Boring apparatus

Abstract

Boring apparatus featuring a frame having a primary axis of rotation and a flushing fluid inlet; and a plurality of hole-enlarging assemblies mounted on the frame and having separate axes of rotation radially outward of the primary axis; each assembly having a working member rotatable about its respective axis for acting upon the wall of the hole being bored, a flushing fluid passage extending along the direction of the respective axis to below the working member and communicating with the inlet, and a nozzle in communication with the passage below the working member, the nozzle having an orifice opening in a direction having at least a component directed upwardly for directing flushing fluid upwardly along the periphery of the working member, the working member having a recess at least at one end with a thrust bearing in the recess for effectively acting against the frame.

Description

BACKGROUND OF THE INVENTION

This invention relates to boring apparatus useful, e.g., in earth or rock.

Typically such apparatus has a frame supported at the lower end of a drill pipe string, with a pilot bit mounted at the bottom of the frame and reamers for enlarging the pilot hole mounted on the frame above the pilot bit.

SUMMARY OF THE INVENTION

The invention, in various aspects, provides compact (particularly along the drilling axis), rugged, inexpensive apparatus capable of efficient boring and chip removal. Improvements are provided in the flow of flushing fluid to both the pilot bit and the enlarging members, as well as in lubrication and protection of the bearing systems in the hole-enlarging assemblies.

In general the invention features, in one aspect, a frame having a primary axis of rotation and a flushing fluid inlet; and a plurality of hole-enlarging assemblies mounted on the frame and having separate axes of rotation radially outward of the primary axis; each assembly having a working member rotatable about its respective axis for acting upon the wall of the hole being bored, a flushing fluid passage extending along the direction of the respective axis to below the working member and communicating with the inlet, and a nozzle in communication with the passage below the working member, the nozzle having an orifice opening in a direction having at least a component directed upwardly for directing flushing fluid upwardly along the periphery of the working member. In another aspect the invention features frame-mounted hole-enlarging assemblies each having a shaft fixed to the frame, a working member rotatable on the shaft about its respective axis of rotation for acting upon the wall of the hole being bored, the working member having a recess at least at one end, and a thrust bearing in the recess for effectively acting against the frame. In preferred embodiments a pilot bit is mounted at the bottom of the frame; frame struts and hole-enlarging cutters are arranged alternately around the primary axis of rotation of the frame, with flushing fluid being supplied to the pilot bit through the struts and to the cutters through the cutter shafts; the nozzles are formed between the frame and the cutter bodies; a thrust shoulder and a thrust collar are provided in cutter body counterbores; seals between the thrust shoulder and collar and the cutter bodies are kept clean by the flow of flushing fluid outwardly adjacent those seals; the frame includes annular inserts for determining the orifice sizes of the nozzles; rotatable plugs are arranged in the upper ends of the cutter shaft fluid passages to control the flow cross-sections between the flushing fluid inlet and the shaft passages; and an annular collar, held against the frame by the pipe string, is provided to prevent cutter shaft rotation and to seal the flushing fluid manifold at the upper end of the frame. In some embodiments the upper thrust shoulders are integral with the cutter shafts. The overall envelope of the apparatus tapers from top to bottom, as does each cutter body.

Other advantages and features of the invention will be apparent from the description and drawings herein of a preferred embodiment thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation of apparatus embodying the invention, connected to a fragment of a pipe string;

FIG. 2 is a view similar to FIG. 1, from a different angle, with the pipe string and pilot bit omitted;

FIG. 3 is an enlarged view of a portion of FIG. 1, partially in section;

FIGS. 4-8 are sectional views taken respectively along 4--4, 5--5, 6--6, 7--7, and 8-8 of FIG. 1; and

FIG. 9 is a sectional view taken along 9--9 of FIG. 3 with the cutter shafts removed.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings, there is shown a main frame 10 connected at its top through externally threaded connector 12 to pipe string 14 which extends back to the surface drill rig, and at its bottom through internally threaded connector 16 to conventional tricone pilot bit 18. Frame 10 tapers from top to bottom along three circumferentially spaced struts 20 extending between upper and lower frame portions 22 and 24. Three cutters 26, 28, and 30 are respectively arranged between struts 20.

Each cutter has tooth inserts 32 in a body 33 mounted to rotate about shaft 34 (FIG. 3) having an axis 35 which not only generally follows the taper of struts 20 but is also skewed (e.g., by 2.degree.-4.degree., FIG. 2) with respect to the vertical axis 36 of frame 10. In overall operation rotation of frame 1 causes cutters 26, 28, and 30 to rotate and to enlarge the pilot hole produced by bit 18. The skew of the cutters produces vertical force components between the hole wall and the cutters, causing the apparatus to be at least partially self-advancing.

Body 33 is tapered where it receives inserts 32, and has fixed to itself in counterbores 40 and 42 annular upper and lower thrust bearings 44 and 46 and, on the inside cylindrical surface of its central bore 48, axially spaced radial bearing inserts 50 and 52. The upper bearing 44 runs against enlarged upper portion 54 of shaft 34, which acts as a thrust shoulder integral with the shaft. Lower thrust bearing 46 runs against a thrust collar 55 inserted in cutter body counterbore 42 and pinned (not shown) to the shaft to prevent rotation of the collar about the shaft while allowing relative axial movement between collar and shaft. O-rings 62 and 64 respectively provide the primary dynamic seals between stationary collar 54 and collar 55 and the rotating cutter body. Static seal 70 is provided between the collar 55 and shaft 34, to keep dirt out of the internal system and to hold lubricant in. The location of the shoulder and thrust collar within counterbores in the ends of the cutter bodies minimizes the overall length of the assembly, including the length of the struts and shafts, thereby increasing strength.

The lower ends of shafts 34 extend into cylindrical bores 80 in frame portion 24. The upper shaft ends are notched at 82 (and at 82', to allow for 180.degree. rotation of the shaft after wear) to receive generally annular retainer collar 84, which holds all three shafts in place and prevents them from rotating. In particular, collar 84 has three pockets 86 (FIG. 4) to receive the notched shaft ends, collar surfaces 88 acting against the shaft flats to prevent shaft rotation. Collar 84 is press fitted around frame portion 22 just below connector 12. Threaded pipe string portion 92 screwed on connector 12 acts as a hold down, pressing collar 84 against the shafts and frame portion 22.

Provision is made for supplying flushing fluid (e.g., air, clear water, or mud, etc.) to pilot bit 18 and to cutters 26, 28, and 30, to flush the rock removed during the drilling process. Thus, axial fluid inlet passage 100 communicates with a diagonal inlet 104 in each shaft 34 and an axial passage 106 in each strut 20. (Each shaft 34 has a second inlet 104' for use when the shaft is rotated.) Inlet 104 in turn feeds axial passage 108 within the shaft. Passages 108 dead end at the bottoms of the shafts. Plug 110 (FIG. 3) fits (without sealing) in the top of passage 108, and is cut off obliquely at its lower end extending into inlet 104. Rotation of the plug changes the effective flow cross-section between inlet 104 and passage 108, thus metering the rate of fluid flow to passage 108. Cap 112 on plug 110 can be indented into recess 114 in the end of shaft 34 to fix the angular position of the plug once it has been adjusted. Collar 84 seals against the pipe string at 116 and against the frame at 118 to prevent leakage of flushing fluid to the atmosphere.

Passage 108 communicates in the region of thrust shoulder 54, through radial holes 120 in shaft 34, with generally annular buffer chamber 122 formed in the outer surface of the shoulder, just above seal 62. A narrow clearance 124 (e.g., 0.005 inch radially) is provided between shoulder 54 and cutter body 33, communicating with chamber 122 and thus providing for a continuous small escape of fluid from the buffer chamber, so that clean fluid is always kept outside seal 62, despite the dirty environment in which the apparatus operates.

Just below thrust collar 55 passage 108 communicates, through radial holes 130 in shaft 34 and aligned radial slots 132 (FIG. 9) in the frame below shoulder 60, with annular buffer chamber 134. Relatively large clearance 136 (e.g., 0.02 inch) is provided between cutter body 33 and frame portion 24, so that a substantial amount of fluid flows through chamber 134 and upwardly past teeth 32. Not only is clean fluid thus kept outside of seal 64, but the cutter is cooled, the conical portion of the hole being drilled is flushed, and the jet pump effect of the upwardly flowing fluid helps to draw upwardly further chips and fluid from the region of the pilot bit. To precisely control the size of clearance 136 (which thus acts as a nozzle), replaceable split ring insert 138 fits in frame portion 24, surrounding (but spaced from) cutter body 33. Flange 140 of ring 138 fits in frame slot 142. The thickness of ring 138 thus determines the nozzle width. The relative rotation between the opposing nozzle-defining walls of clearance 136 gives the nozzle an advantageous self-cleaning quality in use.

Collar 84 seals the tops of strut passages 106, which at their other ends communicate with lower plenum 150. Plenum 150 in turn communicates with axial passage 152 (FIG. 1) and, through that passage, with conventional flushing jets 154 in pilot bit 18. Bores 80 communicate through reduced diameter extensions 80a with plenum 150, simply to provide access to the bottoms of shafts 34 (e.g., with a push rod) for disassembly. Shafts 34 rest against shoulders 80b to prevent fluid communication between bores 80 proper and plenum 150.

A removable jet fitting 160 extends axially through the bottom wall 162 of plenum 102. The fitting has an axial orifice 164 to project a jet of flushing fluid down the center of frame 10, adjacent the three cutters 26, and three radial orifices 166 to flush between frame wall 162 and the tops of the cutters.

A system for distribution of pressurized lubricant (e.g., grease) is also provided. A grease reservoir 170 (FIG. 3) extends in the wall of each shaft 34, parallel to passage 108. A movable pressure piston 172 is located at the upper end of each reservoir 170, with O-ring 174 providing a seal between the piston and the inner wall of the reservoir. Flushing fluid communicates with the top of piston 172 to pressurize the grease in the reservoir at the flushing fluid pressure. Lube passage 176 extends down from the reservoir, and provides grease through holes 178 to lube grooves 180 at opposite sides of the shaft 34. Grooves 180 may be provided by flats on shaft 34, or may be of any other suitable shape. From grooves 180 the lubricant moves along the outside of the shaft to feed the thrust and radial bearing areas. Seal 70 isolates the lubricant from the atmosphere.

As shown in FIG. 8, upper and lower portions 22 and 24 of frame 10 are of reduced diameter between the positions of the three cutter shafts 34, thus providing, in effect, recesses along which can flow rock cuttings produced by the drilling process. Carbide inserts 200 in the frame periphery at portions 22 and 24 protect the frame against wear.

Other embodiments are within the following claims:

Claims

I claim:

1. Boring apparatus comprising

a frame having a primary axis of rotation and a flushing fluid inlet, and

a plurality of hole-enlarging assemblies mounted on said frame and having separate axes of rotation radially outward of said primary axis, each said assembly having

a working member rotatable about its respective said axis of rotation for acting upon the wall of the hole being bored,

means defining a flushing fluid passage extending along the direction of said respective axis to below said working member and communicating with said inlet, and

a nozzle in communication with said passage below said working member, said nozzle having an orifice opening in a direction having at least a component directed upwardly, for directing flushing fluid upwardly along the periphery of said working member.

2. The apparatus of claim 1 further comprising a wall of said frame spaced above said working members, and a nozzle member in said wall and communicating with said inlet, said nozzle member having nozzles directed toward the space between said wall and said working members.

3. The apparatus of claim 1 wherein said passage is defined within the respective said working member.

4. The apparatus of claim 1 further comprising a pilot bit mounted at the bottom of said frame, and means defining at least one additional fluid flow passage communicating between said inlet and said bit.

5. The apparatus of claim 4 wherein said frame comprises a plurality of struts respectively located between said assemblies, each said strut having, internally thereof, one of said additional fluid flow passages communicating between said inlet and said bit.

6. The apparatus of claim 1 wherein said nozzles are formed by said frame and said working members.

7. The apparatus of claim 6 wherein said nozzles surround said axes of said working members, and said frame includes annular inserts for determining the orifice sizes of said nozzles.

8. The apparatus of claim 1 wherein each said assembly has a shaft mounted in said frame, said working members being respectively rotatable on said shafts, said passages respectively extending within said shafts.

9. The apparatus of claim 8 wherein in each said assembly said passage extends through the upper end of said shaft, an oblique connector passage communicates between said fluid passage and said inlet through a wall of said shaft, and a plug is mounted in the upper end of said fluid passage, said plug including a metering portion extending into the junction between said fluid and connector passages, said plug being rotatable to vary the flow cross-section through said junction.

10. The apparatus of claim 8 wherein the upper ends of said shafts are in pressure communication with said inlet, lube passages are provided in the walls of said shafts, and sealing pistons are provided in said lube passages adjacent the upper ends of said shaft.

11. The apparatus of claim 8 wherein said frame includes a threaded portion defining said inlet and adapted for connection to a pipe string, said shafts extend upwardly through said frame and having portions radially outwardly of said threaded portion, and a shaft-retaining collar is provided between the upper ends of said shafts and said threaded portion, adapted to be held in place when said pipe string is connected to said threaded portion.

12. The apparatus of claim 11 wherein, when said threaded portion is connected to said pipe string, said collar provides a seal against said frame radially outward of said shaft, and provides a further seal against said pipe string.

13. The apparatus of claim 11 wherein said shafts and said collar have cooperating flats to prevent rotation of said shafts.

14. The apparatus of claim 8 wherein each said working member has a counterbore at its bottom end and a thrust bearing in said counterbore for effectively acting against said frame.

15. The apparatus of claim 14 further comprising a thrust collar insert in each said counterbore fixed against rotation relative to said shaft, said thrust bearing acting against said frame through said collar.

16. The apparatus of claim 6 wherein each said passage extends below said collar, and radial openings in said shafts communicate between said passages and said nozzles.

17. The apparatus of claim 6 further comprising seals between said collars and said working members, flow of fluid from said passages to said nozzles serving to keep said seals clean.

18. The apparatus of claim 8 wherein each said working member has a counterbore at its upper end, and a thrust bearing in said counterbore for effectively acting against said shaft to transfer thrust via said shaft to said frame.

19. The apparatus of claim 18 further comprising a thrust shoulder in each said counterbore in contact with said thrust bearing.

20. The apparatus of claim 19 wherein said shoulder is integral with said shaft.

21. The apparatus of claim 19 wherein a seal is provided between said shoulder and said working member.

22. The apparatus of claim 21 wherein said shoulder and said working member define above said seal a chamber in communication with said inlet and having a leakage outlet, whereby flow of fluid through said chamber keeps said seal clean.