| 摘要 |
A pneumatic percussion rock drilling hammer has a tubular housing for connection to a drill rod through which compressed air is introduced, the shank of a drill bit with an anvil at the top being slidable in the bottom of the housing, a piston being reciprocally slidable in the housing. Enlargements of the internal diameter of the housing define top, central and bottom pressure chambers. Air from the drill rod passes through a feed tube to an upper axial passage in the piston, and on the down-stroke of the piston a lower axial passage therein engages a sliding seal tube leading to an air passage through the bit. Pressure ports in the piston direct air from the piston's upper axial passage to the top pressure chamber when the piston is raised, and to the bottom pressure chamber when the piston is lowered, and exhaust ports in the piston conduct air between its lower axial passage and the central pressure chamber and from the central chamber to the top pressure chamber when the piston is lowered.
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