EP1565613B2 - Papermaking screen - Google Patents

Abstract

A paper machine sieve, consists of at least one single fabric for the paper side, and a single fabric for the running side, which consist of weft fibres (4,6) and chain fibres (1,5). The individual fabrics are joined together using binding fibres (3). The latter pass over the chain fibres at the points where the weft fibres pass underneath.

Description

The invention relates to a papermaking fabric.

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 screens that they have to 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.

In order to meet these requirements and, in particular, to achieve a connection of the individual fabrics of the paper side and the running side with one another, there are basically two different approaches to solution in the prior art. The one solution is characterized in that the two individual fabric layers are joined together by means of a weft or transverse thread. Another solution provides that the connection is made by means of a longitudinal or warp thread. Especially if you want to use different Kettdurchmesserauf the run and the paper side, these known approaches are no longer in question.

Accordingly, if the formation of the two individual fabrics is to be specifically aimed at a fine paper side with thin diameters and a coarse running side with thick diameters in order to achieve high stability values, the two layers must be joined by a weft, in particular a binding weft. Again, the state of the art offers corresponding proposals.

Thus, it is possible to interweave both individual fabrics by means of an additional binding or stitching thread which belongs either in the weave pattern of the upper fabric (paper side) or the lower fabric (running side). Such a solution is, for example, through the paper machine screen the US 5,238,536 is known, which provides a plain weave for the upper fabric and a five-shaft weave for the lower fabric. Furthermore, there are also approaches to solutions with additional stitching threads, which at the same time produce the connection between the two fabric layers and moreover serve as filler threads. Such a solution is for example in the US 5,518,042 shown.

In such known solutions, the binding threads additionally used change the very homogeneous upper side, which in practice leads in part to unwanted markings in the paper. To counter this, the binding threads are always thinner, but this has the disadvantage that the durability for the connection of the individual layers of fabric decreases accordingly. Furthermore, it has been found in practical use that it can come to "looping" of the binding weft threads, resulting in the separation of the individual layers and the fabric is unusable.

In another known solution, complete upper shots are replaced by pairs of binding structural threads. Depending on the selected type of fabric, the ratio of real excesses through weft or warp threads to the pairs of binding weft can vary. So are by the PCT publications WO 99/06630 and WO 99/06632 Such fabrics are known in which the upper fabric is realized in the manner of a plain weave by the combination of two binding weft threads. The lower fabric is again formed in these known solutions in the form of a five-shaft bond.

Despite the good connection of the two individual fabrics together, a major disadvantage of these known solutions is that the upper chain of the paper side is not supported at the crossing points of the binding shots. Looking at the course of a "complete" upper weft in these known solutions, it can be seen that both threads are at a height level due to the alternating binding of the upper weft and the upper weft, with the result that both the warp and the weft offsets are in one plane lie. The use of binding pairs now lacks this support at all intersections and all the threads absorb the major forces along their respective longitudinal axis, which points into the tissue interior at the intersections. This disadvantage of the lack of support arises in particular when the upper weft and binding pair are used in an alternating sequence, that is to say, for example, a complete upper weft follows a binding pair and then again an upper weft. In order then to realize the preferably known plain weave, the next following upper weft must extend over the warp thread, which previously lay above the crossing point, and thereby becomes additional pulled into the fabric interior. As a result, either every other upper warp thread lies deeper in the fabric or none of the warp threads can be at the level of the weft threads. This results in uneven webbing on the paper side, which can lead to unwanted marks in the paper.

By the DE 42 29 828 A is a paper machine screen in the form of a composite fabric known, in particular for the sheet forming zone, consisting of at least two superimposed screen fabrics, which are formed at least one ply and connected by transverse in and / or longitudinal binding threads together, wherein one of the screen fabric as a definition fabric with the mechanical properties of the composite fabric in terms of elongation and stiffness determining training and the other screen fabric is designed as a reaction fabric with a higher elongation and lower stiffness than the definition fabric. With the known solution it is achieved that the so-called internal wear is reduced so much that the service life is essentially determined by the external wear, that is to say the abrasion occurring on the outer surface of the sieve. The internal wear of a composite fabric is primarily due to the fact that in the Siebumlenkungen, as they occur in the range of guide rollers in the wire section over which the composite fabric is guided, the individual Siebgewebelagen be stretched or compressed to varying degrees. In the known composite fabric solution, these relative movements are avoided because the reaction fabric is able to adapt to the definition fabric due to its lower rigidity and higher elongation according to the requirements. Despite these measures, however, in the known solution, the binding threads which hold the upper and lower fabric together are not so uniform and completely integrated in the fabric structure than that they are not damaged by lack of support in the relevant areas of attack to wear in the known papermachine fabric could come. Further disclosed US 5,482,567 A a three-ply fabric for use in the sheet forming area of a paper machine, US 5,826,627 A discloses a papermaker wire with paired weft binder threads, and US 4,729,412 A discloses a double-layered forming screen with binding warp threads.

Based on this prior art, the invention has the object to help avoid the disadvantages described in the prior art, in particular to create a paper machine screen, which is characterized by high strength values, in particular has a high degree of lateral stability and offers comparable drainage services, how the known solutions as well as the formation of markings in the paper helps to avoid. Such a problem solves a papermaking machine with the features of claim 1 in its entirety.

Characterized in that according to claim 1, the respective binder thread on the paper side engages at defined locations warp threads of the individual fabric, which are attacked on its opposite side under investment of at least one weft of this single fabric, the compound of the two fabric layers (paper side and running side) turn by binding threads realized, but then completely integrate into the fabric structure of the paper side and thereby support by the special type of connection each binding point thus created, so that the binding threads thus remain on a plane with the shots and the remaining warp threads. With this idea of bonding a high-strength paper machine screen is achieved with very good drainage performance and uniform structure, especially on the paper side, so that the unwanted marks in the paper are avoided.

With the inventive solution, it is sufficient that the warp threads are supported from below by the associated weft thread of the single fabric of the paper side at the points where they are pulled through the binding thread into the fabric interior. Through the functional separation of upper and binding shot is also possible to use for the upper weft (paper side) a material that supports the transverse stability of the fabric, so for example a polyester material, whereas in the above-mentioned known solutions when using a pair of binding shot both materials the same have to be optimized and with respect to the layer connection, usually using polyamides. Although in the solution according to the invention only one binding thread is used in a predefinable viewing plane, the number of binding sites, ie the contact between the binding weft and upper or lower chain of the paper side and running side, does not decrease compared to the known solutions.

The diameter of the binding thread corresponds to that of the upper weft, which leads to a high strength of the connection between the fabric layers.

Fig. 1 und 2

in der Art von Schnittbildern zwei bekannte Verbindungslösungen nach dem Stand der Technik,

Fig. 3

eine Draufsicht auf einen Ausschnitt der Ober- oder Papierseite des erfindungsgemäßen Papiermaschinensiebes,

Fig. 4 und 5

Schnitte längs der Linien A-A bzw. B-B in Figur 3,

Fig. 6

eine Draufsicht auf die Ober- oder Papierseite einer zweiten Ausführungsform des erfindungsgemäßen Papiermaschinensiebes,

Fig. 7 und 8

Schnitte längs der Linien C-C und D-D in Figur 6,

Fig. 9

eine Draufsicht auf die Ober- oder Papierseite eines dritten, der ersten Ausführungsform entsprechenden Ausführungsbeispieles jedoch in Realisierung mit wechselnder Schußfolge des Ober- und Bindeschusses.

Further advantageous embodiments of the paper machine screen according to the invention are the subject of the other dependent claims. In the following the paper machine wire according to the invention will be explained in more detail with reference to three different embodiments of the drawing. This show in principle and not to scale representation of the

Fig. 1 and 2

in the manner of sectional images, two known connection solutions according to the prior art,

Fig. 3

a plan view of a section of the top or paper side of the papermaker's fabric according to the invention,

4 and 5

Cuts along the lines AA and BB in FIG. 3 .

Fig. 6

a top view of the top or paper side of a second embodiment of the paper machine wire according to the invention,

FIGS. 7 and 8

Cuts along the lines CC and DD in FIG. 6 .

Fig. 9

a plan view of the top or paper side of a third embodiment corresponding to the first embodiment, however, in realization with changing firing order of the top and binding shot.

1

Oberkette

2

Oberschuß (mit Bindeschuß)

3'3

Bindeschuß

4

Oberschuß

5

Unterkette

6

Unterschuß

7

Übergriff

8

Untergriff

9

Übergriff durch Unterschuß 6

Furthermore, the following number assignment is implemented in all the illustrations used:

1

upper chain

2

Upper shot (with binding shot)

3'3

binding weft

4

top shot

5

under chain

6

deficit

7

encroachment

8th

undercling

9

Assault by deficit 6

In the known in the prior art detectable solution according to the Fig. 1 consists of the paper machine screen of two individual fabrics, looking in the direction of the Fig. 1 The upper single fabric consists of a set of weft yarns 2 as upper weft yarns and warp yarns 1 as upper warp yarns. The underlying running side is also formed from a set of wefts 6 as Unterschußfäden and warp threads 5 as Unterkettfäden. As a binding method for the paper side, the known solution has a plain weave and the lower fabric is designed as a five-shaft fabric in relation to a repeat. As the Fig. 1 shows the two individual fabrics are connected to each other via a binding weft thread 3, wherein in the drawing plane and out of this a plurality of pertinent binding weft threads 3 (not shown) are arranged in sequence and thus produce the necessary connection of the individual fabric layers for the papermaking fabric. In these known solutions, the binding threads 3 are used in the direction of the fabric in front of and behind the upper weft threads 2 used to establish the connection of the individual fabric layers, so that thereby the actually very homogeneous top of the paper side of the screen is adversely affected such that it is in the Practice may come to unwanted marks in the paper. Accordingly, in order that the known binding weft threads 3 interfere as little as possible, they are always thinner, so that when using the known papermachine sieves separation of the individual tissue layers can occur and consequently failure of the sieve as such.

In the other known solution according to the Fig. 2 In contrast, two binding weft threads 3 and 3 'are used, the diameter of which is chosen to be particularly greater than the diameter of the known binding weft thread 3 after the Fig. 1 , By using the two binding weft threads 3 and 3 ', no complete upper weft is present at these locations, but the plain weave of the upper side is realized by the combination of two binding threads 3, 3'. Again, only a portion of the papermaking screen is again shown in section and a plurality of binding threads 3 and 3 'are present in various possible planes of drawing in a series arrangement. In this known solution, a significant disadvantage is the fact that at the crossing points of the binding shots 3 and 3 ', the upper warp threads 1 are not supported. Also in this solution, there are irregularities and thus markings in the paper, based on the paper side of the screen, since to realize the plain weave, the next upper shot has to go over the warp, which was previously above the intersection and thus additionally in the Tissue inside is pulled. Thus, either every other Oberkettfaden deeper in the fabric or none of the warp threads at the level of wefts, resulting in the disadvantages described.

In the following, the paper machine wire solution according to the invention will now be described, wherein for the sake of simplicity and better understanding, the same reference numerals will be used accordingly for the solutions shown below, as in the known solutions already presented.

The first embodiment of a papermaking machine after the Fig. 3, 4 and 5 is provided on the paper side with a plain weave and formed on the bottom or running side in the manner of a five-shaft binding. Fig. 3 shows a detail of the top view of the top or paper side of the paper machine wire according to the invention and the section AA according to Fig. 4 refers to the view of the upper shot without binding shot, whereas the section BB the view of the upper shot with binding shot after the Fig. 3 concerns.

especially the Fig. 5 shows how the connection of the two single fabric layers for paper and running side is realized by binding threads 3, of which exemplified in Fig. 5 shown in detail the course of such a binding thread 3, which is completely integrated into the fabric structure on the paper side, in which overlaps on the paper side at defined locations of the respective binding thread 3 the assignable warp threads 1 of the individual fabric, at least on its opposite side a weft 2 of this individual tissue are under attack. This encroachment or attack is in the Fig. 5 represented by the reference numerals 7 and 8. By such an arrangement in which a warp thread 1 overlapped under the attachment of the assignable binding thread 3 and is under attacked by the assignable Oberschußfaden 2, the binding point is supported by the opposite side, so as to ensure that this on one level with the other shot - And warp threads 4 and 1 remains. The upper weft thread 2 thus also runs evenly at the point at which a weave is made without being integrated into the lower weave. Only at the points where the binding shot 3 runs over the upper chain, a short exchange of upper 2 and binding shot 3 is made. As a result, the intervening warp threads 1 at the points where they are pulled through the binding thread 3 into the fabric interior, in the direction of the Fig. 5 seen supported from below by the upper weft thread 2, wherein for supporting even the larger diameter diameter warp threads 5 of the deficit 6 contribute, in particular the Unterkettfaden 5, which lies in a vertical orientation under the undercut and overlapped warp thread 1.

As further from the Fig. 5 results limited the respective binding weft yarn 3 at the location of the overlap 7 of the assignable warp 1 to this an angle that is equal to the correspondingly formed angle of the cross-weft 2 at this point. These angular dimensions are on the type of paper machine screen training in these areas between 90 ° and 130 °. These angular dimensions create a kind of roof surface once on the side of the overlap 7 and in the opposite direction at the location of the undergrip 8, which proves favorable for the incorporation behavior and the overall force behavior of the papermachine screen.

The inventively designed binding solution based on a repeat as a five-shaft binding provides that four warp threads 5 are engaged by the weft threads 6 of the lower weave and a warp thread 5 is overlapped in succession, the respective binding weft thread 3 rising obliquely from the lower weave into the upper fabric at the location of this overlap 9 replaced. The respective binding weft thread 3 has substantially the same diameter as the respective weft thread 2 of the single fabric on the paper side. Furthermore, the warp threads 5 and the weft threads 6 of the lower fabric, that is, on the running side, each have a larger diameter in diameter than the assignable thread systems on the upper or paper side of the papermachine fabric. Relative to the top or paper side of the screen, the respective overlap 7 of the respective binding thread 3 is consequently separated with respect to a weft thread 2 from three intervening warp threads 1, wherein at the location of the middle warp thread 1 of this trimming group the binding thread 3 briefly comprises an underlying warp thread 5 engages under the overlap 6 before the attack 9. Due to the functional separation of upper weft threads 2 of the upper fabric and binding weft threads 3, these may consist of different materials, preferably to increase the transverse stability of the screen, the upper weft threads 2 made of a polyester material and the binding wefts 3 of a polyamide material.

The upper weft 4 after the Fig. 4 corresponds to its embodiment of the upper weft thread 2 with previously shown binding weft thread 3. The different numbering was chosen only to be in the representation of the Fig. 3 to achieve a better understanding of the tissue pattern in the plan view.

In the modified embodiment of the FIGS. 6, 7 and 8 this embodiment corresponds largely to the first embodiment described first; only instead of a five-shaft underside, the lower fabric or the underside (running side) a four-shaft binding was used for this purpose. In the pending Vierschaftbindung after the Fig. 8 the warp thread 1 overlapped by the binder thread 3 and undercut by the upper weft thread 2 is in turn supported by a vertically underlying warp thread 5 of the lower fabric, the lower weft thread 6 extending above the lower warp thread 5 at the support point. The binding of the binding thread 3 is then carried out for the lower fabric in the range of three successive Unterkettfäden 5, wherein the middle Unterkettfaden 5 of a triad of the binding yarn 3 and the two adjacent Unterkettfäden 5 are so overlapped by the binder yarn 3. The roof-like configuration in the region of the overlap 7 for the upper warp thread 1 is then in a parallel arrangement its equivalent, in the underlying overlap 9 of the supporting Unterkettfadens 5 through the lower weft thread. 6

In the embodiment of the Fig. 9 A change of order of upper weft 2 with binding weft 3 takes place with the consequence that all floats of the warp threads 1 on the upper side have the same length L despite the slightly offset binding points. This ensures that the warp pitches in both the transverse and in the longitudinal direction in a plane on the upper side, which is favorable in terms of low possible marking of the paper and on a high strength of the screen. With the paper machine wire solution according to the invention a high degree of stability is achieved; The sieve has a very good drainage performance and can also be produced inexpensively.

Claims (5)

1. A paper machine screen consisting of at least one individual fabric for the paper side and at least one individual fabric for the machine side which respectively consist of a set of weft yarns (4, 6) and warp yarns (1, 5), at least a part of the superimposed individual fabrics being interconnected via binder yarns (3), wherein the respective binder yarn (3) on the paper side engages from above (7) with warp yarns (1) of the individual fabric at those positions which on their opposite side are engaged with from below (8) by at least one adjacent weft yarn (2) of this individual fabric, and wherein in order to form the screen exactly two individual fabrics, one in the manner of an upper fabric for the paper side, one in the manner of a lower fabric for the machine side, are used, wherein the engagement from above (7) of the respective binder yarn (3) in the upper fabric in relation to a weft yarn (2) is separated by three warp yarns (1) lying therebetween, and at the position of the central warp yarn (1) of this group of three the binder weft yarn (3) engages from below with a warp yarn (5) of the lower fabric lying beneath, wherein the respective binder weft yarn (3) has substantially the same diameter as the respective weft yarn (2) of the individual fabric on the paper side, wherein the lower fabric is a four or five shaft binding, three or four warp yarns (5) are engaged from below and respectively one warp yarn (5) is engaged from above by the weft yarns (6) of the lower fabric, and the respective binder weft yarn (3) changes from the lower fabric into the upper fabric outside of or at the position of this engagement from above (9).
2. The paper machine screen according to Claim 1, characterized in that as binder yarns (3) only a respective first type of binder weft yarns undertakes the joining of the individual fabrics.
3. The paper machine screen according to Claim 1 or 2, characterized in that the upper fabric is formed in the manner of a plain weave and that the respective binder weft yarn (3) limits at the position of engagement from above (7) of the assignable warp yarn (1) with regard to the latter an angular dimension which is equal to the correspondingly formed angular dimension of the weft yarn (2) engaging from beneath.
4. The paper machine screen according to any of Claims 1 to 3, characterized in that the engagement from above (7) of the respective binder yarn (3) on the upper side is supported by a warp yarn (1) which extends between the assignable weft yarn (2) of the upper fabric and that of the lower fabric.
5. The paper machine screen according to any of Claims 1 to 4, characterized in that by the functional separation of the upper weft yarns (2) of the upper fabric and the binder weft yarns (3), these are made of different materials, preferably in order to increase the lateral stability of the screen the upper weft yarns (2) consisting of a polyester material and the binder weft yarns (3) of a polyamide material.

Images