| 摘要 |
PURPOSE:To make it possible to certainly detect an ink residual amount, by providing a negative pressure detecting means such as a pressure sensing switch in the ink sub-tank on a carriage connected to a main ink tank. CONSTITUTION:When there is a sufficient amount of ink in the ink bag 1 in a main ink tank, negative pressure is hardly generated in the air layer 8 above the liquid level 7a of an ink sub-tank 6 but the pressure of the air layer 8 is lowered when an ink residual amount is reduced and a diaphragm 9 comprising a conductive rubber is downwardly curved while the protrusion 9a thereof is separated from a fixed contact 10 to bring an OFF-state and an alarm is informed by an alarm apparatus. The negative pressure degree of said air layer 8 is set so as to slightly approach an atmospheric side from a limit value for retracting the meniscus formed to the nozzle orifice of an ink jet nozzle 13. By this method, an ink residual amount can be certainly detected and the retraction of the meniscus of the nozzle orifice can be prevented. |
