Weaving process for making an impregnated conveyor belting

Abstract

 A problem encountered in increasing the tensile strength of conveyor belting is that when the belting is made thicker to increase its strength, it becomes difficult to impregnate the interior of the belting carcass. To overcome this difficulty, the invention provides a method for manufacturing solid woven beltings which comprises weaving a textile fabric carcass having a plurality of integrally woven layers of weft and subsequently impregnating and coating said carcass with a polymeric material, the textile carcass having five or seven integrally woven layers of weft and being woven in such a manner that the warp yarns define a plurality of continuous flow paths along which the impregnant can travel from the outer surfaces of the carcass to the interior core and each of the warp yarns defines such a path. The weft layers may be interlocked solely by dual function warp yarns all of which serve simultaneously to impart tension resistant strength to the fabric.

Description

[0001] This invention relates to conveyor beltings comprising a textile fabric carcass impregnated and coated with a polymeric material and more particularly to such beltings wherein the carcass consists of an integrally woven structure having a plurality of weft layers. Such belting is sometimes referred to as solid woven belting.

[0002] Impregnation of a textile carcass whether by rubber latex or by a plastics material such as poly (vinylchloride) (PVC) requires great care in order to ensure thorough and uniform penetration of the impregnatn into the core of the fabric, that is without penetration into the interior of the core being limited to quite localized areas. In the latter event, the resultant belting exhibits inferior qualities of tensile strength and durability. Moreover, even with the inclusion of flame retardant materials in the polymer compound, inadequately impregnated carcasses cannot be rendered fire resistant to the high standard required for use underground in coal mines.

[0003] In one widely used method of belting manufacture, impregnation of loose or open weave solid woven multiple ply textile carcasses with PiC has been found to produce belting of a surprisingly solid and durable structure. However, these solid woven beltings have, hitherto, been limited to, at most, four layers of weft. Attempts to produce beltings having more than four layers of weft have not been successful because of the inability to achieve satisfactory impregnation, particularly at the innermost core of the fabric.

[0004] The trend towards higher horsepower drives on conveyor installations has made it desirable to produce beltings having greater working strengths. This has led belting manufacturers to incorporate increasingly greater proportions of synthetic filament yarn into their constructions to the exclusion of natural or staple fibre which has inherently lower tensile strength.

[0005] Unfortunately, adhesion of the impregnant to the relatively smooth surfaced chemically inactive filament yarn is poor in comparison with natural fibre. To overcome this problem, it is known to incorporate natural or staple fibre yarn into the carcass either in the weft where tensile strength is not so important or in the warp in the form of a pile or as binder threads. The difficulty can then arise that, if the staple fibre yarn or cotton or other natural fibre yarns are incorporated into the weave to improve the impregnant adhesion, the tighter nature of the resulting weave and to some extent precisely the fibrous nature of the binders which gives the improved adhesion also tend to block the flow paths available to the impregnant in the weave with the result that the penetration of the impregnant into the weave is seriously inhibited.

[0006] An object of the present invention is to provide a method for manufacturing a relatively thick, high strength, solid woven conveyor belting which can be rendered fire resistant, for example to the standard required for use underground in coal mines in the United Kingdom.

[0007] According to one aspect of the present invention, a method for manufacturing solid woven beltings comprises weaving a textile carcass having five or more integrally woven layers of weft and subsequently impregnating and coating said carcass with a polymeric material, (such as PVC), said carcass being woven in such a manner that the warp yarns define a plurality of continuous flow paths along which the impregnant can travel from the outer surfaces of the carcass to the interior core and each of the warp yarns defines such a path. Thus in the case of a five ply carcass, the flow paths may be provided by warp yarns, each of which passes from an outermost ply to the central ply.

[0008] Viewed from another aspect, the present invention provides a method for manufacturing solid woven beltings wherein a textile fabric carcass consisting of five or more layers of weft is woven to form an integrated structure, said weft layers being interlocked solely by dual function warp yarns all of which serve simultaneously to impart tension resistant strength to the fabric, said carcass being subsequently impregnated and coated with a polymeric material, such as PPC.

[0009] In the method according to the invention, therefore, each of the warp yarns serves the dual function of imparting tension resistant strength to the carcass whilst simultaneously constituting means whereby five separate weft layers are interlocked.

[0010] The invention includes solid woven beltings whenever produced by the methods of the invention. The invention also includes a textile carcass woven as above for use in the methods of the invention.

[0011] In one construction for use in the invention, the fabric has five plies, that is to say at each weft position there are five weft yarns traversing the fabric in superposed relationship and, in order to provide a ready flow path for the impregnating material, each warp yarn passes (1) over (or under) a weft yarn in an outermost ply, (2) between two adjacent weft yarns in an intermediate ply and then (3) under (or over, respectively) a weft yarn in the centre ply, the said weft yarns in the intermediate ply being in columns of weft yarns lying between columns containing respectively the said weft yarn in the outermost ply and the said weft yarn in the centre ply. Preferably the columns containing the said weft yarns in the outermost and centre plies are immediately adjacent to the said weft yarns in the intermediate ply.

[0012] In an alternative construction for use in the invention, the fabric has seven plies, that is to say at each weft position there are seven weft yarns traversing the fabric in superposed relationship. In one embodiment of the seven ply construction, each warp yarn passes (1) over (or under) a weft yarn in an outermost ply, (2) between two adjacent weft yarns in each of two intermediate plies and then (3) under (or over respectively) a weft yarn in the centre ply, the weft yarns in the intermediate plies lying between columns containing respectively the weft yarn in the outermost ply and the weft yarn in the centre ply. Preferably the columns containing respectively the weft yarn in the outermost and centre plies are immediately adjacent to the weft yarns in the intermediate plies.

[0013] Although the invention may readily be used for the production of fabric from natural yarns such as cotton, it is particularly advantageous when used in the weaving of fabrics which incorporate a substantial proportion of synthetic filament yarns such as polyesters or polyamides or which consist wholly of such synthetic yarns.

[0014] By virtue of the construction provided by the invention, the fabric has an interstitial structure and a plastics flow path which present proper interstices for maximum take-up of impregnating material and adhesion with the fabric together with substantially uniform penetration of the impregnating material throughout the whole cross-section of the fabric. Where the fabric is a textile core for conveyor or power transmission belting, the invention thus provides a core in which all the plies are interlocked as woven and before impregnation with a polymer, for example P.V.C. is effected. A significant advantage of this construction lies in the excellent adhesion between the interconnected plies and between the fabric core and the enveloping surface coating of the impregnating material, in the latter case due to the surface pockets presented by the fabric. These features in turn impart a significant improvement to the ability of belt fasteners to engage the finished belting and, since all the warp yarns are load bearing yarns rather than simply binders, to the tension which may be applied to the belting before the fasteners yield or fail. It is preferred, although not essential, that the nature and arrangement of the warp yarns is such that the load experienced by them when the fabric is subjected to tension is shared equally and uniformly between them. This is most conveniently achieved by employing warp yarns which are identical to one another and equally spaced across the width of the fabric.

[0015] The invention will be described further, by way of example, with reference to the accompanying drawings in which:-

Fig.l is a longitudinal cross-section of a portion of a textile fabric for use in the invention;

Fig.2 is a fragmentary perspective view of a portion of a power transmission or a conveyor belt; and

Fig.3 is a longitudinal cross-section of a portion of another textile fabric for use in the invention.

[0016] The fabric illustrated in Fig.l of the drawings is a five ply fabric and accordingly at each weft position there are five weft yarns 10,12,14,16,18 traversing the fabric and arranged in superposed relationship in columns. The series of weft yarns 10 and 18 define outermost plies, the series of weft yarns 12 and 16 define intermediate plies and series of weft yarns 14 defines a centre ply. These five plies are interlocked solely by the warp yarns which are designated 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42. To achieve the required interlocking, the warp yarns are arranged to lock the outermost plies to the centre ply and pass through the intermediate plies; this is accomplished by taking each warp yarn, for example the warp yarn 20 over a weft yarn 10 in the top ply, between adjacent weft yarns 12 in an intermediate ply and then under the next but two weft yarn 14 (viewed in the warp direction) of the centre ply, and so one along the length of the fabric. Similarly, the warp yarn 42 is taken under a weft yarn 18 in the bottom ply, between adjacent weft yarns 16 in an intermediate ply and over the next but two weft yarn 14 in the centre ply, and so on.

[0017] It will be seen that this five ply construction is achieved by the use of twelve warp yarns and that the fabric may readily be woven on a conventional twelve shaft loom (giving 30 picks per repeat of the weave). The binder warp yarns all follow identical paths for a full tensile contribution. Each warp yarn binds together three plies, repeating over six picks in each ply. The arrangement of the binder warp yarns is symmetrical about -the centre ply and consists of oppositely disposed pairs of warp yarns, each pair containing 1,3,5 picks on the outermost, intermediate and centre plies respectively.

[0018] The configuration of warp yarns employed by the invention will be seen to provide a relatively open weave in the resulting fabric and although the five plies in the fabric are securely locked together, the warp yarns nevertheless will be seen to create well-defined flow paths leading to the centre of the fabric so that when the fabric is presented for impregnation by a plastics compound such as a polyvinyl compound, the latter readily penetrates completely through to the centre of the core and, due to the open nature of the weave, is also able to surround and enclose completely each weft and warp yarn. This is important from the standpoint of fire resistance since the plastics compound normally incorporates fire retardants.

[0019] It will be noted that since all the warp yarns contribute to the load bearing strength of the eventual fabric (that is to say no conventional binders or stuffers are used in the weave) the fabric is economic to produce. In the particular example illustrated it will also be observed that, because there is an odd number of plies in the fabric, the weave is symmetrical about the centre ply and this produces a substantially uniform cross- sectional strength in the impregnated fabric.

[0020] Other constructions of weave may be used within the scope of the invention. The precise weave chosen in any particular case is determined by such factors as the operational performance expected of the fabric, the nature of the plastics impregnant and the degree of plastics take-up required.

[0021] The fabric which is illustrated by way of example in Fig.l is a five ply fabric and one such fabric which is suitable as the carcass for belting is of the five ply construction shown, with the following additional characteristics:

Warp 12 ends per repeat of weave (12 shafts) 8 fold 1260d nylon (1400 Decitex) or 10 fold 1000d polyester (1100 Decitex) 8 repeats of weave per inch in the finished belt

Weft 4 ends of 840d nylon (933 Decitex) folded with 3 ends of 4's cotton at 24 picks per inch (Decitex is the count of weight per unit length of the yarn)

Take-up Actual, 220% by weight on impregnation with PVC (ratio 1:2.2) at 29 inches of mercury impregnation pressure

[0022] For belting applications, the belting carcasses may comprise five plies as illustrated in Fig.l, but in general, carcasses comprising an odd number of plies of at least five may be used. The practical limitation is the carcass itself because the thickness and stiffness of a carcass having an excessive number of plies is such as to make it almost impossible to flex round pulleys. With a five ply construction it is possible to achieve a belting strength as high as 15,000 to 20,000 lbs/inch width which is capable of coping with all but the very exceptional high horsepower drives which are encountered. However, for even higher belting strengths, the seven ply construction illustrated in Fig.3 and described below may be used.

[0023] For completeness, Fig.2 shows a portion of belting suitable for conveyor belting or for power transmission belting and indicates, entirely diagrammatically, the plastic outer sheathing 50 which remains after the textile carcass generally designated 52 has been impregnated. Where the impregnant is a material such as polyvinylchloride, impregnation is readily effected by passing the carcass 52 through a liquid suspension or dispersion of ungelled polyvinyl chloride together with a plasticiser and thereafter subjecting the impregnated fabric to a heat treatment in order to gel the polyvinyl chloride. As previously mentioned, the open nature of the weave resulting from the invention facilitates the flow of the impregnant into the core and acts strongly against the formation of cavities at the belt centre.

[0024] The fabric illustrated in Fig.3 of the drawings is a seven ply fabric and accordingly at each weft position there are seven weft yarns, 60, 62, 64, 66, 68, 70, 72 traversing the fabric and arranged in superposed relationship in columns. These seven plies are interlocked solely by the warp yarns which are designated 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 102, 104, 106, 108, 110. The principle of construction for the seven ply fabric of Fig.3 is the same as for the five ply fabric of Fig.l. Thus, to achieve the required interlocking in Fig.3, the warp yarns are arranged to lock the outermost plies to the centre ply and pass through the intermediate plies.

Claims

1. A method for manufacturing solid woven beltings which comprises weaving a textile fabric carcass having a plurality of integrally woven layers of weft and subsequently impregnating and coating said carcass with a polymeric material, characterised by weaving a textile carcass having five or more integrally woven layers of weft and further characterised in that the carcass is woven in such a manner that the warp yarns define a plurality of continuous flow paths along which the impregnant can travel from the outer surfaces of the carcass to the interior core and each of the warp yarns defines such a path.

2. A method as claimed in claim 1, characterised in that the weft layers are interlocked solely by dual function warp yarns all of which serve simultaneously to impart tension resistant strength to the fabric.

3. A method as claimed in claim 1 or 2, characterised in that the fabric has five plies, that is to say, at each weft position there are five weft yarns traversing the fabric in superposed relationship, and that each warp yarn passes (1) over (or under) a weft yarn in an outermost ply, (2) between two adjacent weft yarns in an intermediate ply and then (3) under (or over respectively) a weft yarn in the centre ply, the weft yarns in the intermediate ply being in columns of weft yarns lying between columns containing respectively the weft yarn in the outermost ply and the weft yarn in the centre ply.

4. A method as claimed in claim 3, characterised in that the columns containing the weft yarns in the outermost and centre plies are immediately adjacent to the weft yarns in the intermediate ply.

5. A method as claimed in claim 1 or 2, characterised in that the fabric has seven plies, that is to say at each weft postion there are seven weft yarns traversing the fabric in superposed relationship.

6. A method as claimed in claim 5, characterised in that each warp yarn passes (1) over (or under) a weft yarn in an outermost ply, (2) between two adjacent weft yarns in each of two intermediate plies and then (3) under (or over respectively) a weft yarn in the centre ply, the weft yarns in the intermediate plies lying between columns containing respectively the weft yarn in the outermost ply and the weft yarn in the centre ply.

7. A method as claimed in claim 6, characterised in that the columns containing the weft yarns in the outermost and centre plies are immediately adjacent to the weft yarns in the intermediate plies.

8. A method as claimed in any one of claims 1 to 7, characterised in that the warp yarns are identical to one another and equally spaced across the width of the fabric.

9. A method as claimed in any one of claims 1 to 8, characterised in that the fabric incorporates a substantial proportion of synthetic filament yarns.

10. A method as claimed in any one of claims 1 to 9, characterised in that the polymeric material is polyvinyl chloride.

Drawing