GB2296297A

GB2296297A - Bearing support avoiding play between bearing and support

Info

Publication number: GB2296297A
Application number: GB9425720A
Authority: GB
Inventors: Gert Eichberger
Original assignee: Black and Decker Inc
Current assignee: Black and Decker Inc
Priority date: 1994-12-20
Filing date: 1994-12-20
Publication date: 1996-06-26
Also published as: GB9425720D0

Abstract

The bearing support (31) eg. for power tools such as a plain comprises a first surface (33) against which a bearing rests, in use, a second surface (35) substantially perpendicular to the first surface (33) and a recess (45) in the second surface (35) accommodating a boss (41) for receiving means eg. a screw (43, Fig. 2c) for retaining a bearing in the bearing support (31), wherein the boss (41) includes a wall (47) which, when retaining means are entered into the boss (41) to retain a bearing, deforms out of the recess (45) to abut the bearing. The support can be of plastics and can be formed in a portion of the housing of the power tool. <IMAGE>

Description

A BEARING SUPPORT This invention relates to a bearing support which, in combination with retaining means, may be used to retain a bearing for a shaft of a power tool, for example. The invention is, however, not limited to bearing supports for power tools.

When a bearing for receiving a shaft is to be mounted in a housing of a power tool, for example, it is necessary to retain the bearing in position. In the past, this has been achieved by forming a seat in the housing in which the bearing sits. A circlip is a normal way of retaining the bearing in the seat, but this does not restrict any radial clearance or play which may exist between the bearing and the cylindrical part of the seat and may not prevent the outer race of bearing from rotating. This may have serious results if the bearing is in a plastics material housing, as rotation of the bearing may generate heat which could damage the housing. It is known, therefore, for the bearing to be received first in a rubber sleeve or cup to take up such play and prevent rotation of the bearing, but this is expensive.

In view of the foregoing, the present invention has been made to overcome the problem of radial clearance and play between a bearing and its seat. Further, by virtue of the present invention, a simple bearing retainer may be provided which is cheap to manufacture, easy to use and simple to assemble.

In accordance with the foregoing, the present invention provides a bearing support comprising a first surface against which a bearing rests, in use, a second surface substantially perpendicular to the first surface and a recess in the second surface which accommodates a boss for receiving means for retaining a bearing in the bearing support, wherein the boss includes a wall which, when retaining means are entered into the boss to retain a bearing, deforms out of the recess to abut the bearing.

Thus, in use, the retaining means urge the bearing against the first surface of the support to restrict axial motion of the bearing and the wall of the boss abuts the bearing to restrict radial play of the bearing.

The wall of the boss may be substantially flush with the second surface before retaining means are entered into the boss. As a result of this, as soon as retaining means are entered into the boss, causing the wall of the boss to deform, the wall of the boss will begin to reduce the play between the bearing and the bearing support.

Preferably the wall of the boss is resilient. As a result, when the retaining means are removed from the boss, the wall of the boss will return to its original position, thereby allowing the bearing within the support to be removed from the support.

In a particular embodiment, the wall of the boss has a cross-section which is substantially semi-circular with a portion removed to accommodate the retaining means. Any other appropriate cross-section could, alternatively, be used.

The wall of the boss may be arranged to bend about a line which lies in the plane of the first surface. As will be appreciated by those skilled in the art, this feature is, of course, not essential to the working of the invention.

In a particular embodiment, the first surface is substantially annular and the second surface is substantially cylindrical.

Preferably the bearing support is formed of plastics material, thereby enabling the support to be moulded in one piece.

The present invention further provides a bearing retainer comprising a bearing support as herein defined in combination with means for retaining a bearing in the support.

The retaining means may comprise a screw of appropriate size to achieve the required deformation of the wall of the boss, in use.

Retaining means other than a screw could, however, be used.

If the retaining means comprise a screw, the head of the screw may bear against a bearing, in use, to urge the bearing into contact with the first surface of the support. Alternatively, the retaining means may further comprise a washer for overlying a portion of a bearing in the bearing support.

Although the present invention is particularly suitable for use with power tools, such as an electric planer which incorporates a motor and a shaft supported by a bearing in a bearing retainer, the present invention is applicable to any application which requires the retention of a bearing (or any other article) in a support (or seat) requiring a reduction in the radial clearance or play between the device and its seat.

Specific embodiments of the present invention are now described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic plan view of an electric planer which incorporates two bearing supports according to the present invention; Figure 2A is a sectional side view of a bearing support according to the present invention; Figure 2B is a plan view of the bearing support of Figure 2A; Figure 2C is sectional side view as shown is Figure 2A, but this time with a bearing in position in the support; Figure 2D is a plan view of the arrangement shown in Figure 2C; Figures 3 and 4 are schematic plan views of alternative bearing retainer configurations; and Figure 5 is a schematic perspective view of a further embodiment of bearing support according to the present invention.

With reference to Figure 1 of the drawings, an electric planer 1 comprises a housing 3 formed with a handle 5 and a knob 7 for gripping by a user. The housing 3 incorporates a cutting blade 9 mounted on a shaft 11 supported by bearings 13, 15. The shaft 11 extends through the bearing 15 and is rotated by means of a belt 17 driven by an armature 19 of an electric motor 21. The shaft 23 of the armature 19 is carried by bearings 25, 27 in a similar fashion to the shaft 11 of the blade 9.

In use, power applied to the motor 21 causes the armature 19 to rotate, thereby driving the band 17 to cause the blade 9 to rotate on the shaft 11. The planer 1 can then be moved across a workpiece (not shown) using the handle 5 and knob 7 to plane the workpiece.

The bearings 13, 27 are shown mounted in the housing 3 without any retention. Instead, the bearings 15, 25 are contained in bearing retainers according to the present invention. Examples of such bearing retainers will now be described with reference to Figures 2-5.

With specific reference to Figures 2A-2D, a bearing support 31 is formed in a portion of the housing 3 of the planer 1. The bearing support 31 includes a first surface 33 and a second surface 35 extending substantially perpendicularly to the first surface 33. The first surface 33 is essentially annular, as seen clearly in Figure 2B, and the second surface 35 is substantially cylindrical. An opening 37 in the housing 3 is provided coaxially with the cylindrical second surface 35 through which an appropriate shaft 11, 23 passes.

Although the second surface 35 is shown formed on the inside surface of an upstanding wall 39, the wall 39 could be of any thickness and, indeed, the housing 3 could have a thickness equal to the height of the wall 39.

A boss 41 for a screw 43 is formed in a recess 45 in the second surface 35 of the bearing support 31. A wall 47 of the boss 41 defines a surface 49 which lies flush with the second surface 35 (cf. Figure 2B) when a screw 43 has not been inserted into the boss 41. Further, the wall 47 is an upstand extending from the plane in which the first surface 33 lies, as seen clearly in Figures 2A and 2C.

A bearing 51, comprising a plurality of balls 53 between an outer ring 55 and an inner ring 57 may be inserted into the bearing support 31, as shown in Figures 2C and 2D. Although the bearing 51 should ideally be able to slide into position, excessive free play between the bearing 51 and the cylindrical second surface 35 should be avoided.

However, there will undoubtedly be some degree of free play between the bearing 51 and the cylindrical second surface 35, particularly when taking into account the tolerances involved in the molding of plastics components such as the housing 3. This free play is taken up by the bearing retainer when the screw 43 is driven into the boss 41. More particularly, as the screw 43 is screwed into the boss 41, the wall 47 of the boss 41 is forced out of the recess 45 and into contact with the bearing 51. Hence, a tight contact is produced between the wall 47 and the bearing 51, which removes any free play in the radial direction of the bearing 51. Additionally, as the screw 43 is driven further into the boss 41, the head 43a of the screw 43 abuts the bearing 51, as shown in Figure 2C. In this way, axial movement of the bearing 51 out of the bearing support 31 is prevented.

As shown in Figure 1 of the drawings, a washer 59 may be provided between the head 43a of the screw 43 and the boss 41.

Further, if the washer 59 has a larger diameter then the head 43a of the screw 43, the retaining force is applied to the bearing 51 over a greater area.

The bearing support 31 is preferably formed at the same time as the housing 3 is formed. This is easy to do if the housing 3 is formed of plastics materials. Further, if the bearing support 31 is formed of plastics material, the screw 43 can be easily screwed into the boss 41 and the wall 47 is easy to deflect into contact with the bearing 51.

Although a bearing support 31 with only one boss 41 is shown in Figures 2A-2D, a bearing support could be formed with any number of bosses 41. For example, alternative embodiments are shown in Figures 3 and 4 of the accompanying drawings. In Figure 3, two bosses are shown spaced approximately 900 about the axis of the cylindrical second surface 35. Positive retention of the bearing 51 in all three orthogonal directions is thereby provided. In contrast, Figure 4 shows two bosses spaced approximately 45" about the axis of the second surface 35. In this embodiment, a single wall 47 is provided for both bosses, which wall is forced into contact with the bearing 51 by the two screws 43.

Turning now to Figure 5 of the drawings, an alternative arrangement is shown wherein the recess 45 includes a part cylindrical back face 46 which faces the inside of a part annular tongue or wall 47 to define a boss 41. In this embodiment, the tongue or wall 47 has only a small portion which lies flush with the second surface 35 of the bearing support 31. However, this small portion of the wall 47 is sufficient to contact the bearing 51, in use.

As will be appreciated from the foregoing, a bearing retainer as herein described is extremely simple to manufacture, easy to use and effective in overcoming the problems associated with the prior art.

Further, such a bearing support may be used in any apparatus incorporating a shaft mounted in a bearing or, indeed, any apparatus requiring positive positioning of an appropriate component.

It will of course be understood that the present invention has been described above purely by way of example, and that modifications of detail can be made within the scope of the invention.

Claims

CLAIMS:

1. A bearing support comprising a first surface against which a bearing rests, in use, a second surface perpendicular to the first surface and a recess in the second surface accommodating a boss for receiving means for retaining a bearing in the bearing support, wherein the boss includes a wall which, when retaining means are entered into the boss to retain a bearing, deforms out of the recess to abut the bearing.

2. A support as claimed in claim 1, wherein the wall of the boss is substantially flush with the second surface before retaining means are entered into the boss.

3. A support as claimed in claim 1 or claim 2, wherein the wall of the boss is resilient.

4. A support as claimed in any preceding claim, wherein the wall of the boss has a cross-section which is substantially semi-circular with a portion removed to accommodate the retaining means.

5. A support as claimed in any preceding claim, wherein the wall of the boss is arranged to bend about a line which lies in the plane of the first surface.

6. A support as claimed in any preceding claim, wherein the first surface is substantially annular.

7. A support as claimed in any preceding claim, wherein the second surface is substantially cylindrical.

8. A support as claimed in any preceding claim, which is formed of plastics material.

9. A bearing support substantially as hereinbefore described with reference and is showing in any one of Figures 2-5 of the accompanying drawings.

10. A bearing retainer comprising a bearing support according to any preceding claim and means for retaining a bearing in the support.

11. A bearing retainer according to claim 10, wherein the retaining means comprise a screw.

12. A bearing retainer as claimed in claim 11, further comprising a washer for overlying a bearing in the support.

13. A bearing retainer substantially as hereinbefore described with reference to and as shown in any one of Figures 1-5 of the accompanying drawings.

14. A power tool comprising a motor and a shaft, wherein the shaft is supported by a bearing mounted in a bearing retainer according to any one of claims 10-13.

15. A power tool substantially as hereinbefore described with reference to and as shown in Figure 1 and any one of Figures 2-5 of the accompanying drawings.