US2804208A - Vibrating screen - Google Patents

Description

A g- 27, 7 A. VAN HARDEFELD EIAL 2,804,208

VIBRATING SCREEN Filed July 14, 1953 2 Sheets-Sheet l M 5 Van Hn 'c efi 4 ana ranc/scans M' Van Ti/lo 3 M12 vawaw g- 27, 1957 A. VAN HARDEFELD ETAL 2,304,208

VIBRATING SCREEN Filed July 14, 1953 2 Sheets-Sheet 2 '1 T 'T T'C 35 3'2 s1 33 FIG. 4

3d will WWL United States Patent VIBRATING SCREEN Andries van Hardefeld, Hoensbroek, and Franciscus M. van Tillo, Stein, Netherlands, assignors to Stamicarbon N. V., Heerlen, Netherlands Application July 14, 1953, Serial No. 367,874

Claims priority, application Netherlands July 19, 1952 11 Claims. (Cl. 209-403) This invention relates generally to improvements'in vibrating screens. More particularly, the invention relates to vibrating screens of the type having a number of wire screening cloths arranged in series in the direction in which material is transported when it is being screened, which screening cloths are pulled taut transversely by means of a stretching device.

In vibrating screens of the aforesaid type, employed hitherto, the successive screening cloths are arranged in such a way, that the adjacent edges of successive cloths overlap each other in order to avoid gaps between the cloths through which material being screened might fall. As each screening cloth has to be tensioned separately, only that part of the transverse edges of the cloths which is situated between the overlap zone ends of the cloths can be gripped by the stretching device in this arrangement. The result of this is that the overlapping front and rear edges of the cloths are unstressed, so that these edges will beat against each other and against the supporting structure of the screening deck during the screening operation. This will soon lead to wire breakage due to fatigue of the wire material. In consequence, the life of the screening cloths is comparatively short.

Having in mind the defects of the prior art of screening it is the primary object of the invention to provide a vibrating screen in which the life of the screening cloths is considerably increased compared with that of known screening apparatus.

Another object of the invention is to provide a vibrating screen in which the successive screening cloths of the screening deck are assembled in an improved manner.

Still another object of the invention is to provide a vibrating screen in which the risk of fatigue ruptures of the wires of the screening cloths is considerably decreased.

Still another object of the invention is to provide a vibrating screen in which beating of the adjacent front and rear edges of successive screening cloths against each other is prevented.

Still another object of the invention is to provide a vibrating screen in which the screening cloths are tensioned uniformly over their whole surface.

A further object of the invention is to provide a vibrating screen in which the transverse edges of the screening cloths are gripped over their whole length in the stretching device.

A still further object of the invention is to provide a vibrating screen in which the thickness of material clamped in the stretching device is equal at the whole length of the transverse edges of the screeningrcloths.

The foregoing and other objects of the invention we prefer to accomplish as follows:

According to a preferred embodiment of our invention, in a vibrating screen comprising a number of wire screening cloths arranged in series in the direction of travel of the material to be screened, the successive screening cloths are spaced apart edgewise in the screening box if ice and rubber stripping is secured to one of the spaced edges of the successive screening cloths so that it bridges the gap between the adjacent edges and overlaps the confronting edge of the adjacent screening cloth.

In this way the adjacent edges of any of two adjacent screening cloths no longer overlap each other to. give wire-to-wire contact. This makes it possible to tension the cloths uniformly over their whole length, so that fatigue ruptures due to the unstressed front and rear margins of the cloths beating against each other and against the supporting structure are avoided.

The overlapping stripping lies preferably in advance of the appertaining edge of the screening cloth with respect of the direction of travel of the material to be screened in order to prevent this material from passing under the overlapping portions of the stripping.

We prefer to provide both of the adjacent edges of successive screening cloths with rubber stripping, wherein one of the strippings coincides with its appertaining cloth edge and the other stripping extends beyond its appertaining cloth edge, so that it overlaps the coinciding rubber stripping.

The overlapping rubber strippings may be joined, for example, cemented together to prevent completely unscreened particles to pass underneath the overlapping.

In prior constructions, where the adjacent edges of the screening cloths are connected by means of bolts or rivets, damage to the cloths will be caused, while connection by soldering will form stiff zones in the screening cloths, which soon will lead to wire breakage due to fatigue of the material, as in this case the wires of the cloths will be bent sharply up and down during operation of the screen.

To prevent in the present construction sharp bending of the longitudinal wires of the screening cloths at the border line between a rubber stripping and its cloth during the screening operation, the part or the strip which is secured to the cloth may be provided at its inner edge with an indented or serrated, or undulating or the like edge, so that the transition from rubber to cloth in longitudinal direction will be more gradual. This reduces the risk of fatigue ruptures of the wires of the cloth.

By making the length of the rubber stripping substantially equal to the distance between the margins engaged by the stretching devices on either side of the cloths the thickness of material in the marginal clamps is equal over the whole length of the transverse edges. As a result of this the screening cloths may be stressed uniformly over their whole surface, so that valleys in the screen surface, in which material piles into relatively thick layers diificult to screen, are eliminated.

In another embodiment of our invention we have the screening cloths surrounded at their edges by a marginal rubber stripping, which stripping at one of the four edges of the cloths extends beyond the cloth. Also in this case the thickness of material clamped in the stretching device is equal over the whole length of the transverse edges.

The term rubber as used in this specification includes natural and synthetic rubber and elastomers having like mechanical properties to rubber.

A vibrating screen in accordance with the above brief description is hereinafter more fully described, and is shown in the accompanying drawings in which:

Figure 1 is a longitudinal vertical sectional view of a vibrating screen according to the invention;

Figure 2 is an enlarged fragmentary sectional view of one side of the screen;

Figure 3 is a plan view of adjacent screening cloths of the screen deck; and

Figure 4 is a plan view of a wire screening cloth embodying a modification of the invention,

raises-woe ldwiiig ti 9] v, ported as ndicated bythe arrows F gure tinted was tr the pale tes; length of the weight ca d ih y t 'd1sfposed t tans v If aimewTt i r mqspn tw .jwfltevi reting mechan sm "niay bc of w l'k'nown co struction and clamped in the stretching devices 3 'ar'ids'o arranged that be n d ac n cloths asmal 2W iaPi 'q t t ppears Figure 3, The transverse edges 5 of each of i fi i ,C 7. 'f't 3?? 1 ,1 W i t rlu 'l p d dl si 1 i ars d b tw efi he WI f h? 632m 6 i t i t d?- d hh inner U-fsh'a p'ed ending 7, whichen'gage's w thinthe edging ha shown if t fe'l-w h ength, t qt in: 6, and

is equal to the length of the transverse edges 5 of the re in fli na. 1 v. .t t i, S re b9 3 th' weinw dlr turn Pe 8, which engage within the inner U sha'ped e'dging n n The vertical side wall s pf frarne 2 are. provided witli s ots Band 10. In the upper slots 9 bolts 11 having, a late i he 2.7 am issued by mean? f e t? 3- The head 1'2 ,is providedwith a horizontal groove 14 Lin up e B C! PQ Qn 1516 Stretcher i k l 3, 1-

P N N the were an 1'11 a e H pr y th I 1L a .j i tt t 'ts s" 9 bolts 11in the denied height 6f p a es, 1 an va e 3 is greeted by securing insl'ots9, g H I a I Longitudinal hooks 20 are .at't'ached to the fran c 2, on which hooks trans verse beams 21 re rnour ted. Beams 21 carry longitudinal girders '22 provided with rubber-linings 23 at their upper edges 24 for supporting screening deckil. I, i l i i v U v Each or the screeningfcloths 1c, 1" and 1. is provided Ialongits rear edge 25 with arubber strip 26 which is vi lcaniied into the screening cloth so 'as not to extend beyond said 'edge. A broader strip 27' is vulcanized fto the front edge 28 of the cloths and extends beyondsaid 'edge fso as to ovefrlap and cover strip :26 onthe rear edge 25 of the adjacent cloth If desired the 's' o overlapped rubber strips 26 and 27 may be joined,'for example-"ad- 'v -h a 7 As the weight oi the rubber lined edges 25 and 27 "is greater than the'uncoat'ed portions of the screening cloths 1', 1" and 1f" the amplitude of the margins difiers from it that of the uncoated portions during screening operation. Th"- will result in a bending of the longitudinal wires of the screening cloths at the border line between the'rubb'er '"strips zs'and 27 andtheuncoveredportion of the cloth which will give rise to fatigue rupturesin cla'sie this bendiiig is effected ov'er alsriiall radius. To over eqrn; objection I preferio prdvide thestrip's with a mannered,

a "4 I for instance an indented edge 29 at the border line between the rubber stripping and the uncovered cloth to avoid an abrupt transition from the strips to the uncovered portion of the screening cloths, as shown in Figmre 3. In this case the wires ofthe cloths will be bent over a region defined by the depth of the recess 29 in the indented edge 29 which results in a rnuch greater bending radius. As appears in Figure 3 only "the larger strip 27 is providedwith an indented edge 29', whereas the smaller strip 26, which is lighter'in weight concides with the stressed edge 25 of the clothand which therefor has substantially the sarne amplitude as the uncovered portion of cloth 1" is unchamfered. It will however, he understood that it falls within the scope of this invention to provide also strip 26 with a chamfered edge, as shown in Figure 4 at 26'. 1

The length of the rubber strips 26 and 27 is such that the transverse rnarginsfi which are clamped in the stretching eneas are .tuned ife'd. As a consequence, the thickness o f riiaterial in the 'edg'ing's 6 and 7 is equal along the entiriefljerigth otith'escre'en' deck 1, so that the screening cloths 1", 1 and 1" can be readily tensioned u'iii forntly ,The sariie result canbe obtained when, as shown in'Figiire 4, e enin'g cloths aresurrounded atth eir edg es byia arginal rubberlining 30, which at one of the edges iitends bfeyohd the cloth; The width 'ng 'portion 32 is s'u chth at on both sides of the po 'o recesses 2:3 am Ip'r'es'eii tof a width substanliq the width rqfithje transverse margins 5' to be clamped'in the stretching device. When H ening boir 2 the extending'p ortion 32 o'f th'e rubber liningfii} overlaps the rubber lining of an ad acent cree'nlng cloth.

appe s '1; Figure l material to befscreened is supplied'ait'fl Qon thefentrance 'plate 35 rr ofunted transversely in the scr'e' ing bfogtiZ Entranceplate 35 is provided at its'fr nt cdgelwithja rubber strip 36 overlapping the firs't SCI CCD II Ig CiOLIh of the series. Strip '36 prevents matc'rial n'o'm passing uiis'cree'rjedthrough the gap between entrance 'piat e, 35 arid screening cloth l and may be joined, for i'nsta'nce ented, to the rubber strip 26 on the rear edge 25:61? screening cloth 1". The mate rial to be screened passes subsequently the successive screening cloths 1'-, and 11", whereby the undersize particles having adimeri'slon sinaller than the mesh of the screen ing cloths pass th 'ough the nies'lies of the screen and are collected in areceiv'er, not's'hown in the drawings, 'disposed below the screen box The oversize particles are jcharg e'd'at 37 over a discha g'eplate 38 arrangedtransyersely "at the jend of the screening box 2. Theilargger rubber str'ip LZf/ at the fronted'g'e of the last screening cloth '1' overlaps the discharge plate 38 and may be vulcanized thereto.

Example A vibratingscreen'accbrdingtothe invention operated witha frequency of lZOQvibrations per ininnt'e atan arhp litude oii 1'2 was used tor screening coal fines at an average capacity of 30 tons'p er hour. i

i The screening deck was co 'posed of four screening cloths each of 914 it 1750 rnrnhand formed of s tainless steel wovenwire of 0.5 m. in diameter and a width of "mesh of 015 'it 3.75 The successive cloths were spaced at a distance of about 3 min. At both shorter edges of the cl th's'afnargin of min. was bent in reinforcingedging's and tensioned in the stretching device. Rubber strips having a thicknessof 1.5 min. and a length of 'ISOO mm'. wre vulcani'z'ed to the longer edges of each "of the cloth's, "the strip on the rearea e coinciding with this edge and having a widthjof 2O and the strip on the f nteagqhavinga 'width of '9'0 of which 35 w1than'indented inneredge, the recesses therein The screen was in use for 2200 hours before it became necessary to replace the screening deck.

In a customary screen, where the screening cloths overlapped each other in such a way as to give direct wire-to-wire contact of unstressed edges it became necessary to replace the screening deck after 300 operating hours, although the operating conditions were practically the same as those in the previous case.

The terminology used in the specification is for the purpose of description and not for limitation, the scope of the invention being defined in the claims.

We claim:

1. In a vibrating screen a screening box, a number of wire screening cloths arranged in series in said screening box, said successive screening cloths being spaced apart edgewise, reinforced margins provided on the whole length of the transverse edges of said cloths, stretching means attached to the side walls of said screening box and engaging said reinforced margins to apply tension to said cloths, and rubber strippings secured to the spaced edges of the cloths, the rubber stripping secured to one of said edges having a width substantially equal to the distance between said reinforced margins on either side of the cloths and a length suificient to bridge the gap between adjacent cloths and to overlap the confronting edge of the successive cloth.

2. A vibrating screen comprising a number of wire screening cloths arranged in series in the direction of travel of the material to be screened, said successive screening cloths being spaced apart edgewise, and means for tensioning said screening cloths transversely, the confronting spaced edges of adjacent cloths both being provided with rubber stripping, the stripping on one of said cloths coinciding with its appertaining edge and the stripping on the other of said cloths extending beyond its appertaining edge, said extending rubber stripping bridging the gap between said adjacent cloths and overlapping said coinciding rubber stripping on the one of said cloths, the overlapping rubber strippings of adjacent cloths being joined together.

3. A vibrating screen comprising a number of wire screening cloths arranged in series in the direction of travel of the material to be screened, said successive screening cloths being spaced apart edgewise, stripping of a rubber-like material secured to one of the spaced edges of each of said successive screening cloths, and means secured to the transverse edges of said cloths for tensioning the latter transversely, said stripping of each cloth extending beyond its appertaining edge between the transverse edges of said cloth secured in said tensioning means and overlapping the confronting edge of the adjacent cloth whereby the transverse edges secured in said tensioning means are of uniform thickness, said over lapping stripping serving to prevent the material to be screened from entering between the spaced apart edges of said cloths.

4. A vibrating screen as defined in claim 3 wherein said confronting edge of each adjacent cloth is also provided with a stripping of rubber-like material coinciding with its appertaining edge, the stripping on the confronting edge of each cloth engaging the overlapping stripping of the adjacent cloth.

5. A vibrating screen as defined in claim 4 wherein said strippings of each cloth form a part of a marginal lining of rubber-like material surrounding each cloth.

6. A vibrating screen as defined in claim 3 wherein said stripping of each cloth overlaps the confronting edge of the adjacent cloth in the direction of transportation of the material to be screened.

7. A screen for use in a vibrating screen apparatus of the type having a number of such screens spaced apart edgewise and arranged in series in the direction of travel of the material to be screened and means for tensioning said screen transversely, said screen comprising a wire screening cloth having one of its longitudinal edges provided with a continuous stripping of rubber-like material, said stripping extending longitudinally beyond said edge between points spaced inwardly from the transverse edges thereof a short distance so as to overlie and engage the adjacent edge of the adjacent screen when arranged in series therewith and hence bridge the gap therebetween.

8. A screen as defined in claim 7 wherein the part of said stripping secured to said cloth is provided with a chamfered inner edge.

9. A screen 'as defined in claim 7 wherein the opposite longitudinal edge of said cloth is provided with a stripping of rubber-like material having an outer edge coincident with said edge.

10. A screen as defined in claim 9 wherein said strippings form a part of a marginal lining of rubber-like material surrounding said cloth.

11. A screen as defined in claim 9 wherein the part of both of said strippings secured to said cloth is provided with a chamfered inner edge.

References Cited in the file of this patent UNITED STATES PATENTS 344,021 Vickery June 22, 1886 2,015,087 Rafton Sept. 24, 1935 2,020,013 Bailey Nov. 5, 1935 2,651,419 Overstrom Sept. 8, 1953 FOREIGN PATENTS 552,632 Great Britain Apr. 16, 1943

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