U.S. patent application number 10/444539 was filed with the patent office on 2003-12-18 for rotating cutter bit assembly having hardfaced block and wear washer.
Invention is credited to Mondy, Michael C., Webb, Kirk E..
Application Number | 20030230926 10/444539 |
Document ID | / |
Family ID | 29739873 |
Filed Date | 2003-12-18 |
United States Patent
Application |
20030230926 |
Kind Code |
A1 |
Mondy, Michael C. ; et
al. |
December 18, 2003 |
Rotating cutter bit assembly having hardfaced block and wear
washer
Abstract
A rotatable cutting bit, and rotatable cutting bit-bit holder
assembly and washer that have increased wear resistance
characteristics. The assembly incorporates a new holding washer
design that has improved wear resistant characteristics between the
cutter bit and top surface of the bit holder during operation. The
cutter bit assembly includes a bit holder having a top surface, a
generally flat washer, the top surface includes a top face forming
a bearing surface for the cutting bit to enhance rotation of the
cutter bit. The wear rate caused by the relative rotation between
the rear face of the washer and top surface of the block face is
reduced in the present invention. The top surface of the bit holder
is hardfaced to limit and reduce wear. The improved wear resistance
properties of the invention reduce the amount of necessary
maintenance of rotary drums in the field resulting in reduce
downtime and increase productivity.
Inventors: |
Mondy, Michael C.; (Everett,
PA) ; Webb, Kirk E.; (Harrison, TN) |
Correspondence
Address: |
Kevin P. Weldon
Kennametal Inc.
P.O. Box 231
Latrobe
PA
15650
US
|
Family ID: |
29739873 |
Appl. No.: |
10/444539 |
Filed: |
May 23, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60385683 |
Jun 4, 2002 |
|
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|
Current U.S.
Class: |
299/105 ;
299/110 |
Current CPC
Class: |
B28D 1/188 20130101;
E21C 35/183 20130101 |
Class at
Publication: |
299/105 ;
299/110 |
International
Class: |
E21C 025/10 |
Claims
What is claimed is:
1. A cutter block assembly for use in mining, road working or earth
moving comprising: a bit holder block having a top surface, a
cutting tool, and a washer between said cutting tool and bit holder
block for reducing wear between the cutting tool and said bit
holder block, wherein said top surface has a hardface coating.
2. The cutter block assembly according to claim 1 wherein said
cutting tool is rotatable.
3. The cutter block assembly according to claim 2 wherein said bit
holder block is constructed from a steel alloy.
4. The cutter block assembly according to claim 3 wherein said
steel alloy has a Rockwell "C" hardness number between 45-55
R.sub.c.
5. The cutter block assembly according to claim 3 wherein said
hardface coating has a Rockwell "C" hardness number between 57-63
R.sub.c.
6. The cutter block assembly according to claim 4 wherein said
hardface coating has a Rockwell "C" hardness number between 57-63
R.sub.c.
7. The cutter block assembly according to claim 6 wherein said
washer has a Rockwell "C" hardness number between 43-48
R.sub.c.
8. The cutter block assembly according to claim 1 wherein said
coating has a depth of between {fraction (1/16)}"-{fraction
(3/32)}".
9. The cutter block assembly according to claim 8 wherein said
hardface coating has a Rockwell "C" hardness number between 57-63
R.sub.c.
10. The cutter block assembly according to claim 3 wherein said
hardface coating comprises Silicon, Chromium, Iron, Boron and
Nickel.
11. The cutter block assembly according to claim 1 wherein said
hardface coating comprises by percent weight composition:
0.75%-5.0% Silicon, 8.0-15.0% Chromium, 2.0%-5.0% Iron, 1.0%-5.0%
Boron, and 68%-78% Nickel.
12. The cutter block assembly according to claim 11 wherein said
hardface coating has a Rockwell hardness value between 57-63
R.sub.c.
13. The cutter block assembly according to claim 11 wherein said
Silicon is about 3.6%, said Chromium is about 10.8%, said Iron is
about 3.8%, said Boron is about 2.35% and said Nickel is about
75.7%.
14. The cutter block assembly according to claim 1 wherein said
hardface coating comprises by percent weight composition: about 78%
Nickel, about 11.7% Chromium, about 4.1% Iron, about 0.9% Silicon,
about 0.5% Tungsten, and having a hardness value between 57-63
R.sub.c.
15. A bit holder for a rotating cutter bit for use in mining, road
working or earth moving comprising: a top surface having a hardface
coating, wherein said coating has a Rockwell "C" hardness number
between 57-63 R.sub.c.
16. The bit holder according to claim 15 wherein said bit holder
block is manufactured from a steel alloy.
17. The bit holder according to claim 16 wherein said steel alloy
has a Rockwell "C" hardness number between 45-55 R.sub.c.
18. The bit holder according to claim 15 wherein said hardface
coating comprises Silicon, Chromium, Iron, Boron and Nickel.
19. The bit holder according to claim 15 wherein said hardface
coating comprises by percent weight composition: 0.75%-5.0%
Silicon, 8.0-15.0% Chromium, 2.0%-5.0% Iron, 1.0%-5.0% Boron, and
68.0%-78.0% Nickel.
20. The bit holder according to claim 15 wherein said hardface
coating comprises by percent weight composition: about 78.0%
Nickel, about 11.7% Chromium, about 4.1% Iron, about 0.9% Silicon,
about 0.5% Tungsten, and having a hardness value between 57-63
R.sub.c.
Description
[0001] This application is a nonprovisional application of U.S.
Provisional Application No. 60/385,683, filed Jun. 4, 2002.
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
[0002] This invention relates to an article for improving the
efficiency of operation of carbide-tipped cutting bits utilized in
rotary machines adapted for pulverizing concrete and asphalt
roadways and similar surfaces. More particularly, the invention
relates to articles for improving the cutting action of rotatable
carbide bits, and for protecting the support blocks in which the
bits are mounted.
[0003] In the prior art, cutting bits are mounted to be rotatable
about the central axis of the cutting bit mounted in a support
block. The rotation of the cutting bit provides for uniform wear of
the cutting bit improving the effective life of the cutting tool.
The rotatable cutting bits have a flange bottom face that bears
against the top face of the support block.
[0004] During the operation of prior art cutting bits, the support
block experienced wear due to the contact between the cutting bit
and the support block, as well as the impingement of the debris
from the cutting operation. While the cutting bit was replaced on a
periodic basis after the expiration of the useful life thereof, the
support block was typically intended to be functional much longer
than the cutting bit. As the bore and front face of the support
block became worn, the support block lost its effectiveness due to
deformation and wear of the bore and the front face thereof. In the
case of the bore, it lost its initial cylindrical shape by becoming
out-of-round, oversized or bell-mouthed at its opening. In the case
of the front face of the support block, it lost its flatness. Each
one of these conditions impeded the satisfactory rotation of the
cutting bit in the support block.
[0005] Although providing the capability for free rotation of the
cutting-bit results in more uniform wear and extended life of the
bit, wear of the bit support block continues to be a problem. The
flat, upper transverse face of the bit support block is
continuously impacted with abrasive materials during the operation
of the rotary drum pulverizers or wheel machines. Also, if a bit
wears down to the extent that it extends only a short distance out
from the face of its support block, more rapid and destructive wear
of the support block occurs. Excessively worn bit-support blocks
must be removed from the pulverizer drum or wheel with a cutting
torch, and a new support block welded onto the drum or wheel. This
replacement process is time consuming, and therefore, costly.
Furthermore, it frequently happens that replacement of support
blocks under field conditions results in a misalignment of the bore
axis of the holding support block from its optimum orientation,
decreasing the effectiveness of machine operation.
[0006] Efforts have been made in the industry to alleviate the wear
problems discussed above. In the prior art, bearing washers, such
as U.S. Pat. No. 4,818,027, are comprised essentially of a flat,
hardened steel annular ring or washer which is adapted to fitting
between the enlarged base of a cylindrical cutting bit, and the
transverse outer face of the holding block which rotatably supports
the bit. In addition to absorbing wear, which would otherwise be
experienced by the bit holding block, this bearing washer provided
other advantages. One advantage is the reduction of cutting bit
friction; the bearing washer was free to rotate allowing the
cutting bit to rotate more freely. This results in cooler operation
and more even wear of the cutting bit, substantially extending its
life.
[0007] Although providing the capability for free rotation of the
cutting bit results in more uniform wear and extended life of the
bit, wear of the bit holding block in prior art continued to be a
problem. The flat, upper face of the bit holding block is
continuously impacted with abrasive materials during the operation
of the rotary pulverizers. Wear in such prior art designs also
occurred on account of relative rotation between the bearing washer
and face of the holding block. It should be noted that the rate of
wear to the holding block due to the bearing washer was much less
than the rate of wear caused by a rotating cutting bit without a
bearing washer. Wear of the bit holding block requires that the
worn blocks be removed from the pulverizer drum with a cutting
torch, and a new block welded onto the drum. This is a time
consuming, and therefore, costly operation. Furthermore, it
frequently happens that replacement of holding blocks under field
conditions results in a misalignment of the bore axis of the
mounting block from its optimum orientation.
[0008] Other efforts have been made to reduce the undesirable wear
that occurred on the top face of the support block. U.S. Pat. No.
5,931,542, to Britzke et al., discloses a method of protecting the
front face of a cutter bit holder block. Britzke '542 illustrates a
thrust-bearing washer at 50. The washer is keyed with sleeve 42 so
as to be fixed in position. Accordingly no wear occurs between the
washer and top face of the bit holder block. The cutting bit on
this prior art design did not rotate as freely as cutting bits
having bearing washers that were also free to rotate as discussed
above.
[0009] The Ojanen U.S. Pat. No. 5,251,964 discloses an attempt in
the prior art to protect the face of a block wherein a plurality of
carbide inserts are brazed to the face of the block to limit the
rate of wear to the front face of the block. This design was
ineffective because the cutter bits are made from hardened steel in
order to limit wear to the tool during use. The bottom face of the
cutter bit shoulder in contact with the top face of the support
block is made from such hardened steel. The contact of prior art
cutter bit hardened steel against the top face of the support block
shaved and fractured the plurality of carbide inserts.
[0010] It would, therefore, be very advantageous to provide a
cutting bit, which, during operation, protects the bore of the bit
holder, as well as the front face of the support block, from
deformation. By providing this protection, a cutting bit would help
prolong the useful life of the support block, as well as, help the
rotation of the cutting bit.
OBJECTS OF THE INVENTION
[0011] An object of the present invention is to provide an
efficient means for protecting holding support blocks, of the type
used to hold rotating cutting bits used in a pulverizer and rotary
drum or wheel machines, from excessive abrasion and impact
damage.
[0012] Another object of the invention is to provide a cutter block
assembly which has both great hardness for providing high abrasion
resistance and high impact strength to limit damage to a support
mounting block.
[0013] Another object of the invention is to provide a combination
of elements for cutter bit holding block assemblies which is free
to rotate with respect to the shank of the cutting bit providing
uniform wear of the cutting bits.
[0014] Various other objects and advantages of the present
invention, and its most novel features, will become apparent to
those skilled in the art by perusing the accompanying
specification, drawings and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a side view of the cutter block assembly of the
present invention.
[0016] FIG. 2 is a front view of the block for the present
invention.
[0017] FIG. 3 is a side view of the cutting bit assembly of the
present invention.
DESCRIPTION OF THE INVENTION
[0018] The cutter block assembly 10 of the present invention is
illustrated in FIG. 1. The cutter block assembly 10 includes a
holder block 12 and a rotatable cutter bit 14 fixed therein. As
best seen in FIG. 2, the top face 11 of the block has a hardfacing
material deposited thereon represented by the speckled/shaded
grit.
[0019] The cutter bit assembly is best shown in FIG. 3. The cutter
bit assembly includes a cutter body having an integral conical head
18 and shaft 24, cutting tip 16, a retainer 22 and a bearing washer
20. The cutter bit assembly 14 is first inserted and manually
knocked into the bore 15 of the holder block, typically with a
hammer. The retainer sleeve 22 is made from Spring Steel that is
held in a compressed loaded position by the holding washer 20 as
shown in FIG. 3. In the compressed loaded position the external
diameter of the sleeve is less than the internal diameter of the
bore. When the cutter bit assembly 14 is hammered into the bore 15
of the holder block the bearing washer 20 moves upward toward the
conical head 18 above the retainer sleeve 22 releasing the retainer
sleeve so that it tensions against the interior of the bore holding
the shaft inside the bore. U.S. Pat. No. 4,818,027 is hereby
incorporated by reference in its entirety.
[0020] The holder block of the present invention is constructed
from a steel alloy heat treated to a Rockwell hardness number of
between 45-55 Rockwell "C". In one embodiment, the steel alloy is
constructed from AISI 8740 heat treated to Rockwell Hardness of
between 45-50 RHc. The composition of AISI steel is 0.40 Carbon,
0.75-1.1 Manganese, 0.4-0.7 Nickel, 0.4-0.6 Nickel, 0.4-0.6
Chromium, 0.2-0.3 Molybdenum and 0.2-0.35 Silicon. It is
contemplated that the steel alloy might be made of another or other
suitable steel alloy having the same general desirable wear
characteristics of AISI 8740, 4140, 1020, and 4030.
[0021] The hardfacing could be applied to the block with a
well-known torch having a hopper for feeding powder into
combustible gases discharged from the torch nozzle to melt the
powder to form a metallurgical bond with the block. Alternatively,
the hardfacing could be applied by an electroplasma gun or other
suitable means well known in the art for depositing metal powder
onto a metal body. A suitable powder torch for applying hardfacing
is disclosed in U.S. Pat. No. 3,995,811. The depth of the coating
applied onto the top face of the block is between {fraction
(1/16)}"-{fraction (3/32)}".
[0022] In one embodiment the hardfacing material is a composition
of nickel metal, iron-nickel and has a Rockwell Hardness "C" value
of between 57-63. A suitable powder for hardfacing the support
block of the present invention has a particle size of 32 microns
and a percent weight composition as follows: Silicon: 0.75%-5.0%,
Chromium: 8.0%-15%, Iron: 2.0%-5.0%, Nickel: 68%-78%, Carbon:
0.0%-1.5%, and Boron: 1.00%-5.00% %. In one embodiment the
hardfacing composition is about 75.7% Nickel, about 3.8% Iron,
about 3.6 % Silicon, about 2.35% Boron, about 10.8% Chromium, and
the remainder a variety of impurities. Another contemplated powder
composition is 78% Nickel, 11.7 % Chromium, 4.1% Iron, 0.9% silicon
and 0.5% tungsten.
[0023] The holding washer is made from typical Spring Steel
employed and well known in the industry, including but not limited
to AISI 1060, 1070 & 1080 steel. The holding washer may or may
not be heat-treated, but is a softer material than the material
used to make the cutter bit. A Rockwell hardness value between
43-48 can provide for satisfactory results in some environments,
whereas different Rockwell hardness values of the Spring Steel are
more suitable for other environments. It is believed that the
cooperation of the holding washer's softer material with the top
face of the support block is less destructive to the top face of
the block than direct rotational contact between the harder surface
of the cutter bit and the top face of the support block.
[0024] The cutter tip 16 is typically made from a cemented carbide
material such as, for example, a cobalt-tungsten carbide alloy.
Although the specific grade of cemented carbide depends upon the
particular application for the cutting tool, rotatable cutting
tools used in road planing applications may use a hard insert made
of cobalt cemented tungsten carbide wherein the cobalt content
ranges between about 5 weight percent to 13 weight percent, with
the balance comprising tungsten carbide. The hardness of the
cemented tungsten carbide may range between about 86 and about 90.4
Rockwell A. A preferred grade of cemented tungsten carbide for a
road planing application has a cobalt content that ranges between
about 5.2 weight percent and about 6.3 weight percent, with the
balance being essentially tungsten carbide and the hardness ranging
between 88.2 and 89.4 Rockwell A.
[0025] The shape and sizes of the cutter bit, holding washer and
mounting support block are merely a representative cutter bit
assembly to help present the invention, and are not intended to
limit the scope of application of the present invention. The novel
features of this invention and the invention itself, both in
structure and operation, are best understood from the accompanying
drawings considered in connection with the accompanying
description. It should be noted that the illustrated embodiments
and corresponding description are merely one of many designs for
the invention and merely representative. The invention is not
intended to be limited to the disclosed embodiments and description
herein.
* * * * *