Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2002-01-30
2004-03-09
Hsieh, Shih-Wen (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S029000
Reexamination Certificate
active
06702423
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cleaning device for an inkjet printing head and a method for cleaning such a head. The present invention also relates to a wiper to be used for cleaning the inkjet recording head, and an inkjet recording apparatus having such a wiper.
2. Description of the Related Art
Printing apparatuses have their respective functions of printing, copying, and facsimile machines, or used as output devices of complex electronic devices (e.g., computers and word processors) and workstations. Each of such printing apparatuses is configured to print an image on an object to be printed (hereinafter, referred as a printing medium) such as a sheet of paper or a plastic sheet in accordance with image information. In addition, the printing apparatus may be classified into one of several types, i.e., inkjet type, wire-dot type, thermal type, laser-beam type, and the like by its printing procedure.
For a serial-type printing apparatus, a printing means performs a main-scanning movement in the direction (i.e., a main-scanning direction) that intersects the direction (i.e., a sub-scanning direction) of transferring a printing medium. The serial-type printing apparatus prints information throughout the printing medium by repeating the following procedure. First, the printing medium is arranged in a predetermined printing position, and subsequently one line of image is printed on the printing medium by the printing means mounted on a carriage that moves along the printing medium in the main-scanning direction. After that, the printing medium shifts its position at a predetermined pitch in the sub-scanning direction (i.e., a pitch transfer) and then a subsequent line of image is printed on the printing medium being stopped again.
For a line-type printing apparatus, on the other hand, a printing means does not perform a main-scanning movement and an image can be printed by a sub-scanning movement of printing medium in its transfer direction. The line-type printing apparatus prints information throughout the printing medium by repeating the following procedure. First, the printing medium is arranged in a predetermined printing position. Then, the printing means placed in a predetermined position prints one line of image on the printing medium at a time. Subsequently, the printing medium shifts its position at a predetermined pitch in the sub-scanning direction (i.e., a pitch transfer), followed by printing a subsequent line of image on the printing medium at a time.
Among the printing apparatuses, the inkjet type printing apparatus (also simply referred as an inkjet printing apparatus) prints information on a printing medium by ejecting ink thereon from a printing means (i.e., a printing head). Such an inkjet printing apparatus can be configured so as to easily make the printing means as compact as possible and print an image with extraordinary definition at high speed on a piece of ordinary paper without a specific treatment thereon. In addition, the inkjet printing apparatus has the advantages of: its excellent cost/performance ratio, an operation mode with a low noise level (i.e., a non-impact operation mode), and a multi-color print using multiple colors with ease. A line-type inkjet printing apparatus, in particular, uses a line-type-printing head where a plurality of orifices is arranged in the width direction of printing medium and allows a high-speed printing more than ever.
Particularly, an inkjet printing head that ejects ink using thermal energies can be easily made as one having a high-density liquid path arrangement (a high-density orifice arrangement) by means of semiconductor fabrication process including etching, sputtering, and deposition to form electrothermal conversion elements, electrodes, liquid-path walls, and a top plate on a substrate, resulting in compact more than ever.
There is a wide variety of demands on the material of printing medium. In recent years, the use of thin paper and converted paper (e.g., paper punched with holes or perforated for filing, and paper with some specified shape) has come to be demanded by a person skilled in the art in addition to the use of ordinary printing media such as ordinary paper and resin thin plate (e.g., OHP sheet).
For the inkjet printing apparatus described above, an ink-supplying path from an ink tank to the inkjet printing head may be contaminated with foreign substances such as dust and air bubbles. As an inner diameter of a liquid path communicating with an orifice formed on the printing head is small on the order of a few tens of micrometer, there is the fear of preventing a flow of ink passing through the liquid path by the depositing of the foreign substances on the interior wall of the liquid path when such substances arrive in the liquid path, resulting in the decreased efficiency of ink ejection and the decreased responsivity of ink ejection to printing signal. If such conditions become serious, ejection failures including a failed ink ejection may be caused as a result of clogging the orifice. The consistency of ink composition becomes increased when the ink ejection has not been performed even though ink remains in the liquid path of the inkjet printing apparatus. As a result, the ejection failures may be also caused by fixing the ink components on the liquid path.
There is also the possibility of the depositing of ink droplets, waterdrops, and foreign substance such as dust on a surface (also referred as an orifice surface) of ink-ejecting orifices of the inkjet printing head. Such a deposit may pull an ejected ink droplet to change the direction of ink ejection. As a result, an image degradation may be occurred.
For the sake of resolving those disadvantages, the inkjet printing apparatus has a specific configuration that cannot be found in other printing apparatuses. That is, an ejection-failure recovering system having means for cleaning ink in the liquid path and means for keeping the favorable condition of the orifice surface is provided on the inkjet printing apparatus.
Approaches for recovering the ejection failure by such a recovering system includes the introduction of fresh ink into the liquid path. For the introduction of fresh ink, there is a method known as “a preliminary ejection” or “an empty ejection”, where ink which is not responsible for printing an image is ejected from the printing head into a predetermined ink receiver by driving an element that ejects energy for ejecting ink (an ejection energy generating element). Alternatively, there is another method known as “a pumping”, where ink is forced to be discharged from an orifice by applying a predetermined pressure on the liquid path or by drawing in ink from the orifice by suction or the like.
Furthermore, there is a method known as “a wiping” using a wiping member that moves over an orifice surface of the inkjet printing head while maintaining continuous contact. In the wiping method, the orifice surface can be wiped clean of an ink droplet or a foreign substance (e.g., dust) being deposited in the vicinity of the orifice by relatively moving the printing head and the cleaning member.
For the wiping member, an elastic material such as urethane rubber is generally used. The performance of the wiping member depends on the quality of its material and the mechanical set-up condition. For maintaining the performance all the time, it is preferable to keep a surface of the wiping member clean. Thus, most of the inkjet printing apparatuses has a cleaning mechanism in which the wiping member wipes or scratches viscous ink or foreign substances and then pushes them to an absorber or the like so as to absorb the wiped or scratched one into the absorber.
If the ink being collected by the wiping member turns into the side of the printing head, the following problems may be caused. That is, for example, the accumulation of such viscous ink adheres on a pitch roller portion (a transfer means for a printing medium) and smears on the printing medium fed in place; the ink makes user&apo
Okamura Yoshitaka
Yazawa Takeshi
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