Abstract: An image formation apparatus obtains optimum double-face print output results aligned in a binding direction even if plural recording sheet sizes mixedly exist in one document. To do so, a CPU of a formatter unit judges consistency between image formation directions on different-size recording sheets on the basis of a designation state of a short edge binding double-face mode or a long edge binding double-face mode designated to a print job by a PC/WS and a designation state of the recording sheet size independently designated to each page of the print job, and it is then controlled based on the judged result that double-face image formation to the recording sheet of either of the designated sizes is performed based on the other double-face mode than the double-face mode actually designated to the print job.

Abstract: There is disclosed a printing method and a printing system for printing a pair of images on both sides of a recording sheet. When printing a first image on a first side of a recording sheet, a printer records directional marks records on the recording sheet to indicate the direction of the first image on the recording sheet. Thereafter when the recording sheet with the first image is manually set in the printer for printing a second image on the back side, the directional marks are detected from the recording sheet to detect the posture of the recording sheet in the printer: the direction of the recording sheet with respect to the first image, as well as which side of the recording sheet is oriented for printing. If the back side is not oriented for printing, the printer stops printing the second image, and makes a warning.

Abstract: An image scanner connected to a host computer to transfer data to the host computer in accordance with a predetermined interface includes a first read unit and a second read unit in a double-side read mode to read image data on a right side and a reverse side of a first document, respectively. A third read unit in a one-side read mode reads image data on a right side of a second document. A read control unit controls the first and second read units so that the image data can be read simultaneously and controls the third read unit. A signal processing unit produces the image data on the right and reverse sides of the first or second documents. A data transfer unit transfers the image data on the right and reverse sides of the first document or second document at a predetermined speed in accordance with the predetermined interface.

Abstract: A modular duplex media handling system is installable for use with a print recording system having a simplex media handling system. During first side printing a media sheet is fed along a first media path in the simplex system from feed rollers to metering rollers and into a print zone. After first side printing and prior to releasing the media sheet, the metering rollers feed the media sheet back along the first media path to the feed rollers. The feed rollers in turn feed the media sheet completely into the duplex module where the media moves along a loop path (in effect flipping the media sheet). The media sheet then is fed back to the feed rollers and along the first media path for second side printing. A humidity sensor in the duplex module signals to the print recording system whether the duplex handling system is installed.

Abstract: An image forming apparatus is equipped with a document reading device for reading image data on a document at a reading section; a memory to store the image data therein, the memory capable of storing the image data of plural pages of documents; and an image recording system for recording an image on a recording sheet based on the image data stored in the memory. A recording sheet reversing system receives the recording sheet from the image recording system, wherein the image is recorded on one side of the recording sheet, reverses the recording sheet, and refeeds the reversed recording sheet to the image recording system without stacking the recording sheet, whereby another image is recorded on the other side of the recording sheet by the image recording system.

Abstract: A feed out controller controls the feed out of a receiving substrate from an inverting station. Sensors mounted in the transfer station assist the feed out controller in determining the required adjustments to feed out. In a duplex copy mode, first and second receiving substrates are transported along a transport path. Feeding out the receiving substrate from the inverter station is adjusted based on a determined relationship between the trailing edge of the first receiving substrate and the leading edge of the second receiving substrate at the registration station and the inverting station. The stop time of the inverting roller is adjusted based the determined relationship. The feed out controller determines the trailing edge/leading edge relationships and then monitors the relationships during the print run.

Abstract: A printing assembly comprises a first printer for printing documents encoded in computer generated signals and a second printer for printing documents encoded in computer generated signals, the documents including alphanumeric characters, charts and graphics. The printers are disposed one above the other and are connected in tandem to one another via a multiple-page continuous web of paper extending along a U- or C-shaped path from a paper output port of the first printer to a paper feed port of the second printer. A computer for generating a signal encoding a multiple page document is coupled via connection componentry to the printers for transmitting odd pages in encoded form to one of the printers and even pages to the other printer.

Abstract: A method and apparatus of processing sheet media such as document sheets to be duplex scanned or media sheets on which two sided printing is to take place includes automatic positioning of an active sheet guide gate and drag clutch by the rotation of a transport roller with which the active gate and drag clutch is frictionally engaged. The transport roller may comprise one or more coaxial rollers in an assembly positioned in the media path and is rotatable in different directions such that the leading edge of a moving media sheet is moved through one or the other of two nips defined between the transport roller assembly and associated upper and lower pinch rollers. The direction of rotation of the transport roller assembly can be reversed before the sheet leaves the nip to thus re-position the sheet guide gate and re-route the sheet back in a desired path to a scanner or printer for further sheet processing.

Abstract: A method and apparatus for printing individual sheets gathers the sheets in groups and feeds the sheets past a printer unit. Paper paths are provided in two ring shapes and two printers are provided to permit printing on one side in one color, both sides in one color, one side in two colors and two sides in two colors or one color on one side and two colors on the other side.

Abstract: A unit exclusive use power source is provided for a duplexer printing unit which is coupled to a color printer main body of an electrophotography apparatus. The unit exclusive use power source has a circuit for presenting an “on” state and “off” state of a supply of electric power to respective constituting components in the duplexer printing unit in accordance with an indication of a controlling device. When the color laser printer main body is in an electric power saving mode and when an abrupt duplex printing after release of the electric power saving mode is unnecessary, the controlling device enables an “off” state of the unit exclusive power source. Since an operation of the coupled duplexer printing unit is unnecessary, such as in the electric power saving mode time, the power source of the duplexer printing unit is presented to the “off” state. Thereby, the electrophotography apparatus satisfies electric power regulation value therefor.

Abstract: According to a document transport device of a preferred embodiment, when reading images of a plurality of one-sided documents, these one-sided documents are accommodated in a first accommodating portion with the document surface facing upward. The held documents are fed sequentially from the uppermost document to the first document transport path, inverted front-to-back, and transported with the document surface facing downward to the predetermined position, i.e., the document reading position. When the reading of the document is completed at the document reading position, the read document is transported to a second document transport path, inverted front-to-back, and accommodated in a second accommodating portion with the document surface facing upward. Thereafter, the document is transported to a third document transport path, inverted front-to-back, and accommodated in a third document accommodating portion with the document surface facing downward.

Abstract: The invention provides a stackless continuous dual-sided copying method in photocopying machines.

Abstract: A media sheet handling system for duplex printing is disclosed. During duplex printing, the media sheet whose first side is printed is directed into a duplex print path, wherein the media sheet is reversed to a flipped over state with respect to its original position and the original leading edge is maintained to be the leading edge for subsequent printing.

Abstract: A perfecting apparatus for executing prints on double surfaces of a recording medium is capable of minimizing a blank space on the recording medium. The perfecting apparatus has a first image forming unit, disposed downstream in a carrying direction of the recording medium, for forming a toner image on one surface of the recording medium, a second image forming unit, disposed upstream in the carrying direction of the recording medium, for forming the toner image on the other surface of the recording medium, a fixing unit for fixing the toner images onto the double surfaces of the recording medium, and a control unit for controlling the first and second image forming units. The control unit controls, when in one-side printing, the first image forming unit disposed downstream in the carrying direction. A distance between the fixing unit and the first image forming unit is short, and hence the blank space on the recording medium can be minimized.

Abstract: When the front and rear side (the first and second side) image data to be formed on both sides of the first paper and the front side data to be formed on one side (the first side) of the second paper are input in this sequence, the first paper is fed from a paper feed portion to an imaging portion, and is imaged on its first side with the image data and then is stored into the first intermediate tray. While the first paper is being stored into the first intermediate tray, the second sheet is fed from the paper feed portion to the imaging portion and formed on its first side with the image of the image data, and then is discharged to the paper output portion. While the second sheet is being discharged to the paper output portion, the first sheet is fed from the first intermediate tray to the imaging portion and formed on its second side with the image of the image data and then is discharged to the paper output portion.

Abstract: A modular duplex media handling system is installable for use with a print recording system having a simplex media handling system. During first side printing a media sheet is fed along a first media path in the simplex system from feed rollers to metering rollers and into a print zone. After first side printing and prior to releasing the media sheet, the metering rollers feed the media sheet back along the first media path to the feed rollers. The feed rollers in turn feed the media sheet completely into the duplex module where the media moves along a loop path (in effect flipping the media sheet). The media sheet then is fed back to the feed rollers and along the first media path for second side printing. A humidity sensor in the duplex module signals to the print recording system whether the duplex handling system is installed.

Abstract: An image forming device includes an image forming part which forms an image on a recording medium; a recording medium switchback portion which receives the recording medium on a first run, one side of which has been printed when passing the image forming part, and sends the recording medium for a second run; a recording medium path which communicates with the recording medium switchback portion so as to send the recording medium to and from the recording medium switchback portion; an inverted recording medium transfer path through which the recording medium is sent to the image forming part again with an upper surface and a lower surface of the recording medium reversed; and a recording medium transfer part which transfers the recording medium along the inverted recording medium transfer path.

Abstract: A method of aligning duplex images on an imaging device such as a printer or copier includes duplex imaging a test sheet having indicia on each side of the sheet that communicate, when observed in a single visual context, duplex imaging adjustment parameters for the imaging device. The method further includes modifying imaging parameters of the imaging device based on the duplex imaging adjustment parameters communicated. The indicia on each side of the sheet are seen in a single visual context by observing certain of the indicia through the media, as when the media is held up to a light source. In a preferred embodiment, the indicia on each side of the sheet includes respective portions of a vernier scale. The imaging parameters are modified by entering the adjustment parameters at a control panel of the imaging device. Imaging parameters modified include timing parameters associated with the process of writing data on the imaging device.

Abstract: A method for operating a printer or copier is disclosed.

Abstract: A scheduling system determines the order of specific operations in a printing apparatus which is capable of outputting simplex or duplex prints. If the actuation of a module associated with the apparatus, such as stapling or switching paper supplies, requires a delay in the operation of the apparatus, this delay is entered as at least one deliberately blank pitch in the schedule. The scheduling system creates a special finite state machine which can take into account delays of arbitrary length caused by the actuation of one or more modules.

Abstract: A media sheet is picked and moved along a media path toward a print zone. During the operation a media sensor detects whether the media sheet is properly oriented to receive print recording. For example, for glossy paper, photographic paper or letterhead there is a proper side of the paper for recording and a backside of the paper which typically does not receive print recording. If the proper side is not oriented to receiving print recording, then the media sheet is flipped by a modular duplex media handling system.

Abstract: During first side printing a media sheet is fed along a first media path from feed rollers to metering rollers and into a print zone. After first side printing, the metering roller stops prior to releasing the media sheet into the output tray. The metering roller reverses direction to move the media sheet back along the first media path onto the feed roller, and into the modular duplex handling system. The media sheet is flipped, then fed back for second side printing. Second side printing is performed in either one of book mode or tablet mode. In book mode, the top of the page is the same edge of the media sheet for the first side and the second side. In tablet mode, the media sheet edge at the top of the first side corresponds to the bottom of the second side.

Abstract: An image forming apparatus of the present invention includes a main body, a fixing device arranged in the main body and supported so that it can be pulled out of the main by for fixing an image formed on one side of a paper, a duplex device arranged in the main body and supported so that it can be pulled out of the main body for once housing a paper having an image fixed on one side and taking it out with the other side having no image fixed facing toward the fixing device; and a coupling unit for coupling so that the fixing device and the duplex device can be pulled out of the main body simultaneously.

Abstract: A continuous web substrate duplex printing system which can utilize a single and otherwise conventional or existing xerographic print engine (normally printing conventional cut sheet print substrates) of a standard width without substantial structural modification. Separate first and second image transfer stations are positioned in line with one another in the direction of movement of the endless surface imaging member, with said second image transfer station downstream of the first, for respectively transferring print images to the first and second sides of the continuous web sequentially without requiring a dual width imaging member or dual imaging members for duplex printing.

Abstract: A method is provided for copying in which a duplex copy can be smoothly made. In making N sets of double-sided copies of M one-sided documents, a method of copying includes a first document circulating step of copying images of even ordinal numbered documents on unused sheets and then stores these sheets into an intermediate tray. The second document circulating step of copying images of odd ordinal numbered documents on rear faces of one-side copied sheets forming double-sided copied sheets which are discharged. A cycle detecting solenoid for separating each circulation of the one-sided documents is provided and breakdown judging step of judging by a controlling device that a cycle detection sensor is out of order in the case where the cycle detecting solenoid is operated and a polarity of the cycle detection sensor is not changed.

Abstract: A printing system including three print engines. One of the print engines is non-operational while the other two print engines are operational. The non-operational print engine is redundant and only actuated in the event that one of the operational print engines develops a malfunction causing it to be non-operational. At that time, the previously non-operational print engine becomes operational. In this way, two print engines are continually in operation with one print engine being non-operational. This printing system significantly improves reliability and minimizes maintenance requirements.

Abstract: The invention provides an image forming apparatus such as a coin-operated copy machine, which has an upper limit value to the number of copies which are authorized to be made and which also copies both sides of originals fed to the image forming apparatus. The image forming apparatus is configured so that its intermediate tray, which temporarily stores sheets copied on their first side, is empty at the end of a copy cycle and despite the image forming apparatus being fed more double-sided originals to copy than are authorized to be copied. The image forming apparatus compares the upper limit value of the number of copies authorized to be made to the number of single-sided copies already made in the current copying cycle and begins copying the second side of the originals onto sheets from the intermediate tray when the upper limit value equals a constant K plus twice the number of images formed.

Abstract: Disclosed is the printing system 1 including the printer 2 and the personal computer 51 through which the command combination is selected according to kind of the print sheet A among four command combinations (the first combination is defined by both the print order standard command and the print direction standard command, and corresponds to pattern 1; the second combination is defined by the sheet plane standard command and the print direction standard command, and corresponds to pattern 2; the third combination is defined by the print order standard command and the sheet direction standard command, and corresponds to pattern 3; the fourth combination is defined by the sheet plane standard command and the sheet direction standard command, and corresponds to pattern 4), further the print condition is determined by the selected command combination, thereby image printing is conducted in the two-sided printing mode by the printer 2 under print control by the personal computer 51 while reversing the feed direct

Abstract: A sheet transport system for an image-forming apparatus including a scanner unit on an upper part of an image-forming unit. A paper ejecting path ejects an image formed paper sheet to an ejected paper stacker via the image-forming unit. A scanning sheet path conveys an original document through an original document platform to a scanned paper stacker via the scanner unit. A sheet path selector selects one of the paper ejecting path or scanning sheet path, the scanning sheet path and the paper ejecting path crossing each other.

Abstract: A digital copying machine capable of two-sided copying, which forms an image on one side of a paper sheet, transports the paper sheet through a sheet re-feeding path provided with a sheet turning over unit, forms an image on the other side of the paper sheet, and finally delivers the paper sheet outside. When two-sided copy mode is set in accordance with an instruction from the user, paper sheets are supplied at sheet intervals shorter than sheet intervals at which paper sheets are supplied in one-sided copy mode.

Abstract: Whether the number of prints is equal to or larger than a predetermined number or not is judged. Whether the total number of pages in a job is equal to an odd number or not is judged. When the total number of prints is equal to or larger than the predetermined number and when the total number of pages is equal to the odd number, the printer controller controls in a manner such that a final paper is fed by only a first feed and an image is printed to only the first side of the paper and the paper is ejected out. In the case where the total number of prints is less than the predetermined number and the total number of pages is equal to the odd number, the printer controller controls in a manner such that the final paper is fed by the first feed and an image is printed to the first side of the paper and, subsequently, the paper is fed by a second feed and an image is printed to a second side of the paper on the basis of blank page data and the paper is ejected out.

Abstract: An image forming apparatus such as a copying apparatus capable of executing copy operations with excellent efficiency, when executing multi-sort copying even when there is a large number of document pages or a large number of copy bundles, by executing controls to calculate the number of sorting bins required to accommodate ejected recording sheets per document bundle based on the number of document pages and the sheet accommodation capacity per each bin of a sorter, and calculate the number of copies possible in a single multi-sort copy operation from the total number of bins of the sorter and the number of bins required to accommodate the ejected recording sheets per document bundle, and divide the number of copies in a plurality of multi-sort copy operations when the number of set copy bundles exceeds the number of copies possible in a single multi-sort copy operation.

Abstract: A continuous web substrate duplex printing system which can utilize a single otherwise conventional or existing xerographic, print engine (normally printing conventional cut sheet substrates) without substantial structural modification, and without requiring plural print engines on opposite sides of the web. The continuous web may be fed uncut into the print engine to two transfer stations alternatingly engaging a single endless belt imaging surface, which two alternating transfer stations are in line with one another in the direction of movement of the imaging surface, with web inversion and a controlled expandable/contractible web loop in between those two transfer stations, for respectively transferring the page print images onto the two respective sides of the continuous web in sequential batches of plural first and second side images, in the proper page sequence and positions and without any spaces between page images along the web.

Abstract: An image forming apparatus in which a sheet conveying path and a sheet discharging path are exposed when a side cover is opened for removing a jammed sheet. The side cover, together with attached copy exit guide plate for sheets is exchangeably and detachably mounted to the main body of the apparatus and serves commonly as a side cover for a simplex type copying machine and a duplex type copying machine. Separate units, attached to each other and aligned, establish sheet discharging paths to different destinations, for example, sheet discharging trays. Sheets are guided to the paths by a course selecting pick. One of the two units includes rollers for directing sheets to a mail box or duplex copying unit, selectably. Disclosed embodiments enable copy sheets to be delivered selectably to face up and face down discharging trays or selectably to mail box and face down discharging trays.

Abstract: A photocopier having a duplex copy unit unable to stack a plurality of recording media thereon, wherein an image scanner is controlled such that the scanner reads the first document, then reads the first document and the second document alternately, and finally reads the second document. A medium feed device and the duplex copy unit are controlled such that one recording medium is fed from the medium feed device, then recording media are alternately fed from the medium feed device and duplex copy unit one at a time, and finally one recording media is fed from the duplex copy unit, thereby reducing the period of time necessary for reproducing the images of a document or documents on both sides of recording media and enhancing the productivity of the copier.

Abstract: In printing both sides of plural sheets of paper by using a digital copy machine having a circulating-type duplexing unit, when a back face of the first page is printed after printing a front face thereof, if it is likely to collide with a sheet of paper for the second page, priority is given to printing of the back face of the first page. If the front faces of both first and second pages are already printed, then control proceeds so as not to collide with the sheet of paper for the back face of the second page irrespective of delay in printing the back face of the first page.

Abstract: A printing apparatus prints toner powder images on both sides of an image receiving support (e.g. paper). The apparatus includes an image recording medium for forming a toner powder image thereon; a transfer device for transferring a toner powder image from the image recording medium to the image receiving support; and fixing devices for fixing a transferred toner powder image on the image receiving support by pressure surfaces coming into contact with both sides of the image receiving support. The apparatus further includes image receiving support transport devices for transporting an image receiving support provided with a toner powder image on a first side back to the transfer device for transferring a toner powder image to a second side of the image receiving support.

Abstract: There is disclosed a facsimile apparatus comprising a reading circuit for reading an image of an original, a shift arrangement for shifting a position of the image read by the reading circuit, and a transmitting arrangement for transmitting to another facsimile apparatus the image read by the reading circuit. The facsimile apparatus further comprises a control circuit for use in selecting which one is transmitted, the image shifted by the shifting arrangement or the image not being shifted, depending on whether one side of the original is read by the reading circuit or both sides thereof is read by the reading circuit, and depending on whether the another facsimile apparatus performs one side recording or perfect recording.

Abstract: In a system for scheduling a sequence of operations in an apparatus for outputting, for example, simplex and duplex digitally-printed documents, a schedule is derived for obtaining a desired output order of documents, and this schedule is proposed to the apparatus in real time. As individual operations are accepted for execution by the apparatus, the accepted operation is recorded in an execution table. If a proposed operation is rejected by the apparatus, the execution table can be used to revise the schedule quickly to take into account the rejected operation while still obtaining the desired output order.

Abstract: An image forming apparatus which forms identical images both on a sheet of a first type (overhead projector sheet) and on a sheet of a second type (normal paper sheet). One-side image formation is performed to form images on front sides of OHP sheets which are then discharged into a non-sort bin. Two-side image formation is performed to form images on the both sides of normal paper sheets which are then sorted and discharged into sort bins. Thus, sets of document sheets for presentation can be prepared in a sorted state. Since images are formed on both sides of the normal paper sheets, the normal sheets can be economized and saved.

Abstract: A compact ADF (auto-document feeder) for feeding a duplex document includes, a first feeding path starting from a document setting table to an exposing area and is formed in a U-shaped state, a second feeding path starting from the exposing area to an ejecting roller, a switch-back path disposed downstream of the second feeding path and above a document ejecting tray, and an inverting path starting from an entrance of the switch-back path to the first feeding path. A switching gate is pivotally disposed downstream of the second feeding path and above the ejecting tray to selectively lead the document either to the ejecting tray, or the switch-back path, or to the inverting path each from the second feeding path.

Abstract: A sheet processing device which is mounted on an image forming apparatus having a both-side copy mode of forming an image on each side of a sheet member, including a bin module provided with a plurality of bins for accepting sheet members exhausted from the image forming apparatus, and a processor for taking out sheet members exhausted from the bin and processing the sheet members. When the maximum number of sheets continuously producible per unit in the both-side copy mode for the image forming apparatus is N, and the number of bins is m, the number of bins m is set to satisfy the following relational expression:m.gtoreq.N.

Abstract: A data transfer method and apparatus for an image reading apparatus suitably used with an image scanner is improved in that a transfer line apparatus is simplified in construction and produced with a reduced cost by an improved transferring technique of data.

Abstract: In an image processing apparatus, determination is made whether an interruptive print wait state is attained during interruptive printing. When determination is made that the apparatus is in an interruptive print wait state, an interruption recover process is effected. Then, the apparatus returns to the normal mode prior to interruption. Thus, an image processing apparatus is provided that can have the waiting time caused by an interruption in the normal job reduced.

Abstract: A miniature duplex sheet feeding device for an image forming apparatus is disclosed. A duplex unit is positioned above an ordinary sheet feed tray loaded with a stack of sheets. The duplex unit has an intermediate tray for stacking sheets each carrying an image on one side thereof, and a bottom plate movable back and forth in an intended direction of sheet refeed. The sheet feed tray and duplex unit share a single sheet pay-out means. The bottom plate includes separators for retaining the leading edge of the sheet stack and allowing the stack to be bodily shifted to a preselected refeed position.

Abstract: An image forming apparatus which performs image transfer on the rear side of a sheet by retransporting the sheet inverted via inverting section to a transfer drum in duplex copy mode. After an image has been transferred onto a rear surface of the sheet, the transfer drum is separated from an image bearing member, thereby separation agent, which is adhered to the transfer drum due to refeeding of the sheet that has once passed through fixing unit, is removed from the transfer drum without adhering to the image bearing member.

Abstract: A system of improved duplex color printing by reducing copy sheet feeding jams due to first side color printing sheet curl by feeding and printing a first plural color image on a first side of a copy sheet with the copy sheet in a first orientation, then automatically rotating the copy sheet by 90 degrees from the first orientation into a second orientation and feeding and printing a second plural color image on the second side of the copy sheet with the copy sheet in the second orientation. Additionally disclosed is, in coordination therewith, automatically rotating the image for the second side of the copy sheet by 90 degrees from the first plural color image for the printing of the second plural color image on the second side of the copy sheet with the copy sheet in the second orientation, so that commonly oriented images are provided on the first and second sides of the copy sheet. The first printing pass orientation of the copy sheet may be long edge first, and the second short edge first.

Abstract: An image forming apparatus for performing a one-side image formation to form an image of a designated page on a recording sheet is disclosed. Selected from a plurality of pages each carrying an image to be formed, a page can be designated by an operation section. Image formation on one side of a recording sheet carrying an image of the designated page formed on the other side thereof is prohibited. Thus, the recording sheet carries the image of the designated page formed only on one side thereof. Where images on two-sided document original sheets are copied to prepare a set of document copies, for example, one-side image formation is performed to copy an image on a cover sheet or on an inter-sheet for chaptering, while two-side image formation is performed to copy images of the other pages on normal sheets.

Abstract: A copying system which has a copying machine for forming an image on a sheet, a circular transporting device for receiving a sheet which has obtained an image on one side from the copying machine and refeeding the sheet to the copying machine for image formation on the other side of the sheet, and an automatic document feeder with a document reversing mechanism. The automatic document feeder sets a document at a specified position on a document table and discharges the document from the document table. Further, in handling a double-side document which has images on both sides, the automatic document feeder turns over the document after scanning of an image of one side. When a number of copies over the capacity of the circular transporting device are to be made in a double-side document/duplex copy mode, the document is turned over every time a number of copies corresponding to the capacity of the circular transporting device has been made.

Abstract: A digital copy machine includes an image reading unit IR, an image memory, an image formation unit PRT, and a circulation type sheet transportation mechanism having a transportation path of a length that can accommodate n (n.gtoreq.2) sheets for reversing the side of the sheet having a copy image formed on one side to the opposite side and refeeding the same to a copy position. In duplex copying using at least n sheets, the timing of feeding the first sheet is set so that the n-th sheet arrives at the copy position only after the time when the copy of an original image of the (2n-1)th page can be initiated in order to set the number of circulating sheets to n.