Note: Descriptions are shown in the official language in which they were submitted.
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Background_o~ the Invention
Diamond bits employing natural or synthetic diamonds
positioned on the face of a drill shank and bonded to the
shank in a matrix of a secondary abrasive, such as tungsten
5 carbide, by means of a metal bond, are well known in the art.
There are two general types: One in which the
diamonds usually of very small gage are randomly distributed
in the matrix; another type contains diamonds, usually of
larger size, positioned in the surface of the drill shank in
10 a predetermined pattern referred to as surface set. (See
U.S. Patents 3,709,308; 3,825,083; 3,871,840; 3,757,878; and
3,757,879.)
Drill bits formed according to the above procedure
are subject to damage when used as bore-hole drill bits. Such
15 damage results from localized destruction of the diamond
matrix complex. When this occurs, the useful life of the bit
may be terminated and extensive repairs or salvage of the bit
is required by separating the diamonds and tungsten carbide
from the steel shank.
20 Statement of the Invention
Instead of using individual diamond particles
distributed either in random orientation in the secondary
abrasive matrix, such as tungsten carbide with a metallic
bonding agent, or as surface set bits, we employ a cutter
25 preform. The cutter preform may be made as described in U.S.
Patent 3,745,623 or by molding mixtures of diamond particles,
secondary abrasive particles, and particles of a metallic
bonding agent employing the techniques of the above patents
in suitable shaped molds, for example, by the hot press methods
30 described in Patents 3,841,852 and 3,871,840. We prefer a
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preform formed as in Patent 3,745,623. According to our
invention, the preforms are mounted in the body of the drill
bit, such as described above, to be placed in spaced relation
from the part adjacent to the central axis to close to the
gage of the bit. The arrangement of the preforms in the bit
is such that on rotation o~ the bit about its axis
substantially the entire surface of the earth traversed by the
bit on rotation is engaged by the preforms.
In order to assure that the preforms can cut without
undue stress, the preforms are set at a negative rake and the
preforms are backed by an adjacent portion o~ the body of the
bit to take the thrust on the preform cutters imposed during
drilling. Bending stresses are thus minimized and in a
practical sense avoided in the preforms.
Provisions are made to move the cuttings away from the
preforms. The drilling fluid is passed through a central
bore to provide a flushing action. For this purpose, channels
are provided in fluid communication with the bore in front of
the cutter preforms. The channels extend across the face of
the bit from the central bore to the gage of the bit. While,
for some uses, the channels may be omitted, the channels, as
in our preferred embodiments, aid in establishing the bit
hydraulics to clean the face of the bit. The cutters may be
set with a zero but preferably with a negative side rake~ so
as to provide for a snowplow effect to move the cutting to the
gage of the bit. The channels in our preferred embodiment
extend in front of the cutter preforms which are oriented as -
described above. The orientation of the rake and the fluid
through the channels move the cutting to the annulus between
the bit and bore hole to be carried up the annulus to the
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surface. The preform cutters are carried in sockets positioned
in the base of the drill bit, preferably in a drill bit, coated,
for example, with metal-bonded secondary abrasives having a
hardness value less than diamonds. Coating of the drill bit
with such hard material is conventional, but in such case, the
diamonds are mounted as described in the above patents. We
prefer to prepare sockets in the drill, so oriented about the
drill bit, and with the preforms so oriented in the sockets,
as to give the pattern previously referred to.
The cutters according to our invention may be mounted in
sockets formed in the matrix-coated drill, so formed as to
orient the preforms which are mounted by insertion into the
sockets, to provide the pattern and rakes described above.
Instead, the preforms may be mounted in receptacles positioned
on studs which are inserted in sockets formed in the matrix-
coated drill. The studs and sockets are formed so that on
insertion of the studs in the receptacles, the preforms are
oriented in the pattern and with the rakes described above.
We prefer to use the bits carrying the studs in
relatively soft formations and to use the preforms mounted
directly in the sockets for hard formations.
The arrangements, both that employing preform cutters
mounted on studs positioned in the sockets and the preforms
mounted directly in the sockets formed in the face of the bit,
have the advantagè that the cutters may be backed so that they
are in compression rather than in tension due to binding~
We prefer to arrange the cutters in an array in the
manner and for the purposes described above and more fully
described below and to arrange the fluid channels to be
~0 positioned in front of the cutter arrays. This arrangement
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controls the flow pat~ern across the cut~ing surface in
immediate proximity of the cutters and aids in removing
cuttings and flushes them away from the cutters.
One of the advantages of the mounted preform cutters
according to our invention is that, on destruction or other
damages to a preform, the damaged preform may be removed and
replaced without requiring the salvage of the entire bit.
The above design of the diamond bit of our invention
is particularly suitable when using synthetic diamonds, such
as are employed in the formation of the cutting elements
described in Patent 3,745,623. Such diamonds are weakened to
a much greater degree than are natural diamonds at temper-
atures normally employed in production of drill bits by
processes, such as are described in United States Patents
3,709,308; 3,824,083; and 3,757,879. Such processes entail
exposing diamonds to temperatures which are used in the
infiltration or hot press processes of the aforesaid patents.
The temperatures employed in such procedures are in the order
of above about 2000 F., for example, 2150F. Such
temperatures, while suitable for natural diamonds, are
excessive for synthetic diamonds and weaken them excessively.
The design of the drill bit of our invention permits
the use of synthetic diamonds as well as natural diamonds in
that the preforms using synthetic diamonds or natural diamonds
may be formed at temperatures suitable for synthetic diamonds
as is described in said Patent 3,7~5,623.
The design of our invention thus permits the formation
of the drill bit body at high temperatures and the formation
of the preforms when using natural diamonds by the high
0 temperature methods previously described or when using
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synthetic diamonds by forming them at lower temperatures, ~or
example, as described in Patent 3,745,623. Thus the preforms
employing, for example, natural diamond~ may be formed by the
hot press method referred to in Patent 3,871,840 employing
molds of suitable shape to form the preform of the desired
geometric configuration.
Other features and objects of the invention will be
understood by reference to the drawings of which:
Figure 1 is a view partly in elevation and partly in
quarter section of an earth-boring bit according to our
invent.ion;
Figure 2 is a plan view of the bottom of the bit taken
on line 2-2 of Figure l;
Figure 3 is a fragmentary section taken on line 3-3 of
Figure 1 with parts in elevation;
Figure 4 is a section taken on line 4-4 of Figure 3;
Figure 5 is a section on line 5-5 of Figure 4;
Figure 6 is a fragmentary detail of Figure 2 showing
the side rake;
Figure 7 is.a fragmentary section on line 7-7 of
Figure 2;
Figure 8 is a section similar to Figure 1 prior to
installation of the studs;
Figure 9 is a vertical section of another form of a
bit according to our invention;
Figure 10 is a view taken on line 10-10 of Figure 9;
Figure 11 is a fragmentar~ detail on line 11-11 of
Figure 10;
Figure 12 is a section taken on line 12-12 of Figure 11;
Figure 13 is a section taken on line 13-13 of Figure 12.
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In the form of Figures 1-7, the tubular shank 1 of the
bit is of conventional shape and is connected to the drill
collar 2 and is coated internally and externally of the shank
1 with a hard material 3, for example, such as metal-bonded
tungsten carbide to form the face 4 of bit section and the
stabilizer section 5, as in prior art diamond drill bits used
or earth bore-hole drilling. The hard coating 3 of the bit
extends circumambiently about the central axis of the bit and
is positioned between the gage 6 of the bit and across the
face of the bit. The hart coating at 5 extends to form the
gage 6.
Sockets 7 are positioned in the coating 3 spaced as
herein described in the face 4 in accordance with a pattern
for the purposes herein described. The cutters 8 are mounted
1~ in the receptacles 9 carried on studs 14 positioned in sockets
7. We prefer, especially where the cutters are mounted in
studs as described below, to form the face of the bit in steps
26 extending circumambiently about the :Eace of the bit, as is
described in a copending Canadian application filed jointly with
2a applicants and another, S.N. 288,987. As is shown in the
copending application and in Figures 1, 2, 7, and 8, the steps
extend as a spiral from an intermediate portion 10 of the
bit 1 to the portion of the face of the bit adjacent the gage
6, as will be more fully described below. The sockets in the
case of the bit, shown in said copending application and in
Figures 1-7, are formed in the angle between 1 and 31 of one
step and the rise 30 of the adjacent step.
In the form shown in Figures 1-7, each of the cutters
is positioned in a stud-mounted receptacle. The studs 14 are
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formed with a receptacle 9 whose axis 16 is at an obtuse angle
to the central axis of the stud 14. The stud is formed of
steel or material of similar physical properties and ls coated
with a hard surface 18 coating formed, for example, of material
of the same kind as is used in the coating 3. The stud may be
held securely in the socket by an interference fit or by
brazing or other means of securing the stud in the socket.
Secured in the receptacles as by soldering or brazing
are preform cutters 8 formed as described above. They may be
of any desired geometric configuration to fit into the
receptacle. For convenience, we prefer cylindrical wafers
whose axial dimension is but a minor fraction of the diameter
o~ the wafer. The acute angle 20 thus establishes a negative
vertical cutting rake.
The studs 14 are provided with indexing means, for
example, flat sections 21 tFigure 4) so as to orient the studs
as is described below. Positioned in the sockets 7 are means
which cooperate with indexing means on the studs, for example,
the flat section 22 (Figure 4). The indexing means are
arranged to position the studs in a longitudinal array
extending from adjacent the gage 6 across the face 4 towards
the axis of the bit.
The aforesaid longitudinal array extends circumambiently
about the bit spaced from each other as is illustrated in
25 Figures 1 and 2. The arrays are separated by fluid channels ~ ;
23 which extend from the central portion 10 of the bit to the
gate 6 of the bit at the stabilizer section 5 where it joins
the grooves 24. The studs are positioned in each array spaced
from each other in said arrays. The cutters are arranged in
0 each longitudinal array so that they are in staggered
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1 position with respect of the cu-tters in adjacent array. The
cutters overlap each other in the sense that the portion of
the earth, not traversed by a cutter of one array, is
traversed by a cutter in the following array during rotation.
The indexing flats in the socket and stud are
positioned so that the cutting face of the preform cutters
in each array face in the same angular direction as the
intended direction of rotation of the bit. The bit is designed
for rotation in the usual manner by a clockwise rotation of
the drilling string connected to the collar 2.
This arrangement assures that all sections of the
surface to be cut by the bit are traversed by a series of `
cutters during each rotation oE the bit.
A convenient arrangement is to position the sockets
and studs in a generally spiral configuration extending from
the center of the bit to the gage.
While the studs may be mounted in sockets formed in
the face of the bit in any geometric form, for example, that
shown in Figures 8-12 or in any form employed in the prior
art, we prefer to mount the studs in sockets formed in the
face as described and claimed in the copending Canadian
application, S.N. 288,987.
The form is shown in Figures 1 and 2; the face is
formed with a central portion 10 having a substantially
~S circular perimeter 25. The portion of the face of the bit
extending from the perimeter 25 to the gage 6 of the bit is
formed with steps 26 in a spiral configuration. ~s is shown
in Figure 2, the spiral 27 starts at the tangent 29 at the
rise 30 and traverses the face 4 as a spiral to form the
lands 31.
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The sockets 7 are formed in the face of the bit with
the axis of the sockets intersecting the apex of the angle
between the rise and the land oE the steps. The geometry of
this arrangement allows the bit to constitute a jig to assure
that the sockets will be in a spiral configuration.
The positioning of the studs in the angle between the
rise and the land aids in the protection of the preform.
Impact loads are absorbed by the lands and rises where the
studs are located.
As a result of this arrangement, on rotation of the bit,
the preform cutter elements follow each other to cut the
spaces which had been missed by the cutters of the preceding
array. The result is that all portions of the earth are
traversed by a series of cutters during each rotation.
In order to facilitate the cleaning of the bit and
prevent clogging between the cutters, we provide, as described
above, fluid channels to join the grooves 24 in the stabilizer
section. The fluid channels are in the form of grooves
positioned between ad~acent longitudinal arrays of cutters
and extending adjacent to the face of the cutters in the
array. Nozzles 3~ (see Figures 1, 2, and 7) are positioned
in the body of the face to connect with each channel. The
nozzles are connected by bores 35 with the central tubular
bore of the shank 1. They are positioned at various radial
distances from the center around the bit in a ~enerally
spiral arrangement.
The flushing action of the fluid in the channels 23
may be sufficient to clean the cutters and prevent clogging.
In such case, the face of the cutters may be set at a zero
rake, that is, perpendicular to the direction of rotation or
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with the negative side rake described below. Drilllng fluid,
conventionally used, is discharged from the nozzles 34 into
the channels 23 to flush cuttings, and flows upwardly by the
stabilizer 5 directed by grooves 24 through the annulus
between the d~ill string and the bore-hole wall to the surface.
To facilitate the discharge of the cuttings and to
clean the bit, the cutters, in addition to the vertical
negative rake shown in Figure 3, may be set in a horizontal
rake as shown in Figure 6. In order to assist in movir.g the
cutting to the gage ~ o~ the bit, we prefer to orient the
cutters so that the cutting surfaces of the preform cutters 8
are rotated about a vertical axis counterclockwise to provide
a negative sideways rake 36 (see Figure 6).
The negative horizontal rake angle 36 may be, for
example, about 1 to 10, preferably about 2. The effect of
the negative sideways rake is to introduce a snowplow effect
and to move the cuttings to the gage of the bit where they
may be picked up by the circulating fluid and carried up the
grOoves 24 of the stabilizer 5. The vertical negative rake
angle 20 may be from about 4 to about 20.
As will be seen, the space taken by the receptacle and
the preforms makes impractical the positioning oF a large
multiple of preform cuttiny elements at the center of the bit.
The portion may thus produce a core. This is aggravated if
any of the preforms are lost from the central portion because
of damage occurring during use.
We prefer to supplement the cutting effect at the
center by including diamonds 37, either in a pattern or in
random distribution~ We also provide for diamonds positioned
at the gage where the side impacts during drilling are large,
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employing conventional techniques in setting the diamonds as
described above.
For practical reasons, this portion of -the bit is
first formed before setting of the preform cutters.
One of the features of the above construction is that,
should any one or more of the preform cutters be destroyed
or the studs damaged, they may be removed; and a new stud and
preform may be inserted.
The form of cutters of our invention, which is the
presently preferred form, especially for use in hard formations,
employs preforms mounted directly in position on the face of
the bit.
As shown in Fi~ures 9 and 10, the bit is formed by a
shank 101, coated as in the form of Figure 1 by a hard coating
15 102. The face of the bit 103 is of generally conical shape
facing into the central opening 104. As is shown in Figure 10,
the central opening may be the form of a threefold manifold
with three branches 10~. The mani~olds connect with channels
105 extendin~ to the gage 106. They connect with the grooves
~0 107 in the stabilizer section 108.
On the face of the bit are formed protuberances 109
spaced in longitudinal arrays about the face of the bit. Each
of the protuberances carries an extension 110 and a socket 111
in which is mounted a preform cutter 112 of the above
25 composition. As is shown in Figures 11, 12, and 13, the
cutters are positioned in sockets 111 and at the extensions
110 which are formed on the face of the bit and which act as
receptacles. The entire back of the preform i5 supported by
the socket and the extension 110 which acts as a receptacle
to receive the preform.
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As in the case of the cutters of Figures 1-7, the
receptacles support the cutters with both vertical and
horizontal rakes as is described for the cutters of Figures
1-7. As is shown in Figure 12, the preform is mounted with a
vertical negative rake 120 and, as is shown in Figure 11, with
a horizontal negative rake 136. The rake angles may be as
described above for the forms of Figures 1-8.
The protuberances are spaced in a longitudinal array
from each other adjacent the channels 105, about the face of
the bit. The protuberances and ~heir contained receptacles are
spaced from each other in arrays, as is described for the form
of Figures 1-8~ The cutters positioned in the receptacles in
the protuberances are thus arrayed in a staggered overlapping
arrangement with respect of the cutters in the protuberances
lS in adjacent longitudinal arrays similar to the arrangement of
the stud supported preforms. The cutting surface of the
cutters faces in the same angular direction as the direction
of rotation of the bit. Fluid channels 105 are positioned in
front of the array of cutter 113. The fluid which is fed
through the central bore of the tubular drill shank 101
discharges into the manifold 104 and thus through the channel
105 to flush the cuttings, which have been moved towards the
gage, upward into the annulus.
In both forms, the cutters are preforms which may be
replaced as they are damaged or lost. They permit the cutters
to be placed in receptacles formed in the hard coating of the
diamond bit, in a predetermined array to efficiently cut an
entire surface. The preforms may use fine primary abrasives
such as diamonds or equivalent hard abrasive particles in a
preform arranged in a predetermined array on the bit. The use
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of such preforms mounted in a pattern to cover substantially
the entire surface to be cut bu-t which would permit
replacement o~ individual damaged cutters, has the advantage
that a worn bit may be readily repaired and need not be
discarded or require salvage. In order to permit the mounting
of preforms which tend to be brittle in a bit where they will
meet impact forces, our invention provides for a support which
preserves the integrity of the preform.
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