Patent ID: 8177070

Claim:
An air sieving method comprising the steps of: feeding a powdered material onto a single bottom plate disposed to cover a lower open end of a screening case, defining therein an internal space divided into an upper space and a lower space by a screen, with at least one gap formed in side parts of the screening case between a lower end surface of the screening case and the bottom plate; generating ascending air currents in the upper space of the screening case by suction produced by a suction device; generating currents of outside air entering the screening case through the at least one gap in the side parts of the screening case into the lower space by the ascending air currents in the upper space, wherein the screening case is configured so that the currents of outside air enter the screening case in a direction substantially parallel to the bottom plate; causing the currents of outside air sucked into the lower space to flow between the bottom plate and the screen to produce swirling air currents in the lower space; causing the powdered material fed onto the bottom plate to be carried and dispersed by the swirling air currents in the lower space; and causing the dispersed powered material to flow through the screen into the upper space to sieve the dispersed powdered material.