EP1627260B1 - Transfer station for an electrographic printer or copier - Google Patents

Description

Electrographic printing or Kopiergräte are for example from the US Pat. No. 6,072,977 known. They have, for example, a photoconductive drum as an intermediate carrier on which a charge image of the image to be printed on a recording medium, for example a paper web, is generated by means of a laser or LED comb. Subsequently, the intermediate carrier is moved past a developer station, through which the charge image on the intermediate carrier is colored with toner. In a transfer printing station, the toner image is transferred from the intermediate carrier to the recording medium and then fixed in a fuser station. This completes the printing or copying process for an image. The subcarrier is unloaded and then available for a new print or copy operation.

The toner image should be transferred as error-free as possible from the intermediate carrier to the recording medium. Print image errors in the transfer printing processes currently used in continuous presses in the speed range up to about 1.5 m / s consist mainly in the occurrence of defects (data loss) or brightening in grid areas, in blurred grid areas and horizontal stripes in grid areas on the recording medium. In printing devices with multiple printing devices, especially the 2nd printer of a twin system is critical (or the 3rd printer of a triple system, etc.), which is stressed on a paper from the fusing station of the previous printer (wavy, shrunk, loss of moisture) must print.

The state of the art in continuous printers is transfer printing with a transfer corotron, this is eg off DE 197 49 386 C2 known. Here, the recording medium without additional contact pressure in the transfer area is passed to the intermediate carrier and with the help of the transfer corotron, the printed image is transferred from the intermediate carrier to the recording medium. The force generated by the electric field between transfer corotron and toner on the intermediate carrier is often insufficient to completely transfer the toner to the recording medium when the recording medium is wavy. This results in printed image errors such as defects and halftone blurs. Furthermore, due to the low electrostatic adhesion to the intermediate carrier, the recording medium may slip uncontrollably abruptly. This is shown by horizontal stripes in grid areas.

In order to bring the recording medium mechanically to the intermediate carrier and thereby to reduce the problems described above, additional transfer aids (transfer blade, pressure roller, transfer printing etc.) were combined with a transfer corotron. As a result, however, the problems described above could not be completely eliminated since the mechanical pressure of the recording medium on the intermediate carrier together with a transfer corotron can not take place in the actual transfer area.

Furthermore, it is known ( WO 02/077719 A1 ), as a transfer means to use a transfer roller which presses the record carrier in the Umdruckbereich to the intermediate carrier. Structure and function of such a transfer station can WO 02/077719 A1 be removed. There, the transfer station is designed so that this principle can also be used in high-speed printing or Hochgeschwindigkeitskopiergeräten. For this it had to be achieved that the record carrier In Umdruckbereich securely rests on the intermediate carrier, resulting in printing operation no jumps in the relative speed between the recording medium and subcarrier and no print image errors occur on the recording medium.

Under various environmental conditions, the following disturbing variables may occur in a transfer station with transfer roller: part tolerances, concentricity deviations (photoconductor, transfer roller), temperature fluctuations, contamination, wear (photoconductor, transfer roller), variable web tension in the record carrier, asymmetric webbing transfer roll, different thickness, stiffness, waviness recording medium. In this case, e.g. must be taken into account that transfer roller and intermediate carrier must be replaced and then a perfect transfer must be given. The problem to be solved by the invention is to provide a transfer station with a transfer roller which functions properly under variable environmental conditions.

• Mit einer derart gelagerten Transferrolle wird der Aufzeichnungsträger über die gesamte Breite an den Zwischenträger gleichmäßig angedrückt. Das Tonerbild wird somit einwandfrei auf den Aufzeichnungsträger übertragen.
• Elektrische Feldlinien und Andruckkraft auf den Aufzeichnungsträger wirken am gleichen Ort - im Umdruckbereich - und in gleicher Richtung.
• Durch die geeignet gewählte Andruckkraft der Transferrolle werden Sprünge in der Relativgeschwindigkeit zwischen Aufzeichnungsträger und Zwischenträger und die oben angegebenen Druckbildfehler wirksam vermieden.
• Durch die Antriebseinheit kann die Transferrolle exakt bewegt werden. Dadurch werden beim An- und Abschwenken Relativgeschwindigkeiten zwischen Aufzeichnungsträger und Zwischenträger vermieden.
• Eine konstante Andruckkraft der Transferrolle an den Zwischenträger ist gewährleistet. Die Andruckkraft kann je nach Eigenschaft des Aufzeichnungsträgers eingestellt werden.
• Die Eigenschaften des Antriebssystems passen sich an die Bedingungen im Druckgerät an. Auch über die Lebensdauer (Verschleiss, auch elektrischer Verschleiss der Transferrolle) wird immer ein gleich gutes Ergebnis erzielt (gleiche Andruckkraft, Kompensation verschiedener Lagen der Umdrucklinie). Vorteil ist, dass eine höhere Geschwindigkeit des Aufzeichnungsträgers realisiert werden kann.

This problem is solved according to the features of claim 1. The solution according to the invention provides the following advantages over conventional systems:

• With a transfer roller mounted in this way, the recording medium is uniformly pressed over the entire width of the intermediate carrier. The toner image is thus properly transferred to the recording medium.
• Electric field lines and pressing force on the recording medium act at the same location - in the transfer area - and in the same direction.
• By suitably selected pressure force of the transfer roller jumps in the relative speed between recording medium and intermediate carrier and the above-mentioned printed image error effectively avoided.
• By the drive unit, the transfer roller can be moved exactly. As a result, relative speeds between the recording medium and the intermediate carrier are avoided when swiveling in and out.
• A constant pressure force of the transfer roller to the intermediate carrier is guaranteed. The pressing force can be adjusted depending on the property of the recording medium.
• The characteristics of the drive system adapt to the conditions in the pressure equipment. Also over the life (wear, also electrical wear of the transfer roller) always the same result is achieved (same contact pressure, compensation of different layers of the transfer line). The advantage is that a higher speed of the recording medium can be realized.

Further developments of the invention will become apparent from the dependent claims.

In order to avoid printing errors caused by (asymmetric) imbalance or (asymmetric) radial impact of the intermediate carrier, the transfer roller or the recording medium or by non-parallelism of the transfer roller and intermediate carrier, at least one compensating device may be provided in the transfer unit which acts unevenly across the width of the transfer roller and thereby compensates for tolerances in transfer roller or intermediate carrier. Depending on the application, it is also possible to use two or more compensating devices.

The drive unit thus compensates for unbalance, radial shock or thickness changes in the recording medium uniformly over the subcarrier width.

The drive unit used may be a motor which can operate in the position-controlled mode and in the torque-controlled mode. The motor may be a rotary motor, e.g. a brushless DC motor, or to act a linear motor.

It is expedient if the transfer unit has a pressure beam mounted on one side, on which the transmission element engages, and at least one, suitably at least two, mounted on the pressure beam bearing rocker, in which the transfer roller is mounted. The bearing rockers and the pressure bar can be rotatably mounted about a common pivot bearing. The bearing rockers are also movable about the axis of rotation with respect to the Andruckbalken so that the transfer roller can create parallel to the intermediate carrier. When moving a bearing rocker against the Andruckbalken at least one compensating device can be stretched or relaxed. Then, the transfer unit and with it the transfer roller can be pivoted or swung by the transmission element to the intermediate carrier. The pivoting operation can be achieved in that the transmission element is connected via a coupling arm with an eccentric, which is arranged on the drive shaft of the drive unit. However, it is also possible to use a linearly operating drive unit (linear motor) instead of the rotary drive unit (motor with transmission element).

To be able to correct with the help of the transfer roller the radial impact of the intermediate carrier or the transfer roller, is that is, they are supported in such a way that the at least one compensating device exerts a pressure in the direction of the intermediate carrier. The compensating device may for example consist of resilient elements. The drive unit then equalizes the radial impact uniformly across the width of the transfer roller (transfer roller remains parallel to the axis of rotation). If two balancing device are provided, one per bearing rocker, they act unevenly across the width of the transfer roller, namely front and rear with different radial impact, ie wobble and obliquity of the transfer roller to the intermediate carrier.

The pressure bar can be provided with a deflection roller for the recording medium. This deflection roller can produce a tangential web run to the intermediate carrier in the ON position. When the diverting pulley is placed on the pressure bar, the compensating device does not act on the diverting pulley. Thus, also recording medium webs that do not run symmetrically to the transfer roller, can be processed because the pulley can not unilaterally lift in one-sided webbing, i. the axis of the pulley remains parallel to the axis of the intermediate carrier. The transfer roller does not lift off at one-sided web tension, since the wrap angle of the recording medium on the transfer roller is almost zero and thus hardly any forces from the web train to the compensation devices.

By a corresponding arrangement of the deflection roller, it is possible to guide the recording medium tangentially past the surface of the transfer roller and a drum-shaped intermediate carrier. Such a guide can also be achieved if rollers or jaws are arranged in a corresponding manner in the deflection unit. The advantage of such Management of the record carrier is that the toner flight is minimized and the print image is more uniform.

The transfer station according to the invention is particularly suitable for printing devices that print a tape-shaped recording medium at high speed and in which the intermediate carrier is a photoconductor drum.

The angle by which the drive shaft is to be moved from the AB position to the ON position can be determined by means of a position counter, wherein the AB position or the ON position is assigned a first or second counter reading. The second meter reading acts as a setpoint or control specification for the torque control. If a defined position deviation is exceeded, the torque can be adjusted.

When a transfer station is installed in a printing device, it is advantageous to measure the AB position and the ON position. This ensures that the transfer roller always rests with the necessary pressure on the intermediate carrier. The AB position can be found such that the drive shaft is rotated until, for example, a Hall switch arranged at the AB position responds or the eccentric bears against a mechanical stop. The thereby achieved first count of the position counter can then be stored or the position counter is reset to a predetermined output value. The AB position is then given by a defined difference to the first meter reading. Subsequently, the drive shaft, the transfer unit torque controlled to move to the intermediate carrier until the drive shaft blocks after hitting the transfer roller on the intermediate carrier. In the process, disturbances such as eg web tension in the record carrier canceled or can be determined. The then achieved second count of the position counter can be stored again. To compensate for tolerances, this Anschwenkvorgang can be repeated, for example, at different intermediate carrier positions, this can also be done with continuous rotation of the intermediate carrier. The intermediate carrier does not have to be removed. From the determined second counter readings, an average value can then be formed, which is used as the second counter reading during printing operation. Of course, a corresponding measuring process can also be carried out during printing pauses, for example to compensate for wear on the transfer roller or the intermediate carrier.

When printing, the transfer unit is initially in the AB position. To be printed, the transfer unit is swung to the intermediate carrier until the second count is reached. The Anschwenkvorgang is thus position-controlled. When the second count is reached, the drive unit switches to torque control, so that the transfer roller is applied to the intermediate carrier with a (by the torque) adjustable pressure force. If a defined position deviation is exceeded, the torque can be adjusted during printing (superimposed position control). During the printing pause, the transfer unit is again swiveled in a position-controlled manner by the intermediate carrier until the first meter reading is reached. Of course, the end positions of the transfer unit can also be determined by other means, for example, could each be arranged in the end positions of a Hall switch whose sensor signal is evaluated.

With reference to an embodiment, which is illustrated in the figures, the invention will be further explained.

Fig. 1

eine Seitenansicht des Antriebssystems für den Fall, dass die Umdruckeinheit angeschwenkt ist (ANPosition);

Fig. 2

eine Seitenansicht des Andrucksystems für den Fall, dass die Umdruckeinheit abgeschwenkt ist (AB- Position);

Fig. 3

eine Schnittansicht an der Stelle K-K der Fig. 2;

Fig. 4

eine Prinzipdarstellung des Schwenkbereiches des Antriebssystems;

Fig. 5

eine Steuerschaltung für das Antriebssystem;

Fig. 6

ein Beispiel einer tangentialen Führung des Aufzeichnungsträgers über Transferrolle und Zwischenträger mit Umlenkrollen;

Fig. 7

ein Beispiel einer tangentialen Führung des Aufzeichnungsträgers über Transferrolle und Zwischenträger mit Umlenkbacken.

Show it

Fig. 1

a side view of the drive system in the event that the transfer unit is pivoted (ON position);

Fig. 2

a side view of the pressure system in the event that the transfer unit is pivoted (AB position);

Fig. 3

a sectional view at the point KK the Fig. 2 ;

Fig. 4

a schematic representation of the pivoting range of the drive system;

Fig. 5

a control circuit for the drive system;

Fig. 6

an example of a tangential guide of the recording medium via transfer roller and intermediate carrier with deflection rollers;

Fig. 7

an example of a tangential guide of the recording medium via transfer roller and intermediate carrier with deflection jaws.

From the following figures, only the transfer printing station is shown by an electrographic printing or copying machine, which is shown in principle. The remaining components of the printing or copying machine can be constructed in a known manner.

Out Fig. 1 and 2 results in the structure of the transfer station US, where Fig. 1 the transfer station in the swiveled position (ON position) shows, Fig. 2 in the pivoted position (AB position).

The transfer printing station US is used in a known manner to transfer toner images from an intermediate carrier 3, for example a photoconductive drum, to a recording medium 2, for example a paper web. The transfer takes place with the aid of a transfer roller 1, whose function eg in WO 02/0777 19 is described.

• eine Antriebseinheit AE, z.B. einen Motor mit Steuerung, wobei die Antriebseinheit AE sowohl in einem Position- gesteuerten Modus als auch in einem Drehmomenten- gesteuerten Modus betreibbar ist;
  • ein mechanisches Übertragungselement UE;
  • eine Umdruckeinheit UD.
  • zusätzlich kann mindestens eine Ausgleichsvorrichtung 9 vorgesehen werden, zweckmäßigerweise zwei Ausgleichsvorrichtungen 9a, 9b.

The transfer station US has a drive system AS which comprises the following components:

• a drive unit AE, eg a motor with control, wherein the drive unit AE can be operated both in a position-controlled mode and in a torque-controlled mode;
  • a mechanical transmission element UE;
  • a transfer unit UD.
  • In addition, at least one compensating device 9 can be provided, expediently two compensating devices 9a, 9b.

The drive unit AE may consist of a motor 4 with motor control ( Fig. 5 ), on the drive shaft 11, the transmission element UE attacks. This has an eccentric 5 and a coupling arm 6. The eccentric 5 is arranged on the drive shaft 11 ( Fig. 3 ), the coupling arm 6 is rotatably and eccentrically mounted on the eccentric 5, and rotatable on the transfer unit UD. Upon movement of the drive shaft 11 of the coupling arm 6 performs a movement to the intermediate carrier 3 out.

• einen Andruckbalken 7, an dem der Koppelarm 6 gelagert ist und der z.B. am einen Ende beidseits jeweils in einem Drehlager 12a, 12b angeordnet ist;
• im Ausführungsbeispiel zwei Lagerschwingen 8a, 8b, in der die Transferrolle 1 gelagert ist; die Lagerschwingen 8a, 8b sind ebenfalls um die Drehlager 12a, 12b drehbar angeordnet;
• evtl. eine Umlenkrolle 10 für den Aufzeichnungsträger 2 auf dem Andruckbalken 7.

The transfer unit UD has the following components:

• a pressure bar 7, on which the coupling arm 6 is mounted and which is arranged, for example, at one end on both sides in each case in a rotary bearing 12a, 12b;
• in the embodiment, two bearing rockers 8a, 8b, in which the transfer roller 1 is mounted; the bearing rockers 8a, 8b are also arranged rotatably about the pivot bearings 12a, 12b;
• possibly a deflection roller 10 for the recording medium 2 on the pressure bar. 7

The possibly provided compensating devices 9a, 9b act between pressure bars 7 and bearing rockers 8a, 8b in such a way that pressure is exerted on the bearing rockers 8a, 8b and thus on the transfer roller 1 in the direction of the intermediate carrier 3. For this purpose, it is expedient if the bearing rockers 8a, 8b are movable relative to the pressure beam 7. The balancing devices 9a, 9b may, for example, a resilient or possibly damping element, as in the Fig. 1 to 3 shown have. The transfer roller 1 can thereby create parallel to the intermediate carrier 3. In this case, possibly the bearing rockers 8a, 8b move relative to the Andruckbalken 7, wherein the balancing devices 9a, 9b slightly more excited or relaxed. Furthermore, it is expedient if at least two compensating devices 9a, 9b are provided within the transfer printing unit UD in order to achieve a uniform contact pressure against the intermediate carrier 3 over the entire width of the transfer roller 1.

Furthermore, guide rollers 13 can additionally be provided for the recording medium 2.

Fig. 1 shows the state in which the transfer unit UD and thus the transfer roller 1 is pivoted to the intermediate carrier 3 = ON position. The eccentric 5 stands in a favorable position for the torque control about 90 ° away from the rear dead center HT (linear transmission behavior). In order to swing the transfer unit UD from the intermediate carrier 3, the drive shaft 11 is correspondingly Fig. 2 rotated, the eccentric 5 pulls on the coupling arm 6, the transfer unit UD and thus the transfer roller 1 from the intermediate carrier 3 away in the AB position. The transfer unit UD rotates about the pivot bearings 12a, 12b.

As long as there is no pressure between the transfer roller 1 and intermediate carrier 3, the balancing devices 9a, 9b press the bearing rockers 8a, 8b at a respective stop 34 on the pressure bar 7, in these phases the bearing rockers 8a, 8b and the pressure bar 7 move synchronously.

Out Fig. 3 the view KK of the Fig. 2 , The drive unit AE has a drive shaft 11, on which the eccentric 5 is mounted. The coupling arm 6 is rotatably mounted on both the eccentric 5 and the Andruckbalken 7. In the bearing rockers 8a, 8b, the bearing pins 1a, 1b of the transfer roller 1 are mounted. The bearing 1a, 1b (eg a ball bearing) of the transfer roller 1 in the bearing rockers 8a, 8b can receive an inclination of the axis of transfer roller 1 to the pivot bearing 12. The bearing rockers 8a, 8b are further movably mounted relative to the pressure beam 7 about the axis 12a, 12b. The transfer roller 1 can thus be adjusted in the direction of the intermediate carrier 3 via the compensating devices 9a, 9b so that the pressing force across the width of the recording medium 3 is evenly distributed even in the event of a wobble. The balancing devices 9 can have damping properties Moreover, the available compensation path is chosen so small that the drive system AS has no tendency to oscillate.

Out Fig. 4 results in a schematic representation of the rotational movement of the drive shaft from the ON position to the AB position and vice versa. In order to be able to determine these end positions, Hall switches H, for example, can be arranged thereon, which emit a sensor signal when, for example, a marking on the drive shaft passes by the corresponding Hall switch. Starting from the AB position (Hall switch H2), for example, a rotation of the drive shaft to the right takes place until the ON position is reached, at which a Hall switch H1 can be arranged. Before the AN position is reached, the transfer roller 1 already touches the intermediate carrier 3 at the location BER. In Fig. 4 the individual positions of the drive shaft are shown with tolerance range. The AB position can also be determined with a mechanical reference stop 35. The eccentric 5 may be located in the ON position about 90 ° from a dead center HT, to facilitate a torque control.

If, for example, a transfer printing station US or a new transfer roller 1 is inserted into a printing device, it is expedient to set the drive unit AE in its rotational movement so that the transfer unit UD and thus the transfer roller 1 are swiveled exactly from the AB position into the ON position can be compensated and tolerances, for example, in the intermediate carrier 3, the transfer roller 1 or the recording medium 2. For this purpose, the AB position, but in particular the ON position must be specified exactly. This can be done for example with the aid of a position counter whose count indicates the position of the drive shaft 11.

Then the AB position is set first. For this example, the Hall switch H2 can be used, which emits a sensor signal when a mark of the drive shaft 11 passes this. However, it is also possible to arrange at this point a mechanical stop 35 which limits the rotational movement of the drive shaft 11. The count of the position counter in this position is stored as a first count. The AB position can, like Fig. 4 shows, lie at a defined distance from the reference stop 35. Now, the drive unit AE is switched to the torque-controlled mode and the drive shaft 11 is moved until it blocks. This is the case when the transfer roller 1 is applied to the intermediate carrier 3 with a corresponding pressing force. This pressure force can thus be influenced by the torque. In this position, the count of the position counter is stored as a second count. This second search can be repeated several times, for example, to compensate for tolerances of the intermediate carrier 3 or the transfer roller 1. From the various second counter readings, an average value can then be formed, which is used in the printing operation.

In the printing operation, starting from the AB position, the drive unit AE is initially operated in the position-controlled mode. The drive shaft 11 moves the transfer unit UD and the transfer roller 1 to the intermediate carrier 3. When the position counter has reached its second count, the transfer roller 1 is in operating position for the transfer printing. From now on, the drive unit AE is switched to the torque-controlled mode, whereby the transfer roller 1 is applied to the intermediate carrier 3 with the desired pressure force.

After completion of the transfer printing the transfer unit UD and the transfer roller 1 is pivoted away from the intermediate carrier 3. For this purpose, the drive unit AE is switched to the position-controlled mode and the drive shaft 11 is moved until the first count is reached.

Out Fig. 5 results in a structure of the drive unit AE. It has a motor 4, a motor controller 22 and a controller 26 for the recording medium 2. An incremental motor encoder 16 is disposed on the motor to enable incremental position monitoring with high resolution, eg 360 ° / 8196 incremental signals. From this lead lines 17 to the motor controller 22, via which the incremental signals to the position counter, realized on the motor controller 22, are transmitted. Furthermore, leads 18 for power supply to the motor 4. In addition, the motor controller 22 via a line 21, a signal for pivoting or swiveling, for example, be supplied for security reasons.

The motor controller 22 is further connected to the record carrier controller 26 via lines 23, 24 and 25. The line 23 is a BUS line for transmitting parameters (eg torque, operating mode, error message), via the line 24 start-stop signals for the transfer station can be transmitted, such as triggering actions such as pivoting or swiveling, via the line 25 reset signals to put the engine control in an initial state. The controller 26 are supplied via the lines 27 sensor signals such as force sensors, train train sensors, via the line 28 trigger signals and the bus 29 device data from the device bus 30. By force sensors for the balancing devices 9, position-controlled motors (eg stepper motors) can be used for the drive.

The invention has been described in connection with a rotary drive. However, it is also possible to use a linear motor as the drive, which, however, must also be operated in the two operating modes described above. Finally, it is also possible to use two or more drive units, which can then be arranged at different locations of the transfer unit UD. In addition, the transfer roller 1 may have resilient or damping properties achieved e.g. by a rubber coating, then it may be possible to dispense with the balancing device 9.

The function of the transfer roller 1 is further improved when the recording medium 2 is guided tangentially on the surfaces of the transfer roller 1 and the intermediate carrier 3. This ensures that the toner transfer direction is perpendicular to the plane of the recording medium 2 and corresponds to the electric field between intermediate carrier 3 and transfer roller 1. The result is that the toner flight is minimized and the print image is uniform.

Two implementations of such a management of the record carrier emerge Fig. 6 and 7 , In Fig. 6 the corresponding guidance of the recording medium 2 is achieved by means of deflection rollers 31, in Fig. 7 with the aid of deflection jaws 32. The tangents 33 are drawn in each case. In the Fig. 6 and 7 are not necessary for the representation of the principle elements of the transfer station US after the Fig. 1 to 3 been omitted.

LIST OF REFERENCE NUMBERS

US

transfer station

UD

transfer printing

AS

drive system

AE

drive unit

UE

transmission element

HT

bottom dead center

1

transfer roller

1a, 1b

pivot

2

record carrier

3

subcarrier

4

engine

5

eccentric

6

coupling arm

7

pression

8th

bearing rocker

9

balancer

10

idler pulley

11

drive shaft

12a, 12b

pivot bearing

13

guide rollers

14

Incremental motor encoder

15

Storage pressure bar

17

Cable: Incremental signals, rotor position detection

18

Cable: power transmission

19

power supply

20

logic supply

21

Signal line: Swing, swivel

22

motor control

23

Data lines (BUS line)

24

Start-stop line (trigger line)

25

Reset line

26

Control: Award bearer

27

sensor Cable

28

Trigger signal line

29

bus

30

Device data bus

31

guide rollers

32

Umlenkbacken

33

tangential

34

Stop in the pressure bar

35

reference stop

Claims (26)

1. A transfer printing station for an electrographic printer or copier device,

   - in which a transfer roller (1) for the transfer of a toner image generated on an intermediate carrier onto at least one recording medium (2) is provided in a transfer printing region of the transfer printing station (US),

   - in which at least one drive system (AS) is provided, comprising

   • a transfer printing unit (UD) in which the transfer roller is mounted,

   • a drive unit (AE) which via a transfer element (UE) pivots the transfer printing unit (UD) and thus the transfer roller (1) towards the intermediate carrier (3) into an ON position and away from the intermediate carrier into an OFF position, and which is designed such that it is position-controlled in the pivot-towards operation until reaching the ON position and is torque-controlled in the ON position.
2. The transfer printing station according to claim 1, in which at least one compensation device (9) is provided which is arranged between the transfer printing unit (UD) and the mounting of the transfer roller (1) and which is designed such that it uniformly presses the transfer roller (1) onto the intermediate carrier (3) over a width of said transfer roller.
3. The transfer printing station according to one of the preceding claims, in which the transfer printing unit (UD) comprises the following components:

   - a one-side mounted pressure bar (7) on which the transfer element (UE) engages,

   - at least one bearing rocker (8) which is mounted in the pressure bar (7) and in which the transfer roller (1) is mounted.
4. The transfer printing station according to claim 3, in which the transfer element (UE) comprises an eccentric (5) which is arranged on a drive shaft (11) of the drive unit (AE) and comprises a coupling arm (6) which is rotatably mounted on the eccentric (5) and the transfer printing unit (UD) and which transfers the motion of the eccentric (5) to the transfer printing unit (UD).
5. The transfer printing unit according to claim 3 or 4, in which the transfer roller (1) has bearing pins (1 a, 1 b) at both ends that are mounted in two bearing rockers (8a, 8b).
6. The transfer printing station according to claim 5, in which two compensation devices (9a, 9b) are provided, one per bearing rocker (8a, 8b).
7. The transfer printing station according to claim 6, in which the bearing rockers (8a, 8b) are mounted in the pressure bar (7) such that they are movable relative to the pressure bar (7), so that the compensation devices (9a, 9b) effect that the transfer roller (1) is pressed against the intermediate carrier (3) uniformly over its width.
8. The transfer printing station according to one of the claims 2 to 7, in which the at least one compensation device (9) is comprised of elastic elements.
9. The transfer printing station according to one of the claims 3 to 8, in which a deflection roller (10) around which the recording medium (2) is guided is arranged on the pressure bar (7).
10. The transfer printing station according to claim 9, in which a pivot bearing (12) for the one-side mounting of the pressure bar (7) is provided, the deflection roller (10) being arranged on the side of the pressure bar (7) facing away from the pivot bearing (12).
11. The transfer printing station according to one of the preceding claims, in which the drive unit (AE) has a position counter that counts the rotation of the drive shaft (11) step-by-step.
12. The transfer printing station according to one of the preceding claims, in which in the drive unit (AE) a Hall switch (H) is arranged, one for the determination of the OFF position and one for the determination of the ON position.
13. The transfer printing station according to one of the claims 1 to 12, in which for determining the OFF position, a reference stop (35) is arranged in the drive unit (AE).
14. The transfer printing station according to one of the preceding claims, in which the drive unit (AE) has a rotatory motor or a linear motor.
15. The transfer printing station according to one of the preceding claims, in which the transfer roller (1) exhibits damping properties.
16. The transfer printing station according to one of the preceding claims, in which the transfer printing unit (UD) has deflection means for the recording medium (2) which are arranged such that the recording medium (2) is guided between the intermediate carrier (3) and the transfer roller (1) tangentially on the surfaces of the intermediate carrier (3) and the transfer roller (1).
17. The transfer printing station according to claim 16, in which the deflection means are deflection rollers (31).
18. The transfer printing station according to claim 16, in which the deflection means are deflection jaws (32).
19. The transfer printing station according to one of the preceding claims, in which the recording medium (2) is belt-shaped.
20. A method for transfer printing of toner images applied on an intermediate carrier (3) onto a recording medium (2) using the transfer printing station according to one of the claims 1 to 18.
21. The method according to claim 20, in which for determining the OFF position of the transfer printing unit (UD) the drive unit (AE) moves the transfer printing unit until a Hall switch (H2) responds for the OFF position or until it reaches a mechanical reference stop (35) and in which then the position of the drive shaft (11) reached is stored.
22. The method according to claim 20 or 21, in which the ON position of the transfer printing unit (UD) is determined such that the drive unit (AE) moves the transfer printing unit (UD) torque-controlled to the intermediate carrier (3) until the transfer roller (1) rests on the intermediate carrier (3) and the drive shaft (11) is blocked and then this position of the drive shaft (11) is stored.
23. The method according to claim 21 or 22, in which the position of the drive shaft (11) is measured with the aid of a position counter (14).
24. The method according to one of the claims 20 to 23, in which upon pivoting the transfer printing unit (UD) from the OFF position, the drive unit (AE) is moved at first position-controlled until the ON position is reached and then is switched into the torque-control in order to adjust a constant pressing force of the transfer roller (1) to the intermediate carrier (3).
25. The method according to one of the claims 20 to 24, in which the pivot-away operation is effected position-controlled until the OFF position is reached.
26. The method according to one of the claims 20 to 25, in which the OFF position and the ON position are determined from the counter reading of the position counter (14).

Images