Aerosol generating device and aerosol generating system

Abstract

The aerosol generating device (10) includes a heating chamber (18) that contains an aerosol-generating article (100) and at least one inductively heatable susceptor (42) that is mounted within the heating chamber (18) such that there is an outer air gap (59) between the susceptor (42) and the chamber wall (30) and such that there is an inner air gap (58) between the susceptor (42) and the aerosol-generating article (100) when the aerosol-generating article (100) is contained in the heating chamber (18). When a user inhales on the aerosol-generating article (100), incoming air flows through the inner and outer air gaps (58, 59) and absorbs heat from the inner and outer surfaces of the susceptor (42), thereby effectively pre-heating the air that is drawn into the aerosol-generating article.

Description

[Technical Field]

[0001] The present disclosure relates generally to aerosol-generating devices, and more particularly to aerosol-generating devices for heating an aerosol-generating substrate to generate an aerosol that is inhaled by a user. Embodiments of the present disclosure also relate to aerosol-generating systems that include an aerosol-generating device and an aerosol-generating substrate. The present disclosure is particularly applicable to portable (handheld) aerosol-generating devices. Such devices heat an aerosol-generating substrate (e.g., tobacco or other suitable material) by conduction, convection, and / or radiation, rather than by combustion, to generate an aerosol that is inhaled by a user. [Background technology]

[0002] In recent years, the popularity and use of risk-reducing or risk-modifying devices (also called aerosol-generating or vapor-generating devices) has grown rapidly as an alternative to the use of traditional tobacco products. A variety of devices and systems are available that heat or warm an aerosol-generating substrate to generate an aerosol that is inhaled by the user.

[0003] Commonly available risk reduction or risk modification devices are substrate-heated aerosol generators, i.e., so-called non-combustion-heated devices. This type of device generates an aerosol or vapor by heating an aerosol-generating substrate, typically to a temperature in the range of 150-300°C. Heating the aerosol-generating substrate to this temperature range without burning or combusting generates a vapor, which typically cools and condenses to form the aerosol that is inhaled by the user of the device. Generally speaking, a vapor is a substance that is in the gas phase below its critical temperature, meaning that the vapor can be condensed into a liquid by increasing the pressure without decreasing the temperature. On the other hand, an aerosol is a suspension of fine solid particles or liquid droplets in air or another gas. However, it should be noted that the terms "aerosol" and "vapor" may be used interchangeably herein, particularly with respect to the form of inhalable medium generated for inhalation by the user.

[0004] Currently available aerosol-generating devices utilize several different techniques for heating the aerosol-generating substrate. One such technique is to provide an aerosol-generating device that employs an induction heating system. In such devices, an induction coil and an inductively heatable susceptor are provided within the device to heat the aerosol-generating substrate. When a user activates the device, electrical energy is supplied to the induction coil, which generates an alternating electromagnetic field. The susceptor couples with this electromagnetic field to induce local eddy currents and / or larger circulating currents that flow within the susceptor. The flow of current within the susceptor generates resistive heating. Depending on the susceptor material, the susceptor may also be subject to heating due to magnetic hysteresis. Heat is transferred (e.g., by thermal conduction) from the susceptor to the aerosol-generating substrate, heating the aerosol-generating substrate and generating an aerosol.

[0005] Rapid heating of the aerosol-generating substrate is generally desirable to achieve and maintain a temperature within the aerosol-generating substrate high enough to generate vapor. The present disclosure aims to provide an aerosol-generating device that rapidly heats the aerosol-generating substrate to a desired temperature while maximizing the energy efficiency of the device. Summary of the Invention [Means for solving the problem]

[0006] According to a first aspect of the present disclosure, there is provided an aerosol generating apparatus comprising: a heating chamber for accommodating an aerosol-generating article, the heating chamber including a chamber wall defining an interior space of the heating chamber; and at least one inductively heatable susceptor mounted in the interior space of the heating chamber such that an outer air gap is formed between the susceptor and the chamber wall and such that an inner air gap is formed between the susceptor and the aerosol-generating article when the aerosol-generating article is accommodated in the heating chamber. The heating chamber is open to the atmosphere at a proximal end and closed at a distal end, the inner air gap providing a first air path from the proximal end to the distal end, and the outer air gap providing a second air path from the proximal end to the distal end.

[0007] The inner air gap reduces heat transfer between the susceptor and the aerosol-generating article, and the outer air gap reduces heat transfer between the susceptor and the chamber wall. By providing air gaps near both the inner and outer surfaces of the susceptor, heat is efficiently transferred from the susceptor to the ambient air.

[0008] The apparatus may be configured so that no part of the susceptor comes into contact with the aerosol-generating article when the aerosol-generating article is contained in the heating chamber. This reduces the risk of burning the wrapper or substrate of the aerosol-generating article due to heat being conducted directly from the susceptor. By flowing preheated air through the aerosol-generating article, rather than heat being conducted directly from the susceptor, heat is more evenly distributed throughout the aerosol-generating substrate.

[0009] The apparatus includes multiple susceptors arranged circumferentially around the axis of the heating chamber, which may facilitate manufacturing or assembly of the apparatus and may be electrically isolated from one another to prevent continuous circulation of induced currents around the apparatus.

[0010] Each susceptor may be in the form of a plate curved in an arc about an axis, which is easy to manufacture and can be combined to form a segmented cylindrical surface, evenly spaced from both the chamber wall and the aerosol-generating article.

[0011] The apparatus may include a frame housed in the heating chamber, the frame not being inductively heatable, and at least one susceptor mounted within the frame, which facilitates manufacturing of the apparatus. The frame may also be configured to be removable from the heating chamber, for example, to allow for cleaning or replacement of the susceptor.

[0012] The frame may include a guide for centering the aerosol-generating article in the heating chamber, thereby ensuring the necessary spacing to form an internal air gap between the susceptor and the aerosol-generating article, and may also help to hold the aerosol-generating article within the apparatus.

[0013] The frame may include a seat for the distal end of the aerosol-generating article, which allows an air gap to be established between the distal end of the aerosol-generating article and the base of the heating chamber, ensuring that air can flow from the heating chamber to the distal end of the aerosol-generating article.

[0014] Such an apparatus may be used in a method comprising inserting at least a portion of an aerosol-generating article into a heating chamber and pulling air from a distal end of the heating chamber through the aerosol-generating article, causing the incoming air to flow along first and second air paths toward the distal end of the heating chamber, while at least one susceptor is inductively heated to increase the temperature of the incoming air as it flows past the susceptor along the first and second air paths.

[0015] The air in the first air path flows over the inner surface of the susceptor, and the air in the second air path flows over the outer surface of the susceptor. By having the air flow over both the inner and outer surfaces of the susceptor, heat is efficiently transferred from the susceptor, increasing the temperature of the air drawn into the aerosol-generating article.

[0016] According to another aspect of the present disclosure, an aerosol generating apparatus may include a heating chamber that accommodates an aerosol-generating article, the heating chamber including a chamber wall that defines an interior space of the heating chamber, and a method of assembling the aerosol generating apparatus may include the steps of mounting one or more inductively heatable susceptors in a frame and inserting the frame and the one or more susceptors into the heating chamber so that there is an outer air gap between each of the one or more susceptors and the chamber wall and so that there is an inner air gap between the susceptor and the aerosol-generating article when the aerosol-generating article is accommodated in the heating chamber.

[0017] The susceptor preferably comprises an electrically conductive and magnetically permeable material, preferably a metallic material. When formed from such a material, the susceptor is inductively heatable. The metallic material is typically selected from the group consisting of stainless steel and carbon steel. However, the inductively heatable susceptor material may include any suitable material, including, but not limited to, one or more of aluminum, iron, nickel, stainless steel, carbon steel, and alloys thereof (e.g., nickel-chromium or nickel-copper).

[0018] The aerosol generating device may include a power supply and a controller (e.g., including control circuitry), which may be configured to operate at high frequencies. The power supply and circuitry may be configured to operate at frequencies between about 70 kHz and 1 MHz, in some cases between about 150 kHz and 250 kHz, and in some cases about 200 kHz. The power supply and circuitry may be configured to operate at higher frequencies (e.g., in the MHz range) depending on the type of inductively heatable susceptor used.

[0019] The aerosol-generating substrate may comprise any type of solid or semi-solid material. Examples of types of aerosol-generating solids include powders, granules, pellets, shreds, strands, particles, gels, strips, loose-leaf, cut filler, porous materials, foam materials, or sheets. The aerosol-generating substrate may comprise a plant-derived material, particularly tobacco. The aerosol-generating substrate may advantageously comprise reconstituted tobacco, for example, tobacco and any one or more of cellulose fiber, tobacco stem fiber, and inorganic fillers (such as CaCO).

[0020] Accordingly, aerosol-generating devices may be referred to as "heated tobacco devices," "non-combustion heated tobacco devices," "tobacco product vaporization devices," etc., and are to be interpreted as devices suitable for achieving these effects. The features disclosed herein are equally applicable to devices designed to vaporize any aerosol-generating substrate.

[0021] The aerosol-generating substrate may form part of the aerosol-generating article and may be surrounded by a paper wrapper. When the aerosol-generating substrate is contained in the heating chamber of the aerosol-generating device, other parts of the aerosol-generating article may remain outside the heating chamber, for example to provide a mouthpiece for the user.

[0022] The aerosol-generating article may be shaped approximately like a stick and may roughly resemble a cigarette with a tubular region in which the aerosol-generating substrate is disposed in a suitable configuration. The aerosol-generating article may include a filter segment at its proximal end, the filter segment comprising, for example, cellulose acetate fibers. The filter segment may constitute a mouthpiece filter and may be coaxial with the aerosol-generating substrate. Depending on the design, one or more vapor-collection regions, cooling regions, and other structures may also be included. For example, the aerosol-generating article may include at least one tubular segment upstream of the filter segment. The tubular segment may operate as a vapor-cooling region. The vapor-cooling region may advantageously allow heated vapor generated by heating the aerosol-generating substrate to cool and condense, forming an aerosol with suitable properties for inhalation by a user (e.g., through the filter segment).

[0023] The aerosol-generating substrate may contain an aerosol former. Examples of aerosol formers include polyhydric alcohols such as glycerin or propylene glycol, and mixtures thereof. Typically, the aerosol-generating substrate may contain from about 5% to about 50% aerosol former by dry weight. In some embodiments, the aerosol-generating substrate may contain from about 10% to about 20% aerosol former by dry weight, and in some cases, about 15% aerosol former by dry weight.

[0024] The aerosol-forming substrate may, upon heating, release volatile compounds, which may include nicotine or flavor compounds, such as tobacco flavorings. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a schematic longitudinal cross-sectional view of an aerosol generating system useful for understanding the present invention, including an aerosol generating device and an aerosol-generating article arranged to be placed in a heating chamber of the aerosol generating device. [Figure 2]2 is a schematic longitudinal cross-sectional view of the aerosol generating system of FIG. 1, showing the aerosol-generating article positioned within the heating chamber of the aerosol generating device. [Figure 3] 1 is another schematic longitudinal cross-sectional view showing the air flow through the heating chamber of an aerosol generating device according to the present invention; FIG. [Figure 4] 1 is a schematic transverse cross-sectional view showing an example of a susceptor configuration according to the present invention. [Figure 5] 1 is a schematic transverse cross-sectional view showing an example of a susceptor configuration according to the present invention. [Figure 6] 1 is a perspective view of a first embodiment of a susceptor frame according to the present invention; [Figure 7] FIG. 7 is a partially exploded perspective view of the susceptor frame of FIG. 6. [Figure 8] FIG. 2 is a perspective view of a second embodiment of a susceptor frame according to the present invention. [Figure 9] FIG. 9 is an exploded perspective view of the susceptor frame of FIG. 8. DETAILED DESCRIPTION OF THE INVENTION

[0026] 1 and 2, an example aerosol generation system 1 is shown schematically. The aerosol generation system 1 includes an aerosol generation device 10 and an aerosol-generating article 100 for use with the device 10. The aerosol generation device 10 houses the various components of the aerosol generation device 10 in a body 12. The body 12 may be of any shape that is sized to fit the components described in the various embodiments presented herein and to be comfortably held by a user in one hand without support.

[0027] 1 and 2 will be referred to for convenience as the distal end, bottom end, proximal end, or lower end of the aerosol generation device 10. The second end 16 of the aerosol generation device 10, facing upward in Figures 1 and 2, will be referred to as the proximal end, top end, or upper end of the aerosol generation device 10. During use, a user will typically orient the aerosol generation device 10 so that the first end 14 faces downward and / or is distal to the user's mouth, and so that the second end 16 faces upward and / or is proximal to the user's mouth.

[0028] The aerosol generating device 10 includes a heating chamber 18 disposed within the body 12. The heating chamber 18 defines an interior space in the form of a cavity 20 having a generally circular cross section for receiving at least a portion of the generally cylindrical aerosol generating article 100. A longitudinal axis of the heating chamber 18 defines a longitudinal direction. A proximal end 26 of the heating chamber 18 opens toward the second end 16 of the aerosol generating device 10. The heating chamber 18 is typically spaced apart from the inner surface of the body 12 to minimize heat transfer to the body 12.

[0029] The aerosol generating device 10 further includes a power source 22 (eg, one or more batteries, which may be rechargeable) and a controller 24 .

[0030] The aerosol generating device 10 may optionally include a sliding cover 28 that is movable laterally between a closed position (see FIG. 1 ) that covers the open end 26 of the heating chamber 18 to prevent access to the heating chamber 18 and an open position (see FIG. 2 ) that exposes the first open end 26 of the heating chamber 18 to provide access to the heating chamber 18. In some embodiments, the sliding cover 28 can be biased to the closed position.

[0031] The heating chamber 18, and in particular the cavity 20, is configured to accommodate a correspondingly shaped, generally cylindrical or rod-shaped aerosol-generating article 100. The aerosol-generating article 100 typically includes a pre-packaged aerosol-generating substrate 102. The aerosol-generating article 100 is a disposable, replaceable item (also referred to as a "consumable") and may, for example, contain tobacco as the aerosol-generating substrate 102. The aerosol-generating article 100 has a proximal end 104 (mouth end) and a distal end 106. The aerosol-generating article 100 further includes a mouthpiece segment 108 disposed downstream of the aerosol-generating substrate 102. The aerosol-generating substrate 102 and the mouthpiece segment 108 are coaxially aligned within a wrapper 110 (e.g., a paper wrapper) to hold the components in place and form the rod-shaped aerosol-generating article 100.

[0032] The mouthpiece segment 108 may include one or more of the following components (not shown in detail): a cooling segment, a central hole segment, and a filter segment, which are sequentially and coaxially aligned in a downstream direction, i.e., from the distal end 106 toward the proximal (mouth) end 104 of the aerosol-generating article 100. The cooling segment typically comprises a hollow paper tube that is thicker than the wrapper 110. The central hole segment may comprise a hardened mixture containing cellulose acetate fibers and a plasticizer and functions to increase the strength of the mouthpiece segment 108. The filter segment typically comprises cellulose acetate fibers and acts as a mouthpiece filter. As heated vapor flows from the aerosol-generating substrate 102 toward the proximal (mouth) end 104 of the aerosol-generating article 100, the vapor cools and condenses as it passes through the cooling segment and central hole segment, forming an aerosol with suitable properties for a user to inhale through the filter segment.

[0033] The heating chamber 18 has a sidewall (chamber wall) 30 extending between the open end 26 and a base 32 located at the distal end 34 of the heating chamber 18. The chamber wall 30 and the base 32 are connected to one another and may be integrally molded as a single piece. In the illustrated embodiment, the chamber wall 30 is tubular, more specifically cylindrical. In other embodiments, the chamber wall 30 may have any other suitable shape, such as a tubular shape with an oval or polygonal cross section. In yet other embodiments, the chamber wall 30 may be tapered. The chamber wall 30 and the base 32 are molded from a high-temperature plastic material, such as polyetheretherketone (PEEK).

[0034] In the illustrated embodiment, the base 32 of the heating chamber 18 is closed (e.g., sealed or airtight), i.e., the heating chamber 18 is cup-shaped. This ensures that air drawn in through the open end 26 is prevented by the base 32 from exiting the second end 34, and instead is guided through the aerosol-generating substrate 102. This also ensures that the user can insert the aerosol-generating article 100 into the heating chamber 18 only a predetermined distance and not further.

[0035] The aerosol-generating device 10 includes at least one inductively heatable susceptor 42. The aerosol-generating device 10 may include a plurality of inductively heatable susceptors 42 spaced circumferentially around the heating chamber 18. The inductively heatable susceptors 42 may extend longitudinally of the heating chamber 18.

[0036] The aerosol generating device 10 includes an electromagnetic field generator 46 that generates an electromagnetic field. The electromagnetic field generator 46 includes a generally helical induction coil 48. The induction coil 48 has a circular cross section and extends helically around the generally cylindrical heating chamber 18. The induction coil 48 may be energized by a power source 22 and a controller 24. The controller 24 includes, among other electronic components, an inverter configured to convert direct current from the power source 22 into high-frequency alternating current for the induction coil 48.

[0037] The chamber wall 30 of the heating chamber 18 includes a coil support structure 50 formed on the outer surface 38. In the illustrated example, the coil support structure 50 includes a coil support groove 52 that extends spirally around the outer surface 38. The induction coil 48 is positioned within the coil support groove 52 and is therefore in a safe and optimal position relative to the inductively heatable susceptor 42.

[0038] To use the aerosol-generating device 10, a user slides the sliding cover 28 (if present) from the closed position shown in Figure 1 to the open position shown in Figure 2. The user then inserts the aerosol-generating article 100 into the open end 26 of the heating chamber 18, so that the aerosol-generating substrate 102 is received in the cavity 20 and at least a portion of the mouthpiece segment 108 protrudes from the open end 26 for placement in the user's mouth.

[0039] When a user activates the aerosol-generating device 10, the induction coil 48 is energized by the power supply 22 and controller 24, supplying an alternating current to the induction coil 48, causing the induction coil 48 to generate a time-varying, alternating electromagnetic field. This electromagnetic field couples with the inductively heatable susceptor 42, generating eddy currents and / or magnetic hysteresis losses within the susceptor 42, causing the susceptor 42 to heat. The heat is then transferred (e.g., by conduction, radiation, or convection) from the inductively heatable susceptor 42 to the aerosol-generating substrate 102, which heats the aerosol-generating substrate 102 without burning it, thereby generating vapor. The generated vapor cools and condenses into an aerosol that can be inhaled by a user of the aerosol-generating device 10 through the mouthpiece segment 108 (more specifically, the filter segment).

[0040] Vaporization of the aerosol-generating substrate 102 is facilitated by the addition of air from the ambient environment (e.g., through the open end 26 of the heating chamber 18), which is heated as it flows between the aerosol-generating article 100 and the inner surface 36 of the chamber wall 30. More specifically, when a user draws on the filter segment, air is drawn into the heating chamber 18 from the open end 26, as shown by arrow A in FIG. 2 . The air entering the heating chamber 18 flows between the aerosol-generating article 100 and the chamber wall 30 from the open end 26 toward the closed end 34. Upon reaching the closed end 34 of the heating chamber 18, the air makes an approximately 170° turn and enters the distal end 106 of the aerosol-generating article 100. The air, along with vapor generated from the substrate 102, is then drawn through the aerosol-generating article 100 from the distal end 106 toward the proximal (mouth) end 104, as shown by arrow B in FIG. 2 .

[0041] A user can continue to inhale the aerosol as long as the aerosol-generating substrate 102 is capable of generating vapor, i.e., as long as the aerosol-generating substrate 102 contains vaporizable components that can be vaporized into a suitable vapor. The controller 24 may adjust the temperature of the inductively heatable susceptor 42 and, therefore, the magnitude of the alternating current passing through the induction coil 48 so that the temperature of the aerosol-generating substrate 102 does not exceed a threshold level. Specifically, at a certain temperature, depending on the configuration of the aerosol-generating substrate 102, the aerosol-generating substrate 102 will begin to burn. This is not a desired effect, and temperatures above this temperature are avoided. The materials forming the chamber walls 30 and base 32 are selected to withstand repeated heating to a threshold temperature over the life of the aerosol-generating device.

[0042] To assist in temperature regulation, in some embodiments, the aerosol-generating device 10 includes a temperature sensor (not shown). The controller 24 is configured to receive a reading of the temperature of the aerosol-generating substrate 102 from the temperature sensor and use that reading to control the magnitude of the alternating current supplied to the induction coil 48. Means (not shown), such as a pressure or flow sensor, may be provided to detect airflow through the heating chamber 18 and energize the induction coil 48 only when the user is actively inhaling on the device 10.

[0043] A single inhalation by a user is commonly referred to as a "puff." In some scenarios, it is desirable to emulate the experience of smoking a cigarette; that is, it is desirable for the aerosol-generating device 10 to be capable of holding enough aerosol-generating substrate 102 to provide typically 10-15 puffs.

[0044] To emulate the smoking experience, the power source 22 is typically sufficient to repeat this cycle (heating the aerosol-generating substrate 102 to the desired temperature and maintaining that temperature and vapor generation for 10-15 puffs) 10 or even 20 times, thereby emulating the user experience of smoking a pack of cigarettes before the power source 22 needs to be replaced or recharged.

[0045] In general, the efficiency of the aerosol-generating device 10 is improved by using as much of the heat generated by the inductively heatable susceptor 42 as possible to heat the aerosol-generating substrate 102. To this end, the aerosol-generating device 10 is typically configured to heat the aerosol-generating substrate 102 in a controlled manner while simultaneously reducing heat loss to other parts of the aerosol-generating device 10. In particular, heat flow to parts of the aerosol-generating device 10 that a user touches with their hands is minimized, keeping these parts cool and comfortable to hold.

[0046] 3 shows the airflow pattern through the heating chamber 18 of the aerosol-generating device 10. The heating chamber 18 is cup-shaped and has a closed distal end 34 and an open proximal end 26. An induction coil 48 surrounds a generally cylindrical chamber wall 30. An aerosol-generating article 100 is housed within the heating chamber 18, with the aerosol-generating substrate 102 located entirely within the chamber 18, but the proximal end 104 of the aerosol-generating article 100 remaining outside the heating chamber 18. The distal end 106 of the aerosol-generating article 100 does not extend completely to the base 32 of the chamber 18 to allow for a gap 56 through which air can enter the distal end 106 of the aerosol-generating article 100 from the heating chamber 18.

[0047] One or more susceptors 42 are circumferentially arranged around the interior space 20 of the heating chamber 18. The susceptors 42 are aligned axially parallel to the induction coil 48. Each susceptor 42 is radially arranged such that there is an inner air gap 58 between the susceptor 42 and the wrapper 110 of the aerosol-generating article 100, and an outer air gap 59 between the susceptor 42 and the chamber wall 30. When a user draws on the aerosol-generating article 100, air is drawn out from the distal end of the heating chamber 18, lowering the pressure within the heating chamber 18. This allows ambient air to flow in from the proximal end 26 of the heating chamber to equalize the pressure. An inner air gap 58 between the susceptor 42 and the aerosol-generating article 100 provides a first path 60 for air to flow from the proximal end 26 to the distal end 34 of the heating chamber 18. An outer air gap 59 between the susceptor 42 and the chamber wall 30 provides a second path 61 for air to flow from the proximal end 26 to the distal end 34 of the heating chamber 18. Air flowing along the first air path 60 passes over the inner surface of the susceptor 42, while air flowing along the second air path 61 passes over the outer surface of the susceptor 42. Thus, air flowing along both paths 60, 61 remains close to the susceptor 42 for a sufficient distance to transfer heat from the susceptor 42 to the air. The air flowing over both the inner and outer surfaces of the susceptor 42 improves heat transfer efficiency. Thus, the air is preheated to a high temperature before entering the distal end 106 of the aerosol-generating article 100. The hot air is then dispersed throughout all parts of the aerosol-generating substrate 102. However, heat that may be transferred from the susceptor 42 by conduction or radiation has a greater impact on the radially outer parts of the substrate 102, potentially posing a risk of burning the substrate 102 or wrapper 110 of the aerosol-generating article 100.

[0048] FIG. 4 shows, in transverse cross-section, a first example of a possible susceptor configuration for the apparatus of FIG. 3 . The apparatus includes a single susceptor 42 in the form of a plate or sheet, which is curved in an arc about the axis of the heating chamber 18 to form a C-shape or a nearly perfect cylinder. Opposing edges 64 of the plate are spaced slightly apart from one another to form a small circumferential gap 65. As previously shown in FIG. 3 , the susceptor 42 is radially positioned so that there is an inner air gap 58 between the susceptor 42 and the wrapper 110 of the aerosol-generating article 100, and an outer air gap 59 between the susceptor 42 and the chamber wall 30. Because no part of the susceptor 42 contacts the aerosol-generating article 100, there is less risk that the wrapper 110 or substrate 102 of the aerosol-generating article 100 may burn due to excessive heat transfer.

[0049] The circumferential gaps 65 in the susceptor 42 can be beneficial when the current induced in the susceptor 42 does not need to be able to circulate continuously around its circumference. The gaps 65 can also facilitate assembly of the device, as described below. As will be readily understood, additional gaps 65 may be provided to divide the plate to form two, three, four, or more discrete arc-shaped susceptors 42, which collectively form a segmented cylinder. It will also be readily understood that a single susceptor 42 without any gaps 65 may be formed as a continuous cylinder.

[0050] There are several potential advantages to having the susceptor 42 or susceptors 42 in such a generally cylindrical configuration. First, because the susceptors 42 are uniformly spaced from the induction coil 48, they are expected to generate heat uniformly. Second, because the susceptors 42 are uniformly spaced from the aerosol-generating article 100, they are expected to radiate heat uniformly around the circumference to the aerosol-generating substrate 102. Third, because the inner and outer air gaps 58, 59 have uniform cross sections around the circumference, air flow along the first and second air paths 60, 61 may be smoother or more uniform. However, such a susceptor 42 also has disadvantages. Namely, because the susceptor 42 does not contact the aerosol-generating article 100, an alternative means (not shown in FIG. 3 ) must be provided to support the aerosol-generating article 100 within the apparatus.

[0051] FIG. 5 shows, in transverse cross section, an alternative possible susceptor configuration for the apparatus of FIG. 3. In this example, four susceptors 42 are distributed around the circumference of the heating chamber 18. Each susceptor 42 comprises a flat plate that is generally tangential to the surface of the aerosol-generating article 100. A rib 66 projects radially inward from the center of each susceptor plate 42 and abuts the wrapper 110 of the aerosol-generating article 100 along a narrow line. The ribs 66 of the four susceptors 42 thus sandwich and support the aerosol-generating article 100. The ribs 66 may be formed as beads on the susceptor plates 42, as shown, or may be formed by deforming the susceptor plates. The ribs 66 serve to minimize the contact area between the susceptor 42 and the aerosol-generating article 100, although alternatively the ribs 66 may be omitted and the aerosol-generating article 100 may instead be supported by direct tangential contact with the inner surface of the susceptor plate 42. As will be readily appreciated, in alternative examples the number of susceptors 42 may be more or less than four.

[0052] 5 provides an inner air gap 58 between the susceptor 42 and the wrapper 110 of the aerosol-generating article 100, and an outer air gap 59 between the susceptor 42 and the chamber wall 30. Air flowing within the heating chamber 18 along the first air path 60 and the second air path 61 thereby passes over the inner and outer surfaces of the susceptor 42 and is heated before entering the distal end 106 of the aerosol-generating article 100.

[0053] 6 and 7 show a susceptor assembly according to a first embodiment of the present invention. This embodiment includes two susceptors 42, each of which is generally semicircular in cross section so that together they form a cylinder with two opposing gaps. The susceptors 42 are mounted within a frame 70, which holds the susceptors 42 in a desired relationship to each other and to other components of the steam generation system. The frame 70 is molded from a material, such as PEEK, in which no significant current is induced when the induction coil 48 operates.

[0054] Frame 70 comprises a generally cup-shaped cage having several longitudinal struts 72, 73 connected at a distal end by a base 74 and at a proximal end by a collar 76. Struts 72, 73 have radially outer surfaces 78 so that frame 70 fits snugly inside heater chamber 18 (not shown in FIGS. 6 and 7 ). Collar 76 may have an oversized radius to abut against the rim of open end 26 of heater chamber 18. Collar 76 may be used to withdraw frame 70 and susceptor 42 from heater chamber 18 (e.g., for cleaning or replacement). Struts 72, 73 have radially inner surfaces 79 that support aerosol-generating article 100 within heater chamber 18. A ramp 80 may be provided at the proximal end of the inner surface 79 to guide the aerosol-generating article 100 into position and to compress slightly when the aerosol-generating article 100 is pushed distally, thereby allowing the inner surface 79 to hold the aerosol-generating article 100 stable within the device 10. The distal end of the aerosol-generating article 100 is stopped at the base 74 of the frame 70 and does not reach the base 32 of the heating chamber 18. The base 74 thereby forms a seat for the aerosol-generating article 100 and also defines an air gap 56 through which air can flow from the heating chamber 18 into the aerosol-generating article 100.

[0055] Two opposing struts 72 are used to mount the susceptors 42. Each strut 72 includes a pair of back-to-back, circumferentially opposed blind slots 82. Each slot 82 receives the longitudinal edge 64 of one of the susceptors 42. A middle strut 73 supports the susceptor 42 so that the susceptor 42 is held within the slots 82. The slots are formed at radial locations in the frame 70 such that, when the frame 70 is inserted into the heating chamber 18 of the apparatus 10, an outer air gap 59 is defined between the susceptor 42 and the chamber wall 30, and when an aerosol-generating article 100 is inserted into the frame 70, an inner air gap 58 is defined between the susceptor 42 and the aerosol-generating article 100.

[0056] 8 and 9 show a susceptor assembly 83 according to a second embodiment of the invention. This embodiment also includes two susceptors 42, each having the general shape of an arcuate plate forming a portion of a cylinder centered on the axis of the apparatus 10, although in this example the gap between the susceptors 42 is larger than in FIGS. 6 and 7. The longitudinal edges of the susceptors are bent outward to form flanges 84.

[0057] In this embodiment, the frame 86 includes a pair of longitudinal struts 88 whose distal ends are joined together by a ring 90. A notch 91 is formed in the proximal edge of the ring 90, immediately adjacent to the strut 88. The proximal end of each strut 88 is bent outward to form a flange 92. A longitudinal slot 94 is formed in each strut 88 and extends to the proximal end of the strut 88. A retention feature 95 is located midway within each slot 94, where the slot 94 narrows slightly. A separate collar 96 includes two outward-facing recesses 97. Within each recess 97 is a protrusion 98 that extends radially outward and is T-shaped in configuration.

[0058] The components are assembled as shown in FIG. 8 to form the susceptor assembly 83. Each susceptor 42 slides between a pair of struts 88 until the distal end of the susceptor flange 84 enters the notches 91 in the ring 90. The collar 96 then slides distally, and the projections 98 on the collar 96 engage and move along the longitudinal slots 94 in the struts 88. At the end of the slots 94, the projections 98 snap into place behind the retention features 95, retaining the collar 96 to the frame 86. Furthermore, notches 99 are created where the struts 88 abut the recesses 97 in the collar 96, and the proximal ends of the susceptor flanges 84 enter those notches 99 to secure the susceptor 42 in place.

[0059] Flanges 92 at the proximal ends of the struts 88 may be used to insert the susceptor assemblies 83 into the heating chamber 18 of the steam-generating apparatus 10, or to subsequently remove the susceptor assemblies (e.g., for cleaning or replacement). When the susceptor assemblies 83 are placed in the heating chamber 18, the outwardly bent flanges 84 ensure an outer air gap 59 between the cylindrical outer surface of each susceptor 42 and the chamber wall 30. The radius of the inner surface of the susceptors 42 is larger than the radius of the aerosol-generating articles 100 used with the apparatus 10, thereby ensuring an inner air gap 58 between each susceptor 42 and the aerosol-generating article 100. The illustrated susceptor assembly 83 does not include any means for mounting the aerosol-generating article 100, although a collar 96 and ring 90 could easily be adapted to guide the aerosol-generating article 100 into position. Additionally, the ring 90 does not provide any end stop for the aerosol-generating article 100 to secure the gap 56 for air to flow into the distal end 106 of the aerosol-generating article 100. However, the base 32 of the heating chamber 18 itself may be formed to provide such a function, for example, as shown in FIG.

[0060] While exemplary embodiments have been described in the preceding paragraphs, it should be understood that various modifications may be made to those embodiments without departing from the scope of the appended claims. Thus, the breadth and scope of the claims should not be limited to the above-described exemplary embodiments.

[0061] Any combination of the above-described features in all possible variations thereof is encompassed by the present disclosure unless otherwise indicated herein or clearly contradicted by context.

[0062] Unless the context clearly dictates otherwise, throughout this specification and the claims, the words "comprise," "comprising," and the like are to be construed in an inclusive sense, i.e., "including, but not limited to," rather than in an exclusive or exhaustive sense.

Claims

1. An aerosol generating device (10), comprising: a heating chamber (18) containing an aerosol-generating article (100), the heating chamber (18) including a chamber wall (30) defining an interior space (20) of the heating chamber (18); at least one inductively heatable susceptor (42) mounted in the interior space (20) of the heating chamber (18) such that an outer air gap is formed between the susceptor (42) and the chamber wall (30) and such that an inner air gap is formed between the susceptor (42) and the aerosol-generating article (100) when the aerosol-generating article (100) is contained in the heating chamber (18); Including, The heating chamber (18) is open to the atmosphere at a proximal end (26) and closed at a distal end (34), the inner air gap providing a first air path from the proximal end (26) to the distal end (34), and the outer air gap providing a second air path from the proximal end (26) to the distal end (34). An aerosol generating device (10).

2. 2. The aerosol generating device (10) of claim 1, wherein when the aerosol-generating article (100) is contained in the heating chamber (18), no portion of the susceptor (42) comes into contact with the aerosol-generating article (100).

3. 3. The aerosol generating device (10) of claim 1 or 2, comprising a plurality of susceptors (42) spaced circumferentially about the axis of the heating chamber (18).

4. 4. The aerosol generating device (10) of claim 3, wherein each susceptor (42) is in the form of a plate curved in an arc about said axis.

5. The aerosol generating device (10) of any one of claims 1 to 4, further comprising a frame housed in the heating chamber (18), the frame not being inductively heatable, and the at least one susceptor (42) being mounted within the frame.

6. 6. The aerosol generating device (10) of claim 5, wherein the frame includes a guide for centering the aerosol-generating article (100) in the heating chamber (18).

7. 7. The aerosol generating device (10) of claim 5 or 6, wherein the frame comprises a seat for a distal end (106) of the aerosol-generating article (100).

8. A method of using an aerosol generating device (10) according to any one of claims 1 to 7, comprising: inserting at least a portion of an aerosol-generating article (100) into said heating chamber (18); pulling air from the distal end (34) of the heating chamber (18) through the aerosol-generating article (100) so that incoming air flows along the first air path and the second air path toward the distal end (34) of the heating chamber (18); A method comprising:

9. 9. The method of claim 8, further comprising inductively heating the at least one susceptor (42) to increase the temperature of the incoming air as it flows past the susceptor (42) along the first air path and the second air path.

10. A method for assembling an aerosol generating device (10), comprising the steps of: The device (10) includes a heating chamber (18) containing an aerosol-generating article (100), the heating chamber (18) including a chamber wall (30) defining an interior space (20) of the heating chamber (18), the heating chamber (18) being open to the atmosphere at a proximal end (26) and closed at a distal end (34); The assembly method includes: Mounting one or more inductively heatable susceptors (42) in a frame; inserting the frame and the one or more susceptors into the heating chamber such that an outer air gap is formed between each of the one or more susceptors and the chamber wall, and such that an inner air gap is formed between the susceptor and the aerosol-generating article when the aerosol-generating article is housed in the heating chamber, whereby the inner air gap provides a first air path from the proximal end to the distal end, and the outer air gap provides a second air path from the proximal end to the distal end; A method comprising:

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