Method and Apparatus for Impact Drilling of Overburden (Patent No: 758467)

Inventor: Becker, Floyd W.

Location: Calgary

Comments: N/A

Description:
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. The method of making a borehole in overburden comprising impressing a steady axial load on an annular toothed bit body carried by the lower end of a rigid tubular drill pipe having a central conduit, while delivering impact energy by repeated blows transmitted by way of said drill pipe to said bit body, said axial load and said impact energy being sufficient to fracture and displace axially and laterally boulders occluded in said overburden along said borehole and to force overburden materials and fragments upward into said conduit, and withdrawing said drill pipe from said overburden.

2. The method of making a straight borehole in overburden which consists in continuously subjecting an annular toothed bit body carried at the lower end of a rigid drill pipe to axially directed loading of at least about 1000 pounds per inch of borehole diameter while intermittently delivering impact energy to the upper end of said drill pipe at a rate in excess of about 500 foot pounds per blow per inch of borehole diameter to effect displacement and shattering of boulders occluded in said overburden along said borehole and to force overburden materials upward into said drill pipe, and raising said drill pipe with its contents out of said borehole.

3. The method of making a straight borehole in overburden comprising, impressing a steady axial load on an annular toothed bit body carried by a hollow drill pipe, while delivering impact energy by repeated blows to said bit body, the said axial load and said impact energy being sufficient to effect displacement and shattering of gravel obstructing progress of said bit body along said borehole, while also injecting fluid inwardly of said annular bit body to entrain fragments loosened therein and to continuously remove said fragments from said bit body.


4. The method of making a straight borehole in overburden comprising, subjecting an annular toothed bit body carried at the lower end of a rigid drill pipe to a force of at least about 1000 pounds per inch of borehole diameter while transmitting impact energy along said drill pipe to said bit body by repeated blows delivered to said drill pipe at a rate in excess of about 500 foot pounds per blow per inch of borehole diameter and sufficient to effect displacement and shattering of boulders impeding progress of said bit body, while flowing a fluid inwardly of said bit body at a rate sufficient to continuously convey fragments of said overburden materials passed through said annular bit body along said drill pipe and to eject said materials above ground level.

5. The method of Claim 4 wherein said fluid is compressed gas.

6. The method of intensively transferring energy into the ground to drill a borehole which comprises impressing an annular bit body having an axial bore and a plurality of radially aligned chisel tooth edges and a circular cutting edge depending from said body into the ground under a steady pressure applied to a rigid drill pipe fixed to said body such that each inch of tooth edge supports at least 400 pounds dead weight while delivering energy of impact to said bit body by repeatedly impacting a heavy mass axially on the upper end of said drill pipe to abruptly increase the stress in the contact zones adjacent said tooth edges, said energy being in excess of 500 foot pounds per blow per inch of diameter of said borehole, said energy being sufficient to fracture brittle objects encountered by said bit body and to displace fragments axially and laterally.

7. Apparatus for making straight boreholes in overburden comprising, a hammer means, a rigid tubular drill pipe having double walls defining a central conduit and an annular chamber between said walls, an annular cutting bit body having depending teeth and having an axial bore registered with said central conduit carried by one end of said drill pipe, passages in said bit extending axially within said teeth and communicating with said chamber and opening into said axial bore, and an anvil cap closing the end of said annular chamber remote from said bit body, said cap being adapted to support said hammer means thereby to impress a steady axial load on said bit body and to receive impact energy delivered by said hammer means to drive said bit through said overburden, and having an inlet duct for admitting fluid to said chamber under pressure, and having an exhaust duct for leading fluid and fragments of overburden out from said central conduit laterally of said cap.

8. Apparatus as set forth by Claim 7 wherein said hammer means comprises a superposed impact engine which contributes a gravity load on said bit body such that the total load is at least about 1000 pounds per inch of borehole diameter.

9. The apparatus set forth by Claim 8 wherein said impact engine is capable of delivering impact energy to said anvil cap by repeated blows at an energy input rate exceeding about 500 foot pounds per blow per inch of borehole diameter.

10. The apparatus set forth by Claim 7 wherein said teeth have chisel cutting edges and said edges are radially aligned and circumferentially spaced, and have a radial extent such that said edges project respectively radially inwardly of said axial bore and radially outwardly beyond said drill pipe.

11. The apparatus set forth by Claim 10 wherein the radial breadth of annular portions of said bit body between said teeth decreases downwardly to a lower peripheral edge spaced above said cutting edges.

12. In a drilling apparatus for making a borehole in overburden the combination of a hammer means, a thick-walled outer drill pipe having a bit end and an open impact receiving end, a toothed cutting bit of annular cross-section carried by said bit end, said bit comprising an annulus having an axial bore therethrough coaxial with the pipe axis, a second pipe contained within said outer pipe and defining a chamber between said pipes, the interior cross-section of said second pipe being at least as large as the least cross-section of said axial bore and providing a conduit for guiding therealong fragments capable of moving through said axial bore, an anvil cap removably received on said impact receiving end, said cap being adapted to support said hammer means whereby to impress a steady axial load on said bit and to receive impact energy delivered by said hammer means and having a fluid inlet duct and a fluid exhaust duct respectively communicating with an end of said chamber and with an end of said conduit when said cap is received on said impact receiving end, said chamber being closed at said bit end by said bit, and passages in said annulus communicating with said chamber and opening into said axial bore.

13. Apparatus as set forth by Claim 12 wherein said bit carries a plurality of chisel teeth depending from said annulus and tapering in the axial direction to cutting edges spaced about the said axis and extending transversely of the periphery of said bit, and each of said passages comprises a portion extending parallel with said axis within each tooth and opening upwardly into said chamber and a lateral portion extending inwardly adjacent the cutting edge of the tooth and terminating in a nozzle opening into said axial bore.

14. Apparatus as set forth by Claim 13 wherein the wall of said axial bore has a like plurality of grooves extending upwardly and communicating with said nozzles and with said conduit.

15. Apparatus as set forth b¥ Claim 13 wherein said axial bore and said conduit are each substantially cylindrical and said bit comprises sectoral portions constituting thickened root ends of said teeth disposed between and integrally joined with intervening sectoral portions, the outer surfaces of said intervening sectoral portions lying on the surface of a cone which is coaxial with said axis, the lower ends of said intervening sectoral portions terminating in arcuate cutting edges lying in a plane which is transverse to the pipe axis and which lies intermediate said chisel cutting edges and the upper face of said annulus.

16. Drilling apparatus for extracting a fragmented core from a borehole as said borehole is produced in a formation of the class consisting of overburden and conglomerates, comprising a rigid tubular drill pipe having double walls defining a central conduit and an annular chamber between said walls, an annular peripherally toothed bit body detachably secured at the lower end of said drill pipe and having an axial bore coaxial with and registered on said central conduit and a plurality of axially extending, peripherally spaced teeth integral with said bit, each tooth having a passage formed therein connecting with said annular chamber and with said axial bore for jetting fluid into said central conduit from said chamber, an explosion-actuated hammer means, an anvil cap removably positionable upon the upper end of said drill pipe, hammer positioning means adapted to lower said hammer means for support by said cap whereby said bit is subjected to a steady axial load and intermittent impact to drive said bit through said overburden and conglomerates, fluid supply means connected with said anvil cap effective to supply fluid under pressure to said annular chamber, and exhaust duct means having a diameter not less than the diameter of said central conduit communicating with said central conduit for ejecting fluid and fragments of said formation entrained by jetting fluid above ground level.

17. In impact drilling apparatus for making a straight borehole in unconsolidated ground, the combination with a rigid hollow drill pipe having a central duct for receiving earth material and fragments and carrying at its lower end an annular sharp-edged cutting bit having an axial bore registered on said central duct, of a hammer means, an anvil cap removably supported on the upper end of said drill pipe and adapted to support said hammer means for applying a steady axial load and for transmitting impact energy delivered by said hammer means to said drill pipe to cause said bit to shatter and displace brittle obstructions, said cap comprising a stout rigid body having an upper impact receiving anvil face and a lower tubular seating portion, said seating portion having a downwardly extending sleeve adapted to freely receive the upper end of said drill pipe therein, said sleeve having a lateral shoulder projecting inwardly for guidedly seating said upper end thereagainst in load-bearing and impact transfer relation with said sleeve.

18. Impact drilling apparatus as set forth in Claim 17 wherein said seating portion further comprises a depending conic guiding boss extending below said sleeve adapted to enter into said upper end of said drill pipe to guide said end into seating relation in said cap, said shoulder forming a bottom wall of a recess defined by said sleeve and said boss.

19. Impact drilling apparatus as set forth in Claim 18 wherein said drill pipe includes a second pipe inside it, said pipes defining a central conduit and an annular chamber, and wherein said bit has passages communicating with said annular chamber and with said axial bore, said outer drill pipe having a tapering internally pipe-threaded female coupling end having a conic inner surface bearing a predetermined length of threading and adapted
to be freely received in said recess and to seat against said shoulder in load-bearing and impact transfer relation thereagainst, said female coupling having axial passages opening at their upper ends into a peripheral internal groove intermediate the ends of said threading, and opening at their lower ends into said annular chamber, a central passage in said anvil cap opening downwardly and registering on said central conduit, and upwardly-laterally curving exhaust duct opening outwardly through the side of said cap above said seating portion and communicating with said central passage, a toroidal fluid supply channel in said cap having vertical passages communicating with said recess, a fluid supply duct extending through a side of said cap and communicating with said fluid supply channel, said boss having a conic face adapted to be received within said female coupling in fluid-tight sealing relation between said conic face and said conic inner surface of said female coupling below said threading.

20. Apparatus for earth boring of water-pervious gravels comprising, a rigid tubular drill pipe having relatively fixed inner and outer pipes defining a central conduit and an annular chamber, an annular peripherally toothed cutting bit body having axially extending teeth and having an axial bore registered with said central conduit fixed to the lower end of said drill pipe and closing the lower end of said annular chamber, passages in said bit body extending axially within said teeth and opening into said axial bore and into said annular chamber, impact receiving cap means removably supported on the upper end of said outer pipe, a power hammer means of high energy yield per blow adjustably supported on said cap means effective to strike said cap to drive said bit downwardly through said gravels, the weight of said hammer means being effective to hold said cap on said upper end of said outer pipe in closing relation with said annular chamber and effective to apply a steady axial load on said bit body, said cap means having an inlet duct for supplying gaseous fluid to said annular chamber under pressure, and having an exhaust duct communicating with said central conduit for discharging material conveyed up said central conduit by flow of said fluid.

21. Apparatus as set forth in Claim 20 wherein said fluid is air.

22. Apparatus as set forth in Claim 20 wherein said cap means has its upper end formed as an anvil surface and its lower end formed as a hollow depending boss axially insertable into the upper end of said outer pipe, said lower end having a surrounding cylindrical depending sleeve adapted to enclose the upper end of said drill pipe to provide a gas seal therewith.