Patent ID: 8056466

Claim:
A pneumatic actuator, comprising: an actuator body closed by head flanges and defining a chamber; two pistons housed in said chamber and moving in parallel in opposite directions powered by a fluid under pressure to move said pistons away from or towards each other; and an output shaft rotatably supported in said body, connectable to the shutter member of a valve to be operated and actuated to turn by said two pistons through means of transforming a rectilinear movement into rotary motion, wherein two adjusting screws are mounted on the head flanges of the actuator body, one for each flange, in a position to intercept and stop the pistons when said pistons move away from each other, wherein from at least one side of the body of the actuator an adjusting device is provided which includes stop means at a variable distance from each other, in a direction parallel to the movement of the pistons and each associated with a piston, said stop means being in a position to intercept said pistons for a restriction controlled by approach stroke of said pistons, wherein the adjusting device comprises a supporting element fixed to the actuator body and forming a housing open towards the inside of said body, an adjusting screw supported by said housing parallel to the movement direction of the pistons with only the possibility to turn, and having a right-threaded and a left-threaded section, and in which said stop means comprises two blocks respectively conjugated with the right-hand threading section and the left-hand threading section of the threading of the adjusting screw, moveable in parallel in opposite directions to vary a distance between said blocks in response to the rotation of said screw and designed to intercept the tailpieces of said pistons.