EP1488289A1

EP1488289A1 - Method and device for printing individual sheets with an inverter device

Info

Publication number: EP1488289A1
Application number: EP03718702A
Authority: EP
Inventors: Hans Manzer
Original assignee: Oce Printing Systems GmbH and Co KG
Current assignee: Canon Production Printing Germany GmbH and Co KG
Priority date: 2002-03-22
Filing date: 2003-03-21
Publication date: 2004-12-22
Anticipated expiration: 2023-03-21
Also published as: DE50313014D1; JP2005527845A; EP1488289B1; US7636534B2; DE10212840A1; US20050175384A1; WO2003081343A1

Abstract

An electrographic printing device, especially a printer or a copier, comprising a printing unit (50) which is located opposite a guide track (54) and which prints the side of a respective single sheet facing it. An inverter device (52) inverts single sheets (18) that have been fed after a first printing process and guides them to the printing unit (50) so that they can be printed on the other side. The printing unit (50) contains at least one printing group (10) comprising at least two exposure units (40,60), at least two charging corona devices (38,44) and at least two developer stations (42,48). A single rotation of the intermediate carrier results in the production of two latent images which are successively inked with toner by the two developer stations (42, 48).

Description

Method and device for printing single sheets. with a turning device

The invention relates to an electrographic printing device, in particular a printer or copier, in which at least one printing unit is used which contains at least two exposure units, at least two charging corona devices and at least two developer stations, which are arranged along the circumference of a toner intermediate carrier. The invention further relates to a method for printing.

In a conventional printing device, an intermediate toner carrier is applied using an electrographic process, e.g. latent light is applied by exposing a photoconductor or by magnetizing a magnetically sensitive layer. According to the image-like distribution of the electrical charges or the magnetic field lines, toner is deposited on the latent image. On a carrier material, e.g. a paper web, the toner is then transferred to the transfer location. The toner image on the carrier material is fixed later.

Modern printing technology demands that a single device prints the carrier material on both sides at high speed. This mode of operation is commonly referred to as duplex printing. In addition, the operating mode "spot color printing" or "two-color printing" is required, in which two-color printing is carried out on both sides of the carrier material. There is also a need for full-color printing with the four process colors "yellow, magenta, cyan and black". In order to implement the duplex printing mode, for example, it is known to print a continuous carrier web first on one side, then the carrier web The transport path of the carrier web in the printer and in the required web turning device is relatively long and requires a complicated and also prone to failure transport device for the carrier material.

A further disadvantage is that the toner image which has not yet been fixed on one side of the carrier web can be blurred during transport and the print quality is thus reduced or rejects are produced. In order to avoid this, the toner image can be temporarily fixed, but this increases the technical outlay. Because of the long transport route between the first transfer printing point for the first transfer printing of a toner image and the second transfer printing point, the maintenance of a high accuracy of fit of the carrier web can only be guaranteed with great technical effort.

From US-A-6, 141, 523 (corresponding to the parallel WO 98/27466) by the same applicant, an electrographic printing device is known which contains two identical printing units, the transfer printing points of which are arranged opposite one another. A continuous carrier web is passed between the two printing units and the front and back of the carrier web are printed simultaneously. The printing units can each contain several exposure units and several developer stations, so that multicolor printing can be realized on each side of the continuous carrier web. The aforementioned document is hereby incorporated by reference into the disclosure content of the present application.

An electrostatic printer is known from EP 0 629 931 AI (applicant: XEIKON), in which a continuous carrier web is passed in the vertical direction between a large number of toner image carriers. Each toner image carrier has a toner image forming device. The toner is transferred from the toner image carrier to the carrier web at one transfer printing point. By arranging toner image Duplex printing with different toner colors is possible sluggishly along the vertical carrier web.

A printer is also known from EP 0 433 444 B1 (applicant: Eastman Kodak Company), in which a plurality of developer stations are arranged along a photoconductor belt as a toner image carrier. Each developer station can color the charge image generated by an exposure station with toner of a predetermined color. The toner image generated on the photoconductor belt is then transferred to the carrier material at a single transfer printing point.

From WO 98/18052 by the same applicant, a printing device with two identical printing units is known, to which single sheets are fed via a common input. The single sheets are fed to the two printing units in the printing device via guide tracks in such a way that both the front side and the back side of the single sheets are printed in a single pass of the single sheets through the printing device. For this purpose, the transport paths for the single sheets are connected to two rings via connecting paths. Each ring contains a printing unit. The single sheets can be fed to one ring or the other ring and can also run through the two rings one after the other, whereby the individual sheets can optionally be turned. Turning devices are also described in this document. This document is also incorporated by reference into the disclosure content of the present patent application.

A color printer is known from US-A-5, 526, 107, which contains a printing unit with a printing roller. The printing roller prints an image at one first transfer location on one side of the sheet and during further transport the same printing roller prints an image at the second transfer location opposite the first transfer location. The sheet is turned during transport. A tandem development system is known from Xerox Disclosure Journal 22, No. 4, pp. 197-200. To print a colored image, toner images are successively superimposed on a ribbon-shaped image carrier. These superimposed toner images are transferred to a carrier material.

As a further prior art reference is made to WO 98/27465, DE-A-39 06 60, DE-A-39 35 231 and WO 99/09459.

It is an object of the invention to provide a printing device and a method which allow duplex printing to be carried out with one color or a plurality of colors with high economy.

This object is achieved for a printing device by the features of claim 1.

According to the invention, single sheets are used as the carrier material. With the help of such single sheets, a high degree of flexibility in print jobs can be achieved. For example, with the help of single sheets, quickly changing jobs can be carried out in a simple manner and different paper qualities, different print formats and also different carrier materials can be used. The rejects that occur with continuous webs, also known as waste, are completely avoided.

According to the invention, a turning device is provided which turns the single sheets after a first printing operation and feeds the printing unit again for printing on the other side. Due to the use of single sheets, this turning device can be arranged relatively close to the printing unit, which results in a compact construction. The printing unit contains at least one printing unit, which in turn contains at least two exposure units, at least two charging corona devices and at least two developer stations. - -

holds, which are arranged along the circumference of the intermediate toner carrier. In this way, both single-color printing and multi-color printing can be realized on both sides of the single sheets.

An endless toner carrier belt, along the circumference of which the image-forming devices are arranged, is preferably used as the intermediate toner carrier. Because of the possible arrangement of the toner carrier tape as an elongated loop, a compact construction for the entire printing device can also be realized here.

According to a further aspect of the invention, a method is specified with the features of claim 14. The advantages that can be achieved with this method correspond to those in the printing device described.

For a better understanding of the present invention, reference is made below to the preferred exemplary embodiments illustrated in the drawings, which are described using specific terminology. However, it should be pointed out that the scope of the invention is not intended to be limited thereby, since such changes and further modifications to the devices and / or the methods shown, as well as such further applications of the principle of the invention, are regarded as the current current or future specialist knowledge of a competent expert become.

In the drawings for the embodiments shows

FIG. 1 shows a typical structure of a printing group with two developer stations,

FIG. 2 shows a basic illustration of an exemplary embodiment of the invention with a printing device that contains a printing unit and with a turning device, and

Figure 3 shows an example with two printing units.

In Figure 1, a printing unit 10 is shown schematically, which can be used in a printing unit as described below. The printing unit 10 has a photoconductor belt 12, the outer circumferential surface of which can be charged with latent charge images, as is known per se from electrophotography. The photoconductor belt 12 is guided past a transfer printing location 16 in the direction of arrow 14 in order to transfer a toner image onto a single sheet 18. Arranged opposite a transfer roller 20 is a transfer printing corotron 22, which deposits the toner particles on the photoconductor belt 12 by the action of an electrostatic force field on the surface of the single sheet 18, so that a toner image which can still be blurred is formed on the single sheet 18.

As seen in the transport direction 24 of the single sheet 18, the transfer printing corotron 22 is preceded by a conditioning corotron 26, which sets the single sheet 18 in a defined electrostatic initial state.

Arranged opposite the transfer roller 20 is a deflection roller 28 which deflects the photoconductor track 12. The photoconductor track 12 is designed as an elongated loop, the longitudinal axis of which runs essentially vertically. This makes it possible to arrange the units necessary for the generation of the toner image along this longitudinal axis on both sides of the photoconductor 12 in a space-saving manner. The length of the photoconductor belt 12 is selected so that there is sufficient space for the units to be described.

As can be seen in FIG. 1, the photoconductor belt 12 is guided on a plurality of rollers 30. A clamping element 32 with a roller can be switched in two positions. In the shown Position, the photoconductor belt 12 is tensioned. In the other position (not shown), the mechanical tension of the photoconductor belt 12 is reduced. In this position, the photoconductor belt 12 can be exchanged or maintenance work can be carried out.

A two-tone toner image can be generated on the photoconductor belt 12 with the aid of the printing unit 10. Viewed in the direction of rotation of the photoconductor belt 12, a cleaning corotron 34 and a cleaning station 36 are arranged after the transfer printing corotron 22. Both units have the function of removing the residual toner which is still present at the transfer printing location 16 from the photoconductor belt 12 in order to bring it into a defined initial state for the subsequent exposure and renewed toner absorption. To generate a first toner image, a first charging corotron 38 is provided, which generates a defined state of charge on the surface of the photoconductor belt 12. Subsequently, the charge image is influenced in accordance with the print image to be printed with the aid of a first character generator 40, for example with the aid of a laser or with the aid of LEDs or an LED comb. The charge image is then colored using a first developer station 42 with a toner of a first color.

In the further course, the photoconductor belt 12 is guided past a second charging corotron 44, a second character generator 46 and a second developer station 48. When the photoconductor belt 12 rotates, a first latent charge image is generated by the first charging corotron 38 and the first character generator 40 and a first toner image on the photoconductor belt 12 by the first developer station 42. Subsequently, the second character generator 46 in combination with the second charging corotron 44 generates a second latent charge image on the developed first charge image, which is colored by the second developer station 48 with a toner of a second color. Thus, the first th toner image on the photoconductor belt 12 overlaid a second toner image. The resulting toner image is two-tone and is transferred to the surface of the single sheet 18 at the transfer printing location 16. In this way, a two-color toner image can be printed at the transfer location 16 at high printing speed. It is also possible to arrange a further charging corotron, a further exposure unit and a further developer station, preferably with a further toner color, along the photoconductor belt 12 in order to superimpose more than two toner images on the photoconductor belt 12 which then jointly onto the Single sheet 18 are transferred.

Figure 2 shows an embodiment of the printing device according to the invention. The printing device has a printing unit 50 which contains a printing unit 10 according to FIG. 1. This printing unit 10 prints the single sheet 18 in the state shown. This single sheet 18 is moved along a guideway 54 e.g. promoted with the help of controlled roller drives. In the operating mode "simplex operation", in which the single sheets 18 are printed on one side with the printing unit 10 in one or more colors, these single sheets 18 run in a straight path along the guideway 54.

In a "duplex operation", in which the single sheets 18 are printed on both sides in one or more colors, these single sheets 18 pass through a turning device 52 which turns the single sheets 18 after the first printing process on the printing unit 10 and the printing unit 10 for printing on the other side The turning device 52 contains a switch 55 connected downstream of the printing unit 50 as well as a switch 56 connected upstream of the printing unit 50 and a return path 58 along which the individual sheets 18 are conveyed.

The downstream switch 55 has three operating states. In the first operating state, the switch 55 allows a single sheet 18 arriving from the printing unit 50 to pass undeflected, so that this single sheet 18 is conveyed straight along the guideway 54. In a second operating position, the switch 55 deflects the single sheets 18 arriving from the printing unit 50 into the return path 58. This return path 58 conveys the single sheets to the upstream switch 56. This switch 56 is designed as a turning switch. The side printed by the printing unit 50 lies at the top when conveyed along the return path 58. The single sheet 18 is first transported through the switch 56 in the direction of the arrow 60 for a predetermined turning distance, ie the switch 56 conveys the single sheet guided over the return track 58 into the guide track 54. Then the transport direction for the single sheet now located in the guide track 54 18 reversed, ie the transport direction is now opposite to the transport direction 60. The switch 56 is then switched so that this single sheet 18 is transported straight on, so that it can be fed again to the printing unit 50 for printing. The switches 55 and 56 thus work together in such a way that the single sheet 18, once printed, can be fed back along the return path 58 and can be fed again along the guide path 54 to the same printing unit 50 and can then be led out of the printing device after being printed again.

The switches 55 and 56 can also cooperate in a further mode of operation, the “bypass mode”, in such a way that the individual sheets 18 arriving along the guide track 54 are conveyed via the switch 56 to the return track 58 and are guided by the switch 55 into the guide track 54. In this mode of operation, the individual sheets 18 are thus conveyed in the printing device, omitting the printing unit 50, in order, for example, to transport unprinted intermediate sheets through the printing device.

Figure 3 shows a further variant. The printing unit 50 here contains two printing units 10 of the same type, which are arranged in series one after the other. Each printing unit 10 prints two beige toner images. In this way, a four-color duplex operation can be realized, ie the front and back of the single sheets can be printed with four different-colored image patterns. For example, full-color printing with the four process colors, “yellow, magenta, cyan and black” is possible in this way, each of the two printing units 10 printing two process colors.

Downstream of the printing unit 50 is a fixing station 62, which fixes the multicolored toner image printed by the printing unit 50. For example, fixation can be carried out with the aid of rollers 64, 66 under pressure and heating temperature. Alternatively, an infrared radiation fixation or a combination of radiation fixation and roller fixation can take place. After the toner image has been fixed, the single sheets are turned in the turning device 52 and fed again to the printing unit 50 in order to print the back of the single sheets in multicolor printing. A fixing station 62, which is arranged between the printing unit 50 and the downstream switch 55, is also required in the example according to FIG. 2.

Numerous variants are possible. Thus, the printing unit 10 can also work according to a different method than the electrostatic imaging method described, e.g. using a magnetic process. In addition to a photoconductor belt 12, a photoconductor drum can also be used as the intermediate toner carrier.

Although in the drawings and in the foregoing description preferred embodiments shown and de ^¬ described fitted, this should be an example as pure and the invention are not restrictive. It is pointed out that only the preferred exemplary embodiments are shown and described and that all changes and modifications which are presently and in the future within the scope of the invention are to be protected. LIST OF REFERENCE NUMBERS

10 printing unit 12 photoconductor tape

14 arrow

16 transfer point

18 single sheets

20 transfer roller 22 transfer corotron

24 Transport direction

26 conditioning corotron

28 deflection roller

30 rollers 32 clamping element

34 Cleaning corotron

36 cleaning station

38 First loading corotron

40 First character generator 42 First developer station

44 Second loading corotron

46 Second character generator

48 Second developer station

50 printing unit 52 turning device

54 guideway

55 Downstream switch

56 Upstream switch 58 Return path 60 Direction arrow

Claims

Expectations :

1. electrographic printing device, in particular printer or copier,

in which single sheets (18) of a print carrier are transported along a guideway (54),

a printing unit (50) opposite the guideway (54) prints the side of the respective single sheet (18) facing it,

a turning device (52) is provided, which turns the single sheets (18) after a first printing operation and feeds the printing unit (50) again for printing on the other side,

the printing unit (50) contains at least one printing unit (10) which contains at least two exposure units (40, 46), at least two charging corona devices (38, 44) and at least two developer stations (42, 48), which run along the circumference of a toner intermediate carrier (12) are arranged,

and in which the exposure units (40, 46) generate two latent images in a single revolution of the intermediate carrier (12), which are successively colored with toner by the two developer stations (42, 48).

2. Printing device according to claim 1, wherein the developer stations (42, 48) have different colored toners.

3. Printing device according to claim 1 or 2, wherein the intermediate carrier is a toner carrier tape (12), preferably a photoconductor tape (12).

4. Printing device according to one of the preceding claims, in which, when the intermediate carrier (12) rotates with the aid of the first charging corona device (38) and the first exposure unit (40), a first latent charge image is generated which is generated by the first developer station (42 ) is colored with toner of a first color,

then the second charging corona device (44) and the second exposure unit (46) generate a second latent charge image which is superimposed on the colored first charge image,

and wherein the second charge image is colored by the second developer station (48) with a toner of a second color.

5. Printing device according to one of the preceding claims, in which the printing unit (50) contains at least two printing units (10), to which the individual sheets (18) are fed directly in succession and which in turn print two different-colored printed images on the same side of the same single sheet (18) ,

6. Printing device according to claim 5, wherein the printing units (10) are of the same type, but use differently colored toner.

7. Printing device according to claim 5 or 6, in which each printing unit uses two toners, the colors of which are selected from the process colors yellow, magenta, cyan and black for full-color printing.

8. Printing device according to one of the preceding claims, wherein the turning device (52) contains a switch (55) connected downstream of the printing unit (50), a return path (58) and a switch (56) connected upstream of the printing unit (50).

9. Printing device according to claim 8, wherein the downstream switch (55) in a first operating position passes single sheets (18) without deflection.

10. Printing device according to one of claims 8 or 9, in which the downstream switch (55) in a second operating position directs the individual sheets (18) arriving from the printing unit (50) into the return path (58).

11. Printing device according to one of claims 8 to 10, wherein the downstream switch (55) conveys the individual sheets (18) arriving from the return path (58) into the guide path (54).

12. Printing device according to one of claims 8 to 11, wherein the upstream switch (56) in the turning operating position a single sheet (18) arriving from the return path (58) by a predetermined turning distance into the guide path (54) against the normal conveying direction (24) conveys the single sheets (18), and the upstream switch (56) then conveys the single sheet (18) along the guideway (24) in the direction of the printing unit (50).

13. Printing device according to one of claims 8 to 12, wherein the upstream switch (56) directs incoming single sheets (18) into the return path (58) which feeds the single sheets (18) to the downstream switch (55).

14. method of printing,

in which single sheets (18) of a print carrier are transported along a guideway (54), a printing unit (50) opposite the guideway (54) prints the side of the respective single sheet (18) facing it,

15. The method according to claim 14, wherein the intermediate carrier is an endless toner carrier belt (12), preferably a photoconductor belt (12).

16. The method according to any one of claims 14 or 15, wherein when the intermediate carrier (12) rotates with the aid of the first charging corona device (38) and the first exposure unit (40), a first latent charge image is generated, which is generated by the first developer station (42 ) is colored with toner of a first color,

then the second charging corona device (44) and the second exposure unit (46) generate a second latent charge image which is superimposed on the colored first charge image, and wherein the second charge image is colored by the second developer station (48) with a toner of a second color.

17. The method according to any one of the preceding claims, wherein the printing unit (50) contains at least two printing units (10), to which the individual sheets (18) are fed directly in succession and which print two different-colored print images in succession on the same side of the same single sheet (18) ,

18. The method according to claim 17, wherein the printing units (10) are of the same type, but use differently colored toner.

19. The method according to claim 17 or 18, wherein each printing unit uses two toners, the colors of which are selected from the process colors yellow, magenta, cyan and black for full-color printing.

20. The method according to any one of the preceding claims, wherein the turning device (52) contains a switch (55) connected downstream of the printing unit (50), a return path (58) and a switch (56) connected upstream of the printing unit (50).

21. The method according to claim 20, wherein the downstream switch (55) in a first operating position passes single sheets (18) without deflection.

22. The method according to any one of claims 20 or 21, wherein the downstream switch (55) in a second operating position directs the individual sheets (18) arriving from the printing unit (50) into the return path (58).

23. The method according to any one of claims 20 to 22, wherein the downstream switch (55) from the return path (58) incoming single sheets (18) in the guideway (54) promotes.

24. The method according to any one of claims 20 to 23, wherein the upstream switch (56) in the turning operating position a single sheet (18) arriving from the return path (58) by a predetermined turning distance into the guide path (54) against the normal conveying direction (24) conveys the single sheets (18), and the upstream switch (56) then conveys the single sheet (18) along the guideway (24) in the direction of the printing unit (50).

25. The method according to any one of claims 20 to 24, wherein the upstream switch (56) directs incoming single sheets (18) into the return path (58), which feeds the single sheets (18) to the downstream turnout (55).