WOVEN FABRICS

TEXTILES TISSES

English Abstract

A woven fabric comprises at least two layers of cross-machine
direction yarns, one layer having yarns of a larger diameter and the other
layer having yarns of a smaller diameter. 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 diameter yams is displaced towards the opposite side
of the fabric. The last two larger yarns may be displaced towards the
smaller yarn layer, and the third yarn of the larger yarn layer may have an
intermediate diameter.

Claims

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CLAIMS
1. A woven fabric comprising at least two layers of cross-machine
direction (CD) yarns, comprising a first layer of yarns having a larger
diameter, and a second layer of yarns having a smaller diameter, 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 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 the last two larger diameter CD
yarns are displaced towards the plane of said second layer from the plane
of said first layer.
3. A fabric according to claim 1 wherein the third layer diameter CD
yarns from the edge is of a.diameter intermediate the diameters of the yarns
of the larger and smaller diameter layers.

Description

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WOVEN FABRICS
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.
In particular in papermachine clothing, it is well known to weave
fabrics having two 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.
A frequently used form of seam is a looped seam or a spiral loop
seam. In the latter, a flattened helical coif 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.

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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 CD yarns to the face, the neutral line is displaced
towards the fine yarn side. As a result, depending on the weave structure,
the seam coils tie to the fine yarn side of the fabric and will thus tend to
1 O stand proud of the fabric on the fine yarn side, and may be recessed on
the
coarse yarn side. The projection of the seam proud of the paper contacting
surface (fine 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
7 5 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.
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
20 fabric is reduced or substantially eliminated in asymmetric fabrics,
According to the invention a woven fabric comprises at least two

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layers of CD yarns, comprising a first layer of larger diameter yarns and a
second layer of smaller diameter 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 diameter yarn is displaced to the
opposite side of the fabric from the plane of said second layer.
Preferably, in consequence, the last two larger diameter yarns are
displaced towards the plane of said second layer from the plane of said first
layer.
1 O The third larger diameter CD yarn from the edge may be of a diameter
intermediate the diameters of the yarns of the larger and smaller diameter
layers.
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.
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 yarns 13, the smaller diameter yarns 13

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being spaced between and to the paper-side of the larger diameter yarns 11.
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.
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
1O interdigitated loops.
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 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.
The penultimate CD yarn 21 in machine side layer 10 is of a diameter
intermediate between the diameters of the larger diameter yarns i 1 of layer
10, and the smaller diameter yarns 13 of layer 12.
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

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yarns, not shown, may be looped about the terminal larger diameter CD
yarn 16.
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.
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.
In a further feature of the invention, the MD yarn 20 is preferably
twisted as it passes around the binding yarn 17 through '! 80°, so that
the
crimp pattern of the yarn is mainta :red, 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
wea r.
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

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used.
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.

Representative Drawing