Abstract:
An agricultural implement having an infeed cutter is operable to automatically accommodate large objects that pass through the infeed cutter and detect and counteract jams that occur or might otherwise occur in the infeed cutter. The implement includes a plurality of knives mounted on a vertically moveable knife bed. The bed is associated with a hydraulic load-sensing system that is operable to lower the bed if a load threshold has been reached and raise the bed when the load has decreased sufficiently. Each knife is also associated with a hydraulic load-sensing system that is operable to lower the respective knife if a load threshold has been reached and raise the respective knife when the load has decreased sufficiently.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Application No. 61/581,010 filed Dec. 28, 2011, entitled “AGRICULTURAL IMPLEMENT HAVING KNIFE LOAD RESPONSIVE INFEED CUTTER”. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This invention relates to agricultural balers, and more particularly, to a knife load responsive infeed cutter configured to accommodate large objects that pass through the infeed cutter and detect and counteract jams that occur or might otherwise occur in the infeed cutter. 
       SUMMARY OF THE INVENTION 
       [0003]    An agricultural implement having an infeed cutter is operable to automatically accommodate large objects that pass through the infeed cutter and detect and counteract jams that occur or might otherwise occur in the infeed cutter. The implement includes a plurality of knives mounted on a vertically moveable knife bed. The bed is associated with a hydraulic load-sensing system that is operable to lower the bed if a load threshold has been reached and raise the bed when the load has decreased sufficiently. Each knife is also associated with a hydraulic load-sensing system that is operable to lower the respective knife if a load threshold has been reached and raise the respective knife when the load has decreased sufficiently. 
         [0004]    In a first preferred embodiment, the raising and lowering of the bed and knives is controlled by monitoring the pressure of the hydraulic system of the infeed cutter. More particularly, the pressure in the hydraulic load-sensing systems associated with the knives is monitored. For each knife, if the associated pressure is found to exceed a given threshold (which can be set by the operator, if desired), the respective knife is retracted to an inoperative position. The pressure is also monitored for the bed. If the pressure associated with the bed hydraulics is found to be acceptable, each of the previously lowered knives is returned to its operative position. If the pressure for the bed exceeds a given threshold (which can be set by the operator, if desired), however, the bed is lowered. The pressure is again analyzed for the bed. If it has not decreased sufficiently, manual maintenance may be necessary. If it has reached an acceptable level, however, the bed is returned to its original position. If the pressure remains acceptable after the bed has returned to its original position, each of the previously retracted knives is raised, and the monitoring process begins anew. If the pressure has returned to an unacceptable level after the bed has returned to its original position, however, the bed-lowering process is again repeated. 
         [0005]    In a second preferred embodiment, the raising and lowering of the bed and knives is controlled by monitoring the pressure of the hydraulic system of the infeed cutter. More particularly, the pressure in the hydraulic load-sensing systems associated with the knives is monitored. For each knife, if the associated pressure is found to exceed a given threshold (which can be set by the operator, if desired), the respective knife is retracted to an inoperative position. The knife-based monitoring and, if necessary, retractions continue until all knives have been retracted or the pressure is acceptable for all remaining active knives. The pressure is also monitored for the bed. If the pressure associated with the bed hydraulics is found to be acceptable, each of the previously lowered knives is returned to its operative position. If the pressure for the bed exceeds a given threshold (which can be set by the operator, if desired), however, the bed is lowered. The pressure is again analyzed for the bed. If it has not decreased sufficiently, manual maintenance may be necessary. If it has reached an acceptable level, however, the bed is returned to its original position. If the pressure remains acceptable after the bed has returned to its original position, each of the previously retracted knives is raised, and the monitoring process begins anew. If the pressure has returned to an unacceptable level after the bed has returned to its original position, however, the bed-lowering process is again repeated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
         [0006]    Preferred embodiments of the invention are described in detail below with regard to the attached drawing figures, wherein: 
           [0007]      FIG. 1  is a side elevational view of a baler having features found in a preferred embodiment of the present invention; 
           [0008]      FIG. 2  is an enlarged, fragmentary, longitudinal cross-sectional view through the infeed part of the baler of  FIG. 1 , illustrating the relationship between the pickup, cutter apparatus, packer, and stuffer; 
           [0009]      FIG. 3  is fragmentary longitudinal cross-sectional view similar to that of  FIG. 2  but taken somewhat deeper into the baler of  FIGS. 1 and 2  to illustrate the relationship between the cutter rotor and strippers associated with the rotor; 
           [0010]      FIG. 4  is a fragmentary side elevational view of the infeed area of the baler of  FIGS. 1-3 , illustrating the latching and release mechanism for the knife bed associated with the cutter apparatus; 
           [0011]      FIG. 5  is a fragmentary side elevational view similar to  FIG. 4  but showing the knife bed of the baler of  FIGS. 1-4  in its fully lowered position; 
           [0012]      FIG. 6  is a left, front isometric view of the cutter apparatus of the baler of  FIGS. 1-5 ; 
           [0013]      FIG. 7  is a left, rear isometric view of the cutter apparatus of the baler of  FIGS. 1-6 ; 
           [0014]      FIG. 8  is a flowchart depicting a preferred sequence of system analyses and resulting actions that occur during the course of a cutting operation using the inventive baler; and 
           [0015]      FIG. 9  is a flowchart depicting another preferred sequence of system analyses and resulting actions that occur during the course of a cutting operation using the inventive baler. 
       
    
    
       [0016]    The drawing figures do not limit the present invention to the specific embodiments disclosed and described herein. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the preferred embodiment. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]    In a preferred embodiment, the agricultural machine featuring the inventive knife load responsive infeed is a baler for making rectangular crop bales. However, it is within the scope of the present invention for the knife load responsive infeed to be part of any of a variety of agricultural machines having an infeed cutter. These machines include round balers, silage trailers, forage harvesters, and others. 
         [0018]    As best shown in  FIG. 1 , the baler  10  preferably includes a fore-and-aft extending baling chamber, broadly indicated by numeral  12 , within which bales of hay are prepared and forced incrementally out the back end of the chamber  12 . The baler  10  is hitched to a towing vehicle (not shown) by a fore-and-aft tongue  16 , and power for operating the various components of the baler  10  is supplied through a drive line  18  supported by the tongue  16 . Preferably, the baler  10  is an “in-line” type of baler wherein crop is picked up directly beneath and slightly ahead of the baling chamber  12  and loaded up into the bottom of the chamber  12  in a straight line path of travel as viewed from the top, although other crop routing configurations may be used without departing from the spirit of the present invention. In keeping with the preferred in-line arrangement, the baler  10  shown in  FIG. 1  has a pickup  20  positioned under the tongue  16  such that the pickup  20  is significantly forward of the baling chamber  12 . A duct  22 , barely visible in  FIG. 1 , extends generally rearwardly and upwardly from behind the pickup  20  to an opening  24  (see  FIG. 2 ) in the bottom of the baling chamber  12 . The duct  22  serves as part of a passage through which crop materials travel from the pickup  20  to the baling chamber  12  during operation of the baler  10 . 
         [0019]    With primary reference to  FIG. 2 , it will be seen that the infeed area of the baler  10  generally comprises a passage broadly denoted by the numeral  26  for crop flow that begins just rearwardly of the pickup  20  and ends at the opening  24  in the bottom of the baling chamber  12 . Although the crop materials are initially lifted off the ground by the pickup  20  in a relatively wider configuration than the width of the duct  22 , such materials are immediately consolidated centrally by an auger mechanism  28  before entering the passage  26 . As the consolidated stream of crop materials moves rearwardly from the auger mechanism  28 , it passes through a cutting zone  30  immediately behind the pickup  20 . The crop materials then pass through a packing zone  32  behind the cutting zone  30  and through an accumulating zone  34  behind the packing zone  32 . Within the cutting zone  30 , the crop materials are cut into smaller pieces. Within the packing zone  32 , the materials have a packing and feeding force applied to them in the downstream direction of flow. Within the accumulating zone  34 , the materials accumulate into a charge that is compressed by the packing force and that assumes the configuration of the duct  22  in that area. A stuffer  40  then sweeps the charge up into the baling chamber  12  through the opening  24 . 
         [0020]    In order to carry out the cutting function within the cutting zone  30 , the baler includes a cutter apparatus broadly denoted by the numeral  36 . The cutter apparatus  36  comprises three primary components: a cutter rotor  46 , a bank of strippers  48  for the rotor  46 , and a knife bed  50  cooperating with the rotor  46  to sever the crop materials into smaller pieces. The rotor  46  preferably comprises a series of generally star-shaped blades  60  arranged in a helical or spiral pattern as shown, although V-shaped arrangements or a variety of others are permissible, as well. 
         [0021]    Preferably, the rotor  46  is driven in a counter-clockwise direction as viewed from the vantage point of  FIG. 2 , such that the blades  60  sweep downwardly and forwardly into the cutting zone  30  on the front side of the axis of rotation of the rotor. Conversely, the blades  60  swing upwardly and rearwardly out of the cutting zone  30  behind the axis of rotation of the rotor  46 . Thus, crop materials lifted from the field by the picker  20  are propelled by the rotor  46  rearwardly through the cutting zone  30 . Crop materials which might tend to be carried by the rotor  46  after the crop materials have passed behind the axis of rotation of the rotor  46  are stripped therefrom by the strippers  48 , at which point the crop materials enter the packing zone  32 . 
         [0022]    Referring primarily to  FIGS. 2 and 3 , the knife bed  50  includes a series of knives  74  that cooperate with the points  64  of the blades  60  to reduce incoming crop materials into small pieces when the knives  74  are in their raised, operating positions as illustrated, for example, in  FIG. 3 . The knives  74  are arranged to project upwardly between each pair of blades  60  so that as the points  64  on a pair of blades sweep downwardly and then rearwardly through the cutting zone  30 , they pass on opposite sides of a corresponding knife  74 . As shown in  FIG. 3 , each of the knives  74  has a serrated cutting edge  76  that faces generally upwardly and forwardly when the knife is in its operating position. Although they are not visible in the provided figures, the sides of knives  74  opposite the serrated cutting edge  76  are generally smooth. As shown in  FIG. 6 , the knives  74  project up through slits  78  in a top wall  80  of the bed  50  when knives  74  are in their operating positions. 
         [0023]    As shown in  FIG. 3  and others, the knives  74  are carried by a subframe  82  forming another part of the bed  50 . Subframe  82  is connected to the supporting frame  58  for the rotor  46  adjacent the lower forwardmost extremity of frame  58  by a transverse pivot shaft  84  so that the entire knife bed  50  can be raised and lowered between the two extreme positions illustrated in  FIGS. 4 and 5 . Such raising and lowering is preferably controlled by a pair of hydraulic cylinders  86  on opposite sides of the baler (see, for instance,  FIGS. 4 and 5 ), although a variety of control means fall within the scope of the present invention. 
         [0024]    The knives  74  are all mounted at their forward ends onto a common cross shaft  110  that extends the full width of bed  50 . A generally circular notch  112  (best viewed in  FIGS. 2 and 3 ) in the lower edge of each knife  74  receives the cross shaft  110 . Cross shaft  110  has a pair of opposed flat sides which enable each individual knife  74  to be removed from cross shaft  110  when cross shaft  110  is rotated to a position aligning the flat sides thereof with the entrance into the notch  112  of the knife. At other times, the cross shaft  110  is maintained in such a rotative position that the flat sides thereof are generally transverse to the entrance to the notch  112  of each knife so that the knives cannot be removed from cross shaft  110 . As seen in  FIG. 5 , access to the knives  74  for removing and replacing the same is provided when the bed  50  is in its lowered position. 
         [0025]    As best shown in  FIGS. 2 ,  3 , and  7 , each of the knives  74  of the illustrated baler is individually linked to a spring  118  at the back of the knife bed  50 . Thus, if a particular knife  74  is raised up into an operating position within the cutting zone  30  as illustrated in  FIGS. 2 and 3 , the knife can swing down about the cross shaft  110  against the force of its spring  118  in the event that an obstruction or solid object passes through the cutting zone  30  and engages the knife. 
         [0026]    The number of knives  74  which are raised up into their operating position when the bed  50  is in its operating position can be selectively varied through control of actuators  120 . More particularly, this can be carried out by controlling which of the actuators  120  are allowed to rotate back into their actuated positions by the springs  118  as the bed  50  is raised up into its operating position. In a preferred embodiment, this is accomplished by having the total set of actuators  120  constructed in four different configurations that render it possible to prevent every third actuator from returning, prevent every other actuator from returning, or prevent none of the actuators from returning. In the lattermost situation, all of the knives  74  are thus raised back up to their operating position. 
         [0027]    In a preferred embodiment, the knife bed  50  comprises left and right knife beds  50   a , 50   b  that retain the features described above but are additionally mobile laterally away from the center of the baler  10  into accessible positions near the lateral margins of the baler  10 . In these accessible positions, the beds  50   a , 50   b  and, in turn, the knives  74  carried on them, can be easily accessed by an operator for maintenance purposes, troubleshooting, etc. 
         [0028]    The movement of knife beds  50   a , 50   b  can be manual or automatic and may be implemented by a variety of means. For instance, a handle could be provided for manual sliding upon release of a latch, or a hydraulic system controlled by the operator from the cab could be implemented. 
         [0029]    A variety of paths and means of movement of the beds  50   a , 50   b  to accessible positions can also be implemented. For instance, each of the beds  50   a , 50   b  could be horizontally slideable, laterally pivotable about a vertical axis, or be mounted on rollers carried on laterally extending tracks. 
         [0030]    In a preferred embodiment, the pickup  20  has a width of three (3) meters, while each of the knife beds  50   a , 50   b  has a width of six tenths of a meter (0.6 meters). However, dimensional variations in any of the components of the baler  10  may be made without departing from the spirit of the present invention. 
         [0031]    In a preferred embodiment, between eight (8) and twelve (12) knives  74  are provided on each of the beds  50   a ,  50   b . However, any number of knives  74  may be present without departing from the spirit of the present invention. 
         [0032]    Although the preferred embodiments just described refer to left and right knife beds  50   a , 50   b , it is within the scope of the present invention for any number of knife bed sections to be provided, including a single knife bed that is not sectioned. Furthermore, regardless of the number of knife bed sections, it is preferred that at least one and preferably two hydraulic cylinders  86  be provided for controlling swinging movement of each of the knife bed sections. 
         [0033]    In a preferred embodiment, at least one knife-sharpening assembly is carried on the baler  10  to provide onboard at least partly automated sharpening of the knives  74 . However, a baler  10  providing only for manual sharpening of the knives  74  falls within the scope of the present invention. 
         [0034]    In a preferred embodiment, a sensing system (not shown) is provided to allow for continuous monitoring or on-demand reading of the pressure in each of the hydraulic cylinders  86 . The pressure readings taken by the sensing system correspond to the forces applied to the respective knife beds  50  or, if applicable, knife bed sections  50   a , 50   b , etc. and can be used as indicators of a large object in or a jam or blockage of the cutting zone  30 . 
         [0035]    For the sake of clarity, further discussion herein of the sensing system will, unless otherwise noted, refer to the system as applicable to a single knife bed  50 . However, it should be understood that it is within the scope of the present invention for the sensing system to be applied to any number of knife bed sections. 
         [0036]    In a preferred embodiment, each of the springs  118  is replaced with or supplemented by a hydraulic knife cylinder (not shown). In addition to monitoring the pressure in cylinders  86 , the sensing system monitors the pressure in each of the knife cylinders, either continuously or on demand. These pressure readings correspond to the forces applied to the individual knives  74  and can be used as indicators of a large object in or a jam or blockage of the cutting zone  30 . 
         [0037]    In an alternate embodiment, a single hydraulic knife cylinder could be associated with multiple knives  74 . 
         [0038]    A variety of hydraulic system arrangements for the sensing system are suitable for use with the inventive baler  10 , as long as (1) the system is arranged such that pressure readings taken at appropriate locations correspond to appropriate forces on the knives  74  and the knife bed  50 , and (2) sufficient “cushioning” is available in the system (due to judicious placement of accumulators, for instance) to allow raising and lowering of the knives  74  and knife bed  50 . 
         [0039]    As will be described below, the baler  10  is operable via the sensing system to automatically detect and counteract jams or obstructions caused by crop materials or other matter that has entered the cutting zone  30 . 
         [0040]    Although many variations are acceptable, the flowchart in  FIG. 8  illustrates a preferred operational sequence. First, upon initiation of the cutting operation (which typically corresponds with baling operations by the baler  10 ), the system monitors the pressure of the cylinder associated with each individual knife  74  and compares this to a user- or system-defined threshold level. As described previously, each pressure reading corresponds to the force applied to the associated knife. If the crop is flowing smoothly, a relatively low reading (below the threshold pressure) will result. If the crop is jammed or if a large object engages one or more of the knives  74 , however, the force applied to these knives  74  at or near the jam (or object) will increase, resulting in a relatively high reading (presumably a pressure that will exceed the threshold). Therefore, if the pressure for each knife  74  is acceptable, one can reasonably assume that the crop is flowing freely through the cutting zone  30  and that no action beyond continued monitoring (which may be either continuous or intermittent) is necessary. If the reading for a given knife  74  is greater than the threshold, however, that knife  74  should be retracted through a respective slit  78  so that it is positioned below the top wall  80  of the bed  50 . The number of knives  74  that are (essentially simultaneously) retracted at this stage can therefore range from zero to all. Such retraction reduces the risk of knife damage and undue knife wear. Further, the block (or object) will hopefully be permitted to pass through the cutting zone  30  and on to the baling chamber  12 . Preferably, before any retracted knives  74  are returned to the operating position, the bed pressure is sensed, as described below. 
         [0041]    Again, in some instances, refraction of a knife  74  associated with a high force will allow the jammed material located near the respective knife  74  to pass on through the cutting zone  30  and into the packing zone  32  and the baling chamber  12 . In the case of a large jam, however, the material may remain stuck between the rotor  46  and the top wall  80  of the knife bed  50 , despite a knife or knives  74  having been previously retracted. Therefore, as briefly noted, the system also involves monitoring of the pressure of the cylinder(s) associated with the knife bed  50 . Preferably, subsequent to the knife pressure exceeding its threshold value for one or more knives  74 , the system will analyze the pressure associated with the knife bed  50  to avoid premature lowering of the bed  50 . If the knife bed pressure (and thus the force being applied to it) is acceptable, again based on a user- or system-defined threshold, this indicates that the jam has likely cleared and the previously refracted knife or knives  74  can be raised. Furthermore, the acceptable reading indicates that lowering of the knife bed  50  is unnecessary. The original monitoring of individual knife pressures can then continue as previously. If the bed pressure is unacceptably high, however, this indicates that the jam likely has not passed through to the packing zone  32 , in spite of the retraction of the selected knife or knives  74 . The knife bed  50  is then lowered to allow significant clearance between the top wall  80  of the knife bed  50  and the bottom margins of the rotor  46  so that remaining jammed materials can pass freely therebetween. 
         [0042]    As shown in  FIG. 8 , after lowering of the knife bed  50 , the system again analyzes the knife bed pressure. In most instances, the jam will have cleared, and an acceptable pressure will have been restored. If this is the case, the knife bed  50  is raised again to its original position. If not, manual maintenance may be necessary to clear the jam or, if no jam is present, to identify the cause of the high pressure reading. 
         [0043]    The system can be configured to lower the bed  50  only incrementally to progressively “widen” the cutting zone  30  until the bed pressure drops below the threshold, or the bed  50  can be lowered completely so that the material (or object) may be permitted to drop to the ground. Furthermore, any remaining operable knives  74  can be retracted prior to lowering of the bed  50 , despite no high pressure reading having been previously associated with them, in order to maximize the available clearance area between top wall  80  of the knife bed  50  and the bottom margins of the rotor  46 . 
         [0044]    Assuming the knife bed  50  has been raised, the next step is to confirm the clearance of the jam by again analyzing the knife bed pressure. As before, if the pressure is too high, the knife bed must be lowered. If the pressure is acceptable, however, the previously retracted knife or knives  74  can be raised, and the sequence begins anew with analysis of the pressures associated with each individual knife  74 . 
         [0045]    An alternative preferred operational sequence is illustrated by the flowchart in  FIG. 9 . As shown, the initial monitoring of pressures associated with knives  74  and, if necessary, retraction of individual knives  74  is the same as that for  FIG. 8 . However, the procedure illustrated in  FIG. 9  is designed to, as much as possible, avoid the cutting stoppage that would occur if the bed  50  were lowered. 
         [0046]    Consider, for instance, a jam that occurs against a first blade  74 . After retraction of the first blade  74 , the jam might shift or enlarge so as to apply a force to a second blade  74 . Following the procedure shown in  FIG. 8 , which includes only one round of retractions of knives  74  before the pressure associated with the bed  50  is analyzed, the continued presence of the jam would result in lowering of the bed  50  and either a decrease in bale quality as crop material passes uncut into the packing zone  32  or a loss of crop material that falls out of the baler  10 . As shown in  FIG. 9 , however, a process could be implemented whereby a jam or blockage would not result in lowering of the bed  50  unless all of the knives  74  had already been retracted due to associated high pressure readings. In other words, the bed  50  would only be lowered under two circumstances. In the first of these circumstances, all knives  74  have been retracted (either simultaneously or over the course of multiple rounds of analysis) due to associated high pressure readings, yet the pressure reading for the bed  50  is unacceptably high. That is, the jam could not be cleared by simply retracting all of the knives  74 ; so the bed  50  must be lowered. In the second circumstance, the initial retraction of a high-pressure knife or knives  74  has not led to a shift or enlargement of the jam to result in increased pressure to another knife or knives  74  (as indicated by acceptable pressure readings for all remaining knives  74 ), and the pressure reading for the bed  50  is unacceptably high. The jam therefore cannot be cleared by simply retracting additional knives  74 , so the bed  50  must be lowered. 
         [0047]    Although the physical actions taken in the second instance are identical to those shown in the sequence of  FIG. 8 , these actions would have been taken in the  FIG. 8  sequence regardless of whether or not simply retracting an additional knife  74  would have allowed clearance of the jam. That is, in the  FIG. 8  sequence, a single failed attempt to clear the jam based on retraction of a knife or knives  74  (as indicated by a high pressure reading being associated with the bed  50  after the knife or knives  74  were retracted) always leads to lowering of the bed  50 . This sequence would hopefully lead to consistently quick clearance of jams, but at the expense of lost cutting time. In contrast, in the  FIG. 9  sequence, a single failed attempt to clear the jam based on retraction of a knife or knives  74  (as indicated by a high pressure reading being associated with the bed  50  after the knife or knives  74  were retracted) would only lead to lowering of the bed  50  if no additional knife or knives  74  presented an associated high pressure reading. That is, the bed  50  would be lowered only if it were indicated that additional knife  74  retractions would provide no benefits (i.e., the remaining knives  74  were associated with acceptable pressure readings and therefore were not contributing to the jam). This sequence would hopefully avoid lowering of the bed  50  unless absolutely necessary, with small jams being dealt with by sequential knife  74  retractions (i.e., retractions taking place over the course of several rounds of analysis) rather than by a single round of knife  74  retractions followed by bed  50  movement, to ensure that cutting operations could continue uninterrupted for the remaining knives  74 . 
         [0048]    The remainder of the sequence corresponds to that described above with reference to  FIG. 8 . Ultimately, however, as briefly noted above, the sequence illustrated by  FIG. 9  may allow greater total cutting time than that illustrated by  FIG. 8 . For instance, using the sequence of  FIG. 8 , a jam at the leftmost end of the bed  50  that cannot be cleared by retraction of the leftmost knife  74  would result in lowering of the entire bed  50  and subsequent stoppage of all crop cutting. Using the process of  FIG. 9 , however, the same jam could potentially be cleared through the retraction first of the leftmost knife  74  and next of the adjacent knife  74 . Only two knives  74  would be inoperable during this time, with the bed  50  remaining raised and the cutting process continuing for the remaining knives  74 . Of course, either of these approaches would save significant time relative to that required for an operator to leave the cab of the baler  10  and manually remove any blockages. 
         [0049]    The timing of the above-described processes could be varied as necessary to optimize the system. In the case of the  FIG. 9  sequence, for instance, frequent knife  74  pressure analyses to trigger, if necessary, very rapid retraction of multiple knives in sequence would be desirable to ensure that little time is lost in case of a jam large enough to ultimately necessitate lowering of the bed  50 . In contrast, in both of the main discussed procedures, a knife bed  50  pressure analysis might ideally be delayed for some time after lowering of the knife bed  50  occurs so that a high pressure reading would not take place until sufficient time had been provided for the rotor  46  to sweep the jammed material away. This would ensure that an unacceptably high reading, which would indicate the potential need for manual maintenance, would not usually be a result of pressure from a blockage that was only moments away from be successfully cleared by the rotor  46 . 
         [0050]    Although two preferred sequences have been described in detail herein, a variety of algorithms could be implemented without departing from the spirit of the present invention. For instance, the system could include multiple analyses over a set period of time at each stage or selected stages. The multiple analyses could be used to, for example, confirm that a high pressure reading is not simply a result of a transient condition such as rock glancing off a knife  74  or a jam that quickly worked itself out. 
         [0051]    As briefly noted, the threshold values could be user- or system-defined. They could also be a combination of both. In one embodiment, the user could input information about the crop material being baled and the current baling environment, and the system would provide suggested threshold values that the user could either accept or modify. Furthermore, the threshold values could vary for retraction/lowering versus raising, or they could vary according to the position at which the measurement was taken. That is, the pressure threshold for a knife  74  at one position on the knife bed  50  could be different from that for a knife  74  at a different position on the knife bed  50 . 
         [0052]    Furthermore, if a split knife bed  50  were used, as described previously, the sensing system could be modified to analyze each of the bed sections and the respective knives  74  carried thereon independently of the other bed sections and associated knives  74 . In such an embodiment, even less disruption to the cutting process could be expected, since a jam that spreads across multiple bed sections to the extent that more than one bed section required lowering would be unlikely. 
         [0053]    Even further, if a single hydraulic knife cylinder were associated with several knives  74 , groups of knives  74  could be raised and lowered rather than individual knives  74 . 
         [0054]    The preferred forms of the invention described above are to be used as illustration only and should not be utilized in a limiting sense in interpreting the scope of the present invention. Obvious modifications to the exemplary embodiments, as hereinabove set forth, could be readily made by those skilled in the art without departing from the spirit of the present invention. 
         [0055]    The inventors hereby state their intent to rely on the Doctrine of Equivalents to determine and assess the reasonably fair scope of the present invention.