PROCESS TO CUT OFF CYLINDRICAL HOLLOW BILLET IN HOLE AND GEAR FOR ITS REALIZATION Russian patent published in 2003 - IPC

FIELD: mining industry. SUBSTANCE: invention specifically refers to cutting off of large-diameter hollow billets from rock mass won during drilling out operation by special diamond tool from solid of rock. Gear includes separable undercutting unit including cutting members, bracket, reduction gear, fixing arm and electric motor placed off-center. Gear is equipped with adapter for installation of undercutting unit coupled through drill pipe to drilling rig. Cutting members of separable undercutting unit are presented by abrasive disks. Rotation axis of abrasives disks is mounted for turn together with reduction gear around axis of electric motor placed off-center. Distance between abrasive disks satisfies mathematical relationship given in formula of invention. Undercutting unit can be replaced with separable unit breaking partition between kerfs. Breaking unit comes in the form of hollow piston with ring made of elastic material, for example, rubber. Ring is put on outer surface of piston between two rings stops. One stop can move under action of axial load. Separable breaking unit can be replaced with separable undercutting unit with one cutting member left to cut billet through to outer diameter of cylindrical hollow billet. Cutting tool is moved through specified depth and billet is cut off from internal space by movement of tool towards outer surface of billet. Several circular kerfs are cut in wall from internal space of cylindrical billet to depth established by relationship where H is depth of kerf; R is radius of internal space of cylindrical billet. Kerfs being cut separable undercutting unit is replaced with breaking unit. Drilling rig forms axial load, compressing ring of elastic material till partition between kerfs is touched. Kerfs are filled with fluid in turn and hydraulic pressure is abruptly increased to value exceeding ultimate strength of partition. Pressure differential between formed ring spaces leads to breaking of partition. Breaking load on partition can be created with use of fluid expanding while frozen. EFFECT: ensured cutting-off of cylindrical hollow thick-walled large-diameter billet in hole from hard rock of granite type to required depth with simultaneous formation of smooth face surface. 4 cl, 5 dwg