Press jacket with reinforcing threads formed as twisted yarns

Description

[0001] The present invention relates to a press cover comprising at least one polymer layer in which a reinforcing structure is embedded, wherein the reinforcing structure is designed as a thread layer which comprises a first, radially inner layer made of a plurality of longitudinal threads extending in the axial direction of the press cover and a second, radially outer layer made of at least one circumferential thread extending substantially in the circumferential direction of the press cover, wherein the longitudinal threads of the first layer and preferably also the at least one circumferential thread of the second layer are each designed as a reinforcing thread which is designed as a twisted yarn by first twisting a plurality of individual fibers or fiber bundles together in a first twist direction and at a first twist rate to form a pre-twisted yarn and then twisting a plurality of such pre-twisted yarns together in a second twist direction opposite to the first twist direction and at a second twist rate.Furthermore, the invention relates to a press roll and a shoe press for treating a fibrous web with such a press cover, as well as the use of such a press cover in a press, in particular a shoe press, for treating a fibrous web, in particular a paper, cardboard or tissue web.

[0002] Such a press sleeve was already described by the inventor in the publication DE 10 2019 126 077 A1, the disclosure of which is hereby incorporated in its entirety into the present application. The inventor has already recognized that the use of special twisted yarns as reinforcement threads has a beneficial effect on the press sleeve, as it reduces the risk of premature failure due to an – often only local – overload in the nip. In other words, reinforcement threads designed as twisted yarns can help increase the service life of the press sleeve.

[0003] However, there is still a risk that the radially inner longitudinal threads could fail during a slug pass if, viewed in the radial direction of the press sleeve, they are arranged in such a way that they touch the at least one radially outer circumferential thread. Simulation results by the inventors show that this is caused by significant stress concentrations that act locally on the longitudinal threads at the intersection points of the longitudinal threads with the at least one circumferential thread when the at least one circumferential thread presses directly on the longitudinal threads during a slug pass. In the press sleeve from the above-mentioned document DE 10 2019 126 077 A1, the longitudinal threads and the at least one circumferential thread are therefore deliberately arranged in such a way that they do not touch one another. In this way, there is no direct force transmission between these threads, and the matrix material arranged between them, such as polyurethane, can have a dampening effect.The disadvantage of this, however, is that the arrangement of the longitudinal threads and the at least one circumferential thread at a distance from each other is relatively complex in terms of manufacturing technology.

[0004] Therefore, there is still room for improvement, so the inventor has set himself the task of researching further measures to make the press sleeve even more resistant to overload situations, such as so-called lump penetration, and thus further increase its service life. At the same time, the manufacturing effort should be kept as low as possible.

[0005] This object is achieved by the independent claims, the dependent claims relating to advantageous developments of the present invention.

[0006] Specifically, after intensive root cause analyses and numerous experiments, the inventor surprisingly discovered that this problem can be solved if, in the generic press sleeve described above, the first rotation rate is selected to be lower than the second rotation rate. At the same time, the manufacturing effort can be kept low by arranging the longitudinal threads and the at least one circumferential thread in such a way that they touch each other, as seen in the radial direction of the press sleeve.

[0007] Such a choice of twist rates for twisted yarns is extremely unusual. As experts in the field of textile technology, especially yarns, know, the characteristic behavioral properties of a twisted yarn depend less on its twist rate, i.e., the number of twists per meter of the yarn, but rather on the twist angle of the individual strands from which the yarn is produced by twisting. This twist angle, in turn, depends significantly on the diameter of the yarn. The relationship between the twist diameter and the twist angle is shown schematically in Figure 1 where d is the diameter of the thread, l is the length of the thread for one complete turn of one of the strands, and θ is the twist angle. The formula is: tan θ = πd l

[0008] This shows that the larger the diameter of the thread, the larger the twist angle. Furthermore, as mentioned previously, it is known that the characteristic behavior of the thread depends on the twist angle. For example, the twist increases as the twist angle increases.

[0009] As a rule, one wants to keep the twist of a thread low, as this would otherwise lead to curling. Therefore, the twist directions in two-stage threads, i.e., threads made from pre-twist yarns, are always opposite to each other. For example, the pre-twist yarn can be twisted in the S-direction, and the final thread made from several pre-twist yarns can be twisted in the Z-direction, as shown in the example in Figure 2shown. Since the pre-twisted yarns naturally have a much smaller diameter than the final twist produced from them, their twist rate must be significantly higher than the twist rate of the final twist. Only in this way can a similar or identical twist angle and thus similar or identical characteristic behavior properties be achieved for the pre-twisted yarn. In particular, this compensates for the twist that the final twist receives in the second twisting stage due to the twisting of the pre-twisted yarns. This means that the final twist can be laid straight on a flat surface even without pre-tensioning and has no tendency to curl. For this reason, the first twist rate is almost always selected to be higher than the second twist rate for two-stage twisted yarns.

[0010] In the field of car tire production, there are already twisted yarns used as reinforcement threads which consist of a pre-twist having a first twist rate which is lower than the twist rate of the final twist formed from several pre-twists. Reference is made, for example, to the publication US 4 787 200 A from Bridgestone. However, since the structure of the reinforcement structure in a car tire is fundamentally different from the structure of the reinforcement structure in a press sleeve described above, the same problems do not arise here, in particular local overstresses at the intersection points of longitudinal and circumferential threads. In car tires, there are also usually no longitudinal threads which are touched radially outwards by at least one circumferential thread. The specific problems which are to be solved here are of a different nature, even if they ultimately result in a longer service life of the car tire.Consequently, the press sleeve specialist would have no motivation to resort to this state of the art from a completely different field.

[0011] The same applies to the technical field of timing belt production, as described, for example, in the publication EP 3 770 309 A1 by Nippon.

[0012] In any case, there is no obvious reason for a specialist in the field of press sleeve production to select or have specially manufactured twisted reinforcement threads that deviate from the usual basic principle.

[0013] Thus, it is to the inventor's credit that he recognized that, in terms of overload resistance, it is advantageous for press sleeves to select a lower first twist rate than the second twist rate for a twisted reinforcement thread. The tendency of the reinforcement thread to curl can be counteracted by applying appropriate pre-tension to embed it in the polymer matrix.

[0014] Figure 3 shows a schematic of the test setup for determining the radial hardness of a reinforcement thread in the form of a twisted yarn. The greater the deformation ΔL in the radial direction of the reinforcement thread at a given force (here 9.8 N), the softer the reinforcement thread is in its radial direction.

[0015] The inventor has recognized that a twisted yarn with a first twist rate that is selected to be lower than the second twist rate behaves significantly softer in the radial direction at low pretension than the same twisted yarn with high pretension. This difference in hardness is considerably greater than in conventionally used twisted yarns in which the first twist rate is selected to be higher than the second twist rate. This behavior can be positively utilized in a press cover. There, the reinforcing threads arranged radially further inwards, in particular longitudinal threads extending in the axial direction of the press cover, which form a first fabric layer, are typically provided with a greater pretension than the at least one reinforcing thread arranged radially further outwards, in particular at least one circumferential thread extending substantially in the circumferential direction.As a result, when using one and the same twisted thread material, it can be achieved that the at least one reinforcing thread arranged radially further outwards is softer in the radial direction than the reinforcing threads arranged radially further inwards.

[0016] This is advantageous because the at least one reinforcement thread arranged further radially outward, which is relatively soft, reduces the risk of cracks starting to form on the outer surface of the press sleeve when the press sleeve is exposed to an overload situation. Such cracks, as the inventor has observed, often begin at the base of grooves with which such a press sleeve is typically provided on its outer surface. However, the stress peaks in the polymer material, particularly at the groove base, of the press sleeve can be reduced if the at least one radially outer reinforcement thread is relatively soft.

[0017] At the same time, it was recognized that it is advantageous if the radially inner reinforcement threads are as hard as possible. These threads tend to be the first to break during a lump pass, but this risk is counteracted by making them sufficiently hard.

[0018] Tests have shown it to be advantageous if the first rotation rate corresponds to 70% to 90% of the second rotation rate, the first rotation rate preferably being between 70 and 90, more preferably between 75 and 85, and even more preferably 80 rotations per meter.

[0019] Similar to what is common with sewing threads, for example, the first twist direction can be the S-direction and the second twist direction the Z-direction. A typical sewing thread of this kind is shown in Figure 2 shown.

[0020] Unlike the one in Figure 2For the typical sewing thread shown, it is preferred for the reinforcing thread according to the present invention if each pre-twist is formed from two individual fibers or fiber bundles, and if the finished thread is formed from three pre-twists. This allows for a particularly stable reinforcing thread to be achieved. The reinforcing thread should, in particular, also be able to withstand tensile forces along its longitudinal direction.

[0021] As already mentioned above, it is very advantageous from a manufacturing point of view if, according to the present invention, the reinforcing structure is designed as a thread layer comprising a first layer of several longitudinal threads extending in the axial direction of the press cover and a second layer of at least one circumferential thread extending substantially in the circumferential direction of the press cover, wherein the longitudinal threads and the at least one circumferential thread are arranged relative to one another in the radial direction of the press cover such that they touch one another. "Substantially in the circumferential direction" can be understood in particular to mean that the at least one circumferential thread extends helically around the longitudinal axis of the press cover. More than one circumferential thread can also be included in the second layer, which can then be arranged relative to one another in a similar way to a screw with multiple threads.Preferably, the longitudinal threads of the first layer and / or the at least one circumferential thread of the second layer correspond to the at least one reinforcing thread formed as a twisted yarn.

[0022] In a further development of this idea, it is proposed that the longitudinal threads of the first layer in the press sleeve have a first pre-tension, whereas the at least one circumferential thread of the second layer has a second pre-tension, wherein the first pre-tension is greater than the second pre-tension and wherein the first pre-tension preferably corresponds to at least 7 times and / or at most 13 times the second pre-tension. This leads to the advantageous different hardnesses of the reinforcing threads in the two layers already described above, even if the same thread material is used there.

[0023] It is sufficient if the entire reinforcement structure of the press sleeve consists only of the first layer and the second layer.

[0024] It has also proven advantageous if the at least one reinforcing thread formed as a twisted yarn has a coating. The coating can support the bonding of the twisted yarn to the surrounding polymer matrix.

[0025] It is advantageous if the at least one reinforcing thread designed as a twisted yarn has a fineness between 800 dtex and 1500 dtex, preferably between 1000 dtex and 1200 dtex, more preferably 1100 dtex. The unit dtex is an abbreviation for decitex, as 10 tex, whereby the official tex system is a weight numbering, i.e. it indicates the fineness of a yarn. The fineness is defined by the weight that a certain length of yarn has. tex indicates how many grams 1 km of yarn weighs (e.g. 1 dtex = 10 tex: 1 km of yarn weighs 10 grams). If the reinforcing thread is too fine, it cannot absorb the tensile forces in the press sleeve to the required extent. If, on the other hand, the reinforcing thread is too coarse, this leads to problems when bonding to the polymer matrix.

[0026] It has proven advantageous if the pre-twisted yarns are each formed from several fiber bundles, each fiber bundle having between 180 and 230 individual filaments.

[0027] Preferably, all threads of the reinforcing structure of the press cover correspond to the at least one reinforcing thread formed as a twisted yarn. This applies in particular with regard to the first and second twist rates.

[0028] It is particularly preferred if all threads of the press sleeve's reinforcement structure are identical to one another. This allows large quantities of the same thread material to be purchased and installed, keeping the costs of producing the press sleeve low.

[0029] A further aspect of the present invention relates to a press roll for a shoe press for treating a fibrous web, wherein the press roll has at least one press cover according to the invention as described above.

[0030] A still further aspect of the present invention relates to a shoe press for treating a fibrous web, in particular a paper, board or tissue web, comprising a press roll and a counter roll which together form or delimit an extended press nip, wherein the press roll comprises a circumferential press shell which is designed according to the present invention.

[0031] The present invention also relates to the use of a previously described press cover according to the invention in a press, in particular a shoe press, for treating a fibrous web, in particular a paper, cardboard or tissue web.

[0032] The invention is explained below using schematic and not-to-scale figures. The figures show in detail: Fig. 1 shows a schematic diagram illustrating the general relationship between twist diameter and twist angle; Fig. 2 shows an example of a typical twist, such as a sewing thread, in which three pre-twisted yarns twisted in the S-direction are twisted together in the Z-direction; Fig. 3 shows a schematic diagram illustrating how the radial hardness of a reinforcing yarn can be determined; Fig. 4 shows a comparison of the radial hardness of various reinforcing yarns at different pre-tensions; Fig. 5 shows a reinforcing yarn for a press cover according to the present invention; Fig. 6 shows a shoe press with a press cover according to the invention; and Fig. 7 shows a schematic diagram illustrating a manufacturing process for the press cover according to the invention.

[0033] Figure 5shows an example of a reinforcing thread 10 which is designed according to the present invention to be used as a component of a reinforcing structure 100 in a press cover 200 according to the invention (see Figure 6 ) to be installed. The reinforcing thread 10 is designed as a twisted yarn, wherein first two fiber bundles 30 are twisted in the S-twist direction at a first twist rate to form a pre-twist 20, and then three such identically produced pre-twist 20 are twisted in the Z-direction at a second twist rate to form the final twist or the reinforcing thread 10. The reinforcing thread 10 can then be coated.

[0034] According to the present invention, the first twist rate is smaller than the second twist rate. In this embodiment, the first twist rate is 80 and the second twist rate is 100 twists per meter. The thread also has a fineness of 1100 dtex. Thus, the reinforcing thread 10 according to the present invention can be characterized using the following abbreviation: dtex 1100 × 2 × 3 S 80 / Z 100 .

[0035] This embodiment of a reinforcing thread 10 for a press cover according to the invention, which embodiment is referred to below as AB-1, has now been tested with regard to its radial hardness according to the method described above with regard to Figure 3 described experimental setup and compared with two examples AB-2 and AB-3 of a respective reinforcement thread from the prior art. The reinforcement threads according to AB-2 and AB-3 have the same basic structure (as in Figure 5shown) like the embodiment AB-1, but with these reinforcement threads, the first rotation rate is greater than the second rotation rate. In short, the reinforcement thread according to AB-2 can be characterized as follows: dtex 1100 × 2 × 3 S 165 / Z 150 . and the reinforcement thread can be characterized according to AB-3 as follows: dtex 1100 × 2 × 3 S 100 / Z 80 .

[0036] For AB-2, the first rotation rate is 165 rotations per meter and the second rotation rate is 150 rotations per meter, whereas for AB-3, the first rotation rate is 100 rotations per meter and the second rotation rate is 80 rotations per meter.

[0037] Figure 4 shows the result of this comparison, with the preload in Newtons (N) to which the reinforcement threads were subjected during the test noted on the x-axis. The hardness in Pussey & Jones (P&J) is plotted on the y-axis. It should be noted that a smaller P&J value indicates greater hardness than a larger P&J value.

[0038] How the Figure 4 As can be seen, at a low prestress of 4N, the P&J hardness of the exemplary embodiment AB-1 according to the present invention is 34, which is significantly higher than that of AB-2 (where it is only 21) and also somewhat higher than that of AB-3 (where it is 32). In other words, at low prestress, the reinforcing thread 10 according to the invention is relatively soft in the radial direction compared to reinforcing threads from the prior art. At a significantly greater prestress of 50N, however, the P&J hardness of the exemplary embodiment AB-1 according to the present invention is only 20. It is therefore below the P&J hardness of AB-3 (where it is 24) and only slightly above the P&J hardness of AB2 (where it is 18). In other words, at high prestress, the reinforcing thread 10 according to the invention is harder or at least similarly hard in the radial direction to the reinforcing threads from the prior art.

[0039] The press cover 200 of the present invention advantageously utilizes this large deviation in the radial hardness of the reinforcing thread 10 according to the invention. Several of these reinforcing threads 10, which extend as longitudinal threads 220 parallel to the axis 1 of the press cover 200, form a first layer of a reinforcing structure 100. Furthermore, at least one of these reinforcing threads 10, which is wound helically around the axis A as a circumferential thread 230 radially outwardly of the first layer (cf. Figure 7 ), a second layer of the reinforcement structure 100. Preferably, the entire reinforcement structure 100 of the press cover 200 according to the invention consists only of these two layers.

[0040] The press jacket 200 can be used as in Figure 7 shown schematically. Figure 7shows, in a highly schematic side view, a device for producing the press sleeve 200 according to the invention. In the present case, the device has precisely one cylindrical winding mandrel. A plurality of the reinforcing threads 10 designed as longitudinal threads 220 are spaced apart from one another on the circumference. A polymer is applied to the radially outermost surface of the winding mandrel in order to apply a polymer layer 240. In addition, for example, a circumferential thread 230 is introduced helically into the polymer of the polymer layer 240. After being embedded in the polymer, the circumferential thread 230, together with the longitudinal threads 220, forms the reinforcing structure 100 of the finished press sleeve 200 according to the invention. According to the invention, the circumferential thread 230 touches the longitudinal threads 220, ie there is no distance between them when viewed in the radial direction of the press sleeve 200.

[0041] The winding mandrel is mounted for rotation about its longitudinal axis, which corresponds to the longitudinal axis A of the press sleeve 200 to be produced. The longitudinal axis here runs orthogonally into the plane of the drawing. The casting material, such as a pourable, curable elastomeric polymer, e.g. polyurethane, is applied from above via a line 300 through a pouring nozzle 310 onto the radially outermost surface of the winding mandrel or onto the longitudinal threads 220. Such a casting material can, for example, be selected with regard to its pot life and viscosity such that it does not drip off the winding mandrel during pouring. During this time, the winding mandrel is rotated in the direction of the arrow about its longitudinal axis. Simultaneously with this rotation, the pouring nozzle 310 is pressurized via a suitable Fig. 7A guide (not shown in detail) is guided parallel to the longitudinal axis A along this axis relative to the winding mandrel. Simultaneously with the pouring of the casting material, the at least one circumferential thread 230 is unwound and wound helically onto the rotating winding mandrel to form coils. The casting material can thereby pass through the longitudinal threads 220 to the winding mandrel. In this example, after the curing step, the polymer forms a radially innermost and preferably elastomeric polymer layer, which e.g. is the polymer layer 240. In addition, if necessary, further polymer layers can be applied radially outward. Preferably, however, the entire reinforcement structure 100 is completely embedded in the radially innermost polymer layer 240.

[0042] The casting material emerging from the casting nozzle 6 is a mixture of a prepolymer and a crosslinker. The prepolymer is provided from a prepolymer container (not shown), in which it is stored or mixed. The prepolymer can comprise an isocyanate according to the invention and a polyol. In the prepolymer container, it can be present, for example, in the form of a prepolymer made of the substances just mentioned. The crosslinker can be provided in a crosslinker container. The prepolymer container and crosslinker container are assigned to the device for producing the press sleeve 200. They are fluidly connected via lines (likewise not shown) to a mixing chamber (not shown) arranged upstream of the casting nozzle 310 in the flow direction. The prepolymer-crosslinker mixture is thus produced upstream of and outside of the casting nozzle 310, i.e., mixed in the mixing chamber.Regardless of the preparation of the mixture, it is then applied to the surface of the winding mandrel to form the at least one polymer layer of the press sleeve 200.

[0043] By means of such a continuous casting process, which is also known as rotational casting, an endless, cylindrical tube-shaped press sleeve 200 is gradually produced across the width of the winding mandrel, which is closed around its longitudinal axis a, the inner circumference of which essentially corresponds to the outer circumference of the winding mandrel 4.

[0044] Preferably, the longitudinal threads 220 are prestressed with a greater prestress, for example, a prestress of 50N, than the at least one circumferential thread 230, which can be prestressed with a prestress of only 4N when the reinforcing structure 100 is embedded in the polymer layer 240. As a result, the reinforcing threads 10 according to the invention, which form the first layer of the reinforcing structure 100 as longitudinal threads 220, are significantly harder than the at least one reinforcing thread 10 according to the invention, which forms the second layer of the reinforcing structure 100 as the circumferential thread 230. This has an advantageous effect on the resistance of the press cover 200 according to the invention during a batch pass.

[0045] In Figure 6A partially sectioned, schematic side view of a shoe press 500 is shown, which in this case comprises a press roll 400 according to the invention, namely a shoe press roll, and a counter roll 450. The shoe press roll 400 and the counter roll 450 are arranged parallel to one another with respect to their longitudinal axes. Together, they form or delimit an extended press nip 510.

[0046] While the counter roll 450 here consists of a cylindrically designed roll rotating about its longitudinal axis, the shoe press roll 400 is composed of a shoe 410, a stationary yoke supporting the shoe, and the press sleeve 200 according to the invention. The shoe 410 and the yoke are arranged stationary with respect to the counter roll 450 and the press sleeve 200, respectively. This means that they do not rotate. The shoe 410 is supported by the yoke and pressed by hydraulic pressing elements (not shown) against the radially innermost surface of the press sleeve 200, which rotates relative to it. The press sleeve 200, which circumferentially surrounds the shoe 410 and the yoke, rotates about its longitudinal axis A in the opposite direction to the counter roll 450. Due to the concave design of the shoe 410 on its side facing the counter roll 450, a comparatively long press nip 510 results.

[0047] The shoe press 500 is particularly suitable for dewatering fibrous webs FB. During operation of the shoe press 500, a fibrous web FB is guided through the press nip 510 with one or two press felts 520. In the present case, there are exactly two press felts 520 that sandwich the fibrous web FB between them. As it passes through the extended press nip 510, pressure is indirectly exerted on the fibrous web FB by the press felts 520 in the extended press nip 510. This occurs because the radially outermost surface of the counter roll 450, on the one hand, and the radially outermost surface of the press sleeve 200, on the other hand, come into direct contact with the corresponding press felts 520. The liquid emerging from the fibrous web FB is temporarily absorbed by the press felt(s) 520 and any depressions, in particular grooves, provided in the press sleeve surface (not shown).After leaving the extended press nip 510, the liquid absorbed by the recesses of the press sleeve 200 is spun off before the press sleeve 200 re-enters the press nip 510. In addition, the water absorbed by the press felt 520 can be removed with suction elements after leaving the press nip 510.

[0048] In a further embodiment of the invention, not shown in the figures, the press felts 520 can be omitted. In such a case, the fibrous web FB is in direct contact with the press cover 200 on the one hand and with the counter roll 450 on the other, which together form a press nip 510. The latter can then be designed as a heated drying cylinder. List of reference symbols

[0049] 10 Reinforcing thread 20 Pre-twist 30 Fiber bundle 100 Reinforcing structure 200 Press cover 220 Longitudinal thread 230 Circumferential thread 240 Polymer layer 300 Line 310 Pouring nozzle 400 (Shoe) press roll 410 Shoe 450 Counter roll 500 Shoe press 510 (Extended) press nip 520 Press felt A Axis (of the press cover) AB-1 Embodiment 1 (according to the present invention) AB-2 Embodiment 2 (according to the prior art) AB-3 Embodiment 3 (according to the prior art) FB Fibrous web

Claims

1. Press cover (200) comprising at least one polymer layer (240) in which a reinforcing structure (100) is embedded, wherein the reinforcing structure (100) is formed as a scrim which comprises a first, radially inner layer made of multiple longitudinal threads (220) extending in the axial direction of the press cover (200) and a second, radially outer layer made of at least one circumferential thread (230) extending substantially in the circumferential direction of the press cover (200), wherein the longitudinal threads (220) of the first layer and preferably also the at least one circumferential thread (230) of the second layer are each formed as a reinforcing thread (10) which is formed as a twisted yarn, in that firstly several individual fibers or fiber bundles (30) are twisted together in a first twist direction at a first turn rate so as to form a pre-twist (20), and then several such pre-twists (20) are twisted together in a second twist direction, opposite the first twist direction, at a second turn rate, characterized in that the first turn rate is lower than the second turn rate, and viewed in the radial direction of the press cover (200), the longitudinal threads (220) and the at least one circumferential thread (230) are arranged relative to one another such that they touch.

2. Press cover (200) according to Claim 1, characterized in that the first turn rate corresponds to 70% to 90% of the second turn rate, wherein the first turn rate is preferably between 70 and 90, further preferably between 75 and 85, and even further preferably 80 turns per meter.

3. Press cover (200) according to Claim 1 or 2, characterized in that the first twist direction is the S direction and the second twist direction is the Z direction.

4. Press cover (200) according to any of the preceding claims, characterized in that each pre-twist (20) is formed from two individual fibers or fiber bundles (30), and the final twisted yarn is formed from three pre-twists (20).

5. Press cover (200) according to any of the preceding claims, characterized in that the longitudinal threads (220) of the first layer in the press cover (200) have a first pretension, whereas the at least one circumferential thread (230) of the second layer has a second pretension, wherein the first pretension is greater than the second pretension.

6. Press cover (200) according to Claim 5, characterized in that the first pretension corresponds to at least 7 times and / or at most 13 times the second pretension.

7. Press cover (200) according to any of the preceding claims, characterized in that the entire reinforcing structure (100) of the press cover (200) consists only of the first layer and the second layer.

8. Press cover (200) according to any of the preceding claims, characterized in that the at least one reinforcing thread (10) formed as a twisted yarn has a coating.

9. Press cover (200) according to any of the preceding claims, characterized in that the at least one reinforcing thread (10) formed as a twisted yarn has a fineness between 800 dtex and 1500 dtex, preferably between 1000 dtex and 1200 dtex, further preferably 1100 dtex.

10. Press cover (200) according to any of the preceding claims, characterized in that the pre-twists (20) are each formed from several fiber bundles (30), wherein each fiber bundle (30) has between 180 and 230 individual filaments.

11. Press cover (200) according to any of the preceding claims, characterized in that all threads of the reinforcing structure (100) of the press cover (200) correspond to the at least one reinforcing thread (10) formed as a twisted yarn.

12. Press cover (200) according to any of the preceding claims, characterized in that all threads of the reinforcing structure (100) of the press cover (200) are formed identically to one another.

13. Press roll (400) for a shoe press (500) for processing a fibrous material web (FB), characterized in that the press roll (400) has at least one press cover (200) according to any of the preceding claims.

14. Shoe press (500) for processing a fibrous material web (FB), in particular a paper, cardboard or tissue web, comprising a press roll (400) and a counter-roll (450) which together form or delimit an extended pressing gap (510), wherein the press roll (400) comprises a circumferential press cover (200), characterized in that the press cover (200) is configured according to any of Claims 1 to 12.

15. Use of a press cover (200) configured according to any of Claims 1 to 12 in a press, in particular a shoe press (500), for processing a fibrous material web (FB), in particular a paper, cardboard or tissue web.