| 摘要 |
<p>The pneumatic drill utilises an axially reciprocating piston (2) in a cylindrical housing (1), tool rotation being effected during the piston recovery stroke. The piston extends forward in the form of a shaft (2a) of reduced dia. the frontal shaft section incorporating the tool-holder (3), and the aft shaft section being mounted in an axially immobilised sleeve (4). The piston and the sleeve are connected by helicoidal grooves, piston descent causing the sleeve to rotate, and the piston rotating relative to the sleeve during ascent. A series of pivoting pawls prevents rotation of the sleeve relative to the housing during the latter phase. Each pawl has a comma shape with the bulb located in a sleeve barrel groove, and each, when activated, engaging longitudinal 'V' grooves in the housing bore. Pivoting of the pawls into the active position may be effected by centrifugal action.</p> |
