SE439651B - The forming fabric - Google Patents

Description

8305857-3 The machine is now increasingly being replaced by double wire Formation, where a mass jet is directed directly into a converging nip between two wires running at the same speed.

The pulp is compressed between the wires, whereby the water is forced out of the pulp.

In both cases, the slurry of Fibers contains the so-called the stock, usually over 99% of water, of which the greater part is to be removed, by allowing the water to flow through the wire; It is important that these flow points are very small, ie. the wire must be very fine mesh to avoid fiber loss.

At the same time, the permeability of the formation wire must be of a certain size to allow the flow of large amounts of water. The wire surface closest to the fiber web must thus be designed with many and small flow points, which means that the material of the wire surface must consist of thin threads. However, a fine mesh wire becomes less abrasion resistant and less stable and its service life is thereby severely limited.

Due to its poor stability, synthetic fiber material wires have not been able to be used in large and high-speed Fourdrinier paper machines. The forming wire is exposed in such machines to a considerable tensile stress which it must be able to absorb without its longitudinal elongation and transverse contraction reaching such values that it can no longer be used for its purpose.

It was only through the advent of the so-called double-layered forming wires as synthetic fiber material Got greater use in these large and high-speed paper machines.

These wires consist of two layers of synthetic weft threads together with the layers of unifying, synthetic warp threads.

In these wires, these opposing requirements for a fine-mesh forming surface, consisting of fine threads, and a wear surface, where the threads are coarser and more durable, can to a certain extent be met by using different thread dimensions aan / anar Fiber material in the two waffle layers. However, these opposing requirements cannot be met by the skibton United warp threads. From a shaping point of view, these threads should preferably be as Fine as possible, but in their capacity as machine direction threads, they must have the ability to absorb Occurring tensile stresses, without their Elongation becoming abnormally high.

The next step in the development was the interconnection of two single-layered tissues with each other as described in: sa-Ps 7806764-2. The object of this invention was to provide blending without interference on the paper side.

This succeeded in Fullo and this type of forming wire was now used to form such fine paper grades, where hitherto synthetic forming wire had been unusable. However, the difficulty in coordinating the elongation / load properties between the two fabrics has meant that one of these fabrics has absorbed most of the load and that the property has deteriorated somewhat compared with the double-graded wire. In addition, the strength of the wire seam has not been satisfactory.

Characteristic of the present invention is that the First fabric has a First and a second system of threads, which are perpendicular to each other and are combined with the second fabric, which consists of a first and a second system of threads parallel to each other and substantially located in levels one above the other and a third system of wires, which are perpendicular to said two systems and which connect these two systems.

Preferably, both systems of the second fabric consist of weft threads, while the third system consists of warp threads.

Preferably, the first fabric has threads of smaller diameters than the threads of the second fabric. A Forming Wire according to the invention can be designed with a first fabric with such a Fine Mesh structure, which gives a very even water flow without Fiber losses and tendencies to wire marking. At the same time, an improved stability is obtained only through the second tissue. In this case, the first tissue does not need to be designed for air to absorb any load. The seam strength, which has been unsatisfactory in previous forming wires comprising double tissues, has been considerably improved.

The wire can furthermore be provided with a loop stitch in the other tissue in a more expedient manner. The dimension of the owls can be chosen smaller than the thickness of the other tissue and thus protected against wear.

The one of the two parallel wire systems in the second fabric, which is closest to the drainage element of the machine, can in its entirety consist of very abrasion-resistant material.

An advantage of double-wire machines is the ability of the wire to hold water. An additional advantage is the stiffness of the wire, which means that the wire will run more flat without a tendency to form.

In the following, the invention is elucidated with reference to the attached schematic drawing, which in Figs. 1-4 shows sections along one thread direction, preferably the warp thread direction, in some different bonding patterns.

The forming wire according to the invention is preferably woven flat and spliced endlessly. In this case, the warp threads constitute the machine direction threads of the wire, while the weft threads form the transverse threads in the position of use of the wire. Alternatively, the wire can also be endlessly woven, with the relationship of the wire to the machine direction being the opposite.

The embodiments according to Figs. 1 - 4 show a first fabric 1, which is suitably fine-mesh and in which the position of use of the wire is turned towards the material to be tumbled. This' x 8305857-8 fabric - hereinafter referred to as top cloth - has been illustrated in Figures 1, 2 and 4 in a two-shaft pattern, which means that each thread 2 in the other direction, for example the warp thread direction, binds over every other thread 3a and under every other thread 3b in the other direction, for example the weft thread direction. Other weave patterns can also be used for the top fabric, for example batavia patterns illustrated by Fig. 3.

A second fabric 4 is placed under the top fabric and forms the bottom fabric of the wire, which faces the drainage elements.

This second fabric 4 is preferably coarser mesh and consists of double thread systems 5, 6 in one direction, for example the weft thread direction, which thread systems are parallel to each other and located above each other. An additional thread system 7 is located in the other direction, for example warp thread directions fi, perpendicular to the double thread systems 5, 6. The threads 7 can connect the threads 5, 6 in any pattern, for example eight-shaft patterns, as illustrated in Figures 1, 2 and 3. or Four-shaft pattern, as illustrated in Fig. 4. The two wire systems 5 and 6 may have different numbers of wires. For example, wire system 5 may have twice the number of wires compared to wire system 6, as illustrated in Fig. 2.

The two tissues are connected to each other (not shown). Preferably, special binding warp threads are used which connect warp threads from the two fabrics.

It is also possible to use warp threads. Some of the threads included in the thread system of one fabric may also be connected with perpendicular threads from the other fabric.

A forming wire according to the invention may consist of a fine-mesh top cloth with 30 threads / cm of 0.17 mm polyester monofilament 2, 3 in both directions. The bonding thread system 7 of the bottom fabric can be 0.25 mm polyester monofilament with a thread density of 30 threads / cm. Of the double parallel thread systems 5, 6 in the bottom fabric, the threads 5 closest to the fabric 8305857-8 can consist of 0.22 mm polyester monofilament with a thread density of 15 threads / cm. The lower 6 of the two parallel thread systems is preferably wholly or partly of abrasion-resistant monofilament material, for example polyamide, which, however, does not preclude the use of other material. The child dimension in thread system 6 is suitably 0.30 mm and the thread density is 15 threads / om or 7.5 threads / cm. If the pattern according to Fig. 2 or the like is used.

The invention is not limited to illustrated and exemplified embodiments but may exist in many other forms within the scope of the claims. fi

Claims (6)

8305857-8 P A T E N T K R A V Forming wire for paper, cellulose or similar machines consisting of a First fabric, which in the mode of use faces the material to be Formed, and a second fabric, associated with the First fabric, characterized by, that the First fabric (1) has a First and a second system of threads (2, 3), which are perpendicular to each other and are combined with the second fabric (4), which consists of a First and a second system of wires (5, 6) parallel to each other and substantially located in levels above each other and a third system of wires (7), which are perpendicular to said two systems (5, 6) and which interconnect these two systems (5, 6). Forming wire according to claim 1, characterized in that the two parallel systems (5, 6) of the second fabric (4) consist of wet threads, while the third system (7) consists of warp threads. The reinforcement wire according to claim 1, characterized in that the threads (2, 3) of the tissue (1, 3) have smaller diameters than the threads (5, 6, 7) of the other tissue (4). Forming wire according to one of the preceding claims, characterized in that the two fabrics (1, 4) are connected to each other by means of special blending threads. Furmerlngsvira according to one of Claims 1 to 5, characterized in that the two fabrics (1, 4) are connected to one another by means of special binder warp threads. Formulation fabric according to one of Claims 1 to 3, characterized in that the two fabrics (1, 4) are connected to one another in that some of the threads which are part of the thread system of one fabric are unbonded with wire. ~ straight threads L ded other tissue.