Abstract:
A method and system for controlling distribution of crop material to a cleaning sieve of an agricultural combine, for reducing grain loss, including while the combine is tilted sidewardly relative to horizontal, involving controlling the angular orientation of a distributor disposed between a threshing system of the combine and the sieve, for distributing a mat of the crop material onto the sieve evenly across an extent thereof. The angular orientation of the distributor can be set in advance of tilting of the combine, to adjust for a variety of conditions, including uneven outputting of the crop material from the threshing system, and the set orientation can be automatically maintained or actively adjusted to control a desired operating parameter such as grain loss, even as the combine is variously tilted and the angular orientation of the sieve relative to the combine is independently adjusted to maintain the sieve horizontal.

Description:
[0001]    This application claims the benefit of U.S. Provisional Application No. 60/901,228, filed Feb. 13, 2007. 
     
    
     TECHNICAL FIELD 
       [0002]    This invention relates generally to distribution leveling for a combine, and more particularly, to a system and method for leveling or evening the distribution of threshed crops being delivered from the threshing system to the cleaning system of a combine, including when the receiving component of the cleaning system is tilted to accommodate uneven terrain, such as when the combine is traveling along a hillside. 
       BACKGROUND ART 
       [0003]    U.S. Provisional Application No. 60/901,228, filed Feb. 13, 2007, is incorporated herein by reference in its entirety. 
         [0004]    Combines are used all over the world to harvest a good many different crops. A typical combine configuration utilizes a separation or threshing system including one or more rotors partially or fully surrounded by a perforated concave, wherein threshed crop material will fall through the perforations of the concave enroute to a cleaning system operable for separating grain of the threshed crop material from material other than grain (MOG). Often, the region of discharge of this threshed crop material from the separating system is not directly or completely above the cleaning system, and a pan or pans, conveyors, or the like are used for conveying and directing the crop material to the cleaning system. It has been observed that not all types of crops will separate in the same manner, and/or exit the threshing system evenly, and, as a result, the cleaning system may be loaded unevenly, even if an intermediate pan or conveyor system is used between the threshing and cleaning systems. For instance, when viewing a separating system from the front or rear, the threshed crop material may be observed to exit the threshing system more heavily on one side or the other. In other instances, the crop material may exit more or less evenly. This characteristic can also vary for an individual crop, and within a field and during a single crop harvesting session, for a variety of reasons, such as, but not limited to, variances in crop population, yield, moisture content and maturity level. A significant problem that can result from uneven distribution of crop material to the cleaning system is increased grain loss resulting from overloading of regions of the cleaning system sieve or sieves. 
         [0005]    A variety of devices and systems have long been used for addressing uneven loading problems, but primarily in the context of those arising from operation of a combine on a side slope. Reference in this regard, Hyman et al., U.S. Pat. No. 4,557,276, issued Dec. 10, 1985 to Sperry Corp. which discloses a four-way leveling mechanism for a combine cleaning apparatus. Reference also in this regard with respect to a grain pan disposed between the threshing system and the cleaning system, Hagerer et al., U.S. Pat. No. 4,875,889, issued Oct. 24, 1989 to Deere &amp; Co. which discloses use of adjustable vanes for compensating for uneven material distribution over a grain pan for delivery of threshed crop material to a cleaning system; and Grobler European Patent No. EP0212183 B1 published Mar. 4, 1987, which discloses a combine harvester including a preparation floor intermediate the threshing system and an upper screen of a cleaning system, wherein the preparation floor and screen are independently pivotable laterally. 
         [0006]    An observed shortcoming of the apparatus of U.S. Pat. Nos. 4,557,276 and 4,875,889, is that when used alone, such that system is leveled relative to a side slope on which the combine is located, crop material distribution on one or more regions of the sieve may still be concentrated or heavier, as a function of the crop material flow from the threshing system, and significant grain loss can still occur. The independently tiltable, two section preparation floor of European Patent No. EP0212183 B1, because of the split between the two sections, may not allow adequate distribution of crop material over the entire width thereof, particularly if crop deposition thereon from the threshing system is significantly greater on one of the sections, and if the preparation floor is used for adjusting only for a side hill condition, it may not remedy heavier crop material deposition on one side thereof at all. 
         [0007]    In light of the capabilities and limitations of the apparatus discussed above for distributing crop material delivery to a cleaning system of a combine, what is sought is a system and method which allows optimizing this capability for accommodating both uneven threshing system output, and uneven terrain, particularly side slope conditions. 
       SUMMARY OF THE INVENTION 
       [0008]    What is disclosed is a system and method for distributing crop material to a cleaning system of a combine, which allows optimizing the capability for accommodating both uneven threshing system output, and uneven terrain, particularly side slope conditions. 
         [0009]    According to a preferred aspect of the invention, the method and system is operable for controlling distribution of crop material to a cleaning sieve of the cleaning system, for reducing grain loss, including while the combine is tilted sidewardly relative to horizontal. The angular orientation of the sieve can also be controlled to compensate for the tilt as a separate function under control of a separate leveling system, or under control of the system of the invention. The system of the invention functions by controlling the angular orientation of a distributor disposed between the threshing system and the sieve, for distributing the crop material onto the sieve evenly across an extent thereof. The angular orientation of the distributor can be set in advance of tilting of the combine, to adjust for a variety of conditions, including uneven outputting of the crop material from the threshing system, and the set orientation can be automatically maintained as the combine is variously tilted, and the cleaning system sieve is leveled if a leveling system is present, or is tilted with the combine. 
         [0010]    According to another preferred aspect of the invention, the angular orientation of the distributor is controlled by a control system, which can be, but is not limited to, a suitable programmable controller currently used for controlling combine operations. The system can also include an input device to enable an operator to input positional commands for the distributor, to enable the operator to determine and set the distributor angular position. Here, it should be understood that a threshing system will often discharge crop material at higher rates, or heavier, from some regions thereof compared to others. This can occur for a variety of reasons, such as, but not limited to, crop type, population, and moisture content, and can vary at least somewhat over the course of a harvesting episode. This can also occur, at least in part, as a result of combine settings, such as, but not limited to, a speed of operation of a rotor of the threshing system, and a gap between a rotor and concave of the threshing system. 
         [0011]    According to another preferred aspect of the invention, the distributor setting can be a function of an indicator of performance, such as that of the cleaning system, which can include, but is not limited to, grain loss, and which can be determined and monitored on an ongoing basis, in real-time, or near real-time, using monitors or sensors, such as, but not limited to, conventional, commercially available grain loss sensors. Grain loss sensors are typically located adjacent an edge of the cleaning sieve past which elements of material other than grain are propelled for removal from the cleaning system. Generally, in operation, grain in the crop material will fall through the sieve, while a flow of air directed upwardly through the sieve and toward the edge operates in cooperation with vibration of the sieve, for urging the lighter elements of the crop material other than grain (MOG) toward and over or past the edge. Some grain will typically be mixed with the MOG, so as to be lost. As discussed above, it has been found that the amount of grain mixed with the MOG can vary as a function of crop material distribution over the surface of the sieve, which, in turn, can be a function of factors including, but not limited to, the evenness of the delivery of a mat of the crop material onto the sieve (which can be a function of factors discussed above, e.g., crop type, population, and moisture content, and threshing system settings, e.g., rotor speed and concave gap), and the angular orientation of the sieve, such as a tilting thereof resulting from operation of the combine on a hillside. 
         [0012]    Grain loss sensors are operable in the conventional, well-known manner, for instance, by sensing electrical capacitance change, for measuring or quantifying the amount of grain loss past the edge of the cleaning sieve, and can be disposed, for instance, adjacent opposite ends of the edge of the sieve, and at one or more intermediate locations therealong, for determining grain losses at those locations, which information can be used for determining a distribution of grain losses across the edge or extent of the sieve. Grain loss sensors can be used alone, or with one or more other sensors, for instance, a load sensor, mass sensor, optical sensor, or the like, for determining crop material distribution on or to the cleaning sieve, and/or on or a crop material distributor disposed intermediate the threshing and cleaning systems, such as, a grain pan, sieve, preparation floor, or the like. 
         [0013]    According to still another preferred aspect of the invention, the control system can control the angular orientation of the distributor for distributing crop material to the cleaning sieve in a desired or required manner for minimizing grain loss, during sideward tilting of the combine, and while the cleaning sieve is controlled at different angular orientations for accommodating the tilt, and/or for further distributing the crop material thereover. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a side view of an agricultural combine, including a system for distributing crop material to a cleaning system of the combine, according to the present invention; 
           [0015]      FIG. 2  is an enlarged fragmentary end view of a representative crop material distributor or cleaning sieve of the combine of  FIG. 1 , showing an actuator in combination therewith and controllably operable for positioning the distributor or sieve in a selected angular orientation within a range of angular orientations; 
           [0016]      FIG. 3  is a fragmentary perspective representation of the crop material distributor or cleaning sieve and actuator of  FIG. 2 ; 
           [0017]      FIG. 4  is a diagrammatic representation of one embodiment of the system of the invention; 
           [0018]      FIG. 5  is a simplified schematic rear view of the combine of  FIG. 1 , shown tilted sidewardly, and illustrating angularly oriented positions of a crop material distributor and cleaning sieve of the combine, respectively; 
           [0019]      FIG. 6  is another rear view of the combine tilted sidewardly and showing the crop material distributor and cleaning sieve angularly oriented, and illustrating representative flows of crop material discharge from a threshing system onto the distributor, and resulting crop material flow from the distributor to an upper cleaning sieve, and grain flow through the cleaning system; 
           [0020]      FIG. 7  is a simplified schematic rear view of the combine, tilted sidewardly, and illustrating representative crop material discharge from the threshing system onto the distributor, and crop material flow from the distributor to an upper cleaning sieve; 
           [0021]      FIG. 8  is another simplified schematic rear view of the combine, tilted sidewardly in a different direction, and illustrating representative crop material discharge; 
           [0022]      FIG. 9  is a high-level flow diagram illustrating steps of a method of the invention; 
           [0023]      FIG. 10  is a diagrammatic representation of another embodiment of the system of the invention; and 
           [0024]      FIG. 11  is another simplified schematic rear view of the combine, tilted sidewardly, illustrating representative crop material discharge from the threshing system onto the distributor, and with the distributor and the sieves positioned at different angular orientations for distributing the crop material. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    Referring now to the drawings, wherein preferred embodiments of the present invention are shown, in  FIG. 1 , a typical self-propelled agricultural combine  10  is shown, including a header  12  mounted on a front end thereof, and operable for severing crops from a field during forward motion of combine  10 . Combine  10  includes a feeder  14  operable for conveying the cut crops to a rotary threshing system  16  within combine  10 . Threshing system  16  generally includes one or more rotors  18  rotatable within a corresponding number of perforated concaves  20 , for threshing and separating smaller elements of crop material including grain from larger elements such as stalks, leaves and the like. Flows of the smaller elements of the crop material are discharged through the perforations of concave  20 , as denoted generally by arrows A. Generally, the flows of crop material denoted by arrows A will be uneven, so as to be more concentrated or heavier in some regions, and lighter in other regions, which unevenness will be the result of one or more of a variety of factors, as discussed above. 
         [0026]    The flows of crop material, denoted by arrows A, will fall mostly onto a crop material distributor  22  disposed beneath threshing system  16 , which distributor  22  can comprise a conventionally constructed grain pan operable for conveying crop material rearwardly thereover to a rear edge thereof, over which the crop material will be propelled so as to fall as a mat onto an upper cleaning sieve  24  of a cleaning system  26  of combine  10 . Alternatively, distributor  22  can comprise a sieve. As the crop material mat drops onto upper cleaning sieve  24 , that sieve will be vibrated while a flow of air is directed upwardly and rearwardly therethrough, as denoted by arrows B, such that larger, lighter elements of the crop material other than grain will be directed over or past a rear edge  28  of sieve  24 , for disposal, in the well-known manner. Smaller, heavier elements of the crop material, including grain, will be allowed to pass downwardly through sieve  24  to a lower sieve  30 , for further cleaning, again, in the well known manner. 
         [0027]    Referring also to  FIGS. 2 ,  3  and  4 , crop material distributor  22 , and also at least upper cleaning sieve  24 , are configured so as to be positionable within a predetermined range of angular positions when viewed from the front or rear, as controlled by an actuator  34  and an actuator  36 , respectively. To provide this capability, distributor  22  and at least sieve  24  are supported within combine  10  for sideward pivotal movement, here, about a forward and rearward extending pivotal axis  38  and a similarly extending pivotal axis  40 , disposed beneath distributor  22  and sieve  24 , respectively. Actuator  34  preferably comprises a suitable device connected between a structural element  42 , and an arm  44  projecting from distributor  22 , and is operable for controllably sidewardly pivoting the distributor about axis  38 , as generally denoted by arrow C in  FIGS. 2 and 3 . Actuator  36  can be similarly constructed and operable, or can be of different construction. Here, actuators  34  and  36  are both illustrated as being linear actuators which can be suitably powered, for instance, electrically or fluidly, in the well-known manner. Alternatively, the actuators could comprise rotary actuators, motors, or the like. As another alternative, one or both of distributor  22  and sieve  24  can be supported in a different manner, such as pivotally from one side. As still another alternative, actuator  34  and distributor  22  can be supported on cleaning system  26 , and both sieves  24  and  30  of cleaning system  26  can pivot together, such that distributor  22  will be pivoted by pivotal movement of the sieves, as illustrated by the embodiment in  FIG. 5 . And, as a further alternative, sieve  24  and the entire cleaning system can be of a non-leveling variety, in which case, and actuator  36  and the pivoting support structure for sieve  24  would not be present. 
         [0028]    In the embodiment of combine  10  shown, actuators  34  and  36  are both operatively connected to a single controller  46 , which preferably comprises a conventional programmable processor based controller commonly utilized for controlling various combine operations and functions in the well-known manner. In this regard, controller  46  can control actuator  34  for controlling the position of distributor  22  for controlling grain distribution to sieve  24  as a function of a desired parameter according to the present invention, which here has been selected to be grain loss, while separately controlling actuator  36  for controlling the position of sieve  24  responsive to tilting of combine  10 , as a function of a leveling system feature. Thus, system  32  comprises controller  46 , but it should be recognized that controller  46  can perform a variety of other functions, including, but not limited to, cleaning system leveling. System  32  additionally is illustrated as comprising an optional input device  50 , which can be for instance, an interactive device such as a touch screen or the like, or a switch, connected to controller  46  and located within an operator cab  52  of combine  10 , usable for inputting positional and other commands to system  32 , and optionally for viewing system information. System  32  preferably also comprises at least one sensor operable for sensing or detecting a condition indicative of performance thereof, and/or the effects of performance thereof, to facilitate monitoring and controlling operation thereof, which, in this embodiment of the system, preferably includes at least two grain loss detectors  54  and  56  disposed adjacent opposite ends of, or at spaced apart locations along, rear edge  28  of sieve  24 . Additionally, if combine  10  includes a leveling system for cleaning system  26 , this will typically include a tilt sensor operable for inputting information to controller  46 , or another controller of the leveling system, for use in controlling the leveling of the cleaning system. This information, if present, can also be used by the system of the invention. 
         [0029]    Controller  46  is connected to actuator  34 ; to actuator  36 , if present (if a cleaning system leveling capability is provided); to input device  50 ; and to grain loss detectors  54  and  56 , via suitable conductive paths  58 , which can include, for instance, but are not limited to, wires of a wiring harness, and/or one or more communications networks, such as a controller area network. 
         [0030]    Controller  46  is automatically operable for controlling the angular position of distributor  22  as a function of system  32 , and at least sieve  24  of cleaning system  26  (sieves  24  and  30  being jointly or separately controllable, as desired for a particular application) as a function of the leveling system. Here, as explained above, under at least some circumstances, threshing system  16  will discharge crop material at higher rates, or in heavier concentrations, from some regions of concave  20  compared to others. This can occur for a variety of reasons, such as, but not limited to, crop type, population, and moisture content, and can vary at least somewhat over the course of a harvesting episode. This can also occur, at least in part, as a result of combine settings, such as, but not limited to, a speed of operation of rotor  18 , and a gap between rotor  18  and concave  20 . This is undesirable, as also explained above, as it can affect the performance of cleaning system  26 , particularly the amount of grain loss, as heavy build ups of crop material, particularly on upper sieve  24 , can result in increased grain loss over or past rear edge  28 . A problem identified above in this regard is that crop material build ups and concentrations on distributor  22  will typically be conveyed onto upper sieve  24 . Sideward tilting of the combine can also result in increased crop material concentrations and build ups, particularly toward the downhill side of the combine. Such build ups can be particularly problematic when the threshing system of a combine is more heavily discharging crop material toward the downhill side of the distributor. 
         [0031]    Referring also to  FIGS. 5 ,  6 ,  7 ,  8  and  9 , system  32  is automatically operable for addressing and substantially reducing or eliminating crop material build ups on upper sieve  24  resulting from uneven flow of the crop mat from threshing system  16 , by controlling the angular orientation of distributor  22  so as to even the feeding of the crop material mat onto upper sieve  24 . As examples, in  FIGS. 5 ,  6  and  7 , combine  10  is illustrated tilted downwardly toward the left-hand side; in  FIG. 8 , combine  10  is illustrated tilted upwardly toward the left-hand side, and, in both instances, distributor  22  is illustrated as being angularly oriented as required for evening the crop flow therefrom to upper sieve  24 . 
         [0032]    More particularly, in  FIGS. 6 and 7 , crop material flow A from concave  20  of threshing system  16  is illustrated as being heavier toward the left-hand side. As a result, the crop material deposition on the left-hand side of distributor  22  is heavier compared to the right-hand side. Responsively, actuator  34  is operated to position distributor  22  in an angular orientation extending downwardly by a required amount toward the right-hand side, such that the crop material mat falls evenly from distributor  22  onto upper sieve  24 . Here, it should be observed that at least upper sieve  24  of cleaning system  26  is also tilted downwardly toward the right hand side relative to combine  10 , as a function of the leveling system operation, so as to be level, or horizontal in the sideward direction, to thereby correct for the sideward tilt of combine  10 . This serves to maintain performance of the cleaning system at a high level. 
         [0033]    Referring more particularly to  FIG. 8 , combine  10  is illustrated tilted in the opposite direction, that is, upwardly toward the left-hand side, and crop material flow A from concave  20  of threshing system  16  is illustrated as being heavier toward the right-hand side. So as not to deposit the crop material mat onto sieve  22  in this uneven concentration, distributor  22  is automatically controlled so as to be angularly oriented by system  32 , so as to extend downwardly by a required amount toward the left-hand side, to correct this distribution problem. As a result, as the material mat is conveyed over distributor  22  toward the rear end thereof, it will be spread toward the left-hand side so as to be more even. As in the previous example, the crop material mat will then drop in this more evenly distributed manner, onto upper sieve  24 . Here, it should be noted that at least upper sieve  24  of cleaning system  26  is also tilted upwardly toward the right-hand side of combine  10 , as a function of the leveling system operation, so as to be level, that is, horizontal in the sideward direction, to thereby correct for the sideward tilt of combine  10 , to maintain performance of the cleaning system. 
         [0034]    As a further detail, one can see that the sieve or sieves of cleaning system  26  could be tilted to one side, for instance, the left-hand side of combine  10 , and distributor  22  tilted to the opposite side, for instance the right-hand side. The cleaning sieve would be tilted relative to the combine, but level to horizontal, to maintain minimal grain loss resulting from the slope of the ground, whereas distributor  22  would be tilted relative to the combine and horizontal to get material distributed to the cleaning system in an even mat or flow. The difference between the angular orientations of the distributor and cleaning sieve or sieves would be controlled as a function of the amount of grain loss sensed by the grain loss detectors. One should also note that it would be possible for the distributor and the cleaning sieve or sieves to be positioned at the same angular orientation, as would be the case if the threshing system delivered the crop material evenly to the distributor. 
         [0035]    Further, controller  46  of system  32  is automatically operable for determining an angular orientation of distributor  22  required for evening out crop material flow to cleaning system  26 , in an ongoing manner, in real-time, or near real-time, responsive to a sensed condition or conditions indicative of performance and/or another selected parameter, which here is grain loss, as sensed by grain loss detectors  54  and  56 . The angular orientation of distributor  22  can also be set by an operator, via commands inputted using input device  50 . System  32  can then automatically operate to maintain a performance parameter achieved by the inputted setting, for instance, a satisfactory or set grain loss level, and can operate to even out the grain loss between the two sides of the cleaning system, as a function of comparison of the signals from grain loss sensors  54  and  56 . Thus, if grain distribution from the threshing system changes, for instance, as a function of any of the factors discussed above, and grain loss from one side of the cleaning system exceeds loss from the other side by a certain amount, system  32  can automatically detect this. Controller  46  can then responsively make an appropriate adjustments in the angular position of distributor  22  via actuator  34 , as required. 
         [0036]      FIG. 9  is a high level flow diagram  58  illustrating steps of one possible method of operation of system  32  for controlling the orientation of distributor  22 , in cooperation with a leveling system for controlling orientation of at least sieve  24  of cleaning system  26  responsive to tilting of combine  10 . According to the method, at block  60 , a distributor angle will be determined. This can be via an automatic process as controlled by controller  46 , responsive to a desired parameter, such as grain loss, and the above-described manner. Alternatively, this could be responsive to a manually inputted command, via input device  50 . Controller  46  will then either automatically control distributor  22  for controlling the control parameter, e.g., grain loss, or for maintaining the inputted position. As part of its cleaning system leveling function, controller  46  will also monitor sideward tilting of combine  10 . If a side hill is detected, e.g., tilt, as denoted at decision block  62 , controller  46  will adjust the angular orientation of cleaning sieve  24  (and other elements of the cleaning system if so equipped) so as to be level or horizontal, as denoted at block  64 . Additionally, controller  46  can also operate to adjust the angular orientation of distributor  22  for the tilting condition, such that the control parameter, e.g., grain loss, or inputted command, is maintained, as denoted at block  66 . In this latter regard, it should be recognized that when combine  10  is tilted, the locations of crop material deposition on distributor  22  can vary or change as a function of the degree of tilt. To accommodate this, controller  46  can be programmed to automatically adjust for such tilting, on an ongoing basis, in real-time, or near real-time, to maintain the control parameter, or the commanded angular orientation of distributor  22  in relation to a fixed reference, such as horizontal, so as to maintain system performance. 
         [0037]    With the examples provided above, one can understand that about any combination of angles could be present between a distributor of a combine, and sieves of a cleaning system thereof. It should also be understood that the system of the invention is not limited to use with a self leveling cleaning system. In the event that a machine does not have a self leveling cleaning system, side hill performance can be further enhanced by tilting the distributor to deliver material to the uphill side. This would then allow for additional performance of a fixed cleaning system combine on side hills. 
         [0038]    Referring also  FIGS. 10 and 11 , it is contemplated according to the invention, that system  32  can be configured so as to additionally control the angular orientation of at least upper sieve  24  of cleaning system  26 , for also adjusting or evening distribution of crop material thereon. In this regard, it is contemplated that under some conditions, the possible variations in angular orientation of distributor  22  that can be effected by operation of system  32  may be inadequate to satisfactorily evenly distribute the crop material flow onto sieve  24 , and, as a result, it would be advantageous to also control the angular orientation of that sieve for increasing or improving evenness of the distribution. This will be accomplished by control of actuator  36  via controller  46 , and can be performed instead of or in association with leveling of one or both of the sieves of cleaning system  26 . Additionally, according to this aspect of the invention, it is contemplated that controller  46  can automatically control actuators  34  and  36  for achieving a combination of angular orientations of distributor  22  and at least sieve  24 , that will achieve a desired evenness of crop material distribution. Here, system  32  will be configured as described above, and, in addition to the elements already described, can include one or more additional grain loss detectors  55  disposed between detectors  54  and  56 , so as to provide more detailed information regarding grain loss and thus crop material distribution on sieve  24 . The one or more detectors  55  will be suitably connected to controller  46  via a suitable conductive path  58 , as discussed above. In operation, an elevated grain loss detected by one or two of detectors  54 ,  55  and  56 , would indicate uneven crop material distribution, and controller  46  would responsively determine a corrective angular position of one or both distributor  22 , and sieves  24  and  30 . In this regard, a stepped approach to adjusting the angular position of one or both could be employed, to incrementally approach an even crop material on sieve  24 . Again, this can be performed on an ongoing, real-time, or near real-time basis. 
         [0039]    Examining  FIG. 11  in particular, crop material flow A from concave  20  of threshing system  16  is illustrated as being heavier toward the right-hand side, such that distributor  22  of system  32  is responsively tilted downwardly toward the left-hand side. If warranted, sieve  24  of cleaning system  26 , and also sieve  30 , can be also be tilted as required, here also downwardly toward the left-hand side, for achieving desired evenness of distribution of crop material on sieve  24 , even when combine  10  is tilted. Thus, is demonstrated that system  32  is operable for overriding the leveling function for cleaning system  26 , so as to achieve desired crop distribution thereon, and thus maximum performance. 
         [0040]    It will be understood that changes in the details, materials, steps, and arrangements of parts which have been described and illustrated to explain the nature of the invention will occur to and may be made by those skilled in the art upon a reading of this disclosure within the principles and scope of the invention. The foregoing description illustrates the preferred embodiment of the invention; however, concepts, as based upon the description, may be employed in other embodiments without departing from the scope of the invention. Accordingly, the following claims are intended to protect the invention broadly as well as in the specific form shown.