Image forming apparatus

An image forming apparatus comprising:

• at least one process cartridge including a photosensitive element, a development unit, a toner storage unit, a driven shaft and a driven gear mounted thereon and which is detachably attachable to the image forming apparatus from a top front side thereof;
• a drive shaft;
• a drive gear mounted on the drive shaft and configured to couple with and drive the driven gear to transmit a driving force to the process cartridge;
• an upper cover structured to open and close with respect to the image forming apparatus;
• a front cover structured to open and close with respect to the image forming apparatus;
• and
• at least one block component configured to block coupling of the drive gear and the driven gear by contacting the driven shaft while interlocked with opening and closing of the upper cover,
• wherein the process cartridge is detachably attachable to the image forming apparatus from the front top side thereof by opening and closing the upper cover.