1. Field of the Invention
This invention relates to a device for separating a mixture generally collected as waste into a magnetic material as represented by iron pieces, a nonmagnetic conductive material as represented by aluminum cans, and a nonmagnetic nonconductive material as represented by waste paper and/or wood pieces.
2. Description of the Prior Art
A mixture material collected as waste is largely classified into the magnetic material, the nonmagnetic conductive material and the nonmagnetic nonconductive material. With a view to separating the magnetic material from the mixture, a variety of magnetic separating devices utilizing attraction of magnet have hitherto been proposed. Furthermore, for the purpose of separating the nonmagnetic conductive material and the nonmagnetic nonconductive material from the mixture, from which the magnetic material has been removed beforehand by such a magnetic separation device, a device for separating a nonmagnetic conductive material has been proposed by the U.S. Application Ser. No. 59,648 by the same inventor, now U.S. Pat. No. 4,230,560.
The aforesaid nonmagnetic-conductive-material separating device includes; a drum revolving in one direction about the longitudinal axis thereof serving as the axis of rotation; and a means for generating a magnetic field surrounding the drum and rotating about the aforesaid axis of rotation coaxially with the drum but in a reverse direction to the direction of rotation of the drum. The mixture remaining after the removal of magnetic material therefrom is thrown into the drum, and the nonmagnetic nonconductive material contained in the mixture is directed in the direction of rotation of the drum by rotation of the drum. On the other hand, the nonmagnetic conductive material is directed in a reverse direction to the direction of rotation of the drum by action of an electromagnetic force of the rotating magnetic field and an eddy current generated internally of the drum by the rotating magnetic field.
In the aforesaid separating device, the high speed rotation of the rotary magnetic field rotating in the reverse direction to the direction of rotation of the drum independently of the drum causes the strong electromagnetic force to act on the nonmagnetic conductive material, without causing the strong centrifugal force to act on the mixture existing in the drum, thereby effectively separating the nonmagnetic nonconductive material from the nonmagnetic conductive material.
The aforesaid separating device, however, failed to separate the magnetic material from the mixture. In the event that the mixture contains only a small amount of magnetic material, such a magnetic material remaining in the mixture would undesirably be attracted to the inner peripheral wall of the drum by the magnetic force of the rotating magnetic field and rotated integrally with the drum, thus impairing separation of the nonmagnetic conductive material from the nonmagnetic nonconductive material.