GB2421059A

GB2421059A - A split ball assembly for a spherical bearing arrangement

Info

Publication number: GB2421059A
Application number: GB0427270A
Authority: GB
Inventors: Paul Smith; Allen Clarke; David Shore
Original assignee: Minebea Co Ltd
Current assignee: Minebea Co Ltd
Priority date: 2004-12-13
Filing date: 2004-12-13
Publication date: 2006-06-14
Anticipated expiration: 2024-12-13
Also published as: GB0427270D0; GB2421059B

Abstract

A split ball assembly for a spherical bearing arrangement includes a split ball portion 12 that comprises an outer bearing surface 8, at least one separation face 11 and a smooth transition 13 between the separation face 11 and an adjacent surface. In use a plurality of split ball portions 12 are arranged to form a composite ball (figure 4) with the separation face 11 of one portion lying adjacent a separation face 11 of a neighbouring portion. The portion 12 may also include an inner surface 10 and a pair of separation faces 11 and the smooth transition 13 is preferably formed between the separation face 11 and the inner and outer surfaces 10, 8. The smooth transition 13 is preferably a radiussed edge which can either be a non constant radius or a constant radius of between 0.1 and 0.3mm. The split ball portion 12 is preferably made of titanium and coated using physical vapour deposition (PVD).

Description

PATENTS ACT 1977 P19230GB - LDH!APH/szl/cg/vj

DESCRIPTION OF INVENTION

"SPHERICAL BEARING ARRANGEMENT" THE PRESENT INVENTION relates to a spherical bearing arrangement.

The art of spherical bearings and indeed bearings in general, requires the provision of precision engineered bearing surfaces wherein tolerances must be strictly adhered to to ensure the smooth and effective operation of the bearings.

As a consequence of keeping within these tolerances, bearings, and especially spherical bearings, are often expensive to manufacture.

A known method of mounting a ball into a housing of a spherical bearing arrangement is to provide a single ball and swage a housing around the ball to fixedly retain it therein. However, ensuring the torque of such a bearing remains within a predetermined range has proved difficult.

Spherical bearings comprising a split-ball arrangement alleviate the problems associated with single ball spherical bearings. Such an arrangement commonly comprises two split-ball portions, wherein the splitball portions comprise an outer bearing surface, an inner surface and a pair of separation faces. When mounted together in the bearing housing, the split ball portions collectively define a composite ball which serves, in principle, as the ball of a single-ball spherical bearing arrangement, wherein a separation face of one split ball portion lies adjacent a separation face of a neighbouring split ball portion.

The main advantage of split-ball bearings is that they do not require swaging of the bearing housing and thus reduce manufacturing costs. The split- ball portions are mounted in turn, with one portion being installed into the housing and engaging with the bearing surface, and the second portion being inserted and twisted by 90 to coincide with the other split ball portion.

Consequently, it is easier to produce a split ball spherical bearing having a predetermined clearance or a torque within a predetermined range, since each part can be manufactured separately from one another.

Since spherical bearings are commonly used in the aerospace industry, weight is of paramount importance. It is desirable, therefore, to manufacture spherical bearings from a lightweight material, such as titanium or titanium alloy. However, such a material does not offer the most desirable wear characteristics and a coating is often provided on the surface thereof in an attempt to reduce wear and degradation of the bearing surfaces.

Split ball portions present a sharp edge between the separation faces and the outer bearing surface. When the split ball portions are mounted in a bearing housing, the sharp edges presented by the split ball portions are in sliding contact with a bearing surface of the housing and have been found to degrade the housing bearing surface. However, especially with the provision of a coating on the housing or split ball portions, the sharp edges presented by the split ball portions have been found to cause lifting or galling of the coating, thus causing significant degradation to the bearing surfaces, which is often irreparable. Accordingly, the spherical bearing arrangement must be scrapped at significant financial cost.

The present invention seeks to provide a spherical bearing arrangement that does not suffer from the aforementioned problems.

Accordingly, one aspect of the present invention provides a split ball portion for a spherical bearing arrangement, which split ball portion is to form one of a plurality of split ball portions to be arranged together in a bearing housing of the spherical bearing arrangement to form a composite ball, wherein each split ball portion has a separation face lying adjacent a separation face of a neighbouring split ball portion when forming the composite ball, the split ball portion comprising: an outer bearing surface; and at least one separation face, wherein there is a smooth transition between the separation face and an adjacent surface, which smooth transition reduces wear on a surface in sliding contact with the split ball portion.

Preferably, the separation face and an adjacent surface subtend an angle.

Conveniently, there is a smooth transition between the separation face and the outer bearing surface.

Advantageously, the split ball portion further has an inner surface and a pair of separation faces.

Preferably, there is a smooth transition between the separation face and the inner surface.

Coveniently, the smooth transition is a radiussed edge.

Advantageously, the radius of the radiussed edge is not constant.

Alternatively, the radius of the radiussed edge is constant.

Preferably, the radius is between 0.1 and 0.3mm.

Conveniently, the split ball portion forms part of a spherical bearing arrangement comprising: a bearing housing; and a plurality of split ball portions, wherein the split ball portions are arranged together in the bearing housing to form a composite ball.

Advantageously, there is no separation between the respective separation faces of the split ball portions.

Alternatively, there is separation between the respective separation faces of the split ball portions.

Conveniently, the material of at least one of the split ball portion or bearing housing is titanium or titanium alloy.

Advantageously, a coating is provided on a bearing surface.

Preferably, the coating is provided by PVD.

The present invention will now be described, by way of example, with reference to the accompanying figures, in which: Figure 1 shows a perspective view of a spherical bearing arrangement not embodying the present invention; Figure 2 shows a cross section of the spherical bearing arrangement of Figure 1 along line A-A; Figure 3 shows a perspective view of a split ball portion embodying the present invention; Figure 4 shows a cross section of a spherical bearing arrangement embodying the present invention; and Figure 5 shows an enlarged view of area A of Figure 4.

Figures 1 and 2 show a spherical bearing arrangement 1 comprising a bearing housing 2 with a composite ball 3 mounted therein. The bearing housing 2 is substantially annular and comprises: a cylindrical outer surface; two axial end faces 4; and a spherical housing bearing surface 5.

The composite ball 3 is substantially spherical in shape, providing a spherical composite ball bearing surface 6 conforming to the housing bearing surface 5 such that the bearing surfaces 5, 6 are in sliding contact with one another.

The composite ball 3 is formed from two substantially identical split ball portions 7a, 7b. Each split ball portion comprises: a hemispherical outer bearing surface 8; two axial end faces 9; a semi-cylindrical inner surface 10; and a pair of separation faces 11.

The separation faces 11 of each split ball 7a, 7b portion are substantially co-planar. The angle between a separation face 11 and the bearing surface 8 of a split ball portion 7 will typically be 90 degrees. Accordingly, it will be appreciated that when the split ball portions 7a, 7b are arranged in the bearing housing 2, the sharp edges presented between the separation faces 11 and the bearing surface 8 of the split ball portions 7a, 7b contact and degrade the housing bearing surface 5, reducing the life of the assembly. Should the bearing surfaces be provided with a coating, the sharp edges presented by the split ball portions have been found to cause lifting or galling of the coating. As the sharp edges presented by the split ball portions 7a, 7b degrade the housing bearing surface 5 and causes lifting or galling of the coating, particles removed from either the bearing housing 2 or ball 3, or indeed particles of any lifted coating, will mix with any lubricant present to form an abrasive slurry - which abrasive slurry will then be distributed over the bearing surfaces 5, 6 causing further damage thereto.

Further, split ball portions 7a, 7b of spherical bearing assemblies can be provided with a separation therebetween. It will be appreciated that the provision of such a separation between the separation faces 11 of the split ball portions 7a, 7b can augment the problems associated with the sharp edges presented thereby. However, even when there is no separation between the separation faces 11, the sharp edges have still been found to degrade the bearing housing bearing surface 5 and cause lifting or galling of any coating provided thereon.

Such degradation of the bearing housing bearing surface 5 and any coating provided thereon results in a reduced life of the bearing and the need for the bearing housing 2 to be scrapped at significant financial cost.

A split ball portion 12 embodying the claimed invention seeks to overcome the problems associated with such bearing arrangements, by providing a split ball portion 12 with a smooth transition 13 between the separation face 11 and the outer bearing surface 8.

Preferably, the smooth transition 13 is a radiussed edge. Conveniently, the radius is constant about the smooth transition 13. Advantageously, the radius is between 0.1 and 0.3mm. Most preferably the radius is 0.2mm.

However, it is envisaged that the radius need not be constant in order to provide the benefits of the claimed invention. Thus, the radius of the radiussed edge adjacent the separation face 11 could be less than the radius adjacent the outer bearing surface 8. Conversely, the radius adjacent the separation face 11 could be greater than the radius adjacent the bearing surface 8.

Indeed, the smooth transition 13 between the separation face 11 and the bearing surface 8 can be of any profile, so long as it does not present any sharp edges to the housing bearing surface 5 - which sharp edges of split ball portions have been found to degrade the housing bearing surface 5 and cause lifting or galling of a coating provided thereon.

Preferably, the material of a split ball portion or bearing housing embodying the claimed invention is titanium or titanium alloy.

Advantageously, a coating is provided on a bearing surface. Conveniently, the coating is applied using physical vapour deposition (PVD). Preferably, the coating is titanium nitride (TiN) or another suitable PVD coating such as chromium nitride (CrN) or titanium aluminium nitride (TiA1N). The provision of radius sed edges (radius in the order of between 0.1mm and 0. 3mm) has been found to be especially beneficial in extending the life of bearing arrangements incorporating such a feature.

When assembled in the bearing housing 2, as shown in figures 4 and 5 the split ball portions 1 2a, 1 2b embodying the present invention do not present any sharp edges to the housing bearing surface 5, thus degrading less the bearing surface 5 of the bearing housing 2 or the coating provided thereon.

Whilst the provision of a smooth transition between a separation face and the outer bearing surface has been described in the example above, it will of course be appreciated that a split ball portion embodying the claimed invention can provide a smooth transition between a separation face and an inner surface of the split ball portion. The split ball portion embodying the claimed invention shown in figure 3 could, therefore, be provided with a smooth transition along at least one of the edges subtending the separation faces and both of the inner surface and outer bearing surface or, indeed, any combination thereof.

Whilst the embodiments described above relate to a split ball portion having an inner surface, it will of course be appreciated that a split ball portion embodying the present invention need not have an inner surface. The claimed invention encompasses a split ball portion having merely a single separation face and an outer bearing surface - thus the split ball portion substantially being a hemi-sphere.

Whilst the provision of two split ball portions has been described above, it will readily appreciated that any number of split ball portions can be provided, without departing from the present invention.

It will be appreciated that the benefits of the claimed invention will be apparent when there is separation between the split ball portions. Conversely, however, it is envisaged that there could be no separation between the separation faces, without departing from the scope or benefits of the claimed invention.

Whilst split ball portions embodying the claimed invention reduce wear on the bearing housing bearing surface or damage to any coating provided thereon, it will of course be appreciated that the smooth transition reduces potential damage also to the split ball portions or any coating applied thereon.

When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. A split ball portion for a spherical bearing arrangement, which split ball portion is to form one of a plurality of split ball portions to be arranged together in a bearing housing of the spherical bearing arrangement to form a composite ball, wherein each split ball portion has a separation face lying adjacent a separation face of a neighbouring split ball portion when forming the composite ball, the split ball portion comprising: an outer bearing surface; and at least one separation face, wherein there is a smooth transition between the separation face and an adjacent surface, which smooth transition reduces wear on a surface in sliding contact with the split ball portion.

2. A split ball portion according to Claim 1, wherein the separation face and an adjacent surface subtend an angle.

3. A split ball portion according to any preceding claim, wherein there is a smooth transition between the separation face and the outer bearing surface.

4. A split ball portion according to any preceding claim, wherein the split ball portion further has an inner surface and a pair of separation faces.

5. A split ball portion according to Claim 4, wherein there is a smooth transition between the separation face and the inner surface.

6. A split ball portion according to any preceding claim, wherein the smooth transition is a radiussed edge.

7. A split ball portion according to Claim 6, wherein the radius of the radiussed edge is not constant.

8. A split ball portion according to Claim 6, wherein the radius of the radiussed edge is constant.

9. A split ball portion according to any one of Claims 6 to 8, wherein the radius is between 0.1mm and 0.3mm.

10.. A split ball portion according to any preceding claim, wherein the material of the split ball portion is titanium or titanium alloy.

11. A split ball portion according to any preceding claim, wherein a coating is provided on a bearing surface.

12. A split ball portion according to Claim 11, wherein the coating is provided by PVD.

13. A spherical bearing arrangement comprising: a bearing housing; and a plurality of split ball portions according to any preceding claim, wherein the split ball portions are arranged together in the bearing housing to form a composite ball.

14. A spherical bearing arrangement according to Claim 13, wherein there is no separation between the respective separation faces of the split ball portions.

15. A spherical bearing arrangement according to Claim 13, wherein there is separation between the respective separation faces of the split ball portions.

16. A spherical bearing arrangement according to any one of Claims 13 to 15, wherein there are two split ball portions.

17. A split ball portion substantially as hereinbefore described with reference to and as shown in Figures 3 to 5.

18. A spherical bearing arrangement substantially as hercinbefore described with reference to and as shown in Figures 3 to 5.

18. A spherical bearing arrangement substantially as hereinbefore described with reference to and as shown in Figures 3 to 5.

19. Any novel feature or combination of features described herein.

Amendments to the claims have been flied as follows 1. A split ball portion for a spherical bearing arrangement, which split ball portion is to form one of a plurality of split ball portions to be arranged together in a bearing housing of the spherical bearing arrangement to form a composite ball, the split ball portion comprising: an outer bearing surface; and at least one separation face, which lies adjacent a separation face of a neighbouring split ball portion when forming the composite ball, wherein there is a smooth transition between the separation face and an adjacent surface, which smooth transition reduces wear on a surface in sliding contact with the split ball portion.