Electrophotography – Machine operation – Having power supply
Reexamination Certificate
2002-01-22
2003-11-18
Ngo, Hoang (Department: 2852)
Electrophotography
Machine operation
Having power supply
C399S171000
Reexamination Certificate
active
06650851
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to systems and apparatus for recycling scavenged power from a pin scorotron grid to drive a discorotron grid in an electrophotographic or xerographic system.
2. Description of Related Art
The xerographic imaging process is initiated by charging a charge retentive surface, such as that of a photoconductive member, to a uniform potential. The charge retentive surface is then exposed to a light image of an original document, either directly or via a digital image driven laser. Exposing the charged photoconductor to light selectively discharges areas of the charge retentive surface while allowing other areas to remain unchanged. This creates an electrostatic latent image of the document on the surface of the photoconductive member.
Developer material is then brought into contact with the surface of the photoconductor material to develop the latent image into a visible reproduction. The developer typically includes toner particles with an electrical polarity that is the same as, or that is opposite to, the polarity of the charges remaining on the photoconductive member. The polarity depends on the image profile.
A blank image receiving medium is then brought into contact with the photoreceptor and the toner particles are transferred to the image receiving medium. The toner particles forming the image on the image receiving medium are subsequently heated, thereby permanently fixing the reproduced image to the image receiving medium.
Electrophotographic or xerographic laser printers, scanners, facsimile machines and similar document reproduction devices must be able to maintain proper control over the systems of the image forming apparatus to assure high quality output images. For example, the level of electrostatic charge on the photographic member must be maintained at a certain level to be able to attract the charged toner particles.
FIG. 1
shows an exemplary embodiment of an image forming apparatus
100
having a photoreceptor
120
. The image forming apparatus
100
can be a xerographic printer or other known or later developed xerographic device. It should be appreciated that the specific structures of the image forming apparatus are not relevant to this invention and thus are not intended to limit the scope of this invention.
As shown in
FIG. 1
, one or more latent images can be generated on the photoreceptor
120
in any well known manner, by controlling one or more of a number of different developer units
150
A,
150
B,
150
C and
150
D using controller
110
.
In many xerographic machines, where high image quality targets are desired, the photoreceptor is first charged using a pin scorotron device, and then recharged, or charge leveled, by a discorotron device. For example, as shown in
FIG. 1
, in the direction of movement of the photoreceptor
120
, as indicated by the arrows, to lay a first level of toner onto the photoreceptor, the photoreceptor
120
is charged by charge/recharge device
130
E having a pin scorotron and a discorotron device. Next, the charge laid by the charging device is exposed by exposing unit
140
E and finally, the toner is developed by developing unit
150
E. The process continues in the direction of movement of the photoreceptor until all layers of toner are laid to complete an image-on-image full-color image forming process. Once the full-color image is finished, the completed image is transferred to a sheet of image recording media
160
.
The charging procedure of the charge/recharge device is performed to produce a very uniform charge on the photoreceptor. This uniform charge is especially important in the image-on-image type xerographic color machines, as shown in
FIG. 1
, where the photoreceptor may be buried under multiple layers of toner. Typically, the pin scorotron device is set to charge the photoreceptor to a voltage slightly higher than the final voltage, and the discorotron is then used to discharge the photoreceptor uniformly to the desired voltage.
FIG. 2
represents a typical configuration of a charge/recharge system
200
that is usable in a xerographic system. The left side of the configuration represents the pin scorotron device
270
, while the right side of the configuration represents the discorotron device
210
. In the pin scorotron device
270
, a high-voltage DC signal is applied to the pins
240
by a pin current supply
250
. The applied voltage is sufficiently high to cause corona discharge at the pins
240
. This discharge provides a path for a pin current to be applied to a pin scorotron grid
245
. The pin scorotron grid
245
is located between the photoreceptor
120
and the pins
240
so that the majority of the pin current is absorbed by the pin scorotron grid
245
. The grid is held at a constant voltage by the pin scorotron grid voltage control circuit
260
, which is a simple shunt regulator type circuit. The pin scorotron grid voltage control circuit
260
operates in a linear manner to achieve a variable resistance network to ground. The resistance of the pin scorotron grid voltage control circuit
260
can be controlled to either increase or decrease its voltage drop to achieve the desired grid voltage.
The discorotron device comprises a shield
225
formed of aluminum or the like and having an open lower end, a corona discharge electrode
230
, such as a glass coated tungsten wire or the like, extending within the shield
225
, and a discorotron grid
235
disposed opposite the opening of the shield
235
and between the shield
225
and the photoreceptor
120
. The discorotron device
210
operates in much the same manner as the pin scorotron device
270
. The discorotron grid
235
is typically driven by an active power source, such as the grid voltage active control circuit
215
. The discorotron high-voltage AC source
220
is connected to the corona discharge electrode
230
to produce a corona discharge.
SUMMARY OF THE INVENTION
As shown in
FIG. 2
, the pin scorotron device
270
and the discorotron device
210
are driven by separate power supplies. However, there is available power in the pin scorotron grid voltage control circuit
260
that can be recycled and used to drive and control the discorotron grid
235
.
The inventors have discerned that the power that is dissipated in the pin scorotron grid voltage control circuit
260
can be used to drive the discorotron grid
235
.
This invention provides systems and apparatus that provide reduced power dissipation in the high voltage power supply.
This invention separately provides possible direct programming of the voltage applied to the photoreceptor and the voltage between the pin scorotron grid and the discorotron grid rather than by indirect programming of the voltage applied directly to the pin scorotron grid and the discorotron grid.
This invention separately provides reduced electromagnetic emissions and increased arc immunity of the discorotron due to a better controlled xerographic current path. The reduced emissions is achieved because the discorotron grid is not driven by an active power supply.
In various exemplary embodiments of the systems and apparatus of this invention, the active power source that is typically used to drive the discorotron grid is removed. According to the systems and apparatus of this invention, the discorotron grid instead utilizes a combined circuit which uses the power dissipated in the traditional shunt regulation circuit that drives the pin scorotron grid to drive the discorotron grid through a series pass regulation circuit. The current flow of the combined circuit naturally flows in a direction to allow shunt regulation of the pin scorotron grid while also providing an active drive voltage for the discorotron grid.
These and other features and advantages of this invention are described in or are apparent from the following detailed description of the apparatus and systems according to this invention.
REFERENCES:
patent: 4141648 (1979-02-01), Gaitten et al.
Adams Jerry F.
Fournia Peter G.
Ngo Hoang
Oliff & Berridg,e PLC
LandOfFree
Combined charge/recharge xerographic power supply does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Combined charge/recharge xerographic power supply, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Combined charge/recharge xerographic power supply will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3184547