Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-11-09
2001-08-07
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06270195
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to an image forming apparatus which forms images on a recording medium by causing a developer to jump thereto. It may be used for a printer unit in digital copiers and facsimile machines as well as for digital printers, plotters, and the like.
(2) Description of the Related Art
Recently, as the image forming means for outputting a visual image on recording medium such as paper etc., in response to an image signal, an image forming apparatus has been disclosed in Japanese Patent Application Laid-Open Hei 5 No. 134,581, for example, wherein charged particles are placed in an electric field so that they will jump by electric force to adhere to the recording medium whilst the potential to be applied to the control electrode having a number of passage holes located in the jump passage is being varied, to thereby form an image on the recording medium, directly.
In the above-mentioned related art, a method of controlling the developer is described, but the method suffers from many problems as shown below.
An image forming apparatus of a type of the above related art uses a control means for controlling the passage of charged particles through the gates. In the image forming apparatus of the type of the conventional art, jumping of the toner (developer), either the release or prohibition of the jumping, is controlled by regulating the electric field generated between the gates and the toner support while the strong electric field produced by the opposing electrode causes the toner to transfer to the surface of a paper as a recording medium and form an image thereon.
In the above-mentioned image forming apparatus, no charge having a polarity opposite to that of the toner will be given to the rearside of the recording medium, unlike the transfer process in the Carlson process. Therefore, when the recording medium slides on the metal disposed in its conveyance path, the charge on the toner constituting the image induces a very strong image force with respect to the metal. In this situation, a force acts on the toner on the recording medium in the direction opposite to the direction of movement of the recording medium, especially at the end portion of the metal. This causes the toner on the recording medium to move relatively from each other and form an image with a rubbed-like appearance, resulting in a disturbed developed image.
Further, in the image forming apparatus using plural colors of toner, this type of disturbance in the image causes color mixing of the multiple colors of toner, producing a new problem, that is, a failure in correct color reproduction.
SUMMARY OF THE INVENTION
The present invention has been achieved in view of the above problems and the present invention is configured as follows:
In accordance with the first aspect of the invention, an image forming apparatus includes:
a supplying means having at least one developer support each of which carries a developer of one kind of color;
an opposing electrode disposed facing the developer support;
a high-voltage power source for supplying a high voltage to produce a potential difference between the developer support and the opposing electrode;
a control electrode comprising an insulative substrate, a plurality of gates formed in the insulative substrate for forming the passage of the developer, and one or more electrodes provided around each of the gates, the control electrode being disposed between the developer support and the opposing electrode; and
a control circuit for selectively applying multiple potential states to each of the electrodes around each of the gates, wherein the control circuit controls the passage of the developer through the gates by applying the predetermined voltage to desired electrodes so as to form an image on the surface of a recording medium which is being conveyed over the opposing electrode, and is characterized in that means for reducing the component of an electric force, acting on the developer particles residing on the recording medium, in the direction opposite to the direction of conveying the recording medium, is provided at the downstream side of the opposing electrode.
In accordance with the second aspect of the invention, the image forming apparatus having the above first feature is characterized in that the means for reducing is provided in such a manner that the downstream side portion of the opposing electrode, with respect to the direction of conveying the recording medium, becomes gradually spaced away from the path of the recording medium.
In accordance with the third aspect of the invention, the image forming apparatus having the above second feature is characterized in that a dielectric material is provided between the path of the recording medium and the portion of the opposing electrode which gradually becomes spaced away from the path of the recording medium.
In accordance with the fourth aspect of the invention, the image forming apparatus having the above first or second feature is characterized in that the means for reducing comprises a plurality of reducing structures correspondingly to individual developers having different characteristics and each reducing structure is different from each other.
In accordance with the fifth aspect of the invention, the image forming apparatus having the above fourth feature is characterized in that the means for reducing is adjusted so that an identical configuration can be used for all the reducing structures.
REFERENCES:
patent: 5874973 (1999-02-01), Wakahara
patent: 5-134581 (1993-05-01), None
Ogasawara Hironori
Wakahara Shirou
Barlow John
Conlin David G.
Dike Bronstein Roberts & Cushman IP Group
Gordon Raquel Yvette
Sharp Kabushiki Kaisha
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