Abstract:
It is proposed that a sensor ascertain a parameter of the harvested crop and send a signal used for changing the speed of feeding devices for the chopping and/or the speed of the chopping device in order for automatically obtaining a change in the length of the cut of the chopping device.

Description:
FIELD OF THE INVENTION 
     The invention pertains to a device for adjusting the cutting length of a chopping device. 
     BACKGROUND OF THE INVENTION 
     Field choppers employed in agriculture are used for cutting and picking up harvested crops, for example, grass or corn, which is normally used as fodder for cattle. To promote the digestibility of the fodder, the cut length of the harvested crop is very important. In current field choppers, means have therefore been proposed for adjusting the cutting length of the chopping device wherein hydraulic motors, adjustable either continuously or in steps or shifting transmissions have been used. The operator of the field chopper, however, must make the decision about the cutting length, and in this regard must employ his experience or take other factors into consideration. It is possible that poor cutting lengths will be selected, in particular in the case of inexperienced operators or under unsuitable conditions. 
     The problem underlying the invention is that of relieving the field chopper operator of the task of adjusting the cutting length. 
     SUMMARY OF THE INVENTION 
     According to the present invention, there is provided an improved arrangement for adjusting the cutting length of a chopping device. 
     An object of the invention is to provide an improved cutting length adjusting arrangement wherein a sensor is provided to ascertain one parameter of the crop to be harvested, and to adjust the cutting length of the chopping device as a function of the measured parameter. In one simple embodiment, the measurement value of the sensor, and/or of a cutting length derived from it, is displayed, and the operator will adjust the cutting length accordingly. In one preferred embodiment, the cutting length of the chopping device will be adjusted automatically to a value derived from the measurement value from the sensor. 
     In this manner an optimum digestibility will be obtained, regardless of the properties of the chopped crop. Thus, an optimum utilization of the nutritional value of the harvested crop will be obtained when it is used as animal fodder. 
     For example, the sensor can determine the moisture content of the chopped crop. As a moisture sensor, in particular a microwave sensor, a capacitive sensor, or a conductivity sensor can be used. However, any other kind of sensor suitable for moisture measurement can be used. If the chopped crop is relatively moist and thus more easily digested, then a greater cutting length would be adjusted than in the case of dry chopped material. 
     But instead of, or in addition to moisture, the nutrient content of the crop can be measured, for instance, as determined by an appropriate sensor, as disclosed for example in U.S. Pat. No. 5,991,025. Also, the grain content can be measured optically. Other constituents of the chopped crop can also be ascertained. 
     The cutting length can be adjusted by a suitable control device, which may be either separate or integrated into the existing onboard electronics systems. This is linked with the sensor and controls the cutting length according to its measurement value. The cutting length can be adjusted by changing the rotational speed of a chopping drum and/or by variation in the speed with which the harvested crop is delivered to the chopping drum. As a rule, the second variant will be used, wherein the rotational speed of the front press rollers will be varied by means of an electric motor or hydraulic motor. In this case, a portion of the drive power of the front press rollers can be employed mechanically. Basically, however, it would also be possible to vary the rotational speed of the chopper drum, which can be done by adjusting the rotational speed of the drive motor. 
     In a preferred embodiment, the control device is connected to a memory unit in which information concerning the cutting length and the rotational speed of the chopper drum and/or of the front press rollers is stored as a function of the measurement values of the sensor, e.g., in the form of a table, a database or mathematical curves or functions. This information can be derived from fodder tests or other sources. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The figures show one embodiment of the invention, which is described in greater detail below. 
         FIG. 1  is a schematic, left side elevational view of a harvesting machine with which the present invention is particularly adapted for use. 
         FIG. 2  is a schematic illustration of the device for effecting automatic adjustment of the cutting length. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to  FIG. 1 , there is shown a harvesting machine  10 , illustrated as a type of self-propelled field chopper including a main frame  12  supported on front and rear wheels  14  and  16 . The harvesting machine  10  is operated from a driver&#39;s cab  18 , from which a harvested material pickup device  20  is visible. The crop, e.g., corn, grass or the like, picked up from the ground by the harvested material pickup device  20 , is moved through four front press rollers  30 ,  32 ,  34 ,  36  to a chopper drum  22 , which chops the crop into small pieces and sends it to a conveyor unit  24 . The material passes from the harvesting machine  10  to a side trailer via a discharge chute  26 , which may be adjusted about an upright axis. Located between the chopper drum  22  and the conveyor unit  24  is a post-comminution device including two cooperating rollers  28 , which act to feed the conveyed material tangentially to the conveyor unit  24 . 
     According to the present invention, a device for automatic adjustment of the cutting length is provided which relieves the driver of the task of adjusting the cutting length to a value at which the chopped crop will be best suited as fodder for animals. The cut length of the chopped crop that is ejected from the discharge chute  26  depends on the rotating speed of the front press rollers  30 – 36 , on the speed of the chopper drum  22 , and on the number of blades attached to the chopper drum  22 .  FIG. 2  shows a detailed illustration of the drive unit for the chopper drum  22  and the front press rollers  30 – 36 , and the device for automatic adjustment of the cutting length. 
     An internal combustion engine  42  operating at constant speed, while in a harvest mode, drives a transmission belt  46  via a pulley  44  which includes a disengageable coupling. The transmission belt  46 , in turn, drives a pulley  48  coupled to the chopper drum  22 . The chopper drum  22  includes a solid shaft  50  which drives a cogwheel or gear  52  which is meshed with a ring gear  54  of a planetary gear train  56 . The planetary gear train  56  includes a sun wheel  58  coupled to a hydraulic motor  60 . Planet gears  62  of the planetary gear train  56 , are coupled via a planet carrier with a cogwheel or gear  64  that drives the lower front press rollers  30 ,  32  via an additional cogwheel or gear  66 , and drive the upper front press rollers  34 ,  36  in a direction opposite that of the lower front press rollers, via additional cogwheels or gears  68  and  70 . Due to this configuration, the chopper drum  22  is driven at a constant rotational speed. The rotational speed of the front press rollers  30 – 36  depends on the rotational speed and direction of the hydraulic motor  60 . 
     The hydraulic motor  60  is connected, by a valve unit  72 , to a pressurized hydraulic fluid source  74  and to a hydraulic fluid supply tank  76 . The valve unit  72  is connected electrically to a control device  78  that can be actuated to control the valve unit  72  such that the hydraulic motor  60  will rotate at a rotational speed and direction specified by the control unit  78 . The control unit  78  is thus set up for continuous adjustment of the cutting length of the ejected material. 
     The device for automatic adjustment of the cutting length also comprises a sensor to measure the properties of the crop. In the illustrated embodiment, this sensor is a moisture sensor that is constructed from a microwave transmitter  40  and a microwave receiver  38 . The moisture sensor is mounted on the discharge chute  26  and operates via transmission, i.e., by transmitting radiation through the crop material passing through the discharge chute  26 . Details on the design and operation of this kind of moisture sensor are disclosed in DE 196 48 126 A, whose teaching is hereby incorporated by reference into the present application. The control device  78  is connected to the microwave transmitter  40  and the microwave receiver  38 . Based on the signals received from the microwave receiver  38 , the control device  78  evaluates the moisture content of the chopped crop. It then takes, from a memory unit  80 , a value for an optimal cutting length corresponding to the measured moisture content, and controls the valve unit  72  accordingly. The cutting length values might originate from tests or from experienced experts. In general, the cutting length will be greater the more moisture is contained in the chopped material. The memory unit  80  contains a table or database in which the cutting lengths or the rotational speed of the hydraulic motor  60 , as a function of the moisture in the harvested crop, are saved. Any intermediate values could be computed by interpolation. The use of algorithms, i.e., mathematic functions, would also be possible. Thus, even in the event of changes in the moisture of the harvested crop during the harvesting process, an optimal cutting length will be achieved without any delay and without manual intervention by the operator. 
     It should be mentioned that different modifications to the invention are possible. For example, it would be possible to use any type of moisture sensor instead of, or in addition to, the microwave sensor  38 ,  40 , such as, for example, a capacitive sensor, an optical sensor, or a conductivity sensor. The sensor can also be located at a point on the harvesting machine  10  between the chopper drum  22  and the rotating track of the discharge chute  26 , or upstream from the chopper drum  22 . Furthermore, any other sensors can be used, alternatively or additionally, that ascertain the moisture or other parameters of the harvested crop, and whose signals can be used for adjusting of the cutting length. For example, the protein content of the chopped crop could be measured by a sensor operating in the near-infrared range. Based on the measurement value of the parameter and on information saved in the storage unit  80 , the cutting length could again be adjusted accordingly. If several sensors are used that measure different parameters of the chopped crop, then the control unit  78  will take from the storage unit  80  a cutting length value which best fits with the combination of measured parameters. 
     In certain cases, automatic adjustment of the cutting length can be switched off by an operator in the cab  18  and replaced with a manual setting. 
     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.