FI93034C - Paper machine fabric with edge reinforcement and method for applying the edge reinforcement - Google Patents

Description

93034

The invention relates to a paper machine weaving apparatus having a reinforcement against wear in the edge areas in the form of a plastic pulp applied to the areas exposed to wear, wherein the plastic mass partially covers the weaving equipment of the paper machine in these areas. The invention further relates to a method for applying a plastic mass.

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The service life of paper machine weaving equipment, especially the sheeting wire, is usually limited by wear on the passage side. In most sheet-forming fabrics, the passage side does not wear evenly over the width of the fabric, but the wear is substantially greater in the edge regions than in the intermediate central region. Sometimes the wear 15 is twice as high in the edge areas as in the middle area. Once the forming wire has been abraded at any point, it must be removed from the paper machine.

The reasons for the uneven wear of the sheeting wire are not exactly known. Heavily worn edge areas correspond to the vacuum constraints of the planar boxes and suction roll 20. Uneven wear is not only present in plastic wires, but is also known from the more rigid metal wires used in the past. It occurs regardless of whether it is a single-ply, two-ply or multi-ply fabric. If the original fabric thickness was 0.7 mm and the wire had to be removed from the paper machine because the fabric thickness 25 was only 0.45 mm at the edge, then the center of the fabric was worn only to 0.56 to 0.58 mm, so that the central region would still have been usable.

In order to counteract the increased wear of the edge area, the fabric has already been reinforced in the edge areas by sewing fabric strips (DE-OS 35 01 980) 3 0 on them or by weaving additional, thick longitudinal metal wires on it. However, such edge reinforcements have not proven to be good because the fabric structure has changed on the passage side due to the extra, thick longitudinal wire wires. The extra longitudinal metal wires have been abraded very quickly and dropped off. The deformed structure of the passage side, which has already been woven, has then been abraded at these points very quickly, so that, overall, no improvement in service life has been achieved.

It is known from DE-OS 29 22 025 to reinforce the edge region by sewing additional longitudinal threads. However, the sewing threads protruding on the passage side practically abrade rapidly, and the damaged edge area due to sewing is then abraded rapidly. It is further known from this publication to reinforce the edge areas of the sheeting wire with longitudinal strips 10 of plastic which are applied in the molten state. Copolyamides and special polyurethanes are generally used as plastics. Indeed, in use, plastic strips also protect the actual fabric of the sheeting wire from wear. However, due to the fact that the loops of the fabric are completely closed with longitudinal strips, the longitudinal strips can only be placed on the outermost edge of the fabric and thus most often outside the area of the paper web final width nozzles and the most abrasive wear area. Namely, in many paper machines, the area of increased wear extends to a distance of about 20 to 30 cm from the edge. However, the paper web covers the sheeting wire except for the edge area, which is only about 10 cm. However, due to the disadvantage of dewatering, the 20 plastic strips cannot be placed in the area covered by the paper web. Thus, an edge area is left which is subject to more severe wear.

It is known from DE-OS 39 28 485 to apply plastic strips at an angle to the direction of travel or as wavy lines. However, this does not change the fact that the sheeting wire no longer removes water in the area of the plastic strips, so that the plastic strips must be placed outside the area of the paper web and thus cannot protect the area most exposed to wear.

It is known from US-PS 3,523,867 to fit reinforcing wires to the edge area of a metallic dewatering wire and to mold the entire edge area with a plastic mass. This would completely prevent dewatering in the periphery.

«3 93034

In order to preserve the dewatering as far as possible, it is known from DE-OS 39 09 534 to apply the plastic mass so as to only partially cover the passage side of the edge area which is very susceptible to wear. For this purpose, the plastic mass is applied as a parallel running line structure, in a point or 5 line form. It consists of polyester or polyamide mixed with a hot-melt adhesive, and may in addition be formed in part of monofilaments or multifilaments which are applied with an adhesion promoter.

The object of the invention is to provide a weaving equipment of a paper machine which is reinforced in the edge area highly susceptible to wear, without, however, the reinforcement hampering the drainage so much that the paper web becomes unusable.

According to the invention, this object is solved by applying the plastic mass in an irregular pattern with an open surface area of at least 30%.

The plastic mass preferably consists of a moisture-curable polyurethane which develops its adhesion and strength only after a reaction time of about 40 hours. In this case, it is an easily meltable polyurethane with free isocyanate groups which react with the moisture of the air. After crosslinking of the polymer molecules, the plastic mass becomes insoluble and insoluble. It adheres well to the fabric and v has good abrasion resistance.

The invention further relates to a method for applying an edge reinforcement, wherein the plastic mass is sprayed. The plastic then exits in the form of a wire from the central hole of the nozzle and is sprayed with side-flowing air currents and thus distributed on a larger surface of the edge area of the sheet-forming wire. Airflows are produced through a plurality of laterally oblique slots in the direction. The protruding plastic yarn hits the surface of the sheet-30 dosing wire in the form of fine particles and small droplets and thus cannot close the loops of the relatively large area. In this case, it has been shown that the dewatering efficiency is not substantially adversely affected »· t 4 93034 as long as only the individual loops are closed with the plastic mass. Apparently, water can flow out through adjacent loops fast enough. For this reason, the applied reinforcement does not interfere with the formation of the paper web. In this way, it is possible to avoid that the dewatering efficiency does not decrease by more than about 10%.

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An embodiment of the invention will now be described with reference to the drawing. In the drawing: Fig. 1 shows a part of the edge area of the passage side of the sheet forming wire in which the reinforcement is applied, Fig. 2 shows a spray gun for applying the reinforcement, and Fig. 3 shows the nozzle of the spray gun in a longitudinal sectional view.

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Fig. 1 shows a bottom view of the passage side of a multilayer sheet-forming wire with interwoven longitudinal yarns 1 and transverse yarns Z The sheet-forming wire becomes a transverse yarn mat with a longitudinal tension by conventional thermal attachment, i. the running side consists mainly of transverse wires Z The direction of Kul-20 is shown in Fig. 1 by an arrow.

. On the passage side, a reinforcement consisting of plastic mass 3 is sprayed on the edge area, which is subject to very heavy wear. The amount of plastic mass 3 sprayed per unit area is then dispensed so that on the one hand all longitudinal yarns 1 and transverse yarns 2 forming the passage are covered with plastic mass 3 -tehosta. The open surface of the plastic mass is about 30%, the longitudinal yarns 1 and the transverse yarns 2 forming the passage side are covered with a maximum of about 70% plastic mass 3 and a maximum of 30% of the loop openings are closed with a plastic mass 3. Plastic 11 5 93034 mass 3 is applied suitably 60 to 120 g / m2.

To apply the plastic mass, the pre-cut and fixed sheeting wire is guided through rollers from below the spray guns 10, which are traced at a distance of 10 to 15 cm vertically above the edge areas of the sheeting wire. Figure 2 shows a spray gun 10. The spray gun 10 includes a cartridge 12 for the plastic mass to be sprayed. The cartridge is surrounded by a heating element 14 for heating the plastic mass. By means of compressed air supplied through the air connection 16, the lever release 18, the three-way valve 20 and the reduction valve 22 to the other end of the cartridge 10, the plastic mass is compressed at the other end of the cartridge 12 through the central hole 24 (Fig. 3). Compressed air is supplied simultaneously through the spray air heating element 28 and the valve 27 to a sequential annular distribution chamber 32 through the nozzle 26, from which it is directed through five passages 34 converging towards the nozzle tip into outlets 36 spaced a short distance around the central hole 24. The molten plastic mass coming out of the central hole 24 is sprayed by means of air jets flowing from the expansion grooves 36, so that the plastic mass 3 arrives evenly distributed on the passage side of the sheet-forming wire and lands on it. It then forms an unevenly network-like structure with a large number of openings. The travel time of the sheet-forming wire 20 from the spray gun 10 to the roll is so large that the polyurethane mass has already hardened and strengthened to such an extent that the rolls no longer stick.

Example: 25 A curable hot melt adhesive consisting of moisture-curable polyurethane (2000) with a basis weight of 80 g / m2. The application temperature is 30,100 ° G. The sheeting wire is then guided at a speed of 8 m / min and a distance of 11 cm below the spray head of type TS215 HS (manufacturer: 93034 6

Beyer and Otto, 8752 Kleinostheim). The lateral air jets come out of five side slots at a pressure of 3 kPa and spray the outgoing plastic mass. The angle of the spray cone is 35 ° and the plastic mass is applied to a width of 6 cm. The initial permeability of the sheet-forming wire, which is 325 cfm, is reduced to 297 cfm due to the mass of plastic-5 applied. The service life of the wire is improved by approx. 30% thanks to the plastic reinforcement.

Claims (4)

7 93034 Paper machine weaving apparatus with anti-wear reinforcement in the edge areas in the form of a plastic pulp applied to the running side, which mass 5 partially covers the edge area of the weaving machine, characterized in that the plastic pulp (3) is applied to the running side in an irregular mesh pattern with an open surface of approx. %. Woven fabric according to Claim 1, characterized in that the yarns (1, 2) forming the 10 running sides are covered with at least 70% of their length by a plastic mass (3). Woven fabric according to Claim 1 or 2, characterized in that at most 30% of the openings in the loops are closed with a plastic mass 15 (3). A method for applying a plastic mass (3) for reinforcement to the edge area of the passage side of a paper machine weaving machine, characterized in that the molten plastic yarn compressed from the nozzle is sprayed by laterally impinging air jets and thus sprayed onto the passage side. m 4 e 93034