Incremental printing of symbolic information – Electric marking apparatus or processes – Electrostatic
Reexamination Certificate
2001-10-30
2003-08-05
Pendegrass, Joan (Department: 2852)
Incremental printing of symbolic information
Electric marking apparatus or processes
Electrostatic
C347S132000, C347S133000, C347S237000, C347S240000
Reexamination Certificate
active
06603496
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image recording apparatus, more particularly to an image recording apparatus that supplies adjustable driving current to a driven element by which an image is recorded, and to a method of recording an image using an apparatus of this type.
2. Description of the Related Art
Referring to
FIG. 1
, in an electrophotographic apparatus, a photosensitive member such as a photosensitive drum
51
is charged by a charging unit (CH)
35
, then selectively illuminated by one or more light-emitting elements in, for example, a light-emitting-diode (LED) head
3
according to information to be printed, forming an electrostatic latent image on the photosensitive drum
51
. The electrostatic latent image is developed by selective application of toner in a developer
52
to form a toner image, which is transferred to recording medium such as recording paper
53
by a transfer unit (T)
36
, then fused to the paper. The elements shown in
FIG. 1
form a type of printing mechanism
60
.
One type of electrophotographic apparatus is an electrophotographic printer. A more detailed description of an electrophotographic printer will be given below with reference to
FIG. 2
, which is a block diagram of the control circuits of a conventional electrophotographic printer, and
FIGS. 3 and 4
, which are timing diagrams illustrating the operation of the conventional electrophotographic printer.
The printing control unit
1
in
FIG. 2
is a computing device comprising a microprocessor, read-only memory (ROM), random-access memory (RAM), input-output ports, timers, and other facilities. Receiving signals SG
1
, SG
2
, etc. from a higher-order controller
55
, the printing control unit
1
generates signals that control a sequence of operations for printing dot-mapped data given by signal SG
2
(sometimes referred to as a video signal because it supplies the dot-mapped data one-dimensionally). The printing sequence starts when the printing control unit
1
receives a printing command from the higher-order controller by means of control signal SG
1
. First, a temperature (Temp.) sensor
43
is checked to determine whether the fuser
44
is at the necessary temperature for printing. If it is not, current is fed to a heater
44
a
to raise the temperature of the fuser
44
.
When the fuser
44
is ready, the printing control unit
1
commands a motor driver
33
to drive a develop-transfer process motor (PM)
37
, activates a charge signal SGC to turn on a charging power source
32
, and thereby applies a voltage to the charging unit
35
to charge the surface of the photosensitive drum
51
.
In addition, a paper sensor
41
is checked to confirm that paper is present in a cassette (not visible), and a size sensor
42
is checked to determine the size of the paper. If paper is present, a paper transport motor (PM)
38
is driven according to the size of the paper, first in one direction to transport the paper to a starting position sensed by a pick-up sensor
39
, then in the opposite direction to transport the paper into the printing mechanism
60
.
When the paper is in position for printing, the printing control unit
1
sends the higher-order controller
55
a timing signal SG
3
(including a main scanning synchronization signal and a sub-scanning synchronization signal) as shown in FIG.
3
. The higher-order controller
55
responds by sending the dot data for one page in the video signal SG
2
. The printing control unit
1
sends corresponding print data (HD-DATA) to the LED head
3
in synchronization with a clock signal (HD-CLK). The LED head
3
comprises a linear array of LEDs for printing respective dots (also referred to as picture elements or pixels).
After receiving data for one line of dots in the video signal SG
2
, the printing control unit
1
sends the LED head
3
a latch signal (HD-LOAD), causing the LED head
3
to store the print data (HD-DATA), then sends the LED head
3
a strobe signal (HD-STB), causing the LED head
3
to output light according to the stored print data (HD-DATA), thereby forming one line of dots in the electrostatic latent image. Output of the strobe signal (HD-STB) may overlap the transfer of the next line of the video signal SG
2
and print data (HD-DATA), as illustrated in
FIGS. 3 and 4
.
Subsequent lines of print data are sent and received in the video signal SG
2
in the same way. After each line has been stored, the LED head
3
is driven to emit light, selectively exposing the negatively charged surface of the photosensitive drum
51
to add another line of dots to the electrostatic latent image. When the printing control unit
1
activates control signal SG
5
, the developer power source
54
is switched on, applying a voltage to the developer
52
, and negatively charged toner particles are attracted to the parts of the electrostatic latent image that were exposed to light, forming a toner image comprising black pixels (dots).
The photosensitive drum
51
continues to turn, carrying the toner image to the transfer unit
36
. The high-voltage transfer power source
32
is turned on by control signal SG
4
and supplies a positive voltage to the transfer unit
36
, whereby the toner image is transferred onto the paper
53
as it passes between the photosensitive drum
51
and the transfer unit.
A temperature-humidity sensor
30
monitors the temperature and humidity inside the printer. The printing control unit
1
reads the temperature and humidity in the printer as necessary from the temperature-humidity sensor
30
, thereby obtaining information about environmental conditions.
The printing control unit
1
has a table of transfer conditions corresponding to different ambient temperature and humidity conditions, and uses this table to select the optimum transfer conditions according to the environmental data read from the temperature-humidity sensor
30
.
The paper
53
bearing the transferred toner image is transported to the fuser
44
. When the paper
53
meets the fuser
44
, the toner image is fused onto the paper
53
by heat generated by the heater
44
a.
Finally, the printed sheet of paper passes an exit sensor
40
and is ejected from the printer.
The printing control unit
1
controls the high-voltage transfer power source
32
according to the information detected by the size sensor
42
and pick-up sensor
39
so that voltage is applied to the transfer unit
36
only while paper
53
is passing between the transfer unit
36
and photosensitive drum
51
. When the paper
53
passes the exit sensor
40
, the printing control unit
1
turns off the high-voltage charging power source
31
and halts the developer-transfer process motor
37
.
When a series of pages are printed, the above operations are repeated.
FIG. 5
shows the conventional circuit structure of an LED head
3
. The print data signal HD-DATA and clock signal HD-CLK are received by a shift register
121
comprising, for example, two thousand four hundred ninety-six flip-flops FF
1
, FF
2
, . . . , FF
2496
(this number of flip-flops is suitable for printing three hundred dots per inch on A4-size paper). The latch signal HD-LOAD is received by a latch unit
122
comprising a corresponding number of latches LT
1
, LT
2
, . . . , LT
2496
, which latch the data output by the shift-register flip-flops. The strobe signal HD-STB is supplied to a circuit
123
comprising an inverter G
0
, NAND gates G
1
, G
2
, . . . , G
2496
, and switching elements (transistors) TR
1
, TR
2
, . . . , TR
2496
which are interconnected to drive a linear array of light-emitting elements (LEDs) LD
1
, LD
2
, . . . , LD
2496
when the latch and strobe signals are both low, provided the print data output from the corresponding latches are high (indicating black dots or, more generally, high-intensity pixels). The transistors TR
1
, TR
2
, . . . , TR
2496
operate as an array of driving elements, while the LEDs LD
1
, LD
2
, . . . , LD
2496
operate as an array of driven elements. The power source of the current that drives t
Nagumo Akira
Sato Toshiki
Oki Data Corporation
Pendegrass Joan
LandOfFree
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