Apparatus for preventing urging rotation of a ball screw shaft for a linear working machine

An apparatus for preventing rotation of a ball screw shaft in a linear working machine including a driving motor, a ball screw shaft made to rotate in either a clockwise or counterclockwise direction by said driving motor, a ball nut reciprocating along said ball screw shaft, and an output shaft attached to said ball nut and linearly moving to-and-fro with respect to a housing of said linear working machine, wherein said apparatus for preventing rotation of a ball screw shaft comprises:

• a compressive force receptive rotation member loosely fitted around a base end portion of said ball screw shaft;
• a tensile force receptive rotation member loosely fitted around said base end portion of said ball screw shaft;
• a shaft compressive step portion, formed at said base end portion of said ball screw shaft, for pressing against said compressive force receptive rotation member when a compressive force is exerted on said ball screw shaft;
• a shaft tractive step portion means, fixed on said base end portion of said ball screw shaft, for pressing against said tensile force receptive rotation member when a tensile force is exerted on said ball screw shaft;
• a thrust bearing interposed between said compressive force receptive rotation member and said tensile force receptive rotation member;
• a compressive force stopper means, mounted on said housing, for receiving said tensile force receptive rotation member pressed, through said compressive force receptive rotation member and said thrust bearing, by said shaft compressive step portion when said compressive force is exerted on said ball screw shaft;
• a tensile force stopper means, mounted on said housing and being operative for preventing axial movement of said compressive force receptive rotation member when pressed, through said tensile force receptive rotation member and said thrust bearing, by said shaft tractive step portion when said tensile force is exerted on said ball screw shaft;
• a collar fixed to said housing interposed between said compressive force receptive rotation member and said tensile force stopper so that said compressive force receptive rotation member is not pressed against said tensile force stopper means, and a coil spring tightly mounted on the outer periphery of said compressive force receptive rotation member and said tensile force receptive rotation member, wherein when an external axial force, applied to said output shaft in an axial direction thereof, is exerted, through said ball nut, on said ball screw shaft so that a rotary force is generated in the clockwise or counterclockwise direction at said ball screw shaft, either of said compressive force receptive rotation member or said tensile force receptive rotation
• member rotates, thereby tightening said coil spring and restraining said ball screw shaft against axial movement.