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TECHNICAL FIELD 
   The present subject matter relates generally to a leveling system for equipment mounted to the front of a vehicle. More specifically, the subject matter relates to an automatic leveling system for reversing assembly equipment mounted to a vehicle, such as, for example, a snowplow. 
   BACKGROUND 
   The practice of removing snow from road surfaces and parking lots dates back many years, and is an ever increasing necessity today, as the number of miles of road increases. Snowplow equipment generally consists of the following six main components. 
   1. A blade to push snow to the side of the roadway or path. The blade usually has a wear bar bolted to its lower horizontal edge. 
   2. A table weldment to which the blade is attached. 
   3. An A-frame weldment to which the table is rotatably attached. 
   4. Linear actuators to rotate the table with respect to the A-frame, thus providing an automatic reversing assembly. 
   5. A means to attach the A-frame to the front of a motor vehicle. 
   6. A lift bar attached to the front of the motor vehicle to lift the snowplow assembly for transport. 
   The reversing assembly allows an operator to have the plow oriented in a straight position, discharge left position or discharge right position. In the straight position the plow blade is generally perpendicular to the direction of travel of the motor vehicle when viewed from above the vehicle. The straight position is also referred to as the bulldoze position. In the discharge left and discharge right positions, the plow blade is angled to the left or right, respectively, so as to move the snow to the left or right of the motor vehicle when the vehicle is moving in a forward direction. 
   In the typical arrangement, when the snowplow is lifted into a transport position for travel, the snowplow will tend to list to the side that it is angled. The problem is inherent in the geometry of the plow assembly. The center of gravity of the plow assembly moves towards the side of the vehicle to which the plow assembly is angled and causes the plow to drop to that side. Accordingly, the efficiency and the safety of the snowplowing assembly is negatively impacted. The negative effects include, but are not limited to the following. 
   1. The plow can list so far as to cause contact with the road surface and thereby damage the road surface or the plow. 
   2. The listing can also place the lower edge in the way of obstructions and cause the plow to “catch” on the obstructions causing damage to the plow and danger to the driver of the vehicle. 
   3. Most of these assemblies are carried with a chain or a cable that is slidably attached to the lift bar in such a way as to prevent efficient “reversing” of the plow while it is being carried in the transport position. Reversal in transport position causes significant stress to the chain or cable and the plow is subject to choppy and erratic movement. Consequently, the operator must set the plow down on the road surface to reverse it before raising the plow again for transport. 
   4. Listing of the plow to one side inherently causes the other side of the plow to rise. If the listing is severe, the plow can obstruct the driver&#39;s view. 
   5. Without a leveling device to hold the plow level, an operator can not carry the plow an inch or so off the ground while plowing in “soft conditions.” 
   Level lift systems exist; however, these level lift systems suffer from the following significant drawbacks. 
   1. The entire mechanism, excluding the lift chains, resides under the table and A-frame, putting it close to the road surface and subject to snow and ice buildup, which causes failure of the mechanism. 
   2. The mechanism includes two sliding chain hookups attached to or part of the front member of the table. The sliding mechanism is subject to binding if not properly and frequently lubricated and maintained. Binding causes failure to the mechanism. 
   3. Maintenance of the unit is difficult because the mechanism is located underneath the table. 
   4. The mechanism only works with a fixed length lift bar and cannot be simply adjusted to work with different lengths. Accordingly, in order to adjust the level, the lift arm must have some mode of adjustment. 
   Other level lift systems incorporate a single lift chain fixed at one end to the lift and at the other end to a framework welded to the table. Although this design allows the plow to settle into a level position under ideal conditions, it fails to secure the plow in a stable level position when debris builds up on either end of the plow. 
   SUMMARY 
   The present subject matter relates generally to a leveling system for equipment mounted to the front of a vehicle. More specifically, the subject matter relates to an automatic leveling system for equipment mounted to a vehicle such as a snowplow. 
   It is one of the principal objectives of the present invention to provide a leveling system that provides for level operation of the plow assembly at all times. 
   Another objective is to provide a leveling system having no sliding mechanisms that may be jammed by debris. 
   A further objective is to provide a leveling system that incorporates rotating hinges residing on the top of a table to keep the hinges away from road debris. 
   Yet another objective is to provide a leveling device rotatably attached to an A-frame, not slidably attached to a table front beam. 
   Still another objective is to provide a leveling device that does not require positioning bars to achieve the side-to-side motion necessary for leveling. 
   Another objective is to provide a leveling device that requires little to no maintenance to operate consistently over an extended period of time. 
   Moreover, it is an objective to provide a leveling device that may be adjusted to achieve level lifting for various lengths of lift beams without modifying the lift beam in any way and without using cutting torches and welders. 
   Additional objects, advantages and novel features of the examples will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following and the accompanying drawings or may be learned by production or operation of the examples. The objects and advantages of the concepts may be realized and attained by means of the methodologies, instrumentalities and combinations particularly pointed out in the appended claims. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     The drawing figures depict one or more implementations in accord with the present concepts, by way of example only, not by way of limitations. In the figures, like reference numerals refer to the same or similar elements. 
       FIG. 1A  is a plan view of a snowplow system. 
       FIG. 1B  is a side view of the snowplow system of  FIG. 1A . 
       FIG. 2  is a perspective view of a reversing assembly. 
       FIG. 3  is a perspective view of the reversing assembly of  FIG. 2  further including a leveling system. 
       FIG. 4  is a plan view of the reversing assembly and leveling system of  FIG. 3 , wherein the table is reversed to the discharge left position. 
       FIG. 5  is a plan view of the reversing assembly and leveling system of  FIG. 3 , wherein the table is in the bulldoze position. 
       FIG. 6  is plan view of the reversing assembly and leveling system of  FIG. 3 , wherein the table is reversed to the discharge right position. 
       FIG. 7  is a front side elevation of the front of the reversing assembly and leveling system of  FIG. 3  with the leveling assembly raised and in the discharge right position. 
       FIG. 8  is a front side elevation of the front of the reversing assembly and leveling system of  FIG. 3  with the leveling assembly raised and in the bulldoze position. 
       FIG. 9  is a side front side elevation of the front of the reversing assembly and leveling system of  FIG. 3  with the leveling assembly raised and in the discharge left position. 
   

   DETAILED DESCRIPTION 
   The leveling system of the present invention is described herein with respect to a typical snow removal assembly. However, the leveling system may be utilized with any reversing assembly, such as, for example, other snow removal assemblies, broom assemblies, scraper assemblies, snow blowers, paving equipment, etc. 
   A typical snow removal assembly including a snowplow  10  mounted to a vehicle  12  is shown in  FIGS. 1A and 1B . As shown in  FIGS. 1A and 1B , the snowplow  10  includes a moldboard  14 , a reversing table  16 , a frame  18  and a lift arm assembly  20 , including a lift arm  22  and linear lift arm actuator  24 . Note that the frame  18  is described below and shown as an A-frame  18 , however other frame sizes and shapes can be used as well. The snowplow  10  shown in  FIGS. 1A and 1B  is a typical snowplow  10 . The moldboard  14  is rotatably mounted to the reversing table  16 , which is in turn rotatably mounted to the A-frame  18 , which is hingedly mounted to the vehicle  12 . The moldboard  14 , reversing table  16  and A-frame  18  may be lifted for transportation by the lift arm assembly  20  attached to the vehicle  12 . The lift arm  22  is operated by the linear lift arm actuator  24 . The reversing table  16  is reversed, or rotated, on the A-frame  18  by a pair of linear table actuators  26 . The linear table actuators  26  allow the operator of the vehicle  12  to reverse the snowplow  10  between a left discharge, a bulldoze and a right discharge position as shown in  FIGS. 4–9  and described further herein. 
   The reversing table  16 , A-frame  18  and lift arm assembly  20  are shown in  FIG. 2 . The reversing table  16  includes a set of hinge ears  28  for mounting the moldboard  14  to the reversing table  16 , a front horizontal table beam  30 , a pair of side table members  32 , a pivot bushing  38 , a rear table member  40  and a pair of hinge bushings  42  for mounting the first end of each of the linear table actuators  26 . 
   As further shown in  FIG. 2 , the pivot bushing (not shown) of the reversing table  16  is rotatably attached to the A-frame  18  at an A-frame front bushing  44 . In the configuration shown in  FIG. 2 , the pivot bushing is positioned within the A-frame front bushing  44 . The A-frame  18  includes a pair of A-frame tube members  46 , an A-frame rear plate  48 , an A-frame top plate  50 , an A-frame hinge bushing  52  for mounting the second end of each of the linear table actuators  26  and an A-frame rear swivel bushing  54 . The reversing table  16  may rotate around an approximately vertical axis passing through the A-frame front bushing  44 . As a result, the linear table actuators  26  operate to rotate the reversing table  16  around the A-frame front bushing  44 , thereby rotating the snowplow  10  between the left discharge, the bulldoze and the right discharge positions, as shown in  FIGS. 4–9 . 
   As further shown in  FIG. 2 , the A-frame  18  is rotatably attached to a swivel bar  56  via the A-frame rear swivel bushing  54 . The swivel bar  56  includes a swivel bar main beam  58  and a pair of swivel bar hookup ears  60 . Thus, the A-frame  18  and reversing table  16  may rotate around an approximately horizontal axis passing through the A-frame rear-swivel bushing  54 . The swivel bar  56  is further hingedly connected to the vehicle  12  along a vehicle frame  62  via the pair of swivel bar hookup ears  60 , thereby allowing rotation of the swivel bar  56 , the A-frame  18  and the reversing table  16  with respect to the vehicle  12 . The swivel bar  56  and pair of swivel bar hookup ears  60  are merely one example of establishing freedom of rotation between the A-frame  18  and the vehicle  12 . Alternatively, freedom of rotation between the A-frame  18  and the vehicle  12  may be accomplished using a ball and socket assembly, a dog and loop assembly, or other hinging or rotating means. 
     FIG. 2  further illustrates the lift arm assembly  20  attached to the vehicle frame  62 . The lift arm assembly  20  includes a lift arm  22  hingedly attached to the vehicle frame  62  at a first end of the lift arm  22 . The lift arm  22  includes a lift arm hinge ear  66  near a second end of the lift arm  22 . A linear lift arm actuator  24  attaches the lift arm hinge ear  66  to the vehicle frame  62  such that the linear lift arm actuator  24  operates to rotate the lift arm  22  upwards and downwards to raise and lower the lift arm  22  with respect to the vehicle frame  62 . 
     FIG. 3  shows a leveling carriage assembly  70  for coupling the lift arm assembly  20  to the A-frame  18 . The leveling carriage assembly  70  includes a leveling carriage  72 , which may be rotatably attached to a leveling base plate  74  between a leveling carriage hinge hole, either  76   a ,  76   b  or  76   c , and a base plate hinge hole  78 , either  78   a ,  78   b  or  78   c . As shown, the attachment between the leveling base plate  74  and the A-frame  18  places the leveling carriage hinge holes  76   a ,  76   b  or  76   c , a fixed distance relative to the A-frame front bushing  44 . The leveling carriage assembly  70  further includes a pair of parallel bars  80 , a pair of parallel bar anchors  82  and a pair of lift chains  84  attached to the lift arm assembly  20  at a pair of lift chain slots  85 . The opposite ends of the pair of lift chains  84  are attached to the leveling carriage assembly  70 . It is important to note that equal lengths of the pair of lift chains  84  are securely anchored at both ends and are not slidable. The lift chains  84  shown in  FIG. 3  are attachment members for attaching the lift arm assembly  20  to the leveling carriage  70  and other types attachment members may be substituted in place of the lift chains  84 . Further, the lift arm assembly  20  is not required to be located above the leveling carriage assembly  70  and may be repositioned, such as, for example, below or to the side of the carriage assembly  70 . 
   In  FIG. 3 , the parallel bar anchors  82  are fixedly attached to the front horizontal table beam  30  at positions equidistant from the pivot point at the A-frame front bushing  44 , where the reversing table  16  is rotatably attached to the A-frame  18 . Although the pair of parallel bar anchors  82  are shown in  FIG. 3  to be welded or otherwise fixedly attached to the horizontal table beam  30  using parallel bar anchors  82 , the pair of parallel bars  80  may alternatively be attached to the reversing table  16  itself without the need for the parallel bar anchors  82 , weldings or castings. The leveling base plate  74  is fixedly attached to the A-frame  18  and the leveling carriage  72  is rotatably attached to the leveling base plate  74 . Further, the leveling carriage  72  is rotatably attached to the pair of parallel bars  80  at a pair of parallel bar hinging holes, either  92   a ,  92   b  or  92   c , located at positions equidistant from the center of the leveling carriage  72 , as well as equidistant from the parallel bar anchors  82 . The pair of parallel bars  80  are also rotatably attached to the leveling carriage  72  through a pair of leveling carriage connecting holes, either  86   a ,  86   b  or  86   c.    
   As shown in  FIG. 3 , the leveling base plate  74  and the parallel bars  80  include a series of base plate hinge holes  78   a ,  78   b  or  78   c  and a series of parallel bar hinging holes  92   a ,  92   b  or  92   c , respectively. By varying which of the series of base-plate hinge holes and the series of parallel bar hinging holes are utilized, the degree of motion of the leveling carriage  72  around the A-frame front bushing  44  may be varied. The greatest degree of motion of the leveling carriage  72  is accomplished by using the base plate hinge hole  78   a  and the parallel bar hinging holes  92   a  located closest to the vehicle  12 . Additional base plate hinge holes and bar hinging holes may be provided and utilized to further vary the degree of motion of the leveling carriage  72 . Further, the series of plate hinge holes  78   a ,  78   b  and  78   c  and the series of parallel bar hinging holes  92   a ,  92   b  and  92   c  allows the leveling carriage  72  to be adaptable to reversing tables  16 , A-frames  18 , lift arm assemblies  20  of various sizes. 
   The equal lengths of the pair of lift chains  84  and the equidistant positioning of both ends of the pair of parallel bars  80  from the A-frame front bushing  44  ensure the front horizontal table beam  30  will always be maintained parallel to ground level. Based on the geometry between the lift chains  84 , the parallel bars  80  and the A-frame front bushing  44 , when the linear table actuators  26  cause the reversing table  16  to rotate around the A-frame front bushing  44 , the parallel bars  80  act upon the leveling carriage  72  such that the front edge of the leveling carriage  72 , to which the lift chains  84  are attached, is maintained parallel to the front horizontal table beam  30 . For example, when the snowplow  10  is reversed to the discharge right position as shown in  FIGS. 6 and 7 , a first hinge point  88  at which the left lift chain  84  attaches to the leveling carriage  72  moves closer to the A-frame front bushing  44  and a second hinge point  90  at which the right lift chain  84  attaches to the leveling carriage  72  moves further from the A-frame front bushing  44 ; however, the fixed length of the lift chains  80  ensures the leveling carriage  72  and the horizontal table beam  30  remain level, i.e., parallel to the ground. Further, movement of the lift arm  22  acts equally along both lift chains  84  thereby causing the horizontal table beam  30  to remain parallel to the ground at all times, including when the lift arm  22  is raised and lowered. Similarly, the horizontal table beam  30  remains parallel to the ground when the snowplow  10  is reversed to bulldoze position, as shown in  FIGS. 5 and 8 , the discharge left position as shown in  FIGS. 4 and 9  or at any other position between the discharge left and discharge right positions. 
   It should be noted that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the present invention and without diminishing its attendant advantages. It is, therefore, intended that such changes and modifications be covered by the appended claims.

Summary:
A leveling system designed for use with a vehicle having a reversing assembly including a table, an A-frame and a swivel member. The reversing assembly may be rotatably mounted to the vehicle with a lifting mechanism designed to elevate the reversing assembly for transportation when not in use. The leveling system is rotatably mounted to the A-frame and stabilized with parallel bars which function to achieve leveling of the assembly. Two chains of equal length are fixed to opposite ends of the leveling system, each at an equal distance outward from the center of the system and each connected at its other end to the lifting member of the vehicle. The chains aid in the lifting and leveling of the system.