Abstract:
An improved grain cart is able to hold more grain with reduced field compaction to derive greater yield from a farm field. The grain cart includes a frame which supports a grain hopper and is supported by a plurality of wheels, some of which are steerable so the cart also has an acceptable turning radius.

Description:
BACKGROUND OF THE INVENTION 
     I. Field of the Invention 
     The present invention relates to grain carts used in harvesting grain crops. More specifically, the present invention relates to improvements to grain carts to increase the capacity of the grain cart and, at the same time, reduce compaction of the soil of the farm field in which the grain cart is used. 
     II. Description of the Prior Art 
     One of the factors that affect the yield of a farm field is the degree to which the soil in the field is compacted. The higher the degree of compaction, the lower the yield. The use of heavy farm equipment in a farm field can cause such compaction resulting in an adverse impact on the yield of the field. 
     A study was recently performed at Kansas State University relating to the effect of compaction resulting from farm equipment traversing a field. The results of the study suggests that if the farm equipment applies pressure to the soil in excess of 18 pounds per square inch, there is an adverse impact on the field&#39;s yield of up to 10% the next year. 
     Yield is, of course, only one factor that can be used in evaluating the efficiency of a farm operation. Another significant factor is the time it takes to plant a field, treat the field, and harvest the crop. In the past 50 years, the size and weight of farm equipment has grown significantly. Ideally, such equipment will be designed not only to reduce the time it takes to plant, treat or harvest a field, but also to reduce compaction of the field. 
     One important piece of equipment used in harvesting grain is the grain cart. Many grain carts made today include a single axle and a pair of wheels. These carts are typically designed to hold 500 to 800 bushels of grain. Other grain carts include a single axle and four wheels mounted to the axle. These carts are designed to hold up to 975 bushels of grain. There are two problems with such grain carts. First, they do not have a large enough capacity. Second, depending upon the load carried by the cart and the wheel size, the pressure applied by the cart to the field can be in the range of 25 pounds per square inch. This pressure exceeds that typical of tractors and various other equipment. The compaction created by such pressure is certainly great enough to adversely effect field yield. 
     SUMMARY OF THE INVENTION 
     The present invention provides a grain cart with an increased hauling capacity. At the same time, the grain cart of the present invention is designed to reduce the degree of compaction of the field by reducing the pressure applied by the cart to the field. Carts incorporating the present invention can have a capacity of up to 1500 bushels, and thus hold in excess of 50% more grain than prior art carts. At the same time, carts incorporating the present invention provide a maximum pressure to the field in the range of 13 to 15 pounds per square inch. Thus, carts of the present invention provide less compaction force than a typical tractor and less than the 18 pounds per square inch threshold referenced in the Kansas State University study. 
     The benefits of the present invention discussed above result from the use of either a tandem or tridem axle arrangement. In the tandem axle arrangement, the weight is distributed over two axles and four tires. In the tridem axle arrangement, the weight is distributed over three axles and six tires. In the tandem axle arrangement, the wheels on the back axle pivot so as to be steerable. The wheels on the front axle are not steerable. In the tridem axle arrangement, the wheels on both the front and back axles are steerable and the wheels on the center axle are not steerable. These arrangements allow the cart to have a turning radius approaching that of a single axle cart without the risk of damaging the axles, hubs, wheels and tires while turning. The steerable wheels steer in a controlled fashion. In one embodiment, this steering effect is the result of ground pressure. In another embodiment, a hydraulic power steering system is provided. 
    
    
     Other objects and advantages of the invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings which set forth by way of illustration certain embodiments of the invention. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a tridem grain cart built in accordance with the present invention. 
     FIG. 2 is a perspective view of the tridem grain cart of FIG. 1 with the grain hopper removed to reveal the frame assembly of the grain cart. 
     FIG. 3 is a perspective view showing an axle and wheel assembly of the type used to mount the front and back tires to the frame of the grain cart of FIG.  1 . 
     FIG. 4 is a diagram used to hydraulically control the steering of the back wheels or the front and back wheels of the grain carts of the two embodiments shown in the figures. 
     FIG. 5 is a side view of a tandem grain cart built in accordance with the present invention. 
     FIG. 6 is a front view of the grain cart shown in FIG.  5 . 
     FIG. 7 is a side view of the grain cart shown in FIG. 5 with the grain hopper removed to better show the frame of said grain cart. 
     FIG. 8 is a top view of the frame of the grain cart shown in FIG.  5 . 
     FIG. 9 is a top view of the hub assembly shown at the bottom of FIG.  8 . 
     FIG. 10 is a side view of the hub assembly shown in FIG. 9 with the tires and wheels removed. 
     FIG. 11 is an exploded view of the axel holding assembly. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Grain carts made in accordance with the present invention all have various features in common. The first such feature is the hopper  10 . As shown in FIG. 1, the hopper  10  has a front wall  12 , a back wall  14 , a pair of sloped side walls  16  and  18 , and an open top. The cart is designed so that grain is deposited through the open top and flows toward the bottom. 
     A second feature common to each of the embodiments is a discharge auger assembly  20 . A first auger (not shown) runs the length of the hopper  10  and carries the grain to a second auger  22  which is used to direct and carry the grain to the desired location during the unloading of grain from the hopper  10 . Also located within the hopper  10  is a screen  24  covering the bottom of the hopper  10 . Screen  24  serves at least two functions. It separates large debris from the grain. It also guards the auger to prevent injury. 
     The hopper  10  is mounted above a frame  30 . The frame  30  shown in FIG. 2 includes a pair of longitudinal support members  32  and  34  which define first and second sides of the frame  30 . Extending between the support members  32  and  34  are a plurality of cross members  36 . One end of each cross member  36  is welded to longitudinal support member  32 . The other end is welded to longitudinal support member  34 . Two triangularly shaped gussets  38  and  39  help to secure each cross member  36  to the longitudinal support members  32  and  34  and strengthen the frame  30 . 
     In each embodiment of the invention, a tongue  40  projects from the front of the frame  30 . The tongue  40  is pivotally attached to each of the longitudinal support members  32  and  34  of the frame  30  by a pair of links  42  and  43 . The tongue is used to hitch the grain cart to a tractor or other powered vehicle in a conventional manner. 
     In the tridem embodiment of the invention shown in FIGS. 1-4 three transverse axle support members  50 ,  52  and  53  are positioned below the frame  30 . The transverse support members  50 ,  52  and  53  are each long enough to extend beyond the longitudinal support members  32  and  34 . The manner in which each of the transverse axle support members  50 ,  52  and  53  is pivotally secured to the frame  30  will now be described. 
     As shown in FIG. 2, axle support member  50  has two pairs of mounting plates  60  projecting in a forward direction. The first pair of mounting plates  60  is positioned below the longitudinal support member  32 . The second pair of mounting plates  60  is positioned below the longitudinal support member  34 . Each longitudinal support member  32  and  34  has a pair of triangularly shaped brackets  62  extending downwardly at a position in front of the axle support member  50 . Extending between each pair of mounting plates  60  and each pair of triangularly shaped brackets  62  are a pair of links  64  and  66 . One end of each link  64  and  66  is positioned between and pivotally secured to the first pair of mounting plates  60 . The other end of each link  64  and  66  is positioned between and pivotally secured to the pair of triangularly shaped brackets  62  projecting downwardly from longitudinal support member  32 . Likewise, a link  64  and a link  66  are pivotally joined at their opposite ends to the second pair of mounting plates  60  and the triangularly shaped brackets  62  extending downwardly from longitudinal support member  34 . In this fashion, the mounting plates  60 , triangularly shaped brackets  62  and the links  64  and  66  cooperate to pivotally secure the axle support member  50  to each of the longitudinal support members  32  and  34 . This same technique is used to pivotally join the other two axle support members  52  and  53  to the longitudinal support members  32  and  34 . 
     Those skilled in the art will immediately recognize that a grain cart must be able to traverse rough terrain. Therefore, it is desirable to buffer the effect traversing the rough terrain would have on the cart and its load. Doing so vastly improves the stability and durability of the grain cart. In the present invention, these advantages are achieved in the following manner. Two hydraulic dampeners  70  and  72  dampen the movement of the frame relative to each axle support member  50 ,  52 , and  53 . For example, hydraulic dampener  70  is coupled to the axle support member  50  by a dampener bracket (not shown) and the other end of the hydraulic dampener  70  is coupled to longitudinal support member  32  by a pair of dampener arms  74  and  75 . Similarly, one end of hydraulic dampener  72  is coupled to the axle support member  50  by a dampener bracket and the other end of hydraulic dampener  72  is coupled to longitudinal support member  34  by dampener arms  76  and  77 . 
     As mentioned above, in the tridem embodiment shown in the drawings, the wheels mounted to axle support members  50  and  53  are steerable while the wheels mounted to axle support member  52  are not. More specifically, axle support member  52  has a stub axle  80  fixed to and projecting from each of its opposite ends. The stub axles  80  each include a hub  82 . A wheel and tire are mounted to each of the hubs in a standard fashion. 
     FIG. 3 shows the manner in which a stub axle  80  is mounted to one of the axle support members  50  or  53  so that the wheels are steerable. As shown in FIG. 3, the mounting assembly  90  includes a stub axle  80  joined to the end of the axle support member  50  by a hinge assembly  94 . Mounted to the stub axle  80  in a conventional fashion is the wheel hub  82 . Given this arrangement, the stub axle  80  and hub  82  can partially revolve around the hinge assembly  94  to enable the wheel and tire mounted to the hub  82  to steer. To control the steering motion of the steerable stub axle  80  and wheel hub  82 , a hydraulic cylinder  95  is provided. One end of the hydraulic cylinder  95  is coupled to the axle support member  50  by a first bracket  96  and pin  97 . The other end of the hydraulic cylinder is coupled to the steerable stub axle  92  by a second bracket  98  under pin  99 . Hydraulic cylinder  95  precludes erratic over-steering of the wheel hub  80 . 
     FIGS. 5 through 10 show a tandem version of the invention. FIGS. 5 and 6 show the hopper  10 , the discharge auger assembly  20 , a frame  30 , and a tongue  40 . The hopper  10 , of course, is positioned above and mounted to the frame  30 . 
     In the tandem version of the grain cart, there are four tires mounted to four wheels. Two of the wheels are positioned on one side of the frame  30 . The other two wheels are positioned on the opposite side of the frame  30 . The back wheels are designed to be steerable while the front wheels are not. 
     The manner in which the wheels are coupled to the frame  30  is best shown in FIGS. 8-10. As shown in FIG. 8, a cylindrical beam  100  extends in a transverse direction beneath the frame  30  and is coupled to the frame  30  by a plurality of bearings  102 . Some of the bearings  102  are held in position by gussets  103 . Secured to each end of the cylindrical beam  100  is an oscillating axle support member  104 . The oscillating axle support member  104  can rotate about an axis definded by the cylindrical beam  100 . A stub axle  80  is secured to the opposite ends of the oscillating axle support member  104 . The stub axle  80  secured to the front end of the axle support member is secured in a fixed fashion. The stub axle  80  has a hub  82 . The wheel is secured to the hub  82  in a standard fashion. The stub axle  80  secured to the back end of the axle support member is secured in a pivotal, steerable fashion by a hinge assembly  94 . To provide rigidity a gusset  106  can be provided to help secure the stub axels  80  to the oscillating arm  104 . 
     The manner in which the steerable wheels are mounted to the back of the oscillating axle support  104  is slightly more complex. First, a mounting plate  110  is secured to the oscillating arm  104 . A gusset  112  can be provided to strength the connection between the oscillating arm  104  and the mounting plate  110 . The mounting plate  110  includes the collars  114 . A steerable stub axle  80  having a collar  118  of its own is secured to pin  120  of mounting plate  110  by hinge  94 . Given this configuration, the collars  114  and  118  and the pin  120  act as a hinge so that the steerable stub axle  80  can revolve about the axis of the pin  120  used to join the mounting plate&#39;s collar  114  to the steerable stub axle&#39;s collar  118 . The tires are mounted to the wheels in a standard fashion. Likewise, the wheels are mounted to the hubs (not shown) associated with the steerable stub axles  80  in a standard fashion. 
     Steering of the front and back wheels of the tridem embodiment and the back wheels of the tandem embodiment can be non-powered or hydraulically powered. FIG. 4 shows a hydraulic circuit for the steerable wheels of the invention. 
     To control or buffer the steering of the steerable axles, the frame  30  has a first lug  130  and the steerable axle has a second lug  132 . A hydraulic cylinder  95  extends between the two lugs  130  and  132  to control the manner in which the steerable stub axle  80  revolves around the axis of the pin  120 . While not shown, a shock absorber can also be positioned between the frame and oscillating axle support arm to limit or control the motion of the oscillating axle support arm. 
     FIG. 4 shows a hydraulic system  200  having hydraulic fluid used in the steering system. For a six wheel cart the front and rear wheels use the hydraulic system, For a four wheel cart only the rear wheels use the system. Hydraulic line  210  leads form the hydraulic system  200  to the hydraulic cylinders  95 . When the grain cart turns the force of the ground exerted on one wheel will pivot the wheel with respect to the frame  30  by an angle related to the tightness of the turn. The turning wheels will pivot relative to the frame  30  and the hydraulic cylinders  95  on the left and right sides will move in opposite directions, with one piston extending and the other contracting. With hydraulic linkage of the wheels as shown in FIG. 4 the wheels will pivot at about the same time to about the same angle to facilitate the turn. The hydraulic lines  220  and  230  are attached to the opposite sides of the hydraulic piston  95  for extending and retracting the piston rod. When the left wheel begins to turn and contracts the piston arm length, hydraulic fluid will flow in line  230  from the left hydraulic piston to the corresponding chamber on the right hydraulic piston tending to turn both wheels to the same angle during the turn. Similarly the hydraulic fluid from the right hydraulic cylinder will be forced into the corresponding chamber of the left hydraulic cylinder in contracting hydraulic line  220  to balance the wheels so that they pivot by the same angle. A damping force for the turns can be provided by an orifice in the lines  220  and  230 . Other damping forces may be provided by valves or other means well known in the art. 
     With a tandem cart only two wheels have the hydraulic system for pivoting the wheels during a turn. For a tridem cart the foremost and rearmost wheels are hydraulically linked as shown in FIG.  4 . with the front wheels hydraulically linked to each other and the rear wheels hydraulically linked to each other. 
     With a power assist the wheels can be steered hydraulically, as in any power steering system, which may be needed for heavily loaded large carts. In the power steering embodiment a hydraulic power steering system  270  can be inserted in the hydraulic system  200  such that with the proper valving and control systems, the power steering will assist in pivoting the wheels of the cart to the proper angle for turning. 
     Many different embodiments of the hydraulics may be utilized for powered or non-powered steering. The embodiments shown are for illustration of the principle only and not the design of the system. Further the front wheels may use power steering and the rear wheels may have non-powered steering or visa versa. 
     The hydraulic system  200  can be connected to the tractor hydraulic system or derive its power from the motion of the trailer or other sources. 
     Further the power steering system  270  need not be a hydraulic system. The power steering can be mechanical, electrical or some hybrid system providing power assistance to the wheels for turning them. 
     Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.