| 摘要 |
A drill head is disclosed, for use to drill a hole in a front of hard material such as rock, which comprises a main body acting at a central support, an upwardly projecting spindle secured on top of the main body, the spindle having a vertical axis, a fixation head on top of the spindle for detachably connecting it to a drill shaft operable in use to rotate the drill head about the vertical axis of the spindle and to pull it up toward the front hard material to be drilled, and at least two impact hammers mounted onto the main body in such a manner as to fragment, in use the hard material of the front along at least one circular path centered onto the vertical axis, each impact hammer having a hollow casing, a pneumatically-operated, impact generating assembly enclosed within the casing, and a drill bit actuated by the impact-generating assembly. Advantageously, the hollow casings of the impact hammers are integral with the main body and form therewith a single structural piece, the central cavities of the hollow casings consisting of longitudinal holes made in this single piece and extending in directions substantially parallel to the vertical axis of a spindle at short distances from this axis.
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