Sheet feeding or delivering – Feeding – With means to align sheet
Utility Patent
1999-05-17
2001-01-02
Ellis, Christopher P. (Department: 3651)
Sheet feeding or delivering
Feeding
With means to align sheet
C271S226000, C271S228000
Utility Patent
active
06168153
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 wider 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, to provide deskewing and/or side registration of much longer sheets without losing positive sheet feeding control over much shorter sheets, including subsequently fed sheets in the sequence of sheets in the sheet path. 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 engaging or disengaging an appropriate number of sequential plural spaced sheet feed-in nips of the sheet transport in the sheet path into the sheet deskewing system in accordance with a control signal corresponding to the length of the sheet to be deskewed and/or laterally registered. [The sheet “length” here is the sheet dimension in the sheet feeding or sheet movement direction of the sheet path, otherwise known as the “process direction”, as such terms may be used in the art in that regard, even though, as is well known, smaller sheets are often fed “long edge first”, rather than lengthwise, whereas in contrast very large sheets are more often fed lengthwise. Sheet “width” as referred to herein is thus the orthogonal sheet dimension as the sheet is being fed, i.e., the sheet dimension transverse to the sheet path and the sheet movement direction.
As shown in the embodiment example, these features and improvements can be accomplished in one exemplary manner by automatically disengaging, from a long sheet being deskewed, a sufficient sequential number of upstream sheet feeding units to allow the deskewing of that long sheet, the number disengaged depending on the length of the sheet. Yet positive nip feeding engagement of the next adjacent upstream sheet being fed can be simultaneously maintained while its closely immediately preceding sheet is being deskewed, even for very short sheets.
As shown in this example, this different selectable disengagement of otherwise engaged nips sheet feeding units may even be simply and reliably provided by variable control of a plurality of otherwise structurally identical units. As also disclosed in this example, controlled partial rotation of respective nip idler engagement control cams by the controlled partial rotation of a stepper motor can be utilized for reliable sheet feeding nip disengagement or engagement in each unit. That control may even be provided as shown by a single stepper motor with plural cams on a common shaft variably controlling all of the plural spaced idlers of all of the plural spaced non-skew sheet feeding 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 and 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. This is accomplished in the disclosed embodiment by a simple, low cost, fixed position, system which does not require repositioning of any of the system components relative to the paper path, only automatically selected different nip engagements in different positions of the paper path.
The present system is particularly well suited for cooperation and combination with an automatic deskewing an side registration system of the known general type comprising a differentially driven spaced pair of sheet deskewing nips, for which references are cited below. [In another disclosed feature of this specification, which is the subject of the above cross-referenced related application, the spacing between a pair of such operative deskewing nips can be automatically changed between a spacing more suitable for large sheets and another spacing more suitable for small sheets.]
Examples of such 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, 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, along which the subject sheet feeding units here are spaced. Such a long and planar sheet feeding path to the deskewing system 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 while those sheet are planar, rather than a path that bends sheets to cause sheet beam strength normal forces pressing against the path baffles, thus reducing any tendency for that to cause excessive resistance and/or scuffing or slippage by both the sheet feeding nips and the deskewing or steering nips.
As further disclosed in the embodiment herein, the subject improved sheet input feeding system in the upstream sheet feeding path provides for the automatic release or disengagement of a selected variable number (from 1 to 3 in the illustrated embodiment) of plural upstream sheet feeding plural nip stations or units spaced apart along the sheet path upstream of the sheet deskewing station. That selected release is automatic, and may be in response to a sheet length control signal (such as a signal from a sensor or other signal generator indicative of the approximate sheet dimension along or in the process or sheet path movement 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 automatic deskewing and/or side registration system. Yet once a sheet is acquired in the steering nips of the deskew system a sufficient number of said upstream sheet feeding nips can be automatically released or opened to allow for unrestrained sheet rotation and/or lateral movement by the subject system, even of very long sheets. As is well know in the art, standard sizes of larger size sheets are both longer and wider, and are often
Benedict Lawrence R.
D'Angelantonio David A.
Ford Brian R.
Richards Paul N.
Crawford Gene O.
Ellis Christopher P.
Xerox Corporation
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