FIELD OF THE INVENTION  
         [0001]    The present invention is directed to a cleaning assembly for an agricultural combine, wherein the cleaning shoe is provided with a sieve having adjustable blades. The position of the blades is adjusted by an adjustment element that is coupled to a drive element located on the cleaning shoe. The sieve is removeably mounted to the cleaning shoe so that the sieve can be removed without disassembling the connection between the drive element and adjustment element.  
         BACKGROUND OF THE INVENTION  
         [0002]    In a combine some chaff and straw is mixed with the grain after threshing and separation. The cleaning assembly removes these contaminants from the grain. In most combines, the cleaning assembly contains three main components: a blower, an upper sieve and a lower sieve. The blower has its own housing, whereas the upper sieve and lower sieve are mounted on a cleaning shoe.  
           [0003]    An adjustable sieve is designed from a series of transversely extending blades with rows of teeth. Each of these blades is fastened to a cranked shaft that has a crank arm engaged with an axially extending adjustment bar. All blades are moved simultaneously by axial displacement of the adjustment bar.  
           [0004]    The adjustable upper sieve and lower sieve are adjusted as a function of the conditions of the harvested product. The blades of the upper sieve are opened or closed far enough so that the grain falls through the upper sieve before it travels the length of the upper sieve. If the upper sieve is opened too wide, the lower sieve can be overloaded with chaff. When the upper sieve is not opened wide enough and the grain cannot be separated from the chaff and straw, this reaches the upper sieve extension, which can lead to overloading of the return. If the grain cannot be separated there, either, as a result of a sieve being opened too widely, the grain is returned to the field over the end of the sieve as cleaning losses. The blades of the lower sieve must be opened wide enough to permit the grain to fall easily through them, but not wide enough that the straw and chaff can fall through.  
           [0005]    In many combines, an operator, depending on the actual type of crop and the harvesting conditions, must reach between the side walls on the back side of the thresher in order to make these adjustments via hand levers mounted on the sieve. This makes the adjustments cumbersome and time-consuming. A common feature of hand-operated adjustment devices with linkages is that the operating elements are mounted in the cleaning shoe to avoid unnecessary deflection and therefore form a clogging hazard, that can adversely affect air conduction through the cleaning shoe.  
           [0006]    Various remotely operated adjustment mechanisms have been proposed. U.S. Pat. No. 4,897,027 A discloses a cable drive mechanism that permits an operator to adjust the blade angle from an operator&#39;s position. U.S. Pat. No. 5,586,033 A discloses an apparatus that drives the blades via a motor-driven cable mechanism for automatic control. A drawback of these sieve adjustments lies in the play of the operating devices, which leads to imprecise sieve adjustment. A relatively high disassembly expense is also required when the sieves, for example, must be disassembled for cleaning purposes.  
           [0007]    A self-propelled combine is described in DE 198 24 462, in which the removable blade sieves are equipped with a spring that automatically brings the blades into the closed or open position. A lever rigidly mounted on the combine comes to bear on an adapter mounted with the adjustment bar of the blades when the sieves are incorporated in the cleaning shoe. The lever can therefore displace the adapter against the action of the spring in a first direction, in order to adjust the blades. If the lever is adjusted in the opposite direction, the adapter is pushed back by the action of the spring. This solution permits the sieve to be removed from the cleaning shoe without loosening a connection between the lever and the adapter. A shortcoming is that the sieves can no longer be closed or opened when they operate so sluggishly from contaminants or mechanical imprecision that the spring can no longer move the adjustment bars. It is also possible that the spring can fail because of barley glumes that are situated between the spring windings, so that the sieve can no longer be closed even when the blades are readily accessible.  
         SUMMARY OF THE INVENTION  
         [0008]    It is an object of the present invention to provide an improved cleaning assembly having an easily removeable sieve with adjustable blades.  
           [0009]    The invention refers to a cleaning assembly for a combine comprising a cleaning shoe having a removable sieve. The sieve has a frame with adjustable blades. The blades of the sieve can be moved by an adjustment element arranged on the sieve. The adjustment element is movable by a drive element that is mounted on the cleaning shoe. The drive element is not removable from the cleaning shoe with the sieve. The drive connection between the drive element and adjustment element is automatically disengaged when the sieve is disassembled and automatically reengaged when the sieve is reengaged. The drive element is set up so that it can drive the adjustment element in two directions. The adjustment element is therefore moved by the drive element in a first direction to open the blades and in the opposite direction, in order to close the blades. The drive element is therefore set up to actively drive the adjustment element in two opposite directions. A spring to return the adjustment elements is not required.  
           [0010]    In this manner, the position of the blades is adjusted exclusively by the drive element, so that the spring is spared and the sieve remains adjustable even when the blades are difficult to access.  
           [0011]    The drive connection between the drive element and the adjustment element can be any number of connections that readily disengage and engage. For example, the drive element may comprise a friction wheel that cooperates with a friction surface on the adjustment element. Such a friction drive system may encounter slippage in the drive element driving the adjustment element. A positive drive power transmission is preferred. For example, the drive element may comprise a gear that cooperates with a gear or rack on the adjustment element. The gear can be a standard spur gear or a worm gear. In the illustrated preferred embodiment, the adjustment element is provided with a rack, which is moved axially by the drive element that comprises a gear. The gear is mounted to the cleaning shoe. The described power transmission mechanisms automatically disengage on removal of the sieve from the cleaning shoe without additional assembly demands, and automatically reengages on incorporation of the sieve back into the cleaning shoe.  
           [0012]    The sieves of the cleaning assembly are provided with a number of blades that normally extend transversely to the direction of travel of the combine. Each blade is generally equipped with a cranked shaft, which has a crank arm in order to adjust the angular position of the blade. The crank arms are accommodated in slots situated in an axially extending (i.e., along the forward direction of travel) adjustment bar. The angle of the blades and the opening produced between them is varied by movement of the adjustment bar forward or backward, produced by the adjustment element. However, it is also conceivable to rotate the adjustment bar and to convert the rotation to a displacement movement of the blade by appropriate mechanisms.  
           [0013]    The drive element can be driven by an electrically, pneumatically or hydraulically powered motor, although a manual drive is also conceivable. The latter can be effected, in particular, from the operating cabin via appropriate power transmission elements. If the drive element is motorized, the motor can be controlled manually by appropriate switches in the operator&#39;s cabin or by an automatic control or regulation device.  
           [0014]    For reasons of flow, it is advisable to arrange as few elements as possible of the drive train of the drive element in the interior of the cleaning shoe. In a preferred variant, only the drive element and a shaft connected to it are therefore arranged in the cleaning shoe. The other elements of the drive train are then situated outside of the cleaning shoe.  
           [0015]    The sieve is preferably fastened in the cleaning shoe by a retaining element. After removal of the retaining element, the sieve can be removed out the rear of the cleaning shoe.  
           [0016]    Removal and insertion of the sieve can be effected by the drive element. After the retaining element has been removed, the drive element is placed in operation, which initially brings the blades into the closed or open position. If the blades are closed or opened, the adjustment element preferably cooperates with a stop so as not to unduly load the blades or even deform them. Since the retaining element was removed, the entire sieve is now removed from the cleaning shoe. Insertion of the sieve occurs in the opposite direction, also through the drive element. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 is a semi-schematic side view of an agricultural combine, in which the threshing, separation and cleaning assemblies are shown.  
         [0018]    [0018]FIG. 2 is a perspective side view of the sieve and the corresponding adjustment mechanism.  
         [0019]    [0019]FIG. 3 is a rear view of the sieve and the adjustment mechanism.  
         [0020]    [0020]FIG. 4 is a partial rear view of a portion of the sieve and the side rail of the cleaning shoe. 
     
    
     DETAILED DESCRIPTION  
       [0021]    In the following disclosure the term axial direction means the longitudinal direction of travel of the combine. FIG. 1 shows a side view of a self-propelled agricultural combine  10 . The combine  10  comprises a support structure  12  with wheels  14 . The support structure  12  comprises two axially extending side walls, between which the different crop processing devices for the harvested product are arranged. A cutting mechanism  16  extends forward from combine  10 , which feeds the harvested product to feeder house  18 . The feeder house  18  guides the harvested product to the threshing, separation and cleaning assemblies, which are arranged between the side walls of the combine  10 . Although the present invention is disclosed as applicable on a rotary combine, it can also be used on any combine having a cleaning assembly.  
         [0022]    In the combine depicted, the feeder house  18  guides the harvested product to a transversely extending accelerator beater  20 , which feeds the product through an inlet transition section  22  to an axial threshing and separation assembly  24 . The grain and chaff are fed by the axial threshing and separation assembly  24  to a cleaning assembly  26 . The cleaning assembly  26  feeds the clean grain back to a grain tank  28  and the chaff is blown by the cleaning blower  30  out the rear of combine  10 . The harvested product that is neither grain nor chaff is fed by the axial threshing and separation assembly  24  to a transversely arranged discharge beater  32  that conveys the material out onto the field out the rear of the combine  10 . Clean grain is temporarily stored in the grain tank  28  and can be unloaded by an operator from the operator&#39;s cab  34  actuating an unloading auger  36 . The threshing and separation assembly  24  and the cleaning assembly  26  are arranged between the side walls of the support structure  12 .  
         [0023]    The cleaning shoe  38  is equipped with an upper sieve  40  and a lower sieve  42 . The upper sieve  40  and the lower sieve  42  are provided with transversely running adjustable blades  44 , which are shown in FIG. 2. The blades  44  are fastened in a rectangular frame  46  that is supported by the side walls of the cleaning shoe  38 . As shown in FIG. 2, each of the blades  44  is equipped with a cranked shaft  48 , which has a crank arm  50 . The crank arm  50  is arranged in a slot  52  of an axial adjustment bar  54 . By axial movement of the upper and lower adjustment bars  54 , the angular position of all blades  44  of the upper sieve  40  or all blades  44  of the lower sieve  42  can be adjusted. The adjustment bar  54  is mounted movably on frame  46  (in a manner not further shown in the figures). If the adjustment bar  54  is moved in the direction of travel, i.e., from right to left in FIG. 2, or vice versa, the cranked shafts  48  of blades  44  are rotated in their bearings on frame  46  and the position of the blades  44  is adjusted. The spacing between adjacent blade tips is then changed. Displacement of the adjustment bar  54  to the left causes a reduction in the spacing and therefore closure of sieve  40  or  42 . On the other hand, displacement of the adjustment bar  54  to the right results in opening of the blade tips and thus opening of the sieve  40  or  42 .  
         [0024]    An adjustment element  64 , whose bottom is equipped with a rack  66 , is bolted onto the adjustment bar  54 . However, it is also possible to appropriately design the adjustment bar  54  itself to have an integral rack. The longitudinal direction of the rack  66  runs in the direction of travel so that the individual teeth run transverse to the direction of travel. A gear  68  meshes with the rack  66  of adjustment element  64 , which is rotatable on a shaft  70  running transverse to the direction of travel. Rotation of gear  68  causes displacement of the adjustment element  64  in or opposite to the direction of travel (leftward or rightward in FIG. 2). In that way, the spacing between adjacent blade tips is achieved.  
         [0025]    In order to prevent the rack  66  (or a toothed adjustment bar  54 ) from being clogged with contaminants during operation, the rack  66  can be encapsulated. The encapsulation would have overlapping flexible sealing lips slot on the bottom. The encapsulation would be attached to the rack  66  and removed with sieves  40  and  42  from the cleaning shoe  38 . From the standpoint of flow, the encapsulation should be designed to be as small as possible. As an alternative or in addition, it is conceivable to occasionally place the gear  68  in rotation in order to run the length of rack  66  and remove the contaminants. So as not to adversely affect operation of the combine  10 , a sensor can be provided that recognizes the absence of product flow, for example, during turning at the end of a field, or during road travel, and places motor  78  in operation.  
         [0026]    It is apparent, with reference to FIG. 3, that the gear  68  is driven via a drive train, which comprises shaft  70 , a first pinion  72 , a chain  74 , a second pinion  76  and a motor  78 . The first pinion  72  sits outside the cleaning shoe  38  on shaft  70  arranged transverse to the direction of travel. The chain  74  travels around the two pinions  72  and  76 . The motor  78  drives the second pinion  76 . Instead of chain  74 , a smooth or toothed belt could also be used that cooperates with the corresponding pinions or sheaves  72  and  76 . The motor  78  is therefore set up to rotate gear  68  via the drive train. The motor  78  is preferably an electric motor. It can be controlled manually or by an automatic control or regulation device of the cleaning assembly  26 . It should also be noted that the chain drive train could be replaced by a flexible rotatable drive shaft that can be located inside the cleaning shoe.  
         [0027]    If the frame  46  of sieve  40  or  42  is to be disassembled from cleaning shoe  38  for purposes of repair, inspection or cleaning, only a rear retaining element  60  needs to be removed from the plane of the frame  46 . The frame  46  can be pulled rearwardly along side rail  62  on the cleaning shoe  38 . The adjustment element  64  is also removed from the cleaning shoe  38  with the frame  46 . The gear  68  and the corresponding drive train, however, remain in cleaning shoe  38 . The drive connection between the bottom rack  66  of adjustment element  64  and gear  68  is releasable without problem by easy lifting of frame  46  and is reengaged automatically, and with limited play, after reincorporation of the upper sieve  40  and lower sieve  42 . As an alternative, the gear  68  can be adjusted downward in order to be able to remove the sieve without problem, if upwardly closed lateral guide rails are present in the cleaning shoe  38 .  
         [0028]    If the adjustment element  64  is dimensioned to be sufficiently long (or the adjustment bar  54  is designed as a rack), the motor  78  can also be used to eject or insert the lower sieve  42  or upper sieve  40  into the cleaning shoe  38 . In this case, the retaining element  60  is removed and the motor  78  is rotated, so that the gear  68  rotates clockwise in FIG. 2. The blades  44  are initially brought to the open position, until the adjustment bar  54  engages on a stop (not shown) on frame  46 . The frame  46  is now pushed out rearward from the cleaning shoe  38  by the adjustment element  64  driven by the gear  68 . In order to avoid jamming of frame  46  in cleaning shoe  38 , roller-mounted guides can be provided between cleaning shoe  38  and frame  46 .  
         [0029]    Insertion of frame  46  occurs in the opposite manner, in which the adjustment element  64  will first pull the adjustment bar  54  to a stop corresponding to the closed position of blades  44  before the frame  46  is retracted into cleaning shoe  38 .  
         [0030]    In order to achieve a situation in which the blades  44  assume a defined position at a specific position of gear  68 , corresponding marks can be made on the gear  68  and adjustment element  64 . The operator adjusts the blades  44  and the adjustment bar  54  with the drive connection released between gear  68  and rack  66  (for example, with the raised frame  46  or lowered gear  68 ), so that the marks coincide. This achieves a situation in which the blades  44  have a known position corresponding with a known position of motor  78 . Instead of marks, mechanical devices (for example, double teeth) can be provided that permit engagement of the gear  68  into rack  66  only at a defined position. If corresponding sensors (light barriers, ultrasonic sensors, etc.) are present that can determine the actual sieve opening, the described expedients are unnecessary.  
         [0031]    It should be noted that (as an alternative to the aforementioned mechanical solution) information concerning the corresponding position of blades  44  can be fed to an automatic control or regulation device for sieve opening. This information can be obtained via a corresponding sensor, arranged, for example, on the cleaning shoe  38  or frame  46 , which cooperates with the adjustment bar  54  and determines its position. For example, a movable potentiometer can be used whose slide cooperates with the adjustment bar  54 . It is also conceivable to drive the motor so that it moves the blades  44  in the direction of their open or closed position. Reaching of the stop by the adjustment bar  54  in the open or closed position is recognized by an increased motor operating current (based on blocking of the adjustment bar  54  by the stop). The motor can then be placed in the operating mode for a predetermined time corresponding to the desired position of blades  44 , if a DC motor is used. A stepping motor can also be used, which is operated by drive signals according to the desired position of the blades  44 . Another conceivable possibility is the use of a motor  78  with a built-in sensor that is calibrated between the end positions.  
         [0032]    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.
The invention is directed to a cleaning assembly for an agricultural combine having a cleaning shoe with at least one sieve. The sieve is provided with adjustable blades. The sieve is provided with an adjustment element for adjusting the position of the blades. A driving element is connected to the adjustment element. The sieve can be removed from the cleaning shoe without disassembling the connection between the drive element and adjustment element. The connection is automatically disengaged when the sieve is being removed from the cleaning shoe and automatically engaged when the sieve is being reinstalled in the cleaning shoe.