Combine harvesters having reversible return systems, and related methods

1 . A combine harvester comprising:

a feederhouse configured to convey a crop material from a harvesting header;

a threshing system configured to receive the crop material from the feederhouse and separate straw therefrom;

a cleaning system below the threshing system and configured to separate grain from chaff of the crop material, the cleaning system comprising:

a reversible return system configured to receive the crop material from the threshing system;

a grain pan below the return system;

at least one oscillating sieve configured to receive the crop material from the grain pan; and

a blower configured to direct air rearward and upward through the at least one oscillating sieve;

wherein the return system comprises a return pan configured to be tilted between a first orientation and a second orientation, wherein in the first orientation, a major upper surface of the return pan is sloped downward toward a forward end of the combine harvester, and wherein in the second orientation, the major upper surface of the return pan is sloped downward toward a rear end of the combine harvester, wherein the return system is operable to deliver the crop material to a forward end of the grain pan in a first operating mode, and wherein the return system is operable to deliver the crop material to a rearward end of the grain pan in a second operating mode.

2 . The combine harvester of claim 1 , further comprising a motor configured to oscillate the return pan.

3 . The combine harvester of claim 1 , wherein in the first orientation, the return pan is coupled to a rear pan such that oscillation of the rear pan drives oscillation of the return pan.

4 . The combine harvester of claim 1 , wherein in the second orientation, the return pan is coupled to the grain pan such that oscillation of the grain pan drives oscillation of the return pan.

5 . The combine harvester of claim 1 , wherein the return system comprises at least one reversible endless conveyor belt.

6 . The combine harvester of claim 5 , further comprising at least one sloping wall configured to direct the crop material from the threshing system to the at least one reversible endless conveyor belt.

7 . The combine harvester of claim 1 , wherein the return system comprises at least one reversible auger.

8 . The combine harvester of claim 7 , further comprising at least one sloping wall configured to direct the crop material from the threshing system to the at least one reversible auger.

9 . The combine harvester of claim 1 , wherein the threshing system comprises:

at least one threshing rotor configured to thresh the crop material and separate straw therefrom; and

at least one separator grate below the at least one threshing rotor.

10 . The combine harvester of claim 1 , wherein the at least one oscillating sieve comprises:

a chaffer; and

a lower sieve below the chaffer.

11 . A method of operating a combine harvester having a reversible return system configured to receive crop material from a threshing system and deliver the crop material to a chaffer, the method comprising:

cutting a first crop in a first agricultural field;

threshing the first crop in the threshing system;

transferring the threshed first crop to the reversible return system;

translating the threshed first crop with the return system forward relative to a direction of travel of the combine harvester to the grain pan;

stratifying and transferring the threshed first crop rearward on the grain pan to a chaffer;

changing an operating mode of the reversible return system;

cutting a second crop in a second agricultural field;

threshing the second crop in the threshing system;

transferring the threshed second crop to the reversible return system;

translating the threshed second crop with the return system rearward relative to the direction of travel of the combine harvester; and

transferring the threshed second crop to the chaffer.

12 . The method of claim 11 , wherein harvesting the second crop comprises harvesting corn.

13 . The method of claim 11 , wherein translating the threshed second crop rearward relative to the direction of travel of the combine harvester with the return system comprises transferring the threshed second crop to a rear of the grain pan.

14 . The method of claim 11 , wherein a mass flow rate of the second crop to the chaffer is higher than a mass flow rate of the first crop to the chaffer.