Recirculating ball bearing spline joint

A unit of a ball spline and a shaft with a polygonal cross section, the ball spline including an outer sleeve, a pair of holders, and a desired number of balls, the outer sleeve formed with first axially extending parallel ball grooves facing each other, second axially extending parallel ball grooves spaced circumferentially around the inner peripheral surface of the outer sleeve a distance away from the first ball grooves, and escape portions and clip receiving grooves formed in the opposite end portions of the outer sleeve for connecting the first and second ball grooves, the holder each having its inner surface including a center vertical surface, upper and lower vertical surfaces, and slant surfaces connecting the center vertical surface to the upper vertical surface and the center vertical surface to the lower vertical surface, each of the holders having its outer surface including a center curved surface with the same curvature as the first ball groove bottom of the outer sleeve, upper and lower curved surface, intermediate curved surfaces with the same curvature as the land surface of the outer sleeve, slant surfaces connecting the upper curved surface to the intermediate curved surface and the lower curved surface to the intermediate curved surface, and slant surfaces formed in the upper and lower portions of the holder, each of the holders formed with endless ball circulating recesses in the portions corresponding to the first and second ball grooves and the escape portions formed in the inner peripheral surface of the outer sleeve, and the endless ball circulating recesses formed with elongated holes, the balls charged between the outer sleeve and the holders, and clips 41 fitted in the grooves;

• and the shaft formed with four ball-circulating grooves in the opposite sides of its opposite two sides and inserted in the ball spline.