Abstract:
A saw tooth for a circular saw for a feller includes, in one embodiment, a square saw tooth body having a multi-faceted shape to be mounted on a holder and for receiving inserts fastened to inwardly sloping seating surfaces on the cutting end of the tooth body. The inserts are provided with cutting tips and cutting edges to form angled cutting edges about the entire periphery of the cutting end of the tooth body. Notches are made in the seating surfaces and inserts in order to permit adjacent inserts to overlap one another, such that the angled cutting edges are strengthened at their junctions, thereby reducing damage of the inserts and improving the cutting performance of the saw tooth.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to an improved saw tooth for circular saws, and more particularly, to a saw tooth having inserts to provide multiple angled cutting edges.  
         BACKGROUND OF THE INVENTION  
         [0002]    Saw teeth for circular saws of the type mounted on a feller head for a tree felling apparatus have undergone considerable change in the last few years.  
           [0003]    U.S. Pat. No. 4,932,447, Morin, 1990, and U.S. Pat. No. 5,205,199, MacLennan, 1993, represent saw teeth which have become the standards in the industry. Morin &#39;447 and MacLennan &#39;199 both teach a replaceable saw tooth with four sides which can be rotated when the active cutting tips and edges become dull or worn. The saw tooth generally has a four-sided main body with a mounting end and a cutting end. The MacLennan patent further provides V-shaped cutting edges at the cutting end, with four planar surfaces defining cutting tips at the apex of these somewhat triangular surfaces. Flat triangular carbide inserts can overlie the flat surfaces to reinforce the cutting edges. These inserts are brazed to the tooth head.  
           [0004]    MacLennan et al, in their U.S. Pat. No. 5,644,965, 1997, describe an improved saw tooth having V-shaped cutting edges. The four-sided main body of the saw tooth includes seats for receiving inserts. The inserts which are made of hardened material are provided with cutting tips and cutting edges and are retained against the main body by a clamp nut. Thus, when the edges and tips are worn or damaged from impact, the inserts can be replaced without rotating the tooth. The tooth is rotated only when the seat of the main body is damaged.  
           [0005]    The saw tooth, which has fixed or replaceable hardened inserts forming V-shaped cutting edges, provides good cutting performance. However, it should be noted that in those prior art saw teeth, adjacent inserts abut each other, thereby forming weak points at the junction of the respective V-shaped cutting edges. In a worst case scenario, a slight gap may exist between adjacent inserts and, therefore, the V-shaped cutting edges are not actually continuous at those junctions thereof, which will adversely affect the cutting performance of the saw tooth.  
           [0006]    In U.S. Pat. No. 5,307,719, issued on May 3, 1994, MacLennan describes a saw tooth similar to those described in U.S. Pat. No. 5,205,199. The improvement of MacLennan &#39;719 lies in that adjacent insert ends of the hardened inserts overlap at the intersection of the two adjacent surfaces. The overlap of the hardened inserts is provided by forming a V-shaped notch in an end of an edge which is adapted to receive an angled end of an edge of an adjacent hardened insert. However, because it is limited by the thickness and angled position of the hardened inserts, the V-shaped notch only provides very limited space for the overlap. Therefore, such an overlap configuration cannot significantly prevent weakened areas in the cutting end of the tooth.  
           [0007]    There is a need for improved configuration of the saw tooth having inserts forming V-shaped cutting edges, to overcome these shortcomings.  
         SUMMARY OF THE INVENTION  
         [0008]    It is an object of the present invention to provide a saw tooth having inserts forming angled cutting edges about the periphery of a cutting end of the saw tooth, wherein adjacent inserts are overlapped to provide strengthened cutting edges at the junctions of adjacent inserts.  
           [0009]    A construction in accordance with the present invention includes a saw tooth for a circular saw blade wherein the tooth comprises a multi-faceted shaped body having a mounting end, a larger cutting end and a plurality of sides extending between the mounting end and the cutting end. The sides form corners at the cutting end where they meet. A seating surface is provided on the cutting end at each of the corners. Each of the seating surfaces slopes inwardly and is defined between two edges diverging from a corresponding corner. A hardened insert is fastened to each seating surface to form a single cutting tip with a pair of receding cutting edges. Adjacent inserts overlap one another and provide angled cutting edges about the entire periphery of the cutting end. A seat-notch in each of the seating surfaces and an insert-notch in each of the inserts are provided so that the seat-notch and the insert-notch in combination form a groove for receiving a section of an adjacent insert, in order to permit the overlapping of adjacent inserts.  
           [0010]    The inserts can either be permanently fastened to the tooth head or can be detachably fastened to the tooth head in order to permit the inserts to be replaceable when they are worn or damaged.  
           [0011]    Other advantages and features of the present invention will be better understood with reference to the preferred embodiment described hereinafter. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    Having thus generally described the nature of the present invention, reference will now be made to the accompanying drawings, showing by way of illustration the preferred embodiment thereof, in which:  
         [0013]    [0013]FIG. 1 is a perspective view of an embodiment of a saw tooth in accordance with the present invention;  
         [0014]    [0014]FIG. 2 is a cross-sectional view taken along line  2 - 2  of FIG. 1;  
         [0015]    [0015]FIG. 3 is a perspective view of the embodiment shown in FIG. 1, with one insert removed;  
         [0016]    [0016]FIG. 4 is a top plan view of a tooth body of the embodiment of FIG. 1;  
         [0017]    [0017]FIG. 5 is a perspective view of the tooth body of FIG. 4;  
         [0018]    [0018]FIG. 6 is an enlarged partial perspective view taken from the circle  6  in FIG. 5, showing the detail of seat-notches;  
         [0019]    [0019]FIG. 7 is a perspective view of a triangular insert to be used in the embodiment of FIG. 1 before one side tip thereof is cut away;  
         [0020]    [0020]FIG. 8 is a bottom plan view of the insert used in the embodiment of FIG. 1 after one side tip is cut away; and  
         [0021]    [0021]FIG. 9 is a perspective view of the insert of FIG. 8, showing a notch formed therein. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0022]    Referring now the drawings and in particular FIGS. 1 and 2, there is shown a four-sided saw tooth  10  adapted to be mounted on a holder (not shown) which in turn is bolted to the periphery of a circular saw blade used on a de-limber (not shown). The saw tooth  10  includes a tooth body  12  and four inserts  14  fastened to the tooth body  12  in an overlapping relationship with one another and providing angled cutting edges  16  about the periphery of the tooth body  12 .  
         [0023]    The tooth body  12 , more clearly shown in FIGS. 4 and 5, includes a mounting end  18  and a cutting end  20  with four flat and slightly tapered lateral side walls  22  which extend outwardly from the mounting end  18  to the cutting end  20 , forming a frusto-pyramidal configuration. Four corners  24  are formed at the cutting end  20  where the four lateral side walls  22  meet. The cutting end  20  of the tooth body  12  is recessed, as shown in the drawings, and includes flat seating surfaces  26  corresponding to the respective corners  24 . Each flat seating surface  26  slopes inwardly and is defined between two straight edges  28 ,  30 , diverging from a corresponding corner  24 .  
         [0024]    The tooth body  12  further includes a center portion  32  at the cutting end  20  with a center bore  34  extending through the tooth body  12  and through the mounting end  18 . The center bore  34  may be provided with inner threads, as shown in the drawings, so that the tooth body  12  can be conveniently secured to the holder of the circular saw blade. The center portion  32  has a front surface  36  which is parallel to a rear surface  38  of the tooth body  12  at the mounting end  18 , as shown in FIG. 2. The center portion  32  is defined by four side surfaces  40  extending downward from the front surface  36 , perpendicular to and terminating at the respective seating surfaces  26 . Thus, each of the seating surfaces  26  is formed in a substantially triangular shape.  
         [0025]    Each of the substantially triangular seating surfaces  26  intersects at its side corners, the respective adjacent substantially triangular seating surfaces  26 , thereby forming a seat-notch  42  in each of the adjacent seating surfaces  26 . Seat-notch  42  in each seating surface  26 , which is more clearly shown in FIG. 6, is formed between surface  44  and surface  46 . Surface  44  is an extension of an adjacent seating surface  26  and is disrupted by a seat-notch  42  of that adjacent seating surface  26 . Surface  46  is on the same plane as one of the side surfaces  40  of the center portion  32 . This side surface  40  terminates at and is perpendicular to that adjacent seating surface  26 , so that surface  44  is perpendicular to surface  46 .  
         [0026]    Reference is now made to FIGS.  7 - 9 . Inserts  14  have a uniform size and shape, and each of the inserts  14  is made of a triangular piece of metal having a uniform thickness. Insert  14  includes a top surface  48 , a bottom surface  50 , two side surfaces  52  and an end surface  54 . Bottom surface  50  is slightly smaller than top surface  48 , such that the two side surfaces  52  are slightly tapered from the top surface  48  towards the bottom surface  50 . The shape and size of inserts  14  correspond to the respective substantially triangular seating surfaces  26  (of FIGS. 4 and 5) in order to ensure that inserts  14  fit into the frusto-pyramidal configuration of tooth body  12 , as shown in FIGS. 1 and 2, when inserts  14  are received on the respective seating surfaces  26 . The end surface  54  of insert  14 , which is perpendicular to top and bottom surfaces  48 ,  50 , rests on the side surface  40  of the center portion  32  of the tooth body  12  when the insert  14  is received on the inwardly sloping seating surface  26  of the tooth body  12 . The side surface  40  of the central portion  32 , which is right-angled with the inwardly sloping seating surface  26 , functions as a stopper to provide accurate positioning for the insert  14  which is to be seated on the seating surface  26 .  
         [0027]    In order to achieve the overlapping of adjacent inserts  14 , one side corner  56  is cut away from each insert  14 . The cut side corner  56  can be made at either side of an insert  14  but must be at the same side of every insert  14  which is to be positioned on the same tooth body  12 . An insert-notch  58  is formed in the insert  14  after the side corner  56  is cut and removed. The insert-notch  58  of insert  14  includes surfaces  60  and  62  which are perpendicular to each other. Thus, when an insert  14  is received in one seating surface  26  of tooth body  12  and rests on the corresponding side surface  40  of the center portion  32 , surface  60  of the insert-notch  58  will be parallel to and spaced apart from surface  44  of the seat-notch  42  in the corresponding seating surface  26 , as shown in FIG. 3, and surface  62  of the insert-notch  58  in the insert  14  will be on the same plane as surface  46  of the seat-notch  42  in the corresponding seating surface  26 . Thus, as illustrated in FIG. 3, surfaces  44 ,  46 ,  60  and  62  in combination form a groove which is slightly wider than the thickness of insert  14 , for receiving a significant section of an adjacent insert  14 , thereby resulting in the desired overlapping configuration of adjacent inserts  14  fastened to the tooth body  12 , as illustrated in FIG. 1.  
         [0028]    Referring now to FIGS. 1, 5 and  8 , insert  14  fastened to each seating surface  26  of a tooth body  12  will have a pair of cutting edges  52   a  and  52   b  which are formed at the intersections of the top surface  48  and the respective side surfaces  52  of the substantially triangular insert  14 , and correspond to similarly defined edges of the seating surface  26  of the tooth body  12 . A cutting tip  24   a  of each insert  14  corresponds with the corner  24  of the seating surface  26  to which the insert  14  is fastened. The cutting edges  52   a  and  52   b  of each insert  14  recede from the cutting tip  24   a . The receding cutting edges  52   a ,  52   b  of the respective adjacent inserts  14 , as illustrated in FIG. 1, form an angled, or V-shaped, cutting edge at the cutting end  20  on each side of the tooth body  12 , thereby providing angled cutting edges about the entire periphery of the cutting end  20  of the tooth body  12 .  
         [0029]    It should be noted that a significant section of cutting edge  52   b  extends under cutting edge  52   a  at each side of the cutting end  20 . When a small fraction of cutting edge  52   a  at its distal extremity relative to its cutting tip  24   a  is broken under impact during a cutting operation, a corresponding small section of cutting edge  52   b , which was overlapped by the broken small fraction of cutting edge  52   a , will be exposed so that the cutting performance of this angled cutting edge which is formed by the adjacent overlapping cutting edges  52   a  and  52   b  will not immediately be significantly affected.  
         [0030]    The inserts  14  may be made of steel or they may be of a hardened material, such as tungsten carbide, depending on the environment in which the tooth is being used. The inserts  14  can be permanently fastened to the tooth body  12 , for example, by brazing, as suggested in U.S. Pat. No. 5,205,199. Inserts  14  may also be detachably fastened to the tooth body  12 , for example, by a clamp nut which retains the inserts against the tooth body  12 , as described in U.S. Pat. No. 5,644,965. It should be noted that the substantially triangular inserts having uniform thickness are used only as an example to illustrate the principle of the invention. The above described overlapping configuration of inserts may be modified and thereby applied to inserts which are not substantially triangular or are not of a uniform thickness. With necessary modifications the overlapping inserts configuration can be applied, for example, to inserts of a somewhat pentagonal outline with uniform thickness and to inserts of a somewhat pentagonal outline with a varying thickness, both described in U.S. Pat. No. 5,644,965, the entire specification of which is incorporated herein by reference.  
         [0031]    Other modifications and improvements to the above-described embodiment of the present invention may become apparent to those skilled in the art. The foregoing description is intended to be exemplary rather than limiting. The scope of the invention is, therefore, intended to be limited solely by the scope of the appended claims.