Abstract:
A cutting and grinding wheel made of a circular disk having a center, two opposing surfaces, an outer circumference, and a center defining a bore hole. A plurality of teeth are evenly distributed around the disk&#39;s outer circumference, with each tooth having an apex and a pair of opposing sidewalls generally parallel to the disk opposing surfaces. The teeth formed in a generally sinusoidal pattern, and each adjacent pair of teeth are separated by a gullet. An abrasive coating is disposed to be concentrated upon the wheel teeth apexes and opposing teeth sidewalls.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to cutting wheels for use in rotary power tools. More specifically, the present invention is concerned with an improved tooth formation with an abrasive coating which provides simultaneous cutting and grinding operations on known soft and composite materials.  
           [0002]    Cutting wheels for use in rotary power tools are well known. One known wheel is disclosed in Hariu U.S. Pat. No. 5,876,274. The Hariu patent discloses a corrugated electrodeposited diamond cutting wheel having diamond abrasive particles electrodeposited on the outer circumference of a circular substrate. Corrugated ridges and grooves are employed for cooling apertures during use on heat-softening materials. For additional cooling, the diamond wheel employs a plurality of aperture holes for cooling around the body of the substrate.  
           [0003]    Apertures in the body of the wheel, however, weaken the structural strength of the wheel, causing it to bend or flex in operation, and sometimes break. Operational flexing limits the utility of the wheel for precision operations. Furthermore, ridges and grooves do not provide sufficient cooling of the cut material edge at the point of contact from the wheel cutting edge. Because softer materials often begin to melt from the friction of cutting, insufficient cooling often requires an additional grinding or sanding operation to smooth the cut edge. In addition, diamond particles are expensive to use as an abrasive material, and they are difficult to apply to metal surfaces.  
           [0004]    It is also known to provide a cutting wheel formed of metal and being completely covered on both sides with an abrasive material. The abrasive material is secured to the wheel by painting, spraying, or dipping. The wheel includes cooling aperture holes positioned throughout the wheel body, and along an outer circumference.  
           [0005]    Due to the fact that the outer cooling apertures are large relative to the diameter of the cutting wheel, these apertures create a strong kickback during both low and high speed operations of the wheel. Furthermore, the wheel is formed from a relatively soft metal and tends to flex and distort during operation. The large inner cooling apertures further weaken the structural strength of the wheel body, thereby increasing the wheel&#39;s distortion during use. Additionally, the abrasive coating disposed across the entire surface of the wheel body tends to collect waste material from the cutting operation, and thus reduces both the cutting ability of the wheel and its cooling efficiency. Another disadvantage is that painting, spraying, or dipping does not create a secure bond between the abrasive particles and the wheel, and the wheel tends to shed these individual particles during operation. Yet another drawback of this conventional wheel is that abrasive particle loss greatly reduces the useful life of the wheel.  
           [0006]    Accordingly, one object of this invention is to provide a new and improved cutting and grinding wheel for use with a rotary power tool.  
           [0007]    Another object of the present invention is to provide an improved cutting wheel that will simultaneously grind and smooth the cut edge of a material being cut.  
           [0008]    A further object of the present invention is to provide an improved cutting and grinding wheel which is subject to relatively negligible distortion during high speed or rigorous use.  
           [0009]    Yet another object of the present invention is to provide an improved cutting and grinding wheel that provides sufficient cooling without sacrificing structural strength.  
           [0010]    A still further object of the present invention is to provide an improved cutting and grinding wheel that has little to no kickback during cutting operations or in side-to-side grinding operations.  
         BRIEF SUMMARY OF THE INVENTION  
         [0011]    The above-listed objects are met or exceeded by the present cutting and grinding wheel, which features a solid and rigid body structure, with a plurality of gear-like teeth around the outer circumference of the wheel. Each tooth is armed at its peak with an abrasive grit material coating. A gullet between each adjacent tooth allows airflow that,cools the wheel and the cut material. The grit material is structured to surround the outer edge of each tooth apex and both of its adjacent sides, thereby forming the abrasive cutting edge. This cutting edge is thicker than the wheel body itself, and therefore facilitates airflow and cooling around the cutting edge. By armoring only the outer or peripheral edge and adjacent sidewalls of the wheel with abrasive grit, a cutting or kerf width is provided which is wider or thicker than the blade disk or body.  
           [0012]    More specifically, the present invention provides a cutting and grinding wheel formed of a circular disk having a center, two opposing surfaces, an outer circumference, and a center defining a bore hole. A plurality of teeth are evenly distributed around the outer circumference, each of the teeth having an apex and a pair of opposing sidewalls generally parallel to the disk opposing surfaces. The teeth are formed in a generally sinusoidal pattern, and each of the adjacent teeth in the pattern are separated by a gullet. An abrasive coating is disposed to be concentrated upon the wheel teeth apexes and the opposing outer teeth surfaces.  
           [0013]    The cutting edge of this wheel, with its improved cooling features, is effective for cutting known soft and composite materials. The wheel is pairticuilarly useful for slicing and cutting, slotting, and general material removal of rubbers, elastomers, soft woods, and hard wools. Because of this improved cutting edge, the resulting simultaneous cutting and grinding operations provide smoother and cleaner cuts. Another feature is that the relatively small teeth provide little or no kickback, making the present wheel easier to control and useful for fine precision work. One embodiment of the present cutting and grinding wheel is particularly effective for vehicle rubber tire repair. This improved design has a longer useful working life than conventional cutting wheels that are known in the art.  
           [0014]    In an alternate embodiment, the present wheel is provided without teeth, instead having a relatively continuous outer edge. An abrasive coating as described above is still applied to the outer peripheral edge and immediate sides of that edge, as in the preferred embodiment. The relatively thicker peripheral edge, compared to the remainder of the disk, promotes cooling of the wheel, the workpiece, and the evacuation of cut material.  
           [0015]    In the preferred embodiment, the present cutting and grinding wheel is attached to a chuck for insertion into a known hand-held rotary power tool. For this application, the present cutting and grinding wheel has an enhanced ability to perform fine detailing and precision work. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0016]    [0016]FIG. 1 is a front elevational view of a cutting and grinding wheel according to the invention;  
         [0017]    [0017]FIG. 2 is a fragmentary elevational view of the cutting and grinding wheel illustrated in FIG. 1;  
         [0018]    [0018]FIG. 3 is a sectional view of the cutting and grinding wheel taken along the line  3 - 3  in FIG. 1, and in the direction indicated generally;  
         [0019]    [0019]FIG. 4 is an elevational view of the present cutting and grinding wheel and chuck assembly in partial section;  
         [0020]    [0020]FIG. 5 is an end elevational view of another embodiment of the present invention; and  
         [0021]    [0021]FIG. 6 is a front elevational view of a prior art cutting wheel. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]    Referring now to FIGS. 1 and 2, a cutting and grinding wheel is generally designated  10 . The cutting and grinding wheel  10  includes a planar, generally circular disk  12 , preferably having a plurality of teeth  14 , and a center bore hole  16 . In the preferred embodiment, the circular disk  12 , and also the teeth  14 , are formed from metal, and preferably from spring steel AISI 1095. Other, relatively high grade metals are contemplated, and show reduced tendency to distort at high-speed operations. The disk  12  has parallel opposing surfaces  18  which are preferably planar, so as to minimize the thickness of the cutting edge. In the preferred embodiment, the diameter of the wheel  10  is preferably 1″, but other sizes of wheels are contemplated depending on the application. Located in the center of the disk  12 , the bore hole  16  provides an attachment point for rotary power tools. Preferably, the hole  16  is round, but can also be square, hexagonal, or a variety of other shapes that would provide secure attachment and prevent slipping within a rotary power tool.  
         [0023]    Referring now to FIGS. 1 and 2, at an outer circumference  20  of the disk  12 , the teeth  14  are evenly distributed and are configured to define a generally sinusoidal pattern, and preferably formed into a generally gear-like pattern. This tooth pattern on the disk  12  may be stamped, laser cut, ground, molded, or created by any number of other methods well known in the art. With a wheel diameter of 1″, the plurality of teeth  14  preferably numbers  45 , however it is contemplated that the number of teeth may vary to suit the application.  
         [0024]    Measured between a pair of adjacent teeth apexes  22 , and having a vertex located at the center of the disk  12 , is a pitch angle Θ. In the preferred embodiment, Θ measures between 5 and 10 degrees. Best seen in FIGS. 1 and 3, the height H of each tooth  14  is generally small relative to the diameter of the disk  12 . This relatively large number of comparatively small teeth  14  allows for a smoother cutting and grinding operation, that provides little or no kickback. Kickback is further reduced in that the apexes  22  of the teeth  14  are preferably radiused, however, in some applications sharpened teeth are contemplated.  
         [0025]    Referring now to FIG. 2, between each pair of adjacent teeth  14  a gullet  24  is formed. The gullets  24  allow airflow between the teeth  14  for better cooling at the point where cutting is performed. Additionally, the gullets  24  are preferably radiused to keep from collecting waste material generated during the cutting operation, however other gullet shapes are contemplated, depending on the application.  
         [0026]    Referring now to FIG. 3, an opposing sidewall  26  of each tooth  14  is generally parallel to, and preferably coextensive with, a respective adjoining disk opposing surface  18 . Waste material is therefore more easily shed during the cutting operation.  
         [0027]    Surrounding the upper portion of each sidewall  26  and each tooth apex  22  is an abrasive grit structure  28 , made up of individual grit particles  30 . It is preferred that the grit structure  28  does not continue down the sidewall  26 , or down the circular disk  12 . By completely surrounding the tooth apex  22  and adjoining upper sidewall  26  near the peripheral edge  20 , only the abrasive grit structure  28  will come in contact with the material to be cut during high speed operation. Therefore, the abrasive grit structure  28  forms the actual cutting edge of the wheel  10 .  
         [0028]    A width or thickness W C  of the grit structure  28  edge is wider or thicker than a width or thickness W D  of the disk  12 . The difference in the widths W C  and W D  is important during operation because it provides even more airflow, and therefore more cooling, around the cutting edge and down the opposing surfaces  18  of the disk  12 . A cutting edge wider than the disk  12  is also useful in allowing more waste material to be shed during the cutting operation.  
         [0029]    The abrasive grit structure  28  may be either single or multi-layer, though a single layer is preferred to provide a relatively narrow cutting edge for precision work. In the preferred embodiment, this grit structure is formed of tungsten-carbide particles, and formed on the tooth apexes  22  of the disk  12  by magnetic structuring. However, other known particularate grinding media are contemplated, including, but not limited to diamond grit. This process of magnetic structuring is described in Oliver U.S. Pat. No. 3,918,217, which is herein incorporated by reference. The preferred size of the individual grit particles 30 is 100 grit or smaller, although it is contemplated that grit particle size may vary with the application. Though the grit structure may be adhered to the wheel  10  by a number of methods known in the art, the structure is preferably adhered by a process of brazing with stainless eutectic brazing metal. A NiCr alloy is the preferred brazing metal, however other alloys are contemplated as are known in the art, and any eutectic brazing alloy capable of bonding to metal carbides, carbon of diamond and/or to boron composed grits will be suitable.  
         [0030]    In an alternate embodiment, designated  10 ′, the blade  10 ′ may be made similar to the description above, changing only by eliminating the tooth gullets  24 . Thus, the teeth apexes  22  form a generally continuous outer peripheral edge  20 . The abrasive grit structure  28  has the same configuration as depicted in FIG. 3, as does the cross section of the grinding wheel  10 ′. Thus, it is concentrated on the peripheral edge  20  of the wheel,  10 ′ and on the sidewalls  26 ′ adjacent the peripheral edge. The only difference is that this cross-section extends about the entire periphery of the wheel  10 . Since, as described above, the grit structure  28  actually does most of the cutting, the performance of the wheel  10 ′ should not be that different from the wheel  10 . As is the case with the wheel  10 , in the wheel  10 ′, the relatively wider width W C  compared to the width or thickness W D  is important during operation because it provides even more airflow, and therefore more cooling, around the cutting edge and down the opposing surfaces  18  of the disk  12 . A cutting edge wider than the disk  12  is also useful in allowing more waste material to be shed during the cutting operation. As another alternative, the abrasive grit structure  28  may also be formed to have included angle β at the peripheral edge  20 , as seen on the right side of the wheel  10  in FIG. 3. This configuration results in a sharper edge for enhanced penetration.  
         [0031]    Referring now to FIG. 4, an assembly  40  is formed by engaging the cutting and grinding wheel  10  to the chuck of a rotary power tool (not shown) using a mandrel  42 . In the preferred embodiment, the wheel  10  is secured to an end  44  of the mandrel  42  by a threaded fastener  46  passing through the bore hole  16  and into a threaded blind-end bore  48  (shown hidden) of the mandrel  42  to form the assembly  40 . The assembly  40  is of particular use for attachment to most hand-held rotary power tools.  
         [0032]    It has also been found that a wheel according to this embodiment of the present invention is useful as a grinding tool. In operation at high rotational speeds, the assembly  48  can be used solely as a grinding wheel. By moving the cutting edge perpendicularly along a metal blade, or by moving a metal blade along the stationary rotating cutting edge, an edge on a metal blade may be sharpened.  
         [0033]    Referring now to FIG. 5, another embodiment of the cutting and grinding wheel is generally designated  50 . Shared components with the wheel  10  are designated with identical reference numerals. In this embodiment, the cutting and grinding wheel  50  includes a generally circular disk  12  with opposing sides  18 , having a plurality of teeth  14 , and a center bore hole  18 . In this embodiment, the disk  12  is not planar, but instead defines a serpentine, or “wiggle-waggle” shape when viewed on end. The wiggle-waggle shape provides a thicker cut and allows significantly more airflow at the point where cutting is performed. This shape is particularly useful where large amounts of material are to be cut, and where less precision is required. Because less precision is required, the tooth apex  22  is not radiused, but pointed in this embodiment. On this pointed apex  22 , is formed the abrasive grit structure  28  according to the same process disclosed for the wheel  10 .  
         [0034]    It has been found that a cutting wheel  10  according to the present invention provides, on average, a 17% faster, as well as a smoother cut to known soft and composite materials (soft wood, plastics, etc.) at 30,000 rpm than the prior art wheel  60  shown in FIG. 6. The prior art wheel  60  has a pair of opposing surfaces  62  totally covered with grit  64 , a central bore hole  66  for mandrel mounting, and a plurality of apertures  68  for cooling. As described above, these apertures  68  weaken the structure of the wheel  60 . The large, arcuate shaped tooth gullets  70  also weaken the structure of the wheel  60 , in addition to creating undesirable kickback during operation.  
         [0035]    Furthermore, because the grit  64  is secured to the wheel  60  by painting or dipping, the wheel  60  tend to shed the grit  64  during operation, thereby shortening the useful working life of the wheel  60 . In contrast, the wheel  10 ,  50  according to the present invention was found to provide a substantially longer useful working life with little to no kickback, than was the prior art wheel  60 .  
         [0036]    While a particular embodiment of the cutting and grinding wheel with an improved abrasive tooth structure of the invention has been shown and described, it will be appreciated by those skilled in the art that changes and modifications may be made thereto without departing from the invention in its broader aspects and as set forth in the following claims.