WO2010049304A1

WO2010049304A1 - Forming fabric

Info

Publication number: WO2010049304A1
Application number: PCT/EP2009/063653
Authority: WO
Inventors: Johann Boeck; Matthias Hoehsl
Original assignee: Voith Patent Gmbh
Priority date: 2008-10-28
Filing date: 2009-10-19
Publication date: 2010-05-06
Also published as: CN102197176A; CA2741604A1; BRPI0914025A2; DE102008043222A1; KR20110079850A; JP2012506959A

Abstract

The invention relates to a paper machine fabric, particularly a forming fabric, comprising an upper and a lower fabric layer and binding threads for connecting the two fabric layers. The invention is characterized in that within the lower repeating pattern - each binding thread of each pair forms at least one binding segment with lower longitudinal threads and each binding segment is formed by the respective binding thread of the pair continuously crossing two or more directly consecutive lower longitudinal threads on the outside of the lower fabric layer and - the binding segments of each binding thread pair are arranged relative to the lower transverse threads flanking said binding segments in such a way that i) on the outside of the lower fabric layer, the two flanking lower transverse threads continuously cross at least the same lower longitudinal threads that form the binding segments together with the binding threads of the pair, ii) one of the two flanking lower transverse threads forms a bend in each case with the lower longitudinal thread that directly precedes the corresponding binding segment, and iii) the other of the two flanking lower transverse threads forms a bend in each case with the lower longitudinal thread that directly follows the corresponding binding segment.

Description

Voith Patent GmbH File: HPF13546 WOK D-89510 Heidenheim "Forming screen with 5-shaft LS"

forming fabric

The invention relates to a papermaking wire, in particular a forming fabric, according to the preamble of patent claim 1.

Forming fabrics are used in the forming section of a paper machine. In the forming process, a fiber suspension is applied from the headbox of the paper machine to a forming fabric or to two forming fabrics (Gap formers). An object of the forming fabric here is to dewater the fiber suspension and form a fibrous web, as little as possible pulp fibers and fillers from the fiber suspension should be washed during the dewatering process.

The quality of the fibrous web formed is strongly influenced by the structure of the fibrous web-facing surface (paper side) of the forming fabric. On the other hand, the life of the forming fabric is greatly affected by the structure of the paper machine facing surface (machine side) of the forming fabric.

In order to be able to take these partly contradictory requirements into account, multilayer paper machine screens with an upper, ie paper-side and a lower, ie machine-side, fabric layer have been developed, wherein the two fabric layers are connected to each other by so-called binding threads. In order to ensure the most uniform possible paper-side fabric structure, the binding threads are preferably an integral part of the paper-side weave structure (integral binding threads), whereby

Marking tendencies are reduced due to the connection of the stitching threads. In the art-known shot-bonded paper machine screens with integral mutually exchanging binding threads, the binding threads weave alternately with warp yarns of the upper and lower fabric layers, each binder yarn usually being interwoven with a plurality of upper warp yarns prior to the latter on the outside of the lower fabric layer crosses single lower warp thread to form a tether and then re-interweave with several upper warp threads.

The so-called sieves have the disadvantage that the lower fabric layer is always connected at each attachment point only a warp thread to the upper fabric layer, with the result that a high force acts on this warp thread, which pulls this into the interior of the screen, which has a negative effect on the planarity of the sieve.

Furthermore, in the so-called screens, the binding threads often cover a large distance between the upper and lower layers of fabric, as a result of which the screens known from the prior art are often very thick and therefore carry a great deal of water.

In addition, the screens known from the prior art often provide a drainage behavior which varies greatly over the screen surface, which can lead to hydaulic marking of the paper formed on such screens.

In addition, the binding threads between the fabric layers are often exposed to high wear in the known sieves, as they are often not sufficiently fixed between the fabric layers.

It is the object of the present invention to propose a papermaking screen in which the disadvantages mentioned at the beginning do not occur or at least only diminish. The object is achieved by the features of claim 1.

The paper machine wire according to the invention, in particular forming fabric, has an upper and a lower fabric layer and binding threads for joining the two fabric layers. The outside of the top fabric layer provides the web-contacting side of the fabric as the outside of the bottom fabric layer provides the machine-contacting side of the fabric.

Further, in the papermaking fabric, the lower fabric layer is formed by the binding yarns, lower transverse yarns, and the binding yarns and the lower transverse yarns interwoven with these extending lower longitudinal yarns. The lower fabric layer has a weave pattern, which is repeated in lower repeats. In the paper machine wire according to the invention, the binding threads are arranged in pairs. Furthermore, the binding threads of each pair are interwoven with each other in an intermeshing manner with upper and lower longitudinal threads. Furthermore, each pair of binder threads is flanked on each side by a lower transverse thread, wherein each of the two flanking lower transverse threads is interwoven in a periodic sequence with lower longitudinal threads as follows:

i) the flanking lower transverse thread continuously crosses a plurality of directly following lower longitudinal threads on the outside of the lower fabric layer,

ii) the flanking lower transverse thread continuously crosses a lower transverse thread between the upper and lower layers of fabric and forms a thread crease.

The papermaker's fabric according to the invention is characterized in that, within the lower repeat, each binding yarn of each pair of lower longitudinal yarns forms at least one lower segment and each segment is formed by continuously passing two or more of the respective bonding yarn of the pair on the outside of the lower fabric layer - A -

intersecting successive lower longitudinal yarns and that within the lower repeat the segments of each pair of binder yarns are arranged relative to the lower transverse yarns flanking them so that i) the two flanking lower transverse yarns on the outside of the lower fabric layer continuously intersect at least the same lower longitudinal yarns together with the binding threads of the pair form the lower segments,

ii) one of the two flanking lower transverse threads each forms a bend with the lower longitudinal thread, which immediately precedes the corresponding lower segment and

Ni) the other of the two flanking lower transverse threads each forms a bend with the lower longitudinal thread, which immediately follows the corresponding lower segment.

Characterized in that the binding threads in interweaving with the lower longitudinal threads form segments which extend over two or more consecutive lower longitudinal threads, the binding threads extend to a greater extent on the outside of the lower fabric layer and not between the fabric layers, whereby the thickness of the screen and the Significantly reduce associated disadvantages.

Due to the features according to the invention, that each binding thread weaves over at least two successive lower longitudinal threads is further achieved that each binding thread when weaving with the lower longitudinal threads "flat" on the outside of the lower fabric layer passes and through these flanking on both sides lower transverse threads, the In addition, within the lower repeat, one of the two flanking lower transverse threads each forms a bend with the lower longitudinal thread which immediately precedes the corresponding binding segment and the other of the two Flanking lower transverse threads each forming a bend with the lower longitudinal thread, which follows the corresponding binding segment immediately, each binding segment of the lower repeat is held firmly in position, whereby a relative movement of the binding threads between lower and upper fabric layer is prevented and as a result, the inner wear of Siebs is significantly reduced.

Furthermore, in the lower fabric layer by the long floats of the lower transverse threads on the outside of the lower fabric layer drainage channels are formed in areas extending between two side by side extending and floating on the outside lower transverse threads. Characterized in that the two flanking lower transverse threads on the outside of the lower fabric layer continuously cross at least the same lower longitudinal threads, which form the binding segments together with the binding threads of the pair, the cross sections of the drainage channels formed by the flotations are reduced, whereby the otherwise uniform dewatering rate and thereby the resulting Marking tendency is reduced.

Advantageous embodiments and further developments of the invention are specified in the subclaims.

The invention will be further explained with reference to schematic drawings. Show it:

1 shows a first embodiment of a sieve according to the invention in the transverse thread direction.

2 shows a second embodiment of a sieve according to the invention in the transverse thread direction.

Fig. 3, the lower fabric layer of the screen of Figure 2; Fig. 4 is a representation corresponding to Figure 1 of an alternative embodiment.

5 shows a view of the lower fabric layer of the forming fabric produced according to FIG. 4, viewed from below; FIG.

Fig. 6 is a representation corresponding to Figure 5, in which drainage areas of the lower fabric layer are marked.

FIG. 7 shows a plan view of the upper fabric layer of a forming fabric produced according to FIG. 4, viewed from above; FIG.

FIG. 8 shows a plan view of the lower fabric layer of the forming fabric produced according to FIG. 4, viewed from above; FIG.

FIG. 9 is a simplified representation corresponding to FIG. 8 of the lower fabric layer of the forming fabric produced according to FIG. 4.

FIG. 1 shows a first embodiment of a paper machine wire 100 according to the invention in the form of a forming fabric in the transverse thread direction. In the illustration of FIG. 1, a repeat unit of the weave structure of the wire 100 is shown.

The forming fabric 100 has upper longitudinal threads 1, 3,5, 7, 11, 11, 13, 15, 17 and 19 designed as warp threads and lower longitudinal threads 2, 6, 6, 8, 10, 12, 14, 16, which are formed as warp threads, 18 and 20. The longitudinal threads extend perpendicularly from the drawing plane of FIG. 1.

Furthermore, the forming fabric 100 has binding yarns i1 to i20, which are arranged in pairs of binding yarns i1 and i2, i3 and i4 to i19 and i20. Further, the forming fabric 100 has upper transverse threads T1 to T20 formed as weft threads and lower transverse threads B1 to B20 formed as weft threads. In the forming fabric 100 shown in Figure 1, the ratio of the number of pairs of binder yarns i1 and i2 to i19 to i20 and upper transverse yarns T1 to T20 together with the number of lower transverse yarns B1 to B2 is 3: 2. The forming fabric 100 according to the invention has an upper fabric layer 101 and a lower fabric layer 102, wherein the two fabric layers 101 and 102 are connected to one another by the binding threads i1 and i2 to i19 and i20.

The upper fabric layer is defined by the binding threads i1 to i20, by the upper transverse threads T1 to T20 and by the upper longitudinal threads 1, 3,5,7 extending transversely to the binding threads i1 to i20 and the upper transverse threads T1 to T20 and interwoven therewith , 9,11, 13,15,17 and 19 formed. It would also be conceivable to form the upper fabric layer only by upper longitudinal threads and with these interwoven binding threads.

The lower fabric layer 102 is formed by the binding threads i1 to i20, the lower transverse threads B1 to B2 and by the interwoven and extending transversely to these lower longitudinal threads 2,4,6,8,10,12,14,16,18 and 20 formed.

The binding threads of a pair are mutually exchangeable with upper longitudinal threads 1, 3,5,7,9,11, 13,15,17 and 19 and with lower longitudinal threads 2,4,6,8,10,12,14,16, As a result, when the first binding thread of the pair is woven with upper longitudinal threads, the second binding thread of the pair is interwoven with lower longitudinal threads and if the second binding thread of the pair is woven with upper longitudinal threads, the first binding thread of the pair is interwoven with lower longitudinal threads.

The weave pattern of the upper fabric layer 101 forms a plain weave, whereby the weaving threads i1 to i20 mutually exchange interweaving the binder thread pairs with the upper longitudinal threads 1, 3,5,7,9,11, 13,15,17 and 19 by the weaving of the upper longitudinal threads 1, 3,5,7,9,11, 13,15,17 and 19 continues with the upper transverse threads T1 to T20 weave pattern is continued. Accordingly, during weaving, each binding thread i1 to i20 alternately crosses on the outer side 103 of the upper fabric layer 101 and between the two fabric layers 101, 102 during interweaving with successive upper longitudinal threads 1, 3, 5, 7, 9, 11, 13, 15, 17 and 19 extending upper longitudinal threads 1, 3,5,7,9,11, 13,15,17 and 19.

As can be seen from the figure 1, the lower fabric layer has a weave pattern, which is repeated in lower repeats, the lower repeat through the lower longitudinal threads 2,4,6,8,10,12,14,16,18 and 20th , the binding yarns i1 to i20 and the lower transverse yarns B1 to B20 are formed.

Each pair of binding threads i1 and i2 to i19 to i20 is flanked on each side by one of the lower transverse threads B1 to B20, wherein each of the two flanking lower transverse threads B1 to B20 is arranged in a periodic sequence with lower longitudinal threads 2,4,6,8,10,12, 14,16,18 and 20 is interwoven as follows:

i) the flanking lower transverse thread continuously crosses on the outside 104 of the lower fabric layer 102 four directly successive lower longitudinal threads,

ii) the flanking lower transverse thread continuously crosses between the upper 101 and lower fabric layers 102 a lower longitudinal thread and forms a

Fadenkröpfung.

By way of example, the binding thread pair i1 and i2 is flanked on one side by the lower transverse thread B2 and on the other side by the lower transverse thread B3.

In the present embodiment, all lower transverse threads B1 to B20 of Sieves 100 woven in periodic sequence with lower longitudinal threads in the order given above.

According to the invention, within the lower repeat, each binding thread of a pair with lower longitudinal threads forms at least one binding segment S1 to S20 and each binding segment S1 to S20 is formed in which the respective binding thread of the pair on the outer side 104 of the lower fabric layer 103 runs continuously at least two directly successive lower longitudinal threads crossed.

Thus, within the lower repeat, for example, the binding thread i1 of the binding thread pair i1 and i2 forms the binding segment S1 and the binding thread i2 of the binding thread pair i1 and i2 forms the binding segment S2. In this case, the binding segment S1 is formed in that the binding yarn i1 of the pair on the outside 104 of the lower fabric layer 102 continuously crosses the two immediately consecutive lower longitudinal threads 14 and 16. Furthermore, the binding segment S2 is formed in that the binding yarn i2 of the pair on the outer side 104 of the lower fabric layer 102 continuously crosses the two immediately consecutive lower longitudinal yarns 4 and 6.

Furthermore, the segments are such that between two successive binding segments formed by the same binding thread, for example, i1, this binding thread, for example, i1, on the outer side 103 of the upper fabric layer 101 at least one upper longitudinal thread, eg. 1 and 5, crosses.

Further, within the lower repeat, the binding segments of each pair of binder yarns are positioned relative to the lower transverse yarns flanking them such that the two flanking lower transverse yarns on the outside of the lower fabric layer continuously intersect at least the same lower longitudinal yarns which together with the binding yarns of the pair form the binding segments. By way of example, in each case the lower transverse thread B2 and the lower transverse thread B3 on the outer side 104 of the lower fabric layer 102 continuously cross the lower longitudinal threads 4 and 6 as well as 14 and 16, which also form the binding segments S1 and S2.

Furthermore, one of the two flanking lower transverse threads each forms a bend with the lower longitudinal thread, which immediately precedes the corresponding binding segment. Thus, for example, the lower transverse thread B2 forms a bend with the lower longitudinal thread 2 and with the lower longitudinal thread 12, wherein the lower longitudinal thread 2 immediately precedes the binding segment S2 and the lower longitudinal thread 12 the binding segment S1.

Further, the invention provides that the other of the two flanking lower transverse threads each forms a bend with the lower longitudinal thread, which immediately follows the corresponding binding segment.

By way of example, the lower transverse thread B3 forms a bend with the lower longitudinal thread 8 and with the lower longitudinal thread 18, the lower longitudinal thread 8 immediately following the binding segment S2 and the lower longitudinal thread 18 following the binding segment S1.

As can be seen from the illustration of FIG. 1, the binding segments of the two binding threads are arranged alternately in each binding thread pair. Thus, for example, the binding segments S1 and S2 alternate. In this case, three lower longitudinal threads are always arranged between immediately adjacent binding segments of a pair of binder threads. Thus, for example, between the immediately successive binding segments S1 and S2 are the three lower longitudinal threads 8, 10 and 12 or the three lower longitudinal threads

18,20 and 2 arranged. Further, each binder thread pair has a binding yarn of the first kind i2, i4, i6, i8, i10, i12, i14, i16, i18 and i20 and a binder yarn of the second kind i1, i3, i5, i7, i9, i11, i13, i15, i17 and i19, wherein in the upper repeat unit, the binding yarn of the first kind i2, i4, i6, i8, MO, i12, i14, i16, i18 and i20 crosses two upper longitudinal yarns when it runs on the outer surface 103 of the upper fabric layer 101 and the binder yarn second type i1, i3, i5, \ i, i9, i11, i13, i15, i17 and i19 crosses three upper longitudinal threads when it runs on the outer side 103 of the upper fabric layer 101.

Furthermore, the binding segments formed by binding threads of the same type are immediately adjacent binding thread pairs in FIG

Cross thread direction arranged offset to one another about a lower longitudinal thread and therefore partially overlapping. Thus, for example, the binding threads of the first type i2, i4, i6, i8, i10, i12, i14, i16, i18 and i20 form the corresponding lower ones

Longitudinal threads the binding segments S2, S4, S6, S8, S10, S12, S14, S16, S18 and S20, where, for example, the immediately adjacent binding segments

S2 and S4 in the transverse thread direction are arranged to overlap the lower longitudinal thread 6 next to each other.

FIG. 2 shows a second embodiment of a paper machine wire 110 according to the invention designed as a forming fabric.

The screen 110 shown in FIG. 2 differs substantially from the screen 100 shown in FIG. 1 in that the ratio of the number of pairs of binder yarns i1 and i2 to i19 and i20 and upper transverse yarns T1 to T10 adds up to the number lower transverse threads B1 to B10 is 2: 1.

Furthermore, in contrast to FIG. 1, binding segments formed by binding threads of the same type immediately adjacent adjacent pairs of binding thread in the transverse thread direction directly adjoin one another. Thus, for example, the binding threads of the first type i2, i3, i6, i7, i10, i11, i14, i15, i18 and i19 with the corresponding lower transverse threads form the binding segments S2, S3, S6, S7, S10, S11, S14, S15. S18 and S19, where, for example, the next to each other arranged binding segments S2 and S3 in the transverse thread direction directly - ie are arranged next to each other without overlap or spacing of one or more lower longitudinal threads.

In the forming fabrics shown in FIGS. 1 and 2, furthermore, the lower transverse threads have a larger cross-sectional area than the binding threads.

FIG. 3 shows a representation of the lower fabric layer 112 over a part of the lower repeat with a view of the outer side 114 of the lower fabric layer 112.

The features according to the invention can be clearly seen, namely, that within the lower repeat

- Each binding yarn i1 to i20 of each pair with lower longitudinal threads 2,4,6,8,10,12,14,16,18 and 20 forms at least one binding segment S1 to S20 and each binding segment S1 to S20 is formed by the respective Binding yarns i1 to i20 of the pair on the outer side 114 of the lower fabric layer 113 continuously two or more immediately consecutive lower longitudinal threads 2,4,6,8,10,12,14,16,18 and 20 crosses and

the binding segments S1 to S20 of each pair of binding threads are arranged relative to the flanking transverse threads B1 to B10 flanking them

i) the two flanking lower transverse threads B1 to B10 on the outer side 114 of the lower fabric layer 112 continuously intersect at least the same lower longitudinal threads which, together with the binding threads i1 to i20 of the pair, form the binding segments S1 to S20,

ii) one of the two flanking lower transverse threads each forms a bend with the lower longitudinal thread which immediately precedes the corresponding binding segment and iii) the other of the two flanking lower transverse threads each forms a bend with the lower longitudinal thread which immediately follows the corresponding binding segment.

By way of example, the binding thread pair i3 and i4 are picked out. Within the lower repeat, the binding thread i3 forms the binding segment S3 with the lower longitudinal threads 14 and 16, and the binding thread i4 forms the binding segment S4 with the lower longitudinal threads 4 and 6. The binding segment S4 is formed in that the binding thread i4 on the outside 1 14 of the lower fabric layer 113 continuously crosses the two immediately consecutive lower longitudinal threads 4 and 6. The binding segment S3 is formed in that the binding yarn i3 on the outside 114 of the lower fabric layer 113 continuously crosses the two immediately consecutive lower longitudinal threads 14 and 16.

Further, the binding segments S3 and S4 are arranged relative to the flanking transverse threads B2 and B3 flanking them

the two flanking lower transverse threads B2 and B3 on the outer side 114 of the lower fabric layer 112 continuously intersect the same lower longitudinal threads 4 and 6 which, together with the binding thread i4 of the pair, form the binding segments S4,

the two flanking lower transverse threads B2 and B3 on the outer side 114 of the lower fabric layer 112 continuously intersect the same lower longitudinal threads 14 and 16 which, together with the binding yarn i3 of the pair, form the binding segment S3,

the flanking lower transverse thread B2 forms a bend with the lower longitudinal threads 2 and 12, wherein the longitudinal thread 2 immediately precedes the binding segment S4 and the longitudinal thread 12 the binding segment S3 and the flanking lower transverse thread B3 a bend with the lower longitudinal threads 8 and 18 forms, wherein the longitudinal thread 8 the binding segment S4 and the longitudinal thread 18 immediately following the binding segment S3.

With reference to FIGS. 4 to 6, a further embodiment variant of a forming fabric 100 constructed according to the invention is explained below.

In principle, in the forming fabric 100, the principles described above are implemented with regard to the position or incorporation of the lower transverse threads flanking a respective pair of binder yarns and also with respect to the course of the binding yarns i1 to i20 of the first type and the second type. For example, in the case of the binding thread pair i1, i2, it can be seen that the binding thread i1 binds to form the plain weave over the three upper longitudinal threads 1, 5 and 9 where it is bound into the upper, ie paper-side fabric layer 101, thus crossing it before it changes back to the lower fabric layer 102 and there on the outside, the lower longitudinal threads 14, 16 crosses to form the binding segment S1. The binding thread i1 is therefore a binding thread of the second kind. Accordingly, the binding thread i2 is a binding thread of the first type which, where it is integrated into the upper fabric layer 101 to form the plain weave, crosses two upper longitudinal threads 13, 17, ie at the Outside of the same binds. With regard to the position of the binding segments of the various adjacent pairs of binder thread with respect to each other, the arrangement already shown in Fig. 1 is also realized. It can be seen, for example, that the binding segments S3, S4 of the pair of binding yarns i3, i4 with respect to those of the pair of yarns i1, i2 are shifted by one longitudinal thread in the transverse direction, ie the weft direction. It should be noted that, of course, the arrangement described with reference to FIG. 2 could also be selected, in which an overlap of such binding segments of adjacent pairs of binding thread is not present.

A substantial difference compared to the embodiment shown in Fig. 1 lies in how the binding threads of various kinds adjacent pairs of binder threads follow each other. In Fig. 1 it can be seen that in successive pairs of binder yarns always first denoted by odd number binder thread, so the binding yarn i1, i3, i5, etc., a binding yarn of the second kind, ie a binding yarn, where it in the upper fabric layer 101 is bound to form the plain weave, binds over three upper longitudinal threads or crosses them.

The second following binding yarn of a respective pair of binder yarns, that is, the binding yarns i2, i4, i6, etc., is a binder yarn of the first type which intersects two upper longitudinal yarns where it is bound in the upper fabric layer 101 to form the plain weave. This can be seen on the basis of the assigned in association with the respective binding threads i1, i2, etc. in Fig. 1 digits 3, 2, wherein the numeral 3 each denotes a binding thread of the second type, while the numeral 2 denotes a binding thread of the first kind. In the embodiment variant shown in FIG. 4, however, it is now provided that in each case the binding threads of the same kind of the different pairs of binder threads are adjacent to one another in the direction of the longitudinal threads of successive pairs of binder threads. Thus, as FIG. 4 clearly shows, in addition to the binding yarn i2 of the binder yarn pair i1, i2, which is a binder yarn of the first type, ie sets over the two upper longitudinal yarns 13, 17, the binder yarn pair i3, i4 also serves as binder yarn the first type trained binding thread i3. In addition to the binding thread i4 of the binding thread pair i3, i4, which is a binding thread of the second type and thus sets or crosses over three upper longitudinal threads 3, 7, 11, the binding thread i5 of the binding thread pair i5, i6 lies. This binding thread i5 is also a binding thread of the second type, thus crossing two upper longitudinal threads 1, 17 for forming the plain weave in the upper fabric layer 101.

This change in the types of binding threads in the respective pairs of binder threads takes place in the production of such a forming fabric when the

Binding threads or transverse threads are formed as weft threads, characterized in that always in relation to the succession to be introduced in the temporal sequence Bindefäden always first a binder yarn of a kind of a pair, then the binder yarn of another kind of one pair, then the binding yarn of another kind of the next pair and then the binding yarn of a kind of the next pair, etc. is introduced, of course, between each pair then the upper and lower transverse threads are introduced, so for example, between the binding thread pairs i1, i2 and i3, i4 the upper transverse threads T3, T4 and flanking in the lower fabric layer 102 lower transverse threads B3, B4 are introduced.

From this sequence of binding threads of different types in the successive pairs of binding threads results in a recognizable in Figs. 5 and 6 structure. In particular, it can be seen in FIGS. 5 and 6 that, due to this change in the binding threads of different types of adjacent pairs of binder yarns, for example in the region of the lower longitudinal threads 2 to 12, the binding threads i2, i3 of two adjacent pairs of binder yarns are comparatively close to each other, whereas in the following one Area the two binding yarns i1, i4 of the same pairs of binder yarns have a comparatively large distance. This sequence of smaller distance and greater distance in the different adjacent pairs of binder yarns is continued both in the transverse direction, so for example, the weft direction, as well as the longitudinal direction, so for example, the warp direction. This leads to the drainage regions E1, E2, E3, E4, which are enclosed in ellipses and designated with different patterns in FIG. 6, which are each enclosed between the binding threads of the same type of different pairs of binder yarns. These four different dewatering areas, which continue correspondingly over the successive repeats, have slightly different and high regularity layers to each other and in the fabric structure, thus enabling low-marking retention of fillers and fibers from the fiber suspension used for papermaking, and promoting homogeneous and undirected drainage. The effect is explained by the drainage areas E1, E2, E3, E4 arranged alternately in the binding diagonal, which are determined by the placement of the outside Tie segments are formed and appear alternately open and dense and thus cause a homogeneous non-directional drainage. If the drainage channels E1, E2, E3, E4 are arranged regularly, this can lead to a marking corresponding to this regularity by a washing out of fibers and an increased washing out of fillers.

FIG. 5 further shows that the diagonals L1, L2 formed between the respective binding segments of the binding threads of the same type of adjacent pairs of binder yarns, differing from a basically rectilinear main diagonal D of the fabric structure of the lower fabric layer 102, alternately have different angular positions relative to the transverse or transverse diagonal ., The longitudinal direction of the forming 100 has. These diagonals each extend between the cross-directionally viewed middle regions of the binding segments binding threads of the same type of adjacent pairs of binder threads. Thus, a dotted line L1 defines a diagonal which is e.g. connecting the center regions, viewed in the transverse direction, of binding segments S5, S8 of the binding threads i5, i8 of the first kind. A dashed line L2, starting from the binding thread i8, continues this diagonal to the next binding thread or the connecting thread i9 of this pair, which, like the binding threads i5, i8, is a binding thread of the second kind. It can be seen that here there is no straight line extending through the lower fabric layer 102 diagonal. Rather, it results in a zigzagging line. Due to this more irregular course compared to a straight running diagonal the marking tendency is reduced.

It has been found that the arrangement of binding threads of various types described above with reference to FIGS. 4 to 6 is particularly advantageous in terms of drainage and marking properties when combined with the weft ratio of FIG. 3 which can also be seen in FIGS. second In principle, however, it should be noted that this arrangement of binding threads of various types can also be applied to shot ratios of 2: 1 or 1: 1. Further, in connection with the above-described arrangement of binding yarns of various kinds, a ratio of the open area of the running side fabric layer to the open area of the paper side fabric layer of less than 1, preferably less than 0.95, most preferably less than 0.9, is particularly advantageous , This means that the paper side, ie upper fabric layer 101 is formed with an open structure, ie higher porosity, than the running side, lower fabric layer 102, this also helps to reduce the leaching of fillers from the paper side.

The definition of the open areas of the upper, ie paper-side fabric layer or of the lower, ie machine-side or running-side fabric layer is explained below with reference to FIGS. 7 to 9.

FIG. 7 shows a view of the upper fabric layer 101, viewed from above, that is to say from the side in contact with the paper material to be produced. The various transverse threads T1, 12, T3, etc., or longitudinal threads 1, 3, 5, etc. can be seen. It can also be seen that the binding thread pair i1, \ 2, which in this view in the upper fabric layer 101, actually acts as a single transverse thread contributing to the plain weave is looked at.

Between the intersecting and thus the plain weave forming Längsbzw. Transverse threads of the upper fabric layer 100 are formed in the illustrated case substantially square, not covered in the plan view by threads surface areas F, which are shown dotted in Fig. 7. The open area of the upper fabric layer 101 is defined by the ratio of the area, not covered by threads, formed by all these surface areas F to the entire surface considered, which covers the sum of all surface areas F and all in plan view by the longitudinal and transverse threads Represents surfaces.

FIG. 8 shows a representation corresponding to FIG. 7 in the viewing direction lower fabric layer 102. This is therefore also viewed in the view of FIG. 8 from the top, ie from one of the upper fabric layer side facing. FIG. 8 also shows the various longitudinal and transverse threads as well as the binding threads i1 to i10 of the various pairs of binder threads which likewise run in the transverse direction. FIG. 9 shows a schematic representation in which the various longitudinal threads 2 to 10 are shown extending in a dark vertical direction. The lines labeled B1 to B5 represent the various longitudinally successive and transverse transverse threads. Lightly marked are Abbindebereiche A. These are those areas in which a transverse thread over a longitudinal thread sets before he returns to the bottom of the four then floats along following longitudinal threads.

Spotted are area areas F 'whose total area is again set in relation to the total area of the considered lower fabric layer 102 in order to determine the size "open area of the lower fabric layer." It can be seen that, on the one hand, those areas are considered as such surface areas F' 8, bottom left between the transverse yarns B1 and B2 are marked in Fig. 8. At the same time, as such surface regions F ', surface areas are interspersed between two immediately adjacent transverse yarns Thus, binding threads are generally not considered to be thread material that reduces the surface areas F 'Such a surface area F' is marked bottom left between the transverse threads B2 and B3 in Fig. 8. Further, as derar Considered surface areas F 'those portions of the transverse threads B1, B2, etc., which float adjacent to the binding areas A under the then following longitudinal threads. Such a surface area F 'is shown in FIG. 8 in association with the transverse thread B2 on the right next to a setting area A. Thus, while the lying between the longitudinal threads 10 and 14 and the longitudinal thread 12 at its top intersecting portion of the transverse thread B2 not as Surface area F 'is taken into account, the then following surface areas F' or corresponding preceding surface areas are considered in the determination of the open area of the lower fabric layer as not covered by a thread.

With the construction according to the invention of a forming fabric, the advantage is achieved that the wrap angles with respect to the longitudinal threads are reduced by the floats formed in the binding threads, in particular also in the region of the binding segments, which generally results in less wear due to reduced friction between the longitudinal and transverse threads is due. Also, by incorporating more than one longitudinal thread of the lower fabric layer by means of the binding threads, a stronger bond between the two fabric layers is achieved, which generally leads to a smaller thickness of the forming fabric and a faster or better drainage at a lower open volume. It can thus be achieved with such a constructed forming fabric higher production speeds in papermaking.

Claims

Voith Patent GmbH File: HPF13546 WOKD-89510 Heidenheim "Forming screen with 5-shank LS" FormieriebPatentansprüche

A papermaker's fabric, in particular a forming fabric, having an upper and a lower fabric layer and binding threads for joining the two fabric layers, wherein the lower fabric layer is formed by the binding threads, lower transverse threads and interwoven therewith transversely extending lower longitudinal threads, wherein the lower fabric layer has a weave pattern that repeats in lower repeats, wherein the binding threads are arranged in pairs and the binding threads of each pair are mutually interwoven with top and bottom longitudinal threads, each pair of binder threads flanked on both sides by a lower transverse thread and each of the two flanking lower transverse threads interwoven periodically with lower longitudinal threads as follows:

ii) the flanking lower transverse thread continuously crosses a lower longitudinal thread between the upper and lower layers of fabric and forms a thread crease, characterized that within the bottom repeat

each binding thread of each pair with lower longitudinal threads at least one

Binding segment forms and each binding segment is formed by the fact that the respective binding thread of the pair on the outside of the lower fabric layer continuously crosses two or more immediately successive lower longitudinal threads and the binding segments of each pair of binder yarn are arranged relative to the flanking these transverse transverse threads that

i) the two flanking lower transverse threads on the outside of the lower fabric layer continuously intersect at least the same lower longitudinal threads, which together with the binding threads of the pair

Form binding segments,

ii) one of the two flanking lower transverse threads one each

Forming bend with the lower longitudinal thread, the corresponding

Binding segment immediately precedes and

iii) the other of the two flanking lower transverse threads one each

Forming bend with the lower longitudinal thread, which immediately follows the corresponding binding segment.

2. Papermaking fabric according to claim 1, characterized in that between two successive binding segments formed by the same binder yarn, this binder yarn on the outside of the upper fabric layer continuously crosses at least one upper longitudinal thread.

3. paper machine screen according to claim 1 or 2, characterized in that within the lower repeat of each binding thread of a Binding thread pair with lower longitudinal threads forms exactly one binding segment.

4. Papermaking fabric according to one of the preceding claims, characterized in that all the lower transverse threads are interwoven in a periodic sequence with lower longitudinal threads as follows:

5. Papermaking fabric according to one of the preceding claims, characterized in that each lower transverse thread in periodic succession on the outside of the lower fabric layer continuously four immediately successive lower longitudinal threads crossed before this crosses a thread cross-forming running between the upper and lower fabric layer a lower longitudinal thread.

6. Papermaking fabric according to one of the preceding claims, characterized in that between immediately successive bonding segments of a

Binding thread pair three lower longitudinal threads are arranged.

7. Papermaking fabric according to one of the preceding claims, characterized in that the upper fabric layer is formed by the binding threads, by upper transverse threads and by transversely to the binding threads and the upper transverse threads extending upper longitudinal threads, which interwoven with these are.

8. Papermaking fabric according to one of the preceding claims, characterized in that is continued by the mutually exchanging interweaving of the binding threads of the binder thread pairs with the upper longitudinal threads, the woven pattern formed by the weaving of the upper longitudinal threads with the upper transverse threads.

9. Papermaking fabric according to one of the preceding claims, characterized in that each binding thread intersects the weaving with successive upper longitudinal threads alternately on the outside of the upper fabric layer and extending between the two fabric layers upper longitudinal threads.

10. Papermaking fabric according to one of the preceding claims, characterized in that each pair of binder yarn has a binding yarn of the first kind and a binding yarn of the second kind, wherein in the upper repeat unit of the binding yarn of the first kind crosses two upper longitudinal threads, if this on the

Outside of the upper fabric layer runs and the binding yarn of the second kind crosses three upper longitudinal threads when it runs on the outside of the upper fabric layer.

11. Papermaking fabric according to claim 10, characterized in that in the direction of the longitudinal threads successive pairs of

Bindefäden the binding threads of the same kind of different pairs follow each other.

12. Papermaking fabric according to one of claims 10 or 11, characterized that binding segments formed by binding threads of the same type of binding yarn pairs immediately adjacent to each other in the cross-thread direction are arranged adjacent to each other in an overlapping manner or adjoin one another directly.

13. Paper machine screen according to one of the preceding claims, characterized in that the upper fabric layer forms a weave pattern as a weave pattern.

14. Papermaking fabric according to one of the preceding claims, characterized in that all binding segments comprise the same number of directly consecutive lower longitudinal threads.

15. Papermaking fabric according to one of the preceding claims, characterized in that the ratio of the number of pairs of binder yarn and upper

Cross threads together to the number of lower transverse threads 1: 1 or 2: 1 or 3: 2.

16. Papermaking fabric according to one of the preceding claims, characterized in that the lower transverse threads have a larger cross-sectional area than the binding threads.

17. Papermaking fabric according to one of the preceding claims, characterized in that a ratio of the open area of the lower fabric layer to the open surface of the upper fabric layer is less than 1, preferably less than 0.95, most preferably less than 0.9.

18. Papermaking fabric according to one of the preceding claims, characterized in that the longitudinal threads are warp threads and the transverse and binding threads are weft threads.