US Patent 7415220 Local suppression of unwanted toner emissions

A developer apparatus for a printing device includes a rotatable developer carrying member which carries developer thereon. A magnet assembly is disposed in the developer carrying member. The magnet assembly includes a plurality of magnets for conveying the developer. The magnets generate a magnetic field over a larger proportion of a circumference of the developer carrying member in an edge region adjacent an end of the developer carrying member than in a mid-region longitudinally spaced from the end of the member by the edge region. The apparatus enables unwanted toner emissions to be reduced by the development of a stable annular magnetic brush in the edge regions.