Aerosol-forming device and method for detecting user inhalation

Abstract

An aerosol-forming device (1) for forming aerosol from an aerosol- forming article is described. The device (1) comprises a heating chamber (30) configured to receive at least a part of the aerosol- forming article; an upstream airflow path (40a) arranged upstream of the heating chamber (30), the upstream airflow path (40a) in fluid communication with an external environment of the aerosol-forming device (1), such that air is drawable by a user in a user inhalation from the external environment through the upstream airflow path (40a) towards the heating chamber (30); a first heating device (6a) arranged at the heating chamber (30) and configured to perform a first heating operation; a second heating device (70) arranged in thermal contact with the upstream airflow path (40a) and configured to perform a second heating operation; and control circuitry (5) configured to control a power supply from a power source of the aerosol-forming device (1) to at least one of the first heating device (6a) and the second heating device (70) based on determining a change in a temperature of at least one of the first heating device (6a) and the second heating device (70) associated with a change in an airflow through the airflow path caused by the user inhalation.

Description

[0001] FTR4068

[0002] 1 / 89

[0003] AEROSOL-FORMING DEVICE AND METHOD FOR DETECTING USER INHALATION The present disclosure generally relates to the field of aerosol-forming devices and systems for generating aerosol, also referred to as aerosol-generating devices and aerosol-generating systems. In particular, the present disclosure relates to an electronic aerosol-forming device and an electronic aerosol-forming system configured to generate or form aerosol, for example aerosol inhalable by a user in one or more user inhalations or puffs. Further, the present disclosure relates to a method of detecting a user inhalation or puff at an aerosol-forming device or system.

[0004] Aerosol-forming or aerosol-generating devices are typically designed as handheld devices that can be used by a user for consuming or experiencing, for instance in one or more usage sessions, aerosol generated from an aerosol-forming substrate or an aerosol-forming article. Therein, aerosol is typically generated by heating at least a part of the substrate to a certain temperature sufficient to release aerosol from the substate. The aerosol-forming devices the present disclosure pertains to are, in particular, directed to the field of heated tobacco products (HTP), heat-not-burn (HNB) devices, tobacco and tobacco-substitute products. However, the present disclosure may at least in some instances also be applicable to e-vapor devices, e-cigarettes, vaporizers, as well as other types of inhalers, dispensers, or atomizers, for example inhalers, dispensers, or atomizers for medical or pharmaceutical applications.

[0005] Typical aerosol-forming systems can be designed as one-part systems or devices including an aerosol-forming device that can be operated by a user to generate aerosol, for example from a removable or non-removable aerosol-forming article. Alternatively, aerosol-forming systems can be designed as two-part systems or devices comprising an aerosol-forming device and a companion device for storing and / or charging the aerosol-forming device. In either design or configuration, the aerosol-forming system or device can be used by a user for consuming or inhaling, for instance in one or more usage sessions, aerosol generated based on heating an aerosol-forming article or substrate couplable to or at least partly insertable into the aerosolforming system. In the context of the present disclosure, an aerosol-forming device can refer to both a one-part device and a two-part device, unless explicitly specified otherwise.

[0006] The aerosol-forming article, also referred to as aerosol-generating article, can comprise an aerosol-generating or aerosol-forming substrate. Generally, the aerosol-forming substrate may include a solid material, a liquid material, or both liquid and solid material. Exemplary aerosolforming substrates can comprise solid substrate material with one or more ingredients, such as tobacco material, tobacco cast leaves (TCL) material or cannabis-based material.

[0007] The solid, liquid, or a mixed-form of solid and liquid aerosol-forming substrate may contain one or more ingredients, active ingredients or active agents, which may be vaporized during a usage session and inhaled by the user in one or more user inhalations. A user inhalation is synonymously and interchangeably used herein with “puff” of the user. Exemplary ingredients ofFTR4068

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[0009] the aerosol-forming article or substrate include nicotine, nicotine-containing substances, water, aroma, sugar, moisturising agent, botanicals, preservative, flavouring, for example cocoa, liquorice, menthol and lactic acid or other additives or ingredients. Other exemplary ingredients of the aerosol-forming substrate include one or more pharmaceutical agents, one or more drugs, one or more adjuvants or other active agents. Accordingly, the aerosol formed from a corresponding substrate may contain one or more of these ingredients, active ingredients or active agents and / or may be inhalable by the user in one or more user inhalations or puffs.

[0010] The aerosol-forming article may be configured in shape and size to be removably inserted at least partly into the aerosol-forming device or system. In some conventional systems or devices, the aerosol-forming article is usually formed as a stick that can be at least partly inserted into a heating volume, heating cavity or heating chamber of the aerosol-forming device for aerosol consumption. Alternatively or additionally, aerosol-forming substrates can comprise one or more liquids and / or solids, which can, for example, be supplied to the aerosol-forming device in the form of a cartridge, capsule, or container. Corresponding exemplary aerosol-forming articles can comprise a cartridge containing or being fillable with the liquid and / or solid substrate, which can be vaporized during aerosol consumption by the user based on heating the substrate and / or liquid. Usually, such cartridge, capsule, or container can be coupled to, attached to or at least partially inserted into the aerosol-forming device. Alternatively, the cartridge may be fixedly mounted to the aerosol-forming device and refilled by inserting liquid and / or solid into the cartridge.

[0011] For generating the aerosol during use or consumption, heat can be supplied by a heating element, heating device, heater arrangement or heat source to heat at least a portion or part of the aerosol-forming substrate. At least a part of the heating device can be arranged in the handheld device or a handheld part of the aerosol-forming device. Alternatively or additionally, at least a part of or the entire heating device can be fixedly associated with or arranged within an aerosol-forming article.

[0012] Exemplary heating elements, heating devices, or heater arrangements can be based on one or more of resistive heating, inductive heating, conductive heating, convective heating, infrared heating or other radiative heating, dielectric heating and microwave heating using electrical energy supplied via, drawn from or stored in an energy storage or battery of the aerosolforming device.

[0013] Typically, aerosol-forming devices comprise an energy storage or power source, for example a rechargeable energy storage, providing the electrical energy needed to operate the aerosol-forming device and especially for heating the aerosol-forming substrate and / or article, for example to generate aerosol in one or more usage sessions using one or more aerosol-forming articles.FTR4068

[0014] 3 / 89

[0015] To actually store electrical energy, the energy storage may include one or more battery cells, one or more rechargeable battery cells, one or more accumulators, one or more capacitors or one or more other devices or components for storing electrical energy. Exemplary energy storages may include a plurality of rechargeable battery cells, such as for example between two and ten, preferably between two and four battery cells. Further, exemplary re-chargeable battery cells may be based on lithium-ion battery cells. For example, a cathode material may comprise lithium-cobalt-oxide (LCO), lithium-manganese-oxide (LMO), lithium-nickel-manganese-cobalt-oxide (NMC or NCM), lithium-iron-phosphate (LFP), and / or lithium-nickel-cobalt-aluminum-oxide (NCA). Alternatively or additionally, an anode material may comprise carbon (e.g. graphite), silicon and / or lithium-titanate-oxide (LTO).

[0016] The aerosol-forming device the present disclosure pertains to may, for example, refer to a handheld, battery-powered, lightweight, and / or portable device. However, the present disclosure is not limited in this respect, but can be implemented in various forms and designs of aerosolforming devices and systems.

[0017] In the context of the present disclosure, the aerosol-forming device and / or the aerosolforming system may be a portable device and / or system. It may be battery powered. Particularly, the aerosol-forming device and / or the aerosol-forming system may be pocket-size, hand-held, suitable for one-hand use and / or may weigh less than 300 g, preferably less than 200 g. It may be shaped and / or sized to fit snugly into a user’s hand. It may be carried in jacket and / or trouser pockets. Particularly, the aerosol-forming device and / or the aerosol-forming system may be configured to provide aerosol for human inhalation and / or human consumption, particularly inhalation and / or consumption through the mouth.

[0018] As used herein, the term “usage session” may, generally, refer to a period of time, during which a user may use the aerosol-forming device to generate, consume, experience or inhale aerosol. In a single usage session an aerosol-forming article may be consumed by the user completely or partly. Also, a plurality of aerosol-forming articles may be consumed by the user in a single usage session. Further, the user may take one or more puffs or user inhalations during a usage session. Generally, a usage session may be finite in time. In otherwords, a usage session may have a start, an end, and a duration. The duration of the usage session as measured by time may be influenced by use during the usage session. Optionally, the duration of the usage session, for example monitored by a control circuitry of the aerosol-forming device, may have a maximum duration determined by a maximum time from the start of the usage session. The duration of the usage session may be less than the maximum time if one or more monitored parameters reach a predetermined threshold before the maximum time from the start of the usage session. By way of example, the one or more monitored parameters may comprise one or more of: i) a cumulative puff count of a series of puffs drawn by a user since the start of the usage session, and ii) aFTR4068

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[0020] cumulative volume of aerosol evolved from the aerosol-forming substrate since the start of the usage session. Other parameters can be used instead or in addition.

[0021] Depending on the habits and preferences of the user, the number of user inhalations taken during a usage session or taken per unit time may differ across usage sessions and across users. For example, some users may take more user inhalations or puffs per unit time, respectively, have a higher inhalation or puff rate, than other users. Accordingly, an inhalation pattern, frequency, rate or characteristic may depend at least to a certain extent on the operation of the aerosol-forming device by the user. At least some conventional devices and systems are limited in terms of operational control and, for example, do not take the actual use or operation of the device by a user into consideration.

[0022] Also, for example for puff-on-demand operations, also referred to as puff-on-demand or response-to-draw heating operations, of aerosol-generating devices and systems, a puff triggering mechanism is usually required, for example by the user manually activating the puff or inhalation, or by a puff detection sensorthat can detect when the user is taking a puff or inhalation. However, the use of manual activation is not favored by many users, as being imprecise with respect to the puff timing, and can lead to dry burning of liquid transfer elements or parts of the aerosol-forming substrate, for example when heat is generated during the moments where the user does not take a puff. With respect to automated detection, the puff detection sensor can become clogged or otherwise impeded to thereby cease proper operation. Also, it requires additional components for the aerosol forming device or system, that leads to additional costs and complexity.

[0023] Therefore, it may be desirable to provide for an improved aerosol-forming device, system and corresponding method, which at least partly mitigates or overcomes the drawbacks of conventional systems and devices. In particular, the aerosol-forming device, system and method described herein may enable or allow for an improved control of the device, for example a control in accordance with an actual use or operation of the device by a user.

[0024] These advantages may be achieved by the features described herein.

[0025] Aspects of the present disclosure relate to an aerosol-forming device, an aerosol-forming system, and to a method of detecting a user inhalation at an aerosol-forming device or system. It is noted that any disclosure presented herein with reference to an or one aspect of the present disclosure, equally applies to any other aspect of the present disclosure, unless explicitly stated otherwise. In particular, it is emphasized that any disclosure presented herein with respect to an aerosol-forming device equally applies to an aerosol-forming system comprising such aerosolforming device and optionally a charger case or companion device.

[0026] According to an aspect, there is provided an aerosol-forming device, also referred to herein as aerosol-generating device, for forming aerosol from an aerosol-forming substrate or article.FTR4068

[0027] 5 / 89

[0028] The aerosol-forming device comprises a heating chamber configured to receive at least a part of the aerosol-forming article, and an upstream airflow path arranged upstream of the heating chamber, the upstream airflow path being in fluid communication with an external environment or surrounding of the aerosol-forming device, such that air is drawable by a user in a user inhalation from the external environment through the upstream airflow path towards or in direction of the heating chamber. The aerosol-forming device further comprises a first heating device arranged at the heating chamber and configured to perform a first heating operation. The aerosol-forming device further comprises a second heating device arranged in thermal contact with the upstream airflow path and configured to perform a second heating operation. Further, the aerosol-forming device comprises a control circuitry configured to control a power supply or supply of electrical power from a power source of the aerosol-forming device to one of or both the first heating device and the second heating device based on determining a change in a temperature of one of or both the first heating device and the second heating device associated with a change in an airflow through the upstream airflow path caused by the user inhalation.

[0029] Accordingly, the aerosol-forming device, respectively, the control circuitry thereof can detect or determine a temperature change caused by the change in the airflow through the upstream airflow path that is induced by or results from the user inhalation or puff taken by the user. For example, if the user inhales, air or fresh air may be drawn from the external environment into the upstream airflow path, such that an airflow, also referred to as upstream airflow, is generated in the upstream airflow path. The fresh air drawn from the external environment may substantially have room or ambient temperature, and hence can depart a cooling effect onto one or both the first heating device and the second heating device. Therefore, the change in temperature, which in this example is a decrease in temperature, can be indicative of the user inhalation, of a start of the user inhalation and / or of occurrence of the user inhalation at the aerosol-forming device. Hence, by determining the change in temperature of one of or both the first and second heating devices, the control circuitry can gain information about or can be enabled to detect the user inhalation at the aerosol-forming device. Moreover, if the user stops inhaling, the airflow through the upstream airflow path stops or is at least reduced, which can cause a further change in the temperature of one of or both the first heating device and the second heating device. Specifically, termination or stop of the user inhalation can lead to or cause an increase in temperature of one of or both the first heating device and the second heating device, which can be determined or detected by the control circuitry. Thereby, the control circuitry can be enabled to detect or determine termination or stop of the user inhalation at the aerosol-forming device.

[0030] Hence, based on determining one or more changes in the temperature of one of or both the first heating device and the second heating device, the control circuitry can be enabled or configured to detect one or more user inhalations, for example without relying on manualFTR4068

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[0032] activation of a puff triggering mechanism by a user and / or without necessarily relying on other components or sensors. Hence, an improved aerosol-forming device with improved detection means for detecting a user inhalation can be provided. In turn, this can allow for an operational control of one or more of the first heating device, the second heating device and the power source or energy source in accordance or correspondence with the one or more detected changes in the temperature of one or both the first heating device and the second heating device.

[0033] In conventional aerosol-forming devices or systems, typically a dedicated puff sensor, for example a pressure sensor or flow sensor, is utilized to detect user inhalations or puffs at the aerosol-forming device. In the aerosol-forming device described herein, a reading or signal of such dedicated puff sensor can either be validated or checked for plausibility by additionally determining the change in the temperature of one of or both the first heating device and the second heating device, and optionally by detecting the user inhalation based thereon. Accordingly, the detection means to detect the user inhalation described herein can constitute a redundant puff detection means that can supplement an existing puff sensor. This can, for example, allow to improve reliability of the aerosol-forming device, and for example also allow for operation of the device even in case the dedicated puff sensor fails.

[0034] As used herein, the terms "upstream" and "downstream" may describe the relative positions of components or elements of the aerosol-forming device or system in relation to the direction of the airflow through the heating chamber and / or the aerosol-generating article towards the mouth of the user for inhalation. The airflow through the aerosol-forming article may refer to the flow through the article, when placed or situated in the aerosol-generating device. The airflow through the heating chamber and / or aerosol-forming article that is caused by a user inhalation may be substantially directed along a longitudinal axis of the aerosol-forming device and / or article.

[0035] As used herein, “upstream” may refer to a location that comes before a particular point of reference in the direction of the airflow. Unless specified otherwise, the reference point or location is the heating chamber and / or aerosol-forming article, when placed or situated in the heating chamber. For example, an upstream part or element of the device may refer to a part or element where the air comes from before reaching the heating chamber and / or aerosol-forming article. Accordingly, the upstream airflow path refers to an airflow path where the air comes from before reaching the heating chamber and / or aerosol-forming article.

[0036] As used herein, “downstream” may refer to a location that comes after a particular point of reference in the direction of the airflow, in particular after the heating chamber and / or aerosolforming article. For example, a downstream part or element of the device may refer to a part or element where the air goes or flows to after leaving the reference point, in particular the heating chamber and / or article.FTR4068

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[0038] The upstream airflow path can be in fluid communication with the external environment or a surrounding of the aerosol-forming device. This may mean that the upstream airflow path is fluidly coupled or connected to the surrounding or external environment of the device. The airflow through the upstream airflow path may also be referred to herein as upstream airflow. Unless explicitly stated otherwise in the following, a reference to an airflow path or the airflow path, refers to the upstream airflow path.

[0039] For example, the upstream airflow path may be fluidly coupled to the external environment via one or more air inlets, also referred to herein as main air inlets or device inlets. Optionally, the upstream airflow path and the one or more air inlets may be fluidly interconnected by one or more airflow path structures or elements configured to guide or convey the air from the one or more air inlets towards or to the upstream airflow path. The one or more airflow path structures or elements may, for example, be defined by one or more walls or components arranged in a housing or device body of the aerosol-forming device.

[0040] The second heating device being arranged in thermal contact with the upstream airflow path may mean or include that at least a part of the second heating device is thermally coupled to the upstream airflow path, such that heat or thermal energy can be exchanged between a heatexchange element of the second heating device and the upstream airflow path or the airflow through the upstream airflow path. For example, at least a part of the second heating device may be arranged in or protrude into the upstream airflow path to form the heat-exchange element, such that air can pass along at least a part of the surface of heat-exchange element the second heating device. The heat-exchange element may also be referred to as resistive heating element of the second heating device. Alternatively or additionally, the second heating device may exchange heat or thermal energy with the air in the upstream airflow path via at least one thermally conductive element.

[0041] The control circuitry, as used herein, may refer to a control means for controlling operation of the first heating device, the second heating device, optionally the power source or energy storage of the device, and further optionally one or more other functions of the aerosol-forming device. The control circuitry may include one or more processors, for example a microcontroller unit (MCU), and / or one or more other data processors. The control circuitry may generally be configured to execute programmed instructions, for example stored in a data storage or memory of the device, to manage the heating process of an aerosol-forming substrate or article based on controlling the first heating device, controlling the second heating device, controlling power supply to one or both the first heating device and the second heating device, and / or controlling the power source or energy storage of the aerosol-forming device. The control circuitry may be implemented partly in software and partly in hardware. At least a part of the control circuitry and / or at least a part of its functionalities may be implemented as Application-Specific Integrated Circuit (ASIC),FTR4068

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[0043] on a printed circuit board with one or more discrete components, as a microcontroller-based implementation, as Field-Programmable Gate Array (FPGA), or hybrid implementation using a combination thereof.

[0044] The “power source” may also be referred to herein as energy storage of the aerosol-forming device or system. The energy storage or power source may be a rechargeable energy storage, providing the electrical energy needed to operate the aerosol-forming device and especially for heating the aerosol-forming substrate and / or article, for example to generate aerosol in one or more usage sessions using one or more aerosol-forming articles. As mentioned above, to actually store electrical energy, the energy storage may include one or more battery cells, one or more rechargeable battery cells, one or more accumulators, one or more capacitors such as supercapacitors, or one or more other devices or components for storing electrical energy.

[0045] The control circuitry may be configured to determine or detect the user inhalation or puff at the aerosol-generating device based on determining one or more changes in the temperature of at least one of the first heating device and the second heating device. As explained above, such change in the temperature can, for example, be caused by a cooling effect departed by an airflow through the upstream airflow path past at least one of the first heating device and the second heating device, wherein the airflow is associated with the user inhalation. Hence, the change in the temperature of one of or both the first heating device and the second heating device can be a decrease in temperature. Accordingly, the control circuitry may be configured to determine or detect one or more of the user inhalation, occurrence of the user inhalation, a duration of the user inhalation, an onset of the user inhalation, and a start of the user inhalation at the aerosolgenerating device based on determining or detecting a change or decrease in the temperature of at least one of the first heating device and the second heating device.

[0046] Alternatively or additionally, a change in temperature, in particular an increase in temperature, of one or both the first heating device and the second heating device may occur when the user stops inhaling, respectively when the user inhalation is terminated or ended. Accordingly, the control circuitry can be configured to determine or detect one or more of the start of the user inhalation, occurrence of the user inhalation, termination of the user inhalation, an end of the user inhalation and a duration of the user inhalation based on determining or detecting a change or an increase in the temperature of one of or both the first heating device and the second heating device.

[0047] Accordingly, the control circuitry can be configured to detect or determine a start of an user inhalation, the user inhalation and / or occurrence of the user inhalation at the aerosol-forming device based on one of or both detecting a decrease in the temperature and an increase in the temperature of one of or both the first heating device and the second heating device. Hence, the control circuitry can provide the functionality of a puff sensor based on determining changes inFTR4068

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[0049] the temperature of the first and / or second heating device. Also, the control circuitry can be configured to detect a decrease in the temperature of only one of the first and the second heating device and to detect an increase in the temperature of the respective other one of the first heating device and the second heating device.

[0050] In an exemplary implementation, the aerosol-forming device may be configured to detect a user inhalation or puff solely based on determining one or more changes in the temperature of one or both the first heating device and the second heating device. Accordingly, a dedicated or separate puff sensor may not be required for detecting the user inhalation. As a consequence, space for the puff sensor in the aerosol-forming device may be saved, which may be of particular advantage when the aerosol-forming device is designed as handheld device. Also, an electrical power to operate the dedicated puff sensor may be saved, which can allow for energy efficient operation of the aerosol-forming device. This can be of particular advantage in case the aerosolforming device is powered by a rechargeable or replaceable energy storage, for example including one or more battery cells. In addition, it is possible to increase the reliability of the device, and puff sensors can become clogged or unclean and can provide for inaccurate and unreliable results.

[0051] As used herein, detecting or determining a user inhalation at the aerosol-forming device may refer to or include one or more of detecting an onset or start of the user inhalation, detecting that a user inhalation is being performed, detecting an occurrence of the user inhalation, detecting that the user inhalation has been performed or has occurred, and detecting termination or an end of a user inhalation. In particular, the term “detecting the user inhalation” can be synonymously or interchangeably used herein with detecting one or more of an occurrence, an onset, a start, a duration, or an end of the user inhalation.

[0052] The control circuitry, in an example, can be configured to detect the start of the user inhalation based on determining a decrease in temperature of one of or both the first heating device and the second heating device, and to detect termination of the user inhalation based on determining an increase in temperature of one of or both the first heating device and the second heating device. Optionally, the control circuitry may be configured to determine or check whether the decrease in temperature and the increase in temperature occurred within a predetermined period of time or time window.

[0053] By detecting the user inhalation based on determining one or more changes in the temperature of one of or both the first heating device and the second heating device, an operation or control of the device in accordance or in correspondence with one or more user inhalations of the user may be enabled. For instance, control or operation of one or more of the first heating device, the second heating device, and the power source may be synchronized with an inhalation pattern of the user based on determining one or more change in temperature of the first heatingFTR4068

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[0055] device and / or the second heating device. In turn, this can enable an energy efficient operation of the device. Also, an improved aerosol quality or taste may be provided, for example across multiple user inhalations or across multiple usage sessions.

[0056] In an example, one of or both the first heating device and the second heating device can be operated in a puff-on-demand heating operation based on detecting the change in the temperature of one or both the first heating device and the second heating device.

[0057] In the context of the present disclosure, a "puff-on-demand" heating operation, also referred to as response-to-draw heating operation, may refer to a method of controlling the first heating device and / or the second heating device based on or in accordance with a user inhalation or puff being performed or occurring. For instance, at least one of the first heating device and the second heating device may be activated only during at least a part of the user inhalation or only powered at a power level sufficient to generate aerosol during at least a part of the user inhalation, rather than being continuously heated throughout an entire usage session. Puff-on-demand heating can be designed to optimize energy efficiency and, for example, enhance user experience by providing aerosol only when needed, thereby reducing unnecessary heating and potential degradation of the aerosol-forming substrate. A puff-on-demand heating operation of the aerosolforming device, as used herein, may include or refer to operation of the aerosol-forming device, respectively, one or both the first heating device and the second heating device, according to a puff-on-demand heating scheme.

[0058] The first heating device may be or include a resistive heating device configured to heat at least a part of a substrate of the aerosol-forming article by conductive heating. The first heating device or resistive heating device may, for example, include one or more heating elements, for example resistive heating elements, configured to heat the substrate or article by conduction. Generally, conductive heating can be advantageous in terms of providing rapid and efficient heat transfer, which can lead to quick vaporization of substrate material.

[0059] As used herein, heating by conduction may involve or include a direct transfer of heat or thermal energy from one or more of the first heating device, the resistive heating device and / or the one or more heating elements to the aerosol-forming article or substrate. For example, at least a part of the first heating device, the resistive heating device and / or at least one of the heating elements may be configured or arranged to contact or directly contact the aerosol-forming article or substrate to heat the article or substrate.

[0060] In an example, the first heating device may comprise two opposing heating elements comprising electrically conductive material and being configured to be resistively heated. Optionally, the two opposing heating elements may be part of a resistive heating device of the first heating device. Accordingly, the heating elements of the first heating device may be resistive heating elements, also referred to as Joule-type heating elements.FTR4068

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[0062] Further, as used herein, “resistive heating” means that the electrical resistance of the respective component is used to generate heat or thermal energy. Specifically, when applying electrical power to an electrically conductive element having a defined electrical resistivity, at least a part of the electrical energy is converted to thermal energy or heat due to the electric losses in the material. This effect can be used to heat-up at least a part of the first heating device, the resistive heating device and / or the at least one heating element to increase the temperature of the corresponding component. Further, the resistively generated heat can at least partly be transferred to the aerosol-forming article or substrate based on conduction.

[0063] Alternatively, the two opposing heating elements of the first heating device may each include a susceptor configured to be inductively heated. For example, the first heating device may comprise one or more heating coils configured to heat the heating elements based on or by induction. Alternatively or additionally, the aerosol-forming article or substrate may include or comprise a susceptor that can be inductively heated.

[0064] For inductive heating, an alternating magnetic field may be generated by the one or more heating coils. The heating elements and / or susceptors may be at least partly arranged in the alternating filed, such that eddy currents can be induced in the susceptors of the heating elements and / or aerosol-forming article, which are at least partly converted to heat in the susceptor material, thereby heating the heating elements and / or substrate, for example by conduction.

[0065] Also, a combination of resistive and inductive heating elements may be used or included in the first heating device. For example, one heating element may be heated resistively and the other one may be heated by induction. Further optionally, the first heating device may include one or more further heating elements, for example, configured to heat one or more lateral side faces of the aerosol-forming article. The heating elements heating the main faces and the one or more further heating elements heating the lateral side faces of the aerosol-forming article can employ different heating technologies. For instance, the heating elements may be resistive heating elements and the one or more further heating elements may be heated inductively, or vice versa.

[0066] Alternatively, the first heating device may include a dielectric heating device configured to dielectrically heat the aerosol-forming article. For instance, the two opposing heating elements of the first heating device may constitute electrodes of a load capacitor configured to dielectrically heat the substrate based on generating an alternating electric field with the load capacitor.

[0067] In such configurations, optionally a separate external temperature sensor may be used to monitor the temperature of one or more of the heating elements of the first heating device, the temperature of the heating chamber, and the temperature of the substrate, respectively to monitor temperature changes in one or more of these components.

[0068] The heating chamber, as used herein, may generally refer to a space or volume within the aerosol-forming device that is configured to at least partly receive or accommodate the aerosol-FTR4068

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[0070] forming article in order to heat it during a usage session. The heating chamber may also be referred to herein as or may comprise a heating volume of the aerosol-forming device. At least a part of the first heating device may define at least a part of the heating chamber. For example, the first heating device may comprise at least two opposing and spaced-apart heating elements which define the heating chamber and / or heating volume, for example as the space between the opposing heating elements.

[0071] The second heating device may include a resistive heating device configured to heat air in the upstream airflow path to at least heat a part of the substrate of the aerosol-forming article by convective heating.

[0072] As used herein, convective heating can relate to heat transfer from a heating device, in particular the second heating device, that involves the movement of hot air or gas to heat the aerosol-forming substrate or article. For instance, the second heating device can be configured to be resistively heated and to heat the air around, for example flowing past a heat exchange element and / or heating element of the second heating device or at least a part thereof. The heated air may then be conveyed or guided through the upstream airflow path towards the heating chamber, where the aerosol-forming article or substrate may be situated. Hence, the aerosolforming substrate or article can be heated by the flow of hot or heated air generated by the second heating device. The airflow for efficiently heating the aerosol-forming article or substrate may be provided or driven by the actual user inhalation or puff.

[0073] The change in the temperature of one or both the first heating device and the second heating device, which can be determined or detected by the control circuitry, can be associated with a change in an airflow past the first heating device, the heating chamber and / or the second heating device caused by the user inhalation. As mentioned above, when the user inhales or puffs, air may be sucked through one or more air inlets and into the upstream airflow path. The airflow through the upstream airflow path can then pass the second heating device, the first heating device and / or the heating chamber. Thereby, the airflow can cause a decrease in the temperature of one of or both the first heating device and the second heating device, thereby indicating start or onset of the user inhalation. Likewise, when the user stops inhaling, the airflow through the upstream airflow path and past the first heating device, the second heating device and / or the heating chamber stops, which can lead to an increase in the temperature of one or both the first heating device and the second heating device that can be detected by the control circuitry, thereby indicating termination or end of the user inhalation.

[0074] As used herein, the control circuitry being configured to control a power supply to one of or both the first heating device and the second heating device “based on determining a change in a temperature of one of or both the first heating device and the second heating device associated with a change in an airflow through the upstream airflow path caused by the user inhalation” is toFTR4068

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[0076] be construed broadly. In particular, the control circuitry does not necessarily have to determine one or more changes in the temperature, but any one or more operational parameter or quantity indicative of or correlating with the temperature of one of or both the first heating device and the second heating device may be used by the control circuitry to determine the change in the temperature.

[0077] In an example, the electrical resistance of one of or both the first heating device and second heating device may correlate with or be indicative of the temperature of the respective first and / or second heating device. Hence, a change in temperature may be determined by the control circuitry based on determining a change in the electrical resistance of one of or both the first heating device and the second heating device.

[0078] In a further example, the aerosol-forming device may comprise a temperature control mechanism, which may mean that the temperature of one of or both the first heating device and the second heating device may be substantially kept at a particular value during operation or during a usage session or at least part thereof. If the temperature of at least one of the first and second heating device changes, the change in temperature may be compensated by the temperature control mechanism based on adjusting the electrical power or energy per unit time provided to the respective first and / or second heating device. In particular, a decrease in temperature may be compensated by provision of a higher electrical power, power supply or energy per unit time to the respective first and / or second heating device, and vice versa. Hence, a change in temperature of at least one of the first and second heating device may be determined by the control circuitry based on determining a change in the power consumption or energy consumption per unit time of the respective at least one of the first and second heating device.

[0079] The control circuitry can be configured to determine the change in the temperature of the first heating device based on determining or measuring a change in an electrical resistance of the first heating device. Alternatively or additionally, the control circuitry can be configured to determine the change in the temperature of the second heating device based on determining a change in an electrical resistance of the second heating device. Hence, the temperature of one of or both the first heating device and the second heating device can be determined based on measuring or determining an electrical resistance of the respective first and / or second heating device, in case a material is chosen for the first and / or second heating device that changes its resistivity with temperature. Thus, a dedicated or separate temperature sensor may not be required, which can save space in the device for other components and can reduce the overall energy consumption of the device.

[0080] For example, the electrical resistance of the first and / or second heating device, respectively, a change thereof, can be measured or determined by the control circuitry by or based on one or more of determining a voltage across the first and / or second heating device, determining a currentFTR4068

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[0082] across the first and / or second heating device, and determining a voltage drop across a shunt resistor.

[0083] For certain materials, the electrical resistance of a material depends on the temperature of the material, which particularly applies to electrically conductive materials that show an increase in the electrical resistance with increasing temperature. Therefore, the temperature of one of or both the first heating device and the second heating device can be precisely and reliably determined based on determining or measuring the electrical resistance thereof. Similarly, also changes in the temperature of the first heating device and / or the second heating device can be reliably and precisely determined based on determining changes in the electrical resistance of the respective first and / or second heating device.

[0084] It should be noted that any reference to a “resistance” in the following, relates to the electrical resistance, unless explicitly stated otherwise.

[0085] Also, any reference to or disclosure related to a determination or measurement of a temperature of one or both the first heating device and the second heating device can include a determination or measurement of the electrical resistance of the respective one of or both the first heating device and the second heating device, and vice versa.

[0086] Optionally, one or more conversion or calibration values for computing one or more temperature values based on determined one or more resistance values may be stored in a data storage or memory of the aerosol-forming device, for example in the form of a look-up table, correlation table, correspondence table, or matrix. The control circuitry may access or process the one or more conversion or calibration values to compute temperature values based on determined resistance values. Alternatively or additionally, one or more conversion or calibration values for computing one or more resistance values based on determined one or more temperature values may be stored in a data storage or memory of the aerosol-forming device, for example in the form of a look-up table, conversion table or matrix. The control circuitry may access or process the one or more conversion or calibration values to compute resistance values based on determined temperature values.

[0087] In an example, the control circuitry can be configured to determine a decrease in the temperature of the first heating device based on determining a decrease in an electrical resistance of the first heating device. Alternatively or additionally, the control circuitry can be configured to determine an increase in the temperature of the first heating device based on determining an increase in an electrical resistance of the first heating device.

[0088] In a further example, the control circuitry can be configured to determine a decrease in the temperature of the second heating device based on determining a decrease in an electrical resistance of the second heating device. Alternatively or additionally, the control circuitry can beFTR4068

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[0090] configured to determine an increase in the temperature of the second heating device based on determining an increase in an electrical resistance of the second heating device.

[0091] In an example, the control circuitry can be configured to determine the change in the temperature of at least one of the first heating device and the second heating device based on at least one temperature sensor. Also a plurality of temperature sensors may be utilized, for example at least one for sensing the temperature of the first heating device, and at least one further temperature sensor for sensing the temperature of the second heating device.

[0092] The control circuitry can further be configured to control the power supply from the power source or energy storage to the first heating device based on determining a change in the temperature of the second heating device. Optionally, the control circuitry can be configured to determine or detect a user inhalation based on determining a change in the temperature of the second heating device, for example a decrease or increase in temperature, and control the power supply from the power source or energy storage to the first heating device based on the detected user inhalation. Accordingly, the control circuitry may be configured to detect the user inhalation using the second heating device, and to control the power supply to the first heating device based thereon.

[0093] Therein, controlling the power supply can include one or more of activating the power supply to the first heating device, increasing an amount of electrical power or energy supplied to the first heating device, decreasing an amount of electrical power or energy supplied to the first heating device, and deactivating the power supply to the first heating device.

[0094] At least in some configurations or designs, the second heating device may have a lower thermal mass compared to the first heating device. This can be particularly true in case the second heating device is designed or configured as convective heater that can heat the aerosol-forming article or substrate by convective heating. Due to the lower thermal mass, the temperature of the second heating device may adapt more quickly to the temperature of the air surrounding or flowing past the second heating device, when compared to the first heating device. Hence, a response time for detecting an actual change in the temperature of the second heating device, and hence a response time for detecting the user inhalation, can be reduced by using the second heating device compared to relying on the first heating device, at least in certain designs and configurations of the first and second heating devices. Hence, utilizing the second heating device as temperature sensor and / or as puff detection sensor, can allow for a fast and precise control of the first heating device or aerosol-forming device in general.

[0095] Alternatively, however, the control circuitry can be configured to control the power supply from the power source to the second heating device based on determining the change in the temperature of the first heating device. Optionally, the control circuitry can be configured to determine or detect the user inhalation based on determining the change in the temperature ofFTR4068

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[0097] the first heating device, for example a decrease and / or increase in temperature, and control the power supply from the power source or energy storage to the second heating device based on the detected user inhalation. Accordingly, the control circuitry may be configured to detect the user inhalation using the first heating device, and to control the power supply to the second heating device based thereon.

[0098] The control circuitry can be configured to determine the change in the temperature of at least one of the first heating device and the second heating device based on two or more consecutive measurements of the temperature of at least one of the first heating device and the second heating device. Optionally, the control circuitry can be configured to perform the two or more measurements within a predetermined period of time or time window. Accordingly, two or more measurements may be performed at different times, optionally within a predetermined period of time. For example, the control circuitry may be configured to perform two or more measurements of the temperature of the first heating device and / or the second heating device within a predetermined period of time of less than about 250 ms, less than about 200 ms, less than about 150 ms, for example less than about 100 ms, in particular less than about 50 ms, preferably less than about 25 ms, and even more preferably less than about 10 ms or even less than about 5 ms. This may allow to reliably and quickly detect the start or onset of the user inhalation, as well as termination thereof. One or more of such predetermined periods of time may be stored in a data storage or memory of the device.

[0099] Further optionally, one or more threshold values for one or more changes in the temperature of one or both the first heating device and the second heating device may be utilized by the control circuitry to detect one or more user inhalations, in particular to detect one or more of a start or onset of the user inhalation, a duration of the user inhalation, a termination or end of the user inhalation, and an occurrence of the user inhalation. For example, the control circuitry may be configured to detect a user inhalation based on determining a change in the temperature of one of or both the first heating device and the second heating device, which determined change reaches or exceeds one or more predefined threshold values for the change in temperature, optionally within a predetermined period of time. Since changes in the temperature can include increases and decreases, either the same or different threshold values for an increase and decrease in the temperature of one of or both the first and second heating device can be utilized by the control circuitry, and for example stored in a data storage or memory thereof. Therein, the one or more threshold values may be absolute threshold values or relative threshold values.

[0100] Alternatively or additionally, the control circuitry may be configured to determine a change in temperature of one of or both the first and second heating device based on sampling, monitoring or repeatedly measuring the temperature of one of or both the first and second heating device, and based on spectral analysis of the sampled or measured temperature values. ForFTR4068

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[0102] example, a first order derivative, a second order derivative and / or one or more higher orders of derivative with respect to time may be computed by the control circuitry to detect a change in the temperature of one of or both the first and second heating device.

[0103] For example, one or more absolute threshold values for a change, decrease and / or increase in temperature of the first heating device and / or the second heating device may be about 5°C to about 150°C, for example about 10°C to about 100°C, in particular about 15°C to about 50°C. Optionally, negative threshold values may be used for the decrease. Alternatively or additionally, one or more relative threshold values for relative a change, decrease and / or increase in the temperature of the first heating device and / or the second heating device may be about 5% to about 50%, for example about 10% to about 30%, in particular about 15% to about 20%.

[0104] In an example, the control circuitry may be configured to monitor, determine, measure and / or sample, during at least a part of a user inhalation, one or more user inhalations and / or one or more usage sessions, the temperature of one of or both the first and second heating device. Alternatively or additionally, any other one or more parameters correlating with the temperature of the first and / or second heating device may be monitored, determined, measured and / or sampled during at least a part of a user inhalation, one or more user inhalations and / or one or more usage sessions. For example, one or more of electrical resistance and power supplied to or consumed by one of or both the first and second heating devices may be monitored, determined, measured and / or sampled during at least a part of a user inhalation, one or more user inhalations and / or one or more usage sessions. Optionally, corresponding data indicative of the timely evolution of the monitored or sampled temperature and / or one or more other parameters may be recorded by the aerosol-forming device.

[0105] In a further optional implementation, the data indicative of the timely evolution of the monitored or sampled temperature and / or one or more other parameters, for example recorded or sampled during at least a part of a user inhalation, one or more user inhalations and / or one or more usage sessions, can be evaluated or analyzed by the control circuitry to determine one or more characteristics of one or more user inhalations and / or one or more usage sessions. Such evaluation or analysis can optionally include spectral analysis of the sampled or measured values. For example, a first order derivative, a second order derivative and / or one or more higher orders of derivative with respect to time may be computed by the control circuitry to derive one or more characteristics of one or more user inhalations and / or one or more usage sessions. By way of example, the control circuitry may be configured to determine one or more of a flow velocity, flow profile, or speed of air drawn in one or more user inhalations, a duration of one or more user inhalations and / or usage sessions, a timing of one or more user inhalations, an air pressure during one or more user inhalations, an air volume drawn in one or more user inhalations and / or usage sessions, a puff duration, a puff rate, a puff frequency, or other parameters. Accordingly, a flow-FTR4068

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[0107] sensor or other sensor may be implemented based on evaluating or analyzing data indicative of the timely evolution of the monitored or sampled temperature and / or one or more other parameters, such as electrical power supplied, power consumed and / or electrical resistance, for example recorded or sampled during at least a part of a user inhalation, one or more user inhalations and / or usage session.

[0108] In an example, the control circuitry may be configured to determine or detect a start or onset of a user inhalation based on two or more consecutive temperature measurements of the temperature of one of or both the first heating device and the second heating device, the two or more measurements being performed within a first period of time. Therein, the control circuitry may be configured to compute the difference, for example relative or absolute difference, between the two or more measured temperatures or temperature values, and hence compute the temperature increase, and compare the difference to at least one first threshold value, which may be a relative or absolute threshold value. Upon determining or confirming that the computed difference reaches or exceeds the threshold value, the control circuitry may determine or detect the user inhalation, respectively its start, onset or occurrence.

[0109] Further optionally, the control circuitry may be configured to determine or detect termination or the end of the user inhalation based on further two or more consecutive temperature measurements of the temperature of one of or both the first heating device and the second heating device, the further two or more measurements being performed within a second period of time, which may be equal to or differ from the first period of time. Therein, the control circuitry may be configured to compute the difference, for example relative or absolute difference, between the two or more measured temperatures or temperature values, and hence compute the temperature decrease, and compare the difference to at least one second threshold value, which may be a relative or absolute threshold value. The second threshold value may be equal to or differ from the first threshold value. Upon determining or confirming that the computed difference reaches or exceeds the threshold value, the control circuitry may determine or detect the user inhalation, respectively its termination or end.

[0110] Further optionally, the control circuitry may compute a duration of the user inhalation based on time information associated with the determination of the increase and the decrease in the temperature.

[0111] In an example, the control circuitry can be configured to determine the change in the temperature of at least one of the first heating device and the second heating device with respect to a reference temperature, also referred to as reference temperature value, of the respective at least one of the first heating device and the second heating device. For example, the control circuitry may be configured to determine the change in the temperature of the first heating device with respect to a reference temperature of the first heating device. Alternatively or additionally,FTR4068

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[0113] the control circuitry may be configured to determine the change in the temperature of the second heating device with respect to a reference temperature of the second heating device. Therein, the same reference value may be utilized for the first and second heating devices, or for different reference temperatures may be used for the first and second heating devices.

[0114] The one or more of reference temperatures or reference temperature values may be stored in a data storage or memory of the aerosol-forming device, either in the form of actual temperature values or in the form of one or more reference resistance values for the first and / or second heating devices, which can optionally be converted by the control circuitry into reference temperature values, respectively, which allow to compute the corresponding reference temperature values by the control circuitry.

[0115] For example, one or more reference temperatures and / or reference resistance values may be experimentally determined for one of or both the first heating device and the second heating device, for example in one or more calibration measurements at one or more predetermined temperatures. Alternatively or additionally, a reference value may be provided by one of two or more measurements of the temperature or resistance performed by the control circuitry to detect a change, respectively, a decrease or increase in the temperature, as described above. For example, the first measurement among a plurality of measurements of the temperature or resistance of the first and / or second heating device may serve as reference value to determine or compute the change in temperature.

[0116] Also, it is noted that the change in the temperature of at least one of the first heating device and the second heating device can be determined by the control circuitry as a relative change, for example relative to the situation where no user inhalation occurs, such as at a time before or shortly before start of the user inhalation. For instance, the change in the temperature of at least one of the first heating device and the second heating device can have a particular value when the device is switched on and heated in order to be used in a usage session. The temperature and / or resistance of at least one of the first heating device and the second heating device, for example when the device is ready for being used by the user and / or before the first user inhalation occurs in a usage session, can be used as baseline or reference for detecting the actual change in the temperature and / or resistance of one or both the first heating device and the second heating device. Accordingly, the change in the temperature of at least one of the first heating device and the second heating device can refer to a change of the temperature of the respective heating device occurring during the user inhalation with respect to or compared to the temperature of the respective heating device before start of the user inhalation, for example at the start of a usage session, preferably when the device is heated-up and / or ready for being used in one or more user inhalations.FTR4068

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[0118] Generally, one or more of the reference temperature of the first heating device and the reference temperature of the second heating device can be determined or set by the control circuitry based on or by determining the ambient air temperature, respectively, the temperature of the ambient air surrounding the device or being in the external environment of the device, for example based on a measurement at the start of a usage session and / or when activating the aerosol-forming device. This can enhance the reliability of the detection of the temperature change and / or the detection of the user inhalation. Also, a detection reaction time that may be required to actually detect a user inhalation after its start can be consistent for different temperatures of the ambient air.

[0119] The first heating operation performed by the first heating device can differ from the second heating operation performed by the second heating device. In other words, the first and second heating devices can perform different heating operations. This may allow for precise temperature control, which can be beneficial in terms of taste and user experience. Also, a more energy efficient and / or more rapid heating may be provided when using two heating devices that are configured to perform different heating operations rather using heating device that perform the same heating operation.

[0120] In an example, the second heating device may be configured to perform a puff-on-demand heating operation. Alternatively or additionally, the control circuitry can be configured to control the second heating device to perform a puff-on-demand heating operation. For example, the second heating device may only be powered or supplied with electrical energy during a user inhalation or while a user inhalation occurs at the aerosol-forming device. Alternatively or additionally, the second heating device may be deactivated or switched off when no user inhalation occurs or is performed. Alternatively, the second heating device may be operated or powered at a lower power level at times when no user inhalation occurs or is performed, compared to times when a user inhalation occurs or is performed by the user. Generally, operating the second heating device in a puff-on-demand heating operation can allow to reduce energy consumption. Also, a boost in temperature during the user inhalation can be provided, thereby allowing to rapidly heat-up the substrate to generate aerosol inhalable by the user.

[0121] The first heating device can be configured to perform a continuous heating operation during a usage session. Alternatively or additionally, the control circuitry can be configured to control the first heating device to perform a continuous heating operation during a usage session. For example, the first heating device may be continuously powered by the power source or may be continuously supplied with electrical power during the usage session. Therein, “continuous heating” may include heating the first heating device with pulses of voltage and / or current having a comparatively high repetition or pulse frequency, for example a pulse frequency in the range of deciseconds, milliseconds, microseconds or even higher. For example, continuous heating manyFTR4068

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[0123] include heating based on pulse width modulation, bang-bang or hysteresis control mode, sliding control mode, or other type of on-off control mode.

[0124] The control circuitry can further be configured to control or operate the first heating device according to a first heating profile, and to control or operate the second heating device according to a second heating profile, wherein the first heating profile differs from the second heating profile. In particular, the first and second heating profiles each can define an evolution or course of the temperature of the respective heating device overtime during a usage session. For instance, the first and / or second heating profile may define one or more target temperatures that should be reached by the respective first and / or second heating device after a certain period of time during the usage session or from the start of the usage session. The first heating profile can instruct the control circuitry to control the temperature of the first heating device according to the first heating profile, and / or the second heating profile can instruct the control circuitry to control the temperature of the second heating device according to the second heating profile.

[0125] By way of example, the first heating profile may define that the first heating device shall perform a continues heating at one or more target temperatures or temperature values during the usage session, for example, which one or more target temperatures should be reached during one or more predetermined periods of time from the start of a usage session. Alternatively or additionally, the second heating profile may define one or more target temperatures or temperature values to which the second heating device shall be heated or operated during a puff, and optionally one or more further temperature values at which the second heating device shall be shall be heated or operated in absence of a user inhalation during the usage session.

[0126] The control circuitry can further be configured to, based on controlling the power supply from the power source to the second heating device, operate the second heating device at a first power level to heat the second heating device to a pre-heating temperature above ambient temperature and below a target temperature, wherein the control circuitry can be configured to determine the change in the temperature or monitor the temperature of the second heating device when the second heating device is operated at the first power level. Optionally, the control circuitry can be configured to detect the user inhalation when the second heating device is operated at the first power level. Alternatively or additionally, the control circuitry may be configured to power the second heating device at the first power level in order to detect a user inhalation at the aerosolforming device. For instance, the second heating device may be powered at the first power level while no puff or user inhalation occurs at the device, but optionally after start or activation of the device to be used in a usage session.

[0127] As used herein, “powering” the first and / or second heating device to the first power level may mean or include supplying electrical power to the first and / or second heating device at the first power level, such that the first and / or second heating device is heated to the pre-heatingFTR4068

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[0129] temperature. This can include one or more of supplying a voltage at a first power level and a current at a first level to the first and / or second heating device. Alternatively or additionally, this can involve adjusting a duty cycle of the first and / or second heating device, such that the first and / or second heating device is heated to the pre-heating temperature.

[0130] Further, powering the first and / or second heating device at a second power level may mean or include supplying electrical power to the first and / or second heating device at the second power level, such that the first and / or second heating device is heated to a target temperature, for example to at least a volatilization temperature or vaporization temperature of one or more ingredients or components of the aerosol-forming substrate. This can include one or more of supplying a voltage at a second power level and a current at a second level to the first and / or second heating device. Alternatively or additionally, this can involve adjusting a duty cycle of the first and / or second heating device, such that the first and / or second heating device is heated to the target temperature, for example to at least the volatilization temperature or vaporization temperature.

[0131] The volatilization temperature may also be referred to as vaporization temperature and may denote a temperature sufficient to vaporize one or more ingredients from the substrate. The preheating temperature may be selected such that the temperature of the second heating device, and optionally of the substrate or article, is between an ambient temperature of the surrounding air and the volatilization temperature of the one or more ingredients of the substrate. Pre-heating above ambient or room temperature can increase the cooling effect that can be departed by the user inhalation, which can then be detected by the control circuitry with high accuracy and within a short reaction time based on detecting the corresponding change or decrease in temperature of at least one of the first and second heating device. Also, pre-heating below the volatilization temperature can ensure that no or only neglectable vaporization and / or degradation of the substrate material occurs at times where the user is not puffing or inhaling.

[0132] Moreover, pre-heating the second heating device for puff detection, respectively, for detecting the user inhalation, more specifically to detect a start of the inhalation or puff, can also allow to have the aerosol-forming substrate at an elevated temperature above the room temperature before the puff or user inhalation, but still before any vaporization of the one or more ingredients of the substrate occurs. This can allow to shorten a response time for vaporizing the substance or substrate material, which can improve the user experience. In addition, a liquid substrate material can be brought into a less viscous state by the pre-heating, which can bring advantages for vaporization, liquid delivery and aerosol formation.

[0133] Generally, the higher the pre-heating temperature of the second heating device and / or substrate is relative to the environmental, ambient or room temperature, the better or faster may be the detection response for detecting the user inhalation, because the cooling effect caused byFTR4068

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[0135] the user inhalation increases with higher temperature difference or gradient between the airflow drawn by the user and the second heating device. On the other hand, the lower the temperature difference or gradient is, the less energy may be required for the pre-heating. Accordingly, the pre-heating temperature should preferably be chosen to balance these effects.

[0136] By way of example, the pre-heating temperature may be above about 25°C, above about 30°C, preferably above about 40°C, more preferably above about 50°C, and even more preferably above about 60°C. Such temperatures may allow for an accurate detection of the user inhalation within a short period of time.

[0137] Alternatively or additionally, the pre-heating temperature may be below about 120°C, below about 100°C, preferably below about 90°C, more preferably below about 80°C, and even more preferably below about 70°C. Such temperatures may avoid degradation or vaporization of substrate material. For example, with temperatures below 100°C, the vaporization of water that might be present in the substrate can be prevented. Exemplary ranges for the pre-heating temperature may be about 50°C to about 100°C, preferably about 60°C to about 80°C, more preferably about 60°C and about 70°C.

[0138] Optionally, the control circuitry may be configured to determine the ambient temperature and adjust the pre-heating temperature in accordance with the ambient temperature. For instance, in cool areas or locations, a lower pre-heating temperature may be used compared to areas or locations with higher temperature.

[0139] The control circuitry may be configured to monitor or determine the temperature and / or resistance of the second heating device, when the second heating device is powered to the first power level, alternatively or additionally, when the second heating device and / or substrate has reached the pre-heating temperature. For instance, the control circuitry may be configured to monitor or determine the temperature and / or resistance of the second heating device upon powering the second heating device to the first power level and / or upon reaching the pre-heating temperature with the second heating device.

[0140] The control circuitry may be configured to power the second heating device to the first power level in response to one or more of:

[0141] a sensor signal of at least one sensor of the aerosol-forming device;

[0142] insertion of an aerosol-forming article at least partly into the aerosol-forming device; coupling of an aerosol-forming article to the aerosol-forming device;

[0143] mechanical decoupling of the aerosol-forming device from a companion device; and a control signal from one or more user interfaces triggered by a user of the aerosol-forming device. Such events or actions may reliably indicate the user’s intention to activate or use the aerosol-forming device for aerosol consumption, and hence may constitute reliable triggers for the control circuitry to power the second heating device to the first power level.FTR4068

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[0145] In an example, one or more sensors configured to provide a sensor signal indicative of a potential imminent use of the aerosol-forming device for aerosol-consumption may be used to trigger powering one of or both the first heating device and the second heating device at the first power level. Such potential imminent use of the device may be indicative of a potential imminent user inhalation or puff taken by the user. Non-limiting examples of sensors that could be used for this purpose include, accelerometers, motion detection sensors, inertial sensors, gyroscopes, presence detection sensors, proximity detection sensors, near field sensors, touch sensors, capacitive sensors and others.

[0146] For example, the control circuitry can be configured to configure or operate the aerosolforming device, and in particular the second heating device, in a “dummy heating mode”, upon or in response to detecting one or more of the aforementioned events or actions, respectively, upon activating the aerosol-forming device. Optionally, the first heating device can be configured into a “maintenance heating mode”, upon or in response to detecting one or more of the aforementioned events or actions, respectively, upon activating the aerosol-forming device. In the maintenance heating mode, the first heating device can initiate heating of the substrate to one or more predefined target temperatures, for example as defined in a first heating profile. Therein, configuring the aerosol-forming device, the first heating device and / or second heating device into a particular heating mode, or another mode of the device described herein, can include or refer to switching the device, by the control circuitry, into the respective mode. Optionally, this can comprise loading or setting one or more settings of the device.

[0147] In the dummy heating mode and / or while powering the second heating device at the first power level, the aerosol-forming device or its control circuitry can be enabled to detect the first user inhalation in the usage session, and optionally one or more further user inhalations. This can be done without causing vaporization or meaningful vaporization of the substrate material due to the heat generated by the second heating device, as the second device is only heated to the preheating temperature. At the same time, the first heating device can be in the maintenance heating mode and the control circuitry can be configured to maintain the first heating device, and optionally the substrate, at one or more target temperatures during the usage session, which one or more target temperatures may be above the vaporization temperature of the substrate material. Accordingly, the first heating device may maintain the substrate at a temperature sufficiently high to generate aerosol, while the second heating device may only be powered to the first power level or the pre-heating temperature below the vaporization temperature in order to detect the first and / or one or more further user inhalation in a usage session.

[0148] Upon detecting a user inhalation at the aerosol-forming device by the control circuitry based on detecting a change or decrease in temperature of the second heating device, the control circuitry can increase, for example immediately increase, the power level supplied to the secondFTR4068

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[0150] heating device to the second power level above the first power level, such that the temperature of the second heating device increases to a value of or above the volatilization temperature. As a consequence, also the air flowing past or around the second heating device is raised, which ultimately reaches the aerosol-forming substrate and heats it by convective heating. Hence, upon detecting the user inhalation, the power supplied to the second heating device can be increased to allow for a rapid heating of the incoming airflow past the second heating device caused by the user inhalation, for example to avoid any delay in the heating. This operational mode of the second heating device may also be referred to as “air heating mode” that is activated upon detecting a user inhalation, respectively, during a puff or user inhalation. Accordingly, the second heating device may provide a boost in heat or thermal energy during a user inhalation. Overall, this can allow for energy efficient operation of the device, while also improving user experience and taste.

[0151] For example, when powering the second heating device at the second power level, the temperature of the heat exchange element and / or resistive heating element of the second heating device can increase about 100°C within about 0.05 to 1 seconds, or about 100°C within about 0.05 to 0.5 seconds, for example about 100°C within 0.075 to 0.25 seconds, preferably about 100°C within about 0.1 to 0.2 seconds.

[0152] The control circuitry may continue to monitor the temperature of the second heating device while the second heating device is powered at the second power level. Upon determining that the puff or user inhalation has ended, for example by a further change in the temperature of the heat exchange element of the second heating device, in particular an increase in temperature, the control circuitry may either cut a power supply to the second heating device completely or reduce the power to the first power level again in order to detect the next or subsequent user inhalation, and optionally increase the power level again upon detecting the subsequent user inhalation. It should be noted that powering the second heating device at the first power level may not be necessary, in particular not for the second and further user inhalations during a usage session, because the second heating device may be at an elevated temperature above room temperature after the first user inhalation and after the second heating device has been powered to the first and second power levels at least once. Optionally, however, also for the second and one or more further user inhalations of a usage session, the second heating device may be powered at the first power level, when no user inhalation occurs.

[0153] As mentioned above, the second heating device may have a lower thermal mass and thermal capacity than the first heating device that can be used to conductively heat the aerosolforming substrate at the heating chamber. Hence, utilizing the second heating device as puff detector in the dummy heating mode can allow for a faster response time and detection time to detect user inhalations, compared to using the first heating device. Nonetheless, the sameFTR4068

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[0155] principle can be applied with reverse functionalities of the first and second heating device, as will also be described hereinbelow.

[0156] The control circuitry may be configured to operate the second heating device at the first power level based on supplying a first DC voltage and / or current to the second heating device that is smaller than a second DC voltage and / or current supplied by the control circuitry to the second heating device to heat the second heating device to a target temperature, for example a target temperature of the second heating device that should be reached during occurrence of a puff, such as a target temperature of about or above the volatilization temperature. The second voltage and / or current may be supplied when powering the second heating device at the second power level. Alternatively or additionally, the control circuitry may be configured to power the second heating device to the first power level based on operating the second heating device at a first duty ratio that is smaller than a second duty ratio supplied by the control circuitry to the second heating device when powering the second heating device at the second power level, for example to heat the aerosol-forming article to form aerosol.

[0157] The control circuitry can further be configured to, in response to detecting the change, for example decrease, in the temperature of the second heating device, operate the second heating device at the second power level for heating the second heating device to the target temperature to form aerosol from the aerosol-forming article.

[0158] Optionally, the control circuitry can be configured to, in response to detecting the change or decrease in the temperature of the second heating device, operate the first heating device to heat the aerosol-forming article to a volatilization or vaporization temperature sufficient to release aerosol from the aerosol-forming article. Accordingly, also the temperature of the first heating device may be boosted upon detecting occurrence of the user inhalation based on detecting one or more temperature changes of the second heating device.

[0159] In particular, the control circuitry may be configured to increase the heating power or energy supplied to the second heating device, and optionally also the first heating device, immediately upon detecting the puff or user inhalation. The increase in the heating power from the first power level to the second power level can be implemented or provided in various ways. For example, a DC supply voltage to the second heating device may be increased by means of a DC-DC converter. Another way would be to increase the duty cycle, for example by an immediate increase of the on time during periodic heating intervals. Other implementations, however, are possible and envisaged by the present disclosure.

[0160] In an example, the first power level is below about 80%, below about 70%, below about 60%, below about 50%, below about 40%, below about 30%, below about 20%, below about 10%, below about 5%, or below about 2% of the second power level. Accordingly, powering the second heating device at the first power level to detect the user inhalation, may only require aFTR4068

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[0162] fraction of the energy or power required to power the second heating device at the second power level during a puff to generate aerosol. Hence, a significant amount of electrical energy can be saved by this approach.

[0163] In an example, the target temperature of the of the first heating device, can be above about 200°C, above about 250°C, above about 270°C, preferably above about 280°C, more preferably above about 290°C, even more preferably about 300°C. For example, the target temperature can be between about 50°C and 300°C, more preferably between about 100°C to 300°C.

[0164] For example, when increasing the temperature of the second heating device upon detecting a user inhalation, the temperature of the second heating device and / or substrate can increase about 100°C within about 0.05 to 1 seconds, for example about 100°C within about 0.05 to 0.5 seconds, or for example about 100°C within 0.075 to 0.25 seconds, preferably about 100°C within about 0.1 to 0.2 seconds. In an example, the temperature of the second heating device may increase from ambient temperature to about 300°C within about 100 ms and / or to about 500°C within about 700 ms.

[0165] A target temperature of the second heating device, to which it may be heated during occurrence of a user inhalation, may be in a range from about 270°C to about 500°C, for example from about 270°C to about 450°C, or for example from about 270°C to about 320°C, in particular from about 280°C to about 310°C, preferably about 300°C. These temperature ranges have been found to lead to rapid heating of the substrate at minimum risk for overheating.

[0166] The control circuitry can further be configured to, based on controlling the power supply from the power source to the first heating device, operate the first heating device at a first power level to heat the first heating device to a pre-heating temperature above ambient temperature and below an volatilization or vaporization temperature sufficient to release aerosol from the aerosolforming article, wherein the control circuitry can be configured to determine the change, for example decrease, in the temperature or monitor the temperature of the first heating device when the first heating device is operated at the first power level. Optionally, the control circuitry can be configured to detect the user inhalation when the first heating device is operated at the first power level.

[0167] As mentioned above, the roles of the first and second heating devices can be reversed, such that the first heating device can be operated in a dummy heating mode to detect the user inhalation or puff, and optionally the second heating device can be operated in the maintenance heating mode to maintain the substrate at an elevated temperature throughout the usage session.

[0168] As for the preheating of the second heating device, a pre-heating temperature of the first heating device can be above about 25°C, above about 30°C, preferably above about 40°C, more preferably above about 50°C, and even more preferably above about 60°C. Alternatively or additionally, the pre-heating temperature of the first heating device may be below about 120°C,FTR4068

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[0170] below about 100°C, preferably below about 90°C, more preferably below about 80°C, and even more preferably below about 70°C.

[0171] The control circuitry can be configured to operate the first heating device at the first power level based on supplying a first DC voltage and / or current to the first heating device that is smaller than a second DC voltage and / or current supplied by the control circuitry to the first heating device to heat the first heating device to a target temperature of the first heating device. Alternatively or additionally, the control circuitry can be configured to, in response to detecting the change or decrease in the temperature of the first heating device, operate the first heating device at a second power level for heating the first heating device to a target temperature to form aerosol from the aerosol-forming article. The second voltage and / or current may be supplied when powering the first heating device at the second power level. Alternatively or additionally, the control circuitry may be configured to power the first heating device to the first power level based on operating the first heating device at a first duty ratio that is smaller than a second duty ratio supplied by the control circuitry to the first heating device when powering the first heating device at the second power level, for example to heat the aerosol-forming article to form aerosol.

[0172] Generally, the target temperature of the first heating device and the target temperature of the second heating device may be substantially equal to or may exceed the volatilization or vaporization temperature that is required to release inhalable aerosol from the substrate. Further, the target temperature of the first heating device may substantially correspond to the target temperature of the second heating device. Alternatively, the target temperature of the first heating device may be lower than the target temperature of the second heating device. Also, it should be noted that a plurality of target temperatures may be used for the first and / or second heating devices. For instance, different target temperatures may be applied at different phases or stages of a usage session. While the different target temperatures used for the first and second heating devices may differ from one another, all target temperatures may at least correspond to the volatilization temperature of the substate or article, or exceed the volatilization temperature.

[0173] In an example, the first power level supplied to the first heating device can be below about 80%, below about 70%, below about 60%, below about 50%, below about 40%, below about 30%, below about 20%, below about 10%, below about 5%, or below about 2% of the second power level. Accordingly, powering the first heating device at the first power level to detect the user inhalation, may only require a fraction of the energy or power required to power the first heating device at the second power level during a puff to generate aerosol. Hence, a significant amount of electrical energy can be saved by this approach.

[0174] In another example, the control circuitry can be configured to, in response to detecting the change or decrease in the temperature of the first heating device, operate the first and / or second heating device to heat the first and / or second heating device to a target temperature, preferablyFTR4068

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[0176] wherein the target temperature of the first and / or second heating device is above about 200°C, above about 250°C, above about 270°C, preferably above about 280°C, more preferably above about 290°C, even more preferably about 300°C.

[0177] A target temperature of the second heating device, to which it may be heated during occurrence of a user inhalation, may be in a range from about 270°C to about 500°C, for example from about 270°C to about 450°C, or for example from about 270°C to about 320°C, in particular from about 280°C to about 310°C, preferably about 300°C. These temperature ranges have been found to lead to rapid heating of the substrate at minimum risk for overheating.

[0178] As described above for the second heating device, the control circuitry can be configured to operate one of or both the first heating device and the second heating device at the first power level in response to one or more of:

[0179] a sensor signal of at least one sensor of the aerosol-forming device;

[0180] insertion of an aerosol-forming article at least partly into the aerosol-forming device; coupling of an aerosol-forming article to the aerosol-forming device;

[0181] mechanical decoupling of the aerosol-forming device from a companion device; and a control signal from one or more user interfaces triggered by a user of the aerosol-forming device. Such events or actions may reliably indicate the user’s intention to activate or use the aerosol-forming device for aerosol consumption, and hence may constitute reliable triggers for the control circuitry to power one of or both the first heating device and the second heating device to the first power level.

[0182] In an example, the at least one sensor, based on which the control circuitry may power the one of or both the first heating device and the second heating device to the first power level, can include one or more of a motion sensor, an accelerometer, a gyroscope, an image sensor, a pyrometer, a presence sensor, a touch sensor or any other sensor or sensing means that allows to detect that the user intends using the device in a usage session.

[0183] By way of example, the control circuitry can configure the first or second heating device in the dummy heating mode in response to the user manually pressing a button, by automatic detection of use of the device based on a motion detector, such as an accelerometer, gyroscope, or camera with analysis of motion, or other type of motion detector such as pyrometer motion detector, detecting that the user has picked-up the device, presence detection of the user, touch detection, or proximity sensing to detect that the user has taken the device into his or her hands and / or is holding the device. It is also possible that the insertion of an aerosol-forming article triggers the dummy heating mode for the first and / or second heating device, or some other engagement of the aerosol-forming article with the heating chamber. The latter may be of particular advantage in Heat-not-Burn applications, where usually the aerosol-forming article isFTR4068

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[0185] replaced for the next usage session, respectively, a new aerosol-forming article is inserted to start the usage session.

[0186] The control circuitry can further be configured to determine an end of the user inhalation and / or whether the user inhalation has ended based on determining a further change, for example an increase, in the temperature of at least one of the first heating device and the second heating device. As discussed hereinabove, when the user stops inhaling, the airflowthrough the upstream airflow path and heating chamber may be reduced or stop, which can lead to a temperature increase of one of or both the first heating device and the second heating device, which, in turn, can be detected by the control circuitry as termination or end of the user inhalation.

[0187] The control circuitry can be configured to decrease the power supplied to at least one of the first heating device and the second heating device from a second power level to a first power level below the second power level in response to determining that the user inhalation has ended. Alternatively or additionally, the control circuitry can be configured to interrupt or stop the power supply to at least one of the first heating device and the second heating device in response to determining that the user inhalation has ended. Once the first and / or second heating devices have been heated to a target temperature during the first puff of a usage session, the temperature of the first and / or second heating device may still be sufficiently high or above the room temperature to allow for the detection of a subsequent or next user inhalation. Optionally, at least one of the first heating device and the second heating device can be powered at the first power level, for example upon detecting termination of a previous user inhalation, to heat the respective heating device to the pre-heating temperature, such that the next or subsequent user inhalation can be quickly and reliably detected.

[0188] The control circuitry can further be configured to determine at least one reference or calibration temperature of at least one of the first heating device and the second heating device, when the power supply to the respective at least one of the first heating device and the second heating device is interrupted or cut. For instance, the at least one reference value may be determined at a fixed ambient temperature and when the respective first and / or second heating device is in thermal equilibrium with the ambient air.

[0189] The aerosol-forming article can have a substantially rectangular parallelepiped, oblong and / or cuboid shape defining two opposing main faces and two opposing side faces or lateral faces, the aerosol-forming article including an aerosol-forming substrate arranged between the two opposing main faces, preferably wherein the aerosol-forming article comprises an air inlet and an air outlet or aerosol-outlet located opposite of each other on the smallest faces of the rectangular parallelepiped shaped aerosol-forming article. The air inlet of the aerosol-forming article may also be referred to herein as upstream air inlet of the article, and the air or aerosol outlet of the article may also be referred to herein as downstream air or aerosol outlet of theFTR4068

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[0191] aerosol-forming article. Generally, however, the present disclosure is not limited to substantially rectangular parallelepiped-shaped aerosol-forming articles, but other geometries, such as for example cylindrical or stick-like shaped aerosol-forming articles, are possible

[0192] The aerosol-forming device may have a longitudinal axis, a transverse axis, and a normal axis, each being transverse, in particular orthogonal, to each other. The longitudinal direction of the aerosol-forming device may be parallel to the longitudinal axis and / or may extend from a proximal end or portion towards a distal end or portion of the aerosol-forming device. Therein, the proximal end or portion may be associated with a downstream element of the device, also referred to as mouthpiece portion, or a mouthpiece that can be contacted by a user’s mouth during aerosol generation or consumption. The longitudinal axis may be coaxial to or define a center axis and / or an insertion axis of the aerosol-forming device for inserting the aerosol-forming article into the device. Unless otherwise stated, a reference to a longitudinal axis may mean the center axis or longitudinal center axis. A transverse direction of the aerosol-forming device may be parallel to the transverse axis, and a normal direction of the aerosol-forming device may be parallel to the normal axis. When the transverse axis and the longitudinal axis of the aerosol-forming device are both arranged, oriented or aligned in a horizontal plane, the normal axis of the aerosol-forming device defines a vertical axis of the aerosol-forming device. Therefore, the normal axis or direction may also be referred to herein as vertical axis or direction of the aerosol-forming device.

[0193] The longitudinal axis of the aerosol-forming device may define or be coaxial to a longitudinal axis of the heating chamber. The transverse axis of the aerosol-forming device may define or be coaxial to a transverse axis of the heating chamber. The normal axis of the aerosol-forming device may define or be coaxial to a normal axis of the heating chamber.

[0194] Accordingly, at least when the aerosol-forming article is at least partly inserted in the heating chamber, the longitudinal axis of the aerosol-forming device may define or be coaxial to a longitudinal axis of the aerosol-forming article. The transverse axis of the aerosol-forming device may define or be coaxial to a transverse axis of the aerosol-forming article. The normal axis of the aerosol-forming device may define or be coaxial to a normal axis of the aerosol-forming article.

[0195] Further, the longitudinal direction may define and / or may be parallel to an insertion direction, along which the aerosol-forming article may be inserted into the heating chamber. Accordingly, the longitudinal axis may define and / or may be parallel to the insertion axis.

[0196] An extension, length or size of the aerosol-forming device, the heating chamber and / or the aerosol-forming article may be longer in longitudinal direction than in directions transverse, for example orthogonal, thereto. Specifically, the aerosol-forming device, the heating chamber and / or the aerosol-forming article, respectively, may have a length measured along the longitudinal direction or axis, a width measured along the transverse direction or axis, and a thickness or height measured along the normal axis or direction of the aerosol-forming device, the heatingFTR4068

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[0198] chamber and / or the aerosol-forming article, respectively. The transverse axis may also be referred to herein as width axis, and the transverse direction may also be referred to herein as width direction. Further, the normal axis may also be referred to herein as height or thickness axis, and the normal direction may also be referred to herein as height or thickness direction of the aerosol-forming device, the heating chamber and / or the aerosol-forming article, respectively.

[0199] The aerosol-forming article may have a substantially rectangular parallelepiped shape. Alternatively or additionally, the aerosol-forming article may be plate-like or cuboid formed. The aerosol-forming article may comprise two opposing main surfaces, which may be substantially flat or planar. When the aerosol-forming article is inserted into the aerosol-forming device, a surface normal vector of the two opposing main surfaces may be parallel to the normal axis of the aerosol-forming device. Further, the aerosol-forming article may comprise two end faces or surfaces, in particular substantially flat or planar end faces, which are arranged opposite to each other and are spaced apart from each other in longitudinal direction of the aerosol-forming device, when the aerosol-forming article is inserted into the aerosol-forming device. The two end faces or surfaces may form the smallest surfaces of the aerosol-forming article, and are thus also referred to as smallest faces or surfaces of the aerosol-forming article. Moreover, the aerosol-forming article may comprise two lateral faces or side faces, in particular substantially flat or planar lateral faces or surfaces, which are arranged opposite to each other and are spaced apart from each other in transverse direction of the aerosol-forming device, when the aerosol-forming article is inserted into the aerosol-forming device. Accordingly, each of the lateral faces or side faces of the aerosol-forming article may have a surface normal vector substantially parallel to the transverse axis of the aerosol-forming device, when the aerosol-forming article is inserted into the aerosol-forming device.

[0200] The heating chamber may have a substantially rectangular parallelepiped shape and / or may be configured to receive a substantially rectangular parallelepiped shaped aerosol-forming article. The heating chamber may comprise two opposing main surfaces, which may be substantially flat or planar. Optionally, each of the two main surfaces may be defined or provided by heating element of the aerosol-forming device, for example a substantially flat or planar heating element. A surface normal vector of the two opposing main surfaces may be parallel to the normal axis of the aerosol-forming device. Further, the heating chamber may comprise two end faces or surfaces, in particular substantially flat or planar end faces, which are arranged opposite to each other and are spaced apart from each other in longitudinal direction of the aerosol-forming device. The two end faces or surfaces may form the smallest surfaces of the heating chamber. It is noted that these surfaces or faces may refer to an open volume provided by the heating chamber. For example, at least one of the end faces or surfaces may be an open end, for example defining an insertion opening for the aerosol-forming article. Moreover, the heating chamber may compriseFTR4068

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[0202] two lateral faces, in particular substantially flat or planar lateral faces or surfaces, which are arranged opposite to each other and are spaced apart from each other in transverse direction of the aerosol-forming device. Accordingly, each of the lateral faces of the heating chamber may have a surface normal vector substantially parallel to the transverse axis of the aerosol-forming device.

[0203] As mentioned above, the aerosol-forming article may have an air inlet, for example arranged at a distal end of the article, and air or aerosol outlet, for example arranged at a proximal end of the article. The air inlet and aerosol-outlet may be located opposite of each other on the smallest faces or surfaces of the substantially rectangular parallelepiped shaped aerosol-forming article. The air inlet and the air outlet and may be spaced apart from each other along the longitudinal direction.

[0204] The aerosol-forming article may have a length, for example as measured along the insertion axis and / or along the longitudinal direction or axis of the aerosol-forming device or article, in a range between 20 mm and 40 mm, preferably between 25 mm and 35 mm, more preferably about 30 mm. The aerosol-forming article may have a width, for example as measured along the transverse direction of the aerosol-forming device or article, in a range between 7 mm and 15 mm, preferably between 9 mm and 13 mm, more preferably about 11 mm. The aerosol-forming article may have a thickness or height, for example as measured along the normal direction of the aerosol-forming device or article, of between 1 mm and 10 mm, for example between 2 mm and 5 mm, preferably between 2.5 mm and 4 mm, more preferably about 3.1 mm. Therein, the length may refer to a minimum, mean or maximum length, the width may refer to a minimum, mean or maximum width and the thickness may refer to a minimum, mean or maximum thickness, respectively, height of the aerosol-forming article.

[0205] The aerosol-forming substrate may have a substantially planar, cuboid, or rectangular parallelepiped shape and may be located between a top and bottom cover sheet inside the aerosol-forming article, wherein the substrate may have a length, for example as measured along the insertion axis and / or along the longitudinal direction of the aerosol-forming device or article, of about 8 mm to 15 mm, preferably about 12 mm. The substrate may further have a width, for example as measured perpendicularly to the insertion direction and / or along the transverse direction of the aerosol-forming device or article, of about 6 mm to 13 mm, preferably about 8 mm. Therein, the length may refer to a minimum, mean or maximum length, and the width may refer to a minimum, mean or maximum width of the aerosol-forming substrate.

[0206] The substrate may particularly be or include a solid substrate material, although it is not limited thereto. Alternatively or additionally, the aerosol-forming substrate may be a solid substrate. For example, the substrate may include tobacco-based material, herbs, Cannabisbased material, or other solid substrate material. Optionally, however, also moisture, other liquidFTR4068

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[0208] constituents and / or one or more active ingredients may be comprised in the substrate. It is noted, though, that the present disclosure is not limited to solid substrates or substrates containing solid material, but can be applied to vaporizers or vaping devices that generate aerosol by vaporizing liquid substrate material.

[0209] A weight or mass of the aerosol-forming substrate weight may be in a range between about 100 mg and about 260 mg, more preferably between about 130 mg and about 240 mg, even more preferably about 150 mg and about 210 mg, most preferably about 180 mg.

[0210] The aerosol-forming substrate may comprise a plurality of granules or beads of substrate material, wherein a bulk density of the aerosol-forming substrate may be in a range of about 0.4 g / cm3to about 0.8 g / cm3, preferably about 0.6 g / cm3. Therein, the bulk density may be defined as the mass of the particles divided by the total volume they occupy. This volume can include the space between granules or beads as well as the space within the particles themselves.

[0211] The aerosol-forming substrate may comprise a plurality of granules or beads of substrate material, wherein a density of single granules or beads of the substrate may be at least 0.75 grams per cubic centimetre, more preferably at least 0.8 grams per cubic centimetre, more preferably at least 0.9 grams per cubic centimetre, more preferably at least 1 gram per cubic centimetre, more preferably at least 1.1 grams per cubic centimetre, more preferably at least 1.2 grams per cubic centimetre.

[0212] The aerosol-forming substrate may comprise a plurality of granules or beads of substrate material, wherein a density of single granules or beads of the substrate of the may be less than or equal to 2 grams per cubic centimetre, more preferably less than or equal to 1.95 grams per cubic centimetre, more preferably less than or equal to 1.9 grams per cubic centimetre, more preferably less than or equal to1.85 grams per cubic centimetre, more preferably less than or equal to 1.8 grams per cubic centimetre.

[0213] The aerosol-forming article can comprise a cavity, also referred to as substrate chamber, and a frame positioned between the two opposing main faces of the aerosol-forming article. The frame may at least partly define the cavity. The cavity may be configured and / or arranged to accommodate or receive the aerosol-forming substrate. In particular, the cavity may be at least partially, preferably entirely filled with aerosol-forming substrate.

[0214] The cavity may have a length, for example measured along the longitudinal axis of the aerosol-forming article or device, of at least 10 millimetres, or at least 12 millimetres. The cavity may have a length of less than or equal to 20 millimetres, or less than or equal to 15 millimetres. For example, the cavity may have a length of between 10 millimetres and 20 millimetres, or between 12 millimetres and 15 millimetres.

[0215] The cavity may have a width, for example measured along the transverse axis or width direction of the aerosol-forming device, of at least 5 millimetres, or at least 6 millimetres. TheFTR4068

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[0217] cavity may have a width of less than or equal to 10 millimetres, or less than or equal to 8 millimetres. For example, the cavity may have a width of between 5 millimetres and 10 millimetres, or between 6 millimetres and 8 millimetres.

[0218] The cavity may have a depth or thickness, for example measured along the normal direction of the aerosol-forming device, of at least 2 millimetres, or at least 3 millimetres. The cavity may have a depth of less than or equal to 5 millimetres, or less than or equal to 4 millimetres. For example, the cavity may have a depth of between 2 millimetres and 5 millimetres, or between 3 millimetres and 4 millimetres, for example between 2.5 millimetres and 4 mm millimetres.

[0219] The cavity may have a volume of at least 200 cubic millimetres, or at least 250 cubic millimetres. The cavity may have a volume of less than or equal to 400 cubic millimetres, or less than or equal to 350 cubic millimetres. For example, the cavity may have a volume of between 200 cubic millimetres and 400 cubic millimetres, or between 250 cubic millimetres and 350 cubic millimetres. The cavity may substantially be completely filled with substrate material, for example a plurality of beads or granules. Accordingly, the dimensions of the cavity may correspond to dimensions, volumes and sizes of the aerosol-forming substrate may substantially correspond to or define the dimensions, volumes and sizes of the aerosol-forming substrate.

[0220] The aerosol-forming substrate may have a length, for example measured along the longitudinal axis of the aerosol-forming article or device, of at least 10 millimetres, or at least 12 millimetres. The aerosol-forming substrate may have a length of less than or equal to 20 millimetres, or less than or equal to 15 millimetres. For example, the aerosol-forming substrate may have a length of between 10 millimetres and 20 millimetres, or between 12 millimetres and 15 millimetres.

[0221] The aerosol-forming substrate may have a width, for example measured along the transverse axis or width direction of the aerosol-forming device, of at least 5 millimetres, or at least 6 millimetres. The aerosol-forming substrate may have a width of less than or equal to 10 millimetres, or less than or equal to 8 millimetres. For example, the aerosol-forming substrate may have a width of between 5 millimetres and 10 millimetres, or between 6 millimetres and 8 millimetres.

[0222] The aerosol-forming substrate may have a depth or thickness, for example measured along the normal direction of the aerosol-forming device, of at least 2 millimetres, or at least 3 millimetres. The aerosol-forming substrate may have a depth or thickness of less than or equal to 5 millimetres, or less than or equal to 4 millimetres. For example, the aerosol-forming substrate may have a depth or thickness of between 2 millimetres and 5 millimetres, or between 3 millimetres and 4 millimetres, for example between 2.5 millimetres and 4 mm millimetres.

[0223] The aerosol-forming substrate may have a volume of at least 200 cubic millimetres, or at least 250 cubic millimetres. The aerosol-forming substrate may have a volume of less than orFTR4068

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[0225] equal to 400 cubic millimetres, or less than or equal to 350 cubic millimetres. For example, the aerosol-forming substrate may have a volume of between 200 cubic millimetres and 400 cubic millimetres, or between 250 cubic millimetres and 350 cubic millimetres.

[0226] The main faces or surfaces of the aerosol-forming article may comprise or be made of a cover sheet, which may comprise paper-based material, for example rolling paper, which may be fixed to the frame and, together with the frame, may define the substrate chamber or cavity, which may be filled with any type of aerosol-forming substrate, in particular solid substrate material, for example in bulk form or in the form of a plurality of granules or beads. Accordingly, each of the main faces or surfaces of the aerosol-forming article may comprise or constitute a cover-sheet, which may be heated by the first heating device and / or the heating elements thereof.

[0227] A distance or separation between the two opposing heating elements of the first heating device may be such that the aerosol-forming article fits therebetween, and / or such that the two opposing heating elements contact the two opposing main faces of the article. Accordingly, a distance or separation between the heating elements, for example measured along the normal direction of the aerosol-forming device or article, may substantially correspond to, be equal to, match or be slightly smaller than the thickness of the aerosol-forming article, such that heating surfaces of the heating elements of the first heating device may contact the two opposing main faces of the aerosol-forming article, for example when the aerosol-forming article is inserted into the heating chamber. Alternatively or additionally, a distance or separation between the two opposing heating elements of the first heating device, for example as measured along the normal direction of the aerosol-forming device or article, may be between 1 mm and 10 mm, for example between 2 mm and 5 mm, preferably between 2.5 mm and 4 mm, more preferably about 3.1 mm.

[0228] The heating chamber may be configured to at least partially receive the aerosol-forming article having a length, e.g. as measured along the insertion axis in longitudinal direction, and / or parallel to the longitudinal axis, in a range between 20 mm and 40 mm, preferably between 25 mm and 35 mm, more preferably about 30 mm, having a width, e.g. measured in transverse direction of the aerosol-forming device, in a range between 7 mm and 15 mm, preferably between 9 mm and 13 mm, more preferably about 11 mm, and a thickness or height, e.g. measured in normal direction of the aerosol-forming device, of between 1 mm and 10 mm, for example between 2 mm and 5 mm, preferably between 2.5 mm and 4 mm, more preferably about 3.1 mm. Therein, the length may refer to a minimum, mean or maximum length, the width may refer to a minimum, mean or maximum width and the thickness may refer to a minimum, mean or maximum thickness, respectively, height of the aerosol-forming article.

[0229] The heating chamber may be configured to have an insertion depth along the insertion axis in a range between 10 mm and 35 mm, preferably in a range between 15 mm and 30 mm, more preferably between 15 mm and 25 mm. The insertion depth may refer to a distance by which theFTR4068

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[0231] aerosol-forming article can be inserted into the heating chamber. The insertion depth may for example correspond to a distance, for example minimum, mean or maximum distance, between a proximal end face of the heating chamber and a distal end face of the heating chamber. The insertion depth may refer to a minimum, mean or maximum distance or insertion depth.

[0232] The insertion depth may define or substantially correspond to a length of the heating chamber, for example measured in longitudinal direction of the aerosol-forming device. Accordingly, a length of the heating chamber may be in a range between 10 mm and 35 mm, preferably in a range between 15 mm and 30 mm, more preferably between 15 mm and 25 mm. The length may refer to a minimum, mean or maximum length.

[0233] The heating chamber may be configured to have an insertion depth that is shorter than a length of the aerosol-forming article. Accordingly, the aerosol-forming article, when inserted into the heating chamber, may protrude from a proximal end of the heating chamber, for example by about 1 mm to 30 mm, for example 2 mm to 20 mm, preferably about 5 mm to 15 mm, more preferably about 5 mm to about 10 mm.

[0234] The heating chamber may have a width, for example measured along the transverse direction of the aerosol-forming device, between the two inner small side faces or lateral faces between 7.2 mm and 15.2 mm, preferably between 9.2 mm and 13.2 mm, more preferably about 11.2 mm. The width may be minimum, mean or maximum width.

[0235] The heating chamber may have a width, for example measured along the transverse direction of the aerosol-forming device, between the two inner small side faces or lateral faces to provide for an interference fit, a press-fit, or a friction-fit with the small side surfaces or lateral faces of aerosol-forming article. Hence, the aerosol-forming article may be laterally positioned or fixed in the heating chamber.

[0236] The heating chamber may have a height or thickness, for example measured along the normal direction of the aerosol-forming device, between two inner large side faces or main faces of a heater casing or heating elements between 2 mm and 10 mm, more preferably between 3 mm and 8 mm, even more preferably between 4 mm and 6 mm. The height may be minimum, mean or maximum height.

[0237] The aerosol-forming device may comprise one or more main air inlets, device inlets or air inlets configured to receive an airflow from the external environment of the aerosol-forming device, wherein the one or more main air inlets are in fluid communication with the upstream airflow path arranged upstream of the heating chamber. For instance, one or more airflow path structures of the device may fluidly couple the one or more main air inlets with the upstream airflow path.

[0238] The aerosol-forming device may further comprise a device body, also referred to as body or body part, defining a main axis of extension of the aerosol-forming device, which may beFTR4068

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[0240] parallel to the longitudinal axis of the device and / or the insertion direction for inserting the aerosolforming article into the aerosol-forming device. The aerosol-forming device may further comprise a downstream element movably attached to the device body or body, such that the device body and the downstream element are movable relative to each other between an open position and a use position, wherein access to the heating chamber is provided in the open position, such that the aerosol-forming article is removable from or insertable into the heating chamber in the open position, and wherein the heating chamber is closed in the closed position. The downstream element may also be referred to herein as mouthpiece portion, and may generally refer to a part of the device or the housing thereof that is displaceable or movable relative to the device body.

[0241] The downstream element of the aerosol-forming device may be slidably and / or rotatably attached or coupled to the device body, such that the downstream element is movable, for example relative to the device body, from the open position to the use position. The downstream element and the device body may be moved or displaced relative to each other along the longitudinal direction, parallel to the longitudinal axis between the open position and the use position, or in another direction.

[0242] The use position and the open position of the aerosol-forming device may generally refer to two different configurations of the aerosol-forming device. Also, the terms open position and closed position may be used herein with reference to one or more elements or components of the aerosol-forming device, thereby describing different configurations of said components or elements.

[0243] For example, between the open position and the use position, the device body may be moved or displaced relative to the downstream element of the aerosol-forming device. The device body may be moved relative to the downstream element, for example parallel to the longitudinal axis or along the longitudinal direction of the aerosol-forming device. The aerosol-forming device being in the open position, respectively, being in the closed position, may be interchangeably or synonymously used herein with the device body and / or downstream element being in the open position, respectively, being in the closed position.

[0244] In the use position, the heating chamber may be closed and / or covered by the downstream element and the device body. Accordingly, the heating chamber may not be accessible, respectively, may be inaccessible for a user to insert the aerosol-forming article or remove it therefrom. Alternatively or additionally, the aerosol-forming article may only be inserted into the heating chamber when the device body and the downstream element are displaced or moved relative to each other out of the use position, for example are displaced towards the open position. Optionally, generation of aerosol may only be allowed in the use position.

[0245] In the open position, the heating chamber may be accessible, for example for inserting an aerosol-forming article into or removing it from the heating chamber.FTR4068

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[0247] A relative displacement or movement of the device body and the downstream element from the open position towards or into the use position may refer to a displacement or movement of the downstream element from a proximal end towards a distal end of the aerosol-forming device, and / or may refer to a displacement or movement of the device body from a distal end towards a proximal end of the aerosol-forming device. Accordingly, the device body and the downstream element may be moved or displaced towards each other, for example along or parallel to the longitudinal axis of the aerosol-forming device, when moving the device body and the downstream element from the open position towards or into the use position. Alternatively or additionally, the device body and the downstream element may be moved or displaced away from each other, for example along or parallel to the longitudinal axis of the aerosol-forming device, when moving the device body and the downstream element from the use position towards or into the open position. Alternatively or additionally, the device body and the downstream element may be moved away from each other based on rotating at least one of the device body and the downstream element.

[0248] As used herein, the terms “distal” and “proximal” describe the locations of components or elements in relation to a user holding or using the aerosol-forming device, for example using the aerosol-forming device to consume or inhale aerosol. Therein, “distal” can refer to a location or element that is farther away from the user, and “proximal” can refer to a location or element that is closer to the user.

[0249] The aerosol-forming device may further comprise an interconnection mechanism arranged between the downstream element and the device body, and permitting the movement between the open and the use position, wherein the movement includes a rotational movement, a linear movement, or combination of a rotational and linear movement. In particular, any mechanism described herein for moving or displacing the device body and the downstream element relative to each other between the open position and use position can be used.

[0250] The aerosol-forming device may further comprise a heating module arranged at least partly in the device body, wherein the heating chamber is arranged in the heating module, optionally, wherein the heating module is removable from the device body of the aerosol-forming device.

[0251] The heating module may be slidably arranged inside the device body to slide along the main axis of extension or longitudinal axis, wherein a spring biasing mechanism may optionally be configured to push the heating module to be at least partially outside the device body when the downstream element is in the open position. In other words, in the open position, the heating module may protrude from an end of the device body. For instance, this may allow to remove or replace the heating module.

[0252] The aerosol-forming device may further comprise an upstream fluidic interconnection element configured to provide a fluidic connection between the upstream airflow path upstream and the aerosol-forming article, wherein the upstream fluidic interconnection element comprisesFTR4068

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[0254] a blade structure surrounding the upstream airflow path along a central axis of the upstream airflow path, the blade structure having a first end configured to face an upstream air inlet of the aerosol-forming article, and a second end arranged opposite of the first end, wherein an outer wall of the blade structure has a sloped or tapered shape thereby increasing a thickness of the blade structure in a direction from the first end to the second end. In particular, the upstream fluidic interconnection element or its blade structure can be configured to cut or press into a wall or frame around an upstream air inlet of the aerosol-forming article, to provide for a fluidic connection and / or fluidic coupling between the upstream airflow path and the substrate of the aerosol-forming article.

[0255] By means of the blade structure of the upstream fluidic interconnection element cutting or pressing into the wall or frame surrounding the upstream air inlet, a substantially or at least partially sealed or fluid-tight coupling between the upstream airflow path and the substrate of the aerosol-forming article can be ensured or provided.

[0256] A cross-sectional area of an opening provided around an outer edge of the blade structure may be larger than a cross-sectional area of the upstream air inlet of the aerosol-forming article. This may ensure that the cross-sectional area of the upstream air inlet of the aerosol-forming article is not decreased by the blade structure at least partially pressing or cutting into the wall around or surrounding the upstream air inlet. Accordingly, the upstream air inlet may be kept open to let air pass therethrough.

[0257] A cross-sectional area of an opening provided around an outer edge of the blade structure may have one or more of a circular shape, an oval shape, a rectangular shape, and an irregular shape.

[0258] For example, a cross-sectional area of a flow path provided by the blade structure may have a rectangular shape with rounded corners. By means of the rectangular shape with rounded corners obstructions for air flowing therethrough may advantageously be avoided.

[0259] The aerosol-forming device may further comprise a downstream airflow path configured to provide an aerosol from the aerosol-forming article to an aerosol outlet of the device, and a downstream fluidic interconnection element configured to fluidically interconnect the downstream airflow path with the aerosol-forming article, wherein the downstream fluidic interconnection element includes a blade structure configured to cut or press into a wall around a downstream air outlet of the aerosol-forming article, to provide for a sealed fluidic connection between the aerosolforming article and the downstream airflow path.

[0260] By means of the blade structure of the downstream fluidic interconnection element cutting or pressing into the wall or frame surrounding the downstream air outlet, a substantially or at least partially sealed or fluid-tight coupling between the substrate of the aerosol-forming article and the downstream airflow path can be ensured or provided.FTR4068

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[0262] The downstream fluidic interconnection element, with or including the blade structure, may be in fluidic interconnection with the downstream airflow path and optionally with a mouthpiece of the aerosol-forming device, which mouthpiece may be movable relative to the heating chamber by either a rotational movement, a linear movement, or a combination of a rotational and linear movement. Accordingly, air flowing or passing through the downstream fluidic interconnection element with the associated blade structure may flow into downstream airflow path and optionally into the mouthpiece. In other words, the downstream fluidic interconnection element may guide the air or air flow from the aerosol-generating article and the downstream air outlet into the downstream airflow path and optionally into the mouthpiece, for example towards a user’s mouth.

[0263] The blade structure of the downstream fluidic interconnection element may be tapered or conical towards a center axis of the downstream airflow path, such that one or more tapered or conical walls of the blade structure are configured to press against an inner wall an inner wall of the aerosol-forming article, preferably wherein the blade structure of the downstream fluidic interconnection element forms a cutting end edge, such that the cutting end edge of the blade structure is configured to cut into the wall around a downstream aerosol outlet of the aerosolforming article. The downstream air outlet may also be referred to herein as aerosol outlet or downstream aerosol outlet of the aerosol-forming article.

[0264] The downstream and upstream fluidic interconnection elements may be formed and shaped corresponding to each other, and may be arranged opposite to each other at the air inlet and aerosol outlet of the aerosol-forming article.

[0265] In an exemplary configuration, the second heating device may be arranged at least partly within, at, in thermal contact with or close to the upstream airflow path upstream. For instance, at least a part of the second heating device may protrude into the upstream airflow path, for example protrude from a wall of the upstream airflow path. Optionally, at least a part of a surface of the second heating device may be in direct contact with air in the upstream airflow path. Generally, this can allow to efficiently heat the air in the upstream airflow path, which can then heat the aerosol-forming article based on convective heating.

[0266] In an example, at least a part or portion of the upstream airflow path upstream of the heating chamber may be slit-like shaped. Hence, at least a part or portion of the upstream airflow path may be comparatively narrow, such that the airflow therethrough can be quickly and efficiently heated.

[0267] Alternatively or additionally, the second heating device may comprise a slit-shaped air channel and a resistive heating element, for example a substantially or preferably planar resistive heating element, arranged inside the slit-shaped (synonymously used herein with slit-like shaped) air channel, such that two narrow airflow channels are formed above and below the resistive heating element, respectively, on two opposite sides of the resistive heating element. The slit-FTR4068

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[0269] shaped or slot shaped air channel may also be referred to herein as convective heating chamber. For instance, the air channels or gaps may be formed on two opposite sides, for example, on two planar sides or surfaces, of the resistive heating element.

[0270] By means of the second heating device with the resistive heating element, an efficient preheating or flash heating of the airflow may be ensured, for example such that air with elevated temperature can be directed into or towards the aerosol-forming article for generating aerosol.

[0271] The two narrow air flow channels (or air flow channels or gaps) may have a width in a range between 3 mm to 15 mm, and have a height of less than 0.5 mm and more than 0.05 mm, preferably less than 0.3 mm and more than 0.1 mm, preferably less than 0.25 mm to 0.1 mm. The width may, for example, be measured along the transverse or width direction of the aerosolforming device, and the height may be measured along the normal or height direction of the aerosol-forming device, or vice versa. Such dimensions, heights and / or widths may allow for an efficient and fast heating of the air flowing through the air flow channels.

[0272] In an example, two opposing walls forming the slit-shaped air channel of the second heating device and having the resistive element therebetween may not be heated. The walls may be made from an insulating material, avoiding heat transfer from the convective heating chamber into other parts of the device through other paths than the heated air flow. This may provide for efficient heating.

[0273] Generally, the configuration or design of the second heating device can ensure that the second heating device and / or its resistive heating element has a low thermal mass or generally low mass, which can allow to change its temperature based on a small airflow, while the walls of the convective heating chamber, respectively, the walls defining the slit-shaped air channel of the second heating device can have low thermal conductivity, to avoid taking on heat and thereby providing for a high thermal capacity to the upstream airflow path. Preferably, the walls should have a low thermal conductivity and a high specific heat capacity. Further, the walls should withstand the heat and comprise tox-appropriate material. For example, a ceramic material, zirconia, alumina or a combination thereof can be used for the walls defining the convective heating chamber and / or defining the walls of the slit-shaped air channel of the second heating device.

[0274] The two opposing walls forming the slit-shaped air channel of the second heating device and having the resistive element therebetween may have a structured, for example roughened or ragged, surface for causing an air flow turbulence. Additionally or alternatively, the surface of the resistive heating element may be structured, for example roughened or ragged, to cause turbulences. Also such air flow turbulence may be beneficial in terms of an efficient heating, for example as it may allow for a more homogenous temperature distribution.FTR4068

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[0276] An air flow direction in the second heating device may be in axis with an air flow direction in the heating chamber. For example, the air flow direction may be substantially parallel or along the longitudinal axis of the aerosol-forming device and / or article. By being in axis, obstructions in the flow path can be avoided, thereby also potentially preventing overheating.

[0277] The resistive heating element of the second heating device may be formed as a meandering or serpentine structure, wherein the meandering or serpentine structure may extend in-plane of the resistive heating element. For example, the resistive heating element may extend in a plane, and the meandering or serpentine structure may be directed along an extension direction thereof in said plane, wherein portions of the meandering or serpentine structure may alternately traverse the actual extension direction of the meandering or serpentine structure. The extension direction of the meandering or serpentine structure may, for example, extend in a direction transverse to the longitudinal direction of the aerosol-forming device, for example along the transverse or normal direction thereof.

[0278] For example, the resistive heating element of the second heating device may comprise a strip of a metal sheet, for example stainless steel, which may be perforated and / or include one or more perforation openings or holes. In other words, the resistive heating element may comprise a meshed metal strip. The strip may be bent into a stack of serpentine branches spanning between the two terminals of the resistive heating element. The branches may all be formed similarly, for example by having the same dimensions and / or extensions. The direction in which the stack of serpentine branches extends may be referred to as the stack direction, and the stack direction may be perpendicular or parallel to the longitudinal axis or direction of the aerosolforming device. The resistive heating element may be configured and / or arranged so that the air flowing through the convective heating chamber passes through the perforations forming the mesh of the strip, particularly along the stack direction. By flowing along the stack direction, the air may pass through perforations of every single branch in the stack, which ensures efficient and quick heat transfer to the air in the upstream airflow path. Also this configuration or design can ensure that the second heating device and / or its resistive heating element has a low thermal mass or generally low mass, which can allow to change its temperature based on a small airflow in a short period of time. Hence, temperature changes, and thus user inhalations, can be detected quickly and reliably.

[0279] The heating chamber of the aerosol-forming device may be configured to removably receive the aerosol-forming article, the aerosol-forming article having a substantially rectangular parallelepiped shape defining two opposing main faces and an aerosol-forming substrate arranged between the opposing main faces. Therein, the first heating device can comprise two opposing heating elements, for example resistive heating elements, forming a substantially rectangular parallelepiped heating volume therebetween for removably and at least partiallyFTR4068

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[0281] receiving the aerosol-forming article, the heating volume arranged at least partially inside the heating chamber. Further, at least one of the two heating elements can made of an electrically conductive material. Accordingly, at least one of the heating elements may be configured to heat the substrate or article.

[0282] In an example, both heating elements of the first heating device can be made from electrically conductive material and both heating elements can be configured to heat the substrate or article from the two opposing main faces or surfaces of the aerosol-forming article. Optionally, the first heating device may comprise one or two further heating elements which may be arranged opposite to each other in transverse direction and may be configured to heat the one or more lateral surfaces or faces of the aerosol-forming substrate.

[0283] The first heating device and / or the heating elements thereof may be arranged inside the heating chamber, wherein upon insertion of the aerosol-forming article into the heating chamber, at least a part of the first heating device and / or at least one of the heating elements thereof can be configured to move towards an adjacent side face of the heating chamber so that at least one heating element is pressed against one of the main faces of the aerosol-forming article. For example, at least a part of at least one of the heating elements may be moved by the insertion of the aerosol-forming article into the heating chamber.

[0284] Preferably, both heating elements can be moved towards the aerosol-forming article, such that both heating elements are pressed against a respective one of the main faces of the aerosolforming article. This can ensure good thermal contact between the one or both heating elements and the aerosol-forming article, thereby ensuring efficient heat transfer and heating of the substrate.

[0285] At least one of the heating elements, preferably both heating elements, of the first heating device can include a heating plate formed as a meandering track in the shape of a leaf spring. Optionally, the at least one heating element, preferably both heating elements, of the first heating device can include a heating plate with a plurality of parallelly-arranged heating tracks arranged in parallel to an insertion direction and / or longitudinal axis of the aerosol-forming device.

[0286] The aerosol-forming device may further include a heater casing made of a non-conductive material forming an outer shell around the two opposing heating elements of the first heating device. The heater casing may be part of a heater module or heating module of the aerosolforming device. Therein, two smaller inner side faces or lateral faces of the heater casing may form or define the inner small side faces or lateral faces of the heating chamber. Generally, the heater casing may insulate the housing or device body of the aerosol-forming device, such that heat dissipation can be reduced, for example such that the housing may not heat-up that much during a usage session and / or such that the heat is confined to the interior of the aerosol-forming deviceFTR4068

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[0288] For example, the two heating elements of the first heating device may oppose each other in normal direction and the small or smaller inner side faces of the heater casing may refer to lateral faces of the inner casing that define or constitute two lateral faces of the heating chamber, wherein the two lateral faces of the heater casing and / or the heating chamber may oppose each other in transverse direction of the aerosol-forming device.

[0289] According to a further aspect of the present disclosure, there is provided an aerosol-forming system comprising an aerosol-forming device, as described hereinabove and hereinbelow. The aerosol-forming system comprises one or both an aerosol-forming article for generating aerosol, and a companion device for charging and / or storing the aerosol-forming device.

[0290] As mentioned above, any disclosure herein related to the aerosol-forming device equally applies to the aerosol-forming system, and vice versa.

[0291] The companion device may also be referred to as charger case. The aerosol-forming device may be mechanically couplable to the companion device in order to store the aerosol-forming device and / or in order to charge an energy storage or power source of the aerosol-forming device via the companion device.

[0292] A mechanical coupling of the aerosol-forming device and the companion device may, in the context of the present disclosure, include a contact between a part or surface of the companion device and a part or surface of the aerosol-forming device. For instance, when coupling the aerosol-forming device with the companion device, a part of a housing or outer surface of the aerosol-forming device may be in contact or direct contact with a part of a housing, compartment or surface of the companion device. Accordingly, a mechanical coupling of the aerosol-forming device and the companion device can include a mechanical or physical contact between the aerosol-forming device and the companion device.

[0293] For example, the aerosol-forming device may be mechanically couplable to the companion device based on at least partly inserting the aerosol-forming device into the companion device, for example into a cavity, compartment or recess of the companion device. Alternatively or additionally, the companion device may be mechanically couplable with the aerosol-forming device based on at least partly receiving the aerosol-forming device in the companion device.

[0294] In an exemplary configuration, the companion device may comprise a compartment, cavity or recess for at least partly receiving the aerosol-forming device, for example, such that the aerosol-forming device is at least partly encompassed in or surrounded by the companion device.

[0295] Alternatively or additionally, the aerosol-forming device may be mechanically couplable to the companion device based on attaching a housing of the aerosol-forming device to the companion device. To attach the housing to the companion device, the companion device may, for example, comprise engagement means configured to engage with the housing of the aerosol-FTR4068

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[0297] forming device or corresponding engagement elements formed at or by the housing of the aerosol-forming device.

[0298] The control circuitry of the aerosol-forming device or a dedicated charging circuitry of the aerosol-forming device may be configured to charge the energy storage or power source of the aerosol-forming device upon, based on or in response to mechanically coupling the aerosolforming device with the companion device.

[0299] According to a further aspect of the present disclosure, there is provided a method of detecting a user inhalation at an aerosol-forming device or system. The aerosol-forming device or system comprises a heating chamber configured to receive at least a part of an aerosol-forming article, an upstream airflow path arranged upstream of the heating chamber, wherein the upstream airflow path is in fluid communication with an external environment of the aerosolforming device, such that air is drawable by a user in a user inhalation from the external environment through the upstream airflow path towards the heating chamber. The aerosolforming device or system further comprises a first heating device arranged at the heating chamber and configured to perform a first heating operation, and a second heating device arranged in thermal contact with the upstream airflow path and configured to perform a second heating operation. The method comprises:

[0300] supplying electrical power or energy to at least one of the first heating device and the second heating device; and

[0301] detecting a user inhalation at the aerosol-forming device based on determining a change in a temperature of at least one of the first heating device and the second heating device associated with a change in an airflow through the airflow path caused by the user inhalation.

[0302] The aerosol-forming device may comprise the elements, functions and characteristics, as described hereinabove and hereinbelow. Accordingly, any disclosure herein related to the aerosol-forming device or system equally applies to the method, and vice versa.

[0303] Detecting the user inhalation at the aerosol-forming device may include determining one or more of:

[0304] a change in an electrical resistance of the first heating device;

[0305] a change in an electrical resistance of the second heating device.

[0306] a decrease or increase in an electrical resistance of the first heating device;

[0307] a decrease or increase in the temperature of the second heating device; and a sensor reading or a change in a sensor reading of at least one temperature sensor. Based on one or more of these, the control circuitry may reliably detect one or more of a start, an onset, a duration, an occurrence, an end, and a termination of one or more user inhalations.FTR4068

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[0309] The method may further comprise one or more of controlling a power supply from the power source or energy storage to the first heating device based on determining a change in the temperature of the second heating device, and controlling a power supply from the power source or energy storage to the second heating device based on determining a change in the temperature of the first heating device.

[0310] Alternatively or additionally, the method may comprise one or more of controlling a power supply from the power source or energy storage to the first heating device based on determining a change in the temperature of the first heating device, and controlling a power supply from the power source or energy storage to the second heating device based on determining a change in the temperature of the second heating device.

[0311] The method may further comprise controlling the second heating device to perform a puff-on-demand heating operation, and controlling the first heating device to perform a continuous heating operation during a usage session.

[0312] In an example, supplying electrical power to at least one of the first heating device and the second heating device can comprise operating the second heating device at a first power level to heat the second heating device to a pre-heating temperature above ambient temperature and below a target temperature, wherein the user inhalation is detected when the second heating device is operated at the first power level.

[0313] Optionally, the method may further comprise operating, in response to detecting the change, for example decrease, in the temperature of the second heating device, the second heating device at a second power level for heating the second heating device to a target temperature to form aerosol from the aerosol-forming article.

[0314] Generally, a target temperature of the first heating device and / or the second heating device may correspond to or be higher than a volatilization or vaporization temperature required to release inhalable aerosol from the aerosol-forming article or substrate.

[0315] Further optionally, the method may comprise operating, in response to detecting the change, for example decrease, in the temperature of the second heating device, the first heating device to heat the aerosol-forming article to the volatilization temperature sufficient to release aerosol from the aerosol-forming article.

[0316] In an example, the method may further comprise operating the first heating device at a first power level to heat the first heating device to a pre-heating temperature above ambient temperature and below a volatilization or vaporization temperature sufficient to release aerosol from the aerosol-forming article, wherein the user inhalation is detected when the first heating device is operated at the first power level.

[0317] Further, the method may comprise operating, in response to detecting the change, for example decrease, in the temperature of the first heating device, the first heating device at aFTR4068

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[0319] second power level for heating the first heating device to the target temperature to form aerosol from the aerosol-forming article.

[0320] Alternatively or additionally, the method may comprise operating, in response to detecting the change in the temperature, for example a decrease, of the first heating device, the second heating device to heat the second heating device to a target temperature.

[0321] The method may further comprise determining termination of the user inhalation based on determining a further change, for example increase, in the temperature of at least one of the first heating device and the second heating device, and optionally decreasing the power supplied to at least one of the first heating device and the second heating device in response to determining termination of the user inhalation.

[0322] The invention is defined in the claims. However, below there is provided a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

[0323] Example 1: An aerosol-forming device for forming aerosol from an aerosol-forming article, comprising:

[0324] a heating chamber configured to receive at least a part of the aerosol-forming article; an upstream airflow path arranged upstream of the heating chamber, the upstream airflow path in fluid communication with an external environment of the aerosol-forming device, such that air is drawable by a user in a user inhalation from the external environment through the upstream airflow path towards the heating chamber;

[0325] a first heating device arranged at the heating chamber and configured to perform a first heating operation;

[0326] a second heating device arranged in thermal contact with the upstream airflow path and configured to perform a second heating operation; and

[0327] control circuitry configured to control a power supply from a power source of the aerosolforming device to at least one of the first heating device and the second heating device based on determining a change in a temperature of at least one of the first heating device and the second heating device associated with a change in an airflow through the airflow path caused by the user inhalation.

[0328] Example 2: The aerosol-forming device according to the preceding example, wherein the first heating device includes a resistive heating device configured to heat at least a part of a substrate of the aerosol-forming article by conductive heating.

[0329] Example 3: The aerosol-forming device according to any one of the preceding examples, wherein the second heating device includes a resistive heating device configured to heat air in the upstream airflow path to at least heat a part of a substrate of the aerosol-forming article by convective heating.FTR4068

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[0331] Example 4: The aerosol-forming device according to any one of the preceding examples, wherein the change in the temperature of the first heating device is associated with a change in an airflow past the first heating device caused by the user inhalation; and / or wherein the change in the temperature of the second heating device is associated with a change in an airflow past the second heating device caused by the user inhalation.

[0332] Example 5: The aerosol-forming device according to any one of the preceding examples, wherein the control circuitry is configured to determine the change in the temperature of the first heating device based on determining a change in an electrical resistance of the first heating device.

[0333] Example 6: The aerosol-forming device according to any one of the preceding examples, wherein the control circuitry is configured to determine the change in the temperature of the second heating device based on determining a change in an electrical resistance of the second heating device.

[0334] Example 7: The aerosol-forming device according to any one of the preceding examples, wherein the control circuitry is configured to determine a decrease in the temperature of the first heating device based on determining a decrease in an electrical resistance of the first heating device; and / or

[0335] wherein the control circuitry is configured to determine an increase in the temperature of the first heating device based on determining an increase in an electrical resistance of the first heating device.

[0336] Example 8: The aerosol-forming device according to any one of the preceding examples, wherein the control circuitry is configured to determine a decrease in the temperature of the second heating device based on determining a decrease in an electrical resistance of the second heating device; and / or

[0337] wherein the control circuitry is configured to determine an increase in the temperature of the second heating device based on determining an increase in an electrical resistance of the second heating device.

[0338] Example 9: The aerosol-forming device according to any one of the preceding examples, wherein the control circuitry is configured to determine the change in the temperature of at least one of the first heating device and the second heating device based on at least one temperature sensor.

[0339] Example 10: The aerosol-forming device according to any one of the preceding examples, wherein the control circuitry is configured to control the power supply from the power source to the first heating device based on determining a change in the temperature of the second heating device.FTR4068

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[0341] Example 11: The aerosol-forming device according to any one of the preceding examples, wherein the control circuitry is configured to control the power supply from the power source to the second heating device based on determining the change in the temperature of the first heating device.

[0342] Example 12: The aerosol-forming device according to any one of the preceding examples, wherein the control circuitry is configured to detect the user inhalation at the aerosolgenerating device based on determining the change in the temperature of at least one of the first heating device and the second heating device based on a cooling effect departed by an airflow past at least one of the first heating device and the second heating device caused by the user inhalation.

[0343] Example 13: The aerosol-forming device according to any one of the preceding examples, wherein the control circuitry is configured to determine the change in the temperature of at least one of the first heating device and the second heating device with respect to a reference temperature of the respective at least one of the first heating device and the second heating device.

[0344] Example 14: The aerosol-forming device according to any one of the preceding examples, wherein the first heating operation differs from the second heating operation.

[0345] Example 15: The aerosol-forming device according to any one of the preceding examples, wherein the second heating device is configured to perform a puff-on-demand heating operation; and / or

[0346] wherein the control circuitry is configured to control the second heating device to perform a puff-on-demand heating operation.

[0347] Example 16: The aerosol-forming device according to any one of the preceding examples, wherein the first heating device is configured to perform a continuous heating operation during a usage session; and / or

[0348] wherein the control circuitry is configured to control the first heating device to perform a continuous heating operation during a usage session.

[0349] Example 17: The aerosol-forming device according to any one of the preceding examples, wherein the control circuitry is configured to control or operate the first heating device according to a first heating profile, and to control or operate the second heating device according to a second heating profile, wherein the first heating profile differs from the second heating profile.

[0350] Example 18: The aerosol-forming device according to any one of the preceding examples, wherein the control circuitry is configured to, based on controlling the power supply from the power source to the second heating device, operate the second heating device at a first power level to heat the second heating device to a pre-heating temperature above ambient temperature and below a target temperature, andFTR4068

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[0352] wherein the control circuitry is configured to determine the change in the temperature or monitor the temperature of the second heating device when the second heating device is operated at the first power level.

[0353] Example 19: The aerosol-forming device of the preceding example, wherein the control circuitry is configured to detect the user inhalation when the second heating device is operated at the first power level.

[0354] Example 20: The aerosol-forming device according to any one of examples 18 and 19, wherein the pre-heating temperature is above about 25°C, above about 30°C, preferably above about 40°C, more preferably above about 50°C, and even more preferably above about 60°C; and / or

[0355] wherein the pre-heating temperature is below about 250°C, below about 200°C, below about 150°C, below about 120°C, below about 100°C, preferably below about 90°C, more preferably below about 80°C, and even more preferably below about 70°C.

[0356] Example 21 : The aerosol-forming device of the preceding example, wherein the control circuitry is configured to operate the second heating device at the first power level based on supplying a first DC voltage to the second heating device that is smaller than a second DC voltage supplied by the control circuitry to the second heating device to heat the second heating device to the target temperature.

[0357] Example 22: The aerosol-forming device according to any one of examples 18 to 21, wherein the control circuitry is configured to, in response to detecting the change in the temperature of the second heating device, operate the second heating device at a second power level for heating the second heating device to the target temperature to form aerosol from the aerosol-forming article.

[0358] Example 23: The aerosol-forming device according to any one of examples 18 to 22, wherein the control circuitry is configured to, in response to detecting the change in the temperature of the second heating device, operate the first heating device to heat the aerosolforming article to a target temperature or volatilization temperature sufficient to release aerosol from the aerosol-forming article.

[0359] Example 24: The aerosol-forming device according to any one of examples 18 to 23, wherein the target temperature of the second heating device is above about 200°C, above about 250°C, above about 270°C, preferably above about 280°C, more preferably above about 290°C, even more preferably about 300°C, or even above about 400°C to about 450°C.

[0360] Example 25: The aerosol-forming device according to any one of the preceding examples, wherein the control circuitry is configured to, based on controlling the power supply from the power source to the first heating device, operate the first heating device at a first power level to heat the first heating device to a pre-heating temperature above ambient temperature andFTR4068

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[0362] below a volatilization or vaporization temperature sufficient to release aerosol from the aerosolforming article, and

[0363] wherein the control circuitry is configured to determine the change in the temperature or monitor the temperature of the first heating device when the first heating device is operated at the first power level.

[0364] Example 26: The aerosol-forming device of the preceding example, wherein the control circuitry is configured to detect the user inhalation when the first heating device is operated at the first power level.

[0365] Example 27: The aerosol-forming device according to any one of examples 25 and 26, wherein the pre-heating temperature is above about 25°C, above about 30°C, preferably above about 40°C, more preferably above about 50°C, and even more preferably above about 60°C; and / or

[0366] wherein the pre-heating temperature is below about 120°C, below about 100°C, preferably below about 90°C, more preferably below about 80°C, and even more preferably below about 70°C.

[0367] Example 28: The aerosol-forming device of the preceding example, wherein the control circuitry is configured to operate the first heating device at the first power level based on supplying a first DC voltage to the first heating device that is smaller than a second DC voltage supplied by the control circuitry to the first heating device to heat the first heating device to the target temperature.

[0368] Example 29: The aerosol-forming device according to any one of examples 25 to 28, wherein the control circuitry is configured to, in response to detecting the change in the temperature of the first heating device, operate the first heating device at a second power level for heating the first heating device to the target temperature to form aerosol from the aerosolforming article.

[0369] Example 30: The aerosol-forming device according to any one of examples 25 to 29, wherein the control circuitry is configured to, in response to detecting the change in the temperature of the first heating device, operate the second heating device to heat the second heating device to a target temperature, preferably wherein the target temperature of the second heating device is above about 200°C, above about 250°C, above about 270°C, preferably above about 280°C, more preferably above about 290°C, even more preferably about 300°C, or even above about 400°C to about 450°C.

[0370] Example 31: The aerosol-forming device according to any one of examples 18 to 30, wherein the control circuitry is configured to operate at least one of the first heating device and the second heating device at the first power level in response to one or more of:

[0371] a sensor signal of at least one sensor of the aerosol-forming device;FTR4068

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[0373] insertion of an aerosol-forming article at least partly into the aerosol-forming device; coupling of an aerosol-forming article to the aerosol-forming device;

[0374] mechanical decoupling of the aerosol-forming device from a companion device; and a control signal from one or more user interfaces triggered by a user of the aerosol-forming device.

[0375] Example 32: The aerosol-forming device of the preceding example, wherein the at least one sensor includes one or more of a motion sensor, an accelerometer, a gyroscope, an image sensor, a pyrometer, a presence sensor, a touch sensor.

[0376] Example 33: The aerosol-forming device according to any one of the preceding examples, wherein the control circuitry is configured to determine whether the user inhalation has ended based on determining a further change in the temperature of at least one of the first heating device and the second heating device.

[0377] Example 34: The aerosol-forming device according to the preceding example, wherein the control circuitry is configured to decrease the power supplied to at least one of the first heating device and the second heating device from a second power level to a first power level below the second power level in response to determining that the user inhalation has ended; and / or wherein the control circuitry is configured to interrupt or stop the power supply to at least one of the first heating device and the second heating device in response to determining that the user inhalation has ended.

[0378] Example 35: The aerosol-forming device according to any one of the preceding examples, wherein the control circuitry is configured to determine at least one reference temperature of at least one of the first heating device and the second heating device, when the power supply to the respective at least one of the first heating device and the second heating device is interrupted.

[0379] Example 36: The aerosol-forming device according to any one of the preceding examples, wherein the aerosol-forming article has a substantially rectangular parallelepiped shape defining two opposing main faces and two opposing side faces, the aerosol-forming article including an aerosol-forming substrate arranged between the two opposing main faces, preferably wherein the aerosol-forming article comprises an air inlet and an air outlet located opposite of each other on the smallest faces of the rectangular parallelepiped shaped aerosol-forming article.

[0380] Example 37: The aerosol-forming device according to any one of the preceding examples, wherein the heating chamber has a substantially rectangular parallelepiped shape and / or is configured to receive a substantially rectangular parallelepiped shaped aerosol-forming article.

[0381] Example 38: The aerosol-forming device according to any one of the preceding examples, wherein the aerosol-forming device comprises a main air inlet configured to receive anFTR4068

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[0383] airflow from the external environment of the aerosol-forming device, wherein the main air inlet is in fluid communication with the upstream airflow path arranged upstream of the heating chamber.

[0384] Example 39: The aerosol-forming device according to any one of the preceding examples, further comprising:

[0385] a device body defining a main axis of extension of the aerosol-forming device and / or defining an insertion direction for inserting the aerosol-forming article into the aerosol-forming device; and

[0386] a downstream element movably attached to the device body, such that the device body and the downstream element are movable relative to each other between an open position and a use position, wherein access to the heating chamber is provided in the open position, such that the aerosol-forming article is removable from or insertable into the heating chamber, and wherein the heating chamber is closed in the closed position.

[0387] Example 40: The aerosol-forming device of the previous example, further comprising: an interconnection mechanism arranged between the downstream element and the device body, and permitting the movement between the open and the use position, wherein the movement includes a rotational movement, a linear movement, or combination of a rotational and linear movement.

[0388] Example 41: The aerosol-forming device according to any one of the preceding examples, further comprising a heating module arranged at least partly in the device body, wherein the heating chamber is arranged in the heating module, optionally, wherein the heating module is removable from the device body of the aerosol-forming device.

[0389] Example 42: The aerosol-forming device according to any one of the preceding examples, further comprising an upstream fluidic interconnection element configured to provide a fluidic connection between the upstream airflow path upstream of the heating chamber and the aerosol-forming article, wherein the upstream fluidic interconnection element comprises:

[0390] a blade structure surrounding the upstream airflow path along a central axis of the upstream airflow path, the blade structure having a first end configured to face an upstream air inlet of the aerosol-forming article, and a second end arranged opposite of the first end, wherein an outer wall of the blade structure has a sloped or tapered shape thereby increasing a thickness of the blade structure in a direction from the first end to the second end.

[0391] Example 43: The aerosol-forming device of the preceding example, wherein the blade structure of the upstream fluidic interconnection element is configured to cut or press into a wall around an upstream air inlet of the aerosol-forming article, to provide for a fluidic connection between the upstream airflow path upstream and the air inlet of the aerosol-forming article.

[0392] Example 44: The aerosol-forming device according to any one of examples 42 and 43, wherein a cross-sectional area of an opening defined by or provided around an outer edge of theFTR4068

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[0394] blade structure is larger than a cross-sectional area of the upstream air inlet of the aerosol-forming article.

[0395] Example 45: The aerosol-forming device according to any one of the preceding examples, further comprising:

[0396] a downstream airflow path configured to provide an aerosol from the aerosol-forming article to an aerosol outlet of the device; and

[0397] a downstream fluidic interconnection element configured to fluidically interconnect the downstream airflow path with the aerosol-forming article,

[0398] wherein the downstream fluidic interconnection element includes a blade structure configured to cut or press into a wall around a downstream air outlet of the aerosol-forming article, to provide for a sealed fluidic connection between the aerosol-forming article and the downstream airflow path.

[0399] Example 46: The aerosol-forming device of the preceding example, wherein the blade structure of the downstream fluidic interconnection element is tapered or conical towards a center axis of the downstream airflow path, such that one or more tapered or conical walls of the blade structure are configured to press against an inner wall of the aerosol-forming article, preferably wherein the blade structure of the downstream fluidic interconnection element forms a cutting end edge, such that the cutting end edge of the blade structure is configured to cut into the wall around a downstream aerosol outlet of the aerosol-forming article.

[0400] Example 47: The aerosol-forming device according to any one of the preceding examples, wherein the second heating device is arranged at or close to the upstream airflow path upstream of the heating chamber.

[0401] Example 48: The aerosol-forming device according to any one of the preceding examples, wherein the upstream airflow path upstream of the heating chamber is slit-like shaped.

[0402] Example 49: The aerosol-forming device according to any one of the preceding examples, wherein the second heating device comprises a slit-shaped air channel and a resistive heating element, for example a substantially or preferably planar resistive heating element, arranged inside the slit-shaped air channel, such that two narrow airflow channels are formed above and below the resistive heating element.

[0403] Example 50: The aerosol-forming device of the preceding example, wherein the two narrow air flow channels have a width in a range between 3 mm to 15 mm, and have a height of less than 0.5 mm and more than 0.05 mm, preferably less than 0.3 mm and more than 0.1 mm, preferably less than 0.25 mm to 0.1mm.

[0404] Example 51 : The aerosol-forming device according to any one of examples 49 and 50, wherein the resistive heating element of the second heating device is formed as a meandering or serpentine structure, extending in-plane of the resistive heating element.FTR4068

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[0406] Example 52: The aerosol-forming device according to any one of examples 49 to 51, wherein the resistive heating element is formed from a single sheet of metal; and / or wherein the resistive heating element comprises at least one strip of a metal sheet, optionally wherein the strip of metal sheet is perforated and / or includes one or more perforation openings or holes.

[0407] Example 53: The aerosol-forming device according to any one of examples 49 to 52, wherein the resistive heating element comprises at least one strip of a metal sheet, the at least one strip being bent or formed into a stack of a plurality of serpentine-like formed branches, preferably the branches of the stack spanning between two terminals of the resistive heating element; and optionally wherein the stack extends along a stack direction perpendicular or parallel to a longitudinal axis of the aerosol-forming device.

[0408] Example 54: The aerosol-forming device according to any one of the preceding examples, wherein the heating chamber is configured to removably receive an aerosol-forming article, the aerosol-forming article having a substantially rectangular parallelepiped shape defining two opposing main faces and an aerosol-forming substrate arranged between the opposing main faces,

[0409] wherein the first heating device comprises a heating structure including two opposing heating elements forming a substantially rectangular parallelepiped heating volume therebetween for removably and at least partially receiving the aerosol-forming article, the heating volume arranged at least partially inside the heating chamber and defining an insertion axis for inserting the aerosol-forming article into the aerosol-forming device; and

[0410] wherein at least one of the two heating elements is made of an electrically conductive material.

[0411] Example 54A: The aerosol-forming device according to any one of the preceding examples, wherein the first heating device comprises two opposing and optionally substantially flat heating elements defining the heating chamber or a heating volume therebetween that is configured to receive at least a part of the aerosol-forming article.

[0412] Example 54B: The aerosol-forming device according to the preceding example, wherein a distance or separation between the two opposing heating elements of the first heating device may be such that the aerosol-forming article fits therebetween and / or such that the two opposing heating elements contact the two opposing main faces of the article.

[0413] Example 54C: The aerosol-forming device according to any one of examples 54A to 54B, wherein a distance or separation between the two opposing heating elements of the first heating device, is between 1 mm and 10 mm, for example between 2 mm and 5 mm, preferably between 2.5 mm and 4 mm, more preferably about 3.1 mm.

[0414] Example 55: The aerosol-forming device of the preceding example, wherein the heating structure of the first heating device is arranged inside the heating chamber, wherein upon insertionFTR4068

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[0416] of the aerosol-forming article into the heating chamber, the heating structure is configured to move towards an adjacent side face of the heating chamber so that at least one heating element of the heating structure is pressed against one of the main faces of the aerosol-forming article.

[0417] Example 56: The aerosol-forming device according to example 54 or 55, wherein at least one heating element of the first heating device includes a heating plate formed as a meandering track in the shape of a leaf spring.

[0418] Example 57: The aerosol-forming device according to any one of examples 54 to 56, wherein at least one heating element of the first heating device includes a heating plate with a plurality of parallelly-arranged heating tracks arranged in parallel to an insertion direction.

[0419] Example 58: The aerosol-forming device according to any one of examples 54 to 57, further comprising a heater casing made of a non-conductive material and forming an outer shell around the two opposing heating elements, wherein two smaller inner side faces of the heater casing form inner small side faces of the heating chamber.

[0420] Example 59: An aerosol-forming system comprising an aerosol-forming device according to any one of the preceding examples and one or more of:

[0421] an aerosol-forming article for generating aerosol; and

[0422] a companion device for one or more of storing the aerosol-forming device and charging the aerosol-forming device.

[0423] Example 60: A method of detecting a user inhalation at an aerosol-forming device comprising a heating chamber configured to receive at least a part of an aerosol-forming article, an upstream airflow path arranged upstream of the heating chamber, wherein the upstream airflow path is in fluid communication with an external environment of the aerosol-forming device, such that air is drawable by a user in a user inhalation from the external environment through the upstream airflow path towards the heating chamber, a first heating device arranged at the heating chamber and configured to perform a first heating operation, and a second heating device arranged in thermal contact with the upstream airflow path and configured to perform a second heating operation, the method comprising:

[0424] supplying electrical power to at least one of the first heating device and the second heating device; and

[0425] detecting a user inhalation at the aerosol-forming device based on determining a change in a temperature of at least one of the first heating device and the second heating device associated with a change in an airflow through the airflow path caused by the user inhalation.

[0426] Example 61: The method according to the preceding example, wherein detecting the user inhalation at the aerosol-forming device includes determining one or more of:

[0427] a change in an electrical resistance of the first heating device;

[0428] a change in an electrical resistance of the second heating device.FTR4068

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[0430] a decrease or increase in an electrical resistance of the first heating device;

[0431] a decrease or increase in the temperature of the second heating device; and

[0432] a sensor reading or change in sensor reading of at least one temperature sensor.

[0433] Example 62: The method according to example 60 or 61 , further comprising one or more of:

[0434] controlling a power supply from the power source to the first heating device based on determining a change in the temperature of the second heating device; and

[0435] controlling a power supply from the power source to the second heating device based on determining a change in the temperature of the first heating device.

[0436] Example 63: The method according to example 60 to 62, further comprising one or more of:

[0437] controlling the second heating device to perform a puff-on-demand heating operation; and controlling the first heating device to perform a continuous heating operation during a usage session.

[0438] Example 64: The method according to any one of examples 60 to 63, wherein supplying electrical power to at least one of the first heating device and the second heating device comprises:

[0439] operating the second heating device at a first power level to heat the second heating device to a pre-heating temperature above ambient temperature and below a target temperature, wherein the user inhalation is detected when the second heating device is operated at the first power level.

[0440] Example 65: The method according to the preceding example, further comprising: operating, in response to detecting the change in the temperature of the second heating device, the second heating device at a second power level for heating the second heating device to the target temperature to form aerosol from the aerosol-forming article.

[0441] Example 66: The method according to example 64 or 65, further comprising: operating, in response to detecting the change in the temperature of the second heating device, the first heating device to heat the aerosol-forming article to a target temperature or volatilization temperature sufficient to release aerosol from the aerosol-forming article.

[0442] Example 67: The method according to any one of examples 60 to 66, further comprising: operating the first heating device at a first power level to heat the first heating device to a pre-heating temperature above ambient temperature and below a volatilization temperature sufficient to release aerosol from the aerosol-forming article, wherein the user inhalation is detected when the first heating device is operated at the first power level.

[0443] Example 68: The method according to the preceding example, further comprising:FTR4068

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[0445] operating, in response to detecting the change in the temperature of the first heating device, the first heating device at a second power level for heating the first heating device to the target temperature to form aerosol from the aerosol-forming article.

[0446] Example 69: The method according to example 67 or 68, further comprising: operating, in response to detecting the change in the temperature of the first heating device, the second heating device to heat the second heating device to a target temperature.

[0447] Example 70: The method according to example 60 to 69, further comprising: determining termination of the user inhalation based on determining a further change in the temperature of at least one of the first heating device and the second heating device; and optionally decreasing the power supplied to at least one of the first heating device and the second heating device in response to determining termination of the user inhalation.

[0448] Examples will now be further described with reference to the figures in which:

[0449] Figure 1 shows an aerosol-forming system comprising an aerosol-forming device;

[0450] Figure 2 shows an aerosol-forming article;

[0451] Figure 3 shows an aerosol-forming article;

[0452] Figure 4 shows a schematic exploded view of a heating module for an aerosol-forming device;

[0453] Figure 5 shows a schematic exploded view of a heating module and heating chamber for an aerosol-forming device;

[0454] Figure 6 shows a schematic exploded view of a heating module for an aerosol-forming device;

[0455] Figure 7 shows a cross-sectional view of a heater module and a second heating device for an aerosol-forming device;

[0456] Figure 8 illustrates an airflow path through the aerosol-forming device;

[0457] Figure 9 illustrates a heating profile for a first heating device of an aerosol-forming device; Figure 10 illustrates a heating profile for a second heating device of an aerosol-forming device;

[0458] Figure 11 illustrates detection of a user inhalation at an aerosol-forming device; and Figure 12 shows a flow chart illustrating a method of detecting a user inhalation at an aerosol-forming device.

[0459] Herein, identical reference numerals are used, where possible, to designate identical elements that are common to the figures. Also, the images in the drawings are simplified and schematic for illustration purposes and may not be depicted true to scale.

[0460] The present disclosure shows and describes several embodiments which may comprise alternative or supplementary solutions for specific cases or considerations. However, it is noted that the present disclosure pertains to a complete device which may comprise any combinationFTR4068

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[0462] of features described herein. In particular, Figures 1 to 12 show and illustrate exemplary aerosolforming systems, aerosol-forming devices and / or various components, elements, and features thereof. While some of Figures 1 to 12 may show some elements or components in greater detail and according to an exemplary embodiment, the variations, examples and embodiments of Figures 1 to 12 can be combined with each other. Especially, it is noted that any of the features of any of the described embodiments may be freely combined with any other features of any other embodiments of the present disclosure. The disclosure is presented in embodiments for explanatory purposes only, and the presentation as specific embodiments does not mean that the features of one embodiment may not be complementary to other features, for example of other embodiments.

[0463] In the following, it can be mutually referred to any of Figures 1 to 12 which each show and illustrate exemplary aerosol-forming systems, aerosol-forming devices, one or more components, one or more features or one or more functions thereof.

[0464] Figure 1 shows an aerosol-forming system 4 for generating aerosol, for example for consumption or inhalation by a user in one or more usage sessions. The system 4 may comprise an aerosol-forming device 1 or aerosol-generating device 1 for generating aerosol and optionally a companion device 3 for at least partially receiving the aerosol-forming device 1. The companion device 3 may be a charging device for charging the aerosol-forming device 1 and / or an energy storage 15 or battery thereof.

[0465] The aerosol-forming device 1 may comprise an insertion opening for at least partially inserting an aerosol-forming article or aerosol-generating article 20, which is explained in more detail below with reference to Figures 2 and 3. The aerosol-forming article 20 may comprise an aerosol-forming substrate 23, such as a tobacco containing substrate and / or other active ingredient. Alternatively or additionally, the aerosol-forming article 20 may comprise a cartridge comprising a liquid, for example a liquid that can be aerosolized or vaporized for inhalation. The aerosol may be inhaled by a user, optionally using a mouthpiece 901. The aerosol may contain nicotine.

[0466] The aerosol-forming device 1 may further include processing circuitry or control circuitry 5, for example with at least one processor, microcontroller or controller 17. For generating aerosol during use or consumption of the aerosol-forming article 20, the aerosol-forming device 1 may comprise a first heating device 6a arranged at a heating chamber 30 of the aerosol-forming device 1. As will be explained in greater detail hereinbelow, the heating chamber 30 can be sized and shaped to accommodate or receive at least a part of the aerosol-forming article 20 to heat the substrate 23.

[0467] The first heating device 6a can be configured to perform a first heating operation to heat the substrate 23. For example, the first heating device 6a may be configured to heat the substrateFTR4068

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[0469] 23 or article 20 by or based on conductive heating in a continuous heating operation during a usage session.

[0470] For this purpose, the first heating device 6a can comprise at least one heating element 6, 7 or heater device for applying heat to at least a portion of the aerosol-forming substrate 23 and / or at least a part of the aerosol-forming article 20. Instead of the heating element 6, 7, a non-heat or non-thermal aerosolization device can be used, for example an ultrasonic device (not shown) may also be used to generate aerosol from the aerosol-forming article.

[0471] The control circuitry 5 and / or the processor 17 may be configured to control actuation, activation and / or deactivation of the first heating device 6a and / or of the at least one heating element 6, 7.

[0472] In the following, heating elements 6, 7 will be described with a focus on resistive heating elements 6, 7, also referred to herein as Joule-type heating elements. However, the first heating device 6a does not necessarily have to be a resistive / Joule-type heater heating device, but other heating means or approaches can be used, as also described herein. For instance, the heating elements 6, 7 may alternatively be configured as inductive heaters, radiation-based heaters such as infrared heaters, as well as microwave or dielectric heaters. For example, heating elements 6, 7 may be dielectric heaters, where opposing electrodes of a load capacitor supplied with an oscillating voltage are spring-loaded or movable to create a firm contact with opposing surfaces of the aerosol-forming article 20, with the substrate 23 located between the electrodes. It is possible that the two heating elements 6, 7 may be acting as external susceptors to the substrate that are heated by one or more coils wound around the two heating elements 6, 7 supplied with an AC voltage, for example a coil that is part of a heater casing 35, as will be described hereinbelow. The coil axis may coincide with the insertion axis for the aerosol-forming article 20 into the heating chamber 30. As another variant, heating elements 6, 7 may be dielectric heating plates of a load capacitor, that can be subjected to an radiofrequency, RF, voltage feed. Alternatively, heating elements 6, 7 or the first heating device 6a may include a resonant cavity that can be supplied by a high-frequency electromagnetic field for dielectrically heating the substrate 20 that can be situated in the resonant cavity. The features described for the first heating device 6a and / or the optionally resistive heating elements 6, 7 herein are also applicable to these alternatives.

[0473] The aerosol-forming device 1 further comprises a second heating device 70 arranged upstream of the heating chamber 30 and in thermal contact with an upstream airflow path 40a. The airflow path 40a is arranged upstream of the heating chamber 30 and fluidly connected or coupled to a surrounding, exterior or external environment of the aerosol-forming device 1 via one or more air inlets 46, also referred to herein as main air inlet 46 or device air inlet 46. When a user performs a user inhalation, air can be drawn by the user through the optional mouthpieceFTR4068

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[0475] 901 or an end of the device 1, wherein the mouthpiece 901 or end of the device 1 can be fluidly coupled to the upstream airflow path 40a and air inlet 46, such that fresh air is drawn via the air inlet 46 through the upstream airflow path 40a and towards the second heating device 70 and / or heating chamber 30. As will be described in greater detail hereinbelow with reference to Figure 10, for example, the upstream airflow path 40a may be a section or part of a complex or multisection airflow path structure in the aerosol-forming device 1.

[0476] As the second heating device 70 is in thermal contact with the upstream airflow path 40a, the second heating device 70 can heat the airflow towards the heating chamber 30 and aerosolforming article 20. Also, since the second heating device 70 as well as the first heating device 6a are subject to a changes in the airflow caused by the user inhalation, a temperature or change in the temperature of one or both the first heating 6a and second heating device 70 can be used by the control circuitry 5 to detect one or more of a start, onset, occurrence, duration, end and termination of a user inhalation, as described in detail hereinabove and hereinbelow.

[0477] The second heating device 70 can be configured to perform a second heating operation, which may differ from the first heating operation performed by the first heating device 6a. For example, the first heating device 6a may be configured to provide a continuous heating to the aerosol-forming article 20 or substrate 23 during a usage session, and the second heating device 70 may be configured for a puff-on-demand heating, which can mean that the second heating device 70 can be activated by the control circuitry 5 in accordance or correspondence with occurrence of a user inhalation or puff.

[0478] Further, the second heating device 70 may be particularly configured to heat the aerosolforming article 20 and / or substrate 23 based on convection. This can mean that the second heating device 70 is configured to heat the airflow in the upstream airflow path 40a towards the heating chamber 30 and indirectly heat the aerosol-forming substrate 23 or article 20 via the heated airflow. Therefore, the second heating device 70 may also be referred to herein as upstream heating device 70 or convective heater assembly 70. In a non-limiting example, the second heating device 70 may include at least one resistive heating element 71 to heat the airflow in the airflow path 40a. Other heating means or elements can be used instead or in addition. Details of an exemplary second heating device 70 with resistive heating element 71 is shown in Figure 7.

[0479] For powering the first heating device 6a, the at least one heating element 6, 7, and / or the second heating device 70 with electrical power, the aerosol-forming device 1 may further comprise at least one energy storage 15 or power source 15, for example in the form of a removable and / or rechargeable battery, for storing electrical energy or power.

[0480] The control circuitry 5 can be configured to control one or more of the energy source 15, the first heating device 6a, the at least one heating element 6, 7, and the second heating deviceFTR4068

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[0482] 70, for example to heat the aerosol-forming substrate 23 or article 20 in a usage session. In particular, the control circuitry 5 can be configured to control a supply of electrical power from the energy storage or power source 15 to the first heating device 6a and / or the second heating device 70, thereby controlling the heating, a heating operation, activation and / or deactivation of the first heating device 6a and / or the second heating device 70.

[0483] Both the aerosol-forming device 1 and the companion device 3 may each comprise an energy storage 15, 15a and the energy storage 15, 15a may be electrically coupled to the respective device 1, 3. In particular, energy storages 15, 15a may be removably couplable to the aerosol-forming device 1 and / or the companion device 3. In other words, energy storages 15, 15a may be a replaceable energy storages or batteries. The connection between the energy storages 15, 15a and the respective devices 1 , 3 may be configured so that the devices 1 , 3 may be run by electrical energy provided by the respective energy storage 15, 15a. Additionally, the connection between the energy storages 15, 15a and the aerosol-forming device 1 and / or the companion device 3 may be configured so that data may be transmitted between the processing or control circuitries of the aerosol-forming device 1 and / or the companion device 3 and the energy storages 15, 15a.

[0484] The aerosol-forming device 1 may further comprise at least one electrical connector 12 for coupling to a corresponding at least one electrical connector 13 of the companion device 3 and / or an electrical connector of an external power supply (not shown), e.g., a USB connector with a USB charger. In an example, energy storage 15 of the aerosol-forming device 1 may be charged based on coupling the device 1 to the companion device 3, for example based on at least partly inserting the device 1 into a compartment or recess of the companion device 3. Upon mechanically coupling the devices 1, 3, an electrical connection between the one or more electrical connectors 12 of the aerosol-forming device 1 may be coupled with the one or more electrical connectors 13 of the companion device 3 to charge the energy storage 15 of the aerosolforming device 1 via the energy storage 15a of the companion device 3. The energy storage 15a of the companion device 3 can, for example, be re-charged via connection to a main power supply, e.g., a USB charger. Any of the charging processes can also be performed wirelessly.

[0485] The aerosol-forming device 1 may further comprise a communications arrangement 9 or communication circuitry 9 with one or more communications interfaces 10 for communicatively coupling the aerosol-forming device 1 with the companion device 3, server, smartphone or other devices, for example, via an Internet connection, a wireless LAN connection, a WiFi connection, a Bluetooth connection, a mobile phone network, a mobile data connection for example but not limited to a 3G / 4G / 5G connection, an edge connection, an LTE connection, a BUS connection, a wireless connection, a wired connection, an optical data connection such as but not limited to IrDa, a radio connection, a near field connection, and / or an loT connection.FTR4068

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[0487] The aerosol-forming device 1 may further comprise a data storage 11 or memory for storing information, program code or data. Data storage 11 may also store collected values of sensors and / or one or more mathematical functions or formulas, software and computer instructions that can be executed by the control circuitry 5 and / or processor 17. One or more sensors 16 may be arranged on, at or in the aerosol-forming device 1 or the companion device 3 to collect data. One or more of the sensors 16 may for example be temperature sensors, strain sensors, accelerometers or any other suitable sensors.

[0488] The aerosol-forming device 1 may further comprise user interface components, for example comprising an input element or input device 19, for example in the form of a pushbutton, touch display or a capacitive button. The input device 19 may be used as a power button to activate or deactivate the first heating device 6a and7or the second heating device 70 thereby to activate or deactivate the aerosol-forming device 1.

[0489] Upon activation of the aerosol-forming device 1, the first heating device 6a and / or second heating device 70 may be activated and heat may be applied to at least a part of the aerosolforming article 20, such that aerosol can be generated for consumption or inhalation by the user, for example in a usage session. The actual control or operation of the first heating device 6a and the second heating device 70 will be described in more detail hereinbelow.

[0490] The aerosol generating device 1 and / or the companion device 3 may each comprise one or more output elements, such as a display device 18 and / or one or more LEDs, for outputting a signal and / or displaying information to a user, for example a user interface such as a GUI, or haptic and acoustic data output devices. The display device 18 may be, for example, a touchscreen and may therefore be configured as both an output and an input element.

[0491] Figure 2 shows three different views of an exemplary aerosol-forming article 20, or consumable, which may be used with the aerosol-forming device 1 of Figure 1 or any of the other figures. In the top left, an end view is shown. Bottom left shows a perspective view, and the right side of Figure 2 shows a side view of the aerosol-forming article 20. A further detailed view of the aerosol-forming article 20 of Figure 2 is shown in Figure 3, which shows a perspective view at the top of Figure 3 and a cross-sectional view along a longitudinal axis A-A at the bottom of Figure 3.

[0492] Although the present disclosure is applicable to conventional and not limited in use of rectangular parallelepiped shaped aerosol-forming articles, Figures 2 and 3 and many other Figures illustrate an aerosol-forming article 20 that may have a flat or planar shape. Other shapes or geometries of the aerosol-forming article 20 are possible. And encompassed by the present disclosure.

[0493] The aerosol-forming article shown in Figures 2 and 3, for example, can have the basic shape or foot-print of a rectangle, optionally with rounded corners. For instance, the aerosolforming article 20 may be a cuboid or parallelepiped or rectangular parallelepiped, optionally withFTR4068

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[0495] rounded corners. It may have a length L which is greater than its width W, which is in turn greater than its thickness T.

[0496] For example, the length L of the aerosol-forming article 20 may be from 20 mm to 40 mm, for example from 25 mm to 35 mm. In a non-limiting example, the length L of the aerosol-forming article 20 may be 30 mm. The width W of the aerosol-forming article 20 may be from 7 mm to 15 mm, for example from 9 mm to 13 mm. In a non-limiting example, the width W of the aerosolforming article 20 may be 11 mm. The thickness T of the aerosol-forming article 20 may be from 1 mm to 10 mm, for example 2 mm to 5 mm, for example from 2.5 mm to 4 mm. In a non-limiting example, the thickness T of the aerosol-forming article 20 may be 3.1 mm.

[0497] The aerosol-forming article 20 may comprise a frame 21 and an aerosol-forming substrate 23, which may be arranged in a centre section of the article 20 The centre section of the article 20 may also be referred to as central section or middle section of the article 20. The frame 21 may comprise or be made of a cellulose fibre material, for example a cardboard material. The frame 21 may define the circumference or perimeter of the aerosol-forming article 20 along the edges and / or corners.

[0498] The aerosol-forming article 20 comprises two opposing sides, surfaces or main faces 20a, 20b that make up the majority of the surface of the aerosol-forming article 20. The main faces or surfaces 20a, 20b may comprise or be made of a cover sheet, which may comprise paper-based material, for example rolling paper, which may be fixed to the frame 21 and, together with the frame 21, may define a substrate chamber or cavity 22, which may be filled with any type of aerosol-forming substrate or capsule mentioned herein, or a combination of one or more substrate and a capsule. In particular, solid substrate material may be used.

[0499] The present disclosure provides an aerosol-forming device 1 which may be configured to use such an aerosol-forming article 20. In particular, the heating chamber 30 of the aerosolforming device 1 may be configured, shaped and arranged to removably accommodate or receive a rectangular parallelepiped shaped aerosol-forming article 20, as described herein. Optionally, the heating chamber 30 may be defined by or comprise a heating module 34 configured to removably accommodate such an aerosol-forming article 20 with predominantly planar form factor, maximizing the heating efficiency and increasing the consumable extraction, without quickly depleting the aerosol. To do so, a full contact between the at least one heating element 6, 7 of the first heating device 6a and the aerosol-forming article 20 may be ensured during the heating phase or usage session. As will be shown below, substantially flat or planar heating elements 6, 7 may provide the benefit of keeping a high ratio of surface heated versus substrate volume, which, in turn, can provide for a faster and more homogeneous substrate heating.

[0500] The aerosol-forming article 20 may also comprise an airflow path through the frame 21 and the substrate 23 in the substrate chamber. A detailed view of the aerosol-forming article 20 isFTR4068

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[0502] given in Figure 3. The aerosol-forming article 20 may be predominantly flat or planar. It may be shaped as a rectangular parallelepiped or cuboid. It may comprise the frame 21 or consumable frame 21 having a cavity 22 designed to accommodate the aerosol-forming substrate 23.

[0503] The aerosol-forming article 20 can have a substantially rectangular parallelepiped shape defining two opposing main faces 20a, 20b, which constitute the majority of the surface of the article 20. The aerosol-forming article 20 further defines two opposing side faces 20e, 20f or lateral faces 20e, 20f. The two opposing side faces or lateral faces 20e, 20f may extend parallel to a longitudinal direction of the aerosol-forming article 20. The aerosol-forming article 20 further defines or comprises two opposing smallest faces or surfaces 20c, 20d, which oppose each other in longitudinal direction of the aerosol-forming article 20.

[0504] On the sides or main faces 20a, 20b of the cavity 22, where no frame 21 may be located, the cavity 22 may be closed off from the outside environment by a sheet of cellulose fiber material, for example paper or rolling paper, or paper-like material. Such a sheet may be provided on both sides of the aerosol-forming article 20.

[0505] The frame 21 or article 20 may further comprise a consumable air inlet 24 arranged at one of the smallest faces 20c and an air or aerosol outlet 25 arranged at the opposite smallest face 20d, which may be arranged substantially in-axis with a direction of longitudinal extension of the aerosol-forming article 20 at the smallest faces 20c, 20d. Accordingly, the air inlet 24 and the aerosol outlet 25 can define a longitudinal direction or axis of the aerosol-forming article 20.

[0506] The air inlet 24 and the air outlet 25 may be arranged at the smallest opposing faces or surfaces 20c, 20d of the aerosol-forming article 2. The air inlet 24 and the air outlet 25 may be fluidically connected to a consumable air inlet channel 26 and a consumable air outlet channel 27, respectively. These channels 26, 27 may be configured to be in fluid communication with the consumable cavity 22.

[0507] The air inlet 24, the air inlet channel 26, the air outlet channel 27 and the air or aerosol outlet 25 each may have a cross-section shaped to correspond in surface area and ratio with the cross-section of the aerosol-forming article 20 and also the substrate 23. For example, the crosssection of the air inlet 24, the air inlet channel 26, the air outlet channel 27 and the air or aerosol outlet 25 is smaller than the cross-section of the aerosol-forming article 20, but the shape of the cross sections may be similar to each other. In other words, the air inlet 24, the air inlet channel 26, the air outlet channel 27 and the air outlet 25 may have a rectangular cross-section, optionally with rounded corners. Therefore, the cross-section may be in the shape of an oblong or ovally-shaped or oval-shaped hole. In this way, the air flowing thorough the airflow path provided by this cross-section may enter and stream through the similarly arranged substrate 23 in an optimal way. The cross-section as used herein may be perpendicular to a longitudinal axis of the aerosolforming article 20 and / or the direction of the airflow path through the aerosol-forming article 20.FTR4068

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[0509] An exemplary heating concept for the aerosol-forming article 20 as described above is shown in Figure 4 and subsequent Figures. The aerosol-forming device 1 can optionally comprise a heating module 34, as shown in Figure 4. The heating module 34, also referred to as heater module 34, may comprise at least part of or the entire first heating device 6a. In particular, the heating module 34 may comprise two heating elements 6, 7 of the first heating device 6a, for example substantially flat or planar heating elements 6, 7, which may be arranged parallel and opposite to each other, for example in a sandwich configuration with the aerosol-forming article 20 between them.

[0510] An interior of or the entire heating module 34 may define the heating chamber 30. The aerosol-forming article 20 may be at least partially or fully inserted into the heating chamber 30. Outer walls of the heating chamber 30 may be defined or provided by an optional heater casing 35, which may also contain the heating elements 6, 7. The heater casing 35 may be arranged in an insulating casing 2 to prevent heat from the heating elements 6, 7 from dissipating and / or reaching the user’s fingers, and for concentrating the heat to the heating chamber 30. The heating elements 6, 7 may be arranged parallel to the two main surfaces 20a, 20b of the aerosol-forming article 20 and define a heating volume therebetween to heat the aerosol-forming substrate 23. The heating elements 6, 7 may be arranged parallel to an inner surface of the heating chamber 30 and / or heater casing 35. The heating chamber 30 may be a substantially cuboid receptacle or space configured to at least partially receive the aerosol-forming article 20. It may be defined by at least one side or two parallel, opposite sides configured as a planar cavity surface extending substantially in a plane. The heating element 6 and / or the heating element 7 may extend substantially in a plane parallel to the plane of the planar cavity surface.

[0511] A more detailed view of the heating chamber 30 and its arrangement in the aerosol-forming device 1 is shown in Figures 5 and 6. The heating chamber 30 may comprise the two heating elements 6, 7 of the first heating device 6a. The two heating elements 6, 7 are also referred to herein as first heating element 6 and second heating element 7 of the first heating device 6a. The heating elements 6, 7 are arranged in a parallel configuration and opposed to each other. In the specific embodiment shown, the two heating elements 6, 7 may be resistive or Joule-type heaters that transfer heat by heat conduction to the substrate 23 of the aerosol-forming article 20. However, other heating technologies or a combination of different heating technologies may be used.

[0512] The heating chamber 30 may further comprise an insulation casing 2 or insulating casing 2 which may act as an outer first insulation element and may provide an airgap for the airflow. The airgap may have a constant size or cross-section along its extension or may have sections differing in size or cross-section, as will be described with reference to Figure 10. The heating chamber 30 may further comprise the heater casing 35 which may be defined at least at one sideFTR4068

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[0514] by a planar cavity surface extending substantially in a plane and which may be configured to enclose the heating elements 6 and 7, wherein the heating elements 6, 7 may be further held in place by a clamp element 8. The heater casing 35 may have a rectangular cross section and may be configured such to receive at least a portion of an aerosol-forming article 20 that is substantially planar (like the one shown in Figures 2 and 3) and to heat the aerosol-forming article 20 from the outside. In addition, an air space may be provided between the heating elements 6,7 and the inner walls of the heating chamber 30, respectively, that may be thermally insulated.

[0515] The heater casing 35 and / or the heating chamber 30 may have walls with heat-reflecting properties. This may allow to reduce the thermal losses when resistively heating and concentrate the heat within the heating chamber 30, and may also provide for an integrated mechanism for a user being able to firmly hold the aerosol-forming device 1 at a given place without being subjected to unsafe or unpleasant temperatures. The heater casing 35 may also be designed with grooves, channels or any generic means along inner walls of the heating chamber to provide an air flow channel for the air flow through portions of the aerosol-forming device 1, for example a channel that is formed at the longer side faces of the rectangular parallelepiped shape heating chamber 30.

[0516] As shown in Figure 6, the heating elements 6, 7 of the first heating device may be curved towards or in direction of the two opposing main surfaces 20a, 20b of the aerosol-forming article. This can ensure good thermal contact. Further optionally, the heating elements 6, 7 may be formed as heating plates or may heating structure in the form of heating tracks, as shown in Figure 6.

[0517] As further shown in Figure 6, the second heating device 70 can be configured as a convective heater assembly 70, which may be arranged upstream the aerosol-forming article 20, the heating chamber 30 and upstream the first heating device 6a, respectively, the first and second heating elements 6, 7 thereof, in order to heat the air entering the aerosol-forming article 20.

[0518] Second heating device 70 may comprise at least one resistive heating element 71 or convective heater 71 which may be a resistive component which may transfer heat by convection to the surrounding air. The resistive heating element 71 may be arranged inside a convective heater casing 72 and may be held in place by a bottom cap 75.

[0519] As also shown in Figure 6, the heater casing 35 and / or the insulation casing 2 may be composed by two shells, for example an upper shell and a bottom shell, which may be designed to be engaged and / or combined during assembly. Heater casing 35 and / or insulation casing 2 may be made of a plastic material such as polyether ether ketone (PEEK) and / or polyaryletherketone (PAEK) and / or polyetherimide (PEI), preferably PEEK. Heater casing 35 can also have thermal insulation properties like insulating casing 2, for example having a high thermalFTR4068

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[0521] resistivity or low thermal conductivity, preferably a thermal conductivity below 1 W / (m • K), more preferably below 0.5 W / (m • K).

[0522] It is also possible that the entire heating module 34 comprising the heating chamber 30 may be removably placed inside the body 800 or device body 800 of the aerosol-forming device 1, for example with electric connection terminals that may be arranged to be in parallel with the main axis of extension or the longitudinal axis of the aerosol-forming device 1, and which can interconnect to corresponding terminals inside the body 800 of device 1. The longitudinal axis of the device 1 may be the same as and / or parallel to the insertion axis or the insertion direction of the aerosol-forming article 20 into the heating chamber 30. The connection may be formed only by the movement of the heating chamber 30 when being inserted into the device body 800.

[0523] As indicated in Figure 5, the aerosol-forming device 1 can include a device body 800 or body 800 and a downstream element 802. The downstream element 802 can also be referred as second housing part or mouthpiece portion 802. Optionally, the mouthpiece 901 may be arranged at the downstream element 802.

[0524] The downstream element 802 may be movably attached to the device body 800, such that the device body 800 and the downstream element 802 can be movable relative to each other between an open position and a use position. In the open position access to the heating chamber 30 can be provided, such that the aerosol-forming article 20 is removable from or insertable into the heating chamber 30. In the closed position, as shown in Figure 5, the heating chamber is closed. Also the heater module 34 may be removed from or inserted into the device body 800 in the open position.

[0525] The downstream element 802 and the device body 800 can be coupled to each other via an interconnection mechanism 802 arranged between the downstream element 802 and the device body 800, and permitting the movement between the open and the use position. Therein, the movement can include a rotational movement, a linear movement, or combination of a rotational and linear movement.

[0526] Figure 7 shows a cross-sectional view of a heater module 34 and a second heating device 70 for an aerosol-forming device 1. The top depiction of Figure 7 shows a top view of the section of the device 1 comprising the heating chamber 30.

[0527] With reference to Figure 7, the heating chamber 30 may be associated with the second heating device 70 or convective heater assembly 70, for example to boost the extraction of the aerosol compounds from the aerosol-forming article 20. The bottom depiction of the Figure shows a lateral or side view of the second heating device 70.

[0528] The second heating device 70 may contribute to the definition of the upstream airflow path 40a and may be arranged upstream the heating chamber 30 to guarantee a continuous route for the airflow through the aerosol-forming device 1. The air may therefore enter the convectiveFTR4068

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[0530] heating assembly 70, be heated, and then enter the heating chamber 30 with the aerosol-forming article 20. Preferably, the convective heater assembly 70 is arranged such that an airflow path from the resistive heating element 71 to the upstream inlet 24 of article 24 is as short as possible, to avoid a drop of temperature to the air after passing the resistive heating element 71. In a variant, it is also possible that the resistive heating element 71 protrudes into the upstream air inlet 24 of the article 20, when the article 20 is in an inserted position.

[0531] The second heating device 70 may include the resistive heating element 71 and a convective heater casing 72, wherein the convective heater casing 72 may have a convective heating chamber 73 configured to receive the resistive heating element 71, without getting in direct contact with inner walls of the convective heating chamber 73. This configuration may define two gaps 74 above and below the heating element 71 (best visible in the lateral cross-sectional view of the bottom of Figure 7) which allows a convective heat exchange between the resistive heating element 71 and the surrounding air passing through the gaps 74. In other words, the gaps 74 may form a part of the airflow channel through the aerosol-forming device 1 leading through the second heating device 70.

[0532] The resistive heating element of the second heating device may be formed as a meandering or serpentine structure, extending in-plane of the resistive heating element.

[0533] The resistive heating element 71 can comprise at least one strip of a metal sheet, optionally wherein the strip of metal sheet is perforated and / or includes one or more perforation openings or holes. Alternatively or additionally, the resistive heating element 71 can comprise at least one strip of a metal sheet, the at least one strip being bent or formed into a stack of a plurality of serpentine-like formed branches, preferably the branches of the stack spanning between two terminals of the resistive heating element 71.

[0534] Further, a bottom cap 75 can ensure that the second heating device 70 and the heating chamber 30 are held together. Preferably, the convective heater casing 72 is made of a material that has low thermal conductivity, so that a heating of the inner walls of the heater casing 72 is reduced, with the goal to provide the heating energy preferentially or predominantly to the incoming air. For example, preferably, the heater casing 72 is not made of metal, but of a thermoplastic with high temperature resistivity and low thermal conductivity, preferably PEEK or PEI.

[0535] The dimensions of the cavity or heating volume provided by the heating chamber 30 may reflect the dimensions of the aerosol-forming article 20 in order to ensure that the article 20 can be inserted to the heating chamber 30 and arranged between heating elements 6,7, although a part of the aerosol-forming article 20 may protrude out of the heating chamber 30. The fit of the aerosol-forming article 20 in the heating chamber 30 is shown in Figure 13. Preferably, the fit should be a light press-fit or a light interference fit with the aerosol-forming article 20 betweenFTR4068

[0536] 71 / 89

[0537] heating elements 6, 7. For example, the heating chamber 30 may have a length L3 of from 10 mm to 35 mm, for example of from 15 mm to 30 mm or from 15 mm to 25 mm. This may also be referred to as the insertion depth of the heating chamber 30. The heating chamber 30 may have a width W3 of between 7.2 mm and 15.2 mm, preferably between 9.2 mm and 13.2 mm, more preferably about 11.2 mm. The heating chamber 30 may have a thickness T3 of between 2 mm and 10 mm, more preferably between 3 mm and 8 mm, even more preferably between 4 mm and 6 mm. These values may pertain to the inside clearances of the heating chamber 30 in the respective directions. Again, these values are purely exemplary, and any other suitable dimensions may be chosen.

[0538] A benefit of using substantially flat or planar heating elements 6, 7 for the first heating device as described may be the provision of a faster and more homogeneous substrate heating. This may be achieved by the high ratio of surface heated to substrate volume. To further improve aerosol extraction from the aerosol-forming article 20, the contact pressure between the aerosolforming article 20 and the heating element 6, 7 may be increased.

[0539] According to at least some aspects of the present disclosure, heating elements 6, 7 can be provided, that allow to firmly contact a to-be-heated surface of the aerosol-forming article 20 for example at a location where the substrate 23 is located inside the article 20. The heating elements 6, 7 can be resistive or Joule-type heater elements, but other types of heating are also possible, for example inductive heating with elements 6, 7 acting as susceptors, or dielectric heating where heating elements 6, 7 act as capacitor plates. In addition, an air space may be provided around the heating elements 6, 7 to thermally insulate the heating chamber 30 and the heater casing 35.

[0540] Figure 6 also schematically shows a fluidic interconnection element 88, which is also referred to as upstream fluidic interconnection element 88. The fluidic interconnection element 88 may be configured to provide for a fluidic connection between the air inlet 24 of the article 20 and the downstream airflow path 40. A further or downstream fluidic interconnection element may connect the aerosol outlet 26 of the article 20 to the downstream element 802 or an airflow path therein.

[0541] The fluidic interconnection element 88 can have a blade or blade structure, which may surround the upstream airflow path 40. The blade may define an opening of the fluidic interconnection element 88 through which the airflow path can be arranged. The opening may have an oblong shape, for example in cross-section, for example perpendicular to the air flow direction

[0542] The blade structure may be tapered on both the inside and the outside surface of the fluidic interconnection element 88, i.e. both the inside surface contacting the air in the airflow path or channel and the surface directed away from the airflow path or channel. Alternatively, the blade structure may be tapered only or exclusively on the outside surface of the fluidic interconnectionFTR4068

[0543] 72 / 89

[0544] element 88. By only tapering the outside surface of the fluidic interconnection element 88 and leaving the inside surfaces completely flat and smooth, the airflow in the airflow path or channel may not be influenced in any way. A tapered inside surface may, otherwise, act as a flow restriction, possibly negatively affecting the airflow. Additionally, by leaving the inside surface of the fluidic interconnection element 88 straight and only tapering the outside surface, when the fluidic interconnection element 88 is inserted into the frame 21 of the aerosol-forming article 20 by penetration, the material of the frame 21 may be only or substantially only displaced by the tapered outside surface, displacing the material in a direction away from the airflow path or channel. In this way, no displaced material of the frame 21 is displaced or otherwise pressured into the airflow path or channel, which would again possibly affect the airflow negatively and impact aerosol formation. This can be avoided by the specific shape of the hollow blade structure as explained herein.

[0545] Figure 8 shows several cross-sections through an aerosol-forming device 1, and illustrates an exemplary airflow through the aerosol-forming device 1. The top of Figure 8 shows a crosssection through heating chamber 30 or module arranged in the aerosol-forming device 1, and the middle and bottom sections of Figure 8 show a cross-section primarily through the heating module 34. It is noted that the airflow path shown and described with reference to Figure 8 is exemplary only. Many variations are possible.

[0546] Via one or more air inlets 46, device inlets 46 or main air inlets 46, air can enter the body 800, downstream element 802 and / or housing of the aerosol-forming device 1. The exemplary airflow path through the aerosol-forming device 1 of Figure 8 may begin with a first airflow path portion 40 beginning at the air inlet 46. The device air inlet 46 may comprise a peripheral gap between the mouthpiece portion 900 and the device body 800. The peripheral gap may be continuous around the entire device 1, or may have several, potentially separate, sections or portions or openings around the device body 800. In another variant, there is one gap on each side between downstream element 802 and device body 800.

[0547] The gap forming the device air inlet 46 may have a diameter or clearance of at most 0.05 mm or at most 0.075 mm or at most 0.1 mm or at most 0.125 mm or at most 0.15 mm or at most 0.175 mm or at most 0.2 mm. The gap or clearance may be provided around a portion of the perimeter or the circumference of the aerosol-forming device 1, the portion for example being at least 50 % or at least 75 % or at least 90 % of the perimeter or the circumference. Alternatively, the device air inlet 46 may be configured as one or more lateral holes or channels. The lateral holes may be placed at the interface of an outer surface of the downstream element 802 and the device body 800. This placement of the device air inlets 46 may present several advantages, as it may allow for easy cleaning of the airflow path to remove obstructions when the mouthpiece 901 is removed, and it may allow to conceal or make the inlets less visible. Finally, obstruction byFTR4068

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[0549] the hand and / or fingers of the user may be made less likely. That the device air inlet 46 may be hidden may also enhance design aspects, e.g., the device air inlet 46 may be arranged inside a groove, behind a hinge, or behind a snap, or the like.

[0550] The airflow path may proceed in a second airflow path portion 41 , which may be provided by a gap between the insulation casing 2 and the heater casing 35, or through a channel inside the heater casing 35 itself. The insulating casing 2 and the heater casing 35 may have a rectangular parallelepiped shape. This makes several suitable airflow paths possible between these two elements. For example, there may be two parallel flow path portions on two opposite sides of the aerosol-forming article 20. In these, the air may flow parallel to an axis of longitudinal extension of the aerosol-forming article 20 along the larger side surfaces, or there may be two parallel flow path portions at the two smaller side surfaces of the aerosol-forming article 20 or consumable. In the latter option, the air may flow parallel to the axis of longitudinal extension of the aerosol-forming article 20 along the smaller lateral sides. Also, a combination of these flow paths may be used. With the two parallel flow path portions 41 on the smaller side surfaces 20e, 2 Of , and the heater elements 6, 7 arranged to face the larger side surfaces 20a, 20b of the aerosolforming article 20, it is possible to separate a heating of the substrate 23 and a heating of the incoming airflow, such that the air heating is mainly performed by the second heating device 70, and not by the heater elements 6, 7. In case the second heating device 70 is operated on a puffbasis, e.g. is only heated when a puff occurs, this separation of these heating aspects allows to save energy and better control a temperature of the heat departed to the airflow by the second heating device 70.

[0551] Once the airflow reaches the bottom or distal end part of the insulation casing 2, which may mean the part of the insulating casing 2 opposite the mouthpiece 901 , it may then be redirected towards the second heating device 70 that may accommodate the resistive heating element 71. For this, there may be provided a further airflow path portion 48 which leads the air radially or laterally inwards towards the longitudinal central axis of the aerosol-forming device 1. The airflow path from the entry into the second heating device 70 parallel to the longitudinal axis of the device 1 onwards may constitute the upstream airflow path 40a, as described herein, which is exemplary shown as third airflow path portion 42 in Figure 8.

[0552] The air may enter the second heating device 70 and pass along the resistive heating element 71. In one variant, the airflow may change direction from a direction parallel to the longitudinal axis of the aerosol-forming device 1 by approximately 90° to progress towards a center axis or longitudinal axis of the aerosol-forming device 1, and then may change direction again by 90° to pass through the second heating device 70 which may be arranged in parallel with the longitudinal axis of the aerosol-forming device 1. Therefore, the airflow may change flow direction by 180° or make a U-turn between the second airflow path portion 41 and third airflowFTR4068

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[0554] path portion 42. This U-turn may be the further airflow path portion 48. In another variant, the resistive heating element 71 may be arranged orthogonal to the longitudinal axis of the aerosolforming device 1, and the airflow may pass through the resistive heating element 71 while progressing towards the center axis or longitudinal axis of the aerosol-forming device 1. In this case, the second heating device 70 may be part of or arranged in the further airflow path portion 48. The airflow may then change direction again by 90° to leave the resistive heating element 71 and / or the second heating device 70 to directly enter the aerosol-forming article 20 through air inlet 24, optionally via the upstream fluidic interconnection element 88. The third airflow path portion 42 may then shorten. Two parallel airflow path portions 41 can be fluidically reunited, for example merged or combined, at element or portion 42. This allows for redundancy if one of them is blocked. The parallel arrangement reduces the overall resistance-to-draw.

[0555] The passage of the air through the resistive heating element 71 and / or the second heating device 70 may be particularly relevant because it may allow the air coming from the outside environment and having ambient temperature (passing through airflow path portions 40 and 41) to be heated by the resistive heating element 71 in very close proximity before arriving at the substrate 23. The bottom and / or distal end part of the insulating casing 2, which is directed away from the mouthpiece 901 or inhalation side of the device 1, may be referred to as the convective heating chamber 73, and may be configured with a convective or heat exchange heater placed therein to heat up the air upstream of the article 20. Different configurations of the second heating device 70 and resistive heating element 71 are possible. In general, it may be desirable to use a resistive heating element 71 with a heating surface as large as possible, so that a large air surface may come into contact with the heated surfaces of the resistive heating element 71.

[0556] An exemplary heating profile 200 for the first heating device 6a is illustrated in Figure 9 and an exemplary heating profile 300 for the second heating device 70 is illustrated in Figure 10.

[0557] It is noted that Figures 9 and 10 illustrate exemplary temperature profiles 200, 300, wherein Figures 9 and 10 particularly show measured temperatures of the first heating device 6a and the second heating device 70a. More specifically, the temperature values shown in Figure 9 may correspond to measured temperature values of the heating elements 6, 7 of the first heating device 6a. These temperature values can be average temperature values of the surfaces of the heating elements 6, 7, which contact the aerosol-forming substrate 23 or article 20. Likewise, the temperature values shown as curve 302 in Figure 10 may correspond to measured temperature values of the second heating device 70 and / or its resistive heating element 71. The actual heating profile 300 may rather be represented by the dashed curve 304 in Figure 10. These temperature values can be average temperature values of the surface of the resistive heating element 71 that is exposed to air. As can be seen in Figures 9 and 10, the measured temperature values fluctuate around the course of the temperature defined in the respective heating profiles 200, 300. Hence,FTR4068

[0558] 75 / 89

[0559] the measured temperature values shown in Figures 9 and 10 illustrate the heating profiles 200, 300 and the one or more target temperatures defined therein. It should further be noted that the fluctuations in the temperature profiles 300 of the second heating device 70 shown in Figure 10 occurring between the puffs or user inhalations result from measurement only and do not represent the actual heating profile 300 of the second heating device 70. As explained in detail herein, the second heating device 70 may be deactivated between puffs or user inhalations, or may at least be powered at the first power level, respectively, a comparatively low power level.

[0560] Figure 9 illustrates a heating profile 200 for the first heating device 6a of the aerosol-forming device 1. As noted above, the first heating device 6a can be configured to heat the substrate 23 in a continuous heating operation during a usage session.

[0561] The heating profile 200 is illustrated in Figure 9 in the form of a curve of a temperature (in °C) of the first heating device 6a versus time (in seconds) during a usage session. However, the heating profile 200 may alternatively or additionally be defined in terms of one or more other parameters indicative of or correlated with the temperature of the first heating device 6a, such as the resistance of the first heating device 6a.

[0562] The heating profile 200 defines a plurality of target temperatures 202 that the first heating device 6a should be heated to based on corresponding control by the control circuitry 5. Accordingly, the control circuitry 5 may be configured to operate the first heating device 6a with the heating elements 6, 7, such that at least a part of the first heating device 6a reaches the target temperature as defined for the respective moment or time during the usage session, for example from start of the usage session.

[0563] The exemplary heating profile 200 shown in Figure 9 has a maximum duration of about 500 seconds (around 8 minutes), and a maximum heating temperature of about 280 to 290 °C. Generally, the maximum duration may vary between 3 minutes and 12 minutes, and the target temperatures defined by the heating profile 200 may be in the range of about 200°C to about 300°C.

[0564] When the aerosol-forming device 1 is started or activated by the user for aerosol consumption, the control circuitry 5 can be configured to operate or power the first heating device 6a according to the heating profile 200. Accordingly, the heating profile 200 for the first heating device 6a, and optionally the heating profile 300 for the second heating device 70, may be started upon activation of the device 1 by the user for aerosol-consumption. The actual usage session, where user can inhale aerosol in one or more user inhalations, may start after a predetermined period of time or heat-up phase after activation of the aerosol-forming device 1 by the user for aerosol consumption, respectively after start of the heating profile 200. The predetermined period of time for the heat-up phase may be between about 5 seconds and about 35 seconds, for example about 20 seconds. Alternatively or additionally, a usage session may start upon reachingFTR4068

[0565] 76 / 89

[0566] a predetermined temperature, for example a temperature close to, corresponding to or above the volatilization temperature of the substrate 23. Accordingly, the first heating device 6a and optionally the second heating device 70 may be powered or operated by the control circuitry 5 upon activation of the device 1 by the user according to one or more heating profiles 200, 300, and the usage session where the user takes one or more user inhalations may start afterwards, for example after expiry of the predetermined time and / or after reaching a predetermined temperature. Hence, the temperature profile 200 may show a timely evolution of the temperature of the first heating device 6a and / or its heating elements 6, 7, for example starting at 0 seconds in Figures 9 to 13, where the first heating device 6a may begin to heat, while the usage session may only start once a predetermined temperature of the substrate 23 has been reached and / or a predetermined period of time has expired or elapsed.

[0567] When the aerosol-forming device 1 is started or activated by the user for aerosol consumption, the control circuitry 5 can be configured to rapidly increase the temperature of the first heating device 6a, during a first phase 204 of the usage session, to a target temperature of the first phase 204 between about 270°C and 300°C, for example approximately 285°C. A duration of the first phase 204 may be between 2 and 40 seconds, for example about 20 seconds.

[0568] The control circuitry 5 can be further configured, upon reaching the first target temperature, to maintain the first target temperature during a second phase 206 of the usage session. A duration of the second phase 206 may be between 10 and 40 seconds, for example about 20 seconds.

[0569] The control circuitry 5 can be further configured to, in a third phase 208 of the usage session, to reduce the temperature of the first heating device 6a to a target temperature of the third phase between 200°C and 260°C, for example about 220°C. A duration of the third phase 208 may be between 5 and 40 seconds, for example about 10 seconds.

[0570] In a fourth phase 210 of the usage session, which usually lasts until the end of the usage session, the control circuitry 5 can be configured to gradually ramp up the temperature of the first heating device 6a from the target temperature of the third phase to a final or target temperature of the fourth phase, which may be between about 220°C and 300°C, for example about 280°C. A duration of the fourth phase 210 may be between about 300 seconds to about 800 seconds.

[0571] A plurality of such or similar heating profiles 200 may be utilized by the aerosol-forming device 1 or control circuitry 5 to heat an aerosol-forming article 20 in a usage session. For example, different heating profiles may differ in length and average temperature during the usage session. Also, different heating profiles for different types of aerosol-forming articles 20 may be used. Different heating profiles 200 may be selected by the user, for example based on user input, or automatically, for example based on one or more sensors of the aerosol-forming device, for example to detect a type of article 20 inserted into the device 1.FTR4068

[0572] 77 / 89

[0573] The temperatures and durations of the phases 204-210 shown for the heating profile 200 of Figure 9 are exemplary only.

[0574] The control circuitry 5 can be configured to control the temperature of the first heating device 6a, and / or the first and second heating element 6, 7 thereof based on measuring the resistance or electrical resistance of one or both the first and second heating elements 6, 7. The electrical resistance can change with the temperature, and hence the temperature can be controlled based on measuring the electrical resistance and controlling the energy storage 15 and / or first and second heating elements 6, 7. The first and second heating elements 6, 7 can be connected together in series. The control circuitry 5 can measure the current and the voltage to get the total resistance for both heating elements 6, 7 in series. The electrical resistance of the heater material can increase with the temperature. So, the total electrical resistance value given as the sum of the resistances of both heating elements 6, 7 can be used to control the temperature. In fact, the first heating device 6a can act as temperature sensor, which can also be used for puff detection, as described in detail above and in subsequent figures.

[0575] Alternatively or additionally, the aerosol-forming device may comprise one or more temperature sensors for determining the temperature and / or change in temperature of one of or both the first heating device 6a and the second heating device 70.

[0576] The resistances of the first and second heating elements 6, 7 can be very close to each other and the mechanical design around the first heating device 6a can be symmetric so that both heating elements 6, 7 can have substantially the same temperature. Contact surfaces of the heating elements 6, 7 that contact the two opposing main faces 20a, 20b of the aerosol-forming article 20 can have the same width for the area in contact with the article 20.

[0577] A calibration to determine the temperature to resistance relation can be operated with thermocouples placed at the center of the article 20. A calibration process can be carried out with a fake aerosol-forming article 20 with two thermocouples inside the device 1 and then going through different fix temperature targets. Then based on this data, one or more, for example three, reference or calibration values of resistance versus temperature can be set or stored in the device memory.

[0578] Figure 10 illustrates a heating profile 300 for the second heating device 70 of an aerosolforming device 1, as described herein. As noted above, the second heating device 70 can be configured to heat the substrate 23 by convection by use of a heat exchange element and / or resistive heating element 71 in thermal communication with the upstream airflow path 40a in a puff-on-demand heating operation.

[0579] The heating profile 300 is illustrated in Figure 10 in the form of measured temperature values fluctuating around a temperature curve 304 with target temperatures (in °C) that the second heating device 6a should reach versus time (in seconds) during a usage session, andFTR4068

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[0581] specifically during each puff or user inhalation. Curve 304 can also reflect the different power levels, at which the second heating device 70 can be operated during a usage session, which are indicated at the second y-axis of Figure 10. Moreover, curve 302 in Figure 10 shows the actual temperature of the second heating device 70 during the usage session.

[0582] As shown in Figure 10, the heating profile 300 comprises a series of pulses or peaks 301, which correspond to single user inhalations or puffs taken by the user during the usage session. When a user inhalation occurs, the second heating device 70 can be operated by the control circuitry 5 at a second power level P2, such that the second heating device 70 and / or the resistive heating element 71 thereof is heated to a target temperature between about 270°C to about 500°C, for example from about 270°C to about 450°C, or for example from about 270°C to about 320°C, in particular from about 280°C to about 310°C, preferably about 300°C. In an example, the target temperature of the second heating device 70 can be above about 200°C, above about 250°C, above about 270°C, preferably above about 280°C, more preferably above about 290°C, even more preferably about 300°C, or even above about 400°C or about 1450°C. For example, the target temperature can be between about 50°C and 500°C, more preferably between about 100°C to 450°C, for example between 200°C and 350°C.

[0583] At times where no puff or user inhalation occurs, the second heating device 70 and / or resistive heating element 71 can be deactivated or switched off. Alternatively, at times where no puff or user inhalation occurs, the second heating device 70 and / or resistive heating element 71 can be operated by the control circuitry 5 at a first power level P^ which can be much lower than the second power level P2. In an example, the first power level PT can be below about 80%, below about 70%, below about 60%, below about 50%, below about 40%, below about 30%, below about 20%, below about 10%, below about 5%, or below about 2% of the second power level P2. Accordingly, powering the second heating device 70 at the first power level PT at times where no user inhalation occurs, may only require a fraction of the energy or power required to power the second heating device 70 at the second power level P2during a puff or user inhalation to generate aerosol. Hence, a significant amount of electrical energy can be saved by this approach, and less heat can be generated that could impact the safe handling of the aerosol-forming device.

[0584] It should be noted that the first power level PT can be zero, which can mean that the voltage and current to the second heating device 70 can be cut completely between two consecutive puffs, respectively, that the second heating device 70 is deactivated when no user inhalation occurs. Alternatively, the first power level PT can be non-zero, such that the second heating device 70 is heated to a pre-heating temperature at times where no puff or user inhalation occurs. Also a combination thereof may be applied, which means for or after some puffs the power level may be reduced to zero and for or after some other puffs in a usage session a non-zero power level PT may be applied.FTR4068

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[0586] As noted above, Figure 10 shows measured temperature values of the resistive heating element 71 and / or second heating device 70. Therefore, fluctuations in the measured temperature values are shown in Figure 10 that occur between user inhalations or puffs. These fluctuations result from measurement only and do not correspond to the temperature profile 300, shown in dashed line 304, of the second heating device 70 between puffs or user inhalations, where the second heating device 70 may be deactivated or powered at the constant power level

[0587]

[0588] Accordingly, the second heating device 70 and / or its resistive heating element 71 can be activated or switched to the second power level P2in correspondence of the occurrence of a puff or user inhalation. This can provide a boost of energy to preheat the incoming air in the upstream airflow path 40a, which then will cross the substrate 23 placed between the heating elements 6, 7 of the first heating device 6a. For controlling the second heating device 70 in correspondence with the user inhalations taken by the user, the user inhalations can be detected by the control circuitry 5 based on determining one or more of a change in the temperature of the first heating device 6a and a change in the second heating device 70, as will be described in detail with reference to Figure 11.

[0589] The pre-heating temperature, to which the second heating device 70 may optionally be heated may be above about 25°C, above about 30°C, preferably above about 40°C, more preferably above about 50°C, and even more preferably above about 60°C. Alternatively or additionally, the pre-heating temperature can be below about 120°C, below about 100°C, preferably below about 90°C, more preferably below about 80°C, and even more preferably below about 70°C.

[0590] The second heating device 70 can particularly be used as puff or inhalation sensor based on sensing, monitoring or determining one or more changes in the temperature of the second heating device 70 by the control circuitry 5, because the second heating device 70 and / or its resistive element 71 can have a much lower thermal mass compared to the heating elements 6, 7 of the first heating device 6a. Alternatively or additionally, however, one or more changes in the temperature of the first heating device 6a or its heating elements 6, 7 can be determined by the control circuitry 5 to detect a user inhalation. The principle of detecting a user inhalation is in the following described with particular reference to the second heating device 70, but can likewise be applied or expanded to the first heating device 6a, as also described herein.

[0591] Figure 11 illustrates the detection of a user inhalation or puff at the aerosol-forming device 1 by the control circuitry 5 and the respective operational control of the second heating device 70. As mentioned, the same principle can be applied for detecting the user inhalation and / or operating the first heating device 6a.

[0592] Figure 11 exemplary illustrates detection of and operation during the first user inhalation occurring during a usage session. Specifically, Figure 11 shows a curve 310 of the temperatureFTR4068

[0593] 80 / 89

[0594] of the second heating device 70 and / or resistive heating element 71 , for example as determined or monitored by the control circuitry 5, versus the time during the usage session and / or during a single user inhalation in arbitrary units. The temperature of the second heating device 70 can, for example, be measured or monitored by the control circuitry 5 based on measuring, determining or monitoring the electrical resistance of the second heating device 70 and / or resistive heating element 71, for example with a comparatively high repetition rate or frequency in the Hertz to Megahertz range, or by monitoring the temperature value of a separate temperature sensor that is configured to measure the temperature of the heating element 71, e.g. a heat exchange element of the second heating device 70. It is emphasized that times are only schematically shown in Figure 11.

[0595] The aerosol-forming device 1 may be switched on or activated at time t0, for example by corresponding user command, actuation of the user interface 19 or insertion of an aerosol-forming article 20 into the aerosol-forming device 1, or by one or more sensors that can determine imminent use of the aerosol-forming device 1 by the user for inhalation or puff taking. The control circuitry 5 can then supply electrical energy at the first power level PT to the second heating device 70, such that the second heating device 70 and / or resistive heating element 71 are heated to the pre-heating temperature, shown as Tpin Figure 11.

[0596] At time t^ the user starts the user inhalation or puff, which causes a change ATi in temperature as shown by curve 310 in Figure 11. Specifically, when the user inhales, air can be drawn from the external environment into the upstream airflow path 40a, for example via the one or more main air inlets 46. The fresh air drawn from the external environment may substantially have room or ambient temperature, and hence can depart a cooling effect onto the second heating device 70, but also the first heating device 6a.

[0597] The cooling effect departed by the airflow through the upstream airflow path 40a leads to a decrease ATT in the temperature of the second heating device 70, which can be detected by the control circuitry 5, thereby enabling the control circuitry 5 to detect the start, onset, or occurrence of the user inhalation.

[0598] The change or decrease ATi in temperature can, for example, be determined by the control circuitry 5 based on temperature and / or resistance measurements. Moreover, the change or decrease AT can be determined with respect to one or more reference values for the temperature and / or resistance, for example measured at the current ambient conditions, e.g. at start of the usage session at time t0, or at predetermined ambient conditions. Alternatively or additionally, a temperature or resistance measurement at time can constitute a reference or baseline for detecting the change or decrease ATi between times and t2.

[0599] Optionally, the control circuitry 5 may use one or more threshold values for the change or decrease ATT in temperature to actually detect the user inhalation. For instance, the controlFTR4068

[0600] 81 / 89

[0601] circuitry 5 may detect the user inhalation, respectively, its start or onset by confirming that the decrease or change ATT reaches or exceeds at least one predetermined threshold value for the change or decreaseAT-] . , which can be an absolute or relative threshold value for the temperature and / or electrical resistance.

[0602] For example, one or more absolute threshold values for a change, decrease and / or increase in temperature of the second heating device 6a may be about 5°C to about 150°C, for example about 10°C to about 100°C, in particular about 15°C to about 80°C, preferably about 20°C to about 50°C, for example 80°C or less. Optionally, negative threshold values may be used for the decrease. Alternatively or additionally, one or more relative threshold values for relative a change, decrease and / or increase in the temperature of the second heating device 6a may be about 5% to about 50%, for example about 10% to about 30%, in particular about 15% to about 20%.

[0603] Further optionally, the control circuitry 5 may be configured to determine or detect the change in temperature ATT within a predetermined period of time, for example within a predetermined period of time of less than about 250 ms, less than about 200 ms, less than about 150 ms, for example less than about 100 ms, in particular less than about 50 ms, preferably less than about 25 ms, and even more preferably less than about 10 ms or even less than about 5 ms

[0604] The time difference between and t2should be as short as possible. Hence, the response time for detecting the start of the user inhalation should be as short as possible, which can allow for a fast detection of the start or occurrence of the user inhalation.

[0605] Upon detecting user inhalation based on detecting the change or decrease ATT in the temperature, the control circuitry 5 can increase the power level of electrical power supplied to the second heating device 70 immediately at time t2from the first power level PT to the second power level P2, such that a temperature of the second heating device 70 and / or resistive heating element 71 can rapidly increase to heat the incoming air flowing through the upstream airflow path 40a. When powering the second heating device 70 at the second power level P2, the temperature of the second heating device 70 can increase about 100°C within about 0.05 to 1 seconds, or about 100°C within about 0.05 to 0.5 seconds, for example about 100°C within 0.075 to 0.25 seconds, preferably about 100°C within about 0.1 to 0.2 seconds.

[0606] The second heating device 70 and / or resistive heating element 71 can then be heated by the control circuitry 5 to the target temperature Tt, which may be maintained until the end of the user inhalation or puff.

[0607] It is also possible to heat or power the second heating device 70 for a fixed or predetermined time period upon detecting a puff or user inhalation. Thie predetermined period of time may, for example, correspond to an average duration of a puff or user inhalation, for example between about 0.5 to about 2.5 seconds, in particular between about 0.5 to about 1.5 seconds. This timeFTR4068

[0608] 82 / 89

[0609] period could be automatically adjusted based on user puff preferences, or depending on statistic values specific to the user, behavior of the user or a usage history of the device.

[0610] The end or termination of the user inhalation can be determined by the control circuitry 5 analogue to detection of its start or onset. As shown in Figure 11, the user stops inhaling at time t3. Hence, the airflow through the upstream airflow path 40a stops or is reduced, which can lead to a further change or increase AT2in the temperature of the second heating device 70 and / or resistive element 71. This change or increase AT2in temperature can be detected by the control circuitry 5, for example based on two or more consecutive measurements between t3and t4or based on one or more predefined reference values, for example. Optionally, the actual termination or end of the user inhalation may be determined by the control circuitry 5 based on confirming that the determined change or increase AT2reaches or exceeds at least one threshold value for the change or increase. The threshold value for the increase may be same or as or differ from the threshold value for the decrease to detect start of the user inhalation. Further optionally, the control circuitry 5 may be configured to determine or detect the change in temperature ATi within a predetermined period of time, which may be the same or a may differ from the predetermined period of time used by the control circuitry 5 to detect start of the user inhalation.

[0611] Upon detecting termination or end of the user inhalation, the control circuitry 5 may immediately reduce the electrical power supplied to the second heating device 70 to the first power level P^ such that the second heating device 70 can maintain the pre-heating temperature Tpto detect the next or subsequent user inhalation.

[0612] The time difference between t3and t4should be as short as possible. Hence, the response time for detecting termination of the user inhalation should be as short as possible, which can allow for a fast detection of the termination of the user inhalation.

[0613] As mentioned hereinabove, it might not be necessary to pre-heat the second heating device 70 after all user inhalations in the usage session. Rather, at the latest after one or a few user inhalations have been taken, the power may be completely cut, respectively, the second heating device 70 may be switched off when no user inhalation occurs, because the second heating device 70 should have a temperature well above room temperature, allowing to quickly detect the user inhalation. Hence, the power level PT may be reduced to zero for at least some puffs or user inhalations. Also the power level PT may be gradually reduced towards the end of the usage session or may be varied by the control circuitry 5 during the usage session as needed.

[0614] Generally, however, pre-heating above ambient or room temperature can increase a cooling effect or can ensure that a cooling effect can be departed by the user inhalation, which can then be detected by the control circuitry 5 with high accuracy and within a short reaction time based on detecting a change.FTR4068

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[0616] As mentioned above, the same principle can be used to detect user inhalations based on detecting one or more changes in the temperature of the first heating device 6a. Moreover, also the power supplied to the first heating device 6a can be increased in accordance or correspondence with the occurrence of user inhalations, for example in addition to providing a maintenance heating during the usage session.

[0617] Figure 12 shows a flow chart illustrating a method of detecting a user inhalation at an aerosol-forming device 1 or system 4, in particular an aerosol-forming device 1 or system 4 as described with reference to the foregoing figures.

[0618] At step S1, the method comprises supplying electrical power to at least one of the first heating device 6a and the second heating device 70, for example to heat one or both to the preheating temperature, based on powering one or both at the first power level Pr

[0619] At step S2, the method comprises detecting a user inhalation at the aerosol-forming device 100 based on determining one or more of a change in a temperature of at least one of the first heating device 6a and the second heating device 70 associated with a change in an airflow through the airflow path 40a caused by the user inhalation.

[0620] For instance, detecting the user inhalation at the aerosol-forming device 1 at step S2 can include determining a decrease in temperature in one of or both the first and second heating devices 6a, 70. Alternatively or additionally, detecting the user inhalation at the aerosol-forming device 1 at step S2 can include determining an increase in the temperature of one or both the first and second heating devices 6a, 70.

[0621] Optionally, a power level of electrical power supplied to one or both the first and second heating devices 6a, 70 may be increased to a second power level P2upon detecting the user inhalation.

[0622] Further optionally, the control circuitry 5 may determine a further change, for example increase, in temperature to detect the termination or end of the user inhalation. In response thereto, the control circuitry may reduce the power level to the first power level PT or deactivate one or both the first and second heating devices 6a, 70.

[0623] For the purpose of the present description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term "about". Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein. In this context, therefore, a number A is understood as A ± 10% of A. Within this context, a number A may be considered to include numerical values that are within general standard error for the measurement of the property that the number A modifies. The number A, in some instances as used in the appended claims, may deviate by the percentages enumerated above provided that the amount by which A deviatesFTR4068

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[0625] does not materially affect the basic and novel characteristic(s) of the claimed invention. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.

[0626] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art and practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

[0627] In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

FTR406885 / 89CLAIMS1. An aerosol-forming device for forming aerosol from an aerosol-forming article, comprising:a heating chamber configured to receive at least a part of the aerosol-forming article; an upstream airflow path arranged upstream of the heating chamber, the upstream airflow path in fluid communication with an external environment of the aerosol-forming device, such that air is drawable by a user in a user inhalation from the external environment through the upstream airflow path towards the heating chamber;a first heating device arranged at the heating chamber and configured to perform a first heating operation;a second heating device arranged in thermal contact with the upstream airflow path and configured to perform a second heating operation; andcontrol circuitry configured to control a power supply from a power source of the aerosolforming device to at least one of the first heating device and the second heating device based on determining a change in a temperature of at least one of the first heating device and the second heating device associated with a change in an airflow through the airflow path caused by the user inhalation,wherein the control circuitry is configured to, based on controlling the power supply from the power source to the second heating device, operate the second heating device at a first power level to heat the second heating device to a pre-heating temperature above ambient temperature and below a target temperature, andwherein the control circuitry is configured to determine the change in the temperature or monitor the temperature of the second heating device when the second heating device is operated at the first power level,wherein the control circuitry is configured to, in response to detecting the change in the temperature of the second heating device, operate the second heating device at a second power level for heating the second heating device to the target temperature to form aerosol from the aerosol-forming article.

2. The aerosol-forming device according to the preceding claim, wherein the first heating device includes a resistive heating device configured to heat at least a part of a substrate of the aerosol-forming article by conductive heating; and / orwherein the second heating device includes a resistive heating device configured to heat air in the upstream airflow path to at least heat a part of a substrate of the aerosol-forming article by convective heating.FTR406886 / 893. The aerosol-forming device according to any one of the preceding claims, wherein the change in the temperature of the first heating device is associated with a change in an airflow past the first heating device caused by the user inhalation; and / orwherein the change in the temperature of the second heating device is associated with a change in an airflow past the second heating device caused by the user inhalation.

4. The aerosol-forming device according to any one of the preceding claims, wherein the control circuitry is configured to control the power supply from the power source to the first heating device based on determining a change in the temperature of the second heating device.

5. The aerosol-forming device according to any one of the preceding claims, wherein the control circuitry is configured to detect the user inhalation at the aerosol-generating device based on determining the change in the temperature of at least one of the first heating device and the second heating device based on a cooling effect departed by an airflow past at least one of the first heating device and the second heating device caused by the user inhalation.

6. The aerosol-forming device according to any one of the preceding claims, wherein the first heating operation differs from the second heating operation.

7. The aerosol-forming device according to any one of the preceding claims, wherein the second heating device is configured to perform a puff-on-demand heating operation; and / or wherein the control circuitry is configured to control the second heating device to perform a puff-on-demand heating operation.

8. The aerosol-forming device according to any one of the preceding claims, wherein the control circuitry is configured to detect the user inhalation when the second heating device is operated at the first power level.

9. The aerosol-forming device according to any one of the preceding claims, wherein the pre-heating temperature is above about 25°C, above about 30°C, preferably above about 40°C, more preferably above about 50°C, and even more preferably above about 60°C; and / or wherein the pre-heating temperature is below about 250°C, below about 200°C, below about 150°C, below about 120°C, below about 100°C, preferably below about 90°C, more preferably below about 80°C, and even more preferably below about 70°C.FTR406887 / 8910. The aerosol-forming device according to any one of the preceding claims, wherein the control circuitry is configured to, in response to detecting the change in the temperature of the second heating device, operate the first heating device to heat the aerosol-forming article to a target temperature or volatilization temperature sufficient to release aerosol from the aerosolforming article.

11. The aerosol-forming device according to any one of the preceding claims, wherein the control circuitry is configured to determine whether the user inhalation has ended based on determining a further change in the temperature of at least one of the first heating device and the second heating device.

12. The aerosol-forming device according to the preceding claim, wherein the control circuitry is configured to decrease the power supplied to the second heating device from a second power level to a first power level below the second power level in response to determining that the user inhalation has ended; and / orwherein the control circuitry is configured to interrupt or stop the power supply to the second heating device in response to determining that the user inhalation has ended.

13. The aerosol-forming device according to any one of the preceding claims, wherein the aerosol-forming article has a substantially rectangular parallelepiped or oblong shape defining two opposing main faces and two opposing side faces, the aerosol-forming article including an aerosol-forming substrate arranged between the two opposing main faces, preferably wherein the aerosol-forming article comprises an air inlet and an air outlet located opposite of each other on the smallest faces of the rectangular parallelepiped shaped aerosol-forming article.

14. An aerosol-forming system comprising an aerosol-forming device according to any one of the preceding examples and one or more of:an aerosol-forming article for generating aerosol; anda companion device for one or more of storing the aerosol-forming device and charging the aerosol-forming device.

15. A method of detecting a user inhalation at an aerosol-forming device comprising a heating chamber configured to receive at least a part of an aerosol-forming article, an upstream airflow path arranged upstream of the heating chamber, wherein the upstream airflow path is in fluid communication with an external environment of the aerosol-forming device, such that air is drawable by a user in a user inhalation from the external environment through the upstreamFTR406888 / 89airflow path towards the heating chamber, a first heating device arranged at the heating chamber and configured to perform a first heating operation, and a second heating device arranged in thermal contact with the upstream airflow path and configured to perform a second heating operation, the method comprising:supplying electrical power to at least one of the first heating device and the second heating device; anddetecting a user inhalation at the aerosol-forming device based on determining a change in a temperature of at least one of the first heating device and the second heating device associated with a change in an airflow through the airflow path caused by the user inhalation, wherein supplying electrical power to at least one of the first heating device and the second heating device comprises:operating the second heating device at a first power level to heat the second heating device to a pre-heating temperature above ambient temperature and below a target temperature, wherein the user inhalation is detected when the second heating device is operated at the first power level,wherein the method further comprises:operating, in response to detecting the change in the temperature of the second heating device, the second heating device at a second power level for heating the second heating device to the target temperature to form aerosol from the aerosol-forming article.

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