U.S. patent application number 10/061215 was filed with the patent office on 2003-08-07 for stump grinding bit and tip therefor.
Invention is credited to Carlsson, Lars-Ake, Monyak, Kenneth.
Application Number | 20030145904 10/061215 |
Document ID | / |
Family ID | 22034373 |
Filed Date | 2003-08-07 |
United States Patent
Application |
20030145904 |
Kind Code |
A1 |
Monyak, Kenneth ; et
al. |
August 7, 2003 |
STUMP GRINDING BIT AND TIP THEREFOR
Abstract
A stump cutter includes a rotary drum, holders mounted on the
drum, and cutting bits mounted in respective bores of each holder
for rotation relative thereto. Each cutting bit includes a shank
having a pocket formed in a front end thereof in which the cutting
tip is brazed, wherein an outer lip of the shank tightly grips an
outer side surface of the cutting tip with a thermal shrink fit.
The cutting tip includes a circular cutting edge formed by the
intersection between portions of the front surface and side surface
of the cutting tip, which surface portions intersect at a ninety
degree angle. The front surface of the cutting tip includes raised
radial ribs spaced circumferentially therearound for inducing
rotation of the cutting bit during a cutting operation.
Inventors: |
Monyak, Kenneth; (Abingdon,
VA) ; Carlsson, Lars-Ake; (Sandviken, SE) |
Correspondence
Address: |
Ronald L. Grudziecki, Esq.
BURNS, DOANE, SWECKER & MATHIS, L.L.P.
P.O. Box 1404
Alexandria
VA
22313-1404
US
|
Family ID: |
22034373 |
Appl. No.: |
10/061215 |
Filed: |
February 4, 2002 |
Current U.S.
Class: |
144/241 |
Current CPC
Class: |
B23C 2200/045 20130101;
Y10T 83/9331 20150401; Y10T 407/24 20150115; A01G 23/067 20130101;
Y10T 407/23 20150115; Y10T 407/1932 20150115; Y10T 83/9362
20150401; B23C 2200/081 20130101; B23C 5/202 20130101 |
Class at
Publication: |
144/241 |
International
Class: |
B27C 001/00; B27C
005/00; B27G 013/00 |
Claims
What is claimed is:
1. A cutting tip for stump cutting comprising a body formed of a
hard material, the body having a rear supporting surface, a front
cutting surface, and a side surface extending between the
supporting surface and the cutting surface; an outer peripheral
portion of the cutting surface and a forward portion of the side
surface intersecting one another to form a substantially circular
cutting edge; an inner portion of the cutting surface disposed
radially inwardly of the outer peripheral portion and being axially
recessed relative to the outer peripheral portion; a center hole
extending axially through the body from the cutting surface to the
supporting surface; and a plurality of circumferentially spaced,
raised ribs extending generally radially along at least a portion
of the cutting surface.
2. The cutting tip according to claim 1 wherein each of the ribs
extends from substantially the cutting edge to substantially the
center hole.
3. The cutting tip according to claim 1 wherein the outer
peripheral portion of the cutting surface intersects the forward
portion of the side surface at substantially a ninety degree angle,
the outer peripheral portion extending substantially parallel to
the supporting surface.
4. The cutting tip according to claim 3 wherein each rib is
situated on both the outer peripheral portion of the cutting
surface and the inner portion of the cutting surface.
5. The cutting tip according to claim 1 wherein a rearward portion
of the side surface forms an acute angle with the forward portion
thereof and converges toward the supporting surface.
6. The cutting tip according to claim 1 wherein the body comprises
cemented carbide.
7. A cutting bit comprising: a shank defining a center axis and
having a rear mounting portion and a front head portion, the head
portion including a front face having a center post projecting
axially from the front face, and a generally circular lip
projecting forwardly and extending around an outer periphery of the
front face, wherein the front face and the lip form a pocket
surrounding the post, the post extending forwardly past the pocket;
and a cutting tip brazed in the pocket, and comprising a body
formed of a harder material than the shank, the body having a front
cutting surface, a rear supporting surface engaging the front face
of the shank, and a side surface extending between the supporting
surface and the cutting surface, the side surface engaging the lip
of the shank, an inner portion of the cutting surface being
disposed radially inwardly of the outer peripheral portion, and a
center hole extending through the body from the cutting surface to
the supporting surface and receiving the post.
8. The cutting bit according to claim 5 wherein a plurality of
raised ribs extend generally radially along at least a portion of
the recessed inner portion and the outer peripheral portion.
9. The cutting bit according to claim 8 wherein each rib extends
from substantially the cutting edge to substantially the center
hole.
10. The cutting bit according to claim 7 wherein the outer
peripheral portion of the cutting surface intersects the forward
portion of the side surface at substantially a ninety degree angle,
the outer peripheral portion oriented substantially parallel to the
supporting surface.
11. The cutting bit according to claim 10 wherein each rib is
situated on both the outer peripheral portion of the cutting
surface and the inner portion of the cutting surface.
12. The cutting bit according to claim 7 wherein a rearward portion
of the side surface forms an acute angle with the forward portion
thereof and converges toward the supporting surface, the lip
including an inner surface engaging the rearward portion of the
side surface and inclined complementarily thereto.
13. The cutting bit according to claim 7 wherein the lip comprises
steel and the cutting tip comprises carbide, the lip gripping the
side surface with a thermal shrink fit.
14. A rotary stump cutter comprising: a rotary member; holders
mounted on the member, each holder forming a bore extending
generally tangentially relative to an axis of rotation of the
member; and a cutting bit mounted in each bore and comprising: a
shank having a mounting portion disposed in the bore and rotatable
relative to the holder about a longitudinal axis of the bore, the
shank further including a front head portion, the head portion
including a front face having a center post projecting axially from
the front face, and a generally circular lip projecting forwardly
and extending around an outer periphery of the front face, wherein
the front face and the lip form a pocket surrounding the post, the
post extending forwardly past the pocket; and a cutting tip brazed
in the pocket, and comprising a body formed of a harder material
than the shank, the body having a front cutting surface, a rear
supporting surface engaging the front face of the shank, and a side
surface extending between the supporting surface and the cutting
surface, the lip engaging the side surface with a thermal shrink
fit, an outer peripheral portion of the cutting surface and a
forward portion of the side surface intersecting one another at
substantially a ninety degree angle to form a generally circular
cutting edge, an inner portion of the cutting surface disposed
radially inwardly of the outer peripheral portion and being
recessed relative to the outer peripheral portion thereof, and a
center hole extending through the body from the cutting surface to
the supporting surface and receiving the post.
15. The stump cutter according to claim 14 wherein each holder
includes two bores with respective cutting bits mounted therein,
the two bits being forwardly divergent and inclined at an acute
angle with respect to a line oriented tangentially to the rotary
member.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to cutting tools for use in an
apparatus for disintegrating material, such as a tree stump
grinding machine.
[0002] Conventional stump grinders are disclosed in U.S. Pat. No.
5,135,035; No. 5,279,345; No. 5,497,815; No. 5,582,353; and No.
5,743,314, for example. A typical tree stump grinding machine
comprises a rotatable wheel having a plurality of cutting
assemblies mounted thereon. The wheel is rotated while adjacent to
the stump, and the cutter teeth are moved into contact with the
stump. As a result, the stump is gradually disintegrated.
[0003] A stump grinder of the type disclosed in U.S. Pat. No.
5,135,035 is depicted herein in FIG. 1. That cutter device 10
includes a rotary shaft 12 to which a hub 14 is attached. A
plurality of cutters 16 is mounted around the outer periphery of
the hub. Each cutter 16 includes a holder 18, and a cutter plate 20
soldered in a groove formed in an outer end of each holder 18. Each
holder includes a fork-shaped base comprised of two parallel legs
22 (only one depicted). The legs straddle the hub and are secured
thereto by a fastening screw 24.
[0004] A stump grinder of the type disclosed in U.S. Pat. No.
5,135,035 is depicted herein in FIGS. 2 and 3. That grinder 30
includes a holder 32 and a cutter bit 34 mounted therein. The
holder 32 is adapted to be secured to a rotary hub (not shown). The
cutter bit 34 includes a base 36 and a carbide cutting tip 38
affixed thereto. The base 36 includes a forwardly facing flat
surface 40 having a center cylindrical pin 42 projecting forwardly
therefrom. The carbide tip 38 has a center hole for receiving the
pin 42, and a concavely recessed front face 44 bordered by a
circular cutting edge 46. The cutting edge is formed by the
intersection of the front face 44 and a side face which intersect
one another at an acute angle a. The base 34 includes a cylindrical
shank 48 mounted in a hole 50 of the holder 32 by a roll pin 52,
permitting the cutter bit to rotate freely about its center axis x,
thereby enabling wear to be distributed more evenly around the
cutting edge. That is in contrast to the cutter of FIG. 1 wherein
the plate 20 is stationary relative to the body in which it is
mounted.
[0005] The cutter bit 34 of FIGS. 2-3 works satisfactorily when
cutting in wood, but when the bit contacts the ground, e.g., to cut
parts of the stump close to, or buried in, the ground, the cutting
edge tends to quickly fracture, causing large chunks of the tip to
fall off. Thus, catastrophic failure of the tip quickly occurs.
Also, although the shank is mounted for free rotation in the
holder, to produce more uniform wear around the cutting edge, the
rotation of the shank induced by contact with the material being
cut is somewhat haphazard and may not result in a satisfactorily
uniform wear distribution, resulting in a premature failure of the
tip.
[0006] Therefore, it would be desirable to provide a cutter bit
which is less susceptible to catastrophic failure, and exhibits a
more uniform wear distribution.
SUMMARY OF THE INVENTION
[0007] One aspect of the present invention relates to a cutting tip
for stump cutting, which comprises a body formed of a hard material
(for example, cemented carbide). The body has a rear supporting
surface, a front cutting surface, and a side surface extending
between the supporting surface and the cutting surface. An outer
peripheral portion of the cutting surface and a forward portion of
the side surface intersect one another at substantially a ninety
degree angle to form a generally circular cutting edge. An inner
portion of the cutting surface disposed radially inwardly of the
outer peripheral portion is axially recessed relative to the outer
peripheral portion. A center hole extends through the body from the
cutting surface to the supporting surface. A plurality of
circumferentially spaced, raised ribs extend generally radially
along at least a portion of the cutting surface.
[0008] Another aspect of the invention pertains to a cutting bit
which comprises a shank. The shank defines a center axis and has a
rear mounting portion and front head portion. The head portion
includes a front face having a center post projecting axially from
the front face. A generally circular lip projects forwardly and
extends around an outer periphery of the front face. The front face
and the lip form a pocket surrounding the post. The post extends
forwardly past the pocket. The lip engages a side surface of the
cutting tip, and the post extends through the center hole of the
cutting tip.
[0009] Another aspect of the invention pertains to a rotary cutter
which comprises a rotary wheel, a holder mounted on the wheel and
forming a bore, and a cutting bit mounted in the bore. The cutting
bit comprises the shank and the cutting tip brazed thereto.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The objects and advantages of the invention will become
apparent from the following detailed description of a preferred
embodiment thereof in connection with the accompanying drawings in
which like numerals designate like elements and in which:
[0011] FIG. 1 is a fragmentary side elevational view of one type of
prior art stump cutter.
[0012] FIG. 2 is a side elevational view, partly broken away, of a
cutting bit of another type of stump cutter.
[0013] FIG. 3 is a longitudinal sectional view taken through the
cutting bit of FIG. 2.
[0014] FIG. 4 is a fragmentary side elevational view of stump
cutter according to the present invention, with a portion of a
holder thereof broken away to expose a cutting bit according to the
present invention.
[0015] FIG. 5A is a front elevational view of FIG. 4.
[0016] FIG. 5B is a top view of FIG. 5A.
[0017] FIG. 6 is a side elevational view of a shank portion of the
cutting bit of FIG. 4.
[0018] FIG. 7 is a fragmentary longitudinal sectional view of the
shank depicted in FIG. 6.
[0019] FIG. 8 is a side elevational view of the cutting bit
including the shank of FIG. 6 and a cutting tip according to the
present invention.
[0020] FIG. 9 is a front elevational view of the cutting bit
depicted in FIG. 8.
[0021] FIG. 10 is a side elevational view of a cutting tip
according to the present invention.
[0022] FIG. 11 is a front elevational view of the cutting tip of
FIG. 10.
[0023] FIG. 12 is a cross sectional view taken along the line
XII-XII in FIG. 11.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
[0024] Depicted in FIGS. 4 and 5 is a section of a stump grinder 60
which includes a rotary drum 61 having a plurality of lugs 62
mounted thereon, e.g., by welding. Only one lug 62 is depicted, but
typically the drum would have lugs arranged in axially and
circumferentially spaced relationship with reference to the drum
axis. Attached to each lug 62 is a cutting tool which includes a
holder 63 and a pair of cutter bits 68 mounted in respective
sockets 65 of the holder for rotation relative thereto. The holder
63 includes a pair of legs 63a which straddle the lug 62 and are
attached thereto, e.g., by a bolt 66. The drum rotates in the
direction of the arrow R in FIG. 4. Rotation of the holders 63
relative to the lugs 62 can be prevented in any suitable way, e.g.,
by stop blocks 67 attached to the drum behind each holder 63.
[0025] Each cutter bit 68 includes a shank 70 and a tip 72 brazed
thereto. The holder 63 includes a bore 74 in which a rear mounting
portion 76 of the shank 70 is disposed. That mounting portion 76
includes a recess 78 for enabling the shank to receive a
conventional elastic split-sleeve retainer 80 which frictionally
retains the shank within the bore, while permitting the shank to
rotate relatively freely under the action of cutting forces.
Alternatively, a roll pin of the type shown at 52 in FIG. 2 could
be employed.
[0026] A front enlarged head portion 82 of the shank 70 includes a
flat front face 84 having a center post 86 projecting forwardly
therefrom along the longitudinal axis X-X of the shank (see FIG.
7). A diameter of the post is equal to at least one-half of a
diameter of the front face 84. A circular lip 88 projects forwardly
and extends around an outer periphery of the front face 84. The lip
88 is spaced radially from the post 86, so a pocket 90 is formed
around the post 86, with the post projecting forwardly past the
pocket.
[0027] An inner face 92 of the lip 88 is inclined in a forward and
radially outward direction to form an acute angle b relative to the
axis (see FIG. 7).
[0028] The cutting tip 72, which is best shown in FIGS. 10-12, is
formed of a harder material than the shank 70. For example, the
cutting tip 72 is formed of a hard material such as cemented
carbide, whereas the shank is formed of a tough but softer material
such as steel. The cutting tip 72 comprises a body having a rear
supporting surface 100, a front cutting surface 102, and a side
surface 104 extending between the cutting surface 102 and the
supporting surface 100. An outer peripheral portion 102a of the
cutting surface intersects a front portion 104a of the side surface
104 to form a circular cutting edge 106.
[0029] Those two surface portions 102a, 104a intersect at a ninety
degree angle C (FIG. 12). That is, the outer peripheral portion
102a is oriented perpendicular to a center axis Y of the insert,
and the front portion 104a is oriented parallel to that axis Y.
[0030] A center portion 102b of the front surface 102 is recessed
relative to the outer peripheral portion 102a, wherein the recessed
center portion 102b intersects the outer peripheral portion 102a by
an acute angle d preferably of about 7.degree. (FIG. 12).
[0031] The rear portion 104b extends from the front portion 104a to
the supporting surface 100 at an acute angle e, corresponding to
the angle b which the inside surface 92 of the lip forms with the
center axis X-X. Also, the tip body includes a center through-hole
108 sized to receive the post 86 of the shank. Furthermore, an
outer diameter of the supporting surface 100 corresponds to the
outer diameter of the flat front face 84 of the shank. Accordingly,
when the cutting tip 72 is mounted on the shank, the supporting
surface 100 of the tip enters the pocket 90 of the shank, and the
center hole 108 receives the post 86, as shown in FIGS. 8 and
9.
[0032] After brazing the tip 72 to the shank 70, the steel of the
shank cools and shrinks more than does the carbide tip 72.
Accordingly, the lip 88 tightly grips the side surface 104 of the
tip with a thermal shrink fit, to resist a tendency for chunks of
the tip to break-off during a cutting operation after fractures
have formed in the tip. Hence, the fractured cutting tip is held
together and catastrophic failure of the tip is less likely to
occur.
[0033] The cutting surface 102 of the tip further includes a
plurality of radially extending, circumferentially spaced-apart
upstanding ribs 110. Each of the ribs is preferably disposed on
both the recessed portion 102b and the outer peripheral portion
102a of the cutting surface 102 and extends preferably from the
cutting edge 106 to the through-hole 108. Those ribs tend to
promote rotation of the bit 68 during a cutting operation as they
are engaged by the material being cut. Consequently, the cutting
edge is worn more uniformly as compared with a prior art bit whose
rotation is more haphazard.
[0034] Each cutter bit 68 is formed by brazing the cutting tip 72
in the pocket 90, and to the post 84 of the shank. Upon cooling,
the lip 88 of the shank shrinks and tightly grips the side surface
104 of the tip with a thermal shrink fit. Cutter bits 68 are held
in respective bores 74 of the holder 63 by means of the split
retainer sleeve 80, to enable the bits to be rotatable about the
respective axes X-X. The two bits 68 of each holder 63 are
forwardly divergent, as shown in FIG. 5B. That is, the axes of the
bits form an acute angle a, e.g., 10 degrees. Also, with the holder
63 bearing against the stop block 67, the bit axes are inclined
upwardly by a slight acute angle .beta. relative to a line T
oriented tangentially to the drum.
[0035] To cut stumps, the drum 61 is rotated and moved toward the
stump to bring the cutting tips 72 into engagement therewith to
gradually disintegrate the stump. The bits 68 are caused to rotate
about the axis X-X during the cutting operation. Such rotation is
induced by the presence of the ribs 110 which are abutted by the
material, e.g., wood or soil, engaged thereby. Consequently the
cutting edge 106 wears in a highly uniform manner.
[0036] Moreover, even if fractures occur in the cutting tip 72,
catastrophic failure of the tip 72 is less likely to occur, because
the radial support of the tip imparted by the lip 88 resists a
tendency for large pieces of the tip to fall-off.
[0037] Although the present invention has been described in
connection with a preferred embodiment 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.
* * * * *