| 摘要 |
PROBLEM TO BE SOLVED: To implement smooth linear reciprocating movement of a nut member by rotations of a screw shaft, without forming a ball returning passage, when a linear moving distance of the nut member is short. SOLUTION: A ball screw has a lot of balls B interposed between a screw groove 11 of a screw shaft 1 and nut member 2. Tubular retainers 3, for retaining the balls 13 so that the balls 13 penetrate to the inside and the outside and are prevented from coming off to the outside, are interposed between the nut member 2 and the screw shaft 1. The screw shaft 1 is set to be longer than the moving distance of the nut member 2.
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