Abstract:
The subject matter of the present invention relates to a cleaning device for a combine harvester, with a precleaning sieve, to the upper surface of which a mixture of grain and chaff can be fed during the operation, an upper sieve, to which the mixture of grain and chaff rearwardly discharged from the back surface of the precleaning sieve can be fed, a lower sieve, to which the mixture of grain and chaff passing through the precleaning sieve can be fed, and with a fan for applying currents of air to the precleaning sieve, the upper sieve and the lower sieve. On its way between the precleaning sieve and the lower sieve, the mixture of grain and chaff that has passed through the precleaning sieve be passed via a grating which is permeable to air and disposed separately from the lower sieve, to which grating a current of air can be applied by the fan as well.

Description:
FIELD OF THE INVENTION  
       [0001]     The subject matter of the present invention relates to a cleaning device for a combine harvester, with a precleaning sieve, to the upper surface of which a mixture of grain and chaff can be fed during the operation, an upper sieve to which the mixture of grain and chaff discharged from the upper surface of the precleaning sieve can be fed, a lower sieve, to which the precleaned mixture of grain and chaff passing through the precleaning sieve can be fed, and with a fan for applying currents of air to the precleaning sieve, the upper sieve and the lower sieve.  
       BACKGROUND OF THE INVENTION  
       [0002]     A combine harvester with a multi-drum threshing system has been described in the German Patent DE 30 42 734 C. The mixture of grain and chaff passing through openings in the threshing concave and the downstream separating baskets is fed via grain pans to a cascade pan to which a rearwardly directed current of air is applied via an upper fan outlet. Disposed below this cascade pan is a precleaning sieve to which a current of air is also applied via the upper fan outlet, and disposed below said precleaning sieve is an additional grain pan. The rearwardly moving mixture on the upper surface of the precleaning sieve falls on an upper sieve, while the precleaned grain and chaff which fall downwardly through the precleaning sieve are transported via the additional grain pan to a lower sieve. A rearwardly directed current of air is applied to the upper and lower sieves by means of a lower fan outlet.  
         [0003]     The disadvantage of this design is that the precleaned mixture of grain and chaff which has been passed through the additional grain pan to the lower sieve is compacted to a relatively high degree since it was passed only through the precleaning sieve and was subsequently transported through the additional grain pan. A cascade pan is, in fact, disposed between the additional grain pan and the lower sieve, but only a relatively low current of air is applied to said cascade pan. Thus, compacted material falls onto the lower sieve, which, given a certain sieve opening, limits the potential throughput through the lower sieve and thus through the combine harvester. It is possible to further open the fins of the lower sieve in order to increase the throughput; however, this has a detrimental effect on the cleanness of the ultimately harvested grain.  
       SUMMARY OF THE INVENTION  
       [0004]     The problem to be solved by the present invention is to make available an improved cleaning device which makes it possible to obtain a higher throughput and improved cleanness of the grain in the grain tank.  
         [0005]     This problem is solved according to the present invention by the teaching of claim  1 , with characteristics that improve the solution in a useful manner being addressed in the other claims.  
         [0006]     It is proposed that on its way to the lower sieve, the precleaned mixture of grain and chaff that passes through the precleaning sieve be passed over a grating that is permeable to air and that a rearwardly directed current of air be applied to it. The grating is disposed separately from the lower sieve and defines a horizontally extending conveying track, along which the mixture is transported.  
         [0007]     In this manner, the mixture fed from the precleaning sieve to the lower sieve is subjected to an additional precleaning process since the current of air flowing through the grating removes part of the chaff from the mixture that is conveyed above the grating by blowing it away. In addition, the mixture is loosened up and can be more readily separated by the lower sieve. This makes it possible to achieve a higher throughput and/or a higher degree of cleanness of the ultimately harvested grain.  
         [0008]     In a preferred embodiment, the fan comprises a first and a second fan outlet. During operation, the second fan outlet supplies the precleaning sieve with a rearwardly and upwardly directed current of air while the first fan outlet applies a rearwardly and upwardly directed current of air to the lower sieve and the grating. Via the grating and/or the lower sieve, the upper sieve is preferably supplied with a current of air which is directed rearwardly and upwardly as well. If a cascade pan which allows a separation of lighter components from the mixture of grain and chaff is disposed downstream of the precleaning sieve in the transition region toward the upper sieve, the first fan outlet can advantageously supply said cascade pan with a current of air by way of the grating as well.  
         [0009]     The grating is preferably disposed in the plane of the lower sieve and upstream with respect to the direction of travel. As a result, no additional conveyers are needed to transport the mixture from the grating to the lower sieve.  
         [0010]     In a preferred embodiment, the grating comprises a plurality of fins, the longitudinal axis of which runs at right angles to the direction of travel, with the fins being arranged in series one behind the other in the direction of travel. The fins are flat and slope rearwardly and upwardly. All or a part of said fins can be disposed about their longitudinal axis so as to be angularly adjustable, or they can be rigidly mounted. It has also been found useful if the fins disposed in front with respect to the direction of travel (i.e., the distance between the leading and trailing edge of the fins) are shorter than fins disposed further toward the rear.  
         [0011]     During operation, the grating is preferably made to vibrate together with the lower sieve. It is, however, also conceivable to connect said grating rigidly to the frame of the combine harvester. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     The drawings show two practical examples of the present invention which will be described in greater detail below. As can be seen,  
         [0013]      FIG. 1  shows a diagrammatic lateral view of a combine harvester with a cleaning device according to the present invention,  
         [0014]      FIG. 2  shows an enlarged diagrammatic lateral view of the cleaning device seen in  FIG. 1 , and  
         [0015]      FIG. 3  shows an enlarged diagrammatic lateral view of a second embodiment of a cleaning device. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]      FIG. 1  shows a self-propelling combine harvester  10  with a frame  12  which, by way of driven front wheels  14  and steerable rear wheels  16 , supports itself off the ground and is propelled by said wheels. The wheels  14  are made to rotate by means of a driving mechanism not shown in the drawing in order to move the combine harvester  10 , e.g., across a field that is to be harvested. Hereinafter, any specifications as to directions, such as front and rear, refer to the direction of travel V of the combine harvester  10  during the harvesting operation.  
         [0017]     Removably connected to the front end region of the combine harvester  10  is a harvesting device  18  in the form of a cutting unit so as to be able to harvest crops in the form of cereal or other threshable grain from the field during harvesting operations and to feed it upwardly and rearwardly through an inclined conveyer  20  to a multi-drum threshing system which—arranged in series one behind the other in the direction of travel—comprises a threshing drum  22 , a stripper drum  24 , an overshot conveyer drum  26 , a tangential separator  28 , and a turning drum  30 . Located downstream of the turning drum  30  is a straw walker  32 . The lower and rearward region of the threshing drum  22  is enclosed by a threshing concave  34 . Below the conveyer drum  26 , a cover  35 , either with openings or solid, is disposed, while above the conveyer drum  26 , a stationary cover, and below the tangential separator  28 , a separating basket  36  with adjustable finger elements is disposed. Disposed below the turning drum  30  is a finger rake  38 .  
         [0018]     Located below the multi-drum threshing system is a front grain pan  40  which, during operation, executes an alternatingly rearwardly and forwardly directed vibratory movement. A rear grain pan  42  is disposed below the straw walker  32  and, during operation, also executes an alternatingly forwardly and rearwardly directed vibratory movement. The front grain pan  40  transports the mixture of grain and chaff, which passes in a downward direction through the threshing concave  34  and through the tangential separator  36 , toward the rear while the rear grain pan  42  transports the mixture of grain and chaff flowing through the straw walker  32  toward the front. At its front end, the rear grain pan  42  transfers the mixture to the front grain pan  40  which subsequently discharges it downwardly through a rear finger rake  44 . The mixture discharged from the front grain pan  40  subsequently arrives in a cleaning device  46  which is shown in greater detail in  FIG. 2 .  
         [0019]     The grain which has been cleaned by the cleaning device  46  is fed by means of a grain auger  48  to an elevator not shown in the drawing, which auger transports it into a grain tank  50 . A tailing auger  52  returns unthreshed parts of the grain ears via an elevator not shown in the drawing to the threshing process. The chaff can be discharged from the rear end of the sieve device by means of a rotating chaff distributor, or it is discharged through a straw chopper (not shown in the drawing) that is disposed downstream of the straw walker  32 . The cleaned grain from the grain tank  50  can be unloaded by means of an unloading system with cross augers  54  and an unloading conveyer  56 .  
         [0020]     The systems mentioned are driven by an internal combustion engine  58  and can be controlled and steered by an operator from a driver&#39;s cab  60 . The various means for threshing, conveying, cleaning and separating are disposed inside the frame  12 . Disposed outside the frame  12  is an outer cover, most of which can be opened up.  
         [0021]     In this context, it should be noted that the multi-drum threshing system shown in the drawing is no more than a practical example. It could also be replaced with a single transversely disposed threshing drum and a downstream separating device with a straw walker or one or a plurality of separator rotors. It is, however, furthermore also conceivable to use a rotating axial separator which comprises a threshing section and a separating section. It is possible to use a single axial separator or two (or more) axial separators that are placed side by side.  
         [0022]     In  FIG. 2 , the cleaning device  46  is shown in an enlarged lateral view. It includes a fan  62  comprising a rotor  64  which can be made to rotate (in a counterclockwise direction, as shown in  FIG. 2 ) and a housing  66  that encloses the rotor  64 . The housing  66  has a first fan outlet  68  and a second fan outlet  70 .  
         [0023]     In addition, the cleaning device  46  comprises a precleaning sieve  72  with sieve fins that are supported in a sieve frame and mounted so as to be angularly adjustable about their longitudinal axis, which precleaning sieve is disposed below the finger rake  44  and extends approximately from the rearward edge of the front grain pan  40  horizontally toward the rear and slightly upwardly. Connected to the rearward end of the precleaning sieve  72  are a solid plate  74  which extends to form a downwardly inclined guide surface  76  and a finger rake  78  disposed behind the plate  74 .  
         [0024]     Located below the front half of the precleaning sieve  72  is a grain pan  80 , under which the upper portion of the housing  66  of the fan  62  is disposed. The second fan outlet  70  is directed forwardly and guides the air into a rearwardly and upwardly curved channel  82  which guides the air into the gap  84  between the front grain pan  40  and grain pan  80  in which it flows rearwardly. Part of this air reaches a cascade pan  86  which is disposed vertically between the rearward end of the front grain pan  40  and the precleaning sieve  72  and which already partially separates the heavier grain from the lighter chaff which is discharged rearwardly. The remaining portion of the air flowing through gap  84 , which air is in part deflected by the guide surface  76 , reaches the lower surface of the precleaning sieve  72  and passes through it by flowing rearwardly and upwardly. Grain and to some extent also chaff fall through the sieve fins of the precleaning sieve  72  while the remaining mixture of grain and chaff falls downwardly through the finger rake  78  on the back surface of the precleaning sieve  72 .  
         [0025]     Via an additional cascade pan  88 , the mixture of grain and chaff then reaches an upper sieve  90 , below which a lower sieve  92  is disposed. The upper sieve  90  and the lower sieve  92  each comprise sieve fins which are disposed in a frame and which are angularly adjustable independently of one another about their longitudinal axis. Between the front end of the lower sieve  92  and an upper guide plate  94  which is connected to the housing  66  in the area of the first fan outlet  68  and which slopes rearwardly and upwardly, a grating  96  is disposed. Above an edge  98  adjacent to grating  96 , the upper guide plate  94  slopes forwardly and upwardly in region  100  and ends in the vicinity of the rearward end of the grain pan  80 .  
         [0026]     In the embodiment shown, grating  90  comprises five flat fins which are arranged in series one behind the other at right angles to the direction of travel V. The fins are located in rearwardly and upwardly sloping planes. The more forwardly disposed a fin is, the shorter is the length of the fins (viewed in the direction of the current of air). The fins are mounted in a frame (not shown in the drawing) that is connected to the lower sieve  92 .  
         [0027]     Rearwardly with respect to the first fan outlet  68 , the lower portion of the housing  66  of the fan  62  extends rearwardly to form a lower guide plate  102  which, below region  100 , extends into a funnel-shaped trough  104  of the grain auger  48 . Connected to the rearward end of the upper sieve  90  is a rearward bottom plate  106  which slopes downwardly and forwardly and extends into a funnel-shaped trough  108  of the tailing auger  52 . A lower grain pan  110  slopes forwardly and downwardly from the rearward end of the lower sieve  92  above the rearward bottom plate  106  and above the trailing auger  52  and ends above the trough  104  of the grain auger  48 . Disposed below the lower sieve  92  are air guiding plates  112 .  
         [0028]     By means of drives not shown in the drawing, the grain pans  40 ,  42  and  80  and the precleaning sieve  72  with the guide surface  76  and the finger rake  78 , the upper sieve  90 , the lower sieve  92  with grating  96 , the bottom plate  106  and the lower grain pan  110  and the air guiding plates  112 , all of which are mounted via oscillating arms on the frame  12 , during operation are propelled mainly in a forward and rearward direction. For this purpose, they are disposed in a sieve pan which vibrates in the directions specified. They all can move in the same direction or, at least in part, in the opposite direction. In this context, reference is made to the disclosure of DE  30   42   734  C which by reference is included in the existing documents. Fan  62  with its housing  66  and the walls of channel  82 , the guide plates  94  and  102 , the troughs  104  and  108  and the grain auger  48  and the tailing auger  52 , however, are rigidly connected to the frame  12 . The width of the cleaning device  46  and its components approximately corresponds to at least the width of the multi-drum threshing system and of the straw walkers  32 .  
         [0029]     When in operation, fan  62  also generates a current of air in the first fan outlet  68 , part of which current of air flows rearwardly and upwardly through grating  96 . The remaining current of air from the first fan outlet  68 , partly guided by the air guiding plates  112 , reaches the lower surface of the lower sieve  92  and flows through it. The current of air exiting through grating  96  and through the lower sieve  92  reaches the cascade pan  88  and the lower surface of the upper sieve  90 .  
         [0030]     As already mentioned earlier, the mixture of grain and chaff, which on the back surface of the precleaning sieve  72  flows through the finger rake  78  or along its upper surface and thus reaches the upper sieve  90 , is cleaned in a conventionally known manner by the current of air and the sieve fins of the upper sieve  90 . The mixture of grain and chaff passing through the upper sieve  90  reaches the lower sieve  92 , while the remaining chaff is transported rearwardly by the current of air and is preferably discharged from the combine harvester  10  by means of the already mentioned chaff distributor or straw chopper. As the mixture of chaff and grain on the lower sieve  92  passes through the lower sieve  92 , it is again cleaned in a conventionally known manner, and the grain passing through the sieve fins of the lower sieve  92  flows through the lower grain pan  110  to the grain auger  48  and from there into the grain tank  50 . At the rear surface of the lower sieve  92 , the tailings are moved by the bottom plate  106  to the tailing auger  52 .  
         [0031]     Part of the mixture of grain and chaff already mentioned earlier which passes the sieve fins of the precleaning sieve  72  falls directly (i.e., the mixture passing the rearward area of the precleaning sieve  72 ) and part of it falls via the grain pan  80  (i.e., the mixture passing the front portion of the precleaning sieve  72 ) above the fan  62  onto the grating  96 . The mixture of grain and chaff lying on the grating  96  moves rearwardly along the upper surface of the grating  96  and subsequently reaches the lower sieve  92  on which it is separated into grain and tailings in the manner mentioned earlier. The current of air flowing upwardly and rearwardly through the grating  96  loosens the mixture and entrains lighter particles (chaff) in its stream. Thus, a loosened-up mixture which to a certain extent has been precleaned once more reaches the lower sieve. As a result, the sieving efficiency of the lower sieve  92  is improved, which leads to an increase in the potential throughput of the combine harvester and to an improved cleaning effect.  
         [0032]     The grating  96  could also allow a portion of the grain contained in the mixture to pass directly downwardly so that the grain would fall into the funnel-shaped trough  104  of the grain auger  48  and into the extension thereof which slopes upwardly toward the front and would be transported from there directly into the grain tank  50 . This portion of the grain thus does not need to be handled by the lower sieve  92 .  
         [0033]      FIG. 3  shows a lateral view of a second embodiment of a cleaning device  46 . Elements corresponding to those of the first embodiment are designated by the same reference characters. The most important difference between it and the first embodiment is that the second fan outlet  70  and the channel  82  disposed downstream of the second fan outlet  70  and leading to the cascade pan  86  and to the precleaning sieve  72  slope directly rearwardly and upwardly. As a result, the grain pan  80  above the housing  66  of fan  62  is therefore shorter, and there is no gap  84  between the front grain pan  40  and grain pan  80  above the housing  66  of fan  62 .  
         [0034]     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.