Sheets stacking system with disk type inverter-stacker at right angle to printer output

A printed sheets output inverting and stacking system for printers printing normal size sheets oriented widthwise and long size sheets oriented lengthwise, with a disk type rotatable sheet inverting and stacking system positioned adjacent to one side of the printer output path with its axis of rotation parallel to the direction of sheet movement of the printer. A scuffer or other lateral sheet feeding system receives the printed sheet output of the printer and laterally moves each sheet towards one side of the printer output path, at right angles to the original direction of sheet movement, and into the sheet inverting slots of the rotatable disk inverter-stacker, so that the long size sheets are inverted widthwise, for increased stacking reliability.

Disclosed in the embodiment herein is an improved sheet stacking system for 
the stacking of printed sheets of different sheet sizes being outputted by 
a printer, including large sheets, utilizing an inverter-stacker. In the 
disclosed embodiment, long sheets are outputted by the printer lengthwise, 
but inverted and stacked sideways by the inverter-stacker. This provides 
improves substantially more reliable sheet stacking of such longer sheets. 
It can be provided even with known, conventional disk-type 
inverter-stackers by inverting and stacking all of the printer outputted 
sheets at right angles to the output path of the printer, from one side of 
the output path. 
The disclosed system is particularly suitable for any of the various known 
commercial printers which feed and print standard sizes of sheets and 
smaller sheets widthwise, but which feed and print longer sheets 
lengthwise. This is due to well known conflicting goals for a printing 
machine. It is desired on one hand to have a paper path width limitation 
for machines so as not to make the machine too wide, but on the other hand 
higher printing speeds, more sheets per minute, can be obtained by feeding 
and printing paper width-wise whenever possible. 
It will be understood that the term "printer", as used herein, encompasses 
various reproduction apparatus, especially xerographic printers or 
copiers, for printing or imaging on typical print media, such as flimsy 
paper or plastic sheets in the various standard copy sheet sizes (letter, 
legal, A4, B4, ledger, 11".times.17", etc). 
The disclosed system is simple and low cost, yet overcomes serious problems 
with the proper stacking of long sheets in an inverter-stacker system, 
especially those which are thin, limp or otherwise have low beam-strength 
sheets. Typical long and flimsy printed sheets have stacking problems when 
being outputted, inverted, and stacked lengthwise. Typical such long 
sheets include U.S. 11".times.17" sheets of normal or light paper weights, 
or European A3 size short grain paper sheets. It is known in the art that 
such large and flimsy sheets can have stacking failures in a disk-type 
inverter-stacker system when the trail end area of the long sheet 
collapses back down over the preceding leading portion of the sheet in the 
output tray to form a loop thereon rather than rolling out fully onto the 
stacking tray to lay flat thereon. Such sheet miss-stacking can prevent 
the stacking of the subsequent sheets being outputted to the 
inverter-stacker from a printer or copier, and cause jams. 
By way of relevant background, some prior patents specifically addressing 
those well known long sheet stacking problems, by modifications or 
additions to disk type inverter-stackers, include Xerox Corp. U.S. Pat. 
No. 5,842,695 issued Dec. 1, 1998 to Daniel J. McVeigh, with sheet 
corrugating fingers; and U.S. Pat. No. 5,145,167 issued Sept. 8, 1992 to 
Thomas C. McGraw, et al., with an overlying transport belt system 
assisting the trail edge flipping over movement of long sheets being 
inverted and stacked. The present system does not require those 
modifications of the disk inverter-stacker. However, they can be 
additionally provided, for additional stacking reliability, if desired. 
Another example of a modern disk type inverter-stacker in general is Xerox 
Corp. U.S. Pat. No. 5,409,201 issued Apr. 25, 1995 to William E. Kramer. 
It also shows integral set stapling. Also, Xerox Corp. U.S. Pat. No. 
5,409,202 issued Apr. 25, 1995 to Raymond A. Naramore and William E. 
Kramer. The theory, operation, and advantages of such disk type sheet 
inverting and stacking systems are well known from the above and other 
references, and other art cited therein, and need not be repeated in 
detail herein. However, they are briefly discussed further below. 
It is important to note that, in contrast to the system disclosed herein, 
all of the above-cited disk type inverter-stacker systems are directly in 
the sheet path from the printer, and have an axis of rotation transverse, 
extending across, the sheet output path of the printer, so that the 
printer output feeds sheets directly, linearly, into the disk fingers of 
the disk inverter-stacker. Thus, the sheets stack in the same direction as 
the sheets are being outputted by the printer in those prior systems, the 
disk inverter-stacker increases the length of the overall or combined 
printing and stacking unit, and usually requires unloading the stacked 
sheets sideways or from one side end of the combined unit. 
In a typical disk type inverter-stacker, as shown and described in the 
cited and other references, printed copy sheets are sequentially fed from 
the printer or copier (IOT) output straight on into the sheet entrance of 
the disk-type inverter-stacker, which may comprise a modular finisher 
output unit. Typically in such disk type output units, plural spaced 
rotatable semi-cylindrical disks have, or define, fingers forming arcuate 
sheet receiving slots. The entrances to these slots are normally initially 
positioned at the top of the output unit so that the lead edge of the next 
incoming sheet may be fed into these disk slots. The disk slots 
temporarily hold at least the leading edge area of the sheet within the 
slots for the inversion and stacking of that sheet as the disks are 
centrally rotated. When the disks, with these fingers and slots, have all 
been commonly rotated on their central shaft by approximately 180 degrees, 
the lead edge of the sheet in the slots has been inverted and engages a 
registration stripping surface edge or fingers positioned under the disk 
unit. That strips the sheets out from the disk slots as the disks continue 
to rotate, and frees that now inverted sheet for stacking onto an 
associated output stacking tray. 
Such a disk type inverting and stacking system presupposes that the 
remainder (the trailing area) of a long sheet which does not fully fit 
into the disk slots will be flipped over to fall out flat on the stacking 
tray from this same rotational movement of its leading area in the slots. 
However, as noted above, this may not always occur with a sufficiently 
lengthy and flimsy sheet of paper. The printer or copier, which has 
necessarily continued to feed the long sheet out after the lead edge of 
this sheet has already been fed fully into the disk slots to the end of 
the disk slots, can form a large loop of the trailing area portion of the 
long sheet which is now hanging down over the tray, as illustrated in FIG. 
3 of the above-cited U.S. Pat. No. 5,842,695. When the lead edge of this 
long sheet is released from the disk fingers, that loop should roll out 
slowly onto the tray. However, instead, it may, as illustrated in the 
stacking failure example of FIG. 4 of that same U.S. Pat. No. 5,842,695 
cause the trail end area of the sheet to fall down directly onto the front 
area of the stack instead. In that stacking failure mode the long sheet 
forms a loop on top of the stack, rather than a laid out sheet. That is, 
the trail end of the large sheet collapses onto the upstream portion of 
the stack, onto the front portion of that same sheet, to cause a stacking 
failure, as shown, which prevents further proper stacking or finishing, 
and typically results in a jam which can cause or required a printing 
stoppage. 
The disclosed system can overcome the above and other stacking problems for 
such large and flimsy sheets for many typical printers. 
Further by way of background, output stacker modules with inverters, such 
as disk type inverter-stackers, are particularly useful, for example, for 
accepting sheets from a printer desirably printed face-up in forward or 1 
to N serial page order, for stacking those sheets face-down, so as to 
provide properly collated output sets, i.e., printed output documents in 
proper 1 to N order when picked up from the output tray. Or, for duplex 
printed sheets in which the second or even page sides are printed face 
down. The inverter-stacker may also be part of a print job output system 
providing another selectable but non-inverting output stacking tray, to 
provide a selection between face up or face down stacking for different 
printing modes and/or to avoid having to use or provide an internal sheet 
inverter within the printer. An internal sheet inverter is usually more 
difficult to clear sheets from, in the event of a machine jam, than an 
easily externally accessible disk-type stacker unit. 
It will also be noted that in disk type inverter-stackers the fingers 
defining the sheet transporting slots can be integral the outer edges of 
the rotating disks and define a slot therebetween, or be pivotally mounted 
thereto and have slots defined within the pivotal fingers. 
The specific embodiment disclosed herein desirably does not need or require 
a separate sheet rotator for printers of the type described above, i.e., 
printers which already print and output long sheets oriented differently 
than (at ninety degrees to) standard size or smaller sheets. However, 
various means of copy sheet rotation before or at the printer output could 
be used with other printers. Suitable sheet rotators are well known, and 
need not be disclosed in detail herein. Xerox Corp. U.S. patents on 90 
degree sheet rotators include U.S. Pat. Nos. 5,090,683; 4,955,965; 
4,877,234; 4,733,857; 4,727,402, and other art cited therein. Printing and 
outputting different copy sizes of copy sheets with 90 degree different 
orientations of the sheets (for different reasons--transverse stacking 
with extending edge areas for printed banner sheets) is also taught in 
Xerox Corp. U.S. Pat. No. 5,316,279. Another example of printer sheet 
rotation (albeit for 180 degree rather than 90 degree rotation, for duplex 
printing) is disclosed in a Xerox Disclosure Journal publication of 
September/October 1984, Vol. 9, No. 5, pp. 323-324, by R. E. Shaeffer, 
entitled "Copy Rotator/Inverter". 
By way of further background, various angled (two-axis) scuffer wheel or 
other diagonal or lateral sheet sifting devices are well known per se for 
corner registration of documents or lateral repositioning of printer 
output sheets being stacked, and need not be re-described in detail 
herein. For example, Xerox Corp. U.S. Pat. Nos. 5,120,047; 4,087,087; 
4,358,197; 4,462,527; 4,621,801; 4,411,418 and 4,335,954, and other art 
cited therein. 
Further by way of general background, in most reproduction apparatus such 
as xerographic and other copiers and printers or multifunction machines, 
it is increasingly important to provide more automatic and reliable 
handling of the physical image bearing sheets, especially reduced sheet 
jams. Especially for shared or networked printing systems in which the 
sheet printing and outputting may be unattended, at a remote printer. A 
remote printer's sheet jams may well be unobserved, and not readily 
cleared to avoid printer stoppages, unless and until an operator is 
remotely electronically notified by the system and arrives at the remote 
printer location. 
A specific feature of the specific embodiment disclosed herein is to 
provide in a printed sheets output inverting and stacking system for a 
printer, which printer provides an output of normal size printed sheets 
oriented widthwise, and an output of long size sheets oriented lengthwise, 
sequentially in a printer output path having a first direction of sheet 
movement; wherein said printer output inverting and stacking system 
comprises a rotatable sheet inverting and stacking system rotatable about 
an axis of rotation, said sheet inverting and stacking system having sheet 
retaining and transporting slots for receiving therein, and inverting by 
said rotation about said axis of rotation, said printed sheets output of 
said printer, the improvement wherein: said rotatable sheet inverting and 
stacking system is positioned adjacent to one side of said printer output 
path with said axis of rotation parallel to said first direction of sheet 
movement; and wherein there is a lateral sheet feeding system operatively 
positioned in said printer output path between said printer output and 
said rotatable sheet inverting and stacking system for sequentially 
receiving said printed sheets output of said printer and laterally moving 
said printed sheets output of said printer towards one side of said 
printer output path in a second direction of sheet movement at right 
angles to said first direction of sheet movement and into said sheet 
retaining and transporting slots of said rotatable sheet inverting and 
stacking system, so that said long size sheets are inverted widthwise in 
said rotatable sheet inverting and stacking system for increased 
reliability, and said normal size printed sheets are inverted lengthwise 
in said rotatable sheet inverting and stacking system. 
Further specific features disclosed herein, individually or in combination, 
include those wherein said lateral sheet feeding system comprises at least 
one angled sheet scuffer system; and/or wherein said lateral sheet feeding 
system includes a sheet lead edge registration stop transverse said first 
direction of sheet movement; and/or wherein said lateral sheet feeding 
system includes a sheet lead edge registration stop transverse said first 
direction of sheet movement and aligned with a operative end of said 
rotatable sheet inverting and stacking system; and/or wherein said printer 
output path first direction of sheet movement is transverse the front of 
said printer yet said rotatable sheet inverting and stacking system stacks 
said sheets towards the front of said printer. 
In the description herein the term "sheet" refers to a usually flimsy 
physical sheet of paper, plastic, or other suitable physical substrate for 
images, whether precut or initially web fed and cut into sheets 
internally. A "copy sheet" may be abbreviated as a "copy", or called a 
"hardcopy". A "job" or "print job" is normally a set of related sheets, 
usually a collated copy set copied from a set of original document sheets 
or electronic document page images, from a particular user, or otherwise 
related. 
As to specific components of the subject apparatus, or alternatives 
therefor, it will be appreciated that, as is normally the case, some such 
components are known per se in other apparatus or applications which may 
be additionally or alternatively used herein, including those from cited 
art. All references cited in this specification, and their references, are 
incorporated by reference herein where appropriate for appropriate 
teachings of additional or alternative details, features, and/or technical 
background. What is well known to those skilled in the art need not be 
described here.

Describing now in further detail with reference to these figures the 
exemplary sheet output inverting and stacking system 10 embodiment, there 
is schematically shown an otherwise known disk-type inverter stacker 
output unit 12, like that shown in the above-cited patents thereon, for 
inverting and stacking in an associated sheet stacking tray 14 the sheets 
16 being sequentially outputted by a printer 20 of the type previously 
described. That is, a printer 20 which prints and feeds out defined 
standard sizes of sheets (such as letter size and legal size or smaller 
sheets) widthwise, but which automatically prints and feeds out sheets of 
a defined longer length (including U.S. 11".times.17" sheets in 
particular) lengthwise, for the reasons explained above. In the 
xerographic printing arts these two ninety degree different sheet feeding 
orientations, widthwise and lengthwise, are more usually respectively 
referred to as feeding the sheets "long edge first" and "short edge first" 
in the "process direction". The printer 20 is merely one example of any of 
various such reproduction machines with which the present system may be 
utilized, and hence only its output is shown, specifically, the output 
rollers 22 in FIG. 1. The printed sheets 16 are inverted and stacked by 
the inverter-stacker unit 12 as previously described above and/or in the 
cited references. The unit 12 may also include jogging or tamping and 
stapling or other set finishing, as also described in those patents, if 
desired. 
Specifically, all of the printed copy sheets 16, including (as shown in the 
top view of FIG. 1) a long flimsy 11".times.17" sheet 16A, are 
sequentially fed from the printer 20 output 22 in their normal process and 
output movement direction, shown by the associated sheet movement arrow. 
(A normal letter size sheet 16B is also shown fed out here in FIG. 1, but 
in phantom, for comparison, since obviously only one sheet at a time is 
fed out of the printer 20.) 
In this system 10, instead of printed sheets being fed directly from the 
printer output into the sheet entrance of a disk-type inverter-stacker 
output unit in the output path of the printer, the sheets are all first 
fed into a baffled skew plate area 30, with a sheet lead edge registration 
stop wall 34, where the incoming sheet are all reoriented and laterally 
moved by a conventional angularly driven frictional scuffer roll 32 
imparting a lateral or sideways movement towards the disk inverter-stacker 
unit 12, with registration along the registration wall 34. That is, the 
scuffer roll 32 acquires each entering sheet and moves it laterally along 
a path defined by wall 34 into the then-adjacent entrances of the slots 40 
of the fingers 42 of the rotatable disks 44 of the inverter-stacker unit 
12. For more positive feed-in for small sheets, an auxiliary scuffer such 
as 33 in FIG. 1 may be provided. This and various other suitable such 
lateral sheet feeding systems for providing such a relatively small ninety 
degree or right angle sheet movement, transverse to the output movement 
direction of the sheet as it exits the printer, are taught in the 
references cited thereon in the above introduction. 
The disk finger slots 40 temporarily hold at least the leading edge area of 
the sheet within the slots 40 for the sheet inversion, which is 
accomplished by automatically rotating the disks 44 approximately 180 
degrees. As discussed in the introduction and the cited references, this 
rotates the lead edge area of the sheet therein around by that same 
amount, until the sheet lead edge engages a registration edge or fingers 
46 under the disk unit 12, which strips the sheet out from the disk slots 
as the disks 44 continue to rotate. The rest of the now substantially 
inverted sheet then falls and stacks neatly onto the underlying output 
stacking tray 14. The spacing between the disks is of course 
conventionally less than the smallest sheet to be handled. Also, as shown, 
the registration wall 34 aligns the lead edge of all incoming sheets to be 
adjacent to one end of the disk inverter-stacker 12, and hence laterally 
aligns the sheets to the disks and finger slots. 
Because of the above-described and illustration operation of the system 10, 
long sheets, such as 11".times.17" size sheets, desirably printed and 
outputted lengthwise (short edge first) by the printer 20, are inverted 
and stacked sideways (long edge first). Thus, in the disk inverter-stacker 
unit 12, the dimension of the 11".times.17" size sheets being inverted and 
stacked is their 11" dimension instead of their 17" inch long (jam prone) 
dimension, as it was in previous disk inverter-stacker systems. Yet the 
fixed width of the printer 20 does not have to be increased, because long 
sheets can still be fed and printed lengthwise with the system 10. 
In this simple system 10, the U.S. letter size sheets are inverted and 
stacked lengthwise (in their 11" dimension) instead of widthwise (as they 
are desirably printed and outputted by the printer 20). Likewise, U.S. 
legal size sheets are also inverted and stacked lengthwise (in their 14" 
dimension). While that may be slightly less desirable in some cases, 
inverting and stacking such normal 11 inch or 14 inch sheet lengths does 
not pose nearly the difficulties, such as sheet settling times on the 
stack and sheet trail end collapse or fold-over jam rates, of doing so for 
flimsy long sheets, such as 11".times.17" size sheets. Also, for all 
sheets in the system 10, because of the reduced inverting length of long 
sheets, two sheets can be inverted and stacked in each rotation of the 
disk inverter-stacker with an appropriate disks 44 circumference, i.e., 
using both of the finger slots 40. Stack jogging or tamping may also be 
more effective by the stacking of the long sheets sideways. 
In this system 10 all of the sheets conveniently stack towards the front of 
the printer 20 rather than at one side or end of the printer, as is 
conventional. 
While the embodiments disclosed herein are preferred, it will be 
appreciated from this teaching that various alternatives, modifications, 
variations or improvements therein may be made by those skilled in the 
art, which are intended to be encompassed by the following claims.