High-speed magnetic brush developer apparatus

Claim 1

A magnetic brush assembly for a brush developer adapted to develop electrostatic images carried on a sheet material at highspeed comprising: an applicator drum comprising a rotatable hollow cylinder having a fixed magnetic flux generating assembly disposed adjacent the inside surface of the cylinder for attracting and releasably retaining a mass of developer mix on the surface thereof, a supply station for supplying developer mix juxtaposed a portion of the outer surface of the cylinder, a developing station having ingress and egress means for said sheet material and feeding said sheet material immediately adjacent the cylinder, a developer mix collecting statIon, mixing means disposed between said supply and collecting stations for mixing the developer mix and feeding it from the collecting station to the supply station, said magnetic flux generating assembly including a series of radially spaced magnet means with said cylinder creating at least four distinct developer mix handling zones extending along the path of rotation of the cylinder from a point adjacent the supply station to a point beyond the developing station, a first zone being located adjacent the supply station for picking up a mass of developer mix, a second zone being located adjacent the developer station for causing the developer mass to become upstanding on the cylinder surface, a third zone for conveying the mass between said first and second zones, and a fourth zone for conveying the developer mass away from the developing station toward the collecting station, the strength of the magnetic field in the second zone where the developer mass becomes upstanding on the cylinder surface being low compared to other of the zones so as to reduce abrasion of the sheet material during developing.