DUPLEX PRINTING SYSTEM FOR CUT SHEETS AND A METHOD THEREFORE

Abstract

The present invention relates to a printing system for cut sheets. The printing system comprises a control unit for controlling the printing of image data on a plurality of sheets which comprise at least one speciality sheet intended to be one-sided printed and at least one duplex sheet intended to be two-sided printed. The control unit schedules the plurality of sheets in a printing order. A paper path of the printing system comprises a duplex printing loop, a first turn station arranged in the duplex printing loop for turning a sheet of the plurality if both sides of the sheet are scheduled to be printed in two passes along a print engine arranged in the duplex printing loop and configured to dispose marking material on the sheets according to the image data, in two passes, one side per pass, and a second turn station arranged in an output section for turning the sheet before laying the sheet off in an output holder of the output section. Speciality sheets and simplex sheets in a duplex print job are treated in a special way to avoid productivity loss.

Claims

1. A printing system for cut sheets, the printing system comprising a control unit for controlling the printing of image data on a plurality of sheets comprising at least one speciality sheet intended to be one-sided printed and at least one duplex sheet intended to be two-sided printed, and for scheduling the plurality of sheets in a printing order, a paper path comprising a duplex printing loop, a first turn station arranged in the duplex printing loop for turning a sheet of the plurality if both sides of the sheet are scheduled to be printed in two passes along a print engine arranged in the duplex printing loop and configured to dispose marking material on the sheets according to the image data on one side per pass, wherein the speciality sheet has predetermined unexchangeable opposite edges, the control unit comprises a scheduler to schedule a sheet for a first pass along the print engine and for a second pass along the print engine by using the duplex printing loop and a logic module to determine whether or not the sheet is a speciality sheet, the printing system comprises a second turn station arranged in the paper path of the printing system near an inlet of the output section for turning the sheet before laying the sheet off in an output holder of the output section when activated, and the control unit is configured, for a sheet determined not to be a speciality sheet by means of the logic module, to activate the first turn station to turn the sheet after the first pass and before the second pass of the sheet along the print engine, and, for a sheet determined to be a speciality sheet by means of the logic module, to deactivate the first turn station as to behave as a pass-through for the sheet after the first pass and before the second pass of the sheet along the print engine.

2. A printing system according to claim 1, wherein the first turn station and the second turn station are arranged to turn a sheet in a feed direction such that a trailing edge of the sheet becomes a leading edge of the sheet.

3. A printing system according to claim 1, wherein the first turn station and the second turn station are arranged to turn a sheet in a direction perpendicular to the feed direction of sheets through the paper path such that a left edge of the sheet in the non-feed direction becomes a right edge of the sheet in the direction perpendicular to the feed direction.

4. A printing system according to claim 1, wherein the control unit is configured to schedule a simplex sheet intended to be printed on only one side for the first pass and/or for the second pass along the print engine as if the simplex sheet is a speciality sheet.

5. A printing system according to claim 4, wherein the print engine comprises an inkjet print head with a plurality of nozzles and the control unit comprises a spitting scheduler for keeping the plurality of nozzles fit, the spitting scheduler configured to prohibit a spitting action during the second pass along the print engine on a side of the simplex sheet which is intended to be printed upon and on a side of a speciality sheet which is intended to be printed upon.

6. A printing system according to claim 4, wherein the print engine comprises an inkjet print head with a plurality of nozzles and the control unit comprises a spitting scheduler for keeping the plurality of nozzles fit, the spitting scheduler configured to activate a spitting action during the first and the second pass along the print engine on a same side of the simplex sheet which is intended to be printed upon and on a same side of a speciality sheet which is intended to be printed upon.

7. A printing system according to claim 1, wherein the second turn station is part of the output section of the printing system.

8. A printing system according to claim 1, wherein the control unit is configured, for a sheet determined not to be a speciality sheet by means of the logic module, to activate the second turn station after the second pass of the sheet along the print engine and before the sheet is laid off in the output holder, and, for a sheet determined to be a speciality sheet by means of the logic module, to deactivate the second turn station as to behave as a pass-through for the sheet after the second pass of the sheet along the print engine and before the sheet is laid off in the output holder.

9. A printing system according to claim 1, wherein the control unit is configured, for a sheet determined to be a speciality sheet by means of the logic module, to activate the second turn station after the second pass of the sheet along the print engine and before the sheet is laid off in the output holder, and, for a sheet determined not to be a speciality sheet by means of the logic module, to deactivate the second turn station as to behave as a pass-through for the sheet after the second pass of the sheet along the print engine and before the sheet is laid off in the output holder.

10. A method for controlling the printing of image data by means of a printing system on a plurality of cut sheets comprising at least one speciality sheet intended to be one-sided printed and at least one duplex sheet intended to be two-sided printed, and for scheduling the plurality of sheets in a printing order, the printing system comprising a paper path with a duplex printing loop, a first turn station arranged in the duplex printing loop for turning a sheet of the plurality if both sides of the sheet are scheduled to be printed in two passes along a print engine arranged in the duplex printing loop and configured to dispose marking material on the sheets according to the image data on one side per pass, and a second turn station arranged in the paper path of the printing system near an inlet of an output section for turning the sheet before laying the sheet off in an output holder of the output section, wherein the speciality sheet has predetermined unexchangeable opposite edges, and wherein the method comprises the steps of scheduling a sheet for a first pass along the print engine and for a second pass along the print engine by using the duplex printing loop and determining whether or not the sheet is a speciality sheet, for a sheet determined not to be a speciality sheet, activating the first turn station to turn the sheet after the first pass and before the second pass of the sheet along the print engine, and, for a sheet determined to be a speciality sheet, deactivating the first turn station as to behave as a pass-through for the sheet after the first pass and before the second pass of the sheet along the print engine.

11. A software product comprising program code on a non-transitory computer-readable medium, wherein said program code, when loaded into a computer that is connected to a printing system causes the computer to act according to a method of claim 10.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Preferred embodiments will now be described in conjunction with the drawings, wherein:

[0025] FIG. 1 is a schematic view of a first embodiment of the printing system according to the present invention;

[0026] FIG. 2 is a schematic view of a second embodiment of the printing system according to the present invention;

[0027] FIG. 3 is a flow diagram of a first embodiment of the method according to the present invention; and

[0028] FIG. 4 is a flow diagram of a second embodiment of the method according to the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[0029] FIG. 1 shows schematically a first embodiment of a printing system 1 according to the present invention. The printing system 1, for purposes of explanation, is divided into an output section 5, a print engine and control section 3, a local user interface 7 and an input section 4. While a specific printing system is shown and described, the disclosed embodiments may be used with other types of printing system such as an ink jet printing system, an electrographic printing system, etc.

[0030] The output section 5 comprises a first output holder 52 for holding printed image receiving material, for example a plurality of sheets. The output section 5 may comprise a second output holder 55. The printed image receiving material is transported from the print engine and control section 3 via an inlet 53 to one of the output holders 52, 55 in the output section 5. When a stack ejection command is invoked by the control unit 37 for the first output holder 52, first guiding means 54 are activated in order to eject the plurality of sheets in the first output holder 52 outwards to a first external output holder 51. When a stack ejection command is invoked by the control unit 37 for the second output holder 55, second guiding means 56 are activated in order to eject the plurality of sheets in the second output holder 55 outwards to a second external output holder 57.

[0031] The output section 5 is digitally connected by means of a cable 60 to the print engine and control section 3 for bi-directional data signal transfer and/or data signal control.

[0032] The print engine and control section 3 comprises a print engine 31 and a control unit 37 for controlling the printing process and scheduling the plurality of sheets in a printing order before they are separated from input holders 44, 45, 46.

[0033] The control unit 37 is a computer, a server or a workstation, connected to the print engine 31 and connected to the digital environment of the printing system 1, for example a network N for transmitting a submitted print job to the printing system 1. In FIG. 1 the control unit 37 is positioned inside the print engine and control section 3, but the control unit 37 may also be at least partially positioned outside the print engine and control section 3 in connection with the network N in a workstation N1.

[0034] The control unit 37 comprises a print job receiving section 371 permitting a user to submit a print job to the printing system 1, the print job comprising image data to be printed on a plurality of sheets and a plurality of print job settings. The print job may be a duplex print job for duplex sheets to be printed on both sides of the sheet. The duplex print job may also comprise speciality sheets according to the print job settings, like tab sheets to discern chapters or provide other divisions of a document which is intended to be double-sided printed according to the print job settings.

[0035] The control unit 37 comprises a print job queue section 372 comprising a print job queue for print jobs submitted to the printing system 1 and scheduled to be printed.

[0036] The control unit 37 comprises a logic module 373 for determining whether or not the sheet is a speciality sheet which need not be turned by a first turn station 35A in the print engine and control section 3 and by the second turn station 38 near the outlet 53 of the output section 5. The logic module 373 unit may use information about the sheets derived from the print job properties per page of the print job, knowledge of the type of sheets provided in the input holders 44, 45, 46, and/or input from sensors (not shown) positioned in the input holders 44, 45, 46 and/or in the paper path which are able to sense the type of sheets. A print job property may be a print medium type property and additional information about the print medium type may be retrieved or derived from a media database available in memory of the control unit 37.

[0037] The control unit 37 comprises a sheet scheduling section 374 for determining for each of the plurality of sheets of the print jobs in the print job queue an entrance time in the paper path of the print engine and control section 3, especially an entrance time for the first pass and an entrance time for the second pass in the duplex printing loop in the paper path according to the present invention.

[0038] Sheets of media type material are located in the input section 4, marking material is located in a reservoir 39 near or in the print head or print assembly 31 of the print engine, or finishing material may be located near the print head or print assembly 31 of the print engine or located in the output section 5 (not shown).

[0039] The paper path comprises a plurality of paper path sections 32, 33, 34, 35 for transporting the image receiving material from an entry point 36 of the print engine and control section 3 along the print head or print assembly 31 to the inlet 53 of the output section 5. The paper path sections 32, 33, 34, 35 form a loop according to the present invention. The loop enables the printing of a duplex print job and/or a mix-plex job, i.e. a print job comprising a mix of sheets intended to be printed partially in a simplex mode—like speciality sheets and simplex sheets—and partially in a duplex mode—like duplex sheets. The paper path sections 32, 33, 34, 35 also define the feed direction of the sheets through the paper path of the printing system 1.

[0040] The print engine 31 is suitable for disposing marking material to the sheets. The print engine 31 comprises a print head or print assembly which is positioned near the paper path section 34. The print head or print assembly may be an inkjet print head, a direct imaging toner assembly or an indirect imaging toner assembly.

[0041] While a sheet is transported along the paper path section 34 in a first pass in the loop, the sheet receives the marking material through the print head or print assembly 31. Directly downstream of the print head or print assembly 31 a rotational functional component may be situated (not shown), for example, a fixation drum, a fixation belt, a fixation device, a drying device, a drying drum, a drying belt, a fusing device, a fusing belt, a fusing drum, a UV curing station, etc. A surface of the rotational functional component is configured to fix the marking material to the sheet or to dry the marking material on the sheet.

[0042] A next paper path section 32 is a split unit 32 for selecting a different subsequent paper path for simplex, duplex or mix-duplex printing of the image receiving material.

[0043] In case of duplex printing on a sheet, the sheet is transported along the loop via the first turn station 35A in order to turn the sheet for enabling printing on the other side of the sheet. In case of a speciality sheet in a mixed-plex print job as according to the present invention, the sheet is transported along the loop via the first turn station 35A which is deactivated in order to not turn the speciality sheet and to act as a pass-through for the speciality sheet.

[0044] The sheet is further transported along the paper path section 35 until it reaches a merging point 34A at which sheets entering the paper path section 34 from the entry point 36 interweave with the sheets coming from the paper path section 35. The sheets entering the paper path section 34 from the entry point 36 are starting their first pass along the print head or print assembly 31 in the duplex loop. The sheets coming from the paper path section 35 are starting their second pass along the print head or print assembly 31 in the duplex loop. When a sheet has passed the print head or print assembly 31 for the second time in the second pass, the sheet is further transported via the split unit 32 to the second turn station 38.

[0045] The second turn station 38 may be activated to turn a sheet before the sheet is guided to the inlet 53 of the output section 5.

[0046] In a first case (X1) of printing on a speciality sheet or a simplex sheet, the speciality sheet or the simplex sheet is transported via the split unit 32 to the second turn station 38 in order to pass-through the sheet instead of turning the sheet. In this first case the second turn station 38 is deactivated and acts as a pass-through for the speciality sheet to further transport the speciality sheet to the inlet 53 of the output section 5. In this first case the second turn station 38 is activated and turns a normal sheet to further transport the normal sheet to the inlet 53 of the output section 5.

[0047] In a second case (X2) of printing on a speciality sheet or a simplex sheet, the speciality sheet or the simplex sheet is transported via the split unit 32 to the second turn station 38 in order to turn the sheet instead of let the sheet pass through. In this case the second turn station 38 is activated and turns speciality sheet to further transport the speciality sheet to the inlet 53 of the output section 5. In this second case the second turn station 38 is deactivated and passes through a normal sheet to further transport the normal sheet to the inlet 53 of the output section 5.

[0048] In both the first and the second case the face orientation of the normal sheet and the speciality sheet in the output holder will be the same.

[0049] The input section 4 may comprise at least one input holder 44, 45, 46 for holding the image receiving material before transporting the sheets of image receiving material to the print engine and control section 3. Sheets of image receiving material are separated from the input holders 44, 45, 46 and guided from the input holders 44, 45, 46 by guiding means 42, 43, 47 to the entry point 36 for entrance in the print engine and control section 3. Each input holder 44, 45, 46 may be used for holding a different kind of image receiving material, i.e. sheets having different media properties like speciality sheets.

[0050] The local user interface 7 is suitable for displaying user interface windows for controlling the print job queue residing in the control unit 37. In another embodiment a computer N1 in the network N has a user interface for displaying and controlling the print job queue of the printing system 1.

[0051] FIG. 2 shows schematically a second embodiment of a printing system 2 according to the present invention. The printing system 2 only differs from the first embodiment in FIG. 1 by the arrangement in the printing system of the second turn station. While in printing system 1 in FIG. 1 the second turn station 38 is arranged in the print engine and control section 3 near the inlet 53 of the output section 5, the second turn station 58 in printing system 2 is arranged in the output section 5 near the inlet 53 of the output section 5.

[0052] The first embodiment of the printing system in FIG. 1 and the second embodiment of the printing system in FIG. 2 may be combined into another embodiment having two turn stations in the print engine and control section 3 as well as a turn station in the output section 5 of the printing system. When the output section 5 is an OEM finisher it may have a turn station inside according to a standard implementation of the OEM finisher.

[0053] FIG. 3 is a schematic view of the steps applied to a sheet guided along the paper path through the printing system 1 of FIG. 1 or the printing system 2 of FIG. 2 according to the first case (X1). A first stack 20 is provided with normal sheets in the input section 4 of the printing system 1,2. A second stack 21 is provided with speciality sheets in the input section 4 of the printing system 1,2. Sheets are separated 22 from the first stack and the second stack according to the printing order as determined by the scheduler of the control unit 37 of the printing system 1,2. The sheets are guided along the print engine for a first pass printing 23. In a next step 24 it is checked if the sheet is a duplex normal sheet, a speciality sheet and/or a normal simplex sheet, by means of the logic module 373.

[0054] If the sheet is a duplex normal sheet, the sheet is turned 25A in the first turn station 35A. Then the sheet is printed 26A upon in a second pass along the print engine. When printed on both sides the sheet is turned 27A again in the second turn station 38, 58 and transported to an output holder of the output section 5 and deposited 28—for example face-down—in the output holder.

[0055] If the sheet is a speciality sheet and/or a simplex sheet, the sheet is not turned 25B in the first turn station 35A. Then the sheet is guided along the print engine without printing 26B in a second pass. According to an embodiment also a spitting process for keeping nozzles of a print head fit, is halted during this second pass 26B and postponed until after the second pass 26B. According to an alternative embodiment the spitting process for keeping nozzles of a print head fit, is not halted during this second pass 26B and is also applied during the second pass 26B. The sheet is not turned 27B by the second turn station 38, 58 and transported to an output holder of the output section 5 and deposited 28 in the output holder, for example face-down.

[0056] FIG. 4 is a schematic view of the steps applied to a sheet guided along the paper path through the printing system 1 of FIG. 1 or the printing system 2 of FIG. 2 according to the second case (X2). The steps resemble the steps of FIG. 3 with the following differences.

[0057] If the sheet is a duplex normal sheet, the sheet is turned 25A in the first turn station 35A. Then the sheet is printed 26A upon in a second pass along the print engine. When printed on both sides the sheet is not turned 77A in the second turn station 38, 58 (pass through action) and transported to an output holder of the output section 5 and deposited 28—for example face-down—in the output holder.

[0058] If the sheet is a speciality sheet and/or a simplex sheet, the sheet is not turned 25B in the first turn station 35A. Then the sheet is guided along the print engine without printing 26B in a second pass. According to an embodiment also a spitting process for keeping nozzles of a print head fit, is halted during this second pass 26B and postponed until after the second pass 26B. According to an alternative embodiment the spitting process for keeping nozzles of a print head fit, is not halted during this second pass 26B and is also applied during the second pass 26B. The sheet is turned 77B by the second turn station 38, 58 and transported to an output holder of the output section 5 and deposited 28 in the output holder, for example face-down.

[0059] In case that the speciality sheet and/or the simplex sheet needs to be printed on the front side of the sheet a selection can be made to print on the sheet during the first pass along the print engine or during the second pass along the print engine.

[0060] A speciality sheet may be a tab sheet, a pre-printed sheet, a pre-punched sheet, a pre-perforated sheet, a self-adhesive sheet, a sheet having a front side and a back side which have a different media structure like one-sided coated sheets or one-sided colored sheets. A sheet having a side for which it is prohibited to touch a heated fusing device, a heated fixation device, a drying device and/or a UV curing device may also be classified as a speciality sheet.

[0061] Opposite edges of such a speciality sheet are unexchangeable and predetermined and should not be changed during the passes in the printing system which is assured by the present invention. The opposite edges may be a leading and trailing edge of the speciality sheet in the feed direction through the paper path or a left and right edge of the speciality sheet in a direction perpendicular to the feed direction.

[0062] The described embodiments of the printing system according to the present invention may be varied upon and/or combined according to skills of a skilled person in the art. The described embodiments of the method according to the present invention may be varied upon and/or combined according to the skills of a skilled person in the art. The skilled person will recognize that other embodiments are possible within the scope of the appended claims.