Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
1999-07-28
2001-05-01
Le, N. (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S130000, C347S237000
Reexamination Certificate
active
06226027
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an electrophotography apparatus such as electrophotographic printers and copying machines, and more particularly to an exposing unit having an electrode that prevents soiling of the exposing unit with toner.
DESCRIPTION OF THE PRIOR ART
An electrophotographic printer is a well-known prior art apparatus that performs the steps of charging, exposing, developing, transferring, and fixing. For example, Japanese Patent Preliminary Publication (KOKAI) No. 63-208878 discloses an electrophotography apparatus in which the surface of a photoconductive body is uniformly charged by the contact charging method.
An exposing unit for an electrophotography apparatus usually takes the form of a semiconductor laser or an LED (light emitting diode) head. A semiconductor laser type exposing unit requires a polygon mirror and a f &thgr; lens, making the electrophotography apparatus large in size. An LED type exposing unit is in the form of a combination of light emitting diodes with a SELFOC lens, lending itself to a miniaturizing of the electrophotography apparatus.
FIG. 9
illustrates a general construction of a conventional exposing unit.
An LED print head
10
includes an LED array
1
, an LED board
2
, a base
3
, a SELFOC lens array (referred to as SLA hereinafter)
5
, and an SLA holder
6
. The LED array
1
is an array of a plurality of light emitting diodes arranged in a long row. The LED array
1
is mounted on the LED board
2
. The base
3
supports the LED board
2
thereon. The SLA
5
illuminates the surface of a photoconductive drum
4
to form an electrostatic latent image on the surface as the photoconductive drum
4
rotates about an axis parallel to the direction of the row of light-emitting diodes in the LED array
1
.
During the exposing process, the LED print head
10
receives print data from a main body of a printer, not shown, and energizes the LED array
1
. When an LED is energized to emit light, the light is directed through the SLA
5
to the uniformly charged surface of the photoconductive drum
4
, thereby forming an electrostatic latent image on the surface. The electrostatic latent image is subsequently developed with colored toner, charged to a certain potential. As the photoconductive drum
4
rotates, the developed image reaches a transfer unit where the developed image is transferred to a recording medium. The recording medium is then advanced to a fixing unit where the developed image is fused into a permanent image.
The subsequent cleaning process removes the residual that still remains on the surface of the photoconductive drum
4
.
The LED printhead
10
is effective in miniaturizing a printer. In order to form an image of the light emitted by the LEDs, the aforementioned LED array
1
is disposed such that the surface of the lens of the SLA
5
is very close to the charged surface of the photoconductive drum
4
(e.g., 2-5 mm).
With the aforementioned electrophotography apparatus, some of the toner cannot be transferred from the photoconductive drum
4
to the recording medium and remains on the photoconductive drum
4
. The residual toner is carried to the exposing unit, i.e., the LED printhead
10
as the photoconductive drum
4
rotates.
There occurs an electric field between the negatively charged surface of the photoconductive drum
4
and the LED printhead
10
at the ground potential. Thus, the residual toner is pulled toward the SLA
5
and adheres to the SLA
5
. The toner adhering to the SLA
5
not only reduces the effective amount of light emitted from the LED printhead
10
but also presents a problem of poor print quality.
SUMMARY OF THE INVENTION
The present invention was made in view of the aforementioned drawbacks.
An object of the invention is to provide an electrophotography apparatus that provides stable print quality.
Another object of the invention is to provide an exposing unit having an electrode that prevents the soiling of the printhead with toner.
An electrophotography apparatus has a charging unit, and an exposing unit, and a developing unit. The charging unit charges the surface of a rotating image bearing body, for example, photoconductive drum having an axis of rotation. The exposing unit emits light to illuminate the surface of the image bearing body to form an electrostatic latent image on the surface. The developing unit applies charged fine powder particles (i.e., toner) to the electrostatic latent image to develop the electrostatic latent image into a visible image. The electrophotography apparatus includes at least one power supply and a plurality of electrodes supplied with voltages therefrom. The electrodes are disposed between the light-emitting surface of the exposing unit and extend parallel to the axis of rotation of the photoconductive drum. The electrodes are aligned on opposite sides of the light emitted from the exposing unit. The electrodes receive voltages from the power supply, creating electric lines of force at an angle with the direction of the light so that the charged powered particles remaining on the image bearing body fly in a direction deviating from the direction of light.
The electrodes include a first electrode and a second electrode that are disposed in a plane perpendicular to the direction of light. The first and second electrodes may receive voltages of different values and of the same polarity as the charged powdered particles.
The first and second electrodes may be disposed in different planes perpendicular to the direction of light, the first electrode being closer to the image bearing body than the second electrode. Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
REFERENCES:
patent: 5790920 (1998-08-01), Teramura et al.
patent: 63-208878 (1988-08-01), None
Ashida Kenichi
Nakajima Norio
Le N.
Nguyen Lamson D.
Oki Data Corporation
Rabin & Champagne PC
LandOfFree
Electrophotography apparatus and exposing unit therefor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electrophotography apparatus and exposing unit therefor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electrophotography apparatus and exposing unit therefor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2513207