Electrophotography – Control of electrophotography process – Control of fixing
Reexamination Certificate
2000-12-01
2002-10-15
Royer, William J. (Department: 2852)
Electrophotography
Control of electrophotography process
Control of fixing
C219S216000, C399S328000, C399S334000
Reexamination Certificate
active
06466750
ABSTRACT:
TECHNICAL FIELD
This invention generally relates to a technology for fusing variable portions of a print medium as it passes through a fuser assembly of an electrophotographic device.
BACKGROUND
FIG. 1
shows a printer
100
. More specifically, the printer is a “laser printer,” which is a type of printer that utilizes a laser beam to produce an image on a photoconductive drum (which is known as the “photoreceptor”). The light of the laser alters the electrical charge on the drum wherever it hits. The drum is then rolled through a reservoir of toner, which is picked up by the charged portions of the drum. Finally, the toner is transferred to the paper through a combination of heat and pressure. This is also the way copy machines work.
Because an electrophotographic process is used to print, laser printers may be generically called “electrophotographic printers.” In addition to the laser printer, there are two other types of printers that fall under the generic category of electrophotographic printers. However, they do not use lasers at all. One category uses an array of LEDs to expose the drum, and the other category uses LCDs. Both of these types of printers may be called “light-array printers.” Once the drum is charged, however, all electrophotographic printers (including laser and light-array printers) operate the same.
In conventional electrophotographic printers, a transfer unit cooperating with the photoconductive drum deposits toner onto the print medium, which is then cured or otherwise affixed to the print medium by a heated fuser assembly. An example of a print medium is paper, transparencies, envelopes, and the like.
Photocopier
Conceptually, the print engine in a laser printer is substantially identical to the print engine used in electrophotographic copying machines (i.e., “photocopiers”). The fundamental difference between the two is the source of the image to be printed.
In the case of a copier, an original is illuminated by a high-intensity light and the image from the illuminated original is focused onto the photoreceptor. In the case of a laser printer, control circuitry is used to turn a laser beam on and off as it sweeps a raster pattern over the surface of the photoreceptor to directly create the image to be reproduced. Once the electrostatic image is created on the photoreceptor, the principle of operation of a laser printer and a photocopier are identical.
Unless expressly stated otherwise, references herein to the operation of an electrophotographic printer apply to the operation of an electrophotographic copier. Furthermore, examples of an “electrophotographic device” include an electrophotographic printer (either laser or light-array) and an electrophotographic copier.
The fundamentals of electrophotographic devices are well known to those of ordinary skill in the art.
Fuser Assembly
The purpose of a typical fuser assembly (i.e., “fuser”) of a printer is to permanently affix the toner on the paper to the paper. Typically, the fuser heats the paper and the toner thereon as the paper passes through. The heat melts the toner onto the paper. By this process, a so-called hardcopy of an electronic document (“softcopy”) is generated.
FIGS. 2A and 2B
show two views of a conventional fuser
200
. Such a fuser is typically formed from a heated roller
202
having a heated compressible surface
202
a
and a compression roller
204
, which is urged against the heated compressible surface. A print medium
206
(such as a piece of paper or any other form of sheet medium) bearing the developed image of toner (not shown) is passed between the heated roller
202
and the compression roller
204
. The heated roller
202
is, for example, made of a heat-conductive material, such as an aluminum tube coated with a layer of a heat-durable resin and is fitted with an internal built-in heater.
Alone or in combination with other rollers (not shown), the pair of rollers
202
and
204
may pull the print medium through the fuser
200
. Alternatively, other rollers may provide the main locomotion to send the print medium through the fuser. Any device used to move the print medium through the fuser may be called a “medium-transporter.”
In
FIG. 2A
, the print medium
206
travels vertically from bottom to top. In
FIG. 2B
, the print medium
206
travels horizontally from left to right. The print medium
206
travels from an unfused condition to a fused condition. In
FIGS. 2A and 2B
, area
206
a
is a portion of the print medium that has yet to pass through the fuser; thus, the toner in area
206
a
is unheated and unaffixed to the print medium. Area
206
b
is a portion of the print medium that has already passed through the fuser; thus, the toner in area
206
b
is heated and affixed to the print medium.
Notice, in
FIG. 2A
, that the rollers (of which only heated roller
202
is visible) extend across the full width of the print medium
206
. The entire breadth of the print medium
206
passes through the fuser
200
. The width of a print medium is along the x-axis and the breadth is along the y-axis.
In a conventional fuser (with laterally unmovable rollers such as fuser
200
of FIGS.
2
A and
2
B), the fuser is “on” (i.e., heated) while the print medium passes there through. Therefore, the medium is fused along its entire width and breadth.
More precisely, a print medium passing through a conventional fuser is fused along the entire width and breadth of the medium's printable area. A small unusable border (e.g., eighth of inch or less) around the perimeter of a print medium is common. In describing the background and this present invention, this unprintable perimeter is ignored.
Notice also that the rollers
202
and
204
do not move laterally relative to the print medium. Lateral movement of the fuser is movement along the x- or y-axes of the medium. Although the print medium
206
passes through the fuser, no part of the fuser moves laterally across the print medium.
The roller configuration shown in
FIGS. 2A-2B
is one example of a conventional fuser. Another example includes a fuser used for duplex printing. Such a fuser may include two heated rollers (one for each side of a page). Of course, those of ordinary skill in the art understand and appreciate that there are other roller configurations in a conventional fuser.
When fusing a page, a conventional fuser is either on or off. Without the ability to control where and when the fusing occurs, print media such as envelopes with cellophane windows, pages with special inks, adhesive labels, and the like cannot be printed because the heat of the fuser may cause them to melt or degrade. Conventional fusers can only fuse along the entire width and breadth of a page.
SUMMARY
Described herein is a technology for fusing portions of a print medium as it passes through a fuser assembly of an electrophotographic device, such as a laser printer. An implementation, described herein, of the claimed invention includes a fuser of an electrophotographic device that can selectively fuse portions of a print medium passing through the fuser. Rather than fusing the entire width and breadth of a print medium passing through the fuser, an implementation, described herein, of the claimed invention fuses selected portions of the normal printable area of the print medium.
This summary itself is not intended to limit the scope of this patent. For a better understanding of the present invention, please see the following detailed description and appending claims, taken in conjunction with the accompanying drawings. The scope of the present invention is pointed out in the appending claims.
REFERENCES:
patent: 4434353 (1984-02-01), Marsh et al.
patent: 5151719 (1992-09-01), Akutsu et al.
patent: 5402211 (1995-03-01), Yoshikawa
patent: 5402220 (1995-03-01), Tanaka et al.
patent: 5436710 (1995-07-01), Uchiyama
Hewlett--Packard Company
Royer William J.
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