{HEAD ~ An apparatus} 4, wherein {TAIL ~ said pocket inner surface} of said retainer is formed into 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 
wherein
{ HEAD ~ An apparatus } 4 , wherein { TAIL ~ said pocket inner surface } of said retainer is formed into 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
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL TAIL TAIL 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 OTH OTH OTH OTH OTH OTH OTH OTH