US PATENT SUBCLASS 251 / 196
.~.~.~ In both closed and open positions

Current as of: June, 1999
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251 /   HD   VALVES AND VALVE ACTUATION

157  DF  WITH MEANS TO INCREASE HEAD AND SEAT CONTACT PRESSURE {8}
193  DF  .~ Gate valve {3}
195  DF  .~.~ Bifaced {4}
196.~.~.~ In both closed and open positions

DEFINITION

Classification: 251/196

(under subclass 195) Devices the valve head having also a flow passage the boundary of which is expanded when the valve is in open position.