[0001] The present invention relates a cutter for mounting to a rotary drill bit of the
kind referred to in the prescribing clause of claim 1.
[0002] Rotating diamond drill bits were initially manufactured with natural diamonds of
industrial quality. The diamonds were square, round or of irregular shape and fully
embedded in a metallic bit body, which was generally fabricated by powder metallurgical
techniques. Typically, the natural diamonds were of a small size ranging from various
grades of grit to larger sizes where natural diamonds of 5 or 6 stones per carat were
fully embedded in the metal matrix. Because of the small size of the natural diamonds,
it was necessary to fully embed the diamonds within the matrix in order to retain
them on the bit face under the tremendous pressures and forces to which a drill bit
is subjected during rock drilling.
[0003] Further, an enlarged cutter for use in a rotary percussion bit is known (US-A-4 299
297) comprising a plurality of raised sections containing a plurality each of cutting
elements made of carbide alloy and being discretely embedded in a filler material
to approximately one half of their height. In a similar cutter (US-A-3 902 864) boron
fibres as hard cutting elements are used discretely embedded in sponge iron and then
compressed and heated to form various enlarged cutters. Again, such cutters are characterized
by low temperature stability and a cutting face only comprising individual cutting
elements arranged in a spaced-apart pattern and in no way acting together.
[0004] Later, the commercial production of synthetically produced diamond grit and polycrystalline
stones became a reality. For example, synthetic diamond was sintered into larger disk
shapes and were formed as metal compacts, typically forming an amalgam of polycrystalline
sintered diamond and cobalt carbine. Such diamond tables are commercially manufactured
by General Electric Company under the trademark STRATAPAX. The diamond tables are
bonded, usually within a diamond press to a cobalt carbide slug and sold as an integral
slug cutter. The slug cutters are then attached by the drill bit manufacturers to
a tungsten carbide slug which is fixed within a drill bit body according to the design
of the bit manufacturer (GB-A-2 081 347).
[0005] However, such prior art polycrystalline diamond (PCD) compact cutting slugs are characterised
by a low temperature stability. Therefore, their direct incorporation into an infiltrated
matrix bit body is not practical or possible at this time.
[0006] In an attempt to manufacture diamond cutting elements of improved hardness, abrasion
resistance and temperature stability, prior art diamond synthesizers have developed
a polycrystalline sintered diamond element from which the metallic interstitial components,
typically cobalt, carbide and the like, have been leached or otherwise removed. Such
leached polycrystalline synthetic diamond is manufactured by the General Electric
Company under the trademark GEOSET, for example 2102 GEOSETS, which are formed in
the shape of an equilateral prismatic triangle 4 mm on a side and 2.6 mm deep (3 per
carat), and as a 2103 GEOSET shaped in the form of an equilateral triangular prismatic
element 6 mm on a side and 3.7 mm deep (1 per carat). However, due to present fabrication
techniques, in order to leach the synthetic sintered PCD and achieve the improved
temperature stability, it is necessary that these diamond elements be limited in size.
Therefore, whereas the diamond compact slug cutters, STRATAPAX, may be formed in the
shape of circular disks of 3/8" (9.5 mm) to 1/2" (12.7 mm) in diameter, the leached
triangular prismatic diamonds, GEOSETS, have maximum dimensions of 4 mm to 6 mm. It
is well established that the cutting rate of a diamond rotating bit is substantially
improved by the size of the exposed diamond element available for useful cutting.
Therefore, according to the prior art, the increased temperature stability of leached
diamond products has been achieved only at the sacrifice of the size of the diamond
elements and therefore the amount of diamond available in a bit design for useful
cutting action.
[0007] It is an object of the invention to provide a thermally stable enlarged diamond cutter
for use in drill bits having cutting surface of enlarged size and improved wear properties.
[0008] Persuant to the invention, this object is accomplished by a cutter as claimed in
claim 1. With regard to further embodiments, reference is made to claims 2 to 5.
[0009] By arranging PCD cutting elements in a compact array wherein each cutting element
is immediately proximate to at least one adjacent cutting element with no matrix intermediate
the exposed diamond material of said cutting elements simulates a unitary diamond
table of an enlarged size and provides a thermally stable cutter performing well in
terms of length of bit life and rate of penetration due to an optimized diamond concentration
within its cutting surface.
[0010] The invention and its various embodiments can best be understood by considering the
following figures of the drawing wherein like elements are referenced by like numerals.
Figure 1 is a diagrammatic perspective view of a first embodiment incorporating a
triangular PCD cutting element.
Figure 2 is a perpective view of a second embodiment of the invention incorporating
a triangular cutting element.
Figure 3 is a plan view of a third embodiment of the invention incorporating a triangular
cutting element.
Figure 4 is a perspective view of a fourth embodiment of the invention incorporating
a rectangular cutting element.
Figure 5 is a diagrammatic perspective view of the fifth embodiment of the invention
incorporating a higher order polyhedral shaped diamond element.
[0011] The invention is an enlarged diamond cutter in a rotating bit comprised of a plurality
of synthetic polycrystalline diamond elements. The diamond elements are bonded or
embedded in a cutting slug formed of matrix material. The matrix material further
incorporates diamond grit so that the arrayed PCD elements, each of which have exposed
surfaces on the cutting face of the cutting slug, together with the diamond impregnated
matrix material therebetween simulates an integral enlarged diamond table. However,
the composite diamond table made from the these components in turn is characterised
by the physical, temperature and wear characteristics of the smaller components which
may be chosen from leached diamond product. Therefore, diamond cutters having the
geometric size and design configuration of the traditionally larger unleached diamond
compacts can be fabricated using a multiple component array of leached diamond elements
according to the invention. The invention is better understood by first considering
the embodiment in Figure 1.
[0012] Turn now to Figure 1 wherein a diamond cutter, generally denoted by reference numeral
10, is diagrammatically depicted in perspective view as forming the diamond table
for an infiltrated integral matrix tooth, also generally denoted by reference numeral
12. Diamond cutter 10 is comprised of a plurality of synthetic PCD elements 14. In
the illustrated embodiment, diamond elements 14 are triangular prismatic elements
such as are sold by General Electric Company under the trademarks 2102 GEOSETand 2103
GEOSET. This material is leached diamond material which exerts greater temperature
stability and improved wear characteristics than unleached diamond material, such
as sold by General Electric Company under the trademark STRATAPAX.
[0013] Diamond elements 14 are arranged and grouped in an array which collectively comprises
diamond cutter 10. In the case of Figure 1, wherein diamond elements 14 are equilateral
triangular prismatic elements, four such elements can be arranged to collectively
form a larger equilaterial triangular prismatic shape. For example, in the case where
2103 GEOSETs are used as diamond elements 14, four such elements can be combined to
form an equilateral prismatic triangular shape having a side of 12 mm, and not 6 mm
as in the case of a 2103 GEOSET. Clearly, the number of PCD elements 14 can be increased
to construct even larger triangular arrays than that depicted in Figure 1.
[0014] The triangular array formed by diamond cutter 10 contemplates a compact array of
diamond elements 14 wherein each diamond element is in contact with, or in the immediate
proximity of, at least one adjacent diamond element 14. In the illustrated embodiment,
each diamond element 14 disposed in a compact array actually touch each other or being
immediately proximate to the adjacent cutting element with no matrix material intermediate.
[0015] Matrix material 16 as shown in Figure 5, for example, gennerally constituted of tungsten
carbide and such other elements and compounds as are well known in the art in powder
metallurgy for inclusion in such metallic matrices, includes diamond grit dispersed
at least in that portion of matrix material 16 in the proximity of the cutting face
of diamond cutter 10. The mesh or grit size of the natural or synthetic diamond incorporated
then matrix material 16 may be of any magnitude or range according to the granularity
and wear resistance properties ultimately desired as dictated by well known principles.
Generally, a grit diameter in the range of 0.01 inch (0.254 mm) to 0.05 inch (1.27
mm) suffices. Generally, a diamond grit concentration uniformly dispersed through
matrix material 16 of 50% to 100% by volume is utilized.
[0016] Turn now to Figure 2, wherein the second embodiment is illustrated in perspective
view.
[0017] In the second embodiment a cutting slug, generally denoted by reference numeral 40,
is comprised of a plurality of compactly arrayed diamonds 14. More particularly, diamonds
14 are bonded together in groups of six to form a regular hexagonal slug 40. Individual
diamond elements 14 are bonded together by a thin matrix layer 16 between each adjacent
diamond element 14. As with the prior embodiments, cutting slug 40 is fabricated by
a conventional hot press or infiltration technique. The completed cutting slug 40
is similarly bonded to a stud 42 by soldering, brazing or other means as diagrammatically
depicted by brazing layer 44.
[0018] The equilateral triangular prismatic diamond elements 14 of the embodiment of Figure
2 can be generalized to form larger structures as shown in plan view in Figure 3.
Thus, a number of hexagonal arrays, each generally denoted by reference numeral 48,
can be combined to form a larger cutting slug 46. Each hexagonal subarray 48 which
forms part of larger array 46 is bonded together by diamond impregnated matrix material
16 as previously described.
[0019] Turn now to Figure 4. Heretofore, the cutting slugs in each embodiment have been
described as being built up of triangular prismatic prefabricated synthetic PCDs.
The embodiment of Figure 4 generalizes the teachings of the prior embodiments by incorporating
prefabricated rectangular prismatic PCD or cubic diamond elements 50. Cubic diamond
elements 50 are then combined to form a larger cutting slug, generally denoted by
reference numeral 52.
[0020] Matrix material 16 may frame or provide an outer encapsulating rectangular enclosure
for the array of diamonds 50 for additional security. The rectangular or square cutting
slug 52 of the embodiment of Figure 4 can then be bonded to a stud cutter or integrally
formed within a matrix body bit.
[0021] Turn finally to the embodiment of Figure 5 wherein a higher order, regular polyhedral
shaped diamond element 54 is combined with other like-shaped diamond elements of the
same or different orders of polyhedral shapes in a compact array to form an enlarged
cutting slug, generally denoted by reference numeral 56. In the embodiment of Figure
5, pentagonal elements 54 are employed in an array wherein some of the elements 54
may contact each other while others remain in spaced-apart relationship. Elements
54 are bound in cutting slug 56 by amalgamation in a diamond impregnated matrix material
16 formed by hot pressing or infiltration.
[0022] The various of Figures 1 to 5 respectively are formed as part of an infiltrated matrix
body bit, only the tooth of which is diagrammatically shown in the figures. Cutting
slugs 10, 40, 46, 52, 56 can be formed by conventional hot press techniques or by
infiltration techniques separately from the matrix body bit or may be formed simultaneousy
through infiltration techniques with the bit body. Consider first a fabrication technique
using a hot press method. Prefabricated synthetic diamonds are placed within an appropriately
shaped mold in the desired array. Thereafter, a mixture of metallic powder containing
the dispersed diamond grit is tamped into the mold and distributed across diamond
elements.
[0023] Typically, a substantially greater thickness of diamond bearing metallic powder is
placed in the mold than the thickness of PCDs 14, 48, 50, 54. This differential thickness
is to compensate for the greater compressibility of the powder as compared to the
relatively noncompressible diamonds. Thereafter, the mold is closed by one or more
anvils, typically made with the same material as the mold, such as carbon. The filled
mold and anvils are then placed with a conventional hot press which typically heats
the mold and its contents by an induction heater. Pressure and temperature is then
applied to the filled mold, causing the diamond impregnated metallic powder to amalgamate
and sinter, ultimately compressing to the shape of cutting slug 10 or 20, as defined
by the mold. For example, a pressure of 200 psi and a temperature of 1900°F held for
3 minutes is generally suitable for producing the desired cutting slug. The pressures
and temperatures employed are well outside the diamond synthesis or diamond-to-graphite
conversion phase regions so that substantially no diamond is created or destroyed
in the process.
[0024] An infiltration technique may also be employed to either separately manufacture cutting
slugs 10, 40, 46, 52, 56 or to manufacture cutting slugs integrally with the matrix
tooth. In the case where the cutting slugs are separately manufactured, an appropriately
shaped carbon mold is fabricated and diamonds set therein in the desired array. Once
again, diamond impregnated metallic matrix powder is filled within the mold and mold
then furnaced. The power is allowed to sinter and infiltrate between diamonds 14 to
form the finished cutting slug. Thereafter, the preformed cutting slug may then be
placed within a carbon mold for a matrix bit and fabricated into the bit in a conventional
manner. Alternatively, diamond elements may be individually glued into a mold for
a matrix body bit in the desired array and position. Thereafter, the matrix body bit
is filled first with a layer of diamond impregnated metallic powder and then is continued
to be filled with various grades of metallic powder according to conventional matrix
bit fabrication techniques. The entire mold is then furnaced so that the cutting slug
is simultaneously and integrally formed with the body of the matrix bit.
[0025] Many other modifications or alterations may be made by those having ordinary skill
in the art without departing from the scope of the invention. The illustrated embodiment
has only been shown by way of an example and should not be taken as limiting the invention
which is defined in the following claims.
1. A cutter for mounting on a rotary drill bit, comprising a matrix (16) and a plurality
of hard cutting element (14, 48, 50, 54) disposed in said matrix (16) to form a cutting
slug (10, 40, 46, 52, 56) including at least one exposed end face (34), characterized
in that
- the cutting elements (14,48,50,54) comprise polyhedrally-shaped synthetic thermally
stable polycrystalline diamond (PCD),
-said PCD elements (14, 48, 50, 54) are grouped in a spatially predetermined relationship
in said exposed end face (34) such that each PCD element (14, 48, 50, 54) has at least
one fully exposed surface substantially coplanar with said matrix (16) at said end
face (34) to form a cutting slug (10, 40, 46, 52, 56),
- said PCD elements (14, 48, 50, 54) are disposed within said cutting slug (10, 40,
46, 52, 56) in a compact array wherein each PCD element is immediately proximate to
at least one adjacent PCD element with no matrix material (16) intermediate to collectively
comprise a cutting surface of said cutting slug (10, 40, 46, 52, 56) by exposed diamond
material comprising said PCD elements (14, 48, 50, 54) and no matrix (16) intermediate
at said end face (34), whereby an enlarged diamond cutter simulating a unitary diamond
table is provided for mounting in a drill bit.
2. A cutter as claimed in claim 1 wherein said matrix material (16) incorporating
a dispersion of diamond grit at least in that portion of said matrix material (16)
adjacent to said cutting face of said cutting slug (10, 40, 46, 52).
3. A cutter as claimed in claim 2 wherein said diamond grit being uniformly dispersed
throughout the volume of said matrix material (16).
4. A cutter as claimed in one of claim 1-3 wherein said plurality of PCD elements
(14, 48, 50, 54) are arranged and configured in said cutting slug (10, 40, 46, 52,
56) in a plurality of distinguishable arrays.
5. A cutter as claimed in one of claims 1-4 wherein matrix material (16) frames or
provides an outer encapsulating enclosure for the array(s) of PCD elements (14, 48,
50, 54).
1. Schneidglied für eine Anbringung auf einem Drehbohrmeißel, mit einer Matrix (16)
oder einer Mehrzahl von harten Schneidelementen (14, 48, 50, 54), die in der Matrix
(16) zur Bildung eines Schneidkörpers (10, 40, 46, 52, 56) angeordnet sind, der zumindest
eine freiliegende Endfläche (34) aufweist, dadurch gekennzeichnet, daß die Schneidelemente
(14, 48, 50, 54) aus polyedrisch geformten, synthetischen, thermisch stabilen, polykristalinen
Diamantmaterial (PCD) besteht,
- die PCD-Elemente (14,48,50,54) in räumlich vorbestimmtem Verhältnis in der exponierten
Endfläche (34) derart gruppiert sind, daß jedes PCD-Element (14, 48, 50, 54) zumindest
eine voll freiliegende Oberfläche hat, die an der Endfläche (34) im wesentlichen koplanar
mit der Matrix (16) unter Bildung eines Schneidkörpers (10, 40, 46, 52, 56) ausgerichtet
ist,
- die PCD-Elemente (14, 48, 50, 54) in dem Schneidkörper (10,40,46,52,56) in einer
kompakten Anordnung vorgesehen sind, in der jedes PCD-Element zumindest einem benachbarten
PCD-Element unmittelbar ohne Matrixmaterial (16) dazwischen benachbart ist, um gemeinsam
eine Schneidfläche des Schneidkörpers (10, 40, 46, 52, 56) aus exponiertem Diamantmaterial
der PCD-Elemente (14, 48, 50, 54) ohne Matrixmaterial (16) zwischen diesen an der
Endfläche (34) zu bilden, wodurch ein vergrößertes Diamantschneidglied für eine Anbringung
an einem Drehbohrmeißel gebildet ist, in der eine einheitliche Diamanttafel simuliert.
2. Schneidglied nach Anspruch 1, bei dem das Matrixmaterial (16) eine Dispersion aus
Diamantgrieß zumindest in jenem Teil des Matrixmaterials (16) aufweist, der an die
Schneidfläche des Schneidkörpers (10, 40, 46, 52) angrenzt.
3. Schneidglied nach Anspruch 2, bei dem der Diamantgrieß über das Volumen des Matrixmaterials
(16) gleichförmig verteilt ist.
4. Schneidglied nach ewinem der Ansprüche 1 bis 3, bei dem die Mehrzahl der PCD-Elemente
(14, 48, 50, 54) im Schneidkörper (10, 40, 46, 52, 56) in einer Mehrzahl von unterschiedlichen
Anordnungen angeordnet und konfiguriert sind.
5. Schneidglied nach einem der Ansprüche 1 bis 4, bei dem Matrixmaterial (16) für
die Anordnung(en) von PCD-Elementen (14, 48, 50, 54) eine Einrahmung oder einen äußeren
kapselnden Abschluß bildet.
1. Organe de coupe à monter sur un trépan de forage rotatif, comprenant une matrice
(16) et une pluralité d'éléments de coupe durs (14,48, 50, 54) disposés dans la matrice
(16) pour former une plaquette de coupe (10, 40, 46, 52, 56) comprenant au moins une
face d'extrémité exposée (34), caractérisé en ce que:
- les éléments de coupe (14, 48, 50, 54) comprennent du diamant polycristallin, thermiquement
stable, synthétique, de forme polyédrique (DPC);
- les éléments DPC (14, 48, 50, 54) sont groupés dans une relation prédéterminée dans
l'espace dans la face d'extrémité exposée (34) de telle façon que chaque élément DPC
(14, 48, 50, 54) présente au moins une surface entièrement exposée, en substance coplanaire
avec la matrice (16) au niveau de la face d'etrémité (34) pour former une plaquette
de coupe (10, 40, 46, 52, 56);
-les éléments DPC (14, 48, 50, 54) sont disposés dans la plaquette de coupe (10, 40,
46, 52, 56) en un arrangement compact dans lequel chaque élément DPC est tout proche
d'au moins un élément DPC adjacent sans matière de matrice (16) entre eux afin de
constituer collectivement une surface de coupe de la plaquette de coupe (10, 40, 46,
52, 56) par de la matière diamantée exposée comprenant les éléments DPC (14, 48, 50,
54) sans matrice (16) intermédiaire au niveau de la face d'extrémité (34), de sorte
qu'un organe de coupe surcalibré simulant une table de diamant d'une seule pièce à
monter dans un trépan de forage est réalisé.
2. Organe de coupe suivant la revendication 1, dans lequel la matière de matrice (16)
comprend une dispersion de grains de diamant au moins dans la partie de la matière
de matrice (16) adjacente à la face de coupe de la plaquette de coupe (10, 40, 46,
52).
3. Organe de coupe suivant la revendication 2, dans lequel la grenaille de diamant
est dispersée uniformément dans la totalité du volume de la matière de matrice (16).
4. Organe de coupe suivant l'une quelconque des revendications 1 à 3, dans lequel
les éléments DPC (14,48,50,54) de la pluralité sont disposés et agencés dans la plaquette
de coupe (10, 40, 46, 52, 56) de manière à former plusieurs arrangements distinguables.
5. Organe de coupe suivant l'une quelconque des revendications 1 à 4, dans lequel
la matière de matrice (16) encadre le ou les arrangements d'éléments DPC (14, 48,
50, 54) ou forme une enceinte d'encapsulation extérieure pour ce ou ces arrangements.