Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-07-08
2001-11-06
Le, N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S029000, C347S023000
Reexamination Certificate
active
06312089
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet recorder having a purging device for sucking ink from a ink jet head and a purging method therefor.
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. 9
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
. The ejection nozzles eject different colored inks including black, yellow, cyan and magenta, respectively. Four ink cartridges P
1
containing the respective colored inks are mounted replaceably on the head unit P
3
, and each connected to the corresponding nozzle 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
.
The printer is provided with a purging device having a cap P
6
and a suction pump (not shown) in order to purge the nozzles P
4
. 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
. The purging is also performed for introducing the ink into the recording head P
2
when the ink cartridge P
1
is replaced. 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.
Conventionally, when the purging operation is performed for all four ejection nozzles P
4
, the four ejection nozzles P
4
will be successively purged using one suction cap P
6
. The order in which the nozzles will be subjected to purging is determined by the lightness of the ink for the following reason. For example, when the purging operation is performed on two nozzles, the ink from one nozzle purged earlier may be deposited on the surface of the other nozzle to be purged next by the suction cap P
6
. In this situation, if the ink color ejected from the other nozzle is darker than that from the earlier purged nozzle, the printed color is little damaged because the darker color ink from the other nozzle might not be affected by the lighter color ink.
However, there has been a problem when the purging operation is performed in such a way that the ejection nozzle for the lighter color ink is purged earlier than the nozzle ejecting the darker ink. When the recording starts immediately after the purging, non-ejection of the darker ink might occur because of the air bubbles remaining in an ink passage after the purging. The non-ejection results in a noticeable lack of color on the printing medium. In order to avoid the problem, a certain waiting time was needed after the completion of purging before the recording could be started, so that the air bubbles in the passage could be absorbed into the ink, and thereby vanish therein.
U.S. patent application Ser. No. 09/053,756 filed on Apr. 2, 1998, which will be assigned to the present Assignee and corresponds to Japanese Patent Application No. 9-85366 filed on Apr. 3, 1997, discloses an ink jet printer provided with a recording head having a plurality of ejection surfaces each containing a nozzle for ejecting a different ink and a purging device for purging the nozzle of one ejection surface at a time. The printer also has a controller for controlling the purging device such that a nozzle having an ink with higher dry resistance is purged before a nozzle having an ink with lower dry resistance. The printer can prevent the nozzles from drying during the purging operation.
U.S. patent application Ser. No. 08/995,516 filed on Dec. 22, 1997, which will be assigned to the present Assignee and corresponds to Japanese Patent Application No. 9-85684 filed on Mar. 19, 1997, discloses an ink jet recorder provided with a plurality of recording heads each having ejection nozzle for ejecting a different color ink, an ink suction device for sucking ink from each head, and a pre-ejecting device for ejecting ink toward a portion for receiving used ink after sucking ink. When the ink is sucked from at least two heads within the plurality of heads, the ink suction device sucks the ink in an order which is different from an order of lightness of the ink color. As the ink for pre-ejection has a lighter color, the pre-ejection device pre-ejects the ink in larger amount.
SUMMARY OF THE INVENTION
It is an object of the invention, made in consideration of the aforementioned problem, to provide an ink jet recorder which can perform good color recording without noticeable lack of color even when the recording starts immediately after the purging operation. It is another object of the invention to provide a method for purging nozzles of the ink jet recorder, which can result in good color recording without noticeable lack of color even when the recording starts immediately after the purging operation.
According to a first aspect the invention, an ink jet recorder comprising: a recording head having a plurality of ejection surfaces each containing a nozzle for ejecting a different ink; a purging device that purges the nozzle of one ejection surface at a time within the plurality of ejection nozzles; and a controller that controls the purging device in such a manner that a nozzle for ejecting a darker color ink is purged before a nozzle for ejecting a lighter color ink.
As described above, if the lack of color occurs during ink jet recording due to defective recording, the lack of darker color ink on the color printed medium becomes more noticeable than the lighter color ink. However, the inventive ink jet recorder performs the purging operation such that the nozzle for the darker color ink is purged before the nozzle for the lighter color ink. In other words, the ejection nozzle for the darker color can have a longer waiting time than the nozzle for the lighter color ink until the recording is started after completion of the purging for all the nozzles. During this waiting time, the air bubbles remaining in the nozzle or the ink passage can be absorbed into the darker color ink and vanish. Thus, the lack of the darker color ink can be eliminated. Although the defective ejection of the nozzle might occur in the nozzle for the lighter color ink, the lack of color will be less noticeable due to the lightness of the color.
The purging device may comprise a suction cap to cover the one ejection surface and a suction pump to suck an ink in the recording head through the suction cap and the nozzle. The recorder may further comprise a moving device for moving the suction cap relative to the nozzle. The ink jet recorder may also comprise a carriage for holding the recording head thereon and moving relative to the purging device. The controller may control a position of the carriage relative to the purging device so that the nozzle for ejecting the darker color ink is purged before the nozzle for ejecting the lighter color ink.
The ink jet recorder may further comprise a wiper for wiping an ink deposited on the ejection surface. The controller may control the wiper so as to wipe the ink deposited on the ejection surface after the purging of each ejection surface. By using the wiper, ejection characteristics can be maintained as they were designed to be, and thus excellent color recording can be ensured.
The ink jet recorder may further comprise an ink receiver for receiving an ink flashed by the recording head. In this case, the controller may control the recording head so as to f
Brother Kogyo Kabushiki Kaisha
Hsieh Shih-Wen
Le N.
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