Abstract: An ink jet print unit storing case having a case main body 30 with a cap 40 and a cover member 32 with a plate spring 46. The case main body 30 has the cap 40 at a position confronting a recording head 12 when a print unit 6 is accommodated in the case main body 30. The cap 40 not only is such that a peripheral edge thereof 40a comes in resilient contact with the recording head 12 so as to form a space with respect to the nozzle openings of the recording head, but also communicates with the atmosphere through a fluid resisting passage so as to prevent the evaporation of ink from the nozzle openings which maintains the meniscus of the recording head in a printing ready state, even in the presence of temperature and pressure fluctuations. The cover member 32 is arranged on the case main body 30 so as to be opened and closed, and has the plate spring 46 that resiliently urges the print unit 6 toward the cap 40.

Abstract: An ink supply communication path is formed so that one end thereof is arranged outside a region confronting a pressure producing chamber at a region confronting a reservoir chamber; and an ink supply constricted port is arranged at a portion of the ink supply communication path, the portion being remotest from the pressure producing chamber. Since the pressure producing chamber is connected to the ink supply constricted port through the elongated ink supply communication path, a jet flow from the ink supply constricted port grows into a large flow along the ink supply communication path, which in turn allows air bubbles susceptible to stagnation in the vicinity of the ink supply constricted port to be discharged by such large flow.