Crop Header with Wing Balance Calibration

Abstract

In a crop harvesting header with a center section and two wings where each wing is pivotal relative to the center section about a pivot axis extending in a generally forward direction which includes a balance system to maintain a balanced ground force distribution across the width of the header there is provided an automatic adjustment system for maintaining proper balance. The system includes angle or other sensors which detect the pivot angle of the wing section. This can be used in a static testing system where the position to set to a detected midpoint and/or in a dynamic system where repeatedly, over a time period during which the header is operating, data is detected relating to the positions of each wing frame portion.

Claims

1. A crop harvesting header for use in a harvesting operation comprising: a main frame structure extending across a width of the header for movement in a forward direction generally at right angles to the width across ground including a crop to be harvested; a mounting assembly for carrying the main frame structure on a propulsion vehicle; a cutter bar across a front of the table arranged to move over the ground in a cutting action; the main frame structure including a center frame portion, a first wing frame portion and a second wing frame portion; each of the wing frame portions being connected to the center frame portion by a pivot coupling arranged for pivotal movement of the wing frame portion relative to the center frame portion about a pivot axis extending in a generally forward direction; each of the wing frame portions being movable about the pivot axis to different angles of the wing frame portion relative to the center frame portion; each wing frame portion being movable from a mid position, in which the wing frame portion lies on a common line with the center frame portion, upwardly to a raised position in which the angle changes so that the wing frame portion is inclined upwardly from the pivot axis, and downwardly to a lowered position in which the angle changes so that the wing frame portion is declined downwardly from the pivot axis; the first wing frame portion including a first balance system for applying a first lifting force to the center frame portion and a balanced first wing lifting force to the first wing frame portion to support the first wing frame portion to provide a balanced ground force distribution across the width of the header including the center frame portion and the first wing frame portion; the first balance system including a first adjustment member which changes a first ratio of the first lifting force relative to the first wing lifting force; the second wing frame portion including a second balance system for applying a lifting force to the center frame portion and a balanced wing lifting force to the second wing frame portion to support the second wing frame portion to provide a balanced ground force distribution across the width of the header including the center frame portion and the second wing frame portion; the second balance system including a second adjustment member which changes a second ratio of the second lifting force relative to the second wing lifting force; and calibration system arranged to calibrate the first and second balance systems, the calibration system comprising: at least one first sensor which directly or indirectly provides first data relating to the angle between the first wing frame portion and the center frame portion; at least one second sensor which directly or indirectly provides second data relating to the angle between the second wing frame portion and the center frame portion; a first actuator operating said first adjustment member; a second actuator operating said second adjustment member; and a processor which receives said first and second data and provides therefrom first and second set point data for said first and second actuators.

2. The header according to claim 1 wherein said at least one sensor operates, for detecting said positions of each wing frame portion relative to the center frame portion, by detecting movement of a component of the wing frame portion relative to a component of the center frame portion.

3. The header according to claim 1 wherein said at least one sensor operates by detecting a change of angle of a component of the wing frame portion relative to a component of the center frame portion, which change is proportional to the change in angle at the pivot axis.

4. The header according to claim 3 wherein the sensor comprises an angle sensor mounted at a pivot point.

5. The header according to claim 4 wherein the angle sensor is mounted between two components of the balance linkage which pivot relative to one another as the wing frame portion pivos about the pivot axis.

6. The header according to claim 1 wherein said at least one sensor operates, for detecting said positions of each wing frame portion relative to the center frame portion, by detecting a distance of each of the wing frame portions and the center frame portion from the ground and there is provided a plurality of sensors detecting the height of the portions from the ground.

7. The header according to claim 1 wherein said at least one sensor operates, for detecting said positions of each wing frame portion relative to the center frame portion, by detecting relative force of the wing frame portions and the center frame portion on the ground and there is provided a plurality of sensors detecting the pressure of the portions on the ground at spaced positions across the header.

8. The header according to claim 1 wherein said processor receives data repeatedly from said first and second sensors, over a time period during which the header is operating in said harvesting operation.

9. The header according to claim 8 wherein the processor calculates first and second set point data for said first and second actuators by a determination as to whether the wing frame portions are predominantly raised or predominantly lowered during the time period.

10. The header according to claim 8 wherein the processor records the data while harvesting over a set period of time.

11. The header according to claim 10 wherein the processor calculates as said value an average position of said wing frame portions over the set period of time.

12. The header according to claim 11 wherein the processor includes a look up table for determining an amount of adjustment in relation to the calculated value.

13. The header according to claim 1 wherein the processor operates, with the header stationary and running, for each of the first and second respective balance systems independently: -a- to operate the actuator to move the respective adjustment member to a position in which the respective wing frame portion is in the raised position; -b- to operate the actuator to move the adjustment member from the position until the respective wing frame portion moves to the mid position and to record a first position of the adjustment member at the mid position of the respective wing frame portion; -c- to operate the actuator to move the respective adjustment member to a position in which the respective wing frame portion is in the lowered position; -d- to operate the actuator to move the respective adjustment member from the position until the respective wing frame portion moves to the mid position and to record a second position of the respective adjustment member at the mid position of the respective wing frame portion; -e- to determine from the first and second positions the set point data for the respective balance system.

14. The header according to claim 13 wherein the set point data is mid-way between the first and second positions.

15. The header according to claim 13 wherein there is provided a wing locking device for locking the other wing frame portion when the respective wing frame portion is moved.

16. The header according to claim 13 wherein said set point data forms an initial set point from a static test taken while the header is stationary and subsequently further dynamic tests are carried out while the harvester is moving in a harvesting action.

17. The header according to claim 16 wherein, in said dynamic tests, said processor receives data repeatedly from said first and second sensors, over a time period during which the header is operating in said harvesting operation.

18. The header according to claim 17 wherein the processor calculates first and second set point data for said first and second actuators by a determination as to whether the wing frame portions are predominantly raised or predominantly lowered during the time period.

19. The header according to claim 18 wherein the processor calculates an average position of said wing frame portions over the set period of time.

20. The header according to claim 16 wherein said mid position is detected by detecting a change of angle of a component of the wing frame portion relative to a component of the center frame portion.

21. The header according to claim 16 wherein said mid position is detected by detecting a distance of each of the wing frame portions and the center frame portion from the ground by a plurality of sensors detecting the height of the portions from the ground.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Embodiments of the invention will now be described in conjunction with the accompanying drawings in which:

[0070] FIG. 1 is taken from U.S. Pat. No. 6,675,568 and shows a schematic rear elevational view of header of the general type with which the present invention is concerned with the combine harvester which acts as a propulsion vehicle and the associated adapter being omitted for convenience of illustration. A sensor system according to the present invention which is responsive to the load applied by the center section and wing sections to the ground is included.

[0071] FIG. 2 is taken from U.S. Pat. No. 6,675,568 and shows the PRIOR ART schematic top plan view of the header of FIG. 1.

[0072] FIG. 3 shows an isometric view from the rear and one side of one embodiment of the header with the adapter removed and showing one embodiment of the adjustment system of the present invention.

[0073] FIG. 4 shows a rear view of the header with the adapter removed and showing another embodiment of the adjustment system of the present invention.

[0074] FIG. 5 is a schematic illustration of the system logic of the apparatus according to the present invention.

[0075] FIG. 6 is a schematic illustration of the adjustment logic of the apparatus according to the present invention.

DETAILED DESCRIPTION

[0076] Reference is made to U.S. Pat. No. 6,865,871 (Patterson) issued Mar. 15, 2005 which disclose details of an adapter for mounting a header on a combine harvester, the disclosure of which is incorporated herein by reference.

[0077] Reference is also made to U.S. Pat. No. 6,675,568 (Patterson) issued Jan. 13, 2004 which disclose details of a flexible header of the general type with which the present invention is concerned, the disclosure of which is incorporated herein by reference. FIGS. 1 and 2 and part of the following description are taken from that patent for the convenience of the reader. Further details not included herein can be obtained by reference to that patent.

[0078] Reference is also made to U.S. Pat. No. 7,918,076 (Talbot) issued Apr. 5, 2011 which disclose in FIG. 3 in rear elevational view a header 10 carried on an adapter 11 or mounting assembly attached to the feeder house 12 of a combine harvester. In FIG. 1 the adapter is omitted for convenience of illustration.

[0079] The header 10 includes a frame 13 defined by a main rear beam 14 and a plurality of forwardly extending arms 15 which extend downwardly from the beam 14 and then forwardly underneath a table 16 which extends across the header. At the forward end of the table 16 is provided a cutter bar 17. On top of the table 16 is provided a draper transport system 18 which carries the crop from the cutter bar across the header to a discharge location at the feeder house 12. The draper system 18 thus include two side drapers 18A extending from respective ends of the header inwardly toward the feeder house and a center adapter section 18B which acts to feed the crop from the side drapers 18A rearwardly to the feeder housing.

[0080] The header further includes a reel 19 including a beam on which is mounted a plurality of reel bats (not shown) which are carried on the beam for rotation with the beam around the axis of the beam. The beam is carried on reel support arms 19B which extend from the beam rearwardly and upwardly to a support bracket attached to the transverse main beam 14. The reel arms can be raised and lowered by hydraulic cylinders 19D connected between the respective arm and the beam 14.

[0081] The above description of the header refers only schematically to the construction since the details of the construction are well known to one skilled in the art.

[0082] Referring also to FIG. 2, the adapter 11 comprises a frame 20 which attaches to the feeder house 12 and carries at its lower end a pair of forwardly extending pivotal arms 21 which form respective first and second spring biased lifting members and which extend forwardly underneath respective ones of the frame members 15 of the header. The pivotal arms 21 can pivot upwardly and downwardly about respective pivot pins 23 each independently of the other arm. Each arm is supported by a respective spring 24 attached to the respective arm 21. Thus the respective springs 24 provide respective first and second spring lifting forces which act to pull up the respective arm 21 and provide a lifting force underneath the header at a lifting point partway along the respective frame member 15 and underneath the draper 18 and the table 16.

[0083] At the center of the adapter is provided a link 26 which extends from the frame 20 forwardly in the form of a hydraulic cylinder which allows adjustment of the length of the cylinder thus pivoting the header forwardly and rearwardly about the support point of the arms 21 on the underside of the header. Thus the attitude of the header, that is the angle of the table 16 to the horizontal can be tilted by operation of the cylinder forming the link 26.

[0084] In addition the attitude of the header about an axis extending forwardly of the direction of movement that is at right angles to the transverse beam 14 is effected by the independent pivotal movement of the arms 21 provided by the springs 24 which act as a floatation system. In addition the whole header can float upwardly and downwardly on the springs 24 with the link 26 pivoting to accommodate the upward and downward movement and the arms 21 pivoting about the respective pin 23.

[0085] The table 16 provides behind the cutter bar 17 a skid plate 16A which is arranged to engage the ground. Thus upward force is provided from the ground which tends to lift the header taking weight off the support springs 24. In practice the springs are adjusted so that the springs act to support the majority of the weight of the header leaving a relatively small proportion of the weight to rest on the ground. Thus the header can float upwardly and downwardly as the ground provides areas of different height with one end of the header being movable upwardly independently of the other end by independent flexing of the springs 24. Thus the header tends to follow the ground level.

[0086] The beam 14 forms a main frame structure which is divided into a number of separate pieces 14A, 14B depending upon the number of sections of the header. In the embodiment shown there are three sections including a center section or center frame portion 10A, a first wing section or wing frame portion 10B and a second wing section or wing frame portion 10C. The center section 10A is mounted at the adapter so that the arms 21 extend into engagement with the center section. The wing sections are pivotally connected to the center section such that each can pivot upwardly and downwardly about a respective pivot axis generally parallel to the direction of movement.

[0087] The beam 14 is split into three portions each co-operating with a respective one of the sections 10A, 10B and 10C and defining a main beam therefor. Each section of the beam 14 includes respective ones of the frame members 15 which support the respective portion of the table. Thus as best shown in FIG. 4, there is a break 14C between the beam sections 14A and 14B of the center section 10A and one wing section 10B. The end most frame member 15A of the wing section 10B is arranged at the break. The end frame member 15B of the center section 10A is spaced inwardly from the break leaving space for a pivot coupling 27 extending from the frame member 15A to the frame member 15B and defining a pivot pin 27A defining a first pivot connection lying on the pivot axis between the wing section 10B and the center section 10A.

[0088] The two sections 10A and 10B are supported each relative to the other for pivotal movement of the wing section 10B about an axis extending through the pin 27A and through the break 14A so that the wing section is supported at its inner end on the center section but can pivot downwardly at its outer end so that the weight at the outboard end is unsupported by the center section and causes downward or counter clockwise pivotal movement of the wing section 10B.

[0089] The wing section 10C is mounted in an identical or symmetrical manner for pivotal movement about the other end of the center section 10A. The amount of pivotal movement allowed of the wing section relative to the center section about the axis of the pivot pin 27A is maintained at a small angle generally less than 6 degrees and preferably less than 4 degrees as controlled by suitable mechanical stop members which are provided at a suitable location with the required mechanical strength to support the wing frame section against upward or downward movement beyond the stop members.

[0090] In one example, the outboard weight of the wing section 10B is supported on a balance linkage generally indicated at 30 which communicates that weight from the inner end of the beam 14 of the section 10B through to the support for the center section 10A at the springs 24. The linkage is shown particularly in FIG. 3 and includes a tension link 31 extending from the inner end of the beam 14 to a bell crank 32 at the outer end of the center section 10A on the beam 14 together with a further compression link 33 which extends downwardly from the bell crank to a balance beam 34 located on the center section 10A at its interconnection with the arm 21.

[0091] The balance linkage 30 operates to transfer the outboard weight of the wing section inwardly to the center section and at the same time to balance the lifting force provided by the springs 24 so that it is proportionally applied to the center section and to the wing section.

[0092] The header is attached to the combine feeder house using the float system described previously that supports the header so that it can be moved up when a vertical force about 1% to 15% of its weight is applied to the cutter bar from the ground. The reaction of the float linkage that typically supports 85% to 99% of the header weight on the header is used to balance the weight of the wings.

[0093] The system is designed so that if the operator sets the float so that the float system supports 99% of the header weight then the remaining 1% will be evenly distributed across the cutter bar. If the operator changes the float so that 85% is supported by the combine harvester then the remaining 15% is also evenly distributed across the cutter bar without the operator making adjustments. Thus, not only is the total lifting force to each section varied in proportion to the total lifting force but also that lifting force on each section is balanced across the width of section. As the sections are rigid between the ends, this requires that the lifting forces be balance between the ends to ensure the even distribution across the cutter bar of each section and thus of all the sections. This is achieved in this embodiment by a balancing system which includes a linkage connecting the force to the wing section and particularly the balancing beam 34. Thus the balance beam 34 balances the lifting force applied to the ends of the center section relative to the lifting force which is applied to the outboard weight of the wing section so that the lifting force is even across the width of the header.

[0094] The inboard weight of the wing section is transferred through the pivot 27 to the outboard end of the center section and that weight is transferred directly to the balance beam 34. Also the outboard weight of the wing section is transferred through the link 31 and the bell crank 32 to the balance beam 34. Yet further a lifting force from the arm 21 is applied to the balance beam.

[0095] Thus reviewing FIGS. 3 and 4, the balance beam 34 is located above the arm 21. The balance beam 34 has a forward end 34A which is pivotally connected to the frame member 15 at a transverse pivot pin 34B. The arm 21 extends forwardly to a forward lifting point 21A which engages underneath a forward end 34A of the balance beam. The lifting force from the arm 21 is applied upwardly at the point 21A which is forward of the beam 14 and underneath the table 16.

[0096] The balance beam 34 extends rearwardly from the forward end 34A rearwardly to a rear end 34C to which is connected the compression link 33 at a bushing 33A. The compression link or compression member 33 thus applies an upward pushing force which acts to support the outboard weight of the wing section and also applies some lifting force to the center section through the bell crank 32.

[0097] The pivot pin 34B is attached to the center section so that some weight from the center section, which is not carried on the bell crank, is transferred to the pivot pin and through that pin to the balance beam 34.

[0098] The lifting force from respective one of the first and second lift arms 21 is wholly applied at the respective one of the first and second lifting positions 21A of the balance beam. These three forces are all applied to the balance beam and the balance beam acts to automatically proportion the forces relative to the lifting force.

[0099] The support assembly includes a first component which is the pin 34B to provide a lifting force for the center frame portion. The support assembly which is the linkage includes a second component which is a tension link 33 arranged to provide a lifting force F2 for the outboard weight of the second or wing frame portion.

[0100] The whole support assembly including the balance beam 34, the lift arm 21 and the springs 24 are arranged to provide a floating movement for each of the first and second frame portions that is the center and wing frame portions relative to each other and relative to the propulsion vehicle such that upward pressure from the ground on the skid element 16A which is greater in a downward force for a part of the weight of the header and supported by the lifting force tends to lift each of the center and wing frame portions relative to the propulsion vehicle.

[0101] The balance beam 34 is arranged such that the first and second lifting forces F1 and F2 are varied proportionally as the total lifting force FT is varied. As the force F2 includes the force lifting the wing section and a part of the force lifting the center section, this can be balanced relative to the lifting force F1 which applies a lifting force to the center section. The geometry of the balance beam and the linkage including the bell crank is arranged such that the balancing system defined thereby provides the lifting forces to the center section and wing section as defined above.

[0102] It will be noted that the linkage provided by the tension link 31, compression link 33 and the bell crank 32 includes no spring connection and is a direct mechanical linkage so that the spring action or floating action of the wing section is provided by the spring 24.

[0103] The balance beam 34 extends parallel to the arm 21 so that the pivot pins or bushings 34B and 33A have an axis at right angles to the balance beam and to the arm 21. The forces extend generally at right angles to the arm 21 since the arm 21 is generally horizontal underneath the header frame and underneath the balance beam.

[0104] The bell crank 32 is located and supported on the beam 14 so that the link 31 extends along the length of the beam 14 across the space 14A. The link 31 is located above the pivot 27A and communicates forces by tension.

[0105] The compression link 33 is pivotally attached to the bell crank at a pivot connection pin 32B. The length of the arm 32C of the bell crank 32 can be adjusted by sliding the pin 32B along a slot 32D thus adjusting the mechanical advantage of the bell crank to vary the mechanical advantage or moment of the force F2 transferred to the outboard weight of the wing section. The bell crank can be adjusted so that the forces F1 and F2 are balanced to produce approximately uniform contact pressure between the ground and the skid shoe. The bell crank 32 is pivoted at pin 32E carried on a support 32F attached to the frame. The link 31 attaches to the bell crank 32 at the pin 32G.

[0106] It will be appreciated that the balance system using the balance beam 34 and the links 32 and 33 is merely one of many examples of design of balance system which can be used.

[0107] In the system shown in the above patents and as manufactured and sold by MacDon there is a requirement for the operator to periodically adjust the wing balance by adjusting the position of the pin 32B along the link 31.

[0108] According to the present arrangement, there is provided an adjustment system one embodiment of which is shown in FIG. 3 and is generally indicated at 40. This arrangement 40 is arranged to provide adjustment automatically of the balance system to maintain the balanced ground force distribution.

[0109] The adjustment system 40 includes a first sensor 41 at the pivot pin 27A to the left wing 10B and a second sensor (not visible) at the corresponding pivot pin of the second wing 10C. In this embodiment the sensors 41 are angle sensors mounted at the pin 27A which detect the angle of the wing 10B relative to the center portion 10A and any changes therein over time as the wing floats upwardly and downwardly as described above. In addition or as an alternative, a sensor 41A can be provided at a pivot pin 31A at the end of the tension link where the link pivotally connects to the bell crank 32 since the angle of movement at the pin 21A is directly proportional to the angle at the at the pin 27A.

[0110] A lock pin 51 is provided which can lock the pivotal movement of the wing frame portion 10B relative to the center frame portion 10A so that when actuated by an actuator 51, the pin 50 engages into a receptacle 52 to hold the beams 14A and 14B against pivotal movement about the pin 27A. Such a locking arrangement can be provided at many locations but is most conveniently provided directly at the beam 14.

[0111] An adjustment actuator 43 at the adjustment 32B is provided to move the adjustment 32B to required positions.

[0112] A sensor 46 provides an input indicative of header operation for example from the cutter bar. A processor 42 is provided to receive the inputs from the sensors and from a look-up table 45 and to provide output control to the lock pin actuator 51 and the adjustment actuator 43.

[0113] In the dynamic adjustment system, the sensors 41 or 41A of the two wing frame portions independently act repeatedly, over a time period during which the header is operating in said harvesting operation, to detect the changing positions of each wing frame portion 10B relative to the center frame portion 10A.

[0114] The processor 42 is arranged in response to the positions sensed by the sensors 41 to calculate a value representative of the positions of the wing frame portions over a set time period.

[0115] As shown in FIGS. 5 and 6, the processor 42 receives the signals from the sensors 41, or 41A, on each wing frame portion and independently records the left and right wing positions determined by the angle sensors 41 repeatedly, for example once per second, over a set period of time, for example 15 minutes. The processor 42 then calculates from these signals an average value. These calculations are carried out only when the harvesting system is operating to avoid distorting the results from stationary data or data obtained when the header is not on the ground. The sensor 46 provides an input indicative of header operation for example from the cutter bar. For example, the sensor 45 for detecting whether the header is operating can receive data from a knife speed sensor.

[0116] Based on the difference of the average value calculated from the nominal zero difference expected when the header is operating properly, the processor accesses the look-up table 45 to determine how much out of setting the adjustment is presently determined to be. In response to this value from the look up table 45, the actuator 43 at the adjustment 32B is operated to move the adjustment to the newly determined proper location.

[0117] In effect, the average values calculated allow the processor to provide an indication as to whether the wing frame portions are predominantly raised or predominantly lowered during the time period. That is the wings will be raised and lowered at different times during operation depending on ground height but the average over a set time period should be zero.

[0118] As two separate sensors are provided, one for each wing, this allows the processor to use in calculation independent sensor data relating to the independent positions of the wing frame portions to determine independent adjustment values for the separate wing frame portions from the independent sensor data. However in some balance systems the wings may be adjusted as a common single adjustment by common actuation of the adjustments 32B by linked actuators 43.

[0119] The processor 42 and/or the look up table 45 may provide an output such that when the value is within a predetermined range of acceptability outside of the nominal zero value, no adjustment is made.

[0120] As discussed above, the system also provides a static calibration system where the static auto calibration logic is as follows:

[0121] -a- user presses start

[0122] -b- the system prompts the user to start header

[0123] -c- the system locks one of the wings using the lock 50 and unlocks the other wing.

[0124] -d- the system moves the actuator 43 in the fully inboard direction that is toward the right as shown so that the effect of the link 33 is reduced and the wing portion lowers or droops to its lowest position into a wing frown position.

[0125] -e- the system moves the actuator 43 in the outboard direction thus causing the wing to move upwardly until the wing is level or in the mid position as determined by the wing position sensor 41. The position of the adjustment 32B of the compression link 33 is recorded by data from the actuator 43.

[0126] -f- the system moves the actuator 43 in the fully outboard direction that is toward the left as shown so that the effect of the link 33 is increased and the wing portion rises to its highest position into a wing smile position.

[0127] -g- the system moves the actuator 43 in the inboard direction thus causing the wing to move downwardly until the wing is level or in the mid position as determined by the wing position sensor 41. The position of the adjustment 32B of the compression link 33 is recorded by data from the actuator 43.

[0128] The two previous steps e) and g) determine both bounds of the hysteresis. The system now moves the compression link to the position mid way between the two hysteresis values. It is important that the header is operating during this static test as it increases the reliability in finding the bounds of the hysteresis.

[0129] The system now repeats the steps on the other wing with the first wing locked and the static calibration is complete.

[0130] The processor 42 also records the adjustment positions from the static or dynamic tests after an adjustment is completed. The processor 42 can also halt the dynamic adjustment system to allow the operator to override the input values and re-set to a required operator value or to the value from the static test or to a factory default setting. In the event that the static test is not available or is not provided, the the system can look up values from a table which will set the flex linkage to a theoretically correctly adjusted position based on the header size and optional equipment. The factory reset can used instead of the static test as a starting point. Using a starting point close to the required position allows the continual refinement provided by the dynamic calibration to be carried out more effectively and quickly while the header is harvesting.

[0131] As shown in FIG. 4 there is provided an alternative system 40A in which the processor 42A receives signals from a series of height sensors 48A, 48B, 48C and 48D at ends of the wing portions 10A and 10C and at the ends of the center portion 10A. These act to detect the height of the sensor and thus the portion on which it is mounted from the ground. In this way the system detects a distance of each of the wing frame portions and the center frame portion from a component relative to which each of the portions moves, in this case the ground. Over the period of time, all three sections should statistically have the same average distance from the ground and any variation in this distance is indicative of the wings being too heavy or too light thus requiring an adjustment as set forth above.

[0132] As shown in FIG. 1, there is provided a further alternative system in which there is provided a plurality of separate ground engaging elements 50 at spaced positions along the main frame structure 14 for supporting the cutter bar from the ground. There are center elements 50 which generally support the center section and wing elements which are mounted at or adjacent the outer end of each wing. Each element includes a load sensor 51 for providing an output related to a force applied by the header through the respective ground engaging elements to the ground. The system operates, for detecting data relating to a condition of the balance system, by detecting a force applied by each of the wing frame portions and the center frame portion to the ground.

[0133] This data is then monitored over a selected time period and provides information on the load applied by each of the sections to the ground which is indicative of its position relative to the other sections. This data when collected over time can be used to generate a value for effecting the adjustment of the balance system.