Abstract:
A grinding arrangement for grinding knives of a chopper drum of a forage harvester includes a movement arrangement for effecting movement of a grinding stone over the length of each of the knives, where individual locations of the knives can be associated with differing grinding times in order that the knives be ground to produce a desired cylindrical profile. A control for the movement arrangement may include either a sensor for determining the need for grinding a given knife at a precise location along the knife and the grinding time required for achieving a desired profile, or predetermined information stored in memory which operates to automatically cause a certain amount of grinding time to elapse in accordance with a specific axial position of the grinding stone.

Description:
FIELD OF THE INVENTION 
     The invention concerns a grinding assembly or arrangement for a rotary cutterhead or chopper arrangement, the grinding assembly including a grinding stone for the grinding of the knives of the cutterhead or chopper arrangement, and a stone positioning apparatus or stone moving arrangement for effecting movement of the grinding stone over the width of the cutterhead, where individual locations of the knives can be associated with differing grinding times. 
     BACKGROUND OF THE INVENTION 
     U.S. Pat. No. 4,843,767 describes a grinding arrangement for a chopper arrangement, in which the grinding stone traverses the width of the chopper drum back and forth with constant velocity. At each of the reversal points at the left and the right end of the chopper drum, the grinding stone remains stopped for a dwell time so that at that location the knives of the chopper drum are ground over an interval of time that is longer than the grinding time that is associated with the parts of the knives located between the reversal points. 
     During the operation of a forage harvester, the knives fastened to the chopper drum wear over time. While the knives around the circumference of any given location along the width of the chopper drum, as a rule, wear approximately at a uniform rate, the wear across various locations along the width of the chopper drum may vary considerably. Hence the diameter of the enveloping cylinder described by the cutting edges of the knives can vary across the width of the chopper drum. A cylindrical or slightly concave shape of the entire enveloping cylinder is desired in order to simplify an automatic adjustment of the shear bar or to make this possible in the first place, depending on the adjustment system. A parallel and exact in-feed of the shear bar towards the circumference of the chopper drum is indispensable for an effective chopping process. 
     With known grinding arrangements no possibilities are provided to equalize automatically the deviations from the cylindrical shape of the chopper drum during the grinding process. 
     SUMMARY OF THE INVENTION 
     According to the present invention, there is provided an improved grinding assembly or arrangement for grinding the knives of the cutterhead or chopper drum of a forage harvester. 
     An object of the invention is to provide a grinding assembly or arrangement including a stone positioning or moving apparatus having a control for controlling the movement of the grinding stone of the grinding assembly or arrangement relative to a cutterhead in such a way that the amount of time the grinding stone occupies any one location along the width of the cutterhead may be selectively varied. 
     A more specific object of the invention is to provide an arrangement for controlling the movement of a grinding stone by selecting the path and time characteristic of the movement of the grinding stone as desired so that the grinding stone dwells for a longer time at certain locations along the width of the cutterhead, where the knife edges are worn very little, than at other locations along the width of the cutterhead where the knife edges are worn relatively heavily. 
     Yet a more specific object of the invention is to provide an arrangement for controlling the movement of a grinding stone by establishing, and storing in memory in advance, grinding times based on empirical values (as result of tests) or values determined by experience, and by storing a desired target shape of the cutting edges of the knives. 
     These and other objects of the invention will become apparent from a reading of the ensuing description together with the appended drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 a - 1   d  are schematic views of chopper drums with knives worn to produce different drum profiles. 
     FIG. 2 is a schematic left side view of a harvesting machine with a chopper drum with which a grinding arrangement constructed in accordance with the present invention is particularly adapted for use. 
     FIG. 3 is a front view of a first embodiment of a grinding arrangement. 
     FIG. 4 is a flow diagram that illustrates a grinding process. 
     FIG. 5 is a flow diagram that illustrates another grinding process. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1 a - 1   d  will be described below in conjunction with the description of the operation of the grinding arrangement. 
     The harvesting machine  10 , shown in FIG. 2 in the form of a self-propelled forage harvester, is supported on a frame  12 , that is carried by front and rear wheels  14  and  16 . The harvesting machine  10  is operated from an operator&#39;s cab  18  from which a crop recovery arrangement  20  can be viewed and controlled. Crop taken up from the ground by 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 crop leaves the harvesting machine  10  to an accompanying trailer over a discharge duct  26 , that is mounted for rotating about an upright axis. Between the chopper drum  22  and the conveyor arrangement  24 , a post-chopper reduction arrangement  28  is provided for use during the harvesting of corn, the arrangement  28  operating to conduct the crop tangentially to the conveyor arrangement  24 . 
     FIG. 3 shows a schematic view of a cutterhead or chopper drum  22  and a grinding assembly or arrangement associated with it, as can be seen by a look at the harvesting machine  10  in FIG. 2 from the front, with regard to the direction of forward travel. The chopper drum  22  is provided with a number of knives  38  distributed over its width and its circumference that chop crop taken up by the crop recovery arrangement  20  in interaction with a rigid shear bar  46 . The chopper drum  22  includes a central shaft  32  that can be driven in rotation through a belt pulley  36  at its end face and belts, not shown, by a motor of the harvesting machine  10 . The shaft  32  is supported through two bearings arranged respectively on each side of the chopper drum  22 , not shown in FIG. 3, on the frame  12  of the harvesting machine  10 . 
     In order to be able to sharpen the knives  38  after a certain operating time, without having to disassemble the individual knives  38  or the entire chopper drum  22 , the grinding assembly or arrangement is provided above the chopper drum  22  close to the enveloping cylinder described by the knives  38 , and includes a grinding stone  42 , a grinding stone retainer  40  associated with the grinding stone and an axle  44 , on which the grinding stone retainer  40  is supported in bearings so that it can be slid. 
     If the knives  38  are to be sharpened, the chopper drum  22  is brought into rotation, as a rule in the reverse direction of rotation and/or with reduced rotational speed, compared to normal chopper operation. The grinding stone retainer  40 , with the grinding stone  42  attached thereto, is slid by means of a stone positioning apparatus or stone movement arrangement  48  out of a rest or park position, not shown, in which it is arranged alongside the chopper drum  22 , over the entire width of the chopper drum  22 . At that time, the underside of the grinding stone  42  is in contact with the knives  38 , and sharpens these. During the grinding process, the grinding stone  42  traverses the width of the chopper drum  22  several times. The end or reversal points of this sliding movement are shown in FIG. 3 by the grinding stone retainer with the number call-outs  40 , at the left reversal point, and  40 ′, at the right reversal point. 
     Between the sliding movements, an in-feed of the grinding stone  42  can be performed, that is, a minute movement of the grinding stone  42  towards the knives  38 . In the embodiment shown, a mechanical element, for example a ratchet gear, is used for this purpose which interacts with a stationary element upon reaching one or both reversal points of the grinding stone retainer  40 . The rotation of the mechanical element is converted by means of a threaded component into a sliding movement so that the grinding stone  42  is fed-in towards the chopper drum  22 . By a movement of the grinding stone  42  only through a limited sliding region towards the side, an in-feeding can be avoided, since the mechanical element then does not come into contact with the stationary element. A grinding process of this type without in-feeding is appropriate for the planing at the conclusion of the grinding process. The stone positioning apparatus or movement arrangement  48  of the grinding assembly or arrangement is controlled by a position controller  52 , shown schematically in FIG. 3, which controls the sliding of the grinding stone  42  along the axle  44  by means of the positioning apparatus  48  as well as the in-feeding, in the manner described above. The stone positioning apparatus controller  52  is supplied with information about the immediate position of the grinding stone  42  which can be performed by a corresponding sensor, not shown in the drawing, for example, a linear potentiometer which is integrated into a motor of the stone positioning apparatus  48 , or by the positioning apparatus controller  52  having available information into which position it has brought the stone positioning apparatus  48 . For this purpose, for example, the number of impulses that have been transmitted to a stepper motor of the stone positioning apparatus  48  can be stored in memory. Furthermore, the stone positioning apparatus controller  52  can also control the drive of the chopper drum  22 . 
     It should be noted that the in-feeding can be performed by a separate motor, in particular an electric or hydraulic motor that would also have to be connected with the stone positioning apparatus controller  52 . In place of an in-feeding by shifting the grinding stone  42 , the entire grinding stone retainer  40  could be in-fed instead. 
     The stone positioning apparatus controller  52  is connected with a memory  54  and a knock sensor  50  attached to the grinding stone retainer  40 , used as a measurement arrangement. A grinding process, as illustrated in FIG. 4, takes its course as follows: 
     After the beginning of the grinding process step  100 , the stone positioning apparatus controller  52  initially causes the grinding stone  42  in step  102  to be moved by the stone positioning apparatus  48  to traverse the width of the chopper drum  22  and return again into the initial position. Here the grinding stone  42  can remain in the position relative to the grinding stone retainer  40  in which it was brought during the preceding grinding process, or, if necessary, in contrast thereto, in-fed towards the chopper drum  22 . Step  102  can be used to determine whether an in-feeding of the grinding stone  42  is necessary. That is the case if no signal, or only a very minute signal, is generated by the knock sensor  50  in at least one location along the width of the chopper drum  22 . In this case, there is a dent, depression or the like in the knives  38  that cannot be equalized without in-feeding. 
     During the traversing of the width of the chopper drum  22 , the knock sensor  50  attached to the grinding stone retainer  40  generates a signal that is a function of the spacing of the cutting edges of the knives  38  from the grinding stone  42 . The control arrangement  52  is supplied over an appropriate analog/digital converter with information about the amplitude of this signal. 
     With a chopper drum that has the shape shown in FIG. 1 a,  a signal characterized in the following as a spacing signal, which contains information about the spacing, would decrease from left to right, with the amplitude of the signal transmitted by the knock sensor  50  increasing. In the case of the chopper drum  22  shown in FIG. 1 b,  that can be the result of the crop supplied or excessive dwell time at the ends of the shifting movement of the grinding stone  42  across the width of the chopper drum  22 , so that the knives  38  are more heavily worn there, the spacing signal would continually decrease the closer the grinding stone  42  approaches the center of the chopper drum  22 . If the shape is the result of long dwell times at the ends of the chopper drum  22 , so that it can be recognized by the stone positioning apparatus controller  52  during grinding, the dwell times stored in the memory  54  can be shortened automatically. The shape of the chopper drum  22  shown in FIG. 1 c  results in the largest spacing in the center, and, with the shape shown in FIG. 1 d,  results in a spacing varying irregularly over the width. The shape in FIG. 1 c  can be the result of dwell times at the end of the chopper drum  22  that are too short. If this is recognized by the stone positioning apparatus controller  52  during grinding, the dwell times stored in the memory  54  can be extended automatically. However, the shapes illustrated in FIGS. 1 c  and  1   d  can also be the result of non-uniform supply of crop or a defective shear bar  46 . 
     In the grinding process shown in FIG. 4, the grinding stone  42  is initially not in-fed further. In step  104  the grinding stone  42  is brought into a first position at the chopper drum by the stone positioning apparatus  48 , which, as a rule is adjacent to the park position and is located at the left or right outside. It remains in this position until the knock sensor  50  generates an output signal that corresponds to a desired spacing between the shaft  32  and the cutting edges of the knives  38  so that an adequate sharpness of the components of the knives  38  interacting with the grinding stone  42  is attained. Therefore, step  106  poses the question whether the signal of the knock sensor  50  is smaller than a threshold value. If the result is “No”, step  106  follows, otherwise step  108 . There the grinding stone  42  is transported by the stone positioning apparatus  48  through a distance corresponding to its width further to the left or the right and grinds the knives  38  there. Step  110  follows in which the question is posed, whether the chopper drum  22  has already been processed over its entire width. If “No”, step  106  follows, otherwise the process is ended in step  112 . Therefore the grinding stone  42  always remains standing at one location along the width of the chopper drum  22 , until the knock sensor  50 , in each case, transmits the desired output signal. These processes are repeated until the entire width of the chopper drum  22  has been processed. In this way, the result is that with varying grinding times across the width of the chopper drum  22 , the chopper drum  22  is brought into a cylindrical shape. Upon a traversing of the width of the chopper drum  22  with the grinding stone  42 , the output signal of the knock sensor  50  would now be constant. In case the chopper drum  22  is found to have a particularly small radius at a few locations, so that the knock sensor  50  cannot detect any contact between the knives  38  and the grinding stone  42 , an in-feeding of the grinding stone  42  and a repetition of the grinding process over the entire width of the chopper drum  22  can be performed. As a rule, the process described is repeated with reversed direction of movement of the grinding stone  42  and/or performed several times. To conclude the grinding process, a normal grinding and/or planing for the entire chopper drum  22  can be performed in a manner known in itself. Finally, the grinding stone  42  is brought into its park position. 
     FIG. 5 shows a time-sequence diagram for the control of the grinding process  42  in which the grinding times varying over the width of the knives  38  are stored in memory ahead of time. Thereby the sensor  50  shown in FIG. 3 can be omitted. In the grinding process according to FIG. 5, after the start in step  120 , the grinding stone  42  is brought out of the park position at the left edge of the chopper drum  22  by the stone positioning apparatus  48 . Step  124  follows, according to which the grinding stone  42  remains standing for a period t(x) that is a function of its immediate position x. The time intervals t(x) are stored in memory  54  in the form of a table, list, mathematical function or the like. Step  126  follows in which the question is posed whether the entire width of the chopper drum  22  has already been traversed by the grinding stone  42 . If this is not the case, step  128  follows in which the grinding stone  42  is traversed to the right through a distance Δx. The distance Δx corresponds preferably as a maximum to the width of the grinding stone  42 , so that after a traverse of the chopper drum  22  all points of the knives  38  have been sharpened, however, it may be smaller than the width of the grinding stone  42 . After step  128 , step  124  again follows. 
     In case step  126  has determined that the entire width of the chopper drum  22  has already been traversed, step  130  follows, in which a planing is performed in a manner known in itself. Following this, the grinding stone  42  is brought into its park position in step  132  and the grinding process ends in step  134 . 
     It should be noted that the grinding stone  42  can also be returned to the left, with steps  124  through  128  corresponding steps, however, in which the grinding stone  42  is moved to the left. The chopper drum  22  can also be traversed multiple times in the manner described. Instead of remaining stationary each time for a certain length of time, the grinding stone  42  can be driven over the width of the chopper drum  22  with a velocity varying over the width of the chopper drum  22 , or moved with a varying step pattern. 
     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.