Abstract

An apparatus for classifying particles by size comprising: a source of direct potential having first and second terminals, a sieve electrode connected to the first terminal, a solid electrode connected to the second terminal. Particles are fed to a transfer point located between the sieve electrode and the solid electrode such that the particles disperse and oscillate between the sieve electrode and the solid electrode whereby smaller particles pass through the sieve electrode. The new equipment has five adjustable operating parameters, screen angle, spacing between electrodes, field strength, powder input rate and electrode taper. The taper between electrodes is usually small, 0.3 to 0.4 of a degree with the larger opening at the top. The taper is used when the input powder is fine and the particle size differential is skewed either towards the high or low side. The purpose of the taper is to reduce the possibility of arcing at the input as well as to control dispersion of the particles. The solid electrode may be flat, or contoured in side-to-side sine wave, step or sawtooth patterns, or in dimples across the surface, to increase the oscillation of particles. A plurality of parallel wire electrodes may be added perpendicular to the long axis of the sieve and solid electrodes at the same potential as the solid electrode in order to increase turbulence and particle oscillation.