Patent ID: 7562599

Claim:
A ball screw assembly comprising: a screw shaft, a nut, a plurality of balls and a plurality of cassettes, the nut is screwed on the screw shaft, the cassette is inserted in the nut and is fixed therein, the balls are sequentially filled in a helical groove of the screw shaft, so that the cassette can enable the balls to circulate endlessly, the ball screw assembly is characterized in that: the helical groove is formed in an outer surface of the screw shaft without extending to an end surface of a shoulder portion of the screw shaft, and an escape portion is formed in the screw shaft in the form of a slot extending in an axial direction of the screw shaft, with one end of the escape portion connected to one end of the helical groove of the screw shaft, and the other end of the escape portion doesn't extend to the end of the shoulder portion of the screw shaft; and the cassette has a protruding tongue portion sized just large enough to be engaged in the escape portion, the tongue portion of the cassette is screwed in the helical groove along with the cassette which is inserted in the nut; wherein a depth of the escape portion approximately equals a width of the helical groove, and a length of the tongue portion approximately equals a width of the escape portion.