| 摘要 |
A down hole hammer assembly for percussive drilling of ground holes has a drill bit (23) slidably carried in a chuck (22) housed within a barrel (21) of the assembly. Drill bit (23) travel is limited by a retainer sleeve (24) in place about a reduced segment (25) of the drill bit. The sleeve (24) includes a ring portion (24A) limiting bit travel and a skirt portion (26) for confinement within a component of the hammer assembly to prevent loss of the retainer sleeve (24) and drill bit during barrel (21) separation.
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