APPARATUS FOR TREATMENT OF SHEET MATERIAL WITH THE USE OF FERROMAGNETIC POWDER

摘要

An apparatus comprises a pair of rolls having a gap therebetween for the passage of sheet material to be treated and rotatable in opposite directions. There is also provided a means for generating a magnetic field, with the lines of force passing along the axes of the rolls and across the gap formed therebetween. The rolls, therefore, serve as opposite poles of magnetic system which enables the ferromagnetic powder to be retained on the surfaces of said rolls under the effect of the magnetic field. Mounted underneath a bottom roll is a net with a mesh size slightly less than a minimum permissible size of the powder grains. The net is disposed within the zone of the magnetic field of said magnetic system. The apparatus desirably includes a switch adapted to discontinue the action of magnetic field, whereupon the powder pours down on the net and through it if unsuitable for further use. Upon subsequent generation of the magnetic field, the powder is lifted from the net and onto the bottom roll wherefrom it is further transferred onto the top roll during rotation of the rolls. The action of magnetic field is discontinued after treating a prescribed amount of sheet material. The magnetic field is initiated prior to feeding a sheet material into the gap between the rolls.