MATERIAL CONVEYANCE SYSTEM IN A COMBINE HARVESTER

Abstract

A combine harvester is provided with a conveyance system for transporting crop material discharged by overhead grain separating apparatus to a grain cleaning shoe. The conveyance system comprises a series of oscillating pans which move the grain in a generally longitudinal direction. A return pan conveys the collected material forwardly to a front discharge edge from where the material falls onto a stratification pan below. The stratification pan conveys the collected material rearwardly to a rear discharge edge from where the material falls into the grain cleaning shoe. At least one of the return pan and the stratification pan is non-rectangular and has a non-transverse discharge edge.

Claims

1. A combine harvester having a normal forward direction of travel which defines a longitudinal and a transverse direction, the harvester comprising: a crop material conveyance pan having an unperforated floor with a non-rectangular profile as viewed from above; a drive mechanism coupled to the crop material conveyance pan and configured to drive the crop material conveyance pan in an oscillating manner.

2. The combine harvester of claim 1, wherein the crop material conveyance pan has a discharge edge disposed at a non-zero angle to a transverse vertical plane.

3. The combine harvester of claim 2, further comprising a grain separating apparatus, wherein the crop material conveyance pan comprises a return pan positioned under the grain separating apparatus and configured to catch crop material separated by the grain separating apparatus and convey the crop material in a generally forward direction to the discharge edge.

4. The combine harvester of claim 3, further comprising an oscillating grain pan positioned to catch crop material falling from the discharge edge of the return pan, and convey the crop material rearward to a grain cleaning shoe.

5. The combine harvester of claim 3, wherein the grain separating apparatus comprises an axial-flow crop processing rotor having a rotation axis which is aligned fore and aft, the rotor having a downturning side and an upturning side.

6. The combine harvester of claim 5, wherein the grain separating apparatus comprises a pair of axial-flow crop processing rotors having respective rotation axes which are aligned fore and aft and mutually side-by-side, and wherein each rotor has a downturning side and an upturning side.

7. The combine harvester of claim 6, wherein the rotors are driven to rotate in opposite directions defining transversely inner upturning sides and outer downturning sides.

8. The combine harvester of claim 3, further comprising first and second oscillating return pans positioned under the grain separating apparatus, wherein the first and second oscillating return pans are longitudinally offset from one another, wherein the first and second oscillating return pans are each configured to catch crop material separated by the grain separating apparatus and convey the collected material in a generally forward direction to a respective discharge edge, and wherein at least one of the first and second oscillating return pans has a non-transverse discharge edge.

9. The combine harvester of claim 8, wherein the first oscillating return pan is positioned under a front portion of the grain separating apparatus and the second oscillating return pan is positioned under a rear portion of the grain separating apparatus.

10. The combine harvester of claim 8, wherein the first and second oscillating return pans each exhibit non-transverse discharge edges.

11. The combine harvester of claim 8, wherein a rear edge of the first oscillating return pan is positioned aft of, and higher than, at least a portion of the discharge edge of the second oscillating return pan.

12. The combine harvester of claim 8, wherein a transverse section of at least one of the first and second oscillating return pans is horizontal.

13. The combine harvester of claim 3, wherein the return pan comprises a transversely inclined floor portion.

14. The combine harvester of claim 13, wherein the return pan comprises a contoured floor portion configured to guide the crop material sideways under gravity to a trough, wherein the discharge edge comprises a forward edge zone and a rearward edge zone disposed rearward of the forward edge zone, and wherein the trough is configured to guide the crop material to the forward edge zone.

15. A crop material conveyance pan for a combine harvester having an unperforated floor with a non-rectangular profile as viewed from above.

16. The crop material conveyance pan of claim 15, wherein a discharge edge of the crop material conveyance pan is curved.

17. The crop material conveyance pan of claim 15, wherein a discharge edge of the crop material conveyance pan is linear and oriented at an angle relative to an opposite edge of the crop material conveyance pan.

18. The crop material conveyance pan of claim 15, wherein a discharge edge of the crop material conveyance pan comprises a plurality of linear portions, wherein at least one of the linear portions is oriented at an angle relative to an opposite edge of the crop material conveyance pan.

19. The crop material conveyance pan of claim 15, wherein the crop material conveyance pan comprises a transversely inclined floor portion.

20. The crop material conveyance pan of claim 15, wherein a floor portion of the crop material conveyance pan has a curved profile as viewed from behind.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Further advantages of the invention will become apparent from reading the following description of specific embodiments with reference to the appended drawings in which:

[0068] FIG. 1 is a schematic sectional view of a combine harvester having a known crop processing architecture;

[0069] FIG. 2 is a schematic perspective view of a crop material conveyance system in a combine harvester in accordance with a first embodiment of the invention;

[0070] FIGS. 3 and 4 are schematic plan and sections views respectively of the crop material conveyance system of FIG. 2;

[0071] FIG. 5 is a schematic perspective view of a crop material conveyance system in a combine harvester in accordance with a second embodiment of the invention;

[0072] FIG. 6 is a schematic plan view of the crop material conveyance system of FIG. 5;

[0073] FIG. 7 is a schematic perspective view of a crop material conveyance system in a combine harvester in accordance with a third embodiment of the invention;

[0074] FIG. 8 is a schematic sectional view of the crop material conveyance system of FIG. 7;

[0075] FIG. 9 is a schematic perspective view of a return pan in a combine harvester in accordance with a fourth embodiment of the invention;

[0076] FIG. 10 is a schematic plan view of the crop material conveyance system of FIG. 9;

[0077] FIG. 11 is a schematic sectional view of the return pan of FIG. 10 taken along the line XI-XI and showing the vertical stratification of grain and MOG;

[0078] FIG. 12 is a schematic perspective view of a crop material conveyance system in a combine harvester in accordance with a fifth embodiment of the invention;

[0079] FIG. 13 is a schematic plan view of the crop material conveyance system of FIG. 12;

[0080] FIG. 14 is a schematic sectional view of the return pan of FIG. 13 taken along the line XIV-XIV and showing the vertical stratification of grain and MOG;

[0081] FIG. 15 is a schematic perspective view of a crop material conveyance system in a combine harvester in accordance with a sixth embodiment of the invention;

[0082] FIG. 16 is a schematic plan view of the crop material conveyance system of FIG. 15;

[0083] FIG. 17 is a schematic perspective view of a crop material conveyance system in a combine harvester in accordance with a seventh embodiment of the invention;

[0084] FIG. 18 is a schematic plan view of the crop material conveyance system of FIG. 17;

[0085] FIG. 19 is a schematic perspective view of a crop material conveyance system in a combine harvester in accordance with a eighth embodiment of the invention; and,

[0086] FIG. 20 is a schematic plan view of the crop material conveyance system of FIG. 19.

DETAILED DESCRIPTION

[0087] The combine harvester depicted in FIG. 1 has been described above in relation to the component architecture and the general crop material flow through the combine. Reference is invited to the description above. Reference numbers used in FIG. 1 for the stratification pan 40, and cleaning shoe will be reused in the following embodiments.

[0088] The present invention relates to the material conveyance system disposed below the grain separating apparatus and employed to convey the grain and MOG falling therefrom to the cleaning shoe 42. Although aspects of the invention can be applied to the stratification pan 40, or a cascade pan, the specific embodiments described hereinafter involve application of the present invention to the return pan 44, or a return pan system, for conveying the collected material forwardly in the direction F.

[0089] Relative terms such as forward, rearward, transverse, lateral, longitudinal, and sideways will be made with reference to the normal forward direction of travel of the combine 10 and indicated by arrow F. The terms vertical and horizontal will be made with reference to the level ground 101 upon which the combine 10 is disposed. In other words the Cartesian axes of ‘longitudinal’, ‘transverse’, and ‘vertical’ are made in relation to the frame 12 of combine 10 and are not affected by any slope in the ground. The terms “upstream” and “downstream” are made with reference of the general direction of crop flow along the material conveyance systems described.

Planar Return Pan

[0090] In a first embodiment illustrated in FIGS. 2, 3 and 4, a crop material conveyance system 100 comprises a return pan 138 and a stratification pan 40. It should be understood that the conveyance system 100, and further systems to be described, can replace the return pan 38 and stratification pan 40 of the combine 10 described with reference to FIG. 1.

[0091] Both the return pan 138 and stratification pan 40 are coupled to a drive mechanism (not shown) for driving the respective pans in an oscillating manner. The pans 138, 40 are disposed below grain separating apparatus 126 which, in this example, comprises a single axial flow crop processing rotor having a rotation axis X.sub.1 which is aligned fore-and-aft and transversely centered. The grain separating apparatus 126 is represented schematically (in dashed lines) to reveal the underlying conveying system 100.

[0092] It should be understood that although referred to as grain “separating” apparatus, the axial flow processing rotors described in the following embodiments may additionally serve a threshing function. For example, a front portion of the processing rotor may comprise threshing elements whereas a rear portion of the rotor comprises separating elements.

[0093] As will now be apparent from reading the above description, the material conveyance system 100 serves to collect grain and MOG discharged by the grain separating apparatus 126 and convey the collected material to the cleaning shoe 42. As in known systems the return pan 138 conveys the collected grain and MOG forwardly to a front discharge edge 144 from which the material falls onto the underlying stratification pan 40 which then conveys the material rearwardly to a rear discharge edge 46. As will be apparent from FIG. 4, grain and MOG falling from the front of separating apparatus 126 falls directly onto stratification pan 40.

[0094] Return pan 138 is mounted inside the envelope of combine 10 so as to be inclined downwardly towards the front end so as to exploit gravity for forward conveyance of the collected material. As with known return pans, the major, upward facing, surface thereof defines a floor which may include a rippled or corrugated surface profile which assists in conveyance of the material. The return pan 138 is trapezium-shaped having a first long side 171, a second shorter side 172 opposite the first long side 171, a rear edge 173 and a front discharge edge 144 which is aligned at a non-zero angle θ.sub.1 to a hypothetical transverse vertical plane indicated in FIG. 3 by dashed line T.sub.1. The two longitudinal sides 171,172 and the rear edge 173 are provided with a material retaining lip 174 whereas the front discharge edge 144 is open to allow material to fall therefrom.

[0095] Discharge edge 144 is disposed at an angle θ.sub.1 to the transverse direction or to a transverse vertical plane T.sub.1. As a result the effective discharge edge has a length w′ which is longer than the width w of pans 40, 138. Although the height h between the discharge edge 144 and the underlying stratification pan 40 remains the same, the increase in length of the effective discharge edge w′ increases the window through which material can pass between the pans 40, 138 thus reducing the risk of blockage and/or allowing for increased material throughput.

[0096] As has been described above, axial-flow grain separating apparatus discharges a higher volume of material on the down-turning side d than the up-turning side u, as is the case with single rotor processor 126 illustrated. The transverse angle θ.sub.1 of the discharge edge 144 is such that material incident on down-turning side dis carried further forward onto stratification pan 40 than material incident on up-turning side u. This is illustrated in FIG. 3. Grain and MOG falling on down-turning side d is conveyed generally forwardly as shown by arrows D to a first forward edge zone z.sub.1 of discharge edge 144 from where the material falls onto the stratification pan 40. Grain and MOG falling onto up-turning side u is conveyed forwardly and longitudinally as indicated by arrows u to a second, rearward, edge zone z.sub.2 which is disposed rearward (towards the rear of the combine) than forward edge zone z.sub.1.

[0097] It is recognized that the high volume of material falling onto down-turning side d has a higher grain-to-MOG ratio than the material falling onto upward turning side u. Advantageously, the grain-rich material on the down-turning side d is carried further forward onto the stratification pan 40 thereby increasing the transit path thereof and increasing the opportunity for the grain on the stratification pan 40 to settle to the bottom layers before being presented to the cleaning shoe 42. This is in contrast to the more MOG-rich material on the up-turning side u which falls from rearward edge zone z.sub.2 towards the rear of stratification pan 40 and onto the top of grain already settled thereon having falling directly from the front end of grain separating apparatus 126.

[0098] In a second embodiment illustrated in FIGS. 5 and 6, the above-described angled discharge edge is applied to a grain conveyance system 200 disposed below a twin-rotor, axial-flow, grain separating apparatus having rotors 226 represented by dashed lines. In the embodiment illustrated, and as is common with twin rotor systems, the grain separating rotors rotate in opposite directions as indicated by arrows R wherein the sides adjacent the longitudinal center line of the combine turn upwardly and the sides nearest the outside of the combine turn downwardly. The rotation axes of rotors 226 are illustrated in FIG. 6 by lines X.sub.R and X.sub.L. The rotation directions of the rotors 226 define a central up-turning zone u and two outer down-turning zones d.

[0099] The grain conveyance system 200 comprises a return pan 238 and a stratification pan 40, the latter having the same rectangular profile to that described above.

[0100] Focusing on the differences with respect to the first embodiment, the discharge edge 244 comprises a central rearward edge zone z.sub.3 and forward edge zones z.sub.4, z.sub.5 disposed forwardly and to each side of the rearward edge zone z.sub.3. It should be understood from FIG. 6 that the rearward edge zone z.sub.3 resides below the up-turning zone u of rotors 226 whereas each forward edge zone z.sub.4, z.sub.5 resides below the respective down-turning zones d. Adopting the same principles as in the first embodiment, the high volume of grain-rich material falling on the down-turning sides d is conveyed forwardly to forward edge zones z.sub.4, z.sub.5 whereas the more MOG-rich material falling on up-turning side u is discharged onto the stratification pan 40 further back.

[0101] Discharge edge 244 is predominantly curved having a concave-shaped profile when viewed from above. However, it should be understood alternative profiles can be employed whilst still embodying the invention, wherein the edge zone z.sub.3 corresponding to the up-turning zone u is disposed rearward of the edge zones z.sub.4, z.sub.5 corresponding to the down-turning zone d. It should also be understood that the embodiment of FIGS. 5 and 6 can be adapted for grain separating rotors which turn in different directions to those shown.

[0102] It will be appreciated that the effective discharge edge 244 is longer than the width of the pans 40, 238 and, as a result, the risk of blockage is reduced whilst increasing the capacity of higher material throughput.

[0103] In a third embodiment (FIGS. 7 and 8) a material conveyance system 300 comprises a dual return pan system and a stratification pan 40. The principle of a dual return pan is described in International Patent Application Publication WO 2015/062965 A1, wherein two separate return pans are employed one behind the other, each having respective front discharge edges. A rear return pan 338 is disposed under a rear portion of twin rotor separating apparatus 226 and has a similar construction and floor profile to that of return pan 238 described in the previous embodiment. A second, front, return pan 378 is located in front of the rear return pan 338 and serves to collect grain and MOG from a front portion of the separating apparatus 226.

[0104] In short, the dual return pan system exploits the recognition that the majority of the grain discharged by the separating apparatus 226 falls from a front portion. The front return pan 378 collects this high volume of grain rich material and conveys this to a front region of stratification pan 40 whereas the rear return pan 338 collects material richer in MOG and discharges such onto a rear region of the stratification pan. As a result, a higher proportion of the separated grain has an increased transit path on the stratification pan thus increasing the effect of stratification upstream of the cleaning shoe 42. The MOG-rich material discharged from the discharge edge 344 of rear return pan 338 falls onto the grain layers on a rear region of stratification pan 40 thus enhancing the stratification further. Furthermore, the dual return pan system spreads the total volume of material falling from the separating apparatus 226 thus reducing the risk of blockage and increasing potential throughput capacity.

[0105] As can be seen from FIG. 7, both the front and rear return pans 378, 338 have a respective discharge edge 380, 344 which includes a central rearward edge zone corresponding to the up-turning side of separating rotors 226 and forward edge zones located either side of the rearward edge zones. The effective length of each discharge edge 344, 380 is increased as per the above-described embodiments thus reducing the risk of blockage. Furthermore, the grain-rich material falling on the down-turning sides of the separating rotors 226 is conveyed further forward onto the stratification pan 40 than the material falling onto the up-turning side.

[0106] The discharge edge 380 of the front return pan 378 has a substantially V-shaped profile whereas the discharge edge 344 of rear return pan 338 is curved. It should be understood that the profiles of the discharge edges are shown merely by way of example.

[0107] In an alternative (not illustrated) embodiment, the rear edge of front return pan 378 may be shaped so as to have a concave-shaped profile which present a larger ‘window’ to material falling from the front edge 344 of the rear return pan 338, thus reducing the risk of blockage and improving capacity thereof.

[0108] The return pan, or pans, of the above-described embodiments each have a substantially planar floor, albeit corrugated for assisting material conveyance. Advantageously, implementation of such return pans, and their associated benefits, into today's combine models is relatively straightforward and simply requires adaptation of the profile of the leading discharge edge without any requirement to adapt the drive mechanism or substructure of the pan.

Contoured Return Pans

[0109] In a further aspect of the invention the return pan may be mounted inside the combine so as to have a transversely inclined floor portion which, with the assistance of gravity, imparts a sideways or lateral force on the conveyed material so as to shift the material sideways as it is conveyed forwardly to the discharge edge. Such action can be exploited to laterally distribute the collected grain and MOG to achieve a more balanced distribution of crop material in terms of volume on the stratification pan and ultimately across the width of the cleaning shoe.

[0110] Employed in conjunction with an angled discharge edge as described above, the contoured floor portion preferably guides the crop material sideways to a trough which guides the material to a forward edge zone for reasons which will become apparent below.

[0111] A fourth embodiment is depicted in FIGS. 9, 10 and 11. A single rotor, axial-flow, grain separating apparatus similar to that shown in FIG. 4 has a central longitudinal rotation axis X.sub.1 shown in FIG. 10 and which defines a down-turning side d and an up-turning side u. (The separating apparatus is omitted from FIGS. 9,10 and 11 for reasons of clarity.) As has been mentioned above, a significant proportion of the grain and MOG discharged by the separating apparatus falls from the down-turning side d. Furthermore, a higher proportion of the material volume falls from the front of the separating apparatus than the rear. With reference to FIGS. 9 and 10, a significant proportion of the grain falls from the front end of the down-turning side d directly onto zone ‘A’ of stratification pan 40.

[0112] Return pan 438 has a front discharge edge 444 which is angled with respect to a transverse vertical plane so as to provide a forward edge zone z.sub.6 and a rearward edge zone z.sub.7. As best seen in FIG. 10, the forward edge zone z.sub.6 resides under the up-turning side u of the separating apparatus whereas the rearward edge zone z.sub.7 resides under the down-turning side d. (This is in contrast to the embodiment of FIG. 3 involving a planar return pan).

[0113] A significant proportion of the floor of return pan 438 is transversely or laterally inclined so as to form a lateral angle θ.sub.2 with the horizontal, represented by dashed line L in FIG. 11. In the embodiment shown the entire length of the floor of return pan 438 is transversely inclined. However, in alterative embodiments only portions of the floor are inclined.

[0114] Grain and MOG incident on the down-turning side d of return pan 438 is guided sideways and forwardly by the slope of the return pan 438 and the oscillating motion thereof towards a trough 482 residing on the up-turning side u. This is represented in FIGS. 9 and 10 by zone ‘B’ and by arrows D.

[0115] Trough 482 is aligned fore and aft and guides grain and MOG to the forward edge zone z.sub.6 on the up-turning side u. Advantageously, the grain and MOG collected by the return pan 438, the majority of which is collected on the down-turning sided, is shifted laterally by the sloping return pan 438 to the up-turning side u thus laterally balancing the volume of separated material on the stratification pan 40, and ultimately in the cleaning shoe 42.

[0116] The transit of grain and MOG across the floor of stratification pan 438 leads to some degree of vertical stratification with the heavier grain sinking to the floor whilst the lighter MOG rises to the top. The stratification of grain and MOG on the return pan 438 is enhanced by the provision of trough 482 wherein, as shown in FIG. 11, grain G comes to reside in the bottom of the trough 482 with MOG M resting on top. Due to the transverse inclination θ.sub.2 a lateral spreading of the MOG-rich upper layers occurs as shown in FIG. 11.

[0117] The grain-rich lower layer is discharged from the forward edge zone z.sub.6 whereas only MOG is discharged from the rearward edge zone z.sub.7. Due to the transversely angled discharge edge 444 the grain G is deposited further forward on the stratification pan 40. The MOG-rich material falling from the rearward edge zone z.sub.7 falls on top of the grain that was incident on zone A and has settled on the pan. As a result the stratification of grain and MOG on stratification pan 40 is enhanced.

[0118] In a fifth embodiment (FIGS. 12, 13 and 14) the previous embodiment is adapted for use under a twin-rotor, axial-flow, grain separating apparatus similar to that shown in FIG. 5 but omitted from the drawings in this case for reason of clarity. The two grain separating rotary processors have rotation axes indicated as X.sub.R and X.sub.L and are located above material conveyance system 500 which comprises a return pan 538 and stratification pan 40. The rotation axes X.sub.R, X.sub.L together define a central zone u extending longitudinally and corresponding with the up-turning sides of the rotary processors, and a pair of outer zones d extending longitudinally and corresponding to the respective down-turning sides of the rotors.

[0119] The floor of return pan 538 slopes away transversely from the outer zones d and towards a central longitudinal trough 582. A significant proportion of the grain and MOG falls onto outer zones d from where the material is conveyed forwardly and inwardly towards the trough 582 as indicated by arrows D. As in the previous embodiment, the grain G and MOG M stratify as the material is conveyed across the return pan 538.

[0120] FIG. 14 shows the grain-rich material G residing in the base of trough 582 whilst the MOG M sits on top thereof. Due to the laterally-inclined floor the MOG layer M is laterally stretched leaving the grain focused towards the transverse center.

[0121] Front discharge edge 544 of return pan 538 has a V-shaped protruding profile with a central forward edge zone z.sub.8 flanked by rearward edges z.sub.9, z.sub.10. As in the previous embodiment, forward edge zone z.sub.8 resides under the up-turning sides u of the separating rotors whereas the outer rearward edge zones z.sub.9, z.sub.10 each reside under a respective down-turning side d. This is in contrast to the return pan located under a twin-rotor processor of the second embodiment shown in FIG. 6.

[0122] The transverse extent of the respective edge zones z.sub.8, z.sub.9, z.sub.10 are super-imposed on FIG. 14. It can be seen that the majority of the grain G falls from the forward edge zone z.sub.8 which is more forward on the stratification pan 40 than the MOG M falling from rearward edge zones z.sub.9, z.sub.10. Advantageously, the grain G collected by return pan 538 is disposed towards the front of the stratification pan 40 thereby increasing the transit path thereof and thus the opportunity to stratify upstream of the cleaning shoe 42.

[0123] The laterally spread MOG M falling from the rearward edge zones z.sub.9, z.sub.10 falls onto a rearward zone of the stratification pan 40 thus on top of grain already settled on the pan. In addition to the advantageous longitudinal spread of material on the stratification pan 40, the lateral incline of the return pan 538 deposits the grain G on to a transverse central zone of the stratification pan thus providing a more balanced load thereon.

[0124] In a sixth embodiment (FIGS. 15 and 16) a material conveyance system 600 comprises a stratification pan 40 and a dual return pan system having a rear return pan 638 and front return pan 678. Both the front and rear return pans 678, 638 have transversely-inclined floor portions which steer the collected grain and MOG sideways into a respective trough 682, 684.

[0125] The material conveyance system 600 in accordance with a sixth embodiment is configured to be used under a single-rotor axial flow grain processor having a rotation axis X.sub.1. The floor of front return pan 678 slopes transversely downwardly to the down-turning side d of the rotor whilst the floor of the rear return pan 638 slopes transversely downwardly to the up-turning side u of the processing rotor.

[0126] Front return pan 678 has a transversely angled discharge edge 680 having a forward edge zone z.sub.11 on the down-turning side d and rearward edge zone z.sub.12 on the up-turning side u. Grain and MOG caught by the front return pan 678 is guided laterally to the forward edge zone z.sub.11. Vertical stratification of the grain MOG thereon and the consequential lateral spreading of the grain and MOG layers occurs on front return pan 678 in a similar manner to that of the embodiments described above.

[0127] The design of the rear return pan 638 can be considered a mirror image of the front return pan 678 wherein material caught thereby is laterally steered into trough 682 disposed on the up-turning side u and leading to a portion discharge edge 644 that is displaced forwardly of the portion on the down-turning side d. The movement of material on rear return pan 638 is indicated by arrows D.

[0128] The opposite transverse inclination of the floors of front and rear return pan 678, 638 improves the transverse distribution of crop material in terms of load on the stratification pan 40 whilst also exploiting the advantages of a dual return pan system.

[0129] It should be noted from FIG. 16 that the rear edge 686 of front stratification pan 678 is also transversely angled in the same direction as that of the front edge 680. When viewed from above a gap 688 exists between the rear edge 686 of the front return pan 678 and the front edge 644 of rear return pan 638. This gap permits material to fall directly from the processing rotor overhead directly on to the stratification pan 40.

[0130] In a seventh embodiment (FIGS. 17 and 18) a material conveyance system 700 is adapted to cater for a twin-rotor, axial flow, grain separating processor and comprises a stratification pan 40 and a dual return pan system having a front return pan 778 and a rear return pan 738.

[0131] The front return pan 778 has a floor which is transversely inclined downwardly towards a central zone, or trough, 782 which resides under the up-turning sides of the overhead rotors and corresponds to a central longitudinal zone u. The front discharge edge 780 comprises a central forward edge zone z.sub.13 flanked by rearward edge zones z.sub.14, z.sub.15.

[0132] Although shown as having a V-shaped profile, the discharge edge 780 may take on many alternative forms including a stepped profile or a curved profile by way of example.

[0133] Forward edge zone z.sub.13 corresponds to the zone u whereas the rearward edge zones z.sub.14, z.sub.15 reside under respective down-turning sides d. The central longitudinal trough 782 guides the collected grain and MOG to the forward edge zone z.sub.13 which deposits such material towards the front of the stratification pan 40 in the center thereof. The rearward offset of the outer portions z.sub.14, z.sub.15 of discharge edge 780 allows a significant proportion of grain to fall directly from the separating rotors above onto zones ‘A’ of the stratification pan 40.

[0134] Advantageously, the front return pan 778 serves to balance the volume of material on the stratification pan by depositing the majority of the collected grain onto the central portion between zones A. Any material discharged from rearward edge zones z.sub.14, z.sub.15 is rich in MOG and is thus deposited on top of the already-settled grain on stratification pan 40.

[0135] Rear return pan 738 comprises sloping floor portions which are inclined transversely and downwardly towards a pair of troughs 790 disclosed below the downward turning sides d. A central longitudinal crest 792 is also provided in the profile of the floor of rear return pan 738. Grain and MOG collected by the rear return pan 738 is steered laterally outwardly into troughs 790 all the while stratifying wherein the grain comes to rest in the base of the troughs 790 and the MOG rises to the top and spreads laterally outwardly due to the lateral slope of the floor. The front discharge edge 744 of rear return pan 738 comprises outer forward edge zones z.sub.16, z.sub.17 disposed either side of a central rearward edge zone z.sub.18 together forming an inward V-shaped profile. The grain collecting in the trough 790 is therefore deposited onto the underlying stratification pan 40 further forward than the MOG which is discharged by the rearward edge zone z.sub.18 thus enhancing stratification on the stratification pan 40.

[0136] The rear edge 786 of front return pan 778 has a cut-out section or rather has a concave-shaped profile which reveals a gap 788 when viewed from above. Advantageously, the gap 788 enlarges the window through which material can pass from the discharge edge 744 of the rear return pan 738 thereby reducing the risk of blockage.

[0137] In an eighth embodiment (FIGS. 19 and 20) the dual return pan system described above is configured as a single unitary return pan 838 for use under a twin-rotor axial flow grain separating apparatus having rotation axes X.sub.R, X.sub.L. The return pan 838 comprises a rear portion having a longitudinal central crest 892 and outwardly-inclined floor portions leading to troughs 890, and a front portion having a longitudinal central trough 882 and inwardly-sloping floor portions. An opening 888 is formed in the floor of return pan 838 between the rear portion and the front portion. The opening 888 defines a secondary discharge edge 894 from which material collected on the rear portion of the return pan 838 can be discharged onto the underlying stratification pan 40.

[0138] Grain and MOG incident on the rear portion of return pan 838 is steered laterally outwardly away from the crest 892 and towards troughs 890. The troughs 890 guide the majority of the grain around the opening 888 onto the front portion of return pan 838. Due to the lateral spread of MOG on top of the grain, a portion of the MOG is caused to fall through the opening 888 onto a rear portion of the underlying stratification pan 40. The secondary discharge edge 894 has an inward V-shaped profile as per the discharge edge 744 of the previous embodiment for the same reasons.

[0139] Grain and MOG incident on the front portion of return pan 838, together with grain and MOG conveyed around the opening 888, is steered laterally inwardly towards central trough 882 as shown by arrows Y. Front discharge edge 444 has a positive V-shaped profile similar to that of discharge edge 780 of the previous embodiment for the same reasons.

[0140] In summary, there is provided a combine harvester with a conveyance system for transporting crop material discharged by overhead grain separating apparatus to a grain cleaning shoe. The conveyance system comprises a series of oscillating pans which move the grain in a generally longitudinal direction. A return pan conveys the collected material forwardly to a front discharge edge from where the material falls onto a stratification pan below. The stratification pan conveys the collected material rearwardly to a rear discharge edge from where the material falls into the grain cleaning shoe. At least one of the return pan and the stratification pan is non-rectangular and has a non-transverse discharge edge.

[0141] It should be emphasized that the above-described embodiments of the present disclosure are merely possible examples of implementation, merely set forth for a clear understanding of the principles of the disclosure. Many variations and modifications may be made to the above-described embodiments of the disclosure without departing substantially from the spirit and principles of the disclosure.