Apparatus for constituting a rotary magnetic brush

Apparatus for constituting a rotary magnetic brush, said apparatus comprising a generally cylindrical member having a longitudinal axis of symmetry and installed so as to rotate about said axis and on whose periphery longitudinally extending magnetic poles are installed to extend parallel to the axis in a uniformly spaced out configuration with alternating outwardly-directed north and south poles, a tube made of a non-magnetic substance surrounding said member without touching it and intended to have its surface covered along at least a part of its length with particles of magnetic powder, and drive means for making said member rotate inside said tube with a view to forming a rotating layer of particles of said magnetic powder on the surface of the tube, the rotation being obtained by the effect of said magnetic poles rotating inside said tube, said rotating layer of magnetic particles constituting said magnetic brush, wherein said member extends beyond the brush-forming region on which the magnetic particles rotate and has an end drive portion intended not to be covered with said layer of magnetic particles, said magnetic poles extending over said drive portion which co-operates with an electromagnetic stator being a cylindrical surface delimited by magnetic poles arranged so as to cause said member to be driven in rotation by co-operation between the poles of the electromagnetic stator and the poles of said member in said drive portion, thereby constituting said drive means.