CA1081686A

CA1081686A - Drill bit air clearing system

Info

Publication number: CA1081686A
Application number: CA322,926A
Authority: CA
Inventors: Percy W. Schumacher, Jr.
Original assignee: Reed Tool Co
Current assignee: Reed Tool Co
Priority date: 1978-05-01
Filing date: 1979-03-07
Publication date: 1980-07-15
Also published as: GB2019921B; GB2019921A

Abstract

ABSTRACT OF THE DISCLOSURE

An earth boring drill employing roller cutters is provided with a peripheral seal surrounding the bearing shaft and engaging a peripheral surface of the open end of the cutter to prevent entry of solids to and retain lubricant in the bearing. The drill bit is provided with one or more passageways arranged for pressurization with air provided through the drill string and having an opening into the space between the leg of the drill bit and the adjacent rotating surface of the cutter. The size of the passageway is preferably related to the size of the peripheral clearance between the cutter and the leg of the drill bit, such that a positive pressure of air is maintained in said peripheral space to blow out detritus which would tend to erode the seal.

Description

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D~ILL BIT AIR CL,E~RING SYS
BACKGROUND OF l`llE INVENTION
This invention relates to new and useful improvements in earth boring drill bits of the roller cutter type and more particularly to bits for use in air drilling wherein air is circulated to remove cuttings from the drill hole.
DESCRIPTION OF THE PRIOR ART
The prior art discloses the extensive use of air in drill bits for removing cuttings from the drill hole. It is also well known to provide air circulation through a drill bit to cool the bearings and to keep the bearings clear of detritus. Peripheral seals of various types are also well known for purpose of retaining lubricant in the bearings of a drill bit and to prevent thc ~ntly oE ~ Lrit~n.
into the bearings.
The following United States issued patents, Neilson 3127942, Bercaru 3303898, Frederick 3534823, Schumacher 3761145, Murdoch, et al 3765495, and Williams 3844363, show ` a variety of peripheral seals used in drill bits for retaining lubrication and Eor protecting against entry o detritus. The Frederick and Williams patents also show the use of circula~in~
air in such drill bits. Additionally, the following United States patents, Tupica 1945240, Woods 2661932, Peter 2749092, Carle, et al 2783971, McEachern 2803436, Pike,et al 2814464, Peter, et al 2815936, Madson 3198267, Lichte 3449024, Robinson 3656764, and Dysart 3788408, disclose a variety of bits having circulating air for flushing cuttings and/or cooling the bearings, with some of the references disclosing seals to protect the bearings.
The prior art does not consider the problem of preventing the packing of cuttings around the exterior of the seal which results in rapid deterioration of the seals.
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108~686 SUMMARY OF THE INVENTION

This invention relates to improved drill bits and particularly drill bits for use in drilling with air or equivalent gaseous circulating fluid.
Prior drill bits having air or equivalent gas circulation have had seals to protect the bearings and have also had air circulation through the bearings for cooling.
The seals have deteriorated badly from accumulation of cuttings and other detritus adjacent to the seal between the rolling cutter and its support. This invention provides air circulation to remove the cuttings from the exterior of the bearing seals.
An object of the present invention is to provide an improved drill bit for use in drilling with air or equivalent gas circulation, which bit has extended life and improved bit footage.
A further object is to provide an improved roller cutter drill bit with an air circulation system which will remove cuttings and other detritus from the exterior of the bearing seals.
Still another object is to provide an improved roller cutter drill bit with an air circulation system in which air is circulated into the space between the roller cutter and its support exterior to the bearing seals to remove cuttings and other detritus therefrom.

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2--iO~ 86 At least the broad object of the invention is attained by a drill bit which comprises a head defining an internal chamber, a leg depending from the head with that leg terminating in a bearing shaft, a roller cutter adapted to be mounted on the bearing shaft, and bearing means support-ing the roller cutter for rotation about the bearing shaft.
An annular seal surrounds the bearing shaft and engages a peripheral surface of the open end of the cutter to prevent entry of solids to and retain lubricant in the bearing means, and at least one passageway is open at one end to the internal chamber and open at another end to the space between the leg and the rotating peripheral surface of the opcn clld of the cutter at a point exterior to the seal.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a sectional view of one-segment of a drill bit to illustrate the relationship of the air and lubricant circulation passages.

Fig. 2 is a section view taken on the line 2-2 of Fig. 1.

Fig. 3 is a section view of one segment of a drill bit similar to that shown in Fig. 1 but having a different bearing seal.

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Fig. 4 is an enlarged detail section view of the bearing ~r seal in the embodiment of the invention shown in Fig. 3.
~ DESCRIPTION OF THE PREFERRED EMBODIMENTS
!~ In the drawings, the drill bits are shown by showing details of one segment, it being understood that the drill bit will normally have two or more, and preferably three, I
segments. The drill bit segment 10 has a component of a roller cone cutter type of earth drill. Drill bit segment 10 - comprises a bit head 11 and threaded shank 12 for connection to a drill stem (not shown). A cutter support or the leg 13 extends downwardly from the head or body 8 which defines and encloses an internal chamber 9 which during drilling is in communication with the circulating fluid passage in a drill string when the drill bit is connected to the lower end of the drill string for drilling. The leg 13 terminates in bearing shaft 14.
A roller cutter 15 of generally conical shape is mounted on bearing shaft 14 and is supported on friction bearing 16 on the shaft 14 and has a peripheral groove or bearing race 17 in which there are provided ball bearings 18. The cutter 15 has an inner bore 19 providing a bearing surface which rides on a bushing l9a of the floating type. Bushing l9a floats between the bore or bearing surace 19 of roller cone cutter 15 of the outer surface of bearing shaft 14. Bushing l9a may be of any suitable material of construction such as borided steel or hardened beryllium-copper alloy or the like.
The bushing should be of sufficient strength and toughness to stand the wear of the roller cutter and should be of sufficient hardness and surface lubricity to resist extrusion and galling.

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In assembling the cutter 15 on shaft 14 the ball bearings 18 are inserted through passage 20 and held in place by a retaining pin 21. Retaining pin 21 is welded in place as indicated at 22. Retaining pin 21 serves to hold the ball bearings in place and has a curvature at its end portion matching the curvature of the ball bearing race 17. The cutter 15, shaft 14, leg l3 and associated parts may be made of alloy steel and cutter 15 preferably has inserts 23 therein of tungsten carbide or other suitable cutting elements. In some applications cutters having integrally formed teeth may be used instead of cutters provided with tungsten carbide inserts.
The cutter 15 has a groove 24 extending radially outward from bearing shaft 14 adjacent to the open end of the cutter 15. A sealing ring 25, which may be made of a suitable elastomeric material, such as Buna-N or the like, is positioned in groove 24. The seal ring 25 may be an "0" ring, but preferably is of generally rectangular cross-section or oval or other elongated cross-section in a radial dimension. The radial dimension of the ring is preferably of the order of one and one-half times the axial dimension. A sealing ring of this general type is disclosed in U.S. Patent 3765495.
: The sealing ring is preferably maintained in hoop compression and is compressed radially by an amount less than 10% of its radial dimension.
A flange portion 26 lies between groove 24 and a counter-bore 14a in the open end of the cutter 15. Counterbore 15a `is spaced from the surface of leg 13 and defines an annular chamber or passage having a relatively small outlet clearance between the surface of cutter 15 and the surface of leg 13.
The groove 24 confines seal 25 so that it does not tip or tilt axially to any substantial extent. The groove finish 1~ 81 ~6 may be relatively rough since it is preferred that the seal ring 25 rotate with cutter 15 and slide on bearing shaft 14.
A grease reservoir 26 is provided in bit head 11 to provide lubricant to the cutter bearing through aperture 27 and passageway 28 in the bit head 11 and support or leg 13 and channels 29 and 30 in the retaining pin 21. The reservoir 26 has a closure 31 sealed in place with a snap ring 32.
The closure 31 also serves to keep in place spring 33 which abuts a piston 34 having a peripheral sealing ring 35. The force of spring 33 and also of air pressure, as will be s~bsequently described, urges piston 34 to maintain continuous pressure on lubricant in reservoir 26 to force the lubricant into continuous lubricating contact with the various bearings and bearing surfaces. The closure 31 has a passageway 36 in communication with passages 37 and 38 in piston 34 to balance the pressure on the system.
In Fig. 2, there is shown a sectional view illustrating the relation between passage 28 which conducts a lubricant to the bearings and other bearing surfaces and the passages which conduct air under pressure to flush cuttings from the exterior of the bearing seals. In Fig. 2, it is seen that there are provided a plurality of passages 39 and 40 which open through outlet openings 41 and 42 into the space between counterbore 15a and the surface of leg 13.
The size of passages 39 and 40 and openings 41 and 42 is selected so that the area of the openings is greater than the area of the peripheral opening from the annular passage defined by counterbore 15a and the surface of leg 13. There is enough difference in the size of the openings 41 and 42, in total area, and the area of the peripheral opening around the base of the cutter 15 such that when compressed air is introduced from internal chember 9 through passages 39 and 40 a positive pressure ~ 6 is maintained in the peripheral passage defined by counterbore 15a and causing a continuous outflow of air therefrom which will continuously flush cuttings and other detritus away from the bearing seal 25. The location of the passages 39 and 40 with openings 41 and 42 is such that the air is circulated exterior to the bearing seal 25 to flush away cuttings and detritus and prevent wear of the bearing seal which often occurs when cuttings and detritus become packed around the bearing seal.
The internal chamber 9 is also provided with a passageway 39 which opens into the portion of reservoir 26 above the piston 34. As piston 34 is moved under the influence of spring 33, air pressure is introduced through passageway 39 to add the air pressure to the force of spring 33 urging piston 34 against the lubricant to force the same into continuous contact with the various bearing surfaces.
The arrangement of passages in this drill bit which causes the circulation of air exterior to and adjacent the bearing seal 25 and which causes a continuous outflow of air keeps the bearing seal cleared of cuttings and other detritus which results in substantially improved life for the bearing seals and improved life and extended footage for the drill bit.
In Figs. 3 and 4, there is shown another embodiment of the invention in which a differing bearing seal is used. The structure of the drill bit is substantially the same as that shown in Fig. 1 except for the different bearing seal. The bearing shaft 14 is not shown in the same detail as in Fig. 1 since the feature representing the improvement of this embodiment is the different bearing seal and the relationship of the seal to the air flushing passages.

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In Fig. 3 counterbore 15a in roller cutter 15 has the seal 25a positioned therein and passage 39a is provided with openings 41a and 42a extending into the annular cavity or space defined by counterbore 15a and the surface of leg 13 exterior to the bearing seal 25a.
The bearing seal 25a is of an elastomeric material with a metal spring 25b embedded therein which urges the surfaces 25c and 25d against the surface of the leg 13 and the counterbore 15a in roller cutter 15, respectively. The surface 25c of seal 25a is preferably cemented to leg 13 to maintain the seal in a stationary position so that roller cutter 15 will slide relative to the surface 25d of bearing seal 25a.
In this embodiment, the air pressure supplied from internal chamber 9 enters through passage 39a and opens 41a and 42a and maintains a positive pressure inside the peripheral opening from the space into which the compressed air is introduced that a positive pressure is maintained in that space with a substantial outflow of air therefrom which will keep the space adjacent to the bearing seal flushed clear of cuttings and other detritus.
While this invention has been described fully and clearly with special emphasis upon two preferred embodiments, it will be obvious to those skilled in the art that within the scope of the appended claims the invention may be practiced otherwise than as specifically described as above.

Claims

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

1. A drill bit, comprising:
a head defining an internal chamber, a leg depending from said head, said leg terminating in a bearing shaft, a roller cutter adapted to be mounted on said bearing shaft, bearing means supporting said roller cutter for rotation about said bearing shaft, an annular seal surrounding said bearing shaft and engaging a peripheral surface of the open end of said cutter to prevent entry of solids to and retain lubricant in said bearing means, and at least one passageway open at one end to said internal chamber and open at another end to the space between said leg and the rotating peripheral surface of the open end of said cutter at a point exterior to said seal.

2. A drill bit according to Claim 1 in which the opening of said passageway into the space between said leg and said cutter is of a size relative to the peripheral opening from said space such that a positive air pressure is maintained therein when air pressure is introduced to said internal chamber.

3. A drill bit according to Claim 1 in which there are provided a plurality of passageways extending from said internal chamber to points spaced around the peripheral space between said leg and the rotating peripheral surface of the open end of said cutter exterior to said seal.

4. A drill bit according to Claim 3 in which the opening of said passageways into the space between said leg and said cutter is of a total size relative to the peripheral opening from said space such that a positive air pressure is maintained therein when the air pressure is introduced to said internal chamber.

5. A drill bit according to Claim 1 in which said roller cutter has a peripheral groove adjacent to the open end thereof, and said seal is positioned in said groove and engaging said shaft in sealing relation.

6. A drill bit according to Claim 1 in which said roller cutter has a counterbore at the open end thereof defining an annular passage into which said one passageway opens.

7. A drill bit according to Claim 6 in which said seal is positioned in said counterbore.

8. A drill bit according to Claim 5 in which said roller cutter has a counterbore at the open end thereof defining an annular passage into which said one passageway opens.

9. A drill bit according to Claim 1 in which there are provided a plurality of passageways extending from said internal chamber to points spaced around the peripheral space between said leg and the rotating peripheral surface of the open end of said cutter exterior to said seal, and in which said roller cutter has a peripheral groove adjacent to the open end thereof and said seal is positioned in said groove and engaging said shaft in sealing relation.

10. A drill bit according to Claim 9 in which the opening of said passageway into the space between said leg and said cutter is of a size relative to the peripheral opening from said space such that a positive air pressure is maintained therein when air pressure is introduced into said internal chamber.