HK1183642B - Roller for high pressure roller grinder, roller grinder, and method for assembling a roller for a roller grinder - Google Patents

Description

Roller for a high-pressure roller mill, roller mill and method for assembling a roller of a roller mill

Technical Field

The invention relates to a roller for a roller mill, comprising a shaft and a grinding shell in the form of a substantially tubular sleeve having an inner surface held around the shaft. The invention further relates to a roller mill and a method for assembling a roller for a roller mill.

Background

High pressure roller mills for grinding rock and the like are subject to a high degree of wear from the material being processed for obvious reasons. Each roller of a roller mill therefore typically grinds the shell with an outer cylinder of wear resistant material covering the roller. When worn by the material being processed, the grinding housings eventually must be replaced, causing an interruption in the operation of the device.

The crushing or disintegrating shells must be mounted firmly around the hub of the shaft, with high friction between the parts to avoid loosening of the shells during operation of the mill. The hub portion of the shaft may have a cylindrical shape or may be slightly tapered to allow easy installation and removal of the mill housing. The taper is preferably minimal to prevent the grinding shell from being undesirably released during operation of the grinding mill.

In known constructions, the outer grinding shell is designed to be mounted around the axial center of the shaft by thermal expansion and contraction. The outer grinding shell is heated to exhibit thermal expansion sufficient to allow it to slide axially about the shaft until reaching the mounted position, where the device keeps it cooling and contracting with great interference about the hub portion of the shaft, which is generally cylindrical.

This known mounting solution presents some inconveniences. The outer grinding shell may crack upon cooling, particularly when it is made of hard high carbon steel, and may lose its uniformity and its cylindrical tubular geometry due to the stresses caused by the application of heat. The mounting solution by means of thermal expansion contraction of the outer grinding shell also presents inconveniences when detaching the grinding shell from the axial center portion of the shaft. Disassembly is extremely difficult due to the high level of frictional interference between the two components. This difficulty is so great and time consuming that it is often preferable to replace the entire shaft-grinding housing assembly, undesirably increasing the cost of replacing a grinding housing that has become worn. This problem is a particular cost incentive when the frequency of such replacement is high due to the high degree of wear of the outer shell. In this case, the shaft is also frequently damaged during disassembly, further increasing the replacement cost of the grinding shell. In many cases, bearings, which are often expensive components, are integrated in the shaft assembly, further increasing the cost of replacement when the outer housing cannot be removed.

There are also known mounting solutions that make use of an internal conical grinding shell that runs around a wedge arranged between the hub of the shaft and the grinding shell and is pushed towards the central area of the roll, generating inward and outward radial forces against the shaft and against the grinding shell, respectively, generating the required high level of frictional interference between the grinding shell and the shaft. While overcoming the inconvenience associated with installation by thermal expansion-contraction, the use of a wedge and an internal conical grinding shell presents the following inconveniences: making axial and radial alignment difficult and making the grinding shell replacement operation complicated and expensive.

Patent US-5,060,874 describes a mounting solution according to which each shaft carries, intermediately, a pair of external conical hubs, each operatively associated with a contraction disc, a wedge and an expansion ring, to establish a high level of frictional interference between the grinding shell and the shaft, without the need for thermal expansion-contraction of the receiver. This prior solution requires a large number of components, which undesirably increases its cost.

Disclosure of Invention

The object of the present invention is to solve the above problems in whole or in part and to provide an improved roller for a roller mill with an outer grinding shell, which is easy to mount and dismount, thereby reducing costs when replacing worn grinding shells, while also providing a grinding shell which does not loosen during operation of the mill.

These and other objects are achieved by a roller for a roller mill, said roller comprising a shaft and a substantially cylindrical grinding shell having an inner surface held around said shaft. The shaft is characterized in that the shaft comprises two shaft parts, wherein the shaft parts comprise a connecting part arranged to connect the shaft parts to each other, thereby forming the shaft.

By dividing the shaft in two parts, the grinding shell in the form of a tubular sleeve can be easily removed after wear by the grinding device, in contrast to the prior art. One of the shaft portions is simply removed by releasing the connection portion to allow the grinding shell to be pulled away from the roller shaft for replacement with a new grinding shell.

In an embodiment, the grinding shell is in the form of a generally tubular sleeve.

According to an embodiment, preferably each shaft portion has a respective inner end portion, wherein the inner end portions are arranged to be positioned facing each other and connected to each other by the connecting portion.

In one embodiment, each shaft portion has a respective inner end, wherein the inner ends are arranged to be positioned facing each other at and connected to respective ends of the roller. In this way, the shaft portions need not pass all the way through the grinding shell and the shaft portions may be indirectly connected to each other via the grinding shell, thereby forming the shaft.

Further preferably, the connecting portion is arranged to axially urge the shaft portions towards each other.

Further preferably, each shaft portion includes a respective hub element against which the inner surface of the grinding shell rests. The shape of the hub element preferably corresponds to the inner surface of the grinding shell to ensure a high frictional interference between the two parts so that the grinding shell will not move in any direction relative to the shaft.

Further preferably, each hub element has a frustoconical shape, and wherein the inner surface of the grinding shell has two inner surface portions, each having a frustoconical shape corresponding to the frustoconical shape of the corresponding hub element, said inner surface portions of the grinding shell being arranged such that the smaller bases of the respective frustoconical shapes face each other and the larger bases of the respective frustoconical shapes face away from each other.

By using such a double truncated cone geometry, the clamping of the grinding shell on the shaft is ensured. When mounting the grinding shell, the shell is mounted axially on the first part of the removed shaft until the conical shape of the shaft and the inner part of the grinding shell stops further axial movement. The second portion of the shaft is then installed by pushing the second portion of the shaft axially into the housing until the conical shape of the second shaft portion and the grinding housing ceases to move. The outer sides of the shaft portions then abut the inner sides of the grinding shell, respectively, over their entire surface, creating a large frictional force between the components. The double conical geometry of the securing mechanism of the grinding shell may use a larger angle than the slightly single conical shape of the prior art. In the prior art, a large angle single cone shape may risk loosening the grinding shell during operation of the roller mill. Using the double conical shape presented here, cones of any angle can be used. Practical angles may be, for example, 2 to 5 degrees, so that both the assembly and disassembly processes are convenient.

It is further preferred that the larger base of each frustoconical shape of the inner surface portion of the grinding shell is arranged at the corresponding axially outer end of the grinding shell. Advantageously, the frusto-conical shape of the end of the shaft portion at the outside of the surrounding grinding shell is such that the shaft portion does not get stuck inside the grinding shell when the shaft portion and the grinding shell are disassembled.

It is further preferred that the smaller bases of the respective frustoconical shapes of the inner surface portions of the grinding shell coincide so that no edge is formed against which the shaft portion can be pressed when the shells are not correctly aligned. It is also easier to make the two inner sides of the outer shell have the same conical shape and angle during the manufacturing process. The mounting is also simplified, since the grinding shell is symmetrical and can be placed on the shaft from either side with respect to its longitudinal axis. Another advantage is that if the shell wear during operation of the roller mill is asymmetric, the grinding shell is removed and turned 180 degrees.

Further preferably, the coupling is arranged to axially urge said hub elements towards each other, thereby pressing said hub elements against the inner surface of the grinding housing and retaining the grinding housing on said shaft.

The frusto-conical shape of the components as described above will cause an increase in frictional interference between the grinding shell and the shaft when the axial force pressing the shaft portions towards each other increases. The friction between the shaft and the grinding shell can thus be adjusted to be high enough to ensure that the grinding shell does not loosen or move relative to the shaft part during operation, but low enough not to crack the grinding shell due to material tension between the parts.

Further preferably, the connection of at least one of the shaft portions comprises a mechanical, pneumatic, hydraulic or magnetic connection. The choice of what coupling means to provide the axial force to press the shaft parts together depends on the amount of force required, what is practical and what is achievable at a reasonable cost. Preferably, the connecting portion of at least one of the shaft portions comprises a clamping device disposed longitudinally through the corresponding shaft portion, the clamping device having an actuating end external to the shaft and an engaging end projecting from the corresponding inner end and engaging in the other corresponding shaft portion.

In one embodiment, the connecting portion of at least one of the shaft portions comprises a clamping device disposed longitudinally through the corresponding shaft portion, the clamping device having an actuating end external to the shaft and an engaging end projecting from the corresponding inner end and intended to be engaged in the grinding housing. Thereby, the shaft portion can be firmly fixed in the grinding shell.

According to a further embodiment, the dismounting of the shaft part may be difficult after long and intensive use of the roller mill, which further comprises extracting means arranged to push said shaft parts axially away from each other for dismounting said shaft. Preferably, the extracting means comprises a chamber defined between the inner ends of said shaft portions and a duct provided through at least one of said shaft portions, having an end opening into said chamber and another end opening out of the corresponding shaft portion arranged to be connected to a source of pressure to allow selective pressurisation of said chamber to urge said shaft portions away from each other in opposite axial directions. When the shaft part is dismounted, the chambers will be pressurized and the parts will be pushed away from each other and thus removed.

In another embodiment, the extracting means may comprise socket means arranged to push said shaft portions away from each other in opposite axial directions. The socket device may generate the force required to remove the shaft from the grinding shell. Furthermore, the socket means may be arranged to urge the shaft portions towards each other. A particularly secure connection of the shaft part and the grinding shell is thereby achieved.

Further preferably, one of the inner ends of the shaft portions comprises a guide portion and the other axial core element comprises a guide receiving portion, the guide portion being arranged to connect in the guide receiving portion when the shaft portions are connected to each other, thereby keeping the two shaft portions axially aligned with each other. If axial alignment is not ensured, the grinding shell will oscillate and cause unnecessary and uneven wear of the wear resistant layer of the grinding shell.

Further preferably, the guide portion includes at least one end axial projection of the corresponding inner end portion, the guide receiving portion includes an end axial groove provided in the other inner end portion, and the end axial groove is sized to slidably receive and axially guide the corresponding end axial projection when the shaft portions are connected to each other.

It is a further object of the invention to provide a method of assembling a roller for a roller mill, the roller comprising a shaft and a substantially cylindrical grinding shell having an inner surface held around the shaft, the shaft further comprising two shaft portions. The method comprises the following steps: the grinding housing is mounted on the first shaft part, the second shaft part is pushed into the grinding housing towards the first shaft part, and the shaft parts are releasably connected to each other using the connecting part, the two shaft parts thus forming the shaft. By using the inventive roller described above, the invention thus provides a method for easy and quick assembly and disassembly of a roller for a roller mill, the roller having a shaft comprising two parts connected by a tubular grinding shell. This method is advantageous when replacing worn grinding shells of the rollers of the grinding mill.

It should be noted that the method of the invention can combine any of the features described above with the roller of the invention for a roller mill and have the same corresponding advantages. In a particular variant of the method, the shaft parts are connected to each other via a grinding shell.

Drawings

In the following, by way of non-limiting example, several embodiments will be described in more detail. In the drawings:

fig. 1 shows a cross-sectional side view of a roller mill according to an embodiment of the invention, showing two shaft parts in a mounted state inside a grinding shell in the form of a tubular sleeve;

FIG. 1A shows an enlarged detail of FIG. 1, showing the sealing areas between the clamping device and the respective shaft portions carrying the clamping device;

FIG. 2 shows an end view of a roll constructed in accordance with the present invention, the end view being taken according to line II-II in FIG. 1;

fig. 3 shows a cross-sectional side view of a roller mill according to another embodiment of the invention;

fig. 4 shows the roller mill of fig. 3 during disassembly.

Detailed Description

Fig. 1 shows one roller R of a preferred embodiment of a roller mill (not fully shown) according to the invention. Each roll R comprises a shaft S which is held in the roller mill by two bearings M. The shaft S is constituted by a first shaft portion 20 and a second shaft portion 10, each of the first shaft portion 20 and the second shaft portion 10 comprising a respective end portion 21, 11 of the shaft S and a respective axial core element 22, 12, in this preferred but not limiting embodiment the axial core elements 22, 12 comprising a frustoconical portion 23, 13.

The hub element 12 of the second shaft part 10 has a guide means 14, which guide means 14 is to be connected to a guide receiving means 24 provided in the other hub element 22 of the first shaft part 20 for keeping the shaft parts 10, 20 axially aligned with each other.

Each frustoconical portion 13, 23 has its larger base turned towards the corresponding axial end 11, 21 of the shaft S and its smaller base turned towards the other shaft portion 10, 20. The larger base area and the smaller base area of the frustoconical portions 13, 23 are greater than the area enclosed by the areas of the ends 11, 21 of the shaft S. The angle of the conical shape of the frusto-conical portions 13, 23 may vary between items but is generally maintained between about 2 degrees and about 5 degrees about the axis of the assembly.

The guide means 14 carried by one hub element 12 comprise at least one end axial projection 14a, the end axial projection 14a having a substantially cylindrical cross section smaller than the cross section of the adjacent smaller base of the corresponding frustoconical portion 13. The guide receiving means 24 of the other hub element 22 comprises an end axial groove 24a, the end axial groove 24a having a similar cross-section to the axial projection 14a, i.e. substantially cylindrical, dimensioned to slidably receive and axially guide a corresponding end axial projection 14a of the hub element 12 when said hub elements 12, 22 are pushed axially towards each other. In fig. 1, the guide means 14 is in an end position inside the groove 24a of its receiving means 24.

As shown in fig. 1, the two shaft portions 10, 20 are axially pushed towards each other by the connecting portion 40 for connecting the guide device 14 to the guide receiving device 24. In fig. 1, the connection is a mechanical clamping device 40 arranged longitudinally through the shaft part 10, which clamping device 40 has an actuating end 43 outside the shaft S and an engaging end 42 protruding from the hub element 12 into the hub element 22 engaging the shaft part 20.

In fig. 1, the clamping means 40 are defined by a plurality of bolts 41, the plurality of bolts 41 being fixed in corresponding longitudinal through holes 15 provided in the shaft portion 10. Each bolt 41 has an engagement threaded end 42, the engagement threaded end 42 being engaged in the longitudinal threaded hole 25 of the other shaft portion 20. An actuating end 43 opposite the engaging end 42 projects outwardly from the end 11 of the shaft 10 and is also threaded and configured to engage a pulling device 46, shown in fig. 1 as a nut.

As can be seen in fig. 2, the bolts 41 are evenly distributed through the two shaft portions 10, 20, preferably in a circular arrangement, angularly spaced from each other, so that a controlled clamping of the pulling means 46 in the form of a nut produces an axial displacement of the two shaft portions 10, 20 towards each other in the axial direction of the shaft.

Referring again to fig. 1, the grinding shell 30 has the form of a tubular sleeve constructed of a hard material sufficient for grinding or shredding work. The inner surface of the grinding shell 30 has two frustoconical surfaces 31, each tapering with its larger base turned towards the corresponding end of the grinding shell 30. The smaller bases of the frustoconical surfaces 31 are directed towards the middle of the grinding shell facing each other and, in fig. 1, coincide with each other, resembling an hourglass shape. The bolt 41 of the mechanical clamping device 40 will push the two shaft portions 10, 20 axially towards each other, pushing the frustoconical portions 13, 23 into position against the corresponding inner surfaces of the grinding shell 31.

Tightening the gripping means 40 and pulling means 46 will gradually increase the radial pressure of the shaft portion on the respective frusto-conical inner surface 31 of the grinding shell 30, resulting in an increase in the friction between the grinding shell and the shaft portion 10, 20, preventing movement of the grinding shell relative to the shaft portion. The bolts 41 of the clamping device 40 are dimensioned to create a degree of frictional interference between the frusto-conical portions 13, 23 and the grinding shell 30 sufficient to lock the grinding shell 30 about the shaft S during all grinding and grinding operations within the specification of the roller mill 10.

The roll R may be provided with extraction means E to push the shaft portions axially in opposite directions, to separate the respective axial elements 12, 22 from each other and to separate the axial elements 12, 22 from the inner surface 31 of the grinding shell 30 when the grinding shell 30 is detached from the shaft portions 10, 20. With reference to fig. 1, the extracting device E comprises a chamber C defined between the two axial core elements 12, 22 and a duct 18 arranged through the shaft 10, the duct 18 having an opening to the outside of the shaft 10 so as to allow the chamber C to be selectively pressurized through the duct 18.

In fig. 1, the end axial grooves 24a of the guide-receiving means 24 present an axial extension greater than that of the respective end axial projections 14a of the guide means 14, so as to define a chamber C between the free ends of said end axial projections 14a and the inside of the end axial grooves 24 a. The conduit 18 allows to selectively pressurize the chamber C to push the shaft portions 10, 20 in opposite axial directions away from their positioning against the inner surface portion 31 of the grinding shell 30 for replacement operations of the grinding shell 30. The purpose of the pressurization of the chamber C is to assist the axial movement for releasing the two shaft parts 10, 20. The greater the importance of this pressurization, the smaller the taper of the frustoconical portions 13, 23 and 31.

To ensure a better sealing of the chamber C, sealing means 50 in the form of an O-ring supported by friction-resistant metal or elastomer material are provided around the base portion 14b, which sealing means 50 act against the enlarged portion 24b of the end axial groove 24 a. In this case, the annular seal device 50 is mounted between the base portion 14b and the enlarged portion 24 b.

Considering that the bolts 41 may be provided through the chamber C, preferably, as shown in fig. 1A, the bolts 41 are also provided through a sealing ring 47 arranged inside the longitudinal through holes 15 to obtain a high tightness to the annular gap defined between each bolt 41 and the opposite wall of the respective longitudinal through hole 15. In the illustrated construction, the second shaft portion 10, i.e. the portion not connected to the motor unit (not shown), has a plate 60 at its end, the plate 60 being operable as an external axial stop for the bearing M, and in the embodiment of fig. 1, the plate 60 is fastened to the adjacent shaft portion 10 by means of bolts 41.

The replacement of the grinding shell will be described with reference to fig. 1 to 3. Starting from the roller R assembled with the grinding shell 30 tightly seated on the two frustoconical shaft portions 10, 20, as described above, the shaft portion 10 is pressed towards the shaft portion 20 by the frictional force caused by the force applied by the bolt 41 and the nut 46, thereby exerting a radial pressure on the frustoconical inner surface 31 of the grinding shell 30. Assuming that the grinding shell 30 has been worn out due to the normal operation of the roller mill and has to be replaced, the shell will have to be replaced to ensure good grinding quality and no risk of damaging the roller mill shaft.

Disassembly is initiated by loosening and removing the nut 46. The end plate 60 and optionally the bearing holding the shaft part 10 are removed. During disassembly of the shaft part 10, the bolt 41 is also removed by unscrewing the bolt 41 from the threaded hole 25 in the shaft part 20, in order to avoid damaging the bolt. The shaft part 10 can now be freely detached. However, it is still likely to be difficult to axially remove the shaft portion due to frictional forces from the inner surface 31 of the grinding shell 30. The extraction device E is then used for assistance during the disassembly process. A source of pressurised fluid (not shown) is connected to the conduit 18 in the second shaft part 10, applying pressure to the chamber C between the shaft parts 10, 20. Pressurization of chamber C will urge the second shaft portion 10 to move away from the first shaft portion 20. The grinding shell 30 is then freely removed and replaced with a new one.

The reassembly of the roll R is then naturally carried out in a reverse manner compared to the disassembly process just described. A new grinding shell 30 is placed on the first shaft portion 20 until the conical shape of the shaft and the position allowed by the inner surface 31 of the grinding shell 30. The second shaft part 10 is then put in place and pushed towards the first shaft part 20. The guide means 14 guides the second shaft part 10 into an axially aligned position by sliding into the receiving means 24 of the first shaft part 20. The bolt 41 is screwed back into the thread 25 of the first shaft part 20 and the bearing (if removed from the second shaft part 10) is put back in place. The end plate 60 slides over the end of the bolt 41 and the assembly is suitably tightened by tightening the nut 46 to apply a suitable radial pressure from the shaft portion 10 to the new grinding shell 30 so that the grinding shell 30 does not move relative to the shaft portions 20, 21 during operation of the roller mill.

The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims.

For example, the conical shape of the shaft portions 10, 20 corresponding to the internal shape of the grinding shell 30 may be formed in different ways. For example, the frustoconical portions 13, 23 of the shaft portions 10, 20 may have a structure which is integral in the radial direction, e.g. a wedge-shaped portion, the inner surface 31 of the grinding shell then naturally having a corresponding groove. The shaft part may also have a cogged configuration in the radial direction of the frusto-conical part 13, 23 of the shaft part 10, 20.

The connection 40 that urges the shaft portions 10, 20 towards each other is in the described embodiment a mechanical form of a clamping device 40 with a bolt 41 and a nut 46. It should be understood, however, that the connecting means may also be pneumatic, hydraulic, magnetic or any other form capable of pushing the two shaft portions 10, 20 together.

The mechanical clamping device 40 may be configured otherwise, for example. A projection of the shaft part 20, on which a thread is provided, may for example be arranged through the shaft part 10, which projection passes completely through the shaft part 10 for fastening a nut. The nut then pushes the parts together in the same way as in the embodiment of figure 1.

An alternative embodiment of the grinder roll of the present invention may be shown in fig. 3. In this embodiment, details corresponding to those of the embodiment of fig. 1 are given the same reference numerals, but increased by 100. For details denoted with reference letters, corresponding details in the embodiment of fig. 3 are denoted by the same letters followed by' marks.

Like the roller mill R of fig. 1, the roller mill R 'of fig. 3 has an axis S' consisting of two shaft parts 110, 120. The shaft S' carries the grinding housing 130. In contrast to the previously described embodiments, the first shaft portion 120 and the second shaft portion 110 do not pass all the way through the grinding housing 130 to be directly connected to each other. Conversely, the inner end 121 of the first shaft portion 120 engages the first end 126 of the grinding housing 130 and the inner end 111 of the second shaft portion 110 engages the second end 116 of the grinding housing 130. In this way, the shaft portions 110, 120 are indirectly connected to each other via the grinding housing 130, thereby forming the shaft S 'of the grinding roller R'. Thus, in this embodiment, the axis S' is not a single continuous axis. The shaft portions 110, 120 are connected to the ends 116, 126 of the grinding housing 130 by a connection 140, the connection 140 being in the form of a bolt having an inner engagement end 142 and an outer actuating end 143. The inner engagement end 142 of each bolt 140 is tightened into a corresponding hole 115 in the grinding housing 130. By tightening the bolt 140, the shaft portions 110, 120 are pushed towards each other and abut closely against the frusto-conical inner surface portions 131 of the corresponding recesses 117, 127 at the ends 116, 126 of the grinding housing 130.

The grinding shell 130 may be replaced when the grinding shell 130 has become worn by the grinding operation. The bolt 140 is screwed out of the hole 115 in the grinding housing 130 and extraction means E' in the form of socket means 170 are used for pushing the shaft portions 110, 120 away from each other. As can be seen in fig. 4, the inner ends 111, 121 of the shaft portions 110, 120 exit the grooves 117, 127 in the ends 116, 126 of the grinding housing 130. The socket device 170 moves the bearing M' on the left hand side of the figure in such a way that the first shaft part 120 is distanced from the second shaft part 110, thereby completely freeing the grinding housing 130. The worn grinding shell 130 can now be removed and replaced by a new grinding shell. The worn abrasive shell 130 may be discarded or alternatively repaired and provided with a new wear resistant abrasive surface.

The socket device 170 may also be used to push the shaft portions 110, 120 towards each other. Thus, additional force is provided to hold the shaft portions 110, 120 and the grinding housing 130 together.

In the embodiment shown in fig. 3, the grinding housing 130 is a hollow cylinder or sleeve. However, the grinding shell may also be a more or less solid cylinder, with the grooves 117, 127 extending only a short axial distance into the grinding shell 130 from the respective ends 116, 126. Naturally, the length of the groove may be adapted to any shape and size of the inner end of the shaft portion.

A corresponding hybrid variant between the grinding shell 130 of fig. 1 and the grinding shell 130' of fig. 3 is also possible, wherein parts of the shaft parts similar to the inner ends 111, 121 of the shaft parts 110, 120 of fig. 3 are fastened in grooves similar to the grooves 117, 127 in fig. 3, and wherein the smaller diameter shaft part of each shaft part extends further into the grinding shell, so that the ends of these small diameter shaft parts can be connected to each other in a manner similar to the connection in fig. 1.

According to one aspect, the invention may be defined in accordance with the following.

1. A roller for a roller mill, the roller comprising a shaft and a generally cylindrical grinding shell supported by the shaft, wherein the grinding shell has a groove at each axial end, and wherein the shaft comprises two shaft portions, each shaft portion having a respective inner end, each inner end being arranged to be positioned in a corresponding groove of the grinding shell, and the shaft portions having a connecting portion arranged to connect the shaft portions to the grinding shell, thereby forming the shaft.

2. The roller of item 1, wherein the grinding shell is a generally tubular sleeve.

3. The roller of item 1, wherein the grinding shell is a substantially solid cylinder, the groove extending only part way along the axial length of the grinding shell.

4. A roller according to any preceding claim, wherein each shaft portion comprises a hub element against which an inner surface of the groove is located.

5. The roller as claimed in item 4, wherein each groove of the grinding shell has an inner surface portion having a frustoconical shape corresponding to the frustoconical shape of the axial core element, the inner surface portions of the grooves being arranged such that the smaller bases of the respective frustoconical shapes face each other and the larger bases of the respective frustoconical shapes face away from each other.

6. The roller of item 5, wherein the larger bases of the frustoconical shape of the inner surface portions are arranged at respective axial ends of the grinding shell.

7. A roll according to any of claims 4-6, wherein the connecting portions can be arranged to push the hub elements axially towards each other, thereby pressing the hub elements against the inner surface of the groove and retaining the grinding shell on the shaft formed by the two shaft portions.

8. The roll of any preceding claim, wherein the connection of at least one shaft portion comprises a mechanical, pneumatic, hydraulic or magnetic connection.

9. The roller of any preceding claim, the connection portion of the at least one shaft portion comprising bolts secured in corresponding through holes provided in the at least one shaft portion, each bolt having an engagement end defined by an end to be engaged in the grinding shell, and an actuation end defined by an opposite end, the actuation end projecting outwardly from the end of the at least one shaft portion.

10. A roller according to any one of the preceding claims, further comprising extracting means arranged to urge the shaft portions axially away from each other for dismounting the shaft.

11. A roller as in item 10, wherein the extracting means comprises socket means arranged to urge the shaft portions away from each other in opposite axial directions.

12. A roller mill for grinding material such as minerals comprising at least one roller as described in any one of the preceding claims.

13. A method for assembling a roller of a roller mill, the roller comprising a shaft and a substantially cylindrical grinding shell, wherein the grinding shell has a groove at each axial end, and wherein the shaft comprises two shaft portions, the method comprising the steps of:

engaging one of said grooves in one of said grooves,

the other shaft portion is pushed into the other groove,

the shaft portion is releasably connected to the grinding housing using a connecting portion, whereby two shaft portions form the shaft.

14. The method recited in item 13, further including the step of using the connecting portion to axially urge the shaft portions toward each other and into the groove.

15. The method as recited in item 14, further comprising the steps of:

axially urging the shaft portions towards each other until the inner surface portions of the recesses having a frustoconical shape are positioned against the respective frustoconical portions of the shaft portions, the inner surface portions of the recesses being arranged with the smaller bases of the respective frustoconical shapes facing each other and the larger bases of the respective frustoconical shapes facing away from each other.

Claims (15)

1. A roller for a roller mill, said roller comprising a shaft (S) and a substantially cylindrical grinding shell (30; 130) having an inner surface held around said shaft (S, S'),

wherein the shaft (S, S') comprises two shaft parts (10, 20; 110, 120), wherein the shaft parts (10, 20; 110, 120) comprise a connecting part (40, 140) arranged to connect the shaft parts (10, 20) to each other, thereby forming the shaft (S),

it is characterized in that the preparation method is characterized in that,

each shaft portion (10, 20) having a respective inner end (11, 21), wherein the inner ends (11, 21) are arranged to be positioned facing each other and to be connected to each other by the connecting portion (40),

each shaft portion (10, 20; 110, 120) comprising a respective axial core element (12, 22; 112, 122), against which the inner surface of the grinding shell (30, 130) is positioned, and each axial core element (12, 22; 112, 122) having a frustoconical shape, and wherein the inner surface of the grinding shell (30, 130) has two inner surface portions (31, 131),

each inner surface portion (31, 131) has a frustoconical shape corresponding to the frustoconical shape of the corresponding axial core element (12, 22; 112, 122), said inner surface portions (31, 131) of the grinding housings (30, 130) being arranged such that the smaller bases of the respective frustoconical shapes face each other and the larger bases of the respective frustoconical shapes face away from each other.

2. The roller of claim 1, wherein the grinding shell (30, 130) is in the form of a generally tubular sleeve.

3. A roller according to any one of the preceding claims, wherein said connecting portions (40, 140) are arranged to axially urge said shaft portions (10, 20; 110, 120) towards each other.

4. A roll according to claim 1, wherein the larger base of each frustoconical shape of the inner surface portion (31, 131) of the grinding shell (30, 130) is arranged at the respective axially outer end of the grinding shell (30, 130).

5. A roll according to claim 1 or 4, wherein the smaller bases of the respective frustoconical shapes of the inner surface portions (31) of the grinding shells (30) coincide.

6. A roll according to claim 3, wherein the connections (40, 140) are arranged to push the hub elements axially towards each other, thereby pressing the hub elements (12, 22; 112, 122) against the inner surface of the grinding shell (30, 130) and retaining the grinding shell (30, 130) on the shaft (S, S').

7. A roller according to claim 1, wherein the connecting portion (40, 140) of at least one of the shaft portions (10, 20; 110, 120) comprises a mechanical, pneumatic, hydraulic or magnetic connection.

8. A roller according to claim 1, wherein the connection portion of at least one of the shaft portions (10, 20) comprises a gripping device (40) longitudinally disposed through the corresponding shaft portion (10, 20), having an actuating end (43) external to the shaft (S) and an engaging end (42) projecting from the corresponding inner end (11, 21) and engaging in the other corresponding shaft portion (10, 20).

9. A roller according to claim 1, further comprising extracting means (E, E ') arranged to push said shaft portions (10, 20; 110, 120) axially away from each other for dismounting said shafts (S, S').

10. A roller according to claim 9, wherein the extracting means (E) comprises a chamber (C) defined between the inner ends (11, 21) of the shaft portions (10, 20) and a duct (18) provided through at least one of the shaft portions (10, 20), the duct (18) having an end opening into the chamber (C) and another end opening out of the corresponding shaft portion (10, 20) arranged to be connected to a pressure source to allow selective pressurization of the chamber (C) to push the shaft portions (10, 20) away from each other in opposite axial directions.

11. A roller according to claim 9, wherein the extracting means comprise socket means (170) arranged to push said shaft portions (110, 120) away from each other in opposite axial directions.

12. A roll according to claim 1, wherein one of the inner ends (11, 21) of the shaft portions (10, 20) comprises a guide portion (14), the other axial core element (12, 22) comprising a guide receiving portion (24), the guide portion (14) being arranged to be connected in the guide receiving portion (24) when the shaft portions (10, 20) are connected to each other, thereby keeping the two shaft portions (10, 20) axially aligned with each other.

13. A roller according to claim 12, wherein the guide portion (14) comprises at least one end axial projection (14a) of the corresponding inner end portion (11), the guide receiving portion (24) comprises an end axial groove (24a) provided in the other inner end portion (21), and the end axial groove (24a) is dimensioned to slidably receive and axially guide the corresponding end axial projection (14a) when the shaft portions (10, 20) are connected to each other.

14. A roller mill for grinding mineral material comprising at least one roller as claimed in any one of the preceding claims.

15. A method for assembling a roller of a roller mill, the roller comprising a shaft (S; S ') and a substantially cylindrical grinding shell (30; 130) having an inner surface held around the shaft (S, S '), characterized in that the shaft (S, S ') further comprises two shaft portions (10, 20; 110, 120), the method comprising the steps of:

mounting a grinding shell (30, 130) on the first shaft portion (20, 120),

pushing the second shaft part (10, 110) into the grinding housing (30, 130) towards the first shaft part (20, 120),

the shaft parts are releasably connected to each other using a connecting part (40, 140), the two shaft parts (10, 20; 110, 120) thus forming the shaft (S, S'),

the shaft parts (10, 20; 110, 120) are axially pushed towards each other using the connecting part (40, 140) until the frusto-conical inner surface parts (31, 131) of the grinding housings (30, 130) are positioned against the respective frusto-conical parts (13, 23; 113, 123) of the shaft parts (10, 20, 110, 120), the inner surface parts (31; 131) of the grinding housings (30, 130) being arranged such that the smaller bases of the respective frusto-conical shapes face each other and the larger bases of the respective frusto-conical shapes face away from each other.