Aerosol-generating device

Abstract

The present disclosure relates to an aerosol-generating device comprising: a heater assembly; a reservoir; a liquid delivery mechanism; a power supply; a mouthpiece; and a control circuit configured to control the power supply to the heater assembly wherein the control circuit is configured to supply a first power to at least one heating element of the heater assembly between user suction, or supply power sufficient to maintain the at least one heating element of the heater assembly at a first temperature between 150 degrees Celsius and 200 degrees Celsius, and configured to supply a second power to the at least one heating element of the heater assembly during suction by a user, the second power being higher than the first power, or sufficient to raise the temperature of at least one heating element of the heater assembly to a second temperature between 200 degrees Celsius and 250 degrees Celsius higher than the first temperature.

Description

[0001] This divisional application is a divisional application based on the Chinese patent application with application number 201980058041.7, application date September 25, 2019, and invention name “Aerosol generating system for providing preferential evaporation of nicotine”. This Chinese patent application is the Chinese national phase of the international application with international application number PCT / EP2019 / 075936. Technical Field

[0002] The present invention relates to aerosol generating systems and, in particular, to aerosol generating systems for generating an aerosol containing nicotine by heating an aerosol-forming substrate. Background Art

[0003] One type of heated aerosol generating system that generates an aerosol containing nicotine is an electronic cigarette. Electronic cigarettes typically heat a liquid containing nicotine and an aerosol former to generate an aerosol.

[0004] Nicotine-containing liquids for consumer use in aerosol-generating devices such as electronic cigarettes typically contain relatively low concentrations of nicotine. High concentrations of nicotine can irritate the skin and may be harmful if ingested. The nicotine concentration of the liquid is regulated in some jurisdictions, for example, to no more than 20 mg / ml.

[0005] However, in order for former conventional cigarette smokers to be satisfied with electronic cigarettes, electronic cigarettes must deliver a comparable amount of nicotine per puff as the cigarettes they used to smoke. Without this level of nicotine delivery, users are likely to revert to smoking conventional cigarettes.

[0006] Using a nicotine-containing liquid with a relatively low concentration of nicotine (such as 20 mg / ml or less) as a substrate to generate an aerosol, it is challenging to deliver enough nicotine in each user puff to satisfy a habitual smoker. Previous attempts to solve this problem include providing an auxiliary nicotine source in solid form within the aerosol generating device, from which nicotine is released by heating or by drawing steam through or through the auxiliary nicotine source. However, this significantly increases the complexity and cost of the electronic cigarette. And it is difficult to obtain consistent nicotine delivery with this type of system. Summary of the invention

[0007] It would be desirable to provide an aerosol generating system that is capable of delivering higher amounts of nicotine per user puff using a nicotine-containing liquid having a given nicotine concentration, without the need for an additional nicotine source.

[0008] In a first aspect of the present invention, there is provided an aerosol generating device comprising:

[0009] a heater assembly comprising at least one heating element;

[0010] an aerosol-forming substrate proximate the heater assembly, the aerosol-forming substrate comprising a liquid mixture comprising nicotine and a first aerosol-forming agent having a boiling temperature higher than that of nicotine;

[0011] a power source for supplying power to the heater assembly to generate an aerosol from the aerosol-forming substrate;

[0012] a mouthpiece on which a user draws suction to draw aerosol from the aerosol generating device; and

[0013] A control circuit configured to control power to the heater assembly, wherein the control circuit is configured to supply a first power to at least one heating element of the heater assembly between user puffs, or to supply power sufficient to maintain the at least one heating element of the heater assembly at a first temperature or a first temperature range, and is configured to supply a second power to the at least one heating element of the heater assembly during user puffs, the second power being higher than the first power, or being sufficient to raise the temperature of the at least one heating element of the heater assembly to above the first temperature or the first temperature range to vaporize nicotine in preference to the first aerosol former.

[0014] Advantageously, the aerosol-forming substrate is heated by the heating element both during puffing and between puffs by the user. Preferably, the aerosol-forming substrate remains in contact with or near the heating element throughout operation of the device. The aerosol-forming substrate may comprise a liquid held in a retaining material or capillary tube that is in contact with or near the heating element. By heating the aerosol-forming substrate between puffs by the user, preferential evaporation of nicotine is promoted.

[0015] This temperature control strategy promotes the preferential evaporation of nicotine over the first aerosol former. In other words, the steam produced will have a higher proportion of nicotine than the liquid relative to the first aerosol former. This means that the generated aerosol formed by the steam will provide a larger amount of nicotine each time the user draws a puff compared to simply heating the liquid during the user's puff. By continuously maintaining the liquid at a temperature close to the boiling point of nicotine, thermodynamic equilibrium is maintained. This ensures that there is a significant preferential evaporation of nicotine compared to the first aerosol former. During the user's puff, the temperature of the heating element or the power supplied to the heater assembly increases to ensure that sufficient aerosol density and a sufficient amount of nicotine are delivered to the user during each puff. In this way, a liquid with a relatively low nicotine concentration can still be used to provide a satisfactory user experience.

[0016] Advantageously, the first temperature or first temperature range is below the boiling point of the first aerosol former. More preferably, the first temperature or first temperature range is below the boiling point of nicotine. This results in a greater difference in evaporation rate between nicotine and the first aerosol former.

[0017] As used herein, an aerosol former refers to any suitable known compound or mixture of compounds that facilitates the formation of a dense and stable aerosol in use and is substantially resistant to thermal degradation at the operating temperature of the system. Suitable aerosol formers are well known in the art and include, but are not limited to: polyols such as triethylene glycol, 1,3-butylene glycol and glycerol; esters of polyols such as glycerol mono-, di- or triacetate; and fatty acid esters of mono-, di- or polycarboxylic acids such as dimethyl dodecanedioate and dimethyl tetradecanedioate.

[0018] The boiling point of a liquid is the temperature at which the vapor pressure of the liquid equals the external pressure surrounding the liquid. As used herein, boiling point refers to the normal boiling point or atmospheric boiling point, which is the temperature at which the vapor pressure of the liquid equals the pressure at sea level (1 atmosphere).

[0019] The first aerosol former may be glycerol, which is also known as glycerol. Glycerol has a higher boiling point than nicotine. Glycerol is commonly used as an aerosol former for aerosols to be inhaled by a person.

[0020] The aerosol-forming substrate may include a second aerosol-forming agent having a boiling temperature lower than that of the first aerosol-forming agent. The second aerosol-forming agent is propylene glycol. Providing a second aerosol-forming agent having a lower boiling point allows for finer control of the proportion of nicotine contained in the generated aerosol. The second aerosol-forming agent may have a boiling point lower than that of nicotine. The first temperature or first temperature range may be higher than the boiling point of the second aerosol-forming agent.

[0021] The control circuit may be configured by the user to select a first temperature or a first temperature range or a first power. This may allow the user to select the relative amounts of nicotine and aerosol former in the aerosol. The first temperature or first temperature range may be constant during use, or may vary during the course of a use period.

[0022] The control circuit may be configured to calculate the second power based on the first power or the first temperature or the first temperature range. For example, the second temperature may be a predetermined number of degrees higher than the selected first temperature. Or the second power may be a predetermined number of watts greater than the first power. The first power may be a predetermined power or the power required to maintain a predetermined first temperature of the heating element or aerosol-forming substrate.

[0023] The heater assembly may comprise a plurality of heating elements. The control circuit may be configured to power only a portion of the plurality of heating elements between puffs by the user. The control circuit may be configured to power a greater portion or all of the heating elements during a puff by the heater. In this way, the temperature of the liquid aerosol-forming substrate may be maintained between puffs by the user and increased during a puff by the user as required.

[0024] The first power may be a power sufficient to maintain the temperature of the heating element or aerosol-forming substrate at about 200 degrees Celsius. In one embodiment, the heating element is a resistive heating element having a resistance between 0.7 ohms and 0.8 ohms, and the first power is about 2 watts. The first power may be between 1 watt and 3 watts, and more preferably between 1.4 watts and 2 watts.

[0025] The first temperature may be between 150 degrees C and 200 degrees C. This is below the boiling point of nicotine, but high enough to cause significant evaporation of the nicotine.

[0026] The first temperature range may be between 150 degrees Celsius and 200 degrees Celsius.

[0027] The second power can be selected to provide a desired total amount of nicotine delivered per puff and a desired total amount of aerosol condensate material (ACM) delivered per puff. The duration of application of the second power will also affect the total amount of nicotine delivered per puff and the total amount of aerosol condensate material delivered per puff.

[0028] The second power may be between 2 Watts and 6 Watts, and more preferably between 2.4 Watts and 3 Watts. The second power may be between 1 Watt and 4 Watts greater than the first power. In one embodiment, the second power is 3 Watts and the first power is 2 Watts.

[0029] The second power may be sufficient to maintain the heating element of the aerosol-forming substrate at a second temperature or within a second temperature range. The second temperature or second temperature range may be between 200 degrees Celsius and 250 degrees Celsius. In one embodiment, the second temperature is 220 degrees Celsius.

[0030] The device may also include a liquid reservoir holding a liquid aerosol-forming substrate and a liquid delivery mechanism configured to deliver the liquid aerosol-forming substrate from the reservoir to the heating element. The liquid delivery mechanism may be an active mechanism, such as a pump, or may be a passive mechanism, such as a capillary material, which is described in more detail below.

[0031] The heater assembly may include a heating element that is heated in one of a number of different ways. For example, the heating element may be resistively heated by passing an electric current through the heating element, the electric current being provided by a power source. Alternatively or additionally, the heating element may be a susceptor that is inductively heated by a time-varying magnetic field.

[0032] The heater assembly may also have a variety of different forms. In some embodiments, the heater assembly includes a mesh or perforated heating plate of the heating element. The heater assembly may include a substantially flat heating element, thereby allowing simple manufacturing. The heating element may include a flat heating track, such as a serpentine shape.

[0033] The heating element may comprise an array of filaments, for example arranged parallel to each other. Preferably, the filaments may form a mesh. The mesh may be woven or non-woven. The mesh may be formed using different types of braiding or mesh structures. Alternatively, the conductive heating element consists of an array of filaments or a fabric of filaments.

[0034] In a preferred embodiment, the substantially flat heating element may be constructed from wires formed into a wire grid. Preferably, the grid is of a plain weave design. The heating element may be a wire grid made from a mesh belt.

[0035] The filaments may define interstices between the filaments, and the interstices may have a width of between 10 and 100 microns. Preferably, the filaments create capillary action in the interstices so that, in use, liquid to be vaporised is drawn into the interstices, thereby increasing the contact area between the heating element and the liquid aerosol-forming substrate.

[0036] The area of ​​the grid, array or fabric of conductive thread may be smaller, for example, less than or equal to 50 square millimeters, preferably less than or equal to 25 square millimeters, more preferably about 15 square millimeters.Size is selected so that heating element is incorporated into handheld system.The grid, array or fabric of conductive thread is set to be less than or equal to 50 square millimeters and can reduce the total power required for the grid, array or fabric of heating conductive thread, while still ensuring that the grid, array or fabric of conductive thread fully contact with liquid aerosol formation substrate.The grid, array or fabric of conductive thread can be, for example, rectangular, and have a length between 2 millimeters and 10 millimeters and a width between 2 millimeters and 10 millimeters.Preferably, the grid has a size of about 5 millimeters multiplied by 3 millimeters.

[0037] The filaments of the heating element may be formed of any material having suitable electrical properties. Suitable materials include, but are not limited to, semiconductors such as doped ceramics, electrically "conductive" ceramics (such as molybdenum disilicide), carbon, graphite, metals, metal alloys, and composite materials made of ceramic materials and metallic materials. Such composite materials may include doped or undoped ceramics. Examples of suitable doped ceramics include doped silicon carbide. Examples of suitable metals include titanium, zirconium, tantalum, and platinum group metals.

[0038] Examples of suitable metal alloys include stainless steel; Constantan; nickel-containing alloys, cobalt-containing alloys, chromium-containing alloys, aluminum-containing alloys, titanium-containing alloys, zirconium-containing alloys, hafnium-containing alloys, niobium-containing alloys, molybdenum-containing alloys, tantalum-containing alloys, tungsten-containing alloys, tin-containing alloys, gallium-containing alloys, manganese-containing alloys, and iron-containing alloys; and superalloys based on nickel, iron, and cobalt; stainless steel, Timetal®, iron-aluminum-based alloys, and iron-manganese-aluminum-based alloys. Timetal® is a registered trademark of Titanium Metals Corporation. The filaments may be coated with one or more insulators. Preferred materials for the conductive filaments are stainless steel and graphite, and more preferably 300 series stainless steels such as AISI 304, 316, 304L, 316L, etc. In addition, the conductive heating element may include a combination of the above materials. A combination of materials may be used to improve the control of the resistance of the substantially flat heating element. For example, a material with a high intrinsic resistance may be combined with a material with a low intrinsic resistance. This may be advantageous if one of the materials is more favorable to other aspects, such as price, processability, or other physical and chemical parameters. Advantageously, the substantially flat filament arrangement with increased resistance reduces parasitic losses. Advantageously, the high resistivity heater allows for more efficient use of battery energy.

[0039] Preferably, the filament is made of wire. More preferably, the wire is made of metal, most preferably made of stainless steel.

[0040] The resistance of the heating element may be between 0.3 ohms and 4 ohms. Preferably, the resistance is equal to or greater than 0.5 ohms. More preferably, the resistance of the heating element is between 0.6 ohms and 2 ohms, and most preferably is about 0.7 ohms.

[0041] The liquid reservoir may include a liquid retaining material for retaining the liquid aerosol-forming substrate. The liquid retaining material may be a sponge of foam and fiber assembly. The liquid retaining material may be formed by a polymer or copolymer. In one embodiment, the liquid retaining material is a spinning polymer. The retaining material may be, for example, porous ceramic or glass fiber.

[0042] Preferably, the device comprises a capillary material for conveying the liquid aerosol-forming substrate to the heating element. The capillary material may be provided in contact with the heating element. Preferably, the capillary material is arranged between the heating element and the retaining material.

[0043] The capillary material may be made of a material capable of ensuring that the liquid aerosol-forming substrate is in contact with at least a portion of the surface of the heating element. The capillary material may extend into the void of the heating element. The heating element may draw the liquid aerosol-forming substrate into the void by capillary action.

[0044] Capillary material is a material that actively transfers liquid from one end of the material to the other end. Capillary material can have a fibrous or spongy structure. Capillary material preferably includes a capillary bundle. For example, the capillary material can include a plurality of fibers or threads or other fine-pore tubes. The fibers or threads can be roughly aligned to transfer the liquid aerosol to form the substrate toward the heating element. Alternatively, the capillary material can include a spongy or foamy material. The structure of the capillary material forms a plurality of small holes or small tubes, and the liquid aerosol-forming substrate can be transported through the plurality of small holes or small tubes by capillary action. The capillary material can include any suitable material or combination of materials. Examples of suitable materials are sponge or foam materials, ceramic or graphite-based materials in the form of fibers or sintered powders, foamed metals or plastic materials, such as fibrous materials made of spun or extruded fibers, such as cellulose acetate, polyester or bonded polyolefins, polyethylene, polyester or polypropylene fibers, nylon fibers or ceramics. The capillary material can have any suitable capillary action and porosity, so as to be used with different liquid physical properties. The liquid aerosol-forming substrate has physical properties including, but not limited to, viscosity, surface tension, density, thermal conductivity, boiling point and vapour pressure, which allow it to be transported through the capillary medium by capillary action.

[0045] The liquid retaining material and the capillary material may be heat resistant up to 250 degrees C. The liquid retaining material and the capillary material preferably have a relatively weak interaction with nicotine.

[0046] The aerosol-forming substrate comprises a liquid mixture comprising nicotine and a first aerosol-forming agent. Preferably, the liquid mixture comprises no more than 4% by mass nicotine, more preferably 2% by mass or less nicotine. The liquid mixture preferably comprises no more than 20 mg / ml.

[0047] The liquid mixture may comprise up to about 98% by mass of the first aerosol former. Preferably, the liquid mixture comprises no more than 75% by mass of the first aerosol former. The first aerosol former may be glycerol.

[0048] Preferably, the liquid mixture comprises no more than 25 mass % of the second aerosol former.Preferably, the liquid mixture comprises about three times as much first aerosol former as second aerosol former by mass.

[0049] The liquid mixture may comprise water.The liquid mixture may comprise a flavor compound.

[0050] The power source is advantageously a battery, such as a lithium ion battery. Alternatively, the power source may be another form of charge storage device, such as a capacitor. The power source may need to be recharged. For example, the power source may have sufficient capacity to allow continuous generation of aerosols for a period of about six minutes or an integral multiple of six minutes.

[0051] The control circuit may include a microcontroller. The microcontroller is preferably a programmable microcontroller. The circuit may include further electronic components. The circuit may be configured to regulate the power supply to the heater assembly. The power may be supplied to the heater assembly in the form of current pulses.

[0052] The control circuit may include an airflow sensor positioned to detect a user puff on the system. The airflow sensor may include a microphone or a capacitive sensor. Alternatively or additionally, the user puffs may be indicated to the control circuit by the user pressing a button on the system immediately before or during each user puff.

[0053] Preferably, the aerosol generating device is a handheld device. Preferably, the aerosol generating device is portable. The aerosol generating device may have a size comparable to a conventional cigar or cigarette. The device may have an overall length of between about 30 mm and about 150 mm. The device may have an outer diameter of between about 5 mm and about 30 mm.

[0054] The device may be an electronic smoking device, such as an electronic cigarette. The device may include a reusable portion containing a power supply and control circuitry, and a consumable portion containing an aerosol-forming substrate. The heater assembly may be in the reusable portion, or in the consumable portion, or partially in both. Alternatively, the heater assembly may be provided in a separate component. The liquid aerosol-forming substrate may be held in a reservoir. The reservoir may be refillable.

[0055] In a second aspect of the invention there is provided a method of generating a nicotine-containing aerosol from an aerosol-forming substrate in an aerosol-generating system on which, in use, a user draws a puff, the aerosol-forming substrate comprising a liquid mixture comprising nicotine and a first aerosol-former having a boiling temperature higher than that of nicotine, the method comprising:

[0056] maintaining the aerosol-forming substrate within a first temperature range between puffs by a user; and

[0057] The aerosol-forming substrate is heated to a second temperature above the first temperature range during user puffing to vaporize nicotine in preference to the first aerosol-former.

[0058] Preferably, the second temperature is below the boiling temperature of the first aerosol-former.The aerosol-forming substrate may comprise a second aerosol-former having a boiling temperature below that of the first aerosol-former.

[0059] The first temperature range may be below the boiling temperature of nicotine and the second aerosol former.

[0060] It will be appreciated that features described in relation to the first aspect of the invention may be applicable to the second aspect of the invention.

[0061] The present invention provides preferential evaporation of nicotine, resulting in a higher nicotine concentration in the generated aerosol than in the liquid aerosol-forming substrate. This allows for a satisfactory user experience even when using liquids with low concentrations of nicotine. This helps people quit conventional cigarettes. It also allows for the use of liquids with low concentrations of nicotine, which are easier to handle during delivery and during use, particularly for refillable systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0063] Figure 1 is a simplified cross-section of an aerosol generating system according to an embodiment of the present invention;

[0064] Figure 2 yes Figure 1 A perspective view of the system;

[0065] Figure 3 Shown by Figure 1 The airflow of the system;

[0066] Figure 4 is a curve of applied power versus time over the course of the system's lifetime. DETAILED DESCRIPTION

[0067] In an aerosol generating system that generates an aerosol for inhalation by heating an aerosol-forming substrate, there are generally two different types of heating control. The most common type of heating control for liquid aerosol-forming substrates is so-called "flash" heating, in which a certain amount of liquid is rapidly heated in a short period of time to generate vapor. Flash heating can be timed to coincide with the user's puff or inhalation, so that aerosol is generated only during the user's puff. Flash heating is also used to vaporize a film or coating of an aerosol-forming substrate. Another type of heating control is so-called "continuous" heating, in which the aerosol-forming substrate is heated for a continuous period of time, regardless of the user's puff or inhalation. This type of heating control is more common when heating a larger mass of solid aerosol-forming substrate (such as a tobacco rod).

[0068] The embodiments described herein use a combination of continuous heating and flash heating to provide preferential evaporation of nicotine from a liquid mixture while generating more aerosol condensed material (ACM) during user suction. Preferential evaporation of nicotine means that nicotine vaporizes at a significantly higher rate than at least one other component of the liquid mixture, so that the nicotine concentration in the generated steam is higher than the nicotine concentration in the liquid mixture. By using a liquid mixture comprising an aerosol former having a boiling temperature higher than nicotine (or a vapor partial pressure lower than nicotine) and a mixture of continuous heating and flash heating, a significant increase in nicotine concentration in the steam can be achieved, and therefore a significant increase in nicotine concentration in the generated aerosol can be achieved. Between suctions, the liquid mixture is maintained at a temperature closer to the boiling point of nicotine than the boiling point of the aerosol former, which promotes preferential evaporation of nicotine. Increasing the temperature during user suction or enhancing the power supplied to the heating element allows the desired total amount of ACM and nicotine to be delivered in each user suction.

[0069] Preferential vaporization of nicotine allows the use of liquid mixtures with lower concentrations of nicotine. This is advantageous because lower nicotine concentrations in the liquid make the liquid easier to handle during manufacture, delivery and use, and is particularly advantageous if the end user is required to refill the aerosol generating system with liquid. It also allows the use of liquids that clearly comply with national or international regulations while still providing a satisfying experience for the user.

[0070] Figure 1 is a simplified cross-section of an aerosol generating system 10 according to an embodiment of the present invention. Figure 1 The system comprises a cartridge 20 and a device portion 40 coupled together.

[0071] The cartridge comprises a supply of a liquid aerosol-forming substrate and a heater assembly. The device portion comprises a power supply and a control circuit. The device portion is used to supply power to the heater assembly in the cartridge so as to evaporate the liquid aerosol-forming substrate. The evaporated aerosol-forming substrate is entrained in an airflow through the system, which is generated by a user drawing on the mouthpiece of the cartridge. The evaporated aerosol-forming substrate is cooled in the airflow to form an aerosol before being drawn into the user's mouth.

[0072] Figure 2 yes Figure 1 A perspective view of the system shown in . A system including the same hardware components is described in WO2018 / 019485.

[0073] The device portion 40 includes a housing 46 that houses a lithium-ion battery 42 and a control circuit 44. The device portion also includes a spring-loaded electrical contact element (not shown) that is configured to contact electrical contact pads on the heater assembly in the cartridge. A button 41 is provided that actuates a switch in the control circuit to activate the device. When the device is activated, the control circuit supplies power from the battery to the heater in the cartridge.

[0074] The barrel 20 has a mouthpiece end including a mouthpiece 23 on which a user can draw. The mouthpiece end is distal to the device portion. The device end of the barrel is proximal to the device portion.

[0075] The cartridge 20 comprises a housing 22. Within the housing, there is a reservoir or storage container 24 that holds a liquid aerosol-forming substrate 26. The storage container is open at the device end. A heater assembly comprising a flat mesh heating element is held on a heater cap 30. The heater cap fits onto the open end of the storage container. A liquid retaining 32 material is located within the cap. A capillary material 31 is located between the heater assembly 28 and the retaining material 32. A protective cap 33 fits to the housing and holds the heater assembly and the heater cap to the storage container. The protective cap also covers the heating element and protects the heating element from damage.

[0076] The heater cap 30 has an opening formed in the front surface and the heater assembly extends across the opening. The heater assembly includes a pair of electrical contact pads secured to the heater cap and the heating element, the electrical contact pads comprising a web of electrically conductive heater filaments spanning the opening and secured to electrical contacts on opposite sides of the opening. This type of heater assembly is described in WO2015 / 117702.

[0077] If you can Figure 1 It can be seen that when the protective cover 33 is in place in the cartridge, the protective cover compresses the periphery of the heater assembly but does not contact the heating element. The air flow path to and from the heating element is provided between the protective cover 33 and the heater assembly 28 and the storage container 24, as will be referred to in Figure 3 Described in more detail.

[0078] The protective cover is shaped to provide a barrier between the airflow path through the heating element and the electrical contact pad. The protective cover contacts the heater assembly between the exposed portion of the contact pad and the central portion of the heating element to provide this barrier and secure the heater assembly to the storage container. This arrangement reduces the possibility of leaking or condensing liquid aerosol-forming substrate contaminating the contact surface of the electrical contact pad and the electrical contact element. In addition, in order to further reduce the possibility of liquid leaking or condensing from the airflow path flowing out and contaminating other components of the system, a layer of liquid retaining material (not shown in the figure) can be provided on the interior of the protective cover or on the exterior of the storage container to absorb liquid that has condensed in the airflow path.

[0079] The cartridge 20 is coupled to the device portion 40 by a push-fit joint. The cartridge housing is shaped to allow the cartridge 20 to be coupled to the device portion 40 in only two orientations, thereby ensuring that the spring-loaded electrical contact element is received in the opening and contacts the contact pads of the heater assembly. The connecting ribs 48 of the device portion engage the notches 25 on the cartridge housing to hold the cartridge and device portion together.

[0080] The cartridge housing 22 and storage container 24 are molded in one piece and are formed of polypropylene. The liquid retaining material 32 is formed of polypropylene PET copolymer. The capillary material 31 is formed of fiberglass. The heater cap is formed of polyetheretherketone (PEEK). The heating element is formed of stainless steel and the electrical contact pads are formed of tin. The protective cover is formed of liquid crystal polymer (LCP).

[0081] In order to assemble the tube, the storage container is first filled with an aerosol-forming substrate. Subsequently, the liquid-retaining material 32 is placed in the open end of the storage container, and the capillary material 31 is placed on the liquid-retaining material. Subsequently, the heater cap to which the heater assembly has been fixed is placed in the open end of the storage container. The storage container and the heater cap can include keying features to ensure that the heater cap is placed on the storage container in the correct orientation. The protective cover 33 is subsequently assembled on the housing 22 to keep all tube assemblies in place.

[0082] The system is a handheld system sized to fit comfortably in the user's hand. In operation, after the cartridge and device portions have been coupled together, the user presses the button 41 to activate the device. The user then draws air on the mouthpiece 23 to draw air through the system. As will be described, the control circuit continuously supplies power to the heater assembly after the device is activated and based on detected user draws. The vaporized aerosol-forming substrate passes through the heating element and into the airflow through the system.

[0083] The user's puff is detected by a flow sensor (not shown) within the device portion, but in fluid communication with the airflow through the device. However, in another embodiment, the flow sensor may be omitted and the user may need to press the button 41 immediately before each puff.

[0084] Figure 3Shown is the airflow through the tube when the user draws on the mouthpiece 23. Air is drawn into the system through an inlet 60 formed between the housing of the device body and the housing of the tube 22. The air then passes through the hole formed in the connecting portion of the device part and enters the cavity formed between the device part and the protective cover 33. Subsequently, the air is drawn into the tube through the air inlet hole 37 on the front wall of the protective cover and through the dilution air inlet 50. The air drawn through the air inlet hole 37 hits the heating element and entrains the evaporated aerosol forming substrate. A mixture of air and steam is drawn away from the heating element along the airflow path 54 between the protective cover 33 and the storage container 24. The air drawn through the dilution air inlet 50 mixes with the steam / air mixture from the heater assembly. When the mixture passes through the airflow path 54, the steam cools and forms an aerosol. This aerosol is drawn into the user's mouth through the mouthpiece 23.

[0085] The airflow path contains a 90 degree bend after the exterior of the storage container. Any large droplets or debris in the airflow will not bypass the bend, but will hit the protective cap 33. This helps ensure that the desired aerosol reaches the user.

[0086] Figure 4 Shown in Figure 1 During the operation of the system of the type shown, power is delivered to the heating element so as to vaporize nicotine in preference to glycerol in the liquid mixture. The system is activated at time t=0 by the user pressing button 41. The control circuit 44 supplies about 2 watts of power to the heating element. This raises the temperature of the liquid near the heating element to between 180 degrees Celsius and 200 degrees Celsius. When the flow sensor detects that the user is puffing, the control circuit supplies a short pulse of higher power. In this example, the control circuit supplies 3 watts of power in 3 seconds. Since the airflow passes through the heating element during the user's puff, the heating element is cooled, and the pressure near the heating element is also reduced. This means that during the period of providing higher power, the heating element temperature increases only to a limited extent, but the liquid vaporization increases significantly. In this example, during each user's puff, the heating element reaches a temperature of no more than 220 degrees Celsius.

[0087] In a first example, the liquid aerosol-forming substrate 26 contains 74% by weight glycerine, 24% by weight propylene glycol, and 2% by weight nicotine. The mixture can be heated so that nicotine evaporates preferentially compared to glycerine. The normal boiling point of nicotine is 247 degrees Celsius, the normal boiling point of glycerine is 290 degrees Celsius, and the normal boiling point of propylene glycol is 188 degrees Celsius.

[0088] It has been found that over the first eight puffs of a use period, this heating control strategy results, on average, in a delivered aerosol of nearly 4% nicotine and less than 74% glycerin.

[0089] The additional power applied during the puff increased aerosol condensation material (ACM) and total nicotine delivered compared to applying only 2 watts for the entire period. Specifically, ACM increased from 1.4 mg / puff to 2 mg / puff, and nicotine increased from approximately 20 μg / puff to 50 μg / puff.

[0090] In another example, the liquid aerosol-forming substrate 26 comprises 98 wt % vegetable glycerin, 24 wt % and 2 wt % nicotine. Figure 4 The resulting aerosol contained an average of 2.8% nicotine by weight over the first eight puffs, which is again greater than the nicotine concentration in the liquid.

[0091] The additional power applied during the puff increased aerosol condensation material (ACM) and total nicotine delivered compared to applying only 2 watts for the entire period. Specifically, ACM increased from 1.4 mg / puff to 2.25 mg / puff, and nicotine increased from approximately 32 μg / puff to 40 μg / puff.

[0092] It was found that applying power above 3 W during user puff further increased the ACM and total nicotine delivered, but did not significantly increase the weight percent of nicotine in the delivered aerosol.

[0093] In the above examples, power is supplied based on a predetermined power level. Instead, control may be based on a desired temperature. The temperature of the heating element may be determined by monitoring the resistance of the heating element or by using a separate dedicated temperature sensor. For example, the heating element may be maintained at a first temperature, such as 200 degrees Celsius, between user puffs, and the power is increased by 1 watt or the temperature is increased by 20 degrees Celsius during each user puff. Different combinations of power- or temperature-based control may be used. Temperature control may be based on a temperature range rather than a single target temperature. Power control may be based on control of the duty cycle of the current supplied to one or more heating elements.

[0094] The same control strategy can also be used with different types of heaters.The required power level will depend on the characteristics of the heating element and, if the heating element is a resistive heater, specifically on its resistance.

[0095] Different users may prefer different aerosol characteristics. Therefore, the user may also be allowed to set the first power, or the first temperature of the first temperature range, or the second power, or the second temperature, or any combination of these parameters. The user may program the control circuit on the system or on a connected computer, tablet or smartphone using a suitable user interface.

[0096] The first power, or the first temperature of the first temperature range, or the second power, or the second temperature, or any combination of these parameters may also be automatically set based on the properties of the liquid mixture used as the aerosol-forming substrate. The properties of the liquid mixture may be determined by detecting a bar code or other markings on the cartridge, or may be entered by the user on the system or on a connected computer, tablet or smartphone using a suitable user interface. Different liquid mixtures may benefit from being heated to different temperatures.

[0097] The exemplary embodiments described above are illustrative and not limiting. In view of the above exemplary embodiments, other embodiments consistent with the above exemplary embodiments will now be apparent to those of ordinary skill in the art.

Claims

1. An aerosol generating device, comprising: a heater assembly comprising at least one heating element; a reservoir for holding a liquid aerosol-forming substrate proximate the heater assembly; a liquid delivery mechanism configured to deliver the liquid aerosol-forming substrate from the reservoir to the at least one heating element; a power source for supplying power to the heater assembly to generate an aerosol from the aerosol-forming substrate; a mouthpiece on which a user draws suction to draw aerosol from the aerosol generating device; as well as A control circuit configured to control the power supplied to the heater assembly, wherein the control circuit is configured to supply a first power to at least one heating element of the heater assembly between user puffs, or to supply power sufficient to maintain the at least one heating element of the heater assembly at a first temperature between 150 degrees Celsius and 200 degrees Celsius, and is configured to supply a second power to at least one heating element of the heater assembly during user puffs, the second power being higher than the first power, or being sufficient to raise the temperature of the at least one heating element of the heater assembly to a second temperature between 200 degrees Celsius and 250 degrees Celsius that is higher than the first temperature.

2. An aerosol-generating device according to claim 1, wherein the reservoir contains the liquid aerosol-forming substrate (26), wherein the liquid aerosol-forming substrate (26) comprises nicotine and a first aerosol-forming agent.

3. An aerosol generating device according to claim 2, wherein the first aerosol former is glycerol.

4. An aerosol generating device according to claim 2, wherein the first aerosol former has a boiling temperature higher than nicotine.

5. An aerosol-generating device according to claim 2, wherein the aerosol-forming substrate comprises a second aerosol-forming agent having a lower boiling temperature than the first aerosol-forming agent.

6. An aerosol generating device according to claim 4, wherein the second aerosol former is propylene glycol.

7. An aerosol generating device according to claim 1 or 2, wherein the control circuit is configurable by a user to select the first temperature or the first power.

8. An aerosol generating device according to claim 1 or 2, wherein the control circuit is configured to calculate the second power according to the first power or the first temperature.

9. An aerosol generating device according to claim 1 or 2, wherein the heater assembly comprises a plurality of heating elements, and wherein the control circuit is configured to power only a portion of the plurality of heating elements between user puffs.

10. An aerosol generating device according to claim 1 or 2, wherein the heater assembly comprises a mesh or a perforated heating plate of a heating element.

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