US PATENT SUBCLASS 251 / 33
.~.~ Choked pressure type servo motor

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.~.~ Choked pressure type servo motor {8}
34  DF  .~.~.~> With reverse flow prevenging (nonsiphoning)
35  DF  .~.~.~> Variable choke passage according to valve position
36  DF  .~.~.~> With separate dashpot or choked fluid retarding chamber
37  DF  .~.~.~> With choke or restrictor in main line
38  DF  .~.~.~> Pilot valve seated in motor or valve element {2}
41  DF  .~.~.~> Remote pilot valve actuation
42  DF  .~.~.~> Adjustable opening limit for main valve
43  DF  .~.~.~> Main valve biased open by line pressure {2}

DEFINITION

Classification: 251/33

(under subclass 25) Subject matter in which the servo-motor is of the type having an expansible pressure chamber the pressure in which is equalized with either a high or a low pressure region by means of a constantly open but restricted passage or communication therebetween to cause the main valve to assume one position, but in which the pressure conditions can be reversed by the opening of a pilot valve in an open or less restricted passage between the chamber and a pressure region other than that connected by the restricted passage to cause the main valve to assume an opposite position.

(1) Note. Expansible chamber devices which are constantly open to a single pressure region, even though the opening is restricted, are not servo-motors because motor action can result only by receiving fluid at a higher pressure and exhausting to a lower pressure. Such devices are either a form of fluid bias or a dashpot or other vented chamber.

SEE OR SEARCH THIS CLASS, SUBCLASS:

50+, for dashpot of fluid controlled retarders or timers receiving pressure from the line controlled. See (1) Note.

SEE OR SEARCH CLASS

137, Fluid Handling, 489+, for line condition responsive valves having servo-motors of the choked pressure type.