Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1997-10-22
2001-05-01
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06224193
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 control for 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 recording head and a counter electrode which is disposed behind the recording medium to form an electric field between it and the recording head. The electrostatic inkjet recording 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. A recording head such as this is disclosed, for example, in Japan Laid-Open Patent Publication No. 60-228162.
Particularly, In the Publication (60-228162), there is disclosed an electrostatic inkjet printer head where a plurality of ejection electrodes are disposed in an slit, and the front end of each ejection electrode is formed on the projecting portion of a head base which projects from the slit. The front end of this projecting portion has a pointed configuration, and the ejection electrode is formed in accordance with the direction of the pointed end. An ink meniscus is formed near the front end of the ejection electrode.
In the conventional electrostatic inkjet device as mentioned above, when voltage pulses are consecutively applied to an ejection electrode in relatively short intervals, the particulate matter is supplied to the front end of the ejection electrode and then is jetted toward the counter electrode. However, in cases where the time interval between voltage pulses is long, the particulate matter withdraws from the front end of the ejection electrode because of reduced electrostatic force during the interval. In such a state, when the voltage pulse is applied, the particulate matter cannot be instantly jetted. Therefore, no ink may be jetted by that ejection electrode, resulting in deteriorated quality of printing.
Further, in the conventional electrostatic inkjet device, an ejection electrode which is not driven is grounded. Therefore, when an ejection electrode is driven and the adjacent ejection electrodes are not driven, an electric field is generated between the driven ejection electrode and the adjacent ejection electrodes. The electric field generated between them causes the particulate matter in the ink to drift away from the driven ejection electrode, resulting in deteriorated quality of printing.
SUMMARY OF THE INVENTION
It is an objective of the present invention to provide an inkjet recording apparatus which can eject ink from an ejection electrode with reliability and stability.
Another objective of the present invention is to provide method and apparatus which are capable of stably forming ink meniscus at an selected ejection electrode.
According to the present invention, an inkjet recording apparatus includes a plurality of ejection electrodes arranged in an ink chamber containing ink including particulate matter and a gate electrode plate. The gate electrode plate has a plurality of gate electrodes therein corresponding to the ejection electrodes, respectively. Each of gate electrodes has an opening therein, wherein each ejection electrode is directed to an opening of a gate electrode corresponding to the ejection electrode. In such a constitution, a controller generates a voltage difference between the ejection electrode and the gate electrode, the voltage difference changing between a first value and a second value depending on an input signal. The first value is equal to or greater than a predetermined value and the second value is smaller than the predetermined value. The predetermined value is a minimum value which causes ejection of particulate matter from each ejection electrode.
According to an aspect of the present invention, when the ejection electrode is selected for ejection, a control voltage varying depending on the input signal may be applied to the ejection electrode and the gate electrodes may be kept at a predetermined voltage to produce the voltage difference. In this case, the control voltage may change between a first voltage and a second voltage depending on the input signal when the ejection electrode is selected for ejection and the second voltage may be applied to the ejection electrodes other than the ejection electrode which is selected for ejection, wherein the first voltage is applied to the ejection electrode for a predetermined period to perform ejection of particulate matter and the second voltage is applied to the ejection electrode during periods other than the predetermined period.
According to another aspect of the present invention, a first control voltage varying depending on the input signal may be applied to the ejection electrodes and a second control voltage changing depending on the input signal may be applied to the gate electrode to produce the voltage difference. In this case, the first control voltage may change between a first voltage and a second voltage depending on the input signal such that the first voltage is applied to the ejection electrodes for a predetermined period and the second voltage is applied to the ejection electrodes during periods other than the predetermined period. The second control voltage may change between a third voltage and a fourth voltage depending on the input signal such that the third voltage is applied to the gate electrode corresponding to the ejection electrode when the ejection electrode is selected for ejection and otherwise the fourth voltage is applied to the gate electrode.
REFERENCES:
patent: 4477869 (1984-10-01), Rudd, III
patent: 4504844 (1985-03-01), Ebi et al.
patent: 4684957 (1987-08-01), Miura et al.
patent: 5742412 (1998-04-01), Minemoto et al.
patent: 5886723 (1999-03-01), Kubelik et al.
patent: 0 703 080 (1996-03-01), None
patent: 0813965 (1997-12-01), None
patent: 60-228162 (1985-11-01), None
patent: 93/11866 (1993-06-01), None
Hagiwara Yoshihiro
Minemoto Hitoshi
Mizocuchi Tadashi
Shima Kazuo
Suetsugu Junichi
Barlow John
Gordon Raquel Yvette
NEC Corporation
Ostrolenk Faber Gerb & Soffen, LLP
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