Ball-threaded shaft anti-slipout type linear actuator

Abstract

To prevent a ball-threaded shaft from slipping out of a linear actuator, a linear actuator 10 has an output shaft 18 threaded in a nut 16 for moving forward and backward linearly with respect to an outer tube 22 secured to a housing 20. Linear reciprocating movement of the nut 16 is effected by a ball-threaded shaft 14 rotated normally and reversely by a driving motor 12. The shaft is held against axial displacement by a bearing assembly 8 having an axial disk 32 secured to a proximal end 24 of the ball-threaded shaft 14. On the nut side of the disk within the assembly are disposed a first tension receiving rotational body 36, a thrust bearing 45 and a second tension receiving rotational body 58. The assembly 8 is retained by a tension stopper 62 spread and inserted into an annular central groove 60 in the tube 22. The second tension receiving rotational body 58 is formed with a reduced diameter preventing circumferential surface 66 corresponding to an inner peripheral circumferential surface of the C-shaped tension stopper 62. Even if tension and a rotating force are exerted on the tension stopper 62, causing it to be reduced in diameter, the inner peripheral surface thereof comes into contact with the reduced diameter preventing surface 66.