Typewriting machines – Sheet or web
Reexamination Certificate
2000-06-30
2001-09-25
Colilla, Daniel J. (Department: 2854)
Typewriting machines
Sheet or web
C400S693000, C347S104000
Reexamination Certificate
active
06293716
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to methods and apparatus for printing on two sides of a media sheet, and more particularly, to a media handling system which first feeds a media sheet with a first side exposed to a print source, then feeds the media sheet with a second side exposed to the print source.
Printing to two sides of a media sheet, referred to as duplex printing, is a desirable feature in printing systems. The advantages of duplex printing include reducing the amount of paper required compared to one-sided (simplex) printing, and generating print sets with layouts resembling that of professionally printed books. Conventional duplex printing devices employ complex paper handling mechanisms. Typically, an extra tray is used for temporary storage of pages having printing on a first side. In an alternative approach a second paper path is provided to route a first printed page around the existing paper supply.
Similarly, duplex copying typically is accomplished by either one of two methods. In one method, first side copies are stacked in a duplex tray. When a set of first side copies is complete, the copies are fed out of the duplex tray and returned with an odd number of inversions along, a duplex path to receive second side imaging. In an alternative method first side copies are returned directly to receive second side imaging without stacking.
Conventional devices tend to have long paper paths and many parts. A substantial challenge with systems having these complex duplex printing paper paths is handling paper jams. Accordingly, there is a need for a simplified method and apparatus for duplex media handling at a desktop print recording device.
SUMMARY OF THE INVENTION
According to the invention, a modular duplex media handling system is used in conjunction with a simplex media handling, print recording apparatus. The simplex media handling system includes firmware for operating either in a simplex mode or in a duplex mode, (where the modular duplex media handling system is installed to operate in duplex mode).
According to one aspect of the invention, the modular duplex media handling system includes linkage to the print recording system drive motor. The drive motor drives the feed rollers and the metering rollers of the simplex media handling system and the duplex handling drive rollers of the duplex media handling system. A transmission apparatus allows the duplex handling drive rollers to be disengaged, engaged for rotation in the same direction as the feed rollers, or engaged for rotation in the opposite direction as the feed rollers.
One advantage of the invention is that the transmission switches gears in response to a lever activated by the media sheet motion, rather than in response to a drive motor jogging, action. As a result, the time to shift gears is reduced. Correspondingly, the time to perform a duplex handling print cycle is reduced, and the printer throughput is increased. Another advantage is that by avoiding activation by the drive motor, a larger design margin is tolerated by the gear trains ill the transmission. Another advantage is that a lighter friction load is placed on the drive motor by the interference member. In the embodiment where the clutch is activated by the drive motor a higher, undesirable friction load is placed on the drive motor. Such load is not constant over the life of the printer. Also, placing a higher friction load on the drive motor reduces accuracy in controlling print media stopping, thereby compromising printed image quality. The interference member places a much lower, less critical friction load on the drive motor. According to another advantage of the invention, by activating the transmission drive modes directly in response to the media sheet position, precise drive motor position control is not needed (as it would in embodiments where the clutch is driven by the drive motor). The direct actuation of the transmission drive mode frees up bandwidth for the print controller. These and other aspects and advantages of the invention will be better understood by reference to the following detailed description taken in conjunction with the accompanying drawings.
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Blackman Jeffrey R.
Driggers Matt G.
Ruhe Thomas W.
Colilla Daniel J.
Hewlett--Packard Company
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