Screening device and process

Apparatus for screening and separating particulate material comprising:

• support means for supporting the apparatus about a central vertical axis thereof including
• a lower support housing having
• upper and lower support walls, and
• an air conduit extending upwardly beyond the upper support wall;
• a lower collecting housing mounted on the upper support wall of the support housing and having
• a lower wall extending around and outwardly from the air conduit and upwardly around a lower collecting chamber to a lower outer flange thereof, and
• air inlet and outlet means in the lower wall for passing air through the lower collecting chamber;
• screening means, with openings of substantially uniform size, extending horizontally above and across the lower collecting chamber and clamped to the lower outer flange;
• an air distributor rotor rotatable within the lower collecting chamber and having
• at least one elongated hollow radial arm extending radially outwardly from a central hub and having
• an inner open end connected to the air conduit and
• an upper edge including an upper elongated slot therein, extending horizontally and rotatable a predetermined distance below the screening means;
• rotor drive means mounted on the lower support wall of the support housing for rotating the air distributor rotor;
• an upper receiving housing situated above the lower housing and having
• an upper wall extending outwardly and downwardly around an upper receiving chamber to an upper outer flange thereof adapted for clamping an outer portion of the screening means to the lower outer flange;
• rotary feed distributor means on the upper receiving housing for distributing particulate material containing oversize and undersize particles into the upper receiving chamber and onto the screening means;
• collector means rotatable within the upper receiving chamber and adapted for removing accumulated oversize particles from the screening means;
• collector and distributor drive means adjacent the rotary feed distributor means for rotating the feed distributor means and the collector means;
• feed means connected to and for feeding the particulate material to be screened and separated to the rotary feed distributor means;
• first means connected to the air conduit for supplying a first air flow of predetermined volume and pressure into the air conduit, into each hollow radial arm and out each elongated slot therein and through the screening means to fluidize the particles collecting thereon, up into the upper receiving chamber and back downwardly with and helping to carry the undersize particle through the screening means and into and out of the lower collecting chamber;
• second means connected to the air outlet means in the lower wall for drawing the first air flow and an additional second air flow together into and through the lower collecting chamber and out the outlet means for carrying and collecting screened undersize particles therefrom;
• and
• third means connected to the collector means for drawing a third air flow of predetermined sufficient volume to remove and carry oversize particles accumulated on the screening means up into and out through the collector means.