US2969581A - Papermaker's screen with a wavy longitudinal shape and edges longer than the center potion thereof - Google Patents

Description

Jan. 31, 1961 c; BISCHOFF 2, PAPERMAKERS SCREEN WITH A WAVY LONGITUDINAL SHAPE AND EDGES LONGER THAN THE CENTER PORTION THEREOF Filed Sept. 13, 1956 INVENTOR ATTORNEY 2,969,581 Patented Jan. 31, 1961 United States Patent OfiFice maintain the paper-making machine screens longer at the 2,969,581 edges than in the middle, so that, so-to-say, play is available for the stretching of the middle portion. As long PAPERMAKERS SCREEN WITH A W O as the middle portion does not become longer than the gg THAN 5 edges these edge tears do not occur and as a result by Giinther Bischoif, Kanalstrasse 2, Heidenlieim (Brenz), Germany rolling the screen with copper rollers, especially at the Filed Sept- 1956 609,694 edges and by one-sided stressing on a stretching machine or by similar measures.

Clalms pnonty apphcatlon Germany Sept. 1955 These methods, however, fail completely in the case 9 Claimsof a screen with synthetic warp or a screen composed entirely of plastic wires, because the screen, when subjected to stressing for a short period for the purpose of lengthening the edges according to the method hitherto generally employe would immediately spring back into its initial shape.

The lengthening of the screen edges can beefl'ected by winding the screen on a roller which is turnedslightly concave towards the middle, whereon the screen fabric is set when on the roller in a state with its edges stretched and with a roving forced therein.

Another method of lengthening the edges consists in stretching an endless screen, such as an ordinary papermaking machine screen, over a device which comprises three rollers maintained at a predetermined distance apart by means of rigid distance pieces but themselves capable of sagging or deflecting under shrinkage stressing to The invention relates to a paper-making machine 15 screen in which at least the warp wires are made from synthetic material. The object of the invention is to imthe direction of travel.

It could not be predicted with certainty that the grooving of the warp wires would also take place in the case of screen fabrics made from known synthetic materials; i) this was, however, actually the case. Experiments to overcome this objection by using the same weaving-technical measures i in the case of P Screens screen fabrics with plastic Warp and plastic weft are suitgq the rovmg fii have fafled so that able for applying the method according the invention. or t paper'ma. ng mac screen.s made from 40 Further features of the invention vand the advantages sypthenc fabnc Plastlcnietal mixed fabncs could not thereof will become apparent from the following descripgam a firm footing m Practlce' tion of examples of forms of construction, from the It has now been found that when making screens with drawings and from the claims The drawings are a synthetic warp and a metal weft or screens with syngrammatic illustrations showing in thetic warp and web, this roving can be achieved in Fig. 1 a top plan i of a d i e for forcing a rova manner which is just as simple and effective by impartin the Warp wire of a Screen fabric. 1 n I ing to the warp of the screen fabric already woven with Fig 2 a Section of a screen fabric Provided with a a straight warp, a wavy shape by transversely stressing in i plane the.fabr m alternate dlrectlon, Fig. 3 a section of a screen fabric with lengthened edges. mg and settmg m thls Shape The f i 1s Fig. 4 a section of a screen fabric which is both propreferably exerted on the screen fabric while it 1s being 59 vided with a and also has lengthened edges;

Fig. 5 an elevation of a concave-turned roller for lengthening the edges of the screen; v I Fig. 6 a side view of a device composed of three rollers according to the predetermined wave length and ampliproducing a lengthening of the edges of an endless tude' The Wave length can m to betweemso and screen seen at the commencement of the stretching or 500 centimeters and the amplitude between 0.2 and 2 lengthning operation centimeters Fig. 7 a device according to Fig. 6 at the end of the The method is preferably applied to paper-making mat chine screens which are made from thermoplastic synjgig gf s i g ggg operation Wlth stretched screen thetic materials and the screen, after being wound on the 6 roller or roller aggregate is then thermoset in a suitable g g i z f gg View of a device for both edge apgaraglls such ashan a g c r n o th sore S of First the production of the roving will be described no i g i g g i g i efieczvel g with reference to Figs. 1 and 2. l0 designates a storage 533221 1255 g s p the present invention g gz roller, with a winding roller 11, hereinafter called the 35 setting roller; 12 is a web of screen fabric which may in edge tears which occur as a result of the action of moisbe made from thermoplastic synthetic material based on ture and tension over a long period of time, because the 1 middle of the screen stretches in relation to the edge polyvmylchonde super polyamlde polyvmyhde chloride or the like.

zones of the screen and consequently the edge zones be- T come overstressed, with the result that the edges tear, Uniform 9 {movements are lmpafted t0 the g roller in the direction of the two headed arrow 13' in such as stated, and roll in. For a long time this phenomenon has been combatted by employing suitable measures which a manner that the screen fabric 12 winds itself in wavy a concave turned roller. Screen fabrics for paper-making machines with synthetic warp and metal weft, as well as a screen with systhetic warp and plastic coated metal weft and finally also shape on the setting roller 11, namely with a wave length in the order of 50 to 500 centimeters and an amplitude of 0.2 to 2 centimeters.

Due to the winding process, the wavy shape forced into the screen fabric web is'held, firmlyand the setting roller 11, when a thermoplastic synthetic material is used, is introduced, for example, into an autoclave and therein subjected to. a thermosetting process, known per se.

The screen 12, unwound from the setting roller 11, then has. the wavy shape illustrated diagrammatically in Fig. 2, that is the warp 14 is now provided with a roving while the weft 15 has remained substantially straight.

In the case of the screen fabric web illustrated in Fig. 3 and designated as a whole by the reference 56, the edge zones 50a are lengthened in relation to the middle zone 55b of the screen, as indicated by the hatching.

In the case of the screen fabric web illustrated in Fig. 4 and designated as a whole by 106, the edge zones 10011 are not only lengthened in relation, to. the middle zone 100b, but also the fabric web itself is provided with a roving.

The lengthening of the edges can be effected with the aid of a roller illustrated in Fig. 5 and designated by 150. This roller is turned so that it is slightly concave at 150a.

Figs. 6 and7 show the lengthening of the screen edges of an endless, for examplesewn screen 209. The screen 200 is slipped onto two cylinders 291 and 202 and, after a third cylinder 203 -has been applied, the whole screen is wound under tension into a kind of packet (Fig. 7). At the end of the winding. operation, the cylinders are held at a predetermined distance apart by means of rigid distance pieces and the whole is then subjected to a steam and setting treatment so that, due to the shrinkage stress which then occurs, the cylinders sag or bend to a predetermined extent, with the result that the screen can shrink less at the edges than in the middle and as a consequence the same effect is obtained as in the case of the winding on the cylinder or roller 150 (Fig. 5). To provide a combined edge stretching and roving, this can be accomplished by apparatus illustrated in Fig. 8 in which the cylinder 150 moves transversely as indicated by the double arrow 13. The web 12 of screen fabric is set on the roller 150" and as shown there is a combined operation of stretching and roving.

1 claim:

1. A paper-making machine screen comprising weft and warp monofilaments of which the warp filaments are composed of a synthetic material and the weft filaments are metal, and the longitudinal edges on both sides of the screen being longer than. the longitudinal center length of the screen.

2. A paper-making machine screen comprising weft and warp monofilaments of which the warp and weft filaments are composed of a synthetic material and the longitudinal edges on both sides of the screen being longer than the longitudinal center length of the screen.

3. A paper-making machine screen comprising weft and warp monofilaments of which the warp filaments are composed of a synthetic material and the weft filaments composed of a metal core with a synthetic covering material, and the longitudinal edges on both sides of the screen being longer than the longitudinal center length of the screen.

4. A paper-making machine screen comprising weft and Warp monofilaments of which the warp filaments are composed of a synthetic material and the weft filaments are metal, and the warp having a wavy shape in alternating directions in the plane of the web the edges of the screen being wavy and parallel to each other as viewed in plan.

5. A paper-making screen comprising weft and warp filaments composed of a synthetic material, the warp having a wavy shape in alternating directions in a plane of the web the edges of the screen being wavy and parallel to each other as viewed in plan.

6. A paper-making machine screen comprising weft and warp filaments, the warp being composed of a synthetic material and the weft having a metal core and synthetic covering, and the warp having a wavy shape in alternating directions in the plane of the web the edges of the screen being wavy and parallel to each other as viewed in plan.

7. A paper-making machine screen comprising weft and; warp monofilaments of which the warp filaments are composed of a synth tic material and the weft filaments are metal, and the warp having a wavy shape in alternating directions in the plane of the web and the longitudinal edges on both sides of the screen being longer than the longitudinal center length of the screen.

8. A paper-making machine screen comprising weft and warp monofilaments of which the warp and weft filaments are composed of a synthetic material and the longitudinal edges on both sides of the screen being longer than the longitudinal center length of the screen, the warp having a wavy shape in alternating directions in a plane of the web.

9. A paper-making machine screen comprising weft and warp monofilaments of which the warp filaments are composed of a synthetic material and the weft filament composed of a metal core with a synthetic covering material, and the longitudinal edges on both sides of the screen being longer than the longitudinal center length of the screen, and the warp having a wavy shape in alternating directions in the plane of the web.

References Cited in the file of this patent UNITED STATES PATENTS

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