Abstract:
A self-propelled forage harvester includes an overload clutch inserted into the driveline of a crop conveying element of crop pick-up arrangement of the harvesting machine. The overload clutch generates acoustic and/or mechanical vibrations when a defined torque is exceeded, and a knock sensor is provided for sensing when the overload clutch is operating in an overloaded condition. The knock sensor sends a signal to a control arrangement including a signal processor which recognizes a vibration pattern representative of an overload, and in response to such a pattern, sends a control signal for shutting off the drive to various driven components of the harvester.

Description:
FIELD OF THE INVENTION 
   The invention concerns a detection arrangement for the detection of a crop jam in a harvesting machine. 
   BACKGROUND OF THE INVENTION 
   DE 199 18 552 A describes a harvesting machine with a harvested crop take-up arrangement, that is equipped with an adjustable hold-down arrangement for the harvested crop that limits its flow in the upward direction. In case of a harvested crop jam that is detected by a crop jam sensor, the hold-down arrangement is raised automatically in order to simplify the ejection of the jammed harvested crop during the reverse operation. The jam sensor detects the drive torque of one of the supply rolls or of the chopper drum of a forage harvester. In another embodiment, the jam sensor measures the torque on the shaft of the upper roll of the slope conveyor of a combine. The jam sensors described can detect jams within the harvesting machine, but are not arranged to detect jams in the front harvesting attachment. 
   In the subsequently published European patent application EP 02100450.2, a front harvesting attachment is described with a torque sensor inserted into the driveline of its crop conveying elements. The torque sensor transmits a torque signal that is conducted to a control arrangement which compares it with an allowable maximum value. If the torque signal exceeds the maximum value, the drive of the front harvesting attachment is automatically turned off. Here, as in the case of the harvesting machine according to DE 199 18 552 A, an additional sensor is provided that must be connected electrically with the harvesting machine. Therefore, a certain expense is required in order to be able to recognize a crop jam. 
   From U.S. Pat. No. 5,070,682 A, an acoustic detector has become known for sensing of an airborne noise that is expected to detect stones intruding into the crop supply mechanism of a forage harvester. This detector is not appropriate for the detection of a crop jam. 
   SUMMARY OF THE INVENTION 
   The problem underlying the invention is seen in the need to make available an improved arrangement for the detection of a crop jam in a front harvesting attachment or a harvesting machine that is distinguished by low cost and high reliability. 
   An object of the invention is to provide a crop harvesting machine including an acoustical sensor for detecting when a crop feeding condition has occurred, which indicates that there is a crop jam. 
   It is proposed that an overload clutch be inserted into the driveline of a crop conveying element of the harvesting machine that interrupts the driveline, in the case that an established torque limit is exceeded due to a crop jam, and that generates acoustic or mechanical vibrations. The detection arrangement is equipped with a sensor that can, if necessary, receive these vibrations and detects them with the use of an appropriate analog and/or digital signal processor. A control arrangement connected with the sensor can inform the operator of the harvesting machine acoustically and/or optically in case of a crop jam, or even take appropriate steps automatically to remove the crop jam, particularly turning off the drive of the crop conveying element, raising the hold-down arrangement of a pick-up or a reel of a cutter head, and/or reversing the drive of the crop conveying element. 
   In this way, the result is a relatively simple and low cost detection arrangement for a crop jam. Only a single sensor is required that can interact with as many overload clutches as desired. 
   The sensor is preferably an acoustic sensor (microphone) to which the vibrations generated by the overload clutch are transmitted by airborne sound (acoustically) and/or structure-borne sound (mechanically). Preferably, a commercially available knock sensor can be used as it is applied to engines for the detection of undesirable knock noises. Such a knock sensor can also be used to control other elements of the harvesting machine, in which a forage harvester, for example, uses such a device for the positioning of the spacing between a chopper drum and a shear bar. The vibrations generated by the overload clutch are transmitted to knock sensors of this type, primarily mechanically, that is by structure-borne sound. 
   An advantage of the detection arrangement according to the invention lies in the fact that it is also appropriate for the detection of a crop jam in a front harvesting attachment, for example, a pick-up, a corn head, a cutter head or a corn picker of a combine. For this purpose, the overload clutch is inserted into the driveline of the front harvesting attachment. The overload clutch may be located on the harvesting machine or on the front harvesting attachment. As a rule, the sensor is attached to the harvesting machine, which obviates the routing of additional lines or the provision of a wireless connection for the front harvesting attachment, although it would also be possible to fasten the sensor to the front harvesting attachment. The vibrations generated by the overload clutch are transmitted—as a rule mechanically—through the frame of the front harvesting attachment and over the intake housing to the harvesting machine, where they are detected by the sensor. 
   All configurations of mechanical overload clutches can be considered that generate detectible vibrations when an established torque in the driveline is exceeded. Appropriate clutches are, for example, cam-controlled clutches and star ratchets. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The drawings show an embodiment of the invention that shall be described in greater detail in the following. 
       FIG. 1  is a schematic left side view of a harvesting machine with a detection arrangement according to the invention. 
       FIG. 2  is a schematic plan view of the drive elements of the harvesting machine. 
       FIG. 3  shows an example of an analog signal processing circuit of the detection arrangement. 
       FIG. 4  is a section taken through an overload clutch. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 1 , there is shown a harvesting machine in the form of a self-propelled forage harvester  10 , in which a detection arrangement is provided for the detection of a crop jam. The forage harvester  10  is supported on a frame  12  that is carried on front and rear wheels  14  and  16 . The forage harvester  10  is controlled from an operator&#39;s cab  18  from which a crop take-up arrangement  20  can be viewed and controlled. Crop taken up from the ground by means of the crop take-up arrangement  20 , for example, corn, grass or the like is conducted over supply or feed rolls  30  that are arranged within an intake housing  32  to a chopper drum  22  that chops the crop into small pieces in interaction with a shear bar  46  and delivers it to a conveyor or blower arrangement  24 . The crop leaves the forage harvester  10  to a transport vehicle operating alongside it or a trailer over a discharge duct  26  which is mounted for being adjusted about an upright axis. A post-chopper reduction arrangement or kernel processor  28  extends between the chopper drum  22  and the conveyor arrangement  24 , through which the crop to be conveyed is conducted tangentially to the conveyor arrangement  24 . 
   In this embodiment, the crop take-up arrangement  20  is configured as a so-called pick-up and arranged as an independent unit. However, this crop take-up arrangement  20  could also be an attached implement that is attached, for example, to a flange at the front region of a cutter head of a combine. During operation on the field, the crop take-up arrangement  20  is supported on the ground by support wheels  40 . The assignment of the crop take-up arrangement  20  consists of taking up harvested crop of the most varied types and conditions deposited in swaths on the ground and to conduct it to the forage harvester  10  for further processing. For this purpose, the harvested crop take-up arrangement  20  is moved across the field at a small distance from the ground during the harvesting operation, while it is raised for transport on a public road or on paths. 
   The harvested crop take-up arrangement  20  includes a conveyor arrangement  34  in the shape of a screw conveyor that conveys the crop taken up, in a manner known in itself, from the sides of the harvested crop take-up arrangement  20  to a discharge opening, not shown, located in the center. Located to receive the crop, when it passes to the rear through the discharge opening, are the supply rolls  30 . A take-up device  36  is driven to rotate like the conveyor arrangement  34 , and is arranged underneath and forward of the conveyor arrangement  34 , and raises the crop from the ground with its conveying tines in order to transfer it to the conveyor arrangement  34 . A hold-down  38  in the form of a sheet metal part is arranged above the take-up device  36 . Alternatively, the hold-down  38  could be in the form of a roll or be provided with several bars. The axes of rotation of the conveyor arrangement  34  and of the take-up device  36  extend parallel to each other and to the ground and transverse to the direction of operation of the forage harvester  10 . 
   Referring now also to  FIG. 2 , it can be seen that during the harvesting operation, the conveyor arrangement  34  and the take-up device  36  are driven mechanically by the internal combustion engine  110  of the forage harvester  10 . The internal combustion engine  110  drives a hydrostatic pump  114  and an auxiliary hydraulic pump  116  over a bevel gearbox  112 . The bevel gearbox  112  drives a drive belt  118  over a hydraulically actuated and electronically controlled main clutch  120 . The belt drives the chopper drum  22  and the blower  24  of the forage harvester  10 . Furthermore, the drive of the chopper drum  22  is connected over a usual electrically actuated clutch  122 , with a length-of-cut gearbox  124  for the supply rolls  30 , that drives the supply rolls  30 . A reversible hydraulic motor  126  is coupled with the length-of-cut gearbox  124  in order to drive the supply rolls  30  during reverse operation. The reversible motor  126  is supplied with pressurized hydraulic fluid provided by the auxiliary pump  116  and is conducted to the reversible motor  126  over an electromagnetically actuated valve  128 . An electromagnetically actuated valve  130  controls the fluid connection between the pump  116  and the main clutch  120 . A control arrangement  44  controls the valves  128  and  130  as well as the clutch  122 . It should be noted that the length-of-cut gearbox  124 , in another embodiment, may be equipped with a planetary gearbox that makes possible a continuously variable adjustment of the length of cut by means of a hydraulic motor from the operator&#39;s cab  18 . In this respect, reference is made to the disclosure of DE 198 12 500 A, which is incorporated into the present application by reference. 
   A removable articulated shaft  132  extends between the length-of-cut gearbox  124  and the rear side of the crop take-up arrangement  20 . The conveyor arrangement  34  and the take-up device  36  are driven by means of the articulated shaft  132 . 
   The relative position of the conveyor arrangement  34  to the take-up device  36  could be invariable, however as a rule, it is variable due to the support in bearings of the conveyor arrangement  34  on lever arms. The aforementioned lever arms on both sides are spring loaded in order to force the conveyor arrangement  34  against the crop. The position of the hold-down device  38  can be repositioned between the operating position, shown in  FIG. 1  in solid lines, in which the hold-down device  38  interacts with the take-up device  36 , and a non-operating position in which the hold-down device is shown in dashed lines indicated by number call-out  38 ′. For this purpose, a hydraulic cylinder  42  is used (which could also be replaced by an electric motor), that is arranged to rotate the hold-down device  38  about a horizontal axis  43  extending transverse to the direction of operation of the forage harvester  10 . The non-operating position of the hold-down device  38  has been shown to be useful during reverse operation, in which the supply rolls  30 , the conveyor arrangement  34 , and the take-up device  36  (optionally also the chopper drum  22 ) are operated in a direction of rotation opposite to the normal harvesting operation, in order to be able to eject jammed material. The reverse operation is performed by the reversible hydraulic motor  126  at the length-of-cut gearbox  124 . Even when a metal detector, not shown, arranged within one of the supply rolls  30 , responds and turns off the drive of the supply rolls  30 , a reverse operation is appropriate. 
   The control arrangement  44  is provided in order to be able to move the hold-down device  38  automatically between the operating position and the non-operating position and to activate the reverse operation. It is connected (preferably over a CAN bus) with one or more knock sensors  48  at the shear bar  46  and an electromagnetically controlled valve  50 , which controls the load on the hydraulic cylinder  42 . The knock sensor  48  is used to automatically reposition the spacing between the shear bar  46  and the chopper drum  22 , since it detects the noises resulting from the impact of the knives of the chopper drum  22  on the shear bar  46 . Furthermore, the control arrangement  44  is also connected over the CAN bus with the clutch  124 , the valves  128  and  130  (see FIG.  2 ), a display arrangement  52  within the range of vision of the operator in the operator&#39;s cab  18 , and a torque sensor  56  that is arranged to measure the torque of a supply roll  30 . 
   An overload clutch  54 , in the form of a cam-controlled clutch, is inserted into the driveline of the conveyor arrangement  34  between the conveyor arrangement  34  and the articulated shaft  132 , that connects it with the length-of-cut gearbox  124 , used for its mechanical drive at the side of the intake housing  32  of the forage harvester. An embodiment of the overload clutch is explained below on the basis of FIG.  4 . The overload clutch  54  separates the driveline of the conveyor arrangement  34 , when the torque transmitted by the overload clutch  54  exceeds an established limit value determined by the overload clutch  54 . In such a case, that as a rule, is caused by a crop jam in the conveyor arrangement  34 , that results in particular from an excessive amount of crop taken up, the overload clutch  54  generates mechanical vibrations in the form of a rattle. These vibrations are transmitted by the frame of the crop take-up arrangement  20  and the intake housing  32  to the knock sensor  48 . 
   The control arrangement  44  is arranged to monitor the signals from the knock sensor  48  and from the torque sensor  56  during the harvesting operation. If the signal of the torque sensor  56  indicates that a threshold value has been crossed, which points to a crop jam at the supply rolls  30 , the mechanical drive of the chopper drum  22 , the supply rolls  30 , the conveyor arrangement  34  and the take-up device  36  is turned off by means of the valve  130  and the main clutch  120 . Concurrently, the hold-down  38  is raised by actuation of the valve  50  and, after the expiration of a pre-determined time interval, reverse operation is initiated, in that the clutch  122  is disengaged and the reverse motor  126  is activated over the valve  128 . Furthermore, the operator is notified about the crop jam over the display arrangement  52 . 
   Analogously, the procedure is performed as soon as the knock sensor  48  receives signals generated by the overload clutch  54 . For this purpose, an analog signal processing circuit is inserted between the knock sensor  48  and the digital control arrangement  44 , as shown in FIG.  3 . The signal processing circuit includes an amplifier  68 , whose input is connected with the knock sensor  48 . The amplified signal is conducted to a band pass filter  62  that only permits frequencies that are generated by the overload clutch  54  to pass to the knock sensor  48 . The filtered signals are rectified in a rectifier  64  and are compared in a comparator  66  with a comparable value. When the signals from the knock sensor  48  exceed a threshold value from which the presence of a crop jam can be assumed, the comparator  66  transmits a corresponding signal to the control arrangement  44 . It would also be possible to replace the analog signal processing circuit shown in  FIG. 4  with a digital signal processor that can be realized as a process running in the control arrangement  44  or by an external circuit to which a digitized signal of the knock sensor  48  is conducted. The digital signal processor could perform the operation of the analog signal processing circuit shown in  FIG. 3  in order to analyze the signal spectrum made available by the knock sensor  48  for frequencies that are characteristic of a disengaged overload clutch  54 . 
   If the output signal of the signal processor points to the fact that the torque of the overload clutch  54  has exceeded the threshold or limit value, the normal drive of the chopper drum  22 , the supply rolls  30 , the conveyor arrangement  34 , and the take-up device  36  is turned off. As is the case when a crop jam of the supply rolls  30  has occurred, the hold-down  38  is raised, the operator is informed over the display device  52 , and the reverse operation is initiated. In the case of a response from the metal detector, the control arrangement  44  also proceeds in a corresponding manner, that is, it turns off the aforementioned elements, raises the hold-down device, and after a time delay, begins the reverse operation. The result is that the raising of the hold-down device  38  occurs before the point in time that the reverse operation begins. If these events occur simultaneously, a jam could possibly occur during the reverse operation. The operator can initiate the normal harvesting operation manually after the crop jam has been removed. After a certain reverse operating time interval, the normal harvesting operation can also be resumed automatically by the control arrangement  44 . It should be noted that the signal of the knock sensor  48  can also be used for the detection of the presence of a crop flow as it is disclosed in DE 102 11 800, whose contents is incorporated into the present application by reference. 
     FIG. 4  shows a section through an appropriate overload clutch  54  in its torque transmission position. After the occurrence of an overload, the overload clutch  54  rotates at a reduced ratchet torque. The overload clutch  54 , shown in  FIG. 4 , consists generally of a clutch sleeve  201 , in which a clutch hub  202  is retained. Driver bodies  206  are guided, free to move radially, in the clutch hub  202  and retained radially outward by support cams  207  loaded in the inward direction by springs  208 . The forces of the springs  208  are supported at the radially outer side on end stops of a common pin  209 , with the result that the spring forces are completely balanced at all times. Recesses  210  are provided uniformly distributed around the circumference in the clutch sleeve  201 , in each of which two rolling bodies  203  are retained. The recesses  210  are provided with centrally arranged cams  205  that are used as stops for the rolling bodies  203  after the occurrence of an overload, in which the rolling bodies  203  are carried along by the head parts  204  of the driver bodies  206 . The effective length of the recesses  210  in the circumferential direction is reduced by the sliding of one of the rolling bodies  203  up to the cam  205  so that the clutch runs with a reduced ratchet torque. By reducing the rotational speed, a condition can be attained in which the head parts  204  of the driver bodies  206  are in a position to return the rolling bodies  203  that were shifted out of their end positions into their torque transmission position, and thereby to enable the head parts  204  to re-occupy the torque transmission position between two rolling bodies  203 . When the predetermined torque is exceeded, the driver bodies  106  that knock against the rolling bodies  203  generate rattling vibrations that are taken up by the knock sensor  48  and are detected by the control arrangement  44 . 
   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.