US PATENT SUBCLASS 175 / 274
.~ With shifting mechanism spring biased to operative position

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

263  DF  CUTTER ELEMENT LATERALLY SHIFTABLE BELOW GROUND (E.G., EXPANSIBLE) {13}
274.~ With shifting mechanism spring biased to operative position {3}
275  DF  .~.~> With separate latch {2}
279  DF  .~.~> Cam or gear means movable to shift cutter element {1}
281  DF  .~.~> Cutter element substantially longitudinally movable on shaft {2}

DEFINITION

Classification: 175/274

(under subclass 263) Apparatus in which the laterally movable cutter element is moved by a mechanism which is biased by a resilient means to move the cutter element to its operative position.

(1) Note. A mechanism for classification in this subclass includes a system of parts having a link, cam or similar element between the cutter element and the resilient means but a simple link connecting a cutter element and a spring is excluded, see subclass 291 below.