GB2485815A

GB2485815A - Bearing retainer of a shearing handpiece

Info

Publication number: GB2485815A
Application number: GB1019999.0A
Authority: GB
Inventors: Robin James Howell; Alun Williams
Original assignee: Lister Shearing Equipment Ltd
Current assignee: Lister Shearing Equipment Ltd
Priority date: 2010-11-25
Filing date: 2010-11-25
Publication date: 2012-05-30
Also published as: GB201019999D0; AU2011253546A1

Abstract

A shearing handpiece body (12, fig.1) has a through bore (13, fig. 2) and a bearing (22, fig. 1) which is seated against a forward shoulder (28) provided in the through bore. The bearing is prevented from moving from its seated position by a resilient bearing retainer 58. The retainer comprises an oval ring 60 having on opposite sides a pair of laterally extending lugs 62 that are aligned on the ringâ s major axis 64a. Each lug also has a bearing abutment face 73. The ring is movable between an undeflected state where the lugs are at a maximum separation from one another and a deflected state where the separation of the lugs is less than the maximum separation. The lugs are urged towards the maximum separation distance when the ring is in the deflected state. The lugs are received in opposed recesses (78, fig. 3) of the handpiece body and the ring is in the deflected state when the lugs are received in the recesses.

Description

Improvements In or Relating To The Retention of Bearings The present invention relates to a shearing handpiece body and particularly to the retention of a bearing within a shearing handpiece body.

A shearing handpiece typically includes a handpiece body having a crank spindle which drives a crank pin. The crank pin is in turn connected to a fork assembly which converts the rotational motion of the crank pin into reciprocal lateral motion. The crank spindle is typically supported within the handpiece body by a front bearing which is mounted to the handpiece body, and a rear bearing which is mounted to a portion of the shearing handpiece known as the back joint. The front bearing is typically seated against a forward shoulder within the handpiece body. During assembly of the shearing handpiece, the front bearing is inserted into the handpiece body from the rear and moved into engagement with the forward shoulder. The shoulder thus prevents further axial movement of the front bearing in a forward direction.

During use of the shearing handpiece the forward bearing may become disengaged from the shoulder and move axially in a rearward direction. The present invention seeks to overcome this problem.

According to a first aspect of the present invention there is provided a shearing handpiece body having a through bore, the handpiece body including a bearing which is seated against a forward shoulder provided in the through bore of the handpiece body, the bearing being prevented to moving from the seated position against the forward shoulder by a resilient bearing retainer, wherein the bearing retainer comprises a substantially oval ring having a pair of laterally extending lugs, each of said lugs being provided on an opposite side of the ring to the other of the lugs and said lugs being aligned on the major axis of the oval ring, each lug being further provided with a bearing abutment face, wherein the ring is movable between a undeflected state where the lugs are at a maximum separation distance from one another and a deflected state where the separation of the lugs less than the maximum separation, the lugs being urged towards the maximum separation distance when the ring is in the deflected state, wherein further the lugs are received in opposed recesses of the handpiece body and the ring is in the deflected state when the lugs are received in said opposed recesses.

Movement of the bearing in a direction away from the shoulder is prevented by the bearing retainer.

Each lug is provided with a further abutment face on the opposite side of the lug to the bearing abutment face. The bearing abutment faces may lie on a common plane to a face of the ring which faces the bearing. The further abutment faces of the lugs may be spaced from a face of the ring which faces in an opposite direction to the bearing.

The further abutment faces may be provided on a plane that is spaced from and parallel to the plane of the face of the ring which faces in an opposite direction to the bearing.

The through bore of the shearing handpiece body may further be provided with a tubular bush, wherein the bush is provided with opposed cut-outs within which the lugs are received with a clearance. The bush may be provided with such cut-outs at each end.

According to a second aspect of the present invention there is provided a method of retaining a bearing in a shearing handpiece body comprising the steps of: providing a resilient bearing retainer comprising a substantially oval ring having a pair of laterally extending lugs, each of said lugs being provided on an opposite side of the ring to the other of the lugs and said lugs being aligned on the major axis of the oval ring, each lug being further provided with a bearing abutment face, wherein the ring is movable between a undeflected state where the lugs are at a maximum separation distance from one another and a deflected state where the separation of the lugs less than the maximum separation, the lugs being urged towards the maximum separation distance when the ring is in the deflected state; and, fitting said resilient bearing retainer to a shearing handpiece body such that said lugs abut a bearing to be retained and further are received in corresponding recesses of the shearing handpiece body such that the ring is maintained in the deflected state.

According to a third aspect of the present invention there is provided a resilient bearing retainer comprising a substantially oval ring having a pair of laterally extending lugs, each of said lugs being provided on an opposite side of the ring to the other of the lugs and said lugs being aligned on the major axis of the oval ring, each lug being further provided with a bearing abutment face, wherein the ring is movable between a undeflected state where the lugs are at a maximum separation distance from one another and a deflected state where the separation of the lugs less than the maximum separation, the lugs being urged towards the maximum separation distance when the ring is in the deflected state.

Each lug is provided with a further abutment face on the opposite side of the lug to the bearing abutment face. The bearing abutment faces may line on a common plane to a face of the ring which faces the bearing. The further abutment faces of the lugs may be spaced from a face of the ring which faces in an opposite direction to the bearing.

An embodiment of the present invention will now be described with reference to the accompanying drawings in which: Figure 1 shows a longitudinal cross-sectional view of a shearing handpiece in accordance with the present invention; Figure 2 shows a longitudinal cross-sectional view of a shearing handpiece body in accordance with the present invention; Figure 3 shows a transverse cross-sectional view of the shearing handpiece bodyoffigure2; Figure 4 shows a front view of a bearing retainer in accordance with the present invention; Figure 5 shows a rear view of the bearing retainer of figure 4; Figure 6 shows a perspective view from the front and to one side of the bearing retainer; Figure 7 shows a perspective view from the rear and to one side of the bearing retainer; Figure 8 shows a side view of the bearing retainer; Figure 9 shows another side view of the rearing retainer; Figure 10 shows a front view of the bearing retainer in an undeflected state; Figure 11 shows a front view of the bearing retainer in a first deflected state corresponding to the state of the retainer when filled to a shearing handpiece body; Figure 12 shows a front view of the bearing retainer in a second deflected state corresponding to the state of the retainer during fitting of the retainer to a shearing handpiece body; and Figure 13 shows a perspective view of a bush configured for use with the bearing retainer of the present invention.

Referring firstly to figures 1 to 3 there is shown a cross-sectional view of a shearing handpiece generally designated 10. The shearing handpiece 10 includes a handpiece body 12 having a through bore 13, a crank spindle 14 and a fork assembly 16. The crank spindle 14 includes a crank pin 18 which is offset in relation to the rotational axis 20 of the crank spindle 14. The crank spindle 14 is supported by a front bearing 22 and a rear bearing 24. The terms "front" and "rear" are construed with reference to the front end 26 of the handpiece body 12 from which the fork assembly 16 projects.

The crank spindle 14 is further provided with a drive cog 32 which meshes with a corresponding cog 34 of a drive spindle 36 of the shearing handpiece 10.

The front bearing 22 abuts a forward shoulder 28 of the handpiece body 12. The front bearing 22 is press-fitted into a bearing section 30 of the handpiece through bore 13 to the rear of the shoulder 28. The rear bearing 24 is carried by a front or inner part 38 of the back joint 40. The drive spindle 36 is carried by a back or outer part 42 of the back joint 40. The inner part 38 of the back joint 40 includes a tubular portion 44 which extends into the through bore 13 of the handpiece body 12. The tubular portion 44 of the inner part 38 of the back joint 40 is received within a tubular bush 46 which is fitted to a section 48 of the handpiece through bore 13 which is rearward of the bearing section 30 which receives the front bearing 22. The tubular bush 46 has a sliding fit with the handpiece body 12 locates against a further shoulder 50 of the handpiece through bore 13. The further shoulder 50 is positioned such that when the bush 46 is fitted to the handpiece body 12 the forward end 52 of the bush 46 does not contact the front bearing 22. The bush 46 is retained in the handpiece body 12 by a circlip 54 which is received within an annular recess 56 to the rear of the handpiece through bore 13.

The front bearing 22 is prevented from moving in a rearward direction by the provision of a retainer 58 which is fitted to the handpiece body 12 to the rear of the front bearing 22. The retainer 58 is shown in greater detail in figures 4 to 12. The retainer 58 comprises a ring 60 having a pair of opposed lugs 62. The ring 60 is resiliently deflectable between an undeflected state shown in figures 4 to 10, and deflected states shown in figures 11 and 12. I the undeflected state the ring 60 has a substantially oval or elliptical shape such that the ring 60 has a major diameter 64 along a major axis 64a and a minor diameter 66 along a minor axis 66a. The lugs 62 are aligned along the major axis 64. The retainer 58 is moved from the undeflected state to the deflected states by moving the lugs 62 towards one another along the major axis 64 of the ring 60. It will thus be appreciated that in moving from the undeflected state to the deflected states the major diameter 64 of the ring 60 decreases and the minor diameter 66 of the ring 60 increases. The retainer 58 is moulded from a resilient plastic material. Alternatively the retainer 58 may be formed from metal.

For example, the retainer may be formed wire or stamped from sheet.

The retainer 58 has a front side 68 and a rear side 70. The front side 68 has a substantially flat face 72 which, in use, faces the rear of the front bearing 22. Each lug 62 is provided with a bearing abutment face 73 which, in use, rests against the outer race of the front bearing 22. Each lug 62 further extends in a rearward direction and is provided with a handpiece body abutment face 74 which, in use, opposes corresponding abutment surface 76 of the through bore 13 of the handpiece body 12.

As will be described in greater detail below, the co-operation of the handpiece body abutment faces 74 of the lugs 62 with the abutment surfaces 76 of the handpiece body 12 prevent rearward movement of the retainer 58 and, correspondingly, rearward movement of the front bearing 22.

Figure 3 shows a cross sectional view of the handpiece body 12 indicated by arrows X-X of figure 2. The through bore 13 of the handpiece body 12 is provided with a pair of opposed cut-outs 78 within which the lugs 62 of the retainer 58 are received, in use. The provision of the cut-outs 78 in the handpiece body 12 creates the aforementioned abutment surfaces 76 for the retainer abutment faces 74. Each cut-out 78 has a curved profile. The profile may be formed such that it merges smoothly with the wall of the handpiece body through bore 13. The outer edge 80 of each lug 62 has a complementarily curved shape which follows the curve of the cut-out 78.

Figure 13 shows the tubular bush 46 of the handpiece 10. Each end of the bush 46 is provided with a pair of cut-outs 82 into which, in use, the lugs 62 of the retainer 58 are received. The cut-outs 82 are sized such that the lugs 62 are received with a clearance therearound. The cut-outs 82 at each end of the bush 46 are equally sized with the result that it does not matter which way round the bush 46 is inserted into the handpiece body 12. It will be understood that the cut-out pair 82 which do not, in use, fit over the bearing retainer lugs 62 instead face the rear of the handpiece body 12. As will be described in greater detail below, these rearward facing lugs 62 may be used in order to facilitate the subsequent removal of the bearing retainer 58.

Fitting and retention of the front bearing 22 of a shearing handpiece 10 is achieved as follows. The front bearing 12 is inserted into the rear of the through bore 13 of the handpiece body 12 and then press fitted into the bearing section 30 such that the outer race of the front bearing 22 abuts the forward shoulder 28. The bearing retainer 58 is then inserted into the rear of the through bore 13. In order to be able to be inserted into the through bore 13, the bearing retainer 58 is deflected into the state shown in figure 12 such that distance between the outer edges 80 of the lugs 62 is slightly less than the diameter of the handpiece body through bore 13. The deflected bearing retainer 58 can then be advanced through the bush section 48 of the through bore 13 until the lugs 62 are received in the handpiece body cut-outs 78. As the width of the through bore 13 between the cut-outs 78 is greater than the diameter of the bush section 48 of the through bore 13, it will be understood that the lugs 62 move apart from one another as they are received in the cut-outs 78. The bearing retainer 58 thus adopts the deflected state shown in figure 11. As the retainer 58 is still in compression between the cut-outs 78, the lugs 62 are urged into the cut-outs 78 by the S resilient nature of the ring 60. When fitted to the handpiece body cut-outs 78 the ring of the bearing retainer 58 has a substantially circular shape as shown in figure 11. The retainer 58 is sized such that the diameter of the ring 60, when in the aforementioned substantially circular shape, is greater than the crank spindle 14 and the inner race of the front bearing 12.

Once the bearing retainer 58 has been fitted, the tubular bush 46 can be inserted into the hand-piece body 12. As described above, the lugs 62 of the bearing retainer 58 are received in the cut-outs 82 of the bush 46.

It will be appreciated that the tubular bush 46 does not act directly to seat the front bearing 22 against the forward shoulder 28. A gap is provided between the bush 46 and the front bearing 22 as the bush 46 rests against the further shoulder 50 provided within the handpiece body 12. Typically the bush 46 is spaced from the front bearing 22 by a gap of around 0.5mm.

It will further be appreciated that the tubular bush 46 does not act indirectly to seat the front bearing 22 against the forward shoulder 28. The front bearing 22 is retained against the forward shoulder 28 by the bearing retainer 58, which itself is directly retained by the cut-outs 78 in the handpiece body 12. The bush 46 will not usually touch the bearing retainer 58 because the bush 46 has cut-outs 82 which have clearance around the lugs 62 of the bearing retainer 46. The retainer 58 is sized such that the diameter of the ring 60, when in the aforementioned substantially circular shape, is less than the inner diameter of the bush 46 and hence cannot foul the bush 46 when it is inserted into the handpiece body 12. If the bush 46 is assembled with a slight rotational mis-alignment so that it touches the lugs 62 of the bearing retainer 58, the bush 46 does not act to seat the bearing retainer 58. When fitted to the handpiece body cut-outs 78, the bearing retainer 58 is in compression, and this force acts to keep the lugs 62 in the cut-outs 78, and to prevent the bearing retainer 58 from rotating.

The bearing retainer 58 may act to prevent the bush 46 from rotating relative to the handpiece body 12. Such rotation can occur if the back joint 40 seizes in the bush 46.

During the life of the shearing handpiece 10 it may become necessary to replace the front bearing 22. This may be achieved either with or without first removing the bearing retainer 58. In the instance where the bearing retainer 58 is not removed, the front bearing is pressed out of the handpiece body 12 in the reverse direction to that in which it was fitted. This rearward movement of the front bearing 22 causes one or both of the lugs 62 to break. The bearing retainer 58 is thus removed from the handpiece body 12 in pieces and a new bearing retainer 58 is required when the replacement front bearing 22 is fitted to the handpiece body 12.

Alternatively, the bearing retainer 58 may be removed whole if first it is rotated such that the lugs 62 are moved out of the cut outs 78 such that they contact the regions 84 of the wall of the handpiece body though bore 13 between the cut outs 78. The retainer abutment faces 74 are thus moved out of engagement with the abutment surfaces 76 of the handpiece body 12, and the bearing retainer 58 subsequently pressed out of the handpiece body 12 with the forward bearing 22. Rotation of the bearing retainer 58 may be achieved by manipulation of the tubular bush 46. An appropriate drive member may be inserted into the rearwardly facing cut-outs 82 of the tubular bush 46 and the bush 46 rotated. The forward facing cut-outs 82 of the bush 46 engage the lugs 62 of the bearing retainer 58 with the result that the bearing retainer 58 is rotated.

While the bearing retainer has been described with reference to a shearing handpiece 10, it will be appreciated that the bearing retainer of the present invention may be used in other devices where it is desired to locate a bearing.