US PATENT SUBCLASS 175 / 218
.~ With valve

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

207  DF  WITH ABOVE-GROUND MEANS FOR HANDLING DRILLING FLUID OR CUTTING {9}
218.~ With valve

DEFINITION

Classification: 175/218

(under subclass 207) Apparatus including valve means to stop or regulate the flow of drilling fluid.

(1) Note. The valve may be located below ground.