US PATENT SUBCLASS 251 / 158
.~ With positive reduction

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}
158.~ With positive reduction {3}
159  DF  .~.~> Seat pressed to valve
160  DF  .~.~> Rotary valve {3}
167  DF  .~.~> Bifaced {2}

DEFINITION

Classification: 251/158

(under subclass 157) Devices having means to also positively

return the valve or seat from its extra seat or head contacting condition.

SEE OR SEARCH CLASS

137, Fluid Handling,

246.18, and 246.19 for means for reducing the pressure in combination with liquid sealing at the valve interface.