Patent ID: 7431440

Claim:
A replaceable ink cartridge for an inkjet printhead of a printer, the ink cartridge comprising: a rigid housing forming sealed ink storage volume, the housing having a docking face for abutting a complementary face on the printer; an ink outlet in the docking face for establishing sealed fluid communication between the printhead and the ink storage volume, the ink outlet valve that is biased closed and opens upon installation in the printer; and, an air bag in the ink storage volume with an air inlet in the docking face and spaced from the outlet valve, the air inlet is for allowing external air into the air bag and having a frangible seal which is ruptured by a raised formation on the complementary face upon installation of the cartridge in the printer; wherein the outlet valve and air inlet are configured for engagement with complementary formations on the printer such that the ink outlet and the air inlet are both opened upon installation of the cartridge in the printer wherein during use, the air bag inflates as the ink is drawn from the ink storage volume.