Abstract: The present invention provides a powder classifier using a classification rotor capable of classifying powder with high efficiency and high accuracy. The classification rotor is attached to a rotating shaft as a body and rotatably supported in a casing. Within the classification rotor, a cavity is formed from the outer edge to the center and classifying vanes are provided around the circumference. The cavity is bent downwardly near the center with the lower end connected through a fine powder passage to a fine powder outlet. The outer edge of the classification rotor is connected to a coarse powder outlet. After feeding powder from a powder supply port, the powder is rotated by the classifying vanes such that coarse powder particles are taken out from the rough outlet by centrifugal force and fine powder particles are taken out by airflow from the fine powder outlet.

Abstract: A mechanical grinding apparatus of the present invention, which includes a rotor supported by a rotary shaft and having a plurality of grooves defined on the outer peripheral surface thereof and a liner inserted to the outside of the rotor so as to form a desired gap between the liner and the rotor and having a plurality of grooves defined on the inner peripheral surface thereof for grinding a substance to be ground in the gap, is characterized in that the grooves of at least one of the rotor and the liner incline in a direction preventing the flow of the substance to be ground with respect to a direction parallel with a rotary shaft. Since the mechanical grinding apparatus of the present invention can make a ground substance having a small particle size, no large particles mixed therein and a sharp particle size distribution width at a high efficiency, the grinding apparatus is preferably applicable to powder composed of resin or mainly composed of resin to be finely ground.