Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-12-16
2001-06-05
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06241343
ABSTRACT:
This application is based on application No. H9-352797 filed in Japan on Dec. 22, 1997, the content of which is hereby incorporated by reference.
FIELD OF THE INVENTION
The present invention relates to a direct printing apparatus for use in a color copying machine and printer.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 5,477,250 issued on Dec. 19, 1995 discloses a direct printing apparatus. In the direct printing apparatus, four printing stations are disposed along a sheet conveying direction. Each printing station comprises a toner carrier retaining toner on its outer periphery, a backing electrode opposed to the toner carrier and a printing head disposed between the toner carrier and the backing electrode, the printing head having a plurality of apertures and a plurality of electrodes surrounding each aperture. On the outer periphery of the toner carrier in each printing station are retained toner having different colors, for example, magenta, cyan, yellow and black. The backing electrode of each printing station is electrically connected to a power source, thereby between the toner carrier and the backing electrode is formed an electric field for attracting the toner on the toner carrier and propelling it toward the backing electrode through the apertures of the printing head. Between the printing head and the backing electrode in each printing station is formed a passage for a sheet.
When an ON voltage is applied to the electrode of the printing head in the printing station positioned at the most upstream side in the sheet conveying direction, for example, the magenta printing station, the toner attracting force due to the electric field between the toner carrier and the backing electrode propels the toner on the toner carrier through the apertures toward the backing electrode and adheres it to the sheet. When an OFF voltage is applied to the electrode of the printing head, the toner attracting force does not affect the toner on the toner carrier, whereby the toner is never propelled. Thus, when ON and OFF voltage applied to the electrode of the printing head are controlled on the basis of a desired image signal, a magenta image corresponding to the image signal is printed on the sheet. In the same manner, by controlling the ON and OFF voltage applied to the electrode of the printing head in each of the downstream printing stations a different color of image is laid on the previously printed image to form a desired image.
In the aforementioned direct printing apparatus, due to eccentricity or looseness of the toner carrier for retaining toner on its outer periphery, a distance between the toner carrier and the printing head becomes unstable, resulting in unevenness of image density.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been accomplished to solve the aforementioned disadvantages of the prior arts. An object of the present invention is to provide a direct printing apparatus having a constant distance between printing particles bearing member and printing head, enabling to print an image with no unevenness of image density.
In order to achieve the aforementioned object, according to the present invention, there is provided a direct printing apparatus for depositing printing particles on a print medium, comprising:
a sleeve for bearing charged printing particles thereon;
a drive roller provided in the sleeve, the drive roller having a smaller outside diameter than an inside diameter of the sleeve;
a backing electrode opposed to the sleeve;
a power supply connected to the backing electrode for generating an electric field that attract the charged printing particles on the sleeve to propel the same toward said backing electrode;
a printing head disposed between the sleeve and the backing electrode, the printing head having a plurality of apertures through which the printing particles can propel and a plurality of electrodes disposed around the plurality of apertures; and
a driver for applying the plurality of electrode with a voltage for allowing the printing particles to be propelled and a voltage for forbidding the printing particles to be propelled in response to an image signal;
wherein a spacer is provided between the sleeve and the printing head and the sleeve has a slack through which the sleeve comes into contact with the spacer.
In the direct printing apparatus of the present invention having such construction as described above, since the slack of the sleeve comes into contact with the spacer positioned between the sleeve and the printing head, the distance between the sleeve and the printing head is held stable even if the drive roller has an eccentricity or looseness.
Preferably, the spacer may be provided with a slit through which the printing particles can pass and which is opposite to the plurality of apertures.
Preferably, the spacer may come into contact with the printing head. In this case, the spacer may comprise at least one wire-like spacer. The direct printing apparatus of the present invention may further comprise a container in which the printing particles are accommodated, wherein the sleeve, the drive roller, and the spacer are provided to the container, and wherein the container is detachable to a body of the printing apparatus.
Preferably, the spacer may be separable from the printing head and the spacer may be such a shape that a portion of the spacer at the side of the printing head comes into approximately point-contact with the printing head. In this case, the spacer may be a wire-like member. The spacer may be provided at only the downstream side of the moving direction of the sleeve with respect to the aperture of the printing head.
REFERENCES:
patent: 5206691 (1993-04-01), Mizuno et al.
patent: 5448272 (1995-09-01), Kagayama
patent: 5477250 (1995-12-01), Larson
patent: 5495273 (1996-02-01), Kitamura
patent: 0 816 944 (1998-01-01), None
patent: 6-297753 (1994-10-01), None
patent: 8-129293 (1996-05-01), None
patent: WO 95/24675 (1995-09-01), None
Patent Abstracts of Japan, vol. 95, No. 008, Sep. 29, 1995 & JP 07 117258, May 9, 1995 abstract.
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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