Typewriting machines – Sheet or web – Including friction-feed means
Reexamination Certificate
2002-10-02
2004-02-24
Hirshfeld, Andrew H. (Department: 2854)
Typewriting machines
Sheet or web
Including friction-feed means
C400S602000, C400S617000, C400S636200, C400S636300
Reexamination Certificate
active
06695503
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention.
The present invention relates to an imaging apparatus, and more particularly, to a print media feed system for an imaging apparatus.
2. Description of the Related Art.
A typical ink jet printer forms an image on a print medium by ejecting ink from a plurality of ink jetting nozzles of an ink jet printhead to form a pattern of ink dots on the print medium. Such an ink jet printer typically includes a reciprocating printhead carrier that transports one or more ink jet printheads across the print medium along a bi-directional scanning path defining a print zone of the printer. Typically, the mid-frame provides media support at or near the print zone. A sheet feeding mechanism is used to incrementally advance the print medium sheet in a sheet feed direction, also commonly referred to as a sub-scan direction or vertical direction, through the print zone between scans in the main scan direction, or after all data intended to be printed with the print medium at a particular stationary position has been completed.
One such sheet feed mechanism includes a feed roller and corresponding pinch roller arrangement located upstream of the print zone, and an exit roller and corresponding exit pinch roller arrangement, such as a plurality of star wheels, located downstream of the print zone. The exit roller is often slightly over-driven to place the sheet in a state of slight tension during printing. Following printing, the sheet is advanced to an exit tray by the exit roller. Such a sheet feed mechanism, however, does not easily permit printing adjacent the trailing edge of the sheet, as in attempting borderless printing, since as the sheet is released from the feed roller, the sheet lunges forward due to the state of tension of the sheet. Also, once the sheet is released by the feed roller, the trailing edge of the sheet tends to rise toward the printhead, a phenomena commonly referred to as “tail-flip”, thereby decreasing the distance between the printhead and the sheet, and thereby adversely affecting printing quality.
In order to provide more control of the position of the print medium sheet during printing, another sheet feed mechanism includes a feed roller and corresponding pinch roller arrangement located upstream of the print zone, a first exit roller and corresponding exit pinch roller arrangement located downstream of the print zone, and a second exit roller and corresponding exit pinch roller arrangement positioned downstream from the first exit roller/pinch roller arrangement. In this sheet feed mechanism, the second exit roller, i.e., the exit roller furthest downstream from the print zone, is designed to be of high precision in comparison to the lower precision first exit roller, and thus the further downstream feed roller controls the advancement of the sheet through the print zone following release of the sheet by the feed roller.
One disadvantage of the sheet feed mechanism having two exit roller/exit pinch roller pairs is the increased cost of providing the second downstream exit roller/exit pinch roller pair. Another disadvantage is that, in addition to the first exit pinch roller arrangement, the second exit pinch roller arrangement also contacts the printed side of the sheet, thereby increasing the risk of damage to the printed image.
What is needed in the art is a print media feed system that provides precise control of the position of a sheet of print media following release by the feed roller without the need of a second exit pinch roller arrangement.
SUMMARY OF THE INVENTION
The present invention relates to a print media feed system that provides precise control of the position of a sheet of print media following release by the feed roller without the need of a second exit pinch roller arrangement.
The present invention, in one form thereof, is directed to a print media feed system for advancing a sheet of print media having a leading edge and a trailing edge in a sheet feed direction through a print zone in an imaging apparatus. A drive unit provides a rotational force. A feed roller is coupled to the drive unit. The feed roller is positioned upstream from the print zone in relation to the sheet feed direction. An exit roller is coupled to the drive unit. The exit roller is positioned downstream from the print zone in relation to the sheet feed direction. An exit pinch roller arrangement is positioned adjacent the exit roller. The exit roller and the exit pinch roller arrangement cooperate to advance the trailing edge of the sheet of print media through the print zone. A rotating support is coupled to the drive unit. The rotating support is positioned downstream of the exit roller in relation to the sheet feed direction. The rotating support provides a rotating support surface that engages a non-printed side of the sheet of print media downstream of the exit roller while the trailing edge of the sheet of print media is advanced through the print zone by the exit roller, the rotating support not contributing to advance the trailing edge of the sheet of print media through the print zone, but contributing to advance the sheet of print media after the sheet of print media is released by the exit roller.
An advantage of the present invention is reduction of component count and associated costs over that of systems that include multiple exit roller/exit pinch roller pairs.
Another advantage of the present invention is reduction of the risk of damage to the printed image as the sheet of print media is advanced to the exit tray over that of systems that include multiple exit roller/exit pinch roller pairs.
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Buxton Patrick Andrew
Ward Ryan Timothy
Ghatt Dave A.
Hirshfeld Andrew H.
Lexmark International Inc.
Taylor & Aust P.C.
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