| 摘要 |
A fluid-pressure operated mechanism such as a clutch has a radial wall (14) with a fluid-receiving and exhausting chamber (34) therein. The clutch is of the hydraulic-apply, spring-release type, fluid pressure being supplied to engage the clutch by means of a piston (36) and fluid pressure being exhausted to release the clutch under the action of springs (40). Fluid pressure release is often not rapid enough to enable quick release of the clutch and a relief valve (44) of the centrifugal type is provided to accelerate fluid release. The improvement resides in a spring (66) in combination with the centrifugal valve to prevent operation of that valve during rotation of the clutch at speeds below a predetermined value, whereby to prevent complete dumping of fluid, so as to enable the released clutch to retain a volume of fluid consistent with rapid re-engagement of the clutch when fluid pressure is applied.
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