GB2027366A

GB2027366A - Reinforced Jigging Screens

Info

Publication number: GB2027366A
Application number: GB7922123A
Authority: GB
Original assignee: TRELLEBORG RUBBER Ltd
Current assignee: TRELLEBORG RUBBER Ltd
Priority date: 1978-05-31
Filing date: 1979-06-26
Publication date: 1980-02-20

Abstract

Conventional jigging screens, for example for classifying material in the coal industry, are often made of steel but suffer the disadvantage of being noisy and having a high rate of abrasion. The invention provides a wear- resistant jigging screen having a jigging surface essentially composed of synthetic polymeric material, the screen being rectangular in shape and possessing a regular pattern of sized apertures 4 such that elongate reinforcing members 5, or notional elongate reinforcing zones of uniform cross-section, can pass within, or along the back surface of, the polymeric material parallel to the short edge 1 of the screen and extending between the two longitudinal edges 2 so as to separate single rows of the apertures. <IMAGE>

Description

SPECIFICATION Reinforced Jigging Screens This invention relates to jigging screens, that is to say, perforated surfaces which are given a jerky reciprocating motion to assist classification of material placed thereon into oversized and undersized fraction.

In the coal industry, it is commonplace to grade material coming directly from the face. The equipment used for this is very heavy duty in nature, and to attain reasonable periods of use without down time for maintenance and reconstruction has to be designed with a particularly strong and wear resistant surface.

It is commonplace to make jigging screens directly from steel, but the resultant noise level and rates of abrasion are definite disadvantages in such constructions. Some thought has accordingly been given to producing the jigging screens in a wear resistant material, but generally speaking too thin a wear resistant layer abrades too quickly and too thick a layer detrimentally affects the rigidity of the screen.

We have now realised that, for a relatively small sacrifice in total jigging aperture, a composite screen can be constructed of adequate rigidity and good wear resistance, utilizing synthetic polymeric material as the main constructional feature.

The invention accordingly consists in a wearresistant jigging screen having a jigging surface essentially composed of synthetic polymeric material, the said screen being rectangular in shape and possessing a regular pattern of sized apartures therethrough such that elongate reinforcing members, or notional elongate reinforcing zones of uniform cross-section can pass within or along the back surface of said polymeric material parallel to the short edge of said screen and extending between the two longitudinal edges so as to separate single rows of such holes.

In non-definitive language, therefore, the invention envisages a rectangular screen with reinforcements extending through it or behind it parallel to the shorter edge and avoiding any of the holes.

The holes are preferabiy although not essentially arranged on hexagonal pattern of centres. In any event they are usually from one quarter to three quarters of the total area of the jigging surface.

Most preferably, the holes are such that in vertical cross-section they have a pronounced inward taper, with the aperture at the jigging surface being smaller than the aperture at the back. A purely cylindrical hole in a thick layer is detrimental to the screen efficiency, since pieces tend to enter but become blocked or at least take an undue time to transit the screen. However, the hole can be cylindrical for part of its depth, and this cylindrical portion can be defined by a surrounding harder polymeric, or metallic ring.

Within the general scope of the invention there are two main embodiments. In one embodiment elongate reinforcing members extend within the screen separating rows of holes and parallel to the short side. Such a reinforcing element can be a multi-strand cable stretched between two sides of the jigging screen. Although wire cable can be used, it is also envisaged to utilize stretched high tensile polymer yarn or mono filament.

The other main embodiment of the invention involves the provision of a metal backing place behind the screen and constituting a back surface thereof. Although this place is per se an apertured integral unit, with suitable spacing of the holes as defined above it can be seen that there is a notional reinforcing zone extending to separate in each case a row of holes from its neighbouring row and terminating at the sides of the frame.

We have found that in each instance, whether reinforcing internal cables or a steel back-up plate is used, that provided there is this feature of a transverse un-interrupted reinforcement an improved performance of the screen is obtained.

The present invention is not to be confused with the provision of a composite screen of rectilinear shape, in which the holes are so dimensioned and located that no edge-parallel reinforcement, or notional reinforcement member, can exist. Any hexagonal pattern of relatively large holes will exhibit some diagonal or angles direction in which such a notional reinforcement exists, but we have found specifically that the holes, if spaced somewhat further apart having regard to their diameter, allow for reinforcement parallel to the short edge of a rectangular frame.

The invention will be further described with reference to the accompanying drawing, in which: Figure 1 shows one corner of a jigging frame; Figure 2 shows a section along the stepped section line 2-2 of Figure 1; Figure 3 shows a corner of another embodiment of jigging frame; Figure 4 shows a section along a stepped section line 4-4 of Figure 3; Figure 5 shows by way of comparison only a pattern of circular apertures in a plate which does not permit any parallel reinforcement members or zones, but only such zones at an angle to the edges of the frame; and Figure 6 shows a section through a portion of an alternative embodiment of frame.

Figure 1 shows an end wall 1 and a side wall 2 of a rectangular frame, only one corner of which is shown. The walls 1 and 2 are made from a polyurethane shee 3. This sheet 3 is provided with its regular pattern of circular holes 4, each of which, can be seen from Figure 2, tapers upwardly so as to present a smaller orifice at the top surface than at the rearward surface. Within the frame there are transverse reinforcement cables 5, extending between transverse rows of holes but not obstructing their orifice. As can be seen in more detail from Figure 2, a typical cable is 7-strand and located within a notional uniform reinforcing member 8 which corresponds to the nearest approach to the notionally dividing line of holes in adjacent tranverse rows.

Figures 3 and 4 are generally similar to Figures 1 and 2. In this instance, however, the mild steel walls 1 and 2 have welded to them a backing plate 9 which forms effectively the whole back surface of the screen. However, there is in this instance no reinforcing member extending through the polyurethane surface 3, there is a notional strip of the backing plate, shown at 10 in Figure 4, which extends from one side of the jigging screen to the other as a tranverse reinforcement.

Figure 5 is a diagram showing how it is possible to aperture a screen with an hexagonal pattern of holes 11 in such a way that no reinforcement parallel to either side edge can be accommodated. It is conceivable that some form of diagonal reinforcement e.g. along the line 12 could be arranged but we have found according to the present invention that parallel transverse reinforcement is valuable.

Figure 6 shows an improvement of detail to the screen again with the purpose of increasing its effective life. The screen material 13, of polyurethane is formed with apertures which have a frustoconical portion 14 opening toward the back or underside and a cylindrical portion 15, of larger diameter than the narrow end of portion 16, opening toward the front. This structure defines a circular shoulder 1 7 to receive ring 1 of harder polymeric, or metallic, material to avoid damages to the edge of the aperture from harder material.

Claims

1. A wear-resistant jigging screen having a jigging surface essentially composed of synthetic polymeric material, said screen being rectangular in shape and possessing a regular pattern of sized apertures therethrough, such that elongate reinforcing members, or notional elongate reinforcing zones of uniform cross-section, can pass within, or along the back surface of, said polymeric material parallel to the short edge of said screen and extending between the two longitudinal edges so as to separate single rows of such holes.

2. A screen as claimed in Claim 1 in which the holes are arranged on a hexagonal pattern of centres.

3. A screen as claimed in Claim 1 or Claim 2 in which the aperture of the holes constitute from one quarter to three quarters of the total area of the jigging surface.

4. A screen as claimed in Claims 1, 2 or 3 in which the vertical cross-section of each hole is such that it has a pronounced inward taper with the aperture at the jigging surface being smaller than the aperture at the back surface.

5. A screen as claimed in Claim 4 in which the hole is cylindrical from the top surface for part of its depth.

6. A screen as claimed in Claim 5 in which the cylindrical portion is defined by a harder polymeric, or metallic, ring located in a corresponding recess in the screen to reinforce the edge of the aperture.

7. A screen as claimed in any one preceding claim in which elongate reinforcing members extend within the screen separating rows of holes and parallel to the short side.

8. A screen as claimed in Claim 7 in which each reinforcing member is a multi-strand cable of metal or polymer.

9. A screen as claimed in any one preceding claim in combination with a metal backing plate behind the screen and constituting a back surface thereof, whereby the spacing of the holes in this back surface defines notional reinforcing zones separating in each case a row of holes from its neighbouring row, and terminating at the sides of the frame.