| 摘要 |
A down-the-hole rock drill including a drill bit provided at the lower end of a drill rod, which is rotatably driven by an above-the-ground motor. To increase the drilling efficiency and facilitate drilling of large-diameter holes a machine casing is positioned between the drill rod and the drill bit, said casing enclosing a hydraulic pump which is rotatably driven by the drill rod. The hydraulic pump delivers pressurized liquid to and drives the percussion unit including a hammer, the latter delivering blows against the drill bit at regular intervals. The machine casing also encloses at least one hydraulic motor driven by the pressurized liquid and arranged to rotate the drill bit. Hydraulically controllable blocking means prevent the machine casing from rotating relative to the drill hole wall while the drill bit is in operation.
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