Patent Publication Number: US-2021161070-A1

Title: Flexible header with sectional height adjustment

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/770,915, “Flexible Header with Sectional Height Adjustment,” filed Jun. 8, 2020, which is a national phase entry under 35 U.S.C. § 371 of International Patent Application PCT/IB2018/057892, filed Oct. 11, 2018, designating the United States of America and published in English as International Patent Publication WO 2019/111069 A1 on Jun. 13, 2019, which claimed the benefit of the filing date of U.S. Provisional Patent Application 62/596,646, “Flexible Header with Sectional Height Adjustment,” filed Dec. 8, 2017, the entire disclosures of each which are incorporated herein by reference. 
    
    
     FIELD 
     The present invention relates to harvesting headers, and more particularly, embodiments concern a flexible harvesting header having multiple sections supported by support arms, with the height of each support arm being adjustable in response to changing loads. 
     BACKGROUND 
     A traditional grain harvesting implement or machine, such as a self-propelled combine, is used to harvest a variety of grains, such as wheat, soybeans, and rice. Combines typically include a harvesting header that cuts the crop and gathers the crop material into a feeder house for threshing and other operations. For some grains, such as wheat, the sickle of the header can be spaced from the ground during the cutting operation. For other grains, the sickle must be positioned close to the ground, often with the header in sliding contact with the ground, in order to collect most of the grain. Flexible headers are used to follow the natural contours of the field while cutting the grain. 
     Conventional grain harvesters are problematic and suffer from various limitations. For example, flexible headers that include a flexible cutterbar are ineffective at receiving all of the severed crop material when following the ground contour at a high speed. Prior art flexible headers are also deficient because they fail to convey all of the received cut crop material to the feeder house. Furthermore, harvesters with flexible headers ineffectively control the header height, particularly when the header is in sliding contact with the ground. Yet further, prior art flexible headers become damaged when operating in close proximity to the ground, particularly when the terrain has a significant contour. 
     Some crops, such as second crop beans, can accumulate in front of the skid plates. This can also occur when harvesting on the ground and the material is damp or loose. Additionally, when raising the header, there is an initial tendency for the guards to tip downwardly, causing them to dig into the ground, which can damage the header and reduce productivity. The header is meant to “float” over the ground during harvesting. When material accumulates in front of the header, ground pressure increases, which can further exacerbate the problem. One solution has been to use bigger hydraulic cylinders on both ends of the header to better adjust for the increased weight. However, while this keeps the outer tips pointed upward, it does nothing for the intermediate support arms. 
     This background discussion is intended to provide information related to the present invention which is not necessarily prior art. 
     BRIEF SUMMARY 
     Embodiments address the above-described and other problems by providing a flexible harvesting header having multiple sections supported by support arms, with the height of each support arm being adjustable in response to changing loads. In one embodiment of the present invention, a header for harvesting a crop may broadly comprise a flexible cutter bar assembly, a plurality of laterally spaced apart support arms, a plurality of load sensors, a plurality of hydraulic cylinders, and a controller. The flexible cutterbar assembly may extend lengthwise in a lateral direction relative to a normal direction of travel of the header. The support arms may be configured to support the flexible cutter bar assembly, with each support arm including a first end attached to the flexible cutterbar assembly, and a second end pivotal about a laterally extending axis so that the flexible cutterbar assembly is configured to flex in response to changes in terrain as the header is advanced. Each load sensor may be located at the first end of one of the support arms and configured to sense a load on the first end and generate an electronic load signal. Each hydraulic cylinder may be located at the second end of one of the support arms and actuatable to adjustably raise and lower the first end of the support arm. The controller may be configured to receive the electronic load signals generated by the load sensors, determine whether the load signals indicate that actuating one or more of the hydraulic cylinders is warranted due to a changing load at the first ends of one or more of the support arms, and if so, send a control signal to change a hydraulic pressure in the one or more hydraulic cylinders to raise or lower the first ends of the one or more support arms to offset the changing load. 
     Various implementations of the foregoing embodiments may include any one or more of the following additional features. The header may further include a plurality of skid plates, with each skid plate being associated with the front end of one of the support arms, and wherein each load sensor is associated with one of the skid plates. The header may further include a hydraulic assembly include a pressure line for increasing a hydraulic fluid and thereby increasing the hydraulic pressure; a return line for decreasing the hydraulic fluid and thereby decreasing the hydraulic pressure; a plurality of valves, with each valve being associated with one of the hydraulic cylinders, coupled with the pressure line and return lines, and configured to open to allow the hydraulic fluid to move into or out of the hydraulic cylinder; and a plurality of valve lines, with each valve line being coupled with one of the hydraulic cylinders and one of the valves, and configured to allow the hydraulic fluid to move into or out of the hydraulic cylinder via the open valve. 
     The controller may determine whether actuating one or more of the hydraulic cylinders is warranted by determining whether the changing load exceeds a pre-determined changing load value. The pre-determined changing load value may be at least five percent, or at least ten percent. All or only some of the support arms may be provided with one of the load sensors, all or only some of the support arms may be provided with one of the hydraulic cylinders, and/or all or only some of the hydraulic cylinders may be actuatable by the controller. The entire flexible cutter bar may be configured to be raised in response to an electronic raise signal, and the controller may be configured to receive the electronic raise signal and determine whether the electronic raise signal is present for at least a pre-determined time period, and if so, cause the hydraulic pressure in all of the hydraulic cylinders to be increased to raise the front ends of all of the support arms. The pre-determined time period may be no longer than five seconds, or no longer than one second. 
     This summary is not intended to identify essential features of the present invention, and is not intended to be used to limit the scope of the claims. These and other aspects of the present invention are described below in greater detail. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention are described in detail below with reference to the attached drawing figures, wherein: 
         FIG. 1  is a left front perspective view of a harvesting header constructed in accordance with a first embodiment of the present invention; 
         FIG. 2  is a left rear perspective view of the harvesting header shown in  FIG. 1 ; 
         FIG. 3  is an enlarged fragmentary left front perspective view of the harvesting header shown in  FIGS. 1 and 2 , showing a header frame, draper arms pivotally attached to the header frame and supporting a cutterbar assembly, a left end tilt arm pivotally attached to the header frame and supporting the cutterbar assembly and a cutterbar drive, and a left side draper with a draper belt of the draper assembly removed; 
         FIG. 4  is an enlarged fragmentary left front perspective view of the harvesting header shown in  FIGS. 1-3 , showing the end tilt arm pivotally mounted to the header frame and showing pivot adjustment pins attached to the header frame to restrict pivotal movement of the end tilt arm between uppermost and lowermost arm positions, with the illustrated left end tilt arm being in an arm pivoting configuration and in the uppermost arm position; 
         FIG. 5  is an enlarged fragmentary lower right front perspective view of the harvesting header shown in  FIGS. 1-5 , showing the left end tilt arm pivotally mounted to the header frame, with the left end tilt arm in the arm pivoting configuration and in the uppermost arm position; 
         FIG. 6  is a fragmentary left side view of the harvesting header shown in  FIGS. 1-5 , showing one of the draper arms in the arm pivoting configuration and in the uppermost arm position; 
         FIG. 7  is a fragmentary left side view of the harvesting header shown in  FIGS. 1-6 , showing the left end tilt arm in the rigid configuration and in the uppermost arm position, and showing the cutterbar drive supported by the left end tilt arm for up-and-down swinging arm movement, with an epicyclic drive in an uppermost position relative to a rear gearbox; 
         FIG. 8  is a fragmentary left side view of the harvesting header shown in  FIGS. 1-7 , showing the left end tilt arm in the arm pivoting configuration and in the uppermost arm position, and showing the laterally extending pivot location of the left end tilt arm; 
         FIG. 9  is a fragmentary left side view of the harvesting header shown in  FIGS. 1-8 , showing the left end tilt arm in the arm pivoting configuration and in a lowermost arm position, and showing the epicyclic drive in a lowermost position relative to the rear gearbox; 
         FIG. 10  is a fragmentary left front perspective view of the harvesting header shown in  FIGS. 1-9 , showing the left end tilt arm pivotally attached to the header frame and supporting the cutterbar drive, and showing the draper belt of the left side draper; 
         FIG. 11  is a fragmentary upper right front perspective view of the harvesting header shown in  FIGS. 1-10 , showing a crop deflector of the left end tilt arm spaced above an outboard end of the left side draper; 
         FIG. 12  is a fragmentary lower right front perspective view of the harvesting header shown in  FIGS. 1-11 , showing the left end tilt arm with the cutterbar drive being covered by the crop deflector, showing skid plates of the cutterbar assembly, and showing an end skid of the left end tilt arm; 
         FIG. 13  is a fragmentary lower left front perspective view of the harvesting header shown in  FIGS. 1-12 , showing the left end tilt arm with the cutterbar drive being covered by the crop deflector, and showing the skid plates and the end skid; 
         FIG. 14  is a rear perspective view of the harvesting header shown in  FIGS. 1-13 , showing an elongated rod of the crop deflector projecting through an opening in an upright panel of the header frame; 
         FIG. 15  is a fragmentary left rear perspective view of the harvesting header shown in  FIGS. 1-14 , showing a header sensing system including a pair of left side potentiometers operably coupled to the left end tilt arm and one of the draper arms; 
         FIG. 16  is a fragmentary right rear perspective view of the harvesting header shown in  FIGS. 1-15 , showing the header sensing system including a pair of right side potentiometer assemblies operably coupled to a right end tilt arm and another one of the draper arms; 
         FIG. 17  is an enlarged fragmentary front left perspective view of the harvesting header shown in  FIGS. 1-16 , showing the potentiometer and linkage of the potentiometer assembly interconnected with a clevis portion of the left end tilt arm; 
         FIG. 18  is a partly exploded perspective view of the harvesting header shown in  FIGS. 1-17 , showing the potentiometer and mounting bracket exploded from the header frame and from the left end tilt arm; 
         FIG. 19  is a schematic view of the header sensing system including the potentiometers and a sensing circuit assembly; 
         FIG. 20  is a partly exploded perspective right front view of the harvesting header shown in  FIGS. 1-18 , showing interlocking belt guards of the header in an overhanging relationship to a leading margin of the left side draper; 
         FIG. 21  is an enlarged fragmentary side view of the harvesting header shown in  FIGS. 1-18 and 20 , showing the cutterbar assembly and left side draper, with the interlocking belt guards attached to the cutterbar assembly and extending rearwardly to overhang the side draper belt and to extend adjacent to a crop-retaining rib of the side draper belt; 
         FIG. 22  is a front perspective view of a pair of belt guards shown in  FIG. 20 , showing the belt guards in an interlocking configuration; 
         FIG. 23  is a cross-sectional view of the pair of belt guards taken along line  23 - 23  in  FIG. 22 ; 
         FIG. 24  is a rear perspective view of the pair of belt guards shown in  FIGS. 20, 22, and 23 , showing underlying tabs of each of the belt guards positioned in an underlying relationship to the opposite belt guard; 
         FIG. 25  is a fragmentary left front perspective view of the harvesting header shown in  FIGS. 1-18 and 20-21 , showing a center draper of the harvesting header spaced between left and right side drapers; 
         FIG. 26  is a left rear fragmentary perspective view of the harvesting header shown in  FIGS. 1-18, 20-21, and 25 , showing a counterbalance mechanism of the center draper positioned adjacent to a rear end of the center draper; 
         FIG. 27  is a top fragmentary view of the harvesting header shown in  FIGS. 1-18, 20-21, and 25-26 , showing the sliding interconnection between the center draper and the cutterbar assembly, and showing the side drapers in an overlapping relationship with the center draper; 
         FIG. 28  is a partly exploded right front fragmentary view of the harvesting header shown in  FIGS. 1-18, 20-21, and 25-27 , showing a central guard and a reinforcing brace of the header exploded away from a central section of the cutterbar assembly, with the central section being spaced in front of the center draper and with the central section extending between laterally outermost margins of the center draper; 
         FIG. 29  is a left side cross-sectional view of the harvesting header shown in  FIGS. 1-18, 20-21, and 25-28 , showing the center draper and a center crop deflector spaced forwardly of the center draper, and showing the center draper spaced below the right side draper, and also showing the counterbalance mechanism of the center draper, with the center draper projecting forwardly therefrom; 
         FIG. 30  is a fragmentary side view of the harvesting header shown in  FIGS. 1-18, 20-21, and 25-29 , showing the position of the center crop deflector relative to the center draper and relative to the right side draper; 
         FIG. 31  is a fragmentary side view of a harvesting header constructed in accordance with a second embodiment of the present invention; 
         FIG. 32  is a fragmentary left side view of a harvesting header constructed in accordance with a third embodiment of the present invention, showing one of the draper arms having a load sensor and a hydraulic adjustment mechanism; and 
         FIG. 33  is a fragmentary left side view of the harvesting header of  FIG. 32 , showing one of the tilt arms having the load sensor and the hydraulic adjustment mechanism; and 
         FIG. 34  is a fragmentary left rear perspective view of the harvesting header of  FIGS. 32 and 33 , showing the hydraulic adjustment mechanism. 
     
    
    
     The figures are not intended to limit the present invention to the specific embodiments they depict. The drawings are not necessarily to scale. 
     DETAILED DESCRIPTION 
     The following detailed description of embodiments of the invention references the accompanying figures. The embodiments are intended to describe aspects of the invention in sufficient detail to enable those with ordinary skill in the art to practice the invention. Other embodiments may be utilized and changes may be made without departing from the scope of the claims. The following description is, therefore, not limiting. The scope of the present invention is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled. 
     In this description, references to “one embodiment,” “an embodiment,” or “embodiments” mean that the feature or features referred to are included in at least one embodiment of the invention. Separate references to “one embodiment,” “an embodiment,” or “embodiments” in this description do not necessarily refer to the same embodiment and are not mutually exclusive unless so stated. Specifically, a feature, component, action, step, etc. described in one embodiment may also be included in other embodiments, but is not necessarily included. Thus, particular implementations of the present invention can include a variety of combinations and/or integrations of the embodiments described herein. 
     Broadly, embodiments concern a flexible harvesting header having multiple sections supported by support arms, with the height of each support arm being adjustable in response to changing loads. Turning initially to  FIGS. 1 and 2 , a harvesting header may include a flexible header  40  and a header height sensing system  41 . The harvesting header may form part of a harvesting combine, and the header  40  may be configured for cutting and collecting a crop by being advanced in a generally forward direction D so that the crop can be fed to a feeder house (not shown) and further processed by other components (not shown) of the harvesting machine to produce grain. However, at least some aspects of the present invention could be used in other machines, such as a swather or mower. 
     The header  40  may broadly include a header frame  42 , draper arm assemblies  44 , end tilt arm assemblies  46 , a cutterbar assembly  48 , and a draper assembly  50  which may include side drapers  52  and a center draper  54 . The header  40  may also include a central collecting auger  55  spaced rearwardly of the center draper  54  and a reel (not shown) that extends the length of the header frame  42  and is configured to direct upstanding crop into the header  40 . The cutterbar assembly  48  and draper assembly  50  may be flexible so that the header  40  is configured to closely follow an undulating ground contour. However, for some aspects of the present invention, the cutterbar assembly  48  may be substantially inflexible, i.e., the cutterbar assembly  48  may be rigidly mounted relative to the header frame  42 . Similarly, there are aspects of the present invention in which one, more, or all of the drapers  52 ,  54  may be substantially inflexible relative to the header frame  42 . 
     Turning to  FIGS. 1-3 , the header frame  42  may include an upper beam assembly  56  extending across the entire width of header  40 , and a lower beam assembly  58  that likewise extends across the full width of header  40 . The header frame  40  may further include a number of upright channels  60  that interconnect beam assemblies  56 ,  58  along the back of header  40  at spaced locations thereacross. Yet further, the header frame  40  includes an end frame member  62  (see  FIG. 20 ) and upright rear panels  64  (see  FIGS. 1 and 10 ) attached along the front side of channels  60 . The rear panels  64  may cooperatively define an upright rear wall of the header  40 , with a centrally located opening  66  (see  FIG. 29 ) being defined by the rear wall and serving as a crop outlet from header  40  to the feeder house (not shown) of the harvester machine upon which header  40  is mounted. Thus, the opening  66  may be spaced between left and right sides of the header  40 , when the header  40  is viewed from behind, and the opening  66  may be centrally located on the header  40 . 
     Turning to  FIG. 6 , the cutterbar assembly  48  may broadly include a cutterbar  68 , skid plates  70 , and a sickle assembly  72 . The cutterbar  68  may include a substantially continuous and flexible bar that extends lengthwise along substantially the entire width of the header  40  and thereby extends in a lateral direction relative to the normal direction of travel of the header  40 . The skid plates  70  may each comprise formed pieces of sheet metal that are secured to a lower side of the cutterbar  68  and are spaced along the length of the cutterbar  68  (see  FIG. 5 ). The underside of each skid plate  70  may be covered with a low friction material (e.g., a panel formed of ultra-high molecular weight polyethylene), if desired. The skid plates  70  may be spaced apart from one another so as to permit flexing movement of the cutterbar assembly  68 . In the usual manner, the sickle assembly  72  may be slidably mounted on the cutterbar  68  for severing the crop. As will be discussed further, the cutterbar assembly  48  may be operably coupled to the header frame  42  and to drapers  52 ,  54  to cut the crop so that severed crop material falls onto one of the drapers  52 ,  54 . Furthermore, severed crop material that falls onto the side drapers  52  may be carried by the side drapers  52  onto the center draper  54 , which carries crop material rearwardly toward the opening  66 . 
     Adjustable Cutterbar Travel Range for a Flexible Cutterbar Header 
     Turning to  FIGS. 3-9 , upright channels  60  may each carry a number of arm assemblies  44 ,  46  that project forwardly therefrom, with the arm assemblies  44 ,  46  cooperatively supporting the cutterbar assembly  48 , as will be discussed in greater detail. The end tilt arm assembly  46  may include, among other things, a tilt arm  74 , a drive bracket  76 , an end skid  78 , and a spring  80 . The tilt arm  74  may present opposite front and rear ends, with the drive bracket  76  and end skid  78  being attached to the front end. The tilt arm  74  may include an arm portion  81  and a clevis portion  82  that forms the rear end and a pivot bushing  84  positioned between the ends. The tilt arm  74  may be pivotally mounted to the corresponding channel  60  to pivot about a laterally extending axis, with a bolt that extends through the channel  60  and the pivot bushing  84  to secure the tilt arm  74 . The spring  80  may be attached to a bracket mounted to the channel  60  and the clevis portion  82 , and may be configured to urge the rear end of tilt arm  74  downwardly in order to counterbalance loads applied adjacent the front end. 
     The draper arm assembly  44  may include a draper arm  86  with front and rear ends and a spring  88 . The draper arm  86  may include an arm portion  90  and a clevis portion  92  that forms the rear end, with a pivot bushing  94  positioned between the ends. The draper arm  86  may be pivotally mounted to the corresponding channel  60  to pivot about a laterally extending pivot axis, with a bolt extending through the channel  60  and the pivot bushing  94  to secure the draper arm  86 . The spring  88  may be attached to a channel bracket and to the clevis portion  92 , and may be configured to urge the rear end of draper arm  86  downwardly in order to counterbalance loads applied adjacent the front end. In one implementation, the springs  80 ,  88  may each include a hydraulic cylinder that is fluidly coupled to a hydraulic system (not shown) that permits the cylinder to operate as a spring (e.g., where the springs  80 ,  88  are fluidly coupled to a gas-charged accumulator). However, it is also within the scope of the present invention for the springs  80 ,  88  to include a conventional mechanical spring such as a coil spring. As will be discussed further, the draper arm assemblies  44  may cooperatively support the side drapers  52 . 
     The arm assemblies  44 ,  46  may be pivotally mounted and cooperatively support the cutterbar assembly  48  so that the cutterbar assembly  48  is configured to flex relative to the header frame  42  along the entire length thereof. Alternatively, the arm assemblies  44 ,  46  may be constructed to permit flexing movement of the cutterbar assembly  48  (e.g., where the arm assemblies  44 ,  46  are slidably attached to the header frame  42  and slidable along an upright direction) without departing from the scope of the present invention. The supporting arm assemblies  44 ,  46  may be configured to be selectively pivotal to provide flexible and non-flexible header configurations, as will be discussed. In particular, the header  40  may include threaded pins  96  and quick-release pins  98 . The threaded pins  96  may each be secured above the respective arm assembly  44 ,  46  to restrict upward pivotal movement thereof. The quick-release pins  98  may be removably received within corresponding openings  100  presented by the channels  60 . The openings  100  may be generally spaced forwardly of the corresponding arm pivot axis and present a pair of pin-receiving sections that define discrete locked and unlocked locations  102 ,  104  for receiving the quick-release pins  98 . The quick-release pins  98  may be located below the corresponding arm assembly  44 ,  46  to restrict downward pivotal movement thereof. Alternatively, other types of pins may be used to restrict pivotal arm movement. Furthermore, other types of stop mechanisms could be used to selectively provide limited arm movement without departing from the scope of the present invention. For example, the pins  96 ,  98  could be mounted on the arm assemblies  44 ,  46 , with the channels  60  presenting pin engaging surfaces and with pins  96  or  98  being selectively positionable among locations on the arm to provide selective pivoting movement. 
     Each tilt arm  74  and draper arm  86  may include a single arm, but could alternatively take another form, such as a four-bar linkage as shown in U.S. Patent Publication 2007/0193243, “Combine Harvester Draper Header Having Flexible Cutterbar,” published Aug. 23, 2007, which is hereby incorporated in its entirety by reference herein. 
     Turning to  FIGS. 7-9 , the arm assemblies  44 ,  46  may be configured to shift between an uppermost fixed position and a lowermost position. In the uppermost fixed position, the quick-release pin  98  may be selectively secured in the locked location  102  so that the arm assembly  46  is in a rigid arm configuration and is restricted from pivoting, with the header  40  thereby being in the non-flexible header configuration. With the quick-release pin  98  secured in the unlocked location  104 , the arm assembly  46  may be in an arm pivoting configuration and may be permitted to pivot through a limited range of angular movement, with the cutterbar assembly  48  having a corresponding range of generally vertical movement, so that the header  40  may be in the flexible header configuration. The cutterbar assembly  48  may have a range of vertical movement of about eight (8) inches, but it is within the scope of the present invention that the range of vertical movement may be greater or smaller. 
     Flexible Draper and Cutterbar with Tilt Arm for Cutterbar Drive 
     Turning to  FIGS. 10-14 , each of the end tilt arm assemblies  46  may be pivotally mounted adjacent to opposite ends of the header frame  42  and may be supported for selective pivotal movement. As discussed above, the arm assemblies  44 ,  46  may be attached to and cooperatively support the cutterbar assembly  48 . The cutterbar  68  may be flexible and support the sickle assembly  72 . In particular, the sickle assembly  72  may include a split sickle that includes a pair of flexible sickle bars  106  and knives  108  that may be attached to and spaced along the length of the flexible sickle bars  106 . The sickle assembly  72  may also include knife guards  110  attached to the cutterbar  68 , with the sickle bars  106  and knives  108  being configured to slide in a reciprocating manner relative to the cutterbar  68  and flex with the cutterbar  68 . The sickle bars  106  may reciprocate in opposite directions relative to one another. Alternatively, the cutterbar assembly  48  may include a single continuous sickle bar. Again, the cutterbar  68  may also support the spaced-apart skid plates  70  that extend below the cutterbar  68  and are configured to engage the ground and thereby cause flexing movement of the cutterbar  68 . 
     Turning to  FIGS. 8-14 , the header  40  may further include a pair of cutterbar drive assemblies  112  that may be attached to respective ones of the end tilt arm assemblies  46  and serve to power the sickle assembly  72 . The cutterbar drive assembly  112  may broadly include a gear drive  114 , a telescopic drive shaft  116 , universal joints  118 , and a forward gear box in the form of epicyclic drive  120 . 
     The epicyclic drive  120  may include a gear box with input and output shafts  122 ,  124 , with the output shaft  124  being drivingly attached to a corresponding one of the sickle bars  106 . The epicyclic drive  120  may serve to offset the inertial forces of the sickle during its abrupt acceleration and deceleration at opposite ends of its path of travel. Alternatively, another type of drive could be used to transfer power to the sickle bar  106 . Additional details of the epicyclic drive  120  are disclosed in issued U.S. Pat. No. 7,121,074, “Balanced Epicyclic Sickle Drive,” issued Oct. 17, 2006, which is hereby incorporated in its entirety by reference herein. 
     The epicyclic drive  120  may be attached to the drive bracket  76  so as to be fixed to the end tilt arm assembly  46  and be pivotal about a laterally extending axis therewith. The gear drive  114  may include input and output shafts  126 ,  128  (see  FIG. 5 ), and may be mounted to the header frame  42  with bracket  130 . The telescopic drive shaft  116  is drivingly connected to the input shaft  122  of the drive  120  and the output shaft  128  of the drive  114  with universal joints  118 , with the telescopic drive shaft  116  extending through an opening in the tilt arm  74 . The input shaft  126  of gear drive  114  may be powered by a power take-off shaft (not shown) of the harvesting machine. In this manner, the shaft-driven cutterbar drive assembly  112  may power the sickle assembly  72 . Alternatively, another type of transmission, e.g., a belt drive, or hydraulic drive, for transmitting power to the epicyclic drive  120  and to the sickle assembly  72  may be used. 
     The drive assembly  112  may be attached to and partly supported on the end tilt arm assembly  46 , with the epicyclic drive  120  and telescopic drive shaft  116  being configured to pivot with the end tilt arm assembly  46 . In particular, the universal joints  100  may permit relative pivotal movement between the epicyclic drive  120  and the gear drive  114 . Furthermore, the telescopic drive shaft  116  may permit relative lateral movement between the drives  114 ,  120 . Although the drive assembly  112  is shown attached to the end tilt arm assembly  46 , the drive assembly  112  may alternatively be attached to an inboard pivotal arm, such as one of the draper arm assemblies  44 . 
     In addition, the end skid  78  of the end tilt arm assembly  46  may be spaced apart from the adjacent skid plate  70 . In this manner, the end tilt arm assembly  46  may be configured to shift relative to the inboard adjacent draper arm assembly  44  while the adjacent arm assemblies  44 ,  46  cooperatively support the cutterbar assembly  48 . Thus, the arm assemblies  44 ,  46  may be configured to substantially independently pivot with the cutterbar assembly  48  when the header  40  is advanced over uneven terrain. 
     The illustrated orientation and configuration of the cutterbar drive assembly  112  may provide a substantially smooth constant rotational velocity of the output shaft  124 . In particular, the epicyclic drive  120  may be spaced above an axis of the tilt arm  74  and the gear drive  114  may be spaced below the tilt arm axis, with the drive shaft  116  extending through the tilt arm opening. The output shaft  128  of the gear drive  114  may rotate at a uniform rotational velocity and drive the universal joint  100 , which drives the drive shaft  116 . However, due to the angle between the output shaft  128  and the drive shaft  116 , the universal joint  100  may drive the drive shaft  116  at a non-uniform rotational velocity. The input shaft  122  of the epicyclic drive  120  may be angled relative to the drive shaft  116  at an angle α, and the output shaft  128  of the gear drive  114  is angled relative to the drive shaft  116  at an angle θ (see  FIG. 9 ). However, the illustrated arrangement of drives  114 ,  120  and the drive shaft  116 , with the illustrated angles α, β therebetween, the use of a universal joint  100  between the drive shaft  116  and drive  120  may unsubstantially cancel out any non-uniformity in the rotational velocity so that the output shaft  124  provides a uniform rotational velocity. The cutterbar drive assembly  112  may pivot so that the angle α lies within an angular range. The angle θ may generally fall within that angular range so that the rotational velocity of the output shaft  124  remains substantially uniform as the cutterbar drive assembly  112  is operated. 
     Flexible Draper and Cutterbar Having Shiftable Crop Divider with Deflector 
     Turning to  FIGS. 3, 10-14, and 25-26 , the header  40  may include side drapers  52  and center draper  54  that are both positioned behind the cutterbar assembly  48 . As will be discussed further, the side drapers  52  may be spaced on either side of the center draper  54  and configured to direct severed crop material from locations along the cutterbar assembly  48  to the center draper  54 . Each side draper  52  may broadly include oppositely spaced inboard and outboard rollers  132 ,  134 , belt support panels  136 , a side draper belt  138 , and a belt tensioning mechanism  140 . 
     Each of the rollers  132 ,  134  may be rotatably mounted to a corresponding draper arm assembly  44 . In particular, the inboard rollers  132  may be rotatably mounted to the draper arm assemblies  44  with brackets  142  and thereby extend adjacent a respective laterally outermost side margin of the center draper assembly  54  (see  FIG. 25 ). The outboard rollers  134  may be rotatably and slidably mounted to respective draper arm assemblies  44  with the belt tensioning mechanism  140 . The belt tensioning mechanism  140  may include slides  144  that interconnect and permit relative sliding movement between the draper arm  86  and the roller  134  for tensioning the side draper belt  138 . The rollers  132 ,  134  may be mounted so as to pivot with the respective draper arm assemblies  44  about the lateral arm pivot axis. 
     The belt support panels  136  may be elongated metal strips that extend laterally between the rollers  132 ,  134 . The belt support panels  136  may be cooperatively supported by respective draper arm assemblies  44  and serve to evenly support the weight of the side draper belt  138  and any severed crop material on the side draper belt  138 . As will be discussed in greater detail, the side draper belt  138  may be an endless belt that is particularly configured for conveying the severed crop material toward the center draper  54 . The side draper belt  138  may be rotatably mounted to surround the rollers  132 ,  134  and the corresponding draper arm assemblies  44 , with the side draper belt  138  presenting opposite endmost margins defined by the rollers  132 ,  134 . Furthermore, the side draper belt  138  may present upper and lower runs, with the upper run extending over the belt support panels  136  so that the panels  136  restrict the upper run from sagging. The lower run of the side draper belt  138  may extend below the panels  136 . The outboard roller  134  may be powered by a drive (not shown), with the outboard roller  134  driving the side draper belt  138  so that an upper run of the side draper belt  138  moves inwardly toward the center draper  54 . While the illustrated embodiment includes left and right side drapers  52 , an alternative conveyor mechanism may be used. For example, multiple end-to-end side drapers could be used to convey crop material. Also, a conventional auger conveyor could be used in some of the inventive aspects to convey crop material. 
     Turning to  FIGS. 11-14 , the end tilt arm assembly  46  may further include a crop divider  146  that serves to direct crop into the header  40  and deflect severed crop material onto the side draper  52 . The crop divider  146  may operate as a substantially unitary structure and includes a divider panel  148  that presents front and rear ends, an end bracket  150  that secures a forwardmost tip of the divider panel  148  to an arm bracket  152  of the end skid  78 , and an elongated support  154  that is fastened to an underneath surface of the divider panel  148  and extends rearwardly from the rear end of the divider panel  148 . 
     The divider panel  148  may also include inner and outer walls  156 ,  158  joined along a top margin of the divider panel  148  to cooperatively form a hollow body, with the inner wall  156  including an upright section  160  and a deflector section  162  that is angled relative to the upright section  160 . The inner wall  156  may also present a lowermost margin  164  that extends between the front and rear ends of the divider panel  148 . The walls  156 ,  158  may extend rearward from the forward tip of the divider panel  148 , with the walls  156 ,  158  cooperatively presenting a generally expanding wall structure in the rearward direction. 
     The elongated support  154  may include a rod section that is shiftably received in an opening  166  presented by one of the upright rear panels  64 . Thus, the front end of the divider panel  148  may be supported by the end skid  78 , with the rear end being supported by the header frame  42  so that the rod section can pivot and slide relative to the header frame  42 . As the end tilt arm assembly  46  pivots up or down, the crop divider  146  may also pivot in the same direction. 
     Furthermore, the divider panel  148  may be positioned so that the lowermost margin  164  is spaced apart from the adjacent side draper belt  138  as the end tilt arm assembly  46  pivots between the uppermost and lowermost positions. The divider panel  148  may be positioned to extend over part of the side draper belt  138  and encourage severed crop material to fall onto the side draper belt  138 . In addition, the divider panel  148  may be spaced to permit sliding adjustment of the outboard roller  134 , e.g., for tensioning or maintenance of the side draper belt  138 . 
     Header Height Control System with Multiple Potentiometer Input 
     Turning to  FIGS. 15-19 , the header height sensing system  41  may provide feedback to a header height adjustment system (not shown) for controlling the height of the header  40 . The header height sensing system  41  may include a plurality of potentiometer assemblies  168  and an electronic module  170  that are operably coupled to one another, with the potentiometer assemblies  168  being operably coupled to respective arm assemblies  44 ,  46 . The potentiometer assemblies  168  may each include a potentiometer  172 , a mounting bracket  174 , and a linkage  176 . In the usual manner, the potentiometer  172  may include a sensor arm  178  that pivots to control the voltage output of the potentiometer  172 . The potentiometer  172  may be attached to a corresponding channel  60  adjacent to the pivot of the arm assembly  44 ,  46  using the mounting bracket  174 . The linkage  176  may directly interconnect the sensor arm  178  and the clevis portion  92 , with the potentiometer  172  providing an output signal associated with the angular position of the arm assembly  44 ,  46 . The arm position signal may also be associated with the generally vertical position of a portion of the cutterbar assembly  48  adjacent a forward end of the arm assembly  44 ,  46 . As the arm assembly  44 ,  46  may swing upwardly or downwardly, the linkage  176  causes the sensor arm  178  to swing accordingly, with the arm position signal, i.e., the voltage output, of the potentiometer  172  changing accordingly. In this manner, the potentiometer  172  may be configured to sense movement of the adjacent portion of the cutterbar assembly  48  as the header  40  moves over uneven terrain. 
     For each of the arm assemblies  44 ,  46  having a potentiometer  172  to sense pivotal arm movement and provide an arm position signal, the potentiometer  172  may only be coupled to sense movement of that particular arm. Alternatively, the movement of multiple arm assemblies  44 ,  46  may be sensed by the same transducer. While the potentiometer  172  may be for sensing angular movement of the arm assembly  46 , other types of transducers may be used to sense angular arm movement, such as an angular encoder. 
     Four potentiometers  172   a ,  172   b ,  172   c ,  172   d  may be installed on the header  40  to sense angular arm movement of respective arm assemblies  44 ,  46  and provide corresponding arm position signals, with two potentiometers  172   a ,  172   b  on the left side of the header  40  and two potentiometers  172   c ,  172   d  on the right side of the header  40  (see  FIGS. 15 and 16 ). For each side of the header  40 , one potentiometer  172  may be installed to sense movement of the end tilt arm assembly  46  and provide a corresponding end tilt arm position signal, and another may be installed to sense movement of an inboard one of the draper arm assemblies  44  and to provide a corresponding draper arm position signal. Alternatively, other sensing configurations may be used. For example, more than two potentiometers  172  could be installed on each side of the header  40 . For another example, three (3) potentiometers  172  could be installed on each side of the header  40 , with one associated with the end tilt arm assembly  46  and two associated with corresponding draper arm assemblies  44 . Furthermore, a plurality of sensors could be installed so that each arm assembly  44 ,  46  has a respective potentiometer  172  associated therewith, with the system  41  thereby being configured to sense the angular arm movement of all of the arm assemblies  44 ,  46  and provide arm position signals corresponding to the position of the arm assemblies  44 ,  46 . 
     Turning to  FIG. 19 , the electronic module  170  may be configured to provide an output signal to the harvesting machine for controlling the header height when the header  40  is in the flexible header configuration. As will be discussed, the electronic module  170  may provide the output to indicate when a controller (not shown) of the harvesting machine should automatically raise the header  40 , e.g., by hydraulically raising the feeder house. The electronic module  170  may include a pair of minimum input voltage selector circuits  180 . Each selector circuit  180  may include a pair of buffer circuits  182  that each receive an output signal from the corresponding potentiometer  172 , with each buffer circuit  182  including resistors  184 ,  186 , diodes  188 , and operational amplifier  190 . The resistors  184  may be 470 k-ohm resistors, the resistors  186  may be 1 k-ohm resistors, the diodes  188  may be 1N4004 diodes, and the operational amplifiers  190  may be TS924IN op amps. The selector circuit  180  may also include selector diodes  192  electrically coupled to the output of respective buffer circuits  182  and each electrically coupled to the input of another operational amplifier  194 . The selector circuit may further include pull-up resistors  196  and feedback diode  198 . The diodes  192  may be 1N4004 diodes, the operational amplifiers  194  are TS924IN op amps, and the resistors  196  are 220 k-ohm resistors. The module  170  may also include a potentiometer circuit  200  coupled to all of the potentiometers  172 , via common nodes  202 ,  204 . The circuit  200  may include a zener diode  206  and capacitors  208 ,  210 . The capacitor  208  may be a 0.1 microfarad capacitor and the capacitor  210  is a 10 microfarad capacitor. 
     The arrangement of selector diodes  192  may cooperatively provide a selected voltage signal to the operational amplifier  194  that is substantially the same as the lowest of the output signals received from corresponding potentiometers  172  by the corresponding buffer circuits  182 . The operational amplifier  194  may provide an output signal of the corresponding selector circuit  180  that is substantially the same as the selected voltage signal. In this manner, the selector circuit  180  may select the lowest one of analog voltage signals provided by the respective potentiometers  172  and provide a corresponding selected analog output signal at selector output  211 . Alternatively, the circuit may provide another signal, e.g., the circuit may select the highest one of the voltage signals and provide a corresponding signal output. Furthermore, the circuit could provide another signal, e.g., a digital signal that corresponds to a selection of one of the voltage signals provided by the potentiometers  172 . 
     The potentiometers  172  may provide an input voltage to the module  170  that ranges from about 0.5 volts to about three (3) volts based on the position of the arm assembly  44 ,  46  and the corresponding vertical position of the adjacent portion of the cutterbar assembly  48 . In particular, the potentiometers  172  may provide a voltage of about three (3) volts corresponding to the arm assembly  44 ,  46  being in the lowermost arm position and about 0.5 volts corresponding to the arm assembly  44 ,  46  being in the uppermost arm position. Again, the cutterbar assembly  48  may have a range of generally vertical travel of about eight (8) inches when the arms swing between the uppermost and lowermost positions. Therefore, vertical movement of the cutterbar assembly  48  through that range of travel may cause the potentiometers  172  to range between about 0.5 volts to about 3 volts. 
     The module  170  may provide selected signal outputs that correspond to the position of the cutterbar assembly  48 . In particular, the potentiometers  172   a ,  172   b  may be configured to sense the position of a left side section of the cutterbar assembly  48  and the potentiometers  172   c ,  172   d  may be configured to sense the position of a right side section of the cutterbar assembly  48 . Furthermore, the selector circuits  180  may each provide a selector signal associated with the highest position of the arms corresponding to respective potentiometers  172 . In this manner, the selector circuits  180  may each provide a single cutterbar position signal associated with the highest vertical position of that section of the cutterbar assembly  48 . 
     The potentiometers  172 , module  170 , and header height adjustment system may cooperate so that the controller of the harvesting machine automatically raises the header  40  when at least one of the arm assemblies  44 ,  46  pivots above a predetermined angular position. The header height adjustment system may control the header  40  in response to the cutterbar position signals received from the module. When a voltage of one of the potentiometers  172  goes below a threshold level of about 1.5 volts, which voltage corresponds to the cutterbar assembly  48  being positioned approximately four (4) inches from the uppermost position, the controller may raise the header  40 . Additionally or alternatively, the output from the module  170  could be used for other purposes, such as triggering a warning indicator for an operator. 
     Draper Belt with Crop-Retaining Rib 
     Turning to  FIGS. 20 and 21 , the side draper belt  138  may include an endless belt that includes a belt body  212  and presents leading and trailing belt margins  214 ,  216 . The side draper belt  138  may further include a plurality of fore-and-aft extending crop-engaging slats  218  projecting outwardly from an outer surface of the belt body  212  and extending between the belt margins  214 ,  216 . Yet further, the side draper belt  138  may include an endless crop-retaining rib  220  that projects from the outer surface of the belt body  212 . The rib  220  may include a cross-sectional shape that is constant along its length and tapers outwardly toward an outermost tip. The rib  220  may project at least about one-half inch from the outer surface of the belt body  212 . The crop-retaining rib  220  may endlessly extend adjacent to the leading belt margin  214  so that the rib  220  is spaced between the margin  214  and the slats  218 . Alternatively, the side draper belt  138  may be configured to carry crop material. For example, the side draper belt  138  could include a plurality of crop-retaining ribs  220 , or the rib  220  could be formed in segments to present discrete rib sections. 
     The side draper belt  138  may be rotatably received onto the rollers  132 ,  134  so as to define upper and lower belt runs  222 ,  224 , with the upper belt run  222  configured to move toward the center draper  54 . The arm assemblies  44 ,  46  may be positioned so that the side draper belt  138  slopes downwardly toward the leading belt margin  214 . In this manner, any severed crop material supported on the upper belt run  222  may be urged by gravity toward the leading belt margin  214 , with the crop-retaining rib  220  being configured to catch the crop material and restrict the crop material from falling off of the upper belt run  222  until the crop material is disposed onto the center draper  54 . 
     Interlocking Belt Guards for a Draper Header 
     Turning to  FIGS. 20-28 , the header  40  may further include a flexible belt guard assembly with a central guard  226  and a plurality of interlocking belt guards  228 , with the belt guards  228  extending along the leading belt margins  214 . Each belt guard  228  may be unitary and include a formed piece of sheet metal that presents opposite first and second ends  230 ,  232 . The belt guard  228  may include a lower flange section  234 , an upright section  236 , and an upper overhanging section  238 , all of which extend substantially from the first end  230  to the second end  232 . The belt guard  228  may also include a rear tab  240  projecting from the overhanging section  238  at the first end  230  and a front tab  242  projecting from the upright section  236  at the second end  232 . The central guard  226  and an endmost belt guard  243  may also include sections  234 ,  236 ,  238 , with the central guard  226  including tabs  242 , and the endmost belt guard  243  including a tab  240  on one end thereof. 
     The belt guards  228  may be configured to be attached to the cutterbar  68  by fasteners that extend through holes in the flange section  234 . Pairs of belt guards  228  can be mated to each other by positioning the rear tab  240  of one belt guard  228  underneath the overhanging section  238  of the other belt guard  228 . Furthermore, the front tab  242  of the other belt guard  228  may be positioned underneath the upright section  236  of the one belt guard  228 . In this manner, each pair of mated belt guards  228  may have mating ends that cooperatively form an interlocking joint so that the mating ends each restrict relative up-and-down movement of the other mating end. However, the interlocking joint may permit relative angular movement between mated pairs of belt guards  228  and also permit a limited amount of relative lateral movement between mated pairs of belt guards  228  in the direction along the leading belt margin  214 . In addition, the pairs of mated belt guards  228  may be configured so that uppermost surfaces presented by the overhanging sections  238  are substantially flush with one another and thereby minimize any resistance to crop flow provided by the belt guards  228 . 
     Interlocking Belt Guards and the Crop-Retaining Rib 
     Turning to  FIG. 21 , the belt guards  228  may extend rearwardly and upwardly from the cutterbar  68  and extend over the leading belt margin  214 . The belt guards  228  may also extend over and adjacent to the crop-retaining rib  220 . While the illustrated belt guards  228  and crop-retaining rib  220  are slightly spaced apart, in alternative implementations some sliding contact may occur therebetween. In particular, the overhanging sections  238  may present a downwardly facing surface that extends in close proximity along the tip of the rib  220 . The gap between the surface and the tip may be less than about one-quarter of an inch. In this manner, the belt guards  228  and the crop-retaining rib  220  may cooperatively form a joint that restricts severed crop material from falling between the cutterbar  68  and the leading belt margin  214 . 
     Spring Flotation for Center Deck of Draper Header 
     Turning to  FIGS. 25-30 , the center draper  54  may serve to collect severed crop material from the side drapers  52  and carry the material in a rearward direction toward the opening  66  and toward the feeder house of the harvesting machine. The center draper  54  may broadly include a draper chassis  244 , front and rear rollers  246 , belt support  248 , and center draper belt  250 . The draper chassis  244  may include a pair of side plates  252  that are pivotally mounted to corresponding channels  60  and pivot about pivot axis  254 . The draper chassis  244  may further include a floor panel  256  that is connected to and extends along a bottom margin of the side plates  252 . Thus, the side plates  252  and floor panel  256  may cooperatively pivot about the pivot axis  254 . The illustrated draper chassis  244  presents a lateral width, measured from one side plate  252  to the other, of at least about five (5) feet, or about six (6) feet, but in alternative implementations the draper chassis  244  may be larger or smaller. 
     The floor panel  256  may also present a forward margin  258  that is secured to the corresponding skid plates  70  with multiple fasteners. In particular, the fasteners may each include a rearward-extending finger that is spaced upwardly from the skid plate  70  to present an elongated slot, with the finger being attached at a forward end thereof with fasteners. The forward margin  258  may be slidably received within the slot to create a sliding joint that permits relative fore-and-aft sliding movement between the floor panel  256  and the skid plates  70  and restricts relative vertical movement therebetween. The draper chassis  244  may also include a counterbalance mechanism  260  for supporting the center draper  54 , as will be discussed further. 
     The rollers  246  may be rotatably mounted between the side plates  252  by mounting the rollers  246  on respective shafts  262  and by mounting the shafts  262  onto bearings (not shown) secured in the side plates  252 . The belt support  248  may be attached to the side plates  252  and is spaced between the rollers  246 . The center draper belt  250  may include an endless belt with a belt body and a plurality of crop-engaging slats  264 . The center draper belt  250  may present upper and lower runs  266 ,  268 . The lower run  268  may extend below the belt support  248  and the upper run  266  may extend above the belt support  248 , with the belt support  248  being configured to restrict sagging of the upper run  266 . The draper belt  250  may be driven by the rear shaft  262 , which is powered by a drive (not shown) so that the upper run  266  is configured to normally move in a rearward direction and the lower run  268  is configured to normally move in a forward direction. Alternatively, the belt rotation direction may be reversed so that the upper run  266  moves forwardly and the lower run  268  moves rearward (such that crop is conveyed by the lower run). While the illustrated center draper  54  is centrally located relative to the rest of the header  40 , in an alternative implementation the center draper  54  may be located toward one side of the header  40 . 
     Turning to  FIG. 29 , the counterbalance mechanism  260  may serve to support the center draper  54  by counteracting the weight of the center draper  54  about the pivot axis  254 . The counterbalance mechanism  260  may include a lever  270 , mounting lug  272 , rod  274 , and compression spring  276 . The lever  270  may be attached to a rear end of the corresponding side plate  252  and extends rearward through the opening  66 . The mounting lug  272  may be attached to an inner wall of the adjacent channel  60  and is spaced below the lever  270 . Adjacent a lower end thereof, the rod  274  may be secured to the mounting lug  272  and extends up through a rear end of the lever  270  and through the spring  276 . A stop  278  may be secured adjacent to an upper end of the rod  274 , with the spring  276  being captured between the rear end of the lever  270  and the stop  278 . Thus, the spring  276  may be configured to bias the lever  270  in a generally downward direction. The generally downward spring force provided by the spring  276  may counteracts the weight W of the center draper  54  so that the spring  276  reduces the load that the center draper  54  applies to the skid plates  70  and to the cutterbar assembly  48 . 
     The center draper  54  may collect severed crop material from the side drapers  52  by being generally spaced below the side drapers  52 . Furthermore, inboard ends of the side drapers  52  may overhang corresponding laterally outermost side margins of the center draper  54  so as to restrict crop material from falling between the drapers  52 ,  54  (see  FIG. 27 ). 
     Draper Head with Flexible Cutterbar Having Rigid Center Section 
     Turning to  FIGS. 25-29 , the cutterbar assembly  48  may further include an elongated brace  280  that includes a substantially uniform length of angle iron. Alternatively, another structure may be used with some vertical dimension to resist bending of the cutterbar assembly  48  caused by gravity or other loads. For example, the brace  280  could include an L-shaped beam made from a material other than steel, or a beam having another cross-sectional shape, e.g., a box shape, that serves to rigidify the cutterbar assembly  48 . The brace  280  may be positioned to lie on top of the flange section  234  of central guard  226  and engage the upright section  236 . Fasteners may secure the brace  280  and central guard  226  to the cutterbar  68  and thereby define an inflexible length  282  of the cutterbar assembly  48  between ends of the central guard  226 . In other words, the brace  280  and central guard  226  may cooperatively restrict the cutterbar assembly  48  from bending along the inflexible length  282 . 
     The center draper  54  may include laterally outermost side margins that are spaced so that the inflexible length  282  extends between the margins. The center draper  54 , particularly the rollers  246 , may flex to only a minimal degree along the length of the cutterbar  68 . Therefore, because the illustrated cutterbar assembly  48  is rigid along the inflexible length  282 , the front roller  246  and the inflexible length  282  may cooperatively maintain a substantially uniform spacing between a forward end of the draper belt  250  and the cutterbar assembly  48  so that the cutterbar  68  and center draper  54  generally move together with one another. In this manner, the inflexible length  282  may permit the center draper  54  to travel over uneven terrain without parts of the center draper  54 , such as the draper belt  250 , contacting the side drapers  52  and without the center draper  54  damaging itself. 
     Center Crop Deflector for Draper Header 
     Turning to  FIGS. 25-30 , the center draper  56  may also include a center crop deflector  284  that is substantially unitary and configured to direct crop material from the side drapers  52  so that crop flow from one side draper  52  to the other is restricted. The center crop deflector  284  may include a substantially flat plate with front and rear deflector portions  286 ,  288  and also includes a lower flange  290 . The rear deflector portion  288  may present a height  292  of at least about one (1) inch so that the rear deflector portion  288  resists bending relative to the front deflector portion  286 . The rear deflector portion  288  may also present a portion length  294  in the range of about one (1) inch to about six (6) inches. The rear deflector portion  288  may present upper and lower edges  296 ,  298  that are substantially linear. The front deflector portion  286  may present an upper edge  300  that includes a lower section  302  that is substantially linear and a curvilinear transition section  304  defined between the lower section  302  and the upper edge  296  of the rear deflector portion  288 . 
     The flange  290  of the center crop deflector  284  may be attached to the forward margin  258  of the floor panel  256 , with the front deflector portion  286  extending forwardly up to the cutterbar assembly  48  and the rear deflector portion  288  extending over the draper belt  250 . The rear deflector portion  288  may extend over the draper belt  250  a length less than half the length of the upper run  266 . The length of extension over the draper belt  250  may range from about one (1) inch to about six (6) inches. Also, the upper edge  296  of the rear deflector portion  288  may be spaced above the draper belt  250  a distance  306  in the range of about three (3) inches to about five (5) inches. The illustrated length of extension over the draper belt  250  and the height of the upper edge  296  relative to the draper belt  250  may permit the center crop deflector  284  to direct the severed crop material while providing minimal restriction to material flow in the aft direction. In addition, the lower edge  298  may be spaced above the draper belt  250  a distance less than about 1.5 inches so that the center crop deflector  284  is restricted from contacting the draper belt  250  while sufficiently restricting crop material from flowing from one side draper  52  to the other. Those of ordinary skill in the art will appreciate that such untoward crop flow is particularly problematic when cutting with only one side of the header  40 . For example, when cutting crop only on the left side of the header  40 , the left side draper  52  will convey crop material toward the center draper  54 . Because the right side draper  52  is conveying little or no crop material toward the center draper  54 , the crop material from the left side meets little resistance when reaching the center draper  54  and can continue to flow past the center draper  54  and into the right side draper  52 . Therefore, the center crop deflector  284  may serve to provide sufficient resistance so that material deposited from one side draper  52  is restricted from flowing entirely across the center draper  54  to the other side draper  52 . 
     Operation 
     In operation, the harvesting header may be advanced by the harvesting machine in a field to cut the crop and collect the severed crop material for disposal into a feeder house of the harvesting machine. As the header is advanced in the forward direction, the crop divider  146  of the end tilt arm assembly  46  may define a crop cutting path of the header and push crop along the sides of the path in an inboard direction. At the same time, the cutterbar assembly  48  may sever the crop and the reel (not shown) pushes the severed crop material onto the drapers  52 ,  54 . Severed crop material located on the side drapers  52  may be carried inwardly toward and deposited onto the center draper  54 . In particular, both the left and right side drapers  52  may carry any crop material inwardly, with the center crop deflector  284  restricting crop flow from one of the side drapers  52  to pass over to the other side draper  52 . Crop material on the center draper  54  may be carried in a rearward direction toward the collecting auger  55 , and then deposited through the opening  66  and into the feeder house. 
     The harvesting header may cut and collect crop material in either the flexible header configuration or the non-flexible header configuration by configuring the arm assemblies  44 ,  46  in corresponding arm pivoting and rigid arm configurations. The arms may be placed in the rigid arm configuration by positioning the corresponding quick-release pin  98  into the locked location. With all of the arm assemblies  44 ,  46  in the rigid configuration, the header may be placed into the non-flexible header configuration. In the non-flexible configuration, the header can be advanced through the field so that the cutterbar assembly  48  and drapers  52 ,  54  substantially do not flex relative to the header frame  42 . Furthermore, any contact between the ground and the cutterbar assembly  48  will cause substantially no flexing movement of the cutterbar assembly  48  or the drapers  52 ,  54 . 
     Similarly, the arm assemblies  44 ,  46  can be placed in the arm pivoting configurations by positioning the quick-release pin  98  into the unlocked location. The flexible header configuration may be achieved by configuring all of the arm assemblies  44 ,  46  in the arm pivoting configuration. In the flexible header configuration, the header can be advanced through the field so that the cutterbar assembly  48  and drapers  52 ,  54  flex relative to the header frame  42  between lowermost and uppermost positions. Any contact between the ground and the cutterbar assembly  48  may cause the cutterbar assembly  48  and at least one of the drapers  52 ,  54  to flex upwardly relative to the header frame  42 , provided that the adjacent arm assemblies  44 ,  46  have not already reached the uppermost position. When the arm assemblies  44 ,  46  pivot upwardly beyond a predetermined arm movement threshold between the lowermost and uppermost positions, a controller of the harvesting machine may sense the threshold condition and raise the header in response to the condition until the arm assemblies  44 ,  46  pivot downwardly below the threshold. The flexible header configuration may be particularly suited for cutting crop close to the ground where some intermittent contact occurs between the header and the ground. 
     Alternative Embodiment 
     Turning to  FIG. 31 , an alternative header  400  is shown constructed in accordance with a second embodiment of the present invention. For the sake of brevity, the description will focus primarily on the differences of this alternative embodiment from the first embodiment described above. The header  400  may include a header frame  402  and an end tilt arm  404  pivotally mounted to the header frame  402 . The header  400  may further include fixed and adjustable pins  406 ,  408  that are attached to an upright  410  of the header frame  402 . The upright  410  may present an opening  412  that includes three discrete pin-receiving sections that define locked locations  414  and unlocked locations  416 ,  418 , each of which is configured to receive the adjustable pin  408  so that the pin can be selectively positioned in one of the locations. The unlocked locations  416 ,  418  may provide two distinct lowermost arm positions that correspond with distinct ranges of angular arm movement. Thus, the unlocked location  418  may permit a full range of angular arm movement of the end tilt arm  404 , while the unlocked location  416  may permit a range of movement that is about half of the full range of angular arm movement provided by location  418 . The locked location  414  may serve to provide an uppermost arm position that corresponds with a locked arm position, with substantially no range of angular arm movement being permitted. Each of the support arms of the illustrated header  400  may have a similar stop arrangement that provides similar locked and unlocked locations. 
     Draper Header with Flexible Cutter Bar and Sectional Height Adjustment 
     Turning to  FIGS. 32-34 , an alternative header  500  is shown constructed in accordance with a third embodiment of the present invention. For the sake of brevity, the description will focus primarily on the differences between this third embodiment from the embodiments described above. As such, except as noted, the components and their functions may be substantially similar or even identical to the corresponding components described above, and the same reference numerals will be used when appropriate. 
     The header  500  may broadly include the header frame  42 , the draper arm assemblies  44 , the end tilt arm assemblies  46 , the cutterbar assembly  48 , and the draper assembly  50 . The cutterbar assembly  48  and the draper assembly  50  may be flexible so that the header  40  is able to follow an undulating ground contour. The draper arm assembly  44  may include the supportive draper arm  86  having front and rear ends, the skid  70  associated with the front end, and the hydraulic cylinder  88  associated with the rear end. The end tilt arm assembly  46  may include the supportive tilt arm  74  having front and rear ends, the end skid  78  associated with the front end, and the hydraulic cylinder  80  associated with the rear end. In contrast to the forgoing embodiments, the hydraulic cylinders  80 ,  88  may operate not only as passive springs but may also be independently actuatable in reaction to changes in the loads, or vertical forces, on the front ends of the arms  74 ,  86  to apply offsetting vertical forces on the rear ends of the arms  74 ,  86  in order to raise and lower the front ends of the support arms in order to facilitate more closely and consistently maintaining a desired ground pressure. 
     More specifically, the header  500  may further include a hydraulic assembly  502 , a plurality of load sensors  504 , and a controller  506 . The hydraulic assembly  502  may be configured to actuate some or all of the hydraulic cylinders  80 ,  88 , and may include a pressure line  508 , a return line  510 , a plurality of valves  512 , and a plurality of valve lines  514 . Hydraulic fluid may be added (from a reservoir, not shown) via the pressure line  508  to increase hydraulic pressure, and may be removed (to the reservoir) via the return line  510  to decrease hydraulic pressure. Each valve  512  may be coupled with the pressure and return lines  508 ,  510 , and may be further coupled with a respective hydraulic cylinder  80 ,  88  via a respective valve line  514 , and may be openable to allow hydraulic fluid in a respective hydraulic cylinder  80 ,  88  to move into or out of the cylinder  80 ,  88  via the valve line  514 . Increasing or decreasing hydraulic fluid pressure in a particular hydraulic cylinder  80 ,  88  may, respectively, raise or lower the front end of the respective support arm. 
     The load sensors  504  may be provided at the front ends of some or all of the support arms  74 ,  86 , and each load sensor  504  may sense a changing load (e.g., an increasing load due to an accumulation of crop material) in front of or on the skid plate  70 ,  78  or other portion of the front end, and may generate and send an electronic load signal via a sensor signal line  518  reporting the change in load. The load sensors  504  may be employ substantially any suitable technology, such as piezoelectric, hydraulic, or pneumatic technologies. 
     The controller  506  may be configured to receive the load signals from the load sensors  504 , determine whether actuating one or more of the hydraulic cylinders  80 ,  88  is warranted, and if so, accordingly increase or decrease the hydraulic fluid pressure to the hydraulic cylinders  80 ,  88  to raise or lower the front ends of the respective support arms  74 ,  86 . In one implementation, determining whether actuating one or more of the hydraulic cylinders  80 ,  88  is warranted may involve determining whether the change in load on the front ends of the support arms  74 ,  86  exceeds a pre-determined changing load value. The pre-determined changing load value may be a numerical value or a percentage value (of, e.g., five (5) percent or more, or ten (10) percent or more) above or below a current load setting of the hydraulic cylinders  80 ,  88 . For example, if the pre-determined changing load value is five (5) percent, and the load sensors  504  report an increase in load of seven (7) percent, then the controller  506  may increase the hydraulic pressure in the hydraulic cylinders  80 ,  88  to raise the front ends of the support arms  74 ,  86  to, e.g., pass over an accumulation of crop material which created the increased load. In various implementations, some or all of the arms  74 ,  86  may be provided with the actuatable hydraulic cylinder  80 ,  88 , some or all of the arms  74 ,  86  may be provided with the load sensors  504 , and/or the controller  506  may be configured to actuate the hydraulic cylinders  80 ,  88  individually, as a subgroup, and/or all at once. For example, in some embodiments, multiple ones of the arms  74 ,  86  may be raised and lowered by a single cylinder (or cooperatively by a plurality of cylinders that are different in number than the arms). 
     In one implementation, when the header  500  is being raised off the ground, the controller  506  may receive the raise command, determine that the raise command exceeds a pre-determined time period (of, e.g., less than five (5) seconds, or less than one (1) second), and if so, increase the hydraulic pressure in each hydraulic cylinder  80 ,  88  to raise the guard tips at the front ends of the support arms  74 ,  86  and thereby reduce the risk of the header digging into the soil. 
     The 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. 
     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 as pertains to any apparatus not materially departing from but outside the literal scope of the invention as set forth in the following claims.