Incremental printing of symbolic information – Electric marking apparatus or processes – Electrostatic
Reexamination Certificate
2002-09-16
2004-02-17
Pendegrass, Joan (Department: 2852)
Incremental printing of symbolic information
Electric marking apparatus or processes
Electrostatic
C399S049000, C399S301000
Reexamination Certificate
active
06693654
ABSTRACT:
BACKGROUND OF THE INVENTION
1) Field of the Invention
This invention relates to a tandem color image formation apparatus and a tandem color image formation method.
2) Description of the Related Art
Conventionally, tandem color image formation apparatuses each of which has a plurality of image processing sections have been widely spread. One example of the tandem color image formation apparatus of this type will be explained with reference to
FIGS. 7
to
10
.
FIG. 7
is a schematic diagram which shows the overall configuration of a color image formation apparatus.
FIG. 8
is a perspective view which shows apart of the color image formation apparatus.
FIG. 9
is an explanatory view which shows alignment marks transferred onto a conveyor belt and sensors which detect the marks.
FIG. 10
is an explanatory view which shows density adjustment marks transferred onto the conveyor belt and a sensor which detects the marks.
This color image formation apparatus includes four image processing sections
1
Y,
1
M,
1
C and
1
K which form images of different colors (yellow Y, magenta M, cyan C and black K) and a conveyor belt
3
which transfers a sheet
2
onto which a formed image is transferred. The conveyor belt
3
is an endless belt which is supported by a driving roller
4
and a driven roller
5
and which is driven to rotate. The four image processing sections
1
Y,
1
M,
1
C and
1
K are aligned along the moving direction of this conveyor belt
3
.
The four image processing sections
1
Y,
1
M,
1
C and
1
K form images of yellow Y, magenta M, cyan C and black K, respectively, and are equal in structure. Therefore, only the image processing section
1
Y will be concretely explained hereafter while the other image processing sections
1
M,
1
C and
1
K are shown only in FIG.
7
and
FIG. 8
by denoting the constituent elements of the image processing sections
1
M,
1
C and
1
K by reference symbols replacing the corresponding reference symbols for those of the image processing section
1
Y.
A paper feed tray
6
which contains sheets
2
is arranged below the conveyor belt
3
. In forming an image, the sheets
2
contained in the paper feed tray
6
starting at the uppermost sheet
6
are sequentially fed out and attached to the conveyor belt
3
by electrostatic chucking. The sheets
2
attached to the conveyor belt
3
are transferred to the first image processing section
1
Y in which a yellow toner image is transferred onto the sheets
6
, respectively.
The image processing section
1
Y consists of a photosensitive drum
7
Y serving as an image carrier, a charger
8
Y disposed around the photosensitive drum
7
Y, an exposure device
9
, a developer
10
Y, a photosensitive cleaner
11
Y, a transfer device
12
Y and the like. The exposure device
9
is employed by not only the image processing section
1
Y but also the other image processing sections
1
M,
1
C and
1
K. A yellow image laser beam LY is applied to the photosensitive drum
7
Y, a magenta image laser beam LM is applied to a photosensitive drum
7
M, a cyan image laser beam LC is applied to a photosensitive drum
7
C and a black image laser beam LK is applied to a photosensitive drum
7
K.
Each of the sheets
2
conveyed by the conveyor belt
3
onto which the yellow toner image is transferred, is then subjected to the transfer of a magenta toner image in the image processing section
1
M, the transfer of a cyan toner image in the image processing section
1
C and the transfer of a black toner image in the image processing section
1
K. The sheet
6
onto which these images are transferred is peeled off from the conveyor belt
3
, fed into a fixing device
13
in which a toner image fixing processing is conducted to the sheet
6
.
Three sensors
14
,
15
and
16
which are arranged to face the front surface of the conveyor belt
3
in a direction (main scan direction) orthogonal to the moving direction (sub-scan direction) of the conveyor belt
3
, below the conveyor belt
3
and near the driven roller
5
. These sensors
14
,
15
and
16
are used to detect alignment marks
17
formed by the image processing sections
1
Y,
1
M,
1
C and
1
K and transferred onto the conveyor belt
3
. Among them, the sensor
14
is used to detect density adjustment marks
18
(see
FIG. 10
) formed by the image processing sections
1
Y,
1
M,
1
C and
1
K and transferred onto the conveyor belt
3
.
A belt cleaner
19
which cleans the alignment marks
17
and the density adjustment marks
18
transferred onto the conveyor belt
3
, is provided slightly downstream of the sensors
14
,
15
and
16
along the moving direction of the conveyor belt
3
.
As shown in
FIG. 9
, the alignment marks
17
are formed at positions opposed to the sensors
14
,
15
and
16
, respectively, on the conveyor belt
3
. Each alignment mark
17
consists of a line mark (lateral line mark) parallel to the main scan direction and a line mark (inclined mark) inclined relative to this lateral line mark. The sensors
14
,
15
and
16
read the alignment marks
17
, respectively. A control section, not shown, which includes a main CPU performs an arithmetic operation for an image slippage quantity and that for a correction quantity to eliminate the slippage and issues a correction execution instruction for each color based on the read result. It is thereby possible to adjust the following five positional slippages, 1 a sub-scan registration slippage caused by the error of the axial distance among the photosensitive drums
7
Y,
7
M,
7
C and
7
K provided in the image processing sections
1
Y,
1
M,
1
C and
1
K, respectively, 2 an inclination slippage caused by the uneven inclinations of the photosensitive drums
7
Y,
7
M,
7
C and
7
K provided in the image processing sections
1
Y,
1
M,
1
C and
1
K, respectively in the main scan direction, 3 a main scan resist slippage caused by the slippage of respective image write positions, 4 a scaling slippage caused by the different lengths of scanning lines for the four colors, respectively, and 5 a scaling error deviation slippage caused by a partial error in the scaling of the main scan direction. If the positional slippages 1 to 4 are to be adjusted, it suffices to employ only the two sensors
14
and
16
.
As shown in
FIG. 10
, the density adjustment marks
18
are formed on positions facing the sensor
14
on the conveyor belt
3
and formed as gradation images by changing densities for the respective colors, respectively. The sensor
14
reads the density adjustment marks
18
. The control section, not shown, performs an arithmetic operation for density and that for a correction quantity for the density and issues a correction execution instruction for each color, whereby the density of a resultant image can be optimally controlled.
Conventionally, the density adjustment mark
18
for adjusting the density of the image of each color is detected by the sensor
14
which detects the alignment mark
17
for aligning the images of the respective colors to one another. Concrete procedures for the detection of the alignment marks
17
and the density adjustment marks
18
are as follows.
Alignment marks
17
are first formed, transferred onto the conveyor belt
3
, detected by the sensors
14
,
15
and
16
, respectively, and cleaned by the belt cleaner
19
after being detected. After cleaning, density adjustment marks
18
are formed, transferred onto the conveyor belt
3
, detected by the sensor
14
and cleaned by the belt cleaner
19
after being detected.
That is, after the completion of the formation, transfer, detection and cleaning of the alignment marks
17
, the formation, transfer, detection and cleaning of the density adjustment marks
18
start. As a result, a lot of time is required until operations for the alignment of the images of the respective colors and the density adjustment thereof are finished, disadvantageously deteriorating work efficiency for image formation.
SUMMARY OF THE INVENTION
It is an object of the present invention to reduce time required for the alignment
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Pendegrass Joan
Ricoh Company Limited
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