Pneumatic actuator

A double-acting, piston driven actuator for providing a double action rotary powered output, comprising:

• an actuator housing defining a stepped bore, the stepped bore defining a larger diameter bore and a smaller diameter bore;
• a double acting piston reciprocally inserted within the stepped bore, the double acting piston having a larger diameter end and a smaller diameter end for matching slidable engagement within the respective larger diameter bore and smaller diameter bore;
• a pressurized fluid delivery system having a first passage communicating with the larger diameter end of the stepped bore and a second passage communicating with the smaller end of the stepped bore;
• a first end of each of said first and second pressure passages communicating with a constant pressurized fluid source supplying an equal pressure thereto;
• a three way valve positioned in the first passage between the first end and stepped bore, the valve being controlled by a solenoid and having a first position wherein pressurized fluid supplied to the first end of the first passage is supplied to the larger diameter bore, and a second position wherein the larger diameter bore is exhausted to the atmosphere;
• the pressurized fluid delivery system provides the fluid from the source continuously to the smaller diameter portion of the bore;
• and
• a safety mechanism having a spring biased second piston for biasing the double acting piston to a safe position upon failure of the pressurized fluid delivery system.