| 摘要 |
In an apparatus for drilling long holes in the surface of a rock bed for installation of roof bolts where the working distance perpendicular to the surface is limited, a flexible, segmented shaft drill string is fed along a curved path to a mechanism positioned directly under the working surface. The mechanism straightens the drill string perpendicular to the surface, and supplies torque and thrust to the string to drill the holes. Since torque and thrust are supplied to only the straightened portion of the drill string, rather than to the curved portion, greater thrust is imparted to the drill head with minimum wear of the segments. A special guide sleeve, mounted to a rigid starter section of the drill string behind the head, guides the string along a straight path in the rock.
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