BRAKE BEARING AND CAMSHAFT ASSEMBLIES

Abstract: A self-aligning plain bearing assembly (6) for a vehicle brake camshaft (1) has a housing and bearing bush (13) with cooperating part spherical surfaces, the part spherical surface of the bush having an axially extending recess (14) in which a protrusion of the housing engage, enabling the bush to tilt with respect to the housing whilst restraining the bush from rotation relative to the housing. Half housing members (9, 11) of the housing receive sealing rings (12) beyond the bush (13). One (11) of those members has a clearance hole (15) in which a grease nipple (16) is received and sealed for lubrication of the bearing surfaces of the housing and bush. Between the bearing assembly and the camshaft (6) located in the bush a sealing boot or boots (5, 7) may be fitted at one or each of opposite ends of the housing to inhibit access of foreign matter to the bearing surfaces. The arrangement provided enhances the life of the bearing assembly and the effectiveness of its lubrication.

Description: BRAKE BEARING AND CAMSHAFT ASSEMBLIES This invention concerns brake bearing and camshaft assemblies for vehicle brakes. Camshafts for vehicle brakes, particularly internal expanding shoe and drum brakes, are supported in bearing assemblies for rotation to operate the brakes. Such bearing assemblies generally comprise self-aligning plain bearings and this invention concerns such bearing assemblies, which are also suitable for use in other applications in which a shaft is supported for rotation. According to the present invention a self aligning plain bearing assembly for a vehicle brake camshaft comprises a housing having a part spherical inner bearing surface within which a bearing bush is retained, the bush having a plain bore providing a journal adapted in use to receive and rotatably support a camshaft and a part spherical outer surface which co-operates with the part spherical inner surface of the housing, characterised in that the bush has an axially extending recess, and the housing has an inwardly projecting protrusion engaged in the recess whereby the bush is enabled to tilt with respect to the housing but is restrained from rotating relative thereto. The housing may comprise two assembled half housing members with complementary part spherical inner bearing surfaces which retain the bush for articulation therein. Each half housing member may extend beyond the bearing bush to receive and retain an elastomeric sealing ring, for example an O ring, the extension having a part spherical inner surface for engagement by the O ring, to be followed by the O ring as the bush articulates. A half housing member may be provided with a clearance hole to receive, and allow movement of, a grease nipple inserted though the hole and into a receiving hole in the bush. An elastomeric seal may be provided between the half housing member and a flange of the nipple to inhibit ingress of foreign matter through the clearance hole to the bearing surfaces. In such an arrangement, the bush may have a transfer hole opposite the receiving hole to permit passage of lubricant from the bush bore to the part spherical surfaces. Preferably the housing or bush will incorporate a channel or channels to distribute lubricant around the part spherical surfaces from the transfer hole to the clearance hole in the housing, where excess lubricant has ab escape passage past the elastomeric seal. An end, or each of the axially opposed ends, of the housing may be formed or arranged to provide a surface to receive a sealing boot adapted to be fitted between the bearing assembly and a camshaft received in and supported by the bearing assembly in use, to inhibit access of foreign matter to the bearing surfaces of the bearing assembly and shaft. In such an assembly of the bearing assembly and camshaft, the shaft may have an annular groove adjacent the bearing assembly and in which a sealing boot as aforementioned is received and located. Where it is desired to fit a sealing boot at each end of the bearing housing an annular groove may be provided in the shaft to receive and locate each sealing boot. An embodiment of the invention will now be described by way of example with reference to the accompanying drawing which shows a bearing assembly and a camshaft supported therein for rotation. Referring to the drawing, a camshaft 1 has an S cam 2 at one end. There is a shoulder 3 at the junction of the cam 2 and camshaft 1. Adjacent to the shoulder 3 an annular groove 4 is machined in which a first sealing boot 5 is received and located. A bearing assembly 6 is assembled to the camshaft, being located relative to the camshaft by a spring ring and groove arrangement such as is described in our prior British Patent No. EP 0504243. This is followed by a second sealing boot 7 which is engaged in a tapered groove 8 in the camshaft 1. The bearing assembly 6 has a housing formed by first and second half housing members 9, 11 which are secured together to retain sealing rings 12 and bush 13. The half housing members 9, 11 and bush 13 have part spherical bearing surfaces whereby the bush is supported and retained with freedom to articulate. The first half housing member 9 is punched in to form a key which engages in an axially arranged slot 14 in the bush 13 to prevent rotation of the bush, whilst allowing articulation. The second half housing member 11 has a clearance hole 15 through which the stem of a grease nipple 16 is inserted into a hole in the bush 13 which is countersunk to receive it. A sealing ring 17 is interposed between the grease nipple 16 and the second half housing member 11. The grease nipple 16 may be a press fit in, or for example screw threaded into, the bush 13 and the depth of the countersink may control the compression of sealing ring 17 to effect a seal and ensure lubricant is retained in the bearing assembly 6. As is customary, the bore of the bush 13 is provided with channels to convey lubricant from the grease nipple 16 across the bearing area of the bush. Those parts of the half housing members 9, 11 which retain and are engaged by the O rings 12 are preferably shaped to be part spherical internally so that when the bush 13 articulates the O rings maintain sealing effectiveness between bush, half housing and shaft. As shown in the drawing, the first sealing boot 5 is generally L shaped and has two sealing lips which sealingly engage on the first half housing member 9. The second sealing boot 7 is generally Z shaped and has two sealing lips which sealingly engage on the second half housing member 11. The arrangements which have been described enhance the life of the bearing assembly 6 in use by preventing rotation of the bush 13 in the housing, ensuring lubrication is directed to the bearing surfaces and is better retained by the O rings 12 than in prior constructions. Also, assembly of the bearing assembly and the camshaft supported thereby is effectively protected from the ingress of foreign matter which would be detrimental to its performance and reliability.

Claims: CLAIMS 1. A self aligning plain bearing assembly (6) for a vehicle brake camshaft comprising a housing (9, 11) having a part spherical inner bearing surface within which a bearing bush (13) is retained, the bush having a plain bore providing a journal adapted for use to receive and rotatably support a camshaft and a part spherical outer surface which co-operates with the part spherical inner surface of the housing characterised in that the bush (13) has an axially extending recess (14) in its outer surface, and the housing (9, 11) has an inwardly projecting protrusion engaged in the recess (14) whereby the bush (13) is enabled to tilt with respect to the housing (9, 11) but is restrained from rotating relative thereto. 2. A bearing assembly (6) as claimed in claim 1 characterised in that the housing comprises two assembled half housing members (9, 11) with part spherical inner bearing surfaces complementary to the part spherical outer surface of the bush (13) which retain the bearing bush for articulation therein. 3. A bearing assembly (6) as claimed in claim 2 characterised in that one half housing member (11) is provided with a clearance hole (15) to receive and allow movement of a grease nipple (16) inserted through the hole (15) and into a receiving hole in the bush (13) . 4. A bearing assembly (6) as claimed in claim 3 characterised in that the bush (13) has a transfer hole opposite the clearance hole (15) to permit passage of lubricant from the bush bore to the part spherical surfaces. 5. A bearing assembly (6) as claimed in claim 4 characterised in that the housing (9, 11) or bush (13) incorporates a channel or channels to distribute lubricant around the part spherical surfaces from the transfer hole to the clearance hole (15). 6. A bearing assembly (6) as claimed in any of claims 3 to 5 characterised in that a seal (17) is arranged between a flange of the grease nipple (16) and the half housing member (11) to retain lubricant in the bearing assembly. 7. A bearing assembly (6) as claimed in claim 6 as dependent from claim 5 characterised in that the seal (17) has an escape passage for excess lubricant distributed from the channel or channels to pass the seal (17) . 8. A bearing assembly (6) as claimed in any preceding claim characterised in that the housing (9, 11) has housing extensions which extend beyond the bearing bush (13) at each end to a reduced diameter to receive and retain sealing rings (12) . 9. A bearing assembly (6) as claimed in claim 8 characterised in that the sealing rings (12) are received and retained in part spherical formations in the housing extensions. 10. A bearing assembly (6) as claimed in claim 8 or claim 9 characterised in that at least one of the housing extensions is adapted to receive and co-operate with a sealing surface of a sealing boot (5, 7) . 11. In combination a bearing assembly (6) as claimed in any preceding claim and a camshaft (1) received in and supported by the bearing assembly (6) . 12. The combination as claimed in claim 11 characterised in that the bearing assembly (6) is as claimed in claim 10, the sealing boot (5, 7) being arranged between the camshaft (1) and an adjacent end of the housing (9, 11) . 13. The combination as claimed in claim 12 characterised in that the camshaft (1) has an annular groove (4) in which a part of the sealing boot (5) is received and located. 14. The combination as claimed in claim 13 characterised in that the camshaft (1) is a brake camshaft having an S cam (2) at one end for operating a brake, the camshaft (1) is supported by the bearing assembly (6) adjacent the cam (2) , and the sealing boot (5) is arranged between the camshaft at that end and the adjacent housing (9, 11). 15. A bearing assembly (6) as claimed in claim 10 or the combination as claimed in any one of claims 11 to 14 characterised in that the sealing boot (5) has a sealing surface which comprises two spaced sealing lips which engage on a respective one of the housing extensions. 16. The combination as claimed in claim 13 or claim 14, or claim 15 as dependent from claim 13 or claim 14 characterised in that a second sealing boot (7) is arranged between the camshaft (1) and the housing (9, 11), being located in a second annular groove (8) in the camshaft remote from the first mentioned groove (4).

Inventors: FANNING DAVID JAMES, FANNING, DAVID, JAMES
Applicants: FANNING DAVID JAMES, MERITOR HEAVY VEHICLE SYS LTD, FANNING, DAVID, JAMES, MERITOR HEAVY VEHICLE SYSTEMS LIMITED
Application year: 1998
Main classification: F16D65
IPC codes: F16C23, F16C33, F16D65