BELT EDGE

Abstract

The present invention relates to a belt comprising a warp yarn and a weft yarn, wherein the belt comprises a fused region along each longitudinal edge of the belt, said fused region being formed from the warp yarn, the weft yarn and a yarn provided for fusing the warp yarn and the weft yarn together.

Claims

1. A filter belt comprising a warp yarn and a weft yarn, wherein the belt comprises a fused region along each longitudinal edge of the belt, said fused region being formed from the warp yarn, the weft yarn and a yarn provided for fusing the warp yarn and the weft yarn together.

2. A filter belt according to claim 1, wherein the melting point of the fusing yarn is below the melting point of the weft yarn and the warp yarn.

3. A filter belt according to claim 1, wherein the melting point of the fusing yarn is between 70 and 180° C.

4. A filter belt according to claim 1, wherein the melting point of the fusing yarn is between 70 and 140° C.

5. A filter belt according to claim 1, wherein the fusing yarn comprises a low density polyethylene, a polyester, a polyamide, a copolyester a copolyamide or a mixture thereof.

6. A filter belt according to claim 1, wherein the fusing yarn has a density below the density of the warp and weft yarns.

7. A filter belt according to claim 1, wherein the fusing yarn comprises low density polyethylene and the warp and weft yarns comprise polyethylene.

8. A filter belt according to claim 1, wherein the fusing yarn comprises low density polyethylene and the warp and weft yarns comprise polypropylene.

9. A filter belt according to claim 1, wherein the fusing yarn is a bi-component yarn.

10. A filter belt according to claim 9, wherein the bi-component yarn comprises a core sheath structure, said sheath having a melting point below the melting point of the warp and weft yarns.

11. A filter belt according to claim 10, wherein the bi-component yarn comprises polyester and copolyester or polyimide and copolyamide yarns.

12. A filter belt according to claim 1, wherein the fusing yarn has a monofilament, staple or multifilament structure.

13. A filter belt according to claim 1, wherein the ratio of fusing yarns to warp yarns is 1:1, 1:2, 1:3, 1:4, 2:1, 3:1 or 4:1.

14. A filter belt according to claim 1, wherein each fused edge region has a width between 5 mm and 70 mm.

15. A filter belt according to claim 1, wherein the fused edge region has a width between 30 and 70 mm.

16. A filter belt according to claim 1, wherein the fused edge region has a width between 50 and 70 mm.

17. A filter belt according to claim 1, wherein the diameter of the fusing yarn is between 0.10 mm and 0.60 mm.

18. A filter belt according to claim 1, wherein the warp yarn and/or the weft yarn comprises a polymer selected from polypropylene, polyethylene terephthalate, polyethylene, polybutylene terephthalate, polyphenylene sulphide, poly-paraphenylene terephthalamide or a combination thereof.

19. A filter belt according to claim 1, wherein the linear density of the warp yarn and/or the weft yarn is from 150 to 4400 dtex.

20. A filter belt according to claim 1, wherein the warp yarn has a monofilament, multifilament, or staple fibre structure.

21. A filter belt according to claim 1, wherein the belt comprises a plain weave, double plain weave, a twill weave or a satin weave.

22. A filter belt according to claim 1, wherein the belt comprises a tracer yarn.

23. A method for producing a filter belt comprising: a. providing a plurality of warp yarns; b. providing a plurality of weft yarns; c. providing a plurality of yarns for fusing the warp yarns and the weft yarns where they meet, said fusing yarns being provided along each longitudinal edge of the belt; d. weaving the plurality of weft yarns through the warp yarns and fusing yarns for bonding the warp and weft yarns, and e. subjecting the belt thus formed to a heat treatment to form a fused region from the warp yarns, the weft yarns and the fusing yarns.

24. A method according to claim 23, wherein the fusing yarn is provided substantially parallel to the warp yarn.

25. A method according to claim 23, comprising hot-knife slitting the filter belt after the heat treatment.

26. (canceled)

27. A filter belt according to claim 1, wherein the filter belt is a tower press filter belt.

28. A filtration apparatus comprising a filter belt according to claim 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0054] In order that the invention may be more clearly understood an embodiment/embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, of which:

[0055] FIG. 1 shows a cross section of belt comprising warp yarns, weft yarns and a fused region formed from the warp yarn, the weft yarn and the yarn for fusing the warp and weft yarns.

[0056] The above embodiment is described by way of example only. Many variations are possible without departing from the scope of the invention.

[0057] FIG. 1 shows a cross section of a belt (1) comprising a plurality of interlocking warp yarns (2) and weft yarns (3). The warp yarns are longitudinal (i.e. they run in machine direction) and the weft yarns are woven through the warp yarns in a direction perpendicular to the machine direction. Further yarns (4) for fusing the warp yarns and the weft yarns are provided substantially parallel with the warp yarns (i.e. they also run in the machine direction) at each longitudinal edge of the belt.

[0058] In this example the warp yarn (2) is made of multifilament polypropylene and has a linear density of 2200 dtex. The weft yarn is made of monofilament polypropylene with a diameter of 0.5 mm. The fusing yarn (4) is made of low-density polyethylene having a diameter of 0.22 mm.

[0059] The following formula may be used to determine the optimum number of fusing yarns (FY) at each belt edge, where WT is the number of warp threads per cm, WE is the width of the edge (cm) and R is the desired ratio of FY:WT:

No. of FY=(WT)×(WE)×(R)

[0060] In this example, the frequency of fusing yarns to warp yarns at the belt edges is 1:1, with the fusing yarns being provided in an alternating arrangement with the warp yarns. Further, the edge width is 3 cm and there are 27 warp threads per cm, such that 81 fusing yarns are provided at each belt edge.

[0061] The belt (1) comprising warp (2), weft (3) and fusing yarns (4) is subjected to a heat treatment in order to heat set the belt. The polypropylene belt with fusing yarns is heated to a temperature between 135 and 140° C. The heat treatment causes the low-density polyethylene fusing yarns, having a melting point below that of the polypropylene warp and weft yarns, to melt. This melting allows the polymer to flow over the belt surface giving an appearance similar to that imparted when a “hot melt” glue is used to seal edges of a belt. This provides a good aesthetic appearance, but importantly the warp and weft yarns are physically bonded/fused together where they meet. The region in which bonding/fusing of the yarns occurs may be termed a fused region” or a “fused edge region”. In this example, each fused edge region is 3 cm in width.

[0062] A “Hot-knife” is then used to slit and seal the outermost 1-2 cm of the belt edge. This prevents or at least reduces fraying, without any significant differential in tensile properties compared to the main body of the belt.

[0063] Tensile strength tests were performed according to DIN EN ISO 13934 (ZWICK/ROELL, Type 1465, Ser. No. 11/437,404) on belts having an identical warp and weft construction and weave design in order to determine the strength of the main body of the belt (C1), the strength of an embossed edge of the belt (C2) and the strength of a fused edge of the belt (E1). The test samples were 25 mm wide and 50 mm in length. The results of the test are shown in Table 1.

[0064] The comparison work showed that a reduction in tensile strength within the embossed edge takes place, whereas the tensile strength of the fused edge remains nearly the same. The embossing damages the structure of the warp and weft yarns in the edge region, thus weakening the yarns. The resulting belt edge is significantly reduced in strength as a result. In the case of the present invention the warp and weft are not weakened. The belt edge is at least as strong as the main body of the belt, the main body corresponding to the filtration region of a filter belt. The belt of the present invention also exhibits improved edge durability.

TABLE-US-00001 TABLE 1 F/max L @ F- Yarn-diameter Weave Samples (N/cm) max (%) (warp/weft) Polymer pattern C1 2706.7 32.7 dtex 2200/dtex Polypropylene Twill 2200 tape C2 1463.1 16.4 dtex 2200/dtex Polypropylene Twill 2200 tape E1 2979.8 34.7 dtex 2200/dtex Polypropylene Twill 2200 tape