| 摘要 |
A drill bit retention system for a percussive drill 10 comprising a chuck 12 and retention sleeve 11. The chuck 12 and the retention sleeve 11 comprise first co-operating engagement means 44, such that when the retention sleeve 11 and chuck 12 are engaged the retention sleeve and chuck are constrained to rotate together in at least one direction. The first cooperating engagement means 44 may be a raised diameter portion 49 formed by a shoulder 48 of the chuck 12 with an external screw thread 47 to co-operate with an internal screw thread 63 on the retention sleeve 11. The engagement means may also be splines (Fig 8, 64) on the sleeve that interlocks with recesses (Fig 8, 67) formed between external rounded splines (Fig 8, 66) on the chuck 12. The system further comprises housing 13, with engagement means 19 for securing to the chuck; and a drill bit 22 mounted in the sleeve and chuck, with third engagement means 43 between the chuck 12 and drill bit 22 and fourth engagement means 59 between drill bit 22 and retention sleeve 11. |
