| 摘要 |
<p>A rotary or linear valve actuator comprises a cylinder (1), a piston (6, 7) movable in the cylinder (1), a valve actuating member (9) actuable by the piston (6, 7) and means for supplying pressurised fluide, for example a hydraulic fluid, to the cylinder (1) for moving the piston (6, 7) in the cylinder. The pressurised fluid-supplying means includes a pressure intensifier (13) driven by a pressurised medium, for example compressed air, at a first pressure and arranged to deliver said pressurised fluid to the cylinder (1) of the actuator at a pressure higher than that of said pressurised medium. The pressure intensifier (13) conveniently comprises a first double-acting piston and cylinder assembly having a first piston (17) which is mechanically connected to a second piston (16) of a second double-acting piston and cylinder assembly, the second piston (16) having an area which is smaller than the area of the first piston (17) and the cylinders (15, 14) of the two piston and cylinder assemblies having their axes aligned with one another, and means (34-38) for supplying pressurised medium atsaid first pressure to the first piston and cylinder assembly for the purpose of reciprocating the first piston (17) in its cylinder (15). The second piston and cylinder assembly then constitutes the means for supplying pressurised fluid at said higher pressure to the actuator cylinder (1).</p> |
