EP3849815A1

EP3849815A1 - A dryer for an inkjet printer

Info

Publication number: EP3849815A1
Application number: EP19765249.8A
Authority: EP
Inventors: Albert M. Van Beek; Marcel J.H.M. HAENEN; Antonius G.H. Albers; Johannes H.L. Smeyers; Wilhelmus H.J. Nellen
Original assignee: Canon Production Printing Holding BV
Current assignee: Canon Production Printing Holding BV
Priority date: 2018-09-13
Filing date: 2019-09-06
Publication date: 2021-07-21
Anticipated expiration: 2039-09-06
Also published as: WO2020053103A1; EP3849815B1; EP3849815C0

Abstract

The present invention relates to an air impingement module for an inkjet printer. The air impingement module for an inkjet printer comprises a plate for creating an array of air beams comprising a plurality of impingement holes. Further, the air impingement module for an inkjet printer comprises a width adjustment arrangement for blocking the array of air beams of the air impingement modules in a direction (z) substantially perpendicular to the transport direction of a printing substrate (y) and substantially perpendicular to the normal to the plane of the surface of a printing substrate (x) which is also the impingement direction, such that the array of air beams are restricted to a particular width, and such that directions x, y, and z form a substantially orthogonal axes system.

Description

l

A dryer for an inkjet printer

FIELD OF THE INVENTION The present invention relates to a dryer for an inkjet printer, especially a dryer for accelerated ink evaporation in an inkjet printer, and more particularly to an air impingement unit for use in said dryer. The present invention also relates to an ink drying method using said dryer. BACKGROUND OF THE INVENTION

In printing or copying systems, and especially in ink jet systems, dryers are used for accelerated ink evaporation. Said dryers comprise impingement units or modules. The velocity of the air coming from those units enables accelerated drying of the sheets. Usually, the heating of the air that impinges on the sheets is performed by a plurality of air heaters or air impingement modules.

In these prior art systems a substantial direct heating of the drum and/or substrate occurs, which leads to irregularities in the temperature gradients of a printing substrate transport device, e.g. a drum. Said irregularities lead to deformation of the printing substrate, which is substantially increased when high levels of ink coverage are used.

Also, in typical prior art configurations a plurality of impingement units or modules are arranged above a printing substrate transport device. However, known impingement units or modules comprise mechanically complex mechanisms to restrict the area in which hot air impinges, and are usually bulky. Further, the mechanisms to restrict the area in which hot air impinges do not perfectly direct the hot air towards the printing substrate. As a consequence, a substantial overhead capacity of heaters is needed in order to enable the drying of the printing substrates.

In order to overcome the aforementioned problems, a new drying system has been developed that provides improved temperature gradients in the printing substrate transport device, as for example a drum. Also, a new impingement unit has been developed that provides a more compact arrangement. SUMMARY OF THE INVENTION

In an aspect of the present invention, an air impingement module for an inkjet printer according to claim 1 is provided.

The air impingement module for an inkjet printer of the present invention comprises a plate for creating an array of air beams comprising a plurality of impingement holes. Said plate creates an array of beams through which the air flows through to impinge onto printed media. Further, the air impingement module for an inkjet printer of the present invention comprises a width adjustment arrangement for blocking the array of air beams of the air impingement module in a direction (z) substantially perpendicular to the transport direction of a printing substrate (y) and substantially perpendicular to the normal to the plane of the surface of a printing substrate (x) which is also the impingement direction, such that the array of air beams are restricted to a particular width, and such that directions x, y, and z form a substantially orthogonal axes system.

In an embodiment, the air impingement module for an inkjet printer of the present invention further comprises a heat source for heating air entering the air impingement module.

In an embodiment, the plate for creating an array of beams is part of a housing of the air impingement module. This arrangement allows the air impingement module for an inkjet printer of the present invention providing a more compact arrangement in comparison with known air impingement modules.

In an embodiment, the width adjustment arrangement blocks the array of air beams symmetrically in the z-direction. This additional feature allows improving the drying process of printed media by allowing centering the printed media under the impingement unit for an inkjet printer, thereby reducing the temperature gradients in the surface on which the printed media is transported.

In an embodiment, the width adjustment arrangement in the impingement unit for an inkjet printer comprises an air blocking device comprising a plurality of slits configured for restricting the array of air beams to a particular width. This implementation provides a compact width adjustment arrangement that allows restricting the width of the impingement area by simply displacing the air blocking device, thereby providing a simple configuration that allows restricting the array of air beams to a particular width.

In an embodiment, the width adjustment arrangement further comprises a mechanism configured to gradually displace the air blocking device such that the width of the impingement beams is gradually restricted.

In an embodiment, an impingement module for an inkjet printer further comprises the mechanism configured to gradually displace the air blocking device comprising a stepper for displacing the air blocking device, a static part attached to the housing of the air impingement module, a guiding slide for the air blocking device to slide when the stepper is activated, means for receiving the attachment means, and a leaf spring for exerting a downwards force on the air blocking device. The stepper in this configuration allows gradually displacing the air blocking device such that said air blocking device is displaced a distance d, which allows defining a plurality of different displacements of the air blocking device that leads to different widths in the restriction of the plurality of air beams such that the air blocking device adapts to different media widths. This improves the process of drying printed media. The leaf spring exerts a downwards force on the air blocking device, thereby impeding the air flow between the air blocking device and the plate for creating an array of air beams, which in turn improves the drying efficiency of the impingement unit for an inkjet printer.

In an embodiment, an impingement module for an inkjet printer further comprises the plate for creating an array of air beams having a smaller radius than the air blocking device in the x-direction. The configuration with different radii of this arrangement, in which the air blocking device has a bigger radius, allows improving the contact between the plate for creating an array of air beams and the air blocking device, particularly when a downwards force is applied by the leaf spring on the air blocking device, thereby restricting the flow of air between the air blocking device and the plate for creating an array of air beams, which further improves the drying efficiency of the air impingement module. Further, this particular configuration reduces the mechanical friction between the plate for creating an array of air beams and the air blocking device, when the air blocking device displaces on top of the plate for creating an array of air beams.

In an embodiment, the air blocking device of the air impingement module of the present invention comprises one or more moving plates comprising a plurality of slits.

In an embodiment, the air blocking device of the air impingement module of the present invention comprises two moving plates comprising a plurality of slits.

In an embodiment, the air blocking device of the air impingement module of the present invention comprises two moving plates which displace in the same direction.

With reference firstly to Fig. 1 of the drawings, a schematic perspective cross-sectional view of an impingement unit is provided. In Fig. 1 , several features of the present invention can be observed. The impingement unit 10 of Fig. 1 comprises an air suction module comprising a plurality of suction holes 12 arranged to allow recirculation of the hot air by redirecting the array of air beams after impinging on the printing substrate towards an air outlet. Further the impingement unit 10 for an inkjet printer of Fig. 1 also comprises an air impingement module for hot air arranged above the printing substrate transport device optionally comprising a heat source for heating air entering the air impingement module, and a plate for creating an array of air beams comprising a plurality of impingement holes 1 1.

In Fig. 1 , the impingement module comprises an air suction module for recirculating air by redirecting the array of air beams after impinging on the printing substrate towards an air outlet 15. As mentioned above, this additional feature allows the air around the impingement unit to be directly sucked into a recirculation circuit, thereby enhancing the energy efficiency, especially when the air has been heated, and allowing the

temperature around the impingement unit to be kept as low as possible.

In a particular embodiment, a dryer for an inkjet printer comprises a printing substrate transport device having a large thermal mass of at least 25.000 J/(K-m²) and a high conductivity of at least 120 W/(m-K) for transporting a printing substrate on the surface of the printing substrate transport device. Said printing substrate transport device may have different shapes and configurations, e.g. a drying drum, a belt, etc. In a specific embodiment, the printing substrate transport device is a drum on which surface a printing substrate is transported. In all the embodiments of the present invention, the printing substrate transport device has both a large thermal mass and a high conductivity. The large thermal mass allows the printing substrate transport device to act as a buffer for thermal load variations like paper width variations, ink amounts, etc., while the good conductivity of the printing substrate transport device averages the temperature gradients on the surface of the printing substrate transport device.

Further, the dryer for an inkjet printer comprises a suction box associated with the printing substrate transport device for providing an under pressure for holding down the printing substrate onto the surface of the printing substrate transport device, wherein the suction box comprises a plurality of suction holes arranged to provide an under pressure to the printing substrate. The suction box allows fixing the printing substrate to the surface of the printing substrate transport device, such that the printing substrate can be reliably transported in the expected position centered on the surface of the printing substrate transport device.

Additionally, the dryer for an inkjet printer comprises one or more air impingement modules for hot air, arranged above the printing substrate transport device comprising a heat source for heating air entering the air impingement module, and a plate for creating an array of air beams comprising a plurality of impingement holes. The one or more air impingement modules create an array of air beams such that hot air impinges on the printing substrate in order to dry the printing substrate.

Finally, the dryer for an inkjet printer comprises one or more width adjustment arrangements for blocking the array of air beams of each of the one or more air impingement modules in a direction (z) substantially perpendicular to the transport direction of a printing substrate (y) and substantially perpendicular to the normal to the plane of the surface of a printing substrate (x) which is also the impingement direction, such that the array of air beams are restricted to a particular width, and such that directions x, y, and z form a substantially orthogonal axes system. In this embodiment, the array of air beams is restricted to the width of the printing substrate.

In the above described dryer for an inkjet printer, the combination of a large thermal mass, which acts as a buffer for thermal load variations like paper width variations, changes in ink amounts, etc., and the inclusion of one or more width adjustment arrangements for blocking the array of air beams of each of the one or more air impingement modules in a direction (z) reduces the direct heating of the printing substrate transport device, thereby improving the temperature gradients of the surface of the printing substrate transport device. Reduced temperature gradients on the surface of the printing substrate transport device reduce the deformation of the printed substrate, thereby improving the printing process. Further, the aforementioned combination of a large thermal mass, which acts as a buffer for thermal load variations like paper width variations, changes in ink amounts, etc., and the inclusion of one or more width adjustment arrangements for blocking the array of air beams of each of the one or more air impingement modules in a direction (z) also reduces peak power requirements. In the prior art, a direct heating of the printing substrate transport device occurs, which generates a temperature overshoot. As a consequence, the present invention allows significantly reducing the installed heating power.

In a particular embodiment, a dryer for an inkjet printer comprises the printing substrate being transported centered in the direction (z) on the surface of the printing substrate. This configuration further reduces the direct heating of the printing substrate transport device.

In a particular embodiment, a dryer for an inkjet printer comprises an air suction module for recirculating air by redirecting the array of air beams after impinging on the printing substrate towards an air outlet. This additional feature allows the air around the impingement unit to be directly sucked into a recirculation circuit, thereby enhancing the energy efficiency, especially when the air has been heated, and allowing the temperature around the impingement unit to be kept as low as possible.

In a particular embodiment, a dryer for an inkjet printer comprises width adjustment arrangements that comprise movable blocks or shutters in the impingement module. These width adjustment arrangements comprising movable blocks or shutters outside the impingement module provide the simplest construction for blocking the array of air beams of each of the one or more air impingement modules in a direction (z) substantially perpendicular to the transport direction of a printing substrate (y) and substantially perpendicular to the normal to the plane of the surface of a printing substrate (x) which is also the impingement direction, such that the array of air beams are restricted to a particular width, and such that directions x, y, and z form a substantially orthogonal axes system. The movable blocks or shutters in the impingement module may be placed inside or outside the impingement module.

In a particular embodiment, a dryer for an inkjet printer comprises width adjustment arrangements that comprise a foil or sheet on a roll inside the impingement module. These width adjustment arrangements comprising a foil or sheet on a roll inside the impingement module, which provides a more compact arrangement, as the foil is in a roll similar to an interior roller-blind. These more compact arrangements allow designing compacter impingement units. In turn, as explained later in relation with the Figures, compacter units allow configurations in which a plurality of impingement units are positioned around the printing substrate transport device in such a way that a printed substrate is heated by hot air only on the last part of the trajectory of the printed media on the printing substrate transport device, while in the first part of the journey the printed substrate is heated up by contact by the printing substrate transport device. This configuration gives more time for the ink to be absorbed by the printed substrate, because there is no accelerated evaporation. As a consequence, this configuration allows printing with improved robustness.

In a particular embodiment, a dryer for an inkjet printer comprises width adjustment arrangements that comprise a plurality of valves in the impingement module which block air flow in discrete width steps. The movable blocks or shutters in the impingement module may be placed inside or outside the impingement module. The plurality of valves in the impingement module may be placed inside or outside the impingement module. This arrangement allows more easily controlling the leakage to the blocked sections in comparison with other embodiments, thereby providing improved blocking of the hot air impinging on the printed substrate.

In a particular embodiment, a dryer for an inkjet printer comprises a suction box that provides an under pressure corresponding to the width of the printing substrate. This configuration of the suction box allows maintaining the printing substrate fixed onto the surface of the printing substrate transport device such that the drying of the printed substrate can be reliably performed, and further prevents overheating of the printing substrate transport device by restricting the amount of suctioning air needed. In a particular embodiment, a dryer for an inkjet printer comprises the plurality of air impingement modules being arranged such that the printing substrate follows a trajectory over the printing substrate transport device, wherein the trajectory through the dryer comprises a first part defining a diffusion path, and a second part defining an enhanced evaporation path which are traversed by the printing substrate, wherein the one or more impingement modules are arranged in said second part of a trajectory of the printing substrate onto the printing substrate transport device. Due to the more compact design of the impingement modules of the present invention, a design in which when a printed substrate is transported onto the surface of the printing substrate transport device can be devised, in which the printing substrate enters a diffusion path in which there are no impingement modules for hot air above the printing substrate transport device. In this first part of the path, the printed substrate is only heated up by the printing substrate transport device, so that there is no accelerated evaporation when ink has been recently jetted onto the printed substrate, which might lead to defects in the image on the printed substrate. In a second stage of the path onto the printing substrate transport device, the printed substrate enters an evaporation path, in which the printed substrate on the printing substrate transport device travels underneath a plurality of air impingement modules for hot air arranged above the printing substrate transport device once the ink has had time enough to diffuse in the printed substrate. The dryer and drying method of this embodiment generate printed substrates with better robustness of the printed image.

In a particular embodiment, a dryer for an inkjet printer comprises one or more width adjustment arrangements that are symmetric arrangements. The use of symmetric arrangements further reduces the direct heating of the printing substrate transport device in comparison with other embodiments due to symmetric parts of the printing substrate transport device being left at each of the sides of the symmetric width arrangements, thereby allowing the large thermal mass to better absorb the heat imparted by the impingement units. As a consequence, it provides more even temperature gradients of the surface of the printing substrate transport device. As explained above, reduced temperature gradients on the surface of the printing substrate transport device reduce the deformation of the printed substrate, and also enable the correct functioning of the system without needing heat pipes in the printing substrate transport device.

In a particular embodiment, a dryer for an inkjet printer comprises the printing substrate transport device being a drum.

In a particular embodiment, a dryer for an inkjet printer comprises a printing substrate transport device that has a large thermal mass between 25.000 and 55.000 J/(K-m²), preferably around 50.000 J/(K-m²), and a high conductivity of between 120 and 180 W/(m-K), preferably around 150 W/(m-K), for transporting a printing substrate on the surface of the printing substrate transport device. The mentioned values of thermal mass allow this mass to act as a buffer for thermal load variations, while the mentioned values of conductivity allow the printing substrate transport device to average temperature gradients quicker, reaching faster temperature equalization across the surface of the printing substrate transport device.

In a particular embodiment, the present invention relates to a plurality of methods for a dryer for an inkjet printer.

In a particular embodiment, the drying method comprises adjusting the suction width of a suction box. This step allows maintaining the printing substrate fixed onto the surface of the printing substrate transport device such that the drying of the printed substrate can be reliably performed.

Further, the printed substrate is transported onto a printing substrate transport device and holding the printed substrate down by the suction box, wherein the printing substrate transport device has a large thermal mass of at least 25.000 J/(K-m²) and a high conductivity of at least 120 W/(m-K).

In a particular embodiment of the present invention, transporting the printed substrate such that it is centered on the surface of the printing substrate transport device allows leaving a part of the printing substrate transport device at each of the sides of the printed substrate, which allows reaching more even temperature gradients on the surface of the printing substrate transport device. Further, the printed substrate is transported held down underneath one or more air impingement modules for hot air arranged above the printing substrate transport device, wherein the one or more air impingement modules comprise a heat source for heating air entering the air impingement module, and a plate for creating an array of air beams comprising a plurality of impingement holes, such that hot air is jetted onto the printed substrate. This step performs the drying of the printed substrate.

In this particular embodiment, the one or more width adjustment arrangements block the array of air beams of each of the one or more air impingement modules in direction (z) substantially perpendicular to the transport direction of a printing substrate (y) and substantially perpendicular to the normal to the plane of the surface of the printing substrate (x) which is also the impingement direction, such that the array of air beams are restricted to a particular width, and such that directions x, y, and z form a substantially orthogonal axes system. The combination of a large thermal mass with the inclusion of one or more width adjustment arrangements for blocking the array of air beams of each of the one or more air impingement modules in a direction (z) reduces peak power requirements, making it possible to disregard the presence of infrared lamps. In the prior art, a direct heating of the printing substrate transport device occurs, which generates a temperature overshoot. As a consequence, the present invention allows reducing the installed heating power. Further, if the printed substrate is transported centered on the surface of the printing substrate transport device, leaving a part of the printing substrate transport device at each of the sides of the printed substrate, the good conductivity and large thermal mass also allow reducing the temperature gradients on the surface of the printing substrate transport device.

In a particular embodiment, the drying method of the present invention comprises one or more width adjustment arrangements that are symmetric arrangements. The use of symmetric arrangements further reduces the direct heating of the printing substrate transport device in comparison with other embodiments, as it allows focusing the impinging hot air on the printed substrate. As a consequence, it provides more even temperature gradients of the surface of the printing substrate transport device. As explained above, reduced temperature gradients on the surface of the printing substrate transport device reduce the deformation of the printed substrate, and also enable the correct functioning of the system without needing heat pipes in the printing substrate ll transport device.

In a particular embodiment, the drying method of the present invention comprises a suction width of the suction box that is adjusted to correspond to the width of the printed substrate. This step allows maintaining the printing substrate fixed onto the surface of the printing substrate transport device such that the drying of the printed substrate can be reliably performed, and further prevents overheating of the printing substrate transport device by restricting the amount of suctioning air needed. In a particular embodiment, the drying method of the present invention comprises the plurality of air impingement modules being arranged such that the printing substrate follows a trajectory over the printing substrate transport device, wherein the trajectory through the dryer comprises a first part defining a diffusion path, and a second part defining an enhanced evaporation path which are traversed by the printing substrate, wherein the one or more impingement modules are arranged in said second part of a trajectory of the printing substrate onto the printing substrate transport device. As mentioned before, the dryer and drying method of this embodiment generate printed substrates with better robustness of the printed image. BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the invention and the advantages thereof, exemplary embodiments of the invention are explained in more detail in the following description with reference to the accompanying drawing figures, in which like reference characters designate like parts and in which:

Fig. 1 is a schematic perspective cross-sectional view of an impingement unit which forms part of an air impingement module for an inkjet printer; Fig. 2 is a schematic perspective cross-sectional view of an impingement

module for hot air in which the width adjustment arrangements comprise movable blocks or shutters outside the impingement module;

Fig. 3 is a schematic perspective cross-sectional view of an impingement module for hot air in which the width adjustment arrangements comprise a foil or sheet on a roll inside the impingement module;;

Fig. 4 is a schematic perspective cross-sectional view of an impingement

module for hot air in which the width adjustment arrangements comprise a plurality of valves inside the impingement module which block air flow in discrete width steps;;

Fig. 5a is a block description of a state of the art drying unit comprising a suction box, an impingement unit together with a side perspective of said drying unit;

Fig. 5b is a block description of the drying unit of the present invention together with a side perspective of said drying unit;

Figs. 6a - 6b are schematic perspective views of a plate for creating an array of beams comprising a plurality of holes;;

Figs. 1 - 16 are schematic perspective views of a width adjustment

arrangement for blocking the array of air beams;

Figs. 8a, 8b are schematic perspective views of a mechanism to adjust the width of the width adjustment arrangement; Figs. 9, 9a are schematic perspective views of the air impingement module of the present invention;

Fig. 10 is a perspective view of the plate for creating an array of beams and the air blocking device of the present invention;

Fig. 11 is a schematic perspective view of the trajectory of printing media under the air impingement module of the present invention;

The accompanying drawings are included to provide a further understanding of the present invention and are incorporated in and constitute a part of this specification. The drawings illustrate particular embodiments of the invention and together with the description serve to explain the principles of the invention. Other embodiments of the invention and many of the attendant advantages of the invention will be readily appreciated as they become better understood with reference to the following detailed description.

It will be appreciated that common and/or well understood elements that may be useful or necessary in a commercially feasible embodiment are not necessarily depicted in order to facilitate a more abstracted view of the embodiments. The elements of the drawings are not necessarily illustrated to scale relative to each other. It will further be appreciated that certain actions and/or steps in an embodiment of a method may be described or depicted in a particular order of occurrences while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used in the present specification have the ordinary meaning as is accorded to such terms and expressions with respect to their corresponding respective areas of inquiry and study, except where specific meanings have otherwise been set forth herein.

DETAILED DESCRIPTION OF THE DRAWINGS

In an aspect of the present invention, an impingement unit for an inkjet printer device according to claim 1 is provided.

With reference firstly to Fig. 1 of the drawings, a schematic perspective cross-sectional view of an impingement unit is provided. In Fig. 1 , several features of the present invention can be observed. The impingement unit 10 of Fig. 1 comprises a suction box associated with the printing substrate transport device for providing an under pressure for holding down the printing substrate onto the surface of the printing substrate transport device, wherein the suction box comprises a plurality of suction holes 12 arranged to allow recirculation of the hot air by redirecting the array of air beams after impinging on the printing substrate towards an air outlet. Further the impingement unit 10 for an inkjet printer of Fig. 1 also comprises an air impingement module for hot air arranged above the printing substrate transport device comprising a heat source for heating air entering the air impingement module, and a plate for creating an array of air beams comprising a plurality of impingement holes 11.

An embodiment of the present invention is also shown in Fig. 1 , in which the

impingement module further comprises an air suction module for recirculating air by redirecting the array of air beams after impinging on the printing substrate towards an air outlet 15. As mentioned above, this additional feature allows the air around the impingement unit to be directly sucked into a recirculation circuit, thereby enhancing the energy efficiency, especially when the air has been heated, and allowing the

temperature around the impingement unit to be kept as low as possible.

With reference to Fig. 2 of the drawings, a cross-sectional view of an impingement unit wherein the width adjustment arrangements comprise movable blocks or shutters outside the impingement module is shown. Fig. 2 shows an air impingement module for hot air 20 arranged above the printing substrate transport device 22 comprising a heat source for heating air 21 entering the air impingement module, and a plate 23 for creating an array of air beams comprising a plurality of impingement holes. Further, Fig. 2 shows two width adjustment arrangements 25 for blocking the array of air beams of each of the one or more air impingement modules in a direction (z) substantially perpendicular to the transport direction of a printing substrate (y) and substantially perpendicular to the normal to the plane of the surface of a printing substrate (x) which is also the impingement direction, such that the array of air beams are restricted to a particular width, and such that directions x, y, and z form a substantially orthogonal axes system of the printing substrate 24. Said two width adjustment arrangements 25 comprise movable blocks or shutters outside the impingement module. The presence of the width adjustment arrangements 25 allows restricting the impingement of the air beams to the width of the printing substrate 24. This restriction reduces the deformation of said printing substrate 24. Also, the combination of a printing substrate transport device 22 having a large thermal mass and a high conductivity with the use of the width adjustment arrangements 25 provides smaller temperature gradients on the surface of the printing substrate transport device 22, as the direct heating of the printing substrate transport device 22 is avoided. As a consequence, better robustness of the printing can be reached, especially with high ink amounts. Further, this design provides more compact units than the prior art, making it possible to add more units around the printing substrate transport device 22, thereby improving the drying functionality. With reference to Fig. 3 of the drawings, a cross-sectional view of an impingement unit wherein the width adjustment arrangements comprise a foil or sheet on a roll inside the impingement module. Fig. 3 shows an air impingement module 30 for hot air 31 arranged above the printing substrate transport device comprising a heat source for heating air entering the air impingement module (not shown), and a plate 33 for creating an array of air beams comprising a plurality of impingement holes. The air impingement module of Fig. 3 is arranged above a printing substrate transport device in a similar way as shown in Fig. 2. Further, Fig. 3 shows two width adjustment arrangements 35 for blocking the array of air beams of each of the one or more air impingement modules in a direction (z) substantially perpendicular to the transport direction of a printing substrate (y) and substantially perpendicular to the normal to the plane of the surface of a printing substrate (x) which is also the impingement direction, such that the array of air beams are restricted to a particular width, and such that directions x, y, and z form a

substantially orthogonal axes system. The presence of the width adjustment

arrangements 35 allows restricting the impingement of the air beams to the width of the printing substrate. Said two width adjustment arrangements 35 comprise a foil or sheet on a roll inside the impingement module. As in the previous embodiment, this restriction reduces the deformation of said printing substrate. Also, the combination of a printing substrate transport device having a large thermal mass and a high conductivity with the use of the width adjustment arrangements 35 provides smaller temperature gradients on the surface of the printing substrate transport device, as the direct heating of the printing substrate transport device is avoided. As a consequence, better printing quality can be reached, especially with high ink amounts. Further, this design provides even more compact units than the previous embodiment, making it possible to add more units around the printing substrate transport device, thereby further improving the drying functionality.

With reference to Fig. 4 of the drawings, a cross-sectional view of an impingement unit wherein the width adjustment arrangements comprise a plurality of valves inside the impingement module which block air flow in discrete width steps is shown. Fig. 4 shows an air impingement module 40 for hot air 41 comprising a heat source for heating air entering the air impingement module, and a plate 43 for creating an array of air beams comprising a plurality of impingement holes. The air impingement module of Fig. 4 is arranged above a printing substrate transport device in a similar way as shown in Fig. 2, which is not shown in Fig. 4. Further, Fig. 4 shows two width adjustment arrangements 42, 44 for blocking the array of air beams of each of the one or more air impingement modules in a direction (z) substantially perpendicular to the transport direction of a printing substrate (y) and substantially perpendicular to the normal to the plane of the surface of a printing substrate (x) which is also the impingement direction, such that the array of air beams are restricted to a particular width, and such that directions x, y, and z form a substantially orthogonal axes system. The presence of the width adjustment arrangements 42, 44 allows restricting the impingement of the air beams to the width of the printing substrate. Said two width adjustment arrangements 42, 44 comprise a plurality of valves inside the impingement module which block air flow in discrete width steps. As in the previous embodiment, this restriction reduces the deformation of said printing substrate. Also, the combination of a printing substrate transport device having a large thermal mass and a high conductivity with the use of the width adjustment arrangements 42, 44 provides smaller temperature gradients on the surface of the printing substrate transport device, as the direct heating of the printing substrate transport device is avoided. As a consequence, better printing quality can be reached, especially with high ink amounts. Further, this design also provides more compact units than the previous prior art, making it possible to add more units around the printing substrate transport device, thereby further improving the drying functionality. It can be observed in Fig. 4 that the width of the plate 43 is divided in segments, wherein an open valve 42 provides air to a segment, whereas a closed valve 44 blocks the air from impinging a segment. The additional advantage of this embodiment is that it is easier to control the leakage of air to the blocked sections using valves, thereby providing better control of the impingement of hot air onto printed substrate.

With reference to Fig. 5a of the drawings, a block description of a state of the art impingement unit comprising, from left to right, an air suction module, an impingement unit, and a heat source is shown. In the lower part of Fig. 5a a side perspective of said drying unit is shown. It can be observed that there are three different units coupled together, namely an air suction module, an impingement unit, and a heat source.

With reference to Fig. 5b of the drawings, a block description of the impingement unit of the present invention together with a side perspective of said impingement unit is shown. In the lower part of Fig. 5b a side perspective of said drying unit is shown. It can be observed that in the present invention the air suction module, one or more impingement modules and one or more width arrangements are integrated into a single unit.

With reference to Figs. 6a and 6b of the drawings, a schematic perspective cross- sectional view of a plate for creating an array of air beams 60 which forms part of an air impingement module for an inkjet printer is provided. In Figs. 6a and 6b, several features of the present invention can be observed. As it can be observed, the plate for creating an array of air beams 60 comprises a plurality of impingement holes 61. Said plate for creating an array of air beams 30 is part of the housing of the air impingement module, as it can be easily recognized in Fig. 6b. Said impingement holes 61 are disposed in a plurality of columns. The plurality of impingement holes 61 are of a diameter d_h through which the impinging hot air passes. The distance between two consecutive columns of impingement holes is d_pitch· The diameter d_h should be significantly smaller than the distance between two consecutive columns of

impingement holes, e.g. at least ten times smaller.

With reference to Figs. 7 - 7d of the drawings, a schematic perspective view of a width adjustment arrangement 70 for blocking the array of air beams is shown. Said width adjustment arrangement 70 comprises two plates 71 and 72 comprising a plurality of slits 73.. The plurality of slits have preferably a rectangular shape, with the shortest side slightly larger than the diameter d_h of the holes of the plate for creating an array of beams. The distance between slits d_sn_t is arranged such that when the plate comprising a plurality of slits is displaced on top of the plate for creating an array of beams a subsequent slit does not reopen a previously closed hole. Further, Figs. 7 - 7d shows attachment means 74 for attaching the two plates comprising a plurality of slits to a mechanism configured to equally displace the two moving plates 71 and 72 in the same direction. This assembly allows constructing a simpler and more compact arrangement for the mechanism configured to equally displace the two moving plates in comparison with a mechanism to displace the two moving plates in opposite directions.

Fig. 7b shows a first layout in which the two plates 71 and 72 are positioned such that none of the holes of the plate for creating an array of beams is occluded by the plates 71 and 72, thereby providing the maximum area of air impingement. In this way, the air is not restricted to flow through any of the holes of the plate for creating an array of beams. Fig. 4b further shows a marker 45 indicating the original position of plate 41. Accordingly, Fig. 7c shows a second layout in which the two plates 71 and 72 have been displaced a distance d-i to the right from the position depicted in Fig. 7b, in which the air is not restricted to flow through any of the holes of the plate for creating an array of beams. It can be observed in Fig. 7b that said displacement causes the first two columns of impingement holes in both sides of the plate for creating an array of beams to become occluded, thereby restricting the impingement area in the impingement direction. Fig. 7c further shows a marker 75 indicating the original position of plate 71 and marker 76 indicating the position of plate 71 when the two plates 71 and 72 have been displaced a distance d-i to the right. A person skilled in the art would readily recognized that there exists a displacement distance d < d-i, which causes exclusively the first column of impingement holes in both sides of the plate for creating an array of beams to become occluded.

Similarly, Fig. 7d shows a third layout in which the two plates 71 and 72 have been displaced a distance d₂ > d-i to the right. It can be observed in Fig. 7d that said displacement causes the two additional columns of impingement holes in both sides of the plate for creating an array of beams to become occluded in comparison with Fig. 7b, thereby further restricting the impingement area in the impingement direction. Fig. 7d further shows a marker 75 indicating the original position of plate 71 and marker 77 indicating the position of plate 71 when the two plates 71 and 72 have been displaced a distance d₂ > di to the right.

With reference to Figs. 8a - 8b of the drawings, a schematic perspective view of a mechanism for adjusting the width of the width adjustment arrangement 80 is shown. Said mechanism 80 is configured for displacing the air blocking device, and comprises a stepper for displacing the air blocking device, a static part 82 which is fixed to the housing of the air impingement device of the present invention, a guiding slide 83 comprising two wide slits arranged in the static part 82 through which the air blocking device slides when the air blocking device is displaced when the stepper is activated, such that the movement of the air blocking device is restricted in the direction z, means for receiving the attachment means 84, and a leaf spring for exerting a downwards force on the air blocking device, such that the air blocking device and the plate for creating an array of beams come into an air-tight connection.

In an embodiment of the present invention, the curvature of the plate for creating an array of beams, and the curvature of the air blocking device have a different radius. Namely, the curvature of the air blocking device is higher than the curvature of the plate for creating an array of beams. As a consequence of this feature, the air blocking device and the plate for creating an array of beams still come into an air-tight connection when the leaf spring exerts a downward force of the air blocking device, but at the same time the air blocking device is capable of displacing over the plate for creating an array of beams with less mechanical friction.

With reference to Figs. 9 - 9a of the drawings, a schematic perspective view of the air impingement module 90 of the present invention is shown. Said impingement module comprises the previously described plate for creating an array of beams 61. Further, the air impingement module comprises width adjustment arrangements formed of two plates 71 and 72 comprising a plurality of slits 73, and also comprises a mechanism 80 configured to equally displace the two moving plates in the same direction attached to the two moving plates by attachment means 84.

In the embodiments shown in Figs. 9 - 9a the distance between slits d_sn_t is arranged such that when the two moving plates are displaced on top of the plate for creating an array of beams a subsequent slit does not reopen a previously closed hole.

In the embodiment shown in Fig. 9, a first relative position between the plate for creating an array of beams and the two moving plates of the width adjustment arrangement exists, wherein the latter plates are on top of the plate for creating an array of beams, such that the slits correspond to the holes of the plate for creating an array of beams, such that the air is not restricted to flow through any of the holes of the plate for creating an array of beams.

In the embodiment shown in Fig. 9 the two moving plates can be displaced on top of the plate for creating an array of beams a distance di. In this manner, the slits of the two moving plates restrict the flow of air in a symmetric manner such that the first row of holes in each side of the plate for creating an array of beams does not allow hot air to pass through, thereby restricting the width of the area of media that will be impinged with hot air. In this embodiment, the distance between the first and second slits is such that the second slit does not reopen the hole closed by the displacement of the first slit.

The plate for creating an array of beams and the two moving plates can be displaced a second relative position between tern, in which the two moving plates has been displaced on top of the two moving plates a distance d₂ > d-i. In this manner, the slits of the two moving plates restrict the flow of air in a symmetric manner such that a further column of holes in each side of the plate for creating an array of beams does not allow hot air to pass through, thereby further restricting the width of the area of media that will be impinged with hot air. In this embodiment, the distance between the first and second slits is such that the second slit does not reopen the hole closed by the displacement of the first slit. Also, the distance between the second and third slits is such that the third slit does not reopen the hole closed by the displacement of the second slit.

The previously described air impingement modules provide a more compact

arrangement than the air impingement modules known in the art, which allows creating a trajectory of the printing substrate over the printing substrate transport device in which several air impingement modules are placed after a first part of the trajectory in which there is no air impingement module. This is explained in more detail with reference to Fig. 11. The more compact arrangement is provided by the air impingement module of the present invention comprising an impingement module, a suction module, and optionally a heat source for heating air into one single module, thereby allowing a higher freedom of design around the printing substrate transport device, where impingement modules are typically placed.

With reference to Fig. 10 of the drawings, a perspective view of the plate for creating an array of beams and the air blocking device of the present invention is shown. In Fig. 10 the radius 101 of the plate for creating an array of beams can be observed. Further, the radius 102 of the air blocking device can also be observed. In an embodiment of the present invention, the radius of air blocking device 102 is bigger than the radius 101 of the plate for creating an array of beams. As mentioned above, this particular

configuration reduces the mechanical friction between the plate for creating an array of air beams and the air blocking device, when the air blocking device displaces on top of the plate for creating an array of air beams. Simultaneously, this configuration produces a more air-tight connection between the plate for creating an array of beams and the air blocking device.

With reference to Fig. 11 of the drawings, an embodiment is illustrated in which the plurality of air impingement modules are arranged such that there are no impingement modules in the first part of a trajectory of the printing substrate over the printing substrate transport device. When a printed substrate is transported onto the surface of the printing substrate transport device 1 10, it enters a diffusion path 11 1 in which there are no impingement modules for hot air above the printing substrate transport device 110. In this first part of the path, the printed substrate is only heated up by the printing substrate transport device 110, so that there is no accelerated evaporation when ink has been recently jetted onto the printed substrate, which might lead to defects in the image on the printed substrate. In a second stage of the path onto the printing substrate transport device 1 10 the printed substrate enters an evaporation path 1 12, in which the printed substrate on the printing substrate transport device 110 travels below a plurality of air impingement modules for hot air arranged above the printing substrate transport device 113 once the ink has had time enough to be absorbed by the printed substrate. The dryer and drying method of this embodiment generates printed substrates with better robustness of the printed image.

In another embodiment, a dryer for an inkjet printer comprises: a printing substrate transport device having a large thermal mass of at least 25.000 J/(K-m²) and a high conductivity of at least 120 W/(m-K) suitable for transporting a printing substrate on the surface of the transport device; a suction box associated with the printing substrate transport device for providing an under pressure for holding down the printing substrate onto the surface of the printing substrate transport device, wherein the suction box comprises a plurality of suction holes arranged to provide an under pressure to the printing substrate; one or more air impingement modules for hot air arranged above the printing substrate transport device comprising a heat source for heating air entering the air impingement module, and a plate for creating an array of air beams comprising a plurality of impingement holes; andone or more width adjustment arrangements for blocking the array of air beams of each of the one or more air impingement modules in a direction (z) substantially perpendicular to the transport direction of a printing substrate (y) and substantially perpendicular to the normal to the plane of the surface of a printing substrate (x) which is also the impingement direction, such that the array of air beams are restricted to a particular width, and such that directions x, y, and z form a

substantially orthogonal axes system.

In another embodiment, the printing substrate is transported centered in the direction (z) on the surface of the transport device. In another embodiment, the impingement module of the dryer of any preceding claim, further comprises an air suction module for recirculating air by redirecting the array of air beams after impinging on the printing substrate towards an air outlet.

In another embodiment, the width adjustment arrangements of the dryer comprise movable blocks or shutters in the impingement module.

In another embodiment, the width adjustment arrangements of the dryer comprise a foil or sheet on a roll inside the impingement module.

In another embodiment, the width adjustment arrangements of the dryer comprise a plurality of valves in the impingement module which block air flow in discrete width steps.

In another embodiment, the dryer comprises a suction box which provides an under pressure corresponding to the width of the printing substrate.

In another embodiment, the plurality of air impingement modules of the dryer are arranged such that the printing substrate follows a trajectory over the printing substrate transport device, wherein the trajectory through the dryer comprises a first part defining a diffusion path, and a second part defining an enhanced evaporation path which are traversed by the printing substrate, wherein the one or more impingement modules are arranged in said second part of a trajectory of the printing substrate onto the printing substrate transport device.

In another embodiment, the one or more width adjustment arrangements are symmetric arrangements.

In another embodiment, the printing substrate transport device is a drum.

In another embodiment, the printing substrate transport device has a large thermal mass between 25.000 and 55.000 J/(K-m²), preferably around 50.000 J/(K-m²), and a high conductivity of between 120 and 180 W/(m-K), preferably around 150 W/(m-K), for transporting a printing substrate on the surface of the printing substrate transport device.

In another embodiment, a drying method for a dryer for an inkjet printer comprises: adjusting the suction width of a suction box; transporting the printed substrate onto a printing substrate transport device, and holding the printed substrate down by the suction box, wherein the printing substrate transport device has a large thermal mass of at least 25.000 J/(K-m²) and a high conductivity of at least 120 W/(m-K); transporting the held down printed substrate underneath one or more air impingement modules for hot air arranged above the printing substrate transport device, wherein the one or more air impingement modules comprise a heat source for heating air entering the air impingement module, and a plate for creating an array of air beams comprising a plurality of impingement holes, such that hot air is jetted onto the printed substrate; and wherein one or more width adjustment arrangements blocks the array of air beams of each of the one or more air impingement modules in a direction (z) substantially perpendicular to the transport direction of a printing substrate (y) and substantially perpendicular to the normal to the plane of the surface of a printing substrate (x) which is also the impingement direction, such that the array of air beams are restricted to a particular width, and such that directions x, y, and z form a substantially orthogonal axes system.

In another embodiment of the method, the one or more width adjustment arrangements are symmetric arrangements.

In another embodiment of the method, the suction width of the suction box is adjusted to correspond to the width of the printed substrate.

In another embodiment of the method, the plurality of air impingement modules are arranged such that the printing substrate follows a trajectory over the printing substrate transport device, wherein the trajectory through the dryer comprises a first part defining a diffusion path, and a second part defining an enhanced evaporation path, which are traversed by the printing substrate, wherein the one or more impingement modules are arranged in said second part of a trajectory of the printing substrate onto the printing substrate transport device. It will 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.

Claims

1. An air impingement module for an inkjet printer comprising: a plate for creating an array of air beams comprising a plurality of impingement holes; a width adjustment arrangement for blocking the array of air beams of the air impingement modules in a direction (z) substantially perpendicular to the transport direction of a printing substrate (y) and substantially perpendicular to the normal to the plane of the surface of a printing substrate (x) which is also the impingement direction, such that the array of air beams are restricted to a particular width, and such that directions x, y, and z form a substantially orthogonal axes system.

2. The air impingement module of claim 1 , further comprising a heart source for heating air entering the air impingement module.

3. The air impingement module of any preceding claim, wherein the plate for creating an array of air beams is part of a housing of the air impingement module.

4. The air impingement module of any of the preceding claims, wherein width adjustment arrangement blocks the array of air beams symmetrically in a direction (z).

5. The air impingement module of claim 4, wherein the width adjustment arrangement comprises an air blocking device comprising a plurality of slits configured for restricting the array of air beams to a particular width.

6. The air impingement module of claims 4 or 5, wherein the width adjustment arrangement further comprises a mechanism configured to gradually displace the air blocking device such that the width of the impingement beams is gradually restricted.

7. The air impingement module of claim 6, wherein the mechanism configured to gradually displace the air blocking device comprises a stepper for displacing the air blocking device, a static part attached to the housing of the air impingement module, a guiding slide for the air blocking device to slide when the stepper is activated, means for receiving the attachment means, and a leaf spring for exerting a downwards force on the air blocking device.

8. The air impingement module of any of claims 2 to 7, wherein the plate for creating an array of air beams has a smaller radius than the air blocking device in the x-direction.

9. The air impingement module of any of claims 5 to 8, wherein the air blocking device comprises one or more moving plates comprising a plurality of slits.

10. The air impingement module of claim 9, wherein the air blocking device comprises two moving plates comprising a plurality of slits.

11. The air impingement module of claim 10, wherein the air blocking device comprises two moving plates which displace in the same direction.