Retractable drill bit apparatus

Claim 2

A retractable bit assembly comprising, a tubular drill sub for mouNting on the lower end of a drill string, an annular drill bit assembly at the bottom of said drill sub formed by tightly interfitting groups of bi-directionally tapered sectors having upper shank portions forming a divided mounting boss extending upwardly into the lower end of said drill sub, a clamping sleeve disposed in said drill sub in extension into said mounting boss in tight slidable fit therewith, flexible translational support stem assemblies attached to the bit sector groups and extending upward therefrom around said clamping sleeve, and radially fixed stop shoulder means affiliated with said drill sub, said clamping sleeve, and said support stem assemblies, cooperable with axial movement of said clamping sleeve to effect sequential contraction and expansion of said bit sector groups to and from said annular bit assembly.

Claim 3

The retractable bit assembly of claim 1, including in combination therewith, a core barrel removably affiliated therewith to receive a formation core bored by said annular drill bit assembly.

Claim 4

A retractable drill bit assembly comprising, a tubular drill sub for mounting on the lower end of a drill string, said drill sub having a downwardly flaring tapered annular shoulder at its lowermost end and an inwardly projecting annular stop shoulder disposed above such lowermost end; plural tightly interfitting groups of drill bit sectors forming a continuous divided annular array in assembled position on the lowermost end of said drill sub, each of said drill bit sectors having an outer segmented annular shoulder in engagement with respective portions of said downwardly flaring tapered annular stop shoulder at the lowermost end of said drill sub, the bit sectors of the several groups being tapered lengthwise and widthwise to permit sequential expansion and contraction of such groups to and from said annular array by simultaneous axialwise and radialwise movement thereof, and each of said bit sectors having corresponding bi-directionally tapered shank portions extending vertically upward which form a continuous divided mounting boss configuration coaxial with said annular array; a clamping sleeve disposed in said drill sub in tight-fitting disposition within said divided mounting boss thereby forced outwardly against an inner cylindrical wall of said drill sub disposed beneath its aforesaid inwardly projecting annular stop shoulder, said clamping sleeve having a thick-walled upper end that affords an elongated annular clearance space therebelow between its outer cylindrical surface and the inner cylindrical surface of said drill sub, said thick-walled upper end of said clamping sleeve being adapted to receive a cable-operated releasable elevator-and-hammer tool for imparting suspension forces and bi-directional vertical percussive blows to such upper end, and said clamping sleeve having a plurality of combined longitudinal stop and circumferential spacer tabs extending radially outward therefrom near the bottom of said sleeve in abutting engagement with the aforesaid annular stop shoulder within said drill sub; a plurality of vertically extending translational supports stems disposed in the aforesaid annular clearance space in circumferentially spaced-apart array between the aforesaid longitudinal stop and circumferential spacer tabs on said clamping sleeve, said translational support stems being connected at their lower ends to respective shank portions of said bit sectors and being relatively rigid longitudinally for delivery of longitudinal thrust and pull forced to such bit sectors during their assembly and disassembly to and from the aforesaid annular array, while also being flexural to permit radial movement of such bit sectors during such assembly and disassembly, said translational support stems consisting of stem groups, equal in number to the number of bit sector groups, the stems of each group being equal and interconnected at their upper ends by a rEspective lift ring in close sliding fit with the outer surface of said clamping sleeve, the stems of the several stem groups being of sufficiently different length to permit sequential radial contraction of the bit sector groups from the aforesaid annular array to different vertical positions by progressive upward movement of said longitudinal stop and circumferential spacer tabs sequentially into displacing abutment with the several lift rings; and a plurality of vertically extending longitudinally rigid stop means attached at their upper ends to the several lift rings, respectively, and in abutment at their lower ends with the aforesaid annular stop shoulder in said drill sub.

Claim 5

A retractable drill bit assembly comprising, a tubular drill sub for mounting on the lower end of a drill string, said drill sub having a downwardly flaring tapered annular shoulder at its lowermost end and an inwardly projecting annular stop shoulder disposed above such lowermost end; plural tightly interfitting groups of drill bit sectors forming a continuous divided annular array in assembled position on the lowermost end of said drill sub, each of said drill bit sectors having an outer segmented annular shoulder in engagement with respective portions of said downwardly flaring tapered annular stop shoulder at the lowermost end of said drill sub, the bit sectors of the several groups being tapered lengthwise and widthwise to permit sequential expansion and contraction of such groups to and from said annular array by simultaneous axialwise and radialwise movement thereof, and each of said bit sectors having corresponding bi-directionally tapered shank portions extending vertically upward which form a continuous divided mounting boss configuration coaxial with said annular array; a clamping sleeve disposed in said drill sub in tight-fitting disposition within said divided mounting boss thereby forced outwardly against an inner cylindrical wall of said drill sub disposed beneath its aforesaid inwardly projecting annular stop shoulder, said clamping sleeve having a thick-walled upper end that affords an elongated annular clearance space therebelow between its outer cylindrical surface and the inner cylindrical surface of said drill sub, said thick-walled upper end of said clamping sleeve being adapted to receive a cable-operated releasable elevator-and-hammer tool for imparting suspension forces and bi-directional vertical percussive blows to such upper end, and said clamping sleeve having a plurality of combined longitudinal stop and circumferential spacer tabs extending radially outward therefrom near the bottom of said sleeve in abutting engagement with the aforesaid annular stop shoulder within said drill sub; a plurality of vertically extending translational supports stems disposed in the aforesaid annular clearance space in circumferentially spaced-apart array between the aforesaid longitudinal stop and circumferential spacer tabs on said clamping sleeve, said translational support stems being connected at their lower ends to respective shank portions of said bit sectors and being relatively rigid longitudinally for delivery of longitudinal thrust and pull forced to such bit sectors during their assembly and disassembly to and from the aforesaid annular array, while also being flexural to permit radial movement of such bit sectors during such assembly and disassembly, said translational support stems consisting of stem groups, equal in number to the number of bit sector groups, the stems of each group being equal and interconnected at their upper ends by a rEspective lift ring in close sliding fit with the outer surface of said clamping sleeve, the stems of the several stem groups being of sufficiently different length to permit sequential radial contraction of the bit sector groups from the aforesaid annular array to different vertical positions by progressive upward movement of said longitudinal stop and circumferential spacer tabs sequentially into displacing abutment with the several lift rings; and a plurality of vertically extending longitudinally rigid stop means attached at their upper ends to the several lift rings, respectively, and in abutment at their lower ends with the aforesaid annular stop shoulder in said drill sub.

Claim 6

The retractable drill bit assembly of claim 1, wherein, said clamping sleeve is adapted for releasable connection with said elevator-and-hammer tool by inclusion of an upwardly flaring annular groove in its inner surface near its upper end, and said elevator-and-hammer tool comprises pivotal latching fingers for end engagement with said annular groove, a lower abutment member for engagement with the upper end of said clamping sleeve, a vertical guide member attached to said flange and having an upper abutment member disposed above said lower abutment member, a weight member vertically movable on said guide member to strike hammer blows on such upper and lower abutment members selectively, and cable means for effecting raising and lowering of said tool and vertical actuation of said weight member.