Rotary Actuators

Rotary actuators produce oscillating power by rotating an output shaft through a fixed arc. They are compact, simple, and efficient. They produce high instantaneous torque in either direction and require only a small space and simple mountings. use fluid pressure to drive a piston connected to a gear rack, which rotates a pinion. Standard units are available with rotation of 90, 180, or 360°. They can be obtained with two parallel piston-rack units to double output torque. Outputs to 35 million lb-in. are available. consist of a shaft mounted in a cylindrical housing, with one or more vanes attached to the shaft. Applying fluid pressure to the vanes produces shaft rotation. An internal barrier between housing OD and shaft divides interior volume into two chambers. For this reason, single-vane actuators are normally limited to about 280° of rotation, and double-vane actuators to about 100°. Torque is directly proportional to vane area and effective fluid pressure. Vane actuators have torque outputs as high as 500,000 lb-in. have helical grooves in the piston rod that convert linear to rotary motion. Helical actuators are available with standard rotations varying from 100 to 370° with outputs to 15,000 lb-in. A relatively new actuator gaining wide acceptance uses double helical gearing. This design features two moving parts: the piston sleeve, which reciprocates and rotates; and the output shaft, which only rotates. As the piston sleeve reciprocates in helical actuators, the outer spline engages the ring gear and causes sleeve rotation. At the same time, the inner spline engages another set of helical teeth on the output shaft. This causes relative shaft rotation in addition to that of the piston sleeve. increase helix angle and reduce actuator length by replacing sliding action with rolling action. Planetary rollers on the piston between the helical shaft and housing grooves