Patent ID: 8428490

Claim:
A color electrophotographic image forming apparatus for forming a color image on a recording material, said color electrophotographic image forming apparatus comprising: a plurality of cartridge mounting portions for dismountably mounting cartridges; an intermediary transfer member onto which developed images formed on a plurality of electrophotographic photosensitive drums are transferred, said intermediary transfer member being provided opposed to said electrophotographic photosensitive drums; an image forming unit comprising said cartridge mounting portions and said intermediary transfer member, said image forming unit being movable between a transfer position for transferring, onto the recording material, the developed images transferred onto said intermediary transfer member from the electrophotographic photosensitive drums, a cartridge mounting and dismounting position for mounting and dismounting said cartridges relative to said cartridge mounting portions, and an intermediary transfer member mounting and dismounting position for mounting and dismounting said intermediary transfer member relative to a main assembly of the apparatus, wherein the intermediary transfer member mounting and dismounting position is different from the cartridge mounting and dismounting position; and a unit movement preventing means for permitting said image forming unit to move to the intermediary transfer member mounting and dismounting position when no cartridge is mounted to any of said cartridge mounting portions, and for preventing said image forming unit from moving to the intermediary transfer member mounting and dismounting position when at least one of said cartridges is mounted to at least one of said cartridge mounting portions, wherein said at least one cartridge includes a cartridge side engageable member, and said unit movement preventing means is a main assembly side engageable member provided in said main assembly, and wherein said unit movement preventing means prevents said image forming unit from moving to the intermediary transfer member mounting and dismounting position in the state that said at least one cartridge is mounted to said at least one cartridge mounting portion, and said cartridge side engageable member is in engagement with said main assembly side engageable member.