US 6,202,536 B1 · Pneumatic reciprocatory actuator and method of operating it

Abstract

In a pneumatic reciprocating actuator of the kind comprising a cylinder which defines a forward-motion chamber and a return-motion chamber, and a piston which is reciprocal in the cylinder and separates the forward-motion chamber and the return-motion chamber, a start stroke forwardly is initiated by admission of gaseous operating fluid from an inlet port in to the foreword-motion chamber with both the forward-motion chamber and the return-motion chamber initially at zero pressure. The operating fluid is also passed from the inlet port into the return-motion chamber during the start stroke until a back pressure of a predetermined magnitude has been produced in the return-motion chamber. Then the return-motion chamber is automatically closed by a pressure control valve unit, whereby the return-motion chamber will form a cushioning chamber for cushioning the movement of the piston in the forward direction, thereby preventing piston over speeding during the start stroke.

Claims9

Dependent claims

A method of operating a pneumatic reciprocatory actuator (1-3) of the kind comprising a cylinder (1) which defines a forward-motion chamber (5) and a return-motion chamber (7), and a piston (2) which is reciprocable in the cylinder (1) and separates the forward-motion chamber (5) and the return-motion chamber (7), in which a start stroke in a direction to expand the forward-motion chamber is initiated by admission of a gaseous operating fluid from an inlet port (4) into the forward-motion chamber with both the forward-motion chamber (5) and the return-motion chamber (7) initially at substantially zero pressure, characterised by

also admitting the operating fluid from the inlet port (4) into the return-motion chamber (7) during the start stroke until a back pressure of a predetermined magnitude has been produced in the return-motion chamber (7), and
then closing the return-motion chamber (7), whereby the return-motion chamber (7) will form a cushioning chamber for cushioning the movement of the piston (2), thereby preventing piston overspeeding during the start stroke,
the admission of the operating fluid from the inlet port (4) into the return-motion chamber (7) being effected through a pressure control valve device (20, 21) adapted to close a flow passage (28, 29, 31) between the inlet port (4) and the return-motion chamber (7) in response to the pressure in the return-motion chamber (7) reaching the predetermined magnitude.

A pneumatic actuator comprising

a cylinder (1) having an inlet port (4) for operating fluid and defining a forward-motion chamber (5) and a return-motion chamber (7),
a piston (2) which is reciprocable in the cylinder and separates the forward-motion chamber (5) and the return-motion chamber (7), and
a valve device (V, 20, 21) controlling flow of operating fluid into and out of the forward-motion chamber (5) through a first fluid passage (V1,V2) extending between the inlet port (4) and the forward-motion chamber,
characterised
in that the valve device (V, 20, 21) includes a pressure control valve unit (20, 21) which is disposed in a second flow passage (28,29,31) extending between the inlet port (4) and the return-motion chamber (7) and openable in response to the application to the inlet port (4) of a predetermined first pressure to pass operating fluid from the inlet port (4) to the return-motion chamber and closable in response to pressurisation of the return-motion chamber (7) by a predetermined second pressure lower than the first pressure to block flow of operating fluid from the return-motion chamber (7), and
in that the pressure control valve unit (21, 20) includes
a first valve (21) having a first valve member (25), a first valve seat associated therewith, and a spring (26) biassing the first valve member (25) to a closed position in sealing engagement with the second valve seat, said first valve member (25) being displaceable by said predetermined first pressure to an open position against the spring bias,
a second valve (20) including a second valve member (22), a second valve seat associated therewith, and a spring (23) biassing the second valve member (22) to a closed position in sealing engagement with the second valve seat, and
a valve operating member (24) for keeping the second valve member (22) in an open position by means of the first valve member (26) when the first valve member is in the closed position and allowing the second valve member (22) to move to the closed position in response to the first valve member (25) becoming displaced to the open position.

6 more elements

Dependencies are inferred from the claim text.

Pneumatic reciprocatory actuator and method of operating it

Life of this patent

Pneumatic reciprocatory actuator and method of operating it

Life of this patent

Abstract

Claims9