Sheet feeding or delivering – Feeding – Pack holders
Reexamination Certificate
1999-11-23
2001-09-18
Ellis, Christopher P. (Department: 3651)
Sheet feeding or delivering
Feeding
Pack holders
C271S030100, C271S147000, C271S126000, C271S152000
Reexamination Certificate
active
06290225
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates generally to a sheet feeder for an image forming engine of an image forming apparatus.
2. Description of Related Art
To supply image recording media, generally referred to as “sheets”, to the image forming engine, individual copy sheets are acquired from the top of a stack and are transported forward by a translating vacuum feed head into a set of take away nip rolls. Sheet fluffers separate a sheet from the top of the stack. The translating vacuum feed head acquires the separated sheet and feeds the separated sheet into the set of take-away nip rolls. The time for the translating vacuum feed head to acquire the sheet is relatively short. The height of the stack must be monitored and adjusted during sheet feeding to maintain the sheet acquisition time as short as possible. The stack height must also be monitored and adjusted to correct for problems caused, for example, by edge welding and/or poor separation between sheets. Current stack height monitoring methods rely on contact with the stack. This may cause marking of the sheets or reduction in the fluffing of the stack. Optical sensors are also currently used to monitor stack height. The optical sensors, however, may not be reliable when looking at the edge or top of a fluffed stack.
SUMMARY OF THE INVENTION
In accordance with various exemplary embodiments of the systems and methods according to this invention, a sheet feed apparatus for an image forming apparatus includes sheet fluffers to separate a top sheet from the stack, a vacuum source that is selectively actuable, a translating vacuum feed head attached to the vacuum source to acquire the top sheet of the stack, a unidirectional rotating drive mechanism, and a control circuit. The unidirectional rotating drive mechanism causes the translating vacuum feed head to reciprocate from a first position to a second position. The control circuit dynamically adjusts the stack height to maintain the lowest possible sheet acquisition time. The sheet acquisition time is the time interval between the opening of a vacuum manifold valve and the acquisition of the sheet by the translating vacuum feed head. In various exemplary embodiments, the control circuit controls the stack height based on the measured sheet acquisition time for a predetermined number of previously successfully fed sheets and the average stack height for the predetermined number of previously successfully fed sheets.
Other features of the invention will become apparent as the following description proceeds and upon reference to the drawings.
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Haag William R.
Linder Michael J.
Ellis Christopher P.
Mackey Patrick
Oliff & Berridg,e PLC
Xerox Corporation
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