Abstract:
A float arm load compensation system for a header of an agricultural harvester includes a header frame; a plurality of header float arms pivotally coupled to the header frame; a cutter bar fixed to forward ends of the plurality of header float arms; at least one conveyor belt supported on the plurality of header float arms and configured to traverse the header perpendicular to the direction of travel of the header, wherein the conveyor belt is further configured to receive crop material cut by the cutter bar; and a plurality of springs, wherein each spring is coupled to an associated header float arm of the plurality of header float arms to exert a force on the associated header float arm compensating for the weight of cut crop material supported by the associated header float arm.

Description:
RELATED APPLICATIONS 
       [0001]    This invention claims priority to U.S. Prov. Pat. App. Ser. No. 60/825,857, attorney docket number 17720, entitled “Header Float Arm Load Compensation”, which was filed on Sep. 15, 2006 by the same inventors. 
     
     FIELD OF THE INVENTION 
       [0002]    This invention relates generally to harvesters. More particularly, it relates to conveying systems for conveying cut crop material to the harvester vehicle. 
       BACKGROUND OF THE INVENTION 
       [0003]    Harvesters have headers (typically called “Draper platforms”) that carry cut crop material on conveyor belts. These conveyor belts extend across the width of the header to a central discharge region of the header. The conveyor belts are supported on rollers that, in turn, are mounted on header float arms that are elongated and extend forwardly. These arms are pivotally mounted to a frame of the header. The forward ends of the header float arms are coupled to and support a cutter bar that extends across the width of the header. 
         [0004]    The cutter bar and/or the forward ends of the arms skid across the surface of the ground as the harvester goes through the field harvesting crop. As the harvester is driven through the field, the ground rises and falls underneath the header and the arms pivot up and down responsibly, thereby permitting the cutter bar to follow the contours of the ground more closely. 
         [0005]    If the cutter bar and/or the front ends of the arms apply too much pressure to the ground they will dig into the ground and be damaged. Controlling the downforce is therefore important in keeping the header and harvester operating properly. 
         [0006]    To reduce the downforce applied by the header to the ground, each arm is partially supported by a hydraulic, pneumatic, or mechanical spring. The springs are coupled to the frame of the header and transmit some of the crop weight to the frame. They do this by exerting a lifting or “up” force on the arms that counteracts the weight of the arms and the additional downforce exerted on the arms by the cut crop material that falls backward onto the conveyor belts after it is cut by the cutter bar. The springs transfer some of the weight of the header float arms and cut crop material to the feeder house on which the header is supported and transfer the weight off the cutter bar and ground. 
         [0007]    The cut crop material is not evenly distributed across the width of the header conveyors. The crop is cut by the cutter bar across the entire front of the header and then falls backwards onto the conveyor belts, a left conveyor belt and a right conveyor belt. The left conveyor belt carries the cut crop material from the left side of the header to the center section of the header, and the right conveyor belt carries the cut crop material from the right side of the header to the center section of the header. Once the cut crop material reaches the center section of the header, the left and right conveyors dump the cut crop material into a center conveyor that carries the cut crop material backwards, through the feeder house, and into the self-propelled vehicle portion of the harvester. 
         [0008]    Depending upon its position across the front of the header, each header float arm needs a different amount of upward counterbalancing force in order that each header float arm exerts the same downforce against the ground that all the other header float arms do. In the ideal situation, each header float arm provides the same, optimal downforce against the ground. 
         [0009]    In order for each header float arm to provide the same downforce against the ground, each spring must apply a different upforce to its associated header float arms. This is necessary since different portions of the conveyor (and hence each header float arm) support different quantities of cut crop material. As the conveyors move laterally across the width of the header toward the lateral midpoint of the header, more and more cut crop material falls onto the conveyor belt. And the header float arms closer to the lateral midpoint of the header carry a greater and greater weight of cut crop material. This additional crop material resting on the header float arms closer to the lateral midpoint or center of the header means that the header float arms closer to the lateral midpoint require a greater counterbalancing upforce—the force exerted by the springs—if each header float arm is to apply a constant downforce against the ground. 
         [0010]    What is needed, therefore, is a control system for applying to each header float arm in the header a counterbalancing upforce that is appropriate to support the crop load and to maintain constant the downforce exerted by each header float arm against the ground (either directly, or through the cutter bar). It is an object of this invention to provide such a system. 
       SUMMARY OF THE INVENTION 
       [0011]    in accordance with the first aspect of the invention of float arm load compensation system for a header of an agricultural harvester is provided, comprising a header frame; a plurality of header float arms pivotally coupled to the header frame; a cutter bar fixed to forward ends of the plurality of header float arms; at least one conveyor belt supported on the plurality of header float arms and configured to traverse the header perpendicular to the direction of travel of the header, wherein the conveyor belt is further configured to receive crop material cut by the cutter bar; and a plurality of springs, wherein each spring is coupled to an associated header float arm of the plurality of header float arms to exert a force on the associated header float arm compensating for the weight of cut crop material supported by the associated header float arm. 
         [0012]    The springs of the plurality of springs that support float arms closer to the lateral midpoint of the header may be configured to exert a greater upforce on their associated header float arms than other springs of the plurality of springs that support float arms farther from the lateral midpoint of the header. The plurality of springs may be configured to maintain constant the downforce exerted by their associated header float arms against the ground across a width of the header. The load compensation system may further include a control circuit configured to monitor an operational parameter of the agricultural harvester indicative of the load on the at least one conveyor belt. The control circuit may monitor an operational parameter indicative of a load on the rotor of the harvester. The control circuit may be configured to automatically change the forces exerted by the plurality of springs on their associated header float arms in response to changes in the operational parameter. The load compensation system may further include an accumulator containing gas charged hydraulic fluid coupled to the plurality of springs. The load compensation system may further include a valve configured to simultaneously change the force is applied by the plurality of springs by filling and emptying the accumulator. The load compensation system may further include at least first and second accumulators containing hydraulic fluid under pressure, wherein the first accumulator is coupled to a first group of springs of the plurality of springs, and wherein the second accumulator is coupled to a second group of springs of the plurality of springs. The plurality of springs may be mechanical springs. The mechanical springs may be coil springs. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a plan view of a harvester having a header in the form of a Draper platform in accordance with the present invention. 
           [0014]      FIG. 2  is a side view of the harvester of  FIG. 1 . 
           [0015]      FIG. 3  is a fragmentary cross-sectional view of the header of  FIGS. 1-2  taken at section line  2 - 2  in  FIG. 1 . 
           [0016]      FIG. 4  is a schematic diagram of the header of  FIGS. 1-3  with alternative springs and a control circuit for controlling the alternative springs. 
           [0017]      FIG. 5  is a schematic diagram of the header of  FIG. 4  with an alternative control circuit for controlling the alternative springs. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0018]    An “upforce”, as that term is used herein, refers to a force applied to a header float arm that tends to lift the forward end of the header float arm upward and away from the ground thereby reducing the force of the header float arm against the ground. It does not imply or require that the force itself be directed upward at its point of application to the header float arm. Indeed, depending upon the geometry of the header float arm, the force may be applied to the header float arm in any direction and at any point along the arm. 
         [0019]    Referring now to  FIGS. 1-2 , a combine harvester  100  is illustrated, comprising a vehicle  102  that is wheeled and self-propelled, and also comprising a header  104  which is a Draper platform that is mounted on the front of the vehicle  102 . 
         [0020]    Vehicle  102  further comprises a feeder house  106  that is pivotally coupled to the front of chassis  108  of vehicle  102 . Header  104  is supported on the front of feeder house  106 . 
         [0021]    Header  104  comprises a frame  112 , a plurality of arms  114  (identified collectively as header float arms  114   a - j ), a plurality of springs  116  (identified as springs  116   a - j ), conveyor belts  118 ,  120 , a center conveyor  122 , and a cutter bar assembly  124  that is fixed to the leading ends of the arms  114 . 
         [0022]    Referring now to  FIG. 3 , arms  114  extend fore and aft and are pivotally coupled at their rear ends to frame  112 . This arrangement permits them to pivot about a substantially horizontal and laterally extending axis  126  with respect to frame  112 . This pivotal movement permits the front ends of arms  114  to move up and down with respect to frame  112  as the harvester traverses the ground. 
         [0023]    Each arm has an associated spring  116  (identified collectively as springs  116   a - j ) that is coupled to the arm and to the frame to provide an up will force on its associated arm  114 , thereby reducing the force applied by the arm downward on the ground. 
         [0024]    Each arm supports a roller  128  that is supported at its front and rear ends on arm  114 . Roller  128  is disposed generally parallel to arm  114  and is configured to roll about its longitudinal axis. 
         [0025]    Arms  114  located on the left side of the header  104  centerline support a left side conveyor belt  118 . Left side conveyor belt  118  is driven such that it carries material falling on its top surface inwards towards the center region of header  104 . 
         [0026]    Arms  114  located on the right side of the header  104  centerline support a right side conveyor belt  120 . Right side conveyor belt  120  is driven such that it carries material falling on its top surface inwards towards the center region of header  104 . 
         [0027]    Left side conveyor belt  118  and right side conveyor belt  120  are supported on rollers  128 . 
         [0028]    Cutter bar assembly  124  extends laterally across the width of the header  104  and is fixed to the front ends of arms  114 . A lower portion  130  of cutter bar assembly  124  functions as a skid plate, sliding along the ground as vehicle  102  transports header  104  across the field. A portion of the weight of the arms, the conveyor belts, and the crop material riding on the conveyor belts is communicated to cutter bar assembly  124  and thence to the ground. The remainder of the weight is communicated to feeder house  106 . 
         [0029]    Cutter bar assembly  124  is flexible in the lateral direction to permit individual arms  114   a - j  to rise and fall somewhat independently of each other as the cutter bar assembly  124  follows the contours of the ground. This permits the header to more closely follow the contours of the ground. In turn, this close ground-following ensures that the header  104  picks up all of the plant material bearing crop. 
         [0030]    Each arm  114   a - j  is provided with a spring  116   a - j  that is coupled to the arm and to the frame  112  of the header  104 . Spring  116  may be mechanical, hydraulic, or pneumatic. It applies an upward force to arm  114   a - j , reducing the downforce exerted by arm  114   a - j  on the ground via cutter bar assembly  124 . Springs  116   a - j  transfer the weight of their associated arms (and the loads they carry) from the ground to frame  112 . 
         [0031]    The force that each spring  116   a - j  applies is not the same, however. Springs  116  that are closer to the center of header  104  apply a greater upforce to their associated arms  114   a - j  than springs  116   a - j  located farther from the center of header  104 . This differential additional upforce applied to arms  114   a - j  closer to the center of header  104  compensates for the increased weight of crop material on the conveyor belt  118 ,  120  supported on those arms. The weight of the plant material on the conveyor belts  118 ,  120  resting on arms  114   a - j  changes as more and more crop accumulates on the conveyor belts. The weight of the plant material at the outer ends of the conveyor belts is relatively light. As the conveyor belt (supported on rollers  128 ) moves towards the lateral midpoint of the header  104 , more and more plant material is cut by the cutter bar assembly  124  and falls on the conveyor belts. This builds up a thick layer of cut plant material on the conveyor belt that reaches a maximum thickness when the conveyor belt reaches the lateral midpoint of the header  104  and center conveyor  122 . At this point, conveyor belts  118 ,  120  on the left and right sides, respectively, of header  104  deposit their accumulated cut plant material on center conveyor  122 , which moves the cut plant material backward, through feeder house  106 , and into vehicle  102  for further processing. 
         [0032]    In order to maintain a relatively constant downforce across the entire width of the cutter bar assembly  124 , each of the arms  114   a - j  is counterbalanced by its associated spring  116   a - j  such that each arm  114   a - j  applies the same downforce on the section of the cutter bar assembly  124  to which it is attached. This provides an even ground load across the width of the header  104 . 
         [0033]    There are several ways that the springs  116   a - j  can be configured to provide different upforces to arms  114   a - j  such as by adjusting their mounting locations on the frame of the header or the arms, or by varying up reload to the springs. 
         [0034]    Referring now to  FIG. 3 , spring  116   h  has an upper end  132  that can be coupled to frame  112  at several different mounting points  134  and a lower end  136  that can be coupled to arm  114   h  at several different mounting points  138 . Spring  116   h  has a preload adjuster  139 , here shown as an adjustable screw on the barrel of the spring to vary the preload of the spring. By mounting the lower end of spring  116   h  closer to the pivot  141 , the ground force at the end of arm  114   h  can be increased. By mounting the lower end of spring  116   h  farther from the pivot, the ground force at the end of arm  114   h  can be decreased. By mounting the upper end of spring  116   h  farther upward, the ground force at the end of arm  114   h  can be decreased. By mounting the upper end of spring  116   h  farther downward, a ground force at the end of arm  114   h  can be increased. By increasing the spring preload on spring  116   h , the ground force at the end of arm  114   h  can be decreased. By decreasing the spring preload one spring  116   h , the ground force at the end of arm  114   h  can be increased. The arrangement of spring  116   h  and arm  114   h  in  FIG. 3  is typical of all the springs  116   a - j  and arms  114   a - j  in header  104 . The springs  116   a - j  are individually adjusted to provide a greater upforce on the arms  114   a - j  that are closer to the lateral midpoint or center of header  104  and to provide a smaller upforce on the arms  114   a - j  farther from the lateral midpoint or center of header  104 . 
         [0035]    Header  104  of  FIGS. 1-3  is divided into several zones, comprising a first zone including the two outer arms  114   a ,  114   b  on the far left side of the header and the two outer arms  114   i ,  114   j  on the far right side of the header. A second zone includes the two arms on each side of the header just inside the first zone,  114   c ,  114   d ,  114   g ,  114   h , and the third zone including the two center arms  114   e ,  114   f.    
         [0036]    Springs  116   a ,  116   b ,  116   i ,  116   j  of the first zone are configured to provide a first upforce to their associated arms. Springs  116   c ,  116   d ,  116   g ,  116   h  are configured to provide a second upforce to their associated arms  114   c ,  114   d ,  114   g ,  114   h  that is greater than the first upforce applied to the arms in the first zone. This accommodates the additional weight of cut crop matter falling on conveyor belts  118 ,  120  as the belts move from the first zone to the second zone. 
         [0037]    Springs  116   e ,  116   f  are configured to provide a third upforce to their associated arms  114   e ,  114   f  that is greater than the second upforce applied to the arms in the second zone. This accommodates the additional weight of cut crop matter falling on conveyor belts  118 ,  120  as the belts move from the second zone to the third zone. 
         [0038]    In an alternative embodiment, each of the springs  116   a - j  is configured to apply an upforce that is greater than the upforce applied to the arm immediately adjacent to it and farther away from the centerline of the vehicle. In other words, the upforce applied by spring  116   e  to its arm is greater than that applied by spring  116   d  to its arm, which is greater than that applied by spring  116   c  to its arm, which is greater than that applied by spring  116   b  to its arm which is greater than that applied by spring  116   a  to its arm. An upforce applied by spring  116   f  to its arm is greater than the upforce applied by spring  116   g  to its arm, which is greater than the upforce applied by spring  116   h  to its arm, which is greater than the upforce applied by spring  116   i  to its arm, which is greater than the upforce applied by spring  116   j.    
         [0039]    One drawback of this arrangement is the need to mechanically adjust each spring  116   a - 116   j  for different crops and crop conditions. Any particular adjustment of springs  116   a - j  in  FIGS. 1-3  anticipates a particular crop load on conveyor belts  118 ,  120 . If the actual crop load is different from this, the ground force exerted by each of arms  114  will not be ideal. Indeed, if a very large crop load is expected on conveyor belts  118 ,  120 , the compensating upforce generated by springs  116   a - j  may be so great that the arms may actually be lifted above the ground if the crop is not as heavy as anticipated and therefore the compensating upforce generated by springs  116   a - j  is too great. 
         [0040]    To provide easier adjustment of the upforces generated by springs  116   a - j , other spring arrangements may be employed. In  FIG. 4 , for example, each of springs  116   a - j  is a hydraulic cylinder. Springs  116   a - j  in  FIG. 4  are all coupled to an accumulator that is gas charged and contains hydraulic fluid under pressure. This pressure is applied equally to all of the springs  116   a - j  in  FIG. 4 . In one arrangement, springs  116   a - j  exert an equal upforce on their associated arms  114   a - j  to counterbalance the weight of the arm  114   a - j  and the weight of the crop material on conveyor belts  118 ,  120  that the arms support. In an alternative arrangement, springs  116   a - j  in  FIG. 4  are configured to exert different upforces on their associated arms  114   a - j  to counterbalance the weight of the arm  114   a - j  and the weight of the crop material on conveyor belts  118 ,  120  that the arms support. In this alternative arrangement, the upforces exerted by springs  116   a - j  on arms  114   a - j  may be divided into multiple zones, such as the three zones described above with regard to the header  104  of  FIGS. 1-3 . Alternatively the upforces exerted by springs  116   a - j  on arms  114   a - j  may be arranged such that the upforce generated by spring  116   e  is greater than the force generated by spring  116   d , which is greater than the force generated by spring  116   c , which is greater than the force generated by spring  116   b , which is greater than the force generated by spring  116   a . The upforce generated by spring  116   f  is greater than the upforce generated by spring  116   g , which is greater than the upforce generated by spring  116   h , which is greater than the upforce generated by spring  116   i  to its arm, which is greater than the upforce generated by spring  116   j  to its arm. 
         [0041]    In order to generate different upforces when the hydraulic fluid pressure applied to each of the springs  116   a - j  is the same, springs  116   a - j  may be made with different piston diameters, or alternatively may be coupled to arms  114   a - j  and frame  112  of header  104  at different locations with different mechanical advantages, such as at the different locations along the arms and the frame shown in  FIG. 3 . 
         [0042]    In the arrangement of  FIG. 4 , the amount of upforce generated by all of the springs  116   a - j  can be varied simultaneously by filling or emptying the accumulator  132 . A valve  134  is provided that is coupled to a hydraulic fluid supply  136  and a hydraulic fluid reservoir  138 . The valve  134 , when opened, can selectively empty hydraulic fluid from the accumulator  132  to the hydraulic fluid reservoir  138 , or fill the accumulator  132  with hydraulic fluid from the hydraulic fluid supply  136 . As the accumulator  132  is emptied, the pressure in the accumulator  132 , and hence the pressure in each of springs  116   a - j  decreases. As the accumulator  132  is filled, the pressure in the accumulator  132  and hence the pressure in each of springs  116   a - j  increases. The change in pressure in springs  116   a - j  causes a proportional change in the upforce applied by the springs to arms  114   a - j . Thus, by changing the fluid in the accumulator  132 , all of the compensating upforces applied to arms  114   a - j  are simultaneously and proportionally changed across the width of header  104 . 
         [0043]    Electronic control unit (ECU)  140  is coupled to the valve  134  to selectively fill or empty the accumulator  132  under computer control. Electronic control unit  140  is preferably a microprocessor based digital computer including the memory circuit containing a program configured to perform all functions of the electronic control unit described herein. A sensor  142  is coupled to the electronic control unit  140  to transmit to the electronic control unit  140  a value indicative of a desired compensating upforce to be generated by springs  116   a - j . In one embodiment, the sensor  142  is a rotor load sensor, responsive to and indicative of the load on a threshing rotor in the vehicle  102  (not shown). In another embodiment, the sensor is a strain gauge coupled to a rotor drive element such as a rotor shaft or gear responsive to and indicative of the load on the rotor. In another embodiment, the sensor is a pressure sensor responsive to and in indicative of the hydraulic pressure in the hydraulic circuit driving the rotor. In another embodiment, the sensor is a pressure sensor responsive to and indicative of the hydraulic pressure in the hydraulic circuit that drives conveyor belts  118 ,  120 . In another embodiment, the sensor is a load sensor responsive to and indicative of the weight of conveyor belts  118 ,  120 . In any of these embodiments, the sensed parameter is indicative of the load on the harvester, and hence the volume of crop material being harvested. The volume of crop material being harvested is indicative of the weight of the crop material. The weight of the crop material is indicative of the downforce exerted by arms  114   a - j  and thus is indicative of the desired compensating upforce each spring  116   a - j  needs to apply to its associated arm  114   a - j  to maintain the downforce exerted by arms  114   a - j  on the cutter bar (and hence the force the cutter bar and arms exert on the ground). The electronic control unit  140  is configured to monitor the sensor and to open the valve an amount appropriate to maintain constant the downforce exerted by arms  114   a - j  on the cutter bar (and hence the force the cutter bar and arms exert on the ground). 
         [0044]    In another embodiment, the sensor  142  is configured to sense the position of an operator input device, for example a joystick, knob, dial, or lever, that the operator uses to directly command a desired compensating upforce. In this arrangement, the operator monitors the crop load and selects the desired upforce to be generated by springs  116   a - j . Once the operator has selected the desired upforce, he adjusts the operator input device to indicate the desired upforce. The sensor  142  is responsive to this change in the operator input device and signals the electronic control unit. The electronic control unit  140 , in turn, is programmed to open or close the valve  134  as necessary to generate the desired upforce. In this manner, and even while the vehicle is underway, the operator can simultaneously adjust the desired upforce of all the springs  116   a - j.    
         [0045]      FIG. 5  illustrates another embodiment of the system in which a different control circuit is provided to control the operation of springs  116   a - j , the control circuit including three accumulators  144 ,  146 ,  148  to apply a different hydraulic pressure to three different groups of springs  116   a - j . This embodiment is the same as the embodiment of  FIG. 4  in all respects, except the control circuit includes three valves and three accumulators to apply three different pressures to three different groups of valves  116   a - j . In the embodiment of  FIG. 5 , the control circuit includes a first accumulator  144  containing gas charged hydraulic fluid that is coupled to springs  116   a ,  116   b ,  116   i , and  116   j . A second accumulator  146  containing gas charged hydraulic fluid is coupled to springs  116   c ,  116   d ,  116   g , and  116   h . A third accumulator  148  containing gas charged hydraulic fluid is coupled to springs  116   e  and  116   f . These three groups of springs  116   a - j  define three different zones of the header  104 . These three accumulators are coupled to a first valve  150 , a second valve  152 , and a third valve  154 , respectively that conduct hydraulic fluid to and from their respective accumulators  144 ,  146 ,  148 . Each of the three valves  144 ,  146 ,  148  are also coupled to the hydraulic fluid supply  136  and the hydraulic fluid reservoir  138 . As in the example of  FIG. 4 , the electronic control unit  140  opens and closes the valves responsive to the signal provided by the sensor  142  in order to maintain constant a desired downforce exerted by arms  114   a - j  and the cutter bar on the ground. In the embodiment of  FIG. 5 , however, the electronic control unit  140  is separately coupled to each of the three valves  150 ,  152 ,  154  such that it can change the hydraulic pressure in each of the three zones independently of the hydraulic pressure in the other zones. 
         [0046]    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.