Abstract:
A steering device for an agricultural harvesting machine having steerable rear wheels. The rear wheels are mounted to a rear axle. The steering device comprises a pivot support mounted on the rear axle and a wheel carrier that is pivotally supported on the pivot support. The rear wheel is rotaively supported on the wheel carrier and defines a rotational axis. The wheel carrier is pivoted relative to the pivot support about a pivot axis for steering the vehicle. The pivot axis is inwardly inclined toward the longitudinal central plane of the harvesting machine and/or rearward with respect to the normal forward driving direction

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention is directed to a steering device for an agricultural harvesting machine, wherein the steering device comprises a pivot support and a wheel carrier that define a pivot axis that is inwardly inclined toward the longitudinal central plane of the harvesting machine and/or rearward with respect to the normal forward driving direction  
         BACKGROUND OF THE INVENTION  
         [0002]    Many types of self-propelled agricultural harvesting machines, for example combines and forage harvesters, are equipped with driven front wheels and steerable rear wheels. Since the width of the harvesting machines is subject to legal restrictions, the width of the tires on the rear wheels, as well as their pivoting range that defines the maneuverability, limits the available space between the rear wheels in which structural components of the harvesting machine could be accommodated. It is desirable in many instances to make this space as large as possible, for example, in order to install screens between the rear wheels of a combine harvester.  
           [0003]    U.S. Pat. No. 6,267,198 discloses an agricultural harvesting machine having steerable rear wheels. The pivot pin for the steerable rear wheels is located in front of the rotational axis of the rear wheel. Due to this measure, the largest portion of the wheel is situated behind the pivot axis. Sufficient space for the steering motion of this portion of the wheel is available behind the chassis of the harvesting machine. The front portion of the wheel which approaches the chassis when steering is significantly shorter than the rear portion, such that larger steering angles can be realized and the components of the harvesting machine that are situated between the rear wheels can be wider than in a steering arrangement in which the wheel is pivoted about a pivot axis that intersects the rotational axis of the wheel. However, the disclosed steering device requires higher steering torques due to the trailing relationship between the pivot axis and the rotational axis of the wheel.  
           [0004]    DE 197 49 195 C and U.S. Pat. No. 5,454,444 disclose harvesting machines in which the wheels of the front axles are steerable. The pivot axes, about which the front wheels are turned when steering are angled rearward. Due to the fundamentally different configuration, these publications do not inspire a person skilled in the art to improve the above-described steering device.  
         SUMMARY OF THE INVENTION  
         [0005]    It is an object of the present invention to provide an improved steering device for harvesting machines having steerable rear wheels.  
           [0006]    The harvesting machine has driven front wheels that are typically mounted on the chassis such that they cannot be steered. Viewed in the normal forward driving direction of the harvesting machine, a rear axle that carries steerable rear wheels that are arranged behind the front wheels. The rear wheels may either be driven or not driven. The rear wheels are respectively supported in a rotatable fashion on a wheel carrier, about which the wheels rotate when the harvesting machine is in motion. The wheel carriers are respectively coupled to pivot supports that are arranged on the rear axle. The wheel carrier is pivoted on the pivot support about a pivot axis when steering. The invention proposes that the pivot axis be inclined inward and/or rearward relative to the normal forward driving direction. If the pivot axis is inclined inward, an upper mounting point of the wheel carrier is preferably arranged on the pivot support farther inward than a corresponding lower mounting point (closer to the central longitudinal plane of the harvesting machine) relative to the horizontal direction transverse to the driving direction. Due to this provision, the upper side of the rear wheel is inclined outward when the wheel is turned from the straight ahead position. This means that additional space is available between the rear wheels. The pivot axis is alternatively or additionally inclined rearward, in such a manner that an upper mounting point of the wheel carrier is arranged on the pivot support farther to the rear than a corresponding lower mounting point, relative to the normal forward driving direction. This incline makes it possible to reduce the torques required to steer the harvesting machine.  
           [0007]    The invention makes it possible to lower the required steering torques and to enlarge the available space between the wheels. If the pivot support is offset forward, relative to the rotational axis of the wheel, in the forward driving direction, the steering torques are comparable to those required without this offset arrangement, and a self-stabilization of the steering device is also achieved.  
           [0008]    It is preferred to incline the rotational axis of the rear wheel downward, relative to a horizontal line, in its straight position, i.e., the rear wheel is cambered in order to achieve an additional self-stabilization of the steering device. This also results in an enlargement of the space available above the wheels in the intermediate space between them.  
           [0009]    The steering device according to the invention is particularly suitable for self-propelled harvesting machines such as combines, forage harvesters or self-propelled balers. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a side view of a harvesting machine with a steering device according to the invention.  
         [0011]    [0011]FIG. 2 is a perspective view of the steering device, viewed from the front.  
         [0012]    [0012]FIG. 3 is a front view of part of the steering device.  
         [0013]    [0013]FIG. 4 is a side view of part of the steering device. 
     
    
     DETAILED DESCRIPTION  
       [0014]    The harvesting machine  10  shown in FIG. 1 is a combine that is supported on driven front wheels  12  and steerable rear wheels  14 . The combine is provided with a driver&#39;s cabin  16  from which a driver operates the combine. During harvesting operations and when driving on roads, the harvesting machine  10  is propelled in the normal forward driving direction V that is defined by the viewing direction of the driver in the driver&#39;s cabin  16 . However, the harvesting machine can also be driven in reverse to position the vehicle. A grain tank  18  is located behind the driver&#39;s cabin  16 . The grain tank  18  is used to temporarily store accumulated crop material. The crop material is discharged from the grain tank  18  by an unloading auger  20 . The grain tank  18  is supported on a chassis  22 , within which the harvested material is separated into its large and small components by means of a threshing cylinder  24 , a threshing concave  26  and a beater  28 . Grain trapped in threshed crop material is released by the downstream straw walkers  30 . Grain and chaff falling from the threshing concave  26  and straw walkers  30  is deposited on a grain pan  32 . The grain pan  32  directs the grain and chaff to the cleaning system for separating the grain from the chaff. The cleaning system is provided with screens  34  through which the clean grain falls to the floor of the combine; and from which the chaff is blown out the back of the combine by cleaning fan  36 . The clean grain is conveyed from the floor to the grain tank by an elevator, not shown. The large crop components other than grain are dropped to the ground by the straw walkers  30 . The crop is harvested by a harvesting assembly, not shown, that directs the harvested crop to a feeder house  38 . The feeder house  38  in turn directs the harvested crop to the threshing assembly. In the following description, all directional indications such as front, rear, top and bottom are made with reference to the normal forward driving direction V.  
         [0015]    The driven front wheels  12  are conventionally arranged rigidly on the chassis  22 , by means of a spring suspension or, in case of a hillside combine, by an assembly that provides a mechanism for adjusting the height of the wheels  12 . However, the driven front wheels cannot be steered, so that their mounting requires no additional explanation. The rear wheels  14  are mounted on the chassis  22  by means of the steering device that is illustrated in FIGS.  2 - 4  and is identified by the reference symbol  40 . The steering device  40  comprises a rear axle  42  that extends transverse to the forward driving direction V and is coupled to a frame construction  46  by means of a pendulum suspension  44 . Another pendulum suspension  80  (FIG. 4) is situated above the central section of the axle  42  and serves to support the axle  42  on the chassis  22 . The pendulum suspensions  44  and  80  make it possible for the rear axle  42  to pivot about an axis  48  that extends in the forward driving direction V when the combine is driven over uneven terrain (or when operating a hillside combine with front wheels  12  of adjustable height on a sloping field). The rear axle  42  is arranged within and mounted on a crossbeam  50  that is connected to the pendulum suspension  44 .  
         [0016]    The two ends of the rear axle  42  respectively carry a yoke-shaped pivot support  52  that comprises an upper arm  54  and a lower arm  56  arranged beneath the upper arm  54 . A hollow member  58  of a wheel carrier  74  extends between the arms  54  and  56 , with said wheel carrier being connected to a hub  60  that carries a flange  62 . The flange  62  is mounted on the hollow member  58  by means of the hub  60  such that it is rotatable about its axis. The rim  64  of the right rear wheel  14  is mounted on the flange  62 . The axis of the flange  62  coincides with the rotational axis of the wheel  12 . The hollow member  58  of the wheel carrier  74  is supported on the lower arm  56  and on the upper arm  54  of the pivot support  52 . For this purpose, a steering pin  66 , which has the shape of a regular cylinder and is arranged coaxially with the opening of the hollow member  58  of the wheel carrier  74 , extends through the lower arm  56 , the opening of the hollow member  58  and the upper arm  54 . The steering pin  66  defines the pivot axis of the wheel carrier  74  relative to the pivot support  52 . The steering pin  66  may be joined to the hollow member  58  or the pivot support  52 .  
         [0017]    In order to provide a better overview, only the right pivot support  52  and the right wheel carrier  74 , relative to the forward driving direction, are shown in FIG. 2; the oppositely arranged complementary elements for receiving the left rear wheel  14  are realized in mirror-image fashion. A steering cylinder  68  that is linked by means of a rod  70  to a cantilevered bracket  72  connected to the hollow member  58  is arranged between the pendulum suspension  44  and the crossbeam  50 . The steering cylinder  68  pivots the wheel carrier  74 , relative to the pivot support  74 , about the pivot axis defined by the pivot pin  66  in order to achieve steering movement of the rear wheel  12 .  
         [0018]    [0018]FIG. 3 shows a front view of part of the steering device  40 . According to this figure, the pivot axis of the wheel carrier  74  on the pivot support  52  is not oriented in exactly the vertical direction, but rather extends at an angle  76  of approximately 10 degrees. The lower arm  56  consequently extends farther outward than does the upper arm  54 , such that the upper mounting point of the wheel carrier  74  on the pivot support  52  lies closer to the central longitudinal plane of the harvesting machine  10  than does the lower mounting point of the wheel carrier  74  on the pivot support  52 . In addition, the rotational axis of the wheel  14 , which is defined by the hub  60  and the flange  62 , does not extend horizontally and parallel to the axle  42 , but rather is angled downward at an angle  78  of approximately 10 degrees. In the straight position of the wheel that is illustrated in FIG. 3, the lowest point of the wheel  14  (contact point with the ground) is situated farther inward, i.e., closer to the central longitudinal plane of the harvesting machine, than is the upper region of the wheel  14 .  
         [0019]    [0019]FIG. 4 shows a side view of the steering device  40 . According to this figure, the steering pin  66  and consequently the pivot axis are additionally inclined rearward by an angle  82  of approximately 10 degrees. The mounting point of the hollow member  58  of the wheel carrier  74  on the lower arm  56  is arranged farther forward, relative to the forward driving direction V, than is the mounting point of the hollow member  58  on the upper arm  54 . The pivot axis consequently is inclined rearward in the plane that extends in the forward driving direction V. In addition, the two aforementioned mounting points of the wheel carrier  74  on the pivot support  52  are situated in front of the rotational axis of the wheel  14 , relative to the forward driving direction V, in order to enlarge the space available between the rear wheels  14  for structural elements of the harvesting machine  10  at a given steering radius (or vice versa). It would also be conceivable to reduce the forward offset of the pivot axis relative to the rotational axis of the wheel  14  such that in other embodiments only one (or none) of the mounting points of the wheel carrier on the pivot support would be situated in front of the rotational axis of the wheel  14 .  
         [0020]    The invention consequently proposes that the pivot axis be offset forward relative to the rotational axis of the rear wheel  14 , inclined rearward by an angle  82  (FIG. 4) and inclined inward by an angle  76  (FIG. 3). In connection with the camber of the wheels  14  by the angle  78  (FIG. 3), these three angles cause a self-stabilization of the steering device  40  and reduce the steering torques. The above-indicated angles merely represent values given as examples, and can be varied in accordance with respective requirements.  
         [0021]    Having described the illustrated 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.