Abstract: Disclosed is a pneumatic actuator which includes a housing comprised of two halves and having at least two passages defined therethrough, including a “loop” groove defined in an inner peripheral wall of the housing into which a seal member is inserted. A rotary piston is rotatably received in the housing. The piston has a top and a bottom with an intermediate wall connected there between, and an actuating shaft extending through the housing, which is rotated by movement of the rotary piston. The seal member extends into the housing and is in contact with the top and bottom of the rotary piston all the times. The rotary piston moves free of contact with the interior surface of the housing and this one seal member provides a seal for the joint created between the halves of the housing, the chambers of the housing as well as the actuating shaft. Movement of the piston is effected by air pressure and return motion of the piston can be air driven or spring assisted.

Abstract: Disclosed is a pneumatic actuator which includes a housing comprised of two halves and having at least two passages defined therethrough, including a “loop” groove defined in an inner peripheral wall of the housing into which a seal member is inserted. A rotary piston is rotatably received in the housing. The piston has a top and a bottom with an intermediate wall connected there between, and an actuating shaft extending through the housing, which is rotated by movement of the rotary piston. The seal member extends into the housing and is in contact with the top and bottom of the rotary piston all the times. The rotary piston moves free of contact with the interior surface of the housing and this one seal member provides a seal for the joint created between the halves of the housing, the chambers of the housing as well as the actuating shaft. Movement of the piston is effected by air pressure and return motion of the piston can be air driven or spring assisted.