Woodworking – Special-work machine – Stump removing
Reexamination Certificate
2002-02-04
2003-08-05
Bray, W. Donald (Department: 3725)
Woodworking
Special-work machine
Stump removing
C083S840000, C083S853000, C144S241000, C144S334000, C299S108000, C299S111000, C299S113000, C407S046000, C407S113000, C407S115000
Reexamination Certificate
active
06601620
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to cutting tools for use in an apparatus for disintegrating material, such as a tree stump grinding machine.
Conventional stump grinders are disclosed in U.S. Pat. Nos. 5,135,035; 5,279,345; 5,497,815; 5,582,353; and 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.
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
.
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.
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.
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
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.
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.
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.
REFERENCES:
patent: 4626140 (1986-12-01), Zweekly et al.
patent: 4738291 (1988-04-01), Isley
patent: 5135035 (1992-08-01), Mills
patent: 5168907 (1992-12-01), Herrington et al.
patent: 5261306 (1993-11-01), Morey et al.
patent: 5279345 (1994-01-01), LeMaux et al.
patent: 5478175 (1995-12-01), Kraemer
patent: 5497815 (1996-03-01), Bowling
patent: 5582353 (1996-12-01), Willibald
patent: 5653274 (1997-08-01), Johnson et al.
patent: 5743314 (1998-04-01), Puch
patent: 5827016 (1998-10-01), Strand
patent: 6047749 (2000-04-01), Lamb
Carlsson Lars-Åke
Monyak Kenneth
Bray W. Donald
Burns Doane , Swecker, Mathis LLP
Sandvik Rock Tools, Inc.
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