Abstract:
Provided are a tripod constant velocity joint, and a method and a device for assembling the joint. The opening of a through-hole formed in an inner member of the tripod constant velocity joint has formed therein a tapered, reduced diameter section having a diameter tapered from the opening toward the inside. A first annular groove is formed in the side wall of a driving power transmission shaft, and a clip serving as an engaging member is engaged with the first annular groove. A second annular groove is formed in the inner wall of the through-hole in the inner member. In inserting the driving power transmission shaft through the through-hole in the inner member, the tapered, reduced diameter section guides the shaft in such a manner that the clip is contracted toward the bottom surface of the first annular groove. The clip expands and contracts due to the elasticity thereof when the positions of the first annular groove and the second annular groove coincide with each other.

Description:
TECHNICAL FIELD 
     The present invention relates to a tripod constant velocity joint in which roller members mounted on trunnions of an inner member are slidably engaged in track grooves defined in an inner wall of an outer member, as well as to a method of and an apparatus for assembling the same. 
     BACKGROUND ART 
     As is well known in the art, tripod constant velocity joints have an outer member including a bottomed tubular cup-shaped portion with a shaft projecting from one end thereof, and an inner member positioned on and fixed to the distal end of a drive power transmitting shaft that is inserted in the outer member. The drive power transmitting shaft has splines (teeth) on a circumferential side wall thereof, and the inner member has a through hole defined therein, which has splines (teeth) on an inner wall thereof. When the distal end of the drive power transmitting shaft is inserted into the through hole, the splines mesh with each other, thereby joining the drive power transmitting shaft and the inner member to each other. 
     The distal end of the drive power transmitting shaft has an annular groove defined in a side wall thereof. A substantially C-shaped clip engages in the annular groove, which is exposed out of the through hole, thereby preventing the inner member from becoming dislodged from the drive power transmitting shaft (see, for example, Japanese Patent No. 2692030). 
     Japanese Patent No. 3626127 proposes that in order to prevent the inner member from becoming dislodged from the drive power transmitting shaft, annular grooves are defined both in the inner wall of the inner member and in the side wall of the drive power transmitting shaft. Also, a clip engages in the annular grooves, as is the case with a Birfield constant velocity joint. 
     The cup-shaped portion of the outer member has a plurality of (generally, three) track grooves defined in an inner wall thereof, and the inner member has trunnions projecting from a side wall of a ring-shaped annular portion. 
     The trunnions extend toward the track grooves. Roller members are rotatably held in engagement with the respective trunnions by rolling members such as needle bearings or the like, and the roller members are slidably inserted in the track grooves. 
     The tripod constant velocity joint of the above structure is generally assembled manually by a worker in the following manner. First, the worker brings the splines of the inner member into mesh with the splines on the distal end of the drive power transmitting shaft. Thereafter, the worker places the roller members on the respective trunnions with the rolling members held on the inner walls thereof, and inserts the roller members into the track grooves of the outer member. 
     It is tedious and time-consuming, and not of good working efficiency, for the worker to assemble the tripod constant velocity joint manually. In view of this drawback, there has been a demand for an assembly apparatus for automatically assembling a tripod constant velocity joint. For example, Japanese Laid-Open Patent Publication No. 06-312326 proposes an assembly apparatus, which is focused on the timing required to fill a cup-shaped portion with grease. 
     According to the assembly apparatus disclosed in Japanese Laid-Open Patent Publication No. 06-312326, as can be understood from  FIGS. 7 and 8  thereof, an inner member including roller members mounted on trunnions and a joint boot are installed on the distal end of a drive power transmitting shaft, and then the roller members are inserted into track grooves provided in a cup-shaped portion, thereby assembling the tripod constant velocity joint. If the inner member including the roller members mounted on the trunnions is inserted beforehand in the cup-shaped portion, and then the drive power transmitting shaft is passed through a through hole of the inner member, then a clip needs to be shrunk and passed through the through hole of the inner member, irrespective of whether the clip engages in the annular groove of the drive power transmitting shaft, which is exposed outside of the through hole of the inner member, as disclosed in Japanese Patent No. 2692030, or whether the clip engages both in the annular groove provided in the inner wall of the through hole of the inner member, and in the annular groove of the drive power transmitting shaft, as disclosed in Japanese Patent No. 3626127. Unless the clip is shrunk, the clip cannot pass through the through hole. 
     In other words, the assembly apparatus disclosed in Japanese Laid-Open Patent Publication No. 06-312326 is capable only of automating a process of housing the inner member mounted on the drive power transmitting shaft in the cup-shaped portion, but is unable to automate the process of installing the inner member on the drive power transmitting shaft. 
     In order to shrink the clip, it may be necessary to employ a shrinker, which has been used in the assembly of Birfield constant velocity joints. However, such a shrinker fails to reach into deep areas of the track grooves, because the track grooves tend to be long in a tripod constant velocity joint. Consequently, it is highly difficult to shrink the clip automatically. 
     SUMMARY OF INVENTION 
     It is a general object of the present invention to provide a tripod constant velocity joint, which allows an engaging member such as a clip or the like to be shrunk at a time when the drive power transmitting shaft is passed through a through hole of an inner member. 
     A major object of the present invention is to provide a tripod constant velocity joint, which lends itself to being automatically assembled on a machine. 
     Another object of the present invention is to provide an assembly method, which is capable of automatically performing a process of installing an inner member on a drive power transmitting shaft. 
     Still another object of the present invention is to provide an assembly apparatus, which enables such an assembly method to be carried out. 
     According to an embodiment of the present invention, there is provided a tripod constant velocity joint including an outer member having track grooves defined in an inner wall thereof, and an inner member having a through hole defined therein with teeth disposed on an inner wall thereof, which are held in mesh with teeth on a drive power transmitting shaft, and trunnions projecting from a side wall thereof and extending toward the track grooves, wherein:
         the through hole of the inner member has a tapered progressively-smaller-diameter portion, which is progressively smaller in diameter in a tapered fashion inwardly from an opening of the through hole;   the drive power transmitting shaft has a first annular groove defined therein across the teeth, and the through hole has a second annular groove defined in the inner wall thereof;   the inner member is prevented from becoming dislodged from the drive power transmitting shaft by a single engaging member that engages both in the first annular groove and in the second annular groove; and   the tapered progressively-smaller-diameter portion of the through hole guides the engaging member, which engages with the first annular groove of the drive power transmitting shaft, so as to shrink the engaging member toward a bottom of the first annular groove when the drive power transmitting shaft is inserted into the through hole.       

     With the above arrangement, the tapered progressively-smaller-diameter portion automatically shrinks the engaging member, and then the engaging member and the drive power transmitting shaft are inserted into the through hole of the inner member. The above arrangement thus makes it possible to shrink the engaging member easily. 
     According to the present invention, therefore, the drive power transmitting shaft can be coupled mechanically to the inner member, which has been housed in advance in the outer member, using an assembly apparatus or the like. Therefore, the number of tedious and time-consuming manual steps is reduced, and the tripod constant velocity joint can be assembled efficiently. 
     As described above, the tapered progressively-smaller-diameter portion, which is provided in the opening of the through hole of the inner member, automatically shrinks the engaging member, which engages in the first annular groove of the drive power transmitting shaft, thereby making it possible to insert the drive power transmitting shaft together with the engaging member easily into the through hole. Consequently, the tripod constant velocity joint can easily be mechanically assembled automatically using an assembly apparatus or the like. 
     A preferred example of the engaging member may be a C-shaped elastic clip. When the first annular groove and the second annular groove are positionally aligned with each other, at a time when the drive power transmitting shaft is inserted into the through hole of the inner member, the clip tends to be restored to its original shape, i.e., to expand, under its own elasticity. When expanded in this manner, the clip engages easily both in the first annular groove and in the second annular groove. 
     According to an embodiment of the present invention, there also is provided a method of assembling a tripod constant velocity joint by fitting a drive power transmitting shaft, having an engaging member engaging in a first annular groove defined therein, into a through hole defined in an inner member, the inner member being housed in an outer member having track grooves defined in an inner wall thereof, and having on a side wall thereof trunnions with roller members mounted thereon, which are slidably inserted in the track grooves, the method comprising the steps of:
         holding an end of the drive power transmitting shaft;   aligning an axis of the drive power transmitting shaft and a center of the through hole with each other;   bringing the axis of the drive power transmitting shaft and the center of the through hole into phase with each other; and   displacing the outer member, which houses therein the inner member with the roller members mounted on the trunnions and being slidably inserted in the track grooves, relatively with respect to the drive power transmitting shaft, thereby fitting the drive power transmitting shaft into the through hole of the inner member,   wherein the engaging member is reduced in diameter and inserted into the through hole while being guided by a tapered progressively-smaller-diameter portion defined in an opening of the through hole of the inner member, and the engaging member engages in a second annular groove defined in an inner wall of the through hole.       

     According to the present invention, the engaging member is automatically shrunk by the tapered progressively-smaller-diameter portion of the inner member of the tripod constant velocity joint, and the drive power transmitting shaft together with the engaging member is inserted into the through hole of the inner member. Therefore, it is possible to shrink the engaging member easily, and to cause the engaging member to engage both in the annular groove of the inner member and in the annular groove of the drive power transmitting shaft. 
     According to the present invention, therefore, the drive power transmitting shaft and the inner member can be coupled to each other simply by pressing the drive power transmitting shaft into the through hole of the inner member, which has been housed in advance in the outer member. When the drive power transmitting shaft is pressed automatically by an apparatus, the number of tedious and time-consuming manual steps is reduced, and the tripod constant velocity joint can be assembled efficiently. 
     In summary, according to the present invention, the tapered progressively-smaller-diameter portion is provided in the opening of the through hole of the inner member of the tripod constant velocity joint, so that when the drive power transmitting shaft is pressed into the through hole of the inner member, which has been housed in advance in the outer member, the tapered progressively-smaller-diameter portion automatically shrinks the engaging member, which engages in the first annular groove of the drive power transmitting shaft. Therefore, when the drive power transmitting shaft together with the engaging member is inserted into the through hole, the drive power transmitting shaft and the inner member are coupled to each other. Therefore, it is possible to automatically assemble the tripod constant velocity joint. 
     In the above process, a joint boot may be mounted on the outer member when the drive power transmitting shaft is fitted in the through hole of the inner member. In this case, it is preferable to release the joint boot temporarily from the outer member, and thereafter to mount the joint boot again on the outer member. In this manner, air can be removed from the joint boot. 
     According to another embodiment of the present invention, there is provided a constant velocity joint assembly apparatus for assembling a tripod constant velocity joint by fitting a drive power transmitting shaft with an engaging member engaging in an annular groove defined therein into a through hole defined in an inner member, the inner member being housed in an outer member having track grooves defined in an inner wall thereof, and having on a side wall thereof trunnions with roller members mounted thereon, which are slidably inserted in the track grooves, the constant velocity joint assembly apparatus comprising:
         a shaft holding mechanism for holding an end of the drive power transmitting shaft;   a centering mechanism for aligning an axis of the drive power transmitting shaft and a center of the through hole with each other;   a turning mechanism for bringing the drive power transmitting shaft and the through hole of the inner member into phase with each other; and   an outer member displacing mechanism for displacing the outer member, which houses the inner member therein, with respect to the drive power transmitting shaft.       

     With the above arrangement, the drive power transmitting shaft and the inner member can be coupled to each other simply by pressing the drive power transmitting shaft into the through hole of the inner member, which has been housed in advance in the outer member. This is because, as the drive power transmitting shaft is pressed progressively into the through hole, a tapered progressively-smaller-diameter portion of the inner member of the tripod constant velocity joint automatically shrinks the engaging member, until finally the engaging member engages both in the annular groove defined in the inner member and in the annular groove defined in the drive power transmitting shaft. 
     According to the present invention, the tripod constant velocity joint can be assembled and installed simultaneously on the drive power transmitting shaft automatically. Therefore, the number of tedious and time-consuming manual steps is reduced, and the tripod constant velocity joint can be assembled efficiently. 
     The constant velocity joint assembly apparatus should preferably further include a boot gripping mechanism for gripping a joint boot, which has been mounted in advance on the drive power transmitting shaft. The boot gripping mechanism temporarily releases the joint boot from the outer member when the drive power transmitting shaft is fitted in the through hole of the inner member, and thereafter mounts the joint boot again on the outer member. In this manner, air can easily be removed from the joint boot. 
     The constant velocity joint assembly apparatus should preferably further include an engaging member pressing mechanism for pressing the engaging member. The engaging member pressing mechanism causes the engaging member to engage with the annular groove of the drive power transmitting shaft reliably. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic cross-sectional view, shown partially in side elevation, of an overall structure of a drive power transmitting mechanism incorporating a tripod constant velocity joint according to an embodiment of the present invention; 
         FIG. 2  is an exploded fragmentary perspective view of the tripod constant velocity joint incorporated in the drive power transmitting mechanism shown in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view taken along line III-III of  FIG. 2 ; 
         FIG. 4  is a front elevational view showing an overall structure of an engaging member (clip) of the tripod constant velocity joint shown in  FIG. 2 ; 
         FIG. 5  is a schematic side elevational view, partially in vertical cross section, of a constant velocity joint assembly apparatus according to the embodiment; 
         FIG. 6  is an enlarged fragmentary side elevational view of the constant velocity joint assembly apparatus shown in  FIG. 5 ; 
         FIG. 7  is a view, partially cut away, taken along the direction indicated by the arrow L in  FIG. 6 ; 
         FIG. 8  is a view, partially cut away, taken along the direction indicated by the arrow M in  FIG. 6 ; 
         FIG. 9  is a view, partially cut away, taken along the direction indicated by the arrow N in  FIG. 6 ; 
         FIG. 10  is a view, partially cut away, showing a boot gripping mechanism illustrated in  FIG. 9 , with a first finger and a second finger thereof being in an open state; 
         FIG. 11  is an enlarged fragmentary side elevational view of the constant velocity joint assembly apparatus shown in  FIG. 5 ; 
         FIG. 12  is a view, partially cut away, taken along the direction indicated by the arrow O in  FIG. 11 ; 
         FIG. 13  is a view, partially cut away, taken along the direction indicated by the arrow P in  FIG. 11 ; 
         FIG. 14  is a fragmentary vertical cross-sectional view showing a state in which, after the engaging member has engaged in a first annular groove defined in a drive power transmitting shaft, the drive power transmitting shaft is passed through a through hole of an inner member; 
         FIG. 15  is an enlarged fragmentary view showing a state in which a shaft of an outer member of a Birfield constant velocity joint and a shaft of an outer member of a tripod constant velocity joint are inserted respectively in a first outer member holder and in a second outer member holder; 
         FIG. 16  is an enlarged fragmentary view showing a state in which the clip is pressed by pressing teeth of a clip pressing mechanism; 
         FIG. 17  is an enlarged fragmentary view showing a state in which the outer member of the tripod constant velocity joint is lifted to insert an end of the drive power transmitting shaft slightly into the through hole of the inner member; 
         FIG. 18  is an enlarged fragmentary view showing a state in which the first finger and the second finger are spaced from each other in order to release a joint boot; 
         FIG. 19  is a fragmentary vertical cross-sectional view showing a state in which the clip starts to be compressed and shrunk, as the diameter of a tapered progressively-smaller-diameter portion becomes progressively smaller; 
         FIG. 20  is a fragmentary vertical cross-sectional view showing a state in which the clip moves in the through hole, as the diameter of the clip is reduced to a diameter corresponding to the inside diameter of the through hole; 
         FIG. 21  is a fragmentary vertical cross-sectional view showing a state in which the clip engages in the first annular groove defined in the drive power transmitting shaft, and in a second annular groove defined in an inner wall of the through hole of the inner member; 
         FIG. 22  is an enlarged fragmentary view showing a state in which the joint boot is compressed when the parts are in the state shown in  FIG. 21 ; 
         FIG. 23  is an enlarged fragmentary view showing a state in which the outer member is lowered from the state shown in  FIG. 22 ; 
         FIG. 24  is an enlarged fragmentary view showing a state in which the joint boot is released from the lowered outer member; 
         FIG. 25  is an enlarged fragmentary view showing a state in which the joint boot is mounted again on the outer member; and 
         FIG. 26  is an enlarged fragmentary view showing a state in which the drive power transmitting mechanism is released from clamps. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A tripod constant velocity joint according to a preferred embodiment of the present invention, in relation to an assembly method for assembling the tripod constant velocity joint and an assembly apparatus for carrying out the assembly method, will be described in detail below with reference to the accompanying drawings. 
     First, a drive power transmitting mechanism as a completed product will be described below with reference to  FIGS. 1 through 3 . The drive power transmitting mechanism  10  includes a drive power transmitting shaft  12  with a Birfield constant velocity joint  14  mounted on one end thereof, and a tripod constant velocity joint  16  according to the present embodiment mounted on the remaining other end thereof. 
     The Birfield constant velocity joint  14  may be of the type disclosed in Japanese Laid-Open Patent Publication No. 2000-046061, for example, or of any other known design. Therefore, details of the Birfield constant velocity joint  14  will not be described below. 
     The tripod constant velocity joint  16  includes an outer member  18  and an inner member  20  fitted over a portion of the drive power transmitting shaft  12  in the vicinity of an end thereof, as shown in  FIG. 2 , which is an exploded fragmentary perspective view of the tripod constant velocity joint  16 , and  FIG. 3 , which is a cross-sectional view (sectional side elevational view) taken along line III-III of  FIG. 2 . In  FIG. 3 , the drive power transmitting shaft  12  and the inner member  20  are shown as being coupled to each other outside of the outer member  18 . Actually, however, the drive power transmitting shaft  12  is coupled to the inner member  20  within a cup-shaped portion  22  of the outer member  18  (to be described later). 
     The outer member  18  includes the cup-shaped portion  22 , which is of a bottomed tubular shape, and a shank  24  that projects from one end of the cup-shaped portion  22 . The shank  24 , which is coupled to the rotational shaft of a transmission (not shown), for example, transmits rotational drive power of the transmission to the drive power transmitting shaft  12  through the cup-shaped portion  22  and the inner member  20 . 
     The cup-shaped portion  22  has three track grooves  26   a  through  26   c  defined on an inner wall thereof, which are angularly spaced at intervals of 120°. As shown in  FIG. 3 , the track grooves  26   a  through  26   c  extend to the bottom of the inner wall of the cup-shaped portion  22 . 
     As shown in  FIG. 3 , the inner member  20  includes a ring-shaped annular portion  30  serving as a disk-shaped member, with a through hole  28  defined therein, and three trunnions  32   a  through  32   c  (see  FIG. 2 ) projecting from a side wall of the annular portion  30 . The through hole  28  extends along a direction in which the cup-shaped portion  22  and the drive power transmitting shaft  12  extend. The through hole  28  has an inner wall including splines  34  (teeth), which extend along the axis of the through hole  28 . 
     The through hole  28  includes a tapered progressively-smaller-diameter portion  36 , which is progressively smaller in diameter in a tapered fashion inwardly from the opening thereof (the end face of the annular portion  30 ). The tapered progressively-smaller-diameter portion  36  serves as a shrinker, as described later. In the present embodiment, the tapered progressively-smaller-diameter portion  36  has a bevel angle θ (see  FIG. 3 ) of about 30°. 
     Each of the trunnions  32   a  through  32   c  is in the form of a cylinder, which bulges slightly at a middle portion thereof in the heightwise direction. Adjacent ones of the trunnions  32   a  through  32   c  are angularly spaced from each other at equal intervals of 120°. Therefore, the trunnions  32   a  through  32   c  are kept in phase with the respective track grooves  26   a  through  26   c . The trunnions  32   a  through  32   c  extend toward the respective track grooves  26   a  through  26   c.    
     Roller members  38   a  through  38   c  are mounted respectively on the trunnions  32   a  through  32   c , with a plurality of rolling members, such as needle bearings  40  or the like, being interposed between the roller members  38   a  through  38   c  and the trunnions  32   a  through  32   c . Therefore, the roller members  38   a  through  38   c  are rotatable about the trunnions  32   a  through  32   c , respectively. 
     Each of the roller members  38   a  through  38   c  has a set of flanges  42   a ,  42   b  that project radially inward. All of the needle bearings  40  are held on the roller members  38   a  through  38   c  as a result of being sandwiched by the flanges  42   a ,  42   b.    
     The drive power transmitting shaft  12  serves as a relay shaft for transmitting rotational drive power of the transmission, which is transmitted through the outer member  18 , to a hub (not shown) via the Birfield constant velocity joint  14 . As shown in  FIG. 3 , one end of the drive power transmitting shaft  12  is inserted into the cup-shaped portion  22  and extends through the through hole  28  of the inner member  20 , while the other end of the drive power transmitting shaft  12  extends through a through hole  46  defined in an inner member  44  of the Birfield constant velocity joint  14  (see  FIG. 1 ). 
     As shown in  FIG. 3 , one end of the drive power transmitting shaft  12  has splines  48  (teeth) thereon. The splines  48  mesh with the splines  34  on the inner wall of the through hole  28 , when the one end of the drive power transmitting shaft  12  extends through the through hole  28  of the inner member  20 . 
     As can be understood from  FIG. 3 , the one end of the drive power transmitting shaft  12  including the splines  48  has a first annular groove  50  defined therein, which extends across the splines  48 . The inner wall of the through hole  28  of the inner member  20  also has a second annular groove  52  defined therein, which extends across the splines  34 . A substantially C-shaped clip  54  (engaging member), as shown in  FIG. 4 , engages both in the first annular groove  50  and in the second annular groove  52 , thereby preventing the inner member  20  from becoming dislodged from the drive power transmitting shaft  12 . 
     The joint boot is omitted from illustration in  FIGS. 2 and 3 . Actually, the joint boot  56  (see  FIG. 1 ) is mounted on the cup-shaped portion  22  of the outer member  18  and the drive power transmitting shaft  12 , so as to extend from the cup-shaped portion  22  to the drive power transmitting shaft  12 . A lubricant (not shown) such as grease or the like, for example, is filled in the cup-shaped portion  22 . 
     A constant velocity joint assembly apparatus (hereinafter referred to simply as an “assembly apparatus”) according to the present embodiment will be described below. In the drawings referred to below, certain members may be shown as cut away, or certain members and mechanisms may be omitted from illustration, in order to clarify the structure of the constant velocity joint assembly apparatus. 
       FIG. 5  is a schematic side elevational view, partially in vertical cross section, of an assembly apparatus  60  for assembling the drive power transmitting mechanism  10 . The assembly apparatus  60  serves to produce the drive power transmitting mechanism  10  referred to above, by mounting the tripod constant velocity joint  16  on the remaining other end of the drive power transmitting shaft  12 , while the Birfield constant velocity joint  14  is mounted on the one end thereof. The assembly apparatus  60  is supported on a support column  64 , which is vertically mounted on a floor  62  of a working station. 
     As shown in  FIG. 5 , the assembly apparatus  60  includes a first outer member holder  66  for holding the outer member  18  of the tripod constant velocity joint  16 , a first ball screw mechanism  68  serving as an outer member displacing mechanism for displacing the outer member  18  together with the first outer member holder  66 , a centering mechanism  70  for aligning the axis of the drive power transmitting shaft  12  with the center of the through hole  28  of the inner member  20 , a boot gripping mechanism  72  for gripping the joint boot  56 , which is mounted on the outer member  18  of the tripod constant velocity joint  16  and the drive power transmitting shaft  12 , and a shaft holding mechanism  78  for holding the drive power transmitting shaft  12  by holding a shank  76  of an outer member  74  of the Birfield constant velocity joint  14 . The shaft holding mechanism  78  includes a second outer member holder  80  and a second ball screw mechanism  82 , which function as a displacing mechanism for displacing the second outer member holder  80 . The shaft holding mechanism  78  also includes a turning mechanism  83  for turning the second outer member holder  80  through a predetermined angle, at a time when the drive power transmitting shaft  12  is brought into phase with the through hole  28  of the inner member  20 . The turning mechanism  83  thus functions as a phase aligning mechanism. 
     A first mount plate  84  and a second mount plate  86  are fixed to the support column  64 . The first ball screw mechanism  68  and the second ball screw mechanism are supported respectively on the first mount plate  84  and the second mount plate  86 . 
     The first ball screw mechanism  68  includes a first motor  88 , a first ball screw  90  coupled to a rotary shaft of the first motor  88 , and a first movable nut  92  threaded over the first ball screw  90 . The first outer member holder  66  is coupled to the first movable nut  92 . When the first motor  88  is energized, the first ball screw  90  rotates about its axis, thereby guiding the first movable nut  92  to move vertically, which in turn enables the first outer member holder  66  to move vertically. 
     As shown in  FIGS. 5 and 6 , a linear guide support plate  94  substantially in the form of a flat plate is disposed between the first mount plate  84  and the second mount plate  86 , and extends in the direction indicated by the arrow X 1 . On a lower end face of the linear guide support plate  94 , as shown in  FIG. 6 , there are disposed in combination a first linear guide  98  and a second linear guide  100  for displacing a shaft positioning member  96  of the centering mechanism  70  in directions indicated by the arrows X 1 , X 2  as well as in directions indicated by the arrows Y 1 , Y 2 . On the upper end face of the linear guide support plate  94 , there are disposed in combination a third linear guide  102  and a fourth linear guide  104  for displacing the boot gripping mechanism  72  in directions indicated by the arrows X 1 , X 2  as well as in directions indicated by the arrows Y 1 , Y 2 . In other words, as shown in  FIG. 6 , the centering mechanism  70  is displaceable individually in directions indicated by the arrows X 1 , X 2  and in directions indicated by the arrows Y 1 , Y 2 , by the first linear guide  98  and the second linear guide  100 . Also, as shown in  FIG. 6 , the boot gripping mechanism  72  is displaceable individually in directions indicated by the arrows X 1 , X 2  and in directions indicated by the arrows Y 1 , Y 2 , by the third linear guide  102  and the fourth linear guide  104 . 
     As can be understood from  FIG. 7 , which is a view, partially cut away, taken along the direction indicated by the arrow L in  FIG. 6 , and from  FIG. 8 , which is a view, partially cut away, taken along the direction indicated by the arrow M in  FIG. 6 , the first linear guide  98  has a first guide rail  106  and a second guide rail  108 , with a slider  110  that slidably engages with the first guide rail  106 , and sliders  112 ,  113  that slidably engage with the second guide rail  108  (see  FIG. 7 ). A first bridge plate  114  is mounted thereon and extends from the slider  110  to the sliders  112 ,  113  (see  FIG. 7 ). The first bridge plate  114  is omitted from illustration in  FIG. 8 . 
     As shown in  FIGS. 7 and 8 , a first cylinder  116  is supported on the linear guide support plate  94 , although the first cylinder  116  is omitted from illustration in  FIGS. 5 and 6 . The first cylinder  116  has a first rod  118  coupled to the first bridge plate  114  by a first coupling member  120 , which has a bent shape (see  FIG. 7 ). When the first cylinder  116  is actuated to extend and contract the first rod  118 , the first bridge plate  114  together with the shaft positioning member  96  on the centering mechanism  70  are displaced in unison with the second linear guide  100  in directions indicated by the arrows X 1 , X 2 . 
     The second linear guide  100  includes a third guide rail  122  which, as shown in  FIG. 6 , extends in a direction (the direction indicated by the arrow Y 1 ) perpendicular to the first guide rail  106  and the second guide rail  108 . As shown in  FIGS. 6 and 7 , a slider  126  and a slider  128 , which are joined mutually to each other, slidably engage with the third guide rail  122 . A second bridge plate  130  is mounted on and extends from an end face of the slider  126  to an end face of the slider  128 . The second bridge plate  130  is coupled to a second rod  136  of a second cylinder  134  by a second coupling member  132 , as shown in  FIG. 8 . When the second cylinder  134  is actuated, the second bridge plate  130  is displaced along the third guide rail  122  in directions indicated by the arrows Y 1 , Y 2  in  FIGS. 6 and 9  (i.e., in directions extending perpendicular to the sheet in  FIG. 7 ). 
     As shown in  FIG. 6 , a columnar member  138  that extends parallel to the first guide rail  106  and the second guide rail  108  is mounted on an end face of the second bridge plate  130 . The columnar member  138  has a fitting hole  140  defined therein, and the shaft positioning member  96  is firmly fitted in the fitting hole  140  and extends parallel to the third guide rail  122 . The shaft positioning member  96  includes a substantially cylindrical body portion and a tapered engaging portion, which becomes progressively smaller in diameter in a tapered fashion toward the tip end thereof. As described later, the tapered engaging portion of the shaft positioning member  96  engages in a bottomed hole (not shown) defined in a distal end face of the drive power transmitting shaft  12 . 
     The body portion of the shaft positioning member  96  extends through a through hole  146  defined in a support member  144  in the form of a flat plate, which is fitted in a guide sleeve  142  vertically mounted on the columnar member  138 , and a through hole  148  defined in an end face of the guide sleeve  142 . The through holes  146 ,  148  have diameters corresponding to the diameter of the body portion of the shaft positioning member  96 . The shaft positioning member  96  is thus firmly supported and is prevented from swinging. 
     The columnar member  138  also is firmly supported by a triangular plate  150 , which is mounted on the end face of the second bridge plate  130 . Therefore, the shaft positioning member  96  also is protected against swinging movements, which would otherwise occur if the columnar member  138  were swingable. 
     As can be seen from  FIG. 7 , the linear guide support plate  94  has a substantially U-shaped recess  152  defined therein. As shown in  FIG. 8 , a pressing tooth cylinder  154 , which serves as a clip pressing mechanism for pressing the clip  54  (see  FIGS. 3 and 5 ), is disposed in the recess  152 . 
     The pressing tooth cylinder  154  has a set of pressing tooth rods  156 ,  158 , which are movable in synchronism toward and away from each other. Pressing tooth coupling plates  160  are mounted respectively on distal ends of the pressing tooth rods  156 ,  158 . Pressing teeth  162 , shown in  FIG. 6 , are disposed respectively on the pressing tooth coupling plates  160 . When the pressing tooth cylinder  154  is actuated, the pressing tooth rods  156 ,  158  move toward and away from each other to open and close the pressing teeth  162 . 
     The boot gripping mechanism  72  is displaceable in directions indicated by the arrows X 1 , X 2  (directions perpendicular to the sheet of  FIG. 8 ) when a third cylinder  164 , as shown in  FIG. 8 , is actuated. The boot gripping mechanism  72  also is displaceable in directions indicated by the arrows Y 1 , Y 2  in  FIG. 6  when a fourth cylinder  166  is actuated. 
     More specifically, as shown in  FIGS. 6 and 8 , sliders  172 ,  173  and sliders  174 ,  175  are disposed above a fourth guide rail  168  and a fifth guide rail  170 , respectively, of the third linear guide  102 , and a third bridge plate  176  is mounted on and extends between end faces of the sliders  172 ,  173  and the sliders  174 ,  175 . As shown in  FIG. 8  and  FIG. 9 , which is a view, partially cut away, taken along the direction indicated by the arrow N in  FIG. 6 , a third cylinder  164  is supported on an end face of the linear guide support plate  94 , which is remote from the end face that supports the first cylinder  116  thereon. The third cylinder  164  has a third rod  178  coupled to the third bridge plate  176  by a bent third coupling member  180  (see  FIG. 9 ). When the third cylinder  164  is actuated in order to extend and contract the third rod  178 , the third bridge plate  176  together with the boot gripping mechanism  72  on the fourth linear guide  104  are displaced in unison with the fourth linear guide  104  in directions indicated by the arrows X 1 , X 2 . 
     The fourth linear guide  104  includes a sixth guide rail  182  and a seventh guide rail  184 , which are mounted on the third bridge plate  176  so as to extend in the direction indicated by the arrow Y 2  (see  FIG. 9 ). A fourth bridge plate  190  is mounted on and extends from a slider  186  on the sixth guide rail  182  to a slider  188  on the seventh guide rail  184 . The fourth bridge plate  190  is coupled to a fourth rod  194  of the fourth cylinder  166  by a fourth coupling member  192 , as shown in  FIG. 8 . When the fourth cylinder  166  is actuated, therefore, the fourth bridge plate  190  is displaced in directions indicated by the arrows Y 1 , Y 2  (i.e., directions perpendicular to the sheet of  FIG. 9 ) along the sixth guide rail  182  and the seventh guide rail  184 . 
     As shown in  FIG. 9 , the boot gripping mechanism  72  includes a fifth cylinder  196  mounted on the fourth bridge plate  190 , and a first finger  200  and a second finger  202 , which can be opened and closed in response to movement of a fifth rod  198  of the fifth cylinder  196 . 
     A pulling member  208 , which has a first U-shaped slot  204  and a second U-shaped slot  206  defined therein, is mounted on a distal end of the fifth rod  198 . The first U-shaped slot  204  and the second U-shaped slot  206  are angularly spaced from each other by about 180°. 
     The first finger  200  and the second finger  202  are fitted respectively in a first bracket  210  and a second bracket  212  having a first guide pin  214  and a second guide pin  216 , respectively, which are inserted respectively in the first U-shaped slot  204  and the second U-shaped slot  206 . A pivot shaft  218  extends through the first bracket  210  and the second bracket  212 . 
     As shown in  FIG. 10 , when the fifth cylinder  196  is actuated to retract the fifth rod  198 , the first guide pin  214  and the second guide pin  216 , which are inserted respectively in the first U-shaped slot  204  and the second U-shaped slot  206 , are pulled by the pulling member  208 , thereby spacing the first finger  200  and the second finger  202  apart from each other and opening the boot gripping mechanism  72 . When the fifth rod  198  is extended, the first finger  200  and the second finger  202  are brought toward each other, thereby closing the boot gripping mechanism  72 , as shown in  FIG. 9 . 
     According to the present embodiment, as shown in  FIGS. 5 and 11 , a clamp mechanism  230  is disposed displaceably between the first linear guide  98  and the second ball screw mechanism  82 . More specifically, as shown in  FIG. 12 , which is a view, partially cut away, taken along the direction indicated by the arrow O in  FIG. 11 , a fifth linear guide  232  is mounted on the second mount plate  86  (see  FIG. 5 ), and the clamp mechanism  230  is displaceable in directions indicated by the arrows Y 1 , Y 2  along an eighth guide rail  234  and a ninth guide rail  236  of the fifth linear guide  232 . 
     A slide plate  242  is mounted on and extends from a slider  238  on the eighth guide rail  234  to a slider  240  on the ninth guide rail  236 . As shown in  FIG. 13 , which is a view taken along the direction indicated by the arrow P in  FIG. 11 , the slide plate  242  is coupled by a coupling plate  250  to a third displaceable nut  248 , which is threaded over a third ball screw  246  of a third ball screw mechanism  244 . When the operator grips and turns a handle  252  to displace the third displaceable nut  248  along the third ball screw  246 , the slide plate  242 , which is coupled to the third displaceable nut  248  by the coupling plate  250 , also is displaced. 
     A columnar support member  254  (see  FIGS. 12 and 13 ), which is substantially inversely T-shaped in cross section, is mounted on the slide plate  242 . A planar support member  256  extends along the direction of the columnar support member  254 , and is attached to a side surface of the columnar support member  254 . The columnar support member  254  is prevented from falling over due to being supported by the planar support member  256 . 
     As shown in  FIG. 13 , a gripping cylinder  262 , including a first synchronizing rod  258  and a second synchronizing rod  260 , which are drivable in synchronism with each other, is mounted on a side surface of the planar support member  256 . The first synchronizing rod  258  and the second synchronizing rod  260  grip the columnar support member  254  and a panel  264 , respectively, from the side of the columnar support member  254  and the panel  264 . 
     The panel  264  is coupled to an end face of the columnar support member  254  by a coupling pin  266 . The coupling pin  266  has a body substantially in the form of a rectangular parallelepiped, which is coupled to an end of a planar clamp mechanism support plate  270  by a coupling jig  268 . 
     A protruding plate  272  is mounted on an end face of the panel  264  and lies substantially perpendicular to the end face of the panel  264 . The clamp mechanism support plate  270  is placed on upper end faces of the panel  264  and the protruding plate  272 . 
     As shown in  FIG. 12 , the coupling jig  268  includes a short wall  274  and a long wall  276 , which extend in surrounding relation to the body of the coupling pin  266 . A securing pin  278  extends between and is mounted on the short wall  274  and on the long wall  276 . The securing pin  278  extends through the body of the coupling pin  266 , thereby positioning and securing the coupling jig  268 , and hence the clamp mechanism support plate  270 , with the coupling jig  268  coupled to the end thereof. 
     The long wall  276  has an end face, which faces the panel  264 , and which is held in abutment against a distal end face of the protruding plate  272 , thereby positioning the clamp mechanism support plate  270 . 
     A placement base  280  for supporting the drive power transmitting shaft  12  is disposed on the clamp mechanism support plate  270 . The placement base  280  has a V-groove  284  having a substantially V-shaped cross section defined therein for gripping the drive power transmitting shaft  12 , which has a circular cross-sectional shape, in cooperation with a clamp  282 . 
     The clamp  282  is fixed to a seat  286  disposed on the clamp mechanism support plate  270 . The clamp  282  includes a lever  288  movable by the operator, and a pressing bar  290 , which moves toward the seat  286  when the lever  288  is moved to the imaginary-line position shown in  FIG. 12 . As shown in  FIG. 12 , the pressing bar  290  becomes locked when the lever  288  is moved to the imaginary-line position. At this time, the lever  288  also is locked. The lever  288  remains locked until the lever  288  is unlocked by the operator. 
     Even when the lever  288  and the pressing bar  290  are locked, the drive power transmitting shaft  12  remains slidable along the slanted surfaces of the V-groove  284 . 
     When there is play developed in the second outer member holder  80 , the shank  76  of the outer member  74  of the Birfield constant velocity joint  14  is inserted into the second outer member holder  80 . As described above, by operation of the turning mechanism  83 , the second outer member holder  80  is displaced by the second ball screw mechanism  82 , and upon displacement thereof, is turned through a predetermined angle. 
     The second ball screw mechanism  82  is identical in construction and operation to the first ball screw mechanism  68 . More specifically, the second ball screw mechanism  82  includes a second motor  292 , a second ball screw  294  coupled to the rotational shaft of the second motor  292 , and a second movable nut  296  threaded over the second ball screw  294 . The second outer member holder  80  is coupled to the second movable nut  296 . When the second motor  292  is energized, the second ball screw  294  rotates about its axis, thereby guiding the second movable nut  296  to move vertically, which also enables the second outer member holder  80  to move vertically. 
     The assembly apparatus  60  thus constructed is housed in a casing  298 , which is fixed to the support column  64  (see  FIG. 5 ). Reference numeral  300  in  FIG. 5  represents a door member, which is openable and closable with respect to the casing  298 . 
     The assembly apparatus  60  according to the present embodiment is basically constructed as described above. Operations and advantages of the assembly apparatus  60  will be described below in relation to a method of assembling a constant velocity joint according to the present embodiment. 
     First, the Birfield constant velocity joint  14  is installed on one end of the drive power transmitting shaft  12 . The Birfield constant velocity joint  14  is installed by an assembly apparatus, not shown, which is different from the assembly apparatus  60 . Although not shown, a dynamic damper is fitted over a longitudinal middle portion of the drive power transmitting shaft  12 . The joint boot  56  of the tripod constant velocity joint  16  is mounted on the drive power transmitting shaft  12  in the vicinity of the other end thereof (see  FIG. 15 ). 
     As shown schematically in  FIG. 14 , the clip  54  is placed in the first annular groove  50  in the drive power transmitting shaft  12 . Although not shown in  FIG. 14 , the inner member  20  is inserted in advance in the cup-shaped portion  22  of the outer member  18 , as described later. 
     When the clip  54  does not engage in the second annular groove  52 , the clip  54  has an inside diameter D (see  FIG. 4 ), which is greater than the distance from the center of the drive power transmitting shaft  12  to the bottom of the first annular groove  50 . Therefore, when the clip  54  engages only in the first annular groove  50 , a clearance is formed between the inner wall of the clip  54  and the bottom of the first annular groove  50 . Stated otherwise, the clip  54  engages with the first annular groove  50  with a certain amount of play therebetween. 
     Then, in order to construct the drive power transmitting mechanism  10 , the drive power transmitting shaft  12  with the clip  54  mounted in the first annular groove  50  is passed through the through hole  28  of the inner member  20  (see  FIG. 14 ). The tripod constant velocity joint  16  is thereby installed on the other end of the drive power transmitting shaft  12 . 
     The tripod constant velocity joint  16  is assembled in the following manner by the assembly apparatus  60 .  FIG. 15  and subsequent figures have been simplified to clarify the operation of each mechanism. 
     First, as shown in  FIG. 15 , the shank  76  of the outer member  74  of the Birfield constant velocity joint  14  is inserted into the second outer member holder  80 . As described above, since there is a slight amount of play between the shank  76  and the second outer member holder  80 , the drive power transmitting shaft  12  is swingable about a portion thereof, which is held by the second outer member holder  80 . 
     The drive power transmitting shaft  12  is inserted into the V-groove  284  in the placement base  280  (see  FIG. 12 ). Since the drive power transmitting shaft  12  abuts against the walls of the V-groove  284 , the drive power transmitting shaft  12  is prevented from swinging. 
     A predetermined number of needle bearings  40  are placed between the flanges  42   a ,  42   b  of each of the roller members  38   a  through  38   c . The roller members  38   a  through  38   c  then are mounted respectively on the trunnions  32   a  through  32   c  of the inner member  20 . 
     Then, the inner member  20  is housed in the cup-shaped portion  22  of the outer member  18 . More specifically, the roller members  38   a  through  38   c , which are mounted on the trunnions  32   a  through  32   c , are inserted into the track grooves  26   a  through  26   c.    
     The shank  24  of the outer member  18  then is inserted into the first outer member holder  66 . Upon insertion of the shank  24 , the roller members  38   a  through  38   c  are moved by gravity to an endpoint on the bottom of the cup-shaped portion  22 . 
     Then, the first motor  88  of the first ball screw mechanism  68  and the second motor  292  of the second ball screw mechanism  82  are energized in order to displace the first movable nut  92  and the second movable nut  296  along the first ball screw  90  and the second ball screw  294 , respectively. Since the first movable nut  92  and the second movable nut  296  are displaced in this manner, the drive power transmitting shaft  12  is fed to a given location in the assembly apparatus  60 . 
     Then, the shaft positioning member  96  of the centering mechanism  70  is displaced to a position at which the shaft positioning member  96  can engage in the bottomed hole, which is defined in the distal end face of the drive power transmitting shaft  12 . More specifically, the first cylinder  116  and the second cylinder  134  are actuated to extend or retract the first rod  118  and the second rod  136 , thereby displacing the first bridge plate  114  along the directions indicated by the arrows X 1 , X 2  in  FIG. 7 , and displacing the second bridge plate  130  along the directions indicated by the arrows Y 1 , Y 2  in  FIGS. 6 and 8 . The directions and the distances over which the first bridge plate  114  and the second bridge plate  130  are displaced are adjusted, so as to cause the tapered engaging portion of the shaft positioning member  96  to engage in the bottomed hole of the drive power transmitting shaft  12 . Thus, the axis of the drive power transmitting shaft  12  and the center of the through hole  28  are aligned with each other. At this time, the pressing teeth  162 , the first finger  200 , and the second finger  202  are open. 
     Thereafter, the operator operates the lever  288  of the clamp  282  in order to move the pressing bar  290  of the clamp  282  toward the placement base  280 . As a result, the drive power transmitting shaft  12  is gripped between the pressing bar  290  and the placement base  280  (the walls of the V-groove  284 ). In  FIG. 15 , the drive power transmitting shaft  12  is shown schematically as being gripped between the pressing bar  290  and the placement base  280 . 
     The operator may rotate the handle  252  to displace the slide plate  242 , for thereby placing the clamp mechanism  230  in a desired position in advance. 
     Then, the turning mechanism  83  is actuated in order to turn the drive power transmitting shaft  12  clockwise or counterclockwise intermittently about its axis through a prescribed angle. As a result, the drive power transmitting shaft  12  is brought into phase with the through hole  28  of the inner member  20 . As described above, since the drive power transmitting shaft  12  can slide even while the drive power transmitting shaft  12  is gripped by the pressing bar  290  of the clamp  282  and the placement base  280 , the process of bringing the drive power transmitting shaft  12  into phase with the through hole  28  is not impaired as a result of the drive power transmitting shaft  12  being clamped by the clamp mechanism  230 . 
     Then, the pressing tooth cylinder  154  (see  FIGS. 7 and 8 ) is actuated to bring the pressing tooth rods  156 ,  158 , and hence the pressing tooth coupling plates  160 , into close proximity with each other, thereby closing the pressing teeth  162 , as shown in  FIG. 6 . At this time, the clip  54  is pressed by the pressing teeth  162 . 
     About or exactly at the same time, the fifth cylinder  196  (see  FIGS. 9 and 10 ) is actuated to extend the fifth rod  198 . The first finger  200  and the second finger  202  are brought into close proximity with each other (see  FIG. 9 ) and grip the joint boot  56  (see  FIG. 16 ). 
     Thereafter, the first cylinder  116  and the second cylinder  134  are actuated to extend or retract the first rod  118  and the second rod  136 , thereby spacing the shaft positioning member  96  from the drive power transmitting shaft  12 . About or exactly at the same time, the pressing tooth cylinder  154  is actuated in order to open the pressing teeth  162 , thereby releasing the clip  54 . 
     Then, the first motor  88  is energized again to displace the first movable nut  92  toward the Birfield constant velocity joint  14 . As the Birfield constant velocity joint  14  is displaced, the outer member  18  of the tripod constant velocity joint  16  is lifted in unison with the first outer member holder  66  along the first ball screw  90  until the end of the drive power transmitting shaft  12  is inserted slightly into the through hole  28  of the inner member  20 . 
     Then, the first motor  88  is temporarily de-energized, so as to stop the outer member  18  from being lifted, and also to stop the drive power transmitting shaft  12  from being inserted into the through hole  28  of the inner member  20 . Thereafter, the fifth cylinder  196  is actuated to retract the fifth rod  198  (see  FIG. 10 ). As a result, as shown in  FIG. 18 , the first finger  200  and the second finger  202  are spaced from each other, thereby releasing the joint boot  56 . 
     Then, the first motor  88  is energized again to lift the outer member  18  of the tripod constant velocity joint  16  along the first ball screw  90  in unison with the first outer member holder  66 . As the outer member  18  is lifted, the drive power transmitting shaft  12  is inserted further into the through hole  28 , thereby bringing the splines  34  on the drive power transmitting shaft  12  and the splines  48  on the inner wall of the through hole  28  into meshing engagement with each other. 
     Simultaneously, as shown fragmentarily at an enlarged scale in  FIG. 19 , as the diameter of the tapered progressively-smaller-diameter portion  36  becomes progressively smaller, the clip  54  is compressed toward the bottom of the first annular groove  50 , thereby reducing the diameter thereof. Thus, it is understood that the tapered progressively-smaller-diameter portion  36  functions as a guide for guiding the clip  54  into the through hole  28 , while at the same time reducing the diameter of the clip  54 . 
     When the drive power transmitting shaft  12  is inserted further, as shown in  FIG. 20 , the clip  54  becomes further reduced in diameter, so that the outside diameter thereof becomes substantially equal to the diameter of a constant-diameter portion of the through hole  28 . At this time, the drive power transmitting shaft  12  is not blocked by the clip  54 , which is reduced in diameter. Stated otherwise, the clip  54 , having been reduced in diameter, does not prevent the drive power transmitting shaft  12  from being inserted. 
     When the drive power transmitting shaft  12  is inserted further as the outer member  18  is further lifted, the first annular groove  50  and the second annular groove  52  become positionally aligned with each other, as shown in  FIGS. 21 and 22 . At this time, the clip  54  tends to be restored elastically to its original shape. As a result, the clip  54  engages simultaneously both in the first annular groove  50  and in the second annular groove  52 . The clip  54 , which engages both in the first annular groove  50  and in the second annular groove  52 , prevents the inner member  20  from becoming dislodged from the drive power transmitting shaft  12 . 
     In some cases, the clip  54  may not engage in the second annular groove  52 , and the distal end face of the drive power transmitting shaft  12  may abut against the bottom of the cup-shaped portion  22 . If this happens, the rotational drive power of the transmission is not appropriately transmitted to the drive power transmitting shaft  12 . Accordingly, the operator needs to be able to recognize that the drive power transmitting shaft  12  has been positioned by the clip  54 , which engages in the second annular groove  52 . 
     According to the present embodiment, as described above, the roller members  38   a  through  38   c  together with the inner member  20  are inserted up to the endpoint on the bottom of the cup-shaped portion  22 . Therefore, the inner member  20  is maintained in a constant position. 
     The end of the drive power transmitting shaft  12  is then inserted into the through hole  28  of the inner member  20 . When the drive power transmitting shaft  12  is positioned by the clip  54 , which engages both in the first annular groove  50  and in the second annular groove  52 , the drive power transmitting shaft  12  stops at a substantially constant position in all identical tripod constant velocity joints  16 . Stated otherwise, if a plurality of tripod constant velocity joints  16  are assembled, then the drive power transmitting shafts  12  are inserted into the cup-shaped portions  22  at substantially identical distances. 
     If the clip  54  does not engage in the second annular groove  52 , and the distal end face of the drive power transmitting shaft  12  abuts against the bottom of the cup-shaped portion  22 , then the distance by which the drive power transmitting shaft  12  is inserted is greater than the distance by which the drive power transmitting shaft  12  is inserted when it is positioned by the clip  54 , which engages both in the first annular groove  50  and in the second annular groove  52 . Therefore, the distance by which the drive power transmitting shaft  12  is inserted is determined, and if the determined distance is greater than it should be, the operator recognizes that the clip  54  has not engaged in the second annular groove  52 . Conversely, if the determined distance remains substantially constant, then the operator judges that the clip  54  has engaged in the second annular groove  52 . 
     The roller members  38   a  through  38   c  are positioned in the track grooves  26   a  through  26   c  at the endpoint on the bottom of the cup-shaped portion  22 , and then the end of the drive power transmitting shaft  12  is inserted into the through hole  28  of the inner member  20 , whereupon the distance by which the drive power transmitting shaft  12  is inserted is determined. It is then possible to determine with ease whether or not the clip  54  engages both in the first annular groove  50  and in the second annular groove  52 , and hence, whether the drive power transmitting shaft  12  has been coupled to the inner member  20  or not. 
     When the clip  54  engages both in the first annular groove  50  and in the second annular groove  52 , the joint boot  56  becomes compressed as shown in  FIG. 22 . Stated otherwise, pressure is applied to the joint boot  56 , and therefore, air is removed from the joint boot  56 . 
     More specifically, the rotational shaft of the first motor  88  together with the first ball screw  90  are rotated in a direction that is opposite to the direction in which they have been rotated thus far. As a result, as shown in  FIG. 23 , the outer member  18  that is held by the first outer member holder  66  is lowered, so that the inner member  20  is elevated relatively to be positioned at longitudinal middle portions of the track grooves  26   a  through  26   c.    
     Thereafter, the fifth cylinder  196  (see  FIGS. 9 and 10 ) is actuated in order to extend the fifth rod  198 , and to thereby close the first finger  200  and the second finger  202  for gripping the joint boot  56  (see  FIG. 23 ). The fourth cylinder  166  (see  FIG. 8 ) is actuated in order to extend the fourth rod  194  in the direction indicated by the arrow Y 2  in  FIGS. 8 and 24 . 
     As described above, the first finger  200  and the second finger  202  are disposed on the fourth bridge plate  190  (see  FIG. 8 ), which is displaced in the directions indicated by the arrows Y 1 , Y 2  in  FIGS. 6 ,  8 , and  24  upon extension of the fourth rod  194 . Therefore, as shown in FIG.  24 , the first finger  200  and the second finger  202  are displaced in the direction indicated by the arrow Y 2 . As a result, the joint boot  56  temporarily is released from the outer member  18 , whereupon air is removed from the joint boot  56 . 
     After the joint boot  56  has been bled in the foregoing manner, the fourth cylinder  166  (see  FIG. 8 ) is actuated again in order to retract the fourth rod  194  in the direction indicated by the arrow Y 1  in  FIGS. 8 and 25 . The joint boot  56  is mounted again on the cup-shaped portion  22  of the outer member  18 , thereby bringing assembly of the tripod constant velocity joint  16  to an end. In other words, the drive power transmitting mechanism  10  is produced. 
     After the joint boot  56  has been mounted on the cup-shaped portion  22  of the outer member  18 , the fifth cylinder  196  (see  FIGS. 9 and 10 ) is actuated in order to retract the fifth rod  198  and to open the first finger  200  and the second finger  202 , thereby releasing the joint boot  56  (see  FIG. 25 ). 
     Finally, as shown in  FIG. 26 , the operator manually operates the lever  288  of the clamp  282  in order to release the drive power transmitting shaft  12  from the pressing bar  290 . In addition, the operator releases the outer member  18  of the tripod constant velocity joint  16  and the outer member  74  of the Birfield constant velocity joint  14  from the first outer member holder  66  and the second outer member holder  80 , respectively, so that the drive power transmitting mechanism  10  can be removed from the assembly apparatus  60 . 
     According to the present embodiment, as described above, the drive power transmitting shaft  12  can be coupled to the inner member  20 , which has been housed in advance in the cup-shaped portion  22  of the outer member  18 , since, as described above, the tapered progressively-smaller-diameter portion  36 , which is defined in the opening of the through hole  28  of the inner member  20 , functions as a shrinker for reducing the diameter of the clip  54 . The tripod constant velocity joint  16  having the above construction can automatically be assembled by the assembly apparatus  60 , rather than being manually assembled by an operator. 
     Consequently, the number of tedious and time-consuming manual steps is reduced. Furthermore, since the assembly apparatus  60  reduces the time required until the drive power transmitting shaft  12  is inserted into the cup-shaped portion  22  and becomes coupled to the inner member  20 , assembly efficiency is increased. In other words, productivity of the tripod constant velocity joint  16  can be increased. 
     The present invention is not limited to the above embodiment, but various changes may be made to the embodiment without departing from the scope of the present invention. 
     For example, the engaging member that engages in the first annular groove  50  and the second annular groove  52  is not limited to a substantially C-shaped clip  54 , but may be an elastic member, which is capable of being reduced in diameter by the tapered progressively-smaller-diameter portion  36  in the opening of the through hole  28 , and which can be restored to its original shape when the first annular groove  50  and the second annular groove  52  are positionally aligned with each other. The clip  54  is not limited in particular to having an inner diameter D, which is greater than the distance from the center of the drive power transmitting shaft  12  to the bottom of the first annular groove  50 . 
     The trunnions  32   a  through  32   c  may be of a simple cylindrical shape, and the rolling members may be balls or the like. 
     In the above embodiment, the tripod constant velocity joint  16  is installed after installation of the Birfield constant velocity joint  14 . However, tripod constant velocity joints  16  may be installed on both ends of the drive power transmitting shaft  12 . In this case, after one of the tripod constant velocity joints  16  has been installed on one end of the drive power transmitting shaft  12 , the shank  24  of the outer member  18  of the installed tripod constant velocity joint  16  is inserted into the second outer member holder  80 , and then, in accordance with the procedure described above, the other tripod constant velocity joint  16  may be installed on the remaining other end of the drive power transmitting shaft  12 . 
     Furthermore, the drive power transmitting shaft  12  may be displaced with respect to the outer member  18 , instead of displacing the second outer member holder  80 , or stated otherwise, instead of displacing the outer member  18  of the tripod constant velocity joint  16 .