US PATENT SUBCLASS 166 / 318
.~ Operated by dropped element

Current as of: June, 1999
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166 /   HD   WELLS

316  DF  VALVES, CLOSURES OR CHANGEABLE RESTRICTORS {5}
318.~ Operated by dropped element

DEFINITION

Classification: 166/318

(under subclass 316) Devices in which there is an element or member dropped into the well to operate the valve to open or closed position.

SEE OR SEARCH THIS CLASS, SUBCLASS:

317, for an element which is dropped to effect destruction of a valve.