Electrophotography – Control of electrophotography process – Responsive to copy media characteristic
Reexamination Certificate
2000-06-08
2001-10-16
Lee, Susan S. Y. (Department: 2852)
Electrophotography
Control of electrophotography process
Responsive to copy media characteristic
C399S067000, C399S068000, C399S069000
Reexamination Certificate
active
06304731
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an electrophotographic printer, and more particularly, to a laser printer for printing narrow media with high throughput that does not overheat the fuser.
BACKGROUND OF THE INVENTION
An electrophotographic printer prints an image on media, such as sheets of paper, from toner contained in a toner cartridge. A developer roller or sleeve is mounted within the toner cartridge in proximity to a photoconductive drum. The photoconductive drum is charged, and a laser scans the charged photoconductive drum with a laser beam to discharge the surface and form a latent image thereon. The developer roller attracts statically charged toner from the toner container. Toner is transferred from the developer roller to the photoconductive drum to develop the latent image formed on the photoconductive drum. The developed image is then transferred to statically charged sheets of media. The sheets are fed through a heated fuser assembly, where the heat fixes the visible image.
Sheets of narrow media, such as envelopes, are aligned with a reference edge in the feed path of the printer. Because the narrow sheets do not extend across the full width of the feed path, the consecutive printing of several sheets of narrow media creates a temperature imbalance in the fuser assembly. The sheets of media, when fed past the fuser assembly to fuse the image to the sheets, remove heat therefrom. Since sheets of narrow media do not extend fully across the width of the fuser assembly, the portion of the fuser assembly away from the reference edge, where the narrow media do not contact the fuser assembly, becomes hotter than the portion adjacent the reference edge, where the narrow media contact the fuser assembly. The fuser assembly can overheat so much after printing several consecutive sheets of narrow media that it becomes damaged.
One proposed solution to the problem of the overheating in a fuser assembly with a hot roller has been to make the fuser roller out of very thick material, so that the heat diffuses more evenly across the entire width. This has been unsatisfactory, as the cost of a thick fuser roller is high. This solution, of course, is not applicable to a fuser assembly with a fuser belt.
A second proposed solution to the problem of the overheating of the fuser assembly has been the insertion of gaps between the sheets of narrow media. Inter-sheet gaps permit the fuser assembly to equilibrate between sheets. However, this solution has also been unsatisfactory, as the insertion of inter-sheet gaps for all sheets of narrow media dramatically reduces the throughput of the printer.
A third proposed solution to the problem of the overheating of the fuser assembly has been to reduce the operating temperature of the fuser assembly and the transport speed. Consequently, all the sheets of media, regardless of width, are fed past the fuser assembly at a very slow speed, so that enough heat is transferred to the media to fuse the image thereto. However, this solution has also been unsatisfactory, as the slow feeding speed for all the sheets of media severely reduces the throughput of the printer.
SUMMARY OF THE INVENTION
A printer in accord with the present invention overcomes the foregoing problems by determining when narrow media are to be printed, aligning the narrow media with a side reference edge of the media path, lowering the temperature of the fuser assembly and feeding the narrow media through the media path at a reduced speed, and, for certain conditions, increasing the gap between fed sheets.
In accord with one aspect of the present invention, a printer comprises a media feed path for feeding sheets of media through the printer, the path including a side reference edge, and a media transport mechanism for feeding the sheets of media at a standard speed and at a reduced speed along the media feed path. A narrow media detector generates a narrow media signal when sheets of narrow media are fed through the media feed path. A controller responds to the narrow media signal and adjusts the media transport mechanism to feed the narrow media aligned with the reference edge at the reduced speed.
In accord with another aspect of the present invention, a printer system comprises a media feed path for feeding sheets of media through the printer, the path including a reference edge, and a media transport mechanism for feeding the sheets of media at a standard speed and at a reduced speed along the media feed path. A narrow media detector generates a narrow media signal when sheets of narrow media are fed through the media feed path. A programmed microcomputer responds to the narrow media signal and adjusts the media transport mechanism to feed the narrow media aligned with the reference edge at the reduced speed.
An advantage of a printer in accord with this invention is that sheets of narrow media are printed without damaging the printer even though use of a side reference edge adds to heat stress at the fixing mechanism when fixing narrow media.
Another advantage of a printer in accord with this invention is that sheets of narrow media are printed without overheating and damaging the fuser assembly.
A further advantage of a printer in accord with this invention is that narrow media are printed with a high printer throughput.
A still further advantage of the present invention is that it can be used in a printer with a fuser assembly having either a hot fuser roller or a fuser belt.
Other objects and advantages of the invention will be readily perceived from the following description, claims, and drawings.
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Able Douglas Anthony
Cheek Charles Jerome
Clarke Cyrus Bradford
Gilmore James Douglas
Hamilton Douglas Campbell
Brady John A.
Lee Susan S. Y.
Lexmark International Inc.
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