CUTTER ASSEMBLY WITH CUTTER DEVICE AND METHOD OF ASSEMBLING

Abstract

A cutter assembly for an undercutting machine for cutting a rock workface and a method of assembling a cutter assembly is provided. The cutter assembly includes a shaft mountable on the machine with one end extending from the machine, and a cutter device arranged in connection to the extended end of the shaft. The cutter device is connected releasably and rotationally rigid to the shaft with a locking arrangement. The locking arrangement includes a first locking device arranged to transfer substantially axial loads, and a second locking device arranged to transfer substantially radial loads.

Claims

1. A cutter assembly for an undercutting machine for cutting a rock workface, the cutter assembly comprising: a shaft mountable on the machine with one end extending from the machine; and a cutter device arranged in connection to the extended end of the shaft, wherein the cutter device is connected releasably and rotationally rigid to the shaft with a locking arrangement, wherein the locking arrangement includes a first locking device arranged to transfer substantially axial loads, and a second locking device arranged to transfer substantially radial loads.

2. The cutter assembly as claimed in claim 1, wherein the first and second locking devices are radially spaced apart from each other.

3. The cutter assembly as claimed in claim 1, wherein the second locking device is arranged to center the cutter device on the shaft and/or the first locking device is arranged to transfer bending moments.

4. The cutter assembly as claimed in claim 1, wherein the first locking device includes one, two or more fastening elements for fastening the cutter device to the shaft.

5. The cutter assembly as claimed in claim 1, wherein the second locking device includes a tapered locking assembly, including at least one fixing element for fixing a tapered outer surface and a tapered inner surface relative to each other.

6. The cutter assembly as claimed in claim 5, wherein the tapered locking assembly includes a locking ring including the tapered outer surface.

7. The cutter assembly as claimed in claim 5, wherein the tapered locking assembly includes a further locking ring including the tapered inner surface.

8. The cutter assembly as claimed in claim 5, wherein the tapered inner surface is formed on the cutter device.

9. The cutter assembly as claimed in claim 1, wherein the cutter device and the shaft contact each other in sections at a butt joint.

10. The cutter assembly as claimed claim 1, wherein a sealing carrier is releasably arranged on the shaft for carrying at least a part of a sealing arrangement.

11. The cutter assembly as claimed in claim 10, wherein the sealing carrier is fixed rotationally rigid to the shaft.

12. The cutter assembly as claimed claim 10, wherein the sealing carrier is sealed against the shaft.

13. The cutter assembly as claimed claim 1, wherein the cutter device is a cantilevered cutter ring.

14. A cutter module comprising two or more cutter assemblies as claimed in claim 1.

15. A method of assembling a cutter assembly for an undercutting machine for cutting a rock workface, the method comprising: providing a cutter assembly, the cutter assembly including a shaft mountable on the machine with one end extending from the machine and a cutter device arranged in connection to the extended end of the shaft; and connecting the cutter device releasably and rotationally rigid to the shaft with a locking arrangement, the locking arrangement including a first locking device arranged to transfer substantially axial loads, and a second locking device arranged to transfer substantially radial loads, by: applying an initial tension to the second locking device; applying an initial tension to the first locking device; applying a target tension to the second locking device; and applying a target tension to the first locking device.

Description

[0064] Preferred embodiments of the invention shall now be described with reference to the attached drawings, in which

[0065] FIG. 1: shows a longitudinal section of an exemplary embodiment of a cutter assembly along section A-A as indicated in FIG. 2;

[0066] FIG. 2: shows a cross section of the cutter assembly according to FIG. 1;

[0067] FIG. 3: shows a part of a top view of the cutter assembly according to FIG. 1; and

[0068] FIG. 4: shows a longitudinal section of the cutter assembly with an indication of the centre plane of the first rolling element and the centre of the sphere formed by outer surfaces of second rollers of the second rolling element.

[0069] FIGS. 1 to 4 show an exemplary embodiment of a cutter assembly 1 for an undercutting machine for cutting a rock workface comprising a shaft 100 and a shaft supporting structure 10 in the form of a housing. The shaft 100 is at least partly arranged within the shaft supporting structure 10 and has an extended end 102 extending from the machine provided with a cutter device 200 and a rear end 101 for mounting the shaft 100 to the machine. Rear end 101 of the shaft 100 is provided with a pretensioning washer 22 which is connected to the rear end 101 of the shaft 100 via pretensioning bolts 23. At the rear end 20 of the cutter assembly 1, a rear cover 21 is sealingly, via o-ring seal 24, connected to the shaft supporting structure 10 covering the rear end 101 of the shaft 100 with the pretensioning washer 22. The shaft supporting structure 10 comprises several bores 11 for connecting the shaft supporting structure to an undercutting machine for cutting a rock workface.

[0070] The shaft 100 has a central hollow interior 110 and a longitudinal axis X or axial direction. The central hollow interior 110 is covered by an end element 120. Between the shaft 100 and the shaft supporting structure 10, a first rolling element 510 is arranged in a floating or slidable manner in the axial direction. Further, a second rolling element 520 is arranged between the shaft supporting structure 10 and the shaft 100. Further, an optional, but preferred third rolling element 530 is arranged between the shaft supporting structure 10 and the shaft 100. The second rolling element 520 is arranged further distant from the cutter device 200 in the axial direction or along the longitudinal axis X of the shaft 100 than the first rolling element 510. The third rolling element 530 is arranged further distant from the cutter device 200 in the axial direction or along the longitudinal axis X of the shaft 100 than the first rolling element 510 and the second rolling element 520.

[0071] In the exemplary embodiment shown herein, the first rolling element 510 is a toroidal roller bearing, the second rolling element 520 is a spherical thrust bearing and the third rolling element 530 is a tapered roller bearing. The first rolling element 510 comprises first rollers 511 surrounded by inner and outer ring race ways 512, 513. The second rolling element 520 comprises second rollers 521, shaft and housing washers 522, 523, and cage 524. The third rolling element 530 comprises third rollers 531, inner and outer rings 532, 533, and cage 534.

[0072] At the extended end 102 of the shaft 100, the cutter device 200 is connected releasably and rotationally rigid to the shaft 100 with a locking arrangement 800. The locking arrangement 800 comprises a first locking device 300 arranged and adapted to transfer substantially axial loads and a second locking device 400 arranged and adapted to transfer substantially radial loads. The first and the second locking devices 300, 400 are radially spaced apart from each other, wherein the first locking device 300 is located radially outwardly from the second locking device 400.

[0073] The first locking device 300 comprises a plurality of fastening elements for fastening the cutter device 200 to the shaft 100. In the present example, the fastening elements are fastening bolts extending through mating bores 290 in the cutter device 200 and extending into dead bores 190 in the shaft 100. The fastening elements may be threaded bolts and engage mating threads in the bores 290 and 190 in the cutter device 200 and the shaft 100. Preferably, the fastening elements are arranged equidistant in a circumferential manner.

[0074] Further, the cutter device 200 and the shaft 100 contact each other in sections at a butt joint 103 in the area of or around the first locking device 300. In particular, an inner axial end face or inner axial contact face 240 of the cutter device 200 contacts a corresponding contact face on the shaft 100 for creating the butt joint 103. This butt joint provides an effective way for transferring axial loads in a pushing direction from the cutter device 200 to the shaft 100. This can be advantageous to increase the capacity to transfer axial loads in the direction of pushing forces in addition to the capacity to transfer axial loads in both axial direction (pushing and pulling forces) provided by the fastening elements in the form of threaded bolts, for example. This is particularly advantageous, since during usual operating conditions of cutter assemblies for undercutting machines for cutting rock work faces, the pushing forces that need to be transferred from the cutter device 200 to the shaft 100 usually are considerably higher than pulling forces that need to be transferred in the opposite direction. Therefore, by providing a butt joint 103 in addition to fastening elements at the first locking device 300, an efficient axial load transfer can be provided.

[0075] Further, by being adapted and arranged to transfer axial loads in opposite directions, the first locking device 300 is also arranged and adapted to transfer bending moments, since, in particular due to the relatively larger diameter of the first locking device 300 compared to the second locking device 400, occurring bending moments can be split into positive and negative axial forces occurring on two opposite fastening elements.

[0076] The second locking device 400 comprises in the example shown in FIGS. 1 to 4 a tapered locking assembly 420 including a plurality of fixing elements 410 for fixing a tapered outer surface and a tapered inner surface relative to each other. In the example of a tapered locking assembly 420 shown herein, the tapered locking assembly 420 includes an inner locking ring 422 comprising the tapered outer surface and an outer locking ring 421 comprising the tapered inner surface. However, in an alternative embodiment, the tapered inner surface could be formed on the cutter device 200, in which case an outer locking ring would not need to be provided. With the plurality of fixing elements 410, which are preferably arranged equidistant in a circumferential manner, the inner and outer tapered surfaces can be fixed relative to each other, thereby centring the cutter device 200 on the shaft 100. Further, the tapered locking assembly 420 is efficient in transferring radial loads between the cutter device 200 and the shaft 100.

[0077] This locking arrangement 800 with the first and second locking devices 300 and 400 has the advantage that the cutter device 200 can be removed in a substantially non-destructive way and overhauled and reinstalled or replaced by a new cutter device, without having to bring the whole cutter assembly 1 to a workshop, but rather leave the cutter assembly 1 installed on the undercutting machine and exchange only the cutter device 200 in situ. When exchanging the cutter device 200, in particular installing the cutter device 200 on the shaft 100, it is preferred to arrange the second locking device 400 and the cutter device 200 on the shaft and to arrange the first locking device 300 in place. In particular, it is preferred that the following steps are carried out in the following order: Firstly, applying an initial tension to the second locking device, which preferably is less than 50% of a target tension of the second locking device; secondly, applying an initial tension to the first locking device, which is preferably less than 50% of a target tension of the first locking device; thirdly, applying the target tension to the second locking device; and lastly, applying the target tension to the first locking device. The target tension of the first and second locking device (and correspondingly, the initial tension of the first and second locking device) may differ and depend on the kind of locking devices employed as first and second locking devices and, in particular, the kind of fixing or fastening elements employed in the first and second locking devices.

[0078] By installing the cutter device on the shaft in this manner, it can be assured that the second locking device 400 properly centres the cutter device 200 on the shaft 100 while at the same time the connection at the first locking device is put in place properly for a correct transfer of axial loads.

[0079] The bearing arrangement with the first, second and third rolling elements 510, 520, 530 has been designed to allow for clearer defined load cases for each rolling element than in the prior art, and allows to design and dimension the bearings more precisely, resulting in a higher bearing lifetime. The first rolling element 510 is floating or slidable in an axial direction, such that the first rolling element 510 substantially transfers radial loads. Axial loads are transferred primarily by the second and third rolling elements 520, 530.

[0080] The third rolling element 530 and the second rolling element 520 are adapted and arranged such that an inclination direction of the contact angle and/or the rotation axes of the second rollers 521 of the second rolling element 520 is different from an inclination direction of a contact angle and/or rotation axes of third rollers 531 of the third rolling element 530. In this way, the third rolling element 530 primarily serves to take axial forces in a direction opposite to the forces which are taken primarily by the second rolling element 520. In addition, the third rolling element 530 serves to pretension or bias the second rolling element 520.

[0081] In order to achieve that the second rolling element 520 primarily serves to take axial loads and to ensure that the radial loads are primarily taken by the first rolling element 510, a line orthogonal to an outer surface of a second roller 521 of the second rolling element 520 crosses the longitudinal axis X of the shaft 100 at a centre plane 519 of the first rolling element 510, as can be seen in FIG. 4. In particular, since the second rolling element 520 is a spherical thrust bearing, in the longitudinal section the outer surfaces of the second rollers 521 form a (virtual) sphere 528 with a (virtual) centre P. In the example shown herein, this (virtual) centre P of the (virtual) sphere 528 formed by the outer surfaces of the second rollers 521 of the second rolling element 520 lies on the longitudinal axis X and within the (virtual) centre plane 519 of the first rolling element 510, as can be seen in FIG. 4. Alternatively, good results are also achieved in case the centre P of the sphere 528 lies within a range of +/?25% or less, as described above, of the axial extension of the first rolling element 510, in particular its first rollers 511, from that centre plane. In other words, the centre P of the sphere 528 may deviate from the centre plane 519 along the longitudinal axis X of the shaft 100 to some extent within the range mentioned above.

[0082] Preferably, all three rolling elements 510, 520, 530 remain installed in their positions between the shaft supporting structure 10 and the shaft during disassembly of the cutter assembly, for example during removal and/or reinstallation of the cutter device and/or the sealing arrangement and/or the sealing carrier.

[0083] The cutter device 200 in the embodiment shown herein is a cutter ring, but may also have the shape of a cutter disc, for example. Preferably, the cutter device is a cantilevered cutter ring. As shown in the embodiment in the Figures, the cutter device 200 has an outer radial end 210 and an inner radial end 220, wherein the radius of the outer radial end 210 is larger than the radius of the inner radial end 220. Adjacent to the outer radial end is an outer axial end face 230 and adjacent to the inner radial end 220 is an inner axial end face or inner axial contact face 240. Preferably, the outer axial end face 230 and the inner axial end face 240 are parallel to each other.

[0084] The cutter assembly 1 further comprises a sealing carrier 700, which is fixed rotationally rigid to the shaft 100. In the embodiment shown herein, the sealing carrier 700 is ring-shaped and fixed rotationally rigid to the shaft 100 by pins 720 and is sealed against the shaft 100 by an o-ring seal 710. The sealing carrier 700 serves to carry at least a part of a sealing arrangement 600. The sealing arrangement 600 in the embodiment shown herein comprises two o-ring seals 611, 612 sealing the shaft supporting structure 10 and the sealing carrier 700 against the shaft 100. By arranging the sealing carrier 700 releasably on the shaft it is possible to disassemble, in particular service, for example exchange or overhaul, the sealing arrangement 600 or parts thereof easily and in a non-destructive manner. In the embodiment shown herein, it is necessary to first remove the cutter ring 200, before the sealing carrier 700 can be removed.

[0085] In FIGS. 1 to 4, a preferred example of cutter assembly with a releasable cutter ring 200 connected via a locking device 800 and with a special bearing arrangement with a first and second rolling element 510, 520 and a preferred, but optional rolling element 530, is shown. Although in the Figures, these aspects are shown in combination, the different aspects described herein also can be applied separately.

TABLE-US-00001 List of Reference Signs 1 cutter assembly 10 shaft supporting structure 100 shaft 101 rear end 102 extended end 103 butt joint 11 bores 120 end element 190 dead bores 20 rear end 200 cutter device 21 rear cover 210 outer radial end 22 pretensioning washer 220 inner radial end 23 pretensioning bolts 230 outer axial end face 24 o-ring seal 240 inner axial end face 290 bores 300 first locking device 400 second locking device 410 fixing elements 420 tapered locking assembly 421 outer locking ring 422 inner locking ring 510 first rolling element 511 first roller 512 inner ring race way 513 outer ring race way 519 centre plane 520 second rolling element 521 second roller 522, 523 shaft and housing washers 524, 534 cage 528 sphere 529 line 530 third rolling element 531 third roller 532 inner ring 533 outer ring 600 sealing arrangement 611, 612 o-ring seal 700 sealing carrier 710 o-ring seal 720 pin 800 locking arrangement X longitudinal axis P centre