| 摘要 |
The automatic feed drill includes a spindle mounted therein for rotating and reciprocating movement. The spindle is rotated by a spindle rotation gear that is engaged with the main drive gear which is ultimately driven by an air motor or the like. The feed and retraction movement (reciprocation) is caused by a spindle feed gear that is threaded onto the spindle. The spindle feed gear is engaged with a feed gear which, during normal feed movement, is driven by the main drive gear, and during retraction and rapid feed movement, is shifted into a position wherein the feed gear is prevented from rotating. During rapid feed the motor direction is reversed by a reversing valve. The apparatus also includes a yieldable stop device that holds the feed gear stopped during retraction and rapid feed movement. In the event that excessive torque is encountered, such as by a lower collar on the spindle engaging the housing or the drill bit encountering the work piece during rapid feed, the yieldable stop member rotates at the same speed as the spindle feed gear and thus, prevents further retraction or feeding of the spindle and avoids damage to the drill.
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