The influence of filler plates between adjacent rasp bars during corn cobs threshing

Abstract

When rotating inside the combine harvester, the threshing cylinder generates the airflow in the threshing clearance. Part of the airflow is directed through grate-bars of concave [1], It is commonly accepted that the rate of airflow generated by the threshing cylinder in the threshing clearance has to be lower than the terminal velocity of the grain. Otherwise, part of the grain will be blown off the surface of the concave on to the straw walkers. Analysis of the material captured by high-speed video recording camera showed that part of the threshed (loose) grains move inside the airflow generated in the threshing clearance. Impact to the rasp bars results in grain damage [2]. When investigating wheat and having the aim to intensify grain separation as well as to reduce grain damage, it was suggested to cover spaces between adjacent rasp bars [3]. Covering spaces between adjacent rasp bars (using filler plates) results in altered form of the part of the cylinder in contact with the crops being threshed [4], When threshing corn cobs, spaces between adjacent rasp bars are covered in order to prevent cobs from entering into the cylinder. However research on the effect of filler plates between adjacent rasp bars on grain damage and separation are still rare.