Combine harvester with multi-stage grain preparation and related methods for operating a combine harvester

1. A combine harvester comprising:

a cleaning arrangement comprising one or more sieves and a main blower; and

a preparation arrangement configured to receive a mixture of grain and residue material from a threshing system and to transport the mixture towards the cleaning arrangement, wherein the preparation arrangement comprises multiple preparation stages, each of said stages being configured to transport the mixture over a given distance between a front edge and a rear edge of the respective stage, with an air gap being present between each pair of consecutive stages, and wherein the preparation system further comprises a separate blower that is separate from the main blower, the separate blower configured to direct air towards at least one of the air gaps, to thereby blow at least a portion of the residue material from the mixture towards the rear of the combine harvester, wherein the preparation arrangement comprises a plate provided with fins mounted transversally with respect to the longitudinal direction of the harvester, each fin representing one of said preparation stages, said plate further comprising one or more openings between at least one pair of consecutive fins, said one or more openings being suitable for allowing the passage of an air stream produced by the separate blower, and directed towards the gap between the pair of consecutive fins,

wherein the openings are sized to prevent a substantial portion of the grain and residue material from passing through the openings in the direction opposite the air stream produced by the separate blower.

2. Combine harvester according to claim 1 , wherein at least one of the preparation stages comprises a preparation pan, configured to exhibit a reciprocating movement for transporting said mixture.

3. Combine harvester according to claim 1 , wherein the plate is inclined at a downward slope from the front to the back of the harvester, and wherein the fins are horizontal or upwardly inclined.

4. Combine harvester according to claim 1 , wherein the plate is configured to be subjected to a reciprocating movement, to thereby move the mixture from the front edge to the rear edge of each fin.

5. Combine harvester according to claim 4 , wherein one of the preparation stages consists of a preparation pan configured to undergo a reciprocating motion, and wherein the plate is attached to said preparation pan.

6. Combine harvester according to claim 1 , wherein at least one of said preparation stages comprises a conveyor comprising a carrier surface configured to exhibit a movement from the front edge of the stage to the rear edge of the stage.

7. Combine harvester according to claim 1 , wherein at least one of said preparation stages comprises an auger bed.

8. Combine harvester according to claim 1 , wherein said separate blower is a fan.

9. Combine harvester according to claim 1 , wherein said separate blower is mounted on the preparation stage immediately preceding the air gap which said separate blower is configured to direct an air stream to.

10. Combine harvester according to claim 1 , wherein said separate blower is mounted on the chassis of the combine harvester.

11. Combine harvester according to claim 1 , wherein at least one of the preparation stages is provided at its rear edge with a deflector for deflecting the direction of the air flow directed at the air gap between said stage and the subsequent stage.

12. Combine harvester according to claim 11 , wherein said deflector is configured to establish a progressive narrowing and subsequent widening of the gap.

13. Combine harvester according to claim 11 , wherein said deflector is provided at the rear edge of at least one of the fins.

14. Combine harvester according to claim 1 , wherein the preparation arrangement consists of the single plate provided with fins.