Method and wind sifter for grading comminuted charging material

The invention relates to the classification of size-reduced charging material in an air separator (1) that is provided with a sizing rotor (3). According to the inventive method, the sizing air (6) and the charging material (7) are introduced into a sizing chamber (8) and retention air (20) is blown into a annular sealed zone (14) in the zone of transition between the sizing rotor (3) and a stationary discharge channel (12). The aim of the invention is to adjust the grain distribution range in the fine product/finished product reliably and with relatively few constructive elements. To this end, the grain distribution of the discharged fine product is specifically adjusted by means of a bypass flow (17) that flows in an adjustable flow, controlled by the supply of retention air, from the sizing chamber into the discharge channel (12) and that is charged with charging material for the air separation or with grains to be sized.