FR2534564A1 - Method and apparatus for printing on both sides. - Google Patents

Abstract

The invention relates to a printing apparatus intended to print on both sides or to print only on one side. This apparatus comprises a device 10 which is intended to store the printing control information which defines the images of documents to be printed. A printer 12 prints these images on sheets which are entrained along a closed circuit causing them to pass into a printing unit 14. The closed circuit is sufficiently long in order to permit the simultaneous transport of a certain number of sheets. A device 40 enables the sheets to be turned over when they are to be printed on both sides before being directed towards an output device 54 via a selectively lowered flap 46. Field of application: rapid reproduction of documents, by printing only on one side or by printing on both sides, onto sheets of paper.

Description

The invention relates to a printing apparatus and more particularly to a

  printing apparatus in which multi-page documents can receive

double-sided printing.

  A number of different prior printing devices have the possibility of duplex printing. In most of these devices, only one sheet is present at a time on the path followed by

  paper In an apparatus of the prior art, after printing

  pressure on the first face of a sheet, the latter is transported to an output accumulator, turned over,

  sent back to the printing station, then again

  carried to the output accumulator It is only at this time that the next sheet of paper is brought in the path or the course of the paper Consequently, the duplex printing speed of this machine is limited by the fact that it takes a relatively long time interval

  long between successive printing operations, inter-

  valley during which a sheet is turned over, or removed from the paper path and a new sheet brought along the paper path The actual printing operation takes only a relatively small part of the time requested

  for the production of each double-sided printed sheet.

  In a second type of printing device, each sheet of paper is driven so as to pass successively through a first printing station, through a turning station and finally through a second printing station. The opposite faces of each sheet are

  printed in the first and second printing stations.

  This machine requires several printing stations to perform two-sided printing Although it is capable of operating at a speed higher than that of the machine described above, it nevertheless requires a

relatively large space.

  It therefore appears necessary to have a

  improved printing apparatus in which a printing

  high speed duplex printing of multiple sheets

  can be done in one printing station.

  According to a characteristic of the invention, a duplex printing apparatus for several document images on several sheets comprises a memory device intended to memorize print order information defining the images of the documents. A printer selectively prints the images of documents on sheets as they pass through a printing station

  sheets, which feeds the sheets into the printer station

  pressure, defines a path or a closed circuit for the sheets, of sufficient length for a predetermined number of sheets to pass through this circuit simultaneously A sheet feeding device supplies sheets to the drive device and a turning device receives sheets one after the other from the pickup device after printing on a first side of those sheets, and it immediately returns them to the pickup device in an inverted orientation An output device receives the sheets from the device after completion of duplex printing A controller selectively directs the sheets in the

  closed circuit to the output device or to the

  positive flipping, after printing, so

  that several sheets transported by the feeder

  in the printer are printed on one side, turned over, then printed on the second

  face before being directed towards the output device.

  The control device comprises means for controlling the operation of the sheet feeding device, so that printed sheets directed towards the output device are replaced, on the sheet circuit, by sheets coming from the feeding device so that the predetermined number of sheets is maintained in the closed circuit The sheet turning device may include means intended to return each sheet returned to the sheet driving device, before the next sheet received by

the turning device.

  The printing apparatus may further comprise a device intended to extract the print order information from the memory device, in a first order to perform printing on the first faces of the sheets, and to extract the information from command to print the memory device in a second order for printing the second sides of the sheets, so that the document images formed on the first and second sides of the sheets have their upper parts

  adjacent to the edges of the leaves.

  The method by which the printing apparatus operates may include the steps of (a) sequentially passing a predetermined number of sheets from the sheet supply to the sheet circuit; (b) successively driving the sheets along the sheet circuit in order to pass them through the printing station to print certain selected images of documents on the first sides of the sheets (c) to successively print certain selected images of the documents on the first faces of the portfolios; (d) successively withdraw from the circuit

  sheets each of the sheets to be printed recto

  back and turn over each sheet; (e) successively returning the returned sheets to the sheet circuit and driving the returned sheets to pass them through the station

  printing so that some selected images of the docu-

  be printed on the second sides of the sheets to produce double-sided printed sheets; and

  (f) feeding the sheets printed recto

back to the exit.

  The step of successively printing certain selected images of the documents on the second sides of the inverted sheets may include printing images on the second sides of the returned sheets in an orientation which is reversed with respect to that of the images of the documents printed on the first faces

leaves.

  The method can also comprise the steps which consist of:

  (a) extracting the ordering information from

  pressing the memory in a first order to order printing on the first sides of the sheets; and

  (b) extracting order control information

  pressing the memory in a second order to order printing on the second sides of the sheets in an orientation which is different, relative to the printing station, from the orientation in which the first

sides of the sheets are printed.

  The method may further include the step

  which consists in passing periodically and sequentially-

  an additional and predetermined number of sheets

  from the sheet feed to the leaf circuit-

  for printing the first faces of these sheets, after printing the second faces of at least some

  sheets previously introduced in a predetermined number.

  The step 'consisting in introducing sequential-

  periodically an additional and predefined number

  finished sheets, from the sheet feed to the sheet circuit, can consist in introducing the additional and predetermined number of sheets in the

  leaf circuit so that the leaves

  follow the predetermined number of intro leaves

  previously picked in the leaf circuit Les

  second sides of previously introduced leaves may

  may be printed before printing the first

  sides of additional sheets.

  The subject of the invention is therefore a printing apparatus and method in which several sheets are transported simultaneously on a closed circuit which passes through a printing station and in which each sheet moves so as to pass twice through the station before being removed from the closed circuit

  so that each sheet is printed on both sides; linen-

  vention also relates to a printing apparatus and method in which a sheet turning device is placed in the immediate vicinity of the circuit in order to receive sheets therefrom and return the sheets almost immediately to the circuit, in a returned orientation; and the invention also relates to an apparatus in which the sheets, which have been printed on both sides, are directed towards an outlet

in a desired order.

  The invention will be described in more detail below.

  gard of the attached drawings by way of example in no way limited

  tatif and on which FIG. 1 is an elevation of the printing apparatus according to the invention, illustrating the circuit of the paper through the apparatus; and Figure 2 is a diagram illustrating the duplex printing cycle of multiple documents

  pages, with varying numbers of pages.

  Figure 1 shows schematically the apparatus

  printing board according to the invention capable of performing

  single-sided printing or one-sided printing

  verso A computer 10, comprising an appropriate memory such as a disk drive, makes it possible to store print order information which defines several

  images of document pages to be printed

  print order training is transmitted from the

  computer memory 10 to a printer 12, for example-

  ple a thermal printer, a laser printer, a dot printer, or any other known printer in which the printed image can be controlled by

  electrical signals Printer 12 prints selectively

  Vely the desired images of documents on sheets transported in a printing station indicated generally at 14 A sheet feeding device comprises a feeding station 16 and a feeding roller 18 which feeds white sheets of paper towards an associated section 20 in advance comprising rollers 22 and 24 and a vacuum belt 26

  paper from vacuum belt 26 are applied

  quées on belts 28 with depression which pass on

  drums 29, 30, 31 and 32 with vacuum and on wheels

  leaux 33, 34, 35 and 36 Vacuum chambers are arranged between the drums 29 and 30, between the drums and 31 and between the drums 32 and 29 to hold the sheets against the belts 28, while a belt 37 passes over rollers 38 and 39 and constitutes a means for transporting a sheet from the vacuum drum 31 to the vacuum drum 32 The sheets supplied to the drum 29 are driven on the belts 28 so

  to pass in the printing station 14.

  When the second side of the sheet is to be printed, the sheet is fed to a device

  sheet turning device The device 40 for turning over

  There are a number of wedge-shaped sheet deflectors-41 which rise between the belts 37 The deflectors 41 deflect a sheet upwards, between guides 42 of metal wire and inwards

  space between two pressure rollers 43 and 44.

  The rollers 43 and 44 initially rotate so as to raise a sheet vertically The rollers 43 and 44 are then rotated in opposite directions in order to bring down a sheet to bring it into contact with the deflectors 41, then on the belt 37 Le edge of the sheet which was previously the front edge now becomes the rear edge and the inversion is complete The sheet is then transported to the left, as shown in Figure 1, and raised to contact a vacuum roller 38 at means of guides 45 in

metal wire.

  At a later stage of the printing operation

  duplex, or when printing on one side only, the sheets can be removed from the belts 28

  by a door 46 which can be tilted downwards

  that it is thus tilted, the door -46 lifts the leaves from the belt 28 and directs them towards a device for

  output The latter includes belts 48 and wheels

  leaux 50 and 52 which advance the leaves towards a

output 54 battery.

  It therefore appears that the printer dominates a certain number of belts, vacuum drums and rollers which act together to form a sheet transport device intended to make the sheets follow a closed circuit passing them through the station 14 d This closed circuit is long enough, relative to the size of the copy sheets, for

  several of these sheets can run through it simultaneously-

  is lying. A control device comprising a door 46, selectively directs the copy sheets located on the circuit towards the output device or towards the turning device 40, after printing by the printer 12 As described in more detail below. afterwards, this facilitates a duplex printing operation during which several sheets are entrained by the transport device in the printer, printed on one side, turned over, then printed on the second side before being sent to the output device A motor 56, controlled by the computer 10, allows

  place door 46 in the chosen position The computer

  tor receives signals from photo-optical detectors (not shown) placed along the sheet circuit, so that the synchronism between the printing operations,

  door operation and other functions of the im-

  primante can be properly established in accordance

  the movement of the leaves along their circuit.

  When printing on one side only,

  the sheets are advanced from the feeder

  mentation, transported so as to pass through the printing station 14, printed on one side, deflected by the door 46 and accumulated on the stack 54 By initially pivoting the door 46 upwards, a recto printing can be carried out back side on a sheet of copy paper The sheet is advanced from the feeder 16 and printed on a first

  face by the printer 12 passing in the station 14 of im-

  pressure The sheet is directed towards the turning device 40 and then returned to the closed circuit of the paper in an inverted orientation The sheet is then transported by the belts 28 which make it

  pass into the printing station 14, its second side turns

  born towards the printer 12 The sheet is then printed on its two faces It is removed from the belts 28 by the door 46 and directed towards the stack 54, as may be

  be chosen by the operator of the device.

  The closed circuit of the sheets is long enough that several sheets can be driven simultaneously along this circuit, under the control of the computer 10, by the transport device. In the printing apparatus shown, five sheets are transported. simultaneously along the closed circuit It should be noted, however, that when sheets of

  longer lengths are printed, it may be necessary

  reduce the number of sheets circulating simultaneously-

lying on the circuit -

  The sequence in which the page images

  are printed varies according to the number of pages of the docu-

  Figure 2 illustrates a number of these sequences.

  Each printing sequence is based on the assumption that five sheets are kept in the closed circuit, continuously; that is, when double-sided printed sheets are fed to the output, they are replaced by unprinted sheets from the sheet feeders. Note, however, that the printing sequence may not be exactly as shown in Figure 2 when a very low number of copies of a document to

  multiple pages printed on both sides must be produced.

  For example, if a two-page document, one sheet, is to be printed, only two copies of this document being desired, the printing sequence would be 2-2-1-1 rather than that shown in Figure 2, because it would be useless to introduce more than two copy sheets in the closed circuit In addition, if fewer or more copy sheets are put into circulation

  simultaneously in the closed circuit, the sequences of im-

  pressure are necessarily-modified The line underlining the sequences indicates a repetition of the sequences of page numbers The letter "X" is used to indicate that no page image is printed on a sheet

  as it passes through the printing station.

  Note that the device and the pro-

  printing assignments according to the invention have advantages

  important steps in relation to devices and processes

  The leaves are not stacked on a plate.

  intermediate flip-flop after * a first printing operation and before a second printing operation, as is common in previous two-sided printers Therefore, the risk for the ink to spread or stain other sheets from a stack is eliminated Using a closed sheet circuit O in which several sheets are continuously and repeatedly circulated by

  the printing station, maximum use is made of the possibilities

  printer print units Therefore the number of sheets that can be printed in a period

  of time given by the printing apparatus according to the invention

  tion is significantly larger than that obtainable with prior devices of the type in which both sides of a sheet are printed before other sheets are advanced towards the device

  transport of printer sheets.

  In the foregoing description, it has not

  been question of the orientation of the images of documents to be printed on both sides of the sheets In general, each of the sheets is driven along the closed circuit so that one of its

  short edges or the front edge If a sheet is

  dragged so as to pass through the printing station 14 so that one of its short edges is the front edge 10 and the first face of the sheet is printed, and if, after turning over, this sheet passes through the printing station so that its other short edge is the front edge, it appears that the image formed on the second face of the sheet is reversed with respect to the image formed on the first face of the sheet if the two images are printed from top to bottom In the case of sheets having to be joined by their left edges to form a book-like work, it appears that such an orientation of the images is unacceptable

  In order for the images to be properly oriented

  the data used must be rotated by 1800

  to order printing on both sides of the sheets.

  This can be obtained by two successive rotations of 90 One rotation out of 90 is conveniently carried out as described in one of the patents of the United States of America

  N O 4 084 195, N O 4 271 476 and N O 4 168 488.

  It goes without saying that many modifications can be made to the process and to the apparatus described.

  and represented without departing from the scope of the invention.

Claims (9)

  1 Printing process which, in a printing apparatus of the type in which print order information is stored in a memory (10) and defines several images of documents to be printed on both sides of several sheets, and in which one circuit   (28) of sheets passes through a device (16) for feeding   tion in sheets, a station (14) for printing, a station (40) for turning over and an outlet (54), is characterized in that it consists in advancing successively several   sheets of said feed device (16) towards the circuit   cooked (28) sheets, to successively transport the sheets along the circuit (28) to pass them through the printing station (14) in order to print certain selected images of documents on the first faces of the   sheets, to print successively some selected images   sies-of documents on the first sides of the sheets,   to successively turn over the sheets to be printed   recto-verso and immediately return the sheets returned to the printing station (14), to successively print certain selected images of documents on the second sides of the sheets returned to produce sheets printed duplex, and to transport the   sheets printed on both sides towards the exit (54).   2 Method according to claim 1, characterized in that the successive printing of certain selected images of documents on the second faces of the inverted sheets consists in printing images on the second faces of the inverted sheets, in an orientation which is reversed with respect to the orientation in which document images are printed on the first leaf faces.   3 Method according to claim 1, characterized in that it further consists in extracting said print ordering information from the memory (10) in a first order to order printing on the first faces of the sheets, and in extracting said print ordering information of the memory (10) in a second order for ordering the printing on the second faces of the sheets, in an orientation which is different, relative to the printing station (14), from the orientation in which   the first sides of the sheets are printed.   4 Method according to claim 3, characterized   in that the document images printed on the pre-   first and second sides of sheets printed recto   reverse side have their upper parts adjacent to the same edges of said sheets.   5 Method according to claim 1, characterized in that it consists in advancing successively and periodically an additional number of sheets from said feed device (16) to the circuit (28) of sheets to print the first sides after the printing of the second faces of at least some of the sheets previously advanced. 6 Method according to claim 5, characterized in that the step of advancing successively and periodically an additional number of sheets from the device (16) for feeding to the circuit <28) of sheets also consists in advancing the additional number of sheets to the circuit (28) so that the additional sheets follow the sheets   having been previously advanced in the sheet circuit.   7 Method according to claim 6, characterized in that the second faces of the sheets having been advanced previously are printed before the first faces   additional sheets are printed.   8 Double-sided printing apparatus for multiple document images on multiple sheets, comprising   a memory device (10) for storing information   print command mation defining multiple   document images, a printer (12) for printing   selectively sea said document images on sheets transported so as to pass through a printing station (14), a device (28) intended to transport   the sheets and pass them through the station (14) of im-   pressure, a device (16) for feeding sheets of the transport device (28), a device (40) for turning sheets, an output device (54)   for receiving sheets from the transfer device (28)   port after they have been printed, and a control device (10, 46, 56), the printing apparatus being characterized in that the sheet transport device forms a closed circuit (28) of sheets a sufficient length so that several sheets of copies can be driven simultaneously along this circuit by the transport device, the turning-over device   comprising means (43, 44) intended to receive successively   sheets of the transport device (28) and immediately return them to the transport device (28) in an inverted orientation, the control device comprising means (10, 46, 56) for selectively directing sheets of the circuit (28) to the output device (54) or to the turning device (40), after printing, so that several sheets driven by the transport device (28) so as to pass through the printer ( 12) are printed on a first side, turned over, then printed on the second side before being directed towards the device (54) Release.   9 The printing apparatus of claim 8, further characterized in that the control device   includes an element (18) for controlling the operation   ment of the device (16) for feeding sheets of   so that printed sheets directed towards the dispo-   output sitive (54) are replaced, in the sheet circuit, by sheets from the feed device (16) so that a predetermined number of sheets   is maintained in the closed circuit.   The printing apparatus of claim 8, further characterized in that said print control information can be extracted from the device to   memory (10) in a first order for printing   say first sides of the leaves, and extracted from the dispo-   second-order memory device for printing said second sides of the sheets, the document images formed on said first and second sides of the sheets having their upper parts adjacent to the same edges leaves.