U.S. patent application number 11/712567 was filed with the patent office on 2008-02-07 for rotary cutting bit with material-deflecting ledge.
This patent application is currently assigned to SANDVIK AB. Invention is credited to Gary A. Fuller, Gregory David Mercier.
Application Number | 20080030066 11/712567 |
Document ID | / |
Family ID | 34136265 |
Filed Date | 2008-02-07 |
United States Patent
Application |
20080030066 |
Kind Code |
A1 |
Mercier; Gregory David ; et
al. |
February 7, 2008 |
Rotary cutting bit with material-deflecting ledge
Abstract
A cutting bit includes a body having a front surface and a side
surface, the side surface including a shoulder below the front
surface and extending substantially perpendicular to a central axis
of the body, and a ring that is harder than the body attached to
the body at a front surface of the shoulder. Wear life of the
cutting bit is enhanced by maintaining particular dimensional
relationships regarding the position of the ring on the body, and
the diameter of portions of the body.
Inventors: |
Mercier; Gregory David;
(Bristol, VA) ; Fuller; Gary A.; (Abingdon,
VA) |
Correspondence
Address: |
DRINKER BIDDLE & REATH (DC)
1500 K STREET, N.W.
SUITE 1100
WASHINGTON
DC
20005-1209
US
|
Assignee: |
SANDVIK AB
|
Family ID: |
34136265 |
Appl. No.: |
11/712567 |
Filed: |
March 1, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10641138 |
Aug 15, 2003 |
7204560 |
|
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11712567 |
Mar 1, 2007 |
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Current U.S.
Class: |
299/105 |
Current CPC
Class: |
B28D 1/186 20130101;
E21C 35/183 20130101; E21C 35/1837 20200501 |
Class at
Publication: |
299/105 |
International
Class: |
E21C 25/10 20060101
E21C025/10 |
Claims
1. A cutting bit, comprising: A body having a front surface and a
side surface, the side surface including a shoulder below the front
surface and extending substantially perpendicular to a central axis
of the body, the body being no larger in diameter above the
shoulder than at the shoulder; and a ring that is harder than the
body attached to the body at a front surface of the shoulder.
2-26. (canceled)
Description
BACKGROUND AND SUMMARY
[0001] The present invention relates to cutting tools used to cut
through soft ground or through relatively soft material that has
been laid on the ground, such as asphalt roadways.
[0002] Mining, excavating, and road resurfacing operations are
typically performed by forcing rotary cutting bits through the
material being cut. The cutting bits are mounted on a driven
support, such as a rotary drum, fixed beam, or the like to be
forced through the material. A typical cutting bit comprises a hard
cemented carbide tip that is brazed to the front surface of a steel
shank. The shank is to be mounted in a holder by means of a
retainer sleeve which permits the bit to rotate freely relative to
the holder about the bit's center axis, while being restrained
against axial dislodgment from the holder. Due to being freely
rotatable, the tip is basically self-sharpening.
[0003] It should be understood that cutting mechanisms of the type
described above have been used to cut through hard materials, such
as rock and ice, in addition to cutting through softer materials
such as asphalt. During the cutting of rock, the highest rate of
bit wear occurs at the carbide tip, so the wear life of the bit is
determined by the carbide tip. However, during the cutting of
relatively softer material, such as asphalt, coal, and salt, the
highest rate of wear occurs at the shank, i.e., erosion caused by
cut asphalt rubbing and impacting against the shank. Thus, when
cutting asphalt during a road resurfacing operation, the wear life
of the cutting bit is determined by the shank.
[0004] It would be desirable to provide a cutting bit that has an
increased wear life when used for cutting softer materials such as
asphalt.
[0005] Disclosed in U.S. Pat. No. 4,725,098, which is incorporated
by reference, is a cutting bit in which a groove is machined in a
tapering side surface of the bit head closely behind a carbide tip
mounted in the bit head. Hardfacing is deposited into the groove to
form an erosion-resistant annular ring which can be flush with, or
project slightly radially beyond, the side surface. Despite being
formed of hard material, the ring will be subjected to considerable
erosion by cuttings and thus will have a somewhat limited life.
[0006] U.S. patent application Ser. No. 10/058,387, filed Jan. 30,
2002, entitled Rotary Cutting Bit with Material-Deflecting Ledge,
naming Kent Peay and Timothy J. Shean as inventors, which is
incorporated by reference, discloses a cutting bit having a tapered
side surface with a ledge projecting from the tapered surface. The
ledge can be integral with the rest of the bit body or formed as a
separate ring held on the body. The ledge is of sufficient diameter
relative to the portion of the body above it that material cut
tends to accumulate on the ledge and shields the body material
underneath from erosion. However, it has been found that the ledge
in such a cutting bit is highly prone to wear.
[0007] It would be desirable to provide a cutting bit with an
erosion-resistant structure which has an enhanced life. It would
also be desirable to provide a cutting bit that is simple to
manufacture and involves relatively few manufacturing
operations.
[0008] In accordance with an aspect of the present invention, a
cutting bit includes a body having a front surface and a side
surface, the side surface including a shoulder below the front
surface and extending substantially perpendicular to a central axis
of the body, the body being no larger in diameter above the
shoulder than at the shoulder, and a ring that is harder than the
body attached to the body at a front surface of the shoulder.
[0009] In accordance with another aspect of the present invention,
a cutting bit includes a body having a front surface and a
cylindrical side surface portion, the cylindrical side surface
portion including a shoulder below the front surface and extending
substantially perpendicular to a central axis of the body, and a
ring that is harder than the body attached to the body at a front
surface of the shoulder. A distance between the front surface and a
top of the ring divided by a distance between the front surface and
a bottom surface of the body is 0.15 to 0.5.
[0010] In accordance with yet another aspect of the present
invention, a cutting bit includes a body having a front surface and
a cylindrical side surface portion, the cylindrical side surface
portion including a shoulder below the front surface and extending
substantially perpendicular to a central axis of the body, a
cutting tip attached to the front surface, and a ring that is
harder than the body attached to the body at a front surface of the
shoulder. A diameter of a bottom of the cutting tip divided by the
diameter of the body at the bottom of the cuffing tip is 0.72 to
0.95.
[0011] In accordance with yet another aspect of the present
invention, a cutting bit includes a body having a front surface and
a cylindrical side surface portion, the cylindrical side surface
portion including a shoulder below the front surface and extending
substantially perpendicular to a central axis of the body, a
cutting tip attached to the front surface, and a ring that is
harder than the body attached to the body at a front surface of the
shoulder. A diameter of the cutting bit divided by an outside
diameter of the ring is 0.60 to 0.80.
[0012] In accordance with yet another aspect of the present
invention, a cutting bit includes a body having a front surface and
a side surface, the side surface including a first shoulder below
the front surface and extending substantially perpendicular to a
central axis of the body, the body being no larger in diameter
above the first shoulder than at the first shoulder, and a second
shoulder below the first shoulder, the body being no larger in
diameter above the second shoulder than at the second shoulder, and
a first ring and a second ring attached to the body at a front
surface of, respectively, the first shoulder and the second
shoulder.
[0013] In accordance with still another aspect of the present
invention, a cutting tip for being attached to a cutting bit
includes a base portion, a tip portion, the tip portion being
generally convex in shape, and a side portion extending between the
base portion and the tip portion, the side portion being generally
concave in shape.
[0014] In accordance with still another aspect of the present
invention, a cutting bit includes a cutting tip having a base
portion, a tip portion, the tip portion being generally convex in
shape, and a side portion extending between the base portion and
the tip portion, the side portion being generally concave in shape
and intersecting with the tip portion at a junction. The cutting
bit also includes a body having a front face to which the cutting
tip is attached, a bottom portion, and a shoulder below the front
surface and extending substantially perpendicular to a central axis
of the body, and a ring that is harder than the body attached to
the body at a front surface of the shoulder. An imaginary cone is
defined by the junction and the bottom portion and the ring is
disposed inside of the cone.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The objects and advantages of the invention will become
apparent from the following detailed description of preferred
embodiments thereof in connection with the accompanying drawings in
which like numerals designate like elements and in which:
[0016] FIG. 1 is a side elevational view of a rotary cutting bit
according to an embodiment of the present invention;
[0017] FIG. 2 is a side elevational view of a rotary cutting bit
according to an embodiment of the present invention showing an
accumulation of cut material on the bit; and
[0018] FIG. 3 is a side elevational view of a rotary cutting bit
according to another embodiment of the present invention.
DETAILED DESCRIPTION
[0019] A cutting bit 21 according to an embodiment of the present
invention is shown in FIGS. 1 and 2. The cutting bit 21 includes a
body 23 having a front surface 25 and a side surface 27. The side
surface 27 includes a shoulder 29 below the front surface 25 and
extending substantially perpendicular to a central axis of the
body. A cutting tip 31 is preferably attached to the front surface
25, usually by brazing, the cutting tip preferably being harder
than the body 23.
[0020] A ring 33 that is preferably harder than the body 23 is
attached to the body at a front surface 35 of the shoulder 29, such
as by brazing. The body 23 is preferably no larger in diameter
above the shoulder 29 than at the shoulder and, preferably, at
least a portion 37 of the side surface 27 of the body 23 is
cylindrical, more preferably circularly cylindrical, above the
shoulder 29 so that a ring having a circular inside diameter can be
slid over the body to the shoulder. Because the body 23 is
preferably no larger in diameter above the shoulder 29 than at the
shoulder, it is not necessary to incur machining costs for
machining a groove in the body. Also, the body 23 can be cold
formed. The ring 33 is preferably positioned above the shoulder 29
and brazed to the body 23 in the same operation, which can minimize
manufacturing costs, particularly when compared with bits wherein a
groove must be formed. If desired or necessary, however, the
shoulder 29 can be part of a groove in the side surface and the
ring can be, for example, a split ring that is held in place by
upper and lower surfaces of the groove. The ring 33 is illustrated
as being a substantially circular shape, however, it will be
appreciated that the ring can be any desired shape, such as
hexagonal, octagonal, etc.
[0021] In the cutting bit 21' shown in FIG. 3, the body 23'
includes a second shoulder 39 below the first shoulder 29. Again,
the body 23' is preferably no larger in diameter above the second
shoulder 39 than at the second shoulder to facilitate sliding a
second ring 41 over the body to the second shoulder where it is
attached to the body at a front surface of the second shoulder.
Again, if desired or necessary, however, the shoulder 39 can be
part of a groove in the side surface and the ring 41 can be, for
example, a split ring that is held in place by upper and lower
surfaces of the groove.
[0022] A distance A between the front surface 25 and a top 43 of
the ring 33 divided by a distance B between the front surface and a
bottom surface 45 of the body is preferably 0.15 to 0.5. It is
intended that material being cut will accumulate on the ring 33 and
the material will prevent erosion of the body 23 between the ring
and the cutting tip 31 by deflecting further material. A flange 47,
which is preferably integral with the body, is preferably provided
at the bottom of the body 23. Cut material tends to accumulate on
the flange 47 in a manner similar to the manner in which material
accumulates on the ring 33.
[0023] In the past, a wear pattern between a cutting tip and a
bottom flange on a body would tend to approximate the "golf tee"
shape shown by the dotted line X in FIG. 2. It has been found that
providing the ring 33 in a region that would ordinarily be subject
to significant erosion results in a substantially reduced volume
loss of material from the body 23 and tends to approximate the
double "golf tee" shape shown as the shaded area Y in FIG. 2. While
it is desirable to prevent body wear, it is also desirable to
ensure that the ring 33 is at a sufficient distance from the
cutting tip 31 to avoid a dulling of the cutting action, which can
be achieved by keeping the relationship between distance A and
distance B in the range of 0.15 to 0.5. If a second shoulder 39 and
ring 41 are provided as in FIG. 3, it is preferred that a distance
A' between the front surface 25 and a top 49 of the second ring 41
divided by the distance B between the front surface and a bottom
surface 45 of the body is, as with the first ring 33, 0.15 to 0.5.
This tends to place both the first ring 33 and the second ring 41
in what would otherwise be a region of maximum erosion on the body
23.
[0024] A diameter C of the cutting tip 31 divided by a diameter D
of the body 23 at the bottom of the cutting tip is preferably 0.72
to 0.95. The front surface 25 is preferably recessed to define a
dam wall 51 in which the cutting tip 31 is attached by brazing.
Purposes of the dam wall 49 include preventing brazing liquid from
flowing out from between the cutting tip 31 and the front surface
25 and acting as a stress reliever when the body 23 cools off. As
C/D becomes closer to 1, the thickness of the dam wall 49 is
reduced and less material is needed to form the body 23. As C/D
moves from 1 toward 0, the body 23 has more material and its useful
life span tends to approach that of the cutting tip 31 made of
harder material.
[0025] The diameter C of the cutting tip 31 divided by an outside
diameter E of the ring is preferably 0.60 to 0.80. As seen in FIGS.
1-3, the cutting tip 31 preferably has a bottom surface 52 that is
brazed to the front surface 25 inside the dam wall 49, a concave
surface portion 53 extending upwardly to a break point 55, and a
tip portion 57 that is generally convex. As seen in FIGS. 2 and 3,
an imaginary cone 59 extends through a point 61 on the outer edge
of the flange 47 and the break point 55 to a point 63 above the tip
portion 57 along the center axis of the body 23. It has been found
desirable to keep all points on the cutting bit 21, including
points on the ring 33, inside or at least substantially inside of
this cone 59. Points extending outwardly beyond the cone tend to be
too vulnerable to erosion. By keeping C/E in the range of 0.60 to
0.80, particularly when A/B is 0.15 to 0.50 and C/D is 0.72 to
0.95, the outermost point on the ring 33 tends to fall on or inside
of the cone 59 and is less subject to wear. The relationships
described above in connection with the cutting bit having only the
ring 33 are preferably also true for bits having two or more rings,
e.g., the bit 21' including the ring 41 shown in FIG. 3.
[0026] Although the present invention has been described in
connection with preferred embodiments thereof, it will be
appreciated by those skilled in the art that additions, deletions,
modifications, and substitutions not specifically described may be
made without departing from the spirit and scope of the invention
as defined in the appended claims.
* * * * *