Abstract:
A device for holding a rotary element stationary relative to a fixed body, the device comprising at least one element, adapted to engage with the rotary element to hold the device in a fixed position relative to the rotary element; and an engaging member, adapted to engage with the body to hold the device relative to the body.

Description:
BACKGROUND TO THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The invention relates to a device for holding a rotary element stationary relative to a fixed body.  
           [0003]    The invention has been devised, particularly but not exclusively, for the purpose of holding a camshaft or a fuel injection pump of an internal combustion engine stationary relative to an engine casing. Commonly, a camshaft or fuel injection pump is driven in timed relation to the engine crankshaft by a toothed drive belt (timing belt) or chain entrained around toothed pulleys or sprockets (hereafter referred to as sprockets) on the crankshaft and the drive shaft of the camshaft or fuel injection pump. In order to prevent failure in service and possible engine damage, service schedules usually specify that the timing belt be replaced at predetermined time and/or mileage intervals. It is essential, when removing the timing belt for any reason, to ensure that the timing relationship between the camshaft or fuel injection pump and the crankshaft is not lost. Therefore it is desirable to hold the camshaft and/or fuel injection pump against rotation relative to the engine casing whilst the old timing belt is removed and a new timing belt fitted.  
           [0004]    2. Description of the Prior Art  
           [0005]    Service tools for holding camshafts and/or fuel injection pumps against rotation are known, but as supplied by motor manufacturers they are usually specifically designed for one engine or family of engines and are not usable for other engines. If a service establishment wishes to perform such work on many different engines, but does not wish to keep a large number of special tools, there is a requirement for a more versatile holding device, which is capable of being used on a wide range of engines.  
           [0006]    In our UK Patent No.2340539 a holding device is disclosed for the purpose of holding stationary, relative to one another, the camshafts of a double overhead camshaft internal combustion engine, or a camshaft and a fuel injection pump driving shaft of an engine, e.g. in a motor vehicle. In our U.S. Pat. No. 6,332,256 a holding device is shown for the same purpose as that of the holding device in our UK Patent No.2340539, however the holding device in our U.S. Pat. No. 6,332,256 is multi-adjustable. Neither of these devices address the problem of holding a single rotary element stationary relative to a fixed body.  
         SUMMARY OF THE INVENTION  
         [0007]    It is therefore the object of the present invention to provide a device which satisfies the above requirement.  
           [0008]    According to the present invention there is provided a device for holding a rotary element stationary relative to a fixed body, the device comprising:  
           [0009]    holding means, adapted to engage with the rotary element to hold the device in a fixed position relative to the rotary element; and  
           [0010]    engaging means, adapted to engage with a surface of the body to hold the device relative to the body.  
           [0011]    The holding means may comprise clamping means operable to clamp the rotary element.  
           [0012]    The clamping means may comprise two clamping elements connected to and displaceable relative to one another to clamp the rotary element therebetween.  
           [0013]    The clamping elements may be adapted to engage opposing radially extending faces of the rotary element, i.e. by being relatively displaced in a direction parallel to the axis of rotation of the rotary element.  
           [0014]    Alternatively, or possibly in addition, the clamping elements may be adapted to engage opposing internal and external surfaces of a peripheral region or regions of the rotary element.  
           [0015]    At least one of the clamping elements may comprise an engaging surface adapted to engage the periphery of the rotary element, thereby holding the device from circumferential movement relative to the rotary element.  
           [0016]    The engaging surface may frictionally engage the periphery of the rotary element.  
           [0017]    The engaging surface may comprise a formation adapted to engage with a formation on the rotary element, e.g. between adjacent teeth on the circumference of a toothed rotary element.  
           [0018]    Engagement of the device with rotary elements of different thicknesses may be facilitated by providing adjustable abutment means operable between the clamping elements, to ensure the clamping elements, in use, engage squarely with the rotary elements and that over-tightening of the clamping elements is inhibited.  
           [0019]    The engaging means may be arranged frictionally to engage the body, thereby holding the device relative to the body.  
           [0020]    The engaging means may be adapted to urge the device away from the body.  
           [0021]    A screw threaded element may be provided for urging the clamping elements together with sufficient force to hold the rotary element securely therebetween. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]    These and other features of the invention will now be described by way of example with reference to the accompanying drawings, in which:  
         [0023]    [0023]FIG. 1 is an exploded perspective view of a first embodiment of a holding device in accordance with the invention;  
         [0024]    [0024]FIG. 2 is a perspective view of the holding device of FIG. 1, in use holding a rotary element;  
         [0025]    [0025]FIG. 3 is a cross-sectional view through the plane X-X of FIG. 2;  
         [0026]    [0026]FIG. 4 is an exploded perspective view of a second embodiment of holding device in accordance with the invention;  
         [0027]    [0027]FIG. 5 is an exploded view of a third embodiment of holding device in accordance with the invention;  
         [0028]    [0028]FIG. 6 is an exploded view of a fourth embodiment of holding device in accordance with the invention; and  
         [0029]    [0029]FIG. 7 is a perspective view of a fifth embodiment of holding device in accordance with the invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0030]    Referring firstly to FIGS. 2 and 3, there is shown a first embodiment of holding device in accordance with the invention in use with a sprocket  50 . The sprocket  50  is connected to a body in the form of an engine block  51  (not shown in FIG. 2) by a shaft  52  (also not shown in FIG. 2). The shaft  52  allows for rotation of the sprocket  50  about an axis  54 . References to the radial and axial directions hereinafter, unless otherwise specified, are in relation to the axis  54 .  
         [0031]    [0031]FIG. 1 shows an exploded perspective view of the first embodiment of holding device. It comprises a holding means, shown generally at  10 . The holding means  10  comprises two clamping elements  12 ,  14 , which are displaceable from one another along an axis  15 , the axis  15  being substantially parallel, in use, to the axis  54 . The clamping element  12  is part annular, having an external arcuate wall  16  and an internal arcuate wall  18 . The internal arcuate wall  18  has, at its lower end, a radially inwardly extending lip  19 , the lip  19  being substantially perpendicular to the arcuate wall  18  and shaped so as to engage with a radial face of the sprocket (not shown). The arcuate wall  18  also has a formation, in the form of an inwardly facing tooth  20 , shaped so as to engage with a recess between two adjacent teeth on a toothed section of the sprocket. The clamping element  12  is also provided with an adjustable abutment means in the form of a pair of adjusting bolts  21 . The adjusting bolts  21  have substantially flat heads with knurled circumferential walls to allow for manual adjustment of the distance between the lip  19  of the clamping element  12  and the clamping element  14 , so that the device can be used on varying thicknesses of sprockets. The adjusting bolts  21  should be adjusted so that they are level with each other, thereby providing an even surface.  
         [0032]    The clamping element  14  is also part annular and has a downwardly extending lip  22  with an inwardly facing arcuate wall  23  and an external arcuate wall  24 . The lip  22  is shaped so as to substantially engage with an internal annular wall of the sprocket. Extending generally perpendicularly downwardly of the clamping element  14 , towards the clamping element  12 , is a locating pin  26 . The locating pin  26  is a cylindrical rod (although other shapes may be used), and assists in maintaining alignment of the clamping elements  12 ,  14  relative to each other. The pin  26  engages in a bore  28  on the clamping element  12 , when the clamping elements  12 ,  14  are aligned on top of each other. The clamping element  12  has an axially extending externally threaded bolt  32 , which extends towards the clamping element  14 . The clamping element  14  has an aperture  30  through which bolt  32  extends. The pin  26  and the bolt  32  together ensure that the clamping elements  12 ,  14  align correctly with respect to each other, thus providing good engagement with the sprocket. A knob  36 , with a threaded portion  38  is engaged with the screw thread on the bolt  32  and can be tightened to urge the clamping element  12 ,  14  towards one another and grip the sprocket. The knob  36  is shaped so as to provide an easily grippable surface for turning by a user.  
         [0033]    The bolt  32  has an internally threaded bore  34 , which extends its full length, to the lower surface of the clamping element  12 . An engaging means is provided in the form of a screw or threaded pin  40 , engaging the screw thread in the bore  34  of the bolt  32 , and having a conical tip  42 . The pin  40  has a knurled knob  44  to facilitate insertion and threading of the pin  40  into the internally threaded bore  34 . The length of the pin  40  is such that it protrude from the lower surface of the clamping element  12 .  
         [0034]    Referring now to FIG. 4 there is shown a second embodiment of a holding device in accordance with the present invention. Similar parts of the holding device shown in FIG. 2 have the same reference numerals as those of the holding device shown in FIG. 1, with the addition of 100.  
         [0035]    The holding device shown in FIG. 4 is a compact version of the holding device shown in FIG. 2. Firstly, the locating pin  26  and adjusting bolts  21  have been combined to provide an adjusting bolt  121  with a locating pin  126  extending upwardly from the flat head of the adjusting bolt  121 . The locating pin  126  assists in maintaining alignment of the clamping elements  112 ,  114 . The locating pin  126  engages in the bore  128  on the clamping element  114 , when the clamping elements  112 ,  114  are aligned on top of each other. Secondly, the sides of both clamping elements  112 ,  114 , parallel to the axis  115 , taper towards one another as they extend away from the internal arcuate wall  118 . Finally, the knurled knob  44  has been replaced with a knob  144 , similar to the knobs  36 ,  136 , to facilitate easier tightening of the threaded pin  140 .  
         [0036]    [0036]FIGS. 5, 6 and  7  show further embodiments of holding devices in accordance with the present invention. Similar parts of the holding devices shown in FIGS. 5, 6 and  7  have the same reference numerals as those of the holding device shown in FIG. 1, with the addition of 200, 300 and 400 respectively.  
         [0037]    [0037]FIG. 5 shows a holding device similar to that of FIG. 1, i.e. circumferential movement of the holding device relative to the sprocket  50  is inhibited by clamping elements  212 ,  214 , which clamp the sprocket  50  therebetween. However, the embodiment shown in FIG. 5 differs from the holding device of FIG. 1 in that the bolt  232 , knob  236  and pin  240  pass between adjacent spokes of the sprocket  50 , within the envelope of the sprocket  50 .  
         [0038]    [0038]FIG. 6 is a similar embodiment to FIG. 5, in that the pin  340 , knob  336  and bolt  332  pass between adjacent spokes of the sprocket  50 . However, in this embodiment, circumferential movement of the holding device relative to the sprocket  50  is inhibited by clamping of the sprocket  50  with the clamping elements  370 ,  372 . The clamping elements  370 ,  372  clamp a spoke  374  of the sprocket  50 .  
         [0039]    Finally, FIG. 7 shows a holding device which again is like that of FIG. 5 in that the bolt  432  passes between adjacent spokes of the sprocket  50 . However, in this embodiment the sprocket  50  is clamped relative to the holding device by a clamp having a part  480  and a relatively displaceable part  414 . A screw-threaded pin  484  extends through the part  480  and has threaded engagement therewith, and is turnable by a knob  484 . The pin engages the part  484  which can be caused to move generally radially of the sprocket towards the periphery thereof by appropriate turning of the pin  484 , to clamp the sprocket.  
         [0040]    Referring again to FIGS. 2 and 3 there is shown the holding device in use with a rotary element in the form of a toothed sprocket  50  of a camshaft or fuel injection pump. When servicing an engine of a motor vehicle, the timing belt may need to be removed, e.g. for replacement so as prevent failure in service and hence possible engine damage, or for some other reason. It is therefore necessary to hold the sprocket  50  stationary relative to the engine block  51  whilst the timing belt is removed.  
         [0041]    Before the device  10  can be engaged with a sprocket  50 , either:  
         [0042]    the knob  36  must be unscrewed sufficiently for the clamping elements  12 ,  14  to be moved far enough away from one another for the periphery of the sprocket  50  to be inserted therebetween and engaged therewith as follows; or  
         [0043]    the pin  40  and the knob  36  can be removed completely from the clamping element  14 , after which the clamping elements  12 ,  14  are then separated from each other and engaged with the sprocket  50  as follows.  
         [0044]    The clamping element  12  is engaged with the sprocket  50  so that the upper surface of the lip  19  engages with a lower radial face  56  of the sprocket  50  and the internal arcuate wall  18  engages with a circumferential annular wall  58  of the sprocket  50 . The inwardly facing tooth  20  on the internal arcuate wall  18  engages between two adjacent teeth on the sprocket  50 , thereby preventing circumferential movement of the clamping element  12  relative to the sprocket  50 . The adjusting bolts  21  are adjusted so that the vertical distance between the lip  19  and the top of both of the adjusting bolts  21  is very slightly less than the thickness of the sprocket  50 . This ensures that the clamping elements  12 ,  14  can engage squarely and that the holding means cannot be over tightened.  
         [0045]    The clamping element  14  is aligned with the clamping element  12  (if it has been completely removed from the device), with the downwardly extending lip  22  pointing towards the sprocket  50  and is then engaged with the adjusting bolts  21 , such that the pin  26  enters into the bore  28  and the bolt  32  extends through the aperture  30 . The lip  22  engages with an internal annular wall  60  of the sprocket  50 , such that the holding means  10  cannot move in an axial or radial direction. The knob  36  is then threaded onto the bolt  32  to lock the clamping elements  12 ,  14  together. Thus the clamping elements  12 ,  14  hold the holding device stationary relative to the sprocket  50 .  
         [0046]    In order to hold the holding means  10  stationary relative to the engine block  51 , the pin  40  is threaded into the bore  34  being turned by its knob  44  until it protrudes from the lower surface of the clamping element  12  and engages with the surface of the engine block  51 . Upon such engagement, further turning of knob  44  forces the end of the pin into tighter frictional engagement with the engine block, urging the sprocket  50  away from the engine block. The conical tip  42  of the pin may slightly indent the surface of the engine block, to assist the frictional engagement in holding the device stationary relative to the block.  
         [0047]    Once the old timing belt has been removed and a new one installed, the holding device can be removed by reversing the sequence of installation steps above.  
         [0048]    In the device described above the clamping elements  12 ,  14 ,  112 ,  114  may be moulded or machined from a rigid plastics material, the adjusting bolts  21 ,  121 , the bolts  32 ,  132  and the locking nuts  38 ,  138  may be of a steel, the screw threaded elements  36 ,  136  and the knob  144  are moulded from a plastics material and the knob  44  is aluminium. However, other materials and methods of manufacturing may be utilised so long as components with desirable properties are produced, capable of being utilised in the present invention.  
         [0049]    It is also possible to exclude the inwardly facing teeth  20 ,  120  from the devices shown in FIGS. 1 and 2. Circumferential movement of the holding devices  10 ,  110  relative to the sprocket can be inhibited by providing a frictional surface coating on the internal arcuate walls  18 ,  118 , the upper surface of the lips  19 ,  119  or the upper side of the clamping elements  12 ,  114 .  
         [0050]    Screw threaded pins  40  of different lengths may be provided to suit different distances by which they have to extend to engage with the blocks of different engines.  
         [0051]    In the present specification “comprises” means “includes or consists of” and “comprising” means “including or consisting of”.  
         [0052]    The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.