Abstract

An electrostatic sieve having a circular solid electrode, preferably with sawtooth contours arranged on its lower side concentrically around a center hole. The solid electrode is supported by insulating brackets around its perimeter. The brackets are attached to a conical outer structure, which also serves to collect the coarse particles. Underneath the solid electrode, with a gap between, is the sieve electrode, which is supported by a stretcher, preferably a circular ring of tubing with a square cross-section, itself supported on insulating brackets, which rest on an inner cone. The inner cone tapers toward the bottom to collect the fine powder passing through the sieve electrode, which passes through the hole in the bottom of the cone and falls into a collecting tray. The outer surface of the inner cone forms the inner surface of a conical passage, the outer surface of which is the outer conical support. Powder to be sieved is fed into the opening in the center of the solid electrode. As the powder passes through the hole into the gap between the solid electrode and the sieve electrode, it flows radially outward toward the perimeter of the electrodes under the influence of an electric field between the solid and sieve electrodes, and is induced to oscillate between the electrodes. As the particles flow outward, they are tried against the sieve electrode, and the finer particles flow through the sieve and down into the inner cone, passing out of the cone through the bottom and falling into the fines collection tray. The coarser particles continue to flow radially outward, oscillating and being tried all the way, until they finally flow off the perimeter of the sieve electrode and into the conical outer support. The coarse particles then flow through the gap between the inner and outer cones until they pass out of the bottom of the outer conical support into a donut-shaped collection tray. The contouring of the solid electrode causes increased oscillation as the particles move radially outward, which increases the number of trials against the sieve electrode. If required by the powder used, vibrators may be attached to the inner or outer cones to aid in passage of the particles along the walls of the cones.