| 摘要 |
A piston (16) is mounted between a mounting structure (12,36) and a top sub (14) for axial reciprocation in a casing (11). A piston lower portion is set to travel downwardly in the central passageway (39) of the bit-mounting structure and to strike the anvil (30) of a drill bit (13), such that downwardly facing surface (22) of a piston top portion is spaced above the drill bit and the mounting structure. The down-the-hole percussive hammer (10) includes the bit-mounting structure mounted in the lower portion of the cylindrical casing, forming the upwardly open central passageway. The drill bit is mounted in the bit-mounting structure such that its anvil is projected upward into the central passageway. Two passageways (24,25) are extended from an axial through-hole (31) to the outer peripheral side surface of the piston and respectively intersected with lower and upper ends of the passageways (17,18) which are downwardly extended from the upwardly facing surface (19) and the downwardly facing surface of the piston. The passageways (24,25) intermittently communicate with the lower aperture (21) of a feed tube (15) in reciprocation of the piston for exposing a casing inner surface to lubricating air. An Independent claim is also included for a piston. |
