FIELD OF THE INVENTION
[0001] 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.
BACKGROUND OF THE INVENTION
[0002] In printing or copying systems, and especially in inkjet 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.
[0003] US2014/028767 A1 discloses a printer comprising a heating system to produce hot-air flow impinging
on a print media.
[0004] GB1215791 A discloses an apparatus for drying ink on a surface of a web of print substrate, the
drying apparatus comprising means for directing drying gas towards the web.
[0005] US2014/009546 A1 discloses a system for supplying ink printed on a print medium, the system comprises
a heater to heat air, an impingement plate with a plurality of holes, and a blower
for blowing heated air through the hole of the impingement plate onto the print medium.
The impingement flux length in the system may be defined as the length of the impingement
plate through which heated air is blown, which width is adjustable.
[0006] US2010/141725 A1 discloses a recording apparatus including a dryer for accelerating the drying of
the recordable medium by ejecting gas to the recordable medium, wherein the dryer
is configured such that the ejection range of the gas in a direction perpendicular
to the transportation direction of the recordable medium is changeable.
[0007] JP 2011 056900 A discloses a dryer that supplies air to the paper along a first direction advancing
from one side to the other side of the conveyance width direction, and along a second
direction advancing from the other side to one side of the conveyance width direction.
Specifically, a shutter capable of advancing/retracting along the conveyance width
direction is arranged, and according to the width size of the paper, the shutter is
moved to vary an opening distance of an opening face of the dryer.
[0008] JP 2013 215981 A discloses a liquid ejection apparatus that includes a hot air room provided with
multiple vents for discharging hot air to be blown against multiple portions of the
medium with the image formed thereon. The number of vents which blow the hot air can
be changed, based on at least one of position information in the medium of the image
and lateral length information of the medium.
[0009] US2825979 A discloses a device for drying paper on a paper making machine and more particularly
to a longitudinal dryer having a plurality of selectively adjustable apertures.
[0010] 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.
[0011] 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.
[0012] 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
[0013] In an aspect of the present invention, an air impingement module for an inkjet printer
according to claim 1 is provided.
[0014] 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 is restricted to a particular
width, and such that directions x, y, and z form a substantially orthogonal axes system.
[0015] In the present inventiont, the width adjustment arrangement blocks the array of air
beams symmetrically in the z-direction. This 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.
[0016] In the present invention, the air blocking device of the air impingement module of
the present invention comprises two moving plates 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.
[0017] The air blocking device of the air impingement module of the present invention comprises
two moving plates which displace in the same direction.
[0018] 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.
[0019] 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.
[0020] 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 the present 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
δ, 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.
[0021] In an embodiment, the impingement module for an inkjet printer further comprising
the plate for creating an array of air beams has a curvature substantially perpendicular
to the impingement direction (z) and having a radius 101 and wherein the air blocking
device has a curvature substantially perpendicular to the impingement direction (z)
and having a radius 102, wherein the radius 101 of the curvature of the plate for
creating an array of air beams is smaller than the radius 102 of the curvature of
the air blocking device. 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.
[0022] 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 11.
[0023] 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.
[0024] 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·m
2) 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.
[0025] 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.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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.
[0035] 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.
[0036] 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.
[0037] In a particular embodiment, a dryer for an inkjet printer comprises the printing
substrate transport device being a drum.
[0038] 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·m
2), preferably around 50.000 J/(K·m
2), 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.
[0039] In a particular embodiment, the present invention relates to a plurality of methods
for a dryer for an inkjet printer.
[0040] 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.
[0041] 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·m
2) and a high conductivity of at least 120 W/(m·K).
[0042] 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.
[0043] 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.
[0044] 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.
[0045] 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 transport
device.
[0046] 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.
[0047] 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
[0048] 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. 7 - 7d
- 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;
[0049] 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.
[0050] 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
[0051] In an aspect of the present invention, an impingement unit for an inkjet printer
device according to claim 1 is provided.
[0052] 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.
[0053] 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.
[0054] 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.
[0055] 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.
[0056] 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.
[0057] 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.
[0058] 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.
[0059] 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.
[0060] With reference to Figs. 7 - 7d of the drawings, a schematic perspective view of a
width adjustment arrangement 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
slit 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.
[0061] 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.
[0062] Accordingly, Fig. 7c shows a second layout in which the two plates 71 and 72 have
been displaced a distance δ
1 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
δ
1 to the right. A person skilled in the art would readily recognized that there exists
a displacement distance δ < δ
1, which causes exclusively the first column of impingement holes in both sides of
the plate for creating an array of beams to become occluded.
[0063] Similarly, Fig. 7d shows a third layout in which the two plates 71 and 72 have been
displaced a distance δ
2 > δ
1 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 δ
2 > δ
1 to the right.
[0064] 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.
[0065] 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.
[0066] 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.
[0067] In the embodiments shown in Figs. 9 - 9a the distance between slits d
slit 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.
[0068] 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.
[0069] 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 δ
1. 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.
[0070] The plate for creating an array of beams and the two moving plates can be displaced
a second relative position between tem, in which the two moving plates has been displaced
on top of the two moving plates a distance δ
2 > δ
1. 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.
[0071] 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.
[0072] 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.
[0073] 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 110, it enters a diffusion path 111 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 110 the printed substrate enters an evaporation
path 112, 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.
[0074] 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·m
2) 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.
[0075] In another embodiment, the printing substrate is transported centered in the direction
(z) on the surface of the transport device.
[0076] 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.
[0077] In another embodiment, the width adjustment arrangements of the dryer comprise movable
blocks or shutters in the impingement module.
[0078] In another embodiment, the width adjustment arrangements of the dryer comprise a
foil or sheet on a roll inside the impingement module.
[0079] 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.
[0080] In another embodiment, the dryer comprises a suction box which provides an under
pressure corresponding to the width of the printing substrate.
[0081] 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.
[0082] In another embodiment, the one or more width adjustment arrangements are symmetric
arrangements.
[0083] In another embodiment, the printing substrate transport device is a drum.
[0084] In another embodiment, the printing substrate transport device has a large thermal
mass between 25.000 and 55.000 J/(K·m
2), preferably around 50.000 J/(K·m
2), 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.
[0085] 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·m
2) 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.
[0086] In another embodiment of the method, the one or more width adjustment arrangements
are symmetric arrangements.
[0087] In another embodiment of the method, the suction width of the suction box is adjusted
to correspond to the width of the printed substrate.
[0088] 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.
[0089] 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.
[0090] Generally, this application is intended to cover any adaptations or variations of
the specific embodiments discussed herein.
[0091] 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.