Abstract: A fluid-pressure operated actuator has a body and an end cap which when telescoped in the body provides confronting grooves which receive a circlip in the form of a flexible length of wire spring. The end cap carries an O-ring seal axially only outwards of the circlip. Relative rotation between the body and end cap draws the circlip into position. A threaded plug, which may be secured to the outer end of the circlip, sealingly connects the body and end cap and may permit relative axial and angular movement.

Abstract: A fluid-pressure-operated actuator is arranged to have three set positions and preferably a fail-safe characteristic in one of the three positions. In one embodiment an H-section piston moves in an actuator body and is set in its two extreme positions by fluid pressure introduced behind the web of the piston through one or other of spindles having heads and bores. To set the intermediate position, annular pistons can be moved along the spindles by pressure introduced at inlet pipes in the body until those pistons contact the heads of the spindles. The spindles are adjustable in the body to set the intermediate position of the piston and adjusting bolts set the extreme positions of the piston. For a fail-safe situation, a reservoir and control valve are introduced. As an alternative to annular pistons springs acting through top-hat shaped buffers can be used giving a fail-safe situation in the intermediate position of the piston.

Abstract: A fluid-pressure operated actuator comprises a housing, at least one piston reciprocable in the housing, a rotatable output shaft having a portion thereof within the housing, means operatively connecting the piston and the output shaft, and stop means mounted on the housing and engageable with the shaft portion for limiting rotary movement of the shaft.