Up-hole overshot and safety drilling apparatus

Drilling apparatus mountable to the outer end of a drill string that has an axial inner bit end, comprising an overshot adaptor and an overshot assembly fluidly propellable axially inwardly in a drill string from the drill string outer end to a position to couple to a drilling tool at the drill string bit end and retractable axially outwardly by a wire line, the overshot assembly including an axially elongated overshot main body having an axial outer end portion and an axial inner end portion, a pair of pulling dogs having axial outer ends, axial intermediate portions and axial inner jaws for releasably coupling to the drilling tool, means for mounting the pulling dogs to the main body for movement between a drill tool coupling position and an overshot release position, an axially elongated overshot tube having an outer end portion, an axial intermediate portion and an inner end portion mounted to the main body outer end portion to extend axially outwardly thereof, annular fluid seal means mounted to the axial intermediate portion of the overshot tube for forming a fluid seal between the drill string and the overshot tube, a valve seat in one of the overshot tube and the main body outer end portion and a port opening to the overshot tube and radially outwardly axially inwardly of each of the valve seat and the fluid seal means, a valve member mounted by at least one of the main body and the overshot tube, valve member mounting means for mounting the valve member for movement between a closed position blocking fluid flow through the valve seat and an open position, means for resiliently retaining the valve member in its closed position, and the overshot adaptor being removably threaded to the overshot tube and having an adaptor tube extending into the overshot tube when the overshot is threaded thereto for retaining the valve member in its open position and permitting the valve member moving to its closed position when the adaptor tube is withdrawn from extending within the overshot tube.

Drilling apparatus usable with a drilling tool and a drill string having an axial outer end and an axial inner bit end, comprising an annular safety sub having an axial inner annular end portion adapted for being threadedly connectable to the drill string outer end, an annular outer end portion and an axial intermediate reduced diameter bore portion of a smaller inner diameter than the inner diameter of the inner annular sub end portion and opening to the inner annular sub end to provide an axially inwardly facing shoulder and of a smaller inner diameter than that of the axial outer sub end portion and opening thereto to provide an axial outwardly facing second shoulder, an overshot assembly that includes an axially elongated overshot tube having an axial inner end portion and an axial outer end portion of an outer diameter slidably extendable through the reduced diameter portion, a pair of axially elongated pulling dogs having axial outer ends, axial intermediate portion and axial inner jaws, overshot means mounted to the overshot tube inner end portion for mounting the pulling dogs for movement between a drilling tool coupling position and a drilling tool release position and an overshot adaptor removably connected to the overshot assembly, the overshot adaptor having an axial inner adaptor tube extendable into the overshot tube and an axial outer head portion joined to the adaptor tube and abuttable against the second shoulder for limiting the axial inward movement of the overshot assembly relative to the sub, the overshot assembly including means abuttable against the first shoulder for limiting the movement of the overshot assembly and the overshot adaptor axially outwardly relative to the safety sub.

Drilling apparatus usable with a drilling tool and a drill string having an axial outer end and an axial inner bit end, comprising an annular safety sub having an axial inner annular end portion adapted for being threadedly connectable to the drill string outer end, an annular outer end portion and an axial intermediate reduced diameter bore portion of a smaller inner diameter than the inner diameter of the inner annular sub end portion and opening to the inner annular sub end to provide an axially inwardly facing shoulder and of a smaller inner diameter than that of the axial outer sub end portion and opening thereto to provide an axial outwardly facing second shoulder, an overshot assembly that includes a main body, a pair of axially elongated pulling dogs having axial outer ends, axial intermediate portion and axial inner jaws, means mounted to the main body for mounting the pulling dogs for movement between a drilling tool coupling position and a drilling tool release position and annular fluid seal means for sealingly engaging the drill string and an overshot adaptor removably connected to the overshot assembly for limiting the movement of the overshot assembly inwardly relative to the sub, the overshot adaptor and overshot assembly having cooperating means extending axially through the fluid seal means for forming a fluid bypass channel to permit axial inwardly flow bypassing the fluid seal means when the overshot adaptor is mounted to the overshot assembly while blocking axial outward fluid flow bypassing the fluid seal means, said cooperating means extending axially through the fluid seal means, the overshot assembly having means abuttable against the first shoulder to limit the axial outward movement relative to the sub.