Patent ID: 7029106

Claim:
An ink tank, comprising: a main ink chamber, opened to atmosphere; a sub ink chamber comprising: a first sub ink chamber, formed below the main ink chamber relative to gravity so as to allow ink and air both coming from the main ink chamber to enter therein; a second sub ink chamber, formed below the first sub ink chamber relative to gravity and adapted to reserve ink therein; and an ink passage, configured to lead the ink and air bubbles, which are formed in the first sub ink chamber, from the first sub ink chamber to the second sub ink chamber; an ink outlet, disposed below the second sub ink chamber relative to gravity; and a detected portion, provided in either one of the second sub ink chamber and the ink passage, the detected portion being operable to optically detect whether the ink is used up in accordance with an amount of air flowed from the main ink chamber to the sub ink chamber.