Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
3 1. Field of the Invention.
; This invention relates in general to earth boring
6 bits, particularly to those utilizing diamonds for
7 cutting elements used to disintegrate geological
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2. Description of the Prior Art.
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12 Commercially available earth boring bits can be
13 generally divided into the rolling cutter bits, having
14 either steel teeth or tungsten carbide inserts, and
diamond bits, which utilize either natural diamonds or
16 artificial or man-made diamonds. The artificial diamonds
17 are "polycrystalline", used either individually or as a
18 component of a composite compact or insert on a cemented
19 tungsten carbide substrate. Recently, a new artificial,
polycrystalline diamond has been developed which is
21 stable at higher temperatures than the previously known
22 polycrystalline diamond. Both types of polycrystalline
23 diamond are available in a wide variety of shapes and
24 sizes.
26 The diamond earth boring bits can be generally
~7 classified as either steel bodied bits or matrix bits.
28 The steel bodied bits are machined from a steel block and
29 typically have cutting elements which are press-fit into
recesses provided in the bit face. The matrix bit is
31 formed by coating a hollow tubular steel mandrel in a
32 casting mold with metal bonded hard material, such as
33 tungsten carbide. The casting mold is of a configuration
34 which will give a bit of the desired form. The cutting
elements are typically either polycrystalline diamond
36 compact cutters bra7ed within a recess provided in the
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l matrix backlng or are thermally stable polycrystalline
2 diamond cutters which are cast wlthin recesses provided
3 in the matrix backing.
Placement of the cutter elements on the bit face of
6 matrix bits has fallen into two general schemes. In the
7 first of these, the cutters are placed in a str`aight row
8 extending from a central location on ~he bit face out to
9 the full bit diameter. The performance of these bits is
' sometimes limited by the fact that cuttings dislodged at
ll the center of the bit face must move in a straight line
12 down the cutting blade before exiting the bit face. There
13 is a tendency for cuttings to collect on the bit face and
14 restrict fluid flow across the bit face. In addition,
cuttings from the bit center are reground along the
16 entire length of the blade, accelerating wear.
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18 In the second scheme, cutters are set in individual
l9 mountings placed strategically around the bit face.
~ These bits are disadvantaged by the fact that individual
21 cutter mounts are more susceptible to gross failure by
22 shearing.
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SUMMARY OF THE INVENTION
It is the general object of the invention to provide
an earth boring drill bit with co-joined cutters mounted
on the bit face so as to offer increased resistance to
gross failure by shearing without interfering with the
flow of fluid and entrained cuttings exiting the bit
face.
Accordingly, an earth boring drill bit is provided
having one end that includes means for connection to a
drill string member, and having a matrix formed on the
opposite end with a plurality of cutting elements mounted
thereon. ~he cutting elements include groups of at least
two but less than Pour cutters which are co-joined by a
common backing of the matrix, the co-joined groups being
spaced-apart from adjacent co-joined groups mounted on
the matrix.
According to a broad aspect, the invention relates
to an earth boring bit, comprising:
a body including a metallic shank on one end with a
tubular bore and with means for connection to a drill
string member and rotation about a longitudinal axis;
a cast matrix bonded to the metallic shank and
forming a face of the bit, the bit face having a
plurality of cutting elements mounted within backings of
the matrix and extending radially on the bit face from a
central location to an outermost gage portion, the
cutting elements having cutting surfaces for dislodging
geological formations;
at least one fluid opening communicating the bit
face with the tubular bore of the bit for circulating
fluids to the bit face; and
wherein the cutting elements are arranged in
groupings, the groupings including a plurality of cutter
blades comprised of at least four cutters joined by a
common backing, the cutter blades being mounted on the
bit face adjacsnt the fluid opening and ext~nding
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radially on the bit face from the central location in the
direction of the gage portion but terminating short of
the gage portion, the groupings on the bit face also
being provided as pairs of cutters which are co-joined
by a common backing of the matrix, the co-joined pairs
being spaced-apart radially and circumferentially from
adjacent co-joined pairs and from the cutter blades, the
bit groupings on the bit face further being characterized
in that none of the groupings extend from the central
location completely to the outermost gage portion, so
that fluid circulated through the fluid opening to the
face of the bit can pass through the spaces defined
between the groupings of cutterq in an unchanneled
fashion.
The above as well as additional objects, features
and advantages of the invention will become apparent in
the following description.
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BRIEF DESCRIPTION OF THE DRAWINGS
3 Figure 1 is a perspective view as seen looking from
4 the side of an earth boring bit embodying the principles
S of my invention.
7 Figure 2 is a close-up, fragmentary side view of the
8 bit head, showing the preferred cutting elements.
lOFigure 3 is a head-on view of the bit face of the
l earth boring bit of Fig. 1, showing the placement of the
~2 cutting elements thereon.
4Figure 4 is a simplified, side view of one type of
cutting element mounted on the bit face.
-7Figure 5 is a side, isolated view of another type
8cutting element.
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20Figure 6 is a simplified, side view of the cutting
21 element of Figure 5 mounted on the bit face.
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1 ~ESCRIPTION OF THE PREFE~ED EMBODIMENT
3The numeral 11 in the drawing designates an earth
4 boring bit having a body 13 with a threaded shank 15
formed on one end for connectLoll with a drill string
6 member (not shown~. The body 13 further includes a pair
7 of wrench flats 17 used to apply the appropriate torque
8 to properly "make-up" the threaded shank 15. The body 13
9 has a tubular bore 27 which communicates with the
interior of the drill string member, and which
11 communicates by internal fluid passageways (not shown)
'2 with one or more fluid openings 29 which are used to
13 circulate fluids to the bit face.
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15On the opposite end of the bit body 13, there is
16 formed a bit head or "matrix" 19 in a predetermined
17 configuration to include cutting elements 21,
18 longitudinally extending lands 23, and fluid courses or
19 channels 25. The matrix 19 is of a composition of the
~ same type used in conventional diamond matrix bits, one
21 example being that which is disclosed in U.S. Pat. No.
~23,175,629 to David S. Rowley, issued March 30, 1965.
23 Such matrices can be, for example, formed of copper-
24 nickel alloy containing powdered tungsten carbide.
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;~6Matrix head bits of the type under consideration are
27 manufactured by casting the matrix material in a mold
28 about a steel mandrel. The mold is first fabricated from
~9 graphite stock by turning on a lathe and machining a
negative of the desired bit profile. Cutter pockets are
31 then milled in the interior of the mold to the proper
32 contours and dressed to define the position and angle of
33 the cutters. The fluid channels and internal fluid
34 passageways are formed by positioning a temporary
displacement material within the interior of the mold
36 which will later be removed.
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A steel mandrel is then inserted into the interior
of the mold and the tungsten carbide powders, binders and
flux are added to the mold. The steel mandrel acts as a
ductile core to which the matrix material adheres during
the casting and cooling stage. After firing the bit in a
furnace, the mold is removed and the cutters are mounted
on the exterior bit face within recesses in or receiving
pockets of the matrix.
The bit head 19 in Fig. 1 has a ballistic or
"bullet-shaped" profile which is generally conical in
cross-section and which converges to a central nose
location 31 on the bit face. The backings 33 for the
cutting elements 21 are portions of the matrix which
protrude outwardly from the face of the bit and which are
formed with cutter receiving pocket~ or recesses 35
during the casting operation.
As shown in Fig. 4, the cutting elements 21 are of
a hard material, preferably polycrystalline diamond
composite compacts, referred to hereafter as PDC's. Such
cutting elements are formed by sintering a
polycrystalline diamond layer 22 to a tungsten carbide
substrate 24 and are commercially available to the
drilling industry from General ~lectric Company under the
"STRATAPAX" trademark. The PDC i8 then preferably
mounte~d in the recess 35 provided in the matrix 19 by
brazing the PDC within the recess. The preferred cutting
elements (21 in Figure 4) are generally cylindrical.
Figure 5 show6 another type of cutting element
which can be mounted on the bit face. The cutting
element 26 is formed by sintering a polycrystalline
diamond layer 26 to a tungsten carbide substrate 28 which
is bonded to a tungsten carbide stud 30 which i5 then
preferably mounted into a recess (32 in Figure 6)
provided in the matrix 19
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1 by brazing, welding, cementing, or press fitting. U.S.
2 Pat. No. 4,539,018 to Whanger et al., lssued September 3,
3 1985, shows a method for manufacturing this type of stud
q mounted cutter.
6The new thermally stable polycrystalline artificial
7 diamond useful as cutting elements in the invention are
8 currently being sold by General Electric Company under
9 the "GeoSet" trademark. These cutters are available in
cylindrical ~ s and can be cast in place of the
ll bit face in recesses similar to recess 35 in Fig. 4.
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13As shown ln Figs. 1-3, the bit of the invention has
14cutting elements which include groups of at least two but
5less ~han rour cutters, such as the groups ~7 and 39 in
16Fig. 1, which are co-joined by a common backing 41, 43 of
17 the matrix. Preferably, the co-joined groups include
18 pairs of cutters which are co-joined by a common backing.
19 The distance between the cutters in a co-joined cutting
group ranges from about 0.010 inches to a maximum of
21 about one half the diameter of one of the cutters in the
22 cutting group. The co-joined groups are themselves
23 spaced-apart from adjacent co-joined groups mounted on
24 the face of the bit to improve the flow of fluid and
entrained cuttings exiting the bit face. The co-joined
26 groups radiate outwardly from the central location 31
27 generally along the bit face in the direction of the gage
28 portion 55.
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30As shown in Fig. 3, the bit face can be provided
31with a plurality of cutter blades 45, 47, 49, 51, 53
32 comprised of at least four cutters joined by a common
33 backing. The cutter blades 45-53 are mounted on the bit
34 face adjacent the fluid openings 29 and extend radially
on the bit face from the central location 31 in the
36 direction of the bit gage portion 55. The cutter blades
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1 45-53 do not extend the entire distance to the gage
2 portion 55, however. The pairs of co-jolned cutters are
3 located in the region of the bit face between the cutter
4 blades ~5-53 and the gage portion 55. The co-joined
pairs, 1.e. pair 38 in Fig. 2, are spaced-apart from
6 adjacent co-joined pairs, i.e. pair 40, and from the
7 cutter blades.
9 The use of co-joined cutters which share a common
backlng of the matrix provides several advantages. The
ll co-joined cutters improve the strength of the cutting
12 elements and resist shearing. Because traditional full-
13 length blades are not utilized, cuttings can swirl across
14 the bit face without causing a build-up or forming a dam.
Improved fluid flow over the bit face is achieved without
16 decreasing the resistance of the cutting elements to
17 shearing and failure.
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19 While the invention has been shown ln only one of
its forms, it is not thus limited but is susceptible to
21 various changes and modifications without departing from
22 the spirit thereof.
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