Method and apparatus for sorting non-ferrous metal pieces

Abstract

Mixed pieces of different non-ferrous metals are sorted by initially moving the pieces through a high density, rapidly changing magnetic flux field, and immediately thereafter, freely moving the pieces along unsupported forwardly and downwardly directed trajectories resulting from the momentum of the pieces, the force of gravity and the magnetically induced repulsive forces developed in the pieces by the flux field. The magnitude of the magnetically induced repulsive forces differ for different non-ferrous metals so that the lengths of the trajectories of generally similar size and shape pieces vary accordingly for separating pieces formed of different metals. The magnetic field is provided by a horizontally axised, rapidly rotating, hollow, liquid cooled, iron wall drum having magnets affixed to its outer surface. The magnets are arranged in rows that are formed of numerous, tile-like, small, permanent magnets which are positioned end to end, with their like polarity ends adjacent. A belt conveyor, which moves the pieces across the top of the drum, has its discharge end pulley coaxially surrounding the drum so that the pieces freely move off the end of the conveyor belt after passing through the magnetic field. Hence, the lengths of the trajectories may be controlled by adjusting the speed of the conveyor, which adjusts the momentum of the pieces, and by adjusting the rotational speed of the drum for adjusting the frequency of the changes in the magnetic field and, consequently, the magnitude of the induced repulsive forces.