NO127411B - - Google Patents

Description

This invention relates to an endless wire for a paper machine, with warp running in—and weft across the longitudinal direction of the wire, with the warp threads running in a zigzag fashion.

Such wires are used in the wet section of Fourdrinier paper or board machines to feed and dewater paper pulp to form a mat or layer of fibers. The wire can be woven using metallic or synthetic warp and weft, or with metal warp and synthetic weft, or with synthetic warp and metal weft, the wire being formed by joining the ends of the wire together with the warp threads running in the longitudinal direction of the wire.

Due to the woven construction, the warp threads form elevations or knuckles on the underside and top side, of the woven wire and during operation the warp knuckles on the underside are exposed to strong abrasive wear when the wire slides over suction boxes, forming tables, ironing strips etc.

Under certain conditions, the warp knuckles wear grooves in the surface of the upper sides of the suction boxes and on the front edges of the wiper blades, and these grooves are a copy of the longitudinal pattern of the underside warp knuckles.

Wear marks in the upper side of a suction box can result in a very serious shortening of the wire's service life and produce defects in the paper or cardboard that is produced.

During operation, the wire tends to move to one side or the other of the machine under the action of guide rollers. When the upper side of a suction box has such grooves, the wire "hangs" on the box and counteracts the wire's normal lateral movement.

Increasing side force is built up by automatic guide rollers which cause strong lateral pressure on the warp knuckles in the grooves and strong wear on the sides of the knuckles. If the wire is released from the grooves, due to either sufficient side pressure or to a discontinuity present in the pattern of the underside warp knuckles, such as by

the joint or seam which makes the cloth endless, the wire slips over the top-pen of the grooves which grate the warp knuckles, causing further wear and often a disturbance in the smoothness of the web formation.

A grooved box top also causes serious difficulty when fitting a new wire. Differences in warp patterns in relation to the tracks cause strong local wear and greatly reduce the service life of the wire.

Manufacturers of paper machines and wires have for several years tried to overcome the aforementioned disadvantages. It has thus been proposed to move the wire boom axially back and forth with the result that the warp is deflected at an angle. However, this solution has not proven to be satisfactory in practice, because the warp threads straighten out very quickly because they are not fixed, permanently in this zigzag-like deflected position. Attempts have also been made to give the warp threads of the wire a zigzag course by stretching the wire cloth in the longitudinal direction and at the same time subjecting it to lateral displacement... Such a wire represents a better solution to the problem, but creates a new problem, namely that the cloth must be used in a special machine. This reduces the machine costs as the fabric requires special treatment.

Attempts have also been made to solve the problem by weaving the cloth for the wire with a slow back and forth moving loom to give the warp knuckles on the underside a sinusoidal course. The disadvantage in this case is that if one tries to make the pattern amplitude sufficiently large to avoid digging in the machine, difficulties arise as a result of variation in the mesh number and the weft number due to displacement of the loom with subsequent friction against the warp threads during weaving. Displacement of the loom also causes the formation of furrows in the cloth itself and this cannot be allowed for wires for the production of paper. A loom built or rebuilt for weaving this cloth cannot be used for weaving other patterns.

Attempts have also been made to weave tablecloths with zigzag woven warp threads using the same method. The disadvantage, however, is that the warp threads straighten out quite quickly because there is no fixation of the zigzag pattern. Mån has also proposed to weave a paper machine cloth with the warp threads curved in a wave shape by weaving the cloth with a straight warp and then by transverse pulls an alternating wave shape is imposed. In this case, the cloth is made of plastic, so that it can be heat treated to fix the wave course. This additional heat treatment brings with it additional costs.

The purpose of the invention is to avoid the disadvantages just mentioned and this has been achieved by providing a wire which is distinguished by the features specified in the patent claims.

The advantage of the embodiment according to the invention is that the zigzag pattern is permanent, that no further treatment and especially no heat treatment is required to fix the pattern, that the manufacture is simple because the reversal mechanism for reversing the twill pattern is simple and cheap, and finally, that the loom used to make the cloth can also be used for weaving cloths with other hair patterns' necessary..

An embodiment of the invention will now be described as an example with reference to the drawings, where: Fig. 1 schematically shows a plan view of a typical conventionally woven wooden shaft twill wire for a paper machine, in which the twill pattern A^- A^ runs from right to left when. it is seen in the direction of. the arrow, fig. 2 is a partial view corresponding to fig. 1, on a larger scale, where the twill pattern A^-^ goes from right to left in the direction of the arrow, fig. 3 shows the upper side of a typical conventionally woven wooden shaft twill, in which the twill pattern A3~A3 goes from left to right hair seen in the direction of the arrow, and fig. 4 shows the upper surface of a wire field in accordance with the invention in which the twill patterns A^-A^, A^-Aj/ and Ag~Ag are reversed from left to right, right to left and then left to right when seen in the direction of the arrow.

In fig. 1, the warp threads run parallel to the running axis 27 of the wet part of the paper machine. The seam 28 is made in the usual welded, soldered or sewn manner and runs at an angle with the fabric's transverse axis 29 which forms a right angle with the axis 27. In a typical twill weave, each warp thread is interwoven with the weft threads so that it passes over one weft thread and under the next two. Adjacent warp threads follow the same interlacing pattern, but are offset by a weft thread. In such twill woven fabric, the upper side knuckles of a number of adjacent warp threads created by passing over the weft threads will follow diagonal lines A^-A^ across the width of the fabric.

Those in fig. 1 details of the fabric are shown in fig. 2 and the pattern can be changed to form a knuckle line running in a diagonally opposite direction A3_A3 across the wire by changing the interweave, as shown in fig. 3.

It has now been found that if the weave is changed by turning the twill pattern at regular intervals, the warp threads follow a zig-zag pattern as shown in fig. 4. The inclination angle is affected by the warp and weft thread's flexibility and diameter and the number of warp and weft threads per empty. In fig. 2, 3 and .4, the warp threads are designated 25 and the weft threads 26.

During the weaving of one wire as a wooden shaft warp, the wire had 60 warp threads with a diameter of 0.244 mm per inch. and 45 weft threads with a diameter of 0.274 mm per empty. The twill pattern was reversed, at 229 mm intervals, with the result that the warp of the twill pattern formed a zigzag shaped pattern with a zigzag angle of 178°, which corresponds to

an increase in the warp direction of 4.2 mm per 229 mm wire cloth. However, it is clear that the space between the turning points can be varied, e.g. from 50 mm up to 1220 mm - at the same time as. the details of the twill pattern can be varied within wide limits. The mesh density for the wire cloth can be, for example, between 40 and 110 mesfr.

1. Endless wire for a paper machine, with warp running in and weft across the longitudinal direction of the wire, with the warp threads running in a zigzag shape, characterized in that the wire is made of twill woven cloth in which the twill pattern is reversed at predetermined intervals in the longitudinal direction of the wire or cloth as follows that the warp forms a zigzag pattern in the lengthwise direction of the wire. 2. Wire according to claim 1, characterized in that the twill pattern is turned at intervals of 5 to 122 cm and that the fabric is 40 to 110 raesh. 3. Wire according to claim 1, characterized in that the twill pattern is reversed with intervals of approx. 23 cm and that the zigzag angle is approx. 178°.