Sheet feeding or delivering – Feeding – With means to align sheet
Reexamination Certificate
2001-07-27
2003-06-10
Bollinger, David H. (Department: 3653)
Sheet feeding or delivering
Feeding
With means to align sheet
Reexamination Certificate
active
06575458
ABSTRACT:
Disclosed in the embodiments herein is an improved, lower cost, system for sheet deskewing. Various types of automatic sheet deskewing systems are known in the art. The following previous patent disclosures are noted by way of examples. They demonstrate the long-standing efforts in this technology for more effective yet lower cost sheet deskewing, particularly for printers (including, but not limited to, xerographic copiers and printers). Also, they show that it is known to be desirable to have a sheet deskewing system that can be combined with a lateral sheet registration system, in the same or a modified apparatus. Also, to show that it is desirable for either or both sheet deskewing and lateral registration to be done while the sheets are moving along a paper path (“on the fly”, without sheet stoppages). Especially for faster printing rates, requiring faster sheet feed rates, which can reach more than, for example, 100-200 pages per minute, the above systems and functions become even more difficult and expensive, as will be explained. However, it will be noted that the deskewing systems disclosed herein are not limited to just such high speed printing applications, nor limited only to combinations of sheet deskewing and sheet lateral (sideways) registration.
Disclosed in the embodiments herein is an improved system for controlling, correcting or changing the orientation and/or position of sheets traveling in a sheet transport path, in particular, sheets being printed in a reproduction apparatus, which may include sheets being fed 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.
Disclosed in the embodiments herein is a simple system for deskewing, and, optionally, also transversely repositioning, sheets with a simpler, lower cost, mechanism which needs only one single main drive motor for two feed roll drives, together with a much lower power, and lower cost, deskewing differential drive. This is in contrast to various of the below-cited and other systems which require two or even three separate, and separately controlled, servo or stepper motor drives. Yet the disclosed embodiments can provide active automatic variable sheet deskewing and optional, active variable side shifting for lateral registration, while the sheet is moving uninterruptedly at process speed. It is applicable to various reproduction systems herein generally referred to as printers, including high speed printers, and other sheet feeding applications. Furthermore, the deskewing system of the disclosed embodiments can provide reduced total mass, and therefor provide improvements in integral lateral registration systems involving rapid lateral movement thereof, such as the TELER type described below.
Various types of variable active sheet side shifting or lateral registration and/or deskew systems are known in the art. A recent example of this technology is Xerox Corp. U.S. Pat. No. 6,173,952 B1 issued Jan. 16, 2001 to Paul N. Richards, et al (and art cited therein). Furthermore, that patent's disclosed additional feature of variable lateral nip spacing, for better control over variable size sheets, may be readily combined with or into various applications of the present invention, if desired.
As noted, it is particularly desirable to be able to do so “on the fly,” while the sheet is moving through or out of the reproduction system at normal process (sheet transport) speed. Also, to be able to do so with a system that does not substantially increase the overall sheet path length, or increase paper jam tendencies. The following additional patent disclosures, and other patents cited therein, are noted by way of some examples of sheet lateral registration systems with various means for side-shifting or laterally repositioning the sheet: Xerox Corporation U.S. Pat. No. 5,794,176, issued Aug. 11, 1998 to W. Milillo; U.S. Pat. No. 5,678,159, issued Oct. 14, 1997 to Lloyd A. Williams, et al; U.S. Pat. No. 4,971,304, issued Nov. 20, 1990 to Lofthus; U.S. Pat. No. 5,156,391, issued Oct. 20, 1992 to G. Roller; U.S. Pat. No. 5,078,384, issued Jan. 7, 1992 to S. Moore; U.S. Pat. No. 5,094,442, issued Mar. 10, 1992 to D. Kamprath, et al; U.S. Pat. No. 5,219,159, issued Jun. 15, 1993 to M. Malachowski, et al; U.S. Pat. No. 5,169,140, issued Dec. 8, 1992 to S. Wenthe; and U.S. Pat. No. 5,697,608, issued Dec. 16, 1997 to V. Castelli, et al. Also, IBM U.S. Pat. No. 4,511,242, issued Apr. 16, 1985 to Ashbee, et al.
Various optical sheet lead edge and sheet side edge position detector sensors are known which may be utilized in such automatic sheet deskew and/or lateral registration systems. Various of these are disclosed the above-cited references and other references cited therein, or otherwise, such as the above-cited U.S. Pat. No. 5,678,159, issued Oct. 14, 1997 to Lloyd A. Williams, et al; and U.S. Pat. No. 5,697,608 to V. Castelli, et al.
Various of the above-cited and other patents show that it is well known to provide sheet deskewing systems, which may also provide lateral registration, in which a sheet is deskewed while moving through two laterally spaced apart sheet feed roller-idler nips, where the two separate sheet feed rollers are independently driven by two different respective drive motors. Temporarily driving the two motors at slightly different rotational speeds provides a slight difference in the total rotation or relative pitch position of each feed roller while the sheet is held in the two nips. That moves one side of the sheet ahead of the other to induce a skew (small partial rotation) in the sheet opposite from an initially detected sheet skew in the sheet as the sheet enters the deskewing system. Thereby deskewing the sheet so that the sheet is now oriented with (in line with) the paper path.
However, especially for high speed printing, sufficiently accurate continued process (downstream) sheet feeding requirements typically requires these two separate drive motors to be two relatively powerful and expensive servo-motors. Furthermore, although the two drive rollers are desirably axially aligned with one another to rotate in parallel planes and not induce sheet buckling or tearing by driving forward at different angles, the two drive rollers cannot both be fixed on the same common transverse drive shaft, since they must be independently driven.
For printing in general, the providing of either, and especially both, sheet skewing rotation or side shifting while the sheet is being fed forward in the printer sheet path is a technical challenge, especially as the sheet path feeding speed increases. Print sheets are typically flimsy paper or plastic imageable substrates of varying thinnesses, stiffnesses, frictions, surface coatings, sizes, masses and humidity conditions. Various of such print sheets are particularly susceptible to feeder slippage, wrinkling, or tearing when subject to excessive accelerations, decelerations, drag forces, path bending, etc.
The above-cited Xerox Corp. U.S. Pat. No. 4,971,304, issued Nov. 20, 1990 to Lofthus (and various subsequent patents citing that patent), is of interest as showing that a two nips differentially driven sheet deskewing system, as described above, can also desirably provide sheet lateral registration in the same unit and system, by differentially driving the two nips to provide full three axis sheet registration with the same two drive rollers and two drive motors, plus appropriate sensors and software. That type of deskewing system can provide sheet lateral registration by deskewing (differentially driving the two nips to remove any sensed initial sheet skew) and then deliberately inducing a fixed amount of sheet skew with further differential driving, and driving the sheet forward while so skewed, thereby feeding the sheet sideways as well as forwardly, and then removing that induced skew after providing the desired amount of sheet side-shift providing the desired lateral registration position of the sheet edge. This Lofthus-type lateral registrat
deJong Joannes N. M.
Dondiego Matthew
Savino Michael J.
Williams Lloyd A.
Bollinger David H.
Xerox Corporation
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