Patent ID: 8055168

Claim:
A magnetic knife assembly for a toner developing device which comprises: a support body, and a ferromagnetic strip held between like poles (N) of two permanent magnets, said ferromagnetic strip and said permanent magnets being disposed within said support body, said ferromagnetic strip extending between these poles to form a knife edge that faces outwardly of the support body and an inner edge that faces inwardly of the support body whereby the ferromagnetic strip is held such that an outer knife edge portion projects outwardly beyond the two magnets and is subjected to a magnetic force that tends to urge the strip in a direction where the knife edge portion projects further out of the magnets, wherein a length L 0 of the strip from said knife edge to the inner edge is selected such that a portion of the strip opposite to the knife edge and closer to the inner edge is subject to a magnetic force that is larger than the force acting upon the knife edge portion, and the strip is held in position relative to the support body only by the magnetic forces of the magnets that urge the inner edge of the strip against the support body in the direction from the knife edge to the inner edge.