GB2486712A

GB2486712A - A split plain bearing for supporting a rotating shaft

Info

Publication number: GB2486712A
Application number: GB201021859A
Authority: GB
Inventors: Martin Janek Caspall
Original assignee: Cooper Roller Bearings Co Ltd
Current assignee: Cooper Roller Bearings Co Ltd
Priority date: 2010-12-23
Filing date: 2010-12-23
Publication date: 2012-06-27
Also published as: WO2012085537A1; GB201021859D0

Abstract

A bearing comprising an inner bearing 11 removably mounted to a shaft so that the inner bearing rotates with the shaft 22; an outer bearing 12 comprising first and second separable outer bearing portions 31, 32, each having an outer bearing surface and an inner bearing surface which slidingly engages with an outer bearing surface of said inner bearing, the inner surface of said inner bearing portion is cylindrically-profiled, said outer surface of said inner bearing is cylindrically-profiled, said inner surface of said outer bearing is cylindrically-profiled, and said outer surface of said outer bearing is partial-spherically-profiled, and a bearing housing including first and second separable housing portions which jointly support said outer bearing, said first and second bearing housing portions together provide a partial-reverse-spherical contour to support the partial-spherically-profiled outer surface of said outer bearing, said first and second inner bearing portions each being generally semi-cylindrical and engaged with one another to form the inner bearing, said first and second outer bearing portions each being generally semi-cylindrical and engaged with one another to form the outer bearing, engaging edges of the first and second inner and/or the first and second outer bearing portions extending at an angle 0 to the axis of the shaft, where Î â 0Â°

Description

BEARING FOR A SHAFT

BACKGROUND OF THE INVENTION

The present invention relates to a bearing for a shaft. Bearings for shafts are well-known.

However, there are particular problems to be dealt with where the shaft is of a particularly large size and difficult to move, where the geometry of the shaft is such that a bearing cannot be assembled over the end of the shaft (such as here where the bearing is in a sunken journal), where the shaft is long and a bearing may be provided intermediate the length of the shaft, and where the shaft is used in a particularly dirty environment, such as a mine.

A particularly difficult environment is that of providing a bearing for supporting a shaft where the shaft is for an auger used in highwall mining operations.

Such a bearing is likely to require servicing at intervals because of the environmental conditions. Because of the considerable amount of dust and particulate material, the bearing should be designed so as to be able to avoid problems relating to the dust and particulate material.

There is also considerable axial thrust in such circumstances.

A bearing for such use is described in US Patent 7,523,996. This specification describes a bearing in which an inner bearing 18 is provided in two identical semi-circular halves 1 8a, 1 8b which are welded to the outer surface of a shaft 60. The outer surface of the inner bearing is cylindrical. Surrounding and supporting the inner bearing is an outer bearing 14 having an inner bearing surface rotationally engaging with the outer bearing surface of the inner bearing 18. The outer bearing 14 comprises two identical semi-circular halves 14b, 14c joined together.

The outer bearing surface of the outer bearing 14 is partial-spherical-profiled. A support housing is provided to mount the bearing and the inner surface of the housing comprises a partial-cylindrical-profiled surface which matches the similar profiled outer surface of the outer bearing. This arrangement allows relative movement between the housing and the outer bearing which allows for distortions in the shaft of the auger. Such distortions, such as slight bends in the shaft, are readily produced by the extremely tough conditions in which it operates with large rocks being moved by the auger. Such an arrangement makes the bearing "self-aligning".

Another problem in the use of the bearing in these circumstances is that the auger produces considerable axial thrust and means needs to be provided to absorb this thrust.

In US Patent 7,523,996, this is done by providing upstanding edges of the inner bearing which engage with corresponding edges of the outer bearing which, in turn, is mounted in the housing.

It is also clear from the drawings of US Patent 7,523,996 that the two components of the inner bearing and outer bearing are split axially, that is, they are semi-circular and they are split in a direction parallel to the axis of the shaft. This means that twice through its rotation, the parallel edges of the inner and outer bearings will pass over each other. This produces rough rotation because the relevant edges will tend to bump over one another.

Also, as they wear, dust and rock particles will tend to collect in the edges as they wear.

Because of the environment, it is necessary to maintain the bearings. At intervals, the bearing surfaces need to be replaced. Because the outer bearing is split into two halves parallel to the axis, as is the housing, these may be removed, as is well-known in the art.

However, the inner bearing is welded to the shaft and thus in resurfacing or replacing the bearing it must be removed, which is a difficult operation.

The present invention aims to mitigate or overcome these problems.

SUMMARY OF THE INVENTION

According to a first aspect, the present invention provides a bearing for a shaft, comprising: an inner bearing comprising at least first and second inner bearing portions each having an outer bearing surface and an inner surface, in use, the inner bearing being removably mounted to the shaft so that the inner bearing rotates with the shaft; an outer bearing comprising at least first and second separable outer bearing portions, each having an outer bearing surface and an inner bearing surface which slidingly engages with said outer bearing surface of said inner bearing, wherein said inner surface of said inner bearing portion is cylindrically-profiled, said outer surface of said inner bearing is cylindrically-profiled, said inner surface of said outer bearing is cylindrically-profiled, and said outer surface of said outer bearing is partial-spherically-profiled, and a bearing housing including at least first and second separable housing portions which jointly support said outer bearing, said first and second bearing housing portions each having an inward facing bearing surface which together provide a partial-reverse-spherical contour to support the partial-spherically-profiled outer surface of said outer bearing, said first and second inner bearing portions each being generally semi-cylindrical and mounted with one another to form the inner bearing, said first and second outer bearing portions each being generally semi-cylindrical and mounted with one another to form the outer bearing, adjacent edges of the first and second inner bearing portions and/or adjacent edges of the first and second outer bearing portions extending at an angle ® to the axis of the shaft, where 0!= 00.

Where both the inner and outer bearing portions both have angled edges, they are arranged at opposite angles so they are not parallel to one another as they pass one another.

In a preferred arrangement, the adjacent edges of the first and second inner bearing portions extend at an angle 0 to the axis of the shaft, where 0!= 00 and in a further preferred embodiment 0 1 -100, preferably 3 -80.

Where the adjacent edges of the first and second inner bearing portions and/or the first and second outer bearing portions are at an angle other than 0 o they meet one another at a point which point moves from side to the other as the inner and outer bearings edge portions pass over one another. At no time do the edges of the inner and outer bearing meet one another in parallel which would cause them to "bump" over one another. In this way, the rotational movement is much smoother. Furthermore, if any grit or dust or dirt does lodge in between the edges of either the inner or outer bearing, this wiping movement of the point of contact from one side to the other will tend to move it to one side, along the mating edges. Effectively, the gap between edges will keep itself clean.

The smooth rotation is further assisted by providing a relief at one or more of the edges of the outer bearing surface of the inner bearing and/or the inner bearing surface of the outer bearing. The or each relief can extend along part or the whole length of the respective edge, and can be a straight slope or preferably arcuate and the depth is chosen for the particular circumstances.

The bearing is readily removed from and attached to a shaft in situ without removing the shaft which is important particularly where the shaft is large and not easily lifted by providing the inner bearing, outer bearing and bearing housing in two sections each of which may be removed from around the shaft without removing the shaft.

The inner bearing is removably mounted to the shaft for servicing or replacement. A preferred way to do this is by providing clamp means to clamp the first and second inner bearing portions together whereby to removably fixedly mount the inner bearing to the shaft. Preferably the clamp means comprises two ring clamps, the ring clamp clamping the inner bearing at or adjacent respective axially opposite ends of the inner bearing.

Preferably each ring clamp comprises two semicircular ring clamp sections joined at their adjacent ends by means of a releasable connection means.

Preferably at least one of said ring clamps includes a side surface defining a thrust load-receiving face. The or each said thrust load receiving surfaces are preferably planar and normal to the axis of the shaft.

In a preferred arrangement, the bearing housing mounts means to limit movement of the outer bearing. Said means to limit movement of the outer bearing preferably comprises a protrusion engaging in a slot in the outer bearing or a protrusion on the outer bearing engaging in a slot in the housing The shaft may be an auger shaft for use in highwall mining.

Preferred embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings in which: Figure 1 is an exploded perspective view of a bearing according to the invention; Figure 2 is a partial axial end view of an end surface of an inner bearing portion: and Figure 3 is a side view of the shaft, inner bearing and clamp illustrating the angle between the edges of the first and second inner bearing portions and the shaft axis.

DESCRIPTION OF PREFERRED EMBODMENT OF THE INVENTION

Figure 1 shows a bearing for supporting a shaft, for example, in an auger in a highwall mining apparatus. The bearing 10 comprises an inner bearing 11, an outer bearing 12, and a bearing housing 13.

The inner bearing 11 comprises first and second inner bearing portions 16, 17 which are each identical and generally semi-cylindrical. The first and second inner bearing portions 16, 17 are mounted relative to one another so as to form a cylindrical bearing, wherein the edges 18 of the first and second inner bearing portions, are adjacent and parallel to one another. The inner bearing 11 comprised of the first and second inner bearing portions 16,17 has an inner surface 19 and an outer bearing surface 21. The inner surface 19 is of cylindrical form to engage with the outer surface of a shaft 22 (the shaft 22 not being shown in Figure 1).

As is clear from Figure 1 and 3, the edges 18 of the first and second inner bearing portions extend generally parallel to the length of the shaft 22 but at an angle to the axis 23 of the shaft, the angle 0 between the edges 18 and the axis of the shaft is not zero and is greater than 0 o and in a particular embodiment 0 = 1 -100, preferably 3 -8 o This provides the advantages of smoother rotation of the shaft as outlined above.

In use, the first and second inner bearing portions 16, 17, are clamped together and mounted with one another by means of two ring clamps 26, 27, each ring clamp comprising two semi-circular rings which are engaged with one another and held by means of screws 28 passing from the adjacent end of one semi-circular ring to a threaded bore 29 in the adjacent end of the other semi-circular ring portion. The semi-circular ring portions of the ring clamp have a generally square or a rectangular cross-section, the inner surface of which clamps against the outer surface of the inner bearing 11 It will be noted that the ring clamps 26,27 are arranged to clamp the inner bearing 11 at opposite axial ends.

In this way, the inner bearing 11 may be clamped in a fixed manner to the shaft, the inner surface 19 of the inner bearing 11 gripping the outer surface of the shaft so that the inner bearing 11 is fixed to and rotates with the shaft. However, although fixed to the shaft 22 by means of the ring clamps 26, 27, the inner bearing may in use be released from the shaft by releasing the screws 28 from the threaded bores 29. This enables removal of the inner bearing for replacement and servicing during the lifetime of the bearing 10.

The outer bearing 12 comprises first and second outer bearing portions 31,32 which are generally semi-cylindrical and which in use are held together to comprise the outer bearing 12 by means of screws 33 passing through bores in one of the outer bearing portions into threaded bores 36 in the other outer bearing portion. Once again, by releasing the screws 33, the first and second outer bearing portions 31, 32 may be separated for replacement or servicing in use.

The outer bearing 12 comprises an inner bearing surface 37 and an outer bearing surface 38. The inner bearing surface is cylindrical and is profiled so as to slidingly engage the cylindrical outer bearing surface 21 of the inner bearing 11. The outer bearing surface 38 has a partial-spherical-profile. The axial length of the outer bearing 12 is slightly less than the distance between facing side surfaces 39 of the two ring clamps 26,27 whereby, in use, axially opposite edges 40 of the outer bearing 11 slidingly engage with those facing side surfaces 41 of the ring clamps 26,27. These side surfaces 41 are planar and normal to the axis of the shaft 22. In use, these relatively sliding surfaces 41 form thrust bearings to absorb any axial thrust of the shaft 22.

The bearing housing 13 is provided to support the outer bearing 10 and hence the shaft 22. The bearing housing 13 surrounds the outer bearing 12 in a radial direction. The bearing housing 13 is formed of upper and lower bearing housing portion 43, 44. The lower bearing housing portion 44 is mounted on a pedestal 45, and the upper bearing housing portion 43 is attached to the lower bearing housing portion 44 by four bohs 46 which pass through bores 47 in the lower bearing housing portion 44 and are secured by nuts 45.

The inside bearing surface of the bearing housing 13 is provided by inwardly facing bearing surface 50 on the first and second bearing housing portions 43,44 and has a partial-reverse-spherical profile to support the partial-spherically profiled outer surface of said outer bearing. In this way, slight bends or misalignments of the shaft 22 which occurs, for example, after use, may be compensated for by allowing the outer bearing 12 to move or rock to compensate for the misalignment of the shaft. Such an arrangement is referred to as a self-aligning' bearing.

Bolted through a threaded bore through the upper part of the upper bearing housing portion 43 is a peg 48 which extends downwardly into a slot 49 in the outer bearing surface 38 of the first (upper) outer bearing portion 31. Such an arrangement is generally well-known and allows the peg 48 operating in the slot 49 to limit the rotation of the outer bearing 12 around the shaft and also limits its rocking movement parallel to the axis of the shaft 22. The limits to rotation in each direction are set by the shape and dimensions of the slot 49. However, in an alternative arrangement, the peg 48 may be mounted in the outer bearing 12 and extend into a slot in the housing portion 13.

In a preferred arrangement of the invention represented in Figure 2, the smooth rotation of the shaft is further enhanced by providing the outer bearing surface 21 of each of the first and second inner bearing portions 16, 17 of the inner bearing 11 with a relief zone 51 adjacent one of the edges 18. Normally each inner bearing portion 16, 17 would have two such relief zones 51, one at each edge. Each relief zone 51 extends along at least part of the length of the relevant edge 18 and preferably along the complete length.

Although the relief zone may be a straight slope, in a preferred arrangement, each relief zone 51 has an arcuate profile Rr commencing from a junction A with the outer bearing surface 21 and ending at the edge 18. The centre of curvature B of the zone 51 lies on a radial plane Rt extending between the axis 52 of the inner bearing and the junction line A. The circumferential extent W of each relief zone 17 is such as to smoothly guide and support the corresponding edge of the inner bearing surface 37 of the outer bearing 12 as it passes the edge 18 of the inner bearing portion 11.

As is clear from Figure 3, the bearing 10 is situated to support a sunken journal 60 formed on the shaft 22 between two oppositely facing shoulders 61, 62. Such an arrangement precludes the removal of the bearing from the shaft or fitting the bearing on the shaft from one end or of the shaft 22. The angle 0 between the axis 14 of the shaft and the edges 18 is clearly shown.

The invention is not restricted to the details of the foregoing examples.

For example, the angled edges 18 may be provided on the outer bearing 12 in place of or in addition to the inner bearing 11. Where there are provided angled edges on both inner and outer bearings, they should be angled oppositely so that they pass smoothly over one another.

Relief zones 51 may be provided adjacent the edges of the inner bearing surface 37 of the outer bearing 12 in place of or in addition to the relief zones 51 on the inner bearing 11.

Claims

CLAIMS1. A bearing for a shaft, comprising: an inner bearing comprising at least first and second inner bearing portions each having an outer bearing surface and an inner surface, in use, the inner bearing being removably mounted to the shaft so that the inner bearing rotates with the shaft; an outer bearing comprising at least first and second separable outer bearing portions, each having an outer bearing surface and an inner bearing surface which slidingly engages with said outer bearing surface of said inner bearing, wherein said inner surface of said inner bearing portion is cylindrically-profiled, said outer surface of said inner bearing is cylindrically-profiled, said inner surface of said outer bearing is cylindrically-profiled, and said outer surface of said outer bearing is partial-spherically-profiled, and a bearing housing including at least first and second separable housing portions which jointly support said outer bearing, said first and second bearing housing portions each having an inward facing bearing surface which together provide a partial-reverse-spherical contour to support the partial-spherically-profiled outer surface of said outer bearing, said first and second inner bearing portions each being generally semi-cylindrical and engaged with one another to form the inner bearing, said first and second outer bearing portions each being generally semi-cylindrical and engaged with one another to form the outer bearing, engaging edges of the first and second inner bearing portions and/or the first and second outer bearing portions extending at an angle 0 to the axis of the shaft, where 0!= 00.
2. A bearing for a shaft as claimed in claim 1 in which the adjacent edges of the first and second inner bearing portions and/or the first and second outer bearing portions extend at an angle 0 to the axis of the shaft, where 0 = 1 -100
3. A bearing for a shaft as claimed in claim 2 in which the adjacent edges of the first and second inner bearing portions and/or the first and second outer bearing portions extend at an angle 0 to the axis of the shaft, where 0 = 3 -8°.
4. A bearing for a shaft as claimed in any of claims 1 to 3 wherein a relief zone is provided at one or more of the edges of the outer bearing surface of the inner bearing and/or the inner bearing surface of the outer bearing.
5. A bearing for a shaft as claimed in claim 4 wherein the relief zones are arcuate.
6. A bearing for a shaft as claimed in any of claims 3 or 4 wherein the relief zones have a depth chosen for the particular circumstances.7 A bearing for a shaft as claimed in any of claims 1 to 6 in which clamp means is provided to clamp the first and second inner bearing portions together whereby to removably fixedly mount the inner bearing to the shaft.8. A bearing for a shaft as claimed in claim 7 in which the clamp means comprises two ring clamps, the ring clamps clamping the inner bearing at or adjacent respective axially opposite ends.9. A bearing for a shaft as claimed in claim 8 in which each ring clamp comprises two semicircular ring clamp sections joined at their engaging end edges by means of a releasable connection means.10. A bearing for a shaft as claimed in any of claims 7 to 9 in which at least one of said ring clamps includes a side surface defining a thrust load-receiving face.11. A bearing for a shaft as claimed in claim 10 in which each of said ring clamps includes a side surface defining a thrust load-receiving face.12. A bearing for a shaft as claimed in claim 10 or 11 in which the or each said thrust load receiving surfaces are planar and normal to the axis of the shaft.13. A bearing for a shaft as claimed in any preceding claim in which the bearing housing or outer bearing mounts means to limit movement of the outer bearing.14. A bearing for a shaft as claimed in claim 13 in which said means to limit movement of the outer bearing comprises a protrusion engaging in a slot.15. A bearing for a shaft as claimed in any of the preceding claims in which said shaft is an auger shaft for use in high wall mining