Patent ID: 7178908

Claim:
A buffer tank for an ink jet printer, on whose upper side is attached an ink cartridge containing an ink which is drawn into the buffer tank, the buffer tank comprising: a main body having a top plate; an air intake through which air outside the buffer tank is taken into the buffer tank; an air outlet passage which comprises at least a part extending in the main body downward from the top plate, so as to flow the air in the buffer tank out into the ink cartridge; and an ink inlet passage which comprises at least a part extending in the main body downward from the top plate, so as to draw the ink in the ink cartridge into the buffer tank, wherein each of the air outlet passage and the ink inlet passage comprises a hollow needle disposed at the top plate and vertically extends, and the air outlet passage comprises a hollow tubular member which is configured so as to extend down from the top plate to a level below a lower end of the hollow needle of the air outlet passage and above a lower end of the ink inlet passage, with an inner space of the hollow tubular member being in communication with an inner space of the hollow needle of the air outlet passage, and a cross-sectional area of a hollow of the tubular member at least at a lower end thereof being larger than a cross-sectional area of a hollow of the hollow needle of the air outlet passage.