U.S. patent application number 10/139541 was filed with the patent office on 2003-11-13 for rotatable point-attack bit with protective body.
Invention is credited to McAlvain, Bruce William.
Application Number | 20030209366 10/139541 |
Document ID | / |
Family ID | 29399335 |
Filed Date | 2003-11-13 |
United States Patent
Application |
20030209366 |
Kind Code |
A1 |
McAlvain, Bruce William |
November 13, 2003 |
Rotatable point-attack bit with protective body
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 diamond-coated tungsten carbide wear tip that is
rotationally symmetric about its longitudinal axis and contiguous
with a protective tungsten carbide intermediary body, which is
contiguous with the third section steel shank at the rear end.
Inventors: |
McAlvain, Bruce William;
(Henderson, KY) |
Correspondence
Address: |
BRUCE WILLIAM MCALVAIN
5110 HEATHFIELD CT
HOUSTON
TX
77084-2387
US
|
Family ID: |
29399335 |
Appl. No.: |
10/139541 |
Filed: |
May 7, 2002 |
Current U.S.
Class: |
299/113 ;
299/111 |
Current CPC
Class: |
E21C 35/1831 20200501;
E21C 35/183 20130101 |
Class at
Publication: |
175/427 |
International
Class: |
E21B 010/36 |
Claims
What I claim as my invention is:
1. A rotatable cutting bit for impacting, fragmenting and removing
a substrate comprising of: a ferrous body or shank having a
longitudinal axis and forward end; a protective cemented carbide
mid section body rotationally symmetric about said longitudinal
axis; a diamond coated cemented carbide insert rotationally
symmetric about said longitudinal axis.
2. The rotatable cutting tool of claim 1 wherein the forward end of
the protective body contains a seat or radiused socket defining a
volume.
3. The rotatable cutting tool of claim 1 wherein the axially
rearward section of the insert has a protruding segment that
generally corresponds to, and fits into, the shape of the seat or
radiused socket of the protective body.
4. A braze joint joining the protruding or radiused extension
axially rearward section of the insert of claim 1 to the mating
seat or radiused socket of the axially forward section of the
protective body.
5. The rotatable cutting tool of claim 1 wherein the steel third
section of the tool body contains at its forward point a seat or
radiused socket defining a volume.
6. The rotatable cutting tool of claim 1 wherein the protruding
shape at the base of the protective body corresponds to the shape
of the seat or radiused socket defined in claim 5.
7. The rotatable cutting tool of claim 1 wherein said protective
body is affixed to the pocket of the steel shank of claim 5 by
brazing.
8. A rotatable cutting bit for impacting, fragmenting and removing
a substrate comprising of: a ferrous body or shank having a
longitudinal axis and forward end; a protective cemented carbide
mid section body rotationally symmetric about said longitudinal
axis; a diamond coated cemented carbide insert rotationally
symmetric about said longitudinal axis.
9. The protective cemented carbide mid section body of claim 8
having a forwardly facing socket extending forwardly therefrom by
way of a continuous radius to the forward most point of said
body;
10. The first forwardly facing surface of the protective mid
section and the mating rearwardly facing surface of the insert of
claim 8 are bonded by a brazed joint.
11. The protective cemented carbide mid section body of claim 8
having a frusto conical surface or surfaces leading from the front
of the body, where it is attached to the insert, to the rear of the
body, where it is attached to the steel shank. The resulting
diameter at the rear of the body being larger than the diameter at
the front of the body.
12. The protective cemented carbide mid section body of claim 8
having a second rearwardly facing surface with a first rearwardly
radiused surface leading to the rearwardly facing surface.
13. The protective cemented carbide mid section body of claim 8
wherein a second rearwardly facing surface is located radially
inside and rearward of the first radiused rear surface.
14. The protective cemented carbide mid section body of claim 8
wherein the first forwardly facing surface of the steel body and
the secondly rearwardly facing surface of the protective cemented
carbide mid section are bonded by a brazed joint.
15. The steel shank of claim 8 having 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
FIELD OF INVENTION
[0001] The present invention relates to a rotatable cutting bit
design for use in construction and excavation of the type having an
improved head portion and depending shank.
BACKGROUND OF THE INVENTION
[0002] The invention is directed to a rotatable cutting tool having
a diamond coated hard carbide insert brazed to an elongated body
consisting of a protective cemented carbide secondary body segment
and a third steel 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 the protective mid section, of less
chance for methane gas ignition and explosion. The protective hard
carbide mid section that supports the 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. Past
applications have suffered from 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 thus leading to catastrophic failure of the bit. This
invention of a protective carbide body holding the cutting tip and
protecting the steel shank prevents erosion of support around the
tip insert and erosion of steel below the carbide body thus
significantly extending the life of the cutting tool. The present
invention also reduced 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. A common belief is that
the primary cause of such ignition is the heat generated through
friction as the bits move through the coal and rock during the
mining operation. It is also possible that the sparking, which may
occur when the steel base portions of the bits strike rock, causes
ignition of the methane gas. 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 reducing the possibility of gas
ignition.
[0003] 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.
[0004] 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.
[0005] The steel 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.
[0006] 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 secondary cemented carbide body segment of the present
invention, the uneven wear pattern shown by conventional tools, is
greatly diminished or not noticeable when the tool clears and
resumes its rotation.
SUMMARY OF THE INVENTION
[0007] The present invention overcomes the shortcomings associated
with known constructions and teaches the construction and operation
of an insert for mining attack tools. The present invention of a
protective cemented carbide mid body segment, which fully retains
the diamond coated insert, and at its base is brazed to the steel
shank, serves to protect the diamond coated insert from premature
support erosion, and the steel shank from premature wear and
failure, which is the most common mode of failure with all diamond
tipped previous inventions. Thus, the protective carbide segment
prevents the common failure of wash out around the tip and channels
the flow of material away from the steel shank so as to
significantly reduce erosive wear of the steel shank below the
protective segment.
[0008] 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.
[0009] The protective 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 suitable base for inserting and brazing a diamond
insert and at the bottom a radiused contour 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.
DETAILED DESCRIPTION
[0010] Referring to the drawings more particularly by reference
numbers wherein like numerals refer to like parts, number 3 in FIG.
2 identifies a protective hard body constructed according to the
teachings of the present invention. Shown in FIG. 1 is a segmented
preferred embodiment of the invention of a rotatable cutter bit 1
having a diamond coated cemented tungsten carbide tip 2 having a
rearward radiused cylindrical stem surface that mates, and is
brazed, into the radiused segment cavity 4 of protective middle
body 3.
[0011] The cemented carbide body 3 is joined to a steel body 15 by
a braze joint 6. The head portion 2, the mid section 3, and the
shank 15 are coaxially aligned. The shank 15 having at its widest
diameter, an enlarged section 7, which prevents the tool from being
forced into the opening in the mounting block.
[0012] The rearward steel member 15 may be seen to include a
generally cylindrical shank portion 16 having an annular groove 17
near the rearward end and a frusto conical portion 18 adjacent
forward to the shank portion 16. The frusto conical portion 18 has
a radiused socket 19 at the forward end.
[0013] FIG. 2 shows the present invention protective second or
middle segment body 3, which includes a head end portion 10 which
is circular, containing a cavity or radiused socket 11 to retain
after brazing, the diamond coated insert which protrudes forwardly
in the direction of engagement with a work surface to be mined and
a tail end section 12 which is brazed into a cavity or radiused
socket 19 of the steel shank 15. The head end portion of 3 has an
angle A leading away from the insert cavity towards the base of the
body. The resulting frusto conical surface 14 is centered about the
longitudinal axis and intersects with a second frusto conical
surface 20 formed by an angle B with the base that further leads
down the length of the body to point 13 meeting a wider band that
serves to strengthen and seat the body into the steel shank 15. The
values of angle A and, or angle B 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 5-15 degrees has been
found to be most effective for angle B.
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