Note: Descriptions are shown in the official language in which they were submitted.
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: REINFORCED ROTARY DRILL BIT
This invention relates to drill bits, and more
particularly to rotary drill bits with diamond cutting
elements used in the drilling of bore holes in earth
formations.
Earth boring diamond drill bits may typically
include an integral bit body which may be of steel faced
with an abrasion-resistant material such as tungsten
carbide or may itself be fabricated of a hard metal matrix
material such as tungsten carbide. A plurality of diamond
cutting elements are mounted along the exterior face of
the bit body. Each diamond cutter typically may be
mounted on a stud the other end of which is mounted in a
recess in the exterior face of the bit body, or the cutter
mount may be integrally cast with the matrix of the bit
body.
The cutting elements are positioned along the
leading edges of the bit body so that as the bit bodv is
rotated in its intended direction of use, the cutting
elements engage and drill the earth formation. In use,
tremendous forces are exerted on the cutting elements,
particularly against the face thereof in the forward to
rear direction as the bit is rotated. Additionally, the
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bit and cutting elements are subjected to substantial
abrasive forces. In some instances, impact, late~al,
and/or abrasive forces have caused drill bit failure and
cutter loss.
A significant problem encountered when drilling
in certain earth formations such as shales, clay, and
other water reactive, sticky formations known as "gumbo"
has been the tendency of such bits to become clogged
during operation. In dealing with such earth formations,
bits have been designed with relatively large cutters with
strong hydraulics in the proximity of the cutters to
remove the cuttings from the cutter faces with a high
volumer high velocity, hydraulic fluid flow.
As synthetic diamond technology has advanced, it
is now possible to provide large diamond disc cutters up
to two inches in diameter for use on bits. These very
large cutters have been helpful in drilling in "gumbo"
formations. However, the large diameter of the cutting
elements has caused problems in providing secure
attachment thereof to the exterior face of the rotary
drill bits. To accommodate such large diameter cutters,
drill bits have been fabricated with outwardly extending
shoulders or protrusions on which the cutters may be
mounted. However, this leaves a relatively small
structure beneath and behind the cutter faces to support
the cutters. Additionally, blades, ridges and other
structures having multiple cutters mount thereon and
extending significant distances from the main profile of
the bit body are also becoming more common, presenting
similar problems
While tungsten carbide or other hard metal
matrix bits are highly erosion ~esistant, such materials
are relatively brittle and can crack upon being subjected
to the impact forces encountered during drilling.
Typically, such cracks have occurred proximate where the
cutting element support structures join the matrix body.
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The shoulders or protrusions on the exterior of the drill
bits to accommodate large diameter cutting exposes these
areas of the bit to high i~pact and shear forces. Bits
having large cutter elements thereon extending outwardl~
s from the body of the bit are particularly susceptible to
cracking and failure due to these high impact and shear
forces. If the cutting elements are sheared from the
drill bit body, the expensive diamonds on the cutter
elements are lost, and the bit may cease to drill.
_ 10 Accordingly, there is a need in the art for a
drill bit having increased impact strength and resistance
to cracking, particularly in areas supporting the cutter
elements.
The present invention meets that need b~
providing a rotary drill bit in which the areas supporting
the cutter elements are reinforced to provide those areas
with increased impact strength. In accordance with one
asp2ct of the present invention, a rotary drill bit is
provided which includes a main body portion of a hard
metal matrix material and at least one shoulder or
protrusion formed of the same hard metal matrix material.
The protrusion is integral with the mai~ body portion of
the bit and extends outwardly from the exterior surface of
the bit. As used in this specification, the term
protrusion encompasses protrusions, shoulders, blades,
ridges, or other structures extending outwardly from the
main profile of the bit body.
A cutting element is mounted on the protrusion
and is angled as known in the art to accomplish drilling
of an earth formation. There may be one or a plurality of
individual cutter elements mounted on each protrusion.
Means for reinforcing the protrusions are provided and
extend between the main body portion of the bit and
individual protrusions.
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In a preferred em~odiment, the reinforcing
structure comprises a solid preformed arrangement
positioned rearwardly of the cutting elements and
extending at an acute angle with respect to the main body
portion of the bit. The reinforcing structure may be in
the form of one or more rods, bars, disks, or wires which
are preferably of metal. While steel is the preferred
composition for the reinforcing structure, other metals
and metal alloys such as stainless steel, nickel alloys or
molybdenum may be utilized.
The present invention also encompasses drill
bits having a plurality of such protrusions and cutting
elements and is particularly suited for use with rotary
bits having relatively ~arge diameter cutting elements.
; 15 The portions of the matrix on which the elements are
mounted are reinforced to provide the bit with greater
impact strength and greater resistance to cracking ar.d
failure of the bit matrix. Accordingly, it is an object
of the present invention to provide a rotary drill bit
matrix having improved impact strength and resistance to
cracking over prior bits. This, and other objects and
advantages of the present invention, will become apparent
from the following detailed description, the accompanying
drawings, and the appended claims.
Fig. l is a perspective view of the rotary drill
bit of the present invention;
Fig. 2 is a diagrammatic sectional view taken
through one of the cutting elements along line 2--2 of
Fig. l and illustrating the reinforcing structure; and
Fig. 3 is also a diagrammatic sectional view
similar to Fig. 2 illustrating the reinforcing structure
in a bit having a somewhat different structure.
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~he invention is illu~tcated in the drawing~ with
refe~ence to a typical constcuction of a rotary ea~th
boring bit. In particular, ~he invention is illustrated
and desccibed with re~erence to the large compact cutter
rotacy bit described in g~eater detail in commonly
assigned, copending Canadian Application Serial
No. 546,521. It will al o be recognized by
: tho~e skilled in the aet that the configuration of the
cutt~ng element along the exte~ior face of the mat~ix may
be varied depending upon ~he de~ired u~e of the bit.
Thus, the bit may be designed for ei~her a flat,
parabolic, or extended blade c~own profile. The invention
may also be useful in any ha~d metal matrix bit
configuration which has one or more shoulder~, ridges,
blades, or other protcusion~ extending outwa~dly from the
main body of the bit.
Referring now to Fig. 1, rota~y drill bit 10 of
the ty~e discloaed in the above referenced copending
I ap~lication include~ an exteEior genecally cylind~ical
surface o~ gage 12 having a bit face 14 on it~ lowermost
portion. Both gage 12 and bit face 14 are formed of the
ha~d metal matrix material of the bit body, such a~
tungsten ca~bide. Defined within gage 12 are a plurality
of 3unk ~lots 16 and lB. The jun~ slots aEe designed to
facilitate the upwald flow of the drilling fluid and
cuttlngs away ~rom the bit face 14. A number of fluid
nozzle~ 20 are also located on bit face 14. Each of fluid
nozzles 20 is designed to provide directed fluid ~low to a
j ~peci~ic cutting element 22. Each cu~ting element 22
: 30 comp~i~es a tungs~en carbide backing 25 having de~osited
thereon a thin fiynthetic diamond cutting face 23 which
pe~focm~ the cut~ing operation.
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Cutting elements 2Z are mounted on shoulders or
protrusions 2~ which extend outwardly from the bit face
14. The cutting elements are secured in place by brazing
o~ otherwise fixing them to ~he bit face in a conventional
manner~ For example, cutting elements 22 may be secured
to the matrix and to tung~ten carbide slug 26 cast into
the trailing portion of sockets 28 (best shown in Fig. 2)
on bit face 14 by brazing or other suitable means. In a
preferred embodiment, the cutting faces Z3 of cutting
elements 22 are one inch in diameter or larger.
A shown, each cutte~ element 22 has an
associa~ed fluid nozzle Z0 which provides a dicected
hydLaulic flow of fluid to the face of the cutting
element. This fluid flow applies a force to chips cut
from the ea~th focmation, loo~ening and removing the chip~
from the faces of the cu~ting elements. Additionally, bit
10 includes a plurality of gage cutting elements 30 which
comprise smaller diametec diamonds which a~e mounted on
the gage 12 of bit face 14. The gage cutters insure that
the drill cut~ a path of the desired diameter through the
earth formation.
AB shown in Fig. 2, positioned rearwardly of each
cutting element 22 is ~einforcing means 32 extending
between the main body portion of drill bit 10 and
~rotru~ion o~ shoulder 24. AB illustrated and previously
noted, cutting element 22 includes a hard metal matrix
backing 25 of tung~ten carbide or the like, and is
pre~erably ~ubstantially late~ally symmetrical.
The backing 25, having cutting face 23 thereon,
i8 beazed into socket 28 in the bit mat~ix. Backlng 25
provides shock protection and load eesistance to the
cutting face 23. As shown in Fig. 2, the bit 10 rotates
in the direc~ion of the arrow and encounters impact forces
.
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on cutting face 23 as indicated by the a~row shown in
ehantom lines. Typically, the cutting element 22 will
have a predetermined ~ake angle to the ~ormation
encountered depending upon placement of cutting element 2Z
and the bit profile and the desired operation of the bit,
which depend~ upon the focmations to be drilled.
Reinforcing means 32 may comprise a
longitudinally extending element which takes the form of a
rod, bar. disk, or wire. It may also comprise a plurality
of such structures. In a preferred embodiment.
reinforcing means 32 comprises a thceaded rod of
cylindrical steel stock, such as 1018 or 1020 steel.
Preferably, the steel stock ha~ no coatings on it and the
stock i~ cleaned of any oxides prior to being used.
As can be seen, reinforcing means 32 i6
po~itioned rearwardly of cutting element 22 and extends
between the main body of the bit and substantially the
outecmost extent of proerusion 24. Reinforcing means 32
is eositioned at an acute angle with ceseect to the main
body of the bit. At such an angle, the reinforcing means
is pointed slightly towa~d cuttinq element 22~
Rein~orcing mean~ 32 also extends at least paetially
behind cutting element 22 and is also preferably centered
with respect to cutting element ZZ so that impact forces
will be fo~used theceon.
In the embodiment of the invention illus~rated in
Fig. 3, a somewhat differently configured bit ha~ a
shoulder or protrusion Z4, which may be a blade-shaped
protrusion emanating from ~he center of a "fishtail" bit
; 3~ toward the gage of the bit. Cutting elemen~ 22 is mounted
into socke~ 28 in the bit matrix. As shown, reinforcing
rod 32 i~ po~itioned rearwardly of cutting elemen~ 22 and
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extend~ between the bit matrix and substantially the
outermost extent of shoulder or protrusion 34.
Reinforcing rod 3Z is pceferably angled so that it is
roughly parallel or at a slight angle (as shown) to the
~urface of cutting element 22 (as shown). Reinforcing rod
32 i~ disposed in a substantially perpendicular
orientation to the profile of the main body portion of the
bit.
_ Rotary drill bits employing the present invention
are generally made by powder metallurgical techniques
which are known in the art. The bit is formed in a carbon
mold having an internal configuration corresponding
generally to the eequired sueface shape of the bit body,
including erotrusion6 for mounting cutting elements.
lS Thus, the areas whe~e the junk slots are found on the
finished bit body contain carbon or clay displacement
material in the mold.
The aceas in the mold which correspond to where
the cutting elements are to be mounted after furnacing of
the bit body are ~illed with a displacement material such
as cacbon di~c~ of like size to the cutting elements
having clay adj~cent thereto so that the furnaced bit body
ha~ mounting sockets 28 formed therein. Reinforcing means
32 are po6itioned in the mold by embedding them in the
clay di~placement material placed at the outermo~t extent
of the ~rotrusion cavitities from the body mold cavity.
Reinforcing means 32 are positioned rearwardly of
where the cutting elemen~s 22 aEe to be mounted.
Preferably, the reinforcing means 32 i6 a threaded steel
rod which is desirably positioned to be pecpendicular to
the mold profile from which it protrudes. In othee words,
when viewed ~rom the per~pective of the finished bit,
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reinfoleing means 32 extend6 fcom the main profile or
sucface of the bit in a perpendicUlar manner to the point
on the profile ~rom which it extends.
~s is conventional, elements which will ~orm the
internal fluid passages and nozzles in the finished bit
are al~o po~itioned in the mold at this time. A steel
blank i6 also eositioned in the mold at this time. A hard
metal matrix matecial such as tung6ten carbide iB then
added to the mold. A binder material, prefeeably a
copper-based alloy, in the form of pellets or other small
particles, i6 then poured over the matrix material. The
filled mold i8 then placed in a furnace and heated to
above the melting point of the binder, ty~ically above
about 1100 degrees C. The molten binder passes through
and in~iltrates the matrix material.
After cooling, the matrix and binder are
consolidated into a solid body which is bonded to the
6teel blank. After further cooling, the bit body is
removed from the mold. The steel blank is then welded or
otherwise secuced to an upper body or shank. Clay and
other displacement material i6 removed at this time.
Because reinforcing means 32 was embedded in the clay, the
poction of the eeinforcing means which extends ~rom the
bit body i5 machined off flush to ~he trailing edge of the
protrusion.
Cutting elements 22 ace then mounted to the bit
body. A~ i6 conventional, cutting element 22 is mounted
into socket 28 and backing 25 secured therein by bra2ing
with a suitable metal brazing material. The gage cutting
elements may also be mounted to the exterioc of the bi~
body at this time.
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In ocde~ that the invention may be more readily
unde~stood, ceference is made to the following example,
which i intended to illustrate the invention, but is not
~o be taken as limiting the scope thereof.
Example
In o~dec to demonstrate the ceinforcing
capabilities of the st~uc~uce of the present invention an
impact tes~ was made. The test measured the resistance ~o
fra~ture by impac~ forces of a matrix material ceinforced
by a steel rod such as ~he pceferred reinforcing rods of
the p~esent invention.
Samples of matrix material were fabeica~ed in a
conventional manner by filling a cylindrical mold with
tungsten carbide matrix material and a copper-based alloy
bindeE. The mold was sized to produce a sample specimen
8iX inches in length with a 1/2 inch diameter. The
matrices we~e furnaced at 2150 degrees F ~or 60 minutes.
Previou~ testing established that such a sample, when
sub3ected to an ;mpact ~orce with a Charpy Impact Tester,
would fracture at an impact force o~ about 3.5 ftlb.
Sample specimen 1 included a 3/16 inch diameter
mild 1018 steel rod positioned centrally wi~hin the
specimen. Sample specimen 2 included a 3/16 inch diameter
thr~aded mild 101~ steel rod positioned centrally within
the see~imen. Sample s~ecimen 3 included a 1/8 inch
diameter tool steel rod positioned centrally within the
specimen. All steel rods were grit blasted prior to
placement in the respective mold to remove any oxides.
All sample speci~ens were then cut in ~wo to ~ocm
two three inch long bars (labeled ~ and ~ below) and
te~ted using a Charpy Impact Testec. The cesults are
ceported in Table I below.
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TABLE I
Specimen #Impact Force Result
:
lA 25.0 ftlb incomplete break
lB Z3.5 f~lb break
2A 11.0 ftlb break
2B 11.7 ftlb break
2A 4.75 ftlb break
2B 5.75 ftlb break
While certain representative embodiments and
details have been 6hown foc purpose~ of illustrating the
invention, it will be aeparent to those skilled in the art
tha~ various changes in the methods and ap~aratus
di~closed heeein may be made without departi~g from the
~cope of the invention, which is defined in the appended
claim~. For example, multiple cutting element~ may be
mounted on each erotrusion: half-circular or other shape
cutting elements may be used: several reinforcing elements
may be employed for a single peotrusion: U or V-shaped
reinfoccing elemants may be used either right side up or
upside down: reinforcing elements of a variety o~
ccoss-sections, including but not limited to square,
recta~gula~, triangulae, elliptical, half-circular, etc
may be smployed.
r ~ i~
