| 摘要 |
PURPOSE:To make it possible to perform a suction process efficiently by providing a piston valve which closes a discharge path between a negative pressure generation chamber and a discharge outlet when a piston is activated in a direction in which the volume of the negative pressure generation chamber increases and opens the discharge path when the piston is activated in an opposite direction during the reciprocating action of the piston. CONSTITUTION:If the volume of a negative pressure generating chamber 1' increases due to the descent of a piston 3, then the negative pressure increases gradually and the energization force of a return spring 9 becomes smaller than a downward force generated by a difference between an atmospheric pressure and a generated negative pressure, an operating valve 7 is set in 'open' state, and the negative pressure of the chamber 1' is transmitted to a cap 20. As a result, the suction process of a recording head takes place. In this case, a piston valve 6 is set in 'closed' state. If the descent of the piston 3 is ended and later, the value of a negative pressure at the negative pressure generation chamber 1' becomes low due to the inflow of a sucked ink, the operating valve 7 becomes closed. In addition, when a pump cam 25 rotates, the piston 3 begins to ascend. In this case, the piston 3 becomes out of contact with the O ring 6A on account of a flange 38 on the piston 3 and the piston valve 6 becomes open so that ink is discharged to the bottom of a cylinder 2. |
