| 摘要 |
A mode change mechanism for a rotary percussive drill comprises locking balls (13) engaged in axial recesses (10) in a beat piece (7) that transmits percussion from a percussive drive (5, 6) to a drill bit and a rotary collar (16) for moving the locking balls (13) and the beat piece (7) from a position in which the beat piece is able to transmit percussion to one in which transmission cannot take place. |
