Note: Descriptions are shown in the official language in which they were submitted.
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METAL-CUTTING SAW BLADE HAVING STRENGTHENED GULLET
AND NEGATIVE TOOTH RAKE
CLAIM FOR PRIORITY
The present patent claims priority to U.S. Provisional Application Serial
Number 60/191,043, entitled METAL-CUTTING SAW BLADE HAVING
STRENGTHENED GULLET AND NEGATIVE TOOTH RAKE, filed on March
21, 2000.
BACKGROUND OF THE INVENTION
The present invention relates to rotary saw blades for cutting thin-
gauge metal sheeting. In particular, the present invention relates to a saw
blade having a strengthened gullet structure and a tooth rake combination for
efficiently cutting metal workpieces.
Portable electric rotary tools are often used to make cuts in metal
workpieces at a worksite. Typically, non-toothed grinding blades are used on
stationary tools for trimming smaller workpieces, while different blades are
used in conjunction with handheld tools to make longer, more substantial cuts
in the metal. These longer cuts often require a toothed blade to provide more
aggressive movement through the workpiece. This is time-efficient and also
prevents the excessive buildup of heat caused by friction between the blade
and the metal.
Toothed blades typically include peripheral tooth supports projecting
radially from a round metal plate. To control kickback and guide the teeth
attached to the supports, anti-kickback shoulder.structures are often provided
ahead of each tooth. These typical structures as available in the prior art,
for
example in U.S. Patent No. 5,261,306 to Morey et al., may not be appropriate
for cutting metal. Use of such blades for cutting metal sheeting may
compromise the life of the blade and may be dangerous to the user.
Moreover, the deterioration of a conventional blade structure or a
conventional metal blade cutting structure will often contribute ,to
inaccuracies
in the cut. As more aggressive blades are used in metal, warping caused by
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frictional heat and stress damage may cause the teeth to fall out of
alignment.
This results in uneven cut edges or chipped edges in the workpiece.
There is therefore a need for a blade structure more tailored to the
needs of aggressive metal cutfiing applications.
BRIEF SUMMARY OF THE INVENTION
To obviate one or more of the above shortcomings, one embodiment of
a rotary saw blade for cutting a metal workpiece is provided. The blade
includes a generally circular main body plate having an opening at a center of
the plate and a plurality of raised tooth support members disposed about the
periphery of the plate. Each of the support members has a tooth attachment
portion generally facing the direction of rotation of the blade and a
peripheral
guide member extending away from the tooth attachment portion. A plurality
of cutting teeth are each mounted on one of the tooth attachment portions.
Each of the tooth support members define gullets between each of the guide
members and extending generally radially inwardly toward the center of the
blade. The gullets are further defined by a throat area and a rounded area,
wherein the throat area defines a gap width between a peripheral guide
member and a tooth. Preferably, a portion of the rounded area is located
substantially forwardly of the throat area.
In another aspect of the invention, another embodiment of a rotary saw
blade is provided wherein the plurality of raised tooth support members have
a forwardly directed tooth attachment portion generally facing the direction
of
rotation of the blade and a peripheral guide member having a finger extending
rearwardly away from the tooth attachment portion. Each of the cutting teeth
are mounted on one of the tooth attachment portions so that a radially
outermost edge of the tooth is positioned at an angle between approximately
0 and 7 degrees from a radial line on the blade. Each of the support
members, fingers and teeth substantially define a gullet having a throat area
and a rounded area located radially inwardly from an outer circumference of
the blade.
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The invention may also be embodied in a method for cutting a metal
workplace. The method includes the steps of providing a hand-held power
tool, attaching a generally circular blade to the power tool, and cutting the
workplace using the power too( and the blade. The blade includes a main
body plate having an opening at a center of the plate and a plurality of
peripherally spaced tooth support members. Each of the support members
has a tooth attachment portion inclined negatively relative to a radius of the
blade, and successive ones of the support members define gullets having a
throat area and a rounded area. The throat area defines a gap width
substantially smaller than the radius of an arc of the rounded area.
The present invention therefore provides a saw blade having a unique
structure to allow the efficient and accurate cutting of thin metal
workplaces.
The negative tooth rake angle is integrated into~the structure of the blade
tooth support to provide greater strength to the overall blade while allowing
the teeth to make smoother cuts into the workplace. Furthermore, the
stocking-shaped gullet structure defined between tooth supports efficiently
spreads the linear tensile forces along the elongated, rounded edges of the
gullet to more efficiently absorb the stress produced by the guide structures
and the tooth supports.
It is to be understood that both the foregoing general description and
the following detailed description are exemplary and explanatory and are
intended to provide further explanation of the invention as claimed. The
invention, together with further objects and attendant advantages, will best
be
understood by reference to the following detailed description, taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
These and other advantages of the present invention will -become more
fully apparent as the following description is read in conjunction with the
drawings, wherein: .
FIG. 1 illustrates a plan view of one embodiment of the rotary saw
blade of the present invention;
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FIG. 2 illustrates a detailed plan view of a circumferential edge section
of the saw blade similar to that of FIG. 1 in a modified second embodiment
having the teeth removed from the blade;
FIG. 3 illustrates a detailed plan view of a circumferential edge section
of the saw blade of FIG. 1 with the teeth installed to the blade;
FIG. 4 illustrates an edge plan view of the blade of FIG. 1;
FIG. 5 illustrates a detailed view showing the forward face of one tooth
and associated blade structure of the embodiment of FIG. 1; and
FIG. 6 illustrates a detailed view similar to that of FIG. 5 showing the
forward face of another tooth of the embodiment of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF
THE INVENTION
Referring to the figures, FIG. 1 shows a side view of the circular saw
blade 20 in a preferred embodiment having forty teeth. Other numbers of
teeth may be implemented. The preferred blade 20 preferably includes a
plate 22 having a 5/8-inch hole 24 defined in the center thereof for mounting
the saw blade 22 onto an arbor. Preferably, the metal plate 22 is generally
circular in shape and is machined from flat-surface tool steel, and the
thickness of the blade is approximately .063 inches. The arbor hole 24 is
preferably for use on standard arbors for hand-held circular saws.
In this embodiment, a plurality of raised tooth support members 26 are
distributed about the periphery of the plate 20. The support members 26
preferably include forward portions attaching cutting teeth 28 on a tooth
attachment portion 27 of each support member 26. Each tooth is preferably
made from carbide, or other suitable hard material. As shown more clearly in
FIGS. 2 and 3, each tooth includes a reverse-beveled outer cutting edge 31
positioned at the outermost circumferential extent of the blade 20, a contact
face 33, a bottom inward face 35 and a rear face 37 extending generally
parallel to the contact face 33. Each tooth 28 is preferably brazed to the saw
plate 22 at points of contact of the rear face 37 and the bottom face 35 on a
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stepped forward edge portion 29 of the tooth attachment portion 27 of each
support member 26.
The tooth support members 26 generally extend rearwardly from each
tooth 28 at a radial distance less than that traced by the cutting edge 31 of
the
5 tooth 28. The rearmost receding portion of the member 26 extends as a
finger 32 directed towards a succeeding tooth 28. The outermost edge 40 of
the support member 26 preferably traces a v-shaped arc or valley 42 at a
radial distance less than the outermost cutting edge of the tooth 28. The
receding configuration of the edge 40 allows only a minimal amount of the
blade plate 22 to contact the cut portion of the metal workpiece after the cut
is
made by each tooth 28. The finger portion 32 further acts as a guide to
prepare for the cutting entry of the succeeding tooth 28 rearwardly of the
finger portion 32.
The outermost edge 40 of the tooth support member 26 includes a
generally straighf inwardly sloping portion 44 and an outwardly sloping
portion
46. The sloping portions 44 and 46 on each member 26 preferably meet in a
peak 48. The two portions 44 and 46 preferably meet at angle Vii, which
preferably is 170 degrees. The peak 48 may be either a sharp edge or a
slightly rounded portion having a radius smaller than approximately 2 mm. In
the preferred embodiment, the inwardly sloping portion 44 has a length 11 and
the outwardly sloping portion 46 has a length 12. Preferably, the length 11,
which is approximately 0.22 inches in the preferred embodiment, is longer
than the length 12, which is preferably 0.15 inches in the preferred
embodiment. Although other lengths and angles may be utilized, however, it
has been found that these dimensions produce the most desirable results in
the preferred embodiment.
Preferably, the teeth 28 in the preferred embodiment are formed from a
carbide metal material and the hook or rake angle a, of the cutting face 33 is
in
a negative relationship with the radius of the blade 20. In particular, the
rake
angle d of the cutting face 33 is approximately 5 degrees relative to a radial
line 50 from the center of the blade 20. It has been found that for the
preferred embodiment and its application to cutting metal workpieces, the
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rake angle may effectively be varied between 0 and 7 degrees from the radial
line 50. It should be noted that other tooth materials, such as other hardened
metals, may also be utilized.
As indicated in FIG. 1, in the preferred embodiment, the inner
circumference is preferably approximately 6.54 inches in diameter as shown
by diameter line 66. The circumference of cut 68 is preferably approximately
7.25 inches in diameter as shown by diameter line 69, which extends to the
outermost cutting edges 31 of the teeth 28.
Referring back to FIGS. 2 and 3, open gullets 60 are defined inwardly
between successive tooth support members 26. In particular, the gullets 60
are defined by an interior edge 62. The edge 62 comprises the inwardly
extending portion 32a of the finger 32 of the rear portion of the support
member 26 and continues in a stocking-shaped formation to an inner
circumference 64 at the maximum depth of the gullet 60. The edge 62 then
75 proceeds outwardly fio curve toward the successive tooth area and tooth
attachment portion 27.
As noted above, the finger 32 projects rearwardly toward the
succeeding tooth support member 26. The gullet 60 is initially defined by a
throat area 70, which extends between a rear edge 32b of the finger 32 and
the cutting face 33 of the succeeding tooth on the succeeding tooth support
member 26. The throat area preferably defines a gap width.
The rear edge 32b of the finger 32 includes an interior edge 62. The
edge 62 further defines the lower portion of the gullet 60 by defining a first
arc
having radius R1 below the finger 32. A forward arc 62a having a
substantially semicircular trace and radius R2 comprises a forward portion of
the gullet 60. The arc 62a is preferably located substantially forwardly of
the
throat area 70. The forward arc 62a transitions to a lower arc 62b, which
preferably has a longer radius. Finally, the lower arc 62b transitions to a
radialiy outward direction via a transition arc 62c having a radius R4. This
arc
62c preferably joins the cutting face 33 and extends the final portion of the
gullet 60 towards the throat area 70. While other radii and arc profiles may
be
utilized and would of course change with the numbers of tooth supports, the
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size of the blade, etc., it has been found that the present values produce the
best results in the preferred embodiment.
In order to support the face 33 of the tooth 28 at the preferred angle
range of between 0 and 7 degrees to a radius line of the blade, the
attachment porkion 27 is preferably angled in a similar fashion relative to
the
radius of the blade 20. In the preferred embodiment of FIG. 3, the attachment
portion 27 is a notched or stepped portion extending inwardly into the tooth
support member 26 by .075 inches. Other attachment interface methods for
the teeth 28 may be utilized. For example, the stepped portion of the
attachment portion 27 need not be utilized at all, and the teeth 28 may be
brazed directly onto a non-stepped surface as shown in the second preferred
embodiment of FIG. 2.
FIG. 4 shows an edge view of the blade 20. In the preferred
embodiment as shown, the largest thickness of the blade 20 is at its
outermost point on the top of the cutting edge 31 of each tooth 28. This
distance, indicated as d1, is preferably .0795 inches thick. The blade 20 has
its smallest thickness at a uniform plate thickness of .063 inches, as
indicated
by distance d2.
FIGS. 5 and 6 show edge views of the tip portions of the blade 20 of
FIG. 1. As shown in the drawing, each tooth 28 has a sloped cutting edge
31 c and 31 d extending toward an edge of the blade 20 from the approximate
midpoint of the cross-section of the blade. The remaining portions 31 a and
31 b of the cutting edge 31 extend horizontally along the axis of rotation of
the
blade 20. In the preferred embodiment, the sloped cutting edges 31 c and 31 d
on alternating tooth support members 26 are angled 20 degrees downwardly
from the horizontal portions 31 a and 31 b, respectively. This is indicated
further as angle P in FIG. 4 above.
In use, the user will preferably attach the blade 20 to a hand-held or
otherwise portable electric saw by tightening the arbor hole 24 around a
shaft.
The user will then operate the saw so that the blade turns in the direction T
as
indicated in FIG. 1 to cut through a metal workpiece. Preferably, the
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maximum speed of the blade is 8300 RPM. The preferred speed of the blade
is approximately 4000 RPM.
Of course, it should be understood that a wide range of changes and
modifications could be made to the preferred embodiment described above.
Thus, it is intended that the foregoing detailed description be regarded as
illustrative rather than limiting and that it be understood that it is the
following
claims, including all equivalents, which are intended to define the scope of
this
invention.
