Abstract:
An extension for a grader blade which is used to dig a concave ditch includes a body for mounting on or integral with one end of the grader blade, the body having a convex outer side edge adapted to scoop out a curved-bottom ditch when the grader blade is angled from the horizontal with the extension at the lowermost end of the blade, and moved through the surface.

Description:
[0001]    This application claims priority on U.S. Provisional Application 60/907,352 filed Mar. 29, 2007. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to a grader blade extension for use in digging curved-bottom ditches. 
       BACKGROUND OF THE INVENTION 
       [0003]    When a road is cut in the side of a hill or mountain, drainage ditches are usually required to carry away water flowing down the hill or mountain towards the road. Such ditches usually have a V-shaped cross-sectional configuration which tends to concentrate water into a small area of the ditch increasing the likelihood of erosion. With a view to reducing or preventing erosion, it is preferable that the bottom of drainage ditches be round so that the flow of water is spread over a greater area, without under-cutting the embankment. 
         [0004]    Round bottom ditches have conventionally been cut using excavators, backhoes or other mechanical digging machines having extensible or articulated booms carrying buckets. The machines is parked on the shoulder of a road, the boom and bucket is extended toward the proposed ditch area, the bucket is dropped or forced downwardly into the soil and curled inwardly, and the boom is simultaneously retracted. The process is repealed two or three times. During the first pass or passes, the soil is disrupted. The number of such passes required to loosen the soil is dictated by a number of factors including the nature of rockiness of the soil, its compaction, the angle of attack of the edge of the bucket engaging the soil, the available power of the machine which may be applied downwardly on the bucket. The last pass or passes service to scoop and clear the loosened soil. Completion of the passes may be considered as a cycle. In the case of conventional square sided buckets, with each cycle a ditch segment the width of the bucket is completed. Conventional square sided buckets are approximately five feet wide, and accordingly each cycle produces approximately five feet of ditch. At the usual speeds, a round bottomed ditch can be produced at a rate of approximately 50 lineal meters per hour. 
         [0005]    The conventional ditch digging method described above using excavators or backhoes suffers from the disadvantage that the quality of the ditch relies heavily on the skill of the operator of the excavator or backhoe. In addition, after each cycle the machine must be moved along the road so as to present the bucket parallel to the road for the next adjacent five foot segment. This results in a relatively short length of ditch that can be produced during a given time period, and presents a danger to passing traffic. 
         [0006]    Graders are used for creating flat surfaces. Graders typically include three axles with a blade disposed between two rear driven axles and a front axle. The blade may be rotatable about the three orthogonal axes of the grader to enable a plurality of graded surface finishes. As a grader proceeds along a surface to be graded, a layer of the surface or a portion thereof is removed by the blade. Rotation of the blade about the three axes of the grader may enable the blade to be oriented such that the more material is removed by one side of the blade. Material may also be removed to either side of the blade, or the blade can be oriented at a greater angle of attack relative to the surface. 
         [0007]    Graders have not been generally used for the creation of drainage ditches although a grader blade may be inclined to dig a ditch using one edge of the blade. Grader blades typically have parallel ends with square corners. Accordingly, any ditch dug with a corner or a grader blade will have a V-shaped bottom. Thus, ditches formed by conventional grader blades will still suffer the same increased likelihood of erosion. 
         [0008]    Accordingly, there is a need for an apparatus for cutting a round-bottom drainage ditch without repetitive repositioning of the ditch digging machine, i.e. by using linear motion of the machine. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    A first embodiment of the present invention is an extension for a grader blade having a pair of ends and a bottom edge. The extension includes a body for mounting on or integral with one blade end, the body having one end edge conforming to the one blade end, and a free curved outer edge adapted to form a curved-bottom ditch in a surface when the grader blade is angled from the horizontal with the extension at a lowermost end of the blade. The body of the extension can be welded or bolted to one end of the grader blade. 
         [0010]    The extension can be two-piece, including a body and a moldboard portion, an outer edge of which defines a blade. The moldboard portion can have a cross section matching the cross section of the moldboard of the grader blade. The moldboard portion has a concave front surface. The concavity of the moldboard portion increases in a direction from the inner attachment end to the outer, blade edge making the moldboard portion somewhat cup-shaped. Alternatively, the concavity of the moldboard portion can decrease in a direction from the inner end to the outer, blade edge. 
         [0011]    The outer blade edge of the extension can be arcuate with a constant radius of curvature. The arcuate shape can be ovoid, ellipsoid or parabolic. The bottom of the outer edge is usually collinear with the bottom edge of the grader blade. 
         [0012]    As mentioned above, the extension can be integral with a grader blade, in which case the blade includes an elongated body having a pair of ends and a bottom end. At least one of the ends defined by the extension has a curved portion is adapted to cut a curved-bottom ditch into an adjacent soil surface when the grader blade is angled from a horizontal orientation such that the ditch digging edge is at a lowermost end of the angled grader blade. As the grader moves forward, the curved portion scoops out a concave ditch. 
         [0013]    In use, the grader blade is tilted around its longitudinal axis so that one end is raised and the other end with the digging edge is lowered. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is an isometric view of a grader having a grader blade extension according to a first embodiment of the present invention; 
           [0015]      FIG. 2  is an isometric view of the grader blade and extension of  FIG. 1 ; 
           [0016]      FIG. 3  is an exploded isometric view of the blade and extension of  FIG. 2 ; 
           [0017]      FIG. 4  is a cross-section taken generally along line  4 - 4  of  FIG. 2 ; and 
           [0018]      FIG. 5  is an isometric view showing a grader with the extension of  FIG. 1  in use. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    Referring to  FIG. 2 , an extension in accordance with the invention is indicated generally at  1 . The extension  1  is mounted on one end  2  of the blade  3  of a grader  4 . The blade  3  is mounted in the usual location between the front and middle wheels  5  and  6  of the grader  4 . The blade  3  is pivotally connected to the grader  4  for rotation with respect to the longitudinal, transverse and yaw axes  7 ,  8  and  9 , respectively of the grader  4 . 
         [0020]    As best shown in  FIGS. 2 and 3 , the blade  3  is defined by an arcuate (concavo-convex) body  10  and a straight, planar moldboard  12 . Of course, the blade can be a conventional one-piece structure without a separate moldboard. The moldboard  12  has a bottom cutting edge  13 . The blade has a top edge  14 . 
         [0021]    The extension  1  is mounted on the outer end  2  of the blade  3 , but could also be mounted on the other end  15  of the blade. It will be appreciated that conventional grader blades  3  do not necessarily have vertical ends as illustrated in  FIGS. 1 to 3 , i.e. the ends are not necessarily perpendicular to the horizontal top edges of the blades. It is merely necessary that the inner end of the extension conforms to the end of the blade  3  to which the extension is attached. 
         [0022]    The extension includes an arcuate body  17  connected to the body  10  of the blade  3 , and a blade or moldboard  18  connected to the corresponding end  19  of the moldboard  12  and to the body  17 . The body  17  of the extension  1  has a wave-shaped inner edge and a generally J-shaped outer and bottom edge  22 . The bottom, concave portion  24  of the inner edge of the body  17  is the same shape and length as the outer end  2  of the blade  3 . The concave top portion  25  of the inside edge  22  curves upwardly to a slightly convex top edge  26  above the top edge  14  of the blade  3 . The height of the extension above the top edge of the blade  3  is chosen on the basis of the intended use of the extension as well as the depth of the ditch to be dug. A higher extension is required for deeper ditches and when soil being removed is to be deposited to an outside surface of the extension. The blade  18  is generally J-shaped and has an inner edge  28  coextensive with the outer edge  22  of the body  17 . The top edge of the blade  18  is colinear with the top edge  25  of the body  17 . The outer edge  29  of the blade  18  curves downwardly and inwardly to a straight vertical bottom inside edge  29 , which is connected to the moldboard  12 . 
         [0023]    It will be appreciated that the blade  3  and the extension can be a one-piece structure. As illustrated in  FIG. 4 , the body  17  of the extension can be concave or slightly cup-shaped. The body  17  can also be flat or convex. The concavity of the extension can vary from side to side and top to bottom. Moreover, the outer edge  29  of the extension can have other shapes such as parabolic or define a portion of an ellipse or oval. The extension  1  is attached to the grader blade  3  by any conventional means such as by a connecting plate (not shown) extending from the extension to the rear of the blade  3 , and bolts and nuts attaching the plate to the blade. The use of bolts and nuts permit quick replacement of a damaged extension or changing extension when a different outer edge profile is required. 
         [0024]    In operation ( FIG. 5 ), the grader blade  3  is inclined relative to the axes  7  and  8  so that the extension  1  is lower than the other end  15  of the blade. As the grader  4  moves forward, the extension  1  scoops out a concave ditch  32 . As shown in  FIG. 5 , the grader blade  3  can be rotated around the vertical axis  9  so that the material scooped out by the extension moves towards the longitudinal axis  7  of the grader and is deposited on the road. The blade  3  can also be oriented so that the scooped material moves beyond the outer edge of the extension  1 , i.e. to the right in  FIG. 5 . 
         [0025]    When forming a ditch, a first cut can be made to remove a portion of the shoulder material using a grader blade without an extension. The extension can then be connected to the blade to form the concave ditch in a second pass. Alternatively, the first cut can be made by a first grader and the concave ditch made by a second grader having an extension on its blade.