Crop processing apparatus in a combine harvester

A combine harvester comprising threshing apparatus arranged to receive and thresh a crop stream, and separating apparatus located downstream and rearward of the threshing apparatus and arranged to receive the threshed crop stream and convey in a rearward direction, both the threshing apparatus and separating apparatus comprising grates for allowing grain and chaff to fall under gravity onto an underlying conveyance arrangement comprising a stratification pan and a return pan, wherein the front of the return pan overlaps the rear of the stratification pan, the stratification pan being driven in an oscillating manner to convey a primary grain/chaff stream rearwardly to a rear edge from where the primary grain/chaff stream falls under gravity into a cleaning unit, the return pan being driven in an oscillating manner to convey a secondary grain/chaff stream forwardly to a front edge from where the secondary grain/chaff stream falls under gravity to combine with the primary grain/chaff stream on the stratification pan, the cleaning unit comprising a fan for generating a cleaning airstream which is directed through the falling grain/chaff stream, and wherein a plurality of downwardly extending crop flow disrupting elements are secured to the underside of the return pan above the stratification pan to disrupt the grain/chaff stream and enhance stratification thereof.