Patent ID: 8229330

Claim:
A developing unit comprising: a developer cartridge that is configured to accommodate developer and comprises a first opening for enabling communication between an inside of the developer cartridge and an outside of the developer cartridge; a first elastic member that comprises a first through hole and protrudes outward from the developer cartridge, the first through hole surrounding the first opening; a housing comprising: a cartridge housing part for housing the developer cartridge, wherein the cartridge housing part includes a shutter; and a second opening that is provided in a position opposite to the first opening and is formed toward the cartridge housing part; and a second elastic member which protrudes from the housing toward the cartridge housing part, which is contactable with the first elastic member, and which comprises a second through hole surrounding the second opening; wherein the shutter comprises a third opening and is movable between an opening position where the third opening is located at a position between the first opening and the second opening and a closing position where the third opening is located at a position different from the opening position between the first opening and the second opening, wherein when the shutter is located at the opening position, an upstream end of the third opening in a movement direction of the shutter from the opening position to the closing position is located more upstream than upstream ends of the first through hole and the second through hole in the movement direction, wherein the shutter comprises a protruding portion provided at an upstream end portion of the third opening in the movement direction, wherein the protruding portion comprises a first end at a side close to the first opening and a second end at a side close to the second opening, the first end protruding more downstream in the movement direction than the second end, and wherein the first end of the protruding portion of the shutter is configured to selectively engage both the first elastic member and the second elastic member.