WO1992008000A1

WO1992008000A1 - Textile for use as a paper machine

Info

Publication number: WO1992008000A1
Application number: PCT/AT1991/000111
Authority: WO
Inventors: Walter Kovar
Original assignee: Hutter & Schrantz Ag.
Priority date: 1990-10-25
Filing date: 1991-10-17
Publication date: 1992-05-14
Also published as: ATA216090A; AT394869B; DE59104097D1; EP0554336B1; EP0554336A1

Abstract

A textile for use in a paper machine has three weft layers (1, 2, 3) joined by a set of warp threads (K). The central weft layer (2) is bound by the same warp system which also joins the upper (1) and lower (3) layers. In order to avoid microturbulence, the weft threads of the central layer (2) lie beneath the even-numbered warp threads (11, 12 ...) of the upper layer (1) and the weft threads of the lower layer (3) lie under the odd-numbered warp threads (11, 12 ...) of the upper layer (1), so that the weft threads of the central layer (2) are staggered with respect to the warp threads of the lower layer (3) in the direction of the thickness of the textile and in the longitudinal direction.

Description

Fabrics for use as paper machine clothing

The invention relates to a fabric for use as paper machine clothing, with three weft layers, which are tied by a family of warp threads, the binding of the middle weft layer being carried out with the same warp thread system, which also binds the upper and lower layers. Such a fabric is e.g. by the applicant's AT-PS 386.026.

Fabrics for use as paper machine clothing, consisting of plastic monofilaments, have been made with two weft layers for several years. It is thus possible to design the barrel side in such a way that the weft protrudes over the warp threads (weft runner) and is therefore used as an abrasion carrier. The mechanical longitudinal strength of the fabric is only weakened towards the end of the term, so that longer terms are achieved compared to the earlier single-layer fabric or screen constructions.

The paper side can be adapted to the requirements of sheet formation by means of different bindings of the warp threads with the upper layer of the weft threads, so that a longitudinal or transverse orientation of the surface supporting the nonwoven fabric arises and the sheet formation process and the sheet removal can thus be influenced.

An improvement of these two-ply fabrics could be achieved by using three-ply fabrics, two fabric layers being connected with a binding thread system, which is referred to as the "third layer". The upper layer is a fine fabric that causes the fiber structure, the lower layer is relatively coarse, with large thread diameters, which increase the abrasion resistance. The disadvantage of this construction is the occurrence of shear forces in the plane between the two fabric layers, which place a great strain on the binding thread when the fabric is deformed. There is an "internal friction" in the tissue be, which leads to wear at the points of contact of the binding threads with the fabric layers. Sieves of this construction are often destroyed by this internal wear before they are ground down on the running side. In general, it can be stated that the abrasion resistance of the fabrics is increased when the volume of the lower weft layer, which is in contact with the running elements of the paper machine, is increased. This can be done by increasing the diameter and the float length. By doubling the number of shafts of the conventional double-layer screens from 7 or 8 to 14 or 16, the float length of the lower weft threads can be increased. By tying the weft threads of this layer with two warp threads that are very close to one another, the diameter can also be increased, sufficient crimping of these reinforced weft threads being achieved, so that abrasion on the warp threads only after extensive use Abrasion of the weft threads occurs.

These strong weft arcs, however, have the disadvantage that microturbulences occur on the underside of the fabric when they run over the drainage elements, which lead to dynamic drainage marking, which is particularly noticeable at higher speeds and thinner sheet weights.

The aim of the invention is therefore to create a tissue of the type mentioned in the introduction in which no troublesome microturbulence occurs. This is achieved in that the wefts of the middle layer are each under the wefts of the upper layer with even numbers, the wefts of the lower layer below the wefts of the upper layer with odd numbers, so that the wefts of the middle layer are in relation to the sieve thickness and the longitudinal direction are arranged offset to the weft threads of the lower layer. The arrangement according to the invention dampens the effect of the microturbulence of the running weft in the upward direction on the underside of the fleece, but also controls the passage of water.

In some cases it is also necessary to control the water penetration of the fabric, especially in the primary drainage zone, in order to build up the primary fleece, which is used for the subsequent

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sufficient drainage of the suspension is decisive.

In order to control the drainage performance of the fabric and to influence the effect of the microturbulence from the lower layer on the sheet formation, the size of the diameter of the middle weft layer lies between the diameters of the weft threads of the upper and lower layer.

In order to create a long sheet for the abrasion on the barrel side, the threads of the lower layer are each tied by two warp threads separated by a warp thread.

Compared to a fabric according to the patent mentioned at the outset, in addition to the advantage of avoiding or substantially reducing microturbulence, the fact that only one warp beam is required for the manufacture of the fabric, whereas for the manufacture of the known fabric, in which two different groups of warp threads, two warp beams are required. In addition, in the case of a fabric according to the invention, compared to the known fabric in the lower layer, there is twice the number of weft threads with the advantage of the higher abrasion volume. The middle shot then controls the damping of the turbulence of the lower shot by varying the diameter.

In an expedient embodiment of the invention, the number of shafts is 14 or 16 and the wefts of the upper layer are overflowed and undershot by the warp threads in the rhythm 2-1-2 or the floating of the chain in the upper layer extends over three wefts before the Thread runs into the fabric interior to tie the middle and lower layers. The invention is described in more detail below on the basis of exemplary embodiments illustrated in the drawings. 1 and 2 show in the warp and weft directions of an exemplary embodiment and FIG. 3 represents a further exemplary embodiment in the warp direction. Example 1

According to FIGS. 1 and 2, a fabric with 60 warp threads / cm in 14-ply weave with a diameter of 0.17 mm in the upper weft layer 1 alternately has 38 weft threads / cm with a diameter of 0.16 / 0.17 mm . The weft thread of the middle weft position 2 -4-

is 0.20 mm thick, the weft thread of the lower weft layer 3 0.30 mm; 19 threads / cm are arranged in each of these two layers.

The chain K 1 binds over the weft thread 3 1 of the lower layer 3 according to FIG. 1, the upper layer 1 in rhythm 2/1/2 and then runs inside the fabric in order to bind the weft thread 3 s of the lower layer 3 below. This weft thread 3s is also tied off by the next but one warp thread K 3, so that, according to FIG. The control of the effect of the turbulence and the dewatering performance of the screen construction can now be carried out by changing the diameter of the weft thread of the middle layer, the applicable diameter range in this example being from 0.17 to 0.30 mm, that is to say the weft diameters used for the upper and lower layer.

Example 2

Another example shown in FIG. 3 in a 14-strand weave has a fabric whose warp thread count is 60 / cm and whose warp diameter is 0.17 mm. Here, the top layer 11 alternately consists of threads 11G with diameters 0.18 mm and threads 11K with diameters 0.12 mm, namely 42 / cm in total. The warp thread K 1 runs above three threads of the upper layer 11 in the repeat and then passes through the middle layer 12 into the interior of the fabric in order to finally tie the lower weft layer 13 as in Example 1. The thread diameters of the middle weft layer 12 and lower weft layer 13 are kept the same as in Example 1, the thread counts are each 21 / cm.

Example 3

In the case of a fourteen-shaft fabric, the number of warp threads is 44 / cm and the warp thread diameter is 0.23 mm. The wefts of the top layer alternately have a diameter of 0.25 / 0.27 mm, there are 24 / cm.

12 threads / cm with a diameter of 0.30 mm are wrapped in the middle layer, 12 threads / cm with 0.40 mm in the bottom layer. The weave pattern is the same as in Example 1.

Claims

PATENT CLAIMS

1. Fabric for use as paper machine clothing, with three weft layers, which are tied by a bevy of warp threads, the binding of the middle weft layer using the same warp thread system that also binds the upper and lower layers, characterized in that the weft threads of the middle ler layer (2) under the weft threads (left, I2 ...) of the upper layer (1) with even numbers, the weft threads of the lower layer (3) under the weft threads (left, I2 ...) of the upper layer ( 1) lie with the odd numbers, so that the weft threads of the middle layer (2) are offset with respect to the fabric thickness and the longitudinal direction to the weft threads of the lower layer (3).

2. Fabric according to claim 1, characterized in that the size of the diameter of the middle weft layer (2) between see the diameters of the weft threads of the upper (1) and lower layer (3) in order to control the drainage performance of the fabric and to influence the effect of the microturn bulbs originating from the lower layer (3) on the sheet formation.

3. Fabric according to claim 1 or 2, characterized in that the weft threads of the lower layer (3) of two, only by one warp thread (K2) separate warp threads (K2, K3) are tied to form a long bow for the to generate lukewarm abrasion.

4. Fabric according to one of claims 1 to 3, characterized gekenn¬ characterized in that the number of shafts is 14 or 16 and the weft threads (li, I2 -) of the upper layer (1) by the warp threads (Kl ...) in Rhythm 2-1-2 overflow and underflow or the floating of the chain in the upper layer (1) extends over three wefts before the thread runs into the inside of the sieve to bind the middle (2) and lower layer (3) .