An electrophotographic system for use as a laser beam printer, a copying machine, or the like has an image carrier for receiving an electrostatic latent image, a developing device for developing the electrostatic latent image into a toner image with toner, and a toner hopper for storing into a toner,...http://www.google.de/patents/US5172168?utm_source=gb-gplus-sharePatent US5172168 - Electrophotographic system haivng a developing device with a plurality of toner feeders
