Abstract: A developer supply system for a dry process electrophotographic copier supplies a single component or dual component type developer to a developing unit. After a used developer has been discharged from the developing unit, a fresh charge of carrier is supplied to the developing unit and, then, a fresh charge of toner to be mixed with the fresh carrier. A circuit is provided for controlling such a sequence. Independent cylindrical cartridges are allocated to the toner of the single composition developer and to the toner and carrier of the dual composition developer. Each of the cartridges is received in a cylindrical cartridge. The cartridge casing is mounted in a hopper casing associated with the developing unit and is driven for rotation therein.

Abstract: A developer replacing and supplying device for a small-size electrophotographic copier is disclosed which removes used developer from a developing unit and supplies a fresh developer instead. After the used developer which is a mixture of carrier and toner has been discharged, fresh carrier is introduced into the developing unit and, then, fresh toner to be mixed with the fresh carrier. The fresh carrier and the fresh toner are stored in physically independent cylindrical cartridges, which are selectively mounted in a cartridge casing. The cartridge casing is mounted in a hopper casing, which is provided integrally with the developing unit, and driven in a rotational motion together with the cartridge.