Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-10-28
2003-05-06
Nguyen, Thinh (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S021000
Reexamination Certificate
active
06557984
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an on-demand type ink-jet printing apparatus, and an ink-jet printing head which can be equipped in the ink-jet printing apparatus.
2. Description of the Related Art
In general, an ink-jet printing apparatus can be generally classified into a continuous ejection type (hereinafter also referred to as continuous type) and an on-demand type. The former continuous type ink-jet printing apparatus continuously ejects ink droplets from a fine nozzle at a predetermined period, and deposits the ink droplets at predetermined positions on printing paper as a printing medium, by subsequently applying an electric charge on the ink droplets for causing deflection toward the predetermined positions. Advantages of such continuous type ink-jet printing apparatus are high frequency response, capability of making the ink-droplet more fine, capability of high speed printing despite of single nozzle, and capability of performing printing of an image with high resolution. On the other hand, since such continuous type ink-jet printing apparatus requires a mechanism for collecting inks, overall construction becomes bulky and thus is not well suited for multiple nozzle construction.
In contrast to this, in the case of the former on-demand type ink-jet printing apparatus, ink can be deposited at predetermined positions on the printing paper as a printing medium by controlling ink ejection from nozzles corresponding to the position to perform image printing in a system ejecting an ink using a pressure by deformation of a piezoelectric element provided in a plurality of fine nozzles or a pressure generated by volume expansion of a bubble generated by heating of the ink for causing film boiling by a heating element. The ink-jet printing apparatus of this type is advantageous in easiness for adaptation to multiple nozzle construction for simple construction and in realization of compact and inexpensive image printing apparatus. On the other hand, since the ink does not always flow through the nozzle, plugging of the nozzle due to drying of the ink, variation of quality of the ink, penetration of dust and so on can be caused. Therefore, a recovery mechanism for solving the problem of plugging becomes inherent.
On the other hand, in the foregoing two types of ink-jet printing apparatus, a common problem is encountered in difficulty of density modulation of the ink droplet. Therefore, expression of more precise gradation in an intermediate tone can be realized only by a system controlling size of the ink droplets among a plurality of steps of sizes of the ink droplets, and by a system performing ejection from different nozzles with a plurality of mutually different densities of inks.
The highest quality of more precise gradation expression is achieved by a system performing printing with varying density of the ink droplets without varying size of the ink droplet.
Such system in the continuous type ink-jet printing apparatus has been proposed in U.S. Pat. No. 4,614,953. On the other hand, such system in the on-demand type ink-jet printing apparatus has been proposed in Japanese Patent Application Laid-open No. 5-201024 (1993) (U.S. Pat. No. 5,371,529).
However, in U.S. Pat. No. 4,614,953 directed to the continuous type ink-jet printing apparatus, difficulty in employing a plurality of nozzles as drawback of the continuous type is not mentioned. Therefore, the continuous type is not applicable for compact and inexpensive printing apparatus.
On the other hand, in Japanese Patent Application Laid-open No. 5-201024 (1993) (U.S. Pat. No. 5,371,529) directed to the on-demand type ink-jet printing apparatus, a mechanism for mixing the inks per the ejection nozzle is disclosed. However, due to the presence of such mixing mechanism, down-sizing can be hindered upon employing the multiple nozzle construction. Furthermore, fluctuation of the ink density between the nozzles can be caused easily.
SUMMARY OF THE INVENTION
The present invention has been worked out for solving the problems set forth above. It is a first object of the present invention to provide an ink-jet printing head and an ink-jet printing apparatus which can reduce fluctuation of density of an ink ejected from each nozzle by ejecting ink of different densities from the same nozzle without varying size of an ink droplet, or by controlling ejection of a mixture ink, in which a plurality of inks are mixed, for forming an image.
A second object of the present invention is to provide an ink-jet printing head and an ink-jet printing apparatus which can minimize consumption of ink.
A third object of the present invention is to provide various modes of implementation associated with the ink-jet printing head and the ink-jet printing apparatus according to the present invention.
To achieve the first object of the present invention, there is provided an ink-jet printing head comprising:
a plurality of ejection openings for ejecting ink;
a plurality of ink passages respectively communicated with the plurality of ejection openings;
means provided in the plurality of ink passages for ejecting ink;
a mixing liquid chamber connected to the plurality of ink passages in common;
a plurality of individual liquid chambers supplying ink to the mixing liquid chamber; and
a valve mechanism, provided between each the individual liquid chamber and the mixing liquid chamber, for controlling a supply amount of the ink supplied from the individual liquid chamber.
With the printing head constructed as set forth above, by providing one mixing liquid chamber communicated with a plurality of ejection openings and a plurality of ink supply passages and by providing control means for controlling ink supply amount to the mixing liquid chamber, it becomes possible to vary the density with maintaining the size of the ink droplet constant to realize printing with higher printing quality. On the other hand, by adjusting the ink density in the mixing liquid chamber, the ink with different densities can be ejected without using a plurality of printing heads and preliminarily prepared inks with different densities. For example, a colored ink is filled in one of two individual liquid chambers communicated with the mixing liquid chamber, and an achromatic ink is filled in the other individual chamber to obtain an ink of the density of half of the colored ink by mixing the colored ink and the achromatic ink within the mixing liquid chamber in a proportion of 1:1. Furthermore, it is possible to fill the ink of cyan color in one of the individual liquid chambers and to fill the ink of yellow color in the other individual liquid chamber to obtain the ink of green color by mixing both inks in a proportion of 1:1 within the mixing liquid chamber.
Here, the ink-jet printing head as claimed in claim
1
, which further may comprise ink moving means for moving the ink by applying energy to the ink sufficient for moving the ink from the individual liquid chamber to the mixing liquid chamber.
The plurality of individual liquid chambers may contain inks having mutually different compositions respectively.
A washing liquid which is supplied for discharging liquid in the mixing liquid chamber, may be stored in one of the plurality of individual liquid chambers.
A plurality of the valve mechanisms may be provided for each of the individual liquid chambers.
The plurality of valve mechanisms may be provided corresponding to ink passages having different open areas between the individual liquid chamber and the mixing liquid chamber.
The plurality of valve mechanisms may be provided corresponding to ink passages having the same open area between the individual liquid chamber and the mixing liquid chamber.
A partitioning wall serving as ink mixing means may be provided in the mixing liquid chamber for promoting mixing of the inks.
A discharge passage for discharging a mixture ink in the mixing liquid chamber.
A plurality of ejection openings may be arranged in a row and the discharge passage may be communicated with a discharge ope
Hyotani Hiroyuki
Ito Akira
Okada Masaaki
Ono Takeshi
Suzuki Noriyuki
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Nguyen Thinh
LandOfFree
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