Electrophotography – Control of electrophotography process – Control of fixing
Reexamination Certificate
2002-09-19
2004-09-28
Ngo, Hoang (Department: 2852)
Electrophotography
Control of electrophotography process
Control of fixing
Reexamination Certificate
active
06799004
ABSTRACT:
BACKGROUND
Printers are output devices utilized to create an image on a sheet of media. One type of conventional printer
10
is shown in FIG.
1
. The printer
10
may be provided with a sheet
12
, a stack
14
and an input tray
16
. The sheet
12
may be located on an uppermost portion of the stack
14
of media. This stack
14
may be located in the input tray
16
.
The printer
10
may also be provided with a pick mechanism
18
, a path
20
, an imaging component
22
, a fuser
24
and an output tray
26
. The pick mechanism
18
may move individual sheets from the stack
14
(e.g. sheet
12
) into the path
20
that extends through the printer
10
. The sheet
12
travels through the printer
10
along the path
20
where a toner image may be formed on the sheet
12
by the imaging component
22
. After forming the toner image on the sheet
12
, the fuser
24
may fuse the toner image on the sheet
12
. This fusing process creates a fused image on the sheet
12
. The fused image on the sheet
12
creates a durable document that can be distributed, read, stored, etc. The output tray
26
may be located at the end of the path
20
for receiving processed sheets, such as sheet
12
.
The printer
10
may be further provided with a temperature sensor
28
, a controller
30
and a heater
32
. The temperature sensor
28
may take the form of a thermistor located in the fuser
24
. The controller
30
may be a pre-programmed application specific integrated circuit (ASIC) or pre-programmed microprocessor operationally associated with the printer
10
. The heater
32
may take the form of a ceramic heater located within (or in thermal communication with) the fuser
24
. In a process that will be described later herein, the heater
32
can be activated to increase the temperature of the fuser
24
. The sensor
28
can report this increase of temperature to the controller
30
; the controller
30
can activate or deactivate the heater
32
as required to maintain a particular temperature of the fuser
24
.
The fuser
24
operates at an operating temperature ‘T1’ that is higher than ambient temperature ‘T0’. As used herein, the term ‘operating temperature’T1 is defined as the temperature of the fuser
24
that allows for proper fusing of toner onto sheets of media. As used herein, the term ‘ambient temperature’ T0 is defined as the temperature of the fuser
24
when the printer
10
is not being used and is essentially dormant (which results in the fuser
24
being deactivated for a long enough period of time to have any residual heat dissipated therefrom, this period of time may be about 45 minutes to one hour).
Overview of Conventional Process
The printer
10
may form and fuse the image on the sheet
12
in a series of steps as it travels along path
20
(FIG.
1
). These steps may include a warm-up step, a feed step, a fusing step and an ejecting step. Timelines shown in
FIGS. 2 and 3
illustrate two types of conventional forming and fusing processes. These processes are illustrated in the timelines as a time graph ‘S’, a sheet velocity graph ‘V’ and a fuser temperature graph ‘T’. The first type of conventional process illustrated in
FIG. 2
is a sequential process. The second type of conventional process illustrated in
FIG. 3
is a fixed delay process.
Conventional Sequential Process
With reference to
FIG. 2
, the sequential forming and fusing process may commence at a start point denoted by ‘A’. During the warm-up step occurring during period ‘S1’, the heater
32
(
FIG. 1
) may be activated to bring the fuser
24
from the ambient temperature T0 towards the operating temperature T1 (shown in the fuser temperature graph T). It takes the entire warm-up step period S1 to bring the fuser
24
to its operating temperature T1. Once the sensor
28
(
FIG. 1
) senses and reports the operating temperature T1, the heater
32
may be deactivated or, alternatively, power supplied thereto may be substantially reduced. By deactivating or reducing power supplied to the heater
32
, the operating temperature T1 is substantially maintained. A preheated point denoted by ‘B’ (
FIG. 2
) denotes when the fuser
24
is at the operating temperature T1. After the preheated point B, the feed step may occur during period ‘S2’.
Referring to
FIG. 1
, during the feed step period S2 (FIG.
2
), the picker
18
may advance the sheet
12
from the stack
14
towards the imaging component
22
along the path
20
. As shown in the velocity sheet graph V (FIG.
2
), the sheet
12
may travel along path
20
at a velocity V1. The sheet
12
passes through the imaging component
22
where the toner image may be formed thereon as it travels along the path
20
. At a fusing point denoted by ‘C’, the fusing step may occur during period ‘S3’ (FIG.
2
).
Referring again to
FIG. 1
, during the fusing step period S3 (FIG.
2
), the fuser
24
may fuse the toner image to the sheet
12
as it travels along the path
20
. Once the toner image is fused to the sheet
12
, it has been converted to a fused image. The fuser
24
may fuse the toner image by applying heat to the toner image and sheet
12
. As shown in the temperature graph T (FIG.
2
), the fuser temperature may vary slightly from, but remain substantially close to, the operating temperature T1 (as previously mentioned, the operating temperature T1 may be maintained by selectively activating of the heater
32
as directed by the sensor
28
and/or the controller
30
). At an ejecting point denoted by ‘D’ (FIG.
2
), the fusing process has ended and the ejecting step may occur during period ‘S4’ (FIG.
2
).
During the ejecting step period S4, the sheet
12
may be ejected from the path
20
. This sheet
12
is ejected to the output tray
26
, FIG.
1
. At an exit point denoted by ‘E’ (FIG.
2
), the sheet
12
may be completely ejected from the path
20
. After the sheet
12
is removed from the path
20
, its velocity returns to zero as shown in the velocity graph V. The sheet
12
with the image formed thereon may be stored in the output tray
26
(
FIG. 1
) along with other sheets that have been processed.
As Illustrated in
FIG. 2
, the accumulation of time from the start point A to the exit point E may be referred to herein as a conventional sequential processing period denoted by ‘S5’. The conventional sequential processing period S5 is an accumulation of the individual steps taken to create the image on the sheet
12
. As shown in
FIG. 2
, the conventional sequential processing period S5 may include the warm-up step period S1, the feed step period S2, the fusing step period S3 and the ejecting step period S4. The conventional processing period S5 may be calculated according to the following equation:
S5
=
S1
+
S2
+
S3
+
S4
,
wherein
:
S1
is
the
warm
-
up
step
period
;
S2
is
the
feed
step
period
;
S3
is
the
fusing
step
period
;
and
,
S4
is
the
ejecting
step
period
.
When a user desires to print a sheet (i.e. creating a durable image on sheet
12
), this type of conventional printer
10
takes the conventional sequential processing period S5 to eject the first sheet with the image formed thereon. The conventional sequential processing period S5 to eject the first sheet is commonly referred to in the art as ‘first page out time’. The first page out time is a common benchmark for comparing printers.
Conventional Fixed Delay Process
Another type of conventional printer
10
that uses a fixed delay period is illustrated in a timeline in FIG.
3
. This fixed delay period is denoted by ‘Sfd’ and is used to decrease the first page out time of printer
10
. This fixed delay period Sfd may be a value that is pre-programmed into the printer at the time of manufacture. The fixed delay p
Hewlett--Packard Development Company, L.P.
Ngo Hoang
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