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A piston-in-cylinder type pneumatic actuator is provided with an automatic cushioning facility to prevent the piston from returning to its fully retracted position at velocities exceeding a predetermined maximum velocity. Integrally-housed in the actuator is a velocity transducer arranged to sense t

A piston-in-cylinder type pneumatic actuator is provided with an automatic cushioning facility to prevent the piston from returning to its fully retracted position at velocities exceeding a predetermined maximum velocity. Integrally-housed in the actuator is a velocity transducer arranged to sense the pressure in a cylinder working volume, which pressure is related to the piston velocity and is used to control the operation of an exhaust valve operable to vary the rate of flow of gas from the cylinder thereby to vary the rate of return of the piston.

대표청구항 ▼

An actuator comprising a cylinder and a piston within said cylinder, a wall of said cylinder being stepped to define a region of reduced cross-section at one end of the cylinder, said piston also being stepped to define a boss provided at one end adjacent said region of reduced cross-section to be d

An actuator comprising a cylinder and a piston within said cylinder, a wall of said cylinder being stepped to define a region of reduced cross-section at one end of the cylinder, said piston also being stepped to define a boss provided at one end adjacent said region of reduced cross-section to be disposed within said region at one extremity of its range of possible movement within the cylinder, a first working chamber defined in said cylinder in said region, an inlet and exhaust passage in said chamber, an orifice in said passage and in communication with said first working chamber, and a pressure relief valve mounted in said passage and operable to control the size of said orifice so that upon a predetermined pressure being produced in said first working chamber said orifice has a fixed cross-sectional orifice exhausting said first working chamber whereby upon said predetermined pressure being produced the pressure in said first working chamber is dependant upon the velocity of said piston in said first working chamber, a second working chamber defined in said cylinder and separated and sealed from said first working chamber by said piston boss when said boss is located in said region to act as a cushion volume to limit the piston velocity, an exhaust passage in communication with said second working chamber, an exhaust valve in said exhaust passage, biasing means biasing said exhaust valve towards an open position, an outlet orifice in said exhaust passage closable by the exhaust valve, and a connecting passage communicating pressure from said first working chamber to said exhaust valve to operate said valve against the action of said biasing means and close said outlet orifice upon a predetermined pressure being produced in said first working chamber.