Shisha device with dielectric heater

Abstract

A shisha device (50) for heating an aerosol-forming substrate (92) to generate an aerosol, an aerosol-generating article (90) for a shisha system, and a shisha system comprising the shisha device (50) and the aerosol-generating article (90), wherein the shisha device (50) comprises: a liquid cavity (54) configured to contain a volume of liquid, the liquid cavity (54) having a headspace outlet (60); an article cavity (14) configured to receive the aerosol-forming substrate (92), the article cavity (14) being in fluid communication with the liquid cavity (54); and an electromagnetic field generator (11) configured to generate a radio frequency (RF) electromagnetic field in the article cavity (14).

Description

Technical Field

[0001] The present disclosure relates to a shisha system for generating an aerosol from an aerosol-forming substrate. In particular, the present disclosure relates to a shisha system, a shisha device, and a shisha article for use with a shisha device.

Background Art

[0002] Conventional shisha devices are sometimes referred to in the art as hookahs, kalyans, narghiles, or water pipes. Conventional shisha devices differ from other aerosol-generating devices in that volatile compounds released from a heated substrate in the shisha device are drawn through a liquid tray before being inhaled by the user. Conventional shisha devices may include one outlet or may include more than one outlet so that two or more users can use the device at once.

[0003] Conventional shisha devices are typically used in combination with a shisha substrate, which may be referred to in the art as hookah tobacco, tobacco molasses, or simply molasses. Conventional shisha substrates contain a relatively high amount of sugar compared to that found in conventional combustible cigarette tobacco, which may be about 20 percent, and in some cases may contain up to about 50 percent sugar.

[0004] Conventional shisha devices also utilize charcoal to heat and sometimes combust the shisha substrate to generate an aerosol for inhalation by the user. By using charcoal to heat the shisha substrate, the tobacco and other ingredients in the shisha substrate can be completely or partially combusted.

[0005] Different types of electrically operated shisha systems have been proposed. These systems replace the charcoal heat source of conventional shisha devices with an electrically operated heater. Almost all proposed electrically operated shisha systems heat the aerosol-forming substrate by one or more of the following: heat conduction from the heating element to the aerosol-forming substrate, heat radiation from the heating element to the aerosol-forming substrate, or the extraction of heated air through the aerosol-forming substrate. Most commonly, heating is achieved by passing an electric current through an electrically resistant heating element, causing Joule heating of the heating element. Induction heating systems have also been proposed, in which Joule heating occurs as a result of eddy currents induced in a susceptor heating element.

[0006] One problem with previously proposed electrically operated hookah devices is that they can result in uneven heating of the aerosol-forming substrate. The portion of the aerosol-forming substrate closest to the heating element heats up faster or to a higher temperature than the portion further away from the heating element.

[0007] It is desirable to be able to provide uniform heating of the aerosol-forming substrate in a manner that allows for greater design flexibility and enables heating control. [Overview of the project]

[0008] This disclosure provides a hookah apparatus for generating an aerosol by heating an aerosol-forming substrate. The hookah apparatus may include a liquid recess configured to contain a volume of liquid. The liquid recess may have a headspace outlet. The hookah apparatus may include an article recess configured to receive an aerosol-forming substrate. The article recess may be in fluid communication with the liquid recess. The hookah apparatus may include an electromagnetic field generator configured to generate a radio frequency (RF) electromagnetic field in the article recess.

[0009] In particular, the present disclosure provides a hookah apparatus for generating an aerosol by heating an aerosol-forming substrate, the hookah apparatus comprising: a liquid cavity configured to contain a volume of liquid and having a headspace outlet; an article cavity configured to receive an aerosol-forming substrate and being in fluid communication with the liquid cavity; and an electromagnetic field generator configured to generate a radio frequency (RF) electromagnetic field in the article cavity.

[0010] These hookah devices are configured to produce dielectric heating of the aerosol-forming substrate. Dielectric heating can be uniform within a large amount of aerosol-forming substrate without the formation of hot spots. Dielectric heating also does not require contact between the heating element and the aerosol-forming substrate. This means that there is no need to clean the heating element, compared to conventional arrangements with electric heating elements on which aerosol residue can accumulate. The hookah device allows for considerable design flexibility with respect to the shape, volume, and composition of the aerosol-forming substrate, and correspondingly, the shape and volume of the article recess.

[0011] The electromagnetic field generator can be any suitable type of electromagnetic field generator configured to generate a radio frequency (RF) electromagnetic field in an article cavity.

[0012] The electromagnetic field generator preferably includes a solid-state RF transistor.

[0013] Using solid-state RF transistors allows for a more compact hookah device. The conventional method for generating RF frequency radiation for heating, such as in household microwave ovens, is the magnetron. Magnetrons are bulky and require high voltages to operate. Furthermore, magnetrons have relatively unstable frequency output and a relatively short lifespan. RF transistors provide consistent operation over many more usage cycles and require much lower operating voltages.

[0014] Advantageously, solid-state RF transistors can be configured to generate and amplify RF electromagnetic fields. Using a single transistor to provide both RF field generation and amplification makes it possible to make hookah devices more compact. Solid-state RF transistors may be, for example, LDMOS transistors, GaAs FETs, SiC MESFETs, or GaN HFETs.

[0015] While the electromagnetic field generator preferably includes a solid-state RF transistor, in some embodiments, the electromagnetic field generator may include a magnetron or other suitable electromagnetic field generator capable of generating an RF electromagnetic field.

[0016] As used herein, radio frequency (RF) refers to frequencies between approximately 3 hertz (Hz) and approximately 3 terahertz (THz). Therefore, the RF frequencies used herein include microwave frequencies. The RF electromagnetic field preferably has a frequency between approximately 1 megahertz (MHz) and approximately 50 gigahertz (GHz). More preferably, the RF electromagnetic field has a frequency between approximately 4 megahertz (MHz) and approximately 30 gigahertz (GHz). The RF electromagnetic field may have a frequency between approximately 100 megahertz (MHz) and approximately 10 gigahertz (GHz). In one embodiment, the RF electromagnetic field has a frequency of approximately 4 megahertz (MHz). In one embodiment, the RF electromagnetic field has a frequency of approximately 3 gigahertz (GHz). In one embodiment, the RF electromagnetic field has a frequency of approximately 2.4 gigahertz (GHz).

[0017] As used herein, the term “aerosol-forming substrate” refers to a substrate having the ability to release volatile compounds that can form aerosols. Such volatile compounds may be released by heating the aerosol-forming substrate. Aerosol-forming substrates are typically part of an aerosol-generating article. For example, an aerosol-forming substrate may be a hookah aerosol-forming substrate.

[0018] Shisha aerosol-forming substrates may also be referred to in the art as water pipes, tobacco molasses, or simply molasses. Shisha aerosol-forming substrates may have a relatively high sugar content compared to conventional combustible cigarettes or tobacco-based consumables intended to be heated without combustion to mimic the smoking experience. Aerosol-forming substrates will be described in more detail later.

[0019] As used herein, the term “aerosol generating article” refers to an article comprising an aerosol-forming substrate having the ability to release volatile compounds capable of forming aerosols. For example, an aerosol generating article may be a cartridge for a hookah device. A cartridge for a hookah device comprises an aerosol-forming substrate. Preferably, a cartridge for a hookah device comprises a hookah aerosol-forming substrate. A cartridge for a hookah device is receivable by a hookah device and is operable with a hookah device to generate an aerosol that can be inhaled by a user pulling it out of the mouthpiece of the hookah device or by inhaling smoke. Aerosol generating articles may be disposable.

[0020] As used herein, the term “shisha apparatus” refers to a device that interacts with an aerosol-forming substrate to generate an aerosol. The shisha apparatus is separate from the aerosol-forming substrate. The shisha apparatus is configured for use in combination with an aerosol-forming substrate to heat the aerosol-forming substrate. The aerosol-forming substrate may be provided as part of an aerosol-generating article. The shisha apparatus is separate from an aerosol-generating article. The shisha apparatus is configured for use in combination with an aerosol-generating article to heat the aerosol-forming substrate of the aerosol-generating article. The shisha apparatus differs from other aerosol-generating devices in that, at least, volatile compounds released from the heated substrate are drawn through the liquid plate of the shisha apparatus before being inhaled by the user. The shisha apparatus may include two or more outlets so that two or more users can use the apparatus at the same time. The shisha apparatus may include an airflow conduit, such as a stem pipe, for directing volatile compounds released from the aerosol-forming substrate into the liquid plate.

[0021] As used herein, the term "shisha system" refers to a combination of an aerosol-forming substrate or an aerosol-generating article containing an aerosol-forming substrate and a shisha device. In a shisha system, the aerosol-forming substrate or an aerosol-generating article containing an aerosol-forming substrate and the shisha device work together to generate aerosols.

[0022] Shisha devices differ from other aerosol generators in that the aerosols generated by the device are drawn through a volume of liquid (typically water) before they are inhaled by the user. More specifically, when a user inhales a shisha device, volatile compounds released from the heated aerosol-forming substrate are drawn through the airflow conduit of the shisha device into the volume of liquid. The volatile compounds are drawn from the volume of liquid into the headspace of the shisha device, where they form an aerosol. The aerosol in the headspace is then drawn out of the headspace at the headspace outlet for inhalation by the user. The volume of liquid (typically water) acts to lower the temperature of the volatile compounds and may impart an additional water content to the aerosol formed in the headspace of the shisha device. This process adds a unique characteristic to the user of using a shisha device and imparts a unique characteristic to the aerosol generated by the shisha device and inhaled by the user.

[0023] In some preferred embodiments, the shisha device includes an airflow conduit for transporting volatile compounds released from a heated aerosol-forming substrate from an article cavity to a liquid cavity. More specifically, the shisha device may include an airflow conduit configured to transport volatile compounds released from a heated aerosol-forming substrate from an article cavity to a volume of liquid in the liquid cavity. Typically, the airflow conduit is configured to transport the aerosol from the article cavity to below the liquid-filling level of the liquid cavity. The liquid-filling level of the liquid cavity is the level at which the liquid cavity is intended to be filled with liquid so that the shisha device can operate optimally. The airflow conduit may have an opening for the liquid cavity below the liquid-filling level of the liquid cavity.

[0024] A hookah device includes a headspace outlet. The headspace outlet is an outlet through which aerosols can be drawn out of the liquid cavity. The headspace outlet may be located above the liquid-filling level of the liquid cavity. The space above the liquid-filling level of the liquid cavity is called the headspace. The headspace of the liquid cavity is the space through which volatile compounds drawn out of the article cavity, through the volume of liquid in the liquid cavity, can condense to form an aerosol suitable for inhalation by the user. The headspace of the liquid cavity is not intended to contain any volume of liquid in the liquid cavity. Therefore, the headspace may be located above the liquid-filling level of the liquid cavity, which is the level through which the liquid cavity is intended to be filled with liquid. The headspace outlet may be positioned to allow aerosols to be drawn out of the liquid cavity. The headspace outlet may be in fluid communication with the headspace.

[0025] The mouthpiece may be fluidly connected to the headspace outlet. The mouthpiece may be configured for the user to inhale the aerosol generated by the hookah device. In some embodiments, the mouthpiece may be fixed to the headspace outlet. In other words, the mouthpiece may be attached to the headspace outlet so that it is not removed from the headspace outlet without damaging either or both the mouthpiece and the headspace outlet. The mouthpiece may be detachably coupled to the headspace outlet. In other words, the mouthpiece may be configured to be attached to and detached from the headspace outlet. In some embodiments, the mouthpiece may be compatible with a single detachable standby air valve. In this way, if multiple headspace outlets are provided, the number of mouthpieces can be adjusted according to the number of users in any given usage session without adversely affecting the draw-to-discharge (RTD) of the device. The mouthpiece may include a hose connected to the headspace outlet. The hose may be a flexible hose.

[0026] The mouthpiece may include an activation element. The activation element may include a switch that can be activated by a user. The mouthpiece may include a smoking sensor arranged to detect when a user smokes the mouthpiece. The activation element may include both switches that can be activated by the user and the smoking sensor. The activation element may be operably coupled to the control circuit of the shisha device. The activation element may be wirelessly coupled to the control circuit of the shisha device. Activation of the activation element may cause the control circuit of the shisha device to activate the heating element rather than constantly supplying power to the heating element. As a result, use of the activation element may function to conserve energy compared to devices that do not employ such elements and may provide heating on demand rather than constant heating.

[0027] The shisha device may include a plurality of headspace outlets. For example, the shisha device may include two, three, four, five, or six headspace outlets. Providing a plurality of headspace outlets may enable a plurality of users to draw aerosol from the liquid reservoir at the same time. In other words, providing a plurality of headspace outlets may enable a plurality of users to use the shisha device simultaneously.

[0028] The shisha device includes an article recess configured to receive an aerosol-generating article that includes an aerosol-forming substrate.

[0029] It is desirable to confine the electromagnetic radiation generated by an electromagnetic field generating device within an article recess. This is to provide efficient heating and avoid radiation leakage. Such radiation leakage can damage other components of the system, including the electromagnetic field generating device itself. Also, it is desirable to minimize the user's exposure to RF radiation. Advantageously, the article recess can comprise one or more outer walls formed from a material that does not pass RF electromagnetic fields. The one or more outer walls of the article recess may include any suitable material that does not pass RF radiation, such as aluminum, stainless steel, silver, or gold. The one or more outer walls of the article recess may have a polished surface to improve the reflection of RF radiation within the recess.

[0030] Also, the entry of radiation into the article recess must be allowed. Thus, one or more slots may be formed in the one or more outer walls to enable the entry of the electromagnetic field into the article recess. By providing one or more slots through which the electromagnetic field can pass, the electromagnetic field can enter the article recess. The one or more slots can have any suitable shape and size that enables the entry of the electromagnetic field into the article recess. For example, at least one of the one or more slots may have an L-shape, S-shape, T-shape, or I-shape.

[0031] The article recess may comprise one or more walls that pass RF electromagnetic fields. In particular, the article recess may comprise one or more walls that pass RF electromagnetic fields, where the aerosol-forming substrate is enclosed in a wrapper or container formed from a material that does not pass RF electromagnetic fields. The one or more slots may be formed in the wrapper or container enclosing the aerosol-forming substrate to enable the entry of the electromagnetic field.

[0032] The article recess may have any suitable shape and size. In particular, the article recess may have a shape and size complementary to the aerosol-generating article.

[0033] The article recess may have any suitable cross-sectional shape. For example, the article recess may have a circular, elliptical, rectangular, square, triangular, or other polygonal cross-sectional shape.

[0034] In some embodiments, the article recess is substantially cylindrical.

[0035] In some embodiments, the article recess is substantially frustoconical. In some embodiments, the width or diameter at one end of the article recess is greater than the width or diameter at the other end. In other words, the article recess may taper from one end to the other. By providing an article recess with one end narrower than the other, it may be possible for the article recess to retain an aerosol-generating article within it under the influence of gravity alone.

[0036] The article recess may have an opening. The article recess may be configured to receive an aerosol-forming article containing an aerosol-forming substrate through the opening. The article recess may have an open end. The article recess may be configured to receive an aerosol-forming article containing an aerosol-forming substrate through the open end.

[0037] In some embodiments, the article recess may include a movable closure. The movable closure may be configured to substantially close the open end of the article recess. If the movable closure is provided to substantially close the open end of the article recess, the movable closure may substantially prevent the aerosol-forming article from being removed from the article recess. The movable closure may be rotatably movable to close the open end of the article recess. The movable closure may be slidably movable to close the open end of the article recess. The movable closure may be detachably coupled to the open end of the article recess to substantially close the open end of the article recess.

[0038] In some embodiments, the article recess may have two open ends. For example, the article recess may have a first open end and a second open end opposite the first end. Advantageously, providing the article recess with two open ends allows air to be drawn through the article recess between the open ends.

[0039] In some embodiments, the article recess may include an open end and a closed end. The closed end may allow the article recess to retain an aerosol-generating article within the article recess.

[0040] In some particularly preferred embodiments, the article recess is substantially frustoconical and has a first end that is narrower than a second end. In these embodiments, the first end of the article recess may be open, and the second end of the article recess may also be open. This may allow air to be drawn through the article recess from the first end to the second end. In these embodiments, the aerosol-generating article configured to be received in the article recess may have a fluid-permeable outer surface at the first end and a fluid-permeable outer surface at the second end. The fluid-permeable outer surfaces at the first and second ends of the aerosol-generating article may allow air to flow between the first and second ends through the article recess when the aerosol-generating article is received in the article recess. In these embodiments, it is preferable that the fluid-permeable outer surfaces at the first and second ends of the aerosol-generating article are impermeable to RF electromagnetic fields. For example, the fluid-permeable outer surfaces at the first and second ends may be formed from a metal mesh.

[0041] The article recess may have any suitable shape and dimensions. The article recess may have a length of about 10 mm to about 100 mm, about 20 mm to about 90 mm, or about 25 mm to about 80 mm. In some preferred embodiments, the article recess may have a length of about 33 mm, about 34 mm, about 35 mm, about 36 mm, about 37 mm, about 38 mm, 39 mm, about 40 mm, about 41 mm, or about 42 mm. The article recess may have a width or diameter of about 5 mm to about 70 mm, or about 10 mm to about 60 mm, or about 10 mm to about 50 mm. In some preferred embodiments, the article recess may have a width or diameter of about 35 mm, about 36 mm, about 37 mm, about 38 mm, 39 mm, about 40 mm, about 41 mm, about 42 mm, about 43 mm, about 44 mm, or about 45 mm.

[0042] As used herein, the term “length” refers to the maximum longitudinal dimension between the base or bottom end and the upper end of the shisha device, components of the shisha device, aerosol generating article, or components of the aerosol generating article. As used herein, the term “width” or “diameter” refers to the maximum transverse dimension of the shisha device, components of the shisha device, aerosol generating article, or aerosol generating article. For example, if the aerosol generating article has a frustoconical shape, the width or diameter of the aerosol generating article is the width or diameter of the base of the frustoconical shape, which is the widest part of the aerosol generating article at any point along the length of the aerosol generating article. A transverse dimension is a dimension measured in a direction that is measured transverse to the longitudinal direction, where the longitudinal direction is the direction in which the longitudinal dimension is measured. As used herein, the term “cross section” refers to a section cut along a cross section.

[0043] As used herein, the terms “top” and “bottom” refer to the relative position of an element or part of an element of a hookah apparatus, a component of a hookah apparatus, an aerosol generating article, or a component of an aerosol generating article.

[0044] The article recess may be located within the heating unit. The heating unit may comprise the article recess and an electromagnetic field generator. The heating unit may further comprise one or more of the following: a control circuit, a power supply, and electromagnetic field manipulators such as waveguides and antennas. The heating unit may further comprise one or more electrical connectors for electrically connecting one or more electrical components, such as the control circuit, power supply, and electromagnetic field manipulators, to the heating unit.

[0045] The heating unit may comprise one or more outer walls formed from a material that does not conduct RF electromagnetic fields. Preferably, all of the outer walls of the heating unit are formed from a material that does not conduct RF electromagnetic fields. The heating unit may comprise an opening that allows an aerosol-generating article to be inserted into an article recess. The heating unit may comprise a movable closure, such as a lid or door, that is movable between an open position and a closed position. The open position may allow the aerosol-generating article to be inserted into the article recess, while the closed position may substantially prevent or hinder the removal of the aerosol-generating article from the article recess. The movable closure may be movably coupled, such as being rotatably or slidably coupled, to the outer wall of the heating unit. The movable closure may be detachably coupled to the outer wall of the heating unit.

[0046] The aerosol generator may further include a resonant recess between the article recess and the electromagnetic field generator. As used herein, the term “resonant recess” refers to a structure capable of confining electromagnetic waves of a given frequency. In this case, the selected frequency of the electromagnetic waves corresponds to the RF region of the spectrum. To confine the electromagnetic waves, the resonant recess is fabricated from a reflective material (e.g., a metal) for that frequency. The structure may be hollow or filled with a dielectric material. The purpose of the resonant recess is to allow the electromagnetic waves to bounce back and forth within it in order to enhance the formation of standing waves and minimize power loss.

[0047] The resonant recess may be designed to match the impedance of the electromagnetic field generator and the load (in this case, the aerosol-forming substrate in the article recess) to amplify the RF electromagnetic field at the resonant frequency, optimize energy absorption by the load, and minimize reflection of radiation from the load. This improves heating efficiency and minimizes radiation leakage from the system. The resonant recess may be positioned between the electromagnetic field generator and the article recess.

[0048] The hookah apparatus may include a waveguide. The waveguide may be adjacent to the article recess. The waveguide may be provided to allow an RF electromagnetic field to enter the article recess through one or more slots or entry points. RF radiation can propagate freely within the waveguide. The waveguide may have an outer wall that does not allow RF electromagnetic radiation to pass through. The waveguide may be positioned between the electromagnetic field generator and the article recess. The waveguide may be positioned between the electromagnetic field generator and the resonant recess.

[0049] The aerosol generator may further comprise an antenna connected to an electromagnetic field generator and configured to direct an RF electromagnetic field. The aerosol generator may further comprise a plurality of antennas connected to an electromagnetic field generator and configured to direct an RF electromagnetic field. One or more antennas may be positioned at least partially within the article recess. When in use, one or more antennas may be positioned at least partially within the article recess together with the aerosol-forming substrate. When in use, one or more antennas may be configured to pierce a container or wrapper enclosing the aerosol-forming substrate. One or more antennas may pass through slots in the outer wall of the article recess. One or more antennas may be coupled to a waveguide. One or more antennas may be coupled to a waveguide coupled to an electromagnetic field generator. One or more antennas may be at least partially disposed within a resonant recess. One or more antennas may be disposed between the electromagnetic field generator and the article recess. One or more antennas may be disposed between the waveguide and the article recess. One or more antennas may be disposed between the waveguide and the resonant recess.

[0050] Providing an antenna to direct the radiation generated by the electromagnetic field generator can improve the efficiency of the device. One or more antennas may include conductive pins.

[0051] The shisha device may be provided with an air intake. The air intake may allow ambient air to be drawn into the shisha device. The device housing of the shisha device may be provided with an air intake. The air intake may allow ambient air to be drawn into the article recess. In embodiments where one or more ends of the article recess are on the external surface of the shisha device, the article recess may be provided with an air intake. In embodiments where the article recess has an open end for receiving an aerosol-generating article, the open end may form an air intake.

[0052] The airflow path may be defined between the air intake and the headspace outlet. The airflow path may extend through the article recess. The airflow path may extend from the article recess into the liquid recess. The airflow path may extend from the article recess through an airflow conduit into the liquid recess below the liquid filling level of the liquid recess. The airflow path may extend from below the liquid filling level of the liquid recess to the headspace of the liquid recess and exit through the headspace outlet.

[0053] The airflow path may include one or more labyrinthine portions extending beyond one or more radiative shielding elements. In embodiments where the airflow path passes through an article recess or through an generated RF electromagnetic field, the airflow path may include labyrinthine portions beyond one or more radiative shielding elements to prevent the escape of RF radiation through an air intake or air outlet. One or more fluid-permeable radiative shielding elements may be provided to the airflow path. For example, a metal mesh may be provided to the airflow path.

[0054] In some embodiments, the article recess is configured such that the airflow path through the article recess aligns with the airflow conduit. In some embodiments, the article recess is configured such that the airflow path through the article recess is substantially aligned with the direction in which the RF electromagnetic field enters the recess. In some embodiments, the article recess is configured such that the airflow path through the article recess is substantially transverse to the direction in which the RF electromagnetic field enters the recess.

[0055] In some embodiments, the article recess comprises a first end, a second end opposite the first end, and a side extending between the first and second ends. In these embodiments, the article recess may be configured to allow air to flow through the article recess between the first and second ends. In these embodiments, the article recess may be configured to allow RF electromagnetic energy to enter the article recess at the side. For example, one or more slots may be provided in the sidewall of the article recess formed from a material that does not conduct RF electromagnetic fields. For example, the sidewall of the recess may include a material that substantially conducts RF electromagnetic fields.

[0056] In some embodiments, the article recess comprises a first end, a second end opposite the first end, a first side extending between the first and second ends, and a second side extending between the first and second ends and opposite the first side. The article recess may be configured to allow air to flow through the recess between the first and second sides. The article recess may be configured at least one of the first and second ends to allow RF electromagnetic energy to enter the article recess.

[0057] By using an RF transistor to generate an RF electromagnetic field, a closed-loop control scheme can be used. The hookah device may include a sensor in or adjacent to the article cavity that provides a signal indicating the temperature in the article cavity, and a controller connected to receive the signal from the sensor and to control the electromagnetic field generator depending on the signal from the sensor.

[0058] The sensor may include a temperature sensor that directly measures temperature. The sensor may comprise one or more sampling antennas configured to detect perturbations of the electromagnetic field in the article cavity, indicating the temperature in the article cavity. The dielectric properties of the aerosol-forming substrate change with temperature. The frequency or amplitude of the electromagnetic field, or both, may be adjusted by a controller based on the signal from the sensor to control the heating provided by the device.

[0059] Overheating may be detected by a sensor, and underheating may also be detected by a sensor. The frequency and amplitude of the electromagnetic field may be adjusted accordingly based on the detection of overheating or underheating. The control circuit of the hookah device may be configured to adjust at least one of the frequencies and amplitudes of the electromagnetic field based on whether or not overheating is detected by a sensor.

[0060] A sensor may detect a malfunction. If a malfunction is detected, the hookah device may be automatically turned off. It may also be possible to detect the presence of inappropriate material in the article recess. If inappropriate material is detected in the article recess, the hookah device may be automatically turned off. Similarly, if the sensor signal indicates that no aerosol-forming substrate is present in the article recess, the device may be automatically turned off. To automatically turn off the hookah device, the control circuit of the hookah device may be configured to prevent power from being supplied to the electromagnetic field generator. This type of control is not possible when a magnetron is used to generate RF radiation.

[0061] It may be desirable to maintain the temperature inside the article cavity within a predetermined temperature range. It may also be desirable to maintain the temperature of the aerosol-forming substrate below the temperature of the aerosol-forming substrate combustion material.

[0062] The ability to control the amount of heat provided by the hookah device based on feedback signals makes it possible to use different aerosol-forming substrates. It may be desirable to heat different aerosol-forming substrates to different temperatures. Therefore, by providing a temperature control mechanism, it becomes possible to achieve optimal conditions for different aerosol-forming substrates or different designs of aerosol-forming articles.

[0063] A shisha device may include a smoke inhalation detector configured to detect when a user inhales smoke from the shisha device. As used herein, the term “smoking” is used to refer to a user inhaling smoke from the shisha device and receiving an aerosol. The smoke inhalation detector may include a temperature sensor. The smoke inhalation detector may include a pressure sensor. The smoke inhalation detector may include both a temperature sensor and a pressure sensor.

[0064] The shisha device may include a control circuit. The control circuit may be configured to control the power supply to the electromagnetic field generator. The control circuit may include one or more of a microprocessor, a programmable microprocessor, a microcontroller, and an application-specific integrated circuit chip (ASIC) or other electronic circuits that can provide control. The control circuit may include further electronic components. For example, in some embodiments, the control circuit may include one or more of a sensor, a switch, and a display element. The control circuit may include an RF power sensor. The control circuit may include a power amplifier.

[0065] In some embodiments, the shisha device is configured to connect to an external power source. For example, the shisha device may be configured to connect to a mains power source.

[0066] In some embodiments, the shisha device includes a power supply. The power supply may be a DC power supply. The power supply may include a battery or another form of charge storage device such as a capacitor. The power supply may include a rechargeable lithium-ion battery. In some embodiments, the power supply is a rechargeable power supply. The shisha device may be configured to connect to an external power supply to recharge the rechargeable power supply.

[0067] The control circuit may be configured to control the power supply from the power source to the electromagnetic field generator.

[0068] The power supply may provide power ranging from approximately 0.5 watts to approximately 50 watts. In some embodiments, the power supply may provide power ranging from approximately 1 watt to approximately 40 watts, or from approximately 2 watts to approximately 30 watts.

[0069] If the electromagnetic field generator is a solid-state RF transistor, the impedance of the electromagnetic field generator may be approximately 100 ohms or less. The impedance of the electromagnetic field generator may be 75 ohms or less. The impedance of the electromagnetic field generator may be greater than approximately 1 ohm. The impedance of the electromagnetic field generator may be greater than approximately 10 ohms. The impedance of the electromagnetic field generator may be between 50 and 75 ohms.

[0070] If the electromagnetic field generator is a solid-state RF transistor, the forward voltage across the electromagnetic field generator may be approximately 100 volts or less. The forward voltage across the electromagnetic field generator may be approximately 1 volt or more. The forward voltage across the electromagnetic field generator may be approximately 1 volt to approximately 100 volts.

[0071] The shisha device may include a vessel. The liquid recess may be the internal volume of the vessel. The vessel may be configured to contain liquid. The vessel may define the liquid recess. The vessel may have a headspace outlet. The vessel may define a liquid filling level. For example, the vessel may include a liquid filling level boundary line. The liquid filling level boundary line is an indicator provided on the vessel to indicate the desired level at which the liquid recess is intended to be filled with liquid. The headspace outlet may be located above the liquid filling level. The headspace outlet may be located above the liquid filling level boundary line. The vessel may include an optically transparent portion. The optically transparent portion may allow the user to observe the contents contained in the vessel. The vessel may be formed from any suitable material. For example, the vessel may be formed from glass or a hard plastic material. In some embodiments, the vessel is removable from the rest of the shisha assembly. In some embodiments, the vessel is removable from the aerosol generating portion of the shisha assembly. Advantageously, the removable vessel allows the user to fill the liquid reservoir with liquid, empty the liquid reservoir, and clean the vessel.

[0072] The vessel may be filled by the user to the liquid-filling level. The liquid preferably contains water. The liquid may contain water infused with one or more colorants and flavorings. For example, the water may contain one or both of plant infusions and herbal infusions.

[0073] The vessel may have any suitable shape and size. The liquid recess may have any suitable shape and size. The headspace may have any suitable shape and size.

[0074] Typically, the shisha apparatus according to this disclosure is intended to be fixed on a surface during use, rather than being carried by the user. Therefore, the shisha apparatus according to this disclosure may have a specific use orientation or range of orientations into which the apparatus is intended to be oriented during use. Accordingly, the terms “above” and “below” as used herein refer to the relative positions of the features of the shisha apparatus or shisha system when the shisha apparatus or shisha system is held in a use orientation.

[0075] In some embodiments, the article recess is located above the liquid recess. In these embodiments, the airflow conduit may extend from the article recess to below the liquid-filling level of the liquid recess. Advantageously, this can ensure that volatile compounds released from the aerosol-forming substrate in the article recess are delivered from the article recess to the volume of liquid in the liquid recess, rather than to the headspace above the liquid recess. In these embodiments, the airflow conduit may extend from the aerosol recess through the headspace of the liquid recess above the liquid-filling level into the liquid recess, and then into the volume of liquid below the liquid-filling level. The airflow conduit may extend into the liquid recess through the top or upper end of the liquid recess.

[0076] In some embodiments, the article recess is located below the liquid recess. In these embodiments, a one-way valve may be located between the article recess and the liquid recess. The one-way valve can prevent liquid from the liquid recess from entering the article recess under the influence of gravity. In these embodiments, the one-way valve may be provided in an airflow conduit extending from the article recess into the liquid recess. In these embodiments, the airflow conduit may extend below the liquid filling level in the liquid recess. The airflow conduit may extend into the liquid recess through the bottom end of the liquid recess.

[0077] According to some particularly preferred embodiments of the present disclosure, a hookah apparatus is provided for heating an aerosol-forming substrate to generate an aerosol, the hookah apparatus comprising: a liquid cavity configured to contain a volume of liquid and having a headspace outlet; an article cavity configured to receive an aerosol-forming substrate and being in fluid communication with the liquid cavity; and an electromagnetic field generator configured to generate a radio frequency (RF) electromagnetic field in the article cavity, the electromagnetic field generator comprising a solid-state RF transistor.

[0078] According to some particularly preferred embodiments of the present disclosure, a hookah apparatus is provided for heating an aerosol-forming substrate to generate an aerosol, the hookah apparatus comprising: a liquid cavity configured to contain a volume of liquid and having a headspace outlet; an article cavity configured to receive an aerosol-forming substrate; an airflow conduit extending between the article cavity and the liquid cavity, the airflow conduit fluidly connecting the article cavity and the liquid cavity; a mouthpiece fluidly connected to the headspace outlet of the liquid cavity; and an electromagnetic field generator configured to generate a radio frequency (RF) electromagnetic field in the article cavity.

[0079] According to some particularly preferred embodiments of the present disclosure, a hookah apparatus is provided for heating an aerosol-forming substrate to generate an aerosol, the hookah apparatus comprising: a liquid cavity configured to contain a volume of liquid and having a headspace outlet; an article cavity configured to receive an aerosol-forming substrate; and a heating unit comprising an external housing formed of a material that does not allow RF electromagnetic fields to pass through; an airflow conduit extending between the article cavity and the liquid cavity, the airflow conduit fluidly connecting the article cavity and the liquid cavity; a mouthpiece fluidly connected to the headspace outlet of the liquid cavity; and an electromagnetic field generator configured to generate a radio frequency (RF) electromagnetic field in the article cavity.

[0080] As mentioned above, this disclosure also provides an aerosol generating article for use with a hookah device.

[0081] The aerosol generating article may be any suitable type of aerosol generating article for use with a hookah device. An aerosol generating article specifically designed for use with a hookah device may be called a cartridge for a hookah device. An aerosol generating article specifically designed for use with a hookah device that has an electromagnetic field generator may be called a cartridge for a hookah device with an electromagnetic field generator.

[0082] The aerosol-generating article may have any suitable shape and size. In particular, the aerosol-generating article may have a shape and size that is complementary to the article recess in the hookah device.

[0083] The aerosol-generating article may have any suitable cross-sectional shape. For example, the aerosol-generating article may have a circular, elliptical, rectangular, square, triangular, or other polygonal cross-sectional shape.

[0084] In some embodiments, the aerosol-generating article is substantially cylindrical.

[0085] In some embodiments, the aerosol-generating article is substantially frustoconical. In some embodiments, the width or diameter of the first end of the aerosol-generating article is greater than the width or diameter of the second end opposite the first end. In other words, the aerosol-generating article may taper from the first end to the second end. By providing an aerosol-generating article having a second end that is narrower than the first end, the aerosol-generating article can be held in a complementary article recess under the influence of gravity.

[0086] The aerosol generating article may have a length of about 10 mm to about 100 mm, about 20 mm to about 90 mm, or about 25 mm to about 80 mm. In some preferred embodiments, the aerosol generating article may have a length of about 33 mm, about 34 mm, about 35 mm, about 36 mm, about 37 mm, about 38 mm, 39 mm, about 40 mm, about 41 mm, or about 42 mm. The aerosol generating article may have a width or diameter of about 5 mm to about 70 mm, or about 10 mm to about 60 mm, or about 10 mm to about 50 mm. In some preferred embodiments, the aerosol generating article may have a width or diameter of about 35 mm, about 36 mm, about 37 mm, about 38 mm, 39 mm, about 40 mm, about 41 mm, about 42 mm, about 43 mm, about 44 mm, or about 45 mm.

[0087] The aerosol-generating article includes an aerosol-forming substrate. The aerosol-forming substrate may be encased in a wrapper or container. In some embodiments, the aerosol-forming substrate may be completely covered with a coating.

[0088] The wrapper may define a substrate recess. The aerosol-forming substrate may be positioned within the substrate recess in the wrapper.

[0089] In some embodiments, the wrapper may include a material that does not transmit RF electromagnetic fields. In some embodiments, at least a portion of the wrapper may include a material that does not transmit RF electromagnetic fields. In some embodiments, the entire wrapper may include a material that does not transmit RF electromagnetic fields.

[0090] One or more slots may be formed in the wrapper to allow the RF electromagnetic field to enter the aerosol-forming substrate. In particular, when the entire wrapper contains a material that does not allow the RF electromagnetic field to pass through, one or more slots may be formed in the wrapper to allow the electromagnetic field to enter the aerosol-forming substrate.

[0091] At least a portion of the wrapper may be fluid-permeable. The fluid-permeable portion of the wrapper may allow volatile compounds released from the aerosol-forming substrate to be released from the aerosol-generating article. A portion of the wrapper containing a material that does not conduct RF electromagnetic fields may also be fluid-permeable. For example, the fluid-permeable material that does not conduct RF electromagnetic fields may be a metal mesh. Thus, at least a portion of the wrapper may be formed from a metal mesh. In some embodiments, the wrapper may be formed from a metal mesh.

[0092] The aerosol-forming substrate may be enclosed in a container. The container may define a substrate recess. The aerosol-forming substrate may be positioned within the substrate recess inside the container.

[0093] In some embodiments, the container may include a material that does not allow RF electromagnetic fields to pass through.

[0094] In some embodiments, the container may have one or more walls. At least one wall of the container may contain a material that does not allow RF electromagnetic fields to pass through. All of the walls of the container may contain a material that does not allow RF electromagnetic fields to pass through.

[0095] The container may include a top wall, a bottom wall, and side walls extending between the top wall and the bottom wall. The top wall may be made of a material that does not allow RF electromagnetic fields to pass through. The bottom wall may be made of a material that does not allow RF electromagnetic fields to pass through. The side walls may be made of a material that does not allow RF electromagnetic fields to pass through. In some embodiments, the top wall, bottom wall, and side walls each include a material that does not allow RF electromagnetic fields to pass through.

[0096] One or more slots may be formed in the container to allow the RF electromagnetic field to enter. In particular, when the top wall and side walls of the container each contain a material that does not allow the RF electromagnetic field to pass through, one or more slots may be formed in the container to allow the RF electromagnetic field to enter the aerosol-forming substrate.

[0097] In some embodiments that include a container, the top and bottom walls of the container include a material that does not allow RF electromagnetic fields to pass through. In some of these embodiments, the side walls do not include a material that does not allow RF electromagnetic fields to pass through in order to allow RF electromagnetic fields to enter at the side walls.

[0098] In some embodiments, including a container, the side walls of the container include a material that does not allow RF electromagnetic fields to pass through. In some of these embodiments, the top wall includes a material that does not allow RF electromagnetic fields to pass through, while the bottom wall does not, in order to allow RF electromagnetic fields to enter at the bottom wall. In some of these embodiments, the bottom wall includes a material that does not allow RF electromagnetic fields to pass through, while the top wall does not, in order to allow RF electromagnetic fields to enter at the top wall.

[0099] In some embodiments, a container comprising a top wall, bottom wall, and side walls made of a material that does not allow RF electromagnetic fields to pass through, one or more slots are formed in the walls of the container to allow the electromagnetic field to enter. In some of these embodiments, one or more slots are formed in the top wall. In some of these embodiments, one or more slots are formed in the bottom wall. In some of these embodiments, one or more slots are formed in the side walls.

[0100] At least a portion of the container may be fluid-permeable. The fluid-permeable portion of the container may allow volatile compounds released from the aerosol-forming substrate to be released from the aerosol-generating article. The walls of the container, which include a material that does not allow RF electromagnetic fields to pass through, may also be fluid-permeable. For example, the fluid-permeable material that does not allow RF electromagnetic fields to pass through may be a metal mesh. Thus, at least a portion of the container may be formed from a metal mesh. In some embodiments, the container may be formed from a metal mesh.

[0101] In some embodiments, at least a portion of the aerosol-forming substrate is covered with a coating. As used herein, the term “coating” refers to a layer of material that covers and adheres to the aerosol-forming substrate. The coating may be applied to cover and adhere to at least a portion of the aerosol-forming substrate by any suitable method known in the art, including but not limited to spray painting, vapor deposition, immersion, mass transfer (e.g., brushing or gluing), electrostatic deposition, or any combination thereof.

[0102] In some embodiments, the coating may include a material that does not allow RF electromagnetic fields to pass through.

[0103] One or more regions of the outer surface of the aerosol-forming substrate may be exposed. In other words, one or more regions of the outer surface of the aerosol-forming substrate may not include any coating. This can ensure that volatile compounds released from the aerosol-forming substrate can escape from the aerosol-generating article. If the coating includes a material that does not allow RF electromagnetic fields to pass through, this can also allow RF electromagnetic fields to enter the aerosol-forming substrate.

[0104] In some embodiments, the coating may include a fluid-permeable material.

[0105] In some embodiments, one or more regions of the outer surface of the aerosol-forming substrate may be covered with a first coating, and one or more regions of the outer surface of the aerosol-forming substrate may be covered with a second coating. One of the first and second coatings may contain a material that does not allow RF electromagnetic fields to pass through. One of the first and second coatings may contain a fluid-permeable material. In some preferred embodiments, one of the first and second coatings contains a material that does not allow RF electromagnetic fields to pass through, and the other of the first and second coatings contains a fluid-permeable material. This allows an RF electromagnetic field to enter the aerosol-forming substrate in one region of the aerosol-forming substrate, without allowing the RF electromagnetic field to exit the aerosol-forming substrate in that region, and allows air to be drawn out through the aerosol-forming substrate in another region of the aerosol-forming substrate.

[0106] In some embodiments, at least a portion of the wrapper or container enclosing the aerosol-forming substrate is covered with a coating. The coating may include a material that does not allow RF electromagnetic fields to pass through.

[0107] The aerosol-forming substrate can be any suitable substrate that has the ability to release volatile compounds upon heating.

[0108] In some embodiments, the aerosol-forming substrate is in the form of a suspension. For example, the aerosol-forming substrate may contain molasses. As used herein, “molasses” means an aerosol-forming substrate composition comprising a suspension having at least about 20 weight percent of sugar. For example, molasses may contain at least about 25 weight percent of sugar, such as at least about 35 weight percent of sugar. Typically, molasses contains less than about 60 weight percent of sugar, such as less than about 50 weight percent of sugar.

[0109] The aerosol-forming substrate is preferably a shisha substrate. As used herein, "shisha substrate" refers to an aerosol-forming substrate composition containing at least about 20 weight percent of sugar. The shisha substrate may also contain molasses. The shisha substrate may include a suspension having at least about 20 weight percent of sugar.

[0110] The aerosol-forming substrate may be a solid or a liquid, or it may contain both solid and liquid components.

[0111] The aerosol-forming substrate may contain nicotine. The nicotine-containing aerosol-forming substrate may contain a nicotine salt matrix. The aerosol-forming substrate may contain plant-derived materials. The aerosol-forming substrate preferably contains tobacco. The tobacco-containing material preferably contains volatile tobacco-flavored compounds released from the aerosol-forming substrate upon heating. The aerosol-forming substrate may contain homogenized tobacco material. The homogenized tobacco material may be formed by agglomerating particulate tobacco. The aerosol-forming substrate may contain non-tobacco-containing materials. The aerosol-forming substrate may contain homogenized plant-derived materials.

[0112] The aerosol-forming substrate may include one or more of the following: powder, granules, pellets, fragments, spaghetti, slivers, or sheets. The aerosol-forming substrate may also contain one or more of the following: herb leaves, tobacco leaves, tobacco stem fragments, reconstituted tobacco, homogenized tobacco, extruded tobacco, or puffed tobacco. The tobacco may be heat-dried.

[0113] The aerosol-forming substrate may contain at least one aerosol-forming compound. A suitable aerosol-forming compound includes a compound, or mixture of compounds, that facilitates the formation of a high-density, stable aerosol during use and is substantially resistant to thermal decomposition at the operating temperature of the hookah device. Suitable aerosol-forming compounds are well known in the art and include, but are not limited to, polyhydric alcohols (e.g., triethylene glycol, 1,3-butanediol, glycerin), esters of polyhydric alcohols (e.g., glycerol monoacetate, diacetate, or triacetate), and aliphatic esters of monocarboxylic acids, dicarboxylic acids, or polycarboxylic acids (e.g., dimethyl dodecanediol, dimethyl tetradecanediol). Particularly preferred aerosol-forming compounds are polyhydric alcohols or mixtures thereof (e.g., triethylene glycol, 1,3-butanediol, most preferably glycerin). The aerosol-forming compound may also be propylene glycol. The aerosol-forming substrate may contain any suitable amount of the aerosol-forming compound. For example, the aerosol-forming content of the substrate may be 5 percent or more on a dry weight basis, and preferably higher than 30 percent by weight on a dry weight basis. The aerosol-forming content may be less than approximately 95 percent on a dry weight basis. The aerosol-forming content is preferably a maximum of approximately 55 percent on a dry weight basis.

[0114] The aerosol-forming substrate preferably comprises nicotine and at least one aerosol-forming agent. In some embodiments, the aerosol-forming agent is glycerin or a mixture of glycerin and one or more other suitable aerosol-forming agents (such as those described above). In some embodiments, the aerosol-forming agent is propylene glycol.

[0115] The aerosol-forming substrate may contain other additives and components (such as flavorings). In some examples, the aerosol-forming substrate contains one or more sugars in any appropriate amount. The aerosol-forming substrate preferably contains invert sugar, which is a mixture of glucose and fructose obtained by splitting sucrose. The aerosol-forming substrate preferably contains about 1% to about 40% by weight of sugar (such as invert sugar). In some examples, one or more sugars may be mixed with a suitable carrier such as corn starch or maltodextrin.

[0116] In some embodiments, the aerosol-forming substrate contains one or more sensory enhancers. Suitable sensory enhancers include flavoring agents and sensory agents (such as cooling agents). Suitable flavoring agents include natural or synthetic menthol, peppermint, spearmint, coffee, tea, spices (such as cinnamon, clove, ginger, or a combination thereof), cocoa, vanilla, fruit flavoring agents, chocolate, eucalyptus, geranium, eugenol, agave, juniper, anethole, linalool, and any combination thereof.

[0117] Any suitable amount of aerosol-forming substrate (e.g., molasses or tobacco substrate) may be provided in the aerosol-generating article. In some preferred embodiments, about 3 grams to about 25 grams of aerosol-forming substrate are provided in the aerosol-generating article. The cartridge may contain at least 6 grams, at least 7 grams, at least 8 grams, or at least 9 grams of aerosol-forming substrate. The cartridge may contain up to 15 grams, up to 12 grams, up to 11 grams, or up to 10 grams of aerosol-forming substrate. Preferably, about 7 grams to about 13 grams of aerosol-forming substrate are provided in the aerosol-generating article.

[0118] The aerosol-forming substrate may be provided on or embedded within a thermally stable carrier. The term “thermally stable” is used herein to indicate a material that does not substantially degrade at temperatures typically heated (e.g., about 150°C to about 300°C). The carrier may comprise a thin layer on which the substrate is deposited on a first main surface, or on a second main outer surface, or on both the first and second main surfaces. The carrier may be formed from, for example, paper or paper-like material, a nonwoven carbon fiber mat, a low-mass coarse mesh metal screen, or a perforated metal foil, or any other thermally stable polymer matrix. Alternatively, the carrier may take the form of powder, granules, pellets, fragments, spaghetti, flaks, or sheets. The carrier may be a nonwoven fiber or fiber bundle incorporating tobacco components. The nonwoven fiber or fiber bundle may include, for example, carbon fibers, natural cellulose fibers, or cellulose derivative fibers.

[0119] In some embodiments, the aerosol-forming substrate may comprise tobacco, sugar, and an aerosol-forming agent. In these embodiments, the aerosol-forming substrate may comprise 10% to 40% by weight tobacco. In these embodiments, the aerosol-forming substrate may comprise 20% to 50% by weight sugar. In these embodiments, the aerosol-forming substrate may comprise 25% to 55% by weight aerosol-forming agent. In some particularly preferred embodiments, the aerosol-forming substrate comprises 20% to 30% by weight tobacco, 30% to 40% by weight sugar, and 35% to 45% by weight aerosol-forming agent. In some particularly preferred embodiments, the aerosol-forming substrate comprises about 25% by weight tobacco, about 35% by weight sugar, and about 40% by weight aerosol-forming agent. In these preferred embodiments, the tobacco may be heat-dried tobacco leaves. In these preferred embodiments, the sugar may be sucrose or invert sugar. In these preferred embodiments, the aerosol-forming agent may be propylene glycol.

[0120] According to some particularly preferred embodiments of the present disclosure, an aerosol generating article for a hookah system is provided, the aerosol generating article comprising an aerosol-forming substrate composition comprising a suspension having at least about 20 weight percent of sugar, and one or more external surfaces formed of a material that does not allow RF electromagnetic fields to pass through.

[0121] According to some particularly preferred embodiments of the present disclosure, an aerosol generating article for a hookah system is provided, the aerosol generating article comprising an aerosol-forming substrate and a coating applied to at least a portion of the outer surface of the aerosol-forming substrate, which is formed of a material that does not allow RF electromagnetic fields to pass through.

[0122] According to some particularly preferred embodiments of the present disclosure, an aerosol generating article for a hookah system is provided, the aerosol generating article comprising an aerosol-forming substrate and a wrapper enclosing the aerosol-forming substrate, the wrapper comprising one or more fluid-permeable regions and one or more regions formed of a material that does not allow RF electromagnetic fields to pass through.

[0123] This disclosure provides a shisha system comprising the aforementioned shisha device and an aerosol generating article containing an aerosol-forming substrate.

[0124] In particular, this disclosure provides a shisha system comprising the aforementioned shisha device and the aforementioned aerosol generating article.

[0125] In particular, this disclosure provides a shisha system comprising a shisha device and an aerosol-generating article. The shisha device comprises a liquid cavity configured to contain a volume of liquid and having a headspace outlet; an article cavity configured to receive an aerosol-forming substrate and being in fluid communication with the liquid cavity; and an electromagnetic field generator configured to generate a radio frequency (RF) electromagnetic field in the article cavity. The aerosol-generating article includes an aerosol-forming substrate.

[0126] In some of these embodiments, the article recess includes one or more walls formed from an RF-impermeable material and an opening that allows an aerosol-generating article to be inserted into the article recess. In these embodiments, the aerosol-generating article may have an outer surface formed from an RF-impermeable material. When the aerosol-generating article is received in the article recess, one or more walls of the article recess formed from the RF-impermeable material align with the outer surface of the aerosol-generating article formed from the RF-impermeable material to form an enclosure around the aerosol-forming substrate surrounded by the surface formed from the RF-impermeable material.

[0127] Naturally, features described in relation to shisha devices or aerosol-generating articles may also be applicable to the shisha system described herein.

[0128] Furthermore, it is naturally possible to independently implement, supply, or use specific combinations of the various features described above.

[0129] Hereinafter, embodiments of the present disclosure will be described, for illustrative purposes only, with reference to the attached drawings. [Brief explanation of the drawing]

[0130] [Figure 1] Figure 1 is a schematic diagram of a dielectric heating system. [Figure 2] Figure 2 is a schematic diagram of a closed-loop control system for a hookah system having a dielectric heating system according to an embodiment of the present disclosure. [Figure 3] Figure 3 is a schematic diagram of one embodiment of a hookah system having a dielectric heating system. [Figure 4] Figure 4 is a schematic diagram of a heating unit for a hookah apparatus according to an embodiment of the present disclosure, and an aerosol generating article configured for use with the hookah apparatus. [Figure 5] Figure 5 is a schematic diagram of a heating unit in a different embodiment of a hookah apparatus according to the embodiments of this disclosure. [Figure 6] Figure 6 is a schematic diagram of a heating unit for a hookah apparatus according to an embodiment of the present disclosure, and an aerosol generating article configured for use with the hookah apparatus. [Figure 7] Figure 7 is a schematic diagram of a heating unit for a hookah apparatus according to an embodiment of the present disclosure, and an aerosol generating article configured for use with the hookah apparatus. [Figure 8] Figure 8 is a schematic diagram of a heating unit for a hookah apparatus according to an embodiment of the present disclosure, and an aerosol generating article configured for use with the hookah apparatus. [Figure 9] Figure 9 is a schematic diagram of one embodiment of a hookah system having a dielectric heating system.

[0131] Figure 1 is a schematic diagram of a heating system using radio frequency electromagnetic radiation (RF), sometimes called dielectric heating. The system comprises a radio frequency signal generator 10, a power amplifier 12 connected to the signal generator to amplify the radio frequency signal, and an antenna 16 positioned inside an article recess 14, the antenna 16 being connected to the output of the power amplifier 12. The output of the power amplifier 12 is fed back to the signal generator 10 to provide closed-loop control. The article to be heated 18 is placed in the article recess 14 and receives radio frequency electromagnetic radiation. Polar molecules within the article 18 align with the vibrating electromagnetic field and are stirred by the electromagnetic field as it vibrates. This causes an increase in the temperature of the article 18. This type of heating has the advantage of being uniform throughout the article (if 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.

[0132] Figure 2 shows a control scheme that may be used in any of the embodiments described in Figures 3 to 9. As previously mentioned, the system includes a control circuit for the electromagnetic field generator. In the embodiment of Figure 2, the electromagnetic field generator 11 includes a solid-state RF LDMOS transistor that performs both the functions of an RF signal generator 10 and a power amplifier 12, and amplifies the generated RF electromagnetic signal. The output of the RF solid-state transistor is passed to a radiating antenna 16, which is positioned to radiate an aerosol-forming substrate 20 located within an aerosol-generating article 18 received in an article recess 14.

[0133] The control circuit includes a microcontroller 26 capable of controlling both the frequency and power output of the RF solid-state transistor. One or more sensors provide input to the microcontroller 26. Based on the sensor inputs, the microcontroller 26 adjusts the frequency or power output of the electromagnetic field generator 11, or both. In the embodiment shown in Figure 2, there is a temperature sensor 28 positioned to sense the temperature within the article recess 14. A sampling antenna 30 may be provided in the article recess 14 as an alternative to or in addition to the temperature sensor 28. The sampling antenna 30 is configured as a receiver and can detect perturbations of the electromagnetic field in the article recess 14, which is an indicator of the efficiency of energy absorption by the aerosol-forming substrate 20. An RF power sensor 32 is also provided to detect the power output from the electromagnetic field generator 11.

[0134] The microcontroller 26 receives signals from the RF power sensor 32, the temperature sensor 28, and the sampling antenna 30. The signals can be used to determine whether the temperature in the article cavity 14 is too low, too high, defective, or absent or with an improper dielectric property.

[0135] Based on the determination made by the microcontroller 26, the frequency and power of the electromagnetic field generated by the RF solid-state transistor are adjusted, or the electromagnetic field is turned off. Typically, it is desirable to provide a stable and consistent volume of aerosol, which means maintaining the aerosol-forming substrate within a specific temperature range. However, the desired target temperature may change over time as the composition of the aerosol-forming substrate changes and the temperature of the surrounding system changes. Also, since the dielectric properties of the aerosol-forming substrate change with temperature, it may be necessary to adjust the electromagnetic field as the temperature rises or falls.

[0136] It is clear that features described in one embodiment may also be applicable to other embodiments. The described embodiments offer the advantages of uniform, non-contact heating of aerosol-forming substrates in a manner that can be controlled to provide specific, desirable aerosol properties. Compared to conventional microwave heating using a magnetron, the use of solid-state RF transistors also allows for better control of frequency and power, as well as a longer operating life.

[0137] The embodiments described with reference to Figures 3 to 8 utilize the basic heating and control principles illustrated in Figures 1 and 2. In addition, the embodiments described with reference to Figures 3 to 8 employ solid-state radio frequency (RF) transistors to perform both the signal generation function and power amplification function illustrated in Figure 1. However, it may be possible to implement the described embodiments using separate electronic components for signal generation and power amplification. It may also be possible to implement the described embodiments using conventional microwave heating systems, such as systems employing a magnetron.

[0138] Figure 3 is a schematic diagram of a hookah system according to an embodiment of the present disclosure.

[0139] The hookah apparatus 50 comprises a vessel 52 defining a liquid recess 54. The vessel 52 is configured to hold a volume of liquid in the liquid recess 54 and is formed from a hard, optically transparent material such as glass. In this embodiment, the vessel 52 has a substantially frustoconical shape and is supported in use by its wide end on a flat, horizontal surface such as a table or shelf. The liquid recess 54 is divided into two sections: a liquid section 56 for receiving a volume of liquid and a headspace 58 above the liquid section 58. The liquid filling level 60 is located at the boundary line between the liquid section 56 and the headspace 58, and the liquid filling level 60 is defined on the vessel 52 by a dashed line marked on the outer surface of the vessel 52. A headspace outlet 62 is provided above the liquid filling level 60 on the side wall of the vessel 52. The headspace outlet 62 allows fluid to be drawn out of the liquid recess 54 from the headspace 58. The mouthpiece 64 is connected to the headspace outlet 62 by a flexible hose 66. The user can draw fluid from the headspace 58 for inhalation by sucking on the mouthpiece 64.

[0140] The shisha apparatus 50 further comprises a heating unit 70 equipped with an electromagnetic field generator according to the present disclosure. Different embodiments of the heating unit are discussed below in more detail with reference to Figures 4, 5, 6, 7, and 8. The heating unit 70 is positioned above the vessel 52 by an airflow conduit 72. In this embodiment, the heating unit 70 is supported above the vessel 52 by the airflow conduit 72, but in other embodiments, it will be understood that the heating unit 70 may be supported above the vessel 52 by the housing of the shisha apparatus or another suitable support. The airflow conduit 72 extends from the heating unit 70 into the liquid recess 54 of the vessel 52. The airflow conduit 72 extends through the headspace 58 and below the liquid filling level 60 into the liquid section 58. The airflow conduit 72 has an outlet 74 in the liquid section 56 of the liquid recess 54 below the liquid filling level 60. This configuration allows air to be drawn from the heating unit 70 to the mouthpiece 64. Air can be drawn from the external environment into the apparatus 50, enter the heating unit 70, pass through the heating unit 70, through the airflow conduit 72, enter the volume of liquid in the liquid section 56 of the liquid cavity 54, exit the volume of liquid and enter the headspace 58, exit the headspace 58 out of the vessel at the headspace outlet 62, pass through the hose 66, and be drawn to the mouthpiece 64.

[0141] During use, the user can inhale the mouthpiece 64 of the shisha device 50 to receive an aerosol from the shisha device 50. More specifically, an aerosol-generating article containing an aerosol-forming substrate may be positioned in an article recess within the heating unit 70 of the shisha device 50. The heating unit 70 may be operated to heat the aerosol-forming substrate within the aerosol-generating article and release volatile compounds from the heated aerosol-forming substrate. When the user inhales the mouthpiece 64 of the shisha device 50, the pressure inside the shisha device 50 decreases, which draws the released volatile compounds from the aerosol-forming substrate into the airflow conduit 72 to the heating unit 70. The volatile compounds are drawn out of the airflow conduit 72 at the outlet 74 into the liquid volume of the liquid section 56 of the liquid recess 54. The volatile compounds are cooled in the liquid volume and released into the headspace 58 above the liquid filling level 60. The volatile compounds in the headspace 58 condense to form an aerosol, which is drawn out of the headspace at the headspace outlet 62 and into the mouthpiece 64 for inhalation by the user.

[0142] Figure 4 shows a schematic diagram of the heating unit 70 of the shisha device 50 of Figure 3, combined with an aerosol generating article 90, forming a shisha system according to an embodiment of the present disclosure. Figure 4a shows the heating unit 70 and the aerosol generating article 90 before the aerosol generating article 90 is inserted into the article recess 14 of the heating unit 70. Figure 4b shows the aerosol generating article 90 received in the article recess 14 of the heating unit 70.

[0143] As shown in Figure 4a, the heating unit 70 includes an external housing 71. The external housing 71 forms a cylindrical tube that is open at one end and substantially closed at the opposite end for the insertion of the aerosol generating article 90. The external housing 71 is made of a material that does not transmit RF electromagnetic radiation, such as aluminum.

[0144] The article recess 14 is defined within the outer housing 71 by a base 78 and side walls 76, extending between the periphery of the base 78 and the open end of the outer housing 71. The article recess 14 is configured to receive an aerosol-generating article 90 and has a shape and size complementary to the aerosol-generating article 90. The diameter of the base 78 of the article recess 14 is smaller than the diameter of the open end of the outer housing 71, such that the side walls 76 are inclined relative to the cylindrical side walls of the outer housing 71. Thus, the article recess 14 has a substantially frustoconical shape, opening at its broad end to receive the aerosol-generating article 90. The side walls 76 and base 78 of the article recess 14 are formed from a material that does not transmit RF electromagnetic radiation, such as aluminum. However, the base 78 of the article recess 14 includes a plurality of slots 79 configured to allow the RF electromagnetic field to propagate through the base 78 into the article recess 14.

[0145] The resonant recess 80 is located below the base 78 of the article recess 14. In this embodiment, the resonant recess 80 is defined between the base 78 of the article recess 14, the substantially closed end of the outer housing 71, and the inner wall 82. The inner wall 82 extends between the base 78 of the article recess 14 and the substantially closed end of the outer housing 71. In this embodiment, the inner wall 82 is formed of a material that does not transmit RF electromagnetic radiation, such as aluminum.

[0146] In other embodiments, it will be understood that the position of the internal wall 82 may be changed to alter the size and shape of the resonant recess 80. It may be necessary to change the position of the internal wall 82 to allow electromagnetic fields of specific frequencies to resonate within the resonant recess 80.

[0147] The base 78 and side walls 76 of the article recess 14, as well as the inner wall 82 and outer housing 71, preferably have polished surfaces to improve the reflection of RF radiation.

[0148] The heating unit 70 further comprises an electromagnetic field generator 11. The electromagnetic field generator 11 includes a solid-state RF LDMOS transistor that performs both the functions of an RF signal generator and a power amplifier, and amplifies the generated RF electromagnetic signal. The output of the RF solid-state transistor is coupled to a waveguide 15. The waveguide 15 extends into a resonant recess 80 through a substantially closed end of the outer housing 71. The waveguide 15 is coupled to an antenna 16, which is positioned within the resonant recess 80 and configured to radiate the RF electromagnetic field generated by the RF solid-state transistor into the resonant recess 80.

[0149] The electromagnetic field generator 11 is connected to a power supply (not shown) and a control circuit (not shown) of the shisha device, and the control circuit is configured to control the power supply from the power supply to the electromagnetic field generator 11. In this embodiment, the power supply is a rechargeable lithium-ion battery, and the shisha device 50 is equipped with a power connector that allows the shisha device 50 to be connected to a main power supply to recharge the power supply. By providing the shisha device 50 with a power supply such as a battery, the shisha device 50 can be made portable and used outdoors or in places where a main power supply is not available.

[0150] The heating unit 70 is positioned above the vessel 52 of the hookah device 50 by an airflow conduit 72. The airflow conduit 72 is fixedly attached to the substantially closed end of the outer housing 71 of the heating unit 70. In other embodiments, it will be understood that the heating unit 70 may be detachably attached to the airflow conduit 72 so that the heating unit 70 may be removed for cleaning or replacement as needed. An opening 73 is provided at the substantially closed end of the outer housing 71 to fluidly connect the resonant recess 80 to the airflow conduit 72. A radiation shielding element in the form of a metal mesh (not shown) is provided above the opening 73 of the outer housing 71 to substantially prevent the RF electromagnetic field from flowing out of the resonant recess 80 into the airflow conduit 72 without substantially affecting the fluid flow between the resonant recess 80 and the airflow conduit 72.

[0151] Accordingly, the heating unit 70 is configured such that air can enter the resonant recess 80 from the article recess 14, through the slot 79 of the base 78, enter the airflow conduit 72 from the resonant recess 80, and be drawn out through the opening 73 and the radiation shielding element.

[0152] The aerosol-generating article 90 includes an aerosol-forming substrate 92. In some embodiments, the aerosol-forming substrate 92 is a shisha substrate containing molasses and tobacco. The aerosol-forming substrate 92 may be enclosed within a container. The container has a substantially frustoconical shape complementary to the container of the article recess 14. The container may include a bottom wall 94, a top wall 96, and side walls 98 extending between the bottom wall 94 and the top wall 96. The bottom wall 94 and side walls 98 of the container are formed from a material that is fluid-permeable and substantially permeable to RF electromagnetic fields, such as perforated corrugated cardboard or plastic material. This allows air to be drawn into or out of the aerosol-generating article through the bottom wall 94 and side walls 98, and allows RF electromagnetic fields to enter the aerosol-generating article through the bottom wall 94 and side walls 98. The top wall 96 includes a material that does not permeate RF electromagnetic fields, such as a metal mesh. This allows air to be drawn into the aerosol-generating article through the upper wall 96, and prevents the RF electromagnetic field from leaving the aerosol-generating article through the upper wall 96.

[0153] As shown in Figure 4b, when the aerosol-generating article 90 is received in the article recess 14 of the heating unit 70, the bottom wall 94 of the aerosol-generating article 90 contacts the bottom wall 78 of the article recess 14, and the side walls 98 of the aerosol-generating article 90 contact the side walls 76 of the article recess 14. The top wall 96, formed from a material that does not allow RF electromagnetic fields to pass through, aligns with and contacts the side walls 76 of the article recess 14, which are also formed from a material that does not allow RF electromagnetic fields to pass through. In this position, the aerosol-forming substrate 92 is surrounded by a material that does not allow RF electromagnetic fields to pass through, by the top wall 96 of the aerosol-generating article 90, and the side walls 76 and base 78 of the article recess 14. The slot 79 in the base 78 of the article recess 14 is the only entry and exit point for the RF electromagnetic field entering and leaving the aerosol-forming substrate 92.

[0154] When a user inhales through the mouthpiece 64 of the hookah device 50, air is drawn into the hookah device 50 through the upper wall 96 of the aerosol generating article 90. The airflow path through the aerosol generating article 90 and the heating unit 70 is indicated by the arrows in Figure 4b. Air is drawn into the aerosol generating article 90 through the upper wall 96, passes through the aerosol forming substrate 92, and enters the resonant recess 80 of the heating unit 70 through the slot 79 in the bottom wall 94 of the aerosol generating article 90 and the bottom wall 78 of the article recess 14. From the resonant recess 80, air is drawn into the airflow conduit 72 through the opening 73 of the outer housing 71 of the heating unit 70.

[0155] When the user activates the shisha device 50 during use, power is supplied from the power source to the electromagnetic field generator 11. In this embodiment, the shisha device is activated by the user pressing an activation button (not shown) provided on the external surface of the heating unit 70. In other embodiments, it will be understood that the shisha device may be activated in a different manner, such as when a smoke-inhalation sensor provided on the mouthpiece 64 detects that the user is inhaling from the mouthpiece 64. When power is supplied to the electromagnetic field generator 11, the electromagnetic field generator 11 generates and amplifies an RF electromagnetic field at a frequency of 900 MHz to 2.4 GHz. The RF electromagnetic field is directed by the antenna 16 along the waveguide 15 into the resonant recess 80. From the resonant recess 80, the RF electromagnetic field propagates through the slot 79 in the bottom wall 78 of the article recess 14 and the bottom wall 94 of the aerosol-generating article 90 into the aerosol-forming substrate 92 of the aerosol-generating article 90. The upper wall 96 of the aerosol-generating article 90 prevents the RF electromagnetic field from escaping from the aerosol-generating article 90. The RF electromagnetic field dielectrically heats the aerosol-forming substrate 90, which emits volatile compounds. As described above, the temperature inside the article recess 14 can be adjusted using a feedback control mechanism. The temperature inside the article recess 14 can be sensed, or another parameter indicating the temperature inside the substrate recess can be sensed, in order to provide a feedback signal to the control circuit of the hookah device 50. The control circuit is configured to adjust the frequency or amplitude, or both, of the RF electromagnetic field in order to maintain the temperature inside the article recess 14 within a desired temperature range.

[0156] When a user inhales the mouthpiece 64 of the hookah device 50, the volatile compounds released from the heated aerosol-forming substrate 90 are carried by the airflow through the aerosol-generating article 90 and drawn out from the aerosol-generating article 90 through the resonance recess 80 into the airflow conduit 72. From the airflow conduit, the volatile compounds are drawn out through the hookah device 50 of the mouthpiece 66 as described above.

[0157] Figure 5 shows a heating unit 70 of a hookah apparatus according to another embodiment of the present disclosure. The heating unit 70 shown in Figure 5 is substantially similar to the heating unit 70 shown in Figure 4, and the same reference numerals are used to indicate similar features.

[0158] The heating unit 70 shown in Figure 5a differs from the heating unit 70 shown in Figure 4 in that the base 78 of the article recess 14 does not have a slot 79, so RF electromagnetic radiation cannot propagate from the resonant recess 80 through the base 78 of the article recess 14 into the article recess 14. In the embodiment of Figure 5a, the slot 83 is provided in the inner wall 82 and the slot 77 is provided in the side wall 76 of the article recess 14. Thus, the RF electromagnetic field can enter the article recess 14 through the slot 83 in the inner wall 82 and through the side wall 76 of the article recess 14. This arrangement changes the size and shape of the resonant recess 80 compared to the embodiment of Figure 4. The change in size and shape of the resonant recess 80 may be necessary when using RF electromagnetic fields of different frequencies to ensure that the RF electromagnetic field resonates within the resonant recess 80.

[0159] The heating unit 70 shown in Figure 5b differs from the heating unit 70 shown in Figure 4 in that, in addition to the slot 79 in the base 78 of the article recess 14, the internal wall 82 also has a slot 83, and the side wall 76 of the article recess 14 has a slot 77, so that the RF electromagnetic field can enter the article recess 14 through both the base 78 and the side wall 76 of the article recess 14. This arrangement provides further alternative sizes and shapes for the resonant recess 80, which may provide a suitable resonant recess for RF electromagnetic fields of alternative frequencies.

[0160] Figure 6 shows a heating unit 70 for a shisha apparatus and an aerosol generating article 90, forming a shisha system according to another embodiment of the present disclosure. The heating unit 70 and aerosol generating article 90 shown in Figure 6 are substantially similar to the heating unit 70 and aerosol generating article 90 shown in Figure 4, and similar reference numerals are used to indicate similar features. Figure 6a shows the heating unit 70 and aerosol generating article 90 before the aerosol generating article 90 is inserted into the article recess 14 of the heating unit 70. Figure 6b shows the aerosol generating article 90 received in the article recess 14 of the heating unit 70.

[0161] The heating unit 70 shown in Figure 6 differs from the heating unit 70 shown in Figure 4 in that the base 78 of the article recess 14, the side walls 76 and the inner walls 82 of the article recess 14 are all formed from a material that substantially allows RF electromagnetic fields to pass through, such as a rigid plastic material, ceramic or clay. In this embodiment, each of the base 78 of the article recess 14, the side walls 76 and the inner walls 82 of the article recess 14 are configured to be fluid-permeable, respectively, so that air can be drawn through each of these walls. In other embodiments, it will be understood that the base 78 of the article recess 14 may be fluid-permeable and the side walls 76 and the inner walls 82 of the article recess 14 may be substantially impermeable to fluid, or the side walls 76 and the inner walls 82 of the article recess 14 may be fluid-permeable and the base 78 of the recess 14 may be substantially impermeable to fluid.

[0162] The aerosol generating article 90 shown in Figure 6 differs from the aerosol generating article 90 shown in Figure 4 in that the bottom wall 94 and side walls 80 of the aerosol generating article are formed from a material that does not allow RF electromagnetic fields to pass through. Multiple slots 95 are provided in the bottom wall 94 and side walls 90 to allow the RF electromagnetic field to enter the aerosol generating article 90 and heat the aerosol forming substrate 92. In some embodiments, it will be understood that only one slot is provided in one of the bottom wall and top wall. It will also be understood that the size and shape of one or more slots may vary depending on the geometric shape of the aerosol generating article and the hookah device. In this embodiment, the slots 95 also make the bottom wall 95 and side walls 98 fluid permeable so that air can be drawn through the aerosol generating article 90 into the heating unit 70 of the hookah device 50.

[0163] The advantage of providing a material that does not allow RF electromagnetic fields to pass through the lower and side walls of an aerosol-generating article is that the number, size, shape, and arrangement of slots in the lower and side walls can be selected depending on the aerosol-forming substrate enclosed within the aerosol-generating article. The number, size, shape, and arrangement of slots in the lower and side walls can affect the RF electromagnetic field within the aerosol-generating article, which in turn can affect the heating of the aerosol-forming substrate and the temperature at which the aerosol-forming substrate is heated.

[0164] Figure 7 shows a heating unit 70 and aerosol generating article 90 of a hookah apparatus according to another embodiment of the present disclosure. The heating unit 70 and aerosol generating article 90 shown in Figure 7 are substantially similar to the heating unit 70 and aerosol generating article shown in Figure 4, and similar reference numerals are used to indicate similar features.

[0165] The heating unit 70 shown in Figure 7 comprises an external housing 71, forming a cylindrical tube that is open at one end and substantially closed at the other. The external housing 71 is made of a material that does not transmit RF electromagnetic radiation.

[0166] The article recess 14 is defined within the outer housing 71 and is sized and shaped to receive the aerosol-generating article 90. The heating unit is positioned above the vessel 52 of the hookah device 50 by an airflow conduit 72, which extends into the substantially closed end of the outer housing 71 of the heating unit 70, fluidly connecting the article recess 14 to the vessel 52 of the hookah device 50. A radiation shielding element (not shown) in the form of a metal mesh is provided within the airflow conduit 72 to prevent the RF electromagnetic field from escaping from the article recess 14 through the airflow conduit 72.

[0167] The heating unit 70 shown in Figure 7 differs from the heating unit 70 shown in Figure 4 in that it includes a closure 75. The closure 75 is movable over the open end of the outer housing 71 of the heating unit 70 to substantially close the open end. The closure 75 has an outer housing similar to the outer housing 71 of the heating unit, is formed from a material that does not allow RF electromagnetic fields to pass through, and is sized and shaped to align with and engage with the outer housing 71 to close the open end. The closure 75 is rotatably connected to the outer housing 71 by a hinge and is rotatable between the open position shown in Figure 7a and the closed position shown in Figure 7b. When the closure 75 is in the open position, the open end of the outer housing 71 is open for inserting the aerosol generating article 90 into the article recess 14 and for removing the aerosol generating article 90 from the article recess 14. When the closing section 75 is in the closed position, the article recess 14 is surrounded by a material that does not allow RF electromagnetic fields to pass through, so that RF electromagnetic fields cannot propagate from the article recess 14.

[0168] In this embodiment, the closure 75 also comprises an electromagnetic field generator 11 in the form of a solid-state RF LDMOS transistor, a waveguide 15 coupled to the output of the solid-state transistor, a resonant recess 80, and an antenna 16 coupled to the waveguide 16 and positioned within the resonant recess 80. In this embodiment, the resonant recess 80 includes a substantially cylindrical body of dielectric material encased in a metal outer vessel. The metal outer vessel of the resonant recess 80 comprises a pair of slots 79, which are provided to allow an RF electromagnetic field generated by the electromagnetic field generator 11 to be directed into the resonant recess 80 and propagate from the resonant recess 80 into the article recess 14 when the closure 75 is in the closed position. A control circuit (not shown) and a battery (not shown) are also included in the closure 75 to provide a controlled power supply to the electromagnetic field generator 11.

[0169] In some embodiments, it will be understood that the shisha device may include electrical components on the vessel 50 or on the mouthpiece 64 that require power from a battery or control from a control circuit. In these embodiments, flexible circuits or wires may be supplied from the control circuit and battery in the housing 75 to components located at other positions on the shisha device 50 via hinges.

[0170] In this embodiment, the closure 75 also includes an air intake (not shown) in the form of a fluid-permeable region of a material that does not allow RF electromagnetic fields to pass through. The air intake allows air to be drawn into the article recess 14 when the closure 75 is in the closed position.

[0171] This embodiment has a particularly advantageous configuration in that it is simple to manufacture and involves a relatively small number of component parts. Furthermore, since the article recess 14 is completely surrounded by a material that does not allow RF electromagnetic fields to pass through, the aerosol-generating article 90 does not need to have any external surface formed from a material that does not allow RF electromagnetic fields to pass through. Since the aerosol-generating article 90 is typically a disposable component of a hookah system, this can reduce the manufacturing cost of the aerosol-generating article 90.

[0172] Figure 8 shows a heating unit 70 and aerosol generating article 90 of a hookah apparatus 50 according to another embodiment of the present disclosure. The heating unit 70 and aerosol generating article 90 shown in Figure 8 are substantially similar to the heating unit 70 and aerosol generating article 90 shown in Figure 7, and the same reference numerals are used to indicate similar features. Figure 7a shows the heating unit 70 and aerosol generating article 90 before the aerosol generating article 90 is inserted into the article recess 14 of the heating unit 70. Figure 7b shows the aerosol generating article 90 received in the article recess 14 of the heating unit 70.

[0173] The heating unit 70 shown in Figure 8 differs from the heating unit 70 shown in Figure 7 in that the heating unit 70 shown in Figure 8 has the electromagnetic field generator 11, waveguide 15, antenna 60, and resonant recess 80 located in the external housing 71, rather than in the closure 75. In this embodiment, the closure 75 is simply a cover for closing the article recess 14 to prevent the RF electromagnetic field from escaping from the article recess 14.

[0174] The resonant recess 80 of the heating unit 70 shown in Figure 8 includes a substantially annular body of dielectric material encased in a metal outer container. The resonant recess 80 has a tapered inner passage that widens toward the open end of the outer housing 71. In this embodiment, the inner passage of the resonant recess 80 is configured to substantially define an article recess 14 and to receive a generally frustoconical aerosol-generating article 90. Multiple slots 79 are provided in the inner passage of the resonant recess 80 in the metal outer container to allow an RF electromagnetic field to propagate into the article recess 14.

[0175] In this embodiment, the airflow path through the heating unit 70 is substantially longitudinal through the article recess 14 in the direction of the airflow conduit 72, and the RF electromagnetic field propagates from the resonant recess 80 into the article recess 14 in a direction substantially transverse to the airflow. This arrangement ensures that the electromagnetic field generator is removed from the airflow path through the heating unit 70. This type of arrangement can facilitate the control of the draw resistance through the heating unit 70. This type of arrangement can also simplify temperature control of the electromagnetic field generator, as the temperature of the electromagnetic field generator is unlikely to fluctuate during use as a result of the user suctioning smoke on the device and drawing air through the electromagnetic field generator.

[0176] Figure 9 shows a shisha system according to another embodiment of the present disclosure. This shisha system is similar to the shisha system shown in Figure 3, and the same reference numerals are used to represent similar features.

[0177] The hookah apparatus 50 comprises a vessel 52 defining a liquid cavity 54 divided into two sections, a liquid section 56 containing the volume of liquid, and a headspace 58 above the liquid section. In this embodiment, the vessel 52 is substantially cylindrical. The liquid filling level 60 is defined at the boundary line between the liquid section 56 and the headspace 58 and is defined by a dashed line 60 on the outer surface of the vessel 52. The headspace outlet 62 is provided on the side wall of the vessel 52 above the liquid filling level and is configured to allow fluid to be drawn out of the liquid cavity in the headspace 58. The mouthpiece 64 is connected to the headspace outlet 62 by a flexible hose 66.

[0178] The vessel 52 is mounted on the heating unit 70, and in this embodiment, the heating unit is a cylindrical unit whose diameter is substantially equal to the diameter of the vessel 52. Thus, when the vessel 52 and the heating unit 70 are mounted together for use, the hookah device 50 forms a substantially cylindrical unit.

[0179] The heating unit 70 is substantially similar to the heating unit shown in Figure 7, and the same reference number is used to indicate similar characteristics.

[0180] The heating unit 70 comprises an external housing 71 formed from a material that does not transmit RF electromagnetic radiation. The external housing 71 forms a cylindrical tube that is substantially closed at both ends. A door (not shown) is formed in the side wall of the external housing 71 and is coupled to the side wall by a hinge. The door is rotatable between an open position and a closed position, allowing an aerosol-generating article to be inserted into and removed from the heating unit 70. The door is lockable in the closed position and is formed from a metal mesh that does not transmit RF electromagnetic radiation but is fluid-permeable, so as to ensure that the door is not open when the hookah device 50 is in operation and so that ambient air can be drawn into the heating unit 70.

[0181] The article recess 14 is defined in the heating unit 70 to receive the aerosol-generating article 90. In this embodiment, the article recess 14 is substantially frustoconical so that it is configured to receive a substantially frustoconical aerosol-generating article 90. The article recess 14 is positioned above the resonant recess 80. In this embodiment, the resonant recess 80 includes a substantially cylindrical body of dielectric material encased in a metal outer vessel. The metal outer vessel of the resonant recess 80 is provided with a pair of slots 79, which are provided to allow an RF electromagnetic field to propagate from the resonant recess 80 into the article recess 14.

[0182] An electromagnetic field generator 11 in the form of a solid-state RF LDMOS transistor is provided below the resonant recess 80. The output of the electromagnetic field generator 80 is coupled to a waveguide 15 in the form of a waveguide. The waveguide 15 is positioned to direct the RF electromagnetic field generated by the electromagnetic field generator 11 to an antenna 16, which is positioned in the resonant recess 80. In this arrangement, the RF electromagnetic field generated by the electromagnetic field generator 11 is directed to the resonant recess 80, exits the resonant recess 80, passes through a slot 79, and propagates into the article recess 14 to heat an aerosol-forming substrate positioned in the article recess 14. The electromagnetic field generator 11 is connected to a control circuit (not shown) and a lithium-ion battery (not shown) and is positioned and configured to control the power supply to the electromagnetic field generator 11 in order to control the RF electromagnetic field generated by the electromagnetic field generator 11.

[0183] The airflow conduit 72 enters the vessel 52 from the article recess 14 and extends to a position in the liquid section 56 below the liquid filling level 60. The airflow conduit 72 fluidly connects the article recess to the liquid section 56 of the vessel 52. To prevent liquid from flowing from the liquid section 56 into the article recess 14 through the airflow conduit 72 under the influence of gravity, a one-way valve (not shown) is provided at the opening 73 between the heating unit 70 and the vessel 52 in the airflow conduit 72. The one-way valve does not allow fluid to flow from the vessel 52 into the heating unit 70 and also requires that a minimum pressure be reached before fluid can flow from the heating unit 70 into the vessel 52.

[0184] When in use, if the user inhales the mouthpiece 64, ambient air is drawn into the hookah device 50 and into the article recess 14 through a mesh door (not shown). A smoke inhalation sensor (not shown), provided in the article recess 14 and connected to a control circuit and battery, senses that the user is inhaling the mouthpiece 64 as air flows into the article recess 14. Upon detecting that the user is inhaling the mouthpiece 64, the control circuit supplies power from the battery to an electromagnetic field generator 11, propagating an RF electromagnetic field into the article recess 14 and heating the aerosol-forming substrate in the aerosol-generating article 90. Volatile compounds are released from the heated aerosol-forming substrate. The air drawn into the article recess 14 carries the released volatile compounds, which are drawn through the airflow conduit 72 and a one-way valve into the liquid section 56 of the vessel 52. The volatile compound is cooled by the volume of liquid in the liquid section 56 and released from the liquid into the headspace 58, where it condenses to form an aerosol. The aerosol is drawn out of the headspace 58 through the headspace outlet 62 and along the hose 66 to the mouthpiece 64 for inhalation by the user.

[0185] The embodiments described above are illustrative only, and it will be understood that various other embodiments of this disclosure are also conceivable. For example, the embodiments of the heating unit described above may be used with any suitable design of a hookah apparatus, such as the apparatus shown in Figures 3 and 9. For example, the vessel, aerosol-forming article, and any other features of the hookah system according to this disclosure may also be of any other desired shape and size. For example, the liquid in the liquid section of the hookah apparatus is preferably water, but may be another suitable liquid.

Claims

1. A hookah apparatus for generating aerosols by heating an aerosol-forming substrate, A liquid recess comprising a headspace outlet, which contains the volume of liquid through which the aerosol generated by the hookah device is drawn before being inhaled by the user, An article recess configured to receive an aerosol-forming substrate, wherein the article recess is in fluid communication with the liquid recess, An electromagnetic field generator configured to generate a radio frequency (RF) electromagnetic field in the recess of the article, comprising an electromagnetic field generator including a magnetron or a solid-state RF transistor, A hookah device wherein the article recess comprises one or more outer walls formed of a material that does not allow the RF electromagnetic field to pass through, and one or more slots are formed in the one or more outer walls.

2. The hookah apparatus according to claim 1, wherein the electromagnetic field generating device includes a solid-state RF transistor, and the solid-state RF transistor is configured to generate and amplify the RF electromagnetic field.

3. The shisha apparatus according to claim 1 or 2, wherein the shisha apparatus comprises a resonant recess fluidly connected to the article recess, the electromagnetic field generator is configured to generate a radio frequency (RF) electromagnetic field in the resonant recess, and one or more slots allow the RF electromagnetic field to enter the article recess from the resonant recess.

4. The hookah apparatus according to any one of claims 1 to 3, wherein the article recess comprises an open end for receiving an aerosol-forming article including the aerosol-forming substrate and a substantially closed end.

5. The hookah apparatus according to any one of claims 1 to 4, further comprising an antenna connected to the electromagnetic field generator configured to direct the RF electromagnetic field.

6. The hookah apparatus according to claim 5, wherein the antenna is at least partially positioned in the recess of the article.

7. The hookah apparatus according to any one of claims 1 to 6, further comprising a resonance recess between the article recess and the electromagnetic field generating device.

8. A hookah apparatus according to any one of claims 1 to 7, comprising: a sensor located in or adjacent to the recess of the article, which provides a signal indicating the temperature in the recess of the article; and a controller connected to receive the signal from the sensor and connected to control the electromagnetic field generator depending on the signal from the sensor.

9. A shisha system comprising a shisha device according to any one of claims 1 to 8, and an aerosol generating article containing an aerosol forming substrate.

10. The hookah system according to claim 9, wherein the aerosol-forming substrate includes tobacco.

11. The hookah system according to claim 9 or 10, wherein the aerosol generating article comprises one or more external surfaces formed from a material that does not allow the RF electromagnetic field to pass through.

12. The hookah system according to claim 11, wherein one or more slots are formed on one or more external surfaces made of a material that does not allow the RF electromagnetic field to pass through.

13. The hookah system according to claim 11 or 12, wherein the material that does not allow the RF electromagnetic field to pass through forms a coating that forms one or more external surfaces.

14. Aerosol generating article for a shisha system, Aerosol-forming substrate and, An aerosol generating article comprising one or more external surfaces formed from a material that does not allow RF electromagnetic fields to pass through, wherein the material that does not allow RF electromagnetic fields to pass through is fluid-permeable.

15. The aerosol generating article according to claim 14, wherein the material that does not allow the RF electromagnetic field to pass through is a metal mesh.

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