Abstract:
A device for holding a rotary element stationaly relative to another rotary element adjacent thereto, comprising a first holding member engageable with one of said rotary elements; a second holding member engageable with one of said rotaly elements; a third holding member engageable with one of said rotary elements; a fourth holding member engageable with one of said rotary elements; and structure connecting said holding members together and providing for adjustment of at least three of said holding members relatively to one another, and for fixing said holding members in set positions relative to one another.

Description:
BACKGROUND TO THE INVENTION 
     1. Field of the Invention 
     This invention relates to a device for holding two rotary elements, disposed alongside one another, stationary relative to one another. 
     The invention has been devised for the purpose of holding stationary relative to one another the camshafts of a double overhead camshaft internal combustion engine, such camshafts being driven in timed relation to the engine crankshaft by a toothed drive belt (timing belt) entrained around toothed pulleys or sprockets (herein called sprockets) on the shafts. With the aim of preventing failure in service and possible consequential engine damage, service schedules usually specify belt replacement at predetermined time and/or mileage intervals, and to ensure that the timing relationship between the cam shafts and the crankshaft of the engine is not lost the camshafts may have to be held against rotation relative to one another while the old belt is removed and a new one fitted. Other rotary elements driven by the timing belt may also have to be held against rotation during the replacement operation, for example if an engine is a compression-ignition engine and there is a fuel injection pump whose timed driving is effected by the belt. 
     Service tools for effecting such holding of the camshafts and/or other rotary elements of engines are available, 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. One problem in the design of such a more versatile holding device is that drive sprockets might be very close together, with very little space between them in which any part of a holding device can be disposed. 
     SUMMARY OF THE INVENTION 
     It is broadly the object of the present invention to provide a holding device in which the above requirement and problem are addressed. 
     According to the present invention, we provide a device for holding a rotaiy element stationary against rotation relative to another rotary element adjacent thereto, comprising first, second, third and fourth holding members engagable each with one or other of the rotary elements; connecting means connecting said holding members to one another and providing for adjustment of at least three of said holding members relative to one another; and means for fixing said holding members in set positions relative to one another. 
     Preferably all the holding members are adjustable relative to one another. 
     In a device according to the invention, the ability of the holding members to be adjusted relative to one another means that the device is usable in a number of different situations, i.e. in different engines. 
     Preferably each holding member is adapted to engage with the periphery of a sprocket, constituting a said rotary element, with which a timing belt cooperates. To this end each holding member preferably comprises a formation which cooperates with one or more teeth of a sprocket, e.g. a protuberance which is able to extend radially inwardly relative to the sprocket into the space between adjacent teeth. 
     In one of the embodiments described hereafter, each holding member further comprises an arcuate or generally arcuate wall portion which is able to lie against the crests of a number of teeth, with a protuberance extending radially inwardly from the wall portion and able to fit between two adjacent such teeth. 
     Preferably the holding members are arranged with the first and second holding members adjustable relative to one another in respect of their position and/or orientation and the third and fourth holding members adjustable relative to one another in respect of their position and/or orientation, the connecting means providing for adjustment of said first and second holding members together, in position and orientation, relative to said third and fourth holding members together. 
     The connecting means preferably comprises an elongate connecting member relative to which said first and second holding members are together movable angularly whilst said third and fourth holding members are together movable angularly and lengthwise thereof. 
     The means for fixing the holding members in set positions relative to the connecting means preferably comprises clamping means. Each clamping means may comprise a screw member having threaded engagement with a holding member and passing through an opening in the elongate connecting member, with the connecting member being arranged to be clamped between a head of the screw member and the holding member when the screw is tightened. 
     Each such screw member may effect clamping of both the first and second or the third and fourth holding members as the case may be together to the connecting means, or may clamp only one holding member relative to the connecting member while the respective associated holding member is separately clamped to the aforesaid holding member, e.g. by a further screw member. 
     In use, the first and second holding members may be engaged one with one sprocket and the other with the other sprocket, at adjacent peripheral regions thereof outwardly of the narrowest part of the space therebetween, whilst the third and fourth holding members are likewise engaged with the two sprockets, but outwardly of the space therebetween in the opposite direction. In this case the connecting member may extend generally chordally or tangentially of the two sprockets or one of them. 
     In another embodiment of the holding device described hereafter, the first and second holding members may be engaged in use with spaced parts of the periphery of one of the sprockets while the third and fourth holding members are engaged with spaced parts of the periphery of the other sprocket. Viewed parallel to the axes of rotation of the sprockets, the connecting member then extends generally transversely across the gap between the peripheries of the sprockets. 
     In either event, the arrangement of the holding members means that there need be nothing in the narrowest part of the space between the sprockets so that the device can be used if the sprockets are very close together or if there is an engine part between them, e.g. a casting rib. The connecting means can be arranged to be spaced from the plane of the end faces of the sprockets. 
    
    
     BRIEF DESCRIPTION OF THE INVENTION 
     The invention will now be described by way of example with reference to the accompanying drawings, of which: 
     FIG. 1 is a perspective view of a first embodiment of holding device in accordance with the invention; 
     FIG. 2 shows, in an underneath view, the disposition of the device of FIG. 1 in use; 
     FIG. 3 is a perspective view of a second embodiment of holding device in accordance with the invention; 
     FIG. 4 shows the disposition of the device of FIG. 3 in use. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring firstly to FIG. 1 of the drawings, the holding device there illustrated comprises the principal components of four holding members  10 ,  11 ,  12 ,  13  and a connecting means  14 . The holding members  10  and  12  are identical to one another, whilst the holding members  11  and  13  are also identical to one another. 
     The holding member  10  comprises a body  15  which is of elongate configuration and from the body  15  at one end thereof there extends an engagement portion indicated generally at  16 . The engagement portion  16  comprises an arcuate wall formation  17  whose curvature is selected so as to be able to lie against the crests of several teeth of a typical camshaft-drive sprocket of an internal combustion engine. 
     Radially inwardly from the wall portion  17  there extends a protuberance  18 , of a size able to engage between two such teeth. 
     At the opposite end of the body  15  from the engagement portion  16  of the first holding member  10 , there is the second holding member  11 . The second holding member  11  also comprises an arcuate wall portion  19  and a protuberance  20  extending inwardly therefrom. The holding member  11  is adjustable relative to the holding member  10 , the body  15  having an arcuate recess beneath it in which a part of the holding member  11  engages so that the holding member  11  is movable in an arcuate path relative to the body  15 . A clamping screw whose head is visible at  21  has a threaded shank which passes through a slot  22  in the body  15  and engages with a screw-threaded bore in the part of the holding member  11  which engages with the body  5 . Thus the holding member  11  is able to be adjusted in respect of its position and orientation relative to the body  15 , and when set in the required relative position is able to be clamped in such position by turning the screw head  21  to tighten the screw. 
     The holding members  12  and  13  are of the same configuration as the holding members  10  and  11 , respectively, and are adjustable relative to one another in the same manner. The aforesaid arcuate recess beneath the body of the holding member  12  is indicated at  41 . 
     The connecting means  14  comprises an elongate connecting member  25  having an elongate slot  26  towards one end. At its other end it has an aperture. It is connected to the body  15  of the holding member  10  by a clamping screw whose head is indicated at  27  and whose threaded shank passes through the aperture at the end of the connecting member  25  and engages with a screw-threaded bore in the body pair  15 . The screw is able to be turned by a manually operable lever  28  which is able to be declutched from the head  27  of the screw by pulling the lever axially of the screw upwardly from the head. Such declutching action enables the screw to be tightened or loosened in increments of rotation if turning of the lever  28  through a complete revolution is not possible due to obstruction or lack of accessibility. 
     A further clamping means indicated generally at  29  and identical to that above described connects the body of the holding member  12  to the connecting member  25 . In this case the shank of the screw passes through the slot  26  in the connecting member, with the result that the third and fourth holding members  12 ,  13  are able together to be moved towards and away from, and adjusted in their orientation relative to, the holdinig members  10 ,  11 . 
     Use of the holding device as described in FIG. 1, to hold two sprockets  31 ,  32  stationary relative to one another, is, shown in FIG.  2 . Engagement of the holding members  10 ,  11  with one of the sprockets and the holding members  12 ,  13  with the other sprocket is illustrated, and it will be appreciated that the above-described possibilities of relative adjustment between all the holding members enables sprockets of different sizes, different tooth spacings, and different spacings between their rotational axes, to be held. In particular, it will be noted that since each of the holding members only has a short length of arcuate wall portion which rests against the crest of only a small number of the sprocket&#39;s teeth, nothing has to be disposed in the narrowest gap part between closely-spaced sprockets so the device is usable with such sprockets. The connecting member  25  and the body  15  of the holding member  10  and the conesponding body part of the holding member  12  lie in front of the end faces of the sprockets. 
     Referring now to FIGS. 3 and 4 of the drawings, these show a further embodiment of holding device in accordance with the invention. It comprises first, second, third and fourth holding members  110 ,  111 ,  112 ,  113  respectively, and a connecting means  114 . The first holding member  110  has a body part  115 , and an engaging part  116  including a formation  118  engagable between teeth on a timing belt sprocket. 
     The second holding member  111  engages and is slidable lengthwise of a groove  119  beneath the body part  115  of the first holding member  110 , and at its end the second holding member  111  has a protuberant formation  120  for engaging between adjacent teeth on a timing belt sprocket. The third and fourth holding members are the same configuration as the first and second holding members respectively. 
     The connecting means  114  comprises an elongate strip of material  125  with an aperture adjacent one end and a longitudinally extending slot  126  at its other end. A clamping screw assembly with head  127  has its shank passing through the slot  126  and engaging with a screw-threaded bore in the second holding member  111 , the shank passing through a slot  142  in the body part  115  between the second holding member  111  and the underside of the connecting member  125 . The slot  142  is in line with the groove  119  with which the holding member  111  engages. Thus the first and second holding members are positionally adjustable relative to one another and adjustable in position and orientation relative to the connecting member  125 , and the clamping screw (which is of the type above described) serves to clamp all these components in a position in which they are set relative to one another. 
     At the opposite end of the connecting member  125  a further clamping screw assembly indicated generally at  129  serves to clamp the third and fourth holding members  112 ,  113  in a position in which they are set relative to one another and these two holding members together in a required orientation relative to the connecting member  125 . Thus in this embodiment also all the four holding members are adjustable relative to one another and are able to be held in a required position in which they are set. 
     In use of the device as shown in FIG. 3, such use being illustrated in FIG. 4, the first and second holding members are engaged one with the teeth of one sprocket and the other with the teeth of the other sprocket, at adjacent peripheral regions thereof outwardly of the narrowest part of the space between. The third and fourth holding members are likewise engaged with the respective sprockets, to the opposite side of the narrowest space therebetween. The connecting member extends chordally or tangentially relative to one or both sprockets, and is clear of the sprockets, lying in a plane parallel to the end faces thereof. 
     Thus both embodiments of the holding device according to the invention are extremely versatile, being capable of being used with sprockets of different sizes and spacing therebetween. Although in the described embodiments all the holding members are adjustable relative to one another, it is possible that a device of great versatility could be provided if only three of the holding elements were to be thus adjustable, with the fourth fixed relative to one of the other holding elements. 
     In the present specification “comprise” means “includes or consists of” and “comprising” means “including or consisting of”. 
     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.