Multi-bit rotary drilling unit for drilling holes and shafts of large diameters

摘要

710,769. Rotary drills. PERKINS, W. H., and GRANT, A. Sept. 17, 1951 [Sept. 27, 1950], No. 21828/51. Class 85 A rotary drilling unit comprises a plurality of rotating bits, the cutting areas of which overlap to produce a non-circular hole, and a driving motor 8 or motors attached to and sinking with said bits The periphery of the drilling unit is so shaped as to have a cross-section that conforms with the configuration of the hole so that, although the unit may move axially in said hole, rotation about the axis of said hole is prevented The unit may have a drill 11 and two diametrically opposed drills 10, which are so positioned as to cut holes 3 intersecting the hole 2 made by the drill 11. Alternately a number of drills may be disposed symmetrically around a main drill, or there may be provided two drills substantially equal in diameter and disposed so that one consistently overlaps the other. Reference has been directed by the Comptroller to Specification 671,793.