EP2657915B1 - Device and method for the serial printing of print media - Google Patents

Description

The invention relates to a device for serial printing of print media according to the preamble of claim 1 and a method for serial printing of print media.

From the US 5,321,436-A For example, a postage meter having an inkjet printhead is known, the printhead having a plurality of ink nozzles arranged along a line and extending transversely to a feed direction of a mailpiece to be printed. On the printhead a spacer plate is arranged with a guide surface which hold the mail pieces to be printed during printing at a predetermined distance from the nozzles of the printhead. The mail items to be printed are conveyed to the print head via conveyor belts, which are guided over resilient rollers. Due to the resilient mounting of the rollers, over which the conveyor belts are guided, the conveyor belts can be deflected in relation to the guide surface of the spacer plate down to adapt to different thicknesses of the mail pieces.

From the US 2011/0074844 A1 a method for printing on print media is known, in which the media to be printed are fed by means of a transport device to a print head. The transport device comprises a plurality of conveyor belts arranged one behind the other in the transport direction, wherein a central conveyor belt is located below the print head and is height-adjustable with respect to the print head to set a suitable distance between the print medium to be printed and the print head for printing the print media is below the printhead. This central conveyor belt is pivotally connected to the adjacent conveyor belts, wherein the transport belt upstream in the transport direction forms a feed ramp and the downstream in the transport direction conveyor belt a discharge ramp for the print media.

To bring a print medium to be printed on the print head in a suitable distance for printing between the surface to be printed of the print medium and a printing surface of the print head, the thickness of the print medium is first detected, while the print medium is transported to the print head with the transport device. When a print medium to be printed on the central transport belt is located below the print head, the central transport belt is moved to a suitable height relative to the print head to set a printable distance between the print medium surface to be printed and the print surface of the print head the detected thickness of the pressure medium is taken into account. As soon as the print medium is at a suitable distance from the print head and below the print head, the printing process is started, wherein the print medium is moved in the transport direction at a speed suitable for printing. After printing, the printed print medium from the central Passing conveyor belt on the downstream in the transport direction conveyor belt and transported away.

This known arrangement for the serial printing of print media proves to be particularly disadvantageous if the print head is a print head which has a certain longitudinal extent in the transport direction of the print media to be printed. This is the case, for example, in the case of inkjet printheads in which a plurality of ink jet nozzles (possibly for different printing inks) are arranged behind one another and at a distance from one another in the longitudinal direction of the printhead (and thus in the transport direction of the print media to be printed). Other printheads, such. B. laser printheads have a certain longitudinal extent in the longitudinal direction of the print head. This has the consequence that the height-variable transport device with which the print media to be printed are serially fed to the print head, while printing a print medium, which has been brought on the central conveyor belt from this to the print head, the height of the central conveyor belt with respect to Printhead can not be changed because the pressure medium located on the central conveyor belt must be kept during printing at the appropriate pressure distance to the print head. For this reason, subsequent print media can only be transferred to the central conveyor belt and be brought from this at a suitable distance to the print head when the previous print medium has been finished printed and handed over to the downstream conveyor belt. This requires a reduction in the possible transport speed of the transport device for the supply and removal of the print media and reduces the throughput of the printing device.

On this basis, the present invention seeks to provide an apparatus and a method for the serial printing of print media, with which a fast supply and removal of the print media is made possible. In particular, the throughput of printed print media in the printing device should be increased.

This object is achieved with a device for serial printing of print media with the features of claim 1 and with a method for serial printing of print media with the features of claim 10. Preferred embodiments of the device are specified in the dependent claims 2 to 9.

The inventive device is particularly suitable for printing on mail, such. B. of envelopes on which z. B. the recipient and sender address and / or a Porto imprint and / or advertising imprints are printed. The inventive apparatus for the serial printing of print media comprises a printing head extending in a longitudinal direction with a printing surface lying in a plane and a printing region extending in the longitudinal direction. Furthermore, the device according to the invention comprises a transport device for feeding the print media to be printed to the print head, wherein the transport device has at least a first transport device and a second transport device, which each move in a transport direction and are movable independently of one another in the orthogonal direction relative to the print surface of the print head to bring a guided on the transport means printing medium to the printing surface of the printhead and to bring the surface to be printed of the printing medium in a suitable for printing distance to the printing surface. According to the invention, the transport device has a transfer region which is located in the printing region of the printing surface so that a printing medium can be transferred from the first transporting device to the second transporting device in the transfer region and thus within the printing region. It is also possible to provide a plurality of transfer areas arranged one behind the other in the longitudinal direction within the printing area.

This arrangement of a transfer area or several transfer areas in the print area of the print head makes it possible for a print medium to be transferred from the first transport device to the second transport device already before, during or at the latest immediately after the end of printing. As a result, the positioning of the front transport device seen in the transport direction with respect to the printing surface can already be adapted to the next printing medium, which is to be printed on the printing medium which is currently in the printing area. This next printing medium may optionally have a different thickness than the printing medium, which is currently in the printing area. The adjustment of the positioning of the front transport device with respect to the printing surface is thus possibly still during the printing of the printing medium, which is currently in the printing area, or immediately after completion of the printing operation. There is therefore a faster adjustment of the positioning of the front transport under Consideration of the thickness of the downstream in the direction of transport pressure medium with respect to the printing surface. As a result, a higher feed and removal speed can be driven with the transport device. Furthermore, a smaller distance can be selected between successive print media, which are supplied to the print head in series with the transport device. Both measures can be achieved in each case an increased throughput of the printing device.

According to the invention, in the apparatus for serial printing of print media, the first transport device and the second transport device can be moved independently of one another in the orthogonal direction relative to the printing surface in order to set suitable distances between the transport surfaces of the first and the second transport device with respect to the printing surface. Suitably, both the first transport device and the second transport device are coupled to a drive for this purpose. The drive may be, for example, a servomotor or a linear motor. Suitably, each drive has a counterweight to compensate for the mass forces.

For detecting the thickness of the print media to be printed and to be supplied serially to the print head by means of the transport device, it is expedient to provide a thickness measuring device which is arranged in front of the print head in the transport direction. The thickness measuring device may be, for example, a rotary encoder. Preferably, an optical sensor is used to detect the thickness of the print media, which detects the thickness of the print media by means of a triangulation method. The thickness of each printing medium detected by the thickness measuring device is taken into account in the adjustment of the positions of the first and the second transport device with respect to the printing surface of the print head, to ensure that the surface to be printed on the optionally different thickness print media at a suitable distance during printing comes to the printing surface.

In a preferred embodiment, the transport device of the device according to the invention comprises a first conveyor belt and a second conveyor belt, wherein each conveyor belt is guided over a roller at its front end and at its rear end. At least one of the two rollers of each conveyor belt is driven by a motor.

Preferably, the conveyor belts of the first transport device and the second transport device are each designed as a suction belt belts, which suck a lying on the transport surface pressure medium by means of negative pressure.

In one embodiment of the device according to the invention, the transfer region of the transport device is formed by an overlap region in which the two transport devices overlap in the longitudinal direction. For this purpose, the two transport devices are expedient laterally offset side by side. The extent of the overlap region in the longitudinal direction expediently corresponds substantially to the longitudinal extent of the print area of the print head.

In order to ensure a secure transfer of a print medium from the first transport device to the second transport device, the transport surfaces of the two transport devices are expediently at the same level in the transfer of a pressure medium.

In a preferred embodiment of the device according to the invention, the first transport device and / or the second transport device with respect to the pressure surface is pivotable. This allows an inclination of the transport surfaces of the transport device with respect to the printing surface. The inclination of the transport surfaces takes place expediently in the direction perpendicular to the direction of transport. This embodiment of the device according to the invention is suitable for the serial printing of print media with a variable thickness or width across its width or length. By an inclined position of the transport surfaces of the transport device can be ensured in this case that the surfaces to be printed on the transport surfaces of the transport means lying print media are brought into a plane parallel to the printing surface.

Figur 1:

Schematische Darstellung einer ersten Ausführungsform einer erfindungsgemäßen Vorrichtung zum seriellen Bedrucken von Druckmedien in einer perspektivischen Ansicht;

Figur 2:

Seitenansicht der Vorrichtung von Figur 1;

Figur 3:

schematische Darstellung einer zweiten Ausführungsform einer erfindungsgemäßen Vorrichtung zum seriellen Bedrucken von Druckmedien in einer perspektivischen Ansicht;

Figur 4:

schematische Darstellung einer erfindungsgemäßen Vorrichtung zum seriellen Bedrucken von Druckmedien mit einem sich unterhalb des Druckkopfes befindlichen Druckmedium;

Figur 5:

Seitenansicht der Vorrichtung von Figur 5 mit dem zu bedruckenden Druckmedium;

Figur 6:

perspektivische Ansicht der Vorrichtung von Figur 4 mit einem ersten zu bedruckenden Druckmedium, welches sich gerade beim Bedrucken unterhalb des Druckkopfes befindet und eines zweiten, noch unbedruckten Druckmediums, welches mit der Transportvorrichtung dem Druckkopf zugeführt wird;

Figur 7:

Seitenansicht der Darstellung von Figur 6;

Figur 8:

Darstellung einer dritten Ausführungsform einer erfindungsgemäßen Vorrichtung zum seriellen Bedrucken von Druckmedien in einer Ansicht in Transportrichtung;

Figur 9:

Darstellung einer vierten Ausführungsform einer erfindungsgemäßen Vorrichtung zum seriellen Bedrucken von Druckmedien in einer Ansicht in Transportrichtung;

These and other advantages of the invention will become apparent from the embodiment described below with reference to the accompanying drawings. The drawings show:

FIG. 1:

Schematic representation of a first embodiment of a device according to the invention for the serial printing of print media in a perspective view;

FIG. 2:

Side view of the device of FIG. 1 ;

FIG. 3:

schematic representation of a second embodiment of an inventive apparatus for the serial printing of print media in a perspective view;

FIG. 4:

schematic representation of a device according to the invention for the serial printing of print media with a pressure medium located below the print head;

FIG. 5:

Side view of the device of FIG. 5 with the print medium to be printed;

FIG. 6:

perspective view of the device of FIG. 4 with a first print medium to be printed, which is just below the print head when printing and a second, still unprinted print medium, which is supplied with the transport device to the print head;

FIG. 7:

Side view of the presentation of FIG. 6 ;

FIG. 8:

Representation of a third embodiment of an apparatus according to the invention for the serial printing of print media in a view in the transport direction;

FIG. 9:

Representation of a fourth embodiment of an apparatus according to the invention for the serial printing of print media in a view in the transport direction;

In FIG. 1 a first embodiment of a device according to the invention for serial printing of print media is shown. The print media to be printed may be, for example, mail items such. As envelopes, acting on which a recipient and sender imprint and possibly a postage and / or advertising imprints is printed. However, the device according to the invention can also be used for printing other print media. The device according to the invention is particularly suitable for the serial printing of print media which have different geometries and in particular different thicknesses. The device according to the invention is for this purpose with a transport device 4 and a Printhead 2 is equipped, wherein the transport device 4, the print media to be printed in a transport direction R, which is colinear to the longitudinal direction of the transport device, transported to the print head 2 and transported away after printing from the print head 2. The transport device 4 is movable in its position in a direction orthogonal to the transport direction with respect to the print head to adjust a setting of a suitable for printing the print media distance with respect to the print head. This adjustment mechanism will become apparent from the following description of the embodiment of FIG. 1 out.

The printhead 2, which may, for example, be an inkjet printhead, has a housing and a plurality of pressure nozzles 2a, 2b, 2c, 2d arranged at a distance from one another in the longitudinal direction. The printing nozzles are, for example, to inkjet nozzles. The exit surfaces of the printing nozzles form an in-plane pressure surface 3, which extends in the longitudinal direction (ie in the direction of transport direction R of the transport device) over a pressure range 3a, which extends from the front pressure nozzle 2a to the rear pressure nozzle 2d. Suitably, the pressure surface 3 is in a horizontal plane, wherein a different arrangement of the print head is possible. As an alternative to an inkjet printhead, it is also possible, for example, to use a laser printhead which has a correspondingly planar printing surface 3 and a longitudinally extending printing region 3 a.

The transport device 4 comprises in the embodiment of FIG. 1 a first transport device 5 and a second transport device 6. The transport devices 5 and 6 each comprise a conveyor belt 15 and 16, which is expediently designed as a suction belt conveyor. Each suction belt belt 15, 16 has a plurality of openings, which are arranged in the longitudinal direction of the respective conveyor belt 15, 16 at a distance from each other. Each suction belt strap 15, 16 can be subjected to negative pressure in order to suck in a pressure medium lying on the transport surface 5c or 6c of the upper run of the suction belt straps 15, 16. The transport surfaces 5c and 6c of the conveyor belts 15 and 16 move expediently synchronously in a transport direction R in order to transport a printing medium resting on the respective transport surface 5c or 6c in the transport direction R. The front transport belt 15 of the first transport device 5 seen in the transport direction R is guided at its front end 5a via a first roller 11 and at its rear end 5b via a second roller 12. In the in FIG. 1 In the embodiment shown, the first roller 11 is rotationally driven by a motor 13 to move the conveyor belt 15 in the direction of transport R. In a corresponding manner, the conveyor belt 16 of the second transport device 6 is guided at its front end 6a via a first roller 11 and at its rear end 6b via a second roller 12, wherein in the FIG. 1 In the embodiment shown, the second roller 12 is driven by a motor 13 in order to move the conveyor belt 16 of the second transport device 6 in the transporting direction R.

In the transverse direction to the transport direction R 15 and 16 transport supports 17 and 18 are arranged on both sides of the conveyor belts. The transport supports 17 and 18 serve to guide the print media located on the transport surfaces 5c and 6c during their transport in the first transport device 5 and the second transport device 6, respectively.

Both the first transport device 5 and the second transport device 6 can be moved perpendicular to the transport direction R with respect to the stationary print head 2. For this purpose, a drive 8 is provided on the first transport device 5 and a drive 9 on the second transport device 6. The drives 8, 9 may be, for example, a servo motor or a linear motor. About the drives 8 and 9, the two transport devices 5 and 6 are moved independently of one another in a direction orthogonal to the transport direction R and relative to the print head 2. As a result, the first transport device 5 can be positioned independently of the second transport device 6 with respect to the stationary printhead 2 so that the distance between the transport surface 5c and the printing surface 3 of the printhead 2 can be infinitely adjusted within predefined limits. In a corresponding manner, the distance between the transport surface 6c of the second transport device 6 and the printing surface 3 of the print head 2 can also be adjusted steplessly within predefined limits and independently of the positioning of the first transport device 5.

The two transport devices 5 and 6 are arranged one behind the other in the longitudinal direction and in alignment with each other. The rear end 5b of the first transport device 5 adjoins the front end 6a of the second transport device 6. The rear end 5b of the first transport device 5 and the front end 6a of the second transport device 6 form a transfer region 7. In this transfer region 7, a pressure medium of the first transport device 5 are transferred to the second transport device 6. The exact length of the transfer region 7 in the longitudinal direction depends on the dimensions of the print media to be transported. The transfer region 7 is defined by the region in the longitudinal direction, in which a secure transfer of a pressure medium from the first transport device 5 to the second transport device 6 can take place.

As can be seen in particular from the side view of FIG. 2 results, this transfer area 7 is below the printhead 2, which in the embodiment of the FIGS. 1 and 2 is arranged so that the pressure surface 3 is in a horizontal plane. The transfer area 7 located below the print head 2 is located within the print area 3a of the print head 2, that is, in the longitudinal direction between the front print nozzle 2a and the rear print nozzle 2d. In order to ensure a secure transfer of a print medium from the first transport device 5 to the second transport device 6, the positions of the transport devices 5 and 6 are suitably adjusted by means of the drives 8 and 9 so that the transport surfaces 5c and 6c during the transfer to the same position (ie the same height) are.

In the FIGS. 4 and 5 is shown schematically in a perspective view and a side view, the supply of a print medium 1 to the print head 2. For feeding the print medium 1 to the print head 2 with which the print medium 1 is to be printed, the print medium 1 located on the transport surface 5c of the first transport device 5 is moved by the transport device 5 in the transport direction R to the print head 2. In order to bring the surface to be printed 1a of the printing medium 1 in a suitable distance for printing on the printing surface 3, the position of the first transport device 5 by means of the drive 8 with respect to the printing surface 3 is moved.

The exact positioning of the first transport device 5 with respect to the print head 2 results from the appropriate distance between the surface to be printed 1a of the print medium 1 and the thickness of the print medium. For detecting the thickness of the printing medium, therefore, a thickness measuring device, not shown in the drawing, is provided, which is arranged in front of the print head 2 in the direction of transport R. The thickness measuring device may be, for example, a rotary encoder. However, to detect the thickness of the print media 1, an optical sensor is preferred used. In this case, in particular an optical sensor has proven to be suitable, which determines the thickness of the print media 1 via an optical triangulation method.

The detected by the thickness gauge thickness of each print medium 1, which is supplied to the print head 2 by means of the transport device 4 is transferred to a control device (not shown here) and determines the control device taking into account the appropriate pressure gap between the surface 1a of the print medium 1 and the printing surface 3 of the print head 3, the position to be set of the first transport device 5 with respect to the printhead 2. The thus determined optimum position of the first transport device 5 is then set via the drive 8 and the printing medium 1 to be printed by the first transport device 5 in this position to the print head 2 approached. If the front edge of the print medium 1 seen in the transport direction R is at the front beginning of the print area 3, the printing process begins. During printing, the printing medium is moved by the first transporting device 5 further in the transporting direction R until the trailing edge of the printing medium 1 has reached the rear end of the printing area 3 and the printing has ended. After completion of the printing process, the printed printing medium 1 is transferred from the first transport device 5 to the second transport device 6. The transfer takes place at the in the FIGS. 1 and 2 After the transfer of the printed print medium 1 from the first transport device 5 to the second transport device 6, the printed print medium is the first embodiment shown by switching on or off the negative pressure in the suction belt belts 15 and 16, respectively from the second transport device 6 further transported in the transport device R and then transferred to a downstream in the transport direction R (not shown here) further transport device or processing device.

In an alternative process control, the transfer of the printing medium 1 from the first transport device 5 to the second transport device 6 already takes place during printing, ie while the printing medium 1 is in the printing region 3 a of the print head 2. With the device according to the invention, it is also possible to transfer a printing medium 1 to be printed from the first transport device 5 to the second transport device 6 even before the beginning of the printing process. The transfer of a print medium 1 is always carried out in the transfer area 7, located in the printing area 3a of the printing surface 3 is located. In the in the FIGS. 1 and 2 In the embodiment shown in which the pressure surface 3 lies in a horizontal plane, the pressure region 3a is defined by the longitudinally extending region between the front pressure nozzle 2a and the rear pressure nozzle 2d. When using other printheads which do not have a plurality of printing nozzles arranged one behind the other, the printing area 3a is defined by the longitudinally extending area in which the printing head 2 emits printing ink.

In FIG. 6 and FIG. 7 is the serial supply of print media 1 to the printhead 2 and their removal after printing shown. In the FIGS. 6 and 7 a first printing medium 1 is shown, which is located on the transport surface 6c of the second transport device 6 and within the printing area 3a and is being printed. A second printing medium 1 'is located on the transport surface 5c of the first transport device 5. The second transport device 6 transports the printing medium 1 during printing through the printing area 3a of the printhead 2 and is therefore in a position in which the surface 1a of the printing medium 1 has a suitable for printing distance to the printing surface 3 of the print head 2. On the other hand, the first transport device 5 is in a lower position relative to the print head 2. In this position, the first transporting device 5 transports a second printing medium 1 'to be printed to the printing head 2. Due to the independent adjustment of the positions of the first transporting device 5 and the second transporting device 6 with respect to the printing head 2, it is possible to change the position (shown in FIG Embodiment, the height) of the first transport device 5 with respect to the print head 2 to the thickness of the print medium 1 'to adjust the optimal distance of the surface to be printed 1a' of the printing surface 3. Since the printing medium 1 'may have a different thickness than the preceding printing medium 1, the first transport device 5 - regardless of the position of the second transport device 6 - with respect to the printhead 2 are set so that the surface 1a' of the print medium 1 'to the Printing has a suitable distance from the printing surface 3 of the print head 2. As a result, the position of the first transport device 5 can already be adapted to the thickness of the print medium 1 ', while the preceding print medium 1 is still in the print area 3a of the print head 2 and is printed there.

The invention is not on the in the FIGS. 1 and 2 shown embodiment limited. FIG. 3 shows, for example, a second embodiment of a device according to the invention, in which the first transport device 5 comprises a plurality of parallel to each other and extending in the longitudinal direction and in the transverse direction spaced apart conveyor belts 15a, 15b and 15c. In a corresponding manner, the second transport device 6 also comprises a plurality of transversely spaced conveyor belts 16a, 16b, 16c and 16d. The conveyor belts 15a, 15b and 15c of the first transport device 5 are arranged offset relative to one another with respect to the conveyor belts 16a, 16b, 16c and 16d of the second transport device 6 in the transverse direction. The transfer region 7, which is provided for transferring a printing medium from the first transport device 5 to the second transport device 6, is thereby formed by an overlap region in which the two transport devices 5 and 6 overlap in the longitudinal direction. To form the overlap region, the rear end 5b of the first transport device 5 is located behind the front end 6a of the second transport device 6. The extent of the overlap region 7 in the longitudinal direction expediently corresponds substantially to the longitudinal extent of the printing region 3a of the print head 2.

In another exemplary embodiment, which is not illustrated here, the first transport device 5 and the second transport device 6 comprise a plurality of transport rollers arranged one behind the other in the longitudinal direction instead of conveyor belts. The transport rollers can be driven separately from each motor associated with each transport roller. It is also possible to provide a single motor for driving the transport rollers and to couple the transport rollers with each other via a drive belt. In this case, it is also possible to provide a plurality of transfer areas 7, which are arranged one behind the other in the longitudinal direction and within the printing area 3a.

In a preferred embodiment of the device according to the invention, a single motor 13 is provided to move the two transport devices 5 and 6 in the transport direction R. In this case, the first transport device 5 is coupled directly to this single motor. The second transport device 6 is connected via a coupling with the motor. In this embodiment, it is possible to set a different transport speed of the first transport device 5 with respect to the second transport device 6 by using a gear coupling. Thereby For example, it is possible to set a faster removal of the already printed print media with the second transport device 6, in comparison to the transport of the still unprinted print media to the print head 2 with the first transport device 5.

In a preferred embodiment of the device according to the invention, it is provided to program the control device of the device in such a way that a printing medium located on the first transport device 5 is transferred to the second transport device 6 and transported therefrom in the transport direction R as soon as the printing medium in the transfer region 7 located.

To compensate for the flywheel masses is also provided in a drawing, not shown embodiment, to provide the two drives 8, 9 each with a counterweight to compensate for the inertial forces. This allows a vibration-free approach of the transport devices 5, 6 to the print head 2.

In the FIGS. 7 and 8th show two embodiments of the device according to the invention, which are particularly suitable for the serial printing of print media, which have over their width or their length a thickness profile. In order to bring the printing surface of such print media with a thickness profile during printing in an optimal position with respect to the print head, is provided in these embodiments of the device according to the invention that the first transport device 5 and / or the second transport device 6 with respect to the pressure surface 3 is pivotable. The pivotability of the transport devices 5, 6 allows an inclination of the transport surfaces 5c and 6c of the transport devices 5 and 6 with respect to the printing surface 3. The inclination of the transport surfaces 5c, 6c is carried out appropriately, as in the FIGS. 7 and 8th By the inclination of the transport surfaces 5c, 6c of the transport devices 5, 6 can be ensured that the surfaces to be printed on the transport surfaces of the transport devices 5, 6 lying print media 1 in a pressure surface. 3 parallel plane. By simultaneously adjusting the height of the transport devices 5, 6 with respect to the print head 2, the surfaces of the print media to be printed can thus be brought into a plane parallel to the printing surface 3 and at a suitable printing distance.

The oblique position of the transport surfaces 5 c, 6 c is expediently carried out by pivoting the first transport device 5 or the second transport device 6 with respect to the print head 2 Fig. 8 illustrated embodiment, each of the two transport devices 5, 6 mounted on at least two spindles 20, 21. These spindles 20, 21 are arranged in the direction perpendicular to the transport direction R direction S at a distance from each other. The spindles 20, 21 are coupled to a motor, for example a servo motor, and can be moved independently therefrom in order to realize the inclination of the transport device 5 or 6.

At the in Fig. 9 the embodiment shown, the two transport devices 5, 6 are each mounted only on a single spindle 20. In this embodiment, the oblique position of the transport surfaces 5c and 6c takes place with respect to the pressure surface 3 by adjusting means not shown here.

Claims (10)

1. Device for serial printing on print media (1), with a printing head (2) with a printing surface (3) lying in one plane and a printing region (3a) extending in a longitudinal direction and with a transport device (4) for conveying the print media (1) on which printing is to be carried out to the printing head (2), wherein the transport device (4) exhibits a first transport unit (5) and at least one second transport unit (6) which move the print media (1) parallel to the printing surface (3) and can be moved in an orthogonal direction relative to the printing surface (3) in order to guide a print medium (1) carried on the transport units (5, 6) to the printing surface (3) of the printing head (2) and position it a suitable distance from the printing surface (3) for printing, characterised in that each of the two transport units (5, 6) has an associated drive (8, 9) with which the respective transport unit (5; 6) can be moved independently of the other transport unit (6; 5) in an orthogonal direction relative to the printing surface (3), and a transfer region (7) is provided which is located in the printing region (3a) of the printing surface (3) in order to transfer a print medium (1) in the transfer region (7) from the first transport unit (5) to the second transport unit (6).
2. Device according to claim 1, characterised in that the transfer region (7) is formed by an overlapping region in which the two transport units (5, 6) overlap in the longitudinal direction.
3. Device according to claim 1 or 2, characterised in that the two transport units (5, 6) are arranged laterally offset next to one another and each of the two transport units (5, 6) exhibits a front end (5a, 6a) viewed in the transport direction (R) and a rear end (5b, 6b), wherein the rear end (5b) of the front transport unit (5) viewed in the transport direction lies behind the front end (6a) of the rear transport unit (6).
4. Device according to one of the preceding claims, characterised in that a print medium (1) located on the front transport unit (5) is transferred to the rear transport unit (6) and then transported further in the transport direction (R) by the latter as soon as the print medium (1) is in the transfer region (7).
5. Device according to claim 4, characterised in that when a print medium (1) is transferred from the front transport unit (5) to the rear transport unit (6) the transporting surfaces (5c, 6c) of the two transport units (5, 6) lie on the same level.
6. Device according to one of the preceding claims, characterised in that the two transport units (5, 6) are each embodied as suction transport belts which suck down a print medium (1) lying on the transporting surface (5c, 6c) by means of vacuum.
7. Device according to one of the preceding claims, characterised in that each of the two transport units (5, 6) has a first roller (11) at its front end (5a, 6a) and a second roller (12) at its rear end (5b, 6b), wherein in each case at least one of the rollers (11) is driven by a motor (13).
8. Device according to one of the preceding claims, characterised in that the transport device (4) exhibits a single motor (13) which is connected to one of the two transport units (5 or 6) in order to set this in motion in the transport direction and in that the other transport unit (6 or 5) is connected to this motor (13) by means of a coupling.
9. Device according to one of the preceding claims, characterised in that the first transport unit (5) and/or the second transport unit (6) can be swivelled with respect to the printing surface (3).
10. Method for serial printing on print media (1), with the following steps:

    - serial conveyance of the print media (1) on which printing is to be carried out to a printing head (2) with a printing surface (3) lying in one plane and a printing region (3a) extending in the longitudinal direction by means of a transport device (4) which comprises a first transport unit (5) and at least one second transport unit (6) which each move in a transport direction (R) running parallel to the longitudinal direction of the transport units (5, 6) and can be moved in an orthogonal direction relative to the printing surface (3) independently of one another for which each of the two transport units (5, 6) has an associated drive (8, 9) with which the respective transport unit (5; 6) can be moved in an orthogonal direction independently of the other transport unit (6; 5),

    - guidance of a print medium (1) on which printing is to be carried out to the printing head (2) to a point a suitable distance therefrom for printing by movement of at least one of the two transport units (5, 6) in an orthogonal direction by means of the drive (8, 9) provided for this,

    - transfer of the print medium (1) from the first transport unit (5) to the second transport unit (6) in a transfer region (7), wherein the transfer region (7) is located in the printing region (3 a) of the printing surface (3).

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