To reduce the weight of an auxiliary leg, costs, and labor by providing a mechanism being elevated or lowered at high speed, releasing the engagement of a female screw with a male screw at low-load application, by means of a pulley and a belt provided on a driving shaft and capable of obtaining thrust bearable to a load, restoring the engagement of the female screw with the male screw at load application.
Rotating a driving shaft 1 by means of a motor rotates a male screw 8 through bevel gears 2, 3 to elevate or lower an engaging female screw 6, and to additionally elevate or lower an stretching part 9 connected to the female screw 6. Where, a belt 5 is freely rotated. Now, exciting a solenoid housed in the female screw 6 opens right and left moving parts on the female screw 6 to release the engagement of the screws. Incidentally, the belt 5 is fixed to the female screw 6 with the aid of the groove of a guide pin at its terminal, resulting in rapid elevation or lowering. In lowering, grounding actuates a sensor 10 to release excitation, engaging the male screw 8 with the female screw 6. Thus, the belt 5 is released to yield thrust bearable to a load. On elevation, a sensor 11 releases the excitation to stop the motor.
SATO YASUHIRO
TSUDA TEIZO
