Formiersieb

Abstract

Fabric belt, in particular a forming fabric, for a machine for producing and / or processing a fibrous web, comprising an upper fabric layer with upper longitudinal threads and first transverse threads interwoven therewith, and a lower fabric layer with lower longitudinal threads and lower transverse threads interwoven therewith, wherein the two fabric layers are arranged one above the other and the weaving pattern of the fabric belt is repeated in repeats, wherein the ratio of upper longitudinal threads to lower longitudinal threads in the repeat is less than one, characterized in that the upper longitudinal threads and the lower longitudinal threads are arranged in several groups in each repeat, with at least one first group and at least one second group,wherein each first group is formed from an upper longitudinal thread and two lower longitudinal threads arranged below it, and each second group is formed from an upper longitudinal thread and a lower longitudinal thread arranged below it, and wherein the upper and lower longitudinal threads in each group, viewed in a vertical projection onto the fabric layers, are not offset from one another or are only slightly offset from one another so that a maximum free space of half the diameter of an upper longitudinal thread is formed between them, wherein the first transverse threads comprise binding threads which are woven with the upper and lower longitudinal threads to connect the two fabric layers, wherein the weave pattern of the upper fabric layer is formed at least partially by the interweaving of the binding threads with the upper longitudinal threads.

Description

[0001] The invention relates to a fabric belt, in particular a forming fabric, for a machine for producing and / or processing a fibrous web, in particular a paper, cardboard or tissue web.

[0002] Modern fabric belts used as forming fabrics in the forming section of a paper, board, or tissue machine typically have an upper fabric layer that provides a paper side that can be brought into contact with the paper web, and a lower fabric layer that provides a machine side that can be brought into contact with machine elements. Different requirements are placed on the upper and lower fabric layers. The upper fabric layer must provide the best possible fiber support during the formation and dewatering of the fibrous web, while the lower fabric layer essentially provides the wear volume and dimensional stability of the fabric belt.

[0003] From the prior art, for example EP 1 586 696 A1, fabric belts designed as forming fabrics are known in which the ratio of the number of longitudinal threads in the upper fabric layer to the number of longitudinal threads in the lower fabric layer is 1:1. Such forming fabrics have the disadvantage that the use of relatively thick longitudinal threads in the lower fabric layer to provide sufficiently high dimensional stability of the fabric leads to a fairly open upper fabric layer with only low fiber support. For example, in EP 2 106 477 A1, fabrics with a ratio of the number of longitudinal threads in the upper fabric layer to the number of longitudinal threads in the lower fabric layer of greater than one, such as 2:1, 3:2 or 5:2, were proposed in the past to overcome the disadvantages of such fabrics.This made it possible to achieve both satisfactory fiber support from the upper fabric layer and satisfactory dimensional stability from the lower fabric layer. Disadvantages of the aforementioned fabrics often include an increased tendency toward visible hydraulic marking of the fibrous web produced on them, as well as insufficient planarity of the upper fabric layer, since the longitudinal threads of the upper fabric layer (upper longitudinal threads) are only inadequately supported by the longitudinal threads of the lower fabric layer (lower longitudinal threads). Insufficient planarity can lead to an undesirable accumulation of fibers and filler in "depressions" in the upper fabric layer.

[0004] These disadvantages are observed in the forming fabrics known from the prior art with increasing ratio of the number of upper longitudinal threads to the number of lower longitudinal threads.

[0005] Furthermore, forming fabrics are known from the prior art in which the upper fabric layer has fewer longitudinal threads (upper longitudinal threads) than the lower fabric layer (lower longitudinal threads). In these fabrics, a high number of upper transverse threads is provided to ensure a not overly open upper fabric layer. The advantage of these fabrics is that the high number of upper transverse threads provides good fiber support for the fibers of the pulp suspension, which are often largely oriented in the longitudinal direction of the fabric, during the formation of the fibrous web.

[0006] A disadvantage of the aforementioned fabrics with fewer upper than lower longitudinal threads per repeat is often the insufficient planarity of the upper fabric layer, as the longitudinal threads of the upper fabric layer (upper longitudinal threads) are only insufficiently supported by the longitudinal threads of the lower fabric layer (lower longitudinal threads). Insufficient planarity can lead to an undesirable accumulation of fibers and filler in the "depressions" of the upper fabric layer.

[0007] A fabric belt designed as a forming fabric according to the preamble of claim 1, in which the ratio of the number of longitudinal threads of the upper fabric layer to the number of longitudinal threads of the lower fabric layer is less than 1, is known from the document DE 10 2010 017 055 A1. In this fabric belt, pairs of functional longitudinal threads are used to connect the two layers of the fabric belt. In other words, the functional longitudinal threads are guided both over the upper transverse threads and under the lower transverse threads. Since the forming fabrics are subject to strong tensile forces in their longitudinal or machine direction, this leads to the functional longitudinal threads being drawn relatively strongly into the fabric. Thus, at regular intervals in the cross-machine direction, "depressions" running in the longitudinal direction of the machine occur on the paper side of such fabric belts, which can lead to undesirable visible markings on the fibrous web to be produced on them.It should be noted that “depressions” that extend in the machine direction on the paper side of the fabric belts are particularly critical in that the fibers of the fibrous web to be produced usually have a preferential orientation in the machine direction and can therefore slip particularly easily into such “depressions”.

[0008] It is the object of the present invention to propose a fabric belt for use as a forming fabric in a machine for producing and / or processing a fibrous web, such as in particular a paper, cardboard or tissue web, which significantly reduces or eliminates the aforementioned disadvantages.

[0009] The object is achieved by a fabric belt, in particular a forming fabric, for a machine for producing and / or processing a fibrous web, comprising an upper fabric layer with upper longitudinal threads and first transverse threads interwoven therewith, and a lower fabric layer with lower longitudinal threads and lower transverse threads interwoven therewith, wherein the two fabric layers are arranged one above the other and the weaving pattern of the fabric belt is repeated in repeats, wherein the ratio of upper longitudinal threads to lower longitudinal threads in the repeat is less than one and the upper longitudinal threads and the lower longitudinal threads in each repeat are arranged in several groups, with at least one first group and at least one second group,wherein each first group is formed from an upper longitudinal thread and two lower longitudinal threads arranged below it, and each second group is formed from an upper longitudinal thread and a lower longitudinal thread arranged below it, and wherein the upper and lower longitudinal threads in each group, viewed in a vertical projection onto the fabric layers, are not offset from one another or are only slightly offset from one another so that a maximum free space of half the diameter of an upper longitudinal thread is formed between them.

[0010] To illustrate this, the Fig. 1 in a section plane running along the transverse thread direction CD and perpendicular to the fabric layers 1, 2 (upper fabric layer 1, lower fabric layer 2) or the planes PS, MS spanned by these, a first group of longitudinal threads 3, 4. Furthermore, the Fig.2 in a cutting plane running along the transverse thread direction CD and perpendicular to the fabric layers 1, 2 or the planes PS, MS spanned by them, a second group of longitudinal threads 3, 4

[0011] It can be seen that the upper and lower longitudinal threads 3, 4 are arranged one above the other in such a way that, viewed in a vertical projection onto the fabric layers 1, 2 or onto the planes PS, MS spanned by them - indicated by the lines AA - they are only slightly offset from one another so that a maximum free space of half a diameter d / 2 of an upper longitudinal thread 3 is formed between them.

[0012] The use of at least one first group and at least one second group per repeat according to the inventive solution ensures that each upper longitudinal thread 3 is sufficiently supported by a lower longitudinal thread 4. This significantly increases the planarity of the upper fabric layer 1 compared to the fabric tapes known from the prior art. Since the first and second groups also result in different drainage behaviors and at least one first and one second group is arranged in each repeat, a regular and thus easily visible hydraulic marking pattern of the fibrous web produced on such a fabric tape is effectively prevented.

[0013] An upper and a lower longitudinal thread are to be regarded as not offset from one another if the connecting line between the center of the cross-sectional area of ​​the upper longitudinal thread and the center of the cross-sectional area of ​​the lower longitudinal thread runs vertically to a plane spanned by the upper fabric layer.

[0014] Advantageous embodiments and further developments of the invention are specified in the subclaims.

[0015] Preferably, a different number of first and second groups is provided in each repeat. Since the first and second groups have different drainage and thus marking behavior, it has been shown that this measure, the different number of first and second groups in the repeat, can create an irregularity in the marking pattern, making the markings significantly less visible. This design also offers the possibility of influencing the drainage behavior of the screen. If, for example, more first groups are used than second groups, a screen with higher drainage performance can be created than if more second groups than first groups are used.

[0016] In this context, it is particularly conceivable that: A=N×B; with A = Number of first groups in the report B = Number of second groups in the report N = integer greater than 1 or C=M×D; with C = Number of second groups in the report D = Number of first groups in the report M is an integer greater than 1

[0017] Specifically, for example, the number of first groups in the repeat can be 1 and the number of second groups in the repeat can be 2. Alternatively, the number of second groups in the repeat can be 1 and the number of first groups in the repeat can be 2.

[0018] If an unequal number of first and second groups is provided in the repeat, it is particularly advantageous if the first and second groups are arranged in the repeat in a plurality of longitudinal thread top groups, wherein each longitudinal thread top group comprises at least one first group and at least one second group and in particular at least one further group selected from the first or second group, and wherein the repeat is formed by an integer number of longitudinal thread top groups arranged next to one another in the transverse thread direction. This means that only an integer number of the longitudinal thread top groups are arranged in the repeat and no other first and / or second group is present which is not part of one of the longitudinal thread top groups.

[0019] By providing several longitudinal thread upper groups arranged next to one another in the repeat, a certain degree of regularity in the arrangement of the first and second groups is achieved, whereby a concentration of a large number of identical groups arranged directly next to one another can be avoided.

[0020] In this context, for example, a longitudinal thread upper group can be formed by a first group and two second groups. It is also conceivable that a longitudinal thread upper group is formed by two first groups and a second group.

[0021] It is conceivable that more first groups than second groups are provided in the report. It is also conceivable that more first groups than second groups are provided in each main group.

[0022] To achieve good fiber support of the fibrous web formed and dewatered on the fabric belt according to the invention, it is preferably provided that the upper fabric layer has an outer side facing away from the lower fabric layer, which, when the fabric belt is used as intended, provides a paper side that can be brought into contact with the fiber. Furthermore, it is preferably provided that the lower fabric layer has an outer side facing away from the upper fabric layer, which, when the fabric belt is used as intended, provides a machine side that can be brought into contact with the machine.

[0023] To further avoid visible hydraulic markings due to a regular marking pattern, it is also advantageous if a maximum of four identical groups of the first or second group are arranged directly next to each other.

[0024] The following embodiments of the invention are possible but not exhaustive with regard to the arrangement of first and second groups within each supergroup (Note: in this case, a first group is identified by the symbol 1:2 and a second group by the symbol 1:1). 1) Each upper group comprises the following three first and second groups 1:1 - 1:2 - 1:1 and has a ratio of the number of upper longitudinal threads to the number of lower longitudinal threads of 3 to 4. 2) Each upper group comprises the following five first and second groups 1:2 - 1:1 - 1:1 - 1:1 - 1:2 and has a ratio of the number of upper longitudinal threads to the number of lower longitudinal threads of 5 to 7. 3) Each upper group comprises the following six five and second groups 1:2 - 1:2 - 1:2 - 1:1 - 1:1 -1:1 - 1:1 and has a ratio of the number of upper longitudinal threads to the number of lower longitudinal threads of 7 to 10. 4) Each upper group comprises the following three first and second groups 1:1 - 1:2 - 1:2 and has a ratio of the number of upper longitudinal threads to the number of lower longitudinal threads of 3 to 5. 5) Each upper group comprises the following five first and second groups 1:1 - 1:1 - 1:2 - 1:2 - 1:2 and has a ratio of the number of upper longitudinal threads to the number of lower longitudinal threads of 5 to 8. 6) Each upper group comprises the following four first and second groups 1:1 - 1:2 - 1:2 - 1:2 and has a ratio of the number of upper longitudinal threads to the number of lower longitudinal threads of 4 to 7. 7) Each upper group comprises the following two first and second groups 1:1 - 1:2 and has a ratio of the number of upper longitudinal threads to the number of lower longitudinal threads of 2 to 3.

[0025] In all of the aforementioned examples 1-3, each supergroup contains more second groups than first groups. In all of the aforementioned examples 4-6, each supergroup contains fewer second groups than first groups. In example 7, there are exactly as many first groups as second groups.

[0026] In all examples shown, the fabric design focuses on a high fiber support index (FSI), as this allows more binding threads and / or upper transverse threads to be incorporated into the comparatively more open upper longitudinal thread arrangement on the paper side of the upper fabric layer.

[0027] The fiber support index according to PCA values ​​the number of upper transverse threads twice as high as the number of upper longitudinal threads. The shape of the openings (pores) formed on the paper side is transversely oriented. The number of pores is equal to the number of fiber support points. This design aims for very uniform sheet formation, as the transversely oriented pores allow the paper fibers to penetrate less deeply into the fabric, thus achieving very smooth fiber web surfaces.

[0028] Preferably, the longitudinal threads of the fabric tape only provide first and second groups. This ensures that each upper longitudinal thread is supported by a lower longitudinal thread.

[0029] In order to achieve a further homogenization of the drainage speeds, it is preferably provided that, viewed in the direction along the transverse threads, the upper longitudinal threads are arranged offset from the lower longitudinal threads.

[0030] According to the invention, the first transverse threads comprise binding threads, wherein the binding threads are woven with the upper and lower longitudinal threads to connect the two fabric layers, and wherein the weave pattern of the upper fabric layer is formed at least partially or completely by the interweaving of the binding threads with the upper longitudinal threads.

[0031] The binding threads can be arranged individually. To provide an upper fabric layer with a low tendency for topographical marking, a further preferred embodiment of the invention provides for the binding threads to be arranged as a binding thread pair or as a binding thread triplet. In this context, it is particularly useful if the binding threads of the respective binding thread pair or binding thread triplet are interwoven with upper and lower longitudinal threads in an interchangeable manner and cross each other when changing from interweaving with upper longitudinal threads to interweaving with lower longitudinal threads and vice versa, forming intersection points.

[0032] At this point it should be noted that when the fabric belt is used as intended in a paper, board or tissue machine, the longitudinal threads extend in the transport or machine direction of the fabric belt and the transverse threads extend in the cross-machine direction.

[0033] There are several possible ways in which the two fabric layers could be formed. According to the first possibility, the upper fabric layer is formed by interweaving the upper longitudinal threads with the binding threads, and the lower fabric layer is formed by interweaving the lower longitudinal threads with the lower transverse threads.

[0034] Preferably, the ratio of binding thread pairs or binding thread triplets to lower cross threads in the repeat is greater than one, in particular greater than or equal to two. Furthermore, it is advantageous if the ratio of binding thread pairs or binding thread triplets to lower cross threads in the repeat is not an integer.

[0035] For example, ratios of 2 to 1, 3:1, 3:2, 5:3, 7:4, 8:5 or 5:2 are conceivable.

[0036] Alternatively, it is conceivable that the first transverse threads comprise upper transverse threads in addition to the binding threads, whereby the upper fabric layer is formed by interweaving the upper longitudinal threads with the upper transverse threads and the binding threads, and the lower fabric layer is formed by interweaving the lower longitudinal threads with the lower transverse threads. This means that the binding threads are an integral part of the upper fabric layer and do not contribute to the formation of the lower fabric layer, but merely connect it to the upper fabric layer.

[0037] In this context, the ratio of upper transverse threads and binding thread pairs or binding thread triplets to lower transverse threads in the repeat is in particular greater than one, in particular greater than or equal to two. Furthermore, the ratio of upper transverse threads and binding thread pairs or binding thread triplets to lower transverse threads in the repeat is preferably not an integer.

[0038] For example, ratios of 2 to 1, 3:1, 3:2, 5:3, 7:4, 8:5 or 5:2 are conceivable.

[0039] The high ratio of binder thread pairs or binder thread triplets to lower cross threads according to the first alternative, or the high ratio of upper cross threads and binder thread pairs or binder thread triplets to lower cross threads according to the second alternative, provides a fabric with a high fiber support index (FSI). Furthermore, the shape of the openings (pores) formed on the paper side is transversely oriented. This design aims at very uniform sheet formation, since the transversely oriented pores allow the paper fibers to penetrate less deeply into the fabric, thus achieving very smooth fiber web surfaces.

[0040] Preferably, the weaving path created by the mutually interchanging interweaving of the binding threads of a binding thread pair or a binding thread triplet with the upper longitudinal threads corresponds to a weaving path formed by interweaving an upper transverse thread with the upper longitudinal threads. In this case, the binding threads are referred to as "integral" because they continue the weaving pattern formed by interweaving the upper transverse threads with the upper longitudinal threads.

[0041] Preferably, each binding thread pair in the repeat provides only two crossing points. Preferably, each binding thread triplet in the repeat provides only three crossing points. The small number of crossing points per repeat contributes to a very smooth and flat paper side of the upper fabric layer.

[0042] Furthermore, it is provided that the binding threads of each binding thread pair or binding thread triplet form first binding segments between immediately consecutive crossing points by interweaving with the upper longitudinal threads, wherein at least one of the first binding segments of each binding thread pair or binding thread triplet is formed in the repeat by the respective binding thread continuously crossing at least two, preferably at least three—such as four—non-immediately consecutive upper longitudinal threads on the outer side of the upper fabric layer. The long length of the first binding segments, like the small number of crossing points per repeat, also contributes to a very smooth and flat paper side of the upper fabric layer.

[0043] Such fabric tapes can preferably be produced using high-shaft technology, in which one repeat of the fabric tape comprises 26 or more longitudinal threads.

[0044] According to a further preferred embodiment of the invention, the binding threads continuously cross a maximum of four directly adjacent, preferably a maximum of three directly adjacent lower longitudinal threads between the two fabric layers when changing from interweaving with the upper longitudinal threads to interweaving with the lower longitudinal threads and vice versa. The relatively short inner float length of the binding threads between the two fabric layers achieves a good balance between the low thickness of the fabric tape according to the invention, on the one hand, and the decoupling of the connection and uncoupling points of the binding threads when connecting the two fabric layers by the binding threads.

[0045] If the binding threads are arranged in binding thread pairs, the binding threads of each binding thread pair in the repeat together preferably form two first binding segments, wherein the one first binding segment is formed in that one binding thread of the pair runs alternately on the outside of the upper fabric layer and between the upper and lower fabric layers when woven with the upper longitudinal threads and continuously crosses at least two upper longitudinal threads on the outside of the upper fabric layer, and wherein the other first binding segment is formed in that the other binding thread of the pair runs alternately on the outside of the upper fabric layer and between the upper and lower fabric layers when woven with the upper longitudinal threads and continuously crosses the same number of upper longitudinal threads as the one binding thread or up to four, in particular up to two, fewer or more upper longitudinal threads than the one binding thread.The relatively long length of the first two binding segments, which are also equal or almost equal in length, also significantly increases the planarity of the upper fabric layer, as this results in fewer crossing points between the mutually exchanging binding threads.

[0046] If the binding threads are arranged in binding thread triplets, the binding threads of each binding thread triplet in the repeat together preferably form three first binding segments, wherein the first first binding segment is formed in that the first binding thread of the triplet, when woven with the upper longitudinal threads, runs alternately on the outside of the upper fabric layer and between the upper and lower fabric layers and, on the outside of the upper fabric layer, continuously crosses at least two upper longitudinal threads, and wherein the second first binding segment is formed in that the second binding thread of the triplet, when woven with the upper longitudinal threads, runs alternately on the outside of the upper fabric layer and between the upper and lower fabric layers and, on the outside of the upper fabric layer, continuously crosses the same number of upper longitudinal threads as the first binding thread or up to four, in particular up to two,upper longitudinal threads less or more than the first binding thread, and wherein the third first binding segment is formed by the third binding thread of the triplet running alternately on the outside of the upper fabric layer and between the upper and lower fabric layers when woven with the upper longitudinal threads, and continuously crossing the same number of upper longitudinal threads as the first binding thread, or up to four, in particular up to two, upper longitudinal threads less or more than the first binding thread, on the outside of the upper fabric layer. The relatively long length of the three first binding segments, which are also equal or almost equal in length, also significantly increases the planarity of the upper fabric layer, as this results in fewer crossing points between the mutually exchanging binding threads.

[0047] According to a further particularly preferred embodiment of the invention, it is particularly conceivable that the upper transverse threads, the binding thread pairs or the binding thread triplets and the lower transverse threads are arranged in first, second, third and fourth transverse thread groups, wherein - a first transverse thread group is formed by an upper and a lower transverse thread and a binding thread pair or binding thread triplet, - a second transverse thread group is formed by two upper transverse threads and two lower transverse threads and a binding thread pair or binding thread triplet, - a third transverse thread group is formed by an upper transverse thread and two lower transverse threads and a binding thread pair or binding thread triplet and - a fourth transverse thread group is formed by two upper transverse threads and one lower transverse thread and a binding thread pair or binding thread triplet.

[0048] The above-mentioned further development may also represent an invention independent of this invention and be the subject of a separate patent application.

[0049] In this context, it is particularly conceivable for the transverse threads and binding threads to be arranged in a plurality of transverse thread upper groups in the repeat, wherein a transverse thread upper group is formed by at least two transverse thread groups selected from the first, second, third, or fourth transverse thread group, and wherein the repeat is formed by an integer number of transverse thread upper groups arranged next to one another in the longitudinal thread direction. This means that only an integer number of the transverse thread upper groups are arranged in the repeat, and no other first and / or second transverse thread group is present that is not part of one of the transverse thread upper groups.

[0050] Preferably, a lower transverse thread is arranged below each upper transverse thread such that each upper transverse thread is supported by a lower transverse thread. This significantly increases the transverse stability of the fabric tape according to the invention.

[0051] Preferably, at least some of the upper and lower transverse threads are offset from one another, viewed in the direction along the longitudinal threads. An upper and a lower transverse thread are considered to be non-offset from one another if the connecting line between the center of the cross-sectional area of ​​the upper transverse thread and the center of the cross-sectional area of ​​the lower transverse thread runs vertically to a plane spanned by the upper fabric layer.

[0052] According to a preferred embodiment of the invention, the weave pattern of the upper fabric layer forms a plain weave.

[0053] According to a further preferred embodiment of the invention, it is conceivable that the lower fabric layer is a regular or irregular satin weave, in particular a satin weave with a pitch number of 3 and / or progression number of 3. Specifically, such satin weaves can be, for example, satin weaves with 5 or 7 or 8 lower longitudinal threads per repeat of the lower fabric layer. A satin weave with 6 lower longitudinal threads per repeat of the lower fabric layer is not preferred here, since in combination with the inventive ratio of upper longitudinal threads to lower longitudinal threads per repeat of less than one, this creates an undesirable grouping of three adjacent lower longitudinal threads, which leads to undesirable, greatly differing drainage behavior and associated hydraulic markings.

[0054] The diameter of the lower longitudinal threads is preferably in the range of 0.15 mm to 0.45 mm, with the upper longitudinal threads in particular having a diameter of 30% to 60%, preferably 38% to 53%, of the diameter of the lower longitudinal threads. This makes it possible to create a fabric belt with a particularly fine upper fabric layer, but whose lower fabric layer is sufficiently stable to provide a high wear volume and / or high dimensional stability.

[0055] In order to achieve a particularly fine paper side that offers high fiber support, it is particularly conceivable that the upper longitudinal threads have a diameter of 0.1 mm or smaller.

[0056] In order to obtain the most uniform upper fabric layer possible, it is particularly useful if the upper transverse threads and / or the binding threads have a diameter of 80% to 120% of the diameter of the upper longitudinal threads.

[0057] If the fabric belt according to the invention is a so-called "weft traveler", ie a fabric belt in which the machine side is essentially provided by the abrasion volume of the lower transverse threads, it is particularly useful if the lower transverse threads have a diameter of 100% to 200% of the diameter of the lower longitudinal threads.

[0058] In the event that the threads do not have a circular cross-sectional area, the term diameter should be understood as the diameter of a circular cross-sectional area that has the same area as the cross-sectional area that does not have a circular cross-section.

[0059] According to a further preferred embodiment of the invention, the upper fabric layer of the fabric tape according to the invention preferably has a fiber support index (FSI) of 260 to 300, calculated according to the publication "Approved Standard Measuring Method" of the Papermachine Clothing Association (PCA), 19 Rue de la République, 45000 Orléans, France, dated June 2004. This makes it possible to ensure very good fiber support and retention.

[0060] On the other hand, in order to achieve high dewatering performance, it is also expedient to provide high permeability despite the aforementioned high FSI value. According to a further particularly preferred embodiment of the invention, the fabric belt has a permeability in the range of 250 cfm to 450 cfm, preferably 300 cfm to 400 cfm, measured at a differential pressure of 100 to 127 Pa, as defined in the April 2005 publication "Approved Standard Measuring Method" of the Papermachine Clothing Association (PCA), 19 Rue de la République, 45000 Orléans, France.

Claims

[1] Fabric belt, in particular a forming fabric, for a machine for producing and / or processing a fibrous web, comprising an upper fabric layer with upper longitudinal threads and first transverse threads interwoven therewith, and a lower fabric layer with lower longitudinal threads and lower transverse threads interwoven therewith, wherein the two fabric layers are arranged one above the other and the weaving pattern of the fabric belt is repeated in repeats, wherein the ratio of upper longitudinal threads to lower longitudinal threads in the repeat is less than one, characterized bythat the upper longitudinal threads and the lower longitudinal threads in each repeat are arranged in several groups, with at least a first group and at least one second group, wherein each first group is formed from an upper longitudinal thread and two lower longitudinal threads arranged below it and each second group is formed from an upper longitudinal thread and a lower longitudinal thread arranged below it and wherein the upper and lower longitudinal threads in each group, viewed in a vertical projection onto the fabric layers, are not offset from one another or are only slightly offset from one another such that a maximum free space of half the diameter of an upper longitudinal thread is formed between them, wherein the first transverse threads comprise binding threads which are woven with the upper and lower longitudinal threads to connect the two fabric layers,wherein the weave pattern of the upper fabric layer is formed at least partially by the interweaving of the binding threads with the upper longitudinal threads., [2] Fabric tape according to claim 1, characterized by that a mutually different number of first and second groups of longitudinal threads are provided. [3] Fabric tape according to claim 1 or 2, characterized by that the first and second groups are arranged in the repeat in a plurality of longitudinal thread upper groups, wherein each longitudinal thread upper group comprises at least one first group and at least one second group and wherein the repeat is formed by an integer number of longitudinal thread upper groups arranged next to one another in the transverse thread direction. [4] Fabric tape according to one of the preceding claims, characterized by that a maximum of four identical ones of the first or second group of longitudinal threads are arranged directly next to each other. [5] Fabric tape according to one of the preceding claims, characterized bythat the upper fabric layer has an outer side facing away from the lower fabric layer, which provides a paper side that can be brought into contact with the fibrous web when the fabric belt is used as intended. [6] Fabric tape according to one of the preceding claims, characterized by that the lower fabric layer has an outer side facing away from the upper fabric layer, which provides a machine side that can be brought into contact with the machine when the fabric belt is used as intended. [7] Fabric tape according to one of the preceding claims, characterized by that the fabric tape has only first and second groups of longitudinal threads. [8] Fabric tape according to one of the preceding claims, characterized by that the binding threads are arranged individually or as a pair of binding threads or as a triplet of binding threads. [9] Fabric tape according to claim 8, characterized bythat the binding threads of the respective binding thread pair or binding thread triplet are interwoven with upper and lower longitudinal threads in a mutually exchanging manner and cross each other when changing from weaving with upper longitudinal threads to weaving with lower longitudinal threads and vice versa, forming crossing points. [10] Fabric tape according to claim 8 or 9, characterized by that each binding thread pair or binding thread triplet in the repeat provides two crossing points. [11] Fabric tape according to one of claims 8-10, characterized bythat the binding threads of each binding thread pair or binding thread triplet form first binding segments between immediately successive crossing points by interweaving with the upper longitudinal threads, and at least one of the first binding segments of each binding thread pair or binding thread triplet is formed in the repeat in that the binding thread in question continuously crosses at least four upper longitudinal threads which are not immediately consecutive on the outside of the upper fabric layer. [12] Fabric tape according to one of claims 8-11, characterized byin that the binding threads of each binding thread pair in the repeat together form two first binding segments, wherein the one first binding segment is formed in that one binding thread of the pair, when woven with the upper longitudinal threads, runs alternately on the outside of the upper fabric layer and between the upper and lower fabric layers and, on the outside of the upper fabric layer, continuously crosses at least two upper longitudinal threads, and wherein the other first binding segment is formed in that the other binding thread of the pair, when woven with the upper longitudinal threads, runs alternately on the outside of the upper fabric layer and between the upper and lower fabric layers and, on the outside of the upper fabric layer, continuously crosses the same number of upper longitudinal threads as the one binding thread or up to four, in particular up to two, fewer or more upper longitudinal threads than the one binding thread. [13] Fabric tape according to one of the preceding claims, characterized bythat the first transverse threads comprise, in addition to the binding threads, upper transverse threads, wherein the upper fabric layer is formed by interweaving the upper longitudinal threads with the upper transverse threads and the binding threads and the lower fabric layer is formed by interweaving the lower longitudinal threads with the lower transverse threads. [14] Fabric tape according to one of the preceding claims, characterized by that the ratio of upper transverse threads and binding thread pairs or binding thread triplets to lower transverse threads in the repeat is greater than one, in particular greater than or equal to two. [15] Fabric tape according to one of the preceding claims, characterized by that the ratio of upper cross threads and binding thread pairs or binding thread triplets to lower cross threads in the repeat is not an integer. [16] Fabric tape according to one of the preceding claims, characterized by that the upper fabric layer forms a plain weave. [17] Fabric tape according to one of the preceding claims, characterized bythat the lower fabric layer forms an atlas weave, in particular an atlas weave with pitch number 3 and / or progression number 3.

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