Sheet feeding or delivering – Feeding – With means to align sheet
Reexamination Certificate
1999-05-17
2001-01-16
Ellis, Christopher P. (Department: 3651)
Sheet feeding or delivering
Feeding
With means to align sheet
C271S254000
Reexamination Certificate
active
06173952
ABSTRACT:
Disclosed in the embodiment herein is an improved system for controlling, correcting and/or changing the position of sheets traveling in a sheet transport path, in particular, for automatic sheet skew correction and/or side registration of a wide range of different sizes of paper or other image bearing sheets in or for an image reproduction apparatus, such as a high speed electronic printer, with differentially driven sheet feed nips, in which the lateral spacing between the differentially driven sheet feed nips can be automatically changed. This may include deskewing and/or side registration of sheets being initially fed in to be printed, sheets being recirculated for second side (duplex) printing, and/or sheets being outputted to a stacker, finisher or other output or module.
More specifically disclosed in the embodiment herein is a system and method for automatically changing the spacing (transverse the sheet path) between the respective operative sheet steering or deskewing nips of the sheet deskewing and side registration system in accordance with a control signal corresponding to the width of the sheet to be deskewed and/or laterally registered.
As shown in the embodiment example, these features and improvements can be accomplished in one exemplary manner by automatically disengaging a first sheet steering nip in a first transverse position and automatically engaging a second sheet steering nip in a second and different transverse position (further inboard or outboard of the paper path), while maintaining a third sheet steering nip engaged so as to continuously provide a transversely spaced pair of sheet nip steering engagements, yet to provide at least two different said transverse spacings.
As shown in this example, this different selectable transverse positioning of at least one of the engaged sheet steering/deskewing nips may be simply and reliably provided by controlled partial rotation of respective nip idler engagement control cams by the controlled partial rotation of a stepper motor. That control may even be provided as shown by a single stepper motor with plural cams on a common shaft variably controlling plural spaced idlers of plural spaced nips. That can provide better control and long-term reliability than trying to hold individual nips open or closed by activation, deactivation, or holding, of individual solenoid actuators for each nip.
The above-described embodiments (or other embodiments of the generic concept) can greatly assist in automatically providing more accurate rapid deskewing rotation and/or edge registration of a very wide range of sheet sizes, from very small sheets to very large sheets, and from thin and flimsy such sheets to heavy or stiff such sheets. It can do so without undesired slippage, sheet scuffing, marking or other damage, even with such a wide range of sheet sizes and/or properties. The increased resistance to sheet rotation and/or lateral repositioning of larger sheets by the nip pair of prior automatic deskewing systems of the type comprising a differentially driven pair of sheet deskewing nips is automatically compensated for. Yet, positive engagement by such a nip pair can also be automatically provided here in the same deskewing station, with the same deskewing apparatus, for much smaller sheets, to automatically provide proper deskewing and edge registration of very small sheets, and positive feeding of very small sheets. The spacing between the pair of operative deskewing nips is automatically changed between a spacing suitable for large sheets and another spacing suitable for small sheets. This is all accomplished in the disclosed embodiment by a simple, low cost, system which does not require repositioning of any of the variable drive system components of the deskewing system, only automatically selected different steering nip engagements. Although two different selected sheet steering nip spacings are illustrated in the embodiment here, it will be appreciated that additional, different, e.g., intermediate, nip spacings can also be provided in the same manner.
The above and other features and advantages allow for accurate registration for imaging of a wider variety of image substrate sheet sizes, weights and stiffness. In reproduction apparatus in general, such as xerographic and other copiers and printers or multifunction machines, it is increasingly important to be able to provide faster yet safer and more reliable, more accurate, and more automatic, handling of a wide variety of the physical image bearing sheets, typically paper (or even plastic transparencies) of various sizes, weights, surfaces, humidity, and other conditions. Elimination of sheet skewing or other sheet misregistration is very important for proper imaging. Otherwise, borders and/or edge shadow images may appear on the copy sheet; and/or information near an edge of the image may be lost. Sheet misregistration or misfeeding can also adversely affect further sheet feeding, ejection, and/or stacking and finishing.
A desirable prior art type of (fixed spacing) dual differently driven nips systems for automatic deskewing and side registration of the sheets to be accurately imaged in a printer (being improved in the embodiment herein), including the appropriate controls of the differently driven sheet steering nips, and including cooperative arrayed sheet edge position detector sensors and signal generators, are already fully described and shown, for example, in prior Xerox Corp. U.S. Pat. Nos. 5,678,159 and 5,715,514 by Lloyd A. Williams, et al., and other patents cited therein, all of which are incorporated herein. Accordingly, that subject matter per se need not be re-described in detail herein. As explained therein, by driving two spaced apart steering nips with a speed differential to partially rotate a sheet for a brief predetermined time, as the sheet is also being driven forward by both nips, so that it is briefly driven forward at an angle, and then reversing that relative difference in nip drive velocities, the sheet can be side-shifted into a desired lateral registration position, as well as correcting any skew that was in the sheet as the sheet entered the steering nips, i.e., straightening out the sheet so that the sheet exits the steering nip pair aligned in the process direction as well as side registered.
The improved system disclosed herein is also desirably compatible and combinable with an elongated and substantially planer sheet feeding path upstream in the paper path from the subject deskewing and/or side registration system station, leading thereto, which reduces resistance to sheet rotation and/or lateral movement, especially for large, stiff, sheets. That is, a planar sheet entrance path longer than the longest sheet to be deskewed, to allow deskewing rotation of even very large and stiff sheets without excessive resistance and/or scuffing or slippage by the deskewing or steering nips.
As further disclosed herein, and as claimed in the related application cross-referenced in the first paragraph of this specification, the subject improved automatic deskewing and/or side registration system may be desirably combined with a further system in the upstream sheet feeding path for the automatic release or engagement of a selected variable number (1 to 3 in the illustrated embodiment) of plural upstream sheet feeding plural nip stations spaced apart along the sheet path upstream of in response to a selected sheet length control signal (such as a signal from a sensor or other signal generator indicative of the sheet dimension along or in the process or sheet path direction). The spacings and respective actuations (releases or engagements) of the selected number of plural sheet feeding nips along the upstream sheet path of that sheet path control system can provide for a wide range of sheet lengths to be positively fed, without loss of positive nip control, even short sheets, downstream to the subject improved automatic deskewing and/or side registration system, yet once a sheet is acquired in the steering nips of the subject system a suffic
Benedict Lawrence R.
D'Angelantonio David A.
Ford Brian R.
Richards Paul N.
Bower Kenneth W.
Ellis Christopher P.
Xerox Corporation
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