Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-09-22
2001-05-08
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06227656
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a direct printing apparatus in which an electrically charged printing material of particles is deposited on a sheet substrate to form an image on the sheet substrate.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 5,477,250 issued on Dec. 19, 1995 discloses a direct printing apparatus. The direct printing apparatus includes a rotatable cylinder or toner carrier, which retains electrically charged toner or printing particles on its outer periphery, and a backing electrode spaced apart from the toner carrier. The backing electrode is electrically connected to a power source, thereby forming an electric field that attracts the charged toner particles on the toner carrier toward the backing electrode. Interposed between the toner carrier and the backing electrode is an insulative plate that includes a plurality of apertures through which the toner particles can pass. A pair of signal and base electrodes surrounds each aperture. The signal electrode is mounted on one surface, adjacent to the backing electrode, of the insulative plate and the base electrode is mounted on the other surface, adjacent to the toner carrier, of the insulative plate.
With the direct printing apparatus, when an image signal is applied to the signal and base electrodes, the toner particles on the toner carrier, opposing to those electrodes, are energized and then propelled through associated apertures onto the sheet substrate, forming an image corresponding to the image signal on the sheet substrate.
An amount of toner particles being energized and then propelled depends upon the Coulomb's force that is inversely proportional to the square of the distance between the toner carrier and backing electrode. When a rotatable cylindrical member is employed as the toner carrier, due to its curvature, a distance between one portion of the cylindrical member and the backing electrode is different from a distance between another portion of the cylindrical member, spaced away in a peripheral direction from the one portion and the backing electrode. This results in that the amount of toner particles moving into the aperture in a closest region where a distance between the toner carrier and the backing electrode is minimized differs from the that moving into another aperture in another region spaced away in a rotational direction of the cylindrical member from the closest region, thereby degrading a quality of the resultant image.
Likewise, if a distance between one end of the cylindrical member and the backing electrode (or the insulative plate) is different from that between the opposite end of the cylindrical member and the backing electrode (or the insulative plate), a density of an image formed at or adjacent to one end of the cylindrical member is not identical to that formed at or adjacent to the other end of the cylindrical member, further degrading the quality of the resultant image.
SUMMARY OF THE INVENTION
The primary object of the present invention is to provide a direct printing apparatus capable of propelling a certain amount of printing material through each aperture.
Another object of the present invention is to provide a direct printing apparatus capable of eliminating a difference of densities of images formed on opposite sides.
For purposes, a direct printing apparatus of the present invention has a bearing member which bears the printing particles thereon, the printing particles being electrically charged to a certain polarity, a backing electrode which opposes to the bearing member, and a power supply which generates an electric field that attracts the charged printing particles born on the bearing member toward the backing electrode. The printing device also includes a printing head that interposes between the bearing member and the backing electrode to cooperate with the backing electrode, thereby forming a passage therebetween through which passage the sheet substrate such as plain paper can pass. The printing head has an electrically insulative sheet member having a plurality of apertures arranged in one or more lines through each of the apertures the printing particles can propel, and a plurality pairs of first and second electrodes, each pair of first and second electrodes being arranged adjacent to the aperture. Each pair of first and second electrodes are connected with a driver which applies the pair of first and second electrodes with first and second pulsating signals, respectively, thereby energizing the printing particles born on the opposing portions of the bearing member to propel the energized printing particles into associated aperture. A voltage level and/or a duration of the second pulsating signal to be applied to the second electrode is determined by a distance between the aperture adjacent to which the second electrode is arranged and an associated portion of the bearing member that opposes to the aperture. This ensures that the same amount of printing particles are propelled through each aperture and then deposited onto the sheet substrate moving past between the printing head and the backing electrode.
Preferably, the first electrode is located on one side, adjacent to the bearing member, of the printing head and the second electrode is located on the other side, adjacent to the backing electrode, of the printing head.
In another aspect of the present invention, a direct printing apparatus has such bearing member, backing electrode and power supply. Also, the printing apparatus includes a printing head having an insulative sheet member that interposes between the bearing member and the backing electrode to cooperate with the backing electrode to form a passage therebetween through which passage the sheet substrate can pass. The insulative sheet member is formed of a plurality of apertures arranged in one or more lines through each of the aperture the printing particles can propel. Also, the insulative sheet member has a plurality of electrodes. Each electrode is arranged adjacent to the aperture and is sized or spaced away from the aperture according to a distance between the aperture adjacent to which the electrode is arranged and an associated portion of the bearing member that opposes to the aperture.
According to the direct printing apparatus of the present invention, depending upon the distance between the aperture and the bearing member, the voltage level and/or the duration of the second pulsating signal to be applied to the second electrode, the size of the electrode, or the distance between the electrode and the associated aperture is determined, so that the same amount of printing particles are propelled through each aperture and then deposited onto the sheet substrate. This ensures that dots formed on the sheet substrate have the same size, forming a high quality image.
REFERENCES:
patent: 5477250 (1995-12-01), Larson
patent: 5880760 (2000-08-01), Desie et al.
patent: 6109730 (2000-08-01), Nilsson et al.
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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