US PATENT SUBCLASS 251 / 34
.~.~.~ With reverse flow prevenging (nonsiphoning)

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

12  DF  FLUID ACTUATED OR RETARDED {12}
25  DF  .~ Pilot or servo type motor {8}
33  DF  .~.~ Choked pressure type servo motor {8}
34.~.~.~ With reverse flow prevenging (nonsiphoning)

DEFINITION

Classification: 251/34

(under subclass 33) Subject matter in which means are provided to prevent back flow of fluid around the main valve through the constantly open choke or restriction under transient conditions of pressure change in the main flow line.

(1) Note. These disclosures usually are described as "anti-siphoning" although there is never any siphonic flow under intended conditions of use.

SEE OR SEARCH CLASS

137, Fluid Handling,

215+, for back flow prevention by vacuum breaking in systems which are not designed to have siphon action in ordinary use.