Filled resonant recess for optimized dielectric heating

Abstract

The present invention provides an aerosol generating device for generating aerosols by heating an aerosol-forming substrate. [Solution] The apparatus comprises an electromagnetic field generator and a resonant chamber. The electromagnetic field generator is configured to generate radio frequency (RF) electromagnetic radiation having a predetermined frequency composition. The resonant chamber has a peripheral wall configured to be substantially opaque to RF electromagnetic radiation within the resonant chamber. A packing material is arranged inside the resonant chamber so as to surround a substrate recess defined within the resonant chamber. The substrate recess is configured to receive an aerosol-forming substrate. The electromagnetic field generator is connected to the resonant chamber to transmit the RF electromagnetic radiation generated by the electromagnetic field generator to the resonant chamber. The packing material has a relative permittivity greater than 1.

Description

Technical Field

[0001] The present invention relates to an aerosol generating device, an aerosol delivery system, and a method of heating a fan aerosol forming substrate to generate aerosol therefrom.

Background Art

[0002] Many different types of personal vaporizers and heat-not-burn products are available that generate inhalable aerosol from an aerosol forming substrate. Some of these systems heat a liquid composition, and others heat a solid tobacco mixture. Almost all available systems heat the aerosol forming substrate by conduction of heat from a heating element to the aerosol forming substrate. Most commonly, this is achieved by passing an electric current through an electrically resistive heating element to cause Joule heating of the heating element. Inductive heating systems have also been proposed, where Joule heating occurs as a result of eddy currents induced in a susceptor heating element.

[0003] One problem with these systems is that they cause non-uniform heating of the aerosol forming substrate. The portion of the aerosol forming substrate closest to the heating element is heated faster or to a higher temperature than the portion of the aerosol forming substrate further away from the heating element. To mitigate this problem, various designs have been used. Some designs use multiple heating elements to provide the ability to distribute heat or heat different portions of the substrate at different times. Other designs transport only a small portion of the aerosol forming substrate to the heating element, so that only that small portion is vaporized before another portion of the aerosol forming substrate is transported to the heating element.

[0004] To overcome the limitations of the known systems described above, it has been proposed to use radio frequency (RF) electromagnetic radiation to impart heat to an aerosol-forming substrate placed within an aerosol generator. Using RF electromagnetic radiation to induce heating of an aerosol-forming substrate offers the advantage of providing generally uniform heating of the substrate without requiring direct contact between the heating element and the substrate. However, when applied to aerosol generators with shape factors that allow the device to be handheld or portable, it has been found that using RF electromagnetic radiation at frequencies commonly found in the Industrial, Scientific, and Medical (ISM) bands often results in insufficient power deposition of radiation onto the substrate. [The ISM band is a portion of the radio spectrum internationally reserved for industrial, scientific, and medical (ISM) purposes other than telecommunications.] Insufficient power deposition results in insufficient heating of the substrate to efficiently generate aerosols from it, thereby providing a poor user experience for the aerosol generator user. Insufficient power deposition and inadequate substrate heating are consequences of the dimensions of the aerosol generator required to make the device handheld and portable not matching the wavelength composition of the RF electromagnetic radiation being applied. For example, the use of RF electromagnetic radiation with a frequency of approximately 2.45 GHz is desirable in aerosol generators, as this frequency falls within the ISM band and is commonly used in household appliances such as microwave ovens. However, a frequency of 2.45 GHz corresponds to a wavelength of approximately 12 centimeters, which far exceeds the dimensions required to make the aerosol generator handheld. [Overview of the project] [Problems that the invention aims to solve]

[0005] Therefore, it is desirable to improve the heating of the aerosol-forming substrate in an aerosol generator through the use of RF electromagnetic heating, in a manner that facilitates the device being handheld or portable. [Modes for carrying out the invention]

[0006] According to one aspect of the present disclosure, an aerosol generator is provided for heating an aerosol-forming substrate to generate an aerosol therefrom. The device comprises an electromagnetic field generator configured to generate radio frequency (RF) electromagnetic radiation having a predetermined frequency composition; a resonant chamber having a peripheral wall configured to be substantially opaque to RF electromagnetic radiation within the resonant chamber; and a packing material disposed inside the resonant chamber so as to surround a substrate recess defined within the resonant chamber, and configured so as to receive an aerosol-forming substrate in the substrate recess. The electromagnetic field generator is connected to the resonant chamber to transmit the RF electromagnetic radiation generated by the electromagnetic field generator to the resonant chamber. The packing material has a relative permittivity greater than 1.

[0007] Relative permittivity ε of the filler r This represents the ratio of the absolute permittivity ε of the filler to the electrical constant ε0. Relative permittivity ε r This term is sometimes also called the "dielectric constant."

[0008] As used herein, the term "aerosol generator" refers to a device that generates an aerosol by interacting with the aerosol-forming substrate of an aerosol-generating article. Preferably, the aerosol generator is a smoking device that interacts with the aerosol-forming substrate of an aerosol-generating article to generate an aerosol that can be directly inhaled into the user's lungs through the user's mouth. The aerosol generator may be a holder for the smoking article.

[0009] The aerosol generating article is preferably a smoking article that generates an aerosol that can be directly inhaled into the user's lungs through the user's mouth. Furthermore, the aerosol generating article is preferably a smoking article that generates a nicotine-containing aerosol that can be directly inhaled into the user's lungs through the user's mouth.

[0010] As used herein, the term "aerosol delivery system" refers to a combination of an aerosol generator and an aerosol generating article, the aerosol generating article and the aerosol generator working together to generate and deliver aerosols to the system's user.

[0011] As used herein, the term "aerosol-forming substrate" refers to a substrate composed of, or containing, an aerosol-forming material that has the ability to generate aerosols by releasing volatile compounds upon heating.

[0012] As used herein, the term radio frequency (RF) means frequencies between 3 Hz and 3 THz, and includes microwaves. Preferably, the RF electromagnetic field may have frequencies between 500 MHz and 50 GHz, and more preferably between 900 MHz and 30 GHz. The RF electromagnetic field may have frequencies between 900 MHz and 5 GHz. In a preferred embodiment, the RF electromagnetic field may have frequencies of about 2.4 GHz.

[0013] In an ideal scenario, a given frequency composition of RF electromagnetic radiation supplied to a resonant chamber corresponds to the chamber's fundamental resonant frequency. This scenario results in standing waves of RF electromagnetic radiation established within the resonant chamber. The amplitude of the standing waves at the fundamental frequency is maximum at a sufficient distance from the chamber's walls. For example, for a resonant chamber with cylindrical walls, the standing waves at the fundamental resonant frequency will have their maximum amplitude along the long axis of the cylindrical walls. Therefore, positioning the substrate along or near the long axis, away from the chamber's walls, facilitates efficient coupling of the RF electromagnetic radiation standing waves with the substrate, resulting in efficient heating of the substrate.

[0014] A relative permittivity ε greater than 1 inside the resonant chamber rProviding a filler having a relative permittivity ε has been shown to have the beneficial effect of reducing the resonant frequency of the resonant chamber compared to the same resonant chamber with no filler at all (i.e., compared to a resonant chamber that is completely hollow and contains only air). In general terms, for a resonant chamber of a given size, the relative permittivity ε of the filler is r The larger the size, the lower the resonant frequency of the resonant chamber. Therefore, if the resonant chamber is sized to match a handheld and portable aerosol generator, the packing material used can be selected so that the resonant frequency of the resonant chamber corresponds to a given frequency composition of RF electromagnetic radiation generated by the electromagnetic field generator. Placing the packing material inside the resonant chamber so as to surround the substrate recess helps to position the substrate away from the periphery of the resonant chamber. This, as a result, helps to increase the coupling of the substrate with any standing waves of RF electromagnetic radiation established within the chamber. These advantages can be achieved without using RF electromagnetic radiation at excessively high frequencies, thus reducing the complexity of the electromagnetic field generator design. The given frequency composition can consist of a single frequency or several distinct frequencies. As an example, the use of packing material allows an aerosol generator using RF electromagnetic radiation at a given frequency of 2.45 GHz to efficiently heat an aerosol-forming substrate located within the substrate recess, while still maintaining dimensions suitable for a handheld and portable aerosol generator.

[0015] Advantageously, the relative permittivity ε of the filler r The predetermined frequency composition and dimensions of the resonant chamber are configured such that, during use, RF electromagnetic radiation having the predetermined frequency composition resonates within the resonant chamber. In this way, efficient heating of the aerosol-forming substrate located within the substrate recess of the resonant chamber by RF electromagnetic radiation is promoted. Preferably, this resonance occurs at the fundamental resonant frequency of the resonant chamber. However, in alternative embodiments, the resonance may occur at one of the harmonic or overtone frequencies of the resonant chamber.

[0016] The filler may consist of a dielectric material or contain a dielectric material. Conveniently, the filler has a relative permittivity ε of 5 to 100. r It has the following advantages: The filler has a relative permittivity of 40-50. The filler may contain or consist of at least one of alumina, MgNb2O6, ZnNb2O6, MgTa2O6, ZnTa2O6, and glass. The following table shows the relative permittivity ε for these exemplary filler materials. r The values ​​of will be described in detail.

[0017] [Table 1]

[0018] Preferably, the aerosol generator includes an air intake configured to receive air from outside the aerosol generator. The aerosol generator may further include a fluid channel extending between the air intake and the resonant chamber to induce a flow of external air through the air intake, along the fluid channel, and into the substrate recess by applying a negative differential pressure between the substrate recess and the air intake. As an example, the negative differential pressure may be applied by the user sucking on the mouth end of the aerosol-generating article containing the aerosol-forming substrate, with the aerosol-generating article positioned such that the aerosol-forming substrate is located within the substrate recess of the aerosol generator. Thus, by the user sucking on the mouth end of the aerosol-generating article, air is drawn through the air intake and along the fluid channel of the device into the resonant chamber, then into the interior of the aerosol-generating article and through the aerosol-forming substrate of the article. The aerosol generated from the substrate by the heating effect of RF electromagnetic radiation in the resonant chamber is then carried towards the user's mouth.

[0019] Conveniently, the filler comprises a sleeve positioned to continuously surround the substrate recess. Providing the filler in the form of a sleeve may allow the filler to form the inner surface of the substrate recess in order to provide support for the aerosol-forming substrate positioned within the substrate recess. However, in alternative embodiments, the filler may comprise a plurality of separate clusters spaced apart from one another, discontinuously surrounding the substrate recess.

[0020] The outer periphery of the substrate recess may be defined by a liner configured to be substantially transparent to RF electromagnetic radiation, the liner positioned between the filler and the substrate recess. The use of such a liner helps to avoid damage to the filler when inserting or removing an aerosol-forming substrate in the recess, while still allowing RF electromagnetic radiation to pass into the substrate recess, bond with the substrate, and act upon it. Preferably, the liner may contain a material that is substantially transparent to RF electromagnetic radiation. As an example, the liner may contain Teflon, high-purity quartz, or polytetrafluoroethylene. These materials can withstand high temperatures and provide a smooth, easy-to-clean surface. Alternatively or additionally, the liner may have a plurality of slots arranged to allow RF electromagnetic radiation to enter the substrate recess during use. The plurality of slots may be provided in a symmetrical or repeating pattern around the substrate recess, thereby providing the advantage of providing RF electromagnetic radiation entering the substrate recess in a uniform manner around the periphery of the recess. Multiple slots may allow the liner to be fabricated from a material opaque to RF electromagnetic radiation. The choice of liner material and design is influenced by the need to avoid or reduce the liner obstructing the passage of RF electromagnetic radiation through the substrate recess of the resonant chamber.

[0021] Having a resonant chamber wall configured to be substantially opaque to RF electromagnetic radiation within the resonant chamber helps ensure that RF electromagnetic radiation introduced into the recess during use of the aerosol generator is confined to the recess. This helps reduce the possibility of the device user being exposed to RF electromagnetic radiation. Furthermore, efficient heating of the substrate located within the substrate recess of the resonant chamber is facilitated by the opacity of the resonant chamber wall to RF electromagnetic radiation. The resonant chamber wall may include any suitable material that does not transmit RF electromagnetic radiation, such as aluminum, stainless steel, silver, or gold. The inward-facing surface of the wall may have a polished surface to improve the reflection of RF electromagnetic radiation from there within the resonant chamber, thereby also enhancing the efficient heating of the substrate located within the substrate recess. Preferably, the material for the wall is selected to act to internally reflect RF electromagnetic radiation within the resonant chamber, thereby helping to enhance the coupling between the RF electromagnetic radiation and the substrate located within the substrate recess.

[0022] However, a small portion of the peripheral wall of the resonance chamber may be substantially transparent to RF electromagnetic radiation so as to allow RF electromagnetic radiation to enter the resonance chamber during use. "Small portion" means a part of the peripheral wall having a cumulative surface area forming less than 20% of the total surface area of the peripheral wall of the resonance chamber. The use of a small portion of the peripheral wall that is transparent to RF electromagnetic radiation helps to facilitate the entry of RF electromagnetic radiation generated by the electromagnetic field generating device into the interior of the resonance chamber. However, in order to promote efficient heating of the substrate located within the substrate recess of the resonance chamber, it is preferable to minimize the proportion of the peripheral wall formed by such small RF-transparent portions. For example, the small portion may have a cumulative surface area forming less than 15%, preferably less than 10%, or preferably less than 5% of the total surface area of the peripheral wall of the resonance chamber. The small portion may include a plurality of slots formed within the peripheral wall of the resonance chamber. The plurality of slots may be arranged to allow RF electromagnetic radiation to enter the resonance chamber during use. Preferably, the plurality of slots may be provided in a symmetric or repeating pattern around the peripheral wall of the resonance chamber, thereby providing the advantage of promoting the entry of RF electromagnetic radiation into the resonance chamber in a uniform manner around the periphery of the chamber. Alternatively or additionally, the small portion may include a material that is substantially transparent to RF electromagnetic radiation. As an example, the small portion may include Teflon, high purity quartz, or polytetrafluoroethylene. When the small portion includes a material that is substantially transparent to RF electromagnetic radiation, the small portion can be regarded as a "window" that allows the passage of RF electromagnetic radiation and can at the same time form part of the structure of the peripheral wall of the resonance chamber.

[0023] The aerosol generating device may comprise a radiation containment chamber, which surrounds the resonance chamber and is configured to be substantially opaque to RF electromagnetic radiation. Providing such a radiation containment chamber serves to provide an additional protective layer against leakage of RF electromagnetic radiation from the resonance chamber. Using such a radiation containment chamber can be particularly beneficial in embodiments of resonance chambers where the chamber's peripheral wall has small portions that are (as described above) substantially transparent to RF electromagnetic radiation. The presence of a radiation containment chamber surrounding the resonance chamber serves to confine any RF electromagnetic radiation that might have leaked from the interior of the resonance chamber within the boundaries of the radiation containment chamber. The radiation containment chamber may comprise any suitable material that does not pass RF radiation, such as aluminum, stainless steel, silver or gold.

[0024] The aerosol-forming substrate used within the aerosol generating device may take various forms. The aerosol-forming substrate may comprise a solid. The aerosol-forming substrate may comprise a liquid. The aerosol-forming substrate may comprise a gel. The aerosol-forming substrate may comprise any combination of two or more of solids, liquids, and gels. The aerosol-forming substrate preferably comprises polar molecules that are susceptible to dielectric heating, such as under the action of RF electromagnetic radiation. As an example, the aerosol-forming substrate may comprise water, which is particularly susceptible to dielectric heating. The aerosol-forming substrate may be provided in solid form but immersed in water or another liquid containing polar molecules. In this way, RF electromagnetic radiation excites the polar molecules of the water or other liquid, thereby generating heat, which is then transferred to the material of the aerosol-forming substrate.

[0025] The aerosol-forming substrate may comprise nicotine, a nicotine derivative, or a nicotine analog. The aerosol-forming substrate may comprise one or more nicotine salts. The one or more nicotine salts may be selected from the list consisting of nicotine citrate, nicotine lactate, nicotine pyruvate, nicotine bitartrate, nicotine pectinate, nicotine alginate, and nicotine salicylate.

[0026] The aerosol-forming substrate may include an aerosol-forming compound. As used herein, “aerosol-forming compound” refers to any suitable known compound or mixture of compounds that, upon use, promotes the formation of a high-density, stable aerosol and is substantially resistant to thermal degradation at the operating temperature of the aerosol-generating article. Suitable aerosol-forming compounds are, but are not limited to, those well known in the art, polyhydric alcohols such as triethylene glycol, 1,3-butanediol, and glycerin; esters of polyhydric alcohols such as glycerol monoacetate, diacetate, or triacetate; and aliphatic esters of monocarboxylic acids, dicarboxylic acids, or polycarboxylic acids such as dimethyl dodecanediol and dimethyl tetradecanediol. Preferred aerosol-forming compounds are polyhydric alcohols or mixtures thereof, such as triethylene glycol, 1,3-butanediol, and glycerin.

[0027] The aerosol-forming substrate may further contain a flavoring agent. The flavoring agent may contain volatile flavor components. The flavoring agent may contain menthol. As used herein, the term "menthol" refers to the compound 2-isopropyl-5-methylcyclohexanol in either of its isomers. The flavoring agent may provide a flavor selected from the group consisting of menthol, lemon, vanilla, orange, wintergreen, cherry, and cinnamon. The flavoring agent may also contain volatile tobacco flavor compounds released from the substrate upon heating.

[0028] The aerosol-forming substrate may further contain tobacco or tobacco-containing material. For example, the aerosol-forming substrate may contain any of tobacco leaves, tobacco stem fragments, reconstituted tobacco, homogenized tobacco, extruded tobacco, tobacco slurry, cast tobacco, and puffed tobacco. Optionally, the aerosol-forming substrate may also contain tobacco powder compressed with an inert material, such as glass or ceramic, or another suitable inert material.

[0029] When the aerosol-forming substrate contains a liquid or gel, in some embodiments the aerosol-generating article may include an absorbent carrier. The aerosol-forming substrate may be coated onto the absorbent carrier or impregnated within the absorbent carrier. For example, the nicotine compound and the aerosol-forming substance may be mixed with water as a liquid. In some embodiments, the liquid may further include a flavoring agent. Such a liquid may then be absorbed by the absorbent carrier or coated onto the surface of the absorbent carrier. The absorbent carrier may be a sheet or tablet of a cellulose-based material on which the nicotine compound and the aerosol-forming substance may be coated or absorbed. The absorbent carrier may be a metal, polymer, or plant-based foam having liquid-retaining and capillary properties on which the liquid or gel aerosol-forming substrate is coated or absorbed.

[0030] Conveniently, the substrate recess may be configured to receive a cartridge of aerosol-forming substrate so that the cartridge is completely sealed within the substrate recess. The cartridge may consist solely of aerosol-forming substrate, and for example, the cartridge may have the form of a plug or pellet of aerosol-forming substrate. Alternatively, the cartridge may comprise a casing that houses the aerosol-forming substrate. As an example, the casing may be filled with aerosol-forming substrate in the form of a liquid or gel. The liquid-filled or gel-filled casing may be configured to rupture when the liquid or gel is heated by RF electromagnetic radiation within the substrate recess of the resonant chamber. The liquid-filled or gel-filled casing may also comprise one or more valves configured to open when the liquid or gel is heated, resulting in expansion of the liquid / gel within the casing and an increase in pressure within the casing. One or more valves may be configured to open when the user draws air through the aerosol generator. The casing is formed to be substantially transparent to RF electromagnetic radiation, thereby very desirable to avoid interference with the interaction between the RF electromagnetic radiation in the resonant chamber and the aerosol-forming substrate. Alternatively, the substrate recess may be configured as a blind recess having an open end and a closed end, and the substrate recess is configured to receive at least a portion of the length of the aerosol-generating article containing the aerosol-forming substrate through the open end. In this alternative example, the substrate recess may be sized to accommodate an elongated aerosol-generating article similar in shape factor to a conventional cigarette, and the user inhales the aerosol generated from the substrate of the aerosol-generating article by placing their mouth against the mouth end of the article.

[0031] Preferably, the aerosol generator may include a mouthpiece that is in fluid communication with a substrate recess. Providing a mouthpiece on the device allows the user to inhale the aerosol generated from the substrate by placing a part of the device, namely the mouthpiece, in their mouth. Providing a mouthpiece on the aerosol generator is particularly advantageous when the substrate recess is configured to receive a cartridge of aerosol-forming substrate such that the cartridge is completely sealed within the substrate recess. The aerosol generator may further include a radiation shield positioned between (or within) the resonant chamber and the mouthpiece to obstruct the passage of RF electromagnetic radiation from the resonant chamber to the outside of the mouthpiece. Providing such a radiation shield is beneficial in reducing the possibility of direct exposure to RF electromagnetic radiation from the resonant chamber when the user places their mouth to the mouthpiece of the device. The radiation shield may be formed of any suitable material that is opaque to RF electromagnetic radiation. As an example, the radiation shield may include any suitable material that does not transmit RF radiation, such as aluminum, stainless steel, silver, or gold. The radiation shield may also be configured to reflect RF electromagnetic radiation. The radiation shield may be fluid-permeable to allow generated aerosols to pass through the shield; for example, the radiation shield may include a metal mesh. Conveniently, the radiation shield may also include a labyrinthine flow path positioned between the resonant chamber and the mouthpiece. The use of a labyrinthine flow path can avoid a direct line of sight of RF electromagnetic radiation in the resonant chamber beyond the radiation shield.

[0032] The aerosol generator may include at least one of a waveguide and an antenna configured to transmit RF electromagnetic radiation generated by an electromagnetic field generator to a resonant chamber.

[0033] Advantageously, the electromagnetic field generator may include a solid-state RF transistor. The use of a solid-state RF transistor allows for the fabrication of an aerosol generator with a compact form factor, thereby helping the device to be handheld or portable. A conventional means for generating RF frequency radiation for heating, such as in household microwave ovens, is the magnetron. Magnetrons are bulky and require very high voltages to operate, making them unsuitable for handheld devices. Furthermore, magnetrons have relatively unstable frequency output and a relatively short lifespan. In contrast, solid-state RF transistors provide consistent operation over many more usage cycles and require much lower operating voltages. Advantageously, solid-state RF transistors are configured to generate and amplify an RF electromagnetic radiation field. Conveniently, the aerosol generator employs a single solid-state RF transistor to provide both generation and amplification of the RF electromagnetic radiation field, thereby reducing the form factor of the device compared to the use of multiple such transistors. The solid-state RF transistor may be, for example, an LDMOS transistor, GaAs FET, SiC MESFET, or GaN HFET.

[0034] The aerosol generator may include a control circuit and a power supply. The control circuit may be configured to control the supply of power from the power supply to the electromagnetic field generator. The control circuit may include a microprocessor, a programmable microprocessor, a microcontroller, or an application-specific integrated circuit chip (ASIC) or other electronic circuitry capable of providing control. The control circuit may include further electronic components. For example, the control circuit may include a sensor, a switch, or a display element. The control circuit may include an RF power sensor. The control circuit may include a power amplifier. The control circuit may include a memory module containing instructions readable by the processor or other components of the control circuit, which are used to control the operation of the electromagnetic field generator. The power supply may be a DC power supply. The power supply may include at least one battery. At least one battery may be a rechargeable lithium-ion battery. Alternatively, the power supply may be another form of charge storage device, such as a capacitor.

[0035] Preferably, the aerosol generator may have an elongated housing, and the electromagnetic field generator and resonant chamber are provided inside the elongated housing. Using an elongated housing for the device provides a geometric aspect ratio of the device that facilitates the user holding the device in their hand. The elongated profile is also found in conventional cigarettes or cigars, and using such a profile in the aerosol generator of this disclosure provides the advantage of user-friendliness for the device. Conveniently, the elongated housing may generally have a cylindrical shape.

[0036] Advantageously, the resonant chamber and packing may be arranged concentrically along the length of the elongated housing. Such arrangement may be beneficial in reducing the shape factor of the aerosol generator and may allow for minimizing the size of the elongated housing in a direction perpendicular to the long axis of the housing (e.g., the diameter of the elongated housing if the housing is cylindrical).

[0037] As described above, this disclosure helps the shape factor of the aerosol generator to be small enough for the device to be handheld or portable. Accordingly, the resonant chamber of the aerosol generator may have a diameter of about 10 mm to about 50 mm, or more preferably about 25 mm to about 35 mm. The resonant chamber may have a length of about 5 mm to about 25 mm, or more preferably about 10 mm to about 20 mm. The substrate recess may have a diameter of about 3 mm to about 15 mm, or more preferably about 5 mm to about 10 mm. The substrate recess may have a length of about 5 mm to about 25 mm, or more preferably about 10 mm to about 20 mm. Since the resonant chamber is part of the aerosol generator, the size of the resonant chamber is a determinant of the size of the device. The aerosol generator may have an overall length of about 30 mm to about 150 mm. The aerosol generator may have an outer diameter of about 10 mm to about 60 mm.

[0038] As described above, the advantageous effect of the packing material made it possible to use RF electromagnetic radiation with a frequency of 2.45 GHz to provide efficient heating of the substrate within the substrate recess of the aerosol generator's resonant chamber, while maintaining a shape factor suitable for the device to be handheld or portable. The frequency of 2.45 GHz corresponds to the frequency commonly used in conventional microwave ovens.

[0039] A second aspect of the present disclosure provides an aerosol delivery system for delivering an aerosol to a user. The system comprises an aerosol generator as described in the preceding paragraph and in any of the claims corresponding to the first aspect of the present disclosure. Additionally, the system comprises an aerosol generating article comprising an aerosol forming substrate. The aerosol generator and the aerosol generating article are two separate entities, which may be i) supplied and sold independently of each other and then combined to form an aerosol delivery system, or ii) supplied and sold as a kit of parts and formed when assembled to form an aerosol delivery system.

[0040] The aerosol generating article may be provided as a disposable cartridge containing an aerosol-forming substrate, the cartridge being configured to be completely sealed within a substrate recess. As discussed in relation to the first embodiment, the cartridge may consist solely of the aerosol-forming substrate, for example, in the form of a plug or pellet of the aerosol-forming substrate. Alternatively, the cartridge may comprise a casing, the casing housing the aerosol-forming substrate. As also discussed in relation to the first embodiment, the casing may be filled with the aerosol-forming substrate in the form of a liquid or gel. The liquid-filled or gel-filled casing may be configured to rupture when the liquid or gel is heated by RF electromagnetic radiation within the substrate recess of the resonant chamber. The liquid-filled or gel-filled casing may also comprise one or more valves configured to open when the liquid or gel is heated, resulting in expansion of the liquid / gel within the casing and an increase in pressure within the casing. One or more valves may be configured to open when the user draws air through the aerosol generator. The casing is formed to be substantially transparent to RF electromagnetic radiation, thereby it is highly desirable to avoid interference with the interaction between the RF electromagnetic radiation in the resonant chamber and the aerosol-forming substrate.

[0041] The substrate recess may be configured as a blind recess having an open end and a closed end, such that at least a portion of the length of the aerosol-generating article is receivable into the substrate recess via the open end, so that the aerosol-forming substrate is positioned within the substrate recess. Providing such a blind recess is particularly preferable when the aerosol-generating article is elongated in a form similar to the shape factors of a conventional cigarette or cigar. As an example, the aerosol-generating article may have a mouth end configured so that, during use, the user places their mouth against the mouth end and inhales the article, thereby inhaling the aerosol generated from the substrate during heating by RF electromagnetic radiation.

[0042] Conveniently, the aerosol generating article may include a wrapper that encapsulates an aerosol-forming substrate and defines a rod, the rod having a mouth end and a distal end. During use, the user can place their mouth against the mouth end of the rod and suck on the rod to inhale the aerosol generated from the substrate during heating by RF electromagnetic radiation. Preferably, the wrapper may be formed of a material substantially transparent to RF electromagnetic radiation, thereby reducing the possibility that the wrapper may interfere with the interaction between the RF electromagnetic radiation in the resonant chamber and the aerosol-forming substrate. As an example, the wrapper may be paper-based. Alternatively, the wrapper may be formed of a material substantially opaque to RF electromagnetic radiation, and the wrapper may further include a plurality of slots arranged to allow RF electromagnetic radiation to enter the interior of the aerosol generating article during use. Advantageously, the aerosol generating article may include a radiation shield positioned within the rod between the aerosol-forming substrate and the mouth end to obstruct the passage of RF electromagnetic radiation through the article to the mouth end. The radiation shield may be formed of any suitable material opaque to RF electromagnetic radiation. As an example, the radiation shield may include any suitable material that does not allow RF radiation to pass through, such as aluminum, stainless steel, silver, or gold. The radiation shield may also be configured to reflect RF electromagnetic radiation. The radiation shield may also be fluid permeable to allow generated aerosols to pass through the shield, and as an example, the radiation shield may include a metal mesh.

[0043] A third aspect of the present disclosure provides a method for heating an aerosol-forming substrate and generating an aerosol therefrom, using an aerosol generator as described in any of the claims corresponding to the preceding paragraph and the first aspect of the present disclosure, or an aerosol delivery system as described in any of the claims corresponding to the preceding paragraph and the second aspect of the present disclosure. The method includes positioning the aerosol-forming substrate in a substrate recess, operating an electromagnetic field generator to generate radio frequency (RF) electromagnetic radiation having a predetermined frequency composition, and transmitting the RF electromagnetic radiation into the interior of a resonant chamber to heat the aerosol-forming substrate positioned in the substrate recess.

[0044] As described in relation to a first aspect of this disclosure, preferably, the dielectric constant of the packing material, a predetermined frequency composition, and the dimensions of the resonant chamber are selected so that, during use, RF electromagnetic radiation having the predetermined frequency composition resonates within the resonant chamber.

[0045] The present invention is defined in the claims. However, a non-exclusive list of non-limiting embodiments is provided below. One or more features of these embodiments may be combined with one or more features of other embodiments, forms, or aspects described herein. [Examples]

[0046] [Example 1] An aerosol generator for heating an aerosol-forming substrate to generate an aerosol therefrom, comprising: an electromagnetic field generator configured to generate radio frequency (RF) electromagnetic radiation having a predetermined frequency composition; a resonant chamber having a peripheral wall configured to be substantially opaque to RF electromagnetic radiation within the resonant chamber; and a packing material disposed inside the resonant chamber so as to surround a substrate recess defined within the resonant chamber, and configured so as to receive an aerosol-forming substrate, wherein the electromagnetic field generator is connected to the resonant chamber so as to transmit the RF electromagnetic radiation generated by the electromagnetic field generator to the resonant chamber, and the packing material has a relative permittivity greater than 1.

[0047] [Example 2] An aerosol generator according to Example 1, wherein the filler is a dielectric or contains one.

[0048] [Example 3] An aerosol generator according to either Example 1 or Example 2, wherein the relative permittivity of the packing material, a predetermined frequency composition, and the dimensions of the resonant chamber are configured such that, during use, RF electromagnetic radiation having a predetermined frequency composition resonates inside the resonant chamber.

[0049] [Example 4] An aerosol generator according to any one of Examples 1 to 3, wherein the filler has a relative permittivity of 5 to 100.

[0050] [Example 5] An aerosol generator according to any one of Examples 1 to 4, wherein the filler has a relative permittivity between 40 and 50.

[0051] [Example 6] An aerosol generator according to any one of Examples 1 to 5, wherein the packing material includes at least one of alumina, MgNb2O6, ZnNb2O6, MgTa2O6, ZnTa2O6, and glass.

[0052] [Example 7] An aerosol generator according to any one of Examples 1 to 6, wherein the aerosol generator is equipped with an air intake configured to receive air from outside the aerosol generator, and the aerosol generator further comprises a fluid channel extending between the air intake and the resonant chamber, thereby inducing a flow of external air that passes through the air intake and enters the substrate recess along the fluid channel due to a negative differential pressure between the substrate recess and the air intake.

[0053] [Example 8] An aerosol generator according to any one of Examples 1 to 7, comprising a sleeve in which the filling material is arranged to continuously surround a recess in the substrate.

[0054] [Example 9] An aerosol generator according to any one of Examples 1 to 7, wherein the packing material includes multiple individual clusters spaced apart from one another so as to discontinuously surround the substrate depression.

[0055] [Example 10] An aerosol generator according to any one of Examples 1 to 9, wherein the outer periphery of the substrate recess is defined by a liner configured to be substantially transparent to RF electromagnetic radiation, and the liner is positioned between the filler and the substrate recess.

[0056] [Example 11] An aerosol generator according to Example 10, wherein the liner has multiple slots arranged to allow RF electromagnetic radiation to enter substrate recesses during use.

[0057] [Example 12] An aerosol generator according to either Example 10 or Example 11, wherein the liner comprises a material that is substantially transparent to RF electromagnetic radiation.

[0058] [Example 13] An aerosol generator according to any one of Examples 1 to 12, wherein a small portion of the peripheral wall of the resonant chamber is substantially transparent to RF electromagnetic radiation, allowing RF electromagnetic radiation to enter the resonant chamber during use.

[0059] [Example 14] An aerosol generator according to Example 13, comprising multiple slots formed in the peripheral wall of a resonant chamber, with the slots arranged to allow RF electromagnetic radiation to enter the resonant chamber during use.

[0060] [Example 15] An aerosol generator according to either Example 13 or Example 14, comprising a material in which a small portion is substantially transparent to RF electromagnetic radiation.

[0061] [Example 16] An aerosol generator according to any one of Examples 1 to 15, wherein the aerosol generator further comprises a radiation containment chamber, the radiation containment chamber surrounding the resonant chamber and configured to be substantially opaque to RF electromagnetic radiation.

[0062] [Example 17] An aerosol generator according to any one of Examples 1 to 16, wherein the substrate recess is configured to receive a cartridge of an aerosol-forming substrate such that the cartridge is completely sealed within the substrate recess.

[0063] [Example 18] An aerosol generator according to any one of Examples 1 to 17, wherein the aerosol generator comprises a mouthpiece that is in fluid communication with a substrate recess, and the aerosol generator further comprises a radiation shield positioned between the resonant chamber and the mouthpiece, or within the mouthpiece, thereby obstructing the passage of RF electromagnetic radiation from the resonant chamber to the outside of the mouthpiece.

[0064] [Example 19] An aerosol generator according to Example 18, comprising a labyrinthine flow path in which a radiation shield is positioned between the resonant chamber and the mouthpiece, or within the mouthpiece.

[0065] [Example 20] An aerosol generating device according to any one of Examples 1 to 16, wherein the substrate recess is configured as a blind recess having an open end and a closed end, and the substrate recess is configured to receive at least a portion of the length of an aerosol generating article containing an aerosol-forming substrate through the open end.

[0066] [Example 21] An aerosol generator according to any one of Examples 1 to 20, further comprising at least one of a waveguide and an antenna configured to transmit RF electromagnetic radiation generated by an electromagnetic field generator to a resonant chamber.

[0067] [Example 22] An aerosol generator according to any one of Examples 1 to 21, wherein the electromagnetic field generator is equipped with a solid-state RF transistor.

[0068] [Example 23] An aerosol generator according to any one of Examples 1 to 22, comprising an elongated housing, an electromagnetic field generator, and a resonant chamber provided inside the elongated housing.

[0069] [Example 24] An aerosol generator according to Example 23, in which the resonant chamber and packing material are arranged concentrically along the length of the elongated housing.

[0070] [Example 25] An aerosol generator according to any one of Examples 1 to 24, wherein the resonant chamber has a diameter of 10 mm to 50 mm, or 25 mm to 35 mm.

[0071] [Example 26] An aerosol generator according to any of Examples 1 to 25, wherein the predetermined frequency composition is a single frequency.

[0072] [Example 27] An aerosol delivery system for delivering an aerosol to a user, the system comprising an aerosol generator according to one of Examples 1 to 26, and an aerosol generating article comprising an aerosol forming substrate.

[0073] [Example 28] An aerosol delivery system according to Example 27, wherein the aerosol generating article is provided as a disposable cartridge containing an aerosol-forming substrate, and the cartridge is configured to be completely sealed within a recess in the substrate.

[0074] [Example 29] An aerosol delivery system according to Example 27, wherein the substrate recess is configured as a blind recess having an open end and a closed end, and at least a portion of the length of the aerosol-generating article is receivable into the substrate recess via the open end, so that the aerosol-forming substrate is positioned within the substrate recess.

[0075] [Example 30] An aerosol delivery system according to either Example 27 or Example 29, wherein the aerosol generating article comprises a wrapper that encloses an aerosol-forming substrate and defines a rod, the rod having an oral end and a distal end.

[0076] [Example 31] An aerosol delivery system according to Example 30, wherein the wrapper is formed of a material substantially opaque to RF electromagnetic radiation, and the wrapper further comprises a plurality of slots arranged to allow RF electromagnetic radiation to enter the interior of the aerosol-generating article when in use.

[0077] [Example 32] An aerosol delivery system according to Example 30, in which the wrapper is formed of a material that is substantially transparent to RF electromagnetic radiation.

[0078] [Example 33] An aerosol delivery system according to any one of Examples 30 to 32, further comprising a radiation shield positioned in a rod between an aerosol-forming substrate and the mouth end, such that the aerosol-generating article obstructs the passage of RF electromagnetic radiation through the article to the mouth end.

[0079] [Example 34] A method for generating an aerosol by heating an aerosol-forming substrate using an aerosol generator according to any one of Examples 1 to 26, or an aerosol delivery system according to any one of Examples 27 to 33, the method comprising: positioning the aerosol-forming substrate in a substrate recess; operating an electromagnetic field generator to generate radio frequency (RF) electromagnetic radiation having a predetermined frequency composition; and transmitting the RF electromagnetic radiation into the interior of a resonant chamber to heat the aerosol-forming substrate positioned in the substrate recess.

[0080] [Example 35] A method according to Example 34, wherein the dielectric constant of the packing material, a predetermined frequency composition, and the dimensions of the resonant chamber are selected so that, during use, RF electromagnetic radiation having a predetermined frequency composition resonates within the resonant chamber.

[0081] Here, we will further describe the examples with reference to the following figures. [Brief explanation of the drawing]

[0082] [Figure 1] Figure 1 shows a schematic diagram of the dielectric heating system. [Figure 2a] Figure 2a shows a schematic diagram of a first embodiment of an aerosol delivery system formed from an aerosol-generating article received in an aerosol generator. [Figure 2b]Figure 2b shows a schematic diagram of the aerosol generator shown in Figure 2a, but the aerosol generating material is not shown. [Figure 3] Figure 3 shows a schematic perspective view of the resonance chamber of the aerosol generator shown in Figures 2a and 2b. [Figure 4] Figure 4 shows an end view of an alternative embodiment of a resonant chamber suitable for use in the aerosol generators of Figures 2a and 2b. [Figure 5] Figure 5 shows a schematic diagram of an exemplary aerosol generating article suitable for use with the aerosol generating apparatus shown in Figures 2a and 2b. [Figure 6a] Figure 6a shows a schematic diagram of a second embodiment of an aerosol delivery system formed from an aerosol-generating article received in an aerosol generator. [Figure 6b] Figure 6b shows a schematic diagram of the aerosol generator shown in Figure 6a, but the aerosol generating material is not shown. [Figure 7] Figure 7 shows a schematic diagram of possible configurations of slots formed within the liner of the resonant chamber of the aerosol generator. [Figure 8] Figure 8 shows a schematic diagram of a third embodiment of an aerosol delivery system formed from an aerosol generator and an aerosol generating article.

[0083] Figure 1 is a schematic diagram of a dielectric heating system 10 using radio frequency (RF) electromagnetic radiation (sometimes called dielectric heating). The system 10 comprises an RF electromagnetic signal generator 11, a power amplifier 12, and a heating chamber 13. The power amplifier 12 is connected to the RF electromagnetic signal generator 11 and functions to amplify the RF signal generated by the RF electromagnetic signal generator. An antenna 14 is positioned to extend into the heating chamber 13. The antenna 14 is connected to the output of the power amplifier 12 and operates to direct the RF signal generated by the RF electromagnetic signal generator 11 towards the heating chamber 13, resulting in an oscillating electromagnetic radiation field within the chamber. The output of the power amplifier 12 is fed back to the RF electromagnetic signal generator 11 to provide closed-loop control. The object to be heated 15 is placed in the heating chamber 13 and receives the RF electromagnetic radiation field. Polar molecules in the object 15 align with the oscillating RF electromagnetic radiation field and are agitated by the oscillating electromagnetic radiation field, resulting in an increase in the object's temperature. This form of heating has the advantage of providing uniform heating throughout the object 15 (assuming the polar molecules are uniformly distributed). It also has the advantage of being a non-contact form of heating that does not require heat conduction or convection from a high-temperature heating element. The embodiments described with reference to Figures 2-8 use the basic heating principle illustrated in Figure 1 and described in this paragraph.

[0084] Figure 2a shows a schematic diagram of a first embodiment of the aerosol delivery system 100. The aerosol delivery system 100 comprises an aerosol generator 200 and an aerosol generating article 300. Figure 2b corresponds to Figure 2a, but the presence of the aerosol generating article 300 is not shown.

[0085] The aerosol generator 200 has an elongated housing 201. The elongated housing 201 includes a power supply 202, a control electronic circuit 203, a radio frequency (RF) electromagnetic field generator 204, and a resonant chamber 205. The electromagnetic field generator 204 includes a solid-state transistor. The power supply 202 is coupled to the control electronic circuit 203 and the RF electromagnetic field generator 204 and supplies them with power. In the illustrated embodiment, the power supply 202 may be a rechargeable battery such as a lithium-ion battery. However, in alternative embodiments, other suitable power sources, such as alternative forms of batteries or capacitors, may be used.

[0086] The resonant chamber 205 has a peripheral wall 206 which is generally cylindrical in shape. In the illustrated embodiment, the peripheral wall 206 is formed of aluminum. In an alternative embodiment, the peripheral wall 206 may instead be formed of stainless steel or another material which is substantially opaque to RF electromagnetic radiation. In a further alternative embodiment, the inward surface of the peripheral wall 206 may be coated with a layer of silver, gold, or another material which is substantially opaque to RF electromagnetic radiation.

[0087] The resonant chamber 205 is positioned so that the length of the resonant chamber lies along the longitudinal axis 207 of the generally elongated housing 201. The resonant chamber 205 defines a blind recess with an opening 208 at one end of the chamber and a closed end 209 at the opposite end of the chamber. A dielectric filler 210 formed of alumina is provided within the resonant chamber 205. The alumina dielectric filler 210 has a relative permittivity ε in the range of 9.3 to 11.5 r It has. In alternative embodiments, the dielectric filler may be formed from one or more of MgNb2O6, ZnNb2O6, MgTa2O6, ZnTa2O6, and glass. In the example shown in Figures 2a and 2b, the dielectric filler 210 is provided as an annular sleeve surrounding the substrate recess 211 within the resonant chamber 205. The aerosol generating article 300 is received into the substrate recess 211 through an opening 208.

[0088] The aerosol generator 200 also includes air intakes 212 defined at various locations around the elongated housing 201. A passage 213 extends from the air intakes 212 to an opening provided within the closed end 209 of the resonant chamber 205. The antenna 214 extends from the RF electromagnetic field generator 204 into the interior of the resonant chamber 205.

[0089] Figure 3 shows a schematic perspective view of the resonant chamber 205 of the aerosol generator 200 shown in Figures 2a and 2b. Figure 3 shows how the dielectric packing sleeve 210 continuously surrounds the substrate recess 211. The dielectric packing sleeve 210 is sized so that its outer surface fits snugly against the inward-facing circumferential surface of the peripheral wall 206 of the resonant chamber 205.

[0090] Figure 4 shows an end view of an alternative embodiment of the resonant chamber 205. In this alternative embodiment, the packing 210 is provided as a plurality of separate clusters of packing material spaced circumferentially from one another, discontinuously surrounding the substrate recess 211. The liner 215 is provided radially toward the inside of the clusters of packing material 210. The liner 215 is formed of a material substantially transparent to RF electromagnetic radiation and helps to hold the separate clusters of packing material 210 in place. For the embodiments described, the liner 215 is formed of either Teflon, quartz, or polytetrafluoroethylene. However, the liner 215 may be formed of other known materials that are substantially transparent to RF electromagnetic radiation.

[0091] Figure 5 shows a schematic diagram of one embodiment of an aerosol generating article 300 suitable for use with an aerosol generator 200. The aerosol generating article 300 takes the form of a rod having an oral end 301 and a distal end 302. The aerosol generating article 300 includes a paper-based wrapper 303. Arranged sequentially within the wrapper 303 are an aerosol-forming substrate portion 304, a tubular support element 305, an aerosol cooling element 306, and a mouthpiece filter 307. The aerosol-forming substrate portion 304 is a plug of crumpled reconstructed tobacco containing an aerosol-forming body and water. The support element 305 is a hollow acetate tube. Laser-perforated lines 308 are formed through the thickness of the wrapper 303. A metal mesh radiation shielding element 309 is located between the mouthpiece filter 307 and the aerosol cooling element 306.

[0092] Here, the operation of the aerosol generator 200 in Figures 2a and 2b and the aerosol generating article 300 in Figure 5 will be described. First, the user positions the aerosol generating article 300 in the substrate recess 211 so that the distal end 302 of the article abuts against the closed end 209 of the resonant chamber 205. Once positioned in this manner, the plug of the aerosol-forming substrate 304 of the article 300 is fully located within the substrate recess 211 of the resonant chamber 205 and surrounded by the sleeve of the dielectric packing 210. Next, the user activates the aerosol generator 200 by pressing a button (not shown) located on the elongated housing 201. Upon activation of the device 200, the control electronic circuit 203 begins supplying power from the power supply 202 to the RF electromagnetic field generator 204. Next, the antenna 214 directs the RF electromagnetic radiation field generated by the RF electromagnetic field generator 204 into the interior of the resonant chamber 205. In the illustrated example, the RF electromagnetic field generator 204 is configured to generate an RF electromagnetic radiation field oscillating at a frequency of approximately 2.45 GHz. However, in an alternative embodiment, the RF electromagnetic field generator 204 may be configured to generate an RF electromagnetic radiation field that includes or consists of one or more other frequencies within the ISM band. In an alternative embodiment, the RF electromagnetic field generator 204 may be configured to generate an RF electromagnetic radiation field having frequencies from 900 MHz to 2.45 GHz.

[0093] Figures 2a and 2b are not drawn to scale. However, the resonant chamber 205 may have a diameter of 10 mm to 50 mm, with a preferred diameter of 30 mm in one example. Furthermore, the resonant chamber 205 may have a length of 5 mm to 25 mm, with a preferred length of 15 mm in one example. Furthermore, the substrate recess 211 may have a diameter of 3 mm to 15 mm, with a preferred diameter of 7 mm in one example. Furthermore, the substrate recess 211 may have a length of 5 mm to 25 mm, with a preferred length of 15 mm in one example.

[0094] The relative permittivity of the alumina dielectric filler 210 helps to reduce the resonant frequency of the resonant chamber compared to the same resonant chamber without such a dielectric filler. The effect of the dielectric filler 210 is that the fundamental resonant frequency of the resonant frequency is 2.45 GHz or within + / - 10% of that, i.e., the frequency of the RF electromagnetic field generated by the generator 204. Standing waves of the RF electromagnetic radiation field are formed within the resonant chamber 205, and because the surrounding walls are formed of a material substantially opaque to RF electromagnetic radiation, the waves are reflected off the inward surface of the surrounding walls 206 of the chamber 205. The formation of standing waves helps to couple the RF electromagnetic radiation with the plug of the aerosol-forming substrate 304 provided inside the aerosol-generating article 300. To elaborate further, the oscillations of the RF electromagnetic radiation within the resonant chamber 205 play a role in exciting polar molecules present in the plug of the aerosol-forming substrate 304, such as water present in the substrate. The excitation of polar molecules manifests as heat, which diffuses throughout the plug of the aerosol-forming substrate 304. As a result of heating the plug of the aerosol-forming substrate 304, vapor is generated from the substrate.

[0095] When a user inhales the mouth end 301 of the aerosol generating article 300, the suction generated at the mouth end induces the inflow of outside air from the outside of the elongated housing 201 through the air intake port 212. This inflow of outside air is indicated by the arrow in Figure 2a. The air flows along the passage 213, through the opening provided at the closed end 209 of the resonant chamber 205, and into the interior of the aerosol generating article 300 via the distal end 302. The air entering the distal end 302 mixes with the vapor generated from the plug of the aerosol forming substrate 304 to form an aerosol. The suction generated by the user inhaling the mouth end 301 draws out the aerosol along the interior of the aerosol generating article 300 (again, indicated by the arrow in Figure 2a), along the channel defined by the tubular support element 305, and through the aerosol cooling element 306 (see Figure 5). The suction also induces the inflow of ventilation air through the perforated lines 308 formed within the wrapper 303, thereby aiding in further cooling of the aerosol. The aerosol then passes through the mouthpiece filter 307, which is inhaled by the user. The metal mesh structure of the radiation shield element 309 serves to allow the aerosol to pass through and be inhaled by the user, while simultaneously functioning to reflect any waves of RF electromagnetic radiation that could enter the aerosol generating article 300. In this way, the radiation shield 309 reduces the possibility of the user being directly exposed to RF electromagnetic radiation emitted from the resonant chamber 205.

[0096] In a resonant chamber 205 having a predetermined size and structure, selecting different frequencies for the RF electromagnetic radiation field generated by the electromagnetic field generator 204 may require using different materials for the dielectric filler 210 to ensure a close match between the frequency of the RF electromagnetic radiation field and the resonant frequency of the resonant chamber 205, which is tuned by the dielectric filler. “Different materials” means materials with different relative permittivity. For example, if the electromagnetic field generator 204 is tuned to generate an RF electromagnetic radiation field with a frequency of 900 MHz instead of 2.45 GHz, this requires using a material for the dielectric filler 210 with a higher relative permittivity to tune the resonant frequency of the resonant chamber 205 to provide efficient coupling and heating with the plug of the aerosol-forming substrate 304 at this lower frequency.

[0097] Figure 6a shows a schematic diagram of a second embodiment of the aerosol delivery system 100'. Similar reference numerals are used where the features do not change from those of the aerosol delivery system 100 in Figures 2a and 2b. An aerosol generating article 300 of the same design as described for system 100 is used for system 100'. The aerosol delivery system 100' comprises an aerosol generator 200' and an aerosol generating article 300. Figure 6b corresponds to Figure 6a, but does not show the presence of the aerosol generating article 300. The aerosol delivery system 100' in Figure 6a differs from that in Figure 2a with respect to the design of the aerosol generator 200'. In the device 200', the resonant recess 205 is surrounded by a radiation containment chamber 216' formed of a material substantially opaque to RF electromagnetic radiation, in this case the radiation containment chamber is formed of steel. However, other suitable materials opaque to RF electromagnetic radiation may be used instead. The radiation containment chamber 216' provides an additional protective layer against RF electromagnetic radiation leaking from the resonant chamber 205. A further difference between apparatus 200' and apparatus 200' is that a slotted liner 215' is used between the sleeve of the dielectric filler 210 and the substrate recess 211. By supplying slots 217' within the liner 215', RF electromagnetic radiation can enter and exit the substrate recess 211 of the resonant chamber 205, and the liner material provides structural support to the dielectric filler. To reduce the possibility that the material of the liner 215' will interfere with RF electromagnetic radiation within the resonant chamber 205, the liner is formed of either Teflon, quartz, or polytetrafluoroethylene. However, the liner 215' may be formed of other known materials that are substantially transparent to RF electromagnetic radiation. In all other respects, the structure of the aerosol generator 200' and aerosol delivery system 100' in Figures 6a and 6b corresponds to the structure of the aerosol generator 200 and aerosol delivery system 100 in Figures 2a and 2b. The operating modes of the aerosol generator 200' and aerosol delivery system 100' in Figures 6a and 6b correspond to the modes of the aerosol generator 200 and aerosol delivery system 100 in Figures 2a and 2b.

[0098] Figure 7 provides schematic diagrams of various exemplary configurations for the slots 217' of the slotted liner 215'.

[0099] In other embodiments (not shown), the perimeter wall 206 of the resonant chamber 205 may have multiple slots, similar to the liner 215'. Providing such slots in the perimeter wall 206 of the resonant chamber 205 may allow RF electromagnetic radiation to enter resonant recesses at various locations near the periphery of the resonant chamber. As an alternative to using slots, the perimeter wall 206 of the resonant chamber 205 may instead include multiple windows formed of a material substantially transparent to RF radiation, and these “windows” provide entry of RF electromagnetic radiation into the interior of the resonant chamber 205. If the perimeter wall 206 of the resonant chamber 205 is provided with multiple such slots or windows, the slots or windows may have the configuration of a slotted liner 215'' as shown in Figure 7. When the perimeter wall 206 of the resonant chamber 205 includes multiple such slots or windows, the resonant chamber 205 is preferably surrounded within a radiation containment chamber, such as the chamber 216' shown in Figures 6a and 6b.

[0100] Figure 8 shows a schematic diagram of a third embodiment of the aerosol delivery system 100''. Similar reference numerals are used where the features do not change from those of the aerosol delivery system 100 in Figures 2a and 2b. The aerosol delivery system 100'' in Figure 8 differs from those in Figures 2a and 2b in terms of the design of both the aerosol generator 200'' and the aerosol generating article 300''. The aerosol generator 200'' in Figure 8 includes a mouthpiece 219'' that is in fluid communication with a substrate recess 210 of the resonant chamber 205. The mouthpiece 218'' closes one end of the device 200''. A metal mesh radiation shielding element 219'' is located within the mouthpiece 218'', and the shielding element extends across the interior of the mouthpiece. The aerosol generating article 300'' used in the aerosol delivery system 100'' is in the form of a cartridge 310'' of an aerosol forming substrate 304''. The aerosol-forming substrate 304'' consists of a crumpled reconstituted tobacco containing an aerosol-forming material and water. However, in an alternative embodiment (not shown), the cartridge 310'' is in the form of a casing containing a gel-like or liquid aerosol-forming substrate.

[0101] For the purposes of this specification and the appended claims, unless otherwise indicated, all numbers representing amounts, quantities, percentages, etc., should be understood in all cases as being modified by the term “approximately.” Furthermore, all ranges include the disclosed maximum and minimum points and any intermediate ranges therewith, which may or may not be specifically listed herein. Thus, in this context, the number “A” is understood as “A” ± 10%. In this context, the number “A” may be considered to include a number that falls within the general standard error of the measurement of the characteristic that the number “A” modifies. In some cases as used in the appended claims, the number “A” may deviate by the percentages listed above, provided that the amount of deviation does not substantially affect the basic and novel characteristics(s) of the claimed invention. Furthermore, all ranges include the disclosed maximum and minimum points and any intermediate ranges therewith, which may or may not be specifically listed herein.

Claims

1. An aerosol generating device for heating an aerosol-forming substrate and generating an aerosol therefrom, wherein the device is An electromagnetic field generator configured to generate radio frequency (RF) electromagnetic radiation having a predetermined frequency composition, A resonant chamber comprising a peripheral wall configured to be substantially opaque to RF electromagnetic radiation within the resonant chamber, The chamber comprises a packing material, which is disposed inside the resonant chamber so as to surround a substrate recess defined within the resonant chamber, and is configured such that the substrate recess receives the aerosol-forming substrate, The electromagnetic field generator is connected to the resonant chamber so as to transmit the RF electromagnetic radiation generated by the electromagnetic field generator to the resonant chamber. An aerosol generator wherein the packing material has a relative permittivity greater than 1.

2. The aerosol generating apparatus according to claim 1, wherein the filler is a dielectric or contains a dielectric.

3. The aerosol generator according to claim 1 or 2, wherein the relative permittivity of the packing material, the predetermined frequency composition, and the dimensions of the resonant chamber are configured such that, during use, the RF electromagnetic radiation having the predetermined frequency composition resonates inside the resonant chamber.

4. The aerosol generating apparatus according to any one of claims 1 to 3, wherein the filler has a relative permittivity of 5 to 100.

5. The aerosol generating apparatus according to any one of claims 1 to 4, wherein the filler has a relative permittivity of 40 to 50.

6. The aforementioned filler is alumina, MgNb 2 O 6 , ZnNb 2 O 6 MgTa 2 O 6 , ZnTa 2 O 6 an aerosol generator according to any one of claims 1 to 5, comprising at least one of the following: glass.

7. The aerosol generator according to any one of claims 1 to 6, wherein the aerosol generator comprises an air intake configured to receive air from outside the aerosol generator, and the aerosol generator further comprises a fluid flow path extending between the air intake and the resonant chamber, thereby inducing a flow of external air that passes through the air intake and enters the substrate recess by a negative differential pressure between the substrate recess and the air intake.

8. The aerosol generating apparatus according to any one of claims 1 to 7, wherein the filler comprises a sleeve arranged to continuously surround the substrate recess.

9. The aerosol generator according to any one of claims 1 to 7, wherein the packing material includes a plurality of individual clusters spaced apart from one another so as to discontinuously surround the substrate recess.

10. The aerosol generator according to any one of claims 1 to 9, wherein the outer periphery of the substrate recess is defined by a liner configured to be substantially transparent to RF electromagnetic radiation, and the liner is positioned between the filler and the substrate recess.

11. The aerosol generator according to claim 10, wherein the liner comprises a material that is substantially transparent to RF electromagnetic radiation.

12. The aerosol generator according to claim 10 or 11, wherein the liner comprises a plurality of slots arranged to allow the RF electromagnetic radiation to enter the substrate recess during use.

13. The aerosol generator according to any one of claims 1 to 12, wherein a small portion of the peripheral wall of the resonant chamber is substantially transparent to RF electromagnetic radiation, allowing the RF electromagnetic radiation to enter the resonant chamber during use.

14. The aerosol generator according to any one of claims 1 to 13, wherein the resonance chamber has a diameter of 10 mm to 50 mm, or 25 mm to 35 mm.

15. An aerosol delivery system for delivering aerosols to a user, wherein the system is an aerosol generator according to any one of claims 1 to 14, An aerosol delivery system comprising an aerosol generating article having an aerosol-forming substrate.

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