Abstract:
An automatic grinding device for sharpening the knives of a forage harvester chopper drum includes a controller including a counter for counting the number of times the grindstone is adjusted toward the chopper drum during sharpening operation. The controller includes a microprocessor having a non-volatile memory in which may be stored a threshold value, determined by the type of grindstone, to which the count of the counter may be compared for generating a signal indicating the degree of wear of the grindstone so that it may be replaced when worn out.

Description:
FIELD OF THE INVENTION 
     The invention pertains to a grinding device with a grindstone for sharpening a knife, a device for adjusting the grindstone toward the knife and a control unit. 
     The present invention can be utilized in a series of devices with knives to be sharpened. It is, in particular, advantageous in self-contained field choppers or towed harvesting machines with chopping drums. 
     BACKGROUND OF THE INVENTION 
     DE 4133043 A describes a grinding machine in which a grinding device is assigned to knives. Each cutting process is registered by a counting mechanism and the grinding process is carried out depending on the number of cuts. 
     U.S. Pat. No. 4,843,767, granted to Johnson on Jul. 4, 1989, discloses a grinding device for the chopping drum of a self-propelled field chopper. In this case, first and second electric motors, respectively provided for moving the grindstone to and from engagement with the knives of the chopper drum, and for sweeping the grindstone lengthwise of the chopper drum, are controlled by a system including a microprocessor and a counter which counts the number of sweeps or cycles of the grindstone and compares it to a preset threshold of the number of sweeps or cycles required to sharpen the chopper drum knives. 
     U.S. Pat. No. 4,834,303, granted to McClure et al. on May 30, 1989, discloses a grinding device for the chopping drum of a self-propelled field chopper. In this case, a switch, actuated by the grindstone holding arrangement once the grindstone should no longer be adjusted toward the knife due to excessive wear, is arranged in the vicinity of the end of the grindstone which faces the chopping drum. Due to this measure, the operator is informed that the grindstone, which is axially adjustable in its holder, needs to be manually adjusted closer to the knife. In addition to the costs for the switch, it is disadvantageous that the operator is only informed that the grindstone is worn out once the latter needs to be replaced. 
     SUMMARY OF THE INVENTION 
     According to the present invention, there is provided an improved grinding device. 
     An object of the invention is to provide a grinding device having a control unit which informs an operator of the degree to which a grind stone is worn. 
     A more specific object of the invention is to provide a grinding device wherein a control for feeding the grindstone towards a knife being sharpened informs the user when the grindstone is used up. This is done by storing a threshold value representing the number of feeding procedures that can be done for a certain type of grindstone before it is used up and to count either up to, or down from, the threshold value in order to obtain the signal that notifies the user when the grind stone needs to be replaced. 
     These and other objects will become apparent from a reading of the ensuing description together with the appended drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic side view of a harvesting machine that contains a chopping drum equipped with a grinding device. 
     FIG. 2 is a right rear perspective, partially exploded view of a portion of the chopping drum together with a grinding device including the mechanism for adjusting the grindstone vertically to and from contact with the knives of the chopping drum. 
     FIG. 3 is a partially exploded schematic view of the mechanism for sweeping the grindstone back and forth between right- and left-hand end positions during a grinding operation. 
     FIG. 4 is a flow chart of the steps followed for controlling the grinding device. 
     FIG. 5 is a schematic representation of the control for the grinding device. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A harvesting machine  10 , which is shown in FIG.  1  and realized in the form of a field chopper, is arranged on a frame  12  that is carried by front wheels  14  and rear wheels  16 . The harvesting machine  10  is operated from a driver cabin  18 , from which the operator is able to observe a harvest material collection device  20 . Material, e.g., corn, grass or the like, which was picked up from the ground by means of the harvest material collection device  20  is fed to a chopping drum  22  that chops the harvest material into small pieces and delivers those pieces to a transport device  24 . The material is transported by means of a rotatable delivery chute  26  from the harvesting machine  10  to a trailer that drives adjacent to the harvesting machine. A subsequent comminution device  28 , by means of which the material to be transported is tangentially fed to the transport device  24 , extends between the chopping drum  22  and the transport device  24 . 
     Referring now to FIG. 2, there is shown the chopping drum  22  including a plurality of knives  38  that are distributed over its width and its circumference and comminute harvest material picked up from the ground by the harvest material collecting device  20  in cooperation with a rigid counter knife (not shown) positioned adjacent a lower front location of the chopping drum  22 . The chopping drum  22  contains a central shaft  32  (FIG. 1) that is rotationally driven by a motor of the harvesting machine  10  via a pulley (not shown) mounted on an outer end portion of the shaft  32 . The shaft  32  is supported on the frame  12  of the harvesting machine  10  by means of two bearings (not shown) respectively arranged on opposite sides of the chopping drum  22 . 
     In order to make it possible to sharpen the knives  38  after a certain operating time without having to remove the individual knives  38  or the entire chopping drum  22 , a grinding device  40  is provided above the chopping drum  22  near the envelope circle described by the knives  38 . This grinding device  40  essentially includes a grindstone  42  mounted to a grindstone holding arrangement or carriage  43  which, in turn, includes a cylindrical tubular portion mounted for sliding axially along a cylindrical guide shaft or rod  44 . Provided for supporting and selectively lowering and raising the guide shaft  44  towards and away from the cutting circle of the chopping drum  22  so as to selectively position the grindstone  42  for sharpening contact with the knives  38  is a vertical adjustment mechanism  46  including a threaded rod  48  received in a threaded bore extending diametrically through the shaft  44 . The threaded rod  48  is rotatably mounted in, while being prevented from shifting axially in, upper and lower brackets  50  and  52 , respectively. Mounted to the top of the threaded rod  48  is a driven gear  54  meshed with a drive gear  56  that is mounted to a vertical adjustment drive shaft  58  that extends parallel to the guide shaft  44 . Although not shown, the left-hand end of the guide shaft  44  is supported on a threaded rod like rod  48  and a drive gear at the left-hand end of the drive shaft  58  is meshed with a driven gear at the top of the threaded rod. The drive and driven gears  56  and  54 , and the similar gears at the opposite side of the chopper drum  22 , each make up a worm gear set that act to effect vertical movement of the guide shaft  44 , and hence of the grindstone  42 , in response to the drive shaft  58  being rotated in the desired direction to effect the desired vertical movement. Driving of the shaft  58  is accomplished by a reversible electric motor  60  having a tubular receptacle  62  fixed to its output shaft (not visible), the receptacle  62  having a diametrical slot  64  provided in its outer end which engages a cross pin  66  mounted in the outer end portion of the drive shaft  58 . 
     Referring now to FIG. 3, a somewhat schematic grindstone sweep mechanism  70  is shown, which includes a cable and pulley arrangement  72  that works together with a reversible linear electric motor  74  to move the grindstone carriage  43  back and forth along the guide shaft or rod  44 . Specifically, the cable and pulley arrangement  72  includes a right-hand set of fixed pulleys comprising a coaxial pair of upper right-hand pulleys  76  and  78 , and a lower right-hand pulley  80 , and a left-hand set of fixed pulleys located in transverse alignment with the right-hand set and comprising a coaxial pair of upper left-hand pulleys  82  and  84 , and a left-hand lower pulley  86 . Shown in a position halfway between the right-and left-hand fixed pulley sets and in transverse alignment with the upper right-and left-hand pairs of fixed pulleys is a coaxial pair of transversely shiftable pulleys  88  and  90 . For the sake of simplicity, the structure for supporting and guiding the transverse movement of the pulleys  88  and  90  is not shown, with the laterally shiftable portion of the brackets and their connection to the drive motor  74  being indicated by the functional line  91 . A cable  92  is engaged with the various pulleys of the pulley arrangement  72 , with a right-hand end section extending about the. outer portions of pulleys  80  and  78  and then respectively about the right- and left-hand portion of the pulleys  88  and  76 , terminating in a threaded end onto which is threaded a clevis  94  which is pinned to a cable anchor bracket  96 . A left end section of the cable  92  is engaged with the lower and upper, fixed left-hand pulleys  86  and  84 , respectively, and then extends about the moveable center pulley  90  and then back under and about the pulley  82 . The left end section of the cable  92  terminates in an eyelet which is secured to the bracket  94  by a bolt  96 . Extending transversely between the lower pulleys  80  and  86  is a straight cable run  98  having a tubular drive element  100  adjustably fixed thereto by a set screw. The grindstone carriage  43  has a drive connection plate  102  bolted thereto and provided with a parallel pair of upstanding, lugs  104  snugly engaged with opposite ends of the drive element  100  and each having a receptacle receiving the cable run  98 . Thus, it will be appreciated that the pulley arrangement acts to multiply the lateral shifting movement of the output of the drive motor  74  to cause the grindstone carriage  43  to be moved between extreme right- and left-hand positions (not shown) where the grindstone  42  is out of contact with the chopper drum knives  38 . 
     The grinding arrangement for the chopper drum knives, as thus far described, is that disclosed in the above-identified U.S. Pat. No. 4,843,767 to which one should resort if further details of the structure or grinding procedure is desired. Suffice it to say that when the knives  38  need to be sharpened, the chopping drum  22  is set in rotation, usually in  1 the opposite rotating direction and/or with a reduced rotational speed in comparison to the normal chopping operation. The grindstone holding arrangement or carriage  43  with the grindstone  42  mounted thereon is displaced over the entire width of the chopping drum  22  from a (not-shown) idle or parking position, in which it is arranged laterally adjacent to the chopping drum  22 . During this process, the underside of the grindstone  42  is in contact with and sharpens the knives  38 . During the grinding process, the grindstone  42  is displaced or swept over the width of the chopping drum  22  several times by driving the motor  74  first in one direction then the other, with the reversal being made in response to the bracket  114  or other shiftable parts coming into contact with and operating right- and left-hand reverse switches when the grindstone reaches its end points. 
     The grindstone  42  is adjusted between the displacements, i.e., the grindstone  42  is slightly moved toward the knives  38 . This adjustment can be realized by displacing the guide shaft  44  toward the knives by operation of the electric motor  60 . When using grinding arrangements other than that disclosed in U.S. Pat. No. 4,843,767, it would also be conceivable to utilize a hydraulic motor or a mechanical element (ratchet wheel or the like) that cooperates with a stationary element when one or both reversal points is/are reached. In the mechanical arrangements, the rotation of the mechanical element is converted into a displacement by means of a thread such that the grindstone  42  is adjusted toward the chopping drum  22 . During this process, a displacement of the grindstone  42  over a limited lateral range makes it possible to bypass an adjustment because the mechanical element would not come in contact with the stationary element in this case. Such a grinding process without an adjustment is practical during the final smoothing process. 
     As with the grinding device disclosed in the above-described U.S. Pat. No. 4,934,612, the grinding device with the grindstone  42  disclosed here is controlled by a control unit including a microprocessor and serves for realizing the displacement or sweeping of the grindstone  42  as well as its vertical adjustment. The control unit may also control the operation of the chopping drum  22 . With reference to the schematic representation in FIG. 4, a control unit  104  is connected to or provided with a memory  106  (non-volatile when the harvesting machine  10  is switched off), with a counter  108  being stored in a first storage area, and with a threshold value  109  being stored in a second storage area, of said memory. 
     FIG. 5 shows a flow chart, according to which the control unit  104  of the grinding device operates. After the start in step  100 , e.g., after starting the motor of the field chopper  10 , it is inquired in step  112  whether a corresponding (push button) switch for activating the grinding device is actuated or not (it would also be conceivable to automatically sharpen the knives  38  after a certain operating time). If the switch is not actuated, step  112  is repeated. If the switch is actuated, the next step is step  114 , in which the control unit  104  causes the drive of the chopping drum  22  to turn the chopping drum in the opposite direction with a reduced rotational speed in comparison to the normal chopping operation. As soon as the chopping drum  22  turns correspondingly, the grinding process begins. In step  116 , the grindstone  42  is displaced or swept over the width of the chopping drum  22  once or several times such that the knives  38  are sharpened. In step  118 , it is inquired whether the grindstone  42  needs to be adjusted. The control unit  104  is provided with a suitable data bank, table or the like which makes it possible to ascertain after how many displacements the grindstone  42  is adjusted vertically toward the chopping drum. A manual input would also be conceivable. If the control unit  48  determines that no vertical adjustment is necessary, the next step is step  120 , in which it is inquired whether the grinding process should be terminated. The grinding process is usually terminated after a predetermined number of displacements or sweeps; it would also be conceivable to manually input this number or to determine whether the knives  38  are sufficiently sharp or not by means of a sharpness sensor. If the grinding process should be terminated, the next step is step  122 , in which the grinding process is terminated and the routine is completed or step  110  is carried out again, respectively. If the grinding process should not yet be terminated, the next step is step  116 . 
     If it is decided in step  118  that an adjustment needs to take place, the next step is step  124 , in which it is inquired whether the count of the counter  108  is greater than a predetermined threshold value  109  or not. This threshold value  109  represents the maximum number of adjustments allowed for a grindstone  42 . This threshold value depends on the type, in particular, the dimensions and/or the material of the grindstone  42 . The threshold value  109  is correspondingly changed by the operator if a different type of grindstone  42  is installed. This may, for example, be realized by inputting the corresponding values into the software of the control unit  104  or by setting corresponding switches. The counter  108  is also set to zero when a new grindstone  42  is installed. 
     If the inquiry carried out in step  124  shows that the count of the counter  108  is greater than the threshold value  109 , the next step is step  126 , in which an error message is generated. An adjustment process is now no longer possible because the count of the counter  108  indicates that the grindstone  42  is excessively worn out for allowing additional adjustments. Otherwise, damage to the knives  38  and/or the grindstone holding arrangement  43  would result. The operator can now interrupt the grinding process and install a new grindstone  42 . It would also be conceivable to generate a second error message which informs the operator that a new grindstone will soon have to be installed once a certain degree of wear of the grindstone  42  is reached. The second error message may, for example, be generated when the count of the counter  108  corresponds to 90% of the threshold value  109 . If the count of the counter  108  is not greater than the threshold value  109  in step  124 , the next step is step  128 , in which an adjustment process is carried out and the count of the counter is increased by 1. Step  120  follows step  128 . 
     It should be emphasized that the counter  108  could alternatively be set to a value that corresponds to the threshold value and decreased by 1 when a new grindstone  42  is installed. In this case, the error message in step  126  is generated when the counter  108  reaches zero. It should also be emphasized that the displacement of the grindstone  42  over the width of the chopping drum  22  is not required if the grindstone extends over the entire width of the chopping drum. In this case, the counter  108  would count revolutions of the drum  22 . 
     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.