Incremental printing of symbolic information – Electric marking apparatus or processes – Electrostatic
Reexamination Certificate
2000-03-30
2004-02-10
Pendegrass, Joan (Department: 2852)
Incremental printing of symbolic information
Electric marking apparatus or processes
Electrostatic
C347S118000, C347S232000
Reexamination Certificate
active
06690404
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image forming apparatus and method for changeable image forming modes between single color mode and a multiplicity of color modes, more particularly, this invention is concerned with a color image forming apparatus and method selectively operable in a multiple color image forming mode using two, three or four colors or in a single color image forming mode.
2. Discussion of the Background
In general, a number color image forming apparatuses, e.g. full color copy machines, full color printers, have selectable image forming modes which are a multiple color mode and a single color mode. This type of apparatuses can selectably output full color images or single color images like a monochrome images by only one machine.
For further user needs, the image forming apparatus are required to have both a high quantity of output images in full color images and a high output speed in single color image. Referring to
FIG. 1
of the drawings, there is shown a specific construction of single color images forming apparatus of the type electrostatically forming a latent image on a photoconductive drum by controlling a laser in response to image signals.
As shown, a scanning section
200
includes a color CCD (Charge Coupled Device) image sensor
201
for reading an image of a document
100
and producing corresponding electric signals (i.e. image data). An image processing section
400
performs optimal image processing with the electric signal and converts the processed signals to color image signals representative of an image to record.
A writing section
300
receives the color image signals from the image processing section
400
to reproduce the document image on a photoconductive drum
5
. Various conventional units for effecting electrophotography are arranged around the drum
5
. Specifically, a main charger
510
uniformly charges the surface of the drum
5
. The writing section
300
has a laser diode, which emits a laser beam. The laser beam is modulated by particular color image signals and scans the charged surface of the drum
5
. As a result, a latent image representative of the document image is formed on the drum
5
. The laser beam is incident to and deflected by a polygonal mirror
3
being rotated by a scanner motor
1
. The laser beam from the mirror
3
is focused in the form of a spot on the drum
5
by conventional f-theta lenses
4
.
A developing section
500
develops the latent image by a toner to produce a corresponding toner image. The developing section
500
has a yellow (Y) developing unit
500
Y, a magenta (M) developing unit
500
M, a cyan (C) developing unit
500
C, and a black (Bk) developing unit
500
Bk. For details of the developing section
500
, reference may be made to, for example, U.S. Pat. No. 4,928,144, the disclosure of which is herein incorporated by reference. A cleaning section
520
removes the toner remaining on the drum
5
after the transfer of the toner image which will be described.
On the other hand, a sheet feed section
600
is loaded with a stack of sheets
601
. A pick-up roller
602
feeds the sheets
601
one by one toward an image transfer section
700
via a transport roller
604
and a register roller
603
. The image transfer section
700
is available in various forms as taught in, for example, U.S. Pat. Nos. 4,835,582, 4,862,214, 4,864,358 and 4,872,037 the disclosure of which is also incorporated by reference. While a transfer drum
701
drives the sheet
601
, a transfer charger
702
transfers the toner image from the drum
5
to the sheet
601
. To produce a black-and-white copy, a black toner image is formed on the drum
5
by the black developing unit
500
Bk and then transferred to the sheet
601
. Hence, the formation of a latent image, development of the latent image and transfer of the resulting toner image are each effected only once.
In the event of full color copying (i.e. printing), such a sequence of image forming steps are repeated with each of Y, M and C, i.e., three times in total or with each of Y, M, C and Bk, i.e., four times in total. The sheet
601
carrying the toner image thereon is separated from the transfer drum
701
at a sheet separating section
703
and then transported to a fixing section
800
to have the toner image fixed thereon. Finally, the sheet or copy
701
is driven out of the apparatus.
However, this type of a color image forming apparatuses carry out the above same sequence Y, M, C, Bk, four times in total in a full color image forming. Therefore, the image forming apparatus scarify the throughput to form full color images.
There is another known type of color image forming apparatuses. This type of color image forming apparatus employs an intermediate transfer belt or a sheet transfer belt where each developing unit Y, M, C, Bk are arranged in tandem.
Referring to
FIG. 2
illustrates an example of this type of image forming apparatuses. An image transfer unit of this image forming apparatus has four photoconductive drums
1
A,
2
A,
3
A and
4
A on which color data of an image to be recorded with respect to yellow, magenta, cyan and black are optically written to form a latent image of a respective different color thereon and developing devices
1
B,
2
B,
3
B and
4
B each arranged in connection with each of the four photoconductive drums, respectively. The original color is separated to three colors, i.e., blue, green and red each of which is detected by a respective optical sensor. An image processor calculates color data of yellow, magenta, cyan and black on the basis of the luminous intensity of each of the separated three colors. The electrostatic latent images formed on each of the photoconductive drums
1
A,
2
A,
3
A and
4
A are developed by a toner of a corresponding color contained in the respective corresponding developing devices. A sheet is fed onto a transfer belt
5
from a paper container through a resist roller unit
7
and is conveyed by the transfer belt
5
which circulates along the photoconductive drums and comes in contact therewith one after another. The sheet is electrostatically charged and secured to the conveyor belt surface. The visible toner image formed on each of the photoconductive drums
1
A,
2
A,
3
A and
4
A are transferred to the sheet by a function of a corresponding transfer charger
1
C,
2
C,
3
C or
4
C disposed behind the transfer belt
5
at the position of each photoconductive drum in such a manner that the different color toner images are superposed one above the other to form an image of multi-colors on the record sheet. The full color image is subsequently fixed on the sheet by a fixing roller unit
8
.
The color image forming apparatus illustrated in
FIG. 2
has an image reading unit
9
disposed on the apparatus body. The color of an original (not shown) to be copied is optically separated to the above mentioned three colors and read by three CCDs
10
, respectively, arranged in the image reading unit
9
. An image processor device (not shown) calculates image color data for each color on the basis of the output signal from each of the three CCDs
10
. A laser beam source is disposed for each of the photoconductive drums
1
A,
2
A,
3
A and
4
A. Each laser beam source is driven to turn on and off in accordance with the calculated image color data to optically write the image of each separated color on the photoconductive drum.
This type of the image forming apparatus has also another problem such as the fact that an image forming speed is not improved on the single color mode and the multiple color mode. Because the sheet is transferred to on the transfer belt by same speed and same timing between the single color mode and multiple color mode.
For the above problem, a solution is described in Japanese Laid Open Patent Application 04-284,468. The solution is to accelerate a rotation speed of the polygon mirror or a clock speed in order to increase speed of the mono color printing in comparison with one of the full color printing.
However, t
Nakajima Tomohiro
Shimada Kazuyuki
Pendegrass Joan
Ricoh & Company, Ltd.
LandOfFree
Image forming apparatus and method for changeable image... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Image forming apparatus and method for changeable image..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Image forming apparatus and method for changeable image... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3277204