Abstract:
The invention concerns an arrangement for the adjustment of the position of a shearbar with respect to knives of a chopper assembly. The arrangement includes a first adjusting drive to position the first end of the shearbar at a predetermined first spacing from the knives and a second adjusting drive to position the second end of the shearbar with respect to the knives until a spacing measurement arrangement indicates that the spacing between the shearbar and the knives is less than a threshold value. An analogous procedure is applied to the first adjusting drive. On the basis of the measurement values the shearbar is brought into a position that corresponds to a desired gap between the shearbar and the knives. Each of the first spacing and the second spacing are greater than the desired gap between the shearbar and the knives.

Description:
BACKGROUND  
       [0001]     1. Field of the Invention  
         [0002]     The invention concerns an arrangement for the adjustment of the position of a shearbar with respect to the knives of a chopper assembly, for use in a harvesting machine, and a method of adjusting the arrangement.  
         [0003]     2. Related Technology  
         [0004]     In forage harvesters the spacing between the chopper knives and the shearbar is a significant value for the quality of the cut and the power required for the cutting operation. As a rule, shearbars of this type are arranged so that they can be adjusted with respect to the chopper drum by means of electric motors, where each end of the shearbar is associated with an electric motor. A spacing sensor, that as a rule is configured as a knock sensor or a magnetic spacing sensor, detects a signal that contains information regarding the spacing between the shearbar and the nearest knife of the knives on the chopper drum.  
         [0005]     In the state of the art various procedures are known in order to bring the shearbar into the desired position relative to the chopper drum by an automatic control of the electric motors.  
         [0006]     EP 0 291 216 A suggests initially moving both ends of the shearbar away from the chopper drum. Then one end of the shearbar is next moved towards the chopper drum, until a sensor detects a contact between the shearbar and the chopper drum. Then this particular end is moved away from the chopper drum by a first distance and the other end of the shearbar is moved towards the chopper drum, until a sensor detects a contact between the shearbar and the chopper drum. Then the other end is again withdrawn from the chopper drum by the first spacing. This procedure is performed successively until both motors bring about a contact between the shearbar and the chopper drum upon their activation. Then the shearbar is retracted from the chopper drum at both ends by a path of from approximately 0.127 to 0.254 mm.  
         [0007]     EP 0 335 256 A describes an arrangement in which one end of the shearbar is moved in the direction of the chopper drum by a first motor until a contact exists. Then the shearbar is again retracted by the first motor until no contact exists. Then the other adjusting motor is activated until a contact exists and is activated in the opposite direction until the contact between the shearbar and the chopper drum disappears. This adjusting process is repeated once where after each of the last adjustment steps the desired gap on each side is adjusted by retracting the shearbar.  
         [0008]     DE 100 21 659 A proposes that one end of the shearbar be moved at first in the direction of the chopper drum until a contact occurs and then retracting it by a spacing that corresponds to the desired gap. Then the other end is moved to the chopper drum until a contact occurs and then retracted again from the chopper drum by a spacing that corresponds to the desired gap. Alternatively the shearbar is at first brought into a parallel orientation to the chopper drum and then the final spacing is adjusted by moving both ends synchronously. For such an adjusting operation a very precisely-operating spacing sensor is required.  
         [0009]     EP 1 080 630 A proposes that one end of the shearbar be moved at first to the chopper drum until an appropriate gap exists. Then the other end is moved to the desired spacing.  
         [0010]     Thereby the known procedures for the adjustment of the shearbar relative to the chopper drum always include a step in which a first end of the shearbar is brought into the vicinity of the chopper drum. Following this, the other end of the shearbar is moved to the chopper drum. This procedure is based on the fundamental assumption that the chopper assembly is manufactured and ground as a cylinder or a concave shape. The end of the shearbar that was not moved in each case is located at a relatively small spacing from the chopper assembly, so that the assumption can be made that an approach or a contact between the shearbar and the chopper assembly occurs first at the end of the shearbar that was moved on the basis of the cylindrical or concave shape of the chopper drum. In each case the target position of the shearbar is then determined on the basis of the measured values.  
         [0011]     This procedure is problematic if the shape of the chopper assembly is convex. This shape can result, for example, from higher wear in the outer region of the chopper assembly on the basis of greater amounts of crop due to non-uniform supply of crop, in that larger amounts of crop are supplied to the outside of the chopper assembly compared to the supply in the center, or on the basis of grinding processes in which the grinding stone operates for a longer time at the edge than in the center of the chopper assembly.  
         [0012]     To illustrate this point, reference is made to  FIG. 1 . The chopper assembly  22  is convex, where the convexity “a” is shown to an exaggerated degree for purposes of illustration. In actual cases it may amount, for example, to 0.5 mm. at a width of the chopper assembly  22  of approximately 700 to 850 mm. and a diameter of the chopper assembly  22  of approximately 600 mm. Depending on the distance “b” of the end of the shearbar  38  that was not repositioned, the shearbar  38  comes into contact with the knives  48  further towards the edge or in the center of the chopper assembly  22 . The spacing “b” between the chopper assembly and the end of the shearbar  38  that was not adjusted is relatively small, so that the contact between the shearbar  38  and the chopper assembly  22  occurs in the vicinity of its center.  
         [0013]     In case the spacing “b” between the end of the shearbar  38  that was not repositioned and the chopper assembly  22  differs upon the approach of the other end of the shearbar to the chopper assembly the contact thereby occurs at various different axial positions. In a procedure in which the shearbar is moved towards the chopper assembly in successive alternating steps at both ends, the orientation between the enveloping circle described by the knives and the shearbar depends upon chance, and a parallel orientation is difficult to achieve.  
         [0014]     The problem underlying the invention is seen in the need to provide an arrangement for the adjustment of a shearbar, in which a parallel adjustment between the shearbar and the enveloping circle described by the knives is possible even with convex chopper assemblies.  
       SUMMARY  
       [0015]     In overcoming the limitations and drawbacks of the prior art, the present invention provides an arrangement for adjustment of a position of a shearbar relative to knives of a chopper assembly. The arrangement includes a pair of adjusting drives to move respective ends of the shearbar with respect to the knives of the chopper assembly. The arrangement further includes a spacing measurement arrangement to provide information regarding the position of the shearbar with respect to the knives to a control arrangement.  
         [0016]     The first adjusting drive positions the first end of the shearbar a predetermined first spacing from the knives and the second adjusting drive positions the second end of the shearbar with respect to the knives until the second end of the shearbar is equal to or less than a threshold distance from the knives. The adjusting drives then perform an analogous operation on the shearbar to determine the position of a predetermined second spacing and a second threshold distance.  
         [0017]     The adjusting drives then position the ends of the shearbar with respect to the knives such that the ends are respectively located first and second desired distances from the knives. The first and second predetermined spacing from the knives are respectively greater than the first and second desired distances from the knives, such that the ends of the shearbar can be properly aligned with potentially-convex end portions of the chopper assembly.  
         [0018]     Due to the greater distance between the shearbar and the knives compared to the state of the art (the first and the second distance) of each end of the shearbar in each case that was not adjusted, that is greater than the desired gap between the chopper drum and the shearbar, information is generated regarding the position of the enveloping circle of the knives that can be obtained at the edge of the chopper assembly. In a convex chopper assembly, therefore, the situation shown in  FIG. 2  is realized. More specifically, in  FIG. 2  the spacing was selected at a magnitude considerably larger so that the contact between the shearbar  38  and the chopper assembly  22  occurs adjacent to the left edge, at contact point “c”. Therefore, the first threshold distance is shown on the left edge where the respective components  38 ,  22  abut each other, being generally equal to zero. Also, on the right edge of the shearbar  38  in  FIG. 2 , the convexity “a” of the convex chopper assembly and the distance “b” of the predetermined second spacing are shown, where the predetermined second spacing “b” is substantially greater than the convexity “a”. In this way a parallel orientation of the shearbar relative to the chopper assembly can be obtained even with a convex chopper assembly. The quality of the cut is improved and the power requirement during the chopping process is reduced.  
         [0019]     The first and the second spacing “b” in  FIG. 2  can be calculated on the basis of an empirical value “a” for the maximum convexity or crowning of a chopper assembly and the width of the chopper assembly. The value for “b” is the result of the tangent to the enveloping circle of the chopper assembly at the point of contact of the shearbar and its intersection with the vertical of the other end of the chopper assembly.  
         [0020]     After information has been detected regarding the position of the shearbar, in which the spacing measurement arrangement had provided a signal that the spacing is less than the threshold value of the spacing between the shearbar and chopper assembly, the shearbar then must still be brought into the desired position. This movement is preferably performed in such a way that both adjusting drives are activated simultaneously in order to obtain the desired spacing between the shearbar and the chopper assembly in the shortest possible time.  
         [0021]     The generation of the parallelism of the shearbar to the enveloping circle of the knives as described is fundamentally required only after major repairs or modifications to the chopper assembly, for example, after a replacement of several or of all the knives, the shearbar or changes to the adjustment mechanism. All other adjustment processes, for example, after a grinding process fundamentally do not require the establishment of parallelism, that is relatively time consuming. Therefore it is proposed that after first establishing the parallelism the adjustment drives be activated synchronously only without first orienting the ends of the shearbar parallel to the chopper assembly, that is, to bring them into the first or the second spacing from the knives and to bring the other end of the shearbar into contact with the knives. Thereby the adjustment processes can be shortened considerably. On the other hand a further process that must be performed is a further parallel shift of both ends of the shearbar, in order to obtain a desired cutter gap, at which time another approach to the knives can be performed. This proposal deserves independent inventive significance, and it can also be applied to arrangements for the adjustment of the position of a shearbar in which the parallelism of the shearbar to the chopper assembly is performed by methods other than those described here, for example, the state of the art explained initially.  
         [0022]     The adjustment drives have a mechanical play that may be larger or smaller. This play can be detected when the shearbar is moved away from the knives, for example, by generating information about the adjusting path, that is required in order to permit the output signal of the spacing measurement arrangement to drop below the associated output signal, which points to the fact that the spacing between the shearbar and the knives is less than a threshold value. If the shearbar is subsequently to be brought into the position corresponding to the desired gap, the control arrangement considers the measured play automatically. The play of the two different adjusting drives, that may differ in themselves, is particularly relevant here, these can be detected and automatically equalized. With each movement the play of the adjusting drive with the greater play is repositioned in the direction of the subsequent movement of the shearbar by the difference of the two values of play.  
         [0023]     For the subsequent relief of the stress in the adjusting drives the shearbar can be moved again in the direction of the chopper assembly.  
         [0024]     Any desired sensor can be used as spacing measurement arrangement. Knock sensors, in particular, can be used that detect mechanical vibrations caused by contact of the shearbar with the knives and magnetic spacing sensors that interact with permanent magnets and detect changes in the magnetic field generated by knives moving past in the vicinity.  
         [0025]     The control arrangement requires information regarding the immediate position of the adjusting drives or the ends of the shearbar associated with them. This information can be derived from an activation signal conducted to the adjusting drive, for example by the use of a stepper motor as adjusting drive. If the adjusting drive is a direct current motor, information regarding its position can be derived from the duration of the activation of the adjusting drive. Another possibility consists of detecting the position of the end of the shearbar or its adjusting drive by means of an associated position sensor.  
         [0026]     The invention can be applied to any desired chopper assembly with an adjustable shearbar. This may be, in particular, open and closed chopper drums of self-propelled forage harvesters and disk wheel choppers of attached or towed forage harvesters. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]     The drawings show an embodiment of the invention that shall be described in greater detail in the following.  
         [0028]      FIG. 1  shows a schematic view of a convex chopper drum with a shearbar that is in contact at approximately the center of a chopper drum;  
         [0029]      FIG. 2  shows a schematic view of a convex chopper drum with a shearbar that is in contact with a chopper drum at approximately the edge of the chopper drum;  
         [0030]      FIG. 3  shows a partial sectional side view of a harvesting machine to which the arrangement, according to the invention, can be applied;  
         [0031]      FIG. 4  shows a schematic perspective view of the arrangement, according to the invention, for the adjusting of the position of the shearbar with respect to the knives of the chopper assembly;  
         [0032]      FIGS. 5   a  and  5   b  show a flow chart according to which the arrangement for adjusting the position of the shearbar operates; and  
         [0033]      FIG. 6  shows a schematic view of a convex chopper drum with a shearbar that is properly aligned with the chopper drum. 
     
    
     DETAILED DESCRIPTION  
       [0034]      FIG. 3  shows a harvesting machine  10  in the form of a self-propelled forage harvester that is supported on a frame  12  that is carried by 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 controlled visually. Crop taken up from the ground, for example, corn, grass or the like, is conducted to a chopper assembly  22  in the form of a chopper drum that is equipped with knives  48  that chop the crop into small pieces and deliver it to a conveyor arrangement  24 . A post-chopper reduction arrangement  28  extends between the chopper assembly  22  and the conveyor arrangement  24 , through which the crop to be conveyed is conducted tangentially to the conveyor arrangement  24 . The crop leaves the harvesting machine  10  to an accompanying trailer over a rotating discharge duct  26 .  
         [0035]     The crop is transported between the crop recovery arrangement  20  and the chopper assembly  22  by lower rough pressing rolls  30 ,  32  and upper rough pressing rolls  34 ,  36 . The knives  48 , distributed around the circumference of the chopper assembly  22 , interact with a shearbar  38 , in order to chop the crop. The shearbar  38  is provided at its end with a first and a second adjusting drive  40 ,  42 , that are arranged for the movement of the shearbar  38  in the horizontal direction towards and away from the chopper drum  22 . Moreover a spacing sensor  44  is arranged on the shearbar  38 . Furthermore a grinding arrangement  76  is associated with the chopper assembly  22  in order to automatically sharpen the knives  48 .  
         [0036]     An electronic control arrangement  46 , operating digitally, is positioned in the operator&#39;s cab  18 , it is connected with the spacing sensor  44  over an analog-digital converter  50  and with the adjusting drives  40 ,  42  over digital-analog converters  52 ,  54 . The spacing sensor  44  is a knock sensor that is known in the art and it detects mechanical vibrations that are excited in the shearbar  38  by knives  48  which touch the shearbar  38 . The spacing sensor  44  sends signals to the control arrangement  46 , which can detect corresponding information in the case of a contact of the knives  48  with the shearbar  38 . It would also be possible to associate each end of the shearbar  38  with its own spacing sensor  44 . In the embodiment shown the adjusting drives  40 ,  42  are stepper motors. The immediate position of the adjusting drives  40 ,  42 , and thereby the shearbar  38 , are known to the control arrangement  46  on the basis of the number of adjusting impulses supplied by the control arrangement  46  to the adjusting drives  40 ,  42 . In order to calibrate the position of the adjusting drives  40 ,  42  there is the possibility of moving the latter against a fixed stop, for example, against the stationary chopper assembly  22  or against stops arranged at the other end of the adjusting path. When the stop is reached a signal is provided to the control arrangement  46  by an increase in the current requirement for the adjusting drives  40 ,  42 . The adjusting drives  40 ,  42  move the ends of the shearbar  38  by means of threaded rods  56  that interact with threads in sections  58  of the shearbar  38  or a retainer to which the shearbar  38  is fastened.  
         [0037]     After a knife  48  or several knives  48  of the chopper assembly  22  or the shearbar have been replaced, as may occur in the case of wear, damage, or repair of the respective components, the adjustment mechanism between the adjusting drives  40 ,  42  and the shearbar  38  may cause the parallelism of the shearbar  38  to the enveloping circle of the knives  48  may be diminished and the size of the intervening gap may be unknown. In this case, the control arrangement  46  will proceed as shown in  FIGS. 5   a  and  5   b.    
         [0038]     Following a corresponding input from the operator into an input arrangement connected with the control arrangement  46  or automatically, after the operations described have been detected by sensors or corresponding inputs have been provided to the control arrangement  46 , the adjustment routine is initiated in step  100 . In step  102  the control arrangement  46  inquires whether the chopper assembly  22  rotates, because an adjustment of the shearbar  38  is preferably performed while the chopper assembly is rotating. If this is not the case, the process is ended, and if necessary, the operator is notified. If, on the other hand, the chopper assembly  22  is rotating, step  104  follows in which the adjusting drives  40 ,  42  are induced to bring the ends of the shearbar  38  associated with them into a spacing of 2.5 mm. from the chopper assembly  22 . This step  104  is based on the assumption that the shearbar  38  is mounted in its target position and the adjusting drives  40 ,  42  are located in known positions. If this is not the case, corresponding input can be provided to the control arrangement  46 , or a further routine, not shown, is called up with which the position of the shearbar  38  can be detected automatically; for example, it can be moved against an outer stop and the currents to drive the adjusting drives  40 ,  42  can be measured. The step  104  does not require the utmost in precision, but it is sufficient if the adjusting drives  40 ,  42  are brought into the desired position within certain tolerances.  
         [0039]     Following that the first adjusting drive  40  is deactivated and the first end of the shearbar  38  associated with it remains at this relatively large spacing from the chopper assembly  22 .  
         [0040]     If the second adjusting drive  42  is already located before step  104  between the position to which it is to be controlled and a position closer to the chopper assembly  22 , it can also remain there during step  104 , in order to shorten the adjusting time. In step  106  the second adjusting drive  42  is induced to move the second end of the shearbar  38  in the direction of the chopper assembly  22 . In step  108  the spacing sensor  44  determines whether contact has occurred. If the signal does not indicate contact between the shearbar  38  and the chopper assembly  22 , step  106  again follows. Otherwise the assumption is made that the shearbar  38  touches the knives  48  of the chopper assembly  22 . Information regarding the actual position of the second adjusting drive  42  is stored in memory (step  110 ) and the second adjusting drive  42  is instructed in step  112  to again withdraw the second end of the shearbar  38  from the chopper assembly  22 .  
         [0041]     Step  114  asks the question whether the signal of the spacing sensor  44  still points to a contact between the shearbar  38  and the knives  48 . If this is not the case, step  112  follows, otherwise step  116 . In step  116 , information regarding the actual position of the second adjusting drive  42  is stored in memory. The memory of the position generated in step  110  and the memory of the position generated in step  116  cooperate to store information regarding the mechanical play of the adjusting drive  42 . Then, in step  118 , the second adjusting drive  42  is induced to withdraw the second end of the shearbar  38  through a distance of 2.5 mm. from the knives  48 .  
         [0042]     Thereupon, in step  120 , the first adjusting drive  40  is analogously induced to move the end of the shearbar  38  in the direction of the chopper assembly  22 . In step  122  the spacing sensor  44  determines whether contact has occurred. If its signal does not point to a contact between the shearbar  38  and the chopper assembly  22 , then step  120  again follows. Otherwise the assumption is made that the shearbar  38  touches the knives  48  of the chopper assembly  22 . Information regarding the actual position of the first adjusting drive  40  is stored in memory (Step  124 ) and the first adjusting drive  40  is instructed in step  126  to again withdraw the first end of the shearbar  38  from the chopper assembly  22 .  
         [0043]     In step  128  the question is asked whether the signal of the spacing sensor  44  still indicates contact between the shearbar  38  and the knives  48 . If this is not the case, step  126  follows, otherwise step  130 . In step  130 , information regarding the actual position of the first adjusting drive  40  is stored in memory. The memory of the position generated in step  124  and the memory of the position generated in step  130  cooperate to store information regarding the play of the adjusting drive  40 . Then in step  132  the first adjusting drive  40  is induced to withdraw the first end of the shearbar  38  from the knives  48  by a distance of 2.5 mm.  
         [0044]     Now the shearbar  38  is oriented parallel to the enveloping circle of the knives  48  of the chopper assembly  22 , since both ends have been withdrawn by the same distance of 2.5 mm. from the knives. The relatively large distance between the chopper assembly  22  and each of the stationary ends of the shearbar  38  increases the likelihood that the approach or contact between the shearbar  38  and the chopper assembly  22  occurs in each case at the end of the shearbar  38  that was adjusted and not closer to the center of the chopper assembly  22 . Therefore the case shown in  FIG. 1  is avoided; the situation shown in  FIG. 2  is safely assured.  
         [0045]     More specifically, in  FIG. 2  the spacing was selected at a magnitude considerably larger so that the contact between the shearbar  38  and the chopper assembly  22  occurs adjacent to the left edge, at contact point “c”. Therefore, the first threshold distance is shown on the left edge where the respective components  38 ,  22  abut each other, being generally equal to zero. Also, on the right edge of the shearbar  38  in  FIG. 2 , the convexity “a” of the convex chopper assembly and the distance “b” of the predetermined second spacing are shown, where the predetermined second spacing “b” is substantially greater than the convexity “a”. In this way a parallel orientation of the shearbar relative to the chopper assembly can be obtained even with a convex chopper assembly.  
         [0046]     The distance used in steps  104 ,  118  and  132  can also be determined before the adjusting of the shearbar  38  on the basis of actual parameters in which, for example, the operating time of the chopper assembly  22  and the resulting convexity based on experience is determined and used to establish the spacing.  
         [0047]     In steps  106  through  116  and  120  through  130  information was obtained regarding the immediate play of the adjusting drives  40 ,  42 . As a rule these values of play differ in magnitude. In order to assure a parallel adjustment of the shearbar  38  in the following adjustment processes, a play difference equalization is performed before each movement. Here the adjusting drive  40  or  42  with the larger play in each case is moved by the difference in the magnitude of the play in the direction into which the shearbar  38  is to be repositioned.  
         [0048]     A first such movement is performed in step  134 . The one of the adjusting drives  40 ,  42  with the larger play is induced to move the shearbar  38  in the direction of the chopper drum  22  through a distance that corresponds to the difference in the play of the two adjusting drives  40 ,  42 .  
         [0049]     Step  138  follows in which both adjusting drives  40 ,  42  are activated simultaneously in order to move the shearbar  38  in the direction of the chopper assembly  22 . In step  140  the spacing measurement arrangement  44  determines whether contact has occurred. If no contact exists, step  138  follows, otherwise step  142 . In that step the adjusting drive  40  or  42 , whose play is larger as determined by steps  116  and  130 , is moved backwards by the difference in the two magnitudes of play. Thereby non-parallelism are avoided that may be due to unequal magnitudes of play or hysteresis of the adjusting drives  40 ,  42 .  
         [0050]     Step  144  follows in which both adjusting drives  40 ,  42  are induced to withdraw the shearbar  38  from the chopper assembly  22 . In step  146  the question is raised whether the spacing sensor  44  is still delivering a signal that points to a contact between the shearbar  38  and the knives  48 . If this is the case, step  144  again follows, otherwise step  148 , in which the adjusting drives  40 ,  42  are induced to move the shearbar  38  to a spacing from the chopper assembly  22  that corresponds to the desired gap. This gap may be, for example, 0.2 mm. Following this, in step  150  the adjusting drive  40  or  42 , whose play is larger as determined in steps  116  and  130 , is moved ahead by the difference in the magnitudes of the play, in the direction of the chopper assembly  22 . Finally the adjusting drives  40 ,  42  are induced to move the shearbar  38  on both sides in the direction of the chopper assembly  22 , in order to relieve the stress in the mechanism and to avoid any recoil of the shearbar  38  during the following harvesting process.  
         [0051]     Now the shearbar  38  is oriented parallel to the chopper assembly  22  and is spaced from it by the desired gap, as shown in  FIG. 6 . More specifically, the shearbar  38  extends along a line  156  that is parallel to a second line  158  extending through the respective contact points “c”.  
         [0052]     After a grinding process by means of the grinding arrangement  76 , which is performed after a certain operating time, as induced by the operator or automatically, the shearbar  38  must be repositioned anew. Here, however, the steps  102  through  132  can be omitted, so that then the routine for the repositioning of the shearbar  38  includes only the steps  136  through  154 . This process can be performed in a relatively short time.  
         [0053]     It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to define the spirit and scope of this invention.