Flexible shaft drilling system
AssigneeThe United States of America as represented by the Secretary of the Interior
InventorWilliam A. McIlvanie
Life of this patent
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Abstract
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.
Claims18
An apparatus for drilling long holes in a surface of a rock bed wherein a working distance perpendicular to the surface is limited, comprising:
- a flexible drill string having a head, said drill string being formed of a plurality of rigid drill segments in end-to-end engagement to each other;
- and
- means located at said surface directly below a hole to be drilled for straightening a portion of said drill string and guiding said straightened portion perpendicular to said surface, a remaining portion of said drill string extending away from said means along an arcuate path;
- said means including means for applying thrust and torque directly to the straightened perpendicular portion of said drill string for drilling into said surface, a resultant thrust applied to the drill head thereby being maximized with minimim wear on the drill string;
- said remaining portion of said drill string feeding to said straightening and guiding means along the arcuate path during drilling.
A method of drilling a long hole in a surface, where a working distance perpendicular to the surface is limited, including the steps of straightening a portion of a flexible drill string formed of a plurality of rigid drill segments in end-to-end engagement to each other, perpendicular to the surface;
- extending a trailing portion of said string non-perpendicular to the surface;
- contacting the straightened portion of the drill string to a driving member;
- operating the driving member for supplying torque directly to the straightened portion of said drill string for rotation;
- and further operating the driving member for supplying thrust directly to said straightened portion for advancing said drill string into the surface for drilling.
Dependencies are inferred from the claim text.