Method for producing a casing for a spreading roller, use of the casing for a spreading roller, and spreading roller

Abstract

The invention relates to a method for producing a multilayer casing for a spreading roller of a machine for producing and / or treating a fiber web. The invention additionally relates to a spreading roller with a casing produced according to such a method and to the use of a spreading roller casing produced according to such a method.

Description

[0001] The present invention relates to a method for manufacturing a casing for a spreading roller, such a spreading roller and the use of such a roller, in detail according to the independent claims.

[0002] Spreading rollers are used in machines for the production and / or processing of fibrous webs. In the intended use of such machines, spreading rollers, for example in papermaking, come into at least indirect contact with the finished paper web, for instance in coating units where the paper web is coated or in the winding section where the finished paper web is wound into drums. Spreading rollers can also come into at least indirect contact with machine fabrics, such as forming screens, in the forming section. In any case, such spreading rollers are subject to high friction and therefore abrasion during machine operation due to this contact. In the forming section, the high friction is compounded by the humid environment caused by the fiber suspension.

[0003] A spreading roller of this type has a plurality of cylindrical outer bushings (also called segments) arranged successively on a roller core and rotatably mounted about its axis of rotation (called the roller axis). The outer bushings are arranged at intervals – preferably equal intervals – without contact with each other. They are mounted independently of one another on the roller core. A single, continuous sleeve is drawn over the outer cylindrical surfaces of the individual outer bushings. This sleeve is what comes into contact with a paper web during the intended use of the spreading roller, as described above. For this purpose, the paper web or its covering wraps around the spreading roller at least partially in its circumferential direction. Furthermore, spreading rollers are known which are banana-shaped, i.e., with a roller core bent perpendicular to the longitudinal axis of the roller.The shell then essentially follows the outer contour of the roller core, and thus also has a curved shape. A method for manufacturing a shell for a spreading roller is known from DE 20 2016 105130 U1.

[0004] Known from the prior art, spreading rollers tend to wear prematurely due to the aforementioned stresses. If the casings of such spreading rollers are made of multiple layers, unintended separation of the individual layers can occur during normal machine operation.

[0005] The object of the invention is therefore to provide a casing for a spreading roller, specifically one that avoids the disadvantages known from the prior art. In particular, the aim is to reduce the delamination of individual layers in multi-layer spreading rollers and to increase the service life of such spreading rollers. Finally, the manufacturing effort for such a casing should also be reduced.

[0006] The inventors recognized that the manufacturing process according to the invention significantly improves the lifespan of the jacket. This is achieved by producing both polymer layers of the jacket simultaneously, i.e., in a single stroke. The stroke is defined as the movement of the casting nozzles from one axial end to the other axial end – along the axis of rotation of the jacket being manufactured. This corresponds to the concept of the inventive process. This means that the jacket is completed in a single movement of the casting nozzles. The polymers that emerge from the two casting nozzles and, after crosslinking, form the two polymer layers of the jacket, are poured "wet-on-wet" over one another during the inventive casting process.This term means that the first, radially inner polymer layer is not yet fully cross-linked—it is still "sticky"—when the second, radially outer polymer layer is applied to it. Similarly, the reinforcing structure is applied to the first polymer layer after its deposition, but before or at the same moment as the second polymer layer is applied to the first, in order to embed it within the first polymer layer. This process results in a monolithically manufactured shell whose polymer layers and reinforcing structure exhibit improved adhesion, thus reducing delamination due to stress during normal operation. Furthermore, the simplified manufacturing process saves production time.

[0007] The term "successive deposition" refers to the gradual, incremental deposition of a polymer across the entire outer diameter of the casting cylinder or the second polymer layer. This is achieved using the rotational molding process, in which the casting cylinder is driven by a rotary drive, and the two injection nozzles are axially displaced along its axis of rotation. During the superposition of these two relative movements, polymer is dispensed from the two injection nozzles. The cross-sectional area of ​​the injection nozzles for the polymer is only a fraction of the circumferential area of ​​the shell being produced. Therefore, according to the rotational molding process, a strip of polymer is laid down in a spiral pattern on the casting cylinder or the second polymer layer until the entire circumferential surface of the shell is completed in this way.

[0008] When it is stated that the steps of the inventive process take place simultaneously in a single operation, this means that these steps occur at the same time, but on different sections of the outer circumference of the jacket or casting cylinder to be produced, or of the first polymer layer, i.e., only locally offset, i.e., separated by the distance between the two casting nozzles. The distance between the casting nozzles can be a multiple of the width of the nozzle opening, i.e., the width of the polymer strip that can be dispensed from them.

[0009] The term "spreading roller" as used in the invention refers to the aforementioned spreading roller of the generic type.

[0010] A fibrous web within the meaning of the invention is understood to be a woven or tangled mass of fibers, such as wood fibers, plastic fibers, glass fibers, carbon fibers, additives, or the like. The fibrous web can, for example, be designed as a paper, cardboard, or tissue web. It can essentially comprise wood fibers, with small quantities of other fibers or additives also being present. This is left to the expert's discretion, depending on the application.

[0011] A sleeve, as defined in the invention, is a band that is closed in the circumferential direction around its longitudinal axis, forming a loop. At its axial ends, the sleeve is open in the width direction along the longitudinal axis. This allows the sleeve to be drawn over a roller core (or its segments) of the spreading roller via one of its axial ends. In such a case, the inner surface (radially innermost outer surface) of the sleeve rests at least indirectly on the outer surface (radially outermost) of the segments. "At least indirectly" includes the alternatives of indirect (through further means) and direct (directly).

[0012] The casing can be made partially or entirely from a polymer. The polymer used can be a castable, curable, preferably elastomeric polymer, also called a cast elastomer, such as polyurethane.

[0013] A polymer layer is defined as a layer comprising or entirely composed of such a castable, curable, preferably elastomeric polymer. According to the invention, the two polymer layers are cured layers produced in one piece by primary forming. In other words, they are monolithically primary formed, i.e., produced by casting.

[0014] The two polymer layers can be identical with respect to their polymer composition. If exactly two polymer layers are used, the radially inner (or innermost) polymer layer – measured radially around the longitudinal axis of the shell – can have a thickness of approximately 5 mm. The radially outer (or outermost) polymer layer can have a corresponding thickness of approximately 10 to 20 mm. The term "approximately" implies a deviation of up to + / - 20% of the stated value.

[0015] The term "linear structure" refers to a linear structure such as thread or twine. Thread is defined as a long, thin, linear structure made of one or more fibers. Twine is understood to be a linear structure made of several twisted threads. The linear structure can also be made of several fibers twisted together, similar to a rope. These definitions are used regardless of the material or thickness. This means, for example, that a relatively thick metallic thread is referred to as thread and not, as is commonly used in the trade, as wire.

[0016] For the purposes of the present invention, "planar structures" are defined as planar structures – preferably textile structures – such as woven fabrics, knitted fabrics, braids, or nonwovens – which are made from linear structures. The planar structure can be a strip. Here, too, the aforementioned definitions are used regardless of the material used and its thickness.

[0017] The reinforcement structure is manufactured from a base material.

[0018] The term "starting material" refers to the material or semi-finished product used to manufacture the reinforcing structure of the finished coat according to the invention. In the case of sheet structures—particularly textiles—the starting material, i.e., raw material, can be a strip, especially an endless strip, whose width is significantly less than the width of the coat. Preferably, the length is dimensioned such that the (single) reinforcing structure can be produced continuously across the entire width of the coat, i.e., in one continuous stroke—without interruption. The starting material can, for example, be in the form of—preferably strip-shaped—roll material and be unwound lengthwise from a roll.

[0019] A finished coating within the meaning of the invention is one whose two polymer layers have been cured and finally processed, i.e., is ready for use for the aforementioned purpose, e.g., for mounting on the spreading roller or for paper production. Similarly, a finished polymer layer is defined as a layer that has been cured.

[0020] In the context of the invention, the term "reinforcing structure" refers to the reinforcement of at least one layer containing or consisting of the polymer – i.e., the polymer layer. The reinforcing structure can be completely embedded within the polymer layer, such that it does not extend beyond the boundaries of the polymer layer. In other words, the polymer layer acts as a matrix that surrounds the reinforcing structure and binds to it through adhesion or cohesion forces.

[0021] The term "single reinforcing structure" means that the line and / or sheet structure is the sole reinforcement of at least one polymer layer, all polymer layers, and preferably the entire finished sheath itself. This means that exactly one reinforcing structure consisting of a line structure, a sheet structure, or a combination of both is provided, and no other reinforcing structure within the meaning of the invention. In other words, the at least one polymer layer, all polymer layers, and preferably the entire sheath are free of any further (additional) reinforcing structures, such as line structures and / or sheet structures, and preferably free of any other materials.

[0022] A lay-up is understood to be a sheet-like structure consisting of one or more layers of parallel threads that are not fixed at their intersections by material, friction, or form-fitting means. Such a lay-up is not load-bearing once laid, meaning that it loses its shape when displaced. To maintain its shape, the layered threads must be held in place, for example, by being embedded in a polymer layer.

[0023] A woven fabric or woven tape is a textile fabric constructed from warp and weft threads. The warp and weft threads interlace. The fabric can consist of a single thread system or several different systems, preferably several systems with different mechanical properties. However, it is also conceivable to use fabrics in which the warp and weft threads are made of the same material.

[0024] Essentially in the longitudinal or in the transverse direction, this should be understood to mean that deviations of up to 45° from the corresponding direction are possible on both sides.

[0025] Furthermore, the present invention also relates to a machine mentioned at the outset or its components such as a winding device, a forming section or a coating unit, in which the component according to the invention, i.e. the casing and / or the spreading roller, is / are installed.

[0026] The invention is explained in more detail below with reference to the drawings, without limitation of generality. The drawings show: Fig. 1 a highly schematic, partially cutaway view of a spreading roller according to the invention; Fig. 2 a schematic, partially enlarged partial representation of an embodiment for a starting material of the reinforcement structure of a shell according to the invention seen in a cross-section through its longitudinal axis; Fig. 3a, 3b two very simplified representations of the devices for manufacturing the shell.

[0027] In Fig. 1 A highly schematic, partially cutaway view of a spreading roller 7 according to the invention is shown. This illustration is not to scale. The spreading roller 7 has a curved roller core 7.2. The curvature is exaggerated. In this illustration, the roller core 7.2 follows the curvature of its roller axis 7.1. The latter is concentric with the roller core 7.2 and, in the chosen view, curved about a perpendicular to the plane of the drawing. The spreading roller 7 can be designed to be curved, i.e., it can be moved into a curved and an uncurved position during intended use.

[0028] A plurality of cylindrical outer bushings 7.3 are arranged on the roller core 7.2. The outer bushings 7.3 are preferably arranged at intervals along the roller axis 7.1, without contact with one another. They can preferably be arranged evenly distributed over the roller core 7.2. The term "evenly distributed" refers to the smallest distance between the points of symmetry (intersection of the respective axis of symmetry with the roller axis 7.1) of the outer bushings 7.3 that are directly adjacent to one another. In the curved position of the spreading roller 7 shown, the axes of symmetry of the outer bushings 7.3 intersect at a common point when extended. This point of intersection essentially corresponds to the center of a full circle that coincides with or is described by the curved roller axis 7.1.

[0029] The outer bushings 7.3 are independently rotatable on the roller core 7.2 about their longitudinal axis, which may coincide with the roller axis 7.1 in sections (e.g., tangentially). Rotatable mounting means that a rotational movement of the outer bushings 7.3 relative to the roller core 7.2 is possible, particularly during the intended use of the spreading roller 7. Preferably, the outer bushings 7.3 are not designed to be axially displaceable, i.e., in the direction of the roller axis 7.1, at least not during the intended use of the spreading roller 7.

[0030] The present view shows five external bushings 7.3 as an example. A different number would of course be conceivable.

[0031] A bearing can be provided at the axial ends of the roller core 7.2 to absorb the forces acting on the spreading roller 7 during operation. This bearing can be a fixed or rotary bearing. The spreading roller 7, and in particular the roller core 7.2, can be rotaryally driven, i.e., rotating relative to a stationary part such as the frame of a machine in which it is installed, or it can be rigid, i.e., not rotating relative to this stationary part.

[0032] A single, continuous sleeve 1 is drawn over the radially outer cylindrical surfaces of the individual outer bushings 7.3. It extends at least from an axial end of the first outer bushing 7.3 (or beyond) to an axial end of the last, opposite outer bushing 7.3 and beyond.

[0033] Such a coat 1 is used in the Fig. 2 An example is shown. The figure shows a possible embodiment of the invention in a partially depicted cross-section through the longitudinal axis 1.1 of the finished shell 1, not to scale. From a comparison of the Fig. 1 und 2 It can be seen that the longitudinal axis of the finished shell 1 does not initially correspond to the illustrated, curved roller axis 7.1 of the spreading roller 7. However, since the shell 1 is elastic, it follows the curvature of the roller axis 7.1 of the spreading roller 7 after being fitted onto the roller core 7.2.

[0034] The sheath 1 comprises exactly two polymer layers 2 and 2.1. These layers are arranged radially above one another with respect to the longitudinal axis 1.1 of the sheath 1. A reinforcing structure 3 is embedded in the first, radially inner polymer layer 2. In this case, the reinforcing structure 3 is designed as a linear structure, similar to a metallic thread or rope. The coiled helixes of the linear structure are simplified here as hatched circles. Adjacent helixes are equidistant from one another along the entire length of the sheath 1, namely by the pitch S.

[0035] A second polymer layer 2.1 is applied to the outer circumference of the first polymer layer 2. Thus, the first, radially inner polymer layer 2 has the reinforcing structure 3, while, in the case shown, the radially outer polymer layer 2.1 is free of such a structure. However, this is not mandatory. The reinforcing structure 3 can also be arranged in both polymer layers 2, 2.1 simultaneously, or exclusively in the second polymer layer 2.1. In principle, it would be conceivable to provide more than two polymer layers 2, 2.1.

[0036] The reinforcement structure 3 can, in principle, be the depicted linear structure and / or a planar structure not shown. Regardless of the depicted embodiment, the aforementioned "and / or" conjunction means that both a linear and a planar structure can be present in the same polymer layer.

[0037] The Fig. 3a und 3b Figure 1 shows two different devices for manufacturing the jacket 1 according to the invention in a highly schematic, not to-scale representation. Only a portion of a casting cylinder 4 is shown. The illustration depicts an initial stage of the manufacturing process for the jacket 1.

[0038] The casting cylinder 4 is rotatably mounted about its longitudinal axis 5, which corresponds to the longitudinal axis 1.1 of the shell 1 to be produced. Longitudinal axis 5 lies in the plane of the drawing.

[0039] According to the presentation of Fig. 3a Casting material, such as a castable, curable elastomeric polymer, e.g., polyurethane, is dispensed from above via a first casting nozzle 8 onto the radially outermost surface of the casting cylinder 4. Such a casting material can be selected, for example, with regard to its pot life and viscosity, so that it does not drip off the casting cylinder 4 during casting.

[0040] Meanwhile, the casting cylinder 4 is rotated in the direction of the arrow about its longitudinal axis 5. Simultaneously with this rotation, the first casting nozzle 8 is inserted via a suitable [unclear] in the Fig. 3a, 3b The guide (not shown) runs parallel to the longitudinal axis 5 along this axis relative to the casting cylinder 4. The polymer strip emerging from the first casting nozzle 8 gradually solidifies and successively forms the first polymer layer 2.

[0041] Simultaneously with the pouring of the casting material, the starting material 3.1 is unwound and wound into coils on the rotating casting cylinder 4 to produce the reinforcement structure 3. In this process, the starting material 3.1 is completely embedded in the first polymer layer 2, for example.

[0042] Simultaneously with the aforementioned step of embedding the starting material 3.1, the second, radially outer polymer layer 2.1 is cast onto the outer circumference of the first polymer layer 2.

[0043] A second pouring nozzle 9 is provided for this purpose. This nozzle is essentially identical to the first pouring nozzle 8. However, both pouring nozzles 8 and 9 are spaced apart from each other along the longitudinal axis 5 of the pouring cylinder 4. The distance between them is a multiple of the width of the nozzle openings 8 and 9.

[0044] The starting material 3.1 is then rolled off between the two casting nozzles 8, 9 and embedded, for example, in the first polymer layer 2.

[0045] The casting material emerging from the casting nozzles 8, 9 is a mixture of a prepolymer and a crosslinker. The mixture is blended from the two aforementioned components in a mixing head 7, 7.1.

[0046] The prepolymer is provided from a prepolymer container (not shown), in which it is stored or mixed. The prepolymer is the reaction product of an isocyanate and a polyol according to the invention. In the prepolymer container, it can, for example, be present in the form of a prepolymer made from the aforementioned substances. The crosslinker can be provided in a crosslinker container (also not shown).

[0047] Prepolymer containers and crosslinker containers are associated with the device for producing the sheath 1. They are connected to mixing heads 7, 7.1 via flow-conducting lines (not shown). The prepolymer-crosslinker mixture is thus produced upstream and outside the corresponding casting nozzle 8, 9 in the mixing head 7, 7.1, i.e., mixed, in order to subsequently be dispensed from the casting nozzle 8, 9 as a polymer strip.

[0048] If the two polymer layers 2, 2.1 are to be made from different polymers, i.e., different polyurethanes, then according to Fig. 3b Two separate mixing heads 7, 7.1 are provided, which are connected via separate lines to separate prepolymer containers and crosslinker containers.

[0049] If, on the other hand, both polymer layers 2, 2.1 are to be made from the same polymer, then only one mixing head 7 is sufficient, which distributes the prepolymer-crosslinker mixture to both casting nozzles 8, 9 via a distributor 6 ( Fig. 3a The distributor 6 can be designed such that different material flows can be discharged to the casting nozzles 8, 9 via this distributor. In this way, the thickness of the individual polymer layers 2, 2.1 can be easily and independently adjusted.

[0050] Regardless of the embodiment shown, it would be conceivable to provide more than the two depicted casting nozzles 8, 9. These could be connected via appropriate lines to separate prepolymer and crosslinker containers.

[0051] By means of such a continuous casting process, which is also known as rotational casting, an endless, self-contained cylindrical shell 1 is produced over the width of the casting cylinder 4, the longitudinal axis 1.1 of which is closed, and whose inner circumference essentially corresponds to the outer circumference of the casting cylinder 4.

[0052] With the in the Fig. 3a und 3bIn the depicted device, such a two-layer shell 1 can be monolithically produced in just one stroke, i.e., in a single operation. The polymer dispensed from the casting nozzles 8, 9 is selected, for example, with regard to its pot life, such that the polymer layers 2, 2.1 can still be applied to one another "wet-on-wet." In addition, the simultaneous (complete) embedding of the starting material 3.1 in the corresponding polymer layer 2, 2.1 as a reinforcing structure 3 ensures particularly good anchoring within it. All in all, this improves the separation behavior of the individual polymer layers 2, 2.1 from one another and simplifies the manufacturing process of such a shell 1.

Claims

1. A method of manufacturing a sleeve (1) for a spreader roll of a machine for manufacturing and / or treating a fibrous web, comprising the following steps: a) providing a casting cylinder (4); b) successively spreading a first, pourable, curable, preferably elastomeric polymer over the outer circumference of the casting cylinder (4) to produce a first polymer layer (2) of the cover (1) c) embedding a reinforcing structure (3) in the first polymer layer (2) applied to the casting cylinder; d) successively applying a second, castable, curable, preferably elastomeric polymer to the already applied first polymer layer (2) to form a second polymer layer (2.1) of the jacket (1); e) wherein steps b) to d) take place parallel to each other in one operation, preferably in such a way that the two polymer layers (2, 2.1) are produced in one piece by primary molding and preferably the reinforcing structure (3) is completely embedded in at least one of the two polymer layers (2, 2.1), wherein the casting cylinder (4) is driven in rotation so that it rotates about its axis of rotation (5) and a first casting nozzle (8) is provided for discharging the first polymer and a second casting nozzle (9) is provided for discharging the second polymer, wherein the two casting nozzles (8, 9) are arranged at a distance from one another along the axis of rotation (5) of the casting cylinder (4) and are moved together at this distance parallel to and along the axis of rotation (5) of the casting cylinder (4) in order to discharge the two polymers simultaneously, wherein the first polymer and the second polymer are cast "wet-on-wet" on top of each other during the casting process, i.e. the first, radially inner polymer layer (2) is not yet fully crosslinked, while the second, radially outer polymer layer (2.1) is applied to it, and in that the reinforcing structure (3) is formed from a starting material (3.1) by winding a plurality of coils along the longitudinal axis of the sheath (1) to be produced, in that the starting material (3.1) is moved simultaneously with the movement of the casting nozzles (8, 9) along the axis of rotation (5) of the casting cylinder (4) and is applied to the first polymer layer (2) of the rotating casting cylinder (4), wherein the starting material (3.1) is a linear and / or flat structure, and preferably the linear structure comprises a metal - such as steel or stainless steel - or is produced therefrom and is preferably produced from a plurality of fibers twisted around one another in the manner of a rope. and wherein the starting material (3.1) is applied to the first polymer layer (2) after the application of the first polymer layer (2), but before or at the moment of application of the second polymer layer (2.1) to the latter, in order to embed the latter at least in the first polymer layer (2).

2. The method according to claim 1, wherein the polymer discharged from each of the two casting nozzles (8, 9) is a polyurethane which is a reaction product of a prepolymer and a crosslinker.

3. Method according to claim 2, wherein the casting nozzles (8, 9) for discharging the corresponding polymer are connected via a distributor (6) to a common mixing head (7) or to a respective separate mixing head (7, 7.1) in a flow-conducting manner, wherein the or each mixing head (7, 7.1) for producing the reaction product is in turn connected in a flow-conducting manner to a prepolymer container and a crosslinker container.

4. The method according to claim 2 or 3, wherein the prepolymer is a mixture of a polyol and a diisocyanate.

5. The method according to claim 3, wherein the polyol is selected from: Polyethers, Polyesters, Polycarbonates, Polycaprolactones.

6. The process according to claim 4 or 5, wherein the diisocyanate is an aromatic or an aliphatic diisocyanate or a mixture thereof.

7. The process according to claim 6, wherein the aromatic diisocyanate is selected from: paraphenylene diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate or a mixture thereof, and that the aliphatic diisocyanate is hexamethylene diisocyanate, isophorone diisocyanate or a mixture thereof.

8. The process according to any one of claims 2 to 7, wherein the crosslinker is a polyol, a diamine, a diol or a mixture thereof and preferably that the crosslinker is selected from 4,4'-methylene-bis(3-chloro-2,6-diethylaniline) (MCDEA), 4,4'-methylenebis(2-chloroaniline) (MOCA), 1,4-butanediol, 1,3-propanediol, 1,2-ethanediol, trimethylolpropane, diethyltoluenediamines, 4,4'-diaminodicyclohexylmethanes, bis-mercaptomethyltoluene diisocyanate, isophorone diamine, hexamethylenediamine, PACM, polyethers, polyesters, polycarbonates, polycaprolactones or mixtures thereof.

9. The method according to any one of claims 1 to 8, wherein the polymers of the first and the second polymer layer (2, 2.1) are different from each other.

10. The method according to any one of claims 1 to 9, wherein the reinforcing structure (3) is the only reinforcing structure, preferably the only reinforcing structure of the at least one polymer layer (2, 2.1), of all polymer layers (2, 2.1) or of the entire sheath (1).

11. Spreader roll (7) for a machine for producing and / or treating a fibrous web, comprising a roll core (7.2), with a plurality of outer bushes (7.3) rotatably arranged on the roll core (7) and a shell (1) arranged at least indirectly on the outer circumference of the outer bushes (7.3), wherein the shell (1) is produced according to one of the preceding claims.

12. Spreader roller (7) according to claim 11, wherein the roller core (7.2) is bent or designed to be bendable with respect to a roller axis (7.1) extending concentrically thereto.

13. Use of a shell (1) produced according to one of claims 1 to 10 for a spreader roller (7) according to one of claims 11 or 12.

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