Note: Descriptions are shown in the official language in which they were submitted.
10~
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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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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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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108168~
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
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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
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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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1081686
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.
