WO2023067160A1

WO2023067160A1 - Tobacco substrate for use in an aerosol generating device, consumable article and associated producing and optimization methods

Info

Publication number: WO2023067160A1
Application number: PCT/EP2022/079418
Authority: WO
Inventors: Jaakko MCEVOY
Original assignee: Jt International S.A.
Priority date: 2021-10-21
Filing date: 2022-10-21
Publication date: 2023-04-27

Abstract

The present invention concerns a tobacco substrate (25) for use in an aerosol generating device, comprising a first conducting surface (34A) comprising an airflow path (41, 51) formed in recess on the first conducting surface (34A); wherein the airflow path (41, 51) comprises a flow inlet (42, 52A, 52B), a flow outlet (43A, 43B, 53) and a flow groove extending along the first conducting surface (34A) between said flow inlet (42, 52A, 52B) and said flow outlet (43A, 43B, 53); wherein the flow groove's width and/or depth and/or cross-sectional shape vary (ies) along its length.

Description

Tobacco substrate for use in an aerosol generating device, consumable article and associated producing and optimization methods

FIELD OF THE INVENTION

The present invention concerns a tobacco substrate for use in an aerosol generating device, comprising at least one airflow path. The tobacco substrate according to the invention can be used as a consumable article as it or may be a part of a consumable article, in the meaning of the invention.

Particularly, the tobacco substrate according to the invention is configured to operate with an aerosol generating device, also known as a heat-not-burn device or HNB device. Such type of aerosol generating devices is adapted to heat, rather than burn, an aerosol generating substrate comprised in the article.

The present invention also concerns a producing method for producing such a tobacco substrate and an optimization method for optimizing an airflow path arrangement on a conducing surface of such a tobacco substrate.

BACKGROUND OF THE INVENTION

The popularity and use of reduced-risk or modified-risk devices (also known as vaporisers or aerosol generating devices) has grown rapidly in the past few years as an aid to assist habitual smokers wishing to quit smoking traditional tobacco products such as cigarettes, cigars, cigarillos, and rolling tobacco. Various devices and systems are available that heat or warm vaporizable substances as opposed to burning tobacco in conventional tobacco products.

A commonly available reduced-risk or modified-risk device is the heated substrate aerosol generation device or heat-not-burn device, also known as HNB device. Devices of this type generate aerosol or vapour by heating an aerosol generating substrate that typically comprises moist leaf tobacco or other suitable vaporizable material to a temperature typically in the range 150°C to 350°C. Heating an aerosol generating substrate, but not combusting or burning it, releases aerosol that comprises the components sought by the user but not the toxic and carcinogenic by-products of combustion and burning. Furthermore, the aerosol produced by heating the tobacco or other vaporizable material does not typically comprise the burnt or bitter taste resulting from combustion and burning that can be unpleasant for the user and so the substrate does not therefore require the sugars and other additives that are typically added to such materials to make the smoke and/or vapour more palatable for the user.

Some HNB devices can be adapted to operate with consumable articles having reduced dimensions. Such articles can have for example a flat shape and form a substantially cuboid shape of 1 or 2 mm of thickness. Their transversal and longitudinal dimensions can be comprised between 10 and 30 mm. Due to such shape and dimensions, these consumable articles make the heat transfer for vapour generation more efficient compared to a rod-type format.

A consumable article operable with the HNB devices comprises generally a tobacco substrate which is substantially solid and can for example be made by compressing tobacco. Such a tobacco substrate may define one or several airflow paths conducting an airflow during a vaping session. However, it was observed that the flow conduction along such airflow paths is not optimal and can lead to uneven heating of the substrate and as consequence, to its non-optimal using. This can cause unsatisfactory user experience.

SUMMARY OF THE INVENTION

One of the aims of the invention is to propose a tobacco substrate having improved airflow conduction properties. This leads to a more homogeneous heating of the substrate and improves the user experience.

For this purpose, the invention relates to a tobacco substrate for use in an aerosol generating device, comprising a first conducting surface comprising an airflow path formed in recess on the first conducting surface. The airflow path comprises a flow inlet, a flow outlet a flow groove extending along the first conducting surface between said flow inlet and said flow outlet. The flow groove’s width and/or depth and/or cross-sectional shape vary (ies) along its length.

Thanks to these features, cross-sectional dimensions and/or shape of the airflow path are varying along its length. Thus, conduction of the airflow through the airflow path can be optimized in a desired manner. This optimization can be done basing on different criteria, as for example flow rate, pressure drop, temperature and/or material properties optimization across the tobacco substrate. For example, in some cases, it may be advantageous to form an airflow path having greater cross-sectional dimensions near the flow inlet in comparison with those near the flow outlet. In this case, the airflow can be slowed down in a portion of the tobacco substrate adjacent to the flow inlet. This can lead to more homogenous heating of the tobacco substrate in this portion. On the contrary, near the flow outlet, the cross- sectional dimensions of the airflow path can be reduced so as the flow is accelerated avoiding thus overheating of the substrate in the corresponding portion. Optimizing cross- sectional dimensions of the airflow path can also reduce the pressure drop along the substrate.

According to some embodiments, the first conducting surface comprises a plurality of airflow paths.

Thanks to these features, several airflow paths are arranged on a same surface of the tobacco substrate. These airflow paths can be arranged in any suitable manner to allow airflow optimizing as mentioned below. The airflow paths can extend for example substantially parallel between them or cross each other at one or several points. Additionally, their cross-sectional dimensions and/or shape can vary according to a same law or according to different laws. In this last case, the laws can be independent or can be correlated between them. For example, one law can be deduced from another. In variant, no particular law can be associated with varying of the cross-section dimensions and/or shape of at least one airflow path. In this case, these dimensions can for example be chosen randomly within a predetermined interval of values.

According to some embodiments, at least one or each airflow path comprises a plurality of flow outlets and/or a plurality of flow inlets.

Thanks to these features, at least some airflow paths can be split to form several flow inlets and/or several flow outlets. Additionally, at least two airflow paths can share a same flow inlet and at least a common portion adjacent to this inlet. Then, these airflow paths can be split into two independent airflow paths having different flow outlets. Inversely, two airflow paths can be independent near the respective flow inlets and then merge to form a common flow outlet. In a variant, two airflow paths can have a common flow inlet, a common flow outlet and two different flow grooves extending between this flow inlet and this flow outlet. Such arrangements of the airflow paths can contribute to an optimized flow conducting along the conducting surface. The first and/or second conducting surface is/are (a) flow conducting surface(s), which means that the first and/or second conducting surface is/are configured to conduct an airflow.

The skilled person understands that a flow groove presents an opening along a longitudinal direction of the groove, in particular along its whole length, which is not the case for example for a channel.

According to some embodiments, for each airflow path, one or a plurality of straight line(s) may be defined between the flow inlet(s), and the flow outlet(s). In this case, an angle formed between the or each straight line and an article axis may be equal to or smaller than 20 degrees, preferably smaller than 10 degrees. The article axis extends between an inlet end configured to receive the airflow and a mouth end, in particular in parallel to opposite lateral surfaces of the tobacco substrate.

According to some embodiments, comprising a second conducting surface comprising one or several airflow paths formed in recess on the second conducting surface.

Thanks to these features, several surfaces of the tobacco substrate can be used to form airflow paths. Thus, the arrangement of the airflow paths can be further optimized.

According to some embodiments, the second conducting surface is opposite to the first conducting surface.

Thanks to these features, the airflow paths are arranged on either side of the tobacco substrate having for example a flat shape. The airflow paths can be arranged to face one another or to be in offset between them.

According to some embodiments, the or each airflow path is embossed or debossed on the corresponding surface of the tobacco substrate.

Thanks to these features, the tobacco substrate can be simply produced. Additionally, embossing or debossing airflow paths makes it possible to form airflow paths of complex geometry, as for example airflow paths having variable cross-sectional dimensions and/or shapes along their length. Any suitable manufacturing method performing embossing or debossing can be used to this purpose. Some of these methods will be explained here- below.

According to some embodiments, having a flat shape and formed from a tobacco sheet, preferably having a thickness comprised between 0,5 and 5 mm.

A flat shape of the tobacco substrate is particularly advantageous for its homogenous heating. For example, a resistive heater can be applied at either side of the tobacco substrate. Thus, substantially the whole amount of the heat generated by the resistive heaters can be transmitted to the tobacco substrate by conduction and/or convection. Additionally, this shape of the tobacco substrate can be easily produced from for example a tobacco sheet. Some of these producing methods will be explained here-below.

According to some embodiments, the tobacco substrate comprises tobacco, an aerosol forming agent and preferably, a binder.

Thanks to these features, the tobacco substrate is adapted to be used with an aerosol generating device. Particularly, when heated, the aerosol forming agent forms aerosol which is released from the flow outlet. Other components such for example a flavouring agent ensuring a particular taste of the inhaled substance can also be used. For example, flavouring agent with a polysaccharide carrier as described in EP2279677, EP2682007, EP2682008, EP2682009 or EP3533348 can be used.

According to some embodiments, the tobacco substrate comprises an inner volume being devoid at least of inner channels having a width and/or a depth according to crosssection of such channels substantially equal to or larger than an average width and/or average depth of the flow groove of the first and/or second conducting surface. In other words, for example, the inner volume of the tobacco substrate may be devoid of large channels, i.e. devoid of channels having a macroscopic or large width or depth.

The inner volume may be defined as a space between the first and second conducting surface. The inner volume is particular defined by an inner part of the tobacco substrate, non visible from the outside of the tobacco substrate.

According to some embodiments, the inner volume is devoid of any channels forming an airflow path between a flow inlet and a flow outlet opposite to the flow inlet. The present invention also relates to a consumable article comprising a tobacco substrate as defined below.

According to different embodiments of the invention, the tobacco substrate can form itself a consumable article which can be inserted into an aerosol generating device by the user to generate aerosol and extracted from the device when it is exhausted. In some cases, the tobacco substrate can be wrapped in a wrapper comprising aluminum and/or paper which makes it possible to preserve the taste of the tobacco substrate and/or avoid leakages while its using. In some other embodiments, the consumable article can further comprise an additional structure as for example a filtering/cooling structure. This structure can be attached to the tobacco substrate using a wrapper or any other suitable mean. In any case, the filtering/cooling structure and the tobacco substrate can be wrapped into a common wrapper or into different wrappers. As in the previous case, the wrapper can comprise aluminum and/or paper.

The present invention also relates to a producing method for producing a tobacco substrate as defined above, comprising a step of embossing or debossing a tobacco sheet to form an airflow path.

Thanks to these features, the tobacco substrate can be simply produced using for example an embossing roller system. The embossing roller system can comprise an embossing roller embossing or debossing a predetermined pattern on a tobacco sheet. The tobacco sheet can then be cut to form a plurality of tobacco substrates. The embossing roller can for example comprise a solid surface (metal or like) where the predetermined pattern is formed using any suitable method (cold spray, SLS, 6-axis CNC, etc.). Particularly, such a method allows forming thin and complex shape protrusions and grooves of complex geometry on the roller’s surface. The protrusions and grooves can have an irregular curvilinear shape which is complementary to the cross-sectional shape of the airflow path intended to be formed by these protrusions and grooves.

Additionally, a same pattern can be used to form all of the tobacco substrates. In this case, the pattern is repeated along the embossing roller and all tobacco substrates formed by this roller have substantially the same airflow path arrangement. This can for example be used to achieve a repeatable effect. Alternatively, different patterns can be used to form different arrangements of the flow paths on different tobacco substrates. In this case, the embossing roller can define a unique, for example continuous, pattern and different parts of this unique pattern are applied on different tobacco substrates.

According to some embodiments, comprising a step of cutting an embossed or debossed tobacco sheet.

According to some embodiments, the step of cutting is carried out simultaneously with the step of embossing or debossing or after the step of embossing or debossing.

To carry out simultaneously the embossing (or debossing) and cutting steps, a special cutting and embossing roller can be used. For example, such a roller can have a first group of protrusions cutting the tobacco sheet and a second group of protrusions embossing or debossing a specific pattern of the tobacco sheet. The protrusions of the first group can penetrate the tobacco sheet deeper than those of the second group. To carry out consecutive embossing/debossing and cutting, an embossing roller having only protrusions of the second group can be used. Then, the cutting can be carried out using any suitably method, like cutting wheels, static blades, or pneumatically operated blades which oscillate a small amount at high frequency. This allows for clean cuts and reduces the chance of the tobacco consumable sticking to the blades. In any case, the cut material can be collected and reused.

According to some embodiments, further comprising a step of extruding tobacco dough into a tobacco sheet, the step of extruding being carried out before the step of embossing or debossing.

Thanks to these features, a tobacco sheet of desired thickness can be formed from tobacco dough. This thickness can for example be comprised between 0,5 and 5 mm. The tobacco dough used to form the tobacco sheet comprises a vaporizable material comprising for example tobacco, an aerosol forming agent and optionally, a binder. The tobacco dough can be extruded using any suitable mean like for example a pair of facing rollers. The dimensions of the tobacco sheet are adapted to the embossing roller system, for example to reduce the amount of unembossed material.

According to some embodiments, the tobacco sheet is embossed or debossed using a predetermined pattern of an optimized airflow path arrangement on a conducting surface of a tobacco substrate. Thanks to these features, it is possible to obtain a same airflow path arrangement for all tobacco substrates. Thus, each tobacco substrate is able to produce substantially a same effect/taste while a vaping session. Additionally, the predetermined pattern can be developed to achieve an optimized flow path arrangement for given dimensions of the tobacco substrate. This optimized flow path arrangement can for example be determined using an optimization method explained in further detail below.

The present invention also relates to an optimization method of airflow path arrangement on a conducting surface of a tobacco substrate, comprising the following steps:

- providing dimensions and geometry of a tobacco layer and of a built volume intended to be adjacent to the tobacco layer in the tobacco substrate to form said conducting surface and to contain one or several airflow paths;

- providing boundary conditions of the built volume;

- providing material input data;

- determining an internal structure of the built volume by applying a structure construction method inside the built volume respecting the boundary conditions and the material input data, the structure construction method being based on an optimization criterion;

- using the determined internal structure of the built volume, determine a pattern of an optimized airflow path arrangement on said conducting surface of the tobacco substrate, the pattern comprising geometry, shape and number of airflow paths in the built volume.

Thanks to these features, it is possible to determine a pattern which can be used in producing the tobacco substrate according to the invention. This pattern has an optimized airflow path arrangement which ensures efficient heating of the tobacco substrate and airflow conduction. The optimized arrangement is determined basing on numerous parameters including dimensions and geometry of a tobacco layer forming the substrate, boundary conditions and material input data. The optimization method can be implemented at least partially by a computer software product comprising software instructions carrying out at least some of the steps of the optimization method. Such a software product can carried out by a computer comprising notably a processor and a memory. Alternatively, the software product can be carried out by several computers connected between them by a computer network. Advantageously, according to the invention, a “built volume” is used as a starting structure where an optimized topology is created. It is also considered that no optimization is performed in the tobacco layer which remains unchanged after performing the optimization method. The tobacco layer could for example be a flat rectangular shape measuring 0,1x10x20 mm in thickness, width and length and the built volume above this of 1x10x20 mm in thickness, width and length.

The output data produced by the optimization method comprises a pattern which can for example present a computer readable file. For example, the pattern can present a CAD (“Computer Aided Design”) file comprising a 3D geometry of the pattern. The pattern can then for example be applied on a surface of an embossing roller as explained above in order to emboss/deboss this pattern on a surface of a tobacco sheet. The patterned surface of the embossing roller can for example be realised by 3D printing or any other known technique.

According to some embodiments, the method further comprises a verification step verifying whether the internal structure of the built volume meets requirements. The requirements can be determined based on one or several optimization criteria and/or on boundary conditions. If the requirements are met, the determined pattern is output. Otherwise, the structure construction method can be repeated one or several times stating from a built volume obtained after the previous iteration.

According to some embodiments, the boundary conditions comprise at least one of the following elements:

- flow rate;

- input energy;

- pressure;

- temperature.

The boundary conditions can be specified prior to performing the optimization method and each boundary condition can be formed by a fixed value or a range of values. If a range of values is used then the scope of the optimization method increases massively.

According to some embodiments, the optimization criterion comprises at least one the following criteria:

- optimization of the pressure drop across the tobacco substrate; - optimization of the temperature in or at an outlet end of the tobacco substrate;

- optimization of the tobacco temperature inside or at a surface of the tobacco substrate.

Thanks to these features, it is possible to optimize at least one of the pre-cited elements. For example, optimization of the pressure drop makes it possible to optimize the quantity of the aerosol delivered to the user in function of the user’s puffs. Optimization of the temperature in or at an outlet end of the tobacco substrate can optimize the temperature of the aerosol delivered to the user. Optimization of the tobacco temperature inside or at a surface of the tobacco substrate can optimize the temperature of the tobacco substrate so as to ensure aerosol generation while avoiding its burning. It is also possible to use multiple optimization criteria ensuring a simultaneous application of at least some of above cited criteria.

One or several optimization criteria can be carried out using an available computer- implemented optimization tool.

According to some embodiments, the material input data comprises generalized material properties.

According to some embodiments, said material properties comprise at least one of the following elements:

- thermal conductivity;

- specific heat;

- density.

According to some embodiments, said material comprises tobacco, preferably is essentially constituted of homogenized tobacco material.

According to some embodiments, said material properties are modelled using at least one of the following material elements:

- tobacco moisture;

- density;

- tobacco type;

- compression. Since generally the material intended to form a tobacco substrate has a complex composition, it may be not usually possible to optimize an airflow path arrangement directly using detailed properties specific to this composition, as tobacco granule size, moisture, tobacco type, density, composition, etc. Instead, a generalised material which has standard material properties like for example thermal conductivity, specific heat and density, can be defined. The standard material properties can be determined prior to performing the optimization method, basing for example on the above-mentioned specific properties. For example, the thermal conductivity depends on moisture, composition, component density, etc. The specific heat depend on moisture, etc. The density depends on component density, moisture, compressions, etc.

The present invention also relates to a conception and producing method, comprising the optimization method as described above and further comprising the producing method as described above. The producing method is preferably implemented subsequently to at least one implementation of the optimization method.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and its advantages will be better understood upon reading the following description, which is given solely by way of non-limiting example and which is made with reference to the appended drawings, in which:

- Figure 1 is a perspective view of an aerosol generating assembly comprising an aerosol generating device and a consumable article according to the invention, the consumable article being usable with the aerosol generating device;

- Figure 2 is a perspective view of the consumable article of Figure 1 , the consumable article comprising a tobacco substrate according to the invention;

- Figure 3 is a top view of the tobacco substrate of Figure 2;

- Figure 4 is a view illustrating airflow conduction of the tobacco substrate of Figure 2;

- Figure 5 is a schematic view of an installation suitable for producing the tobacco substrate of Figure 2; - Figure 6 is a flowchart of an optimization method according to the invention, the optimization method determining a pattern used to produce the tobacco substrate of Figure 2;

- Figure 7 is a schematic view illustrating one of the steps of the optimization method of Figure 6; and

- Figure 8 is a schematic view illustrating another step of the optimization method of Figure 6.

DETAILED DESCRIPTION OF THE INVENTION

Before describing the invention, it is to be understood that it is not limited to the details of construction set forth in the following description. It will be apparent to those skilled in the art having the benefit of the present disclosure that the invention is capable of other embodiments and of being practiced or being carried out in various ways.

As used herein, the term “aerosol generating device” or “device” may include a vaping device to deliver an aerosol to a user, including an aerosol for vaping, by means of a heater element explained in further detail below. The device may be portable. “Portable” may refer to the device being for use when held by a user. The device may be adapted to generate a variable amount of aerosol, e.g. by activating the heater element for a variable amount of time (as opposed to a metered dose of aerosol), which can be controlled by a trigger. The trigger may be user activated, such as a vaping button and/or inhalation sensor. The inhalation sensor may be sensitive to the strength of inhalation as well as the duration of inhalation to enable a variable amount of vapour to be provided (so as to mimic the effect of smoking a conventional combustible smoking article such as a cigarette, cigar or pipe, etc.). The device may include a temperature regulation control to drive the temperature of the heater and/or the heated aerosol generating substance (aerosol pre-cursor) to a specified target temperature and thereafter to maintain the temperature at the target temperature that enables efficient generation of aerosol.

As used herein, the term “aerosol” may include a suspension of vaporizable material as one or more of: solid particles; liquid droplets; gas. Said suspension may be in a gas including air. Aerosol herein may generally refer to/include a vapour. Aerosol may include one or more components of the vaporizable material. As used herein, the term “vaporizable material” or “precursor” may refer to a smokable material which may for example comprise nicotine or tobacco and an aerosol former. Tobacco may take the form of various materials such as shredded tobacco, granulated tobacco, tobacco leaf and/or reconstituted tobacco. Suitable aerosol formers include: a polyol such as sorbitol, glycerol, and glycols like propylene glycol or triethylene glycol; a non-polyol such as monohydric alcohols, acids such as lactic acid, glycerol derivatives, esters such as triacetin, triethylene glycol diacetate, triethyl citrate, glycerin or vegetable glycerin. In some embodiments, the aerosol generating agent may be glycerol, propylene glycol, or a mixture of glycerol and propylene glycol. The substrate may also comprise at least one of a gelling agent, a binding agent, a stabilizing agent, and a humectant.

Figure 1 shows an aerosol generating assembly 10 comprising an aerosol generating device 1 1 and a consumable article 12, according to the invention. The aerosol generating device 1 1 is intended to operate with the consumable article 12 which is shown in more detail in Figure 2.

Referring to Figure 1 , the aerosol generating device 11 comprises a device body 15 extending along a device axis Y. The device body 15 comprises a mouthpiece 16 and a housing 17 arranged successively along the device axis Y. According to the example of Figure 1 , the mouthpiece 16 and the housing 17 form two different pieces. Particularly, according to this example, the mouthpiece 16 is designed to be fixed on or be received in an insertion opening formed at one of the ends of the housing 17. In this case, the consumable article 12 can be inserted inside the device 11 when the mouthpiece 16 is removed from the housing 17. According to another example (not-shown), the mouthpiece 16 and the housing 17 form one unique piece. In this case, the consumable article 12 can be inserted inside the device 11 through for example an outlet hole. According to both examples, the mouthpiece 16 defines a through hole adapted to receive at least partially the consumable article 12. Particularly, the through hole can be adapted to receive at least a mouth end of the consumable article 12, explained in further detail below. According to still another embodiment (not-shown), no mouthpiece 16 is provided with the aerosol generating device 11 . In this case, the mouth end of the consumable article 12 can form a mouthpiece designed to be in contact with the user’s lips and/or mouth while a vaping session. The housing 17 delimits an internal space of the device 11 receiving various elements designed to carry out different functionalities of the device 1 1. This internal space can for example receive a battery for powering the device 11 , a control module for controlling the operation of the device 11 , a heating chamber for heating the consumable article 12, etc. Particularly, the heating chamber is designed to receive at least partially at least a tobacco substrate of the consumable article 12 and to heat it using an appropriate heater. In the example of Figure 1 , the heating chamber may be for example arranged in the extension of the through hole of the mouthpiece 16, according to the device axis Y.

In reference to Figure 2, the consumable article 12 is for example a flat-shaped cuboid extending along an article axis X between an inlet end 18 and a mouth end 19, and having external dimensions LxWxH. The consumable article 12 is adapted to conduct an airflow from the inlet end 18 to the mouth end 19 as it will be explained in further detail below. In a typical example, the length L of the article 12 according to the article axis X equals substantially to 25-35 mm, for example 33 mm while its width W is comprised between 8 and 15 mm, for example substantially equal to 12 mm and height H is comprised between 0,8 and 2 mm, for example is substantially equal to 1 ,2 mm. According to different examples, the values L, W and H can be selected within a range of +/- 40%, for example.

In the example of Figure 2, the consumable article 12 is wrapped by a common wrapper 21 . In other words, in this example, the wrapper 21 is formed from a unique sheet wrapping substantially the whole length of the consumable article 12 around the article axis X. In other examples, the wrapper 21 extends only along a part of the length of the consumable article 12. For example, the wrapper 21 can extend only along the tobacco substrate of the consumable article 12 and advantageously, wrap only the tobacco substrate. According to another example, the wrapper 21 is formed from two different sheets wrapping separately for example the tobacco substrate and the rest of the consumable article 12. The wrapper 21 can be made of aluminium and/or paper. In some embodiments, when the wrapper 21 comprises aluminium, the aluminium can wrap only the tobacco substrate to prevent condensation leakage and/or vapour leakage. Additionally, aluminium allows a better heat transfer. In some embodiments, the consumable article 12 can be provided and used without the wrapper 21 .

The consumable article 12 comprises a tobacco substrate 25 for generating aerosol and a filtering/cooling structure for filtering and/or cooling the aerosol generated by the tobacco substrate 25. The filtering/cooling structure may also serve to collect the aerosol flow from the tobacco substrate 25 and guide it to the user’s mouth. It may be entirely hollow or comprise flow guides and/or filtering elements. The filtering/cooling structure may be arranged in extension of the tobacco substrate 25 according to the article axis X. Thus, the tobacco substrate 25 is for example adjacent to the inlet end 18 of the consumable article 12 and the filtering/cooling structure is adjacent to the mouth end 19 of the consumable article 12. In some embodiments, no filtering/cooling structure is provided. In this case, the tobacco substrate 25 extends between the inlet end 18 and the mouth end 19.

As shown in Figure 3, the tobacco substrate 25 defines the inlet end 18 of the consumable article 12 and extends according to the article axis X until an outlet end 29. According to different embodiments, the outlet end 29 can be adjacent to the filtering/cooling structure or can form the mouth end 19 of the consumable article 12. Its axial extension length L1 is less than or equal to the length L of the consumable article 12. For example, L1 can be substantially equal to ¹/z L. The tobacco substrate 25 contains a vaporizable material as defined above. The vaporizable material is for example compressed to form a solid structure which is able to release aerosol upon heating.

As the consumable article 12, the tobacco substrate 25 defines for example a substantially flat-shaped cuboid defining a pair of opposite lateral surfaces 33A, 33B (represented as the top and left bottom sides of the substrate in Figure 4), and a pair of opposite conducting surfaces 34A, 34B (only the conducting surface 34A is visible in Figure 4), each of said surfaces extending along the article axis X. The pair of opposite conducting surfaces 34A, 34B is for example at least 5 times, advantageously 10 times, wider than the pair of lateral surfaces 33A, 33B. The pair of opposite conducting surfaces 34A, 34B extends in particular according to a direction perpendicular to a direction along which the lateral surfaces 33A, 33B extend.

The conducting surfaces 34A, 34B form outer surfaces of the tobacco substrate 25. In particular, the conducting surfaces 34A, 34B forming outer surfaces are visible from the exterior of the tobacco substrate 25. In other words, if the tobacco substrate 25 defines a substantially flat-shaped cuboid, the conducting surfaces 34A, 34B form outer surfaces of this cuboid. In particular, the conducting surfaces 34A, 34B are not arranged for example in an inner cavity inside the cuboid.

The conducting surfaces 34A, 34B are designed to be heated by the heating chamber of the device 11 by conduction and/or convection. According to another embodiment, the tobacco substrate 25 comprises susceptors and is designed to be heated by induction further to a magnetic interaction of the susceptors with a magnetic coil. Each lateral surface 33A, 33B can define a generally flat surface which can define rounded edges in each crosssection.

At least one of the conducting surfaces 34A, 34B, advantageously each conducting surface 34A, 34B, of the tobacco substrate 25 defines one or a plurality of airflow paths between the inlet end 18 and the outlet end 29, designed to conduct an airflow along the corresponding conducting surface 34A, 34B.

The first and/or second conducting surface 34A, 34B is/are (a) flow conducting surface(s). By “flow conducting surface”, it is understood that the corresponding conducting surface is configured to conduct or guide or direct an airflow in the airflow path(s) defined by this surface, in particular between the inlet end 18 and the outlet end 29.

Each airflow path can extend generally along the article axis X which means that the airflow conducted by this airflow path is mainly directed from the inlet end 18 to the outlet end 29. In particular, the airflow conducted by the corresponding airflow path may extend over at least 80% of a length of the airflow path, defined along the direction of the airflow conducted by this airflow path or defined by the walls of the airflow path, substantially along the article axis X. In this case, by “airflow path extending substantially along the article axis X” may be preferably understood that the airflow path extends along a direction parallel to the article axis X, with a variation angle equal to, or lower than 20 degrees. The variation angle is defined between a direction according to which the airflow path extends and the article axis X. If the airflow path extends exactly along the article axis X, the variation angle is equal to zero.

At least some of the airflow paths can be rectilinear and/or at least some of the airflow paths can be curvilinear. Each airflow path comprises a flow inlet arranged at the inlet end 18 of the tobacco substrate 25, a flow outlet arranged at the outlet end 29 of the tobacco substrate 25 and a flow groove extending along the corresponding conducting surface 34A, 34B between said flow inlet and said flow outlet.

In the following, examples of the arrangement of each airflow path extending generally along the article axis X are described. Preferably, for each airflow path, a straight line may be defined between the flow inlet arranged at the inlet end 18 of the tobacco substrate 25, and the flow outlet arranged at the outlet end 29. In this case, an angle formed between the straight line and the article axis X may be equal to or smaller than 20 degrees, preferably smaller than 10 degrees.

A transversal distance between the flow inlet and the flow outlet may be defined along a transversal direction perpendicular to the article axis X. The transversal direction extends in particular in parallel to the width W of the consumable article 12. The transversal distance of the flow inlet and the flow outlet may be for example three times, preferably four times, smaller than a total width of the tobacco substrate 25. The total width of the tobacco substrate 25 may be defined along the transversal direction, i.e., with reference to Figure 3, for example perpendicular to the length L1 of the tobacco substrate 25.

At least some of the airflow paths can present a variable cross-sectional dimensions and/or shape along their length. Particularly, the flow groove’s width and/or depth of these airflow paths can vary along their length. The cross-sectional shape of the groove can also vary. For example, in some cross-sections the groove can have a rounded shape and in some other cross-sections a rectangular shape. The variation of the shape and/or dimensions can be smooth (gradual) or discontinuous.

Additionally, at least some of the airflow paths can comprise a plurality of flow outlets and/or a plurality of flow inlets. Moreover, at least two airflow paths can share at least one common flow inlet and/or at least one common flow outlet and/or at least a common portion of the corresponding flow grooves. Particularly, at least two airflow paths at the inlet end 18 can merge into a single airflow path at the outlet end 29. Inversely, at least one airflow path at the inlet end 18 can be split into two separated airflow paths at the outlet end 29. In the example of Figure 3, the airflow path 41 comprises a single flow inlet 42 and two flow outlets 43A, 43B. On the contrary, the airflow path 51 comprises two flow inlets 52A, 52B and a single flow outlet 53.

As shown in Figure 4, in operation, an airflow can be first conducted exterior to the tobacco substrate 25 from a device inlet along the lateral surfaces 33A, 33B of the tobacco substrate 25 until the inlet end 18 of the tobacco substrate 25. For this purpose, the heating chamber of the device 1 1 can have a cup shape defining airflow channels between its lateral walls and the lateral surfaces 33A, 33B of the tobacco substrate 25. Then, the airflow enters inside the tobacco substrate through the flow inlets of the airflow paths formed on each or at least one conducting surface 34A, 34B of the tobacco substrate 25. The airflow is then conducted by the airflow paths until the corresponding flow outlets at the outlet end 29 of the tobacco substrate 25. Finally, the airflow is delivered to the user from the mouth end 19 of the consumable article 12 or through the mouthpiece 16 of the device 11 .

To produce a tobacco substrate 25 according to the invention, different producing installations can be used.

An example of such a producing installation 100 is shown in Figure 5. In reference to this Figure 5, the producing installation 100 comprises a receiving mechanism 105, a prerolling system 1 10, an embossing roller system 120 and a delivering mechanism 130. The receiving mechanism 105 is able to receive a vaporizable material intended to form a tobacco substrate 25, for example in a form of tobacco dough. The pre-rolling system 1 10 is able to pre-roll the tobacco dough in a roller to form a flat sheet. For this purpose, the prerolling system 110 comprises for example a pair of rollers connected to the receiving mechanism 105. The embossing roller system 120 comprises for example an embossing roller 122 and a guiding roller 124. The embossing roller 122 is configured to emboss or deboss a predetermined pattern on the tobacco sheet to form at least one tobacco substrate 25 comprising one or several airflow paths, as explained above. Advantageously, the embossing roller 122 is configured to emboss/deboss a plurality of predetermined patterns on the tobacco sheet to form a plurality of tobacco substrates 25. These patterns can be identical or different. In this last case, different airflow path arrangements can be obtained on different tobacco substrates 25. The embossing roller 122 can for example comprise a solid surface (metal or like) where the predetermined pattern(s) is(are) formed using any suitable method (cold spray, SLS, 6-axis CNC, etc.). In the embodiments where both conducting surfaces 34A, 34B of the tobacco substrates 25 define airflow paths, two embossing rollers 122 facing each other can be used. In some embodiments, the embossing roller 122 can also perform cutting of the tobacco sheet to form a plurality of tobacco substrates 25. In some other embodiments, a special cutting mechanism is arranged between the embossing roller system 120 and the delivering mechanism 130. The delivering mechanism 130 is configured to deliver the tobacco substrates 25 formed after the cutting. In some cases, it can also be configured to form a wrapper around these substrates 25 and/or assemble these substrates 25 with the filtering/cooling structures.

The tobacco dough may be a substrate containing tobacco particles and/or inhalable agent which contains at least one stimulant, e.g., nicotine and/or flavor, aerosol former, and a gelling agent or binder. The aerosol former may represent 20-70 wt. % in dry basis of the substrate. The gelling agent may represent between 1 -8 wt. % in dry basis. The gelling agent may be guar gum, gellan gum, non-protein polysaccharides and mixtures thereof. The substrate may further comprise a degradation preventing and/or thickening stabilizer such as carboxymethylcellulose. An example of pressed tobacco substrate is described in WO 2021094365. The mixture may comprise solid tobacco communiuted to bring them to a particle size (D90) below 300 microns, preferably between 20-220 microns. The tobacco particles may be mixed with aerosol former, the gelling agent, optionally stabilizer and water. A tobacco dough of liquid content of about 30-50 % can be obtained. The production of the tobacco dough may be carried out as described in EP 3852554.

A producing method of a tobacco substrate 25 is carried out for example by the producing installation 100 of Figure 5. The method comprises an initial step of extruding tobacco dough into a tobacco sheet. This step can be performed by the pre-rolling system 110. The method then comprises a step of embossing/debossing the tobacco sheet with a plurality of patterns corresponding to airflow path arrangements intended to be formed on the tobacco substrates 25. This step is performed by the embossing roller system 120. Then, the method comprises a step of cutting the embossed tobacco sheet to form a plurality of tobacco substrates 25. This step can be performed simultaneously with the step of embossing/debossing by the embossing roller system 120 or after the step of embossing/debossing by a separated cutting mechanism. Finally, the tobacco substrates 25 are delivered by the delivering mechanism 130 and are for example wrapped and/or assembled with the filtering/cooling structures, as explained above.

The predetermined pattern used to form one or several airflow paths on a tobacco substrate 25 according to the invention can be determined using an optimization method 200 which is carried out prior to said producing method. Particularly, this optimization method determines an optimized airflow path arrangement on at least one conducting surface of the tobacco substrate 25 by modeling airflow behavior around and inside the tobacco substrate 25.

The optimization method can be implemented at least partially by a computer software product comprising software instructions carrying out at least some of the steps of the optimization method. Such a software product can be carried out by a computer comprising notably a processor and a memory. Alternatively, the software product can be carried out by several computers linked between them by a computer network. The optimization method 200 will now be described in detail in reference to Figures 6 to 8.

Referring to Figure 6 illustrating a flowchart of the optimization method 200, the optimization method 200 comprises initial steps 210 to 230 of providing input data.

Particularly, during step 210 dimensions and geometry of a tobacco layer and of a built volume are provided. The tobacco layer models a layer of the tobacco substrate 25 which is not intended to contain airflow paths. In other words, the tobacco layer remains unchanged after performing the optimization method 200. An example of a tobacco layer 310 is shown in Figure 7. According to this example, the tobacco layer 310 has a rectangular shape extending along an article axis X. It can for example measure 0,1 x10x20 mm in thickness, width and length. The built volume is a volume adjacent to one side of the tobacco layer which is intended to model a layer of the tobacco substrate 25 containing one or several airflow paths. Thus, the built volume is used as a starting structure where an optimized topology is created. Initially, it is for example supposed empty. Additionally, it can be also specified the side of the built volume considered as an inflow end of the tobacco substrate 25 and the side of the built volume considered as an outflow end of the tobacco substrate 25. According to the example of Figure 7, as the tobacco layer 310, a built volume 320 has a rectangular shape which measures for example 1 x10x20 mm in thickness, width and length. This built volume 320 comprises a side 321 considered as an inflow end of the tobacco substrate 25 and a side 322 considered as an outflow end. Additionally, according to the example of Figure 7, only one built volume 320 arranged on one side of the tobacco layer 310 is defined. In this case, the modelled tobacco substrate 25 comprises only one conducting surface comprising one or several airflow paths. In a general case, it is possible to define two built volumes arranged on either side of the tobacco layer. Alternatively, it is possible to model only a half of the tobacco substrate 25 with one built volume. The whole tobacco substrate 25 can be modelled by a symmetric reflexion of the modelled half.

During step 220, boundary conditions of the built volume are provided. The boundary conditions can comprise at least one of the following elements and preferably a combination of at least two or three of the following elements:

- flow rate;

- input energy;

- pressure;

- temperature. Each boundary condition can be formed by a fixed value or a range of values. Advantageously, boundary conditions can be defined only on the sides of the built volume intended to model an inlet end and an outlet end of the tobacco substrate 25. Thus, in the example of Figure 7, boundary conditions can be defined only on sides 321 and 322 of the built volume.

During step 230, material input data is provided. This material input data corresponds to physical properties of the material intended to form the tobacco substrate 25. Particularly, this material can correspond to the vaporizable material and its input data can correspond to physical properties of this vaporizable material as for example tobacco particle size, moisture, tobacco type, density, composition, etc. Alternatively, the material intended to form the tobacco substrate 25 is modelled by a generalised material which has standard material properties like for example thermal conductivity, specific heat and density. In this case, the standard material properties can for example be obtained empirically by observing the behaviour of the vaporizable material.

During step 240, an internal structure of the built volume is determined by applying a structure construction method inside this built volume. This internal structure respects the boundary conditions and the material input data. The structure construction method can be carried out by any commercially available CFD (“Computational Fluid Dynamics”) solver with topology optimization tool. This topology optimization tool comprises an optimization criterion chosen basing on parameters of the modelled tobacco substrate 25 that should be optimized. For example, the optimization criterion comprises at least one of the following criteria:

- optimization of the pressure drop across the tobacco substrate 25;

- optimization of the temperature in or at an outlet end 19 of the tobacco substrate 25;

- optimization of the tobacco temperature inside or at a surface of the tobacco substrate 25.

For example, optimization of the pressure drop makes it possible to optimize the quantity of the aerosol delivered to the user in function of the user’s puffs. Optimization of the temperature in an outlet end 19 of the tobacco substrate 25 can optimize the temperature of the aerosol delivered to the user. Optimization of the tobacco temperature inside or at a surface of the tobacco substrate 25 can optimize the temperature of the tobacco substrate 25 so as to ensure aerosol generation while avoiding its burning. It is also possible to use multiple optimization criteria ensuring a simultaneous application of at least some of the above-cited criteria.

Then, geometry, shape and number of airflow paths are determined in the optimized built volume. For example, as mentioned above, at least some of the airflow paths can have width and/or depth which vary along their length.

Figure 8 shows an internal structure of the built volume 320 determined further to applying for example one iteration of one of the optimization criteria during step 240. Thus, such an internal structure can comprise four walls extending along the article axis X and defining five airflow paths. This internal structure can further be optimized by applying further iterations of one or several optimization criteria, as explained below.

During step 250, it is verified whether the obtained structure of the optimized built volume meets the above-mentioned requirements or not. Particularly, at this step, the boundary conditions as defined at step 220 can be verified. Additionally or alternatively, it can be verified whether one or several optimization criteria with corresponding requirements have been achieved. For example, for the pressure drop optimization criterion, it can be verified whether the pressure drop is less than a predetermined threshold. Similarly, for example, for the tobacco temperature optimization criterion, it can be verified whether this temperature is within a predetermined range.

If the requirements are met, next step 260 is carried out. Otherwise, another iteration of step 240 is carried out starting from the optimized built volume obtained after the previous iteration of step 250.

During step 260, a pattern of an optimized airflow path arrangement on a conducting surface of the modelled tobacco substrate 25 is output. This pattern comprises the determined geometry, shape and number of airflow paths in the built volume. This pattern can for example present a computer readable file. For example, the pattern can present a CAD (“Computer Aided Design”) file comprising a 3D geometry of the pattern. Advantageously, the pattern file can be read and used to carry out the corresponding structure by a 3D printer. Alternatively, the pattern file can be used to carry out a moulding process (for example Computer Numerical Control injection moulding) or laser engraving.

Claims

23 CLAIMS

1. A tobacco substrate (25) for use in an aerosol generating device (1 1 ), comprising a first flow conducting surface (34A) comprising an airflow path (41 , 51 ) formed in recess on the first flow conducting surface (34A); wherein the airflow path (41 , 51 ) comprises a flow inlet (42, 52A, 52B), a flow outlet (43A, 43B, 53) and a flow groove extending along the first flow conducting surface (34A) between said flow inlet (42, 52A, 52B) and said flow outlet (43A, 43B, 53); wherein the flow groove’s width and/or depth and/or cross-sectional shape vary (ies) along its length.

2. The tobacco substrate (25) according to claim 1 , wherein the first flow conducting surface (34A) comprises a plurality of airflow paths (41 , 51 ).

3. The tobacco substrate (25) according to claim 1 or 2, wherein at least one or each airflow path (41 , 51 ) comprises a plurality of flow outlets (43A, 43B) and/or a plurality of flow inlets (52A, 52B).

4. The tobacco substrate (25) according to any one of the preceding claims, further comprising a second flow conducting surface (34B) comprising one or several airflow paths (41 , 51 ) formed in recess on the second flow conducting surface (34B).

5. The tobacco substrate (25) according to claim 4, wherein the second flow conducting surface (34B) is opposite to the first flow conducting surface (34A).

6. The tobacco substrate (25) according to any one of the preceding claims, wherein the or each airflow path (41 , 51 ) is embossed or debossed on the corresponding surface (34A, 34B) of the tobacco substrate (25).

7. The tobacco substrate (25) according to any one of the preceding claims, having a flat shape and formed from a tobacco sheet, preferably having a thickness comprised between 0,5 and 5 mm.

8. The tobacco substrate (25) according to any one of the preceding claims, comprising tobacco, an aerosol forming agent and preferably, a binder.

9. A consumable article (12) comprising a tobacco substrate (25) according to any one of the preceding claims.

10. A producing method for producing a tobacco substrate (25) according to any one of claims 1 to 8, comprising a step of embossing or debossing a tobacco sheet to form an airflow path.

11 . The producing method according to claim 10, further comprising a step of cutting an embossed or debossed tobacco sheet.

12. The producing method according to claim 1 1 , wherein the step of cutting is carried out simultaneously with the step of embossing or debossing or after the step of embossing or debossing.

13. The producing method according to any one of claims 10 to 12, further comprising a step of extruding tobacco dough into a tobacco sheet, the step of extruding being carried out before the step of embossing or debossing.

14. The producing method according to any one of claims 10 to 13, wherein the tobacco sheet is embossed or debossed using a predetermined pattern of an optimized airflow path arrangement on a flow conducting surface (34A, 34B) of a tobacco substrate (25).

15. An optimization method (200) of airflow path arrangement on a flow conducting surface (34A, 34B) of a tobacco substrate (25), comprising the following steps:

- providing (210) dimensions and geometry of a tobacco layer (310) and of a built volume (320) modelling a layer of the tobacco substrate (25) containing one or several airflow paths (41 , 51 ), the built volume (320) being adjacent to the tobacco layer (310) in the tobacco substrate (25) to form said flow conducting surface;

- providing (220) boundary conditions of the built volume (320);

- providing (230) material input data;

- determining (240) an internal structure of the built volume (320) by applying a structure construction method inside the built volume (320) respecting the boundary conditions and the material input data, the structure construction method being based on an optimization criterion; - using the determined internal structure of the built volume (320), determine (260) a pattern of an optimized airflow path arrangement on said flow conducting surface (34A, 34B) of the tobacco substrate (25), the pattern comprising geometry, shape and number of airflow paths in the built volume (320).