US PATENT SUBCLASS 175 / 299
.~ Resiliently biased

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

293  DF  BELOW-GROUND (1) HAMMER, OR (2) IMPACT MEMBERS {7}
299.~ Resiliently biased

DEFINITION

Classification: 175/299

(under subclass 293) Apparatus in which an elastic member acts upon the hammer or impact device to urge said hammer or impact device toward or away from a jarring position.

SEE OR SEARCH CLASS

173, Tool Driving or Impacting,

202+, for an impacting device having a hammer head which is driven by a spring.