US PATENT SUBCLASS 166 / 323
.~.~.~ Locked open or closed

Current as of: June, 1999
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166 /   HD   WELLS

316  DF  VALVES, CLOSURES OR CHANGEABLE RESTRICTORS {5}
319  DF  .~ Fluid operated {4}
321  DF  .~.~ Fluid pressure biased to open position position {3}
323.~.~.~ Locked open or closed

DEFINITION

Classification: 166/323

(under subclass 321) Devices in which the valve element is positively locked in open or closed position to provide flow therethrough in both directions or to prevent flow therethrough in either direction.