US2412562A - Fabric - Google Patents

Description

H. CRAWSHAW Zlg FABRIC I Filed Jung 27. 1944 Ludimw A g E52, v

Inventor H cRAwsHAw Patented ec. i7, i946 emo Harry Crawshaw, London, England, assignor to British Celanese Limited, London, England, a.

company of Great Britain Application June 27, 1944, Serial No. 542,386

lin Great Britain May 21, 1943 Claims. i

This invention relates to fabrics.

For certain purposes, e. g. for the interception of radio waves, there is a demand for a strong, light-weight, flexible fabric which is a good conductor of electricity. This combination of properties is not easily obtained by any of the prior methods of wire-fabric construction. Plainwoven wire fabrics in which successive wires 'in both warp and weft are widely spaced apart to give the desired :flexibility and lightness, and to provide the desired electrical conductivity without excessive consumption of wire, are unsatisfactory since the wires tend to slip over one another and also do not make sulciently tight contact to give the desired conductivity. Wire fabrics having -a true gauze structure are very diicult to weave owing to the extent to which the wire warps must be distorted to produce such a structure.

I have now found that a fabric having the desired properties can be obtained by weaving a fabric in which, in both warp and weft, narrow bands of fine wires alternate with broad bands of textile yarns, at least two warp wires being interlaced with at least two weft wires at each crossing or" the wire bands of warp and weft. Preferably the ratio oil the total area of the spaces between the Wires to the product of the diameter of the wire and the length of wire is not less than about l() z 1.

It is sometimes desirable e. g. when the fabric is to be used in the construction of kites, drogues or pilotless aircraft, which are required to be capable of intercepting radio-signals. for the fabric to be of low wind-resistance. Fabrics having this property can be obtained from the wiretextile yarn fabrics described above by removing the textile yarn locally or throughout. This can be done, e. g. by means vof an agent which dissolves or otherwise destroys the yarn without affecting the'wire. When an open-mesh, all-wire fabric is made in this way, i. e. by weaving a wire-textile yarn' fabric of the structure specied above and subsequently removing the textile yarn, the textile yarns serve to spacel apart and locate the wires during weaving; they enable a tight beat-up to be obtained and assist in kinking the wires at the crossings so that they slip less easily over one another. By local removal of the textile yarns from a wire-textile yarn fabric of the structure speciled'an open-work electrically conducting` fabric can be obtained, in which in certain areas, e. g. round `the margin of the fabric, panels iilled with interwoven textile yarns remain to facilitate attachment of the fabric to other fabrics or materials, e. g..by sewing.

The following examples illustrate the invention.

Example 1 On a two-box loom a fabric of the following each of the regenerated cellulose yarn specified above, alternating with two single picks, each of the wire specied above.

The structure of this fabric is shown in Figs. 1 and 2 of the accompanying diagrammatic drawings wherein Fig. 1 is a plan-view on a. much enlarged scale of a small portion of the fabric and Fig. 2 is a plan-view on a smaller scale of a larger portion of the same fabric.

Referring now to Fig. 1, the pairs of warp yarns it are each composed of two identical yarns il. The pairs of wires i2 are each composed of two identical wires i3, The weft is composed of a number of single picks of textile yarn it alternating with two picks l5 of wire.

The fabric when viewed as a whole appears to consist, as shown in Fig. 2, of rectangular panels it of interwoven textile yarn each panel being about twice as long as it is broad, and being bounded along the two long sides by narrow bands IS of wire and along the two shorter sides by wider bands il of wire.

This fabric may be used as such as an electrical screening fabric, or as a material for picking up or transmitting radio waves. The fabric may be used in the construction of kites intended to intercept or transmit radio signals.

Example 2 materials.

for acetone, which can subsequently be removed without damaging the cellulose acetate in the said marginal portions, and the fabric may then be given an overall treatment, e.. g. in a. bath, with acetone to remove the unreserveJ panels. `.A portion of fabric so treated is shown diagrammatically in plan-view in Fig. 3, where a central area in which the cellulose acetate has been removed leaving vspaces I9 between the bands of wires, is bounded by a marginal area in which the vcellulose acetate panels I8 have remained intact. A fabric of this kind is specially suitable for the construction of kites and the like referred to above, may be made by the saponifl since by virtue of the large spaces between the bands of wires it has low windage whereas the marginal panels of cellulose acetate yarns enable lengths voi the fabric to be sewn together or otherwise attached to one another or to other The fabric described in Example 1 can `be treated as described in Example 2 but substituting for acetone a solvent for regenerated cellulose, e. g. cuprammonium sulphate or ammonium thiocyanate.

Various modifications can be made in .the structure of the wire-textile yarns without departing from the principle of construction outlined above,

viz: that of employing in both warp and weft narrow bands of wires alternating with broad bands of textile yarn, at least two warp wires and at least two weft wires being interlaced at each crossing of the wire bands of .warp and weft. Thus, for example, instead of employing pairs of similarly shedded wires in the warp of the fabric described above, single yarns and wires can be employed although better results qua. flexibility, conductivity and freedom from slip are obtained using the pairs of ends. The bands of `wire in warp and weit may also containmore wires than those of the fabric described, provided that the bands of wire remain sufficiently narrow relative to the bands of'textile yarn to give the desired open texture in the flnal Wire fabric. Thus, for example, .the weft bands may consist of more than two single picks, for example 4 or 6 single picks may be employed (odd numbers of Wires in the weft bands are preferably avoided as involving complication in lthe loom); or two wires may be inserted at each pick. The principle of construction referred to could be applied in the productionof fabrics other than plain woven fabrics, for example twill fabrics, but the best combina `rtiorl of properties has been obtained using a plain weave and especially a construction of .the kind specifically described above.

A measure of the spacing apart of the bands of wire of the wire-fabrics or wire-.textile yarn fabrics of the invention, in the initial'wire-texrtile fabrics, is given by the ratio; total area of y spaces between wires to product 'of diameter of wire by length of wire. This ratio may vary between wide limits, e.v g. from less than 8: 1 to over 50:1. In the preferred form of the invention .the ratio is between about 10:1 and about 20:1, e. g. about 12: 1,

The ratio: total area'of spaces between wire bands to area occupied by the wire bands should not be ,less than about 4:1 and is preferably considerably higher, e. g. between about 6 or 8:1 and about 16:1 or even higher. A useful figure for this ratio using wires of about 0.005" in diameter is about 8:1.

Tinned copper wire has been found the most satisfactory material' for the conductive element of the fabric but other ductile metals of good electrical conductivity could ybe employed, for example aluminium. When high electrical conductivity is not of importance metals of lower conductivity than aluminium can be used, e. g. iron. The diameter of the wire employed may range from less than 0.005" up to 0.01" or even higher, e. g. above 0.02".

The high-tenacity regenerated cellulose ya'n cation of a cellulose acetate yarn which has been stretched to many 'times its original length under the influence `of steam, hot water or an organic stretch-assisting agent. Such regenerated cellulose yarnsl may have a. tenacity considerably greater .than -two grams per denier, for example 3 4, 5 or 6 grams per denier or even higher. High tenacity in the textile material which is interwoven with the wire in carrying out the present invention is of considerable advantage in enabling a strong, tightly-woven fabric .to be obtained. Other textile materials can be employed, however, in the place of regenerated cellulose of the kind referred to. Among such other matef rials are regenerated cellulose yarn made by the viscose or cuprammonium processes; yarn having a basis of an organic derivative of cellulose, for example cellulose acetate. cellulose propionate, cellulose acetate-propionate, cellulose acetatebutyrate, ethyl cellulose and benzyl cellulose;

.yarn having a basis of a polymerised unsaturated substance or substances, for example polystyrene, polyethylacrylate, polymethyl methacrylate, polyvinyl acetate, polyvinyl chloride, polyvinyl chloride-acetate and polyvinylidine chloride; and yarn composed of artificial fibres of a proteinaceous substance such as casein or soya bean protein. Yarns of natural textile fibre, for example cotton, linen, silk or wool can also be employed. The textile material selected should be in the form of strong, fine filaments. When it is intended to produce an open-work fabric by removal of the textile `yarn, this yarn should, of course, be capable of destruction by agents which will not damage the wire. Regenerated cellulose yarns obtained by the saponification of highlystretched cellulose acetate yarns are particularly suitable in all .these respects. Other of the textile fibres referred to above can be employedwith advantage-in the form of yarns having a high tenacity.- For instance high tenacity yarns of any ofthe cellulose derivatives specified may be used.

The nature of the agent employed to disintegrate the textile material will of course depend on the nature of that material. For materials of natural or regenerated cellulose, ex'cellent results have been obtained with cuprammonium sulphate. Other agents capable of disintegrating these materials are strong mineral acids, e. g. lhydrochloric acid, capable of .effecting rapid hydrolysis of cellulose, and salts, for example the alkali metal thiocyanates, capable of dissolving cellulose. In the case of natural and artificial textile materials having a proteinaceous basis, strong alkalies will usually be found effective. For cellulose derivatives and polymerised unsaturated fibre-forming vsubstances appropriate organic solvents can be found, for example, in .the case of cellulose acetate, acetone can be employed. In selecting an agent for disintegrating the textile material, agents which would damage the wire will of course be avoided.

Having described my invention, what I desire n to secure by Letters Patent is:

l. A woven fabric suitable for intercepting ,aalaaea and weft narrow bands of ne copper wire. at least two warp wires being interlaced with at least two weft wires at each crossing of the wire bands of warp and weft, in any sample the ratio of the total area of the spaces between the wires to the product of the diameter of the wire and the length of the wire in said'sample being not less than about 8:1, and the spaces enclosed by the bands of wires being filled with interwoven non-metallic textile yarns. y

2. A woven fabric suitable for intercepting radio signals, said fabric having in both warp and weft narrow bands of fine copper wire, at least two `warp wires being'interlaced with at least two weft wires at each crossing of the wire bands of warp and weft, in any sample the ratio of the total area of thespaces between the wires to the product of the diameter of the wire and the length of the Wire in said sample being between about 10:1 and about 20:1, and the spaces enclosed by the bands of wires being filled with interwoven non-metallic textile yarns.

3. A woven fabric suitable for intercepting radio signals, said fabric having in both warp and weft narrow bands of fine copper wire, at

least two warp wires being interlaced with at` 6 enclosedl by the bands of wires beinglled with interwoven regenerated cellulose yarns of tenacity at least 4 grams per denier. y

4. A woven fabric suitable for intercepting radio signals, said. fabric having in both warp and weft narrow bandszof une copper wire, at least` two warp wires being 'g interlaced with at least two weft wires at each crossing o f the wire bands of 'warp and weft,"in any sample the ratio of the total area of the spaces ybetween the wires to the product of the diameter of the wire and the length of the wire in said 4` sample being between about 10:1 and .about 20:1, the spaces enclosed by the bands of wires being filled with interwovenvno'n-metallic textile yarns and each of said spaces being of area about ya square inch.

5. A woven fabric suitable for intercepting radio signals, said fabric having in both warp and weft` narrow bands of flne copper wire, at least two warp wires being interlaced with at least two weft wires at each'crossing o`f the wire bands of warp and weft, in any sample the ratio of the total area of the spaces between the wires to the product of the diameter of the wire and the length y of the wire in said sample being between about 10:1 and about 20:1, the spaces enclosed by the bands of wires being filled with interwoven-regenerated cellulose yarns of tenacity at least 4 grams per denier and each of said spaces of area about Vg square inch.

HARRY CRAwsnAw.

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