DK3256257T3 - MOLDING ROLL AND PROCEDURE TO PULL A BINDING AND SHRINK A BINDING ON THE SHAFT OF A GRINDING ROLL - Google Patents

Description

Description

The invention relates to a grinding roller of a high-compression roller press, having a shaft, wherein the shaft is rotationally symmetrical in relation to a rotation axis, and at least one wear-resistant strap, wherein the shaft and the at least one strap are mutually coaxial, and wherein the strap in a longitudinal portion of the shaft is shrunk onto the shaft in a force-fitting manner. The invention furthermore relates to a method for separating a strap and a shaft in the case of such a grinding roller, and to a method for connecting a strap and a shaft in a force-fitting manner so as to form such a grinding roller, wherein the strap and the shaft in terms of the diameters thereof are embodied in an interference fit.

Grinding rollers as a component part of high-compression roller presses (roller presses, particle-bed roller mills) are employed for comminuting granular grinding stock, for example cement clinker). Herein, a roller gap is configured between two grinding rollers, grinding stock being drawn into said roller gap by the two counter-rotating rollers, and said grinding stock being comminuted under high compression in said roller gap. High mechanical stresses arise herein, also in respect of the grinding roller. Scoring and micro-cutting by the brittle grinding stock can lead to abrasive wear of the surface and of the outer layers of the roller. In order for cost-intensive repairs and a reduced service life of the high-compression roller press to be avoided, measures aimed at wear protection are implemented. In one widely used form of wear protection, the grinding roller when viewed from the inside out is constructed from a shaft which is mounted accordingly in the high-compression roller press, and from a coaxial strap (cf. DE 20 2011 110 190 Ul, for example) . The strap is composed of a wear-resistant material, in particular of a suitable steel, protects the shaft from abrasion in the region of particular grinding stress, and often promotes the grinding procedure by way of a profiled surface. After a certain operating period, wear also arises in the case of the strap; however, it is not the shaft or the entire grinding roller, respectively, that has to be replaced. Rather, a replacement or refurbishment, respectively, of the strap is sufficient. To this end, and also in the case of other maintenance events in which the strap and the shaft are to be mutually separated, it proves advantageous when the force-fitting connection between the shaft and the strap has been produced by shrinking the strap, that is to say by heating and expanding the outer part (strap) accordingly, fitting said outer part (strap) onto the inner part (shaft) , and compressing said outer part (strap) onto the inner part by contraction during cooling. Stripping the strap can then be performed in the reverse order, that is to say by intensively heating the strap from the outside until the thermal expansion of said strap permits stripping from the shaft in the axial direction.

Such thermally enabled stripping of the shaft and the procedure of shrinking also lead to a heating process for the shaft. The process of disassembly in particular (but also that of fitting) can be significantly facilitated in that the shaft herein is cooled. In this way, the shaft does not expand to the same degree as the heated strap, such that a connection is achieved that can be released earlier than when the shaft is not cooled. In industrial practice, the shafts to this end are provided with a central cooling bore, that is to say a cooling bore that is disposed along the rotation axis. By means of this duct-like cooling bore, cooling of the shaft from the interior in the case of the processes of shrinking or stripping of the strap, respectively is made possible in a simple manner by way of a cooling medium that flows through said cooling bore.

However, specifically the high-compression roller presses that in most recent times have been employed in the cement producing sector are distinguished by particularly large dimensions. For example, grinding roller diameters of up to 3 m are typical, wherein a thickness of approximately half a meter for the strap is not unusual. As has been demonstrated, the system of central cooling for grinding rollers of this size for stripping (and fitting on) straps is now only barely suitable or no longer suitable at all. By virtue of the large distance from the adherent surface between the shaft and the strap, the cooling process does not contribute effectively toward the establishment of a high temperature differential between the external regions of the shaft and the heated strap. On account thereof, inter alia the external thermal effect on the strap has to be increased in order for a release of the connection to be promoted; however, the temperature range elevated in such a manner is not gentle on the material, since in the case of specifically alloys such as steel, structural or phase transformations, respectively, can arise in the temporal profile even at a few hundred degrees Celsius, said transformations reducing the resistance of the grinding roller in relation to forces acting on the latter during the grinding procedure. This is further amplified in that the process of releasing (as well as that of establishing) the force-fitting connection in the case of central cooling is slowed down as the dimensional size of the rollers increases. This does not only mean longer and more energy-intensive operational procedures, but also a longer period of time in which the phase transformations mentioned can arise and take place. Significantly more intensive cooling in terms of temperature in the central region would not only be more intensive in economic terms, but would also lead to high temperature gradients in the radial direction within the shaft per se, said temperature gradients likewise contributing toward material fatigue, for example by way of stress.

Cooling concepts which are based on cooling ducts in the strap or in the region between the strap and the shaft or the roller body, respectively, such as are proposed for example in DE 1 029 723 A for use in briquette compactors, would not be helpful in the case of the process described for stripping the strap, since the focus is on a high temperature differential between a cool shaft and a hot strap specifically in the region of the adherent surface. The system of radial cooling ducts which, as proposed for hot briquette compacting in DE 25 36 688 Al, lead from one or a plurality of cooling ducts in the center of the roller core to the sleeve or the surface, respectively, of the core is also not applicable to the present set of problems since the sleeve in the case of said proposed system, due to the segmentation of said sleeve and to the cooling bores that are axially parallel, is not implementable as a shrinkable strap.

The complex cooling system for a compression roller having a strap in WO 2014/012770 which is improved in relation to the system above, due to the cooling bores thereof being disposed in the strap and to the radial inflow and outflow ducts from the center to the strap that are disposed in the roller core of said complex cooling system, is also not suitable for use in the case of the processes of the thermal removal or shrinking, respectively, of a strap. A further document DE19833456 discloses a method for producing compression rollers or annular straps or annular segments for compression rollers which have at least one cooling duct for dissipating heat. Furthermore, this document relates to a compression roller produced according to this method.

It is therefore an object of the invention to specify a grinding roller of a high-compression roller press in which separating a shrunk strap from the shaft in a manner that is simple, rapid and gentle on the material, and connecting a strap in a force-fitting manner that is simple, rapid and gentle on the material is possible even in the case of a large shaft diameter. It is furthermore an object of the invention to specify a method assigned to this grinding roller for separating the strap and the shaft, and a method for connecting the strap and the shaft in a force-fitting manner.

The object according to the invention is achieved by a grinding roller of a high-compression press, having the features of Claim 1, by a method for separating a strap and a shaft in the case of such a grinding roller, having the features of Claim 6, and by a method for connecting a strap and a shaft in a force-fitting manner so as to form such a grinding roller, having the features of Claim 7. Further advantageous design embodiments are stated in the dependent claims of Claim 1.

It is thus provided according to the invention that the shaft for the perfusion with coolant has cooling bores that run in the axial direction. These duct-like cooling bores herein that for the inflow or outflow, respectively, of the gaseous or liquid coolant are open at both ends and continue through the entire shaft according to the invention are not disposed in or close to the center of the shaft, but in the external region of the shaft, that is to say close to the adherent surface between the shaft and the shrunk strap. The shaft of the grinding roller in the case of high-compression roller presses is suitably mounted at the ends such that the shaft is comprised by the strap and is protected against wear by the latter during the grinding process only in a central region or longitudinal portion, respectively. The cooling bores are disposed in the external region of the shaft in such a manner that said bores in a cross section through the shaft that is performed perpendicularly to the rotation axis in that region of the longitudinal portion of the shaft that has the strapping penetrate the interior of a geometric annulus. The center of this imaginary annulus herein lies on the rotation axis. The external radius rmax of the annulus is equal to the external radius of the shaft rw, and the internal radius rmin of the annulus is one third of the external radius (1/3 rmax), preferably two thirds of the external radius (2/3 rmax) . It has been demonstrated that a cooling is best suited to the method according to the invention for the thermal disassembly and assembly of the straps when said cooling is performed by means of cooling ducts within an external region of the shaft that has been measured in such a manner. The cross sections through the cooling bores herein are entirely within this region, that is to say in particular not open on the surface (or on the external adherent surface, respectively) of the shaft. Such a construction enables effective cooling of the grinding roller, in particular of the shaft, in the external region of the shaft even when the shaft diameter is several meters (typically up to 2.5 m) . In the case of an external thermal influence, the foundation for simple and at the same time substantially more rapid cooling is provided than in the case of the known cooling method by cooling through a central bore in the shaft. To the extent that cooling can thus already be performed also at very high temperatures (during the assembly or disassembly of the strap, respectively) in the region of the adherent surface of the strap, this cooling process proceeds more rapidly, more effectively, and more often having radially flatter temperature gradients in the shaft (at a simultaneous influence of heat), such that undesirable structure and phase transformations in the materials used in the grinding roller (shaft, strap) , that is to say steel, in particular, become more improbable.

For reasons of wear protection, the strap on the surface thereof can be profiled such that an autogenous wear protection layer is configured on the grinding roller in the grinding procedure by the adherence of a layer of comminuted and compressed grinding stock. However, if (for example pintype or plate-shaped) hard elements of highly wear-resistant material are also applied to the strap on its part for further wear protection, these additional elements in terms of terminology in the present context are not considered to be part of the strap. In particular, the assembly or disassembly, respectively, thereof in general is to be carried out in a dedicated and optionally separate manner from the processes of stripping and fitting the strap to the shaft which are described here.

According to the invention, the cooling bores are located in the external region of the shaft. By virtue of the at times heavy stresses on the grinding roller in the grinding procedures, a distribution of the cooling bores that is symmetrical in relation to the rotation axis of the roller is to be preferred because of the forces acting thereon. Therefore, one embodiment of the invention provides that the cooling bores in a cross section through the shaft that is performed perpendicularly to the rotation axis are disposed so as to be symmetrically distributed on a circle (arrangement circle) having the center on the rotation axis and the radius ri which lies between the external and the internal radius of the penetrated geometric annulus (rmin < ri < rmax) . The cooling bores are thus disposed at equidistant spacings on a circle in the external region of the shaft, wherein the arrangement circle is inwardly offset from the shaft surface into the interior of the shaft at least so far that the cooling bores are not cut through, that is to say open, on the shaft surface. The symmetrical arrangement furthermore permits uniform cooling of the shaft in the case of the fitting and stripping procedures of the heated strap.

For reasons pertaining to the material and the dimensions, particularly intensive cooling of the shaft can be required during stripping and optionally also fitting of the strap onto the shaft. In order for the stability of the shaft to not be reduced in the case of the influence of force, a plurality of cooling bores that are comparatively small in terms of the diameter are inter alia more suitable than a few bores having a comparatively large diameter. In the case of a high cooling requirement, this can lead to a comparatively large number of cooling bores. For reasons of statics, it is not recommended here for all the cooling bores to be disposed in a dense sequence on only one arrangement circle. In one alternative embodiment of the invention it is therefore provided that the cooling bores in a cross section through the shaft that is performed perpendicularly to the rotation axis are disposed so as to be symmetrically distributed across at least two concentric circles (arrangement circles) having the center on the rotation axis and radii (ri, r2, ...) which lie between the external and the internal radius of the penetrated geometric annulus ( ^ιπίη < ri < < ... < rmax ), wherein the cooling bores of different arrangement circles in the radial direction are mutually aligned or aligned so as to be mutually offset. In a suitable offset, the bores on one arrangement circle are located so as to be centric below or above, respectively, the intermediate space between two bores on the neighboring arrangement circle. Diameters of the cooling bores that on the arrangement circles decrease from the outside to the inside are adequate for the temperature gradient in the radial direction and suitable for the stability of the shaft body. Further embodiments, for example a number of cooling bores that decreases from the outside to the inside on the arrangement circles are possible and practical.

While intensive and rapid cooling of the shaft in the external region of the latter for stripping and fitting of the strap is indeed intended according to the invention, an intensive drop in temperature in a radial manner from the inside to the outside can in particular cases have negative effects on the shaft material, for example cause stresses. This can, in particular, be in phases in which the operational step of fitting the heated strap is delayed, for example due to unforeseen reasons. One embodiment of the invention therefore provides that a central cooling bore for the perfusion with gaseous or liquid coolant is provided so as to be axially centric through the shaft. If and when required, any potential excessive temperature gradient can be counteracted by way of this cooling in the center of the shaft. This can prove advantageous even when the shaft on its part is assembled from a plurality of concentric hollow cylinders, the force-fitting connection of said cylinders being potentially released in the case of excessive temperature gradients over comparatively long periods.

In one further design embodiment of the invention, cooling pipes for routing the coolant are disposed in the cooling bores. On account thereof, any thermo-chemical modification of the material of the shaft in the region of the walls of the cooling bores that would possibly arise over comparatively long periods is prevented. However, the thermal conductivity of the cooling pipes does not compromise the cooling effect per se.

The construction of the grinding roller according to the invention is aimed at being able to carry out methods for disassembling (stripping) and assembling (fitting), respectively, straps from and onto shafts, respectively, in the case of grinding rollers which have a large roller diameter, in particular a large shaft diameter, said methods being simple, capable of being carried out rapidly, and at the same time gentle on the material. For such a roller according to the invention a method according to the invention for separating the strap and the shaft is provided, said method being characterized by the following steps: heating the strap by suppling external heat for a thermal expansion of the strap; cooling of the shaft performed herein by way of a coolant that perfuses the cooling bores; and stripping the strap from the shaft in the longitudinal direction as established by the rotation axis. For example, if the strap is to be removed from the shaft of the grinding roller according to the invention due to wear, widening of the strap by way of thermal expansion is caused by a rapid very intensive external supply of heat, as is already known per se. Cooling of the shaft is performed simultaneously or optionally commenced even earlier, such that said shaft in terms of the external diameter thereof does not likewise expand to the same relevant degree. In the case of large shaft diameters, cooling by supplying a coolant in the center of the shaft is not adequate. Rather, an effective and sufficiently rapid release of the force-fitting connection between the shaft and the thermally shrunk strap, that is to say a release that is effected even prior to the commencement of thermally caused sustained modifications to the material (in particular phase transformations of steel) is achieved in that the shaft is cooled in the external regions thereof, that is to say close to the adherent surface of the strap. To this end, coolant is routed through the cooling bores which according to the invention are located in the external region of the shaft. On account of this cooling in the proximity of the adherent surface, at most a very minor thermal input into the shaft arises such that no such thermal expansion as in the case of the strap takes place. The strap and the shaft are mutually released so that the strap can be stripped from the shaft in the axial direction. On account of the cooling that is disposed in the external shaft region, and in the case of an approximate compensation of the cooling effect by way of the heating effect by virtue of the heated strap that takes place there, temperature-related material expansions advantageously rarely take place in the center of the shaft under normal conditions .

The construction of the grinding roller according to the invention, having the features of the shaft, also enables a method that is simple and rapid to carry out for the reverse procedure, that is to say for fitting or thermally shrinking a strap onto a shaft, respectively. Of course, the strap and the shaft here have to have dimensional rations which in the case of thermal shrinking as is known per se leads to a sufficiently strong force-fitting connection. Here, a person skilled in the art will perform a suitable interference fit while considering the specific thermal expansion behavior of the materials involved, that is to say choose an internal diameter of the strap which at the ambient temperature is somewhat smaller than the external diameter (joining diameter) of the shaft. The method according to the invention for connecting the strap and the shaft in a force-fitting manner is characterized by heating the strap that is present separately; cooling the shaft by way of a coolant that perfuses the cooling bores; and fitting the strap onto the shaft, wherein the strap that has been pull-fitted shrinks onto the shaft by cooling down or cooling. Cooling of the strap herein advantageously commences prior to the procedure of pull-fitting and continues during the latter. As is already the case in the method of stripping, cooling with the aid of the cooling bores that according to the invention are located in the external region, close to the adherent surface, ensures an only minor thermal input into the shaft such that the latter does not expand and the heated, consequently expanded strap can be pulled over the shaft in the axial direction. The strap contracts by cooling, and a force-fitting connection results. This shrinking can be accelerated by continuous cooling of the shaft and optionally by external cooling, this being performed by a person skilled in the art such that the desired material properties are preserved or are established, respectively.

It has been demonstrated in the case of both methods that stripping or pull-fitting of the strap, respectively, can be carried out by way of cooling according to the invention even in the case of large shaft diameters so rapidly that in the case of the steel types that are typically employed no disadvantageous phase transformations take place yet prior to the completion of the method. The phase and structural formations in the materials involved can thus be influenced in a manner that is gentle on the material by way of the cooling close to the adherent surface.

The methods of stripping and pull-fitting can be carried out in the exact same manner when a plurality of comparatively small straps are disposed beside one another in the axial direction. If hard elements (pins, plates, or the like) are incorporated as profiled elements for configuring a wearprotection layer in the strap, said hard elements in the case of a deviating thermal expansion behavior are typically to be removed in a known manner (turning, abrading, etc.) prior to the strap being stripped.

The invention will be explained in more detail by means of the following figures in which: fig. 1 shows the shaft of a grinding roller according to the invention in a schematic side view; fig. 2 shows a cross section through the grinding roller, with the position of the cooling bores; fig. 3 shows a cross section through the grinding roller in the exemplary embodiment, having two arrangement circles.

The shaft 1 of a grinding roller 2 according to the invention, such as is typical for the use in high-compression roller presses (roller presses), is depicted in a side view in figure 1. The grinding roller 2 is composed of the shaft 1 and a wear-resistant strap 3 (not depicted here) that is connected to the shaft 1 in a force-fitting manner by thermal shrinking. The shaft 1 is mounted so as to be rotatable and rotationally symmetrical in relation to a rotation axis 4, and for the benefit of mounting, of the lower weight, and of the simplified stripping and pull-fitting of a strap 3, tapers toward the ends from or to, respectively, the central portion of the shaft 1 that has the largest diameter. Furthermore, two cooling bores 5 which according to the invention are disposed in the external region of the shaft 1 are schematically plotted. Said cooling bores 5 continue through the shaft 1 in the longitudinal direction, the former having open ends on both sides such that coolant can be routed through the cooling bores 5 when a strap 3 is pull-fitted onto the shaft 1 by thermal shrinking and is connected to the shaft 1 in a forcefitting manner by the method according to the invention, or when a shrunk strap 3 is stripped from the shaft 1 by the method according to the invention. Cooling tubes (not depicted) can be incorporated in the cooling bores 5 herein. The position of the cooling bores 5 in the external region of the shaft 1 enables an adequate temperature differential between the shaft 1 and the externally heated strap 3 to be established in a manner that is rapid, simple and gentle on the material, such that comparatively rapid stripping or pullfitting, respectively, of the strap 3 is promoted by the dissimilar thermal expansion of the shaft 1 and of the strap 3.

Figure 2, in cross section through a grinding roller 1 that is performed perpendicularly to the rotation axis 4 in the portion where the shaft 1 is encompassed by the strap, schematically illustrates the geometric ratios of the position of the cooling bores 5. In the exemplary embodiment depicted, the cooling bores 5 are symmetrically disposed on an imaginary arrangement circle 6. The cooling bores 5 do not intersect the adherent surface 7 between the shaft 1 and the strap 3, but are advantageously disposed in the external region of the shaft 1. Ina manner advantageous to the methods of stripping and pull-fitting the strap 3, said cooling bores 5 according to the invention are disposed in an imaginary annulus 8, 8' which presently is plotted in a symbolic manner by way of the internal circumference thereof, the center of said annulus 8, 8' lying on the rotation axis 4. The annulus 8, 8' herein as the external radius rmax has the same radius as the shaft (rw) . In test measurements, good cooling properties for the methods have been established for an internal radius rmin of the annulus 8 that is equal to one third of the external radius rmax. However, specifically in the case of large grinding rollers, an internal radius r'min for which r'min = 2/3 rmax is to be preferred. The internal circumference of this narrower annulus 8' is also plotted in a symbolic manner.

An exemplary embodiment in which the cooling bores 5 are disposed on two imaginary concentric arrangement circles 6, 6' having the radii ri and r2 within the imaginary annulus 8, 8' (not depicted) is illustrated in figure 3. A plurality of such arrangement circles 6, 6' along only one circular line can be advantageous for a more uniform cooling without an excessive "perforation" of the shaft 1 in the case of large grinding rollers 2. The cooling bores 5 of the two arrangement circles 6, 6' in the exemplary embodiment are disposed so as to be mutually offset for reasons of more uniform cooling.

List of reference signs 1 Shaft 2 Grinding roller 3 Strap 4 Rotation axis 5 Cooling bore 6, 6' Arrangement circle 7 Adherent surface 8, 8' Annulus (geometric) rmax External radius (annulus) rmin, r'min Internal radius (annulus) rw Radius of the shaft ri, r2 Radius (arrangement circle)

Claims (7)

A milling roller (2) for a high-pressure printing roller comprising: - a shaft (1), which shaft (1) is rotationally symmetrical with respect to a axis of rotation (4); and - at least one wear-resistant bond (3), the shaft (1) and at least one bond (3) being coaxial and which bond (3) in a longitudinal portion of the shaft (1) is shrunk on the shaft (1) of a a power adapted manner, characterized in that the shaft (1) comprises a plurality of cooling bores (5) which are continuous through the shaft (1) in the axial direction for flowing a gaseous or liquid refrigerant, which cooling bores (5) are arranged in the outer a region of the shaft (1) such that in the case of a cross section through the shaft (1) perpendicular to the axis of rotation (4) in the region of the longitudinal portion of the shaft (1) having the bond (3), the cooling bores (5) penetrates into the interior of an imaginary geometric annular region (8, 8 '), the center of the latter region lying on the axis of rotation (4), the outer radius rmax of the annular region (8, 8') equal to the outer the radius rw of the shaft (1) and the inner radius rmin of the annular region (8, 8 ') are a one third of the outer radius (1/3 rmax), preferably two thirds of the outer radius (2/3 rax) · The grinding roller (2) according to claim 1, characterized in that the cooling bores (5) in a cross section through the shaft (1) perpendicular to the axis of rotation (4) are arranged symmetrically distributed on a device circle (6, 6 ') which has the center of the axis of rotation (4) and the radius ri which lies between the outer and the inner radius of the penetrated geometric annular region (8, 8 '): rmin <ri <rmax. The grinding roller according to claim 1, characterized in that the cooling bores (5) in a cross-section through the shaft (1) perpendicular to the axis of rotation (4) are arranged symmetrically distributed over at least two concentric device circles (6, 6 ') with centers of the axis of rotation (4) and radii (r1, r2, ...) located between the inner and outer radii of the geometric annular region (8, 8 '): rmin <ri <r2 C. . . C rz, which cooling bores (5) of different device circles (6, 6 ') are arranged radially below each other or offset. Grinding roll (2) according to one of claims 1 to 3, characterized in that a central cooling bore (5) for flowing gaseous or liquid refrigerant is provided axially centered through the shaft (1). Grinding roll (2) according to one of claims 1 to 4, characterized in that cooling tubes for supplying the refrigerant are arranged in the cooling bores (5). Method for separating a bond (3) and a shaft (1) from a grinding roller (2) according to one of claims 1 to 5, characterized in - heating the bond (3) by applying external heat to a thermal expansion. of the bond (3); cooling the shaft (1) with a refrigerant flowing through the cooling bore (5) and withdrawing the bond (3) from the shaft (1) in the longitudinal direction defined by the rotation axis (4). A method of connecting a bond (3) and a shaft (1) to a grinding roller (2) according to one of claims 1 to 5 in a force-adapted manner, which bond (3) and shaft (1) with respect to their diameters is performed by pressing fit, characterized by - heating the bond (3) present separately, to cool the shaft (1) by means of a coolant flowing through the cooling bores (5), and - applying the bond (3) to the shaft. (1), which pull-on bond (3) shrinks on the shaft (1) upon cooling or cooling.