Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
2189216
SAW TOOTH ATTACR FACE AND EDGE STRUCT~RE
Bac~Louud of the Invention
Field of the In~ention
This invention relates to the shape and
configuration of the attack face and cutting edge
structures of a saw tooth, and particularly to such
structures applied to a four-sided rotatable saw tooth
5 for a wood cutting saw.
Discussion of the Prior Art
Four-sided rotatable teeth for circular tree cutting
saw blades in which one edge of the tooth is positioned
radially outermost from the rotary axis of the blade to
cut a kerf in a st~n~;ng tree are known from U.S. Patent
No. 4,932,447. This type of tooth has a four-sided head
with an attack face at one end, each side being
coterminous with the attack face along a cutting edge.
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The tooth is oriented on the blade with one of the sides
on the outside of the blade so that the one side and its
cutting edge are substantially vertical in the cutting
position of the blade, as the blade is advanced through a
S tree. The outside cutting edge forms the kerf by
chiseling off the working (vertical) surface of the kerf,
and chips from the cutting operation flow along the
attack face of the tooth for evacuation from the kerf.
When the outside edge becomes dull, the tooth is rotated
90~ or 180~ about its longitl7r7~;n~l axis and resecured to
present one of its other three edges in the outermost
position for cutting. When all four edges have become
dull, the tooth is replaced or reconditioned.
In this orientation of the tooth on the blade, two
of the sides of the tooth are in a substantially
horizontal plane, one of the horizontal sides being on
the top side of the tooth and the other horizontal side
being on the bottom side of the tooth. The top side of
the tooth is in close proximity or contact with the top
side of the kerf (on the tree trunk) and the bottom side
of the tooth is in close proximity or contact with the
lower side of the kerf (on the top of the stump). This
close proximity or contact results in a certain amount of
wear along the top side edge and bottom side edge of the
tooth during a cutting operation, although most wear
occurs at the outermost side of the tooth which actually
cuts the kerf.
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- Adjacent sides and the attack face of saw teeth meet
at the corner tips of the attack face. Because the mass
of material of the tooth diminishes toward a corner tip
and because abrasion occurs along both of the cutting
edges which define a corner tip between the outermost
edge and the top and bottom edges, wear is most
concentrated at the corner tips of the tooth. Wear of
the corner tips is especially exacerbated under sandy
conditions of cutting, as occurs frequently in the
southeastern part of the United States where sand on the
forest floor can get into the bark of the trees, e.g.
from wind or rain, and abrade teeth severely or where
trees are severed at ground level. In addition, because
the corner tips are at the extremities of the leading or
attack face of the tooth, they are especially susceptible
to damage from impact, for example, from hitting a rock
or another piece of equipment.
It has been known to retard wear in all types of saw
teeth under these conditions by providing one or more
tungsten carbide (or other wear-resistant material, e.g.,
Stellite~) plates to cover the high wear areas of the
attack face. However, this is only a partial solution to
the problem, as the corners still wear more quickly than
the inner edges of the attack face, even when the corners
and the inner edges are carbide. In addition, the wear
plates in prior teeth have typically had sharp points or
tips, which wore or broke off relatively easily.
2185216
Summary of the Invention
-The invention provides a saw tooth of the type
having multiple lateral sides and an attack face at one
end. The intersection of the attack face with each side
forms a cutting edge along the edge of the side and the
intersections of the attack face with each pair of
adjacent sides forms a corner. The attack face has four
quadrants defined by imaginary mutually orthogonal planes
which include an axis of the tooth and bisect the cutting
edges, each quadrant being the same as the other
quadrants, and each quadrant including a corner. The
improvement of the invention is that a plateau with a
flat surface is formed at each corner, and each quadrant
includes a first concave surface adjacent to the plateau
which is defined by a section of a first cylinder of
constant radius and having an axis which is perpendicular
to a plane which includes the axis of the tooth and
extends through the plateau. The plateau and the first
concave surface are coterminous along a first adjoining
edge which adjoins the plateau and the first concave
surface and extends between adjacent cutting edges of the
tooth. This results in more tooth material adjacent to
the corner tip, where abrasion and the possibility of
impact damage is especially high, to result in more even
wear over the length of each cutting edge and over the
- associated areas of the attack face.
- ~189216
In a preferred aspect, the plateaus are coplanar,,, in
a plane which is orthogonal to the longitudinal axis ~of
the tooth. This maximizes the volume of tooth material
adjacent to the corner tip. It also provides the
possibility of sharpening the cutting edges of the tips
by grinding down the plateaus simultaneously on a surface
grinder.
In another useful aspect, the receding edges and
portions of the attack face are curved to provide
efficient chip flow across them and evacuation of chips
from the kerf.
In a form which is especially useful for highly
abrasive cutting conditions, the tooth comprises a body
and wear plates secured to the body, surfac~s of the wear
plates defining the attack face and edges of the plates
defining the cutting edges. The wear plates are thickest
at the plateaus so as to provide more even wear across
the entire plate, for the most efficient use and
consumption of the plates. Preferably, the rear surface
of the plates is flat, so that the rear surface can be
formed easily and so that the mating surfaces of the body
can be easily machined to match the rear surface of the
plates.
In another useful aspect, a surface of the attack
face which is coterminous with a plateau is defined by a
surface of a cylinder, the axis of the cylinder being
perpendicular to a plane which includes the axis of the
- - 2189216
tooth and runs through the plateau. A surface so formed
provides both of its adjacent cutting edges with a
curvature and provides the adjoining surfaces with a
curvature that channels chips out of the kerf, while
still allowing making all of the wear plates identical
and without complex molding, sintering or mach; n; ng
operations.
In this aspect, where tooth life is more important
than quality of severance, a tooth of the invention may
be provided having a single cylindrical surface in each
quadrant, which is coterminous with a relatively large
plateau. Where a better quality of severance is more
important, two or more cylindrical surfaces may be
provided leading up to the plateau in each quadrant.
Other objects and advantages of the invention will
be apparent from the detailed description and the
drawlngs .
Brief Description of the Drawings
Fig. 1 is a perspective view of a saw tooth
incorporating the invention;
Fig. 2 is a side plan view of the saw tooth of Fig.
l; .
Fig. 3 is a plan view of the attack face of the saw
tooth of Fig. 1;
Fig. 4 is a sectional view of the tooth taken along
the plane of the line 4-4 of Fig. 3;
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Fig. 5 is a perspective view of a second embodiment
of a saw tooth incorporating the invention;
Fig. 6 is a fragmentary cross-sectional view of the
saw tooth of Fig. 5 as viewed from the plane of the line
6-6 of Fig. 5;
Fig. 7 is a plan view of the attack face of the wear
plate of Fig. 6 as viewed from line 7-7 of Fig. 6; and
Fig. 8 is a side plan of the wear plate 166A of
Figs. 5-7.
Detailed De~cription of the Preferred Embodiments
Figs. 1-4 illustrate a saw tooth 10 of the invention
which includes a body 12 and four wear plates 14A-D. The
body 12 is of conventional and known configuration. The
body 12 is typically made of steel and has a head portion
16 and a shank portion 18 which in the case of the body
12 is integral with the head 16. A blind bore 20 extends
axially through the body 12 and the shank end of the bore
20 is threaded at 22 so as to be engaged by an axial bolt
to secure the tooth 10 on the periphery of a circular saw
blade disc with one of its four cutting edges radially
outermost from the rotary axis of the saw blade. The
radially innermost side of the tooth typically abuts a
surface of the blade to prevent the tooth from rotating
during a cutting operation. Mounting four-sided
rotatable saw teeth in this manner is well known and
forms no part of the present invention.
- 2189216
The head 16 has four lateral sides 24, each of which
is flat. The head 16 itself is pyramidal, tapering i;n
the direction toward the shank 18. Each side 24 at its
end opposite from the shank 18 is coterminous with a
support surface 26 along edges 28 which generally define
a shallow V. The support surface 26 of the head 16 is
defined by milling flat each corner of the support
surface 26 at an angle as best shown in Fig. 4. The
rotary axis of the milling cutter used in this mach; n; ng
operation could be parallel to the surface being milled
and lie in a plane defined by: (1) the longitudinal axis
27 of the tooth; and (2) a line running from the tip of
the corner being milled to the tip of the diagonally
opposite corner. As such, when the mill is run across
the corner of the surface 26 and nears the edge of the
surface 26, it CUtQ an undercut 30 or 31 in the support
surface 26. The undercut 30 shown in Fig. 2 would be cut
when milling the right corner area of surface 26 (as
viewed in Fig. 2) and the undercut 31 would be cut when
milling the left corner area of surface 26. These
undercuts 30, 31 are a result of the milling process and
perform no useful function.
After all four corner areas of the surface 26 are
milled, a central square 34 of material re~A; ns in the
center of the surface 26 with sides which are
perpendicular to their adjacent corner areas of the
- ~18921~
surface 26. These sides are designated 36A-D in the
drawings.
As stated above, the body 12 is known and is prior
art. The body 12 may be identical to the bodies used in
the Koehring Waterous Series 4000 Carbide Tipped Teeth,
which are commercially available from the Koehring
Waterous Division of Timberjack, Inc. of Woodstock,
Ontario, Canada.
The saw tooth 10 differs from prior art saw teeth by
the shape of its attack face 40 and cutting edges 42-45,
which shapes are largely defined by the wear plates 14A-
D. The attack face 40 is made up of four identical
quadrants separated from one another by mutually
orthogonal (imaginary) planes which bisect the cutting -
edges 42-45 and include the longitudinal axis 27 of the
tooth. Each quadrant has one of the wear plates 14A-D
positioned in it, and each of the wear plates 14A-D are
identical to one another, each having a rear surface 50A-
D to match the corresponding corner area of the support
surface 26. Each rear surface 50A-D is brazed, soldered
or otherwise suitably secured to the corresponding corner
area to mount each wear plate 14A-D at its corresponding
corner or quadrant of the body 12.
Each plate 14A-D has five lateral sides 52-56 as
best shown in Figs. 1 and 3. For each of the reference
numbers 52-56, an alphabetic suffix has been added in the
drawings to correspond to the alphabetic suffix of the
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corresponding wear plate 14A-D. For example, sides 52A-
56A designate the sides of wear plate 14A.
Opposite from each rear surface 50A-D, each wear
plate 14A-D has a corresponding attack face 60 A-D. The
S four attack faces 60A-D and the exposed surface of square
34 define the attack face 40 of the tooth 10.
The following description applies to any one of the
plates 14A-D, therefore the A-D suffix is not applied to
reference numerals 14, S0, 52, 53, 54, 55, 56, 60, 64,
66, 68, etc. in this description, unless necessary to
distinguish one plate 14A-D from another.
Each attack face 60 is defined by a curved surface
64 and a flat plateau surface 66. Each curved surface 64
is defined by a section of a cylinder of constant radius
which has its axis parallel to rear surface 50 and in a
plane which is: (1) perpendicular to the rear surface 50;
and (2) through the outer points on the surface 64 where
the surface 64 meets its adjacent surfaces 64 (in other
words, through the midpoints of the edges 42-45 of the
tooth which define the corner; for example in the case of
plate 14A, these points have been labelled x and y in
Fig. 3, point x bisecting edge 42 and point y bisecting
edge 45). The axis of this cylinder is therefore
perpendicular to a plane which includes the longitudinal
axis 27 of the tooth and extends through the adjacent
plateau 66 and corner tip of the tooth. In the preferred
embodiment, the radius of this cylindrical section is
- ~18921~
approximately 2 inches for a tooth which is approximately
1-7/8" tip to tip along a side. The surface 64 is flat
and parallel to rear surface 50 in its area from a line
through these points (x and y in the case of plate 14A)
to the edge where surface 64 intersects surface 54. When
the plates 14 are mounted on body 12, each surface 64 is
substantially flush with the square 34 at this edge.
The curved portion of surface 64 of each plate 14
extends up to adjoining edge 68, which extends between
adjacent cutting edges of the tooth (e.g., edge 68A
extends between adjacent cutting edges 42 and 45), where
the surface 64 is coterminous with the plateau 66. Each
plateau 66 is flat, in a plane generally perpendicular to
the axis of the tooth 10, and extends from the edge 68 to
cutting edges defined by the cotermination of each
plateau 66 with the corresponding sides 52 and 56 of the
corresponding plate 14.
The cutting edge along the side 52 of each wear
plate 14 is defined by the intersection of the side
surface 52 with the curved surface 64 and with the
plateau 66. This cutting edge is designated 70 in the
drawings. The cutting edge defined by the intersection
of side surface 56 with curved surface 64 and plateau 66
is designated 72. The cutting edges 70 and 72 (and the
sides 52 and 56) meet at each corner tip of the tooth
with a small radius R (see "R" at the tip of plate 14A in
Fig. 3), so as to truncate the sharp tip which would
- 2189216
12
otherwise be formed, thereby reinforcing the tip. Thus,
each plateau 66 is generally triangular, being defined by
adjoining edge 68, which adjoins the concave cylindrical
surface 64 and the plateau 66, and the co-planar
S (straight) end sections of edges 70 and 72, which end
sections are joined at their inside ends by the edge 68
and at their outside ends by the radius R.
Each of the four cutting edges 42-45 of the saw
tooth 10 is made up by one cutting edge 70 and one
. cutting edge 72 of adjacent wear plates 14. Thus, tooth
edge 42 is defined by plate edges 70A and 72B, tooth edge
43 is defined by plate edges 70B and 72C, tooth edge 44
is defined by plate edges 70C and 72D, and tooth edge 45
is defined by plate edges 70D and 72A . The edges 70 and
72 which make up each tooth cutting edge 42-45 meet in
approximately the middle of the corresponding side 24,
where the sides 53 and 55 of adjacent plates 14 meet (for
edge 42, see point x in Fig. 3; for edge 45, see point y
in Fig. 3) .
Thus, the attack face 40 of the tooth 10 has a
complex shape, being defined by the four plateaus 66, the
four curved surfaces 64 and by the exposed surfaces of
the central square 34. Each of the four cutting edges of
the saw tooth 10 also has a complex shape, being defined
at its end sections by straight lines which lay in a
plane perpendicular to the axis 27 of the tooth and form
edges of the plateaus and from the straight lines toward
218921~
the center of the adjacent side being defined by curved
inner sections which meet in the center of the adjacent
side.
The profile of each plate 14 results in increased
S thickness at the corner tips, in the areas of the plateau
66, and reduced thickness at the interior of each plate
14, in particular where each wear plate 14 meets the next
adjacent wear plate 14. Thus, although the corners of
the attack face 40 wear faster than the inner edges of
the attack face 40, additional material is provided there
so that the various areas of the plates 14 wear out at
approximately the same time.
A saw tooth of the invention provides this advantage
in a tooth which is readily manufacturable and which
provides for smooth chip flow over the attack face 40.
The width of each plateau 66 in the radial direction of a
blade to which it is attached preferably exceeds a normal
feed rate of the blade as it is advanced through a tree
(for example, the plateau 66 may typically be .15 inches
as measured along a line through axis 27 from edge 68 to
the extreme tip of the plateau 66). The attack face 40,
which is concave inward of the plateaus 66, is made
curved in the concave area adjacent to the plateaus 66 by
surfaces 64, which helps to smoothly direct the flow of
chips away from the work surface of the kerf.
In addition, the increased wear plate thickness in
the plateau areas and that the plateaus are all coplanar
' . 218g21~
allows sharpening the cutting edges of the plateaus
simultaneously on a surface grinder. Since much of ~he
cutting of a kerf is performed by these edges, a more
efficient cut can be provided over the life of the plates
by sharpening these edges.
Preferably, the wear plates 14 overhang the sides 24
of the head 16 by a small distance, for example .OlS
inches, to protect the sides 24 from wear and prevent
them from "washing out" at their edges 28 directly
beneath the plates 14. Thus, when the wear plates 14
become worn to the point of replacement, they can be
removed from the body 12 and new wear plates affixed to
the body 12 so as to recondition and reuse the body 12.
Also, the rear edge of each side 54 i9 preferably
chamfered as shown in Fig. 4 so that the top edge of
surface 54 is close to the adjacent surface 36 so as to
smoothly direct the flow of chips over the square 34.
Teeth 10 work well for cutting trees which are being
harvested for their fiber, i.e., pulpwood, where the
quality of severance is less important and tooth life is
more important. Figs. 5-8 illustrate a second embodiment
110 of a saw tooth of the invention which is applied when
a superior quality of severance is desired, and some
reduction from the tooth life attainable by the tooth 10
is acceptable. The tooth llO has smaller and therefore
sharper corner tips, which yields a cleaner cut and less
damage to the wood fibers adjacent to the kerf.
-~ ~189216
The tooth 110 is the same as the tooth 10 and
provides many of the same advantages, except respecting
the shape of the attack face and cutting edges as
described below. In the drawings of the tooth 110,
corresponding elements are labelled with the same
reference number as in the tooth 10, plus 100. As in the
tooth 10, the wear plates 166A-D are identical to one
another, so Figs. 6-~ illustrate only plate 166A and the
suffix A-D is not used in the following description.
In the attack face of the tooth 110, two concavely
curved surfaces, both defined by a section of a constant
radius cylinder, define the attack face in each quadrant.
Consequently, another edge or peak is defined in each
quadrant at 169 which extends between cutting edges, is
parallel to edge 168, and along which both curved
surfaces 164 and 165 are coterminous. The radius and
center of the cylindrical section of the surface 164 may
be the same in the tooth 110 as in the tooth 10, i.e., 2"
radius, center positioned as defined above, for a 1-7/8"
square tooth. The radius of the surface 165, however, is
preferably only 1/4 of the radius of surface 164, i.e.,
1/2", and its axis is positioned as illustrated in Fig.
8, parallel to the axis of the cylinder that defines
surface 164 and positioned 3/8 of the radius of surface
164 up from the lower edge of the plate, i.e., up 3/4"
from the side 154A shown in Fig. 8 in the preferred
embodiment, where X is 1/2~'.
-- 218~21~
The dual cylindrical surface configuration of each
plate 156 reduces the amount of carbide material at ~he
tip of each plate 156, where the plateau 166 is located.
While this reduces the life of the tooth 110, it also
enables making the corner tips of the tooth 110 sharper,
the plateaus 166 being smaller and spaced the same
distance from the rear surface 190 of the head 116 as are
the plateaus 66 in the tooth 10. In the preferred
embodiment of the above dimensions, the plateau 166 may
typically be .034 inches as measured along a line through
axis 127 from edge 168 to the extreme tip of the plateau
166.
A preferred embodiment of the invention has been
described in considerable detail. Many modifications and
variations to the preferred embodiment will be apparent
to those skilled in the art. For example, other radii
could be used for the surfaces 64, 164 and 165.
Therefore, the invention should not be limited to the
embodiments described, but should be defined by the
claims which follow.
/
