Patent ID: 7896731

Claim:
A cleaning system for a work vehicle comprising: a sieve mounted within the work vehicle beneath a threshing system thereof so as to be located in a path of a downward airborne flow of crop material output by the threshing system, the crop material including a mixture of grain and particles of material other than grain, including particles lighter than the grain, the flow of crop material having a first portion containing a significantly higher density of crop material compared to a second portion of the flow beyond the first portion in a predetermined direction; the sieve having a first sieve region of a limited extent being disposed for receiving the first portion of the flow of crop material, and including a plurality of rows of first fingers, wherein each row includes a series of first fingers having first spaces extending laterally therebetween, and a second sieve region beyond the first sieve region being disposed for receiving the second portion of the flow of crop material, and including a plurality of rows of second fingers, wherein each row includes a series of second fingers having second spaces extending laterally therebetween wherein the first spaces of the first sieve region are at least about one and one half times greater than the second spaces of the second sieve region; and a fan system configured and operable for directing an air flow stream upwardly through the sieve, the air flow stream having a first air flow portion of limited extent having a significantly higher first air flow rate directed through the first sieve region as compared to a second air flow rate of a second air flow portion directed through the second sieve region, such that the first air flow portion will interact with the downward airborne flow of the first portion of the flow of crop material above the first sieve region such that substantially only grain will fall onto and through the first sieve region and such that substantially all of the particles of material other than grain being lighter than grain will be propelled beyond the first sieve region, wherein baffles are adjacent to the fan system for directing the first air flow portion through the first sieve region and the second air flow portion through the second sieve region.