GB2426795A

GB2426795A - A spherical bearing arrangement

Info

Publication number: GB2426795A
Application number: GB0513180A
Authority: GB
Inventors: Robert Middlemass
Original assignee: Minebea Co Ltd
Current assignee: Minebea Co Ltd
Priority date: 2005-06-02
Filing date: 2005-06-28
Publication date: 2006-12-06
Anticipated expiration: 2025-06-28
Also published as: GB0513180D0; GB2426795B; GB0511268D0

Abstract

A spherical bearing arrangement comprising: ```a ball 2 having a spherical bearing surface 3; and ```a housing 4,8 having a spherical inner bearing surface 5 conforming to the bearing surface 3 of the ball 2 so that the respective bearing surfaces 3,5 are in sliding contact with one another, ```wherein both the ball 2 and housing 4,8 have respective central axes 11, the ball 2 being rotatable in the housing 4,8 to an extent that the respective central axes 11 are misaligned by at least an angle of 22{. The misalignment is preferably in the region of 22{ to 35{.

Description

I

"A SPHERICAL BEARING ARRANGEMENT" The present invention relates to a spherical bearing arrangement and more particularly to a spherical bearing arrangement capable of achieving a high misalignment.

In use, it is often a requirement of a spherical bearing that the ball is able to rotate with respect to the housing surrounding the ball. Rotation of the ball within the housing results in the central axis of the ball becoming non-coaxial (i.e. non parallel) with the central axis of the housing. Such a deviation from the co-axial position is said to be a "misalignment" with respect to the bearing housing. The misalignment capability of a given bearing arrangement is often qualified by measuring the angle between the central axis of the ball and the central axis of the housing. Typically, the ball will have a central bore carrying a shaft. As will be appreciated, due to the dimensions and physical features of the ball, the bearing housing and any shaft in the bore, there is a maximum angle by which a ball may "misalign" with respect to the housing before a part of the ball - or an object fixed thereto or inserted therein (such as a shaft) - will impact on a portion of the housing. The maximum misalignment angle achievable is an important characteristic of a bearing.

Known bearing arrangements only allow a misalignment of a maximum of 22 i.e. the maximum angle achievable between the respective central axes of the ball and bearing housing, before any part of the ball or housing impact on the other, is 22 . It is a requirement of some applications, however, to have a higher misalignment than that which is currently achievable by known bearing arrangements. Indeed, some applications require a misalignment value of up to or in the region of 300, which has hitherto not been possible.

The failure to meet this requirement of a higher misalignment in previous bearing arrangements has been due, in part, to the dimensions of the bearing arrangement. For example, referring to Figure 1, a spherical bearing arrangement 1 is shown as having four characteristics: "D" relates to the diameter of the ball; "d" corresponds to the diameter of a shaft in the ball or any sleeve of the ball; "9" corresponds to the angle of misalignment; and "L" corresponds to the axial length of the housing or at least of that part of the housing which would first abut any sleeve or shaft.

For a given value of "d", the greater the value of "D", the greater the value of misalignment "0" achievable. However, by increasing the value of "D", the overall size of the bearing becomes cumbersome and is thus unacceptable. Thus (for a given value of d'), there is a compromise between the maximum amount of misalignment 0 achievable and the value of "D". It will also be appreciated that a further way of increasing the misalignment "0" of the bearing is to reduce the axial length "L" of the housing. However, as will further be appreciated, if the value of "L" is reduced too far, then the housing will not provide structural integrity and will not serve to adequately entrap the ball therein.

Thus, with prior art arrangements, due to the careful balancing act required between the values, "D", "d" and "L", no bearing arrangement has offered a misalignment in excess of 22 .

The present invention seeks to overcome the problems associated with the prior art and offer a bearing arrangement with a misalignment value higher than that of known arrangements.

Accordingly, the present invention provides a spherical bearing arrangement comprising: a ball having a spherical bearing surface; and a housing having a spherical inner bearing surface conforming to the bearing surface of the ball so that the respective bearing surfaces are in sliding contact with one another, wherein both the ball and housing have respective central axes, the ball being rotatable in the housing to an extent that the respective central axes are misaligned by at least an angle of 22 .

Preferably, the misalignment is in the region of 25 to 35 .

Advantageously, the misalignment is 30 .

Preferably, a spherical bearing arrangement according to the present invention forms part of a rod end bearing arrangement.

Advantageously, the spherical bearing arrangement is held in a rod end housing of the rod end bearing arrangement with an interference fit.

Figure 1 shows a schematic cross section of a bearing arrangement; Figure 2 shows cross section of a bearing arrangement embodying the present invention; Figure 3 shows a perspective view of the bearing arrangement shown in Figure 2, in a non-misaligned configuration; and Figure 4 shows a view from one side of the bearing arrangement shown in Figure 3.

Referring to Figures 2 to 4, a spherical bearing arrangement I is shown (in this embodiment, a rod end bearing). The bearing arrangement 1 comprises a spherical balI 2 having a spherical outer bearing surface 3. The ball 2 is surrounded by an annular inner housing 4 having a spherical inner bearing surface 5, which inner bearing surface 5 conforms to the outer bearing surface 3 of the ball 2, so that the two bearing surfaces 5, 3 are in sliding contact with one another.

The inner housing 4 further has a cylindrical outer surface 6 and two axial end faces 7. The inner housing 4 is held within an annular outer housing 8 (in this embodiment, a rod end housing) having a cylindrical inner surface 9. Preferably, the diameter of the outer surface 6 of the inner housing 4 is slightly more than the diameter of the inner surface 9 of the outer housing 8 such that the inner housing 4 is held in the outer housing 8 with an interference fit. The outer housing 8 further comprises a substantially cylindrical outer surface 10 (with a rod end extending therefrom) and two axial end faces.

Preferably, the inner housing 4 is held within the outer housing 8 by staking at least one axial end of the outer housing over the inner housing 4. Alternatively, at least the ends of the outer housing 8 could be swaged over the inner housing 4. It is preferable that the axial length "L" of the inner housing 4 (i.e. the distance between its two axial end faces) is less than the axial length "L" of the outer housing 8, which aids the staking/swaging process. In any event, it is most preferable that the inner housing 4 cannot move with respect to the outer housing 8 in use. Both the inner 4 and outer 8 housings have respective central axes 11, 12, which axes, when assembled, are coaxial with one another.

The baIl 2 comprises a central bore 13, having a central axis 14. Preferably, a substantially annular sleeve 15 protrudes from each axial end of the ball (i.e. adjacent the axial end of the bore passing through the ball). Thus, the length of the bore 13 of the balI 12 is effectively extended by the provision of the sleeve 15. In addition, each sleeve has an axial end face 16. Preferably, the inner cylindrical surface 17 of the sleeve 15 is of the same diameter as the central bore 13 passing through the ball 2.

Each sleeve 15 has a cylindrical outer surface 18 having a diameter which is greater than the inner diameter of the sleeve 15 (corresponding to the diameter of the bore), so that the sleeve 15 has structural integrity and is substantially annular. Accordingly, the distance from the central axis 14 of the bore to the outer surface 18 of the sleeve is greater than the distance from the central axis 14 to the inner surface 17 of the sleeve.

Preferably, the diameter "d" of the outer surface 18 of the sleeve 15 is in the range of 12.5mm to 13.5mm. More preferably, the diameter is 13.2mm.

Preferably, the diameter "D" of the balI 2 (i.e. the diameter defined by the spherical bearing surface 3 of the ball 2) is in the range of 20.5mm to 22.5mm.

More preferably, the diameter "D" is in the range of 21mm to 22mm.

Advantageously, the diameter "D" is 21.6mm.

Preferably, the bore 13 is sized so as to accommodate, in use, a shaft having a diameter of 10mm.

As will be appreciated, since the sleeves 15 protrude from the axial ends of the ball 2, the axial length of the ball 2, i.e. the distance between the respective axial end faces 16 of the sleeves 15, will be greater than the diameter D of the ball 2.

Preferably, the axial length of the ball is in the range of 21mm to 22. 5mm. More preferably, the axial length is in the range of 21.5mm to 22mm. Advantageously, the axial length is 21.85mm.

The diameter of the outer surface 6 of the inner housing 4 is preferably in the range of 23.5mm to 26mm. More preferably, the diameter is in the range of 24.2mm to 25.2mm. Advantageously, the diameter is 24.76mm.

Preferably, the ball 2 is manufactured from hardened steel. Advantageously, the ball 2 is manufactured from hardened steel having a softer precipitation than AMS 5630 (HRc 56 mm). In addition, the hardened steel ball is preferably chromium plated to both harden the surface even further, and improve wear resistance. Conveniently, the ball is manufactured from AMD5643 H900.

Preferably, the axial length "L" of the inner housing 4 is in the range of 7.5mm to 8.5mm. More preferably, the axial length "L" of the inner housing 4 is 8mm.

Preferably, in use, the maximum misalignment 0 achievable between the respective central axes 14,11 of the ball 2 and inner housing 4, is in the range of 25 to 35 . More preferably, the maximum misalignment 0 achievable is in the range of 28 to 32 . Advantageously, the maximum misalignment achievable is 300.

Preferably, a portion of the inner housing 4 adjacent the inner bearing surface 5 and each axial end face 7 thereof is chamfered. Preferably, the chamfering is such that when the ball 2 is misaligned with respect to the inner housing 4 to its maximum extent, the outer cylindrical surface 18 of the sleeve 15 abuts with, and is parallel to, the chamfered surface of the inner housing 4. Therefore, the chamfered surface of the inner housing 4 acts as an end stop.

In use, a shaft is preferably inserted into the bore 13 of the ball 2 and fixed to an external device (not shown). It will be appreciated, therefore, that the shaft, in use, protrudes from each axial end of the sleeves provided at each axial end of the ball 2. Accordingly, even when the ball 2 is misaligned to its greatest extent, the surface of the shaft inserted in the bore does not contact any part of the spherical bearing arrangement other than the bore of the ball. Instead, as described above, the outer surface 18 of the sleeve 15 abuts the inner housing 4.

Preferably, arrangements embodying the present invention are dimensioned such that the ratio LID is less than 0.45, where L' is the axial length of the inner housing and D' is the diameter of the ball. Advantageously, the ratio is less than 0.4. Conveniently, the ratio is 0.37.

Preferably, arrangements embodying the present invention are dimensioned such that the ratio dID is less than 0.675, where d' is the outer diameter of the sleeve and D' is the diameter of the ball. Advantageously, the ratio is less than 0.62. Conveniently, the ratio is 0.6.

Preferably, arrangements embodying the present invention are dimensioned such that the ratio LdID is less than 5.4, where L' is the axial length of the inner housing, d' is the outer diameter of the sleeve and D' is the diameter of the ball.

Advantageously, the ratio is less than 5. Conveniently, the ratio is 4.81.

Alternatively, the ball 2 of a spherical bearing arrangement according to the present invention may be provided without sleeves 15 at each axial end of the ball 2. Instead, the outer surface 3 of the ball 2 may comprise a purely spherical bearing surface, terminating in two circular apexes adjacent the inner surface of the bore. In such an alternative embodiment, in use, the surface of the shaft inserted into the bore would impact against the chamfered surface of the inner housing 4. Thus, as will be appreciated, a slightly higher misalignment 9 would be achievable in this embodiment, since the diameter "d" of the outer surface of the shaft inserted into the bore 13 is less than the diameter "d" of the outer surface 18 of sleeve 15 provided in the first embodiment.

Tables containing calculations pertaining to the loading capacity of bearing arrangements embodying the present invention, and a discussion of each, follows hereinafter.

Axial load on bearing misaligned at 300 and 7kN load applied = 4041N.

Bearing proof push out load = 4448N x 24.77/25.4 = 4338N Part No: I MMAYIOE I ____________ ____ Housing Width L' (mm) 7.9 ___________ Flat (mm) 0.5 Ball Diameter (mm) 21.63

BEARING AREA AND LOAD _________ ____________ ____

CALCULATION Liner Thickness (mm) 0 M. Pressure Metal/Metal (MPa) 635 Grooves Radial Area 43.26 ________ ______ ___________ Axial Area 4.4 RLBA (mm2) 105.4639 ______ ALBA (mm2) 8.0545 _____ RLBA (in2) 0.1635 ______ ALBA (in2) 0.0125 _____ Radial Load (N) 66970 _____ Axial load (N) 5115 ____ Radial Load Axial load lIbs) 15055 ______ (Ibs) 1150 _____ Radial Load (T) 6.8 [dal load (T) 0.5 I Radial Load Axial load [gN) 6697 (daN) 5iJ The above table shows that the bearing will be capable of taking a higher axial load than the after fitting bearing proof push out load.

The table also shows that the bearing will not fail or be pushed out when misaligned to 30 and a load of 7kN is applied.

Part No: MMAY{O] __________________ _________ Head (mm) 30 Head Width (mm) 8.9 Eye (mm) 24.77 ROD END AREA 450 chamfer / Parallel WITH (mm) 0 PARALLEL BORE M. Pressure (MPa) 635

LOAD CALCULATION

CSA at 900 to Shank (mm2) 42.5771 CSA at 900 to Shank (in2) 0.0660 Radial Load (N) 27036 _______________________ Radial Load (Ibs) 6078 The above calculation table shows that the bearing is capable of taking a 27kN radial static load.

Part No: J MMAYIOE1 Head (mm) 30 Head Width (mm) 8.9 Eye (mm) 24.76 ROD END AREA 450 chamfer (mm) o WITH M. Pressure (MPa) 165

PARALLEL BORE

LOAD CALCULATION GSA at 900 to Shank (mm2) 42.5771 GSA at 900 to Shank (in2) 0.0660 Radial Load (N) 7025 Radial Load (Ibs) 1579 From the above calculation table it can be seen that at a 7kN load the maximum pressure that this would cause in the rod end housing is only I65MPa, which is well within the material proof strength of 635MPa.

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 spherical bearing arrangement comprising: a ball having a spherical bearing surface; and a housing having a spherical inner bearing surface conforming to the bearing surface of the ball so that the respective bearing surfaces are in sliding contact with one another, wherein both the ball and housing have respective central axes, the ball being rotatable in the housing to an extent that the respective central axes are misaligned by at least an angle of 22 .

2. A spherical bearing arrangement according to Claim 1, wherein the misalignment is in the region of 25 to 35 .

3. A spherical bearing arrangement according to any preceding claim, wherein the misalignment is 30 .

4. A spherical bearing arrangement according to any preceding claim, wherein the ball has a sleeve protruding from each axial end, each sleeve having an outer diameter.

5. A spherical bearing arrangement according to Claim 4, wherein the sleeve has an outer diameter (d) of 12.5mm to 13.5mm.

6. A spherical bearing arrangement according to Claim 5, wherein the sleeve has an outer diameter (d) of 13.2mm.

7. A spherical bearing arrangement according to any preceding claim, wherein the ball has a diameter (D) of 20.5mm to 22.5mm.

8. A spherical bearing arrangement according to Claim 7, wherein the ball has a diameter (D) of 21mm to 22mm.

9. A spherical bearing arrangement according to Claim 8, wherein the ball has a diameter (D) of 21.6mm.

10. A spherical bearing arrangement according to any preceding claim, wherein the ball has a bore passing therethrough.

11. A spherical bearing arrangement according to Claim 10, wherein the bore has a diameter of 10mm.

12. A spherical bearing arrangement according to any of Claims 10 and 11, wherein a shaft is inserted in the bore in use.

13. A spherical bearing arrangement according to any of Claims 4 to 12, wherein the distance between the respective ends of the sleeves protruding from the ball is 21.5mm to 22mm.

14. A spherical bearing arrangement according to any preceding claim, wherein the housing has an outer surface having a diameter of 23.5mm to 26mm.

15. A spherical bearing arrangement according to Claim 14, where the diameter of the outer surface of the housing is 24.77mm

16. A spherical bearing arrangement according to any preceding claim, wherein the housing has an axial length (L) of 7.5mm to 8.5mm.

17. A spherical bearing arrangement according to Claim 16, wherein the housing has an axial length (L) of 8mm.

18. A spherical bearing arrangement according to any preceding claim, wherein the ratio LID is less than 0.45.

19. A spherical bearing arrangement according to Claim 18, wherein the ratio LID is less than 0.4.

20. A spherical bearing arrangement according to Claim 19, wherein the ratio LID is 0.37.

21. A spherical bearing arrangement according to any of claims 4 to 20, wherein the ratio dID is less than 0.675.

22. A spherical bearing arrangement according to Claim 21, wherein the ratio dID is less than 0.62.

23. A spherical bearing arrangement according to Claim 22, wherein the ratio dID is 0.6.

24. A spherical bearing arrangement according to any preceding claim, wherein the ratio Ld/D is less than 5.4.

25. A spherical bearing arrangement according to Claim 24, wherein the ratio LdID is less than 5.

26. A spherical bearing arrangement according to Claim 25, wherein the ratio Ld/Dis4.81.

27. A spherical bearing arrangement according to any preceding claim, wherein the material of the ball is AMS5643 H900.

28. A spherical bearing arrangement according to any preceding claim, wherein the ball is coated in chromium.

29. A rod end bearing arrangement, comprising: a rod end housing; and a spherical bearing arrangement according to any preceding claim.

30. A rod end bearing arrangement according to Claim 29, wherein the bearing housing is held in the rod end housing with an interference fit.

31. A rod end bearing arrangement as hereinbefore described and with reference to Figures 2 to 4. ( (

31. A spherical bearing arrangement as hereinbefore described and with reference to Figures 2 to 4.

32. A rod end bearing arrangement as hereinbefore described and with reference to Figures 2 to 4.

33. Any novel matter or combination thereof hereinbefore described.

Amendments to the claims have been filed as follows

1. A spherical bearing arrangement comprising: a ball having a spherical bearing surface and a bore having a central axis passing therethrough; and a housing comprising an opening having a spherical inner bearing surface conforming to the bearing surface of the ball so that the respective bearing surfaces are in sliding contact with one another, the opening having a central axis passing therethrough.

the ball being rotatable in the housing to an extent that the respective central axes are misaligned by at least an angle of 25 15 2. A spherical bearing arrangement according to any preceding claim, wherein the misalignment is 28 to 32 .

3. A spherical bearing arrangement according to any preceding claim, wherein the misalignment is 300.

7. A spherical bearing arrangement according to any preceding claim, wherein the ball has a diameter (D) of 20.5mm to 22 5mm.

9. A spherical bearing arrangement according to Claim 8, wherein the ball :::: has a diameter (D) of 21.6mm.

10. A spherical bearing arrangement according to any preceding claim, wherein the bore has a diameter of 10mm.

11. A spherical bearing arrangement according to any preceding claim, wherein a shaft is inserted in the bore in use.

12. A spherical bearing arrangement according to any of Claims 4 to 6, wherein the distance between the respective ends of the sleeves protruding from the ball is 21.5mm to 22mm.

13. A spherical bearing arrangement according to any preceding claim, wherein the housing has an outer surface having a diameter of 23.5mm to 26mm.

14. A spherical bearing arrangement according to Claim 13, where the diameter of the outer surface of the housing is 24.77mm 15. A spherical bearing arrangement according to any preceding claim, wherein the housing has an axial length (L) of 7.5mm to 8.5mm 16. A spherical bearing arrangement according to Claim 15, wherein the housing has an axial length (L) of 8mm.

17. A spherical bearing arrangement according to any preceding claim, wherein the ratio L/D is less than 0.45, 18. A spherical bearing arrangement according to Claim 17, wherein the ratio LID is less than 0.4.

19, A spherical bearing arrangement according to Claim 18, wherein the ratio L/D is 0.37.

20. A spherical bearing arrangement according to any of claims 4 to 19, wherein the ratio dID is less than 0.675.

21. A spherical bearing arrangement according to Claim 20, wherein the ratio d/D is less than 0.62.

22, A spherical bearing arrangement according to Claim 21, wherein the ratio dID is 0.6.

23. A spherical bearing arrangement according to any preceding claim, wherein the ratio LdID is less than 5.4.

24. A spherical bearing arrangement according to Claim 23, wherein the ratio LdID is less than 5.

25. A spherical bearing arrangement according to Claim 24, wherein the ratio LdID is 4.81.

26. A spherical bearing arrangement according to any preceding claim, wherein the material of the ball is AMS5643 H900.

27. A spherical bearing arrangement according to any preceding claim, wherein the ball is coated in chromium.

28. A rod end bearing arrangement, comprising: a rod end housing; and a spherical bearing arrangement according to any preceding claim.

29. A rod end bearing arrangement according to Claim 28, wherein the bearing housing is held in the rod end housing with an interference fit.

30. A spherical bearing arrangement as hereinbefore described and with reference to Figures 2 to 4. ( ,