Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-06-26
2001-09-11
Le, N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S017000, C347S029000
Reexamination Certificate
active
06286928
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for purging the ink jet head and an ink jet recorder including the ink jet head. In particular, the invention relates to an ink jet head purging apparatus which can suitably change the suction time interval depending on ambient temperature variations, and an ink jet recorder including the ink jet head.
2. Description of Related Art
A conventional ink jet printer includes a print head having a number of nozzles for ejecting ink to print a sheet of paper. While the head is used, air bubbles may be produced in it, and ink may stick to the nozzle walls, resulting in defective ejection of ink. If the printer is not used for a long time, the nozzles may clog with thick ink, resulting in defective ejection of ink. Defective ejection of ink results in defective print. In this case, the nozzles are purged to recover good ejection of ink. The purging includes capping the head with a suction cap, and sucking ink out of the capped head by a pump developing negative pressure. Normally, the nozzles are purged at regular interval of time, which may be five days.
Because the ink ejected from the print head is a viscous liquid, however, its state may change at abnormal temperature. Therefore, at abnormal temperature, if the nozzles are not purged frequently, the ejection of ink from nozzles may become defective. If the purging time interval is short on the assumption that the temperature may be abnormal, the purges at normal temperature are too frequent. This accelerates the ink consumption of the printer, because the purging involves suction of ink.
SUMMARY OF THE INVENTION
In view of the foregoing problem, it is an object of the invention to provide an ink jet head purging apparatus which can change the suction time interval depending on ambient temperature variations. It is another object to provide an ink jet recorder including such a purging apparatus.
In accordance with a first aspect of the invention, an apparatus is provided for purging an ink jet head having nozzles, through which ink can be ejected. The apparatus includes a cap for covering the nozzles. The apparatus also includes a suction pump for sucking ink from the nozzles through the cap covering the nozzles. A memory stores the regular interval at which the pump should suck ink from the nozzles. A temperature sensor measures ambient temperature. Depending on the measured temperature, a suction interval change device can change the stored interval. A controller can operate the pump at the stored interval.
If the ambient temperature measured by the temperature sensor reaches either a low or a high temperature which may cause defective ejection of ink, the suction interval change device changes the suction or purge interval stored in the memory. The changed interval may be shorter than the set interval. The controller causes the suction pump to suck ink at the changed interval. Therefore, the apparatus can purge the ink jet head at suitable interval depending on the temperature history around the head. Consequently, the ejection of ink from the head can be kept in good condition at any temperature.
The purging apparatus may include a counter counting how many times the temperature measured by the temperature sensor is out of a predetermined range of temperature, which may be between 10 and 35 centigrade. If the temperature has been out of the range more than a predetermined number of times, which may be 24 times, the controller may cause the suction pump to suck ink. The reason for this is that it is enough to purge the ink jet head only if the ambient temperature keeps abnormal for a predetermined period. This prevents the head from being purged too often and ink from being wasted.
The purging apparatus may include a timer for clocking the elapsed time after the preceding purge.
The purging apparatus may include a reset device for initializing the stored purge interval after the suction pump sucks ink. For instance, if the suction interval change device has shortened the stored interval from five days to three days, the reset device replaces the shortened interval with five days again. Consequently, after the ink jet head is purged, it is purged at the same interval to keep its ejection of ink in good condition unless the ambient temperature becomes abnormal. After the pump sucks ink, the reset device may reset at least one of the counter and the timer.
The temperature sensor may be a temperature detecting circuit including a thermister.
The controller may be an exclusive purge controller fitted in the purging apparatus. Otherwise, the controller may be a minicomputer connected to the apparatus. The controller may also function as the suction interval change device.
In accordance with a second aspect of the invention, an ink jet recorder is provided. The recorder includes an ink jet head having nozzles, through which ink can be ejected. The recorder also includes an apparatus for purging the head. The apparatus includes a cap for covering the nozzles. The apparatus also includes a suction pump for sucking ink from the nozzles through the cap covering the nozzles. A memory stores the regular interval at which the pump should suck ink from the nozzles. A temperature sensor measures ambient temperature. Depending on the measured temperature, a suction interval change device can change the stored interval. A controller can operate the pump at the stored interval.
Depending on ambient temperature, the purge interval of the purging apparatus (recovery mechanism) of the recorder are controlled. Therefore, regardless of ambient temperature variation, the ejection of ink from the ink jet head can be kept in good condition.
The purging apparatus of the recorder may purge the ink jet head provided that a signal for recording is input to the recorder. Otherwise, whether a signal for recording is input to the recorder or not, the apparatus may be forced to purge the head at the interval stored in the memory.
The recorder may include a timer for clocking the elapsed time after the preceding suction. When a signal for recording is input to the recorder, the controller compares the elapsed time clocked by the timer with the stored interval. As a result of the comparison, if the clocked time is longer than the stored interval, the controller causes the suction pump to suck ink.
The temperature sensor of the recorder may be a temperature detecting circuit including a thermister.
The controller of the recorder may be an exclusive purge controller fitted in the purging apparatus of the recorder. Otherwise, the controller may be a printer control circuit in the recorder, which may be an ink jet printer. Otherwise, the controller may be a minicomputer connected to the apparatus or the recorder. The controller may also function as the suction interval change device.
REFERENCES:
patent: 5781024 (1998-07-01), Kanematsu et al.
patent: 5949447 (1999-09-01), Arai et al.
Brother Kogyo Kabushiki Kaisha
Hsieh Shih-Wen
Le N.
Oliff & Berridg,e PLC
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