Paper machine clothing

Abstract

The invention relates to paper machine clothing, in particular to a press felt for a machine for producing or processing a pulp web, wherein the paper machine clothing comprises a base structure which has a first woven-fabric layer and a second woven-fabric layer which are arranged one above the other and each of which has threads in the machine direction (MD) and threads in the machine transverse direction (CD), wherein both the first woven-fabric layer and the second woven-fabric layer comprise threads which are in the form of monofilaments and threads which are in the form of twisted threads.

Description

[0001] covering

[0002] The invention relates to a clothing, in particular press felt for a machine for producing or processing a fibrous web according to the preamble of claim 1.

[0003] Clothing, especially clothing for paper machines, often comprises one or more fabric layers as part of a basic structure. Continuous fabric layers, so-called belt loops, are typically required for use in a clothing.

[0004] These can either be woven directly as a loop of tape (“round woven”) or they can be woven as a flat piece of fabric which is made endless by joining the two ends.

[0005] Various options for joining two ends of a flat fabric are known from the prior art. For example, US 2014 / 0186579 describes joining two ends using an ultrasonic weld. Alternatively, the connection can also be made using laser welding, for example.

[0006] The documents EP3960932 A1 and WO 2022 / 089843 A1 describe that several such fabric layers can be arranged one above the other to create a multi-layer basic structure.

[0007] The two cited documents address the connection points of the front ends, which were identified as potential defects in the basic structure. The design of the connections and their relative positions are optimized.

[0008] However, it is also desirable to further optimize the performance of the entire basic structure.

[0009] In particular, it would be desirable to improve the shrink obsolescence of the basic structure.

[0010] Furthermore, improved fiber anchoring of the nonwoven fibers across the entire surface of the covering is desirable. The object of the invention is to further develop the prior art accordingly. Furthermore, the object of the invention is to ensure that such a covering can be manufactured as simply and cost-effectively as possible.

[0011] The object is achieved according to the invention by an embodiment according to the independent claim. Further advantageous embodiments of the present invention can be found in the subclaims.

[0012] What is proposed is a clothing, in particular a press felt for a machine for producing or processing a fibrous web, wherein the clothing has a basic structure which comprises a first fabric layer and a second fabric layer which are arranged one above the other and which each have threads in the machine direction (MD threads) and threads in the cross-machine direction (CD threads).

[0013] Both the first fabric layer and the second fabric layer have threads that are designed as monofilaments as well as threads that are designed as twisted threads.

[0014] Coverings according to aspects of the invention can be realized in various ways and have a variety of advantages.

[0015] Variant 1: Endless structure

[0016] In this variant, the first fabric layer consists of a first flat fabric, which is made endless, in particular by joining its end edges. The second fabric layer consists of a second flat fabric, which is also made endless, in particular by joining its end edges.

[0017] Such a basic structure, or such a covering, is referred to as "endless," in contrast to coverings that have seam loops and are only brought into an endless configuration by closing this seam using a pintle wire. In this case, both the first flat weave and the second flat weave can have CD threads that are designed as monofilaments, and both the first flat weave and the second flat weave can have CD threads that are designed as twisted threads.

[0018] Such coverings can be designed in such a way that the ratio of twisted threads to monofilaments (twisted-mono ratio) of the first flat weave differs from the twisted-mono ratio of the second flat weave.

[0019] Alternatively or additionally, such coverings can also be designed in such a way that the CD thread density of the first fabric layer and the second fabric layer are different.

[0020] CD threads are the threads of the fabric which, when the fabric is used as intended, are oriented entirely or essentially in the cross-machine direction (“cross-direction”, “CD”).

[0021] MD threads are the threads of the fabric which, when the fabric is used as intended, are oriented entirely or essentially in the machine direction (“Machine-Direction”, “MD”).

[0022] The inventors have recognized that the provision of twisted threads in the fabric layers has a positive effect on the fiber anchoring of the nonwoven fibers in the subsequent needling process.

[0023] The shrinkage behavior can be influenced by adjusting the ratio of twisted threads and monofilaments.

[0024] In fabrics according to one aspect of the invention, the twist-mono ratio in the first fabric layer differs from that in the second fabric layer.

[0025] To ensure the cost-effective production of such fabrics, it is important that the first and second fabric layers are made of endless flat weaves. In such fabrics, the CD threads are the weft threads of the weaving process, while the MD threads originate from the warp threads. Changing a loom's warp system is a very laborious operation and requires a long downtime of the loom. Changing the weft threads, on the other hand, is comparatively easy.

[0026] This allows the twist-to-mono ratios of the first and second flat weaves to be adjusted very easily and economically. In particular, it's even possible to weave the two flat weaves directly one after the other on the same loom. Changing the weft thread pattern requires very little downtime.

[0027] Instead of changing the twist-mono ratio - or in addition to this - the CD thread density of the first fabric layer and the second fabric layer can also be different.

[0028] The thread density is defined as the number of threads per unit length.

[0029] The thread density of the first CD threads can be between 20 and 200 threads / 10cm, preferably between 50 and 100 threads / 10cm.

[0030] In advantageous embodiments, it can be provided that the CD thread density of the second fabric layer is between 3% and 80%, in particular between 5% and 60%, greater than the CD thread density of the first fabric layer.

[0031] Another advantage of the different thread densities of the two layers is that it can suppress the moiré effect. A difference of less than 3% often does not guarantee sufficient suppression of the moiré effect.

[0032] In particular, it can be provided that the first fabric layer is arranged above the second fabric layer and preferably represents the uppermost fabric layer of the basic structure. The basic structure can also comprise further layers, in particular even further fabric layers. Alternatively, the basic structure can consist only of the first fabric layer (1) and the second fabric layer (2).

[0033] In advantageous embodiments, the twist-to-monofilament ratio of the first flat weave can be between 1:3 and 3:1. Preferably, the proportion of twisted CD threads in the first flat weave can be greater than that of monofilaments. Particularly preferably, the twist-to-monofilament ratio of the first flat weave can be between 1:1 and 2:1.

[0034] It can be provided that the twist-to-monofilament ratio of the second flat fabric is lower than the twist-to-monofilament ratio of the first flat fabric. Preferably, the proportion of twisted CD threads in the second flat fabric can be smaller than that of monofilaments.

[0035] In particular, it can be provided that the twist-mono ratio of the second flat fabric is between 1:4 and 1:1.

[0036] In principle, regular or irregular sequences of monofilaments and twisted yarns can be provided. Sequences with longer repeat units or even quasi-statistical sequences of monofilaments and twisted yarns can be provided. Such deviations from strict regularity can have a beneficial effect on the running behavior of the fabric, as, for example, generated vibrations cannot easily build up (resonance prevention).

[0037] The monofilaments used can have diameters between 0.2mm and 0.8mm, preferably between 0.3mm and 0.6mm,

[0038] The threads can consist of 2 to 9 individual threads; preferably 3 or 4 individual threads.

[0039] The same or different monofilaments can be used in the first flat fabric and the second flat fabric. In particular, the monofilaments can have the same or different diameters. For example, it can be advantageous if the second fabric layer is arranged below the first fabric layer, and the monofilaments of the second fabric layer have a larger diameter than the monofilaments of the first fabric layer.

[0040] A variety of structures are possible for the MD threads of the two fabric layers. While the MD threads can also be twisted, it is often advantageous for all MD threads of the two fabric layers to be filaments.

[0041] The MD threads of the first fabric layer and / or the second fabric layer can in particular have a diameter between 0.2 mm and 1 mm

[0042] The MD thread density of the first fabric layer and / or the second fabric layer can be between 20 and 200 threads per 10 cm.

[0043] It can be provided that the first fabric layer and the second fabric layer have the same MD threads or at least the MD threads that have substantially the same thread cross-section.

[0044] In advantageous embodiments, it can be provided that the diameter of the MD threads of the first fabric layer and / or the second fabric layer is between 0.24 mm and 0.6 mm, preferably between 0.3 mm and 0.5 mm.

[0045] A two-layer base structure, in contrast to single-layer structures, has the advantage that the MD threads of both layers contribute to absorbing tensile forces in the MD direction. This allows the MD threads of the individual layers to be thinner, and in particular, to have diameters of 0.6 mm, 0.5 mm, or less. Furthermore, MD threads with diameters over 0.6 mm impart greater rigidity to the base structure, which makes handling the structure more difficult during further processing, for example, into felt, and during later use.

[0046] The first fabric layer and the second fabric layer can have the same or different MD threads.

[0047] The CD thread density of the first fabric layer and the second fabric layer can be the same or different. The first fabric layer and the second fabric layer can be arranged such that the connection point of the end edges of the first flat fabric and the connection point of the end edges of the second flat fabric, viewed in the machine direction, are at least 10 cm apart, in particular at least 1 m apart, and preferably at most 3 m apart.

[0048] Alternatively or additionally, it can be provided that the connection of the front edges of the first flat fabric and / or the second flat fabric is / are designed as a welded connection, in particular as a laser-welded connection.

[0049] Thus, in a covering according to aspects of the present invention, the features described as advantageous in the prior art EP3960932 A1 and WO 2022 / 089843 A1 can also be realized.

[0050] Typically, the covering will also comprise one or more layers of nonwoven fibers, which can be arranged particularly on the upper side of the base structure. Alternatively or additionally, one or more layers of nonwoven fibers can also be provided on the underside of the base structure.

[0051] Typically, the nonwoven fibers are bonded to the base structure, for example, by mechanical needling. In this process, the nonwoven fibers penetrate fully or partially into the base structure or may even extend through it.

[0052] In advantageous embodiments, at least some of the nonwoven fibers may consist of or comprise a thermoplastic polymer. A thermoplastic polyurethane (TPU) has proven particularly advantageous in this case. The nonwoven fibers may consist of staple fibers with a fineness between 1.5 dtex and 300 dtex, in particular between 6.7 and 200 dtex.

[0053] Variant 2: Hybrid structure

[0054] In this variant, the first fabric layer is formed from an endlessly woven circular fabric, and the second fabric layer is formed from a flat fabric, which is made endless in particular by joining its front edges, wherein the first fabric layer has twisted MD threads, while the second fabric layer has twisted CD threads.

[0055] The front edges can be joined by a material-to-material bond, such as a weld. Transmission welding, such as NIR transmission welding, is a particularly advantageous joining method for this. Alternatively, the weld can also be achieved using ultrasonic welding.

[0056] The described basic structure can be described as a hybrid basic structure because it comprises both a circular weave and a flat weave. It is therefore faster and more cost-effective to manufacture than a basic structure consisting of two circular weaves. On the other hand, sufficient tensile strength of the hybrid basic structure can be achieved much more easily with basic structures composed entirely of flat weaves, as shown in EP 3 960 932 A1.

[0057] A further advantage of the hybrid structure is that by combining a single round weave type with various flat weave structures, a variety of basic structures can be produced and adapted to a wide range of requirements. This eliminates the need to maintain many different round weave types; instead, fewer round weave types, or even just one, are sufficient.

[0058] Different fabric types and weaving patterns can be used for flat weave and round weave.

[0059] It is particularly advantageous if the flat fabric has a plain weave, as this can be produced very quickly and inexpensively.

[0060] The round fabric can also have a plain weave.

[0061] Flat weaves and round weaves can have the same weave structure. Flat weaves and round weaves can have different weave structures. They can differ in weave pattern, thread types, thread densities, thread materials, etc.

[0062] The type of threads used to construct the fabric can be selected depending on the desired properties and the operating conditions of the covering. For example, to improve fiber anchoring in a nonwoven layer, it may be advantageous if some of the fabric threads are twisted.

[0063] In a particularly preferred embodiment, it can be provided that the first fabric layer has twisted MD threads, while the second fabric layer has twisted CD threads.

[0064] This design demonstrates another major advantage of the hybrid base structure. When used as a base fabric, the circular weaves are rotated 90° relative to the weaving direction. This means that the warp threads of the circular weave become the CD threads of the covering, while the weft threads of the circular weave become the MD threads of the covering.

[0065] In flat weaves, this twisting does not occur. Thus, the warp threads of the flat weave are called MD threads, and the weft threads are called CD threads.

[0066] By using a hybrid base structure, it is possible for the base structure to have twisted threads in both the MD direction and the CD direction without the need to use twisted warp threads during weaving.

[0067] This is also advantageous because changing a warp system on a loom is very time-consuming. Especially for smaller production quantities, it is not economically viable to change the warp system. Changing the weft threads, on the other hand, is very easy to implement. Thus, the hybrid basic structure enables clothing that cannot be reasonably produced with either pure circular or pure flat weaves. In an advantageous embodiment, at least 50%, preferably at least 75%, in particular all MD threads in the first fabric layer are twisted MD threads.

[0068] In a further advantageous embodiment, it can be provided that in the second fabric layer at least 30% of the CD threads are twisted CD threads.

[0069] Preferably, 50% of the CD threads in the second fabric layer can be twisted CD threads, with twisted CD threads and untwisted CD threads arranged alternately. However, other ratios between twisted and untwisted threads can also be provided, for example, 1:2; 2:1; 3:1; 2:3; or 3:2.

[0070] It is possible that the same yarns are used for the twisted MD threads as for the twisted CD threads. Alternatively, it is also possible that different yarns are used for the twisted MD threads and the twisted CD threads.

[0071] It is also possible that the same threads are always used within a fabric layer, or that different threads are used within a fabric layer.

[0072] The non-twisted MD and / or CD threads can have a diameter of 0.2mm to 0.8mm, in particular 0.25mm-0.6mm.

[0073] In further advantageous embodiments, it may be provided that some or all of the twisted MD threads and / or the twisted CD threads consist of three or more monofilaments.

[0074] The monofilaments can in particular have a diameter of more than 0.1 mm, in particular between 0.15 mm and 0.6 mm; preferably between 0.2 mm and 0.25 mm.

[0075] Suitable threads are, for example, 0.2 x 2 x 2 (4 ply) and 0.25x2x2 (4 ply).

[0076] The twisted yarns are often made of polyamide, but can also be made of other polymers. The non-twisted CD threads can have a diameter of 0.2 mm to 0.8 mm, particularly 0.25 mm to 0.6 mm.

[0077] It is often advantageous to position the first fabric layer closer to the surface of the fabric that comes into contact with the web than the second fabric layer. This reduces the risk of marks being created in the fibrous web at the junction of the flat weave's front edges. Any irregularities in the second fabric layer at this point can be dampened by the first fabric layer.

[0078] Alternatively, the second fabric layer can be arranged closer to the web-contacting surface of the clothing than the first fabric layer. This can be advantageous, for example, if the running side of the clothing is exposed to severe wear and abrasion in the intended installation position. In this case, a round fabric may offer better wear resistance than the second fabric layer. This can be the case, for example, if the front edges are joined by an ultrasonic weld, which can sometimes become brittle over time under heavy loads.

[0079] The hybrid basic structure according to aspects of the invention can comprise further components in addition to the first and second fabric layers. In particular, additional fabric layers can be provided, namely round fabrics and / or flat fabrics.

[0080] Alternatively or additionally, the basic structure may also comprise non-woven components, such as nonwoven layers, films, membranes, foam layers or similar.

[0081] It is advantageous, especially with regard to costs and time required for production, if the basic structure does not include any additional fabric layers.

[0082] Particularly for use as a press felt, the fabric will generally comprise at least one nonwoven layer, which is attached to the base structure, particularly by needling, and which provides the surface of the fabric in contact with the web. The provision of additional nonwoven layers, particularly nonwoven layers on the running side facing away from the fibrous web, is also possible.

[0083] It may be provided that at least some of the nonwoven fibers consist of or comprise a thermoplastic polymer, in particular a thermoplastic polyurethane.

[0084] The invention is explained in more detail below with reference to a figure. The invention is not limited to these embodiments.

[0085] Figure 1a shows schematically a covering according to one aspect of variant 1 of the invention

[0086] Figure 1 b shows schematically a basic structure according to an aspect of variant 2 of the invention

[0087] Figure 2a shows a first fabric layer for a basic structure according to one aspect of the invention

[0088] Figure 2b shows a second fabric layer according to a further aspect of the invention

[0089] The covering shown in Figure 1a has a basic structure comprising a first fabric layer 1 and a second fabric layer 2. The first fabric layer 1 is arranged above the second fabric layer 2 and represents the uppermost fabric layer of the basic structure 10.

[0090] The covering also has a layer of nonwoven fibers 8, which is arranged on the upper side of the base structure 10. An advantageous material for nonwoven fibers can be a thermoplastic polymer, e.g., polyamide. In advantageous embodiments, at least some of the nonwoven fibers can consist of or comprise a thermoplastic elastomer, e.g., a thermoplastic polyurethane (TPU). The first fabric layer 1 and the second fabric layer 2 comprise both monofilaments 7 and twisted threads 6 as CD threads 5. These are interwoven with MD threads 4 (not shown in Figure 1a).

[0091] The ratio of twisted threads 6 to monofilaments 7 (twisted-to-monofilament ratio) of the first flat fabric 1 differs from the twisted-to-monofilament ratio of the second flat fabric 2. The twisted-to-monofilament ratio of the first fabric layer 1 in Figure 1a is "1:1." This means that the same number of twisted threads 6 and monofilaments 7 are used as CD threads in the first fabric layer 1. Twisted threads 6 and monofilaments 7 are arranged alternately.

[0092] In the second fabric layer 2, the twisted yarn to monofilament ratio is smaller than in the first fabric layer 1. The ratio here is 1:2. Thus, for each twisted thread 6, there are two monofilaments 7.

[0093] Although these twist-mono ratios can be chosen relatively freely, it is often the case that the twist-mono ratio of the first fabric layer 1 is chosen in the range between “1:1” and “2:1”, while the twist-mono ratio of the second fabric layer 2 is chosen between “1:4” and “1:1”.

[0094] Figure 1b shows a basic structure 10 according to one aspect of variant 2 of the invention for a covering, in particular a press felt for a machine for producing or processing a fibrous web. The basic structure 10 comprises a first fabric layer 1 and a second fabric layer 2, which are arranged one above the other. The first fabric layer 1 is formed from an endlessly woven circular fabric, and the second fabric layer 2 is formed from a flat fabric. The flat fabric of the second fabric layer 2 is made endless by a connection 3 of its end edges.

[0095] The connection 3 of the front edges can be realized by a material-to-material connection 3, for example, a welded connection 3. Transmission welding, e.g., NIR transmission welding, is a particularly advantageous joining method for this purpose.

[0096] Figure 1b shows a design in which the first fabric layer 1 is arranged closer to the web-contacting surface of the covering than the second fabric layer 2. Alternatively, a reversed arrangement is also possible. In addition to the first fabric layer 1 and the second fabric layer 2, the basic structure can comprise further components. In particular, additional fabric layers can be provided, namely round fabrics and / or flat fabrics.

[0097] Alternatively or additionally, the basic structure 10 may also comprise nonwoven components, such as nonwoven layers, films, membranes, foam layers or the like.

[0098] In particularly preferred embodiments, the first fabric layer 1 may comprise 6 twisted MD threads 4, while the second fabric layer 2 may comprise 6 twisted CD threads 5.

[0099] Figures 2a and 2b show sections of fabric layers 1, 2 as they can be used for a basic structure 10 according to aspects of the invention.

[0100] The fabric of Figure 2a is intended in particular for a first fabric layer 1. In this fabric, the CD threads 5 all consist of monofilaments 7. In the case of the MD threads 4, at least some are designed as twisted MD threads 4, 6, while the remaining MD threads 4 are designed as monofilaments 7. Figure 2a shows an embodiment in which 50% of the MD threads 4 are designed as twisted MD threads 4, 6. In this case, monofilaments 7 and twisted threads 6 are arranged alternately, for example. In other embodiments, a larger proportion of twisted threads 6 can also be provided in the first fabric layer 1, for example at least 75%. All MD threads 4 can also be twisted MD threads 4, 6.

[0101] The fabric of Figure 2b is intended in particular for a second fabric layer 2. In this fabric, the MD threads 4 all consist of monofilaments 7. In the CD threads 5, at least some are formed as twisted CD threads 5, 6, while the remaining CD threads 5 are formed as monofilaments 7. Here, in the second fabric layer 2, 50% of the CD threads 5 are twisted CD threads 5, 6, with twisted CD threads 5, 6 and untwisted CD threads 5, 7 being arranged alternately. Alternatively, it is also possible for less than 50%, for example only 30%, of the CD threads 5 to be twisted CD threads 5, 6. A higher proportion of twisted CD threads 5, 6 is also possible. The yarns shown in Figures 2a and 2b are made with four filaments (4 ply) as an example. These yarns can be, for example, 0.2x2x2 or 0.25x2x2. Alternatively, other yarns with more or fewer filaments are also possible.

[0102] List of reference symbols

[0103] 1 first fabric layer

[0104] 2 second fabric layer 3 connection

[0105] 4 MD threads

[0106] 5 CD threads

[0107] 6 threads

[0108] 7 Monofilament 8 Layer of nonwoven fibers

[0109] 10 Basic structure

[0110] MD Machine Direction

Claims

Patent claims 1 . Clothing, in particular press felt for a machine for producing or processing a fibrous web, wherein the clothing has a basic structure (10) which comprises a first fabric layer (1) and a second fabric layer (2) which are arranged one above the other and which each have threads in the machine direction (MD) and threads in the cross-machine direction (CD), characterized in that both the first fabric layer (1) and the one second fabric layer (2) have threads which are designed as monofilaments (7) and threads which are designed as twisted threads (6).

2. Covering according to claim 1, characterized in that the first fabric layer (1) consists of a first flat fabric, which is made endless in particular by connecting its end edges, and the second fabric layer (1) consists of a second flat fabric, which is made endless in particular by connecting its end edges, wherein both the first flat fabric and the second flat fabric have CD threads which are designed as monofilaments (7), and both the first flat fabric and the second flat fabric have CD threads which are designed as twisted threads (6), and wherein the ratio of twisted threads (6) to monofilaments (7) (twist-mono ratio) of the first flat fabric differs from the twist-mono ratio of the second flat fabric 3. Covering according to one of claims 1 or 2, characterized in that the first fabric layer (1 ) consists of a first flat fabric, which is made endless in particular by connecting its front edges, and the second fabric layer (1 ) consists of a second flat fabric, which is made endless in particular by connecting its end edges, wherein both the first flat fabric and the second flat fabric have CD threads which are designed as monofilaments (7), and both the first flat fabric and the second flat fabric have CD threads which are designed as twisted threads (6), and wherein the CD thread density of the first fabric layer (1) and the second fabric layer (2) are different.

4. Covering according to one of claims 2 or 3, characterized in that the twist-mono ratio of the first flat fabric is between 1:3 and 3:1; in particular between 1:1 and 2:

1.

5. Covering according to one of the preceding claims, characterized in that the twist-mono ratio of the second flat fabric is lower than the twist-mono ratio of the first flat fabric.

6. Covering according to one of the preceding claims, characterized in that the twist-mono ratio of the second flat fabric is between 1:4 and 1:

1.

7. Covering according to one of the preceding claims, characterized in that the first fabric layer (1) is arranged above the second fabric layer (2) and in particular represents the uppermost fabric layer of the basic structure.

8. Covering according to one of the preceding claims, characterized in that the CD thread density of the second fabric layer (2) is between 3% and 80%, in particular between 5% and 60%, greater than the CD thread density of the first fabric layer (1).

9. Covering according to one of the preceding claims, characterized in that the basic structure has further layers, in particular comprises further fabric layers or consists only of the first fabric layer (1) and the second fabric layer (2).

10. Covering according to one of the preceding claims, characterized in that the first fabric layer (1) and the second fabric layer (2) are arranged such that the connection point of the end edges of the first flat fabric and the connection point of the end edges of the second flat fabric, viewed in the machine direction, are at least 10 cm apart and preferably at most 3 m apart. 11 . Covering according to one of the preceding claims, characterized in that the connection of the end edges of the first flat fabric and / or the second flat fabric is or are designed as a welded connection, in particular as a laser-welded connection.

12. Covering according to claim 1, characterized in that the first fabric layer (1) is formed from an endlessly woven circular fabric, and the second fabric layer (2) consists of a flat fabric which is made endless in particular by joining its front edges, the first fabric layer (1) having twisted MD threads (4,6), while the second fabric layer (2) has twisted CD threads (5,6).

13. Covering according to claim 12, characterized in that in the first fabric layer (1), at least 50%, preferably at least 75%, in particular all MD threads (4) are twisted MD threads (4, 6). Covering according to one of the preceding claims, characterized in that in the second fabric layer (2), at least 30% of the CD threads (5) are twisted CD threads (5, 6).

14. Covering according to claim 13, characterized in that in the second fabric layer (2) 50% of the CD threads (5) are twisted CD threads (5, 6), wherein twisted CD threads (5, 6) and non-twisted CD threads are arranged alternately (5, 7).

15. Covering according to one of claims 12 to 14, characterized in that the same threads (6) are used for the twisted MD threads (4, 6) as for the twisted CD threads (5, 6).

16. Covering according to one of claims 12 to 14, characterized in that different threads (6) are used for the twisted MD threads (4, 6) and the twisted CD threads (5, 6).

17. A covering according to any one of claims 12 to 16, characterized in that some or all of the twisted MD threads (4, 6) and / or the twisted CD threads (5, 6) consist of three or more monofilaments.

18. Covering according to claim 17, characterized in that the monofilaments (7) have a diameter of more than 0.15 mm, in particular between 0.2 mm and 0.25 mm.

19. Covering according to one of the preceding claims, characterized in that the first fabric layer (1) is arranged closer to the web-contacting surface of the covering than the second fabric layer (2).

20. Covering according to one of the preceding claims, characterized in that the basic structure (10) does not comprise any further fabric layer.

21. Covering according to one of the preceding claims, characterized in that the covering has at least one nonwoven layer which is attached to the base structure (10), in particular by needling, and which provides the web-contacting surface of the covering 22. Covering according to one of the preceding claims, characterized in that the covering further comprises a layer of nonwoven fibers (8), which is arranged in particular on the upper side of the basic structure, wherein at least some of the nonwoven fibers consist of or comprise a thermoplastic polymer, in particular a thermoplastic polyurethane.

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