Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-03-09
2001-06-26
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06250744
ABSTRACT:
RELATED APPLICATION
This application is based upon Japanese Patent Application No. 10-56618, the content of which being incorporated by reference.
FIELD OF THE INVENTION
The present invention relates to a printing device for use with an image forming apparatus such as printer, copy machine, and facsimile. In particular, the present invention relates to a printing device for propelling printing particles onto a recording medium such as plain paper to form images thereon.
BACKGROUND OF THE INVENTION
U. S. Pat. No. 5,477,250 issued on Dec. 19, 1995 discloses a printing device. The printing device includes a rotatable cylinder or toner bearing member retaining charged toner particles or printing particles on its outer periphery, and a backing electrode spaced apart from the toner bearing member. The backing electrode is electrically connected to a power source, thereby forming an electric field for attracting the charged toner particles born on the toner bearing member toward the backing electrode. Interposed between the toner bearing member and the backing electrode is an insulating plate having a plurality of apertures through which the toner particles can pass. The insulating plate is provided with individual electrodes each of which electrodes surrounding the corresponding aperture.
In operation of the printing device, when a voltage is applied to the individual electrode in response to a printing signal, the toner particles on a portion of the surface of the toner bearing member facing the electrodes are energized. The energized toner particles are propelled from the toner bearing member into the corresponding apertures, and then passed through the corresponding apertures. Subsequently, the propelled toner particles are deposited on a recording sheet travelling through a passage between the substrate and the backing electrode, thereby forming an image corresponding to the image signal on the recording sheet.
The device, however, has a drawback that the toner particles diverge while being propelled from the toner bearing member and, as a result, each resultant dot formed on the recording sheet tends to be unnecessarily large in its size and low in its density. Further, according to the printing device, an amount of the toner particles to be propelled from the toner bearing member and a size of the resultant dot formed on the recording sheet can be controlled simply by controlling a duration for applying a voltage to the individual electrodes in response to the printing signals. However, this is far from useful for solving the above-mentioned drawback of the divergence of the toner particles.
SUMMARY OF THE INVENTION
Therefore, the object of the present invention is to provide a printing device capable of converging the propelled printing particles and thereby forming dots each having a high density on the recording sheet.
To this end, a printing device includes a bearing member for bearing printing particles each having an electric charge, a backing electrode faced to the bearing member for forming an electric field between the bearing member and the backing electrode so that the printing particles are forced to the backing electrode, and a substrate made from an insulating material located between the bearing member and the backing electrode. The substrate includes a plurality of apertures through which the printing particles can pass. For each aperture, the substrate includes an attracting electrode being located adjacent to the aperture and close to the bearing member but away from the backing electrode for, when applied with a first voltage, enhancing the electric field and, thereby, propelling the printing particles from the bearing member into the corresponding apertures toward the backing electrode. The substrate further includes, for each aperture, two or more converging electrodes being located adjacent to the aperture close to the backing electrode but away from the bearing member for, when applied with a second voltage, forcing the propelling printing particles radially and inwardly and, thereby, converging the propelling printing particles.
With the printing device of the present invention, when the first voltage is applied to the attracting electrode, the toner particles on the bearing member facing the apertures are attracted intensely by the attracting electrode and, thereby, propelled away from the bearing member into the corresponding apertures toward the backing electrode. Also, by applying the second voltage to the converging electrodes, a mass of the toner particles passing through the apertures are forced to converge radially and inwardly. Then, the mass of the converged toner particles are deposited on the recording sheet moving past between the substrate and the backing electrode. Therefore, the deposited toner particles form a dot having a clear contour. Accordingly, a resultant image formed by the arrangement of dots also has a clear and precise contour.
In another aspect of the present invention, the two ore more converging electrodes include a first converging electrode, and a second converging electrode located closer to the backing electrode than the first converging electrode. The first and second converging electrodes are designed so that a force for converging the propelling printing material provided from the second converging electrode is greater than that provided from the first converging electrode. With this arrangement, the propelling printing particles in the aperture is converged step-by-step and effectively.
In another aspect of the present invention, the printing device further includes a power supply for generating the electric field between the bearing member and the backing electrode so that the printing particles are forced from the bearing member to the backing electrode. Also, the first voltage applied to the attracting electrode has a polarity opposite to that of the printing particles, and the second voltage applied to the converging electrodes has a polarity similar to that of the printing particles. In this instance, the printing particles will be converged more effectively
REFERENCES:
patent: 5477250 (1995-12-01), Larson
patent: 5984456 (1999-11-01), Bern
Hiraguchi Hiroshi
Shibata Yoshifumi
Shimada Hirokatsu
Uno Koji
Yamaki Toshio
Barlow John
Gordon Raquel Yvette
Minolta Co. , Ltd.
Morrison & Foerster / LLP
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