US PATENT SUBCLASS 175 / 235
.~.~ Seat engaged to stop upward flow

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

232  DF  WITH MEANS MOVABLE RELATIVE TO TOOL BELOW GROUND TO STOP FLOW TOWARD BORE BOTTOM {8}
234  DF  .~ With longitudinally spaced valve seats {1}
235.~.~ Seat engaged to stop upward flow

DEFINITION

Classification: 175/235

(under subclass 234) Apparatus in which a surface or seat is engaged to stop the flow of material away from the bore bottom.

SEE OR SEARCH THIS CLASS, SUBCLASS:

318, for upward flow stopping movable means.