Abstract:
A harvesting machine includes a harvesting header with a flexiable cutterbar assembly and a draper assembly that flexes with the cutterbar assembly. The draper assembly includes a side draper belt configured to receive severed crop materials from the cutterbar assembly. The draper belt includes an internal guide rib. Pivoting structure is positioned within the interior of the draper belt. The pivoting structure presents a groove that receives the guide rib therein.

Description:
RELATED APPLICATION 
     This is a continuation of U.S. application Ser. No. 13/154,006, filed Jun. 6, 2011, which is a continuation of U.S. application Ser. No. 12/817,690, filed Jun. 17, 2010, which is a continuation of U.S. application Ser. No. 12/608,670, filed Oct. 29, 2009, which is a continuation of U.S. application Ser. No. 12/118,474, filed May 9, 2008, which is a continuation-in-part of U.S. application Ser. No. 11/670,295, filed Feb. 1, 2007, which claims the priority benefit of U.S. Provisional Application Ser. No. 60/771,981, filed Feb. 10, 2006, all of which are hereby incorporated in their entirety by reference herein. 
    
    
     BACKGROUND 
     1. Field 
     The present invention relates generally to a harvesting header. More specifically, embodiments of the present invention concern a harvesting header with a flexible cutterbar and flexible draper conveyor. 
     2. Discussion of Prior Art 
     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 undesirable limitations. For instance, 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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       Preferred embodiments of the 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 preferred 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  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; and 
         FIG. 31  is a fragmentary side view of a harvesting header constructed in accordance with a second preferred embodiment of the present invention. 
       The drawing figures do not limit the present invention to the specific embodiments disclosed and described herein. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the preferred embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Turning initially to  FIGS. 1 and 2 , the harvesting header selected for illustration comprises a flexible header  40  and a header height sensing system  41 . The harvesting header preferably forms part of a harvesting combine. The header  40  is 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 illustrated header  40  broadly includes a header frame  42 , draper arm assemblies  44 , end tilt arm assemblies  46 , cutterbar assembly  48 , and draper assembly  50 , which includes side drapers  52  and center draper  54 . The header  40  also includes 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 operable to direct upstanding crop into the header  40 . The illustrated cutterbar assembly  48  and draper assembly  50  are preferably 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  could be substantially inflexible, i.e., where the cutterbar assembly  48  is rigidly mounted relative to the header frame  42 . Similarly, there are aspects of the present invention where one, more or all of the drapers  52 , 54  could be substantially inflexible relative to the header frame  42 . 
     Turning to  FIGS. 1-3 , the header frame  42  preferably includes 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  further includes 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  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  is spaced between left and right sides of the header  40 , when the header  40  is viewed from behind, and the opening  66  is preferably centrally located on the header  40 . 
     Turning to  FIG. 6 , the cutterbar assembly  48  broadly includes a cutterbar  68 , skid plates  70 , and a sickle assembly  72 . The cutterbar  68  comprises 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  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. Preferably, the skid plates  70  are spaced apart from one another so as to permit flexing movement of the cutterbar assembly  68 . In the usual manner, the sickle assembly  72  is slidably mounted on the cutterbar  68  for severing the crop. As will be discussed further, the cutterbar assembly  48  is 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  is 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  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  includes, among other things, a tilt arm  74 , a drive bracket  76 , an end skid  78 , and a spring  80 . The tilt arm  74  presents opposite front and rear ends, with the drive bracket  76  and end skid  78  being attached to the front end. The tilt arm  74  includes 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  is 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  is attached to a bracket mounted to the channel  60  and the clevis portion  82  and is operable 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  includes a draper arm  86  with front and rear ends and a spring  88 . The draper arm  86  includes 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  is 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  is attached to a channel bracket and to the clevis portion  92  and is operable to urge the rear end of draper arm  86  downwardly in order to counterbalance loads applied adjacent the front end. The illustrated springs  80 , 88  each preferably comprise 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 where springs  80 , 88  include a conventional mechanical spring such as a coil spring. As will be discussed further, the draper arm assemblies  44  cooperatively support side drapers  52 . 
     The arm assemblies  44 , 46  preferably are pivotally mounted and cooperatively support the cutterbar assembly  48  so that the cutterbar assembly  48  is operable to flex relative to the header frame  42  along the entire length thereof. However, the arm assemblies  44 , 46  could be alternatively 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 illustrated supporting arm assemblies  44 , 46  are configured to be selectively pivotal to provide flexible and non-flexible header configurations as will be discussed. In particular, the header  40  includes threaded pins  96  and quick-release pins  98 . The threaded pins  96  are each preferably secured above the respective arm assembly  44 , 46  to restrict upward pivotal movement thereof. The quick-release pins  98  are removably received within corresponding openings  100  presented by the channels  60 . The illustrated openings  100  are 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 . In the illustrated embodiment, the quick-release pins  98  are preferably located below the corresponding arm assembly  44 , 46  to restrict downward pivotal movement thereof. While the illustrated pins  96 , 98  are preferable, other types of pins could 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  preferably comprises a single arm, but could take another form, such as a four-bar linkage as shown in U.S. Patent Publication No. 2007/0193243, published Aug. 23, 2007, entitled COMBINE HARVESTER DRAPER HEADER HAVING FLEXIBLE CUTTERBAR, which is hereby incorporated in its entirety by reference herein. 
     Turning to  FIGS. 7-9 , the arm assemblies  44 , 46  are configured to shift between an uppermost fixed position and a lowermost position. In the uppermost fixed position, the quick-release pin  98  can 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  is in an arm pivoting configuration and is 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  is in the flexible header configuration. Preferably, the cutterbar assembly  48  has a range of vertical movement of about eight (8) inches, but it is within the scope of the present invention where that the range of vertical movement is 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  is pivotally mounted adjacent to opposite ends of the header frame  42  and is supported for selective pivotal movement. As discussed above, the arm assemblies  44 , 46  are attached to and cooperatively support the cutterbar assembly  48 . The illustrated cutterbar  68  is flexible and supports the sickle assembly  72 . In particular, the sickle assembly  72  comprises a split sickle that includes a pair of flexible sickle bars  106  and knives  108  that are attached to and spaced along the length of the flexible sickle bars  106 . The sickle assembly  72  also includes knife guards  110  attached to the cutterbar  68 , with the sickle bars  106  and knives  108  being operable to slide in a reciprocating manner relative to the cutterbar  68  and flex with the cutterbar  68 . The sickle bars  106  preferably reciprocate in opposite directions relative to one another. However, it is within the scope of the present invention for the cutterbar assembly  48  to include a single continuous sickle bar. Again, the cutterbar  68  also supports 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  further includes a pair of cutterbar drive assemblies  112  that are attached to respective ones of the end tilt arm assemblies  46  and serve to power the sickle assembly  72 . The cutterbar drive assembly  112  broadly includes 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  includes 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  serves to offset the inertial forces of the sickle during its abrupt acceleration and deceleration at opposite ends of its path of travel. While the illustrated epicyclic drive  120  is preferred, for at least some aspects of the present invention, another type of drive could be used to transfer power to the sickle bar  106  without departing from the scope of the present invention. Additional details of the preferred epicyclic drive  120  are disclosed in issued U.S. Pat. No. 7,121,074, issued Oct. 17, 2006, entitled BALANCED EPICYCLIC SICKLE DRIVE, which is hereby incorporated in its entirety by reference herein. 
     The epicyclic drive  120  is 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  includes input and output shafts  126 , 128  (see  FIG. 5 ) and is mounted to the header frame  42  with bracket  130 . The telescopic drive shaft  116  is drivingly connected to the input shaft  122  of drive  120  and the output shaft  128  of 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  is powered by a power take-off shaft (not shown) of the harvesting machine. In this manner, the illustrated shaft-driven cutterbar drive assembly  112  powers the sickle assembly  72 . For at least some aspects of the present invention, 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 instead of the preferred shaft drive of the illustrated embodiment. 
     The illustrated drive assembly  112  is preferably 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  permit relative pivotal movement between the epicyclic drive  120  and the gear drive  114 . Furthermore, the telescopic drive shaft  116  permits relative lateral movement between the drives  114 , 120 . Although the illustrated drive assembly  112  is preferably attached to the end tilt arm assembly  46 , it is also within the scope of the present invention where the drive assembly  112  is 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  is spaced apart from the adjacent skid plate  70 . In this manner, the end tilt arm assembly  46  is operable 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  are 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  preferably provides a substantially smooth constant rotational velocity of the output shaft  124 . In particular, the epicyclic drive  120  is spaced above an axis of the tilt arm  74  and the gear drive  114  is 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  rotates at a uniform rotational velocity and drives 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 , it has been found that the universal joint  100  drives the drive shaft  116  at a non-uniform rotational velocity. In the illustrated embodiment, the input shaft  122  of the epicyclic drive  120  is angled relative to the drive shaft  116  at an angle α and the output shaft  128  of the gear drive  114  is angle relative to the drive shaft  116  at an angle β (see  FIG. 9 ). However, it has been determined that the illustrated arrangement of drives  114 , 120  and 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  unsubstantially cancels out any non-uniformity in the rotational velocity so that the output shaft  124  provides a uniform rotational velocity. The cutterbar drive assembly  112  pivots so that the angle α lies within an angular range. Preferably, the angle β generally falls 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  includes 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  are spaced on either side of the center draper  54  and are configured to direct severed crop material from locations along the cutterbar assembly  48  to the center draper  54 . Each side draper  52  broadly includes 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  is rotatably mounted to a corresponding draper arm assembly  44 . In particular, the inboard rollers  132  are rotatably mounted to 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  are rotatably and slidably mounted to respective draper arm assemblies  44  with the belt tensioning mechanism  140 . The belt tensioning mechanism  140  includes 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  are preferably mounted so as to pivot with the respective draper arm assemblies  44  about the lateral arm pivot axis. 
     The belt support panels  136  are elongated metal strips that extend laterally between the rollers  132 , 134 . The belt support panels  136  are 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  is an endless belt that is particularly configured for conveying the severed crop material toward the center draper  54 . The side draper belt  138  is 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  presents 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  extends below the panels  136 . The outboard roller  134  is 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 , it is within the scope of the present invention, for at least some aspects of the present invention, where an alternative conveyor mechanism is used. For instance, 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. As illustrated particularly in  FIGS. 3 and 6 , the plurality of support panels  136  includes rear support panels  136   a  at the rear ends of arms  44  and front support panels  136   b  at the front ends of arms  44 , the front and rear panels being spaced apart in a fore-and-aft direction. As illustrated in  FIG. 14 , belt  138  has adjacent its rear edge a transversely extending interior guide rib  138   a . Rollers  132  have grooves  132   a  ( FIGS. 25 ,  27 ) and rollers  134  have grooves  134   a  ( FIGS. 3 ,  14 ) for guide rib  138   a , while rear support panels  136   a  likewise have indented grooves  139  ( FIGS. 3 ,  6 ) for rib  138   a . Rear support panel  136   a  has a raised, flat central portion  141  ( FIGS. 3 ,  6 ) spaced above the underlying arm  44  ( FIG. 6 ) by a spacer  143  ( FIGS. 3 ,  6 ) and a rear recessed portion that defines groove  139 . A lip  145  ( FIGS. 3 ,  17 ,  18 ,  20 ,  29 ) projects rearwardly from groove  139  at the same level as central portion  141 . The underside of the recessed portion that defines groove  139  engages but is not fastened to arm  44  ( FIG. 6 ). A front recessed portion  147  ( FIGS. 3 ,  6 ) of rear panel  136   a  engages and is fastened to arm  44  by a fastener  149  ( FIGS. 3 ,  6 ). Like rear support panel  136   a , front support panel  136   b  has a raised, flat central portion  151  ( FIGS. 3 ,  6 ) spaced above the underlying arm  44  ( FIG. 6 ) by a spacer  153  ( FIGS. 6 ,  25 ,  26 ,  27 ). A rearwardly projecting recessed portion  155  ( FIGS. 3 ,  6 ) of front panel  136   b  engages and is fastened to the underlying arm  44  by a fastener  157  ( FIGS. 3 ,  6 ). 
     Turning to  FIGS. 11-14 , the end tilt arm assembly  46  further includes 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  operates 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  also includes inner and outer walls  156 , 158  that are 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  also presents a lowermost margin  164  that extends between the front and rear ends of the divider panel  148 . The walls  156 , 158  extend rearwardly from the forwardmost 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  includes 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  is 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  also pivots in the same direction. 
     Furthermore, the divider panel  148  is preferably 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  is 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  is 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  provides feedback to a header height adjustment system (not shown) for controlling the height of the header  40 . The header height sensing system  41  includes 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  each include a potentiometer  172 , a mounting bracket  174 , and a linkage  176 . In the usual manner, the potentiometer  172  includes a sensor arm  178  that pivots to control the voltage output of the potentiometer  172 . The potentiometer  172  is attached to a corresponding channel  60  adjacent to the pivot of the arm assembly  44 , 46  using the mounting bracket  174 . The linkage  176  directly interconnects 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 is also 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  swings 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  is operable 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  is preferably only coupled to sense movement of that particular arm. However, it is also within the scope of the present invention where the movement of multiple arm assemblies  44 , 46  is sensed by the same transducer. While the illustrated potentiometer  172  is preferable for sensing angular movement of the arm assembly  46 , it is also within the ambit of the present invention to use other types of transducers to sense angular arm movement, such as an angular encoder. 
     In the illustrated embodiment, four potentiometers  172   a , 172   b,   172   c,   172   d  are preferably 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 ). Preferably for each side of the header  40 , one potentiometer  172  is installed to sense movement of the end tilt arm assembly  46  and provide a corresponding end tilt arm position signal and another is installed to sense movement of an inboard one of the draper arm assemblies  44  and to provide a corresponding draper arm position signal. However, other sensing configurations could be used without departing from the scope of the present invention. For instance, more than two potentiometers  172  could be installed on each side of the header  40 . For 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 operable 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  is operable 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  provides 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 illustrated electronic module  170  includes a pair of minimum input voltage selector circuits  180 . Each selector circuit  180  includes 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 . Preferably, the resistors  184  are 470 k-ohm resistors, the resistors  186  are  1  k-ohm resistors, the diodes  188  are 1N4004 diodes, and the operational amplifiers  190  are TS924IN op amps. The selector circuit  180  also includes 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 further includes pull-up resistors  196  and feedback diode  198 . Preferably, the diodes  192  are 1N4004 diodes, the operational amplifiers  194  are TS924IN op amps, and the resistors  196  are 220 k-ohm resistors. The module  170  also includes a potentiometer circuit  200  that is preferably coupled to all of the potentiometers  172 , via common nodes  202 , 204 . The circuit  200  includes a zener diode  206  and capacitors  208 , 210 . Preferably, the capacitor  208  is a 0.1 microfarad capacitor and the capacitor  210  is a 10 microfarad capacitor. 
     The illustrated arrangement of selector diodes  192  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  provides 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  selects the lowest one of analog voltage signals provided by the respective potentiometers  172  and provides a corresponding selected analog output signal at selector output  211 . However, it is also within the scope of the present invention where the circuit provides another signal, e.g., where the circuit selects the highest one of the voltage signals and provides 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 illustrated potentiometers  172  preferably 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  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 illustrated cutterbar assembly  48  has 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 causes the potentiometers  172  to range between about 0.5 volts to about 3 volts. 
     The module  170  provides selected signal outputs that correspond to the position of the cutterbar assembly  48 . In particular, potentiometers  172   a,   172   b  are operable to sense the position of a left side section of the cutterbar assembly  48  and potentiometers  172   c,   172   d  are operable to sense the position of a right side section of the cutterbar assembly  48 . Furthermore, the selector circuits  180  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  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 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. Preferably, the header height adjustment system controls the header  40  in response to the cutterbar position signals received from the module. Preferably, 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 preferably raises the header  40 . However, for some aspects of the present invention, 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  comprises an endless belt that includes a belt body  212  and presents leading and trailing belt margins  214 , 216 . The side draper belt  138  further includes 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  preferably includes an endless crop-retaining rib  220  that projects from the outer surface of the belt body  212 . The rib  220  includes a cross-sectional shape that is preferably constant along its length and tapers outwardly toward an outermost tip. Preferably, the rib  220  projects at least about one-half inch from the outer surface of the belt body  212 . The crop-retaining rib  220  preferably endlessly extends adjacent to the leading belt margin  214  so that the rib  220  is spaced between the margin  214  and the slats  218 . However, it is also within the ambit of the present invention where the side draper belt  138  is alternatively configured to carry crop material. For instance, 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  is rotatably received onto the rollers  132 , 134  so as to define upper and lower belt runs  222 , 224 , with the upper belt run  222  operable to move toward the center draper  54 . Preferably, the arm assemblies  44 , 46  are 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  is 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  further includes 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  is preferably unitary and comprises a formed piece of sheet metal that presents opposite first and second ends  230 , 232 . The belt guard  228  includes 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  also includes 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  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  are 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  is positioned underneath the upright section  236  of the one belt guard  228 . In this manner, each pair of mated belt guards  228  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 preferably permits relative angular movement between mated pairs of belt guards  228  and also permits 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 illustrated pairs of mated belt guards  228  preferably are 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  extend rearwardly and upwardly from the cutterbar  68  and extend over the leading belt margin  214 . The belt guards  228  also preferably 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, it is within the scope of the present invention where some sliding contact occurs therebetween. In particular, the overhanging sections  238  present a downwardly facing surface that extends in close proximity along the tip of the rib  220 . Preferably, the gap between the surface and the tip is less than about one-quarter of an inch. In this manner, the belt guards  228  and the crop-retaining rib  220  cooperatively form a joint that restricts severed crop material from falling between the cutterbar  68  and the leading belt margin  214 . Front panels  136   b  have an upwardly projecting front margin  159  ( FIG. 6 ) extending into close proximity with an underside of rearwardly projecting sections  238  of belt guards  228 . As illustrated in  FIG. 6 , the rearwardly projecting sections  238  of belt guards  228  project rearwardly beyond front margin  159  of front panel  136   b . As shown in  FIG. 21 , rearwardly projecting sections  238  of belt guards  228  are disposed at a level above the level of a front edge  161  of the upper run of belt  138  and overhang and project rearwardly beyond front edge  161  into engagement with belt rib  220 . 
     Spring Flotation for Center Deck of Draper Header 
     Turning to  FIGS. 25-30 , center draper  54  serves 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  broadly includes a draper chassis  244 , front and rear rollers  246 , belt support  248 , and center draper belt  250 . The draper chassis  244  includes a pair of side plates  252  that are pivotally mounted to corresponding channels  60  and pivot about pivot axis  254 . The draper chassis  244  further includes 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  cooperatively pivot about the pivot axis  254 . The illustrated draper chassis  244  preferably presents a lateral width, measured from one side plate  252  to the other, of at least about five (5) feet and, more preferably about 6 feet, but it is also within the scope of the present invention where the draper chassis  244  is larger or smaller than the illustrated embodiment. 
     The floor panel  256  also presents a forward margin  258  that is secured to the corresponding skid plates  70  with multiple fasteners. In particular, the fasteners each include a rearwardly 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  is 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  also includes a counterbalance mechanism  260  for supporting the center draper  54  as will be discussed further. 
     The rollers  246  are 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  is attached to the side plates  252  and is spaced between the rollers  246 . The center draper belt  250  comprises an endless belt with a belt body and a plurality of crop-engaging slats  264 . The center draper belt  250  presents upper and lower runs  266 , 268 . The lower run  268  extends below the belt support  248  and the upper run  266  extends above the belt support  248 , with the belt support  248  being operable to restrict sagging of the upper run  266 . The draper belt  250  is 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. However, it is also within the scope of certain aspects of the present invention where the belt rotation direction is reversed so that the upper run  266  moves forwardly and the lower run  268  moves rearwardly (such that crop is conveyed by the lower run). While the illustrated center draper  54  is preferably centrally located relative to the rest of the header  40 , it is also within the scope of the present invention where the center draper  54  is located toward one side of the header  40 . 
     Turning to  FIG. 29 , the counterbalance mechanism  260  serves to support the center draper  54  by counteracting the weight of the center draper  54  about the pivot axis  254 . The counterbalance mechanism  260  includes a lever  270 , mounting lug  272 , rod  274 , and compression spring  276 . The lever  270  is attached to a rear end of the corresponding side plate  252  and extends rearwardly through the opening  66 . The mounting lug  272  is 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  is 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  is 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  is operable to bias the lever  270  in a generally downward direction. The generally downward spring force provided by the spring  276  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  collects 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  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  further includes an elongated brace  280  that comprises a substantially uniform length of angle iron. However, it is also within the scope of the present invention to use another structure with some vertical dimension to resist bending of the cutterbar assembly  48  caused by gravity or other loads. For instance, 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  is positioned to lie on top of the flange section  234  of central guard  226  and engage the upright section  236 . Fasteners 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  cooperatively restrict the cutterbar assembly  48  from bending along the inflexible length  282 . 
     The center draper  54  includes 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 , flex to only a minimal degree along the length of the cutterbar  68 . Therefore, because the illustrated cutterbar assembly  48  is preferably rigid along the inflexible length  282 , the front roller  246  and the inflexible length  282  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  permits 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  also includes a center crop deflector  284  that is substantially unitary and is operable 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  includes a substantially flat plate with front and rear deflector portions  286 , 288  and also includes a lower flange  290 . The rear deflector portion  288  preferably presents 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  also presents a portion length  294  in the range of about one (1) inch to about six (6) inches. The rear deflector portion  288  preferably presents upper and lower edges  296 , 298  that are substantially linear. The front deflector portion  286  presents 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  is 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 . Preferably, the rear deflector portion  288  extends over the draper belt  250  a length less than half the length of the upper run  266 . More preferably, the length of extension over the draper belt  250  ranges from about one (1) inch to about six (6) inches. Also, the upper edge  296  of the rear deflector portion  288  is preferably spaced above the draper belt  250  a distance  306  in the range of about three (3) inches to about five (5) inches. It has been determined that the illustrated length of extension over the draper belt  250  and the height of the upper edge  296  relative to the draper belt  250  permits 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  is preferably 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 instance, 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  serves 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 illustrated harvesting header is operable to 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  defines a crop cutting path of the header and pushes crop along the sides of the path in an inboard direction. At the same time, the cutterbar assembly  48  operates to 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  is carried inwardly toward and deposited onto the center draper  54 . In particular, both left and right side drapers  52  are operable to carry any crop material inwardly, with the center crop deflector  284  being operable to restrict 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  is carried in a rearward direction toward the collecting auger  55  and is then deposited through the opening  66  and into the feeder house. 
     The harvesting header is operable to 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 are 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 is 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 is 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  are operable to flex relative to the header frame  42  between lowermost and uppermost positions. Any contact between the ground and the cutterbar assembly  48  will 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 senses the threshold condition and raises the header in response to the condition until the arm assemblies  44 , 46  pivot downwardly below the threshold. The flexible header configuration is 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 preferred header  400  is 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 preferred embodiment described above. The header  400  includes a header frame  402  and an end tilt arm  404  pivotally mounted to the header frame  402 . The header  400  further includes fixed and adjustable pins  406 , 408  that are attached to an upright  410  of the header frame  402 . The upright  410  presents an opening  412  that includes three discrete pin-receiving sections that define locked locations  414  and unlocked locations  416 , 418 , each of which is operable to receive the adjustable pin  408  so that the pin can be selectively positioned in one of the locations. The unlocked locations  416 , 418  provide two distinct lowermost arm positions that correspond with distinct ranges of angular arm movement. Thus, the unlocked location  418  permits a full range of angular arm movement of the end tilt arm  404 , while unlocked location  416  permits a range of movement that is about half of the full range of angular arm movement provided by location  418 . The locked location  414  serves to provide an uppermost arm position that corresponds with a locked arm position, with substantially no range of angular arm movement being permitted. Preferably, each of the support arms of the illustrated header  400  has a similar stop arrangement that provides similar locked and unlocked locations. 
     The preferred forms of the invention described above are to be used as illustration only, and should not be utilized in a limiting sense in interpreting the scope of the present invention. Obvious modifications to the exemplary embodiments, as hereinabove set forth, could be readily made by those skilled in the art without departing from the spirit of the present invention. 
     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.