Note: Descriptions are shown in the official language in which they were submitted.
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An aerosol-generating device comprising a micro electro-mechanical system
Field of the invention
The present invention relates to an aerosol-generating device.
Aerosol-generating devices allow aerosolization of an aerosol forming
material. The aerosol-generating devices according to the invention are also
commonly called electronic cigarettes.
Aerosolization is the conversion of a substance, for example in liquid
state or solid state, into particles small and light enough to be carried on
the air.
Background of the invention
An aerosol-generating device generally comprises a battery-powered
vaporizer (or vaporisation device) which produces the vapor that is inhaled.
The
usual configuration of the vaporizer used to vaporize a vaporizable material
comprises a resistive heating element able to heat a wick imbibed with
vaporizable
material in liquid form.
Alternative vapor generation units are known, that use a microfluidic
device. Such microfluidic vapor generation unit corresponds to a so-called
"micro
electro-mechanical system", also designated by the acronym "MEMS".
For example, W016064684 and DE102017123869 disclose microfluidic
vapor generation unit which can be used for electronic cigarettes.
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Those microfluidic vapor generation unit comprises a structure called
MEMS die that comprises a plurality of small chambers. The vapor or aerosol is
formed in the structure or at the outlet of this structure, for example by
heating.
Micro electro-mechanical systems can also be used to induce high
frequency vibrations in a small quantity of vaporizable material. These
vibrations
cause or promote the vaporization of the material.
Advantages of aerosol-generating devices using a microfluidic vapor
generation unit or more generally a micro electro-mechanical system include
small
size, compact structure, lower power consumption, lower cost, increased
reliability
and higher precision, and high heat transfer efficiency.
However, aerosol-generating devices using MEMS as vapor generation
unit may be subject to fluid leakage. More particularly, the vaporizable
material in a
liquid form that reaches the vapor generation unit but is not vaporized can
leak from
the aerosol-generating device if said device is shaken or unfavourably
oriented (e.g.
with the outlet down). Generally, an aerosol-generating device using a MEMS as
vapor generation unit is more likely to leak, through the capillary holes of
the
structure comprising such capillary holes, than usual vaporizers using a
heating coil
and an imbibed wick. Even if such leakage is usually a leakage of a small
amount of
product, it should be avoided.
Furthermore, the micro electro-mechanical systems must remain clean
and clear of debris and dust to stay in good working conditions and to
vaporize the
vaporizable material effectively. The aerosol-generating devices are generally
carried by their user in their pockets, and used in various environments and
conditions. Consequently, introduction of foreign particles into the vapor
channel of
the device is likely to occur. These particles will reach the vapor generation
unit and
can soil and/or damage it. For example, they can plug the capillary structure
of the
vapor generation unit. While a cap can be provided to cover the mouthpiece of
the
aerosol-generating device and thus close the vapor channel to protect the
vapor
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generation unit from foreign particles, such cap can be lost and is not fully
convenient
for the user of the aerosol-generating device.
The present invention thus aims to provide an aerosol-generating device
comprising a vapor generation unit comprising a MEMS, which addresses one or
several of the above-mentioned problems.
Summary of the invention
The present invention thus relates to an aerosol-generating device
comprising a vapor generation unit adapted to transform an aerosol forming
material
into vapor, and a vapor channel extending from the vapor generation unit to a
vapor
outlet of the aerosol-generating device. The vapor generation unit comprises a
micro
electro-mechanical system (MEMS). The vapor channel is provided with a movable
cover having a closed position in which it closes the vapor channel and an
open
position allowing vapor to pass. The cover has a lower face and is adapted to
move
from the closed position to the open position under the effect of suction
applied on
the aerosol-generating device by the user to vape. The lower face of the cover
is
provided with a layer of an absorbent material adapted to imbibe the aerosol
forming
material.
The absorbent material can be for example one of a fabric, sponge or
foam. The absorbent material can imbibe the small quantity of liquid that can
leak
from the vapor generation unit. It helps in preventing the device from
leaking.
The movable cover protects the vapor generation unit from any foreign
matter that could damage or obstruct it. It also avoids leakage of liquid from
the vapor
generation unit. As the movable cover is opened by a suction applied on the
aerosol-
generating device, use of a separate cap to close the vapor channel when the
device
is not used is not necessary in some embodiments of the invention.
The lower face of the cover can be in close proximity to the vapor
generation unit when the cover is in closed position. The vapor generation
unit can
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have an upper surface that is substantially flat, the lower face of the cover
being in
contact with the upper surface of the vapor generation unit when the cover is
in
closed position.
This enhances the protection against leaks provided by the movable
cover.
The micro electro-mechanical system advantageously comprises a
MEMS die. In such embodiment, the upper surface of the vapor generation unit
is
generally the upper surface of its MEMS die and said upper surface is provided
with
small chambers.
As vapor generation units based on micro electromechanical systems are
more subject to malfunction due to obstruction than conventional heaters, the
present invention is of particular interest in aerosol-generating devices
using such
vapor generation units.
The aerosol-generating device can comprise a spring which tends to
return the cover to the closed position. The cover can comprise a hinged flap.
According to another embodiment, the cover is constituted by an elastically
deformable piece.
Various embodiments of covers can thus be used in the invention,
depending on many parameters such as the device configuration, the expected
reliability of the cover, its cost, etc.
The vapor generation unit can comprise one or several MEMS dies
provided on a printed card circuit. For example, the vapor generation unit can
comprise two MEMS dies.
Use of a plurality of micro electro-mechanical systems can help to
produce a sufficient quantity of vapor and/or can provide a large vapor
production
surface to obtain a homogeneous aerosol.
The aerosol-generating device can comprise a main body and a cartridge.
The main body can comprise the vapor generation unit and the cartridge can
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comprise a reservoir of vaporizable material, and the cover is comprised in
the main
body.
According to another embodiment, the main body can comprise the vapor
generation unit and the cartridge can comprise a reservoir of vaporizable
material,
5 and the cover is comprised in the cartridge.
Depending on the embodiment of the invention, the cover will thus be
used during the whole lifetime of the device or be replaced each time the
cartridge
is replaced.
Brief description of the drawings
Other particularities and advantages of the invention will also emerge
from the following description.
In the accompanying drawings, given by way of non-limiting examples:
- Figure 1 represents, in a partial schematic sectional view, an aerosol-
generating device according to an example embodiment of the invention, a
movable
cover of the device being in a closed position;
- Figure 2 represents the an aerosol-generating device of Figure 1, the
cover being in an open position;
- Figure 3 represents, in a schematic sectional view, an example
embodiment of a movable cover that can be used in the invention;
- Figure 4 represents, in a schematic three-dimensional view, an
aerosol-generating device according to a second example embodiment of the
invention;
- Figure 5 represents, in a schematic three-dimensional view, an
example embodiment of a vapor generation unit that can be used in the
invention;
and
- Figure 6 represents, in a schematic sectional view, an example
embodiment of a vapor generation unit that can be used in the invention.
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Detailed Description
Figure 1 and Figure 2 represent an aerosol-generating device according to
an example embodiment of the invention.
The aerosol-generating device comprises a reservoir 1. The reservoir 1
defines an inner volume 2 that is adapted to contain an aerosol forming
material.
The term aerosol forming material is used to designate any material that is
aerosolizable in air to form an aerosol. The vaporizable material may, for
example,
be in liquid form, in solid form, or in a semi liquid form, thus comprise or
consist of
an aerosol-generating liquid, gel, paste or wax or the like, or any
combination of
these.
In the present invention, the aerosolization doesn't involve a phase change
from the aerosol forming material to gas. It generally creates an aerosol
using
thermal firing chambers. The working principle is similar for example to that
of the
thermal inkjet functioning. The aerosol forming material droplets are ejected
from at
least one MEMS die by applying a pulse of pressure to the material supplied in
the
chambers of the MEMS die.
To create this pressure pulse "thermal ink jet" principle can be applied as
follows:
MEMS dies have a series of small chambers, each containing a heater
therein;
- water in the material is heated by the heater until it is vaporized
(because boiling point of water is reached) and bubble is created. The
propylene
glycol (PG) and the vegetable glycerine or glycerol (VG) present in the
aerosol
forming material will not vaporize as boiling points of those components are
higher
than the boiling point of water at the same atmospheric pressure); and
- rapid expansion of the bubbles causes the formation of the PG/VG
droplets, which are ejected out of the MEMS dies.
More particularly, the aerosol forming material is heated by the heater of the
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at least one MEMS die until it starts to boil and a gas bubble is created. The
gas
bubble is comprised of a phase change of the aerosol forming material, usually
liquid, and potentially air trapped in the liquid. The amount of the aerosol
forming
material being boiled is about 1% of the total amount. In other words, around
1% of
the aerosol forming material is superheated to form a gas bubble. This 1%
consists
of the amount of aerosol forming material that is the closest to the heater.
Gas being
much more voluminous than liquid, it provides the force to push out from the
vapour
generation unit. This allows approximately 80-90% of the aerosol forming
material
above the gas bubble to be ejected.
Gas bubbles grow as they are heated until being large enough that they force
liquid droplets to be ejected. The gas bubbles also escape when the liquid
droplets
are ejected. This creates a vacuum which causes more liquid to be drawn into
the
vapor generation unit 20 from the reservoir 33. The process then repeats.
It shall be noted that the propylene glycol (PG) and the vegetable glycerine
(VG) that may be present in the aerosol forming material may not vaporize as
boiling
points of these components are higher than the boiling point of water at the
same
atmospheric pressure. However, because the high temperature's heater, it is
very
possible that all of the aerosol forming material near the heater, regardless
of
composition, is superheated and undergoes the phase change to the gas bubble.
In
other words, the 1% amount of the aerosol forming material that is superheated
can
be made up of a mixture of components that is similar to that of the rest of
the aerosol
forming material.
The reservoir can be, by way of example, a one-piece plastic part, for example
obtained by injection moulding.
In the represented first example embodiment of Figure 1, the reservoir 1 is
provided in an upper part of the aerosol-generating device, towards a
mouthpiece 3
of the aerosol-generating device. The reservoir 1 thus can comprise or can
form, at
its upper end, a mouthpiece 3. The mouthpiece 3 comprises a vapor outlet and
is
the part of the aerosol-generating device where the user places his mouth to
vape,
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i.e. to inhale the aerosolized material. A vapor channel 4 connects the
mouthpiece
3 to a vapor generation unit 5 where the aerosol forming material is
aerosolized. In
the represented embodiment, the vapor channel 4 is a central tube that is
mainly
formed by the reservoir 1.
The aerosol-generating device comprises MEMS (micro-electro mechanical
systems) advantageously comprising one or several microfluidic structures
named
MEMS die. More particularly, the MEMS die of the present embodiment as
explained
above is a microfluidic structure comprising a series of small chambers. Each
small
chamber contains a heater therein (not shown), which heats the water contained
in
the aerosol forming material until only the water vaporizes as the boiling
point of the
water is lower than the boiling points of PG (propylene glycol) and VG
(vegetal
glycerin) components contained in the aerosol forming material. Rapid
expansion of
the bubbles causes the formation of the PGNG droplets, which are ejected out
of
the MEMS die.
The vapor generation unit 5 is provided with liquid from the reservoir by a
liquid path 6. The liquid path comprises a liquid channel 7 that fluidically
connects
the reservoir 1 (and more particularly the inner volume 3 of the reservoir 1)
and a
filter chamber 8. The filter chamber 8 comprises a filter 9, for example a
mesh such
as a metallic mesh, preferably a stainless-steel mesh. The liquid coming from
the
reservoir must cross the filter 9 to reach the vapor generation unit. The
filter 9
prevents the passage of particles from the reservoir to the vapor generation
unit.
Such particles, which could be introduced into the reservoir 1 during its
filling
and / or which could come from a poor quality aerosol forming material, could
interfere with the operation of the vapor generation unit. In particular, they
could plug
the small chambers of the microfluidic structure of the MEMS die.
The capillary displacement of the aerosol forming material is effected on the
material in a liquid state. If not already provided by the reservoir as a
liquid, the
transformation of the aerosol forming material into a liquid state can be
obtained by
heating. This may for example be the case if the reservoir 1 contains a
vaporizable
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material consisting of or comprising a wax.
In the represented embodiment of Figures 1 and 2, the aerosol-generating
device comprises several liquid channels 7, namely two liquid channels 7.
According to alternative embodiments of the invention, the reservoir 1 can
comprise a single inner volume 3 or several independent inner volumes 3. Each
inner volume of the reservoir is connected to the filter chamber 8 by one
liquid
channel 7 or several liquid channels 7.
The aerosol-generating device further comprises a movable cover 10.
The cover 10 is configured to move between a closed position in which it
closes the outlet channel and an open position in which the outlet channel is
free,
and vice-versa. The cover is represented in its closed position in Figure 1
and in its
open position in Figure 2.
The cover 10 is adapted to move from the closed position to the open position
under the effect of suction applied on the aerosol-generating device (i.e. on
the
mouthpiece 3) by the user to vape.
Figure 3 represents in detail an example embodiment of a movable cover 10
that can be used in the invention. In Figure 3, the cover 10 is in its closed
position.
The cover 10 comprises a closing plate 11. The closing plate 11 has a shape
that
corresponds (with a functional clearance) to the cross section of the vapor
channel 4.
When the cover 10 is in closed position, the closing plate 11 extends across
the
vapor channel 4. The closing plate 11 thus closes the vapor channel 4. In the
closed
position, the closing plate 11 can bear on a seat 12 provided on the wall of
the vapor
channel 4. The cover 10 comprises a hinge 13. The closing plate 11 is thus
articulated with respect to the rest of the aerosol-generating device. The
movable
cover moves to the open position by rotation of the closing plate 11 around
the hinge
13. In this embodiment, the closing plate is thus a flap. The hinge can be
formed, by
way of example, by a small pivot shaft, or by a part deformable along the
hinge axis.
A spring 17, for example a torsion spring or any other adapted elastic
element,
tends to return the cover to its closed position. The return force of the
spring must
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however be low enough so that the force caused on the cover by suction of the
user
on the mouthpiece 3 is sufficient to open the cover 10.
In Figure 2, in which the movable cover 10 is in open position, the closing
plate 11 is schematically represented in a fully pivoted position, i.e.
extending
5 orthogonally compared to its position when the movable cover 10 is in closed
position. Of course, depending on the configuration of the cover 10 and on the
cross
section of the vapor channel 4, the closing plate 11 can be significantly less
pivoted
in the open position than shown in Figure 2, as long as the passage of vapor
is
possible through the movable cover.
10 The vapor flow is represented by arrows in Figure 2.
The cover 10 has a lower face 14 and an upper face 15. The lower face 14 of
the cover 10 is oriented towards the vapor generation unit 5, i.e. it faces
the vapor
generation unit 5 when the cover 10 is in closed position. In the represented
embodiment, the lower face of the cover 10 corresponds to the lower face of
the
closing plate 11.
The lower face 14 of the cover 10 is advantageously provided with a layer
of an absorbent material 16. The absorbent material 16 is adapted to imbibe
liquid,
in particular a liquid aerosol forming material issued from the reservoir 1.
The
absorbent material 16 is thus adapted to retain liquid that would leak from
the vapor
generation unit 5. Many absorbent materials can be used. Foam, e.g. plastic
foam
can be used. The absorbent material can also comprise fabric (e.g. felt), or
sponge.
When the cover 10 is in closed position, its lower face 14, provided with
absorbent material 16, is in close proximity to the vapor generation unit 5.
By close
proximity, is meant a very short distance (e.g. less than 2mm or less than
lmm) or
in contact.
Thus, the lower face 14 of the cover 10 is advantageously in contact with
an upper surface of the vapor generation unit 5.
More particularly, when the vapor generation unit comprises a microfluidic
structure (MEMS die) comprising small chambers, the upper surface of the vapor
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generation unit is generally also the upper surface of the MEMS die.
If the cover 10 is in contact with the upper surface of the microfluidic
structure when in closed position, it closes the outlets of the small chambers
of the
microfluidic structure. The absorbent material can directly imbibe any liquid
that
would exit from the small chambers.
As the element causing the aerosolization of the liquid is located under
the surface of the microfluidic structure, the cover 10, even if it is in
contact with the
vapor generation unit when it is closed, is not in contact with the element
which
causes the aerosolization.
Thus, providing a layer of absorbent material 16 on the lower face 14 of
the closing plate 11 (or, more generally, of the cover 10) is not a problem
with this
type of vapor generation unit (whereas with a conventional vapor generation
unit
comprising a wick, the contact of the absorbent material with the wick would
cause
the absorbent material to drain liquid from the reservoir).
The movable cover 10 can have various configurations, according to
alternative embodiments of the invention.
The movable cover can for example comprise a plurality of hinged plates or
flaps. The cover can be constituted by an elastically deformable part. This
elastically
deformable part can for example be a deformable foil comprising one or more
slits
which open when a pressure difference exists between the faces of the foil.
The
elastically deformable part can be made of silicone, other rubbery material,
plastics,
or metal.
Figure 4 represents an aerosol-generating device according to a second
example embodiment of the invention. In this embodiment, the aerosol-
generating
device has an elongated shape. The mouthpiece 3 is located at one extremity of
the
aerosol-generating device. The reservoir 1 is located under the vapor
generation unit
5 and forms two separate inner volumes 2. The reservoir 1 is formed, in the
represented embodiment, of two distinct hollow tubes.
A battery 18 provides the vapor generation unit 5 and the other electrical
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components of the system with electricity. The battery 18 is attached to a
main
printed circuit board 19 (PCB) of the aerosol-generating device. The main
printed
circuit board constitutes the main support structure for the various elements
of the
aerosol-generating device.
Figure 5 represents an example vapor generation unit that is particularly
adapted to be used in the example embodiment of Figure 4. The vapor generation
unit 5 of Figure 5 comprises two MEMS dies 20. The two MEMS dies 20 are
fastened, e.g. soldered, to a printed circuit board 21. Each MEMS die 20 has
an
upper surface 22 formed by a microfluidic structure. The two upper surfaces
are
aligned, at a same level, and thus form the upper surface of the vapor
generation
unit 5.
On the opposite side of the printed circuit board 21, the vapor generation
unit
5 comprise two inlet ports 23. Each inlet port 23 is configured to be
fluidically
connected to an inner volume of the reservoir of the aerosol-generating
device.
The device of Figure 4 is covered with a casing (omitted in Figure 4 to show
the inner parts of the aerosol-generating device).
Figure 6 represents in a cross-sectional diagram a portion of an example of
an aerosol-generation device comprising in a different configuration a vapor
generation unit 5. The vapor generation unit 5 of figure 6 is similar to that
of figure 5
and is also particularly adapted to be used in embodiments of the present
invention.
The vapor generation unit 5 also comprises here two microfluidic structures
or MEMS dies 20. Each MEMS die 20 of the vapor generation unit 5 has an upper
surface or vaporization surface 22.
The vapor generation unit 5 is in fluid communication with two fluidic
connections or liquid channels 7 each of which is arranged to transport the
liquid
aerosol forming material from the reservoir 1 to the vapor generation unit 5.
Each
liquid channel 7 is connected to a MEMS die 20 through an inlet port 23.
Liquid
aerosol forming material is drawn from each liquid channel 7 to a MEMS die 20
e.g.
by capillary force.
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Two aerosol flow paths 24 are arranged here to fluidly communicate with the
mouthpiece of the aerosol-generating device. Each aerosol flow path 24 allows
thus
the generated aerosol to flow from a MEMS die 20 of the vapor generation unit
5 to
the mouthpiece. In other words, airflow paths connect air inlets (not shown)
within
the aerosol-generating device to the mouthpiece for the passage of air through
the
aerosol-generating device.
A downstream end of each aerosol flow path 24 forms a nozzle 25. The
nozzles 25 and the vaporization surfaces 22 are usually on parallel planes. In
other
words, each nozzle 25 face a vaporization surface 22.
Each nozzle 25 can be offset from the vaporization surface 22 or
alternatively,
the nozzle 25 and the vaporization surface 22 may align direction one above
the
other.
When a user draws on the mouthpiece of the device, air is brought into the
aerosol flow paths 24 through the air inlets connected to the aerosol flow
paths 24
so as to create a pressure change that draws the generated aerosol flow to the
mouthpiece as it passes over the vaporization surface 22.
In a setup where each nozzle 25 is offset from a corresponding vaporization
surface 22, incoming air through the air inlets can flow sideways along the
vaporization surface 22 and then pulls up from the nozzle 25. Alternatively
incoming
air through the air inlets can flow directly into the aerosol flow path over
the
vaporization surface 22. The nozzle 25 is jetting either perpendicular to, or
in parallel
with the airflow of the mouthpiece.
While the aerosol-generating device of Figure 4 cannot be disassembled, the
aerosol-generating device of Figures 1 and 2 can be composed of a main body
and
a removable cartridge.
The main body comprises the vapor generation unit 5. The main body, which
is only partially represented in Figures 1 and 2, also comprises the battery
and main
electronic components (microprocessor, sensor(s), etc.) of the aerosol-
generating
device.
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The cartridge comprises the reservoir 1, and thus the aerosol forming
material.
According to alternative embodiments of the invention, the cover 10 is
comprised in the main body, or in the cartridge.
The cartridge can be a consumable item. Once the aerosol-forming material
initially contained in the reservoir has been consumed, and the reservoir is
empty,
the cartridge is replaced by another cartridge with a full reservoir. The old
cartridge
can be discarded, preferably for recycling. A change of cartridge can also be
carried
out, even before it is empty, in order to change the product to be vaped. This
allows
for example the user to choose the taste of the product that he consumes.
The aerosol-generating device developed in the invention thus comprises a
combination of a vapor generation unit that uses a micro electro-mechanical
system
and of a movable cover that opens under the effect of a suction applied on the
aerosol-generating device and that has a lower face provided with a layer of
an
absorbent material.
This provides advantages in terms of vapor quality and homogeneity,
energy efficiency, and compactness, without the main drawbacks of this
technology.
More particularly, the movable cover protects the vapor generation unit
from foreign particles, and avoids leakage of liquid from the vapor generation
unit.
Furthermore, the absorbent material prevents the device from leaking by
imbibing
liquid that would exit from the vapor generation unit.
References used for the fioures
1 Reservoir
2 Inner volume
3 Mouthpiece
4 Vapor channel
5 Vapor generation unit
6 Liquid path
7 Liquid channel
8 Filter chamber
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9 Filter
10 Cover
11 Closing plate
12 Seat
13 Hinge
14 Lower face (of the cover)
15 Upper face (of the cover)
16 Absorbent material
17 Spring
18 Battery
19 Main printed circuit board
MEMS die
21 Printed circuit board
22 Upper surface (of a MEMS die)
23 Inlet port
24 Aerosol flow paths
Nozzle
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