Photocopying – Projection printing and copying cameras – Copying both sides of original
Reexamination Certificate
1999-09-28
2001-02-27
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
Copying both sides of original
C355S018000, C355S023000, C399S361000, C399S363000, C399S364000, C346S134000
Reexamination Certificate
active
06195151
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to media sheet handling systems, and more particularly to a printing mechanism that can produce images on both sides of a media sheet.
Printing to two sides of a media sheet, referred to as duplex printing, is a desirable feature in a printing system. The advantages of duplex printing include reducing the amount of paper required in one-sided (simplex) printing, and generating print sets with layouts resembling that of professionally printed books. Conventional duplex printing devices, as exemplified by what is disclosed in U.S. Pat. No. 5,392,092 for “Printing Device Duplexing Mechanism and Method Therefor,” flip the media sheet over with respect to its original position and swap the leading edge for the trailing edge in printing a second side of the media sheet. Since the page is now positioned with what was originally the trailing edge as the leading edge, as the second side of the media sheet is printed, the image has to be written in a bottom-to-top and right-to-left manner. Thus the formatter of the printer has to correspondingly reverse the order of the data supplied to the print engine.
In inkjet printers, drying of media sheet brings another major challenge for duplex printing, because a printed side of a media sheet tends to wrap around the drive roller surface when the second side is printed. U.S. Pat. No. 5,772,343 for “Media Handling System for Duplex Printing,” provides one solution to duplex printing for such printers. In this solution, the media sheet, after its first side is printed and before it is fed back for printing its second side, has to be held in the air space of the printer output region for a predetermined time period for the wet ink to dry. Since the printer is waiting idly for the drying, printing efficiency therefore is unnecessarily degraded.
Accordingly, there is a need for a convenient and efficient way to realize duplex printing.
SUMMARY OF THE INVENTION
In a preferred embodiment, the invention provides a media sheet handling system for duplex printing that adequately reorients the media sheet while drying of wet ink, if necessary, is accomplished simultaneously.
An embodiment of a media sheet handling system according to the invention includes a first driving roller, an output roller, a detractor, a duplex print path and a second driving roller. A media sheet is picked by a pick roller from a stack of media sheets and fed by the first driving roller towards a printing zone for imprinting images on the first side of the media sheet. The output roller then directs the media sheet whose first side has been printed towards an output path. During duplex printing, after the first side of the media sheet is printed, the detractor between the output roller and the output path is activated to direct the media sheet into the duplex print path. In the duplex print path, the media sheet is reversed to a flipped over state with respect to its original position before the first side is printed, and the original leading edge of the media sheet remains the leading edge for subsequent printing. After the reorientation, the second driving roller supplies the media sheet from the duplex print path for printing the second side of the media sheet. The detractor is inactivated and the media sheet is ejected to the output path after the second side is printed.
In another embodiment according to the invention, the media sheet handling system includes a pick roller, a driving roller, an output roller, a detractor and a duplex print path. Similarly, the pick roller picks a media sheet from a stack of media sheets, and the driving roller feeds the media sheet towards a printing zone for printing the first side of the media sheet. Then the output roller drives the printed media sheet forward, the detractor directs the media sheet whose first side has been printed into the duplex print path, and the duplex print path reorients the media sheet. In the duplex print path, the media sheet is reversed to a flipped over state with respect to its original position before the first side is printed; and the original leading edge of the media sheet remains the leading edge for subsequent printing. After the reorientation, the duplex print path directs the media sheet back onto the top of the stack of media sheet. Subsequently, the media sheet whose first side has been printed is picked by the pick roller and forwarded by the driving roller towards the printing zone for printing its second side. After the duplex printing, the detractor is inactivated, and the media sheet is ejected to the output path.
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Lim Chuin Kiat
Ng Danny Lian Hock
Parthasarathy Baskar
Adams Russell
Brown Khaled
Hewlett--Packard Company
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