Sheet feeding or delivering – Feeding – Separators
Reexamination Certificate
1999-10-12
2001-08-28
Skaggs, H. Grant (Department: 3651)
Sheet feeding or delivering
Feeding
Separators
C271S105000, C271S107000, C271S108000, C271S030100, C271S031000
Reexamination Certificate
active
06279896
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 and 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. If the fluffing or vacuum pressures increase, the sheet acquisition time decreases. Accordingly, the risk of more than one sheet being moved into the take away nip rolls (i.e., a multifeed error) also increases. If fluffing pressure decreases, the top sheet may not get close enough to the translating vacuum feed head which may result in no sheet being fed (i.e., a misfeed error) or in late acquisition of the sheet when the translating vacuum feed head moves forward toward the take away nip rolls. The fluffer and vacuum pressures are determined by paper characteristics, such as the sheet basis weight measured in grams per square meter (gsm), size and coating, which are input by the user or determined automatically by sensors in the image forming apparatus.
SUMMARY OF THE INVENTION
In accordance with an exemplary embodiment of the system and method according to this invention, a sheet feed apparatus for an image forming apparatus includes 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 is driven in a single direction while causing the translating vacuum feed head to reciprocate from a first position to a second position. The control circuit dynamically adjusts the positive pressures and the vacuum pressure to prevent multifeed, misfeed and/or late acquisition. The sheet acquisition time is the time interval between opening of a vacuum manifold valve and the acquisition of the sheet by the translating vacuum feed head. In one exemplary embodiment, the control circuit controls the sheet acquisition time based on a running average and standard deviation of a 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.
REFERENCES:
patent: 5184813 (1993-02-01), Schwitzky et al.
patent: 5290023 (1994-03-01), Sasaki et al.
patent: 5645274 (1997-07-01), Ubayashi et al.
patent: 5893554 (1999-04-01), Okahashi et al.
patent: 5988624 (1999-11-01), Nakagawa
patent: 6082728 (2000-07-01), Ubayashi
patent: 6123330 (2000-09-01), Schaal
patent: 2835385 (1979-05-01), None
Dechau Richard L.
Haag William R.
Linder Michael J.
Moore Kenneth P.
Oliff & Berridge. PLC
Skaggs H. Grant
Xerox Corporation
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