Abstract:
There is disclosed a holding device for holding two rotary members relative to one another. The device has two holding members and a connecting member to which the holding members may be clamped by respective clamps. One of the holding members may be selectively positioned along the connecting member and clamped thereto at selected distances from the other holding member.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates to a holding device for holding one cam shaft of an engine relative to another cam shaft of an engine to prevent rotation of the cam shafts.  
         [0002]     The holding device of the invention has been devised for restraining cam shafts of a double overhead cam shaft internal combustion engine against rotation. Where an internal combustion engine has four cam shafts, two holding devices according to the invention may be employed to prevent the cam shafts of each pair of cam shafts from rotating relative to the other cam shaft of that pair.  
         [0003]     In internal combustion engines a toothed timing belt is trained around toothed pulleys or sprockets mounted to ends of the cam shafts. These belts require periodic replacement and to ensure that the timing relationship between the cam shafts and crank shaft of the engine is not lost, the cam shafts may need to be held against rotation relative to one another while the belt is removed and a new timing belt is fitted.  
         [0004]     Tools for effecting such immobilization of cam shafts are available. Often such tools are specifically designed for a particular type of engine and are not usable for other engines. This requires a selection of tools to be stocked in order to enable workshops to perform replacement of timing belts for a variety of different engines types.  
         [0005]     U.S. Pat. No. 6,332,256 discloses a holding device intended to be adjustable so that it may suit engines of a variety of types. The holding device of U.S. Pat. No. 6,332,256 is particularly complex in its construction and has a plurality of holding members arranged in pairs with at least three of the holding members being adjustable relative to one another and in one embodiment four clamps are present in order to allow the holding members to be locked relative to one another in a desired orientation.  
         [0006]     The arrangement of U.S. Pat. No. 6,332,256, whilst being adjustable, is of a particularly complex construction and relatively difficult to operate.  
       SUMMARY OF THE INVENTION  
       [0007]     It is an objection of the invention to provide a holding device which at least minimises the difficulties mentioned above.  
         [0008]     According to one aspect, the invention provides a holding device for holding two rotary elements against rotation relative to one another and having a connecting member, a first unitary holding member with spaced projections for engagement with one of the rotary elements at spaced locations on the one rotary element, a first clamp for clamping the first holding member relative to the connecting member, a second unitary holding member with spaced projections for engagement with the other of the rotary elements at spaced locations on the other rotary element, and a second clamp for clamping the second holding member relative to the connecting member, the holding members being clampable relative to the connecting member at selected distances from one another.  
         [0009]     Preferably, the second holding member is moveable along the connecting member and clampable by the second clamp relative to the connecting member at selected locations along the connecting member.  
         [0010]     The connecting member may consist of an elongated rail relative to which the holding members are clamped by the respective clamps. The elongated connecting rail may comprise an elongated slotted rail with the second clamp being receivable by the slot in the slotted rail to allow the second holding member to be clamped relative to the rail at selected positions along the length of the slot.  
         [0011]     The connecting member may have one continuous slot formed along its length and each of the holding members may be clamped to the connecting member by a clamp which extends through the slot. In an alternative arrangement, the connecting member has an aperture extending through it for receiving one of the clamps and relative to which the holding member may be clamped to the connecting member. A slot may be present relative to which the other clamp may clamp the other holding member relative to the connecting member.  
         [0012]     As previously mentioned, the holding device for the invention includes two clamps for clamping the holding members relative to the connecting member. Each clamp may consist of a clamping fastener adapted to extend through the connecting member. Preferably, each clamping fastener consists of a clamping screw having a head at one end and a threaded shank extending from the head adapted to engage with the holding member whereby rotation of the head may clamp the holding member relative to the connecting member.  
         [0013]     Each holding member may comprise a holding shoe having spaced projections for engagement with a respective rotary element. Preferably, the holding shoe has a body and two spaced flanges from which the projections may extend. Each of the projections is adapted to be received within a space between adjacent teeth or cogs on a rotary element such as a timing gear located on the end of an engine cam shaft.  
         [0014]     In a particular preferred form, each projection has a shoulder or step part way along its height such that a free end of its projection is narrower in transverse cross-section than a base of each projection. By having projections of this particular shape, the device of the invention is more readily suited to use with a variety of different rotary elements. It should be appreciated however that it is not essential to the invention that the projections have this stepped profile.  
         [0015]     It is preferred that a washer be positioned between each of the holding members and the connecting member such that the washer is clamped between the connecting member and the holding member when the holding member is clamped to the connecting member. It is preferable that the holding member be clamped to the connecting member to prevent undesired relative rotation of the holding member with respect to the connecting member. To this end, one or both of the facing surfaces of the holding member and the connecting member may be provided with a friction enhancing surface. In one particular embodiment both facing surfaces are provided with friction enhancing raised dimples. 
     
    
     BRIEF DESCRIPTION OF THE INVENTION  
       [0016]     The invention will now be described by way of example with reference to the accompany drawings in which:  
         [0017]      FIG. 1  is an exploded perspective view of a holding device according to a preferred embodiment of the invention;  
         [0018]      FIG. 2  is an assembled view of the holding device of  FIG. 1  with the holding device shown in one configuration;  
         [0019]      FIG. 3  is an assembled view of the holding device of  FIG. 1  with the holding device shown in a configuration different from the configuration of  FIG. 2 ;  
         [0020]      FIG. 4  is a view of the holding device shown in use;  
         [0021]      FIG. 5  is a detailed view of a portion of the holding device of the invention;  
         [0022]      FIG. 6  is an exploded elevational view of a portion of the holding device of the invention;  
         [0023]      FIG. 7  is a plan view of a holding member;  
         [0024]      FIG. 8  is a detailed fragmentary view of a holding member;  
         [0025]      FIG. 9  is a plan view of a connecting member; and  
         [0026]      FIG. 10  is a fragmentary sectional view through a friction enhancing raised dimple. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0027]      FIG. 1  of the drawing shows an exploded perspective view of a holding device  20  according to a preferred embodiment of the invention. The holding device has a first holding member  21  and a second holding member  22 . The device  20  includes an elongate connecting member  23 . The connecting member has a slot  24  extending along a substantial part of its length. An aperture  25  is located adjacent one end of the connecting member  23 . The holding member  21  may be clamped and held relative to the connecting member  23  by a clamp consisting of a clamping screw  26 , a washer  27  and a nut  28 . The clamping screw  26  has a head  29  with a scalloped appearance. This scalloped appearance is achieved by having concave portions  30  formed around the head. This allows the head  29  to be readily grasped and manipulated by the fingers of a user. The shank  31  of the clamping screw  26  an enlarged unthreaded portion  32  from which extends a reduced diameter threaded portion  33 . The washer  27  is made of a flexible material and has a central aperture  34  through which the threaded portion  33  of the shank  31  may extend.  
         [0028]     The holding member  21  has a central body portion  40  from which extend oppositely directed wings  41  and  42 . An inner face  43  of wing  41  is provided with a projection  44  which is directed towards the body portion  40 . The body portion  40  has an aperture  45  for receiving the threaded portion  33  of the shank  31 .  
         [0029]     Wing  42  has a projection  46  extending from face  47  thereof. The projection  46  is also generally directed towards the body portion  40  of the holding member  21 . The threaded portion  33  of the shank  31  is received within the nut  28  and the nut  28  is held captive by a recess (not visible in this figure) in the side of the holding member  21  not visible in this view. A plurality of raised friction enhancing dimples  48  extend around the aperture  45 .  
         [0030]     The holding member  21  has a plurality of raised projections  49  extending outwardly from the wing  42  and raised projections  50  extending outwardly from the wing  41 . These projections allow the holding member to be more readily grasped by the user and assist in strengthening the wings  41  and  42 .  
         [0031]     The holding member  22  is similar in construction and configuration to holding member  21 . The holding member  22  may be clamped relative to the connecting member  23  by a clamp consisting of a clamping screw  56 , a washer  57  and a nut  58  identical in construction to the clamping screw  26 , washer  27  and the nut  28  which form the clamp which functions to clamp the holding member  21  to the connecting member  23 .  
         [0032]      FIG. 2  of the drawings shows an assembled view of the holding device in a first configuration where the holding member  22  is held clamped to the connecting member  23  at one end of the slot  24  by a clamp including clamping screw  56  as one of the components. The holding member  21  is shown clamped to the connecting member  23  by a clamp which includes clamping screw  26  which extends through the aperture  25  (see  FIG. 1 ) extending through the connecting member  23  and at a location near an end of the connecting member  23  spaced from the location of holding member  22  and the slot  24  in the connecting member  23 .  
         [0033]      FIG. 3  of the drawings shows the holding device  20  of the invention in a configuration different from that of  FIG. 2 . In this view, the holding members  21  and  22  are clamped to the connecting member in a position closer to one another than what is shown in  FIG. 2 . Thus, the holding member  22  is adjustable in position along the connecting member relative to the position assumed by holding member  21 . In addition to the relative positions of the holding members being adjustable so that they are spaced to a desired degree from one another, it is also possible to clamp the holding members  21  and  22  relative to the connecting member  23  at any desired radial position relative to the connecting member  23 . If desired aperture  25  may be omitted and both holding members  21  and  22  may be clamped to connection member  23  by screws  26  and  56  which may both extend through the slot  24 . If desired the slot may extend substantially along the full length of member  23 .  
         [0034]      FIG. 4  of the drawings shows a view of the holding device  20  in a position it would assume in use when secured to sprockets  60  and  61 . The sprockets  60  and  61  are intended to be representative of timing sprockets mounted to the ends of cam shafts of an engine. A timing belt  63  is trained to extend over the sprockets  60  and  61 . The belt  63  would normally have a tensioning device (not shown) associated with it and would extend or be trained over a timing gear (not shown) associated with the engine of which the two cam shafts would form a part. The timing belt  63  has a plurality of teeth  64  adapted to engage within recesses  65  between adjacent teeth  66  and  67  on the sprockets  60  and  61 . The holding members  21  and  22  are clamped to the connecting member  23  by the respective clamps of which the clamping screws  26  and  56  form a part. The projections  44  and  46  extending from the holding members  21  and  22  locate relative to recesses between adjacent teeth on the sprockets  60  and  61  and when the holding members  21  and  22  are clamped in the way shown in  FIG. 4  the holding device functions to prevent relative rotation of the sprockets  60  and  61 .  
         [0035]     With the holding device  20  fitted in the manner shown in  FIG. 4 , the tensioning device mentioned above may be relaxed and this allows the timing belt  63  to be removed from engagement with the sprockets  60  and  61  and replaced. When the timing belt is replaced with a new timing belt the tensioning device may then be used to once again tension that replacement belt and once this is done the holding device of the invention may be removed.  
         [0036]      FIG. 5  of the drawings shows a fragmentary perspective view of part of the holding device  20  of the invention. In this view, the reverse side of the holding member is visible. The nut  58  is received within a recess formed on the reverse side of the holding member  22 .  
         [0037]     The holding member  21  is configured in a manner identical to the holding member  22  shown in  FIG. 5 .  
         [0038]     As shown in  FIG. 5 , the underside of the connecting member  23  is provided with a plurality of raised friction enhancing dimples  70 . These dimples extend around the slot  24  and also around the underside of the member  23  adjacent aperture  25 . These dimples, together with the dimples  48  on the connecting members  21  and  22  assist in preventing movement of the holding members  21  and  22  relative to the connecting member  23  once the holding members  21  and  22  are clamped in position relative to the connecting member  23 .  
         [0039]      FIG. 6  of the drawings shows an exploded part sectional view of a portion of the device  20  of the invention. The nut  28  is shown received in a recess provided in the body portion  40  of the holding member  21 . When the washer  27  is held captive between the connecting member  23  and the holding member  21 , the dimples  70  and  48  may project slightly into the washer  27 . This action together with the clamping action by screw  26  assist in securely holding the holding member  21  relative to the connecting member  23  and prevent it from moving relative to the connecting member.  
         [0040]      FIG. 7  of the drawings shows a plan view of one of the holding members  21 ,  22 . As shown in this figure and in the fragmentary view of  FIG. 8 , the projection  44  has a stepped profile with a reduced width outer end  80  and a wider inner portion  81 . Projection  46  is similarly configured. By having the projections shaped in this way they may more readily locate relative to recesses  65  between adjacent teeth on sprockets of a variety of different sizes.  
         [0041]     As shown in  FIG. 9 , the raised friction enhancing dimples  70  extend around the slot  24  in the connecting member  23  and also extend around the aperture  25 . In this embodiment of the device, the dimples  70  may have a shape like that shown in the enlarged fragmentary sectional view of  FIG. 10 . The dimples  48  which extend around the aperture  45  in the holding member shown in  FIG. 47  may have a configuration the same as that for dimples  70 .