fluorescence Resonance Energy Transfer, (FRET)] assays and other techniques. Primer extension is a simple, robust technique for analyzing single nucleotide polymorphisms (SNPs) such as the two base pair adenosine insertion in SEQ ID NO:3 or the complement thereof. This process is illustrated in FIG. 2 and in the Example. A primer with its 3′ end directly flanking the SNP is annealed to the amplified target and induced to extend by a single ddNTP complementary to the polymorphic base. Based on the molecular weight difference between ddNTPs, extension products vary in weight depending on the incorporated nucleotide. Such extension products can be correlated and identified with a particular sequence and then utlized to detect the particular sequence. DNA sequencing is a technique utilized to determine the sequence of nucleotides in a particular DNA molecule such as the presence or absence of the two base pair adenosine insertion in SEQ ID NO:2. Typical sequencing reactions include appropriate sequencing buffers, nucleotides, dideoxy nucleotides, DNA polymerase and one or more oligonucleotide primers. Clones containing the 5th exon of the cad gene can be sequenced with sequencing primers that flank the cloned insert, e.g. T7 polymerarse primers. Alternatively, PCR products containing the 5th exon of the cad gene, prepared, for example, as described below, can be sequenced directly. The polymerase chain reaction (PCR) is a technique utilized to amplify DNA and can be utlized to detect differences in sequences such as the two base pair adenosine insertion in SEQ ID NO:3 of the complement thereof. Typical PCR reactions include appropriate PCR buffers, nucleotides, DNA polymerase and one or more oligonucleotide primers. Any primer amplifying exon 5 of the cad gene can be utilized. Such primers can be designed by procedures well known in the art, for example those procedures described on the UK Human Genome Mapping Project Resource Centre web site. The primers may be located within 3000 base pairs of exon 5 in pine DNA. Generally, primers should be at least 18 nucleotides in length to minimize the chances of encountering problems with a secondary hybridization site on the vector or insert. Primers with long runs of a single base should generally be avoided. It is generally important to avoid 4 or more G's or C's in a row. For cycle sequencing, primers with melting temperatures in the range 52-58 degrees C., as determined by the (A+T)2+(C+G)4 method, generally produce better results than primers with lower melting temperatures. Primers with melting temperatures above 65 degrees C. should also be avoided because of potential for secondary annealing. If the template is a high “G-C” templates, then a primer with a Tm in the 60-70 degrees C. range may be desirable. It is then advisable to do the sequencing reaction with annealing and extension at 60 C. Primers generally have a G/C content between 40 and 60 percent. For primers with a G/C content of less than 50%, it may be necessary to extend the primer sequence beyond 18 bases to keep the melting temperature above the recommended lower limit of 50 degrees C. Primers should be “stickier” on their 5′ ends than on their 3′ ends. A “sticky” 3′ end as indicated by a high G/C content could potentially anneal at multiple sites on the template DNA. A “G” or “C” is desirable at the 3′ end but the first part of this rule should apply. Primers should not contain complementary (palindromes) within themselves; that is, they should not form hairpins. If this state exists, a primer will fold back on itself and result in an unproductive priming event that decreases the overall signal obtained. Hairpins that form below 50 degrees C. generally are not such a problem. Primers should generally not contain sequences of nucleotides that would allow one primer molecule to anneal to itself or to the other primer used in a PCR reactions (primer dimer formation). If possible, it is generally useful to run a computer search against the vector and insert DNA sequences to verify that the primer and especially the 8-10 bases of its 3′ end are unique. Specific PCR primers, such as those depicted as SEQ ID NO:11 and SEQ ID NO:12, may be utilized in the reaction. Reaction products can be sequenced as described above or separated by gel electrophoresis, e.g. size gel electrophoresis, to identify those pine trees harboring or not harboring the CAD null allele. Various modifications of general DNA sequencing, PCR and primer extension techniques are possible as detailed in Short Protocols in Molecular Biology , 4th Edition ed. F. M. Ausubel, R. Brent, D. D. Moore, K. Struhle, Massachusetts General Hospital and Harvard Medical School (2001) Molecular Cloning, Molecular Cloning , Sambrook et al. (2000) both of which are hereby incorporated by reference. While specific oligonucleotide primer sequences are described herein, it is understood that substantially identical oligonucleotide primer sequences to those described herein will also work to permit detection of the two base pair adenosine insertion in SEQ ID NO:3 or the complement thereof that is absent from SEQ ID NO:1. The term “substantially identical” oligonucleotide primer sequences means that a oligonucleotide primer comprises a sequence that has preferably at least 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, or 89%, more preferably at least 90%, 91%, 92%, 93%, or 94%, and most preferably at least 95%, 96%, 97%, 98%, or 99% sequence identity, compared to a reference oligonucleotide sequence using standard alignment programs using standard parameters. Pine Tree Plant Material The two base pair mutation identifying the mutant cad gene can be detected in pine DNA or possibly RNA from pine tissue, pine cells, or pine cellular extracts. Such pine tissue, pine cells; or pine cellular extracts can be isolated from pine trees, pine tree seedlings, pine tree cell culture material, pine tree tissue culture material, pine tree seeds, pine tree needles, bark, tissue and pine tree megagametophytes. Pine seeds, tissue and wood samples can be isolated as described in MacKay, et al. Mol. Gen. Genet. 247, 537-545 (1995) which is hereby incorporated by reference in its entirety. DNA can be extracted from pine needles and megagametophytes as described in Doyle, et al. Focus 12, 13-15 (1987) which is hereby incorporated by reference in its entirety. Kits The present invention is also directed to a kit for the rapid and convenient, identification of cad/cad-n1; cad/cad and cad-n1/cad-n1 pine trees. The kit may be any kit useful for detecting the presence (depicted in SEQ ID NO:3) or the absence (depicted in SEQ ID NO:1) of the two base pair adenosine insertion in the fifth exon of the CAD gene. The kit may be a primer extension kit, a PCR kit or a DNA sequencing kit. All of the kits include primers useful in the various detection assays such as those described herein. The kits would also include buffers, nucleotides and directions for use. The invention will be better understood be reference to the following non-limiting Example. EXAMPLE Materials and Methods Plant Material Four plant material sources were used for the identification and testing for the presence of the cad-n1 allele: (1) A panel of 32 loblolly pine megagametophytes (Weyerhaeuser Company Federal Way, Wash., USA), including one megagametophyte from clone 7-56, was used for SNP discovery within the cad gene, (2) 167 clones (CellFor Inc., Vancouver, BC, Canada) resulting from nine crosses, using clone 7-56 or 7-56 offspring as parents, was used for testing the FP-TDI assay, (3) A selection of 242 first-generation clones (North Carolina State University Cooperative Tree Improvement Program and Weyerhaeuser Company Federal Way, Wash., USA) from the natural range of loblolly pine was used for estimating the frequency of the cad-n1 allele, and (4) 96 progeny from the VERIFICATION population (Brown et al., submitted) of the QTL pedigree (Groover et al., 1994) was used for investigating the cad-ps1 locus. Seeds from loblolly pine clone 7-56 were germinated and the haploid megagametophytes were removed for CAD isozyme analysis or DNA extraction. CAD isozyme assays were performed as described by MacKay et al. 1995. All DNA extractions were performed using the Plant DNAeasy kit (Qiagen, Valencia, Calif., USA) in either the single tube or 96-well format. All primers for PCR and their purpose are described in Table 1 and their relative position within the cad gene shown in FIG. 1 . TABLE 1 Sequence of oligonucleotide primers listed by their function. Purpose Forward primer Reverse primer Discovery CADF2- (SEQ ID NO:9) CADR2- (SEQ ID NO:10) (PCR and CCTCTGTTATGTGCAGGGGTTACA CGAAGTGCAACGGCTCTGG sequencing) FP- CADF8- (SEQ ID NO:11) CADR2- (SEQ ID NO:12) TDI (PCR) TGAAAAGATGATGTGCGCCAA CGAAGTGCAACGGCTCTGG FP- CAD1528F- (SEQ ID NO:13) CAD1528R- (SEQ ID NO:14) TDI assay ATCCGTTGTGTTGCAGGAA GTAATCTAGGCTCTCTGCTGCTT All PCR reactions were performed on ˜20 ng template in a total volume of 25 μl. Each reaction comprised of 0.8 μM of each primer; 0.65 units of HotStarTaq DNA polymerase (Qiagen, Valencia, Calif., USA); 1×PCR buffer containing 1.5 mM Mg; 100 μM each of dATP, dCTP, dGTP, dTTP (Applied Biosystems, Foster City, Calif., USA). Amplification was performed on a PTC100 thermocycler (MJ Research, Waltham, Mass., USA) with the following parameters: Initial denaturation step of 95° C. for 15 min (for activation of HotStarTaq) followed by 37 amplification cycles of 30 sec at 95° C., 30 sec at 60° C. and 2 min at 72° C. DNA Sequencing and Analysis To provide template for sequencing, 5 μl of PCR product was treated with 1 U of exonuclease 1 (USB, Cleveland, Ohio, USA) and 1 U of shrimp alkaline phosphatase (USB, Cleveland, Ohio, USA) and incubated at 37° C. for 1 hr followed by a heat inactivation step of 85° for 15 minutes. The primers that were used during PCR were also used for sequencing (SEQ ID NO:9 and SEQ ID NO:10). Cycle sequencing was performed using ABI Prism big dye terminator mix (Applied Biosystems, Foster City, Calif., USA) using standard conditions as supplied by the manufacturer. Reactions were run on an ABI 377 Automated DNA sequencer using standard ABI protocols. Sequencher (GeneCodes, Ann Arbor, Mich., USA) was used to assemble sequences into a contig where polymorphic differences could be easily visualized. The cad cDNA and translated protein sequence used for alignment in this study had the genbank accession numbers Z37992 and CAA86073 respectively. The intron and exon structure of the cad gene was inferred from a Pinus radiata genomic sequence (AF060491). Detection of the cad-n1 Allele using Template-directed Dye-terminator Incorporation and Fluorescence Polarization Detection (FP-TDI). Template for the assays was amplified using the primers CADF8 and CADR2 (SEQ ID NO:1 and SEQ ID NO:12) as described in Template-directed Dye-terminator Incorporation and Fluorescence Polarization detection (FP-TDI) the PCR section. The assay design for the forward and reverse reaction is shown in FIG. 2 and the primer sequences listed in Table 1. FP-TDI reactions were performed using the Acycloprime-FP SNP detection kit (Perkin Elmer Life Sciences, Boston, Mass.) as described by the manufacturer, except thermocycling conditions were altered to 25 cycles consisting of 95° C. for 15 seconds and 54° C. for 30 seconds. Fluorescence polarization was measured on a Wallac Victor 2 plate reader (Perkin Elmer Life Sciences, Boston, Mass.) with the manufacturer's recommended filter sets and G-Factor calibration. RESULTS AND DISCUSSION Discovery of the cad-n1 Sequence Mutation SNP discovery within the cad gene was performed on haploid megagametophyte DNA from clone 7-56 and 31 other unrelated individuals. A two-base pair adenosine insertion was identified unique to clone 7-56, known to be deficient in CAD activity. The insertion was located in the second codon of exon five and creates a frame-shift that generates a premature stop codon (FIG. 1 ). Seventeen haploid megagametophytes from the heterozygous 7-56 clone were assayed by isozyme gel electrophoresis and DNA sequence analysis to confirm the sequence mutation discovered was associated with CAD-deficiency. In every case, the two-base pair adenosine insertion corresponded with the absence of CAD activity (data not shown). Genotyping of the cad-n1 Mutation by FP-TDI Design of the forward and reverse FP-TDI assays are shown in FIG. 2 . Trial testing of the assay was performed on 167 plants obtained from nine different crosses involving clone 7-56 or progeny from 7-56. Results from a subset of 96 plants using the forward and reverse FP-TDI assay are shown in FIG. 3 . Controls were included that consisted of all three possible genotype classes and blanks that contained no DNA. Samples that did not fall clearly into a genotype cluster (1-2%) were not scored. When both the forward and reverse reaction results were combined, all plants were accurately assigned to a genotype class and no contradictory genotypes were observed. The absence of homozygous cad-n1 clones was expected based on the parental genotypes used to construct the nine crosses tested. Analyzing an indel mutation by single-base extension has the potential for giving a false result if a substitution occurs in the position examined (FIG. 2 ). For example, if the first nucleotide of codon 241 (G) is substituted to an adenosine (forward assay) or the first base of codon 240 (G) is substituted to an adenosine (reverse assay) a false positive result for the cad-n1 allele would occur. Both of these positions require nonsynonymous amino acid changes to occur, alanine to threonine in the forward and glutamine to lysine in the reverse. These nonsynonymous changes were not observed in any of the clones present on the SNP discovery panel or in a selection of 242 first-generation clones. If both the forward and reverse assay are performed, the probability of an error occurring due to nucleotide substitutions would be extremely low. Since the FP-TDI assay is based on single-base extension it should be amenable to other platforms such as the SureScore SNP Genotyping Kit (Invitrogen, Carlsbad, Calif., USA) and SNaPSHOT (Applied Biosystems, Foster City, Calif., USA). SureScore, an integrated system that requires no specialized instrumentation, makes accessible genomic analysis tools that have traditionally been out of reach for many laboratories. The SureScore Kit includes primer design software, a 96-well assay kit, and data analysis software. The primer design software is used to design amplication and SNP-IT capture primers. The kit allows for genotyping to be conducted on up to 96 samples per SureScore strip-well plate, and commonly available equipment such as a 96-well plate washer and reader can be accommodated. Once the assay is completed, the kit provides data analysis software to interpret experimental results The single base extension reaction for the FP-TDI assay utilizes an internal extension primer, which is designed so that its 3′ end anneals adjacent to the polymorphic base-pair. The reaction is essentially a sequencing reaction containing only dye-terminator nucleotides. Since there are no typical nucleotides, all that can occur is the addition of a single fluorescently-labeled dideoxynucleotide (F-ddNTP), which then cannot be extended further. In the FP-TDI assay, the identity of the base added (or bases if a heterozygote) will be discerned via measuring fluorescence polarization. Primers and dNTPs left over from the original PCR are removed or degraded before running the singe-base extension reaction. Residual PCR primers are problematic because they can compete with the extension primer, effectively extending multiple targets, which would ruin the results. Residual dNTPs are problematic because they can allow extension to proceed beyond a single base. The SNaPSHOT® system works by single base extension and then gel electrophoresis on a sequencer such as those provided by ABI. Frequency of the cad-n1 Allele Frequency of the cad-n1 allele was estimated by analyzing the 242 first generation clones that were distributed across the present-day range of loblolly pine (from Texas to Florida and extending north to Delaware). The mutation was not detected in any of the clones analyzed using the forward FP-TDI assay, confirming the rareness of this mutation. The frequency of cad-n1 might be higher in some populations, such as in the region where 7-56 was discovered (Williamsburg, N.C., USA), however much more extensive sampling would be required. The frequency of cad-n1 in loblolly pine breeding populations and plantations will likely increase due to the inclusion of 7-56 as an elite parent in numerous co-operative and private breeding programmes. The diagnostic tool presented here will allow breeders to rapidly screen for the presence of the cad-n1 allele in their germplasm. 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(1994) Identification of quantitative trait loci influencing wood specific gravity in an outbred pedigree of loblolly pine. Genetics 138, 1293-1300 Hsu, T. M., Chen, X., Duan, S., Miller, R. D., and Kwok, P. Y. (2001) Universal SNP genotyping assay with fluorescence polarization detection. Biotechniques 31, 560-570 (2001) Hu, W. J., Harding S. A., Lung, J., Popko, J. L., Ralph, J., Stokke, D. D., Tsai, C. J., and Chiang, V. L. (1999) Repression of lignin biosynthesis promotes cellulose accumulation and growth in transgenic trees. Nat. Biotechnol . 17, 808-812 Kwok, P. Y. (2002) SNP genotyping with fluorescence polarization detection. Human Mutation 19, 315-323 Lapierre, C., Pollet, B., MacKay, J. J., and Sederoff, R. R. (2000) Lignin structure in a mutant pine deficient in cinnamyl alcohol deydrogenase. J. Agric. Food Chem . 48,2326-2331 MacKay, J. J., Liu, W., Whetten, R., Sederoff, R. R., and O'Malley, D. M. (1995) Genetic analysis of cinnamyl alcohol-dehydrogenase in loblolly pine: single gene inheritance, molecular characterization and evolution. Mol. Gen. Genet . 247, 537-545 MacKay, J., O'Malley, D. M., Presnell, T., Booker, F. L., Campbell, M. M., Whetten, R. W., and Sederoff, R. R. (1997) Inheritance, gene expression, and lignin characterisation in a mutant pine deficient in cinnamyl alcohol dehydrogenase. Proc. Natl. Acad. Sci. USA 94, 8255-8260 Pilate, G., Guiney, E., Holt, K., Petit-Conil, M., Lapierre, C., Leple, J., Pollet, B., Mila, I., Webster, E. A., Marstorp, H. G., Hopkins, D. W., Jouanin, L., Boerjan, W., Schuch, W., Cornu, D., and Halpin, C. (2002) Field and pulping performances of transgenic trees with altered lignification. Nat. Biotechnol . 20, 607-612. Ralph, J., MacKay, J. J., Hatfield, R. D., O'Malley, D. M., Whetten, R. W., and Sederoff, R. R. (1997) Abnormal lignin in a loblolly pine mutant. Science 277, 235-239 Vanin, E. F. (1985) Processed pseudogenes: characteristics and evolution. Annu. Rev. Genet . 19, 253-272 Wu, R. L., Remington, D. L., MacKay, J. J., McKeand, S. E., and O'Malley, D. M. (1999) Average effect of a mutation in lignin biosynthesis in loblolly pine. Theor. Appl. Genet . 99, 705-710 MacKay, J. J., Liu, W., Whetten, R., Sederoff, R. R., and O'Malley, D. M. (1995) Genetic analysis of cinnamyl alcohol dehydrogenase in loblolly pine: single gene inheritance, molecular characterization and evolution. Mol. Gen. Genet . 247, 537-545 MacKay, J., O'Malley, D. M., Presnell, T., Booker, F. L., Campbell, M. M., Whetten, R. W., and Sederoff, R. R. (1997) Inheritance, gene expression, and lignin characterisation in a mutant pine deficient in cinnamyl alcohol dehydrogenase. Proc. Natl. Acad. Sci. USA 94, 8255-8260 Pilate, G., Guiney, E., Holt, K., Petit-Conil, M., Lapierre, C., Leple, J., Pollet, B., Mila, I., Webster, E. A., Marstorp, H. G., Hopkins, D. W., Jouanin, L., Boerjan, W., Schuch, W., Cornu, D., and Halpin, C. (2002) Field and pulping performances of transgenic trees with altered lignification. Nat. Biotechnol . 20, 607-612. Ralph, J., MacKay, J. J., Hatfield, R. D., O'Malley, D. M., Whetten, R. W., and Sederoff, R. R. (1997) Abnormal lignin in a loblolly pine mutant. Science 277, 235-239 Wu, R. L., Remington, D. L., MacKay, J. J., McKeand, S. E., and O'Malley, D. M. (1999) Average effect of a mutation in lignin biosynthesis in loblolly pine. Theor. Appl. Genet . 99, 705-710.

Loblolly pine ( Pinus taeda L.) is the most important commercial tree species in the USA harvested for pulp and solid wood products. Increasing the efficiency of chemical pulping may be achieved through the manipulation of genes involved in the lignin biosynthetic pathway. A null allele of cinnamyl alcohol dehydrogenase (CAD) has been discovered in the loblolly pine clone 7-56 which displays altered lignin composition. During identification of single nucleotide polymorphisms (SNPs) in the cad gene, a two-base pair adenosine insertion located in exon five and unique to clone 7-56 was discovered. The sequence mutation causes a frame-shift predicted to result in premature termination of the protein. For routine detection of the mutation, a diagnostic assay was developed utilising Template-directed Dye-terminator Incorporation and Fluorescence Polarization detection (FP-TDI).

BACKGROUND OF THE INVENTION This invention relates generally to antiviral agents and more particularly to a new antiviral agent comprising 1-β-D-arabinofuranosylthymine as a therapeutically efficacious component and prepared in a pharmaceutical form for absorption through the alimentary canal of the human or lower animal to be treated. Representative examples of antiviral agents heretofore known are 5-iodo-2'-deoxyuridine (hereinafter referred to by the abbreviation "IDU") and 9-β-D-arabinofuranosyladenine (hereinafter abbreviated "ara-A"). IDU, however, produces side effects such as teratosis and by no means can be said to be a safe antiviral agent. Similarly as in the case of IDU, ara-A also strongly inhibits growth of animal cells including those of humans and is also reported to give rise to teratosis, whereby its toxicity is a cause of concern when it is employed as a medicinal remedy. On one hand, 1-β-D-arabinofuranosylthymine (hereinafter abbreviated "ara-T") is known to exhibit high antiviral activity in vitro against herpes simplex virus (HSV) and varicella-zoster virus (VZV) as reported in Virology, Vol. 65, p. 294 through p. 296 (1975); Antimicrobial Agents and Chemotherapy, Vol. 12, p. 243 through p. 254 (1977); and Journal of Virology, Vol. 23, p. 679 through p. 684 (1977). As for the antiviral activity in vivo of ara-T, the only report I am aware of is that concerning a therapeutic experiment with hamsters infected with equine abortion virus (EAV). See Antimicrobial Agents and Chemotherapy, Vol. 12, p. 243 through p. 254 (1977); and Annals, New York Academy of Science, Vol. 284, p. 342 through p. 350 (1977). Anti-DNA virus agents used for clinical treatments or undergoing clinical experiments at present are being administered by non-oral methods such as intravenous administration, and there appear to be none that are effective when administered orally. It is considered that, in general, an inhibitor of DNA synthesis exhibits its efficacy more when administered by a non-oral method than when it is administered orally. Therefore, an antiviral activity test in vivo of ara-T is also being carried out by non-oral administration such as intraperitoneal administration, and there have been no reports whatsoever of its oral administration. As a result of various studies I have carried out with the aim of developing antiviral agents of high efficacy yet low toxicity, I discovered that, when ara-T was administered orally, it exhibited a much more effective antiviral activity and less toxicity than when administered by a non-oral method, and, therefore, a ratio of its tolerance dosage to the effective concentration for treatment became much greater. Furthermore, it was also verified that, when ara-T was orally administered to mice, it was absorbed through the digestive system and was retained at a considerably high concentration in the blood for a definite time. Accordingly, it was confirmed that the method of orally administering ara-T thereby to cause it to be absorbed into the body through the alimentary canal is an extremely effective method of treating DNA viral infections. SUMMARY OF THE INVENTION This invention is based on and has been developed from these findings. More specifically, this invention relates to a new form of preparation of ara-T used in carrying out the method of treating viral infections such as DNA viral infections by causing ara-T to be absorbed through the alimentary canal. According to this invention, briefly summarized, there is provided an antiviral agent which comprises 1-β-D-arabinofuranosylthymine as a therapeutically efficacious component and prepared in a pharmaceutical form for absorption through the alimentary canal of the human or lower animal. The nature, utility, and further features of this invention will be more apparent from the following detailed description beginning with a consideration of general and basic aspects of the invention and concluding with examples of experiments relating to therapy, to toxicity, and to metabolism. DETAILED DESCRIPTION OF THE INVENTION In this invention, "a pharmaceutical form for absorption through the alimentary canal" includes the dosage forms for the oral administration and the administration through the rectum. Examples of the forms of doses for the oral administration are tablets, capsules, soft elastic capsules, granules, slow-release granules, fine grains, powder, and syrup. Carriers and additives such as excipients, diluents, coating agents, binders, disintegrators, lubricants, preservatives, perfumes, coloring matter, seasoning agents, and other additive agents to be used in compounding these agent forms are appropriately selected and blended in accordance with the kind of the agent forms. Ordinary compounding methods are used. The dosage of ara-T per day for an adult in the orally administered agent is ordinarily within the range of 500 to 50,000 mg., preferably 1,000 to 10,000 mg. While the therapeutic dose per pharmaceutical unit differs with the kind of pharmaceutic process and administering schedule, it is ordinarily and preferably from 100 to 500 mg. Examples of the forms for the administration through the rectum are suppositories. For bases used in suppositories, generally used bases are used, and ordinary compounding methods are used. In order to indicate fully the nature and utility of this invention, the following examples of experiments relating to therapy, toxicity, and metabolism are set forth, it being understood that these examples are presented as illustrative only and are not intended to limit the scope of the invention. I. THERAPY EXPERIMENTS Each of 10 mice in one treatment group and 20 mice in one control group (ICR-JCL strain four-week-old mice) was inoculated intracerebrally with 10 LD 50 (50% lethal dose) of herpes simplex virus (HSV). Treatment was started 4 hours thereafter. The states of life or death of the mice were observed for 21 days. The control group was treated with phosphate-buffered saline (PBS), and the mean survival times (days) and survival rates were compared. The results relating to mice surviving 21 days or longer were not included in the calculation of the mean survival times, and the test of the significant difference relative to the control group was according to the t-test. The test of the significant difference of survival rate was according to the Fisher exact test. While, in each example of experiment, the efficacy of treatment against infection with HSV type 1 (HSV-1) is indicated, it is confirmed that ara-T is effective also against infection with HSV type 2 with an efficacy of the same order as that against infection with HSV-1. EXPERIMENT 1 Starting from 4 hours after infection with HSV-1, ara-T was orally administered every 12 hours for a total of 9 treatments. As indicated by the results set forth in Table 1, a significant increase in life span (ILS) was observable at an administered quantity of 100 mg/kg× 9, and both an ILS and a rise in survival rate were significantly detectable at an administered quantities of 200 mg/kg and greater×9. TABLE 1______________________________________Quantity admi- Mean survival timenistered Survivors/total (days) ± standard(mg/kg × 9) treated error______________________________________0 1/18 4.0 ± 0.13100 3/9 8.0 ± 0.71.sup.b200 5/9.sup.a 7.5 ± 0.65.sup.b400 5/9.sup.a 6.0 ± 1.08.sup.a800 7/9.sup.b 9.5 ± 0.50.sup.b______________________________________ .sup.a Probability value < 0.01 .sup.b Probability value < 0.001 EXPERIMENT 2 With the same treatment schedule as in Experiment 1, comparison was made with the effect due to intraperitoneal administration. As is apparent from the results shown in Table 2, the minimum effective quantity in intraperitoneal administration is 40 mg/kg×9, whereas that in oral administration is not more than 27 mg/kg×9. Thus, oral administration had a greater effect than intraperitoneal administration. TABLE 2______________________________________Route of Quantity Survivors/ Mean survival timeadminist- administered total (days) ± standardration (mg/kg × 9) treated error______________________________________p.o. 0 0/9 4.3 ± 0.26(orally) 27 2/9 6.6 ± 0.74.sup.b 40 2/9 7.6 ± 0.57.sup.c 60 1/9 6.8 ± 0.48.sup.c 90 3/9 7.4 ± 0.24.sup.ci.p. 0 0/10 4.7 ± 0.37(intra- 27 0/10 5.7 ± 0.45perito- 40 0/10 5.8 ± 0.33.sup.aneally) 60 2/10 6.8 ± 0.56.sup.b 90 2/10 6.8 ± 0.75.sup.a______________________________________ .sup.a Probability value < 0.05 .sup.b Probability value < 0.01 .sup.c Probability value < 0.001 EXPERIMENT 3 Eight hours after infection with HSV-1, treatment was carried out only once, and the efficacy of the treatment was investigated. As indicated by the results shown in Table 3, no increase in the number of surviving mice was observable, but the ILS due to oral administration was much more remarkable than that due to intraperitoneal administration. TABLE 3______________________________________ Quantity ad- Mean survival timeRoute of ad- ministered (days) (treatedministration (mg/kg) group/control group)______________________________________p.o. 400 1.35.sup.b 800 1.67.sup.ci.p. 400 1.12 800 1.24.sup.a______________________________________ .sup.a Probability value < 0.05 .sup.b Probability value < 0.01 .sup.c Probability value < 0.001 EXPERIMENT 4 Starting from 4 hours after infection with HSV-1, ara-T was administered every 48 hours for a total of 5 treatments. As indicated by the results set forth in Table 4, and ILS was evident with each of doses of 100, 200, and 400 mg/kg/treatment, but intraperitoneal administration did not produce any efficacy even at a dose of 400 mg/kg/treatment. TABLE 4______________________________________ QuantityRoute of administer- Survivors/ Mean survival timeadminist- ed (mg/kg/ total (days) ± standardration treatment) treated error______________________________________p.o. 100 1/10 5.8 ± 0.6.sup.a 200 1/10 6.1 ± 0.6.sup.b 400 0/10 5.8 ± 0.5.sup.ai.p. 200 1/10 5.4 ± 0.8 400 0/10 5.0 ± 0.5Control -- 0/20 4.3 ± 0.3______________________________________ .sup.a Probability value < 0.02 .sup.b Probability value < 0.01 II. TOXICITY EXPERIMENTS In varied therapeutic doses, ara-T was administered orally to some mice (ICR strain) and intraperitoneally to other mice of the same strain to be subjected to an acute toxicity test. The mice were observed for one week. As a result, LD 50 in the case of oral administration was higher than 15 g/kg (zero deaths among 10 mice at 15 g/kg) and in the case of intraperitoneal administration was higher than 10 g/kg (2 fatalities among 10 mice at 10 g/kg). Furthermore, body weight reduction and thymic atrophy were observed at 10 g/kg in the case of intraperitoneal administration, whereas neither was observed at 15 g/kg in the case of oral administration. In addition, ara-T in varied doses was administered to four-week-old mice every 12 hours for a total of 9 administrations, and the mice thus treated were observed for one week thereafter. The resulting relationship between the administration quantity and the mortality rate was as indicated in Table 5. TABLE 5______________________________________Route of Quantity admini- Mortalityadministr- stered (No. dead/totalation (g/kg × 9) treated)______________________________________p.o. 1.5 0/5 3 0/5 6 1/5*i.p. 1 0/5 2 3/5* 4 5/5*______________________________________ *Great reduction of body weight was observed. III. METABOLISM EXPERIMENTS A study was made with the aim of determining whether or not ara-T which has been orally administered is actually absorbed and transferred into the blood. Ara-T was orally administered in a quantity of 200 mg/kg to mice. After a suitable time period, blood samples were taken from the hearts of the mice, and the concentration of ara-T in the plasma of each sample was measured in a high-speed liquid chromatograph. The results thus obtained are shown in Table 6, in which each measured value is the average value of one group comprising four mice. As is apparent from Table 6, ara-T was absorbed well through the alimentary canal, and its concentration in the blood amply rose. Furthermore, the absorption continued up to two hours after administration, and the concentration of the ara-T in blood was sustained for a long time at a high value. (A minimal inhibitory concentration of ara-T against HSV in vitro is a concentration of 1 μg/ml). TABLE 6______________________________________Hours after ad- Concentration of ara-Tministration (hr) in blood (μg/ml)______________________________________0.5 251 332 213 134 126 38 1______________________________________ As described above, when the antiviral agent of this invention is administered in a pharmaceutical form for absorption through the alimentary canal, it boosts the already known activity of ara-T, moreover, greatly reduces the toxicity thereof, and is effective in the treatment of infection with DNA viruses such as herpes virus group including HSV and VSV in mammals. More specific pharmaceutical forms of this antiviral agent are appropriately selected in accordance with factors such as the kind of DNA viral infection, degree of the symptoms, and administration schedule. Furthermore, the corresponding compounding method can be readily selected and practiced by those skilled in the art from known facts and by ordinary techniques. One example of a pharmaceutical form of the anti-viral agent of this invention is presented below. ______________________________________Pharmaceutical example (tablet)______________________________________ara-T 200 mglactose 191 mgstarch 50 mgpolyvinyl pyrolidone 5 mgmagnesium stearate 4 mg Total weight 450 mg______________________________________ It is to be understood that the modes of practice of this invention are not limited to the above example, various compounding designs being possible on the basis of the therapeutic doses as described hereinbefore. Furthermore, the combined use of the antiviral agent of this invention with another antivirally active substance is also possible.

An antiviral agent comprising 1-β-D-arabinofuranosylthymine as a therapeutically efficacious component in a pharmaceutical form for absorption through the alimentary canal of the human or lower animal to be treated.

CROSS-REFERENCE TO RELATED APPLICATIONS The present application relates to subject matter disclosed in copending application Ser. No. 128,863 filed Mar. 10, 1980 now U.S. Pat. No. 4,335,431 and copending application Ser. No. 118,909 filed Feb. 6, 1980, now U.S. Pat. No. 4,321,677 issued Mar. 23, 1982. FIELD OF THE INVENTION This invention relates to a skid control method for controlling the pressure of braking oil when a vehicle slips during a vehicle braking operation and more particularly to such a method using a microcomputer. BACKGROUND OF THE INVENTION In skid control, the slip rate is calculated from the calculated wheel speed and when the calculated slip rate reaches a predetermined value, the brakes are released, while when the slip rate is restored to another preset value, the braking oil pressure is reapplied. The time during which the brakes are released is measured and the next instant of brake release is controlled on the basis of the result of the measurement. Repeating this series of operations thereafter, the frictional coefficient between the wheels and the road surface is kept at a maximum value so that the stopping distance is shortened. The calculation of the wheel speed is one of the most important factors necessary for skid control as a whole and therefore must be processed exactly and swiftly. To calculate the wheel speed from the signal delivered by the wheel speed sensor, there are two methods such as a proposed method in which pulses from the wheel speed sensor are counted for a predetermined constant time and a method in which the time interval between adjacent pulses is measured. The former method is not adapted for an anti-skid apparatus which requires rapid calculations, since this method needs to count pulses and therefore requires a certain time. The latter method, which measures the interval between adjacent pulses, can perform a rapid processing since only a time equal to the pulse-to-pulse period is required in this case. However, the measurement of only the pulse-to-pulse period results in a rather large error and therefore in practical applications it is necessary to measure several numbers of such periods and to figure out the average of them. Accordingly, it becomes difficult also in this case to complete the processing in a very short time. The pulse-to-pulse periods are successively stored in a memory (RAM) and they are read out for processing in the case of the wheel speed being calculated. At the time of calculating the wheel speed, it is necessary to check which data block is to be used. According to methods currently adopted, the program for calculation is very complicated so that the number of locations in memory used for calculation processing is considerable. SUMMARY OF THE INVENTION An object of this invention is to provide a skid control apparatus which has a high speed of processing the calculation of the wheel speed and uses only a small number of memory locations for the calculation. According to the features of this invention, the sampling timing for detecting the wheel speed is varied in accordance with the change in the wheel speed, the newest data representing the pulse-to-pulse period derived from the wheel speed sensor is stored in the head location of the memory, and the data is always subjected to rearrangement from the head location to the succeeding ones in memory according to the order of arrival. Other objects, features and advantages of this invention will be apparent when one reads the following description of the embodiment of thie invention with the aid of the attached drawings, in which: BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 schematically shows a skid control system using a microcomputer, as an embodiment of this invention; FIG. 2 shows in detail the principal part of the skid control system shown in FIG. 1; FIGS. 3 and 4 show flow charts for explaining the operation of the skid control system shown in FIG. 1 or 2; FIG. 5 shows in graphical representation the relationship among the vehicle speed, the virtual vehicle speed, the wheel speed and the operation of the actuator for controlling the brake oil pressure, at the time of panic braking; FIGS. 6 shows the relationship between the brake releasing period and the slip rate S; FIG. 7 is a block diagram useful in explaining the functions of the free-running counter, the register and the register control circuit; FIGS. 8A and 8B are diagrams useful in explaining the operation of the free-running counter; FIG. 9 illustrates how to obtain the period of the wheel speed pulses; FIG. 10 illustrates how to obtain the pulse duration or width of the wheel speed pulses; FIG. 11 is a flow chart for the processing of taking in the content of the free-running counter to the specific memory according to this invention; FIGS. 12 to 15 illustrate how to store data in RAMS; FIG. 16 is a flow chart for the process of calculating the wheel speed; FIG. 17 shows the waveforms of the wheel speed signal and the IRQ signal according to this invention; and FIG. 18 is a flow chart associated with the signals shown in FIG. 17. DETAILED DESCRIPTION OF THE INVENTION FIG. 1 schematically shows a skid control systemm using a microcomputer (hereafter referred to as CPU), as an embodiment of this invention. The mechanical power generated by an engine (not shown) is transmitted through a transmission gear assembly (not shown) and a propeller shaft 13 to a differential gear 15, which in turn drives rear wheels 17. The output signals of a wheel speed sensor 19 attached to the propeller shaft 13 are sent through a signal line 21 to a control apparatus 11. The control apparatus incorporates therein a CPU and an I/O circuit (i.e. input/output circuit). A detailed description thereof will be given later. An actuator 23 has a solenoid 25 energized by an output signal sent from the control apparatus 11 through a signal line 27. The diaphragm chamber in the actuator 23 communicates with the engine manifold having a negative pressure through a pipe 29 and with the surrounding atmosphere through an air filter 31 and pipe 33. The diaphragm of the diaphragm chamber is coupled to a piston rod. The force generated by depressing a brake pedal 35 is converted to an oil pressure by means of a master cylinder 37. The induced oil pressure is transmitted to an oil pressure control valve 39. The oil pressure discharged from the oil pressure control valve 39 is used, through a pipe 41, to brake front wheels 43 and also transmitted to the actuator through a pipe 45. The pressured oil whose pressure was controlled by the piston rod in the actuator 23, is used, through a pipe 47, to brake the rear wheels 17. The control apparatus 11 and the negative voltage terminal of the actuator 23 are connected together through a conductor line 49, to have the same potential. The control apparatus 11 also has a warning lamp 51 connected therewith for warning of a malfunction of the system. A fuse 53 is inserted between the control apparatus 11 and a power source 56, the fuse 53 serving to cut the supply of power to the control apparatus to establish the normal braking condition when an abnormality occurs. When an ignition key switch 55 is turned on, electric power is supplied from the power source 56 to the control apparatus 11 through the fuse 53. At the time of the brake being applied, if the solenoid 25 is turned on, the piston rod coupled to the diaphragm in the actuator 23 is shifted so that the oil pressure decreases to release the braking force. FIG. 2 shows in detail the circuit of the control apparatus 11 shown in FIG. 1. The positive voltage terminal 111 of the control apparatus 11 is connected with the positive electrode of the power source and therefore a voltage V B is supplied to the control apparatus 11. The power source voltage V B is kept constant, for example, at +5 V, by means of a voltage regulating circuit 113. This constant voltage V cc of, for example, +5 V is applied to a CPU 135. The CPU 135 includes therein a MPU (Microprocesser) 115, a RAM (Random Access Memory) 117, a ROM (Read-Only Memory) 119, register control circuits 131 and 133, free-running counters 123 and 125, and registers 127 and 129. The constant voltage V cc is also supplied to an I/O (input/output) circuit 121. The microcomputer unit, MC6801, sold by Motorola Inc. is known as incorporating a free-running counter therein. The wheel speed sensor 19 converts the rotational speed of a rotor 136 to a corresponding AC voltage by its electromagnetic pickup 137. The output of the pickup 137, i.e. the signal representing the rotational speed of the rotor 136, is supplied through a waveform shaping circuit 139 to the I/O circuit 121. The outputs of the I/O circuit 121 are supplied through amplifiers 141, 143 and 145 to the fuse 53, the warning lamp 51 and the solenoid 25. The MPU 115, the RAM 117, the ROM 119, the registers 127 and 129, and the I/O circuit 121 are interconnected with one another through data bus, address bus and control bus 147 (all the buses are indicated by reference numeral 147). A clock signal E is sent from the MPU 115 to the RAM 117, the ROM 119, the free-running counters 123 and 125, and the I/O circuit 121, whereby the data transmission is performed in synchronism with this clock signal E. The free-running counters 123 and 125 count the pulses of the clock signal E. When the count value overflows the counters 123 and 125, they send an overflow signal to the register control circuits 131 and 133 respectively so that the counters 123 and 125 are reset to their initial states and resume counting, repeating these cycles. The register control circuit 131 and 133 control the timing when to store the contents of the free-running counters 123 and 125 in the registers 127 and 129 respectively. Now, description will be given of the operation of the skid control system as an embodiment of this invention. If a rolling body, e.g. a vehicle, moving at a speed of V in a certain direction on a plane, slips, then the associated slip rate S is defined such that ##EQU1## where R is the radius of the rolling body and ω is the angular velocity of the rolling body. Here, it is to be noted that the frictional coefficient μ, defined between the tire of the vehicle and the road surface bearing the tire thereon, is a function of the slip rate S. According to experiments, it has been determined that the frictional coefficient μ takes a maximum value in the direction of forward movement when the slip rate is near 20%, while μ decreases with the increase in S in the case of lateral slipping. Accordingly, if the slip rate S is controlled to be near 20%, the frictional coefficient μ between the tire and the road surface could be made maximum when the car skids. The skid control apparatus according to this invention controls the slip rate S in such a manner that S is near 20% in the case of skidding. FIGS. 3 and 4 show a flow chart for explaining the operation of the control system according to this invention. As shown in FIG. 3, in step 05, the register group is initialized and simultaneously the polarity of a trigger signal for storing the contents of the free-running counters into the registers is specified. In step 10, a self-check of the control circuits, especially the functions of the memories and the I/O circuit, is performed. The MPU generates specific patterns and if a signal corresponding to the patterns is received, the check is determined to be OK in step 15. When an abnormal condition is found by the self-check, the abnormality is indicated by the warning lamp 15 (step 20). In this case the self-checks are performed a predetermined number of times in step 25. If the abnormal condition still remains after all the self-checks have been made, a warning lamp will be turned on and the operation is stopped in step 30. In this case, the normal braking operation is performed, but the skid control is not put into operation. When the self-check is O.K. in the step 15, the brake control operation moves to step 35. In the step 35, stored data is read out and a subtracting calculation operation between the registers yields the wheel speed. In step 37, whether the solenoid of the actuator is energized or not is checked. Initially, the solenoid is deenergized or off. In step 40, whether panic braking is applied or not is checked on the basis of the variation of the wheel speed. Namely, if the decrease in the wheel speed exceeds a preset value, panic braking is identified. This point is explained with the aid of FIG. 5. FIG. 5 shows the relationship among vehicle speed, virtual vehicle speed, wheel speed and the decrease (ON) and increase (OFF) in the brake oil pressure, in the case where the brake oil pressure is so controlled as to cause the frictional coefficient between the wheel and the road surface to be maximum when panic braking is applied. Now, assume that a vehicle is moving at a speed V S . If the vehicle is suddenly braked under this condition, the wheel speed is decreased along curve A as shown in FIG. 5. Turning again to FIG. 3, if there is no panic braking, the step 35 is again reached to calculate the wheel speed. At the time of normal operation (driving without panic braking), a closed loop of the steps 35 to 40 is repeatedly executed. When panic braking is detected in the step 40, step 45 is reached. In the step 45, the virtual vehicle speed is derived from the calculated wheel speed. Here, the virtual vehicle speed should be exactly defined. In the expression for the skid rate S, V is defined as the speed of the rolling body (this corresponds to the vehicle speed). Therefore, the vehicle speed must be calculated to obtain the slip or skid rate S. Since a vehicle is stopped by braking its four wheels, it is impossible to obtain the real vehicle speed directly. Accordingly, the virtual vehicle speed to give the measure of the actual vehicle speed must be obtained to be used and defined as one of the controlling items. In general the virtual vehicle speed is assumed to have a gradient of -1.4--1.7 g (gravity acceleration) and the slip rate S given by the above expression (1) is calculated under this assumption. In FIG. 5, broken curve B represents the virtual vehicle speed, which decreases at the above mentioned gradient at the deceleration starting point 1 . On the basis of the comparison between the wheel speed calculated in the step 35 and the virtual vehicle speed calculated in the step 45, whether the predetermined ON slip rate is reached or not is checked in step 50 in FIG. 4, the ON slip rate being the one for which the solenoid of the actuator is to be turned on. When the predetermined ON slip rate is detected in the step 50, that is, when the point 3 in FIG. 5 is reached, a brake releasing signal is generated in step 55. The ON slip rate at the point 3 is preferably equal to 0.5, as required by empirical factors. The brake releasing signal is stored in the memory in step 56. After the brake releasing signal has been delivered, the control operation is returned to the step 35 in FIG. 3. Since the actuator is turned on in step 37, step 58 in FIG. 4 is then executed. In the step 58, whether the slip rate is equal to the predetermined OFF slip rate or not is checked on the basis of a comparison between the wheel speed and the virtual vehicle speed, the predetermined OFF slip rate being the factor which leads the solenoid of the actuator to be deenergized or OFF. The predetermined OFF slip rate is always kept constant at, for example, 0.2 at the point 7 as well as the point 5 in FIG. 5. If the actual slip rate is below the predetermined OFF slip rate, that is, it corresponds to the point 4 in FIG. 5, then the control operation is returned to the step 35. When the predetermined OFF slip rate is reached, that is, any point after the point 5 in FIG. 5 is reached, step 60 is executed. In the step 60, unless the actuator is being energized, the step 35 is resumed, while if the actuator is being energized the step 65 is executed. In the step 65, the brake releasing signal is interrupted and in step 70 the ON time (the period for which the brake releasing signal lasts) is measured. In step 75, the predetermined ON slip rate necessary for the next control, i.e. the slip rate corresponding to the point 6 in FIG. 5, is taken from the memory on the basis of the ON time measured in the step 70 and the value taken is then stored in the specified memory. The control operation is then transferred to step 35. The ON time for which the brake releasing signal lasts, varies depending on the magnitude of the frictional coefficient. Moreover, the virtual vehicle speed is assumed to have a gradient of -1 g and the timing at which the second and succeeding brake releasing signals are delivered is changed, to correct the virtual vehicle speed, depending on the ON time t ON obtained in the immediately previous control cycle. Namely, the slip rare required in the second or succeeding control is a function of the ON time t ON . FIG. 6 shows the relationship between the ON time t ON and the predetermined ON slip rate S. It is assumed that the n-th brake releasing signal lasts for a period t ON (n) as shown in FIG. 6. Then, the predetermined ON slip rate S for determining the timing at which the (n+1)th brake releasing signal is delivered is calculated to be S n . Thereafter, similar operations are repeated until the wheels stop. Since it is difficult to express the relationship shown in FIG. 6 by an equation, it is stored in the memory with discrete sampling values at specific intervals, e.g. every 10 mS. It is therefore possible that if the ON time t ON (n) is measured, S n is immediately obtained. The points 3 and 6 in FIG. 6 correspond to the points 3 and 6 in FIG. 5. FIG. 7 is a diagram for explaining the operations of the free-running counters 123 and 125, the registers 127 and 129, and the register control circuits 131 and 133. A reference clock signal E generated by the MPU 115 is sent to the free-running counter 123 (hereafter only one of the equivalent members is mentioned for simplicity). The free-running counter 123 counts up or down in synchronism with the clock signal E, starting at the count value specified by the initialization cycle as shown in FIG. 8A or 8B, irrespective of the operation of the MPU 115. According to the mode shown in FIG. 8A, the counter 123 counts up, starting from the value $00 set through the initialization, and when the content of the counter 123 becomes equal to $FF, the count value is reduced to $00 in response to the next coming clock signal E. Thereafter, the above operation is repeated. On the other hand, according to the mode shown in FIG. 8B, the counter 123 counts down from the value $FF set through the initialization and when the count value reaches $00, it jumps up to $FF in response to the next clock signal E, being prepared again for counting down. Either of the modes can be selected depending on the method of control required. The MPU 115 sends to the register control circuit 131 an instruction to cause the circuit 131 to send a trigger signal to the register 127 in response to the leading or trailing edge of the input signal, e.g. WSP (wheel speed pulse). In response to the trigger signal, the register 127 takes in and stores therein the content of the free-running counter 123, reached when the trigger signal is generated. The register 127 is, for example, of 16-bit structure. FIG. 9 illustrates a technique for obtaining the period of the WSP (wheel speed pulse) signal. Software controls the delivery of the trigger signal in response to the leading edge or the trailing edge to take in the wheel speed. In FIG. 9, it is assumed that the trigger signal is delivered in response to the leading edge of the WSP according to the program. This instruction for triggering is effected through the software and the register control circuit 131 shown in FIG. 7 which holds the old instruction unless this instruction is sent to the circuit 131 to rewrite its content. When a signal indicating the leading edge of the WSP is received, the count value at that instant of the free-running counter 123 is stored in the Q register 151 of the register 127 shown in FIG. 7. When a signal indicating the leading edge of the next WSP or the n-th (n<10) following WSP in the case of a high wheel speed is received, the count value of the free-running counter at that instant is stored in the P register 149 of the register 127 shown in FIG. 7. The operation of storing the contents of the free-running counter into the P and Q registers is performed by the event transition of the WSP, that is, the interrupt operation is performed in response to the WSP signal and the count values are stored through the interrupt processing. The time required for storing each content is 4-5 μsec. so that the storing operation by the P and Q registers is finished in about 9 μsec. According to this method described above, the duration or width of a pulse of a pulse signal having a long repetition period can be measured for about 9 μsec. Accordingly, the requirement according to the conventional measuring method that the MPU must be exculsively used over the duration of a pulse in the measurement of the pulse width can now be eliminated. Therefore, each of the times required for various processings necessary for the skid control now in question can be shortened. When the P and Q registers finish storing the contents of the free-running counter, the software generates an instruction to cause the P and Q registers to make a subtracting operation between them. The result of the subtraction is stored in, for example, an S register 153 of the register 127. If the subtraction causes a carry signal, the subtraction is done in consideration of the carry signal. The wheel speed is obtained from the above result. In some cases, it may be difficult due to the mechanical structure of the wheel speed sensor to obtain uniform WSPs and therefore the I/O circuit may receive a signal having various duty cycles from the sensor. In such cases, if the wheel speed is determined by measuring the duration of a single pulse, a large error may be introduced depending on the instant of sampling, degrading the accuracy in measurement. To make the error in measurement minimum, the pulse widths W1, W2, W3, . . . etc. of several wheel speed pulses are measured as shown in FIG. 10 and the average W of them is calculated. By using the calculated average W as the wheel speed data for the succeeding calculation, the deviation of the output of the wheel speed sensor can be compensated to a great extent. In the case of low wheel speed, the state of the wheel being at low speed should be checked in the step 35 in FIG. 3 and signals in synchronism with the leading and trailing edges of a wheel speed pulse can be used as trigger signals. Accordingly, it is possible to obtain sufficient wheel speed data even during low speed drive by measuring the wheel speed data every half a cycle which data has hitherto been measured every cycle. According to this invention, the newest data is stored always in the location of the RAM with the address No. 1 and the next newest data in the location of address No. 2 and so on, and all the data are stored in order of arrival at the RAM so that the program for the calculation of the wheel speed can be easily executed. FIG. 11 is a flow chart illustrating the process of loading the content of the free-running counter into the memory according to this invention. The start step 20 is followed by step 21 where a check is made of whether a pulse is received or not. If a pulse is received, an interruption for a processing operation takes place in step 22. In the step 22, each data location in the RAM is shifted down by one location, that is, the content of the address No. 8 is transferred to the address No. 9, the content of the address No. 7 to the address No. 8, etc. After the content of the addres No. 1 has been transferred to the location of address No. 2, the content, or count value, of the free-running counter is read in step 23, and stored in the location of address No. 1. This process is shown in FIGS. 12 to 15. FIG. 13 shows the state of the data being stored in the RAM when the pulse WSP9 is received. The newest data T9 is stored in the address No. 1 and the successive addresses of the RAM are occupied by the data blocks in order of the arrival. FIG. 14 shows the state of the data blocks being stored in the RAM when the pulse WSP10 is received. FIG. 15 shows the state of the data blocks being stored in the RAM when the pulse WSP12 is received. In both the states, the newest data is held in the address No. 1 and the following addresses are occupied by the data blocks arranged in order of the arrival. With this arrangement of data blocks, the difference between the data blocks stored in the addresses Nos. 1 and 2 may be obtained to calculate the pulse-to-pulse period, the difference between the data blocks in the addresses Nos. 1 and 9 to calculate eight times the period, the difference between those in Nos. 1 and 5 for four times the period, and the difference between those in Nos. 1 and 3 for twice the period. These periods have constant values and since it is unnecessary to check in each operation which addresses in the RAM are to be selected to provide data, the associated program and the resultant processing time can be both shortened. The above described process is shown in flow chart in FIG. 16. The processing is started with step 24, and the difference between the data blocks in the addresses Nos. 1 and 2 is calculated to obtain the pulse-to-pulse period in step 25. The difference, assumed to equal T, is compared with a reference value t o in step 26. If T is smaller than t o , the difference between the data blocks in the addresses Nos. 1 and 9 is calculated in step 27 to obtain 8 times the pulse-to-pulse period. By dividing the resultant period by 8, the average pulse-to-pulse period is obtained with a reduced error. In step 28, whether t o <T<2t o or not is checked. If the condition that t o <T<2t o is satisfied, the difference between the data blocks in the addresses Nos. 1 and 5 is calculated in step 29 to obtain 4 times the pulse-to-pulse period. The obtained period is then divided by 4 to provide an average. In step 30, whether 2t o <T<4t o or not is checked and if the in equality is satisfied, the data difference is calculated between the addresses Nos. 1 and 3 in step 31 to obtain twice the pulse-to-pulse period. Then, to calculate an average, the thus obtained period is divided by two. When T>4t o , the data difference is calculated between the addresses Nos. 1 and 2 to obtain only the pulse-to-pulse period. As described above, by storing the newest data in the head location of the memory and also by occupying the succeeding locations of the memory by the data in order of the arrival, the calculation of the wheel speed can be processed in a short time with a high precision and the number of the steps of the program and therefore the capacity of the memory can be reduced, whereby an excellent anti-skid control apparatus can be provided. FIG. 17 shows the state where the sampling timing for detecting the wheel speed is varied when the wheel speed exceeds a certain value. At points Y and X, the content of the free-running counter is stored in the register and at point A after a time t A the pulse-to-pulse interval PW n is determined to calculate the wheel speed. During a time t B (between points A and B) the calculation results based on PW n is put up, and the IRQ signal, if it is received and the task has not yet been finished, is masked. The interrupt flag is cleared so as to accept the IRQ signal when the processing operation returns again to the starting step of the main routine after the end of the processing of the above task. By doing this, the task processing operation in the main routine is prevented from being retarded by the interrupt processing in response to the IRQ signal so that a normal processing operation is possible. FIG. 18 shows a flow chart of a program for an embodiment of this invention. FIG. 18 is a detailed version of the step 35 shown in FIG. 3, with an instruction for clearing the IRQ mask bit applied to the connector 1/2 shown in FIG. 4. In FIG. 18, the content of the free-running counter that has been stored in a specified memory in response to the IRQ signal is read out in step 100 and the read out contents of the free-running counter are subjected to subtraction to obtain the pulse width PW for the wheel speed signal in step 105. In step 110, the thus obtained pulse width PW is compared with a predetermined pulse width PW o . If PW<PW o , the pulse width is calculated in step 125 and the IRQ mask bit is set in step 130. If PW≧PW o , the steps 37-45 in FIG. 3 and the steps 50-75 in FIG. 4 are executed and after the execution of these steps the IRQ mask bit is cleared in step 120 and again the step 100 is reached. A still faster processing operation would be required in the case of a high speed wheel rotation where the next wheel speed pulse is received while the processing routine (step 115) using the pulse width (i.e. wheel speed difference) obtained through the calculation in the step 125 is under execution. In such a case, to mask the IRQ signal as described above, the IRQ mask bit is set to mask several pulses and an interruption is prevented to increase the speed of processing by clearing the IRQ mask bit at the time when the arithmetic processing routine (step 115) is finished. In FIG. 18, if the pulse width PW becomes smaller than the predetermined pulse width PW o , the step 130 is executed to set the IRQ mask bit. Accordingly, unless the IRQ mask bit is cleared in the step 120 after the execution of the step 115, the IRQ signal for detecting the wheel speed will be ignored even if it is received while the step 115 is under execution in the main program. After the execution of the step 120, the IRQ signal for detecting the wheel speed is accepted to resume the detection of the wheel speed. If the wheel speed is lowered to cause the pulse width to be greater than T o , the wheel speed data is stored in the data addresses in the RAM to execute normal control processing, i.e. tasks such as the check of skid state, the delivery of the brake releasing signal, the release of braking, and the measurement of ON TIME. As described above, by making variable the sampling timing for detecting the wheel speed through the control of software and by detecting the wheel speed at the time of high speed rotation by the use of the variable sampling timing, the MPU can be prevented from being occupied for the purpose of detecting the wheel speed so that the above task is prevented from being retarded.

A skid control device employs a wheel speed sensor and the control circuit which includes a microcomputer. The microcomputer computes wheel speed on the basis of a pulse signal derived from the wheel speed sensor and delivers a break releasing signal when the wheels slip. A brake control apparatus for controlling the pressure of oil for applying the brakes to the wheels responds to the outputs of the microcomputer. The microcomputer contains a free-running counter which counts clock pulses and a memory containing a sequence of storage locations. This sequence of storage locations stores count values of the free-running counter. A pulse signal from the wheel speed sensor is employed to produce an interrupt request for the microcomputer. The contents of successively adjacent locations in memory are employed by the microcomputer for carrying out the necessary calculations and computing wheel speed.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to large, heavy duty powered metal forming equipment, and more specifically to a punch holder for use with a hydraulically or otherwise powered metal forming press brake. The present punch holder provides for the transfer of mechanical force from a separate activator mechanism to operate a series of otherwise independent punch holder clamps, thereby simultaneously engaging or releasing the press brake punches held therein and greatly reducing the time required for configuration changes. 2. Description of the Related Art Press brakes are conventionally used in metal forming, particularly for forming bends in relatively large and/or thick sheets of metal. Such brakes are almost universally actuated by hydraulics, but may be powered by other means (mechanical, electromechanical, etc.) as desired. These brakes commonly have a relatively fixed, lower table or bed which carries a metal forming die (or series of dies), and a relatively movable upper ram which holds a series of complementary punches. When the machine is activated, the ram with its punches is forced downwardly into the die or dies, bending any metal placed therebetween. Punches and dies must frequently be changed due to material and workpiece requirements. While die changes are demanded primarily by material thickness demands, punches are subject to a broader variety of demands. A wide variety of punch profiles, and frequent changeovers, are required to address workpiece demands. With reference to the so-called European style of tooling, multiple independent punch holders function as intermediate spacers between the ram and the punches. These punch holders typically utilize two bolts per punch holder to secure a punch by means of a clamp plate. A ten foot long machine typically utilizes sixteen of these independent punch holders. Thus, it can require the loosening of thirty-two separate bolts to release the entire punch series. The installation of new tools can also require the tightening of thirty-two bolts, in order to secure the new punches. Thus, a total of sixty-four separate mechanical actions may be necessary in order to make a complete punch changeover in such a machine. Accordingly, a need will be seen for a press brake punch holder system which activates the clamps and secures punches, by means of a single mechanism which acts simultaneously upon all of the punch clamps to secure or release the punches as desired, using a single mechanical motion. Two embodiments of the present punch holder are provided, with a first embodiment using a series of laterally disposed wedges for actuating the clamps, and a second embodiment using fluid means (pneumatic or hydraulic pressure). A discussion of the related art of which the present inventors are aware, and its differences and distinctions from the present invention, is provided below. U.S. Pat. No. 3,584,497 issued on Jun. 15, 1971 to William L. Pohjola, titled “Sliding Parallel Ways For Releasing Jammed Press,” describes a series of wedges for installation beneath the dies of a metal forming press or the like. The wedges facilitate release of the press pressure in the event the press actuating mechanism becomes caught on dead center, or overcenter, and cannot be released using standard procedures. In this event, the wedges are knocked loose from their positions, thereby relieving the pressure in the press and allowing the press to be reset normally. Pohjola does not disclose any means of engaging or releasing a series of otherwise independent laterally disposed jaws using his wedges in a punch press, nor do his wedges act laterally, as in the present invention. U.S. Pat. No. 3,889,515 issued on Jun. 17, 1975 to Walter J. Grombka, titled “Wedging Structure For Presses Or The Like,” describes a similar structure to that of the Pohjola wedge assembly discussed immediately above. Grombka provides powered hydraulic means for adjusting or releasing the positions of his wedges, as well as hydraulic fluid under high pressure between the surfaces of his wedges and adjacent surfaces for reducing friction therebetween. However, the Grombka wedge assembly still functions essentially like the Pohjola assembly, and cannot operate laterally for actuating a series of punch clamps. U.S. Pat. No. 3,965,721 issued on Jun. 29, 1976 to Gerald V. Roch, titled “Adjustable Die Holder,” describes the use of a series of vertically acting yedges which may be differentially adjusted to compensate for any bending of the die holder bar under-pressure during the bending operation. As in the devices described above, the Roch wedges act vertically, not laterally, and as they are disposed beneath the relatively stationary die, they do not communicate with the multiple punch holder clamps or jaws in any way. U.S. Pat. No. 4,137,748 issued on Feb. 6, 1979 to Walter J. Grombka, titled “Wedging Structure For Presses Or The Like,” describes a wedge system similar to that of his earlier '515 U.S. Patent discussed further above. The wedge structure of the '748 U.S. Patent includes sealing means capable of preventing blowout under the extremely high hydraulic pressures used. However, the system still operates in essentially the same manner as that of his '515 patent, i. e., vertically, rather than laterally, as in the present invention, and does not provide any means of actuating a series of punch clamps. U.S. Pat. No. 4,354,374 issued on Oct. 19, 1982 to Hideaki Deguchi, titled “Bending Press,” describes a longitudinally acting wedge system, i. e., along the length or span of the press, for compensating for flexure of the stationary die during bending operations. The Deguchi apparatus is thus more closely related to that of the Roch '721 U.S. Patent, discussed further above, than to the present invention. U.S. Pat. No. 4,535,689 issued on Aug. 20, 1985 to Ladislao W. Putkowski, titled “Press With Wedge,” describes a system having opposed, longitudinally acting wedges which act to lift the die in the press to compensate for bending of the structure during forming operations. The Putkowski assembly is thus more closely related to that of the Roch '721 and Deguchi '374 U.S. Patents, than to the present invention. U.S. Pat. No. 4,586,361 issued on May 6, 1986 to Andrei Reinhorn et al., titled “Press Brake Deflection Compensation Structure,” describes a wedge system disposed within the stationary bed of the press, rather than in the movable ram portion, as in the present invention. The Reinhorn et al. assembly includes a tension rod for the lower wedge, to adjust the height and bending of the lower plate in the machine. No lateral wedging or dual action for engaging or releasing a series of punch clamps is provided by Reinhorn et al. U.S. Pat. No. 4,653,307 issued on Mar. 31, 1987 to Vaclav Zbornik, titled “Bending Tool,” describes a press brake having a linear series of mutually adjacent vertical pins forming the bottom of the die. The pins are adjusted vertically by a wedge assembly, to achieve the desired height for the base of the die. Thus, Zbornik is only directed to vertical adjustment, and does not provide any means of lateral adjustment nor engagement with the upper punch clamps of the brake, as provided by the present invention. U.S. Pat. No. 4,736,612 issued on Apr. 12, 1988 to Robert L. Russell, titled “Compensating Die Holder,” describes a wedge assembly disposed beneath the relatively stationary die of a punch press or similar machine. The two wedge components are sloped laterally, and while they move laterally relative to one another, the result is vertical adjustment of the upper wedge component, rather than lateral motion of adjusting members, as in the present invention. Russell does not disclose any means of engaging or releasing the punch clamps or jaws in an upper ram assembly, as provided by the present invention. U.S. Pat. No. 4,895,014 issued on Jan. 23, 1990 to David L. Houston, titled “Failsafe Tool Clamping System For Press Brake,” describes various embodiments of a tool clamping system, including a series of laterally acting wedges for both the punch and die. However, the Houston wedges expand outwardly to release the clamping pressure on the punch and die, rather than using lateral expansion to grip the punches, as in the present invention. The present system secures the clamps to the ram by corresponding bolts, which allow the clamps to rock about the fulcrum defined by the bolts. Outward wedging pressure pushes the opposite lower clamp ends together to clamp the punches therein. Houston states that his wedge release action is safer, as loss of hydraulic pressure for driving the wedges results in the tooling remaining clamped in the machine, rather than being released. The present invention responds to this problem by using a series of relatively light springs which urge the clamps to a securing condition even though the wedge has been released. The machine operator may easily overcome the spring pressure by hand to release the tooling. Houston also cites the use of hydraulics for operating his system, but the hydraulic power acts only to drive the wedges to release the clamps, rather than providing a direct fluid action on a laterally moving plate for securing the tooling in the clamps, as provided by the second embodiment of the present invention. U.S. Pat. No. 5,009,098 issued on Apr. 23, 1991 to Jacobus L. van Merksteijn, titled “Press And Curve-Forming Means Therefor,” describes various embodiments employing wedges in the bed of the machine for imparting a bend or compensating for bending loads. The van Merksteijn wedges act in two mutually perpendicular, generally horizontal planes to impart vertical adjustment to the assembly, whereas the present wedges are disposed in vertical planes to act laterally to apply or release clamping force to the upper ends of the punch clamps of the movable upper ram assembly. U.S. Pat. No. 5,121,626 issued on Jun. 16, 1992 to John B. Baldwin, titled “Adjustable Die Support For A Press Brake,” describes a wedge couple having a front to back oriented slope, for adjusting the height of the die or punch assembly. While the movable portion of the wedge assembly moves generally horizontally, the result is a vertical motion, rather than a horizontal motion, as in the case of the present invention. The Baldwin mechanism is more closely related to the mechanism disclosed in U.S. Pat. No. 6,000,273 issued to the second of the present inventors (discussed further below), than to the present invention. U.S. Pat. No. 5,390,527 issued on Feb. 21, 1995 to Susumu Kawano, titled “Upper Tool Holder Apparatus For Press Brake And Upper Tool Attachable Thereto,” describes a tool or punch clamp having an easily manipulable locking and unlocking lever. Kawano also discloses wedge means for adjusting the relative height of each separate tool clamp, but each of his clamps has a separate, independent wedge, unlike the single wedge assembly of the present invention for actuating a series of otherwise independent mechanisms. The Kawano wedge assemblies adjust vertically, rather than wedging horizontally, as in the present invention. Kawano teaches away from the present invention with his separate locking and unlocking handles for each clamp. U.S. Pat. No. 5,507,170 issued on Apr. 16, 1996 to Susumu Kawano, titled “Upper Tool For Press Brake,” describes a variation upon the mechanism of the '527 U.S. Patent to the same inventor, discussed immediately above. The '170 U.S. Patent is a continuation in part of the '527 U.S. Patent, and does not relate any more closely to the present invention than does the '527 parent U.S. Patent. U.S. Pat. No. 5,511,407 issued on Apr. 30, 1996 to Susumu Kawano, titled “Upper Tool For Press Brake,” describes yet another variation on an upper tool clamping mechanism, similar to those of the '527 and '170 U.S. Patents to the same inventor, discussed above. The same points raised in those discussions, are felt to apply here as well. U.S. Pat. No. 5,513,514 issued on May 7, 1996 to Susumu Kawano, titled “Upper Tool And Upper Tool Holding Device For Press Brake,” describes still another variation on an upper tool clamping mechanism, similar to those of the '527, '170, and '407 U.S. Patents to the same inventor, discussed above. The same points raised in those discussions, are felt to apply here as well. U.S. Pat. No. 5,572,902 issued on Nov. 12, 1996 to Susumu Kawano, titled “Upper Tool Holder Apparatus For Press Brake And Upper Tool Attachable Thereto,” describes another variation on an upper tool clamping mechanism, similar to those of the '527, '170, '407, and '514 U.S. Patents to the same inventor, discussed above. The '902 U.S. Patent is a continuation in part of the parent '527 U.S. Patent discussed further above. The same points raised in those discussions, are felt to apply here as well. U.S. Pat. No. 5,619,885 issued on Apr. 15, 1997 to Susumu Kawano et al., titled “Upper Tool Holder Apparatus For Press Brake And Method Of Holding The Upper Tool,” describes another variation on an upper tool clamping mechanism, similar to those of the '527, '170, '407, '514, and '902 U.S. Patents to the same inventor, discussed above. The ''885 U.S. Patent is a continuation in part of the parent '407 and '514 U.S. Patents discussed further above. The same points raised in those discussions, are felt to apply here as well. U.S. Pat. No. 5,642,642 issued on Jul. 1, 1997 to Susumu Kawano, titled “Upper Tool And Upper Tool Holding Device For Press Brake,” describes an additional variation on an upper tool clamping mechanism, similar to those of the '527, '170, '407, '514, '902, and '885 U.S. Patents to the same inventor, discussed above. The '642 U.S. Patent is a continuation in part of the parent '514 U.S. Patent discussed further above. The same points raised in those discussions, are felt to apply here as well. U.S. Pat. No. 5,685,191 issued on Nov. 11, 1997 to Susumu Kawano et al., titled “Upper Tool For Press Brake,” describes a further variation on an upper tool clamping mechanism, similar to those of the '527, '170, '407, '514, '902, '885, and '642 U.S. Patents to the same inventor, discussed above. The '191 U.S. Patent is a continuation in part of yet another U.S. Patent to the same inventor, not cited herein. The same points raised in the discussions of the earlier Kawano U.S. Patents cited further above, are felt to apply here as well. U.S. Pat. No. 6,000,273 issued on Dec. 14, 1999 to Carl Stover, titled “Press Brake Punch Holder,” describes a longitudinally acting (i. e., the width of the machine) wedge mechanism for securing a series of punches in a corresponding series of clamps in the upper portion of a press brake machine. The mechanism of the Stover '273 U.S. Patent operates generally horizontally to lift a clamp actuating mechanism vertically, rather than acting laterally to apply a lateral clamp actuating force, as in the present invention. The device of the Stover '273 U.S. Patent appears more closely related to the fore and aft wedge system of the Baldwin '626 U.S. Patent discussed further above, than to the present invention. U.S. Pat. No. 6,018,979 issued on Feb. 1, 2000 to Stephen B. Davis, titled “Tool Working Height Adjustment For Press Brake,” describes a series of mating pairs of stepped wedges for independently adjusting the height of each punch relative to the ram. Each punch clamp or holder is secured to its own dedicated step wedge pair for independent adjustment. This teaches away from the present invention, with its single wedge assembly providing actuation of all of the punch clamps simultaneously. The Davis assembly is directed to individual height adjustment of the clamps and their punches, rather than providing any means for securing or releasing the punches in their clamps, as provided by the present invention. German Patent Publication No. 616,783 published on Aug. 5, 1935 illustrates a wedge assembly acting along the width of the machine to compensate for machine structural bending loads during metal bending operations. No means for releasing the punches secured in the machine, is apparent in the drawings. The device of the '783 German Patent Publication thus appears to be more closely related to the mechanisms of the Roch '721 and Deguchi '374 U.S. Patents discussed further above, than to the present mechanism. Japanese Patent Publication No. 62-267,019 published on Nov. 19, 1987 describes (according to the drawings and English abstract) a cam actuated mechanism for simultaneously releasing or locking all of the punches (upper dies) within the upper ram of a punch press. The device of the '019 Japanese Patent Publication includes a series of individual pivoting levers corresponding to the number of punches which may be used with the press. Each lever has a punch engaging end and an opposite cam engaging end. An eccentric cam extends along the entire width of the machine, with its lobe selectively levering the cam engagement end of each lever downwardly to lock the punch engaging end of the levers against their corresponding punches as the cam is rotated. While this system does accomplish the function of the present invention, i.e., simultaneous engagement or release of all of the punches using a single mechanism, the structure and principle of operation are completely different, in that the mechanism of the Japanese '019 Patent Publication does not accomplish this by means of an internally and longitudinally disposed wedge assembly and pivotally mounted punch holders which are pivotally wedged outwardly to hold their corresponding punches, as is the case of the present invention. Soviet Patent Publication No. 1,382,543 published on Mar. 23, 1988 describes (according to the drawings and English abstract) a mechanism for use in a stamping machine. A series of helically threaded clamps are tightened selectively to clamp the two plates together. Wedge adjusting means appears to be used, but the wedges appear to adjust the assembly upwardly and downwardly, i. e., vertically, rather than producing any lateral wedge action for selectively securing or releasing any laterally disposed components, as is the case in the present invention. European Patent Publication No. 569,880 published on Nov. 18, 1993 to Amada Metrecs Company, Limited (Susumu Kawano, inventor) titled “Upper Tool And Upper Tool Holding Device For Press Brake,” describes essentially the same device as that disclosed in U.S. Pat. No. 5,619,885 to the same inventor, discussed further above. The '880 European Patent Publication cites most of the same foreign applications as priority, as cited in the '885 U.S. Patent. The same points raised in the discussions of the earlier Kawano U.S. Patents cited further above, are felt to apply here as well. Finally, Japanese Patent Publication No. 8-057,542 published on Mar. 5, 1996 to Amada Metrecs Co., Ltd. describes (according to the drawings and English abstract) a mechanism very closely related to those of the other U.S. Patents to Kawano (assigned to the same assignee, Amada Metrecs Co.) and the '880 European Patent Publication cited above. It is noted that the first and second inventors shown in the '1542 Japanese Patent Publication (Toshiro Kawano and Mamoro Sugimoto) are also shown respectively as the third and second inventors in the '885 and '191 U.S. Patents cited further above. The same points raised in the discussions of the earlier U.S. Patents to Susumu Kawano and to the same Amada Metrecs assignee cited further above, are felt to apply here as well. None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed. Thus a press brake punch holder solving the aforementioned problems is desired. SUMMARY OF THE INVENTION The present invention is a punch holder for use with large, power operated industrial press brakes, used for bending large and/or heavy gauge sheet metal. Conventionally, such brakes use “punches” or upper tooling members removably secured within a movable upper ram assembly, which engage the sheet metal sandwiched between the punches and one or more relatively fixed dies. When it is necessary to perform a different bending operation, the punches must be removed and exchanged, with bolts typically being used to secure each punch to the ram assembly. A ten foot long machine typically requires sixteen punch holders, with each punch holder typically being six inches wide. Thus, it may be necessary to remove and replace up to thirty two bolts, if all of the punches must be interchanged. The present invention responds to this problem by means of a single actuator which acts to simultaneously secure or release all of the otherwise independent punch clamps or holders in a single operation. Two different embodiments are disclosed herein, with a first embodiment using a laterally acting, laterally symmetrical wedge assembly for urging the upper ends of the clamps apart and thus causing the clamps to grip their respective punches as the clamps pivot about their respective fulcrums. A second embodiment uses fluid pressure (pneumatics or hydraulics) to selectively pressurize a sealed flexible chamber, thereby symmetrically applying outward lateral pressure on the upper ends of the clamps. Accordingly, it is a principal object of the invention to provide a punch holder for a press brake, comprising a single punch clamp activating apparatus communicating with a plurality of otherwise independent punch holding clamps for simultaneously and selectively releasing the clamps by the application or release of a symmetrical lateral force against the upper ends of the pivotally mounted clamps. It is another object of the invention to provide such a punch holder wherein the lateral force is applied by a laterally acting, symmetrical wedge assembly which selectively drives a plurality of fingers outwardly against the upper ends of the clamps. It is a further object of the invention to provide such a punch holder wherein the lateral force is applied by a laterally acting, symmetrical fluid activated flexible chamber for applying outward pressure to the clamp actuating fingers. Still another object of the invention is to provide a punch clamp holding and releasing apparatus including a plurality of relatively light springs for holding the clamps in a secured condition when wedge or fluid pressure is released. It is an object of the invention to provide improved elements and arrangements thereof for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes. These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevation view of a press brake incorporating the punch holder of the present invention, showing its general features. FIG. 2 is a perspective view of a punch clamp assembly incorporating the present punch holder mechanism, showing its general configuration and punch clamp layout and attachment. FIG. 3 is an exploded perspective view of the laterally symmetrical wedge punch clamp activation assembly of the first embodiment, showing details thereof. FIG. 4 is a top plan view of the assembled wedge embodiment of FIG. 3, showing the system activated in the upper portion for clamping the punches and with the system relaxed in the lower portion for releasing the punches. FIG. 5 is an elevation view in section along line 5 — 5 of FIG. 4 showing the entire assembly, again with the left side activated for clamping the punches and the right side relaxed for releasing the punches. FIG. 6 is a top plan view of a second embodiment incorporating fluid clamp activation means, with the left side inflated to clamp the punches and the right side deflated for releasing the punches. Similar reference characters denote corresponding features consistently throughout the attached drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention comprises various embodiments of a punch holder for use in relatively sophisticated metal bending press brakes, with an example of such a press brake machine 10 being illustrated in FIG. 1 of the drawings. The press brake 10 is generally conventional, with the exception of the incorporation of the present punch holder mechanism therein. The press brake 10 of FIG. 1 includes an elongate lower die holding bed portion 12 , with an elongate ram 14 disposed thereabove for holding a series of punches therein. The ram 14 is movable relative to the lower die holding bed 12 , and is actuated by a pair of hydraulic cylinders 16 , with one cylinder 16 disposed at each end of the elongate machine 10 , generally as shown in FIG. 1 of the drawings. Other alternative actuation means, e. g., electromechanical screw jacks, etc., may be used to actuate the mechanism. FIGS. 2 and 5 of the drawings respectively provide perspective and end elevation views in section of the clamp actuator mechanism 18 of the present invention. The clamp actuator mechanism 18 is removably secured to the upper ram 14 by an attachment adapter, designated as adapter 20 a in FIG. 2 and as the attached adapter in the cross sectional view of FIG. 5 . The adapter 20 a provides for the attachment of the present actuator mechanism 18 to an existing, conventional press brake, e. g., the press brake 10 of FIG. 1 . Press brakes are manufactured by various companies, with different manufacturers having different component mounting arrangements. The inverted T cross section adapter 20 a , with its flanged stem, is suitable for use with many American made machines. However, other press brakes use a Wila style adapter having a generally T shaped cross section with a necked stem, designated as adapter 20 b in FIG. 5 . Still other machines utilize the Amada style adapter 20 c having a generally L-shaped cross section. The stem of the T or upstanding portion of the L of each of these adapters 20 a through 20 c , provides for attachment of the adapter to the appropriate type of press brake, as desired. The flat horizontal portion of the adapter is universal between each of the adapter embodiments 20 a through 20 c , and is provided with a series of bolt holes therethrough, for conventionally bolting the clamp actuator assembly 18 to the ram of any practicable type of press brake as desired. The adapter is used to secure an underlying elongate actuator housing 22 to the press brake machine. FIG. 3 of the drawings provides an illustration of a portion of the actuator housing 22 , with FIG. 5 providing a cross sectional view of the housing 22 and other components of the present invention. The housing is bolted to the overlying adapter by means of conventional bolts which pass through a series of bolt holes 24 (shown in FIG. 3) in the actuator housing 22 and corresponding bolt holes (not shown) in the adapter. The actuator housing 22 is laterally symmetrical, as shown in FIG. 5, and includes an elongate central wedge plate channel 26 disposed between the laterally opposite first and second sides, respectively 28 and 30 . Each side 28 and 30 further includes a series of lateral actuator passages 32 extending therethrough. The wedge plate channel 26 includes an elongate, laterally symmetrical central wedge plate 34 therein, which travels longitudinally within the channel 26 . This wedge plate 34 has a first side 36 , an opposite second side 38 , and a series of flat, triangular, laterally disposed and symmetrical wedge elements 40 extending upwardly from the base plate 34 and toward the first and second sides 36 and 38 . A first and a second wedge actuator, respectively 42 a and 42 b , are placed atop the wedge plate 34 and are disposed laterally from the central wedge elements 40 of the wedge plate 34 . The first and second wedge actuators 42 a and 42 b each include a series of inwardly facing first and second wedge members, respectively 44 a and 44 b , having angled faces parallel to the angled faces of the central wedge elements 40 of the wedge plate 34 and cooperating with the central wedge elements 40 . Each of the two wedge actuators 42 a and 42 b includes a series of laterally extending fingers, respectively 46 a and 46 b , extending outwardly therefrom. The fingers 46 a and 46 b extend laterally through the actuator passages 32 of the respective first and second sides 28 and 30 of the actuator housing 22 , generally as illustrated in the top plan view of FIG. 4 . It will be seen that the wedge actuators 42 a and 42 b cannot move longitudinally within the actuator housing 22 , due to their corresponding fingers 46 a and 46 b being captured within the slots or passages 32 of the actuator housing 22 . It will be seen that FIG. 4 shows the central wedge plate 34 as two laterally separate components 34 a and 34 b for illustrative purposes only, to compare the operation of the present mechanism in a single drawing Figure. The wedge plate 34 in reality comprises a single, monolithic, laterally symmetrical device (or series of longitudinally linked such devices) which actuates both of the laterally disposed wedge actuators 42 a and 42 b simultaneously and symmetrically at all times. When the central wedge plate 34 is at rest or in its retracted state, as shown by the wedge plate 34 b of the lower portion of FIG. 4, the wider portion of each central wedge element 40 b is adjacent the narrower portion of each corresponding second actuator wedge member 44 b , thus allowing the second actuator 42 b and its corresponding fingers 46 b to retract laterally inwardly toward the center of the actuator housing 22 . However, when the central wedge plate 34 is moved to the right, as shown by the wedge plate portion 34 a in the upper portion of FIG. 4, the longitudinal movement of the central wedge elements 40 a drives the wider portions of those elements 40 a to positions laterally adjacent the wider portions of the complementary actuator wedge members 44 a , thus pushing the actuator 42 a laterally outwardly, due to its lack of longitudinal movement as describe further above. As the actuator fingers 46 a and 46 b are integral components of their respective actuators 42 a and 42 b , this results in the fingers 46 a of the first actuator 42 a also moving outwardly through the slots or passages 32 formed through the first side 28 of the actuator housing 22 . The elongate adapter 20 a (or 20 b , or 20 c ), actuator housing 22 , wedge plate 34 , and first and second wedge actuators 42 a and 42 b , may each be formed in continuous lengths spanning the entire working width of the press brake 10 , if so desired. However, such industrial press brakes often have a working width on the order of eight feet, which would result in impracticably long components for the present punch holder invention. Accordingly, these components may be provided in a series of shorter lengths which assemble end to end, if so desired. No special end configuration or connections are required for the adapters 20 a , 20 b , or 20 c or for the actuator housing 22 , as the adapters secure linearly to the ram structure and the actuator housing bolts to the adapters. Also, no special end configuration or connections are required for the two lateral wedge actuators 42 a and 42 b , as they cannot move longitudinally due to their respective fingers 46 a and 46 b which pass through the slots or passages 32 of the actuator housing 22 . However, some means of securing a series of shorter wedge plate 34 segments together end to end must be provided, if the present punch clamp mechanism is constructed as a series of shorter components. This may be accomplished as shown in FIG. 3 of the drawings, with each end of the wedge plate 34 having a lateral, angular receptacle 50 formed therein, with a pair of longitudinally symmetrical and complementary links 52 serving to join two such wedge plates 34 together end to end. These links 52 transmit all linear motion between a series of shorter wedge plates 34 , allowing such a wedge plate 34 series to function as a single unit. FIG. 5 provides an illustration of the above described assembly installed within the elongate lower clamp attachment bodies 54 . The lower bodies 54 each include an elongate upper channel 56 therein, for containing the actuator housing 22 therein. The actuator housing 22 includes a pair of laterally symmetrical grooves 58 a and 58 b formed along its length, with each lower body 54 having a mating inwardly extending ridge 60 for securing within the first groove 58 a of the actuator housing 22 . The opposite side of each lower body 54 includes a series of threaded passages formed therethrough, with a series of set screws 62 inserted through the passages to secure into the second groove 58 b of the lower bodies 54 to secure each lower body 54 to the actuator housing 22 , which is in turn bolted to the adapter 20 a (or 20 b or 20 c ) which secures to the ram 14 of the press brake 10 . A series of identical but mutually independent punch clamps or holders 64 is secured laterally along the opposite sides 66 a and 66 b of the lower bodies 54 , with the first sides 66 a having a series of first clamps 64 a attached thereto, and the opposite second sides 66 b having a series of second clamps 64 b attached 20 thereto. It will be seen that only a single series of clamps 64 a or 64 b need be used if so desired, depending upon the configuration of the punches to be used, the specific requirements for the bend(s) to be produced, etc. However, two sets of punch clamps or holders 64 a and 64 b are illustrated in the vertically split view of FIG. 5, in order to illustrate the operation of the present invention more clearly. Each of the punch clamps or holders 64 a and 64 b includes a pair of passages 68 formed generally medially therethrough, and laterally separated from one another. A clamp pivot bolt 70 is inserted through each passage 68 , and threaded into a cooperating passage 72 in the corresponding lower body 54 to removably secure the clamps or holders 64 a and 64 b to the lower bodies 54 . A convex bearing 74 is preferably provided between each clamp or holder 64 a and 64 b and the respective side 66 a and 66 b of its lower body 54 , in order to allow the clamps 64 a and 64 b to rock or pivot about the axis or fulcrum defined by the two pivot bolts 70 securing each clamp 64 a and 64 b to its respective lower body 54 . The lower punch gripping end of each punch clamp or holder 64 a and 64 b has an inwardly facing (when the clamp is secured to the lower body) punch retaining extension, respectively 76 a and 76 b , extending therefrom, for securing a metal bending punch 78 ( 78 a or 78 b , in FIG. 5) between the extension 76 and a depending central extension 80 of the lower body 54 . Each punch 78 a and 78 b includes a slot 82 formed therein, for insertion of a corresponding punch clamp extension 76 therein to secure the punches 78 a or 78 b to the assembly. It will be understood that the punches 78 a or 78 b may be asymmetrical as shown in FIG. 5, with only one series of punches 78 a or 78 b being installed in the machine at any given time. Alternatively, the punches 78 a and 78 b may be formed as a series of single, laterally symmetrical components if so desired, depending upon the specific structure of the press brake machine, the specific bend to be formed in the sheet metal being worked, etc. Each of the punch clamps 64 a and 64 b has an upper actuating end, respectively 84 a and 84 b , opposite the lower punch gripping extension ends 76 a and 76 b . These actuating ends 84 a and 84 b are disposed immediately outwardly of the respective first and second sides 28 and 30 of the actuator housing 22 . The fingers 46 a and 46 b of the two wedge actuators 42 a and 42 b , selectively extending through their respective actuator passages or slots 32 , contact the upper ends 82 a and 82 b of the punch holders 64 a and 64 b , in order to secure or release the punches 78 a and/or 78 b held thereby. The left side of FIG. 5 illustrates the configuration of the above described assembly when the central wedge plate 34 is driven to push the lateral wedge actuators, e. g., wedge actuator 42 a , outwardly, as shown in the upper half of the top plan view of FIG. 4 . As the wedge plate 34 is driven along the channel 26 of the actuator housing 22 , the two wedge actuators (e. g., the wedge actuator 42 a in FIGS. 4 and 5) are driven laterally outwardly, thereby pushing their laterally extending fingers (e. g., left side fingers 46 a , in FIGS. 4 and 5) outwardly as well. The outwardly extended fingers 46 a bear against the upper actuating ends 84 a of the punch holders or clamps, e. g., clamps 64 a , pushing them laterally outwardly away from the actuator housing 22 and lower bodies 54 . As the punch clamps are pivotally secured to the lower bodies 54 by the bolts 70 , this results in the opposite lower ends of the clamps, e. g., lower end 76 a on the left side of FIG. 5, pivoting inwardly to grip the slot 82 of the punch 78 a , thereby retaining the punch in position on the assembly. The punches are released by an opposite longitudinal, linear motion of the central wedge plate 34 , in accordance with the position of the wedge plate 34 b in the bottom portion of FIG. 4, and in the right side of FIG. 5 . When the wedge plate 34 is pulled to the left, as in the wedge plate 34 b of the lower portion of FIG. 4, the two lateral wedge actuators (e. g., the second wedge actuator 42 b of FIG. 4) may be moved inwardly, as a space will open between the mating wedge surfaces of the central wedge elements 40 and the lateral actuator wedge members 44 . However, the punch clamps 64 will remain in their normal, clamping positions as shown on the left side of FIG. 5, due to a series of light compression springs 86 disposed between the upper portions of the clamps 64 a and 64 b , and their lower bodies 54 . These springs 86 continue to hold the upper portions of the clamps outwardly, thereby holding the lower punch retaining end inwardly to grip the punch retained therein, until a laterally inward force is applied to the upper portion of the punch retaining clamp or holder. This assures that the punches cannot fall from their secured positions when the system is deactivated to allow the release of the punches. When removal of the punches is desired, the press brake operator need only grasp the punch to be removed and apply a light inward pressure to the top of the punch holder, pivoting the upper end of the punch holder laterally inwardly, as in the upper ends 84 b of the punch holders 64 b of the lower portion of FIG. 4 and right side of FIG. 5 . This allows the selected punch, e. g., 78 b in FIG. 5, to be removed from the assembly. FIG. 6 illustrates a schematic, top plan view of an alternative embodiment of the present invention, utilizing fluid (i. e., pneumatic or hydraulic) pressure for punch clamp retention. The embodiment of FIG. 6 is divided into an actuated, punch holding configuration in the upper portion of the Figure, and a deactivated or punch release configuration in the lower portion of the Figure in the same manner as that used to show the operation of the first embodiment system in FIG. 4 of the drawings. The actuator housing 22 is essentially the same in both embodiments, i. e., comprising a hollow channel for the actuator. The two sides 28 and 30 each include a series of bolt holes 24 therein, for bolting the adapter 20 a , 20 b , or 20 c thereto, in the manner described further above for the embodiment of FIGS. 3 through 5. A series of punch clamps, e.g., clamps 64 a along the upper side and 64 b along the lower side of FIG. 6, is secured to the lower body portions in the manner illustrated in FIGS. 2 and 5 and described further above. The punch clamp actuator assembly of the embodiment of FIG. 6 includes at least one elongate, flexible, selectively inflatable fluid chamber 100 a (for the upper portion or 100 b (for the lower portion) therein, with the chamber 100 a , 100 b having a first side 102 a and an opposite second side 102 b . The chamber 100 a , 100 b may comprise a series of relatively shorter, longitudinally aligned and interconnected chambers, if so desired. A pressure plate, respectively 104 a and 104 b , is disposed along the corresponding sides 102 a and 102 b of the pressure chamber 100 a , 100 b. Each pressure plate 104 a , 104 b includes a series of fingers, respectively 106 a and 106 b , extending laterally therefrom. These fingers 106 a and 106 b extend through the actuator passages or slots 32 of the actuator housing 22 , in essentially the same manner as that described above for the first embodiment of the present invention and illustrated in FIGS. 5 and 5 of the drawings. Activation of the system of FIG. 6 comprises pressurizing the chamber using an appropriate fluid (pneumatic, hydraulic, etc.), as shown by the expanded chamber side 100 a in FIG. 6 . This presses the pressure plate, e. g., plate 104 a , laterally outwardly, extending the corresponding fingers 106 a outwardly through the slots or passages 32 of the actuator housing 22 , thereby pushing the upper ends of the punch clamps, e. g., clamps 64 a , outwardly to move their opposite ends inwardly to grip the punches therein, generally as shown in the left side of FIG. 5 . When it is desired to release the punches, the pressure in the bladder or chamber is released, as shown in the lower bladder or chamber portion 100 b of FIG. 6 . The chamber 100 b is deflated by means of a series of compression springs 108 between the side walls 28 and 30 of the housing 22 and the corresponding pressure plates 104 a and 104 b , which urge the plates 104 a and 104 b toward the center of the housing 22 , thereby deflating the chamber as shown with the chamber portion 100 b in the lower portion of FIG. 6 . This allows the press brake operator to push the upper ends of the punch clamps inwardly, as shown with the clamps 64 b of FIG. 6, thereby releasing the punches as shown in the right side of FIG. 5 . In conclusion, the present press brake punch holder invention provides a novel means of transferring mechanical force from an activator mechanism which is separate from and independent of the punch holders, but which communicates mechanically with the multiple punch holders to provide simultaneous clamping relaxation of clamping pressure for the entire punch series in the machine. Activation may be achieved by any conventional mechanical, hydraulic, or electrical means (e. g., screw jacks, hydraulic pistons, etc. for advancing the central wedge plate). The present invention provides additional advantages, in that the forces directed to the bending of metal being worked in the press brake, are directed away from the internal punch securing and releasing mechanism. The ability to link a series of separate components together linearly, provides great versatility for virtually any size machine, with the series of adapters for machines of different manufacture providing even further versatility. Using the present invention, a press brake operator may easily install and remove punches from the machine, using only a single, simple operation to activate the mechanism. No tools or tedious removal and securing of a multitude of bolts is required, as in conventional machines. The present invention will thus provide significant savings in time and labor, and therefore expenses, in the setup and operation of a press brake machine for virtually any job, thereby providing significant economies of operation. It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.

A press brake punch holder provides a single actuation assembly to apply symmetrically opposed, lateral forces to a series of otherwise independent punch clamps for securing a corresponding series of punches within the clamps. The clamps are each pivotally secured to the holder assembly by a series of generally centrally disposed bolts therethrough, with the clamps rotating through a limited arc on spherical bearings between the clamps and the holder body. The laterally acting actuator urges the upper ends of the clamps apart, thereby urging their opposite lower ends together to clamp the punches therebetween, or between each clamp and a central structure. Release of lateral pressure allows the punches to be removed as desired, with light spring pressure holding the punches in place when, lateral pressure is removed. Actuation may be provided by a laterally acting wedge assembly, or by laterally acting fluid pressure (hydraulics or pneumatics).

BACKGROUND OF THE INVENTION The process used in the drilling of most oil and gas wells involves the use of a drilling fluid commonly referred to as drilling "mud" in the industry. The mud is injected under pressure through the drill string during drilling and returns to the surface through the drill string-borehole annulus. The mud performs multiple functions which include cooling of the drill bit, lubrication of the drill bit, providing a means of returning the drill cuttings to the surface of the earth and providing hydrostatic pressure to prevent the "blowout" of high pressure geologic zones when such zones are penetrated by the drill bit. Drilling mud comprises a liquid phase and a suspended solid phase. The liquid phase can be either fresh or saline water or even an oil base. The solid phase, which is suspended within the liquid phase, can comprise a multitude of materials blended to meet the particular needs at hand. As an example, barite (barium sulfate), with a specific gravity over 4.0, is often used as a weighting constituent to increase the bulk density of the mud when high pressure formations are being penetrated. Other additives are used to control drilling fluid circulation loss when certain types of high porosity, low pressure formations are penetrated. Once returned to the surface, the drilling fluid contains cuttings from the drill bit. Although most large cuttings are removed at the surface prior to recirculating the mud, smaller sized particles remain suspended within the drilling mud. Upon completion of the drilling operation, the drilling mud can sometimes be reconditioned and used again. Eventually, however, the mud can no longer be reprocessed and becomes classified as a waste product of the drilling operation. Once the well has been successfully drilled and cased, hydrocarbons are extracted or produced from one or more formations penetrated by the borehole. Although hydrocarbons are the primary production fluids of interest, other non hazardous oilfield waste (NOW) is usually generated in the production of hydrocarbons. A water component is usually produced along with the hydrocarbon component, and in most areas of the world, the produced waters are saline. Although there are some secondary uses for produced waters, these waters are in general considered a waste product of the production operation. Solid wastes including sand, paraffin, sludges and other solid materials are also generated during the production operations. Large quantities of these solid wastes have been accumulated for decades in production pits. Environmental regulations have led to the need for disposal solutions for the materials contained in production pits undergoing remediation to acceptable environmental levels. The isotopes uranium-238 and thorium-232, and the radioactive isotopes associated with the decay series of these isotopes, occur in nature in earth formations. In situ, the activities associated with these decay chains are relatively low and do not present a radiation hazard during the drilling operation. During well production, however, these naturally occurring radioactive materials (NORM) are dissolved in the produced waters and are transported to the surface. Over an extended period of time, the NORM becomes concentrated in precipitated scale associated with tubulars and surface equipment such as heater treaters, wellheads, separators and salt water tanks. Although the parent isotopes uranium-238 and thorium-232 are not generally present, the decay products or "daughter" products radium-226, radium-228, radon-222 and lead-210 can be found in oilfield waste. Radium-226, which coprecipitates with carbonates and sulfates of calcium, barium and strontium, is by far the greatest source of radioactive waste resulting from production activities. Once atoms of radium have replaced a sufficient number of atoms of the elements normally found in NOW waste to exceed a specified regulatory level, the waste is classified as NORM. Stated another way, there is no difference between NOW and NORM waste other than the level of radioactivity, which usually results from the radium content of NORM waste. In summary, the drilling and production of oil and gas wells generates much waste. The wastes are classified as nonhazardous oilfield waste (NOW) and naturally occurring radioactive materials (NORM). NOW originating from drilling and production operations is primarily composed of drill cuttings, sand and spent material such as drilling mud which is no longer suitable for use and must be managed as waste under regulatory authority. Such mud might contain salts, non toxic metals such as sodium and calcium, toxic metals such as barium, chromium, lead, zinc and cadmium, and oil and grease contamination from the introduction of diesel oil (oil based mud), crude oil or a multitude of hydrocarbon based additives. The spent mud, with associated contaminants, comprises a liquid and a solid phase. NOW is also generated in production operations where copious amounts of saline water, along with some solids (sand), may be produced with the desired hydrocarbons. NORM originates primarily from production operations wherein the previously described radioactive scale contaminates not only large pieces of hardware such as well heads and separators but also can contaminate produced "waste" fluids such as salt water and associated solids. It is necessary to dispose of all types of waste, including those previously stored in pits, in a manner which will not contaminate the surface of the earth and not contaminate subterranean aquifers used as sources of drinking water. Various methods are used to dispose of both NORM and NOW material. Oil and grease toxicity in NOW can be lowered by dilution techniques. Organics can be converted biologically to less toxic forms. Organics can also be removed by extraction processes. These extraction processes can utilize heat and may include methods such as thermal desorption or incineration. Oils can be removed by separation techniques and possibly produce a byproduct of commercial value. Organics can also be bound to solids thereby reducing their leachability and hazard to drinking water supplies. Salts can be diluted and discharged, chemically destroyed or rendered insoluble. Heavy metals can neither be biologically or chemically changed into less toxic species, therefore dilution with non contaminated materials is one method of controlling possible hazardous pollution. Heavy metals can be bound chemically thereby rendering them immobile and nonleachable into the environment. NORM can not be destroyed or chemically altered, therefore dilution with essentially non radioactive material to prescribed levels is an acceptable method. Other possible methods of disposal and/or storage of NORM include near surface burial, deposition with or without encapsulation into the wellbore of plugged and abandoned wells, and injection into geological formations at high pressures which exceed the fracture pressure of the injection formation. The previous paragraph addresses current practices in the disposal of waste material by type of classification. Another set of disposal criteria has been developed around the physical form of the waste, namely solid or liquid. It should be recalled that spent drilling fluid is in the form of a slurry comprising liquid and solid components. U.S. Pat. No. 4,482,459 (now expired) to Carolyn Shiver, and assigned to the assignee of the current disclosure, teaches a method for continuous processing of a slurry of waste drilling mud fluids and water normally resulting from drilling operations. The process comprises the steps of conducting the drilling mud slurry to a slurry tank for liquid-solid separation by chemical and physical means. The separated solid and liquid components are treated and processed such that they are converted to a state suitable for reuse or release into the environment. There are a number of references which address the separation of liquid and solid components, and the processing of these components to render them harmless to the environment. All of the techniques mentioned above for the disposal of NOW and NORM and the processing of waste slurries are relatively expensive, time consuming, and may involve extensive handling, packaging, transportation and special regulatory permits. The means of injecting liquid waste back into earth formations by means of a disposal well has been used for many years and remains the predominant method of disposal in the oil and gas industry. An injection well must meet certain criteria. Among these criteria are defined geologic conditions surrounding the injection well, proper casing and cementing of wells penetrating the injection zone, a maximum allowable surface injection pressure (MASIP) and specific procedures for periodic testing and reporting to various regulating agencies. MASIP varies from state to state and even from location to location within a given state dependent upon formation depth, hydrostatic pressure, etc. Being regulatory, MASIP is certainly subject to change in the future. These measures, which are established to prevent possible migration of the waste liquid into underground sources of drinking water (USDW), will be detailed in subsequent sections of this disclosure. Current injection technology requires that the particle size of the solid phase of any slurry first be minimized before injection. This is to prevent clogging or "sanding" of the perforations opposite the injection zone and also to prevent the filling of pore space throats of the injection zone thereby reducing permeability. Processing time and cost must be incurred, and the large particle size solid component of the slurry must still be disposed of in an environmentally acceptable manner. The density of the injected liquid is usually relatively low, varying between 1.00 gm/cc (˜8.34 lbs/gal) for fresh water to ˜1.1 to 1.2 gm/cc for brines. Often a considerable amount of pump pressure is required to overcome the pressure of the geologic formation and thereby inject the liquid. Adequate pump capacity can comprise an appreciable percentage of the total injection operation cost. In addition, the MASIP is set so as not to damage the tubular strings and the cement sheaths of the injection well and to not damage the injection formation. In some states disposal wells have been drilled into cavities within salt domes or sulfur deposits. In those states cavities are created within salt domes for this purpose, and in the case of sulfur deposits, result from the leach method of production of sulfur. Both of these formations provide impermeable "containers" for liquids but, unfortunately, are not widely distributed geographically and sometimes require that waste be transported a great distance in order to be disposed of in this type of facility. SUMMARY OF THE INVENTION The present invention is directed toward methods and apparatus for the disposal of both solid and liquid constituents of oil field waste slurry by injection into subterranean formations which are naturally fractured and may be inclined from the horizontal plane or "dipping". The invention is not limited to the disposal of oil field waste and therefore provides means and methods for the disposal of virtually any type of waste slurry stream. Some preparation of the slurry at the earth surface is usually necessary prior to injection. Preliminary screening of the solid particulate material is desirable if the slurry is thought to contain large particulates. As an example, large pieces of cuttings in spent drilling fluids are removed from the slurry, pumped through some type of grinding or shearing equipment, and returned to the slurry only after their size has been reduced so that they pass through the screen of predetermined size. Particulate material can be classified as NOW or NORM type. Processing leading to dilution may be required by regulations affecting the specific injection well. Viscosifiers are used to aid in the suspension of the particulate material in the slurry. The viscosifier can be a naturally occurring clay mineral such as virgin bentonite with a specific gravity of ˜2.7. Montmorillonite is another suitable viscosifier. This type of viscosifier also adds weight to the slurry which assists in the injection process as will be described later. Virgin barite (barium sulfate) or other weighting material can also be used. Man made materials such as polymers can also be used as viscosifiers if the viscosifier is not requires to add additional weight to the slurry. In an alternate embodiment, products from surface recycling of NOW can also be used as a viscosifier, weighting agent, and diluent thereby recycling this NOW waste stream. Stated another way, byproduct generated by one waste processing method may be used as a key ingredient in a second waste disposal means. Surface preprocessing can also be used on slurries containing relatively large concentrations of oil or grease. These components can be removed, or the concentrations reduced substantially, by using well known skimming and separation techniques. As mentioned previously, biodegrative agents and thermal methods can also be used to remove organic constituents such as oil and grease. The selection of the zone or formation into which the slurry will be injected is of prime importance. The injection formation is preferably a limestone formation with high porosity and with a large fraction of the effective porosity being attributed to natural fractures. In addition, formation which have been partially depleted are also preferred. Commercial hydraulic fracturing methods can be used to induce fractures within the injection zone. The radial and vertical extent of induced fractures are usually rather limited thereby limiting the injection formation's capacity to receive injected material. The formation and associated fracture structure are preferably dipping with respect to the horizontal. Commercial acidizing techniques can also be used in carbonate injection formations thereby increasing the formation's receptivity to injected material. Current regulations specify that the injection formation must also be below any USDW and have an impermeable shale with a vertical thickness of at least 250 feet separating the injection formation from the USDW. The injection well can be drilled specifically to the injection zone, or an existing well which penetrates a suitable injection formation can be modified to meet injection well standards. Current and proposed regulations require that the injection tubular of an injection well passing through an USDW be surrounded by two additional strings of casing, and that all tubular-borehole annuli be properly cemented for hydraulic isolation purposes. Tubulars are plugged at the lower vertical extent of the injection formation. The upper vertical extent of the injection formation is isolated by using a packer or other suitable means. Current practice is to first perforate only the lower portion of the injection zone. Should these perforations become plugged over the life of the injection operation, the injection formation can be perforated "up hole". It has been determined that the slurry, processed and suspended with viscosifiers as outlined previously, flows into the selected injection formation with no clogging of the fractures or available pore space. This is because most of the effective porosity of the injection formation is in the form of fractures. The cross sectional areas of these fractures are normally orders of magnitude larger than the interstitial pore "throats" connecting effective pore space in non fractured consolidated or unconsolidated formations. The processed and suspended particulate material within the slurry can pass through the fractures without clogging. Since the injection formation is usually dipping from the horizontal and the injected slurry is weighted as previously discussed, flow is maintained with minimal pump pressure thereby reducing the costs of pumping and reducing the risk of damaging the hydraulic seals of the well and adversely affecting the injection formation. Experience has shown that with all other conditions being equal, the required injection pressure decreases as a function of the increasing dip of the injection zone and associated fracture system. Operational experience has also shown that for injection zones with sufficient dip combined with an appropriately weighted slurry, the slurry actually flows into the fractures due to the hydrostatic pressure head of the slurry column. Normal operation practice is, however, to maintain at least a nominal pump pressure for effective injection rates. The importance of low injection pressures are again emphasized in that pumping costs are reduced, the risk of damage to the well tubulars and cement sheaths are nil, and injection pressures are well below the fracture pressure of the injection formation. In summary, methods and apparatus are presented for the disposal of waste slurry containing both liquids and solids by injecting this slurry into a subterranean formation through an injection well. The injection formation is selected to be a dipping, highly porous formation which is highly fractured thereby permitting the passage of the solid constituent of the slurry. Viscosifier is added to the slurry to (a) assist in suspending the solid particulate material and (b) add weight to the slurry thereby minimizing injection pumping requirements. Weighting material can also be added independently. If the slurry contains NORM, processing at the surface may be required to reduce the concentration of NORM to levels consistent with that permitted for the specific injection well being utilized. Processing may also be necessary to reduce the size of the particulates prior to injection. Furthermore, some preliminary skimming or separating at the surface of an abnormally high concentration of oil or grease may be required. BRIEF DESCRIPTION OF THE DRAWINGS So that the manner in which the above cited features, advantages and objects of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. It is noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. FIG. 1 illustrates a typical injection well which penetrates an USDW, an impermeable shale and the injection formation; FIG. 2 is a schematic diagram of the surface apparatus and processes cooperating with an injection well which penetrates the injection formation; and FIG. 3 depicts in block diagram form the preprocessing steps for the injected slurry prior to injection. FIG. 4 illustrates a reduced feed flow manifold used in the preprocessing of the slurry prior to injection. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Attention is first drawn to FIG. 1 which illustrates a typical injection well. The borehole 10 extends from the surface of the earth 13 through an USDW 30, an impermeable shale zone 32 and into the injection formation 36. Slurry, depicted by the arrows 44, is injected from the surface through a tubular member 16 which is preferably production tubing. Extending from the surface 13 through the aquifer 30 are two additional strings of tubulars 14 and 12 whose longitudinal axes are essentially coincident with the axis of tubing 16. These tubulars are preferably standard steel casings used in the completion of oil and gas wells. The casing 12 terminates below the lowest vertical extent of the USDW 30 at the casing shoe 20. Cement 22 fills all tubular-borehole annuli. The USDW is, therefore, shielded from the flow of injected slurry by three strings of steel tubulars and cement. This arrangement is in compliance with current regulations for injection wells and insures an adequate vertical and radial hydraulic seal of the USDW. Tubing 16 and casing 14 extend through an impermeable shale whose vertical thickness 50 is a minimum of 250 feet to meet current injection well specifications. Through the impermeable shale and down to the packer 34, the casing-borehole annuli are filled with cement 22, again to insure hydraulic sealing to protect the aquifer from any vertical fluids migration. The borehole 10 penetrates an injection formation denoted by the numeral 36. The shale 32 serves as an impermeable barrier between the injection formation 36 and the aquifer 30. Packer 34 is positioned at the top of the injection formation. The casing 14 extends through the injection formation while the tubing 16 terminates in the vicinity of the lower boundary of the injection formation. Cement 22 fills the casing/borehole annulus in this region of the well. A cement plug 40 or other suitable bridging mechanism is positioned within the casing string 14 at the lower boundary of injection zone 36. Perforations are made in the casing 14 and the cement sheath thereby establishing fluid communication between the tubing 16 and the injection formation 36. Perforations are preferably made near the lower boundary of the injection interval. Should these perforations become blocked or clogged over time by the injection of waste slurries, new perforations can be made above the blocked perforations thereby maintaining a suitable flow path between the injection tubing and the injection formation. Characteristics of the injection formation will next be examined. The formation is preferably high porosity with a high permeability in order to accept the injected slurries with minimal resistance. This allows low surface injection pressures which is a novel and critically important feature of the invention as discussed previously. Formations at least partially depleted of their virgin fluids if any are also desirable in that they tend to readily accept injected fluid. It is even more important that the formation dip in angle with respect to the horizontal as shown in FIG. 1. In certain instances, the injection formation might exhibit little or no dip at the point of penetration of the borehole, but dip significantly at distances radially removed from the borehole. An example would be an injection well drilled near the top of a geologic protrusion such as a salt dome. Finally, it is extremely important that a large fraction of the effective porosity of the formation be in the form of fissures or natural fractures as designated by the numeral 38. Such formations are quite commonly found on the flanks of salt domes or any other type of geological protrusion or up thrust. Cap rocks usually associated with these types of geological features provide the required impermeable barrier above the injection formation. Again, the combination of a dipping formation and a well developed system of interconnected fractures minimizes the resistance of the injection formation to the injected slurry thereby minimizing required surface injection pressures. The slurry, being weighted as mentioned previously, tends to flow primarily down dip under the influence of gravity and the hydrostatic pressure head of the slurry column. This flow is in the desired direction in that it is away from the USDW 30 located up hole. Geological studies have indicated that several reservoirs can accommodate on the order of 50 million barrels of waste slurry from a single injection well. To summarize the function of the injection well depicted in FIG. 1, slurry is pumped from the surface of the earth 13 through tubing 16 into a region of the casing 14 isolated by the packer 34 and the cement plug 40. The injected fluid exits the borehole through perforations 46 and flows into the tilted, fractured injection formation 36. The path of flow within the injection zone occurs primarily within the fracture system 38 and the flow is down dip as illustrated by the arrows 48. As an alternate embodiment (not shown), the injection well can be cased and cemented from the surface to the top of the injection zone. This form of open end completion is possible in highly consolidated, vertically fractured injection formations. Since the injection formation is not cased and cemented, perforations are not needed to establish hydraulic communication between the injection zone and the surface of the earth. The functional relationships between the surface elements of the invention, the injection well and the injection formation are illustrated in FIG. 2. The waste slurry, designated by the numeral 70, enters the system at input 74. The water component of the waste can be salt water or fresh water. Waste slurry can be delivered to the disposal site by barge, boat, truck, pipeline or any other operationally and economically feasible means. Certain preprocessing steps are then performed at the block designated as 72. These preprocessing steps include the adding of the viscosifier and weighting agent, screening of particulates and other steps which have been mentioned previously and will be discussed in detail in a following section. Once preprocessing has been completed, the waste slurry exits at output 76 and enters a holding tank. At this point, the waste 70 comprises a slurry of liquid and suspended solid particulate material and has been preprocessed to meet all operational and regulatory requirements. It should also be noted that the slurry is at atmospheric pressure. The slurry is then pumped from the holding tank 70 through fitting 71 into tubing 16 within the injection well. The pressure requirements of the pump are not stringent since the slurry has been weighted and it is being pumped into a highly fractured, dipping injection formation 36. Pumps generating surface pressures of 100 psi or less have been found sufficient to maintain a reasonable disposal rate in suitable injection formations. By contrast, conventional injection requires a much higher MASIP. In some situations, the slurry requires no pumping and flows into the injection formation by means of a siphoning effect driven by the hydrostatic head of the weighted slurry column. That is, if the pump 62 is shut off and the valve 66 in pump bypass line 64 is opened, the waste 70 will flow from tank 60 into the dipping injection formation 36 as depicted by arrows 48. Attention is now directed toward the preprocessing steps, each of which will be discussed in detail. The preprocessing steps are shown in block diagram in FIG. 3. There is some flexibility in the sequence of the steps. The sequence depicted in FIG. 3 is selected for purposes of discussion only. In the previous discussion of non hazardous oilfield waste (NOW) and naturally occurring radioactive material (NORM), it was mentioned that essentially all earth material contains some background level of naturally occurring radioactivity which include isotopes which emit alpha and beta particles as well as gamma radiation. Generally speaking, material classified as NOW are considered "non radioactive" in the sense that their level of naturally occurring radioactivity is below a regulated level. Current regulations classify any material with equivalent radium-226 specific activity below 30 pico Curies per gram of sample in the NOW category. Current regulations also allow NOW material to be disposed in injection wells of the type described in the previous paragraphs. Any waste material received for injection disposal must be monitored to determine if it is classified as NORM or NOW material. If the waste has a radioactive level that exceeds the regulatory limit at which NOW becomes NORM, dilution may be required before disposal into some wells. This step is shown at block 80 of FIG. 3. The diluent might be liquid such as brine or other available waste from drilling or production operations. Alternately, the addition of viscosifier and weighting material might suffice to bring the waste within the NOW category if the order of the steps of FIG. 3 are rearranged. It should be noted that the 30 pico Curie level is a regulatory limit. This limit is subject to change, and injection wells with unregulated or unlimited radioactivity restrictions might be permitted. Excessive concentrations of grease or oil are removed from the waste prior to injection for environmental and possible economic reasons. This process is shown at block 82 of FIG. 3. One method of removal is gravity separation using a commercially available gun barrel separator. If the concentration of oil in the waste is equal to or greater than 1 barrel per 2000 barrels of waste, skimming techniques are used to remove the oil constituent. It is possible that the value of the skimmed oil exceeds the cost of skimming thereby producing a byproduct of net economic value. Although one of the novel features of the invention is the ability to inject solid particulate material along with the liquid phase of the waste, experience has shown that there are some limitations to the size of the particulates in order to achieve an efficient injection program. The waste may include relatively large particles of solid material such as "chunks" of drill bit cuttings. Although the maximum size of particle that can be injected is a function of many factors including the fracture system of the injection zone, experience has shown that particles up to 2-5 millimeters in diameter can be effectively injected in most operations. The incoming waste is screened with, as an example, a 10 mesh screen as shown generally at block 84 of FIG. 3. Particles which do not pass through the screen are diverted to a grinding or shearing system to reduce their size as illustrated at block 88. Such means might be a sand pump or other suitable grinding apparatus. The ground particles are then reintroduced to the main stream of the preprocessing operation at block 84 for a second screening. The screening operation 84 and particle reduction operation 88 are repeated until the particulate material is reduced to or below the predetermined size. It should again be noted that the 10 mesh size specification is rather arbitrary and dependent upon many factors including the fracture system of the injection reservoir. Particulates as large as sand have been successfully suspended and injected, as well as shale cuttings as large as 5 millimeters in diameter It is advantageous to reduce the flow pressure of the slurry during the screening operation 84. This is accomplished in the preferred embodiment of the invention by using a reduced flow feed manifold depicted in FIG. 4. Slurry flows into the manifold through input line 90 and first enters and partially fills an essentially cylindrical portion of the manifold identified by the numeral 92. For a four inch input flow line 90, the dimension identified by the arrow 97 is preferably be about ten inches and the dimension identified by the arrow 95 is approximately four feet. The effective cross section of the flow is significantly increased by the cylindrical portion 92 of the manifold thereby reducing the flow pressure. Slurry flows from the cylindrical portion of the manifold through a slightly constricting conduit 94 with a rectangular cross section. The dimension identified by the numeral 98 is approximately one inch or less. The slurry exits the reduced flow feed manifold as depicted by the arrows 96 and flows to the previously described screening operation. Viscosifiers and possibly weighting material is added to the waste stream at block 86 of FIG. 2. A possible viscosifier is virgin bentonite which is a clay mineral with a specific gravity of approximately 2.7. Since the specific gravity of the viscosifier is relatively large, it may also serve as a weighting agent. It is desirable to bring the viscosity of the waste stream to a funnel viscosity in the range of approximately 60-90 seconds per quart for efficient operation. At this viscosity and with particulates in the ideal size range of 2 millimeters in diameter or less (10 mesh sieve), a slurry containing 15 to 35% solids can be obtained and successfully injected. Barite (barium sulfate) with a specific gravity of over 4 can be used as an independent weighting agent. The amount of material added for the sole purpose of weighting the slurry is, of course, a function of the amount of waste particulates in the slurry. It has been found that a slurry weight of 10 lbs/gal or more is beneficial for most injection operations. A second embodiment of the invention involves the use of waste material from other NOW waste processing operations in place of virgin clays as a viscosifier and weighting material. A surface processing method for NOW material, offered commercially by the assignee of the current invention, generates a material that is very high in clay content and would be very useful as a viscosifier and a weighting agent in the present invention. That is, recycled material from one type of processing could be used in the disposal technique of the present invention thereby eliminating the need to use any virgin material. This is both environmentally and economically desirable as no additional volume of NOW is created. In most operations, it has been found that the pH of most preprocessed slurry falls within the range of 6 to 8. If, for any reason, the preprocessed material is sufficiently corrosive to cause damage the processing or injection apparatus or even to the injection formation, the pH can be adjusted in the preprocessing steps preferably after step 86. The preprocessed waste is output at the point indicated schematically by the numeral 76 and passed to pump 62 for injection into the injection zone. While the methods and apparatus herein described constitute the preferred embodiment of this invention, it is to be understood that the invention is not limited to these precise methods and forms of apparatus and that changes may be made therein without departing from the scope of the invention.

Methods and apparatus for the disposal of solid particulate material in subterranean formations are disclosed. The invention is not limited to the disposal of oil field waste and therefore provides means and methods for the disposal of virtually any type of waste slurry stream. A slurry is formed at the surface of the earth by mixing the solid waste in particulate form with liquid and viscosifier thereby forming a slurry. A borehole is drilled into a selected injection formation and the slurry is pumped from the surface through the borehole and into the injection formation. Some surface pretreating of the slurry may be required including sizing of the particulate solids, adding weighting material, removing excessive amounts of oil and grease and diluting to reduce the level of radioactivity. The injection formation is preferably dipping in angle with respect to the horizontal and highly fractured. The borehole is hydraulically isolated from intervening earth strata between the surface of the earth and the injection formation.

This is a divisional of application Ser. No. 09/096,884, filed on Jun. 12, 1998 now U.S. Pat. No. 6,014,804. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-voltage electromagnetic riveting apparatus and method, and more particularly to a method and apparatus for controlled and efficient low-voltage electromagnetic riveting. 2. Background Information Riveting machines are well known and in wide use throughout the aerospace industry, as well as in other industries. Rivets provide the best known technique for fastening an aerodynamic skin to a frame to provide a strong, aerodynamically smooth surface. Rivets are also used in the interior structure of an aircraft, since they are the lightest and least expensive way of fastening structural components together. One form of riveting uses a low voltage electromagnetic riveting (LVEMR) system 100 , as shown in FIG. 1 . The LVEMR system 100 provides a controlled amount of energy in a single pulse and is typically smaller and less cumbersome than a pneumatic or hydraulic system. Further, the LVEMR system has almost no mass so it only has nominal reactionary forces. The LVEMR system 100 shown in FIG. 1 incorporates two electromagnetic actuators, a first actuator 101 and a second actuator 112 , which are positioned on opposite sides of first and second workpieces 114 and 115 , respectively. The first and second work pieces 114 and 115 are sandwiched together and a hole has been drilled through them to accommodate a rivet 93 . The first and second actuators 101 and 112 each include a body 116 in which is positioned a driver 118 and a coil 120 . A rivet die 92 is coupled to the driver 118 and is forced against the rivet 93 . Also, there may be a recoil mass 123 which is typically secured to a rear surface of the coil 120 . Extending from the recoil mass 123 is an air cylinder rod 124 , which extends out of the body 116 into a two-chamber air cylinder 126 . Associated pressure relief valves and other control elements are shown diagramatically as block 128 . The elements of block 128 are responsible for initially positioning the driver 118 and its rivet die 92 against a head of the rivet 93 . Power is supplied to the system 100 by means of a power supply 130 . A DC output from the supply 130 is used to charge a bank of capacitors in circuit 132 to a selected voltage. The voltage selected is based on the force necessary to accomplish the desired riveting task. The circuit 132 includes an electronic switch positioned between the capacitors and the coil 120 . A trigger signal from a firing circuit 134 activates the electronic switch, dumping the charge of the capacitor bank in circuit 132 into the coil 120 . A current pulse is induced into the coil 120 causing strong eddy currents in a copper plate 119 located at the base of the driver 118 . This creates a very strong magnetic field that provides a repulsive force relative to the coil 120 . The driver 118 is propelled forward with a large force causing the rivet die 92 to upset the head of the rivet 93 . A more detailed discussion of low voltage electromagnetic riveting can be found in U.S. Pat. No. 4,862,043, which is incorporated herein by reference. Once the LVEMR system 100 has upset the rivet 93 , a fastened assembly 140 is created as shown in FIG. 1 B. The assembly 140 includes a deformed rivet 146 , having a head 142 and a tail 154 . The hole drilled into the first and second workpieces 114 and 115 includes a countersink 148 drilled into the second workpiece 115 to receive the head 142 of the deformed rivet 146 . Unfortunately, the fastened assembly 140 , when produced by the LVEMR system 100 described above, has significant gaps 150 between the head 142 of the deformed rivet 146 and the countersink 148 . The gaps 150 are undesirable since they could lead to early corrosion of the deformed rivet 146 , causing it to weaken and prematurely fail. Accordingly, for the foregoing reasons, there is a need in the art for a controlled low-voltage electromagnetic riveting apparatus and process that mitigates the gaps 150 between the rivet head 142 and the countersink 148 . SUMMARY OF THE INVENTION In one aspect, the present invention is directed to a method for minimizing undesirable gaps in riveted assemblies including the steps of selecting a rivet having a head and a tail with identical forming characteristics, positioning the selected rivet in an assembly that is countersunk on one of two sides, and applying a force over time to tile head of the rivet and a force over time to the tail of the rivet that are equal and opposite, compensating for force-unbalancing characteristics of the countersink. In another aspect, the present invention is directed to a method for mitigating gaps between a deformed head of a rivet and a countersink in an assembly that is coupled by a low-voltage electromagnetic riveter having a head side actuator and tail side actuator. The method includes the steps of selecting a rivet that uniformly deforms at a tail and at a head of the rivet, positioning the volume of the rivet within the assembly such that force applied over time to the head of the rivet by the head side actuator equals a force applied over time to the tail of the rivet by the tail-side actuator. In yet another aspect, the present invention is directed to a method for mitigating gaps between a head of a rivet and a countersink within a first workpiece of two workpieces when the rivet is upset by a low voltage electromagnetic riveting process. The method includes the steps of extending a tail of the rivet out of a surface of a second workpiece of the two workpieces by a length from 0.9 to 1⅓ times a diameter of the rivet, extending the head of the rivet out of a base of the countersink by a length that is 5% to 10% less than the length the tail of the rivet was extended out of the second workpiece surface, and upsetting the tail of the rivet with a tail die having a shape substantially similar to a shape of the countersink within the first workpiece. In still another aspect, the present invention is directed to a method for controlled low-voltage electromagnetic riveting of a primary workpiece including a countersink and at least a secondary workpiece with a rivet, having a head, a tail, and a diameter, using a head actuator having a head die to contract the head of the rivet and a tail actuator having a tail die to contact the tail of the rivet. The method includes the steps of selecting the rivet so the rivet is comprised of a homogenous alloy and the rivet has a uniform diameter, positioning the tail of the rivet so that it protrudes from an outside surface of the secondary workpiece by a length from 1 to 1.3 times the diameter of the rivet, positioning the head of the rivet so that it protrudes from the base of the countersink by a length that is 5 to 10 percent less than the length that the tail protrudes from the step of positioning the tail, upsetting the head of the rivet with the head die having a flat contact surface, and upsetting the tail of the rivet with the tail die, wherein the tail die has an upper diameter within 20% of the depth of the countersink, and wherein the tail die has an upper diameter within 10 degrees of the upper angle of the countersink. In another aspect, the present invention is directed to a low-voltage electromagnetic riveter for controlling the force over time applied to a head and a tail of a rivet within an assembly having a workpiece that is countersunk to receive the head of the rivet. The riveter includes a head and a tail actuator that respectively apply a force over time to the head and the tail of the rivet. Each of the actuators includes a die which contacts the rivet, a coil which creates a repulsive force when electrical current is passed therethrough, a driver physically adjacent to the coil and movable along an axis of the rivet by the repulsive force created by the coil, and a load cell positioned between the driver and the die to measure the force over time applied to a designated end of the rivet. A head current source and a tail current source are electrically connected to the coil of the respective head and tail actuator for supplying a controlled amount of current, and a firing circuit is electrically connected to each of the head current source and the tail current source for controlling phase and magnitude of the controlled amount of current supplied to each of the head actuator and the tail actuator. In yet another aspect, the present invention is directed to a method for controlled low-voltage electromagnetic riveting. The method includes the steps of monitoring the force applied over time to a head and tail of a rivet during a deformation of the rivet by the low-voltage electromagnetic riveting, adjusting a phase of the force applied to at least one of a location of the head and the tail of the rivet so that the phase of the force applied to the location of the head of the rivet equals the phase of the force applied to the location of the tail of the rivet, and adjusting a magnitude of the force applied to at least one of the location of the head and the tail of the rivet so that the magnitude of the force applied to the location of the rivet head equals the force applied to the location of the tail of the rivet. In still another aspect, the present invention is directed to a method for mitigating gaps between a deformed head of a rivet and a countersink in an assembly that is coupled by a low-voltage electromagnetic riveter, including a head-side driver, having a first load cell, and a tail side driver, having a second load cell, and a firing control circuit capable of controlling phase and magnitude of force applied by the head-side driver and the tail-side driver. The method includes the steps of positioning a first test rivet within the assembly, monitoring a first output of the first load cell and the second load cell while the first test rivet is upset to determine the phase and the magnitude of the force applied to a head and a tail of the rivet respectively by the head side driver and the tail side driver, comparing the first output of the first load cell and the second load cell that occurred when the first test rivet was upset, and adjusting the phase of one of the force applied by the head driver and the force applied by the tail driver so that the phase of the force applied by the head driver matches the phase of the force applied by the tail driver. The method also includes the steps of positioning a second test rivet within the assembly, monitoring a second output of the first load cell and the second load cell while the second test rivet is upset to determine the phase and the magnitude of the force applied to the head and the tail of the second test rivet respectively by the head side driver and the tail side driver, comparing the second output of the first load cell and the second load cell that occurred when the second test rivet was upset, and adjusting the magnitude of one of the force applied by the head driver and the force applied by the tail driver so that the magnitude of the force applied by the tail driver equals the magnitude of the force applied by the head driver. BRIEF DESCRIPTION OF THE DRAWINGS These and other features, aspects, and advantages of the present invention will be better understood with regard to the following description, appended claims, and accompanying drawings wherein: FIG. 1A shows a block diagram of a prior art low-voltage electromagnetic riveting system; FIG. 1B shows a rivet deformed by the riveting system of FIG. 1A; FIG. 2 shows a force vs. time graph applied to a rivet during its deformation into a hole having a countersink; FIG. 3 shows a force vs. time graph applied to a rivet using a process and apparatus for mitigating gaps according to the present invention; FIG. 4 shows a desired rivet protrusion to mitigate gaps according to a first embodiment of the present invention; FIG. 5 shows a desired forming die configuration according to the first embodiment of the present invention; FIG. 6A shows a schematic diagram of a low-voltage electromagnetic driving system according to a second embodiment of the present invention; FIG. 6B shows a side view of a load cell and driver of the low-voltage electromagnetic driving system of the second embodiment; FIG. 7A shows a force vs. time graph for a rivet head and rivet tail having applied forces that are out of phase and have different magnitudes; FIG. 7B shows a force vs. time graph for the rivet head and the rivet tail having applied forces that are in phase but have different magnitudes, and FIG. 7C shows a force v. time graph for the rivet head and the rivet tail having applied forces that are in phase and have the same peak magnitude. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following process and apparatus assist in controlling and balancing the forces applied to a rivet. Such control mitigates gaps between a head of a rivet and a countersink into which it is deformed. Other advantages include more accurate control over rivet interferences and a reduction in reactive forces applied to an object being riveted. It has been discovered that to mitigate the gaps between the rivet and the countersink, it is essential to maintain an equal force on the head and a tail of the rivet throughout the riveting process. Unfortunately, when the workpiece or assembly to be riveted has been countersunk to receive a deformed rivet head, simultaneous activation of two opposing LVEMR guns will not produce equal forces on the rivet head and the rivet tail over the duration of time that the rivet is deformed. Low voltage electromagnetic rivet (LVEMR) guns are typically dynamic and used in an open loop system, as such, they offer no method of “real-time” force control during the rivet-forming process. Because the LVEMR guns are used in an open loop, they produce a dissimilar force on the head and tail over time, as shown in FIG. 2 . However, the forming process can be manipulated to compensate for the force unbalancing effects of a countersink within a workpiece. This manipulation is accomplished by selecting process variables so that the head and tail of the rivet have similar forming characteristics over time as shown in FIG. 3 . In a first embodiment, as shown in FIGS. 4 and 5, the force-displacement relationship of a head 21 and tail 23 of a rivet 22 are manipulated via the forming characteristics of the rivet 22 to maintain a force balance between the head 21 and the tail 22 . Five factors typically affect the forming characteristics of the rivet 22 , and therefore can be used to affect the force-displacement relationship of the head 21 and the tail 23 . First, there is the mechanical properties of the rivet 22 , i.e. the stress—strain relation. Since rivets are typically composed of a homogenous alloy, there is no difference in the material adjacent the head 21 and the tail 23 . Therefore, this factor does not create a difference in the force-displacement between the head 21 and the tail 23 . Second, the diameter of the rivet will affect the force-displacement along the rivet 22 . Any difference in force-displacement due to diameter effects between the head 21 and the tail 23 can be eliminated by using a slug rivet, which has a constant diameter throughout. The third factor affecting the force-displacement relationship of the rivet 22 is the amount of rivet 22 that extends out of the primary sheet 24 and the secondary sheet 26 . This includes a head protrusion 28 of the rivet 22 above a countersink 25 in the primary sheet 24 to be coupled to the secondary sheet 26 , as shown in FIG. 4 . The third factor also includes a tail protrusion 30 from the secondary sheet 26 . The larger the protrusion values for the head protrusion 28 and the tail protrusion 30 , the more the displacement of the protrusion for a given force, i.e., a soft force-displacement relationship. The fourth factor affecting the force-displacement is the geometry of the countersink 25 , and the fifth factor is the design of a head die 32 and a tail die 34 used to upset the rivet 22 , as shown in FIGS. 4 and 5. Captivating dies, such as the tail die 34 , and deep countersinks, such as the countersink 25 , create a stiffer force-displacement relationship. Therefore, there is less displacement of the rivet 22 for a given force when using dies, such as the tail die 34 , and countersinks, such as countersink 25 , that prevent the material of the rivet 22 from flowing outward when it is upset. In the first embodiment, a preferred combination of the above-described factors maintains a balanced force, i.e. equal force on the tail 21 the head 23 , throughout the riveting process which results in the elimination of any gaps between the deformed head and the countersink 25 . Referring to FIG. 4, the preferred combination has the amount of head protrusion 28 at a length that is five to ten percent less than the length of the tail protrusion 30 . In other words: Head Protrusion=(1−[0.05 to 0.10]) (Tail Protrusion). Further, referring to FIG. 4, the tail protrusion 30 is preferably 0.9 to 1.3 times a diameter 19 of the rivet 22 . In other words: Tail Protrusion=[0.9 to 1.3] Rivet Diameter. Referring to FIG. 5, the depth 44 of a contact surface 36 of the tool die 34 in the preferred combination must be similar to, i.e. within 20% of, the depth 42 of the countersink 25 . The contact surface 38 of the head die 32 is preferably flat. Also, an upper diameter 40 of the tail die 34 must be similar to a countersink diameter 37 , i.e. the upper diameter 40 must be within 20% of the countersink diameter 37 . Finally, an upper angle or taper 48 of the edge of the die surface of the tail die 34 must be similar, i.e. to an upper angle or taper 46 of the countersink, i.e. within 20%. In a second embodiment, the force applied to a head and a tail of a rivet is balanced, i.e applied equally over time, by controlling the rivet upsetting process using a monitoring and application assembly 50 , shown in FIG. 6 A. When riveting a workpiece that has a countersink, using two rivet guns, one at a head side and the other at a tail side of a rivet 22 , the force applied to the head side is usually out of phase with and has a different magnitude than the force applied to the a tail side of the rivet 22 , as shown in FIG. 7 A. However, the assembly 50 can be used to create the proper differential voltage and timing so that the forces applied to the head and tail side of the rivet 22 are balanced, i.e., the forces applied over time to each side are nearly identical. The assembly 50 includes a first load-cell 56 , and a second load-cell 58 , used to monitor the force applied by the electromagnetic riveter during the riveting process. Each of the first and second load-cells 56 and 58 is mounted on respective first and second drivers 52 and 54 , near its respective first and second rivet die 60 and 62 . Preferably, each of the first and second load-cells 56 and 58 is positioned no less than three inches from its respective first and second rivet die 60 and 62 . The first load cell 56 and the second load cell 58 are identical and are described with reference to the first load cell 56 , shown in FIG. 6 B. The load cell 56 includes a piezo-electric quartz cell 66 , preferably a PCB Model 204M device. An integral cable 68 extends from the quartz cell 66 and is coupled to a waveform analyzer 64 , such as a Nicolet Module 2580, which digitally stores the electrical waveform produced by the quartz cell 66 when a force is applied to it. By subjecting the quartz cell 66 to known forces and monitoring the output, a conversion graph can be created, where a particular electrical waveform can be converted to a force-overtime waveform. As shown in FIG. 6B, the quartz cell 66 is coupled to the driver 56 and the head die 60 , so that it will receive and register at least 95% of the force applied by the driver 56 , yet dampen external noise. Two pieces of tape 70 a and 70 b , preferably Capton tape, are positioned on first and second sides of the quartz cell 66 that are orthogonal to a longitudinal axis of the driver 52 . The two pieces of tape 70 a and 70 b help dampen noise produced by the driver 56 , which could interfere with an accurate measurement by the quartz cell 66 . First and second respective steel washers 72 a and 72 b are respectively positioned adjacent the Capton tapes 70 a and 70 b . The first and second steel washers 72 a and 72 b , as well as the quartz cell 66 , are annular, allowing a stud 74 to pass through. The stud 74 is preferably a copper beryllium threaded stud. Copper beryllium is preferred since it may be threaded to the driver 52 and the head die 60 coupling the two physically yet allowing 95% of the force from the driver 52 to pass through the load cell 56 , instead of the stud 74 . Optionally, a portion 76 of the driver 52 may be threadingly detachable to allow easy maintenance and replacement of the load cell 58 . The phase and magnitude of the force applied by the first and second drivers 52 and 54 are directly caused by a “charge dump” from a respective first and second capacitor bank 78 and 80 charged by a power cell 82 and controlled by a firing circuit 84 . The firing circuit has a first phase and amplitude voltage control 86 for controlling the phase and magnitude of force, via voltage, of the first driver 52 , and a second phase and amplitude control 88 for controlling the phase and magnitude of force, via voltage, of the second driver 54 . There are four steps in determining the proper differential voltage and timing delay to balance the forces on the head and tail of the rivet 22 . First, the desired process conditions, i.e. the desired rivet protrusion and die geometry, must be selected The forces are then monitored by the first and second load cells 56 and 58 during the rivet-forming process with no differential voltage and no timing delay, yielding a force-over-time graph as shown in FIG. 7 A. The force over time applied to the rivet 22 is recorded by the waveform analyzer 64 . Next, the timing delay is adjusted to bring the forces into phase. The forces are in phase when the peak forces are reached simultaneously, as shown in FIG. 7 B. It is important to adjust phase first since amplitude often changes when the phase is changed. For example, in FIG. 7A, the head force has the greatest magnitude, while in FIG. 7B, the tail force has the greatest magnitude. The proper amount of delay is approximately equal to the difference in time between the head and tail peak forces. As shown in FIG. 7A, if the phase difference 60 is 50 μs, where the head force precedes tail force, then the head force should be delayed about 50 μs by adjusting the phase using the first control 86 . For the third step, the voltages are adjusted to produce equal force magnitude, i.e. the greater force is reduced or the lesser force is increased by changing charge voltage via the firing circuit 84 . In the example shown in 7 B, the tail force needs to be decreased by adjusting voltage amplitude using the second control 88 until the tail force equals head force. It is most desirable if the entire force on the tail and head matches for their duration. However, if this match is not possible, it is important that the force peaks 61 , i.e., the force having the greatest area, as shown in FIG. 7C, are as equal as possible. If the forces cannot be entirely aligned, then they must at least substantially match in this area. Finally, the second and third steps are repeated until well-matched curves are achieved as in FIG. 7 C. With the present invention, it is possible to apply an equal force to a rivet head and tail, even when the head is upset into a countersink. By these arrangements, gaps between a deformed head and a countersink can be mitigated and interferences better controlled. While the detailed description above has been expressed in terms of specific examples, those skilled in the art will appreciate that many other configurations could be used to accomplish the purpose of the disclosed inventive apparatus. Accordingly, it will be appreciated that various equivalent modifications of the above-described embodiments may be made without departing from the spirit and scope of the invention. Therefore, the invention is to be limited only by the following claims.

The present invention relates to a method for minimizing undesirable gaps in riveted assemblies. The method includes the steps of selecting a rivet having a head and a tail with identical forming characteristics, positioning the selected rivet in an assembly that is countersunk on one of two sides, and applying a force over time to the head of the rivet and a force over time to the tail of the rivet that are equal and opposite, compensating for force unbalancing characteristics of the countersink.

FIELD OF THE INVENTION This invention relates to refiners in general and to rotary refiners in particular. BACKGROUND OF THE INVENTION Disc refiners are utilized in papermaking to prepare wood fibers to be made into paper on a papermaking machine. Disc refiners are generally divided into two types: those for refining high consistency stocks containing 18 to 60 percent fiber by weight; and those for refining low consistency stocks having two to five percent fiber by weight. High consistency refiners produce mechanical and semi-mechanical pulp or furnish from undigested wood chips and semi-digested wood chips. These refiners break down the wood chips and clumps of wood fibers into individual fibers from which paper is formed. Processing of fibers in a low consistency refiner may be performed on both chemically and mechanically refined pulps, and in particular may be used sequentially with a high consistency refiner to further process the fibers after they have been separated in the high consistency disk refiner. In operation, a low consistency disc refiner is generally considered to exert a type of abrasive action upon individual fibers in the pulp mass so that the outermost layers of the individual cigar-shaped fibers are frayed. This fraying of the fibers, which is considered to increase the freeness of the fibers, facilitates the bonding of the fibers when they are made into paper. Paper fibers are relatively slender, tube-like structural components made up of a number of concentric layers. Each of these layers (called "lamellae") consists of finer structural components (called "fibrils") which are helically wound and bound to one another to form the cylindrical lamellae. The lamellae are in turn bound to each other, thus forming a composite which has distinct bending and torsional rigidity characteristics. A relatively hard outer sheath (called the "primary wall") encases the lamellae. The primary wall is often partially removed during the pulping process. The raw fibers are relatively stiff and have relatively low surface area when the primary wall is intact, and thus exhibit poor bond formation and limited strength in the paper formed with raw fibers. It is generally accepted that it is the purpose of a pulp stock refiner to partially remove the primary wall and break the bonds between the fibrils of the outer layers to yield a frayed surface, thereby increasing the surface area of the fiber multi-fold. Disc refiners typically consist of a pattern of raised bars interspaced with grooves. Paper fibers contained in a water stock are caused to flow between opposed refiner discs which are rotating with respect to each other. As the stock flows radially outwardly across the refiner plates, the fibers are forced to flow over the bars. The fiber treating action is thought to take place there, between the closely spaced bars on opposed discs. It is known that sharp bar edges promote fiber stapling and fibrillation due to fiber-to-fiber action. To achieve this, an advantageous method of fabricating bars which wear sharp has been utilized in the construction of refiner plates such as disclosed in U.S. Pat. No. 5,165,592 to Wasikowski. It is also known that dull bar edges result in fiber cutting by fiber-to-bar action. Fiber cutting is undesirable because it results in paper of weaker strength and renders a certain portion of the fibers too small to be retained on the screen on which the paper is formed, thus increasing waste. The preferred action in refining paper fibers is fibrillation. Fibrillation is the breaking down of the primary wall and partially releasing the fibrils of the outer layer to yield the frayed surface, which increases the surface area of the fiber multi-fold. Improved fibrillation with minimal fiber damage has been theorized as possible if a refiner bar having a rough or abrasion resistant edge is used. The rough or abrasion resistant edge, which resists dulling during operation, holds the fibers longer while the sharpness of the rough surface acts to gently abrade the fibers. A rough or abrasion resistant edge is difficult to obtain without affecting all of the surrounding surfaces. If all of the surrounding surfaces are treated, fiber flow through the refiner may be impaired by the loss of open area in the grooves between the refiner bars as well as by the added friction of the abrasive material. Treatment of the entire groove and treatment of the bar surface have been accomplished by surface modification techniques but the edge has not been isolated. Both theory and logic suggests that work is being done to wood fibers passing through a refiner principally as the fibers pass over the outermost surface of the bars. Thus, it is desirable to retain the fibers on the outermost surface and to build up a fiber pad thereon to promote refining. One way to retain fibers on the outermost surface of refiner bars is to make the surface rough. The roughness creates numerous edges to hold the fibers so that they may be refined. There are many ways of depositing a rough surface or other coating on a refining plate bar, but these have all involved adding thin layers of material on top of the bars after they have been finished because the bar surfaces must be ground to obtain flatness and bar depth requirements. Thus, the problem associated with depositing a rough surface or other coating on the outermost surface of the refiner bars is that, on the one hand, it can affect the flatness of the bars, which interferes with the ability to run opposed discs closely spaced; and on the other hand, there is a tendency of the relatively thinly deposited layer to rapidly wear away during operation in a refiner. What are needed are techniques for creating localized areas of surface roughness which resist wearing away. SUMMARY OF THE INVENTION The disk refiner of this invention employs refiner bars integrally formed with the refiner plate which have selected regions of high roughness, resistance to abrasion or other unique characteristics. In one of the embodiments of the invention, an abrasive or other material is deposited or formed in U-shaped, V-shaped, or trapezoidal grooves which are formed down the center of the uppermost surface of the refiner bars. Roughness centrally located in the bars serves to retain wood fibers on the uppermost surface of the bar where the refining action is thought to take place. In this way the fibers are retained for an extended period of time in the location where the most refining action is taking place, thus increasing the fibrillation of the fibers which increases the strength of the papers made from the fibers. Another embodiment places abrasive or other materials on one or both sides of the blade so that the leading edge or trailing edge of the refiner bar is constructed of abrasive materials. Yet another way of achieving an abrasive surface over the entire upper surface of the bar including the leading and trailing edges is to form the bar of a white iron alloy which may be heat treated to form a soft matrix with embedded carbide grains. The carbide grains may be exposed to form a rough surface either by normal wear of the refiner disc in use or by etching the bar surface with an acid such as concentrated sulfuric or hydrochloric acid. Selective regions of roughness are developed by protecting those portions of the refiner plate and bar on which roughness is not desired, mainly the grooves which are formed by the sides of the bars, with a protective material that prevents erosion or etching such as a paint polymer or an etch- and wear-resistant metal. Thus, a refiner disc is formed of a white iron alloy and the entire refining surface together with the bars are coated with an etch-and wear-resistant surface. Subsequent to coating, the normal procedure for forming the uppermost surface of the bars, that of grinding the bars parallel to the plate, is performed. The grinding operation selectively removes the wear- and etch-resistant coating from the top or the uppermost surface of the bars. The bars may then be etched with acid or allowed to wear naturally to form a rough surface on the entire upper surface of the bars. It is a feature of the present invention to provide a refiner disc with refiner bars which have unique characteristics in selected locations. It is another feature of the present invention to provide refiner discs having refiner bars wherein the edges of the bars are rough. It is a further feature of the present invention to provide refiner bars wherein the central portion of the bar is rough to retain a fiber mat thereon. Further objects, features, and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side-elevational view, in particular cross-section, of a low consistency disc refiner. FIG. 2 is a segment of a disc refiner plate of this invention. FIG. 3 is an isometric view, partially cut away in section, of a single bar of the disc refiner of FIG. 2. FIG. 4 is a cross-sectional view of the bar of the disc refiner of FIG. 2. FIG. 5 is a cross-sectional view of an alternative disc refiner bar. FIG. 6 is a cross-sectional view of another alternative disc refiner bar. FIG. 7 is a cross-sectional view of a refiner bar with material of a desired characteristic, such as roughness, placed on the outer edges. FIG. 8 is a cross-sectional view of an alternative embodiment refiner bar. FIG. 9 is a cross-sectional view of another alternative embodiment refiner bar. FIG. 10 is a schematic view of the process of coating the edge of the bar of FIG. 7. FIG. 11 is a cross-sectional, schematic view of the process of FIG. 10. FIG. 12 is a schematic view showing the refining action of two sharp bars. FIG. 13 is a schematic view of the refining action of two dull edge bars. FIG. 14 is a schematic view of the refining action of two rough edge bars. FIG. 15 is a fragmentary, cross-sectional view of a bar formed of white cast iron. FIG. 16 is a schematic cross-sectional view of the bar of FIG. 15 with the matrix shown etched away. FIG. 17 is a schematic cross-sectional view of the bar of FIG. 15. FIG. 18 is a schematic, cross-sectional view of the bar of FIG. 17 after it has been milled away. FIG. 19 is an enlarged, fragmentary view of the rough edge of the bar of FIG. 18. DESCRIPTION OF THE PREFERRED EMBODIMENT Referring more particularly to FIGS. 1-19 wherein like numbers refer to similar parts, a segment for a refiner plate 26 is shown in FIG. 2. Similar segments may be used for a refiner plate 27 operated in opposed, spaced relationship to the plate 26 when installed in a refiner 20. The refiner plates 26, 27 have bars 12 and the bars have selected regions 14 which are constructed of a rough or abrasive material 16. The refiner plates are used to refine fibers in the disc refiner 20. In the description and claims of the present invention, reference to rough or abrasive material will be used for case of description. It should be recognized, however, that the present invention is useful for providing differential properties within a refiner bar, and may be used to provide localized, unique characteristics such as, but not limited to, wear resistance on a ductile bar, areas of differential corrosion or erosion resistance and the like in addition to roughness or abrasiveness. A disc refiner 20, as shown in FIG. 1 has a housing 29 with a stock inlet 22 through which papermaking stock, normally consisting of two to five percent fiber dryweight dispersed in water, is pumped, typically at a pressure of 20 to 40 psi. Refiner plates 26 are mounted on a rotor 24. Refiner plates 27 are also mounted to a non-moving head 28 and to a sliding head 30. The refiner plates 27 which are mounted to the non-moving head 28 and the sliding head 30 are opposed and closely spaced from the refiner plates 26 on the rotor 24. The rotor 24 is mounted to a shaft 32. The shaft 32 is mounted so that the rotor 24 may be moved axially along the axis 34 of the shaft. The rotor has passageways 36 which allow a portion of the stock to flow through the rotor 24 and pass between the refiner plates 26, 27 which are opposed between the rotor and the stationary head 28. A portion of the stock also passes between the refiner plates 26 mounted on the rotor and the refiner plates 27 mounted on the sliding head 30. After being refined by the rotor the stock leaves the housing 29 through an outlet 23. In operation, the gaps between the refiner plates 26 mounted on the rotor 24, and the refiner plates 27 mounted on the non-rotating heads 28 and 30, are typically three to eight thousandths of an inch. The dimensions of the gaps between the refiner plates 26, 27 are controlled by positioning the rotor between the non-moving head 28 and the sliding head 30. Stock is then fed to the refiner 20 and passes between the rotating and non-rotating refiner plates 26, 27 establishing hydrodynamic forces between the rotating and non-rotating refiner plates. The rotor is then released so that it is free to move axially along the axis 34 by means of a slidable shaft 32. The rotor 24 seeks a hydrodynamic equilibrium between the non-rotating head 28 and the sliding head 30. The sliding head 30 is rendered adjustable by a gear mechanism 38 which slides the sliding head 30 towards the stationary head 28. The hydrodynamic forces of the stock moving between the stationary and the rotating refiner plates 26, 27 keeps the rotor centered between the stationary head 28 and the sliding head 30, thus ensuring a uniform, closely spaced gap between the stationary and rotating refiner plates 26, 27. As shown in FIG. 3, the bars 12 that perform the refining action on the plates 26, 27 have sides 39 which define the upstanding bars 12. The sides 39 extend upwardly of a base member 40 and are integrally formed with the base member 40. Flow passages 42 between the bars 12 are defined by the sides 39 and portions 44 of the base 40 which form the bottoms of the flow passages 42. Stock comprised of wood fibers suspended in water flows between the plates 26, 27 as shown in FIG. 1. The flowing stock principally travels in the flow passages 42. However, as the stock traverses the plates 26, 27, the bars 12, as shown for example in FIG. 2, are designed to cause the stock to pass over the bar tops 46. It is while the wood fibers pass over bar tops that they are engaged by the bars on the opposed disc, and thus refined. In existing refiner plates, an abrasive material has been sprayed or coated on the upper surface of the bars. However, the discs and bars operating in a refiner are subject to extensive wear over their useful life and the surface coating of abrasive is rapidly worn away. In accordance with the present invention, the base member and bars of the refiner plate are integrally formed of a first material. The bars are shaped to define reservoirs, and a second material, chosen for a specific characteristic such abrasiveness, fills the reservoir. As shown in FIG. 3, in the refiner plates of this invention, the bars 12 have upwardly extending side members 13 which are spaced from one another to define deep reservoirs such as U-shaped grooves 48 which extend downwardly from the bar top upper surface 50 toward the refiner disc base member 40. The manufacture of the refiner plates 26, together with the bars 12, is preferably formed by sand casting. The rough or abrasive material 16 may be of any granular material with high hardness and wear resistance such as, but not limited to, alumina, silica, zirconia, silicon carbide, tungsten carbide, vanadium carbide, and niobium carbide. Materials having other desired properties also may be used. The material may be placed or formed within the groove 48 by a number of techniques. One technique is set forth in U.S. Pat. No. 5,492,548 which is incorporated herein by reference. The process in the foregoing application involves placing the material in the sand mold used to form the refiner plate 26. In order that the material may become an integral part of the refiner bars 12, it may advantageously be coated with a flux material. The flux material causes the material 16 to be temporarily bonded together and at the same time facilitates the penetration of the granular material by the molten base metal from which the refiner plates 26, 27 are formed. Thus, in the finished product, an abrasive or other material 16 is embedded in a matrix of the material used to form the plates, the plates typically being formed of cast iron, preferably a white cast iron or stainless steel. Thus the bars 12, as shown in FIGS. 3 and 4, have portions 52 of the bar top surfaces 50 which are rough and further remain rough as the upper surface 50 of the bar wears away. This rough portion 52 of the upper surface retains wood fibers as they flow over the bar tops 46, thus increasing the time during which the wood fibers may be subject to the refining action of the opposed plates 26, 27 in a refiner as shown in FIG. 1. The reservoirs filled with abrasive material may be of various groove configurations, as shown in the embodiments of FIGS. 5-9. FIG. 5 shows an alternative embodiment refiner bar 54 with a V-shaped groove 56 filled with material 58. FIG. 6 shows a refiner bar 60 with a trapezoidal groove 62 filled with material 64. The V-shaped groove 56 in the bar 54 and the trapezoidal shaped groove 62 in bar 60 are examples of other groove shapes which may be readily formed in a cast refiner plate. Fibrillation is the external disruption of the lateral bonds between surface layers of a fiber that results in partial detachment of fibers or small pieces of the outer layers of the fibers and internal or lateral bonds between the adjacent layers within the fibers. Fibrillation occurs during the mechanical refining of pulp slurries. In a disc refiner, a substantial portion of the fibrillation is thought to occur between the edges of opposed refiner plates. Paper fibers 74 undergoing refining are shown in FIG. 12. An upper bar 66 has a sharp edge 70, and a lower bar 68 has a sharp edge 72. The fibers 74 are held by the sharp edges 70, 72, and an abraiding or bruising action between the fibers takes place as the bar edges pass over each other as indicated by arrows. FIG. 13, on the other hand, illustrates how refiner bars 76 and 78, with dull edges 80, 82, tear paper fibers 84. Although it is desirable to increase the surface area of the individual fibers by the process of fibrillation so that the fibers may bond better with each other, it is not desirable to completely break the fibers. Greater surface area between paper fibers results in greater adhesion between fibers which results in stronger paper. On the other hand, shorter paper fibers means less total surface area per fiber. Shortened fibers bond with fewer other fibers than do long fibers, and the paper formed from the shortened fibers is of reduced strength. In addition, fiber fragments that are rendered too small are not retained on the forming wire of a papermaking machine and are thus lost as sludge. The dull edged refiner bars 76, 78 result in a loss of fiber and an increased cost of manufacturing paper from a given fiber stock, along with the additional detriment of producing a weaker paper. The refining mechanism of sharp edge bars 70, 72 is not completely understood, but it is thought that the sharp edges staple or hold the fibers in place as the refining action takes place. In practice it has been found difficult to maintain truly sharp edges as the refiner bars 66, 68 are subject to wear in actual use. A number of techniques for causing the bars to wear sharp have been developed. FIG. 14 illustrates an alternative approach to holding fibers 94 by the employment of rough edges 90, 92 on bars 86, 88. Thus the provision of rough edges on refiner bars can facilitate the fibrillation of wood pulp fibers. In addition, rough edged bars which require a less distinctly sharp edge may be more readily obtained. FIG. 7 shows a refiner bar 96 in cross-section. The rectangular bar 96 has an upwardly extending central member 101. Small rectangular, corner wedges 98 are formed of an abrasive or other material 99 deposited in edge channel reservoirs extending between the central member 101 and the sides of the bar 96. FIG. 7 shows how once an abrasive material 99 has been emplaced, the upper surface 100 may be ground down to form a leveled surface as required by the close positioning of opposed bars in the refiner plates. FIGS. 8 and 9 show how the refiner bar 96 may have corner wedges 102 and 104 of varying shapes. FIGS. 10 and 11 show one method of emplacing the abrasive material by the use of a flame spray gun apparatus 106 which is traversed along the bars 108 of a refiner sector 110 which may be used to make up the refiner plates 26, 28. The gun 106 sprays ceramic materials 112 into rectangular grooves 114 to form corner wedges 98. As shown in FIG. 11, the grooves 114 and the corner wedges 98 in some cases will be placed only on the leading edges 116. As shown in FIG. 14, the edges 90, 92 form leading edges of the bars 86, 88. The refining action takes place at the leading edges, and thus the leading edges are most in need of techniques for making them rough. The corner wedges 98, 102, and 104 may also be formed by the technique as set forth in U.S. Pat. No. 5,492,540 as was discussed for the formation of the abrasive material 16. Another approach to forming selected regions of refiner bars of a rough material is to choose a material which tends to wear rough. Table 1 discloses two cast alloys, chromium white iron and nickel chromium white iron (nihard) which when heat treated develop grains of abrasive carbides 120 in a matrix of softer more malleable material 122 as illustrated in FIGS. 15-19. FIG. 15 shows a material after it has been cast and heat treated. FIG. 16 shows the material after it has been exposed to a sulfuric acid etch or has been allowed to wear. As shown in FIG. 16, the softer matrix 122 has worn away to leave exposed grains 124 which form a rough edge 126. TABLE 1______________________________________MATERIAL C MN SI CR NI MO______________________________________Chromium White 2.4- 0.5-1.0 0.5-2.0 15-30 0.-2.0 0.-4.0Iron 4.0Example: 28% 2.8 0.8 1 28 -- 0.5ChromiumNickel Chromium 2.5- 0.5-1.3 0.5-.8 1.1-11 2.7-7.0 0.-.5White iron 3.7(Nihard)Example: Type 1 3.3 0.6 0.8 2 4.2 --______________________________________ Although the materials listed in Table 1 are not new in the application of the formation of refiner discs 26, 28, the materials' tendency to wear rough has proved disadvantageous because the flow channels between the bars have also worn rough and this impedes the flow of stock through the refiner plates because the flow channels tend to clog with fibers. A solution, as illustrated in FIG. 17, is to coat the side surfaces and top surface with a layer of metal or paint or plastic 132,134 which is resistant to abrasive wear, erosion or corrosion. Thus, the flow channel 128 and the sides 136 of the bars 130 are protected from wearing rough or being etched to form rough surfaces. As shown in FIGS. 17 and 18, the upper surface 138 and edges 140 of the bar 130 may be advantageously exposed by grinding the upper surface of the bar to at one time expose it and render it flat and parallel. A grinding operation to render the bars parallel is a normal part of the overall manufacturing process of a refiner plate. FIG. 19 shows an enlarged fragmentary view of the edge of the bar 130 of FIG. 18 where it can be seen how the edges of the bar tend to wear rough. It should be understood that although the improved refiner plates have been described as used with a low consistency refiner, the technique disclosed could be used to form refiner plates for use with high consistency refiners. It should also be understood that where reservoirs are described as filled with an abrasive, the abrasive could be material of other desired characteristics and could be held in place by a number of techniques, including using an adhesive to bond abrasive grit to the grooves or employing solder to bond the abrasive. It should be understood that the invention is not limited to the particular construction and arrangement of parts herein illustrated and described, but embraces such modified forms thereof as come within the scope of the following claims.

A refiner plate has bars integrally formed with the refiner plate base member which have discrete regions of selected physical properties. A material possessing the physical property is deposited in a reservoir in the bar, such as a groove. The reservoir may be positioned in the top of the bar and may be of various shapes. Alternatively, the reservoir with material is positioned on the bar leading or trailing edge. Alternatively, an abrasive surface extends over the entire upper surface of the bar including the leading and trailing edges. The bar may be formed of a white iron alloy which is heat-treated to form a soft matrix with embedded carbide grains. By protecting regions of desired smoothness with a wear-resistant protective coating flow is preserved in selected areas.

RELATED APPLICATIONS This application is a continuation of U.S. application Ser. No. 12/607,496, filed on Oct. 28, 2009, pending, which claims the benefit of U.S. Provisional Application No. 61/109,075, filed on Oct. 28, 2008, both of which are incorporated herein by reference. TECHNICAL FIELD The present disclosure relates to an expiratory treatment device, and in particular, to an oscillating positive expiratory pressure (“OPEP”) device. BACKGROUND Each day, humans may produce upwards of 30 milliliters of sputum, which is a type of bronchial secretion. Normally, an effective cough is sufficient to loosen secretions and clear them from the body's airways. However, for individuals suffering from more significant bronchial obstructions, such as collapsed airways, a single cough may be insufficient to clear the obstructions. OPEP therapy represents an effective bronchial hygiene technique for the removal of bronchial secretions in the human body and is an important aspect in the treatment and continuing care of patients with bronchial obstructions, such as those suffering from chronic obstructive lung disease. It is believed that OPEP therapy, or the oscillation of exhalation pressure at the mouth during exhalation, effectively transmits an oscillating back pressure to the lungs, thereby splitting open obstructed airways and loosening the secretions contributing to bronchial obstructions. OPEP therapy is an attractive form of treatment because it can be easily taught to most hospitalized patients, and such patients can assume responsibility for the administration of OPEP therapy throughout their hospitalization and also once they have returned home. To that end, a number of portable OPEP devices have been developed. BRIEF SUMMARY A portable OPEP device and a method of performing OPEP therapy is described herein. In one aspect, a portable OPEP device includes a housing defining a chamber, a chamber inlet configured to receive exhaled air into the chamber, a chamber outlet configured to permit exhaled air to exit the chamber, a deformable restrictor member positioned in an exhalation flow path between the chamber inlet and the chamber outlet, and an oscillation member disposed within the chamber. The deformable restrictor member and the oscillation member are moveable relative to one another between an engaged position, where the oscillation member is in contact with the deformable restrictor member and a disengaged position, where the oscillation member is not in contact with the deformable restrictor member. The deformable restrictor member and the oscillation member are also configured to move from the engaged position to the disengaged position in response to a first exhalation pressure at the chamber inlet, and move from the disengaged position to an engaged position in response to a second exhalation pressure at the chamber inlet. The first exhalation pressure is greater than the second exhalation pressure. In another aspect, the deformable restrictor member deforms in response to an intermediate exhalation pressure at the chamber inlet, and returns to a natural shape in response to the first exhalation pressure at the chamber inlet. In another aspect, the OPEP device has a biasing member positioned to bias the deformable restrictor member and the oscillation member to the engaged position. The biasing member maybe a spring. Alternatively, the biasing member may have at least one pair of magnets, wherein a first magnet of the at least one pair of magnets is connected to the oscillation member and a second magnet of the at least one pair of magnets is connected to the housing. The position of the biasing member may also be selectively moveable to adjust the amount of bias In yet another aspect, the OPEP device includes a glide surface extending from the housing into the chamber, such that the glide surface is in sliding contact about the oscillation member, and movement of the oscillation member is substantially limited to reciprocal movement about an axis of the oscillation member. In another aspect, the oscillation member includes at least one channel adapted so that the exhalation flow path is not completely restricted when the deformable restrictor member and the oscillation member are in the engaged positioned. In another aspect, the OPEP device includes a mouthpiece connected to the housing that is in fluid communication with the chamber inlet. The mouthpiece may have a cross-sectional area greater than a cross-sectional area of the chamber inlet. In yet another aspect, the housing has a first portion and a second portion, with the second portion being removably connected to the first portion. In another aspect, the OPEP device includes a respiratory portal for receiving an aerosol medicament. Additionally, the oscillation member may comprise a one-way valve configured to permit the aerosol medicament to enter the chamber through the respiratory portal, the respiratory portal being in fluid communication with the chamber inlet when the one-way valve is open. In another aspect, a method of performing oscillating positive expiratory pressure therapy is provided. The method includes passing a flow of exhaled air along an exhalation flow path defined between an inlet and an outlet of a chamber in an oscillating positive expiratory pressure device. The method also includes restricting the flow of exhaled air by maintaining a deformable restrictor member and an oscillation member disposed within the chamber in an engaged position, where the oscillation member is in contact with the deformable restrictor member, until a first exhalation pressure is reached at a chamber inlet. The method further includes unrestricting the flow of exhaled air by moving the deformable restrictor member and the oscillation member to a disengaged position, where the oscillation member is not in contact with the deformable restrictor member, until a second exhalation pressure is reached at the chamber inlet. The method also includes returning the deformable restrictor member and the oscillation member to the engaged position with a biasing force when the second exhalation pressure is reached at the chamber inlet. The first exhalation pressure may be greater than the second exhalation pressure. Finally, the method may also include deforming the deformable restrictor member in response to an intermediate exhalation pressure at the chamber inlet, and returning the deformable restrictor member to a natural shape in response to the first exhalation pressure at the chamber inlet. In another embodiment, a system for providing oscillating positive expiratory pressure therapy in combination with aerosol therapy is provided. The system includes an oscillating positive expiratory pressure apparatus having a housing defining a chamber, a chamber inlet configured to receive exhaled air into the chamber, and a chamber outlet configured to permit exhaled air to exit the chamber. The oscillating positive expiratory pressure apparatus also has an exhalation flow path defined between the chamber inlet and the chamber outlet, and an oscillation member disposed within the chamber and configured to operatively restrict a flow of exhaled air along the exhalation flow path. The oscillation member is moveable relative to the flow path between a restrictive position, where the flow of exhaled air is substantially restricted and an unrestrictive position, where the flow of exhaled air is substantially unrestricted. The oscillating positive expiratory pressure apparatus may also have a respiratory portal for receiving an aerosol medicament. The respiratory portal maybe in fluid communication with the chamber inlet. The system also includes an aerosol therapy apparatus removably connected to the respiratory portal of the oscillating positive expiratory pressure apparatus. The aerosol therapy apparatus includes an aerosol housing having an aerosol chamber for holding an aerosol medicament, and an aerosol outlet communicating with the aerosol chamber for permitting the aerosol medicament to be withdrawn from the aerosol chamber. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front perspective view of a first embodiment of an OPEP device; FIG. 2 is a side perspective view of the embodiment of FIG. 1 ; FIG. 3 is a cross-sectional side view of the embodiment of FIG. 1 , showing a deformable restrictor member and an oscillation member in an engaged position; FIG. 4 is a cross-sectional perspective view of an inlet insert shown in the embodiment of FIG. 1 ; FIG. 5 is a cross-sectional perspective view of a deformable restrictor member, or an elastic lip, shown in the embodiment of FIG. 1 ; FIG. 6 is a front perspective view of an oscillation member shown in the embodiment of FIG. 3 ; FIG. 7 is a rear perspective view of the oscillation member shown in the embodiment of FIG. 3 ; FIG. 8 is a cross-sectional side view of a second embodiment of an OPEP device, showing a deformable restrictor member and an oscillation member in an engaged position; FIG. 9 is a cross-sectional side view of the embodiment of FIG. 8 , showing the flow of air upon a user's inhalation; FIG. 10 is a cross-sectional side view of the embodiment of FIG. 8 , showing the flow of air upon a user's exhalation; FIG. 11 is a cross-sectional side view of an OPEP device connected to a nebulizer, showing the flow of an aerosol medicament upon a user's inhalation; FIG. 12 is a cross-sectional side view of the OPEP device and nebulizer of FIG. 11 , showing the flow of air upon a user's exhalation; and, FIG. 13 is a cross-sectional rear perspective view of a third embodiment of an OPEP device having a biasing member comprised of at least one pair of opposing magnets. DESCRIPTION OF THE PREFERRED EMBODIMENTS OPEP therapy is very effective within a specific range of operating conditions. For example, an adult human may have an exhalation flow rate ranging from 10 to 60 liters per minute, and may maintain a static exhalation pressure in the range of 10 to 20 cm H 2 O. Within these parameters, OPEP therapy is believed to be most effective when changes in the exhalation pressure range from 5 to 20 cm H 2 O oscillating at a frequency of 10 to 40 Hz. In contrast, an infant may have a much lower exhalation flow rate, and may maintain a lower static exhalation pressure, thereby altering the operating conditions most effective for OPEP therapy. As described below, the present invention is configurable so that ideal operating conditions may be selected and maintained. Referring to FIG. 1 , a first embodiment of an assembled OPEP device 100 is shown. The OPEP device 100 comprises a housing 102 having a front portion 104 and a rear portion 106 which together defines a chamber 108 (see FIG. 3 ). The housing 102 may be constructed of any durable material, such as a plastic or a metal. The OPEP device 100 shown in FIG. 1 is substantially spherical in shape, which provides for an easy grasp of the OPEP device 100 in the hands of a user, as well as portability. It should be appreciated, however, that the OPEP device 100 could be any shape, so long as it defines a chamber 108 capable of housing the necessary components, as described herein. Preferably, the housing 102 is openable so the chamber 108 may be accessed for cleaning and replacing components contained therein. As shown, the front portion 104 and the rear portion 106 of the housing 102 are removably connected along a joint 110 , such as by a snap fit or a threaded screw connection. The OPEP device 112 also includes a mouthpiece 112 which may either be formed as an integral part of the housing 102 or removably attached to the housing 102 . Although the mouthpiece 112 is shown as being cylindrical in shape, the mouthpiece 112 could be any number of alternative sizes or shapes to accommodate various users of the OPEP device 100 , such as children or adults. A chamber inlet 114 positioned within the mouthpiece 112 is configured to receive exhaled air into the chamber 108 . In view of the description below, it should be apparent that the cross sectional area of the chamber inlet 114 is an important variable affecting the exhalation pressure generated at the mouth of a user, and maybe modified or selectively replaced according to the desired operating conditions. A side perspective view of the OPEP device 100 is shown in FIG. 2 . The OPEP device 100 further comprises at least one chamber outlet 116 configured to permit exhaled air to exit the chamber 108 . The at least one chamber outlet 116 may comprise any number of apertures, having any shape or size. Furthermore, the at least one chamber outlet 116 maybe located elsewhere on the housing 102 . The OPEP device 100 may also include a grate 117 to prevent unwanted objects from entering housing 102 . Referring to FIG. 3 , a cross-sectional side view of the OPEP device 100 shows the internal components of the OPEP device 100 . The minimal number of components contained in the OPEP device 100 , and its relatively simple operation, make the OPEP device 100 particularly suitable for single patient use. In general, the housing 102 of the OPEP device 100 encloses an inlet insert 118 , a deformable restrictor member 120 , an oscillation member 122 , a coil spring 124 , and a glide surface 126 . As explained below, the various alternatives for each of the inlet insert 118 , the deformable restrictor member 120 , the oscillation member 122 , and the coil spring 124 provide of a highly configurable OPEP device 100 . A cross-sectional perspective view of the inlet insert 118 is shown in FIG. 4 . The inlet insert 118 is removably connectable to the housing 102 and/or mouthpiece 112 of the OPEP device 100 , and includes the chamber inlet 114 . The chamber inlet 114 may be a single narrow aperture, or alternatively, may comprise any number of apertures having any size or shape. Because the inlet insert 118 is removably connectable to the OPEP device 100 , a user may select an inlet insert 118 having the appropriate sized chamber inlet 114 for the prescribed OPEP therapy. It is important, however, that the mouthpiece 112 have a cross-sectional area greater than the cross-sectional area of the chamber inlet 114 . The inlet insert 118 is configured to be snap or compression fit within the front portion 104 of the housing 102 , which maybe accomplished while the front portion 104 and the rear portion 106 are detached. The inlet insert 118 includes an annular recess 128 for receiving a corresponding annular protrusion 130 , which may be located on a rim 131 connected to either the mouthpiece 112 or the housing 102 , as shown in FIG. 4 . Furthermore, the inlet insert 118 is shaped to fit within the spherically shaped OPEP device 100 ; however, the inlet insert 118 could be modified to fit within any other shaped OPEP device. Alternatively, the inlet insert 118 and the chamber inlet 114 may be formed as an integral part of the housing 102 or the mouthpiece 112 . The inlet insert 118 further includes an annular mounting surface 132 for supporting the deformable restrictor member 120 , as described below. Referring to FIG. 5 , a cross-sectional perspective view of the deformable restrictor member 120 , or the elastic lip, is shown. The deformable restrictor member 120 operates as a regulator of the exhalation pressure at the chamber inlet 114 . The deformable restrictor member 120 maybe constructed of an elastic material, preferably having an elasticity of at least 40 durometers (A scale). Like the inlet insert 118 , the deformable restrictor member 120 maybe any number of shapes, but is shown in FIG. 5 as being circular to fit within the spherically shaped OPEP device 100 . The deformable restrictor member 120 , or the elastic lip, generally includes an upper portion 134 , a lower portion 136 , and a reinforcing band 138 of elastic material. As shown in FIG. 3 , the upper portion 134 is configured for mounting the deformable restrictor member 120 on the mounting surface 132 and about the rim 131 , as explained above. When the front portion 104 and the rear portion 106 of the housing 102 are detached, the upper portion 134 of the deformable restrictor member 120 is mountable about the rim 131 of the inlet insert 118 , and the inlet insert 118 maybe snapped into place within the housing 102 . Once the inlet insert 118 is connected to the housing 102 , the deformable restrictor member 120 is retained by the rim 131 , the mounting surface 132 , and the front portion 104 of the housing 102 . Alternatively, the housing 102 or the mouthpiece 112 may be configured to provide the rim 131 and the mounting surface 132 for mounting and retaining the deformable restrictor member 120 . The deformable restrictor member 120 , and in particular, the lower portion 136 , is configured to deform as the exhalation pressure at the chamber inlet 114 increases. Preferably, the lower portion 136 of the deformable restrictor member 120 should be curved inward so that, as the deformable restrictor member 120 deforms, the lower portion 136 expands in a direction away from the upper portion 134 . To improve the elasticity and rigidness of the deformable restrictor member 120 , a reinforcing band 138 of elastic material maybe added to the deformable restrictor member 120 . Depending on the shape of the deformable restrictor member 120 and the desired elasticity, the reinforcing band 138 maybe omitted or located elsewhere on the deformable restrictor member 120 . Referring to FIG. 6 , a front perspective view of an oscillation member 122 is shown. In general, the oscillation member 122 includes a contact surface 140 connected to the end of a post 142 . The contact surface 140 is configured to engage the lower portion 136 of the deformable restrictor member 120 . As shown in FIGS. 3 and 6 , the contact surface 140 maybe hemispherically shaped to fit within a correspondingly shaped portion of the inlet insert 118 , or a correspondingly shaped portion of the housing 102 or mouthpiece 112 if the inlet insert 118 is omitted. Alternatively, the contact surface 140 maybe substantially flat. The contact surface 140 shown in FIG. 6 includes at least one channel 143 which traverses a portion of the contact surface 140 where the deformable restrictor member 120 and the oscillation member 122 engage one another. In this embodiment, the channels 143 are sized such that an air passage from the chamber inlet 114 to the chamber outlet 116 is maintained during both inhalation and exhalation via the space defined by the restrictor member 120 and the channels 143 . This air passage, or collection of air passages, is sized to prevent complete restriction of air flow but selected to allow sufficient build-up of pressure to provide oscillating pressure upon patient exhalation. Although the contact surface 140 is shown in FIG. 6 as having seven separate channels 143 , the contact surface 140 could include any number of channels 143 . Furthermore, the one or more channels 143 may have a variety of sizes, depending upon the desired restriction of exhaled air received from the user. Alternatively, the contact surface 140 may be fabricated without any channels 140 . Because the oscillation member 120 is removably enclosed within the housing 102 of the OPEP device 100 , a user may select an oscillation member 120 having the appropriate shape, size, or number of channels for the prescribed OPEP therapy. A rear perspective view of the oscillation member 122 is shown in FIG. 7 . The post 142 is configured for positioning about the glide surface 126 , as shown in FIG. 3 , so that the post 142 is in sliding contact with the glide surface 126 . When the post 142 is positioned about the glide surface 126 , the oscillation member 122 is substantially limited to reciprocal movement about the central axis of the oscillation member 122 . As shown in FIGS. 3 and 7 , the glide surface 126 and the post 142 are shaped as hollow cylinders, and the post 142 is sized to fit within the glide surface 126 . However, the glide surface 126 and the post 142 may have any shape, and the glide surface 126 maybe alternatively sized to fit within the post 142 . The oscillation member 122 also includes a skirt 144 for aligning a biasing member, such as the coil spring 124 , about the oscillation member 122 when the OPEP device 100 is assembled. Referring to FIG. 3 , the coil spring 124 is positioned to extend from the housing 102 and contact a lower surface 146 of the oscillation member 122 . The coil spring 124 is positioned to bias the oscillation member 122 into engagement with the deformable restrictor member 120 . Similar to the deformable restrictor member 120 and the oscillation member 122 , the coil spring 124 maybe selectively replaced with other springs have a different rigidity or number of coils to achieve the desired operating conditions for the prescribed OPEP treatment. To administer OPEP therapy using the OPEP device 100 described above, a user begins by exhaling into the mouthpiece 112 . In doing so, an exhalation flow path 148 is defined between the chamber inlet 114 and the at least one chamber outlet 116 . The exhalation pressure at the chamber inlet 114 represents a function of the flow of exhaled air permitted to traverse the exhalation flow path 148 and exit the OPEP device 100 through the chamber outlet 116 . As the exhalation pressure at the chamber inlet 114 changes, an equal back pressure is effectively transmitted to the respiratory system of the user. As shown in FIG. 3 , prior to using the OPEP device 100 , the oscillation member 122 is biased to an engaged position, where the deformable restrictor member 120 is in contact with the oscillation member 122 . In the engaged position, the exhalation flow path 148 is substantially restricted by the deformable restrictor member 120 and the oscillation member 122 . As a user exhales into the OPEP device 100 , an initial exhalation pressure at the chamber inlet 114 begins to increase, as only a fraction of the exhaled air is permitted to flow along the exhalation flow path 148 through the at least one channel 142 on the oscillation member 122 . As the exhalation pressure increases at the chamber inlet 114 to an intermediate pressure, the deformable restrictor member 120 begins to expand under the force of the increased pressure. As the deformable restrictor member 120 expands, the lower portion 136 moves in an outward direction, toward the oscillation member 122 . In the engaged position, however, the outward movement of the lower portion 136 is resisted by the oscillation member 122 , which is biased against the deformable restrictor member 120 by the coil spring 124 . As the exhalation pressure continues to increase, the deformable restrictor member 120 continues to deform until a maximum point of expansion is obtained. When the deformable restrictor member 120 obtains its maximum expansion, the exhalation pressure is also at a maximum pressure. At the maximum point of expansion, the increasing exhalation pressure causes the deformable restrictor member 120 to quickly retract, ultimately returning to its natural shape. As the deformable restrictor member 120 retracts, the deformable restrictor member 120 and the oscillation member 122 move to a disengaged position, where the deformable restrictor member 120 is not in contact with the oscillation member 122 . At that time, exhaled air is permitted to flow substantially unrestricted along the exhalation flow path 148 from the chamber inlet 114 to the chamber outlet 116 . Because the retraction of the deformable restrictor member 120 is quicker than the movement of the oscillation member 122 under the biasing force of the coil spring 124 , the deformable restrictor member 120 and the oscillation member 122 remain in the disengaged position for a short period of time, during which the exhalation pressure at the chamber inlet 114 decreases. Depending on multiple variables, including the elasticity of the deformable restrictor member 120 , the biasing force of the coil spring 124 , and the exhalation flow rate, the deformable restrictor member 120 and the oscillation member 122 may remain in the disengaged position for only a fraction of a second. After the deformable restrictor member 120 returns to its natural shape, the oscillation member 122 , under the biasing force of the coil spring 124 , moves back into an engaged position with the deformable restrictor member 120 . Then, as a user continues to exhale, the exhalation pressure at the chamber inlet 114 begins to increase, and the cycle described above is repeated. In this way, the exhalation pressure at the chamber inlet 114 oscillates between a minimum and a maximum so long as a user continues to exhale into the OPEP device 100 . This oscillating pressure is effectively transmitted back to the respiratory system of the user to provide OPEP therapy. A cross-sectional side view of a second embodiment of an OPEP device 200 is shown in FIG. 8 . Like the OPEP device 100 , a housing 202 of the OPEP device 200 encloses a deformable restrictor member 220 , an oscillation member 222 , a coil spring 224 , and a glide surface 226 . The OPEP device 200 also includes a mouthpiece 212 , a chamber inlet 214 , a chamber outlet 216 , and has an exhalation flow path 248 defined therebetween. The OPEP device 200 further comprises an adjustment plate 254 for selectively moving an end of a biasing member, such as the coil spring 224 , to adjust the amount of bias. The adjustment plate 254 is connected to at least one thumb screw 256 extending from the adjustment plate 254 to a location outside the housing 202 . In this way, a user may rotate the at least one thumb screw 256 in one direction to move both the adjustment plate 254 and an end of the coil spring 224 toward the oscillation member 222 , thereby increasing the bias. A user may rotate the at least one thumb screw 256 the opposite direction to decrease the bias. By changing the amount of bias, a user may selectively increase or decrease the resistance the oscillation member 222 applies against the deformable restrictor member 222 while in the engaged position. A change in the bias also changes the rate at which the oscillation member 222 moves from the engaged position to the disengaged position, and back to the engaged position, during the administration of OPEP therapy. The OPEP device 200 shown in FIG. 8 further comprises a respiratory portal 250 and a one-way valve 252 positioned on the oscillation member 222 . The oscillation member 222 shown in FIG. 8 omits the at least one channel and has a substantially flat contact surface 240 to accommodate the one-way valve 252 . The one-way valve 252 is configured to open as a user inhales, and permit air to enter the chamber 208 from the respiratory portal 250 , as shown in FIG. 9 . In contrast, the one-way valve 252 is closed during exhalation, as seen at one point during the administration of OPEP therapy in FIG. 10 , when the deformable restrictor member 220 and the oscillation member 222 are in the disengaged position. Referring to FIG. 11 , the respiratory portal 250 of the OPEP device 200 is also configured to receive an aerosol outlet 260 of a nebulizer 258 . The nebulizer 258 maybe removably connected to the OPEP device 200 by any suitable means for the combined administration of OPEP and aerosol therapies. Any of a number of commercially available nebulizers may be used with the OPEP device 200 . One suitable nebulizer is the AeroEclipse® II breath actuated nebulizer available from Trudell Medical International of London, Canada. Descriptions of suitable nebulizers may be found in U.S. Pat. No. 5,823,179, the entirety of which is hereby incorporated by reference herein. In this configuration, a user receives aerosol therapy upon inhalation. As seen in FIG. 11 , when a user inhales, the one-way valve 252 opens, and an aerosol medicament is drawn from the aerosol output 260 , through the respiratory 250 portal and the chamber 208 , and into the respiratory system of the user. In contrast, OPEP therapy is delivered upon exhalation. As seen in FIG. 12 , when a user exhales, the one-way valve 252 closes, the aerosol medicament is contained within the respiratory portal 250 , and the OPEP device 200 is able to deliver OPEP therapy in accordance with the method described above. A cross-sectional perspective view of a third embodiment of an OPEP device 300 is shown in FIG. 13 . In general, a housing 302 of the OPEP device 300 encloses a deformable restrictor member 320 , an oscillation member 322 having a one-way valve 352 , a glide surface 326 , and an adjustment plate 354 . The OPEP device 300 also includes a mouthpiece 312 , a chamber inlet 314 , a chamber outlet 316 , and a respiratory portal 350 . The OPEP device 300 is different from the OPEP device 200 in that it includes a biasing member comprised of at least one pair of magnets 362 . For each pair of the at least one pair of magnets 362 , one magnet is positioned on the oscillation member 322 and another magnet is positioned on the adjustment plate 354 . The magnets in each pair have opposing polarities. As such, the oscillation member 322 is biased by the at least one pair of magnets 362 into the engaged position with the deformable restrictor member 320 . During the administration of OPEP therapy, the at least one pair of magnets 362 functions in the same manner as the coil spring, as discussed above. Specifically, as a user exhales into the OPEP device 300 and the deformable restrictor member 320 expands, the at least one pair of magnets 362 resist the movement of oscillation member 322 . After the deformable restrictor member 320 has reached its maximum point of expansion and quickly returned to its natural shape, the at least one pair of magnets 362 bias the oscillation member 322 from the disengaged position back to the engaged position. Furthermore, like the OPEP device 200 , the amount of bias supplied by the at least one pair of magnets 362 may be adjusted by rotating the at least one thumb screw 356 , thereby moving the adjustment plate 354 and the magnets positioned thereon closer to the magnets positioned on the oscillation member 322 . The foregoing description of the inventions has been presented for purposes of illustration and description, and is not intended to be exhaustive or to limit the inventions to the precise forms disclosed. It will be apparent to those skilled in the art that the present inventions are susceptible of many variations and modifications coming within the scope of the following claims.

An oscillating positive expiratory pressure apparatus having a housing defining a chamber, a chamber inlet, a chamber outlet, a deformable restrictor member positioned in an exhalation flow path between the chamber inlet and the chamber outlet, and an oscillation member disposed within the chamber. The deformable restrictor member and the oscillation member are moveable between an engaged position, where the oscillation member is in contact with the deformable restrictor member and an disengaged position, where the oscillation member is not in contact with the deformable restrictor member. The deformable restrictor member and the oscillation member move from the engaged position to the disengaged position in response to a first exhalation pressure at the chamber inlet, and move from the disengaged position to an engaged position in response to a second exhalation pressure at the chamber inlet.

This application is a continuation of international application serial number PCT/EP99/09177, filed Nov. 24, 1999. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an architecture, for a transmitter in a mobile communications system and particularly, but not exclusively, to an architecture for a base-station transmitter which supports frequency-hopping in a TDMA environment. 2. Description of the Related Art At present in Europe a GSM standard operates for transmission of information in the mobile communication network. According to that standard, information is transmitted in a sequence of time slots, each time slot having the possibility of being allocated a different carrier frequency for modulating the information to be transmitted. The GSM standard requires that transmitters in base station transceivers can switch their frequency (frequency-hop) between consecutive time slots. This has been achieved according to a known transmitter architecture by providing a so-called “ping-pong” synthesizer which generates different frequencies on a time slot basis. While this technique works, it requires high isolation between the synthesizers which is difficult to achieve. BRIEF SUMMARY OF THE INVENTION According to the present invention there is provided a transmitter for transmitting RF data in an RF communication network using a plurality of carrier frequencies, the transmitter comprising: a data splitter for receiving an information signal at an intermediate frequency lower than the carrier frequency; and two transmitter paths each having an input connected to the data splitter and each having a frequency modulator for upconverting the intermediate frequency to a respective carrier frequency, the carrier frequency being individually selectable for each transmitter path. BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the present invention and to show how the same may be carried into effect the invention will now he described, by way of example only, with reference to the accompanying drawings in which: FIG. 1 is a block diagram showing the principle components of a known transmitter system used in a base-station; FIG. 2 is a block diagram showing a number of separate transmitter paths in the transmitter; FIG. 3 illustrates part of a signal transmitted by one of the transmitter paths; FIG. 4 illustrates the format of a signal transmitted by the transmitter as a whole; FIG. 5 illustrates the construction of a time slot; FIG. 6 is a block diagram illustrating a known frequency hopping control in a transmitter path; FIG. 7 is a block diagram showing the components of a transmitter path according to the present invention; and FIG. 8 is a timing diagram of a time slot in a transmission signal generated by a transmission path. DETAILED DESCRIPTION OF THE INVENTION FIG. 1 is a block diagram of a transmission system 10 for an RF communications system such as that for a mobile telephone network. Such a transmission system may be utilised, for example, at a base-station for the communications network or within mobile stations communicating with the base-station. A data input signal DATA, which may be in analog format, is supplied to the system from a data generator (not shown). The input signal may contain voice information or any other such information which is required to be transmitted. The input signal is fed into a data interface 2 which performs the necessary encoding etc. to generate an information signal 1 for transmission. The precise details depend on the nature of the communications system. The information signal 1 is supplied to a mixer 3 to which there is also supplied an intermediate frequency signal generated by an I.F. generator 4 . The mixer 3 mixes the two signals such that the output therefrom is an intermediate frequency signal i.f modulated by the information signal. In essence, therefore, the information signal is up-converted from the base-band to an intermediate frequency. The up converted information signal i.f. is then amplified by an amplifier 5 and is supplied to a second mixer 6 . A local oscillator 7 generates a radio frequency carrier signal f c which is fed into the second mixer 6 . The carrier frequency fc is selectable by a controller 8 within a transmission band which may lie, for example, between 935.2 MHz and 9598 MHz. The information signal i.f and the carrier signal f c are mixed and output as a transmission signal TX. The transmission signal thus comprises the carrier signal f c modulated by the information signal i.f. Again, in essence the information signal is further up-converted to radio frequencies to facilitate transmission. A pre-amplifiers 9 amplifies the transmission signal to a level to enable the signal to be transmitted via land line to an antenna station 11 , which may be situated remote from the base station 10 , without the signal being attenuated to such an extent that it becomes unusable. Such an antenna station may comprise an antenna and a power amplifier which amplifies the transmission signal to levels which allow the signal to be transmitted as electromagnetic radiation over large distances. Once amplified by the power amplifier, the transmission signal is fed to the antenna as an output signal from where it is radiated out as electromagnetic radiation. Usually, of course, such a transmitter is required to be capable of transmitting to more than one mobile unit simultaneously. To achieve this, a base station transmitter is able to transmit many signals simultaneously at different frequencies. The total bandwidth allocated to the communications network is divided into discrete carrier frequencies (124 in GSM) at 200 KHz intervals. In order to generate these different frequencies, the base-station transmitter further comprises a number of so-called transmitter paths T 1 etc. as shown in FIG. 2 . Each of the transmission paths in FIG. 2 has the components of the transmitter 10 in FIG. 1 . Each transmitter path is capable or generating signals at frequencies different to the other transmitter paths. Furthermore, each transmitter path can usually vary its transmission frequency such that it can generate signals at all of the discrete carrier frequencies if required. As is known in the art, a TDMA system provides for a particular mobile unit to have access to a particular transmission frequency for a limited period of time (a time slot), so that a communication channel is established by reference to a particular times slot. The signal transmitted by the transmitter path is of a form generally illustrated by FIG. 3 . The signal consists of a sequence of frames (A, B, C. . . ). Each frame is sub-divided into 8 time periods called time-slots (0-7). Each time slot (0-7) contains data for one mobile unit. Subsequent data for that mobile unit will, under typical circumstances, be sent in the same time slot in subsequent frames. Thus, time slot 0 in frame A may contain data for mobile G unit MB 0 . Time slot 0 in frame B will then also contain data for mobile unit MB 0 , as will time slot 0 in frames C, D, E . . . etc. This allocation of time slot 0 to mobile unit MB 0 may continue until such time as the connection to mobile unit MB 0 is terminated. The internal clocks of the base station and the mobile unit MB 0 are synchronised such that the mobile unit MB 0 always and only listens for data during time slot 0 of any frame. In other words, the communication channel between the base station and the mobile unit MB 0 are only “open” during its allocated time slot. Similar considerations apply to communication channels with mobile units allocated to other time slots. FIG. 4 illustrates conceptually the structure of data transmitted by the base station transmitter. The transmitter path T 1 has allocated to it the Channel group 1 comprising 8 mobile units MB 0 -MB 7 . It transmits a signal made up of a sequence of frames (A, B, C . . . ) each frame being divided into 8 time slots ( 0 - 7 ) containing data for one of the 8 mobile units. The transmitter path T 2 has allocated to it the Channel Group 2 comprising a further 8 mobile units MB 8 -MB 15 . It transmits a signal (simultaneously but on a different frequency to that of the transmitter path T 1 ) made up of a sequence of frames A, B, C . . . but with each time slot ( 0 - 7 ) containing data for one of its own mobile units MB 8 -MB 15 . As described above, the base station transmitter may be made up of a large number of transmitter paths, some or all of which (depending on the volume of “traffic”) may be transmitting signals simultaneously on different frequencies. The data contained in each time slot is usually made up of several parts as shown in FIG. 5 . The data may comprise: TAIL BITS (TB)—two groups of 3 bits for control/reset purposes, ENCRYPTED BITS—two groups of 58 bits represented transmitted data, TRAINING SEQUENCE—a fixed bit pattern of 26 bits used in generating a channel response, GP denotes the guard space (of 8.25 bits, 30.46 μs in described example) to allow for time/distance propagation delays owing to cell size. FIG. 8 shows a timing diagram of a signal transmitted by a single transmitter path. Each time slot has a time span of 577 μis in the described example. Within each time slot the transmitted signal is firstly “ramped up” to a specified level during the first 28 μs of the time slot. Then the data is transmitted at that level over the following 542.8 μs (147 bits). Finally, the signal is “ramped down” over the subsequent 28 μs. The following time slot is transmitted in a similar way. Part of the GSM requirements are that the communications system must be capable of frequency -hopping. As the name implies, frequency-hopping is the ability to change the transmit frequency of any particular channel at regular intervals. Such frequency-hopping is primarily used to provide a level of security for transmitted signals and to prevent unauthorised parties from “eavesdropping” on mobile telephone transmissions. Frequency hopping may occur between consecutive frames or consecutive time slots. In any event, a frequency change needs to be effected between time slot 7 of frame A and time slot 0 of Frame B. Referring back to FIGS. 2 and 3 , each transmitter path is capable of transmitting signals at different frequencies. In order to provide frequency-hopping, the transmitter path changes the frequency at which it transmits after each time slot. Thus, time slot 0 in frame A may be transmitted by transmitter path T 1 at a frequency f 0 . Time slot 1 of frame A may then be transmitted at a frequency f 1 . Similarly, time slot 2 in frame A may be transmitted at a frequency f 2 and so on. Time slot 0 of frame B may subsequently be transmitted at a frequency f n where n is a number other than (in this case) O, i.e. the frequency at which time slot 0 is transmitted in any frame must be different from the frequency at which it was transmitted in the previous frame. The manner in which the frequencies of each time slot vary is specified in GSM and is determined by an algorithm and controlled by a frequency controller. The varying of the frequencies at which data for a single mobile unit is transmitted ensures that it becomes very difficult for any unauthorised receiver to lock onto the correct signal in order to eavesdrop. FIG. 6 shows a system which provides frequency-hopping in a base station transmitter. As illustrated, the components within the box T 1 represent the transmitter path T 1 shown in FIG. 2 . Each transmitter path comprises a data input into which is fed a data signal DATA containing data to be transmitted (e.g. speech). The data signal, which may be in an analog form, is then sent through a data interface 50 which may be represented by an analog to digital convertor, which encodes the signal such that it is suitable for transmission. The data interface 50 outputs the signal as the information signal i. As described with reference to FIG. 1 , the information signal i is mixed with an intermediate frequency signal f i generated by an I.F generator 52 (up converted) to produce information signal i.f. and then amplified by an amplifier AMP 2 . In order to provide hopping between different transmission frequencies, each transmission path is provided with two local oscillators or synthesizers (S 1 , S 2 ) which are variable in frequency, The two synthesizers S 1 and S 2 are operable to generate radio frequency carrier signals which are mixed with the information signal i by mixer M 3 before transmission. The outputs of the synthesizers are input to a switch SW 1 which provides for the connection of either S 1 or S 2 (but not both simultaneously) to the mixer M 3 in a so-called ping-pong arrangement. An attenuator A 0 is connected downstream of the mixer M 3 and upstream of a filter F 0 . In operation, when transmitter path T 1 (for example) is transmitting time slot 0 in frame A, synthesizer S 1 generates a carrier signal C 0 at a frequency f 0 . Switch SW 1 , under the control of a timing control unit TC 1 , switches to allow S 1 to be connected to mixer M 3 . In this manner, the information signal i.f. (containing data for a particular mobile unit) is mixed with the carrier signal C 0 to produce the transmission signal TX 0 associated with time slot 0 in frame A. At the same time, the synthesizer S 2 tunes itself to a different frequency f 1 to be used for transmitting time slot 1 in frame A. As described above, the frequency to which S 2 tunes is determined by an algorithm in conjunction with the frequency control unit FC. After transmitting the data in time slot 0 , the timing control unit TC 1 then switches to allow the synthesizer S 2 , generating a carrier signal C 1 at frequency f 1 , to be connected to the mixer M 3 . The information signal i.f (now containing information to be transmitted to a different mobile unit) is mixed with the carrier signal C 1 to produce the transmission signal TX 1 associated with time slot 1 . Once again, during the period in which synthesizer S 2 is connected to the mixer via switch SW, synthesizer S 1 tunes itself to a different frequency f 2 to be used for transmitting time slot 2 in frame A, determined by an algorithm in conjunction with frequency control unit FC. This process is repeated for subsequent time slots and subsequent frames. A major problem with the architecture employed by systems such as those of FIG. 6 is that the switch SW 1 must provide a very high degree of isolation between synthesizers S 1 and S 2 . If, within the switch, the connections from S 1 and S 2 are not sufficiently isolated, then interference and phase distortion will occur between the two signals. This interference corrupts the transmission signal. In practice, isolation between the connections of S 1 and S 2 must be provided to a level of around 90 dB in order to prevent these problems. Switches which provide this level of isolation are complex and expensive. FIG. 7 shows an architecture for a transmitter path which aims to address this problem. A data input is connected to a data interface. This interface may be an analog to digital convertor operable to perform a suitable encoding process and has an output to a mixer M 0 . The output of mixer M 0 is connected to a data splitter or switch DS which itself is connected to a timing control unit TC 2 . The Data splitter DS has two outputs, the lines L 1 and L 2 . The line L 1 is connected to a first mixer M 1 . The first mixer M 1 is connected to the synthesizer S 1 and is operable to mix the information signal on the line L 1 with a carrier signal generated by the synthesizer S 1 . The output of the first mixer M 1 is connected to an attenuator A 1 , the output of which is connected to an amplifier AMP 1 . The output of the amplifier AMP 1 is connected to a second attenuator A 2 , the output of which is connected to a power combiner PC. The Line L 2 is connected to a second mixer M 2 . The second mixer M 2 is connected to the synthesizer S 2 and is operable to mix the information signal on the line L 2 with a carrier signal generated by the synthesizer S 2 . The output of the mixer M 2 is connected to an attenuator A 3 , the output of which is connected to an amplifier AMP 2 . The output of the amplifier AMP 2 is connected to a second attenuator A 4 , the output of which is connected to the power combiner PC. The output of the power combiner PC represents the transmission signal which is to be transmitted. Synthesizers S 1 and S 2 are each connected to a frequency control unit FC. Although in FIG. 8 the frequency control units connected to the synthesizers S 1 and S 2 are shown as separate components, they may be provided as a single unit as in FIG. 7 . The attenuators A 1 -A 4 are each connected to a power control unit PC 1 . In operation, data to be transmitted is input to the data interface in a similar manner to the system described above. The data interface performs a suitable encoding process on the data and outputs the data as an information signal i. The information signal is fed to the mixer M 0 which mixes it with an intermediate frequency signal f i generated by an intermediate frequency generator G 1 . The up converted information signal i.f is then fed to the data splitter DS which supplies the information signal to lines L 1 and L 2 . It may be advantageous to switch the information signal such that it is output either on the line L 1 or the line L 2 under control of the timing control unit TC 2 . If the transmitter path T 1 (for example) is to transmit time slot 0 in frame A, the synthesizer S 1 generates an RP carrier signal C 0 at a frequency f 0 . The information signal is output on the line L 1 to the first mixer M 1 . In this manner, the information signal is mixed with the carrier signal C 0 to produce the transmission signal TX 0 associated with time slot 0 . The transmission signal TX 0 is passed through the attenuators A 1 and A 2 and the amplifier AMPl to the power combiner PC. The power combiner PC outputs the transmission signal as the signal to be transmitted in time slot 0 . Simultaneously, the frequency control unit FC sends a signal to the synthesizer S 2 to tune itself to generate an RF carrier signal C 1 at a different frequency f 1 to be used for transmitting time slot 1 in frame A. As in the conventional system, the frequency to which the synthesizer S 2 tunes is determined by an algorithm in conjunction with the frequency control unit FC. Also at this time, the power control unit PC 1 controls the attenuators A 3 and A 4 such that any signal being generated by synthesizer S 2 are attenuated to a low level at the input to the power combiner PC compared to those signals generated by the synthesizer S 1 . After transmitting the data in time slot 0 , the transmitter path T 2 can be used to transmit time slot 1 . The data splitter outputs the information signal, containing information to be transmitted in time slot 1 , on line L 2 to the mixer M 2 . In this manner, the information signal is mixed with the carrier signal C 1 generated by the synthesizer S 2 at a frequency f 1 to produce the transmission signal TX 1 associated with time slot 1 . During the period in which time slot 1 is being transmitted, the synthesizer frequency control FC sends a signal to the synthesizer S 1 to tune itself to a different frequency f 2 . As before, the frequency to which the synthesizer S 1 tunes itself is determined by an algorithm. Also during this period, the power control unit PC 1 controls the attenuators A 1 and A 2 such that any signals being generated by the synthesizer S 1 are attenuated to a low level when they reach the power combiner PC compared to the signals which are generated by the synthesizer S 2 . This process is repeated for subsequent time slots and subsequent frames. It can be seen that in the above described embodiment an advantage resides in providing two separate branches within each transmitter path along which to transmit the information signal. With such an architecture, the carrier signals generated by the synthesizers S 1 and S 2 only come into close proximity with each other in the power combiner PC. At this point, however, at least one of the signals is attenuated to a low level compared with the other such that interference between the two signals in low. The power combiner, therefore, needs only to provide a low level of isolation within the power combiner which can be achieved easily and inexpensively. The second transmitter path branch replaces the expensive switches which are normally needed to provide isolation. In addition to providing inherent isolation between the synthesizers, the architecture also provides simplified power control. Each branch of the transmitter path operates on alternate time slots. This allows for the full use of the guard periods for ramp up and ramp down used in the transmitter. Furthermore, the second branch provides a higher level of redundancy, and hence reliability, for each transmitter path. The architecture itself is suitable for integration to an Application Specific Integrated Circuit (ASIC). In this regard, it may be possible to incorporate this structure into the ASICs currently used in mobile units.

A transmitter for transmitting RF data in an RF communication network using a plurality of carrier frequencies is described. The transmitter has a data splitter for receiving an information signal at an intermediate frequency lower than the carrier frequency, and two transmitter paths each having an input connected to the data splitter and each having a frequency modulator for upconverting the intermediate frequency to a respective carrier frequency, the carrier frequency being individually selectable for each transmitter path.

CROSS-REFERENCE TO RELATED APPLICATION [0001] The present application claims priority to and incorporates by reference the entire contents of Japanese Patent Application No. 2015-255087, filed in Japan on Dec. 25, 2015. BACKGROUND [0002] 1. Related Technical Fields [0003] Related technical fields include network devices, methods, and programs that identify similar users based on physiological characteristics to predict expense trends. [0004] 2. Related Art [0005] Services are present that analyze information about users in relation to the user's asset management so as to introduce asset management methods suitable for the users. [0006] As an example of techniques relating to such services, a technique about a system is known that can efficiently perform simulation to support making a financial plan using the Internet. A conventional technique is described in Japanese Patent Application Laid-open No. 2002-41808, for example. SUMMARY [0007] It is, however, difficult for the conventional technique to provide a user with appropriate information about the user's future plan. For example, the conventional technique only provides the user with a result of the simulation about the asset at various stages in the user's life. The user, thus, obtains only a plan for managing income and expense under a specific situation. As a result, the user does not always obtain appropriate information about asset formation based on a comprehensive viewpoint such as whether a current tendency in expense is appropriate in the user's future life plan, for example. [0008] Exemplary embodiments of the broad inventive principles described herein at least partially solve the problems in the conventional technology. [0009] Network devices, methods, and programs according to exemplary embodiments access a memory that stores expense information for each of a plurality of subjects, the expense information for each of the plurality of subjects being associated with a stored subject profile that identifies physiological characteristics of a corresponding one of the subjects. The devices, methods, and programs receive a user profile from a user terminal via a network interface, the user profile identifying physiological characteristics of the user and an age of the user, and compare the physiological characteristics of the received user profile with the physiological characteristics in each stored profile to identify one of the plurality of subjects having similar physiological characteristics to the user. The devices, methods, and programs analyze the stored expense information that is associated with the identified subject in the memory to determine a trend of the expense of the identified subject, and generate a proposal including a predicted future expense trend for the user based on the determined trend and the user's age. The devices, methods, and programs then transmit the generated proposal to the user terminal via the network interface. [0010] The above and other objects, features, advantages and technical and industrial significance will be better understood by reading the following detailed description of exemplary embodiments, when considered in connection with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0011] FIG. 1 is a schematic diagram illustrating an example of generation processing according to an embodiment; [0012] FIG. 2 is a schematic diagram illustrating an exemplary structure of a generation device according to the embodiment; [0013] FIG. 3 is a schematic diagram illustrating an example of a genetic test result table according to the embodiment; [0014] FIG. 4 is a schematic diagram illustrating an example of a settlement information storage unit according to the embodiment; [0015] FIG. 5 is a flowchart illustrating a processing procedure according to the embodiment; [0016] FIG. 6 is a schematic diagram illustrating an example of generation processing according to a modification; [0017] FIG. 7 is a schematic diagram illustrating an exemplary structure of the generation device according to the modification; [0018] FIG. 8 is a schematic diagram illustrating an example of an attribute information table according to another modification; and [0019] FIG. 9 is a hardware structural diagram illustrating an example of a computer that achieves the functions of the generation device. DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS [0020] The following describes an embodiment of a generation device, a generation method, and a program stored on a computer-readable storage medium in detail with reference to the accompanying drawings. (As used herein the term “storage medium” is not intended to encompass transitory signals.) The following embodiments do not necessarily limit the broader inventive principles for which protection is sought. In the following respective embodiments, the same components are denoted by the same reference numerals and duplicated explanations thereof are omitted. 1. Example of Generation Processing [0021] The following describes an example of generation processing according to the embodiment with reference to FIG. 1 . FIG. 1 is a schematic diagram illustrating an example of the generation processing according to the embodiment. With reference to FIG. 1 , an aspect of the generation processing according to the embodiment is described using a generation system 1 as an example. Specifically, with reference to FIG. 1 , an example of the generation processing is described in which a generation device 100 , which is a server, included in the generation system 1 identifies a similar user who is a user similar to a user serving as the processing object, and generates information indicating a trend of income or expense of the identified similar user. [0022] As illustrated in FIG. 1 , the generation system 1 includes a user terminal 10 and the generation device 100 . The devices (the user terminal 10 and the generation device 100 ) included in the generation system 1 are coupled to each other via a communication network such as the Internet (not illustrated) in a communicable manner. The number of each of the devices included in the generation system 1 is not limited to that illustrated in FIG. 1 . For example, the generation system 1 may include a plurality of user terminals 10 . [0023] The user terminal 10 is an information processing device used by a user. Specifically, the user terminal 10 is used for transmitting certain information to the generation device 100 or receiving information transmitted from the generation device 100 . The user terminal 10 is achieved by a mobile terminal such as a smartphone, a tablet terminal, or a personal digital assistant (PDA), a desktop personal computer (PC), or a notebook PC. In the example illustrated in FIG. 1 , the user terminal 10 is a smartphone used by a user U 01 . In the following explanation, the user terminal 10 is described as the user U 01 in some cases. The user U 01 , thus, can be replaced with the user terminal 10 in the following explanation. [0024] The generation device 100 is a server that provides certain information to the user terminal 10 . Specifically, the generation device 100 identifies the similar user who is a user similar to the user U 01 under a certain condition on the basis of information received from the user terminal 10 . The generation device 100 acquires information about income or expense of the user U 01 and the similar user. The generation device 100 generates information that indicates a trend of income or expense of the similar user on the basis of the acquired information. Specifically, the generation device 100 generates comparison information that indicates a comparison of the trend of income or expense between the user U 01 and the similar user, and provides the generated comparison information to the user U 01 . The information about income or expense is a concept widely including information such as an amount of income, an amount of expense, a breakdown of income or expense, information about an income-expense balance, a difference between income and expense, and an amount of savings derived from balance information. The information about income or expense is described as “asset information” in the present specification in some cases. [0025] The generation device 100 may generate a proposal (recommendation) to the user U 01 together with the comparison information. For example, the generation device 100 generates a proposal relating to actions that the user U 01 could perform in the future. The actions are derived from the comparison of the trend of the asset information about the user U 01 and the trend of the asset information about the similar user. For an exemplary proposal, the generation device 100 indicates an amount of expense the user U 01 is assumed to need for payments in the future and proposes actions relating to the asset management that the user could perform in the future for covering the assumed amount of expense. The generation device 100 generates the proposal relating to the asset formation of the user U 01 on the basis of the trend of the asset information about the similar user, thereby giving certain guidance to the user U 01 for preparing future assets. The following describes a flow of the generation processing performed by the generation device 100 with reference to FIG. 1 . FIG. 1 illustrates medical expense as an example of the amount of expense the user U 01 is assumed to need for payments in the future. [0026] The generation device 100 requests the user U 01 to provide information about the user U 01 as information used for identifying the user who is similar to the user U 01 . For example, the generation device 100 requests the information about health of the user U 01 . The generation device 100 analyzes the information about the health of the user U 01 ' and information about health of another user, determines similarity between the users, and identifies the user who is similar to the user U 01 . [0027] In the embodiment, the generation device 100 requests, as the information about the health of the user U 01 , a result of a genetic test the user U 01 already underwent. The user U 01 transmits the result of the genetic test that the user U 01 already underwent to the generation device 100 via the user terminal 10 (step S 11 ). [0028] The result of the genetic test that the user U 01 underwent includes types of diseases the user U 01 tends to develop and risk values that are values indicating possibilities of developing diseases. In the example illustrated in FIG. 1 , the genetic test result of the user U 01 includes the risk value of developing diabetes is “1.7” while the risk value of developing “high blood pressure” is “2.9.” In the result of the genetic test that the user U 01 underwent, when the risk value corresponding to a type of disease exceeds “2.0,” the possibility (a degree of risk) of developing the disease is determined to be “high.” The determination means that the risk of developing the disease is high, i.e., the possibility of developing the disease is high. When the risk value is between “1.5” and “2.0” in the genetic test result, the possibility of developing the disease is determined to be “medium.” The determination means that the risk of developing the disease is medium, i.e., the possibility of developing the disease is not high enough to be that of the disease determined to be a “high” risk but the possibility of developing the diseases is relatively high. [0029] The generation device 100 receives the genetic test result transmitted from the user terminal 10 and stores the received genetic test result in a genetic test result table 122 . The generation device 100 stores, in the genetic test result table 122 , not only the genetic test result of the user U 01 but also the respective genetic test results transmitted from other users. [0030] When receiving the genetic test result of the user U 01 , the generation device 100 performs processing that identifies a user who is similar to the user U 01 (step S 12 ). Specifically, the generation device 100 compares the types of diseases and the risk values of the respective diseases between the user U 01 and other users. For example, the generation device 100 extracts the genetic test result for each of the other users when the types of diseases included in the genetic test result of the user are same as those included in the genetic test result of the user U 01 , and the percentage of the same disease types is a certain percentage (e.g., 80% or more). The generation device 100 further extracts the genetic test result out of the extracted genetic test results when the degrees of the risks, which are indicated with the risk values of the respective diseases, in the extracted genetic test result are the same as those included in the genetic test result of the user U 01 , and the percentage of the same degrees of risks is a certain rate. The generation device 100 identifies the users corresponding to the extracted genetic test results as the users who are similar to the user U 01 . [0031] In the example illustrated in FIG. 1 , the generation device 100 identifies a user U 02 as the user who is similar to the user U 01 . The user U 02 is a user who underwent the genetic test in which risks of many same diseases as the genetic test that the user U 01 underwent are tested, and many items in whose genetic test result match those in the genetic test result of the user U 01 . For example, the user U 02 was diagnosed that a degree of risk of diabetes is “medium” and a degree of risk of high blood pressure is “high” in the genetic test result. [0032] The user U 01 provides information about assets of the user U 01 to the generation device 100 after transmitting the genetic test result. For example, the user U 01 periodically provides, to the generation device 100 , information about an amount of monthly expense and a breakdown of the amount of expense. In this case, the user U 01 may transmit the information about the assets of the user U 01 by itself or provide information (asset information) about income and expense by providing, to the generation device 100 , an authority allowing access to data indicating the breakdown of the expense (e.g., a use history of a credit card or logs of interaction with financial institutions). The asset information provided by the user U 01 is not limited to the information after the transmission of the genetic test result. The user U 01 may provide asset information before the transmission of the genetic test result. The generation device 100 successively stores the asset information provided from the user U 01 in a settlement information storage unit 125 . [0033] The user U 02 periodically provides the asset information about the user U 02 to the generation device 100 because the user U 02 is also a user serving as the processing object of the generation device 100 besides the user U 01 . The user U 02 is older than the user U 01 and has provided asset information to the generation device 100 for a longer period of time than the user U 01 . The past information at the time when the user U 02 was of the same age as the user U 01 now, is thus, stored in the settlement information storage unit 125 as the asset information about the user U 02 . [0034] The generation device 100 generates information to be presented to the user U 01 on the basis of the acquired asset information (step S 13 ). Specifically, the generation device 100 generates the comparison information that indicates a comparison of a trend of the asset information about the user U 01 and a trend of the asset information about the user U 02 , who is a similar user. In the example illustrated in FIG. 1 , the generation device 100 generates the comparison information using the information about medical expense, which is an example of the asset information, in the expense of the users U 01 and U 02 . [0035] For example, the generation device 100 generates comparison information 30 illustrated in FIG. 1 . As illustrated in FIG. 1 , the comparison information 30 includes a graph 32 that indicates a comparison of the trend of the asset information between the users U 01 and U 02 . In the graph 32 , the age of the user U 01 and the amount of medical expense paid at each age are indicated with the broken line titled “your (user U 01 's) medical expense.” In the graph 32 , the age of the user U 02 and the amount of medical expense paid at each age are indicated with the broken line titled “similar user's (user U 02 's) medical expense.” The ordinate axis of the graph 32 represents the amount of medical expense in unit of ten thousand yen. The generation device 100 generates the comparison information 30 that indicates transition in the amounts of medical expense of the user U 01 and the user U 02 who is similar to the user U 01 as the information to be presented to the user U 01 . [0036] Furthermore, the generation device 100 may generate a proposal to the user U 01 as information included in the comparison information 30 . For example, the generation device 100 compares a trend of the amount of medical expense of the user U 01 from the past to the present and a tendency of the amount of medical expense of the user U 02 when the user U 02 was of the same age as the user U 01 . The generation device 100 obtains information that the user U 01 is predicted to need to pay a larger amount of medical expense than the current amount a few years later as a result of referring to the tendency of the medical expense of the user U 02 . For example, the generation device 100 refers to an amount of savings of the user U 01 in the asset information acquired from the user U 01 and calculates a difference between the amount of savings of the user U 01 and the amount of medical expense when the user U 02 was of the same age as the user U 01 for each of the age of the user U 01 in the future. As a result, the generation device 100 obtains information how much amount of money the user U 01 should save for another few more years. Using the information, the generation device 100 generates, as a proposal to the user U 01 , information about actions such as saving money corresponding to the difference calculated from the amount of medical expense paid by the user U 02 or take out insurance that covers high risk diseases. The generation device 100 may include the generated proposal in the comparison information 30 as the information displayed together with the graph 32 . [0037] The generation device 100 transmits the information such as the generated comparison information 30 to the user terminal 10 to notify the user U 01 of the generated information (step S 14 ). The user U 01 refers to the comparison information 30 displayed in the user terminal 10 , thereby making it possible to obtain information about such as the trend of the amount of medical expense for each age of the user U 02 who underwent the genetic test result similar to that of the user U 01 . When the comparison information 30 includes the proposal generated by the generation device 100 , the user U 01 can grasp the amount of medical expense predicted to be needed for payments in the future or know actions that should be taken in preparation for the future. [0038] As described above, the generation device 100 according to the embodiment identifies the user U 02 who is a user having similarity to the user U 01 who is the processing object under a certain condition. The generation device 100 acquires the asset information about the user U 01 and the identified user U 02 . The generation device 100 generates the comparison information that indicates the comparison of the trend of the acquired asset information about the user U 01 and the trend of the acquired asset information about user U 02 . [0039] Specifically, the generation device 100 according to the embodiment identifies the user U 02 who is the similar user using the similarity to the genetic test result acquired from the user U 01 as the certain condition. The generation device 100 can generate the comparison information 30 that indicates an amount of medical expense assumed to be paid by the user U 01 in the future on the basis of the asset information acquired from the users U 01 and U 02 . The generation device 100 notifies the user U 01 of the generated information, thereby making it possible to transmit, to the user U 01 , the trend of the amount of medical expense of the user U 02 who has the genetic test result similar to that of the user U 01 . As a result, the user U 01 can obtain certain guidance with regard to expenses containing many uncertain factors in the future such as medical expense. The generation device 100 can provide the user U 01 with appropriate information about the future plan. [0040] In the example illustrated in FIG. 1 , the user U 02 is the user who is similar to the user U 01 . The generation device 100 may extract not only the user U 02 but also a plurality of similar users as the users who are similar to the user U 01 . The generation device 100 may present the trend of the asset information statistically obtained from the multiple similar users as the object compared with the trend of the asset information about the user U 01 . The generation device 100 , thus, can generate the information that compares the trend of the averaged asset information obtained from a number of samples with the trend of the asset information about the user U 01 , thereby making it possible to provide comparison information having high reliability to the user U 01 . In the example illustrated in FIG. 1 , the trend of the asset information about the user U 01 and the trend of the asset information about the similar user are displayed together in the graph 32 included in the comparison information 30 . The display manner is, however, not limited to this example. The generation device 100 may generate the information that indicates only the trend of the asset information about the user U 02 instead of the information about the comparison between the users U 01 and U 02 . This information also enables the user U 01 to know the trend of the asset information about the user U 02 who is a similar user, thereby making it possible for the user U 01 to obtain useful information about the future plan of the user U 01 . 2. Structure of Generation Device [0041] The following describes a structure of the generation device 100 according to the embodiment with reference to FIG. 2 . FIG. 2 is a schematic diagram illustrating an exemplary structure of the generation device 100 according to the embodiment. As illustrated in FIG. 2 , the generation device 100 includes a communication unit 110 , a storage unit 120 , and a control unit 130 . The generation device 100 may include an input unit (e.g., a keyboard or a mouse) that receives various types of operation from an administrator, for example, who uses the generation device 100 , and an output unit (e.g., a liquid crystal display) that outputs various types of information. [0042] The communication unit 110 is achieved by a network interface card (NIC), for example. The communication unit 110 is connected to a communication network in a wired or wireless manner, and exchanges information between itself and the user terminal 10 via the communication network. [0043] The storage unit 120 is achieved by a semiconductor memory element such as a random access memory (RAM) or a flash memory, or a storage device such as a hard disk drive or an optical disc drive. The storage unit 120 according to the embodiment includes a user information storage unit 121 and the settlement information storage unit 125 . The following describes the respective storage units one by one. [0044] The user information storage unit 121 stores therein user information that indicates risks relating to the users. In the embodiment, the user information storage unit 121 includes the genetic test result table 122 as one of the data tables that store therein the user information. [0045] The genetic test result table 122 stores therein the information about the genetic test results. FIG. 3 illustrates an example of the genetic test result table 122 according to the embodiment. As illustrated in FIG. 3 , the genetic test result table 122 includes items such as “user ID,” “analysis item,” “risk value,” and “degree of risk.” [0046] The “user ID” indicates identification information to identify the user. In the embodiment, the user ID is in common with the reference sign used in the description. For example, a user having a user ID of “U 01 ” is the “user U 01 .” [0047] The “analysis item” indicates the item analyzed in the genetic test. The analysis item is represented using the name of a disease, for example. The “risk value” indicates a value obtained by quantifying the risk of developing a disease corresponding to the analysis item. [0048] The “degree of risk” indicates a result obtained by determining the risk of developing a disease on the basis of the risk value. In the embodiment, the analysis item having a risk value lower than “1.5” is determined to be “low” in the degree of risk. This determination indicates that a risk of a user developing the disease corresponding to the analysis item is lower than the disease corresponding to the analysis item having “high” or “medium” in the degree of risk. The analysis item having a risk value higher than “2.0” is determined to be “high” in the degree of risk. This determination indicates that a risk of a user developing the disease corresponding to the analysis item is extremely high. The analysis item having a risk value from “1.5” to “2.0” is determined to be “medium” in the degree of risk. This determination indicates that a risk of a user developing the disease corresponding to the analysis item is higher than the disease corresponding to the analysis item having “low” in degree of risk and lower than the disease corresponding to the analysis item having “high” in degree of risk. [0049] FIG. 3 illustrates the genetic test result that the user U 01 identified by the user ID “U 01 ” underwent as an example. The genetic test result shows that the analysis items in the test are “diabetes,” “high blood pressure,” “hay fever,” and “gout,” for example, and the risk values are “1.7,” “2.9,” “1.6,” and “1.2,” respectively, and the degrees of risks are “medium,” “high,” “medium” and “low,” respectively. [0050] As for the degrees of risks illustrated in FIG. 3 , the generation device 100 may employ the standard represented by a company conducting the genetic test or the standard determined uniquely by the generation device 100 on the basis of the risk values of the genetic test results. For example, the generation device 100 may acquire the risk values of the genetic test results and statistical information about the number of users who actually developed the diseases, learn a relation therebetween, and uniquely determine the degrees of risks. [0051] The settlement information storage unit 125 stores therein information (settlement logs) about settlement. FIG. 4 illustrates an example of the settlement information storage unit 125 according to the embodiment. As illustrated in FIG. 4 , the settlement information storage unit 125 includes items such as “user ID,” “age,” “collection time,” “expense item,” and “amount.” [0052] The “user ID” corresponds to the same item illustrated in FIG. 3 . The “age” indicates the age of the user. FIG. 4 illustrates the ages as “AA,” “XX,” and so on in a conceptual manner. Practically, the age of the user when the settlement log is stored, is stored in the item of “age.” [0053] The “collection time” indicates the time when the user performs the expenditure. The “expense item” indicates the breakdown of the expense. The “amount” indicates the amount of expense for each expense item. [0054] FIG. 4 illustrates information stored in the settlement information storage unit 125 as the settlement log relating to the user U 01 . The information indicates that the amount of the “medical expense” is “ 30 , 000 ” yen and the amount of the “food expense” is “30,000” yen out of the expense items collected on November 2015 when the user U 01 was “AA” years old. [0055] In the example illustrated in FIG. 4 , the amount of expense is collected on a monthly basis. The collection manner of the amount of expense to be stored is, however, not limited to the example. For example, an amount of annual expense or a cumulative amount of expenses may be stored for each user in the settlement information storage unit 125 . [0056] The control unit 130 is achieved by various programs (corresponding to an example of a generation program) stored in an internal storage device of the generation device 100 , the various programs being executed by a central processing unit (CPU) or a micro processing unit (MPU) using a RAM as a working area, for example. The control unit 130 is achieved by an integrated circuit such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA). [0057] As illustrated in FIG. 2 , the control unit 130 according to the embodiment includes an acquisition unit 131 , an identification unit 132 , a generation unit 133 , and a notification unit 134 , and achieves or generates functions and operation of the information processing described below. The internal structure of the control unit 130 is not limited to that illustrated in FIG. 2 and may be any other structure that performs the information processing described below. The connection relation among the respective processing units included in the control unit 130 is not limited to that illustrated in FIG. 2 and may be another connection relation. [0058] The acquisition unit 131 acquires various types of information. The acquisition unit 131 acquires the user information about the user as the information used for identifying the user who has similarity to the user serving as the processing object under a certain condition, for example. The acquisition unit 131 acquires information about the health of the user as an example of the user information. Specifically, the acquisition unit 131 acquires, as the user information, a result of the genetic test the user already underwent. [0059] The acquisition unit 131 acquires, from the user serving as the processing object, the information (asset information) about the income or expense of the user. Specifically, the acquisition unit 131 acquires, as the asset information, the settlement information about such as an amount of expense paid by the user or the breakdown of the expense. The acquisition unit 131 may acquire, as the asset information, an amount of the user's income or an amount of the user's savings, for example. [0060] The acquisition unit 131 may acquire various types of information used for the generation processing, which is described later. For example, when recommending the user to take out insurance covering diseases as the information proposed to the user, the acquisition unit 131 acquires information about the insurance. The acquisition unit 131 may acquire the information by receiving input from the administrator of the generation device 100 or by receiving the information from a company providing the insurance. The acquisition unit 131 may acquire information about a definition used for the processing, such as how the similarity is determined under which condition in the genetic test results of a plurality of users or what kind of proposal is generated. [0061] The acquisition unit 131 stores the acquired information in the respective storage units. For example, the acquisition unit 131 stores the acquired user information in the user information storage unit 121 . For another example, the acquisition unit 131 stores the acquired asset information in the settlement information storage unit 125 . The acquisition unit 131 does not necessary store the acquired information in the storage unit 120 but may send the acquired information directly to the respective processing units used for the processing. [0062] The identification unit 132 identifies the similar user who is a user having similarity to the user serving as the processing object under a certain condition. For example, the identification unit 132 identifies the similar user by determining similarity in the user information acquired from the user. [0063] When the acquisition unit 131 acquires the genetic test result from the user, the identification unit 132 identifies, as the similar user, a certain user who satisfies a condition of the genetic test result being similar to that of the user. For example, the identification unit 132 determines whether the genetic test result of a certain user has similarity to the genetic test result of the user serving as the processing object using a matching percentage of the items (types of diseases) analyzed in the genetic test result and a matching percentage of the degrees of risks of the analyzed items in the genetic test result of the certain user. Specifically, the identification unit 132 determines the genetic test result having similarity on the basis of that the matching percentage of the items analyzed in the genetic test result is 80% or more and the matching percentage of the degrees of risks of the analyzed items is 80% or more. The identification unit 132 , thus, can identify, as the similar users, the users who probably develop the same disease on the basis of the genetic test results. The value of the matching percentage can be changed to any value. For example, the identification unit 132 may perform the identification processing on a plurality of users, perform certain learning processing after the identification processing, and determine an appropriate value for the matching percentage. [0064] The generation unit 133 generates information that indicates a trend of the income or expense of the similar user on the basis of the information acquired by the acquisition unit 131 . The generation unit 133 generates the comparison information that indicates a comparison of the trend of income or expense between the user and the similar user, for example. When the acquisition unit 131 acquires, as the information about income or expense, information about the amount of expense with a classification in which the breakdown of the expense is classified into certain items, the generation unit 133 generates the comparison information about the trend of the amount of expense for each certain item. Practically, the generation unit 133 generates the comparison information 30 that indicates the comparison of the amount of medical expense between the user and the similar user as illustrated in FIG. 1 . [0065] When the acquisition unit 131 acquires the information (asset information) about the income or expense of a plurality of similar users, the generation unit 133 may generate the comparison information about the trend of the asset information about the user and the trend of the asset information statistically obtained from the multiple similar users. [0066] The generation unit 133 may generate a proposal to the user together with the comparison information notified to the user. For example, the generation unit 133 calculates an assumed amount of medical expense of the user in the future, and generates, as the proposal, the information about actions to secure money for the medical expense in the future. Specifically, the generation unit 133 generates the proposal that indicates actions (e.g., save money or make an investment) relating to the asset formation performed by the user and insurance the user should take out, for example. The generation unit 133 may generate a proposal that indicates a specific amount such as a proposal of how much amount of expense the user should reduce or a proposal of a slight increase in an amount of expense being acceptable. [0067] When generating a proposal to the user, the generation unit 133 may use definition information that indicates contents of proposed actions. The definition information is generated by the administrator of the generation device 100 and held in the generation device 100 , for example. The definition information includes a definition used for the processing such as a definition in which an action proposed to the user is “to save money” when a certain difference is present between an amount of expense of the user serving as the processing object and an amount of the expense of the similar user when the similar user was of the same age as the user. The generation device 100 can generate an appropriate proposal to the user in accordance with the definition information. The definition information may be appropriately amended or changed by the administrator, for example, of the generation device 100 or by the generation device 100 . Information about types of insurance (insurance covering diseases) proposed to the user or an appropriate investment destination based on an assumed amount of medical expense may be stored as the definition information. [0068] The notification unit 134 makes notification of various types of information. For example, the notification unit 134 transmits the information generated by the generation unit 133 to the user terminal 10 to notify the user of the trend of the asset information about the similar user. Specifically, the notification unit 134 transmits the comparison information generated by the generation unit 133 to the user terminal 10 to notify the user of the information that indicates the comparison of the asset information between the user and the similar user. [0069] The notification unit 134 notifies the user of the information that indicates the comparison of the trend of the asset information between the users U 01 and U 02 as represented by the graph 32 in the comparison information 30 illustrated in FIG. 1 , for example. When the information generated by the generation unit 133 includes a proposal to the user, the notification unit 134 notifies the user of the generated proposal. For example, the notification unit 134 notifies the user of a proposal that encourages the user to save more money on the basis of the comparison of current asset information about the user and the asset information about the similar user when the similar user was of the same age as the user. The user can obtain guidance for actions that the user could perform by referring to the information via the user terminal 10 . 3. Processing Procedure [0070] The following describes a procedure of the processing performed by the generation device 100 according to the embodiment with reference to FIG. 5 . FIG. 5 is a flowchart illustrating a processing procedure performed by the generation device 100 according to the embodiment. [0071] As illustrated in FIG. 5 , the acquisition unit 131 of the generation device 100 determines whether a genetic test result is received from a user as the user information (step S 101 ). If no genetic test result is received (No at step S 101 ), the acquisition unit 131 stands-by until the reception of the genetic test result. [0072] If the acquisition unit 131 receives the genetic test result (Yes at S 101 ), the identification unit 132 identifies a user whose genetic test result is similar to that of the user (step S 102 ). [0073] The generation unit 133 generates the comparison information about the comparison of the user serving as the processing object and the user identified by the identification unit 132 (step S 103 ). The generation unit 133 generates a proposal to the user (step S 104 ). The notification unit 134 transmits the information generated by the generation unit 133 to the user, thereby notifying the user of the information (step S 105 ). [0074] The generation unit 133 does not have to generate a proposal to the user in case of notifying the user only of the comparison information about the comparison of the trend of the asset information. In this case, the processing at step S 104 is skipped. 4. Modifications [0075] The generation device 100 according to the embodiment may be implemented in various forms besides the embodiment. The following describes other embodiments of the generation device 100 . 4-1. Attribute Information [0076] In the embodiment described above, the generation device 100 generates the comparison information on the basis of the genetic test result acquired from the user. The generation device 100 may further acquire detailed information about the user as the user information to generate the comparison information. The following describes the generation processing with reference to FIG. 6 . [0077] FIG. 6 is a schematic diagram illustrating an example of the generation processing according to a modification. In the example illustrated in FIG. 6 , the user U 01 who uses the user terminal 10 further provides detailed information about the user U 01 to the generation device 100 together with the genetic test result. The generation device 100 generates the comparison information on the basis of the information provided from the user U 01 . [0078] As illustrated in FIG. 6 , the user terminal 10 transmits the user information serving as the information about the user U 01 (step S 21 ). The user information transmitted from the use terminal 10 is attribute information that indicates attributes of the user U 01 , for example. The attribute information about the user U 01 is the information that indicates a family structure, an academic history, an annual income, an occupation, or a residential area, for example. [0079] The generation device 100 acquires the attribute information about the user U 01 transmitted from the user terminal 10 . The generation device 100 stores the acquired attribute information in an attribute information table 123 . The generation device 100 specifies a similar user on the basis of the attribute information about the user U 01 (step S 22 ). [0080] For example, the generation device 100 extracts other users having attribute information including the same items as the attribute information about the user U 01 . Examples of the items include the family structure, the academic history, the annual income, the occupation, and the residential area. The generation device 100 identifies a user as the similar user when the certain number or more of items in the attribute information of the user are the same as those of the attribute information about the user U 01 , for example. The generation device 100 may further identify a user who has the attribute information more similar to that of the user U 01 out of the extracted users who are similar to the user U 01 and are extracted on the basis of the genetic test results illustrated in FIG. 1 . [0081] The generation device 100 generates, as the information to be presented to the user U 01 , comparison information 34 about the comparison of the user U 01 and the similar user identified at step S 22 (step S 23 ). [0082] In FIG. 6 , the comparison information 34 generated by the generation device 100 includes a graph 36 . As illustrated in FIG. 6 , the graph 36 includes an amount of income of the similar user in addition to the amount of your (user U 01 's) expense and an amount of expense of the similar user. In this way, the generation device 100 acquires the attribute information from the user serving as the processing object, thereby generating the comparison information 34 including more information than that of the comparison information 30 illustrated in FIG. 1 . [0083] The generation device 100 transmits the information such as the generated comparison information 34 to the user terminal 10 to notify the user U 01 of the generated information (step S 24 ). As a result, the user U 01 can browse the comparison information including not only the amount of expense but also the comparison of the attribute information between the user U 01 and the other user. [0084] When the generation device 100 according to the modification acquires the information about the attributes of a user, and the information about the acquired attributes of the user and the information about the attributes of another user have similarity, the generation device 100 may perform processing in such a mariner that the other user is identified as the similar user. [0085] The generation device 100 acquires, as the user information, not only the genetic test result but also the attribute information about the user U 01 , thereby making it possible to identify the user who is similar to the user U 01 on the basis of the acquired information. For example, a difference occurs, in some cases, in the trend of an amount of income or expense of a user who is similar to the user U 01 in the genetic test result depending on whether the residential area of the user who is similar to the user U 01 in the genetic test result is a city or a countryside. The generation device 100 according to the modification identifies the user using further the attribute information about the user U 01 , thereby making it possible to accurately identify the user who is similar to the user U 01 . As a result, the user U 01 can obtain the comparison information about the comparison with an appropriate similar user as a further reference to the asset formation of the user U 01 in the future. [0086] The following describes a structure of the generation device 100 according to the modification. FIG. 7 is a schematic diagram illustrating an exemplary structure of the generation device 100 according to the modification. As illustrated in FIG. 7 , the generation device 100 according to the modification further includes the attribute information table 123 in addition to the structure of the generation device 100 illustrated in FIG. 1 . [0087] The attribute information table 123 is one of the data tables included in the user information storage unit 121 . The attribute information table 123 stores therein the information about the attribute information about the user. FIG. 8 illustrates an example of the attribute information table 123 according to the modification. As illustrated in FIG. 8 , the attribute information table 123 includes items such as “user ID,” “attribute,” and “content.” [0088] The “user ID” corresponds to the same item illustrated in FIG. 3 . The “attribute” indicates the type of attribute information about the user. The “content” indicates the content of each type of the attribute information. [0089] FIG. 8 illustrates the attribute information about the user U 01 as an example of the information stored in the attribute information table 123 . In the example, types of attribute information such as “gender,” “age,” “family structure,” “academic history,” “annual income,” “occupation,” and “residential area” are stored. The contents of the respective types of attribute information about the user U 01 indicate that the gender is “male,” the age is “AA,” the family structure is “single,” the academic history is “graduate of BBB university,” the annual income is “5,000,000” yen, the occupation is “CCC,” and the residential area is “DDD.” [0090] The generation device 100 according to the modification can determine similarity between users or generate the comparison information about the attribute information using the attribute information about the respective users stored in the attribute information table 123 . 4-2. Condition Setting [0091] In the embodiment described above, the generation device 100 identifies the similar user of the user serving as the processing object on the basis of conditions such as similarity to the genetic test result and similarity to the attribute information. The generation device 100 may preliminarily receive a condition from the user serving as the processing object and identify the similar user serving as the comparison object. [0092] For example, the user transmits, to the generation device 100 , a condition of a user (hereinafter described as a “designated user”) who is the target person, i.e., a person the user wants to compare with. Specifically, the user sets a similar user who has an amount of savings more than “10,000,000” yen at the age of “50 years old” among the similar users as a condition of the designated user who will be the comparison object of the user, and transmits the condition to the generation device 100 . The generation device 100 receives the condition from the user, and extracts the designated user who matches the condition out of the similar users. The generation device 100 generates the comparison information about comparison of the asset information between the designated user and the user serving as the processing object. [0093] In this case, the user can know the trend of the asset information about the designated user who has an amount of savings more than 10,000,000 yen at 50 years old as the generated information. The user, thus, can check how the designated user, who achieves the target set by the user, formed the asset that the user aims to build up in addition to the similarity with regard to the genetic test result. As a result, the user can obtain the information that is more useful for the user's future plan. 4-3. User Information [0094] In the embodiment described above, the generation device 100 acquires, as the user information, the genetic test result and information about the attribute information. The user information acquired by the generation device 100 is, however, not limited to the examples. For example, the generation device 100 may use various types of information as the user information as long as the various types of information include the information capable of identifying a similar user. For example, the generation device 100 may use a result of a medical examination that the user U 01 underwent as the user information instead of the genetic test result. 4-4. Display of Risk [0095] In the embodiment described above, a risk of the user developing a certain disease is indicated by the risk value or the degree of risk evaluated in three stages such as “high,” “medium,” and “low.” The generation device 100 , however, does not have to use such displays when determining or evaluating the risk. For example, the generation device 100 may indicate whether the possibility of the user U 01 developing a certain disease is higher or lower than those of other general users with a percentage or rate. 5. Others [0096] In the processes described in the embodiment, all or a part of the processes described to be automatically performed can also be manually performed. Alternatively, all or a part of the processes described to be manually performed can also be automatically performed by known methods. In addition, the processing procedures, the specific names, and information including various types of data and parameters described in the above description and drawings can be changed as required unless otherwise specified. [0097] Furthermore, the components of the devices illustrated in the drawings are functionally conceptual ones, and are not always required to be physically configured as illustrated in the drawings. That is, specific forms of distributions and integrations of the devices are not limited to those illustrated in the drawings. All or a part of the devices can be configured to be functionally or physically distributed or integrated in arbitrary units in accordance with various loads, the usage states, and the like. [0098] For example, the user information storage unit 121 and the settlement information storage unit 125 , which are illustrated in FIG. 2 , do not have to be included in the generation device 100 but may be included in an external storage server. In this case, the generation device 100 accesses the storage server to acquire the user information and the settlement information. [0099] The generation device 100 may be separated into a front-end server side that primarily executes processing relating to external devices such as receiving the user information from the user terminal 10 , and a back-end server side that executes internal processing such as generating the comparison information, for example. 6. Hardware Structure [0100] The generation device 100 according to the embodiment is achieved by a computer 1000 having the structure illustrated in FIG. 9 , for example. FIG. 9 is a hardware structural diagram illustrating an example of the computer 1000 that achieves the functions of the generation device 100 . The computer 1000 includes a CPU 1100 , a RAM 1200 , a read only memory (ROM) 1300 , a hard disk drive (HDD) 1400 , a communication interface (I/F) 1500 , an input-output interface (I/F) 1600 , and a media interface (I/F) 1700 . [0101] The CPU 1100 operates on the basis of a program stored in the ROM 1300 or the HDD 1400 , and controls the respective components. The ROM 1300 stores therein a boot program executed by the CPU 1100 when the computer 1000 is booted, and programs dependent on the hardware of the computer 1000 , for example. [0102] The HDD 1400 stores therein programs executed by the CPU 1100 and data used by the programs, for example. The communication I/F 1500 receives data from other apparatuses via a communication network 500 and sends the data to the CPU 1100 . The communication I/F 1500 transmits data generated by the CPU 1100 to other apparatuses via the communication network 500 . [0103] The CPU 1100 controls an output device such as a display or a printer and an input device such as a keyboard or a mouse via the input-output I/F 1600 . The CPU 1100 acquires data from the input device via the input-output I/F 1600 . The CPU 1100 outputs generated data to the output device via the input-output I/F 1600 . [0104] The media I/F 1700 reads a program or data stored in a recording medium 1800 and provides it to the CPU 1100 via the RAM 1200 . The CPU 1100 loads the program in the RAM 1200 from the recording medium 1800 via the media I/F 1700 and executes the loaded program. The recording medium 1800 is an optical recording medium such as a digital versatile disc (DVD) or a phase change rewritable disc (PD), a magneto-optical recording medium such as a magneto-optical disc (MO), a tape medium, a magnetic recording medium, or a semiconductor memory. [0105] For example, when the computer 1000 functions as the generation device 100 , the CPU 1100 of the computer 1000 executes the generation program loaded in the RAM 1200 to achieve the functions of the control unit 130 . The HDD 1400 stores therein the various types of data in the storage unit 120 . The CPU 1100 of the computer 1000 , which reads the programs from the recording medium 1800 and executes them, may acquire the programs from another device via the communication network 500 . 7. Advantages [0106] As described above, the generation device 100 according to the embodiment includes the identification unit 132 , the acquisition unit 131 , and the generation unit 133 . The identification unit 132 identifies the similar user who is a user having similarity to the user serving as the processing object under a certain condition. The acquisition unit 131 acquires the information about income or expense of the similar user identified by the identification unit 132 . The generation unit 133 generates the information that indicates a trend of the income or expense of the similar user on the basis of the information acquired by the acquisition unit 131 . [0107] The generation device 100 according to the embodiment identifies the similar user who is similar to the user and generates the information that indicates a trend of income or expense of the identified similar user. The generation device 100 , thus, can give certain guidance to the user for concerns including many items the user hardly foresees such as the asset formation in the future. As a result, the generation device 100 can provide the user with appropriate information about the user's future plan. [0108] The acquisition unit 131 acquires the information about income or expense of the user. The generation unit 133 generates the comparison information that indicates a comparison of the trend of income or expense between the user and the similar user. [0109] The generation device 100 according to the embodiment generates the information about the comparison of the similar user and the user when generating the information about the income or expense of the similar user. The user, thus, receives the information that allows the user to check at a glance the comparison of the settlement information and the trend of the assets between the user and the similar user. As a result, the user can more clearly obtain the information about the asset formation. The generation device 100 can provide the user with appropriate information about the user's future plan. [0110] The acquisition unit 131 acquires the information about the health of the user. When the information about the health of the user acquired by the acquisition unit 131 and the information about the health of another user have similarity, as a certain condition, the identification unit 132 identifies the other user as the similar user. [0111] The generation device 100 according to the embodiment uses the information about the health of the users, when determining similarity between the users. The generation device 100 , thus, can provide the user with appropriate information about the trend of medical expense, which contains many uncertain factors, out of the expense of the user in the future. [0112] The acquisition unit 131 acquires the genetic test result of the user. When the genetic test result of the user acquired by the acquisition unit 131 and the genetic test result of another user have similarity, as a certain condition, the identification unit 132 identifies the other user as the similar user. [0113] The generation device 100 according to the embodiment acquires the genetic test result as a specific example of the user information. The genetic test highly accurately detects characteristics relating to the health of the user, such as a constitution that easily develops diseases. The generation device 100 uses the genetic test result, thereby making it possible to determine similarity with extremely high accuracy. The generation device 100 , thus, can generate the comparison information about the comparison of the user and the similar user who is assumed to tend to be more similar to the user, thereby making it possible to more appropriately provide the user with guidance for the user's asset formation in the future. [0114] The acquisition unit 131 acquires the genetic test result in which the degrees of the risks are indicated for the respective types of diseases. The identification unit 132 identifies another user as the similar user on the basis of the matching percentages of the types of diseases and the degrees of the risks corresponding to the types of diseases that are included in the genetic test results of the user and the other user. In other words, the identification unit 132 determines the similarity between the genetic test result of the user and the genetic test result of the other user on the basis of the matching percentages of the types of diseases and the degrees of the risks corresponding to the types of diseases that are included in the genetic test results. [0115] The generation device 100 according to the embodiment determines the similar user on the basis of the types of diseases the analysis results of which are indicated and the degrees of the risks corresponding to the types of diseases in the genetic test result. As a result, the generation device 100 can accurately identify a similar user. [0116] The acquisition unit 131 acquires, as the information about income or expense, the information about the amounts of expense of the user and the similar user. The generation unit 133 generates the comparison information that indicates a comparison of the trend of the amount of expense between the user and the similar user. [0117] The generation device 100 according to the embodiment can generate, on the basis of the actual result of the similar user, the information capable of serving as certain guidance for the expense in the future, which is uncertain information for the user. As a result, the generation device 100 can provide the user with appropriate information about the user's future plan. [0118] The acquisition unit 131 acquires the information about the amount of expense the breakdown of which is classified into certain items. The generation unit 133 generates the comparison information that indicates a comparison of the trend of the amount of expense for each certain item between the user and the similar user in the information about the amounts of expense of the user and the similar user. [0119] As a result, the generation device 100 can provide the user with the more detailed information about the expense indicated for respective expense items. The generation device 100 , thus, can provide the user with useful information about the user's future plan. [0120] The acquisition unit 131 acquires the information about income or expense of a plurality of similar users. The generation unit 133 generates the comparison information that indicates a comparison of the trend of income or expense of the user and the trend of income or expense statistically obtained from the multiple similar users. [0121] The generation device 100 according to the embodiment generates the comparison information about the trend of income or expense from not only data of a specific person but also data statistically obtained from a plurality of samples. As a result, the generation device 100 can provide the user with appropriate comparison information suppressing inclinations. [0122] The generation unit 133 generates, as the information included in the comparison information, a proposal for the user's actions on the basis of the comparison of the trend of income or expense between the user and the similar user. [0123] The generation device 100 according to the embodiment can generate a proposal to the user in addition to the comparison information. As a result, the generation device 100 can provide the user with appropriate information about the user's asset formation. [0124] The generation unit 133 generates, as the proposal for the user's actions, the proposal for the asset management performed by the user or the proposal for insurance the user should take out. [0125] The generation device 100 according to the embodiment can provide the user with information useful for the user's future such as a proposal that can be used as a factor to determine whether the user should save money or make an investment, and a proposal for an insurance according to the types of diseases. [0126] The acquisition unit 131 acquires the information about the attributes of the user. When the information about the attributes of the user acquired by the acquisition unit 131 and the information about the attributes of another user have similarity, as a certain condition, the identification unit 132 identifies the other user as the similar user. [0127] The generation device 100 according to the embodiment may identify the similar user on the basis of not only the information about the health such as the genetic test result but also the information about the attributes of the user. As a result, the generation device 100 can increase the accuracy in identifying the similar user. As a result, the generation device 100 can provide the user with the comparison information about the comparison with the similar user assumed to be more similar to the user. [0128] The identification unit 132 identifies the designated user who is a user matching a condition designated by the user out of similar users. The acquisition unit 131 acquires the information about income or expense of the designated user identified by the identification unit 132 and the information about income or expense of the user. The generation unit 133 generates the comparison information that indicates a comparison of the trend of the income or expense between the user and the designated user on the basis of the information acquired by the acquisition unit 131 . [0129] The generation device 100 according to the embodiment may receive any condition from the user, and identify, as the designated user, a user who matches the condition. The generation device 100 , thus, can generate the comparison information that allows the user to refer to the information about income or expense of the other user who achieves the condition that the user aims for, for example. As a result, the generation device 100 enables the user to obtain the information more useful for the future plan. [0130] The embodiments are described in detail with reference to the accompanying drawings as a way of example. The broad inventive principles can be implemented in other embodiments changed or modified on the basis of the knowledge of the persons skilled in the art besides the embodiments described herein. [0131] The generation device 100 may be achieved by a plurality of server computers. The structure thereof can be changed flexibly. For example, some functions are achieved by calling external platforms using an application programming interface (API) or a network computing system. [0132] The above-described embodiments have an advantage of providing the user with appropriate information about the user's future plan. [0133] Although the inventive principles have been presented in the context of specific exemplary embodiments for a complete and clear disclosure, the appended claims need not be limited by those examples and should be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.

Network devices, methods, and programs identify similar subjects based on physiological characteristics to predict income and expense trends. The devices, methods, and programs receive a user profile from a user terminal via a network interface, the user profile identifying physiological characteristics of the user and an age of the user, and compare the physiological characteristics of the received user profile with physiological characteristics in stored subject profiles to identify a subject having similar physiological characteristics to the user. The devices, methods, and programs analyze expense information that is associated with the identified subject to determine a trend of the expense of the identified subject, and generate a proposal including a predicted future expense trend for the user based on the determined trend and the user's age. The devices, methods, and programs then transmit the generated proposal to the user terminal via the network interface.

BACKGROUND OF THE INVENTION DSA (Digital Subtraction Angiography) and other angiographic tests based on computer images are being used for diagnosis of vascular and tumorous diseases. In such angiographic tests, in inserting a catheter from a puncture hole in a blood vessel into a target artery, the front end of the catheter must be freely moved in the direction of travel and along curves by applying an external force on the hand side in a remote control fashion. In recent years, it has been required to perform not only a selective operation for inserting a catheter into a primary branch of the aorta but also a super-selective operation for inserting a catheter into secondary and tertiary branches of said primary branch. Thus, a higher technique and rich experience have become indispensable for said remote control. To secure the remote controllability (torque controllability), it has been common practice to resort to selection of a material for catheters. That is, if such material of a catheter is soft (highly flexible), it is difficult to effect remote control on the hand side. Thus, as suggested by Japanese Utility Model Application Laid-Open Specification No. 500013/1985 (International Application PCT/US 83-864) and Japanese Patent Application Laid-Open No. 218966/1983, excluding a predetermined short region on the front end side where softness is required in view of stability of a catheter, the entire portion on the hand side is reinforced by steel wire mesh or is constructed in the form of a double tube made of materials having different entire portion on the hand side is rigid with reduced flexibility, thereby giving torque controllability to the catheter. Making catheters slender is an adverse factor for said torque controllability, making it difficult to secure safety for remote control. For this reason, there has not been established an operating method for inserting a catheter through a puncture hole in the brachial artery, which is thin and long, for angiographic tests; at present, angiographic tests with respect to the general artery are conducted by inserting a catheter through a puncture hole in the femoral artery, which is thick. However, it may be said that said controllability for catheters with respect to blood vessels can be secured by simultaneously using a catheter introducing guide wire which is highly flexible and which will not form a fixed bend (a so-called bending habit) even if subjected to an operating external force, said guide wire being inserted into a catheter and operated for piloting the catheter. In other words, unlike the technique resorting to the selection of a material for catheters, this idea is to look to a guide wire for torque controllability and, as it were, to reflect the controllability of the guide wire on the catheter. In the case where such special technique is adopted, if the entire portion on the hand side is made rigid as by double-tube construction or steel wire mesh, this arrangement will destroy the superior flexibility that the guide wire possesses. That is, in inserting a catheter into a puncture hole in the brachial artery, since, anatomically, the region extending from the sub-clavian artery via the aortic arch to the downwardly extending artery is sharply bent at less than 90 degrees, the catheter, even if made rigid, will form a corresponding bending habit under the action of body heat. Further, in inserting a catheter into a puncture hole in the femoral artery, if this artery is abnormally bent or deformed owing to severe arteriosclerosis, the catheter inserted therein is heated by body heat and forms a bending habit corresponding to such abnormal bend. As a result, the guide wire expected to guide the catheter correctly is "defeated" by the catheter and its inherent torque controllability is impaired, so that the catheter cannot be correctly operated until it reaches the target artery. Further, the more rigid the catheter material, the more strongly the catheter is urged against the blood vessel wall when it is retained in the blood vessel. As a result, the danger of formation of a thrombus or occlusion of blood vessel taking place increases. In brief, when it is desired to utilize the torque controllability of a guide wire to be used for remote-controlling a catheter, it is preferable that the main portion of the catheter be made soft with high flexibility, since this makes it possible to precisely reflect the free movement of the catheter introducing guide wire; thus, the performance of the guide wire can be efficiently and reasonably developed. On the other hand, a catheter is a medical instrument for injecting a contrast agent into a target artery. If, however, its front end portion is made soft with high flexibility, as in the known example described above, the front end portion of the catheter is subjected to the pressure under which the contrast agent is injected, swinging to and fro, with the result that the control agent cannot be injected into the target artery correctly and without loss and concentratedly. In this connection, even if a superior DSA apparatus by which target locations can be graphically represented with diagnostic contrast agent, there would be the danger of said contrast agent being misdirected. In the case where it is desired to effect plastic working to provide an intrinsic bend suitable for the primary, secondary and tertiary branches of the artery so as to provide the front end portion of the catheter with the pilot function for inserting the catheter into a blood vessel, the softer the front end portion, the more difficult it is to form such bend in a stable manner. Thus, so long as the above-described technique of inserting and operating a catheter to be used simultaneously with a guide wire is adopted, it is preferable that the front end portion of the catheter have the necessary minimum of rigidity (low flexibility). It goes without saying that the necessary minimum means a degree which does not hurt the blood vessel wall nor impair the torque controllability of the guide wire. It appears that a catheter for angiography meeting the necessary conditions described above has not been developed yet. SUMMARY OF THE INVENTION The present invention has for its object the provision of a catheter for angiography which meets such demand. Thus, a first object of the invention is to provide an arrangement wherein while a catheter as a whole possesses a degree of flexibility which allows the catheter to follow the bending of an introducing guide wire, the main portion thereof in the region to be introduced into a blood vessel is made softer with high flexibility than its front end portion which is shorter than said main portion, whereby the movement of the guide wire is precisely reflected so that the catheter efficiently follows the movement thereof, with the torque controllability of the guide wire being developed to a maximum, and there is no danger that when the catheter changes direction or stays in a blood vessel, it forms a bending habit, not impeding the blood flow though it contacts the blood vessel wall, thus contributing to prevention of formation of a thrombus. A second object is to provide an arrangement wherein the front end portion in the remaining region to be introduced into a blood vessel is made rigid with low flexibility, so that the front end portion of the catheter is hardly subjected to the reaction force due to spouting of a contrast agent and while maintaining a stable attitude, the catheter enables the contrast agent to be injected into a target artery correctly and without loss and concentratedly, and wherein in the case where an intrinsic bend suitable for various branches of the aorta is to be formed so as to provide the front end portion of bend can be made stably and plastically deformed. A third object of the invention is to provide an arrangement wherein the main portion of the catheter is made soft with high flexibility and the controllability of a guide wire for introducing the same is utilized, thereby making it possible to make the catheter itself slender and hence selective and super-selective operation of catheter in connection with the trans-brachial artery (which is thin) catheterization technique. Other objects of the present invention, together with the concrete construction of the invention, will become more apparent from the following description of preferred embodiments. BRIEF DESCRIPTION OF THE INVENTION FIG. 1 is an external view, partly cut away, of a catheter for angiography according to the present invention; FIG. 2 is an external view, also partly cut away, of a catheter introducing guide wire to be simultaneously used with the catheter; FIG. 3 is a fragmentary enlarged sectional view; FIG. 4 is a fragmentary developed enlarged sectional view; FIGS. 5 through 7 are sectional views showing various modifications of catheters corresponding to FIG. 4; and FIG. 8 (I), (II) and (III) are sectional views showing the steps of insertion of a catheter into a blood vessel. DESCRIPTION OF THE PREFERRED EMBODIMENTS In an external view shown in FIG. 1, a catheter for angiography according to the invention is collectively indicated by the numeral 10 and it is made from a synthetic resin having suitable degrees of bursting strength and flexibility, such as polyamide elastomer, polyurethane elastomer, polyester elastomer or polyethylene, into a tube form, the proximal end portion thereof on the hand side having an on-off valve 12 for contrast agent injection connected thereto through a hub or connector 11. The numeral 13 in FIG. 2 collectively indicates a catheter introducing guide wire to be used simultaneously with the catheter 10. As suggested from a fragmentary enlarged sectional view in FIG. 3, the guide wire comprises a metal core wire 14 and a covering wire 15 densely wound in coil form around the outer peripheral surface thereof, and is longer than the catheter 10. Even if an operating external force for forward or rotational movement is applied to the guide wire 10 from the hand side thereof, the guide wire 10 will not form a bend (or so-called bending habit), so that its torque controllability can be transmitted to the catheter 10. In the front end portion 13b of the guide wire 13, said core wire 14 is made gradually thin from the main portion 13a, whereby it is made soft to have the same or higher degree of flexibility than the catheter 10; thus, when it is inserted into a blood vessel, it will not hurt the blood vessel wall. Since the overall length of the catheter 10 varies in connection with a target artery, it cannot be made constant; however, if the entire region of the catheter 10 to be inserted into a blood vessel has a fixed length comprises the catheter main portion 10a having a fixed length l1 and being made soft to have a high degree of flexibility, and the catheter front end portion 10b having a less length l2 and being made rigid to the necessary minimum degree to have a low degree of flexibility. The necessary minimum degree means that when the catheter is inserted into a blood vessel, there is no danger of hurting the blood vessel wall and that the torque controllability of the catheter introducing guide wire used simultaneously with the catheter can be satisfactorily transmitted. That is, although the main portion 10a of the catheter 10 differs in flexibility from the front end portion 10b, the region L to be inserted into a blood vessel has a certain degree of flexibility required to follow the free bending of the guide wire 13. As to the concrete arrangement of the catheter 10 for obtaining such change in flexibility, various forms shown in FIGS. 4 through 7 may be freely adopted. FIG. 4 is a fragmentary developed view of FIG. 1. In this figure, the main portion 10a of a synthetic resin tube 16 forming the whole of the catheter 10 is reduced in wall thickness, whereas the remaining front end portion 10b of the synthetic resin tube 16 is increased in wall thickness. The catheter 10 of such construction, which uses a common synthetic resin tube 16 for the main portion 10a and front end portion 10b, can be mass produced by inserting a core (not shown) in the form of a tapered conical bar into the hollow region thereof and, after molding, withdrawing said core. As is clear from FIG. 5 showing a first modification corresponding to FIG. 4, the wall thickness of a synthetic resin tube 17 forming a catheter 10 is uniform, but the outer diameter of the main portion 20a is small, while the front end portion 20b is large. The greater the outer diameter, the greater the bending rigidity of the catheter 10, and hence its flexibility can be made low. And the catheter 10 of such construction can be easily formed of a synthetic resin tube 17 common to the main portion 20a and front end portion 20b by using a core (not shown) in the form of a reversely tapered conical bar. FIG. 6 shows a second modification corresponding to FIG. 4, wherein the front end portion 30b of a synthetic resin tube 18 forming a catheter 30 is integrated with a separate reinforcing tube 19 of flexible synthetic resin material in two layers, so that it is rigid with low flexibility as compared with the remaining single-layer main portion 30a in the form of a synthetic resin tube 18. Such reinforcing tube 19 can be satisfactorily integrated with the inner wall surface of the synthetic resin tube 18 forming the outer layer by heat seal or other fixing means. FIG. 7 shows a third modification corresponding to FIG. 4, wherein only the front end portion 40b of a synthetic resin tube 21 forming a catheter 40 is integrally lined with a separate reinforcing tube 23 of flexible synthetic resin integrally covered with non-metallic mesh 22. As a result, the front end portion 40b is made rigid, having lower flexibility than the main portion 40a. Such catheter 40 can also be easily produced by covering the outer peripheral surface successively with said mesh 22 and synthetic resin tube 21. At any rate, since the catheter 10 in the present invention has its main portion 10a made more flexible and softer than the front end portion 10b, the catheter 10 smoothly and efficiently follows the piloting bending movement of the guide wire used simultaneously therewith and the torque controllability that the guide wire 13 possesses can be precisely reflected on the catheter 10. And there is no danger of the catheter forming a fixed bend (bending habit) when it changes its direction in a blood vessel or is retained therein; although it contacts the blood vessel wall, it does not impede the blood flow and contributes much to prevention of formation of a thrombus. In this connection, in FIG. 1 which is a schematic view, the boundary position P between the main portion 10a and the front end portion 10b of the catheter 10 has been shown as an easily distinguishable definite demarcation line; however, as is suggested from the arrangements shown in FIGS. 4 through 7, concerning the outer diameter, inner diameter, wall thickness and the degree of flexibility of the catheter 10, it is preferable that the main portion 10a and the front end they obscurely steplessly and smoothly change to each other across the boundary position P. The reason is that with this arrangement, the above function and effect can be further improved and that the main portion 10a and the front end portion 10b of the catheter 10 can be fabricated in such a manner that they are hardly separable from each other. On the other hand, since the front end portion 10b is made rigid by being made less flexible than the main portion 10a, it is hardly subjected to the reactive force from a contrast agent, thus making it possible to inject the contrast agent into a target artery without loss and accurately while maintaining a stable attitude resisting the spout pressure. Further, to provide the pilot function for insertion into a target location such as a primary branch of the aorta or a sub-branch thereof, the front end 10b of the catheter 10 can be plastically deformed very easily in advance into any form as an intrinsic bend (bending habit) conforming to the target artery, and such various bent forms can be stably held. Concerning the bent form of the front end portion 10b of the catheter 10, in FIG. 1, it is plastically deformed into an arc having a relatively large curvature radius dimension R1 which allows it to contact the inner wall of the aorta, and a shape restoring force. Thereby, it functions as a pilot for inserting the arcuate front end portion 10b into a primary branch of the aorta. Concerning the guide wire 13 to be used simultaneously therewith, the front end portion 13b is plastically deformed into an arcuate form, as shown in FIG. 2, which has a smaller curvature radius dimension R2 than the arcuate front end portion 10b of the catheter 10 and which has a shape restoring force, thereby enabling the arcuate front end portion 13b of the guide wire 13 to function as a pilot for insertion into a secondary or tertiary branch of the aorta. According to this, the catheter 10 is used simultaneously with the guide wire 13 and the required torque controllability is obtained from the guide wire, while the pilot function for insertion into a primary branch of the aorta is imparted to the relatively large arcuate front end portion 10b of the catheter 10 and the pilot function for insertion into secondary and tertiary branches is imparted to the relatively small arcuate front end portion 13b of the guide wire 13. As a result, there is no need to provide various intrinsic bent shapes to the front end portion 10b of the catheter 10. Furthermore, selective and super-selective catheter operation can be effected in connection with the trans-brachial artery catheterization technique while making versatile use of the catheter 10 having the relatively large arcuate front end portion 10b capable of contacting the inner wall of the aorta. That is, FIG. 8 (I), (II) and (III) are schematic views wherein the catheter 10 described above is used for an graphic test of the renal artery B, which is a primary branch of the aorta A. In use, as shown in (I), under the pilot action of said guide wire 13, the catheter 10 is inserted into a descending artery A through a puncture hole (not shown) in the brachial artery, whereupon the front end portion 13b of the guide wire 13 is once retracted from the front end portion 10b of the catheter 10. Then, the front end portion 10b of the catheter 10 is advanced along and in contact with the inner wall of the aorta A while retaining its arcuate bent form, until it is directed to the branch base of the renal artery B. In this case, anatomically, the branches of the descending artery A have angles of not more than 90 degrees as downward from the aorta A. Thus, according to the trans-brachial catheterization technique, the arcuate front end portion 10b of said catheter 10 can be correctly directed into a primary branch of the aorta A. Then, as shown in FIG. 8 (II), the catheter 10 is fed by the guide wire 13, whereby the front end portion 10b of the catheter 10 advances deep into the renal artery B. Therefore, as soon as it reaches the target location, the guide wire 13 is extracted and then a contrast agent will be injected through the catheter 10 from the hand side thereof, as shown in FIG. 8 (III). Since the front end portion 10b of the catheter 10 is made more rigid with low flexibility than the main portion 10a, there is no danger of the front end portion being swung to and fro as if dancing under the pouring pressure of the contrast agent, as described above. The above description relates to an operating method for inserting the catheter 10 into a primary branch of the aorta A. When it is desired to insert the catheter 10 into a secondary or tertiary branch of a primary branch, this can be attained, though not shown, by advancing the guide wire 13 alone from the state of Fig. (II) relative to the catheter 10, thereby exposing the front end portion 13b of the guide wire 13 from the front end portion 10b of the catheter 10. Then, the front end portion 13b of the guide wire 13 maintains said small arcuate bent form by its own shape restoring force, thus performing the versatile pilot function of insertion into a secondary or tertiary branch; thus, under the guiding action thereof, the catheter 10 can be advanced deep into a secondary or tertiary branch. Thereafter, the guide wire 13 alone is extracted, leaving the catheter 10, through which a contrast agent is then injected, of course. At any rate, since the main portion 10a of the catheter 10 is made soft with high flexibility, the catheter precisely follows the movement of the guide wire 13 when it is inserted over a long distance into a secondary or tertiary branch as well as when it is inserted into a primary branch of the aorta A. Therefore, the longer the distance, the more remarkably its function and effect will be developed. When the catheter 10 is used in connection with the trans-brachial catheterization technique, it has to be longer and thinner than when it is used in connection with the trans-femoral catheterization technique. Thus, if the catheter 10 which is used simultaneously with the guide wire 13 as described above is adopted, the selective and super-selective catheter operation in connection with the trans-femoral artery (which is thin and long) catheterization technique can be performed safely and reliably by anyone without relying on high technique or much experience. If a trans-brachial artery catheterization technique is established on the basis of the present invention, this means that angiographic tests which have heretofore been difficult for outdoor patients can be conducted, contributing much to early diagnosis of vascular and tumorous diseases and to injection of an anticancer agent into a target organ. Thus, the invention can be said to be very useful. In addition, it goes without saying that the present invention is also applicable to angiographic tests based on the conventional trans-femoral artery catheterization technique. While the invention has been particularly shown and described in reference to preferred embodiments thereof, it will be understood by those skilled in the art that changes in form and details may be made therein without departing from the spirit and scope of the invention.

The present invention relates to a catheter for angiography adapted to be used simultaneously with a catheter introducing guide wire and advanced into a blood vessel under the pilot action of the guide wire, and is characterized in that in order to secure smooth and reliable remote controllability (i.e., torque controllability) from the hand side, a high degree of flexibility precisely reflecting the movement of the guide wire and an injecting function for accurately directing a contrast agent into a target artery, the catheter is designed so that, although the catheter has, as a whole, a degree of flexiblity to enable it to follow the movement of the guide wire, its main portion in the region to be introduced into a blood vessel has a higher degree of flexibility than that of its front end portion which is shorter than the main portion.

BACKGROUND OF THE INVENTION The present invention relates to an ultrasonic diagnosing apparatus adapted to diagnosing the diseases of mammary glands and mastocarcinoma. When ultrasonic waves are applied to a patient, they are reflected by the boundaries between different tissues of the patient. A sectional slice image of an internal organ or abnormal tissue of the patient can be formed from the echoes of the ultrasonic waves. In order to prevent attenuation and reflection of the ultrasonic waves travelling between the patient and a probe which generates and detects the ultrasonic waves, an acoustic coupler is interposed between the probe and the patient. For the acoustic coupler, water is often used because it resembles the patient in ultrasonic-wave propagation characteristics. FIG. 1 shows a prior art ultrasonic diagnosing apparatus with a receptacle filled with water. A receptacle 10 contains water 2. A patient is held with her breast 4 fitted in an opening 12 of the receptacle 10. A probe 14 is disposed in the receptacle 10 and can be movable in the direction of arrow 6. The probe 14 extends in the direction of arrow 8 (see FIG. 3) perpendicular to the direction of the arrow 6. It has a number of piezoelectric elements 16 arranged in the direction of arrow 8. The elements 16 emit ultrasonic waves toward a region 18 schematically shown in FIG. 3, thereby achieving electronic scanning in the direction of arrow 8. At the same time, the probe 14 moves in the direction of arrow 6, thus performing mechanical scanning. Since the patient's breast 4 directly contacts the water 2, the reflection and attenuation of ultrasonic waves are limited, which results in relatively good sectional slice images. In this prior art apparatus, however, the breast 4 may get wet and foreign matter is liable to enter the water 2. The foreign matter reflects the ultrasonic waves, lowering the image quality. As the patient breathes, her breast moves. This makes it difficult to form an accurate image. FIG. 2 shows another prior art ultrasonic diagnosing apparatus. This apparatus differs from the apparatus shown in FIG. 1 in that the opening 22 of the receptacle 10 is closed by a membrane 24. The membrane 24 is formed of flexible material having acoustic characteristics similar to those of an organism and can closely contact with the breast 4. The receptacle 10 and the membrane 24 form a vessel. This vessel is filled with water. The breast 4 can be supported by the membrane 24. The depth to which a patient's breast 4 may sink is limited within a range as taken from the ultrasonic probe 14. Thus, the breast 4 is kept relatively flat, pressed onto the membrane 24. Accordingly, when the ultrasonic waves are applied to the breast 4, the direction of incidence of the ultrasonic waves and the surface of the breast 4 define a substantially right angle (incidence angle). As a result, the breast 4 reflects less waves, leading to improved sensitivity, reduced artifacts, and increased depth of visual field. As shown in FIG. 3, the ultrasonic propagation region, i.e., a specified zone S is narrow since the waves generated by the piezoelectric elements 16 have both a convergent acoustic field and a diffuse acoustic field, whose envelopes have the shape shown in FIG. 3. An ultrasonic diagnosis should preferably be made by using the zone S which is high in ultrasonic density. Women, as well as men, have breasts of different sizes. Hence, the bottom portion of the breast varies according to the patient although the breast is supported by the membrane 24. The zone S is relatively short in length. Use of a mechanism for adjusting the vertical position of the probe 14 contradicts the requirement for the miniaturization of the ultrasonic diagnosing apparatus. Also, it is very difficult to change the focus point by replacing an acoustic lens in an ultrasonic vibration surface of the probe 14, since the probe 14 is contained in the sealed vessel. Therefore, the region of the breast 4 to be examined by ultrasonic diagnosis may sometimes be off the preferable zone S for the diagnosis. In diagnosing mastocarcinoma, the objective region to be examined is located on that portion of the breast beside the armpit. In this region, however, the contact between the membrane and the breast is loose, so that an air layer is liable to lie between them. Such an air layer makes the ultrasonic diagnosis difficult. These drawbacks of the prior art ultrasonic diagnosing apparatus are fatal especially in, for example, a group examination in which a number of objects are examined without leaving any substantial chance of reexamination. SUMMARY OF THE INVENTION The object of the present invention is to provide an ultrasonic diagnosing apparatus capable of producing distinct and satisfactory sectional slice images despite the variations in size of the breasts to be examined between individuals and adapted for the diagnosis of mastocarcinoma and other diseases. According to an aspect of the present invention, there is provided an ultrasonic diagnosing apparatus for examining a patient comprising a receptacle containing a liquid acoustic coupling medium and having a substantially horizontal upper surface and an opening provided to said surface, an ultrasonic-wave transmitting flexible membrane attached to the receptacle in a liquid-tight manner so as to cover the opening, a portion of the patient to be examined being put on the membrane, an ultrasonic probe disposed in the liquid in the receptacle for transmitting ultrasonic beams into the patient through the membrane and the medium, and pressure increasing means for increasing the pressure of the liquid in the receptacle. According to the ultrasonic diagnosing apparatus of the invention, the liquid medium pressure inside the receptacle can be finely adjusted even though the region to be examined is the breast or another part which is flexible and subject to individual differences in size, so that the region to be examined can be located in an optimum position for ultrasonic diagnosis. Since ultrasonic waves generated by the probe have a convergent acoustic field and a diffuse acoustic field, an ultrasonic beam is constricted for higher density in a specific zone remote from the probe. According to the invention, the region to be examined can be positioned in the zone where the ultrasonic beam is constricted without regard to the individual differences between patients. Thus, it is possible to obtain distinct images of good quality. Since the water pressure can be controlled freely, the membrane can be closely fitted on the region to be examined even if the region is the armpit or another part which cannot easily be brought into close contact with the prior art membrane. Thus, satisfactory sectional slice images can be obtained with high stability over a wide range. BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 are sectional views schematically showing prior art ultrasonic diagnosing apparatuses; FIG. 3 is a diagram for illustrating an ultrasonic-wave propagation region; FIG. 4 is a sectional view showing an ultrasonic diagnosing apparatus according to one embodiment of the present invention; FIG. 5 is a general perspective view of the ultrasonic diagnosing apparatus of FIG. 4; FIG. 6 is a perspective view showing a probe transfer mechanism; and FIG. 7 is a sectional view showing another embodiment of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 4 shows an ultrasonic diagnosing apparatus using a receptacle according to one embodiment of the present invention, and FIG. 5 is a general perspective view of the apparatus. An operator control panel 22 is mounted on a table which is set on a floor panel of a consultation room. A display 24 for mode C and a display 26 for mode B, for example, are arranged beside the operator control panel 22. A receptacle 30 is set beside the table. A patient is expected to step on a platform 28 in front of the receptacle 30, and to position the breast over the receptacle 30 by bending herself forward. The receptacle 30 has an opening 32 at the top. A hat-shaped membrane 34 is disposed near the opening 32 so as to close the same. A brim portion 36 at the periphery of the membrane 34 is laid on the top surface of the receptacle 30. A presser member 37 extending along the edge of the opening 32 is placed on the brim portion 36 of the membrane 34. The presser member 37 is fixed to the receptacle 30 so that the brim portion 36 is held between the presser member 37 and the top surface of the receptacle 30. The presser member 37 causes the membrane 34 to be fixed watertight to the receptacle 30. The membrane 34 is formed from a flexible material resembling a living body in acoustic characteristics, e.g., rubber such as silicone rubber. The presser member 37 includes a core plate 38 formed of a steel sheet extending along the peripheral edge of the opening 32 and a cover 40 of a flexible material covering the core plate 38. The cover 40 serves to protect the breast of the patient. The membrane 34 has a hole to which a pipe 42 is connected. A valve 44 is attached to the pipe 42. The valve 44 is normally closed, and air bubbles, if any, in the receptacle 30 can be removed by opening the valve 44. Two inlet/outlet ports 46 and 48 are formed at the lower end portion of the receptacle 30. A pipe 50 is connected at each end portion to the inlet/outlet ports 46 and 48. Thus, water 2 in the receptacle 30 can circulate through the pipe 50. An exhaust port 52 is bored through the bottom wall of the receptacle 30, and a pipe 54 is connected to the exhaust port 52. A valve 56 is attached to the pipe 54. The valve 56 is normally closed, and the water 2 in the receptacle 30 can be discharged by opening the valve 56. A three-way cock 58 and a pump 60 are attached to the pipe 50. A tank 62 is connected to the three-way cock 58 by means of a pipe 64. The tank 62 contains the water 2 and is adapted to communicate with the pipe 50 when the three-way cock 58 is shifted. The pump 60 and the cock 58 are driven by a driver 68 in a mode which is selected by a switching unit 66 on the operator control panel 22. The switching unit 66 can set three modes for the operation of the cock 58. In a first mode 70, the tank 62 is connected to a pipe section 50a of the pipe 50 which is fitted with the pump 60, and a pipe section 50b on the side of the inlet/outlet port 48 is cut off from the pipe 64 and the pipe section 50a. In a second mode 72, the pipe sections 50a and 50b are connected, and the pipe 64 is cut off from the pipe sections 50a and 50b. In a third mode 74, the pipe section 50 b connects with the pipe 64 so that the water 2 in the receptacle 30 can escape into the tank 62 through the inlet/outlet port 48 and the cross valve 58. The switching unit 66 is provided with a switch 76 for the on-off operation of the pump 60. The driver 68 starts and stops the pump 60 when the switch 76 is turned on and off, respectively. A heating unit 78 heats the water 2 in the receptacle 30, thereby keeping the water 2 at a temperature near the body temperature. A ultrasonic probe 80 is disposed in the receptacle 30 so as to be movable in the direction indicated by the arrow 6. FIG. 6 shows a transfer mechanism 82 for the probe 80. In FIG. 6, the receptacle 30 is indicated by two-dot chain line, and other members than the transfer mechanism are omitted. Having the same construction as the probe 14 shown in FIG. 3, the probe 80 extends in the direction of the arrow 8 perpendicular to the transfer direction indicated by the arrow 6. A number of piezoelectric elements are arranged along the direction of the arrow 8, and ultrasonic waves are used in electrical scanning in the direction of the arrow 8. A pair of toothed belts 84 extending along the direction of the arrow 6 are each stretched between a pair of toothed pulleys 86. The two pulleys 86 on one side of the arrow 6 are mounted individually on support shafts 88 which are rotatably supported in the receptacle 30 by suitable bearings and the like. The remaining two pulleys 86 on the other side are mounted on a driving shaft 90 which is rotatably supported in the receptacle 30. The position of each support shaft 88 can be adjusted by means of a screw or the like to regulate the tension of its corresponding belt 84. One end of the driving shaft 90 projects to the outside of the receptacle 30, and a watertight seal member 92 is interposed between the side wall of the receptacle 30 and the driving shaft 90. A toothed driven pulley 94 is mounted on that portion of the shaft 90 outside the receptacle 30, and a rotary encoder 104 for detecting the rotational position of the shaft 90 is attached to the outermost end of the shaft 90. A reduction gear 100 is mounted on the rotating shaft of a motor 102 and a toothed driving pulley 96 on the output shaft of the reduction gear 100. A toothed belt 98 is stretched between the driving pulley 96 and the driven pulley 94. Thus, the rotation of the motor 102 is reduced at a predetermined reduction ratio by the reduction gear 100, and then transmitted to the driving shaft 90 by the belt 98. The position of the shaft 90 is detected by the rotary encoder 104. A pair of guide shafts 106 extend in the direction of the arrow 6 inside the receptacle 30. A pair of sliding members 108 are fitted individually on the guide shafts 106 so that the former can move along the latter. A mounting base 110 lies fixed on both the sliding members 108 so that the base 110 can move in the direction of the arrow 6 as the sliding members 108 move. The probe 80 is fixed on the base 110 so that its longitudinal direction is in alignment with the direction of the arrow 8. A pair of coupling pieces 112 protrude from the base 110 toward their corresponding belts 84 to be fixed thereto. Thus, the driving shaft 90 reciprocates as the motor 102 rotates alternatingly. As the belts 84 are reciprocated by the alternating rotation of the driving shaft 90, the probe 80 reciprocates in the direction of the arrow 6. The operation of the ultrasonic diagnosing apparatus with the above construction will now be described. The patient steps on the platform 28 and bends herself forward so that her upper body lies on the housing 29. Thereupon, the breast 4 is supported on the membrane 34. Then, the switching unit 66 is shifted to the first mode 70 so that the pipe 64 connects with the pipe section 50a. At the same time, the switch 76 is turned on to start the pump 60. The water 2 in the tank 62 is forced into the receptacle 30 through the pipe 50 by the pump 60. As a result, the water pressure inside the receptacle 30 increases, so that the breast 4 on the membrane 34 is lifted. If the second mode 72 is selected in the switching unit 66, the pipe sections 50a and 50b connect with each other, so that the water 2 in the receptacle 30 circulates through the pipe 50. Thus, the water pressure inside the receptacle 30 is kept at a fixed level, and the temperature of the water 2 heated by the heating unit 78 becomes uniform. The ultrasonic probe 80 is driven in the direction of the arrow 6 by the transfer mechanism 82 so that ultrasonic waves generated by the piezoelectric elements of the probe 80 are used for mechanical scanning as well as for the electrical scanning in the direction of the arrow 8. Reflected echoes of the ultrasonic waves are detected by the probe 80 and applied to the input of an image processing apparatus (not shown). These data are image-processed in so-called mode B, and a cross-sectional slice image of the breast parallel to the drawing plane of FIG. 4 is displayed by the display 26. While observing the sectional slice image in mode B, the operator shifts the switching unit 66 between the first to third modes to regulate the water pressure inside the receptacle 30, thereby locating the breast in the optimum position. As shown in FIG. 3, the ultrasonic waves generated from the piezoelectric elements are constricted in zone S. The position of the breast is adjusted so that the cross section of the ultrasonic beam propagation region is narrow and so that the region to be examined is located within zone S with high beam density. Zone S is located at a distance of, e.g., 8 cm to 12 cm from the ultrasonic-wave generating/detecting surface of the piezoelectric elements. Namely, the length of the zone S is about 4 cm. The water pressure inside the receptacle 30 is adjusted so that the breast is positioned within the 4-cm region. If the region to be examine is a specific part subject to, e.g., mastocarcinoma, the operator adjusts the water pressure so that the region is positioned within zone S while observing the sectional slice image in mode B. Then, the image processing apparatus is switched to so-called mode C, and a vertical-sectional slice image of the breast along a horizontal plane is displayed by the display 24. Zone S is vertically divided into, e.g., 12 parts, and the vertical-sectional slice image of the breast is photographed along each of the 12 horizontal sections. If the breast is fully pressed through the adjustment of the water pressure so that the region to be examined is short, the vertical-sectional slice image of the breast can be obtained at shorter pitches. This leads to an improvement in the accuracy of diagnosis. In the ultrasonic diagnosis in mode C, the switch 76 may be turned off to stop the pump 60. In lowering the pressure of the water 2 in the receptacle 30, the third mode 74 of the switching unit 66 is selected. In this case, the switch 76 is turned off. Thereupon, the pipe 64 and the pipe section 50b connect with each other, so that the water 2 in the receptacle 30 escapes into the tank 62 by gravity. As a result, the water pressure inside the receptacle 30 is lowered. If the water pressure inside the receptacle 30 is raised, the breast is strongly forced up by the membrane 34 as the patient rests her weight on the membrane 34 with the breast in contact therewith. Thus, even though the patient breathes, the organ will hardly move, and almost no air will be allowed to come between the breast and the membrane 34. In diagnosing mastocarcinoma, an image of good quality is preferably obtained by resting the breast 4 on the membrane 34 so as to be closely in contact therewith after increasing the water pressure inside the receptacle 30, and then gradually reducing the water pressure until the armpit region comes into contact with the membrane 34. The membrane 34 is hat-shaped, projecting upward. With such a shape, the membrane 34 can easily be brought into close contact with a wide-ranging portion of the breast, or another undulating region to be examined, by adjusting the water pressure inside the receptacle 30. If air bubbles are produced in the receptacle 30, they can be removed by opening the valve 44 and squeezing the membrane 34 so as to guide the bubbles to the pipe 42. Referring now to FIG. 7, another embodiment of the invention will be described. In FIG. 7, like reference numerals are used to designate like portions shown in FIG. 4, and a description of these portions is omitted. A receptacle 130 has an opening 32, inlet/outlet ports 46 and 48, and an exhaust port 52. A membrane 34 is provided at the opening 32, and a circulating pipe 50 with a pump 60 thereon is connected to the inlet/outlet ports 46 and 48. This second embodiment differs from the first embodiment shown in FIG. 4 in that the receptacle 130 is fitted with a bellows-shaped bag pump 140 in place of the cross valve 58 and the tank 62. In this embodiment, therefore, the pump 60 serves not as a water pressurizing means but as a means for circulating the water 2. The bag pump 140 includes a pipe 144 connected to a port 132 formed in the side wall of the receptacle 130 and a bellows member 142 attached to the pipe 144. The water 2 in the receptacle 130 enters the bellows member 142 through the pipe 144, and the water pressure inside the receptacle 130 can be regulated by moving the bellows member 142 in the direction of an arrow 146. It is to be understood that the present invention is not limited to the above embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention. More specifically, the apparatus of the invention is not limited to the diagnosis of diseases of the breast, and may also be used for the diagnosis of diseases of other regions.

Water is filled in a receptacle, and an ultrasonic-wave transmitting flexible membrane is attached to the receptacle in a watertight manner. An ultrasonic probe is provided in the receptacle for mechanical scanning. The receptacle is coupled with a pipe through which the water in the receptacle can circulate. A pump and a three-way cock are attached to the pipe. A tank containing water is connected to the three-way cock. When the pump is actuated, with the tank and the pipe connected by the three-way cock, the water is introduced from the tank into the receptacle to raise the water pressure. When the receptacle and the tank are connected by the three-way cock, the water escapes from the receptacle into the tank to lower the water pressure in the receptacle. Thus, the water pressure in the receptacle can be adjusted to locate the breast in an optimum position relative to the probe for ultrasonic diagnosis while the breast is supported on the membrane.

[0001] This application claims priority to U.S. Provisional Patent Application Ser. No. 61/624,346, filed Apr. 15, 2012, which is hereby incorporated by reference herein. BACKGROUND AND SUMMARY [0002] As a result of the ever expanding demand for energy, the world's easily accessible oil reserves become swiftly depleted. The oil and gas industry today has a typical recovery of hydrocarbons with value of 30-40% 1,2 which indicates that the majority of the existing oil remains trapped in the pores of the oil bearing porous media. An increase in recovery efficiency (up to 60-80%) 1 will therefore be a key factor for meeting the increasing energy demands. To this end, there is a need for new and more sophisticated mapping and production techniques. [0003] Injection of water, also referred to as water flooding, 3 is commonly applied to produce so-called secondary oil, resulting in an increase of the total recovery efficiency up to 50%. 4 The recovery results of a water flooding process is largely influenced by the rock and fluid characteristics within the particular reservoir. 5 Due to viscosity and capillary effects, water may however bypass confined oil that remains in the reservoir, leading to a so-called water breakthrough, 6 in which preferred water pathways are developed in the reservoir connecting injection sites directly to the producer well where the recovery of water overtakes that of the secondary oil; water breakthrough can set in long before depletion of a reservoir. 5 [0004] These complex and challenging reservoir conditions require an improved knowledge of the subsurface physical and chemical properties. Reservoir flow characterization is regularly performed using isotope tracers, which are injected with the water flooding process to obtain the flow dynamics in a reservoir. 7 This is further extended with complementary techniques to image additional reservoir parameters, such as analysis on production profiles of reservoir fluids, pressure tests, and time lapse seismic examinations. 4 [0005] The limitation of the commonly applied isotope tracers is that they primarily provide information on flow characteristics, and often do not possess any physical and chemical sensor functionality. 10 In addition, a significant number of reported tracers consist of either toxic compounds or radioactive nuclides. 8,9 This limits their use due to health, safety, environmental, and legislation issues. [0006] As any additional information of physical and chemical properties within the reservoir and its fluids can add a significant contribution to improve the production process, there is a quest for an improved sensor system. Key characteristics for these sensors' functionalities are the temperature, amount and nature of dissolved ions, pressure, pH, and reservoir chemistry. As a consequence of the complex and hostile reservoir environment often encountered, many classical sensor materials (e.g., organic chromophores) have shown to be not suitable. 10,11 [0007] Recent publications suggested nanomaterials with extended sensor functionality as one next step in reservoir characterization. 12,13 An important class of these nanomaterials are the so-called quantum dots (“QDs”). QDs are semiconductor nanocrystals, 14 which are not only brightly fluorescent, with a size-tunable fluorescent emission color, but have also proven to be a versatile platform for further functionalization. 15 QDs have been used as fluorescent nanomaterials in areas where stability, endurance, and specialized chemical functionalization are crucial. These areas are typically found in biomedical research where robust nano-sensors are demanded, often extended with dedicated surface functionality. 15,16 [0008] Another and relative new type of “nano” particles are the so-called noble metal clusters. Their bright optical behavior, which is size-tunable, is to a certain extent comparable to that of QDs. 17 Their inert inorganic nature together with their relatively high chemical stability and solution process ability makes these noble metal clusters an interesting material to combine with the earlier discussed QDs in a mixed sensor for reservoir imaging. Water-dispersed nano-sensors are compatible with the commonly applied technique of water flooding and therefore an ideal starting point, as its infrastructure is readily available throughout the oil and gas industry for enhanced oil recovery. 3 Extended information about the specific chemical and physical conditions within the reservoir is beneficial to optimize secondary oil production. [0009] Application of fluorescent nanomaterials as sensors added in a water flooding process for reservoir imaging demands a water-dispersible nanoparticle with a controlled stability. Embodiments of the present invention synthesize brightly luminescent InP/ZnS QDs and silver clusters with different emission colors and various water stabilizing surface coatings. The different emission colors are clearly easy to discriminate from each other, which is beneficial for multiplexing in a dedicated sensor composition. The challenging reservoir conditions (e.g., high salinity, high pH, and temperature) have often been found as the limiting factor on the stability of fluorescent materials for reservoir imaging. The use of inorganic chromophors based on the QDs and metal clusters described herein show improved stability in these challenging conditions. By applying different surface coati the nanomaterials, several sensor applications have been identified with respect t chemical environment, temperature, and presence of solids representative withi reservoir. [0010] In practical situations, the ratio of the photoluminescent intensity of different pa may be measured at the producer well. Direct interpolation of the emission ratios prov unique fingerprint of the reservoir environment with respect to pH, chemical enviror temperature, and present solids. In addition, as the sensors were developed to function water phase, the typical background luminescence of oils showed not to be affected l sensor functionality. [0011] QDs and silver clusters are described herein as a class of materials for applicati luminescent probes with dedicated sensor functionalities for reservoir imaging, exhi stability and a significant freedom for surface chemistry. BRIEF DESCRIPTION OF THE DRAWINGS [0012] FIG. 1A shows a TEM image of orange InP/ZnS QDs. [0013] FIG. 1B shows a graph of normalized fluorescence (λ exc =370 nm; thick line absorbance (thin lines) spectra of InP/ZnS quantum dots and Ag clusters in chlorofor aqueous solutions, respectively, at room temperature. [0014] FIG. 2A shows a graph of relative PL intensity of various nano-sensors upon exp to different reservoir conditions. [0015] FIG. 2B shows a graph of normalized fluorescence spectra of a mixture of Ag el and green emissive PEG-coated QDs; the top line represents the emission spectrum Ag/QD mixture in brine prior to heating; the bottom line represents the Ag/QD mixt brine after heating to 120° C. [0016] FIG. 3A shows a graph of the relative PL intensity of lipid micelle coated In QDs and silver nanoclusters in the presence of clay or calcium carbonate. [0017] FIG. 3B shows a photograph of the behavior of lipid coated QD and nanclusters in the presence of clay. [0018] FIG. 3C shows a photograph of the behavior of lipid coated QD and nanoclusters in the presence of calcium carbonate. [0019] FIG. 4A shows photographs of the behavior of (a) silica and (b) lipid coated InP/ZnS QDs and (c) silver nanoclusters in the presence of crude oil. [0020] FIG. 4B shows a graph of a normalized PL intensity of the silica-coated (top line), lipid-coated (middle line) InP/ZnS QDs and silver nanoclusters (bottom line) dispersed in the water phase in the presence of crude oil, wherein the thin line to the far left represents the emission spectrum of Shell North Sea crude oil. [0021] FIG. 5 shows a digital image of dispersed rolls of foil of 200 nm thick amorphous ZnS using an optical microscope (50×). [0022] FIG. 6A shows a digital image of a piece of silicon wafer with a 200 nm protective layer of SiO 2 before exposure to hot alkaline brine. [0023] FIG. 6B shows a digital image of a piece of silicon wafer with a 200 nm protective layer of SiO 2 after exposure to hot alkaline brine. [0024] FIG. 6C shows a digital image of an unprotected reference piece of silicon, which is however severely damaged by exposure to hot alkaline brine. [0025] FIG. 7 shows a graph of absorbance spectra of API brine dispersed silver clusters prior to heating (top line) and after heating to 120° C. (bottom line). [0026] FIG. 8 shows a graph of size dependence of the band gap energy of InP QDs as a function of the particle size. [0027] FIG. 9 illustrates a system and method for injecting particles into a reservoir in accordance with embodiments of the present invention. DETAILED DESCRIPTION [0028] Referring to FIG. 9 , in embodiments of the present invention, QDs and noble metal clusters are implemented as a nano-sensor with specific functionality customized for reservoir management in a water flooding process. Embodiments of the present invention develop a nano-sensor composition based on InP/ZnS core shell QDs and atomic silver clusters. As these materials lay within the size range of 1-20 nm, there is no size limitation with respect to the pore size of the reservoir formation. 12 Due to the differences in surface chemistry of the nanomaterials, they experience different reactions depending on the specific local conditions. The nano-sensors may be injected into a formation at an injection well, including accompanying a water flooding process. After recovery of the nano-sensors from the production well, they are analyzed and the chemical and optical properties are compared to the initial situation before injection. The differences between both measurements provide a unique fingerprint of the reservoir and allow each of its signals to be attributed to specific chemical and physical parameters. Benefits of these nanoparticles are their proven robustness and chemical stability, 18 combined with the ability for extended surface chemistry to develop a mixed multifunctional sensor composition. To this end, developed were different types of QD and silver cluster based nano-sensors. These nano-sensors have their own specific targeted sensor functionality with respect to the reservoir environment. The relative bright and narrow band photoluminescence typically found for these nanomaterials enables the optical discrimination of the different sensor functionalities. The QD and Ag nano-sensors are completely water dispersible to avoid partition into the oil phase. Partial affinity for oil would increase the retention time tremendously. Water-dispersed luminescent nano-sensors also have a much lower detection limit compared to oil-dispersed QDs because their photoluminescence is not camouflaged by the absorption and background luminescence of crude oil itself. [0029] Materials and Methods: [0030] All quantities, times, temperatures, etc. are approximate. [0031] Reagents: Zinc n-undecylenate, indium chloride, tris(trimethylsilyl)phosphine (TMS) 3 P, hexadecylamine (HDA), stearic acid, sublimed sulfur, n-dodecanethiol, 1-octadecene (ODE), O-[2-(3-mercaptopropionylaminolethyl]-O′-methylpolyethylene glycol 5000, silver nitrate (AgNO 3 ), α-lipoic acid, sodium borohydride (NaBH4), and calcium carbonate were commercially obtained from Sigma Aldrich. PE 18:0/18:0-PEG 2000 was commercially obtained from Lipoid. Natural crude oil (e.g., North Sea) was commercially provided by Shell directly after production without any additional processing. The EXMS75 clay was commercially obtained from Stidchemie, and Rhodamine 101 commercially obtained from Radient Dyes Chemie. [0032] Synthesis of QDs: InP/ZnS quantum dots were synthesized under a nitrogen flow in accordance to a method published by Xu et al. 19 with modifications as described herein. (TMS) 3 P (60 mg; 0.2 mmol) was dissolved in ODE (1 mL) and swiftly injected into a reaction mixture of stearic acid (57 mg; 0.2 mmol), HDA (65 mg; 0.7 mmol), ODE (6 mL), zinc undecylenate (172 mg; 0.39 mmol) and indium chloride (44 mg, 0.2 mmol) at 280° C. After stirring for 20 minutes at 240° C., the reaction was allowed to cool down to room temperature, followed by the addition of 100 mg zinc undecylenate (0.23 mmol), 108 mg HDA (0.45 mmol), and 6 mL ODE. Elemental sulfur (15 mg; 0.47 mmol) dissolved in ODE (2 mL) was added drop-wise during 20 minutes at 230° C., followed by an annealing step of 60 minutes at 200° C. The core shell InP/ZnS crystals were subsequently isolated by dissolving the reaction mixture in chloroform (10 mL), followed by precipitation through addition of acetone (20 mL). The QDs were isolated by centrifugation and re-dispersed in chloroform. [0033] Synthesis of Ag nano-clusters: The Ag atomic clusters were synthesized following a method published by Adhikari et al. 20 with modifications described herein. α-□Lipoic acid (19 mg) and 14 mL of demi water were placed into a 50 ml flask. Subsequently, 7 mg of sodium borohydride was added, while stirring, a clear solution was obtained after 30 minutes. A solution of 2.94 mg of AgNO 3 in 700 μL water was added to the reduced dihydrolipoic acid (DHLA) solution while stirring. This was followed by the addition of an excess of sodium borohydride (10 mg dissolved in 2 ml water). Stirring was continued for more than 5 hours. A clear color change was observed from dark brown to a bright orange color after 4-5 hours. [0034] Surface modification: The silica coating was performed with a procedure similar to the one published by Nann et al. 19 The capping exchange of surface bound ligands (HDA and stearic acid) with, O-[2-(3-mercaptopropionylaminolethyl]-O′-methylpolyethylene glycol 5000 (PEG-SH) or dodecanethiol, was performed following the procedure published by Querner et al. 21 A 2-fold excess amount of thiol ligands was added to a 0.5 ml colloidal dispersion of HDA capped InP/ZnS QDs (10 mg/ml) and stirred at room temperature for >12 hours. Subsequently, the dodecanethiol-capped QDs where isolated by two cycles of precipitation through addition of methanol (0.5 mL) and redispersion in chloroform. [0035] Lipid coating of QDs: A micellar polyethylene glycol (“PEG”) coating was applied to make the QDs water-soluble. 22 This micellar coating comprised a pegylated phospholipid, PEG-DSPE (1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy-(poly(ethylene glycol))-2000]). The 6 mg InP/ZnS dodecanethiol-capped single washed QDs (3.2 mg InP/ZnS from TGA) were dissolved in 2 mL of chloroform and mixed with 18 mL PEG-DSPE (174 mg) dissolved in chloroform. The chloroform solution was slowly added to 70 mL water (1.5 hours) at 80° C. under vigorous stirring and nitrogen flow. Thermogravimetric analysis (“TGA”) showed that on average 52% (w/w) of the single washed quantum dot content consists of InP/ZnS, whereas 48% of the mass was attributed to organic surfactants. [0036] Optical Spectroscopy: UV-vis spectra were recorded (e.g., using a Hitachi U-2001 or Perkin Elmer Lambda 3b spectrophotometer). Steady state fluorescence spectra were measured (e.g., with a Perkin Elmer LS55 spectrophotometer). [0037] Quantum yield: Photoluminescence quantum yields (η F ) were estimated usi rhodamine 101 as a reference (in ethanol+0.01% HCl; η F =100%). 23 All solutions had optical density <0.1 at the excitation wavelength (λ ex =520 nm) to minimize re-absorpti and avoid absorbance saturation. The quantum yield was derived from luminescence spec by correcting for the optical density and the refractive index of the solvents used for sam and reference. 24 [0038] Transmission electron microscopy: TEM images were recorded (e.g., using TECNAI G2 20 (FEI Company) microscope operated at 200 kV). TEM samples w prepared by placing a drop of QDs dispersed in chloroform on a carbon coated copper (e. 400-mesh) TEM grid. The excess liquid was removed with a filtration paper. [0039] Simulated subterranean reservoir conditions: The influence of simulated reserv conditions on the dispersed nano-sensors was tested using different media and the presence solids. The influence of salt concentrations was tested by dispersing the nano-sensors in 2 (w/w) aqueous solution of CaCI 2 , or 8% (w/w) aqueous solution of NaCl. Subsequently, the influence of pH was tested in multi-component API brine solutions, simulating an act reservoir environment To this end, the nano-sensors were dispersed in buffered API bri (pH 6.5 and pH 9), containing 8% NaCl and 2% CaCl 2 . The effect of elevated subterrane temperatures was tested by heating the dispersed nano-sensors in buffered pH 6.5 API bri (8% NaCl and 2% CaCI 2 ) for 10 minutes at 120° C. The acidic API brines were buffer using a 0.1 M acid, sodium acetate buffer (pH 6.5), and the alkaline brines were buffer using 0.1 M glycine at pH 9.5. [0040] The behavior of the nano-sensors in the presence of solids was studied using the A brine pH 6.5 dispersed nano-sensors. Followed by the addition of solid Ca 2 CO 3 or EXM7 clay, after vigorously mixing, the solid and the liquid phase were separated by centrifugi The liquid phase was subsequently characterized using UV-vis and fluorescen spectroscopy. [0041] Testing of influence of crude oil: In a reservoir, crude oil is in close contact with water phase (brine). The influence of the presence of crude oil in the near vicinity of t water-dispersed nano-sensors was tested using a light North Sea crude oil. As-received cru oil was added to the dispersions. Samples were shaken vigorously and left standing for t hours to redistribute in well-separated phases. The PL spectra of the water phase w recorded, and the optical absorbance of the QDs was compared to the initial situation before addition of the oil. [0042] Results: [0043] Challenging reservoir conditions can affect the stability of the nano-sensor materials. Therefore, several different bulk materials, which are commonly used for QDs, were tested under commonly encountered reservoir conditions (see Supplementary Information disclosed hereinafter). These experiments showed stability for both ZnS as well as SiO 2 under the predominant reservoir conditions. Therefore ZnS and/or SiO 2 may be selected as a protective outer surface for the QDs. The InP/ZnS QDs were synthesized from indium chloride and tris(trimethylsilyl)phosphine in a mixture of octadecene, stearicacid, zindundecylenate, and hexadecylamine (HDA) in a similar procedure as described by Xu et al. 19 The InP/Zn core had a diameter of respectively 3.1 nm (orange) and 2.4 nm (green), as determined using the exciton energy derived from the emission maximum reference with literature values (see Supplementary Information hereinafter with respect to FIG. 8 ). The InP/Zn cores were passivated by growing a shell of 2 mono layers ZnS using zincundecylnate and sulfur dissolved in octadecene. 19 The final InP/ZnS quantum dots showed fluorescence maximum at 600 nm (orange) and 531 nm (green) and a quantum yield of η F ≈70% (orange) and η F ≈78% (green). FIG. 1A shows the TEM images of the orange InP/ZnS core shell QDs. [0044] The luminescent Ag clusters with an expected size of 4-5 atoms 20 were synthesized by the reduction of silver nitrate in the presence of α-lipoic acid in a similar method as described by Adhikari et al. 20 The Ag clusters showed a clear deep red emission with a maximum at 654 nm, and a sharp first absorption peak at 495 nm with a typical fluorescence quantum yield of η F =5%. [0045] Sensor functionality of the nanomaterials was studied under simulated reservoir conditions, using the optical properties of the InP/ZnS QDs and Ag clusters. DH LA-coated Ag clusters and InP/ZnS QDs with PEG-SH, Silica, and PEG lipid surface coatings were tested in commonly encountered reservoir conditions as is described hereinafter. The nano-sensors were subjected to the following variables: temperature, pH, and composition (presence of crude oil or additional solids like clay or calcium carbonate, which are added to the API brine). A “high” salinity brine was formulated in accordance with standards set by the American Petroleum Institute (“API”). As shown in FIGS. 2A-2B , the specific environmental influences on the sensors may cause changes in the photoluminescence (PL) intensity and the optical absorbance spectra. The changes in optical properties are a measure of the stability and the sensor functionality upon exposure to different conditions. In FIGS. 2A-2B , the PL intensity is plotted relative to the intensity in pure water as a function of the different particles under different reservoir conditions. The relative PL intensity shows a small decrease in the presence of high salinity (8% NaC) and calcium ions (2%) for most of the particles, except for the PEG-lipid coated QDs, which showed a small increase in PL intensity. These differences in PL intensity can be the result of the difference in polarity between pure water and water with (high) salt concentrations. A similar decrease in PL intensity is described for organic chromophores as a consequence of the interaction of their excited energy state and with the solvents polarity. 25,26 [0046] The influence of the different pH-levels of the brine dispersions showed significant changes between PL intensities of the diverse particles. The silver clusters with an alpha lipoic acid coating showed an overall decrease in PL intensity of ≈50% for both a high pH 9 and a low pH 6.5. However, an opposite behavior pH dependence was found between the silica-coated QDs and the PEG-SH coated QDs, where an average difference in the relative PL intensity was found of ≈40% at the different pH levels (pH 6.5 and pH 9). Here the silica-coated QDs showed a high relative (94%) PL intensity at pH 9, and PEG-SH coated QDs showed low relative (63%) PL intensity. This was opposite at pH 6.5, where the silica-coated QDs showed a low relative (59%) PL intensity and PEG-SH coated QDs showed high relative (100%) PL intensity. The opposite pH behavior found for these two QDs shows a clear application for a reservoir pH sensor. [0047] An exposure of these nanoparticles to a high temperature results, for all particles, in a strong decrease in PL intensity >60%. At these elevated temperatures, several effects can take place which can cause a decrease in PL intensity. The complete disappearance of the silver cluster emission upon heating was subsequently evaluated by the absorbance spectra of the Ag clusters (see FIG. 7 in the Supplementary Information hereinafter). This shows that clusters degrade at 120° C. in API brine, as the optical absorbance shows a strong decrease upon heating. Furthermore, the decrease in PL intensity of the QDs (see FIG. 2A ) can possibly be contributed to an increased mobility of surface-bound ligands and oxidation of the QD surface introducing surface trap states, which reduce the overall PL intensity upon heating. The difference in PL stability of the various nano-sensors enables an application for reservoir temperature monitoring. An example is shown in FIG. 2B where a mixture of Ag clusters (red emission) and PEG-SH coated QDs (green emission) may be used for this purpose in API brines. The emission spectrum shows (upper line) the emission spectrum of the mixture of red thiolated Ag (λ max =650 nm) and PEG-SH green emissive (λ max =531 nm) coated QDs at room temperature (“RT”), and the inset photo of FIG. 2B shows that this mixture has a clear and predominantly orange emission. Upon heating up to 120° ° C., the emission spectrum shows the disappearance of the red Ag clusters emission (λ max =650 nm) and leaves the green QD emission (λ max =520 nm) as the dominant emission. The effect remains preserved after cooling the sample down to RT. This is shown in the inset photo of FIG. 2B revealing a clear green QD emission. [0048] The presence of mineral solids in the reservoir on which the nano-sensors can absorb is an important element for the sensor composition of embodiments of the present invention. Two mineral solids often encountered in reservoirs are clay and limestone. Stability with respect to immobilization of the nano-sensors onto the natural clay (caused by ion exchange) was evaluated using a natural Na-montmorillonite (e.g., EXM757). This clay exhibits a large cationic exchange capacity and therefore closely resembles some natural clays that are commonly encountered in reservoirs. Limestone is a sedimentary rock, which is primarily composed of CaCO 3 crystals. CaCO 3 is the primarily naturally occurring source of divalent calcium ions source in reservoirs. This is of significant consequence as it forms a specific thread with respect to the precipitation of anionic nano-particles dispersions. [0049] The API brine dispersed silver cluster and the PEG-lipid coated QDs were mixed with either the clay or the limestone to study the potential selective binding of these nano-sensors. FIG. 3C confirms that red emitting silver clusters do not show precipitation nor selective binding in the presence of EXM757 clay in API brine (pH 6.5). However, in a presence of CaCO 3 , silver clusters show complete immobilization on the solid CaCO 3 as result of the negatively charged carboxylic acid groups on their surface. The orange emitting PEG-micelle coated InP/ZnS QDs, on the other hand, show the opposite behavior. The PEG-micelle coated QDs remain well dispersed in API brine in the presence of additional calcium carbonate, but they reveal selective binding towards the EXM757 clay. This opposite behavior in selective binding of the negatively charged silver clusters and the PEG-micelle coated QDs confirms that combinations of such particles can be used as a sensor with respect to the solids in the reservoir environment. [0050] The large heterogeneity of the conditions within a reservoir makes the design of the sensor composition challenging. The sensors according to embodiments of the present invention are designed for integration with a water flooding process and should therefore stay confined within the water phase of the reservoir. FIGS. 4A-4B show that the nanoparticles retain their bright luminescence in the presence of crude oil and stay confined in the water phase; they do not partition into the oil phase. The nanoparticles were dispersed in API brine in the presence of Northern sea crude oil. Crude oil is a mixture of a wide variety of hydrocarbons, some of which exhibit fluorescence by themselves. 27 The influence of the crude oil on the stability and luminescence of the nanoparticles is shown in FIGS. 4A (a), (b), and (c). The PL spectra of three types of QD sensors (InP/ZnS-lipid coated, InP/ZnS-silica coated, and Ag-clusters) dispersed in water are shown in FIG. 4B . The presence of crude oil in the vicinity of the QDs did not influence their bright luminescence, which can be clearly discriminated from the crude oil luminescence. Supplementary Information [0051] Stability tests on commonly materials typically used for QDs: [0052] Challenging reservoir conditions are likely to affect the stability of nano-sensor materials; therefore, several different bulk materials, which are typically used for QDs, were tested under commonly encountered reservoir conditions (e.g., acidic and alkaline brine conditions at elevated temperatures). [0053] Materials were tested in bulk form before testing with nanoparticles. An instability of the bulk material is more easily determined and can function as an indication on the expected behavior of the nano-sized form of the materials. The stability of nano-sized materials is in general lower than their macroscopic counterpart. [0054] Bulk CdSe, CdTe, ZnO, ZnS, Si, and SiO 2 powders were exposed to hot acidic API brine as well as hot alkaline API brine (see Table 1, which shows stability with respect to reservoir conditions of bulk materials that are conventionally used for QDots). Both the acidic and alkaline brine were buffered with acetic acid (pH 5) and glycine (pH 9), respectively. Samples were heated for approximately 1 hour at 150° C. (e.g., autoclave conditions) after which they were filtered. Precipitation experiments with the filtrate were conducted to confirm stability of the material. Only ZnS and SiO 2 met the basic stability requirements. Silicon passes halfway, as it is stable in hot acidic brine but not in the hot alkaline brine. [0000] TABLE 1 CdSe CdTe ZnO ZnS Si SiO 2 Hot alkaline API brine X X X Stable X Stable Hot acidic API brine X X X Stable Stable Stable [0055] Subsequently, it was determined if ZnS and SiO 2 remain stable when scaling down to the nano-regime. An amorphous 200 nm film of ZnS was synthesized using chemical vapor deposition techniques. This inorganic film however dissolves in hot brine. As shown in FIG. 5 , dispersed rolls of foil of 200 nm thick amorphous ZnS are clearly visible using an optical microscopy (50×). However, after exposure to hot brine, they cannot be seen anymore due to degradation. [0056] Referring to FIGS. 6A-6C , alternatively, a 500 nm layer of SiO 2 was thermally grown on a common silicon wafer. The silica layer was stable and protected a silicon wafer against degradation under influence of hot alkaline brine. Summarizing these experiments, apart from silica, all conventional QD materials that were tested failed. Other materials are required for the sensors that have a much higher chemical stability. [0057] FIG. 6A shows a piece of silicon wafer with a 200 nm protective layer of SiO 2 before exposure to hot alkaline brine. FIG. 6B shows a piece of silicon wafer with a 200 nm protective layer of SiO 2 after exposure to hot alkaline brine, which looks the same as the piece in FIG. 6A . FIG. 6C shows an unprotected reference piece of silicon that is severely damaged by exposure to hot alkaline brine. [0058] Since it is expected that the divalent nature of the semiconductors could be the main cause of the observed leaching, alternatively, indiumphosphide QD was considered. InP is a trivalent component and therefore more stable compared to cadmiumselenide and other conventionally used QD materials. In addition, the InP core was overcoated with a ZnS shell, which further increased its chemical stability. [0059] Some sulphur components have extremely low dissociation constants, which also explains why ZnS is much more stable than ZnO. Silversulphide is another high stability component. [0060] Degradation of Silver Nanoclusters [0061] The silver nanoclusters revealed a complete disappearance of their luminescence upon heating in API brine. The absorbance spectrum shown in FIG. 7 showed an almost absence of the characteristic absorbance peaks of these silver clusters, indicating that the silver clusters were almost fully degraded upon heating in API brine at 120° C. FIG. 7 shows the absorbance spectra of API brine dispersed silver clusters prior to heating (upper line) and after heating to 120° C. (lower line). Furthermore, precipitation of “reaction products” was observed explaining the slope in the absorbance spectrum as a result of scattering of the incident light. [0062] FIG. 8 is a graph showing size dependence of the band gap energy of InP QDs as a function of the particle size derived from literature. [0063] References, which are all hereby incorporated by reference herein: 1 Smith, R. G.; Mailand, G. C. Trans. I. Chem. E, 1998, 76A, 539-552, 2 Essen, G. M.; Zanvliet, M. J.; Van den Hof, P. M. J.; Bosgra, O. H. IEEE, 2006, 699 3 I. A. Munza, H. Johansen, O. Huseby, E. Rein. O. Scheire, Marine and Petroleum Geology 2010, 27, 838-852 4 Radiotracer applications in industry: a guidebook.—Vienna: International Atomic Energy Agency, 2004, p. 176 5 Buckley S. E.; Leverett. M. C. Trans. AIME 1942, 146, 107-116 6 Elkens, L. F.; Skov A. M. J. Petrol. Technol. 1963, 15, 877-884 7 Dugstad, ø., Aurdal, T., Galdiga, C., Hundere, I., Torgersen, H. J., SPE Paper Number Texas 1999, 56427 8 Gulati, M. S., Lipman, S. C.; Strobel, C. J. Geothermal Resources Councel. Trans. 1978, 2, 237-240 9 McCabe, W. J.; Barry, B. J.; Manning, M. R. Geothermics, 1983, 12, 83-110 10 Zemel, B. Tracers in the Oil Field, Developments in Petroleum Science, 43, Elsevier Science B.V. 1995 11 Home, R. N. J. Perolt. Technol. 1982, 34, 495-503 12 Barron, A. R.; Tour, J. M.; Busnaina, A. A.; Jung, Y. J.; Somu, S.; Kanj, M. J.; Potter, D.; Resasco, D.; Ullo, J. Oilfield Rev. 2010, 22, 38-49 13 Krishnamoorti, R.; Houseten, U. J. Petrol. Technol. 2006, 24 14 Brus, L. J. Phys. Chem. 1986, 90, 2555-2560 15 Gao, X. H., Cui, Y. Y., Levenson, R. M., Chung, L. W. K.; Nie, S. M. Nat. Biotechnol. 2008, 22, 969-976 16 Mulder, W. J. M.; Koole, R.; Brandwijk, R. J.; Storm, G.; Chin. P. T. K.; Strijkers, G. J.; de Mello Donega, C.; Nicolay, K.; Griffioen A. Nano Lett. 2006, 6, 1-6 17 Zheng, J.; Nicovich, P. R.; Dickson, R. M.; Annu. Rev. Phys. Chem. 2007, 58, 409-431 18 Medintz, I. L.; Uyeda, H. T.; Goldman, E. R.; Mattoussi H. Nat. Mater. 2005, 4, 435-446 19 Xu, S., Ziegler, J. & Nann, T. J. Mater. Chem. 2008, 18, 2653-2656. 20 Adhikari, B., Banerjee, A., Chem. Mater. 2010, 22, 4364-4371 21 Querner, C.; Reiss, P.; Bluese, Pron, A. J. Am. Chem. Soc. 2004, 126, 11574-11582 22 Dubertret, B. et al. Science 2002, 298, 1759-1762. 23 Karstens, T.; Kobs, K. J. Phys. Chem. 1980, 84, 1871-1872. 24 Eaton, D. F. J. Photoch. Photobio. B 1988, 2, 523-531. 25 Do, J.; Huh, J.; Kim, E. Langmuir 2009, 25, 9405-9412 26 Nair, R. B.; Cullum, B. M.; Murphy, C. J. Inorg. Chem. 1997, 36, 962-965 27 John, P.; Souter, I. Anal. Chem. 1976, 48, 520-524.

Enhanced oil recovery becomes increasingly important in satisfying the growing demand for fossil fuel. The efficiency of secondary recovery processes like water flooding is however largely influenced by the rock characteristics, fluid characteristics, chemistry and physics. For development of the full potential of secondary oil recovery, it remains a challenge to obtain sufficient knowledge about the reservoir conditions. The present invention provides a novel water-dispersed, nano-sensor composition based on. InP/ZnS quantum dots (“QDs”) and atomic silver clusters, which exhibit a bright visible fluorescence combined with dedicated sensor functionalities. The QD and silver nano-sensors were tested in simulated reservoir conditions to determine their selected functionality to these reservoir conditions. The developed nano-sensors showed improved sensor functionalities towards pH, temperature, and subterranean reservoir rock, such, as clay or limestone.

BACKGROUND OF THE INVENTION This invention relates generally to the support of percussion devices, as for example cowbells; and more particularly relates to cushioning and adjustable cushioning of such devices. When percussionists use drum sticks to forcibly strike cowbells that are rigidly supported, there is considerable shock effect transmitted back to the percussionist's hand and wrist. This reaction “hardness” differs substantially from the lower level impact effect created when a drum head is struck. There is need to alleviate at least in part such shock effect, which can be increasingly undesirable when the cowbell is struck with great force. Also, there is need for adjusting such created reaction effect when the cowbell is struck, i.e. for “tuning” of the cowbell. SUMMARY OF THE INVENTION It is a major object of the invention to provide a solution to the above problem, which meets the percussionist's needs. Basically, the invention is embodied in the provision of a cushioned percussion device that comprises: a) a projecting support for the device, b) a pivot for the support, and c) spring structure located to yieldably resist pivoting of the support. As will be seen, the spring structure may advantageously include a first spring element to resist pivoting in one direction, and a second spring element to resist pivoting in the opposite direction. A carrier typically carries that structure offset from the pivot and offset from a clamp or holder holding the percussion instrument in a position to be struck. It is another object to provide an adjuster to adjust the tension of the spring structure, for controlling the yieldable resistance to pivoting of the support. As will be seen, two adjustable spring elements or portions may be provided to adjust yieldable resistance to pivoting, in two directions. Yet another object includes provision of support structure including a strut yieldably supporting a cowbell lower portion; and a holder or clamp adjustably connecting the cowbell lower portion to the strut in spaced relation to the spring or springs, to enable adjustment of the clamp and cowbell lower portion toward or away from the spring or springs. Accordingly, the cowbell cushioned support apparatus may be “tuned” at up to three locations, to optimize the selectability of cushioned support for the cowbell, to individually suit requirements of different percussionists. These and other objects and advantages of the invention, as well as the details of an illustrative embodiment, will be more fully understood from the following specification and drawings, in which: DRAWING DESCRIPTION FIG. 1 is an elevation showing one preferred form of apparatus; FIG. 2 is a cross-section taken on lines 2 — 2 of FIG. 1; FIG. 3 is a plan view taken on lines 3 — 3 of FIG. 2; FIG. 4 is a section taken on lines 4 — 4 of FIG. 2; FIG. 5 is a section taken on lines 5 — 5 of FIG. 2; and FIG. 6 is an elevation like FIG. 1, but showing a modified form. DETAILED DESCRIPTION In the drawings a percussion instrument or device is shown at 10 , and may take the form of a cowbell. It has a lower wall portion 11 , and upwardly diverging walls 12 . The cowbell is to be forcefully struck as by a drum beater or stick 13 , during a performance or during practice. Upper rim 12 a can also be struck. In accordance with the invention, support structure is provided yieldably and resiliently supporting the cowbell lower portion 11 to enable the cowbell to bodily deflect when struck. The illustrated example shows such support structure to include a projecting support such as a strut 15 connected to the cowbell lower portion, as for example at 16 . That connection may advantageously include a clamp 17 having an upper part 17 a and a lower part 17 b at opposite sides of the strut, and which may be loosened to allow adjustment shifting of the cowbell lengthwise of the strut, toward or away from cushioning spring structure 18 . The clamp 17 may then be tightened, as on a threaded part 17 c . Such adjustment shifting facilitates adjustment of stiffness of cowbell deflection, when struck, to suit the requirements of the percussionist. The strut 15 may comprise a metal rod, which is knurled as shown at 15 a to facilitate non-slip connection of the clamp to the rod. A clamp adjuster is seen at 17 d. The spring structure 18 and strut 15 may be carried by a carrier, as for example a second strut or rod 20 having a projection 20 a . Strut 15 may have connection to rod 20 , as at a pivot 22 , for allowing the cowbell to bodily move up and down. The spring structure is carried for resiliently and yieldably resisting such bodily movement of the cowbell. In the example, a first spring or spring portion 18 a is positioned to resist downward pivoting of the strut 15 ; and a second spring or spring portion 18 b is positioned to resist upward pivoting of the strut 15 . Spring portion 18 a is shown as located below strut 15 and spring portion 18 b above strut 15 ; however, the spring portions may have other positions. In accordance with a further feature of the invention, the stiffness of one or both of the spring portions may be adjusted, to the requirements of the percussionist, whereby the stiffness of cowbell deflection is adjustable. In the example, a first adjuster 25 is provided to adjust the tension of the first spring portion 18 a , and a second adjuster 26 is provided to adjust the tension of the second spring portion 18 b . The first adjuster may have threaded connection to one end of a spring positioner 27 , whereby when rotated at 25 a , the spring portion 18 a is controllably compressed; and the second adjuster may have threaded connection to the opposite end of positioner 28 , whereby when rotated at 26 a , the spring portion 18 b is controllably compressed. The spring portion 18 a is compressed between adjuster 25 and a locater or connector 30 ; and the spring portion 18 b is compressed between adjuster 26 and connector 30 . That connector transmits spring force to the strut 15 , at location 31 , and the latter may include a pivot connection to the strut. See also guide pin 40 , thread connected to 25 and 26 , and tubular housing 41 for 25 , 26 and 30 . Set screws 42 when tightened fix the selected adjustment. Projection 20 a carries housing 41 . In operation, when the cowbell is heavily struck, as by force F, the strut 15 is pivoted downwardly, and coiled spring portion 18 a is momentarily compressed. As the strut 15 thereafter pivots or returns upwardly, upper spring portion 18 b is momentarily compressed; and the compressions of the two spring portions can be adjusted to adjust the stiffness of deflection of the cow bell, during play, to meet the requirements of the percussionist. Carrier rod 20 may be suitably connected to an upright stand, such as a cymbals stand 44 . In FIG. 6 the elements are generally the same as in FIG. 1, except for the following: the carrier pin 40 for the springs has pivotal connection at 60 to the strut 15 ; coil spring 18 a is compressed between an angled region 63 of rod 20 and a nut 61 ; and coil spring 18 b is compressed between angled locater region 63 and a nut 62 . The two nuts are threaded on the pin 40 , for adjustment to adjust the tension of the two springs, which control the yieldability of the cow bell when struck as by drum stick 13 . Such yieldability is indicated by pivoting of the strut 15 about pivot 22 . Nuts 61 and 62 are one form of pushers.

The cushioned percussion device, comprising in combination, a projecting support for the device; a pivot for said support, and spring structure located to yieldably resist pivoting of the support.

TECHNICAL FIELD [0001] The present disclosure relates to lifting systems. More particularly, the present disclosure relates to a load monitoring system for a lifting system. BACKGROUND [0002] During a manufacturing process, a product is typically advanced through a plurality of manufacturing stations within a manufacturing chain. Specifically, the product is transported through each of the manufacturing stations along a transportation system. The transportation systems may include overhead cranes, which are designed to lift and transport loads, within or between manufacturing stations. Overhead cranes, particularly those of the larger type, most commonly embody a bridge girder supported on trucks. The trucks are movable over runway beams supported on columns. In addition, the overhead crane includes one or more lifting components structured to lift loads for transportation. The lifting component, such as hook, strap, magnet, and/or the like, is coupled to a trolley frame slidably mounted on the bridge girder. Such lifting components may have rated capacities for a favorable lift operation. Further, during the lift operation, the lifting components may be subjected to stresses due to the loads being lifted by the lifting components. It may be considered that during the lift operation, the strain caused upon the lifting component, due to the lifted loads, may exceed a pre-determined threshold value. Since, the hoist devices have rated capacities, lifting the loads beyond the rated capacities may impose considerable stress on the lifting component and may result in unfavorable consequences. [0003] U.S. Publication No. 2010/0044332 discloses a method to monitor overstress conditions experienced by a crane component. In the overstress condition, a wireless signal that indicates an overstress condition is generated. In response to receipt of the wireless signal, a record of the overstress condition is stored in a storage module mechanically coupled with a crane component. However, the reference does not discuss a provision for an active overstress prevention based on rated capacities of lifting components. SUMMARY OF THE INVENTION [0004] The present disclosure relates to a load monitoring system for a lifting system. The lifting device is configured to lift a load during a lifting operation. [0005] In accordance with the present disclosure, the load monitoring system includes a lifting link assembly and a controller. The lifting link assembly includes a link body, a strain sensor, and a radio frequency identification (RFID) device. The link body is structured and arranged to couple the lifting device to the load. The strain sensor is fixed to the link body and is configured to generate a signal corresponding to the load. The RFID device is fixed to the link body and is configured to receive the signal. Further, the controller is in communication with the RFID device, and is configured to receive the signal from the RFID device and initiate a safe lifting protocol in response to the signal attaining a pre-determined threshold value. BRIEF DESCRIPTION OF THE DRAWINGS [0006] FIG. 1 is a perspective view of a lifting system engaged with a load, in accordance with the concepts of the present disclosure; [0007] FIG. 2 is a schematic view of a view of a first embodiment of a lifting link assembly of the lifting system of FIG. 1 , illustrating a strain sensor and an RFID device in an enlarged view of the encircled area of an adhesive layer on the lifting link assembly, in accordance with the concepts of the present disclosure; [0008] FIG. 3 a is a perspective view of a second embodiment of a lifting link assembly for use within the lifting system of FIG. 1 , which is embedded with a strain sensor and an RFID device, in accordance with the concepts of the present disclosure; [0009] FIG. 3 b is a perspective view of a third embodiment of a lifting link assembly for use within the lifting system of FIG. 1 , which is embedded with a strain sensor and an RFID device, which are illustrated by a cut-out, in accordance with the concepts of the present disclosure; [0010] FIG. 3 c is a perspective view of a fourth embodiment of a lifting link assembly for use within the lifting system of FIG. 1 , which is embedded with a strain sensor and an RFID device, which are illustrated by a cut-out, in accordance with the concepts of the present disclosure; [0011] FIG. 4 is a perspective view of a fifth embodiment of a lifting link assembly with a lifting eye embedded with the strain sensor and the RFID device illustrating a strain sensor and an RFID device in an enlarged view of the encircled area of the lifting eye of the lifting link assembly, in accordance with the concepts of the present disclosure; and [0012] FIG. 5 is a block diagram of a load monitoring system for the lifting system of FIG. 1 , in accordance with the concepts of the present disclosure. DETAILED DESCRIPTION [0013] Referring to FIG. 1 , there is shown a lifting system 100 . The lifting system 100 may include a plurality of lifting link assemblies 102 mounted to a lifting device 104 . The plurality of lifting link assemblies 102 includes the lifting link assembly 102 ′ and the lifting link assembly 102 ″. The lifting device 104 may include a pair of runway beams 106 , a pair of trucks 108 , an idler girder 110 , a trolley frame 112 , a pair of bridge drives 114 , and a pair of trolley drives 116 as is customary. The runway beams 106 may be supported on columns that may be independent of, attached to, and/or integral with the building columns of a manufacturing facility (not shown). The runway beam 106 includes a first end 118 and second end 120 , which defines a runway rail 122 . The runway rail 122 is structured to allow the pair of trucks 108 to slide between the first end 118 and the second end 120 . Each truck 108 includes the bridge drive 114 to facilitate synchronization of sliding of the truck 108 . [0014] The idler girder 110 is attached between the pair of the trucks 108 . The idler girder 110 includes a first end 124 and a second end 126 , which defines a bridge rail 128 . The first end 124 and the second end 126 include a plurality of end stops 130 . Further, the bridge rail 128 is structured to facilitate slidable movement of the trolley frame 112 . The movement of the trolley frame 112 may slide over the bridge rail 128 ; however, such movement of the trolley frame 112 is restricted by the end stops 130 placed at the first end 124 and the second end 126 . The trolley frame 112 includes a hoist 132 and the pair of trolley drives 116 . The trolley drives 116 on each side of the trolley frame 112 facilitate the slidable movement of the trolley frame 112 over the bridge rail 128 between the first end 124 and the second end 126 of the idler girder 110 . [0015] Further, the lifting device 104 may be coupled to a hook 134 , via the lifting link assembly 102 ′. The lifting link assembly 102 ′ may be a strap, cord or chain member, for example, or any portion of the aforesaid hereof, fitted with a force sensing and communication componentry as will be described herein below. Further, as seen in FIG. 1 , the hook 134 carries a load 136 , such as a partially assembled transmission for transit to an adjacent build station, for example, via the lifting link assembly 102 ″, which is tied around the load 136 . The lifting link assembly 102 ″ facilitates engagement with the lifting device 104 and transmits the weight of the load 136 to the lifting device 104 . The lifting link assembly 102 ′ may be connected in series, with at least one of the lifting link assemblies 102 ″, 102 ″′, 102 ″″, and 102 ″″ (as shown in FIGS. 2-4 ). In exemplary embodiments, the lifting link assembly 102 ′ includes a link body 200 ′, in the form of a chain link (as shown in FIG. 2 ). The lifting link assemblies 102 ″, 102 ″′, 102 ″″ include respective link bodies 200 ″, 200 ″′, 200 ″″, which may be straps (as shown in FIGS. 3 a , 3 b , and 3 c ). Alternatively, the lifting link assembly 102 ″″′ includes a link body 200 ″″′, which may be in the form of a lifting lug (as shown in FIG. 4 ). [0016] Referring to FIG. 2 , there is shown the lifting link assembly 102 ′ having a link body 200 ′. The lifting link assembly 102 ′ is structured to have a strain sensor 202 and an RFID device 204 fixed thereto. The strain sensor 202 and the RFID device 204 may be fixed to the lifting link assembly 102 ′, via an adhesive or glue, as is customary. As illustrated in FIG. 2 , an adhesive layer 206 is applied on the link body 200 ′, to facilitate attachment of the strain sensor 202 and the RFID device 204 . An enlarged view of an encircled portion of the adhesive layer 206 is depicted to illustrate the strain sensor 202 and the RFID device 204 . The strain sensor 202 is placed on the lifting link assembly 102 ′ to measure the strain generated in the lifting link assembly 102 ′, while the load 136 (shown in FIG. 1 ) is lifted during a lift operation. The strain sensor 202 generates a signal that corresponds to the strain in the lifting link assembly 102 ′, which in turn corresponds to the weight of the load 136 (shown in FIG. 1 ). The strain sensor 202 is coupled to the RFID device 204 , which is adapted to receive the signal from the strain sensor 202 , and thus, communicate with the lifting device 104 . [0017] Referring to FIG. 3 a , there is shown a second embodiment of the lifting link assembly 102 ″. The lifting link assembly 102 ″ may be positioned in series with the lifting link assembly 102 ′. The lifting link assembly 102 ″ includes a link body 200 ″, which is a single length of high tension material, such as a nylon composite, for example. The strain sensor 202 and the RFID device 204 may be embedded in the link body 200 ″ to ensure stretch or deflection of the lifting link assembly 102 ″. The strain sensor 202 generates a signal corresponding to a strain experienced by the lifting link assembly 102 ″, while the object is lifted. [0018] Referring to FIG. 3 b , there is shown a third embodiment of the lifting link assembly 102 ″′. The lifting link assembly 102 ′″ may be positioned in series with the lifting link assembly 102 ′. The lifting link assembly 102 ″′ includes a link body 200 ′″, which is a strap having an eye and eye structure. The link body 200 ″′ is composed of high tension material, such as a nylon composite, for example. The strain sensor 202 and the RFID device 204 may be embedded in the link body 200 ″′ to ensure stretch or deflection of the lifting link assembly 102 ″′. The strain sensor 202 generates the signal corresponding to the strain experienced by the lifting link assembly 102 ″′ while the object is lifted. [0019] Referring to FIG. 3 c , there is shown a fourth embodiment of the lifting link assembly 102 ″″. The lifting link assembly 102 ″″ may be positioned in series with the lifting link assembly 102 ′. The lifting link assembly 102 ″″ includes a link body 200 ″″, which is a strap having unilink structure. The link body 200 ″″ is composed of high tension material, such as a nylon composite, for example. The strain sensor 202 and the RFID device 204 may be embedded in the link body 200 ″″ to ensure stretch or deflection of the lifting link assembly 102 ″″. The strain sensor 202 generates the signal corresponding to the strain experienced by the lifting link assembly 102 ″″ while the object is lifted. [0020] The strain sensor 202 is in communication with the RFID device 204 . The strain measured by the strain sensor 202 is wirelessly communicated to a controller (shown as 502 in FIG. 5 ) to effect a safe lift protocol for the lifting device 104 via the RFID device 204 . A safe lift protocol may be one of halting any further movement of the load 136 (shown in FIG. 1 ) and an operator alert, for example. [0021] Referring to FIG. 4 , there is shown a fifth embodiment of the lifting link assembly 102 ″″′, which is a magnet assembly. The lifting link assembly 102 ″″′ may include the link body 200 ″″″ and a lifting eye 400 , which is coupled to the strain sensor 202 and the RFID device 204 , via the adhesive layer 206 ′. The strain sensor 202 may measure the load 136 (shown in FIG. 1 ) experienced by the lifting link assembly 102 ″″′ while performing the lift operation. Since, the strain sensor 202 is in control communication with the RFID device 204 , the strain measured by the strain sensor 202 is communicated to the lifting device 104 , via the RFID device 204 . [0022] Referring to FIG. 5 , there is shown a block diagram of a load monitoring system 500 for the lifting system 100 . The load monitoring system 500 may include a controller 502 , a display 504 , the strain sensor 202 , and the RFID device 204 . The controller 502 may be located on the lifting device 104 . The controller 502 may be adapted to monitor the lift operation, based on the communication with the lifting link assembly 102 , via the strain sensor 202 and the RFID device 204 . The controller 502 may be coupled to the display 504 , which is positioned in the lifting device 104 . The display 504 may be a graphical user interface, a touch screen, and/or the like. INDUSTRIAL APPLICABILITY [0023] In operation, during the lift operation, the load 136 is engaged with the lifting link assembly 102 , which includes the strain sensor 202 and the RFID device 204 . As the lifting device 104 lifts the load 136 off a rest position, the strain sensor 202 in the lifting link assembly 102 stretches in length. By this means, there is an increase in electrical resistance. This results in generation of the signal that corresponds to the strain experienced by the strain sensor 202 . The signal thus generated is communicated to the RFID device 204 , which is connected to the strain sensor 202 . The RFID device 204 then sends the signal to the controller 502 . The controller 502 infers the strain information, which is based on the signal and determines if the measured strain is equal to the pre-determined threshold value for the respective lifting link assembly 102 . The pre-determined threshold value corresponds to the strain beyond which the lifting link assembly 102 may fail. Thus, upon determination that the strain in the strain sensor 202 of the lifting link assembly 102 has reached the pre-determined threshold value, the controller 502 initiates a safe lifting protocol and sends signals to the lifting device 104 to disable or stop the lift operation. The controller 502 also sends alert signals to the display 504 for operator information. The display 504 is adapted to visually represent data that pertains to the lift operation received by the controller 502 . The alert signal may be accompanied with sound alerts. In an embodiment, the controller 502 disables all navigation functions, except for the function that lowers the load 136 . [0024] For example, the lifting system 100 includes the lifting link assembly 102 ′ and 102 ″. In such case, the lifting link assembly 102 ″ may fail at a lower load as compared to the lifting link assembly 102 ′. This implies that the pre-determined threshold value for the lifting link assembly 102 ″ is lower than the pre-determined threshold value of the lifting link assembly 102 ′. Thus, in this case, the controller 502 gives priority to a lower pre-determined threshold value. The lower pre-determined threshold value corresponds to the pre-determined threshold value of lifting link assembly 102 ″. This helps in prevention of the failure of the lifting link assembly 102 ″, while lifting the load 136 . This way failure of the weakest lifting link assembly 102 is prevented. In an embodiment, the RFID device 204 is coupled to loads, fixtures, pallets, and actual parts involved in the lift operation. In such case, an RFID reader is employed to extract information regarding the weight of the loads, fixtures, pallets, and/or actual parts (such as clamping/holding devices) and pre-determined threshold strain value for each of the loads, fixtures, pallets, and/or actual parts. Further, this may indicate whether the loads, fixtures, pallets, actual parts, and/or the current lifting link assembly 102 are favorable for the lift, which prevents any unfavorable results. Accordingly, the load monitoring system 500 notifies the operator about the lift operation via the display 504 . This implies that the load monitoring system 500 notifies the operator if all conditions are optimum for the lift operation or what units need to be replaced to complete the lift operation, for example, if the lifting link assembly 102 does not meet weight limits or the load exceeds limit for the lifting device 104 . The proposed load monitoring system 500 intends to provide a real-time monitoring of the load 136 to increase productivity of the lift operations. The disclosed load monitoring system 500 makes use of strain sensors which provides information of stresses in the lifting link assemblies 102 . On reaching, the pre-determined threshold strain value, the disclosed system stops the raising of the lifting link assembly 102 , thereby halting the lift operation. The existing systems calculate favorable total lift weight based on weight of each object to be lifted. [0025] The many features and advantages of the disclosure are apparent from the detailed specification, and, thus, it is intended by the appended claims to cover all such features and advantages of the disclosure, which fall within the true spirit and scope thereof. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the disclosure to the exact construction and operation illustrated and described, and, accordingly, all suitable modifications and equivalents may be resorted to that fall within the scope of the disclosure.

A load monitoring system for a lifting system that includes a lifting device is provided. The load monitoring system includes a lifting link assembly and a controller. The lifting link assembly includes a link body, a strain sensor, and a radio frequency identification (RFID) device. The link body is structured and arranged to couple the lifting device to a load. The strain sensor is fixed to the link body and is configured to generate a signal corresponding to the load. The RFID device is fixed to the link body and is configured to receive the signal. Further, the controller is in communication with the RFID device, and is configured to receive the signal from the RFID device and initiate a safe lifting protocol in response to the signal attaining a pre-determined threshold value.

BACKGROUND OF THE INVENTION The present invention relates to the control of certain parasitic weeds and to weed control compositions suitable for this purpose, as well as to certain new chemical compounds possessing the requisite biological activity. More particularly the invention relates to the control of the weeds Striga hermonthica, S. asiatica (lutea), Orobanche crenata, O. ramosa and O. aegyptiaca which are parasitic on certain economically important crops such as sorghum, maize, sugar cane and/or broad beans. Striga causes serious losses in sorghum production and its control is highly desirable since sorghum is the principal subsistence cereal grain for more than 300 million people living in arid tropcial countries. One of the reasons it is difficult to control this weed is that its seeds can remain viable in the soil for as long as 20 years, only germinating in close proximity to the host plant. Thus, control of Striga by rotation of crops or leaving the sorghum fields fallow for a year or more is ineffective since the seeds germinate only when the host plant is sown and starts to grow. Control by planting "false hosts", i.e. plants which trigger germination of the parasite but which do not act as hosts, is usually uneconomical since such planting must replace the desired crop. Another reason Striga is difficult to control is that since it is parasitic in nature, it draws all its nourishment from its host plant, e.g. sorghum, and is not readily amenable to control by normal weed killers, even those which are selective against certain classes of the weeds. DESCRIPTION OF THE PRIOR ART It has recently been shown that germination of the Striga seeds is caused by a substance secreted by the roots of the host plant. This substance has been given the name strigol (Cook et al, J. Amer. Chem. Soc. 1972, 94, 6198) and is represented by the structure ##STR1## Neither its synthesis, which has recently been reported, nor its isolation from the root exudate of the sorghum or other host plant, offers an economic route to control of Striga. However, if a readily available stimulant for the germination of Striga seed were available, such a substance could be used to control Striga by application to the soil containing the dormant seed of the parasite at a time when the host plant was not growing, whereupon the Striga seeds would germinate and, having no host plant to parasitize, would die through lack of nutrition. A similar approach to the control of Orobanche would be attractive. Cassady and Howie, J.C.S. Chem. Comm. 1974, p. 512 have recently reported the synthesis of certain dilactones related to strigol. These authors coupled the sodium enolate salt of 2-hydroxymethylene-γ-butyrolactone with 4-bromobut-2-enolide or with its 5-methyl derivative to yield compounds of the structure ##STR2## wherein R is hydrogen or methyl. SUMMARY OF THE INVENTION The present invention is based on the discovery of certain chemical compounds which are able to act as germination stimulants for the seeds of Striga hermonthica, S. asiatica, Orobanche crenata, O. ramosa and O. aegyptiaca, and which are comparatively easily synthesized. According to the present invention, there is provided a method for controlling at least one of the above named parasitic weeds by contacting dormant seeds thereof, in the absence of an actively growing host plant, with a compound corresponding to one of the formulae ##STR3## wherein R is H or C 1 to C 8 alkyl, particularly C 2 H 5 or CH(CH 3 ) 2 , R' is H or C 1 to C 5 alkyl, particularly methyl, X represents a single bond or a --CH 2 -- linkage, and Y represents two hydrogen atoms, an additional bond or an epoxy group. DETAILED DESCRIPTION OF THE INVENTION According to one embodiment of the invention, the compounds of formulae (I), (III) and (IV) above are those of the formulae ##STR4## wherein R in formula (Ia) is H or lower alkyl of up to 8 carbon atoms, particularly C 2 H 5 or CH(CH 3 ) 2 . By the expression "in the absence of an actively growing host plant" is meant either that the host plant is completely absent from the soil containing the parasitic weed seeds being treated, or that the host plant has substantially reached maturity so that any infestation of the host plant by the parasitic weed following germination of the seeds thereof will have a minimal effect on the host plant and harvesting of the latter or natural death at the end of the growing season will prevent the parasitic weed from reaching maturity and consequently re-seeding itself. The invention also consists in herbicidal compositions comprising an active compound of the structure (I), (II), (III) or (IV), together with a suitable carrier. In addition, the invention consists in the new compounds of these structures, i.e. (I) [R is C 3 to C 8 alkyl and R' is H or C 1 to C 5 alkyl] (III) [wherein R' is C 1 to C 5 alkyl and X is a single bond, or wherein X is a --CH 2 -- linkage and R' is H or C 1 to C 5 alkyl] and (IV) [wherein R' is C 1 to C 5 alkyl, X is a single bond and Y is an additional bond or an epoxy group, or wherein R' is C 1 to C 5 alkyl, X is a --CH 2 -- linkage and Y is two hydrogen atoms, a single bond or an epoxy group]. A preferred aspect of the invention consists in compounds of formula (I) wherein R is CH(CH 3 ) 2 and R' is methyl; formula (III) wherein R' is CH 3 and X is a single bond; and formula (IV) wherein R' is methyl, X is a single bond and Y is an additional bond, and methods and compositions utilizing such compounds as well as the compound of formula (I) in which R is C 2 H 5 and R' is methyl. The invention also consists in a process for the preparation of the compounds of formulae (III) and (IV) which comprises coupling an alkali metal salt, such as the sodium salt, of a compound of formula (II) with the methylsulphonate derivative of a compound of formula (I) wherein R is hydrogen. This synthesis has unexpected advantages over the subsequently proposed synthesis employing a bromo derivative of a compound of formula (I) wherein R is hydrogen, namely, it proceeds more readily, gives higher yields and is more economical, since the bromo derivatives are unstable and tend to re-arrange. The active compound of formula (I), (II), (III) or (IV) is preferably applied to the soil containing the dormant parasitic weed seeds in the form of a composition containing the active compound in admixture with a suitable inert carrier or diluent. Suitable carriers or diluents are particularly finely divided solid inert carriers or diluents such as powdered chalk, powdered clays, or powdered conventional fertilizers. Also suitable are liquid carriers. Pre-mixes of a relatively high concentration of the active agent with a carrier may be formulated for ease of handling, particularly for ease of preparing the final composition to be applied to the soil. For instance, such a pre-mix may take the form of a solution of the active compound in an inert organic solvent, such solution also containing a surface active agent selected to promote the formation of an aqueous emulsion when the concentrate is diluted with a large volume of water. The active compound of formula (I), (II), (III) or (IV) may be applied to the soil containing the parasitic weed seeds in amounts of from 100 to 5000 grams/hectare or from 0.01 to 0.5 grams/cubic meter of soil, and for this purpose compositions may be used containing from 0.001 to 1000 parts per million of the active compound, the balance of such compositions being essentially inert diluent or carrier as described above. The actual concentration of the active compound is of little importance compared with its rate of application to the soil. Too little of the active compound may secure insufficient germination of the parasitic weed seeds to afford effective control. Naturally, temperature and moisture conditions in the soil should be suitable for the germination of the parasitic weed seed. While compounds of formula (I) wherein R is C 3 to C 8 alkyl, e.g. CH(CH 3 ) 2 have not previously been reported, they are homologues of the known compound (Ia) wherein R is C 2 H 5 and may be prepared by the usual esterification procedures from the known compound (Ia) wherein R is H, e.g. ##STR5## As illustrative of the preparation of compounds (III) and (IV), compound (IIIa) for instance may be prepared by reacting an alkali metal salt, such as the sodium salt, of the known compound (II) with a sulphonate derivative of the lactone (Ia; R=H): ##STR6## The compound (IVa) may be prepared by an analogous procedure, i.e. ##STR7## Similarly, the compounds (III) and (IV) in X is a --CH 2 -- linkage and Y when present is two hydrogen atoms or a single bond, may be prepared analogously from 2-hydroxymethyl-δ-valerolactone sodium enolate salt or its cyclopentano or cyclopenteno derivative, while the compounds (IV) in which Y is epoxy may be prepared by epoxidation of the corresponding unsaturated compound. The synthesis of some of the active compounds described above from readily available materials is illustrated by the following reaction schemes: ##STR8## In order to demonstrate the activity of the compounds in promoting the germination of seeds of Striga hermonthica, Striga asiatica, Orobanche aegyptiaca, Orobanche crenata, and Orobanche ramosa, the following method was used. Seeds of the host plant (sorghum) and of the parasitic weeds were first sterilized with a 1% aqueous sodium hydrochlorite solution for 15 minutes, and then washed with distilled water until free of hypochlorite. For the purposes of control experiments a natural root exudate of sorghum was prepared by planting sterilized sorghum seeds in pots containing acid-washed silver sand and incubating at 23° C with daily addition of sufficient distilled water to keep moist. After about 1 week the root exudate was extracted by applying suction to the base of the pots. The Striga or Orobanche seeds were pre-treated by incubating at 23° C under moist conditions, e.g. on moist glass fibre filter paper, for 10-14 days. Usually about 25 seeds on 10 mm discs of the filter paper were employed. Discs carrying pre-treated seed of Striga or Orobanche were dabbed to remove surplus moisture. Two discs were then placed in each of two replicate dishes, so there were 4 discs per treatment, carrying a total of about 100 seeds. The compounds to be tested were dissolved in ethanol and diluted to the required concentration with distilled water. The amount of ethanol was never greater than 0.5% v/v in the final solution. Freshly prepared solutions were always used. To each disc was added two 16 μl drops of test solution ("no exudate") or one drop of test solution plus one drop of crude root exudate from 10 day old sorghum plants ("+ exudate"). Dilution of the test solutions by the exudate and/or by moisture in the discs was allowed for so concentrations given were final concentrations. Germination was counted after 2 days at 34° C in the case of Striga and 5 days at 23° C in the case of Orobanche. TABLE I______________________________________Germination tests on Striga hermonthica Concentration % GerminationCompound ppm "no exudate" "+ exudate"______________________________________ 0.001 1 0.01 27IIIa 0.1 51 ; 56* 1 61 10 70 50 -- 70 100 46Control(100% exudate) 72Control(distilled H.sub.2 O) 0______________________________________ *duplicate test carried out subsequently. The substances Ia [R = H; C.sub.2 H.sub.5 ; or CH(CH.sub.3).sub.2 ] and II showed little or no activity in promoting the germination of Striga hermonthica. The substances Ia [R=H; C 2 H 5 ; or CH(CH 3 ) 2 ] and II showed little or no activity in promoting the germination of Striga hermonthica. TABLE I______________________________________Germination tests on Striga hermonthica Concentration % GerminationCompound ppm "no exudate" "+ exudate"______________________________________ 0.001 1 0.01 27IIIa 0.1 51 ; 56* 1 61 10 70 50 -- 70 100 46Control(100% exudate) 72Control(distilled H.sub.2 O) 0______________________________________ *duplicate test carried out subsequently. The substances Ia [R = H; C.sub.2 H.sub.5 ; or CH(CH.sub.3).sub.2 ] and II showed little or no activity in promoting the germination of Striga hermonthica. TABLE II______________________________________Germination tests on Orobanche aegyptiaca Concentration % Germination______________________________________Compound ppm "no exudate" "+ exudate"______________________________________ .001 0 .01 12 .1 19; 27; 44 1 59; 60 Ia(R = H) 10 80; 69 25 79 50 87 75 100 61; 68 200 8 30.sup.t 400 0Control(100% exudate) 84; 66; 78Control(distilled H.sub.2 O) 0; 20; 1 .001 0 .01 0 .1 19; 2 Ia(R = C.sub.2 H.sub.5) 1 34 10 58 25 95 50 88.sup.t 61 100 70; 83.sup.tIa(R-C.sub.2 H.sub.5) 200 19.sup.t 0 400 0 .1 4 1 6II 10 24 50 -- 66 100 64 .001 73 .01 76 .1 82; 77IIIa 1 69.sup. t 10 71.sup.t 50 -- 61.sup.t 100 47.sup.t 0.001 0 0.01 1 0.1 26.sup.t ; 11Ia[R = CH(CH.sub.3).sub.2 ] 1 26.sup.t 10 48.sup.t 50 72 100 67.sup.t______________________________________ t = Evidence of toxicity - some reduction in vigour As in the case of tests on Striga, replicate tests were carried out on different dates. It can be seen from Table II that each of the compounds has some activity in promoting the germination of Orobanche, the best being apparently Compound IIIa TABLE III______________________________________Germination tests on Striga hermonthica, Striga asiaticaand Orobanche aegyptiaca.______________________________________Concentration % Germination______________________________________Compound ppm S.hermonthica S.asiatica O.aegyptiaca*______________________________________IIIa 0.007 3 56 87 0.00007 2 13 87 0.0000007 0 1 94IVa 0.007 22 60 87 0.00007 6 55 89 0.0000007 0 9 91ControlStandardexudate 65 59 89ControlDistilledwater 0 2 78______________________________________ *In this test the Orobanche seeds have little natural dormancy remaining. It is evident from Table III that compound IVa shows slightly higher activity against Striga than compound IIIa. TABLE IV__________________________________________________________________________Germination tests on Striga hermonthia, Striga asiatica andOrobanche ramosa.__________________________________________________________________________ Concentration % Germination__________________________________________________________________________Compound ppm S.hermonthica S.asiatica O.ramosa__________________________________________________________________________IVa 1.0 -- -- 46 0.1 58 10 55 0.01 53 1 51 0.001 16 0 --IV X = single 1.0 45 30 bond Y = 2H 0.1 44 35 R' = CH.sub.3 0.01 21 41 0.001 4 --IV X = single 1.0 41 bond y = epoxy 0.1 18 group R' = CH.sub.3 0.01 3 0.001 0III X = CH.sub.2 1.0 -- linkage R' = CH.sub.3 0.1 17 3 0.01 5 5* 0.001 0 0Standard 58 5 --Sorghum exudate__________________________________________________________________________ *anomaly TABLE V______________________________________Germination tests on Orobanche crenata ConcentrationCompound ppm % Germination______________________________________IIIa 1.0 52.0 0.1 18.0 0.01 0.0 0.001 0.0IVa 1.0 64.3 0.1 49.1 0.01 11.4 0.001 0.0Sorghum exudate 0.0Broad bean exudate 0.0Lentil exudate 0.0Distilled water 0.0______________________________________ For the following field tests the procedure was as follows: 1. Striga asiatica seed was uniformly mixed with black or red soil and the trays were filled on June 18, 1974. 2. Compounds IIIa and IVa were applied at 10, 5 and 1 ppm concentration in both the soils keeping 6 replications for each treatment and one control tray for each soil. 3. Watering was continued everyday up to field capacity. 4. C S H - 1 sorghum seed was planted in both treated and control trays on Aug. 19, 1974. 5. Counting of Striga plants above ground level was taken on Oct. 21, 1974. 6. Counting of Striga plants was also taken after washing the soil between Oct. 31, 1974 and Nov. 8, 1974. The following results were presented. Values in the brackets indicate the number of plants before washing. TABLE VI__________________________________________________________________________BLACK SOILCOMPOUND IIIa COMPOUND IVa__________________________________________________________________________Replica-tions10 ppm 5 ppm 1ppm 10 ppm 5 ppm 1 ppm__________________________________________________________________________1. 66 ( 64) 142 (127) 158 (140) 23 ( 18) 46 ( 22) 47 ( 40)2. 106 (104) 61 ( 59) 78 ( 74) 37 ( 25) 96 ( 77) 48 ( 47)3. 136 (133) 87 ( 84) 125 (112) 50 ( 35) 18 ( 13) 61 ( 43)4. 142 (123) 78 ( 67) 191 (150) 30 ( 24) 8 ( 8) 33 ( 30)5. 222 (167) 60 ( 58) 102 (100) 6 ( 4) 15 ( 11) 2 ( 1)6. 122 ( 95) 182 (159) 103 ( 83) 7 ( 6) 16 ( 9) 36 ( 21)Total806 (686) 610 (554) 757 (659) 153 (112) 199 (140) 227 (182)Mean 134 (114) 102 ( 92) 126 (110) 26 ( 19) 33 ( 23) 38 ( 30)Control126 (115) 90 ( 78)__________________________________________________________________________ Conclusions: 1. Statistical analysis of data indicated that compound IVa recorded the highest significant efficiency (50.00%) over control in controlling Striga. 2. There is no significant difference between concentrations in respect of both the compounds, possibly suggesting that some of the Striga seed was not sensitive to germination at the time the compound was applied. TABLE VII______________________________________RED SOILCOMPOUND IIIa COMPOUND IVa______________________________________Replica-tions 10 ppm 5 ppm 1 ppm 10 ppm 5 ppm 1 ppm______________________________________1. 13 (1) 15 (2) 44 (7) 16 (5) 22 (6) 20 (7)2. 10 (2) 32 (4) 45 (7) 4 (0) 11 (3) 41 (7)3. 9 (1) 38 (6) 47 (8) 10 (0) 31 (6) 16 (3)4. 10 (3) 44 (3) 53 (5) 23 (4) 26 (5) 19 (4)5. 19 (5) 21 (2) 52 (8) 7 (2) 8 (3) 24 (3)6. 8 (3) 18 (3) 45 (6) 5 (0) 12 (2) 19 (3)Control -- 48 (6) -- 45 (7)______________________________________ Conclusions: 1. Statistical analysis of data indicated that the efficiency between compound IIIa and IVa in controlling Striga is significantly different. 2. Highly significant differences were obtained in between three concentrations in respect of both the compounds. 3. Compound IVa has recorded the highest efficiency (35%) at 10 ppm concentration in controlling Striga. 4. At 1 ppm concentration compound IVa has recorded 15.5% efficiency over control whereas compound IIIa has shown 0.5% efficiency. ##STR9## SYNTHESIS OF COMPOUND IIIa i. Preparation of the sodium salt of 3-hydroxymethylene-1,4-butyrolactone -- procedure of F. Korte and H. Machleidt, Ber., 88, 136 (1955). Sodium (11.5g.) was suspended in dry ether (200 ml.) in a 1l. flask equipped with mechanical stirrer. Absolute ethanol (2 ml.) was added and the mixture stirred at room temperture for 3 hrs. A mixture of 1,4-butyrolactone (43g.) and ethyl formate (55.5g., 1.5 equiv.) in ether (100 ml.) was then added over a period of 1 hr. at room temperature. A precipitate was formed immediately and after the addition had been completed no more metallic sodium was present. The mixture was allowed to stand at -20° C overnight. It was filtered under vacuum and washed quickly with dry ether, then transferred while still wet with ether to a vacuum oven. The salt was dried at 40° C in vacuo. Yield, 64.5g. (95%). ii. Preparation of Compound IIIa The mesylate of compound Ia (19.04g.) was dissolved in 1,2-dimethoxyethane (200 ml.) and the sodium salt of 3-hydroxymethylene-1,4-butyrolactone (15g.) was added and this mixture stirred at room temperature for 24 hrs. The mixture was then filtered and the residue washed well with 1,2-dimethoxyethane. The filtrate was evaporated to dryness and the residue taken up in methylene chloride (20 ml.). Ether (60 ml.) was added carefully and the product allowed to crystallize. The white crystalline product was removed by filtration and washed with ether. Yield 12g. (60%), mp 92°-94° C. (Found: C, 57.04; H, 4.7 C 10 H 10 O 5 requires C, 57.14; H, 4.76%). ##STR10## SYNTHESIS OF COMPOUND III (R' = CH 3 , X = --CH 2 --) i. Preparation of the Sodium salt of δ-Valerolactone Sodium metal (2.30g.) was suspended in dry ether (150 ml.) in a 500 ml. 3 neck round-bottom flask equipped with stirrer, heating mantle, dropping funnel and reflux condenser. Ethanol (1.5 ml.) was then added and the mixture stirred at room temperature for 3 hrs. The mixture was then heated to reflux and a mixture of δ-valerolactone (10g.) and ethyl formate (22.2g., 3 equivalents) in ether (50 ml.) added over a period of 1.5 hrs. The mixture was then stirred under reflux for 15 hrs., cooled and the sodium salt removed by vacuum filtration. It was washed well with dry ether and then dried in vacuo at 40° C. Yield 13g. (85.5%). ii. Preparation of Compound III (R' = CH 3 , X = --CH 2 --) The mesylate of compound Ia (1.26g.) was dissolved in 1,2-dimethoxyethane (20 ml.). The sodium salt of 3-hydroxymethylene-δ-valerolactone (1.5g., 1.5 equiv.) was added and the mixture stirred at room temperature for 4 hours. The mixture was then poured into icewater (100 ml.) and extracted with methylene chloride (2 × 100 ml.). The organic extracts were washed with water (2 × 50 ml.), combined, dried over magnesium sulphate, and evaporated to dryness. The semi-crystalline residue was taken up in methylene chloride (1.5 ml.), and ether (6 ml.) carefully added. The product crystallized and was removed by filtration and washed well with cold ether. Yield 1.05g. (71%), mp 105°-107° C. SYNTHESIS OF COMPOUND__________________________________________________________________________IVa ##STR11## ##STR12## Reaction (i) ##STR13## ##STR14## Reaction (ii) ##STR15## ##STR16## Reaction (iii) ##STR17## ##STR18## Reaction (iv) ##STR19## ##STR20## Reaction (v) ##STR21##__________________________________________________________________________ Reaction 1 To a 31. 3-neck flask equipped with mechanical stirrer and heating mantle, was added a solution of freshly prepared cyclopentadiene (156g.) and dichloroacetylchloride (117g.) in n-pentane (2000 ml.). The mixture was brought to reflux and triethylamine (86g.) in n-pentane (500 ml.) was added over a period of 0.5 hrs. The resulting heavy slurry was refluxed for a further 0.5 hrs. then filtered and the residue washed well with n-pentane. The filtrate was reduced in vacuo to 800 ml., transferred to a separating funnel and washed twice with water (2 × 200 ml.). The organic layer was dried over magnesium sulphate, the solvent removed in vacuo and the residue vacuum distilled, bp 72°-73° C at 3.5mm. Yield 108g. (77%). Reaction 2 To a 21. 3-neck flask equipped with a mechanical stirrer was added a solution of the dichloroketone product of reaction 1 (100g.) in 90% acetic acid (aqueous) (900 ml.). Zinc dust (91g., 2.5 equiv.) was added portionwise to the cooled stirred solution over a period of 1 hr., the temperature beinng maintained below 40° C during this period. The cooling bath was replaced with a heating mantle and the mixture heated over 1 hr. to 100° C and maintained at that temperature. After 2 hrs. a further amount of zinc (91g., 2.5 equiv.) was added and the mixture stirred at 100° C for a further 1 hr. The mixture was then cooled to <10° C and filtered. The filtrate was poured into icewater (2000 ml.) and transferred to a separating funnel and extracted 3 times with methylene chloride (3 × 1000 ml.). The extracts were washed with water (4 × 1000 ml.), then with saturated sodium bicarbonate solution (1000 ml.). The combined extracts were dried with magnesium sulphate, the solvent removed in vacuo, and the residue vacuum distilled bp 61°-62° C at 14mm. Yield 51.4g. (86%). Reaction 3 The ketone product of reaction 2 (40g.) was dissolved in acetic acid/H 2 O (7/1; 400 ml.). Hydrogen peroxide (30%) (94.6 ml., 2.5 equiv.) was added when the mixture had been cooled to 0° C. The mixture was then stored at 0° C for 18 hrs. then diluted with icewater (400 ml.) and extracted twice with methylene chloride (2 × 200 ml.). The organic extracts were washed with water (3 × 200 ml.) and with saturated sodium bicarbonate solution (200 ml.). The combined extracts were dried with magnesium sulphate, the solvent removed in vacuo and the residue vacuum distilled, bp 66°-67° at 0.3 mm. Yield 41.4g. (90%). Reaction 4 A 250 ml. 3 neck flask equipped with magnetic stirrer, dropping funnel and nitrogen inlet was charged with dry diethyl ether (100 ml.). Sodium (2.83g.) and ethanol (1 ml.) was added to this mixture and stirred at room temperature for 3 hrs. The dropping funnel was then charged with a mixture of the lactone product of reaction 3 (15g.) and ethyl formate (10.2g.) in ether (50 ml.). This mixture was added dropwise to the sodium/sodium ethoxide slurry over a period of 1 hr. at room temperature. The mixture was then stirred for a further 1 hr. and then cooled to -20° C for 16 hrs. The sodium salt was removed by vacuum filtration and washed quickly with dry ether. The hygroscopic sodium salt, still very wet with ether, was rapidly transferred to a vacuum oven and dried at 40° C in vacuo. Yield 19.3g. (90%). Reaction 5 The mesylate (19.4g.; see below) was dissolved in 1,2 dimethoxyethane (200 ml.) and cooled to 0° C. The sodium salt product from reaction 4 (18.5g.; 1.1 equiv.) was added and the mixture stirred at 0° C for 3 hrs. The precipitated sodium mesylate was removed by filtration and washed well with dimethoxyethane. The filtrate was evaporated to dryness at <40° C and the residue taken up in methylene chloride (200 ml.). The solution was washed with water (2 × 100 ml.), dried with magnesium sulphate and evaporated to dryness. Crude yield 24.6g. (98%). After crystallization from methylene chloride/ether the yield was 16.2g. (65%) mp 128- 130° C. Analysis: C 13 H 12 0 5 requires C, 62.90; H, 4.84. Found: C, 62.96; H, 4.68%. Preparation of Mesylate. A 21. 3 neck flask equipped with cooling bath and mechanical stirrer was charged with the pseudo acid (compound Ia; R = H) (80g.), mesyl chloride (81.15g., 1:01 equiv.) and methylene chloride (800 ml.). This mixture was cooled to 0° C and triethylamine (74.4g.; 102.4 ml., 1.05 equiv.) in methylene chloride (300 ml.) was added over a period of 41/2 hrs. The mixture was then stirred at 0° C for 8 hrs., and then poured into water (500 ml.) in a separating funnel. The organic layer was washed once more with water (250 ml.), dried over magnesium sulphate, and the solvent removed in vacuo. The residue was taken up in warm ether (100 ml.) and allowed to crystallize first at room temperture and then at -20° C. The product was removed by vacuum filtration and washed sparingly with ether. Yield 92g. (70%).

Active compounds, some of which are new, are described for the control of various parasitic weeds of the genus Striga and Orobanche. These compounds all include cyclic lactone structures and are related to the naturally occurring substance strigol. Methods of synthesis of the compounds are given, as well as compositions and methods for controlling the parasitic weeds.

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a generic-type steam iron. 2. Description of the Related Art A steam iron is known from DE-PS 42 14 564 which comprises an electric pump, which conveys water from the water tank via a pressure reservoir to the individual consumers, such as the evaporation chamber, the auxiliary evaporation chamber and the spray device. In order to spray the material which is to be ironed in the region in front of the iron and for steam production, corresponding cut-off valves are actuated from outside the iron by way of manual actuating members. The valves are coupled for the production of steam to control electronics via electric switches. This known steam iron has the disadvantage that an additional electric switch is required for the production of additional steam. This additional switch interrupts the electric circuit of the pump via the control electronics during actuation of the corresponding cut-off valve in order to prevent the auxiliary evaporation chamber from flooding. Consequently, this known steam iron is still too complicated with regard to its control technology. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a steam iron which can be manufactured in a simpler fashion with respect to control technology and can therefore be produced in a more assembly-friendly, reliable and cost-effective manner. Pursuant to this object, and others which will become apparent hereafter, one aspect of the present invention resides in a steam iron having a water tank, individual water consumers, an electric pump for conveying water from the water tank via supply lines to the individual water consumers, a pressure reservoir arranged between the pump and the water consumers, which pressure reservoir includes switch means for signaling a maximum water level in the pressure reservoir, a plurality of manually actuable cut-off valves, a switch associated with one of the cut-off valves, and control electronics operatively connected with the switch, the switch means and the pump for controlling different operating modes of the pump and permitting unlimited pump operation time as a function of actuation of the cut-off valves, the switch and the switch means. The control electronics are further operative to recognize and control different operating modes of the pump associated with the individual water consumers as a function of pressure changes in a pressure control circuit. The control electronics limit the operating time of the pump to a maximum time in accordance with the respective operating mode. As a result of the different dimensioning--as regards flow resistance--of the outlet for the additional steam, comprising a cut-off valve, water hose and metal pipe on the one hand, and the outlet for the spray device, comprising a cut-off valve, water hose and spray nozzle on the other hand, the switch which is coupled to the pressure reservoir carries out different switching cycles, which can be differentiated by the control electronics as an additional steam operation or a spraying operation. The usual spraying operation and the capacity-restricted operation of the electric pump required for this process is actuated by a second switch coupled to the steam valve and the control electronics. In an advantageous manner, the fact that the pump is switched off after a predetermined response time during steam jet mode prevents the auxiliary evaporation chamber from being flooded and the electric pump is prevented from running dry--which would cause damage--when the water tank is empty. As a result of the invention, there is no need for the additional electric switch which is required in the state of the art for generating additional steam and which interrupts the electric circuit via the control electronics upon actuation of the corresponding cut-off valve. Consequently, the invention offers a substantial simplification of the control technology and assembly whilst improving the reliability of the iron. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of the steam iron according to the present invention; FIG. 2 is a circuit diagram of a steam iron according to FIG. 1; FIG. 3 is a circuit diagram of a steam iron according to the prior art; FIG. 4 is a graph illustrating spraying operation; and FIG. 5 is a graph illustrating steam jet operation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The steam iron schematically illustrated in FIGS. 1 and 2 comprises a water tank 1, an electric pump 2, a pressure reservoir 3 and a spray device 4. The cylindrical pressure reservoir 3 is constructed as a pressure-loaded water reservoir. A piston 6 that is displaceable by the pressure of a spring 5 is arranged inside the pressure reservoir 3. The piston rod 7 of the piston 6 is in operative connection with an electric switch 8. The pump 2 and the pressure reservoir 3 are connected via supply lines 9 and cut-off valves 10, 11 and 12 to water consumers, namely an evaporation chamber 13, an auxiliary evaporation chamber 14 and the spray device 4. The actuation of the cut-off valves 10, 11 and 12 is effected manually via manual actuation members 17, 18 and 19. The valve 11 is in operative connection with control electronics 20 via an electric switch 16 connected to the valve 11. Once the maximum water level of the pressure reservoir 3 is reached, the switch 8 is actuated by the piston rod 7 and the pump 2 is switched off. In contrast, if the water level in the pressure reservoir 3 falls below a certain level, the pump 2 is switched on again via the switch 8. The pump 2 and the pressure reservoir 3 thus form a control circuit which ensures that there is always sufficient water at the outlet of the supply line 9 and that the water always has the required water pressure, since the water withdrawn from the pressure reservoir 3 is immediately replaced. The optimum operating pressure for the entire water storage system is adjustable in the pressure reservoir 3. FIG. 3 illustrates the prior art in a schematic drawing similar to FIG. 2. It can be seen that a further switch 21 is required for generating additional steam, the further switch 21 switching off the pump 2 via the control electronics when the valve 12 is actuated, thereby preventing the auxiliary evaporation chamber 14 from flooding. In the operating condition, the iron is switched on and the pump 2 conveys water into the pressure reservoir 3. Once the maximum water level is reached, the pump 2 is switched off and the water is ready for use at the optimum operating pressure upstream of the valves 10, 11 and 12. In order to spray the material which is to be ironed with cold water, the valve 10 is opened via the manual actuating member 17. The water pressure then falls until the reconnection level is reached in the pressure reservoir 3 and the pump 2 conveys more water into the reservoir. The relationship between the conveying rate of the pump 2 and the withdrawal rate of the valve 10 and the spray nozzle 4 is measured in such a manner that water volume in the pressure reservoir 3 can increase even though water is being withdrawn via the open valve 10, so that the maximum water level is quickly reached again and the pump 2 is switched off. The cycle then begins again, as illustrated in FIG. 4. As a result of this cycle, the control electronics 20 recognizes that the spraying operation is activated and allows this function without imposing any time limit on the pump operation. The withdrawal of water is effected at a system pressure which varies throughout the cycle and with intermittent pump operation. In order to generate additional steam, the valve 12 is opened via the manual actuating member 19. As a result of the large quantity of water which is withdrawn, the water level in the pressure reservoir 3 and therefore the system pressure falls extremely rapidly on account of the low flow resistance, so that the pump 2, the switch 8 and the control electronics 20 are actuated. However, the maximum water level in the pressure reservoir 3 cannot be attained due to the large quantity of water which is being withdrawn. When the switch 8 on the pressure reservoir 3 fails to transmit a signal within a given period of time, the control electronics 20 recognize active additional steam operation and restrict the duration of the pump operation to a given maximum time t max . This prevents flooding of the auxiliary evaporation chamber 14. A lack of water also advantageously results in an absence of the signal from the switch 8, since the maximum water level in the pressure reservoir 3 cannot be attained when the tank 1 is empty. As with the additional steam generation, the control electronics 20 then restrict the operating time of the pump 2, which is now running dry, to the maximum time t max . This is shown in FIG. 5. To produce normal steam, the valve 11 is opened by the user via the manual actuating member 18 and the coupled switch 16 is simultaneously actuated. The signal from the switch 16 causes the control electronics 20 to render the pressure control and the time restriction t max inoperative and to set the pump 2 to pulsed half-wave operation, the cycle time being adjustable by the user, e.g. with the aid of a potentiometer on the control electronics 20. The invention is not limited by the embodiments described above which are presented as examples only but can be modified in various ways within the scope of protection defined by the appended patent claims.

A steam iron with an electric pump for conveying water from a water tank to individual water consumers and control electronics, which control the pump as a function of actuated cut-off valves. The control electronics recognize and control the different operating modes associated with the respective water consumers as a function of pressure changes in the pressure control circuit. The operating duration of the pump is restricted to a maximum time in accordance with the respective operating mode.

BACKGROUND OF THE INVENTION The present invention is directed to a support or holder for a portable appliance and in particular for a hand-held electrical hair dryer. Portable hand-held electrical hair dryers are well known and have gained widespread popularity for both home and professional use in the styling and drying of a person's hair. The hair dryer usually includes a casing having a handle portion and a main housing portion which houses a heater, motor and fan assembly. In use the fan is operated by the motor to draw air into the housing through the heater and then outwardly of the housing through a suitable air discharge orifice. Although these hair dryers are not large items, they are of a configuration which usually prevents ready storage thereof when not in use. Since the dryer is frequently used it must be readily available to the user and therefore various storage stands or holders have been provided in the past for storing the dryers to accomplish these ends. Further in certain of these stands operation of the dryer is permitted while the dryer is in a stored position so that the user's hands are free for other purposes such as combing or brushing the hair while it is being dried. In general the prior art holders provide for stands having cradles for receiving the handle or other portion of the hair dryer casing. Although these known stands have proven acceptable for the intended uses, various problems are found in known devices for utilization of the devices both for storing the dryer when not in use yet still maintaining the desirable feature of allowing for operation of the dryer while in the stored position. It is an object of the present invention to provide a novel holder or support for a portable electrical hair dryer. Another object is to provide a holder having novel means for maintaining the dryer in stored position and allowing for operation thereof in a plurality of positions in the stored position. A still further object is to provide a novel holder having novel means for maintaining and locking the hair dryer in stored position which includes means for ready release thereof from the holder. A further object is to provide a novel holder of relatively few parts thereby allowing for a reduction in manufacturing costs both in labor and material. SUMMARY OF THE INVENTION The present invention contemplates a holder for a hair dryer which includes a support member adapted for mounting on a wall surface. An appliance receiving or gripping portion extends from the base of the support and is provided with a grip for receiving and positioning the handle of the dryer. Retractable detent means are provided in the support with actuating means provided for moving the detent means into and out of engagement with the handle to releasably lock and unlock the handle within the gripping portion. The above and other objects and advantages of the present invention will appear more fully hereinafter from a consideration of the detailed description which follows taken together with the accompanying drawing wherein one embodiment of the invention is illustrated. DESCRIPTION OF THE DRAWINGS In the drawing: FIG. 1 is a perspective view of a support member incorporating one embodiment of the present invention and illustrates a hair dryer appliance mounted therein; FIG. 2 is a front elevational view of the support of FIG. 1 and shows the support inverted from the position of FIG. 1; FIG. 3 is a sectional view taken on the line 3--3 of FIG. 2; FIG. 4 is a sectional view taken on the line 4--4 of FIG. 4; and FIG. 5 is a rear elevational view of the support. DETAILED DESCRIPTION Referring now to the drawing for a more detailed description of the present invention a holder incorporating one embodiment thereof is generally indicated by the reference numeral 10 in FIG. 1. A hair dryer 12 is shown in broken line outline form in FIG. 1 and is provided with a handle portion 14 disposed within a tubular shaped receiving or grip portion 15 of holder 10. Hair dryer 12 may be of a usual type which includes within the casing a motor, fan and heater assembly for discharging heated air through discharge orifice 16 when the hair dryer is connected to a suitable electrical outlet via connecting cord 17. Holder 10 is made of premolded plastic material and includes a rectangular shaped base 19 from which projects a hollow extension portion 20. Grip portion 15 of holder 10 is formed at one end of extension 20 and comprises a pair of arcuate shaped arms 22 and 24 conforming to the outer cylindrical surface of handle 14 of hair dryer 12. An opening or slot 25 is provided in grip portion 15 between the ends of arms 22 and 24 to permit passage therebetween of power connecting cord 17 when dryer 12 is removed or deposited in gripping portion 15. Upper and lower metal wall mounting plates 26 and 27 are secured to the rear of base 19 by means of screws 28 fitted into threaded bosses (not shown) formed in base 19. A plurality of keyhole shaped openings 30 are formed in plates 26 and 27 for permitting the mounting of holder 10 to a wall surface either in a vertical (FIG. 2) or horizontal position in accordance with the needs of the user. As mentioned it is a feature of the present invention to provide novel means for maintaining hair dryer 12 in holder 10. To this end a rectangular slide plate 31 is disposed within extension 20 with the spaced side marginal portions 32 and 33 thereof disposed in spaced guide channels 34-35 provided on the inner wall surface of extension 20. A pair of detent arms 36 and 37 (FIGS. 3 and 4) depend from the end of plate 31 and project through openings 38 and 39 in the walls of gripping portion 15. Resilient detenting pads 40 are secured to the ends of detent arms 36 and 37 to engage the surface of handle 14 of hair dryer 12 to frictionally detent handle 14 within grip portion 15. Actuating means for moving plate 31 and detent arms 36 and 37 out of engagement with handle 14 include an actuating button 42 rotatably mounted on wall 43 of extension 20 by means of a peripheral recess 44 seated on the surface of wall 43 about opening 45 therein. A drive shaft 46 located eccentrically on button 42 depends therefrom through opening 45 into driving engagement in opening 47 of slide plate 31. In use of holder 10 with holder 10 mounted on a wall surface and with detent arms 36 and 37 in the retracted position shown in FIG. 4, handle 14 of hair dryer 12 is placed in grip position 15 after first passing electrical connecting cord 17 through slot 25. The handle 14 may then be rotated to any desired position in grip 15 to present the heated air orifice 16 of hair dryer 12 at a desired angle by the user. The user then rotates button 42 to move slide plate 31 in the direction of arrow A in FIG. 4 through drive shaft 46. Plate 31 is moved in guide channels 34-35 together with detent arms 36 and 37 to place pads 40 in detenting frictional engagement with handle 14 locking the latter to holder 10. If desired hair dryer 12 may then be operated through a suitable electrical power connection through cord 17 in mounted position in holder 10. To release handle 14 from grip 15 button 42 is rotated in an opposite direction thereby releasing detent pads 40 from handle 14 whereby hair dryer 10 may be withdrawn from holder 10. It will be apparent from the foregoing description that the novel holder has many advantages in use. One advantage among others is the fact that the holder may be mounted in varied positions on a wall and the air discharge outlet of the dryer set at a desired angle for operation while in mounted position in gripping portion 15 by rotation of handle 14 and then locking the handle at the desired angular position by means of the described detent means. Although one embodiment of the present invention has been illustrated and described in detail, it is to be expressly understood that the invention is not limited thereto. Various changes can be made in the design and arrangement of parts without departing from the spirit and scope of the invention as the same will now be understood by those skilled in the art.

A storage or holder device for an electrical appliance such as a hair dryer adapted for mounting on a wall surface and having an appliance gripping portion for receiving the handle of the appliance and further including selectively releasably detenting means within said holder and operable externally thereof for locking the appliance to the holder.

DESCRIPTION The present invention relates to a plaster for emergency treatment of open thorax injuries. In addition to the high risk of infections, injuries passing through the chest are extremely critical because they may immediately result in an extreme slowing of the respiration. One reason therefor is the fact that the negative pressure normally prevailing within the thorax (approximately 4 to 8 mm Hg) breaks down, since due to the injury a pressure compensation with the environment takes place causing the lobe of the lung on the injured side to deflate. Another impairment of the thoracic respiration of the pulmonary lobe on the uninjured side arises due to the fact that the mediastinum located between the two lobes of the lung is laterally displaced towards the uninjured side because of the resulting pressure conditions. Thus, in addition to the failure of one pulmonary lobe, respiration is restrained due to a reduced respiratory volume of the lung lobe on the uninjured side. In addition, the so-called lesser circulation is stressed so much that an overstrain may result and this means another serious danger to the life of the injured person. Relative to the total number of accidents, thorax injuries amount to 9%. Considering this fact and taking into account that the death rate within the first, approximately 6 hours after the respective accident is very high, one can easily realize the severe problem, both with respect to quality and to quantity. Several suggestions for the first-aid treatment of such sucking wounds have been made, however, as a whole they do not deliver satisfactory results. An example of these proposals is the so-called imbricated bandage, i.e., a compression bandage, where adhesive strips are placed on top of each other in a tile-shaped manner around approximately three quarters of the thorax so that the injury can be closed provisionally. Other forms of pressure bandages have also been proposed. In cases where there is no bandaging material available, it has been proposed to lay the palm on the injury. Another proposal for extreme situations is to pull lung tissue of the injured side into the gap of the wound in order to close the wound provisionally. Except for the fact that this is a questionable treatment, it can obviously only be performed by a physician. Another alternative for emergency bandaging is the "Device for emergency bandaging of an open thorax injury" according to DE 36 31 650 A1. This device is characterized by a substantially cup-shaped hollow body of a gas-tight material having a free edge being formed as an elastic, soft sealing ring which is to be located at the outer side of the thorax and which, when applied, surrounds the thorax injury at a distance; said free edge being provided with a ventilation device by means of which the interior space of said ring can be aerated under formation of negative pressure within the interior space of the hollow body. All of the known measures without accessories at best prevent further passage of air through the wound but do not improve respiration. In addition, the person rendering the first aid is impeded in carrying out additional, probably vital measures. When a hand is laid or pressed on the wound, the injured person who already suffers from heavy breathing in addition may be seized with anxiety. The disadvantage of the device according to DE 36 31 650 A1 is the fact that it is too expensive and too complicated for a person without medical training, i.e., is difficult to handle (cf. Medizingerateverordnung [regulation on medical appliances] of Jan. 14, 1985, §§ 2 and 6, paragraph 3 and 4). The object of the present invention is to provide a device suitable and destined, in particular for a first-aid measure rendered within the limits of emergency treatment until clinical care. Said device shall permit external closure of the wound gap and rapidly and permanently improve the respiration of the injured person to a considerable extent. This object is achieved by providing a plaster with a gas check valve responding to even slight pressure variations. This valve closes during the inspiration phase, in which a negative pressure is built up within the thorax, so that no additional air may enter the chest, whereas it opens during the expiration phase in which positive pressure is formed by lowering the ribs and lifting the diaphragm so that the air which already entered the pleural cavity may escape through the valve. This enables the lobe of the lung to gradually deploy again after each expiration until--in the most favorable case--it achieves its full function. According to an advantageous embodiment of the present invention, the plaster may additionally be provided with a wound dressing and rendered sterile; in this case bandaging of the injury under nearly aseptic conditions is ensured at the same time. Effective treatment in case of larger injuries or those which are difficult to localize can be effected by different sizes of the dressings. The plaster is provided with a carrier layer preferably being substantially air-tight. Said carrier layer may be a textile fabric, such as a woven, non-woven, or a film, e.g., a plastic film or a metal foil. The carrier layer has a pressure-sensitive adhesive coating. In this connection the pressure sensitive adhesive may be a natural one, e.g., a rubber adhesive, or a technical one, such as an acrylic adhesive. The carrier layer exhibits an aperture to accommodate the gas check valve which may be a diaphragm, ball, plug, or a spring-type valve. It responds to even slight pressure variations and operates reliably. On the bottom side of the carrier layer there is a wound dressing consisting of textile material. It may have a multi-layer structure. The material is permeable to air and highly absorptive; its surface is designed in such a way that it does not stick to the wound. The latter may be achieved by aluminizing. The plaster is applied to a protective layer which is removed prior to application. The plaster is preferably aseptically packed in a suitable package (e.g. in a peelable bag). The present invention provides a simple and safe first-aid treatment of an open thorax injury. The plaster may be used in any situation without delay and even an untrained layman can apply it. After application of this plaster the person rendering the first aid has his hands free to perform further, probably vital first-aid measures. The plaster does neither burden nor restrict the injured person as would be the case, e.g., when the hand is pressed on the chest, so that an anxiety condition due to such a treatment will not occur. The figures represent an embodiment example of the present invention; they are described in more detail in the following: FIG. 1: represents a plan view on the plaster with a diaphragm valve after removal of the membrane. FIG. 2: shows a cross-section along line I/I of FIG. 1 of the valve plaster with applied membrane. FIG. 3: is a schematic representation of the thorax with an open injury during expiration. FIG. 4: is the representation according to FIG. 3 during inspiration. FIG. 5: is a representation according to FIG. 3 with the plaster according to FIG. 1 applied during expiration. FIG. 6: is a representation according to FIG. 5 during inspiration. FIG. 1 represents in plan view an embodiment example of the valve plaster for first-aid measures of open thorax injuries; FIG. 2 is a cross-section along line I/I. The plaster has a diaphragm valve 2 positioned in the middle of the carrier material 5. The diaphragm valve 2 consists of a plastic disc with four holes 1 having a diameter of 4 mm; they are covered by a membrane (shown in FIG. 2) being glued thereon. The membrane 6 is capable of closing the holes 1 hermetically. From the bottom side of the carrier material 5 a ring 3 consisting of the same material as the carrier material 5 is glued in order to improve fixation of the diaphragm valve 2; the ring 3 partly sticks on the diaphragm valve 2 and partly on the carrier material 5. The schematic drawing of FIG. 3 shows a sectional view on a part of a chest with thorax injury 10. It can be recognized that the lobe of the lung 8 on the injured side already collapsed to a large extent since the pressure within the respective thoracic cavity 12 has undergone a pressure compensation with the environment; the other pulmonary lobe 7 is in a substantially normal position during expiration shown in FIG. 3, since the mediastinum 11 is also in almost central and thus normal position. During inspiration according to FIG. 4, the mediastinum is displaced towards the pulmonary lobe 7 whereby the lobe 8 continues to collapse. If a plaster 13 according to the present invention is applied on the outer side of the thorax (FIG. 5) in such a way that the wound dressing 4 is lying above the injury 10, a slight positive pressure within the interior 12 of the thorax is formed during expiration. As a result the valve 6 opens and the air flows out through holes 1. If the plaster 14 according to the present invention is applied as shown in FIG. 6, negative pressure within the thoracic cavity is formed during inspiration; the valve closes and the collapsed lobe 8 can slightly recover due to the negative pressure. Each breath thus improves the state of the injured person. It is understood that the specification and examples are illustrative but not limitative of the present invention and that other embodiments within the spirit and scope of the invention will suggest themselves to those skilled in the art.

A plaster which comprises a gas check valve being inserted in an aperture and which, on the side facing the skin, is provided with a carrier being coated with a pressure sensitive adhesive, makes the emergency treatment of open thorax injuries possible.

FIELD [0001] The present disclosure relates to exhaust coolers, and more particularly to a variable geometry exhaust cooler. BACKGROUND [0002] The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. [0003] Diesel engine systems are popular due to their generally high efficiency relative to other kinds of internal combustion engines. This efficiency is due, in part, to the increased compression ratio of the Diesel combustion process and the higher energy density of Diesel fuel. However, the Diesel combustion process does produce particulates that are carried in the exhaust gas produced by the Diesel engine system. [0004] A Diesel particulate filter is often used to remove these particulates from the exhaust gases. Typically, the Diesel particulate filter is coupled to the exhaust system downstream of the Diesel engine. The Diesel particulate filter receives the exhaust gas and filters particulates out of the exhaust gas. While useful for its intended purpose, the Diesel particulate filter can become full over time, and if not cleaned, the operating effectiveness of the Diesel particulate filter can be degraded. [0005] Another solution known in the art is to use a regeneration process to remove particulates trapped in the Diesel particulate filter. These regeneration processes may take various forms, such as, for example, exhaust gas recirculation or using post-combustion fuel injected into the cylinder in order to raise the temperature of the exhaust gas stream. An exemplary regeneration process is found in commonly owned U.S. Pat. No. 7,104,048 B2, hereby incorporated by reference as if fully disclosed herein. These regeneration processes typically heat the exhaust gasses to a high temperature in order to burn the particulates from the Diesel particulate filter. [0006] During conditions when the Diesel engine system is in an idle state, it is desirable to cool the exhaust gasses before they are expelled into the environment. Accordingly, an exhaust gas cooler may be coupled to the Diesel engine system downstream of the Diesel particulate filter to cool the exhaust gas. The exhaust gas cooler is operable to mix the hot exhaust gas with the cooler ambient air, thereby reducing the temperature of the exhaust gas. To do so, however, the amount of exhaust gas entering the exhaust cooler is typically restricted such that sufficient cooling can take place. This restriction of the exhaust gas can lead to back pressure, lowered horsepower, and other inefficiencies in the Diesel engine system when the Diesel engine system is running at a non-idle state and producing large amounts of exhaust gas. Accordingly, there is room in the art for an exhaust cooler that is operable to vary the amount of exhaust gas entering the exhaust cooler based on the operating state of the Diesel engine system. SUMMARY [0007] The present invention provides an exhaust cooler mounted to a tailpipe for receiving exhaust gas. [0008] In one aspect of the present invention the exhaust cooler includes a jet pump connectable to the tailpipe and a nozzle connectable to the tailpipe. The nozzle defines an opening between the tailpipe and the jet pump for communicating the exhaust gas from the tailpipe to the jet pump. A first member is included that is moveable between a closed position and an open position, the open position defining a first opening between the tailpipe and the jet pump for communicating the exhaust gas from the tailpipe to the jet pump. [0009] In another aspect of the present invention the first member is a plate pivotally connectable to the tailpipe. [0010] In yet another aspect of the present invention a hinge is connectable between the tailpipe and the first member to allow the first member to pivot between the open and the closed positions. [0011] In still another aspect of the present invention a second member is included that is moveable between a closed position and an open position, the open position defining a second opening between the tailpipe and the jet pump for communicating the exhaust gas from the tailpipe to the jet pump. [0012] In still another aspect of the present invention the first member and the second member are each semi-circular in shape and are sized to fit overtop the nozzle opening. [0013] In still another aspect of the present invention the first opening and the second opening are each semi-circular in shape. [0014] In still another aspect of the present invention when the first member and the second member are in the closed position, the first opening and the second opening cooperate to form a circular shaped opening. [0015] In still another aspect of the present invention the circular shaped opening has a diameter less than a diameter of the nozzle opening. [0016] In still another aspect of the present invention a biasing member is connectable to the tailpipe to bias the first member to the closed position. [0017] In still another aspect of the present invention the biasing member is a torsional spring. [0018] In still another aspect of the present invention the first member is a valve. [0019] In still another aspect of the present invention the valve is a reed type valve. [0020] In still another aspect of the present invention the nozzle has a frusto-conical shape and the valve is positioned on an outer surface of the frusto-conical nozzle. [0021] In still another aspect of the present invention a plurality of reed valves are spaced equidistance along the outer surface of the frusto-conical nozzle. [0022] In still another aspect of the present invention the jet pump is connectable to the tailpipe by a plurality of struts. [0023] Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. DRAWINGS [0024] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. [0025] FIG. 1 is a schematic view of an exemplary Diesel engine system having a variable exhaust cooler according to the principles of the present invention; [0026] FIG. 2A is an enlarged schematic side view of the variable exhaust cooler of the present invention having throttle plates in a closed position when the exemplary Diesel engine system is in an idle state; [0027] FIG. 2B is an enlarged schematic side view of the variable exhaust cooler of the present invention having throttle plates in an open position when the exemplary Diesel engine system is in a non-idle state; [0028] FIG. 3A is an enlarged schematic side view of a second embodiment of the variable exhaust cooler of the present invention having valves in a closed position when the exemplary Diesel engine system is in an idle state; and [0029] FIG. 3B is an enlarged schematic side view of the second embodiment of the variable exhaust cooler of the present invention having valves in an open position when the exemplary Diesel engine system is in a non-idle state. DETAILED DESCRIPTION [0030] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. [0031] With reference to FIG. 1 , an exemplary Diesel engine system is illustrated and generally indicated by reference number 10 . The Diesel engine system 10 is preferably employed in a motor vehicle (not shown), though the Diesel engine system 10 may be used in various other applications without departing from the scope of the present invention. The Diesel engine system 10 generally includes a Diesel engine 12 . The Diesel engine 12 is in electronic communication with an engine controller 14 . The engine controller 14 is operable to control the Diesel engine 12 based on various parameters. [0032] The Diesel engine 12 is operable to combust Diesel fuel (not shown) in a combustion process within the Diesel engine 12 . The by-product of this combustion process is an exhaust gas. The exhaust gas is discharged from the Diesel engine 12 as an exhaust gas stream into an exhaust pipe 16 , as indicated by the arrows in FIG. 1 . [0033] The exhaust pipe 16 includes a first section 18 that communicates the exhaust gas from the Diesel engine 12 to a catalyst 20 located downstream of the Diesel engine 12 . The catalyst 20 is mounted to the exhaust pipe 16 . The catalyst 20 may be any exhaust scrubbing device, such as, for example, an NOx filter. The catalyst 20 is operable to filter the exhaust gas to meet applicable emissions standards. [0034] A second section 22 of the exhaust pipe 16 carries the exhaust gas from the catalyst 20 to a Diesel particulate filter 24 . The Diesel particulate filter 24 is mounted to the exhaust pipe 16 and is located downstream of the catalyst 20 and the Diesel engine 12 . The Diesel particulate filter 24 filters the exhaust gas stream and traps particulates therein. The Diesel particulate filter 24 may take various forms without departing from the scope of the present invention. For example, the Diesel particulate filter 24 may include a ceramic structure through which the exhaust gas stream passes. The particulates are trapped and accumulate on the walls of the ceramic structure until such time as they are burned off in a regeneration process using hot exhaust gasses. [0035] The exhaust gas stream passes from the Diesel particulate filter 24 to a tailpipe section 26 of the exhaust pipe 16 . An exhaust cooler 30 is mounted to an end of the tailpipe section 26 . As will be described in greater detail below, the exhaust cooler 30 acts to cool the exhaust gas stream before the exhaust gas stream enters the surrounding environment. [0036] Turning now to FIG. 2A , the exhaust gas cooler 30 generally includes a variable geometry nozzle assembly 32 coupled with a jet pump 34 . The nozzle assembly 32 is disposed on an end of the tailpipe section 26 and defines an opening 36 . Preferably, the opening 36 has a diameter equal to the diameter of the tailpipe section 26 . However, it should be appreciated that the opening 36 may have a diameter different than the diameter of the tailpipe section 26 without departing from the scope of the present invention. [0037] The nozzle assembly 32 further includes a first throttle plate 38 A and a second throttle plate 38 B. The throttle plates 38 A and 38 B are each generally semi-circular in shape and each have an outer diameter larger than the diameter of the opening 36 . Alternatively, the throttle plates 38 A and 38 B could have an outer diameter less than the opening 36 such that the throttle plates 38 A and 38 B fit within the opening 36 . The throttle plates 38 A and 38 B each respectively include a semi-circular opening or cut out 42 A and 42 B. The semi-circular cut outs 42 A and 42 B are concentric with the generally semi-circular shape of the throttle plates 38 A and 38 B, and each semi-circular cut out 42 A and 42 B has a diameter less than the outer diameter of the throttle plates 38 A and 38 B. [0038] The throttle plates 38 A and 38 B are each pivotally mounted to the tailpipe section 26 at the opening 36 . In the example provided, a first hinge 44 A pivotally couples the first throttle plate 38 A to the tailpipe section 26 . The first hinge 44 A is mounted to the tailpipe section 26 and is mounted to the circumferential center, or apex, of the semi-circular outer edge of the first throttle plate 38 A. A second hinge 44 B pivotally couples the second throttle plate 38 B to the tailpipe section 26 . The second hinge 44 B is mounted to the tailpipe section 26 at a position opposite the first hinge 44 A. The second hinge 44 B is also mounted to the circumferential center, or apex, of the semi-circular outer edge of the second throttle plate 38 B. While hinges 44 A and 44 B have been illustrated as pivotally coupling the throttle plates 38 A and 38 B to the tailpipe section 26 , it should be appreciated that various other mechanisms that allow the throttle plates 38 A and 38 B to pivot relative to the tailpipe section 26 may be employed without departing from the scope of the present invention. [0039] The throttle plates 38 A and 38 B are respectively biased to a closed position by a first biasing member 48 A and a second biasing member 48 B. In the preferred embodiment, the biasing members 48 A and 48 B are torsional springs, though various other biasing devices may be employed without departing from the scope of the present invention. [0040] The closed position of the throttle plates 38 A and 38 B is illustrated in FIG. 2A . When in the closed position, the throttle plates 38 A and 38 B are positioned to at least partially cover the opening 36 . Furthermore, the cut outs 42 A and 42 B cooperate to define a reduced opening 50 . The reduced opening 50 has a diameter less than the diameter of the opening 36 . [0041] The jet pump 34 includes a cylindrical pipe portion 56 . An intake portion 58 is mounted on one end of the cylindrical pipe portion 56 . The intake portion 58 is generally frusto-conical in shape and defines an intake opening 60 . An output portion 62 is mounted on an opposite end of the cylindrical pipe portion 56 . The output portion 62 is also generally frusto-conical in shape and defines an exhaust output 64 at an end thereof. In an alternate embodiment, the jet pump 34 includes only the cylindrical pipe portion 56 . [0042] The jet pump 34 is mounted to the tailpipe section 26 by struts 66 . The struts 66 extend from the intake portion to the tailpipe section 26 . The jet pump 34 extends out from the tailpipe section 26 away from the nozzle assembly 32 . [0043] With reference to FIG. 1 and continued reference to FIG. 2A , in order to clean the Diesel particulate filter 24 , hot exhaust gas is passed through the exhaust pipe 16 , through the Diesel particulate filter 24 , and on to the exhaust cooler 30 . When the Diesel engine 12 is in an idle state, the hot exhaust gas passes through the nozzle opening 50 . Cooler ambient air is sucked through the intake opening 60 of the jet pump 34 . The hot exhaust gas and the cooler ambient air circulate and mix within the cylindrical pipe portion 56 and the output portion 62 . The hot exhaust gas is cooled and exits the exhaust cooler 30 from the exhaust output 64 . Hot exhaust ranging in temperature from 450-600 degrees Celsius at the nozzle opening 50 may be cooled to less than 300 degrees Celsius at the exhaust output 64 . [0044] As the exhaust gas stream leaves the Diesel engine 12 , the exhaust gas stream flows through the exhaust pipe 16 . As the exhaust gas stream 12 reaches the exhaust cooler 30 , the exhaust gas stream exerts a pressure on the throttle plates 38 A and 38 B. During idle conditions, the exhaust gas stream pressure is less than the force exerted on the throttle plates 38 A and 38 B by the biasing members 46 A and 46 B. Accordingly, the throttle plates 38 A and 38 B remain in the closed position and the nozzle opening 50 speeds up the exhaust gas as it passes through the restricted nozzle opening 50 , thereby entraining more air in the jet pump 34 and achieving increased cooling from the increased volume of entrained ambient air. [0045] When the Diesel engine 12 is running at non-idle conditions, the amount of exhaust gas produced by the Diesel engine 12 increases, and accordingly the pressure of the exhaust gas stream on the throttle plates 38 A and 38 B increases. This exhaust gas pressure is operable to move the throttle plates 38 A and 38 B into an open position. The open position of the throttle plates 38 A and 38 B is illustrated in FIG. 2B . When the exhaust stream pressure exceeds the force exerted by the biasing members 46 A and 46 B on the throttle plates 38 A and 38 B, the throttle plates 38 A and 38 B are pivoted against the biasing members 46 A and 46 B on the hinges 44 A and 44 B. As the throttle plates 38 A and 38 B are pivoted away from each other, the opening from the tailpipe section 26 into the jet pump 34 increases in size from the area provided by the nozzle 50 to the area provided by the opening 36 . Accordingly, a larger amount of exhaust gas is allowed to pass from the nozzle assembly 30 into the jet pump 34 , thereby reducing back pressure and other inefficiencies at non-idle speeds. [0046] With reference to FIG. 3A , a second embodiment of the exhaust gas cooler is generally indicated by reference number 130 . The exhaust gas cooler 130 generally includes the jet pump 34 , as described in FIGS. 2A and 2B , and a nozzle assembly 132 . [0047] The nozzle assembly 132 is disposed on an end of the tailpipe section 26 and includes a nozzle 134 . The nozzle 134 has a generally frusto-conical shape and is hollow such that an interior of the nozzle 134 communicates with the tailpipe section 26 to receive the exhaust gas stream. The nozzle 134 further defines an outlet 136 at an end thereof. The outlet 136 has a diameter less than the diameter of the tailpipe section 26 and therefore restricts the amount of exhaust gas passing from the tailpipe section 26 to the jet pump 34 . [0048] A plurality of valves 140 , only two of which are shown, are located around an outer surface 142 of the nozzle 134 . The valves 140 are in communication with the interior of the nozzle 134 and in turn the exhaust gas stream within the tailpipe section 26 . In the preferred embodiment, six to eight valves are spaced evenly around the outer surface 142 of the nozzle 134 . However, it should be appreciated that any number of valves 140 may be employed with the present invention. The valves 140 are moveable between a closed position, as shown in FIG. 3A , and an open position, as shown in FIG. 3B . The valves 140 are biased toward the closed position. In the preferred embodiment, the valves 140 are reed type valves. However, it should be appreciated that various other types of valves may be employed with the present invention. [0049] During idle conditions, the exhaust gas stream pressure is not sufficient to open the valves 140 , and the valves remain in the closed position as illustrated in FIG. 3A . Accordingly, the outlet 136 speeds up the exhaust gas stream as it passes through the restricted opening of the outlet 136 , thereby entraining more air in the jet pump 34 and achieving increased cooling from the increased volume of entrained ambient air. When the Diesel engine 12 is running at non-idle conditions, the amount of exhaust gas produced by the Diesel engine 12 increases, and accordingly the pressure of the exhaust gas stream on the valve 140 increases. This exhaust gas pressure is operable to move the valves 140 into the open position, as illustrated in FIG. 3B . Accordingly, a larger amount of exhaust gas is allowed to pass from the nozzle assembly 130 into the jet pump 34 , thereby reducing back pressure and other inefficiencies at non-idle speeds. This allows the exhaust gas cooler 130 to automatically adjust to the operating state of the engine 12 . [0050] The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.

The present invention provides an exhaust cooler mounted to a tailpipe for receiving exhaust gas. The exhaust cooler includes a jet pump connectable to the tailpipe and a nozzle connectable to the tailpipe. The nozzle defines a nozzle opening between the tailpipe and the jet pump for communicating the exhaust gas from the tailpipe to the jet pump. A first member is included that is moveable between a closed position and an open position, the open position defining a first opening between the tailpipe and the jet pump for communicating the exhaust gas from the tailpipe to the jet pump.

BACKGROUND OF THE INVENTION The present invention relates to a thermopheumatic actuator especially suited for controlling the temperature in the passenger compartment of an automotive vehicle. Passenger automobiles and trucks are normally provided with heating and air conditioning systems for maintaining the desired temperature in the vehicle passenger compartment. The temperature is controlled by selectively energizing the heating and air conditioning systems and furthermore by positioning a temperature door which controls the mixture of hot and cold air. The temperature door is generally positioned by means of a vacuum actuator which is fed with modulated vacuum from the vehicle intake manifold. The actuator typically comprises a diaphragm which is positioned by opposing forces of the modulated vacuum and a diaphragm spring. The vacuum actuator may be provided with a power diaphragm and a pilot diaphragm to increase the accuracy and decrease the effects of variations in the mechanical resistance encountered in moving the temperature door. The vacuum to the actuator is modulated by means of a thermally controlled valve. A bimetal spring exposed to air from the passenger compartment positions a valve element to bleed air into the vacuum actuator and thereby reduce the vacuum as a function of temperature. Such a thermally controlled valve is generally referred to in the art as a thermostatic vacuum regulator. A system of this type is an open loop control system since there is no mechanical feedback between the diaphragm and the valve. Thus, the system is inherently inaccurate since such factors such as variations in the vacuum applied to the regulator, ageing of the diaphragm, pressure drops between the regulator and the actuator and the like will cause the temperature to be controlled in an erratic manner. In addition, the system is disadvantageous from an installation standpoint since the regulator and actuator are separated units. They must be mounted in separate locations and connected by a conduit, constituting unnecessary consumption of mounting space, installation time and expense. SUMMARY OF THE INVENTION The present invention overcomes the above described drawbacks of the prior art by combining a thermostatic vacuum modulator valve and a vacuum actuator into an integral unit and providing mechanical feedback in the form of a feedback spring between a bimetal spring of the modulator valve and a diaphragm of the vacuum actuator, thereby providing a closed loop control system. It is an object of the present invention to provide a thermopneumatic actuator which is immune to variations in output load. It is another object of the present invention to provide a thermopneumatic actuator comprising a closed loop servo system which is more accurate than prior art open loop servo systems. It is another object of the present invention to provide a thermopneumatic actuator comprising an improved aspirator means for causing air flow through the actuator housing. It is another object of the present invention to provide a thermopneumatic actuator which can be manufactured and installed with increased economy in cost and space. It is another object of the present invention to provide a generally improved thermopneumatic actuator. Other objects, together with the foregoing, are attained in the embodiments described in the following description and illustrated in the accompanying drawing. BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic view of a prior art thermopneumatic actuator; FIGS. 2, 3 and 4 are graphs illustrating the operation of the prior art actuator shown in FIG. 1; FIG. 5 is a schematic view of a thermopneumatic actuator system embodying the present invention; FIG. 6 is a longitudinal sectional view of the present actuator; FIG. 7 is a rear elevation of the present actuator; FIG. 8 is a fragmentary enlarged sectional view of the present actuator; FIG. 9 is an enlarged perspective view of a bimetal spring of the present actuator; FIG. 10 is a schematic view of a first modification of the present actuator; FIG. 11 is a longitudinal sectional view of the first modification; FIG. 12 is a section taken on a line 12--12 of FIG. 11; FIG. 13 is similar to FIG. 12 but shows an alternative arrangement; FIG. 14 is a longitudinal sectional view of a second modification of the present actuator; FIG. 15 is a rear elevation of the second modification; FIGS. 16 and 17 are enlarged sectional views of various portions of the second modification; FIG. 18 is a simplified schematic view of a third modification of the present actuator; and FIG. 19 is a section taken on a line 19--19 of FIG. 18. DESCRIPTION OF THE PREFERRED EMBODIMENTS While the thermopneumatic actuator of the invention is susceptible of numerous physical embodiments, depending upon the environment and requirements of use, substantial numbers of the herein shown and described embodiments have been made, tested and used, and all have performed in an eminently satisfactory manner. Referring now to FIG. 1 of the drawing, a prior art thermopneumatic actuator system is generally designated by the reference numeral 11 and comprises a thermostatic regulator 12. Temperature controlled air is fed into a vehicle passenger compartment (not shown) through a duct 13. Although not shown in FIG. 1, a heater and air conditioner are provided with switch means and a temperature control door to control the air temperature in the duct 13. An inlet hose 14 is connected at one end to the interior of the passenger compartment and at the other end to the interior of the regulator 12. A tube 16 leads from the duct 13 and discharges pressurized air from the duct 13 into the atmosphere. A hose 17 which leads from the regulator 12 has its other end flared as indicated at 18 and disposed coaxially inside the tube 16. The flared end of the hose 17 in combination with the inner wall of the tube 16 constitutes a venturi which creates a low pressure area at the opening of the hose 17. Although the interior of the regulator 12 is not shown in detail, it comprises a bimetal spring and a pressure modulator valve which is controlled by the spring. The initial spring tension and thereby the desired air temperature are set by a dial 19 located inside the passenger compartment and connected to the regulator 12 by a cable 21. The spring is located inside a temperature chamber having an inlet and outlet connected to the hoses 14 and 17 respectively. The tube 16 and flared end of the hose 18 constitute an aspirator which sucks air from the passenger compartment through the regulator 12 by the venturi effect. The valve of the regulator 12 has an inlet connected to the intake manifold of the vehicle (not shown) through a hose 22 of an outlet connected to a vacuum actuator 24 through a hose 23. The regulator 12 serves to modulate the vacuum from the intake manifold in accordance with FIG. 2. In brief, the regulator 12 decreases the vacuum as the air temperature inside the passenger compartment increases. The actuator 24 comprises a housing 26 which is partitioned by a flexible diaphragm 27. A diaphragm spring 28 urges the diaphragm 27 rightwardly through a spring retainer cup 29 which is fixed to the center of the diaphragm 27. Another cup 31 is fixed to the diaphragm 27 and carries an output rod 32 which is connected to the temperature control door and switches to control the temperature in accordance with the axial position of the rod 32. The temperature is increased as the rod 32 is moved leftwardly. The diaphragm 27 constitutes a wall of a pressure chamber 33 inside the housing 26, with the pressure in the pressure chamber 33 being negative gage pressure or vacuum from the vehicle intake manifold as modulated by the regulator 12. The diaphragm 27 and rod 32 are positioned by the opposing forces of vacuum in the pressure chamber 33 and the spring 28. In operation, the bimetal spring in the regulator 12 thermally deforms in accordance with sensed temperature and controls the valve to modulate the vacuum supplied into the pressure chamber 33. The diaphragm 27 and thereby the rod 32 assume and equilibrium position at which the vacuum urging the diaphragm 27 leftwardly equals the rightward force of the diaphragm spring 28. If the sensed temperature rises above the desired value, the regulator 12 decreases the vacuum allowing the spring 28 to move the diaphragm 27 and rod 32 rightwardly to decrease the temperature. The opposite effect occurs if the temperature decreases below the desired value. The temperature regulation of the system 11 is very poor for, among other reasons, a hysterisis effect which is illustrated in FIGS. 3 and 4. For each value of sensed temperature the regulator 12 produces a corresponding value of vacuum. Thus, the system 11 is open loop in the respect that there is no mechanical feedback from the actuator 24 to the regulator 12. The actuator 24 exhibits mechanical hysterisis due to mechanical friction in moving the temperature control door as illustrated in FIG. 3. FIG. 4 is obtained by combing FIGS. 2 and 3. In other words, due to the coefficient of static friction between the temperature control door and its supporting members, a certain change in temperature and thereby vacuum is required to produce any movement whatsoever of the door. This results in very poor temperature regulation. Although the piloted vacuum actuator described hereinabove reduces the hysterisis problem, the addition of a piloted vacuum actuator to the system 11 would still not produce accurate temperature control since there is no mechanical feedback from the actuator to the regulator, and the system would still be susceptible to erroneous operation caused by variations in intake manifold vacuum, deterioration of the diaphragm, pressure drops in the hose 23 and other factors. In addition, the system would still be difficult and expensive to mount since the regulator and actuator are separate and must be connected by the hose 23. These problems are completely overcome by a thermopneumatic temperature control system 41 illustrated in FIG. 5 which comprises a thermopneumatic actuator 42 embodying the present invention. The actuator 42 is illustrated in detail in FIGS. 5 to 9. The system 41 comprises an air conditioning duct 43 through which air is blown into the passenger compartment of an automotive vehicle by a fan 44 in the rightward direction as viewed in FIG. 5. An air conditioner evaporator 46 is disposed inside the duct 43 to cool air passing therethrough. A heater 47 is also disposed in the duct 43 downstream of the evaporator 46. Hot water from the vehicle cooling system is applied to the inlet of a valve 49 through a hose 48. The outlet of the valve 49 is connected to the inlet of the heater 47 through a hose 51. The outlet of the heater 47 is returned to the vehicle cooling system through a hose 52. When the valve 49 is opened, hot water is circulated through the heater 47 to heat air passing through the duct 43 to the passenger compartment. The amount of air passing through the heater 47 is controlled by a temperature control door 53 which is pivotally supported by a shaft 54. The actuator 42 is connected to the door 53 and valve 49 through a link 56 in such a manner that the door 53 is pivoted clockwise thereby unblocking the heater 47 to a greater extent as the link 56 is retracted toward the actuator 42 or pulled upwardly. The link 56 opens the valve 49 to turn on the heater 47 except when the door 53 is in a closed position illustrated in phantom line. The more the door 53 is moved upwardly, the greater the volume of air which passes through the heater 47 and the higher the temperature of the air supplied into the passenger compartment through the duct 43. The intake manifold of the vehicle is symbolically designated as 57 and is connected to the actuator 42 through a hose 58. The passenger compartment of the vehicle is also symbolically shown and designated as 59, the compartment 59 being connected to the actuator 42 through a hose 61. An indicator 62 for setting the desired temperature in the passenger compartment 59 is disposed inside the compartment 59 for ease of adjustment by the vehicle operator and is connected to the actuator 42 through a cable 63. Air from the compartment 59 is caused to flow through the hose 61, actuator 42 and a hose 64 by means of an aspirator 66 provided to the duct 43. The aspirator 66 comprises a venturi tube 67 leading from the duct 43 through which pressurized air is blown from the duct 43. A tube 68 provided at the end of the hose 64 is coaxially disposed inside the venturi tube 67 in such a manner that air is sucked out of the tube 68 by the low pressure created in the venturi tube 67 due to the flow of air therethrough. In operation, the desired temperature is set into the actuator 42 by the indicator 62 and the actuator 42 moves the link 56 to position the door 53. If the sensed temperature is above the desired value the actuator 42 will move the door 53 downwardly to reduce the temperature of the air being fed into the passenger compartment 59 to reduce the temperature. The opposite effect occurs if the sensed temperature is too low. As best seen in FIG. 6, the actuator 42 comprises a diaphragm housing 71 and a valve housing 72 which is fixed to the left end of the diaphragm housing 71 by screws 73 (see FIG. 7). The housing 71 defines therein a pressure chamber 74. Similarly, the housing 72 defines therein a temperature chamber 76. The right wall of the pressure chamber 74 is constituted by a flexible power diaphragm 77 which is fixed at its periphery to the right edge of the housing 71 by an annular cap 78. A spring retainer cap 79 is fixed to the center of the diaphragm 77 by a pin 81. A diaphragm spring 82 is compressed between the left end of the housing 71 and the cap 79, thereby urging the cap 79 and diaphragm 77 rightwardly. The pin 81 also fixes the link 56 and a cap 83 to the right side of the diaphragm 77 so that the diaphragm 77 and link 56 move in an integral manner. The temperature chamber 76 has an inlet 85 connected to the hose 61 and an outlet 84 connected to the hose 64 so that air from the passenger compartment 59 is caused to flow through the temperature chamber 76 due to the action of the aspirator 66. A generally U-shaped bimetal spring 86 is fixedly supported at its lower or right end by a block 87, which is in turn supported by a bolt 88 which threadingly passes therethrough. The bolt 88 is rotatably supported through the left wall of the housing 72 and extends externally therefrom. A compression spring 91 is disposed between the left wall of the housing 72 and the block 87 to take up lost motion and dampen vibration. A rod 89 extends from the left wall of the housing 72 and slidingly passes through the block 87 thereby aiding in the support of the block 87 and preventing rotation thereof. An arm 92 is fixed to the bolt 88 by means of a setscrew 93. The cable 63 is connected to the end of the arm 92. Tension or slackening of the cable 63 caused by adjustment of the indicator 62 causes the arm 92 and bolt 88 to rotate and the block 87 to move left or right as viewed in FIG. 6 carrying the spring 86 therewith. A vacuum modulator valve which is generally designated as 94 is provided to the housing 72 and comprises an outlet 96 which communicates with the pressure chamber 74 through a tube 97. A flow restriction 98 is provided in the tube 97. The outlet 96 leads from a valve chamber 99 defined within the housing 72. A valve element 101 is supported by flexible diaphragms 102 and 103 which hermetically seal the temperature chamber 76 from the valve chamber 99 and pressure chamber 74. While the diaphragms 102 and 103 are equal in area, the diaphragm 102 may be made slightly larger than the diaphragm 103. The diaphragms 102 and 103 allow the valve element 101 to move axially. The right end of the valve element 101 is connected to the pin 81 through a valve or feedback spring 104. The upper or left end portion of the bimetal spring 86 resiliently engages with a shoulder 106 of the valve element 101 and urges the same leftwardly. The left end of the valve element 101 is formed with an inlet valve seat 107 which communicates with the interior of the temperature chamber 76 through a passageway 108. Another inlet valve seat 109 communicates with the hose 58. A double headed valve element 111 is supported by the valve element 101. More specifically, the valve element 111 has a left ball (not designated) which closes the valve seat 109 when moved leftwardly into engagement therewith. The valve element 111 further has a right ball which is disposed to the right of the valve seat 107 inside the passageway 108 and blocks the same when the valve element 111 is moved rightwardly. The detailed construction of the valve 94 is shown in enlarged form in FIG. 8, and the detailed construction of the spring 86 and block 87 is most visible in FIG. 9. In operation, the vehicle driver rotates the indicator 62 to set the desired temperature. This causes rotation of the bolt 88 and adjustment of the preload of the spring 86 against the shoulder 106 of the valve element 101. The spring 86 is compressed inwardly, and exerts a leftward force on the valve element 101. The valve spring 104 exerts a rightward force on the valve element 101. Then, although leftward and rightward forces extert on the diaphragms 102 and 103 respectively, these forces are counterbalanced each other because the diaphragm 102 are equal in area to the diaphragm 103, as mentioned above. Accordingly, the valve element 101 is not affected by these forces, but is affected by both the leftward force of the spring 86 and the rightward force of the spring 104 so as to be positioned. An increase in temperature in the temperature chamber 76, which corresponds to the passenger compartment temperature, causes the spring 86 to thermally deform leftwardly and exert a greater force on the valve element 101 against the force of the spring 104. The valve element 101 is positioned when the forces of the springs 86 and 104 thereon are equal. When the sensed temperature corresponds to the desired temperature, the valve element 101 attains an equilibrium position shown in FIG. 6 whereby the left and right balls of the valve element 111 block the valve seats 109 and 107 respectively. This seals the valve chamber 99 and thereby blocks communication between the pressure chamber 74, the temperature chamber 76 which is at atmospheric pressure and the hose 58 which conducts vacuum to the valve seat 109 from the intake manifold 57. Under equlibrium conditions, the vacuum in the pressure chamber 74 urging the diaphragm 77 leftwardly equals the force of the spring 82 which urges the diaphragm 77 rightwardly. When the temperature in the passenger compartment 59 exceeds the desired temperature the spring 86 thermally deforms or expands leftwardly, thereby moving the valve element 101 leftwardly. The left ball of the valve element 111 abuts against the valve seat 109 blocking the same. The valve element 101 overtravels the valve element 111 with the result that the right ball of the valve element 111 unblocks the valve seat 107 thereby establishing communication between the temperature chamber 76 and the valve chamber 99 through the passageway 108. This has the further effect of connecting the temperature chamber 76 to the pressure chamber 74 through the valve chamber 99 and tube 97, causing air at atmospheric pressure to bleed into the pressure chamber 74 reducing the level of vacuum. As a result, the spring 82 overcomes the force exerted on the diaphragm 77 by the vacuum in the pressure chamber 74 and moves the diaphragm 77 rightwardly. The link 56 moves with the diaphragm 77, moving the temperature control door 53 toward the closed position to reduce the temperature of air being forced through the duct 43 into the passenger compartment 59. Rightward movement of the diaphragm 77 extends the valve spring 104 thereby increasing the rightward force thereof on the valve element 101 in opposition to the leftward force of the bimetal spring 86. The diaphragm spring 82 is designed to be much stiffer than the valve spring 104 so that the spring 104 has essentially no effect on the spring 82. The valve element 101 is moved rightwardly until the force of the spring 104 equals the force of the spring 86. At this point, which is the equilibrium position, the right ball of the valve element 111 closes the valve seat 107 and seals the pressure chamber 74. The opposite effect occurs when the temperature drops below the desired value. The leftward force of the spring 86 on the valve element 101 is decreased and the spring 104 pulls the valve element 101 rightwardly. Due to the arrangement of the right ball of the valve element 111 and the valve seat 107, the valve element 111 is pulled rightwardly by the valve element 101 and the left ball of the valve element 111 unblocks the valve seat 109. This connects the pressure chamber 74 to the intake manifold 57 through the tube 97, valve chamber 99, valve seat 109 and hose 58. Thus, air is sucked out of the pressure chamber 74 increasing the level of vacuum. As a result, the diaphragm 77 and link 56 are pulled leftwardly to further open the temperature control door 53. The spring 104 is slackened by the rightward movement of the diaphragm 77 and the force thereof on the valve element 101 decreases. The valve element 101 is moved leftwardly by the spring 86 until the spring forces are equal and the left ball of the valve element 111 seats against the valve seat 109 to seal the pressure chamber 74. In summary, it will be seen that the link 56 is positioned by the diaphragm 77 as a function of the level of vacuum or negative gage pressure in the pressure chamber 74. The level of vacuum is determined by the valve 94 which is operated by the bimetal spring 86. Mechanical feedback from the diaphragm 77 to the valve 94 is provided by the feedback or valve spring 104 which provides closed loop control. Thus, the above mentioned drawbacks of the prior art are overcome and the present system 41 operates with extremely improved precision. Various obvious modifications to the actuator 42 such as replacing the double headed ball valve element 111 with a sleeve or functionally equivalent valve arrangement and operating the diaphragm assembly with positive gage pressure rather than vacuum such as from a Diesel engine supercharger will become immediately apparent to one skilled in the art. While the diaphragms 102 and 103 are equal in area, the diaphragm 102 may be made slightly larger than the diaphragm 103. FIGS. 10 to 12 illustrate a modification of the present actuator 42 in which an aspirator 66a is provided integrally with the actuator body. This facilitates installation even further since only a simple hose connection is necessary at the duct 43. Like elements are designated by the same reference numerals used in the embodiment of FIGS. 5 to 9 and elements which are essentially similar in function but modified in configuration are designated by the same reference numerals suffixed with the character "a". Further shown in FIG. 10 is a steering wheel 112 and steering column 113 which are located in the passenger compartment 59. An actuator 42a comprises a valve housing 72a which is connected to the passenger compartment 59 through the hose 58. A link 56a is provided in shortened form and a bellcrank lever 50 and connecting link 55 are provided between the link 56a and door 53. The evaporator 46, heater 47 and door 53 are constructed and function in the same manner as above although their relative positions are reversed. Retraction of the link 56a into the housing 71a causes the temperature control door 53 to be opened and the air temperature to increase as above. In the actuator 42a a venturi tube 67a and a tube 68a are provided as integral components of the housing 72a. The venturi tube 67a is connected to the duct 43 by a hose 45. The tube 68a leads directly from a temperature chamber 76a of the housing 72a. In operation, air blown through the venturi tube 67a from the duct 43 through the hose 45 creates a low pressure area at the restriction of the venturi tube 67a which sucks air from the temperature chamber 76a through the tube 68a. Air from the passenger compartment 59 fills the partial vacuum created in the temperature chamber 76a through the hose 58 to cause air circulation through the temperature chamber 76a. A bimetal spring 86a is reversed relative to the spring 86 and deforms inwardly in response to an increase in temperature to urge the valve element 101 leftwardly as above. FIG. 13 illustrates another modification of the actuator 42 in which corresponding elements are designated by the same reference numerals suffixed by the character "b". The embodiment of FIG. 13 is similar to that of FIGS. 10 to 12 except that in an aspirator 66b the relationship of the venturi tube 67a and tube 68a is reversed in FIG. 13. Provided integrally as part of a housing 72b, a venturi tube 67b leads from a temperature chamber 76b to the atmosphere and a tube 68b leading from the duct 43 is coaxially disposed inside the venturi tube 67b. FIGS. 14 to 17 illustrate another modification of the actuator 42, in which corresponding elements are designated by the same reference numerals suffixed by the character "c". As a main point of difference the U-shaped bimetal spring 86 is replaced by a straight bimetal spring 86c, which thermally deforms leftwardly in response to an increase in temperature. Thus, the basic operation of an actuator 42c is essentially similar to that of the actuator 42. As another main point of difference, it will be noted that in the actuator 42 the inlet 85 and outlet 84 of the temperature chamber 76 are not axially aligned. This causes the air in the temperature chamber 76 to flow in a turbulent manner and minimize temperature gradients. Thus, the air acts on the spring 86 in a uniform manner. In some cases where more rapid temperature response is required, it is desirable to provide as shown in FIG. 15 an inlet 85c and outlet 84c in axial alignment and furthermore to align the axes of the inlet 85c and outlet 84c with the center of the spring 86c. This causes essentially laminar flow through the temperature chamber 76c and concentration of the air stream on the central portion of the spring 86c. This causes the spring 86c to deform to a greater extent than if the air acted on the spring 86c in a uniform manner and greater response to variations in air temperature. Several minor modifications are also illustrated in FIGS. 14 to 17. A limit plate 114 provided to the bolt 88 and a stop 116 provided to the housing 72c with which the limit plate 114 is engageable prevent excessive movement of the bolt 88 and spring 86c. As best seen in FIG. 16, the feedback spring 104 is not connected to the pin 81 and thereby to the center of the diaphragm 77 but to a spring retainer cap 79c by means of a stud 115. The stud 115 is offset from the central axis of the diaphragm 77 and rotatably fits in a hole (not designated) formed through the cap 79c. This allows the spring 104 to rotate as it extends and contracts, thereby eliminating variation of the spring constant as a function of the length of the spring 104. As illustrated in FIG. 17 the upper end of the spring 86c is connected to the valve element 101 by means of a resilient sleeve 117 and a nut 118 screwed onto the right end of the valve element 101. The valve element 101 passes through a hole (not designated) formed through the upper end of the spring 86c and the nut 118 is tightened so that the spring 86c is firmly held. The resilience of the sleeve 117 serves to dampen vibration of the spring 86c and valve element 101. FIGS. 18 and 19 illustrate another modification of the actuator 42 in which corresponding elements are designated by the same reference numerals suffixed by the character "d". An actuator 42d is essentially similar to the actuator 42 except that an inlet 85d and an outlet 84d of a temperature chamber 76d are axially aligned with each other and with the central or U-shaped portion of the spring 86. In summary, it will be seen that the present invention provides a thermopneumatic actuator of greatly improved accuracy compared to the prior art. The present actuator is configured as an integral, compact unit which can be installed with substantially reduced space requirements and cost. Various modifications will become possible for those skilled in the art after receiving the teachings of the present disclosure without departing from the scope thereof.

A thermopneumatic actuator of the invention is used to control an automobile heater and/or air conditioner to maintain a desired temperature in the automobile passenger compartment through a mechanical output member of the actuator. The output member is connected to and moved by a diaphragm which is positioned by vacuum introduced from the automobile intake manifold and works against a diaphragm spring. A valve is controlled by a bimetal spring exposed to air from the passenger compartment to modulate the vacuum applied to the diaphragm. A feedback spring connected between the diaphragm and the valve works against the bimetal spring. An aspirator comprising a venturi tube causes air flow from the passenger compartment around the bimetal spring.

RELATED APPLICATION [0001] This patent is a continuation of U.S. patent application Ser. No. 12/494,760, entitled “High Chairs and Methods to Use High Chairs,” filed on Jun. 30, 2009, which is a continuation of U.S. patent application Ser. No. 11/968,526, entitled “High Chairs and Methods to Use High Chairs,” filed on Jan. 2, 2008, which claims priority to U.S. Provisional Patent Application No. 60/883,277, entitled “High Chairs and Methods to Use High Chairs,” filed on Jan. 3, 2007, all of which are hereby incorporated by reference in their entireties. FIELD OF THE DISCLOSURE [0002] This disclosure relates generally to child care products, and, more particularly, to high chairs and methods to use high chairs. BACKGROUND [0003] Small children are typically placed into high chairs that secure and support the child when, for example, the child is being fed. Such high chairs typically include a seat attached to a frame and a tray attached to either the seat or the frame. The seats in conventional high chairs are typically fixed in one position so that the seat is elevated above a floor to a level that is convenient for an adult to feed the child from the adult's sitting position. At times it would be convenient for a parent or other caretaker to adjust the position of the seat on a high chair. Prior attempts at creating adjustable chairs have focused on making the height of the seat variable with respect to the floor. [0004] Conventional high chairs also include trays that can be affixed and removed from the front of the seat. The trays provide a serving surface for providing the child with food, drinks and other items such as eating utensils and/or toys. In addition, the trays may include a tray insert that can be easily removed to clean spills that end up on the tray. BRIEF DESCRIPTION OF THE DRAWINGS [0005] FIG. 1 is a front perspective view of an example high chair showing the chair in an upright position with an example headrest in an extended position. [0006] FIG. 2 is a side view of the example high chair of FIG. 1 . [0007] FIG. 3 is a side view of the example high chair of FIG. 1 with the example tray extended away from the example seat and the example headrest in a retracted position. [0008] FIG. 4 is a partial cross-sectional view of an example slidable connector used to change the distance between the example seat and the example tray of FIG. 1 . [0009] FIG. 5 is a front perspective view of an alternative example high chair with an example threaded connector to change the distance between the example seat and the example tray. [0010] FIG. 6 is a rear view of the high chair of FIG. 1 . [0011] FIG. 7 is an exploded view of the example seat of FIG. 1 . [0012] FIG. 8 is a bottom view of the example seat showing an example catch basin. [0013] FIG. 9 is a partial perspective bottom view of the example highchair of FIG. 1 . [0014] FIG. 10 is a side view of the high chair of FIG. 1 , showing the example seat and example tray in a lower position closer to the support surface. [0015] FIG. 11 is a partial cross-sectional view of an example connector used to change the distance between the example seat and tray of FIG. 1 and the support surface. [0016] FIG. 12 is a side view of the high chair of FIG. 1 showing the chair in a reclined position with the headrest in a retracted position. [0017] FIG. 13A is an exploded, left perspective view of an example rotating joint used to recline the example seat of FIG. 1 . [0018] FIG. 13B is an exploded, right perspective view of an example rotating joint used to recline the example seat of FIG. 1 . [0019] FIG. 14 is a side view of the high chair of FIG. 1 , showing the chair in a folded position. DETAILED DESCRIPTION [0020] FIGS. 1-14 illustrate an example high chair 100 that is adjustable in several respects. The example high chair 100 of FIG. 1 may be fit to a child of virtually any size, and may be adjusted to a child as he/she grows over time. For example, a seat 102 and a tray 104 of the high chair 100 are adjustable along a frame 106 of the high chair 100 . In addition, the distance between the seating surface of the seat 102 and the tray 104 is adjustable. Furthermore, the seat 102 may be reclined with respect to the frame 106 . The high chair 100 also includes an adjustable headrest 108 and an adjustable footrest 110 . The tray 104 is laterally adjustable with respect to a back 112 of the seat 102 . The seat back 112 may be raised or lowered to properly position the headrest 108 relative to the child. In addition, the frame 106 may be collapsed into a folded position, as shown in FIG. 14 . [0021] More specifically, FIGS. 1 and 2 show the example high chair 100 with the tray 104 positioned a first distance above the seating surface of seat 102 . The distance between the tray 104 and the seat 102 as can be seen by comparing FIGS. 2 and 3 (the tray 104 is at a higher position above the seat 102 in FIG. 3 ). In the illustrated example, the tray 104 is coupled to the seat 102 through a first side post 114 and a second side post 116 . Each side post 114 , 166 is located toward a side of the seat 102 and tray 104 . The seat 102 and tray 104 also are coupled through a crotch post 118 . The crotch post 118 serves as a child restraint. Each of the first side post 114 and the second side post 116 includes a plurality of indentations, apertures or holes 120 . A first connector 124 slidably couples the first side of the tray 104 to the first post 114 . A second connector 128 slidably couples the tray 104 to the second post 116 . A first actuator 122 is located on the first slidable connector 124 , and a second actuator 126 is located on the second slidable connector 128 . Each actuator 122 , 126 is capable of selectively releasing a corresponding pin 130 ( FIG. 4 ) from one of the holes 120 . When both actuators 122 , 126 are actuated, the first slidable connector 124 and the second slidable connector 128 are free to slide along the first side post 114 and the second side post 116 , respectively. Although two actuators are shown in the illustrated example, any number of actuators may be used (e.g., only one of the first actuator 122 or the second actuator 126 may be included). A cross-sectional view of one of the connector 128 is shown in FIG. 4 . In the illustrated example, the connectors 124 , 128 are identical or mirror images of each other and, thus, only one connector 128 is shown and described in detail. [0022] To move the seat 102 with respect to the tray 104 , the first actuator 122 and the second actuator 126 are depressed against the force of a spring 129 (see FIG. 4 ) to cause a side pin 130 to disengage a respective one of the plurality of indentations or holes 120 of the posts 114 , 116 . In the illustrated example, a flange 131 of the actuator 126 is moved to engage (e.g., cam) the side pin 130 when the actuator 126 is depressed to thereby cause the pin 130 to rotate out of engagement with the hole 120 . [0023] As noted above, the connectors 124 , 128 and the actuators 122 , 126 are substantially identical, thus, there is a side pin 130 associated with each of the first and second actuators 122 , 126 . With the side pins 130 disengaged from holes 120 , the first and second slidable connectors 124 , 128 may be moved along the first and second posts 114 , 116 , respectively to a desired position. Movement of the first and second slidable connectors 124 , 128 along the first and second posts 114 , 116 changes the distance between the seat 102 and the tray 104 . The first and second slidable connectors 124 , 128 may be moved to a lower position on the first and second side posts 114 , 116 to fit a larger and/or older child in the high chair 100 , and the first and second slidable connectors 124 , 128 may be moved to a higher position on the first and second side posts 114 , 116 to fit a smaller and/or younger child in the high chair 100 . [0024] Furthermore, as the first and second slidable connectors 124 , 128 move along the first and second side posts 114 , 116 , the seat 102 moves along the crotch post 118 . In some examples, the crotch post 118 may telescope. When the seat 102 is in a desired position with respect to the tray 104 , the first and second actuators 122 , 126 are released such that the pins 130 move under the influence of their respective springs 129 and engage with respective ones of the plurality indentations or holes 120 to fix the seat 102 at a distance below the tray 104 . In the example of FIGS. 1 , 2 and 4 , the tray 104 is fixed at the top of the posts 114 , 116 and the seat 102 is adjustable to different positions along the posts 114 , 116 . [0025] In an alternative example shown in FIG. 5 , the seat 102 is height adjustable relative to the tray 104 in a different manner. In the example of FIG. 5 , the tray 104 of the illustrated high chair 500 is fixed on the top of the side posts 514 , 516 . The seat 102 is slidably mounted to the crotch post 518 via the alternative actuator 135 . In this example, the actuator 135 is a knob that is threaded on the crotch post 518 . By rotating the actuator 135 (i.e., the threaded knob 135 shown in FIG. 5 ) beneath the seat 102 at the center of the chair 500 , the seat 102 is moved up or down (depending on the direction of rotation of the knob 135 ) relative to the crotch post 518 and, thus, relative to the tray 104 to thereby adjust the distance between the seat 102 and the tray 104 . As a result of this structure, one control is used to threadingly adjust the position of the seat 102 relative to the tray 104 . The range of travel of the seat 102 relative to the tray 104 in the example of FIG. 5 is may be about one inch, although other ranges of travel would likewise be appropriate. [0026] Referring back to FIGS. 1 and 2 , the example high chair 100 also includes the adjustable footrest 110 . The footrest 110 of the illustrated example is coupled to one or more extension posts 132 . The footrest 110 is couplable to the extension posts 132 at different positions. As a result, the distance between the seat 102 and the footrest 110 is variable and may be changed to accommodate children of varying heights. The footrest 110 may be coupled to the extension posts 132 through any type of fasteners including, for example, Valco® pins and/or actuators and pins similar to the first and second actuator 122 , 126 and pins 130 described above. In the illustrated example, springs loaded pins are used to engage apertures or holes 137 found in the posts 132 . Four height adjustment positions 137 are shown in the illustrated example. However, any number of height adjustment positions may be included. In addition, the distance of travel between each height adjustment and/or the overall range of travel of the footrest may be any desired distance. For example, each height adjustment position may be an inch from an adjacent height adjustment, and the overall range of travel may be, for example, four inches. [0027] As shown in FIGS. 1-3 and 6 , the example high chair 100 also includes the adjustable bolster or headrest 108 . FIGS. 1 and 2 show the headrest 108 in a deployed or extended position (i.e., with the bolster wings 134 of the headrest 108 at least partially pivoted forward). FIG. 3 shows the headrest 108 in a retracted position (i.e., with the wings 134 of the head rest 108 pivoted flat against the back 112 ). The foldable wings 134 pivot outward (away from the seat back) to support a small child's head, for example, during feeding, etc. In the illustrated example, at least a portion of the wings 134 extends to a rear of the seat 102 . A bolster actuator 136 ( FIG. 6 ) located on the rear of the seat 102 is used to retract and/or extend the one or more wings 134 . In the illustrated example, the bolster actuator 136 is an elongated lever or paddle, which, when moved to a deployed position, forces (e.g., cams) the one or more wings 134 outward to an extended position in which the one or more wings 134 are folded outward and able to support the head of a child. The bolster actuator 136 may also be moved to a retracted position to pull the wings 134 to an unfolded position in which the wings 134 are flattened against the front of the seat 102 . In the illustrated example, the bolster actuator 136 may be moved to one or more intermediate positions between the deployed position and the retracted position to move the wings 134 to semi-folded positions. [0028] The illustrated example includes an upholstered the headrest 108 . The headrest 108 also includes padding to form a cushion or pillow. Alternatively, the headrest 108 may be un-upholstered and/or may be upholstered together with the seat 102 . Also, in some examples, the headrest 108 may not include foldable wings. [0029] In the illustrated example high chair 100 as shown in FIGS. 2 , 3 , 7 an 8 , the seat 102 includes a seat pan 138 , a seat support structure 139 , a seat back 112 , and a seat frame 142 . The seat support 139 may be a fabric seat support such as, for example, mesh, or the seat support 139 may be a plastic component or any other suitable material. The seat support 139 of the illustrated example is fabric and includes a seat support frame 141 . In some examples only the seat support frame 141 supports the seat 102 , and no fabric support 139 is included. In this example, the frame 141 is implemented as a metal tube frame. The seat support 139 may be coupled to the seat frame 142 via any suitable mechanical or chemical fasteners. [0030] In the example of FIGS. 7-8 , the seat pan 138 is supported in the seat support 139 via a lip 143 that is integrally formed with the seat pan 138 . The lip 143 is sized to fit over and support the seat pan 138 on the seat support frame 141 of the seat support 139 . In the illustrated example, the seat pan 138 is removably coupled to the seat support 139 . Therefore, the seat pan 138 may be removed from the high chair 100 for cleaning, storage or the like. [0031] The seat pan 138 of the illustrated example high chair comprises a slick polyurethane foam seat. The seat pan 138 is molded as a unitary structure and forms a slick, spill resistant, surface during the molding process. The seat pan 138 is easy to clean and is soft to the touch. [0032] In the illustrated example, the height of the seat back 112 is adjustable. As shown in FIGS. 2 , 3 and 6 , there is a clamp 144 disposed on the rear of the seat back 112 to slidably couple the seat back 112 to the seat frame 142 , a portion of which, as shown in FIG. 6 , forms a U-shaped post. This portion may be a separate component from the remainder of the frame 142 , i.e., not integrally formed therewith. The clamp 144 includes a seat back actuator 146 , which may be implemented by any suitable actuating device such as, for example, a knob, push button, lever, etc. When the seat back actuator 146 is activated, the clamp 146 is released from the seat frame 142 and the seat back 112 may be raised or lowered with respect to the seat pan 138 to accommodate children of varying sizes. When the seat back 112 has been moved to a desired position, the seat back actuator 146 is returned to a locked position to fix the position of the seat back 112 to a particular position relative to the seat frame 142 . In some examples, the seat back actuator 146 may causes the clamp 144 to engage one or more of a plurality of holes (not shown) on the frame 142 via a pin and spring connection similar to the other pin and spring connections described herein. In other examples, the clamp 144 maybe slidably moved to any of an infinite number of positions along the frame 142 and secured to the frame 142 via a friction fit. Adjusting the position of the seat back 112 enables the headrest 108 to be positioned to suit the child. The chair 100 , thus, can grow with the child. In addition, adjusting the height of the seat back 112 adjusts the position of the child restraint 210 to properly conform to the height of the shoulder of a child seated in the chair 100 . [0033] As shown in FIGS. 2 , 3 , and 9 , the example tray 104 includes a base tray 148 and top tray 150 . The base tray 148 , which is only exposed when the top tray 150 is removed, is permanently affixed to the posts 114 , 116 adjacent the front of the seat 102 and may be used in the same manner as the top tray 150 when the top tray 150 is removed (e.g., for holding a child's snacks, meals, drinks, toys, etc.). In addition, the base tray 148 acts as a passive restraint to retain the child in the seat. [0034] The top tray 150 of the illustrated example is laterally adjustable or slidable with respect to the base tray 148 . Consequently, the top tray 150 is laterally adjustable with respect to the seat back 112 . Therefore, the top tray 150 may be adjusted to accommodate children of varying sizes and/or to provide additional room that may be needed, for example, to remove a child occupying the high chair 100 . To adjust the top tray 150 with respect to the base tray 148 , a tray actuator 152 is activated. In the illustrated example, the tray actuator 152 is a push button, but any suitable actuating device may alternatively be used. The tray actuator 152 is depressed to disengage the top tray 150 from the base tray 148 . The example top tray 150 includes one or more cables or tethers 154 (see FIG. 9 ). Each tether 154 has a first end and a second end. The first ends of the tethers 154 are coupled to the tray actuator 152 . The second ends of the tethers 154 are coupled to a respective clasp 156 (one of which is shown in FIG. 9 ). Each clasp 156 includes teeth 158 to engage corresponding detents (not shown) on the base tray 148 . When the tray actuator 152 is depressed, the tethers 154 move to retract the clasps 156 to thereby cause the teeth 158 to disengage the detents and allow the top tray 150 to slide relative to the base tray 148 and/or to be removed therefrom. The top tray 150 is moveable fore/aft to any number of different positions. In the illustrated example, there are four different positions at which the top tray 150 may be laterally secured relative to the seat back 112 . However, other numbers of positions would likewise be appropriate. To fix the top tray 150 in a position relative to the base tray 148 , the tray actuator 152 is released to move the tethers 154 , extend the clasps 156 , and engage the teeth 158 with the detents in the base tray 148 . [0035] The tray 104 of the illustrated example also includes a removable insert or liner (not shown) that can be removed for cleaning. Furthermore, the entire top tray 150 may be completely removed from the base tray 148 to, for example, place the top tray 150 and the insert in a dishwasher for cleaning. [0036] As shown in FIGS. 1-3 and 10 , the seat 102 and the tray 104 may be moved together to different heights along the frame 106 . In the illustrated example, the frame 106 includes one or more front legs 160 and one or more rear legs 162 . The front legs 160 and rear legs 162 are coupled via hubs 164 and, in the illustrated example, form an A-frame structure. In the illustrated example, a crossbar 166 couples the front legs 160 to provide lateral stability. Similarly, a second crossbar 166 joins the rear legs 162 . Each front leg 160 and rear leg 162 of the illustrated example high chair 100 includes a wheel 170 depending from a foot 168 . [0037] To moveably cantilever the seat 102 and tray 106 assembly from the frame 106 , the first side post 114 is coupled to a third slidable connector 172 , and the second side post 116 is coupled to a fourth slidable connector 174 . In the illustrated example, the third and fourth slidable connectors 172 , 174 are coupled to the front legs 160 . However, in other examples, the third and fourth slidable connectors 172 , 174 may be coupled to the rear legs 162 . Each of the third slidable connector 172 and the fourth slidable connector 174 of the illustrated example includes a height actuator 176 . A cross-section of the fourth slidably connector 174 and the height actuator 176 is shown in FIG. 11 . In the illustrated example, the height actuators 176 are identical or mirror images of each other. As with the posts 114 , 116 , each of the front legs 160 includes a plurality of indentations, apertures or holes 178 . [0038] To move the seat 102 and the tray 104 with respect to the frame 106 , the height actuator(s) 176 are depressed against the force of a bias spring 177 to cause a locking pin 179 to disengage a corresponding one of the plurality of holes 178 . The height actuator(s) 176 may operate in a similar manner as the first and second actuators 122 , 126 described above. Thus, after the third and fourth slidable connectors 172 , 174 are moved to a desired position to adjust the overall height of the seat 102 relative to the floor or other support surface, the height actuator(s) 176 are discharged to engage or reengaged the pin 179 with a corresponding one of the plurality of holes 178 to thereby fix the seat 102 and tray 104 at a position on the frame 106 with respect to a ground or floor upon which the high chair 100 is placed. Four height adjustment positions are shown in the illustrated example. However, any number of height adjustment positions may be included. In addition, the distance of travel between each height adjustment and the overall entire range of travel may be any suitable distance. In the illustrated example, each height adjustment position is one inch from an adjacent height adjustment, and the overall range of travel is ten inches. [0039] As shown in FIG. 1 , the seat 102 of the illustrated example is coupled to the first side post 114 via a first joint 180 and also is coupled to the second side post 116 via a second joint 182 . In the illustrated example, the first and second joints 180 , 182 are coupled to the first and second slidable connectors 124 , 128 , respectively. In other examples, the first joint 180 and/or the second joint 182 may be coupled to the first side post 114 and/or the second side post 116 directly, indirectly or otherwise. The joints 180 , 182 are also coupled to opposite ends of a crossbar 184 upon which the seat 102 is mounted. The joints 180 , 182 enable the seat 102 to recline or rotate with respect to the cross-bar 184 , first side post 114 , second side post 116 , frame 106 , tray 104 , etc., as shown in FIG. 12 . [0040] The joints 180 , 182 are substantially identical or mirror images of each other. Thus, in the interest of brevity, only one joint 182 will be described. An exploded view of the joint 182 is shown in FIGS. 13A and 13B . The joint 182 includes an outer, non-rotating or fixed end 186 (also referred to as an outer gear wheel), a cam 188 , an inner gear or lock 190 and a rotating-end 192 . The non-rotating end 186 includes fixed teeth 194 , and the lock 190 includes rotating teeth 196 . The rotating end 192 also has complementary teeth 197 (see FIG. 13B ). A lever 198 ( FIGS. 2 , 3 , 6 and 12 ) on the rear of the seat 102 is operatively coupled to the joint 182 by, for example, a cable (not shown) threaded through one or more components of the chair 100 to the joint 182 . The lever 198 and/or the cable of the illustrated example is spring loaded. To change the tilt angle of the seat 102 , the lever 198 is actuated, which pulls the cable and causes the cam 188 to remove the lock 190 from engagement with the non-rotating end 186 of the joint 182 and move more deeply into the rotating end 192 . When the locking rotating teeth 196 are disengaged from the fixed teeth 194 , the lock 190 and the rotating end 192 , which are coupled via the rotating teeth 196 and the complementary teeth 197 , are freely rotatable relative to the fixed end 186 . The seat 102 , thus, may be moved to a desired angled position. Once the seat 102 is reclined or raised to the desired angle, the lever 198 may be released, which allows a spring 199 to move the lock 190 back into engagement with the non-rotating end 186 . In this position, the rotating teeth 196 of the lock 190 engage both the complementary teeth 197 of the rotating end 192 and the fixed teeth 194 of the non-rotating end. This engagement prevents the rotating end 192 from rotating relative to the fixed end 186 and locks the seat 102 in the desired position. [0041] In the illustrated example, the seat 102 has a large number of reclined positions over approximately 32.5° of rotation. The maximum angle of recline for the seat back of the illustrated example is approximately 43°±5°. However, other numbers of positions, other ranges of rotation and/or other maximum angles of recline would likewise be appropriate. [0042] The example high chair 100 also includes a slot 200 in the seat pan 138 as shown in FIGS. 1 , 7 and 8 . The seat pan 138 is shaped to funnel spilt food, liquids and/or other items to the slot. A catch basin 202 ( FIGS. 2 , 3 , 6 , and 8 ) is removably secured beneath the slot 200 to collect the food, liquid and/or other items that funnel into the slot 200 . The catch basin 202 may be removed, emptied and reassembled around the slot 200 . Funneling spills through the slot 200 into the catch basin 200 increases the efficiency of cleaning the high chair 100 as less food, liquid and other items are likely to end up on the floor and/or remain in contact with a child seated in the chair 100 . The catch basin 202 may be secured adjacent the slot 200 via any suitable means. In the illustrated example, the catch basin 202 is secured to the seat 102 by engaging a ridge 203 that circumscribes at least a portion of the slot, as shown in FIG. 8 . [0043] As shown in FIG. 6 , the example high chair 100 also includes fold actuators 204 , 206 . The fold actuators 204 , 206 are shown as push buttons but any suitable actuating device may be used as well. The fold actuators 204 , 206 are depressed to enable the chair 100 to be folded ( FIG. 14 ) for storage. In the illustrated example, the fold actuators 206 , 204 are spring biased to the locked position. Depressing the fold actuators 204 , 206 against the force of the springs dislocates corresponding pins (not show) carried by the rear legs from bores (not shown) in the hubs 164 to enable the rear legs 162 to pivot forward. The fold actuators 204 , 206 , pins and springs may be implemented by, for example, Valco® pins. As shown in FIG. 14 , the example high chair 100 is proportioned such that the example high chair 100 stands without assistance, even when the high chair 100 is in the folded position. In the illustrated example, the top tray 150 is removed and attached to the rear of the high chair 100 to make the folded high chair 100 more compact. [0044] The illustrated example high chair 100 includes a restraint or harness 210 , as shown in FIGS. 1-3 . The harness 210 is shown as two straps that are coupled to the seat back 112 via the headrest 108 . In other examples, the harness 210 may be coupled to other portions of the seat back 112 . In addition, the straps of the harness 210 may be secured to the seat back via a ring such as, for example, a D-ring or 0 -ring or via any other suitable mechanical or chemical fasteners. In such an example, D-rings are passed through the openings in the seat back 112 in a first orientation and positioned in a second orientation behind the seat to prevent removal of the harness straps from the seat back 112 . In the illustrated example, the material of the harness 210 is sewn onto itself, for example, in the shape of a ‘T’ on the rear side of the seat back 112 to prevent retraction through the opening. Because the seat back 112 is height adjustable and the harness 210 passes through the seat back 112 , the position of the harness 210 can be easily adjusted by adjusting the height of the seat back 112 . The harness 210 in the illustrated example is attached to the crotch post 118 via a clip to form a three-point harness. In other examples, the harness 210 may be coupled to the crotch post 118 via a T- or Y-shaped shield or plate to form a five-point harness. [0045] In an alternative example a three point harness that acts like a five point harness is provided. This harness (referred to as a pseudo 5-point harness) includes three solid points and two soft points of attachment. The three solid points are the fixed connections between the belts of the harness and the seat 102 of the high chair 100 at the seat back 112 with the D-rings and the crotch post 118 . Thus, two of the fixed points are located above the shoulders of the child. The third fixed point is located at the crotch post 118 . A Y-shaped connector is included in the pseudo 5-point harness. The Y-shaped connector has a latch on the bottom of the Y that secures into a latch fixed to the crotch post 118 . The wings of the Y-shaped connector are positioned and dimensioned to resiliently engage opposite side walls of the slick foam seat 102 to form two friction fit locks—one on each side of the child, thereby forming the two soft attachment points noted above. The two soft points are friction fit points. [0046] Returning to the example of FIG. 1 , as a result of the adjustability of the seat back 112 , the seat back 112 need only be provided with two shoulder apertures or holes 212 for the harness 210 , instead of a series of holes to raise or lower the harness 210 as the child grows. Instead, the height of the seat back 112 can be adjusted so that the shoulder belts of the harness 210 are positioned properly relative to the child. The shoulder height of the child harness 210 is automatically adjusted as the seat back 112 is moved to properly locate the headrest 108 for the child, so there is no need for multiple openings on the seat back for the harness 210 to pass through. In the illustrated example the height of the seat back 112 is infinitely adjustable within an approximately 6 inch range of travel. Other approaches such as employing a number of fixed positions and/or other ranges of travel would likewise be appropriate. [0047] Although certain example methods and apparatus have been described herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents.

High chairs and methods to use high chairs are disclosed. An example high chair includes a frame and a seat, wherein the seat defines a slot and is shaped to funnel spills toward the slot.

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority of the German patent application 101 15 837.8 which is incorporated by reference herein. FIELD OF THE INVENTION [0002] The invention concerns a stand, in particular for a surgical microscope. The purpose of such stands is to hold a relatively heavy microscope so that it is movable by an operator with a minimum of resistance. An effort is therefore made to configure all joints, bearings, and the like in as low-resistance a fashion as possible, so that as little resistance as possible is presented to any arbitrary movement by the user. BACKGROUND OF THE INVENTION [0003] In surgery but also in other areas of technology, for example microelectronics, forensics, etc., more and more use is being made of surgical microscopes that, because of their heavy weight, must be supported by stands. Several well-known manufacturers have marketed stands that are well suited, in terms of mechanics and statics, for supporting the load of a surgical microscope. The present applicant, for example, markets stands with the designation OHS or MS1. One example of such a stand is found in EP-A-628290. Zeiss/Deutschland has disclosed a stand, for example, in EP-476552. [0004] Many modern stands have parallelogram supports to allow the load of the surgical microscopes to be carried over the greatest possible distances with no bending or twisting, in order to maximize the freedom of movement and radius of action of the microscopes. In principle, however, the greater the radius of action, the greater the instability of a stand, except if appropriate design actions are taken against instability. However, the more rigid (less unstable) the structures, the more susceptible they are to vibratory behavior, which is similarly counteracted with design features such as selection of varying tube cross sections, material selection, use of damping elements, etc. [0005] The transported weight of the stands also represents a problem whose solution lies fundamentally in weight reduction by means of high-strength materials. [0006] For example, the present applicant has created a stand that uses at least one support made of a fiber-reinforced plastic. This stand is described in the aforementioned WO-A-97/20166. [0007] It has been recognized, however, that weight reduction alone is not sufficient in some circumstances if the quality of the damping properties of the essential components is not sufficiently taken into account. Mere weight reduction results in some circumstances in intensified, higher-frequency vibratory behavior in the structure. This vibratory behavior is amplified in structures having braked arms. Brakes of this kind are to be operated electromagnetically, pneumatically, or even by hand, and create a rigid connection between the components, so that vibrations are transmitted from one component to another and result in a long vibration period that is annoying to the user. [0008] The route of weight reduction by means of fiber composite materials and plastics has been taken in another sector of stand design, namely X-ray technology, as set forth in DE-C1-42 14 858. In this, a C-curve was created from plastic foam as the supporting part that determines the shape, which is surrounded by a fiber-reinforced plastic that assumes the support functions. If this known assemblage is to be particularly light in weight, then according to this previously published teaching a profile of closed shape must be produced from (only) fiber-reinforced plastic. Composite material structures of this kind have inherently low vibratory characteristics. [0009] In stands for the applications mentioned, however, there exist joints, rotary bearings and the like in which vibratory behavior can occur regardless of the quality of the other components. One such point, for example, is the vertical rotary bearing on a vertical upright column for the horizontal carrier arm or arms of the stand. Proceeding from such bearing points, which as a rule can be immobilized using brakes, movements or forces on the microscope also create torsional forces which in turn can preferentially excite torsional vibrations in the components that are loaded in torsion. [0010] For particular vibration damping, the present applicant has already offered solutions that are recited, for example, in WO-A-98/53244. In this, inter alia, elastically damping layers which act to damp the vibration chain from the microscope to the floor are installed under the mounting feet of the tripod foot. With these known assemblages, even the slightest change in the position of the microscope causes a vibratory excitation which nevertheless, once it has passed through the stand, is damped at the mounting feet and therefore reflected only in attenuated fashion. [0011] Damping plates that are inserted between stand components have also been proposed, for example damping shoes at the transition from a support tube to a support tube mount, or damping plates between two flanges of two adjacent support tubes or between a tube and a pedestal. [0012] The advantage of such damping elements in the region of the upper body of the stand is that they help damp the vibrations on their initial path from the microscope to the floor, so that need not even pass through the entire stand. The effectiveness of these known damping shims lies in the damping effect that occurs upon compression of these damping elements, i.e. for example when the tube vibrates in its shoe in the axial direction of the tube or in a direction perpendicular thereto (tilting vibration), or if the mounting feet are loaded in terms of pressure load fluctuations due to vibration of the upright column in a vertical plane. [0013] Attempts to damp torsional vibrations have hitherto been made by way of a particular configuration of the support tubes. For example, aluminum/composite plastic tubes or carbon fiber-reinforced plastic tubes have been created, in which torsion in the tube was counteracted by specific selection of the fiber plies. The OHS of the present applicant that is configured in this fashion has low torsional behavior, however, not only as a result of good selection of the supports, but also because of the balanced configuration about the rotation axis in the upright column. In this known assemblage, the center of gravity of the moving carrier arms and balancing arms lies directly above or in the immediate vicinity of the upright column. Other stands in which the center of gravity of the moving carrier arms is well to the side of the upright column amplify the torsional vibration behavior, especially if the stand is braked via the rotation axis. Mere application or release of the brake, or the slightest movements of the microscope, can generate torsional vibrations. [0014] Torsional vibrations (often horizontal vibrations) are substantially more deleterious in microscopy than vertical vibrations, in particular because in the case of a vertical vibration, the depth of focus that is always present means that a slight vibration is not noticed. Horizontal vibrations, however, result in a severe negative impact when observing through the microscope. SUMMARY OF THE INVENTION [0015] It is the object of the present invention to find solutions which improve the vibratory behavior of the stand, i.e. suppress vibration or optimally damp any vibrations, without thereby sacrificing precise positioning accuracy. The intention in particular is to counteract low-frequency torsional vibrations, e.g. in the range of, for example, 0 to 10 Hz. The new features are intended to effectively counteract torsional vibrations and optionally to be usable in combination with known vibration damping features. [0016] Those skilled in the art know that such objects are difficult to achieve, and that the application of mathematical and physical resources and theories often does not bring the expected results. On the other hand, however, even slight improvements are worth striving for, since they improve convenience for the user and consequently increase operating safety. According to the present invention, this object is achieved by way of the features recited in claim 1. [0017] The invention thus offers, for the components necessarily present on a stand for a surgical microscope, particularly suitable and tuned damping elements with low weight and improved vibratory behavior. The specifications of stand support parts in terms of their vibratory behavior can be slightly reduced, which in this context can result in cost decreases. [0018] Further specific embodiments and variants thereof are described and protected in the claims. The properties of the preferred material lie within approximately the following parameters: Static modulus of elasticity 0.2-3 N/mm2; Dynamic modulus of elasticity 0.5-4 N/mm2; Mechanical dissipation factor 0.1-0.2; Natural frequency of material greater than 5 [0019] Hz, measured in each case on the basis of DIN 53513. The preferred material selected is, by way of example, Sylomer® M12, Sylomer® M25 P14 or Sylomer® P12, Sylomer® P25 P15, or in particular Sylodamp® HD-010-11, HD300/1, HD-030-11, HD-050-21, HD-100-11, HD-150-12, HD-300-10 or 12, but preferably HD-300-1 for the dynamic load range from 0 to 0.3 N/mm 2 . [0020] The dissipation factor at 8 Hz per ISO 10846-2 should preferably be more than 0.1, in particular more than 0.2, at a strain at fracture per DIN 53455-6.4 of more than 100%, preferably more than 200%, and in particular approximately 300%. [0021] Such materials are available under the designation SYLODAMP® from Getzner Werkstoffe GmbH, B{umlaut over (ur)}s (Austria). [0022] Damping materials can also be combined if necessary. Variants with specific shaping of the damping materials also lie within the context of the invention. For example, recesses such as blind holes or the like can be provided in order further to influence the damping characteristics. [0023] Sandwich constructions of different damping materials can be used, for example, for improved torsional stiffness. BRIEF DESCRIPTION OF THE DRAWINGS [0024] The Figures are described continuously. The Description of Figures and the Parts List constitute a unit that is mutually complemented by the other parts of the Specification and the claims for purposes of a complete disclosure. Identical reference characters denote identical parts. Identical reference characters with different indices denote similar, functionally identical parts. The Figures are exemplary only, and not necessarily depicted in correct proportion. In the Figures: [0025] [0025]FIG. 1 is an oblique view of a stand rotary bearing according to the present invention, at the transition between the upright column and a carrier arm; [0026] [0026]FIG. 2 shows a vertical section through the structure of FIG. 1; [0027] [0027]FIG. 3 shows an enlarged detail of FIG. 2; [0028] [0028]FIG. 4 shows a variant with a modified position of the damping material; and [0029] [0029]FIG. 5 shows a sandwich that combines several damping layers; [0030] [0030]FIG. 6 symbolically depicts another damping element; [0031] [0031]FIG. 7 shows a variant of the element according to FIG. 6; [0032] [0032]FIG. 8 shows a variant of a cylindrical damping element arrangement; and [0033] [0033]FIG. 8 a shows a section, in plan view, of the arrangement according to FIG. 8. [0034] The Figures are described in overlapping fashion. Identical reference characters denote identical objects; identical reference characters with different indices denote components with identical or similar purposes but a different construction. The Parts List is an integral constituent of the Description of Figures. DETAILED DESCRIPTION OF THE INVENTION [0035] [0035]FIG. 1 shows a portion of an implemented configuration of the stand according to the present invention. This configuration is directly linked to U.S. patent application Ser. No. ______ (claiming priority of German patent application 101 23 166.0 filed Mar. 30, 2001), which application was filed on the same date as the present application, shares the same applicant as the present application, is incorporated herein by reference in its entirety, and which deals with another detail of possible stand equipment. [0036] A bearing sleeve 33 —which preferably, according to aforementioned U.S. patent application Ser. No. ______, can be brought into plumb—that carries a support member 3 is provided on an upright column 1 (merely indicated). Joined to support member 3 is a carrier arm 2 (merely indicated), such as is, for example, labeled 11 c in FIG. 12 of aforementioned U.S. patent application Ser. No. ______. Carrier arm 2 is rotatable about a rotation axis 30 so that it can bring its load (a microscope) into various spatial positions. In order to retain a selected spatial position, a brake 4 is provided which immobilizes carrier arm 2 in the braked state relative to upright column 1 . Once the braked position has been reached, even very small lateral alternating forces on the load (microscope) can result in a vibratory excitation that causes the load to oscillate back and forth. In that context, torsional forces take effect in brake 4 , in stand column 1 , and in the carrier arm itself (as flexural forces). The principal object of the invention is to suppress or compensate for this back-and-forth oscillation as completely as possible. In the configuration shown in FIG. 1, this is brought about by way of a torsional damping element 5 a that is arranged between brake engagement surface 6 and support element 3 . [0037] Brake 4 substantially comprises a brake body 7 and an armature 8 , as well as an armature flange 9 a . Brake body 7 is nonpositively connected to support element 3 , and armature flange 9 a or armature 8 is nonpositively connected to upright column 1 . The connection to support element 3 is brought about by way of bolts 11 , whereas the connection to upright column 1 is made via bolts 10 . [0038] Also secured to upright column 1 is a pivot limiter 12 that, in combination with a stand foot of specific configuration and an equipment box (cf. FIG. 12) of aforementioned U.S. patent application Ser. No. ______ serving for weight balancing, results in the inventive effect of Patent Application PCT/EP98/03614 (International Publication No. WO 99/01693) and is to that extent also given protection. [0039] Pivot limiter 12 coacts with a stop 13 on support element 3 (FIG. 2). [0040] As is better evident from FIG. 2, upright column 1 comprises a bearing block 14 that carries a bearing 15 in which support element 3 is mounted. Located concentrically inside the support element is an armature bracket 16 that is rigidly joined to bearing block 14 and at its upper end supports armature 8 via armature flange 9 a . Axis 30 of upright column 1 thus constitutes the rotation axis for support element 3 and thus for carrier arm 2 . [0041] The context of the invention of course also encompasses any other assemblages in which no upright column, or a different upright column, is provided, or in which the function of the upright column is assumed by other components, e.g. in ceiling mounts, the ceiling column; or in wall mounts, the wall retainer; or in stands having multiple carrier arms, one of the latter. [0042] The manner of operation of brake 4 (which is electromagnetic in this case) and of the assemblage according to the present invention is as follows: when brake 4 and brake body 7 are in the unenergized state, as depicted in FIG. 2, armature 8 rests against brake engagement surface 6 on brake body 7 . No rotation is therefore possible between support element 3 and armature bracket 16 (and therefore upright column 1 ). The braking force is thus transferred from upright column 1 via bearing block 14 into armature bracket 16 , and from there via armature flange 9 a to armature 8 and brake body 7 , then being transferred from the latter via a damping flange 18 to support element 3 and thus to carrier arm 2 . [0043] Damping flange 18 comprises an upper and a lower flange 17 a, b , between which damping element 5 a is inserted or adhesively bonded. The upper and lower flanges are separated by spacer sleeves 19 that on the one hand make possible a certain preload between the two flanges, but on the other hand also, as a result of a corresponding elongated hole or hole size configuration, also offer a capability of rotation relative to one another about axis 30 . [0044] Spacer sleeves 19 also prevent torsional damping element 5 a from being loaded in tension when the brake is open. This relieves stress on the adhesive bond if, as is preferred, the torsional damping element is adhesively bonded onto flanges 17 . [0045] Armature 8 itself is not depicted in further detail, but is spring-loaded as is usual in such brakes. [0046] The rotation capability about spacer sleeves 19 creates a clearance that allows carrier arm 2 to pivot slightly even when brake 4 is applied. Torsional damping element 5 a counteracts this pivotability with its torsional resilience. In the preferred embodiment, this resilience results in approximately 100% return of a carrier arm 2 moved in the tolerance range. The specific configuration and material selection for torsional damping element 5 a result in the vibration-damping properties of the assemblage. [0047] The assemblage as shown in FIG. 4, in which torsional damping element 5 b is adhesively bonded between armature 8 and armature flange 9 a , is not substantially different. What is disadvantageous about this assemblage, as compared to the one first described, is the fact that torsional damping element 5 b is loaded in tension when brake 4 is applied (i.e. most of the time), which could be disadvantageous for the bonded surfaces. [0048] Torsional damping element 5 c depicted in FIG. 5 comprises multiple damping layers 28 made of damping material, and metal washers 27 a and 27 b joined thereto in sandwich fashion. Such sandwich assemblages are usable in the context of the invention as necessary, and the detailed material choice made by the user depends on the particular requirements in terms of the application and damping. Softer or harder damping materials can be used depending on whether the user desires softer or harder resilience characteristics, more or less damping, or more or less play. The damping materials preferred according to the present invention are recited in the specification and in the claims. [0049] According to a particular embodiment of the invention, the torsional damping element made of a series of different elements is replaceable and/or its preload is adjustable, so that a user can himself select the degree of damping. [0050] [0050]FIG. 8 shows an assemblage similar to the assemblages described earlier. Armature flange 9 b is differently configured, however, in that it directs a pivot pin 29 downward against an armature follower 26 that concentrically surrounds the latter. A rotational clearance, which is damped by a sleeve-shaped torsional damping element 5 d , is thus possible between armature follower 26 (which assumes some of the functions of armature bracket 16 ) and the pivot pin. [0051] [0051]FIG. 8 a shows a section through the region of torsional damping element 5 d in the assemblage of FIG. 8. [0052] [0052]FIGS. 6 and 7 indicate variants of the assemblage shown in FIG. 8, in which there is a departure from the principle of pure shear loading in the torsional damping element, and instead tension-compression components are also used in the particularly configured torsional damping element 5 e , 5 f. [0053] Torsional damping element 5 f shown in FIG. 7 is an element made up of a polygonal tube that is inserted or adhesively bonded into a congruent cavity between two mutually rotatable parts and is thus loaded on the one hand slightly in shear, and in tension-compression. [0054] In torsional damping element 5 e shown in FIG. 6, a tubular element is provided between two mutually rotatable parts and is in that respect loaded in shear, while radially projecting lugs 31 engage into counterpart recesses in the mating part and thus can be loaded in tension-compression and can develop their respective individual damping characteristics. [0055] Parts List [0056] [0056] 1 Upright column [0057] [0057] 2 Carrier arm [0058] [0058] 3 Support member [0059] [0059] 4 Brake [0060] [0060] 5 a - f Torsional damping element [0061] [0061] 6 Brake engagement surface [0062] [0062] 7 Brake body [0063] [0063] 8 Armature [0064] [0064] 9 a, b Armature flange [0065] [0065] 10 Bolts [0066] [0066] 11 Bolts [0067] [0067] 12 Pivot limiter [0068] [0068] 13 Stop [0069] [0069] 14 Bearing block [0070] [0070] 15 Bearing [0071] [0071] 16 Armature bracket [0072] [0072] 17 a, b Flange [0073] [0073] 18 Damping flange [0074] [0074] 19 Spacer sleeves [0075] [0075] 26 a, b Armature followers [0076] [0076] 27 , 27 a, b Metal washers [0077] [0077] 28 Damping layers [0078] [0078] 29 Pivot pin [0079] [0079] 30 Axis [0080] [0080] 31 Lugs [0081] [0081] 32  [0082] [0082] 33 Bearing sleeve [0083] [0083] 34  [0084] [0084] 47 Pivot axis—see aforementioned U.S. patent application Ser. No. ______ (not essential for the present invention).

The invention concerns a novel stand in which at least one support ( 1, 2 ) is torsionally vibration-damped with respect to another ( 2, 1 ).

TECHNICAL FIELD This invention relates generally to non-contact measurement systems for monitoring a web of material, and, more particularly, to an ultrasonic apparatus and method for diagnosing printing press web breakage while minimizing the effect of web wrinkles on the detection process which utilizes an ultrasonic transmitter and at least two ultrasonic receivers. BACKGROUND OF THE INVENTION Measurement systems, particularly ultrasonic measurement systems, are widely used in the printing industry to monitor characteristics of a web of paper ("web") passing through machinery such as a printing press. Ultrasonic technology is popular because of its reliable operation in the often dusty and dirty printing plant environment. The principles of operation of ultrasonic measurement systems are well-known. When ultrasonic energy (i.e., a frequency higher than the audible range, or above 20 kHz) is incident on an object such as a web, part of the energy is reflected, part is transmitted and part is absorbed. Measuring the time between transmission of the energy and return of the reflected energy (the "return echo"), makes it possible to determine the distance from the ultrasonic transmitter and/or receiver to the web. One important function of an ultrasonic measurement system for a printing press is to detect web breaks by checking for the absence or presence of a web within a certain distance from the measurement system. A typical ultrasonic web break detection system generates an emergency shutdown signal if the web is determined to be absent. The web is judged to be absent when no return echo is received by an ultrasonic receiver within certain amount of time, or if the time for receipt of the return echo indicates that the web has traveled outside of acceptable tolerances. Conversely, if there is a return echo within an acceptable time, the measurement system considers the web to be present and does not generate an emergency shutdown signal. When a web breaks, the web is often directed back into the printing press, where it becomes entangled in the press rolls, resulting in substantial down-time and repair expenses. When a web break is detected it is often desirable to deploy a press protection device which stops the printing presses and severs and/or re-directs the web at various points. Accordingly, a false web breakage alarm could cause significant and unnecessary delay and expense. Two well known ultrasonic web break detection systems used in the printing industry include the sonic web break detector disclosed in U.S. Pat. No. 5,036,706 to Gnuechtel et. al. and the model 1127 ultrasonic web break detector manufactured by Baldwin Web Controls. Such systems detect the presence or absence of a web within certain tolerances which vary with the speed of the web. Web break detectors generally mount directly to a printing press, perpendicular to the plane of the web, within a few inches of the web's surface. Known web break detectors typically comprise a pair of piezoelectric transducers functioning in opposite ways, i.e., one transducer transmits ultrasonic energy at a predetermined amplitude, frequency and phase angle and a second transducer receives a return echo of the transmitted energy. The transmitter transducer and the receiver transducer together comprise a sonic head, and are typically tilted toward each other at a slight angle, for example, 5 to 10 degrees. The transmission and reception of sonic energy by the sonic head is typically coordinated by a controller module, which causes the transmitter to emit a short burst of sonic energy every few milliseconds and, if the web is present, looks for the receiver to detect a return echo of sonic energy within a certain time, for example 300 to 780 microseconds, after the beginning of the transmission of the energy burst. In addition, when the web is present, the receiver must generally show the presence of a return echo from the web for a certain number of consecutive transmit signals. The number of absent return echo signals tolerated is dependent on web speed, and decreases as web speed increases. Thus, the number of return echo absences functions as a filter which helps to ameliorate the possibility of the detection system issuing an emergency shutdown signal because of web flutter or small holes in the web. Further, if a web is present, the controller module may continuously monitor the strength of the return echo to determine whether the receiver transducer has become dirty--covered with ink or paper dust, for example. A two-transducer sonic head will not function properly if the receiver transducer is too dirty. Often, a single controller synchronizes multiple web break detection systems, each detection system having one or more sonic heads, so that the timing of sonic energy transmission and reception for each sonic head is synchronized. Synchronizing detection systems which are in close proximity to each other eliminates interference in the detection of return echoes which would result if timing were not precisely synchronized. Typical ultrasonic web break detection systems utilizing a single transmitter-receiver transducer pair per sonic head suffer from the problem of mistaking harmless web angles and wrinkles in the web, which cause marked degradation of the return echo signal, for actual web breaks, thereby shutting down machinery and severing and redirecting webs unnecessarily. Past systems have attempted to solve the false web breakage alarm problem caused by wrinkles by connecting the processed signals from two sonic heads in parallel logic, so that each sonic head must detect the absence of the web before an emergency shutdown signal is generated. Parallel logic connection of the sonic heads suffers from various disadvantages, however. First, space within a detection system is wasted with two sonic heads essentially functioning as one detection unit. Second, cost and complexity are increased, where one transmitter transducer and associated electronics must be utilized for each receiver transducer, then both transmitter transducers must be synchronized to prevent interference between the adjacent transducer pairs. Third, the controller module must perform the same web detection analysis for each receiver transducer input. This wastes controller inputs and increases web break detection times, thus creating the potential for more serious press jams. For example, when two sonic heads are connected in parallel, a small web tear at only one edge (i.e., under only one sonic head), often referred to as an "edge tear", will not result in press shutdown until the tear travels further across the web. This is because, when connected in parallel logic, both sonic heads must detect a web break before an emergency shutdown signal is generated. Accordingly, one object of the invention is to minimize false web breakage alarms resulting primarily from web wrinkles and secondarily from angular web distortions. Another object is to reduce a number of components necessary to detect web breakage and prevent false web breakage alarms resulting from web wrinkles. A further object is to increase reliability of web breakage detection systems. A still further object of the invention is to decrease web tear detection time. SUMMARY OF THE INVENTION According to the present invention, the foregoing objects and advantages are attained by a method of minimizing an effect of a web wrinkle during web break detection including periodically transmitting a burst of energy for a period of time, the burst of energy being reflected off the web and producing an echo signal; receiving a portion of the echo signal by a first transducer and a second transducer; determining strengths of the portions of the echo signal received by the first and second transducers; comparing the strengths to determine which portion of the echo signal is stronger; and analyzing the strongest echo signal to determine the presence of a web break. In accordance with another embodiment of the present invention, an apparatus for detecting a position of a web of material traversing a machine for feeding the web comprises a housing for storing three transducers; a first transducer adapted to periodically emit a burst of energy for a period of time, the burst of energy being reflected off an object and producing an echo signal; a second transducer adjacent to the first transducer, adapted to receive a portion of the echo signal; and a third transducer adjacent to the first transducer, adapted to receive another portion of the echo signal. Other objects and advantages of the present invention will become readily apparent to those skilled in the art from the following description of the preferred embodiment of the invention which has been shown and described by way of illustration, as the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a typical multiple printing unit heat set press system. FIG. 2a illustrates a cut-away side view of an ultrasonic detection module for diagnosing printing press web breakage according to the preferred embodiment of the present invention. FIG. 2b illustrates a cut-away side view of a detector bar for housing up to four detection modules according to the preferred embodiment of the present invention. FIG. 3 illustrates the principle of operation of the ultrasonic detection module for diagnosing printing press web breakage while reducing false web break alarms according to the preferred embodiment of the present invention. FIGS. 4 and 4A-4C are a schematic electrical diagram of the ultrasonic detection module according to the preferred embodiment of the present invention. FIG. 5 illustrates the difference in phase angle of a return echo signal received by a left receiver transducer and a return echo received by a right receiver transducer of a detection module according to the preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to the drawings, wherein like numerals designate like components, FIG. 1 illustrates a typical multiple printing unit heat set press system. As shown, the press may include multiple printing units 10A-10D, each having one or more blanked impression cylinder combinations 5 employed in the printing process. When the printing units 10A-10D are running, the blanked cylinders 5 feed a continuous paper web 30 through the printing units 10A-10D, from an infeed unit 2 upstream from the printing units 10A-10D and then through a web dryer unit 35 and a chill unit 40 downstream of the printing units 10A-10D. Web break detection systems 15, which may be ultrasonic systems, are located at various points in the system above web 30 to detect when the web 30 breaks. As shown, a web break 42 has occurred in the dryer unit 35. FIG. 2a illustrates a cut-away side view of an ultrasonic detection module 50 for diagnosing printing press web breakage according to the preferred embodiment of the present invention. The detection module 50 may be molded plastic, and have dimensions of approximately 4.5 inches long by approximately 1.7 inches high. The detection module 50 may be adjustably located in a detector bar 130, as illustrated in FIG. 2b, which may be extruded aluminum. The detector bar 130 may have a channel 132 sufficiently long to hold up to four detection modules 50 arranged in series logic in slot positions 134a, b, c and d, respectively. Stocking the detector bar with four modules 50 allows for accurate web detection at both full and half-web conditions. The detector module 50 has approximately the same dimensions as a Baldwin model 1127 sonic head, and thus slots 134a, b, c or d may house either detector modules 50 or prior sonic heads such as the Baldwin 1127 model. Referring again to FIG. 2a, a flange 51 may facilitate the insertion and removal of detection module 50 to and from the detector bar 130. A base side 58 of the detector module 50 fits into the detector bar channel 132. The detector bar 130 is mounted to a printing press via brackets (not shown) such that a detection side 60 of the detector module 50 is oriented toward the web 136, perpendicular to the plane of the web, nominally about 2.5 inches from the web's surface. Three dimensionally-identical piezoelectric transducers 62, 64 and 66 are housed within individual transducer housings 52, 54 and 56. The transducers 62, 64 and 66 may be cylindrical, the center of each transducer being approximately 1.2 inches from its neighbor, and may be composed of a can containing a piezoceramic-driven aluminum membrane. Each can may in turn be encased in a rubber boot. Suitable transducers are commercially available from Motorola, product numbers KSN6541A and KSN6540A and from S. Square Enterprise Co., Ltd., Taiwan, Product Nos. RE455ET/R180 or RE400ET/R180. A transducer which oscillates at 45.5 kHz, 40 kHz or another frequency may be utilized. A transmitter transducer 62 may reside in transducer housing 52, held in place by transducer supports 52a and 52b. The transmitter transducer 62 may emit a short burst of four pulses, for example 77 microseconds long, of 45.5 kHz sonic energy toward the web every 10 milliseconds. One receiver transducer 64 may reside in transducer housing 54 supported by transducer supports 54a and 54b, while a second receiver transducer 66, which is approximately 2.4 inches from the first receiver transducer, may reside in transducer housing 56, secured by transducer supports 56a and 56b. The receiver transducers 64, 66 detect the presence of a return echo of the transmitted sonic energy. The transmitter transducer 62 is generally perpendicular to the plane of the web, while the receiver transmitters 64, 66 may be tilted toward the transmitter transducer 62 at a slight angle, for example, 10 degrees. Three cone-shaped horns 53, 57 and 59, which may be integral with the molded plastic of the detection module 50, counteract cross-talk between the transducers 62, 64 and 66. The center horn 57 associated with the transmitter transducer 62 is shorter than horns 53 and 59 associated with the receiver transducers 64, 66 so that, among other things, transmitted sonic energy radiates a wide beam. The beam width may be approximately 60 degrees, whereas past two-transducer sonic heads having angled transmitter transducers emitted total beam widths of only 45 degrees. The receiver transducers 64, 66 are typically immediately active upon transmission of a burst of sonic energy by the transmitter transducer 62. To detect the presence of the web, a receiver transducer 64, 66 generally must detect a leading edge of a return echo of the transmitted sonic energy from 300 to 780 microseconds after initial transmission of the sonic energy toward the web. Measuring the amount of time elapsed between initial transmission of sonic energy by the transmitter transducer 62 and detection of the leading edge of the return echo by the receiver transducer 64, 66, and knowing the speed of sound in air, makes it possible to calculate the distance of the web from the detection module 50. This calculation may be performed by a system controller (not shown) such as the Baldwin Web Controls model 1127 controller using well-known methods. The web is considered present if it is found to be within certain distances, for example, 1 to 4 inches, from the detection module 50. If the web is not detected within 1 to 4 inches of the module 50, an emergency shutdown signal is sent to the printing presses (depicted in FIG. 1) by the web system controller (discussed further below). Connector port 55 allows the detector module 50 to be remotely connected to the system controller via a cable (not shown), which supplies communication between the detection module 50 and the system controller. The system controller is responsible, for example, for (1) generating control signals which cause the transmitter transducer 62 to periodically emit bursts of sonic energy, (2) accepting and analyzing the return echo signals detected by the receiver transducer 64, 66, and (3) for determining whether the web is or is not present beneath the detector module 50 based on the analysis performed on the return echo signals. A web is considered to be absent by the controller when there are no return echo signals from the web (within a given distance, such as 1 inch to 4 inches) for a certain number of consecutive transmit signals, the number of tolerated return echo absences being dependent on web speed. The methods for processing return echo signals based on web speed to determine web presence or absence are well-known to those skilled in the art. The frequency of false web break alarms which occur because of web wrinkles is reduced by using the preferred embodiment of the detection module constructed and oriented as described in connection with FIG. 2, the principle of operation of which is graphically illustrated in FIG. 3. Return echo signal strength 75, i.e., a direct current magnitude of a return echo signal, is plotted against wrinkle distance from a centerline point 73 directly beneath a transmitter transducer, for both a left receiver transducer 70 and a right receiver transducer 72, the left and right receiver transducers being positioned approximately 2.4 inches apart, as a web wrinkle with a height of 0.43 inches passes from left to right under the ultrasonic detection module. The graph 75 demonstrates that the left and right transducer receivers in different locations from the same transmitter have signal losses (and therefore absent return echo signals) as the wrinkle changes position. For example, while the right receiver transducer 72 maintains a relative signal strength of about 5.5 when the wrinkle is near the left of the detection module, the left receiver transducer signal strength drops to about 1. Conversely, as the wrinkle travels toward to the right side of the detection module, the left receiver transducer maintains a signal strength of approximately 5.5, while the right receiver transducer signal strength drops to about 1. A similar situation results when the web is tilted side-to-side, and, as will be appreciated by one skilled in the art, the principles of the present invention which apply to reducing false web break alarms resulting from web wrinkles are also applicable to reducing the false alarms which occur because of web angles. The loss of signal detected by the receiver transducer nearest to the wrinkle may explained by, for example, two general principles of wave mechanics. First, a rise in the web height because of the wrinkle creates an obstruction in the path of the return echo signals--the wrinkle thus blocks most of the return echo signals from being detected by the receiver transducer closest to the wrinkle. Second, the wrinkle causes a phase angle of the return echo signals to shift such that signal cancellation with the transmitted sonic energy results. Thus, it is seen that the effect of web wrinkles on the web break detection process may be reduced by comparing the return echo signal strengths detected by the left and right receiver transducers prior to the system controller performing analysis of the return echo signals. Then, only the stronger of the left or right receiver transducer signal must be analyzed by the controller to determine whether the web is or is not present beneath the detector module. The use of two receiver transducers in the manner described herein increases detector module reliability over prior systems having one transmitter transducer and one receiver transducer. For example, one receiver transducer which breaks or becomes blocked by dirt will not affect the continued operation of a detector module according to the present invention because a second receiver transducer will continue to detect web breaks in a manner comparable to prior two-transducer systems. As will further be recognized by one skilled in the art, the three-transducer detector module according to the present invention eliminates the need for parallel logic connection of detection modules. Thus, web edge tears are quickly detected. FIG. 4 is a schematic electrical diagram of the ultrasonic detection module according to the preferred embodiment of the present invention. The electronics are designed to be used with a Baldwin Web Controls model 1127 system controller, which utilizes well-known methods for providing a 4-pulse signal to a transmitter transducer, and for digitally processing the return echo signals detected by a receiver transducer. Circuitry 80 associated with the transmitter transducer 81 of the preferred embodiment of the detection module described in connection with FIG. 2 receives an input 82 from the system controller (not shown) and is fed via resistor 83 to dual emitter followers 84, 85. The dual emitter followers 84, 85, via coupling capacitor 86 drive the transmitter transducer 81 at its low impedance resonance point, series resonating with inductor 87 and capacitor 88. Circuitry 90a is associated with a first receiver transducer 91a, and identical circuitry 90b is associated with a second receiver transducer 91b, both transducers 91a and 91b being constructed and oriented according to the preferred embodiment of the detection module described in connection with FIG. 2. The inputs from receiver transducers 91a,b are fed to capacitors 92a,b and resistors 93a,b. The capacitor-resistor combinations discriminate against lower frequency interference. Operational amplifier stages 94a,b, along with their associated capacitors 95a,b and resistors 96a,b, provide some gain along with impedance transformation. Stages 97a,b including operational amplifiers 98a,b and their associated components beginning with resistors 99a,b comprise two-pole bandpass filters centered at the transmitter transducer's frequency. Stages 97a,b also provide gain. The outputs of stages 97a,b serve as inputs to stages 118a,b, which provide large, adjustable gain. At this point, the return echo-signals detected by each receiver transducer could be added together and processed by the system controller. The addition method is not preferred, however, because, as illustrated in FIG. 5, the signals from the left receiver transducer 70 and the right receiver transducer 72 may be out of phase. As shown, the signals are 180 degrees out of phase, so that simple addition of the signal magnitudes would be impossible, and could lead to unsatisfactory web detection. Thus, it is preferred that stages 119a,b plus 100a,b perform full-wave rectification of the signals, so that absolute magnitudes or direct current values of the return echo signals detected by each receiver transducer are obtained. The rectified signals represent the relative strengths of the signals. Components 101a,b and 102a,b provide filtering. The rectified and filtered signals are impedance transformed by operational amplifier stages 103a,b and their associated components. Then, each signal is fed into a comparator stage 104, which drives analog switch 105. The analog switch 105 selects the stronger of the two signals. The strongest signal is fed to a final amplifier stage 106 via capacitor 107 and resistor 108. Capacitor 109 provides stabilization. Stage 106 drives dual emitter followers 110, 111, the output 112 of which is capable of driving long cables (not shown) for connecting the detection module to the system controller. It will be apparent that other and further forms of the invention may be devised without departing from the spirit and scope of the appended claims, it being understood that this invention is not to be limited to the specific embodiments shown.

An apparatus for detecting breakage of a web of material traversing a machine for feeding the web, and a method for the same. The apparatus includes a housing for mounting three transducers, a first transducer adapted to periodically emit a burst of energy for a period of time, the burst of energy being reflected off an object and producing an echo signal. A second transducer adjacent to the first transducer receives a portion of the echo signal, and a third transducer also adjacent to the first transducer receives another portion of the echo signal. The strongest portion of the echo signal is used to detect whether the web is broken.

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to the field of power electronics. It is based on a converter module and a converter as claimed in the preamble of claims 1 and 10. 2. Discussion of Background The invention relates to converter modules for high-capacity converters. The converter modules are constructed from a plurality of power semiconductor switches, by means of a busbar system. Such busbar systems have been described, for example, in the article "GTO-Hochleistungsstromrichter fur Triebfahrzeuge mit Drehstromantrieb" GTO high-capacity converters for traction vehicles using three-phase drives!, ABB Technology 4/1995, pages 4-13. Power is supplied to electrically propelled locomotives via a DC intermediate circuit which is coupled on the input side to a DC network or via a mains converter to an AC network and, on the output side, supplies electrical power of variable amplitude and frequency to the three-phase asynchronous traction motors via an in general multiphase drive converter. The busbar system forms the electrical connection between the output of the mains converter--or the overhead wire for a DC network--and the power semiconductor switches or modules of the drive converter. This may be highly complex, may limit the performance of the electrical switching system, and may result in considerable costs. In the course of development of power semiconductor switches, a change has been made from conventional thyristors or gate turn off thyristors (GTOs) to IGBTs (bipolar transistors with an insulated gate) The IGBTs are in general integrated in a module. For relatively high currents and ratings, a plurality of modules are connected in parallel. With respect to converter families of various ratings, busbar systems are sought which allow a multiphase converter which can be designed to be modular, can be scaled easily and has low inductance. It has been proposed in two earlier German Patent Applications (file references 196 00 367.9 and 196 12 839.0), which do not have priority, that this problem be solved by a two-dimensional arrangement of power semiconductor modules over flat DC plates and parallel phase busbars. The flat modules have plug-in contacts extending longitudinally along a narrow, long edge and are pushed into two rows per busbar of lugs, which act as mating connections, parallel to the phase busbars. The closest neighbors are in each case rotated through 180° and are connected to one another in a bridge circuit. They thus form half-bridges or bridge arm pairs, that is to say they make contact with opposite DC plates and feed current half-cycles of opposite polarity into a common phase busbar. The next-but-one neighbors are, in contrast, oriented in the same direction and form parallel-connected modules for power scaling. This configuration still has disadvantages, such as unsatisfactory symmetry, non-ideal inductance and, in particular, structural complexity. The long, different current paths to and between the modules result in current asymmetries and uneven loads on the modules. The resultant suboptimum utilization increases as the power level or the number of modules per phase increases, which necessitates power derating. Other problems with this arrangement relate to the design aspects. A large number of different parts are required for a type range, and assembly is complex. Compliance with the minimum insulation separations and creepage distances requires particular care since the positive and negative connections are very close to one another and penetrate one another. In addition, tailor-made metal sheet sizes and individually matched components are required for each application and rating level. According to DE 44 02 425 A1 it is, furthermore, prior art for an invertor arrangement to connect a plurality of bridge arm pairs of semiconductor switching elements in parallel along one phase busbar. The elements in each bridge arm are oriented front to back or facing away from one another or the same, and are made contact with and screwed together via longitudinal profiles. One special feature is that the phase busbar is folded up at the end and is passed back parallel, in order to reduce the inductance. SUMMARY OF THE INVENTION Accordingly, one object of the invention is to provide a novel busbar system for converters, which is distinguished by simplified, space-saving design and reduced assembly complexity, as well as having improved symmetry with low inductances and a high current capacity. This object is achieved according to the invention by the features of the first claim. Specifically, the essence of the invention is that preferably plug-in power semiconductor switches are coupled in pairs, with their front or rear sides oriented to face one another and very close together, to a positive connection and a negative connection of a DC intermediate circuit and to a phase busbar. In consequence, the current paths are made symmetrical for both the load and commutation currents, and are designed to have low inductance. At the same time, various converter module versions are provided which are easy to assemble and, owing to their modular design, can easily be matched to any desired rating requirement. A first exemplary embodiment is represented by a first single-phase converter module comprising two power semiconductor switches, whose front or rear sides face one another and which are connected in a bridge circuit. A further exemplary embodiment is represented by a second single-phase converter module comprising four power semiconductor switches, two switching elements in each case being opposite one another and being connected in parallel in one bridge arm, and both arms being laterally adjacent, that is to say offset in the direction of the phase busbar. A final exemplary embodiment is represented by a two-phase converter module comprising four power semiconductor switches, two switching elements in each case forming a bridge arm pair in a lateral, parallel position, and both pairs being arranged in mirror-image form with respect to the center plane, and supplying different phases. One advantage of the busbar system according to the invention is the high level of symmetry of the arrangement of power semiconductor switching elements, which makes it possible for the current loading of the elements to be uniform, and thus allows high total current level. It is especially advantageous that parallel-connected power semiconductor switching elements can be controlled largely without any interference, owing to the short distances from a common gate drive electronics device. A further advantage is that a very simple, compact and modular design of a converter module can be achieved using a small number of standard components and plug-in power semiconductor switching elements. BRIEF DESCRIPTION OF THE DRAWINGS A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: FIG. 1 shows a perspective view of a power semiconductor switch or power semiconductor module having elongated plug-in contacts (prior art); FIG. 2 shows a schematic plan view from above of a first converter module according to the invention; FIG. 3 shows a section through a first converter module according to FIG. 2, along the line A--A, with the power semiconductor modules plugged on; FIG. 4 shows a schematic plan view from above of a second converter module according to the invention; FIG. 5 shows a section through a second converter module according to FIG. 4, along the line B--B, with the power semiconductor modules plugged on; FIG. 6 shows a schematic plan view from above of a third converter module according to the invention. DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts through several views, FIG. 1 shows a power semiconductor switch or a power semiconductor module 1, in particular an "Intelligent Power Module" or IPM, as used in converters, voltage converters or invertors. The power semiconductor switch is accommodated, typically together with circuitry components, in a module housing 2. It makes contact with the phase via a visible, elongated plug contact 3 (DC input) with a DC pole, and via a plug contact 3 (phase output), which is concealed by the insulating plate 4. The top and bottom of the module will be referred to as the front and rear side, respectively, or as frontal sides. The power semiconductor is driven via a gate electronics device, or a gate drive, which is not illustrated here. The modules may be fitted with power semiconductors of different technologies, preferably with IGBTs. For traction purposes, a plurality of modules have to be interconnected via a busbar system in order to switch large currents and power levels. The further development of IGBTs is aimed at further increasing the switching capacities, so that the number of modules that have to be connected in parallel can be reduced in the future. FIG. 2 now discloses a first exemplary embodiment of a busbar system according to the invention, which is designed for the minimum number of two power semiconductor modules per phase and is optimized in terms of switching characteristics, space saving and design simplicity. On the left-hand side, the plan view shows a positive connection 6 and a negative connection 7, in the form of busbars, for connection to the DC intermediate circuit, in the center and on both longitudinal sides, first lugs 9 and 10 for the positive connection and negative connection respectively as well as second lugs 11 for a phase connection 8 and, on the right hand side, the phase connection or the phase outgoer busbar 8, which is routed to the exterior on the right. A first and a second lug in each case interact in order to hold and make contact with a power semiconductor switch. The lugs 9, 10, 11 preferably point up at right angles and are oriented parallel to the longitudinal sides, so that the switches are opposite one another, close together, with their front or rear sides facing one another. The section along A--A (FIG. 3) illustrates the arrangement according to the invention. The illustration shows the essentially "L"-shaped cross-section profiles of the positive connection 6 and negative connection 7, and the essentially "W"-shaped cross-sectional profile of the phase busbar 8, as well as its interaction with two power semiconductor modules 1. With regard to the phase busbar 8, the center ridge may be more or less pronounced or may even be absent, to create a "U"-shaped profile. All the profiles are mounted on a baseplate 5, together with holders 12, via insulation elements which are not illustrated, and form a compact component. The holders and insulation elements may, in particular, also be directly integrated in the baseplate. Air, gas, solid insulators or a combination of them may be used as insulation media between the live parts 6, 7 and 8, the minimum separations being governed by the appropriate insulation distance and creepage distance conditions. The surfaces may be, but need not be, coated to be insulating. Finally, the insertion of two power semiconductor modules 1 from above creates an extremely compact and mechanically robust converter module. This arrangement is highly advantageous from many points of view. The current paths are very wide, short, and of virtually the same dimensions for both power semiconductor switching elements. They do not enclose any areas to create inductance, and opposite current directions are close together. In addition to a very high current capacity, these measures achieve, in particular, a very low inductance of about 25 nH in the commutation circuit. Commutation in this case refers to the switching processes, which in some cases are in the order of microseconds, by means of which the power semiconductors exchange high-frequency currents for mutual relief. A second exemplary embodiment is shown in FIG. 4 and the associated sectional view along B--B in FIG. 5. In this case, the positive connection 6 and negative connection 7 have an essentially "U"-shaped cross-sectional profile with first lugs 9, 10 on both longitudinal sides, and the phase connection 8 once again has an essentially "W"-shaped or "U"-shaped cross-sectional profile with two lugs 11 on both longitudinal sides. This converter module has four mounting spaces for power semiconductor switches. Two power semiconductor switches are in each case positioned opposite one another, with their front or rear sides facing one another, and are connected in parallel. They are connected to the adjacent pair at the side, in a half-bridge circuit. In this arrangement, the symmetry is reduced in that the positive connection 6 has to supply the power semiconductor switch pair located further to the rear, via the lugs 9. It is thus made contact with from underneath via a flat feed plate. However, the resultant inductance of the commutation circuit is typically about 50 nH, and thus always achieves very low values. A further advantage is that the parallel-connected power semiconductor switching elements can in each case be driven by a common gate drive, since the problem of dangerous induced voltage spikes is largely suppressed owing to the very short cable run 13. FIG. 6 shows an extremely compact arrangement for supplying two phases. This arrangement is based on FIGS. 4 and 5 by separating the phase busbar 8 along its center line and the gate feed line 13. The resultant phase busbars 14 and 15 have half the width, and have a half-"W"-shaped or a "U"-shaped profile in the region of the lugs 16 and 17, respectively. The two phase busbars run parallel in the longitudinal direction, and lie close to one another. The power semiconductor switches, which are arranged laterally offset on the same longitudinal side and make contact with different "U" profiles 6, 7, each form a half-bridge and make contact with phase connection 14, 15. In a similar way to that in the second exemplary embodiment, but separately for each half bridge, the commutation currents flow through the busbars in the longitudinal direction. In all the examples referred to, the busbar system according to the invention is distinguished by economically significant design advantages. A small number of components are used which can be produced, for example, from aluminum extrusions or bent brass parts with minimal production effort. Very good compliance with mechanical tolerances is equally possible, and the busbar system is also suitable for high currents in the kA range. For power scaling, the compact converter modules can be packed very closely alongside one another (FIGS. 2-6) and can be interconnected for larger units, without components having to be adapted. The converter modules according to the invention are distinguished by very low inductances. In consequence, very steep switching flanks and very high switching frequencies can be achieved, and the loads on the power semiconductors, as well as the reactions on the network, can be kept low. Furthermore, all the embodiments allow the amount of derating of the power semiconductor switches to be very low. This is achieved by the high level of symmetry of the bridge arms. In addition, derating is avoided if the power semiconductor modules are connected in parallel, since potential differences between the gates of parallel modules are minimized owing to the fact that the busbar system between the parallel-connected modules has very low inductance, and the gate drive connecting lines are designed to be very short. A particularly advantageous feature of all the exemplary embodiments is the use of plug-in power semiconductor switches or power semiconductor modules. The first and second lugs then act as plug-in spaces for the power semiconductor switches. In the examples, the roles of the positive connection 6 and negative connection 7 may be reversed. It is also feasible for the arrangement of the DC connections 6, 7 and the phase connection 8 to be interchanged (see, for example, FIG. 3). The first and second lugs then change places, the power semiconductor modules are mounted rotated through 180° C., and a broadened phase connection 8 is passed out underneath the DC connections. Further versions of the invention also result, for example, by arranging a plurality of power semiconductor switches, instead of just one, connected in parallel in the longitudinal direction. This can easily be achieved by using longer lugs or a plurality of lugs, made contact with in the same way, laterally alongside one another. This allows power scaling in all three embodiments (FIGS. 2-6). In the same way, a plurality of converter modules, including different modules, can be interconnected via their phase connections 8, 14, 15, for power scaling. Overall, the invention provides a busbar system by means of which converter modules having optimum switching characteristics and a space-saving, modular design can be achieved. Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein. LIST OF DESIGNATIONS 1 Power semiconductor switch or power semiconductor module 2 Module housing 3 Plug-in contact 4 Insulating plate 5 Baseplate 6 Positive connection 7 Negative connection 8 Phase connection 9 First lugs (positive pole) 10 First lugs (negative pole) 11 Second lugs (phase) 12 Holder 13 Gate feed line 14 Phase connection 1 15 Phase connection 2 16 Second lugs (phase 1) 17 Second lugs (phase 2)

Converter modules have a busbar system for a plurality of power semiconductor switches or, preferably, IGBT power semiconductor modules (IPMs). The power semiconductor switches are arranged in pairs, facing one another or facing away from one another, close together and parallel. In accordance with exemplary embodiments, alternating current is fed in one or two phases via bridge circuits composed of two or four power semiconductor switches.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the field of antiglare coatings in general, and in particular, to coating compositions, methods for preparing coating compositions and methods for applying coating compositions to optical glass surfaces. The invention is particularly directed to reducing specular reflection on the surfaces of cathode ray tubes, for example, computer monitor screens, television tubes, etc. 2. Description of Prior Art Specular reflection or glare is defined as the direct reflection of ambient light from a smooth glass surface. Images on the screens of cathode ray tubes, for example television tubes, are formed behind the glass screen of the tube. Natural and artificial sources of light are reflected from the otherwise smooth glass surface of such screens, interfering with the images formed behind the glass surface. A strong source of sunlight, for example through an unshaded window, is likely to substantially wash out the entire picture. A local light source, for example a lamp, will tend to have its image reflected from the screen, superimposed on the image formed by the cathode ray tube (CRT). This creates a very disturbing local distortion. Coatings have been applied to the surfaces of television tubes with a controlled roughness or surface pattern so that ambient light is scattered and diffused, thereby reducing glare. The roughness should not unduly degrade the resolution of the images to be viewed. A very practical consideration for coatings applied to CRT screens is that the glare-reducing coating should adhere to the glass surface, and should be sufficiently hard to resist abrasion and chemically resistant to moisture, humidity and common household cleaning solutions. It is known in the art to reduce specular reflection with a vitrified, droplet pattern coating. Typically, an aqueous solution of an alkali silicate is sprayed in droplet form on a glass surface. The droplet pattern coating is dried and baked at an elevated temperature to provide a vitrified or glassy coating of corresponding pattern and surface contour. It is desirable to reduce the soda content in the vitrified coatings formed from such solutions in order to impart long-term stability against development of "bloom" on the coating surface. Such a solution is discussed in U.S. Pat. No. 3,114,668, which further teaches that picture or image resolution can be improved by incorporating a minor addition of boric oxide in the alkali silicate coating. Boric acid seemed to reduce the incidence of sharp-sided craters in the coating surface. Another glare reducing coating is disclosed in U.S. Pat. No. 3,635,751, and is prepared by a method comprising the steps of: warming the surface of the glass screen to about 30° C. to about 100° C.; coating the warmed surface with an aqueous solution containing about 1 to 10 weight percent of a lithium-stabilized silica sol; drying the coating; and, heating the dry coating at about 150° C. to 450° C. An improvement to the lithium silicate coating method is described in U.S. Pat. No. 3,940,511. It was observed that glare-reducing lithium silicate coatings on cathode ray tube face plates developed objectionable haze or "bloom" upon standing or storage at normal ambient humidities and temperatures. The haze is objectionable esthetically and reduces the brightness and color fidelity of the transmitted image. A similar haze was observed for sodium and potassium silicate coatings that have been baked at temperatures of about 400° C. to about 500° C. It was further observed that some glare-reducing lithium-silicate coatings which contained light attenuating particles transmitted an image which appeared to have a brownish or other tint. In the method according to the improvement, the dry baked coating is washed or rinsed with hot water subsequent to the baking step. Washing the coating with hot water reduces or eliminates the tendency of the coating to form a haze or bloom. The washing was believed to remove soluble lithium compounds which were present in the coating. In order to correct for any tint in the transmitted image which might be imparted by the glare-reducing coating, the coating might also include a small amount of a color-correcting dye. Glare-reducing coatings are also of interest in applications other than glass screens, for example, on the surfaces of semiconductor solar cells. The object of anti-reflective coatings in this application is to promote transmission of, and to prevent reflection back into the atmosphere of solar radiation. Proper coatings can reduce the amount of light reflected when applied in thicknesses of one quarter of a wave length. Such coatings, as described in U.S. Pat. No. 4,361,598, can be made from clear solutions which contain oxide constituents in a soluble polymerized form and from which uniform and continuous glass-like oxide films can be deposited on substrates at relatively low temperatures. Such a solution is prepared by reacting metal alkoxide with a mixture of critical amounts of water and/or acid in an alcohol diluted medium. Alkoxides may be Ti(OR) 4 or Ta(OR) 5 , or another metal alkoxide such as Si(OR) 4 in admixture with these alkoxides. Acids may be HCl or HNO 3 . Quarter wave inorganic optical coatings are deposited by applying the alkoxide solutions to a substrate and then heating the coating at a temperature above 350° C. Of course, glare reducing coatings for such solar cells must be bounded to a surface of silicon doped with germanium, for example, which can be expected to react differently than glass in bonding with surface coatings. Image quality can be difficult to measure objectively, particularly in evaluating resolution and contrast. Specular reflection has been customarily measured in terms of gloss or glare, objectively, by a gloss meter. Specular reflection can also be measured subjectively in terms of lines per inch and correspondence to a standard pattern. A series of patterns, having different numbers of lines per inch can be projected onto a test panel and reflected to a viewer. The last pattern capable of being distinguished is a valve or measure of the specular reflection. The coatings and methods described herein are effective for producing anti-glare coatings on optical glass screens. The degree of glare reduction by coatings according to this invention has been determined both objectively and subjectively to be every bit as effective as the best known coatings of the prior art, and at the same time, can be prepared and applied at a significant cost savings. Accordingly, anti-glare coatings according to this invention provide very significant advantages over the prior art. SUMMARY OF THE INVENTION It is an object of this invention to provide coatings for reducing specular reflection on optical glass screens. It is another object of this invention to produce coatings for reducing specular reflection on optical glass screens at a significant cost reduction. It is still a further object of this invention to provide coatings for reducing specular reflection on optical glass screens at substantial savings and the coatings are as effective as any known in the prior art. It is yet another object of this invention to provide solutions from which such coatings can be made. It is yet another object of this invention to provide methods by which such solutions can be applied to optical glass screens to form such anti-glare coatings. Briefly, this invention embodies anti-glare coatings for optical glass screens and the like and methods for preparing and applying such coatings, which are considerably less expensive than has been known in the art. Despite the savings in cost, the coating is just as effective in reducing specular reflection on optical glass screens as any coating now available. In the presently preferred embodiment, an anti-glare coating according to this invention comprises a partially hydrolized metal alkoxide polymer. These metal alkoxides have the general formula M(OR) 4 where M is selected from the group consisting of silicon, titanium and zirconium, where R is alkyl with 1 to six carbon. The equivalent titanium and zirconium alkoxides form approximately 10% of the solids, by molar ratio, and approximately 15% of the solid, by weight. The coatings may be produced from a solution formed by creating a partially hydrolized tetraethyl orthosilicate or ethyl silicate 40 (TEOS) with metal alkoxides of titanium and zirconium in alcohol and water, nitric acid being used as a homogeneous catalyst. The solvent of the solution is alcohol, such as ethanol, propanol or higher alcohols. The higher alcohol yields a film or coating with less haze and less sensitivity to humidity. The presently preferred alcohol is 2-propanol. It has been noted that ethanol-based solutions will gel at room temperatures within a month and propanol-based solutions will not gel at room temperature. When ethanol-based solutions are stored at lower temperatures, time of gelation will be greatly extended. With regard to forming TiO 2 , suitable starting components include titanium isopropoxide (TPT) and titanium butoxide (TBT). TBT is preferred as it is less sensitive to humidity. The glass screen or panel to be coated is first cleaned, if necessary, and then preheated to a temperature in the range of approximately 20° C. to 75° C., higher temperatures producing a more defined surface topology, and therefore a greater diffusion effect. After the solution is sprayed onto the screen or panel, the screen or panel is baked at a temperature in the range of approximately 500° C. to 550° C., for a time period in the range of five to twenty minutes. With reference to the schematic illustration of FIG. 3, the panel and coating must be baked for a sufficient period of time, and at a sufficient temperature, to drive off the alcohol and water molecules from the coating. As a result, the coating becomes densified and transformed into a glossy material. At the same time, this material bonds to the glass surface through M-O-Si bonding. Temperatures below 500° C. are insufficient to stabilize the coating by driving off the solvent and water molecules. Temperatures in excess of 550° C. may damage or distort the glass panel. It has been found that baking the panel at a temperature of approximately 520° C. for approximately five minutes, or 500° C. for approximately twenty minutes, is sufficient to completely stabilize and bond the coating to the glass screen or panel. BRIEF DESCRIPTION OF THE DRAWINGS Aspects of this invention are illustrated in the drawings, wherein: FIG. 1 is a section view of a panel to which an anti-glare coating according to this invention has been applied; FIG. 2 is a block diagram illustrating a method according to this invention for applying an anti-glare coating to an optical glass screen or panel; and, FIG. 3 is a diagrammatic illustration of the manner in which a film formed by an anti-glare coating according to this invention is stabilized and bonded to a glass surface by baking. It will be appreciated that this invention is not limited to the precise arrangements, instrumentalities and methodology illustrated in the drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Anti-glare coatings have been applied to optical glass screens or panels in a textured, roughened, or otherwise patterned topology, as illustrated in FIG. 1, wherein an anti-glare film or coating 14 has been applied to the surface 12 of a glass screen or panel 10. As is apparent by the representative shape of the upper or exposed surface 16 of the film or coating 14, the topology or texture of the film is not smooth and flat, but is patterned in order to enhance diffusion of reflected light. Depending upon the particular angle of the surface 16, representative light rays B and C are reflected at different angles, diffusing the light and reflected image of the light source. Some rays of light will be incident at such an angle as to pass through the coating, as in light ray A, and thereafter be reflected by the surface 12 of glass screen or panel 10. Such light rays will be diffused relative to those light rays reflected at the surface 16, and will also be refracted to an extent which depends upon the index of refraction of the film or coating 14. The particular topology of the coating is as already known in the art, and does not form a part of this invention in and of itself. Accordingly, the particular advantages and disadvantages of different surface topologies will not be discussed in detail. The nature of the invention is such that significant savings can be achieved by using coatings according to this invention to form whatever surface topology is desired. The gloss reading, as measured by a conventional gloss meter, such as a "Gardner" meter, will reflect the extent of the diffusion resulting from the patterned topology of the coating. The gloss reading will also be a function of the intensity of the reflected light. The intensity depends upon the refractive index of the coating and its absorption characteristics. The basic steps according to this method for applying an anti-glare coating are illustrated in FIG. 2. The general scheme of applying the solution includes steps which are generally included in prior art methods, such as spraying the solution onto the panel and baking the panel and solution to stabilize the coating. Nevertheless, such basic steps are modified according to the particular coatings according to this invention, and the solutions from which they are formed. As a first step, one must insure that the surface to be coated is clean and free of contaminants which would prevent proper stabilization and bonding of the film to the glass screen or panel. Depending upon the production stage at which the coating is applied, a special cleaning step may or may not be necessary. The clean glass screens or panels are preheated to a temperature in the range of approximately 20° C. to 75° C. Such higher temperatures produce a more defined topology of the surface 16 of the film or coating 14, thereby providing a greater diffusion effect. After preheating, the solution from which the coating is formed is applied to the surface of the optical glass screen or panel. The solution is in effect a partially hydrolized metal alkoxide polymer, in which a proper proportion of metal alkoxides are dissolved. Although the coating may be applied in a number of ways, the presently preferred method is to spray on the solution with an air gun. Certain parameters in particular related to application by spraying will effect the coating. The principal parameters include the size and shape of the spraying head, the distance of the spraying gun from the surface of the panel during application, the amount of air pressure driving the spray gun, the number of coatings or passes over the panel by the spray gun and the liquid pressure of the solution delivered to the spray head and the relative speed of the travel between the spray gun and the panel. Higher liquid pressure or head, measured in inches, will produce films with less haze, but flatter topology. Bringing the spray gun closer to the surface of the panel produces the same effect as high liquid head. Increasing the air pressure driving the spray gun produces finer droplets and more diffusion, but the film tends to have more haze. The greater the number of passes, the thicker the film will be. The thicker the film, the greater the extent of glare reduction. However, if the film becomes too thick, it will be prone to cracking. After the solution has been applied, the coating must be bonded and stabilized to the glass surface as shown in FIG. 3. This is accomplished by baking the panel and the solution applied thereto at a temperature in the range of approximately 500° C. to 550° C. for a sufficient amount of time to drive off the solvent and water in the solution, leavin a silica-titania-zirconia glass. The partially hydrolized metal alkoxides in the solution have the general formula [M(OR) 2-x (OH) x ] n as shown on the film side of the film/glass interface before baking. At the elevated baking temperature, the OR and OH group of the polymer bonds with the SiOH group of the glass surface, forming an alcohol and water. This alcohol and water is then evaporated from the coating. As a result, the coating becomes dense and chemically bonded to the glass surface. When the baking is complete, the solution has completely evaporated, leaving a silica titania-zirconia glass as the anti-glare coating. As set forth in FIG. 2, it has been found that baking at a temperature of approximately 520° C. for approximately five minutes is sufficient. Six different formulations of solutions for forming coatings according to this invention were prepared and tested, the formulations being designated by Roman numerals I-VI. The ingredients of each formulation have been labeled by lower case letters to facilitate comparisons of the quantities of ingredients or components in the formulations. Formulation No. I (a) 101.8 ml of 2-propanol (b) 37.0 gm TEOS (c) 3.18 ml H 2 O+0.5 ml HNO 3 (d) 5.5 gm TPT (titanium isopropoxide; Ti(OC 3 H 7 ) 4 ) (e) 1.6 ml H 2 O+6.0 ml 2-propanol Initially, the TEOS (b) was mixed into the 2-propanol (a), the mixture being then heated to a temperature of approximately 55° C. After heating, the water and nitric acid (c) were added and mixed during a period of approximately thirty minutes. Thereafter, the TPT (d) was added and mixed during a period of approximately fifteen minutes. Finally, the additional water and additional 2-propanol (e) were added and mixed during a period of approximately one and one half hours. At this point, the solution was ready for application to the glass screen or panel, preferably by spraying. Each of the following formulations was prepared in the same fashion. Components or sets of components (a) and (b) were mixed and heated; (c) were added and mixed; (d) was (were) added and mixed; and, (e) were added and mixed. Formulation No. II (a) 80.0 gm 2-propanol (b) 41.0 gm TEOS (c) 3.55 ml H 2 O+0.7 ml HNO 3 (d) 3.36 gm TBT (titanium butoxide; Ti(OC 4 H 9 ) 4 )+3.63 gm zirconium n-propoxide (Zr(OC 3 H 7 ) 4 ) (e) 1.78 ml H 2 O+8.0 ml 2-propanol Formulation No. III (a) 101.8 ml 2-propanol (b) 39.8 gm TEOS (c) 3.2 ml H 2 O+0.5 ml HNO 3 (d) 6.72 gm TBT (e) 1.6 ml H 2 O+6.0 ml 2-propanol Formulation No. IV (a) 80.0 gm 2-propanol (b) 45.22 gm TEOS (c) 3.91 ml H 2 O+0.7 ml HNO 3 (d) 6.72 gm TBT (e) 1.95 gm H 2 O+6 ml 2-propanol Formulation No. V (a) 108.0 ml 2-propanol (b) 41.07 gm TEOS (c) 0.7 ml HNO 3 +3.55 ml H 2 O (d) 5.76 gm TBT+0.93 gm Zr(OC 3 H 7 ) 4 (e) 1.78 ml H 2 O+6.0 ml 2-propanol Formulation No. VI (a) 110.0 ml 2-propanol (b) 41.07 gm TEOS (c) 0.7 ml HNO 3 +3.55 ml H 2 O (d) 3.36 gm TBT+3.625 gm Zr(OC 3 H 7 ) 4 (e) 1.78 ml H 2 O+8.0 ml 2-propanol EXAMPLE 1 Example 1 utilized formulation I, and was intended to demonstrate the effects of fluid pressure or head. During the first part of example 1 the distance from the spray gun to the float glass panel surface was 11 inches, the air pressure was 35 psig (pounds per square inch gauge) and the coating was formed from three passes of the spray gun. When the fluid pressure or head was 17.5 inches the gloss reading was 131; the prior reading was 154. When the fluid head or pressure was increased to 35 inches the gloss reading increased to 138. In the second part of example 1 the distance of the spray gun to the panel was 11 inches, the air pressure was 45 psig and the coating was formed by six passes of the spray gun. When the fluid pressure was 17.5 inches, the gloss reading was 122. When the fluid pressure was raised to 35 inches the gloss reading remained 122. EXAMPLE 2 Example 2 used formulation I and was intended to demonstrate the effect of the distance of the spray gun from the flow glass surface. During this test, the air pressure was 45 psig, the fluid pressure was 17.5 inches and the coating was formed by three passes of the spray gun. When the distance from the spray gun to the panel was 11 inches the gloss reading was 122. When the distance from the spray gun to the panel was increased to 12 inches the gloss reading increased to 141. EXAMPLE 3 Example 3 utilized formulation II, and was intended to demonstrate the effect of the number of passes of the spray gun used to form the coating. In this test, the air pressure was 47 psig, the fluid pressure was 18.5 inches and the distance from the spray gun to the CRT screen panel was 113/4 inches. In the absence of any coating, the gloss reading was 88.5±3.6. When the coating was formed from three passes of the spray gun the gloss reading was 66.2±4. When the coating was formed from four passes of the spray gun the gloss reading was 61±3.7. EXAMPLE 4 Example 4 utilized formulation II, and was intended to demonstrate the effect of preheating the optical glass screen or panel. In part 1 of this test the air pressure was 47 psig, the fluid pressure was 18 inches, the distance from the spray gun to the panel was 113/4 inches and the coating was applied by five passes of the spray gun. In the absence of any coating the gloss reading was 89.4±1.9. When the coating was applied after preheating the panel between 45° C. and 50° C. the gloss reading was 62.2±2.7. When the coating was applied after preheating the panel to 60° C. the gloss reading was 53±3. In part 2 of this test the air pressure was 47 psig, the fluid pressure was 18.5 inches, the distance from the spray gun to the panel was 113/4 inches and the coating was applied by four passes of the spray gun. In the absence of a coating the gloss reading was 88.5±3.6. When the coating was applied after preheating the panel to a temperature between 58° C. and 60° C. the gloss reading was 61±3.7. When the solution was applied after preheating the panel to 67° C. the gloss reading was 60.8±4.1. When the coating was applied after preheating the panel to 77° C. the gloss reading was 58.5±3.3. EXAMPLE 5 Parts 1 and 2 of this test utilized formulations III and IV respectively, and were intended to demonstrate the effect of a reduction in the amount of metal alkoxide. The parameters of this test were held constant for both parts 1 and 2, except as noted. In part 1 of this test the molar ratio of SiO 2 :TiO 2 was 9.65:1. The coating was applied by five passes of the spray gun. The gloss reading was 72.7±2.5. In part 2 of this test, the molar ratio of SiO 2 :TiO 2 was increased to 11:1, while the thickness of the coating was reduced by applying the coating with only four passes of the spray gun. In this part the gloss reading was 65.4±2.2. EXAMPLE 6 This test utilized formulation II, and was intended to demonstrate that additional coatings could be applied after an initial baking of prior coatings. During this test the air pressure was 47 psig, the fluid pressure was 18 inches and the distance from the spray gun to the panel was 113/4 inches. A first coating was applied by three passes of the spray gun and baked at a temperature of 520° C. for approximately seven minutes. The gloss reading was 70.5±3.1. Thereafter, more solution was applied by three additional passes of the spray gun, and once again the panel was heated to a temperature of approximately 520° C. for approximately seven minutes. The gloss reading after the second application was 64.8±3. EXAMPLE 7 Parts 1 and 2 of this test were made with formulations V and VI respectively, and were intended to demonstrate that changing the ratio of TiO 2 to ZrO 2 did not significantly alter the gloss reading, although zirconium imparts better alkali resistance to the stabilized film than does titanium. In each of parts 1 and 2 the parameters were held constant. In each of parts 1 and 2 the solution included 0.2 moles of SiO 2 . In part 1 the molar ratio of TiO 2 :ZrO 2 was 5.67:1. The gloss reading was 74.5±2.5. In part 2, the molar ratio of TiO 2 :ZrO 2 was 1:1. The gloss reading was 75.5±1.3. On the basis of the tests conducted with the various formulations of solution noted herein, the best solution from which the form coatings according to this invention appears to be that of formulation II. Based upon the amounts of components listed, it can be shown that formulation II will result in a coating mixture comprising approximately 11.83 gm SiO 2 , approximately 0.79 gm TiO 2 and approximately 1.26 gm ZrO 2 . The TiO 2 and ZrO 2 therefore form approximately 15% of the solid, by weight. It can also be shown that the formulation results in approximately 0.197 moles of SiO 2 , 0.01 moles of TiO 2 and approximately 0.01 moles of ZrO 2 . Accordingly, the molar ratio of (TiO 2 +ZrO 2 ) is about 10% of the solids in the mixture (SiO 2 +TiO 2 +ZrO 2 ). This invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. Accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention.

A coating for reducing specular reflection on optical glass screens comprises a partially hydrolized metal alkoxide polymer. These alkoxides have the general formula M(OR) 4 where M is selected from the group consisting of silicon, titanium and zirconium where R is alkyl with 1 to 6 carbon. The equivalent titanium and/or zirconium oxides is about 15% of total solids by weight. A presently preferred coating mixture is prepared by dissolving tetraethyl orthosilicate in alcohol, at an elevated temperature; gradually adding a mixture of nitric acid and water; gradually adding titanium butoxide and/or zirconium n-propoxide; and, adding and mixing additional water and alcohol. The coating is applied by a method comprising the steps of cleaning the surface of the optical glass screen; preheating the glass screen; coating the solution onto the glass screen; and, baking the glass screen and solution, at a temperature high enough to drive off the solvent and bond the coating mixture to the glass surface.

BACKGROUND OF THE INVENTION [0001] The present invention is directed to a method of producing cyclic carbonic acid esters. More particularly, the present invention is directed to achieving a low-cost method of producing trimethylene carbonate. [0002] Cyclic carbonic acid esters are used, for example, as building blocks of potentially biodegradable polymers A particular cyclic carbonic acid ester, trimethylene carbonate (trimethylene carbonate or 1,3-dioxan-2-one), may be used in a variety of applications, such as for surgical stitching material, vessel implants, and apparatus for osteo-synthesis. Trimethylene carbonate is a desirable monomer to use because of its property of not decreasing in volume on polymerization. [0003] Trimethylene carbonate may be used as a monomer in the synthesis of poly(trimethylene carbonate) polyols, which are used in flexibilizing acrylic melamine coatings. Trimethylene carbonate may also be used to make surgical sutures and modified polyurethane elastomers. Poly(trimethylene carbonate) polyols improve both ambient and low temperature flexibility and reduced the viscosity of urethane coatings formulated with selected commercial acrylic polyols. [0004] For industrial production of trimethylene carbonate, it would be desirable to find a method of synthesis yielding cyclic carbonates in high yields by a relatively simple industrial process Numerous methods are known for producing carbonic acid esters, such as trimethylene carbonate. For example, the trans-esterfication of diethylcarbonate with 1,3-propanediol in the presence of sodium or sodium methoxide to obtain trimethylene carbonate is one of the oldest methods of production (W. H. Carothers et al., J. Am. Chem. Soc., 52 (1930) 322), but the purity of the product obtained is not sufficient for use in polymerization reactions, which results in a lower grade product. In addition, the low yield makes this method unattractive for industrial use. [0005] U.S. Pat. No. 5,212,321 to Muller et al. discloses a method for producing trimethylene carbonate where 1,3-propanediol is reacted with diethylcarbonate in the presence of zinc powder, zinc oxide, tin powder, tin halide, or an organo-tin compound, at an elevated temperature. However, the Muller et al. process is very expensive as the process, the separation, isolation, and disposal of residues and catalysts or catalyst material are time-consuming and expensive. [0006] U.S. Patent No. 5,091,543 to Grey discloses a method of preparing five- and six-membered cyclic carbonates. The method involves reacting a 1,2- or 1,3-diol with an acyclic diester of carbonic acid in the presence of a catalyst selected from alkylammonium salts, tertiary amines, and ion-exchange resins containing alkylammonium or tertiary amino groups. Cyclic carbonates free of polycarbonate by-products are obtained in high yields. However, the Grey process is also very expensive, as the process requires the use of reactors made from materials of construction that will not corrode when exposed to the halide ions in the process. Isolation and disposal of residues and catalysts are also time-consuming and expensive. [0007] Another process used to prepare trimethylene carbonate involves reacting 1,3-propanediol with urea in the presence of zinc-based catalysts. This type of process is described, for example, in Japanese Patent Nos. 7-330686 and 7-330756. The process requires expensive and time-consuming isolation, recovery, and recycling of the catalysts. [0008] Trimethylene carbonate has also been made by reacting 1,3-propanediol with ethylchloroformate while using two equivalents of triethylamine (Toshiro Agriga et al., Macromolecules, 30 (1997) 737). However this method produces trimethylene carbonate in low yield and requires large amounts of triethylamine. [0009] The vapor-phase reaction between phosgene and an alcohol is known to form the corresponding chloroformate (Saunders et al., J. Am. Chem. Soc., 87 (1965) 2088). Continuous processes for the formation of chloroformates from phosgene and alcohols are disclosed in Japanese Patent Nos. JP 51-043719 and JP 51-043721. [0010] There remains a need for a low-cost method for producing trimethylene carbonate. A low-cost method desirably involves production of trimethylene carbonate in relatively high yields with reduced expenses for clean up and/or recycling or disposing of residues and/or catalyst material. A combination of several or all of these desirable features would be even more desirable. SUMMARY OF THE INVENTION [0011] The present invention is directed to a novel method of synthesizing trimethylene carbonate. The method comprises reacting 1,3-propanediol and phosgene in vapor form while providing a combination of temperature and pressure at which trimethylene carbonate boils or is in a vapor phase, and providing a residence time at those conditions sufficient to react at least some of the 1,3-propanediol and phosgene to trimethylene carbonate. [0012] An advantage of the method of the present invention is that it does not require the use of catalysts and their associated expense of recovery and recycling or disposing of catalyst residues. Although not required, the use of catalysts is not precluded in the method of the present invention if desired. BRIEF DESCRIPTION OF THE DRAWING [0013] [0013]FIG. 1 is a plot of the relationship between the boiling temperature of trimethylene carbonate and pressure. DETAILED DESCRIPTION OF THE INVENTION [0014] Unless otherwise indicated, all numbers or expressions referring to quantities of ingredients, reaction conditions, etc. used herein are to be understood as modified in all instances by the term “about.” All references to pressure refer to absolute pressure unless otherwise indicated. [0015] In the method of synthesizing trimethylene carbonate of the present invention, 1,3-propanediol and phosgene are reacted in vapor form in an appropriate reaction vessel. The proportion of the reactants is most efficiently at or near stoichiometric amounts, but theoretically any amounts can be used. It may be preferred in some cases to employ an excess of phosgene to minimize any unreacted 1,3-propandiol in the product stream, thereby reducing the likelihood of unwanted reactions downstream from the reaction zone. In particular embodiments of the invention, the molar ratio of 1,3-propanediol to phosgene provided to the reaction zone is from 1.0:0.7 to 1.0 to 20, typically from 1.0:0.7 to 1.0:10, and more typically from 1.0:0.7 to 1.0:2.0. When 1,3-propanediol and phosgene are outside of these ranges, the conversion to trimethylene carbonate may be so low as to not be practical for industrial requirements. [0016] In addition to phosgene, phosgene equivalents can be used in the present method. Phosgene equivalents that can be used in the present invention include, but are not limited to, diphosgene and triphosgene. Phosgene equivalents decompose to form phosgene in situ, but are preferable in some cases due to their ease of handling on a commercial scale compared to phosgene. [0017] Gas phase phosgenation of 1,3-propanediol is advantageous in that intermolecular reactions that generate trimethylene carbonate oligomers are minimized. An appropriate combination of temperature and pressure is provided in the present invention in order to maintain the 1,3-propanediol above its boiling point (214° C. at atmospheric conditions) and also to maintain the trimethylene carbonate that is formed in the vapor state in the reaction zone. An estimated boiling point of trimethylene carbonate is determined as described below. [0018] As is known from the basic gas laws, temperature and pressure are inversely related to each other at the boiling point of trimethylene carbonate. FIG. 1 shows an approximate curve defining the relationship of the boiling temperature of trimethylene carbonate with pressure, based on five known data points. Vapor phase conditions for trimethylene carbonate include any combination of temperature and pressure on or to the right of the curve in FIG. 1. Temperatures above the boiling point for a given pressure can be used in the present invention; however, to reduce the likelihood of competing reactions, temperatures of approximately 400° C. are preferably avoided in some embodiments. At atmospheric pressure, trimethylene carbonate has a boiling point of approximately 315° C. [0019] Although a wider range of temperatures and pressures are theoretically possible, the reaction of the present method is typically carried out at temperatures ranging from about 100° C. to about 400° C., with pressures within the reaction vessel between about 1 mm and about 800 mm Hg. In an embodiment of the present invention, the reaction is carried out at sub-atmospheric pressures. Typical sub-atmospheric pressures employed in embodiments of the invention include pressures less than 300 mm Hg, less than 200 mm Hg, less than 100 mm Hg, or less than 20 mm Hg. Lower pressures are preferred in most cases because the reaction then can be run at a lower temperatures, whereby fewer competing reactions are likely to take place. [0020] The residence time in the reaction zone for reacting 1,3-propanediol and phosgene to form trimethylene carbonate and is typically a function of the starting reactant feed rates and the temperature. The residence time can vary considerably, and with some embodiments may range from about 1 to 600 seconds, typically 1 to 30 seconds in the particular embodiments described herein, and most typically 5 to 20 seconds. [0021] The residence time can be shortened by employing a non-reactive sweeping gas to carry the reactants and reaction products through the reactor. Suitable non-reactive gasses include, but are not limited to, nitrogen and the inert gases neon, argon, krypton, xenon, and helium. Nitrogen is a preferred gas due to its low cost. [0022] The trimethylene carbonate vapors in the reaction product stream may be condensed after leaving the reaction vessel. The condensation is accomplished by exposing the trimethylene carbonate vapor to a liquid phase condition (any location to the left of the curve in FIG. 1). Condensation of the trimethylene carbonate not only recovers the product but also serves to separate the trimethylene carbonate from HCl vapors in the product stream. Accomplishing this separation as soon as possible after reaction is desirable for minimizing unwanted reaction of trimethylene carbonate with HCl. Generally, a condenser is used, in which trimethylene carbonate is condensed from the vapor phase to the liquid phase and HCl exits the condenser as a vapor. The inert gas flow aids in separating and removing the HCl vapor from the trimethylene carbonate. The condensed trimethylene carbonate is isolated once condensed. [0023] The trimethylene carbonate can be isolated in any type of container that is free of active hydrogen containing compounds. Active hydrogen containing compounds, such as water, HCl, or alcohols, can react with the condensed trimethylene carbonate. [0024] Suitable containers include heated bulk storage tanks (temperature above the melting temperature of trimethylene carbonate, 47° C.). The condensed trimethylene carbonate can also be placed in a drum or a tote and allowed to solidify therein. [0025] The present method may include the additional step of solidifying the condensed trimethylene carbonate for additional processing. In this situation, the solidified trimethylene carbonate is further processed so it can be easily handled as a solid material. An example of further processing includes, but is not limited to, milling the solidified trimethylene carbonate into granular or powder form. [0026] The present invention is more particularly described in the following examples, which are intended to be illustrative only, since numerous modifications and variations therein will be apparent to those skilled in the art. Unless otherwise specified, all parts and percentages are by weight. EXAMPLE 1 [0027] A vertical glass tube, 2 centimeters in diameter and 22 centimeters in length, was packed with ⅛-inch glass helices. The void volume within the packed glass tube was 49.7 ml and the glass helices occupied 21.4 ml. The glass tube was wrapped with electric heating tape. A thermocouple was placed one-third of the way down the glass tube between the glass and the heating tape. The feed of 1,3-propanediol was allowed to slowly drip from a dropping funnel onto the top of the hot packing within the tube. [0028] Phosgene and nitrogen were also introduced at the top of the hot tube. The downflow, gaseous concurrent flow of phosgene, nitrogen, and 1,3-propanediol vapor passed through the hot tube and reaction products were condensed at ambient temperatures and analyzed by gas chromatography. [0029] Four grams of 1,3-propanediol was added over 15 minutes to the hot tube maintained at 325° C. Simultaneously over this 15 minute period, 15 grams of phosgene gas was also fed into the hot tube. Additionally, nitrogen was swept through the hot tube at 25 ml/min. The condensate was analyzed by gas chromatography to contain 24.0% by weight trimethylene carbonate. EXAMPLE 2 [0030] The method and apparatus of Example 1 was used to prepare trimethylene carbonate. Three grams of 1,3-propanediol was added over 11 minutes to the hot tube maintained at 325° C. Simultaneously, over this 11 minute span, 19 grams of phosgene gas was also fed into the hot tube. Additionally, nitrogen was swept through the hot tube at 56 ml/min. The condensate was analyzed by gas chromatography and found to contain 40.2% trimethylene carbonate. EXAMPLE 3 [0031] The method and apparatus of Example 1 was used to prepare trimethylene carbonate Six grams of 1,3-propanediol were added over 15 minutes to the hot tube maintained at 250° C. Simultaneously, over this 15 minute span, 22 grams of phosgene gas were also fed into the hot tube. Additionally, nitrogen was swept through the hot tube at 86 ml/min. The condensate was analyzed by gas chromatography and found to contain 40.8% by weight of trimethylene carbonate. EXAMPLE 4 [0032] The method and apparatus of Example 1 was used to prepare trimethylene carbonate. Two grams of 1,3-propanediol were added over 7 minutes to the hot tube maintained at 300° C. Simultaneously, over this 7 minute span, 7.7 grams of phosgene gas were also fed into the hot tube. Additionally, nitrogen was swept through the hot tube at 86 ml/min. The condensate was analyzed by gas chromatography and found to contain 43.8% by weight of trimethylene carbonate. [0033] Separation of trimethylene carbonate from the remainder of the reaction products in the condensate in the examples set forth above can be accomplished by conventional techniques known to those of skill in the art, including distillation or crystallization. [0034] In the examples set forth above, the 1,3-propanediol was fed into the reaction zone as a liquid and vaporized by contact with the hot packing material. It should be apparent that an alternative approach would entail vaporizing the 1,3-propanediol in a separate location and conveying the vapors into the reaction zone. [0035] The invention has been described with reference to the preferred embodiments. Obvious modifications and alterations will occur to others upon reading and understanding the detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of appended claims or the equivalents thereof.

A method of synthesizing trimethylene carbonate, which includes the steps of reacting 1,3-propanediol and phosgene in vapor form, providing a combination of temperature and pressure at which trimethylene carbonate is in its vapor phase, providing a residence time sufficient to react 1,3-propanediol and phosgene to trimethylene carbonate, condensing the trimethylene carbonate vapors, and isolating the condensed trimethylene carbonate. The present method advantageously does not require the use of catalysts and the associated expense of recovering and/or recycling or disposing of catalyst residues.

FIELD OF THE INVENTION This application is directed to a means for delivering pharmaceuticals, nutraceuticals and the like to a mammal and more specifically, the control of the water activity of a food product matrix for use in the incorporation of a pharmaceutical, nutraceutical or other bioactive compound into the matrix. BACKGROUND OF THE INVENTION Pharmaceutical and nutraceutical products intended for oral administration are typically provided in tablet, capsule, pill, lozenges and caplet form. These products are swallowed whole or chewed in the mouth for delivery of the active ingredient into the alimentary system of a body. Such oral delivery systems are sometimes made chewable to ease drug administration in pediatric and geriatric patients. Such concerns with ease of administration may be amplified when dealing with pets and other animals. As a result, several approaches have been utilized in formulating oral delivery systems, including gums and candy bases. The use of such delivery systems is limited by the reaction of the active ingredient, whether it be pharmaceutical, nutraceutical or other ingredients, to the existence of water in the system. SUMMARY OF THE INVENTION Therefore, an object of the subject invention is a method of controlling water activity in an oral delivery system and the product thereof. These and other objects are attained by the subject invention wherein there is provided a carrier or product formed of a matrix having starch, sugar, fat, polyhydric alcohol and water in suitable ratios such that there exists a water activity of 0.6-0.75. The water activity of the product matrix is adjusted up or down so that the availability of water in the finished product is not detrimental to the included active ingredient, be it pharmaceutical, nutraceutical, or vitamin mineral complex. A further object of the subject invention is a oral delivery system for pharmaceuticals, nutraceuticals or other active ingredient which matches the water activity of the carrier to the included active ingredient. DESCRIPTION OF THE PREFERRED EMBODIMENTS By the subject invention, a soft chewable oral delivery system is provided. The dosage form may be in tablet form and may contain one or more active ingredients. The active ingredients are incorporated into the system which is described in further detail below and which includes a starch component, a fat or oil, a sugar component, a polyhydric alcohol, water and other minor ingredients. Into this mixture is placed the active ingredient. After mixing and extruding these ingredients, the extrudate is formed into the appropriate shape. The relative proportions of the mixture are as follows. Starch 10-50% Fat or Oil 0-40% Sugar 5-25% Polyhydric Alcohol 10-50% Water 5-20% Salt (NaCl) 1-5% Active Ingredient 0.1-5% Generally speaking, the starch component of the matrix comprises 10 to 50 percent by weight of the matrix. More particularly, the starch component of the matrix comprises 15 to 40 percent by weight of the matrix. While starch for use in the matrix can be of any suitable type, it is most preferred that at least part of the starch in the matrix be a highly derivatized or pregelatinized starch. If a highly derivatized starch is present in the matrix, it should be present in an amount of about ½ percent by weight of the total starch and the balance of the starch being non-derivatized. More preferably, about 20-40 percent by weight of the total matrix and about 45% of the total starch should be the derivatized starch. An example of a preferred pregelatinized starch is A. E. Staley's NU-COL 4227 or SOFT-SET. Other amylaceous ingredients may be used in combination with the derivatized starch or alone, provided the starch limits are not exceeded. The amylaceous ingredients can be gelatinized or cooked before or during the forming step to achieve the desired matrix characteristics. If gelatinized starch is used, it may be possible to prepare the product of the subject invention or perform the method of the subject invention without heating or cooking of any sort. However, if ungelatinized (ungelled) or uncooked starch is used, the matrix must be cooked sufficiently to gel or cook the starch to reach the desired content. Starches that can serve as a base starch for derivatization include regular corn, waxy corn, potato, tapioca, rice, etc. Such types of derivatizing agents for the starch include but are not limited to ethylene oxide, propylene oxide, acetic anhydride, and succinic anhydride, and other food approved esters or ethers, introducing such chemicals alone or in combination with one another. Prior crosslinking of the starch may or may not be necessary based on the pH of the system and the temperature used to form the product. By “amylaceous ingredients” is meant those food-stuffs containing a preponderance of starch and/or starch-like material. Examples of amylaceous ingredients are cereal grains and meals or flours obtained upon grinding cereal grains such as corn, oats, wheat, milo, barley, rice, and the various milling by-products of these cereal grains such as wheat feed flour, wheat middlings, mixed feed, wheat shorts, wheat red dog, oat groats, hominy feed, and other such material. Also included as sources of amylaceous ingredients are the tuberous food stuffs such as potatoes, tapioca, and the like. Another component of the matrix is a fat component such as fat or oil of animal or vegetable origin. Typical animal fats or oils are fish oil, chicken fat, tallow, choice white grease, prime steam lard and mixtures thereof. Other animal fats are also suitable for use in the matrix. Vegetable fats or oils are derived from corn, soy, cottonseed, peanut, flax, rapeseed, sunflower, other oil bearing vegetable seeds, and mixtures thereof. Additionally, a mixture of animal or vegetable oils or fats is suitable for use in the matrix. The fat component of the matrix is about 0 to about 40% by weight of the matrix. More specifically, the fat component of the matrix is about 20 percent by weight of the matrix. The polyhydric alcohol component of the matrix can be selected from glycerol, sorbitol, propylene glycol, 1.3-butanediol, and mixtures thereof with each other and other polyhydric alcohols. Generally the polyhydric alcohol comprises about 10 to about 50 percent by weight of the matrix. More specifically, the polyhydric alcohol comprises about 20 to about 40 percent by weight of the matrix. The sugar component can be employed in a dry or crystalline condition or can be an aqueous syrup having a sugar concentration of from 50 to about 95, preferably from 70 to about 80, weight percent. The sugar used can be lactose, sucrose, fructose, glucose, or maltose, depending on the particular application and price or availability of a particular sugar. Examples of various well established sources of these sugars are, corn syrup solids, malt syrup, hydrolyzed corn starch, hydrol (syrup from glucose manufacturing operations), raw and refined cane and beet sugars, etc. Water must be present in the matrix at least about 5 percent by weight of the matrix. More specifically, water is present in the matrix about 5 percent to about 20 percent by weight of the matrix. The matrix thus formed usually has a water activity of 0.60 to 0.75. While water must be at least 5 percent by weight of the matrix, when the matrix is used in a food product, the moisture of the food product must be adjusted. Generally the moisture content of the matrix is such to give a moisture content of 5-15 percent to the final soft dry food product. More preferred is a moisture content of 5 percent to 14 percent. Most preferred is a moisture content of 8 percent to 13 percent. The desired moisture content may be achieved in any suitable fashion. Normal processing may produce the moisture content desired. A standard drying step is optional and may be used if necessary. The active ingredient may be any drug, nutrition agent, or the like which can be orally administered. Exemplary of such active ingredients are the following: nutraceuticals, such as chromium picolinate, potassium gluconate and methionine amino acid; prescription drugs, such as ivermectin, fenbendazole, piperazine, magnesium hydroxide, stranozole, furosemide, penicillin, amoxicillin, prednisolone, methylprednisolone, acepromazine; and, other pharmaceutical products, such as aspirin, prozac, zantac, and benedryl. Minor amounts of flavorants, colorants, glycerin, flavor enhancers, sweeteners, emulsifiers, antibitterness agents, taste masking agents, stabilizers, preservatives, or combinations thereof may be added. To form the matrix, the starch system, fat, polyhydric alcohol, corn syrup and water are mixed with a screw extruder, permitting addition of ingredients and variable heating at different points along the barrel. Other mixing apparatus, such as a sigma mixer, swept wall heat exchanger or the like may be used. If a coloration is desired in the final product, cooked or pregelled starches are used to form the matrix. The use of these starches avoids high cooking temperatures which would destroy the desired coloration and/or active ingredient. If coloration active temperature sensitivity is not a problem, it is possible to use an uncooked or ungelatinized starch to form the matrix and cook or gel the starch as the process is carried out. The incorporation of a derivatized starch in the product more clearly guarantees the softness of the product for a longer period of time. Softness is also provided by the fats and oils. In this fashion a suitable matrix is provided for use with a wide variety of active ingredients. Having fully described the invention, the following examples are presented to illustrate the invention without limitation thereof. In these examples all parts percentages are by weight unless otherwise specified. EXAMPLE 1 Carrier INGREDIENT PARTS Regular Corn Starch (Purefood GMI) 18.0 Pregel Starch (SOFT SET) 15.0 Corn Syrup (Star Dri Corn Syrup Solids) 15.0 Corn Oil 20.0 Sorbitol 20.0 H 2 O 10.0 Salt 2.0 TOTAL 100.0 The above ingredients are mixed at temperatures of about 125° F., extruded and cut into a suitable tablet size. This product has an oily, bubbly appearance suggesting cutting back on the oil content. Temperature was also adjusted during each of the following examples to eliminate puffing of the product as it exits the extruder. EXAMPLE 2 Guaifenesin INGREDIENT PARTS Regular Corn Starch (Purefood GMI) 17.9 Pregel Starch (SOFT SET) 15.0 Corn Syrup (Star Dri Corn Syrup Solids) 15.0 Sorbitol 39.3 H 2 O 10.0 Salt 2.0 Guaifenesin* 0.8 TOTAL 100.0 *Available from Arrow Chemical Co., N.J. EXAMPLE 3 Vitamins INGREDIENT PARTS Regular Corn Starch (Purefood GMI) 17.9 Pregel Starch (SOFT SET) 15.0 Corn Syrup (Star Dri Corn Syrup Solids) 15.0 Sorbitol 35.1 H 2 O 10.0 Salt 2.0 Vitamin and Mineral Mix* 5.0 TOTAL 100.0 *Commercially available mixture available from Archer Daniels Midland. EXAMPLE 4 Flax INGREDIENT PARTS Regular Corn Starch (Purefood GMI) 17.9 Pregel Starch (SOFT SET) 15.0 Corn Syrup (Star Dri Corn Syrup Solids) 15.0 Sorbitol 35.1 H 2 O 10.0 Salt 2.0 Flax* 5.0 TOTAL 100.0 *Available from Enreco Flax. EXAMPLE 5 Acetaminophen INGREDIENT PERCENT Regular Corn Starch (Purefood GMI) 17.9 Pregel Starch (SOFT SET) 15.0 Corn Syrup (Star Dri Corn Syrup Solids) 15.0 Sorbitol 39.1 H 2 O 10.0 Salt 2.0 Acetaminophen* 0.8 Red Coloring #40 0.1 Flavoring (Cherry) 0.1 TOTAL 100.0 *Available from Mallincrodt as Compap EXAMPLE 6 Carrier INGREDIENT PARTS Regular Corn Starch (Purefood GMI) 17.9 Pregel Starch (SOFT SET) 15.0 Corn Syrup (Star Dri Corn Syrup Solids) 15.0 Sorbitol 40.1 H 2 O 10.0 Salt 2.0 TOTAL 100.0 TABLE 1 Example Active Oil/Sugar A w Extrusion Temp. 1 Premix Corn Oil/Sorbitol N/A 125 2 Guaifenesin 100% Sorbitol 0.656 115 3 Vitamin Mix 100% Sorbitol 0.651 115 4 Flax 100% Sorbitol 0.673 115 5 Acetaminophen 100% Sorbitol 0.666 115 6 Premix 100% Sorbitol 0.61  115 By the above examples and Table 1 it is apparent that an oral delivery system for the administration for pharmaceuticals, nutraceuticals, vitamins and minerals and other active ingredients may be provided in a chewable form by the subject invention. If the active ingredient is water sensitive such as aspirin, then the amount of polyhydric alcohol is increased, the water activity is depressed to about 0.65 and the stability and texture of the resultant product is maintained. If the active ingredient requires or can tolerate the presence of free water for its activity, such as in the case of Guaifenesin, the amount of polyhydric alcohol may be decreased, while maintaining the level of such polyhydric alcohol such that a soft texture of the resulting tablet is maintained. In the case of Guaifenesin, then an A w of 0.70 may be utilized and a softer, more chewable texture achieved. An effective oral delivery system in which the texture and stability of the product and activity of the active ingredient is controllable, is the result. While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments and equivalents falling within the scope of the appended claims. Various features of the invention are set forth in the following claims.

The subject invention is a carrier or product formed of a matrix having starch, sugar, fat, polyhydric alcohol and water in suitable ratios such that there exists a water activity of 0.6-0.75. The water activity of the product matrix may be adjusted up or down so that the availability of water in the finished product is not detrimental to the included active ingredient, be it pharmaceutical, nutraceutical, or a vitamin mineral complex.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to dispensing guns for fluid materials and, more particularly, to a dispensing gun incorporating a double reduction gear for extruding highly viscous materials. 2. Description of the Prior Art Dispensing guns for highly viscous materials must generate extreme amounts of pressure to the material. This is especially true of conventional industrial epoxy guns. Such guns typically accept twin cylinder cartridges which separately contain the epoxy bonding agent and resin. The gun is operated to drive the bonding agent and resin to one end of the cartridge where the materials are combined and are extruded outward through an extended nozzle. In commercial applications, the nozzle typically comprises a thin tube with an interior arrangement of foils to provide a convoluted, internal passageway for the combined materials. As the epoxy materials are forced through the convoluted nozzle, the foils ensure that the resin and bonding agent are properly mixed before being ejected. However, the pressure needed to drive the epoxy materials through the convoluted nozzle is extreme. For this reason, the prior art epoxy dispensing guns inevitably employ a motorized or pneumatic drive system. For example, U.S. Pat. No. 4,583,934 issued to Hata et al. shows a rack and pinion type electric drive system for extruding fluid material from a nozzle 11. The rack and pinion assembly employs a reduction type gear assembly for increasing torque derived from the electric motor. Similarly, U.S. Pat. No. 4,669,636 issued to Miyata shows an electric dispensing gun which employs a motor and clutch for selectively driving a rack and pinion type piston assembly. Various pneumatic counterparts are also known to exist. Unfortunately, electric guns often cannot be operated in the field without a portable generator. Pneumatic guns cannot be operated without a compressor. The guns themselves necessarily incorporate costly precision pneumatic or electrical parts which are inordinately expensive to manufacture. Such constraints render the guns completely useless for many field applications and expensive and impractical for others. Clearly, there would be great advantages in a manually operated dispensing gun which is capable of developing sufficient force to dispense highly viscous materials such as, for instance, epoxy materials from a conventional twin cylinder epoxy cartridge. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an industrial grade, hand-operated dispensing gun which generates sufficient force for dispensing epoxy materials through a conventional twin cylinder epoxy cartridge (with elongate mixing nozzle). It is another object of the present invention to provide a completely portable, hand-operated epoxy dispensing gun which eliminates the need for compressors or generators. It is a further object of the present invention to incorporate a double reduction gear system in a trigger-operated dispensing gun for driving an axial plunger (two plungers in the case of a twin cylinder gun) with an extreme dispensing force. It is still another object to provide a double reduction gear drive as described above which is strong, durable, reliable, and economical to manufacture. According to the present invention, the above-described and other objects are accomplished by providing a double-reduction drive assembly for a dispensing gun. The drive assembly generally includes a housing, an elongate plunger traversing the housing, a trigger connected to the housing for driving the plunger, and a double-reduction gear assembly carried in the housing for mechanically converting manual contractions of the trigger into incremental axial movement of the plunger. The plunger is formed with a toothed rack along its length. The reduction gear assembly further comprises a spur gear coupled to the trigger and rotatable therewith, a larger main drive gear rotatably carried in the housing and engagable with the spur gear, and a smaller pinion gear carried in the housing alongside the main drive gear and engagable with the toothed rack of the plunger for driving the plunger. In operation, each manual contraction of the trigger serves to rotate the spur gear, which engages and rotates the main drive gear, thereby rotating the pinion gear, which in turn advances the plunger in axial increments. The invention also encompasses a twin-cylinder embodiment which employs dual plunger shafts driven by separate coaxial pinion gears. A quick-release camming assembly is also provided for conveniently biasing the main drive gear out of engagement with the spur gear, while simultaneously disengaging the pinion gear(s) from the plunger shaft(s), thereby allowing retraction of the plunger shaft(s) and replacement of a spent cartridge. BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features, and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments and certain modifications thereof when taken together with the accompanying drawings in which: FIG. 1 is a perspective view illustrating the manner of using an industrial twin-cylinder epoxy gun incorporating a double reduction gear drive and quick release assembly according to the present invention; FIG. 2 is a top view of the double reduction gear drive with quick release assembly according to the present invention; FIG. 3 is a partial exploded view of the double reduction gear drive with quick release assembly as in FIG. 2; FIG. 4 is a partial exploded view to be viewed in conjunction with FIG. 3; FIGS. 5A-5C are sequential sectional views of the double reduction gear drive with quick release assembly according to the present invention illustrating the operation during contraction and release of the trigger 24; and FIGS. 6A and 6B are sequential sectional views of the double reduction gear drive with quick release assembly according to the present invention illustrating the operation of the quick release assembly. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a perspective view illustrating the manner of using an industrial twin-cylinder epoxy gun 1 incorporating a double reduction gear drive and quick release assembly according to one embodiment of the present invention. The gun generally includes a support structure 2 for seating a conventional twin cylinder epoxy cartridge. The mixing nozzle 3 of the twin cylinder epoxy cartridge protrudes forwardly from the support structure 2, and a reduction drive assembly 4 with quick release feature according to the present invention is integrally attached rearwardly of support structure 2. Trigger operation of the drive assembly 4 urges a dual plunger internally through the twin cylinder epoxy cartridge to thereby dispense the epoxy materials. The epoxy resin and hardener are combined and mixed in nozzle 3 just prior to dispensation. The detailed design of the drive assembly 4 with quick release feature will now be described with reference to FIGS. 2-4, wherein FIG. 2 is a top view, and FIGS. 3 and 4 are exploded views of the reduction drive assembly 4 of FIG. 1. The drive assembly 4 of the present invention includes cooperating double reduction gears which operatively drive dual plunger 22 (having shafts 23 and 25) to invade a twin cylinder epoxy cartridge (not shown), thereby extruding epoxy compound. The drive assembly 4 includes a housing 210 which contains the double-reduction gears. A handle 30 is secured to the underside of housing 210 and extends downwardly therefrom. A trigger 24 extends downwardly from the housing 210 proximate handle 30, and trigger 24 may be manually contracted as many times as desirable to expel a desired amount of epoxy material. Each incremental contraction of trigger 24 against handle 30 operates to drive the dual plunger 22 by axial increments. The double reduction drive assembly 4 introduces two levels of geared torque augmentation so that the axial driving force of dual plunger 22 far exceeds the manual force necessary to contract trigger 24 against handle 30. Housing 210 may be rectangular with opposing side-walls, front and rear walls, and a partial bottom wall. Housing 210 encloses and seats the cooperating double-reduction gears in the following manner. As seen in FIG. 4, trigger 24 is pivotably mounted on a trigger axle 200 and protrudes downwardly therefrom through an opening in the bottom wall of housing 210. Trigger axle 200 is inserted through housing 210 and is supported by the side-walls thereof. Trigger axle 200 may be formed as illustrated with annular grooves 202 around the opposing ends. The length of trigger axle 200 should slightly exceed the spacing between the side-walls of housing 210. This way, locking C-rings 204 may be inserted in the respective grooves 202 exteriorly of the side-walls to anchor trigger axle 200 within the housing 210. The downward opening in the bottom wall of housing 210 should be sufficient to afford trigger 24 a clearance so that it may be pivoted against handle 30. Trigger 24 is a generally recessed member with two opposing sides bounding a central hollow. A uni-directional bearing 248 is press fit into a ratchet gear 249, and the press-fit assembly is mounted within the hollow of trigger 24 to permit one-way rotation of trigger axle 200 in accordance with the contractions of trigger 24. If the pressure in the epoxy cartridge becomes excessive the uni-directional bearing 248 may slip. A dog assembly 244A and 244B is provided for this circumstance. Dog 244A is mounted on a central pivot which is offset from the trigger axle 200, and a spring 244B is also mounted on the pivot to ensure that dog 244A remains engaged in ratchet gear 249. In operation, trigger 24 is contracted against handle 30 and the internal clutch of uni-directional bearing 248 engages, thereby forcing trigger axle 200 to rotate counterclockwise. If the pressure in the epoxy cartridge becomes excessive the uni-directional bearing 248 may begin to slip during contraction of trigger 24. In this case, dog 244A engages the ratchet gear 249 and continues rotation of the trigger axle 200. As trigger 24 is released, the internal clutch of uni-directional bearing 248 disengages. Both the uni-directional bearing 248 and dog 244A allow the trigger to return to its forward position without any corresponding rotation of ratchet gear 249. Reverse rotation of the main drive gear 300 is prevented by dog 604. A coiled spring 244 is provided within the hollow of handle 30 to return trigger 24 to its original position. The coil(s) of spring 244 are preferably attached within handle 30 by, for example, a transverse rivet 245 or the like. Spring 244 is coiled around rivet 245, and one elongate leg of spring 244 extends downwardly within handle 30. A second leg of spring 244 protrudes against trigger 24 and biases trigger 24 outwardly away from handle 30. This serves to return trigger 24 to its original position while trigger axle 200 is held stationary by uni-directional bearing 248. Consequently, contraction of trigger 24 drives dual plunger 22 while release of trigger 24 does not retract the plunger 22. The uni-directional bearing may be a conventional annular clutch-type component such as, for instance, those which are commercially available from Torrington®. More specifically, Part No. RC-081208 has been employed in a prototype unit. A spur gear 250 is also mounted coaxially on trigger axle 200 adjacent trigger 24, and spur gear 250 should be secured to trigger axle 200 by means of a set screw 251 or otherwise. During incremental contraction of trigger 24, spur gear 250 rotates in unison with trigger axle 200. The balance of the drive assembly 4 is best seen in FIG. 3. A main drive axle 300 is carried directly above the trigger axle 200 within housing 210. Main drive axle 300 may be similarly secured within housing 210 by locking C-rings 304 which engage annular grooves 302 formed around the slightly protruding ends of main drive axle 300. The ends of the main drive axle 300 are carried in the side-walls of housing 210 within two oblong slots 212. Slots 212 provide sufficient vertical clearance to allow a limited degree of upward and downward movement of the main drive axle 300 within housing 210. Three gears are coaxially carried on the main drive axle 300, and these include a first pinion gear 310, a second pinion gear 320, and a main drive gear 330 in between the flanking pinion gears 310 and 320. The first pinion gear 310, second pinion gear 320, and main drive gear 330 are all three secured to main drive axle 300 by means of set screws 311, 331, and 321, respectively, or otherwise. In the preferred embodiment, a tubing spacer 312 is interposed between the first pinion gear 310 and the main drive gear 330 to maintain the proper spacing therebetween. The main drive gear is engaged by downward positioning of the main drive axle 300 within the slots 212 of housing 210. While engaged, the main drive gear 330 bears against and is driven by the smaller spur gear 250 mounted on trigger axle 200. The diameter of the main drive gear 330 is larger than the diameter of the spur gear 250 in order to effect a first level of gear reduction. Conversely, the diameter of pinion gears 310 and 320 are smaller than the diameter of the main drive gear 330 in order to effect a second level of gear reduction. Pinion gears 310 and 320 operate directly on the respective plunger shafts 23 and 25. Dual plunger 22 is carried within housing 210 directly beneath the main axle 300. Opposing plunger shafts 23 and 25 of the dual plunger 22 traverse housing 210 and are carried therein transversely with respect to the trigger axle 200 and main drive axle 300. The upper surface of both plunger shafts 23 and 25 are defined by a rack of parallel teeth. The teeth of plunger shafts 23 and 25 respectively bear against and cooperate with the teeth of pinion gears 310 and 320. Consequently, incremental clockwise angular rotation of pinion gears 310 and 320 results in an incremental axial thrusting of dual plunger 22. In the preferred embodiment, downward support of dual plunger 22 is provided by a plunger bearing assembly which comprises two parallel bearing axles 420 and 430 which are transversely carried in housing 210 beneath the two plungers 23 and 25. The bearing axles 420 and 430 are spaced on opposing sides of the trigger axle 200 and may likewise be anchored in the side-walls of housing 210 by means of locking C-rings 422 and 432 inserted in annular grooves 421, 431 which are formed around the protruding ends of the respective bearing axles 420 and 430. A pair of plunger bearings 410 is carried on each bearing axle 420 and 430. The plunger bearings 410 are aligned such that each plunger shaft 23 and 25 is borne at two points along its length. The proper alignment of plunger bearings 410 may be maintained by interposing a set of three tubing spacers 723 therebetween. The plunger shafts 23 and 25 ride upon the respective bearings 410 and receive downward support therefrom. A front support plate 500 is mounted on the front wall of housing 210 to provide additional support. A spring-loaded coupling including a dog 604, dog axle 602, and main spring 606 is mounted within housing 210 and is secured inwardly of support plate 500 in a facing relation with main gear 330. The spring-loaded coupling also includes a mounting block 600 which may be screwed to front support plate 500 through housing 210 (via screws 601). The dog 604 is pivotably mounted on a dog axle 606 within mounting block 600. The spring 606 bears against the back of dog 604 and biases dog 604 downwardly against the teeth of main gear 330. Dog 604 permits clockwise rotation of main gear 330 to thereby effect the dispensing operation. However, the dispensing operation results in an extreme pressure build-up within the twin cylinder epoxy cartridge, and the elastic property of the epoxy imparts a like backward force on dual plunger 22. Dog 604 engages the teeth of the main gear 330 to prevent counterclockwise rotation, thereby preventing backward movement of dual plunger 22. FIGS. 5A-5C are sequential sectional views showing the operation of the double reduction gear drive 4 according to the present invention during contraction and release of the trigger 24. It is apparent in FIGS. 5A-5C how successive contraction and release of trigger 24 is translated through the two levels of gear reduction to an incremental axial drive of dual plunger 22. FIG. 5A illustrates the engaged position wherein the main drive gear 330 is downwardly positioned within the slots 212 of housing 210. While engaged, the main drive gear 330 bears against and is driven by the smaller spur gear 250 mounted on trigger axle 200. Consequently, as shown in FIG. 5B, contraction of trigger 24 causes an incremental clockwise angular rotation of spur gear 250, which in turn imparts an incremental counterclockwise angular rotation to main drive gear 330. The first and second pinion gears 310 and 320 turn in unison with main drive gear 330, and pinion gears 310 and 320 engage the racks of the plunger shafts 23 and 25 to drive the dual plunger 22 forwardly into the epoxy cartridge. As shown in FIG. 5C, release of trigger 24 disengages the uni-directional bearing 248 and dog 244A overrides the teeth of ratchet gear 249. Hence, the trigger axle 200 remains stationary along with the spur gear 250, main drive gear 330, pinion gears 310 and 320, and dual plunger 22. The dog 604 of the spring-loaded coupling insures that the main drive gear 330 remains stationary (despite any pressure build-up within the twin cylinder epoxy cartridge) by engaging the teeth of the main gear 330 to prevent counterclockwise rotation thereby preventing backward movement of dual plunger 22. The double reduction gear drive 4 is also provided with an improved quick release feature for disengaging the main gear 330 from the spur gear 250 while simultaneously disengaging the first and second pinion gears 310 and 320 from the racks of the respective plungers 23 and 25. The quick release feature comprises a pivoting quick release bar 700 which is carried within a pair of hollow cylindrical sleeves 710A and 720A, the sleeves in turn being integrally attached to a left camming member 710 and a right camming member 720, respectively. Quick release bar 700 protrudes forwardly from housing 210 to facilitate gripping and maneuvering thereof. The left and right sleeves 710A and 720A, respectively, slidably encircle the ends of the quick release bar 700. The camming members 710 and 720 are respectively attached to sleeves 710A and 720A and extend transversely therefrom along parallel planes to embrace the sides of housing 210. The lower lobes of camming members 710 and 720 are provided with holes for pivotal attachment to the respective side-walls of housing 210 and may be conveniently mounted on the trigger axle 200. The upper portion of members 710 and 720 are defined by arcuate camming slots 712 and 722, and the ends of the main axle 300 protrude outwardly through the slots 212 in the side-walls of housing 210 and are carried within the respective camming slots 712 and 722 of camming members 710 and 720. Slots 712 and 722 are contoured so that rearward pivoting of quick release bar 700 (and camming members 710 and 720) operates to bias the main axle 300 upwardly in within slots 212. Similarly, forward pivoting of quick release bar 700 (and camming members 710 and 720) operates to bias the main axle 300 downwardly within slots 212. A resilient catch 730 is attached via screw 731 to the top of the forward wall of housing 210 (in support plate 500) to lock the quick release bar 700 in the forward (engaged) position. Catch 730 is preferably shaped to conform to the rounded quick release bar 700. The operation of the quick release feature is illustrated in FIGS. 6A and 6B. As shown in FIG. 6A, quick release bar 700 is freed from catch 730 by sliding the quick release bar 700 upwardly within sleeves 710A and 720A. As shown in FIG. 6B, the quick release bar 700 may then be freely pivoted over catch 730 and rearwardly of housing 210. This likewise pivots camming members 710 and 720 which serve to bias the main axle 300 upwardly in within slots 212. Consequently, the main gear 330 is removed from engagement with the spur gear 250, and the pinion gears 310 and 320 are likewise disengaged from the racks of the respective plunger shafts 23 and 25. In the above-described disengaged position, the dual plunger 22 can be manually retracted to allow removal of a spent epoxy cartridge and reloading with a fresh cartridge. Dispensing can be resumed by pivoting the quick release bar 700 and camming members 710 and 720 forwardly of housing 210. Slots 712 and 722 then bias the main drive axle 300 downwardly within slots 212 thereby reengaging the gears for further thrusting. Quick release bar 700 may be seated in this engaged position by sliding the quick release bar 700 down into camming members 710 and 720 until it is seated in catch 730. Having now fully set forth the preferred embodiments and certain modifications of the concept underlying the present invention, various other embodiments as well as certain variations and modifications of the embodiment herein shown and described will obviously occur to those skilled in the art upon becoming familiar with said underlying concept. It is to be understood, therefore, that within the scope of the appended claims, the invention may be practiced otherwise than as specifically set forth herein.

A completely portable trigger-operated dispensing gun which employs a simple and reliable double reduction gear system for driving one or more axial plungers with an extreme dispensing force, said force being sufficient for dispensing highly viscous materials such as epoxy resin and hardener from a conventional twin cylinder epoxy cartridge having an elongate mixing nozzle.

RELATED APPLICATION This is a continuation-in-part of Applicant's application Ser. No. 07/990,046 filed Dec. 14, 1992 now U.S. Pat. No. 5,375,891, issued Dec. 27, 1994, for which all right under 35 U.S.C. 120 is claimed. INTRODUCTION AND DESCRIPTION OF THE PRIOR ART The invention disclosed in U.S. Ser. No. 07/990,046 provided a universal hinged connector to connect dissimilarly cross sectioned downspouts and extensions, while still permitting the elevation of the downspout for lawn mowing or whatever purpose required. The connection is achieved by having a tube of approximately circular cross section, or more properly a square cross section with very pronounced rounded corners on the square, hinged with a second tube of approximately square cross section; more properly a square cross section with slightly rounded corners on the square. These are approximations of common forms for both downspouts and drainage extensions; and moreover, the hinged connector in that invention is provided with simple screws with instructions to apply them in appropriate configurations, so that either tube can be connected either on the exterior surface of a downspout or the interior of a drainage extension as required. This invention is directed towards improvements in the shape of the hinged connector portions; which improvements allow more types of common residential downspouts and extensions to be accommodated by the connector. These improvements take three distinct forms: 1. The two main segments that are joined to form the connector are now each fashioned in differently-sized steps, so that multiple types of tubes will fit within the downspout portion and outside the extension portion, respectively. This will be made more clear with reference to the diagrams herein. 2. In the case of the downspout-fitting segment, the cross sections of the stepped portions are varied to conform to specific industry-standard tubing so that this tubing will be held securely. 3. Again in the case of the downspout-fitting segment, a removable face is fashioned so that one specific size of common tubing, being 21/2"×21/2" square vinyl, can be accommodated by removal of the face. With these improvements each end of the hinged connector fits at least six different shapes of industry standard pipe dimensions which are: 3" round metal pipe; 25/8"×25/8" square metal pipe; 21/2"×21/2" square vinyl pipe; 21/4"×3" rectangular vinyl pipe; and 23/4" round vinyl pipe. The present improved connector is able to accommodate an unusually small downspout or unusually large extension simply by reversal of the connector, or by friction fitting the connector inside the downspout or outside the extension; or both. Further sizes may be accommodated by a small amount of bending of the downspouts, extensions, or connector. Details of attachment of the connector to the downspout and extension are identical to those disclosed in U.S. Ser. No. 07/990,046 and are not illustrated or repeated herein. Reference to the aforementioned application and incorporation of its disclosure herein is made as if the aforementioned application is a part hereof. DETAILED DESCRIPTION OF THE INVENTION For this description, refer to the following diagrams, wherein like numerals refer to like parts; FIG. 1, the improved hinged connector, perspective view; FIG. 2, outflow tube segment of the improved hinged connector with ghosted drainage extensions, side elevation view; FIG. 3A, input tube of the invented hinged connector including removable face exploded, cross section along plane 3A of FIG. 1; FIG. 3B, input tube of the invented hinged connector, cross section along plane 3B from FIG. 1; FIG. 3C, input tube of the invented hinged connector, with downspout pipe outlines; end view; FIG. 3D, input tube of the invented hinged connector with removable panel removed to accommodate alternative downspout; end view; FIG. 3E, input tube of the invented hinged connector with alternative downspout outline; cross section along plane 3B from FIG. 1; FIG. 4A, improved hinged connector in usage position during water flow; partial cross section, side elevation; and FIG. 4B, improved hinged connector in usage position during water flow, with alternative downspout and extension; partial cross section, side elevation. DESCRIPTION OF THE INVENTION The preferred embodiment of the improved hinged connector is generally indicated as 10 in FIG. 1. Hinged connector 10 consists of two main sections attached by hinge pins 12; these sections are outflow tube generally indicated at 14 and input tube generally indicated at 18. Outflow tube 14 has an integral projecting U-flange portion 15 which fits alongside and outside U-flange 19 of downspout tube 18. Note that outflow tube 14 steps down in size, as is obvious in FIG. 2, showing a small drainpipe extension 30 (ghosted) snugly fit over a smaller step 14', and a larger drainpipe extension 32 (also ghosted) snugly fit over the larger step 14". Input tube 18, to refer again to FIG. 1, can be seen to have similarly larger step 18" and smaller step 18'. In addition, input tube 18 has removable side panel 28, which snaps on or off from larger step 18". The shape of input tube 18 may be more readily appreciated with reference to FIG. 3A, which is a cross section of larger step 18" along the lines 3A from FIG. 1. Similarly, the cross section of small step 18' is shown in FIG. 3B. These shapes will now be explained in conjunction with the use of the improved connector 10. In FIG. 3C, industry standard 21/4"×31/4" "rectangular" metal pipe external surface 40 (which actually is made with slightly rounded corners 40') fits snugly into corresponding rounded channels 100 in input tube 18. 21/4"×3" rectangular vinyl pipe, owing to its thicker wall, will also fit sufficiently snugly in these same channels 100, and so ghosted pipe 40 can be taken to represent the external surface of this size of vinyl pipe also. Also shown on FIG. 3C is 25/8"×25/8" (approximately square) metal pipe external surface 42, shown ghosted, which fits into lower corners 101 of input tube 18 and underneath removable panel 28. In FIG. 3D, nominal 21/2"×21/2" square vinyl pipe external surface 43 is accommodated by removal of the panel 28. FIG. 3E, a cross section along 3B from FIG. 1 of smaller step 18' shows 3" round metal pipe external surface 44, ghosted, inserted snugly along channel 104 of input tube 18, 23/4" round vinyl pipe external surface would fit in the same path as this metal pipe external surface 44. Support projections 46 held keep surface 44 firmly in place. Two of the thirty-six possible combinations are shown schematically in FIGS. 4A and 4B (this thirty-six is calculated by each of the six types being accommodated on both the input tube 18 and the outflow tube 14; the other thirty-four combinations are not shown). In the example of FIG. 4A, during water flow, connector 10 operates as follows: water flows along path of arrow F from 3" round metal downspout 44, over input U-flange 19, onto output U-flange 15, through outflow larger step 14", through outflow smaller step 14', and into extension 50, which may, for example, be 21/2"×21/2" square vinyl pipe. A second illustrated example of the multiple combinations possible is shown in FIG. 4B, where instead the downspout is 21/4"×3" rectangular vinyl pipe 47 and the extension is 23/4" round vinyl pipe 51. Water flows again along path indicated as arrow F. As described in detail in the corresponding U.S. Ser. No. 07/990,046 which, as mentioned previously, disclosed a connector without the improvements described herein, storage of extending portion of the system described herein (such as extension 51 and attached outflow tube 14, in FIG. 4A) involves merely pivoting the connector 10 at hinge pins 12. (Such pivoting is not illustrated herein.) Securement of connector 10 in the pivoted position, as well as secure attachment of the downspout and extensions to the connector 10, are identical to that disclosed in the corresponding U.S. Pat. No. 5,375,891 and are not itemized herein. Finally, it should be noted that whereas a particular hinged connector 10, such as that shown in FIGS. 1 through 5, is designed to accommodate particular common cross sections of pipe, such a hinged connector 10 will also be fittable by other close sizes and shapes of downspout and drainage extension pipe, with small amounts of adaptation, since such pipe commonly is made of thin metal or plastic that can be easily bent or formed at such a join. Thus virtually all known, and probably many heretofore unknown, residential downspouts and extensions can be fitted to this universal hinged connector. The foregoing is by example only and the scope of the invention should be limited only by the appended claims.

An adaptor for eavestrough downspouts has two portions of different cross sections. The first section fits outside the downspout and the other fits inside the drainage extensions. The two portions are hinged together. The adaptor is formed with step-down sized cross sections and a removable panel to allow more sizes of downspouts and extensions to be connected.