US Patent 9354596 Electrophotographic image forming apparatus

An image forming apparatus includes a main assembly, a developing cartridge, and a drum supporting frame detachably mountable to the main assembly while supporting the developing cartridge. The main assembly includes a door for opening and closing the main assembly, and a main assembly coupling engageable with a development coupling in interrelation with a closing operation of the door to transmit a driving force to the development coupling.