FI92741B - A press felt - Google Patents

Description

! 92741

This invention relates to a needled press felt for removing water from a cellulosic pulp in a papermaking machine comprising a multilayer base fabric having longitudinal and transverse yarn strands.

In pulp dryers for cellulose, the pulp is dewatered and formed into a web in a first step on a forming wire, in a second step in a press section, and the final drying takes place in a hot air stream in a blower dryer or on heated cylinders. In the case where the pulp is air-dried, a large contact surface between the air and the web is required in order for the drying to take place as efficiently as possible. Preferably, a press felt having a rough surface is used to increase the characteristic surface of the pulp web, the rough surface giving the pulp web a clearly embossed surface. The rough surface of the pulp web has a negative effect in cylinder dryers because the heat transfer from the cylinder surface to the web is small due to the smaller contact surfaces.

In order for the press felt to give the desired effect, it must have thick yarns on the side facing the pulp web in order for this to be embossed. The problem is. however, the thick pins make the felt heavy and rigid, and it is difficult to install the felt in a papermaking machine, which in turn limits the use of such a press felt.

The object of the invention is to solve this problem in such a way that it is not necessary to narrow the press felt in order to guide it through the small openings of the machine. The characteristic features of the invention can be found in the appended claims.

An embodiment of the invention is described below with reference to the accompanying drawings.

2,92741

Figure 1 is thus part of a cross-section of a finished press felt, the direction of travel through the papermaking machine being transverse to the plane of the drawing.

Figure 2 is a schematic cross-sectional view of a fabric in a weaving machine.

Figure 3 is a schematic plan view of a fabric seam with a locking wire installed.

Thus, Figure 1 shows a fabric consisting of two layers of filaments 1 and 2, which are weft yarns during weaving. The thicker yarn 3 is woven on the side of the fabric which forms the dewatering side. The weight / length unit of the yarns 3 is at least twice as large as that of the yarns 1 and 2. The thicker yarn 3 forms the upper layer and this layer gives the desired embossing in its cellulosic pulp. In the embodiment shown, the bonding of the yarns 3 is, according to the model, a 4-arm cross stitch with two repeated pattern repetitions. As is known per se, when weaving weft yarns 1 and 2, loops are formed from one of the turning edges. The loops are formed around the bobbin thread 6. The loops are used to form an openable seam.

Figure 2 schematically shows a cross-section of a so-called tubular fabric. The loops 5 are here formed of yarn strands 1 and 2 around the hollow yarn 6. No loops have been made of the thicker yarns 3. It should further be understood that Figure 2 does not show any warp yarn bonding. When the resulting tubular fabric is used as a press felt, the yarns 3 are cut close to the loops and along a line parallel to the loops or the thread yarn 6. When the bobbin thread 6 is later pulled out, the felt can be spread over its entire length. Before that, a layer of cotton can be applied to the felt, which is needled into the felt and which gives it better rigidity. The reinforced cotton flap is made in the area of the loops and thus on the opening seam, cf. SE Patent 447,140.

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It 92741 3 SE patent 429 982 is known per se for forming such a seam.

Once the yarn has been removed, the blanket can be mounted along its entire length in the press of the pulp dryer, and when the blanket is installed, both ends are connected so that the loops 5 are aligned and the locking wire 7 can be inserted through the loops. The press felt thus becomes tubular, cf. Figure 3.

The yarns 1 and 2, which are thus weft yarns during weaving but run longitudinally in a papermaking machine, are preferably monofilaments of polyamide or a polymer having similar properties and a thickness of 0.3 to 0.7 mm, corresponding to about 80 to 430 tex: IA. The yarn 3 is either a monofilament or a stranded thin monofilament or multifilament having a weight / length unit at least twice that of yarns 1 and 2, thus at least 160 tex. Preferably, a stranded thin monofilament or multifilament is used. The warp yarn or binding yarn 4 is preferably a simple monofilament or a stranded thin monofilament.

Claims (3)

A nailed press blanket for dewatering cellulose pulp in a dryer, which blanket consists of a multilayered base fabric of longitudinal and transverse trees, the discharge side having a layer of coarse yarns having a weight per unit length that is at least twice as large as the other parallel ones. yarns (1, 2) in the base fabric, characterized in that the fabric is a round woven structure in which, in a manner known per se, loops (5) are formed by the weft trees (1, 2) along one turning edge to form an openable seam through to which a cargo tree (7) can be inserted, and that the coarse yarns forming the layer (3) consist solely of weft trees, which are bonded to the other weft trees (1, 2) pk the drainage side of the press felt by the warp yarns of the base fabric (4), 3) are cut along a line parallel to and adjacent to the loops. Press felt according to claim 1, characterized in that the stability of the felt is reinforced by a wadding layer of fibers which is attached to the upper surface of the fabric by knitting process and is cut across the felt along the same line as for the yarns (3), so that a opening and readable endless tissue is formed. Γ Press felt according to claim 1, characterized in that the yarns (1, 2) have a weight per unit length of 80-430 tex and yarn (3) a weight per unit length of at least 160 tex.