Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1994-05-26
2003-03-04
Nguyen, Judy (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S024000
Reexamination Certificate
active
06527361
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to ink jet recording on a recording medium, such as paper or cloth, and, in particular, to refreshing and recovering ink discharge in an ink jet recording apparatus.
2. Description of the Related Art
Recording apparatuses, such as printers, copying machines and facsimile apparatuses, record images consisting of dot patterns on recording media, such as paper, cloth or thin plastic films, on the basis of image information.
Depending on the recording method, such recording apparatuses can be classified into ink jet type apparatuses, wire dot type apparatuses, thermal type apparatuses, laser beam type apparatuses, etc. An ink jet apparatus records by ejecting ink (recording liquid) from ejection ports of the recording head so as to cause the ink to adhere to the recording medium.
Recently, various types of recording apparatuses have come into use. The most useful of such apparatuses comply with various requirements, such as providing high-speed, high-resolution, high image quality and low-noise recording.
With that in mind, ink jet type recording systems have been attracting attention because they are very quiet. In particular, an ink jet type recording system utilizing bubble jetting of liquid (hereinafter referred to as “BJ”) by heating has been attracting attention as a high quality and inexpensive high-speed printing method readily allowing an increase in recording density, being very quiet and readily enabling color printing.
Further, because they increase recording speed, recording apparatuses having a recording head with a plurality of recording elements (hereinafter referred to as a “multi head”) have come into general use. Further, to cope with various requirements of color recording, a recording apparatus having a plurality of such multi heads has been developed.
FIGS.
6
(
a
) and
6
(
b
) are perspective views of an example of a conventional ink jet recording head used in a typical ink jet recording apparatus. As shown in these drawings, this ink jet recording head includes: an orifice plate
21
c
having ink discharge ports (orifices)
21
b;
a grooved top plate
23
having grooves
10
forming ink passages (nozzles) communicating with the orifices and a common liquid chamber
13
forming an ink accumulator; and a heater board
16
having heat generators
22
provided in the ink passages and consisting of electro-thermal converters serving as heat energy generating elements for generating heat energy to be utilized in creating bubbles and ejecting ink from the orifices. Numeral
21
a
indicates an ink supply port leading to the common liquid chamber
13
and the ink passages.
An ink jet apparatus equipped with such an ink jet head has a cap used in a suction recovery operation, in which ink is sucked through the discharge ports in order to eliminate defective ejections. The cap also serves to prevent ink from drying in the discharge ports. As ink is being repeatedly ejected during recording, some bubbles in the ink passages may fail to disappear. If too many bubbles remain in the ink passage, or if the volume of the bubbles becomes so large as to block the nozzle outlets, it will become impossible to ensure passage of ink through the ink supply passages. The suction recovery operation mentioned above is often performed for the purpose of removing such bubbles.
An ink jet recording apparatus having a plurality of recording head, for example, a color ink jet recording apparatus having recording heads respectively corresponding to four ink colors, black (Bk), cyan (C), magenta (M) and yellow (Y), is provided, for example, with four suction/shutdown caps and four suction pumps respectively connected thereto, or a single large suction pump connected to all four caps. In such an ink jet recording apparatus, all of the different colored inks may be sucked simultaneously. In a type of ink jet recording apparatus which has a single suction pump, a single cap exclusively used for sucking, and shutdown caps for the recording heads, the suction of the inks in the recording heads is successively effected from head to head.
Conventionally, when performing a suction recovery operation, a cylinder pump has been used, which pump utilizes, instead of the gravitational force of the ink, piston movements, thus enabling the ink to be reliably recovered. This cylinder pump utilizes the surface of its piston when opening or closing a hole through which waste ink is recovered from an ink receiving member such as a cap, and causes the waste ink to be moved, by way of a waste ink transfer passage provided on the piston rod, to a waste ink container having a larger capacity for storing ink than the ink receiving member.
A color ink jet recording apparatus of the type in which a plurality of recording heads are successively sucked by using a single suction cap and a single suction pump, has a problem in that inks of different colors can be mixed in the suction cap when sucked therein, so that such mixed ink can be drawn into a nozzle, resulting in a mixed colored ink being printed on the recording paper.
To copy with this problem, preliminary ink ejection is performed in order to drain any mixed ink in the nozzle. However, to completely drain the mixed ink in the nozzle, the preliminary ejection has to be performed a number of times, which uses excessive ink and takes a long time.
Further, it is known that some of the solvent contained in the ink may evaporate from the ends of the nozzles, resulting in density inconsistencies at the start of the printing. To solve this problem, ink discharge by suction or pressurization is performed when printing is to be performed for the first time after a long shutdown period in order that such density inconsistencies may be mitigated. Further, an ink refreshing operation, such as preliminary ink ejection, can also be performed at a position and timing which do not interfere with the recording.
Further, wiping is performed in order to completely remove any ink remaining on the ejection face of the head after completion of an ejection recovery operation based on suction and pressurization and to remove any ink mist that has settled on the ejection face during and after printing. During this wiping operation, which is performed with a single wiper, some of the ink on the wiper can be transferred to the discharge port and mixed with the ink therein. To remove the resulting mixed ink, it is necessary to perform a discharge operation as in the case when preventing density inconsistencies. Thus, when a single wiping mechanism is used for a head using inks of different colors, inks of different degrees of lightness may be mixed with each other, making it necessary to perform an additional discharge operation in order to eliminate density inconsistencies caused by the recovery operation.
Such additional discharge can be effected, for example, by always performing a recovery operation, such as preliminary ink ejection or suction, whenever printing is performed, independently of how printing has been performed by the apparatus up to that moment. Alteratively, the recording apparatus may be provided with a timer for counting non-printing periods including power-off periods. In that case, a recovery operation is conducted whenever the time counted by the timer exceeds a predetermined length of time. Further, it is also possible to divide the time to be counted by the timer. That is, when the shutdown period has been short and a relatively slight evaporation on ink is expected, the recovery operation consists of preliminary ejection only. When the shutdown period has been long and the density inconsistencies cannot be easily eliminated by such ejection alone, ink discharge is effected by suction and pressurization. When the timer is used in this way, it is possible to attain a reduction in the amount of ink consumed since only preliminary ejection, which consumes a relatively small amount of ink, is conducted in the case where a slight amount of ink has been evaporated.
However, in a case
Fujita Miyuki
Gotoh Fumihiro
Hirabayashi Hiromitsu
Koitabashi Noribumi
Nagoshi Shigeyasu
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Nguyen Judy
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