Abstract:
A replaceable cutter tooth for mounting to a saw blade has a concave front cutting surface extending from and between opposite kerf forming linear side edges, and from and between a radially inner curved edge, radially inner when mounted on a saw blade, and a radially outermost curved cutting edge. A groove extends in the radial direction from the radially inner curved edge to the radially outermost curved edge, generally medially between and substantially parallel to the side edges so as to reduce the surface area of a front face of the front cutting surface of the tooth for ease of re-sharpening in the field

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a Continuation of U.S. patent application Ser. No. 11/634,589 filed Dec. 6, 2006, which is a Continuation-in-Part of U.S. patent application Ser. No. 10/861,381 filed Jun. 7, 2004, which claims priority from U.S. Provisional Patent Application No. 60/476,284 filed Jun. 6, 2003. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a replaceable carbide saw tooth, wherein the leading cutting face is arcuately concave and contains a medial, radially aligned recess. 
       BACKGROUND OF THE INVENTION 
       [0003]    Replaceable cutting teeth are commonly used on circular saws utilized in the wood or pulp manufacturing industry. Generally such teeth are preferably manufactured from a composite material having abrasion resistant properties such as tungsten carbide and are attached by braising or the like to the attack faces of a radial array of gullets formed about the periphery of a saw blank. Alternatively, such cutting teeth can be similarly attached to an elongated tooth holder or shank. A plurality of holder and cutting tooth assemblies may then be removably secured by bolting, pinning or other well known means within a radially aligned array of recesses formed about the periphery of a circular saw blank. 
         [0004]    Such cutting tips when positioned on a circular saw blank have an upper cutting surface which extends radially outwardly of the periphery of the saw blank and extends generally parallel to the axis of saw rotation. Side cutting surfaces extend laterally outwardly of either the saw blank or the tooth holder or shank forming the kerf. 
         [0005]    In the prior art of which applicant is aware U.S. Pat. No. 4,084,470 which issued Apr. 18, 1978 to Reed, discloses a cutting tooth secured to a holder or shank for insertion within a plurality of radially extending slots formed within the periphery of a flat steel disc. 
         [0006]    The applicant is further aware of U.S. Pat. No. 4,765,217 which issued Aug. 23, 1988 to Ludwig, which discloses a cutting tip secured to a holder or shank. The teeth are formed so as to have a leading face which is generally “V” shaped or arcuately shaped in sectional view taken on a plane generally parallel to the axis of saw rotation. 
       SUMMARY OF THE INVENTION 
       [0007]    In the present invention a cutting tip has a generally arcuately concave leading face, when viewed in section, the face having a medial recess so as to reduce the contact surface area of the leading face of the cutter tip for ease of sharpening. 
         [0008]    In summary, the replaceable cutter tooth for mounting to a saw blade according to the present invention includes a substantially concave front cutting surface extending from and between opposite kerf forming side edges, and from a radially inner curved edge, radially inner when mounted on the saw blade, to a radially outermost curved cutting edge. A groove extends in a radial direction, relative to the saw blade when the tooth is mounted thereon, from the radially inner curved edge to the radially outermost curved edge. The groove may be generally medially positioned between, and substantially parallel to, the side edges so as to reduce the surface area of a front face of the front cutting surface. The groove is recessed behind the front face relative to a direction of travel of the tooth when on the saw blade and the saw blade sawing a workpiece. The surface area is thereby reduced for ease of re-sharpening of the tooth. 
         [0009]    The tooth may have a concave top surface, and the front cutting surface, a rear surface, a bottom surface and opposite side surfaces. A top cutting edge is formed at an intersection of the top surface and the front cutting surface. When viewed in side profile, the intersection of the top surface and the cutting surface forms an acute angle. The bottom surface and the front cutting surface may intersect generally at right angles, and the side surfaces may converge toward the bottom and rear surfaces. 
         [0010]    In one embodiment the groove includes an oppositely disposed, laterally spaced apart pair of side groove surfaces defining a rear groove surface therebetween recessed behind the front face. The front face includes a pair of laterally therebetween recessed behind the front face. The front face includes a pair of laterally spaced apart faces on either side of the groove and elongate in the radial direction. The side groove surfaces and the rear groove surface define a channel. The rear groove surface may be planar or concave or otherwise non-planar. 
         [0011]    In an alternative embodiment the groove is a first smoothly concave surface concave about the radial direction in which the groove extends. The groove may extend substantially the entire height of the front cutting surface of the tooth. In one embodiment the groove is formed only of the first smoothly concave surface. A first cross section across the first smoothly concave surface may form a first segment of a circle, wherein the first cross section is substantially orthogonal to the radial direction. A first radius corresponding to the first segment may be substantially constant for all such first cross sections along the groove. 
         [0012]    For example, the first radius may be substantially 0.2 inches, and the acute angle formed between the concave top surface and the front surface may be substantially seventy degrees. The side surfaces may converge toward the bottom or rear surfaces by respective convergence angles. The convergence angles may be substantially between two and four degrees on each side of the tooth. 
         [0013]    The concave top surface advantageously has a second smoothly concave surface. A second cross section across the second smoothly concave surface may form a second segment of a circle, wherein the second cross section is substantially parallel to the radial direction and substantially parallel to the front cutting surface. The top cutting edge is also formed of the second segment of a circle. In one embodiment the second segment of a circle at the top cutting edge has a second radius of substantially two thirds of an inch. The second segment of a circle has a corresponding second radius which is substantially constant for all of the second cross sections across the concave top surface. In one embodiment the second radius is substantially two thirds of an inch. Again, the acute angle may be substantially seventy degrees. The top cutting edge may have a width of substantially one half of an inch, and the front cutting surface may have a height of substantially one half of an inch. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a perspective view illustrating a prior art saw tooth. 
           [0015]      FIG. 2  is a perspective view of the saw tooth of the present invention. 
           [0016]      FIG. 3  is a plan view of the saw tooth. 
           [0017]      FIG. 4  is a front elevation view of the tooth, viewed in the direction opposite to the direction of rotation of the saw. 
           [0018]      FIG. 5  is a left hand side elevation view of the tooth. 
           [0019]      FIG. 6  is a rear elevation view of the tooth. 
           [0020]      FIG. 7  is a plan view of an alternative embodiment of the tooth in which bottom of the recess is arcuate. 
           [0021]      FIG. 8  is a side view of an assembled tooth and holder. 
           [0022]      FIG. 9  is a perspective view of the device illustrated in  FIG. 8 . 
           [0023]      FIG. 10  is a perspective view of a portion of the tooth holder with the cutting tooth removed. 
           [0024]      FIG. 11  is, in front perspective view, a further alternative embodiment of the saw tooth according to the present invention. 
           [0025]      FIG. 12  is, in rear perspective view, the saw tooth of  FIG. 11 . 
           [0026]      FIG. 13  is, in front elevation view, the saw tooth of  FIG. 11 . 
           [0027]      FIG. 14  is, in rear elevation view, the saw tooth of  FIG. 11 . 
           [0028]      FIG. 15  is, in plan view, the saw tooth of  FIG. 11 . 
           [0029]      FIG. 16  is a sectional view along line  16 - 16  in  FIG. 14 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0030]    Saws used for example in sawmills or pulp manufacturing generally have replaceable cutting teeth which are either braised directly to a circular saw or braised to a tooth holder which is secured to the circular saw in one of several methods well known to the art. 
         [0031]    In the prior art saw tooth  44 , illustrated in  FIG. 1 , the front face  45  presents a large continuous surface area. Consequently, re-sharpening this type of tooth presents an undue level of difficulty since the grinding wheel must be applied against face  45  with a large amount of pressure. Further, without a clearly defined groove or notch the flow of sawdust may not be efficiently channelled away from the cutting surface of the tooth. 
         [0032]    As can be seen in  FIGS. 2 through 6 , replaceable cutter tooth  10  has a concave top surface  12 , a front surface  14 , a rear surface  16 , a bottom surface  18  and opposite side surfaces  20  and  20   a  respectively. A top cutting edge  22  is formed at the intersection of top surface  12 , and front surface  14 . When viewed in side profile, as illustrated in  FIG. 5 , the intersection of top surface  12  and front surface  14  forms an acute angle α as a result of surface  12  sloping rearwardly and slightly downwardly with respect to cutting edge  22 . Bottom surface  18  and front surface  14  intersect generally at right angles. Side surfaces  20  and  20   a  converge slightly toward bottom surface  18 , and may in alternative embodiments converge slightly toward rear surface  16 . 
         [0033]    Front surface  14  is arcuately concave with a first radius r 1  of one inch, in the embodiments of  FIGS. 2-7 . Radius r 1  is smaller, as described below, in the embodiments of  FIGS. 11-16 . In the prior art, re-sharpening of face  14  is usually accomplished by hand using a diamond abrasive wheel  24 . Wheel  24  may have various diameters. For example, to form a radius r 2  of one inch, wheel  24  is two inches in diameter. Difficulty has been experienced when field sharpening prior art teeth such as seen in  FIG. 1  since the amount of pressure required to be applied by hand for effective sharpening is difficult to achieve because of the large contact area on the front surface. 
         [0034]    To overcome this difficulty, in the present invention front surface  14  is formed with a medial notch, channel, gulley or groove  28  (collectively referred to as a groove) formed intermediate side surfaces  20  and  20   a . In the embodiment of  FIGS. 2-6  groove  28  has parallel sides  30   a  and  30   b  and a flat back surface  30   c  which is recessed behind the curvature of the surface of front surface  14 . The intersection of sides  30   a  and  30   b  with back surface  30   c  of groove  28  define smoothly radiused corners  32 , which reduce shear stress at the intersection and inhibit breakage of the tooth. Groove  28  separates front surface  14  into surfaces  14   a  and  14   b  and creates cutting surfaces  22   a  and  22   b . Groove  28  further allows greater sawdust flow during rotation of the sawblade in direction A so as to saw workpiece  34  as sawdust is channelled through groove  28 . The intersection of sides  20  and  20   a  of tooth  10  with front surfaces  14   a  and  14   b  creates side cutting edges  26   a  and  26   b.    
         [0035]    An alternative form of groove  28  is illustrated in  FIG. 7  wherein the back surface  30   c  of groove  28  is arcuately concave and is radiused where it intersects sides  30   a  and  30   b.    
         [0036]    As may be viewed in  FIGS. 8 through 10  replaceable cutter tooth  10  may be mounted directly onto a saw or indirectly through the use of a tooth holder or shank  40  as illustrated. Tooth  10  has the rear surface  16  and bottom surface  18  suitably shaped so as to afford a close toleranced fit with tooth holder or shank  40  for subsequent braising thereto. 
         [0037]    Holder  40  is designed for removable mounting on to a saw in a radial aspect in a manner well noted in the prior art so that cutter tooth  10  projects radially outwardly of saw  42 . Such mounting on a saw ensures that front surface  14  and groove  28  are also positioned in a radial aspect so as to project edge  22  radially outwardly relative to the saw  42 . 
         [0038]    In the further alternative embodiment of  FIGS. 11-16 , tooth  10  is modified from the embodiments of  FIGS. 2-7  so as to include on front face  14  a groove  28  having a smoothly concave surface, concave about radial line B when mounted on tooth holder  40 , and tooth holder  40  mounted on saw  42 . Thus instead of groove  28  having parallel sides  30   a  and  30   b  and a back surface  30   c  extending between the parallel sides, groove  28  smoothly curves as a single continuous concave surface  30   d  from and between surfaces  14   a  and  14   b  of front face  14 . Again, top cutting edge  22  extends along the intersection between front face  14 , including surfaces  14   a  and  14   b , and concave surface  30   d , and top surface  12 . 
         [0039]    In this alternative embodiment, radius r 1 , that is the radius forming the concavity of front face  14 , may be approximately 0.45 inches, radius r 2 , being the radius of the concavity of top surface  12  may be approximately 0.69 inches, and radius r 3  being the radius of the vertically extending concavity of groove  28  may be approximately 0.20 inches. As used herein, radius r 2  is also referred to as the second radius and radius r 3  is alternatively referred to as the third radius. By way of example, in this alternative embodiment, the height h 1  of tooth  10  may be approximately 0.51 inches measured parallel to the plane of symmetry C of tooth  10 . 
         [0040]    In the embodiment of  FIGS. 11-16  tooth  10  has a front face width w 1  which may be approximately 0.50 inches, or, in an alternative embodiment, may be approximately 0.47 inches, and groove  28  may have a width w 2  of approximately 0.27 inches. Tooth  10  may have a depth d 1  from the leading edge of the side surface of the tooth to a rear-most edge of rear mounting flanges  26  extending rearwardly from rear surface  16  of approximately 0.33 inches. The rear flanges  26  may extend rearwardly a distance d 2  by approximately 0.08 inches and may be spaced apart distance d 3  of approximately 0.29 inches. The distance d 4  between the deepest recess of groove  28 , which falls on plane of symmetry C, and the rear-most edge of rear mounting flanges  26  may be approximately 0.22 inches. Angle α may be approximately twenty degrees, angle β may be approximately 2.45 degrees and angle θ may be approximately 3.5 degrees. 
         [0041]    As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.