Sheet feeding or delivering – Feeding – Separators
Reexamination Certificate
2000-12-06
2003-07-22
Bollinger, David H. (Department: 3653)
Sheet feeding or delivering
Feeding
Separators
Reexamination Certificate
active
06595512
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sheet feeding system and, more particularly, to a sheet feeding system having a substantially constant nip force.
2. Prior Art
Many different sheet feeding devices are known in the sheet feeding art. For example, U.S. Pat. No. 5,435,540 discloses a sheet feeding and separating apparatus for feeding sheets from a stack by exerting a drive force against the top sheet where the sheet is urged off the stack by a nudger roll toward a retard nip formed where a feed roll contacts a retard roll. Another example, U.S. Pat. No. 5,988,622 discloses a paper feeding device that includes a plurality of horizontally juxtaposed paper cassettes for containing papers. Another example, U.S. Pat. No. 5,978,622 discloses a moving document imaging system in which documents are sequentially fed from a stack. All three of the above referenced patents are incorporated by reference herein in their entirety. Some general examples of sheet separator-feeders include: retard-type spring reverse driven retard roller sheet separator-feeders; similar separator-feeders with driven reverse rotation of retard rollers, instead of springs; fixed retard pad systems; and semi-active retard separator-feeders. In each of these systems, the drag of a retard roll or pad is set to provide resistance, 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. One of the most difficult problems in feeding sheets, including original documents sheets being fed to be imaged and the image stored and/or printed, as here, 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, nonfeeds, 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. Feed and retard rolls serve the purpose of separating sheets from a stack and feeding them into the copier, printer or other document handling device as the case may be. One of the difficult parameters to control in a feed/retard drive system is the normal force exerted between the feed roll and the retard roll. If the normal force is high, the rolls will feed more than one sheet creating an error. If the normal force is too low, the rolls will feed no sheet creating an error. For systems that utilize a spring loaded approach to establishing the normal force exerted between the feed roll and the retard roll, factors such as roll manufactured diameter tolerances, roll wear diameter over time, sheet thickness being fed, spring constant tolerances, spring preload tolerance and mounting component tolerances affect the value of the critical normal force. Accordingly, there is a desire to provide a spring loaded sheet feeding device where the normal force exerted between the feed roll and the retard roll is affected as little as possible by these tolerances and component wear over time.
In the description herein the term “document” or “sheet” refers to various flimsy physical sheets of paper, plastic, or other suitable physical image substrates.
SUMMARY OF THE INVENTION
In accordance with one embodiment of the present invention, a sheet feeder system is provided for use in a document creating apparatus. The feeder has a frame, housing and a roll for individually feeding sheets of material within an image transfer system of the document creating apparatus. The housing is pivotally connected to the frame on a pivot axis. The roll is pivotally connected to the housing on a roll axis that is offset from the pivot axis. A spring is connected to the housing and the frame at an offset distance from the pivot axis. When the offset distance decreases, the force exerted by the spring increases. When the offset distance increases, the force exerted by the spring decreases.
In accordance with another embodiment of the present invention, a sheet feeding apparatus is provided for use in a document creating apparatus. The sheet feeding apparatus has a frame, a linkage and a first and second roll for individually feeding sheets of material. The linkage and the second roll are connected to the frame. The first roll is connected to the linkage. A spring is connected to the frame and the linkage and provided to exert a force between the first roll and the second roll. When the distance between the axis of rotation of the first roll and the second roll is varied, the force exerted by the spring between the first roll and the second roll is maintained substantially constant.
REFERENCES:
patent: 4346880 (1982-08-01), Roller et al.
patent: 4605218 (1986-08-01), Knepper et al.
patent: 4627607 (1986-12-01), Ishii
patent: 4801134 (1989-01-01), Yokoyama et al.
patent: 5004218 (1991-04-01), Sardano et al.
patent: 5011124 (1991-04-01), Sardano et al.
patent: 5016866 (1991-05-01), Takahashi
patent: 5346199 (1994-09-01), Martin et al.
patent: 5435540 (1995-07-01), Martin et al.
patent: 5884910 (1999-03-01), Mandel
patent: 5913268 (1999-06-01), Jackson et al.
patent: 5978622 (1999-11-01), Wenthe, Jr.
patent: 5988622 (1999-11-01), Shigeta
patent: 5988635 (1999-11-01), Ohshima
patent: 5996990 (1999-12-01), Kawashima
patent: 6027111 (2000-02-01), Rubscha et al.
patent: 6059279 (2000-05-01), Wenthe, Jr.
patent: 6318717 (2001-11-01), Daboub et al.
de Koning Petrus T.
Ruthenberg Raymond
Bollinger David H.
Perman & Green LLP
Xerox Corporation
LandOfFree
Constant force sheet feeder does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Constant force sheet feeder, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Constant force sheet feeder will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3017103