Cutting – Tool or tool with support – Toothed blade or tooth therefor
Utility Patent
1998-01-29
2001-01-02
Dexter, Clark F. (Department: 3724)
Cutting
Tool or tool with support
Toothed blade or tooth therefor
C083S855000
Utility Patent
active
06167792
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to saw blades, and deals more particularly with an improved tooth form for providing enhanced discharge of chips from the gullet area of each tooth and improved tooth strength.
BACKGROUND OF THE INVENTION
The terms used herein to describe the profile of a saw blade tooth are to be construed in accordance with the definitions found in International Standard Number ISO 4875/1-1978. In addition, the phrase “effective gullet radius” as used herein should be construed to mean the horizontal distance from the leftmost point of the gullet area, when the saw blade is viewed with the teeth pointing upward, to the point where the gullet depth reaches its maximum value.
In many instances, particularly in production settings, it is desirable to cut materials such as wood, plastic, and metal at the highest feed rates achievable. However, the rate at which a particular material can be presented to the saw blade is governed in large part by the stresses induced in the teeth of the blade, as well as by the rate at which particles or chips generated by the cutting action of the blade are discharged from the gullet area between consecutively spaced teeth.
In prior art tooth forms, the effective gullet radius is relatively small, typically less than approximately 25% of the tooth pitch. In addition, the gullet depth is typically between about 40% and about 50% of the tooth pitch with the length of the rake face accounting for approximately half of the height. As a result of this relatively small effective gullet radius and the relatively long rake face, shear stresses are concentrated at the base of each tooth on the saw blade which often are of sufficient magnitude to tear or shear a tooth from the saw blade during a cutting operation.
Another problem associated with known tooth forms having a profile similar to that described above is that during a cutting operation the long rake face combined with a small gullet radius inhibits the flow of chips out of the gullet area by acting as a barrier. This creates the potential for the chips generated during a cutting operation to become lodged in the gullet area, which in turn diminishes the cutting efficiency of the saw blade. To minimize this problem, the feed rate of the material through the saw, or the cutting speed of the blade, must be reduced resulting in a concomitant reduction in production.
Based on the foregoing, it is the general object of the present invention to provide a saw blade employing a tooth profile that overcomes the above-described drawbacks of prior art saw blade teeth.
It is a more specific object of the present invention to provide a saw tooth profile having enhanced chip discharge characteristics.
SUMMARY OF THE INVENTION
The present invention is directed to a saw blade having a cutting edge defined by a plurality of teeth disposed along the blade. Each of the teeth includes a tip, a rake face, a relief surface, and a curvilinear base surface, with the tip of one tooth and the tip of the next consecutive tooth defining a pitch distance therebetween. The tip of each tooth and the curvilinear base surface disposed between consecutively spaced teeth cooperate to define a maximum gullet depth. In addition, the rake face of each tooth and the curvilinear base surface cooperate to define the effective gullet radius.
To provide enhanced chip discharge capabilities over prior art saw blades, the saw tooth profile of the present invention includes an effective gullet radius that is greater than approximately 25% of the pitch distance, and 55% of the maximum gullet depth. This larger radius extends upwardly toward the tip of the tooth leaving only a small vertical rake face, thereby minimizing any barriers that would inhibit the flow of chips from between the teeth of the blade. To further improve the chip discharge characteristics, the tooth profile can also be formed such that the relationship between the pitch distance and the height of the tooth is optimized. Preferably, the gullet depth of the saw blade of the present invention is greater than approximately 40% of the pitch distance.
In addition to the foregoing, each saw tooth may include a primary relief surface defined by a first relief angle extending from the tip of the tooth in a direction opposite to the cutting direction of the saw blade, and a secondary relief surface extending from the first relief surface and defined by a second relief angle different from, and larger than the first relief angle. Preferably, the first relief angle is approximately 35° and the second relief angle is between about 45° and about 55°, with both the first and second relief angles being measured from a plane approximately perpendicular to the cutting direction of the blade. The presence of the secondary relief surface, coupled with the fact that the second relief angle is larger than the first relief angle, increases the gullet area between consecutive teeth over that which would be achieved if only the first relief angle were present. This increased gullet area reduces the likelihood of chips lodging between consecutively disposed teeth by providing a larger gullet area for chips to collect. The increased gullet area also allows the rate of chip ingress to, and egress from the gullet area to equilibrate during a cutting operation.
In addition to providing enhanced chip discharge capabilities over that of known saw blades, it is also desirable to maximize the stress bearing capabilities of the saw teeth. Accordingly, the teeth of the saw blade of the present invention employ a relatively short rake face, preferably less than 25% of the gullet depth, and a large radius tangent to the rake face which is defined by the curvilinear base surface. The combination of the short rake face and large radius increases the stress bearing characteristics of the saw teeth by providing greater tooth width at the base of each tooth where stresses are greatest, without increasing the gullet depth. This reduces the likelihood of the teeth shearing or tearing during a cutting operation.
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Hampton Stephen
Holston James
Korb William B.
Milton-Benoit John
American Saw & Mfg. Company
Cummings & Lockwood
Dexter Clark F.
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