Apparatus for cutting rumble strips in a road surface

Abstract

A cutting head is provided for milling rumble strip depressions in a road surface. The cutting head has a center rotational axis and a transverse diameter that varies along the length of the rotational axis so that an outer cutting surface of the cutting head defines a plane curve, such as an ellipsoid with truncated ends. The cutting head is mounted on a milling machine and rotated about the rotational axis as it is moved alternately up and down into the road surface. As the milling machine moves down the road, the movement of the cutting head creates spaced apart rumble strip depressions in the road. Because of the elliptical configuration of the cutting head cutting surface, the dimensions of the depressions can be varied along both the forward and lateral axes by simply varying the depth of cut. The curved profile of the cutting head along the rotational axis creates rumble strip depressions that avoid the sharp ninety degree corners and vertical side walls found in conventional rumble strips.

1. A rumble strip milling machine comprising:
 a vehicle movable along a road surface;  
 a cutting head rotatably mounted in associated with said vehicle and mounted for alternating up and down movement into and out of said road surface while said cutting head is rotating, said cutting head comprising: 
 a drum having opposed ends and a center rotational axis extending between said opposed ends, said drum having a convex outer surface in a direction along said center rotational axis;  
 a shaft extending from said opposed ends of said drum along said center rotational axis; and  
 a plurality of milling elements positioned on said outer surface of the drum and having cutting surfaces positioned to define a plane curve as said drum is rotated about said center rotational axis, said plane curve having a transverse diameter taken in a plane transverse to said center rotational axis, said transverse diameter of the plane curve being greatest in a first region and of reduced dimension in regions on opposite sides of said first region; and  
 
 a motor coupled with said shaft of the cutting head for effecting rotation thereof.  
 
     
     
       2. The milling machine of  claim 1 , wherein a vertical plane taken through said plane curve along said center rotational axis has at least a partially elliptical, oval, or round configuration. 
     
     
       3. The milling machine of  claim 1 , wherein said drum and milling elements comprises a plurality of stacked, disc-shaped saw blades with interposed spacers. 
     
     
       4. The milling machine of  claim 1 , wherein said drum is ellipsoidal in configuration. 
     
     
       5. The milling machine of  claim 4 , wherein said milling elements comprise milling teeth mounted to the outer surface of said drum. 
     
     
       6. The milling machine of  claim 5 , wherein said milling teeth are removably mounted within holders secured to said outer surface of the drum. 
     
     
       7. The milling machine of  claim 6 , wherein said milling teeth include cutting tips formed of a material comprising tungsten carbide. 
     
     
       8. A rumble strip milling machine comprising:
 a vehicle movable along a road surface;  
 a cutting head rotatably mounted in associated with said vehicle and mounted for alternating up and down movement into and out of said road surface while said cutting head is rotating, said cutting head comprising: 
 a drum having opposed ends and a center rotational axis extending between said opposed ends, said drum having an outer surface;  
 a shaft extending from said opposed ends of said drum along said center rotational axis; and  
 a plurality of milling elements positioned on said outer surface of the drum and having culling  cutting surfaces positioned to define a plane curve as said drum is rotated about said center rotational axis, said plane curve having a transverse diameter taken in a plane transverse to said center rotational axis, said transverse diameter of the plane curve being greatest in a first region and of reduced dimension in regions on opposite sides of said first region, wherein a vertical plane taken through said plane curve along said center rotational axis has at least a partially elliptical, oval, or round configuration; and  
 
 a motor coupled with said shaft of the cutting head for effecting rotation thereof.  
 
     
     
       9. The milling machine of  claim 8 , wherein said drum and milling elements comprises a plurality of stacked, disc-shaped saw blades with interposed spacers. 
     
     
       10. The milling machine of  claim 9 , wherein said milling elements comprise milling teeth mounted to the outer surface of said drum. 
     
     
       11. The milling machine of  claim 10 , wherein said milling teeth are removably mounted within holders secured to said outer surface of the drum. 
     
     
       12. The milling machine of  claim 11 , wherein said milling teeth include cutting rips  tips formed of a material comprising tungsten carbide. 
     
     
       13. A rumble strip milling machine comprising:
 a vehicle movable along a road surface;  
 a cutting head rotatably mounted in associated with said vehicle and mounted for alternating up and down movement into and out of said road surface while said cutting head is rotating, said cutting head comprising: 
 a drum having opposed ends and a center rotational axis extending between said opposed ends, said drum having an outer surface which is ellipsoidal in configuration;  
 a shaft extending from said opposed ends of said drum along said center rotational axis; and  
 a plurality of milling elements positioned on said outer surface of the drum and having cutting surfaces positioned to define a plane curve as said drum is rotated about said center rotational axis; and  
 
 a motor coupled with said shaft of the cutting head for effecting rotation thereof.  
 
     
     
       14. The milling machine of  claim 13 , wherein said drum and milling elements comprises a plurality of stacked, disc-shaped saw blades with interposed spacers. 
     
     
       15. The milling machine of  claim 13 , wherein said milling elements comprise milling teeth mounted to the outer surface of said drum. 
     
     
       16. The milling machine of  claim 15 , wherein said milling teeth are removably mounted within holders secured to said Outer surface of the drum. 
     
     
       17. The milling machine of  claim 16 , wherein said milling teeth include cutting tips formed of a material comprising tungsten carbide. 
     
     
       18. The milling machine of  claim 1 , including means for moving said cutting head into said road surface with a positive downward pressure while said cutting head is rotating. 
     
     
       19. The milling machine of  claim 18 , including a crankshaft having a rotatable shaft and coupled with said cutting head to cause said alternating up and down movement of the cutting head as the rotatable shaft is rotated. 
     
     
       20. The milling machine of  claim 19 , wherein said rotatable shaft of the crankshaft is rotatably driven by a second motor. 
     
     
       21. The milling machine of  claim 20 , wherein said crankshaft includes at least one eccentric lobe mounted on said rotatable shaft and a crank arm mounted at one end of the lobe by a bearing, said crank arm being coupled at an opposite end with the cutting head. 
     
     
       22. The milling machine of  claim 1 , wherein said cutting head is mounted for rotation in a reverse direction in relation to a forward direction of travel of said vehicle along said road surface so that a cutting action of said cutting head into said road surface resists said forward direction of travel of said vehicle. 
     
     
       23. The milling machine of  claim 1 , wherein said vehicle is movable in a forward direction of travel along said road surface while said cutting head is rotating and moving up and down into and out of said road surface. 
     
     
       24. The milling machine of  claim 1 , wherein said plane curve includes a second region spaced from said first region and having a transverse diameter greater than said reduced dimension in said regions on opposite sides of said first region. 
     
     
       25. The milling machine of  claim 24 , wherein said transverse diameter of said plane curve in said second region is the same as said transverse diameter of the plane curve in the said first region. 
     
     
       26. The milling machine of  claim 1 , used in a method to mill spaced apart rumble strip depressions into said upper surface of the road, comprising the steps of ( a )  rotating said cutting head at a preselected rotational speed about a center rotational axis,  ( b )  moving said rotating cutting head downwardly a preselected distance into said road surface to mill a depression having a concave bottom that curves upwardly along perpendicular first and second axes,  ( c )  moving said cutting head in an upward direction and advancing the milling machine along the road surface, and  ( d )  repeating steps  ( b )  and  ( c )  to form a plurality of said depressions in spaced apart relationship along said road surface.   
     
     
       27. The milling machine of  claim 26 , including the step of removing the cutting head from the road surface before advancing the milling machine along the road surface. 
     
     
       28. The milling machine of  claim 26 , including advancing the milling machine along the road surface during said steps of moving said rotating cutting head down into the road surface and moving said cutting head in an upward direction. 
     
     
       29. The milling machine of  claim 26 , including varying the preselected distance said rotating cutting head is moved down into said surface as said steps ( b )  and  ( c )  are repeated.   
     
     
       30. The milling machine of  claim 1 , wherein said cutting head is rotated at a preselected rotational speed about said center rotational axis. 
     
     
       31. The milling machine of  claim 2 , wherein said cutting head is moved into a road surface a preselected distance so as to mill a depression. 
     
     
       32. The milling machine of  claim 31 , wherein the depression has a concave bottom that curves upwardly along perpendicular first and second axes. 
     
     
       33. The milling machine of  claim 32 , wherein upon forming the depression, said cutting head is moved in an upward direction away from the road surface. 
     
     
       34. The milling machine of  claim 33 , wherein said milling machine is advanced along the road surface so as to locate the machine in spaced positions for forming a plurality of said depressions in spaced apart relationship. 
     
     
       35. The milling machine of  claim 34 , wherein said cutting head is moved in a downward direction upon advancement of the milling machine along the road surface. 
     
     
       36. The milling machine of  claim 35 , including means for moving said cutting head into said road surface with a positive downward pressure while said cutting head is rotating. 
     
     
       37. The milling machine of  claim 13 , including means for moving said cutting head into said road surface with a positive downward pressure while said cutting head is rotating. 
     
     
       38. The milling machine of  claim 1 , wherein said cutting head is housed within a cutter box that extends in a forward direction beyond said cutting head. 
     
     
       39. The milling machine of  claim 38 , including means for moving said cutting head into said road surface with a positive downward pressure while said cutting head is rotating, wherein said means comprises a crankshaft having a rotatable shaft and coupled with said cutting head to cause said alternating up and down movement of the cutting head as the rotatable shaft is rotated, said crankshaft further including at least one eccentric lobe mounted on said rotatable shaft and a crank arm mounted at one end of the lobe by a bearing, said crank arm being coupled at an opposite end with the cutter box.