U.S. patent application number 10/442703 was filed with the patent office on 2004-11-25 for rotary tools or bits.
Invention is credited to Dvorachek, Harold A..
Application Number | 20040231894 10/442703 |
Document ID | / |
Family ID | 33450263 |
Filed Date | 2004-11-25 |
United States Patent
Application |
20040231894 |
Kind Code |
A1 |
Dvorachek, Harold A. |
November 25, 2004 |
Rotary tools or bits
Abstract
Rotary tools or bits carry cutter element including pointed
contact structures and elements for chipping, cutting, and breaking
non-ductile materials such as rock. The cutter elements directly
contact and cut through rock and other materials and have tapered
contact structure ends. Rotary tools or bits for carrying the
cutter elements carry fixed cutter elements, or have sockets for
removable threaded or rotatable cutter elements, arranged in
straight or curved rows on the head opposite a
drill-string-engaging base of the tool. The tools also have
radially-extending buttresses which help to protect the cutter
elements from damage as a drill string and bit are withdrawn from a
bore.
Inventors: |
Dvorachek, Harold A.; (Iola,
KS) |
Correspondence
Address: |
EDWARD L. BROWN, JR.
125 North Market, Suite 1100
Wichita
KS
67202
US
|
Family ID: |
33450263 |
Appl. No.: |
10/442703 |
Filed: |
May 21, 2003 |
Current U.S.
Class: |
175/426 |
Current CPC
Class: |
E21B 10/43 20130101;
E21B 10/58 20130101 |
Class at
Publication: |
175/426 |
International
Class: |
E21B 010/36 |
Claims
I claim:
1. A rotary earth boring bit comprising: a rotatable body having a
drill string attachment side, and a bore-face and a bore wall side
opposite the attachment side; a plurality of cutting elements
rigidly carried on the bore face and bore wall side of the bit in
spaced apart relation, each such cutting element configured to cut
a portion of a bore and a earth formation when the bit is in use;
each of the cutting elements has a concentric cutting tip structure
surrounded by a symmetric tapered structure with an obtuse included
angle; a portion of the cutting elements are located on the bore
wall side of the body having axes that are generally perpendicular
to the bore wall; an additional portion of the cutting elements are
located on the bore face side of the bit with their axes aligned
substantially parallel to the axis of the bit; further cutting
elements are positioned on the bore face with their axes positioned
generally between being perpendicular to the bore wall and parallel
to the axis to the bit; the tip structure of each cutting element
comprises of man-made material harder than 67 on the Rockwood C
scale.
2. The earth-boring bit of claim 1, wherein the tip-structure is a
fine point.
3. The earth-boring bit of claim 1, wherein the axis of each
cutting element is angled between 1.degree. and 37.degree. from a
perpendicular to the bore face surface of the bit body.
4. The earth-boring bit of claim 1, wherein at least a radially
inward portion of each tapered structure is generally symmetrical
in at least four equally spaced directions from the axis of the
tapered structure.
5. The earth-boring bit of claim 1, wherein a portion of said
tapered structures is generally conical.
6. The earth-boring bit of claim 1 wherein at least a portion of
the tip structure is comprised of a material harder than 1864 on
the Vickers scale.
7. The earth-boring bit of claim 1, wherein at least a portion of
said cutting elements are fabricated from one of a group of
materials comprising diamond, a nitride of a metallic element, a
carbide of a metallic element, an oxide of a metallic element
carbide, a boride of at least one metallic element, a silicide of a
metallic element, and carbon nitride.
8. A rotatable earth-boring body for cutting the bore face and the
bore wall comprising: a drill string attachment side; a bore-face
side opposite the attachment side; a plurality of cutting elements
having a tapered screw mounting thread; a plurality of sockets
formed at spaced-apart positions from one another on the bore-face
side of the body, each socket being formed to hold and removably
retain a corresponding cutting element, each of said cutting
elements being rigidly carried in and by one of said sockets on the
bore-face and bore wall side of the body to cut the bore-face and
the bore-wall when the body is in use; the axis of each of said
plurality of sockets is generally normal to said bore-face at it
respective position on the body; the axis of at least one of said
sockets is closer to being parallel to the body axis than being
perpendicular to the body axis; at least three of the sockets have
axis that are closer to being perpendicular to a local portion of
said bore-wall than to being parallel to said portion of the
bore-wall; each of said sockets comprises a tapered screw thread,
said sockets are arranged in a plurality of radially extending rows
and each socket in the row is positioned with a portion of each
socket located behind a portion of an adjacent socket in the row in
the direction of the cutting element rotation.
9. A rotary self-sharpening earth-boring bit comprising: a
rotatable body having an axis of rotation, a drill string
attachment side, a bore-face side opposite the attachment side
along said axis; a plurality of elongated cutting elements, each
having an axis; a plurality of sockets in said rotatable body,
adapted to hold and retain said plurality of elongated cutting
elements, each of said cutting elements comprises: a cutting tip
structure, a cutting tapered structure, and a mounting structure;
the axis of a portion of the cutting elements is more perpendicular
than parallel to the bore face at its socket location; the axis of
at least one of said cutting elements is closer to being parallel
to the bit axis; the axis of at least one of said cutting elements
is perpendicular to the bore wall; and, each of said cutting
elements is rotatable during use about its axis in each of said
sockets.
10. The earth-boring bit of claim 9, wherein said cutting elements
are arranged in a plurality of radially extending rows and wherein
each of a plurality of said cutting elements in a row are
positioned with a portion of each cutting element located behind a
portion of an adjacent cutting element in the direction of cutting
element motion.
11. The earth-boring bit of claim 9, wherein the axis of at least
one cutting element is angled between 1.degree. and 37.degree. from
a perpendicular to a corresponding local portion of said bore-face
at its socket location.
12. The earth-boring bit of claim 9, wherein a portion of each of
said cutting elements is generally conical.
13. The earth-boring bit of claim 9, wherein the included angle of
at least a portion of said cutting tapered structure is obtuse.
14. A self-sharpening, rotary earth-boring drag bit comprising: a
rotatable body having a drill string attachment side and a
bore-face side opposite the attachment side; a plurality of fixed
axis cutting elements rigidly carried on the bore-face side of the
bit and configured to cut a bore-face and a bore-wall when the bit
is in use; each cutting element comprises an outer surface defining
a tip structure and a tapered structure, the outer surfaces of the
tapered structures converging into the outer surfaces of the tip
structure; each of said cutting elements includes an internal body
portion, one region of each of said internal body portion is
present at each tip structure; a cross sectional area of said
internal body near said one region is substantially smaller than
the largest cross sectional area of the tapered structure; at least
a portion of the tapered structure surface adjacent to the tip
structure has an obtuse included angle; at least a portion of each
of said internal body portion has a hardness greater than 1864 on
the Vickers scale; at least a portion of the tapered structure is
more than 300 points softer on the Vickers scale than the internal
body portion; and a region of each said internal body portion is
generally normal to a corresponding local portion of said
bore-face.
15. The earth boring bit of claim 14, wherein at least a portion of
the tapered structure is harder than 67 on the Rockwell C
scale.
16. The earth-boring bit of claim 14 wherein at lease one of said
tapered structures is generally conical.
17. The earth-boring bit of claim 14 wherein the included angle of
an outward surface portion of each tapered structure is obtuse.
18. The earth-boring bit of claim 14 wherein each of said cutting
elements is rotatable about its axis.
19. The earth-boring bit of claim 14 wherein a region of said
internal body is generally perpendicular to said bore-wall.
20. The earth-boring bit of claim 14 wherein at least a portion of
each of said cutting elements is fabricated from at least one of a
group materials comprising diamond, a nitride of a metallic
element, a carbide of a metallic element, an oxide of a metallic
element carbide, a boride of at least one metallic element, a
silicide of a metallic element and carbon nitride.
Description
FIELD OF THE INVENTION
[0001] This invention relates to rotary tools used to drill, mill,
or mine brittle formations, and it relates particularly to tools or
bits using contact structures that are tapered and pointed and to
cutting elements using such contact structures. Several new contact
structures and cutting elements are disclosed for use in a family
of earth-boring bits and of bodies for earth-boring bits.
BACKGROUND OF THE ART
[0002] The mining, construction, and drilling industries make
extensive use of rotary tools. These tools apply intense loads to
small areas to break brittle formation and structures into chips.
Tapered cutting elements are commonly used for this purpose. Such
elements are alternatively referred to as studs, buttons, cutters,
cutting tools, and bits. A plurality of cutting elements may be
attached to a holding tool. This tool may be a rotating drum, disc,
or bit body. Such tools are used to mine minerals, cut trenches,
mill pavement, drill holes, and the like.
[0003] A cutting element is a component of a cutting tool and is
what contacts the formation being cut. The end portion of such a
cutting element, which directly contacts the formation, is called
the contact structure. Tapered cutting elements are well known, and
they commonly have flat, rounded, or pointed contact structures.
The principal, hardest, and most wear-resistant material of a
contact structure is called a contact element, but adjacent parts
of the end of the cutting element may also contact and help cut a
formation, and not all contact structures have discrete contact
elements. Cutting elements comprise at least a contact structure
and a mounting structure. The mounting structure is used to mount
and carry the contact structure, including any contact element. The
mounting structure further comprises a holding structure and often
a projection structure. The holding structure is the part of the
mounting structure and the cutting element that is held in a
cutting tool. When present, the projection structure is located
between the contact structure and the holding structure. The
projection structure distances the contact structure from the
holding structure and thus from a surface of the cutting tool. The
contact structure is then supported by the projection structure,
and the projection structure is supported by the holding structure.
When no projection structure is present, the mounting and holding
structures merge together, and we speak of just the mounting
structure as what carries the contact structure with respect to the
cutting tool.
[0004] Typically, during use, only a portion of each contact
structure is in contact with the formation at any given point in
time. The size and the exact location of the area that is in
contact with the formation depends on the design of the cutting
element, the orientation of the cutting element with respect to the
formation, the properties of the material being cut, and the
operating conditions. Some portions of the contact structure are
more likely than others to make contact with the formation being
cut. The contact element is intended to be the first and principal
point of contact with the formation, in normal use. Portions of the
projection structure will rarely make contact with the formation
being cut. Simply cutting elements may comprise only one part, made
of one material, while more complex cutting elements may comprise
more than one part make from several different materials, such as
sintered tungsten carbide and steel. Usually the material of the
contact element is harder and more resistant to abrasion than the
material(s) of the projection structure and the mounting structure.
The material(s) of the projection structure and mounting structure
are often more ductile and resistant to impact than the material of
the contact element. This selective use of materials in the prior
art has improved performance of cutting elements while reducing
their cost.
[0005] The properties, cost, an availability of sintered tungsten
carbide make it the current material of choice for the majority of
contact elements on most contact structures and cutting elements
used in the construction, mining, and drilling industries. The
sintered tungsten carbide used in such contact elements and
structures is generally harder than Rockwell C 67. Many other
materials are currently known that have similar properties to
tungsten carbide but are not currently used to any significant
degree. Some of the suitable materials are the oxides of metallic
elements, the borides of metallic elements, the nitrides of
metallic elements, the silicides of metallic elements, and the
carbides of metallic elements. Steel is currently the material of
choice for projection structures and for mounting structures, with
hardness of less than Rockwell C 67. A harder surface treatment or
coating may be applied to such projection and mounting
structures.
[0006] FIG. 1 of the drawings shows a simple, prior art, tapered
cutting element with a rounded contact structure 20, which has been
in common use. It has a tapered mounting structure 22 and an
adjoining holding structure 24. The contact structure comprises the
integral rounded tip portion 20, without a separate contact
element, and may include some or all of the tapered mounting
structure 22. Any portion of the tapered structure that would only
rarely contact the formation is located between the contact
structure 20 and the holding structure 24 is part of the projection
structure. The included angle .PHI.1 of the distal end, taken from
the tapered part below the rounded part, is acute. Cutting elements
of this type are permanently installed. An interference fit between
holding diameter D1 and the holding tool the usual method of
retention. The ratio of the total length L1 to the holding diameter
D1 is small, often approximately in the range of from 1 to 2.
Simple cutting elements of this type are fabricated entirely from a
single piece of sintered tungsten carbide.
[0007] FIG. 2 shows a more complex prior art cutting element that
is also in common use in the art. It has two component parts, a
contact element insert 26, which comprises much of the contact
structure, and a mounting body 28, part of which is the holding
structure 38 that is physically received inside a bit body. The
holding structure 38 does not include a bit body socket rim bearing
structure 36. The contact element 26 is shown assembled on the
mounting body 28, on a common axis 30. The contact element 26 is
part of the contact structure, and usually the * contact element is
made of tungsten carbide. Depending on the operating conditions and
size of the contact element 26 in relation to an overall diameter
D2, some of the contact structure may be located on the tapered
portion of the mounting body 28, at 32, adjacent to the contact
element 26. More rarely, some of the contact structure may be
located on a portion of outside diameter D2. The projection
structure on this cutting element normally includes the tapered
face 32 of the mounting body 28 and the outside diameter D2 of this
cutting element. The included angle .PHI.2 of the distal end of the
cutting element is acute, as in FIG. 1. The distal end of the
cutting element is shown as pointed, but it may sometimes be
rounded. The mounting body 28 of the prior art cutting element of
FIG. 2 is commonly made of steel.
[0008] The outside diameter D2 of the projection part of mounting
body 28 in the FIG. 2 prior art device is larger than diameter D3
of an upper part of holding structure 38. A groove 34 is formed in
the diameter D2 portion for engagement of a tool for removing the
cutting element from a bit body. A baring structure 36 is located
at the base of the outside diameter D2. The holding structure 38
has two sections, one with the larger diameter D3 and another
section with a smaller diameter D4. An additional groove 40 in the
lower part of holding structure 38 facilitates engagement of a
retainer for holding the cutting element rotatably in a bit body.
The ratio of the overall length L2 of the cutting element to the
largest holding structure diameter D3 is greater than 3.37 for
known replaceable cutting elements.
[0009] Cutting elements used in the mining and construction
industries are usually mounted so that they can be replaced when
their contact structures become excessively worn. In the drilling
industry, the vast majority of cutting elements now in use are not
replaceable. Some can be sharpened. Usually, however, the entire
drilling tool is replaced when the contact structures, contact
elements, or cutting elements are significantly worn or
damaged.
[0010] In the mining and construction industries, rotary tools are
usually configured so that the cutting elements are rotatable about
their long axes. The cutting elements and contact structures are
angled backward from their direction of motion, and they also are
angled to one side. These angulations cause each cutting element to
rotate about its central axis when engaged, and so, as the sides of
the contact structure wear, the original form of the contact
structure is largely maintained.
[0011] A pointed end required less force to initiate cracks in
formations than other types of contact structure ends, because
point best concentrate stresses. Such a pointed end also causes
fewer unintended fractures in the material being cut than flat or
rounded ends, making it the most energy-efficient type of cutter.
Generally, in the mining and construction industries, large chips
are desirable. Stresses are very high at the point of the contact
structure, especially during impact with material being cut. The
heat generated at the point is intense, and it may build up during
times of continuous use. Abrasion at the point of a contact
structure is much greater than on the flank of the contact
structure, so the point can quickly become rounded. The point may
also itself fracture. Designers have recognized these factors and
have sometimes truncated the tapered end of the contact structure
to create a cutting edge that is better supported and better cooled
than a pointed contact structure. As the contact structure rotates
in use, a new portions of its cutting edge are presented to the
material to be fractured.
[0012] In harder formations, nonetheless, pointed and truncated
contact structures can be damaged so rapidly that they are
impractical to maintain. This limitation has led to use of a radius
or nose on the end of the contact element or structure, and the
equipment employing such contact structures then applies higher
forces. Several inventors have recognized these limitations, and
patents have been issued for improvements in contact structures
that help maintain the pointed form. Hard coatings have been
applied as a means of extending the life of the point or the edge.
Another approach has been to place a harder material in the center
of the cutter that is supported by a softer, less wear resistant
and more ductile material located radially outwardly from the
center (U.S. Pat. No. 4,859,543). In these designs, both the harder
and the more ductile materials have been made of sintered tungsten
carbide with a cobalt binder. Tungsten carbides as hard as 88
Rockwell A have been used in these designs. Such designs have met
with limited success, as the difference in hardness between the two
grades of carbide used has not been great enough. Sintered tungsten
carbide in grades as hard as 92 Rockwell A are readily available
but are not known to have been used in either the center or outer
structures. Contact stresses can fracture prior are contact
structures.
[0013] Several patented bit designs are pointed contact structures.
In one design, a number of angled replaceable cutting elements are
rotatably attached to winged structures attached to a body (U.S.
Pat. No. 5,735,360). Such elements are limited to larger bit sizes,
and their use is limited to shallow holes in relatively soft
formations. In another, somewhat similar design, a pilot cutter is
located in the center of the bit (U.S. Pat. No. 3,720,273). The
added center cutter gives this design better radial and axial
stability than the pilotless type. These bits use a relatively
compact cutting element compared to the cutting elements commonly
used in mining machinery because of the limited space available on
a bit. The numbers of cutting elements per unit of borehole area is
relatively small, so the chips produced are relatively large.
Typically for this type of bit the ratio of cutters divided by the
cross sectional area of the bore has been approximately 0.2
cutters/square inch. As least one patented bit design used pointed
contact structures in rolling cones (U.S. Pat. No. 4,854,405). This
design has not been well accepted in the drilling industry, likely
because in this type of bit the bearings wear out before the
tungsten carbide cutting elements do.
[0014] Drag bits with flat contact structures having curved of
straight cutting edges made of sintered tungsten carbide have been
in use for many years. Within the last two decades, several new
materials have been developed that can significantly improve the
performance of these bits. The new materials are polycrystalline
diamond and cubic boron nitride. The term polycrystalline is used
to describe a multi-crystal composite material either with or
without an additional material binding the individual crystals
together. Polycrystalline materials can be fabricated into desired
shapes an are much more resistant to impact damage than single
diamond crystals. Polycrystalline diamond and cubic boron nitride
are both substantially harder than impact grade of cemented
tungsten carbide but are significantly less impact resistant. Of
the two materials, polycrystalline diamond is the more commonly
used material in the drilling industry. Contact structures of
polycrystalline diamond have substantially increased the life of
fixed cutting element drag bits, and they cut rock formations of
increased hardness. The cost of polycrystalline diamond-coated
contact structures is relatively high, and they are easily damaged
and are generally not replaceable. At least one patent, however,
appears for a replaceable diamond-coated contact structure (U.S.
Pat. No. 4,782,903).
[0015] Polycrystalline diamond contact structures are bonded to
tungsten carbide support structures to reduce the potential damage
during use, to reduce cost, to facilitate processing, and to
facilitate assembly. During use, polycrystalline diamond material
has a tendency to delaminate from the tungsten carbide backing and
to disintegrate. Many patents have been issued for improvements
intended to reduce delamination and disintegration (e.g. U.S. Pat.
No. 5,967,249). These bits are a vast improvement over bits that
used single crystal cutting elements, which have been in use for
over a century. These bits use the edges of the facets as cutting
edges. Large numbers of diamonds are needed because the contact
structures are small, they are irregular and the diamonds are
brittle. As a result the chips cut from the formation face are very
small, and chip flushing is poor. These bits cut very slowly and
are currently used primarily for coring.
[0016] Several materials have been developed recently that show
significant potential for use in contact structures. Two of these
are carbon nitride and aluminum magnesium boride, but neither is
available in such amounts as to presently allow their use
commercially in contact elements.
SUMMARY OF THE INVENTION
[0017] It is an object of the present invention to provide a
versatile family of rock and formation drilling bits that
out-performs existing bits in a variety of conditions, both
physical and economic. This object is achieved by using any of
several different contact structures and any of several different
cutting elements that could be utilized in an otherwise generally
conventional bit design. A bit body and bit tool are disclosed for
use of these cutting elements
[0018] Three different contact structures are disclosed. Each is
adapted to different conditions, and they differ in cost. The first
contact structure design is adapted for use in soft formation and
shallow holes. This is the simplest and should cost the least. A
second contact structure is adapted to cut deeper holes into soft
and medium formations, and should cost more than the first design
due to its increased complexity. A third design is the most complex
and is adapted to cut soft, medium, and medium hard formations, and
will cost the most of the three.
[0019] Five kinds of cutting elements also are described. The first
two embodiments are simple, fixed cutting elements, which are best
adapted to small bit diameters and shallow drilling. The second and
third embodiments are replaceable, although fixed cutting elements
that are best adapted to small bit diameters and shallow drilling;
the third embodiment may alternatively be disposable when
thoroughly worn out. The fourth embodiment has a tapered, threaded
holding structure for threaded engagement and replacement in a bit
body. The fifth embodiment is a rotatable contact structure that is
best adapted for larger bit diameters and deeper holes.
[0020] The above contact structures and cutting elements are
disclosed here but are claimed in a separate patent document. It is
the new holding tools or bits that are not only disclosed but also
claimed here. These tools or bits carry a number of cutting
elements in novel ways.
[0021] Most of these cutting elements are replaceable, so that bits
using them can be rebuilt instead of scrapped. The cost of
replacing cutting elements is a significant part of the cost of
drilling, so all the embodiments of the invention will reduce the
cost of drilling and cutting rock. Other objects of this invention
are to provide improved drilling and cutting speed, reduced
potential for damage to the bit, improved cutting stability both
axial and radial, increased cutting element life, reduced potential
for clogging, and lower bit cost per foot of hole drilled.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a side view of a simple prior art, tapered and
rounded cutting element.
[0023] FIG. 2 is a side view of a relatively complex prior art
pointed cutting element.
[0024] FIG. 3 is a cross sectional view through the axis of a first
embodiment of a contact structure in accordance with the present
invention.
[0025] FIG. 4 is a partial cross sectional view through the axis of
a second embodiment of a contact structure, with a separate contact
element, in accordance with the present invention.
[0026] FIG. 5 is a partial cross sectional view through the axis of
a third embodiment of a contact structure and contact element in
accordance with the present invention.
[0027] FIG. 6 is a partial sectional view through the axis of a
leading cutting element located in a mid-portion of a bit engaged
in and cutting a formation. The cutting element is shown moving
from the right side of the figure to the left.
[0028] FIG. 7 is a partial sectional view, on line VII-VII in FIG.
6, through the axis of a leading cutting element located in a
mid-portion of a bit engaged in and cutting a formation. The
cutting element is shown moving away from the viewer.
[0029] FIG. 8 is a side view of a first embodiment of a cutting
element with a support structure and then a holding structure on
the proximal end.
[0030] FIG. 9 is a side view of a second embodiment of a cutting
element.
[0031] FIG. 10 is a side view of a third embodiment of a cutting
element.
[0032] FIG. 11 is a side view of a fourth embodiment of a cutting
element.
[0033] FIG. 12 is a side view of a fifth embodiment of a cutting
element.
[0034] FIGS. 13 and 14 are top end and side views of an
earth-boring bit embodiment of the present invention.
[0035] FIG. 15 is a partial side view of an earth-boring bit
showing a row of cutters that is curved in two dimensions.
[0036] FIGS. 16 and 17 are top and side views of an earth-boring
bit body embodiment of the present invention.
[0037] FIG. 18 is a cross section of a socket in an earth-boring
bit body.
[0038] FIG. 19 is a partial side view of an earth-boring bit body
showing a row of sockets that is curved in two dimensions.
THE PREFERRED EMBODIMENTS
[0039] Both new contact structures and new cutting elements using
them are disclosed in this document but are claimed in a separate
patent document filed simultaneously herewith. Principally
disclosed and claimed here are new bit bodies in which the new
cutting elements and contact structures are preferably used,
although conventional cutting elements and contact structures could
be used with lesser effectiveness; these bit bodies and completed
bits or tools are claimed here in combination and along.
[0040] FIG. 3 is a partial cross section of a first embodiment of a
contact structure of the invention and a portion of a projection
structure 48 of a cutting element. The contact structure and
cutting element are fabricated from one material. This is the
simplest embodiment of the present invention. The cross section is
taken along the central axis 42 of the contact structure, which is
generally radially symmetrical. A tip 44 at the distal end, a
tapered face structure 46 extending from the distal end, and part
of a projection or mounting structure 48 are shown.
[0041] The tip structure 44 in this embodiment is shown as flat
because it is not possible to make a perfect point or edge in any
material. Additionally, at some level of size for any given job,
sharpness of the point creases to be a factor in how well the
contact structure tip actually cuts or chips material. In any
event, it is sometimes advantageous to limit the sharpness of the
tip structure 44, as is shown in FIG. 3.
[0042] In the present invention, the contact structure includes the
tip structure 44 and at least a portion of the conically tapered
structure 46; surface 46 may alternatively be stepped or have
another configuration. On rare occasions a portion of the
projection structure 48, may also be considered a part of the
contact structure. The tip structure 44 occupies a small to
extremely small portion of the projected area of the distal end and
may be slightly recessed or be raised, rounded, convex, concave,
irregular, flat, polygonal, be a combination of the above, or have
another configuration.
[0043] The sides of the tapered structure 46 extend at an included
angle .PHI. increases, making the contact structure 44, 46 flatter,
the support for the tip 44, where the stresses and abrasion are the
greatest, also increases. Making the contact structure 44, 46
flatter allows the use of harder, more brittle materials at the tip
44 that are more wear resistant.
[0044] Harder and more brittle materials give the contact structure
44, 46 the capacity to cut harder rock materials. The larger part
of the contact structure 44, 46 must be significantly harder and
stronger than the material being cut. Two preferred materials for
the major portion of the contact structure 44, 46 are
polycrystalline diamond and polycrystalline cubic boron nitride. At
least a portion of the contact structure should be harder than 67
on the Rockwell C scale. Testing of prototype samples has shown
that when two different materials are used in a single contact
structure that there must be a significant difference in the
hardness to have a significantly beneficial effect on the wear of
the contact structure. It is found that a difference of at least
300 points on the Vickers scale is needed to have the desired
effect, assuming all other wear factors are the same; the hardness
of the second material should be at least 1000 points on the
Vickers scale.
[0045] FIG. 4 shows a contact element 50 and an end of a cutting
element of a second embodiment, similar in shape to the contact
structure shown in FIG. 3 but fabricated from two different
materials. A first material 50, such as polycrystalline diamond or
polycrystalline cubic boron nitride, provides or forms the contact
element 54, at the tip, and a second material 52, such as cemented
metal carbide, which forms the projection structure 56 and the
tapered face feature 58. The second material supports the first
material 50 through chemical, metallurgical, or mechanical bonding
or through an engaging structure (not shown) as in FIG. 8, at 102,
below. Welding, sintering, and brazing are suitable methods of
attachment also.
[0046] FIG. 5 shows an embodiment of the present invention that
includes a contact element column 60 of very hard material, such as
polycrystalline diamond or polycrystalline cubic boron nitride,
that is configured along the axis 62 of the structure. A second
material 64 such as cemented metal carbide surrounds the column 60,
and there is a metallurgical bond between the two materials. The
contact element column 60 is composed of a material that is
extremely hard and wear-resistant, with great compressive strength
but not high impact resistance. The present invention makes best
use of available materials for the contact structure. Column 60 is
located in the position of the most extreme compressive stress and
also the most extreme wear, to take advantage of the extreme
compressive strength and ear resistance of the material selected.
The contact element column 60 is then surrounded by the more impact
resistant material 64 such as cemented tungsten carbide, to
maximize support for this material. The cross sectional area of the
column of material 60 is preferably less than about 10 percent of
the largest cross sectional area of the shoulder of the cutting
element. The contact structure 66, 68 include the tip structure 66
and at least a portion of the tapered face structure 68. On rare
occasions, a portion of the projection or mounting structure 70 may
be intended to contact the face of the material being cut, and then
it also is part of the contact structure.
[0047] FIG. 6 is a side view of a cutting element that includes
contact structure 72, 74. The projection structure 76 is not a
portion of the contact structure in this embodiment. The cutting
element is moving to the left in the figure, engaged with and
cutting a formation 80. A fracture 82 is shown in formation 80,
creating a chip 84 in front of the moving contact structure 72,
74.
[0048] Angle .PHI.4 of the cutting element in FIG. 6 is the
included angle of the distal end. The angle .PHI.4 is generally
more than 90 degrees and less than 150 degrees. Angles .PHI.5 and
.PHI.6 show two different angles that the cutting element makes to
a perpendicular 78 to the face of the formation or bore. Deploying
the contact structure at an angle to the face of the bore can be
useful in several ways. Angle .PHI.5 shows how much the cutting
element is angled forward or backward. FIG. 6 shows the contact
structure angled back. This gives the contact structure 72, 74 more
support from behind. This angle can be positive or negative and can
vary from 0 degrees to 45 degrees. Angle .PHI.6 is the rake angle
of the lead portion of the face 3 of the cutting element. The rake
angle .PHI.6 can be either positive or negative. As angle .PHI.6
decreases, support for the tip structure increases.
[0049] FIG. 7, angle .PHI.7 measures how much the cutter is tilted
to either side. It can be positive or negative from the vertical
86, which here is also normal to the surface of formation 88. The
movement of the cutting element while tilted at angle .PHI.7 to the
side of the vertical 86 can promote rotation of the cutting element
about its own axis. When the cutting element is located on the
outside of the bit, it can also help support the tip of cutting
element 90. Fractures 92 and chips 94 that have just formed are
shown on both sides of the cutting element.
[0050] In prior art bits the sum of angle .PHI.5 and angle .PHI.7
shown in FIGS. 6 and 7 has been approximately 90 degrees (see U.S.
Pat. No. 4,813,501). In the present invention, this angle is
generally less than 60 degrees. This is an important innovation,
permitting use of a larger included angle .PHI.4 in the contact
structure 72, 74 and, thus substantially more support for the tip
structure 72 where support is needed most. Stresses and abrasion at
the contact element 72 are much greater than at any other location.
The added support allows the use of a very brittle material with
high compressive strength such as polycrystalline diamond at this
location. When polycrystalline diamond or other brittle material
with high wear resistance is used in the contact element 72, wear
on the contact structure 72, 74 and adjacent parts of the cutting
element is minimized. The stresses on the tapered mounting
structure 74 are then made significantly less than those on the
contact element 72, allowing a less wear resistant and less brittle
material to be used in the tapered mounting structure 74.
[0051] The use of two materials with different resistances to wear
beneficially creates a structure that retains the desired form as
it wears during hard use. In several of the embodiments of the
present invention, different materials have been selected for this
reason. The lower sum of .PHI.5 and .PHI.7 in the present invention
also allows for a more compact design and a more compact
arrangement of the cutting elements. Many patents have been issued
that take advantage of different wear rates in different materials
to maintain a desired form (e.g., U.S. Pat. No. 4,859,543). These
other inventions all differ in the material used to maintain the
form, the form that is being maintained, or in both.
[0052] FIG. 8 shows a first form of cutting element that can embody
any of the contact structures of the present invention, as shown in
FIGS. 3, 4, and 5. The contact structure at a distal end 96 is
unusually short and broad when compared to known contact
structures. The distal end 96 of the mounting structure has also
been broadened to protect the mounting structure from exposure to
chips being flushed away from the bore face area. A bearing
structure 98 adjoins a projection structure 100. This bearing
structure supports the outer edge of the tapered mounting portion.
In extremely soft formations, the projection structure 100 can
engage the formation also, although it is not intended normally to
do so. A holding element 102 is shown adjacent the projection
structure, for facilitating assembly to a tool and to increase the
shear and tensile strength of the joint between the contact
structure and a bearing structure 98. It also facilitates the use
of a softer, more ductile, and lower cost material in the mounting
element. The cutting element of FIG. 8 can be mounted directly on
and attached to a bit body, or it can be mounted on and attached to
a mounting body to become a component of another cutting
element.
[0053] FIG. 9 shows a second embodiment of a unified cutting
element. A contact structure 104, 106, a projection structure 108,
and holding structure 110 are fabricated from a single material,
for assembly into a bit body by press fitting. The angle of the
taper at the distal end is obtuse. A circumferential recess 112 is
formed for the engagement of a removal tool (not shown). The recess
112 is a groove, but other forms can be used. The recess 112 is
located in the projection structure 108. The ratio of the length L3
divided by the diameter D5 is between 1 and 3.25, making it an
exceptionally compact cutting element when compared to typical
other, prior art, removable, pointed cutting elements. The
compactness allows more cutting elements to be used on a bit or
other rotary cutting tool.
[0054] FIG. 10 shows a third form of cutting element of the
invention, similar to that of FIG. 9 except that a projecting
holding structure 114 has been added. A recess as 112 in FIG. 9 is
not used, but could be added. The projecting structure 114 can be
engaged by a retaining element in a bit body. The projecting
structure 114 is shown as a ledge, but other forms can be used. The
use of a retaining element makes a contact structure as shown in
FIG. 10 much easier to install and remove than would otherwise
similar cutting elements that are pressed into place, as that in
FIG. 9. The projecting structure 114 is located near the proximal
end 116, but can be located anywhere below the contact structure
118, 120. A cutting element as in FIG. 10 can be either fixed or
rotatable about its axis 122. The cutting element shown in FIG. 10
is also quite compact when compared to typical rotatable or
removable pointed contact structures.
[0055] FIG. 11 shows a contact structure 124, 126 attached to a
mounting structure in a third embodiment of the invention. The
mounting structure comprises a threaded element 128 and a
circumferentially engageable element 130, which permits grasping
and turning the element, as with a wrench. The threaded element 128
is tapered at an angle .PHI.8. The tapered form of the threaded
element 128 allows cutting elements to be assembled more closely to
each other in a bit assembly. The increased cutting element density
helps stabilize the bit while cutting, by distributing the imposed
loads. It also allows for the alignment of cutting elements in
rows. An additional advantage of the tapered, threaded holding
structure 128 is that it is self-locking. In the present invention
the angle .PHI.8 is between 1/2 degree and 60 degrees. The
circumferentially engageable feature 130 is a hexagon, but other
forms can be used. Cutting elements that are threadably engageable
as in FIG. 11 are fixed and are not rotatable. The cutting element
shown in FIG. 11 is also quite compact when compared to typical,
removable, pointed cutting elements.
[0056] FIG. 12 shows a fourth embodiment of contact structures and
cutting elements of the invention, with a cutting element that may
rotate about its own longitudinal axis 132. A first axially
engageable, circumferentially-extending recess 134, or a similar
structure, is formed on the distal part of the cutting element.
This recess 134 is engageable by a tool capable of applying force
in the direction of the axis 132 of the element, for removal of the
element from the bit or tool. A second axially engageable recess
136 is located on the proximal, hold structure part of the element,
for receiving a retaining element for fixing the cutting element in
the bit or tool body. In FIG. 12, the cutting element is comprised
of two components, a contact structure 138 and a mounting body 140,
but a unified structure could equally be used. This embodiment is
also quite compact when compared to typical, rotatable, pointed
cutting elements known to the art.
[0057] FIGS. 13 and 14 are top and side views of a novel
earth-boring bit body 146 provided with contact structures 142 also
according to the present invention. In this view, the contact
structures are not distinguishable, but are attached to projection
structures 148 rising from the bit body 146. The contact structures
142 can be permanently attached or removable, and they may also be
fixed or rotatable. The contact structures 142 may be an integral
part of the bit body 146 or be attached to the projection
structures 148. The projection structures 148 may be formed as
integral parts of either the contact structures 142 or of the bit
body 146. The projection structures 148, arrayed in rows 150,
create a flow path for the cutting to promote efficient fluid flow
for debris removal, but they may be arranged in other patterns. The
points of the contact structures 142 in each row 150 are arranged
in simple arcs, but other forms of arrangement may be used. It is
preferred that the sum of a backward angle plus a sideward angle of
an axis of the cutter element, or a related socket in the bit body,
from a perpendicular to the surface of the body, is less than 70
degrees.
[0058] Protective buttress elements 152 are formed on the bit body
146 in line with the rows 150 of contact structures 142 to protect
the contact structures 142 from snagging as the bit is withdrawn
from a hole. Chamfers 154 are formed on corners of the buttress
elements 152. A holding structure thread 156 is shown on a tapered
stem, and other holding means can be used. A fluid inlet 158 is
formed in the stem, and multiple fluid outlets 160 are formed in
the head 146 of the bit. At least one fluid outlet 160 per row 150
of cutting elements 142 is desirable.
[0059] In these FIGS. 13 and 14, the contact structures 154 are
arrayed so that each extends generally perpendicular to the bore
face. Alternatively, some or all of the cutting elements may be
angled other than perpendicularity to the cutting face, as at
angles .PHI.5 and .PHI.7 as shown in FIG. 6 and FIG. 7, discussed
above. More than three contact structures 142 are arrayed
perpendicularly to the borehole. These elements are generally
redundant. They stabilize the bit radially and help to create a
relatively smooth bore. Bits with few pointed cutting elements cut
rough holes, reducing the effective diameter of the hole and
substantially increasing the amount of cement required to form
cemented casings (not shown).
[0060] FIG. 15 is a partial side view of a bit with a row 162 of
cutting elements 164, wherein the row is advantageously curved both
parallel to the face 166 of the bit and backwards from the axis 168
of the bit. This arrangement may be described as spiral, or that
the curves are in two dimensions on the surface of the curved body.
Other curvatures can be used. Such curvatures allow closer radial
spacing of the contact structures. They also allow the setting of
the contact structures to "shade" a side portion of a following
contact structure, changing the forces applied to the following
structure to cause it to rotate or to prevent it from unscrewing.
Also shown are a buttress 170 and a portion of a mounting thread
172.
[0061] FIGS. 16 and 17 are respectively top and side views of the
bit body 174 without contact elements. Sockets 176 are adapted for
engagement of cutting elements according to the invention, or
conventional ones with suitable mounting arrangements. The sockets
176 are arranged in rows 178 but can be arranged in other patterns.
The sockets may be adapted for fixed or for rotatable mounting of
the contact elements. They may also be adapted for threaded holding
structures. The sockets may also be arranged perpendicularly to the
bore face or angled away from perpendicularity to the bore face, as
in FIGS. 6 and 7.
[0062] FIG. 18 is a partial sectional view of a bit body 180
through a socket 182, similar to socket 176 in FIG. 16, that is
adapted to receive a cutting element without threads. An undercut
184 is shown for the engagement of a retaining means for a cutting
element. The undercut 184 is a circular groove, but other forms can
be used. The undercut 184 can be located anywhere between the
bottom to near the top of the socket.
[0063] FIG. 19 is a partial side view of a bit showing a row 186 of
sockets 188 that is curved in more than one direction. The row 186
is curved in a direction that is parallel to the face 190 of the
bit and in a direction that is backward from the axis 192 of the
bit. Also shown are a buttress 194 and a portion of a thread
196.
[0064] Testing of prototype samples of the present invention have
shown that the size of the chips is reduced when the number of
pointed cutting elements per square inch of bore area is increased
significantly above the number used in current state of the art
bits. The smoothness of the bore also improved. It has been found
that the desirable number is greater than approximately 0.33
pointed contact structures per square inch of the bore area (i.e.,
the area of the cross-section of the hole).
[0065] Many variations may be made in the invention as shown and
its manner of use, without departing from the principles of the
invention as described herein and/or as claimed as our invention.
Minor variations will not void the use of the invention.
* * * * *