Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-09-03
2001-12-18
Gordon, Raquel Yvette (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06331046
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an inkjet recording apparatus which is capable of ejecting particulate matter such as pigment matter and toner matter by making use of an electric field, and more particularly to an improved arrangement of the inkjet recording apparatus.
2. Description of the Related Art
There has recently been a growing interest in non-impact recording methods, because noise while recording is extremely small to such a degree that it can be neglected. Particularly, inkjet recording methods are extremely effective in that they are structurally simple and that they can perform high-speed recording directly onto ordinary medium. As one of the inkjet recording methods, there is an electrostatic inkjet recording method.
The electrostatic inkjet recording apparatus generally has an electrostatic inkjet head and a counter electrode which is disposed behind the recording medium to form an electric field. The electrostatic inkjet head has an ink chamber which temporarily stores ink containing toner particles and a plurality of ejection electrodes formed near the end of the ink chamber and directed toward the counter electrode. The ink near the front end of the ejection electrode forms a concave meniscus due to its surface tension, and consequently, the ink is supplied to the front end of the ejection electrode. If positive voltage relative to the counter electrode is supplied to a certain ejection electrode of the head, then the particulate matter in ink will be moved toward the front end of that ejection electrode by the electric field generated between the ejection electrode and the counter electrode. When the coulomb force due to the electric field between the ejection electrode and the counter electrode considerably exceeds the surface tension of the ink liquid, the particulate matter reaching the front end of the ejection electrode is jetted toward the counter electrode as an agglomeration of particulate matter having a small quantity of liquid, and consequently, the jetted agglomeration adheres to the surface of the recording medium. Thus, by applying pulses of positive voltage to a desired ejection electrode, agglomerations of particulate matter are jetted in sequence from the front end of the ejection electrode, and printing is performed. An inkjet head like this is disclosed, for example, in Japan Laid-Open Patent Publication No. 60-228162.
As another conventional example, there has been disclosed an electrostatic inkjet head having a gate electrode provided in front of an ink electrode in Japan Laid-Open Patent Publication No. 1-165452. The gate electrode has an opening or slit through which ink droplets are jetted. Since the distance between the gate electrode and the ink electrode is relatively short, ink ejection occurs when applying a lower driving voltage to the ink electrode.
However, when the inkjet head starts moving, vibrations from head movement cause the ink in the ink chamber to flow from the nozzle of the inkjet head to outside, which eventually forms an ink bridge between the nozzle and the opening of the gate electrode. There are cases where the opening of the gate electrode is blocked with the ink bridge and ink ejection becomes impossible, resulting in deteriorated printing quality. Even in the case of no ink bridge, the jetted ink is left in meniscus form in the opening of the gate electrode, which may also causes impossible ink ejection.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an inkjet head that can perform ink ejection with reliability and stability.
Another object of the present invention is to provide a novel arrangement of an inkjet head that can effectively remove remaining ink from an opening in front of an ejection electrode.
According to the present invention, an inkjet head is provided with a plurality of ejection electrodes arranged in an ink chamber containing ink including particulate matter. The inkjet head is further provided with a front end plate that is laced at a predetermined distance from the ejection electrodes. The front end plate has a slit formed such that the ejection electrodes are directed to the slit and an ink drain coupled to the slit for draining ink from the slit.
The ink drain may has at least one drain slit formed in the front end plate and a width of the drain slit may be smaller than that of the slit so that capillary action occurs.
Further, the ink drain may include at least one drain slit formed in the front end plate and an ink absorber provided to the front end plate at a position corresponding to the drain slit.
The front end plate may be a conductive plate to which a predetermined voltage is applied to generate a voltage difference causing ink ejection of an ejection electrode when the ejection electrode is driven.
Since the ink drain is coupled to the slit to drain ink from the slit, even though an ink bridge is formed between the ejection electrodes and the front end plate due to vibrations or the like, the ink is immediately removed from the slit through the ink drain. Therefore, reliable and stable ink ejection can be achieved.
REFERENCES:
patent: 4403234 (1983-09-01), Miura et al.
patent: 6059399 (2000-05-01), Suetsugu et al.
patent: 6097407 (2000-08-01), Terasawa et al.
patent: 0780740 (1997-06-01), None
patent: 58-69062 (1983-04-01), None
patent: 60-228162 (1985-11-01), None
patent: 1165452 (1989-06-01), None
patent: 1-165452 (1989-06-01), None
patent: 6-270417 (1994-09-01), None
patent: 9066611 (1997-03-01), None
patent: 10-86380 (1998-04-01), None
Japanese Office Action issued Jun. 28, 1999 in connection with a related application.
English-language translation of relevant portions of the Jun. 28, 1999 Japanese Office Action.
European Search Report (in English) issued Dec. 7, 1999 in a related application.
Hagiwara Yoshihiro
Minemoto Hitoshi
Mizoguchi Tadashi
Shima Kazuo
Suetsucu Junichi
Gordon Raquel Yvette
NEC Corporation
Ostrolenk Faber Gerb & Soffen, LLP
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