METHOD OF AND DEVICE FOR PRINTING IMAGES ON HALVES OF BOTH SIDES OF SHEETS

Abstract: Method of printing images on halves of both sides of sheets by passing each sheet seriatim four times directly in succession through a printing station (4), thereby printing the four halves of the sheet. The sheets thus printed and together folded double form a book in which the sequence of the images corresponds to the sequence of the original images. A device for performing this method comprises a sheet turn-over path (8) along which a sheet passed through the printing station (4) can be returned to the printing station and a sheet discharge path (7) along which a sheet passed through the printing station (4) can be fed to a collector tray (12). Control means control that a sheet after the first three passes is fed into the turn-over path (8) and after the fourth pass into the discharge path (7) and a time element so controls the time of passage of a sheet through the printing sta­ tion (4) that on the first and fourth pass of a sheet an image is printed on a half of the sheet which, as considered in the direction of passage, is other than the half printed in the second and third pass of the sheet. For making a book from a set of originals printed on one side the device is provided with a document feeder (21,22) for feeding origi­ nals from both sides of a stacked set of originals (20) and a deposit device (29) having two deposit plates (30,31), in which, for printing a sheet, first two originals are fed from one side of the stack (20) and deposited on one of the deposit plates (30,31) and then two ori­ ginals are fed from the other side of the stack (20) and deposited in reverse orientation on the other deposit plate. For keeping the last page(s) of a book blank when the number of ori­ ginals is less than a multiple of four, the document feeding opera­ tion can be inhibited at appropriate times in a print cycle being otherwise the same.

Description: This invention relates to a method of printing images on halves of both sides of receiving sheets fed through a printing station, which sheets thus printed and together folded double form a book in which the sequence of the images corresponds to the sequence of the original images. A method of this kind is known from US patent 4334765. To make a book of prints from a number of numbered originals by this known method, half of the first side of a number of sheets is printed with half the odd-numbered originals. The other half of the odd-numbered originals is printed on a half of the other side of said sheets. Half the even-numbered originals is then printed on that half of the first side of the sheets which is still unoccupied by any image and the other half of the even-numbered originals is printed on that half of the other side of the sheets which is still unoccupied by any image. The disadvantage of this known method is that the sheets which together are required to form books must be deposited on a stack after an image has been printed on each such sheet and the sheets again have to be individually withdrawn from the stack to print the next image thereon. This readily leads to errors in the correct sequence of printing images on the sheets, e.g. because sheets that have been joined together continue to stick to one another and pass through the apparatus together. An error of this kind often cannot be corrected and usually causes the entire book production to be unusable. The object of the invention is to provide a method of printing images on halves of both sides of sheets fed through a printing sta­ tion, said sheets together forming a book, as indicated in the preamble, without the said disadvantage. According to the invention this object is attained in that a sheet is passed through the printing station four times directly in succession and after each of the first three passes is turned over for the printing of a following image on the other side of the sheet than that on which the previous image was printed and the sheets, after the last pass, are collected in the correct orientation to form the book. Another object of the invention is to provide a device for per­ forming the method according to the invention. In a device comprising a printing station, a conveyor path along the printing station, a sheet turn-over path and a sheet discharge path following the conveyor path, and a sheet deflector which in a first position guides a sheet from the printing station into the turn-over path and, in a second position, guides the sheet from the printing station into the discharge path, this object is attained in that first control means are provided which hold the deflector in the first position during the first three consecutive passes of a sheet and in the second position during the following fourth pass and in that a time element is provided which so controls the time of passage of a sheet through the printing station that on the first and fourth passes of a sheet an image is printed on a half of the sheet which, as considered in the direction of passage, is other than the half printed in the second and third passes of the sheet. Consequently, each of a number of sheets together required to form a book as referred to in the preamble, can be completely pro­ cessed before processing of a subsequent sheet starts. If the sheets are processed in sequence from the outermost sheet to the innermost sheet, then an additional effect is that the relevant originals can be processed in ascending sequence from the lowest number, or in a descending sequence from the highest number. The invention is particularly attractive for printing originals present in electronic form, but it can also be used for printing orig­ inals in sheet form. In the latter case, an advantageous embodiment of the device according to the invention is provided with a document feeder for individually feeding originals in sheet form from a stack to a scanning station of the device, the feeder comprising two con­ veyor means which can each feed an original from a different side of the stack, and a document deposit device comprising two deposit pla­ tes, the originals which are fed from one side of the stack being deposited on the one deposit plate and the originals fed from the other side of the stack being deposited in the reverse orientation on the other deposit plate. With this embodiment it is possible to perform a cycle in which successively two originals from one side of the stack and two origi­ nals from the other side of the stack are scanned in order thus auto­ matically to make a copy set from an original set consisting of a number of originals which is a multiple of four, the copy set being foldable to form the book referred to in the preamble. In order to make such a book starting from an arbitrary number of originals, this advantageous embodiment further comprises adjust­ ment means which can be set to the number of originals that the stack contains and control means which generate a first count signal corresponding to the next higher figure with respect to the set number, said figure being a multiple of four, in order to perform the said cycle a number of times corresponding to said figure, and which generate a second count signal corresponding to the difference bet­ ween the said figure and the set number and control means which auto­ matically keep one of the conveyor means inoperative from the start of the first cycle for a number of times corresponding to the said difference, the cycle sequence otherwise being the same. The invention will now be explained with reference to the accom­ panying drawings wherein: Figs. 1A to 1D diagrammatically illustrate a device according to the invention showing different stages in the printing of a receiving sheet according to the invention. Fig. 2 diagrammatically illustrates a part of a device according to the invention by means of which it is possible to make a set of copies automatically by the method of the invention from a set of originals printed on one side. Fig. 3 diagrammatically illustrates a part of a device according to the invention by means of which a number of copy sets can be made automatically from a set of originals printed on one side. Figs. 1A to 1D show a holder 10 for a stack of receiving sheets. A take-off roller 6 can separate these sheets from the stack individually and feed them to a feed path 3, along which the sheet is fed to a printing station 4. At the printing station the receiving sheet comes into contact with a continuously moving image support 5. Images may have been applied to the image support 5 at regular intervals by means not shown and can be transferred onto receiving sheets at the printing station 4. After the printing station 4 the feed path 3 is followed by a sheet discharge path 7 and a sheet turn-over path 8. A sheet deflector 9 is provided at the junction and can occupy two positions, a return position shown in Figs. 1A to 1C, in which a sheet fed through path 3 is fed into the turn-over path 8, and a discharge position shown in Fig. 1D, in which a sheet fed through path 3 is fed to the discharge path 7. Discharge path 7 leads into a collector tray 12 in which the sheets completely printed in the printing station can be deposited on one another. The turn-over path 8 leads to the feed path 3. Disposed in feed path 3 is an actuatable retaining means 13 which in an opera­ tive state retains a sheet that has come directly from the holder 10 into the feed path 3 or which has come into the feed path 3 via the turn-over path 8. When rendered inoperative, the retaining means 13 releases the retained sheet for further conveyance to the printing station 4. A control system (not shown) of the printing device is connected to the retaining means in order to release a retained sheet at predetermined intervals so that it can be fed to the printing sta­ tion 4. A book as referred to in the preamble can be formed as follows by means of the printing device shown in Figs. 1A to 1D. The holder 10 is filled with receiving sheets of a size such that two images can be applied next to one another thereon as considered in the direction of passage of the sheets. When the total number of images required in a book is a multiple of four, the relevant images are applied to the continuously moving image support 5 in a sequence in which first the two lowest numbered images and then the two highest numbered images reach the printing station 4 and then, of the remaining images, in each case first the two lowest numbered images and then the two highest numbered images, untill all the images have been applied. If the total number of images is not a multiple of four, then the next higher multiple of four is used and the image locations for the missing highest numbered images are left blank on the image sup­ port 5. When the first receiving sheet is in readiness at the retaining means 13, the printing device control system releases the receiving sheet for further conveyance at at time such that the first lowest numbered image (1) is printed on the leading half of that receiving sheet in the printing station 4. During the printing of the first image (1), the sheet deflector 9 is in a position in which a receiving sheet is fed to the sheet turn-over path 8, so that it returns to the feed path 3 in a turned-over position, being retained in said feed path 3 by the retaining means 13 which has been re­ actuated in the meantime. This is the condition shown in Fig. 1A. The retained receiving sheet is then released by the control system for further conveyance, at a time such that the next image (2) having the next lowest number but one is printed in the printing station 4 on the trailing half of that receiving sheet. The sheet returns to the feed path 3, and this is the condition shown in Fig. 1B. To print the next highest numbered image (n) the latter operation is repeated, giving the condition shown in Fig. 1C. In response to a control signal then generated, the sheet deflector 9 is put into the discharge position and the sheet in readiness at the retaining means 13 is released for further con­ veyance at a time such that the next highest numbered image but one (n - 1) is printed in the printing station 4 on the leading half of the receiving sheet. The sheet, which now has four images, is deposited via discharge path 7 in tray 12 as shown in Fig. 1D with the first printed image (1) facing downwards. This cycle, in which four images can be formed in direct suc­ cession on a receiving sheet, is repeated for each remaining series of four images. The sheets printed in these conditions are deposited on the previously printed sheets. The sheets thus formed into a stack are then together folded double to form a book as meant in the preamble. Prior to folding, the sheets can be joined together by stapling the set at the fold line. Fig. 2 diagrammatically illustrates a part of a device according to the invention by means of which a set of copies can be made auto­ matically from a set of original sheets printed on one side. The device has a magazine 20 in which a stack of originals can be placed. The magazine is provided whith a sheet take-off roller 21 for individually taking sheets from the bottom of the stack and a sheet take-off roller 22 for individually taking sheets from the top of the stack. A sheet taken off by roller 21 can be fed via a path 23 to the exposure platen 24 of the device and a sheet taken off by roller 22 can be fed to the exposure platen 24 via a path 25. A common path 26 extending along the exposure platen 24 is followed by a discharge path 27 along which an exposed original can be fed via a sheet deflector 28 to a receiving tray 29. The tray 29 is formed by two deposit plates 30 and 31 extending obliquely upwards in opposite directions and interconnected by their bottom edge. The sheet deflector 28 in the starting position indicated with solid lines guides a sheet fed through path 27 in the direction of deposit plate 30 and in the broken-line position in the direction of deposit plate 31. The operation of this device for offering a set of originals in the sequence required for automatically performing the method according to the invention is as follows. A set of originals consisting of a multiple of four, or made up to such multiple by blank sheets, is placed in the magazine 20 with the image sides facing downwards. Roller 21 is then actuated to take the bottom original from the magazine 20, said original being fed via path 23 to the exposure pla­ ten 24 to form an image on the image support shown in Figs. 1A to 1D. This original is then fed into the discharge path 27 and fed to the deposit plate 30 by the sheet deflector 28 which is in the starting position, the original being deposited with the image side facing downwards. This cycle is repeated with the next bottom origi­ nal of the originals still in the magazine 20. Roller 22 is then actuated to take off the top original from the magazine 20, this orig­ inal being fed via path 25 to the exposure platen 24 to form a sub­ sequent image on the image support, whereupon the original is deposited on deposit plate 31 with the image side facing upwards via the discharge path 27 and the sheet deflector 28, which has in the meantime been set to the broken-line position. This cycle too is repeated with the next top original of the originals remaining in the magazine 20. The four above-described cycles are repeated for the next four originals until the magazine 20 is empty. A copy set is made in the manner described with reference to Figs. 1A to 1D from the images formed on the image support. The originals deposited on deposit pla­ tes 30 and 31 are folded together and removed as a whole from the tray 29. In the device for feeding originals, shown in Fig. 3, in com­ parison with the device shown in Fig. 2, a tray 35 is added which is provided with a feed path 38 along which exposed originals can be fed into the tray, and a take-off roller 37 which returns the bottom orig­ inal from said tray each time back to the exposure platen via path 36. To make one copy set, the device shown in Fig. 3 operates in the same way as the device described hereinbefore. To make more copy sets from one set of originals, the originals exposed once are fed into tray 35 and then individually returned to platen 24 by take-off roller 37. This cycle is repeated until making the last copy set. During the making of the last copy set the originals are fed to receiving tray 29 where they are deposited in the manner described above. If a fault is signalled during the recycling of originals to and from the tray 35, only the copy set in progress can be defective; the previously made and deposited copy sets are correct. The effects of an error in the stacking and withdrawal of originals are in this case not so serious as the disadvantage of stacking partially printed sheets as referred to in the preamble. Instead of adding blank sheets to the originals placed in maga­ zine 20, to enable a multiple of four originals always to be used, the control system of the device can be so constructed that instead of feeding a blank sheet the take-off roller 22 or take-off roller 37, respectively, is kept inoperative at the relevant times, the cycle sequence otherwise being the same.

Claims: 1. A method of printing images of halves of both sides of receiving sheets fed through a printing station (4), which sheets thus printed and together folded double form a book in which the sequence of the images corresponds to the sequence of the original images, characterised in that a sheet is passed through the printing station (4) four times directly in succession and after each of the first three passes is turned over for the printing of a following image on the other side of the sheet than that on which the previous image was printed and the sheets, after the last pass, are collected in the correct orientation to form the book. 2. A device for performing the method according to claim 1, comprising a printing station, a conveyor path along the printing station (4), a sheet turn-over path (8) and a sheet discharge path (7) following the conveyor path, and a sheet deflector (9) which in a first position guides a sheet from the printing station (4) into the turn-over path (8) and, in a second position, guides the sheet from the printing station (4) into the discharge path (7), characterised in that first control means are provided which hold the deflector (9) in the first position during the first three consecutive passes of a sheet and in the second position during the following fourth pass and in that a time element is provided which so controls the time of passage of a sheet through the printing station (4) that on the first and fourth passes of a sheet an image is printed on a half of the sheet which, as considered in the direction of passage, is other than the half printed in the second and third passes of the sheet. 3. A device according to claim 2, comprising a document feeder for individually feeding originals in sheet form from a stack (20) to a scanning station (24) of the device, characterised in that the feeder comprises two conveyor means (21,22) which can each feed an original from a different side of the stack (20) to perform a cycle in which the said conveyor means (21,22) alternately feed two origi­ nals from one side of the stack and two originals from the other side of the stack to and through the scanning station (24). 4. A device according to claim 3, characterised in that a depo­ sit device (28,29) is provided for scanned originals, comprising two deposit plates (30,31), the originals fed from one side of the stack (20) being deposited on the one deposit plate and the originals fed from the other side of the stack (20) being deposited on the other deposit plate in the reverse orientation. 5. A device according to claim 3 or 4, characterised in that adjustment means are provided which can be set to the number of orig­ inals that the stack (20) contains and in that control means are provided which generate a first count signal corresponding to the next higher figure with respect to the set number, said figure being a multiple of four, in order to perform the said cycle a number of times corresponding to said figure, and which generate a second count signal corresponding to the difference between the said figure and the set number. 6. A device according to claim 5, characterised in that control means are provided which automatically keep one of the conveyor means (22) inoperative from the start of the first cycle for a number of times corresponding to the difference, the cycle sequence otherwise being the same. 7. A device according to any one of claims 2 to 6, characterised in that a holder (35) is provided in which the originals can be depo­ sited after the first scanning, said holder (35) being provided with a conveyor means (37) which can feed said originals one by one from the holder (35) to the scanning station (24) and back, and in that control means are provided to repeat this recycling until the number of scans for making the required number of copy sets has been per­ formed. 8. A device according to claim 6 and 7, characterised in that further control means are provided which automatically keep inopera­ tive that conveyor means (37) which can feed originals from the said holder (35), in accordance with the times in which the said one of the conveyor means (22) was kept inoperative, the cycle sequence otherwise being the same.

Inventors: STIENSTRA, JAN BONNE
Applicants: OCE-NEDERLAND B.V.
Application year: 1986
Main classification: G03G15
IPC codes: G03G21, B41J13, G03G15, B65H1, B65H83, B41F21