EP1387902A1

EP1387902A1 - Paper-making machine wire cloth

Info

Publication number: EP1387902A1
Application number: EP02742912A
Authority: EP
Inventors: Wolfgang Heger; Klaus Fichter
Original assignee: Andreas Kufferath GmbH and Co KG
Current assignee: Andritz Technology and Asset Management GmbH
Priority date: 2001-05-12
Filing date: 2002-04-24
Publication date: 2004-02-11
Anticipated expiration: 2022-04-24
Also published as: PT1387902E; US20040089365A1; DE10123204C2; WO2002092907A1; ATE348218T1; DK1387902T3; EP1387902B1; DE50208955D1; US7048830B2; ES2277617T3; DE10123204A1

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

papermaker

The invention relates to a paper machine screen, consisting of a single fabric for the paper side and a single fabric for the running side, each consisting of a set of weft threads and warp threads, the diameter and the number of warp threads on the paper and running side being essentially the same and that paper-side warp and weft threads form a plain weave together.

Today, more and more high-performance paper machines with speeds of up to 2000 m / min and working widths over 10 m are being used in the paper-producing industry. The sheet formation unit is usually designed as a twin wire former, in many cases also as a gap former. It is characteristic of the machines that the sheet formation process takes place immediately between two paper machine screens in a relatively short dewatering zone. This short distance and the high production speed reduce the time for sheet formation to a few milliseconds. During this period, the solids content or dry content of the fiber suspension must be increased from approximately 1% to approximately 20%. For the paper machine screens, this means that they have a very high drainage capacity but still must not leave any marks in the paper and offer a high level of fiber support. Another important point is the lateral stability of the fabric, which is decisive for the uniformity of the thickness and moisture profile of the paper web. The requirements in this regard are very high, especially for modern machines with large working widths. To improve the formation, formation strips are therefore increasingly used in the sheet formation zone, which are arranged alternately on the running sides of the screens and are pressed against them. This results in a rapidly changing, longitudinal deflection of the fabric covering.

Nowadays, attempts are usually made to meet these requirements by using composite fabrics. Such a composite fabric is described for example in DE 42 29 828 C2. The paper machine sieve known in this regard consists of two superimposed sieve fabrics, which are formed at least in one layer and are connected to one another by binding threads running in the transverse and / or longitudinal direction, one of the sieve fabrics as a definition fabric with the mechanical properties of the composite fabric with regard to elongation and rigidity of certain design and the other screen fabric is designed as a reaction fabric with a higher elongation and less stiffness than the definition fabric. The screen fabrics mentioned thus consist of warp and weft threads, these being connected to one another by additional binding threads. The formation of the screen fabric layers as reaction or definition fabric counteracts the internal wear and in particular the wear of the binding threads and thus increases the service life of the composite fabric and also prevents undesired separation of the screen fabric layers in the long term. The mentioned internal wear of a composite fabric is particularly due to the fact that with the wire deflections, as they occur in the area of guide rolls or wire section over which the composite fabric is guided, the individual fabric layers are stretched or compressed to different degrees.

Since the binding threads mentioned do not belong to the fabric structure, but are independent components, they are kept as thin as possible in diameter so that the drainage is only slightly disturbed. With correspondingly high loads, however, there is then the possibility that the thin binding threads will tear open and the bond between the sieve fabrics will come loose. In the case of a generic paper machine sieve according to EP 0 432 413 B1, which is also constructed as a composite fabric, it has already been proposed to use binding threads as two intrinsic threads and to weave them into the other fabric layer to form the X-shaped crossing points to avoid the disadvantages described in the prior art; just by the accumulation of the known exchange points in the transverse direction, the known fabric is also unintentionally stiffened. In particular over longer weaving lengths, there may then be considerable differences in length, which in turn are noticeable in tension differences, with the result that the binding strands that produce the fabric likewise tear open and can lead to failure of the known paper machine screen. With regard to this known special weave, it is also essentially only possible to process transverse threads of one type, that is to say transverse threads with essentially the same diameter, both for the upper and for the lower fabric, which reduces the possibilities for effective support on the running side , Otherwise, the production of the known composite fabrics described is complex. and expensive. EP 0 698 682 A1 discloses a fabric consisting of a system of top wefts, bottom wefts and chains, the latter being formed from a system pair of a first and a second type of warp threads. The first type of warp threads is interwoven with the top wefts and at certain intervals with the bottom wefts. The second type of warp threads run between the upper and lower wefts and bind with the upper wefts at the point where the first warp thread belonging to the pair binds with the weft. The warp threads are then directly one above the other, except at the point where the second warp threads bind with the top weft. This closest prior art improves the surface uniformity on the paper side in a paper machine screen, so that it is essentially free of markings; however, a separation of layers or a shift of the fabric layers to one another cannot be completely ruled out.

Based on this prior art, the invention has for its object to further improve paper machine screens of the aforementioned type in such a way that they have a longer service life with the same quality standards for paper manufacture and, on the other hand, they can be implemented inexpensively. A paper machine screen with the features of claim 1 in its entirety solves this problem.

Characterized in that, according to the characterizing part of patent claim 1, at least some of the running warp threads change into the paper side at a point at which this warp thread is located over at least one associated running side weft thread and pass over the subsequent paper-side weft thread and then onto the running side returns, on the one hand is a marking-free paper page in canvas bond achieved while improving surface uniformity. In addition, a compact connection of the individual fabrics is created in this way without additional binding threads, a separation of the layers of the individual fabrics or a displacement of the same relative to one another being largely excluded. The paper machine screen according to the invention can therefore achieve a long service life in paper production with high production quality, and the paper machine screen can then also be produced at low cost.

A preferred embodiment of the paper machine screen according to the invention is characterized in that in the region of the change of the running-side warp thread from the running side to the paper side and from this back to the running side at least four assigned running-side weft threads support the changing point. Here, the weft threads can be used on the running side, which lead to a high degree of transverse stability within the fabric composite and form a corresponding abrasion volume, which increases the service life of the paper machine screen. It is also preferably provided that the plain weave is designed as a longer floating float, which improves the surface uniformity in paper manufacture.

In a particularly preferred embodiment of the paper machine screen according to the invention, between the four running-side weft threads forming a first group and a second group with two running-side weft threads in the direction of the paper-side warp thread, a running-side weft thread is arranged above a running-side warp thread, which supports a paper-side weft thread, over which a paper-side weft thread Warp thread is guided. The support points formed in this way result in a high degree of Stability in relation to the two individual fabric layers of the sieve considered.

The direction of support of the paper-side and barrel-side weft threads is preferably arranged to run transversely to the planes of the lower and upper fabrics, whereby it can alternatively also be provided that the direction of support runs in an alternating oblique arrangement to the fabrics. By means of the inclined arrangement selected in this way, the supporting forces are introduced into the lower fabric in such a way that separation of the layers or displacement of the fabrics is effectively counteracted. The latter applies in particular if, in the case of an inclined support arrangement, the successive weft threads on the paper side are at a greater distance from one another than the associated supporting weft threads on the barrel side.

Further advantageous embodiments are the subject of the other subclaims.

The paper machine screen according to the invention is explained in more detail below with the aid of various embodiments. In principle and not to scale, show the

1 shows a section in the longitudinal direction along the line I - I of a first embodiment of the paper machine screen according to FIG. 2;

2 shows the paper side of the first embodiment with a

Shooting ratio of 1: 1; 3 shows a section in the transverse direction along the line

II - II of the first embodiment in Figure 4, with the barrel side down;

4 shows the running side of the first embodiment of the paper machine screen viewed from below;

5 shows a section in the longitudinal direction along the line

IM - IM in Figure 6 and along the line IV - IV in Figure 7, both relating to a second embodiment of the

Paper machine wire;

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

7 shows the running side of the second embodiment of the paper machine screen 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

Sequence of shots repeated after 16 shots or in which a sequence of shots with integration is interrupted by a sequence of shots without integration;

10 shows the second embodiment according to FIGS. 5 to 7 with a shot ratio of 3: 2 (upper to lower shot), in which the sequence of shots is repeated after 20 shots. The figures mentioned above partially show 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 formation zone in conventional paper making machines. Said screen fabric consists of a single fabric for the paper side 12 and an individual fabric for the running side 14. The paper side 12 consists in each case of a set of weft threads 16 and warp threads 18. The running side 14 likewise consists of a set of weft threads 20 and warp threads 22. As shown in particular in FIGS. 8, 9 and 10, the warp threads 18 on the paper side and the associated weft threads 16 form a plain weave with one another. Furthermore, it can be seen from the figures that the diameter and the number of warp threads 18, 22 on the paper and on the running side are essentially the same. The respective warp-side warp thread 22 changes at a change point designated as a whole by 24 from the running side 14 to the paper side 12 and then returns to the running side 14 again. 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 side by side in one plane. Furthermore, between these four running-side weft threads 20 forming a first group 26 and a second group 28 with two running-side weft threads 20 in the direction of the paper-side warp thread 18 above a running-side warp thread 22, a running-side weft thread 20 which supports a paper-side weft thread 16 is arranged, over which the respective paper-side warp thread 18 is guided.

1, 8 and 9, the direction of support of paper-side and barrel-side weft threads 16, 20 can run transversely to the planes of the lower and upper fabrics in the form of paper side 12 and barrel side 14, respectively. According to the illustration in FIGS .5 and 10 can, however the direction of support is in an alternating oblique arrangement to said fabrics 12, 14. It is decisive that to form a support point designated as a whole by 30, a weft thread 16 with a thinner cross section is supported on a weft thread 20 with a thicker cross section and that the relevant support point 30 goes up and down from the warp threads 18 on the paper side as well as the Running-side warp threads 22 is supported. The respective support point 30 can be formed directly in that the weft threads 16 and 20 lie against one another; 5 and 10, however, they can also maintain a predeterminable distance from one another, which, if appropriate, is closed only when loaded and enables the support. In particular in the case of an inclined support arrangement, the successive weft threads 16 on the paper side 12 are at a greater distance from one another than the associated supporting weft threads 20 on the barrel side 14.

The warp and weft threads 20, 22 on the barrel side generally form a long floating floating shaft underside, in which the wefts are bound twice, ie by two adjacent warp threads. The connection from paper side 12 to the running side 14 thus takes place in such a way that the respective running-side warp thread 22 changes to the paper side 12 at a predeterminable point at which it is located above the running-side four weft threads 20 of the first group 26 and there via the paper-side shot 1 6 runs. Since there is usually no space in the plain weave to additionally accommodate this changing warp thread 22, since this would then close the respective stitch, the paper-side warp thread 18 is detached from the top at the same time and runs under three according to the partial illustration in FIG. 1 paper-side weft threads 16. This achieves the connection of the fabric 14 on the running side to the paper side 12 and since the paper-side chain runs under the top side at the respective binding point, the running-side chain also takes over the filling of the paper-side surface in addition to the function of the integration. The paper-side structure is largely preserved, which results in particular from the illustration according to FIG. 2. Since the slope of the binding on the running side is taken over to the binding points 32 in the paper side 12, the binding points 32, as are partially shown in FIG. 2, are evenly distributed in the binding repeat. The relevant binding points 32 thus ensure that the structure of the lower fabric or the running side 14 is not changed in a harmful manner. The double inclusion of the shots on the barrel side also increases the stability of the entire fabric with regard to the so-called diagonal displacement, which occurs when the tensile load across the fabric width is different. The latter occurs particularly with large machine widths, where it cannot always be ensured that the driving and frictional forces occur evenly over the entire width. It then happens that the screen can partially distort, which in the worst case leads to a reduction in the screen width and thus to the paper machine screen becoming unusable.

During production and also during the running of a paper machine screen, the longitudinal threads 18, 22, i.e. the chains, are always subjected to tensile stress. In a normal plain weave, the differently directed forces are balanced out by the inverse adjacent warp threads, which creates a resulting force in the fabric plane and no uneven surface deformations occur. But if you include an upper shot with the lower chain, as with the er. paper machine sieve according to the invention, a proportion of force comes in vertical Direction towards this, which can only be compensated for with difficulty by the paper-side shots and the top chains running next to it. As a result, the lower chain pulls the upper weft into the fabric and the paper side gets a dent. The realization of the layer connection according to the invention by the chain has the effect that the longitudinal bending of the fabric in the paper machine does not lead to displacements of the two individual fabrics and thus to internal wear with eventual layer separation. 1 shows the neutral bending line 34 together with the bending line 36 of the upper fabric and the bending line 38 for the lower fabric. 1 shows the bending force introduced into the paper machine screen with an arrow labeled "F", the corresponding counter bearing points in the lower fabric being represented by two stylized triangular supports. From FIG. 1 it is therefore clear that when bending force is introduced F at the change point 24 by bringing together the three bending lines 34, 36, 38 in the region of the paper-side weft thread 16, which lies below the force introduction point and is received between the warp threads 18 and 22, a type of articulated or predetermined bending point is formed, which counteracts the separation of positions.

The weaving idea according to the invention can be applied to a wide variety of weft ratios from upper to lower fabric, as a result of which the properties of the screens with regard to openness (drainage performance), stability and abrasion volume (running time) can be largely adapted to the particular requirements of the paper machine. Almost any distribution and adjustment of the frequency of the binding points 32 and thus also an optimization of the strength of the connection can be carried out over the length of the weft sequence. On the other hand, if you tie in direction, one is, as shown in the prior art, limited by the finite number of shafts.

8 shows an example of a section from a paper machine screen with a weft ratio of 1: 1, in which the weft sequence is repeated after 16 shots. In the embodiment according to FIG. 9, a weft sequence with integration is interrupted by a weft sequence without integration, the warp threads lying next to one another then being overlapped in such a way that the uniform distribution is nevertheless retained. In the embodiment according to FIG. 10, there is a 3: 2 shot ratio from top to bottom shot, in which the shot sequence is repeated after 20 shots. The above-mentioned exemplary embodiments represent only a part of the possible variety and applications for the paper machine screen according to the invention.

Claims

Patent claims

1 . Paper machine screen, consisting of a single fabric for the paper side (12) and a single fabric for the running side (14), each consisting of a set of weft threads (16; 20) and warp threads (18; 22), the diameter and the number of paper - And running-side warp threads (18; 22) are essentially the same and the paper-side warp threads (18) and weft threads (16) form a plain weave with one another, characterized in that at least some of the running-side warp threads (22) each at one point (24), on which this warp thread (22) is located over at least one associated weft thread (20) on the running side, changes to the paper side (12) and runs over the subsequent paper-side weft thread (16) and then returns to the running side (14).

2. Paper machine sieve according to claim 1, characterized in that in the region of changing 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) at least four assigned running-side weft threads (20 ) support the exchange point (24).

3. Paper machine sieve according to claim 1 or 2, characterized in that the plain weave is designed as a longer floating binding.

4. Paper machine sieve according to claim 2 or 3, characterized in that between the four a first group (26) forming running-side weft threads (20) and a second group (28) with two running-side weft threads (20) in the direction of the paper-side warp thread (18) a weft thread (20) on the running side is attached above a running warp thread (22) is arranged, which supports a paper-side weft thread (16) over which a paper-side warp thread (18) is guided.

5. Paper machine screen according to claim 4, characterized in that the direction of support of paper-side and running-side weft

(16, 20) runs transversely to the planes of the lower and upper tissues or that the direction of support runs in an alternating oblique arrangement to the tissues.

6. Paper machine sieve according to claim 5, characterized in that in the case of an inclined support arrangement (30), the successive weft threads (16) of the paper side (12) are at a greater distance from one another than the associated supporting weft threads (20) of the running side (14).

7. Paper machine sieve according to one of claims 1 to 6, characterized in that there is always an odd number of paper-side weft threads (16) between the changing points (24) of the running-side warp thread (22).

8. Paper machine screen according to one of claims 1 to 7, characterized in that the weft sequences with changing points (24) of weft sequences without changing points (24) are interrupted.

9. Paper machine sieve according to one of claims 1 to 8, characterized in that the weft threads (20) on the running side (14) are dimensioned larger in cross section than the cross section of the respective assignable weft thread (16) on the paper side (12).

10. Paper machine sieve according to one of claims 1 to 9, characterized in that the bending lines (36; 38) of the upper fabric and lower fabric and the neutral bending line (34) converge at the change point (24) and thus form a type of articulation point that is harmful Position separation counteracts.