US2154530A - Screen cloth and method of making the same - Google Patents

Description

S. D. ROBINS April 18, 1939.

HEEGTDNLQJ@ y Patented pr. S, 93

vUNITED STATES SCREEN CLOTH AND METHOD` OF MAKING THE SAME- Samuel Davis Robins, Hewlett, N. Y., assigner to Robins Conveying Belt Company, Passaic, N. J., a corporation of New Jersey Application April 1,4, 1938, Serial No. 201,967

4 Claims.

This invention relates to the art of manufacturing coarse heavy screen cloth, such, for example, as is used in the operation of screening gravel, stone,` coke and other abrasive materials.

VThe customary practice in fabricating coarse screen cloth composed of rods of the common variety of steels, consists in cutting the rods to the determined length, press crimping each of the rods throughout its length by passing it between suitable dies, and, finally, weaving the crimped rods to form a panel of determined area having square meshes composed of intersecting warp or shoot rods or wires. Such cloth is usually woven on a hand loom, the weft or shootfrods being manually introduced in the successive sheds of the warp rods or wires.

In screen cloth wherein the openings are very large (say 2") and the rods are of proportionately large diameter (say the warp rods are clamped in spaced parallel relation on a heavy bench and are then transversely bent one at a time by means of a suitable claw lever to Aproduce in the series of rods aligning bends pointing alternately in opposite directions. A shoot rod is then forced laterally into the aligning bends of the series of Warp rods. The fwarp rods are then similarly bent reversely at spacedY intervals and another shoot rod is laterally forced into the resulting aligning bends; and so on the Warp rods are manually bent by means of the lever, and the shoot wires are successively applied until the screen panel has been completed.

In the cheaper grades of abrasive resistant screen cloth spring steel rods are used, that is,

most of the hardness of the rods is obtained by .the mechanical process of drawing the rods through dies; whereas in the superior grades of cloth greater hardness, without sacrifice of other desirable physical properties, such as fatigue resistance and durability, is obtainable by the use of rods that have been heat treated. In the latter case the service life of the cloth far exceeds that of cloth composed of rods of mild steel. Consequently in the fabrication of abrasive resisting wire cloth the treatment of the rods to high hardness is. a desideratum, but since hard steel will not stand deformation the hardness permissible is necessarily limited by the process of weaving the cloth, (which necessitates bending) and also by the press crimping operation. It is to be noted that the press crimping of steel heat treated to a greater hardness than '45 Rockwell C is possible if subsequent bending voi the rods in weaving can be avoided.

It is also to be noted that it is impractical to press crimp the steel in its mild state, weave the rods into the finished cloth, and then heat-treat the final screen cloth to the desired hardness, because all woven rod screen cloth must have spring set. That is to say, in the finished condition of the cloth there must exist bearing pressure at every intersection of the interwoven rods, as otherwise any looseness of the weave results in rapid wear at the intersections. Heat treating a finished piece of screen cloth is practically impossible without its losing whatever spring set it possesses prior to the quenching temperature, for as soon as the rods become red hot they lose their strength and relax the necessary pressure at the intersections.

The principal object of my invention is the A useful in the screening of hard abrasive materials such as hereinbefore indicated, wherein the cloth has relatively large meshes or openings, say 5/8" or more, made of comparatively large diameter rods, say, in diameter and larger.

'I'he improved screen cloth and the preferred mode of producing the same according to my invention Will be hereinafter described, and the scope of the invention then expressed in the appended claims.

In the drawing- Figure l is a perspective view of a piece of screen cloth embodying the principle of my invention.

Figs. 2, 3 and el are similar views showing succeeding steps in the method of assembling the rod or wire elements of the screen cloth.

Referring to Fig. l of the drawing, I and 2 designate interspersed crimped steel rods arranged in spaced parallel relation; 3 designates similarly crimped rods arranged transversely of and in alternate upper and lower bearing relation to the rods l and 2, and 4 designates rods, straight, or substantially so, which are interwoven with the rods I and 2. The rods 4 are arranged in parallelism and in alternate relation with the rods 3, all the assembled rods being tightly interlocked by the bearing pressure, or spring set, of the rods at the respective Vso Vas

intersections, thus providing a strong unitary screen structure of suitable size for its intended use.

In carrying out my invention in the preferred way, the rods I, 2 and 3 are crimped and then heat-hardened prior to their assembly, the rods` 4 being heat-hardened only. A set of the hardened crimped rods I are then laid on a table in the relative position they are to occupy in the finished piece, as indicated in Fig. 2. In this View two spaced rods I are represented but, of course, in the production of the fabric a predetermined multiplicity of rods, each of suitable length and diameter, are similarly arranged in a row and in spaced parallel relation. Next a set of the rods 3 are laid across the rods I in their respective positions, with the bends 5 of the rods 3 in registry with the opposite bends 6 of the rods I, as seen in Fig. 3. Next the rods 2 are laid parallel to the rods I and across the rods 3 with their opposed bends in registry, as seen in Fig. 4. Finally, with the three sets of rods I, 2 and 3 in the positions indicated, the set of straight rods 4 are introduced by endwise driving them through the space above the rods 2 and beneath the rods I, as seen in Fig. 1, such introduction of the rods 4 being effected in opposition to the spring set without producing permanent set or deformation of the crimped rods. The straight rods 4, which compose no more than one-fourth of all the rods and bound one side of each of the meshes or openings of the screen cloth, efficiently co-act at their intersections with the crimped rods I and 2 to ensure a screen cloth structure possessing throughout its entire area the necessary rigidity and high hardness to resist severe abrasion and withstand long service.

It will be seen that by longitudinally removing or replacing the rods 4 the elements of my improved screen cloth can be disassembled or assembled without subjecting any portion of any of the component rods, or Wires, to severe stresses that will produce permanent set or deformation as distinguished from spring set of the rods.

It will also be seen that the said cloth can be readily and economically repaired after part of it has become broken or worn; that is to say, the broken or worn elements of the cloth can be disassembled and new elements reassembled in the salvaged portions of the screen cloth, all with freedom from bending or overstressing any of the elements.

It will also be seen that the crimping of the rods I, 2 and 3 before the heat-hardening step, reduces the force and resulting Wear on the dies and tools by means of which crimping is accomplished, and also ensures a nal hardness which is unaffected and unlimited by the screen manufacturing process. In fact, by the method described I Vhave made 60 Rockwell C screen cloth, which has lasted twice as long as the best record heretofore attained by several conventionally woven screen cloths.

It is to be understood that in some cases the press crimping of the rods I, 2 and 3 may be accomplished after heat treatment, and such rods together with the rods 4, then assembled n the manner hereinbefore described.

The term substantially straight, as used in the appended claims in relation to the rods 4, is intended to comprehend rods having, for example, slight notches or shallow crimps that serve -to assist their permanent location at the intersections, yet not involving much deflection of themselves or the other rods with which they engage when being driven into the structure.

I claim:

l. Screen cloth of the character described embodying crimped rods arranged in spaced parallel relation, spaced similarly formed rods arranged transversely of and in alternate upper and lower bearing relation to the rst-named rods, and a plurality of substantially straight rods arranged in alternation with the second-named rods and in spring setting relation with the upper and lower crimped portions of the first-named rods.

2. In the manufacture of screen cloth of the character described, the method which includes arranging crimped rods in spaced parallel relation, placing upon and transversely of the said rods similarly formed rods arranged in spaced parallel relation, placing similarly formed rods upon the second-named rods and in alternation with and parallel to the first-named rods, and, finally, spring setting all of the rods by endwise driving substantially straight rods between and in interlocking relation with the opposing crimped portions of the first and third named rods, the said endwise driven rods being in alternation with and parallel to the second-named rods.

3. In the manufacture of screen cloth of the character described, the method which consists in crimping steel rods and then heat-hardening the crimped rods, arranging a set of said rods in spaced parallel relation, placing upon and transversely of the said set of rods a set of similarly formed rodsarranged in spaced parallel relation, arranging a third set of said rods upon the second-named set and in alternation with and parallel to the rods of the first-named set, and, nally, spring setting all of the rods by endwise driving a set of substantially straight rods between and in interlocking relation with the opposing crimped portions of the rods of the first and third named sets, said endwise driven rods being in alternation with the rods of D the second-named set.

4. In the manufacture of screen cloth of the character described, the method which consists in crimping steel rods and then heat-hardening the crimped rods, arranging a set of said rods

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