Image forming device, developing device and toner cartridge

A toner cartridge containing toner for developing an electrostatic latent image, the toner cartridge being attachable to a developing cartridge, comprising:

• a substantially rectangular mounting surface detachably attachable to the developing cartridge, configured to face the developing cartridge, the mounting surface having first and second ends in a longitudinal direction of the mounting surface;
• an agitation mechanism configured to agitate the toner;
• a conveyance mechanism configured to convey the toner to the agitation mechanism;
• a feed port provided in the first end of the mounting surface, the feed port being communicable with the developing cartridge;
• and
• an return port provided in the second end of the mounting surface, the return port being communicable with the developing cartridge, wherein
• the toner cartridge has a cross section perpendicular to the longitudinal direction of the mounting surface, the cross section having a first length in a first direction directed to the mounting surface, and a second length in a direction perpendicular to the first direction and perpendicular to the longitudinal direction of the mounting surface, the first length being greater than the second length, and
• the toner cartridge is divided into a circulating chamber in which the toner is configured to be agitated by the agitation mechanism and circulated through the developing cartridge, and an accumulating chamber in which the toner is configured to be conveyed to the circulating chamber through an opening by the conveyance mechanism,
• the circulating chamber comprises a first cylindrical member, and a second cylindrical member fitted around the first cylindrical member, one of the first and second cylindrical members being rotatable with respect to a remaining one of first and second cylindrical members to open and close the feed and return ports,
• a first positional relationship between the first and second cylindrical members is configured to cause the feed port and the return port to be closed and interrupt a communication between the circulating chamber and the accumulating chamber through the opening, and
• a second positional relationship between the first and second cylindrical members is configured to cause the feed port and the return port to be opened and establish the communication between the circulating chamber and the accumulating chamber through the opening.