Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-04-02
2002-05-14
Le, N (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06386677
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet recorder, such as an ink jet printer having a purging apparatus for sucking ink from a ink jet head, and a purging method and recording method for the ink jet printer.
2. Description of Related Art
Ink jet printers are known generally as ink jet recorders for recording on recording media, such as sheets of paper, by ejecting ink onto them.
FIG. 13
of the accompanying drawings shows part of a conventional ink jet printer, which includes a recording head unit P
3
having a recording head P
2
. The head P
2
has four ejection nozzles P
4
, each of which has ejection holes (not shown) opening in its front surface P
5
. Four ink cartridges P
1
containing link are mounted replaceably on the head unit P
3
, and each connected to one of the nozzles P
4
. After each cartridge P
1
is replaced with a new one, ink is supplied from the new cartridge to the head P
2
, and can be ejected from the associated nozzle P
4
.
While the printer is used, ink may be sucked from the nozzle surfaces P
5
to purge the nozzles. The purging may be started manually by the user operating a switch on the printer, or automatically if a predetermined condition is satisfied.
The purging is performed to prevent the defective ejection of ink which may be caused if the ink in or on the recording head P
2
dries, or if air bubbles are produced in the ink, or if droplets of ink stick to the nozzle surfaces P
5
. Specifically, the purging of each nozzle P
4
involves covering its nozzle surface P
5
with a suction cap P
6
, and then developing negative pressure in the cap P
6
by means of a suction pump (not shown), in order to suck ink from the head P
2
through the cap P
6
and discharge the sucked ink outside.
It is not avoidable that, when each cartridge P
1
is replaced with a new one, air enters the flow passage between the new cartridge P
1
and the recording head P
2
. Therefore, after the new cartridge P
1
is substituted, the purging is repeated consecutively as initial purging to remove the air from the passage and introduce new ink into the head P
2
.
If a recording command is input in the printer, the ejecting function of the printer is recovered by purging depending on the period (days) of nonuse of the printer, and immediately thereafter the printer starts printing. Just after the purging, very small air bubbles may be produced in the ink in the recording head P
2
. For example, air bubbles may be produced by the rapid flow of ink due to the purging. On the other hand, the purging may cause ink to bubble in the suction cap P
6
. In this case, when the cap P
6
is separated from the nozzle surface P
5
of the purged nozzle P
4
, the bubbly ink in the cap is forced into the nozzle by the negative pressure acting from the inner side of the nozzle. If air bubbles thus remain in the ink passages, the bubbles may absorb part of the ejection pressure and block part of the passages when ink is ejected. This impedes or hinders the ejection, and lowers the recording quality.
If quite a long time has passed after the last recording, two or more cycles of purging may be performed to improve the ejection of ink. In particular, the purging is repeated consecutively a plurality of times as the initial purging for introducing new ink into the recording head P
2
after each cartridge P
1
is replaced. After such a series of purges, air bubbles may remain in the purged nozzle P
4
or the associated ink flow passage in the head P
2
. The ink flow velocity is lower toward the wall of the passage, and it is therefore difficult to remove the bubbles near the wall. Consequently, even if the purging causes ink to flow, air bubbles are liable to collect near the passage wall. Because the purging is repeated consecutively, the bubbles near the passage wall grow larger. This is considerable in particular at the corners of the passage, lowering the recording quality.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an ink jet recorder which can perform good recording without its ejecting characteristic worsening even after purging.
It is another object of the invention to provide an ink jet recorder including a recording head having a plurality of ejection nozzles which can be purged individually, the recorder being able to cause the air bubbles produced in the head by purging to vanish effectively, and able to shorten the standby time.
It is still another object of the invention to provide a recording method for enabling the air bubbles produced in the recording head of an ink jet recorder by purging to vanish effectively.
It is a further object of the invention to provide a purging method which enables the air bubbles produced in the recording head of an ink jet recorder by purging to vanish effectively, and which can shorten the standby time. The head has a plurality of ejection nozzles which can be purged individually.
In accordance with a first aspect of the invention, an ink jet recorder is provided. The recorder includes a recording head having an ejection nozzle for ejecting ink onto a recording medium. The recorder also includes a purging apparatus for purging the nozzle to improve the ejection of ink from the nozzle. The recorder further includes a judging device and an authorizing device. If a command for operating the head is input in the recorder, the judging device judges whether a first time period has passed or not after the last purging by the purging apparatus. If the judging device judges that the first period has passed, the authorizing device authorizes the operation of the head. Thereby, the recorder performs recording, not just after the nozzle is purged, but when the first time period has passed after the purging. This period is sufficient for most of the air bubbles produced by the purging to vanish naturally. This eliminates air bubbles from the ink in the recording head, improving the ejecting characteristic. It is therefore possible to secure high recording quality.
The ink jet recorder may further include a purge controller for controlling the purging apparatus. The controller may make the purging apparatus perform purging before the recording head starts the recording authorized by the authorizing device. If the passage of time after the first time period is considerably short, the controller may control the purging apparatus in such a manner that no purging is performed. If the passage of time after this period is considerably long, recording may be started after purging is performed as the need arises. Thereby, the head is restored from the dryness of ink caused after the last purging and/or the production of air bubbles also caused after the last purging in the ink in the head. If this purging is performed, it is possible to cause the bubbles produced by the purging to vanish, by controlling the purging apparatus in such a manner that this apparatus waits a predetermined time after the purging and before the head starts recording.
The recording head may have a plurality of ejection nozzles in place of the single nozzle. In this case, the purging apparatus can purge each nozzle in accordance with an input command. When two or more of the nozzles are purged, the purge controller may make each of the two or more nozzles purged once in order and at least once again in order. After each of these nozzles is purged once and before it is purged at least once again, it may wait a predetermined time so that the air bubbles produced by the purging may vanish. After the predetermined time passes, similar purging may be repeated two or more times for the two or more nozzles. By purging the nozzles in such order, it is possible to effectively secure the time which the bubbles produced by purging take to vanish. The first time period may be one minute so that the bubbles produced by the last purging vanish securely.
The recorder may further include a timer for clocking the second time period after the last purging. If a command for operating the recording head is input in the recorder, the pu
Imai Koji
Nakamura Hirotake
Brother Kogyo Kabushiki Kaisha
Hsieh Shih-wen
Le N
Oliff & Berridg,e PLC
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