Sheet feeding or delivering – Feeding – With means to align sheet
Reexamination Certificate
2002-09-06
2004-05-18
Walsh, Donald P. (Department: 3653)
Sheet feeding or delivering
Feeding
With means to align sheet
C271S228000
Reexamination Certificate
active
06736394
ABSTRACT:
Disclosed in the embodiments herein is an improved system for sheet lateral position registration (sheet rotational position registration) for print media sheets, especially for an improved “TELER” type of combined lateral sheet registration and deskewing system for a printer.
More specifically, there is disclosed in the embodiments herein an improved integral sheet registration system, especially suited for high speed printers, for providing both sheet deskewing and lateral sheet registration, which provides increased re-centering time, and thus increased acceleration and deceleration latitudes, for the lateral translation movement of the lateral sheet registration system. In the disclosed embodiments this is provided by varying radius sheet feeding rollers providing lateral registration by side-shifting, but with automatic nip openings in their rotations. Additionally disclosed are specially positioned non-slip sheet feeding nips positioned in the paper path between said varying radius rollers and the image transfer station of the printer.
Various sheet registration systems are known in the art, and the present system is not limited to any particular such registration, deskew and/or side-shifting system. Various TELER systems of sheet registration have differential roll pair driving for deskew and sheet side-shifting systems in which the entire structure and mass of the carriage containing the two drive rollers, their opposing nip idlers, and their drive motors connected), is axially side-shifted to side-shift the engaged sheet into lateral registration. These may be referred to as “TELER” systems, of, e.g., U.S. Pat. No. 5,094,442, issued Mar. 10, 1992 to Kamprath et al; U.S. Pat. Nos. 5,794,176 and 5,848,344 to Milillo et al; U.S. Pat. No. 5,219,159, issued Jun. 15, 1993 to Malachowski and Kluger (citing numerous other patents); U.S. Pat. No. 5,337,133; and other cited patents.
Additional background of interest includes a Xerox Corp. U.S. Pat. No. 5,278,624, issued Jan. 11, 1994 to David R. Kamprath and Martin E. Hoover, showing another example of a “TELER” type of combined lateral sheet registration and deskewing system for a printer with a single drive motor and reduced mass of the “TELER” lateral translation (side shifting) components. Reduced mass is helpful to allow the re-centering or return to a “home” position of TELER systems in the very short time and space available between successive sheets in the sheet path of a high speed printer. That is because sheet lateral (side-shift) registration is accomplished in a TELER system by side-shifting the TELER sheet drive rolls and their associated components while the sheet is engaged in the feed nip of those TELER sheet drive rolls.
Also of particular background interest is a Xerox Corp. U.S. Pat. No. 5,078,384 issued Jan. 7, 1992 to Steven R. Moore. This is not a TELER system. Rather, it accomplishes sheet deskewing and downstream or forward direction registration by differential driving of two sheet drive rolls
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, by two servomotors, but does not provide sheet lateral (sideways) registration by any side-shifting of those drive rolls. Thus, it does not teach or suggest (or even have the problem of) accomplishing rapid re-centering of a TELER system in between operative sheet nip engagements. However, this U.S. Pat. No. 5,078,384 does show the use of “D” shaped (partially relieved radius) drive rolls
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to disengage those drive rolls from the sheet (opening the drive nip) when those drive rolls are rotated to the position in which the reduced radius “flat” portion of those “D” shaped drive rolls is facing the sheet and becomes spaced therefrom due it the reduced radius of that portion of the roll.
“D” shaped sheet feeding rolls are, of course, used in various other paper sheet feeding applications. For example, Xerox Corp. U.S. Pat. No. 5,449,165, issued Sep. 12, 1995, discloses a 90 degree paper feed transition module with transversely mounted and intermittently rotated “D” shaped feed rolls. Xerox Corp. U.S. Pat. No. 4,929,128, issued May 22, 1990 to Stemmle, shows typical segmented or “D” shaped feed rolls for initial sheet feeding, and for duplex path sheet feeding. However, the present embodiment provides normal and even closed nip sheet nip engagement and feeding, unlike such “D” roller sheet feed systems in which a stationary sheet is unevenly accelerated by initial engagement of a “corner” of the “D” roller (where the “D” roller transitions from it's smaller to it's larger radius) with the sheet.
There is a further, often unappreciated, problem in TELER systems, of particular interest here. A sheet which has just been accurately deskewed and laterally (side) registered by a TELER system cannot be released from the TELER nips until after that same sheet is firmly acquired by a downstream sheet transport in the paper path (normally a transfer station) which will prevent that sheet from losing the lateral registration and deskewed rotational orientation registration just given to that sheet by the TELER system. Thus, the timing of the release of the TELER nips is critically related not only to the time available and needed for re-centering before the next sheet is acquired (as noted above) but also to the timing of the acquisition of the sheet by the next downstream sheet transporting system.
Thus, in the disclosed embodiment, non-slip downstream sheet acquisition nips are specially positioned in relation to the TELER system feed rolls. In particular, in the disclosed embodiment, plural laterally spaced sheet positional stabilization roller nips are positioned downstream from the nips of “D” shaped TELER rollers (having a sheet engaging peripheral circumference area and a non-sheet engaging peripheral circumference area) by a distance downstream which is less than the circumference of the sheet engaging peripheral circumference area, to insure that the sheet will not be released from the sheet lateral and rotational registration position just provided by the TELER system. In the disclosed embodiment those plural laterally sheet positional stabilization roller nips are positioned in the paper path in between the TELER roller nips and the image transfer station of the printer, for further insuring of the maintenance of the side registration and deskewing of that sheet as that sheet is fed into the image transfer station. That is, in this embodiment the sheet is not released from its stabilizing nips until after at least a substantial portion of that sheet is fully acquired by the image transfer station. By “fully acquired” it is meant that a sufficiently substantial area of that sheet has been electrostatically tacked to the photoreceptor by transfer corona electrostatic charges (or acquired by a biased transfer roller nip with the photoreceptor) for further, non-slip, movement of that sheet by and with the moving photoreceptor, as will be well understood in the xerographic arts.
Various other prior automatic sheet lateral registration and deskewing systems are known in the art. The below-cited patent disclosures are noted by way of some further examples. They demonstrate the long-standing efforts in this technology for more effective yet lower cost sheet lateral registration and deskewing, particularly for printers (including, but not limited to, xerographic copiers and printers). They demonstrate that it has been known for some time to be desirable to have a sheet deskewing system that can be combined with a lateral sheet registration system, in a sheet driving system also maintaining the sheet forward speed and registration (for full three axis sheet position control) in the same apparatus. That is, it is desirable for both the sheet deskewing and lateral registration to be done while the sheets are kept moving along a paper path at a defined substantially constant speed. Otherwise known as sheet registration “on the fly” without sheet stoppages.
Yet these various prior systems have had some difficulties, which the novel system disclosed herein addresses, as further shown and described bel
Halvonik Mark R.
Herrmann Douglas K.
Bower Kenneth W
Walsh Donald P.
Xerox Corporation
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