Abstract:
A thin component such as the actuator arm ( 10 ) of a hard disk drive, is mounted on a pivot or pin ( 31 ), such as the pivot assembly of the hard disk drive, using a ring ( 32 ), e.g. a tolerance ring, having one or more projections ( 35 ), wherein the engagement of the component ( 30 ) and the ring ( 32 ) is such as to apply a force to the component ( 30 ) in a direction which is inclined to both the radial and axial directions of the pivot or pin ( 31 ). The pivot or pin ( 31 ) has a flange onto which the component ( 30 ) is pressed by the axial component of the force generated by the ring on the component. The edge of the ring ( 32 ) remote from the component ( 30 ) is engaged with a stop element, e.g. another flange ( 34 ) of the pivot or pin ( 31 ).

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates the fixings of components to a pivot or pin, using a tolerance ring.  
       BACKGROUND OF THE INVENTION  
       [0002]     It is well known to use a tolerance ring to mount a component on a pivot or pin. The component has a bore in it, into which the pivot or pin is received, and the tolerance ring is mounted in the bore, between the pivot or pin and the wall of the bore to act as a link. The tolerance ring provides sufficient rigidity in the connection, but permits the component to move relative to the pivot or pin when excessive loads are applied. Tolerance rings are used, for example, to mount the actuator arm of a hard disk drive onto the pivot assembly for that arm.  
         [0003]     However, recent developments in such hard disk drive arrangements have tended to use actuator arms of reduced thickness, thereby reducing the amount of contact between the tolerance ring and the arm. As the thickness of the arm is reduced, so is the axial length of the bore in the arm, and hence, the engagement of the arm by the tolerance ring also reduces, possibly to a point at which the gripping of the arm by the tolerance ring becomes ineffective. In practice, if the arm has a thickness of less than 3 mm, the normal arrangements for mounting an actuator arm onto its pivot assembly via a tolerance ring made be unsuccessful.  
         [0004]      FIG. 1  of the accompanying drawings illustrates the mounting of a conventional actuator arm for a hard disk drive. The arm  10  has a bore  11  therein into which is received a pivot assembly  12 . The pivot assembly  12  is mounted on a suitable mounting (not shown) to enable to actuator arm to move relative to the hard disk(s) of the drive. In the arrangement of the  FIG. 1 , the arm  10  is intended for use with  3  disks, and the arm  10  divides into three heads  13  at its end, which will move proximate respective disks (not shown) of the drive.  
         [0005]     As illustrated in  FIG. 1 , there is a tolerance ring  14  which is mounted on the pivot assembly  12 , which will engage the walls of the bore  11 . The tolerance ring  14  has ridges  15  thereon which will grip the wall of the bore  11 . Because there are multiple heads  3 , the bore  11  has sufficient axial length for the gripping by the tolerance ring  14  to be sufficient to hold the arm  10  in place on the pivot assembly, at least for the normal range of forces that are applied to the arm.  
         [0006]     However, as the capacity of hard disks is reduced, there is less need for multiple heads and disks in a hard disk drive, and thus the thickness of the arm  10  may be reduced. The axial length of the bore  11  may then be insufficient provides suitable gripping by the tolerance ring  14 .  
         [0007]     It has been suggested that other arrangements may be used to fix the arm of a hard disk drive onto the pivot assembly. Thus, as illustrated in  FIG. 2  the arm  10  may be held onto the pivot assembly  12  by a clip  20 . Alternatively, adhesive  21  may be applied between the arm  10  and the pivot assembly  12 , as in  FIG. 3 . However, such arrangements are not satisfactory, because the arrangement of  FIG. 2  may not provide sufficient radial stiffness, and the use of adhesive as in  FIG. 3  makes manufacturing more difficult.  
       SUMMARY OF THE INVENTION  
       [0008]     Therefore, at its most general, the present invention proposes that a thin component, such as the actuator arm of a hard disk drive, is mounted on a pivot or pin, such as the pivot assembly of the hard disk drive, using a tolerance ring, the engagement of the component and the tolerance ring being such as to apply a force to the component which is inclined to both the radial and axial directions. Moreover, the pivot or pin. has a flange onto which the component is pressed by the axial component of the force generated by the tolerance ring on the component.  
         [0009]     Thus, the present invention may provide a method of mounting a component on a pivot or pin, the component having a bore therein and the pivot or pin having first and second flanges thereon, the method comprising:  
         [0010]     mounting the component on the pivot or pin such that a part of the pivot or pin and the first flange passes through the bore, the mounting being such as to cause the component to abut the second flange; and  
         [0011]     mounting a ring between the component and the first flange, the ring being a split ring with at least one projection projecting radially outward therefrom, the mounting of the ring being such that an edge of the ring remote from the component abuts the first flange and the at least one projection exerts a force on the component, which force is inclined to both the radial and axial directions of the pivot or pin.  
         [0012]     Although the present invention has been devised for the mounting of an actuator arm on the pivot assembly of a hard disk drive, the present invention is not limited to such arrangements and applies to any arrangement in which a thin component is mounted on a pivot or pin.  
         [0013]     Preferably, the thin component is mounted onto the pivotal pin, to abut the flange, and then the ring is slid over the pivot or pin, on the side of the component remote from the flange, to engage the component and to force it onto the flange. Preferably, the pivot or pin has a further flange, which engages the edge of the ring remote from the component, when the ring is in place.  
         [0014]     As the ring is to engage the component via the projection or projections thereon, those projections may be such as to partially deform when they engage the component. Alternatively, or in addition, the bore in the component, into which the ring is received, may be tapered.  
         [0015]     The ring may be a tolerance ring such as those that are used in the known arrangements that were described with reference to  FIG. 1 . Such a ring has a plurality of projections around its circumference, which projections are regularly spaced to define a wave-like circumferential profile. The projections of the tolerance ring then engage the component in a way which generates both axial and radial forces, as previously mentioned. Modified tolerance rings may also be used, e.g. with a circumferential rib which, in use, will adjacent to the first flange and provide some axial resilience to the tolerance ring. Moreover, whilst normal tolerance rings are axially straight, at the parts other than projections, it is possible for the tolerance ring to be bowed in the axial direction, again to provide some resilience.  
         [0016]     However, the present invention is not restricted to the use of tolerance rings. For example, a ring may be used with a single circumferential projection forming a rib around the ring, with that rib then engaging the component. The fact that the rib is bowed in the axial direction gives compressibility to the ring in the axial direction, thus providing the resilience needed. Such a ring may further be varied e.g. by provision of a plurality of projections on either side of the rib, in a manner similar to a tolerance ring.  
         [0017]     Other ring shapes are possible, provided they engage the first flange and the component, and exert a force on the component which has both an axial and a radial component. 
     
    
     BRIEF DESCRIPTIONS OF THE DRAWINGS  
       [0018]     Embodiments of the present invention will now be described in detail, by way of example, with reference to the accompanying drawings, in which:  
         [0019]      FIG. 1  shows the mounting of a conventional actuator arm on a pivot assembly of a hard disk drive, and has already been described;  
         [0020]      FIGS. 2 and 3  show alternative ways of mounting the actuator arm of a hard disk drive on its pivot assembly, and also have already been discussed;  
         [0021]      FIG. 4  shows a first embodiment of the present invention;  
         [0022]      FIG. 5  shows a second embodiment of the present invention;  
         [0023]      FIGS. 6   a  to  6   e  show stages in assembling the second embodiment; and  
         [0024]      FIGS. 7   a  to  7   e  show alternative forms of ring which may be used in the embodiments of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0025]     Referring first to  FIG. 4 , a thin component  30 , such as an actuator arm of a hard disk drive is mounted on a pivot or pin  31 , such as the pivot assembly of a hard disk drive, using a split ring being a tolerance ring  32 . The pivot or pin  31  has a first flange  33  onto which the component  30  is compressed by the tolerance ring  32 , and also has a further flange  34  at its end remote from the flange  33 , against which abuts the axial end of the tolerance ring  32  remote from the component  30 , thereby preventing the tolerance ring  32  moving upwardly in  FIG. 4 .  
         [0026]     As illustrated in  FIG. 4 , the projections  35  of the tolerance ring  32  engage the corner  36  of the bore  37  in the component, and exert on the component  30  a force which has both axial and radial components. The axial component of that force presses the component  30  against the flange  33 , and the radial component provides engagement between the tolerance ring  32  and the component  30 , thereby holding the component  30  in place on the pivot or pin  31 .  
         [0027]     In  FIG. 4 , the tolerance ring  32  is a high wave height tolerance ring, so that the projections  35  deform at the corner  36 .  
         [0028]      FIG. 5  illustrates a second embodiment, which is similar to the embodiment of  FIG. 4  and the same reference numerals are used to indicate corresponding parts. However, in the embodiment of  FIG. 5  the bore  38  in the component  30  is tapered so that the mouth of the bore  38  is narrower at the end at which abuts the flange  33  than it is at the end which abuts the projections  35  of the tolerance ring  32 . Again, however, the tolerance ring  32  applies a force to the component  30  which force has both radial and axial components.  
         [0029]      FIG. 6   a  to  6   e  illustrate stages in the assembly of the embodiment of  FIG. 5 . First, as illustrated in  FIG. 6   a , the component  30  is fitted onto the pivot or pin  31  with the upper part of the pivot or pin  31  passing through the bore  38  in the component. The component  30  is positioned so that it abuts the flange  33 . Next, as shown in  FIG. 6   b , the tolerance ring  32  is slid axially over the upper part of the pivot or pin  31 , to a position in which the projections  35  abut the component  30 . As can be seen in  FIG. 6   b , the tolerance ring  32  must widen to pass the flange  34 . That is achieved due to the conventional split (not shown) in the tolerance ring  32 . Next, an assembly tool  40  is slid over the tolerance ring  32  to compress the tolerance ring axially downwards in  FIG. 6   b . This forces the end of the tolerance ring  32  remote from the component  30  past the flange  34 , so that that end of the tolerance ring abuts the surface of the flange  34  facing the flange  33 . The axial compression of the tolerance ring can occur because the diameter of the bore  41  in the assembly tool  40  is sufficiently wide to pass the flange  34 , but is narrower than the overall diameter of the tolerance ring  32  including the projections  35 . Thus, the tool  40  will bear against those projections  35 , thereby deforming the tolerance ring axially, and permitting its end to pass the flange  34 .  
         [0030]     The result is shown in  FIG. 6   d , in which the end of the tolerance ring  32  remote from the component  30  abuts against the face of the flange  34  which replaces the flange  33 . In that position, a tolerance ring  32  cannot move axially upwards in  FIG. 6   d . Moreover, the axial movement of the tolerance ring  32  between the position shown in  FIG. 6   c  and that shown in  FIG. 6   d  causes the projections  35  to be forced against the component  30 , thereby exerting on that component the clamping force which has already been described, which has both radial and axial components. Finally, the tool is removed, and the structure corresponds to that of  FIG. 6   d , which also is the same as  FIG. 5 .  
         [0031]     The assembly of the embodiment of  FIG. 4  may be identical, although the movement of the tolerance ring between the position shown in  FIG. 6   c  and that shown in  FIG. 6   d  will then cause the deformation of the projections  35  on the corner  36  which has already been mentioned.  
         [0032]     In the embodiments discussed above, the split ring is a tolerance ring, and may be a conventional tolerance ring. However, the present invention is not limited to the use of conventional tolerance rings, and other forms of split ring which may be used in the present invention will now be described with reference to  FIGS. 7   a  to  7   e . It should be noted, however, that the present invention is not limited to these particular ring configurations.  
         [0033]     Thus,  FIG. 7   a  shows a modified tolerance ring  50  with a plurality of projections  51  around it. Those projections  51  are larger than is usual in a tolerance ring, so giving the ring greater strength under axial compression, which it will experience when in the position e.g. shown in  FIG. 4 . Nevertheless, the projections  51  effectively form a wave-like circumferential profile the axial mid-point of the ring  50 .  FIG. 7   a  shows that the ring  50  has a split  52  therein, as is conventional for a tolerance ring.  
         [0034]      FIG. 7   d  shows a modification of the ring of  7   a , and the same reference numerals are used to indicate corresponding parts. However, in the ring shown in  FIG. 7   b , there is a circumferential rib  53  adjacent one axial end of the ring  50 . When the ring  50  is used in the present invention, that rib  53  will be adjacent to the flange  34  shown in FIGS.  4  or  5 . The presence of that rib  53  provides some axial resilience to the ring  50 , in that the rib  53  may be deformed when the ring  50  is under axial load, but that deformation will create a counter-force tending to push the projections  51  of the ring  50  onto the component  30 .  
         [0035]     Normally, a tolerance ring is, except at its projections, straight in the axial direction. Thus, in e.g.  FIG. 7   a , the parts  54  of the ring between the projections  51  are parallel to the axis.  FIG. 7   c  then shows a modified tolerance ring  60  with projections  61  and a split  62  which is generally similar to the tolerance ring of  FIG. 7   a , except that the ring is bowed. Thus, the parts  64  between the projections  61  are not parallel to the axis of the ring  60 , but are curved so that their ends are closer to the axis of the ring  60  than their mid-point. The arrangement of  FIG. 7   c  may thus be considered a modified tolerance ring, although it is not usual for a tolerance ring to be bowed in this way.  
         [0036]     Whilst the split ring of  FIG. 7   a  is a tolerance ring, and the rings of  FIG. 7   b  and  7   c  may be considered modified tolerance rings, the split of  FIG. 7   d  is not a tolerance ring at all. Instead, the ring  70  has a single circumferential rib  71  which forms a projection around the ring  70 . Again, the ring has a split  72  therein, but in the arrangement of  FIG. 7   d  the rib  71  must provide both axial resilience to the ring  70  and also sufficient engagement force with component  30  when used in the arrangements of FIGS.  4  or  5 . The rib  71  thus engages the component  30  in a way which generates both an axial and radial force component.  
         [0037]     Finally,  FIG. 7   e  shows a split ring which combines some of the features of the ring of  FIG. 7   d  with a tolerance ring. It has a central rib  81  therein, and a split  82 . However, on either side of the rib there are projections  83  in a manner similar to a tolerance ring. However, as can be seen in  FIG. 7   e , those projections have an outer face which is inclined to the axis of the ring  80 , with the inclination of the projections  83  above and below the rib  81  being in opposite directions. With such an arrangement, the ribs  83  which are below the rib  81 , when the ring  80  is mounted on the pivotal pin  31 , engage the component  30  and exert both an axial and radial force component because of their inclination to the axis of the ring  80 .  
         [0038]     It can be seen that the rings of  FIG. 7   a ,  7   c ,  7   d  and  7   e  may be inverted and still used in the arrangements of  FIGS. 4 and 5 , but the ring of  FIG. 7   b  has a “direction” in that the rib  53  must be at the end of the ring  50  nearest the flange  34 .