EP0517700B1 - Modular electrophotographic printer - Google Patents

Abstract

An electrophotographic printer, in particular for printing single sheets, contains one or more printing modules (10/1 to 10/4) in which the processing means for carrying out the electrophotographic process are structurally assembled. The printing modules are designed as separate components which can be fastened in a housing of the printer and have fitting elements (32, 33) which enable the printing modules (10/1 to 10/4) to fit snugly side by side in the housing (34). Each printing module (10/1 to 10/4) contains an intermediate carrier (14) with associated fixing elements for transferring a toner image produced on a photoconductor drum (11) onto a recording carrier (15) and fixing it on the recording carrier. The printer can be upgraded from a one-colour simplex printer to a multicolour duplex printer by a multiple arrangement of the printing modules.

Description

The invention relates to an electrophotographic printing device according to the preamble of claim 1.

Such electrophotographic printing devices are e.g. B. from the publications US-A-2 990 278 or GB-A-2 040 226 known.

With the help of an exposure device, a charge image is generated on a photoconductor and is fed to a developer station. The charge image developed is then lifted from an endless belt from the photoconductor with the aid of an intermediate carrier and transferred to a recording medium. In order to be able to fix the toner image on the recording medium, the toner image on the intermediate carrier is heated with the aid of a heating device and the heated toner image is applied to the recording medium by pressure and heat via a roller arrangement. After the transfer of the toner image onto the recording medium, the intermediate carrier is cleaned of adhering toner in a cleaning station.

Furthermore, EP-B1-0 154 695 discloses a non-mechanical printing or copying device for multicolor and reverse side printing, which consists of several devices arranged one behind the other, which are operated simultaneously, the recording medium emerging from the paper exit area of the preceding device being the paper entry area of the following device. A switchable deflection device for the paper web is arranged between the devices. The individual devices can be constructed in a modular manner with fixing modules and printing unit modules that can be combined with one another, with at least one fixing module following after several printing unit modules.

Such a printer or copier takes up a lot of space and requires a great deal of construction.

Depending on the field of application, electrophotographic printing devices are designed differently. In connection with central EDP systems, mainly electrophotographic printing devices are used which work with continuous paper and which print with one or two colors. Electrophotographic printing devices working with single sheets serve as printing devices for personal computers or decentralized EDP devices. They can be designed as single-sided printing machines or as duplex printing machines. Duplex printing machines are used for double-sided printing of the single sheet.

Depending on the desired scope of performance of the printing devices, it was previously common to provide different devices with different equipment features. A later expansion of the existing, used devices was not possible.

This prevents flexible use of the printing devices and increases the cost of manufacture and maintenance.

The object of the invention is therefore to provide an electrophotographic printing device of the type mentioned at the outset which is simple and reliable and can be flexibly adapted to changing performance requirements.

Another object of the invention is to design the printing device in such a way that the user can further expand the printing device without difficulty.

The printing device should be suitable for both single-color and multi-color printing.

This object is achieved in a printing device of the type mentioned at the outset according to the characterizing part of the first claim.

Advantageous embodiments of the invention are characterized in the subclaims.

The electrophotographic printing device, which is preferably designed as a single-sheet printing device, is suitable for black-and-white, color, simplex or duplex printing through the use of printing modules with intermediate supports in conjunction with corresponding paper guide units.

Even a device already in use by the user can be removed without difficulty. Because of the cascadable structure, it can be expanded from a single-color press to a multi-color press. The use of the same structural units simplifies manufacture and simplifies maintenance. The use of a band-shaped intermediate carrier allows small deflection angles at the printing point, which is advantageous for the fixing process and for the subsequent further paper movement.

The printing device is also particularly suitable for multi-color printing. The recording medium is less stressed or deformed than conventional electrophotographic printing devices with printing or heat-fixing units, which is of considerable advantage for the registration accuracy in the subsequent printing units. The accuracy of fit in duplex printing and especially in multi-color printing is increased.

• Figur 1 eine schematische Schnittdarstellung einer elektrofotografischen Druckeinrichtung für Zweifarben-Simplex/Duplexdruck
• Figur 2 eine schematische Schnittdarstellung einer elektrofotografischen Druckeinrichtung mit Zwischenträger für Vierfarben-Simplexdruck.

Embodiments of the invention are shown in the drawings and are described in more detail below, for example. Show it

• Figure 1 is a schematic sectional view of an electrophotographic printing device for two-color simplex / duplex printing
• Figure 2 is a schematic sectional view of an electrophotographic printing device with an intermediate support for four-color simplex printing.

The electrophotographic printing device shown in FIG. 1 is used for printing single sheets in two-color simplex / duplex printing. It contains two printing modules 10/1 and 10/2, on which the process means for printing the single sheets are summarized. These process means comprise: an electric motor-driven photoconductor drum 11 with associated exposure device 12 for generating a charge image on the surface of the photoconductor drum; a developer station 13 for inking the charge image with toner; an endless, belt-shaped intermediate carrier 14 for transferring a toner image formed by coloring the charge image on the photoconductor drum onto the surface of a single sheet; Fixing agents for the heat and pressure fixing of the toner image on the single sheet described later and cleaning agents for cleaning the intermediate carrier 14 and the photoconductor 11. The cleaning agents for the photoconductor consist of a nonwoven belt 16 and a brush cleaning station 17 working with negative pressure Corona discharge and charging devices 18 are also provided in the photoconductor drum. An LED character generator is used as the exposure device 12, which extends over the entire length of the photoconductor drum 11 and which is controlled as a function of the character to generate the charge image on the photoconductor drum 11.

The intermediate carrier 14 arranged for transferring the toner image onto the single sheet consists of one on deflection rollers 19 Mounted rubber or silicone tape, which is deflected in the area of the transfer location 20 and touches the surface of the photoconductor drum 12 by means of the deflection roller 19/1 which can be swiveled in and out via a motorized device ME. By appropriate heating of the intermediate carrier or the photoconductor drum, the temperature at the transfer printing location 20 is set so that the toner of the toner image is in a doughy state and is transferred to the intermediate carrier 14 by adhesive force. In a downstream heating station 21 with heating elements arranged therein, the toner image located on the intermediate carrier 14 is heated so strongly that the toner is almost liquefied, but is still in the solid state. The almost liquid toner image is transferred to the single sheet at a fixed transfer printing point 22 for the single sheet. This transfer printing point 22 contains a roller arrangement consisting of the deflection roller 19/3 and a counter roller 23, between which the single sheet is passed and fixed on the single sheet by heat and pressure. The single sheet is preheated in the paper guide channel on the side to be printed, for example via a heating device WE. This provides better fixability of the record carrier. With multiple printing stations, the heating in the first station 10/1 is sufficient. The warmed up recording medium stores the heat for the subsequent fixing processes. However, depending on the recording medium, several heating stations (heating systems WE) may also be required. The intermediate carrier 14 is then cleaned in a cleaning station 24. For this purpose, the cleaning station 24 contains a cleaning roller 25 with an associated pressure roller 26. The cleaning roller 25 mechanically or chemically removes toner residues from the intermediate carrier 14, which are then stripped from the cleaning roller 25 on a suitably designed flow element 27 or in a cleaning bath.

A combined transport and temperature stabilization unit 28 arranged downstream of the intermediate carrier 14 of the cleaning station 24 contains electrically heated or cooled rollers 29 which set the intermediate carrier 14 to a constant temperature. The photoconductor drum 11 can contain an electrically heated heating element 30 as an additional heating device for heating the transfer printing location 20.

When using photoconductor drums 11 made of amorphous silicon, this drum heating can be omitted.

All the process means described above are arranged on chassis elements 31 via corresponding bearing or fastening means. These consist of die-cast aluminum parts which have fitting surfaces 32 on one side and fitting elements 33 on the other side. To fasten the printing modules 10 in a housing 34 of the printing device 31 support feet 35 are formed on the lower edge of the chassis elements with corresponding elongated holes for receiving fastening elements 36 in the form of clamping screws.

The housing 34 has a plurality of support rails 37 on the bottom. On the support rails 37, support tables 38 are fastened via fastening elements 39. The similarly designed support tables 38 have slot-like fastening openings on their surface for receiving the clamping screws 36, the pressure modules, wherein between the support feet 35 and the support tables 38 elastic elements 40, z. B. are arranged from rubber, which ensure a floating mounting of the pressure module on the support tables 38.

A central supply unit for the printing modules 10 can be arranged under the support tables 37. This central supply unit, not shown here, can have corresponding vacuum-generating devices for the cleaning stations, Contain toner and disposal containers, magnetic storage media with floppy disk etc. and a central control for the printing device (controller).

The housing 34 also serves to receive a paper guide channel 41 arranged above the printing modules with paper rollers 42 as paper transport elements. At the beginning of the paper guide channel 41 there are storage containers 43 for receiving the single sheets 15, at the exit of the paper guide channel 41 there are corresponding receiving containers 44 for the single sheets 15. There is also a separation device 49 e.g. arranged in the form of a paper cutter or tear device, which can serve to separate edge perforations of the record carrier.

In order to enable both simplex and duplex printing, there is a turning device 45 above the paper guide channel 41, which can be designed in accordance with WO-A-89/08282. In the usual way, it contains a return channel 46, turning channels 47 and paper rollers as paper transport elements. The entire turning device can also be arranged in mirror image for reasons of paper flow.

The paper channel 41 is subdivided into individual channels 41/1 and 41/2 according to the number of the arranged printing modules 10, which can be fastened separately and releasably on the housing 34 by means of corresponding fastening elements. The transfer printing points 22 for the individual sheets of the printing modules 10 protrude into corresponding gaps between the individual channels 41/1 and 41/2.

As described at the beginning, the printing modules contain fitting surfaces 32 and fitting elements 33 for mutual matching.

The mating surface of the one printing module 10/2 is based on the mating elements 33 of the other printing module 10/1. Allows this is supported by the floating fastening of the pressure module of the pressure modules 10 on the support tables 38 via the elastic elements 40, with a pre-adjustment taking place via the clamping screws 36. The mating surfaces allow an exact assignment of the print modules to each other regardless of the number of print modules used. This results in a precisely defined distance between the transfer printing points 22 of the printing modules and thus a highly precise paper guide. The distance between the transfer printing points 22 can serve as a reference variable for controlling the individual sheets during transport through the paper guide channel 41.

If, as shown in FIG. 1, the printing device is designed as a two-color simplex duplex device, the printing modules 10/1 and 10/2 contain differently colored toners. The single sheet drawn off from the receptacle 44 is first printed with a first color on the underside of the printing module 10/1. The second printing module 10/2 superimposes a second different-colored print image on this print image. Then the single sheet is returned via the return channel 46 to the printing module 10/1, turned over a turning channel 47 and printed in the order described on its other side again via the printing modules 10/1 and 10/2 and stored in the storage container 44.

If the reverse side of the single sheet is only to be printed in one color, it is already turned in the reversing channel 47/2 assigned to the printing module 10/2 and fed again to the printing module 10/2. One or two-color simplex printing is also possible without using the turning device.

The two-color simplex duplex printing device described with reference to FIG. 1 can easily be expanded to a four-color simplex printing device according to FIG. 2 due to the multiple arrangement of the printing modules. It is alone for this necessary to attach additional support tables 38 to the correspondingly lengthened support rails 37, in order to thereby expand the receiving area for the printing modules. Additional printing modules 10/3 and 10/4 are then attached to the additional support tables in such a way that the printing modules are mutually supported via their mating surfaces 32 and mating elements 33. Additional individual paper guide channels 41/3 and 41/4 can then be arranged between the transfer printing points 22 of the printing modules in the manner described. Due to the exact position assignment of the printing modules 10/1 to 10/4 to each other and the thus defined distance of the transfer printing points 22, it is possible to adjust the position of the individual channels 41/1 to 41/4 according to the respective printing modules 10/1 to 10/4 . The housing 34 itself can be extended by inserting intermediate pieces or by simply coupling two housing parts apart. It is advantageous to subdivide the housing elements in such a way that fixed housing elements are assigned to the storage containers and the storage containers. This makes it easier to insert intermediate pieces.

The invention has been described above with reference to printing devices which work with single sheets. However, it is also possible to use continuous paper instead of single sheets, e.g. B. prefolded continuous paper. Instead of the storage container 43, a storage table would then have to be arranged for receiving a storage stack, and the storage container would have to be replaced by a stacking table.

The use of a single printing module with a turning device is also possible if, for. B. the printing device should be designed as a single-color duplex printing device.

Claims (9)

1. Electrophotographic printer with a housing (34) and with process means for printing recording carriers (15), the process means comprising:

   - a photoconductor (11) with associated exposure device for producing charge images on the photoconductor,

   - a developer station (13) for inking the charge image with toner,

   - a continuous, belt-shaped intermediate carrier (14) for transferring toner images which have been produced by inking the charge image onto the recording carrier (15),

   - fixing means (23, 21, 30) for fixing the toner image onto the recording carrier (15) by pressure or heat and

   - cleaning means (24, 17) for cleaning the intermediate carrier and the photoconductor,

   characterised in that the process means (11, 12, 13, 14, 16, 17, 18) are constructionally combined to form a printing module (10/1 - 10/4) which is designed as a separate constructional unit for mounting in the housing (34) and in that means (32, 33, 35, 40, 38, 37) are provided on the housing and on the printing module for arranging next to one another a variably selectable number of further printing modules (10/1 - 10/4) along a common transport channel (41) for the recording carrier.
2. Printer according to Claim 1, characterised in that the printing modules (10/1 - 10/4) have elements (32, 33) for arranging the printing modules (10/1 - 10/4) in rows in the housing (34) in an exactly fitting manner.
3. Printer according to Claim 2, characterised in that the elements (32, 33) are constructed as fitting faces (32) arranged on chassis elements (31) of the printing modules (10/1 - 10/4) with associated fitting elements (33).
4. Printer according to Claim 3, characterised in that the printing modules (10/1 - 10/4) are floatingly mounted in the housing (34) of the printer.
5. Printer according to one of Claims 1 to 4, characterised in that, for printing sheet-shaped recording carriers (15) on both sides, the transport channel (41) for the recording carrier (15) has a turning device (45) for the recording carrier.
6. Printer according to one of Claims 1 to 5, characterised in that the printer is constructed as a multi-colour printer with a number of printing modules (10/1 - 10/4) with coloured toner corresponding to the number of elementary colours used.
7. Printer according to one of Claims 1 to 6, characterised in that first heating devices (30, 28) are provided which set the temperature of the toner image in a contact area (20) between intermediate carrier (14) and photoconductor (11) in such a way that the toner is in the pasty state and is transferred to the intermediate carrier (14) by adhesive force.
8. Printer according to Claim 7, characterised in that the heating devices comprise heating elements (30) for heating up the photoconductor (11).
9. Printer according to one of Claims 1 to 8, characterised in that second heating devices (21) are provided which set the temperature of the toner image on the intermediate carrier (14) in such a way that the toner is located in a contact area (22/1 - 22/4) between intermediate carrier (14) and recording carrier (15) in the virtually liquid state of aggregation.

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