WO2025103975A1

WO2025103975A1 - Aerosol-generating device with rtd adjustment element

Info

Publication number: WO2025103975A1
Application number: PCT/EP2024/081944
Authority: WO
Inventors: Matteo Bologna
Original assignee: Philip Morris Products SA
Current assignee: Philip Morris Products SA
Priority date: 2023-11-17
Filing date: 2024-11-12
Publication date: 2025-05-22
Anticipated expiration: 2026-05-17

Abstract

The invention relates to an aerosol-generating device. The aerosol-generating device comprises a heating chamber configured to receive an aerosol-forming substrate. The aerosol-generating device further comprises a RTD (resistance to draw) adjustment element. The RTD adjustment element is arranged upstream of and in fluid communication with the heating chamber. The RTD adjustment element is configured to decrease RTD with decreasing pressure in the heating chamber. The invention further relates to an aerosol-generating system comprising the aerosol-generating device and an aerosol-generating article comprising aerosol-forming substrate.

Description

AEROSOL-GENERATING DEVICE WITH RTD ADJUSTMENT ELEMENT

The present invention relates to an aerosol-generating device. The invention further relates to an aerosol-generating system comprising the aerosol-generating device and an aerosol-generating article comprising aerosol-forming substrate.

It is known to provide an aerosol-generating device for generating an inhalable vapor. Such devices may heat aerosol-forming substrate to a temperature at which one or more components of the aerosol-forming substrate are volatilised without burning the aerosol-forming substrate. Aerosol-forming substrate may be provided as part of an aerosol-generating article. The aerosol-generating article may have a rod shape for insertion of the aerosol-generating article into a cavity, such as a heating chamber, of the aerosol-generating device. A heating element may be arranged in or around the heating chamber for heating the aerosol-forming substrate once the aerosol-generating article is inserted into the heating chamber of the aerosol-generating device. In humid climates, an initial puff may be unpleasant due to creating a hot mouth feeling for a user. This is also denoted as hot aerosol effect. The reason is that the aerosol-forming substrate in humid climates may have a higher water content as in low- humid climates. During a preheating phase of the heating element of the aerosol-generating device, this water may be vaporized. During the first puff, this relatively large amount of vaporized water may be inhaled by the user leading to the undesired hot aerosol effect.

It would be desirable to have an aerosol-generating device with improved reliability. It would be desirable to have an aerosol-generating device with improved reliability in humid climates. It would be desirable to have an aerosol-generating device reducing or preventing the hot aerosol effect.

According to an embodiment of the invention there is provided an aerosol-generating device. The aerosol-generating device may comprise a heating chamber configured to receive an aerosol-forming substrate. The aerosol-generating device may further comprise a RTD (resistance to draw) adjustment element. The RTD adjustment element may be arranged upstream of and in fluid communication with the heating chamber. The RTD adjustment element may be configured to decrease RTD with decreasing pressure in the heating chamber.

According to an embodiment of the invention there is provided an aerosol-generating device. The aerosol-generating device comprises a heating chamber configured to receive an aerosol-forming substrate. The aerosol-generating device further comprises a RTD (resistance to draw) adjustment element. The RTD adjustment element is arranged upstream of and in fluid communication with the heating chamber. The RTD adjustment element is configured to decrease RTD with decreasing pressure in the heating chamber.

The RTD adjustment element prevents the hot aerosol effect. The RTD adjustment element prevents the hot aerosol effect by having a high RTD when the heating chamber has ambient pressure or slightly reduced pressure in comparison with ambient pressure. The slightly reduced pressure in comparison to ambient pressure may also be referred to as light vacuum. In this case, which is the case that a user takes a light puff, the RTD adjustment elements prevents this puff by preventing air to be drawn into the heating chamber. The prevention of a light puff prevents the user to predominantly inhale the amount of vaporized water that may have been created during a preheating phase of the aerosol-generating device by heating the aerosol-forming substrate with a relatively high water content. Contrary, the RTD adjustment element is configured to enable only a puff of a certain strength. A puff of a certain strength means that the user inhales a sufficient amount of air such that the vaporized water content of this air is small enough to not be unpleasant to the user.

As used herein, the term “resistance to draw” (RTD), is used to describe the resistance for air to be drawn through a material. As used herein, resistance to draw is expressed with the units of pressure "millimetres of water gauge" and is measured in accordance with ISO 6565:2015.

When referring to the resistance to draw, preferably the resistance to draw of the RTD adjustment element in isolation is meant by that. The total resistance to draw of the aerosolgenerating system comprising the aerosol-generating device and the aerosol-generating article received in the aerosol-generating device is different from the resistance to draw of the RTD adjustment element. Particularly, the overall resistance to draw of the system is influenced by the resistance to draw of the individual portions of the system through which airflow is drawn.

Exemplarily, the aerosol-generating article may comprise a ventilation zone in which perforations are arranged in the sidewall of the ventilation zone. The perforations allow ambient air to be drawn into the ventilation zone. In other words, ambient air drawn into the ventilation zone through the perforations is mixed with the air drawn through the body of the aerosolgenerating article upstream of the ventilation zone, particularly through a substrate portion of the aerosol-generating article comprising the aerosol-forming substrate. This air is, prior to that, drawn through the aerosol-generating device and consequently through the RTD adjustment element. The configuration of the ventilation zone and particularly of the perforations therefore influences the overall resistance to draw of the system. As explained herein, the resistance to draw of the RTD adjustment element is variable upon the force with which a user draws on the downstream end of the aerosol-generating article, which subsequently leads to a negative pressure in the heating chamber. If a user takes a light puff, no or little air is drawn through the aerosol-generating device due to the high resistance to draw of the RTD adjustment element. In this case, the main source of air may be ambient air drawn into the ventilation zone via the perforations of the ventilation zone. If a user takes a strong or strong enough puff, a significant proportion of air will be drawn through the RTD adjustment element of the aerosol-generating device and subsequently through the aerosolgenerating article into the ventilation zone. In this case, a substantial part of the air being drawn into the mouth of a user will be drawn through the aerosol-generating device via the RTD adjustment element and a lesser portion of the air may be drawn into the ventilation zone and subsequently into the mouth of the user through the perforations of the ventilation zone.

The present invention may beneficially automatically adjust the ratio between ambient air being drawn into the ventilation zone of the aerosol-generating article through the perforations of the ventilation zone and air being drawn into the ventilation zone of the aerosolgenerating article through the upstream body of the aerosol-generating article and the aerosolgenerating device via the RTD adjustment element. In other words, a user taking a weak puff primarily inhales ambient air being drawn through the perforations of the ventilation zone while a user taking a strong enough puff may inhale a desired and beneficial mix of ambient air drawn through the perforations of the ventilation zone and aerosol being drawn through the aerosol-generating device via the RTD adjustment element and the substrate portion of the aerosol-generating article.

In case an aerosol-generating article is utilized without a ventilation zone having perforations in the sidewall of the aerosol-generating article, the present invention still has the benefits of preventing the hot aerosol effect by increasing the RTD of the RTD adjustment element in case of a weak puff of a user. In case of a strong enough puff of the user and therefore a correspondingly low pressure in the heating chamber, the RTD of the RTD adjustment element will be lower so as to allow more air to flow into the heating chamber and subsequently into the mouth of the user.

The RTD adjustment element may be configured to prevent ambient air to be drawn into the heating chamber when the pressure of the heating chamber is below a predefined threshold. This threshold may be denoted as negative pressure threshold. Alternatively, the RTD adjustment element may gradually decrease RTD with decreasing pressure in the heating chamber so as to allow an increasing amount of air being drawn into the heating chamber with decreasing pressure in the heating chamber. According to this configuration of the RTD adjustment element, a user needs to apply a certain drawing power to overcome the negative pressure threshold of the heating chamber. In other words, only if a user draws hard enough, the pressure in the heating chamber drops below the threshold value and the RTD adjustment element enables ambient air to be drawn into the heating chamber. The sudden opening of the RTD adjustment element leads to an inflow of a relatively large amount of ambient air into the heating chamber so that this relatively large amount of ambient air is mixed with the vaporized water in the aerosol-forming substrate of the aerosol-generating article received in the heating chamber. The hot aerosol effect is thus prevented due to the vaporized water being mixed into the relatively large amount of ambient air.

The RTD adjustment element may be arranged in an airflow channel, the airflow channel being arranged upstream of and in fluid communication with the heating chamber.

The heating chamber may have an air outlet. The air outlet may at the same time be an opening for receiving the aerosol-generating article comprising the aerosol-forming substrate. A user may draw on the air outlet. Alternatively, a user may draw on a proximal end of the aerosol-generating article. When the aerosol-generating article is received in the heating chamber, the opening may be closed such that air can only be drawn out of the heating chamber through the aerosol-generating article.

The heating chamber may be fluidly connected with the ambient environment by means of the airflow channel upstream of the heating chamber and by means of the air outlet.

The airflow channel may be fluidly connected with the heating chamber via an aperture at a distal end of the heating chamber. The aperture may be circular. An outer diameter of the aperture may be smaller than an inner diameter of the heating chamber. Instead of a single aperture, multiple apertures may be provided at the distal end of the heating chamber. The distal end of the heating chamber may be configured as a base of the heating chamber. The multiple apertures may be configured as perforations in the base of the aperture. The airflow channel may be fluidly connected with the ambient environment via an air inlet of the aerosolgenerating device.

The air outlet of the heating chamber may be arranged at a proximal end of the heating chamber. The air outlet may be circular. The outer diameter of the air outlet may be identical to the inner diameter of the heating chamber. In other words, the heating chamber may be open at the proximal end. The air outlet of the heating chamber may allow insertion of the aerosol-generating article and may allow the aerosol to be drawn out of the heating chamber.

The RTD adjustment element may comprise a one-way valve. The one-way valve may allow air to be drawn into the heating chamber from the airflow channel. The one-way valve may prevent airflow from the heating chamber into the airflow channel. The one-way valve may be pressure sensitive. In other words, the one-way valve may be closed if a pressure gradient between the airflow channel and the heating chamber is below a predefined threshold. The one-way valve may be configured to allow airflow from the airflow channel into the heating chamber if the pressure gradient between the airflow channel and the heating chamber is above a predefined threshold. This threshold of the pressure gradient may be identical to the herein described negative pressure threshold. In other words, if the pressure in the heating chamber falls under the predefined threshold, the one-way valve may be configured to open to allow airflow from the airflow channel into the heating chamber.

The RTD adjustment element may comprise a ball valve.

The ball valve may be configured as one-way valve.

The ball of the ball valve may be arranged in a conical portion of the airflow channel. The ball of the ball valve may prevent airflow through the airflow channel when in contact with the conical portion of the airflow channel. The ball may be configured to clog the airflow channel when in contact with the conical portion of the airflow channel. The ball may be configured to fluidly block the airflow channel when in contact with the conical portion of the airflow channel. An inner diameter of the the conical portion may increase in a downstream direction.

The RTD adjustment element may comprise a biasing element. The biasing element preferably may be a spring.

The biasing element may be attached to or mounted at a sidewall of the airflow channel. The biasing element may be arranged centrally within the airflow channel. The biasing element may be arranged downstream of the ball of the ball valve. The biasing element may be configured to bias the ball of the ball valve in an upstream direction.

The biasing element may bias the RTD adjustment element towards a first position. The first position may be a position in which RTD of the RTD adjustment element may be increased.

The biasing element may bias the ball of the ball valve against the conical portion of the airflow channel. The biasing element may bias the ball of the ball valve into a closed position. In the closed position, airflow between the airflow channel and the heating chamber may be prevented. The first position may be the closed position.

Airflow through the RTD adjustment element may be prevented in the first position. The RTD adjustment element may comprise a side channel enabling airflow through the RTD adjustment element in the first position. The side channel may be elongate. The side channel may be configured as a groove. The side channel may be configured as a debossed region. The side channel may be arranged in the conical portion of the airflow channel which comes into contact with the ball of the ball valve. Air may thus bypass the ball valve even if the ball contacts the conical portion of the airflow channel.

The side channel may enable a minimal airflow between the airflow channel and the heating chamber in the closed position of the RTD adjustment element. A minimal airflow may be desired to give the user a feedback of a successful drawing action. Otherwise, a user may have the impression that the aerosol-generating device is faulty.

A biasing direction into the first position may be an upstream direction of air flowing through the aerosol-generating device.

In other words, the biasing direction may be a direction against airflow being drawn into the heating chamber. This facilitates that if a user draws hard enough, the biasing force of the biasing element is over, airflow is enabled from the airflow channel into the heating chamber.

The RTD adjustment element may comprise a second position in which RTD of the RTD adjustment element may be decreased.

The second position may be an open position. In the second position, airflow between the airflow channel and the heating chamber may be enabled. If the RTD adjustment element is configured as a ball valve, the second position may be a position in which the ball is distanced from the conical portion of the airflow channel therefore enabling airflow around the ball and into the heating chamber.

The RTD adjustment element may comprise an electromagnet. The electromagnet may be configured to adjust the RTD of the RTD adjustment element. The electromagnet may be arranged adjacent the ball of the ball valve and may be configured to adjustably bias the ball of the ball valve.

The electromagnet may enable a variable biasing action of the RTD adjustment element. In other words, the electromagnet main able to adjust the behavior of the RTD adjustment element. This may be particularly beneficial since the prevention of the hot aerosol effect may not be necessary anymore after a first puff. Then, it may be desirable to fully open the RTD adjustment element such that the RTD adjustment element does not hinder airflow from the airflow channel into the heating chamber. Consequently, the electromagnet may be controlled by a controller such that the RTD adjustment element only increases RTD as described herein for first puff of the user. After that, the electromagnet may be controlled by the controller to be an open position (second position) to enable airflow from the airflow channel into the heating chamber unhindered.

The ball of the ball valve may be a magnet and may have a conical shape. The conical shape may be preferred if the airflow channel comprises a corresponding conically shaped portion. Interaction, particularly clogging, of the magnet and the conically shaped portion of the airflow channel may be improved by the magnet having a conical shape.

The ball of the ball valve may be a magnet and may have a cylindrical shape. The ball of the ball valve may be a magnet and may have an elongate shape.

The magnet may have a negative pole and an opposite positive pole. The two poles may enable a two-way interaction between the electromagnet and the magnet. The electromagnet may be enabled to attract or repel the magnet. The electromagnet may be enabled to increase RTD of the RTD adjustment element by attracting the magnet and to decrease RTD of the RTD adjustment element by repelling the magnet or vice versa.

Due to the ball of the ball valve being configured as a magnet in this embodiment, the electromagnet may act upon the ball of the ball valve. The electromagnet may bias the ball of the ball off into the first position when activated. The electromagnet may not act upon the ball valve when deactivated such that the ball of the ball valve may be biased into the second position. The biasing of the ball valve into the second position may preferably be facilitated by a spring. In other words, the electromagnet may be utilized to bias the ball of the ball valve into the first position while the spring may be utilized for biasing the ball of the ball valve into the second position. The biasing action of the electromagnet acting upon the ball of the ball valve may be in an opposite direction as the biasing action of the spring acting upon the ball of the ball valve. The biasing action of the electromagnet may be larger than the biasing action of the spring. Hence, after the first puff of the user, deactivation of the electromagnet may enable opening of the ball valve thereby enabling free airflow from the airflow channel into the heating chamber.

The aerosol-generating device may further comprise a power supply and a controller. The controller may be configured to control supply of electrical energy from the power supply to the electromagnet.

The controller may further control operation of the RTD adjustment element. Particularly preferred, the controller may control the electromagnet as described herein. The controller may control the electromagnet to increase the RTD of the RTD adjustment element for a first puff of a user as described herein, i.e. to only allow a first puff if a negative pressure threshold in the heating chamber is reached. For subsequent puffs, the controller may control the electromagnet such that the RTD of the RTD adjustment element is lowered, e.g. by opening of the RTD adjustment element.

The aerosol-generating device may further comprise a puff sensor. The controller may be configured to control supply of electrical energy from the power supply to the electromagnet based upon a puff sensor output. The controller may be configured to control supply of electrical energy from the power supply to the electromagnet based upon a puff sensor output such as to increase RTD of the RTD adjustment element for a first puff of a user experience.

The puff sensor may be configured to detect a first puff of a user. The controller may use the puff sensor output to control the electromagnet as described herein, e.g. to only allow a first puff if a negative pressure threshold in the heating chamber is reached.

The controller may be configured to control supply of electrical energy from the power supply to the electromagnet based upon a puff sensor output such as to decrease RTD of the RTD adjustment element for subsequent puffs after the first puff of the user experience.

The invention further relates to an aerosol-generating system comprising the aerosolgenerating device as described herein and an aerosol-generating article comprising aerosolforming substrate.

As used herein, the terms ‘proximal’, ‘distal’, ‘downstream’ and ‘upstream’ are used to describe the relative positions of components, or portions of components, of the aerosolgenerating device in relation to the direction in which a user draws on the aerosol-generating device during use thereof.

The aerosol-generating device may comprise a mouth end through which in use an aerosol exits the aerosol-generating device and is delivered to a user. The mouth end may also be referred to as the proximal end. In use, a user draws on the proximal or mouth end of the aerosol-generating device in order to inhale an aerosol generated by the aerosolgenerating device. Alternatively, a user may directly draw on an aerosol-generating article inserted into an opening at the proximal end of the aerosol-generating device. The opening at the proximal end may be an opening of the cavity. The cavity may be configured to receive the aerosol-generating article. The aerosol-generating device comprises a distal end opposed to the proximal or mouth end. The proximal or mouth end of the aerosol-generating device may also be referred to as the downstream end and the distal end of the aerosol-generating device may also be referred to as the upstream end. Components, or portions of components, of the aerosol-generating device may be described as being upstream or downstream of one another based on their relative positions between the proximal, downstream or mouth end and the distal or upstream end of the aerosol-generating device. As used herein, an ‘aerosol-generating device’ relates to a device that interacts with an aerosol-forming substrate to generate an aerosol. The aerosol-forming substrate may be part of an aerosol-generating article, for example part of a smoking article. An aerosol-generating device may be a smoking device that interacts with an aerosol-forming substrate of an aerosolgenerating article to generate an aerosol that is directly inhalable into a user’s lungs thorough the user's mouth. An aerosol-generating device may be a holder. The device may be an electrically heated smoking device. The aerosol-generating device may comprise a housing, electric circuitry, a power supply, a heating chamber and a heating element.

As used herein with reference to the present invention, the term ‘smoking’ with reference to a device, article, system, substrate, or otherwise does not refer to conventional smoking in which an aerosol-forming substrate is fully or at least partially combusted. The aerosol-generating device of the present invention is arranged to heat the aerosol-forming substrate to a temperature below a combustion temperature of the aerosol-forming substrate, but at or above a temperature at which one or more volatile compounds of the aerosol-forming substrate are released to form an inhalable aerosol.

The aerosol-generating device may comprise electric circuitry. The electric circuitry may comprise a microprocessor, which may be a programmable microprocessor. The microprocessor may be part of a controller. The electric circuitry may comprise further electronic components. The electric circuitry may be configured to regulate a supply of power to the heating element. Power may be supplied to the heating element continuously following activation of the aerosol-generating device or may be supplied intermittently, such as on a puff- by-puff basis. The power may be supplied to the heating element in the form of pulses of electrical current. The electric circuitry may be configured to monitor the electrical resistance of the heating element, and preferably to control the supply of power to the heating element dependent on the electrical resistance of the heating element.

The aerosol-generating device may comprise a power supply, typically a battery, within a main body of the aerosol-generating device. In one embodiment, the power supply is a Lithium-ion battery. Alternatively, the power supply may be a Nickel-metal hydride battery, a Nickel cadmium battery, or a Lithium based battery, for example a Lithium-Cobalt, a Lithium- Iron-Phosphate, Lithium Titanate or a Lithium-Polymer battery. As an alternative, the power supply may be another form of charge storage device such as a capacitor. The power supply may require recharging and may have a capacity that enables to store enough energy for one or more usage experiences; for example, the power supply may have sufficient capacity to continuously generate aerosol for a period of around six minutes or for a period of a multiple of six minutes. In another example, the power supply may have sufficient capacity to provide a predetermined number of puffs or discrete activations of the heating element.

The cavity of the aerosol-generating device may have an open end into which the aerosol-generating article is inserted. The open end may be a proximal end. The cavity may have a closed end opposite the open end. The closed end may be the base of the cavity. The closed end may be closed except for the provision of air apertures arranged in the base. The base of the cavity may be flat. The base of the cavity may be circular. The base of the cavity may be arranged upstream of the cavity. The open end may be arranged downstream of the cavity. The cavity may have an elongate extension. The cavity may have a longitudinal central axis. A longitudinal direction may be the direction extending between the open and closed ends along the longitudinal central axis. The longitudinal central axis of the cavity may be parallel to the longitudinal axis of the aerosol-generating device.

The cavity may be configured as a heating chamber. The cavity may have a cylindrical shape. The cavity may have a hollow cylindrical shape. The cavity may have a shape corresponding to the shape of the aerosol-generating article to be received in the cavity. The cavity may have a circular cross-section. The cavity may have an elliptical or rectangular crosssection. The cavity may have an inner diameter corresponding to the outer diameter of the aerosol-generating article.

An airflow channel may run through the cavity. Ambient air may be drawn into the aerosol-generating device, into the cavity and towards the user through the airflow channel. Downstream of the cavity, a mouthpiece may be arranged or a user may directly draw on the aerosol-generating article. The airflow channel may extend through the mouthpiece.

In any of the aspects of the disclosure, the heating element may comprise an electrically resistive material. Suitable electrically resistive materials include but are not limited to: semiconductors such as doped ceramics, electrically "conductive" ceramics (such as, for example, molybdenum disilicide), carbon, graphite, metals, metal alloys and composite materials made of a ceramic material and a metallic material. Such composite materials may comprise doped or undoped ceramics. Examples of suitable doped ceramics include doped silicon carbides. Examples of suitable metals include titanium, zirconium, tantalum platinum, gold and silver. Examples of suitable metal alloys include stainless steel, nickel-, cobalt-, chromium-, aluminium- titanium- zirconium-, hafnium-, niobium-, molybdenum-, tantalum-, tungsten-, tin-, gallium-, manganese-, gold- and iron-containing alloys, and super-alloys based on nickel, iron, cobalt, stainless steel, Timetai® and iron-manganese-aluminium based alloys. In composite materials, the electrically resistive material may optionally be embedded in, encapsulated or coated with an insulating material or vice-versa, depending on the kinetics of energy transfer and the external physicochemical properties required.

As described, in any of the aspects of the disclosure, the heating element may be part of an aerosol-generating device. The aerosol-generating device may comprise an internal heating element or an external heating element, or both internal and external heating elements, where "internal" and "external" refer to the aerosol-forming substrate. An internal heating element may take any suitable form. For example, an internal heating element may take the form of a heating blade. Alternatively, the internal heater may take the form of a casing or substrate having different electro-conductive portions, or an electrically resistive metallic tube. Alternatively, the internal heating element may be one or more heating needles or rods that run through the center of the aerosol-forming substrate. Other alternatives include a heating wire or filament, for example a Ni-Cr (Nickel-Chromium), platinum, tungsten or alloy wire or a heating plate. Optionally, the internal heating element may be deposited in or on a rigid carrier material. In one such embodiment, the electrically resistive heating element may be formed using a metal having a defined relationship between temperature and resistivity. In such an exemplary device, the metal may be formed as a track on a suitable insulating material, such as ceramic material, and then sandwiched in another insulating material, such as a glass. Heaters formed in this manner may be used to both heat and monitor the temperature of the heating elements during operation.

An external heating element may take any suitable form. For example, an external heating element may take the form of one or more flexible heating foils on a dielectric substrate, such as polyimide. The flexible heating foils can be shaped to conform to the perimeter of the substrate receiving cavity. Alternatively, an external heating element may take the form of a metallic grid or grids, a flexible printed circuit board, a molded interconnect device (MID), ceramic heater, flexible carbon fibre heater or may be formed using a coating technique, such as plasma vapour deposition, on a suitable shaped substrate. An external heating element may also be formed using a metal having a defined relationship between temperature and resistivity. In such an exemplary device, the metal may be formed as a track between two layers of suitable insulating materials. An external heating element formed in this manner may be used to both heat and monitor the temperature of the external heating element during operation.

As an alternative to an electrically resistive heating element, the heating element may be configured as an induction heating element. The induction heating element may comprise an induction coil and a susceptor. In general, a susceptor is a material that is capable of generating heat, when penetrated by an alternating magnetic field. When located in an alternating magnetic field. If the susceptor is conductive, then typically eddy currents are induced by the alternating magnetic field. If the susceptor is magnetic, then typically another effect that contributes to the heating is commonly referred to hysteresis losses. Hysteresis losses occur mainly due to the movement of the magnetic domain blocks within the susceptor, because the magnetic orientation of these will align with the magnetic induction field, which alternates. Another effect contributing to the hysteresis loss is when the magnetic domains will grow or shrink within the susceptor. Commonly all these changes in the susceptor that happen on a nano-scale or below are referred to as “hysteresis losses”, because they produce heat in the susceptor. Hence, if the susceptor is both magnetic and electrically conductive, both hysteresis losses and the generation of eddy currents will contribute to the heating of the susceptor. If the susceptor is magnetic, but not conductive, then hysteresis losses will be the only means by which the susceptor will heat, when penetrated by an alternating magnetic field. According to the invention, the susceptor may be electrically conductive or magnetic or both electrically conductive and magnetic. An alternating magnetic field generated by one or several induction coils heat the susceptor, which then transfers the heat to the aerosol-forming substrate, such that an aerosol is formed. The heat transfer may be mainly by conduction of heat. Such a transfer of heat is best, if the susceptor is in close thermal contact with the aerosol-forming substrate.

As used herein, the term ‘aerosol-generating article’ refers to an article comprising an aerosol-forming substrate that is capable of releasing volatile compounds that can form an aerosol. For example, an aerosol-generating article may be a smoking article that generates an aerosol that is directly inhalable into a user’s lungs through the user's mouth. An aerosolgenerating article may be disposable.

As used herein, the term ‘aerosol-forming substrate’ relates to a substrate capable of releasing one or more volatile compounds that can form an aerosol. Such volatile compounds may be released by heating the aerosol-forming substrate. An aerosol-forming substrate may conveniently be part of an aerosol-generating article or smoking article.

The aerosol-forming substrate may be a solid aerosol-forming substrate. The aerosolforming substrate may comprise both solid and liquid components. The aerosol-forming substrate may comprise a tobacco-containing material containing volatile tobacco flavour compounds which are released from the substrate upon heating. The aerosol-forming substrate may comprise a non-tobacco material. The aerosol-forming substrate may comprise an aerosol former that facilitates the formation of a dense and stable aerosol. Examples of suitable aerosol formers are glycerine and propylene glycol. The aerosol-generating substrate preferably comprises homogenised tobacco material, an aerosol-former and water. Providing homogenised tobacco material may improve aerosol generation, the nicotine content and the flavour profile of the aerosol generated during heating of the aerosol-generating article. Specifically, the process of making homogenised tobacco involves grinding tobacco leaf, which more effectively enables the release of nicotine and flavours upon heating.

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.

Example 1. An aerosol-generating device comprising: a heating chamber configured to receive an aerosol-forming substrate, a RTD (resistance to draw) adjustment element, wherein the RTD adjustment element is arranged upstream of and in fluid communication with the heating chamber, wherein the RTD adjustment element is configured to decrease RTD with decreasing pressure in the heating chamber.

Example 2. The aerosol-generating device according to example 1 , wherein the RTD adjustment element is arranged in an airflow channel, the airflow channel being arranged upstream of and in fluid communication with the heating chamber.

Example 3. The aerosol-generating device according to any of the preceding examples, wherein the RTD adjustment element comprises a one-way valve.

Example 4. The aerosol-generating device according to any of the preceding examples, wherein the RTD adjustment element comprises a ball valve.

Example 5. The aerosol-generating device according to example 4, wherein the ball of the ball valve is arranged in a conical portion of the airflow channel of example 2, wherein the ball of the ball valve prevents airflow through the airflow channel when in contact with the conical portion of the airflow channel.

Example 6. The aerosol-generating device according to any of the preceding examples, wherein the RTD adjustment element comprises a biasing element, wherein the biasing element preferably is a spring.

Example 7. The aerosol-generating device according example 6, wherein the biasing element biases the RTD adjustment element towards a first position, wherein the first position is a position in which RTD of the RTD adjustment element is increased.

Example 8. The aerosol-generating device according example 7, wherein airflow through the RTD adjustment element is prevented in the first position. Example 9. The aerosol-generating device according example 7, wherein the RTD adjustment element comprises a side channel enabling airflow through the RTD adjustment element in the first position.

Example 10. The aerosol-generating device according any of examples 7 to 9, wherein a biasing direction into the first position is an upstream direction of air flowing through the aerosol-generating device.

Example 11. The aerosol-generating device according to any of the preceding examples, wherein the RTD adjustment element comprises a second position in which RTD of the RTD adjustment element is decreased.

Example 12. The aerosol-generating device according to any of the preceding examples, wherein the RTD adjustment element comprises an electromagnet, preferably wherein the electromagnet is configured to adjust the RTD of the RTD adjustment element, more preferably wherein the electromagnet is arranged adjacent the ball of the ball valve according to example 4 and is configured to adjustably bias the ball of the ball valve.

Example 13. The aerosol-generating device according example 12, wherein the ball of the ball valve according to example 4 is a magnet and has a conical shape.

Example 14. The aerosol-generating device according example 12 or 13, wherein the aerosol-generating device further comprises a power supply and a controller, wherein the controller is configured to control supply of electrical energy from the power supply to the electromagnet.

Example 15. The aerosol-generating device according example 14, wherein the aerosol-generating device further comprises a puff sensor, wherein the controller is configured to control supply of electrical energy from the power supply to the electromagnet based upon a puff sensor output, preferably wherein the controller is configured to control supply of electrical energy from the power supply to the electromagnet based upon a puff sensor output such as to increase RTD of the RTD adjustment element for a first puff of a user experience.

Example 16. The aerosol-generating device according example 15, wherein the controller is configured to control supply of electrical energy from the power supply to the electromagnet based upon a puff sensor output such as to decrease RTD of the RTD adjustment element for subsequent puffs after the first puff of the user experience.

Example 17. An aerosol-generating system comprising the aerosol-generating device according to any of the preceding examples and an aerosol-generating article comprising aerosol-forming substrate.

Features described in relation to one embodiment may equally be applied to other embodiments of the invention. The invention will be further described, by way of example only, with reference to the accompanying drawings in which:

Fig. 1 shows a sectional side view of an aerosol-generating device and an aerosolgenerating article;

Figs. 2A and 2B show sectional side views of an operation of a RTD adjustment element of the aerosol-generating device;

Fig. 3 shows a further embodiment of the RTD adjustment element in which the RTD adjustment element comprises an electromagnet;

Fig. 4 shows a further embodiment of the RTD adjustment element in which the RTD adjustment element comprises a side channel; and

Fig. 5 shows a further embodiment of the RTD adjustment element in which the RTD adjustment element comprises a conical element.

Figure 1 shows a sectional side view of an aerosol-generating device 10 and an aerosol-generating article 12. The aerosol-generating device 10 comprises a RTD adjustment element 14. The RTD adjustment element 14 is arranged in an airflow channel 16 of the aerosol-generating device 10. The airflow channel 16 is arranged upstream of a heating chamber 18 of the RTD adjustment element 14. The airflow channel 16 is fluidly connected with the heating chamber 18 of the aerosol-generating device 10. The airflow channel 16 is fluidly connected with the heating chamber 18 of the aerosol-generating device 10 via an air inlet channel 20.

The RTD adjustment element 14 is, in the Figure 1 embodiment, configured as a oneway valve, more specifically a ball valve. The ball valve comprises a ball 22 sitting in a conical portion 24 of the airflow channel 16. When the ball 22 touches the conical portion 24 of the airflow channel 16, airflow through the airflow channel 16 and into the heating chamber 18 is prevented. A biasing element in the form of a spring 26 is provided biasing the ball 22 into contact with the conical portion 24 of the airflow channel 16. This position of the ball 22 is also referred to a first position or closed position. The spring 26 is arranged downstream of the ball 22. The spring 26 is mounted at a sidewall of the airflow channel 16. The spring 26 is arranged centrally within the airflow channel 16. The spring 26 is configured to bias the ball 22 into an upstream direction. An inner diameter of the conical portion 24 increases in a downstream direction. In other words, the conical portion 24 opens into a downstream direction. When a user draws on a proximal end of the aerosol-generating article 12, a negative pressure is created in the heating chamber 18. This negative pressure creates a pressure gradient between the airflow channel 16 upstream of the ball 22 of the ball valve and the heating chamber 18 due to the blocking action of the ball 22 sitting in the conical portion 24 of the airflow channel 16. As a consequence, a force acts upon the ball 22 of the ball valve in a downstream direction. This force is against the biasing action of the spring 26 acting upon the ball 22 in an opposite upstream direction. If the pressure gradient becomes large enough, i.e. if a user draws with sufficient strength to overcome this negative pressure threshold, the ball 22 moves in the downstream direction thereby opening the ball valve. Airflow from the airflow channel 16 into the heating chamber 18 is then enabled and a puff can commence. Ambient air is drawn into the airflow channel 16 from an air inlet 28.

The ambient air is thus drawn from the air inlet 28 into the airflow channel 16 and around the ball 22 of the ball valve into the heating chamber 18. The ambient air is subsequently drawn through aerosol-forming substrate of the aerosol-generating article 12. The aerosol-forming substrate is volatilized by heating by a heating element 30. The heating element 30 is configured as an induction heating element 30 comprising an induction coil surrounding the heating chamber 18. A susceptor strip (not shown) is arranged within the aerosol-forming substrate of the aerosol-generating article 12 that is heated by the alternating magnetic field crated by the induction coil. Downstream of the aerosol-forming substrate, the aerosol-generating article 12 comprises a ventilation portion having perforations 32 in a sidewall of the ventilation portion. Ambient air can be drawn into the ventilation portion of the aerosol-generating article 12 by means of the perforations 32 such that the ambient air mixes with the air being drawn trough the aerosol-generating article 12. The volatilized aerosolforming substrate entrained in the airflow through the aerosol-generating article 12 thus cools down and an inhalable aerosol is formed. The aerosol can subsequently be inhaled by the user drawing upon the proximal end of the aerosol-generating article 12.

Figures 2A and 2B show sectional side views of an operation of the RTD adjustment element 14 of the aerosol-generating device 10. In Figure 2A, the ball 22 of the ball valve is shown in the first (closed) position, in which airflow between the airflow channel 16 and the heating chamber 18 is prevented. When a user draws with sufficient strength and correspondingly a high enough negative pressure is created in the heating chamber 18, the biasing force of the spring 26 can be overcome and the ball 22 opens to allow airflow between the airflow channel 16 and the heating chamber 18. This situation is shown in Figure 2B.

Figure 3 shows a further embodiment of the RTD adjustment element 14 in which the RTD adjustment element 14 comprises an electromagnet 34. The electromagnet 34 is arranged upstream of the ball 22 of the ball valve. The electromagnet 34 is arranged upstream of the conical section of the airflow channel 16. The electromagnet 34 is arranged at a base of the conical section of the airflow channel 16. The electromagnet 34 is configured to magnetically act upon the ball 22 of the ball valve. The ball 22 of the ball valve is in this embodiment correspondingly configured as a magnet.

The electromagnet 34 is electrically connected with a controller 36, such as a MCU, and a power supply in the form of a battery 38. The battery 38 and the controller 36 are elements of the aerosol-generating device 10. The battery 38 may be a separate battery 38 only configured for powering the electromagnet 34. Alternatively, the battery 38 may further be configured to power the heating element 30 of the aerosol-generating device 10.

The controller 36 is configured to control the electromagnet 34. The controller 36 is configured to control the electromagnet 34 such as to magnetically force the ball 22 of the ball valve into the open position in which the RTD adjustment element 14 essentially does not impede airflow from the airflow channel 16 into the heating chamber 18. This enables modularity of the RTD adjustment element 14, particularly to increase RTD for a first puff of a user, in which case the electromagnet 34 will be deactivated or aid the spring 26 in biasing the ball 22 into the closed position, and to decrease RTD for subsequent puffs of a user, in which case the electromagnet 34 will be activated to move the ball 22 into the open position.

Figure 4 shows a further embodiment of the RTD adjustment element 14 in which the RTD adjustment element 14 comprises a side channel 40. The side channel 40 may comprise a single side channel 40 or, as shown in Figure 4, multiple side channel 40s. The side channel 40 may be configured as a ridge, groove or embossed region. The side channel 40 enables a limited airflow past the ball 22 of the ball valve even in the closed position of the ball valve.

Figure 5 shows a further embodiment of the RTD adjustment element 14 in which the RTD adjustment element 14 comprises conical element 42. The conical element 42 replaces the ball 22 of the ball valve. The conical element 42 improves the blocking action of the RTD adjustment element 14 by having a corresponding shape to fit in to the conically formed section of the airflow channel 16.

Claims

1. An aerosol-generating device comprising: a heating chamber configured to receive an aerosol-forming substrate, a RTD (resistance to draw) adjustment element, wherein the RTD adjustment element is arranged upstream of and in fluid communication with the heating chamber, wherein the RTD adjustment element is configured to decrease RTD with decreasing pressure in the heating chamber.

2. The aerosol-generating device according to claim 1 , wherein the RTD adjustment element is arranged in an airflow channel, the airflow channel being arranged upstream of and in fluid communication with the heating chamber.

3. The aerosol-generating device according to any of the preceding claims, wherein the RTD adjustment element comprises a one-way valve.

4. The aerosol-generating device according to any of the preceding claims, wherein the RTD adjustment element comprises a ball valve.

5. The aerosol-generating device according to claim 4, wherein the ball of the ball valve is arranged in a conical portion of the airflow channel of claim 2, wherein the ball of the ball valve prevents airflow through the airflow channel when in contact with the conical portion of the airflow channel.

6. The aerosol-generating device according to any of the preceding claims, wherein the RTD adjustment element comprises a biasing element, wherein the biasing element preferably is a spring.

7. The aerosol-generating device according claim 6, wherein the biasing element biases the RTD adjustment element towards a first position, wherein the first position is a position in which RTD of the RTD adjustment element is increased.

8. The aerosol-generating device according claim 7, wherein airflow through the RTD adjustment element is prevented in the first position.

9. The aerosol-generating device according claim 7, wherein the RTD adjustment element comprises a side channel enabling airflow through the RTD adjustment element in the first position.

10. The aerosol-generating device according to any of the preceding claims, wherein the RTD adjustment element comprises an electromagnet, preferably wherein the electromagnet is configured to adjust the RTD of the RTD adjustment element, more preferably wherein the electromagnet is arranged adjacent the ball of the ball valve according to claim 4 and is configured to adjustably bias the ball of the ball valve.

11. The aerosol-generating device according claim 10, wherein the ball of the ball valve according to claim 4 is a magnet and has a conical shape.

12. The aerosol-generating device according claim 10 or 11 , wherein the aerosolgenerating device further comprises a power supply and a controller, wherein the controller is configured to control supply of electrical energy from the power supply to the electromagnet.

13. The aerosol-generating device according claim 12, wherein the aerosolgenerating device further comprises a puff sensor, wherein the controller is configured to control supply of electrical energy from the power supply to the electromagnet based upon a puff sensor output, preferably wherein the controller is configured to control supply of electrical energy from the power supply to the electromagnet based upon a puff sensor output such as to increase RTD of the RTD adjustment element for a first puff of a user experience.

14. The aerosol-generating device according claim 13, wherein the controller is configured to control supply of electrical energy from the power supply to the electromagnet based upon a puff sensor output such as to decrease RTD of the RTD adjustment element for subsequent puffs after the first puff of the user experience.

15. An aerosol-generating system comprising the aerosol-generating device according to any of the preceding claims and an aerosol-generating article comprising aerosolforming substrate.