Electrophotography – Control of electrophotography process – Control of fixing
Reexamination Certificate
2001-03-09
2002-09-17
Lee, Susan S.Y. (Department: 2852)
Electrophotography
Control of electrophotography process
Control of fixing
C219S216000, C399S330000
Reexamination Certificate
active
06453130
ABSTRACT:
FIELD OF THE INVENTION
This invention pertains to image-producing devices and more specifically to fusing an image to a medium in an image-producing device.
BACKGROUND OF THE INVENTION
Various types of prior art image-producing devices are known. When I say “image-producing device” I mean a device that is configured to produce a visual image and further configured to transfer the image to an image medium (medium). One relatively common type of image-producing device is known as a printer. However, it is understood that the term “image-producing device” includes any type of device, including copiers, facsimile machines, and the like.
Generally, image-producing devices are configured to produce images in one or more colors, including the “color” of black. These images are typically transferred to a medium which is in the form of paper sheets, although other forms of medium, such as transparencies and the like, are employed.
Image-producing devices usually employ one of several known methods of producing an image. Two popular methods of producing an image are known as “ink jet printing” and “laser printing.” Both the ink jet printing method and the laser printing method are well known in the art. As the respective names imply, the ink jet method utilizes at least one jet of ink in producing an image, while the laser method utilizes at least one laser in producing an image.
Each method of producing an image has various advantages. One advantage of the laser method is that the image can be substantially bonded to the medium so as to be relatively smear-proof. That is, the laser method is capable of producing images that are generally known to be substantially fixed to the medium so that the image cannot be easily deformed or smeared. The method of fixing the image to the medium in the laser printing method is sometimes referred to as “fusing” the image to the medium.
The laser printing method can be broken down into several steps. A first step is the production of an image on a surface, such as a photoconductor or intermediate transfer surface, which is a component of the image-producing device. This step of producing the image on the surface usually comprises forming the image on the surface by depositing powdered toner onto the surface. A second step of the printing method is the transfer of the toner which makes up the image from the surface to a sheet of medium.
A third step of the printing method is fusing of the image to the sheet of medium. The step of fusing the image to the sheet of medium usually comprises heating the toner and medium to a given temperature to cause the toner to “fuse” to the medium. Generally, the temperature to which the toner is heated is sufficient to substantially melt the toner into a “plastic” state but not to a liquid state. The temperature to which the toner is heated can vary as a function of the composition of the toner. However, the temperature is generally about 190 degrees, Centigrade. The step of heating the toner can also be accompanied by the step of applying pressure to the heated toner to aid in fusing the heated toner to the medium.
With reference to
FIG. 1
, a schematic view is shown of a typical prior art image-producing device
10
. The device
10
typically comprises a production/transfer portion
12
which is configured to produce an image (not shown) and which is also configured to transfer the image onto a sheet of medium “M” such as a sheet of paper or the like. The prior art device
10
can also typically comprise a feed mechanism
22
which is configured to feed the medium “M” through the device
10
at a substantially constant rate of speed. The feed mechanism
22
can comprise a pair of substantially parallel rollers
24
or the like, between which the medium “M” is captured and fed.
The device
10
also typically comprises a medium sensor
32
which is configured to detect the presence of the leading edge “LE” of the medium “M” and can also be configured to detect the trailing edge “TE” of the medium as well. As shown, the device
10
can also comprise a fusing portion
42
which is configured to substantially fuse the image to the medium “M.” When I say “fuse” I mean a process by which an image is substantially fixed or bonded to a medium, wherein the process is performed in conjunction with the use of an image-producing device.
The fusing portion
42
can comprise a heater
44
as well as a pressure roller
46
between which the medium “M” is passed to fuse the image thereto. The pressure roller
46
can be driven by way of a motor or the like (not shown) so as to assist the feed mechanism in moving the medium “M” along the feed path “F.” In addition, the fusing portion
42
can comprise a temperature sensor
48
which is configured to detect the temperature of the heater
44
.
The prior art device
10
can also comprise a controller
52
which is in communication with at least one of the above-described components
12
,
22
,
32
,
42
by way of respective communication links
60
. The controller
52
is configured to control various operational aspects of the prior art device
10
. The controller
52
can comprise a data storage memory
54
which is configured to store various data. The controller
52
can also include a processing portion
55
which is configured to make operational decisions based on various operational parameters. Various algorithms
56
,
57
can also be included in the controller
52
. The algorithms
56
,
57
can be configured to carry out specific operational functions of the device
10
.
The production/transfer portion
12
, the feed mechanism
22
, the sensor
32
, and the fusing portion
42
are supported on a structural base (not shown) or the like so as to each have substantially fixed locations relative to one another. The medium “M” is fed through the device
10
along the feed path “F.” As mentioned above, the feed mechanism
22
is configured to feed the medium “M” through the device
10
and along the feed path “F” at a substantially constant rate of speed.
The physical distances along the feed path “F” and between the various components is generally know. For example, the distance “D” along the feed path “F” and between the sensor
32
and the production/transfer portion
12
is known. Because the rate of speed of the medium “M” along the feed path “F” is known, as well as the distance between the sensor
32
and the production/transfer portion
12
, the position of the medium relative to the production/transfer portion can be determined as a function of time.
For example, once the medium “M” is captured by the feed mechanism
22
, the speed of the medium along the feed path “F” is known. The sensor
32
can substantially detect the exact moment that the leading edge “LE” of the medium “M” passes the sensor, at which moment a timer can be started. The quotient of the rate of speed of the medium “M” along the feed path “F” divided by the distance “D,” represents the elapsed time between the moment the leading edge “LE” passes the sensor
32
and the moment at which the leading edge “LE” reaches the production/transfer portion
12
.
That is, the time at which the leading edge “LE” reaches the production/transfer portion
12
can be determined by dividing the rate of speed of the medium “M” along the feed path “F” by the distance “D” between the sensor
32
and the production/transfer portion. In this manner, the location of the medium “M” along the feed path “F,” and relative to the production/transfer portion
12
, can be determined. The location of the medium “M” along the feed path “F” can be essential for the accurate placement of the image onto the medium by the production/transfer portion
12
.
After the image is transferred to the medium “M” at the production/transfer portion
12
, the medium continues along the feed path “F” to the fusing portion
42
where the image is fused to the medium. As discussed above, the fusing portion
42
comprises a heater
44
and a pressure roller
46
. The medium “M” travels along the feed path “F” and between the heater
44
and the pressure
Hewlett--Packard Company
Lee Susan S.Y.
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