CN114450448A - Shoe press, method for operating same, machine comprising same and use of dye in lubricating fluid thereof - Google Patents

Abstract

The invention relates to a method for operating a shoe press, wherein the shoe press has a press shoe on which a press sleeve slides with its radially inner surface, wherein the press sleeve has at least one polymer layer, in which a reinforcing structure is embedded for the lubrication of a lubricating fluid between the press shoe and the press sleeve, wherein the reinforcing structure comprises at least one reinforcing thread, wherein the lubricating fluid, the at least one polymer layer and/or the at least one reinforcing thread are arranged in such a way that, in the event of a break in the polymer layer, the lubricating fluid reaches the at least one reinforcing thread of the reinforcing structure and can cause a color change of the at least one reinforcing thread. The invention also relates to a shoe press and the use of a press sleeve in such a machine and to a machine comprising such a shoe press.

Description

Shoe press, method for operating same, machine comprising same and use of dye in lubricating fluid thereof

The invention relates to a press sleeve, in particular for a press device for treating a fibrous web, for example for calendering or dewatering of a fibrous web, in particular a press sleeve according to the independent claim. The invention also relates to a shoe press and to the use of a press sleeve in such a shoe press and to a machine comprising such a shoe press, in particular according to the side-by-side claims.

Pressing apparatuses, such as shoe presses, have long been an integral part of modern paper machines. A press apparatus essentially comprises a fixedly arranged press shoe (also called press shoe) extending in the cross-machine direction and a press sleeve running around the fixed press shoe. The latter is deformable and in operation takes a substantially tubular shape. The press shoe is shaped in such a way that it forms a press nip with the mating roll. The press nip is defined by the contact surface of the mating roll on the press shoe. The press shoe is designed to be movable and can be moved onto the mating roll.

The press sleeves are subject to great demands with regard to their stability, namely with regard to surface hardness, compressive strength, heat resistance and hydrolysis resistance. Furthermore, the press sleeve is subjected to strong alternating bending loads during operation. When introduced at the edge of the press shoe before the press nip, viewed in the direction of rotation of the press sleeve, deflection occurs first with a relatively small radius. The deflection immediately becomes a reverse deflection when passing through the press nip. When exiting at the other shoe edge, i.e. the edge of the press shoe after the press nip, viewed in the direction of rotation of the press sleeve, a deflection in the opposite direction is again formed. This deformation of the press sleeve during the introduction and withdrawal is also referred to as the alternating nip. It is readily apparent that the tendency of the press sleeve to break, particularly at this location, is very great due to the high mechanical stresses. Accordingly, a number of measures are known from the prior art which are intended to increase the stability of the press sleeve.

The press sleeve must therefore be sufficiently flexible so that it can be guided around the press shoe, sufficiently hard so that it does not deform or compress too severely in the press nip under pressure load, and sufficiently wear-resistant. The press sleeve therefore consists of one or more polymer layers, preferably made of polyurethane, in which reinforcing threads in the form of a scrim or woven fabric can be embedded.

The invention relates to a subject matter of the type mentioned at the beginning.

The press sleeves known from the prior art are prone to premature failure during regular operation due to the usually only local overload in the press nip. This occurs when foreign bodies pass through the pressure zone in the so-called wet-matter covering process (batzenendurchgan). Such overloading typically results in tearing of the reinforcing strands or the polymer layer in which the reinforcing strands are embedded. For example, a press sleeve lubricated with oil from the inside may become unsealed, so that the oil comes into contact with the fibrous web to be produced. Therefore, the press sleeve must be replaced. This in practice leads to unplanned shutdowns of the press plant and thus to costly, increased down times.

The object of the invention is therefore to provide a press sleeve which avoids the disadvantages of the prior art. In particular, complete failure of the press sleeve due to overload during regular operation, even only partial damage to it, or early detection of such consequences, should be prevented. In particular, the downtime of a press equipped with such a press jacket should be reduced.

This object is achieved by the features of the independent claims. Particularly preferred and advantageous embodiments of the invention are given in the dependent claims.

The inventors have realized that a local overload that has occurred can be better identified on the press sleeve if the lubricating liquid, the reinforcing fibers or both the lubricating liquid and the reinforcing fibers are coordinated or arranged in such a way that the reinforcing fibers can change color in case of a break of the polymer layer in which the reinforcing fibers are arranged. This occurs when the polymer layer breaks, as the reinforcing fibers are now in contact with the lubricating fluid. Upon such contact, for example, a chemical reaction occurs between the two objects, so that discoloration occurs. In this case, it is conceivable, for example, for the reinforcing fibers to be coated with a dye or to contain such a dye, which dye only leads to a (local) discoloration of the reinforcing fibers when it comes into contact with the lubricating fluid. In addition or alternatively thereto, the dye may be comprised in the lubricating liquid, for example by incorporating the dye into the lubricating liquid. Regardless of how the color change occurs, it may be a permanent color change.

The dye may be a dye that reacts with a luminescent or luminescent agent. Luminescence or luminescence means that the energy input to the dye from the outside is not converted completely or partially into thermal energy, but rather the dye is brought into an excited state and emits light (including radiation outside the visible range of the human eye). Luminescence can be divided into two ranges, fluorescence and phosphorescence. Fluorescence is the light that is spontaneously emitted shortly after the material is excited by an electron transition. Here, the emitted light generally has less energy than the previously absorbed light. In contrast, phosphorescence is a property of a substance to re-emit light in the dark after being irradiated with light (visible light or ultraviolet light). The dye that may be added to the lubricating fluid may be a luminescent, i.e. fluorescent or phosphorescent, dye.

Thus, the press sleeve may be illuminated or transilluminated with light, such as an LED light source or a laser. The light may be light invisible to the human eye, such as ultraviolet light. The dye may be chosen such that it has luminescence, i.e. light which is just visible to the human eye due to illumination by light which is not visible to the human eye. The press sleeve can then be illuminated optically by means of light, for example to detect a possible local overload of the press sleeve at a creep speed of the machine, at which the press sleeve rotates at a slower speed than in the intended operation of the machine for producing the fiber web. The pressure sleeve can then be replaced accordingly, so that the subsequent loss of lubricant from the pressure sleeve can be avoided at an early stage. The input of energy, for example in the form of light, from the outside can take place either inside the radial extension of the press sleeve (i.e. from the inside) or outside this radial extension (i.e. outside the press sleeve). The radial extension is with reference to the longitudinal axis of the press sleeve. Accordingly, the energy source may be arranged inside or outside the press sleeve.

In principle, the same applies with regard to the addition of dyes to the lubricating fluid, if the respective dye is not added to the lubricating fluid itself, but to the polymer layer or the reinforcing thread, in order to discolor the at least one polymer layer or the reinforcing structure.

The lubricating fluid may be oil, such as hydraulic oil.

Advantageously, there is a sufficiently large optical contrast between the reinforcing structure and the at least one polymer layer embedding the reinforcing structure. Since if the overload is large enough it will usually lead to local damage of the reinforcing structure, for example in the form of a break in the wire. The broken thread can then be better recognized by the human eye, so that a planned, early change of the press sleeve can be carried out. I.e. an early change of the press sleeve still takes place before the press sleeve becomes unsealed and the lubricating liquid reaches the fibrous web to be produced.

In order to achieve a sufficiently large optical contrast, the materials of the reinforcing structure and the at least one polymer layer may be chosen such that their transmittances for visible light differ from each other. If the transmittance of the material of the at least one polymer layer is selected to be higher than the transmittance of the material of the enhancement structure, the enhancement structure can be illuminated through the polymer layer under corresponding lighting conditions. It can also be said that the material of the at least one polymer layer is more transparent or light-transmitting (and thus less opaque) than the material of the reinforcing structure.

Alternatively, a sufficient optical contrast can be produced if the materials of the reinforcing structure and the at least one polymer layer are selected such that the transmission of visible light of the entire press sleeve is between 15% and 90%, preferably between 15% and 35%.

In optics, transmittance describes the proportion of incident radiation flux or luminous flux that penetrates completely through a transparent component. An incident radiation flux impinging on the component may be transmitted, reflected and absorbed by the component. Thus, the following power balance consisting of transmittance (T), reflectance (R) and absorptance (a) of the radiation flux impinging on the assembly is obtained

R+A+T＝1，

They are divided into each other according to the material properties of the components. The transmission therefore corresponds to that part of the incident radiation flux that is reduced in reflectivity (R) and absorption (a). Another name for transmittance is the term "total transmittance T_t". The latter or transmittance corresponding to the incident radiation flux T₁And the radiation flux T through the transparent component₂The ratio of the reciprocal of (i.e. T)₂/T₁. Thus, if we say that a material such as at least one of the polymer layers has a transmission of 50%, it will only let half the incident radiation flux pass. The transmittance or total transmission is defined and measurable according to ASTM D1003-00. TheThe measurement can be carried out at any point on the press sleeve, for example also at its axial edge, for example in the region of tabs by means of which the press sleeve is fixed to the two lateral clamping disks. The transmittance data can be referred to in this case as the press sleeve just after the factory, i.e. the finished product.

These two definitions are intended to express the fact that the press sleeve is sufficiently transparent to allow better visibility of the discoloration of the reinforcing cords when the at least one polymer layer embedding the reinforcing structure is broken. It can also be said that the one polymer layer or the press sleeve itself is undyed.

A press sleeve according to the invention is to be understood as meaning a closed belt, hose or sleeve which is endless in the circumferential direction about its longitudinal axis and which, as shown, is guided through the nip (press nip) of a shoe press together with the fibrous web. In order to dewater the fibrous web, the radially outermost surface (polymer layer) of the press sleeve can be brought into contact with a press felt during the intended operation, by which press felt the fibrous web to be dewatered is directly supported. Depending on the embodiment of the press, the press sleeve can also be brought into direct contact with the fiber web during the intended operation, for example for calendering the fiber web. The press sleeve is open at its axial ends, viewed in the width direction (along the longitudinal axis). Thus, the press sleeve can be held at the axial end by two lateral clamping discs, so as to form a shoe press roll. Instead of being guided through the two lateral clamping disks, the press sleeve can also be guided through the press shoe and a plurality of guide rollers, as is the case in open-type shoe presses. Whether the press sleeve is guided through the clamping disk or the guide roller, the press shoe (or guide roller) is (temporarily) in contact with a portion of the radially innermost surface of the press sleeve. The radially outermost surface of such a press sleeve, i.e. its, for example, radially outermost polymer layer, may be provided with grooves and/or blind holes.

Longitudinal refers to a direction extending parallel to the longitudinal axis of the press sleeve. The longitudinal axis corresponds at the same time to the axis of symmetry or rotation of the finished press sleeve or roll. The circumferential direction of the press sleeve extends around the longitudinal axis, viewed around its radial boundary. The term "parallel" also includes angular deviations of +/-5 deg. between two reinforcing wires located in different planes.

The press sleeve or the at least one polymer layer may be partly or completely made of a polymer. As polymers, use may be made here of pourable, curable, preferably elastomeric polymers such as polyurethanes. The polymer may thus be provided as a cast elastomer.

By polymer layer is meant a layer comprising or made entirely of a pourable, curable, preferably elastomeric, polymer. The polymer layer may preferably be a cured layer made in one piece by a molding process. In other words, the polymer layer is integrally molded, i.e. made, for example, by casting. The term "one-piece" also includes the case where the one layer is again made of multiple layers of the same material as the polymer is cast. However, this is limited to the fact that after curing, these layers can no longer be seen substantially, but rather only produce a preferably uniform layer. The same applies correspondingly to the finished press sleeve.

If a plurality of polymer layers is provided, these can be arranged one above the other, at least in regions, viewed in the radial direction, over the width of the press sleeve. At least partially over the width of the press sleeve means that the press sleeve is only single-layered, for example at its ends along the longitudinal axis of the press sleeve, while it is designed in two or more layers between the axial ends. The polymer layer may also extend over the entire width of the press sleeve. The thickness of the press sleeve, and thus of the individual polymer layers, can also vary locally along the longitudinal axis in a section through its longitudinal axis. Thus, for example, the radially outermost polymer layer can be smaller in the region of the width edges of the press sleeve than in the middle of the press sleeve. In other words, the radially outermost polymer layer in the region of the width edge may be smaller than the radially inner or radially innermost polymer layer thickness. Preferably exactly one, two or three polymer layers are provided. They can be designed identically in their polymer mode or vary in their hardness or the stoichiometry of the prepolymer. The overall thickness of the finished press sleeve, measured in a section through its longitudinal axis, can be between 5mm and 10mm, preferably between 5mm and 7mm, particularly preferably between 5mm and 6 mm. According to the invention, when only one layer is provided, the press sleeve can be produced from only one casting part, i.e. in one piece, so that the only layer has the above-mentioned thickness.

A finished press sleeve in the sense of the present invention is a press sleeve of which at least one polymer layer has been cured and possibly finally processed, i.e. ready for use in for example a shoe press for the purposes mentioned at the outset. Similarly, the resulting polymer layer is referred to as the cured layer.

A reinforcing thread in the sense of the present invention is understood to be a soft, textile linear structure which has a predominant extent and homogeneity in its longitudinal direction. When referring to fibers, it is meant the only endless fiber in monofilament form. If, on the other hand, a fibre bundle according to the invention is mentioned, it is not a monofilament but is a single thread per se, such as a twisted thread or yarn, i.e. a bundle of endless fibres or a bundle of monofilaments. The fiber bundle itself can be made entirely of fibers twisted with each other.

The definition "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 additionally the longitudinal threads and at least one further circumferential thread are produced in this way. If, for example, a scrim made of circumferential and longitudinal threads is preferably present, it means that at least one longitudinal thread is designed according to the invention.

The term reinforcing structure in the sense of the present invention means a reinforcing structure of at least one layer comprising or consisting of a polymer, i.e. a polymer layer. Here, the reinforcing structure may be completely embedded in the polymer layer, so that the reinforcing structure does not extend beyond the boundary of the polymer layer. In other words, the polymer layer functions as a matrix which surrounds the reinforcing structure and is compounded with the matrix due to adhesive or cohesive forces. Such reinforcing structures may comprise woven linear structures (e.g. twisted threads or yarns) and/or woven planar structures (e.g. woven, knitted, crocheted, braided or scrims) and may be made from corresponding raw materials, for example by winding. In other words, the individual reinforcing threads according to the invention are considered as textile linear structures per se. A plurality of such reinforcing threads can be designed, for example, as longitudinal threads and/or circumferential threads in such a way that they jointly form a textile sheet-like structure. The at least one reinforcing thread embedded in the at least one polymer layer is then the reinforcing structure of the press sleeve or its polymer layer.

The starting material is understood to be the material or semi-finished product from which the reinforcing structure of the press sleeve of the finished product according to the invention is produced, i.e. here the at least one reinforcing thread.

A reinforcing thread or a reinforcing structure may be made of or comprise a polymer. Polyesters, polyethylene naphthalates or polyamides, such as aramids, are suitable as polymers. Thus, the material of at least one polymer layer is different from the material of at least one reinforcing thread or reinforcing structure embedded in the polymer layer.

According to the invention, a press device is understood to be a shoe press for dewatering, treating, for example, a flat fibrous web. The shoe press includes a shoe press roll and a mating roll that together form or define a press nip. The shoe press roll also comprises a press jacket running around and a stationary press element, a so-called press shoe. The latter is supported, for example, by means of a hydraulic press element on a likewise fixed carrying yoke and pressed against a running press sleeve. The press sleeve runs around the fixed press shoe relative to the fixed press shoe and the yoke and is thereby pressed against the mating roll in the press nip. The press shoe and the yoke are arranged radially inside the press sleeve. The term "fixed" is understood to mean that the press element does not run around relative to the shoe press roll or the mating roll, but can move towards and away from the mating roll, preferably in its radial direction and thus relative to the mating roll. In addition to the fibrous web and the press jacket, one or more press felts running endlessly in the circumferential direction and/or further press belts running endlessly are guided through the press nip of the shoe press. Such a shoe press may of course comprise more than one press nip.

A fibrous web according to the invention is understood to be a scrim or entanglement of fibers, such as wood fibers, plastic fibers, glass fibers, carbon fibers, auxiliary materials, additives or the like. The fibrous web can thus be designed, for example, as a paper, cardboard or tissue web. It may essentially comprise wood fibres, wherein minor amounts of other fibres or auxiliary materials and additives may be present. This is determined by one skilled in the art depending on the use case.

The advantages according to the invention are achieved particularly well if a plurality of reinforcing threads are embedded in the polymer layer as a scrim, preferably as longitudinal threads, and at least one reinforcing thread is a circumferential thread which surrounds the longitudinal threads in the circumferential direction. Since the scrim can absorb local overloads particularly well.

The advantages according to the invention are achieved particularly well if the press sleeve is formed from preferably a plurality of polymer layers lying one above the other in the radial direction. If two polymer layers are provided, the radially inner layer is the layer with the reinforcing structure according to the invention. This means that the reinforcing structure is arranged only in the radially innermost polymer layer. If three or more polymer layers are provided, the reinforcing structure is preferably arranged in the second lowest polymer layer, i.e. in the layer located radially above the radially innermost polymer layer.

The invention also relates to a machine, such as a papermaking machine for manufacturing or refining a fibrous web, comprising a shoe press for dewatering the fibrous web.

The invention also relates to a shoe press for dewatering a fibrous web, preferably a paper, cardboard or cellulose web, comprising a press roll and a mating roll which jointly form or define a nip, wherein the press roll comprises a press jacket running around, wherein the press jacket is designed according to the invention.

Finally, the invention relates to the use of the dye according to the invention in a lubricating liquid for a shoe press comprising a press sleeve for dewatering a fibrous web, preferably a paper, cardboard or cellulose web.

The invention is further elucidated below with reference to the drawing without limiting the generality. In the drawings:

fig. 1 shows a partially split schematic side view of a shoe press having a press sleeve according to one embodiment of the present invention.

Fig. 2a and 2b show respective cross sections of an embodiment of the press sleeve, viewed through its longitudinal axis;

fig. 3 shows a highly schematic side view of an apparatus for manufacturing a press sleeve.

In fig. 1, a schematic side view of a shoe press 10 is shown, partially broken away, the shoe press 10 here comprising a press roll according to the invention, such as a shoe press roll 12 and a mating roll 14. The shoe press roll 12 and the mating roll 14 are arranged parallel to each other with respect to their longitudinal axes. Which jointly form or define a nip 22.

The mating roll 14 consists here of a roll of rotating cylindrical design about its longitudinal axis, while the shoe press roll 12 consists of a press shoe 16, a stationary yoke 18 carrying it and a press sleeve 20. The press shoe 16 and the yoke 18 are fixedly arranged relative to the mating roll 14 or the press sleeve 20. This means that they do not rotate. The press shoe 16 is supported by a yoke 18 and pressed against a radially innermost surface of a press sleeve 20 running around opposite it by a hydraulic press element, not shown. The press sleeve 20, which surrounds the press shoe 16 and the yoke 18 in the circumferential direction, rotates about its longitudinal axis in the opposite rotational direction to the counter roller 14. A relatively long nip 22 is created due to the concave design of the press shoe 16 on its side facing the mating roll 14.

The shoe press 10 is particularly suitable for dewatering a fibrous web 24. During operation of the shoe press, the fibrous web 24 is guided through the press nip 22 together with one or two press felts 26, 26'. In the present case, there are precisely two press felts 26, 26', which press felts 26, 26' accommodate the fibrous web 24 in a sandwich-like manner between them. During the passage through the nip 22, a pressure is applied indirectly to the fibrous web 24 in the nip 22 by the press felts 26, 26'. This takes place in such a way that the radially outermost surface of the mating roll 14 is in direct contact with the respective press felt 26, 26 'on one side and the radially outermost surface of the press sleeve 20 is in direct contact with the respective press felt 26, 26' on the other side. The liquid emerging from the fibrous web 24 is temporarily absorbed by a press felt or two press felts 26, 26' and any recesses (not shown) made in the press jacket surface. After leaving the nip 22, the liquid absorbed by the pockets of the press sleeve 20 is thrown away before the press sleeve 20 re-enters the press nip 22. Furthermore, water absorbed by the press felts 26, 26' can be removed by the suction elements after leaving the press nip 22.

In a further embodiment of the invention, which is not shown in the figures, the press felts 26, 26' can be omitted. In this case, the fibrous web 24 is in direct contact with the press sleeve 20 on one side and the mating roll 14 on the other side, which together form a press nip. The latter can then be implemented as a heated drying drum.

Regardless of the embodiment shown, the pressure sleeve 20 slides with its radially inner surface on the pressure shoe 16. The pressure shoe 16 is in fluid communication with a lubricant reservoir 28 for the supply of lubricating fluid. This is indicated by the dashed line. Although not shown, a corresponding device, for example a pump, may be provided for conveying lubricant from the lubricant reservoir 28 to the press shoe 16.

The press sleeve shown in fig. 1 can be designed according to the invention, as shown in the following figures.

In fig. 2a and 2b, cross sections through the longitudinal axis 20' of the finished press sleeve 20, which are not illustrated to scale, show different embodiments of the invention. The distance of the longitudinal axis 20' to the radially innermost surface of the respective polymer layer of the press sleeve 20 is also not shown to scale.

Exactly two polymer layers, namely a first polymer layer 20.1 and a second polymer layer 20.2, are provided according to fig. 2 a. In the present case, the first polymer layer 20.1 is also the radially outermost polymer layer of the press sleeve 20, while the second polymer layer 20.2 is also the radially innermost polymer layer of the press sleeve 20. The two polymer layers 20.1, 20.2, viewed in the radial direction, directly adjoin one another, i.e. there is no intermediate layer between the two polymer layers 20.1, 20.2.

As shown, a reinforcing structure 20 "may be provided in the second polymer layer 20.2. The reinforcing structure is here completely embedded in the polymer layer 20.2. This is indicated by the shaded circles which may be textile planar structures or linear structures such as fibers. This means that the reinforcing structure 20 "does not extend beyond the boundary of the polymer layer 20.2.

The reinforcing structure 20 "here comprises a plurality of reinforcing threads 21 serving as longitudinal threads 21.1. They are arranged at intervals on their circumference in the longitudinal direction of the press sleeve 20 and extend parallel to one another. In addition, at least one further reinforcing thread 21 is provided as a circumferential thread 21.2, which circumferential thread 21.2 preferably extends in the circumferential direction of the press sleeve in the form of an internal spiral in the same polymer layer 20.1, 20.2, 20.3 in which the longitudinal thread 21.1 is also arranged. The longitudinal threads 21.1 and the circumferential threads 21.2 form a scrim with one another, i.e., the scrim is formed such that the longitudinal threads 21.1 are arranged radially inside at least one circumferential thread 21.2, as viewed with respect to the longitudinal axis 20' of the press sleeve 20.

In the present case, the first and second polymer layers 20.1, 20.2 are made of polyurethane. It is obtained, for example, from a prepolymer and a crosslinking agent. The corresponding prepolymers themselves can be obtained by reaction of isocyanates with polyols.

Figure 2b shows a three-layer laminated sleeve in a modified manner with respect to figure 2 a. The press sleeve comprises here a radially outermost first polymer layer 20.1, a radially innermost third polymer layer 20.3 and a second polymer layer 20.2 arranged in sandwich fashion between the first and third polymer layers. As in the illustration of fig. 2a, this arrangement is in terms of its radial direction starting from the longitudinal axis 20' of the press sleeve 20. Here, the (sole) reinforcing structure 20 ″ is provided only in the second polymer layer 20.2. Of course, this can also be different, so that in addition or alternatively also such reinforcing structures 20 ″ can be arranged in the first polymer layer 20.1 and/or the third polymer layer 20.3. The description given for the reinforcing structure 20 "in fig. 2a applies analogously.

If now in fig. 1 a wet stock enters the press nip, it will cause local loads and the polymer layer embedding the reinforcing structure will break. Rupture is therefore a condition where the polymer layers mechanically separate in such a way that the lubricating fluid approaches it or the reinforcing structure. The lubricating fluid may then enter the reinforcing strands. According to the invention, a local color change of the reinforcing threads of the reinforcing structure now occurs in this case. The wet-stock covering process can thus now be detected earlier than before using the device mentioned at the outset. This wet-stock covering process can be detected even before the leakage of lubricating fluid through the press sleeve in the direction of the fibrous web 24 is initiated. In particular, the downtime of a press system equipped with such a press jacket can be significantly reduced.

It has been found that the advantages according to the invention are achieved particularly well if the polyurethane of at least one polymer layer 20.1, 20.2, 20.3 or all polymer layers, as mentioned at the outset, is selected such that it is more transparent than the material of the reinforcing structure 20 ″.

Fig. 3 shows a highly schematic side view of a device for producing a press sleeve 20 according to the invention. The device has exactly one cylindrical winding core 4, wherein, for example, a starting material 20 "' is applied here in a spiral on its radially outermost jacket surface. The raw material 20 "' after embedding the polymer forms the reinforcing structure 20" of the finished press sleeve 20 according to the invention.

The figure shows an initial stage of the manufacturing method. In the present case, one end of the raw material 20' "is fixed to the polymer arranged on the outer circumference of the reeling core 4 for this purpose. In addition to the schematic illustration shown, the one end of the starting material 20 '"is also laid flat or applied directly, i.e. not indirectly, on the reeling core 4 without the need for initially arranging a polymer between the starting material 20'" and the reeling core 4. The starting material 20' ″ can be a textile sheet-like structure or a linear structure.

The reeling core 4 is rotatably supported about its longitudinal axis 20', which longitudinal axis 20' corresponds to the longitudinal axis of the press jacket to be manufactured. The longitudinal axis 20' extends perpendicularly to the drawing plane. Via a line 5, a casting material, such as a pourable, curable, elastomeric polymer, for example polyurethane, is applied from above onto the radially outermost jacket surface or raw material 20 "' of the reeling core 4 by means of a casting nozzle 6. This casting material can be selected, for example, in terms of its pot life and viscosity, so that it does not drip off the core 4 during casting. At the same time, the reeling core 4 is rotated in the direction of the arrow around its longitudinal axis. Simultaneously with this rotation, the pouring nozzle 6 is guided along opposite thereto on the core 4 parallel to the longitudinal axis 20' by suitable guiding means not further shown in fig. 3. While pouring the material, the material 20 "' is unwound and the rotating reeling core 4 is wound into a loop. In this case, the casting compound can pass through the starting material 20' ″ to the core 4. The polymer forms, in this example after the curing step, a radially innermost and preferably elastomeric polymer layer corresponding to the polymer layer 20.2 of the press sleeve of fig. 2a, only a part of which is shown in fig. 3.

The casting material emerging from the nozzle 6 is a mixture of prepolymer and crosslinking agent. The former is provided by a prepolymer-vessel, not shown, in which it is stored or stirred. The prepolymer is the reaction product of the isocyanate of the present invention and a polyol. In the prepolymer vessel, it is present, for example, in the form of a prepolymer composed of the substances mentioned immediately above.

The crosslinking agent may be provided in a crosslinking agent-container.

Prepolymer-container and crosslinker-container dispensing equipment for making the press sleeve 20. They are in fluid communication, through a line also not shown, with a mixing chamber (not shown) placed in the pouring nozzle 6 (not shown) along the flow direction. The prepolymer-crosslinker mixture is thus produced upstream and outside the nozzle 6, i.e. mixed in a mixing chamber. Independently of the production of the mixture, the prepolymer-crosslinker-mixture is then applied to the reeling core 4 to form at least one polymer layer of the press jacket 20.

In principle, it is conceivable to provide two or more pouring nozzles 6. They can be connected to separate prepolymer and crosslinker vessels by means of respective lines in order to convey also different polymers to the plurality of pouring nozzles 6 independently of one another. The nozzles 6 can then be arranged at a distance from one another along the longitudinal axis of the pressure sleeve 20 in order to simultaneously produce a plurality of polymer layers 20.1, 20.2, 20.3 in one casting by simultaneously discharging the polymer from the nozzles 6.

By means of this continuous casting process, also known as spin casting, an endless cylindrical tubular press sleeve 20 closed about its longitudinal axis 20' is thus produced gradually over the width of the reeling core 4, the inner circumference of which corresponds substantially to the outer circumference of the reeling core 4.

In principle, it is conceivable to wind the starting material 20' ″ on more than one winding core 4 shown in fig. 3. For example, two winding cores can be provided, which can be arranged parallel to one another at a distance from one another with respect to their longitudinal axis. Alternatively, it is also conceivable for the polymer to be applied to the radially inner jacket surface of the reeling core 4, for example by centrifugal separation. Regardless of the embodiment described, the finished press sleeve 20 is finally removed from the at least one reeling core 4.

As shown in fig. 3, the press sleeve 20 is designed according to the present invention.

Although this is not shown in the figures, the reinforcing structure 20 "of the at least one polymer layer 20.1, 20.2 may also be constituted by a plurality of raw materials 20'" which are stacked in a radial direction, extending in the direction of the longitudinal axis of the press sleeve 20 and in the circumferential direction of the press sleeve 20, respectively.

Claims (15)

1. Method for operating a shoe press, wherein the shoe press has a press shoe on which a press sleeve slides with its radially inner surface, wherein the press sleeve has at least one polymer layer (20.1, 20.2, 20.3) in which a reinforcing structure (20 ") is embedded for the purpose of introducing lubricating liquid for lubrication between the press shoe and the press sleeve, wherein the reinforcing structure (20") comprises at least one reinforcing thread (21), and the lubricating liquid, the at least one polymer layer (20.1, 20.2, 20.3) and/or the at least one reinforcing thread (21) are arranged such that the lubricating liquid reaches the at least one reinforcing thread (21) of the reinforcing structure (20 ") and causes a discoloration of the at least one reinforcing thread (21) upon breakage of the polymer layer (20.1, 20.2, 20.3).

2. Shoe press comprising a press shoe on which a press sleeve slides with its radially inner surface, the shoe press having a lubricant reservoir for introducing lubricating liquid between the press shoe and the press sleeve, wherein the press sleeve has at least one polymer layer (20.1, 20.2, 20.3), in which at least one polymer layer (20.1, 20.2, 20.3) a reinforcing structure (20 ") is embedded, wherein the reinforcing structure (20") comprises at least one reinforcing thread (21), and the lubricating liquid and/or the at least one reinforcing thread (21) are/is arranged such that, upon breaking of the polymer layer, the lubricating liquid reaches the at least one reinforcing thread (21) of the reinforcing structure (20 ") and can cause a color change of the at least one reinforcing thread (21).

3. A machine comprising the shoe press of claim 2.

4. Use of a dye in a lubricating liquid of a shoe press having a press shoe, a press sleeve and a lubricant reservoir for introducing the lubricating liquid between the press shoe and the press sleeve, the press sleeve sliding with its radially inner surface over the press shoe, wherein the press sleeve has at least one polymer layer (20.1, 20.2, 20.3), a reinforcing structure (20 ") being embedded in the at least one polymer layer (20.1, 20.2, 20.3), wherein the reinforcing structure (20") comprises at least one reinforcing thread (21), and the lubricating liquid and/or the at least one reinforcing thread (21) are arranged such that upon breaking of the polymer layer the lubricating liquid reaches the at least one reinforcing thread (21) of the reinforcing structure (20 ") and can cause a discoloration of the at least one reinforcing thread (21).

5. Method, shoe press, machine or use according to one of the preceding claims, characterised in that the lubricating fluid is added with a dye which discolours the reinforcing threads of the reinforcing structure when the polymer layer breaks.

6. A method, shoe press, machine or use according to claim 5, wherein the dye is selected such that it is a luminescent dye, such as a fluorescent dye or a phosphorescent dye, which emits light by energy input from the outside.

7. A method, shoe press, machine or use according to claim 6, wherein the dye is selected such that it is an ultraviolet-sensitive luminescent dye.

8. Method, shoe press, machine or use according to one of the preceding claims, characterised in that the lubricating liquid is oil.

9. Method, shoe press, machine or use according to one of claims 1 to 8, characterized in that the at least one polymer layer (20.1, 20.2, 20.3) is made of or comprises polyurethane and the at least one reinforcing thread (21) is made of or comprises a polymer, wherein polyester, polyethylene naphthalate or polyamide, such as aramid, is selected as polymer.

10. Method, shoe press, machine or application according to one of claims 1 to 9, characterized in that the material of the reinforcing structure (20 ") and the material of the at least one polymer layer (20.1, 20.2, 20.3) are chosen such that their transmission for visible light differs from each other, and preferably that the transmission of the material of the at least one polymer layer (20.1, 20.2, 20.3) is greater than the transmission of the reinforcing structure (20"), preferably greater than 1.1 to 1.5 times the transmission of the reinforcing structure.

11. Method, shoe press, machine or use according to one of claims 1 to 9, characterized in that the material of the reinforcing structure (20 ") and the material of the at least one polymer layer (20.1, 20.2, 20.3) are chosen such that the transmission of visible light of the entire press sleeve is between 5% and 100%, preferably between 15% and 90%, particularly preferably between 15% and 35%, and preferably corresponds to the total transmission according to ASTM D1003-00, and is preferably measured in the radial direction of the press sleeve.

12. Method, shoe press, machine or use according to one of claims 1 to 11, characterized in that the at least one polymer layer (20.1, 20.2, 20.3) is undyed.

13. Method, shoe press, machine or use according to one of claims 1 to 12, characterised in that one or more reinforcement threads (21) are provided as longitudinal threads (21.1), which longitudinal threads (21.1) are arranged to extend past the circumference of the press sleeve (20) in the longitudinal direction of the press sleeve (20) and to remain parallel to each other at a distance.

14. Method, shoe press, machine or application according to one of claims 1 to 13, characterized in that at least one further reinforcing thread (21) is provided as a circumferential thread (21.2) which extends in the circumferential direction of the press sleeve, preferably helically inside the polymer layer (20.1, 20.2, 20.3), and that the reinforcing thread (21) designed as a longitudinal thread (21.1) and the at least one further reinforcing thread (21) designed as a circumferential thread (21.2) preferably mutually constitute a scrim, preferably mutually constitute a scrim such that the longitudinal thread (21.1) is arranged radially inside the at least one circumferential thread (21.2) seen with reference to the longitudinal axis (20') of the press sleeve.

15. Method, shoe press, machine or application according to one of the claims 1 to 14, characterized in that a plurality of polymer layers is provided and that at least one polymer layer (20.1, 20.2, 20.3) is a radially inner or innermost polymer layer (20.1) seen with reference to the longitudinal axis (20') of the press sleeve (20) and additionally that another radially outermost polymer layer (20.2) is provided seen with reference to the longitudinal axis (20') of the press sleeve (20), and preferably that exactly two polymer layers (20.1, 20.2) are provided and that the radially inner polymer layer (20.2) is simultaneously the radially innermost polymer layer of the press sleeve (20).

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