EP0198773B1 - Apparatus for making a wet press felt or paper screen cloth endless - Google Patents

Abstract

A papermaking screen has a pair of ends secured together at a joint and formed of a plurality of longitudinal warp filaments having warp ends secured together at the joint and weft filaments transversely woven with the warp filaments. One end of each warp filament is formed with a short loop extending longitudinally a short distance past the weft filaments and the opposite end is formed with a long loop extending longitudinally a long distance past the weft filaments longitudinally in line with but longitudinally spaced from the respective short loop. A first portion of the warp filaments has its long loops projecting from one end of the belt and a second portion has its long loops projecting from the opposite end of the belt between the short loops of the first portion. A first joint rod passes transversely through all of the long loops but only through the short loops of the first portion and a second joint rod passes transversely through all of the long loops but only through the short loops of the second portion. The short distance is equal to about half of the long distance.

Description

The present invention relates to a joining device for a wet press felt or stationery fabric, of the type described in the preamble to the single claim and known from document FR-A-2 195 303.

Numerous devices are already known for joining the ends of a stationery fabric so as to transform it into an endless belt used as a conveyor belt in the manufacture of paper. Some devices use external elements such as staples, spirals or pliers.

Other devices are based on the introduction of a connecting rod or similar device between loops formed by warp threads at each end of the strip, in an area devoid of weft threads. It has been proposed in document FR-2 195 303 to form at each end of the strip that it is desired to combine two series of loops of different length, to nest these loops one in the other so as to determine two separate channels each consisting of a small loop at one end and a large loop at the other end, a rod is then introduced into each of the channels to ensure the junction.

It should however be noted that the loop devices of the prior art are not entirely satisfactory. Indeed, the relative arrangement of the loops of the two ends of the same wire, offset with respect to one another and nested one inside the other hinders the longitudinal flow of the water. Furthermore, this arrangement of the loops of the same wire joined by the same rod leads to the formation of a "hard knot" which risks causing the marking of the sheet of paper under the pressure rollers.

Document US-A-4,095,622 furthermore describes a joining device for fabrics commonly known as "dryer covers". The purpose of such a covering is to uniformly apply the sheet of paper against the heating cylinders to facilitate the transfer of heat and therefore the evaporation of the water from the sheet. To do this, it must therefore be breathable but above all have a good surface uniformity.

In the device described in this patent, only one pair out of three loops, formed by the monofilaments, is in line on two different rods.

In addition, and in order to obtain a small thickness of the fabric, the loops are lying in the plane of the fabric, which on the one hand would hinder the flow of water in the case of application to the production of a press felt and on the other hand would make it impossible to assemble the loops of the two ends by engagement of rods, given the lack of alignment of these loops.

The object of the present invention is to overcome these drawbacks by proposing a new joining device which facilitates the longitudinal and vertical flow of water and eliminates the risks of marking the sheet of paper while presenting a resistance to breakage. improved over simple devices of the prior art.

To this end, the groups of loops have an odd number of loops, each of which is separated from the adjacent group by a non-overlapping loop bypassing the last weft thread, the central loop of each group being longer than those which surround it, so that the loops of each group are aligned along the lines converging on the central loop, each loop at one end is aligned opposite the corresponding loop at the other end, the number of rods being equal to three.

This joining device is more particularly intended for covering presses. This type of covering, subjected to pressures greater than 100 bars, comes into contact with a sheet of paper saturated with water, therefore very fragile.

The very regularity required for the covering, in particular at the junction is at the limit of acceptable hydraulic pressure, which excludes any constriction of water drainage channels in the longitudinal direction, as well as any weakening resistance.

Using the device according to the invention, an interval is made which facilitates the longitudinal and vertical flow of water and eliminates the risk of marking the sheet of paper.

According to the invention, the series of loops aligned in front of each other are repaired on three rods.

• Figures 1 et 3 sont des vues à plat de dispositifs de jonction connus à boucles imbriquées;
• Figures 2 et4sont desvues agrandies d'un détail des figures 1 et 3;
• Figure 5 est une vue à plat du dispositif de jonction selon le US-A-4 095 622;
• Figure 6 est une vue à plat du dispositif de jonction selon l'invention;
• Figure 7 est une vue agrandie d'un détail de figure 6;
• Figure 8 est une vue de côté de six paires successives de joncs formant la jonction selon l'invention;

The present invention will be better understood moreover and its advantages will emerge clearly from the following description of an embodiment of the invention, with reference to the appended schematic drawing in which:

• Figures 1 and 3 are plan views of known junction devices with nested loops;
• Figures 2 and 4 are enlarged views of a detail of Figures 1 and 3;
• Figure 5 is a flat view of the joining device according to US-A-4,095,622;
• Figure 6 is a flat view of the joining device according to the invention;
• Figure 7 is an enlarged view of a detail of Figure 6;
• Figure 8 is a side view of six successive pairs of rods forming the junction according to the invention;

And, Figure 9 is a perspective view of this junction.

In the figures, the warp threads are generally represented by (2) and the weft threads by (3).

In the known joining device represented in FIGS. 1 and 2, the warp threads (2) form at each end of the fabric, and in an area devoid of weft threads (3), a series of loops (4) and ( 5) arranged alternately and nested one inside the other so as to form a passage intended to receive a single junction ring (6).

Devices of this type have a certain number of drawbacks, among which one can cite a rather weak solidity of the junction; in fact, only half of the wires participate in this junction.

In the known joining device represented in FIGS. 3 and 4, the warp threads (2) form, at each end of the fabric, and in an area devoid of weft threads (3) two series of loops of different length (7 ) and (8) on the one hand and (9) and (10) on the other.

The loops (7) and (9), formed by the same warp thread on the two ends of the fabric, as well as the loops (8) and (10) are nested one inside the other, the rods (11) and (12) ensuring the junction of the fabric by passing through the loops formed by the same warp thread.

The resistance of the joining device is certainly improved due to the presence of the two rods (11) and (12) but it should be noted that the broken line formed by the nested loops (7) and (9) on the one hand and ( 8) and (10) on the other hand impede the flow of water. This line can also lead to the formation of thickness which risks causing the sheet of paper to be marked under the pressing devices.

In the junction device represented in FIG. 5, which corresponds to that described in US-A-4,095,622, it can be seen that two adjacent wires, belonging to the same plane of the felt, define a loop which cannot be kept perpendicular to this same plane to facilitate the re-entry of the rod, which suggests assembly difficulties.

In addition, a double rod is necessary to match the "bends", which means that the rod does not cross all the loops, and this at the expense of strength.

The joining device according to the invention as shown in Figures 6 to 9 aims to overcome these drawbacks. This device also comprises, at each end of the fabric, in a region devoid of weft threads (3), several series of loops (13, 14, 15, 16, 17 and 18) of different length formed by the warp threads (2). However, unlike the joining devices described above, these series of loops are not nested one inside the other but aligned one opposite the other, while defining channels for the passage of the rods (19, 20 and 21

As can be seen, in fact, in FIG. 7, the loop (14) formed by a warp thread on one end of the fabric and the loop (16) formed by the same warp thread at the other end of the canvas are not offset from each other, as was the case in the embodiments shown in Figures 1 to 4, but aligned one opposite the other. It is the same for the loop (15) and for the loop (17).

The channels intended to allow the passage of the rods (19, 20 and 21) are no longer then formed by the cooperation of two nested loops coming from the same warp thread, but by the cooperation of loops coming from different warp threads; for example, the rod (19) will pass through the series of loops (15) and (18), the rod (20) through the series of loops (14) and (17) and the rod (21) into the series of loops (13) and (16).

The loops (14) and (16) formed, at the two ends of the fabric, by the same warp thread, are kept in alignment by two different rods, respectively (20) and (21); it is the same for the loops (15) and (17) held in alignment by the rods (19) and (20). This alignment is even more clearly represented in FIG. 9. The wires are rigorously superimposed two by two, which avoids the change of plane of the junction device of US-A-4,095,622.

It is clear from Figures 6 to 9 that it is thus created between the loops formed at both ends by the same warp thread intervals facilitating the flow of water under the press along the warp threads; the interstitial flow channels are rigorously maintained without distortion; thickness formation is also avoided, which eliminates the risk of marking the sheet of paper.

According to the invention, all the warp threads of the fabric form, at each end, loops.

The particular arrangement of the loops according to the invention gives them more freedom, which allows the biasing of the frame to limit vibrations and provides the elasticity necessary to compensate for the inevitable jolts which risk causing the junction to break.

Compared to conventional types of junction, it has been possible to determine that the solidity of the junction according to the invention is approximately 166%; indeed, all the wires participate in the tensile force.

Another important advantage of the joining device according to the invention is its ease of assembly, often difficult in part pressing. Indeed, when positioning the loops (15) and (18) intended to receive the first rod (19), only one sixth of the network of loops of the junction is assembled. It is the same for the positioning of the loops (13) and (16) intended to receive the rod (21). The loops (14) and (17) intended to receive the rod (20) are self-positioned by the assembly of the two preceding rods.

Claims (1)

1. Apparatus for making a wet press felt or paper screen cloth, of the type having at each end of the felt or cloth, in an area lacking weft thread (3), several series of overlapping loops formed by the warp threads (2) intended to be joined to the corresponding loops of the other end by means of transverse rods engaged in all or part of the loops of each end, the overlapping loops of the other end of the cloth being set in reverse so as to form complementary groups, each of the overlapping groups being set in a plane which is perpendicular to the plane of the felt or cloth, characterized in that the groups (13, 14, 15, 16, 17, 18) have an uneven number of loops, each of which is separated from the adjacent group by a nonoverlapping loop (22) passing around the last weft thread (3), the central loop (13, 18) of each group being longer than those (14, 17) which surround it, in such a way that the loops of each group are aligned along straight lines which converge on the central loop (13, 18), in that each loop (13,14,15,22) of one end is aligned opposite the corresponding loop (22, 16, 17, 18) of the other end, the number of rods (19, 20, 21) being equal to three.

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