Linear motion ball bearing unit

A linear motion ball bearing unit including a bearing assembly reciprocatingly movable along a track shaft through rolling ball bearings and having a casing, a cylindrical race sleeve fitted in said casing, end lids and a retainer, characterized in that:

• said casing being formed substantially in a rectangular shape and having a tunnel-like axial cavity open on the bottom side thereof;
• said race sleeve having the outer periphery thereof formed in conformity with the inner periphery of said tunnel-like cavity of said casing and provided on the inner periphery thereof with U-shaped axial channels at symmetrical positions on opposite sides of and at an angle of about 60.degree. with a vertical line through the longitudinal axis thereof, said U-shaped channels each having a pair of concave longitudinal load carrying ball raceways substantially of the same curvature as said ball bearings, and on the outer periphery thereof with U-shaped non-load carrying ball grooves of a depth slightly larger than the diameter of said ball, said sleeve further having on the inner periphery thereof a number of longitudinal grooves for location of said retainer;
• said retainer having generally arcuate wall portions, longitudinal ribs in alignment with said locating grooves of said sleeve and trapezoidally folded side wall portions each with an arcuate top wall and a pair of slits formed in the opposing side walls in a width slightly smaller than the diameter of said balls, each slit having guide tongues integrally formed at the opposite ends thereof;
• said end lids being fixedly attached to opposite end faces of said race sleeve and each being provided with a U-shaped turn groove continuously to a load carrying ball raceway and a non-load carrying ball groove of said sleeve;
• the bearing assembly constituted by said sleeve and said retainer having the respective load-carrying and non-load carrying ball grooves filled with a plural number of ball bearings and mounted on said track shaft with longitudinal raceway grooves substantially of the same curvature as said ball bearings.