light fraction upwardly to the outlet end of the passageway application_number US 70660485 A description in the embodiment illustrated in fig1 a mixture of solid materials is separated in an upwardly directed airflow path in a vertically arranged zig zag shaped airflow passageway 2 acting as an air classifier due to its shape the airflow passageway forms a tortuous airflow path 1 as an alternative differently shaped vertical or horizontal air ducts could be used the mixture of solid materials to be separated is introduced into the airflow passageway 2 in the upper third of the passageway entering through a star feeder gate or lock 3 an opening 4 admits the mixture into the airflow passageway 2 and the opening is connected with the star feeder or wheel gate 3 by an inlet channel 5 other means for carrying the mixture to the opening 4 could be used preferably inlet opening 4 is located in the upper third or final third of the airflow passageway 2 as seen in the direction of the airflow path 1 at the transition from the inlet channel 5 into the airflow passageway 2 that is in the region of the inlet opening 4 a base edge a defines in its simplest construction the connection between the lower part of the inlet channel 5 and the airflow passageway 2 the opening 4 defined along its lower edge by the base edge a defines the angle between the inlet channel 5 and the long axis of the airflow passageway 2 the mixture to be separated is introduced into the airflow passageway 2 through the inlet opening 4 and is made up note fig2 of heavier particles 6 and lighter particles 7 so.