Fabric belt

Abstract

The invention relates to a fabric belt, in particular a forming wire, for a machine for manufacturing and / or processing a fibrous web, comprising an upper fabric layer having upper longitudinal yarns and upper transverse yarns interwoven with the upper longitudinal yarns, and a lower fabric layer having lower longitudinal yarns and lower transverse yarns interwoven with the lower longitudinal yarns, wherein the two fabric layers are arranged one above the other such that, in the intended use of the fabric belt, the upper fabric layer faces the fibrous web and the lower fabric layer faces away from the fibrous web, wherein the upper longitudinal yarns are unevenly spaced apart from one another, wherein the upper longitudinal yarns are arranged such that their average spacing has the following sequence, continuously repeated in the cross direction of the fabric belt: wide spacing, wide spacing, narrow spacing, wherein the difference between the average wide spacing and the average narrow spacing corresponds to at least 50% of the diameter of the upper longitudinal yarns.

Description

TECHNICAL FIELD

[0001] The invention relates to a fabric belt, in particular a forming wire, for a machine for manufacturing and / or processing a fibrous web, comprising an upper fabric layer having upper longitudinal yarns and upper transverse yarns interwoven with the upper longitudinal yarns, and a lower fabric layer having lower longitudinal yarns and lower transverse yarns interwoven with the lower longitudinal yarns, wherein the two fabric layers are arranged one on top of the other such that, when the fabric belt is used as intended, the upper fabric layer faces the fibrous web and the lower fabric layer faces away from the fibrous web, wherein the upper longitudinal yarns are unevenly spaced apart from one another. BACKGROUND

[0002] Such a fabric belt has been used very successfully in the paper- and board manufacturing industry since the mid-1990s as a so-called SSB (sheet support binding) forming wire. The multi-layer structure of the fabric belt provides the advantage here that the upper longitudinal yarns and the upper transverse yarns can be designed finer than the lower longitudinal yarns and the lower transverse yarns. Thus, the upper longitudinal yarns and the upper transverse yarns can provide the fibrous web with a surface that is as fine and smooth as possible, while the coarser lower longitudinal yarns and the lower transverse yarns can absorb the tensile forces acting on the fabric in the longitudinal and transverse directions, respectively, and can withstand the wear that the fabric belt is subjected to when it is guided in the machine past stationary dewatering elements, such as suction boxes.

[0003] If the fabric belt has a weave pattern comprising the same number of upper longitudinal yarns and lower longitudinal yarns, then an upper longitudinal yarn is usually arranged above each lower longitudinal yarn. In this case, the "on-stacking" is mentioned. The upper longitudinal yarns and the lower longitudinal yarns are here essentially all spaced apart from one another identically. This weave pattern provides the advantage that the drainage resistance caused by the longitudinal yarns is minimized and, as a result, the fibrous web is formed particularly well. However, if the dewatering speed becomes too high, there is a risk that too much filler material is washed away.

[0004] In a known, alternative weave pattern, it is provided that an upper longitudinal yarn is arranged exactly between two adjacent lower longitudinal yarns, respectively. This is the so-called "off-stacking". Although in this case all upper longitudinal yarns and lower longitudinal yarns are essentially all spaced apart from one another identically, respectively, the water escaping from the fibrous web can no longer pass through the fabric belt so linearly. This reduces the dewatering speed, so that less filler is washed away. However, the reduction in the dewatering speed can result in an undesired reduction in the manufacturing speed.

[0005] Furthermore, it has long been known that fabric tapes, particularly those in the form of SSB forming screens, have a different, and especially larger, number of upper longitudinal yarns than lower longitudinal yarns. This allows the upper longitudinal and upper transverse yarns to be designed more finely than the lower longitudinal and lower transverse yarns, in order to provide a smoother contact surface for the fiber width. Such fabric tapes according to the present invention are exemplified in patent document WO2013 / 160391A1. Figure 1 As shown in d. In this case, the warp yarns are arranged adjacently in different groups, namely, a first group consisting of a lower warp yarn and an upper warp yarn arranged above the lower warp yarn, and a second group consisting of a lower warp yarn and two upper warp yarns arranged above the lower warp yarn. To minimize the undesirable hydraulic marking characteristics caused mainly by the lower warp yarns, the lower warp yarns are spaced substantially evenly from each other. However, this results in the upper warp yarns being spaced differently from each other, which is not optimal for the topographic marking characteristics of the fabric strip. Furthermore, the advantages of "open stacking" and "closed stacking" can be combined. Summary of the Invention

[0006] The technical problem to be solved by this invention is to further improve the marking properties of the fabric strip of the type described in this invention. In particular, the fabric strip of the type described in this invention should be improved in a way that maintains its low hydraulic marking properties as much as possible, and combines the advantages of open and closed stacking while optimizing its topographic marking properties.

[0007] The technical problem is solved by a fabric belt, particularly a forming screen, for a machine used to manufacture and / or process fiber webs. The fabric belt comprises an upper fabric layer and a lower fabric layer. The upper fabric layer has upper longitudinal yarns and upper transverse yarns interwoven with the upper longitudinal yarns. The lower fabric layer has lower longitudinal yarns and lower transverse yarns interwoven with the lower longitudinal yarns. These two fabric layers are arranged such that, when the fabric belt is used as specified, the upper fabric layer faces the fiber web, and the lower fabric layer faces away from the fiber web. The upper longitudinal yarns are unevenly spaced from each other. According to the invention, the upper longitudinal yarns are arranged such that the average spacing of the upper longitudinal yarns has a continuously repeating sequence along the transverse direction of the fabric belt: wide spacing, wide spacing, narrow spacing, wherein the difference between the average wide spacing and the average narrow spacing is equivalent to at least 50% of the diameter of the upper longitudinal yarns. The processing of the fiber web also includes the manufacture of the fiber web within the scope of the invention.

[0008] According to the application, the fabric belt of the type mentioned in the opening is characterized in that the upper longitudinal yarns are arranged in such a way that their average spacing has the following sequence, repeated continuously along the transverse direction of the fabric belt: wide spacing, wide spacing, narrow spacing, wherein the difference between the average wide spacing and the average narrow spacing corresponds to at least 50% of the diameter of the upper longitudinal yarns.

[0009] It has surprisingly been found that this sequence of the spacing of the upper longitudinal yarns has a very advantageous effect on the marking in the fibrous web. Although the upper longitudinal yarns are not spaced from one another exactly the same, the topographical marking in the fibrous web is thus not recognizable or hardly recognizable. Rather, the different spacing of the upper longitudinal yarns appears to contribute to masking the hydrodynamic herringbone marking caused by the weave pattern of the lower fabric layer. In any case, the fabric belt according to the application can be used to produce a fibrous web of very good quality in terms of uniform formation.

[0010] It can occur, especially for SSB forming screens, that the upper longitudinal yarns do not extend exactly straight along the longitudinal direction of the fabric belt, but rather undulate to the left and to the right, i.e. to the side edges of the fabric belt. This undulation is caused by the plating thread, which pushes the upper longitudinal yarns to the right and to the left, if the plating thread is a transverse yarn, depending on which side of the upper longitudinal yarn it sinks down. For this reason, the spacing between two upper longitudinal yarns is not always constant when viewed along the longitudinal direction of the fabric. To take this into account, the present application is based on the "average spacing" between two adjacent longitudinal yarns. In other words, in the case of a fabric belt whose spacing along the longitudinal direction varies, especially in the case of a kind of wave, it should be assumed that the longitudinal yarns extend straight, which longitudinal yarns are arranged on the center line of the wave. This "average" spacing of the upper longitudinal yarns can be adjusted during the manufacture of the fabric belt. Such fabric belts are mostly flat-woven, heat-set and then closed into a continuous belt by means of seams on a sewing machine. In flat weaving, the longitudinal yarns correspond to the warp threads and the transverse yarns correspond to the weft threads. The spacing between the warp threads can be adjusted in the so-called reed.

[0011] It is also possible that the average distance value of the two wide spacings is not exactly the same. The average value of the first wide spacing in the sequence of wide spacing, wide spacing, narrow spacing described above can be slightly smaller or slightly larger than the average value of the second wide spacing. If this is the case, it should apply at least for the wide spacing with the larger average spacing value that the difference between the average wide spacing and the average narrow spacing corresponds to at least 50% of the diameter of the upper longitudinal yarns. For the other wide spacing with the smaller average spacing value, it should preferably apply that the difference between the average wide spacing and the average narrow spacing corresponds to at least 20% of the diameter of the upper longitudinal yarns.

[0012] As is common in most such fabric belts, preferably all of the upper longitudinal yarns have the same cross-sectional shape of the same diameter. If this cross-sectional shape is exceptionally not circular, but for example flat, then the diameter of a circular cross-sectional shape having the same cross-sectional area should be chosen as the diameter. The same applies analogously to the lower longitudinal yarns.

[0013] Each of the flat-woven fabric belts for forming screen applications has to be subjected to a heat-setting process in order to achieve subsequent seaming, in which, under the action of increased temperature and tensile stress, a deformation, in particular a plastic deformation, of the warp threads, which were originally used as straight filaments stretched along the longitudinal direction, at the intersection with the weft threads, which were likewise originally used as straight filaments stretched along the transverse direction, is achieved. Since the tensile stress is specifically exerted on the warp threads during heat setting, the warp threads are slightly flattened under the action of temperature and tensile stress. If a circular cross-sectional shape of the warp threads is mentioned in the context of the present application, this flattening and the resulting deviation from the circular shape are not taken into account. Instead, a circular cross-sectional shape having an equivalent cross-sectional area is assumed.

[0014] In order to provide the fibrous web with a surface that is as smooth as possible, the upper longitudinal yarns preferably have a smaller diameter than the lower longitudinal yarns. The diameter of the upper longitudinal yarns can in particular be only 40% to 60% of the diameter of the lower longitudinal yarns. The diameter of the upper longitudinal yarns can for example be 0.07 mm to 0.30 mm, and / or the diameter of the lower longitudinal yarns can be 0.15 mm to 0.50 mm.

[0015] The wide spacing can preferably be 100% to 300% of the diameter of the upper longitudinal yarns, and / or the narrow spacing can preferably be 30% to 125% of the diameter of the upper longitudinal yarns. This makes it possible to achieve very satisfactory results in the formation of the fibrous web in trials. Even if the spacing between two directly adjacent upper longitudinal yarns is not constant along the longitudinal direction of the fabric belt, but the upper longitudinal yarns for example follow a wavy line, the first and / or second spacing preferably still always moves in the aforementioned range.

[0016] The first embodiment of the fabric belt according to the application provides that the ratio of the upper warp threads to the lower warp threads in the fabric belt is 1 : 1, wherein the lower warp threads are preferably equally spaced from one another. A group of (open stack) longitudinal yarns consisting of a lower longitudinal yarn and an upper longitudinal yarn arranged directly above this lower longitudinal yarn can for example be adjacent to a group of longitudinal yarns consisting of a lower longitudinal yarn and an upper longitudinal yarn that is not arranged directly above this lower longitudinal yarn (closed stack).

[0017] An alternative second embodiment of the fabric tape according to the application provides that the weaving pattern of the fabric tape repeats in a repeating pattern, wherein the upper longitudinal yarns and the lower longitudinal yarns in each repeating pattern are arranged in a plurality of groups, the plurality of groups having a first group and a second group and at least one further first group and / or second group, wherein each first group consists of one upper longitudinal yarn and one lower longitudinal yarn arranged below this upper longitudinal yarn, and each second group consists of one upper longitudinal yarn and two lower longitudinal yarns arranged below this upper longitudinal yarn, respectively. The fabric tape preferably consists of only such first groups and second groups in terms of its longitudinal yarns. It is furthermore preferred that the upper longitudinal yarn and the lower longitudinal yarn in each group are arranged without or only slightly offset relative to each other, as viewed in a vertical projection into the fabric layer, so that at most a free space of half the diameter of the upper longitudinal yarn is formed between the upper longitudinal yarn and the lower longitudinal yarn. The ratio of the number of upper longitudinal yarns to the number of lower longitudinal yarns is preferably not an integer. There can be one or more repeating units, i.e. a fixed sequence of first and second groups of longitudinal yarns, in the repeating pattern. The repeating sequence of groups is preferably at most 15.

[0018] In addition to the uneven spacing of the upper longitudinal yarns according to the application, it can also be advantageous for the lower longitudinal yarns to be unevenly spaced. It can in particular be provided that a first spacing between two directly adjacent lower longitudinal yarns is greater than a second spacing between two directly adjacent lower longitudinal yarns, wherein the difference between the first spacing and the second spacing is 25% to 200% of the diameter of the upper longitudinal yarn. The inventors have surprisingly determined that, contrary to the common belief in the hydraulic marking properties of fabric tapes, it can be advantageous for the lower longitudinal yarns not to be arranged at always the same spacing relative to each other. The inventors' explanation for this observation is that a non-negligible part of the hydraulic marking properties is due to regular hydraulic twill markings, which can be significantly reduced as a result of the lower longitudinal yarns being arranged at irregular spacing relative to each other. The uneven spacing of the lower longitudinal yarns works synergistically with the uneven spacing of the upper longitudinal yarns according to the application to mask or avoid regular hydraulic twill markings, which are primarily caused by the weaving pattern of the lower fabric layer.

[0019] It can be provided here that the two lower longitudinal yarns of a second group have a second spacing between each other, while the two lower longitudinal yarns of a first group and of a second group directly adjacent to this first group and / or the two lower longitudinal yarns of two directly adjacent first groups have a first spacing.

[0020] An alternative third embodiment of the fabric belt according to the present application provides that the weaving pattern of the fabric belt is repeated in a repeating pattern, wherein the upper longitudinal yarns and the lower longitudinal yarns in each repeating pattern are arranged in a plurality of groups, the plurality of groups having a first group and a second group, wherein the first group consists of one upper longitudinal yarn and one lower longitudinal yarn arranged below the one upper longitudinal yarn, and the second group consists of two upper longitudinal yarns and one lower longitudinal yarn arranged below the two upper longitudinal yarns. The fabric belt preferably consists of only such first groups and second groups in terms of its longitudinal yarns. The repeating pattern further preferably comprises as many first groups as second groups. It is furthermore preferred that the upper longitudinal yarns and the lower longitudinal yarns in each group are arranged without or only slightly offset relative to each other as viewed in a vertical projection into the fabric layer, so that at most a free space of half the diameter of the upper longitudinal yarn is formed between the upper longitudinal yarn and the lower longitudinal yarn. The ratio of the number of upper longitudinal yarns to the number of lower longitudinal yarns is preferably not an integer. There can be one or more repeating units, i.e. a fixed sequence of first and second groups of longitudinal yarns, in the repeating pattern, wherein the repeating sequence of groups is preferably at most 15.

[0021] It has furthermore proven to be advantageous that the difference between the average wide spacing of two directly adjacent upper longitudinal yarns and the average narrow spacing of two directly adjacent upper longitudinal yarns is at most 200%, preferably 150%, of the diameter of the upper longitudinal yarn. Otherwise, at too great a difference, it can lead to topographical markings occurring in the fiber web which are visually perceptible.

[0022] As already described in the introduction with regard to the known SSB forming screen, it is also preferred in the fabric belt according to the present application that the first and second fabric layers are connected to each other by pairs of twist threads. These twist threads can extend along the transverse direction of the fabric belt. Furthermore, the two twist threads of a respective pair of twist threads can be interlaced with the upper longitudinal yarns, the lower longitudinal yarns, and cross over when changing from being interlaced with the upper longitudinal yarns to being interlaced with the lower longitudinal yarns and vice versa to form preferably at least two crossing positions.

[0023] The upper fabric layer is preferably constituted by the interlacing of the upper longitudinal yarns with the upper transverse yarns and the twist threads, wherein the lower fabric layer is constituted by the interlacing of the lower longitudinal yarns with the lower transverse yarns. This means that the twist threads are an integral part of the upper fabric layer and do not contribute to the lower fabric layer, but only connect the lower fabric layer with the upper fabric layer.

[0024] According to a preferred design of the application, the weave pattern of the upper fabric layer forms a plain weave. This plain weave is particularly uniform by means of the smallest possible repeating unit. Unlike other weaves, the plain weave does not have, inter alia, connecting ridge lines extending along diagonal directions. Therefore, for the plain weave of the upper fabric layer, the diagonal markings of the liquid forces caused by the lower fabric layer are not reinforced. BRIEF DESCRIPTION OF DRAWINGS

[0025] Further advantageous features of the application according to embodiments are set out in the following with reference to the accompanying drawings. In the drawings:

[0026] Figure 1 A schematic diagram of an embodiment of a fabric belt according to the application is shown;

[0027] Figure 2 A schematic diagram of a second embodiment of a fabric belt according to the application is shown; and

[0028] Figure 3 A schematic diagram of a third embodiment of a fabric belt according to the application is shown. DETAILED DESCRIPTION

[0029] Figure 1 A first embodiment of a fabric belt according to the application is shown schematically. Here, only the upper longitudinal yarns O1-O3 and the lower longitudinal yarns U1-U3, which together form the repeating unit WE, can be seen, whereas the upper transverse yarns interwoven with the upper longitudinal yarns O1-O5 to form the upper fabric layer, the lower transverse yarns interwoven with the lower longitudinal yarns U1-U3 to form the lower fabric layer, and the plating threads connecting the upper fabric layer and the lower fabric layer cannot be seen. The plating threads are here preferably lines that are an integral part of the weave pattern of the upper fabric layer, in particular the plain weave, and do not contribute to the weave pattern of the lower fabric layer.

[0030] The fabric belt is composed of a repeating pattern that repeats itself. For the upper longitudinal yarns O1-O3 and the lower longitudinal yarns U1-U3, the repeating pattern can in principle consist exactly of the unique repeating unit WE. However, the repeating pattern usually comprises a plurality of such repeating units WE. It should be taken into account here that the repeating pattern is defined not only by the longitudinal yarns, but also by the transverse yarns and the plating threads. If the upper fabric layer is, as is preferred, a plain weave, the repeating pattern must have an even number of upper longitudinal yarns. Since the repeating unit WE in the first embodiment according to the application has three upper longitudinal yarns O1-O3, the repeating pattern must comprise an integer multiple of the repeating unit WE, i.e. at least two repeating units WE. Figure 1

[0031] ​In the first embodiment, the repeat unit WE consists of three groups of longitudinal yarns, namely three first groups I, which each only include an upper longitudinal yarn O1-O3 and a lower longitudinal yarn U1-U3. Between the first upper longitudinal yarn O1 and the second upper longitudinal yarn O2, there is a relatively wide first spacing a1. Between the second upper longitudinal yarn O2 and the third upper longitudinal yarn O3 adjacent thereto, there is also the same relatively wide spacing a1. The spacing a2 between the third upper longitudinal yarn O3 and the upper longitudinal yarn O1 of the next repeat unit adjacent to the third upper longitudinal yarn O3 is significantly narrower. This results in the following sequence of the spacings of the upper longitudinal yarns O1-O3 in the transverse direction of the fabric band, namely wide spacing a1, wide spacing a1, narrow spacing a2, wherein this sequence is repeated continuously in the transverse direction. According to the invention, the difference between the average wide spacing a1 and the average narrow spacing a2 is at least 50% of the diameter of the upper longitudinal yarns O1-O3. In the embodiment, all upper longitudinal yarns have the same first circular cross-section, and all lower longitudinal yarns have the same second circular cross-section. Furthermore, in the embodiment, the two wide spacings a1 have the same average value for the sake of simplicity of the description. This is not mandatory, however.

[0032] In the first embodiment, the lower longitudinal yarns U1-U3 have substantially the same spacing A1 from each other.

[0033] Figure 2 A second embodiment of a fabric band according to the invention is shown schematically. Here, only the upper longitudinal yarns O1-O3 and the lower longitudinal yarns U1-U4, which form the repeat unit WE, can be seen, however, the upper transverse yarns, which are interwoven with the upper longitudinal yarns O1-O3 to form the upper fabric layer, the lower transverse yarns, which are interwoven with the lower longitudinal yarns U1-U4 to form the lower fabric layer, and the lacing, which connects the upper fabric layer and the lower fabric layer, cannot be seen. The lacing is here preferably still an integral part of the weave pattern of the upper fabric layer, in particular of the plain weave, and does not contribute to the weave pattern of the lower fabric layer.

[0034] The fabric band is also composed of a repeating repeat pattern. For the upper longitudinal yarns O1-O3 and the lower longitudinal yarns U1-U4, the repeat pattern can in principle exactly consist of the unique repeat unit WE. However, the repeat pattern usually includes a plurality of such repeat units WE. It should be taken into account here that the repeat pattern is not only defined by the longitudinal yarns, but also by the transverse yarns and the lacing. If the upper fabric layer is, as is preferred, a plain weave, then the repeat pattern must have an even number of upper longitudinal yarns. Since, according to the invention, the upper longitudinal yarns O1-O3 are not all identical, the repeat pattern must also have an even number of lower longitudinal yarns. If the upper fabric layer is, as is preferred, a plain weave, then the repeat pattern must have an even number of upper longitudinal yarns. Since, according to the invention, the upper longitudinal yarns O1-O3 are not all identical, the repeat pattern must also have an even number of lower longitudinal yarns. Figure 2The repeating unit WE in the second embodiment also has three upper longitudinal yarns O1-O3, so the repeating pattern must comprise an integer number of repeating units WE, i.e. at least two repeating units WE.

[0035] In said second embodiment, the repeating unit WE is composed of three groups of longitudinal yarns, i.e. a first group I comprising only one upper longitudinal yarn O1 and one lower longitudinal yarn U1, a second group comprising one upper longitudinal yarn O2 and two lower longitudinal yarns U2 and U3, and a further first group I comprising only one upper longitudinal yarn O3 and one lower longitudinal yarn U4. Between the first upper longitudinal yarn O1 and the second upper longitudinal yarn O2, there is a relatively wide first spacing a1. Between the second upper longitudinal yarn O2 and the third upper longitudinal yarn O3 adjacent thereto, there is also the same relatively wide spacing a1. The spacing a2 between the third upper longitudinal yarn O3 and the upper longitudinal yarn O1 of the next repeating unit adjacent to said third upper longitudinal yarn O3 is significantly narrower. This results in the following sequence of spacings of the upper longitudinal yarns O1-O3 along the transverse direction of the fabric strip, i.e. wide spacing a1, wide spacing a1, narrow spacing a2, wherein this sequence is repeated continuously along the transverse direction. According to the invention, the difference between the average wide spacing a1 and the average narrow spacing a2 is at least 50% of the diameter of the upper longitudinal yarns O1-O3.

[0036] In this second embodiment, the lower longitudinal yarns U1-U4 have different spacings from each other. Between the first lower longitudinal yarn U1 and the second lower longitudinal yarn U2, and between the third lower longitudinal yarn U3 and the fourth lower longitudinal yarn U4, there is a relatively large first spacing A1, while between the second lower longitudinal yarn U2 and the third lower longitudinal yarn U3, there is a relatively small second spacing A2. The relatively wide first spacing A1 is also present between the fourth lower longitudinal yarn U4 and the first lower longitudinal yarn U1 of the directly adjacent repeating unit. Thus, in this embodiment, a sequence of first spacing, second spacing, first spacing, first spacing is created continuously along the transverse direction of the fabric strip for the spacings of the lower longitudinal yarns.

[0037] In this embodiment, all upper longitudinal yarns O1-O3 still have the same circular cross-section relative to each other, and all lower longitudinal yarns U1-U4 have the same, however larger, circular cross-section relative to each other. Furthermore, in said embodiment, for the sake of brevity of the description, the two wide spacings a1 have the same average value. However, this is not mandatory.

[0038] The dimensions in this embodiment can for example be chosen as follows:

[0039] Diameter of the upper longitudinal yarns O1-O4: 0.14 mm

[0040] Diameter of the lower longitudinal yarns U1-U3: 0.19 mm

[0041] First distance A1 : 0.095 mm

[0042] Second distance A2: 0.049 mm

[0043] Distance a1 : 0.2645 mm

[0044] Distance a2: 0.145 mm

[0045] The resulting extension of the repeat unit WE is 1.094 mm. The difference between the first distance A1 and the second distance A2 is 0.046 mm, which corresponds to 33% of the diameter of the upper longitudinal yarns.

[0046] It should also be stated in general that these distances, in particular the distances a1 and a2 between the upper longitudinal yarns O1-O3, are not necessarily constant over the entire longitudinal extension of the fabric band. The distances can also become narrower and then wider again. The respective average distance should therefore be based on.

[0047] Figure 3 A third embodiment of a fabric band according to the application is schematically shown. Here, only the upper longitudinal yarns O1-O3 and the lower longitudinal yarns U1-U2, which together form the repeat unit WE, can be seen, however, not visible are the upper transverse yarns interwoven with the upper longitudinal yarns O1-O3 to form the upper fabric layer, the lower transverse yarns interwoven with the lower longitudinal yarns U1-U2 to form the lower fabric layer, and the plating thread connecting the upper fabric layer and the lower fabric layer. The plating thread is here preferably still an integral part of the weave pattern of the upper fabric layer, in particular a plain weave, while the plating thread does not contribute to the weave pattern of the lower fabric layer.

[0048] The fabric band is also composed of a repeating repeat pattern. For the upper longitudinal yarns O1-O3 and the lower longitudinal yarns U1-U2, the repeat pattern can in principle exactly consist of a unique repeat unit WE. However, the repeat pattern usually comprises a plurality of such repeat units WE. It should be taken into account here that the repeat pattern is not only defined by the longitudinal yarns, but also by the transverse yarns and the plating thread. If the upper fabric layer is, as is preferred, a plain weave, the repeat pattern must have an even number of upper longitudinal yarns. Since the repeat unit WE in the third embodiment according to Figure 3 The repeat unit WE in the third embodiment according to the application also has three upper longitudinal yarns O1-O3, the repeat pattern must therefore comprise an integer multiple of the repeat unit WE, i.e. at least two repeat units WE.

[0049] In said third embodiment, the repeat unit WE is constituted by two groups of longitudinal yarns, i.e. a first group I comprising only one upper longitudinal yarn O1 and one lower longitudinal yarn U1 and a second group comprising two upper longitudinal yarns O2 and O3 and one lower longitudinal yarn U2. Between the first upper longitudinal yarn O1 and the second upper longitudinal yarn O2 there is a relatively wide first spacing a1. Between the third upper longitudinal yarn O3 and the first upper longitudinal yarn O3 of the adjacent repeat unit WE adjacent to this third upper longitudinal yarn O3 there is also the same relatively wide spacing a1. The spacing a2 between the second upper longitudinal yarn O2 and the upper longitudinal yarn O3 adjacent thereto is significantly narrower. This results in the following sequence of the spacings of the upper longitudinal yarns O1-O3 in the transverse direction of the fabric band, i.e. wide spacing a1, wide spacing a1, narrow spacing a2, which sequence is repeated continuously in the transverse direction. According to the invention, the difference between the average wide spacing a1 and the average narrow spacing a2 is at least 50% of the diameter of the upper longitudinal yarns O1-O3.

[0050] In this third embodiment, the lower longitudinal yarns U1 and U2 have different spacings from each other. Between the second lower longitudinal yarn U1 and the first lower longitudinal yarn U2 of the adjacent repeat unit WE there is a relatively large first spacing A1, while between the first lower longitudinal yarn U1 and the second lower longitudinal yarn U2 within the repeat unit WE there is a relatively small second spacing A2.

[0051] In this embodiment, all upper longitudinal yarns O1-O3 still have the same circular cross-section with respect to each other and all lower longitudinal yarns U1 and U2 have the same, however larger, circular cross-section with respect to each other. Furthermore, in said embodiment, for the sake of simplicity of the description, the two wide spacings a1 have the same average value. This is, however, not mandatory.

Claims

1. A fabric belt for a machine for processing a fibrous web, the fabric belt comprising an upper fabric layer having upper longitudinal yarns and upper transverse yarns interwoven with the upper longitudinal yarns, and a lower fabric layer having lower longitudinal yarns and lower transverse yarns interwoven with the lower longitudinal yarns, wherein, The two fabric layers are arranged on top of each other in such a way that, when the fabric belt is used as intended, the upper fabric layer faces the fibrous web and the lower fabric layer faces away from the fibrous web, wherein the upper longitudinal threads are unevenly spaced apart from each other, characterized in that the upper longitudinal threads are arranged in such a way that the average spacing of the upper longitudinal threads has the following sequence, which repeats continuously along the transverse direction of the fabric belt: wide spacing, wide spacing, narrow spacing, wherein the difference between the average wide spacing and the average narrow spacing corresponds to at least 50% of the diameter of the upper longitudinal threads.

2. The fabric belt of claim 1, wherein, The fabric belt is a forming screen.

3. The fabric belt according to claim 1, characterized in that the wide spacing is 100% to 300% of the diameter of the upper longitudinal threads, and / or the narrow spacing is 30% to 125% of the diameter of the upper longitudinal threads.

4. The fabric belt according to one of claims 1 to 3, characterized in that the ratio of the upper longitudinal threads to the lower longitudinal threads in the fabric belt is 1 :

1.

5. The fabric belt of claim 4, wherein, The lower longitudinal threads are evenly spaced apart from each other.

6. The fabric belt according to one of claims 1 to 3, characterized in that the weaving pattern of the fabric belt repeats in a repeating pattern, wherein the upper longitudinal threads and the lower longitudinal threads in each repeating pattern are arranged in a plurality of groups, the plurality of groups having first groups and second groups and at least one further first group and / or second group, wherein each first group consists of one upper longitudinal thread and one lower longitudinal thread arranged below the upper longitudinal thread, and each second group consists of one upper longitudinal thread and two lower longitudinal threads arranged below the upper longitudinal thread, respectively.

7. The fabric belt according to claim 6, characterized in that the two lower longitudinal threads of the second group have a second spacing between each other, while the two lower longitudinal threads of the first group and the second group directly adjacent to the first group and / or the two lower longitudinal threads of two directly adjacent first groups have a first spacing.

8. The fabric belt according to one of claims 1 to 3, characterized in that the weaving pattern of the fabric belt repeats in a repeating pattern, wherein the upper longitudinal threads and the lower longitudinal threads in each repeating pattern are arranged in a plurality of groups, the plurality of groups having first groups and second groups, wherein the first groups consist of one upper longitudinal thread and one lower longitudinal thread arranged below the upper longitudinal thread, and the second groups consist of two upper longitudinal threads and one lower longitudinal thread arranged below the two upper longitudinal threads.

9. The fabric belt according to claim 7, characterized in that the first spacing between two directly adjacent lower longitudinal threads is greater than the second spacing between two directly adjacent lower longitudinal threads, wherein the difference between the first spacing and the second spacing is 25% to 200% of the diameter of the upper longitudinal threads.

10. The fabric belt according to one of claims 1 to 3, characterized in that the difference between the average wide spacing of two directly adjacent upper longitudinal threads and the average narrow spacing of two directly adjacent upper longitudinal threads is at most 200% of the diameter of the upper longitudinal threads.

11. The fabric belt according to one of claims 1 to 3, characterized in that The difference between the average wide spacing of two directly adjacent upper longitudinal yarns and the average narrow spacing of two directly adjacent upper longitudinal yarns is 150% of the diameter of the upper longitudinal yarns.

12. The fabric belt according to one of claims 1 to 3, characterized in that The first and second fabric layers are interconnected by pairs of laid threads.

13. The fabric belt according to claim 12, characterized in that The laid threads extend along the transverse direction.

14. The fabric belt according to claim 12, characterized in that The two laid threads of the respective laid thread pair are alternately interwoven with the upper longitudinal yarns and the lower longitudinal yarns and cross over to form a crossover position when changing from interweaving with the upper longitudinal yarns to interweaving with the lower longitudinal yarns and when changing from interweaving with the lower longitudinal yarns to interweaving with the upper longitudinal yarns.

15. The fabric belt according to claim 14, characterized in that Each laid thread pair provides at least two crossover positions for each repeat pattern.

16. The fabric belt according to claim 12, characterized in that The upper fabric layer is constructed by interweaving of the upper longitudinal yarns with the upper transverse yarns and laid threads and the lower fabric layer is constructed by interweaving of the lower longitudinal yarns with the lower transverse yarns.

17. The fabric belt according to one of the preceding claims 1 to 3, characterized in that The upper fabric layer is constructed as a plain weave.

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