WO2007120440A2

WO2007120440A2 - Circular saw blade and method and apparatus for manufacturing same

Info

Publication number: WO2007120440A2
Application number: PCT/US2007/007605
Authority: WO
Inventors: Hideki Akatsuka
Original assignee: Original Product Manufacturing Corporation
Priority date: 2006-03-29
Filing date: 2007-03-29
Publication date: 2007-10-25
Also published as: WO2007120440A3

Abstract

A circular saw blade is provided having a plurality of teeth with hollow point carbide tips, which can be attached to the teeth by brazing. A gullet provided between each tooth is U-shaped or C-shaped. In some embodiments, the gullet is a partial elliptical arc centered around its minor axis, with the major axis oriented perpendicular to a saw blade radius line. The carbide tips can be manufactured by applying the outer peripheral surface of a hollow grinding wheel shaped like a cup or truncated cone to each carbide tip. The grinding wheel can be inclined relative to the saw blade radius line.

Description

TITLE OF THE INVENTION

Circular Saw Blade And Method And Apparatus For Manufacturing Same

BACKGROUND OF THE DISCLOSURE

1. Field of the Invention

[0001] The present invention relates in general to saw blades, and specifically to a saw blade having characteristics which are intended to provide improved blade life and cutting capability. The invention further relates to a method and apparatus for manufacturing saw blades having such improved characteristics.

2. Background

[0002] Various types of circular saw blades are well-known and generally consist of a circular disk with cutting teeth formed into or attached to the periphery of the disk and a bore formed at the center of the disk to allow the mounting of the blade on the arbor of the circular saw. Early circular saw blades were unitary blades and were manufactured from a single piece of material, generally steel, wherein the cutting teeth were formed into the steel disk and were sharpened. Today, circular saw blades are often composite blades manufactured from several materials, such as a steel disk with a plurality of carbide cutting teeth attached thereto. Generally the carbide teeth are bonded to the steel disk by means of soldering or brazing. [0003] In operation, circular saw blades are used to cut materials such as wood. The blade is typically rotated at high speeds, such that the teeth engage, cut and displace the wood. The displaced particles of wood or other material may pile up in the gullet formed in front of the advancing tooth until the tooth exits the work piece and the particles are thrown from the gullet. Continued rotation of the blade directs the tooth around to again engage the wood; the tooth passes back through the path cut in the work piece and around further to where it engages the work piece again to repeat the process until the cut has been completed.

[0004] It was recognized by those skilled in the art of circular saw blades that the area of contact between the blade and the work piece should be kept to a minimum. This helps to reduce the amount of friction between the blade and the work piece. This minimized contact is realized through clearance gaps and clearance angles. Accordingly, some prior art circular saw blades have been designed with these objectives in mind. [0005] Some prior art circular saw blades include teeth that are bent outwardly from the disk, in the case of a unitary circular saw blade. Alternatively, in the case of composite circular saw blades, the teeth attached to the body may have a width greater than the body. Another common feature is an alternate bevel configuration, in which the top surface of each tooth is beveled to one side, with each tooth being beveled in the opposite direction from the adjacent teeth. One such alternate bevel configuration, having flat faces, is illustrated in Figures 9A (plan view), 9B (cross-section of one tip 900) and 9C (cross-section of adjacent tip 910). Another such alternate bevel configuration, having angled faces, is illustrated in Figures 1OA (plan view), 1OB (cross-section of one tip 1000) and 1OC (cross-section of adjacent tip 1010). Such alternate bevel configurations are commonly used to cross-cut wood. A tooth that does not have a bevel to its top surface has a flat top surface and is typically called a flat top tooth. Flat top teeth are popular with blades used in ripping wood. Some circular saw . blades have sharp points at the ends of the cutting edge and under use, these points undergo a high degree of wear and often suffer breakage.

SUMMARY OF THE INVENTION

[0006] In accordance with one aspect of the present invention, a blade for a circular saw includes a thin steel disk, multiple teeth formed at the periphery of the steel disk, and a gullet between each of the teeth which is, at least in part, U-shaped. In some embodiments, the gullet can be shaped as an elliptical arc, with the angle length of the arc exceeding 180 degrees, and the arc being centered around the minor axis of the ellipse. [0007] Each of the multiple teeth may include a hollow point carbide tip, and a shoulder. Each shoulder has a leading edge and a trailing edge, both of which can be substantially shaped as concave elliptical arcs. The outer edge of each shoulder can be approximately the same width as the widest portion of each gullet. In some embodiments, the hollow point carbide tips are oriented with a positive tip angle, and formed from c3 carbide steel. The tips can be attached to the shoulder via brazing. [0008] In accordance with another aspect of the invention, a method for manufacturing a circular saw blade having a plurality of carbide tipped teeth is provided. A grinding wheel is used which has a hollow base portion with a circular cross-section. The outer periphery of the grinding wheel is applied against the face of a carbide tip by interposing an edge of the wheel into a gullet between the carbide tip, and the trailing edge of an adjacent tooth. In so doing, the side of the grinding wheel opposite that applied to the carbide tip is typically positioned outside the gullet, and preferably, outside the periphery of the circular saw blade. The grinding wheel then acts to grind the carbide tip, such that is obtains a hollow point configuration.

[0009] In some embodiments of the invention, the base portion of the grinding wheel may be shaped to form a hollow cone. The outer radius of the grinding wheel may be greater than 10 mm, such as within the range of about 15 mm to about 20 mm radius, and preferably, equal to about 20 mm radius. A diamond coating can be provided on at least a portion of the outside peripheral surface of the grinding wheel, such as the portion that is applied to the carbide tips. The grinding wheel can be inclined relative to a radius line of the circular saw blade. Preferably, the grinding wheel is inclined at an angle of about 10 degrees.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is an elevation of a saw blade, in accordance with a first embodiment of the invention.

[0011] Figure 2 is a perspective view of the tip of a saw blade tooth.

[0012] Figure 3 is a further perspective view of the tip of a saw blade tooth.

[0013] Figure 4 is a perspective view of the tip of a saw blade tooth, as well a U- or C-shaped gullet.

[0014] Figure 5 is an elevation of a saw blade tooth with adjacent gullets.

[0015] Figure 6 is an elevation of a saw blade having heat vents, according to a further embodiment of the invention.

[0016] Figure 7 is an elevation of a prior art tooth configuration, superimposed over a tooth configuration of a preferred embodiment of the present invention.

[0017] Figure 8 comprises drawings of a prior art flat tooth alternate bevel configuration.

[0018] Figure 9 comprises drawings of a prior art angled tooth alternate bevel configuration.

[0019] Figure 10 comprises drawings of a hollow point tooth configuration.

[0020] Figure 11 is a cross-sectional view of a prior art grinding arrangement for forming a flat tooth face.

[0021] Figure 12 is a perspective view of a prior art grinding wheel.

[0022] Figure 13 is a cross-sectional view of a prior art grinding operation for forming a curved tooth face.

[0023] Figure 14 is a perspective view of a prior art grinding wheel.

[0024] Figure 15 is a cross-sectional view of a blade tip grinding arrangement, in accordance with one embodiment of the present invention.

[0025] Figure 16 is a drawing of a grinding wheel, for use in association with one aspect of the present invention. [0026] Figure 17 is a grinding arrangement in accordance with one aspect of the present invention, illustrating engaged and disengaged grinding wheel positions relative to the saw blade.

[0027] Figure 18 is a perspective view of grinding wheels, in accordance with one aspect of the invention.

[0028] Figure 19 is another perspective view of a grinding wheel, in accordance with one aspect of the invention.

[0029] Figure 20 is another perspective view of a grinding wheel, in accordance with one aspect of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0030] While this invention is susceptible of embodiment in many different forms, there are shown in the drawings and will herein be described in detail, certain specific embodiments with the understanding that the present disclosure should be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiments so illustrated.

[0031] Figure 1 is an elevation of a saw blade, according to one embodiment of the invention. In the illustrated embodiment, saw blade 100 is approximately 7-1/4 inches in diameter, having sixteen teeth and being comprised primarily of a steel disk. However, it is understood that the present invention is susceptible for use with blades having differing dimensions and configurations.

[0032] Saw blade 100 includes sixteen saw blade tips 110. Figure 2 illustrates a perspective view of tip 110. Tip 110 is a hollow point design, incoφorating two sharp points 120 and 122, which, in the direction of rotation of the blade, extend "ahead" of curved edge 124, so that the face of tip 110 that meets the material being cut is concave. Points 120 and 122 each score the material being cut, prior to curved edge 124 operating to completely cut out the material on which the blade is operating. The hollow point tip design enables effective operation of the blade with wood in both cross-cut and ripping applications.

[0033] The curved surface of the tip is preferably formed by grinding. Commonly, the face of prior art circular saw blade tooth tips is not ground, but rather is a molded surface from the carbide tip mold that was used to shape the tooth tip. However, by grinding and smoothing the face of the tip, the face is smoother than typical molded tips, and the edges are sharper. These characteristics help to reduce friction, and in turn, heat, to achieve improved cutting performance, and enhanced durability of the blade. [0034] Tip 110 is comprised of c3 carbide steel. Conventionally, softer carbide materials, such as those designated cl, are preferred for applications such as cutting through carpenter wood, where an aggressive, positive tip angle is preferred. Tip angle is the angle between the face of a blade tip and a radius line. Positive tip angle typically permits faster cutting. However, in the event that a blade encounters nails, rocks or other hard objects during cutting, the use of a positive tip angle increases the impact and trauma experienced by the blade tip. In such applications, a softer carbide is often utilized to permit the use of a positive tip angle, while also causing the tip to better absorb impact incurred when hitting hard objects, rather than bouncing off the encountered object. Accordingly, the tips are less likely to chip or break away. Harder carbide compositions, such as c4, c5 or c6, are often used with different tooth designs, such as those having zero or even negative tip angles, whereby the tip experiences reduced levels of force. [0035] The hardness of the c3 carbide of which tip 110 is comprised improves the ability of the blade to retain its hollow point grind during use, while its relative malleability compared to harder types of carbide provides some reduced risk of breakage. Each tip 110 is attached to shoulder 140. The design of shoulder 140, including its width, provides additional force and stability behind tip 110, which is believed to reduce the likelihood of tip breakage and to increase the ability of the blade to power through foreign objects that may be encountered. Thus, it is believed that the design of shoulder 140 permits the use of carbide tips having increased hardness in hollow point and/or positive tip angle applications.

[0036] In the illustrated embodiment, tip 110 is attached to shoulder structure 140 of blade 100 via brazing 130. In addition to physically securing tip 110 to the body of the blade, brazing 130 provides for the absorption of shock, such as that incurred during operation when a carbide tip hits particularly hard material or objects, such as the nails that may be encountered while cutting wood.

[0037] Figure 3 is a perspective view drawing of another embodiment of a hollow point blade tip that may be used in connection with the present invention. Tip 210 includes scoring points 220 and 222, as well as cutting edge 224. [0038] Blade 100 further includes gullets 150 having a configuration that includes a U-shaped bottom portion. Including the carbide tip and back edge of the adjacent tooth, gullets 150 as a whole also form a C-shape. Moreover, in the illustrated embodiment, gullets 150 are also substantially elliptical in shape, defining an arc that is generally a partial ellipse with the major axis of the partial ellipse being oriented generally perpendicular to a radius line. In some preferred embodiments, such as that of Figure 1, the gullet defines an elliptical arc having an angle length greater than 180 degrees, with the elliptical arc being centered around the minor axis of the ellipse. As the blade teeth chip away at the material being cut during a cutting operation, the resulting dust and chips are believed to initially slide down into gullets 150. As the blade continues to rotate and pass out of the cut, gullet 150 operates to propel dust away from the blade. Features including the shape and size of gullet 150 are believed to provide improved effectiveness in collecting and extracting dust from a cut, as compared to other prior art gullet designs. This improved dust extraction enables faster cutting. The increased ability of gullet 150 to remove dust from a cut also reduces mechanical wear on the blade tips. The design of gullet 150 further improves blade life by providing for cooler operation and reduced blade temperatures during extended cutting.

[0039] Blade 100 also includes four heat vents 160. Each heat vent is formed as an aperture in blade 100 which provides for increased ventilation through and around the blade during operation, thereby cooling the blade and possibly mitigating effects of temperature-relating warping of the blade. Blade 100 also includes, at positions 90° apart, slots 170 (see, e.g., Fig. 1), which are provided for purposes of accommodating frictional-heating-induced expansion of the blade.

[0040] Figure 4 is another perspective view of blade 100, illustrating tip 110 and its relation to gullet 150. Figure 5 depicts an elevation of tip 110, shoulder 140 and gullet 150. Figure 6 depicts a perspective view of blade 100, particularly illustrating the configuration of tip 110, shoulder 140, gullet 150 and heat vent 160. Preferably, each gullet is formed similarly. However, it is understood that, for cosmetic or other reasons, a blade can be formed in which some of the gullets are shaped differently from others, without necessarily departing from the scope of the invention.

[0041] Figure 7 illustrates a comparison between a prior art circular saw blade 300, one tooth of which is shown in broken lines, and the saw blade 100 of a preferred embodiment of the present invention, one tooth of which is shown in solid lines. The tooth design of prior art saw blade 300 is similar to that which has been sold in North America under the trademarks MARATHON (from Irwin Indus. Tools Co.) and ORIGINAL (from Original Product Manufacturing Corp.), and which has been manufactured by Iwata Saw Manufacturing Company Limited, of Fukude, Shizuoka Prefecture, Japan. From the drawing, it can be seen that as compared to the prior art blade 300, the tooth design of the present invention has a greater amount of blade plate (steel) directly behind the carbide tip, which supports the tip and is believed to increase the tooth's overall durability and resistance to material loss, as compared to prior art blade 300.

[0042] The features described above and illustrated herein can be beneficially employed independently. However, when used in various combinations, including the particular combination illustrated herein, the blade is capable of surprising improvements in cutting ability and useful life. In particular, the gullet design described herein provides surprising benefits, particularly when used in combination with the above-described tooth configuration.

[0043] Another aspect of the present invention provides for the manufacture of the saw blade tip described herein. In particular, it provides for the manufacture of a ground, hollow point blade tip having a tip face with a large radius of curvature. It is understood that a saw blade can be "manufactured" in accordance with the present invention by either employing the process described and/or claimed below on a newly-created saw blade, or alternatively, by employing the process on a blade which has previously been used or provided, thereby operating to create a newly-sharpened saw blade. [0044] To the extent prior art saw blade tooth tips have been ground, one such prior art grinding technique is illustrated in Figure 12. For each tooth, grinding wheel 1200 is lowered from position 1200A to position 1200B, whereby the tooth contacts circular grinding surface 1201. Grinding wheel 1200 can then be raised back to position 1200A, while the saw blade is rotated to position the next tooth under grinding wheel 1200. Figure 12 depicts an alternative photographic view of prior art grinding wheel 1200. Wheel 1200 rotates vertically about a horizontal axis, as illustrated in Figure 11. The rotation of grinding wheel 1200 causes grinding surface 1201 to grind each saw blade tip. However, the flat circular grinding surface 1201 is only able to grind a flat face on a saw blade tip. Thus, the grinding arrangement of Figure 12 does not facilitate the manufacture of the particular hollow point tip that is preferred in connection with the present invention. [0045] Another grinding technique known in the prior art is illustrated in Figure 13. Cylindrical or conical grinding wheel 1300 is lowered into the gullets and contacted with the face of each tooth. Figure 14 is an alternative, photographic view of prior art grinding wheel 1300. The shape of grinding wheel 1300 enables the preparation of a ground, curved face on each blade tooth. Therefore, a ground, hollow point tip can be produced. However, the curvature that can be effected on the face of each tooth is typically limited by the radius of a grinding wheel that fits into the gullet. Thus, in many applications, the grinding technique illustrated in Figure 13 is capable of creating a maximum radius of curvature of approximately 4R. While the comparatively low radius of curvature formed using the grinding arrangement of Figure 13 can provide fast cutting speed during its initial period of use, it also commonly results in limited blade lifetime and more rapid dulling. [0046] Figure 15 illustrates a different grinding arrangement that can be beneficially employed in manufacturing a saw blade in accordance with other aspects of the present invention. In contrast to the prior art grinding techniques illustrated in Figures 11 and 13, the grinding arrangement of Figure 15 can be employed to quickly and inexpensively generate ground, hollow point tips having sharp edges that enable both quick cutting speed as well as improved blade life.

[0047] The arrangement of Figure 15 permits grinding of hollow point tips having faces with a radius of curvature greater than that created by the grinding arrangement of Figure 13. Typical prior art hollow point tips manufactured using the technique of Figure 13 have a radius of curvature of approximately 2.5 mm radius to 4 mm radius, because the size of the grinding bit is limited by the space available to insert the grinding bit entirely into a blade gullet. The grinding arrangement described herein permits an arbitrarily greater radius of curvature. For example, a hollow point ground tooth tip can be created having a curvature exceeding 10 mm radius, such as within the range of about 15 mm radius to about 20 mm radius or greater. A preferred saw blade embodiment features a ground hollow point tooth having a curved face with nominal radius of curvature of 20mm, with a tolerance range of +0/-1.5 mm, i.e., a radius of curvature in the range of about 18.5 mm to about 20 mm. Such a radius of curvature provides the benefits of a hollow point grind, including cleaner and smoother cutting, while also extending the life of the sub-micron carbide tooth edge, allowing for the overall performance of the blade to remain more consistent throughout the life of the tip. Moreover, this curvature can be achieved through the use of a diamond grinding wheel, which enhances the sharpness of the tip. [0048] While exemplary radii of curvature for the face of hollow point blade tips are described above, it is understood that the present grinding arrangement enables the manufacture of saw blade tips having a wide range of curvatures. It is further understood that different blade tip curvatures may be desirable for specific or particular applications. To the extent such different curvatures can be achieved using the grinding arrangement described herein, they are understood to be within the scope of at least certain aspects of the present invention.

[0049] In practice, grinding wheel 1400 is lowered towards blade 1410 so that the outside surface 1401 of the wheel contacts blade tip 1411. In the embodiment of Figure 15, grinding wheel 1400 is a cup-shaped grinding wheel, tapered near the top, with diamond material deposited on the its outside surface 1401 to form the working surface of the grinding wheel. Grinding wheel 1400 is preferably inclined relative to blade 1410. For example, central axis 1402 of wheel 1400 is preferably inclined relative to radius line 1412 of wheel 1410, at an angle of about 10 degrees. The inclined orientation of wheel 1400 facilitates the use of a wheel having arbitrary diameter, by providing greater clearance to avoid interference of wheel 1400 with portions of blade 1410 other than the tip being ground. Figure 16 illustrates plan and cross-sectional views of grinding wheel 1400. [0050] The cup, or truncated cone, shape of grinding wheel 1400 can be advantageously employed to generate a positive tip angle, despite grinding wheel 1400 being oriented at an inclined angle. However, it is understood that other grinding wheel shapes can be employed in association with the present invention, based on various factors including, without limitation, the desired tip angle and angle of grinding wheel inclination. For example, other variations of grinding wheels having a hollow base portion with circular cross section can be used.

[0051] Figure 17 illustrates alternate positions occupied by grinding wheel 1400 during a grinding operation. Wheel 1400 initially occupies disengaged position 1400A, while blade 1410 is rotated into position. Wheel 1400 is then moved towards blade 1410 into engaged position 1400B, at which point wheel 1400 is contacted with a blade tip to be ground. Once a particular tip has been ground, wheel 1400 returns to disengaged position 1400A, while blade 1410 is rotated until another tip is in position for grinding. [0052] The grinding arrangement illustrated in Figures 15-17 can also be beneficial in that it enables the creation of a precision-ground, hollow point tip using a method of production that is relatively inexpensive and quick — particularly as compared to potential alternative grinding techniques that might involve multiple grinding tips, multiple grinding angles or other coordination of grinding bit movement in a tip machining process. [0053] Figures 18, 19 and 20 depict perspective photographic views of various grinding wheels that may be used to grind blade tips, in accordance with an aspect of the invention. Typical prior art grinding wheels have diamond material deposited onto the top surface of the grinding wheel, such as surface 1900 in Figure 20. However, in accordance with one embodiment of a present invention, diamond grinding material is deposited onto outer side surface 1910 of the grinding wheel.

[0054] The foregoing description and drawings merely explain and illustrate the invention, and the invention is not so limited as those skilled in the art who have the disclosure before them will be able to make modifications and variations therein without departing from the scope of the invention.

Claims

CLAIMS:

1. A blade for a circular saw comprising: a thin steel disk; a plurality of teeth formed at the periphery of the steel disk; a gullet between each of the plurality of teeth having a portion which is U-shaped.

2. The blade of claim 1, in which the perimeter of the gullet is substantially shaped as an elliptical arc.

3. The blade of claim 2, in which: the angle length of the elliptical arc is greater than 180 degrees; and the elliptical arc is centered around the minor axis of the ellipse.

4. The blade of claim 1, in which each of the plurality of teeth is comprised of a hollow point carbide tip and a shoulder portion.

5. The blade of claim 4, in which the shoulder portion of each of the plurality of teeth is comprised of a leading edge and a trailing edge, in which both the leading and trailing edges are substantially shaped as concave elliptical arcs.

6. The blade of claim 4, in which the outer edge of the shoulder portion is approximately the same length as the widest part of the gullet.

7. The blade of claim 4, in which each hollow point carbide tip is: comprised of c3 carbide steel; and oriented with a positive tip angle.

8. The blade of claim 7, in which each hollow point carbide tip is attached to a shoulder portion of one of the plurality of teeth via brazing.

9. A method for manufacturing a circular saw blade comprising: providing a circular saw blade having a plurality of teeth, each tooth having a carbide tip; providing a grinding wheel having a hollow base portion with a circular cross-section; engaging the grinding wheel against a first carbide tip by interposing a first edge of the grinding wheel into a gullet between the first carbide tip and an adjacent tooth, such that a second edge of the grinding wheel opposite the first edge is positioned outside of the gullet; whereby the carbide tip is ground into a hollow point configuration.

10. The method of claim 9, in which the base portion of the grinding wheel forms a hollow truncated cone.

11. The method of claim 10, in which the grinding wheel has a base with an outer radius greater than 10 mm.

12. The method of claim 10, in which the grinding wheel has a base with an outer radius between about 15 mm and about 20 mm.

13. The method of claim 10, in which the grinding wheel has a base with a nominal outer radius of about 20 mm.

14. The method of claim 9, in which the step of providing a hollow grinding wheel is further comprised of the step of providing a grinding wheel having a diamond coating on at least a portion of the outside peripheral surface of the grinding wheel.

15. The method of claim 9, in which the step of providing a hollow grinding wheel having a base portion with a circular cross-section is further comprised of the step of providing a hollowing grinding wheel oriented at an angle that is inclined relative to a radius line of the circular saw blade.

16. The method of claim 15, in which the grinding wheel is inclined by about 10 degrees.