Abstract:
A blade for a saw comprising a generally planar member having a rim with a plurality of teeth, wherein the improvement comprises a carbon composite material reinforcement positioned on at least one of the teeth. A method of using such a saw blade to cut a cement, ground sand and cellulosic fiber material is also disclosed.

Description:
[0001]    This is a continuation of U.S. application Ser. No. 09/626,753, filed Jul. 27, 2000, the specification of which is incorporated herein by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Technical Field  
           [0003]    The present invention relates to cutting devices and more particularly blades which are used on such devices. Still more particularly, this invention relates to saw blades which are adapted for use on cellulosic fiber reinforced cement construction materials.  
           [0004]    2. Background Information  
           [0005]    Saw blades are commonly used to cut raw or processed materials into intermediate or final products. One class of materials which presents particular challenges to the cutting art are certain cellulosic fiber reinforced construction materials which are formed from compositions of cement, ground sand, and cellulosic materials. Such materials are commonly processed with various additives and water and are formed into boards and other useful shapes. One way in which such materials have been cut is with saw blades with a continuous rim design where a thin layer of serrated diamond is welded to the outside rim of the saw blade. Such saw blades, however, have disadvantages for such use in that they tend to heat quickly and are subject to warping when used to cut such cement, ground sand, and cellulosic fiber composite materials.  
         SUMMARY OF THE INVENTION  
         [0006]    It is an object of the present invention to provide a saw blade and a method for its use in which excessive heat and blade warping are avoided when cutting cement, ground sand, and cellulosic fiber composite materials.  
           [0007]    It is another object of the present invention to provide a saw blade which cuts cement, ground sand, and cellulosic fiber composite materials cleanly and with a smooth finish without excessive burred and frayed edges.  
           [0008]    This invention is a blade for a saw comprising a generally planar member having a rim with a plurality of teeth, wherein the improvement comprises a carbon composite material reinforcements positioned on at least one of the teeth. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    The preferred embodiment of the invention, illustrative of the best mode in which applicant contemplated applying the principles, is set forth in the following description and is shown in the drawings and is particularly and distinctly pointed out and set forth in the appended claims.  
         [0010]    [0010]FIG. 1 is a top plan view of a circular saw blade representing a preferred embodiment of the present invention;  
         [0011]    [0011]FIG. 2 is a top plan view of a circular saw blade body used in the manufacture of the circular saw blade shown in FIG. 1;  
         [0012]    [0012]FIG. 3 is a top plan view of the composite polycrystalline diamond and carbide reinforcement used in the manufacture of the circular saw blade shown in FIG. 1;  
         [0013]    [0013]FIG. 4 is an end view of the composite polycrystalline diamond and carbide reinforcement shown in FIG. 3;  
         [0014]    [0014]FIG. 5 is a side elevational view of the composite polycrystalline diamond and carbide reinforcement shown in FIG. 3;  
         [0015]    [0015]FIG. 6 is a top plan view of the carbide only reinforcement used in the manufacture of the circular saw blade shown in FIG. 1;  
         [0016]    [0016]FIG. 7 is an end view of the carbide only reinforcement shown in FIG. 6;  
         [0017]    [0017]FIG. 8 is a side elevational view of the carbide only reinforcement shown in FIG. 6;  
         [0018]    [0018]FIG. 9 is an enlarged view of the area in circle  9  in FIG. 1;  
         [0019]    [0019]FIG. 10 is an enlarged view of the area in circle  10  in FIG. 1;  
         [0020]    [0020]FIG. 11 is an end view from  11 - 11  in FIG. 9; and  
         [0021]    [0021]FIG. 12 is an end view from  12 - 12  in FIG. 10. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]    Referring to FIGS. 1, 9 and  10 , the body of the saw blade is shown generally at numeral  10  wherein there are opposed planar surfaces as at planar surface  12  and a rim generally at numeral  14 . On the rim, there are a plurality of teeth as at tooth  16 . Each of these teeth has a curved outer edge  18 , a tip  20 , and a recessed inner edge  22 . There is a hook angle  23  which is the angle between a radial line  24  and a line  25  which is an extension of the leading edge  26  of a composite polycrystalline diamond and carbide reinforcement  27 , wherein radial line  24  contacts the inner corner  28  of leading edge  26 . Preferably this hook angle is in the range of about 20° to about −20° and more preferably is about −10° (using the convention in circular saw blades that angles clockwise from the radius are negative and counter clockwise are positive). On the planar surface  12  adjacent the tip  20  of tooth  16  there is the composite polycrystalline diamond and carbide reinforcement  27 . A suitable composite polycrystalline diamond and carbide reinforcement is commercially available from Sanvik Hard Materials located at Provo, Utah under part number PCDA 200. The body  10  of the saw blade also includes a central aperture  29  about which the blade rotates and a lock aperture  30 . Two other teeth, tooth  32  and tooth  34 , also have a tip composite polycrystalline diamond and carbide reinforcements  36  and  38  respectively. It will be seen that all the other teeth, as for example at teeth  42 ,  44  and  46 , have carbide only tip reinforcements as at reinforcements  48 ,  50  and  52 , respectively. A suitable carbide only reinforcement is commercially available from Sanvik Hard Materials under part number RAD80-100. The carbide only reinforcements also preferably have a hook angle of from about 20° to about −20° and more preferably about −10°. Like with the composite reinforcement, for the carbide only reinforcement the hook angle is the angle between a radial line contacting the inner corner of the leading edge of the reinforcement and a line which is an extension of the leading edge of the reinforcement.  
         [0023]    Referring particularly to FIG. 1, it will be seen that there is a height H d  which is a radial distance between the center of the blade and the outermost corner of the composite polycrystalline diamond and carbide reinforcements as at reinforcement  36 . For a conventional 7¼ inch circular saw blade, H d  may, for example, be 3.625 inches. There is also a height H c  which is a radial distance between the center of the blade and the outermost corner of the carbide only reinforcements as at reinforcement  48 . For a conventional 7¼ circular saw blade H c  may, for example, be in the range from of 3.575 inches to 3.590 inches. Preferably the ratio of H c  to H d  will be in the range of about 1.0:1.0 to about 1.0:1.5. For the purposes of their disclosure, “height” will have the meaning defined in this paragraph.  
         [0024]    Referring to FIG. 2, the method of manufacturing the blade shown in FIG. 1 begins with a 1075 high carbon steel body  10  shown in FIG. 2 in which the polycrystalline diamond and carbide reinforcements and carbide reinforcements have not yet been fixed. At this stage, the teeth  16 ,  32  and  34  have respectively large reinforcement receiving recesses  54 ,  56  and  58  for receiving the composite polycrystalline and diamond and carbide reinforcements. The remaining teeth, such as teeth  42 ,  44  and  46 , have smaller reinforcement receiving recesses as, respectively, recesses  60 ,  62  and  64  for receiving the carbide only reinforcements. The reinforcements are attached to the steel body  10  by conventional brazing techniques.  
         [0025]    Referring to FIGS.  3 - 5 , the reinforcement  27  is comprised of a composite of a carbide section  66  and a polycrystalline diamond section  68 . Between the carbide section  66  and the polycrystalline diamond section  68  there is a cobalt interface layer  70 . For a 7¼ inch circular saw blade the composite reinforcement  28  preferably has a thickness T d  of 0.090 inch, a width W d  of 0.090 inch and an overall length Lt of 0.125 inch. The overall length Lt is comprised of a length Lc of the carbide section  66  which is preferably 0.090 inch and a length Ld of the polycrystalline diamond section  68  which is preferably 0.030 inch.  
         [0026]    Referring to FIGS.  6 - 8 , the reinforcement  52  is comprised only of carbide. For a 7¼ inch circular saw blade the carbide only reinforcement  52  preferably has a thickness T c  of 0.052 inch, a width W c  of 0.100 inch and an overall length L c  of 0.150 inch.  
         [0027]    Referring to FIGS. 9 and 11, the positioning of the composite reinforcement  28  relative to the tooth  18  is shown in detail. The positioning of the dimensions Lt and W d  are as shown. The thickness T d  is perpendicular to the planar surface  12  of the blade  10 . For a 7¼ inch circular saw blade the thickness T b  of the steel body  10  of the blade is preferably 0.054 inch.  
         [0028]    Referring to FIGS. 10 and 12, the positioning of the carbide only reinforcement  52  relative to the tooth  46  is shown in detail. The positioning of the dimensions Lt and W c  are as shown. It will be appreciated that the thickness T c  is perpendicular to the planar surface  12  of the blade  10 . The thickness T d  of the carbide and polycrystalline diamond composite reinforcement is equal to or greater than the thickness T c  of the carbide only reinforcement. For a 7¼ inch circular saw blade the thickness T b  of the steel body  10  of the blade is also 0.054 inch at this position. The ratio of the thickness T c  of the carbide only reinforcement to the thickness T d  of the composite polycrystalline diamond and carbide reinforcement is preferably in the range of from about 1.0:1.0 to about 1.0:2.0.  
         [0029]    It will also be appreciated that the number of carbide only reinforcements will preferably be equal to or greater than the number of the polycrystalline diamond composite material reinforcements used. Preferably the ratio of the number of polycrystalline diamond composite material reinforcements or other carbon composite material reinforcements to the number of carbide only reinforcements will be in the range of about 1:1 to about 1:20.  
         [0030]    The saw blade and its method of use are further described with reference to the following examples.  
         [0031]    In the method of using this saw blade it has been found that the blade performs well at saw speeds of 3,600 RPM or 5,800 RPM which are standard speeds for 7¼ inch circular saws. On a cement, ground sand, and cellulosic fiber composite board of a thickness of 0.25 inch. This method is further described with reference to the following example.  
       EXAMPLE 1  
       [0032]    A saw as described above was used to cut a HARDIPLANK cement, sand and cellulosic fiber composite material board having a thickness of 0.25 inch which is commercially available from James Hardie Building Products, Inc. located at Mission Viejo, Calif. The saw was operated at a speed of 5,800 RPM. Under such conditions, the saw blade lasted for more than 3,280 board feet. It was also found that the cut made on the board was smooth and without excessive burred or frayed edges or other irregularities. Such a clean cut was believed to result from using a mixture of composite polycrystalline diamond reinforcements in combination with carbide only reinforcements as is disclosed herein.  
       COMPARATIVE EXAMPLE 2  
       [0033]    A conventional 7¼ inch circular saw blade which was similar to the blade used in Example 1 except that each of the blade tips had an all carbide tip similar to the all carbide tips described above was used to cut a HARDIPLANK board having a thickness of 0.25 inch. This saw blade was operated at 5,800 RPM. Under such conditions, the conventional all carbide tip blade lasted for approximately 66.67 board feet.  
         [0034]    It will be appreciated that a saw blade has been described which cleanly and efficiently cuts cement, sand and cellulosic materials without excessive heat and blade warping.  
         [0035]    While the present invention has been described in connection with the preferred embodiments of the various figures, it is to be understood that other similar embodiments may be used or modifications and additions may be made to the described embodiment for performing the same function of the present invention without deviating therefrom. Therefore, the present invention should not be limited to any single embodiment, but rather construed in breadth and scope in accordance with the recitation of the appended claims.