Fluid cylinder having self-locking means

Claim 1

A fluid pressure operated actuator comprising: a tubular housing having an internal bore enclosed at its opposite ends; piston means axially reciprocally disposed in said tubular housing bore and dividing said bore into two pressure chambers; means for communicating pressure fluid to one of said pressure chambers while exhausting the other of said pressure chambers to move said piston means in one direction in said tubular housing bore; an actuating rod carried by said piston means and extending from one side of said piston means through one enclosed end of said tubular housing; a member extending from the opposite side of said piston means and rotatably supported in the other enclosed end of said tubular housing, said member having a threaded portion engaging a mating threaded portion carried by said actuating rod, the engaging threaded portion carried by said actuating rod and the threaded portion of said member being in a self-locking relationship such that said piston means is axially movable only when said one pressure chamber is communicated to said pressure fluid and said member is rotated relative to said piston means; non-locking means operable upon actuation for rotating said member relative to said piston means, said non-locking means being carried by said other enclosed end of said tubular housing; and means coupling said non-locking means to said member such that said non-locking means and said member are rotatable together after a limited amount of independent rotational movement of said non-locking means relative to said member, said non-locking means being coupled to said member in such a manner that said non-locking means does not restrain said member from rotating relative to said piston means whereby the rate of movement of said piston means is controlled by the rate of rotational movement of said member and the force exerted by said piston means and movement thereof is a function of the pressure in said chambers.