Patent Abstract:
A saw blade having a concavely curved sawing edge and two oppositely-directed sets of teeth. During reciprocation of the blade, a first set of the teeth may cut during a first stroke direction and the second set of teeth may cut during a second stroke direction.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of the filing date of U.S. Provisional Patent Application Ser. No. 60/891,610, filed Feb. 26, 2007, the teachings of which are hereby incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure relates to saw blades, and, in particular, to a dual-cut saw blade configured for cutting on each stroke of the blade. 
       BACKGROUND 
       [0003]    Reciprocating saws, such as jig saws, generally cause longitudinal reciprocation of a blade in a continuous cycle of first strokes that are directed away from the saw and second strokes and toward the saw. A conventional blade has a sawing edge for cutting material to be sawn during a “cutting” one of the first or second strokes, and for clearing away residue, such as saw dust or shavings, from the sawing edge during the “clearing” other one of the strokes. When the blade extends completely through the material being sawn during at least a portion of the reciprocation, such a cut is known as a through-cut. When blade projects into the material but not fully through it, such a cut is known as a plunge-cut. The slot or groove created in the sawn material as the blade passes through and makes its cut is known as a kerf. The cut edge of the sawn material left after the cut is complete is known as the sawn edge. 
         [0004]    It is sometimes desirable that the blade leave a kerf or sawn edge that is as smooth, straight, clean, and free of sawing artifacts, chips, burrs and other blade vestiges as possible. It is a common though undesirable result of the differing effects caused by the cutting and clearing strokes that known blades leave different kerf or sawn edge quality during cutting than during clearing. In some materials, the kerf or sawn edge quality may be significantly worse on one side of the material than on the other. Generally, when a cutting tooth exits the material in its cutting direction while cutting, it may leave a less desirable kerf or sawn edge on that side of the material. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    Features and advantages of embodiments of the disclosed subject matter will become apparent as the following Detailed Description proceeds, and upon reference to the Drawings, where like numerals depict like parts, and in which: 
           [0006]      FIG. 1  is a partial close-up view of the cutting teeth of a prior art saw blade; 
           [0007]      FIG. 2  is a profile view of a saw blade according to one exemplary embodiment consistent with the present disclosure; 
           [0008]      FIG. 3  is a partial close-up view of the longitudinally central portion of the sawing edge of the blade of  FIG. 2 ; 
           [0009]      FIG. 4  is a perspective view of the blade of  FIG. 2 ; and 
           [0010]      FIG. 5  is a partial sectional view of a jigsaw having a blade as shown in  FIG. 2 . 
       
    
    
       [0011]    Although the following Detailed Description will proceed with reference being made to illustrative embodiments, many alternatives, modifications, and variations thereof will be apparent to those skilled in the art. Accordingly, it is intended that the claimed subject matter be viewed broadly. 
       DETAILED DESCRIPTION 
       [0012]    Turning to  FIG. 1 , definitions of typical saw blade terminology and features are discussed with reference to a blade of the prior art shown in  FIG. 1 . One exemplary embodiment of a dual-cut saw blade consistent with the present disclosure is then discussed with reference to  FIGS. 2 through 5 . Although the description provided herein is with reference to various exemplary embodiments, it is to be understood that the embodiments described herein are presented by way of illustration, not of limitation. Also, a saw blade consistent with the present disclosure may be incorporated into a variety of systems without departing from the spirit and scope of the invention. 
         [0013]    Saw blades such as prior art blade  100  may share certain common features. Blade shank  102  has spaced longitudinally there-along a plurality of cutting teeth  106 . Each cutting tooth is defined by its rake edge  108  and relief edge  112 , which meet at the tooth&#39;s cutting tip  114 . The distance  105  between successive cutting tips is the tooth spacing. The distance  107  from a cutting tip to the bottom of gullet is the gullet depth or tooth height. 
         [0014]    A sawing edge  104  is defined by the line containing the plurality of cutting tips  114  and may be generally straight and parallel with the cutting and clearing motions of the blade, represented by arrows  124  and  126  respectively. A rake angle  118  is the angle between the rake edge  108  and a line projecting normally outward from sawing edge  104 . A relief angle  122  is the angle between the relief edge  112  and the line defining sawing edge  104 . 
         [0015]    The direction from the relief edge toward the rake edge of a cutting tooth is known as the cutting direction, shown by arrow  124 . Travel of the blade in the cutting direction is termed the cutting stroke. Sawing occurs when blade  100  moves against material in the cutting direction during a cutting stroke. 
         [0016]    The direction from the rake edge towards the relief edge of a cutting tooth is known as the clearing direction, shown by arrow  126 . Travel of the blade in the clearing direction is termed the clearing stroke. Debris and cutting residue is removed from the blade and the cutting tips are cleared when blade  100  moves against material in the clearing direction during a clearing stroke. 
         [0017]    When cutting blades such as blade  100  are adapted for use in jigsaws or other such reciprocating saws, they may include a proximal end and an elongate shank portion. The proximal end may be shaped and configured for engagement with and attachment to the saw. Activation of the saw may cause longitudinal reciprocation of the blade in a continuous cycle of cutting strokes directed away from or toward the saw and clearing strokes directed opposite the cutting strokes. 
         [0018]    The shank portion of such a reciprocating saw blade may extend from the proximal end toward a terminal distal end and into or through a material to be sawn. The shank portion has at least one sawing edge, such as sawing edge  104 . The sawing edge may engage and cut the material to be sawn during the cutting strokes and clear away residue from the sawing edge, such as saw dust or shavings, during the clearing strokes. 
         [0019]    The cutting and clearing strokes may have different effects on the quality of the kerf and/or sawn edge. For example, undesirable burring and chipping may result from the cutting tips as the cutting teeth exit from the material on the rake side of the material in the cutting stroke. In the clearing stroke, undesirable galling may result from pressure applied by the cutting tips as the cutting teeth exit from the material on the relief side of the material. 
         [0020]    Turning now to  FIGS. 2  though  4 , there is shown one exemplary embodiment of a blade  200  consistent with the present disclosure.  FIG. 5  illustrates the blade  200  coupled to a jigsaw. In the illustrated exemplary embodiment, the proximal end  202  of blade  200  is shaped and configured for fixed engagement with a jigsaw, such as jigsaw  300  of  FIG. 5 . The particular shape and configuration of the proximal end may be varied according to any known or later developed shape and configuration to allow the blade to be fixedly engaged with the saw. 
         [0021]    Shank  204  extends from proximal end  202  away from the saw toward distal end  206 , and includes sawing edge  208 . The sawing edge  208  is defined by the concave line containing cutting tips  210  of a first plurality  212 A of cutting teeth  214 A and a second plurality  212 B of cutting teeth  214 B. In the illustrated exemplary embodiment, the first plurality  212 A may be equal or approximately equal to the second plurality. 
         [0022]    Henceforth in this disclosure, when elements or features of the first plurality  212 A are discussed collectively, they will be referred to with an item number ending in a letter “A”, such as “cutting teeth  214 A”, and when elements or features of the second plurality  212 B are discussed collectively, they will be referred to with an item number ending in a letter “B”. When elements or features are discussed individually in a context independent of its plurality, they will be referred to only by their base item number, such as “cutting tooth  214 ”, which tooth could be either one of teeth  214 A or  214 B. 
         [0023]    In the illustrated embodiment, a transition  218  is provided between the first  214 A and second  214 B pluralities of cutting teeth. At least a portion of the transition may be disposed below the sawing edge  208 . In the illustrated embodiment, the transition is defined by a straight line extending between the teeth immediately adjacent opposite sides of the midline and is symmetrically centered on the sawing edge. It is to be understood, however, that the transition  218  may be offset from the longitudinal midline. Also, the transition may take other regular or irregular geometric configurations. For example, the transition may be concave or may include one or more teeth, e.g. a single tooth disposed on the midline  250 . Transition  218  may be beneficial in providing a trap to collect cutting debris and residue during sawing, and to thereby reduce galling, cutting tip dulling, and other undesirable effects caused if such debris and residue were allowed to otherwise remain on and between the cutting teeth or to be forced between the shank of the blade and the inside edges of the kerf. 
         [0024]    Each cutting tooth  214  has a cutting direction from its relief edge  230  towards its rake edge  232 . Sawing by any particular tooth occurs when that tooth moves against material in its cutting direction. Each cutting tooth  214  also has a clearing direction from its rake edge  232  towards its relief edge  230 . Debris and cutting residue is removed from any particular tooth and that tooth&#39;s cutting tip is cleared when that tooth moves against the material in its clearing direction. 
         [0025]    The reciprocating motion of blade  200  may be aligned longitudinally with shank  204  and generally normally to the top surface of the material to be sawn. The reciprocating motion may be parallel with arrows  224 A and  224 B. Arrow  224 A represents a portion of the blade&#39;s cycling stroke that is directed away from the saw, and arrow  224 B represents a portion of the cycling stroke directed toward the saw. 
         [0026]    The cutting direction of cutting teeth  214 A is in the direction of arrow  224 A, and the clearing direction of this plurality of teeth is in the direction of arrow  224 B. Teeth  214 A therefore saw material during that portion of the blade&#39;s reciprocation in the direction of arrow  224 A. Conversely, the cutting direction of cutting teeth  214 B is in the direction of arrow  224 B and teeth  214 B therefore saw material during that portion of the blade&#39;s reciprocation in the direction of arrow  224 B. 
         [0027]    In one embodiment, the blade may have symmetrical tooth configurations on opposite sides of the longitudinal midline  250 . In such an embodiment, the blade  200  may be oriented to act against the material, such as material  400  of  FIG. 5  during stroke portions  224 A and  224 B with generally equal but opposite effects against the material during either stroke portion  224 A or  224 B. It is to be understood, however, that the teeth may be asymmetrically configured on opposite sides of the longitudinal midline and/or the transition may be offset from the longitudinal midline. Also, the effect of the blade on the material may be asymmetrical, e.g. through selective orientation of the angle of the blade to the material during sawing. 
         [0028]    As shown, the sawing edge  208  of the blade  200  is concave relative to a straight line  234  projecting between cutting tip  240  of proximal tooth  252  and cutting tip  242  of distal tooth  254 . Proximal tooth  252  is the tooth of the first plurality  212 A that is closest to proximal end  202  and distal tooth  254  is the tooth of the second plurality  212 B that is closest to distal end  206 . In the illustrated exemplary embodiment, the rear edge  236  of the blade is straight and lies parallel with straight line  234  and with stroke portions  224 A and  224 B. In such an embodiment, the concave cutting edge may curve inwardly toward the rear edge  236 . 
         [0029]    In the illustrated embodiment, the concave sawing edge curves inwardly from the line  234  in a generally continuous arc between the proximal  252  and distal  254  teeth with a generally flat portion between the teeth directly adjacent opposite sides of the transition  218 . It is to be understood, however, that the concave sawing edge may take a variety of regular and irregular geometric configurations. For example, the concave cutting edge may have a generally parabolic shape, v-shape, irregular geometric shape, etc. 
         [0030]    The ratio of the blade&#39;s cutting length to the depth of curvature of the sawing edge  208  may be established depending on the geometry of the concave sawing edge, the tooth configuration, the application and/or desired performance characteristics. The nadir, i.e. the lowest point or region, of the concave sawing edge may occur between the first and second plurality of teeth, e.g. on the longitudinal midline of the shank. In an embodiment including the illustrated exemplary concave geometry, for example, the longitudinal distance  244  between proximal tip  240  and distal tip  242  may be approximately 74 mm and the depth of curvature  246  of sawing edge  208 , measured from line  234  connecting tips  240  and  242  to the nadir  248  of the of the sawing edge may be approximately 1.5 mm. In such an embodiment, the blade  200  has a ratio of cutting length to depth of approximately 50:1. Although any ratio of cutting length to depth may be provided in a blade consistent with the present disclosure, a ratio of cutting length to depth of between about 10:1 and 100:1 may be provided. 
         [0031]    The concave cutting edge in the illustrated embodiment is formed by teeth having a generally uniform tooth height among the first and second plurality of teeth. It is to be understood, however, that a concave cutting edge  208  consistent with the present disclosure may be achieved using a progressive tooth height for the first and/or second plurality of teeth. For example, the tooth height may progressively decrease from the proximal  252  and/or distal  254  tooth to the tooth immediately adjacent the transition  218 . Any one or more of the teeth in the first and/or second plurality of teeth may have height greater than any one or more of the other teeth in the first and/or second plurality of teeth. In fact, a concave cutting edge  208  consistent with the present disclosure may be achieved regardless of the specific tooth geometries or spacing. 
         [0032]    The concave shape of sawing edge  208  may result in a decrease in the pressure applied by teeth  214 A and  214 B during travel in their clearing direction. This may reduce or eliminate undesirable burring and chipping on the rake side of the material and galling on the relief side of the material. The concave sawing edge may also cause each successive cutting tooth to bite deeper into the material than the tooth on its rake edge side thereby increasing overall cutting speed. 
         [0033]    Referring now to  FIG. 5 , blade  200  is shown affixed to a typical jigsaw  300 , in the act of through-sawing a piece of material  400 . In operation, the saw may be disposed on the top surface of the material  400  with a shank of the blade extending beyond the bottom surface of the material. The saw may then be energized to cause continuous reciprocation of the blade. As the blade reciprocates in contact with the material, the blade may saw the material downwardly from the top surface during a down-stroke with a proximal plurality of downwardly-directed cutting teeth and upwardly from the bottom surface during an upstroke with a distal plurality of upwardly-directed cutting teeth. 
         [0034]    Because sawing may occur during reciprocation of blade  200  in both directions, it is found that sawing efficacy and speed are increased compared to traditional blades. In addition, a blade consistent with the present disclosure may provide improved kerf and sawn edge quality during through cutting and plunge cutting, especially on brittle materials such as countertop laminates, which when sawn by traditional blades are especially prone to poor kerf and sawn edge quality on the side of the material exited by teeth during their cutting stroke. 
         [0035]    According to one aspect of the disclosure there is provided a saw blade including: a first plurality teeth, each of the first plurality of teeth having a cutting tip directed toward a first end of the blade, and a second plurality, each of the second plurality of teeth having a cutting tip directed toward a second end of the blade and toward the first plurality of teeth. The first and second pluralities of teeth define a concave cutting edge. 
         [0036]    According to another aspect of the disclosure there is provided a saw blade including: a proximal portion configured for fixed engagement with a saw; a shank portion; a first plurality teeth on the shank portion, each of the first plurality of teeth having a cutting tip directed toward a distal end of the blade; a second plurality on the shank portion each of the second plurality of teeth having a cutting tip directed toward a proximal end of the blade and toward the first plurality of teeth; and transition portion extending between the first and second plurality of teeth. The first plurality teeth include a proximal tooth adjacent a proximal end of the shank portion and having a proximal cutting tip, and the second plurality of teeth include a distal tooth adjacent a distal end of the shank portion and having a distal cutting tip, wherein a straight line connecting the proximal and distal cutting tips is parallel to a cutting direction of the first and second pluralities of teeth. The first and second pluralities of teeth defining a concave cutting edge extending inwardly from the straight line. 
         [0037]    According to another aspect of the disclosure there is provided a method of sawing material including: engaging a blade of a reciprocating saw with the material, the blade including a first plurality teeth, each of the first plurality of teeth having a cutting tip directed toward a first end of the blade, and a second plurality, each of the second plurality of teeth having a cutting tip directed toward a second end of the blade and toward the first plurality of teeth, the first and second plurality of teeth defining a concave cutting edge; and energizing the saw to cause the continuous reciprocation of the blade with the blade in contact with the material. 
         [0038]    The embodiments that have been described herein are set forth herein by way of illustration but not of limitation. Many other embodiments, which will be readily apparent to those of ordinary skill in the art, may be made without departing materially from the spirit and scope of the disclosure.

Technology Classification (CPC): 8