Drive link permitting feed and rotation of drills of various sizes

摘要

A special drive link permits drilling of holes of different diameters with the same drill drive. The drill shaft has a helical pattern of scroll-like projections for removal of cuttings. The drill drive mechanism includes sprockets carrying two chains of drive links which mate with the helical scroll projections to move the drill shaft axially, and projections on the drive links mate together at the center to hold the drive links tightly around the drill shaft. The drill shaft is formed with an elongated axial groove separating the helical projections and defining notch surfaces which mate with projections or tangs extending inwardly from the hollow portion of the drive links where they surround the drill shaft. Rotation of the mechanism results in transferring the rotating force through the sides of the inwardly extending projection of the drive links to the corresponding notch surfaces of the scroll projections. The drive link is configured to accept some maximum diameter of the scroll projections having a specific cross-section. Assuming a smaller drill shaft diameter, the diameter of the scroll projections may be reduced substantially, and it will still be possible for the helical projections to enter the depressions on the links a sufficient amount to provide adequate bearing surface and for the inwardly extending tang to reach sufficient area on the corresponding scroll notch surfaces to provide a positive rotational drive.