A combine harvester comprising a threshing and separating mechanism for threshing and separating crop material and a cleaning device for cleaning threshed and separated grain. The cleaning device comprises a grain pan adapted to receive threshed and separated grain from the threshing and separating mechanism and to progressively convey said grain in the direction of the discharge end of the grain pan. A sieve structure is disposed to receive threshed and separated grain from the grain pan and comprises at least one chaffer sieve having a receiving end at a level below the level of the discharge end of the grain pan. Fan means are operable to direct a cleaning air blast to the sieve structure for cleaning grain therein. A pre-cleaning sieve is disposed between the grain pan and the chaffer sieve and has a receiving end below the grain pan discharge end and further fan means are adapted to direct a cleaning air blast on the fall between the grain pan discharge end and the receiving end of the pre-cleaning sieve.
In a cleaning shoe arrangement for a combine, an elongated grain pan includes a screen portion and receives crop material directly from an open threshing concave and a return pan under the straw walkers. The screen portion is provided with an under air blast and the grain pan thus does double duty--as a conveyor and as a precleaner or "conditioning sieve". Clean grain passing through this screen portion goes directly to the clean grain auger of the cleaning shoe. Remaining material, conditioned and stratified by its passage across the conditioning sieve of the grain pan, is delivered to a chaffer. Beneath the chaffer, a sieve assembly includes a conventional sieve portion and, extending downstream beyond the chaffer, a chaffer extension coplanar with the sieve portion and spaced from it by a transverse tailings slot, disposed above the tailings auger of the cleaning shoe. The chaffer and sieve assembly are provided with a conventional air blast from the cleaning shoe blower.
A cleaning shoe of an agricultural combine is provided with a front chaffer located upstream from the main chaffer. The front chaffer has a closed upstream portion and an open downstream portion. The closed upstream portion is upwardly inclined and the open downstream portion is downwardly inclined. The front chaffer is oriented so that an air blast from the cleaning fan passes beneath the closed upstream portion and upwardly through the declined open downstream portion. The open downstream portion is provided with transversely extending louvers through which the air blast passes. The cleaning fan comprises a plurality of radially and transversely extending fan blades. Blade inserts forming air dams are located near each transverse end. The blade inserts are provided with apertures that limited the transverse air flow along the blades.
