U.S. patent application number 12/273700 was filed with the patent office on 2009-07-23 for pcd percussion drill bit.
This patent application is currently assigned to The William J. Brady Loving Trust. Invention is credited to William J. Brady.
Application Number | 20090184564 12/273700 |
Document ID | / |
Family ID | 40875893 |
Filed Date | 2009-07-23 |
United States Patent
Application |
20090184564 |
Kind Code |
A1 |
Brady; William J. |
July 23, 2009 |
PCD PERCUSSION DRILL BIT
Abstract
The invention is embodied in a percussion drill bit which
comprises a steel body with a working front head portion having a
front central zone and plural wing zones radiating from the central
zone and being spaced at the outer circumferential edges thereof;
first gauge-cutting PCD inserts are secured in the wing zones to
extend forwardly at an angle relative to the axis of the bit, and
of at least one second core-cutting PCD insert is non-axially
secured to extend forwardly from the central zone.
Inventors: |
Brady; William J.; (St.
Louis, MO) |
Correspondence
Address: |
SENNIGER POWERS LLP
100 NORTH BROADWAY, 17TH FLOOR
ST LOUIS
MO
63102
US
|
Assignee: |
The William J. Brady Loving
Trust
|
Family ID: |
40875893 |
Appl. No.: |
12/273700 |
Filed: |
November 19, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61022614 |
Jan 22, 2008 |
|
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Current U.S.
Class: |
299/100 ;
175/389; 76/108.2 |
Current CPC
Class: |
E21B 10/46 20130101;
E21B 17/1092 20130101; E21B 10/36 20130101 |
Class at
Publication: |
299/100 ;
175/389; 76/108.2 |
International
Class: |
E21C 25/50 20060101
E21C025/50 |
Claims
1. A percussion drill bit for drilling bore holes in hard rock and
mineral, comprising: (a) a steel body having a working front head
portion and a rearward shank portion for connection to an impact
driving force; (b) said head portion having a front facing central
zone and plural wing zones extending radially from the central zone
and being spaced apart at the outer circumferential edges thereof
by grooves in the outer wall of the front head portion; (c) a first
gauge-cutting PCD insert secured in the steel head portion of at
least two wing zones and being constructed and arranged to extend
at a predetermined angle to the axis and have a gauge-cutting PCD
surface operable for forming the bore hole dimension; and (d) at
least one second PCD insert non-axially secured in the central zone
to project forwardly of the first PCD inserts and being operable
for impact at the core area of the bore hole to pilot the boring
hole effort of the first PCD inserts.
2. The drill bit of claim 1 in which the head portion has an outer
side wall that tapers inwardly from the circumferential edges of
the wing zones to the shank portion of the steel body.
3. The drill bit of claim 1 wherein there are three side wing zones
each having a first gauge-cutting PCD insert secured therein.
4. The drill bit of claim 3, in which there are plural second
core-cutting PCD inserts projecting forwardly from the central zone
and being asymmetrically and non-axially disposed.
5. The drill bit of claim 4, in which the wing zones have front
faces sloping at a predetermined angle rearwardly from the front
facing central zone to the outer circumferential edge of the head
portion, and a primary socket extending into each sloping front
face and being recessed normal thereto for seating said first
gauge-cutting PCD insert therein.
6. The drill bit of claim 5, wherein the sloping surfaces of the
side wing zones are formed at an angle in the range of 15.degree.
to 35.degree. relative to a plane perpendicular to the axis of the
drill bit.
7. The drill bit according to claim 6 wherein the gauge cutting
inserts have cylindrical body sections and parabolic head sections,
the cylindrical body sections being press-fit into said first
sockets to a depth of about 0.250 to 0.390 inches.
8. The drill bit according to claim 7 in which the cylindrical body
sections extend outwardly from the sloping surface of each side
wing zone to space the domed head sections of these inserts
forwardly of the plane of the front facing central zone.
9. The drill bit according to claim 8, wherein there are at least
two second PCD inserts non-axially secured in the front facing
central zone and extending forwardly from the plane thereof.
10. The drill bit of claim 9, wherein the central zone lies on a
plane perpendicular to the axis of the drill bit, and second socket
means formed in the central zone for seating the second PCD inserts
therein.
11. The drill bit according to claim 10 wherein the first and
second socket means are formed in said head portion to open
outwardly at the wing zones and front-facing central zone on
different radius lines from the axis of the drill bit.
12. The drill bit according to claim 11 wherein said first and
second socket means are formed to extend into said head portion and
have bottoms that are offset axially from each with the bottoms of
the first socket means being below the bottoms of the second socket
means.
13. The drill bit according to claim 10 in which the second PCD
inserts are constructed and arranged as core-cutters for the bore
hole being formed, the second PCD inserts having parabolic working
surfaces extending forwardly beyond the parabolic head sections of
the first PCD inserts.
14. The drill bit of claim 3 in which said head portion of said
steel body is armored with a hard cladding material tougher than
the steel body to thereby reduce outer body wear at the side wing
zones and thereby prolong the PCD insert integrity with a
substantially longer drill bit life.
15. The drill bit of claim 14, in which the hard cladding material
covers the front face of the head portion around the first and
second PCD inserts and circumscribes the outer side wall of the
head portion.
16. The drill bit of claim 15 in which the hard cladding material
includes chromium (CR) and is plated to a hardness of at least 60
Rc and a thickness in the range of 0.001 to 0.030.
17. The drill bit of claim 16 in which the plated chromium material
has a Rockwell hardness of 65 to 68 and a thickness in the range of
0.005 to 0.015.
18. A percussion drill bit comprising: (a) a head portion having a
front-facing central zone and multiple wing zones radiating
symmetrically therefrom and being spaced apart at the outer
circumferential edges thereof; (b) first gauge-cutting PCD inserts
secured in at least two of said wing zones and being constructed
and arranged to extend angularly relative to the axis of the drill
bit and being operable for forming the fore hole dimension; and (c)
at least one second PCD insert non-axially secured in the central
zone to project forwardly of the first PCD inserts and being
operable for piloting the bore hole formation.
19. The drill bit of claim 18, in which said first and second PCD
inserts are seated in primary and secondary angularly related
socket means extending into the head portion, said primary socket
means being deeper than said secondary socket means.
20. The drill bit of claim 18 wherein the first PCD inserts are
relatively large and sized to do the principle drilling work while
the smaller second PCD insert initiate the bore-hole and then work
in conjunction with the first PCD inserts.
21. The method of making an armored percussion bit with PCD inserts
(a) forming a steel bit body having a shank portion and a working
head portion with a central zone and plural spaced wing zones
extending radially from the central zone and being separated
circumferentially by spaced grooves in the outer head portion wall;
(b) bonding a hard cladding material to cover the exposed surface
areas of the head portion; (c) boring the shank portion axially to
provide a threaded means for connecting the drill bit to an impact
driving force, and providing axial passageways for flushing fluid;
(d) boring the head portion to provide flushing fluid passages from
the axial passageway to each of the spaced grooves in the outer
head portion wall (e) forming sockets through the hard cladding
material into the central zone and wing zones of the head portion
to accommodate PCD inserts; and (f) press fitting the PCD inserts
into the sockets.
22. The method according to claim 21, in which the cladding
material comprises chromium.
23. The method according to claim 21 including the step of
constructing and arranging the PCD inserts so that the central zone
PCD inserts project forwardly of the wing PCD inserts whereby to
initiate and pilot the bore hole drilling operation.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a non-provisional of U.S. application Ser. No.
61/022,614, filed Jan. 22, 2008, the entire disclosure of which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to rock drill bits,
and more particularly to rotary percussion drill bits having PCD
inserts constructed and arranged for improved performance and
duration of the drill bit in rock crushing and boring
operations.
[0004] As used in the following disclosure and claims, the term
"polycrystalline diamond" and/or its abbreviation "PCD" refers to a
material formed of diamond crystals fused or sintered under high
pressure and temperature into a predetermined layer or shape. The
PCD material is permanently bonded to a substrate of tungsten
carbide (WC) in a cobalt binder or like carbide matrix, also known
in the art as "precemented carbide" to form a PCD insert. Also, as
used herein, the term "high density ceramic" or its abbreviation
"HCD" refers to a mining tool having an abrasive working insert
embodying a PCD layer.
[0005] 2. Description of the Prior Art
[0006] The three basic ways of drilling bores in rock and earthen
formations are rotary, percussion (or impact) and rotary percussion
(or rotary impact). Percussion drilling is typically carried out by
driving the drill bit into the rock work surface in a reciprocating
manner at a striking or impact force of about 300-500 ft/lbs and
also rotated at about 250-300 rpm during drilling. The impact
frequency is about six (6) blows for each one (1) degree of
rotation. Using pneumatic power this will equate to about 2100-2200
blows per minute; and a much higher impact frequency of 7000 to
8000 striking blows if using hydraulic power. Thus, rotary
percussion drilling is carried out by reciprocatingly driving the
drill bit to crack and crush the rock and rotating the bit to cut
away and remove the crushed rock from the developing bore hole.
[0007] A principal problem encountered in using prior art
percussion drill bits (as in rotary cutting tools), is the rapid
wear and high cost of continual replacement along with machine
down-time for changeover or replacement of these inefficient bits
coupled with the hazardous safety risks involved in hammering off
the worn bits for replacement with new ones. Typically prior art
tools have only been made with tungsten carbide inserts because it
is a cheap and easily worked material, but such tools result in
rapid failure due to wear and breakage--particularly in percussion
drilling. This has led to drill bit redesign using more and bigger
WC inserts, which in turn generally generates higher dust levels
and other health problems.
SUMMARY OF THE INVENTION
[0008] One aspect of the invention is embodied in a percussion
drill bit for drilling bore holes in hard rock (minerals) which
comprises a steel body having a working front head portion and a
rearward shank portion for connection to an impact driving force,
the head portion having a front facing central zone and plural side
wing zones extending radially from the central zone and spaced
apart at the outer circumferential edges thereof by grooves in the
outer wall of the front head portion, first gauge-cutting PCD
inserts are secured in at least two of said side wing zones of the
steel body and are constructed and arranged to extend forwardly and
outwardly at an angle to the axis of the bit and be operable for
forming the bore hole, at least one second PCD insert is
non-axially secured in the central zone and projects forwardly of
the first PCD inserts and is operable for impact at the core area
of the bore hole to pilot the boring effort of the first PCD
inserts.
[0009] In another aspect of the invention the head portion of the
steel body is armored with a hard cladding material tougher than
the steel body to thereby reduce outer body wear at the side wing
zones and to thereby prolong the PCD insert integrity and provide a
substantially longer drill bit life.
[0010] These and other objects and advantages of the invention will
become more apparent from the following description of the
preferred embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] In the accompanying drawings which form a part of the
specification and wherein like numerals refer to like parts
wherever they occur:
[0012] FIG. 1 is a perspective view of a first embodiment of a
percussion drill bit according to the invention;
[0013] FIG. 2 is a side elevational view of the first embodiment,
partly broken away to show a PCD insert socket;
[0014] FIG. 3 is another side elevational view, as rotated
90.degree. from the FIG. 2 position, and broken away to show
flushing fluid distribution;
[0015] FIG. 4 is a top plan view of the first embodiment;
[0016] FIG. 5 is a cross-sectional view taken substantially along
line 5-5 of FIG. 4;
[0017] FIG. 6 is a greatly enlarged diagrammatic and fragmentary
view illustrating the geometry of the working head portion of the
first embodiment;
[0018] FIG. 7 is a side elevational view of a second embodiment of
the invention with portions broken away to show side wall cladding;
and
[0019] FIG. 8 is a section similar to FIG. 5 and showing a metal
cladding of the head portion front face.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] FIGS. 1-6 show a first embodiment of a percussion rock drill
bit of the present invention, generally designated 10. The drill
bit includes a steel body 12 having a working head portion 14 and a
rearward shank portion 16 with a common central axis "a-a" (FIG.
6). The shank portion 16 has a central bore 20 with an internal
rope thread 21 for threaded connection to a hammer driven drill
string apparatus (not shown). The central bore 20 connects to three
flushing channels 22 constructed and arranged to direct flushing
and cooling fluid through the head portion 14 and around the front
facing surface 23 thereof. The front surface is generally
perpendicular to the central axis "a-a" (as shown by reference line
"b-b" in FIG. 6).
[0021] The circumference of the front facing head portion area is
larger than the circumference of the shank portion 16 whereby the
outer side wall 24 of the head portion 14 tapers inwardly from the
front circumference down to the shank portion 16 about 8.degree.
(as shown in FIG. 6). It will be understood that the taper may be
other than 8.degree. within the scope of the present invention. The
head portion 14 is provided with three vertical and elongate
grooves or channels 25 that are symmetrically spaced around the
circumference and extend vertically toward the shank portion 16 and
which define therebetween three symmetrically spaced wing zones 27.
It will be clear that these wedge-shaped grooves 25 are constructed
to receive the flushing fluid ported from the passageways 22 and
channel it toward the working front face (23) of the head portion
14 as well as providing a flow path for removing the rock chippings
(not shown) as the bore hole is being formed.
[0022] The head portion 14 is provided with three first or primary
gauge-cutting PCD inserts 30 symmetrically spaced from each other
and secured in primary sockets 38 into the wing zones 27. The head
portion 14 also is provided with second or secondary PCD inserts 31
constructed and arranged as core-cutters in a central zone 33 of
the front face (23). Three such second PCD inserts are shown in the
preferred embodiment of FIGS. 1-6, and these are asymmetrically and
non-axially arranged in secondary sockets 45 in the central zone 33
at the front of the head portion 14. The circumferential area 35 of
the front face of the tool extending radially outwardly from around
the central zone 33 is sloped axially rearwardly (or downwardly in
the drawings) at an angle of about 15.degree. to 35.degree., and
preferably about 22.degree. to 26.degree. (see "h" in FIG. 6). The
head portion 14 is provided with the three primary sockets 37
formed in each of the wing zones 27 and extending into the steel
body 12 on axes substantially perpendicular to the slope of the
wing zone surface 35, and these sockets 37 are slightly smaller
(i.e., about 0.002 inch) than the base diameter of the first PCD
inserts 30 whereby the pressfit of the inserts under about 5 tons
of force provides a secure seating of the inserts 30 in the sockets
37 through it will be noted that the first gauge-cutting PCD
inserts 30 in the first embodiment are larger than the second
core-breaking PCD inserts 31. The first PCD inserts 30 will
typically have a main body of tungsten carbide with a cylindrical
base section 42 and a domed working end 39 capped with a parabolic
or bullet-shaped domed crown 40 of PCD material (see FIG. 5). When
assembled the base section 42 is deeply seated in the socket 37 of
each wing zone 35 and the cylindrical wall extends beyond the
sloping head portion surface about 1/16 inch (at 41) so that the
gauge-cutting PCD crown caps 40 are precisely set at a
predetermined position (see "e-e" of FIG. 6) in front of the front
face "b-b" of the head portion 14.
[0023] The secondary core-cutting PCD inserts 31 have essentially
the same configuration as the first PCD inserts 30, although they
have a smaller diameter in the preferred first embodiment. The
coring PCD inserts 31 are set in sockets 45 formed in the central
zone 33 of the front face (23) and are non-symmetrically and
non-axially arranged to impact against different adjacent core
areas as the bore hole is being formed. The secondary PCD inserts
31 are also set to extend forwardly of the front face (23), but in
an axial direction and to a precise spaced distance (plane "d-d" in
FIG. 6) that is beyond the plane "e-e" of the gauge-cutting PCD
inserts 30. As shown in FIGS. 1-3, the central zone 33 may be
formed as an elevated or raised platform having a side wall 43.
Thus, in operation, it will be clear that the core-cutting PCD
inserts 31 initiate or pilot the bore hole formation by breaking a
smaller central core area thereof followed by the gauge-cutting
action of the first PCD inserts 30 to complete the full bore hole
drilling. Clearly the flushing fluid carries away the loose
chippings as the hole is formed as well as cools the diamond
inserts 30, 31 to prevent overheating thereof. It will be
understood that a wide variance of non-symmetrical coring insert
arrangements can be made, and that having a side wall 43 larger
diameter inserts 31 may be used on larger sized boring tools
10.
[0024] The geometry of the PCD inserts 30 and 31 in their sockets
37 and 45 can best be seen in FIGS. 5 and 6. This geometry
contributes to the integrity of the drill-bit, 110 and prolongs its
useful life; and includes the angular relationship between the
primary sockets 37 and the secondary sockets 45 and the depth
thereof in the head portion 14 of the drill bit. As shown, the
primary sockets 37 extend deepest (at 38) into the tool body 12.
The primary PCD inserts 30, extend outwardly at an angle to the
axis of the drill bit but are arranged to produce a reaction force
vector in an axial direction to push these primary inserts 30 more
firmly into these sockets 37. The secondary sockets 47 for the
core-cutting PCD inserts 31 extend in an axial direction, but the
bottoms 46 thereof are above the deeper primary sockets 37 and have
no negative influence thereon. It may also be noted that the
spherical cutting face of the respective PCD inserts distribute
impact forces through the insert bodies, and further that the PCD
layer itself does not wear out.
[0025] As shown best in FIGS. 1 and 4, the central zone 33 is shown
as a circular area that is axially centered and is also shown as a
raised platform having a side wall 43 of a minor dimension. The
distance that the contact point of the core-breaking inserts
extends forwardly of the crown of the gauge-cutting inserts is at
least as large as the platform elevation. It will be understood
that the central zone 33 of the front face 23 may be a different
shape such as a triangle, trapezoid or pentagon that will help to
define selected non-asymmetrical locations for orientation of
multiple cone-cutting inserts 31 without interference with the
seating sites (primary sockets 37) for the gauge-cutting inserts
30. In other words, the raised platform 43 facilitates the location
of secondary sockets in an axial direction away from the angularly
related sockets 37 for the outer PCD inserts but without direct
interference or compromising their structural integrity or the
press-fit strength thereof.
[0026] Referring to a second form of the invention shown in FIGS. 7
and 8, the steel body 112 at the head portion 114 of the drill bit
110 can be strengthened to better obviate erosion and wear of the
head portion surface areas if reinforced by a harder metal cladding
150. It will be appreciated that parts of the drill bit 110
corresponding to drill bit 10 will are given the same reference
numeral, plus "100." The use of exotic steels alloyed with chromium
carbide or vanadium carbide would provide the toughest steel bodies
for percussion tools, but at great expense. The present invention
contemplates bonding a chromium or chromium alloy jacket 150 over
the entire head portion 114 of the tool 110. This chromium cladding
layer 150 would have a thickness in the range of 0.005 to 0.010
inches and be tempered to a Rockwell hardness of at least 60 Rc and
preferably 65-68 Rc. In manufacturing the drill tool 110, the
sockets 137 and 145 for the first and second PCD inserts 130 and
131 will be formed after cladding process is completed.
[0027] Although the present invention has been described with
reference to the preferred embodiments, it will be apparent to
those skilled in the art that changes and modifications not
specifically disclosed can be made without departing from the
spirit and scope of the invention as defined in the appended
claims.
* * * * *