DE102024111941A1 - Printing mechanism for an inkjet printing device - Google Patents

Abstract

A printing unit (140) is described which has one or more printing bars (102) for printing on a recording medium (120), wherein the printing unit (140) is designed to deflect the recording medium (120) from the horizontal orientation in a locally limited manner between successive printing bars (102), so that the recording medium (120) is guided essentially in a straight line through the printing unit (140), and so that, due to the locally limited deflection, a tensile force is exerted to smooth the recording medium (120) under the individual printing bars (102).

Description

The invention relates to a printing mechanism for an inkjet printing device.

Inkjet printing devices are used for printing on recording media, such as paper. The printing device comprises at least one printing unit with one or more printing bars, each associated with one or more specific types of ink, particularly one or more specific printing colors. The recording medium can be guided past the individual printing bars of the printing unit along a specific transport path. This transport path preferably has a specific curvature in order to reduce the waviness of the recording medium within the printing unit, particularly below the individual printing bars, by means of the tensile stress caused by the curvature.

The use of a curved transport path of the recording medium through the printing unit of an inkjet printing device is typically associated with increased build space requirements, increased complexity and increased costs.

This document addresses the technical problem of providing a compact and efficient printing unit for an inkjet printing device without affecting the waviness of the recording medium and thus the print quality. This problem is solved by the features of the independent claim.

According to one aspect, a printing unit for an inkjet printing device is described. The printing unit comprises at least one printing bar configured to fire ink droplets along, and in particular parallel to, the vertical axis onto a recording medium, especially a ribbon-shaped recording medium, in order to print an image onto the front of the recording medium. The printing unit further comprises at least one first support element and at least one second support element, each configured to act on the back of the recording medium at a support point of the respective support element while the recording medium is guided through the printing unit past the printing bar along a transport direction. The first support element is arranged behind the second support element with respect to the transport direction. Furthermore, the support points of the first and second support elements are arranged along the vertical axis at a uniform and/or the same height.

• • der Aufzeichnungsträger an dem zweiten Stützelement um einen Umlenkwinkel von einer horizontalen Achse weg ausgelenkt wird; und
• • der Aufzeichnungsträger an dem ersten Stützelement um den gleichen Umlenkwinkel zu der horizontalen Achse hin ausgelenkt wird.

The printing mechanism also includes at least one deflection unit, which is arranged between the second support element and the subsequent first support element, and which is designed to deflect the recording medium away from the printing bar along the vertical axis in such a way that

• • the recording medium is deflected away from a horizontal axis by an angle at the second support element; and
• • the recording medium is deflected at the first support element by the same deflection angle towards the horizontal axis.

The deflection unit is preferably arranged directly downstream of the second support element. Furthermore, the first support element is preferably arranged directly downstream of the deflection unit.

• 1a ein Blockdiagramm einer beispielhaften Tintenstrahl-Druckvorrichtung;
• 1b einen beispielhaften gekrümmten Transportweg durch das Druckwerk einer Tintenstrahl-Druckvorrichtung;
• 2a bis 2c beispielhafte Druckwerke mit einem geradlinigen Transportweg des Aufzeichnungsträgers; und
• 3 ein beispielhaftes Druckwerk mit zusätzlichen Mitteln zur Reduzierung der Welligkeit eines Aufzeichnungsträgers.

Exemplary embodiments of the invention will now be described in more detail with reference to the schematic drawing. These show:

• 1a a block diagram of an exemplary inkjet printing device;
• 1b an exemplary curved transport path through the printing mechanism of an inkjet printing device;
• 2a to 2c Exemplary printed works with a straight transport path of the recording medium; and
• 3 An exemplary printed work with additional means for reducing the waviness of a recording medium.

The in 1a The printing device 100 shown is designed for printing onto a sheet-shaped, flat, disc-shaped, or tape-shaped recording medium 120. The recording medium 120 can be unwound from a roll. The recording medium 120 can have a length along the transport direction 1 that is significantly greater than its width, e.g., by a factor of 10 or more, in particular 100 or more. The recording medium 120 can be made of paper, cardboard, carton, metal, plastic, textiles, a combination thereof, and/or other suitable and printable materials. The recording medium 120 is guided along the transport direction 1, indicated by an arrow, through the printing unit 140 of the printing device 100.

In the illustrated example, the printing unit 140 of the printing device 100 comprises two printing bars 102, each printing bar 102 being usable for printing with ink of a specific color, e.g., black, cyan, magenta. and/or yellow and, if applicable, MICR ink. Different printing bars 102 can be used for printing with different inks. Furthermore, the printing device 100 can include at least one fixing or drying unit 150, which is configured to fix a printed image printed onto the recording medium 120.

A print bar 102 can comprise one or more print heads 103, which may be arranged side by side in several rows to print the pixels of different columns 31, 32 of a print image onto the recording medium 120. In the 1a In the example shown, a print bar 102 comprises five print heads 103, each print head 103 printing the pixels of a group of columns 31, 32 of a print image onto the recording medium 120.

Each printhead 103 of the printing unit 140 comprises in the 1a In the illustrated embodiment, several nozzles 21, 22 are provided, each nozzle 21, 22 being configured to fire or propel ink droplets onto the recording medium 120. For example, a printhead 103 of the printing unit 140 can comprise several thousand effectively used nozzles 21, 22 arranged along several rows transverse to the transport direction 1, i.e., along the print width, of the recording medium 120. By means of the nozzles 21, 22 of a printhead 103 of the printing unit 140, pixels of a line of a printed image can be printed onto the recording medium 120 transverse to the transport direction 1, i.e., along the width of the recording medium 120.

The printing device 100 further comprises a control unit 101, e.g., control hardware and/or a controller, which is configured to control the actuators of the individual nozzles 21, 22 of the individual printheads 103 of the printing unit 140 in order to apply the printed image to the recording medium 120 depending on print data. The print data can indicate for each nozzle 21, 22, i.e., for each column 31, 32 of the printed image, and for each line of the printed image, whether ink should be ejected or not, and if applicable, what quantity of ink should be ejected.

The printing unit 140 of the printing device 100 thus comprises at least one printing bar 102 with K nozzles 21, 22, which can be controlled with a specific line rate to print a line, running perpendicular to the transport direction 1 of the recording medium 120, with K pixels or K columns 31, 32 of a printed image onto the recording medium 120, e.g. with K>1000. In the example shown, the nozzles 21, 22 are fixed in the printing device 100, and the recording medium 120 is moved past the stationary nozzles 21, 22 at a specific transport speed.

1b Figure 1 shows an exemplary curved transport path of the recording medium 120 through a printing unit 140. In transport direction 1, a backup roller 141, also referred to as a support cylinder, can be arranged directly in front of and behind each printing cylinder 102. The recording medium 120 travels in a straight line between the backup rollers 141 for each printing cylinder 102. Furthermore, the printing cylinder 102 is arranged perpendicular to the recording medium 120.

At each of the support rollers 141, the recording medium 120 is deflected by a specific angle 142. A support roller 141 typically acts on the recording medium 120 at a central support point. The angle 142 can be the angle between the path of the recording medium 120 and the orientation of the tangent of the support roller 141 at the support point. The angle 142 can be 2.5° or greater. Optionally, the angle 142 can be less than 2.5°. Preferably, the angle 142 is greater than 0°. The angle 142 enables the support roller 141 to exert a supporting force on the recording medium 120, thereby tensioning the recording medium 120 along the transport direction 1 and reducing the waviness of the recording medium 120 below a pressure bar 102.

The provision of deflection angles 142 on the individual support rollers 141 results in a curved transport path of the recording medium 120 through the printing unit 140, which is associated with an increased requirement for installation space. Furthermore, the individual printing bars 120 must be installed at an angle, which is associated with increased complexity in the mechanical design of the printing unit 140.

In the 2a to 2c Printing units 140 are depicted, which have a transport path for the recording medium 120 that is essentially straight and runs essentially parallel to the horizontal axis. For this purpose, each printing unit 140 has one or more deflection units 200, each configured to effect a first deflection of the recording medium 120 according to the deflection angle 142 in a first direction, e.g. downwards, and immediately thereafter a second deflection of the recording medium 120 according to the deflection angle 142 in a second direction, e.g. upwards, the second direction being opposite to the first direction. Thus, two deflections of the recording medium 120 can occur directly in succession. The recording carrier 120 can be deflected in opposite directions. This ensures a substantially straight transport path with only localized deviations from this straight course. Furthermore, this ensures that the recording carrier 120 maintains a deflection angle 142 at the individual support rollers 141, 241, 242, allowing the recording carrier 120 to be tensioned in the transport direction 1 by the individual support rollers 141, 241, 242.

The printing unit 140 has a pair of backup rollers 241, 242 for each group of one or more printing bars 102, with a first backup roller 241 in the transport direction 1 in front of the printing bar group and a second backup roller 242 in the transport direction 1 behind the printing bar group. The recording carrier 120 is guided over a support point 243 on the first backup roller 241, then passes the printing bar group and is subsequently guided over a support point 243 on the second backup roller 242. Before the support point 243 of the first backup roller 241, the recording carrier 120 has a deflection angle 142 with respect to the tangent of the first backup roller 241 at the support point 243. On the other hand, the recording carrier 120 runs parallel to the tangent of the first backup roller 241, i.e., parallel to the horizontal axis, behind the support point 243 of the first backup roller 241. Conversely, the recording carrier 120 runs parallel to the tangent at the support point 243 of the second backup roller 242 in front of the support point 243 of the second backup roller 242. On the other hand, the recording carrier 120 has a deflection angle 142 behind the support point 243 of the second backup roller 242 with respect to the tangent at the support point 243 of the second backup roller 242.

The support point 243 of the individual backup rollers 241, 242 is typically the highest point of the respective backup roller 241, 242 along the vertical axis. The tangent of a backup roller 241, 242 at the support point 243 of the backup roller 241, 242 typically runs parallel to the horizontal axis.

By means of a pair of support rollers 241, 242, it can thus be ensured that the recording carrier 120 runs parallel to the horizontal axis below a pressure bar group, so that the one or more pressure bars 102 of the pressure bar group can be aligned parallel to the vertical axis, and thus in an efficient manner.

Between the second support roller 242 for a first pressure bar group and the first support roller 241 for a subsequent second pressure bar group, a deflection unit 200 is arranged, which is designed to cause a temporary offset of the path of the recording carrier 120 in a vertical direction downwards, so that a deflection angle 142 is caused at the second support roller 242 for the first pressure bar group and at the first support roller 241 for the second pressure bar group.

In the 2a In the illustrated example, the deflection unit 200 is configured to exert a deflection force 201 on the recording medium 120 from the rear side, causing the recording medium 120 to be temporarily displaced vertically downwards. The deflection unit 200 can be configured to generate a vacuum for this purpose.

In the 2b In the illustrated example, the deflection unit 200 is configured to exert a deflection force 201, in particular a pressure force, from the front of the recording medium 120. The deflection unit 200 can, for example, include a blower that generates an airflow acting on the front of the recording medium 120 to deflect the recording medium 120 downwards in a vertical direction.

In the 2c In the example shown, the deflection unit 200 has a roller 200, in particular a non-contact deflection roller, which acts on the front of the recording carrier 120.

The printing unit 140 may further have means designed to exert a stretching force in the transverse direction, which runs transversely to the transport direction 1 and parallel to the horizontal axis, on the recording medium 120 in order to further reduce the waviness of the recording medium 120 within the printing unit 140. 3 Figure 1 shows, for example, the use of one or more lateral grippers 300, which can exert a stretching force 301 in the transverse direction. The individual grippers 300 can be configured to pull the side edges of the recording medium 120 apart along the transverse direction. Figure 2 further shows 3 The use of stretching rollers 302 in the printing unit 140, particularly at the infeed and/or outfeed of the printing unit 140, by means of which a stretching force 301 can be exerted in the transverse direction on the recording medium 120. This allows the waviness of the recording medium 120 to be further reduced and the print quality to be further improved.

As already explained at the beginning, the pressure bars 102, and in particular the print heads 103 in the individual pressure bars 102, have a relatively small distance, e.g. 1 mm or less, from the The recording medium 120 to be printed, e.g., a paper web, is therefore required. To ensure high print quality, the recording medium 120 should have a reliably flat surface across its entire printing area. To reduce the required build volume and complexity, it is advantageous to guide the recording medium 120, especially the paper web, in a straight line, parallel to the horizontal axis, under the printing bars 102. As described in this document, deflection units 200 can be arranged between the individual printing bars 102 or groups of printing bars. These deflection units are designed to deflect the recording medium 120 in such a way that the effect of a curved, arc-shaped transport path of the recording medium 120 is replicated at the individual backup rollers 141, 241, 242.

The deflection unit 200 can include a suction device designed to pull the recording carrier 120 downwards between two pressure bar groups. This generates the required normal force 201, which acts on the support rollers 241, 242 and thus flattens the recording carrier 120.

Alternatively or additionally, the deflection unit 200 can have a blowing device, e.g., a so-called air knife, which is designed to press the recording carrier 120 downwards by means of an airflow. In this way, the required normal force 201 can be generated, which acts on the support rollers 241, 242 and thus flattens the recording carrier 120.

Alternatively or additionally, the deflection unit 200 can be configured to effect a contactless deflection of the recording medium 120, in particular by means of a deflection rod or a deflection roller, by which the recording medium 120 is pressed downwards. The contactless deflection is carried out in such a way that the unfixed or undried printed image is not damaged by the deflection. This can be achieved, for example, by an air cushion, a microporous guide element, and/or an anti-adhesive surface coating.

Lateral grippers 300 can be used to stretch the recording medium 120 laterally. Alternatively or additionally, the smoothing of the recording medium 120 can be achieved via spreading rollers 302 at the infeed and outfeed of the printing unit 140.

A printing unit 140 for an inkjet printing device 100 is thus described. The printing unit 140 comprises at least one printing bar 102, which is configured to fire ink droplets along the vertical axis onto a recording medium 120 in order to print an image onto the front of the recording medium 120. Typically, the printing unit 140 comprises a sequence of successive printing bars 102. The recording medium 120 is guided past the one or more printing bars 102, in particular the sequence of printing bars 102, along a transport direction 1.

The individual printing bars 102 of the printing unit 140 are preferably aligned such that the ink output occurs along the vertical axis, in particular parallel to the vertical axis. This allows for a cost-effective and space-efficient arrangement of the one or more printing bars 102.

The vertical axis typically runs perpendicular to the floor on which the printing unit 140 stands. The horizontal axis typically runs parallel to the floor on which the printing unit 140 stands.

The printing unit 104 comprises a first support element 241 and a second support element 242, each configured to act on the back of the recording medium 120 at a support point 243 of the respective support element 241, 242, while the recording medium 120 is guided through the printing unit 140 past the one or more printing bars 102 along the transport direction 1. Preferably, and in particular, the first support element 241 and/or the second support element 242 each comprise a support roller. The support point 243 can each correspond to a straight line extending transversely across the width of the recording medium 120, perpendicular to the transport direction 1. The first support element 241 and the second support element 242 typically contact the back of the recording medium 120 at their respective support point 243.

The first support element 241 is arranged behind the second support element 242 with respect to the transport direction 1. The first support element 241 can, for example, be arranged directly in front of, i.e., at the inlet to, a pressure bar 102 of the printing unit 140. The second support element 242 can be arranged directly behind, i.e., at the outlet of, a pressure bar 102 of the printing unit 140.

The support points 243 of the first support element 241 and the second support element 242 are preferably arranged at a uniform and/or the same height along the vertical axis. As a result, the recording carrier 120 has the same height, with respect to the vertical axis, at the support point 243 of the first support element 241 as at the support point 243 of the second support element 242.

• • der Aufzeichnungsträger 120 an dem zweiten Stützelement 242 um einen bestimmten Umlenkwinkel 142 von der horizontalen Achse weg ausgelenkt wird; und
• • der Aufzeichnungsträger 120 an dem ersten Stützelement 241 um den gleichen Umlenkwinkel 142 zu der horizontalen Achse hin ausgelenkt wird.

The printing unit 140 further comprises at least one deflection unit 200, which is arranged between the second support element 242 and the first support element 241, and which is designed to deflect the recording carrier 120 along the vertical axis away from the printing bar 102, i.e. in particular downwards or towards the ground, such that

• • the recording carrier 120 is deflected away from the horizontal axis by a certain deflection angle 142 at the second support element 242; and
• • the recording carrier 120 is deflected at the first support element 241 by the same deflection angle 142 towards the horizontal axis.

The deflection angle 142 can be, for example, between 1° and 5°, particularly around 2.5°. In particular, the deflection angle 142 is preferably greater than 0°. The deflection angle 142 can be selected depending on the normal (tensile) force required to sufficiently smooth out any waves forming on the recording medium 120. Typically, the normal (tensile) force exerted on the recording medium 120 increases with an increasing deflection angle 142.

As already explained, the second support element 242 can be arranged directly behind a pressure bar 102 of the printing unit 140 with respect to the transport direction 1. The printing unit 140 can further be designed such that the recording carrier 120 runs parallel to the horizontal axis below the pressure bar 102 towards the support point 243 of the second support element 242.

Alternatively or additionally, the first support element 241 can be arranged directly in front of a pressure bar 102 of the printing unit 140 with respect to the transport direction 1. The printing unit 140 can be designed such that the recording medium 120 runs away from the support point 243 of the first support element 241 below the pressure bar 102, parallel to the horizontal axis.

The printing unit 140 can have a first pressure bar 102 and a second pressure bar 102 following it in the transport direction 1. The second support element 242 can be arranged directly behind the first pressure bar 102 with respect to the transport direction 1, and the first support element 241 can be arranged directly in front of the second pressure bar 102 with respect to the transport direction 1.

The deflection unit 200 is preferably designed to exert such a high normal force along the vertical axis on the recording carrier 120 that a sufficiently high tensile force in the transport direction 1 acts on the recording carrier 120 at the support point 243 of the first and/or the second support element 241, 242 in order to smooth the recording carrier 120.

As already explained, the printing unit 140 can comprise a sequence of successive printing bars 102 arranged one behind the other along the transport direction 1. The printing unit 140 preferably has, between each pair of, for example, directly successive, printing bars 102, a second support element 242, a subsequent deflection unit 200, and a subsequent first support element 241.

The printing unit 140 can comprise an input roller 302 at the inlet of the printing unit 140 and an output roller 302 at the outlet of the printing unit 140. The printing unit 140 is preferably designed such that the transport direction 1 of the recording medium 120 between the input roller 302 and the output roller 302 runs substantially parallel to the horizontal axis and/or, apart from the deflection at the one or more deflection units 200, runs parallel to the horizontal axis.

A printing unit 140 is thus described, which has one or more printing bars 102 for printing on a recording medium 120. The printing unit 140 is configured to deflect the recording medium 120 between successive printing bars 102 from its horizontal orientation, i.e., from an orientation parallel to the horizontal axis, in a locally limited manner, so that the recording medium 120 is guided essentially in a straight line through the printing unit 140. Due to the locally limited deflection between the printing bars 102, a tensile force is exerted to smooth the recording medium 120 under the individual printing bars 102. In this way, a printing unit 140 with high print quality can be provided efficiently.

The one or more deflection units 200 are preferably designed to deflect the recording carrier 120 away from the pressure bar 102, in particular downwards, without contact along the vertical axis.

• • an der Rückseite des Aufzeichnungsträgers 120 einen Unterdruck zu bewirken und/oder einen Saug-Gasstrom, insbesondere einen Saug-Luftstrom, zu bewirken; und/oder
• • an der Vorderseite des Aufzeichnungsträgers 120 einen Überdruck zu bewirken und/oder einen Gasstrom, insbesondere einen Luftstrom, auf die Vorderseite des Aufzeichnungsträgers 120 zu blasen.

A deflection unit 200 can, for example, be designed to

• • to create a negative pressure and/or a suction gas flow, in particular a suction air flow, on the back of the recording medium 120; and/or
• • to create overpressure on the front of the recording medium 120 and/or to blow a gas flow, in particular an air flow, onto the front of the recording medium 120.

This allows the recording carrier 120 to be deflected away from the pressure bar 102 along the vertical axis in a particularly gentle manner.

A deflection unit 200 can comprise a deflection rod and/or a deflection roller configured to act on the front of the recording carrier 120 in order to deflect the recording carrier 120 away from the pressure bar 102 along the vertical axis. The deflection unit 200 can have a microporous surface and/or an anti-adhesive surface coating. This allows the recording carrier 120 to be deflected away from the pressure bar 102 along the vertical axis in a particularly gentle manner.

The printing unit 140 can comprise at least one stretching unit 300, 302 configured to stretch the recording medium 120 along the transverse direction, which runs perpendicular to the transport direction 1 and parallel to the horizontal axis. The stretching unit 300, 302 can, for example, comprise one or more lateral grippers 300 and/or one or more stretching rollers 302. This further improves the smoothness of the recording medium 120 and thus the print quality of the printing unit 140.

Furthermore, this document describes an inkjet printing device 100 which includes one or more of the printing units 140 described in this document, e.g., a printing unit 140 for printing the front side and another printing unit 140 for printing the back side of the recording medium 120.

List of reference symbols

1

Direction of transport

21, 22

Nozzle (print image)

31, 32

column (of the printed image)

100

Printing device

101

control unit

102

Pressure bar

103

printhead

120

Recording medium

140

Printed matter

141

support roller

142

deflection angle

150

Drying and/or fixing unit

200

Deflection unit

201

Normal force

241, 242

Support element (support roller)

243

base

300

gripper

301

Tensile force

302

Stretching roller

Claims (10)

Printing unit (140) for an inkjet printing device (100); wherein the printing unit (140) comprises: - at least one printing bar (102) configured to fire ink droplets along a vertical axis onto a recording medium (120) to print an image onto a front side of the recording medium (120); - a first support element (241) and a second support element (242), each configured to act on a rear side of the recording medium (120) at a support point (243) of the respective support element (241, 242) while the recording medium (120) is guided through the printing unit (140) past the printing bar (102) along a transport direction (1); wherein the first support element (241) is arranged behind the second support element (242) with respect to the transport direction (1); wherein the support points (243) of the first support element (241) and the second support element (242) are arranged along the vertical axis at a uniform height; and - at least one deflection unit (200) arranged between the second support element (242) and the first support element (241), configured to deflect the recording carrier (120) away from the pressure bar (102) along the vertical axis such that -- the recording carrier (120) is deflected away from a horizontal axis at the second support element (242) by a deflection angle (142); and -- the recording carrier (120) is deflected towards the horizontal axis at the first support element (241) by the same deflection angle (142). Printed matter (140) according to Claim 1 , wherein - the second support element (242) is arranged directly behind a pressure bar (102) of the printing unit (140) with respect to the transport direction (1); and the printing unit (140) is designed such that the recording medium (120) is positioned below the pressure bar gels (102) runs parallel to the horizontal axis towards the support point (243) of the second support element (242); and/or - the first support element (241) is arranged directly in front of a pressure bar (102) of the printing unit (140) with respect to the transport direction (1); and the printing unit (140) is designed such that the recording carrier (120) runs away from the support point (243) of the first support element (241) below the pressure bar (102) parallel to the horizontal axis. Printing mechanism (140) according to one of the preceding claims, wherein - the printing mechanism (140) comprises a first pressure bar (102) and a second pressure bar (102) following in the transport direction (1); - the second support element (242) is arranged directly behind the first pressure bar (102) with respect to the transport direction (1); and - the first support element (241) is arranged directly in front of the second pressure bar (102) with respect to the transport direction (1). Printing mechanism (140) according to one of the preceding claims, wherein - the deflection unit (200) is configured to deflect the recording carrier (120) away from the printing bar (102) along the vertical axis without contact; and/or - the first support element (241) and/or the second support element (242) each comprise a support roller. Printing mechanism (140) according to one of the preceding claims, wherein the deflection unit (200) is configured to: - create a negative pressure and/or a suction gas flow on the rear side of the recording medium (120); and/or - create a positive pressure and/or blow a gas flow onto the front side of the recording medium (120) in order to deflect the recording medium (120) away from the pressure bar (102) along the vertical axis. Printing unit (140) according to one of the preceding claims, wherein - the deflection unit (200) comprises a deflection rod and/or a deflection roller configured to act on the front of the recording carrier (120) to deflect the recording carrier (120) away from the printing bar (102) along the vertical axis; and - the deflection unit (200) in particular has a microporous surface and/or an anti-adhesive surface coating. Printing unit (140) according to one of the preceding claims, wherein the deflection unit (200) is configured to exert such a high normal force along the vertical axis on the recording medium (120) that a sufficiently high tensile force in the transport direction (1) acts on the recording medium (120) at the support point (243) of the first and/or the second support element (241, 242) in order to smooth the recording medium (120). Printing unit (140) according to one of the preceding claims, wherein the printing unit (140) comprises: - a sequence of successive printing bars (102) arranged one behind the other along the transport direction (1); and - between each pair of successive printing bars (102), a second support element (242), a subsequent deflection unit (200) and a subsequent first support element (241). Printing unit (140) according to one of the preceding claims, wherein - the printing unit (140) comprises an input roller (302) at an inlet of the printing unit (140) and an output roller (302) at an outlet of the printing unit (140); and - the printing unit (140) is configured such that the transport direction (1) of the recording medium (120) between the input roller (302) and the output roller (302) -- runs substantially parallel to the horizontal axis; and/or -- runs parallel to the horizontal axis except for the deflection at the one or more deflection units (200). Printing unit (140) according to one of the preceding claims, wherein - the printing unit (140) comprises at least one stretching unit (300, 302) configured to stretch the recording medium (120) along a transverse direction that extends transversely to the transport direction (1) and parallel to the horizontal axis; and - the stretching unit (300, 302) in particular comprises one or more lateral grippers (300) and/or one or more stretching rollers (302).