ROTARY ACTUATOR

The present invention relates to a rotary actuator and, more specifically, to a rotary actuator. An external tube, an axle load, and a piston are coupled together. An external tube or an axle load is rotated for a forward and backward movement of the piston. A ball bearing, a medium for converting the forward and backward movement into a rotary movement, does not follow a hemispheric groove but rotates in a fixed position. Thereby a planar pressure and friction force increases to rotate a weight body having heavy load. The rotary actuator according to the present invention forms a spiral hemispheric groove only on the outer circumference of the piston. Therefore, the manufacture is easier than a traditional one. Since the ball bearing does not move along the hemispheric groove, a high planar pressure or friction force contributes to rotating a weight body having heavier loads.