BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to the field of driven cutter devices for use in roadway surface milling, earthworking, mining, or other in situ disintegration of hard materials. More particularly, the present invention is directed to cutter devices of various geometries and groupings of such cutter devices. 
         [0002]    Roadway surfaces may become damaged over time thus requiring periodic maintenance. Milling may be performed to degrade a layer of the roadway surface to recondition it for travel or prepare it for resurfacing. It may be desirable to leave the roadway surface as smooth as possible after milling to ease travel or optimize adhesion of resurfacing materials. For example, U.S. Pat. No. 5,639,180 to Sulosky, et al., which is incorporated herein for all that it contains, describes a drum assembly for the milling of a roadway substrate to a fine texture. The design of the drum assembly permits the spacing between adjacent points of impingement to be 0.100 inches, and even less than 0.100 inches. The result is a substantially smooth roadway surface with little road noise. 
         [0003]    U.S. Pat. No. 3,325,219 to Guillon, et al., which is incorporated herein for all that it contains, describes how adjacent picks on known cutting machines may follow each other at such relatively great distances that the stresses developed in the material by one of the picks has no influence on the conditions of working of the following picks. To overcome this issue, Guillon discloses distributing picks such that the tracks left by the picks are sufficiently close, such that a ridge becomes sufficiently fragile to be broken-up by the passage of the pick making the next adjacent cut, to provide in the vicinity a substantially plane surface. 
         [0004]    U.S. Pat. No. 4,621,871 to Salani, which is incorporated herein for all that it contains, also describes how, when surface finish is important in road planning, more cutting teeth having a smaller spacing are desired. 
         [0005]    Thus, increases in the smoothness produced by roadway surface milling operations and other in situ disintegration procedures are desired. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    A movable base, such as a rotatable drum, continuous chain or other such driven mass known in the art, may be disposed on a translatable vehicle such as a road milling, mining, or trenching machine for the in situ degradation of a hard surface. The movable base may comprise a plurality of cutting elements disposed thereon. The cutting elements may be detachable from the movable base. The cutting elements may also be interchangeable with other cutting elements. 
         [0007]    Groupings of the plurality of cutting elements may comprise unique cutting surface geometries. For example, a first grouping of cutting elements may comprise conical, cylindrical or dome shaped cutting surface geometries while a second grouping of cutting elements may comprise flat shaped cutting surface geometries. The flat shaped cutting surface geometries may be formed as semicircular cylinders. 
         [0008]    In some embodiments, cutting elements from the first grouping may be alternated with cutting elements from the second grouping when viewed tangentially. This arrangement may be accomplished by alternating cutting elements from the first grouping with cutting elements from the second grouping in a series or disposing cutting elements from the first grouping in a series parallel to a series of cutting elements from the second grouping. Either way, the cutting elements of each grouping may be arranged such that at least two of the cutting elements from the first grouping precede a cutting element from the second grouping in a direction of motion of the movable base. Additionally, the first grouping may be disposed at a greater distance from the movable base than the second grouping. 
         [0009]    Such an arrangement may form a degradable surface comprising a cross-sectional topography resembling a waveform comprising truncated peaks. In various embodiments, the waveform may be triangular or sinusoidal. The waveform may also be uniform or comprise valleys with varied spacing there between. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is an orthogonal view of an embodiment of a road milling machine. 
           [0011]      FIG. 2  is a cross-sectional view of an embodiment of a degradation platform disposed on a road milling machine. 
           [0012]      FIG. 3  is an orthogonal view of an embodiment of a rotatable drum comprising cutting elements with conical and flat cutting surface geometries disposed thereon. 
           [0013]      FIG. 4  is an orthogonal view of another embodiment of a rotatable drum comprising cutting elements with conical and flat cutting surface geometries disposed thereon. 
           [0014]      FIGS. 5   a ,  5   b  and  5   c  are perspective views of embodiments of arrangements of cutting elements comprising various cutting surface geometries. 
           [0015]      FIG. 6  is a perspective view of an embodiment of a cutting element comprising a flat cutting surface geometry. 
           [0016]      FIGS. 7   a ,  7   b  and  7   c  are perspective graphical representations of progressive embodiments of a surface being degraded. 
           [0017]      FIGS. 8   a  and  8   b  are perspective graphical representations of surfaces comprising cross-sectional topographies with truncated peaks and valleys. 
           [0018]      FIG. 9  is an orthogonal view of an embodiment of a trenching machine. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    Referring now to the figures,  FIG. 1  discloses an embodiment of a milling machine  100  traveling over a degradable surface  101 . The degradable surface  101  may be a man-made roadway such as those comprising pavement, concrete, or asphalt or it may be a naturally occurring earthen formation. A degradation platform  102  may be attached to the milling machine  100  such that it may degrade the degradable surface  101 . The degradation platform  102  may comprise a rotatable drum or continuous chain as are known to those of skill in the art. In the embodiment shown, the degradation platform  102  comprises a rotatable drum which may be driven by the milling machine  100 . 
         [0020]      FIG. 2  discloses an embodiment of a degradation platform  202  comprising a plurality of cutting elements  220  disposed on a rotatable drum  203 . The rotatable drum  203  may be driven such that the cutting elements  220  engage and degrade a degradable surface  201 . 
         [0021]      FIG. 3  discloses an embodiment of a rotatable drum  303  with a plurality of cutting elements  320  disposed thereon. Groupings of the plurality of cutting elements  320  may comprise unique cutting surface geometries. For example, cutting elements may comprise conical, flat, cylindrical or dome shaped cutting surface geometries. In the embodiment shown, a first grouping  329  of cutting elements  320  comprises conical shaped cutting surface geometries  330  and a second grouping  332  of cutting elements  320  comprises flat shaped cutting surface geometries  333 . 
         [0022]    The cutting elements  320  may be disposed around an exterior of the rotatable drum  303  in several series. Each series may comprise a plurality of cutting elements  320  each offset a certain angular rotation and axial distance from an adjacent cutting element such as to form a spiral around the exterior of the rotatable drum  303 . In the embodiment shown, the first grouping  329  of cutting elements  320  form a first series  328  that runs parallel to a second series  331  formed by the second grouping  332  of cutting elements  320 . 
         [0023]      FIG. 4  discloses another embodiment of a rotatable drum  403  comprising a plurality of cutting elements  420  disposed thereon. The rotatable drum  403  is similar to the one shown in  FIG. 3  in that it comprises a first grouping  429  of cutting elements  420  comprising conical shaped cutting surface geometries  430  and a second grouping  432  of cutting elements  420  comprising flat shaped cutting surface geometries  433 . However, in the embodiment shown in  FIG. 4 , the cutting elements  420  from the first grouping  429  are alternately disposed with cutting elements  420  from the second grouping  432  in a single series  434 . 
         [0024]      FIGS. 5   a ,  5   b  and  5   c  disclose embodiments of arrangements of cutting elements and illustrate how cutting elements comprising unique cutting surface geometries may work in concert to create a smooth degraded surface. 
         [0025]    The embodiment shown in  FIG. 5   a  comprises a lead cutting element  535   a  comprising a conical cutting surface geometry  530   a,  a subsequent cutting element  536   a  comprising a conical cutting surface geometry  531   a,  and a trailing cutting element  537   a  comprising a flat cutting surface geometry  532   a.  While degrading a surface, the lead cutting element  535   a  may engage the surface first, cutting a first valley in the surface. The subsequent cutting element  536   a  may engage the surface next, cutting a second valley in the surface. The first and second valleys may form a cross-sectional topography in the surface resembling a waveform. In some embodiments, the waveform may be uniform or in other embodiments the waveform may comprise non-uniform spacing. The trailing cutting element  537   a  may then engage the surface and truncate crests of the waveform thus resulting in a smoother surface. 
         [0026]    The embodiments shown in  FIGS. 5   b  and  5   c  are similar to that of  FIG. 5   a  in that they comprise lead cutting elements  535   b,    535   c,  subsequent cutting elements  536   b,    536   c , and trailing cutting elements  537   b,    537   c.  However, the lead cutting element  535   b  and subsequent cutting element  536   b  of the embodiment shown in  FIG. 5   b  comprise cylindrical shaped cutting surface geometries  530   b  and  531   b  respectively. In addition, the lead cutting element  535   c  and subsequent cutting element  536   c  of the embodiment shown in  FIG. 5   c  comprise dome shaped cutting surface geometries  530   c  and  531   c  respectively. The cylindrical shaped cutting surface geometries  530   b,    531   b  and dome shaped cutting surface geometries  530   c,    531   c  may form a cross-sectional topography in a degraded surface resembling a sinusoidal waveform. The crests of the sinusoidal waveform may then be truncated by flat cutting surface geometries  532   b,    532   c  disposed on the trailing cutting elements  537   b  and  537   c  respectively. 
         [0027]      FIG. 6  discloses an embodiment of a cutting element  620  comprising a flat cutting surface geometry  625 . The flat cutting surface geometry  625  may be constructed by splitting a cylindrical polycrystalline diamond compact of the type known in the art through its axis. 
         [0028]      FIGS. 7   a ,  7   b  and  7   c  disclose graphical representations of progressive embodiments of a surface being degraded. Specifically,  FIG. 7   a  discloses a graphical representation of an embodiment of a surface  750 . The surface  750  has been partially degraded by a cutting element comprising a conical cutting surface geometry that has created v-shaped valleys  755  within the surface  750 .  FIG. 7   b  shows the surface of  FIG. 7   a  after having been further degraded by a subsequent cutting element comprising a conical cutting surface geometry that has created additional v-shaped valleys  760 . The plurality of v-shaped valleys  755  and  760  may form a cross-sectional topography resembling a waveform comprising crests  765  disposed between adjacent v-shaped valleys  755 ,  760 .  FIG. 7   c  shows the surface of  FIG. 7   b  after having been further degraded by a trailing cutting element comprising a flat cutting surface geometry that has truncated the crests  765  to form truncated peaks  770  and a cross-sectional topography resembling a truncated waveform. 
         [0029]      FIGS. 8   a  and  8   b  disclose embodiments of surfaces  801   a,    801   b  with cross-sectional topographies comprising truncated peaks  845   a,    845   b  and valleys  844   a,    844   b.  The embodiment shown in  FIG. 8   a  comprises a cross-sectional topography wherein spacing between the valleys  844   a  may vary. For example, a first spacing  847  may be substantially smaller than a second spacing  848 .  FIG. 8   b  shows an embodiment of a surface  801   b  wherein valleys  844   b  have been formed by cutting elements with cylindrical or dome shaped cutting surface geometries resulting in a curved shape cutting profile. The cross-sectional topography of the surface  801   b  may resemble a sinusoidal waveform with truncated peaks. 
         [0030]      FIG. 9  discloses an embodiment of a trenching machine  900  traveling over a degradable surface  901 . A degradation platform  902  comprising a plurality of cutting elements disposed on a continuous chain  903  may be disposed thereon. The continuous chain  903  may be brought in contact with the degradable surface  901  in order to dig a trench therein. 
         [0031]    Whereas the present invention has been described in particular relation to the drawings attached hereto, it should be understood that other and further modifications apart from those shown or suggested herein, may be made within the scope and spirit of the present invention.
Cutting elements may be used to degrade hard surfaces in roadway surface milling, earthworking, mining, or other in situ disintegration processes. A plurality of such cutting elements may be disposed on a movable base and thereby brought into engagement with a degradable surface. Groupings of the plurality of cutting elements may comprise unique cutting surface geometries. Various groupings may be arranged on the movable base such that the degradable surface forms a cross-sectional topography resembling a waveform comprising truncated peaks.