US PATENT SUBCLASS 137 / 522
.~.~ With external means for opposing bias

Current as of: June, 1999
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137 /   HD   FLUID HANDLING

455  DF  LINE CONDITION CHANGE RESPONSIVE VALVES {11}
511  DF  .~ Direct response valves (i.e., check valve type) {14}
522.~.~ With external means for opposing bias {1}
523  DF  .~.~.~> With means for retaining external means in bias opposing position

DEFINITION

Classification: 137/522

(under subclass 511) Valves provided with means external to and independent of the flow path of the fluid controlled for opening the valve against its bias or for relieving the valve of the effect of the bias so that normal fluid pressure will open the valve.

(1) Note. The relief of bias classifiable herein is for the purpose of permitting the valve to blow off a normal pressure which the valve would otherwise contain.

(2) Note. Where a bias adjusting means positively opens the valve, classification is in this subclass.

(3) Note. See the class definition, Lines With Other Classes and Within this Class, (1) Automatic Control, and Subclass References to the Current Class, for search notes on plural valves, at least one of which is automatic.

SEE OR SEARCH THIS CLASS, SUBCLASS:

456+, for safety cut-off valves requiring the use of external means to open them.

481, for suction flow governor valves with manual modifier for the valve. 495, for line condition responsive valves with separate connected fluid reactor surface and having manual or external control means.

SEE OR SEARCH CLASS

251, Valves and Valve Actuation, appropriate subclasses for valves which are regularly operated by means other then the pressure of fluid in the line, but where the fluid in the line may cause return to the original position, especially

12+, for fluid pressure actuators and retarders.