Woven fabrics

Abstract

 A woven fabric comprises at least two layers of cross-machine direction yarns, one layer having yarns of larger dimensions, e.g. diameter, and the other layer having yarns of smaller dimensions and/or 'shaped' (i.e. of non-circular cross-section). A seaming spiral is connected to the fabric by a seam binding yarn secured by at least some machine-direction yarns being looped about the seam binding yarn. The final yarn of the layer of smaller dimensioned or shaped yarns is displaced towards the opposite side of the fabric. The last two larger dimensioned yarns may be displaced towards the smaller dimensioned or shaped yarn layer, and the third yarn of the larger dimensioned yarn layer may have an intermediate diameter.

Description

[0001] This invention relates to the weave structure of a woven fabric, particularly in the edge region of a fabric which is joined by a seam to form an endless tube or belt for use as a conveyor belt, or as papermachine clothing, particularly dryer fabrics.

[0002] In particular in papermachine clothing, it is well known to weave fabrics having one or more weft yarn layers, which are usually disposed extending in the cross-machine direction of the fabric as intended to be fitted on a papermachine. Often the weft yarns will be arranged in layers having larger and smaller yarn diameters, and the smaller diameter yarns are usually provided on the paper contacting side of the fabric, to provide a finer face structure which has a reduced propensity for marking of the paper.

[0003] A frequently used form of seam is a looped seam or a spiral loop seam. In the latter, a flattened helical coil is attached to each end of the fabric, by means of a CD yarn passed through the loops of the spiral and bound onto the fabric by having at least selected machine direction yarns passed about the spiral binding yarn and reincorporated into the fabric. The seam is completed by interdigitating the spirals on opposed edges of the fabric and passing a further CD binding yarn or pintle wire through the interdigitated loops of the spirals.

[0004] It has been found that the seam thus formed will tend to be symmetrical about the so-called 'neutral line' of the fabric. In the case of symmetrically woven fabrics, comprising e.g. two layers of CD yarns of the same diameter, there is no problem as the neutral line lies in the geometric centre plane of the fabric. With asymmetric weaves, however, such as those described which may also comprise a layer of coarse CD yarns to the back and a layer of fine or shaped (i.e. having a cross-section other than circular) CD yarns to the face, the neutral line is displaced towards the fine or shaped yarn side. As a result, depending on the weave structure, the seam coils lie to the fine or shaped yarn side of the fabric and will thus tend to stand proud of the fabric on the fine or shaped yarn side, and may be recessed on the coarse yarn side. The projection of the seam proud of the paper contacting surface (fine or shaped yarn side) of the fabric means that there is an enhanced risk of marking of the paper by the seam, and it is desirable to reduce or substantially eliminate fabric features which may cause such marking, to ensure a consistent quality of paper product. Further, the proudness of the seam can make the seam more susceptible to wear and thereby create a point of weakness in the fabric.

[0005] An object of the invention is to provide a woven fabric which is constructed in such a way that projection of a seam used for joining the fabric is reduced or substantially eliminated in asymmetric fabric constructions.

[0006] According to the invention a woven fabric comprises at least two layers of CD yarns, comprising a first layer of larger dimensioned yarns and a second layer of smaller dimensioned yarns, and at at least one edge thereof, a seaming spiral connected to the fabric by a seam binding yarn, secured by at least selected MD yarns being looped about said seam binding yarn, characterised in that the final smaller dimensioned or non-circular cross-sectioned yarn is displaced to the opposite side of the fabric from the plane of said second layer.

[0007] Preferably, in consequence, the last two larger dimensioned yarns are displaced towards the plane of said second layer from the plane of said first layer. The term "dimensioned" refers to general overall cross-sectional dimensions, including diameter.

[0008] The third larger dimensioned CD yarn from the edge may be of a diameter intermediate the diameters of the yarns of the larger and smaller diameter layers.

[0009] The yarns may be of generally circular cross-section or may be of other cross-sections, e.g. flattened.

[0010] A preferred embodiment of woven fabric will now be further described by way of example, with reference to the accompanying drawing, which is an enlarged diagrammatic cross-section showing part of the weave structure of the preferred woven fabric.

[0011] As shown in the drawing, a specific example of a fabric intended for use as papermachine clothing, specifically a dryer fabric, or a filter belt, etc., comprises a two layer cross-machine direction structure of weft yarns, comprising a machine-side layer 10 of larger diameter yarns 11 and a paper-side layer 12 of smaller diameter or shaped yarns 13, the smaller diameter or shaped yarns 13 being spaced between and to the paper-side of the larger diameter yarns 11.

[0012] This pattern of cross-machine (CD) yarns is maintained until the end region of the fabric, where one smaller diameter yarn 14 is placed on the machine side of the fabric, and the last two larger diameter yarns 15, 16 are displaced towards the paper-side of the fabric.

[0013] A terminal binding yarn 17 is used to bind the loops of a flattened helical spiral 18 to the edge of the fabric, and this in turn is used to join opposed ends of the fabric by interdigitating with the loops of a matching spiral 18a and passing of a pintle wire or seam binding yarn 19 through the interdigitated loops.

[0014] The fabric is completed by weaving of machine direction (MD) warp yarns such as for example 20, which comprises a main reach 20a which is for example floated over pairs of smaller diameter or shaped yarns 13 in layer 12, and over a single larger diameter yarn 11 in layer 10, then looped about binding yarn 17, and a back-woven reach 20b, woven back from the loop about binding yarn 17, into the body of the fabric.

[0015] The penultimate CD yarn 21 in machine side layer 10 is of a diameter intermediate between the diameters of the larger diameter yarns 11 of layer 10, and the smaller diameter yarns 13 of layer 12.

[0016] Selected warp yarns such as yarn 20, are looped about the binding yarn 17, while to create space for the loops of spiral 18, others of the warp yarns, not shown, may be looped about the terminal larger diameter CD yarn 16.

[0017] The effect achieved by the fabric structure according to the preferred embodiment of the invention is to seat the spiral 18 away from the paper-side of the fabric.

[0018] There may be two or more smaller diameter yarns 14 placed on the machine side of the fabric, more than the last two larger diameter yarns 15, 16 may be displaced towards the paper side of the fabric.

[0019] In a further feature of the invention, the MD yarn 20 is preferably twisted as it passes around the binding yarn 17 through 180°, so that the crimp pattern of the yarn is maintained, whilst keeping the longer floats on the paper-side in the return reach 20b of the yarn, as they are on the main reach 20a of the yarn. The twist can sometimes cause proudness, creating sheet marks and/or wear susceptible weak points. As a result of the configuration of the present invention, the geometry of the weave pattern is altered in the seam region, and this in combination with the seating away from the paper-side of the fabric helps to minimise sheet marking and seam wear.

[0020] The MD yarns 20 are preferably rectangular in cross-section, or other flat or profiled section yarns may be used. The CD yarns are preferably round, although flat or other cross-sectional shaped yarns may again be used. In an alternative embodiment, not illustrated, a fabric may comprise a single layer of alternating larger and smaller diameter or shaped yarns. In practice, the smaller diameter or shaped yarns will migrate to form a sub-layer of such yarns above a sub layer formed by the larger diameter yarns left in the plane of the single layer.

[0021] Whilst primarily intended for use in papermachine clothing where avoidance of marking of the paper web is a primary consideration, the fabric construction of the invention and as particularly described may be used on other fabrics formable by seams to form endless belts or tubular fabrics, such as conveyor or filter belts.

Claims

1. A woven fabric comprising at least one layer of cross-machine direction (CD) yarns, comprising first yarns having larger dimensions, and further yarns having smaller dimensions or of non-circular cross-section (i.e. shaped), and at at least one edge of said fabric, a seaming spiral connected to the fabric by a seam binding yarn secured by at least selected machine-direction (MD) yarns being looped about said seam binding yarn, characterised in that the final smaller dimensioned or shaped yarn is displaced to the opposite side of the fabric from the plane of said second layer.

2. A fabric according to claim 1 wherein said first, larger diameter yarns are disposed in a separate layer to said further, smaller diameter or shaped yarns.

3. A fabric according to claim 1 comprising at least one layer of cross-machine direction (CD) yarns, including at least one layer comprising alternating yarns of larger and smaller dimensions or shaped, wherein said smaller dimensioned or shaped yarns are displaced towards one surface of the fabric to form a first sub-layer above the large dimensioned yarn sub-layer.

4. A fabric according to claim 1 wherein the last two larger dimensioned CD yarns are displaced towards the plane of said second layer from the plane of said first layer.

5. A fabric according to claim 1 wherein the third larger diameter CD yarn from the edge is of dimensions intermediate the dimensions of the yarns of the larger layer and of the smaller dimensioned (or shaped) yarn layer.

Drawing