U.S. patent application number 10/213299 was filed with the patent office on 2004-02-12 for monolithic point-attack bit.
Invention is credited to McAlvain, Bruce William.
Application Number | 20040026983 10/213299 |
Document ID | / |
Family ID | 31494432 |
Filed Date | 2004-02-12 |
United States Patent
Application |
20040026983 |
Kind Code |
A1 |
McAlvain, Bruce William |
February 12, 2004 |
Monolithic point-attack bit
Abstract
A rotatable point-attack bit retained for rotation in a block
bore, and used for impacting, fragmenting and removing material
from a mine wall. An improved elongated tool body having at the
front end a monolithic diamond-coated tungsten carbide wear tip
that is rotationally symmetric about its longitudinal axis and
contiguous with its protective tungsten carbide body, which is
contiguous with a second section steel shank at the rear end. The
two distinct parts are joined by a high impact resistant braze at
ratios that prevent tool breakage. The method of making such a
monolithic section comprises of placing within a reaction cell the
diamond powder and the carbide substrate and simultaneously
subjecting the cell and the contents thereof to temperature and
pressure at which the diamond particles are stable and form a
uniform polycrystalline diamond surface on the tip of the carbide
substrate thus forming a monolithic insert providing both cutting
edge and steel body protection for increased durability and
extended cutting tool life.
Inventors: |
McAlvain, Bruce William;
(Henderson, KY) |
Correspondence
Address: |
BRUCE WILLIAM MCALVAIN
5110 HEATHFIELD CT.
HOUSTON
TX
77084
US
|
Family ID: |
31494432 |
Appl. No.: |
10/213299 |
Filed: |
August 7, 2002 |
Current U.S.
Class: |
299/111 ;
299/113 |
Current CPC
Class: |
E21C 35/1837 20200501;
E21C 35/183 20130101 |
Class at
Publication: |
299/111 ;
299/113 |
International
Class: |
E21C 025/10 |
Claims
What I claim as my invention is:
1. A rotatable cutting bit for impacting, fragmenting and removing
material such as asphalt, concrete, rock, and minerals, the
rotatable cutting bit comprised of: a polycrystalline diamond tip,
affixed to a cemented carbide substrate by high temperature and
pressure bonding, forming a monolithic unitary body, positioned at
the forward central axis extremity of the cutter bit, having
coaxially aligned, rotationally symmetric about its longitudinal
axis, two monolithic integral sections, said sections comprising a
tip section, and a base section, having a maximum diameter at said
base section, and having a flat surface or a convex protrusion or
continuously varying radiused extension at its rearward section. a
ferrous body with a head section and elongated shank having a
circular cross section, said body depending from said protective
monolithic body along a longitudinal axis, said head portion having
a flat surface or concave seat or continuously varying radiused
socket at the forward end.
2. The rotatable cutting tool of claim 1 wherein the forward
monolithic section is coated with polycrystalline diamond, cubic
boron nitride, wurtzite boron nitride or mixtures thereof formed by
a method that comprises the placing within a reaction cell
pre-pressed forms of abrasive particles affixed to the tip of the
cemented carbide substrate and simultaneously subjecting the cell
and the contents thereof to temperature and pressure conditions at
which the diamond, cubic boron nitride or wurtzite boron nitride
particles form a super hard abrasion resistant polycrystalline
layer permanently sinter reaction bonded to the tip of the cemented
carbide substrate.
3. The rotatable cutting tool of claim 1 wherein the forward
monolithic section has a cemented carbide substrate, which at its
forward end has from 1-5 staggered concentrically layered rounded
radiused protuberances that serve to support the diamond layer.
4. The rotatable cutting tool of claim 1 wherein the forward end of
the steel shank contains a flat surface or seat or continuously
radiused socket defining a surface area, having an overall depth of
0.001 to 2.00 inches.
5. The rotatable cutting tool of claim 1 wherein the axially
rearward section of said monolithic insert has a flat surface or
protruding or radiused extension that generally corresponds to, and
fits into the shape of the flat surface or seat or continuously
radiused socket of said steel shank.
6. The rotatable cutting tool of claim 1 with a braze joint joining
the surface area of the flat or protruding or radiused extension
axially rearward section of said monolithic body to the flat
surface, mating seat or radiused socket of the axially forward
section of said ferrous shank by means of a medium to high impact
resistant braze alloy.
7. The brazed surface areas in claim 6 of said steel shank axially
forward section flat surface, seat or radiused socket and said
rearward monolithic protective body section flat surface,
protruding or radiused extension to be at a ratio of steel shank
surface area to monolithic body lateral cross sectioned area of 1.0
to 6.5.
8. The rotatable cutting tool of claim 1 wherein the tip is made of
a polycrystalline diamond affixed in situ to the carbide substrate
by high temperature and high pressure.
9. The rotatable cutting tool of claim 1 wherein the tip is made of
a polycrystalline cubic boron nitride affixed in situ to the
carbide substrate by high temperature and high pressure.
10. The rotatable cutting tool of claim 1 wherein the monolithic
cemented carbide section is made of a composition containing grains
of carbide of group IVB, VB, or VIB metals pressed and sintered in
the presence of a binder such as 5.0 to 18.0% cobalt, nickel, iron
or alloys thereof.
11. The rotatable cutting tool of claim 1 wherein the monolithic
cemented carbide section is made of a composition containing
carbide of group IVB, VB, or VIB metals having grain sizes from
0.01 to 30 microns as measured on a sintered, polished and etched
part at 100 to 1500.times. optical magnification.
12. The rotatable cutting tool of claim 1 wherein said monolithic
protective cemented carbide section has a frusto conical surface or
surfaces leading from the diamond tip or front of the body, to the
rear of said body, where it is attached to the head of the ferrous
shank; the resulting diameter at the rear of said protective body
being larger, ranging 0.75 to 2.5 inches, than the diameter at the
front of said protective body, ranging 0.25 to 1.5 inches.
13. The rotatable cutting tool of claim 1 wherein said monolithic
protective cemented carbide section has an overall length of 0.01
to 3.0 inches.
14. The rotatable cutting tool of claim 1 wherein said monolithic
protective cemented carbide section has a plurality of peripherally
spaced, laterally projecting surfaces or vanes extending generally
longitudinally along the bit, each surface or vane being
substantially triangular with a narrow leading end and a wider
trailing end, and having relatively diverging sides that extend
from the leading end to the trailing end, the purpose of which is
to effect a positive rotation of the bit upon contact with material
being impacted, fragmented or removed.
15. The rotatable cutting tool of claim 1 wherein said steel shank
has a means for holding a loosely resilient retainer on the steel
body that allows the cutter bit to rotate about its longitudinal
axis in a mounting block.
Description
BACKGROUND OF THE INVENTION
[0001] The invention is directed to a rotatable cutting tool having
a diamond tipped cemented carbide elongated protective body and a
second steel body segment. The design of the invention is to
provide improved performance and safety characteristics. These
characteristics include a longer performance cycle through
increased wear and fracture resistance resulting in a more
efficient continuously penetrating material removal cycle and an
improvement in safety, due to a monolithic diamond tipped carbide
segment, that results in less chance for methane gas ignition and
explosion. The protective large hard carbide section that has a
high temperature and high pressure bonded diamond coated tip not
only results in increased wear life of the bit body but also serves
to protect the lower steel shank in tougher milling conditions.
[0002] Examples of rotatable cutting tools are on applications with
long wall miners, continuous miners, and road planers. A longwall
mining machine is used for mining coal seems underground. The
machine includes two rotating drums having a plurality of blocks
affixed thereto. Long wall mining tools typically comprise an
elongated steel body with a hard cemented carbide tip brazed into a
socket contained in the forward end of the steel body. One such
point attack bit is described in U.S. Pat. No. 4,065,185. Attempts
to improve performance have been made by hardening the insert tips
of mining attack tools by the use of diamond compacts. One such
diamond compact for use in cutting, machining, drilling and like
operations is disclosed in Hall et al U.S. Pat. No. 4,604,106.
Mining bits incorporating the diamond tips brazed onto steel
inserts and subsequently brazed into steel bodies are shown in
Anderson et al U.S. Pat. Nos. 5,837,071 and 6,051,079.
[0003] During the milling operation, the drums rotate so as to
cause the rotatable cutting tools to impact the mine wall surface.
The tools impact and fracture the wall surface. The surface
fragments of coal chunks and powder are collected by a continuously
moving conveyor belt and carried to the surface of the mine for
processing. During the rotation of a drum, each rotatable cutting
tool rotates about its central longitudinal axis. It is important
that the tools continue to rotate because without adequate rotation
a conventional tool will be locked into position and start an
uneven wear pattern that leads to rapid tool degradation and
ultimate tool failure. Due to the higher wear resistance of the
protective monolithic cemented carbide body segment of the present
invention, if the tool fails to rotate, the uneven wear pattern
shown by conventional tools is greatly diminished or not noticeable
when the tool clears and resumes its rotation.
[0004] The steel cutting tool body includes a reduced diameter
portion adjacent to the rearward end thereof. A retainer is
adjacent the reduced diameter portion of the steel body. The
retainer functions to rotatably retain the rotatable cutting tool
within the bore of the mounting block during the milling operation.
Each block contains a central bore therein. This and other
resilient retainer means useful with the present invention are
described in U.S. Pat. Nos. 3,519,309 and 4,201,421.
[0005] A common mode of failure of polycrystalline diamond
compacts, is the delamination of the diamond from the metal carbide
substrate. Different attempts have been made to find a true bond
that would resist delamination under the severe conditions
employed. U.S. Pat. No. 5,011,515 discusses numerous attempts by
previous inventors to solve the problem of delamination of the
diamond layer from the carbide substrate. U.S. Pat. Nos. 4,592,433
and 4,784,023 teach parallel grooving of substrates to form ridges
for increased bonding. U.S. Pat. No. 6,029,760 teaches the use of
rounded cylindrical posts as support for diamond surfaces in rock
drilling and machining wear resistant materials. These designs
actually produce higher stresses in some portions of the cutter
than that exhibited in the planar interface mounted PCD to carbide.
However, all of the previous patents refer to rock and oil drilling
or machining of parts where the stresses are not the same as for
the application of this invention. This invention specifically
addresses the use of diamond-coated picks, usually mounted on a
rotating drum, for road pavement removal and recycling and coal
mining, such as for continuous and long wall mining machines. A
feature of this invention are the rounded radiused protuberances
located at the tip of the carbide substrate, that serve to decrease
the load stress concentrations and distribute them evenly over the
surface, thus minimizing the potential for diamond
delamination.
[0006] Other features of this invention are provided by a method
for making a monolithic section, which method comprises the placing
within a reaction cell pre-pressed forms of diamond particles
affixed to the tip of the carbide substrate and simultaneously
subjecting the cell and the contents thereof to temperature and
pressure conditions at which the diamond particles solidify and are
permanently reaction bonded to the cemented carbide substrate. The
methods of making polycrystalline diamond in a high temperature,
high-pressure press are well known in the art and further detailed
description thereof is not considered necessary.
[0007] Another method of failure of previous inventions that use a
small carbide, or diamond coated carbide tip bonded to a steel
shank is braze failure at the carbide tip to steel shank junction,
where the severe application forces exceed the tensile strength of
the braze alloy causing bond failure of the small contact area
between two dissimilar metals. This invention having a diamond
tipped monolithic, longer extended carbide portion, makes the
surface area where the carbide post is brazed to the steel shank of
much larger diameter than previous inventions and further increases
the surface area with a continuously varying radius that matches
the profile of the steel shank pocket where it is bonded by a
medium to high impact resistant braze. The larger brazed surface
area ensures that the braze joint will not fail under most severe
loading conditions, thus extending the life of the bit and
contributing to safety by minimizing catastrophic tool failure.
[0008] Another method of failure is due to using diamond coated
carbide tips limited in size as compared to the size of the diamond
tip of the present invention. Having only a limited size carbide or
diamond coated carbide tip results in bit failure when the steel
holding the carbide or diamond coated insert is eroded away during
application, exposing the cutting insert and allowing fracture
thereof followed by catastrophic failure of the bit. In addition to
the much larger protective surface area, the profile of the
monolithic section is so designed as to guide the cuttings away
from the ferrous shank preventing erosion of the steel body below
the carbide section, thus significantly extending the life of the
tool.
[0009] The present invention reduces the potential of sparking and
explosion from ignition of methane gas. The ignition of methane
gas, which is released from pockets where the gas has been trapped
in the material being mined, is a safety problem. The causes of
ignition are believed to be due to the heat generated through
friction as the bits move through the coal and rock during the
mining operation or due to sparking, which may occur when the steel
base portions of the bits strike rock. Since the coefficients of
friction of diamond and tungsten carbide are substantially lower
than that of steel, less heat is generated as the monolithic body
of the present invention cuts through coal and rock, thus reducing
the possibility of gas ignition.
[0010] The protective monolithic body is preferably formed as a
unitary member of cemented carbide or other material, which
provides suitable hardness and abrasion resistance characteristics,
and which at the top provides a diamond insert and at the bottom a
radiused projection to allow inserting and brazing into a steel
shank. The term "cemented carbide" refers to the type of material
resulting when grains of carbide of the group IVB, VB, or VIB
metals are pressed and sintered in the presence of a binder such as
cobalt, nickel, or iron as well as alloys thereof. The term
"diamond" refers to polycrystalline diamond, cubic boron nitride or
wurtzite boron nitride and mixtures thereof.
SUMMARY OF THE INVENTION
[0011] The present invention overcomes the shortcomings associated
with known rotatable cutting tools and teaches the construction and
operation of an insert for road construction or mining attack
tools. The present invention of a monolithic diamond tipped
cemented carbide body segment, joined to the steel shank at a
specified braze area ratio, serves to protect the diamond tip from
base erosion and channels the flow of material away from the steel
shank so as to significantly reduce premature washout wear and
failure, which are the most common modes of failure with all
diamond tipped previous inventions.
[0012] Since the coefficient of friction of tungsten carbide is
substantially lower than that of steel, less heat is generated as
the protective body of the present invention cuts through coal and
rock thus increasing the safety of operation by reducing the
potential of sparking and explosion from ignition.
DETAILED DESCRIPTION
[0013] Referring to the drawings more particularly by reference
numbers wherein like numerals refer to like parts. FIG. 1
identifies a protective hard body constructed according to the
teachings of the present invention. Shown in FIG. 2 is a preferred
segmented embodiment of the invention of a rotatable cutter bit
having a diamond coated cemented tungsten carbide tip 1, a cemented
carbide body 2 and a steel body 3. The base of the carbide
protective post 2 is joined to the steel shank 3 by a medium to
high strength braze alloy. The head portion 2, and the shank 3 are
coaxially aligned. The shank 3 having at its widest diameter, an
enlarged section 4, which prevents the tool from being forced into
the opening of the mounting block. The rearward steel member 3 may
be seen to include a generally cylindrical shank portion 5 having
an annular groove 6 near the rearward end and a frusto conical
portion 7 adjacent forward to the shank portion 5. The frusto
conical portion 7 has a continuously radiused socket 8 at its
forward end.
[0014] FIG. 3 shows the present invention monolithic protective
body segment 2, which includes a circular diamond tipped head end
portion 1 and a continuously varying radiused tail end section 9
which is brazed into a continuously varying radiused socket 8 of
the steel shank 3. The head end portion of 2, has an angular
radiused frusto conical surface 10 leading away from the diamond
tip 1 towards its widest diameter 11, which is centered about the
longitudinal axis formed by varying radius B that leads down the
length of the body to point 11, meeting a wider band 12, and a
convex surface with a continuously varying radius 9, that serve to
retain and strengthen the carbide body when brazed into the
matching shank pocket 8 with a medium to high temperature
braze.
[0015] The values of angle A of the diamond tip and, or the angle
B, leading away from the diamond tip to the widest part of the
carbide section, will vary depending on the particular mining
application. For example, a range from 30 to 60 degrees has been
found by the inventor to be the most effective range for the angle
A, while a range from 5 to 15 degrees has been found to be most
effective for angle B.
[0016] FIG. 4 shows the cemented carbide substrate portion of the
monolithic body prior to affixing the diamond at the forward tip.
The surface 13 serves as a substrate onto which the diamond is
applied. The diamond is applied and covers the rounded tip surface
14, the nodular frusto conical retention surface containing one or
more layers of rounded radiused protuberances 15, and the frusto
conical planar surface 16 until it meets a step in the carbide
substrate at a band 17.
* * * * *