Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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1 The present invention relates to drill bits, and more
particularly to diamond drill bits used in the rotary drilling
of bore holes in earth formations.
Certain earth formations are very hard and abrasive,
resulting in drill bits having a short life, poor penetration
rate, and necessitating the devotion of a large percentage of
rig time in making round trips for the purpose of changing
bits. Giamond drill bits, in which diamonds are surface-set
in a bit matrix of hard metals, perform well in hard rock
formations, but they are quickly damaged in very abrasive
formations where accelerated wear on the diamonds occur, as
well as fracturing of the diamonds, the bit life being
shortened considerably.
By virtue of the present invention, a diamond drill bit
has been developed in which the penetration rates and length
of bore hole drilled have been increased substantially.
Diamond impregnated segments are secured to the hard metal
matrix portion of the bit body, the segments operating upon
the entire area of the bottom of the bore hole being drilled.
These segments include diamonds dispersed throughout the mass
of a matrix, which is designed to release the diamonds as they
become damaged and expose new diamonds at a controlled rate,
in effect resharpening the segment for continued drilling of
the bore hole.
Surface set diamond drill bits of the prior art are not
susceptible to repair after some of the diamonds become
damaged or lost. Another objective of the present invention
is to utilize impregnated segments for cutting members,
because of their increased useful life, and secure such
segments to the matrix portion of the bit body, also referred
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1 to as the "crown", in such manner that worn segments can be
removed readily and replaced, all without disturbing the crown.
Heretofore, as disclosed in United States patent no.
3,696,~3~5, separately prepared sintered segments containing
diamonds have been utilized, which are placed in a carbon mold
and the entire bit crown formed by a known infiltration
process which requires a casting temperature usually of at
least about 2150 degrees F. With this method, the bit cannot
be repaired after segments become worn. Moreover, synthetic
diamonds cannot be utilized as the diamond portions of the
segments, inasmuch as the sintering and casting temperatures
cause thermal degradation of the synthetic diamonds.
By virtue of applicant's invention, the crown portion of
the drill bit is first made with surface-set diamonds mounted
at the inside diameter and along the outside diameter of a
core bit to hold the inside and outside gage of the hole and
core being drilled. In the case of a drill bit, the crown is
first made with surface-set diamonds positioned at its outside
diameter. In both cases, the crown can be formed by the
infiltration method of the prior art which can occur at the
normal casting temperature noted above of about 2150 degrees
F. The synthetic diamond impregnated segments are
manufactured separately by a known hot pressing process, which
enables the segments to be prepared at a much lower
temperature than the infiltation temperature. As an example,
the lower temperature may be about 1830 degrees F. which is
suitable for the manufacture of segments containing synthetic
diamonds and does not lead to thermal degradation of the
diamonds.
The mold used in forming the bit crown also has elements
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1 placed therein at precise locations, so that the casting and
infiltrating operation also results in the crown having
preformed grooves or slots in which the impregnated segments
are placed, and then, by a brazing operation, affixed to the
crown at a low temperature well below the temperature at which
the synthetic diamonds would be thermally damaged. By way of
example, the brazing process can be carried out at a
temperature of approximately 1400 degrees F. Although natural
diamonds could be used in producing the impregnated segments,
it is preferred to use synthetic diamonds since they have a
longer drilling life than natural diamonds.
Because of the relatively low temperature at which the
segments are affixed to the bit crown, worn or damaged
segments can be readily replaced simply by elevating the
temperature of the bit to the brazing temperature, which
énables the individual segments to be removed and new or
undamaged segments mounted in their place. Accordingly, the
bit is susceptible of repair at subst:antial savings in bit
c~st.
During the drilling operation, the drilling fluid is
pumped down through the string of drill pipe and discharges
from the bit. The segments themselves are arranged on the bit
crown and spaced from one another in such a manner as to
provide fluid passages through which the drilling fluid can be
forced under pressure for the purpose of removing the cuttings
and enabling them to be carried along the exterior of the bit
and string of drill pipe to the top of the bore hole, such
drilling fluid also serving to keep the segments and other
cutting elements of the bit in a clean and cool condition,
thereby enhancing their useful lives.
1 ~ccording to a~ aspect of the invention, a rotary drill
bit for drilling bore holes in earth formations is disclosed
comprising a body, a hard metal matrix secured to the body and
providing a face adapted to confront the bottom portion of the
bore hole. The matrix has generally radial preformed grooves
therein opening through the face and extending to an outer
gage portion of the matrix, preformed diamond impregnated
cutter segments in the grooves extending to the outer gage
portion and projecting from the face to drill the bottom
portion of the hole upon rotation of the bit. The matrix also
includes means securing the cutter segments to the walls of
the preformed grooves with the segments being spaced from each
other to provide fluid courses therebetween extending to the
outer gage portions. The body has passage means therein and
means for conducting fluid from the passage means to the fluid
courses to remove cuttings formed by the segments from the
bottom region of the bore hole. The preformed grooves extend
to an inner gage portion of the matrix and the inner portions
of the segments terminate at the inner gage portions. A
conducting means includes passages in the inner gage portion
leading to the fluid courses.
This invention posseses many other advantages, and has
other objects which may be made more clearly apparent from a
consideration of several forms in which it may be embodied.
Such forms are shown in the drawings accompanying and forming
part of the present specification. These forms will now be
described in detail for the purpose of illustrating the
general principles of the invention; but it is to be
understood that such detailed description is not to be taken
in a limiting sense.
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1 Referring to the drawings:
Figure 1 is a combined side elevational view and
longitudinal section through a diamond drill bit embodying the
invention;
Figure 2 is a bottom view of the drill bit shown in
Figure 1 taken along the line 2-2 of Figure l;
Figure 3 is an enlarged fragmentary section taken along
the line 3-3 on Figure l;
Figure 4 is a combined side elevational view and
longitudinal section through a core bit embodying the
invention;
Figure 5 is a bottom plan view taken along the line 5-5
on Figure 4;
Figure 6 is an enlarged fragmentary section taken along
the line 6-6 on Figure 4;
Figure 7 is an enlarged side elevational view through a
portion of the core bit disclosed in Figure 4, one of the
segments having been omitted to illustrate the groove or slot
in which the segment is to be placed;
Figure 8 is an enlarged fragmentary section taken along
the line 8-8 of Figure 7;
Figure 9 is a view similar to Figure 8 of another
embodiment of the invention.
As disclosed in Figure 1 to 3, inclusive, a drill bit 10
is provided for operation upon the bottom of a bore hole, the
cuttings being flushed from the bottom upwardly around the
drill bit and string of drill pipe (not shown) to the top of
the hole. The drill bit includes an upper body or blank 11
having an upper threaded pin 12 for threadedly attaching the
bit to the string of drill pipe The upper body is attached by
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1 a weld 11' and a threaded connection 13 to a lower body or
shank 14, to which a matrix portion or crown 15 of a known
type is secured. Circulating and drilling fluid pumped down
through the drill pipe flows into a central or main passage 16
in the upper and lower body portions 11 and 14 of the tool,
from where it will flow through a plurality of
circumferentially spaced longitudinally extending ports or
openings 17 extending through the bit crown for discharge
against the bottom of the hole. The lower end of each
distribution port 17 communicates with a generally radial
fluid passage 18~ referred to hereinbelow, extending toward
the outer gage portion 19 of the bit.
The gage portion of the crown has diamonds 20, or
similar cutting elements, secured in the outer gage face of the
bit, which are secured to the crown 15 during the formation of
the latter by the infiltration process. The crown has a
plurality of generally radial slots or grooves 21 formed in
its lower face during the production of the crown by the
infiltration process, this face having an outside diameter or
gage portion 22, the lower end of which terminates at a
downwardly tapering conical portion 23 which, in turn, merges
into a lowermost portion or nose 24. The nose merges into an
upwardly tapering generally conical or stepped region 25, more
specifically disclosed as a series of steps 26, 27, 28, the
uppermost step 28 circumscribing a central core tube portion
29 into which a relatively small diameter core, formed by the
bit, can move during the drilling of the hole. The core moves
upwardly until it engages a tapered core breaker face 30 that
will break off the core, enabling it to discharge through an
ejection passage 31 extending laterally to the exterior of the
1 drill bit above the reaming face 19. The central vertical
passage has inner gage stones or diamonds 32 surface-set in
the crown during the infiltration process for cutting the
small diameter core (not shown) which will be broken off by
the core breaker face 30, as described above. Outer gage
diamonds 20 are surface-set in lands 34 defined by vertical
fluid courses or passages 35 extending from the upper end of
the outer conical portion 23 and opening upwardly through an
upwardly tapering surface 36 of the crown and adjacent shank
14.
Preformed impregnated segments 37 are mounted in the
grooves or slots 21 casted into the bit crown 15. Each
segment may be made as a single piece, or a plurality of
pieces. As shown, the upper portion 37a of each segment abuts
a shoulder 38 at the end of a vertical groove portion 39. The
flank or outer portion 37b of the impregnated segment is
received within the downwardly tapering slot 40 preformed in
the crown portion 15, its upper end being integral with the
outer gage portion 37a, or, if made separate therefrom,
abutting such gage portion. The lowermost or nose part 37c of
each segment, which may be made integral with the flank 37b,
or separately and abutting the lower end of the flank, is
received in a companion curved groove portion 41 cast into the
crown.
The nose portions 37c of the segments terminate
substantially short of the axis of the bit, in the specific
design illustrated, to allow space for the mounting of
segmental or one-piece rings 42, 43, 44 in the crown which
progressively decrease in diameter in an upward direction, and
30 which bear against the companion steps or shoulders 26, 27, 28
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1 formed in the crown or matrix portion. The inner portion of
each ring partially overlies the outer portion of the next
adjacent ring, the uppermost ring 44 having an opening 45
conforming to the core tube opening 29. These rings are
diamond impregnated cutters adapted to drill the central
portion of the bore hole.
The impregnated segments and cutters are secured to the
bit crown by brazing, the brazing material flowing along and
coating the sides and inner surfaces of the grooves 21 and
segments 37, the segments extending outwardly of the bit face
to a substantial extent, which, for example, may be about
one-half the depth of each segment. In a similar fashion, the
impregnated rings 42, 43, 44 are brazed to the adjacent
contacting surfaces of the bit crown.
As noted above, the slots or grooves 21 are preformed in
the bit crown 15 during the infiltration step of the process,
in which the outer gage diamonds 20 and the inner gage
diamonds 32, both of which are natural diamonds, are affixed
to and embedded partially in the crown. The steps 26, 27, 28
20 against which the impregnated rings 42, 43, 44 are to bear are
also preformed in the crown during the infiltration process.
The segments and the impregnated rings are manufactured
separately by a known hot-pressing method to precision
dimensions, so as to appropriately fit within the slots or
grooves 21 and against the steps 26, 27, 28 and the adjacent
rises 50, 51, 52 with a precision fit. By use of the brazing
process, the segments and the rings are then secured to the
bit crown.
It is to be noted that the outer end of each flow
passage 17 is disposed between and adjacent to the inner
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1 portions of a pair of segments 37. It is to be noted that,
because of the diameter of the bit illustrated, additional
segments 60 extend inwardly from the outer gage portion of the
bit, but they extend inwardly only partially with respect to
the other segments 37. This arrangement is provided to insure
a sufficient number of segments for drilling the outer
portions of the bore hole. Such additional segments may be
unnecessary for the effective drilling of the inner portion of
the bore hole by the longer segments.
The segments project outwardly of their respective slots
and form flu-d courses 61 through which the fluid discharging
from the fluid passages 17 will be conducted toward the gage
portion of the bit for the purpose of cleaning and cooling the
segments and conveying the cuttings through the fluid courses
61 and then upwardly through the vertical fluid courses 35
extending between the gage portions of the segments. During
the drilling operation, the central portion of the bore hole
will be cut by the impregnated ring members 42, 43, 44, the
small central core remaining passing through the uppermost
ring 44 and past the inner gage stones 32 for engagement with
the core breaker face 30 and discharge through the upwardly
inclined lateral passage 31 to the exterior of the bit.
In the core bit embodiments lOa of the invention
illustrated in Figure 4, the upper body or blank lla has a
threaded box 12a for securing the bit to an outer core barrel
of a coring apparatus (not shown) which is suitably secured to
the lower end of a string of drill pipe (not shown), in a
known manner. The lower end of the blank lla is threadedly
connected to a lower body or shank 14a around which a matrix
body or crown 15a is formed. Diamond impregnated segments
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1 37f, specifically disclosed as of an arcuate or semi-circular
shape, are prefGrmed and are mounted in companion generally
radial preformed qrooves 21a cast into the lower portion of
the matrix body or crown. The inner portion of the crown has
an upwardly tapering face 100 extending from a position above
the inner ends 101 of the segments, this tapered face merging
into an inner gage face 102. Inner fluid courses 103 divide
the inner gage face into inner lands 104, the fluid courses
continuing through the inner tapered face 100. Diamonds are
surface-set in the lands in the tapered and gage faces.
Similarly, the outer gage face 105 of the crown is
divided into lands 106 by vertical fluid courses 107, the
lands receiving surface-set diamonds 108. The lower end of
the outer gage face 105 terminates in a tapered surface lOg
that ends at the outer upper end 110 of the segments 37f
disposed in the grooves 21a, this inner tapered face also
having fluid courses 111 that communicate with the fluid
courses 112 provided between the segments 37f disposed in the
slots or grooves. Similarly, the inner fluid courses 103
communicate with the fluid courses 112 provided by the spaced
segments 37f.
During the coring operation, drilling fluid will pass
through the space between the inner and outer core barrels
(not shown), and through the inner fluid courses 103,
discharging through the fluid courses 112 provided between the
segments 37f and then passing upwardly through the fluid
courses 107 in the outer gage portion of the bit, for
continued upward movement around the outer core barrel and the
string of drill pipe attached thereto. The cuttings will be
flushed through the several fluid courses, the fluid also
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1 cooling and cleaning the segments and the surface-set diamonds.
The core bit segments 37f are produced separately by
hot-pressing, in essentially the same manner as the segments
are produced for the drill bit. Such segments may embody
synthetic diamonds, although natural diamonds can be used, if
desired.
The segments 37f are secured in position within the
grooves 21a by brazing, which can be preformed at a
temperature of about 1400 degrees F.
As shown in Figures 7 and 8, the trailing face 115 of
each slot can be extended by forrning the crown with a beveled
flank 116 that bears against the trailing face 117 of the
adjacent segment. This not only increases the area through
which thrust is transmitted from the segment 37a to the crown
15a, but provides additional surface for the brazing material
to secure each segment 37a to the crown 15a. In Figure 7, one
of the impregnated segments has been purposely omitted to
disclose the large radial face 115 oi- the groove in which the
segment is to be mounted.
A variation of the beveled flank arrangement is
disclosed in Figure 9. Instead of the beveled flank 116 being
formed intergrally with the crown, as in Figure 8, it can be
formed as a separate tungsten carbide ring 130, the inner
portion 132 of which is beveled or triangular in shape. The
rectangular inner portion 131 fits within the trailing part of
the wider groove 115a and the beveled outer portion 132
engages the trailing face 117 of the segment over a much
greater extent than in the form illustrated in Figures 6 and
3, thereby backing up and offering greater support to the
segment 37f than the arrangement disclosed in Figures 3 and
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1 6. The separate tungsten carbide segment 130 is brazed into
the slot 115a and to the segment 37f itself in the same
operation as the segment is brazed to the base and leading
side of the groove or slot and the trailing surface of the
groove or slot.
A number of circumferentially spaced junk slots 150 are
provided along the gage portion of the bits to enable the
flushing Eluid to carry relatively large cuttings upwardly
along the bit to the smaller diameter shank portion
thereabove, for continued upward movement around the drill
pipe string to the top of the bore hole. Such junk slots are
usually provided in diamond drill bits and do not constitute
any portion of the present invention.
Bits are made in accordance with the present invention
have drilled very hard and very abrasive formation at a
greater rate and of a longer longitudinal extent than
surface-set drill bits. Preforming of the segments and their
mounting in preformed slots or grooves in the crown, to which
they are suitably secured, as by brazing or soldering, does
not subject the diamonds to elevated temperatures, that have
heretofore resulted in their deterioration, which is
particularly true of syntehtic diamonds used in the segments.
The preformed segments are prepared at a lower temperature
than the infiltration temperature at which the crown portion
is made which is 2150 degrees F approximately, as compared
with the lower temperature of 1830 degrees F for the
segments. Moreover, the brazing process may be carried out at
a temperature of approximately 1400 degrees F, or well below
the temperature at which synthetic diamonds will be damaged
thermally.
131 ~65i92
1 Because of the low brazing temperature and the fact that
the segments are separate cutting members, damage to or loss
of segments does not require discarding of an entire drill
bit. The damaged segments can be easily removed without any
harmful effects on the remainder of the bit and replaced by
new segments.
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