Ball screw

Claim 1

A drive transmitting mechanism for converting rotary motion into translatory movement comprising, a screw threaded shaft, an internally threaded hollow sleeve member surrounding said shaft and having opposed flat ends, the threads of said shaft and sleeve having the same pitch whereby they define a helical passage between said sleeve and shaft, a plurality of balls of substantially the same diameter located in said passage, and said passage having opposite ends respectively located adjacent the opposed ends of said sleeve; a single pair of identically shaped one piece molded end plates respectively secured to said opposed ends of said sleeve having a central bore receiving said shaft; and means for transferring said balls between said opposite ends of said helical passage, said means consisting of a longitudinal bore extending through the sleeve parallel to said shaft between said opposed ends of the sleeve and having a diameter greater than that of said balls and said end plates having substantially flat end surfaces facing respectively toward and mating with their associated flat end of the sleeve, each of said flat end surfaces of the end plates facing said sleeve having an arcuate recess formed therein consisting of a counter bore coaxial with and extending radially outwardly over only a part of the periphery of said central bore and a groove opening towards the adjacent flat end face of the sleeve and having an inner end which communicates with and is tangential to said arcuate recess and an opposite outer end which communicates with the end of said sleeve bore in the adjacent end of the the sleeve; said arcuate recess having a radial depth greater than the radius of the balls and an axial width greater than the diameter of the balls; said groove in said end plates having a greater cross section than the cross section of said balls to allow said balls to pass therethrough.