A BEARING ASSEMBLY

Abstract: A bearing assembly and a bearing retaining member for such an assembly includes a bearing 3 for a shaft 1 mounted in a seating 8 of a housing 2. The bearing 3 is retained axially in its seating by abutment with a flat, planar spring retaining member 11 having arms 13 which extend radially outwardly and circumferentially in curved or spiral profile from a centre ring 12. The arms 13 flex radially to snap engage in an internal annular recess 10 in the housing 2. The arms 13 have arcuate side edges 15 which engage in annular recess 10 and correspond to the diameter of that recess. The engagement of the arms 13 with the recess 10 provides a wedge action which biases the member 11 axially into abutment with the bearing 3. In a modification the arms of the retaining member extend radially and circumferentially inwardly from an outer ring of that member for snap engagement with an external annular recess on a shaft to retain a bearing axially on that shaft.

Description: TECHNICAL FIELD & BACKGROUND ART The present invention relates to a bearing assembly and a bearing retaining member for such an assembly. Conventionally a bearing for rotatably mounting a shaft in a housing is located in a seating on the shaft and/or in the housing to be restrained from displacement axially of the shaft in one sense of direction by its abutment with a shoulder in the housing or on the shaft. Several proposals have been made for restraining the bearing in the opposite axial direction such as a collar or nut which is screw threaded on the shaft or in the housing to abut the bearing on the side thereof axially remote from the aforementioned shoulder or a ring member which may be force fitted or snap engaged in an annular recess on the shaft or in the housing on the side of the bearing remote from the aforementioned shoulder to provide the appropriate retention. The ring member may be in the form of a split ring, such as a so-called circlip, which is sprung into the annular recess. It is recognised that the use of a screw threaded nut or collar to retain the bearing is expensive and inappropriate in many bearing assembly structures, for example the structure may not have space available to fit such a member or the screw threads may be impractical to machine or locate within the structure. Consequently a most widely adopted means for retaining the bearing in its location against the aforementioned annular shoulder is a split-ring spring clip which corresponds, when fitted, to the diameter of the annular recess in the shaft or in the housing and stands proud of the annular recess to overlie a relatively minor portion of the radial thickness of the bearing. For efficient fitting of such a split-ring spring clip it is advisable to ensure that the diameter of the clip when fitted corresponds to the diameter of the annular recess within which it is accommodated so that different diameter clips are generally provided, as required, for various sized annular recesses in which they are to be accommodated. It is an object of the present invention to provide for, and in, a bearing assembly, a means for retaining the bearing which means is of the spring kind to engage with an annular recess to effect the necessary retention, is inexpensive, easily fitted and can flex to be stably accommodated within annular recesses of different diameters while standing proud of such recesses to a substantial extent. STATEMENT OF INVENTION & ADVANTAGES According to the present invention there is provided a bearing assembly comprising a bearing for a shaft and mounted by a seating; means restraining the bearing from displacement axially of the shaft and relative to said seating in one sense; an annular recess adjacent said seating and spring retaining means engaging with said annular recess to restrain the bearing from axial displacement in the opposite sense, said retaining means comprising a substantially flat, planar spring member having a circumferentially spaced array of radially and circumferentially extending resilient arms which flex in the plane of said spring member for snap engagement with said annular recess. Further according to the present invention there is provided a retaining member for an assembly as specified in the immediately preceding paragraph and which member is substantially flat and planar and comprises a circumferentially spaced array of radially and circumferentially extending resilient arms which are capable of flexing radially in the plane of said member for snap engagement in an annular recess. By the present invention the retaining member for the bearing assembly may simply be formed as a one piece component of resilient material such as plastics or spring steel with its arms extending outwardly radially and circumferentially from a centre part of the member or with its arms extending inwardly radially and circumferentially from an outer ring part of the member. With the arms extending outwardly from its centre part the member may snap engage with an internal annular recess in the housing for retaining a bearing which is mounted in, for example, a cylindrical seating in the housing adjacent to the annular recess; with this arrangement the centre part of the member will usually be in the form of a ring or annulus from which the arms extend outwardly so that a shaft mounted in the bearing can extend through the centre ring part of the retaining member. In the arrangement where the arms of the retaining member extend radially inwardly from the outer ring part, the arms may be flexed to snap engage with an external annular recess on a shaft adjacent to a bearing which is seated on the shaft. It will be apparent that the retaining member for the present invention can easily be fitted by radially displacing the arms, inwardly or outwardly as appropriate depending upon whether the member is of the type to be engaged with an internal annular recess or an external annular recess respectively, locating the so deformed retaining member over the recess and allowing the arms to snap engage with the recess. Although such fitting may be achieved manually and without the use of special tools, for commercial purposes it is likely several of the retaining members will be accommodated in a cartridge or similar device and held in their flexed or stressed condition ready for fitting so that as each member is displaced from the cartridge it can snap engage with a recess. By way of example, the cartridge may comprise a tube within which an array of similar retaining members having arms extending outwardly from centre part are held with their arms flexed radially inwardly so that the tube and members can be located in a housing (and possibly over a shaft) to a position where one of the retaining members can be displaced from the tube to snap engage with an internal annular recess in the housing. Preferably the arms of the retaining member are similarly orientated to extend radially and circumferentially of the retaining member and provide a generally sprial or curved configuration; in this way side edges of part lengths of the arms (usually towards or at the free ends thereof) can engage within the annular recess (rather than merely the extremities of the arms at their free ends) to provide a firm fitting of the arms with the annular recesses. The flexible and spring nature of the arms will permit the retaining member to engage, within reason, with annular recesses of different diameters although it will be realised that for efficient use of its spring characteristics, the retaining member will be manufactured with a particular and preferred diameter of annular recess in mind. On this latter point it is also preferred that the aforementioned side edges of the part lengths of the arms which engage with the annular recess are arcuate to substantially correspond with the diameter of the annular recess with which they are preferably to engage (so that the side edges are arcuately convex for engagement with an internal annular recess and are arcuately concave for engagement with an external annular recess). A further preferred feature of the present invention is that the arms of the retaining member engage in the annular recess with a wedge action so that by this action the retaining member will be seated firmly in the annular recess and restrained against axial displacement by the constant biasing effect of the arms radially into the recess. The aforementioned wedge action may also serve to bias the retaining member axially in a direction towards the bearing which it is to retain and thereby firmly hold the bearing on or in its seating. The wedge action between the arms and the annular recess may be achieved by appropriately tapering the axially opposed faces of the annular recess and/or of the arms. It will be apparent that the arms of the retaining member and also the centre part or the outer ring part from which the arms extend radially will, when the member is fitted to an annular recess, extend from the annular recess and these may project radially for a considerable extent so that a large abutment area can be provided for retaining the bearing. In accordance with the present invention the spring retaining member restrains the bearing from displacement axially in the "opposite sense" but it will be appreciated that a second and similar spring retaining member may be used to restrain the bearing from displacement in the "one sense" (although usually this latter restraint will be provided by a shoulder on the shaft which receives the bearing or in the housing within which the bearing is mounted). DRAWINGS One embodiment of the present invention will now be described, by way of example only, with reference to the accompanying illustrative drawings, in which: Figure 1 is an axial section through a bearing assembly of the invention in which a shaft roller bearing is mounted in a housing and retained by a spring retaining member engaging with an internal annular recess in the housing, and Figure 2 is a side view of a spring retaining member of the invention and which is incorporated in the assembly of Figure 1, the member being shown by the full lines in an un-flexed or un-stressed condition and by the broken lines in a flexed or stressed condition as fitted in the assembly of Figure 1. DETAILED DESCRIPTION OF DRAWINGS The bearing assembly comprises a cylindrical shaft 1 mounted within a housing 2 by a ball bearing 3 having inner and outer races 4 and 5 respectively. The inner race 4 is mounted on a cylindrical seating of the shaft 1 and is restrained from axial displacement relative to the shaft between an annular shoulder 6 of the shaft and a spring clip or circlip type member 7 which is fitted to the shaft 1 (and usually accommodated within a shallow annular groove in the shaft). The outer race 5 of the bearing 3 is seated within a cylindrical rebate 8 of the housing and is restrained from axial displacement in one sense relative to the housing by its abutment with an annular shoulder 9 of the rebate 8. The outer race 5 extends axially from the shoulder 9 to partially overlie an internal annular recess 10 in the housing within which recess is located a spring member 11 that serves to retain the outer race 5 and thereby a bearing 3 in its seating 8 and to restrain the bearing from axial displacement in the opposite sense (that is away from the shoulder 9). The spring retaining member 11 (see Figure 2) is a one piece substantially flat planar component of resilient material, preferably spring steel or plastics, having a generally annular centre part 12 and four arms 13 extending radially outwardly and circumferentially from the part 12. It will be seen from Figure 2 that the arms 13 are circumferentially spaced and similarly orientated relative to the centre annulus 12 to present a generally curved or spiral profile. With the member 11 in an un-flexed or un-stressed condition the arms 13 extend outwardly to provide the retaining member with an overall diameter greater than the maximum internal diameter (indicated by the broken line 10 a ) of the internal annular recess 10. For fitting the retaining member 11 as part of the assembly shown in Figure 1, the arms 13 are flexed radially inwardly to a position where the retaining member has an overall diameter which permits it to be positioned in the housing 2 (through the mouth 14 thereof) to radially overlie the internal recess 10 while the shaft 1 is accommodated within the centre annular part 12. In this condition the arms 13 are allowed to flex under their natural resilience and snap engage with the recess 10 in abutment with the outer race 5 on the side of the bearing axially remote from the shoulder 9. When in engagement with the annular recess 10, the arms 13 adopt the positions illustrated at 13 a in Figure 2 so that the resilience of the retaining member 11 constantly biases the arms radially outwardly and in the plane of the member 11 into engagement with the recess. It will be seen from Figure 2 that the arms 13, when in their positions 13 a , engage with the recess 10 over a considerable part length 15 of those arms. Preferably each part length 15 has its radially outer side edge 15 (which opposes the bottom of the annular recess 10) of arcuate convex form to correspond substantially with the diameter of the part of the annular recess 10 with which the parts 15 will engage; in this way the side edges 15 can engage with the recess 10 with a substantial length of contact. It will be seen from Figure 1 that the annular recess 10 has axially opposed side faces 16 and 17 of which the side face 16 (adjacent to the bearing 3 and which the outer race 5 extends beyond as aforementioned) extends in a radial plane. The side face 17 however is angled from the radial plane to converge towards the side face l6 as the depth of the annular recess 10 increases - thereby providing the recess 10 with a wedge shaped configuration. With this arrangement, it will be realised that as the arms 13 are biased radially into the recess 10, the wedge shaped configuration of the recess provides a firm and stable engagement between the parts 15 of the arms and the recess. Furthermore, the reaction of the radially outward biasing force from the arms 13 abutting the inclined side wall 17 of the recess imparts an axial component of force on the retaining member 11 which biases that member into abutment with the outer race 5; the bearing 3 is consequently biased axially into firm abutment with the shoulder 9 of its seating. It will be realised that a similar axial biasing effect from the retaining member 11 on the bearing 5 can be achieved by locating the side face 17 of the annular recess 10 in a radial plane and appropriately tapering the side faces of the arms 13 which abut the face 17.

Claims: 1. A bearing assembly comprising a bearing for a shaft and mounted by a seating; means restraining the bearing from displacement axially of the shaft and relative to said seating in one sense; an annular recess adjacent said seating and spring retaining means engaging with said annular recess to restrain the bearing from axial displacement in the opposite sense, said retaining means comprising a substantially flat, planar spring member having a circumferentially spaced array of radially and circumferentially extending resilient arms which flex in the plane of said spring member for snap engagement with said annular recess. 2. A bearing assembly as claimed in claim 1 in which the retaining member is a one piece component of resilient material. 3. A bearing assembly as claimed in either claim 1 or claim 2 in which the annular recess is internal and the arms of the retaining member extend outwardly radially and circumferentially from a centre part of the member to engage with said internal annular recess. 4. A bearing assembly as claimed in claim 3 in which the centre part of the retaining member is in the form of a ring or annulus. 5. A bearing assembly as claimed in either claim 3 or claim 4 in which the shaft extends through the centre part of the retaining member. 6. A bearing assembly as claimed in either claim 1 or claim 2 in which the annular recess is external and the arms of the retaining member extend inwardly, radially and circumferentially from an outer ring part of that member to engage with said external annular recess. 7. A bearing assembly as claimed in any one of the preceding claims in which the arms of the retaining member are similarly orientated to extend radially and circumferentially of the retaining member and provide a generally spiral or curved configuration. 8. A bearing assembly as claimed in any one of the preceding claims in which side edges of part lengths of the arms of the retaining member engage within the annular recess. 9. A bearing assembly as claimed in claim 8 in which said side edges of the arms have an arcuate profile substantially to correspond with a predetermined diameter of annular recess with which said side edges engage. 10. A bearing assembly as claimed in either claim 8 or claim 9 when appendent to claim 3 in which said side edges are of convex profile to engage with the internal annular recess. 11. A bearing assembly as claimed in either claim 8 or claim 9 when appendent to claim 6 in which said side edges are of concave profile to engage with the external annular recess. 12. A bearing assembly as claimed in any one of the preceding claims in which the arms of the retaining member engage in the annular recess with a wedge action which is maintained by a constant biasing of the arms radially into the recess. 13. A bearing assembly as claimed in claim 12 in which the wedge action biases the retaining member axially in a direction towards the bearing which that member restrains. 14. A bearing assembly as claimed in either claim 12 or claim 13 in which axially opposed faces of the annular recess or of the arms of the retaining member taper radially to provide the wedge action. 15. A bearing assembly as claimed in any one of the preceding claims in which the bearing is restrained from axial displacement in the opposite sense by abutment with axially directed side faces of the arms of the retaining member. 16. A bearing assembly as claimed in any one of the preceding claims in which the means restraining the bearing from displacement axially in said one sense comprises a second said retaining member having its arms engaging with a second said annular recess. 17. A retaining member for a bearing assembly as claimed in any one of the preceding claims and which member is substantially flat and planar and comprises a circumferentially spaced array of radially and circumferentially extending resilient arms which are capable of flexing radially in the plane of said member for snap engagement in an annular recess. 18. A plurality of retaining members each as claimed in claim 17, said members being accommodated by means from which they are displaced with their legs in a radially flexed or stressed condition for snap engagement with an annular recess.

Inventors: ADAMS, FREDERICK JOHN
Applicants: TRW CAM GEARS LIMITED
Application year: 1987
Main classification: F16C35
IPC codes: F16F1, F16B21, F16C35