GB2216914A

GB2216914A - Link fabrics

Info

Publication number: GB2216914A
Application number: GB8905417A
Authority: GB
Inventors: Gerrit Willem Leuvelink
Original assignee: Scapa Group Ltd
Current assignee: Scapa Group Ltd
Priority date: 1988-03-12
Filing date: 1989-03-09
Publication date: 1989-10-18
Also published as: NL8900595A; GB8905417D0; DE3907561A1; GB8805930D0

Abstract

A method of reducing the permeability of a link-belt, typically a papermakers' fabric, involves the use of elastomeric yarns (13) of such transverse cross-section as to be capable, when stretched, of being freely drawn into the space existing within a coil the transverse dimension (t1) of the yarn (13), in its relaxed state, being not less than the corresponding dimension of the coil space. Yarns having a variety of profiles are disclosed as is the use of plural yarns within a single coil. <IMAGE>

Description

LINK FABRICS 2216914 The invention concerns link fabrics and has

particular, though not exclusive, reference to link fabrics for use in the production of conveyor belts of the kind used in the papermaking industry for supporting and transporting a paper web in its passage through the papermaking machine.

Conveyor belts are known which comprise a multiplicity of helical coils arranged in interdigitated side-by-side disposition, adjacent coils being secured together by hinge wires engaged with the tunnel formed by the overlapping coils. A belt of this kind is disclosed, for example, in GB-B-2051154.

The high permeability of link belts as aforesaid give rise to the necessity in many instances, of introducing filler materials into the coils to reduce such permeability to appropriate levels.

Thus, in GB-B-2083431 it is proposed to control permability by the introduction of a strip or strips of a tape-like material, polyester monofilament or flat yarns into some or all of the coils, whilst US-A-4381612 suggests the inclusion of filler strands of such as nylon or polypropylene which are subsequently subjected to heat treatment so as to effect expansion thereof within the coil.

Mention is made in CH-A-610273 of the possibility of filling the space between the limbs of each coil with foam material to control the free through-flow area, although the specification is silent as to the precise form taken by the foam in the context of the fabric as a whole and as to how the control is achieved in practice.

In a still further proposal, disclosed in GB-B-2148337, the link belt is modified by the provision of a continuous layer of open cell elastomeric foam therein, the foam being of constant permeability throughout the full width of the fabric, or not, according to requirements.

Thus, various ways in which the permeability of a link belt may be controlled have been proposed, some being more effective than others, but none of the proposals hithertofore made has been universally adopted, thus suggesting a short-coming of one kind or another in method and means as proposed.

The present invention is concerned with a still further proposal whereby the permeability of a link fabric may be varied to meet particular needs, and it is the object of such invention to provide a method whereby permeability might be accurately controlled is throughout a wide range.

According to the present invention there is proposed a method of reducing the permeability of a link fabric, the said method including the steps of stretching an elastomeric yarn to reduce the transverse dimension thereof, introducing at least one such yarn into a selected one of the spaces within the respective coils, and releasing the tension to permit transverse expansion of the yarn into engagement with the coil, the transverse dimension of the yarn in a given direction, in the tension-free condition of such yarn, being not less than the transverse dimension of the space within the coil in that direction.

7 -4 is 1 The invention also includes a link-fabric comprising a plurality of helical coil.s arranged in interdigitated sideby-side disposition, characterised by the presence, in the space within some, at least, of the respective coils,of an elongate elastomeric yarn, the cross-sectional dimension of said yarn in a given direction and in the relaxed state of said yarn being at least equal to the corresponding dimension of said space in that direction.

The invention will now be described further, by way of example only, with reference to the accompanying diagrammatic drawings illustrating various embodiments thereof and in which: - Fig. 1 is a plan view of a link fabric showing the introduction of an elastomeric yarn into the space within a coil; Fig. 2 is a view in the direction of arrow A in Fig. 1, drawn to a large r scale, and shows a link fabric produced in accordance with the invention; Fig. 3 is a view taken on line 111-111 of Fig. 2; and Figs. 4 and 5 illustrate various transverse cross-sectional forms of elongate elastomeric material suitable for use in practising the invention.

Referring now to the drawings, and in particular to Fig.

1 thereof, a link fabric comprises a plurality of helical coils 11, 12 alternatively of opposite hand arranged in interdigitated side-by-side disposition and connected by hinge wires engaged with the tunnels formed by the overlapping regions of adjacent coils.

1 In accordance with the invention, a respective elongate elastomeric element 13 is located in the space within each individual coil, the element being of a dimension in a direction transversely thereof in excess of the corresponding dimension of the space 14 within which the element is positioned.

In order to position the element 13 within the space, such element is stretched, thus to reduce the transverse dimensions thereof, and is drawn into the space in the manner illustrated in the upper part of Fig. 1 whilst in such stretched condition, the element being of circular cross-section and its diameter in the relaxed and stretches conditions thereof being t 1 and t 2' respectively.

By arranging that the minimum transverse cross-section dimension T of the space within the coil lies between t 1 and t 2' on release such element will resile to engage the turns of the coil, -and thus be positively located relative thereto.

The relationship between t,, t 2 and T is shown in Figs.

2 and 3, which Figs. illustrate, to a larger scale, the manner in which the elastomeric element 13 is positively located within the space 14 within the coil 11, 12.

Various alternative forms of elongate element are shown in Figs. 4 and 5, Fig. 4 Mustrating elements of circular or rectangular cross-section, and Fig. 5 showing elements of other geometric cross-sectional form. In each instance, in its relaxed state the element has a transverse cr6ss-sectional dimension in excess of the corresponding dimension of the coil space, and such element is drawn 6.

- 5 into position under such tension that the relevant dimension (or dimensions) is reduced to a level less than said corresponding coil-space dimension.

As can be seen, when in position within the respective coil space the element (or elements) will fill the coil space in whole or in part.

The relevant coil-space dimension may extend in a direction perpendicular to the plane of the fabric as in Figs. 1 to 3, or may lie in the plane of the fabric as with various of the examples shown in Figs. 4 and 5. Indeed, if desired the elastomeric element may have relaxed dimensions in multiple transverse directions which are in excess of the corresponding dimensions of the coil space.

The elastomeric element may be profiled o seat against the ends of the coils which engage that coil within which the element is to be located, if desired.

The elastomeric material used may be selected according to the context in which the link fabric is to be used.

Thus, for example, if the link fabric is to be used as a filter element in a non-arduous environment, an elastomeric material appropriate to that context will be selected.

If the link fabric is to be made up into an endless belt for use on a papermaking machine, say in the dryer section of that machine, the material will be such as to be capable of withstanding the heat and temperature of such environment, and more particularly, will be chosen having regard to its resistance to degradation in such environment.

6 Nitrilic rubber or EPDM (ethylene propylene di ene monomer) are thought to be of particular application in this context.

Any excess in a cross-sectional dim-ension of the element relative to the corresponding dimension of the coil space will serve to hold the element in position axially of the coil. However,it may be found desirable to treat the element in the region of the fabric edges to encourage relaxation of the element in such regions, and thus remove residual tension the effect of which might be to shorten the element within the coil space, prior to trimming the element at the fabric edge.

The invention hereinproposed lends itself to the introduction of filler materials into the coil space of link belts for use in the context of papermachine clothing, notwithstanding the significant axial extent of that coil space and the limited transverse dimensions thereof. Difficulty has been experienced heretofore in introducing filler materials into a coil space having a transverse cross-section of, say, 4 mm x 0.7 mm throughout a length of, say 10 metres, since any significant pressure contact between that material and the turns of the coil will inevitably give rise to resistance to further movement axially of the space.

By utilising an elastomeric material and stretching the same for insertion purposes, resistance to movement into the coil space can be reduced merely by further stretching, and consequential reduction in cross-section.

V It is to be appreciated, of course, that the tension applied in drawing the elastomeric element into the coil space must not be such as would exceed the elastic limit of the material of that element, since otherwise the increase in cross-section on removal of tension which is necessary for location purposes would be lost.

Whilst the invention has been disclosed in the context of the reduced permeability of a link-belt, the elongate elastomeric yarn itself serving to effect reduction in permeability, it is to be understood that the elastomeric yarn may be used as a means of locating/ retaining -stuffer or other materials within the coil space by expanding the elastomeric yarn into contact with such stuffer or other material.

1 -1

Claims

1. A method of reducing the permeability of a linkfabric including the steps of stretching an _elastomeric yarn to reduce the transverse dimension thereof, introducing at least one such yarn into a selected one of the spaces within the respective coils, and releasing the tension to permit transverse expansion of the yarn into engagement with the coil, the transverse dimension of the yarn in a given direction, in the tensionfree condition of such yarn being not less than the transverse dimension of the space within the coil in that direction.

2. A link-fabric comprising a plurality of helical coils arranged in interdigitated side-by-side disposition, characterised by the presence, in the space within some, at least, of the respective coils, of an elongate elastomeric yarn, the cross-sectional dimension of said yarn in a given direction and in the relaxed state of said yarn being at least equal to the corresponding dimension of said space in that direction.

3. A link-fabric as claimed in claim 2, wherein 20 the transverse crosssectional dimension of the elongate elastomeric yarn in the relaxed state thereof exceeds the corresponding dimension of the space within the respective coil in at least one direction.

4. A link-fabric as claimed in claims 2 or 3, wherein the transverse cross-sectional dimension of the elongate :9 9 elastomeric yarn in its. relaxed state is at least equal to the corresponding dimension of the space within the respective coil in onetransverse direction only.

5. A link-fabric as claimed in claim 2 or 3, wher6in 5 the elongate elastomeric yarn is of circular transverse cross-section.

6.

2 to 5, coil at in spaced

7. -A link-fabric as claimed in any one of claims 2 to 6, wherein plural elongate elastomeric yarns exist in a common coil, the individual ones of said yarns having a transverse dimension in the relaxed condition of the yarn in at least one direction, which is at least equal to the corresponding dimension of the coil space.

The method of reducing the permeability of a link-fabric substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

9. A link-fabric substantially as hereinbefore des scribed with reference to and as illustrated in the accomp anying drawings.

is A link-fabric as claimed in any one of claims wherein the elongate elastomeric yarn engages the corresponding opposed locations thereon and lies disposition from the coil in other locations.

8 Published 1989 at The Patent Office. State House, rZ,71 High Holborn, London WCIR4TP.Purther copies Maybeobtainedfrom The Patent Office. Sales Branch, St Mary Cray, Orpington, Kent BF.5 3RD- Printed by Multiplex techniques ltd, St Mary Cray, Kent, Con. 1/87