| 摘要 |
There is provided a hammer assembly (10) comprising a hammer casing (11) having a bore (12) therethrough and a drive sub (13) and retainer (15) supporting a drill bit (14). A piston (16) has a hammer end (17) adapted to strike an anvil end (20) of the drill bit (14). A porting body (21) is located in the bore (12) by expandable mounting member (22) frictionally engaged with the bore (12) by a tapered portion of the porting body (21) being urged by a top sub (23) into a tapered bore in the mounting member (22). The porting body (21) supports a non-return val ve (24) in a flushing fluid path communicating with the bit face. The mounting member (22) has a small annular flange (40) adapted to engage a shoulder (41) in the casing (11) and opposed axial slots (42) extending from port apertures (43) to the upper rim (44) of the mounting member (22). The porting body (21) comprises an annular manifold (45) for pressurized fluid supplied via top su b bore (46), non return valve chamber (47) and passages (50). A compressible spacer (52) is located on a shoulder (53) on the porting body (21) to be compressed by a corresponding shoulder (54) on t he top sub (23), the progression of which is limited by a top sub flange (55) bearing on the end (56) of the casing (11).
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