Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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lD9PROVEMENTS IN FABRIC SFOM
This invention relates to improvements in fabric seams, as used for
joining e.g. papermachine clothing, especially press felts, into endless
fabrics.
A common form of seam uses selected yarns extending in the
longitudinal (machine direction, or MD) direction of the fabric to form loops
which ~ extend beyond the fabric end and can be interdigitated with
corresponding loops on the other fabric end, to be joined by a pintle or
binding yarn passed along the tunnel formed by the interdigitated loops. In
an alternative, the interdigitatable loops may be formed by helical seaming
spirals which are bound into the fabric edge by a holding yarn and/ or loops
formed by MD yarns.
Seam constructions of this nature often present a problem particularly
with regard to marking of the paper sheet with hydraulic marks, caused by
a density difference in the seam area due to the seam area being generally
more open than the main body of the fabric. One proposal for alleviating
this problem is discussed in our published International Patent No. WO
98/19077 wherein it is proposed to form the pintle wire or binding yarn
from or incorporating an expansible component to fill some of the void
space in the seam. The said application focuses on the pintle region, to fill
the space within the interdigitated loops. The region where the loops are
joined to the fabric
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edge also however includes a higher proportion of void space than the main
body of the fabric. This is a particular problem when large core yarns form
long seam loops greater than l.4mm in length during the felt basecloth
weaving process, as discussed for example in EP-A-0,287,229.
It is an object of the invention to provide a seam construction
whereby the propensity of the seam to mark the paper web is reduced.
According to the invention a fabric seam construction, for joining an
industrial fabric such as papermachine clothing to form an endless belt, the
seam construction comprising seaming loops formed from yr connected to
the fabric and interdigitatable with similar loops on the opposed fabric edge
for connection with at (east one pintle wire or binding yarn passed through
the interdigitated loops, is characterised in that cross machine direction
extending means are provided for closing the gap between the cross
machine direction extending fabric yarns and the seaming loops of the
opposed fabric end.
Said cross machine direction extending means may be in the form of
a yarn, and may be elastic or resilient in nature.
The said means may be provided as a resilient deformable packing
yarn inserted between the end CD yarn of the fabric and the ends of the
seaming loops of the opposed fabric end.
Alternatively, the means may be provided as an elastic deformable
yam inserted into the end region of the fabric, to resiliently urge the end CD
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yarns into contact with the ends of the seaming loops of the opposed fabric
end.
In an alternative, the said means may comprise an elongate member,
comprising one or more continuous elements, for disposition in the cross
machine direction of the fabric, and an array of transverse elements,
extending across and beyond said continuous elements.
The elongate member may comprise a narrow mesh strip, comprising
for example two, three or four etc continuous elements, and the transverse
elements may be spaced to enter between seaming loops extending from
each end of the fabric.
The elongate member may take the place of one or more CD yarns in
the fabric end region, or may be used as a pintle for interconnecting
interdigitated seaming loops, or as a binding yarn for binding a seaming
spiral into the fabric end.
The elongate member can optionally comprise a spine formed of a
single yarn, with ladder like cross wise members extending from the yarn
to opposite sides thereof. Other variants of the elongate member may
comprise thin woven or knitted strips with frayed selvedges, or hot pressed
or melt bonded yarn tows.
In another embodiment, the means may comprise a strip or tape of
a foamed or foamable material.
In the case of a narrow mesh strip, the mesh may comprise a matrix
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of a suitable synthetic material, such as plastics, and at least one of the
continuous elements preferably incorporates a reinforcing yarn.
The said means may be expansible, or include parts which are
expansible, as set out in the aforesaid International Patent Application.
6 Embodiments of the invention will now be described by way of
example with reference to the accompanying drawings, wherein:-
Figure 1 is a diagrammatic cross section of a first embodiment of seam
construction according to the invention;
Figure 2a is a cross section of a yarn for use in the seam constructions
of Figure 1, in a relaxed uncompressed state;
Figure 2b is a cross section of the yarn of Fig. 2a compressed by contact
with neighbouring yarns etc when the fabric is subjected to
tension in the machine direction;
Figure 3 is a similar view to Figure 1 of a second embodiment of seam
construction according to the invention;
Figure 4 is- a plan view of a part of a member for use in a further
embodiment of the invention;
Figure 5 is a section of the member of Figure 4 in line V-V of Figure 4;
and
Figure 6 is a fragmentary plan view of part of a seam construction
according to the further embodiment of the invention utilising
a member similar to that shown in Figures 4 and 5.
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The embodiment of the invention illustrated in Figure 1 comprises a
fabric 10, the ends 11, 12 of which are joined by seaming loops 13 formed
by yarns 14 extending in the machine direction(MD). The last few cross
machine (CD) yarns 15 of each end of the fabric are shown. The seaming
loops 13 are interdigitated as usual, and a relatively thick yarn 18 is
provided to provide a pintle wire for joining the loops 13.
In accordance with this embodiment of the invention, a packing yarn
17 of resiliently deformable material is inserted at each side of the seam,
between the ends of the loops 13 of the opposing end of the respective
1 O fabric end. These packing yarns 17 are deformed by the pressure exerted
by tensioning of the belt formed when the fabric is joined by the seam.
The deformed packing yarns 17 ensure that the loops 13 are pressed
firmly against the pintle yarn 16, and fill the seam area between the last end
yarns 15a, so that the void space in the seam area is considerably reduced,
preferably to a similar proportion as that of the main body of the fabric 10.
Figure 2a shows one packing yarn 17 in its relaxed, uncompressed
state, and it will be noted that this preferred embodiment of packing yarn
has a tear drop shaped cross section. When compressed, as described
above the cross section of the packing yarn 17 is deformed by the MD
acting pressure created by belt tension to the cross section shown in Figure
2b, with the yarn 17 now double concave in section, the curvature of the
concavities 18 matching the profiles of the end CD yarn 15a, and the loops
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13, with projections 19 located between the loops 13.
In Figure 3, a fabric 20 comprises ends 21, 22 joined by a seam
comprising loops 23, provided by MD yarns 24. The interdigitated loops 23
are joined by a pintle 26 in the usual way. CD yarns 25 extend parallel to
the ends of the fabric. A larger diameter yarn 27 is inserted to extend in
the CD direction parallel to yarns 25, and this yarn 27 is of an elastic
material, acting as a packing yarn to urge the end-most CD yarns 25a of the
fabric into contact with the ends of the loops 23 of the opposed fabric end,
to thereby close up the spaces in the seam area.
Figure 4 is a plan view of a short length of a further embodiment of
packing member 30, which can be arranged In the seam structure,
extending in the CD directions parallel to the CD yarns of the fabric.
Member 30 is in the form of a narrow strip of resilient mesh material,
comprising in this instance three longitudinal members 31, 32, 33, for
extending in the CD direction, and a multiplicity of transverse m~mbers 34,
at right angles to the longitudinal members, forming a ladder like structure,
with the ends of members 34 extending beyond the outer members 31, 33.
These ends provide a comb structure which can be used to locate loops
formed by yarns or spiral seaming members lying in the machine direction.
Figure 5 shows a sectional view of member 30, showing that the member
comprises a matrix of a plastics material with reinforcing yarns 35, 36, 37
running lengthwise numbers 31, 31, 33. These yarns may be of for
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example an aramid, polyester or polyamide material. A narrow strip of
resilient mesh material without reinforcing yarns in the longitudinal members
can also be used.
Figure 6 shows diagrammatically the use of member 30 in a seam,
either as a pintle, joining seaming loops or spirals, or as an edge binder
member, connecting a seaming spiral to binding loops formed by MD yarns
of the fabric. As shown, the protruding ends of members 34 serve to
locate loops 38 extending from one side to interdigitate with loops 39
extending from,the outer side. The member 30 serves to fill in the seam
area, e.g. between CD yarns 40, 41 which may be respective fabric end
yarns, or an end yarn and a pintle depending upon the use of the member
30.
The packing yarn 17 may be a resilient material e.g, thermoplastic
polyurethane, polyether or polybutylene terephthalate, to enable it to deform
as described.
The elastic yarn 27 may be a rubber, such as neoprene or
polynorbornene, silicone rubber, a thermoplastic polyurethane, a
thermoplastic polyethylene or elastomeric polyester. The yarn may be
comprised of two or more elastic filaments, or the shape memory polymer
can be provided as a coated or co-extruded layer on a yarn core.
The member 30 may be of any suitable polymer, mineral or metal
material, especially the longitudinal members, which may be a single spine,
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or two or three or four etc in number. The cross members 34 may be of a
comparatively flexible material such as a thermoplastic polyurethane,
rubber, silicone, polyether, polyamide, or polyester, and these may be yarns
filaments or cast strands.
Any of the above packing members or yarns can be made to be
expansibte, to further fill the seam area, by use of materials disclosed in
our
above identified International Patent Application WO 98/19077.
