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CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to V-blade snowplows, and more particularly to replaceable cutting edges of such plows. 
     2. Description of the Related Art 
     The most common type of snowplow has a straight blade which mounted to and extends across the full width of the front of a vehicle, such as a truck. In the simplest form, the angle of the blade with respect to the front of the vehicle is fixed at an angle so that snow being pushed by the blow is forced to one side. A more versatile straight plow enables blade to pivot with respect to the front of the vehicle so that the snow can be pushed to either side or straight ahead. 
     Another type of snowplow utilizes a V-blade which has two angled sections that meet at a forward edge and push the snow to both sides of the vehicle. This type of plow can incorporate a mechanism to alter the angle of the blades with respect to the each other. Typically, each blade is hinged to a center section of the plow frame and separate double-acting hydraulic cylinder and piston arrangements pivot the blade about the vertical hinge. This enables the two sections of the blade to be positioned in a standard “V” configuration that pushes the snow to each side, in a concave or scoop arrangement, or in a straight line that can be angled to either side of the vehicle. 
     In use, the bottom, or cutting, edge, of the blade scrapes against the surface being plowed. Usually that surface is very hard, often asphalt or concrete, which wears away the cutting edge. As a consequence the typical blade has a sacrificial cutting edge in the form of a metal plate that is removably mounted along the bottom edge. The edge plate, rather than the main section of the blade, is subjected to the wear during use. When most of the cutting edge plate has worn away it is replaced with a new one. It is more economical to replace the sacrificial cutting edge plate than the entire blade. 
     A characteristic of a V-blade is that the two blades are spaced apart under the center frame section which creates a gap through which some of the material being plowed can pass. This could leave in a rib of snow down the center of the area being plowed. To prevent this from occurring, prior blades spanned the gap with a flat rubber belt that was bolted to the cutting edges of each blade extending in front of the hinge on the center section. This belt flexed and stretched as the angle of the two blades changed. U.S. Pat. No. 6,108,946 describes an alternative solution that employs a semi-conical, solid catcher block beneath the center section of the V-blades. The catcher block closed the gap between the blade and its conical shape allowed the two sections to pivot without opening a gap. However the semi-conical catcher wore at a different rate than the cutting edges and had to be replaced at a different time. Furthermore, the solid block of material did not yield when struck by an object, such as a stone or other type of protrusion from the surface being plowed. 
     The outer tips of the blade also are subject to wear when plowing against a curb. In addition, significant force may be exerted on the edge of the blade upon striking a curb, which can adversely affect the blade hinge and the cylinder-piston arrangement used to pivot the blades. These forces, if significant, also can damage other components of the snowplow. 
     SUMMARY OF THE INVENTION 
     A V-blade plow has adjustable first and second blades, each with a bottom edge and an inner end that is rotatably connected to a pivot frame. The plow is provided with a cutting edge arrangement comprising first and second edge segments and a center edge segment there between. The first edge segment is removably attached to the first plow blade and projects downward below the bottom edge of the first plow blade. The second edge segment is removably attached to the second plow blade projecting below the bottom edge of the second plow blade. The center edge segment is mounted beneath the pivot frame and is attached to the first and second plow blades. 
     In a preferred embodiment of the cutting edge arrangement, the center edge segment is formed by a first wall that extends from the first edge segment under the pivot frame and by a second wall that extends from the second edge segment. The first and second walls meet beneath the pivot frame. The first wall may be integral with the first edge segment and the second wall may be integral with the second edge segment with a break between them. Alternatively, the first and second walls can be a single flexible piece of material attached to both the first and second edge segments. In yet another embodiment, the two walls are formed by a plurality of bristles, thereby creating an angled brush below the pivot frame. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of a V-blade snowplow incorporating the present invention; 
         FIG. 2  is an isometric rendering of the lower part of the pivot frame of the snowplow blades illustrating the novel edge guard; 
         FIG. 3  depicts an outer end of the snowplow blade; 
         FIG. 4  is an isometric view of the lower portion of the pivot frame of the snowplow blades showing a second embodiment of an cutting edge according to the present invention; 
         FIG. 5  is an isometric representation of the underside of the pivot frame of the plow blade assembly in  FIG. 4 ; 
         FIG. 6  is an isometric view of the lower portion of the pivot frame of the snowplow blade showing a third embodiment of a cutting edge; and 
         FIG. 7  is an isometric view of a fourth embodiment of a cutting edge. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Although the present invention is being described in the context of a snowplow, the inventive concepts can be applied to V-blade plows for pushing other materials, such as earth, gravel and the like. 
     With initial reference to  FIG. 1 , a snowplow  10  comprises a blade assembly  12  that has a first, or left, blade  14  and a second, or right, blade  16  moveably joined at their inner ends to a pivot frame  18  by a shared hinge  20 . Both blades  14  and  16  is able to pivot about the hinge axis  17  so that the blade assembly  12  can have a V configuration, as illustrated, or an inverse V in which the outer ends of each blade project forward of the pivot frame  18  to form a concave blade, or scoop. Alternatively, the first and second blades  14  and  16  can be aligned as a straight blade that can be rotated left or right about the pivot frame  18 . A hydraulic cylinder and piston assembly  21  is coupled between the pivot frame  18  and the second blade  16  to rotate that blade about the hinge  20 . Although not visible in the drawings, another hydraulic cylinder and piston assembly is coupled between the pivot frame  18  and the first blade  14  to provide pivoting motion there between. 
     The pivot frame  18  is secured to a push frame  22  which extends in a generally horizontal rearward direction from the bottom portion of the pivot frame. The end of the push frame  22  that is remote from the blade assembly  12  is coupled to a vehicle mount  24  in a manner that allows the push frame  22  to pivot about a horizontal axis. That pivot connection permits the push frame and blade assembly  12  to be raised and lowered with respect to the ground. A lift cylinder and piston assembly  26  extends between the push frame  22  and the vehicle mount  24  for that movement. 
     A hydraulic pump and motor  28  and a conventional hydraulic fluid reservoir are mounted on the push frame  22 . The motor of the pump is powered by electricity from the vehicle to which the snowplow is attached. Separate electrically operated control valves and hoses couple the pump and motor  28  to the different hydraulic cylinder and piston assemblies  21  and  26  in a conventional manner. A standard control panel is provided within the cab of the vehicle and has switches that enable the driver to independently operate each of the cylinders to pivot the first and second blades  14  and  16  and raise and lower the entire blade assembly  12 . 
     The vehicle mount  24  has couplings  30  and  32  on opposite sides for detachably engaging a support that is secured to the frame of the vehicle. Any of several well known mounting mechanisms can be provided for this purpose. 
     A cutting edge  38  is mounted along the lower regions of the front surface of the first and second blades  14  and  16  projecting below the bottom edge of the blades. The cutting edge  38  can be made of a rigid material, such as metal or a hard plastic, or a flexible material, such as polyurethane, plastic or a relatively hard rubber. With additional reference to  FIG. 2 , the cutting edge  38  has an elongated first segment  40  that is bolted or otherwise attached to the lower region of the first blade  14  and an elongated second segment  42  is bolted to the lower region of the second blade  16 . The cutting edge  38  further includes a center segment  43  underneath the pivot frame  18  and formed by two center walls  44  and  46 . Specifically, the first segment  40  bends inwardly into the first center wall  44  that extends under the pivot frame  18 , and the second segment  42  bends inward forming the second center wall  46  which also projects under the pivot frame. The bend at the interface between the elongated segment  40  or  42  and the associated center wall  44  or  46  provides a smooth contour to the material being pushed by the plow. If a semi-rigid, yet flexible material is used, the center walls  44  and  46  are able to flex and allow an obstruction to pass under the pivot frame  18 . The interior remote ends of the two center walls  44  and  46  meet in an abutting manner at an interior vertical seam  48  that is aligned with the axis of the hinge  20 . Therefore, as the first and second blades  14  and  16  rotate about the hinge  20  the interior remote ends of the first and second center walls  44  and  46  remain abutting so that a gap is not created through which the material being plowed may pass. 
     By using a flexible material, the entire cutting edge  38  alternatively can be formed as a single piece. In this case, the first and second center walls  44  and  46  are joined at the seam  48  with the material providing a flexible joint between those walls which bends as the blades rotate about the hinge  20 . 
     The entire cutting edge  38  wears at the same rate, and thus, does not employ separate pieces of various sizes and materials which wear at different rates and may have to be replaced at different times. 
     With reference to  FIG. 3 , the cutting edge  38  also protects the outside end of each blade  14  and  16  from damage due to striking a curb or other object extending upward from the surface being plowed. Specifically, the cutting edge  38  extends past the outer end  47  of the first blade  14 , curving into a rearwardly projecting side section  49  that is spaced from the vertical end. Thus, the side section  49  will rub against a curb and preventing wear from occurring on the outer end  47  of the first blade  14  on the left side of the snowplow  10 . Also, the flexible nature of the cutting edge  38 , enables this side section  49  to absorb some of the impact force resulting from striking a curb or other object and does not transfer that force through the first blade  14  into other components of the snowplow  10 . It should be noted that the outside edge  45  of the second blade  16  is similarly protected by the wrap-around end segment of the cutting edge  38 . 
       FIGS. 4 and 5  depict a second embodiment of a snowplow cutting edge  50  that comprises three separate pieces: elongated first and second segments  51  and  52  and a V-shaped center segment  54 . One of the first and second segments  51  or  52  is bolted or otherwise attached to the bottom portion of one of the two blades  14  and  16  in much the same manner as conventional cutting edges attached to existing blades. The V-shaped center edge segment  54  comprises a pair of walls  56  and  57  projecting at an angle from one another and terminating at a tapered edge that abuts the inside surface of two elongated edge segments  51  and  52 . That abutting relationship inhibits the material being plowed from passing between hose elongated sections. Preferably the walls  56  and  57  are formed by a single piece of material, such as polyurethane, plastic or a relatively hard rubber, but could be separate pieces in which case they could also be made of metal. The separate elongated first and second segments  51  and  52  may be made of the same material or metal. However, all the pieces of the cutting edge  50  will wear at the same rate if they are all made of the same material. 
     With specific reference to  FIG. 5 , the center edge segment  54  has a mounting bracket  58  or  59  extending from the inside surfaces of the each wall  56  or  57 , respectively. The mounting brackets  58  and  59  are attached by machine screws or other fasteners to the bottom edges of the first and second blades  14  and  16 , respectively, thereby securing the center edge segment  54  beneath the pivot frame  18  of the snowplow blade assembly  12 . The two walls  56  and  57  the center edge segment  54  is made of a single piece of material that is formed at an angle. This material is flexible so that the pivot frame can bend at the interface between the two walls when one or both of the two blades  14  and  16  pivots about the hinge  20 . 
     With reference to  FIG. 6  a variation of a three-piece cutting edge  60  has individual, elongated first and second segments  61  or  62  attached to the bottom portion of the two blades  14  and  16 . A separate V-shaped center edge segment  64  comprises has a pair of angled walls  65  and  66  located beneath the pivot frame  18  in an orientation identical to that of walls  56  and  57  in  FIGS. 4 and 5 . However, walls  65  and  66  are each formed by a linear array of relatively stiff bristles  68 , thus forming a brush beneath the pivot frame  18 . That brush may comprises several rows of bristles  68  one behind the other. Each bristle  68  may be a thin rod or ribbon of stiff plastic material, for example. The upper ends of the bristles are mounted in a bracket that is attached to the blades  14  and  16  in the same manner as the walls  56  and  57  of the center edge segment  54  in  FIG. 5 . 
     Referring to  FIG. 7 , another version of a cutting edge  70  according to the present invention, utilizes separate elongated first and second segments  72  and  74  that are bolted or otherwise attached to the bottom portions of the first and second blades  14  and  16  respectively. A center cutting edge segment in the form of a conical brush  76  is mounted beneath the pivot frame  18  of the blade assembly  12 . The conical brush  76  comprises a plurality of relatively stiff bristles  78  extending at an angle that projects outward from the pivot frame  18  to form the conical shape. Each bristle may comprise a thin rod or ribbon of stiff plastic material, for example. The brush may comprise a single circular array of bristles, or several concentric arrays, depending upon the stiffness of the bristles in resisting the material being plowed from passing between the two blades  14  and  16 . The conical brush  76  has increased durability and resistance to impact with obstructions as compared to a solid center edge. 
     The foregoing description was primarily directed to a preferred embodiment of the invention. Although some attention was given to various alternatives within the scope of the invention, it is anticipated that one skilled in the art will likely realize additional alternatives that are now apparent from disclosure of embodiments of the invention. Accordingly, the scope of the invention should be determined from the following claims and not limited by the above disclosure.

Summary:
A V-blade plow has adjustable first and second blades, each with an inner end that is rotatably connected to a pivot frame. The plow is provided with a cutting edge arrangement comprising first and second edge segments and a center edge segment there between. The first edge segment is removably attached to the first plow blade and projects downward below the bottom edge of the first plow blade. The second edge segment is removably attached to the second plow blade projecting below the bottom edge of the second plow blade. The center edge segment is mounted beneath the pivot frame and is attached to the first and second plow blades to prevent the material being plowed from passing beneath the pivot frame between the blades.