| 摘要 |
The automatic feed drill includes a spindle mounted therein for rotating in reciprocating movement. The spindle is rotated by 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 feed movement, is driven by the main drive gear, and during retraction movement, is shifted into a position wherein the feed gear is prevented from rotating. The spindle also carries a collar or other abutment that engages a shift lever at the end of the feed movement. The shift lever is moved by the collar, and, due to its interconnection with the feed gear, moves the feed gear out of engagement with the main drive gear and into the position wherein it is prevented from rotating. The apparatus also includes a yieldable stop device that holds the feed gear stopped during retraction movement. In the event that excessive torque is encountered, such as by a lower collar on the spindle engaging the housing, the yieldable stop member rotates at the same speed as the spindle feed gear and thus, prevents further retraction of the spindle and avoids damage to the drill. |
