A typical saw blade has a blade edge made up of a sequence of sharp points which are referred to as teeth. These teeth cut a trench or kerf that allows the free entry of the saw blade to cut an article. The cutting action of the saw blade involves urging the article to be cut transversely into the rotating or longitudinally moving saw blade or transversely urging the moving saw blade into the article. As the saw blade and article are urged together, the teeth of the saw blade dig in and remove particles from the article in a rapidly repetitive action. By this repetitive action, the kerf is increased in depth until the article is cut. This cutting action which remove a portion of the article is substantially different than "slicing" where the fibers of the article are simply moved apart.
FIG. 1 illustrates a portion of a conventional saw blade 10 showing the profile of a conventional tooth 12. Tooth 12 includes a positive hook angle 14, a tooth angle 16 and a clearance angle 18. Other nomenclature used in the description of saw teeth include the tooth pitch or spacing 20, the tooth gullet 22 and the depth of the gullet 24. The direction of cut for saw blade 10 is shown by arrow 26. During the cutting of an article by a saw blade, there must be sufficient clearance between the saw blade and the sawn surfaces or sidewalls of the kerf being created in order to eliminate binding or friction between the saw blade and the cut article. This clearance can be achieved by either taper grinding or offsetting the saw tooth. Taper grinding, shown in FIG. 2A, is a process that removes the material on the sides of the saw blade to make the cutting tip the widest part on the blade. Offsetting, shown in FIG. 2B, is a process that bends or places a "set" in the saw tooth to make the cutting tip the widest part on the blade. Either method, taper grinding or offsetting, provides the necessary clearance between the saw blade and the sidewalls of the kerf being made in the article to eliminate any binding of the saw blade in the kerf.
Various improvements to the conventional tooth profile shown in FIG. 1 have been proffered. FIGS. 3A and 3B illustrate a saw blade 30 cutting into an article 31. Saw blade 30 has a plurality of teeth 32 having a positive hook angle 33 which incorporate "fleam grinding" or alternate beveling of each gullet 34 between the plurality of teeth 32. In particular, the plurality of teeth 32 have their front faces 36 and their rear faces 38 oppositely beveled. This is accomplished by having the bevel on the front gullet of each tooth 32 facing in the opposite direction to the bevel on the rear gullet of each tooth 32 in alternate order throughout the saw blade. This beveled tooth profile generates a tooth point of substantially triangular prismatic shape which better enables the teeth to effect the removal of portions of the article. The triangular prismatic tooth profile is manufactured by grinding each tooth gullet 34 in a direction which is opposite to that of an adjacent tooth gullet 34. Grinding each gullet 34 simultaneously grinds a front face 36 of one tooth and a rear face 38 of the tooth adjacent to it. This grinding or beveling of each gullet 34 is normally done at a compound angle, which causes the bottom of each gullet 34 between the teeth 32 to slope in an upwards and a backwards direction due to the beveled front face of each tooth meeting the beveled rear face of the tooth in front of it in an oblique line. This beveling of the gullets is designed to aid in the removal of cut material from the gullets. However, the conventional fleam ground blade still packs the gullets with chips and dust The compound beveling of the gullets creates a dead space or neutral area in the bottom of the gullet due to one face of the gullet directing chips to one side of the blade with the opposite face of the gullet directing chips to the opposite side of the blade. This dead space or neutral area causes the undesirable accumulation of chips within the base of the gullet. This problem is especially acute when the thickness of the material being cut is large or exceeds the stroke of the blade, which is typically between one-half of an inch and one inch. This conventional compound beveling creates a tooth cutting edge 39 having a conventional negative rake angle 40 (FIG. 3B). A negative rake angle provides an aggressive cutting tooth and causes the highest (relative to the base of the gullet), leading tip of the cutting face on the conventional fleam-ground tooth-form to always contact the workpliece first during the forward stroke of the cutting blade as shown by arrow 41 with the remainder of the cutting face being angled downwardly and rearwardly away from the surface being cut. This can be seen in FIGS. 3A and 3B where the higher, leading tip 42 contacts the workpiece first and the lower, trailing tip 41 will contact the workpiece last during the cutting stroke. A negative rake angle is present when measured from the lowest point to the highest point of the cutting edge, the cutting edge is toward the cut with respect to horizontal as seen in FIG. 3B.
Various other tooth profiles for saw blades have been proposed. However, most of these earlier known designs have not experienced widespread commercial use as they typically do not lend themselves to automated manufacturing processes and therefore are too costly to produce. Consequently, there is a need to continue with the development of saw tooth profiles and there is also a need for improving the known manufacturing processes to mass-produce improved saw tooth profiles in a cost-effective manner.
USPTO Backgrounds
USPTO Backgrounds