Abstract:
A combine harvester has a chopping mechanism and a spreading mechanism. The spreading mechanism is disposed downstream of the chopping mechanism, mechanically driven by a drive train and includes at least two rotors. The drive train of the spreading mechanism has a belt drive engageable by a clutch and configured to drive a first transmission stage via an output shaft, at least one second transmission stage drivably connected to the first transmission stage by a shaft and a braking device. The first and second transmission stages each have an output shaft for driving one or each of the rotors.

Description:
CROSS-REFERENCE TO A RELATED APPLICATION 
     The invention described and claimed hereinbelow is also described in German Patent Application DE 10 2013 108923.2, filed on Aug. 19, 2013. The German Patent Application, the subject matters of which is incorporated herein by reference, provides the basis for a claim of priority of invention under 35 U.S.C. 119(a)-(d). 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a combine harvester comprising a chopping mechanism and a spreading mechanism which is disposed downstream thereof. 
     Document DE 197 50 393 A1 makes known a mechanical drive for a chaff spreader, which is disposed downstream of a cleaning mechanism and comprises two or more fan units that are mechanically driven. To this end, a V-belt pulley is disposed on a shaft in a freely rotatable manner that is connectable in a non-positive manner to the V-belt pulley by a clutch. The V-belt pulley is driven via a drive train of the combine harvester, although this is not specified in greater detail. A universal drive shaft is connected to the shaft. The universal drive shaft transfers an introduced torque to a drive shaft of a bevel gear assembly. A V-belt pulley that drives the other fan units via a V-belt is mounted on the output shaft of the bevel gear assembly, which drives one of the fan units. This form of the drive for a spreading mechanism is characterized by high complexity. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the shortcomings of known arts, such as those mentioned above. 
     To that end, the present invention provides a combine harvester characterized by a simple and energy-efficient drive of the spreading mechanism thereof. 
     In an embodiment, the invention embodies a combine harvester with a chopping mechanism and a spreading mechanism disposed downstream thereof. The spreading mechanism is mechanically driven by a drive train and has at least two rotors. The drive train of the spreading mechanism comprises a belt drive that is engaged by a clutch and which drives a first transmission stage via an output shaft, at least one second transmission stage that is drivably connected to the first transmission stage by a shaft and a braking device. Each transmission stage comprises at least one output shaft for driving the rotor. 
     The mechanical drive of the spreading mechanism has the advantage over a hydraulic drive that the mechanical drive is characterized by the speed stability thereof, which results in greater stability of distribution. In light of safety requirements on the operation of spreading mechanisms, the rotors of which are disposed in an at least partially exposed manner, it is necessary to avoid long run-on times resulting from inertia. A clutch and a brake are therefore integrated in the drive train and disengage said drive train in order to decouple the drive train of the spreading mechanism from the combine harvester and actively brake the rotors. Rapid braking of the spreading mechanism and the rotors is thereby achieved. 
     Preferably, the belt drive is coupled to the chopping mechanism on the drive side. This coupling is advantageous given the fact that the chopping mechanism and the spreading mechanism are always both either active or inactive. If the chopping mechanism is shut off in order to switch to the swath-depositing mode, the drive of the spreading mechanism is also automatically idled. 
     Preferably, the belt drive is driven by a step drive. Given that the belt wraps from a pulley having a relatively large diameter onto a pulley having a relatively small diameter, speed adjustment can be easily implemented. This is significant when processing crop such as corn, for example, which, due to the properties thereof, requires a lower drive speed of the chopping mechanism although the spreading width remains unchanged, and therefore the drive speed of the spreading mechanism must be substantially higher than that of the chopping mechanism. An appropriate gear ratio can be implemented by the step drive. 
     As an alternative, the belt drive is driven by a variator. The variator permits stepless adjustment of the drive speed of the spreading mechanism, thereby improving the adaptation to changing harvesting conditions. The belt drive is used as a clutch in particular. The drive train is interruptible by the belt drive, which is used as a clutch, when the intention is to idle the chopping mechanism and the spreading mechanism. The use of the belt drive as a clutch is a cost-effective solution, since additional components in the drive train can be omitted. 
     To this end, the belt drive comprises a tensioning roller, which is actuated by an actuator. The tensioning roller is necessary in combination with a step drive or a variator in order to maintain the belt tension. The actuator is controlled accordingly in order to apply the necessary belt tension when the belt is installed, for example. On the other hand, if the spreading mechanism and, therefore, the exposed rotors must be halted because the combine harvester is supposed to be switched to a different crop type. For example, the actuator is controlled such that the belt tension is not maintained, namely the clutch is disengaged. 
     In an advantageous embodiment, the actuator is a hydraulically actuatable lifting cylinder. The lifting cylinder is designed as a single-acting lifting cylinder in particular. In this case, the single-acting lifting cylinder comprises a spring element, which subjects the lifting cylinder to a force on the face end that is used to return the lifting cylinder when the clutch is disengaged. The single-acting lifting cylinder is connectable to the tensioning roller via a lever arrangement such that the tensioning roller is pressed against the belt when the connecting rod is retracted, whereas the tensioning roller is moved away from the belt when the connecting rod is extended. The clutch is active when the connecting rod is retracted into the lifting cylinder, whereas the clutch is disengaged when the connecting rod is extended. 
     In particular, the lifting cylinder is coupled to a first hydraulic circuit on the combine harvester and the brake is coupled to a second hydraulic circuit on the combine harvester, wherein these two hydraulic circuits operate using different hydraulic pressures. In this case, the lifting cylinder is permanently subjected to the hydraulic pressure of the second hydraulic circuit and temporarily subjected to the hydraulic pressure of the first hydraulic circuit, whereas the brake is connected only to the first hydraulic circuit or is decoupled therefrom. 
     In a development, the brake and the clutch are engageable via a common valve. The valve is acted upon preferably hydraulically and is used to selectively engage the brake or the clutch. To this end, the valve comprises two switching positions such that the brake is released when the clutch is actuated, whereas the brake is actuated when the clutch is disengaged. This is achieved in the case of a single-acting lifting cylinder by virtue of the fact that, in a first switching position, in which the clutch is engaged and the brake is inactive, the lifting cylinder is subjected on the rod end to the hydraulic pressure of the first hydraulic circuit, which is greater than that of the second hydraulic circuit. Therefore, the lifting cylinder engages the clutch in order to maintain the belt tension by the tensioning roller, whereas the hydraulic pressure of the second hydraulic circuit is present on the face end. 
     In contrast, in the first switching position of the valve, the brake is decoupled from the first hydraulic circuit and is therefore not subjected to a hydraulic pressure, and so the brake is located in a released position. In the second switching position of the valve, in which the clutch is disengaged and the brake is active, the brake is subjected to the hydraulic pressure of the first hydraulic circuit. In the second switching position of the valve, the lifting cylinder is separated from the first hydraulic circuit on the rod end, and therefore the connecting rod of the lifting cylinder is extended by the hydraulic pressure of the second hydraulic circuit, which is present on the face end, and is supported by a spring force present on the face end. As a result, the lever arrangement is actuated such that the tensioning roller is moved away from the belt drive, i.e., the clutch is disengaged. 
     Preferably, the brake is disposed at one of the further transmission stages. Alternatively, the brake can be disposed in a pulley of the drive train. To this end, the brake is designed as a drum brake. 
     In that case, the valve is switchable depending on the operating state of the chopping mechanism. The valve is switched depending on the operating state of the chopping mechanism, wherein, during operation of the chopping mechanism, the valve is switched such that the clutch is actuated in order to drive the rotors of the spreading mechanism, while the brake is held in the released position. When the chopping mechanism is switched off, the valve is controlled such that the brake is actuated, while the clutch is held in the released position, and therefore the belt drive cannot transfer drive torque to the spreading mechanism. Preferably, the valve is designed as a gate valve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features and advantages of the invention will become apparent from the description of embodiments that follows, with reference to the attached figures, wherein: 
         FIG. 1  depicts a schematic side view of a combine harvester; 
         FIG. 2  depicts a perspective view of a chopping and spreading mechanism according to  FIG. 1 ; and 
         FIG. 3  depicts a section of a hydraulic circuit diagram of the spreading mechanism. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following is a detailed description of example embodiments of the invention depicted in the accompanying drawings. The example embodiments are presented in such detail as to clearly communicate the invention and are designed to make such embodiments obvious to a person of ordinary skill in the art. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention, as defined by the appended claims. 
       FIG. 1  depicts a side view of a harvesting machine designed as a combine harvester  1 , comprising a threshing mechanism  2 , which is known per se and is therefore not described in greater detail, and a downstream tray-type shaker  3 , as the separating device  4 . A cleaning mechanism  5  is disposed underneath the tray-type shaker  3  and comprises two sieves  6 ,  7 , which are disposed one above the other, and a cleaning fan  8 . The invention is expressly not limited to types of combine harvesters having this design, however, and, in fact also relates, for example, to combine harvesters having axial separating rotors as the separating device, and to combine harvesters having an axially disposed threshing-separating mechanism. 
     A header  10  is disposed in the front region of the combine harvester  1  and is used to cut and pick up the crop  9 . The header  10  conveys the crop  9  to a feed rake  11 , which is disposed on the front side of the combine harvester  1 . The feed rake  11  transfers the crop  9  to the threshing mechanism  2  disposed in the machine housing  12  in order to be threshed. A grain-chaff mixture  13 , which is composed mainly of grain, is separated at the threshing and separating grate  14  of the threshing mechanism  2  and travels via a grain pan  15  to the cleaning mechanism  5 , in order to separate the grain  16  from the non-grain components, i.e., from stalk parts  17  and chaff parts  18 . 
     In the rear region, a rotating impeller  19  is assigned to the threshing mechanism  2  and receives the crop stream  20  that emerges from the threshing mechanism  2 . Crop stream  20  is composed substantially of threshed stalks. The impeller conveys the crop stream to the tray-type shaker  3 , which conveys the crop stream  20  into the rear region of the combine harvester  1 . Any grain  16  still contained in the crop stream  20  and any short straw  17  and chaff  18  are separated out by falling through the tray-type shaker  3 , which is provided with sieve openings, to a return pan  21 . The return pan  21  transports the grain  16 , short straw  17 , and chaff  18  to the grain pan  15 . 
     The grain  16 , short straw  17  and chaff  18  ultimately reach the cleaning mechanism  5 , likewise via the grain pan  15 , in which the grain  16  is separated from the short straw  17  and the chaff  18 . The straw  22  and a certain percentage of waste grain  23  travel via the tray-type shaker  3  to the rear end of the combine harvester  1 , from where this is conveyed to a chopping mechanism  24  and to a spreading mechanism  30  dedicated thereto. The chopping mechanism  24  comprises, inter alia, a rotating chopper drum  25 , which is supported in a chopper housing  26 . The chopper drum  25  is equipped with movable knives  27 , which mesh with counter-knives  28  which are fixedly disposed in the chopper housing  26 . The knives  27  and the counter-knives  28  are used to chop the straw  22  into chopped crop and accelerate same. 
     A sieve overflow, which is composed largely of chaff and does not pass through the upper sieve  6 , travels via the upper sieve  6  into the rear region of the combine harvester  1  and can be likewise conveyed to the chopping mechanism  24 . The crop stream  29 , which emerges from the chopping mechanism  24  and substantially comprises chopped straw  22  and chaff, is conveyed further to a spreading mechanism  30 , which spreads the crop stream  29  on the field.\ 
     The representation in  FIG. 2  shows a perspective view of a chopping and spreading mechanism  24 ,  30  of a combine harvester  1  according to  FIG. 1 , including a perspective view of the drive train of the spreading mechanism  30 . The chopping mechanism  24  is disposed in the machine housing  12 , as described above. The chopping mechanism  24  is driven by a belt (not shown) that wraps around a drive pulley  31  disposed coaxially to the chopper drum  25 . Two driven pulleys  32   a ,  32   b , which have different diameters and form a step drive  33 , are disposed adjacent and coaxially to the drive pulley  31 . The step drive  33  is connected to an intermediate drive stage  34  by a driven belt  36 . A tensioning device  35  maintains the belt tension of the driven belt  36 . The intermediate drive stage  34  comprises a driven pulley  37 , around which a drive belt  38  is wrapped. The drive belt  38  also wraps around a drive pulley  39 , which is used to drive the spreading mechanism  30 . 
     The belt tension of the drive belt  38  is maintained by a tensioning system  49  comprising a tensioning roller  40 , which can be actuated by an actuator. The actuator is designed as a hydraulically actuatable lifting cylinder  41 , which is single-acting. The connecting rod of the lifting cylinder  41  actuates the tensioning roller  40  by means of a lever arrangement  49  by pressing the tensioning roller  40  against the drive belt  38  or moving said tensioning roller away from said drive belt. In the present exemplary embodiment, a clutch  42  is in an engaged state, and therefore the drive belt  38  can transfer torque from the driven pulley  37  to the drive pulley  39 . 
     An output shaft  43  extends from the drive pulley  39  and leads into a first transmission stage  44 , which is designed as a bevel gear assembly. A drive shaft (not illustrated) extends from the first transmission stage.  44 , perpendicularly to the output shaft  43 , and is used to drive a rotor  45  of the spreading mechanism  30 . In addition, a universal drive shaft  46  extends from the first transmission stage  44  and drivably connects the first transmission stage  44  to a second transmission stage  47 . A drive shaft (not illustrated for clarity) also extends from the second transmission stage  47 , perpendicularly to the output shaft  43 , and is used to drive a further rotor  45  of the spreading mechanism  30 . A brake  48  is disposed at the second transmission stage  47 , coaxially to the output shaft  43 . 
     The mode of operation of the drive train of the spreading mechanism  30  is explained in greater detail in the following. The chopping mechanism  24  is driven by the drive pulley  31 , as described above. A further drive pulley (not identified in  FIG. 2 ) is disposed coaxially to and behind the drive pulley  31  and has a smaller diameter, thereby enabling the chopping mechanism  24  to be driven at different speeds. A relatively slow drive speed is implemented for processing corn, as the crop type, in particular, in order to prevent damage to the chopping mechanism  24 . The step drive  33  compensates for this speed reduction in the case of a mechanical drive of the spreading mechanism  30  by transforming the reduced drive speed of the chopping mechanism  24  to the output speed for driving the spreading mechanism  30  that is required for maintaining a constant spreading width. As an alternative to the step drive  33 , in an advantageous embodiment, a variator can also be provided, which simplifies the adaptation of the speed ratio and ensures the stepless implementation thereof. 
     The belt tension of the drive belt  38 , which wraps around the intermediate drive  34  and the drive pulley  39 , is maintained by a tensioning system  50 . The hydraulically actuatable lifting cylinder  41  is acted upon accordingly by a hydraulic pressure in order to hold the belt tension of the drive belt  38  substantially constant. The lifting cylinder  41  is acted upon by the connection to a hydraulic circuit of the combine harvester  1 , which is explained below by reference to the section of a hydraulic circuit diagram of the combine harvester  1  represented in  FIG. 3 . 
     The belt drive, which comprises the intermediate drive  34 , the tensioning system  50 , the drive pulley  39 , and the drive belt  38 , functions as a clutch  42  when the chopping mechanism  24  is switched off. In this case, the hydraulic pressure required to hold the lifting cylinder  41  in the position thereof that tensions the drive belt  38  against the force of the spring element is not present and the lifting cylinder  41  is therefore retracted. The tensioning roller  40  is withdrawn by the lever arrangement  49 , thereby preventing the drive belt  38  from transferring torque from the intermediate drive  34  to the drive pulley  39 . In order to simultaneously activate the brake  48  at the second transmission stage  47  and thereby actively brake both rotors  45 , the lifting cylinder  41  and the brake  48  are operatively connected via a valve  51 , as shown in the excerpt of the circuit diagram in  FIG. 3 . 
     The valve  51 , which is designed as a 4/2-directional control valve, permits only two switching states, and therefore either the clutch is active due to action thereupon by the lifting cylinder  41 , or the brake  48  is active. The valve  51  is controlled depending on the particular operating state of the chopping mechanism  24 . When the chopping mechanism  24  is non-operational, as shown in the section of the circuit diagram according to  FIG. 3 , a first hydraulic pressure P 1  of a first hydraulic circuit  52  of the combine harvester  1  is present at the valve  51 , wherein this pressure acts on the brake  48  with a hydraulic pressure against the return force of a spring element, and therefore the brake  48  is active and the rotor  45  brakes. In this switching position of the valve  51 , a second hydraulic pressure P 2  of a second hydraulic circuit  54  is present at the single-acting lifting cylinder  41  on the face end, thereby extending the lifting cylinder  41 , and so the lever arrangement  49  moves the tensioning roller  40  away from the drive belt  38 , i.e., the clutch is disengaged. To this end, the first hydraulic pressure P 1  is greater than the second hydraulic pressure P 2 . 
     When the chopping mechanism  24  is switched on, the valve  51  is controlled accordingly in order to activate the clutch  42  and simultaneously deactivate the brake  48 . To this end, the switching of the valve  51  depressurizes the brake  48 , i.e., the hydraulic oil flows back into a tank  53 , while the lifting cylinder  41  is acted upon on the rod end with the first hydraulic pressure P 1 , thereby retracting the piston thereof against the second hydraulic pressure P 2  present on the face end, and thereby activating the clutch  42 . The tensioning roller  40  is therefore pressed against the drive belt  38  by the lever arrangement  49 , as is evident from the representation in  FIG. 2 . 
     LIST OF REFERENCE CHARACTERS 
     
         
           1  combine harvester 
           2  threshing mechanism 
           3  tray-type shaker 
           4  separating device 
           5  cleaning mechanism 
           6  sieve 
           7  sieve 
           8  cleaning fan 
           9  crop 
           10  header 
           11  feed rake 
           12  machine housing 
           13  grain-chaff mixture 
           14  separating grate 
           15  grain pan 
           16  grain 
           17  stalk part 
           18  chaff part 
           19  impeller 
           20  crop stream 
           21  return pan 
           22  straw 
           23  waste grain 
           24  chopping mechanism 
           25  chopper drum 
           26  chopper housing 
           27  knife 
           28  counter-knife 
           29  crop stream 
           30  spreading mechanism 
           31  drive pulley 
           32  driven pulley 
           33  step drive 
           34  intermediate drive stage 
           35  tensioning device 
           36  driven belt 
           37  driven pulley 
           38  drive belt 
           39  drive pulley 
           40  tensioning roller 
           41  lifting cylinder 
           42  clutch 
           43  output shaft 
           44  first transmission stage 
           45  rotor 
           46  universal drive shaft 
           47  second transmission stage 
           48  brake 
           49  lever arrangement 
           50  tensioning system 
           51  valve 
           52  first hydraulic circuit 
           53  tank 
           54  second hydraulic circuit 
         P 1  first hydraulic pressure 
         P 2  second hydraulic pressure 
       
    
     As will be evident to persons skilled in the art, the foregoing detailed description and figures are presented as examples of the invention, and that variations are contemplated that do not depart from the fair scope of the teachings and descriptions set forth in this disclosure. The foregoing is not intended to limit what has been invented, except to the extent that the following claims so limit that.