Patent ID: 7163194

Claim:
An actuator operated by fluid under pressure for selectively positioning a rotor of a rotary valve in any one of at least three positions, the actuator comprising: a carriage adapted for connection to a rotor of a rotary valve, the carriage comprising a first piston disposed in a first cylinder for providing a range of motion to rotate the rotor between a first position and a second position in response to fluid pressure within the first cylinder, wherein the first piston comprises opposed surfaces exposed to respective fluid pressures in a first portion and a second portion of the first cylinder to move the first piston respectively toward the first position and toward the second position; and a stop selectively moveable from a withdrawn position to an extended position to restrict the range of motion of the carriage when the stop is in its extended position to provide a third position of the rotor intermediate the first position and the second position, wherein the stop is connected to a second piston disposed within a second cylinder to move the stop in response to fluid pressure within the second cylinder; a compressed air supply; a normally open solenoid valve connected between the compressed air supply and the first portion of the first cylinder; a first normally closed solenoid valve connected between the compressed air supply and the second portion of the first cylinder; a second normally closed solenoid valve connected between the compressed air supply and the second cylinder; a first electrical supply connected to both the normally open solenoid valve and the first normally closed solenoid valve; and a second electrical supply connected to the second normally closed solenoid valve.