Abstract:
An infeed assembly for a rotary combine has an impeller for directing crop materials outwardly and rearwardly. The impeller is arranged on the infeed section of the rotor and includes impeller blades that redirect the incoming mat-like crop materials into a whirling, circulatory motion and also translates the crop materials rearward towards the rotor&#39;s threshing section. Each blade has a leading edge that is swept back in two dimensions. Each leading edge is simultaneously swept back circumferentially away from the direction of impeller rotation and axially towards the rotor&#39;s threshing section. The pitch of each blade increases for a predetermined distance rearwardly.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to agricultural combines. It relates particularly to rotary combines and, more particularly, to the rotor assembly. 
     BACKGROUND OF THE INVENTION 
     A well-known form of harvesting machine is a rotary combine. A typical combine includes a crop harvesting apparatus which reaps grain stalks and feeds the grain stalks to a separating or threshing apparatus. The grain stalks or other crop materials harvested in the field are moved rearwardly from a crop harvesting header assembly and introduced for threshing to the rotor assembly by a crop feeder assembly. 
     In a rotary combine, the rotor assembly includes a generally tubular rotor housing mounted in the combine body. A driven rotor is coaxially mounted within the housing. The rotor comprises an infeed section and a cylindrical threshing section, and is supported at opposite ends by front and rear bearing assemblies. 
     The cylindrical threshing section of the rotor and the rotor housing mount cooperating threshing elements which separate grain from other material in a threshing zone. The crop material is threshed as it spirals around the rotor threshing section and passes through openings in the rotor housing. 
     As discussed in Tanis U.S. Pat. No. 5,387,153, assigned to the same assignee as the present invention, the ability to transfer crop materials from the feeder assembly to the threshing zone of the rotor assembly is a key to efficient combine operations. Most rotary combine rotors include an infeed section impeller comprised of a series of impeller blades arranged at a forward end of the rotor. The impeller blades rotate within a shroud which is a part of the rotor housing. During harvesting operations, the generally linear movement of the crop materials received from the feeder assembly is converted by the rotating impeller blades into a rotating, circulatory movement, in a rearward and outward direction. 
     When rotary combines are used on certain long-stemmed leguminous or grassy crops, such as windrowed perennial or annual rye grass, clover, and bent grass, there is a potential for portions of such grassy crops to extend into the impeller blades while other portions remain partially engaged with the feeder assembly. The latter portions tend to move toward the axis of rotation of the rotor assembly, and may wrap about the front rotor bearing. 
     Long-stemmed leguminous or grassy crops also have a tendency to wrap around or “hairpin” about the leading edge of the impeller blades. This hairpinning action can create a buildup of crop materials on the aforementioned leading edge, which reduces the effectiveness of the impeller and further reduces combine efficiency. 
     Numerous impeller designs, including that disclosed in the Tanis patent, have been proposed to prevent crop materials from becoming entangled with the front rotor bearing and prevent hairpinning about the impeller blades&#39; leading edges. None has been thoroughly successful in doing so, however. Furthermore, these designs suffer from the complexity associated with assembly from a multitude of individual parts, and the higher costs associated therewith. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the invention to provide an improved infeed section impeller for a rotary combine. 
     It is another object to provide an impeller which directs crop material flow outwardly from the impeller axis in a more effective manner. 
     It is still another object to provide an impeller, including blades, which is cast in one piece. 
     The foregoing and other objects are realized in an infeed impeller which comprises a plurality of impeller blades cast in one piece with a frustoconical impeller body. The impeller blades impart a rotating, circulatory motion to the mat-like crop which flows in from the feeder assembly. Each impeller blade has a leading edge that engages the crop material as it enters from the feeder assembly. This engagement is the first contact between the crop material and the rotating impeller. According to the invention, each leading edge is swept back as it extends outwardly, and circumferentially, away from the impeller body. In addition, according to the invention, the pitch of each impeller blade, or flight as it is sometimes called, varies from front to back along the impeller body. The pitch increases for a predetermined distance along the impeller body and then remains constant for the remainder of the impeller body length. 
     The aforedescribed impeller blade leading edge configuration is created by generating a leading edge trace profile wherein any inner diameter is forward of any outer diameter on that edge. In addition, the leading edge has varying pitch because the blade is formed with an increasing pitch for a predetermined distance rearwardly of the front of the impeller. The pitch starts at 400 mm/rev. and increases to 900 mm/rev., just short of midway along the impeller. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention, including its construction and method of operation, is illustrated more or less diagrammatically in the drawings, in which: 
     FIG. 1 is a side elevational view of a portion of a rotary combine, showing in partial section a crop feeder assembly, a rotor assembly and a rotor including an infeed section with an impeller embodying features of the invention; and 
     FIG. 2 is an enlarged sectional view of the impeller seen in FIG. 1; and 
     FIG. 3 is a front elevational view of the impeller as seen in FIGS. 1 and 2, with parts removed; 
     FIG. 4 is perspective view of the impeller embodying features of the invention; 
     FIG. 5 is a side elevational view of the impeller; and 
     FIG. 6 is a graphic illustration of the blade pitch along the length of the impeller. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, and particularly to FIG. 1, a self-propelled rotary combine is seen generally at  10 . The combine  10  includes a body  14  supported by front wheels  12  (the rear wheels are not shown). The combine  10  also includes an operator&#39;s cab  16 . 
     The combine  10  is powered by an engine (not shown), suitably supported within the body  14 . The transfer of power from the engine to various driven components of the combine is effected conventionally. 
     The combine  10  is provided with a crop harvesting header assembly  18  for cutting and gathering crop materials. The header assembly  18  cuts and directs crop materials into a crop feeder assembly  20 , including a conveyor  21 . The conveyor  21  carries crop materials in a layer or mat toward a rotor assembly  22 , which threshes the grain from materials other than grain. 
     The rotor assembly  22  is supported in a conventional manner inside the body  14 . The rotor assembly  22  includes a tubular rotor housing  24  mounted in a fore-and-aft direction in the body  14 . A rotor  26  is mounted coaxially within the rotor housing  24 , for rotation on the axis A. 
     Referring also to FIG. 2, the rotor  26  is a hollow drum rigidly affixed to a shaft  42  extending coaxially through it. The rotor  26  includes an infeed section  62  and a threshing section  64 . The infeed section  62  comprises an impeller  30  including an impeller body  31  and two impeller blades  32  extending outwardly therefrom. 
     At its forward end, the rotor housing  24  includes a transition shroud  25  around the infeed section  62 . The transition shroud  25  encloses the impeller  30 . The front end  57  of the shroud is closed by a panel  58  over its upper half, and open at  59  over its lower half, for crop materials to enter. 
     The impeller  30  preferably includes two identical impeller blades  32  which are equally spaced from each other around, and extend radially outwardly from, the impeller body  31 . The impeller  30  may comprise more than two blades  32  without departing from the spirit of the present invention, however. 
     Referring now also to FIGS. 3-5, each impeller blade  32  has a front face  33 , a back face  34 , a leading edge  35 , an outer edge  36  and a trailing edge  37 . The trace generated by the outer edges  36  of the two impeller blades  32  during rotation of the impeller  30  approximates the frustum of a cone having a cone angle which is substantially equal to that of the adjacent transition shroud  25 . Accordingly, a narrow, annular space is defined between the outer edges  36  of the impeller blades  32  and the inner surface of the adjacent shroud  25 , as seen in FIG.  2 . Crop material moves rearwardly toward the threshing section  64  through this space during operation, assisted by a plurality of spiral transport vanes  40  mounted inside the transition shroud  25 . 
     As previously pointed out, the rotor drum  26  is fixed to the shaft  42 , which supports the rotor  26  for rotation with the shaft on the axis A. The shaft  42  is rotatably supported in the combine body  14  at its front end in a conventional bearing assembly  46 . The bearing assembly  46  includes a suitable bearing  47  in which the front end of the shaft  42  is journalled. 
     The impeller body  30  is frustoconical in shape, as previously pointed out. At its smaller front end, a cup-shaped front wall  70  is fixed to the shaft  42  on a collar  71 . Extending outwardly from the collar  71 , in the wall  70 , are a pair of anti-winding vanes  80 . 
     As discussed in the aforementioned Tanis patent, anti-winding vanes  80  are used to protect the bearing  47  from debris and other foreign material drawn toward it during operation of the rotor assembly  22 . As the anti-winding vanes  80  rotate with the rotor  26 , they cooperate with vanes (not shown) on the bearing assembly  46  to force debris radially outward away from the axis A of the rotor. 
     According to the present invention, each impeller blade leading edge  35  is swept back in two dimensions from the point near the forward end of the impeller body  31  where the blade  32  originates. The edge  35  is swept back circumferentially relative to the direction of rotor rotation, i.e., each point on an edge  35  leads, in rotation, every other point farther from the axis of rotation A that is on the same leading edge. The leading edge  35  is also swept back axially so that each point on the edge  35  which is further from the axis A is disposed rearwardly of every point closer to the axis on the edge. 
     In the embodiment illustrated, the swept back profile of the leading edge  35  originates at a point on the frustoconical impeller body  30  where the body is 238 mm in outside diameter. The leading edge is swept back 97 mm along the axis A of the impeller body  30  to where it meets the outer edge  36  of the blade  32 . 
     In the embodiment illustrated, the impeller body is 469.9 mm in length from its front face, where the leading edge  35  of each blade  32  starts, to its back face where the trailing edge  37  of each blade terminates. Referring now to FIG. 6, between these points (X and Z), the pitch of each blade varies according to the invention. 
     FIG. 6 illustrates a hypothetical blade without a swept back front edge, in order to better explain blade pitch variations embodied in the invention. Each blade begins its helical path rearwardly from point X at a pitch of 400 mm/rev. For the first 200 mm rearwardly along the axis A, the pitch increases uniformly until at point Y, it is 940 mm/rev. This pitch is then maintained for the remaining 269.9 mm of the impeller body. 
     During operation, incoming crop materials from the feeder assembly  20  engage the rotating impeller blades  32  and are directed outwardly and rearwardly along the swept back leading edges  35 , away from the rotor shaft  42 . This action prevents crop materials from becoming entangled around the forward end of the shaft  42 , and thereby prolongs the useful life of the bearing  48 . Additionally, the swept back leading edge  35  prevents crop materials from hairpinning around the leading edge, which would lead to an inefficient buildup of crop materials about the leading edge. 
     At the same time, the progressively increasing pitch of the impeller blades or flights  32  moves crop materials rearwardly at a faster and faster pace for the first 200 m of axial travel. This also serves to reduce the danger of crop entanglement and hairpinning. 
     According to the invention the impeller body  30  and impeller  31  are preferably cast in one piece. The one piece, cast construction is less expensive than a multiple piece assembly. Additionally, a one piece impeller body  31  and blades  32  has a more smooth, unbroken surface, without crevasses between impeller elements that are associated with multiple piece assemblies, and which could entrap crop materials. 
     While a preferred embodiment of the invention has been described, it should be understood that the invention is not so limited, and modifications may be made without departing from the invention. The scope of the invention is defined by the appended claims, and all devices that come within the meaning of the claims, either literally or by equivalence, are intended to be embraced therein.