EP1746202B1 - Method for manufacturing a paper machine screen - Google Patents

Abstract

The sieve belt includes wefts (116, 118) on both the web- and running sides respectively. At least two warp thread systems (120, 124, 128) are woven with these wefts. Each warp system is allocated a group of heddles, which move them for shed formation. The new method produces a repeating induction scheme for the warp systems, in which for at least one of the warp systems (120, 124, 128) a repeating under-pattern is provided. An independent claim is included for the corresponding sieve belt.

Description

The present invention relates to a method for producing a papermaker's fabric having a paper-side layer of weft threads and a running side layer of weft threads and at least two warp thread systems interwoven in each case with the paper-side weft threads and / or the weft side weft threads.

Such papermaking fabrics serve to receive the papermaking stock, generally in the form of a fiber suspension, from a feed system. This base material is distributed flat on such a paper machine screen or between two such paper machine screens. In the further production of water can be withdrawn through existing in such a sieve openings of the fiber suspension. An essential requirement of such paper machine fabrics is that the paper produced therewith displays as little as possible the fabric structure of the paper-side fabric layer. That is, it should be possible to obtain a smooth as possible, structure-free paper surface.

From the DE 42 29 828 A1 Such a paper machine screen with two layers of fabric is known. A paper-side fabric layer includes a paper-side layer of weft yarns interwoven with warp yarns of a first warp yarn system associated with the paper-side fabric layer. A second fabric layer comprises running weft threads which are interwoven with the warp threads of a second warp thread system assigned to the running side fabric layer. In order to ensure a cohesion between these two fabric layers, so-called binding weft threads are present, which set alternately on warp threads of the running side fabric layer and warp threads of the paper-side fabric layer. Of course that would be it is also conceivable to use binding warp threads here, ie to provide a further warp thread system ensuring the mutual connection of the two fabric layers.

The WO 02/00996 A1 discloses a papermaker's fabric also with two plies of weft yarns, namely a paper side ply with somewhat thinner weft yarns and a running side ply with somewhat thicker weft yarns. Two warp thread systems are provided so that the warp yarns of one system and the warp yarns of the other system are paired with each other, and these respective pairs of warp yarns of two different warp yarn systems alternate with each other in their integration with the weft yarns on the side and weft yarns on the paper side , so that on the one hand on the paper side, a very fine fabric structure is obtained, for example, with plain weave, on the other hand at the same time, however, a connection of the two fabric layers is achieved by these threads.

From the EP 0 264 001 is a double-layered paper machine screen with a coarse textured side and finely textured paper page known.

The US 2,792,851 discloses a method of producing a low shrinkage tissue.

It is the object of the present invention to provide a method of manufacturing a papermaking fabric which has a lower marking tendency in papermaking.

According to the invention, this object is achieved by a method for producing a papermaking fabric having a paper-side layer of weft threads and a running side layer of weft threads and at least two interwoven each with the paper-side weft threads and / or the running side weft yarn warp threads, each Kettfadensys tem is associated with a group of shafts through which the warp threads of the warp yarn systems are to be shed, the method comprising creating a draft scheme with a pull-in repeat for the warp yarn systems, in which pull-in repeat for at least one of the warp yarn systems repeating in the pull-in repeat is provided.

The method according to the invention is based on the finding that the development of stresses within a papermaking screen is an essential factor contributing to the generation of markings in the paper. This development of stresses, which is essentially supported by very uniform patterns or high symmetries, is inventively counteracted by the fact that already in the definition of the feeder, ie the assignment of the individual warp threads of the various warp thread systems to certain shafts, the structure of defined voltages a targeted irregularity is counteracted. This means that for a given weave pattern, which generally has a comparatively high uniformity, a catchment pattern with deliberately introduced or increased nonuniformity is superimposed, and thus at the shedding, which strongly influences the tension course within a then woven wire, To counteract the build up of unwanted stresses within the paper machine screen already.

For example, in the method according to the invention in the drawing repeat for at least one warp thread no Unterrapport be provided. This means that in this at least one warp thread system, the collection pattern is repeated only by joining several collection reports within the collection scheme, but not within each individual collection repeat.

Alternatively or additionally, it may be provided that in each case a repetitive sub-repeat is provided for the retraction repeat for at least two warp thread systems and that the numbers of repetitions of the sub-rapport in the retraction repeat differ. Even if in each case at least two warp thread systems, in each case, subreports are provided within a catchment repeat, but these have a different number of repetitions within the catchment repeat or each Einzugsrapportes occur, a nonuniformity can be achieved within the Einzugsrapportes.

According to a further aspect, it can be provided in the method according to the invention that in the catchment repeat at least the group of shafts, which are assigned to a warp thread system, comprises shanks following one another in the warp direction. Alternatively, the draw-in pattern or draw-in scheme can be further varied in the direction of greater non-uniformity, if in the pull-in repeat at least the two different warp thread systems associated groups of shanks in the warp direction are nested.

Since it is generally attempted to keep the number of shafts used as low as possible in the production of paper machine screens, according to the invention it can further be provided that at least one shank is associated with two warp threads of the same warp thread system in the pull-in repeat. Of course, this depends greatly on the binding structure to be achieved in the fabric layers.

The process according to the invention can be used to particular advantage in the production of paper machine fabrics on weaving machines with at least 25 shafts, preferably with at least 27 shanks and particularly preferably with at least 30 shanks.

The present invention further relates to a papermaker's fabric made by a process according to the invention.

Fig. 1

einen Schnitt durch ein mit zwei Gewebelagen hergestelltes Papiermaschinensieb in Kettrichtung;

Fig. 2

die Darstellung eines gemäß den Prinzipien der vorliegenden Erfindung realisierten Einzugsrapportes;

Fig. 3

die Darstellung eines weiteren gemäß den Prinzipien der vorliegenden Erfindung aufgebauten Einzugsrapportes.

Hereinafter, the invention will be described in detail with reference to the accompanying drawings. It shows:

Fig. 1

a section through a manufactured in two fabric layers papermaking fabric in the warp direction;

Fig. 2

the representation of a realized according to the principles of the present invention Einzugsrapportes;

Fig. 3

the representation of another Einzugsrapportes constructed according to the principles of the present invention.

In Fig. 1 a papermaking fabric manufacturable in accordance with the principles of the present invention is shown in fragmentary and longitudinal warp longitudinal section and indicated generally at 110. This paper machine screen is constructed with two fabric layers 112, 114. The fabric layer 112 is a paper-side fabric layer, that is, at the in Fig. 1 On the upper side, that surface is ready, on which the fiber suspension used for papermaking is applied and subsequently the paper is formed. The fabric layer 114 is to be interpreted as a running fabric layer. This fabric layer thus interacts with the paper machine screen 110 leading or also driving wheels or rollers. The fabric layer 112 comprises a paper-side layer of weft threads 116, while the fabric layer 114 comprises a running side layer of weft threads 118. As is known, these weft threads 116 and 118 extend essentially transversely to the production direction of the papermaking wire 110. To provide the paper-side fabric layer 112, a first warp thread system 120 with warp threads 122 is also provided. These warp threads 122 are interwoven with the weft threads 116 of the paper side layer of weft threads, wherein, for example, the weft threads 116 can realize a plain weave, a twill weave or the like with the warp threads 122 of the first warp thread system 120 lying next to one another in the weft direction.

The running-side fabric layer 114 comprises, in addition to the run-side position of weft threads 118, a second warp thread system 124 with warp threads 126. These warp threads 126 are connected to the weft threads 118 of the running side layer of FIG Woven threads interwoven, in which case a bond pattern may be selected, which is best suited to the particular occurring in terms of mechanical stress and abrasion on the running side requirements.

To be at the in Fig. 1 shown paper machine screen to ensure the cohesion of the two fabric layers 112, 114, a third warp yarn 128 is provided with warp threads 130. These warp threads 130 of the third warp thread system 128, designed to be thinner, for example, in comparison with the warp threads 122 or 126, alternately bind with weft threads 116 of the paper-side fabric layer 112 and the weft threads 118 of the fabric side 114 on the running side. Since, of course, the third warp yarn system 128 has a plurality of such warp yarns 130 in the weft direction, a stable bond between the two fabric layers 112, 114 is ensured over the entire surface of the paper machine wire 110.

In the manufacture of such papermaking fabrics, shedding machines 122, 126, 130 of the various warp yarn systems 120, 124, 128 are generally used to shed machines having a plurality of shafts sequentially arranged in the warp direction for shedding the warp yarns 122, 126. Of these are in the Fig. 1 schematically shafts A, B and C indicated. The shaft A symbolically representative of a group of shanks explained in greater detail below interacts with the warp thread 122 of the first warp thread system 120. For this purpose, this warp thread 122 is passed through an eyelet 132 of a strand 134 of the shaft A. Correspondingly, the shank B cooperates with the warp yarn 130 of the third warp yarn system 128, since this warp yarn 130 is passed through an eyelet 136 of a strand 138 of the shank B. Finally, the shank C cooperates with the warp yarn 126 of the second warp yarn system 124 by passing this warp yarn 126 through an eyelet 140 of a strand 142 of this shank C. For shedding, therefore, these shafts A, B and C are occupied in the height direction, so that with a respective Shank cooperating warp thread with respect to a weft to be introduced in the correct plane, ie above or below to position. In fact, it should be noted that the number of shanks to be provided or used for the shedding depends on the pattern of bonding to be realized. It may be necessary, on the one hand, to provide a separate shaft for each warp thread of a particular warp thread system within a weave repeat viewed in the weft direction in order to be able to move this warp thread independently of all other warp threads of this warp thread system and, on the other hand, separate groups of shafts for the different warp thread systems in order to be able to move the respective warp threads defining or associated with the respective warp threads independently of the warp threads of other warp thread systems for shedding. In fact, those are in the Fig. 1 shown shafts A, B and C representatively for each of the individual warp systems associated groups of shafts, which must include at least two shafts, in general, as explained below, but more than two shafts include.

Before such a paper machine screen 110 can be woven on a weaving machine when performing a weaving operation, it is necessary to generate a collection scheme, ie to create an association between the respective warp threads of the various warp thread systems and the shafts or shafts provided in a loom different warp systems associated groups of shafts. This will be described below with reference to the Fig. 2 explained with reference to a first variant of the invention.

The Fig. 2 FIG. 12 illustrates the weaving scheme constructed in accordance with the principles of the present invention, for example, in FIG Fig. 1 illustrated paper machine screen. It is in Fig. 2 a pull-in repeat is shown, ie a section viewed in the weft direction, which then represents a unit repeating itself in the direction of the shot, that is to say several times in a row. In the presentation of the Fig. 2 For example, the horizontal rows of boxes, numbered 1-25, correspond to the shafts used to make them. This means that 25 shafts are used in the illustrated case. The vertical columns of boxes each represent a warp thread, in which case a collection repeat comprises 48 warp threads. On the right side of the drawn-in repeat, ie to the right of the warp thread 48, the next pull-in repeat, starting with the warp thread 1, would possibly follow, while possibly a further pull-in repeat with its warp thread 48 would follow on the left side of the drawn-in repeat.

In the in Fig. 2 With reference to a collection pattern, each selected box represents the interaction of a particular warp with a particular stock. For example, the shaft 1 interacts with the warp threads 17 and 41. This means that these warp threads 17 and 41 are each guided by loops of strands of the shaft 1, so that during a vertical movement of the shaft 1, these two warp threads 17 and 41 are moved to shedding. The same applies, of course, also for all other shafts 2 to 25 and the warp threads of the respective pull-in repeat with the warp threads 1 to 48 cooperating therewith.

In the presentation of the Fig. 3 the warp threads are the ones referred to above Fig. 1 already explained three warp threads 120, 124 and 128 shown with different patterns. Thus, the warp yarns numbered 1, 5, 9, 13, 17, 21, 25, 29, 33, 37, 41, 45 illustrated with checkered patterns or intersecting lines are the warp yarns of the first warp yarn system 120, ie those which together with the weft threads 16 form the paper-side fabric layer. The warp threads 4, 10, 15, 18, 24, 28, 34, 39, 42 and 48 shown with oblique hatching are the warp threads of the second warp thread system 124, ie those warp threads which together with the weft threads 118 form the running side fabric layer 114. The remaining warp threads, ie the black-marked warp threads 2, 3, 6, 7, 8, 11, 12, 14, 16, 19, 20, 22, 23, 26, 27, 30, 31, 32, 35, 36, 38 , 40, 43, 44, 46, 47, are the warp threads of the third warp thread system 128, ie those warp threads which realize the mutual connection of the two fabric layers 112, 114.

The interaction of the warp threads of the various warp thread systems with the shafts 1 to 25 is in the in Fig. 2 clearly visible on the left sample bar. It can be seen that the warp threads of the first warp threading system 120 cooperate with the shafts 1 to 6, that the warp threads of the third warp threading system 128 cooperate with the shafts 7 to 15 and that the warp threads of the second warp threading system 124 cooperate with the shafts 16 to 25. It should be emphasized here that the numbering of the shanks indicates the sequence of these shafts in the warp direction and in the weaving direction. Associated with each warp yarn system 120, 124 and 128, respective groups of shafts are provided, wherein the group associated with the first warp yarn system 120 comprises the shafts 1 to 6, the group associated with the second warp yarn system 124 comprises the shafts 16 to 25 and that of the third Warp system 128 associated group comprising shafts 7 to 15. One recognizes in Fig. 2 Furthermore, that the stems of the individual groups in the warp direction follow each other directly, so that there is a direct and without mixing existing sequence of these three groups of shafts 1 to 6, 7 to 15 and 16 to 25.

One recognizes by means of in Fig. 2 In addition, the retract repeat illustrated in FIG. 1 illustrates that this repeating smallest unit of the retraction scheme for all three warp thread systems 120, 124 and 128 is associated with the two warp thread systems 120 and 128, ie the warp yarns shown in checkered pattern and the warp yarns shown in black. That is, within the pull-in repeat defined for all three warp thread systems is 120 and 128 respectively for the two warp thread systems an even smaller repeating pattern unit exists. In the warp yarns of the warp yarn system 120, that is, the warp yarns cooperating with the shafts 1 to 6, the associated lower repeat comprises six warp yarns, that is, for example, the warp yarns 1, 5, 9, 13, 17, and 21. By the interaction with the shafts 1 to 6 drawn-in pattern of these warp threads is repeated from the warp thread 25 of this warp thread 120. That is, within the catchment repeat of the Fig. 2 the subreport associated with the first warp threading system 120 is present twice. The same applies to the third warp thread system 120. Here too, the assigned subreport is present twice within the catchment repeat, once with the warp threads 2, 3, 6, 7, 8, 11, 12, 14, 16, 19, 20, 22 23. The second repetition then has the warp thread 26 as the first warp thread occurring in the numbering sequence and furthermore comprises the warp threads 27, 30, 31, 32, 35, 36, 38, 40, 43, 44, 46, 47.

Such a pattern repeating within the draw repeat does not exist in the second warp thread system, ie the warp threads interacting with the shafts 16 to 25. Here, the next repetition actually takes place only at the next repetition of the catchment repeat, which ultimately also serves as the basis for the catch repeat comprising all three warp thread systems 120, 124 and 122 extending over the warp threads 1 to 48.

By providing sub-reports or a sub-repeat in association with at least one of the warp thread systems, while there is no sub-repeat for at least one other warp thread system and its pattern actually repeats only at the next repetition of the feed repeat, a collection scheme is generated which is then executed Weaving contributes to the structure of stresses in a paper machine screen thus produced is suppressed as much as possible. The binding pattern occurring with comparatively high periodicity becomes a comparatively disordered collection pattern superimposed, which obviously has a positive effect in preventing such stresses. Of course, a wide variety of possible variations are conceivable. For example, in the case of Fig. 2 illustrated embodiment of a catchment repeat only in association with a single of the three warp yarns 120, 124 and 128 may be provided a subreport, while repeated in the other two warp yarns, the collection pattern only every 48 threads. Also, the division of the sub-report or the sub-reports with respect to the catchment report could be different. For example, a subreport could be present three times or more in the catchment repeat. It is also conceivable that when there are sub-reports in association with two warp thread systems, they do not occur with the same pitch, but, for example, in one of the warp thread systems, a pattern defined by a sub-repeat occurs twice in the pull-in repeat, whereas in another warp thread system, this occurs through a sub-repeat defined pattern occurs three or more times. Also, the principles of the present invention find application when, for example, only two warp thread systems are present. In the case of in Fig. 2 This could mean that the shafts 7 to 15, for example, are not effective, so that only the two groups of shafts 1 to 6 (in association with the first warp thread system 120) and 16 to 25 (in association with the second warp thread system 124 ) available. In such a catchment repeat or intake scheme, for example, a paper machine screen would then be produced which has no warp threads essentially serving only the mutual connection of the fabric plies 112, 114, but a papermaking fabric in which the warp threads of the two warp thread systems woven together with the weft threads simultaneously the connection is made. In this case too, it would then be ensured in the example set out above that a subreport exists in association with the first warp thread system 120, namely a subreport occurring twice in the pull-in repeat, while no subreport is present in association with the second warp thread system 124. Also when using only two warp systems, it would be conceivable that in each case a sub-repeat is present, in which case the division of the sub-reports must be different, so for example, a sub-repeat repeated twice in Einzugsrapport, while the other Unterrapport in Einzugsrapport occurs three times or three times. Would occur in this case, both or all sub-reports with the same division, this would actually represent a reduction of the entire catchment repeat on the size of the sub-reports, with the result that within a then so defined catchment rapport to none of the warp threads an even finer designed sub-report would be present.

Another variation is in Fig. 3 illustrated. One recognizes in Fig. 3 in that the shanks of the different groups of shanks cooperating with the warp threads of the different warp thread systems do not define a warp-sequential block formation, but that a nesting of the individual groups is present. Thus, the shafts 3, 6, 9, 12, 15 and 18 are effective in association with the first warp thread system 120, ie the warp threads illustrated with crossed lines. In association with the second warp thread system 124, that is to say the warp threads symbolized by oblique hatching, the shafts 14, 16, 17 and 19 to 25 are effective while in association with the third warp thread system 128, ie the warp threads realizing the mutual connection of the fabric layers 112, 114 that shafts 1, 2, 4, 5, 7, 8, 10, 11 and 13 are effective. Nonetheless, here as well, in association with the warp threads of the first warp thread system 120 and the warp threads of the third warp thread system 128, a repeat repeat is present in the repeat pattern, whereas this is not the case with the warp threads of the second warp thread system 124. The consequence of this interleaving of the groups of shafts is that in the catchment repeat thus defined or in the repetition of such a repeat comprising a collection scheme, there is a further increased "disorder" in the allocation of the shanks to warp threads is what is reflected in a corresponding more or less quasi-statistical distribution of the shedding pattern. This also provides a further contribution to avoiding a very regular pattern or shedding pattern and thus also the reduction of tensions then existing in the tissue.

It goes without saying that even at the in Fig. 3 illustrated embodiment with regard to the design of the sub-reports the foregoing with reference to the Fig. 2 explained variation possibilities can be used. Overall, to the within the sub-reports or even those warp thread system that has no sub-repeat, selected collection pattern that here, for example, from the textile weaving known collection pattern can be used. For example, indents with S-indent or Z-indent can be selected, as well as offset indents or intermittent indents. Also a tip feeder, so simple tip feeder or multiple tip feeder, a broken tip feeder or a broken tip feeder can find application. The same applies, of course, to composite indentations and part-to-part indentations.

Finally, it should be noted that the Fig. 2 and 3 show that shafts can interact with a single warp thread or can cooperate with several warp threads. This will depend primarily on which weave pattern is to be weaved and which of the warp threads for this purpose are always to move together to shed training. In general, it will be advantageous to keep the number of shafts used as low as possible, so that, if possible, as many warp threads should cooperate with a shaft. It should be understood, of course, that due to the fact that the warp threads of different warp thread systems are basically to be moved independently of each other, a shaft actually only ever cooperates with warp threads of a warp thread system.

Claims (7)

1. Method for manufacturing a paper machine fabric having a paper-side layer of weft threads (116) and a run-side layer of weft threads (118) and at least two warp thread systems (120, 124, 128) in each case woven with the paper-side weft threads (116) and/or the run-side weft threads (118), each warp thread system (120, 124, 128) being assigned a group of heddles, by which the warp threads of the warp thread systems (120, 124, 128) are to be moved in order to form sheds, the method comprising the production of a draft scheme having a draft repeat for the warp thread systems (120, 124, 128), in which draft repeat a sub-repeat that repeats in the draft repeat is provided for at least one of the warp thread systems (120, 124, 128).
2. Method according to Claim 1, characterized in that, in the draft repeat for at least one warp thread system (124), no sub-repeat is provided.
3. Method according to Claim 1 or 2, characterized in that, in the draft repeat for at least two warp thread systems, in each case a repeating sub-repeat is provided, and in that the numbers of repetitions of the sub-repeats in the draft repeat differ.
4. Method according to one of Claims 1 to 3,
   characterized in that, in the draft repeat, at least the group of heddles assigned to one warp thread system (120, 124, 128) comprises heddles following one another immediately in the warp direction.
5. Method according to one of Claims 1 to 4,
   characterized in that, in the draft repeat, at least the groups of heddles assigned to two different warp thread systems (120, 124, 128) are nested in one another in the warp direction.
6. Method according to one of Claims 1 to 5,
   characterized in that, in the draft repeat, at least one heddle is assigned to two warp threads of the same warp thread system (120, 124, 128).
7. Method according to one of Claims 1 to 6,
   characterized in that the paper machine fabric (10) is woven on a loom having at least 25 heddles, preferably having at least 27 heddles, particularly preferably having at least 30 heddles.

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