KORNREINIGUNGSSYSTEM FÜR EINEN MÄHDRESCHER

A grain cleaning system for a combine harvester, comprises a frame (25) supporting a grain pan (12) and a sieve (16). The grain pan (12) receives grain and chaff separated from the crop by a threshing mechanism and is reciprocable relative to the frame (25) in order to separate the grain from the chaff and to propel the grain and chaff towards the sieve (16). The sieve (16) is reciprocable relative to the frame (25) and is connected to the frame by front and rear support arms (24, 26) that are pivotably secured to the frame (25) and to the sieve (16). In the invention, the front support arms (24) have different geometries from the rear support arms (26) such that when the sieve (16) is reciprocated relative to the frame (25), the vertical component of oscillation is greater at the front end than at the rear end of the sieve (16).