Apparatus for classifying particulate material with air currents

Abstract

An apparatus for classifying particulate material with air currents wherein the particulate material containing various kinds of particles of different sizes is conveyed with air currents and the particles are given with forces of inertia differing from one another depending on particle size, including a supply port for supplying the particulate material to be classified, an air current inlet port for introducing into the apparatus an air current of high flow velocity located in the vicinity of the particulate material supply port, air current inlet ports for introducing into the apparatus other air current of lower flow velocity than the air current of high flow velocity, a main passage formed in the apparatus communicated with the particulate material supply port and the air current inlet ports, and a subsidiary passage branching from the main passage located at the side of the apparatus at which one of the air currents of low flow velocity flows. This flow of air current of low flow velocity constitutes a flow adjusting air current layer interposed between walls defining the main and subsidiary passages and the particulate material conveyed by the air currents for preventing the flow of the particulate material from being disturbed by a vortical air flow occurring along the walls defining the main and subsidiary passages.