| 摘要 |
<p>A double-acting closure valve for use in a coaxial flow system consists of an inner pipe having an inner wall surface including surface portions which are profiled so as to provide a pair of inner valve seats spaced apart axially from one another, an inner body disposed coaxially within the inner pipe and having associated therewith a pair of inner valve closure members movable generally axially so as to abut the inner valve seats and an outer pipe coaxial with the inner pipe and having an inner wall surface including surface portions which are profiled so as to provide a pair of outer valve seats spaced apart axially from one another, an outer wall surface of the inner pipe also including surface portions each of which is profiled to enable one of a pair of outer valve closure members associated therewith to move generally axially so as to abut an outer valve seat. On abutment of the inner and outer valve closure members with respective inner and outer valve seats each of the coaxial passages defined by the inner and outer coaxial pipes is double closed since it is shut off at each of two positions spaced apart axially from one another. In a preferred embodiment a controlled fluid pressure may act upon the valve closure members in such a way that they are actuated in the event of fracture of the pipes or fluid control conduits.</p> |
