An apparatus 4, wherein {HEAD ~ said pocket inner surface} of said retainer is formed into {TAIL ~ a shape} which substantially coincides with the shape of the ball in contact with said pocket inner surface at the major axis position of said cam 
is formed into
An apparatus 4 , wherein { HEAD ~ said pocket inner surface } of said retainer is formed into { TAIL ~ a shape } which substantially coincides with the shape of the ball in contact with said pocket inner surface at the major axis position of said cam
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH