Patent ID: 7756443

Claim:
An image forming device comprising: a casing; an image carrier having an axis extending in a first direction; an image carrier cartridge that holds the image carrier; wherein the image carrier cartridge is configured to be installed in and removed from the casing; a developing cartridge configured to be installed and removed with respect to the image carrier and including a developer carrier configured to carry developer to the image carrier, wherein the developing cartridge includes: a driving input portion extending from the developing cartridge, the driving input portion transmitting a driving force to rotate the developer carrier; and an electrode that is configured to contact a power supply element, which supplies an electric bias to the electrode when the developing cartridge is installed in the image carrier cartridge; a driving rotator configured to be connected with the driving input portion; and a guide extending in a second direction and configured to guide the driving input portion when the developing cartridge is installed and removed with respect to the image carrier, wherein the guide comprises: a first guide wall having a first guiding groove that guides the driving input portion, the first guiding groove having a first width measured along a third direction, which is perpendicular to the first direction; and a second guide wall having a second guiding groove that guides the electrode, the second guiding groove having a second width measured along to the third direction, wherein the first width is larger than the second width.