Patent ID: 8280280

Claim:
A developer cartridge detachably mountable on a tandem type photosensitive unit slidable to a drawn-out position and a mounted position with respect to an image forming apparatus body, comprising: a casing; a developer carrier rotatably supported on a first end portion of the casing for carrying a developer; a pair of upright portions arranged on a second end portion of the casing and spaced apart from each other in the axial direction of the developer carrier to extend from the second end portion of the casing in a detaching direction of the developer cartridge; a coupling portion that is elastically deformable, extending in the axial direction of the developer carrier for coupling the upright portions with each other; and an opposed portion opposed to and spaced apart from the coupling portion on a part of the casing between the upright portions, wherein: the opposed portion is higher in rigidity than the coupling portion, and the opposed portion includes a stopper rib protruding from an end portion of the opposed portion toward the coupling portion, wherein the stopper rib is configured to limit, from a side of the end portion of the opposed portion, elastic deformation of the coupling portion.