Abstract:
A combine harvester with a straw separating system includes a straw chopper and discharge assembly mounted for receiving the straw and having a rotor for chopping the straw and for generating a stream of chopped straw for spreading the chopped straw. A pneumatic air source is provided preferably separately driven from and remote from the rotor for generating a stream of air having an outlet duct forming a stream of air. The air is used either to assist the spreading action from the chopper and can be individually controlled by valves. If used to assist the air stream of the chopper it is fed at the outlet of a rear chopper or directed at the guide wall in an internal chopper arrangement for directing higher velocity air onto the guide fins assisting the spread of the chopped materials.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a combine harvester and to the spreading of straw and/or chaff from the combine harvester using a fan to generate an airflow.  
       BACKGROUND OF THE INVENTION  
       [0002]     Axial flow combines have in recent years taken the vast majority of the market replacing older conventional designs. It is most cost effective in such axial flow combines to provide an internal straw chopper behind the axial flow rotors.  
         [0003]     One example of an arrangement of this type is shown in U.S. Pat. No. 3,863,643 (De Pauw) issued Feb. 4, 1975 to International Harvester which shows a rotary beater transverse to the combine harvester behind the axial rotors. CaseIH produces an optional internal chopper, mounted in place of the rotary beater which feeds the straw onto a guide wall which extends across the width of the housing and the hood of the combine and then extends downwardly and rearwardly at the rear.  
         [0004]     There is commonly used a rotary spreader disk at the rear end of the housing which accelerates the stream of chopped straw to discharge the material to the sides.  
         [0005]     Combine development in recent years have put greater demands on the straw choppers and chaff spreaders. The main reasons are that larger combines and wider cutting widths are creating higher flows of straw and chaff; wider cutting widths create more demanding spreading widths; reduced tilling practices have put more demand on even spreading of both straw and chaff and that plant breeding has resulted in tougher straw, higher yields and more residue.  
         [0006]     A number of different arrangements have been proposed to assist in spreading the straw at the rear of the guide wall and the housing and examples of these are as follows.  
         [0007]     In U.S. Pat. No. 4,735,216 (Scott) issued Apr. 5, 1988 is proposed a pair of counter-rotating fans mounted in a horizontal plane for rotation about vertical axis which direct the, crop material to the sides.  
         [0008]     In U.S. Pat. No. 6,663,485 (Niermann) issued Dec. 16, 2003 to Claas is disclosed a blower and spreading arrangement mounted at the rear of the housing which is intended to improve power efficiency.  
         [0009]     In U.S. Pat. No. 5,232,405 issued Aug. 3, 1993 and U.S. Pat. No. 5,482,508 issued Jan. 9, 1996; one of the inventors herein Redekop discloses an improved rotor which includes a number of fan blades which assist in generating an enhanced air stream while chopping the straw. This arrangement has achieved considerable success.  
         [0010]     Also in published US application 2004/0043804 published Mar. 4, 2004, Redekop et al. disclose a further improved arrangement in which the fan blades are located at respective ends of the rotor concentrating the cutting blades in a center section of the rotor. This arrangement has been shown to provide yet further advantages in generating an effective air stream while causing effective chopping of the straw.  
         [0011]     While improvements to the construction of the rotor enhance the spreading action, there still remains some difficulties in obtaining an effective spread when using an internal chopper without the addition of further chopping action or spreading action at the rear of the guide wall. However enhanced efficiency in the chopping and spreading action is required to reduce power consumption, bearing in mind that power requirements for the operation of the remaining elements of the combine harvester are increasing due to the features set forth above.  
         [0012]     It is known also to provide additional airflow into the chopper in an attempt to increase spreading action. For example U.S. Pat. No. 6,113,491 (Holmen) issued Sep. 5, 2000 to Rekordverden discloses an arrangement in which an additional fan is located at the end of the chopper rotor and generates an air stream which is driven into the area of the rotor at a position angularly ahead of the discharge area. This arrangement has not achieved significant success.  
         [0013]     EP 1187526 (Schratteneker) published 3 Sep. 2003 discloses a straw chopper with fans mounted to each side of the chopper each having a pivotal nozzle which allows the air jet to be directed at various positions on each outer fin only of the tailboard.  
         [0014]     US Application 2004/0137974 (Weichholdt) of Deere and Company discloses a combine harvester with a chopper under the beater at the rear of the threshing rotor where the arrangement can be adjusted to by-pass the chopper.  
       SUMMARY OF THE INVENTION  
       [0015]     It is an objective of the invention to provide an improved straw discharge system for a combine harvester.  
         [0016]     According to a first aspect of the invention there is provided a combine harvester comprising: 
        a housing;     a straw separating system mounted within the housing for separating seed materials from straw for collection of the seed materials and for transport of the straw for discharge;     a straw chopper and discharge apparatus mounted at the discharge of the straw separating system for receiving the straw for chopping the straw and for generating a stream of chopped straw for spreading the chopped straw;     the chopper and discharge apparatus having: 
            a rotor mounted for rotation about a longitudinal axis of the rotor and a plurality of blade members mounted on the rotor for rotation therewith about said axis for chopping the straw and accelerating the chopped materials in a stream for discharge at a discharge location;     a plurality of guide fins at the discharge location for directing the chopped materials into a spread pattern;     and a pneumatic air source for generating a stream of air through an outlet opening of an outlet nozzle forming a stream of air directed at a plurality of the guide fins for assisting the spread of the chopped materials.    
               
 
         [0024]     Preferably the stream of air is arranged such that the velocity of the air is different at different ones of the guide fins.  
         [0025]     Preferably herein the stream of air is adjustable at different positions across the stream.  
         [0026]     Preferably there are provided two separate nozzles each having an outlet opening directed at a plurality of guide fins at a respective side of the discharge location.  
         [0027]     Preferably each nozzle defines a slot shaped opening having a width sufficient to direct air onto a plurality of the guide fins.  
         [0028]     Preferably the nozzle includes a slot shaped opening located so as to extend across a part of the stream of chopped material.  
         [0029]     Preferably the pressure and/or flow of the air source are remotely controlled.  
         [0030]     Preferably the exit air velocity at the outlet opening is controlled.  
         [0031]     Preferably the outlet opening of the nozzle is mounted immediately adjacent the guide fins for directing the air stream onto the fins.  
         [0032]     In one arrangement, the rotor is an internal rotor within the combine housing and there is provided a guide wall extending from the rotor to the discharge location where the guide fins are located and wherein the nozzle opening is mounted at a location adjacent the fins.  
         [0033]     The nozzle may be located above the guide wall so as to direct the air into the stream of chopped material from above the stream. However it may be desirable to mount the nozzle below the stream to apply air tending to press the stream against the guide wall. Alternatively there may be two nozzles mounted n respective sides to the stream.  
         [0034]     In one arrangement, the rotor includes two end fan sections wherein each end fan section communicates air therefrom through a duct alongside the guide wall to a separate nozzle.  
         [0035]     The nozzle may include. a plenum defined above the guide wall wherein one side of the plenum is defined by the guide wall with the nozzle defined at a step in the guide wall. However alternative arrangements below the guide wall can also be used.  
         [0036]     Preferably the guide wall and the fins are arranged to include a movable element arranged to be movable from a first position directing the straw onto the fins to a second position directing the straw to by-pass the fins.  
         [0037]     Preferably the movable element comprises a panel of the guide wall which is mounted for pivotal movement about a transverse axis at a leading edge of the panel so as to move a trailing edge thereof.  
         [0038]     Preferably the panel is arranged in advance of the nozzle.  
         [0039]     Preferably the rotor is mounted in a rotor housing at the rear of the combine for discharge of the material from the rotor housing onto a tailboard located behind the rotor housing and wherein the nozzle is defined by a plenum carried on the rotor housing.  
         [0040]     Preferably the plenum carried on the rotor housing is fed centrally of the rotor housing by a duct from the air source. However there may be two separate nozzles each fed separately from a separate aid source and each arranged on a respective side.  
         [0041]     Preferably the plenum includes guide walls dividing the plenum into two separate paths for the air each feeding a separate one of two nozzles each arranged adjacent a respective side of the rotor housing.  
         [0042]     In another arrangement, the rotor is mounted in a rotor housing at the rear of the combine for discharge of the material from the rotor housing onto a tailboard located behind the rotor housing and wherein the nozzle provides at least one slot shaped opening extending across the rotor housing for adding air into the stream emerging from the rotor housing.  
         [0043]     According to a second aspect of the invention there is provided a combine harvester comprising: 
        a housing;     a straw separating system mounted within the housing for separating seed materials from straw for collection of the seed materials and for transport of the straw for discharge;     a straw chopper and discharge apparatus mounted at the discharge of the straw separating system for receiving the straw for chopping the straw and for generating a stream chopped straw for spreading the chopped straw;     the chopper and discharge apparatus having: 
            an internal rotor within the combine harvester mounted for rotation about a longitudinal axis of the rotor and a plurality of blade members mounted on the rotor for rotation therewith about said axis for chopping the straw and accelerating the chopped materials in a stream for discharge at a discharge location;     a guide wall extending from the rotor to the discharge location;     a plurality of guide fins at the discharge location for directing the chopped materials into a spread pattern;     and a pneumatic air source for generating a stream of air through an outlet opening of an outlet nozzle for assisting the spread of the chopped materials;    
            wherein the nozzle is mounted at a location adjacent the fins and forming a stream of air directed at a plurality of the guide fins.        
 
         [0053]     According to a third aspect of the invention there is provided a combine harvester comprising: 
        a housing;     a straw separating system mounted within the housing for separating seed materials from straw for collection of the seed materials and for transport of the straw for discharge;     a straw chopper and discharge apparatus mounted at the discharge of the straw separating system for receiving the straw for chopping the straw and for generating a stream of chopped straw for spreading the chopped straw;     the chopper and discharge apparatus having: 
            a rotor mounted for rotation about a longitudinal axis of the rotor and a plurality of blade members mounted on the rotor for rotation therewith about said axis for chopping the straw and accelerating the chopped materials in a stream for discharge at a discharge location;     the rotor being mounted in a rotor housing at the rear of the combine for discharge of the material from the rotor housing onto a tailboard located behind the rotor housing;     a plurality of guide fins at the tailboard for directing the chopped materials into a spread pattern;     a pneumatic air source for generating a stream of air;     and a plenum mounted on the rotor housing for receiving the stream of air and defining an outlet nozzle having an outlet opening directed the guide fins for assisting the spread of the chopped materials.    
               
 
         [0063]     According to a fourth aspect of the invention there is provided a combine harvester comprising: 
        a housing;     a straw separating system mounted within the housing for separating seed materials from straw for collection of the seed materials and for transport of the straw for discharge;     a straw chopper and discharge apparatus mounted at the discharge of the straw separating system for receiving the straw for chopping the straw and for generating a stream of chopped straw for spreading the chopped straw;     the chopper and discharge apparatus having: 
            a rotor mounted for rotation about a longitudinal axis of the rotor and a plurality of blade members mounted on the rotor for rotation therewith about said axis for chopping the straw and accelerating the chopped materials in a stream for discharge at a discharge location;     the rotor being mounted in a rotor housing at the rear of the combine for discharge of the material from the rotor housing onto a tailboard located behind the rotor housing;     a plurality of guide fins at the tailboard for directing the chopped materials into a spread pattern;     a pneumatic air source for generating a stream of air;     and a plenum for receiving the stream of air and defining an outlet opening of an outlet nozzle directed at the guide fins for assisting the spread of the chopped materials.    
            wherein the outlet opening is slot shaped extending across the rotor housing for adding air into the stream emerging from the rotor housing.        
 
         [0074]     According to a fifth aspect of the invention there is provided a combine harvester comprising: 
        a housing;     a straw separating system mounted within the housing for separating seed materials from straw for collection of the seed materials and for transport of the straw for discharge;     a straw chopper and discharge apparatus mounted at the discharge of the straw separating system for receiving the straw for chopping the straw and for generating a stream of chopped straw for spreading the chopped straw;     the chopper and discharge apparatus having: 
            an internal rotor within the combine harvester mounted for rotation about a longitudinal axis of the rotor and a plurality of blade members mounted on the rotor for rotation therewith about said axis for chopping the straw and accelerating the chopped materials in a stream for discharge at a discharge location;     a guide wall extending from the rotor to the discharge location;     a plurality of guide fins at the discharge location for directing the chopped materials into a spread pattern;    
            wherein the guide wall and the fins are arranged to include a movable element arranged to be movable from a first position directing the straw onto the fins to a second position directing the straw to by-pass the fins.        
 
         [0083]     It is also intended that the protection provided by this application should extend to the elements necessary to mount the components on an existing combine harvester having a chopper and fins. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0084]     Embodiments according to the present invention will now be described in conjunction with the accompanying drawings in which:  
         [0085]      FIG. 1  is schematic isometric view of the rear section of a rotary combine including the combine rotor, a straw chopper and a discharge guide system for the straw discharged from the chopper, all showing a first embodiment of the present invention.  
         [0086]      FIG. 2  is a schematic top plan view of the embodiment of  FIG. 1 .  
         [0087]      FIG. 3  is an isometric view similar to that of  FIG. 1  but with the guide surfaces shown in full line. rather than in phantom.  
         [0088]      FIG. 4  is a side elevational view, partly in phantom showing the embodiment of  FIG. 1  arranged for spreading of the straw.  
         [0089]      FIG. 5  is a side elevational view similar to that of  FIG. 4  on an enlarged scale showing adjustment of a guide wall to avoid spreading of the straw.  
         [0090]      FIG. 6  is an isometric view partly in phantom showing the air control plenum for mixing the air and straw stream.  
         [0091]      FIG. 7  is a side elevational view similar to that of  FIG. 4  showing a modified arrangement utilizing a separate fan for injecting into the nozzle of  FIG. 6 .  
         [0092]      FIG. 8  is a side elevational view partly in phantom of a further embodiment utilizing an external chopper at the rear of the combine in which air is injected immediately downstream of the chopper.  
         [0093]      FIG. 9  is a side elevational view partly in phantom of the embodiment of  FIG. 8  on an enlarged scale.  
         [0094]      FIG. 10  is a top plan view of the embodiment of  FIG. 8 , again partly in phantom.  
         [0095]      FIG. 11  is an isometric view from the rear and one side of the embodiment of  FIG. 8 .  
         [0096]      FIG. 12  is a rear elevational view of the embodiment of  FIG. 8 .  
         [0097]      FIG. 13  is an isometric view of the air injection manifold separated from the embodiment of  FIG. 8 . 
     
    
       [0098]     In the drawings like characters of reference indicate corresponding parts in the different figures.  
       DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0099]     In  FIGS. 1 through 6  is shown a first embodiment of the invention in which the relevant components of a combine harvester have been extracted and are shown in phantom.  
         [0100]     The combine harvester thus includes a housing (not shown) mounted on rear ground wheels  10  supporting the various components of the combine harvester. A combine harvester of this general type is shown in U.S. Pat. No. 3,863,643 previously mentioned, the disclosure of which is incorporated herein by reference. The combine harvester includes a threshing rotor  11  which operates to separate harvested materials from the straw and discharges the straw at a rear end  12  of the rotor into a straw chopping and discharge system generally indicated at  13 .  
         [0101]     It is conventional that the discharge system  13  includes a rotor  14  which is mounted on a shaft  15  for rotation about a horizontal axis across the rear of the threshing rotor  11 . The chopping rotor is driven in rotation around the axis of the shaft by a drive mechanism mounted on the end of the shaft exposed at  16  with a drive mechanism being omitted for convenience of illustration. The rotor carries pairs of blades  17  at spaced positions around the axis of the rotor and at spaced positions along the axis of the rotor so that the straw emerging from the rear of the threshing rotor  11  is chopped and is accelerated underneath the rotor  14  over a guide surface  18  into a guide and spreading component generally indicated at  19 . This includes a guide wall  20  which carries the straw material rearwardly onto a tailboard  21  carrying a series of fins  22  at spaced positions across the tailboard. The fins  22  are curved rearwardly and outwardly so that outermost ones of the fins are directed at greater angles to a longitudinal centerline than are center ones of the fins so as to provide a spread pattern of the chopped straw across the ground.  
         [0102]     The components described above are generally conventionally used in combine harvesters of this general type but in the arrangement described herein are modified as described hereinafter. The rotor  14  is of the type shown in US application 2004/0043804 published Mar. 4, 2004, Redekop et al., the disclosure of this patent is incorporated herein by reference.  
         [0103]     Thus the rotor  14  is divided into a center section generally indicated at  23  between two end sections  24 . The end sections contain blades on the hub of the rotor which are shaped to provide a fan effect whereas the blades in the center section  23  are primarily or wholly cutting blades and thus are substantially flat in radial planes of the rotor. Thus the cutting action occurs primarily in the center section and the two end sections are arranged primarily for generating airflow.  
         [0104]     In the above stated previous published application, air transferred and material transferred between the center section and the end sections is possible so that some straw may enter the end sections and some air may be driven from the end sections into the center section. In the present arrangement, the intention is that the sections are maintained substantially or wholly separate so that no straw enters the end sections  24  and no air migrates from the end sections  24  into the center section. Thus substantially the whole of the air from the end sections  24  is available for air propulsion as described hereinafter.  
         [0105]     For this reason, covers  25  are provided over the end sections including a part cylindrical outer wall  26  and a part annular side walls  27  and  28 . These walls act to prevent the transfer as set forth above or at least to inhibit the majority of the transfer.  
         [0106]     The end and center sections rotate commonly on the common hub and thus generate a stream of the material discharging from a nozzle  29 . For this reason the rotor is confined at the bottom by the bottom wall  18  and is confined over the top by suitable guide components including bottom panel  30  so that the nozzle  29  is defined between the rear edge of the bottom wall  18  and the bottom of the panel  30 .  
         [0107]     The guide system  19  defined by the walls generally indicated at  20  carries the straw from the center section  23  and the air from the end sections  24  and transports these independently to a plenum generally indicated at  31  after which the air and straw are remixed for entry onto the tail board  21  and the fins  22 .  
         [0108]     The fins are basically of a conventional nature which are mounted on the underside of the tail board and are provided with curvature to provide a spread pattern. The inclination of the fins relative to a center line of the tailboard indicated at  32  can be adjusted by moving a mounting bolt of each fin along a slot  33  of the fin on the tailboard.  
         [0109]     In conventional manner, the tailboard is mounted at its forward end on a transverse pivot mounting generally indicated at  34  which allows the inclination of the tailboard to be adjusted about a horizontal axis on a mounting bracket  35 .  
         [0110]     The guide system  19  as best shown in  FIGS. 2 and 4  includes two guide ducts  36  which have a width equal to the end sections  24  of the chopper rotor so as to receive air directly therefrom and carry that air rearwardly along the guide  19  to the plenum  31 . Each of the ducts  36  is confined by two side walls, a top wall and a bottom wall so as to form a closed duct of rectangular cross section having an open mouth  36 A at the nozzle  29  and an open mouth  36 B at the plenum  31 . An inside side wall of the duct  36  is formed by sheet metal component of the guide walls  20  and an outside wall can be formed by a wall of the housing of the combine and thus is not visible in the figures.  
         [0111]     In between the ducts  36 , the guide system is defined by a top wall  37  of the walls  20  which extends across the top of the ducts  36  and thus forms a channel shaped area between the ducts  36  and underneath the top wall  37  into which straw is ejected from the outlet nozzle  29 . The straw is injected in a stream from the outlet nozzle  29  upwardly and rearwardly so as to impact the surface  37  so as to be guided thereby a movement along the surface  37  upwardly and rearwardly toward the plenum  31  and the tailboard  21 .  
         [0112]     Thus the straw exiting from the nozzle  29  across the full width of the center section  23  is guided rearwardly between the ducts  36  across the walls  37 . The wall  37  has a rear edge  37 A which is spaced forwardly of the rear mouth  36 B of the ducts  36 . AT the rear edge  37 A is mounted a pivotal panel  38  which has a leading edge  38 A at the rear edge  37 A at which the panel is mounted for pivotal movement about the horizontal axis defined transversely of the guide system  19  at the rear edge  37 A. The panel  38  thus has a trailing edge  38 B which can be moved from a first position shown in  FIG. 4  to a second downwardly inclined position shown in  FIG. 5 .  
         [0113]     In the position shown in  FIG. 4 , the panel  38  extends downwardly and rearwardly to take up a position where its rear edge  38 B is contiguous with a front edge  40 A of a bottom panel  40  of the plenum  31 . Thus the crop material sliding over the bottom surface of the wall  37  enters onto the bottom surface of the wall  38  and transfers therefrom to the bottom surface of the wall  40 . The crop material in its chopped condition thus passes over these surfaces and ends up on the bottom surface of the tailboard  21  which is inclined slightly downwardly relative to the downward inclination of the walls  38  and  40 . Thus the crop stream is smoothly carried over the surfaces and onto the under surface of the tailboard where it encounters the fins  21  and is divided into the separate streams which are spread by the orientation of the fins in conventional manner.  
         [0114]     The airstream emerging from the rear open ends  36 B of the ducts  36  enters into the plenum  31  as best shown in  FIG. 6  at a position above the wall  40  and underneath the top wall  41  of the plenum. Between the top and bottom walls  40  and  41  is defined a pair of upstanding side guide walls  42  and  43  defining a nozzle  44  within the plenum  31  for the air emerging from the duct  36 . The nozzle  44  is defined between the walls  42  and  43  with the wall  43  arranged along one side of the plenum  41  and the wall  44  inclined inwardly so that it terminates at a trailing edge  44 A spaced from the trailing edge  43 A of the wall  43  by a distance greater than the width of the duct  36 . At the same time as the nozzle increases in width, it also reduces in height so that the wall  41  approaches the wall  40  leaving a slot shaped open mouth  45  at the trailing end of the nozzle  44 . The opening  45  has a height defined by the spacing between the walls  40  and  41  and a width defined by the spacing between the walls  43  and  44 . Thus the air stream entering the nozzle  44  is transferred in air stream shape from the relatively high duct  36  to the shallow wider nozzle mouth  45 .  
         [0115]     Adjacent the mouth  45 , the nozzle  44  has a plurality of butterfly valves  46  which can be adjusted by rotation of each of the valves about an axis through the wall  41  and a control of a manually operable lever  47 . Each of the valves  46  can be adjusted independently so as to vary the amount of air emerging at different positions across the width of the mouth  45 . In the position shown, the valves have their valve surface generally parallel to the air stream so that they have little or no effect on the movement of the air. However it will be appreciated that rotation of the valve through 90° will close off that particular portion of the mouth  45  thus redirecting the air to another portion of the mouth  45 . In this way individual adjustment of the valves  46  can control the amount of air exiting at required positions through the mouth  45  onto the tailboard  21 .  
         [0116]     It will be appreciated therefore that the straw flowing underneath the wall  40  exits a trailing edge  40 B of the wall  40  and transfers therefrom over a slight step defined by the height of the nozzle mouth  45  and a blanking wall piece  49  between the mouths  45  onto the surface of the tailboard. As the crop material bridges this step, the air stream from the mouths  45  joins with the straw to form a combined stream. It will be appreciated that the straw or crop material at the center adjacent the blanking wall  49  contains less of the air from the ducts  44  and thus is carried primarily by the air from the rotor  14 . Additional air is added into the crop stream as it passes underneath the mouth  45  so the side portions of the crop stream are supplemented by the additional air from the ducts  36 .  
         [0117]     It will be appreciated that the crop stream is confined at the trailing edge  40 B by the walls  43  and particularly a depending portion  43 A thereof underneath the trailing edge  40 B. The walls  43  are spaced by a greater distance than the width of the panel  37  and the panel  38  since they also include the width of the ducts  36 . Thus the straw initially confined between the inside walls of the ducts  36  is allowed to spread out at the rear end of the ducts  36  into the area confined between the walls  43 . The pressure within the stream tends to cause this spread so that the straw takes up a substantially constant quantity across the full width between the walls  43  at the end of the plenum  41 .  
         [0118]     The straw is thus guided by the walls  43  onto the tailboard at a position outboard of the outermost fin indicated at  22 A. It will be noted from  FIG. 2  that the width of the mouth  45  defined by the walls  43  and  44  causes the air stream to enter into the leading end of the first three fins indicated at  22 A,  22 B and  22 C respectively. Thus each of these fins has the stream of material thereon supplemented by air from the mouth  45 . As previously stated the particular amount of air directed to each of the fins can be adjusted by operation of the respective valve  46 .  
         [0119]     As the remaining fins inboard of the third fin  22 C are spaced inward from the mouth  45 , they receive little supplemental air from the duct  36 .  
         [0120]     Thus the supplemental air stream from the ducts  36  is transferred into the stream of straw or crop material on the tail board substantially immediately at the entry onto or at the leading edge of the tailboard at the step defined by the mouth  45  and the plate  49 . Thus the supplemental air is confined to the outermost fins and particularly the outermost three fins where enhanced spreading action is particularly required. It has been found that adding supplemental air to the materials flowing on the three outermost fins causes the best spreading action and the best accuracy of distribution across the full width of the spread pattern.  
         [0121]     As previously stated, in order to prevent straw from entering the ducts  36  and thus providing the potential problem of blockage of those ducts and the nozzles  44 , it is desirable that the shrouding or covers over the end sections  24  be arranged to at least inhibit and possibly prevent the penetration of the straw into the areas of the end sections.  
         [0122]     In an alternative arrangement (not shown), the end sections of the rotor may be entirely external to the straw transportation area of the combine so that the air stream through the ducts  36  is generated by separate elements of the rotor so that the ducts  36  are spaced outwardly of the straw area.  
         [0123]     In  FIG. 7  is shown a further alternative arrangement in which the supplemental air stream is generated by a fan  50  which is entirely separate from the rotor  14 . In this arrangement the fan  50  generates an air stream through a duct  51  which is then transported separately from or away from the straw transportation walls  37  and  38  to the plenum  31 . Thus the duct  51  enters one side wall  43  of the plenum and extends across above the bottom wall  40  of the plenum underneath the top wall  41  of the plenum and thus above the straw stream so as to feed a part of the air stream into one of the nozzles  44  and a part into the other of the nozzles  44 . Thus the duct extends across the width of the plenum and is divided so as to separate the required proportions of the air stream into each of the nozzles  44 .  
         [0124]     As a further alternative, two fans can be provided either driven from the rotor directly on the end of the shaft of the rotor or by suitable drive communication from the rotor. Each of the fans then includes its own separate duct  51  transporting the air stream to the nozzle  44  of the plenum  31 .  
         [0125]     In all of these embodiments the airstream is injected into the straw stream immediately in front of the tailboard. In all of these embodiments the air stream is separated into the two separate sections each adjacent a respective side edge of the straw stream. In all of these embodiments the airstream is adjustable by butterfly valves or other suitable valving arrangements so as to adjust the airflow onto selected ones of the outermost fins of the tailboard.  
         [0126]     In the embodiments where the supplemental air stream is separate from the chopping rotor, the chopping rotor may utilize blades which are wholly chopping blades so that they are substantially in a radial plane of the axis of the rotor to provide an improved chopping action. However some of the blades may be paddle or fan blades which assist in generating an air stream, if it is required to provide additional air stream with the straw stream exiting the rotor. It will be appreciated that the air stream for transporting the straw may be provided by different proportions of air from the supplemental air stream of the ducts  36  or  51  and from the rotor itself depending upon design requirements.  
         [0127]     In the position of the panel or wall  38  shown in  FIG. 5 , the panel is pivoted downwardly so that is causes the stream of crop material carried over its surface to by-pass the fins and the plenum  31  so that the crop material is directed in its stream directly downwardly toward the ground. This avoids a spreading action when no such spreading is required by the operator.  
         [0128]     Turning now to the embodiment in  FIGS. 8 through 13 , there is shown a similar arrangement used with a conventional rear mounted straw chopper generally indicated at  60 . The straw chopper is of a conventional nature and includes a hub  61  carrying blades  62  from an inlet  63  to an outlet  64 . The tailboard  65  is mounted on pivotal movement on a transverse pivot mounting  66  and adjustable by a bracket  67 . The tailboard carries fins  68 . The chopper is surrounded by a housing  69  including a top wall  70  and a bottom wall  71  which confines the flow of the material from the inlet to the outlet  64  and onto the tailboard  65  and the fin  68 .  
         [0129]     As previously described the fins are mounted at varying angles across the width of the tailboard to provide the spread pattern with the fins being adjustable in inclination as previously described.  
         [0130]     The blades  62  co-operate with stationary blades  73  in the chopping action. All these arrangements are of course conventional and well known to one skilled in the art so that the details are necessarily described since they may vary.  
         [0131]     The blades  62  may be wholly straight chopping blades or may include paddle blades as is well known from the previous patents by Redekop defined herein.  
         [0132]     The conventional chopper thus defined is modified by the addition of supplemental air from a duct  75  which communicates the air to a plenum  76 .  
         [0133]     The source for the air to the duct  75  can be provided by any suitable fan arrangement driven from the combine harvester. In the example shown, the fan arrangement comprises an end fan  77  mounted on an end of the rotor and generating an air stream through an outlet nozzle  78  of the fan which enters into the open end  75 A of the duct  75 . However the fan maybe separate from the rotor and it may be mounted at any suitable location on the combine harvester. There may be a single fan generating air to a single duct  75  or there may be two fans generating air separately to two separate ducts  75  which feed the plenum separately. In the embodiment shown, there is a single duct  75  from a single fan mounted at one end of the rotor and the duct  75  communicates to a center location on the plenum  76 . The plenum  76  is shown in more detail in  FIG. 13  and in  FIG. 9 .  
         [0134]     On the bottom wall  71  of the housing of the rotor  61  is mounted the plenum  76 . The plenum includes a bottom wall  80  which generally follows the shape of the bottom wall  71  so that between the walls  71  and  80  is defined an air passageway  82  for the air from the duct  75 . The plenum includes a connecting piece or collar  83  which is shaped to receive the end  75 B of the duct  75  with the collar having an upper wall  84  which extends from the duct upwardly to the underside of the bottom wall  71  so that the upper part of the air duct  82  is closed by the wall  71  without preparation allowing air into the housing of the rotor.  
         [0135]     The duct  82  is defined by two side walls  85  and  86  which diverge outwardly from the duct  75  and the collar  84  to define a discharge nozzle  87  at the trailing edges  85 B and  86 B of the walls  85  and  86 . These trailing edges are spaced apart by the width of the bottom wall  71  so as to define the mouth  87  which extends to the sides of the discharge opening  64  of the straw chopper  60 .  
         [0136]     The air duct  82  is further defined a V shaped guide wall  88  defining two wall portions  89  and  90  which converge to an apex  91  and diverge to trailing edges  89 B and  90 B at the mouth  87 . In this way the wall  85  cooperates with the wall  89  to define a first duct portion  82 A and the wall  90  cooperates with the wall  86  to define a second duct portion  82 B. The duct portion  82 A discharges its air at a discharge mouth  82 C which forms part of the mouth  87  and the duct  82 B discharges air at a discharge mouth  82 D. A central section  87 A of the mouth  87  is free from air since it is prevented from reaching this area by the diverging walls  89  and  90 . Thus again, as in the previous embodiment, the air stream is separated into two stream sections exiting from discharge nozzles  82 C and  82 D located underneath the bottom wall  71  at the discharge  64 . Thus the mouth  87  is located underneath the discharge  64  so as to mix with the straw exiting the discharge  64  as it enters onto the tailboard  65 .  
         [0137]     The airstream through the exit nozzles  82 C and  82 D can be adjusted again by valves or baffles  92  on manually adjustable levers  93  similar to the butterfly valves previously described in the previous embodiment.  
         [0138]     As best shown in phantom in  FIG. 10 , and also in the rear view of  FIG. 12 , the discharge nozzles  82 C and  82 D are arranged to direct air onto the outermost three of the fins indicated at  68 A,  68 B and  68 C. Thus the straw entering onto these three fins has the stream air supplemented by the supplemental airstream to increase the velocity of the straw stream in these areas to again improve the spread and distribution of the straw across the spread pattern.  
         [0139]     While the preferred embodiments of the invention have been described above, it will be recognized and understood that various modifications may be made therein, and the appended claims are intended to cover all such modifications which may fall within the spirit and scope of the invention.