| 摘要 |
<p>A double-block and vent valve having an improved actuator mechanism to allow one part of a composite valve member to be lifted separately from another. The actuator mechanism overlies the valve housing and is connected to the two valve member parts via coaxial rod and tube members. Hold-down cams normally block the upward movement of the tube member to positively lock the upper valve member part against its seat when it is desired to lift only the lower valve member part. A pair of pivotal cams are spring-biased to this blocking position where they bear against lug means carried by the tube member. A small, horizontal, fluid-actuated cylinder pivots the hold-down cams to a non-interfering position whenever it is desired to lift only the upper valve member part or to lift the composite valve member.</p> |
