1. Field of the Invention
The present invention relates to a liquid jet recorder, and more particularly to a liquid jet recorder having means for restoring the liquid discharge function when liquid is not properly discharged.
2. Description of the Prior Art
A liquid jet recorder jets liquid as droplets to print dots on a record medium. A schematic view thereof is shown in FIG. 1.
FIG. 1 shows only major portions with a case removed. Numeral 1 denotes a liquid jet nozzle that acts as a liquid discharge means. The nozzle 1 is mounted on a carriage 2 which is horizontally reciprocated along a guide rod 3. Droplets are discharged from the nozzle 1 when it is at a predetermined print position so that dots are printed on a record paper (not shown) fed by a platen 4.
A sub-tank 5 is mounted on the carriage 2 and liquid such as ink is supplied to the sub-tank 5 from a main tank (not shown). The liquid such as ink is supplied from the sub-tank 5 to the liquid jet nozzle 1.
A liquid discharge function restoring pump 6 acts as a droplet discharge function restoring means and is arranged at the home-position of the recorder. When the liquid jet nozzle 1 is returned to the home position by the carriage 2, the jet nozzle 1 is engaged with the restoring pump 6.
The restoring pump 6 has vacuum means (not shown). As a user depresses a button 7 on the restoring pump 6 at the start of printing, a vacuum is generated so that the liquid such as ink is sucked from the liquid jet nozzle 1 to assure the discharge of droplets by the liquid jet nozzle.
It has been known that the longer the non-print time of the liquid jet nozzle 1 is, the higher is the defective print rate due to evaporation of the liquid at the end of the liquid jet nozzle 1.
This is illustrated in FIGS. 2 to 4.
FIG. 2 shows a relation between the non-print time of the liquid jet recorder and the defective print rate. It is seen that the defective print rate increases in proportion to the non-print time.
FIG. 3 shows the relation between a relative humidity and the non-print time for a given defective print rate and temperature, and FIG. 4 shows the relation between the temperature and the non-print time for a given defective print rate and humidity.
As seen from FIGS. 2 to 4, when the relative humidity is low and the temperature is low, a certain level of defective print rate occurs even if the non-print time is short.
In spite of the fact that the defective print rate largely relates to the non-print time, the prior art recorder merely controls a temporary minimum pressure of the sub-tank sucked by the restoring pump and the restoring function is effected by the manual operation by the user. Accordingly, if the non-print time is long, the defective print rate is high in spite of the restoring function.