WO2021058171A1

WO2021058171A1 - Press jacket, use thereof, press roll, and shoe press

Info

Publication number: WO2021058171A1
Application number: PCT/EP2020/070504
Authority: WO
Inventors: Juanhao ZOU
Original assignee: Voith Patent Gmbh
Priority date: 2019-09-27
Filing date: 2020-07-21
Publication date: 2021-04-01
Also published as: DE102019126077A1

Abstract

The invention relates to a press jacket comprising at least one polymer layer in which a reinforcing structure is integrated. The reinforcing structure comprises at least one reinforcing thread, and the at least one reinforcing thread is made of multiple yarns, comprising at least one fiber or fiber bundle, twisted together in order to form a twine, wherein the twine (21a) has between one and four, preferably between two and three yarn windings, over a length of one centimeter.

Description

Press cover, its use as well as press roll and shoe press

The invention is based on a press cover, in particular for a press device for treating a fibrous web, e.g. for smoothing or dewatering it, in detail according to the independent claims. The invention also relates to a press roll, a shoe press and the use of a press jacket in such, in detail according to the independent claims. Press devices such as shoe presses have long been part of modern paper machines. They essentially comprise a stationary shoe (also called a press shoe), which extends in a cross-machine direction, and a press cover that encircles the stationary shoe. The latter is deformable and essentially assumes a tubular shape in operation. The shoe is shaped in such a way that it forms a press nip (press nip) with a counter roller. The press nip is defined by the contact surface of the counter roll in the shoe. The shoe is designed to be movable and can be moved to the counter roll.

Enormous demands are made on the press jacket with regard to its stability, namely with regard to surface hardness, resistance to pressure, temperature and hydrolysis. The press jacket is also exposed to strong alternating bending loads during operation. When entering the edge of the shoe - seen in the direction of rotation of the press jacket in front of the press nip - there is initially a bend under a relatively small radius. This immediately turns into a bend in the opposite direction when passing through the press nip. When it runs out at the other edge of the shoe, that is - after the press nip as seen in the direction of rotation of the press jacket - there is again a counter-bending. This deformation of the press jacket when it runs in and out is also referred to as a change nip. It is easy to see that the tendency of the press jacket to break, especially at this point, is very great due to the high mechanical stress. Accordingly, many measures are known from the prior art that the stability of the

Press jacket should increase. The press cover must therefore be sufficiently flexible so that it can be guided around the shoe, it must be sufficiently rigid so that it does not deform or compress too much in the nip under the press load, and it must be sufficiently wear-resistant. Press jackets therefore consist of a single or multi-layer polymer layer, preferably made of polyurethane, in which reinforcing threads in the form of scrims or fabrics can be embedded.

The present invention relates to such generic objects mentioned at the outset.

Press sleeves known from the prior art tend to premature failure during normal operation as a result of - often only local - overloading in the nip. This occurs when a foreign body passes through the nip during a so-called lump passage. Such an overload often leads to the reinforcement threads or the polymer layer in which they are embedded breaking. A press jacket that is oil-lubricated from the inside can leak, so that the oil comes into contact with the fibrous web to be produced. As a result, the press jacket must be changed. In practice, this leads to unplanned downtimes of the pressing device and thus to increased, costly downtimes.

It is the object of the invention to provide a press jacket which avoids the disadvantages of the prior art. In particular, even local damage to the press jacket as a result of overloading in normal operation is to be prevented. The press cover should therefore withstand such brief overloads and thus increase its service life and also reduce the downtimes of a press device equipped with such a press cover.

The object is achieved by the features of the independent claims. Particularly preferred and advantageous embodiments of the invention are given in the subclaims. The inventor has recognized that the press cover can compensate for local overloads better than the press cover known from the prior art if the reinforcement threads are specially designed. According to the invention, the reinforcing structure is made from at least one reinforcing thread, which itself is made from several yarns, comprising at least one fiber or fiber bundle (which in turn can be twisted to twisted yarns) by twisting one another to form a twisted yarn, the twisted yarn viewed over a length of one centimeter has between 1 and 4, preferably between 2.5 and 3.5 and preferably between 2 and 3 turns of the yarn. The contiguous turns of the individual yarns resulting from the twist are counted on the one centimeter.

Studies have shown that the use of the invention

Reinforcement threads embedded in a polymer layer, in addition to improved impact strength of the press jacket, also leads to a slight detachment of the polymer material from the reinforcement threads. In other words, the reinforcing threads according to the invention have a lower tendency to detach themselves less strongly from the polymer layer in which they are embedded in the event of a blob. The service life of such a press jacket is increased by a press jacket according to the invention. At the same time, the frequency of downtimes of a press device equipped with the press cover is reduced.

The definition that at least the longitudinal threads are produced as reinforcing threads according to the invention means that only the longitudinal threads are designed in this way or, in addition, the longitudinal threads and at least one further circumferential thread are produced in this way. If, for example, a scrim of circumferential and longitudinal threads is preferably present, this means that at least the longitudinal threads are designed according to the invention. A press jacket in the context of the invention is to be understood as a belt, hose or jacket which, as shown, is guided together with a fibrous web through the press nip of a shoe press. To drain the During normal operation, the fibrous web can come into contact with the radially outermost surface (polymer layer) of the press jacket with a press felt, by which the fibrous web to be dewatered is directly supported. Depending on the embodiment of the pressing device, the press cover can also come into direct contact with the fibrous web during normal operation, for example to smooth it. The press jacket is designed as a closed jacket (hose) which is endless in the circumferential direction around its longitudinal axis. At its axial ends it is open - viewed in the width direction (along the longitudinal axis). In this way, the press cover can be held at these axial ends by two lateral tensioning disks in order to form the shoe press roll. Instead of being guided by the two lateral tensioning disks, the press cover can be guided over the press shoe and several guide rollers, as is the case with open shoe presses. Regardless of whether the press cover is guided by the tensioning disks or the guide rolls, the press shoe (or the guide rolls) comes into contact (temporarily) with part of the radially innermost surface of the press cover. The radially outermost surface of such a press jacket, for example the radially outermost polymer layer of the same, can be provided with grooves and / or blind bores. The longitudinal direction means that direction which runs parallel to the longitudinal axis of the press jacket. The longitudinal axis also corresponds to the axis of symmetry or rotation of the finished press jacket or the press roll. The circumferential direction of the press jacket runs around the longitudinal axis, seen around its radial boundary. The term parallel also includes those angular deviations between two reinforcing threads lying in different planes of +/- 5 ° to one another.

The press jacket or the at least one polymer layer can be produced partially or completely from a polymer. A pourable, curable, preferably elastomeric polymer such as polyurethane can be used as the polymer. The polymer can consequently be set as a cast elastomer. By polymer layer is meant a layer which comprises such a pourable, curable, preferably elastomeric polymer or is produced entirely from it. The polymer layer can preferably be a cured layer produced in one piece by primary molding. In other words, it is originally formed in a monolithic manner, for example by casting. The term “one-piece” also includes cases in which the one layer was again produced from several layers of the same material when the polymer was cast. However, this is only insofar as these layers are essentially no longer visible after curing, but rather a single, preferably uniform layer results. The same applies accordingly to the finished press jacket.

When a plurality of polymer layers are provided, these can be arranged one above the other as seen in the radial direction - at least in sections over the width of the press jacket. At least in sections across the width of the press jacket means that the press jacket is, for example, only single-layered at its axial ends along the longitudinal axis of the press jacket, whereas it has two or more layers between the axial ends. However, the polymer layers can also extend over the entire width of the press jacket. The thickness of the press jacket - and thus the thickness of the individual polymer layers - can also vary in sections along the longitudinal axis in a section through its longitudinal axis. For example, the radially outermost polymer layer in the area of the width edges of the press jacket can be smaller than in the middle of the press jacket. In other words, the radially outermost polymer layer can be less thick in the region of the width edges than a radially inner or radially innermost polymer layer. Precisely one, two or three polymer layers are preferably provided. These can be identical in terms of their polymer or vary in terms of their hardness or stoichiometry of the prepolymer. A total thickness of the finished press jacket in a section through its longitudinal axis, measured in the radial direction, can be 5 to 10 mm, preferably 5 to 7, particularly preferably 5 to 6 mm. According to the invention, when a single layer is provided, the press jacket can be made from only one cast, ie monolithically, so that the single layer has the thickness just mentioned. A finished press cover within the meaning of the invention is one whose at least one polymer layer is cured and possibly finally processed, that is to say ready for use in, for example, a shoe press for the purpose mentioned at the beginning. Similarly, a finished polymer layer means a layer that has cured.

A reinforcing thread within the meaning of the invention is understood to be a pliable, textile line structure that has a dominant extension and uniformity in its longitudinal direction. The reinforcement thread is made from a plurality, that is to say at least two fibers or at least two fiber bundles, by twisting them together. When fiber is mentioned, a single, endless fiber in the manner of a monofilament is meant. If, on the other hand, a fiber bundle is spoken of within the meaning of the invention, it is not a question of monofilaments but, in turn, a single thread, such as a twine, that is, a bundle of continuous fibers or monofilaments. The fiber bundles themselves can be made from fibers twisted together.

The term reinforcement structure in the context of the invention means reinforcement of the at least one layer containing or consisting of the polymer - that is to say the polymer layer. The reinforcement structure can be completely embedded in the polymer layer, so that the reinforcement structure does not go beyond the delimitation of the polymer layer. In other words, the polymer layer takes on the role of a matrix which surrounds the reinforcement structure and binds to the matrix as a result of adhesive or cohesive forces. Such a reinforcement structure can be textile line structures - z. B. yarns or twisted threads - and / or textile fabrics - such. B. fabrics, knitted fabrics, knitted fabrics, braids or scrims - comprise and can be produced from a corresponding starting material, for example by winding. In other words, a single reinforcing thread according to the invention is, considered in and of itself, a textile line structure. Several such reinforcing threads can be designed, for example, as longitudinal and / or circumferential threads, so that together they form a textile fabric. The at least one reinforcement thread, which is embedded in the at least one polymer layer, then represents the reinforcement structure of the press jacket or its polymer layer. Starting material is understood to mean that material or semi-finished product by means of which the reinforcement structure of the finished press jacket according to the invention is produced. Twisting is understood to mean that process in which individual fiber bundles are twisted together. In the manufacture of ropes, twisting corresponds to what is known as beating.

In principle, it is conceivable that the individual fibers or fiber bundles of a respective reinforcement thread can be interwoven around a core, as is the case, for example, with dynamic ropes such as climbing ropes. The core can be made of a different material than that of the fiber or the fiber bundle. It can, for example, have a higher elasticity in order to temporarily store the energy in the soul in the same way as climbing ropes in the event of overload, so that the entire reinforcement thread becomes longer but thinner in the event of local overload.

The reinforcement thread or the reinforcement structure can be produced from a polymer or comprise such a polymer. Polymers are polyester, polyethylene naphthalate or polyamides, such as aramids.

In the context of the invention, a pressing device means, for example, a shoe press, for example for dewatering or treatment, such as smoothing a fibrous web. The shoe press comprises a shoe press roll and a counter roll, which together form or delimit a press nip. The shoe press roll further comprises a revolving press cover and a standing press element, the so-called press shoe. The latter is supported on a supporting, also standing yoke - for example via hydraulic press elements - and is pressed against the surrounding press casing. The press jacket rotates relative to the stationary press shoe and yoke and is thereby pressed against the counter roll in the press nip. The press shoe and yoke are arranged radially inside the press jacket. The term is understood to mean that the press element does not rotate relative to the shoe press roll or the counter roll, but can move in a translatory manner - towards the counter roll and away from it, preferably in the radial direction thereof - and thus relative to the counter roll. In addition to the fibrous web and the press cover, one or more press felts running continuously in the circumferential direction and / or further continuously running press belts can be guided through the press nip of the shoe press. Such a shoe press can of course comprise more than one press nip.

A fibrous web within the meaning of the invention is a scrim or tangle of fibers such as wood fibers, plastic fibers, glass fibers, carbon fibers,

To understand additives, additives or the like. For example, the fibrous web can be designed as a paper, cardboard or tissue web. It can essentially comprise wood fibers, small amounts of other fibers or also additives and additives being able to be present. Depending on the application, this is left to the specialist.

If several reinforcement threads are preferably embedded as longitudinal threads and at least one reinforcement thread as circumferential thread, which surrounds the longitudinal threads in the circumferential direction, as a scrim in the polymer layer, the advantages according to the invention are fulfilled particularly well. Because a clutch is able to absorb local overloads particularly well.

The advantages according to the invention are achieved particularly well if the press cover is constructed from preferably several polymer layers arranged one above the other in the radial direction. If two polymer layers are provided, then the radially inner one is that with the reinforcement structure according to the invention. This means that the reinforcement structure is only arranged in the radially innermost polymer layer. If three or more polymer layers are provided, then the reinforcement structure is preferably arranged in the second lowermost polymer layer, that is to say in that which lies radially above the radially innermost polymer layer. The invention also relates to a press roll, such as a shoe press roll, for a shoe press for dewatering a fibrous web, the press roll having at least one press cover according to the invention. The invention also relates to a shoe press for dewatering a fibrous web, preferably a paper, cardboard, tissue or cellulose web, comprising a press roll and a counter roll which together form or delimit a nip, the press roll comprising a circumferential press cover, the press cover is designed according to the invention.

Finally, the invention relates to the use of a press jacket according to the invention for a press, such as a shoe press, for dewatering a fibrous web, preferably a paper, cardboard, tissue or cellulose web. The invention is explained in more detail below with reference to the drawings without restricting the generality. In the drawings show:

1 shows a partially sectioned, schematic side view of a shoe press with a press cover according to an exemplary embodiment of the present invention.

2a and 2b, embodiments of a press jacket, each seen in a section through its longitudinal axis; Fig. 3 is a highly schematic representation of a device for

Fierstellung of the press jacket in a side view;

4 shows a greatly simplified representation, not to scale, of an end of a reinforcing thread according to the invention.

In Fig. 1, a partially sectioned, schematic side view of a shoe press 10 is shown, which in the present case a press roll according to the invention, such as shoe press roll 12, and a counter roll 14. Shoe press roll 12 and counter roll 14 are arranged parallel to one another with regard to their longitudinal axes. Together they form a nip 22 or delimit one. While the counter roll 14 here consists of a cylindrical roll rotating around its longitudinal axis, the shoe press roll 12 is composed of a shoe 16, an upright yoke 18 carrying it, and a press cover 20. Shoe 16 and yoke 18 are arranged in a fixed manner with respect to counter roll 14 and press cover 20, respectively. That means they don't rotate. In this case, the shoe 16 is supported by the yoke 18 and is pressed against the radially innermost surface of the press jacket 20, which is circumferential relative thereto, via hydraulic press elements (not shown). The press jacket 20, which surrounds the shoe 16 and yoke 18 in the circumferential direction, rotates about its longitudinal axis in the opposite direction of rotation to the counter roll 14. The concave design of the shoe 16 on its side facing the counter roll 14 results in a comparatively long nip 22.

The shoe press 10 is particularly suitable for dewatering fibrous webs 24. When the shoe press is in operation, a fibrous web 24 with one or two press felts 26, 26 ′ is passed through the press nip 22. In the present case there are exactly two press felts 26, 26 'that sandwich the fibrous web 24 between them. When passing through the nip 22, a pressure is exerted indirectly in the nip 22 on the fibrous web 24 by the press felts 26, 26 '. This takes place in that the radially outermost surface of the counter roller 14 on the one hand and the radially outermost surface of the press jacket 20 come into direct contact with the corresponding press felts 26, 26 '. The liquid emerging from the fibrous web 24 is temporarily absorbed by the press felt (s) 26, 26 'and any depressions (not shown) provided in the press jacket surface. After leaving the nip 22, the liquid absorbed by the depressions in the press jacket 20 is thrown off before the press jacket 20 re-enters the press nip 22. In addition the water taken up by the press felt 26, 26 ′ can be removed with suction elements after leaving the press nip 22.

In a further embodiment of the invention not shown in the figures, the press felts 26, 26 'can be dispensed with. In such a case, the fibrous web 24 is in direct contact on the one hand with the press jacket 20 and on the other hand with the counter roll 14, which together form a press nip. The latter can then be designed as a heated drying cylinder. The press jacket shown in FIG. 1 can, as shown in the following figures, be designed according to the invention.

2a and 2b show different embodiments of the invention in a not to scale, partially shown cross section through the longitudinal axis 20 'of the finished press jacket 20. The distance between the longitudinal axis 20 'and the radially innermost surface of the corresponding polymer layer of the press jacket 20 is also not shown to scale.

The illustration in FIG. 2a shows a press jacket 20 with a single polymer layer 20.1. A reinforcing structure 20 ″ is embedded in this. In the present case, the polymer layer 20.1 is made from a polyurethane. This is obtainable from a prepolymer and a crosslinker.

According to the illustration in FIG. 2b, exactly two polymer layers are provided in solid lines, namely a first 20.1 and a second 20.2. In the present case, the first polymer layer 20.1 is also the radially outermost polymer layer of the press jacket 20. The arrangement relates - as in the illustration in FIG. 2a - starting from the longitudinal axis 20 'of the press jacket 20 in its radial direction. In contrast, the second polymer layer 20.2 is at the same time the radially innermost polymer layer of the press jacket 20. Both

Polymer layers 20.1, 20.2, viewed in the radial direction, directly adjoin one another, that is to say there is no intermediate layer between these two. In A third polymer layer 20.3 is also indicated by dashed lines. The latter is arranged radially inside the second polymer layer 20.2. In the present case, a (single) reinforcement structure 20 "is only provided in the second polymer layer 20.2. Of course, this could also be different, so that, alternatively or in addition, such a reinforcement structure 20" could also be arranged in the first polymer layer 20.1 and / or the third polymer layer 20.3. Here, too, the first and second polymer layers 20.1, 20.2 are each made of a polyurethane or contain one. This also applies analogously to FIG. 2a.

The reinforcement structure 20 ″ in the two embodiments of FIG. 2 is completely embedded in the corresponding polymer layer 20.1 or 20.2. This means that the reinforcement structure 20 ″ does not extend beyond the boundaries of the polymer layer 20.1, 20.2. In principle, it would be conceivable that the reinforcement structure 20 ″ would go beyond the delimitation of two directly adjacent polymer layers 20.1, 20.2, 20.3. In other words, the reinforcement structure 20 ″ would be embedded in two adjacent polymer layers 20.1, 20.2, 20.3 at the same time. The reinforcement structure 20 ″ can consist of a plurality of reinforcement threads 21 in the form of longitudinal threads 21.1. These run parallel to the longitudinal axis 20 'of the press jacket 20 and are spaced apart from one another over its circumference. This can best be seen in FIG In addition, one or more reinforcing threads 21 designed as circumferential threads 21.2, each spirally over the circumference of the corresponding polymer layer 20.1, 20.2, can be provided, see again FIG. 2. The latter are shown in FIGS. 2a and 2b with broken circles In the illustration of FIG. 2, the plurality of longitudinal threads 21.1 and the at least one circumferential thread 21.2 form a scrim with one another. The circumferential threads 21.2 are arranged in such a way that they surround the longitudinal threads 21.1, that is to say are arranged further radially outward than the longitudinal threads 21.1. Longitudinal threads 21.1 and the at least one circumferential thread 21.2 cross over, viewed in the radial direction, as a result of the spiral winding of the at least one circumferential thread 21.2. Viewed in the radial direction (that is to say in the sectional view of Fog. 2a and b), however, they do not touch at these intersection points but are arranged at a distance from one another. This has the advantage that a better force distribution of local overloads acting radially on the outside on the press jacket 20 in the radially inward direction is transmitted to the longitudinal threads 21.1 via the at least one circumferential thread 21.2. As indicated in FIG. 2, the radially outermost surface of the press jacket

20 or the corresponding polymer layer 20.1 have grooves or blind bores.

4 shows a greatly simplified, not to scale representation of part of a reinforcing thread 21 according to the invention, which can be designed as a longitudinal thread 21.1 and / or circumferential thread 21.2. It can be used in the reinforcement structure 20 ″ of the press jacket 20, as set out in the preceding figures. For the sake of clarity, the illustration shows how such a reinforcement thread

21 is made.

In the illustration of FIG. 4, the reinforcing thread 21 is made by twisting several, here three threads 23, 24 and 25 to form a thread 21a. However, fewer or more than three yarns could also be twisted into such a thread. The yarns 23, 24 and 25 are made from fibers or fiber bundles 22. Such a fiber bundle 22 is at the right end of the illustration of FIG. 4 by individual lines which the

Represent fibers, partially indicated. For this purpose, the yarns 23, 24 and 25 are twisted together to form the thread 21a. The thread 21a thus corresponds to the reinforcement thread 21. The thread 21a can have between 1 and 4, preferably between 2 and 3, turns of the thread over a length of one centimeter. In the present illustration of FIG. 4, the reinforcing thread, that is to say the thread 21a, has exactly 3 turns per centimeter of length.

It has been shown that the use of reinforcing threads 21 according to the invention, embedded in a polymer layer 20.1, 20.2, 20.3, leads not only to improved impact strength of the press jacket but also to a slight detachment of the material of the polymer from the reinforcing threads. The service life of such a press jacket is increased by a press jacket according to the invention. At the same time, the frequency of downtimes of a press device equipped with the press cover is reduced.

The reinforcing thread 21 can be a double-twisted thread. This means that the fibers of the fiber bundles 22 are themselves made from yarns by twisting them into a twisted thread (not shown).

3 shows, in a highly schematic side view, a device for producing a press jacket 20 according to the invention. In the present case, the device has precisely one cylindrical winding mandrel 4. A plurality of reinforcing threads 21 designed as longitudinal threads 21.1 are spaced from one another on the circumference. A polymer is applied to the radially outermost circumferential surface of the winding mandrel 4 in order to apply a polymer layer 20.1, 20.2, 20.3 - as described in the preceding figures. In addition, a circumferential thread 21.2, for example, is introduced spirally into the polymer of the polymer layer 20.1, 20.2, 20.3. After embedding in the polymer, the circumferential thread 21.2 together with the longitudinal threads 21.1 forms the reinforcement structure 20 ″ of the finished press casing 20 according to the invention. The winding mandrel 4 is rotatably mounted about its longitudinal axis 20 ', which corresponds to the longitudinal axis of the press casing to be produced. Longitudinal axis 20' runs here perpendicular into the plane of the drawing. A line 5 is passed through a Casting nozzle 6, the casting material, such as castable, curable elastomeric polymer, for example polyurethane, is placed from above onto the radially outermost lateral surface of the winding mandrel 4 or onto the longitudinal threads 21.1. Such a casting material can be selected, for example with regard to its pot life and viscosity, in such a way that it does not drip down from the winding mandrel 4 during casting. Meanwhile, the winding mandrel 4 is rotated in the direction of the arrow about its longitudinal axis. Simultaneously with this rotation, the casting nozzle 6 is guided along a suitable guide, not shown in further detail in FIG. 3, parallel to the longitudinal axis 20 ′ along this relative to the winding mandrel 4. At the same time as the casting material is poured on, the at least one circumferential thread 21.2 is unrolled and spirally wound onto the rotating mandrel 4 to form coils. The casting material can reach the winding mandrel 4 through the longitudinal threads 21.1. In this example, after the curing step, the polymer forms a radially innermost and preferably elastomeric polymer layer which, for example, corresponds to the polymer layer 20.1 of the press jacket from FIG. 2a, only a part of which is shown in FIG.

The casting material emerging from the casting nozzle 6 is a mixture of a prepolymer and a crosslinker. The former 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. It can be present in the prepolymer container, for example, in the form of a prepolymer made from 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 a press jacket 20. They are connected in a flow-conducting manner to a mixing chamber (not shown) connected upstream of the pouring nozzle 6 in the direction of flow via lines, which are likewise not shown. The prepolymer / crosslinker mixture is thus produced upstream and outside of the pouring nozzle 6, that is to say is mixed in the mixing chamber. Independently of the production of the mixture, it is then applied to the surface of the winding mandrel 4 in order to form the at least one polymer layer of the press jacket 20. By means of such a continuous casting process, which is also known as rotary casting, an endless, cylindrical tubular press jacket 20, which is closed around its longitudinal axis 20 'and whose inner circumference essentially corresponds to the outer circumference of the winding mandrel 4, is gradually produced over the width of the winding mandrel 4 .

In principle, it would be conceivable to wind the reinforcing threads 21 on more than the one winding mandrel 4 shown in FIG. 3. For example, two winding mandrels could be provided, which could be arranged parallel with respect to their longitudinal axes at a distance from one another. Alternatively, it would also be conceivable to also apply the polymer to the radially inner circumferential surface of the winding mandrel 4, e.g. in the manner of spinning. Regardless of the embodiment mentioned, the finished press cover 20 is finally removed from the at least one winding mandrel 4. As shown in FIG. 3, the press jacket 20 is designed according to the invention.

Although this is not shown in the figures, the reinforcement structure 20 ″ of the at least one polymer layer 20.1, 20.2 could also be made up of several layers of longitudinal and circumferential threads 21.1, 21.2, superimposed in the radial direction, each extending in the longitudinal axis direction and in the circumferential direction of the press jacket 20 be.

Claims

1. Press jacket comprising at least one polymer layer (20.1, 20.2, 20.3) in which a reinforcing structure (20 ") is embedded, the reinforcing structure (20") comprising at least one reinforcing thread (21), the at least one reinforcing thread (21) itself is made from several yarns (23, 24, 25), each comprising at least one fiber or fiber bundle (22) by twisting them together to form a thread (21a), the thread (21a) preferably being between 1 and 4 over a centimeter length has between 2 and 3 turns of the yarn.

2. Press cover according to claim 1, characterized in that the at least one fiber bundle (22) is itself produced by twisting the individual fibers with one another to form a thread.

3. Press cover according to claim 1 or 2, characterized in that the at least one reinforcement thread (21) is provided as a longitudinal thread (21.1) which runs in the longitudinal direction of the press cover (20) and preferably several reinforcement threads (21) as longitudinal threads (21.1) are provided, which are arranged running in the longitudinal direction of the press jacket (20) over the circumference of the press jacket (20) at a distance from and parallel to one another.

4. Press cover according to one of claims 1 to 3, characterized in that at least one further reinforcing thread (21) is provided as a circumferential thread (21.2), which preferably runs helically in the circumferential direction of the press jacket within the polymer layer (20.1, 20.2, 20.3).

5. Press cover according to claim 4, characterized in that the reinforcement threads (21) designed as a longitudinal thread (21.1) and the at least one further reinforcement thread (21) designed as a circumferential thread (21.2) form a scrim with one another, preferably in such a way that the longitudinal threads (21.1 ) are arranged radially within the at least one circumferential thread (21.2) - viewed in relation to the longitudinal axis (20 ') of the press jacket.

6. Press cover according to claim 5, characterized in that seen in the radial direction on the press cover (20) the longitudinal threads (21.1) are spaced apart from the at least one circumferential thread (21.2) at intersections in the radial direction.

7. Press jacket according to one of the preceding claims, comprising at least one, - viewed with respect to the longitudinal axis (20 ') of the press jacket (20) - radially outermost polymer layer (20.1) and one with respect to the longitudinal axis (20') of the press jacket ( 20) in this regard, radially inner polymer layer (20.2), the radially inner polymer layer (20.2) being designed according to one of the preceding claims.

8. Press cover according to claim 7, characterized in that exactly two

Polymer layers (20.1, 20.2) are provided and the radially inner

Polymer layer (20.2) is at the same time the radially innermost polymer layer of the press jacket (20).

9. Press roll, such as shoe press roll (12), for a shoe press (10) for

Treatment of a fibrous web (24), characterized in that the press roll has at least one press cover (20) according to one of the preceding claims.

10. Shoe press (10) for treating a fibrous web (24), preferably one

Paper, cardboard, tissue or cellulose web, comprising a press roll and a counter-roll (14) which together form or delimit a nip (22), the press roll comprising a rotating press cover, characterized in that the press cover (20) according to one of claims 1 to 8 is formed.

11.Use of a press jacket (20) according to one of claims 1 to 8 for a press, such as a shoe press (10) for treating a fibrous web (24), preferably a paper, cardboard, tissue or cellulose web.