US PATENT SUBCLASS 251 / 190
.~ Piston

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}
190.~ Piston {1}
191  DF  .~.~> Packing expands with closing

DEFINITION

Classification: 251/190

(under subclass 157) Subject matter wherein the valve is of the piston type.

SEE OR SEARCH CLASS

137, Fluid Handling,

538, for line condition change responsive piston valves, and subclasses 625.37+ for piston valves where the flow is divided and recombined.