US1934643A - Wire cloth and method of producing the same - Google Patents

Description

Nov. 7, 1933. H. R. RAFTON wmf; CLOTH AND METHOD oF PRoDuoING THE SAME g Mevwjarm/Y @muy iPatented Nov. 7, 1933 UNITED STATES WIRE CLOTH THE AND METHOD 0F PRODUCING SAME Harold Robert Rattan, Andover, Mass., assigner to Rai'ton Engineering Corporation, a corporation of Massachusetts Application January 14,

6 Claims.

This invention relates to wire cloth and a method of producing the same, and has particular reference to the production of a fine mesh wire cloth particularly suitable for use for straining or sifting purposes.

The principal object of my invention is to provide a wire mesh cloth having openings therein smaller than those in any fine mesh wire cloth now manufactured, with openings of similar shape.

A further object is the production of fine mesh wire cloth with openings of substantially any smallness desired.

A further object is to provide a wire cloth of the character referred to which possesses much greater durability than any commercially available wire cloth having openings therein of substantially the same size.

A further object is to provide a line mesh wire cloth which is less distortable than wire cloth with substantially the same size openings now manufactured.

A further object is to make available a fine mesh wire cloth of increased durability and decreased distortability for use in commercial screening machines.

A further object is to provide a cloth of the character referred to with smaller openings than are present in any cloth now available whereby the cloth is particularly adapted for testing purposes.

Other objects and advantages of the invention will become apparent during the course of the following description.

In the separation of coarse particles from fine particles, both in the dry and in the wet state, the process of screening is Widely practiced. For the ner separations, progressively finer screens are employed, and for such purposes, not only for testing, but also for commercial production, woven wire screens are commonly employed and are referred to as wire cloth". Ordinary wire cloth usually is made with warp and shoot (i. e. Woof) wires of substantially equal diameters, and both the warp and shoot wires are interwoven and therefore bent or crimped at the points where they pass over and under a wire at right angles to them. This cloth is produced in a variety of weaves such, for example, as plain and twilled weaves. Wire cloth known as Dutch cloth is also common. In such cloth the warp wires are usually heavier than the shoot wires and are substantially straight, the shoot wires being bent to provide the necessary weave. This cloth also may be obtained in both plain and twilled weaves. Other types of wire cloth and weaves also are known, but need not be referred to in the present description.

Wire cloth of fine mesh which is used for screening material is practically always what is 1930. Serial No. 420,794 (Cl. 204-1) referred to above as ordinary wire cloth, and has openings of substantially rectangular cross section, i. e. rectangular in a plane parallel to the cloth surface. In this connection it may be stated that for the purpose of this description, the expression fine mesh may be considered to include wire cloth of 100 mesh or ner. While the openings in ordinary wire cloth are rectangular and arranged substantially straight through the cloth, those in Dutch cloth are substantially l triangular in cross section and are arranged at an angle to the surface of the cloth. Hence Dutch cloth, especially in the fine meshes, is not very useful for screening as it has little capacity and clogs easily. The openings in the ordinary wire cloth referred to are usually square but some may be more or less oblong according to the relative number of warp and shoot wires used. As the meshes get finer, however, the square opening wire cloths are by far the more common, and if cloth having oblong openings is employed, the length of such openings ordinarily is not greatly different from their width.

Moreover, in the very fine meshes, most of the cloth is of twilled weave which permits the use of wires of larger diameter than in the plain weave, thus increasing the strength and life of the wire cloth, and twilled weave further possesses the additional advantage that it more readily adapts itself without injury to such distortion as occurs in screening devices. l

Of course, wire of any cross-sectional pattern may be used for weaving wire cloth, but wire of circular cross-section is practically the only kind employed for the ne meshes due to the greater ease of drawing and weaving very ne wires of such shape. Likewise wires of various metals may be employed, but for the very ne mesh cloths phosphor bronze is more commonly employed owing to the technologie diculties in drawing and weaving fine wires of other metals.

For commercial screening operations, the use of 100 mesh Wirth cloth has been common, and the use of 150 mesh cloth reasonably common, and even wire cloth as fine as 200 mesh has been occasionally employed. However, a cloth of ner than 200 mesh hitherto has been but infrequently employed commercially because the eXtreme frailty of such wire cloth has rendered its use uneconomical if not impossible in the ordinary screening machinery hitherto available. Wire cloths up to and including 325 mesh however, despite the frailty of such cloths, have been commonlyused for testing purposes, such as in test sieves, and have been suitable therefor, since obviously the amount of wear under testing oonditions is but nominal compared with that to which wire cloth for commercial screening is subjected. Wire cloth of the rectangular opening type finer than 325 mesh has been made, and

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probably 400 mesh wire cloth is the inest which has hitherto been produced. Such cloth is extremely delicate and is suitable only for testing purposes.

Another nne mesh wire cloth of the rectangular opening type, which has been produced commercially has a mesh of approximately 315 to 330 in one direction and 350 to 375 in the other direction. This cloth, although somewhat rmer than the 400 mesh cloth owing to the heavier wire employed therein is still too frail for economical commercial use in the ordinary screening machines hitherto available. Thus it will be apparent that for commercial screening wire cloth of approximately 200 mesh is about as ne as has been heretofore economically used, whereas for testing purposes 325 mesh cloth has been the usual limit, although 400 mesh cloth has been procurable.

From the standpoint of commercial screening, it is highly desirable for some purposes to have a suitably durable wire cloth available 0I finer than 200 mesh. Heretofore, this has been impracticable, and accordingly processes other than screening have been resorted to for separating finer particles from materials. Such separation usually is effected by dierential settling of particles of varying sizes in a fluid medium, either gaseous or liquid. As is Well known, such separation has many disadvantages not inherent in mechanical screening. Hence very ne mesh cloth would in many cases have been employed in the past in preference to the other described methods if sufciently durable cloth had been available in the very fine meshes, or in meshes nner than those which hitherto have been feasible to manufacture.

From the testing standpoint, the laboratory technician hitherto has been limited, as stated above, to wire cloth sieves of 400 mesh. For the separation of particles passing through a 400 mesh wire cloth, he has resorted to an air flotation or liquid elutriation, or to microscopic measures and similar procedures. However, the sieve testing technique is so simple that an extension of the meshes available to the laboratory technician beyond 400 mesh, particularly if such mesh wire cloths be reasonably durable, undoubtedly would have resulted in very great advances in the study of many products, which in turn would have been reilected in discoveries resulting in improvements in industrial products and processes.

From the foregoing it will be apparent that an extension of commercial screening to very ne meshes has been greatly desired, and that such extension would result in great economy and improvement in the technology of processes now practiced. In many cases it also will result in better quality products being made, and in some cases, will result in entirely new products being produced. It also will be apparent from the standpoint of laboratory use in testing and research that wire cloths of finer meshes than hitherto obtainable have been greatly desired as an aid to technologic progress.

I have devised a method whereby Wire cloths of substantial durability may be produced with openings equivalent to those of fine mesh wire cloths. As will become apparent, the method also is applicable to the production of wire cloths having openings which would be equivalent in size to the openings of wire cloths of meshes ner than hitherto have been made.

In the practice of the method, I propose to employ previously woven ne mesh wire cloth of a mesh the suitability of which -is determined by the considerations discussed below, and increase the diameter of the wires of the already woven cloth by suitable means to reduce the size of the mesh openings. I may increase the wire' diameter of such cloths by the coating oi, or the deposition on, the wires of said cloth of any suitable material which will produce a substantially hard. and non-yielding coating which may be non-metallic, such for example as an enamel or japan, but I prefer to deposit metallic material on the wires. In this connection, it should be noted that the term metal or metallic in the present description, as applied to the coating of the wires, is intended to include alloyed as well as substantially or commercially pure metal.

Although there are a number of known methods of depositing metal on surfaces, such as spraying, chemical deposition, plating and the like, I prefer the electrodeposition of metal on the wires of the already woven wire cloth as the method best adapted for my purpose, because of a number of factors among which are the ease of control of thickness of the metallic deposit, and the wide variety of metals made available by such method. In the preferred practice of my invention, therefore, I place ne mesh wire cloth in an electroplating bath and deposit upon this wire cloth a controlled amount of metal. By this means, the diameters of the wires are gradually increased and in consequence the size of the openings also is gradually decreased, but the general geometric shape of the openings is substantially retained.

After the plating has proceeded suciently to produce openings of the desired size in the plated wire cloth, the latter is removed from the plating bath and washed thoroughly, and if desired-,M- the product may be subjected to further treatment. Such treatment may comprise heating in boiling water or in an oven to drive oi occluded gas, or treatment at a higher temperature for annealing or the like, and/or the use of mechanical agencies such as buing machines or the like. '20 Metal treatments of the above kinds are well known in the art and need not be further ccnsidered here.

I have found that it is possible by the present method to produce Wire cloths having openings smaller than the openings of 400 mesh wire cloth, the latter being the finest mesh hitherto obtainable. In fact, the range of the sizes of the openings for screening technology is now extended far beyond what has been hitherto available. I have also found that plated wire cloths are much less frail than the wire cloths from which they were originally made and are of such durability as to render feasible their use in commercial screening machines.

Moreover, I have found that plated wire cloths, and even those possessing only a very thin plating deposit are very appreciably stiiened to the feel. They also possess a further quite noticeable characteristic of great importance which differentiates them from the original wire cloths in that they are very much less subject to distortion than the original wire cloths from which they are made. For example, if a piece of ne mesh wire cloth, such for example, as 325 mesh, is grasped between the thumb and forenger of each hand with the fingers close together, and the two hands are moved back and forth in the plane of the cloth, the openings thereof will be found to be distorted by such movement. On the other hand, 150

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:,esaess if a plated cloth made from the same stock be tested in the same manner, it would be found to be substantially non-distortable by such means, this characteristic being of course, more pronounced- .characteristic displayed by the plated wire cloths and what shape the nal openings assume. The accompanying drawing is illustrative of the general structure of the finished cloth. In the drawmg:

Figure 1 is a face view of a portion of a plated cloth,

Figure 2 is a transverse section, and,

Figure 3 is an enlarged fragmentary face view of a portion of the plated cloth showing the plating in section.

Referring to the drawing the numeral 10 designates a plated wire cloth as a whole in which a foundation cloth is employed including warp threads 11 and shoot threads 12. The drawing, of course, shows the parts greatly enlarged, and it will be apparent that the mesh of the foundation cloth is relatively fine. A cloth of plain weave is illustrated, and in accordance with what may be termed the usual practice in weaving line mesh Wire cloths, the normal mesh openings. that is the openings between the warp and shoot wires, are slightly greater than the thickness of the wires, and are substantially rectangular. As previously stated, however, the invention is applicable to wire cloths of any weave.

The foundation cloth is electroplated in the manner previously stated to deposit a metallic coating on the individual Wire elements indicated by the numerals 13 and 13'. on the Wires l1 and l2 respectively. Numerous observations of plated cloths have been made, particularly cloths plated with nickel and chromium with the deposits varying from very thin coatings up to deposits of plating which almost exclude the passage of light through the cloth. The observations of the nickel plated cloths and individual Wires taken therefrom. indicate that the individual wires 11 and l2 are enclosed in what appear to be substantially continuous coatings or shells of deposited metal, and that there appear to be no unplated spots at the points where the wires cross one another.

The microscopic observations also clearly indicate the reason for the substantial non-distortability which' the nickel plated cloth exhibits. In a single wire, taken from even a lightly nickel plated wire cloth, it will be noticed that at the points where the wires have crossed at right angles to the wire taken from the cloth, there are very slight depressions. These depressions apparently are points at which there is less plating deposited than directly at either side, and are the points at which the wires cross or intersect. Similar observations of wires taken from those running at right angles to the original wires examined show similar depressions. It will be readily understood therefore that such depressions iitting into one another vbring about an interlocking of the wires in the cross directions so that even with a relatively light plating there results a practical avoidance of distortability such as would be occasioned by the sliding of one wire along the other, and of course, it will be readily seen) that-such a structure greatly strengthens the wire cloth.

In the more heavily plated wire cloths, the

same structure egoista-only it is more accentuated. It should be stated that in the case where only an extremely light metallic coating has been deposited, the depressions noted above. although probably existing, would be so shallow as to be dimcult to detect under a microscope. It is probable that in such very light platings the degree of non-distortability imparted to the wire cloth, while possibly due to some extent to the very shallow depressions at the intersecting points of the wires, is probably due in a considerable measure to thel fact that increased wire diameter tightens the cloth, one wire upon another, and this action, combined with the microscopic unevennesses which are present in a plated surface tends to prevent slippage of one wire upon another and thus imparts a degree of non-distorttbility even to a very lightly plated wire clo When wire cloths are very heavily nickel plated, a very peculiar structure exists which is in reality merely an exaggeration'of the structure existing in the less heavily plated cloths. For example. one plated wire cloth, the original cloth of which was 317 x 370 mesh and was of twilled weave, that is the wires in this case in both directions passed over two wires and under two wires, was very carefully examined. The points at which two wires crossed a single wire examined appeared as a yoke on the surface of the single wire, that is, there was a slight ridge between the points where the two wires originally lay, and on the outside edges of the points where the two wires lay there was a .considerable building up of metallic deposit in a plane at right angles to the cloth surface in shape similar to square ns". The plated wires in the direction at right angles to the one originally taken were of course similarly shaped, and it is thus seen that the surface of a wire cloth which has been very heavily plated is comprised merely of the upper edges of these fins, i. e. the heavy deposits on the outwardly exposed portions of the original wire elements of the wire cloth.

The appearance under the microscope of chromium plated wire cloth, and wires extracted therefrom follows in general the appearance of the nickel plated samples described above. However, in several chromium plated samples examined, instances were noted where the phosphor bronze of the original wire cloth showed through at the base of the depressions, that is, at the points where the wires intersected. It is impossible to say whether these sections of plating were torn out in dismembering the cloth or whether no plating had originally deposited at these points. The former seems more likely, as all the chromium plated cloths examined had been given a very light preliminary coat of nickel plating prior to thechromium plating.

As seen above, all nickel plated samples had substantially unbroken continuous plating, hence even though no chromium had deposited at the points referred to, the original nickel deposits still should have been present and visible. As they were not, they apparently had been torn out by the violent wrenching and distortion to which the individual wires necessarily were subjected in detaching them from the cloth. However, regardless of whether any plating. had been present at theindividual points referred to, it may platedwire cloth.

In` some. of the samples of the chromium `plated wire cloth, the irfaces of the wires were distinctly more roughened than in the nickel plated samples. This would have the4 effect of increasing the non-distortability of such cloths plated with a very light coat of chromium, as it would tend to prevent the slippage of one wire along another.

- To summarize the effect o f plating with various metals, such as nickel or chromium, on the rigidity or distortability of the original wire cloth, it is apparent that sucli eiect is brought about by substantially iixedly positioning the wires. In the extremely light platings this probably is due to a considerable extent toie thick-. ening and microscopic roughening of the wires as well as possibly to the slight interlocking of the wires. In the light platings it is due primarily to the interlocking of the wires, and in the heavily plated cloths to the exaggerated interlocking or buttressing of the wires. I have not found any definite microscopic evidence of adherence of the plated wires tb one another at the points at which the wires cross. It is highly probable therefore that the non-distortability ci' the wire cloth results substantially completely from the positioning, interlocking and buttresslng effect explained in detail above.

Furthermore, an examination of the actual openings between the Wires revealsthe fact that these openings are not substantially distorted by the plating. Referring to the drawing it will be noted that the plating provides openings i4 which correspond to the shape of the openings of the original cloth except, of course, that they are smaller due to the plating of the wires. In actual practice, it has been found that there. is no evidence of webbing at the corners of the openings. It is true, of course, that the openings themselves become deeper as the plating becomes heavier, but the general rectangular characteristic of the openings as well as the general direction of the openings continue to correspond to the similar characteristics of the original wire cloth.

As will be understood from the above description, as. the plating becomes thicker, there are certain points on the wire elements where the coating of a wire element, for example a wire element of circular cross-section, does not form a true concentric shell but rather an eccentric shell which in extreme cases deviates considerably in its peripheral cross-sectional shape from a true circle. Thus when the expression that plating increases the wire diameter oi the original elements is used herein, the word diameter is not used in the restricted sense merely as the diameter of a circle, but what is meant is that the cross-sectional area of the plated wire is greater than that of the original wire, and the expression is meant to include both the cases where the shells of the wires are substantially concentric as well as those cases indicated above where the shells are more or less eccentric.

There are several considerations which govern the choice of the proper mesh wire cloth to be used as the base cloth for plating to obtain openings of any given size in the resulting plated wire cloth. As will be apparent, the number of openings per square inch for each individual mesh wire cloth is definite, being the product of the meshes in the two directions (or the square of tinuous", as describing the condition of the shells the mesh number when the mesh is' equal in the two directions). For purposes vof comparison, the following table has been computed." In the first column is given the Mesh", in the second column the Number of openings per square inch", and in the third column the Tercentage number" i. e., the comparative percentage number of holes in the various meshes based on 400v mesh as unity It is obvious that the number of openings in a plated cloth will be the same as the number in the original cloth from which the finished article is made. Thus 'a 150 mesh plated cloth whose openings have been reduced to the size of the openings in a 400 mesh wire cloth will have only approximately 14 per cent. of the number of openings that there are in an equal area of 400 mesh cloth, and accordingly will have only approximately one-seventh the effective screening area, i. e., the combined areas of the openings in a 400 mesh cloth.

On the other hand, if a 325 mesh wire cloth were used as the base for making a plated cloth having openings corresponding in size to those of a 400 mesh cloth, such plated cloth would have 66 per cent. of the number of openings in a 400 mesh cloth of the same area, and hence would possess about two-thirds of the effective screening area of a 400 mesh cloth. However, the 325 mesh plated wire cloth would have approximately 4.7 times as much effective screening area as has the 150 mesh plated wire cloth referred to above.

Thus it will be apparent from the standpoint f the capacity of the wire cloth, that is, the

amount of material which can be passed through a cloth of a given size in a given time, that the plated wire cloth should be made from as fine a mesh of original base wire cloth as possible. With the present method it is possible to take advantage of relatively ne mesh base cloths inasmuch as the plating material stiiIens and strengthens the resulting plated cloth. Moreover, the use of very ilne mesh wire cloths is desirable from the standpoint of the uniformity of the openings, and hence the uniformity of screening. This, of course, is due to the fact that even the very best wire cloths have slight variations in the sizes ofthe openings, and as these openings arenot reduced proportionately in plating, but rather by absolute amounts, the irregularities in the sizes of the openings become proportionately greater, the thicker the plating applied to the originalv wire cloth. It is desirable to employ as fine a mesh wire cloth for the base cloth as feasible inasmuch as the'heavy coatings required on the coarser mesh wire cloths cause the openings in the plated Wire cloth to be deeper than will those in resulting cloths on which the amount of deposited metal is not so great. Thus excessive resistance to the passage of material through the screen may be avoided.

From the foregoing it will be apparent that it feasible for the base cloth, from the standpoint plica-r is desirable to use as ne a mesh cloth as pacity, uniformity of the size of the openings, and the depth of the openings. On the other hand these factors must be balanced against the factors of durability and strength. It is obvious that the heavier the plating on the cloth, the greater will be the rigidity and the resistance to distortion and wear of the resulting cloth. On the other hand, there is a limiting feature which must be considered in ,determining the thickness of the plating and that is. that under some conditions there is a tendency to brittleness with certain metallic coatings, and in such cases it usually occurs that the degree of brittleness increases with the thickness of the metal coating. For this reason, in the cases referred to, it is desirable to avoid the use of too heavy aplating, unless some treatment be given the plated wire cloth to overcome or lessen the tendency toward brittleness.

Thus from the standpoint of commercial utilization it will be necessary to determine by test in any given case just how ne a mesh wire cloth must be used as a base for plating in order 1 that the durability of the plated wire cloth may be such as to make the employment of the cloth economically feasible from the standpoint both of original cost and length of life. Where the durability is not of such great importance, as in the case of testing sieves, the very nest mesh wire cloths procurable are very definitely indicated as the most suitable base wire cloths.

For computation purposes, I set forth below a table showing sieve numbers of various standard sieves, together with the corresponding opening sizes and wire diameters abstracted from a table in Technologie Papers of the Bureau of Standards (Paper #321, page 603, Aug. 5, 1926).

Sieve open- Wire diam., Sieve No. ing, mm mm.

These gures not in original table, buil:1 were furnished by the manufacturer of 400 mesh wire clot In the above table the Sieve No. corresponds approximately but not lexactly, to the number of meshes per inch. The correspondence, how-1 ever, is suciently close so that for the purpose of this description the Sieve No. may be considered the same as the number of meshes per inch. The `opening of each standard sieve above differs from the one below it in the ratio of the fourth root of 2:1. In other words, the opening in any sieve in the group under Sieve No. is approximately half the opening of the fourth sieve above it. Similarly it will be noted that the Sieve No. of every sieve is approximately' double the number of the fourth sieve above it.

On the basis of these relationships, vI have prepared the following table which is an approximate extrapolation of the above table. The object of this table is to show the approximate sieve numbers (i. e., the approximate mesh numbers) of sieves finer than 400 mesh together with the sieve openings. These two columns of the table are a direct extension of the first tWO c01- umns o1' the preceding table and are derived according to the relationships shown in the latter table. On the assumption that a 400 mesh wire cloth is to be the base wire cloth used for plating, the required plated wire diameter is com- 80 puted for a sieve with openings equivalent to each sieve number, and also the thickness of the plating required to be deposited on the original 400 mesh wire cloth to give openings equivalent to any give'n Sieve No. The thickness of the plat- 85 ingl is computed on the radial measurement of wire, i. e., the wire diameter will actually be increased by twice the thickness of the plate. As' will be apparent, the total of column 2 and column 3 fcr any given sieve number is equal to 90 la 1/400th`of 25.4 mm (1") i. e., .0635 min. Column 4 for any sieve number is equal to (column 3-.025) +2.

Columnl Column2 C0lumn3 Co1umn4 95 Wire diam. .esta of opening plating on equivalent #4.02 nllell; to given wir -c t 100 Estimated sieve No., require o Estimated o enin but havin produce sieve N o. pmm g only 160 00% plated sieve openings'per with @enmgs sq in. Le' equivalent with #400, mesh as base l wire cloth N 0. mm.

400* .038' .025-x 00000* 400 .osi .0325 .00375 540 .0205 .0370 .00600 650 .022 .0415 .00825 soo .010 .0445 .00975 920 .0155 .0480 .01150 1080 0133 0502 01200 1300 .011 .0525 01375 1000 .0095 .0540 01450 1840 .007s .0557 01535 Figures on original purpose of comparison.

unplated wire cloth inserted for tions suitable for a guide in producing plated wire cloth with openings equivalent to the several numbers given starting with 400 mesh wire cloth as a base for plating. With this illustration and the data given herein as a guide, it is a simple matter to make calculations for plating any base Wire cloth from 100 mesh up, to 125 give any required size openings.

The'thickness of the plating required is readily computed as shown above. Any given thickness of plating, of course, can be applied by the customary plating methods. It is well, however, to check up on the plating results by actual measurement of the wire diameters and openings under the microscope, or better still, to use the optical projection4 device referred to in the Bureau of Standards Technologie Paper #321 referred to above. This will furnish a simple means by which the time and other plating conditions may be adequately determined with a few test pieces whereupon the conditions so standardized may be employed for large scale production of the desired `plated wire cloth. The size of the desired opening is of course the nally controlling factor in each case.

As will be obvious, any metal which can be electroplated can be utilized for plating, depending on the requirements, and the conditions to which the plated wire cloth is to be subjected.

In practice I have found that both nickel and chromium are particularly adapted for such plating. 150

for commercial screening purposes was producedby plating a 817x370 meshphosphor bronze wire cloth with ni l to produce openings estimated to correspond oximately in the long dimension to those of e540 mesh cloth. A number of plated cloths for use as testing sieves also have been produced, and most of such cloths have V'openings therein nner than those of 400 mesh standard wire cloth. a

It has been customary at times to roll wire cloths to reduce the size of the openings somewhat, but such practice greatly reduces the strength of the clothparticularly in the ilne meshes. ByV the present method, however, such rolled ilne mesh wire cloth can be greatly strengthened as well as having its openings decreased in size, and accordingly it becomes practicable to use rolled fine mesh wire cloth for commercial screening after it has been plated.

It will be obvious that the present invention is primarily intended for the production of wire cloths for screening, but it is equally suitable for the production of wire cloths other than those having substantially rectangular openings, and particularly wire cloths which are used for filter cloths, and which may be of the so-called Dutch weave or the like. In auch filter cloths it is diillcult at times to produce suillciently iine openings to retain precipitates of certain sizes. By the present. method, such cloths may have the openings therein reduced to anydesired size. The present invention accordingly constitutes an important improvement in the art of iiltering with wire cloth and leads to a dennite extension o! the use of such cloth.

Whereas I have described in detail several illustrative examples of my invention, it is to be understood that I do not intend to be limited thereby, as it is apparent that various changes in procedure, materials and the like may be resorted to in the practice of my invention without departinglrom the spirit of the invention or the scope of the subjoined claims.k

I claim:

. 1. As a new article of manufacture a nne mesh wire screening cloth having openings of a size smaller than substantially .074 mm. (the sieve opening for a 200 mesh standard sieve), .consisting of a wire cloth having a mesh of a ilneness between 150 and 200 mesh inclusive and having a metallic coating thereon to reduce the openings to such smaller size, providing mutually engaging depressions at the crossing points of the wires thereof, whereby the wires are substantially held against relative movement, and wear by friction between crossed wires substantially reduced, the cross sections of the openings, after reduction, being of substantially their original, general geometric shape.

2. As a new article of manufacture a ilne mesh vwire screening cloth having openings of a size smaller than substantially .074 mm. (the sieve opening for a 200 mesh standard sieve), consistving of a wire cloth having a mesh of a flneness between 150 and 200 mesh inclusive, electroplated to reduce the openings to such smaller size, providing mutually engaging depressions at the crossing points of the wires thereof, whereby the wires are substantially held against relative movement, and wear by friction between grossed wiresmbstantiallyreducedthecrosssectionsof the openings, after reduction, being of substantially their original, general geometric shape.

3. As a new article of manufacture a tine mesh wire screening cloth having' openings of a size smaller than substantially .038 mm. (the sieve opening of the 400 mesh wire cloth herein referred to), consisting of a wire cloth having a mesh of a iineneas between 150 and 400 mesh inclusive and having metal deposited thereon to reduce the openings to such smaller size, providing mutually engaging depressions at the crossing points of the wires thereof, whereby the wires are substantially heldv against relative movement, and wear by friction between crossed wires substantially reduced, the cross sections of the openings, after reduction, being of substantially their original, general geometric shape.

4.' As a new article o! manufacture, a ilne mesh wire screening cloth having openings of a size smaller than substantially .038 mm. (the sieve opening of the 400 mesh wire cloth herein referred tof, consisting of a wire clothhaving a mesh of ahneness between 15o and 40o mesh 1nclusive, electroplated to reduce the openings to such smaller size, providing mutually engaging depressions yat'the crossing points of the wires thereof, whereby. the wires are substantially held against relative movement, and wear by friction between crossed wires substantially reduced, the cross sections of the openings. after reduction, being of substantially their original, general geometric shape.

5. As a new article of manufacture a nne mesh wire screening cloth having openings of a size smaller than substantially .038 mm. (the sieve opening of the 400 mosh wire cloth herein referred to), consisting of a wire cloth having a mesh of a ilneness between 150 and 400 mesh inclusive, formed of drawn metallic core elements, having a substantially continuous and substantially non-yielding shell deposited thereon to reduce the openings to such smaller size, the shells of the elements at the crossing points thereof having mutually engaging depressions, whereby the elements are substantially held against relative movement, and wear by friction between crossed elements substantially reduced, the cross sections of the openings, after reduction, being of substantially their original, general geometric shape. t

6. The method of producing a fine mesh wire-4 screening cloth having openings of a size smaller than substantially .038 mm. (the sieve 'opening of the 400 mesh wire cloth herein referred to), which comprises forming a substantially continuous and substantially non-yielding shell of metal about the elements of a wire cloth having a mesh of a ilneness between 150 and 400 mesh inclusive, by electroplating the cloth, thereby to reduce the openings to such smaller size, simultaneously forming mutually engaging depressions at the crossing points of the wire elements, whereby the elements are substantially held against rel- Y ative movement, and wear by friction between A" crossed elements substantially reduced, controlling the electro-deposition to determine the size of the openings, and maintaining the cross sections of the openings in substantially their original, general geometric shape, regardless of size, throughout the process.

HAROLD ROBERT RAFION.

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