Abstract:
A drive arrangement for selectively repositioning a discharge spout of an agricultural harvesting machine by rotating it about a substantially vertical axis includes a drive motor coupled to a driveline incorporating a slip clutch operable for interrupting power flow to the spout in response to the driving torque exceeding a predetermined threshold value so as to prevent damage to the spout and/or drive motor when the spout impacts or is driven against an obstacle. The overload clutch is constructed so as to resist spout movement after the clutch has interrupted the flow of power through the driveline and to automatically reestablish power flow once the cause for the overload no longer exists.

Description:
FIELD OF THE INVENTION  
         [0001]    The invention concerns an arrangement for driving a discharge spout of an agricultural harvesting machine, and more specifically, concerns a drive including a motor, that is connected with the discharge spout over a driveline, and is arranged to pivot the spout about an approximately vertical axis, where an overload clutch is inserted into the driveline that interrupts the driveline when a threshold value of the torque transmitted to the discharge spout is exceeded.  
         BACKGROUND OF THE INVENTION  
         [0002]    In harvesting machines with discharge spouts that can be rotated about a vertical axis, such as combines with ejection ducts and forage harvesters with curved ejection ducts, there is the danger that the discharge spout can be damaged if it is thrown against an obstacle, such as a tree standing at the edge of the field, a power line pole or a transport vehicle operating alongside.  
           [0003]    EP 0 492 195 A proposes that the drive arrangement including a worm gear meshed with a turning circle of a curved discharge duct of a forage harvester will automatically disengage when excessive torques are applied to the discharge duct. Thereby the curved discharge duct can rotate freely and avoid an obstacle. The worm gear is blocked in the disengaged position by a blocking pawl. Therefore an operator must again release the blocking pawl after the trouble has been removed. The operator must therefore climb out of the operator&#39;s cab in order to release the blocking pawl at a location that is difficult to access and can continue the operation only after that. The free rotation of the curved discharge duct after the worm gear has been disengaged also has its problems, because after a first impact with an obstacle it can then recoil and collide with another obstacle and be damaged thereby.  
           [0004]    EP 0 672 339 A proposes that a shear pin be inserted into the driveline of the curved discharge duct of a forage harvester which shears upon unusual loading of the curved discharge duct. After the end of the unusual overload the shear pin must be replaced since it is usually located in a relatively inaccessible location this is possible only with a considerable time delay. If no shear pin is available the forage harvester cannot be used for an extended period of time. Furthermore the aforementioned disadvantages of the ability to rotate freely still remains.  
           [0005]    EP 1 092 342 A discloses a forage harvester whose curved discharge duct can be moved by a hydraulic motor. A pressure relief valve and feeder valve are arranged between the supply line and/or the return line of the hydraulic motor and the oil leakage line. The result is that in the case of a collision the hydraulic motor acts as a pump and brakes the curved discharge duct with a specified force. If it is driven for repositioning of the curved discharge duct just at the point of impact, the oil pressure that drives it is bled off by the pressure relief valve. The disadvantage here is that the hydraulic motor provides a relatively high braking effect on the basis of the gear ratio of the intervening gearbox, so that damage to the curved discharge duct remains conceivable. This solution is also relatively expensive and costly due to the necessary hydraulic elements.  
           [0006]    The problem underlying the invention is seen in the need to define an arrangement that is not too costly for the drive of a discharge spout that avoids damage to the discharge spout in the case of an impact of the discharge spout with an obstacle and that is distinguished by operator friendliness.  
         SUMMARY OF THE INVENTION  
         [0007]    According to the present invention, there is provided an improved drive for repositioning the discharge duct or spout of an agricultural harvester.  
           [0008]    An object of the invention is to provide a drive arrangement for a discharge spout which includes an overload clutch that automatically reestablishes the driving connection between the drive motor and the discharge spout as soon as the excessive torque acting upon the discharge spout is reduced. In normal operation the overload clutch transmits the driving torque from the drive motor to the discharge spout. Thus, the overload clutch separates the driveline, that connects the drive motor with the discharge spout so as to transmit normal torque, in the event the torque to be transmitted exceeds a threshold value, as may be caused by the discharge spout striking an obstacle during the operation, resulting in the discharge spout transmitting a torque to the drive motor, or as may be caused by the drive motor forcing the discharge spout against a fixed obstacle resulting in an applied load exceeding the normal torque. When the discharge spout no longer interacts with the obstacle the overload clutch again engages automatically, so that normal operation is again possible. Appropriate overload clutches are, for example, cam controlled clutches and star ratchets.  
           [0009]    In this way damage to the discharge spout is avoided by simple means and after an impact with an obstacle normal operation is again immediately possible.  
           [0010]    Yet another object of the invention is to provide a drive for a discharge spout that includes a clutch that is operable for providing a braking force that acts to prevent the discharge spout from swinging freely after an impact with an obstacle. An example of an overload clutch which is operable to provide a braking torque after it has interrupted the driveline is a friction clutch. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is a schematic left side elevational view of a harvesting machine, which is an exemplar of a machine with which the present invention is particularly adapted for use.  
         [0012]    [0012]FIG. 2 is a schematic view showing a drive coupled for rotating the discharge spout of the harvesting machine of FIG. 1.  
         [0013]    [0013]FIG. 3 shows a cross section of the overload clutch illustrated in FIG. 2. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0014]    Referring now to FIG. 1, there is shown a harvesting machine  10  in the form of a self-propelled forage harvester including a main frame  12  that is carried on front and rear wheels  14  and  16 . The operation of the harvesting machine  10  is controlled from an operator&#39;s cab  18  from which a crop recovery arrangement  20  can be viewed. Crop taken up from the ground by means of the crop recovery arrangement  20 , for example, corn, grass or the like is conducted to a chopper drum  22  that chops it into small pieces and delivers it to a conveyor arrangement  24 . The conveyor arrangement  24  conveys the crop in a rigid ejection tower  42 , that extends approximately vertically, that is followed by a discharge spout  26  that can be rotated relative to the ejection tower  42  about an approximately vertical axis and is in the form of a curved ejection duct. The crop leaves the harvesting machine  10  over the discharge spout  26  and is thrown to a container of a transport vehicle operating alongside. Between the chopper drum  22  and the conveyor arrangement  24  a post-chopper reduction arrangement  27  extends, that can be selectively inserted and removed from the flow of the crop, by means of which the crop to be conveyed is conducted tangentially to the conveyor arrangement  24 .  
         [0015]    The position of the discharge spout  26  can be changed by three actuators  30 ,  34  and  38 . A first actuator or drive arrangement  30 , described in greater detail below, is used for the rotation of the discharge spout  26 , that is supported in bearings, free to rotate, about a vertical axis on a turning circle  28 . The actuator  30  thereby makes it possible to rotate the discharge spout  26  to the rear into the transport position shown in FIG. 1, or to rotate it to the left or the right alongside the harvesting machine  10 . A second actuator  34  in the form of a hydraulic cylinder is arranged to pivot the discharge spout  26  about a horizontal axis  32  located at its upstream end. Thereby the second actuator  34  defines the height of the downstream end of the discharge spout  26 . A third actuator  38  in the form of a hydraulic cylinder is used to pivot an ejection door  36  at the downstream end  40  of the discharge spout  26 . The ejection door  36  can be adjusted so as to make it possible to control the angle at which the harvested crop leaves the discharge spout  26 . The actuators  34  and  38  are single acting or double acting hydraulic cylinders, where in the case of single acting hydraulic cylinders the weight of the discharge spout  26  itself or the ejection door  36  itself make possible the return movement.  
         [0016]    [0016]FIG. 2 shows the turning circle  28  and the actuator or drive arrangement  30 , which is provided for the rotation of the discharge spout  26  about the vertical axis, in greater detail. In the interior of the turning circle  28 , the underside of the discharge spout  26  is supported relative to the ejection tower  42  in rolling contact bearings, free to rotate (but not shown for the sake of clarity). At the outer circumference of the turning circle  28 , a first, ring-shaped gear  29  is arranged that is locked to transmit torque to the discharge spout  26 . The gear teeth of the first gear  29  mesh with a second gear  46 , that is connected for receiving torque transmitted to it by a first, vertical shaft  58 . The first shaft  58  is connected so as to be driven by an overload clutch  48  which is connected over a second shaft  60 , that is also vertical, to a third gear  50  so as to transmit driving torque to the clutch  48 . The third gear  50  meshes with a worm gear drive  52 , that rotates about a horizontal axis which is coupled to a drive motor  54  in the form of a hydraulic motor. The shafts  58  and  60  as well as the worm drive gear  52  are supported in bearings, not shown, directly or indirectly on the frame  12  of the harvesting machine  10 . The drive motor  54  is also connected directly or indirectly to the frame  12  of the harvesting machine  10 .  
         [0017]    Thereby the drive motor  54  is arranged to pivot the discharge spout  26  about the vertical axis over a driveline consisting of the worm gear drive gear  52 , the third gear  50 , the second shaft  60 , the overload clutch  48 , the first shaft  58 , the second gear  46  and the first gear  29 . The drive motor  54  is controlled by an operator in the operator&#39;s cab  18 .  
         [0018]    A sensor  56  is provided that can determine the angle of rotation of the discharge spout  26  by any desired means in order to display to an operator in the operator&#39;s cab  18  information about the immediate angle of rotation of the discharge spout  26  or in order to use this information for the control of the control arrangement that is arranged to bring the discharge spout  26  into a desired position by control of the drive motor  54 , which position can be provided as input by the operator or otherwise automatically controlled. The sensor  56  may, for example, be an incremental angle transmitter that operates optically and interacts with corresponding markings on the discharge spout  26 . It can also operate on an inductive basis and interact with permanent magnets attached to the discharge spout  26 .  
         [0019]    The overload clutch  48  is configured in such a way that it disengages when a defined torque transmitted by the second shaft  60  to the first shaft  58  (or the reverse) is exceeded, that is, it interrupts the transmission of torque between the first shaft  58  and the second shaft  60 . In this way the discharge spout  26 —otherwise not supported on the frame  12 —becomes able to rotate about the vertical axis in the case of an overload and can avoid being damaged by coming into contact with obstacles. The result is that the discharge spout  26  is not damaged, if the drive motor  54  forces the discharge spout  26  against an obstacle, for example, the transport vehicle operating alongside the harvesting machine for the chopped crop, or if the discharge spout  26  collides with an obstacle during the operation. Furthermore, in such cases, any damage to the drive motor  54  and the other mechanical elements of the actuator  30  need not be feared.  
         [0020]    The overload clutch  48 , according to the invention, interrupts the driving connection, as soon as the difference of the torques between the first and second shafts  58  and  60 , respectively, exceeds a defined threshold. When the threshold value is no longer exceeded, the driving connection is automatically re-established. For the overload clutch  48 , a device known in itself, such as a star ratchet, a friction clutch or a cam controlled clutch can be employed. Overload clutches of this type are commercially available from the firm GKN Walterscheid, 53797 Lohmar, Del. under the designations K32B, K94B or K64/1. Appropriate overload clutches are also disclosed in the publications DE 31 51 486 C, DE 34 18 558 C, DE 41 37 829 A, DE 195 38 351 C, DE 196 11 622 C, DE 197 15 269 C and DE 197 44 154 C, whose disclosures are incorporated into the present application by reference.  
         [0021]    A possible embodiment of an overload clutch  48  is shown in FIG. 3. The overload clutch  48  includes a cylindrical housing  62  having a bottom  64  and a cover  66 . The bottom  64  is connected with the second shaft  60  and oriented coaxially to it. The cover  66  is screwed onto the housing  62  and contains a central opening through which the first shaft  58  extends. A first friction lining  68  is fastened to the bottom  64 . A second friction lining  70  is located on the first friction lining  68  and is connected with a carrier  74  on its surface opposite the first friction lining  68 . The carrier  74  is connected with a stub shaft  72 , that is arranged coaxially to the first shaft  58 . The stub shaft  72  and the lower end of the first shaft  58  engage each other and can slide relative to each other in the vertical direction, but are coupled to each other so as to transmit torque, since their cross sections are non-circular. The inner cross section of the lower end of the first shaft  58  and the outer cross section of the stub shaft  72  may, for example, be square. The first shaft  58  carries a ring  76  on which a helical spring  78  is supported, which forces the carrier  74  downward and thereby forces the second friction lining  70  against the first friction lining  68 . Obviously it would be conceivable to subdivide the first shaft  58  into two partial parts that can be separated from each other of which only one extends into the housing  62 . Thereby the assembly and the replacement of the overload clutch  48  would be simplified. The second shaft  60  could also be separable from the overload clutch  48 .  
         [0022]    The torque from the second shaft  60  is transmitted over the bottom  64  to the first friction lining  68 . From there it is transmitted to the second friction lining  70  and over the carrier  74  and the stub shaft  72  to the first shaft  58 . If the torque transmitted exceeds a threshold value, that is a function of the material and the dimensions of the friction linings  68  and  70  and the force of the helical spring  78 , the friction linings  68  and  70  begin to rotate relative to each other. The driving connection is interrupted. In the case of an impact of the discharge spout  26  against an obstacle, the spout  26  can therefore avoid being damaged by the impact. If the discharge spout  26  is blocked mechanically by an obstacle, it can then not be damaged when the drive motor  54  is in operation because of the interrupted driving connection. Simultaneously, the friction linings  68  and  70  rubbing against each other generate a braking torque that prevents a free rotation of the discharge spout  26  and possible impact with a second obstacle. As soon as the torque transmitted no longer exceeds the threshold value, the driving connection is reestablished. The operator in the operator&#39;s cab  18  or the control arrangement described above can thereby rotate the discharge spout  26  again by operation of the drive motor  54 , as soon as the discharge spout  26  is no longer blocked.  
         [0023]    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.