Abstract:
An implement wheel assembly includes two individual wheel arms tied together by a linkage that pivots about a fore-and-aft extending axis at a location above the wheels and generally above the plane of the implement frame. The linkage constrains the wheel arms to pivot in opposite vertical directions as the implement moves over irregular ground surfaces to improve weight distribution on the wheels. Spring structure may be interposed between the ends of a pivoting linkage and the individual wheel arms to lower frame impact forces. The structure allows two wheels to be placed side-by-side with their axes generally aligned and reduces under-frame hardware to improve crop and soil and trash flow.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to wheel assemblies for ground working implements and, more specifically, to such assemblies which include a walking beam support arrangement. 
       BACKGROUND OF THE INVENTION 
       [0002]    Implement wheel assemblies often include a walking beam arrangement to allow relative vertical movement of two fore-and-aft offset wheels as the implement moves over irregular ground surfaces. Opposite ends of a fore-and-aft extending walking beam support the wheels, and the central portion of the beam is pivotally connected for rocking about a pivot location in line with the wheels to maintain a generally equal load on each of the wheels. Such an arrangement, although adequate for many implement configurations, can present space problems for some applications such as those requiring high crop clearance tires for row crop applications or for implements which are used to sidedress material. Currently, space-consuming larger diameter tires provide the necessary ground offset. Also, as the implements increase in size, the support structure for the increased weight and loads also has to be made larger and becomes more expensive. 
       SUMMARY OF THE INVENTION 
       [0003]    To provide proper weight transfer without sacrificing crop clearance for row crop applications, two individual wheel arms are tied together by a linkage that pivots about a fore-and-aft extending axis at a location above the wheels and generally in line with a portion of the implement frame. The linkage assures a balance of weight transfer to the two transversely spaced wheels so that a single wheel is not overloaded. Spring members may be interposed between the ends of the pivoting linkage and the individual wheel arms to lower frame impact forces and reduce the size and weight of the frame structure. The structure allows two wheels to be placed side-by-side in weight-sharing relationship. An above-frame mounting arrangement reduces under-frame hardware and crop and soil flow impedance. Tools such as fertilizer openers may be advantageously arranged under the frame forwardly of the wheels, and the wheel support arrangement facilitates sufficient under-frame clearance for sidedressing fertilizer in tall crops. 
         [0004]    These and other objects, features and advantages of the present invention will become apparent from the description which follows taken in view of the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a rear perspective view of a portion of an agricultural implement with a main frame supported above the ground by wheel assemblies. 
           [0006]      FIG. 2  is an enlarged rear perspective view of one of the pivotal support arrangements for a wheel assembly of  FIG. 1 . 
           [0007]      FIG. 3  is an enlarged side view the pivotal support arrangement of  FIG. 2 . 
           [0008]      FIG. 4  is a view similar to  FIG. 2  but showing an alternate embodiment of a pivotal support arrangement having cushioning structure. 
           [0009]      FIG. 5  is a rear perspective view of the bracket for the pivotal support arrangement of  FIGS. 2 and 4 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0010]    Referring to  FIG. 1 , therein is shown a portion of an agricultural implement  10  having a main frame  12  with a generally rectangular center section  12   c  with a rear transversely extending frame member  12   r  supported for forward movement F over the ground by forward wheel assemblies  14  and  16  and aft wheel assemblies  18 . The lowermost portions of the frame  12  lie generally along a horizontal plane P ( FIG. 2 ). Earthworking tools  20  depend from the frame  12  and extend downwardly and rearwardly from central rockshaft structure  22  and from forward rockshaft structure  23  located ahead of the wheel structures  18 . 
         [0011]    As shown, the implement  10  is a high-speed nutrient applicator for applying chemicals such as anhydrous ammonia (NH 3 ) to the soil adjacent growing crops. The tools  20  each include a disk opener assembly  24  to open a slit in the soil and direct the chemical deep into the slit, and closing wheel structure  26  to seal the chemical within the slit. The implement  10  can operate in tall crops such as corn to sidedress NH 3 , and therefore sufficient under-frame clearance is necessary to prevent damage to plants. Lift structure  30  rotates the rockshaft structures  22  and  23  about an axis transverse to the forward direction F to move the tools  20  downwardly into earthworking positions and to raise the tools from the ground for transport. The implement  10  includes folding wing sections  32 ,  34  and  36  which are movable upwardly and inwardly over the center section  12   c  of the main frame  12  to a transport position (not shown). In the transport position, the weight of the implement  10  is carried by the wheel assemblies  18  and by a hitch  38  connected to a towing vehicle (not shown). 
         [0012]    Referring to  FIG. 2 , the wheel assemblies  18  include wheel bracket structure  40  bolted or otherwise fixed to the rear frame member  12   r  and pivotally supporting leading or upper ends of wheel arms  42  and  44  for rocking about wheel arm axes  42   a  and  44   a . The wheel arms  42  and  44  have lower or trailing ends supporting a pair of generally identical transversely spaced wheels  18   w  having rotational axes  18   a . On level surfaces, the wheels  18   w  are side by side with the axes  18   a  generally coextensive. Linking structure  48  operably connects the wheel arms  42  and  44  for constraining the wheel arms to move generally in opposite vertical directions as the frame passes over the irregular surfaces to help equally distribute loads on the wheels  18   w.    
         [0013]    The linking structure  48  includes a transversely extending beam or connecting member  50  pivotally connected to the frame member  12   r  for rocking about a fore-and-aft extending axis  50   a  having an upward extending component in the rearward direction (see  FIG. 3 ). Opposite ends of the member  50  are connected by links or upright members  52  and  54  to the wheel arms  42  and  44 , respectively, at locations on the wheel arms offset from the pivotal axes  42   a  and  44   a  so that as one of the wheels  18   w  moves downwardly over uneven terrain, the linking structure  48  constrains the opposite wheel  18   w  to move upwardly to evenly distribute loading between the two wheels  18   w.    
         [0014]    The bracket  40  is shown as a single casting or weldment ( FIG. 5 ) and includes a transversely extending L-shaped attaching portion  60  having an upright apertured rear wall or leg  62  adapted for positioning against the rear wall of the rear frame member  12   r . A horizontally disposed leg  64  abuts the bottom of the rear frame member and extends forwardly to an apertured front wall  66  that embraces the front wall of the frame member  12   r . Upper bolts  68  ( FIGS. 2 and 3 ) extend through the rear frame member  12   r  and apertures in the rear wall  62 . Lower bolts  70  extend through apertures in the rear wall  62  and the front wall  66 . The bolts  68  and  70  firmly secure the bracket  40  to the frame  12 . Pivot brackets or wheel arm supports  72  and  74  depend from opposite ends of the bracket  40 , and a beam pivot bracket  78  extends rearwardly and upwardly from the rear wall  62  and the bottom leg  64 . 
         [0015]    The wheel arms  42  and  44  are similar in construction and include spaced side plates  80  having upper forward ends connected by pivot pins  82  and  84  to bushings  86  and  88  centrally located on the pivot brackets  72  and  74  below the rear frame member  12   r . The plates  80  extend rearwardly from the pivot pin locations and are joined by a transversely extending connecting member  90  ( FIG. 2 ) located behind the rear frame member  12   r . An extension arm  92  fixed to the connecting member  90  extends upwardly and rearwardly from the plates  80  to an aft end pivotally connected to the lower portion of the corresponding upright link  52  or  54 . Transversely extending pivot pins  96  and  98  extend through the arms  92  and through the lower portions of the respective links  52  and  54 . 
         [0016]    The connecting member  50  includes first and second fore-and-aft spaced plates  100  pivotally connected to the frame  12  by a pin  102  extending though bushings  104  and  106  in the pivot bracket  78 . The upper ends of the upright links  52  and  54  extend between the plates  100  and are pivotally connected to the ends of the connecting member  50  by fore-and-aft extending pins  112  and  114 . To provide necessary link freedom of motion as the member  50  pivots and as the wheels  18   w  pivot in opposite vertical directions about the respective arm pivotal axes  42   a  and  44   a , additional pivotal connections are provided at link locations  116  and  118  by a transversely extending upper pivot pin  122  and a lower fore-and-aft extending pivot pin  124  to define universal joint connections between the opposite ends of the connecting member  50  and the respective wheel arms  42  and  44 . The pivotal connections provide multiple degrees of freedom of movement between the wheel arms and the connecting member  50 . 
         [0017]    The above-described linking of the connecting member  50  to the wheel arms  42  and  44  provides some load transfer from the wheels  18   w  to the frame  12  at a location rearwardly of the wheel arm pivotal axes  42   a  and  44   a  to reduce wheel arm pivot loads. The pivotal axis  50   a  of the pin  102  is approximately perpendicular to a plane passing through the wheel axes  18   a  and the wheel arm pivotal axes  42   a  and  44   a  when the wheels  18   w  are side-by-side on a level surface. 
         [0018]    In the embodiment shown in  FIG. 4 , links  52 ′ and  54 ′ include cushioning members  152  and  154 . As shown, the cushioning members  152  and  154  are elastomeric blocks which absorb shock impacts and reduce loading on the wheel bracket structure  40 ′, although other cushioning or resilient members such as springs, air bags, hydraulic cylinders or accumulation devices could also be used. A single cushioning member could also be used instead of two or more members. 
         [0019]    Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.