Sheet feeding or delivering – Feeding – Separators
Reexamination Certificate
1998-12-16
2001-02-06
Ellis, Christopher P. (Department: 3651)
Sheet feeding or delivering
Feeding
Separators
C271S121000, C271S010110, C271S258030, C271S225000, C271S124000, C271S263000
Reexamination Certificate
active
06182961
ABSTRACT:
Typical flimsy sheets of paper or the like image bearing substrates which have been printed on both sides, commonly referred to as duplex documents, are becoming increasingly common, particularly as environmental concerns lead to greater use of duplex printing and copying reproduction machines. Automatic duplex printing preset default modes in newer machines encourage more such duplexing. The various different types of papers, inks and imaging systems which may be used in duplex printing, e.g., xerographic, ink jet, ink ribbons, offset, etc., and their release agents, if any, may impose different frictional properties and image smearing pressure or frictional sensitivities between adjacent sheets being separated from one another by friction and/or pressure.
Disclosed in the embodiments herein is an improved document feeding system for duplex documents, for preventing or reducing the smudging or contamination of document sheets by the reverse-side image of a duplex document sheet when such sheets are being separated from a stack thereof in frictional retard nip types of document sheets separating and feeding systems for sequentially feeding document sheets for imaging, finishing or other processing from the stack thereof.
Retard type frictional sheet separator-feeders are in widespread use in document scanners, printers, copiers, interposers, inserters, collators, and other reproduction or finishing systems. Retard type separator-feeders typically have a frictional retard nip of elastomeric material, and a normal force system, such that the adjacent sheets are in relative frictional movement with one another during the separating-feeding cycles of document sheets being separated and fed from the stack of documents, especially in the retard nip, where the adjacent sheets may be pressed against one another by the nip normal force. A simplex document has a non-printed side facing the next, adjacent, document to be fed, and thus separation-feeding of simplex documents does not normally have the subject smearing problems that duplex documents can have.
The present system provides a simple, low-cost, yet effective, system for overcoming these and other problems in duplex document feeding by an improved, simple, cycling operation of a retard type document separator-feeder. It may even be incorporated into existing retard type document separator-feeders simply by a simple software control change in the operation thereof.
By way of background in document separator-feeders, one of the most difficult problems in feeding imaged sheets, including original document sheets being fed to be imaged, is separating and feeding the sheets sequentially, only one at a time, at the desired time, from a stack of sheets. That is, to avoid “double feeds”, sheet overlaps, non-feeds, or other misfeeds. Sheets can vary widely in size and weight, stiffness, age, humidity, curl, size and other properties complicating the separation and feeding at the proper time of only one sheet at a time.
Some general examples of prior patents on retard-type spring reverse driven retard roller sheet separator-feeders are disclosed in Savin U.S. Pat. No. 4,368,881; and Konika U.S. Pat. No. 5,039,080. Other retard systems, with driven reverse rotation of retard rollers, instead of springs, are disclosed in U.S. Pat. Nos. 3,108,801, 2,979,330 and 4,801,134. Other retard sheet separators, and general principles thereof, including fixed retard pad systems, are described in Xerox Corporation U.S. Pat. No. 3,768,803 issued Oct. 30, 1993 to Klaus K. Stange.
Of particular interest to the specific semi-active retard separator-feeder of the specific embodiment herein is the above-cited copending application and Xerox Corporation U.S. Pat. No. 5,435,538 issued Jul. 25, 1995 to Philip A. Billings and Ermanno C. Petocchi; U.S. Pat. No. 5,421,569 issued Jun. 6, 1995 to Harry A. Davidson; U.S. Pat. No. 5,709,380 issued Jan. 20, 1998 to Ermanno C. Petocchi and Bruce J. DiRenzo; U.S. Pat. No. 5,769,410 issued Jun. 23, 1998 to Harry A. Davidson and Donald J. Lyon; U.S. Pat. No. 5,461,468 issued Oct. 24, 1995 to Neil J. Dempsey et al; and other patents cited therein. Said U.S. Pat. No. 5,461,468 is of particular interest for its document feeding timing and sequencing. Said U.S. Pat. No. 5,435,538 is of particular interest for its teaching of details of a frictional elastomer retard roller with an integral wrap spring slip biasing device to retard and separate underlying sheets while the top sheet is being fed out by a driven frictional elastomer feed wheel, forming the retard nip by a normal force engagement of the retard roll against the feed roll. The retard roll is allowed to slip-rotate in the downstream or forward sheet feeding direction, driven by the rotation of the feed roll, once the predetermined torque drag level is exceeded (in contrast to a fixed retard pad or roller). The rotational torque drag of the retard roll is set to provide considerable resistance to rotation, so that if two or more sheets are in the retard nip, normally only the one sheet engaged by the feed roll will be driven downstream out of the retard nip, and the others will be retarded there.
Of particular interest is U.S. Pat. No. 3,937,453 to Richard C. Hickey et al, which shows a multi-feed detection system where upon detection of more than one document passing through separator rollers, a clutch is energized to cause one of the rollers to rotate in a direction opposite of the other to separate the documents and only allow the top one to be forwarded.
Also of interest is U.S. Pat. No. 5,316,285 issued May 31, 1994 to Allan G. Olson, et al, disclosing a sheet feeder that has a sheets kick-back lever system for kicking back underlying sheets that may have partially advanced towards the feed zone by frictional forces between the fed sheet and the sheets beneath it.
Further by way of background, in sheet feeder-separator systems, including retard types, the single sheet being fed forward or downstream (while the other sheets are being retarded) is typically fed downstream to a “take-away” rolls nip located less than one sheet dimension downstream. The take-away nip positively engages and pulls the fed sheet on downstream, and may pull the rest of that sheet out of the retard nip (which is typically a less positive sheet engagement system with potential or actual slip, and/or overdriven or under-driven as compared to the takeaway rollers). Additionally, an upstream intermittently engaged elastomeric frictional nudger wheel, as also shown in above-cited references such as U.S. Pat. No. 5,461,468, may also engage the surface of the document sheet to be fed downstream and imaged over a platen imaging area.
As shown in the exemplary embodiments, the retard separator-feeder embodiment further described herein is utilized in a document feeder for reliably separating and sequentially feeding a variety of original document sheets to be scanned sequentially in an electronic image scanner. The embodiment here corresponds closely in that regard to the document handler of Xerox Corporation U.S. Pat. No. 5,534,989 issued Jul. 9, 1996 to Robert F. Rubscha et al.; U.S. Pat. 5,461,468 issued Oct. 24, 1995 to Neil J. Dempsey et al.; U.S. Pat. No. 5,339,139 issued Aug. 20, 1994 to Jack K. Fullerton, et al; and the above-cited U.S. Pat. No. 5,461,468; but this invention is not limited to that particular application.
The problems addressed herein could occur even if there was a fixed retard roll or pad in the separator-feeder. Even in the exemplary embodiment system, where the retard roll is being rotated forward, it is with high resistance, as the fed sheet is fed out of the retard nip (first by the feed roll and then by the downstream take-away rolls). The feed rolls in this embodiment must pull against and overcome the drag force set in the retard roller, which may be provided by an internal wrap spring as in the above-cited U.S. Pat. No. 5,435,538. This drag resistance of the retard roll may be considerable, e.g., 39 Newton-millimeters of torque.
In the description herein the term
Ellis Christopher P.
Ridley Richard
Xerox Corporation
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