DOWN-THE-HOLE DRILL HAMMER

摘要

A down−the−hole drill hammer comprises a sleeve (46) which defines a cylinder in which a piston is reciprocable. A plurality of axially extending ribs are formed on the outer surface of the sleeve, and conduits are formed in at least one of the ribs for conveying compressed air or another drive fluid to ports in the sleeve, to operate the piston. This arrangement makes it possible to increase the effective diameter of the hammer as a percentage of the bit diameter, which is particularly useful in relatively small drill hammers.