Abstract: A rotary actuator for a damper shaft controls the angular position of the damper shaft in accordance with variations in fluid pressure inside of the actuator. The actuator includes a housing, a flexible diaphragm within the housing separating it into a fluid-tight compartment and a second compartment open to the atmosphere. The fluid-tight compartment is provided with a fluid pressure receving port open to a control source of variable pressure. The piston and piston rod are slidably mounted in the second compartment in contact with the diaphragm. The piston rod includes a longitudinally extending rack, and a crank arm rotatably mounted in the housing has a gear segment in meshing relationship with the rack. The actuator shaft to be controlled extends through the housing and is mounted in the crank arm to support the rotary actuator, and the rotary actuator is clipped to an air conditioning duct to prevent it from rotating on the damper actuator shaft axis.

Abstract: A flat, elongate, laminated plate of ceramic piezoelectric material is fixedly mounted on one end to permit movement of the other end responsive to the application of a variable electronic control signal to electrodes on the outer surfaces of the laminated plate. The movement and force applied by the movable end of the plate controls the release of air pressure from the pressure chamber so that the pressure in the chamber varies in response to the variations of the electronic control signal.