U.S. patent application number 14/652355 was filed with the patent office on 2016-09-22 for drill bit.
The applicant listed for this patent is GROUPE FORDIA INC.. Invention is credited to Philippe Alix, Benjamin Boyer, Ariel Schtenbarg.
Application Number | 20160273272 14/652355 |
Document ID | / |
Family ID | 50977458 |
Filed Date | 2016-09-22 |
United States Patent
Application |
20160273272 |
Kind Code |
A1 |
Boyer; Benjamin ; et
al. |
September 22, 2016 |
DRILL BIT
Abstract
A drill bit (26), the drill bit (26) comprising: a substantially
tubular bit body (30) defining a body proximal end (32) and a
substantially longitudinally opposed body distal end (34); a crown
(38) extending from the bit body (30) at the body distal end (34),
the crown (38) having a generally annular configuration defining
crown inner and outer diameters (48 and 50); the crown (38)
including a plurality of segments (46) provided between the crown
inner and outer diameters (48 and 50), at least one of the segments
(46) extending only partially radially across the crown (38)
between the crown inner and outer diameters (48 and 50).
Inventors: |
Boyer; Benjamin; (Laval,
CA) ; Schtenbarg; Ariel; (Laval, CA) ; Alix;
Philippe; (St-Jean-sur-Richelieu, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GROUPE FORDIA INC. |
Dollars des Ormeaux |
|
CA |
|
|
Family ID: |
50977458 |
Appl. No.: |
14/652355 |
Filed: |
December 16, 2013 |
PCT Filed: |
December 16, 2013 |
PCT NO: |
PCT/CA2013/001048 |
371 Date: |
June 15, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 10/48 20130101;
E21B 10/43 20130101; E21B 10/485 20130101; E21B 10/605 20130101;
E21B 10/02 20130101 |
International
Class: |
E21B 10/02 20060101
E21B010/02; E21B 10/48 20060101 E21B010/48; E21B 10/43 20060101
E21B010/43; E21B 10/60 20060101 E21B010/60 |
Claims
1. A drill bit, said drill bit comprising: a substantially tubular
bit body defining a body proximal end and a substantially
longitudinally opposed body distal end; a crown extending from said
bit body at said body distal end, said crown having a generally
annular configuration defining crown inner and outer diameters;
said crown including a plurality of segments provided between said
crown inner and outer diameters, at least one of said segments
extending only partially radially across said crown between said
crown inner and outer diameters.
2. A drill bit as defined in claim 1, wherein each of said segments
extends only partially radially across said crown between said
crown inner and outer diameters.
3. A drill bit as defined in claim 2, wherein said segments are
divided in inner segments and outer segments, said outer segments
all extending radially outwardly further than said inner segments
and said inner segments all extending radially inwardly further
than said outer segments, said segments alternating
circumferentially between outer segments and inner segments.
4. A drill bit as defined in claim 3, wherein said inner and outer
segments overlap circumferentially.
5. A drill bit as defined in claim 3, wherein said inner and outer
segments are circumferentially spaced apart from each other so as
to have no circumferential overlap therebetween.
6. A drill bit as defined in claim 1, wherein all virtual circles
contained in and concentric with said crown intersect at least one
of said segments.
7. A drill bit as defined in claim 1, wherein said crown defines a
plurality of waterways devoid of said segments, each waterway
extending between said crown inner and outer diameters.
8. A drill bit as defined in claim 7, wherein said waterways are
substantially equidistantly spaced apart from one another
circumferentially around said crown.
9. A drill bit as defined in claim 7, wherein said segments define
segment groups circumferentially spaced apart from each other by
said waterways, each segment group including at least two of said
segments.
10. A drill bit as defined in claim 9, wherein each segment of each
segment group is closer to at least one other segment from the same
segment group than to all of said segments outside of said same
segment group.
11. A drill bit as defined in claim 9, wherein at least two
segments from at least one of said segment groups contact each
other.
12. A drill bit as defined in claim 9, wherein said segment groups
each extend from said crown inner diameter to said crown outer
diameter.
13. A drill bit as defined in claim 1, wherein said bit body
defines a plurality of segment receiving recesses extending
thereinto at said body distal end and said segments each define a
segment attachment portion inserted in one of said segment
receiving recesses and a segment abrading portion provided outside
of said segment receiving recesses.
14. A drill bit as defined in claim 13, wherein said segment
attachment portions and said segment receiving recesses are
threaded and said segment attachment portions are screwed in said
segment receiving recesses.
15. A drill bit as defined in claim 13, wherein said segments are
glued to said bit body.
16. A drill bit as defined in claim 13, wherein said segments are
soldered to said bit body.
17. A drill bit as defined in claim 13, wherein said segments are
brazed to said bit body.
18. A drill bit as defined in claim 1, wherein at least some of
said segments have a substantially constant transversal
configuration longitudinally therealong.
19. A drill bit as defined in claim 1, wherein at least one of said
segments has at least a portion thereof tapering in a direction
leading towards said bit body.
20. A drill bit as defined in claim 1, wherein at least one of said
segments has at least a portion thereof tapering in a direction
leading away from said bit body.
21. A drill bit as defined in claim 1, wherein at least one of said
segments has a substantially circular transversal cross-sectional
configuration.
22. A drill bit as defined in claim 1, wherein at least one of said
segments has a substantially triangular transversal cross-sectional
configuration.
23. A drill bit as defined in claim 1, wherein at least one of said
segments has a substantially trapezoidal transversal
cross-sectional configuration.
24. A drill bit as defined in claim 1, wherein said crown protrudes
radially inwardly and outwardly relative to said bit body.
25. A drill bit as defined in claim 1, wherein said segments each
include abrasive particles contained in a metal matrix.
26. A drill bit as defined in claim 25, wherein said abrasive
particles include diamond particles.
27. A drill bit as defined in claim 1, wherein said drill bit
defines a drill string attachment substantially adjacent said body
proximal end, said drill string attachment being configured and
sized for attaching said drill bit to a drill string.
28. A drill bit as defined in claim 27, wherein said drill string
attachment includes threads for screwing said drill bit to said
drill string.
29. A drill bit as defined in claim 1, wherein said segments are
all in a spaced apart relationship relative to each other.
30. A drill bit usable with a fluid, said drill bit comprising: a
bit body, said bit body defining a body proximal end and a
substantially longitudinally opposed body distal end, said bit body
defining a body passageway extending substantially longitudinally
therethrough for receiving said fluid and conveying said fluid
through said bit body; a substantially annular crown extending
substantially longitudinally from said bit body, said crown
defining a crown distal end and a substantially longitudinally
opposed crown proximal end, said crown extending from said bit body
with said crown proximal end located substantially adjacent to said
body distal end, said crown defining a crown passageway extending
substantially longitudinally therethrough, said crown passageway
being in fluid communication with said body passageway for
receiving said fluid from said body passageway, said crown
extending between a crown inner diameter and a crown outer
diameter; said crown including a plurality of segments, each of
said segments extending only partially circumferentially and
radially across said crown.
Description
[0001] This application claims priority from U.S. provisional
patent application Ser. No. 61/737,946 filed on Dec. 17, 2012, the
contents of which is hereby incorporated by reference in its
entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to the general field of
drilling, and is particularly concerned with a drill bit.
BACKGROUND
[0003] In the geological exploration, mining and construction
industries, among others, drill bits 10, an example of which is
shown in FIG. 1, are used to drill through rock, concrete and other
materials. Typically, as seen in FIG. 1, the drill bit 10 includes
a bit body 12 and a crown 14 extending substantially longitudinally
from the bit body 12. Slots 16 are formed into the crown 14 and
define drilling segments 18. The crown 14 is the portion of the
drill bit 10 that cuts or erodes the material through which a bore
is drilled. The bit body 12 and the crown 14 define a central
passageway 20 through which water (not shown in FIG. 1) is
injected. The slots 16 allow water and debris (not shown in the
drawings) to flow out of the central passageway 20.
[0004] By design, there are only limited variations in the
parameters defining the drilling segments 18, such as distance
between drilling segments 18, or width of the slots 16, and the
number of drilling segments 18. Also, typically, the drilling
segments 18 are relatively large. These limitations limit the heat
dissipation and debris clearance characteristics of the drill bit
10.
[0005] Against this background, there exists a need in the industry
to provide an improved drill bit. An object of the present
invention is therefore to provide an improved drill bit.
SUMMARY OF THE INVENTION
[0006] In a broad aspect, the invention provides a drill bit, the
drill bit comprising: a substantially tubular bit body defining a
body proximal end and a substantially longitudinally opposed body
distal end; a crown extending from the bit body at the body distal
end, the crown having a generally annular configuration defining
crown inner and outer diameters; the crown including a plurality of
segments provided between the crown inner and outer diameters, at
least one of the segments extending only partially radially across
the crown between the crown inner and outer diameters.
[0007] Advantageously, the proposed drill bit allows for more
variations in mechanical and hydrodynamic properties of the crown
than conventional drill bits, which allows adapting the drill bit
to different drilling conditions. In some embodiments, this allows
for an improvement in cooling and debris evacuation characteristics
of the drill bits when compared to conventional drill bits.
[0008] Also, the proposed drill bit is relatively easily
manufacturable using known methods and materials.
[0009] In some embodiments of the invention, each of the segments
extends only partially radially across the crown between the crown
inner and outer diameters.
[0010] In some embodiments of the invention, the segments are
divided in inner segments and outer segments, the outer segments
all extending radially outwardly further than the inner segments
and the inner segments all extending radially inwardly further than
the outer segments, the segments alternating circumferentially
between outer segments and inner segments. In a variant, the inner
and outer segments overlap circumferentially. In another variant,
the inner and outer segments are circumferentially spaced apart
from each other so as to have no circumferential overlap
therebetween.
[0011] In some embodiments of the invention, all virtual circles
contained in and concentric with the crown intersect at least one
of the segments.
[0012] In some embodiments of the invention, the crown defines a
plurality of waterways devoid of the segments, each waterway
extending between the crown inner and outer diameters. For example,
the waterways are substantially equidistantly spaced apart from one
another circumferentially around the crown.
[0013] In some embodiments of the invention, the segments define
segment groups circumferentially spaced apart from each other by
the waterways, each segment group including at least two of the
segments.
[0014] In some embodiments of the invention, each segment of each
segment group is closer to at least one other segment from the same
segment group than to all of the segments outside of the same
segment group.
[0015] In some embodiments of the invention, at least two segments
from at least one of the segment groups contact each other.
[0016] In some embodiments of the invention, the segment groups
each extend from the crown inner diameter to the crown outer
diameter.
[0017] In some embodiments of the invention, the bit body defines a
plurality of segment receiving recesses extending thereinto at the
body distal end and the segments each define a segment attachment
portion inserted in one of the segment receiving recesses and a
segment abrading portion provided outside of the segment receiving
recesses. For example, the segment attachment portions and the
segment receiving recesses are threaded and the segment attachment
portions are screwed in the segment receiving recesses. In other
examples, the segments are glued, soldered or brazed to the bit
body, sometimes in combination with being screwed thereto.
[0018] In some embodiments of the invention, at least some of the
segments have a substantially constant transversal configuration
longitudinally therealong.
[0019] In some embodiments of the invention, at least one of the
segments has at least a portion thereof tapering in a direction
leading towards the bit body.
[0020] In some embodiments of the invention, at least one of the
segments has at least a portion thereof tapering in a direction
leading away from the bit body.
[0021] In some embodiments of the invention, at least one of the
segments has a substantially circular transversal cross-sectional
configuration.
[0022] In some embodiments of the invention, at least one of the
segments has a substantially triangular transversal cross-sectional
configuration.
[0023] In some embodiments of the invention, at least one of the
segments has a substantially trapezoidal transversal
cross-sectional configuration.
[0024] In some embodiments of the invention, the crown protrudes
radially inwardly and outwardly relative to the bit body.
[0025] In some embodiments of the invention, the segments each
include abrasive particles contained in a metal matrix. For
example, the abrasive particles include diamond particles.
[0026] In some embodiments of the invention, the drill bit defines
a drill string attachment substantially adjacent the body proximal
end, the drill string attachment being configured and sized for
attaching the drill bit to a drill string. For example, the drill
string attachment includes threads for screwing the drill bit to
the drill string.
[0027] In some embodiments of the invention, the segments are all
in a spaced apart relationship relative to each other.
[0028] In another broad aspect, the invention provides a drill bit
usable with a fluid, the drill bit comprising: a bit body, the bit
body defining a body proximal end and a substantially
longitudinally opposed body distal end, the bit body defining a
body passageway extending substantially longitudinally therethrough
for receiving the fluid and conveying the fluid through the bit
body; a substantially annular crown extending substantially
longitudinally from the bit body, the crown defining a crown distal
end and a substantially longitudinally opposed crown proximal end,
the crown extending from the bit body with the crown proximal end
located substantially adjacent to the body distal end, the crown
defining a crown passageway extending substantially longitudinally
therethrough, the crown passageway being in fluid communication
with the body passageway for receiving the fluid from the body
passageway, the crown extending between a crown inner diameter and
a crown outer diameter; the crown including a plurality of
segments, each of the segments extending only partially
circumferentially and radially across the crown.
[0029] All embodiments and examples mentioned hereinabove also
apply to the drill bit described in the preceding paragraph.
[0030] Other objects, advantages and features of the present
invention will become more apparent upon reading of the following
non-restrictive description of preferred embodiments thereof, given
by way of example only with reference to the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] In the appended drawings:
[0032] FIG. 1, already described, in a perspective view,
illustrates a prior art drill bit;
[0033] FIG. 2, in a perspective view, illustrates a drill bit in
accordance with an embodiment of the present invention;
[0034] FIG. 3, in a top plan view, illustrates the drill bit shown
in FIG. 2;
[0035] FIG. 4A, in a top plan view, illustrate a drill bit in
accordance with an alternative embodiment of the invention;
[0036] FIG. 4B in a perspective view, illustrate the drill bit
shown in FIG. 4A;
[0037] FIG. 4C in a top plan view, illustrate a drill bit in
accordance with another alternative embodiment of the
invention;
[0038] FIG. 4D in a perspective view, illustrate the drill bit
shown in FIG. 4C; and
[0039] FIG. 5, in a perspective exploded view, illustrates part of
a drill bit illustrating features of yet other alternative
embodiments of the invention.
DETAILED DESCRIPTION
[0040] Referring to FIG. 2, there is shown a drill bit 26 usable
with a fluid (not shown in the drawings). Typically the fluid
includes water to which additives may have been added. The drill
bit 26 includes a substantially tubular bit body 30 and a crown 38.
The drill bit 26 is typically used to drill cores in rock or other
materials. However, other uses of the drill bit 26 are within the
scope of the invention.
[0041] For the purpose of this document, the terminology proximal
and distal refers to a distance from an operator located on the
surface who operates the drill bit 26 down a bore hole. Therefore,
distal elements are provided lower in the bore hole, or further
away from the operator, than proximal elements. This terminology is
used to facilitate the description of the drill bit 26 and should
not be used to restrict the scope of the present invention.
[0042] The present document also uses directional terminology such
as "longitudinal", "radial", "circumferential" and their adverbs.
This terminology is relative to the general cylindrical
configuration of the drill bit 26. Also, the terminology
"transversal" is used to denote a plane perpendicular to the
general longitudinal direction.
[0043] Also, the terminology "substantially" is used to denote
variations in the thus qualified terms that have no significant
effect on the principle of operation of the drill bit 26. These
variations may be minor variations in design or variations due to
mechanical tolerances in manufacturing and use of the drill bit 26.
These variations are to be seen with the eye of the reader skilled
in the art.
[0044] The bit body 30 defines a body proximal end 32 and a
substantially longitudinally opposed body distal end 34. The bit
body 30 also defined a body distal surface 31 at the body distal
end. For example, the body distal surface 31 is substantially
annular and generally transversal. The bit body 30 further defines
a body passageway 36 extending substantially longitudinally
therethrough for receiving the fluid and conveying the fluid
through the bit body 30. Typically, the drill bit 26 defines a
drill string attachment 25 (only partially shown in FIG. 2)
substantially adjacent the body proximal end 32. The drill string
attachment 25 is configured and sized for attaching the drill bit
26 to a conventional drill string (not shown in the drawings). To
that effect, for example, the drill string attachment 25 takes the
form of threads formed inside the bit body 30 for screwing the
drill bit 26 to the drill string.
[0045] The crown 38 extends from the bit body 26 at the body distal
end 34. The crown 38 has a generally annular configuration defining
crown inner and outer diameters 48 and 50 (as better seen in FIG.
3). The general annular configuration of the crown 38 does not
imply that the crown is a solid element of annular configuration,
but that the various elements forming the crown 38 are contained in
a volume that has a generally annular shape. The crown 38 includes
a plurality of segments 46 provided between the crown inner and
outer diameters 48 and 50, at least one of the segments 46
extending only partially radially across the crown 38 between the
crown inner and outer diameters 48 and 50. The crown inner and
outer diameters are the diameters of the smallest and largest
circles concentric to the crown 38 that intersect at least one of
the segments 46. Typically, each of the segments 46 extends only
partially radially across the crown 38 between the crown inner and
outer diameters 48 and 50. This is to be contrasted to conventional
drill bits, such as the previously described drill bit 10 shown in
FIG. 1, in which all the segments 18 extend radially between the
crown inner and outer diameter.
[0046] The segments 46 are elements of the crown 38 that may or may
not contact other segments 46, but that are physically distinct
entities which do not extend integrally from each other. The
segments 46 form the portion of the drill bit 10 that removes the
rock or other materials from the bore to be created with the drill
bit 10. In some embodiments of the invention, all the segments 46
extend either to the crown inner diameter 48 or to the crown outer
diameter 50. In these embodiments, all the segments 46, in addition
to cutting or eroding the material in which the drill bit 10 is
used, also maintain either the diameter of the bore hole that is
created or the diameter of the central portion of the material that
is received in the drill bit 10. This central portion often forms a
core that is retrieved for further analysis. Also, in some
embodiments of the invention, all the segments 46 are
non-contacting and separated from each other by a gap. In other
words, in these embodiments, the segments 46 are all in a spaced
apart relationship relative to each other.
[0047] Returning to FIG. 2, the crown 38 defines a crown distal end
40 and a substantially opposed crown proximal end 42. The crown 38
extends from the bit body 30 with the crown proximal end 42 located
substantially adjacent to the body distal end 34. The crown 38
defines a crown passageway 44 extending substantially
longitudinally therethrough, the crown passageway 44 being in fluid
communication with the body passageway 36 for receiving the fluid
from the body passageway 36. Typically, but not necessarily, the
segments 46 extend proximally further than the crown proximal end
42 to allow attachment of the segments 46 to the bit body 30, as
detailed hereinbelow.
[0048] In opposition to some drill bits that include cutting disks
or inserts, in some embodiments of the invention, the segments 46
are configured and sized such that every circumference of the crown
38 between the crown inner and outer diameters 48 and 50 intersect
at least one segment 46. In other words, all virtual circles
contained in and concentric with the crown 38 intersect at least
one of the segments 46. Also, in some embodiments of the invention,
the segments 46 are used both to create a longitudinally constant
diameter of the bore hole and of the core and to remove rock and
other ground material from the bottom of the bore hole. To that
effect, the crown 38 protrudes radially inwardly and outwardly
relative to the bit body 30.
[0049] Typically, the crown 38 defines a plurality of waterways 47
(better seen in FIG. 3) devoid of the segments 46. Each waterway 47
extends between the crown inner and outer diameters 48 and 50. The
waterways 47 can be substantially radially extending in a
substantially rectilinear manner, as seen in FIG. 3, or can also be
oriented partially along the circumference of the crown 38. The
waterways 47 can have any suitable shape and can taper in either a
direction leading radially inwardly or radially outwardly, or show
no such taper. In some embodiments of the invention, the waterways
47 are substantially equidistantly spaced apart from one another
circumferentially around the crown 38.
[0050] Referring to FIG. 3, in some embodiments of the invention,
the segments 46 define segment groups 52. The segment groups 52 are
circumferentially spaced apart from each other by the waterways 47
and each segment group 52 includes at least two of the segments 46.
Typically, each segment 46 of each segment group 52 is closer to at
least one other segment 46 from the same segment group 52 than to
all of the segments 46 outside of the same segment group 52.
Segment groups 52 are therefore in these embodiments subsets of the
segments 46 that are closer to each other than they are to other
segment groups 52.
[0051] In some embodiments of the invention, some or all of the
segments 46 from each of the segment groups 52 contact at least one
other segment 46 from the same segment group. However, in other
embodiments, the segments 46 are all spaced apart from each other
in the segment group 52.
[0052] In some embodiments of the invention, each segment group 52
extends the entire radial extension of the crown 38. In other
words, in these embodiments, the segment groups 52 each extend from
the crown inner diameter 48 to the crown outer diameter 50 so that
in each segment group 52, there is at least one segment 46 that
reaches the crown inner diameter 48 and at least another segment 46
that reaches the crown outer diameter 50. Within each segment group
52, there is an intra-group gap 54 between the segments 46.
Inter-group gaps 56 extend between the segment groups 52, the
inter-group gaps defining the waterways 47.
[0053] The bit body 30 is typically made out of a metal, such as
steel, while the segments 46 each include abrasive particles
contained in a metal matrix. For example, the abrasive particles
include diamond particles and the segments 46 include
diamond-encrusted matrices of conventional composition that are
relatively abrasive, robust and wear resistant.
[0054] In some embodiments of the invention, each segment 46 is
individually selectively attachable to the bit body 30. This
attachment can be made in the field, just prior to use of the drill
bit 26, or during the manufacturing process. This provides great
flexibility in having a drill bit 26 suitable for a particular
drilling situation. For example, referring to FIG. 2, the bit body
30 defines segment receiving recesses 58 extending thereinto at the
body distal end 34. Typically, the segment receiving recesses 58
extend substantially longitudinally in the bit body 30 from the bit
distal surface 31, but this is not necessarily the case in all
embodiments as the segment receiving recesses 58 may extend from
other surfaces of the bit body 30 and/or extend obliquely relative
to the bit body 30. Each segment receiving recess 58 receives a
respective segment 46 thereinto. More specifically, each segment 46
defines a segment attachment portion 57 inserted in one of the
segment receiving recesses 58 and a segment abrading portion 59
provided outside of the segment receiving recesses 58. However, in
other embodiments, the segments 46 are molded together as a single
unit in a conventional manner.
[0055] In a variant, as seen for example in FIG. 5, the segment
receiving recesses 58A and the segments 46A, and more specifically
the segment attachment portion 57A thereof, are threaded and the
segment attachment portions 57A are simply screwed in the segment
receiving recesses 58A. In another variant, also seen in FIG. 5,
the segments 46B, and more specifically the segment attachment
portions thereof 57B, are slidably inserted in the segment
receiving recesses 58B and soldered, glued or brazed to the bit
body 30. It is also possible to have segments 46A that are both
screwed in the segment receiving recesses 58A and either soldered,
glued or brazed to the bit body 30. It should be noted that FIG. 5
illustrates two types of segment attachment portions 57A and 57B
and two corresponding types of segment receiving recesses 58A and
58B in the same Figure to better illustrate these two variants.
While it is possible to mix these two types of segment attachment
portions 57A and 57B and segment receiving recesses 58A and 58B in
a single device, in a typical embodiment only one type is used.
[0056] Various shapes and configurations are possible for the
segments 46 and segment groups 52. For example, as seen in FIG. 2,
the segments 46 can have a constant transversal configuration
longitudinally therealong. Now referring to FIG. 5, in other
embodiments, as in segment 46A, the segment 46A has at least a
portion thereof, for example the segment abrading portion 59A, that
tapers in a direction leading away from the bit body 30. In yet
other embodiments, as in segment 46B, the segment 46B has at least
a portion thereof, for example the segment abrading portion 59B,
that tapers in a direction leading towards the bit body 30.
[0057] In some embodiments of the invention, as seen in FIGS. 2 and
3, the segments 46 have a substantially cylindrical configuration
and therefore have a circular transversal cross-sectional
configuration. In alternative embodiments, such as in the drill
bits 26C and 26D shown respectively in FIGS. 4A and 4C, the
segments 46C, 46CC, 46D and 46DD have respectively substantially
triangular (for segments 46C and 46CC) or substantially trapezoidal
(for segments 46D and 46DD) transversal cross-sectional
configurations.
[0058] Also, in some embodiments, as seen in FIGS. 4A to 4D, the
segments 46C, 46CC, 46D and 46DD are divided between outer segments
46CC and 46DD and inner segments 46C and 46D. Inner and outer
segments 46C and 46CC are shown in FIGS. 4A and 4B while inner and
outer segments 46D and 46DD are shown in FIGS. 4C and 4D. For each
drill bit 26C and 26D, the outer segments 46CC and 46DD all extend
radially outwardly further than the inner segments 46C and 46D and
the inner segments 46C and 46D all extend radially inwardly further
than the outer segments 46CC and 46DD.
[0059] The segments 46C, 46CC, 46D and 46DD alternate
circumferentially between outer segments 46CC and 46DD and inner
segments 46C and 46D. Typically, the outer segments 46CC and 46DD
extend from the crown outer diameter 50 towards the crown inner
diameter 48 without reaching the latter and the inner segments 46C
and 46D extend from the crown inner diameter 48 towards the crown
outer diameter 50 without reaching the latter. As seen in FIG. 4A,
in some embodiments, the inner and outer segments 46C and 46CC
overlap circumferentially such that at least some radii of the
drill bit 26C intersect both one of the outer segments 46CC and one
of the inner segments 46C. However, in alternative embodiments, as
seen in FIG. 4C, the inner and outer segments 46D and 46DD can be
circumferentially spaced part so as to have no circumferential
overlap therebetween. In these embodiments, no radius of the drill
bit 26D intersect both one of the outer segments 46DD and one of
the inner segments 46D.
[0060] In some embodiments of the invention, the segments 46 do not
all have identical transversal cross-sectional configurations. In
yet other embodiments of the invention, the segments 46 have
transversal cross-sectional configurations that vary longitudinally
therealong. Typically, but not necessarily, the segments 46 have a
larger longitudinal dimensions than transversal dimensions.
[0061] Although the present invention has been described
hereinabove by way of preferred embodiments thereof, it can be
modified, without departing from the spirit and nature of the
subject invention as defined in the appended claims.
* * * * *