EP1387902B1 - Wire cloth for paper-making machine - Google Patents

Abstract

At a location (24) where they pass over nominated backing side wefts (20), backing side warps (22) alternate over paper side wefts (16) and return to the backing side. Preferred features: At the alternation (24), at least four nominated backing side wefts (20) provide support. A long floating binding is used. Between the first four backing wefts (20) forming a group (26), and a second group (28) with two backing wefts (20), towards the paper side warp (18), above a backing side warp (22) a backing side weft (20) is arranged. This supports a paper side weft (16), over which a paper side warp (18) is led. The support direction of paper side and backing side wefts (16, 20) runs transversely with respect to the planes of the lower and upper webs. A variant with inclined support arrangement is described. There is always an odd number of paper side wefts between alternations. Warp succession with alternations is interrupted by weft sequences without them. The wefts on the backing side have greater cross section than the allocated wefts on the paper side. Lines of deflection from upper and lower webs and neutral lines of deflection at the alternations, run together and form a kind of hinge, tending to prevent damaging layer separation.

Description

The invention relates to a papermaking fabric consisting of a single fabric for the paper side and a single fabric for the running side according to the feature configuration of the preamble of claim 1.

Today, more and more high-performance paper machines with speeds up to 2000 m / min and working widths over 10 m are used in the paper-producing industry. The sheet forming unit is usually designed as a twin-wire former, in many cases as a gap former. Characteristic of the machines is that the sheet forming operation takes place immediately between two paper machine wires in a relatively short dewatering zone. Due to this short distance and the high production speed, the time for sheet formation is reduced to a few milliseconds. During this period, the solids content or dry content of the pulp suspension must be increased from about 1% to about 20%. This means for the paper machine sieves that they must have a very high dewatering performance but still can leave no markings in the paper and provide a high fiber support.

Another important point is the transverse stability of the screen covering, which is decisive for the uniformity of the thickness and moisture profile of the paper web. Especially in the modern machines with large working widths, the relevant requirements are set very high. In order to improve the formation, forming strips are therefore increasingly used in the sheet-forming zone, which are mutually arranged on the running sides of the wires and pressed against them. This leads to a rapidly changing, longitudinally extending deflection of the fabric of the screens.

Nowadays, one usually tries to meet these requirements through the use of composite fabrics. A pertinent composite fabric is described for example in DE 42 29 828 C2. The paper machine screen known in this respect consists of two superimposed screen fabrics, which are formed at least one ply and connected by transversely and / or longitudinally extending binding threads, wherein one of the screen fabric as a definition fabric with the mechanical properties of the composite fabric in terms of elongation and rigidity of certain training and the other Screen fabric is designed as a reaction fabric with a higher elongation and lower stiffness than the definition fabric. The mentioned screen fabric thus consist of warp and weft threads, which are connected by additional binding threads together. By forming the Siebgewebelagen as a reaction or definition fabric the inner wear and in particular the wear of the binding threads is counteracted and thus increases the life of the composite fabric and an unwanted separation of Siebgewebelagen avoided even in the longer term. The mentioned internal wear of a composite fabric is characterized in particular conditionally that in the screen deflections, as they occur in the range of guide rollers or wire section over which the composite fabric is guided, the individual Siebgewebelagen be stretched or compressed to varying degrees.

Since the mentioned binding threads do not belong to the fabric structure, but are independent components, they are kept as thin as possible in diameter in order to disturb the drainage only slightly. With correspondingly high stresses then there is the possibility that the thin binding threads tear and the bond between the meshes dissolves. In a known papermaking machine according to EP 0 432 413 B1, which is also constructed as a composite fabric, although it has already been proposed to use binding threads as two fabric-own threads and weave them into the respective other fabric layer to form X-shaped intersections to the to avoid disadvantages described in the prior art; alone by the accumulation of the known change points in the transverse direction unintentionally also creates a stiffening of the known tissue. In particular over larger web lengths, it can then lead to significant differences in length, which in turn make noticeable in differences in tension, with the result that the fabric-making binding threads producing the compound also tear and can lead to failure of the known papermachine fabric. Also, in view of this known special weave, it is essentially only possible to process transverse threads of one type, that is to say transverse threads with substantially identical diameters, both for the upper and for the lower fabric, which reduces the possibilities of effective support on the running side , Moreover, the production of the known composite fabrics described is complicated and expensive.

EP 0 698 682 A1 discloses a fabric consisting of in each case a system of upper shots, lower shots and chains, the latter being formed from a system pair of a first and a second type of warp threads. In this case, the first type of warp threads with the upper shots and at predetermined intervals intermittently interwoven with the defaults. The second type of warp yarns run between the upper and lower shots and bind with the upper shots at the point where the first warp yarn belonging to the pair binds with the undershoot. The warp threads lie directly above each other, except at the point where the second warp threads bind with the upper weft. By this closest prior art, the surface uniformity is improved on the paper side in a papermaker's fabric, so that it is substantially free of mark; Nevertheless, a layer separation or a shift of the fabric layers to each other can not be completely excluded.

From DE 30 36 409 A a double-layered screen for the sheet forming part of a paper machine is known with pairs of weft threads arranged one above another and with warp threads, all warp threads being integrated into the upper layer of the wire. Only a part of the warp threads is integrated as a so-called construction chain in the lower layer of the sieve. By this paper machine screen, it is also known to let a running side warp from the running side to the paper side and from this back to the running side change. Again, the positional separation described in long-term use can not be excluded.

From US-A-3 127 308 a generic papermaking fabric is known, consisting of a single fabric for the paper side and a single fabric for the running side, each consisting of a set wefts and Warp threads are made, wherein the diameters and the number of paper and running side warp threads are substantially the same and the paper side warp threads and weft threads form a plain weave with each other, wherein at least a part of the running side warp threads each at a point at which this warp over at least an associated running-side weft thread, changes to the paper side and passes over the subsequent paper-side weft thread and then returns to the running side. Also in this known solution, it may lead to a layer separation of upper and lower tissue with a view to a possible displacement of the fabric layers to each other.

Based on this prior art, the present invention seeks to further improve paper machine screens of the aforementioned type such that they have the same quality standards for paper production over a longer service life and on the other can be realized inexpensively. A pertinent task solves a papermaking machine with the features of claim 1 in its entirety.

Characterized in that according to the characterizing part of claim 1, the bending lines of upper fabric and lower fabric and the neutral bending line converge at the change point and form such a kind hinge point that counteracts a harmful paving, beyond a mark-free paper side in plain weave while improving the surface uniformity reached. The result is a compact connection of the individual fabric without additional binding threads, with a layer separation of the individual fabric or a shift of the same to each other due to the bending line design to create a kind of hinge point is largely excluded. Thus, with the paper machine wire according to the invention with high production quality, long service life can be achieved in papermaking, and the paper machine wire can then also be realized cost-effectively.

A preferred embodiment of the Papierrriaschinensiebes invention is characterized in that in the area of the change of the running side warp from the running side to the paper side and from this back to the running side at least four associated running side weft threads support the change point. In this case, the weft threads can be used on the running side, which lead to a high transverse stability within the fabric composite and form a corresponding abrasion volume, which increases the service life of the paper machine wire. Preferably, it is further provided that the plain weave is formed as a longer-floating binding, which improves the surface uniformity in papermaking.

In a particularly preferred embodiment of the papermaking fabric according to the invention a running side weft thread is arranged between the four a first group forming running weft threads and a second group with two running side wefts in the direction of the paper side warp above a running side warp, which supports a paper side weft over which a Papierseitiger Warp thread is guided. Due to the supporting points thus formed results in a high degree Stability based on the considered two single fabric layers of the screen.

Preferably, the support direction of Papierseitigem and running side weft yarn is arranged transversely to the planes of lower and upper fabric extending, which may alternatively also be provided that the support direction extends in an alternating oblique arrangement to the tissues. As a result of the oblique arrangement selected in this way, the supporting forces are introduced into the lower tissue such that a ply separation or a displacement of the tissue is reliably counteracted with certainty. The latter is especially true when obliquely extending support arrangement, the successive weft threads of the paper side occupy a greater distance from each other than the associated supporting weft threads of the running side.

Further advantageous embodiments are the subject of the other dependent claims.

Fig.1

einen Schnitt in Längsrichtung entlang der Linie I - I einer ersten Ausführungsform des Papiermaschinensiebes nach der Fig.2;

Fig.2

die Papierseite der ersten Ausführungsform mit einem Schußverhältnis von 1 : 1;

Fig.3

einen Schnitt in Querrichtung entlang der Linie II - II der ersten Ausführungsform in Fig.4, wobei die Laufseite unten ist;

Fig.4

die Laufseite der ersten Ausführungsform des Papiermaschinensiebes von unten betrachtet;

Fig.5

einen Schnitt in Längsrichtung entlang der Linie III - III in Fig.6 sowie entlang der Linie IV - IV in Fig.7, beides betreffend eine zweite Ausführungsform des Papiermaschinensiebes;

Fig.6

die Papierseite der zweiten Ausführungsform mit einem Schußverhältnis von 3 : 2;

Fig.7

die Laufseite der zweiten Ausführungsform des Papiermaschinensiebes von unten betrachtet;

Fig.8 und 9

das erste Ausführungsbeispiel nach den Fig.1 bis 4 mit einem Schußverhältnis von 1 : 1, in dem sich die Schußfolge nach 16 Schüssen wiederholt bzw. bei dem eine Schußfolge mit Einbindung durch eine Schußfolge ohne Einbindung unterbrochen ist;

Fig.10

das zweite Ausführungsbeispiel gemäß den Fig.5 bis 7 mit einem Schußverhältnis von 3 : 2 (Ober- zu Unterschuß), bei dem sich die Schußfolge nach 20 Schüssen wiederholt.

In the following, the papermaking wire according to the invention will be explained in more detail with reference to various embodiments. This show in principle and not to scale representation of the

Fig.1

a longitudinal section along the line I - I of a first embodiment of the papermaking fabric of Figure 2;

Fig.2

the paper side of the first embodiment with a shot ratio of 1: 1;

Figure 3

a section in the transverse direction along the line II - II of the first embodiment in Figure 4, wherein the running side is below;

Figure 4

the running side of the first embodiment of the papermaker's wire viewed from below;

Figure 5

a longitudinal section along the line III - III in Figure 6 and along the line IV - IV in Figure 7, both relating to a second embodiment of the papermaking wire;

Figure 6

the paper side of the second embodiment with a shot ratio of 3: 2;

Figure 7

the running side of the second embodiment of the papermaking fabric viewed from below;

8 and 9

the first embodiment according to Figures 1 to 4 with a shot ratio of 1: 1, in which the firing sequence repeated after 16 shots or in which a firing sequence is interrupted with involvement by a firing sequence without involvement;

Figure 10

the second embodiment according to Figures 5 to 7 with a shot ratio of 3: 2 (top to bottom), in which the firing sequence repeated after 20 shots.

The abovementioned figures show, in part, different embodiments of screen fabrics for a paper machine screen, not shown as a whole, which can be used in particular for the so-called sheet forming zone in conventional paper-making machines. The paper screen 12 consists in each case of a set of weft threads 16 and warp threads 18. The running side 14 also consists of a set of weft threads 20 and warp threads 22. As in particular 8, 9 and 10 show, form the paper-side warp threads 18 and the associated weft threads 16 together a plain weave. Furthermore, it can be seen from the figures that the diameters and the number of paper and running side warp threads 18,22 are substantially equal. The respective running-side warp thread 22 changes at a designated as a whole by 24 change point from the running side 14 on the paper side 12 and then returns to the running side 14 back. In the area of this change of the running-side warp thread 22 from the running side 14 to the paper side 12 and from this back to the running side 14, the changing point 24 is supported by four running side weft threads 20 lying next to one another in a plane. Further, a four-side weft yarn 20 forming a first group 26 and a second group 28 having two weft yarns 20 in the direction of the paper-side warp 18 are disposed above a running-side warp 22, a weft yarn 20 supporting a paper-side weft yarn 16 over the the respective paper-side warp thread 18 is guided.

As shown in FIGS. 1, 8 and 9, the direction of support of Papierseitigem and running side weft 16,20 transverse to the planes of lower and upper fabric in the form of the paper side 12 and the running side 14. As shown in FIGS However, .5 and 10 can the support direction in an alternating oblique arrangement to the said tissues 12,14 run. It is crucial that to form a designated as a whole by 30 support point in a cross-section thinner paper-sided weft thread 16 is supported on a cross-section thicker running side weft 20 and that the pertinent support point 30 up and down from the paper side warp threads 18 and the running side Warp threads 22 is supported. The respective support point 30 may be formed directly by the fact that the weft threads 16 and 20 abut each other; these can according to the representations according to FIGS. 5 and 10 but also comply with a predetermined distance from each other, which is optionally closed only when loaded and allows the support. Particularly in the case of an obliquely extending support arrangement, the successive weft threads 16 of the paper side 12 occupy a greater distance from each other than the associated supporting weft threads 20 of the running side 14.

The running-side warp and weft threads 20,22 usually form a long-floating eight-shaft underside, in which the shots are doubly involved, ie by two adjacent warp threads. The connection from paper side 12 to the running side 14 is thus in the form that the respective running side warp 22 at a predetermined position at which it is on the running side four wefts 20 of the first group 26, changes to the paper side 12 and there over the paper-side shot 16 is running. Since there is usually no room in the plain weave to additionally accommodate this alternating warp thread 22, since this would then close the respective stitch, the paper-side warp thread 18 is removed from the top at the same time and runs according to the partial illustration according to FIG Paper-side weft threads 16.

This achieves the connection of the running side fabric 14 to the paper side 12 and since the paper-side chain extends at the respective binding point under the top, the running side chain takes over the filling of paper-side surface at the same time in addition to the function of integration. The paper-side structure remains largely intact, which results in particular from the illustration according to FIG. Since the slope of the running-side binding is taken over the binding sites 32 in the paper side 12, the binding sites 32, as shown in part in Figure 2, evenly distributed in the binding repeat. By the pertinent binding sites 32 is thus ensured that the structure of the lower fabric or the running side 14 is not changed in a harmful manner. The double inclusion of the running shots also increases the stability of the entire fabric in terms of so-called. Diagonal shift, which occurs when the tensile load on the fabric width is different. The latter occurs especially in large machine widths, which can not always ensure that the drive and friction forces occur uniformly over the entire width. It then happens that the screen can distort partially, which leads in the worst case to a reduction of the wire width and thus to unusability of the paper machine screen.

During production and also during the course of a paper machine screen, the longitudinal threads 18, 22, ie the chains, are always subjected to tensile stress. In a normal plain weave, the differently directed forces offset by the inverse adjacent warp threads, resulting in a resultant force in the tissue plane and no uneven surface deformations occur. But if one binds an upper weft with the lower chain, as in the paper machine wire according to the invention, a force component comes in vertical Direction to that can be compensated by the paper-side shots and the adjacent upper chains only bad. As a result, the lower chain pulls the upper weft into the fabric and the paper side gets a dent. By the realization of the layer connection according to the invention by the chain is effected that it can not come to displacements of the two individual fabrics and thus to internal wear with final layer separation at Längsbiegungen the fabric in the paper machine. In Fig. 1, the neutral bend line 34 is shown along with the bend line 36 of the top fabric and the bend line 38 for the bottom fabric. Furthermore, in FIG. 1, the bending force introduced into the paper machine screen is represented by an arrow labeled "F", the corresponding counter bearing points in the lower fabric being represented by two stylized triangular editions. It is thus clear from FIG. 1 that when bending force F is introduced at change point 24, the three bending lines 34, 36, 38 in the region of paper-side weft thread 16 which lies below the force introduction point and is received between warp threads 18 and 22, a kind of joint or predetermined bending point is formed, which entgegenwi the ply separation.

The bonding idea according to the invention can be applied to a wide variety of weft ratios from top to bottom fabric, as a result of which the properties of the fabrics can be largely adapted to the respective requirements of the paper machine with regard to openness (drainage performance), stability and abrasion volume (running time). In this case, over the length of the firing sequence, an almost arbitrary distribution and adjustment of the frequency of the binding sites 32 and thus also an optimization of the strength of the connection can be made. In contrast, if you tie in the transverse direction, is limited, as shown in the prior art, by the finite number of shafts.

FIG. 8 shows an example of a section of a paper machine screen with a shot ratio of 1: 1, in which the shot sequence is repeated after 16 shots. In the embodiment according to FIG. 9, a weft sequence is interrupted with involvement by a weft sequence without involvement, the adjacent warp threads then being overlapped so that the uniform distribution is nevertheless maintained. In the embodiment according to FIG. 10, a shot ratio of upper to lower shot of 3: 2 is present at which the shot sequence is repeated after 20 shots. The above-mentioned embodiments represent only a part of the possible variety and applications for the paper machine wire according to the invention.

Claims (9)

1. Paper machine sieve, consisting of a single mesh for the paper side (12) and a single mesh for the running side (14), each consisting of a set of weft threads (16; 20) and weave threads (18; 22), whereby the diameter and the number of the paper and running side weave threads (18; 22) are substantially identical and the paper side weave threads (18) and weft threads (16) form a screen connection with each other, whereby at least a part of the running side weave threads (22) each alternate to the paper side (12) at an alternation point (24) where this weave thread (22) is located above at least one associated running side weft thread (20) and extends across the next paper side weft thread (16) as well as subsequently returning to the running side (14), characterised in that the bend lines (36; 38) of the upper mesh and the lower mesh as well as the neutral bend line (34) join at the alternating point (24) and form a kind of joint in this way, which counteract harmful layer separation.
2. Paper machine sieve according to Claim 1, characterised in that at least four associated running side weft threads (20) support the alternation point (24) in the area of the alternation of the running side weave thread (22) from the running side (14) to the paper side (12) and from this back to the running side (14).
3. Paper machine sieve according to Claim 1 or 2, characterised in that the screen connection takes the form of a long flocking connection.
4. Paper machine sieve according to Claim 2 or 3, characterised in that a running side weft thread (20) is located in the direction of the paper side weave thread (18) above a running side weft thread (22) between the four running side weft threads (20) forming a first group (26) and a second group (28) with two running side weft threads (20), the same supporting a paper side weft thread (16) over which a paper side weave thread (18) is guided.
5. Paper machine sieve according to Claim 4, characterised in that the support direction of the paper side and the running side weft threads (16, 20) extends transverse to the level of the lower and upper mesh, or in that the support direction extends in an alternating diagonal arrangement to the meshes.
6. Paper machine sieve according to Claim 5, characterised in that the adjacent weft threads (16) of the paper side (12) take up a greater distance from each other with a diagonally extending support arrangement (30) than the associated supporting weft threads (20) of the running side (14).
7. Paper machine sieve according to one of the Claims 1 to 6, characterised in that an uneven number of paper side weft threads (16) is always located between the alternation points (24) of the running side weave thread (22).
8. Paper machine sieve according to one of the Claims 1 to 7, characterised in that the weft sequences with alternation points (24) are broken with weft sequences without alternation points (24).
9. Paper machine sieve according to one of the Claims 1 to 8, characterised in that the cross-section of the weft threads (20) on the running side (14) is larger than the cross-section of the relevant associated weft thread (16) on the paper side (12).

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