Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
2002-01-30
2003-10-28
Hsieh, Shih-Wen (Department: 2861)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
Reexamination Certificate
active
06637874
ABSTRACT:
This application is based on Patent Application Nos. 2001-024549 filed Jan. 31, 2001 in Japan and 2002-003917 filed Jan. 10, 2002 in Japan, the contents of which are incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid ejection head, a suction recovering method, a head cartridge incorporating the liquid ejection head and an image forming apparatus using the liquid ejection head.
In this Specification, a word “print” refers to not only forming a significant information, such as characters and figures, but also forming images, designs or patterns on a printing medium and processing such as etching and so forth in the printing medium, whether the information is significant or insignificant or whether it is visible so as to be perceived by humans.
The term “printing medium” includes not only paper used in common printing apparatus, but also sheet materials such as cloths, plastic films, metal sheets, glass plates, ceramic sheets, wood panels and leathers or three-dimensional materials such as spheres, round pipes and so forth which can receive the ink.
Further, the word “ink” should be interpreted in its wide sense as with the word “print”, refers to liquid that is applied to the printing medium for forming images, designs or patterns, processing such as etching in the printing medium or processing such as coagulating or insolubilizing a colorant in the ink and includes any liquids used for printing.
2. Description of the Related Art
Ink jet printers may inappropriately eject a liquid, that is, ink and/or a treatment liquid that adjusts the printability of the ink on a printing medium, when the entire apparatus may not be used over a long period or the liquid is rarely ejected from particular ones of many ejection ports compared to the others. This is because the liquid evaporates in the ejection ports or liquid channels that are in communication therewith, thereby increasing the viscosity of the ink. Ejected droplets of the liquid or water or dusts may be accreted to an ejection surface of an ink jet head having the ejection ports disposed therein, and newly ejected liquid droplets may pulled by these depositions and thus ejected in a biased direction.
To prevent these inconveniences, conventional ink jet printers comprise the following means as what is called an ejection recovering device, e.g. preliminary ejecting means for ejecting the liquid to liquid receiving element before a print operation to remove viscosity-increased ink, liquid sucking means for sucking the liquid from the ejection ports or a common liquid chamber to remove the depositions, and capping means for preventing the liquid from evaporating through the ejection ports.
Ink jet printers which can print colored images have been developed which comprise one ink jet head having a group of ejection ports for black color as well as ejection port groups for color inks, for example, yellow, magenta, and cyan inks, an independent ink tank and an independent ink supply system provided for each group of ejection ports, and a common recovering cap and a common ejection recovering means shared by all the ejection port groups. Ink jet printers of this kind form color print images other than black ones using two or three colors. In this case, if the amount of color ink ejected per dot is equal to that of black ink ejected per dot, ink dots printed on the printing medium such as paper have an excessively large diameter. Thus, the ejection ports for the color inks have a smaller diameter than those for the black ink or the liquid channels that are in communication with the ejection ports for the color inks have a cross sectional area different from that of the liquid channels which are in communication with the ejection ports for the black ink. With what is called a bubble jet method of ejecting liquid droplets on the basis of heating by electrothermal transducers or the like, the electrothermal transducers for the color inks have a smaller area or the distance between the electrothermal transducers and ejection ports for the color inks is different from that for the black ink. With ink jet printers using plural types of inks having different shading, the same ink jet head or head cartridge has a plurality of ejection port groups formed therein, and the ejection ports of each ejection port group and the liquid channels that are in communication with the ejection ports have different diameters and cross sectional areas, respectively.
To improve the quality of print images and printing speed, ink jet heads have been designed which use the above described ink jet head technique for multicolor inks or inks with different colorant concentrations to eject common ink from a plurality of ejection port groups having different opening areas.
It is assumed that a suction recovering process is performed on a liquid ejection head comprising a liquid supplying port to which a liquid is supplied, liquid supplying passages having one end in communication with the liquid supplying port, a common liquid chamber that is in communication with the other end of each of the liquid supplying passages, and ejection port groups from which liquid droplets are ejected. In this case, when the liquid is simultaneously sucked through a ejection port group having a larger sum of opening areas of the ejection ports and from a ejection port group having a smaller sum of opening areas of the ejection ports, a larger amount of liquid tends to be sucked in the former case.
If the individual liquid channels that are in communication with the ejection port groups have substantially the same volume, substantially the same amount of liquid is discharged during suction recovery. Thus, when the suction recovering process is performed in favor of the ejection port group having a smaller sum of opening areas of the ejection ports, more than a required amount of liquid is sucked and ejected from the ejection port group having a larger sum of opening areas of the ejection ports. As a result, the liquid is wastefully consumed.
With ink jet heads using liquid tanks incorporating porous members such as sponge which holds the liquid, if different amounts of liquid are sucked and ejected from the respective tanks, then bubbles may be contained in the liquid supplying passages in an ink jet head having liquid tanks connected thereto and from which larger amounts of liquid are discharged.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a liquid ejection head wherein when a liquid is simultaneously sucked through a plurality of ejection port groups having different passage resistances, substantially the same amount of liquid is sucked through the individual ejection port groups or the amounts of liquid sucked through the individual ejection port groups are adjusted to be the same.
It is another object of the present invention to provide a liquid ejection head wherein when a liquid is simultaneously sucked through a plurality of ejection port groups having different ejection port configurations, the liquid can be efficiently sucked, and bubble are prevented from being taken in liquid channels, while restraining the liquid from being wastefully consumed.
It is yet another object of the present invention is to provide a suction recovering method wherein when a liquid is simultaneously sucked through a plurality of ejection port groups having different ejection port configurations, the liquid can be efficiently sucked, and bubble are prevented from being taken in liquid channels, while restraining the liquid from being wastefully consumed, as well as a head cartridge and an image forming apparatus both incorporating a liquid ejection head that can implement such a suction recovering method.
A first aspect of the present invention is in a liquid ejection head comprising a liquid supplying passage having one end in communication with a liquid supplying port to which a liquid is supplied, the liquid supplying passage branching into a plurality of branching paths by the way, a plur
Chikuma Toshiyuki
Iwasaki Osamu
Nishikori Hitoshi
Otsuka Naoji
Seki Satoshi
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