Patent ID: 7506972

Claim:
A sub-tank comprising: an ink inlet for receiving ink; an ink outlet for supplying ink; an ink storage chamber connected to said ink outlet; a valve housing chamber connected to said ink inlet; a valve disposed in said valve housing chamber; a partition wall provided between said ink storage chamber and said valve housing chamber, and formed with a communicating hole communicating with said ink storage chamber and said valve housing chamber; and an urging unit disposed in said valve housing chamber and urging said valve toward said partition wall wherein when a pressure in the ink storage chamber is above a predetermined value, said valve is brought into contact with said partition wall and seals said communicating hole; and wherein when the pressure in the ink storage chamber is below a predetermined value, said valve is seperated from said partition wall and opens said communicating hole, so that ink flows through said communicating hole from said valve housing chamber to said ink storage chamber.