CA1123465A - Apparatus for producing collated copies in page sequential order - Google Patents

Abstract

APPARATUS FOR PRODUCING COLLATED COPIES
IN PAGE SEQUENTIAL ORDER

ABSTRACT OF THE DISCLOSURE
Apparatus for producing duplex or simplex collated copies from duplex and simplex originals comprising a copier having a duplex section with two transfer stations separated by a copy-sheet inverter. A document feeding section circulates and recirculates original sheets, one-after-another, for pro-ducing sets of copies in page sequential order. The document feeder is provided with a single hopper for receiving and maintaining the originals in their usual page sequence or order so that no preparation (i.e., special arrangement) of an original is necessary prior or subsequent to copying for making collated copies. The duplexing section requires only a single fuser that is positioned so that the copy sheets pass through both transfer stations before entering the fuser, thus permit-ting transfer of images under similar conditions in both transfer stations.

Description

- -CROSS-REFhRENCE TO RELATED_APPLICATIONS . -Reference is made to Canadian Patent A~plication Serial No. 278,847 entitled APPARATUS FOR PRODUCING COLLATED
COPIES FROM lWO-SIDED ORIGINALS, filed in the name of G. B. Gustafson on May 20, 1977; and Canadian Patent A~plication Serial No. 278,846 entitled APPARATUS FOR PROD[JCING DUPLEX
COLLATED COPIES, filed in the name of JO Connin, also on May 20, 1977u ''' . ~

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This application is a d~visional of application S,N, 296,833, filed 13 February, 1978, and is directed to a document feeder'for feeding sheets to an exposure position for copying while the paren~ application is directed to a copier'including a process section, a document feeder'and a copy `duplexing section. Another divisional application, S.N.3~)3~ filed ~6~ R`¦ Iq~ is also directed to a document feeder.
BACKGROUND OF THE INVENTION
The present invention relates to reproduction apparatus. More specifically, the invention relates to convenience copiers having duplexing capabilities and collating document feeders that invert the original document sheets automatically, for producing duplex collated copies in page-sequential order without a sorter.
It is well known in the prior art to provide convenience copiers with duplexing capabilities, with document feeders that circulate the original in a manner suitable for producing collated copies, or with document inverters ~ ' that present both faces of the document for copying. Examples include:
1) in relation to the first feature - U.S. Patent Numbers 3,31~,212; 3,536,398;
3,548,783; 3,615,129; 3,630,607; 3,645,615; 3,671,118; 3,672,765; 3,687,541; '; ;' 3,697,171; 3,775,102; 3,844,654; 3,856,295; 3,862,802; 3,866,904; 3,869,202; ~ ' 3,947,270, and ''Research Disclosure", Vol. 142, No. 14237, February 1976 '~
(available from Industrial Opportunities Ltd., Homewell,~Havant, Hampshire, P. O. 9-lEF, United Kingdom) 2) in relation to the second feature - U. S.
Patent Numbers RE 27,976; 3,552,739; 3,556,511; and 3,709,595; 3) and, in ~' relation to the third feature U. S. Patent Numbers 3,227,444; 3,416,791 and ' 3,675,999.
It is also known in the pTior art to combine certain of the above mentioned features in a unified structure or control. U.S. Patent No.
3,630,607 might be cohsidered especially relevant in its disclosure of a ~
collating feeder on a convenience copier having duplex capabilities. U.S. ' ~' Patent No. 3,844,653 discloses'a convenience copier having duplex capabilities '' with a document inverting mechanism. U.S. Patent No. 3,862',802 discloses a ., 3'1~i5 duplex copier with a document inverting mechanism, and is said to be usuable with a sorter to produce collated copies. "Research Disclosurel', Vol. 133, No. 13329, May 1975, discloses a manual approach for producing collated duplex copies without a sorter.

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.23~65 The cross-referenced patent applications Serial Nos.
278,846 and 278,847 present further improvemen~s in copy and document handling. Both teach approaches capable of yielding duplex or two-sided copies in a fully automa~ic ~anner, and for collating the copies without the burden of a sorterO Both also include collating, inverting document feeders and duplex-ing copy processors that are particularly conduclve to simpli- -fied finishing operations. One of the applications, Serial No.
278,847, includes advances for producing copies in page-sequential order, thus enhancing still further the convenience and efficiency of copying.
The above-mentioned patents and applications disclose an impressive number of features for supplementing the basic ~
copying function to facilitate the total copying operation. ~;
Certain disadvantages remain, however, and it is to the allevia-tion of these disadvantages that the present invention is directed. In some cases, for example, prior approaches include two document hoppers and a document preparation step. While satisfactory for their intended purposes, the two hopper approaches suffer from the disadvantages of multiple feeders, extended guide channels and undesireable document preparation steps. In addition, and referring now to copy handling aspects, prior approaches suggest a "double pass" approach, where the copy sheets are transported along a somewhat tortuous path through the fuser and back to the photoconductor between the transferring of images to opposite faces of the sheetsO Such approaches, because of the intermediate fusing operation and the effects it has on the copy-sheet condition, can complicate copy handling~ StilL another problem relates to relatively long copy-sheet paths. When short documents of two or three pages are copied, for example, it may take longer for the

-3-~.23465 first copy sheet to return the second time to the photoconductor than to present all of the other copy-sheets the first time, This reduces the ability of the copier to handle all types of jobs efficientlyO
SUMMARY OF THE XNVENTION
The present invent~on alleviates the above and other deficiencies of prior copiers without sacrificing the advantages of producing copies in page-sequential order. In accordance with one feature, a copier can operate with simplex or duplex originals in their usual sequence, so tha~ no particular prepara-tion of the original is necessary prior or subsequent to copy-ing. In accordance with another feature, images can be trans- -ferred to both faces of a copy sheet prior to fusing, so that the condition of the copy sheet, and especially its moisture :~
content, will be the same for both transfers. Still another :~
feature reduces the copy path from that required for conven~
tional double pass duplexing so that more types of jobs, and~
especially those concerned with documents of only a few pages, ; :~
can be run more efficiently, In accordance with preferred embodiments of the invention a document feeding section presents one or both faces ~~ of the original sheets to be copied, A process section estab- - ~
lishes representations of the original-sheet faces, A copy . .
duplexing section presents one or both faces of the copy sheets to receive the representations established in the process :
section O
A preferred document feeding section receives the originals face-up in their normal page-sequential order, re-peatedly circulates the simplex or duplex document sheets for copying one-sheet-after-another, in page-sequential order,

-4- -' ,,' -13~.23~65 ~last-page first, and returns the copied sheets to their original page-sequential order. During each circulation of a duplex document shee~, it is fed along a non-inverting path (i.e.~ -it is inverted zero or even number of times) before it is copied.
Then it is inverted an odd number of times before it is copied again, and finally an odd number of times before it is re~urned face up to its original p~sition in its normal sequence. Dur-ing each circulation of a simplex document sheet, it is inverted an odd number of times before it is copied and an odd number of times befoxe it is returned face up to its original position, A copy section for use with such a feeding section includes two transfer stations and between the stations there is a copy sheet inverter. Means are provided for transporting the copy sheets through the respective stations and inverter to transfer ;muges to both faces of the copy sheets. Thereafter the images are fused to the copy sheets. When simplex copies are to be produced, one transfer station and the inverter are bypassed Still other aspects and more specific features will become apparent to those skilled in the ar~ from the following descriptions with reference to the accompanying drawings BRIEF DESCRIPTION OF THE DRAWINGS ~ ~-In the detailed description of the preferred embodi-ment of the invention presented below~ reference is made to the accompanying drawings, in which:
Figure 1 is a schematic representation of a copier having simplex and duplex capabilities in accordance with a preferred embodiment of the present invention;
Figure 2 is a schem~tic view depicting in general suitable logic and control for use with the copier represented in Figure l;

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4~5 Figure 3 is a schem~tic illustration of the feeder depicted in Figure 1, but depicting additional structural features thereof;
Figure 4 is a schematic view depicting the document path and mode of operation of t~e document feeding section in accordance with the preferred embodiment; and Figure 5 is a schematic view depicting the copy path and mode of operation of the copy processor in accordance with `~
the present invention and as described more fully in the description of the preferred embodiment that follows.
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DESCRIPTION OF THE PREF RRED EMBODIMEN~
Referring now to the drawings, and especially to Figure 1, a convenience copier is depicted in accordance with a preferred embodiment of the present invention, comprising a process section 3, a document feeding sec~ion 5, a copy duplexing section 7, and a logic and control unit 9. The process section 3 includes an imaging device or projector 10 and a processor 11 for establishing visible representations of original document sheets, typically as image-wise distri- -~
butions of marking particles. The document feeding section presents the original sheets to the process section for establishing the visible representations, while the copy duplexing section, in synchronism with the feeding section, presents the copy sheets to the process section for receiving

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the visible representations forming the final copies. The logic and control unit coordinates the operation of the three sections as required.
The term "original" as used in the present appli-cation refers to the object to be copied, including documents and masters in cut or sheet form and comprising one or more sheets or pages. A "sheet," "support" or "supporting medium"
of the original is used in reference to a single expanse of thin, essentially flat material, such as paper, microfilm ~
or a transparency having two opposed faces or sides. A "page" ~ -of an original is a face or side of one sheet bearing an image, marking or information to be copied. A single sheet or an original may include one or two pages depending on whether one or both faces include material to be copied. A
"simplex" original includes one page per sheet; a "duplex"
original, two. Reference to sides or pages by number or as "odd" or "even" refers to a sequential numbering of the sides or pages in order from what conventionally is considered the front of the original to its back, and does not depend on how the pages are actually numbered. A simplex original would have pages 1 and 2 on separate sheets. In a duplex original~
pages 1 and 2 conventionally would be on opposite sides of the ;~ -same sheet. "Page-sequential order" refers-to the order:
page 1, page 2, page 3, page 4, etc, whether in connection with simplex or duplex originals, and to the reversed order: page 4, page 3, page 2, and page 1. ;
The term "copy" refers to duplicates of the original in the usual sense, including receivers or supporting mediums -and having sheets, faces or sides, and pages as those terms 3o are defined above. A "collated" copy is one that has its -;

~ 65 pages in the same sequential order as the original, but not necessarily the same page arrangement. A simplex original can be duplex in its copy, and still be collated.
Process Section (Fig. 1) The process section 3 can be selected from suitable designs known to those skilled in the art, and a brief reference to its general configuration is considered sufficient for the purpose of the present specification. A scan/drum arrangement is depicted in which the imaging device 10 includes scanning optical and illumination mechanisms for viewing originals placed on transparent platen 14, ~hile the processor 11 includes a photoconductor 15 supported on a drum 16 for movement in a cylindrical or closed path.
As the photoconductor moves in its path, it is acted upon by various processing stations. Proceeding counterclock-wise, in the direction of drum rotation, the photoconductor is sensitized by a corona charger at station 17, is exposed by the imaging device at station 19, is developed by a magnetic brush at a station 21, moves through corona transfer and detack stations to be described hereinafter, is erased by illuminators ^
and corona chargers at stations 25 and 26, respectively, and is cleaned by a vacuum brush or the like at station 27. Two addi-tional processing stations 28 and 29 are spaced from the photo-conductor in a copy duplexing path. These stations include a -registration device and fuser, respectively.
In operation, the imaging device 10 sequentially scans the images from successlve original sheets onto successive frames along the photoconductor, where visible representations of the ~
original sheets are established as image~wise distributions of -marking particles which successively are transferrable to copy ~.2 taE~
sheets 9 A further description of the above-mentioned stations, and the imaging device, is presented in Research Disclosure Publication No. 14144, VolO 141, clated January 1976, published by Industrial Opportunities, Ltd.,Homewell, Havant, Hampshire, PO9 lEF, United Kingdom.
Other arrangements that could be modified to practice ;~
the invention in accordance with the teachings of the present specification are disclosed in U.S. Patent Numbers 3,914,047 ~;
entitled SYNCHRONIZING CONTROL APP~RATUS FOR ELECTROPHOTOGRAPHIC
APPARATUS UTILIZING DIGITAL COMPUTER, issued on October 21,1975 in the name of William E. Hunt et al; and 3,876,106 entitled TONER CONCENTRATION MONITORING APPARATUS UTILIZING PROGRAMMA~LE
DIGITAL COMPUTER, issued on April 8, 1975 in the name of Stephen R Powell et al. These last-mentioned patents disclose ;
copiers of the so-called flash/web typeO ~
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Doc1 ~Pnt Feeding Section (Figures 1 and 3) ~ e document feeding section 5 includes a hopper 31, a sheet presenting portion 33 and a sheet returning portion 35 The hopper is adapted to receive a set of original sheets face 20 up in their normal page-sequential order, to deliver the sheets one-after-another, last sheet first, from the bottom of the docu-ment set, and to receive the sheets, each sheet on top of pre-viously delivered sheets, at the top of the document set, The sheet presenting portion 33 removes the sheets sequentially from one end at the bottom of the hopper,presents the removed sheet with one face engaging the platen 14 for copy~ng, and then re-presents the sheet with its other face engaging the platen, Ihe sheet-returning portion 35 removes the sheet from the platen after both of its faces have been copied and returns the sheet to the hopper in the original order of the document set, _g_ , .:

~.234~i - Referring now more specifically to the structural details of the document feeding section, and to Figure 3 in particular, the hopper 31 is located above and spaced from the platen 14 where it is readily accessible for receiving and sup-porting the set of original document sheets Of conventional design, the hopper includes a sloping tray 37 for assisting in aligning the document sheets against forward wall 38, suitable side guides and joggers, not shown, and a set-completed detector 39 for determining, without counting, when (each time) the set ~ 'r of original sheets has been copied. Further details of the preferred hopper are illustrated and described in commonly assigned British Patent No. 1,492,466, entitled RECIRCULATING
SHEET FEEDER FOR DOCUMENT COPYING, issued March 22, 1978 in the name of Matthew J Russel.
The sheet presenting section 33 includes a first part defined by an oscillating vacuum pick-off device 41, a driving nip between ring 43 and back-up roller 45, and a sheet diverter 47; a second part including closed-end, non-inverting sheet path 61, 49, the curved portion 49 being generally in the shape of ~` a snail shell 49 and two driving rollers 51 and 53; and a third part including means defining first and second sheet inverting paths 55 and 57, respectively.
The first part of the sheet presenting section removes the sheets from an exit 59 at one end of the hopper tr~y 37 and directs the removed sheet into a selected one of the inverting path 55 or non-inverting path 49, depending on the position of ~ `
diverter 47. As depicted more -fully in the above-mentioned British Patent No. 1,492,466, the sheets are removed at first by the vacuum pick-off device, which draws one end of the sheet out i of the exit, and then by the driving nip, which propels the sheet into the selected path.

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The second part of the sheet presenting section directs the removed sheet to the platen 14 without inverting the sheet;
or, stated differently, with the last face (even page) of the document engaging the platen. In one sense, as men~ioned above, this part defines a non-inverting document path leading from the hopper to the platen~ In another sense~ however, it is a dis~
abling device which renders the in~erting path 55, through which the sheets subsequently pass, ineffective to invert the sheetO
In operation, a sheet entering this part via diverter 47 will be directed through path 61 and into the snail shell 49. m e motive force of rollers 51 and 53 advance the sheet until the trailing end of the sheet clears the diverter, The diverter is moved and rollers 51 and 53 are then reversed to dri~e the sheet from the non-inverting path into path 55 and then onto the platen 14. The sheet is moved across the platen by rollers 670 The third part of the sheet-presenting section temporar~
ily removes the sheet from the platen, after the first face of the sheet has been copied, and inverts or turns the sheet over for copying its other face. This is accomplished by the rollers 67 ~hich advance the sheet into the inverting path 57, and the driv- - ;
ing rollers 63 and 65, which propels the sheet around path 57, through 360 degrees and back onto the platen.
A sheet registration and exposure station comprises platen 14, rollers 67 and a registration gate 69. On entering the exposure station, a document sheet is driven by the rollers 67 into a registered position~against the gate, After the first face of the sheet is copied, the rollers are reversed, once to drive the sheet into the second inverting path 57, and again to re-register the sheet f~r copying the second faceO Then, after the second face has been copied, the gate is remDved by solenoid 71 and the rollers 67 drive the sheet lnto the sheet returning portion 35 of the feeder~

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The sheet returning portion 35 includes a sheet inverting path 73 and two drive rollers 75 and 79 for returning the document sheet from the platen to hopper 31 and on top of the set from which it originally was removed.
The non-inverting path 6}, 49, as described above maintains the original orientation of the sheet faces from the hopper to the platen in the sense that the sheet, while it may be -curled ~n the snail shell, is never turned over entirely.
It should be apparent to those skilled in the art, however, that an even number o sheet inverSiQns also would present the sheet to the platen with the same side down for copying~ The snail shell could be eliminated, for example, and the inverting path 57 could then be used twice (i.e. an even nu~ber of times) before copyingO This would present the original faces in the same order as the structure described above. In similar respect, the inverting paths 55, 57 and 73 could have one or any other ~-odd number of inversions and still operate for the purpose described~
The feeder is referred to sometimes as a circulating or recirculating feeder because the sheets move in the feeder repeatedly from the hopper to the exposure platen and back to the hopper in a manner which simulates a closed-loop or circuitous path. It is a collating feeder because it is capable of feeding sheets in an appropriate sequence for produc- `
ing collated copies without a sorterO m is aspect of the feeder will become more apparent from the following description. It `
is also a duplex~lg feeder in the sense that it can feed simplex or duplex document sheets in a manner suitable for gene~ating duplex copiesO

. ~............................ ~ ., l~.Z3a~65 For the purposes of simplifying this description, it will be assumed throughout most of this specification that the feeder and copier are operating in a collating duplexing mode with a duplex originalO It should be understood, however, that many of the feederls advantages re:Late to its flexibility and convenience in other modes of operation. Such other modes might include, for example, capabilities for eeding without. : ~
collating, for producing simplex copies from simplex originals, ~.
for producing duplex copies from simplex originals, and for :
producing simplex copies fro~ duplex originals, In the non-collating mode, each page would be presented to the platen once regardless of the number of copies to be made, When making simplex, collated copies from simplex originals, the ~-feeder would operate generally as described in the above-mention-ed British Patent No. 1,492,466. The same would be true for .~:
duplex copies from simplex originals, insofar as the feeder is concerned, but the copy duplexing section would present both faces of the copy sheets to the photoconductor for receiving visible representations as described hereinafterO

Copy uplexin~ Section (Figures 1 and ~
The copy duplexing section 7 includes one or more supply hoppers 81, for receiving and sequentially feeding copy -supports 82 to the process section, the registration device~ 28, ~3.~3~i5 , first and second transfer stations 83 and 84 (Fig. 1), inclu-ding transfer and detacking coronas 85, 86, 87, and 88, a sheet inverter 89, a vacuum stripping roller 91 and an exit hopper 93.
The supply hopper can be similar in many respects to the hopper 31 of the document feeder, including a support tray 9~ and pick-off device 97 for withdrawing support sheets, one after another, from a stack of such sheets, and for directing the withdrawn sheets toward the photoconductor along suitable guide channels.
Registration device 28 momentarily interrupts move-ment of the copy sheets for their proper alignment with the appropriate image frame on the photoconductor, after which the sheets are directed into engagement with the photoconductor with the same relative velocity as the photoconductor.
At the first transfer station 83j a D.C. transfer corona 85 applies a charge to the face of the copy sheet adjacent the charger. This electrostatically tacks the copy ,. ..
sheet to the photoconductor and transfers the visible repre-sentation or image-wise distribution of marking particles, formed by the previously described process section, from the photoconductor to the copy support. The detacking corona 86, an A.C. corona, then eliminates the electrostatic forces tacking the copy to the photoconductor for facilitating the ¦
removal of the copy sheet from t-he photoconductor with the visible image on the just removed face of the copy support. ~ ~
Sheet inverter 89 includes a relatively short .
vacuum transport 101, and stripping and diverting fingers 103, for removing the sheet from the photoconductor and re-presenting its opposite face thereto. The vacuum transport is coupled ~ .

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to an appropriate source for maintaining a vacuum in end roller 107 and plenum 109, which vacuum communica~es with the copy support by way of perforations in belt 112. As the copy support exits from the first detaching corona 83, it is drawn off of the photoconductor and onto the belt 112 by the vacuum in roller 107. Stripping finger 103 also may be of assistance, but pre~erably contacts-only that face of the copy support which has not received an image, since the image has not been fixed and may be somewhat easy to smear. When the copy support is completely removed from the photoconductor, and its trailing end has cleared the diverting finger 103, the belt 112 is reversed for returning the copy support to the photoconductor along path 113, de- ,~
fined by the diverting finger 103, with its other side en-gaging the photoconductor and in registration with the next appropriate image on the photoconductor.
The second transfer station 84 is substantially ~ ;
~den~ical to the first, and operates to transfer another image to the face of the copy support then engaging the photoconductor, after which the detacking corona 88 prepares the support for its removal the second time from the photo-conductor. This transfer and detack are accomplished ~ithout disturbing the unfused toner on the first face Or the copy support. , The vacuum stripping roller 91 draws the copy support ;
from the photoconductor and directs the support through the fuser 29 and on to exit hopper 93, where each sheet is~de-livered on top of previously delivered sheets, and with the image last-transferred facing up. or course other stripping devices could be used in place of the roller 91. In a copier employing a flexible web, for example, the web may be trained to follow a relatively sharp contour which will separate the -15- ~
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copy support from the web. Similarly, once stripped from the photoconductor, the copy support could be transported to the fuser without contacting either face of the support. A number of devices for accomplishing this purpose are available in the prior art An exemplary device of this type is described and illustrated in commonly assigned copending Canadian Application Serial No. 295,455 filed on January 23, 1978 in the name of Charles T. Hage et al.
The duplexing approach just described is referred to as single-pass duplexing because no in~ermediate hopper is ~-required Instead, the copy supports move directly from a supply hopper to an exit hopper or finisher and with only a single pass through a fuser. Other examples of single pass duplexers are presented in previously referenced U.S. Patent Numbers 3,672,765; 3,869,202 and 3,947,270.
Overall Operation . . .
Referring now to the overall operation of the copier, a document or other original comprising a set of individual sheets is circulated and recirculated one-sheet-after-another from the hopper 31 to the exposure station or platen 14 and back to the hopper 31. Using the example of a six-page duplex origi-nal, the sheet defining pages five and six is circulated first, for copying page six and then page five, followed by the sheet defining pages four and three and finally the sheet defining pages two and one. The sheets are presented for copying in sequential order, from page six to page one, and each page is expos~d only once during each respective circulation, for produc-ing collated copies without a sorter. Multiple copies of a set of original sheets are generated by circulating and recirculating the sheets a number of times equal to the number of set copies desired . ., ~. ' .. . . . .

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As the pages sequentially are presented for copying, a succession of images representing the presented pages are established in frames of the photoconductor, one~following-another, in the same sequential order as the original pages were presented, i.~., page 6, page 5, page 4, page 3, page 2 and page 1. The images are rendered visible at the development station 21 and are moved by the rotating photoconductor into position for sequential transfer to alternate sides of copy supports at the first and second transfer stations 83 and 84 m e even pages would be transferred at the first station 83 and the odd pages at the second station 84, For each circulation or recirculation of a duplex ;
document sheet, it is presented twice for exposure and two images are established. Similarly, one copy support is presented to the process section for receiving the two images, first on one face and then the other. The first copy support will receive an image representing page six on one side and then page five on the otherO The next copy support will receive pages four and three, and the following copy support pages two and one.
Of course additional copies will be generated in the same order and deposited on top of ~he earlier copies in the exit hopperO
Lo~ic and Control nit (Figures 1 and 2) A logic and control unit for accomplishing the above "
modes o~ operation is depicted in Figures 1 and 2. Its function generally is to coordinate the activities of the process section, ;
the feeding section, and the duplexing section, Such a co-~
ordinating function could be implemented by relays, transistors, ~
small and medium scale digital integrated circuits and the like. `
In this particular embodiment, a microcomputer 121 (Figure 2) is utilized. The combination and sequential logic requirements . ~ , , , ,~ , , .
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~.~.23~5 of the process are established in a control program 129, which provides instructions to a central processing unit 125 to control the states of output signals, based upon the status of input and timing signals. The timing signals can be de-rived from incremental encoder 114 (Fig. 1) connected to the drive means of the photoconductor drum, to provide information required to relate the position of the moving photoconductor to the positions of the fixed process stations.
The input and output signals are represented in ,~ Figure 1 by reference characters 139-154. Taken in order, these characters identify control leads as follows:
139 leads to the registration gate 69, of the document feeder, for controlling its two positions (raised and lowered or present and removed); -140 leads to the set-completed detector 39 for counting the number of copies com-pleted 3 141 leads to the sheet propelling rollers 67 for establishing their direction of rotation;
142 leads to the sheet diverter 47, of the document feeder, for controlling its two positions (inverting and not in-verting);
143 leads to propelling rollers 51 and 53 for determining their directions of rotation; -~
144 leads to the illumination source 156 for 3a controlling the intensity of illumin-ation and scanning control;

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~ - -18-.... , .. . , .. .. , ., . . ... . . , .,, .. , . , . . .. : .. .. .. . , , .: . .... : , 145 leads to the image projector 10 for controlLing optical scanning in synchronism with the illumination source; ~:
146 leads to the primary charger 17 for maintaining uni~orm charging;
147 leads to the fuser 21 for bias control;
"C" and '~" lead to the shaft encoder ~or acquiring timing signals (count and frame signals);
148 leads to sheet feeding roller 97 for '` :~
initiating sheet feeding from hopper 81;
149 leads to the transfer and detacking coronas in the first transfer station for transfer control;
150 leads to the turn around device 89 for ~ ~
determining the direction of movement ~ :
of belt 112; ~;
151 leads to the transfer and detacking coronas ~
87 and 88 in the second transfer station ~ --again for transfer control;
152 leads to the stripping roller 91 for controlling its stripping action; ~ ;~
153 leads to the fusing station 29 for tem- ~
perature control; and ~-154 leads to the erase and cleaning stations 25, and 26, for controlling their in-tensities o~ operation. .~ ~.
Of course additional leads could be applied as de-sired to effect the intended operation, including on and off operation of the various stations. Further descriptions of suitable contr;~l devices are presented in pre~iously refer-enced UOSO Patent ~umber 3,914,047, and in commonly assigned ~:
U.SO Defensive ~Iblication No. T957,006, entitled ORIGINAL : .

.Z3~

DOCUMENT REARRANGEMENT APPARATUS FOR USE IN RECIRCULATING
FEEDERS, published April 5, 1977 in the name of M,G, Reid, et al.
Under the influence of the logic and control unit, the presentation to the process section of the original and copy sheets, and their inversion, is coordinated so that the copies will be collated in the page-sequential order described aboveO For each presentation of an original sheet, an exposure -is made to establish a visible representation of one face of that sheet, and for each visible representation that is estab-lished, a copy sheet face is presented to receive it~ ~hus,the original and copy sheet faces are fed on a one-for-one basis.
This is not to say that there are an equal number of original and copy sheets, which would not be the case, of course, when multiple copies are generated, but rather that there is one-for-one correspondence in the presentations of the respective sheet faces to the process section. Nor is it intended that the original and corresponding copy sheets must be ed at the same `
timeO Generally, the feeding of an original sheet is displaced in time from the feeding of its corresponding copy sheet, either forward or backward, depending upon the machine configuration.
The logic and control unit also tracks the copies as they are made, and directs the document feeding and copy duplex-ing sections so that the first and second faces of the copies will properly correspond with the irst and second aces of the original.
Offset stacking, stapling and other finishing opera-tions have not been depictedO It is intended, however, that such apparatus be controlled for operation in synchronism with the copier, preferably by the logic and control unit 9O
It should be understood that the present invention contemplates modes of operation that will account for the usual ,''~ '.

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variations in originals. A duple~ original that ends on the first face of the last sheet, for example, need not be copied on the blank face. In a similar respect, it should be recog-nized that all of the capabilities that are available in accordance with the present invention need not be used in every mode. Thus, the document feeder can have a non-collating mode and a simplex mode in addition to its collating duplex mode of operation.
Numerous advantages of the present invention now should become apparent to those skilled in the art. A first copy is completed on both sides before other copies are ini-tiated. This reduces the first-copy time. Each copy sheet ;
passes through the fuser only once, and only after receiving both of its images, so the sheets maintain their optimal relatively humid condition in both transfer stations.
The total copy path from initial supply to final exit is re-duced for improved copying efficiency, especially for docu-ments of only a few pages, and no sorter is required.
Additionally, a relatively simple collating inverting document feeder is rendered possible with only a single hopper while retaining the convenience of face-up, ordered presentation of the document to the feeder.
Although the invention has been described in detail with particular reference to preferred embodiments thereof, it will be readily understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

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Claims (2)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A recirculating document feeder for feeding one or more document sheets to an exposure position for copying of the sheets, the feeder comprising:
a document hopper for receiving the document sheets in a set of such sheets, and means for circulating the document sheets, one-after-another from the bottom of the set in said document hopper to said exposure for a first presentation, away from and back to said exposure position for a second presentation, and then to the top of the set in said document hopper, said circulating means including means for inverting the respective document sheets zero or an even number of times between said hopper and the first presentation at said exposure position, an odd number of times between the first and second presentations to said exposure position, and an odd number of times between the second presentation at said exposure position and said document hopper.

2. The invention as set forth in claim 1, wherein said circulating means further comprises means for inverting the respective document sheets an odd number of times between said hopper and the first presentation at said exposure position, and the invention further comprising means for controlling said circulating means to present either one face or both faces of a document sheet to the exposure position for copying.