EP0946902B1 - Electrographic printing device with opposite-lying printing units - Google Patents

Description

The invention relates to an electrographic printing device, especially a printer or a copier with at least two essentially identical printing units one transfer point between each one to be printed Carrier web is guided. The invention further relates to a Method for operating a printing device.

In a conventional printing device, a toner image carrier is used with the help of an electrographic process, e.g. by exposing a photoconductor or by magnetizing a magnetically sensitive layer, a latent image is applied. According to the pictorial distribution of the electrical Charges or the magnetic poles are attached to the latent Image toner on. On a backing, in general a paper web, then the toner at the transfer location transfer. The toner image on the carrier material becomes later fixed.

Modern printing technology requires that only one Applies the carrier material on both sides at high speed printed. This mode is commonly called Called duplex printing. Furthermore, the operating mode spot color printing or two-color printing, where two-color is required is printed on at least one page. Moreover there is a need for full-color printing with the four Process colors. For example, the duplex printing mode it is known to realize the continuous carrier web first to print on one side, then the carrier web and the second page with the same printing unit to print on. In this solution there is a web turning device required. The transport route of the carrier web through the printer through it is relatively long and requires a complicated one and thus also susceptible to malfunctioning transport device for the Support material.

Another disadvantage of the known printer is that that if the toner image is on one side of the carrier web is not yet fixed, it can be blurred and therefore the print quality is reduced or rejects are produced becomes. To avoid this, an intermediate fixation of the Toner image done, but this means the technical effort gets big. In addition, the carrier web has to be printed on go through the fixing process a second time on the second side, as a result of which it is subjected to high thermal stress, shrinkage problems occur and the accuracy of the print is reduced becomes. Because of the long transport route between the first Transfer point for the first transfer printing of a toner image and the second transfer point can ensure compliance with a high Fitting accuracy of the carrier web only with great technical effort be guaranteed.

The aforementioned problems also occur with a so-called "Twin-System" with two identical printers in a row can be switched together to turn the carrier web two-sided printing, i.e. to realize duplex printing. In addition to the high cost of two printers, it is also disadvantageous that a large footprint must be provided and the device control of the two printers with a relatively high technical effort must be coordinated.

From EP 0 629 931 A1 (applicant XEIKON) is an electrostatic Printer known in which a carrier web in vertical Direction between a variety of toner image carriers is passed through. Each toner image carrier has a toner image generating device. The toner is on one Transfer the transfer point of the toner image carrier to the carrier web. By arranging toner image carriers on both sides lengthways the vertically running carrier web is a duplex print with different toner colors possible. The well-known device has a complex structure, a complicated substrate management and is voluminous.

From EP 0 433 444 B1 (applicant: Eastman Kodak Company) a printer is known in which along a photoconductor belt several developer stations arranged as a toner image carrier are. Every developer station can do this from an exposure station generated charge image with toner of a predetermined Color. The toner image created on the photoconductor belt is then at a single transfer location on the carrier material transfer. This printer is also technically complex and can only be slight in the different operating modes Realize printing speeds.

From EP-A-0 629 924 is a similar printing device as in EP-A-0 629 931 described known, which contains the features of the preamble of claim 1. As a photoconductor or toner carrier a photoconductor tape can also be used.

EP-A-0 742 496 discloses an electrographic printing device, especially printer or copier, with at least two essentially identical printing units are known. A Carrier web is arranged between the opposite one another Printing units carried out and printed. The printing units enable multi-color printing.

From Patent Abstracts of Japan, Volume 15, No. 20 (P1154), 17th January 1991; Pub. No .: JP-A-02264276, is a printing device known in which a repetitive operation is realized is. This printing device prints single sheets on only one side. The single sheets are in repeating operation moved back and forth. With one direction of movement the photoconductor tape is both with a development unit as well as brought into contact with the single sheets. When moving the single sheets in the other direction becomes the photoconductor tape both from the single sheets and from the Development unit moved away.

It is an object of the invention to provide an electrographic printing device specify that works at high printing speed and has a compact structure. Furthermore, a high Flexibility with regard to different printing modes can be achieved.

This is achieved by a device according to independent device claim 1 and by a method according to independent method claim 23.

According to the invention, an electrographic printing device with at least two essentially identical printing units each with a transfer location between which a carrier web to be printed is guided. The transfer points are with little lateral offset in the direction of movement the carrier web arranged opposite each other. each Printing unit has a toner carrier tape on its endless peripheral surface toner can be applied according to an image-shaped distribution is the one at the respective transfer printing station opposite surface of the carrier web is transferable.

In the invention, toner is transferred to a toner carrier belt which is a latent on its endless circumferential surface Image carries. Any tape can be used as the toner carrier tape be, which is a magnetic or electrical way can generate latent charge image. Preferably a Photoconductor tape used, which is an electrical by exposure Charge image is generated, with toner particles when Develop according to the charge distribution on the peripheral surface attach the photoconductor tape. Using the toner carrier tape can create an elongated loop be, which enables the for the creation of a Toner image required along the length of the Agreggate Toner carrier tape can be arranged distributed. On this is a compact arrangement of two toner carrier webs possible, the transfer points opposite each other are arranged so that a single printer can contain two printing units without a bulky device arises. By using toner carrier webs in the printing units, it is also possible to use the two transfer printing points with a small lateral offset to each other to be arranged opposite one another. Preferably the side one Distance between the two transfer printing points only by the Dimensions of the to be arranged between the transfer printing points Transfer corona device limited. In this way they move two transfer points close to each other, so that the transport route minimal for the carrier web between these transfer printing points is. This ensures a high accuracy of fit for both of them Printing units generated print images achieved.

If, in the invention, both printing units are operating in printing mode, the operating mode can be operated at high speed Duplex printing can be realized. The carrier web is turning not mandatory. Because both transfer points are close together are arranged from each other, the fit of the printed images due to shrinking processes, change of Moisture etc. not affected.

The carrier web is on a straight path between the transfer printing points guided. The applied by the two printing units Toner images are no longer by any guide elements touched until they have gone through a fixing process. Thereby is the danger of blurring those not yet fixed Toner images excluded and there will be high print quality reached.

An embodiment of the invention is characterized in that that the carrier web runs essentially horizontally. This horizontal arrangement has the advantage that a Operator to check the print image from above on the Carrier web can look. The examiner takes one natural and comfortable posture.

In the invention, each printing unit contains a swivel device, through which the photoconductor belt is pivoted away from the carrier belt and can be pivoted to the carrier tape. Through these measures, the carrier tape at a start and Stop operation itself cannot be moved. Appropriate technical Facilities can thus be omitted. When swiveling of the photoconductor tape becomes the length of the photoconductor tape not changed. This will reduce the risk of blurring in the Print image reduced. In the swung-away state of the swivel device it is also possible on the photoconductor tape collect several toner images and collect them later transfer-print.

According to an embodiment with a photoconductor tape as The toner image carrier is the outer peripheral surface of the photoconductor belt fully rechargeable with a latent charge pattern. The use of a continuous endless photoconductor belt is known per se for single sheet printers. Such a photoconductor band has an interface at which no charge pattern can be generated. This interface is usually through marked an index hole and when exposed by the Exposure unit taken into account by the device control. When feeding single sheets, it is then ensured that that the seam is becoming more and more consecutive between two ends Single sheets are located so that the seam not noticeable in the printed image. When using of tape material as the carrier material is now according to the embodiment the seam is as small as possible or it is no interface available. So the photoconductor tape is perfect to coat with photoactive material so that it along its circumferential surface with a latent charge pattern is rechargeable. In this way, the tape material be printed without interruption - there is none Pressure gap.

According to a further exemplary embodiment, the contains a toner image generating first and / or second device each several developer stations. If these developer stations Having toners with different colors is multi-color printing possible. This multi-color printing can in the simple case a spot color print or with appropriate process control full-color printing with the process colors yellow, magenta, Be cyan and black.

A repetitive can be used to apply different toner images Operation can be provided in which the carrier material the transfer points repeated by a forward movement and a backward movement is made. With every passing in the forward direction, a toner image is placed on the carrier material transfer. In this way, toner images can be different Color from the various development stations a peripheral portion on the photoconductor belt generated, collected on the substrate and then fixed together. With every backward movement the photoconductor tape has to be swung away from the carrier web, around the applied toner image or images Don't blur toner images.

According to a further aspect of the invention, a method for operating an electrographic printing device according to Claim 23 specified. In continuous operation is a Fast transfer printing with at least one color possible. In repetitive Operation is a slow down transfer with several Colors possible.

Figur 1

schematisch die elektrografische Druckeinrichtung mit zwei einander gegenüberstehenden Druckwerken,

Figur 2

die Anordnung nach Figur 1, wobei die Druckwerke mehrere Entwicklerstationen enthalten,

Figur 3

eine Druckeinrichtung mit zwei Paaren von gleichartigen Druckwerken,

Figur 4

eine Druckeinrichtung, deren Paare von Druckwerken unterschiedlich sind,

Figur 5

eine Druckeinrichtung nach Art der Figur 2 mit vertikal verlaufender Trägerbahn,

Figur 6

schematisch eine Anordnung mit zwei Belichtungseinheiten und zwei Entwicklerstationen in einem Druckwerk,

Figur 7

die paarweise Anordnung von Druckwerken nach Figur 6 mit geneigter Längsachse,

Figur 8

eine Anordnung mit zwei Paaren von Druckwerken nach Figur 6, und

Figur 9

eine Anordnung mit vier Druckwerken nach Figur 6, wobei zwischen je zwei Druckwerken die Trägerbahn gewendet wird.

Embodiments of the invention are explained below with reference to the drawing. In it shows

Figure 1

schematically the electrographic printing device with two opposing printing units,

Figure 2

the arrangement according to Figure 1, wherein the printing units contain several developer stations,

Figure 3

a printing device with two pairs of similar printing units,

Figure 4

a printing device whose pairs of printing units are different,

Figure 5

2 a printing device of the type of FIG. 2 with a vertically running carrier web,

Figure 6

schematically an arrangement with two exposure units and two developer stations in a printing unit,

Figure 7

the paired arrangement of printing units according to Figure 6 with an inclined longitudinal axis,

Figure 8

an arrangement with two pairs of printing units according to Figure 6, and

Figure 9

an arrangement with four printing units according to Figure 6, wherein the carrier web is turned between two printing units.

In Figure 1 is schematically a printing device according to the Invention shown. The printing device contains two Printing units 6, 8, which are constructed in the same way. Hereinafter only the lower printing unit 6 is explained, its agreggate are designated by reference numerals with the addition a. The same Agreggate are also used in the upper printing unit 8, are there with corresponding reference numerals and referred to the letter b.

The printing unit 6 has a photoconductor belt 10a, the endless of which The peripheral surface can be fully charged with a latent charge pattern is. The photoconductor belt 10a is rotated in Guided in the direction of arrow 11a past a transfer printing point 12a, to supply toner to a continuous paper web 15 transfer. A transfer roller 14a is a transfer printing corotron 16a associated with the toner particles on the photoconductor belt 10a by the action of an electrostatic Force field accumulates on the paper web 15, so that a still smearable toner image is formed on the paper web. The transfer printing corotron 16a is in the transport direction of the paper web 15 seen a conditioning corotron 18a, which the paper web 15 in a defined electrostatic initial state added.

Opposing the transfer roller 14a is a deflecting roller 20a arranged, which deflects the photoconductor 10a. The Photo conductor 10a is designed as an elongated loop, whose longitudinal axis is essentially vertical. This makes it possible to create the necessary ones Agreggate along this longitudinal axis on both sides of the photoconductor 10a, which makes it possible to arrange the two Transfer points 12a and 12b with a small lateral offset in Arrange the transport direction of the paper web 15. The length of the Photoconductor tape 10a is selected so that there is sufficient space for the mentioned Agreggate remains.

As can be seen in FIG. 1, the photoconductor band 10a opens multiple rollers (not specifically identified), among others guided the rollers 14a and 20a. A tension member 22a is switchable in two positions. In one position it is Photoconductor tape 10a tensioned. In the other position the reduced mechanical tension of the photoconductor belt 10a. In this position the photoconductor belt can be replaced or it maintenance work can be carried out.

On the deflecting roller 20a is designed as a character generator 24a Exposure unit arranged, the light emitting Contains diodes and is also referred to as an LED exposure unit becomes. The character generator 24a generates on the photoconductor belt 10a shows a latent charge image with a charge distribution according to the characters or picture elements to be printed. Seen in the direction of rotation is after the character generator 24a a developer station 26a is provided, which is the charge image colored with toner. This toner image is, as mentioned, on the Transfer transfer point 12a to the underside of the paper web 15.

In the start and stop mode, the photoconductor belt 10a must be the paper web 15 are pivoted away. For this purpose a pivoting device 28a is provided which holds the photoconductor belt 10a either in the dashed lines in Figure 1 drawn position or in the dashed line Holds position. In the position shown in dashed lines is the photoconductor belt 10a pivoted away from the paper web 15; a transfer of toner is excluded. It should be noted that the pivoting of the photoconductor belt 10a without change the length of the photoconductor tape takes place so that the electrophotographic Process, for example exposing the photoconductor tape, does not have to be interrupted. This also serves the clamping element 22a, which depends on the pivot position the swivel device 28a adjustable in two positions is. In each of these positions, the photoconductor tape 10a kept under tension. It should also be pointed out that in the position pivoted away from the paper web 15 the swivel device 28a it is possible to take several toner images to collect on the photoconductor belt 10a, then the to print overlaid toner images. This operating mode is explained further below.

Seen in the direction of rotation of the photoconductor belt 10a after Transfer corotron 16a, a cleaning corotron 30a and one Cleaning station 32a arranged. Both Agreggate have that Task that after printing at the transfer location 12a to remove existing toner from the photoconductor belt 10a in order to this for subsequent exposure and toner ingestion bring a defined initial state. Before the character generator 24a there is a charging corotron 34a which a defined one on the surface of the photoconductor belt 10a State of charge generated. The process of charge imaging and the coloring with toner is known per se and must not explained in detail here.

As mentioned, the upper printing unit 8 has the same structure as the explained printing unit 6. Its marked with the addition b Agreggate therefore do not need to be explained again become. Only the conditioning corotron should be mentioned 18b, which the paper web 15 after printing on both sides through the printing units 6, 8 in a largely neutral brings electrostatic condition.

In the following, the transport of the paper web 15 through the Printing device described. The paper web 15 is in the direction of the arrow P1 via a deflection roller 35 of a transverse alignment device 36 fed to the paper web 15 in the direction roughly aligned transversely to the transport direction P1. Subsequently the paper web 15 is guided past a vacuum brake 38, which sucks the paper web 15 with negative pressure, to keep the longitudinal tension in it at a defined value to be able to. The paper web 15 then passes through a side guiding device 40, which is an exact lateral guidance of the Paper web 15 for the subsequent transfer printing on the printing units 6, 8 controls. In terms of lateral guidance the rough alignment device 36 for rough alignment and the Lateral guide device 40 for fine lateral alignment the paper web 15.

A pair of friction rollers 43 is used for the forward transport of the Paper web 15. The paper web 15 runs on a straight line Walk horizontally past the transfer locations 12a, 12b and will there in simplex printing operation through the upper printing unit 8 and printed in duplex printing mode by both printing units 6, 8. The printing unit 6 thus becomes inactive in simplex printing operation switched to the top of the paper web 15 the toner image to print. This has the advantage that an operator Check the top when setting up the print image can. However, it is also conceivable for simplex printing to switch the upper printing unit 8 inactive and the pressure to accomplish that under printing unit 6.

An advantage of the chosen arrangement is that if one Printing unit, e.g. the printing unit 6, the other printing unit, e.g. the printing unit 8, maintain the simplex printing operation can.

The paper web 15 provided with toner images arrives in a Fixing device 42 with an elongated, horizontal extending fixation 44. In the present case works the fixing device 42 with infrared radiation. However, it can also be used a fixing device Hot pressure fixation by means of two pressing against each other Rolling realized. In duplex printing, they are double-sided toner images applied to the paper web 15 simultaneously fixed. It is essential that between the last transfer point 12b and passing through the fixation zone to none mechanical contact with the toner images on the paper web 15 is coming. This means that the paper web 15 in one tensioned state must be kept, what by the pair of transport rollers 48 is reached, which is the paper web 15 transported under tension. The fixing device 42 is a cooling device 46 downstream, which the heated Paper web 15 cools.

As can be seen from the exemplary embodiment according to FIG. 1, can perform duplex printing at the same speed like a simplex printing operation. Because the two transfer points 12a and 12b are almost opposite each other or in one are arranged at a small lateral distance from one another the fit of the printed images produced is very high, i.e. optimal print quality is achieved.

In the example according to FIG. 1, the paper web is transported 15 without intervention in an edge perforation of the paper web. Of course, a paper transport can also be used Intervention in an edge perforation of the paper web 15 take place. To the Paper drives are then used to drive the tractor by means of transport spikes in the edge holes of the paper web 15 intervention. In this way, the edge-precise guidance of the Paper web 15 secured and components such as transverse alignment device, Lateral guiding device, vacuum brake, suction table can be omitted.

Because of the short paper path between the two transfer points 12a and 12b is a high accuracy of fit to be printed Given toner images. This allows temporary storage of data for the character generators 24a and 24b are omitted. The photoconductor tape 10a or 10b is exposed only staggered by a time that results from the Transport speed and the paper path between the two Transfer points 12a and 12b results.

In Figure 2, a printing device is shown schematically, which essentially corresponds to that of Figure 1. However, the two printing units 6, 8 contain several Developer stations 50a, 50b, 50c, 50d. In a repetitive Operation, i.e. with forward and backward movement the paper web 15 at the transfer printing points 12a, 12b can each according to the number of developer stations used, in the present Case four developer stations 50a to 50d, several Toner images are collected one above the other on the paper web 15. The print speed works in this mode according to the required forward and backward movement back. The fixation of all superimposed toner images takes place together in the single fixing device 42 Transfer rollers 14a, 14b are with each backward movement the paper web 15 to pivot away from her to blur avoid the not yet fixed toner images. Using the well-known process colors yellow, magenta, cyan and Black as a toner in the developer stations 50a to 50d can with appropriate process control, full-color printing in simplex printing or generated in duplex printing.

FIG. 3 shows a further variant of the printing device according to the invention. There are two pairs of printing units 6a, 8a and 6b, 8b connected in series. Each pair of printing units 6a, 8a and 6b, 8b has essentially the structure shown in FIG. With the arrangement shown in Figure 3 is particular fast two-color duplex operation possible. To do this on the bottom by the printing unit 6a from the developer station 52a, a toner image with a first color is printed on. Then through the lower printing unit 6b of the second Pairs of printing units a second toner image on the paper web 15 applied by the developer station 52b. The Top of the paper web 15 is in an analogous manner by the Printing units 8a and 8b printed. The toner images on both sides the paper web 15 are in the single fixing device 42nd fixed together.

FIG. 4 shows a further variant with pairs Printing units according to Figure 3. The pair of printing units with the Printing units 6b, 8b have four developer stations 50a to 50d equipped, as is also shown in Figure 2. The printing units 6a, 8a correspond to those of Figure 1. Die Arrangement according to Figure 4 can be advantageous for the alternate Duplex printing mode, the two-color duplex mode and one Multi-color duplex operation can be used. With a continuous Movement of the paper web 15 can by the first Printing couple 6a, 8a with the developer stations 52a, 52a Toner image of a first color can be applied on both sides. If the second pair of printing units 6b, 8b is switched to inactive, a single-color duplex printing operation is thus realized. If the printing couple 6b, 8b is activated, so at rapid continuous passage of the paper web 15 Two-color duplex operation can be realized by using one of the Developer stations 50a to 50d a toner image with a corresponding Color on the respective photoconductor tape 10a, 10b applies. With different toner colors of the printing units 6a, 8a and 6b, 8b, a multi-color duplex printing operation can be realized become. Repeated operation can be done accordingly the developer stations present in the printing units 6b, 8b 50a to 50d and toner colors a multi-color duplex printing company will be realized. Between the operating mode with continuous Printing operation (without repeating) and the repeating Printing operations can be done quickly without mechanical changes change.

Figure 5 shows another example in which the paper web 15 for printing by the two printing units 6, 8 and the fixing device is moved in the vertical direction. The Printing units 6, 8 are constructed as in FIG. 2. This arrangement has the advantage that the paper web 15 between the transfer printing point of the last printing unit 8 and the pair of transport rollers 48 do not sag due to their own weight can. The risk of injury and blurring the printed image when moving along a long fusing line is avoided. The longitudinal axes of the Grinding the photoconductor tapes 10a, 10b of the printing units 6, 8 are arranged essentially horizontally in this case.

FIG. 6 shows a printing device with a printing unit 54, which is constructed in the manner of the printing unit 6 according to FIG. 1. The same parts are labeled the same. In addition to the printing unit 6, the printing unit 54 contains a second loading corotron 35a, a second line generator 31a and one second development station 27a. During the circulation of the photoconductor belt 10a is replaced by the charging corotron 34a, 20a and the character generator 24a after one from Océ Printing Systems GmbH developed a first latent charge pattern and then a first toner image through the developer station 26a generated. Then the second character generator 31a generates in conjunction with the charging corotron 35a on the developed first charge pattern by superimposing a second latent one Charge image developed by the developer station 27a becomes. Preferably, the two developer stations 26a, 27a different toner colors, so there will be another one The first toner image on the photoconductor belt 10a superimposed. The resulting toner image is then at the transfer location transferred to the paper web 15. In this way can with high printing speed at the transfer location two-tone toner image can be printed. It is also possible, another charging corotron, another exposure unit and another developer station, preferably with one further toner color to be arranged along the photoconductor belt 10a, to take more than two toner images on the photoconductor belt overlay, which are then transferred together to the paper web 15 become.

The printing unit 54 shown in FIG. 6 can be of various types Variants according to the principles shown in Figures 1 to 5 be used. For example, 7 shows the printing unit 54 a similar printing unit 56 arranged opposite. The entire arrangement is essentially the same as that Figure 1 match. The same parts are again labeled the same. After passing through the fixing device 42 Paper web on a deflector 58, which is an air cushion generated, deflected virtually without contact and the cooling device 46 fed. With the printing device shown in Figure 7 is a two-color duplex printing operation with high printing speed possible.

A further variant is shown in FIG two pairs of printing units in the manner of printing pair 54, 56 are connected in series. Each printing unit 54a, 54b, 56a, 56b can repeat a two-tone toner image at a time without repeating apply one side of the paper web. Because of the arrangement with a short paper path between the first printing unit 54a and the last printing unit 56b a high registration accuracy is achieved. A four-color duplex printing operation can be realized. If the process colors are yellow, magenta, cyan and Black can be used as toner in the developer stations is full color printing with appropriate process control both sides of the paper web 15 possible without repeating must be printed.

Figure 9 shows a variant with four similar printing units 54a, 54b, 54c, 54d, each according to the type shown in FIG shown printing unit are constructed. Between the printing units 54a, 54b and the printing units 54c, 54d is a turning device 60 arranged, which turns the paper web 15. With this Arrangement can also be a four-color duplex printing operation can be realized with high printing speed without that the paper web 15 must be repeated. The order 9 has the advantage that the overall height of the printing units 54a to 54d in a housing-accommodating printer is reduced. The turning device 60 is as Cross turner, which is on the bottom of the Paper web 15 through the printing units 54a, 54b printed toner image is not mechanically damaged.

LIST OF REFERENCE NUMBERS

6.8

printing unit

10a, 10b

Photoconductor web

12a, 12b

transfer printing

11a, 11b

Direction arrow

14a, 14b

transfer roller

16a, 16b

Transfer printing corotron

18a, 18b

Conditioning corotron

20a, 20b

deflecting

22a, 22b

clamping element

24a, 24b

character generator

26a, 26b

developer station

27a, 27b

developer station

28a, 28b

swivel device

30a, 30b

Cleaning corotron

32a, 32b

cleaning station

34a, 34b

Charging corotron

35a, 35b

Charging corotron

36

lateral alignment

38

Vacuum brake

40

Lateral guide device

42

fixing

43

Friktionswalzenpaar

44

fixing path

46

cooler

48

Transport roller pair

50a, 50b 50c, 50d

developer station

52a, 52b

developer station

54, 56

printing unit

58

deflecting

60

turning device

P1

Transport direction arrow

Claims (25)

1. Electrographic printer device, particularly printer or copier,

   comprising at least two essentially identical printing units (6, 8) each having a respective transfer printing location (12a, 12b) between which a carrier web (15) to be printed is conducted,

   whereby the transfer printing locations (12a, 12b) are arranged lying opposite one another with slight lateral offset in moving direction of the carrier web (15),

   whereby each printing unit (6, 8) has a toner carrier band (10a, 10b) on whose endless circumferential surface toner can be applied according to an image-shaped distribution, said toner being transferrable at the respective transfer printing location (12a, 12b) onto the surface of the carrier web (15) lying opposite it,

   characterized in that each printing unit (6, 8) contains a swivel mechanism (28a, 28b) with which the toner carrier band (10a, 10b) can be swivelled away from the carrier band and can be swivelled against the carrier band (15) only in the region of the transfer printing location, whereby a tensioning element (22a, 22b) holds the toner carrier band (10a, 10b) tensed and the swivelling ensues without changing the length of the toner carrier band (10a, 10b).
2. Printer device according to claim 1, characterized in that the carrier web (15) proceeds essentially horizontally.
3. Printer device according to claim 1 or 2, characterized in that the toner carrier bands of the two printing units (6, 8) form an elongated loop whose longitudinal axes proceed essentially vertically.
4. Printer device according to claim 1 or 2, characterized in that each toner carrier band forms an elongated loop whose longitudinal axis describes an angle of 15° with the vertical; and in that the longitudinal axes of both toner carrier bands proceed essentially parallel to one another.
5. Printer device according to one of the preceding claims, characterized in that the outer circumferential surface of the toner carrier band (10a, 10b) fashioned as photoconductor band can be completely charged with a latent charge image.
6. Printer device according one of the preceding claims, characterized in that each printing unit (6, 8) contains at least one illumination unit (24a, 24b), preferably a laser illumination unit or a LED illumination unit.
7. Printer device according to claim 6, characterized in that the illumination unit (24a, 24b) is arranged at the deflection drum (20a, 20b) for deflecting the photoconductor band (10a, 10b) that lies essentially opposite the transfer printing location (12a, 12b).
8. Printer device according to one of the preceding claims, characterized in that each printing unit (6, 8; 5, 4) contains a plurality of developer stations (50a through 50d; 26a, 27a).
9. Printer device according to claim 8, characterized in that each printing unit (6, 8) contains four developer stations (50a through 50d) that preferably have toner in the four process colors for full-color printing.
10. Printer device according to one of the preceding claims, characterized in that the carrier web (15) is repeatedly conducted past the respective transfer printing location with a forward motion and a reverse motion; and in that a toner image is transferred onto the carrier web (15) given every passage in forward direction.
11. Printer device according to claim 10, characterized in that the photoconductor band (10a, 10b) is swivelled away from the carrier web (15) given every reverse motion thereof.
12. Printer device according to one of the preceding claims, characterized in that a pair of further printing units of the type of said printing units are arranged at both sides of the carrier web (15).
13. Printer device according to one of the preceding claims, characterized in that the carrier web (15) is supplied after printing to a fixing means that fixes the toner image (42).
14. Printer device according to claim 13, characterized in that the fixing means (42) has a fixing path (44) that proceeds essentially horizontally.
15. Printer device according to claim 13, characterized in that the fixing means has a fixing path that proceeds essentially vertically.
16. Printer device according to one of the preceding claims, characterized in that the lateral spacing of the transfer printing locations from one another is defined by the dimension of the transfer printing corona means.
17. Printer device according to one of the preceding claims, characterized in that each printing unit (6, 8) contains a tensioning element (22a, 22b) that can be adjusted into two positions dependent on the swivelled condition of the swivel mechanism (28a, 28b) and which keeps the photoconductor band (10a, 10b) under tension in every position.
18. Printer device according to one of the preceding claims, characterized in that each printing unit (54, 56; 54a, 56a; 54a, 54b) contains at least two illumination units (24a, 31a; 24b, 31b), at least two charging corona devices (34a, 35a; 34b, 35b) and at least two developer stations (26a, 27a; 26b, 27b) that are arranged along the circumference of the toner carrier band (10a, 10b); and in that, given a single circulation of the toner carrier band (10a, 10b), the illumination units (24a, 31a; 24b, 31b) generate two latent images that superimpose on one another and that can be successively coated with toner by the developer stations (26a, 27a; 26b, 27b).
19. Printer device according to claim 18, characterized in that the toners employed by the developer stations (26a, 27a; 26b, 27b) are of different colors.
20. Printer device according to one of the preceding claims, characterized in that a transfer printing corotron (16a) is arranged at the transfer printing location (12a), a conditioning corotron (18a) preceding said transfer printing corotron (16a) as viewed in conveying direction of the carrier web (15).
21. Printer device according to one of the preceding claims, characterized in that a transfer printing corotron (16b) is arranged at the transfer printing location (12b), a conditioning corotron (18b) following said transfer printing corotron (16b) as viewed in conveying direction of the carrier web (15).
22. Printer device according to one of the preceding claims, characterized in that, in the position of the swivelling mechanism (28a) wherein it is swivelled away, a plurality of toner images are collected on the toner carrier band (10a), these then being transfer-printed onto the carrier web (15) as superimposed toner images.
23. Method for the operation of an electrophotographic printer device, particularly a printer or copier, whereby a carrier web (15) to be printed is supplied to at least one printing unit (6, 8) having a transfer printing location, the printing unit (6, 8) contains a toner carrier band (10a) on whose endless circumferential surface toner is applied according to an image-shaped distribution, said toner being transferred at the respective transfer printing location onto the surface of the carrier web (15) lying opposite it,

    the printing unit (6, 8) contains a plurality of developer stations (50a through 50d),

    in a repeating mode at the respective transfer printing location, the toner carrier band (10a, 10b) is repeatedly conducted past on the basis of a forward motion and a reverse motion; and in that [sic] a toner image is transferred onto the carrier web (15) at every passage in forward direction, whereby the photoconductor band (10a, 10b) is swivelled away from the carrier web (15) only in the region of the transfer printing location (12a, 12b) given every reverse motion of said carrier web (15), whereby the swivelling ensues without changing the length of the toner carrier band (10a, 10b),

    in a continuous mode, only one of the developer stations (50a through 50d) is activated and the photoconductor band (10a) is kept continuously in contact with the carrier web (15), and the toner image developed by the one developer station is transfer-printed,

    and whereby the repetitive or the continuous mode is optionally set, whereby a tensioning element (22a, 22b) keeps the toner carrier band (10a, 10b) tensed in both operating modes.
24. Method according to claim 23, whereby the printing unit (6, 8) contains four developer stations (50a through 50d) that preferably have toner in the four process colors for full-color printing.
25. Method according to claim 23, whereby a turn-over means (60) for turning the carrier web (15) over is arranged between a plurality of printing units (54a, 54b; 54c, 54d).

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