U.S. patent application number 14/899742 was filed with the patent office on 2016-10-13 for aerosol-forming substrate and aerosol-delivery system.
This patent application is currently assigned to Philip Morris Products S.A.. The applicant listed for this patent is PHILIP MORRIS PRODUCTS S.A.. Invention is credited to Oleg Mironov, Ihar Nikolaevich Zinovik.
Application Number | 20160295921 14/899742 |
Document ID | / |
Family ID | 50732945 |
Filed Date | 2016-10-13 |
United States Patent
Application |
20160295921 |
Kind Code |
A1 |
Mironov; Oleg ; et
al. |
October 13, 2016 |
AEROSOL-FORMING SUBSTRATE AND AEROSOL-DELIVERY SYSTEM
Abstract
There is described an aerosol-forming substrate for use in
combination with an inductive heating device. The aerosol-forming
substrate comprises a solid material capable of releasing volatile
compounds that can form an aerosol upon heating of the
aerosol-forming substrate, and at least a first susceptor material
for heating of the aerosol-forming substrate. The first susceptor
material has a first Curie-temperature and is arranged in thermal
proximity of the solid material. The aerosol-forming substrate
comprises at least a second susceptor material having a second
Curie-temperature which is arranged in thermal proximity of the
solid material. The first and second susceptor materials have
specific absorption rate (SAR) outputs which are distinct from each
other. Alternatively or in addition thereto the first
Curie-temperature of the first susceptor material is lower than the
second Curie-temperature of the second susceptor material, and the
second Curie-temperature of the second susceptor material defines a
maximum heating temperature of the first and second susceptor
materials. There is also described an aerosol-delivery system.
Inventors: |
Mironov; Oleg; (Neuchatel,
CH) ; Zinovik; Ihar Nikolaevich; (Peseux,
CH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PHILIP MORRIS PRODUCTS S.A. |
Neuchatel |
|
CH |
|
|
Assignee: |
Philip Morris Products S.A.
Neuchatel
CH
|
Family ID: |
50732945 |
Appl. No.: |
14/899742 |
Filed: |
May 21, 2015 |
PCT Filed: |
May 21, 2015 |
PCT NO: |
PCT/EP2015/061218 |
371 Date: |
December 18, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A24B 15/12 20130101;
H05B 2206/023 20130101; A24F 40/20 20200101; H05B 6/105 20130101;
A24B 15/16 20130101; A24F 47/008 20130101 |
International
Class: |
A24F 47/00 20060101
A24F047/00; H05B 6/10 20060101 H05B006/10; A24B 15/16 20060101
A24B015/16 |
Foreign Application Data
Date |
Code |
Application Number |
May 21, 2014 |
EP |
14169193.1 |
Claims
1. An aerosol-forming substrate for use in combination with an
inductive heating device, the aerosol-forming substrate comprising
a solid material capable of releasing volatile compounds that can
form an aerosol upon heating of the aerosol-forming substrate, and
at least a first susceptor material for heating the aerosol-forming
substrate, the first susceptor material having a first
Curie-temperature and being arranged in thermal proximity of the
solid material, the aerosol-forming substrate comprising at least a
second susceptor material having a second Curie-temperature and
being arranged in thermal proximity of the solid material, the
first and second susceptor materials having specific absorption
rate (SAR) outputs which are distinct from each other and/or the
first Curie-temperature of the first susceptor material being lower
than the second Curie-temperature of the second susceptor material,
and the second Curie-temperature of the second susceptor material
defining a maximum heating temperature of the first and second
susceptor materials.
2. The aerosol-forming substrate according to claim 1, wherein the
first and second Curie-temperatures of the first and second
susceptor materials are selected such, that upon being inductively
heated an overall average temperature of the aerosol-forming
substrate does not exceed 240.degree. C.
3. The aerosol-forming substrate according to claim 1, wherein the
second Curie-temperature of the second susceptor material does not
exceed 370.degree. C.
4. The aerosol-forming substrate according to claim 1, wherein at
least one of the first and second susceptor materials is one of
particulate, or filament, or mesh-like configuration.
5. The aerosol-forming substrate according to claim 4, wherein at
least one of the first and second susceptor materials is of
particulate configuration having an equivalent diameter of 10
.mu.m-100 .mu.m and being distributed within the aerosol-forming
substrate.
6. The aerosol-forming substrate according to claim 4, wherein the
first and the second susceptor materials are of particulate
configuration and are generally homogenously distributed within the
aerosol-forming substrate.
7. The aerosol-forming substrate according to claim 4, wherein the
first and second susceptor materials are of particulate
configuration and are arranged in heaped formation at different
locations within the aerosol-forming substrate, the first susceptor
material being arranged in a central region of the aerosol-forming
substrate, preferably along an axial extension thereof, and the
second susceptor material being arranged in peripheral regions of
the aerosol-forming substrate.
9. The aerosol-forming substrate according to claim 4, wherein at
least one of the first and second susceptor materials is of
filament configuration and is arranged within the aerosol-forming
substrate.
10. The aerosol-forming substrate according to claim 9, wherein the
at least one of the first and second susceptor materials which is
of filament configuration, is arranged in a central region of the
aerosol-forming substrate, preferably extending along an axial
extension thereof.
11. The aerosol-forming substrate according to claim 4, wherein at
least one of the first and second susceptor materials is of
mesh-like configuration and is arranged within the aerosol-forming
substrate or at least partly forms an encasement for the solid
material.
12. The aerosol-forming substrate according to claim 4, wherein the
first and second susceptor materials are assembled to form a
mesh-like structural entity which is arranged within the
aerosol-forming substrate or at least partially forms an encasement
for the solid material.
13. The aerosol-forming substrate according to claim 1, wherein the
aerosol-forming substrate is attached to a mouthpiece, which
optionally comprises a filter plug.
14. An aerosol-delivery system comprising an inductive heating
device and an aerosol forming substrate according to claim 1.
15. An aerosol-delivery system according to claim 14, wherein the
inductive heating device is provided with an electronic control
circuit, which is adapted for a successive or alternating heating
of the first and second susceptor materials of the aerosol-forming
substrate.
16. The aerosol-forming substrate according to claim 2, wherein the
second Curie-temperature of the second susceptor material does not
exceed 370.degree. C.
17. The aerosol-forming substrate according to claim 5, wherein the
first and the second susceptor materials are of particulate
configuration and are generally homogenously distributed within the
aerosol-forming substrate.
18. The aerosol-forming substrate according to claim 5, wherein the
first and second susceptor materials are of particulate
configuration and are arranged in heaped formation at different
locations within the aerosol-forming substrate, the first susceptor
material being arranged in a central region of the aerosol-forming
substrate, preferably along an axial extension thereof, and the
second susceptor material being arranged in peripheral regions of
the aerosol-forming substrate.
19. The aerosol-forming substrate according to claim 2, wherein at
least one of the first and second susceptor materials is one of
particulate, or filament, or mesh-like configuration.
20. The aerosol-forming substrate according to claim 3, wherein at
least one of the first and second susceptor materials is one of
particulate, or filament, or mesh-like configuration.
Description
[0001] The present invention relates to an aerosol-forming
substrate for use in combination with an inductive heating device.
The invention also relates to an aerosol-delivery system.
[0002] From the prior art aerosol-delivery systems are known, which
comprise an aerosol-forming substrate and an inductive heating
device. The inductive heating device comprises an induction source
which produces an alternating electromagnetic field which induces a
heat generating eddy current in a susceptor material. The susceptor
material is in thermal proximity of the aerosol-forming substrate.
The heated susceptor material in turn heats the aerosol-forming
substrate which comprises a material which is capable of releasing
volatile compounds that can form an aerosol. A number of
embodiments for aerosol-forming substrates have been described in
the art which are provided with diverse configurations for the
susceptor material in order to ascertain an adequate heating of the
aerosol-forming substrate. Thus, an operating temperature of the
aerosol-forming substrate is strived for at which the release of
volatile compounds that can form an aerosol is satisfactory.
[0003] However, it would be desirable to provide an aerosol-forming
substrate which allows an even better and more efficient production
of aerosol upon heating.
[0004] According to one aspect of the invention an aerosol-forming
substrate for use in combination with an inductive heating device
is provided. The aerosol-forming substrate comprises a solid
material capable of releasing volatile compounds that can form an
aerosol upon heating of the aerosol-forming substrate, and at least
a first susceptor material for heating of the aerosol-forming
substrate. The first susceptor material has a first
Curie-temperature and is arranged in thermal proximity of the solid
material. The aerosol-forming substrate comprises at least a second
susceptor material having a second Curie-temperature which is
arranged in thermal proximity of the solid material. The first and
second susceptor materials have specific absorption rate (SAR)
outputs which are distinct from each other. Alternatively or in
addition thereto the first Curie-temperature of the first susceptor
material is lower than the second Curie-temperature of the second
susceptor material, and the second Curie-temperature of the second
susceptor material defines a maximum heating temperature of the
first and second susceptor materials.
[0005] By having at least first and second susceptor materials with
first and second Curie-temperatures distinct from one another, the
prerequisite for a more efficient and controlled heating of the
aerosol-forming substrate and thus of a more efficient production
of an aerosol is provided. The first and second susceptor materials
may have different specific absorption rate (SAR) outputs. The SAR
output here is defined as Joule-output per kg susceptor material
per cycle, at a given frequency and at a defined strength of an
electromagnetic induction field. Due to the distinct SAR outputs,
the first and second susceptor materials have different
efficiencies with regard to their heat losses. Alternatively, or in
addition to this specific property of the susceptor materials the
first and second susceptor materials, each having its specific
first or second Curie-temperature, may be activated separately.
This may be achieved, e.g., with different frequencies of an
alternating induction current and/or with different frequencies of
an magnetic field causing the induction heating of the first and
second susceptor materials. This allows for a more efficient
distribution of the first and second susceptor materials within the
aerosol-forming substrate, in order to achieve a customized
depletion thereof. Thus, if, e.g., it is desired to have an
increased heat deposition into peripheral regions of the
aerosol-forming substrate, the second susceptor materials having
the higher second Curie-temperature, may be arranged preferably in
the peripheral regions of the aerosol-forming substrate, while the
first susceptor material may be arranged preferentially in a
central region thereof. It is to be noted that if is deemed
appropriate, the arrangement of the first and second susceptor
materials of the aerosol-forming substrate can also be inverted,
thus, the first susceptor material being arranged in the peripheral
regions while the second susceptor material may e.g. be arranged in
a central portion of the aerosol-forming substrate. The
aerosol-forming substrate in accordance with the invention allows
for a customized composition thereof in accordance with specific
requirements. An overheating of the aerosol-forming substrate may
be prevented by selecting the second susceptor material, which has
the higher second Curie-temperature such, that it defines a maximum
heating temperature of the first and second susceptor materials.
When the second susceptor material has reached its second
Curie-temperature, its magnetic properties change from a
ferromagnetic phase to a paramagnetic phase. As a consequence
hysteresis losses of the second susceptor material disappear.
During the inductive heating of the aerosol-forming substrate this
phase-change may be detected on-line and the heating process
stopped automatically. Thus, an overheating of the aerosol-forming
substrate may be avoided. After the inductive heating has been
stopped the second susceptor material cools down until it reaches a
temperature lower than its second Curie-temperature, at which it
regains its ferromagnetic properties again and its hysteresis
losses reappear. This phase-change may be detected on-line and the
inductive heating activated again. Thus, the inductive heating of
the aerosol-forming substrate corresponds to a repeated activation
and deactivation of the inductive heating device. The first
susceptor material is of no further concern for this overheating
prevention, because its first Curie-temperature is already lower
than the second Curie-temperature of the second susceptor
material.
[0006] The aerosol-forming substrate is preferably a solid material
capable of releasing volatile compounds that can form an aerosol.
The term solid as used herein encompasses solid materials,
semi-solid materials, and even liquid components, which may be
provided on a carrier material. The volatile compounds are released
by heating the aerosol-forming substrate. The aerosol-forming
substrate may comprise nicotine. The nicotine containing
aerosol-forming substrate may be a nicotine salt matrix. The
aerosol-forming substrate may comprise plant-based material. The
aerosol-forming substrate may comprise tobacco, and preferably the
tobacco containing material contains volatile tobacco flavour
compounds, which are released from the aerosol-forming substrate
upon heating. The aerosol-forming substrate may comprise
homogenised tobacco material. Homogenised tobacco material may be
formed by agglomerating particulate tobacco. The aerosol-forming
substrate may alternatively comprise a non-tobacco-containing
material. The aerosol-forming substrate may comprise homogenised
plant-based material.
[0007] The aerosol-forming substrate may comprise at least one
aerosol-former. The aerosol-former may be any suitable known
compound or mixture of compounds that, in use, facilitates
formation of a dense and stable aerosol and that is substantially
resistant to thermal degradation at the operating temperature of
the inductive heating device. Suitable aerosol-formers are well
known in the art and include, but are not limited to: polyhydric
alcohols, such as triethylene glycol, 1,3-butanediol and glycerine;
esters of polyhydric alcohols, such as glycerol mono-, di- or
triacetate; and aliphatic esters of mono-, di- or polycarboxylic
acids, such as dimethyl dodecanedioate and dimethyl
tetradecanedioate. Particularly preferred aerosol formers are
polyhydric alcohols or mixtures thereof, such as triethylene
glycol, 1,3-butanediol and, most preferred, glycerine.
[0008] The aerosol-forming substrate may comprise other additives
and ingredients, such as flavourants. The aerosol-forming substrate
preferably comprises nicotine and at least one aerosol-former. In a
particularly preferred embodiment, the aerosol-former is glycerine.
The susceptor materials being in thermal proximity of the
aerosol-forming substrate allow for a more efficient heating and
thus, higher operating temperatures may be reached. The higher
operating temperature enables glycerine to be used as an
aerosol-former which provides an improved aerosol as compared to
the aerosol-formers used in the known systems.
[0009] In an embodiment of the aerosol-forming substrate according
to the invention the second Curie-temperature of the second
susceptor material may be selected such that upon being inductively
heated an overall average temperature of the aerosol-forming
substrate does not exceed 240.degree. C. The overall average
temperature of the aerosol-forming substrate here is defined as the
arithmetic mean of a number of temperature measurements in central
regions and in peripheral regions of the aerosol-forming substrate.
By pre-defining a maximum for the overall average temperature the
aerosol-forming substrate may be tailored to an optimum production
of aerosol.
[0010] In another embodiment of the aerosol-forming substrate the
second Curie-temperature of the second susceptor material is
selected such that is does not exceed 370.degree. C., in order to
avoid a local overheating of the aerosol-forming substrate
comprising the solid material which is capable of releasing
volatile compounds that can form an aerosol.
[0011] In accordance with another aspect of the invention the first
and second susceptor materials comprised in the aerosol-forming
substrate may be of different geometrical configurations. Thus, at
least one of the first and second susceptor materials,
respectively, may be of one of a particulate, or a filament, or a
mesh-like configuration. By having different geometrical
configurations, the first and second susceptor materials may be
tailored to their specific tasks and may be arranged within the
aerosol-forming substrate in a specific manner for an optimisation
of the aerosol production.
[0012] Thus, in an embodiment of the aerosol-forming substrate
according to the invention at least one of the first and second
susceptor materials may be of particulate configuration. The
particles preferably have an equivalent diameter of 10 .mu.m-100
.mu.m and are distributed within the aerosol-forming substrate. The
equivalent spherical diameter is used in combination with particles
of irregular shape and is defined as the diameter of a sphere of
equivalent volume. At the selected sizes the particulate first
and/or second susceptor material(s) may be distributed within the
aerosol-forming substrate as required and they may be securely
retained within aerosol-forming substrate. The particulate first
and/or second susceptor material(s) may be distributed about
homogeneously, or they may be distributed throughout the
aerosol-forming substrate in heaped formation with local
concentration peaks. Thus, in an embodiment of the aerosol-forming
substrate according to the invention the first susceptor material
may be arranged in a central region of the aerosol-forming
substrate, preferably along an axial extension thereof, and the
second susceptor material may be arranged in peripheral regions of
the aerosol-forming substrate. With this embodiment of the
aerosol-formation substrate heating is not only concentrated in a
central region thereof along its axial extension, but it may also
be accomplished in the peripheral regions. The degree of heat
deposition into the solid material capable of releasing volatile
compounds that can form an aerosol upon heating of the
aerosol-forming substrate will also depend on the concentration of
first and second susceptor materials at the respective
locations.
[0013] In another embodiment of the aerosol-forming substrate at
least one of the first and second susceptor materials may be of a
filament configuration being arranged within the aerosol-forming
substrate. The first or second susceptor material, respectively, of
filament configuration may e.g. be combined with a second or first
susceptor material, respectively, of particulate configuration. In
another embodiment of the invention the first and second susceptor
materials, both, may be of a filament configuration. In yet another
embodiment of the aerosol-forming substrate according to the
invention the first or second susceptor material, respectively, of
filament configuration may be arranged such that it extends about
axially throughout the aerosol-forming substrate. First and/or
second susceptor materials, respectively, of filament configuration
may have advantages with regard to their manufacture, and their
geometrical regularity and reproducibility. The geometrical
regularity and reproducibility also may prove advantageous in a
controlled local heating of the solid material at the respective
locations.
[0014] In yet another embodiment of the aerosol-forming substrate
according to the invention at least one of the first and second
susceptor materials may be of a mesh-like configuration. The first
or second susceptor material, respectively, of mesh-like
configuration may be arranged inside of the aerosol-forming
substrate or it may at least partly form an encasement for the
solid material. The first or second susceptor materials,
respectively, of mesh-like configuration may be combined with
second or first susceptor materials, respectively, having a
particulate configuration, or they may be combined with second or
first susceptor materials, respectively, of filament configuration.
The term "mesh-like configuration" includes layers having
discontinuities therethrough. For example the layer may be a
screen, a mesh, a grating or a perforated foil.
[0015] In a still further embodiment of the aerosol-forming
substrate the first and second susceptor materials may be assembled
to form a mesh-like structural entity. The mesh-like structural
entity may e.g. extend axially throughout the aerosol-forming
substrate. In another embodiment of the aerosol-forming substrate
the mesh-like structural entity of the first and second susceptor
materials may at least partly form an encasement for the solid
material. The term "mesh-like structural entity" designates all
structures which may be assembled from the first and second
susceptor materials and have discontinuities therethrough,
including screens, gratings and meshes.
[0016] It should be noted that in some of the embodiments of the
aerosol-forming substrate it may be desirable that the first and
second susceptor materials be of a geometrical configuration
distinct from each other. In other embodiments of the
aerosol-forming substrate it may be desirable, e.g. for
manufacturing purposes of the aerosol-forming substrate, that the
first and second susceptor materials be of similar geometrical
configuration.
[0017] The aerosol-forming substrate may be of a generally
cylindrical shape and may be enclosed by a tubular casing, such as,
e.g., an overwrap. The tubular casing, such as, e.g. the overwrap,
may help to stabilize the shape of the aerosol-forming substrate
and to prevent an accidental disassociation of the solid material
which is capable of releasing volatile compounds that can form an
aerosol, and the first and second susceptor materials.
[0018] In another embodiment the aerosol-forming substrate may be
attached to a mouthpiece, which optionally may comprise a filter
plug. The aerosol-forming substrate comprising the solid material
which is capable of releasing volatile compounds that can form an
aerosol upon heating of the aerosol-forming substrate and the first
and second susceptor materials, and the mouthpiece are assembled to
form a structural entity. Every time a new aerosol-forming
substrate is to be used in combination with an inductive heating
device, the user is automatically provided with a new mouthpiece,
which might be desirable from a hygienic point of view. Optionally
the mouthpiece may be provided with a filter plug, which may be
selected in accordance with the composition of the aerosol-forming
substrate.
[0019] An aerosol-delivery system according to the invention
comprises an inductive heating device and an aerosol-forming
substrate according to any one of the afore-described embodiments.
With such an aerosol-delivery system an improved generation of
aerosol may be achieved. By a controlled arrangement of the first
and second susceptor materials an optimised heating of the
aerosol-forming substrate and thus an improved generation of
aerosol may be achieved.
[0020] In an embodiment of the aerosol-delivery system the
inductive heating device is provided with an electronic control
circuitry, which is adapted for a successive or alternating heating
of the first and second susceptor materials of the aerosol-forming
substrate. Thus, also depending on the distribution of the first
and second susceptor materials throughout the aerosol-forming
substrate, a customized control of the induction heating of the
aerosol-forming substrate may be reached and, in consequence, a
customized depletion of the solid material comprised in the
aerosol-forming substrate of volatile compounds that can form an
aerosol of may be achieved.
[0021] The afore-described embodiments of the aerosol-forming
substrate and of the aerosol-delivery system will become more
apparent from the following detailed description, reference being
made to the accompanying schematic drawings which are not to scale,
in which:
[0022] FIG. 1 is a schematic drawing of an aerosol-delivery system
comprising an inductive heating device and an aerosol-forming
substrate inserted into the device;
[0023] FIG. 2 shows a first embodiment of an aerosol-forming
substrate comprising first and second susceptor materials of
particulate configuration which are about homogenously distributed
within the aerosol-forming substrate;
[0024] FIG. 3 shows a second embodiment of an aerosol-forming
substrate comprising first and second susceptor materials of
particulate configuration which are distributed in heaps in central
and peripheral regions of the aerosol-forming substrate;
[0025] FIG. 4 shows a third embodiment of an aerosol-forming
substrate comprising a second susceptor material of particulate
configuration and a first susceptor of filament configuration;
[0026] FIG. 5 shows a fourth embodiment of an aerosol-forming
substrate comprising a first susceptor material of particulate
configuration and a second susceptor material of mesh-kind
configuration; and
[0027] FIG. 6 shows another embodiment of an aerosol-forming
substrate comprising first and second susceptor materials which
have been assembled to form a mesh-like structural entity.
[0028] Inductive heating is a known phenomenon described by
Faraday's law of induction and Ohm's law. More specifically,
Faraday's law of induction states that if the magnetic induction in
a conductor is changing, a changing electric field is produced in
the conductor. Since this electric field is produced in a
conductor, a current, known as an eddy current, will flow in the
conductor according to Ohm's law. The eddy current will generate
heat proportional to the current density and the conductor
resistivity. A conductor which is capable of being inductively
heated is known as a susceptor material. The present invention
employs an inductive heating device equipped with an inductive
heating source, such as, e.g., an induction coil, which is capable
of generating an alternating electromagnetic field from an AC
source such as an LC circuit. Heat generating eddy currents are
produced in the susceptor material which is in thermal proximity to
a solid material which is capable of releasing volatile compounds
that can form an aerosol upon heating of the aerosol-forming
substrate and which is comprised in an aerosol-forming substrate.
The term solid as used herein encompasses solid materials,
semi-solid materials, and even liquid components, which may be
provided on a carrier material. The primary heat transfer
mechanisms from the susceptor material to the solid material are
conduction, radiation and possibly convection.
[0029] In schematic FIG. 1 an exemplary embodiment of an
aerosol-delivery system according to the invention is generally
designated with reference numeral 100. The aerosol-delivery system
100 comprises an inductive heating device 2 and an aerosol-forming
substrate 1 associated therewith. The inductive heating device 2
may comprise an elongated tubular housing 20 having an accumulator
chamber 21 for accommodating an accumulator 22 or a battery, and a
heating chamber 23. The heating chamber 23 may be provided with an
inductive heating source, which, as shown in the depicted exemplary
embodiment, may be constituted by an induction coil 31 which is
electrically connected with an electronic circuitry 32. The
electronic circuitry 32 may e.g. be provided on a printed circuit
board 33 which delimits an axial extension of the heating chamber
23. The electric power required for the inductive heating is
provided by the accumulator 22 or the battery which is accommodated
in the accumulator chamber 21 and which is electrically connected
with the electronic circuitry 32. The heating chamber 23 has an
internal cross-section such that the aerosol-forming substrate 1
may be releasably held therein and may easily be removed and
replaced with another aerosol-forming substrate 1 when desired.
[0030] The aerosol-forming substrate 1 may be of a generally
cylindrical shape and may be enclosed by a tubular casing 15, such
as, e.g., an overwrap. The tubular casing 15, such as, e.g. the
overwrap, may help to stabilize the shape of the aerosol-forming
substrate 1 and to prevent an accidental loss of the contents of
the aerosol-forming substrate 1. As shown in the exemplary
embodiment of the aerosol-delivery system 100 according to the
invention, the aerosol-forming substrate 1 may be connected to a
mouthpiece 16, which with the aerosol-forming substrate 1 inserted
into the heating chamber 23 at least partly protrudes from the
heating chamber 23. The mouthpiece 16 may comprise a filter plug 17
filter plug, which may be selected in accordance with the
composition of the aerosol-forming substrate 1. The aerosol-forming
substrate 1 and the mouthpiece 16 may be assembled to form a
structural entity. Every time a new aerosol-forming substrate 1 is
to be used in combination with the inductive heating device 2, the
user is automatically provided with a new mouthpiece 16, which
might be appreciated from a hygienic point of view.
[0031] As shown in FIG. 1 the induction coil 31 may be arranged in
a peripheral region of the heating chamber 23, in vicinity of the
housing 20 of the inductive heating device 2. The windings of the
induction coil 31 enclose a free space of the heating chamber 23
which is capable to accommodate the aerosol-forming substrate 1.
The aerosol-forming substrate 1 may be inserted into this free
space of the heating chamber 23 from an open end of the tubular
housing 20 of the inductive heating device 2 until it reaches a
stop, which may be provided inside the heating chamber 23. The stop
may be constituted by at least one lug protruding from an inside
wall of the tubular housing 20, or it may be constituted by the
printed circuit board 33, which delimits the heating chamber 23
axially, as it is shown in the exemplary embodiment depicted in
FIG. 1. The inserted aerosol-forming substrate 1 may be releasably
held within the heating chamber 23 e.g. by an annular sealing
gasket 26, which may be provided in vicinity of the open end of the
tubular housing 20.
[0032] The aerosol-forming substrate 1 and the optional mouthpiece
16 with the optional filter plug 17 are pervious to air. The
inductive heating device 2 may comprise a number of vents 24, which
may be distributed along the tubular housing 20. Air passages 34
which may be provided in the printed circuit board 33 enable
airflow from the vents 24 to the aerosol-forming substrate 1. It
should be noted, that in alternative embodiments of the inductive
heating device 2 the printed circuit board 33 may be omitted such
that air from the vents 24 in the tubular housing 20 may reach the
aerosol-forming substrate 1 practically unimpeded. The inductive
heating device 2 may be equipped with an air flow sensor (not shown
in FIG. 1) for activation of the electronic circuitry 32 and the
induction coil 31 when incoming air is detected. The air flow
sensor may e.g. be provided in vicinity of one of the vents 24 or
of one of the air passages 34 of the printed circuit board 33.
Thus, a user may suck at the mouthpiece 16, in order to initiate
the inductive heating of the aerosol-forming substrate 1 Upon
heating an aerosol, which is released by the solid material
comprised in the aerosol-forming substrate 1, may be inhaled
together with air which is sucked through the aerosol-forming
substrate 1.
[0033] FIG. 2 schematically shows a first embodiment of an
aerosol-forming substrate which is generally designated with
reference numeral 1. The aerosol-forming substrate 1 may comprise a
generally tubular casing 15, such as, e.g., an overwrap. The
tubular casing 15 may be made of a material which does not
noticeably impede an electromagnetic field reaching the contents of
the aerosol-forming substrate 1. E.g. the tubular casing 15 may be
a paper overwrap. Paper has a high magnetic permeability and in an
alternating electromagnetic field is not heated by eddy currents.
The aerosol-forming substrate 1 comprises a solid material 10 which
is capable of releasing volatile compounds that can form an aerosol
upon heating of the aerosol-forming substrate 1 and at least a
first susceptor material 11 for heating the aerosol-forming
substrate 1. The first susceptor material 11 has a first
Curie-temperature and is arranged in thermal proximity of the solid
material 10. The term solid as used herein encompasses solid
materials, semi-solid materials, and even liquid components, which
may be provided on a carrier material. The aerosol-forming
substrate 1 further comprises at least a second susceptor material
12 having a second Curie-temperature which too is arranged in
thermal proximity of the solid material. The first
Curie-temperature of the first susceptor material 11 is lower than
the second Curie-temperature of the second susceptor material 12.
The second Curie-temperature of the second susceptor material 12
defines a maximum heating temperature of the first and second
susceptor materials 11, 12.
[0034] By having at least first and second susceptor materials 11,
12 with specific first and second Curie-temperatures distinct from
one another, the prerequisite for a more efficient and controlled
inductive heating of the aerosol-forming substrate 1 and thus of a
more efficient production of an aerosol is provided. The first and
second susceptor materials 11, 12, each having its specific first
or second Curie-temperature, may be activated separately. This may
be achieved, e.g., with different frequencies of an alternating
induction current and/or with different frequencies of an magnetic
field causing the inductive heating of the first and second
susceptor materials 11, 12. This allows for a more efficient
distribution of the first and second susceptor materials 11, 12
within the aerosol-forming substrate 1, in order to achieve a
customized depletion thereof. Thus, if, e.g., it is desired to have
an increased heat deposition into peripheral regions of the
aerosol-forming substrate 1, the second susceptor material 12
having the higher second Curie-temperature, may be arranged
preferably in the peripheral regions of the aerosol-forming
substrate 1, while the first susceptor material 11 may be arranged
preferentially in a central region of the aerosol-forming substrate
1. It is to be noted that if is deemed appropriate, the arrangement
of the first and second susceptor materials 11, 12 of the
aerosol-forming substrate 1 can also be inverted; thus, the first
susceptor material 11 being arranged in the peripheral regions
while the second susceptor material 12 may e.g. be arranged in a
central portion of the aerosol-forming substrate 1. The
aerosol-forming substrate 1 in accordance with the invention allows
for a customized composition thereof in accordance with specific
requirements. An overheating of the aerosol-forming substrate 1 may
be prevented by selecting the second susceptor material 12, which
has the higher second Curie-temperature such, that it defines a
maximum heating temperature of the first and second susceptor
materials 11, 12. When the second susceptor material 12 has reached
its second Curie-temperature, its magnetic properties change from a
ferromagnetic phase to a paramagnetic phase. As a consequence
hysteresis losses of the second susceptor material 12 disappear.
During the inductive heating of the aerosol-forming substrate 1
this phase-change may be detected on-line and the heating process
may be stopped automatically. Thus, an overheating of the
aerosol-forming substrate 1 may be avoided. After the inductive
heating has been stopped the second susceptor material 12 cools
down until it reaches a temperature which is lower than its second
Curie-temperature, at which it regains its ferromagnetic properties
again and its hysteresis losses reappear. This phase-change may be
detected on-line and the inductive heating may be activated again.
Thus, the inductive heating of the aerosol-forming substrate 1
corresponds to a repeated activation and deactivation of the
inductive heating device. The first susceptor material 11 is of no
further concern for this overheating prevention, because its first
Curie-temperature is already lower than the second
Curie-temperature of the second susceptor material 12.
[0035] The first and second susceptor materials 11, 12, both, may
be optimized with regard to heat loss and thus heating efficiency.
Thus, the first and second susceptor materials 11, 12 should have a
low magnetic reluctance and a correspondingly high relative
permeability to optimize surface eddy currents generated by an
alternating electromagnetic field of a given strength. The first
and second susceptor materials 11, 12 should also have relatively
low electrical resistivities in order to increase Joule heat
dissipation and thus heat loss.
[0036] The second Curie-temperature of the second susceptor
material 12 may be selected such that upon being inductively heated
an overall average temperature of the aerosol-forming substrate 1
does not exceed 240.degree. C. The overall average temperature of
the aerosol-forming substrate 1 here is defined as the arithmetic
mean of a number of temperature measurements in central regions and
in peripheral regions of the aerosol-forming substrate. In another
embodiment of the aerosol-forming substrate 1 the second
Curie-temperature of the second susceptor material 12 may be
selected such that is does not exceed 370.degree. C., in order to
avoid a local overheating of the aerosol-forming substrate 1
comprising the solid material 10 which is capable of releasing
volatile compounds that can form an aerosol.
[0037] The afore-described basic composition of the aerosol-forming
substrate 1 of the exemplary embodiment of FIG. 2 is common to all
further embodiments of the aerosol-forming substrate 1 which will
be described hereinafter.
[0038] As shown in FIG. 2 the aerosol-forming substrate 1 comprises
first and second susceptor materials 11, 12, which, both, may be of
particulate configuration. The first and second susceptor materials
11, 12 preferably have an equivalent spherical diameter of 10
.mu.m-100 .mu.m and are distributed throughout the aerosol-forming
substrate. The equivalent spherical diameter is used in combination
with particles of irregular shape and is defined as the diameter of
a sphere of equivalent volume. At the selected sizes the
particulate first and second susceptor materials 11, 12 may be
distributed throughout the aerosol-forming substrate 1 as required
and they may be securely retained within aerosol-forming substrate
1. The particulate susceptor materials 11, 12 may be distributed
throughout the solid material 10 about homogeneously, as shown in
the exemplary embodiment of the aerosol-forming substrate 1
according to FIG. 2.
[0039] FIG. 3 shows another embodiment of an aerosol-forming
substrate 1 which again is generally designated with reference
numeral 1. The aerosol-forming substrate 1 may be of a generally
cylindrical shape and may be enclosed by a tubular casing 15, such
as, e.g., an overwrap. The aerosol-forming substrate comprises
solid material 10 which is capable of releasing volatile compounds
that can form an aerosol upon heating of the aerosol-forming
substrate 1 and at least first and second susceptor materials 11,
12. The first and second susceptor materials 11, 12, both, may be
of particulate configuration again, preferably having an equivalent
spherical diameter of 10 .mu.m-100 .mu.m. The particulate first and
second susceptor materials 11, 12 may have a distribution gradient
e.g. from a central axis of the aerosol-forming substrate 1 to the
periphery thereof, or, as shown in FIG. 3, the particulate first
susceptor material 11 may be concentrated along a central of the
aerosol-forming substrate 1, while the particulate second susceptor
material 12 may be distributed in peripheral regions of the
aerosol-forming substrate 1 with local concentration peaks, or vice
versa.
[0040] In FIG. 4 a further embodiment of an aerosol-forming
substrate is shown, which again bears reference numeral 1. The
aerosol-forming substrate 1 may be of a generally cylindrical shape
and may be enclosed by a tubular casing 15, such as, e.g., an
overwrap. The aerosol-forming substrate 1 comprises a solid
material 10 which is capable of releasing volatile compounds that
can form an aerosol upon heating of the aerosol-forming substrate 1
and at least first and second susceptor materials 11, 12. The first
susceptor material 11 may be of a filament configuration. The first
susceptor material of filament configuration may have different
lengths and diameters and may be distributed throughout the solid
material. As exemplarily shown in FIG. 4 the first susceptor
material 11 of filament configuration may be of a wire-like shape
and may extend about axially through a longitudinal extension of
the aerosol-forming substrate 1. The second susceptor material 12
may be of particulate configuration and may be distributed
throughout the solid material 10 with local concentration peaks.
Alternatively the second susceptor material may also be
homogeneously distributed throughout the solid material 10. It
should be noted though, that as need may be, the geometrical
configuration of the first and second susceptor materials 11, 12
may be interchanged. Thus, the second susceptor material 12 may be
of filament configuration and the first susceptor material 11 may
be of particulate configuration.
[0041] In FIG. 5 yet another exemplary embodiment of an
aerosol-forming substrate is shown, which again is generally
designated with reference numeral 1. The aerosol-forming substrate
1 may again be of a generally cylindrical shape and may be enclosed
by a tubular casing 15, such as, e.g., an overwrap. The
aerosol-forming substrate comprises solid material 10 which is
capable of releasing volatile compounds that can form an aerosol
upon heating of the aerosol-forming substrate 1 and at least first
and second susceptor materials 11, 12. The first susceptor material
11 may be of a mesh-like configuration which may be arranged inside
of the aerosol-forming substrate 1 or, alternatively, may at least
partially form an encasement for the solid material 10. The term
"mesh-like configuration" includes layers having discontinuities
therethrough. For example the layer may be a screen, a mesh, a
grating or a perforated foil. The second susceptor material 12 may
be of particulate configuration and may be distributed throughout
the solid material 10. Again it should be noted, that, as need may
be, the geometrical configuration of the first and second susceptor
materials 11, 12 may be interchanged. Thus, the second susceptor
material 12 may be of a mesh-like configuration and the first
susceptor material 11 may be of particulate configuration.
[0042] In FIG. 6 still another exemplary embodiment of an
aerosol-forming substrate is shown, which again is generally
designated with reference numeral 1. The aerosol-forming substrate
1 may again be of a generally cylindrical shape and may be enclosed
by a tubular casing 15, such as, e.g., an overwrap. The
aerosol-forming substrate comprises solid material 10 which is
capable of releasing volatile compounds that can form an aerosol
upon heating of the aerosol-forming substrate 1 and at least first
and second susceptor materials 11, 12. The first and second
susceptor materials 11, 12 may be assembled to form a mesh-like
structural entity. The mesh-like structural entity may, e.g.,
extend axially within the aerosol-forming substrate 1.
Alternatively the mesh-like structural entity of first and second
susceptor materials 11, 12 may at least partially form an
encasement for the solid material 10. The term "mesh-like
structure" designates all structures which may be assembled from
the first and second susceptor materials and have discontinuities
therethrough, including screens, meshes, gratings or a perforated
foil. The mesh-like structural entity may be composed of
horizontally extending filaments of first susceptor material 11 and
of vertically extending filaments of second susceptor material 12,
or vice versa.
[0043] While different embodiments of the invention have been
described with reference to the accompanying drawings, the
invention is not limited to these embodiments. Various changes and
modifications are conceivable without departing from the overall
teaching of the present invention. Therefore, the scope of
protection is defined by the appended claims.
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