US PATENT SUBCLASS 166 / 319
.~ Fluid operated

Current as of: June, 1999
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166 /   HD   WELLS

316  DF  VALVES, CLOSURES OR CHANGEABLE RESTRICTORS {5}
319.~ Fluid operated {4}
320  DF  .~.~> Variably opened
321  DF  .~.~> Fluid pressure biased to open position position {3}
325  DF  .~.~> One way, e.g., check valve type {2}
329  DF  .~.~> Loose ball closure with limited reverse flow

DEFINITION

Classification: 166/319

(under subclass 316) Devices wherein the valve is actuated in response to fluid pressure or fluid flow. The operating fluid may be derived from a source externally of the valve or it may be the fluid which flows through the valve.