Abstract: A pneumatic rotary actuator includes a housing formed of a front shell and a rear shell, a shaft tube inserted through the housing, a piston fixedly mounted on the shaft tube and dividing the inside space of the housing into a front air chamber and a rear air chamber, a rotary member provided around the shaft tube and defining an air gap around the shaft tube in communication with the rear air chamber, an inner race mounted around the rotary member, a locknut fastened to the rotary member to lock the inner race to the rotary member, and a locating frame supported on a bearing around the inner race and having a first air inlet for guiding compressed air to the front air chamber through a first air passageway to move the piston and the shaft tube backwards and to further force a chucking head to grip the workpiece and a second air inlet for guiding compressed air into the rear air chamber to move the piston and the shaft tube forwards and to further release the chucking head from the workpiece.

Abstract: A jaw assembly used with the rotary driving member of an air cylinder to process a workpiece, including a casing having a center through hole into which the rotary driving member of the air cylinder is inserted, a springy jaw holder covered on the casing, the springy jaw holder having two springy thinner areas and a rigid thicker area concentrically arranged around a center through hole thereof, a plurality of jaws and a pair of rails radially provided at an outer side, and a T-block moved in between the rails and fixed at the desired location to hold the jaws on the jaw holder, a socket mounted in between the casing and the springy jaw and coupled to the rotary driving member of the air cylinder, a plurality of counterweights mounted around the socket and connected between the casing and the jaw holder, the counterweights each having a plurality of through holes, and a plurality of axle bushes respectively mounted in the through holes at the counterweights and connected between the casing and the jaw holder