NL2032611B1 - A printer with a definition roller for an endless belt - Google Patents

Abstract

A printer (1) may comprise a transport device comprising an endless transport belt (4, 104) supported on a pair of support rollers (3A, 3B, 30), which between them define a medium support plane, over which medium support plane a print station (7) is provided. When transporting the print medium (15, 16) in steps the displacement of the print medium can be irregular over the width over the print medium (15, 16). When this occurs below the print station (7) subsequent printed swaths are not fully parallel, resulting in print artifacts. These print artifacts can be prevented by a definition roller (26, 126) provided between the support rollers (3A, 3B, 3C) opposite the print station (7), wherein the definition roller (26, 126) is provided with protrusions (27, 127) for engaging the transport belt (4, 104) across a width of the transport belt (4, 104).

Description

11012666NL01 1

A printer with a definition roller for an endless belt

BACKGROUND OF THE INVENTION

1. Field of the invention

The invention relates to a printer, specifically a large format hybrid printer, and to a method for printing. 2. Description of Background Art

Large format hybrid printers are configured to print both rigid substrates as well as flexible print media. Such a printer may comprise a transport device comprising an endless transport belt supported on at least one pair of support rollers, which between them define a medium support plane. Over the medium support plane a print station is provided. The print station generally comprises a printhead carriage translatable over the belt to print an image on a print medium on the belt in consecutive swaths. The print medium is moved in steps in between passes of the printhead carriage. It was found that while stepping, the print medium did not move forward by the same distance across the full width of the print medium. The displacement was not constant over the entire width of the print medium. A waviness was thereby introduced in the print medium, which could be visible as print artifacts due to consecutively printed swaths not being aligned with one another.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a printer with an improved print quality.

In accordance with the present invention, a printer according to claim 1 and a method for printing according to claim 10 are provided.

The present invention relates to a printer comprising a transport device comprising an endless transport belt supported on a pair of support rollers, which between them define a medium support plane, over which medium support plane a print station is provided.

The printer is characterized in that a definition roller is provided between the support rollers opposite the print station, wherein the definition roller is provided with protrusions for engaging the transport belt across a width of the transport belt. By engaging the protrusions, that area of the belt engaged by the definition roller is temporarily prevented from deforming. The stiffness of the definition roller prevents and/or reduces

11012666NL01 2 deformation of the area of the belt below the print station. That area then is moved forward as a substantially straight line, thus displacing the belt and thereby the print medium by the same distance across the full width of the belt. Thus, each time a new area of the print medium is to be moved below the print station, the area of the belt below it is temporarily fixed by the definition roller to maintain a straight line. This fixing occurs opposite or below the print station. A consecutive print swath is thereby printed parallel to a previously printed swath. Print artifacts due to local bending of the print medium are thereby reduced or prevented. Thereby the object of the present invention has been achieved.

More specific optional features of the invention are indicated in the dependent claims.

In an embodiment, a rigidity of the definition roller and/or the protrusions is greater than that of the belt, such that a rigidity of the area of the belt engaged by the protrusions is greater than the rigidity of the belt elsewhere. A greater stiffness of the definition roller and its protrusion enhances its ability to prevent deformation of the belt. The belt is relatively flexible to allow it to curve around its support rollers. Where the belt is engaged by the protrusions, the belt is effectively relatively stiff or rigid, since the rigidity or stiffness of the definition roller extends there to that area of the belt. Said increased rigidity of that area of the belt is temporary until that area of the belt is released from the definition roller.

In an embodiment, said area corresponds to a printing area wherein the print station is to print on a print medium supported on the belt. The area engaged by the protrusions is opposite or below print station, specifically below its printheads. The stiffness or rigidity of the belt is thus locally increased at the printing area. In consequence, in the final step before printing on an area of the print medium, that area is moved while maintaining its straightness due to the engagement of the belt below said area with the definition roller.

This repeats for every area of the print medium to be printed on. All areas of the print medium are consecutively moved below the print station in this manner. During every step the definition roller ensures that the to be printed area maintains its straight line in the lateral direction when moving into and/or through the printing area. In consequence, consecutively printed swaths are printed in parallel alignment with each across their full widths in the lateral direction.

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In an embodiment, protrusions are provided over the full circumference as well as over the full width of the definition roller. The protrusions extend across the full circle of definition rollers periphery to allow it to constantly and/or continuously engage the areas of the belt moving below the print station. The protrusions further extend, either continuously or intermittently, across the substantially full width of the definition roller.

The belt is thereby engaged at multiple positions across its entire width. The protrusions are further preferably spaced relatively near one another to prevent the belt from deforming in between protrusions.

In an embodiment, at least one of the support rollers comprises a drive for rotating the respective support roller, wherein the definition roller is freely rotatably supported on bearings, such that the definition roller is rotated by the at least one support roller with the drive moving the belt. The definition roller is supported to be freely rotatable. No drive is provided at the definition roller. Movement of the belt is achieved by at least one drive connected to one of the support rollers. The drive rotates the support roller, which moves the belt. The belt via engagement with the protrusions rotates the definition roller.

In an embodiment, the print station comprises an actuator for moving a printhead carriage in a transport direction of the belt to correct for deviations in transport steps of the print medium. The definition roller ensures that the print medium is displaced by a constant step spacing across its full width. It may however be that the step spacing varies per step. The large dimensions of the printer and the print medium generally make it difficult to precisely move the print medium, as well to correct for this, while maintaining productivity. The smaller dimensions of the printheads allow the printhead position with respect to the print medium to be adjusted relatively easily. Such an adjustable printhead carriage is described in US 9840098 B2. The actuator is able to move the printheads in the transport direction of the belt. The printheads are thus movably connected to the guide beam along which the printhead carriage translates, so that the printheads can be displaced in the transport direction of the belt. The deviation between the actual step spacing of the print medium and the intended step size setting is generally small. Since the area below the printhead carriage has been moved with a constant displacement across its full width, any deviation can be easily corrected by

11012666NL01 4 adjusting the printheads’ position in the transport direction.

In an embodiment, the printer is a scanning inkjet printer, wherein the printhead carriage is translatable over the belt in a lateral direction of the belt.

In an embodiment, a plurality of recesses are provided on the inner surface of the belt for receiving the protrusions. The recesses are positioned and dimensioned to receive the protrusions. Preferably, the recesses and/or the protrusions are tapered, such that the insertion of a protrusion into the recess centers the recesses around the protrusion.

In an embodiment, the belt is air permeable and extends over a suction chamber for applying an underpressure to a print medium on the belt, wherein the protrusions are tapered, such that the underpressure pulls the recesses onto the protrusions. The above mentioned centering is enhanced by the underpressure, which forces protrusions effectively into the recesses. The underpressure between the suction chamber and the print medium causes a force acting on the print medium towards the suction chamber, directing the recesses further onto the protrusions. Thereby, the centering effect is enhanced and the print medium can be accurately transported.

The invention further relates to a method for printing, comprising the steps of: - transporting a print medium adhered to an endless transport belt along a print station, wherein the belt is engaged by protrusions on a definition roller, such that de definition roller substantially prevents deformation of the belt below the print station, thereby moving the engaged portion of the belt by a substantially constant displacement over its full width; and - the print station printing and/or jetting an image on the print medium.

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the present invention will become apparent to those skilled in the art from this detailed description.

11012666NL01

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 5

Fig. 1 is a schematic perspective view of a printing system according to the present invention in a first printing mode;

Fig. 2 is a schematic perspective view of a printing system in Fig. 1 in a second printing mode;

Fig. 3 is a schematic diagram of a control unit of a printer according to Fig. 1 or 2;

Fig. 4 is a schematic cross-sectional side view of the transport device of the printer according to Fig. 1 or 2;

Fig. 5 is an enlargement of a central portion of the transport device according to Fig. 4;

Fig. 6 is schematic, top-down view of the transport device according to Fig. 4 with the belt;

Fig. 7 is a schematic cross-sectional side view of another embodiment of the transport device of the printer according to Fig. 1 or 2; and

Fig. 8 is a schematic block diagram illustrating the steps of a method for printing on the printer according to Fig. 1 or 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described with reference to the accompanying drawings, wherein the same reference numerals have been used to identify the same or similar elements throughout the several views.

Printing system

Fig. 1 shows a wide format inkjet printer 1. The wide-format printer 1 comprises an inkjet printing assembly 7 for printing on a print medium 15. The print medium 15 in Fig. 1 is a relatively rigid substrate, such as a panel. The print medium 15 is supplied from a media input unit 14, which may be configured for storing a plurality of such print media 15 and supplying these to the printer 1. The printer 1 comprises transport means for receiving and transporting the print medium 15 along the inkjet printing assembly 7. In

Fig. 1, the transport means comprise an endless transport belt 4 supported on a plurality of support rollers 3A, 3B, 3C. At least one of the support rollers 3A, 3B, 3C is provided

11012666NL01 6 with driving means for moving the belt 4. Additionally, one or more one of the support rollers 3A, 3B, 3C may be configured to be moved and/or tilted to adjust and control the lateral position of the belt 4. The inkjet printing assembly 7 may be provided with a sensor 8, such as a CCD camera, to determine the relative position of belt 4 and/or the print medium 15. Data from said sensor 8 may be applied to control the position of the belt 4 and/or the print medium 15. The belt 4 is further provided with through-holes and a suction box 5 in connection with a suction source (not shown), such that an underpressure may be applied to the print medium 15 via the through-holes in the belt 4. The underpressure adheres the print medium 15 flatly to the belt 4 and prevents displacement of the print medium 15 with respect to the belt 4. Due to this holding the belt 4 is able to transport the print medium 15. It will be appreciated that other suitable transport means, such as rollers, steppers, etc, may alternatively be applied. The print medium 15 may be transported stepwise and/or in continuous movement.

The inkjet printing assembly 7 is configured to translate along a first guide beam 6 in a scanning direction. The scanning direction is perpendicular to the direction in which the print medium is transported by the belt 4. The inkjet printing assembly 7 holds a plurality of print heads (not shown), which are configured to jet a plurality of different marking materials (different colors of ink, primers, coatings, etc.) on the print medium 15. Each marking material for use in the printing assembly 7 is stored in one of a plurality of containers arranged in fluid connection with the respective print heads for supplying marking material to said print heads to print an image on the print medium 15.

The ejection of the marking material from the print heads is performed in accordance with data provided in the respective print job. The timing by which the droplets of marking material are released from the print heads determines their position on the print medium 15. The timing may be adjusted based on the position of the inkjet printing assembly 7 along the first guide beam 6. The above mentioned sensor 8 may therein be applied to determine the relative position and/or velocity of the inkjet printing assembly 7 with respect to the print medium 15. Based upon data from the sensor 8, the release timing of the marking material may be adjusted.

Upon ejection of the marking material, some marking material may be spilled and stay

11012666NL01 7 on a nozzle surface of the print heads. The marking material present on the nozzle surface, may negatively influence the ejection of droplets and the placement of these droplets on the print medium 15. Therefore, it may be advantageous to remove excess of marking material from the nozzle surface. The excess of marking material may be removed for example by wiping with a wiper and/or by application of a suitable anti-wetting property of the surface, e.g. provided by a coating.

The marking materials may require treatment to properly fixate them on the print medium. Thereto, a fixation unit 10 is provided downstream of the inkjet printing assembly 7. The fixation unit 10 may emit heat and/or radiation to facilitate the marking material fixation process. In the example of Fig. 1, the fixation unit 10 is a radiation emitter, which emits light of certain frequencies, which interacts with the marking materials, for example UV light in case of UV-curable inks. The fixation unit 10 in Fig. 1 is translatable along a second guide beam 9. Other fixation units 10, such as page-wide curing or drying stations may also be applied. Further, the inkjet printing assembly 7 may be provided with a further fixation unit on the same carriage which holds the print heads. This further fixation unit can be used to (partially) cure and/or harden the marking materials, independent of or interaction with the fixation unit 10.

After printing, and optionally fixation, the print medium 15 is transported to a receiving unit (not shown). The receiving unit may comprise a take-up roller for winding up the print medium 15, a receiving tray for supporting sheets of print medium 15, or a rigid media handler, similar to the media input unit 14. Optionally, the receiving unit may comprise processing means for processing the medium 8, 9 after printing, e.g. a post- treatment device such as a coater, a folder, a cutter, or a puncher.

The wide-format printer 1 furthermore comprises a user interface 11 for receiving print jobs and optionally for manipulating print jobs. The local user interface unit 11 is integrated to the print engine and may comprise a display unit and a control panel.

Alternatively, the control panel may be integrated in the display unit, for example in the form of a touch-screen control panel. The local user interface unit 11 is connected to a control unit 12 connected to the printer 1. The control unit 12, for example a computer, comprises a processor adapted to issue commands to the printer 1, for example for controlling the print process. The printer 1 may optionally be connected to a network.

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The connection to the network can be via cable or wireless. The printer 1 may receive printing jobs via the network. Further, optionally, the control unit 12 of the printer 1 may be provided with an input port, such as a USB port, so printing jobs may be sent to the printer 1 via this input port.

Hybrid printing system

The printer 1 in Fig. 1 is a so-called hybrid printer, capable of handling both flexible media and rigid substrates. In Fig. 1, the printer 1 operates in a first print mode, wherein the printer 1 is configured for transporting rigid substrates, such as the print medium 15.

Such rigid print media 15 may be panels for doors, walls, etc, corrugated media, plates formed of plastic or metal, etc. To handle these rigid print media 15, the printer 1 in Fig. 1 is configured with a substantially linear transport path: from the media input device 14, the print medium 15 moves forward along the inkjet printing assembly 7 at a at substantially constant height. The media input unit 14 and the receiving unit are positioned at the level of the medium support surface of the belt 4. In Fig. 2, a flexible web medium 16 is supplied to the printer 1, which web medium 16 may be composed of e.g. paper, label stock, coated paper, plastic or textile. The web medium 16 is supplied from the input roller 2A and extends across the belt 4 to the take-up roller 2B, where the web medium 16 is re-wound. The printer 1 is configured to swiftly and efficiently switch between print modes.

Control

An embodiment of the control unit 12 is in more detail presented in Fig. 3. As shown in

Fig. 3, the control unit 12 comprises a Central Processing Unit (CPU) 31, a Graphical

Processor Unit (GPU) 32, a Random Access Memory (RAM) 33, a Read Only Memory (ROM) 34, a network unit 36, an interface unit 37, a hard disk (HD) 35 and an image processing unit 39 such as a Raster Image Processor (RIP). The aforementioned units 31 - 37 are interconnected through a bus system 38. However, the control unit 12 may also be a distributed control unit.

The CPU 31 controls the printing system 1 in accordance with control programs stored in the ROM 34 or on the HD 35 and the local user interface panel 5. The CPU 31 also controls the image processing unit 34 and the GPU 32. The ROM 34 stores programs and data such as boot program, set-up program, various set-up data or the like, which

11012666NL01 9 are to be read out and executed by the CPU 31. The hard disk 35 is an example of a non-volatile storage unit for storing and saving programs and data which make the CPU 31 execute a print process to be described later. The hard disk 35 also comprises an area for saving the data of externally submitted print jobs. The programs and data on the HD 35 are read out onto the RAM 33 by the CPU 31 as needed. The RAM 33 has an area for temporarily storing the programs and data read out from the ROM 34 and

HD 35 by the CPU 31, and a work area which is used by the CPU 31 to execute various processes. The interface unit 37 connects the control unit 12 to the client devices 21 - 24 and to the printing system 1. The network unit 36 connects the control unit 12 to the network N and is designed to provide communication with the workstations 22 - 24, and with other devices 21 reachable via the network N. The image processing unit 39 may be implemented as a software component running on an operation system of the control unit 12 or as a firmware program, for example embodied in a field-programmable gate array (FPGA) or an application-specific integrated circuit (ASIC). The image processing unit 39 has functions for reading, interpreting and rasterizing the print job data. Said print job data contains image data to be printed (i.e. fonts and graphics that describe the content of the document to be printed, described in a Page Description

Language or the like), image processing attributes and print settings.

Definition roller

Fig. 3 shows a cross-sectional side view of the printer 1 in Figs. 1 and 2. The configuration is as described with respect to Figs. 1 and 2. The cross-section in Fig. 4 reveals a definition roller 26 positioned below the belt 4 underneath the printhead carriage 7. The definition roller 26 extends across the full width of the printable area of the belt 4 in the lateral direction Y. The definition roller 26 is freely rotatable on its rotation axis 28, which extends across the suction box 5. The definition roller 26 has a plurality of radially outward protrusions 27, which at the highest point of the definition roller 26 engage the belt 4. The belt 4 is brought into movement by means of a drive positioned at any of the support rollers 3A, 3B, 3C. That movement is transferred to the definition roller 26 by the protrusions 27 engaging the belt 4.

The definition roller 26 has a relatively high stiffness or rigidity as compared to the belt 4. The belt 4 is preferably flexible. Since the protrusions 27 extend across the full width of the belt 4, the stiffness or rigidity of the belt 4 is locally increased. The area where the

11012666NL01 10 belt 4 is engaged by the stiff or rigid protrusions 27 moves forward at a constant rate across its entire width, because the engaged area is unable to deform. The belt 4 below the printhead carriage 7 is thereby displaced by the same step spacing across the entire lateral direction Y. Basically, the definition roller 26 locally and momentarily “freezes” a line on the belt 4, and prevents this line from deforming when the belt 4 is moved a step forward. In consequence, a print medium 15, 16 on the belt 4 also does not deform when being moved into a print area below the printhead carriage 7. A newly printed swath will therefore be parallel to the previously printed swath. The definition roller 26 ensures that the print medium 15, 16 is always moved as a consistently parallel line into the print area.

The definition roller 28 is positioned in between the support rollers 3A, 3B, which define the plane of the medium support plane. The medium support plane extends along the print station with the printhead carriage 7 and comprises the print area, where the ink from the printheads 24 is to be jetted onto the print medium 15, 16. Below the medium support plane, the suction box 5 is provided, such that the print medium 15, 16 is pulled flat against the belt 4 as it traverses the print area. The definition roller 26 is positioned such that the flatness or planar nature of the medium support plane is not affected. The definition roller 26 however does contact the belt 4 on a side of the belt 4 opposite the side facing the print station 7 in the print area.

In practice, deviations in the step spacing between different steps of the print medium 15, 16 may occur. The printhead carriage 7 is provided with an actuator 23 that allows the printheads 24 to be displaced in the transport direction X of the belt 4 with respect to the first guide beam 6. The actual displacement of the print medium 15, 16 is measured for example by means of the sensor 8. The measured step spacing is compared to a predetermined step size setting (for example the width of individual printed swaths in the transport direction X). Any difference between the measured step spacing and the intended step size setting can be corrected by adjusting the position of the printheads 24 in the transport direction X. The printhead carriage 7 comprises an actuator 23, which is able to move the printheads 24 in the transport direction X with respect to the first guide beam 6. The actuator 23 displaces the printheads 24 such that a deviation between the measured step spacing and the intended step size setting is corrected.

Since the definition roller 26 ensures that that the print medium is displaced by the same

11012666NL01 11 step spacing across its full width, the actuator 23 can accurately correct deviations in the step spacing. In the example in Fig. 4, the printhead carriage 7 is translatable along the first guide beam 6. By letting the definition roller 26 maintain a straight line in the print medium 15, 16 as it is moved into the print area, swaths can be accurately aligned with respect to one another, in terms of both step spacing and parallel orientation, resulting in high quality and productive printing.

Fig. 5 shows an enlargement of the printer 1 in Fig. 4, focusing on the engagement between the belt 4 and the definition roller 26. In Fig. 5, it is shown that the belt 4 is provided with recesses 29 on the side facing the definition roller 26. The recesses 29 are dimensioned and positioned corresponding to the protrusions 27 on the definition roller 26. The recesses 29 are formed to fittingly receive a protrusion 27. Fig. 5 further illustrates the through-holes 30 that provide air permeability to the belt 4. The print medium 15 is adhered to the belt 4 by applying an underpressure in the suction chamber below the belt 4. The underpressure is also applied to the print medium 15 via the through-holes 30. The underpressure results in a downward force on the belt 4.

Thereby, the belt 4 is pulled downwards onto the definition roller 26. The recesses 29 are pulled down onto their respective protrusion 27. The protrusions 27 and/or the recesses 29 are tapered. The downward force then causes the recesses 29 to be centered onto the respective protrusions 27. This prevents or reduces play between the belt 4 and the definition roller 26, allowing for accurate positioning of the print medium 15.

Fig. 6 illustrates the definition roller 26 in top down view. In Fig. 8, the definition roller 26 is positioned inside and/or as part of the suction chamber 5. It will be appreciated that the suction chamber 5 can also be formed such that the definition is positioned outside and/or adjacent the suction chamber 5. In Fig. 8, the protrusions 27 are divided intermittently across the full width of the definition roller 26. In an another embodiment, the protrusions may extend continuously, as e.g. ridges, over the full width. Additionally, belt supports 31 are provided at the belt facing side of the suction chamber 5 to prevent the belt 4 from locally sagging. The belt supports 31 may be in any suitable form or be omitted in case a belt 4 with sufficient stiffness is used. Preferably, the belt supports 31 extend over the definition roller 26 in between protrusions 27.

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Fig. 7 discloses another embodiment of the definition roller 126 and the belt 104. The belt 104 in Fig. 7 is air permeable. In contrast to the belt 4 in Fig. 4 the air permeability of the belt 104 was not formed by forming through-holes in an air tight sheet material, but by using an intrinsically air permeable sheet as the belt material. One example of such a belt is a so-called mesh belt 104. Such a mesh belt 104 is formed of intertwining threads, creating an open structure which allows air to pass through. The open structure of the mesh belt 104 allows the material to be easily protruded. The definition roller 14 is provided with needle-shaped protrusions 127. The needle-shaped protrusions 127 are stiff, so that these provide added stiffness or rigidity to the area of the mesh belt 104 engaged by the needle-shaped protrusions 127. Basically, the mesh-shaped belt 104 is locally pinned onto the definition roller 128. In consequence, the belt 104 and the print medium 15, 16 are moved with a constant or equal displacement across the full width of the belt 104.

Fig. 8 discloses the steps of a method of printing. In step i a print medium 15, 16 is adhered to an air permeable belt 4, 104. In step ii, the belt 4, 104 is moved by the driven support roller 3A, 3B, 3C. In step iii, the belt 4, 104 is engaged by the protrusions 27, 127 on the definition roller 26, 126 below the print station 7. The greater stiffness of the definition roller 26, 126 imbues additional stiffness to the area of the belt 4, 104 engaged by the protrusions 27, 127. Thereby, in step iv, the print medium 15, 16 is moved forward by a step spacing. Due to the added stiffness or rigidity added to the area of the belt 4, 104 below the print station 7, the belt 4, 104 and the print medium 15, 16 are brought forward by a constant distance across the full width of the belt 4, 104.

Basically, the area of the print medium 15, 16 below the print station 7 moves forward as a straight line, the straightness of which is maintained due to the definition roller 26, 27. In step v, the actual displacement of the print medium 15, 16 is measured by the sensor 8. This displacement is the same or constant across the full width of the belt 4, 104. In step vi, the measured displacement is compared to a predetermined step size setting. In case the actual displacement deviates from this intended step size setting, the actuator 23 in step vii is controlled to correct for this deviation. The printheads 8 are displaced in the transport direction X by the difference between the step size setting and the measured displacement. With respect to the printheads 8, the print medium 15, 16 has then moved by a distance equal to the step size setting. In step viii, a swath is printed on the print medium 15, 16 by translating the printhead carriage in the lateral

11012666NL01 13 direction Y. The printed swath is positioned with respect to the previous with the intended step size spacing. The swath is also printed as a straight line, fully parallel to the previous swath over the full width. Steps iv to viii are repeated until the printed image is complete.

Although specific embodiments of the invention are illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations exist. It should be appreciated that the exemplary embodiment or exemplary embodiments are examples only and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing at least one exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents. Generally, this application is intended to cover any adaptations or variations of the specific embodiments discussed herein.

It will also be appreciated that in this document the terms "comprise", "comprising", "include", "including", “contain”, "containing", "have", "having", and any variations thereof, are intended to be understood in an inclusive (i.e. non-exclusive) sense, such that the process, method, device, apparatus or system described herein is not limited to those features or parts or elements or steps recited but may include other elements, features, parts or steps not expressly listed or inherent to such process, method, article, or apparatus. Furthermore, the terms "a" and "an" used herein are intended to be understood as meaning one or more unless explicitly stated otherwise. Moreover, the terms "first", "second", "third", etc. are used merely as labels, and are not intended to impose numerical requirements on or to establish a certain ranking of importance of their objects.

The present invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

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Embodiments 1. A printer (1) comprising a transport device comprising an endless transport belt (4, 104) supported on a pair of support rollers (3A, 3B, 3C), which between them define a medium support plane, over which medium support plane a print station (7) is provided, characterized in that a definition roller (26, 126) is provided between the support rollers (3A, 3B, 3C) opposite the print station (7), wherein the definition roller (26, 126) is provided with protrusions (27, 127) for engaging the transport belt (4, 104) across a width of the transport belt (4, 104). 2. The printer (1) according to claim 1, wherein a rigidity of the definition roller (26, 126) and/or the protrusions (27, 127) is greater than that of the belt (4, 104), such that a rigidity of the area of the belt (4, 104) engaged by the protrusions (27, 127) is greater than a rigidity of the belt (4, 104) elsewhere. 3. The printer (1) according to claim 3, wherein said area corresponds to a printing area wherein the print station (7) is to print on a print medium (15, 16) supported on the belt (4, 104). 4, The printer (1) according to any of the previous claims, wherein the protrusions (27, 127) are provided over the full circumference as well as over the full width of the definition roller (26, 126). 5. The printer (1) according to any of the previous claims, wherein at least one of the support rollers (3A, 3B, 3C) comprises a drive for rotating the respective support roller (3A, 3B, 3C), wherein the definition roller (26, 126) is freely rotatably supported on bearings, such that the definition roller (26, 126) is rotated by the at least one support roller (3A, 3B, 3C) with the drive moving the belt. 6. The printer (1) according to any of the previous claims, wherein the print station (7) comprises an actuator (23) for moving a printhead (24) in a transport direction (X) of the belt (4, 104) to correct for deviations in transport steps of the print medium (15, 16). 7. The printer (1) according to claim 6, wherein the printer (1) is a scanning inkjet printer (1), wherein the printhead (24) is translatable over the belt (4, 104) in a lateral direction (Y) of the belt (4, 104).

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8. The printer (1) according to any of the previous claims, wherein a plurality of recesses (29) are provided on the inner surface of the belt (4, 104) for receiving the protrusions (27, 127). 9. The printer (1) according to any of the claim 8, wherein the belt (4, 104) is air permeable and extends over a suction chamber (5) for applying an underpressure to a print medium (15, 16) on the belt (4, 104), wherein the protrusions (27, 127) are tapered, such that the underpressure pulls the recesses (29) onto the protrusions (27, 129). 10. A method for printing, comprising the steps of:

- transporting a print medium (15, 16) adhered to an endless transport belt along a print station (7), wherein the belt (4, 104) is engaged by protrusions (27, 127) on a definition roller (26, 126), such that de definition roller (26, 126) substantially prevents deformation of the belt (4, 104) below the print station (7), thereby moving the engaged portion of the belt (4, 104) by a substantially constant displacement over its full width; and

- the print station (7) printing an image on the print medium (15, 16).

Claims (10)

11012666EN01 16 Conclusions 1. Printer (1) with a conveyor device comprising an endless conveyor belt (4, 104) carried by a pair of carrier rollers (3A, 3B, 3C), defining a media bearing surface between these carrier rollers (3A, 3B, 3C), over which a printing device ( 7) is provided, characterized in that a defining roller (26, 126) is provided between the support rollers (3A, 3B, 3C) opposite the printing device (7), wherein the defining roller (26, 126) is provided with projections (27 , 127) for engaging the conveyor belt (4, 104) over a width of the conveyor belt (4, 104). Printer (1) according to claim 1, wherein a stiffness of the defining roller (26, 126) and/or the projections (27, 127) is greater than that of the belt (4, 104), so that a combined stiffness of a area of the {4, 104) that engages the protrusions (27, 127) is greater than the stiffness of the band {4, 104) elsewhere. Printer (1) according to claim 3, wherein said area corresponds to a printing zone in which the printing device (7) is intended to print on a print medium (15, 16) provided on the belt (4, 104). Printer (1) according to any one of the preceding claims, wherein the projections (27, 127) are provided over an entire circumference as well as over an entire width of the defining roller (26, 126). 5. Printer (1) according to any of the preceding claims, wherein at least one of the carrier rollers (3A, 3B, 3C) comprises a drive for rotating the relevant carrier roller (3A, 3B, 3C), wherein the defining roller (26) , 128) is freely rotatable on bearings, so that the defining roller (26, 126) is set into rotation because the at least one carrier roller (3A, 3B, 3C) moves the belt (4, 104) with the drive. 6. Printer (1) according to any one of the preceding claims, wherein the printing device (7) comprises an actuator (23) for moving a print head (24) in a transport direction (X) of the belt (4, 104) to prevent deviations in transport steps of the print medium (15, 16). 7. Printer (1) according to claim 6, wherein the printer (1) is a translatable 11012666EN01 17 inkjet printer (1), wherein the print head (24) is translatable over the belt (4, 104) in a lateral direction (Y) of the belt (4, 104). A printer (1) according to any one of the preceding claims, wherein a plurality of recesses (29) are provided on an inner surface of the belt (4, 104) for receiving the protrusions (27, 127). 9. Printer (1) according to claim 8, wherein the belt (4, 104) is air-permeable and extends over a suction chamber (5) for applying a negative pressure to a print medium (15, 16) on the belt (4, 104). ), wherein the protrusions (27, 127) are tapered, so that the underpressure pulls the recesses (29) over the protrusions (27, 129). 10. Method of printing, comprising the steps of: - moving print medium (15, 18) held on an endless conveyor belt extending along a printing device (7), the belt (4, 104) being engaged with projections (27, 127) on a defining roller (26, 126), so that the defining roller (26, 126) substantially prevents deformation of the belt (4, 104) under the printing device (7), whereby the engaged area of the belt ( 4, 104) is moved by a substantially the same distance over its full width; and - printing an image on the print medium (15, 16) by the printing device (7).