GB2216198A

GB2216198A - Bearing assembly having main and secondary seals

Info

Publication number: GB2216198A
Application number: GB8903885A
Authority: GB
Inventors: Heinz Strathmann; Gregor Patzulla
Original assignee: Gelenkwellenbau GmbH
Current assignee: Gelenkwellenbau GmbH
Priority date: 1988-02-24
Filing date: 1989-02-21
Publication date: 1989-10-04
Anticipated expiration: 2009-02-21
Also published as: GB8903885D0; GB2216198B; IT1233462B; FR2627562B1; FR2627562A1; DE3805672C1; IT8905119A0

Description

216198 _GMD/87112GB1 BEARING ASSEMBLY HAVING MAIN AND SECONDARY SEALS This

invention relates to a bearing assembly comprising a bearing bush and main and secondary seals engagable with a journal supported in the bearing bush. Bearing assemblies according to the invention are usable especially in Hookes universal joints, to support the journals of the cross-member of the joint in the yokes of the joint.

More particularly the invention relates to the arrangement of the seals of the bearing assembly and the manner in which they are held relative to the bearing bush. In a Hookes universal joint it is usual to arrange the main seal, whose purpose is to retain lubricant in the needle roller bearings by which the journal is supported in the bearing bush, to be held in the bearing bush and to have sealing engagement with the journal. The secondary seal includes a sealing lip which engages a surface at or adjacent the end of the bearing bush, and in the complete joint is held on the journal. The main function of the secondary seal is to prevent the penetration of external dirt to the region of the main seal. For assembly purposes, however, it is convenient for the secondary seal to be held in a pre-assembled relationship with the bearing bush so that when the bearing bush is fitted to the respective yoke of the joint from the outside thereof, over the journal of the cross-member already positioned in the yoke, the secondary seal is pushed onto the journal without requiring a separate assembly operation to fit it.

2 Bearing assemblies are known, for example from DE-G-8213146.5 and DE-P2908713, wherein the secondary seal is held to the bearing bush by formations on the secondary seal which extend into the bearing bush axially thereof and engage frictionally with a sheet metal carrier for the main seal. In order that the sealing action of the secondary seal when fitted is not jeopardised, the frictional force between the formations of the secondary seal and the carrier of the main seal cannot be made very great; if the secondary seal were highly pre-stressed to generate a high frictional holding force the sealing lip of the secondary seal may lift off the bearing bush. To ensure safe holding of the secondary seal to the bearing bush, it is necessary to provide a secondary seal with a large number of holding -formations with narrow gaps therebetween, which hinder lubrication of the bearing assembly by possibly leading to a build-up of pressure therein.

DE-OS-2144172 shows a bearing 'assembly wherein the secondary seal is engaged behind an inwardly flanged edge of the bearing bush. The expedient of inwardly flanging the edge of the bearing bush is only possible, however, with a bearing bush drawn from sheet metal, because thick walled bushes made from the solid cannot be inwardly flanged. Further, there is a disadvantage in that forces arising axially of the bearing bush in use, which attempt to displace the needle roller bearings axially in the bush, have to be resisted by the main seal itself, with consequent detriment to the seal performance.

It is the object of the present invention to provide a bearing assembly which as far as possible overcomes the problems and meets the requirements above described. In particular, the arrangement of the seals should be 3 suitable for use with solid bearing bushes as well as sheet metal bushes, the main seal should not be subject to axial forces from the needle roller bearings in the bush, and the secondary seal should be held in assembled relation to the main seal for assembly purposes without any negative effects on its function in an assembled universal joint.

According to the present invention, we provide a bearing assembly comprising:

a bearing bush for supporting a journal therein; a main seal held in the bearing bush by a carrier, the carrier including projections engaging an annular groove in the interior of the bearing bush; and a secondary seal including a sealing lip for engagement with a surface at or adjacent the end of the bearing bush, the secondary seal further including a surface engagable with the journal when fitted to hold the secondary seal thereon; the secondary seal being held in a preassembled relation with the bearing bush by a number of circumferentially spaced resilient tongues extending into the bearing bush axially thereof and provided with nose formations which engage radially with the annular groove in the spaces between the projections of the main seal carrier.

Because the secondary seal in a bearing assembly according to the invention engages the annular groove in the bearing bush, it is held in pre-assembled relation to the bearing bush without having to be under stress as is the case when the seal is held by friction to the bearing bush. The secondary seal is able to move freely in the rotational sense relative to the bearing bush. Because 4 the main seal is held by the carrier, it is possible to arrange for the needle roller bearings to abut the carrier so that any tendency for them to move axially in the bearing bush is resisted without imposing forces on the main seal itself. Thus the sealing efficiency of the main seal is not impaired.

Preferably the circumferential extent of the spaces between the projections of the main seal carrier is substantially greater than the circumferential extent of the nose formations of the secondary seal, so that the secondary seal is able to move angularly about the bearing bush by a substantial amount before the nose formations contact the tongues. When the dimensions of the secondary seal are such that it is a firm fit on the journal in the assembled joint and will not readily rotate on the journal, the range of movement possible of the secondary seal relative to the carrier of the main seal, which will not rotate in the bearing bush, is preferably such as to accommodate normal articulations of the joint In service. During assembly of the joint, articulation thereof while the bearing assemblies are not fully fitted in the joint yokes will ensure that the secondary seals will be so angularly positioned on the journal as to be able to accommodate joint articulation in subsequent service.

Preferably the carrier of the main seal takes the form of a sleeve having a collar extending rad ially inwardly of the bearing bush. If the carrier is of sheet metal, the main seal if of rubber may be vulcanised to the carrier. However, the carrier and main seal may be of plastics, in which case only the sealing lip or lips of the main seal are of a flexible nature.

The noses and/or the tongues of the secondary seal may be provided with predetermined breaking points so that, in an assembled joint, if large angles of articulation are required the noses will be deformed or sheared off so that free rotation of the secondary seal relative to the bearing bush and main seal is possible. If the tongues of the secondary seal are very narrow, no such predetermined point of weakness is necessary because they will bend readily.

Preferably there are provided three circumferentially spaced tongues with nose formations.

The invention will now be described by way of example with reference to the accompanying drawings, wherein:- Figure 1 shows a universally jointed drive shaft; Figure 2 shows, partly in section, the cross-member with associated bearing assemblies of one of the Hookes universal joints provided in the drive shaft; Figure 3 is a section through a pre-assembled bearing unit of a Hookes joint, incorporating the invention; Figure 4 is a view of the bearing bush only of the assembly of Figure 3, in the direction of arrow X; Figure 5 is a view of the secondary seal only of the assembly of Figure 3, in the direction of arrow Y; Figure 6 shows diagrammatically the functioning of the invention.

6 Referring firstly to Figure 1 of the drawings, there is shown a universally jointed drive shaft such as is typically provided as a propeller shaft in a motor vehicle. The shaft, indicated generally at 1, comprises two Hookes universal joints 2, 3 connected to one another by an intermediate shaft 4. Each of the joints comprises two yokes 5, 6 interconnected by a cross-member 10 whose journals are received in bearing bush assemblies 11 held in bores 12 of the spaced limbs of each yoke. The yoke 5 of each of the joints 2, 3 is in the form of a flange for bolted connection to a complementary drive element, while the yoke 6 of the joint 2 is connected to a sleeve 8 within which a shaft element 7 is supported. The sleeve 8 and shaft element 7 have torque transmitting connection by interfitting splined teeth 9, so that relative axial movement therebetween is permitted. The shaft element 7 is connected, by way of an intermediate tubular shaft element, to the yoke 6 of joint 3.

Referring now to Figure 2 of the drawings there is shown the assembly of the cross-member 10 of one of the Hookes universal joints 2, 3, and its associated bearing bush assemblies. The cross-member 10 comprises four journals 13 at right angles to one another, the journals being supported in cup-shaped bearing bushes 11 with the intermediary of needle roller bearings 15. The end of each journal engages, at 14, with a bottom face of the bearing bush 11. Two seals are provided in each bearing bush 11 at the open end thereof, namely a main seal 16 and a secondary seal 17. As will be described in greater detail hereafter, the main seal 16 is held in the bearing bush 11 and engages an outer circumferential surface 27 of the journal 13, whilst the secondary seal 17 is held on a circumferential surface of the journal 13 at the 7 -root thereof and engages the bearing bush 11 at its open end.

It will be appreciated that assembly of each of the Hookes universal joints of the drive shaft is carried out by positioning the cross-member of the joint relative to each of the joint yokes and then fitting the respective bearing bush assemblies into their bores in the yokes from the outside thereof, so that the cross- member journals enter the bearing bushes. Usually, the bearing bushes are then retained in the yokes by circlips or the like, not shown.

Referring now to Figures 3, 4 and 5 of the drawings, these show in greater detail a pre-assembled bearing unit. Figure 3 shows in greater detail the cup-shaped bearing bush 11 having the needle roller bearings 15 therein and the main and secondary seals 16, 17. The needle roller bearings 15 run against a cylindrical internal surface 28 of the bearing bush, and at their ends abut thrust washers 18 one of which is interposed between the rollers and the bottom wall at the closed end of the bearing cup whilst the other of which is interposed between the rollers and the main seal 16. The main seal 16 is a rubber or plastic's component, supported by a seal carrier 20 which is of sheet metal, comprising a sleeve 22 and a collar 31 extending radially inwardly of the bearing bush and engaged by the adjacent one of the thrust washers 18. The sleeve or shank region 22 of the carrier 20 has a number of circumferentially spaced projections 21 extending axially of the bearing bush towards the open end thereof. The main seal has two sealing lips 19 engagable with the external circumferential surface of a journal received in the bearing bush and supported therein by the needle roller 8 bearings 15, and if the main seal is of a rubber material it is preferably vulcanised to the carrier 20. As an 7.

alternative, however, the main seal and its carrier 20 could be manufactured as a single component of a suitable plastics material using the two component injection moulding process, the sealing lips 19 being of a softer material than the rest of the seal forming a carrier portion.

The projections 21 of the main seal carrier 20 are resilient in the direction radially of the bearing bush, and shaped to engage in an annular groove 23 provided in the interior of the bearing bush adjacent the open end thereof. As can be seen in Figure 4, the projections 21 are provided in three groups equally circumferentially spaced around the carrier 20, each group comprising three projections. Between each adjacent two groups of projections 26, there is a space whose circumferential extent is greater than the circumferential extent of each group of projections.

The engagement of the projections 21 in the annular groove 23 in the bearing bush has the effect that should any axial force be exerted on the main seal 16 and its carrier 20 by the needle roller bearings 15, through the intermediary of thrust washer 18, such force is transmitted by the carrier 20 directly to the bearing bush, and the main seal 16, particularly in the region of its sealing lips 19, is not subject to any axial forces. Thus the sealing effectiveness of the main seal 16 is not affected. It will be noted that the two lips 19 of the main seal 16 face generally towards the open end of the bearing bush.

9 The secondary seal 17 is shown in Figure 3 held in pre-assembled relationship to the bearing bush 11, so as to be fitted to the root portion of the cross-member journal when the bearing bush is fitted to its joint yoke as-above described. The secondary seal 17 is generally U- or V-shaped in cross-section, with a portion 30 shaped to fit securely on the root portion of the cross-member journal, and a sealing lip 29 to engage a circumferential surface of the bearing bush 11 at its open end. From the portion 30 of the secondary seal 17 there extend axially into the bearing bush three circumferentially spaced resilient tongues 24, terminating in respective nose formations 25 which extend radially outwardly of the bearing bush to engage in the annular groove 23 in the interior thereof. The nose formations 25 extend into the groove 23 in the spaces 26 defined between the groups of projections 21 in the carrier 20 of the main seal 16.

The circumferential extent of the spaces 26 is much greater than the circumferential extent of the tongue formations 24; for example, and as illustrated in Figure 4, each of the spaces 26 may subtend an angle of 660 at the axis of the bearing bush, whilst each of the tongues 24 with its nose formation 25 subtends an angle of only 7.5. This permits the secondary seal to move angularly about the axis of the bearing bush relative to the main seal and its carrier through a large angle JP as seen in Figure 6 before such relative movement is limited by contact between the nose formations 25 and projections 21.

The size of the permissible relative angular movement row on either side of a mean position is such that it will not be exceeded during normal articulation of a joint having the bearing bush and seal assembly according to the invention. When the joint is first assembled, and the bearing bushes fitted into the yokes thereof, it will be appreciated that as the joint is first assembled, the nose formations 25 may not be exactly positioned half-way between the adjacent groups of projections 21 when the joint is in the aligned (not articulated) condition. When the joint is completely assembled so that the secondary seal 17 is a tight fit on its seating surface at the route of the cross-member journal, the secondary seal is not readily able to move angularly about the journal but in an intermediate assembly position, when the journal has entered the bearing bush but not completely, the secondary seal will still be able to move angularly on the journal. In such an intermediate assembly condition, articulation of the joint will cause the secondary seal to be moved, by engagement of its nose formations 25 with projections 21, angularly about the journal until the nose formations 25 centralise themselves between the projections 21 when the joint is not articulated. Thereafter, the bearing bushes can be pressed fully home so that the secondary seal 17 is firmly held on its journal.

However, it is also possible to provide the nose formations 25 and/or the tongues 24 with points of weakness such that if the nose formations 25 or tongues 24 contact projections 21 during first articulation of the joint the nose formations or tongues will be sheared off circumferentially so that joint articulation is not hindered. The sheared off nose formations remain in the free space between the main seal and secondary seal, but because of their small size they will not have any negative effect on the effectiveness of the seals.

Because of the large spaces provided between the projections 21 and the tongues 24 and nose formations 25, there is no hindrance to escape of excess lubricant from the bearing assembly past the seals when fresh lubricant is.introduced into the bearing assembly.

I 12

Claims

141 1. A bearing assembly comprising: a bearing bush for supporting a journal therein; a main seal held in the bearing bush by a carrier, the carrier including projections engaging an annular groove in the interior of the bearing bush; and a secondary seal including a sealing lip for engagement with a surface at or adjacent the end of the bearing bush, the secondary seal further including a surface engagable with the journal when fitted to hold the secondary seal thereon; the secondary seal being held in a preassembled relation with the bearing bush by a number of circumferentially spaced resilient tongues extending into the bearing bush axially thereof and provided with nose formations which engage radially with the annular groove in the spaces between the projections of the main seal carrier.

2. A bearing assembly according to Claim 1 wherein the circumferential extent of the spaces between the projections of the main seal carrier is substantially greater than the circumferential extent of the nose formations of the secondary seal.

3. A bearing assembly according to Claim 2 wherein the dimensions of the secondary seal are such that it is a firm fit on the journal and will not readily rotate on the journal.

4. A bearing assembly according to any one of the preceding claims wherein the carrier of the main seal takes the form of a sleeve having a collar extending radially inwardly of the bearing bush.

13

5. A bearing assembly according to Claim 2, Claim 3, or Claim 4 as appendant to Claim 2, wherein the noses and/or the tongues of the secondary seal are provided with predetermined breaking points so that the noses can be deformed or sheared off so that free rotation of the secondary seal relative to the bearing bush and main seal is possible.

6. A bearing assembly according to any one of the preceding claims wherein there are provided three circumferentially spaced tongues with nose formations.

7. A bearing assembly substantially as hereinbefore described with reference to Figures 2 to 6 of the accompanying drawings.

8. A Hookes universal joint having bearing assemblies according to any one of the preceding claims.

1 Published 1989 stThePstexxtOffIoe, State House, 66/71 High Holborn, London WCIR4TP. FVrther COPies Ineybe obtainedfrom The PatentOffice. Wes Branch, St Mary Cray, Orpington, Kent BRS 3W. Printed by Multiplex tecbniques Itd, St Mary Cray, Kent, Con. 1/87