US PATENT SUBCLASS 175 / 318
.~ Valve prevents upward flow

Current as of: June, 1999
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175 /   HD   BORING OR PENETRATING THE EARTH

317  DF  WITH MEANS MOVABLE RELATIVE TO TOOL OR SHAFT TO CONTROL BELOW-GROUND PASSAGE {1}
318.~ Valve prevents upward flow

DEFINITION

Classification: 175/318

(under subclass 317) Apparatus in which the means comprises a subsurface valve so mounted in the tool or tool shaft as to prevent the upward flow of fluent material in the tool or tool shaft.

SEE OR SEARCH THIS CLASS, SUBCLASS:

233, for means movable to seal a sample receiver at bore bottom pressure.

235, for the combination of valve seats engaged by movable means to stop upward and downward flow.