Press cover with reinforcing fibers formed as twisted yarns

Abstract

The present invention relates to a press cover (200) having at least one polymer layer (240) in which a reinforcement structure (100) is embedded, the reinforcement structure (100) being formed as a fiber reinforcement including a radially inner first layer of a plurality of longitudinal fibers (220) extending in the axial direction of the press cover (200) and a radially outer second layer of at least one circumferential fiber (230) extending in a substantially circumferential direction of the press cover (200), the longitudinal fibers (220) of the first layer and preferably also at least one circumferential fiber (230) of the second layer being each formed as a reinforcement fiber. The present invention further relates to a press cover (200) in which the reinforcing fibers are formed as twisted yarns by first twisting a plurality of filaments or fiber bundles together in a first twist direction with a first twist per unit length to form a roving and then twisting a plurality of such rovings together in a second twist direction opposite to the first twist direction with a second twist per unit length, the first twist per unit length being smaller than the second twist per unit length, and the longitudinal fibers (220) and the at least one circumferential fiber (230) are arranged relative to one another in such a way that they are in contact with one another as viewed in the radial direction of the press cover (200).The present invention further relates to a press roll and shoe press for processing a textile material web, which are provided with such a press cover (200), as well as to the use of such a press cover (200) in a press, in particular a shoe press, for processing a textile material web.

Description

[Technical field]

[0001] The present invention relates to a press cover having at least one polymer layer in which a reinforcing structure is embedded, the reinforcing structure being formed as a fiber reinforcement including a radially inner first layer of longitudinal fibers extending in the axial direction of the press cover and a radially outer second layer of at least one circumferential fiber extending substantially in the circumferential direction of the press cover, the longitudinal fibers of the first layer and preferably also the at least one circumferential fiber of the second layer each being formed as a reinforcing fiber, the reinforcing fiber being formed as a twisted yarn by first twisting together a plurality of single fibers or fiber bundles in a first twist direction with a first twist number per unit length to form a roving and then twisting together a plurality of such rovings in a second twist direction opposite to the first twist direction with a second twist number per unit length. The invention further relates to press rolls and shoe presses for processing fibrous material webs, which are provided with such press covers, as well as to the use of such press covers in presses, in particular shoe presses, for processing fibrous material webs, in particular paper webs, cardboard webs or tissue webs.

[0002] Such press covers have already been described by the inventor in the publication DE 102019126077 A1, the disclosure content of which is hereby incorporated in its entirety into the present application. In this case, the inventor has already recognized that the use of special twisted yarns as reinforcing fibers has an advantageous effect on the press cover, since the risk of failure, which can occur as a result of - often only local - overloads in the nip, is reduced. In other words, the reinforcing fibers formed as twisted yarns serve to extend the service life of the press cover.

[0003] However, if the radially inner longitudinal fibers are arranged in contact with at least one radially outer circumferential fiber when viewed in the radial direction of the press cover, there is still a risk that the radially inner longitudinal fibers may be damaged during the passage of the mass. The inventor's simulation results show that for this reason, when at least one circumferential fiber is pressed directly against the longitudinal fibers during the passage of the mass, significant stress concentrations arise locally on the longitudinal fibers at the intersections of the longitudinal fibers and at least one circumferential fiber. In the press cover according to the above-mentioned publication DE 10 2019 126 077 A1, the longitudinal fibers and the at least one circumferential fiber are therefore deliberately arranged so that they do not come into contact with each other. In this way, no direct force transmission occurs between these threads, and the matrix material arranged between these threads, for example polyurethane, can exert a damping effect. The disadvantage here, however, is that the spacing of the longitudinal fibers and at least one circumferential fiber from one another is relatively complex in terms of production technology.

[0004] There is therefore still room for improvement, and the inventor has set himself the task of finding further measures to make the press cover still resistant to overload situations, such as so-called mass passages, and thus to further extend its service life. At the same time, it is desirable to keep the manufacturing expenditure as low as possible.

[0005] This problem is solved by the independent claims, with the dependent claims being directed to advantageous developments of the invention.

[0006] In particular, the inventors have surprisingly found, after rigorous cause analysis and several tests, that this problem can be solved in a press cover of the type mentioned at the beginning if the first number of twists per unit length is selected to be smaller than the second number of twists per unit length, while at the same time keeping the manufacturing effort low, since in this case the longitudinal fibers and the at least one circumferential fiber are arranged so as to be in contact with one another, viewed in the radial direction of the press cover.

[0007] Such a choice of twists per unit length in twisting is extremely rare. As known to those skilled in the art of textile technology, especially in the field of spinning, the characteristic behavioral properties of a twisted yarn do not depend so much on the number of twists per unit length, i.e. on the number of twists per meter of the length of the yarn, but rather on the twist angle (also called "twist angle") of the individual strands from which the yarn is produced by twisting. This twist angle, in turn, is highly dependent on the diameter of the yarn. The relationship between the twist diameter and the twist angle is shown diagrammatically in FIG. 1, where d is the diameter of the yarn, I is the length of the yarn when one of the strands makes one complete turn, and θ is the twist angle. In this case, the equation holds: tanθ=πd / I

[0008] It follows that the larger the diameter of the twisted yarn, the larger the twist angle. Furthermore, as already mentioned above, it is known that the characteristic behavioral properties of a twisted yarn depend on the twist angle. Thus, for example, it applies that the larger the twist angle, the stronger the twist.

[0009] It is desirable to keep the twist of the twisted yarns low, since this would normally result in the twisted yarns shrinking. Therefore, in a two-stage twist, i.e. a twist produced from rovings, the twist directions are always opposite to each other. Thus, as illustrated in FIG. 2, the rovings can be twisted in the S direction, and the finished yarns produced from several rovings can be twisted in the Z direction. Since the rovings naturally have a much smaller diameter than the finished yarns produced from these rovings, the number of twists per unit length of the rovings must be significantly greater than the number of twists per unit length of the finished yarns. Only in this way can a similar or identical twist angle be reached for the rovings, and thus similar or identical characteristic behavior properties be obtained. In particular, the twist of the rovings can thereby compensate for the twist that the finished yarns contain in the second twisting stage. As a result, the finished yarns can be placed on a flat base without preloading and without showing any tendency to shrink. For this reason, in two-stage twist spinning, the first number of twists per unit length is usually selected to always be greater than the second number of twists per unit length.

[0010] Indeed, from the field of automobile tire manufacturing, twisted yarns consisting of rovings with a first twist per unit length that is smaller than the twist per unit length of the finished yarn formed from a plurality of rovings already exist as reinforcing fibers. See, for example, the publication US Pat. No. 4,787,200 of Bridgestone Corporation. However, the construction of the reinforcing structure in automobile tires is fundamentally different from the construction described at the beginning of the reinforcing structure in press covers, so that the same problems do not arise here, in particular local overstresses at the intersections of longitudinal and circumferential fibers. In automobile tires, there are also usually no longitudinal fibers that are contacted from the radial outside by at least one circumferential fiber. The specific problems to be solved in this case are of a different nature, even if they ultimately aim at a longer service life of automobile tires. Therefore, the skilled person in the art of press covers has no motivation to use this prior art from a completely different technical field.

[0011] The same reasonably applies to the technical field of toothed belt manufacturing, as described, for example, in the publication EP 3 770 309 by Nippon Sheet Glass Co., Ltd.

[0012] In any event, those skilled in the art of press cover manufacturing have no apparent reason to select or specially manufacture twisted reinforcing fibers that deviate from conventional ground rules.

[0013] The inventors therefore made the merit of realizing that, when twisting the reinforcing fibers, the first number of twists per unit length is selected to be smaller than the second number of twists per unit length, nevertheless, in the press cover, there is an advantage in terms of resistance to overloads, whereby the tendency of the reinforcing fibers to crimp can be countered by a corresponding preload when embedding the reinforcing fibers in the polymer matrix.

[0014] Figure 3 shows a schematic diagram of a test setup for determining the radial hardness of a reinforcing fiber formed as a twisted yarn. The greater the radial deformation ΔL of a reinforcing fiber when a given force is applied (in this case 9.8 N), the softer this reinforcing fiber is in the radial direction.

[0015] The inventors have determined that a twisted yarn with a first twist per unit length selected smaller than a second twist per unit length behaves significantly softer in the radial direction at low preload than the same twisted yarn at high preload. Such a difference in hardness is significantly greater than in the case of conventionally used twisted yarns in which the first twist per unit length is selected larger than the second twist per unit length. In the press cover, such a behavior can be advantageously utilized. That is to say, in the press cover, the reinforcing fibers arranged radially further inwardly, which form the first tissue layer, in particular the longitudinal fibers extending in the axial direction of the press cover, are typically preloaded higher than at least one reinforcing fiber arranged radially further outwardly, in particular at least one circumferential fiber extending substantially in the circumferential direction. This makes it possible to achieve that, when using the same twisted fiber material, the at least one reinforcing fiber arranged radially further outwardly is radially softer than the reinforcing fiber arranged radially further inwardly.

[0016] This is advantageous, since the risk of cracks starting from the outer surface of the press cover, even if the press cover is subjected to overload, is reduced by the at least one reinforcing fiber that is made relatively soft and is arranged radially further outward. As the inventors have been able to observe, such cracks often start from the bottom of the grooves that such press covers are typically provided with in their outer surface. However, stress peaks in the polymer material of the press cover, especially at the bottom of the grooves, can be reduced if the at least one radially outer reinforcing fiber is made relatively soft.

[0017] At the same time, it has been determined that it is advantageous if the radially inner reinforcing fibers are designed as hard as possible, since these fibers are almost always the first to crack when passing through the mass, and this risk is countered if these fibers are designed to be correspondingly hard.

[0018] In tests it has been found to be advantageous for the first number of twists per unit length to correspond to 70% to 90% of the second number of twists per unit length, the first number of twists per unit length being preferably 70 to 90 turns per meter, more preferably 75 to 85 turns per meter, even more preferably 80 turns per meter.

[0019] For example, as is common in sewing threads, the first twist direction may be an S direction and the second twist direction may be a Z direction. Such an exemplary sewing thread is shown, for example, in FIG.

[0020] Unlike the case of the typical sewing thread shown in Fig. 2, it is preferred for the reinforcing fibres according to the invention if each roving is formed from two single fibres or fibre bundles and the finished twisted yarn is formed from three rovings. This results in a particularly stable reinforcing fibre. It is also desirable that the reinforcing fibre can withstand tensile forces, especially along its longitudinal extension.

[0021] As already mentioned above, it is highly advantageous in terms of manufacturing technology if the reinforcing structure according to the invention is formed as a fiber reinforcement comprising a first layer of longitudinal fibers extending in the axial direction of the press cover and a second layer of at least one circumferential fiber extending substantially in the circumferential direction of the press cover, the longitudinal fibers and the at least one circumferential fiber being arranged so as to be in contact with each other when viewed in the radial direction of the press cover. "Substantially in the circumferential direction" may in this case be understood to mean that at least one circumferential fiber extends in a spiral around the longitudinal axis of the press cover. It is also possible to provide the second layer with two or more circumferential fibers, which can be arranged relative to each other in the same way as in the case of a multi-threaded screw. Preferably, in this case the longitudinal fibers of the first layer and / or at least one circumferential fiber of the second layer correspond to at least one reinforcing fiber formed as a twisted thread.

[0022] In a development of this idea, it is proposed that the longitudinal fibres of a first layer of the press cover have a first prestress, whereas at least one circumferential fibre of a second layer has a second prestress, the first prestress being greater than the second prestress, preferably the first prestress corresponding to at least 7 times and / or at most 13 times the second prestress, resulting in the already mentioned further advantageous different hardness of the reinforcing fibres in both layers, even if the same fibre material is used in both layers.

[0023] In this case, it is sufficient for the entire reinforcing structure of the press cover to consist only of the first layer and the second layer.

[0024] It has been shown to be further advantageous if at least one reinforcing fiber formed as a yarn has a coating, which can promote bonding of the yarn with the polymer matrix surrounding it.

[0025] It is preferred if the at least one reinforcing fiber formed as a twisted yarn has a fineness of 800 dtex to 1500 dtex, preferably 1000 dtex to 1200 dtex, and even more preferably 1100 dtex. The unit dtex is an abbreviation of decitex, which is 1 / 10 tex, and the official tex system is a numbering of weight, i.e. the fineness of the yarn. In this case, the fineness is defined by the weight of a given length of yarn. tex represents how many grams 1 km of yarn has (for example, 1 dtex = 1 / 10 tex: 1 km of yarn is 10 g). If the reinforcing fiber is too fine, it cannot absorb the tensile forces in the press cover to the necessary extent. On the other hand, if the reinforcing fiber is too coarse, problems arise when bonding it to the polymer matrix.

[0026] It has proven to be advantageous if the rovings are each formed from a number of fibre bundles, each fibre bundle having 180 to 230 single filaments.

[0027] Preferably, all threads of the reinforcing structure of the press cover correspond to at least one reinforcing fiber formed as a twisted thread, this applies in particular with respect to the first number of twists per unit length and the second number of twists per unit length.

[0028] It is quite particularly preferred if all the threads of the reinforcing structure of the press cover are formed identically to one another, which makes it possible to purchase and incorporate large amounts of identical fiber material, thereby keeping the production costs of the press cover low.

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

[0030] Yet another aspect of the invention relates to a shoe press for processing a fibrous material web, in particular a paper web, a cardboard web or a tissue web, comprising a press roll and a counter roll forming or defining an extended press gap together, the press roll including a circumferentially surrounding press cover, the press cover being formed according to the invention.

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

[0032] In the following the invention is explained with reference to schematic drawings which are not to scale. [Brief description of the drawings]

[0033] [Figure 1] FIG. 1 is a principle diagram showing the general relationship between yarn diameter and twist angle. [Diagram 2] FIG. 1 shows an example of a typical twisted yarn, such as a sewing thread, in which three rovings twisted in the S direction are twisted together in the Z direction. [Diagram 3] FIG. 2 is a principle diagram for explaining how to determine the radial hardness of a reinforcing fiber. [Figure 4] FIG. 13 shows a comparison of radial hardness of various reinforcing fibers subjected to different preloads. [Diagram 5] FIG. 1 shows reinforcing fibers for a press cover according to the present invention. [Figure 6] FIG. 1 shows a shoe press with a press cover according to the present invention. [Figure 7] 1 is a principle diagram showing a manufacturing method for a press cover according to the present invention;

[0034] Figure 5 illustrates a reinforcing fiber 10 formed according to the invention for incorporation as a component part of a reinforcing structure 100 in a press cover 200 (see Figure 6) according to the invention. The reinforcing fiber 10 is formed as a twisted yarn, where first two fiber bundles 30 are twisted together in the S twist direction with a first twist per unit length to form a roving 20, and then three such rovings 20 made in the same way are twisted together in the Z direction with a second twist per unit length to form a finished yarn or reinforcing fiber 10. The reinforcing fiber 10 can then be further coated.

[0035] According to the invention, the first twist per unit length is smaller than the second twist per unit length. The first twist per unit length is in this example 80 turns per meter and the second twist per unit length is 100 turns per meter. Furthermore, the yarn has a fineness of 1100 dtex. The reinforcing fiber 10 according to the invention can therefore be characterized in the following abbreviated form: dtex1100×2×3 S80 / Z100.

[0036] This example of a reinforcing fiber 10 for press covers according to the invention, hereinafter referred to as AB-1, was tested for its radial hardness according to the test configuration described above with reference to FIG. 3 and compared with two examples of reinforcing fibers according to the prior art, AB-2 and AB-3. The reinforcing fibers according to AB-2 and AB-3 do indeed have the same basic structure as the example AB-1 (as shown in FIG. 5), but in these reinforcing fibers the first number of twists per unit length is greater than the second number of twists per unit length. In shorthand form, the reinforcing fiber according to AB-2 can be characterized as follows: dtex1100×2×3 S165 / Z150. And the reinforcing fibers according to AB-3 can be characterized as follows: dtex1100×2×3 S100 / Z80.

[0037] Thus, for AB-2, the first number of twists per unit length is 165 turns per meter and the second number of twists per unit length is 150 turns per meter, whereas for AB-3, the first number of twists per unit length is 100 turns per meter and the second number of twists per unit length is 80 turns per meter.

[0038] The results of this comparison are shown in Figure 4, where the X-axis shows the preload in Newtons (N) applied to the reinforcing fibers during testing. The Y-axis plots hardness from the Pussey & Jones (P&J) test. Note that in this case, a relatively small P&J value means a higher hardness than a relatively large P&J value.

[0039] As can be seen from FIG. 4, at a low preload of 4 N, the P&J hardness of the example AB-1 according to the invention is 34, which is clearly higher than that of AB-2 (only 21 in this case) and somewhat higher than that of AB-3 (32 in this case). In other words, the reinforcing fiber 10 according to the invention is relatively soft in the radial direction compared to the reinforcing fibers of the prior art at low preloads. However, at a significantly higher preload of 50 N, the P&J hardness of the example AB-1 according to the invention is only 20. This is therefore lower than that of AB-3 (24 in this case) and only slightly higher than that of AB-2 (18 in this case). In other words, the reinforcing fiber 10 according to the invention is harder in the radial direction than the reinforcing fibers of the prior art at high preloads, or at least as hard as the reinforcing fibers of the prior art.

[0040] Such a large deviation in the radial hardness of the reinforcing fibers 10 according to the invention is advantageously utilized in the press cover 200 according to the invention: in this case, several of these reinforcing fibers 10, which run parallel to the axis 1 of the press cover 200 as longitudinal fibers 220, form a first layer of the reinforcing structure 100. Furthermore, at least one of these reinforcing fibers 10, which is wound around the axis A radially outwardly in a spiral manner in the first layer as a circumferential fiber 230, forms a second layer of the reinforcing structure 100 (see FIG. 7). Preferably, the entire reinforcing structure 100 of the press cover 200 according to the invention consists exclusively of these two layers.

[0041] In this case, the press cover 200 can be produced as shown diagrammatically in FIG. 7. FIG. 7 shows in this case an apparatus for producing the press cover 200 according to the invention in a highly diagrammatic side view. The apparatus in this case has exactly one cylindrical winding mandrel. A plurality of reinforcing fibers 10 formed as longitudinal fibers 220 are arranged at a distance from one another on the periphery. On the radially outermost peripheral surface of the winding mandrel, a polymer is applied in order to provide a polymer layer 240. Additionally, circumferential fibers 230 are introduced, for example in a helical manner, into the polymer of the polymer layer 240. After being embedded in the polymer, the circumferential fibers 230 together with the longitudinal fibers 220 form the reinforcing structure 100 of the press cover 200 produced according to the invention. According to the invention, in this case the circumferential fibers 230 are in contact with the longitudinal fibers 220, i.e. there is no spacing between them, seen in the radial direction of the press cover 200.

[0042] The winding mandrel is supported so that it can rotate about a longitudinal axis that corresponds to the longitudinal axis A of the press cover 200 to be produced. In this case, the longitudinal axis extends perpendicularly into the plane of the drawing. A pourable, curable elastomeric polymer, for example polyurethane, is applied from above through a casting nozzle 310 via a line 300 onto the radially outermost periphery of the winding mandrel or onto the longitudinal fibers 220. When poured, the casting material can be selected, for example, for its drip time and viscosity, so that it does not run down the winding mandrel. Meanwhile, the winding mandrel rotates in the direction of the arrow about its longitudinal axis. Simultaneously with this rotation, the casting nozzle 310 is guided relatively along the winding mandrel along its longitudinal axis parallel to the longitudinal axis A via suitable guides, which are not further shown in FIG. 7. At the same time as pouring the casting material onto the surface, at least one circumferential fiber 230 is unwound and spirally wound onto the rotating winding mandrel to form a helix. In this case, the casting material can pass through the longitudinal fibers 220 and up to the winding mandrel. The polymer, in this example, forms a radially innermost and preferably elastomeric polymer layer, e.g., polymer layer 240, after a curing step. Additionally, if necessary, further polymer layers can be applied radially outward. However, preferably, all of the reinforcing structures 100 are completely embedded within the radially innermost polymer layer 240.

[0043] The casting material flowing out of the casting nozzle 6 is a mixture consisting of a prepolymer and a crosslinker. The prepolymer is provided from a prepolymer container (not shown) in which the prepolymer is stored or stirred. The prepolymer may comprise an isocyanate and a polyol according to the invention. In the prepolymer container, a prepolymer may be present, for example as a prepolymer consisting of the materials just mentioned. The crosslinker may be provided in a crosslinker container. The prepolymer container and the crosslinker container are assigned to an apparatus for producing the press cover 200. These containers are connected to a mixing chamber (not shown) which is connected upstream of the casting nozzle 310 in the flow direction so as to guide the flow via a pipe line, also not shown. The prepolymer-crosslinker mixture is produced, i.e. upstream, outside the casting nozzle 310, i.e. mixed in the mixing chamber. Independently of the production of the mixture, this mixture is then applied to the surface of the winding mandrel for the formation of at least one polymer layer of the press cover 200.

[0044] That is, by this continuous pouring process, also known as rotary casting, gradually across the width of the winding mandrel, an endless cylindrical press cover 200 is produced, closed about the longitudinal axis a, the inner circumferential surface of which substantially corresponds to the outer circumferential surface of the winding mandrel 4.

[0045] When the reinforcing structure 100 is embedded in the polymer layer 240, the longitudinal fibres 220 are preferably preloaded with a higher preload, for example a preload of 50 N, than the at least one circumferential fibre 230, which is preloaded with a preload of only 4 N. This results in the reinforcing fibres 10 according to the invention forming the first layer of the reinforcing structure 100 as the longitudinal fibres 220 being significantly stiffer than the at least one reinforcing fibre 10 according to the invention forming the second layer of the reinforcing structure 100 as the circumferential fibres 230. This has an advantageous effect on the resistance of the press cover 200 according to the invention when passing through a mass.

[0046] 6 shows a shoe press 500 in a schematic side view, partly in section, which in this case comprises a press roll 400 according to the invention, i.e. a shoe press roll, and a counter roll 450. The shoe press roll 400 and the counter roll 450 are arranged parallel to each other with respect to their longitudinal axes. Together the shoe press roll and the counter roll form or define an extended press gap 510.

[0047] In this case, the counter roll 450 consists of a cylindrically formed roll rotating about its longitudinal axis, and the shoe press roll 400 is composed of a shoe 410, a stationary yoke supporting said shoe, and a press cover 200 according to the invention. The shoe 410 and the yoke are arranged stationary with respect to the counter roll 450 or the press cover 200, meaning that they do not rotate. In this case, the shoe 410 is supported by the yoke and is pressed via a hydraulic pressing element (not shown) against the radially innermost surface of the press cover 200, which rotates relative to said shoe. The press cover 200, which circumferentially surrounds the shoe 410 and the yoke, rotates in this case about its longitudinal axis A in the opposite direction of rotation to the counter roll 450. A relatively long press gap 510 results due to the shoe 410 being concavely formed on the side facing the counter roll 450.

[0048] The shoe press 500 is particularly suitable for dewatering a fibrous material web FB. During operation of the shoe press 500, the fibrous material web FB with one or two press felts 520 is guided through the press gap 510. In this case, exactly two press felts 520 are used, which hold the fibrous material web FB in a sandwich-like manner between them. When passing through the extended press gap 510, the fibrous material web FB is indirectly subjected to pressure in the extended press gap 510 via the press felts 520. This is achieved by the radially outermost surface of the counter roll 450 on the one hand and the radially outermost surface of the press cover 200 directly contacting the corresponding press felts 520. The liquid flowing out of the fibrous material web FB is temporarily received by the one or two press felts 520 and by recesses, in particular grooves (not shown), which may be provided in the press cover surface. Liquid received in the recesses of the press cover 200 is expelled after exiting the extended press gap 510 and before the press cover 200 re-enters the press gap 510. Additionally, water absorbed by the press felt 520 can be removed by suction elements after exiting the press gap 510.

[0049] In another, not shown, embodiment of the invention, the press felt 520 can be omitted. In such a case, the fibrous material web FB is in direct contact with the press cover 200 on the one hand and with the counter roll 450 on the other hand, which together form a press gap 510. In this case, the counter roll can be configured as a heated dry cylinder. [Explanation of symbols]

[0050] 10 Reinforcing Fibers 20 Coarse thread 30 Fiber bundle 100 Reinforcement structure 200 Press Cover 220 Longitudinal Fibers 230 Circumferential Fiber 240 Polymer Layer 300 conduit 310 Casting Nozzle 400 (Shoe) Press Roll 410 Shoe 450 opposing roll 500 Shoe Press 510 (Extended) Press Gap 520 Press Felt A (press cover) axis AB-1 (according to the invention) Example 1 AB-2 (Prior Art) Example 2 AB-3 (Prior Art) Example 3 FB Fiber Web

Claims

1. A press cover (200), having at least one polymer layer (240) in which the reinforcement structure (100) is embedded; the reinforcing structure (100) is formed as a fiber reinforcement including a radially inner first layer of longitudinal fibers (220) extending in the axial direction of the press cover (200) and a radially outer second layer of at least one circumferential fiber (230) extending in a substantially circumferential direction of the press cover (200); A press cover (200) in which the longitudinal fibers (220) of the first layer, and preferably also the at least one circumferential fiber (230) of the second layer, are each formed as a reinforcing fiber (10), the reinforcing fiber being formed as a twisted yarn by first twisting together a plurality of single fibers or fiber bundles (30) in a first twist direction with a first twist number per unit length to form a roving (20), and then twisting together a plurality of such rovings (20) in a second twist direction opposite to the first twist direction with a second twist number per unit length; The press cover (200) is characterized in that the first number of twists per unit length is smaller than the second number of twists per unit length, and the longitudinal fibers (220) and the at least one circumferential fiber (230) are arranged so as to contact each other when viewed in the radial direction of the press cover (200).

2. 2. The press cover (200) of claim 1, wherein the first number of twists per unit length is equivalent to 70% to 90% of the second number of twists per unit length, and the first number of twists per unit length is preferably 70 to 90 turns per meter, more preferably 75 to 85 turns per meter, and even more preferably 80 turns per meter.

3. The press cover (200) of claim 1 or 2, wherein the first twist direction is an S direction and the second twist direction is a Z direction.

4. 3. A press cover (200) according to claim 1 or 2, wherein each roving (20) is formed from two monofilaments or fiber bundles (30), and the finished twisted yarn is formed from three rovings (20).

5. 3. The press cover (200) of claim 1 or 2, wherein the longitudinal fibers (220) of the first layer of the press cover (200) have a first preload, while the at least one circumferential fiber (230) of the second layer has a second preload, the first preload being greater than the second preload.

6. The press cover (200) of claim 5, wherein the first preload is at least seven times and / or at most thirteen times the second preload.

7. 3. The press cover (200) of claim 1 or 2, wherein the entire reinforcing structure (100) of the press cover (200) consists solely of the first layer and the second layer.

8. 3. The press cover (200) according to claim 1 or 2, wherein the at least one reinforcing fiber (10) formed as a twisted yarn has a coating.

9. 3. The press cover (200) according to claim 1 or 2, wherein the at least one reinforcing fiber (10) formed as a twisted yarn has a fineness of 800 dtex to 1500 dtex, preferably 1000 dtex to 1200 dtex, and more preferably 1100 dtex.

10. The press cover (200) according to claim 1 or 2, wherein each of the rovings (20) is formed from a plurality of fiber bundles (30), each fiber bundle (30) having 180 to 230 single filaments.

11. 3. The press cover (200) according to claim 1 or 2, wherein all threads of the reinforcing structure (100) of the press cover (200) correspond to at least one reinforcing fiber (10) formed as a twisted yarn.

12. 3. The press cover (200) according to claim 1 or 2, wherein all threads of the reinforcing structure (100) of the press cover (200) are formed identically to one another.

13. A press roll (400) for a shoe press (500) for treating a fibrous material web (FB), comprising: A press roll (400), characterized in that the press roll (400) comprises at least one press cover (200) according to claim 1 or 2.

14. A shoe press (500) for processing a fibrous material web (FB), in particular a paper web, a cardboard web, or a tissue web, comprising a press roll (400) and an opposing roll (450) forming or defining an extended press gap (510) together, the press roll (400) including a circumferentially surrounding press cover (200), A shoe press (500) characterized in that the press cover (200) is formed according to claim 1 or 2.

15. 3. Use of a press cover (200) according to claim 1 or 2 in a press, in particular a shoe press (500), for processing a fibrous material web (FB), in particular a paper web, a cardboard web or a tissue web.

Images